Wood v.s. Charcoal
Greenwood
|
|
Wood v.s. CharcoalGreenwood |
I have compared wood feed against charcoal feed keeping the diameter of the reactor same.
1.Biomass Feed Analysis
For comparison purposes, performance of dried wood containing 20 wt. % of water was estimated.
|
20 % Water Wood Analysis (wt. %) |
Charcoal Analysis (wt. %) |
| Carbon | 35.8 | 88.4 |
| Hydrogen | 4.7 | 0.1 |
| Oxygen | 36.6 | 2.5 |
| Water | 20.0 | 6.0 |
| Ashes | 3.0 | 3.0 |
2.Equipment Specifications
| Items | Unit | 20% Water Wood | Charcoal |
| Adiabatic Reaction Temperature | deg. C | 1,300 | 1,200 |
| Thermal Conductivity of Insulation | kcal/deg. C/m/h | 0.12 | 0.12 |
| Insulation Thickness | mm | 28.7 | 255 |
| Engine Size | cc | 609 | 210 |
| Engine Speed | rpm | 3,600 | 3,600 |
| Engine Type | cycle | 4 | 4 |
3.Performance
Wood showed far superior characteristics for both power output and thermal efficiency.
Due to the lack of oxygen in charcoal, addition of air is needed. As a result, nitrogen dilute flammable gas. It is possible to raise reaction temperature up to 1000 deg. C by applying more insulation.
Gassifier conversion efficiency of charcoal becomes 50% which is lower than any wood case of 77.5%. If you add energy loss of 40% during charcoal manufacturing process, overall efficiency is much lower. It is a waist of biomass.
Adiabatic reaction temperature of wood containing 20% water is over 1,300deg. C, while that of charcoal is 1,200deg. C. In the case of half dried wood containing 30 % water, adiabatic reaction temperature becomes 650 deg.C.
Gas from charcoal contains 46mol% CO and 1mol% Methane.
| Items | Unit | 20% Water Wood | Charcoal |
| Wood Consumption | kg/h | 15 | 3 |
| Batch Volume | kg | 54.3 | 20.4 |
| Batch Duration | h | 3.6 | 6.8 |
| Air Feed Rate | m3/h | 0 | 10.7 |
| Gas Heating Value | kcal/Nm3 |
3,443 |
836 |
| Air/Gas Ratio (Excess Air 5%) | vol./vol. |
3.49 |
0.6 |
| Gas Air Mixture Intake Volume | Nm3/h |
64.9 |
20.1 |
| Flammable Gas Contents | % | 15.1 | 16.2 |
| Lower Flammability Limit | % | 6.3 | 12.2 |
| Higher Flammability Limit | % | 50.6 | 71.9 |
| Total Gas Energy | kW | 57.8 | 12.2 |
| Biomass Heating Value | kcal/kg | 4,276 | 6,996 |
| Gassifier Conversion Efficiency(Gas Energy/Biomass Energy) | % | 77.5 | 50 |
| Engine Efficiency | % | 33.6 | 30.5 |
| Engine Power Output | PS | 26.4 | 5.05 |
| Engine Power Output/Biomass Quantity | PS/(kg/h) | 1.76 | 1.68 |
| Engine Power Output/Engine Cylinder Volume | PS/cc | 0.043 | 0.024 |
May 6, 2003
Rev. April 27, 2004