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Energy Procedia
Energy Procedia 00 (2011) 000–000 Energy Procedia 14 (2012) 1684 – 1688 www.elsevier.com/locate/procedia
2011 2nd International Conference on Advances in Energy Engineering
The Experimental Study on Pyrolysis of the Cassava Rhizome in the Large Scale Metal Kiln Using Flue Gas Karan Homchata*, Thawan Sucharitakula, Preecha Khantikomolb b
a Chiang Mai University, 239 Huay Kaew Road, Muang District, Chiang Mai, 50200 , Thailand Research and Development of Renewable Energy Laboratory (RDREL), Rajamangala University of Technology Isan, 744 Suranarai Road, Muang District, Nakhon Ratchasima, 30000, Thailand
Abstract The pyrolysis characteristics of the cassava rhizome in the large scale metal kiln using flue gas have been studied experimentally. The effect of inclined metal kiln of 0.57 m3 was also considered. It was found that at 70 degree of incline angle of the metal kiln, the pyrolysis time was shortest due to the good temperature distribution throughout the kiln. At 70 degree of incline angle of the kiln, the pyrolysis time of the dry cassava rhizome was 95 minutes, while the fresh one was longer owing to more moisture content. The pyrolysis temperature distribution throughout the kiln of the flesh cassava rhizome was poor due to the high shrinkage of fresh one. The charcoal yield obtained from the dry cassava rhizome (11.22% moisture content) is 25-28% (db), while the charcoal yield from the fresh cassava rhizome (35.5% moisture content) is 35.65%(db) which is higher than that of the dry one due to effect of moisture content.
© 2011 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of the organizing committee 2011 Published Conference by Elsevieron Ltd. All rightinreserved. of©2nd International Advances Energy Engineering (ICAEE). Open access under CC BY-NC-ND license. Keywords: Pyrolysis; biomass; Cassava rhizome; Metal kiln; Flue gas; Charcoal
1. Introduction Presently, the shortage of the energy leads to increasing in cost of all kinds of fuel. Some products obtaining from burning fossil fuel are the cause of greenhouse effect, which result in the global warming phenomenon. Additionally, this effect also causes violent natural disasters. The alternative energy sources, therefore, should be replacing the fossil fuel and natural gas. Some of energy sources, which is of less interest, is the energy from the agricultural waste or waste biomass i.e. rice husk, straw, corn cobs, cassava stems, cassava rhizomes etc. Biomass has been widely recognized as a source of renewable *
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1876-6102 © 2011 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of the organizing committee of 2nd International Conference on Advances in Energy Engineering (ICAEE). Open access under CC BY-NC-ND license. doi:10.1016/j.egypro.2011.12.1152
Karan Homchat\ / Energy Procedia 14 (2012) 1684 – 1688 Karan Homchat et al. / Energy Procedia 00 (2011) 000–000
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energy with increasing potential to replace conventional fossil fuels in the energy market. In Thailand, the planted area of the cassava is about 11,840 km2, which was surveyed by the Office of Agricultural Economics in year 2000 [1]. Each year, Thailand has a large amount of the agricultural waste which is comparable to million liters of petroleum [2]. Furthermore, the application of residue or waste biomass is less utilized due to a lot of smoke from direct combustion and stains of the tar gum sticking to the equipment. Usually, most farmers burnt the waste biomass in preparation for the new planting season leading to a lot of smoke and dust in the atmosphere. Especially, the carbon dioxide that is the product of burning waste biomass causes the global warming problem. The energy contained in the biomass can be recovered by its thermochemical conversion: direct combustion, pyrolysis and gasification. A significant advantage of biomass in comparison with other renewable sources of energy is that it can be converted to liquid, solid and gaseous fuels. The pyrolysis describes the process of anaerobic decomposition of solid fuel using only heat at elevated temperature to produce gas, oil and charcoal. The pyrolysis can be divided into three subclasses i.e. slow, flash and fast pyrolysis. The slow pyrolysis occurs under a low heating rate which obtain more charcoal yield. The flash pyrolysis is a rapid heating rate process occurring at moderate temperatures (400–600oC) that obtains