Training programme on Energy Efficient technologies for climate change mitigation in Southeast Asia Biomass Gasifier: Principle and application
Biomass as a Fuel Age-old and most widely used fuel source Annual consumption was estimated to be of the order of 20 million tonnes a few years ago A Cheap, abundantly available fuel A very Clean fuel Biomass has no Sulphur content Short CO 2 fixation cycle Renewable
Why Biomass Gasification? Biomass Producer Gas Allows better process control and convenience Cleaner combustion in connected equipment Elimination of all pollution related to Biomass use Gasification is highly efficient process Can be applied over a range of output ratings (few to hundreds of kws) Can be used for thermal applications & electricity generation Low initial investment and cost of power production Biomass is CO 2 neutral fuel Organized biomass feedstock supply can contribute to rural livelihood and uplift of rural economy
Comparative energy cost for different fuels (For Q useful = 10,000 kcal/hr)
What is Gasification? Basic Process Chemistry Conversion of solid fuels into combustible gas mixture called producer gas (CO + H2 + CH4) Involves partial combustion of biomass Four distinct process in the gasifier viz. Drying Pyrolysis Combustion Reduction
Gasification Basic Process Chemistry Schematic
Biomass gasification
Types of gasifier Up-draft gasifier: Efficient but gives comparatively dirty gas, good for thermal applications Down-draft: Comparatively clean gas, good for power generation Cross draft: in between above two.
Producer Gas Properties
Comparison of producer gas characteristics Component Wood Gas (vol. %) Charcoal Gas (vol. %) Rice Husk gas (vol. %) Nitrogen 50 54 55 65 52-54 Carbon monoxide 17 22 28 32 20-22 Carbon dioxide 9 15 1 3 13-14 Hydrogen 12 20 4 10 10-12 Methane 2 3 0 2 Up to 4 Gas heating value KCal/m³ 1194-1409 1075-1338 > 1000 Rated gas production per kg husk : 2.1-2.5 Nm³ Gasification temperature : 900-1000 oc Fuel feed for 120 kw : 300 kg/hr Fuel feed for 58 kw : 150 kg/hr
Gasifier system performance specifications Biomass consumption < 1.3 kg/hr/kwe (woody biomass) < 2.4 kg/hr/kwe (non-woody biomass) Gas production 2 ± 0.2 Nm3 / hr/kwe Turn down ratio 3:1 Gas quality Tar<100 mg Nm3 Particulate matter <50 mg//nm3 Diesel replacement >65% Avg. CV from woody biomass >1075 KCal/NM3 Avg. CV from non woody biomass >955 KCal/NM3
Gasifier : Performance Rated Electrical output in KW 74.4 144 240 500 Wood/ rice husk consumption in kg/hr 57 106 169 320 Acceptable moisture content % < 20 < 20 < 20 < 20 Average gas calorific value (kcal/nm 3 ) 1100 1100 >1100 >1100 Gas flow required Nm 3 /hr 125 231 369 700 Thermal rating (000 kcal/hr) 50 260 660 1120 Diesel replacement (lt/hr) 13.85 25.73 41.1 83.7 Hopper capacity in kgs 150 500 1100 1500 Auxiliary power consumption in kw 1.5 7.5 11.2 15 Water requirement in lt/hr 250 Gas composition CO H 2 CH 4 CO 2 N 2 V/V % 16-22 16-20 < 3 7-13 50 Approximate price of gasifier (US $) 16667 34267 47111 81378 Total project cost ( US $ ) 26667 47044 65444 102489
Cost Economics of fuel replacement in Updraft gasifier
Cost Economics of fuel replacement in Updraft gasifier
Applications
Thermal use of producer gas Thermal energy of the order of 4.5 to 5.0 MJ/m 3. Flame temperatures as high as 1200 o C can be obtained by optimal pre-mixing of air with gas. Few of the applications: Dryers: Drying applications in farm products, food and spices industry like large cardamom, ginger, rubber and tea (Temp. requirement 80 130oC). Kilns: Baking of tiles, potteries(temperature requirement 800 950oC). Furnaces:For melting metals and alloys in non-ferrous (Temperature requirement ~650-1000oC). Boilers: Process industries, which require steam or hot water like silk reeling, dyeing, turmeric boiling, cooking, jaggery making etc.
Electricity generation from producer gas Electric power generation from few kw to MW, either for local consumption or for grid power To operate diesel engine on dual fuel mode with 80-85% diesel replacement To operate gas engine on 100% mode To operate water pumps for irrigation purpose
Range of applications
Schematic : Power generation mode
Schematic : Thermal mode (scrubbed gas)
Schematic : Thermal hot gas mode
Case :Gasifer based dual fuel power generation in rural areas, India Why gasifier based Dual fuel power generation is suitable for rural area? Employment issues : Diversion of excess manpower to rice husk transportation and preparation Utilization of the rice residues unsuitable for industrial processing Considerably lower costs per produced kwh electricity with wood-gas dual fuel than with diesel oil. Low capital cost involvement compared to even min/micro hydel project and no threat to ecological balance as in the case of every hydel project A renewable & clean non polluting fuel suitable for rural environment.
