Advanced Materials Research Vols. 875-877 (2014) pp 1831-1836 ...

Advanced Materials Research Vols. 875-877 (2014) pp 1831-1836 Online available since 2014/Feb/27 at www.scientific.net © (2014) Trans Tech Publications, Switzerland doi:10.4028/www.scientific.net/AMR.875-877.1831

Gasification of Biomass in a Fixed Bed Reactor Emilio Delgado 1,2, a, Oscar Avilés2,b, William Aperador 2,c 1

Escuela Colombiana de Ingeniería Julio Garavito, Colombia. 2 Universidad Militar Nueva Granada, Colombia

a

[email protected], [email protected], c [email protected]

Keywords: Gasification, hydrogen production, fixed bed reactor

Abstract: Currently, there are different kinds of alternative fuels called "clean fuels" within which hydrogen gas is considered. The hydrogen can be produced by various methods. The aim of this research is producing hydrogen gas by gasification of biomass in a fixed bed reactor, using a gaseous mixture with a high energy potential. 1. Introduction Because of the worldwide industrialization, population growth and globalization, the world has the need to develop alternative energy sources, with visible consequences such as global warming and loss of animal and plant species, altering the cycle of life on earth. In this manner, the demand is so great that it has become an environmental problem. It is clear that the implementation of gasification systems contributes to the self-sustainability of the processes since these systems have competitive advantages over other systems of electricity or heat generation from an environmental point of view. In order to obtain a gaseous mixture with high energy potential, in this study was completed the assembly of a gasification system for the Amazonic specie, Maraco (Theobroma bicolor), with a countercurrent fixed bed reactor for the production of the biofuel. 2. Raw material characterization 2.1 Maraco (Theobroma bicolor) The tree (Theobroma bicolor) is a rustic plant native of the Amazonic America [1]. The tree can reach from 25 to 30 meters of high if it develops freely in the natural forest. Its outer bark is rough, cracked and gray-brown, their leaves are simple, reddish and elliptical [2]. Its trunk is straight and cylindrical with a diameter of 20 to 30 centimeters. The Maraco, also called Macambo, can be seen within the potential species for biomass production and carbon sequestration because it produces approximately 71.87 tons of total biomass per hectare and can capture 32.34 tons of carbon per hectare [3]. 2.2 Physicochemical analysis The total content of C, H, N, O present in the shells of the fruit, was measured using a technique for elemental analysis. The samples were burned subjected to combustion, and then the produced gases were separated to be analyzed by chromatography. The proximate analysis for obtaining moisture, ash, volatile matter and fixed carbon in weight percent, was conducted on an equipment at the Coals Laboratory from the Instituto Colombiano de Geología y Minería - INGEOMINAS in Bogota. The humidity calculation was developed with the procedure of the norms ISO 5068-1993 or DIN 51718, whereby the sample should be dried in an oven at constant temperature of 106 ° C. The volatile combustible material was determined with the norms DIN 51720 or ISO 562-1996. The ash content in the sample was assessed with the norms DIN 51719 or ISO 1171-1996. The fixed carbon content was obtained with the norm ASTM D3172. The calorific value was calculated using a bomb calorimeter. 3. Biomass transformation Nowadays, there are various methods for biomass transformation and obtaining different products (see Figure 1). The thermochemical methods are characterized because there is a breakdown of the All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of TTP, www.ttp.net. (ID: 186.155.238.2-07/01/15,16:47:13)

1832

Material Research and Applications

cellular links by heat action. Also, there is a relationship between the temperature level and the products quality, so that direct combustion, pyrolysis and gasification are considered different thermochemical technologies [4]. This research is based on a thermochemical method using gasification.

