some engineering factors affecting handlling of ...

Minoufiya University Faculty of Agriculture Agricultural Engineering Department

SOME ENGINEERING FACTORS AFFECTING HANDLLING OF RESIDUALS AND ITS RELATION TO ENVIRONMENT By Said Fathi Badwey El-Sisi B.Sc. Agric. Science (Soil, water and Agric. Engineering) 2007

THESIS Submitted to the Department of Agricultural Engineering, Faculty of Agriculture, Minoufiya University In Partial Fulfillment Of The requirements for the degree Of MASTER of Science (M.Sc) In Agricultural Science (Agricultural Engineering) To Department of Agricultural Engineering Faculty of Agriculture Minoufiya University Shibin El-kom Egypt 2012

SUPERVISION COMMITTEE SOME ENGINEERING FACTORS AFFECTING HANDLLING OF RESIDUALS AND ITS RELATION TO ENVIRONMENT By: Said Fathi Badwey El-Sisi B.Sc. Agric. Science (Soil, water and Agric. Engineering) 2007

Supervision committee: Signature,

Prof. Dr. Ayman H. Amer Eissa

…..................................

Professor of Agricultural Engineering, Faculty of Agriculture, Minoufiya University. Dr. Gamal Rashad Gamea

......................................

Associate professor of Agricultural Engineering, Faculty of Agriculture, Minoufiya University. Dr. Ehab Abd-Elazez Elsaiedy

.....................................

Lecturer of Agricultural Engineering, Faculty of Agriculture, Minoufiya University

Committee in charge Shibin El-Kom:

26/ 6 /2012

ACKNOWLEDGMENTS

ACKNOWLEDGMENTS First of all thanks my merciful God for his continuous help during all my life, my work and this study. The author desires to express his full and deep thanks and his appreciation for Prof. Dr. Ayman H.Amer Eissa, professor of Agricultural Engineering, for valuable suggestions, his encouraging spirit, continuous supervision, reading and correcting the thesis, kind assistance during the course of this work and evaluation of the manuscript. I ask ALLAH to help him and making him always Happy Praying to ALLAH to make the Paradise his Residence. The author desires to express his deep personal gratitude and sincere appreciation to Dr. Gamal Rashad Gamea, Associate professor of Agricultural Engineering, for supervision and encouragement throughout the duration of the graduate program. I wish to thank him for his effort, during the preparation of this dissertation, reading and correcting the thesis. I ask ALLAH to help him and making him always Happy Praying to ALLAH to make the Paradise his Residence. I would also like to express my deepest thanks to Ehab AbdElaziz El Saeidy, lecturer of Agricultural engineering, for his highly useful advices and technical judgments and orientation he provided me during all my research work, for correction and highly valuable comments in revising my manuscript of this thesis, as well as for all help he extended me. I ask ALLAH to help him and making him always Happy Praying to ALLAH to make the Paradise his Residence. The author expresses his thanks to the staff members of the Department of Agricultural Engineering, Minoufiya University, Shibin El-Kom, Egypt for their help and cooperation. I am especially grateful to the members of my family for their constant encouragement and moral support.

ABSTRACT

ABSTRACT The aim of this work is to study of some engineering factors affecting handlling of residuals and its relation to environment. The items to achieve this aim are:1. Study of some physical and mechanical properties of cotton stalks. 2. Performance evaluation of local chopping machine for cotton stalks and rice straw. 3. Press these chopped residuals in screw press machine at a pressure 100 MPa and temperature of 160˚C at three moisture contents for cotton stalks (8, 10 and 12%), rice straw (8, 10 and 12.80 %) without binder and with binder (urea-formaldhyde) by 10% of the quantity chopped materials. 4. Study some quality properties of cotton stalk and rice straw briquettes such as durability, compression stress, hardness, bulk density, compression ratio, resiliency and gases emission to achieve the best criteria for handling process and conservation of the environment. The main results obtained can be summarized as a follow: 1. The average length and diameter of cotton stalks were 147.69 cm and 1.03 cm, respectively. 2. Maximum shear stress for cotton stalks was 5.26 MPa at moisture content 8%. 3. Maximum compressive stress for cotton stalks was 5.77 MPa at moisture content 8 %. 4. Minimum net power requirement for cotton stalks and rice straw were (4.11, 3.54 and 3.00 kW) and (4.74, 4.21 and 3.63 kW) at moisture - VIII-

ABSTRACT

contents (8, 10 and 12%) and (8, 10, and 12.8%), respectively. It can be obtained at 1200 rpm cutting drum speed. 5. The maximum machine production for cotton stalks was 0.66 ton/h at 2000 rpm cutting drum speed at 12% moisture content. It was 0.37 ton/h for rice straw at 2000 rpm cutting drum speed and 12.8% moisture content. 6. The optimum cutting efficiency for cotton stalks and rice straw were 86.21% and 73.1%, respectively. It is achieved at 2000 rpm cutting drum speed and moisture content 10%. 7. The maximum values of compression stress, hardness and durability for cotton stalks briquettes were 8.95 MPa, 23.15 KN and 97.06%, respectively, at 7.4% moisture content, without binder. While were 10.39 MPa, 20.16 KN and 93.64%, respectively, at 7.13% moisture content, without binder for rice straw briquettes. 8. The maximum values of bulk density and compression ratio for cotton stalks briquettes were 1180 kg.m-3 and 7.02, respectively, without binder. While were 950 kg.m-3 and 23 for rice straw briquettes. 9.

Reduction of gases emission (CO2 and CO) from cotton stalks and rice straw briquettes (without binder) about (with binder and loose) at each moisture contents. So the study recommends using cotton stalks and rice straw briquettes (without binder) environmentfriendly fuel.

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CONTENTS

1. 2. 2.1. 2.2. 2.2.1. 2.2.2. 2.3. 2.3.1. 2.3.2. 2.4. 2.5. 2.5.1. 2.5.2. 2.6. 2.6.1. 2.6.2. 2.6.2.1. 2.6.2.2. 2.6.2.3. 2.6.2.4. 2.6.3. 2.6.3.1. 2.6.3.2. 2.6.3.3. 2.6.3.4. 2.7. 2.7.1. 2.7.2. 2.7.3. 2.7.4. 2.7.4.1. 2.7.4.2. 2.7.4.3. 2.7.4.4. 2.7.5 2.7.5.1. 2.7.5.2. 2.7.5.3. 2.7.5.4.

LIST OF CONTENTS INTRODUCTION …………………………………………………………………..………….…. REVIEW OF LITERATURE ………………………………………….….......………….. Why Biomass? ………………………………………………………………………..…………….… Agricultural residuals ……………………………….……………………………………..……. Cotton stalks …………………………………………………………………………..…………..…… Rice straw ……………………………………………………………..…….……………...……………. Agricultural residuals quantity ……………….……………………...…………..………. Cotton stalks ……………………………….………………..……………………..…..……………… Rice straw ………………………………………………………......………………..…..……….......... Problems resulting from the burning of agricultural residuals……………………………………………………………………………………….………..…... Recycling agricultural residuals………………..……………..…….…..……………..… Cotton stalks …………………………………………………………..……………..………….…..… Rice straw………………………………………………………………………….…………….….…… Cutting Processes ……...………………………………………………………………….…….….. Definitions of cutting ……………..………………………….……….…………...………….... Equipments used in cutting of agricultural residuals ……...……….…… The flywheel-type cutter head ……………………………………………..……….……. The cylinder-type cutterhead………………….……………………………..…………….. Hammer mills …………………………………………………………………..…..………...…....... Impact – type cutters ………………………………………………….………..….……………. Factors affecting cutting of agricultural residuals.………..….…………..… Disc cutters……………………………..………………………………….……………………….……. Feeding rate……………………………..………………………………….……………...…….……… Knives……………………………..……………………………………………….…………..….….……... Cutting Speed………………………..………………………………….……………………..……..… Press and Briquetting Processes………………………….……………………..……..… Briquetting of agricultural residuals …………….…………………………………… Cotton stalks briquettes ……………..………………………………..……….……………….. Rice straw briquettes …………………………..……………………………..………….………. Briquettes machines……………………………..…………………………………….….……… Mechanical piston press……………………………..…………………………..…….….……. Screw press……………………………..………………………………….…………….……………… Hydraulic press……………………………..……………………………………….……….………. Pellet press……………………………..………………………………….…………………………….. Factors affecting quality properties of agriculture residuals briquettes………………………………………………………………………..…............……....……..… The bending Materials ………………………………………………………....……....……..… Moisture content………………………..…………………………………….………………..……. Briquetting mechanism…………..………………………………….…….……………..…..….. Pressing pressure and temperature…………..……………………….……………..…..

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1 3 3 5 8 8 9 10 10 11 13 14 15 16 16 17 17 18 18 19 20 20 21 21 22 23 23 25 26 26 26 27 28 29 40 30 32 33 33

CONTENTS

2.8. 2.8.1. 2.8.2. 2.8.3. 2.8.4. 2.8.5. 3. 3.1. 3.1.1. 3.1.1.1. 3.1.1.2. 3.1.2. 3.2. 3.2.1. 3.2.2. 3.3. 3.3.1. 3.3.2. 3.3.3. 3.3.4. 3.3.5. 3.3.6. 3.3.7. 3.3.8. 3.4. 3.4.1 3.4.2. 3.4.2.1. 3.4.2.2. 3.4.3. 3.4.4. 3.4.5. 3.4.6. 3.4.7. 3.4.9. 3.4.9.1. 3.4.9.2. 3.4.9.3. 3.4.9.4. 3.4.9.5.

Quality properties of cotton stalks and rice straw briquettes………..………………………………….………………….….…………….…………….…… Briquettes durability ……………..………………………………….………………….....……… Compression stress ………………………..………………………………….…………….…...…. Bulk density …………………………..……..………………………………….…………………..….. Water resistance …………………………………………..………………………..….….……..….. Emissions from combustion of briquettes………………………….…...………… MATERIALS AND METHODS ………………………………..….………………..…. Materials ………………….……………………………………………...…………….……….……….…. Residuals …………………………………..……………….…………………………………..……..….. Cotton stalks …………………….……………………..……………….……….………………….….. Rice straw…………………….…………………………….……………….……………………………. The binder (urea-formaldehyde)…………………………….....……………………..… Equipments ……………………………………………………..………………………………….…… Chopper machine ……………………………………………...……………..……………………… Screw press ………………………………….…………………………………..……………………… Measuring instruments………………………………..……………………..……………...….. Digital balance …………………………………………..…….……………………..………….…… Stopwatch …….………………………………………………………….……………….…………..…. Drying oven ………………..………………………………………………………..…………….…… Digital force gauge ………………………………………………..……………..………….….… Rotational speed of the rotating shaft …………………………...…………..………. Briquette durability instrument……………..…………………………..………………... Compression test instrument……..…………………………………………….…..…..…... Measuring gases emissions ……………………...………………………………..……........ Methods ………………..…………………………………………………………….………………..….… Factors under study………………………………………………………….……………….……. Physical and mechanical properties of crop residues …………….....…... Physical characteristics experiments ……………………………………….….….…. Determination of mechanical properties ……………..……….………….….….… Moisture content ………………………………………………………………………...……..….… Machine productivity…………..……………………………………………………..……….….. Cutting efficiency ………… ………………………………………………..…………….…….…. Power requirement …… ……………………………………………………………….………..… Energy consumption ……………………………………………...…………………….……...…. Quality of briquettes product …….……..……………..…………………………………… Bulk density ………………………………………………………………………………….………… Compression ratio ………………………………………..…………………………..……………. Resiliency …………………………………….................................................................................... Hardness ……………………………………………………………………………………..……………. Water resistance ……………………………………………………………………...………..……

- II -

35 36 37 37 38 38 40 41 41 41 41 42 42 43 46 48 48 48 48 49 51 51 53 54 56 56 56 56 56 60 60 60 61 61 62 62 62 62 63 63

CONTENTS

4. 4.1. 4.1.1. 4.1.2. 4.2. 4.2.1. 4.2.1.1 4.2.1.2. 4.2.1.3. 4.2.1.4. 4.2.2. 4.2.2.1 4.2.2.2. 4.2.2.3. 4.2.2.4. 4.3. 4.4. 4.5. 4.5.1. 4.5.2. 4.5.3. 4.5.4. 4.5.5. 4.5.6. 4.5.7. 5. 6. 7. 8.

RESULTS AND DISCUSSION ………………………..…………….….…..………….. Physical and mechanical properties of cotton Stalks ………..………..… Physical properties of cotton stalks ……………………….…………….............…… Mechanical properties of cotton stalks ………………….………………..….…..... Evaluation of Local Chopping Machine with cotton stalks and rice straw………………………………………………………………………..……………..……….….. Chopping performance evaluation for cotton stalks………….…..……….. Power requirements…………………………………………………….………………....……..… Machine production………………………………………………..…………………….………… Energy consumption…………………………………………….………….……………….…..… Cutting efficiency………………………………………….……………………………………..… Chopping performance evaluate for rice straw…………………………….…. Power requirements…………………………………………………..………………………….… Machine productivity…………………………………………………….……...…………...…… Energy consumption…………………………………………….……….…………….…..…..… Cutting efficiency…………………………………………….……….…………………….…..….. The explosion problem of the briquettes machines.……………….………. Moisture content for cotton stalks and rice straw briquettes……….. Evaluate the quality of cotton stalks and rice straw briquetting product ……….........................................................................................................................................…… Effect of moisture content on compression stress and durability for cotton stalks and rice straw briquettes ….……….…………….…………..…. Effect of moisture content on compression stress and hardness for cotton stalks and rice straw briquettes….……….…………………………….. Effect of moisture content on compression stress and bulk density for cotton stalks and rice straw briquettes….………………...…….. Effect of moisture content on compression stress and compression ratio for cotton stalks and rice straw briquettes….…... Effect of moisture content on compression stress and resiliency for cotton stalks and rice straw briquettes….……….……………………............. Briquettes water resistance …………………………..………………….….……….……… Effect of moisture content on gases emission of cotton stalk and rice straw…………………………….…………………………….….………………..……………..….. SUMMARY AND CONCLUSION ………………………………………...….…….. REFERENCES…………………………………..…………................................................................. APENDIX………………………………..…………................................................................................... ‫…………………………اﻟﻤﻠﺨﺺ اﻟﻌﺮﺑﻰ‬..…………......................................................................................

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64 64 64 64 68 68 68 69 70 72 72 72 74 74 76 77 78 78 78 83 87 91 95 99 101 104 112 125 8 -1

CONTENTS

LIST OF FIGURES Residues of cotton stalks and rice straw…………..…………........................... Schematic of the chopping machine…………..…………...................................... A photographic picture of the chopping machine…………..…….…..... The cutting disk of chopping machine…………..…………............................... The Screw Press Machine…………..…………................................................................. Photograph of the Screw Press Machine…………..…………......................... Photograph Screw briquettes…………..…………............................................................ Photograph Die briquettes…………..…………................................................................... Schematic exprimental arrangement for Shear test, Compression test and Bending test a universal testing machine................ Schematic diagram of the fabricated fixture device................................ 3.9 3.10 Multi-range hand tachometer for measuring the rotational speed)…………..…………........................................................................................................................... 3.11a Photograph test machine for briquette durability............................................ 3.11b Schematic test machine for briquette durability............................................... 3.12 Universal compression testing machine (UH-500KN, Shimadzu)…………………………………………………………………………………………..….. 3.13 The measuring emissions device (Rize 700) EIUK................................. 3.14 Chimney and measuring data of emissions....................................................... 3.15 The fixture and digital force gauge for shear force ……….……............ 3.16 The fixture and Digital force gauge for compressive force…….……. 3.17 The fixture and Digital force gauge for bending moment…………...... The relation between shear stress and moisture content for 4.1 cotton stalks at different positions of stalk (bottom, middle and top)………….................................................................................................................................................. The relation between compressive stress and moisture content 4.2 for cotton stalks at different positions of stalk (bottom, middle and top)…………....................................................................................................................................... The relation between bending moment and moisture content for 4.3 cotton stalks at different positions of stalk (bottom, middle and top)………….................................................................................................................................................. The relation between cutting drum speed and total power 4.4 requirement at different levels of moisture content (8%, 10% and 12%) and) for cotton stalk…………........................................................................... The relation between cutting drum speed and net power 4.5 requirement at different levels of moisture content (8%, 10% and 12%) and) for cotton stalk……….............................................................................. The relation between cutting drum speed and machine 4.6 production at different levels of moisture content (8%, 10% and 12%) and) for cotton stalk units………............................................................................

