Effectiveness of briquetting bio mass materials with different ratios in 10 kw down draft gasifier K.Sivakumar 1* B. Sivaraman 2 and N.Krishna Mohan 3 1*, Assistant Professor, Department of Mechanical Engineering, Annamalai University, Annamalai Nagar, Chidambaram-608 002, Tamil Nadu, India. 2 Associate Professor, Department of Mechanical Engineering, Annamalai University, Annamalai Nagar, Chidambaram-608 002,Tamil Nadu, India. 3 Professor, Department of Mechanical Engineering, Annamalai University, Annamalai Nagar, Chidambaram- 608 002,Tamil Nadu, India. e-mail: ksr_aufeat@yahoo.co.in Abstract This paper discuss about the effectiveness of using Briquetting of rural bio mass material in Down draft gasifier for easy operation and power generation, during winter and rainy season. Sawdust a milling residue is available in huge quantity. Apart from the problems of transportation, storage, and handling, the direct burning of loose saw dust biomass in conventional grates is associated with very low thermal efficiency and widespread air pollution. The conversion efficiency is as low as 40% with particulate emissions in the flue gases in excess of 3000 mg/ Nm. In addition, a large percentage of unburnt carbonaceous ash has to be disposed off. Briquetting of the sawdust with cow dung could mitigate these pollution problems while at the same time making use of the important domestic energy resources. The easily available rural bio mass material saw dust and rurally available binder material cum bio mass cow dung is used for briquetting. This experiment was carried out with briquetting of saw dust and binder cow dung at different ratio. It is experimentally investigated at 800 0 C using gasification technique in a downdraft gasifier. The air flow rate and pressure drop across the gasifier has been measured. The percentage of combustible gases like H 2, CO, CH 4, CO 2, and N 2 formed during gasification are found. The calorific value of the producer gas for different ratio of briquetting biomass material has been found out. Experimental results indicate that briquetting at 75:25 ratio of sawdust and cow dung is the best suitable biomass Briquette for gasifier compared to the other two ratios considered. The result shows that the gas composition of methane is comparably high in this ratio (i.e. 75:25) than other two ratios i.e.(50:50) and (25:75). The results also show that pressure drop across the gasifier and producer gas composition increases with increase in air flow rate. Also found that, thermal efficiency is comparatively high at 75:25 ratio briquettes than other two ratios and it increases with air flow rate. Key Words: Briquette saw dust, cow dung biomass, gasification, producer gas, binding material, combustion, air flow rate, pressure drop, thermal efficiency. Introduction Application of technology on rural electrification through biomass gasifier is facing lot of difficulties during climate change and seasonal changes. Using rural biomass materials either wood chips or any other materials poses lot of difficulties during rainy and winter season in the bio mass gasifier. The impact of relative humidity and moisture content of air affect the quality of bio mass material, gasification process and in turn power generation. It is known fact that, the application of biomass gasifier is hardly needed during this period. Transportation, storage and gasification of loose bio mass material in downdraft gasifier create more air pollution. To address these problems, briquetting of bio mass materials will be helpful. Briquetting of saw dust with rurally available cheap binding material will be best for rural gasification and power generation [1]. If the binder itself is a biomass; it will be more useful. Every village in India having plenty of cow dung and traditionally it is used as fuel for burning process. Cow dung is a best suitable bio binder and biomass for gasification. This experimental research, cow dung is used as biomass as well as binder for briquetting. Manually operated blending and briquetting machines are compatible and reliable for rural biomass briquetting. Blending of cow dung with saw dust have been carried out by manual mixing and briquetting of ISSN : 0975-5462 Vol. 3 No.11 November 2011 7959
