Proceedings of SEEP2014, 23-25 November 2014, Dubai
RESEARCH ON THE POSSIBILITY OF USING AGRICULTURE BIOMASS RESIDUES FOR ENERGY PURPOSES Risto V. Filkoski1 and Ilija J. Petrovski2 1. University ”Sts Cyril and Methodius”, Faculty of Mechanical Engineering, Skopje, Republic of Macedonia; email:
[email protected] 2. University ”Sts Cyril and Methodius”, Faculty of Mechanical Engineering, Skopje, Republic of Macedonia; email:
[email protected] Abstract The purpose of the work is to examine the effectiveness of the utilisation of agriculture residues as energy source, combined with wood pellets, in steam and hot water boilers. One of the investigation aims is to evaluate the efficiency of hot water boilers, designed to use pellets as main fuel, when operated with a blend of pellets and wineyard twigs in different ratios. The experimentally obtained biomass properties, such as the moisture content, calorific value, bulk density, ultimate analysis, ash composition and melting properties, are compared with the properties of wood pellets produced according to the EU standards. A performance test procedure for boilers that will use fuel blend of wood pellets and wine twigs is adopted and initial tests conducted. Although there are some technical challenges, the use of fuel blend of wood pellets and prepared agriculture residues, such as wine twigs, in conventional pellet fuelled boilers, should be possible. In that sense, the recovery of vineyard pruning residues may represent a substantial source of biomass fuel in wineproducing regions that may reduce the costs for heating in commercial, public and residential sector. Keywords: Agriculture biomass, vineyard residues, renewable energy, combustion, boiler, harmful emission 1 INTRODUCTION The perspective and problems of renewable energy in making of strategies for a sustainable development, with ultimate goal of converting present energy systems into 100 % renewable ones are discussed in [1]. The main conclusion is that such development is possible. Biomass is a desirable and promising renewable energy source, due to its low, close to neutral, net greenhouse gas emissions, and potential sustainability, if the economic, environmental and social impacts are properly managed. Energy utilisation of biomass, as the only carbon-based renewable fuel, becomes more important everyday. Taking different forms, biomass energy accounts for about 14-15 % of the primary energy consumption in the world [2]. It contributes with over 10 % of primary energy supply in countries such as Sweden and Austria, and about 4 % in the US [3]. Biomass energy is particularly important for the developing countries, accounting almost 40 % of the primary energy consumption [2], much of this through low efficient and highly polluting combustion in poorly controlled heating and cooking fires [4]. Recently, there has been an expansion of interest of using waste biomass in co-firing of coal-fired boiler plants, as well as
co-firing of biomass and wood pellets. At the same time, there is an expanding market of wood pellet in many European countries. The total global consumption of wood pellets in 2011 was about 14.4 million tonnes and about 80 % of that amount was consumed in Europe [5]. Combustion and co-combustion of biomass from the viewpoint of available technologies in a wide size range, as well as with regards to the pollutants formation and measures for emissions reduction, are analysed in [6]. The agriculture sector provides different types of vegetative biomass that may be used for energy purposes. Various types of biomass can be characterised in different ways, but one simple method defines the following main types: woody plants, herbaceous plants/grasses, aquatic plants and manures [7]. The cultivation of grapes is common all over the world, often representing a profitable endeavour. The agricultural area covered with vineyards in 2008 amounted to almost 8 million hectares worldwide [8]. This crop requires proper tending, including pruning that generates a substantial amount of residues. Finding some effective way of utilisation for the vineyard residues would convert a disposal problem into a collateral energy generation. Annually, about 1-3 t/ha of pruning residues are generated from a vineyard, which depends on
Proceedings of SEEP2014, 23-25 November 2014, Dubai water boilers. Another goal is to make adequate the type of vine, age, way of harvesting, preparations for practical evaluation of the configuration of terrain etc. [2]. These residues effectiveness of boilers, primarily designed to are often burned directly on the field, a use wood pellets, when operated with a blend of traditional practice in many regions; but they are pellets and vineyard twigs. also used as a fuel or as an organic fertiliser and the rest are dumped. Therefore, one of the most 2 METHODOLOGY OF THE RESEARCH important environmental aspects of using The methodology of the work consists of the pruning residues as fuel is to avoid their open following main steps: burning on the fields. Pruning residue harvesters - Prescription of the procedure for biomass have been recently developed, which may sampling for laboratory analysis; effectively recover vine twigs and make them - Laboratory research and analysis regarding available to the markets [9]. Pruning residues the heating value, moisture and ash content, could partly replace the energy use of traditional composition, content of elements related to wood assortments in vineyard areas. Locally, combustion and emissions [17], done in they may play an important subsidiary role in accordance to [18, 19]; supplying energy plants with fuel [10]. - Comparison of results regarding the biomass The biomass contributes with a significant share composition to literature findings, and to the overall energy balance in the Republic of - Preparation/adoption of procedure for biomass Macedonia. Research on the available biomass fueled boilers’ performance testing. as energy source in the country dates from the The twigs sampling for laboratory tests is early 80-ies, being a subject of interest in conducted in accordance to the procedure various works [11-14]. The total practical availaprescribed in [20]. This document provides a bility of vegetative biomass from forestry, wood systematic method of sampling biomass fuel, processing and agriculture is about 120,000 which will obtain a sample from a larger stock t/year, which is 20 % of the theoretical available of fuel in such a way that (1) systematic errors vegetative biomass [13]. The assessed practical will be avoided and (2) random errors will be availability of wine twigs in the country is about equilised as much as possible [20]. Considering 50,000 t/year, concentrated in several regions. the fact that the test facilities are public heating The main biomass material properties of interest, plants and industrial energy facilities, it is very during subsequent processing as an energy important that the document comprises safety source, relate to: moisture content, calorific precautions, general sampling guidelines, sample value, proximate analysis, i.e. proportions of preparation and treatment, instructions for fixed carbon and volatiles, ash/residue content, sampler, fundamental sampling principles, alkali metal content and cellulose/lignin ratio number of individual samples, minimum size of [7]. Bustos et al. in [15] reported that the individual samples, sampling scheme and pruning twigs contain 34.1 % cellulose, 19 % directions for the preparation of test report [20]. hemicellulose and 27.1 % lignin on dry weight The wine twigs samples, collected from the basis, indicating significant energy potential. Tikvesh region, have been tested for a number of Properties of biomass relevant to the combustion parameters [17]: calorific value, moisture process are reviewed in [4], emphasizing the content, bulk density, ash composition and variability of the biomass types composition, melting properties, content of basic elements particularly with respect to inorganic related to the combustion process; oxides of constituents that are important to the problems various metals and content of other elements of fouling and slagging. Evaluation of the related to emissions to air. The results of the technical and environmental performance of a present research have been compared to similar small scale pellet boilers when operated with cases [8, 9, 16]. different pelletised biomass fuels is the objective The quality standards for pellets in European of the research presented in [16]. countries have been reviewed in [21]. The The objective of the present work is to examine adopted procedure for boilers’ performance the properties of vineyard pruning residues testing in the present case is in accordance to the important for their energy utilisation and to methodology described in [22,23]. The assess the possibilities for mixing twigs and procedure provides the methodology to carry out wood pellets for combustion in steam and hot the energy and material balances and to calculate
Proceedings of SEEP2014, 23-25 November 2014, Dubai ratios. Considering the (H/C)x10 ratio, which is the efficiency of a boiler plant utilising biomass 1.5, and the atomic ratio of O/C, which is about as fuel. The procedure can be used for testing of 1, the vineyard pruning residues lie in the upper a biomass fueled boiler by principally defining right part of the diagram. The O/C and H/C [21]: (1) the boundary for the equipment to be proportions are higher, compared with coals, tested, (2) fuel sampling, analysis and flow reducing the energy value of the vineyard measurement and (3) ash sampling, analysis and residues, due to the lower energy contained in Cflow measurement. O and C-H bonds, than in C-C bonds [7]. Most of the biomass combustion systems with hot water boilers in range up to few thousand Table 1. Ultimate analysis of the wine twigs kilowatts have certain distinct components, [17, 24] shown schematically in Figure 1, needed for the Parameter Value entire system to operate properly, including the Calorific 16010 kJ/kg, 14250 kJ/kg as main parameters that are monitored. The tests value received are conducted with different mass ratios Moisture 11.4 % (April 2012) pellets/vine twigs, starting with mass percentage content (W) ratio of 5:95, up to 30:70 ratio. Gas analyser Carbon (C) 46.3 % dry ash-free (daf) (O , CO, ...), t 11 Hydrogen (H) 6.9 % (daf) 5 Fly ash, t Oxygen (O)