3.1 3.2a 3.2b 3.3 3.4 3.5 3.6 3.7 3.8

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42 44 45 45 47 47 47 48 50 51 51 52 52 54 55 55 58 59 59 67 67 67 70 71 71

CONTENTS

4.7

4.8

4.9 4.10 4.11 4.12

4.13 4.14 4.15 4.16

The relation between cutting drum speed and energy consumption at different levels of moisture content (8%, 10% and 12%) and) for cotton stalk………............................................................................... The relationship between cutting drum speed and cutting efficiency at different levels of moisture content for cotton stalks........................................................................................................................................................... The relation between cutting drum speed and total power requirement at different levels of moisture content (8%, 10% and 12.8%) and) for rice straw………............................................................................... The relation between cutting drum speed and net power requirement at different levels of moisture content (8%, 10% and 12.8%) and for rice straw………................................................................................. The relation between cutting drum speed and machine production at different levels of moisture content 8%, 10% and 12.8%) and for rice straw………............................................................................................ The relation between cutting drum speed and energy consumption at different levels of moisture content (8%, 10% and 12.8%) and for rice straw………................................................................................. The relationship between cutting drum speed and cutting efficiency at different levels of moisture content for rice straw The Processed briquette of cotton stalks and rice straw.......................... The effect of pressing on the moisture content for cotton stalks and rice straw briquettes………............................................................................................... The effect moisture content on compression stress and durability of cotton stalks briquettes (without and with binder) ……….................................................................................................................................................................

4.17 4.18 4.19 4.20 4.21 4.22

The effect moisture content on compression stress and durability of rice straw briquettes (without and with binder)……….............................................................................................................................................. The effect of moisture content of compression stress and hardness of cotton stalks briquettes (without and with binder)………............................................................................................................................................ The effect of moisture content of compression stress and hardness rice straw briquettes (without and with binder)……….............................................................................................................................................. The effect of moisture content of compression stress and bulk density of cotton stalks briquettes (without and with binder)……….............................................................................................................................................. The effect moisture content on compression stress and bulk density of rice straw briquettes (without binder and with binder)………............................................................................................................................................. Effect of moisture content on compression stress and compression ratio of cotton stalks briquettes (without binder and with binder).............................................................................................................................................

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71 72 75 75 75 76 76 77 78 81 82 85 86 89 90 93

CONTENTS

4.23

4.24 4.25 4.26 4.27 4.28 4.29

Effect of moisture content of compression stress and compression ratio of rice straw briquettes (without and with binder)………............................................................................................................................................. Effect of moisture content of compression stress and resiliency of cotton stalks briquettes (without and with binder)………............................................................................................................................................... Effect of moisture content of compression stress and resiliency of rice straw briquettes (without binder and with binder)...................... The relation between moisture content and time dispersion of cotton stalks briquettes………................................................................................................... The relation between moisture content and time dispersion of rice straw briquettes……….......................................................................................................... Effect of moisture content and binder (urea-formaldhyde) on gases emission for cotton stalks (loose and briquettes)……..…........ Effect of moisture content and binder (urea-formaldhyde) on gases emission for rice straw (loose and briquettes)…….......................

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94 97 98 100 100 102 102

CONTENTS

LIST OF TABLES 4.1 4.2

4.3

4.4

4.5 4.6

Average values of some physical properties of tested farm residuals……….......................................................................................................................................... 65 The relation between moisture content (and durability, compression stress, bulk density, resilience and compression ratio) at without binder and with binder (urea-formaldehyde) for cotton stalks briquettes………........................................................................................ 80 The relation between moisture content and (durability, compression stress, bulk density, resilience and compression ratio) at without binder and with binder (urea-formaldehyde) for rice straw briquettes……….............................................................................................. 81 The relation between moisture content and water resistance at without binder and with binder (urea-formaldehyde) for cotton stalks briquettes……….................................................................................................. 100 The emission gases for cotton stalks (loose and briquettes)........... 103 The emission gases for rice straw (loose and briquettes)................... 103

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INTRODUCTION

INTRODUCTION Biomass is considered one of the main renewable energy resources of the future due to its large potential, economic viability and various social and environmental benefits. It was estimated that by 2050 biomass could provide nearly 38% of the world’s direct fuel use and 17% of the world’s electricity. It remains the primary source of energy for more than half the world’s population, and provides about 1250 million tons oil equivalent (Mtoe) of primary energy which is about 14% of the world’s annual energy consumption (Purohit, et al 2006). The material of plants and animals, including their wastes and residues, is called biomass. It is organic, carbon-based, material that reacts with oxygen in combustion and natural metabolic processes to release heat. Such heat, especially if at temperatures >4000C, may be used to generate work and electricity. Disposal of farm residuals is one of the main problems facing Egyptian farmers which estimate about 35million ton/year (Shaban and Sawan, 2010). Cotton stalk and rice straw are considered as the one of the main environmental problems in Egypt. Where are estimated quantities to be around 0.6-0.8 million ton dry every Year and 2.3 million ton dry every Year, respectively, (MALR, 2010). The briquetting technology

improves

transportation,

storage,

the

characteristics

feeding

into

of

furnaces,

agro-residues and

for

combustion.

Briquetting of the carbonized agricultural residuals represents one of the possible solutions to the local energy shortages in many developing countries. It constitutes a positive solution to the problem of increasing rates of desertification in many areas worldwide. Agricultural residuals are not attractive as a household fuel source for urban areas because they are very bulky and have low energy intensity. Also, to eliminate the smoke generation when burning agricultural residues requires processing it by carbonization before being used as a house-hold indoor fuel. -1-

INTRODUCTION

Previously investigated, briquetting machines lacked high productivity and were of complicated designs(Yousif, et al 2006). The aim of this study is to use cotton stalks and rice straw by chopped and pressed into briquettes to be used as a biofuel. This aim could be achieved by studying the following objectives: 1. Study of some physical and mechanical properties of cotton stalks. 2. Performance evaluation of chopper machine locally manufactured for cotton stalks and rice straw. 3. Performance evaluation of screw pressed machine at three moisture content without binder and with a binder (ureaformaldehyde) for chopped residuals. 4. Study of some physical and mechanical properties of product. 5. Evaluate the quality of final product according to the international standards.

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REVIEW OF LITERATURE

2. REVIEW OF LITERATURE 2.1. Why Biomass? Biomass is the third largest primary energy in the world, after coal and oil (Bapat, et al 1997). With the onset of the First Oil Shock in the mid 1970s, biomass was again realized by many governments and policy makers to be a viable domestic energy resource that has the potential of reducing oil consumption and imports and improving the balance of payments and deficit problems caused by dependency on imported oil (Klass, 1998). Correctly managed, biomass is a renewable and sustainable fuel that can deliver a significant reduction in net carbon emissions when compared with fossil fuels. It is therefore likely to be an attractive clean development mechanism option for reducing greenhouse gas emission (Li and Hu, 2003). Biomass is constantly undergoing a complex series of physical and chemical transformation and being regenerated while giving off energy in the form of heat to the atmosphere. To use biomass for energy needs we can simply tab into this energy source. In its simplest form a basic open fire is used to provide heat for cooking, warming water or warming the homes (El Bassam and Maegaard, 2004). Biomass energy is one of humanity’s earliest sources of energy particularly in rural areas where it is often the only accessible and affordable source of energy. Worldwide biomass ranks fourth as an energy resource, providing approximately 14% of the world’s energy needs all human and industrial processes produce wastes, that is, normally unused and undesirable products of a specific process. The use of biomass fuels provides substantial benefits as far as the environment is concerned. Biomass absorbs carbon dioxide during growth, and emits it

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during combustion. Utilization of biomass as fuel for power production offers the advantage of a renewable and CO2 neutral fuel (Demirbas, 2004). Fossil fuel combustion is the prime source of carbon dioxide (CO2) emissions, which are growing at the rate of 0.5 % per year. Present levels have reached 377 parts per million by volume (ppm) up from 278 ppm at the dawn of the industrial revolution two centuries ago. It was added that, emissions of anthropogenic greenhouse gases, mostly from the production and use of energy, are altering the atmosphere in ways that are affecting the climate. As stated in the Third Assessment Report of the Intergovernmental Panel on Climate Change (IPCC), there is new and stronger evidence that most of the warming observed over the past 50 years is attributable to human activities, and that significant climate change would result if 21st century energy needs were met without a major reduction in the carbon emissions of the global energy system during this century (Abmann, et al 2006). From a sustainable view point, fossil fuels are limited and nonrenewable energy source. In addition, there are environmental problems associated with extracting, transporting, and using fossil fuels. An unavoidable solution to reducing the world’s dependency on fossil fuel is the use of renewable resources. Biomass is one of the renewable resources that can contribute significantly to the reduced use of fossil fuel. Biomass is organic materials that are plant or animal based, including but not limited to dedicated energy crops, agricultural crops and trees, food, feed and fiber crop residues, aquatic plants, forestry and wood residues, agricultural wastes, biobased segments of industrial and municipal wastes, processing byproducts and other non-fossil organic materials (Fasina, 2008).

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The main resources for biomass energy production in rural ecosystems are cereal straw residues, energy crops, organic sediments and emergent vegetation from wetlands. Developing biomass energy from agro-residues can: (a) Provide clean and sustainable energy for rural areas. (b) Promote economic development in rural areas. (c) Enhance rural incomes. (d)Accelerate industrialization of agriculture and small and medium town construction. (e) Reduce risk of environmental pollution (NDRC, 2008). Khan, et al (2009) pointed out that, due to increasing environmental concerns especially related with the use of fossil fuels, new solutions to limit the greenhouse gas effect are continuously sought. Among the available alternative energy sources, including hydro, solar, wind etc. to mitigate greenhouse emissions, biomass is the only carbonbased sustainable option. On one hand, the versatile nature of biomass enables it to be utilized in all parts of the world, and on the other hand, this

diversity

makes

biomass

a

complex

and

difficult

fuel.

Especially the high percentages of alkali (potassium) and chlorine, together with high ash content, in some brands of biomass prove to be a major source of concern. 2.2. Agricultural Residuals. Agricultural waste resulting from various farming activities including, Agricultural crop remains suitable for recycling and the production of energy or animal feed and fertilizers, Pesticides residues and agricultural fertilizers which are regarded as hazardous waste and Animal manure and sludge of sewage pits and sanitary waste water tanks (EEAA, 2001).

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El- Gharabilly (1983) stated that, some agricultural raw material is not suitable for human in food processing such as feather, skin, and bones in the case of processing from farm animal. Also, leaf stems, some fruits pits, and external leaf in vegetables. This material can affect on the operation of processing itself, such as some fruits peels and can affect on the quality of food processing such as un-grown fruits or overgrown fruits or any agricultural raw material could reduce from sorting and grading. The residual were also divided according to moisture content to: 1) Farm residuals that have a high moisture content more than 15% this kind of farm residuals can be used for direct feeding the animals or desiccate with the solar energy or by hot air. Also, it is possible to reserve the residuals as silage. 2) Farm residuals that have a low moisture content less than 15%. This can be divided to: a- Residuals have fiber content less than 20%. This kind can be used directly or mix with some organic. b- Residuals have fiber content more than 20%. This kind can used directly or mix with some organic or treat with some chemical to increase the percentage of digestion food materials. Aly, et al (1988) stated that, in general Agricultural residues are those materials including rice straw which is defined as rice plants after separation of grains during harvesting, maize plants after taking off corn cubs, and cotton stalks which is defined as stems and leaves after picking cotton. These materials constitute one of the latest proportions of residues in Arab Republic of Egypt. Craig (1993) stated that, long straw varieties of wheat are preferred because it’s high value. Straw is used as animal feed in the -6-


summer and for brick-making in the villages of some regions. Therefore it is not used for bioenergy purposes. Rice straw is used mainly for animal feed and bedding. A small amount is used in the paper industry. EL-Dali (1993) said that, the agricultural residual or secondary production on every thing can get after harvest the main crop. It is remains of production which remain until the stage of getting the main crop in a form that suitable for the human consumption or the purpose that planted for. Also, it is better to say worn-out agricultural materials instead of plant residue if there is no economical purpose for using like fallen fruits from trees. ASAE STANDARDS (1998) mentioned that, agricultural wastes normally associated with the production and processing of food and fiber on farms, feed lots, branches, ranges, and forestes, which may include both animal manure and crop residues. Jekayinfa and Omisakin (2005) reported that, numerous agricultural residuals and wastes are generated, but they are poorly utilized and badly managed, since most of these wastes are left to decompose or they are burned in the field resulting in environmental pollution and degradation. Wilaipon (2007) mentioned that, among several kinds of biomass, agricultural residuals have become one of the most promising choices. Some agricultural wastes such as wood can be directly utilized as fuels. Nevertheless, a majority of them are not suitable apparently because they are bulky, uneven, and have low energy density. All these characteristics make them difficult to handle, store, transport, and utilize in their raw form. Hence, there is the need to subject them to conversion processes in order to mitigate these problems. One of the promising solutions to these problems is the application of briquetting technology.

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2.2.1. Cotton stalks O’Dogherty and Wheeler (1984) mentioned that, the main problem with cotton stalks lies in its high transportation and storage cost due to their low bulk density. This could be solved through a densification process. The behavior of the materials during densification is dependent on their physical and biochemical properties and the variables of the processing plant. The design of Compression plants require knowledge of the force and pressure needed to obtain a desired compressed density. A number of researchers have determined the pressure density relationships for different agricultural materials. Gad, et al (1987) described the general shape of cotton stalks ranges from columnar through pyramidal to round. The shape is determined by the length of the branches.

The

stems

have

a

moderately thick, tough bark in which bast fibres are prominent. The outer layer of the bark is quite corky. It is of a yellowish brown colour on the older parts of the stems and greenish to reddish on the younger. The larger side of stems consists of well developed wood structure with prominent wood rays and water carrying vessels. 2.2.2. Rice straw Beall (2000) stated that, rice straw is characterized by lower amounts of cellulose and lignin and higher amounts of extractives. The somewhat lower amount of cellulose and much lower amount of lignin suggest that the cell wall makeup of rice straw may be quite different than that of softwood. This will have an effect of properties and should be investigated further. Perhaps more significant for the utilization of rice straw is the amount of extractives present. Ash content is very high relative to wood and this is primarily made up of silica, 75-80%.

