A Feasibility Study on Production of Solid Fuel from Glycerol and Agricultural Wastes

Transcription

1 International Transaction Journal of Engineering, Management, & Applied Sciences & Technologies. International Transaction Journal of Engineering, Management, & Applied Sciences & Technologies A Feasibility Study on Production of Solid Fuel from Glycerol and Agricultural Wastes Channarong Asavatesanupap a*, and Malee Santikunaporn b a Department of Mechanical engineering, Faculty of Engineering, Thammasat University, THAILAND b Department of Chemical Engineering, Faculty of Engineering, Thammasat University, THAILAND A R T I C L E I N F O Article history: Received 23 August 2010 Received in revised form 23 September 2010 Accepted 26 September 2010 Available online 26 September 2010 Keywords: solid fuel glycerol agricultural waste durian shell bagasse A B S T RA C T A main goal of the study is to produce solid fuel from glycerol and agricultural wastes in order to find an alternative energy suitable for household usage. In the study, durian shell and bagasse, which are leftover raw materials, were selected to be mixed with by-product glycerol waste from biodiesel process. Durian shell and bagasse were dried and grinded before mixing process. Heating values of each raw material were measured using an adiabatic bomb calorimeter. In order to evaluate feasibility of the production, the various mixing proportions of the mixture were tested by several means, i.e. strength test, heating value measurement, and exhaust gas analysis International Transaction Journal of Engineering, Management, & Applied Sciences & Technologies. Some Rights Reserved. 1. Introduction Fuels derived from petroleum are the majority of energy in the world. However, due to crude oil price fluctuations and environmental concerns, alternative and renewable energy become more preferable than conventional fuels. In past decades, the use of agricultural waste to produce alternative fuel has drawn interest from several countries, especially from agricultural countries. Thailand is an agricultural country where has a clear advantage over other industrial countries due to high yield of agricultural products and huge leftover wastes that could turn to be alternative 43

2 fuels, such as palm seed, jatropha, bagasse, etc. (Husain et al., 2002), (Sathitruangsak et al., 2004), (Phethuayluk et al., 2006). Solid fuel is a solid material that has been used as fuel to provide heating for a long time such as wood, charcoal, coal. In the past, solid fuels mostly obtain from the raw materials not from wastes, especially from small piece of wood or charcoal. At present, the production of solid fuels can be achieved from unwanted materials, especially agricultural wastes, which have some advantages in terms of reducing garbage and adding value to agricultural waste. A waste glycerol, a by-product from transesterification of triglycerides, becomes a major problem for the commercial biodiesel industry due to high yield of glycerol to biodiesel of 1:10. Even though, glycerol can turn into more value products, such as cosmetic product, but glycerol from biodiesel industry requires purification process of which the cost is fairly high. As a result of the high purification cost of glycerol, the alternative uses of glycerol have recently become interesting subject. One of alternative uses is to use glycerol as one composition in fuel production. In 2006, Kung-Hae and et al. studied on the feasibility of solid fuel production from sawdust and raw glycerol. The result shows that the produced fuel has potential to be used as alternative fuel, with the heat value of cal/g. In this study, the production of solid fuel from wastes is studied. Durian shell and bagasse, which come from agricultural wastes, are selected as aggregate to mix with glycerol in order to produce a solid fuel. The thermal and physical properties of the product are examined. In addition, exhaust gases produced from the combustion are analyzed. 2. Materials and Methods Agricultural waste, Durian shell and bagasse, and glycerol, a by product from biodiesel production were chosen as raw materials in this study. Both durian shell and bagasse were first chopped into small pieces and dried for 5 days. Dried durian shell and dried bagasse then were grinded and screened to obtain fine grains as shown in Figure 1. Raw glycerol from bio-diesel production process is used in this study. It is noticed that the raw glycerol is separated into 2 layers after sedimentation. The top layer is a residue of bio-diesel while the bottom layer is pure glycerol. Prepared durian shell and bagasse were mixed with raw glycerol at various weight ratios. The ratios of each agricultural waste to glycerol are 95:5, 90:10, 85:15, 80:20, 75:25, 70:30, 65:45, 60:40, 55:45 and 50:50. After mixing process, the mixture was compressed by a piston in order to form a cylindrical-shape sample. Finally, the sample was dried for 5 days to obtain a solid fuel. 44 Channarong Asavatesanupap, and Malee Santikunaporn

