Project Summery
- Client: Samson Industries Ltd, a subsidiary of the DSI group
- Industry: Export Quality Rubber Products Production
- Application: Boiler Retrofit
- Fuel Type Replaced: HFO
- Fuel Rate Replaced: 45 liters/hour
- Monthly Fuel Replacement: 27,000
- Total Operational Months: 10
- Operational Since: June 2007
- Gasifier Model: WBG-350
- Thermal Rating: 1050 kW
- Fuel Wood (Gliricidia) Consumption Rate: 350kg/h
- Monthly Fuel Wood (Gliricidia) Consumption: 210 ton
- Steam Generation: 2 ton/hour
Samson Industries Ltd, a subsidiary of the DSI group, is a leading rubber producer in Sri Lanka. The factory, located in Bogahagoda, Galle District, have been operating a WBG-350 thermal gasifier since June 2007. A steam boiler of capacity 2 ton/hr was retrofitted to operate on SynGas. The retrofit was done by installing a gasifier and replacing the HFO burner with a SynGas burner. Before the gasifier was installed, the factory used to consume over 45 liters of HFO per hour and over 25,000 liters of HFO per month. At present, the factory operates the gasifier 24 hours, replacing an equivalent of 27,000 liters with 210 ton of Gliricidia fuel wood per month.
WBG 350 gasifier at Samson Industries
Boiler Retrofit
the existing diesel burner was replaced by a SynGas (see bellow) burner. since the flame temperature of SynGas is much lower than that of furnace oil, the boiler was de-rated by about 75%. this is one of the main disadvantages in boiler retrofits.
samson industries had two options:
- purchase a new biomass fired boiler
- retrofit the furnace oil boiler
cost wise the purchasing a biomass boiler is considerably cheaper. however, the retrofit option gives the versatility of operating the same boiler with furnace oil. there were no changes done in the steam circuits. in fact the only change done to the whole steam system was replacing the boiler burner. samson industries thought this option is a low risk option, although they could have purchased a brand new boiler for the price of the gasifier
What is a Gasifier?
A Gasifier converts a solid fuel (like wood or coal) to a gaseous fuel. This gas is called SynGas / Producer Gas. SynGas produced off biomass (such as wood and paddy husk) is called SynGas. The combustible components of SynGas are mainly (~20% each) hydrogen and carbon monoxide.
Colombo Town Gas
Colombo's gas supply was once powered off several coal gasifiers. The gas produced from coal gasification was then called Town Gas. The Gas Paha Handiya was a distribution location for Town Gas.
Solid Fuels vs Gaseous Fuels
Gaseous fuels are preferred to solid fuels as they have better combustion performances. Also gaseous fuels can be transported via pipelines from the point of generation / storage to where it is consumed as opposed to solid fuels where they have to be transported via conveyors or trucks!. Well one main drawback of using gaseous fuels is that it must be handled safely. SynGas consists of H2 and CO, which can easily be ignited by a small spark.
SynGas Flame produced by the specially designed burner. Adiabatic Flame temperature: 1100°C
SynGas
Typical Dry Gas Composition (%)
- CO: 19 - 22
- CO2: 10 - 13
- N2: 50
- H2: 18 - 20
- CH4: 3
Typical Wet Gas Composition (%)
- H2O: 8 - 10
- CO: 17 - 12
- CO2: 13 - 15
- N2: 44 - 42
- H2: 18 - 19
- CH4: 2
SynGas Heating Value
Heating Value: 4.3 MJ/m3 at STP
SynGas is a low energy density gas, like methane. So combustion science is different to that of LPG or Diesel.
Gasifier Performance
Typical gas flow rate of reactor type down-draft gasifier (like the WBG 350) is 2.5-3.0 m3/h.kg wood. That is WBG 350 will have a gas flow rate of 875-1225 m3/h
The conversion efficiency of a WBG-series gasifier ranges from 75-85% depending on the mode of operation and how clean (free of char) the gas is. That is, 75-85% of the energy contained in the wood gets transfered to SynGas. About 10% is consumed in the exothermic reactions, 5-15% is lost as heat / entropy
Gasification Chemistry
The Chemistry
Biomass consists of (by mass, on dry ash free basis): 50% Carbon, 6% Hydrogen and 44% Oxygen
Represented Chemical Formula: CH1.44O0.66
Combustion
Heat for the pyrolysis reactions and reduction reactions (see bellow) is obtained when char, tar and biomass combusts with oxygen. The combustion zone is the hottest region in the gasifier.