-8-


Matsumura, et al (2005) said that, the main agricultural residues in Japan are rice straw and rice husk. These residues are collected as is the rice product, the size, cost, and CO2 emission for power generation were evaluated. Assuming a steam boiler and turbine with an efficiency of 7%, power generation from rice straw biomass can supply 3.8 billion (kW.h) of electricity per year, or 4.7 % of the total electricity demand in Japan. With heat recovery at 80% efficiency, the simultaneous heat supplied via cogeneration reaches 10% of that supplied by heavy oil in Japan. Further cost incentives will be required if the rice residue utilization is to be introduced. It will also be important to develop effective technologies to achieve high efficiency even in small-scale processes. 2.3. Agricultural Residuals Quantity. El-Haggar, et al (2000) indicated that, the estimated amount of agricultural waste in Egypt ranges from 22 to 26 million dry tonnes per year. Some of the agricultural waste is used as animal fodder, other waste is used as fuel in very primitive ovens which causes many health problems and damage to the environment. The rest is burned in the field, causing air pollution problems. The type and quantity of agricultural waste in Egypt changes from one village to another and from one year to another because farmers always cultivate the most profitable crops suited to the land and the environment. The five crops with the highest amount of waste are rice, corn, wheat, cotton and sugar cane. MALR, (2010) stated that, disposal of farm residues are one of the main problems facing Egyptian farmers which estimates about 35.22 million ton/year

-9-


Shaban and Sawan (2010) said that, agricultural wastes in Egypt amount range from 30-35 million tons a year of which only 7million tons as animal feed and 4 million as organic manure are being utilized. These crop residues results after harvesting in the farm of leaves, stem and shelves which are characterized as coarse plant by products and big size, chemically low in protein and fat contents. Also it is high in lignin and cellulous contents. 2.3.1. Cotton stalks In Egypt, crop residuals are considered to be the most important and traditional source of domestic fuel in rural areas. These crop residues are by-products of common crops such as cotton, wheat, maize and rice. The total cultivated area of cotton in Egypt is about 370×103 feddan. The average yield of cotton stalks reaches about 0.6-0.8 million tons/year. The total amount of residues reaches about 35 million tons of dry matter per year. Cotton residues represent about 2.3% of the total amount of residues. These are materials comprising mainly cotton stalks, which present a disposal problem. The area of cotton crop cultivation accounts for about 4.4% of the cultivated area in Egypt. (MALR, 2010). 2.3.2. Rice straw Egypt is the largest rice producer in the Near East region, where rice cultivation area occupies over 1,093,303 feddan. The average yield of rice straw reaches about with 2.3 million tons/year. Rice straw represent about 6.6% of the total amount of agricultural residues. These are materials comprising mainly rice straw, which present a disposal problem. The area of rice crop cultivation accounts for about 13% of the cultivated area in Egypt (MALR, 2010).

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2.4. Problems resulting from the burning of agricultural residuals. El- Dally (1993) mentioned that, many farmers get rid of farm residuals either by burning which pollutes the environment or by unsafe storage which hosts insects and rats. Also, this may ignite and is considered a source of fire risks. In some trials 30% of farm residuals are utilized in inefficient ways either in feeding livestock or as inefficient source of energy in rural areas. Hamdy (1998) stated that, about 52% of the agricultural residuals are burnt directly on the fields or in inefficient burners (less than 10% efficiency) in small villages. Both methods result in loss of energy as well as negative impact on the environment. Moreover, the traditional storage in the farms and on roofs gives a large chance for insects and other disease carriers to grow and re-attack human, animals or new crops. Dubey, et al (2007) stated that, the burning of agricultural wastes causes air pollution, soil erosion, and a decrease in soil biological activity, which eventually leads to lower yields. However, burning yields smoke and other pollutants which adversely effect air quality, visibility, and human and environmental health. The low sulphur content of crop residues (cotton stalks, rice husk and maize stalks) as compared to fossil fuels and their use as fuel does not add to the CO2 content to the atmosphere. A tonne of crop residues is used to replace 0.5 tonnes coal prevents addition of 1.5 tonnes of CO2 to the atmosphere. Proper use of 150 Mt of anticipated biomass could reduce CO2 emission by over 250 Mt each year. Shijian, et al (2008) mentioned that, in China many pollutants are released because of crop residual burning in the field, resulting in serious pollution of ambient air. Suqian with 4523 km2 of total area under cultivation was selected as a case to be studied, where wheat–rice double

- 11 -


cropping system is widely adopted. Based on the data of crop output from 2001 to 2005, the annual average amount of crop residue generated was estimated as 3.04×102 ton. About 82% of wheat straw and 37% of rice straw were burned in the field. Awasthi, et al (2010) studied variations in pulmonary function tests (PFTs) due to agriculture crop residue burning (ACRB) on children between the age group of 10 to 13 years and the young between 20 to 35 years are studied. The effects of exposure to smoke due to rice–wheat crop residue burning on pulmonary functions like Force Vital Capacity (FVC), Force Expiratory Volume in one second (FEV1), Peak Expiratory Flow (PEF) and Force Expiratory Flow in 25 to 75% of FVC (FEF25– 75%) on 40 healthy subjects of rural agricultural area of Sidhuwal village of Patiala City were investigated for a period from August 2008 to July 2009. Measurements were taken by spirometry according to the American Thoracic Society standards. Shaban and Sawan (2010) said that, the problem of agriculture wastes becomes very obvious and aggregated after the harvest of summer crops. That is because at this time of the season, the farmer is in a rush to re-cultivate his land therefore getting ride of the wastes has his highest priorities, usually by burning. This burning not only is considered an economic loss but also has harmful effects on the environment. These harmful effects are emission of poisons gases to the air and reducing the microbial activities in the soil. In addition, storing these wastes in the field after compacting may make it suitable environment for reproduction and growth of pests and pathogens that will attack new crops. Mostafa, et al (2011) said that In Egypt, burning of rice straw releases large amounts of air pollutants causing serious environmental problems. It is not expected to have significant operating problems or - 12 -


different emission compared with wheat straw and rice husk under similar operating condition. 2.5. Recycling agricultural residuals. Mohamed, et al (2001) mentioned that, farm residuals may be treated and transferred either to be used as organic fertilizer or used in livestock. Ndiema, et al (2002) mentioned that, briquetting of biomass has been found to be a viable technology for upgrading biomass materials, including agricultural residues, particularly in developing countries where there is abundant biowaste resources. The technology converts the biowaste into forms which are combustible in typical burners. The physical (elongation and voidage) characteristics and, hence, combustion characteristics of the briquettes formed depend on several factors among which the die pressure is prominent. This was confirmed by experimental investigations during which the samples were densified under die pressure ranges of 20–140 MPa. Oladeji (2010) stated that, the selection or choice of agro-waste briquettes for domestic and industrial cottage applications depends on the fuel properties. Investigations were carried out on properties of briquettes produced from corncob and rice husk residues with a view to finding out which of the two residues examined can be used more efficiently and rationally as fuel. Ultimate and proximate analyses were carried out to determine the average composition of their constituents. A simple prototype briquetting machine was fabricated to facilitate densification of these residues into briquettes.

- 13 -


Shaban and Sawan (2010) pointed out that, utilizations of agriculture wastes in any other environmentally friendly way are very important. These can be done by: 1- Compost production by fermenting the agricultural residuals in the main way for recycling them. This will help in are fertilizing the soil organically and reduce the production cost. 2- Animal feed production by treating some wastes such as rice straw by Urea or ammonia to increase its nitrogen content hence its nutritional value. 3- Food production. • This can be done by growing mushroom on agricultural wastes such as rice straw as a substrate. This means the conversion of wastes to economic, nutritional human food. • Growing vegetables on rice straw compacted bales in areas where soil disease and saline. 4- Energy production (Biogas). It can be concluded that recycling agriculture wastes is a must for environment as well as economical saving. This recycling will not only increase agricultural production but also will improve its quality. 2.5.1 Cotton stalks Sundaram, et al (1989) stated that, the production of boards from cotton stalks is reported to be cheaper than the conventional process as pulverization consumes much less power compared to hard woods. Efforts have been made to produce lightweight, fire proof, corrugated roofing material, similar to asbestos cement sheets.

- 14 -


Rosario, et al (1999) produced cement bonded particle board (CBP) from cotton stalks involved the use of simple tools and equipment and procedures. The other materials used in the production process such as cement and a cement-setting accelerator are available locally. CBP is a good substitute for plywood, fiber board, particle board, hollow block, and tiles. The manufacture of cement-bonded particle boards can generate employment of 50 people while cotton farmers can gain additional income of 3.000 P /ha from the sale of cotton stalks. Haykir (2009) produced bioethanol from lignocellulosic wastes by investigating various promising pretreatment methods for cotton stalk. Cotton stalk containing cellulose 36 g/100 g of biomass is one of the main lignocellulosic feedstocks in Turkey. El Saeidy (2009) produced briquettes of cotton stalks to be the optimum solution of problems burning and handling of cotton stalks and used as biofuel. 2.5.2. Rice straw Rahman (1987) stated that, rice straw based brick is one of the agriculture by-products internationally acknowledged such as through the development of either clay sand or cement mixtures with rice straw. Atchison, (1996) mentioned that, rice straw is attractive as a fuel because it is renewable and consider to be carbon dioxide neutral but has not yet been commercially used as a feedstock for heat and energy because of insufficient incentives or benefit for farmers to collect rice straw instead of field burning. Direct comparison of straw with coal, still the dominant solid fuel in electricity and heat generation, often reveal inferior properties of straw.

- 15 -


Magdi, et al (2003) used rice straw compost and studied its effects on growth and yield of faba bean and soil properties was studied in pot experiments at Gifu University, Japan in 2001/2002. The composts reached maturity in 90 days, were rich in organic matter and mineral nutrients, had a high level of stability, and no phytotoxicity. Foday, et al (2010) said that, the exploitation of rice straw as renewable energy has gained momentum since the present energy crisis and global warming threat. In comparison with fossil fuel such as coal and oil still the dominant fuel in electricity and heat generation, often reveals inferior properties of straw. It is low grade with high volatile, low calorific and density values, is a bulkier fuel (with poorer handling and transportation characteristics), its fibrous nature and high content of alkali compounds could potentially causing slagging, fouling, and grate sintering this makes it difficult to handle, transport and store efficiently, a major constraint to its use as an energy source. 2.6. Cutting Processes. 2.6.1. Definitions of cutting. Persson (1987) mentioned that, cutting was defined as the process of mechanically dividing a solid body along a predetermined line using a cutting tool. In most cases, the original body of the different farm wastes will be divided into parts that have newly created surfaces called cut. It was mentioned also that the cutting tool is characterized by a clearly defined edge. Cutting has been given other names in many special cases, describing the special kind of cutting device or cutting procedure such as edge and the blade (which includes the edge). Chopping, mowing, sawing, splitting, slicing, dicing and chipping. Many other names are used for cutting tools of special shape and use, as

- 16 -


for instance shear, shear, scissor, blades, flail, tooth, saw tooth, cutter, jaw, scythe, shank, chopper and axe. Functionally the knife may considered having two parts. The cutting of agricultural materials may be performed either individually or in bundles depending on their types and the cutting process technology. The most frequently used cutting processes of these materials are: a) Cutting processes involving counter-moving blades, where both sets of blades participate in cutting. The counter-shear in this case is moving in the opposite direction of the cutting tool motion. b) Cutting processes performed by means of a moving knife and a stationary counter-shear. Where, the counter shear used to support the body and assist it in the cutting process. c) Cutting processes of thin layers, where the stress distribution around the cutting edge is significantly distorted by the free surface found close to the cutting plane. d) Cutting processes of free cutting blades, where one end of a relatively long stalk is fixed and a counter-support is ensured by the moment of inertia of the stalk. In this case, the velocity of the cutting edge is a significant parameter for establishing the cutting process successfully. 2.6.2. Equipments used in cutting of agricultural residuals. 2.6.2.1. The flywheel-type cutter head: Kepner, et al (1992) stated that, flywheel-type cutterhead usually have 4 or 6 knives. Most cylinder-type cutterhead have 6 knives and diameter of 380 to 460 mm or 9 knives and diameter of about 610 mm. With either type, some of the knives can be removed to increase

- 17 -


the length of the cut. The remaining knives must be equally spaced to maintain cutterhead balance. A flywheel-type cutterhead has 3 or 4 impeller blades around the periphery that throw or impel the chopped material up the discharge pipe and into the wagon. ASAE STANDERD (1998) mentioned that, knives flywheel-type cutter head mounted essentially radially with the cutting edges describing a plan perpendicular to the axis of rotation. The number of the knives, the number of forage impellers blower paddles, if so equipped, and the rotational speed (r/min) shall be specified. The inner and outer effective knives cutting diameters about the axis of rotation shall be expressed in millimeters. The diameter formed by the blower paddles, if so equipped, and the blower housing inside width shall be expressed in millimeters. The flywheel-type cutter head usually has the knives for cutting and impeller paddles for throwing and blowing are mounted on the wheel separately. 2.6.2.2. The cylinder-type cutterhead: Kepner, et al (1992) stated that, cylinder-type cutterhead usually has the knives designed both to cut blow. Some cylinder cutter head required a separate impeller blower. Each type of cutter head has cretin advantage and disadvantages. The cylinder type may have built-in sharpness, but the knives must be removed from the flywheel for sharpness. Cylinder- type cutterheads either obtain a direct- throwing action from the knives in a close- fitting housing or employ a separate impeller- blower located immediately behind the cutter head. 2.6.2.3. Hammer mills: Smith (1976) divided, the fastened of hammers on the cylinder to ridged type and swinging type. The free-swinging hammers is hinged, but

- 18 -


the redied is fastened to a rotor shaft or cylinder by jam nuts. The shape of the hammer edge varies to the idea of the designers. The hammer should be made of high grade hardness steel to prevent excessive wear. A screen, usually of one piece, encloses screens, in most machines, the lower half of the cylinder. It consists of holes punched through sheet steel. Various sized holes are used, depending upon the fineness of grinding desired. The smaller holes are used when grinding grains, while the larger sizes are used when grinding roughage, such as sorghum stalks, corn stalk, or hay (Grover and Mishra, 1996). 2.6.2.4. Impact – type cutters: Kepner, et al (1992) mentioned that, there are more than 175 different models of rotary cutters and 60 models of flail shredders were commercially available from over 40 manufacturers in the United States. A rotary cutter has knives rotating in horizontal plane (as on a rotary lawn mower), whereas a flail shredder has knives rotating in vertical plants parallel with the direction of travel. These implements were first developed for cutting up stalks, small brush, cover crops, and other vegetables matter to facilitate incarnation into the soil, for cutting weeds, and for other similar jobs, in the early 1950s, rotary cutters are hazardous because of the tendency to throw solid objects outwards from beneath the housing in violent manner. They also tend to leave the material windrower. Flail shredders have free-swinging knives or flails, 2 to 6 in. wide, attached to the rotor in 3 to 4 rows and staggered so the cuts overlap slightly. The knives are some times attached through a loop or chain link, rather than trough a pivot axis, to provied greater flexibility for rocky

- 19 -


conditions. Cutting widths of present speeds are some times lowers than rotary cutters, usually ranging from 9000 to 11000 rpm. 2.6.3. Factors affecting cutting of agricultural residuals. Abd EL-Ghany (2003) recommended that, experiment in the chopping cotton stalks and rice straw the minimum fuel consumption rate was 2.48 l/h (Required power is 7.83 Kw) and 3.51 l/h (Required power is 11.09 Kw) at following factors: 1 mm clearance distance, 20 degree knife edge angle, 1300 rpm cutting drum speed, 300 rpm feeding speed and 25.27% ,15.46% moisture content for cotton stalks and rice straw, respectively. 2.6.3.1. Disc cutters. ASAE STANDERD (1998) mentioned that, disc cutter is a multiple disc device, using two or more knives per disc, driven about vertical axes behind at sufficiently high rotational speeds to achieve impact cutting. The cutter drum is a multiple drum device, using two or more blades per drum, driven about vertical axes from above at sufficiently high rotational speeds to achieve impact cutting. The blades are located at or near the drum bottom. The flail cutter is a device using multiple, radically mounted blades that are pivotally mounted on a horizontal rotor to impact cut. The rotor is positioned transverse to direction of travel. The rotary impact knives is a rotary cutting device using high velocity knives driven about vertical or horizontal axes to impact cut standing crop (no stationary knives used).