3 The properties of solid fuel sample such as calorific value, strength, and exhaust gas were determined. Dried (a) Durian shell Grinded Dried (b) Bagasse Grinded Biodiesel residue Glycerol (c) Glycerol Figure 1: Selected agricultural waste and glycerol. 45

4 2.1 The calorific value The heating value of each solid fuel sample was obtained by use of a bomb calorimeter (Model 1261). The calorimeter was initially calibrated with a known amount of benzoic acid having a known amount of heat of combustion. A 0.5 gram sample of solid fuel was used to test in the calorimeter for each examination. The combustion reaction of the sample and oxygen took place inside the combustion chamber at pressure of 450 lb/in 2. The heat of combustion therefore was measured. In this study, each fuel sample was examined to determine the heating value for 3 examinations and then the average heating value was obtained. 2.2 Strength test At this point, strength of solid fuel sample was examined. Of course, the testing method used in this study is not conventional. The purpose of this test is to know that solid fuels have adequate strength rather to obtain a certain value of the strength. Here, samples with various compositions and drying durations were tested by dropping at height of 0.5 m and then the results were observed. Air A Combustion chamber Sample bag Sample Figure 2: Exhaust gas collecting process. 2.3 Exhaust gas analysis After strength test, the sample of best suitable composition was tested for toxic exhaust gases. The schematic diagram of exhaust gas collecting process is shown in Figure 2. The sample was grinded and contained in a combustion chamber. Air was introduced to the chamber for 46 Channarong Asavatesanupap, and Malee Santikunaporn

5 combustion reaction. During combustion process, exhaust gas was collected by use of 5 litre gas sample bag and then was analyzed by a gas chromatography. 3. Results and Discussion 3.1 Characterization of durian shell, bagasse and waste glycerol Table 1 shows physical properties of dried durian shell, dried bagasse and waste glycerol. The results show that bagasse contains more water content than durian shell. The energy contents of durian shell and bagasse after drying process are 16.69±0.15 MJ/kg and 16.58±0.07 MJ/kg, respectively. In case of glycerol, the upper layer is less viscous and contains higher energy content due to bio-diesel contaminant. The energy contents of the upper and the lower are 38.84±0.15 MJ/kg and 18.63±0.12 MJ/kg, respectively. The energy content of the mixture between the upper and the lower is 20.73±0.26 MJ/kg. Table 1: Properties of durian shell, bagasse and waste glycerol. Moisture content Energy content (%) (MJ/kg) Durian shell ±0.15 Bagasse ±0.07 Waste glycerol Upper layer ±0.15 Lower layer ±0.12 Mixed ± Caloric value of prepared solid fuel at different compositions There are 2 sets of prepared solid fuel, which are the mixture between either dried durian shell or dried bagasse and waste glycerol at 95:5, 90:10, 85:15, 80:20, 75:25, 70:30, 65:35, 60:40, 55:45 and 50:50 weight ratios. It is found that the weight ratio of agricultural waste to waste glycerol at 95:5, 60:40, 55:45 and 50:50 were not able to form a solid fuel. Thus, the mixtures with suitable weight ratio were examined by a bomb calorimeter. From Table 2, the results shows that energy 47

6 contents of dried durian shell mixtures are fairly proportional to the composition. The highest energy content is observed at weight ratio of 70:30. Table 2: Energy contents of a mixture between dried durian shell and glycerol at various weight ratios. Dried durian and glycerol Energy content (MJ/kg) Weight ratio average 90: : : : : : The results of dried bagasse mixtures are presented in Table 3. It is evident that the highest energy content is observed at weight ratio of 65:35. Table 3: Energy contents of a mixture between dried bagasse and glycerol at various weight ratios. Dried bagasse and glycerol Energy content (MJ/kg) Weight ratio average 90: : : : : : For the sake of comparison, the following equation is used to calculate an approximate energy content of the mixture: n ( x i H i ) Heating value = (1) i 48 Channarong Asavatesanupap, and Malee Santikunaporn

