Wood v.s. Charcoal

Greenwood

 

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


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