- 20 -


2.6.3.2. Feeding rate: ASAE STANDERD, (1998) mentioned that, Precision cut forage harvesters is a forage harvester that uses a feeding mechanism to meter the crop into cutting or shearing mechanism at a uniform velocity; thus the crop is cut off at regulate, particle lengths generally ranging from 3 to 50 mm. El-Iraqi and El Khawaga (2003) designed a cutting machine for rice straw and maize stalks. It was operated at five cutting speeds ranged (6.48 – 10.09 m/s), three clearness between knives (1.5, 3and 4.5 mm) and three feeding rates (0.257, 0.514 and 0.771 ton/h). Their results indicated that the maximum percentages in cutting length of less than 5 cm of 87.80 and 92% were obtained for rice straw and corn stalks residues respectively, at cutting speed of 10.09 m/s, feeding rate of 0.771 ton/h and knife clearance of 1.5 mm. The energy consumed was found to be 6.36 and 6.17 kW.h /ton at the same previous parameters for rice straw and corn stalks, respectively. Imbabi (2003) tested the performance of a cutting machine for crop residues. The results showed that the highest values of both cut length and machine productivity were obtained at feeding drum speed 300 rpm and cutting drum speed 1500 rpm. The lowest costs were 12.97 LE/ton with feeding rate 1.873 ton/h. 2.6.3.3. knives. Kamel and Imbabi (2003) evaluated forage chopper with 12 knives for chopping rice straw. The results can be summarized as follows: • Increasing forward speed increased the distribution percentage of short pieces (from 0.5 to 2 cm) and decreased the distribution percentage of long pieces (from 2 to > 5 cm).

- 21 -


• The maximum distribution percentage of short pieces (56.53%) was obtained at 1.22 m/s forward speed. • The maximum energy requirement (27.4 kW.h/fed) and the maximum values of chopping cost were 22.07 LE/ fed. (12.46 LE/ton) were obtained for chopping rice straw under forward speed of 0.53 m/s. 2.6.3.4. Cutting Speed: Guzel and Zeren (1990) mentioned that, some basic engineering data were determined for rotary cutters for cotton stalks energy consumption of the blades ranged between 240 – 289 kg.m, power consumption was as 4.2 hp for departure, 1.74 hp at 540 rpm and 0.86 hp at work. the maximum and minimum velocities for blade were between 68.97 – 51.87 and 33.64 – 36.52 m/s, respectively. Habib (2002) studied the effect of cutting velocity on the fuel consumption. It was found that the fuel consumption increases with increasing the cutting velocity. Where, the ratio of this increase at a constant feeding velocity 0.012 m/s is 24% and 29% for maize and cotton stalks, respectively. It is found also, that the fuel consumption for the cutting process of cotton stalks is greater than that of the cutting of maize stalks by 44.6% at cutting velocity of 0.84m/s and feeding velocity 0.012m/s. Lotfy (2002) found that, the power consumption for cutting different residues was increased with increasing cutting and feeding speeds. The minimum values of power consumption were (13.68, 15.24, and 15.66 kW) noticed for cutting corn stalks, rice straw and cotton stalks at 24.08 m/s cutting speed and 1.0 m/s feeding speed. The maximum values of power consumption were ( 22.97, 23.92 and 25.82 kW) for cutting corn stalks, rice straw and cotton stalks at 43.35 m/s cutting speed and 2.5 m/s feeding speed. - 22 -


Younis, et al (2002) resulted that, the average values of required power and consumed energy of developed chopper increased by increasing of rotor speed. The minimum values of required power and consumed energy, 1.94 kW and 5.1 kW.h/ton, were found at rotor speed 1000 rpm (25m/s), while the maximum value of required power, (11.77 kW) was found at rotor speed 2200 rpm (55m/s). The maximum value of consumed energy, 12.9 KW.h/ton, was found at rotor speed 1600 rpm (40 m/s). Abd EL-Ghany (2003) recommended that, the fuel consumption increased with increasing cutting drum speed, fuel consumption for cutting cotton stalks increased from 2.48 L/h to 5.40 L/h with increasing cutting drum speed from 1300 rpm to 1600 rpm at 1 mm clearance distance and 20 degree knife edge angle. For cutting rice straw found that, the fuel consumption increased from 3.51 L/h to 6.41 L/h with increasing cutting drum speed from 1300 rpm to 1600 rpm at 1 mm clearance distance and 205 degree knife edge angle. Elfatih, et al (2010) studied the relationship between cutting drum speed and chopper productivity at different concave holes diameter. Chopper productivity increased by increasing the cutting drum speed. And also the relationship between cutting drum speed and cutting efficiency at different concave holes diameter. The machine productivity increased by increasing the concave hole diameter. While cutting efficiency increased by increasing the cutting drum speed. 2.7. Press and Briquetting Processes. 2.7.1 Briquetting of agricultural residuals. Grover and Mishra (1996) mentioned that, as the number of industries is growing day by day. The energy required is also increasing

- 23 -


proportionately and the present power supply is unable to meet the energy demand. To combat this energy shortage, developed as well as developing countries are putting more efforts into R&D to tap alternative energy sources. Briquetting of biomass can be considered for its economics, reliability and ease of operation. Briquettes of small size can be used in gasifiers for power generation. If the plant sites are chosen properly for easy availability of raw material, the agro-residues can be briquetted to reduce further transportation costs and associated pollution. This also improves the handling characteristics of biomass. The briquettes so obtained are very good fuels for local small scale industries and domestic purposes. It was also added that, the advantages of briquette are: • It is one of the alternative methods to save the consumption and dependency on fuel wood. • Densification make handle, transport and store it easy. • They are uniform in size and quality. • The process helps to solve the residual disposal problem. • Air pollution is minimizing. Tabares, et al (1999) appreciated that, briquettes can be an alternative fuel to fossil fuels but they are conditioned by two premises: in the first place, the cost of the raw material: and in the second, the distance to the point of consumption can mean a considerable increase in cost. Mc Mullen, et al (2005) stated that currently, there is tremendous interest in using biomass materials in the U.S. for producing liquid transportation fuels, combined heat and power, chemicals, and bioproducts. In addition to numerous advantages, use of biomass materials in place of fossil fuels would result in low emissions of greenhouse and acid gases. In order to make the biomass materials available for a variety of

- 24 -


applications, the challenges with the use of biomass materials in their original form must be resolved. Because of high moisture content, irregular shape and sizes, and low bulk density, biomass is very difficult to handle, transport, store, and utilize in its original form. One solution to these problems is densification of biomass materials into pellets, briquettes, or cubes. Densification increases the bulk density of biomass from an initial bulk density (including baled density) of 40–200 kgm-3 to a final bulk density of 600–800 kg.m-3. Singh, et al (2007) mentioned that, the briquettes can be used for domestic purposes (cooking, heating, barbequing) and industrial purposes (agro-industries, food processing) in both rural and urban areas. 2.7.2. Cotton stalks briquettes. Abasaeed (1992) obtained briquetting of carbonized cotton stalks to provide an environmentally sound and socially accepted fuel and also solve a waste disposal problem. Scholz and Berg (1998) said that, briquetting of cotton stalks is a technological and economical solution to reuse the stalks as a cheap, safe and environmentally friendly fuel. The well processed briquettes are hard and stable so that they are easy to be handled and stored. Singh, et al (2007) reported that, a minimum 4–5 times increase in bulk density of roughage-based feed materials, with an increase in compression pressure from 21 to 42 MPa during the densification process in the form of blocks. Jha, et al (2008) stated that, chopped cotton stalks having moisture content varying from 8.5% to 21.45% (w.b.). It was also densified into square blocks (80 mm by 80 mm) at compression pressures ranging between 13.79 and 34.47 Mpa.

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2.7.3. Rice straw briquettes. Lucy and Jenkins (1995) reported that, densification of wheat straw, saw dust and shavings into fuel briquettes at 75 MPa pressure. Sawdust briquettes were found to be the most durable and exhibited the least degree of length expansion whereas the wheat straw briquettes were the least durable and expanded the most. The optimum moisture content was reported to be 12–20% (w.b). Chou,

et

al

(2009)

investigated

the

preparation

and

characterization of the solid fuel briquette, which was made from rice straw and rice bran. This work included, developing a machine to smash the rice straw into pieces, compressing the smashed rice straws and the rice bran into the biomass briquette and characterizing the properties of the briquette (such as the percentage of change in briquette volume, the percentage of loss of briquette mass, the air-dry density, the compressive strength, and the heating value). 2.7.4. Briquettes machines. 2.7.4.1. Mechanical piston press. Richard and Mills (1978) used piston type presses in which the pressure is either developed against the closed end of the die or as the result of friction between the material and the wall of the die. It has been shown that, by heating the material to a determined temperature, a more stable product with smaller dimensions could be obtained than was possible with unheated materials. The piston press acts in a discontinuous fashion with material being fed into a cylinder which is then compressed by a piston into a slightly-tapering die. The compressed material is heated by frictional forces as it is pushed through the die. The lignins contained in all woody- 26 -


cellulose materials begin to flow and act as a natural glue to bind the compressed material. When the cylinder of material exits from the die, the lignins solidify and hold it together to form cylindrical briquettes which readily break into pieces 10-30 cm long. Piston-presses can be driven either by mechanical means from a massive flywheel via a crankshaft or hydraulically. The mechanical machines are usually larger, ranging in size from 0.45 to 0.3 t/h, whilst hydraulic machines normally range up to 0.25 t/h though some models are somewhat larger. Mechanical presses generally produce hard and dense briquettes from most materials whilst hydraulic presses, which work at lower pressures, give briquettes which are less dense and are sometimes soft and friable (FAO, 1990). Zeng, et al (2007) used the piston press to obtain a briquette. The piston press has long life of wearing parts and low power consumption. It can be used to compress a wide range of raw biomass materials which include corn straw, peanut shell, ground nut shell, cotton stalks, sun flower stalks, etc. However, the piston press needs a higher level of maintenance and the briquettes has lower quality and cannot be carbonized if compared to the screw press. 2.7.4.2. Screw press. Grover and Mishra (1996) stated that, the press being used as part of the test work reported here is the Shimada SPMM-850 KS, which has a screw which rotates at a speed of 600 rpm and this compresses the material against a heated die. The die is heated to a temperature of 280 to 290° C to give a smooth extrusion of the briquettes. The production capacity of the machine depends on the briquette size. At present briquettes of 55 mm diameter are produced with a capacity of 400 kg/hr. If a 65 mm diameter die is used then the

- 27 -


capacity increases to 650 kg/hr. This factor is quite important in the financial analysis of the whole plant and in the calculation of the manufacturing cost of the briquettes, and hence selling price. Bhattacharya and Kumar (2005) reported that, heated-die screw press briquetting is a popular densification method suitable for small-scale operations in developing countries. In this method, the raw material from the hopper is conveyed and compressed by a screw that forces it through a heated die. This process can produce denser and stronger briquettes compared with piston presses. El Saeidy (2009) mentioned that, Briquettes produced from screw press are stable, dense and homogenous to be used as a Biofuel. This environmentally friendly fuel is suitable for the domestic purposes in the villages and in the new reclaimed lands. It can be also used in Poultry farms for heating. 2.7.4.3. Hydraulic press Abasaeed, et al (1989) achieved by the double piston hydraulic press, which produced about 25 kg/h of briquettes of a density of about 500 kg/m3. The present work is showing the result of the ERC efforts to replace the hydraulic system with a more productive and reliable briquetting system, and to improve the quality of the product to be more suitable for the household needs in Sudan. Grover and Mishra (1996) stated that, the hydraulic piston press is different from the mechanical piston press in that the energy to the piston is transmitted from an electric motor via a high pressure hydraulic oil system. This machine is compact and light. Because of the slower press cylinder compared to that of the mechanical machine, it results in lower outputs. The briquettes produced have a bulk density lower than

- 28 -


1000 kg/m³ due to the fact that pressure is limited to 40-135 kg/h. This machine can tolerate higher moisture content than the usually accepted 15% moisture content for mechanical piston presses. 2.7.4.4. Pellet press Zeng, et al (2007) stated that, roller press uses smaller dies (approximately 30 mm) so that the smaller products are called pellets. It has a number of dies arranged as holes bored on a thick steel disc or ring. And the material is forced into the dies by means of two or three rollers. The two main types of pellet presses are: flat type, which has a circular perforated disc on which two or more rollers rotate, the second is ring type, which features a rotating perforated ring on which rollers press onto the inner perimeter. Tumuluru, et al (2010) mentioned that, pelletizing is similar to briquetting except that it uses smaller dies (30 mm) to produce smaller densified products called pellets. There are two main types of pellet presses: ring die and flat die. In general the die remains stationary and the rollers rotate. However, some pellet mills have dies that rotate and rollers that remain stationary during production. The die of a pelletizer is made of hardened steel that is perforated allowing the biomass to be forced through by the rotating die or rollers. 2.7.5. Factors affecting quality properties of agriculture residuals briquettes. Nalladurai and Yang (2009) stated that, Factors affecting of constituents the briquettes such as fiber, lignin, moisture content, particle size and its distribution, conditioning temperature, preheating of briquettes, added binders and densification equipment variables (forming pressure, pellet mill and roll press variables) on the strength and durability of the densified products are reviewed.

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2.7.5.1. The bending Materials. Margosian (1990) found that, formaldehyde is an important component of most adhesives used in pressed wood products. It is used as adhesives, the primary bonding agents for particleboard, medium density fiberboard (MDF), and hardwood plywood. When UF adhesives are used to bond wood-based panels, small amounts of free formaldehyde are emitted for a period of time after manufacture. Formaldehyde's role in indoor air quality continues to be widely studied by scientists and regulatory agencies. The U.S. Environmental Protection Agency (EPA) and other regulatory agencies carry out exposure assessments, which are estimates of the long-term exposure that building occupants could have to formaldehyde emissions from pressed-wood products and other sources. Since formaldehyde emissions from wood products decrease with time ("decay"). Sellers, et al (1991) investigated that, three-layer particleboards made of southern pine were bonded with urea-formaldehyde resins containing post-added ester and/or urea. The ester was a water-soluble active methylene compound [(2-hydroxyethoxyethyl) aceto-acetate], which was added to the face resin over a range of 0.015 to 0.100 % based on dry face wood weight. A series of panels was also bonded without a scavenger, as a control. For comparison, a series was bonded with resin containing 0.300 % urea (% based on dry face wood weight) as a formaldehyde (HCHO) scavenger. The particleboards were physically tested for density, internal bond strength, and HCHO emission. HCHO emission assessment was determined by the 2-hour desiccators test method. Tabares, et al (1999) found that, a series of briquettes made from forest or industrial waste are evaluated from both an energy and economic - 30 -


viewpoint. Lignocellulosic densification improves the briquettes’ behavior as a fuel by increasing the homogeneity and by being easier to transport

and

manage.