C + O2 → CO2 + heat
Pyrolysis
Biomass is decomposed under a zero (or very low) level oxygen environment to form char and tar (and traces of methane, carbon monoxide, carbon dioxide and hydrogen which we are not too worried about as they are in minute quantities).
C + heat → char + tar + CH4 + other hydro carbons
Reduction Zone
There are several intermediate reactions which contributes in forming the Producer Gas mixture. Composition of carbon monoxide, hydrogen and methane will depend on the rates of these intermediate reactions.
C + H2O + heat → CO + H2
C + 2H2 → CH4 + heat
3H2 + CO → CH4 + H2O + heat
H2O + CO → CO2 + H2 + heat
4H2 + CO2 → CH4 + 2H2O + heat
There are other reactions which takes place, but the above reactions are the most significant.
energy savings from switching to gliricidia
1 kg of gliricidia replaces 4kg of hfo / diesel / lpg
replacing diesel
energy calculation
- 1 liter of diesel = 4 kg of gliricidia biomass
- diesel burners have a combustion efficiency of about 85%
- dual fuel burners have a combustion efficiency of about 70%
- diesel has a heating value of 42 MJ/kg with a density of 0.851 kg/liter
- to produce 1MJ of heat 33 milliliters of diesel are required
- biomass gasifiers operate at 80% thermal efficiency
- biomass fuel-wood - gliricidia has a heating value of 13.5 MJ/kg (20% moisture)
- to produce 1MJ of heat 132 grams of gliricidia are required
- 1 liter of diesel can be replaced by 4 kg of gliricidia biomass
savings in energy cost
- 1 liter of diesel sells at rs 80
- 1 kg of gliricidia biomass sells at rs 8.25
- by switching from diesel to gliricidia biomass saves you rs 46.85 per liter of diesel
- 59% of your thermal energy cost can be reduced by switching from diesel to gliricidia biomass
replacing HFO
basic energy calculation
- 1 liter of HFO = 4 kg of gliricidia biomass
- HFO burners have a combustion efficiency of about 85%
- dual fuel burners have a combustion efficiency of about 70%
- HFO has a heating value of 40 MJ/kg with a density of 0.9 kg/liter
- to produce 1MJ of heat 33 milliliters of HFO are required
- biomass gasifiers operate at 80% thermal efficiency
- biomass fuel-wood - gliricidia has a heating value of 13.5 MJ/kg (20% moisture)
- to produce 1MJ of heat 132 grams of gliricidia are required
- 1 liter of HFO can be replaced by 4 kg of gliricidia biomass
savings in energy cost
- 1 liter of HFO sells at rs 61.7
- 1 kg of gliricidia biomass sells at rs 8.25
- by switching from HFO to gliricidia biomass saves you rs 28.31 per liter of HFO
- 46% of your thermal energy cost can be reduced by switching from HFO to gliricidia biomass
replacing LPG
basic energy calculation
- 1 kg of LPG = 4 kg of gliricidia biomass
- LPG burners have a combustion efficiency of about 85%
- dual fuel burners have a combustion efficiency of about 70%
- LPG has a heating value of 45 MJ/kg
- to produce 1MJ of heat 26 kg of LPG are required
- biomass gasifiers operate at 80% thermal efficiency
- biomass fuel-wood - gliricidia has a heating value of 13.5 MJ/kg (20% moisture)
- to produce 1MJ of heat 132 grams of gliricidia are required
- 1 kg of LPG can be replaced by 4 kg of gliricidia biomass
savings in energy cost
- 1 kg of LPG sells at rs 130
- 1 kg of gliricidia biomass sells at rs 8.25
- by switching from LPG to gliricidia biomass saves you rs 96.61 per kg of LPG
- 74% of your thermal energy cost can be reduced by switching from LPG to gliricidia biomass
Pictures
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