cow dung and saw dust is done with the help of manually operated press. The cylindrical shaped briquettes are formed for easy and complete combustion. It will increase the thermal efficiency and reduces air pollution Briquetting biomass materials having different ratio of saw dust and cow dung with net calorific values between 15000 kj/kg and 19500 kj/kg is used for this experimental analysis[2],[3]. Combustible gases H 2, CO, CH 4, CO 2, and N 2 were formed in the reactor during the process of gasification. Briquetting biomass with different ratios: Sawdust, a waste product from the processing of wood, is an important source of energy for biomass gasifier. Cow dung a binder material used for briquette is a cheap and easily available bio mass material[4]. Quality of briquette of different bio mass will differ with different ratio [5]. In this experimental analysis, three different ratios of briquetting bio mass of saw dust and cow dung is used. Cylindrical briquette material of 40 mm outside diameter, 10 mm inside diameter and 60 mm length is used for this experiment as shown in Fig.1. The properties of briquette with varying ratio of bio mass are as follows. Fig-1: Briquette of Saw dust and binder material in different ratios 75:25- Saw dust with Cow dung: The heating properties of 75:25 ratio of saw dust and cow dung briquette are experimentally found as follows. The proximate analysis of this briquette is as follows: volatile matter 70.5%, fixed carbon 27.0% and ash 2.5%.The ultimate analysis are C 49.37%, H 6.4%, N 2.02%, S 0.00%, O 42.2%. 50:50- Saw dust with Cow dung: Briquette of 50:50 ratio of saw dust and cow dung and its heating values are experimentally found as follows. The proximate analysis of this briquette is as follows: volatile matter 66.2%, fixed carbon 27.3% and ash 6.5%The ultimate analysis are C 47.4%, H 5.0%, N 2.0%, S 0.1%, O 45.5%. 25:75- Saw dust with Cow dung: Briquette of 25:75 ratio of saw dust and cow dung and its heating values are experimentally found as follows. The proximate analysis of this briquette is as follows: volatile matter 64.1%, fixed carbon 21.0% and ash 14.9%. The ultimate analysis are C 46.6%, H 5.18%, N 6.12%, S 0.4%,O 41.7%. Experimental setup and procedure Bio mass gasification is the conversion of solid biomass in to a high quality gaseous fuel at very high overall efficiencies and thereby offers excellent opportunities for using renewable biomass resource in place of conventional fuels. The experimental model is one of the reliable units from a wide range of systems having different output ratings (5 to 10 kw) application modes in power generation. The set up is made up of using variety of feed stocks for briquetting biomass [6]. It is designed to use the village bio mass wastes like agriculture waste and wood waste. The experimental set up of the down draft gasifier plant is shown in Fig.(2) ISSN : 0975-5462 Vol. 3 No.11 November 2011 7960
18 18. Thermo couple Figure.2: Schematic diagram of 10 kw downdraft Bio mass gasifier Equipment: The Briquetted biomass is fed through the feed door and is stored in the hopper. Limited and controlled amount of air for partial combustion is allowed through air nozzles. The throat (or hearth) ensures relatively clean and good quality gas production. The reactor holds charcoal for reduction of partial combustion products while allowing the ash to escape through perforated sheet provided in reactor which in turn taken out through manual ash collection cone after eight hours of operation. The gas passes through the annulus area of reactor from upper portion of the perforated sheet. The gas outlet is connected with the various downstream systems viz venturi scrubber, water junction box, fine filter, safety filter, flare with valve and gas control valve. Gas produced in gasifier is scrubbed and cooled in scrubber with recirculating cooling water in cooling pond with the help of DC scrubber pump. Gas is separated from water in water junction box and introduced in fine filter and a safety fabric filter, cool and clean gas and air is then sucked in to the engine through a gas train consisting of piping and valves arrangement. The gasifier is started with a battery (12v), which initially provides auxiliaries power to DC scrubber pump, to start the gasifier system. A battery operated electric starter starts the engine or can be hand cranked also. The producer gas then starts the engine on gas mode. Governor linked control butterfly is provided to vary the gas quantity as per electrical load on the generator, keeping frequency within limits. Engine gasifier control panel provides facility for all switching, indications and safety of operation. An electric driven biomass cutter and engine hot exhaust based briquette drying arrangement is also provided to make the system self sufficient. Experimental Procedure and Instrumentation Initially the reactor was filled with charcoal in the bed and briquette bio mass material is loaded on the hopper. The blower was switched on to supply the air for combustion. Start up fire was put on the hole placed over the charcoal for easy firing. In the down draft gasifier, both the fuel and the gas flow downwards through the reactor enabling the pyrolysis gases to pass through a throat and hot bed of char which is supported