Lignocellulosic

binderless

briquettes’

characteristic lower heating value (LHV) and remaining amount of fuel during combustion (Weight) have been investigated to obtain a general expression function of production and raw material factors. Singh, et al (2007) resulted that, by adding small quantity of burnt engine oil, thermal conductivity of sawdust improved and heat penetrates up to the center of briquettes thus uniform temperature distribution exist and better quality briquettes were obtained. Nalladurai and Morey (2010) found that, role of the natural binders in corn stover and switch grass to make durable particle–particle bonding in briquettes/pellets was investigated by micro-structural analyses. Scanning Electron Microscopy (SEM) images of briquettes made by using a uniaxial piston-cylinder densification apparatus in the laboratory, briquettes made by using roll-press briquetting machine, and pellets made by using a pilot-scale conventional ring-die pelleting machine were analysed. The SEM images showed that, the bonding between particles was created mainly through solid bridges. The solid bridges between particles were made by natural binders in the biomass expressed during the densification process. UV auto-fluorescence images of briquettes and pellets further confirmed that the solid bridges were made mainly by natural binders such as lignin and protein. Sotannde, et al (2010) resulted that, briquettes bonded with starch gave better performance based on density of 0.546 g.cm-3, durability rating of 95.93%, heating value of 33.09 MJ·kg-1, percentage of fixed carbon of 84.70% and low ash and volatile matter of 3.35% and 11.95%, respectively, while briquette bonded with gum arabic has density of 0.425

- 31 -


g·cm-3, durability rating of 94.85%,heating value of 32.76 MJ·kg-1, percentage of fixed carbon of 87.30% and low ash and volatile matter of 4.45% and 8.75, respectively. 2.7.5.2. Moisture content. Grover and Mishra (1996) mentioned that, the percentage of moisture in the feed biomass to extruder machine is a very critical factor. In general, it has been found that when the feed moisture content is 8-10 %, the briquettes will have 6-8% moisture. At this moisture content, the briquettes are strong and free of cracks and the briquetting process is smooth. But when the moisture content is more than 10%, the briquettes are poor and weak and the briquetting operation is erratic. Swedish Standard (1998) mentioned that, drying of wood-based biofuels is important, since wet wood results in low combustion temperatures, low energy efficiency and high emissions of hydrocarbons and particles compared to pellets. If biofuels are dried and compressed to pellets or briquettes, the fuel will have controlled moisture content (MC), have a higher energy density and be easier to transport. It will also take up less room and be less susceptible to mould and insect attacks during storage. The shape of the pellet, diameter 6–8mm and a length of 4 or 5 times. Stahl, et al (2004) recommended that, to produce high quality pellets, the feedstock has to be dried to a moisture content of about 10% (raw weight). Since it is not possible to reach such low moisture contents by natural drying, the material has to be artificially dried. However, a wide range of temperatures and retention times can be used in the drying process. Rhen, et al (2005) mentioned that, In the pelletizing process the raw material is dried to a moisture content of 9–12% and milled to a

- 32 -


specific but rather broad particle size distribution, usually less than 4 mm, screened to remove oversized and fine particles and finally pressed by rollers through the holes of a die. The friction between the wood material and the die during the passage results in a rise in temperature. This together with the moisture content of the material is important for the thermal softening and self-bonding of individual wood particles in the pellets. El Saeidy (2009) recommended that, the moisture content is an important factor which affects the Briquetting process. 8% moisture content and less was the optimum to do this process easy and safety. The briquettes quality and the process emissions are also better than the higher ranges of moisture content. 2.7.5.3. Briquetting mechanism. Grover and Mishra (1996) stated that, in a screw press the biomass is extruded continuously through a heated taper die, which is heated externally to reduce the friction. The advantages of screw press are high quality of briquettes (superior storability and combustibility), smooth and noiseless operation. The two major impediments for the screw press: high wear of the screw and the comparatively large specific power consumption required. 2.7.5.4. Pressing pressure and temperature. Smith, et al (1997) mentioned that, wheat straw could be compressed and stabilized to a density of 10 times that of normal bales by the application of pressure between 20 and 60 MPa after heating to a temperature between 80 and 140˚C. Demirbas (1999) studied the effects of the briquetting pressure on the density, moisture content and compressive strength of the briquettes were examined at six different pressures (300, 400, 500, 600,

- 33 -


700 and 800 MPa). The optimum moisture contents and briquetting pressures were found to be 18% and 780 MPa for waste paper, 22% and 710 MPa for wheat straw and 18% and 750 MPa for a 20 % (w) waste paper-straw mixture. The effect of the temperature on the briquette density of wheat straw was determined. The best wheat straw briquettes were obtained at 385 K°. Ndiema, et al (2002) stated that, there was considerable influence of the die pressure on the size and the form of briquettes. For a given die size and storage condition, there was a maximum die pressure of 80 MPa beyond which no significant gain in the cohesion of briquette could be achieved. Christofer, et al (2005) found that, high compression strength was strongly correlated with the density of the pellets. High temperature (at least up to 144

C) and low moisture content at the start of

compression (down to 6.3 wt. % increased the dry density of the pellets. Remarkably, compression force had very little effect in the tested range of 46–114 MPa, indicating that pressure in the die does not need to be higher than 50 MPa. Tore, et al (2011) resulted that, pelletization of 11 months stored wood compared to fresh material and high drying temperature (450°C) compared to 75°C resulted in higher energy consumption, probably due to increased friction in the matrix caused by the loss of extractives. However, the pellets produced were of higher density than those made from fresh material dried at a low temperature. Hasan, et al (2010) mentioned that, soda weeds were first chopped coarsely in a local tresher, and then chopped finely in a hammer mill. Weed materials at three moisture levels (7%, 10%, and 13%) were prepared in the lab. Chopped weed materials were filled in cylindrical and

- 34 -


square dies and compressed using a hydraulic press at three pressure levels of 15.7, 19.6 and 31.4 MPa. Optimum temperature, moisture rate, and pressure values were determined to produce stable briquettes. Further experiments were conducted to produce briquettes using sawdust and walnut shells as additives in conical dies of two different sizes. 2.8. Quality Properties of Cotton stalks and Rice straw Briquettes. Back (1987) stated that, the mechanical properties of pellets include density, compression strength and moisture absorption during storage, are influenced by the moisture content of the pellets and by manufacturing parameters such as compression pressure and temperature. Nalladurai and Morey (2009) mentioned that, densification process to create strong and durable bonding in densified products such as pellets, briquettes, and cubes can be determined by quality testes which include testing the strength (compressive resistance, impact resistance and water resistance) and durability (abrasion resistance) of the densified products. These tests can indicate the maximum force/stress that the densified products can withstand, and the amount of fines produced during handling, transportation and storage. Aivars, et al (2010) pointed out that, to guarantee the quality of biomass briquettes in the handling and usage process, sufficient durability of briquettes should be provided. Density 1.0 g.cm-3 has been obtained in densification of straw and reed stalk material particle compositions with peat, if peat proportion exceeds 20 %. Crushing force dependence on particle size for arranged structure briquettes is stated in laboratory experiments. In comparison with unarranged structure briquetting crushing force for arranged structure briquettes increases on average from 3 to 5 times.

- 35 -


2.8.1. Briquettes durability. Lucy and Jenkins (1995) determined that, the possibility of producing durable briquettes from wheat straw and sawdust as fuel for Kenyan households and small-scale industries. These consumers are burning an increasing amount of these materials, which in their raw form are poor quality fuels. The moisture content and durability of these briquettes were measured after a storage period of 2 weeks at approximately 20°C and 50% relative humidity. Blending straw with sawdust improved this durability considerably. There appears to be a direct relationship between length expansion and the durability rating of the briquettes. All the briquettes had relatively low moisture content. Briquettes can be manufactured without a binder but with poor durability in the case of straw. Vinterback (2002) mentioned that, durability and particle density are the main parameters describing the physical quality of densified solid biofuels like pellets and briquettes. Both fuel types are susceptible to mechanical wear, which leads to production of fine particles or dust during transport, transhipment and storage. Dust emissions are not only an inconvenience for the consumer; they are also a health hazard. El Saeidy (2004) stated that, the durability of briquettes is a very important factor for transportation processes and feeding combustion equipment. The stability of hemp and poplar (pressed hydraulically) briquettes was tested. Because of the abrasion between the briquettes themselves and between the briquettes and the baffle, some particles of the briquette surface were separated. The rotating motion of the experimental box leads the briquettes to move up and down. This movement leads the briquettes to lose some particles from their surface. The results showed that, the durability of hemp briquettes was 81%, and - 36 -


of poplar briquettes 75.8%. The average moisture content of the briquettes was 7.8%. Nalladurai and Morey (2009) mentioned that, the durability of briquettes is a measure of the ability of the briquettes to withstand the destructive forces such as compression, impact and shear during handling and transportation. The possible amount of fines (dust) generated from the briquettes due to the mechanical handling and transportation can be estimated by equation (100 – durability %). In addition, the durability values represent the relative strength of the particle–particle bonding in the briquettes/pellets. 2.8.2. Compression stress. Yamnan, et al (2001) indicated that, the mechanical strength of the briquettes produced from Ku¨tahya-Seyito¨mer lignite can be improved by adding some biomass samples. For example, the presence of paper mill waste increased the shatter index of the briquettes obtained. Similarly, sawdust and paper mill waste increased compressive strength of the briquettes. Water resistance of the briquettes can be augmented by adding olive refuse, cotton refuse, and pine cone or paper mill waste. Husain, et al (2002) studied an attempt has been made to convert agricultural residues into solid fuel. The palm shell and fibre is densfied into briquettes of diameter 40, 50 and 60 mm under moderate pressure of 5–13.5 MPa in a hydraulic press. 2.8.3. Bulk density. Jha, et al (2008) evaluated the physical characteristics of chopped cotton stalks and studied the physical characteristics of blocks, namely bulk density, compression ratio, resiliency and hardness, were evaluated. The bulk density of blocks varied from 542 to 794 kg.m-3,

- 37 -


resiliency from 11% to 47%, hardness from 15 to 134 kg and compression ratio from 5.2 to 8.6. A compression pressure of 34 MPa and a moisture content of 15% (w.b.) were found to be the most appropriate for high stability compressed blocks. Saving in transportation costs in block form could be up to 76% where as maximum savings in storage cost of blocks could be as much as 88%. El Saeidy (2009) studied correlation between the moisture content and the briquette density. Generally, increasing the moisture content will increase the briquette density. Increasing the moisture content from 8% to 9% will increase the briquette density to about 6%. Increasing the moisture content to 15% will increase the briquette density about 28%. 2.8.4. Water resistance. Lindley and Vossoughi (1989) Measured the water resistance as the percentage of water absorbed by a briquette (50-mm diameter, 18mm thick) when immersed in water. Each briquette was immersed in water at 27 °C for 30s. Because the briquettes proposed of high humidity conditions during transportation and storage could adversely affect the quality of the densified products. 2.8.5. Emissions from combustion of briquettes. Elsaeidy (2004) found that, a main advantage of biofuel is that it can be used without damaging the environment its advantage lies not only in the contribution to CO2 mitigation, but also extends to include other elements. Combustion of the experimental materials (poplar, hemp and straw) was undertaken. The materials were burned in the form of both loose materials and briquettes. Kristensen and Kristensen (2004) stated that, there is increasing concern with regard to the environmental problems associated with the - 38 -


increasing levels of CO2, SO2, and oxides of nitrogen (NOx) emissions resulting from the increased use of fossil fuels. Kimiko, et al (2008) investigated that, the abatement of indoor pollution achieved when two types of coal-biomass briquettes (L-BBs and H-BBs) were used in place of honeycombed coal briquettes (H-coal) in household stoves in rural Chongqing, China. Indoor concentrations of sulfur dioxide (SO2), carbon monoxide (CO), and gaseous fluoride were measured. Additionally, were evaluated the factors that affected indoor concentrations of these gases, including the amount of fuel used as well as its sulfur content, the sulfur-emission ratio determined from the amount of sulfur retained in the combustion ash, and the combustion temperature in the stoves. El Saeidy (2009) studied the relationship between CO levels of the pressing process and moisture content ratio to produce cotton stalks briquettes. He resulted that, increasing the moisture content ratio, increase the CO amount. It is however very dangerous for the workers in the processing place. That in other words means, the process must to be carried out in open air or in well airy place with suction fans to pull the polluted air away and also, The CO2 levels were generally environmentally friendly. Panwar, et al (2011) mentioned that, pellet biomass fuels are compressed, homogenized and dried biomass fuels that possess several advantages during handling, storage and combustion when compared to unprocessed biomass fuels. Environmentally, pellet biomass fuels provide advantages of less ash, smoke and other compound emissions, including carbon particles, CO, NOx and SOx. Because the use of biomass pellets produces much fewer greenhouse gases when the biomass is sustainably harvested, there has been a recent push to replace fossil fuels with biomass fuels.

- 39 -


- 40 -

MATERIALS AND METHODS

3. MATERIALS AND METHODS The experiments were carried out in the Department of Agric. Eng. Faculty of Agric. Minoufiya Univ., resistance of concrete Laboratory, Civil Engineering Department, Faculty of Engineering, Minoufiya Univ., Agriculture Engineering Research Institute (AEnRI) and biomass laboratory of the New and Renewable energy authority , Nasr City, Cairo. To determine the parameters leads to achieve the best criteria for handling process. The experimental work involved four stages as follows: 1. Measuring some physical and mechanical properties for cotton stalks. 2. Evaluation of local Chopping machine for determining the optimum productivity, power consumption and cutting length at three cutting speeds (1200, 1600, and 2000 rpm) (33.91, 45.21, and 56.52 m/s) and at different three moisture content for cotton stalks (8%, 10 % and 12%) and rice straw (8 %, 10 % and 12.8 %). 3. Evaluation of screw press machine at a pressure of 100 MPa and temperature of 160˚C at three moisture contents of cotton stalks (8, 10 and 12%), rice straw (8, 10 and 12.8 %) without binder and with binder. The binder (urea-formaldhyde) used as 10% of the quantity chopped materials. 4. Measuring some quality properties of pressed briquettes such as the durability, compression stress, hardness, bulk density, compression ratio, and resiliency.

- 40 -


3.1. Materials 3.1.1. Residuals: The residuals used in this work were obtained from private farms in Gharbia governorate and quisna, Minoufiya governorate and were stored in the workshop at room temperature of the agricultural engineering department until being used. The residuals, which used in this work, Fig. (3.1). which represent both cotton stalks and rice straw. 3.1.1.1. Cotton stalks Cotton stalks (Gossypium Barbadense) used at three different moisture content (8%, 10 % and 12%).The initial moisture content of samples was about 12 % (Wet base) as mean, then the samples under study were dried to achieve the required level of moisture content(8 and10%). Then the amount of water was added for the sample to reach the moisture content of 16%. The stem length of cotton stalks ranged from 98 to 182 cm, stem diameter ranged from 7.3 to 15 mm, weight of one stalk ranged from 35 to 200 g and number of branches ranged from 6 to 27. 3.1.1.2. Rice straw Rice straw (Oryza Sativa, Giza 101) used at three different moisture content (8, 10 and 12.8%). The average stem length was 80cm (from 70 to 90 cm), stem diameter ranged from 3 to 4.5 mm and number of branches ranged from 5 to 12.

- 41 -


Rice straw

cotton stalks

Fig. (3.1) Residuals of cotton stalks and rice straw.

3.1.2. The binder (urea-formaldehyde) The used material in this study as binder called Urea-formaldehyde (thermal glue) Characterized by the following: Color

: Milky white

Focus

: 55 to 66% solids

Density : 1.25 g / cm 3 Viscosity: from 200 - 1000 cm Boaz PH

: 7-8

Percentage of free formaldehyde: not more than 1% Urea-formaldehyde is added by a rate 10% of the total weight of residuals to be pressed. 3.2. Equipments. The main equipments used in this work were Chopper machine and screw press. The specific components of each machine can be summarized as following. - 42 -


3.2.1. Chopper machine: The cutting machine, which used in this work, is illustrated schematically in fig. (3.2a) and photographed in fig. (3.2b). it consists of the following parts: 1. The main frame: The base of the chopping machine is consists of two channel section of dimensions 4x7cm of metal sheet (St. 37). The length, width and height were 60, 60 and 70cm, respectively. The three hitch point the tractor were holding on the base. 2. Cutting-head: Cutting-head of a diameter 54 cm has two radial knives which are fixed on it by four bolts. It was rotate with speed of 1200, 1600 and 2000 rpm, respectively. It is illustrated schematically in Fig (3.3). 3. Feeding drum: Feeding drum dimension of 37 cm length, 14 cm diameter and 5.5cm height was constructed in the machine. It considered an assistant element in the cutting process, which was used to push the plant stems to the cutter-head for cutting. 4- Power transmission: The power was transmitted to the cutter-head and feeding drum from the tractor PTO by a universal joint. Two pulleys (driver and driven) transport the power to the cutter-head through and four "V" belts. 5- Feeding tray: Feeding tray with a dimension of 90 cm length, 60 cm outer width and 37 cm inner width was used in the machine. The side wall height was 20 cm. - 43 -

- 44 2

1

3

Elevation. v

4

Fig. (3.2a) Side view and elevation of the chopping machine.