7 where x i is the weight fraction of component i H i is the heating value of component i. The comparisons of the measured and calculated energy contents at different compositions are presented in Figure 3a and 3b Energy content (MJ/kg) measured calculated Glycerol (wt%) (a) Solid fuel obtained from dried durian shell and glycerol Energy content (MJ/kg) measured calculated Glycerol (wt%) (b) Solid fuel obtained from dried bagasse and glycerol Figure 3: Comparison between measured and calculated energy contents. 3.3 Strength test Strength is one of important property for solid fuels. Due to the transportation, solid fuels may be broken or damaged during transported from one to another place. In this study, the samples of solid fuels were prepared at different compositions and different time setting. The 49

8 weight ratio of each agricultural waste to glycerol are 90:10, 85:15, 80:20, 75:25, 70:30 and 65:35. While each composition was also varied the time settings which are 12 h, 24 h and 48 h. It is found that both solid fuel with 65:35 weight ratio shows the highest strength for all time settings. In addition, the solid fuel obtained from dried durian shell has more strength than that from dried bagasse at all compositions and time settings. 3.4 Exhaust gas analysis The major concern of glycerol combustion is the production of toxic gases, especially acrolein. Acrolein, an unsaturated aldehyde, is produced from the heating decomposition of glycerol. In particular, combustion reaction in this study took place in the close system as shown above. The exhaust gases were collect directly from the combustion chamber and then were analyzed by a GC. Table 4 shows the analysis of exhaust gases from the combustion of each solid fuel in the system. 4. CONCLUSION Solid fuel derived from either dried durian shell or bagasse and glycerol can be used as a alternative ful according to their energy contents. The optimum weight ratio for the mixture is roughly 65:35 for both durian shell and bagasse. Even though amount of acrolein which is a toxic gas from combustion is fairly excessive, but this may be due to gas-collecting process. The more dilute exhaust gases are expected if the combustion takes place in an open environment. In addition, the strength of solid fuel may be improved by use of binding material. The further studies therefore need to be done in order to obtain usable and environmental-friendly alternative fuel. Table 4: Analysis of exhaust gases from combustions. 50 Channarong Asavatesanupap, and Malee Santikunaporn

9 5. Acknowledgements The partial funding from the Department of Mechanical Engineering, Faculty of Engineering, Thammasat University is gratefully acknowledged. 6. References Husain, Z., Z. Zainac, and Z.Adullah (2002) Briquetting of palm fibre and shell from the processing of palm nuts to palm oil, Biomass and Bioenergy, 22; pp Sathitruangsak, P., T. Madhiyanon, and S.Soponronnarit (2004) Briquette fuel producing from coconut shell by extrusion technique using molass as binder, The 18 th Conference on Mechnical Engineering Network of Thailand, Khon Khean University, Kon Khean. Phethuayluk, S., C. Polnak,, T. Incharein,, and P. Plaoleh. (2006) Physical property of fuel briquette from oil palm residual. Proceedings of the 2 nd Conference on Energy Network of Thailand, Suranaree University of Technology, Nakornratchasrima. Kung-Hae, P. and V. Lekpetch. (2006) A feasibility study of solid fuel production from sawdust and raw glycerol. Prince of Songkhla University, Songkhla. Dr. Charnnarong Assavatesanupap is an Assistant Professor of Department of Mechanical Engineering at Thammasat University. He earned his PhD (Mechanical Engineering) from University of Southern California, USA. His research work is focusing on heat transfer, fluid dynamics, and energy conservation Dr. Malee Santikunaporn is now with the Department of Chemical Engineering, Thammasat University. She obtained B.S.(Chemical Engineering, Honors) and M.S.(Petrochemical Technology) from Chulalongkorn University, Thailand. In 2006, she received PhD (Chemical Engineering) from the Oklahoma University Norman, USA. During years 1999 and 2000, she was a visiting researcher at Tokyo Institute of Technology, Japan. She is currently interested in catalysis and membrane filtration. 51