by a grate. This results in cracking of most of the tars into non condensable gases and water. Furthermore air is admitted to the fuel bed through air intake nozzles causing pyrolysis to charcoal and volatiles that partially burn as they are produced [10]. The gaseous products of this flaming pyrolytic combustion then consume the charcoal produced during the pyrolysis and reduced to fuel gas. Manometer has been used to measure the pressure drop across the gasifier. Moisture content has been measured by using infrared moisture balance. Control panel consists of vibrator motor start and comp rotor measuring arrangement. A 12 V battery has been used for initial start up of pump. Temperature measurement is done by using thermocouple. ISSN : 0975-5462 Vol. 3 No.11 November 2011 7961
Results and Discussion: Under this experimental set up, gasification process was carried out on the gasifier using briquetted bio mass material of different ratios The volumetric flow rate of wet producer gas was measured with a gas flow meter. Drying, pyrolysis and oxidation zone temperature of the gasifier and the water scrubber and box filter outlet temperature were also monitored with the aid of thermocouples [9]. The amounts of tar, dust and condensate in the product gas were determined before and after cleaning the product gas. Pressure drops across the gasifier for different air flow rate also been measured. Figure.3: Producer gas exit through the chimney Gas components and Gas composition in % In order to identify the gas components, gas composition in percentage of the producer gas was calculated for the Briquetted biomass materials of different ratios. It was carried using gas chromatographic equipment. The results were measured and tabulated. The Fig (4-6) shows the components and gas composition of Briquetting saw dust and cow dung at different ratios at 800 0 C.It is found that the CO, CH 4 and CO 2 increases with increase in percentage of cow dung in the briquette and N 2 and H 2 decreases with increases in cow dung in the briquettes. There is a significant increase in CO 2 from 9.5% to 11.5% with increase in quantity of cow dung in briquettes. The result shows that the gas composition of 75:25 ratio of briquetted saw dust and cow dung is superior than other two ratios used for this experimental analysis. Figure.4: Gas components and gas composition in 75:25 Briquettes of sawdust and cow dung ISSN : 0975-5462 Vol. 3 No.11 November 2011 7962
Figure.5: Gas components and gas composition in 50:50 Briquettes of sawdust and cow dung Figure.6: Gas components and gas composition in 25:75 Briquettes of sawdust and cow dung Moisture content: Moisture content of bio mass fuel affects the combustion process and also affects the heating value of producer gas. High moisture content will contribute for the low heating value. The dry biomass will burn at low temperature. The moisture content will reduce the thermal efficiency and in turn the heat produced is used for heating the wet bio mass. So moisture content must be minimum for any bio mass material [7, 8]. The fig. -7 shows the moisture content of briquetting of saw dust and cow dung with different ratio used for this experimental study. Since cow dung is used as binder cum bio mass material for briquette, the moisture content increases with increase in ratio of cow dung. The moisture content of briquette increased from 20% to 30% with increase of cow dung from 25:75. ISSN : 0975-5462 Vol. 3 No.11 November 2011 7963
Figure.7: Comparison of moisture content of briquettes of different saw dust and cow dung ratios. Calorific value: Calorific value is the measure of quality of briquetting bio mass fuel. It is the heat energy liberated during the combustion of briquetting bio mass material in the gasifier. The higher calorific value denotes the high quality of bio mass. The calorific value of different ratios of briquetting bio mass material used for this experimental set up is shown in Figure.8. It reveals that, the increase in cow dung will decreases the calorific value of Briquetting. Figure.8: Comparison of calorific value for different ratios of briquetting bio- mass materials Pressure drop: Test for pressure drop measurement along the depth of biomass bed and hopper were carried out under forced, downdraft mode with throat, in the unfired condition of gasifier. The bottom opening of the diverging portion below the throat of gasifier was closed with a wiremesh. A known quantity bio mass materials was charged into the gasifier up to the level of topmost pressure tapping.the top surface of biomass bed is taken as the reference for describing the position of pressure measurement. Manometers were connected across the orifice meter to measure airflow rate. The blower was started and delivery valve was kept fully open. Under this condition, the ISSN : 0975-5462 Vol. 3 No.11 November 2011 7964