Side .v

7

6

Dim. cm

5

Parts name Cutter head Driver pulley Driven pulley Feeding drum Feeding tray Duct Main fram

No 1 2 3 4 5 6 7



Fig. (3.2b) A photographic picture of the chopping machine.

Fig. (3.3) the cutting disk of chopping machine.

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6- The source of power: Belarus tractor of 90 HP power was used in this work to be a source of power for the chopping. 7- Knives: The cutting knives of spring steel were sharpened at angle 30° to be used as a chopping member. The cutting knives were 25cm length, 6 cm width and the thickness was 1.2 cm. 3.2.2. Screw press machine. The screw press machine Shimada (Type SPMM-850 KS). The production capacity of the machine was 400 kg/h. The press machine is powered by 30 kW electric motor. It has 2 electrical ceramic heater bands each required 3 kW for operation and has an integrated "T" Stirrer with a 1.5 kW Motor. The press requires a standard 220/380 Volt, 50 Hz and 3 phase electrical power supply. The machine has also a control panel. The chopped materials were put in a container above the machine. The materials feeding were rotated with different velocities with a belt. The operating velocity of the belt was 0.38 m/s. The screw press illustrated schematically in fig. (3.4) and photographed in Fig. (3.5). The main parts of the machine are screw and die; the rotating screw takes the material from the feet port and compacts it against the die which assists the build up of a pressure gradient along the screw. During this process, a frictional effect causes at the die wall. In addition, the combined effect due to the internal friction in the material and the high rotational speed of the screw cause an increase in temperature in the closed system which helps in heating the material. Then it forced through the die, where the briquette with the required shape is formed. fig. (3.6). and Fig. (3.7) show the screw and die.

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Fig. (3.4). the Screw press machine. 1-Colling zoon

2- Heaters

3- Motor (1.5 HP)

6- Motor (40 HP) 7- Base

4- Hopper

8- Control panel

Fig. (3.5). photograph of the Screw Press Machine

Fig (3.6) photograph Screw briquettes.

- 47 -

5- Die


Fig. (3.7) photograph Die briquettes

3.3. Measuring instruments: 3.3.1. Digital balance: The digital balance used in this work, was used for determining the weight samples of chopping cotton stalks and rice straw. It has the following data: Source of manufacture

: Germany

Type

: GP4102

Power source

: Electricity

Maximum measurement, Kg

: 5 kg

Accuracy, gm

: 0.01g

3.3.2. Stopwatch: It was used to estimate the time requirement for each test during the cutting process. Its accuracy is 1/1000 second. 3.3.3. Drying oven: The electrical drying oven was used to dry the samples of residues to calculate the moisture content. It has the following data:

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Source of manufacture

: Germany

Type

: Binder ED-53

Oven capacity

: 53 liter

Source of power

: Electrical, 220 V, (2.6A) AC.

Operating power

: 1.2 kW

Adjustment accuracy

: ± 1° C

Rang of temperature

: 5 – 240 ºC

3.3.4. Digital force gauge: The Digital force gauge was used to measure the acting force (shear force, compression force at horizontal plane and maximum bending force) for cotton stalks. Its data are as follow: Source of manufacture

: Japan

Model

: FGN-50

Measuring range

: ±500 N

Source of power

: NiCd battery& AC adapter (DC 9V 200 Ma).

Accuracy

: ±0.2% of maximum load+ 1/2 digit at 23ºC

Operating temperature

: 0 - 40ºC

Dimensions

: (W 75×H 38× L 147mm)

Weight

: 450 g.

A small fixture was fabricated to hold samples to help for produce shear, compression and maximum bending force testes. The small fixture used in this work is illustrated schematically in fig. (3.8) and fig. (3.9).

- 49 -


Stalk speci

Clam

Stationary

Instron

plate

base plate

(1)

Stalk speci

Clam

Stationary plate

(2) Clam

Stalk speci

Stationary plate

(3)

Fig. (3-8): Schematic exprimental arrangement for 1. Shear test 2. Compression test and 3. Bending test a universal testing machine. - 50 -


Fig. (3.9) schematic diagram of the fabricated fixture device.

3.3.5. Rotational speed of the rotating shaft: This velocity was measured by means of a multi-range tachometer as shown in Fig. (3.10). the apparatus gives the velocity in (rpm).

Fig. (3.10). Multi-range hand tachometer for measuring the rotational speed.

3.3.6. Briquette durability instrument. The durability (Du) of the briquettes was determined according to ASAE Standard S269.4, (2003). A 500 g sample of briquettes was tumbled at 50 rpm for 10 min, in a dust tight enclosure. A No. 5 US Sieve with an aperture size of 4.0 mm was used to retain crumbled briquettes after tumbling. Fig. (3.11a) shows the durability test instrument and photographed in Fig. (3.11b). Durability is expressed by the percent ratio

- 51 -


of mass of briquettes retained on the sieve after tumbling (mpa) to mass of briquettes tumbling (mpb) according to with the following equation (3.1). (Fasina, 2008)

Du =

m pa m pb

× 100 ……………………….. (3-1)

Fig. (3.11a) Testing machine for briquette durability.

Fig. (3.11b). Schematic diagram of the testing machine for briquette durability 1-Annotation

2- Rolled steel thickness (12mm)

4-Container for receiving samples

5- Direction of rotation 7- Concrete pillar.

- 52 -

3- Slot (200 mm) 6- Diameter (1250mm)


3.3.7. Compression test instrument. The compressive stress of each briquette was measured using a universal testing machine (UH-500KN, Shimadzu) as shown Fig. (3.12). The flat surface of the briquette sample was placed on the horizontal metal plate of the machine. A motorized screw slowly reduced the distance between this metal plate and a second one parallel to it. An increased load was applied at a constant rate until the test sample failed by cracking or breaking. The load at the fracture point and the maximum load were converted to compression stress using the following equation (Gibiiz and Kucukbayrak, 1996). Compression stress =

Load at fracture ….... (3.2) Cross sectional area of plane of fracture

The testing machine has the following data: Type

:Universal testing machine.

Capacity

:500,250,100,50,25,10 (kN).

Model

:UH-500 KNA.

Working condition

: 1- Voltage 2- Warm-Up

: + 10% :15 min.

3- Temperature : 5- 40 C

Source of manufacture

:Japan

- 53 -


Fig. (3.12) Universal compression testing machine (UH-500KN, Shimadzu).

3.3.8. Measuring gases emissions. The emission gases were measured using analyzer (Rize 700 EIUK) as shown Fig. (3.13). Estimated emissions were carbon monoxide (CO), carbon dioxide (CO2), oxides of nitrogen (NOX), and sulfur dioxide (SO2) for cotton stalks and rice straw (Loose and briquettes) samples were at moisture content (7.4, 8.57 and 10.35%) and (7.13, 9.21 and 10.98%) for cotton stalks and rice straw, respectively. The samples were burned in the stove and took the data of emissions from the chimney height of 180 cm as shown Fig (3.14). Ethyl Alcohol was used as an assistant at the start of the burning process and the readings taken during the ignition samples. The emission analyzer has the following data:

- 54 -


Model:

Rize 700 EIUK

Serial number: 303119 Power supply: 5 v/ 0.5- 1.2 A Mfg/ Date:

Jan/ 2012

Made in:

Germany

Combustion efficiency (η) was calculated from the following equation: η = CO2 % / (CO %*CO2 %)

Fig. (3.13)The measuring emissions device (Rize 700) EIUK.

Fig (3.14). Chimney and measuring data of emissions.

- 55 -


3.4. Methods: 3.4.1. Factors under study. Many parameters and factors were affecting on the performance, productivity and efficiency of chopping processes of agricultural crop residuals. Some of these parameters and factors are related to the plant materials (moisture content and stem size), some others are related to the cutting tools (cutting edge), and the others are related to the performance of the chopping machine (cutting speeds) and also quality properties of briquettes at press these cutting materials to briquettes. The plane of the experimental work was executed through the following: 1- Kinds of crop residuals, two kinds of crops residues (cotton stalks and rice straw). 2- Moisture content level: for cotton stalks was (8, 10 and 12%) and rice straw was (8, 10 and 12.8%). 3- Cutting disc speed: were (1200, 1600 and 2000 rpm). 4- Add binder (urea-formaldehyde): (chopped residuals were pressed with binder and without binder). 3.4.2. Physical and mechanical properties of crop residuals: 3.4.2.1. Physical characteristics experiments: The dimensional description of each stalk in all residuals implied the measure of samples number, length and diameter. The average diameter of each sample was determined using a digital slide caliper. 3.4.2.2. Determination of Mechanical properties: Mechanical tests including force deformation and compressive strength for all residuals were measured.

- 56 -


a- Shear test ( σ s ) The indices which determine the shearing behavior of the plant material is maximum stress. The shear stress σ s was calculated by the equation (3-3) (Chattopdhyay and Pandy 1999).

σ

s

=

F max A

…………………………… (3-3)

Where: σs

= the maximum shear stress, N/mm2

Fmax = the maximum shear force, N. A

= the cross-sectional area of stalk at the plane of shear, mm2.

The fabricated fixture was fixed rigidly on the base platform of the test machine under the cross head put with the help of two boltes. A chisel measuring heads perpendicular to the length of stalks specimen as showing in Fig. (3.15). The stalk sample was held on the fixture with the help of two Utype clamps at both ends of the specimen. During the down ward movement of the crosshead, the chisel cut the speciment by shear and passed through the slots provided in the fixture below the specimen. The force required for shearing the stalk was recorded. The maximum shear strength was determined using equation (3.2). The shear test was conducted for the length of the stalk at three positions (bottom, middle and top).

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Fig. (3.15) The fixture and digital force gauge in shear force

b -Compression test ( σ

c

):

The indices which determine the compression behaviour of plant material is compression stress. The compression stress ( σ

c

) was calculated by the following

equation (Chattopdhyay and Pandy 1999):

σ

c

=

Fc …………………. (3-4) A

Where: σ

c

= compression stress, N/mm2.

Fc = the compressive force, N. A = the cross-sectional area of stalk at the plane of compression, mm2. The

specimen

stalk

was

placed

on

the

base

platform

perpendicularly. The compressive force on the stalk sample was applied by a flat heads as shown in Fig. (3.16).

- 58 -


Fig (3.16) the fixture and digital force gauge for compressive force.

c- Bending test (M) The indices which determine the bending behavior of plant material is beam failure stress. The maximum bending moment was calculated by the following equation: (Chattopdhyay and Pandy 1999) M = Fb × L ……………………………... (3-5) Where: M = Maximum bending moment (N.mm). Fb= Maximum bending force (N). L = Lever arm of the bending force (mm). The bending property of the stalk was determined at following a cantilever test as suggested by persson (1987). One end of the stalk specimen was fixed rigidly to the fixture with the help of a screw clamp with two inner semi-circular rims. The vertical force was applied by the chisel heads at the free end of the mounted specimen at a distance of 100 mm from the fixed point as shown in Fig. (3.17).

Fig. (3.17) A photographic of the fixture and Digital force gauge bending moment.

- 59 -


3.4.3 Moisture content (M.C): Plant samples were oven dried at 105° C for 24 h by using electrical oven. The samples were weighted before and after drying and the moisture content was determined by using the following equation: (AOAC, 1990).

M.C. =

SB − SA ×100 SB

% (Wet base)……… (3-6)

Where: SB = Sample weight before drying (g). SA = Sample weight after drying (g). 3.4.4. Machine productivity(Pm): It was calculated by the following equation: Pm = W/t

ton/h …………………………………... (3-7)

Where: Pm = Machine productivity (ton/h). W = residuals weight of machine output (ton). t = Machine operating time (hr). 3.4.5. Cutting efficiency (ηc): The cutting length of final product is an important parameter to evaluate the performance of cutting process. Where, the suitable cutting length that can be used to produce compost and the forage is in the range of 0 < Lc < 50 mm. Stander sieves used for segregation of a specific weight, Sb, from the chopped production to several weight, having cutting length 0 < Lc < 50 mm. Consequently, the cutting efficiency can be calculated as following:

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ηc = Sa / Sb * 100 ……………………………..…….. (3-8) Where: Sb = Weight of the chopped production before segregation, g. Sa = Weight of the chopped production after segregation of cutting length 0 < Lc < 50 mm, g. 3.4.6. Power requirement (EP): The power was calculated by using the following equation (Embaby, 1985) EP =

FC × ρ r × L .C .V × 427 ×η m ×ηth , KW .................(3.9) 3600 × 75 ×1.36

Where: EP = Power requirements consumption during the chopping operation (kW) FC = Fuel consumption (L/h). ρr = Density of the fuel (0.85 kg/L). L.C.V = Lower calorific value of fuel (10000 kcal/kg). 427 = Thermo mechanical equivalent (kg.m/kcal). ηm = Mechanical efficiency of engine, 80%. ηth = Thermal efficiency of the engine, (considered to be about 40% for diesel engine). 3.4.7. Energy consumption: Estimation of the energy required was carried out using the following equation: Energy requirements (kW.h/ton) = (power requirements, kW)/ (machine productivity, ton/h).

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3.4.9. Quality of briquettes product. 3.4.9.1. Bulk density (ρb) Bulk density is an indicator of savings in storage, transportation space and cost of blocks. The bulk density of the briquettes was calculated using Eq. (3.10) with the sample weight and the measured volume. The volume was determined by the cross sectional area and variable thickness of the blocks. The thickness of blocks, which varies during post-compression recovery. (Jha et al 2008)

ρb =

W L × B × T ………………….… (3.10)

ρb = bulk density of cotton stalk briquette (kgm-3) W = weight of cotton stalk briquette (kg) B = width of cotton stalk briquette (mm) L = length of cotton stalk briquette (mm) T = thickness of cotton stalk briquette (mm) 3.4.9.2. Compression ratio (CR) The compression ratio indicates volume reduction during compression. It was obtained from the ratio of bulk density of compact block to the initial density of the material being compressed and can be calculated of follows. (Jha et al 2008)

CR=

ρb ρ ra w

…………………………. (3.11)

CR = compression ratio

ρb = bulk density of cotton stalk briquettes (kgm-3) ρraw = bulk density of loose cotton stalk (kgm-3)

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3.4.9.3. Resiliency (R) Resiliency was determined as the ratio between the increases in thickness to the initial thickness of the briquette according to Eq. (3.12).as follows. (Jha et al 2008)

R=

T −Ti × 100...................(3.12) Ti

R = resiliency (%) T = thickness of stabilised cotton stalk briquette (mm) Ti= initial thickness of cotton stalk briquette (mm) 3.4.9.4. Hardness. Hardness reflects the degree of binding. It was measured as the maximum force recorded while a briquette was broken by a probe incorporated in a Texture Analyser. (Jha et al 2008) 3.4.9.5. Water resistance. The water resistance of the briquettes was tested by immersing them in a glass container filled with cold tap water and measuring the time required for onset of the dispersion in water (Yamnan, et al 2001 and Debdoubi, et al 2005).