maximized volatile products at short residence time. The fast pyrolysis, occurs at high temperature and longer residence times leading to increase the biomass conversion and return more gas product [3]. Ayhan Demirbas [4], reported that the charcoal yield decreased gradually with an increase of temperature but the gas yield increased. Adum [5] has illustrated that the efficiency of furnace was about 30-42% and the pyrolysis time decreased from 4-7 days into 1012 hours. Patil [6] showed the gas product from the pyrolysis was returned to burn in the furnace for accelerating the speed of pyrolysis process leading to only 3 hours for charcoal production. Yu-Jen Lin [7] proposed the earth kiln for charcoal production from biomass residues of a Cryptomeria, the charcoal yield was 29% and the pyrolysis time was 9-13 days. Homchat et al. [8], investigated the pyrolysis of cassava rhizome utilizing the flue gas in the lab-scale metal kiln. They reported that the charcoal yield for the dry cassava rhizome varied from 26% to 35% depending on the pyrolysis temperature which the pyrolysis time was quite fast only 19-38 minutes. The pyrolysis of the cassava rhizome in the large scale metal kiln using flue gas by the slow pyrolysis at moderate temperature process is the main aim of the experimental present study. The effect of the incline angle of the metal kiln is investigated to improve the acceleration of the pyrolysis process. Moreover, the temperature distribution within the metal kiln and pyrolysis time are significantly considered. 2. Experimental Apparatus and Procedures 2.1 Property of Materials Table 1. Physical property of the dried cassava rhizome Proximate analysis(% by weight, Dry basis) Moisture content 0.83 Volatile matter 76.21 Ash 3.72 Fix carbon 20.08 Ultimate analysis (% by weight, Dry ash-free basis) Carbon 52.33 Hydrogen 5.95 Nitrogen 1.03 Total sulphur 0.08 Oxygen 40.62 H/C molar ratio 1.36 O/C molar ratio 0.58 Empirical formula CH1.36O0.58
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2.2 The experimental setup
T1
T4 T2
T7 T5
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Fig. 1 The schematic diagram of the experimental apparatus
Figure 1 shows the schematic diagram of the experimental apparatus that the metal kiln is constructed by the metal sheet 2 mm thickness, 1.22 m width and 2.44 m length which is rolled into the tube and covered with thermal insulator. The incline angle of the kiln at 60, 70 and 80 degree are investigated. The cassava rhizome is contained into the metal kiln. Several type-K thermocouples are employed to measure the temperature inside the kiln. Firstly, the flue gas from the burner is supplied into the kiln. The wet pyrolysis gas from the top of the kiln is condensed in the condenser. The dry pyrolysis gas is supplied to the burner. The pyrolysis results of the dry and fresh cassava rhizome are investigated comparatively. 3. Results and Discussion 3.1 Analysis of temperature profile in metal kiln 200
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Maximum temperature Average temperature Minimum temperature Pyrolysis time
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Fig. 2 Relation of the pyrolysis temperature and the pyrolysis time with the incline angle of the metal kiln
Fig. 3 The temperature distribution within the kiln at maximum temperature
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Figure 2 indicates the relationship between the pyrolysis temperature and the pyrolysis time of the 11.22% moisture content of cassava rhizome with the incline angle of the 0.57 m3 metal kiln. The result shows that the shortest pyrolysis time is 95 minutes at 70 degree of inclined angle of the kiln owing to the good distribution temperature throughout the kiln as shows in Fig.3. The temperatures in the metal kiln at 60 degree inclined angle are low because of the poor distribution temperature leading to longer pyrolysis time. 800
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Fig. 4 The distribution temperature profiles inside the 70 degree incline angle metal kiln of the dry cassava rhizome (11.22% wb)
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Fig. 5 The distribution temperature profiles inside the 70 degree incline angle metal kiln of the flesh cassava rhizome (35.5% wb)