Operating Economics Diesel Dual fuel Diesel Dual fuel Diesel Dual fuel DG set capacity (KW) 74.4 144 240 Gross Heat Rate on LCV at standard reference conditions 2500 2625 2400 2520 2300 2415 Diesel fuel required in lt/hr 20.22 6.37 37.56 11.83 60 18.9 Qty. of bio-gasified gas required in NCM Equivalent wood mass kg/hr (70% DR) Available energy KWH (10% loss) per hour Available energy KWH per year (10 hr x 300 days) Cost of diesel per hour (@ Rs.35.50 per ltr) 124.29 230.92 368.84 56.9 105.71 168.84 66.96 66.96 129.6 129.6 216 216 200880 200880 388800 388800 648000 648000 717.81 226.14 1333.38 419.97 2130 670.95 US $ 15.95 5.03 29.63 9.33 47.33 14.91 Cost of wood per hour (@ Rs.2.5/kg) 142.25 264.275 422.1 US $ 0 3.2 0 5.9 0 9.4 Total running cost Rupees per hour 717.81 368.39 1333.38 684.24 2130 1093.05 US $ 15.95 8.19 29.63 15.21 47.33 24.29 Running Cost per unit (Rs. Per KWH) 10.72 5.5 10.29 5.28 9.86 5.06 US Cents 24 12 23 12 22 11
Capital Expenditure Diesel Dual fuel Diesel Dual fuel Diesel Dual fuel DG set capacity (KW) 74.4 144 240 Miscellaneous and commissioning cost 9556 12778 18333 Gasifier dual fuel project cost 26667 47044 65444 Bank loan 17778 31356 43622 Maintenance cost (Cents/kWh) 0.67 0.60 0.51 Interest cost per unit (cents/kwh) 1.29 0.73 0.60 Depreciation cost per unit (cents/kwh) 1.33 1.20 1.00 Cost of generation cents/kwh 12.00 12.00 11.00 Total cost (cents/kwh) 24 15.51 23.00 14.27 22.00 13.36 Benefit per unit (cents/kwh) 8.31 8.60 8.56
Payback period Diesel Dual fuel Diesel Dual fuel Diesel Dual fuel DG set capacity (KW) 74.4 144 240 Payback for 10 hours, 300 days operation Total yearly kwh generated and available 200880 388800 648000 Total savings per year by dual fuel operation (US $) 16689 0 33444 0 55444 Pay back period in months for total investment 19 17 13 Payback for 16 hours, 300 days operation Total yearly kwh generated and available 321408 622080 1036800 Total savings per year by dual fuel operation (US $) 26711 53489 88711 Pay back period in months for total investment 12 11 7
*Case : Tobacco curing, Myanmar Tobacco curing is a traditional industry practiced Tobacco plantations are traditionally livelihoods activity in and along the banks of Ayeyarwadi River. Tobacco planting period is from October to January. Tobacco leaves are to be cured within 72 hours after picking them up from the plants. The curing season is usually from February to May. There are about 108 tobacco plants running in Myingyan Township. * Project implemented by TERI India
Case.Contd. The maximum temperature needed is 80 C In curing of tobacco, hot air is used by passing through the flue pipes. Fuel wood consumption for one process is 7500 kg. At present, firewood, obtained by cutting and collecting the trees Prosopies, juliflora from the remaining natural forest.
Curing Plant : front View
Different views
Comparison between Traditional Method and Gasifier Method No Description Traditional Method Gasifier Method 1 Type of fuel Wood-fuel Biomass (Pigeon bean stalk) 2 Wt. of tobacco to be cured 3500 kg About 3500 kg 3 Total wt. of fuel required 7500-10000 kg 1600 kg 4 Working days for curing 5 6 days Max. 5 days 5 Total time of curing 110 hours 120 hours About 90 hours 6 Wt. of cured tobacco (expected) 500 550 kg About 575 kg 7 Labor requirement 3 5 workers 1 2 workers 8 Quality of output Good grades than traditional method
Case : Large cardamom drying Large cardamom is major cash crop of Sikkim Cardamom is small farmers business (more than 85% with small <2ha area) Still primitive smoking method used for in poor quality product Traditional bhatti system: low (5--10%) efficiency: huge fuel wastage (estimated wastage: 20,000 MT in Sikkim)
Improved system More than 60% fuel wood saving Retains 35% more volatile oil Retains natural colour (better appeal) Pays back itself in one curing season
Important lessons: Thermal Applications Introduction of a gasifier is not just an addition, but an integration (both technological and cultural) with the existing traditional/conventional practice Strong QA/QC (specially material selection, welding quality, casting and curing of high temperature insulation) needs to be enforced User education/training is critical for ensuring Use of properly sized/dried wood Safety Options for short term/long term linkages for sustainable biomass supply need to be explored
Important lessons: Gasifier power plant Major scope where biomass is produced in-situ e.g. rice mills High degree of social mobilization needed for running rural power plants sustainably. Tariff collection on a continued basis is a big challenge, which can probably be leveraged by livelihood and income generation activities (Needs substantial state support). The capital costs of establishing distributed generation and microgrids are about 50% higher than centralized power at present and can be brought down further. The economic costs of providing electricity to remote users are also comparable for both routes. Plant availability can be made as high as desired through training of local operators. Increasing the PLF, however, needs sustained efforts. Control of engine is largely manual. Servicing of engines and gasifier systems is a major cost item at present
Other implemented cases Wood/coconut shells/cashew shells/stalks etc replacing Wood Charcoal ENTERPRISE TYPE MICRO SMALL COMMUNITY Silk,Cardamom in India Nepal, Bhutan: Arecanut processing MgCl 2 ; PoP, Tobacco curing Green brick drying, Bamboo mat factory CO2 manufacturing Community cooking, Residential Hostels, Crematoria (D) Diesel/Furnace Oil Silk dyeing Rubber drying Canteens Bakeries Electricity Crematoria Water heaters in hostels LPG Other Fuels (tyres /rice husk) Sweet making Puffed rice
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