static pressure readings along the depth of biomass bed and orifice meter reading were noted. The air flow rate was then reduced in equal steps by regulating the blower valve. For each valve opening all the static pressure readings along the depth of the biomass and orifice meter reading were noted.the experimental procedure was refrated for briquettes difference ratios and pressure drop was measured. It is found that pressure drop increases with increase in the air flow rate in hopper as shown in fig (9). Figure. 9: Variation of Pressure drop Thermal efficiency: Thermal efficiency is the ratio of thermal power of the product gas produced to the thermal power of the input briquette bio mass material supplied. It gives general idea about the how much energy from briquetting bio mass material is effectively utilized. Generally thermal efficiency of briquetting bio mass depends up on the moisture content of briquettes. Thermal efficiency of briquetting saw dust and cow dung at different ratios were calculated with different air flow rate.. It is found that, briquetting bio mass material of 75% saw dust and 25 % cow dung yield higher thermal efficiency than other two ratios and it increases with increase in air flow rate. Fig 10: Variation of efficiency Producer gas consists of carbon di oxide, carbon monoxide, hydrogen, nitrogen and methane. The amount of methane present in the produces gas determines the quality of gas. The methane content in the producer gas increases with increase of the mass flow rate of air. The figure 11 shows the methane generation in producer gas with the mass air flow rate of different ratios of briquetting bio mass used in this experiment. The experimental results show that the amount of methane produced from the 75:25 ratio of briquetting saw dust and binder material cow dung is higher than the other ratios. ISSN : 0975-5462 Vol. 3 No.11 November 2011 7965
Fig. 11 Mass of air flow rate vs Methane Gas Composition Conclusion: The following conclusions are drawn from the experimental analysis carried out on 10kW down draft gasifier by using briquetting of saw dust and cow dung bio mass materials. They are Combustible gases can be produced from briquetting bio mass of saw dust and binder cow dung for power generation. Cow dung can be useful as binder cum bio mass material in downdraft gasifier. The carbon monoxide, nitrogen and methane content of the 75:25 ratio of briquette bio mass saw dust and cow dung is comparably more than the other two ratios. Thermal efficiency of Briquette of 75% saw dust with 25% cow dung is higher than the other two ratios as well as raw bio mass of saw dust and it increases with increase in air flow rate. Moisture content of briquette of 75% saw dust and 25% cow dung is less than other two ratios in natural drying of briquettes. Calorific value of Briquette for 75:25 saw dust and cow dung is higher than the other two ratios. Pressure drop across the hopper increases with increase in the mass flow rate of air for different biomass material used. Composition of methane in producer gas is comparatively higher in briquette of 75% saw dust and 25% cow dung than other two ratios. References [1] Paulo R.Wanders,Carlos R.Altafini,Ronaldo M Barreto Assessment of a small sawdust gasification unit. Biomass and [2] Bioenergy 27, 467-476, 2004. [3] H.V.Sridhar, G.Sridhar Experience of using various biomass Briquettes in IBG (IISC BIORESIDUE GASIFIER),Indian Institute of science, Bangalore. [4] Savitri Garivait, Ulonwan Chaiyo, Physical and Chemical properties of Thai Biomass Fuels from Agricultural Residues, the second international conference on Sustainable Energy and Environment,2006. [5] Final report on the project powdery biomass gasifier CGPL,IISC, Bangalore,1999 [6] S.C.Bhattacharya.A study improved biomass briquetting,resources [7] and Development Asian Institute of Technology,Thailand. [8] Canburak sisman and Erhan Gezer.Effects of rice husk ash on characteristicsof the briqutte produced for masonary units.vol:6(4).p.p:784-99,2011. [9] Pattarporn Chairprasert, Tharapong vitidsant. Promotion of coconut shell Gasification by steam Reforming on Nickle- Dolomite, American Journal of Applied sciences, 6(2) : 332-336,2009. [10] Prokash C.Roy,Amitava Datta,Niladri chakraborty.assessment of cow dung as a supplementary fuel in a downdraft biomass gasifier.renewable Energy 3,379-386, 2010. [11] Zainal Z.A, Raifau AQuadier G.A, Seetharamu K.A.Experimental investigation of downdraft biomass gasifier. Biomass and Bio- energy; 23:283-9, 2002. [12] Anil K.Rajvanshi, Biomass Gasification, Director. Nimbkar Agricultural Research Institute. ISSN : 0975-5462 Vol. 3 No.11 November 2011 7966