Fig.1 Biomass transformation processes components

Fig. 2 Gasification equipment

3.1 Biomass gasification Gasification is the thermal decomposition process where the organic solid material is partially oxidized because of the pyrolysis, and then it reacts with a restricted amount of gasification agent like air, water vapor, carbon dioxide, oxygen, hydrogen or a mixture of them to produce synthesis gas of low or medium calorific value (methane, ethane, ethylene, hydrogen), as well as small amounts of carbonaceous solid residue (ash) and tars [5]. Biomass gasification has potential in power generation, because produces versatile fuel, which can totally or partially replace the conventional fossil fuels. [6]. 3.1.1 Process variables The system operating conditions determines the physicochemical properties of the gas mixture obtained, therefore, it is important verifying each of the variables affecting the process: temperature, pressure, gasification agent and raw materials. 3.1.2 Gasification equipment The gasification equipment developed was a countercurrent fixed bed. It formed by: reactor, sensor system, control system, heat transfer system, gas collection systems, supply system and gas extraction system (see Figure 2). 4. Materials and methods The gasification agents used were water vapor and air. Thus, 5 grams of material for gasification (Maraco peel) and 5.88 ml of water vapor or air were introduced into the system, plus 50% in excess, for a total of 8.82 ml of water vapor as gasification agent (meeting with the parameters of overdesign). As inert gas was used nitrogen packedin a gas cylinder of 6.5m3, with a pressure of 2000-2500pounds. Temperature sensors were in different sectors of the system: inside the furnace, a thermocouple (Nickel-Chromium Nickel) K type; to know the temperature of the exhaust gases were used a thermometer brand Baird and Tatlockof low temperature. As a control system was used a temperature controller brand WATLOW 935A connected to the thermocouple. The particle size reduction was performed first by grinding the material in a disc type mill, and then by sieving it until to obtain the required size. The selected meshes were from 20 to 100 mesh, because they showed the highest fraction of retained material. The levels studied for the bed height were: Height No. 1 (3 cm)

Advanced Materials Research Vols. 875-877

1833

and Height No. 2 (5 cm). The study levels of bed height represent the maximum and minimum radial length that can be used in designed equipment with the understanding that a change in the diameter represents a change in the filling height while the amount of mass is constant. 4.1 Methods 4.1.1 Gasification equipment operation The operation of the gasification equipment follows the sequence shown in Figure 3, in each test:

Fig. 3 Procedure for the gasification equipment operation 15 g of Maraco fruit shell was got into the biomass feed basket, according to the desired bed height, then the expander and the rest of the equipment was installed. Also, it connects the heat exchangers and the inert gas with the gasification agent. All equipment is coupled to the gas collection system. Once the system is ready, ignition starts on the gas suction pump, activated with 150 to 200 mm Hg of pressure and the nitrogen admission flow was 0.5 l / min by 2 minutes. The cooling flow of the heat exchanger is maintained to ensure a heating rate of 10 ° C / min, up to 1000 ° C after 120 min. Every five minutes the temperature readings are performed in the inlet and outlet of the reactor with the mass loss reading. The data collection is interrupted when the scale indicates a constant amount of mass. Then, the temperature was stabilized for 20 min and it was started the input of the gasification agent with the off of the suction pump and the catching of the sample. Once the sample is in a vial, it is kept in an incubator at 4 ° C in order to preserve the product as long as possible. 4.1.2 Chromatographic Analysis After performing the gasification test, the gaseous sample obtained was analyzed in a gas chromatograph. Additionally, it was quantified H2, CO, O2, N2, and CO2 by thermal conductivity detector (TDC) and CH4, C2H6, C2H4 by a flame ionization detector (FID). 4.2 Statistical Analysis The experiment was performed using a 2k factorial design with two levels and 4 factors. Thus, treatments were applied like is shown in Table 1. Table 1.Treatments applied in the experimental design.

1834


5. Results and Discussion 5.1Physicochemical Analysis of Maraco The characterization of Maraco shells use as feedstock in the gasification, were conducted at the INGEOMINAS Coals Laboratory. These results are shown in Table 2. These features facilitate the comparison with other commonly used solid fuels and allow a screening of the obtainable products in the process. Table 3 lists the physicochemical characteristics of Maraco fruit shells with other materials such as wood, bagasse and coffee husks, which have been extensively studied for use as fuel. Table 2.Proximate and elemental analysis of Maraco shell

Table3.Data from solid fuels [7]