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RESULTS AND DISCUTION

4- RESULTS AND DISCUSSION The results obtained from this work can be summarized as the following headings: 1- Physical and mechanical properties of cotton stalks. 2- Performance evaluation of local chopping machine with cotton stalks and rice straw. 3- Measurements of quality criteria of cotton stalks and rice straw briquettes produced by screw press. 4.1. Physical and mechanical properties of cotton stalks. 4.1.1 Physical properties of cotton stalks: The results obtained from measuring cotton stalks samples showed that, the maximum value of stem length was 182 cm, while the minimum value was 98 cm. The maximum value of stem diameter was 1.5 cm, while the minimum value was 0.73 cm. The maximum value of stem weight was 200 gm, while the minimum value was 35 gm. The maximum number of branches was 27, while the minimum number of branches was 6 .The initial moisture content of the stored samples was about 12% (Wet base) as mean, then the samples under study were modified (dried) to achieve the required level of moisture content (8, 10 %) and amount of water was added for the sample to reach the moisture content of 16%. The average values of the obtained results are listed in Table (4.1). 4.1.2. Mechanical properties of cotton stalks: The mechanical properties which studied for cotton stalks were shear stress, compressive stress and bending moment. The mechanical properties of the (cotton stalks) may be defined as those properties that determine the behavior of material under applied loads.

- 64 -


Table (4.1). Average values of some physical properties of the tested cotton stalks at moisture content 12%. Characteristics

Range

Average

Stem length, cm

98 - 182

147.69

Stem diameter, cm

0.73 – 1.5

0.783

Weight of one stalk, (g)

35 - 200

106.72

Number of branches

6 - 27

15.95

1. Shear stress: Shear stress of cotton stalks at the three level of moisture content (8, 10, 12and 16%) presented in fig (4.1). It is clear that, increasing shear stress values from the bottom stem is than the top of cotton stalks. The greatest value of shear stress obtained at the bottom. This due to its more fiber and a thicker stem wall than at the top part. This behaviour may be explained on the basis of the fact that the plant stalk possesses the behaviour of viscoelastic material and therefore, the maximum shear stress was greatest for the stalks at the bottom because the stress of the outer layer of the stem (stem wall) increases with the age of the crop due to the gradual accumulation of lignin in the stem wall. Added to that the reduction in moisture content which, in turn, enhance the stiffness of the stem wall. Table (A) in appendix (A) represent that, the data of shear stress changed with moisture content. The shears stress increasing from 3.52 to 5.26 MPa with decreasing moisture content from 16% to 8% at the bottom part. The shear stress was (5.26, 4.00, 3.63 MPa) at bottom, middle, upper part of the stalk at 8% moisture content, respectively. 2. Compression stress: Compression stress of cotton stalks at different moisture contents (8, 10, 12 and 16%) is presented in fig (4.2), it is showed clear that, - 65 -


increasing compression stress at the bottom stem more than top stem part of cotton stalks. The maximum compression stress was found at the bottom part of cotton stalks. This may be due to its more fiber and a thicker stem wall than at the top part.

Table (A) in appendix (A)

represent that, the data of compression stress changed with moisture content. It is indicate the some results at different position of cotton stalks stem (bottom, middle and upper). The compression stress increasing from 3.84 to 5.77 MPa with decreasing moisture content from 16% to 8% at the bottom. The maximum compression stress was greatest for the stalks at the bottom. The compressive stress was (5.77, 4.48, 4.12MPa) at bottom, middle and top part of the stalk at 8% moisture content, respectively.

3- Bending moment: Fig (4.3) and Table (A) in appendix (A) showed that, the bending moment increased with decreasing moisture content of cotton stalks. Fore example, the bending moment increasing from 14.10 to 25.20 N.m with decreasing moisture content from 16% to 8% at the bottom part. The maximum bending moment was greatest for the stalks at the bottom. Fore example, the bending moment was (25.20, 10.12, 4.19 N.m) at bottom, middle and top part of the stalk at 8% moisture content, respectively. Because the determined force to do bending and fracture for stalk increase at bottom more than at the middle and top part result of the accumulation of lignin, which increases hardening by decrease moisture content.

- 66 -


shear stress

shear stress MPa

6 5 4

bottom

3

middle

2

upper

1 0 6

8

10

12

14

16

18

MC %

Fig (4.1) The relationship between shear stress and moisture content for cotton stalks at different positions of stalk (bottom, middle and top)

Compressive stress compressive stress MPa

7 6 5 4 3 2 1 0

bottom middle upper

6

8

10

12

14

16

18

MC %

Fig (4.2) The relationship between compressive stress and moisture content for cotton stalks at different positions of stalk (bottom, middle and top)

Bending moment ( N.m)

Bending moment 30 25 bottom

20

middle

15

upper

10 5 0 6

8

10

12

14

16

18

MC %

Fig (4.3) The relationship between bending moment and moisture content for cotton stalks at different positions of stalk (bottom, middle and top).

- 67 -


4.2. Evaluation of local chopping machine with cotton stalks and rice straw. Cotton stalks and rice straw were used to evaluate the chopping machine in this study at different moisture content (8, 10 and 12%) and (8, 10 and 12.8%), respectively. 4.2.1. Chopping performance evaluation for cotton stalks: Performance evaluation of chopping machine used for cotton stalks includes the following parameters. 4.2.1.1. Power requirements: 1. Total power requirements: Fig. (4.4) showed that, the total power requirements increased with increasing cutting drum speed. This may be due to increasing in amount of material to be cut by increasing cutting drum speed. For example, the total power requirements increased from 5.69 to 6.32 kW with increasing cutting speed from 1200 rpm to 2000 rpm at 8 % moisture content. The total power requirements increased with decreasing moisture content. That is due to decrease in moisture content, shear stress, compression stress and bending moment increase therefore total power requirement increases. The total power requirements increasing from 4.93 to 6.32 kW with decreasing moisture content from 12% to 8% at 2000 rpm cutting speed. The minimum value of total power requirement was 4.58 kW at 1200 rpm cutting speed, and 12 % moisture content while, the maximum value of total power requirement was 6.32 kW at 2000 rpm cutting speed and 8% moisture content. Over all, the total power requirement increased with decrease of moisture content and increase of cutting speed. - 68 -


Generally, the total power requirement depends on the cutting drum speed and the moisture content for cotton stalks. This result in agreement with those obtained by Arif (1999), Elfatih, et al (2010) and Ibrahim (2006). 2. Net power requirements: Fig. (4.5) showed that, the net power requirements increased with increasing cutting drum speed. This may be due to increasing in the amount of material to be cut by increasing cutting drum speed. The net power requirements increased from 4.11 to 4.90 kW with increasing cutting speed from 1200 rpm to 2000 rpm at 8% moisture content. The net power requirements increased with decreasing moisture content. Decreasing the moisture content cause that shear stress, compression stress and bending moment increase therefore total power requirement increases. The net power requirements increased from 3.51 to 4.90 kW with decreasing moisture content from 12% to 8% at 2000 rpm cutting speed. The minimum value of net power requirement was 3.00 kW at 1200 rpm cutting speed and 12% moisture content while, the maximum value of net power requirement was 4.90 kW at 2000 rpm cutting speed and 8% moisture content. Over all, the net power requirement increased with decrease of moisture content and increase of cutting speed. The cutting power requirements were affected by cutting drum speed and the moisture content for cotton stalks. 4.2.1.2. Machine productivity: Fig (4.6) showed that, the machine productivity increased with increasing the cutting drum speed. The machine productivity was 0.58, - 69 -


0.60 and 0.66 ton/h with increasing cutting speed from 1200, 1600 and 2000 rpm, respectively, at 8% moisture content. The minimum value of machine productivity was 0.44 ton/h at 1200 rpm cutting speed and 12% moisture content while, the maximum value of machine production was 0.66 ton/h at 2000 rpm cutting and 8% moisture content. The machine productions were affected by cutting drum speed. 4.2.1.3. Energy consumption: Fig. (4.7) and Tables (B-1) in appendix B showed that, the energy consumption decreased with increasing the cutting speed. The energy consumption was 14.37, 12.52, and 10.16 kW.h/t with increasing cutting drum speed from 1200, 1600 and 2000 rpm, respectively, at 8% moisture content. The minimum value of energy consumption was 6.49 kW.h/t at 2000 rpm cutting speed and 12% moisture content while, the maximum value of energy consumption was 14.37 KW.h/t at 1200 rpm cutting

total power required (KW)

speed and 8% moisture content.

6.5 6 5.5

8% 10%

5

12%

4.5 4 1200

1600

2000

Cutting speed (rpm)

Fig (4.4) The relationship between cutting drum speed and total power requirement at different levels of moisture content (8%, 10% and 12%) for cotton stalk

- 70 -


Net power required (Kw)

5.5 5 4.5 4 3.5 3 2.5 2

8% 10% 12%

1200

1600 cutting speed (rpm)

2000

Fig (4.5) The relationship between cutting drum speed and net power requirement at different

machine productivity (t/h)

levels of moisture content (8%, 10% and 12%) for cotton stalk.

0.7 0.6 8%

0.5

10%

0.4

12%

0.3 1200

1600 cutting speed (rpm)

2000

energy consumption (KW.h/t)

Fig. (4.6) The relationship between cutting drum speed and machine production at different levels of moisture content (8%, 10% and 12%) for cotton stalk.

16 14 12 10 8 6 4 2 0

8% 10% 12%

1200

1600

2000

cutting speed (rpm)

Fig. (4.7) The relationship between cutting drum speed and energy consumption at different levels of moisture content (8%, 10% and 12%) for cotton stalk.

- 71 -


4.2.1.4. Cutting efficiency: Fig. (4.8) showed that, the cutting efficiency increased with increasing cutting drum speed and decreasing moisture content. The cutting efficiency increased with increasing cutting drum speed, that is due to an increase in the number of cuts per time unite and this increase the weight of the suitable cutting length. The cutting efficiency increased from 85.72 % to 97.77 % with increasing cutting speed from 1200 rpm to 2000 rpm at 8 % moisture content. The results showed also that, increasing the cutting drum speed from 1200 to 2000 rpm cutting efficiency increased from (85.72, 83.5 and 81.85 %) to (97.77, 95.43 and 93.87 %) at 8, 10 and 12 % moisture

Cutting effeciency %

content, respectively. 100 95 90

8%

85

10%

80

12%

75 70 1200

1600

2000

M.C %

Fig (4.8) the relationship between cutting drum speed and cutting efficiency at different levels of moisture content for cotton stalks.

4.2.2. Chopping performance evaluatation for rice straw. Evaluation performance of chopping machine used for rice straw includes the following parameters. 4.2.2.1. Power requirements: 1. Total power requirements: Fig (4.9) showed that, the total power requirements increased with increasing cutting drum speed. This due to increasing in amount of

- 72 -


material to be cut by increasing cutting drum speed. The total power requirements increased from 6.22to 6.99 kW with increasing cutting speed from 1200 rpm to 2000 rpm at 12.8 % moisture content.

The total power requirements increased with increasing moisture

content. The total power requirements increasing from 5.66 to 6.99 kW with increasing moisture content from 8 to12.8 % at 2000 rpm cutting speed. The minimum value of total power requirement was 5.01 kW at 1200 rpm cutting speed, and 8 % moisture content while, the maximum value of total power requirement was 6.99 kW at 2000 rpm cutting speed and 12.8 % moisture content. Over all, the total power requirement increased with increase of moisture content and increase of cutting speed. Generally, the total power requirement depends on the cutting speed and the moisture content for rice straw. 2. Net power requirements: Fig (4.10) showed that, the net power requirements increased with increasing cutting drum speed. The net power requirements increased from 4.74 to 5.53kW with increasing cutting speed from 1200 rpm to 2000 rpm at 12.8 % moisture content. The net power requirements increased with increasing moisture content. The net power requirements increasing from 4.14 to 5.53kW with increasing moisture content from 8to 12.8 % at 2000 rpm cutting speed. The minimum value of net power requirement was 3.63 kW at 1200 rpm cutting speed and 8 % moisture content while, the maximum value of net power requirement was 5.53 kW at 2000 rpm cutting speed and 12.8% moisture content. - 73 -


Over all, the net power requirement increased with increase of moisture content and increase of cutting speed. The cutting power requirements were affected by cutting drum speed and the moisture content for rice straw. 4.2.2.2. Machine productivity: Fig (4.11) showed that, the machine productivity increased with increasing the cutting drum speed. The machine production was 0.34, 0.35 and 0.37 ton/h with increasing cutting speed from 1200, 1600 and 2000 rpm, respectively, at 8% moisture content. The minimum value of machine productivity was 0.27 ton/h at 1200 rpm cutting speed and 12.8% moisture content while, the maximum value of machine production was 0.37 ton/h at 2000 rpm cutting and 8% moisture content. The machine productions were affected by cutting drum speed. 4.2.2.3. Energy consumption: Fig (4.12) showed that, the Energy consumption decreased with increasing the cutting seed. The energy consumption was 27.6, 22.59, and 17.79 kW.h/t with increasing cutting drum speed from 1200, 1600 and 2000 rpm, respectively, at 12.8 % moisture content. The minimum value of energy consumption 14.37 kW.h/t was at 2000 rpm cutting speed and 8 % moisture content. The maximum value of energy consumption was 27.67 kW.h/t at 1200 rpm cutting speed and 12.8 % moisture content.

- 74 -


total power required (Kw)

7.5 7 6.5 6

8%

5.5

10%

5

12.80%

4.5 4 1200

1600

2000

Cutting speed (rpm)

Fig (4.9) The relationship between cutting drum speed and total power requirement at

Net power requier (Kw)

different levels of moisture content (8%, 10% and 12.8%) for rice straw.

6 5.5 5

8%

4.5 4

10% 12.80%

3.5 3 1200

1600

2000

Cutting speed (rpm)

Fig (4.10) The relationship between cutting drum speed and net power requirement at

Machine productivity (t/h)

different levels of moisture content (8%, 10% and 12.8%) for rice straw.

0.4 0.35 8% 0.3

10% 12.80%

0.25 0.2 1200

1600

2000

M.C %

Fig (4.11) The relationship between cutting drum speed and machine production at different levels of moisture content (8%, 10% and 12.8%) for rice straw.

- 75 -


Energy consumption (Kw.h/t)

30 25 20

8%

15

10%

10

12.80%

5 0 1200

1600

2000

Cutting speed (rpm)

Fig (4.12) The relationship between cutting drum speed and energy consumption at different levels of moisture content (8%, 10% and 12.8%) for rice straw.

4.2.2.4. Cutting efficiency: Fig (4.13) show that, the cutting efficiency increased with increasing cutting drum speed and increased with decreasing moisture content.

The cutting efficiency increased with increasing cutting drum speed, the cutting efficiency increased from 71.32 % to 89.67 % with increasing cutting speed from 1200 rpm to 2000 rpm at 8 % moisture content. The results showed also that, increasing the cutting drum speed from 1200 to 2000 rpm cutting efficiency increased from (71.32, 68.5 and 63.85%) to (89.67, 84.89 and 81.48%) at 8, 10 and 12.8 % moisture

Cutting effeciency %

content, respectively. 100 80 8% 60

10% 12.80%

40 20 1200

1600

2000

M.C %

Fig (4.13) the relationship between cutting drum speed and cutting efficiency at different levels of moisture content for rice straw.

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4.3. The explosion problem of the briquettes machine. Before pressing, the heaters must be heated to about 180 ºC. This is necessary for producing stable briquettes. The lignin contained in the cotton stalks and rice straw begins to flow when increasing the temperature and acts as a natural glue to bind the briquettes (FAO, 1990). A piece of briquette which is a rest from the former process is still found in the heaters zone. It started to lose their moisture content. In addition, the chopped materials were also heated and lost part of its moisture. Water vapor is collected in the press die. The produced briquettes are shown in Fig (4.14).

Without binder

Without binder

With binder

With binder

Cotton stalk briquettes

Rice straw briquettes

Fig (4.14) The Processed Briquette of cotton stalks and rice straw.

- 77 -


4.4. Moisture content for cotton stalks and rice straw briquettes. Fig (4.15) shows that, after the pressing of the chopped cotton stalks and rice straw to briquettes, the moisture content decreased compared with before the pressing. Moisture content of cotton stalks briquettes were pressed at 8, 10 and 12 % decreased to 7.4, 8.57 and 10.35 %, respectively. While moisture content of rice straw briquettes were pressed at 8, 10 and 12.8 % decreased to 7.13, 9.21 and 10.98 %, respectively. Rice straw

cotton stalks

M.C after pressing %

12 11 10 9 8 7 6 5 4 6

8

10

12

14

M.C before pressing %

Fig. (4.15) The effect of pressing on the moisture content of cotton stalks and rice straw briquettes.