Figure 4 reveals the relationship between the distribution temperature profiles inside the 70 degree incline angle of the metal kiln of the dry cassava rhizome (11.22% (wb) of moisture content). Considering during the first 25 minutes, the temperatures increase linearly with times and distribute regularly throughout the kiln that is the drying process. From 25th minute, the temperatures within the kiln are different owing to the shrinking of the cassava rhizome leading to an increase the free space inside the kiln. From 50th minute, the temperature at the top of the kiln is higher than 250oC which is the starting pyrolysis of cassava rhizome. The pyrolysis occurs throughout the kiln at 70th minute which the temperature is higher than 300oC. The pyrolysis gas from the condenser starts burning at the burner and supplied to the kiln in order to accelerate the pyrolysis process. The temperature rises to the peak at 90th minute and the pyrolysis is complete at 95th minute. After that, the fuel is terminated and goes to the cooling process. Figure 5 indicates the distribution temperature profiles inside the 70 degree incline angle of metal kiln of the fresh cassava rhizome (35.5% (wb) of moisture content). During the first 20 minutes, the temperatures in the kiln increase linearly. After that, the temperatures within the kiln are quite different on account of the high shrinkage of fresh cassava rhizome leading to the large free space inside the kiln, which is larger than the dry one. In this case, the complete pyrolysis is at 115th minute; that is the pyrolysis time is longer than the previous case. 3.2 The charcoal yield The charcoal yield (ychar) can be obtained by ychar = ( mchar / mbio ) × 100%
(1)
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Where mchar is the mass of dried charcoal (kg) and mbio is the mass of the dried biomass supplying to the kiln (kg). Table 2. The summary of experimental cassava rhizome pyrolysis in the incline metal kiln
Angle of kiln(degree) 60 80 70 70
Raw material (kg) 44 48.8 42 50
Moisture content %(wb) 11.22 11.22 11.22 35.5
Maximum temperature (oC) 605 709 685 750
Pyrolysis time (min) 150 105 95 115
Fuel (kg)
Charcoal (kg)
Charcoal yield (%db)
18 12 9.8 20
11 12.1 9.4 11.5
28.48 27.93 25.24 35.65
From table 2, the results show that the charcoal yield obtained from the dry cassava rhizome is 2528%(db), while the charcoal yield from the fresh cassava rhizome (35.5% of moisture content) is 35.65%(db). Obviously, the charcoal yield obtained from the fresh material is higher than that the dry one due to effect of moisture content. 4. Conclusions The important finding of the study can be concluded that the pyrolysis time is shortest at 70 degree incline angle of the metal kiln. The distribution temperatures within the kiln of the dry cassava rhizome are regular throughout the kiln leading to the short pyrolysis time. While the distribution temperatures within the kiln of fresh cassava rhizome are poor leading to longer pyrolysis time due to high shrinkage of the fresh cassava rhizome. The charcoal yield obtained from the dry cassava rhizome is lower than that of the fresh one due to effect of moisture content. 5. Acknowledgment The author would like to deeply acknowledge the National Science and Technology Development Agency (NSTDA) for the scholarship. Especially, the author wishes to thank the Department of Mechanical Engineering, Faculty of Engineering and Architecture, Rajamangala University of Technology Isan, Nakhonratchasima for supporting the tools and equipment. References [1] Office of Agricultural Economics. http://oae.go.th/yearbook/2000-01. [2] Biomass Clearing House. Energy for Environment Foundation. Biomass. Q Print Management Ltd. Bangkok; 2006. [3] Zabaniotou, A. et al. Evaluation of utilization of corn stalks for energy and carbon material production by using rapid pyrolysis at high temperature. Fuel ; 2008, Vol. 87, p.834–843. [4] Ayhan Demirbas. Carbonization ranking of selected biomass for charcoal, liquid and gaseous products. Energy conversion and Management. 2001, 42, 1229-1238. [5] J.C. Adum. Improved and more environmentally friendly charcoal production system using a low-cost retort-kiln (Ecocharcoal). Renewable Energy; 2009. [6] K.N. Patil, P.V. Ramana and R.N. singh. Performance evaluation of natural draft based agricultural residues charcoal system. Biomass and Bioenergy; 2000. Vol. 18, p.161-173. [7] Yu-Jen Lin and Gwo-shyong Hwang. Charcoal from biomass residues of a Cryptomeria plantation and analysis of its carbon fixation benefit in Taiwan. Biomass and Bioenergy; 2009. Vol. 33, p.1289-1294. [8] Karan Homchat and Thawan Sucharitakul, The Experimental Study on Pyrolysis of Cassava Phizome Utilizing Flue Gas, Journal of Energy Procedia, 2011, In Press