The moisture of Maraco fruit shell is the lowest value compared to other fuels (see Table 3). This is favorable since high moisture content may cause agglomeration (it is less than other fuels such as rice hulls; waste paper and coal (Table 3)). High ash content in biomass reduces the ability of management and burned, slowing combustion and increasing fuel leak. A low amount of volatile allows better control of the decomposition reactions with gas and char that is produced during gasification. The fixed carbon percentage represents the amount of material that can be consumed in a combustion process. From the data obtained, the Maraco has potential in the manufacture of activated carbon due to its high carbon content, but should be subject to future research. Also, the Maraco can be used as fuel, as its calorific value obtained is in the same range of other fuels, being even better than waste paper and rice hulls (see Table 3). Elemental analysis of the Maraco shells yields low values of sulfur content (0.10%), compared with other fuels, such as the Cerrejon coal (0.85%). This is an undeniable environmental advantage. 5.2 Effect of particle size on the loss of mass. To evaluate the effect of particle size, it was used treatment III, where factors like particle diameter (mesh 100), bed height (No.2) and gasification agent (air) remain constant. Likewise, it was used treatment VI where particle diameter is mesh 20, bed height is No.1 and air is the gasification agent. Figure 4 shows that both curves has a downward trend. The particle diameter given by the mesh 20

Advanced Materials Research Vols. 875-877

1835

maximum 0.833mm (treatment VI), registers a stabilization of biomass after 220°C, while with those of mesh100, maximum particle size of 0.147 mm (Treatment III), the biomass is maintained after the 380°C. Thus, it is greater the loss of biomass with the increase of the particle size.

Fig. 4 Mass loss in treatments III and VI 5.3 Carbonized Product The values for the carbonized product obtained from the gasification process are show in Table 4. Table 4.Carbonized product obtained by gasification

As shown in Figure 5, the bed height has an opposite effect because of the medium used for gasification: while using air there is more product using a bigger height (5cm), the opposite happens when the medium is water vapor. However, it is evident that the production of carbonized material tends to be lower by using water vapor. In figure 6, it is shown that there is a tendency to generate more carbonized product using a larger particle size (20 mesh: maximum 0.833mm).

Fig. 5 Influence of gasification medium in the carbonized product

Fig. 6 Influence of particle size in the carbonized product

1836


In this situation, bigger height increases the production of carbonized material, however, in Figure 7 can be seen that with air is further potentiated the effect. In summary, the best combination for char production is using air with 5cm of height and a larger particle size (20 mesh: max 0.833mm)

Fig. 7Influence of height in the carbonized product 6. Conclusions Maraco fruit shells have physicochemical properties that allow its use as energy source through the gasification process, since it has a calorific value comparable with the wood and low content of volatile material, moisture, ash and sulfur. The biomass loss during heating is faster, when it is working with a particle size that pass through mesh 20 (0.833mm max), getting less time for stabilization. In the equipment employed, the combination that favors the production of carbonized material is air as a gasification agent with bed height of 5 cm and a particle size that pass through mesh 20 (0.833mm max) 7. Acknowledgements The authors express their gratitude to Marvi Baron and Andres Villada, for their valuable contributions to the development of this research. 8. References [1] BARRERA. "Determination of some physical and mechanical properties of Maraco seed (Theobroma bicolor HBK) and obtaining Bacalate. "Food Engineering Thesis. Foundation University Jorge Tadeo Lozano, Bogota. (1999) p 18 to 19. [2] RIVAS, E. LOZANO, F. Promising species of the Amazon. Conservation, Management and Utilization of Germplasm. Editorial CORPOICA C.I. Macagual - Caquetá - Putumayo. (2001). p72-74. [3] GONZALES AGUSTIN, Macambo Culture Manual. Research Institute of the Peruvian Amazon IIAP, (2010) [4] TORRES MAURICIO, Gasification of oil palm waste research in a rotary kiln. Bogota D.C. (2002). 29p. Thesis (Mechanical Engineer).National University of Colombia, Faculty of Engineering, Department of Mechanical Engineering and Mechatronics. [5] PEREZ JUAN, "Biomass gasification" Antioquia University. (2009). p17-18 [6] NOGUÉS SEBASTIAN, "Biomass energy". Spain, (2010). p 401 [7] DE ESCELES, MECAR. Conference on Waste Disposal, New York, 1968, quoted by Robert Perry, Chemical Engineering Handbook, 6 ed. McGraw-Hill., 1992 Volume III. 9-9 p.

Material Research and Applications 10.4028/www.scientific.net/AMR.875-877

Gasification of Biomass in a Fixed Bed Reactor 10.4028/www.scientific.net/AMR.875-877.1831