4.5 Evaluate the quality of cotton stalks and rice straw briquetting product. 4.5.1. Effect of moisture content on compression stress and durability for cotton stalks briquettes and rice straw. The relation between compression stress and durability with moisture content for cotton stalks briquettes presented in Fig. (4.16a and 4.16b). It can be noticed that, increase of moisture content decreased the compression stress and durability. The fig show also that, the values of the moisture content and compression stress for briquettes presented as contour (line dark) red on the horizontal plane. It shows the highest values for the durability, ( 90%) for cotton stalks briquettes without

- 78 -


binder and (

80%) for cotton stalks briquettes with binder at 7.4%

moisture content. Table (4.2) show that, the increment percentages of compression stress were 40.45 % and 50.39 % during decrement of moisture content from 8.57 % to 7.4 % and from 10.35 % to 7.4 %, respectively, for briquettes without binder. Also, the increment percentage of compression stress were 40.64 % and 48.9 % during decrement of moisture content from 8.57 % to 7.4 % and from 10.35 % to 7.4 %, respectively, for briquettes with binder.The increment percentage of durability were 8.87 % and 16.28 % during decrement of moisture content from 8.57 % to 7.4 % and from10.35% to 7.4 %, respectively, for briquettes without binder. While the increment percentages of durability were 1.86 % and 22.35 % during decrement of moisture content from 8.57 % to 7.4 % and from10.35 % to 7.4 %, respectively, for briquettes with binder. While, the relation between compression stress and durability with moisture content for rice straw briquettes presented in Fig. (4.17a and 4.17b). It can be noticed that, increase of moisture content decreased the compression stress and durability. The fig shows also that, the values of the moisture content and compression stress for briquettes presented as contour line (dark red) on the horizontal plane. It shows the highest values for the durability, (> 94 %) for rice straw briquettes without binder and (> 94 %) for rice straw briquettes with binder. Table (4.3) shows that, the increment percentages of compression stress were 28.77 and 32.91 % during decrement of moisture content from 9.21% to 7.13 % and from 10.98 % to 7.13 %, respectively, for briquettes without binder. Also, the increment percentage of compression stress were 30.71 and 37.44 % during decrement of moisture content from 9.21% to 7.13 % and from 10.98 to 7.13 %, respectively, for briquettes with binder. The increment percentages of durability were 3.03 % and 3.8 % during decrement of - 79 -


moisture content from 9.21 % to 7.13 % and from10.98 % to 7.13 %, respectively, for briquettes without binder. While the increment percentage of durability were 16.9 % and 20.65 % during decrement of moisture content from 9.21 % to 7.13 % and from 10.98 % to 7.13 %, respectively, for briquettes with binder. As a result, the higher value of durability cotton stalks and rice straw briquettes at maximum value the compression stress and less moisture content for briquettes without binder. Where the value of the durability briquettes cotton stalks of 97.06 % at the highest compression stress 8.95MPa at 7.4 % moisture content for cotton stalks briquettes without binder. While the value of the durability briquettes rice straw of 87.8% at the highest compression stress 7.75MPa and 7.13% moisture content for rice straw briquettes without binder. Table (4.2): The relation between moisture content (Durability, Compression stress, Bulk denisty, Resiliency and compresion ratio) for briquettes without binder and with binder (ureaformaldhyde) for cotton stalks briquettes.

Resiliency

ratio

%

0.99

6.6

9.75

19.02

0.8

5.33

13.63

5.33

14.4

1.00

6.65

12.00

86.17

4.6

13.00

0.92

5.87

17.12

Without binder

81.26

4.44

12.00

1.18

7.86

17.02

With binder

68.17

3.96

8.00

0.95

6.33

19.04

The binder

Durability

Compression

Hardness

%

(urea-formaldhyde)

%

stress (MPa)

(KN)

7.4

Without binder

97.06

8.95

24.15

With binder

87.8

7.75

Without binder

88.45

With binder

8.57 10.35

Bulk

compresion

M.C

- 80 -

denisty (g.cm-3)


Table (4.3): The relation between Moisture content and( Durability, Compression stress, Bulk density, Resiliency and compresion ratio) at without binder and with binder (urea-formaldhyde) for rice straw briquettes. Hardness

Bulk denisty -3

compresion

Resiliency

(KN)

(g.cm )

ratio

%

10.39

20.97

0.61

20.33

9.75

89.81

8.92

20.16

0.47

15.66

10.86

Without binder

90.8

7.4

16.38

0.7

21.87

11.11

With binder

74.63

6.18

13.42

0.64

18.28

11.88

Without binder

90.08

6.97

14.6

0.95

23.27

13.04

With binder

71.26

5.58

11.1

0.77

19.25

13.86

formaldhyde)

%

Without binder

93.64

With binder

stress (MPa)

Durability % = -192.6402+44.1899*x+31.6109*y-1.8471*x*x-2.4109*x*y-0.7676*y*y (7.4 ≤ x ≥10.35 %, 4.44 ≤ y ≥ 8.95 MPa)

Durability %

100 90 80 > 90 < 84 < 74 < 64 < 54

70 60 50

10.5 10.0 9.5

7

9.0 6

8.5 8.0

5

7.5

4

10.98

Compression

8

9.21

Durability

9

7.13

The binder (urea-

10

M.C%

Compression stress %

7.0

M.C %

Fig (4.16a) Effect moisture content on compression stress and durability of cotton stalks briquettes. (Without binder)

- 81 -


Durability % = -378.5166+55.5382*x+101.6147*y-1.6143*x*x-7.2083*x*y-3.9764*y*y (7.4 ≤ x ≥10.35 %, 3.96 ≤ y ≥ 7.75 MPa)

Durability %

120 100 80 60 40 20

> < < < <
94 < 94 < 93 < 92 < 91 < 90

91 90

6.0

6.5

6.5

7.0

7.0

Compression stress (MPa

7.5

7.5

8.0

8.0

8.5

MC%

11.5

11.0

10.0

8.5

9.0

9.0

9.5

11.0 10.5 10.0 9.5

10.5

89

Fig (4.17a) Effect moisture content of compression stress and durability of rice straw briquettes (Without binder).

- 82 -


Durability% = 678+5.2009*x+0.3272*y-0.1333*x*x-0.5945*x*y+0.4481*y*y (7.13 ≤ x ≥10.98 %, 5.58 ≤ y ≥ 8.92 MPa)

Durability %

100 95 90 85 > 94 < 91 < 87 < 83 < 79 < 75 < 71

80 75 70

11.5

11.0

10.5

10.0

9.5

9.0

8.5

8.0

7.5

7.0

11.0 10.5 10.0 9.5 9.0 8.5 8.0 7.5 7.0 6.5 6.0 Compression stress (MPa) 5.5

6.5

65

MC%

Fig (4.17b) Effect moisture content of compression stress and durability of rice straw briquettes (With binder).

4.5.2. Effect of moisture content on compression stress and hardness for cotton stalks and rice straw briquettes. The relation between compression stress and hardness with moisture content for cotton stalks briquettes as shown in Fig. (4.18a and 4.18b). It can be noticed that, increase moisture content decreased the compression stress and hardness. The fig show also that, the values of the moisture content and compression stress for briquettes presented as contour line (dark red) on the horizontal plane. It shows the highest values for the hardness, ( 24 KN) for cotton stalks briquettes without binder and ( 18 KN) for cotton stalks briquettes with binder at 7.4% moisture content. Table (4.2) show that, the increment percentages of hardness were 37.79 % and 48.16 % during decrement of moisture content from 8.57 % to 7.4 % and from 10.35% to 7.4 %, respectively, for briquettes without binder. Also, the increment percentage of hardness was

- 83 -


31.65 % and 57.9 % during decrement of moisture content from 8.57 % to 7.4 % and from10.35 % to 7.4%, respectively, for briquettes with binder. While the relation between compression stress and hardness with moisture content for rice straw briquettes presented in Fig. (4.19a and b4.19b). It can be noticed that, increase of moisture content decreased the compression stress and hardness. The fig also shows that, the values of the moisture content and compression stress for briquettes presented as contour line (dark red) on the horizontal plane. It shows the highest values for the durability, (>20 KN) for rice straw briquettes without binder and (>20 KN) for rice straw briquettes with binder. Table (4.3) show that, the increment percentages of hardness were 21.88 and 30.37 % during decrement of moisture content from 9.21 to 7.13 % and from 10.98 to 7.13 %, respectively, for briquettes without binder. Also, the increment percentage of hardness 33.43 and 44.94 % during decrement of moisture content from 9.21 to 7.13 % and from 10.98 to 7.13 %, respectively, for briquettes with binder. As a result, the higher value of hardness of cotton stalks and rice straw briquettes was at maximum value the compression stress and less moisture content without binder. Where the value of the hardness of 24.15 KN at the highest compression stress 8.95 MPa and 7.4 % moisture content for cotton stalks briquettes without binder. While the value of the hardness of 20.97 KN at the highest compression stress 10.39 MPa and 7.13 % moisture content for rice straw briquettes without binder.

- 84 -


Hardness (KN) = 44.4976-5.4253*x+0.1372*y+0.2284*x*x-0.0814*x*y+0.1222*y*y (7.4 ≤ x ≥10.35 %, 4.44 ≤ y ≥ 8.95 MPa) Hardness (KN)

28 26 24 22 20

> 24 < 24 < 22 < 20 < 18 < 16 < 14 < 12

18 16 14 12 10

8.0

6 7.5

5 4

10.0

MC%

7.0

Compression stress (MPa)

8.5

7

9.0

8

9.5

9

10.5

10

Fig (4.18a) Effect moisture content of compression stress and hardness of cotton stalks briquettes. (Without binder) Hardness (KN) = -91.2014+17.5205*x+10.0661*y-0.9261*x*x-0.4067*x*y-0.3869*y*y (7.4 ≤ x ≥10.35 %, 3.96 ≤ y ≥ 7.75 MPa)

Hardness (KN)

22 20 18 16 14

> 18 < 17 < 15 < 13 < 11 1 < 0.6 < 0.1 < -0.4 < -0.9 < -1.4

-0.5 -1.0 -1.5 -2.0

4

7.0


7.5

5

8.5

6

8.0

7

9.0

10.0

8

9.5

9

10.5

10

MC%

Fig (4.20a) Effect of moisture content of compression stress and bulk density of cotton stalks briquettes (Without binder) -3

Bulk density (g.cm ) = 3.1059+0.3306*x+1.1893*y+0.0002*x*x-0.0776*x*y-0.0588*y*y (7.4 ≤ x ≥10.35 %, 3.96 ≤ y ≥ 7.75 MPa)

Bulk density(g.cm3)

1.2 1.0 0.8 0.6 0.4

> < < < <
< < <
0.8 < 0.7 < 0.3 < -0.1 < -0.5 < -0.9

-0.4 -0.6 -0.8 -1.0

5.5 5.0

7.0


7.5

6.0

8.0

6.5

8.5

7.0

9.0

7.5

9.5

8.0

10.0

8.5

10.5

9.0

11.0

9.5

MC%

Fig (4.21b) Effect of moisture content of compression stress and bulk density of rice straw briquettes (With binder)

- 90 -


4.5.4. Effect of moisture content on compression stress and compression ratio for cotton stalks and rice straw briquettes. The relation between compression stress and compression ratio with moisture content for cotton stalks briquettes presented in Fig. (4.22a and 4.22b). It can be noticed that, increase of moisture content the decreased compression stress and compression ratio increased. The fig show also that, the values of the moisture content and compression stress briquettes presented as contour line (dark red) on the horizontal plane. It shows the highest values for the compression ratio, ( 7) for cotton stalks briquettes without binder and (> 6) for cotton stalks briquettes with binder. Table (4.2) show that, the increment percentages compression ratio were 6.48 % and 5.35 % during increment of moisture content from 7.4 to 10.35 % and from 8.57 % to 10.35%, respectively, for briquettes without binder. Also, the increment percentages of compression ratio were 15.79 % and 7.26 % during increment of moisture content from 7.4 to 10.35 % and from 8.57 % to 10.35 %, respectively, for briquettes with binder. While the relation between compression stress and compression ratio with moisture content for rice straw briquettes presented in Fig. (4.23a and 4.23b). It can be noticed that, increase of moisture content decreased the compression stress and compression ratio increased. The fig shows also that, the values of the moisture content and compression stress briquettes presented as contour line (dark red) on the horizontal plane. It shows the highest values for the compression ratio, (>23) for rice straw briquettes without binder and (>22) for rice straw briquettes with binder. Table (4.3) shows that, the increment percentages compression ratio were 35.79 % and 26.32 % during increment of moisture content from 7.13 to 10.98 % and from 9.21 to 10.98 %, respectively, for briquettes

without

binder.

Also, the increment percentages of

compression ratio were 18.64 and 5.04 % during increment of moisture - 91 -


content from 7.13 to 10.98 % and from 9.21 to 10.98 %, respectively, for briquettes with binder. As a result, the lower value of compression ratio was at maximum value the compression stress and less moisture content for cotton stalks and rice straw briquettes without binder. Where the value of the compression ratio of 20.33 at the highest compression stress 10.39 MPa and 7.13 % moisture content for cotton stalks briquettes without binder. While the value of the compression ratio was 6.6 at the highest compression stress 8.95 MPa and 7.4% moisture content, for rice straw briquettes without binder.

- 92 -


Compression ratio = 12.5982-2.2256*x+2.0061*y+0.161*x*x-0.1575*x*y-0.0767*y*y (7.4 ≤ x ≥10.35 %, 4.44 ≤ y ≥ 8.95 MPa) Compression ratio

8 7 6 5 4

>7 14%) for rice straw briquettes with binder. Table (4.3) show that, the increment percentages resiliency were 25.23 % % and 14.8 % during increment of moisture content from 7.13 % to 10.98 % and from 9.21 % to 10.98 %, respectively, for briquettes without binder. Also, the increment percentages of resiliency were 21.64 % and 14.28 % during

- 95 -


increment of moisture content from 7.13 % to 10.98 % and from 9.21% to 10.98 %, respectively, for briquettes with binder. As a result, the lower value of resiliency was at maximum value the compression stress and less moisture content for cotton stalks and rice straw briquettes without binder. Where the value of the resiliency of 9.75 % at the highest compression stress 10.39 MPa and 7.13 % moisture content for cotton stalks briquettes without binder. While the value of the resiliency was 9.75% at the highest compression stress 8.95MPa and moisture content 7.4% for rice straw briquettes without binder.

- 96 -


Resiliency% = -261.7925+39.5444*x+34.4434*y-1.2361*x*x-2.9141*x*y-0.8675*y*y (7.4 ≤ x ≥10.35 %, 4.44 ≤ y ≥ 8.95 MPa)

Re silience

%

30 20 10 0 -10

> 10 < 10 19 < 18.5 < 17.5 < 16.5 < 15.5 < 14.5 < 13.5 < 12.5

16 15 14 13 12 11

5.5 8.0

5.0 7.5

4.5 4.0 3.5

7.0


8.5

6.0

9.0

6.5

9.5

7.0

10.0

7.5

10.5

8.0

MC%

Fig (4.24b) Effect of moisture content of compression stress and resiliency of cotton stalks briquettes (With binder)

- 97 -


Resiliency % = -155.2246+23.4389*x+13.6606*y-0.7622*x*x-1.0636*x*y-0.2461*y*y (7.13 ≤ x ≥10.98 %, 6.97 ≤ y ≥ 10.39 MPa)

Resilience % 16 14 12 10

> 12 < 11 2.5 2.5