Wood gas as engine fuel

Table of Contents

Mechanical Wood Products Branch
Forest Industries Division
FAO Forestry Department

The designations employed and the presentation of material in this publication do not imply the expression of any opinion whatsoever on the part of the Food and Agriculture Organization of the United Nations concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries.

ISBN 92-5-102436-7

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© FAO 1986

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Table of Contents


Chapter 1 - Introduction

1.1 Background
1.2 The present case for wood gasifiers
1.3 Overview of the contents of this publication
1.4 What to expect from a wood gasifier system

Chapter 2 - Small wood and charcoal gasifiers for operation of internal combustion engines

2.1 Fuelling of engines by producer gas

2.1.1 Possibilities of using producer gas with different types of engines
2.1.2 Engine power output using producer gas
2.1.3 Maximizing the power output in producer-gas operation
2.1.4 Resulting power output
2.1.5 Gas quality requirements for trouble-free operation
2.1.6 Use of Stirling engines or gas turbines with producer gas

2.2 Theory of gasification

2.2.1 Prediction of the gas composition
2.2.2 Gasifier efficiency

2.3 Types of gasifiers

2.3.1 Updraught or counter current gasifier
2.3.2 Downdraught or co-current gasifiers
2.3.3. Cross-draught gasifier
2.3.4. Fluidized bed gasifier
2.3.5 Other types of gasifiers

2.4 Gasification fuels

2.4.1 Need for selection of the right gasifier for each fuel
2.4.2 Energy content of the fuel
2.4.3 Moisture content of the fuel
2.4.4 Volatile matter content of the fuel
2.4.5 Ash content and ash chemical composition
2.4.6 Reactivity of the fuel
2.4.7 Particle size and size distribution
2.4.8 Bulk density of the fuel
2.4.9 Charring properties of the fuel
2.4.10 Assessment of the suitability of various types of biomass as gasifier fuel

2.5 Design of downdraught gasifiers

2.5.1 Processes occurring in the down-draught gasifier
2.5.2 Design guidelines for downdraught gasifiers

2.6 Gas cleaning and cooling

2.6.1 Cleaning dust from the gas
2.6.2 Gas cooling

2.7 Applications of biomass gasification

2.7.1 Production of fuel gas
2.7.2 Production of mechanical or electrical power in stationary installations
2.7.3 Mobile applications

2.8 Health and environmental hazards associated with the use of producer gas

2.8.1 Toxic hazards
2.8.2 Fire hazards
2.8.3 Explosion hazards
2.8.4 Environmental hazards

Chapter 3 - Recent Swedish experiences with operation of vehicles on wood and charcoal gas

3.1 Overview of development work and testing carried out at the national machinery testing institute

3.1.1 Scope of the work
3.1.2 Gasifier for wood chips
3.1.3 Fibre glass fabric filter system
3.1.4 Conversion of diesel engines to producer gas operation
3.1.5 Tests with different fuels

3.2 Experiences gained from conversion and operation of modern vehicles

3.2.1 The need for continued practical tests
3.2.2 Conversion and operation of a Massey Ferguson 1100 farm tractor
3.2.3 Conversion and operation of a Scania truck
3.2.4 Experiences related to service, maintenance and equipment failures

3.3 Producer gas vehicles recently operated in other countries

3.4 Economic evaluation of operation of vehicles on wood gas

3.4.1 The case for wood gasifiers
3.4.2 Method used for the economic evaluation
3.4.3 Economic baseline assumptions
3.4.4 Marginal costs for the wood gasifier system
3.4.5 Economy of a producer gas tractor
3.4.6 Economy of a producer gas truck

3.5 Feasibility of using the vehicle gasifier technology for stationary applications

3.6 Operating hazards

Chapter 4 - A small wood gas power plant at a sawmill in Paraguay

4.1 Description of the wood gas power plant

4.1.1 Fuel supply
4.1.2 The wood gasifier
4.1.3 Wood gas cooling and washing installations
4.1.4 Wood gas filter
4.1.5 Engine and electric generator

4.2 Operating experience

4.2.1 Fuel consumption
4.2.2 Manpower employed and operating procedure
4.2.3 Safety
4.2.4 Environmental impact

4.3 Economic evaluation

4.3.1 Capital investment
4.3.2 Operation and maintenance costs
4.3.3 Fuel costs
4.3.4 Total operating costs
4.3.5 Costs for electricity generation for family homes of sawmill personnel
4.3.6 Comparison with other alternatives for the electricity supply

Chapter 5 - A small gasifier power plant in Sri Lanka

5.1 Description of the plant

5.1.1 General system layout
5.1.2 The gasifier
5.1.3 Cyclone
5.1.4 Impingement separator
5.1.5 Glass fibre cloth filter
5.1.6 Cooler
5.1.7 Engine and alternator
5.1.8 Start-up fan and flare
5.1.9 Safety devices
5.1.10 Auxiliaries

5.2 Operational procedures

5.2.1 Start-up
5.2.2 Closing down
5.2.3 System maintenance

5.3 Operational experience

5.3.1 Operating record and observations on the performance
5.3.2 Disturbances of the operation
5.3.3 Desirable modifications

5.4 Economic evaluation of electricity generation costs at Giriulla mill

5.5 Concluding remarks

Chapter 6 - A 1.4 MW wood gas fuelled power plant in Paraguay

6.1 Historical background of the gasifier installations
6.2 Wood-fuel supply and preparation
6.3 Description of the down-draught gasifiers
6.4 Electricity production with the gas engine alternator sets
6.5 Operating experiences
6.6 Profitability of using wood gas at Loma Plata

Chapter 7 - The future of wood gas as engine fuel

7.1 Prerequisites for extensive use of wood gasifiers
7.2 Industrialized countries
7.3 Developing countries
7.4 The need for international cooperation

Appendix 1 - Calculation of the power output of a producer gas engine

Appendix 2 - Design calculation of downdraught gasifier

Table of conversion factors and symbols (used in this manual)