Break your dependence on oil! This is probably not very practical in our modern society, but, if all you have is a car with no gas and a pile of wood…
Florida Cooperative Extension Service
University of Florida
School of Forest Resources and Conservation
K. M. Eoff
D. M. Post
Originally published by the Florida Cooperative Extension Service, University of Florida, Institute of Food and Agriculture Service in 1980.
The University of Florida’s School of Forest Resources and Conservation began to study the gasification of wood and other biomass early in 1979. The initial project was to power an internal combustion engine on woodgas to demonstrate the possibilities of the process. A six cylinder Chevrolet pick-up truck was converted to operate on woodgas as a mobile demonstration unit. Since that time, the School of Forestry Resources and Conservation has joined with other IFAS fculies to develop other application of gasification technology. This report describes the gasifier system that was developed for the truck.
Gas generated from wood or coal has been used to power internal combustion engines since their invention. However, the use of liquid petroleum fuels has displaced the use of woodgas in engines almost completely. Some reasons for this are listed below:
1. Storage. Liquid fuels has advantages in storage and transfer through the system.
2. Energy content. For the same volume or the same weight petroleum fuels provide more energy that wood.
3. Start up time. For most petroleum fuels the start up time is negligible; It takes 10-15 minutes, to generate engine gas from wood even in the smallest installations.
4. Maintenance. The gas generator, cooler and cleaners require considerable maintenance not required with liquid fuels (neglect of the filters will lead to engine damage).
5. Power. An engine without modification operated on wood gas produces only about half the power of the same engine using gasoline.
6. Danger. Wood gas is typically 20% carbon monoxide, an odorless, colorless, tasteless and very poisonous gas. Many people have been killed by carless use of wood gas generator. The gas generator system should never be operated in a closed space and any excess gas should be burned before it is released into the atmosphere.
Even considering these disadvantages, the current need to conserve petroleum fuels makes the use of wood gas a viable alternative in certain applications. These applications include powering gasoline engines as is illustrated here and also the gas generated from wood or other biomass can be used for space heating or drying operations.
A down draft wood gas generator for producing engine grade gas is illustrated in figure #1. Air enters the generator through the air inlets, passes through the air manifold and is distributed to the fuel by the nozzles. Heat from the burning of fuel in the combustion zone produces charcoal from the wood above by driving off water vapor and volatile components. Excess water and a small amount of tar or creosote which condenses on the sides and top of the fuel hopper is caught in the condensate trap. Otherwise, everything produced from the wood is forced down through the combustion zone and burned. All the oxygen in the air that enters the generator should be used in the combustion zone so that no oxygen enters the
reduction zone below the choke plate. In the reduction zone carbon in the hot charcoal combines chemically with carbon dioxide and water vapor to produce the fuel gases carbon monoxide and hydrogen. The gas leaving the generator should be about 20% carbon monoxide, 20% hydrogen, 10% carbon dioxide and 50% nitrogen plus traces of other gases, vapors, soot, ash and water vapor. It is the purpose of the coolers and cleaners to remove any component of the fuel gas which would damage the engine.
The gasifier illustrated in figure #4 will operate for 1 to 2 hours on a fuel charge of 100 pounds. The fuel should be small wood blocks no bigger than a 6″ piece of 2 x 4. From the generator the gas passes thru a cyclone seperator (figure #5) which removes approximatly 75% of the particulate matter from the gas. The gas is cooled and the cleaning is finished in the cooler and cleaning unit (figure #6). In the cooling process excess water vapor is condensed and removed from the gas and the density and hence the energy content is increased. From the cooler the gas goes to the Mixing Box (figure #7) where it is mixed with an equal volume of air before it is drawn into the engine. The exhaust emissions from this system have not been analyzed and the long term effects on the life of the engine operating with this clean up system are unknown.
The system illustrated in figures #2 through 7 was built as quickly and cheaply as possible and was used to power a pick-up truck to demonstrate the potential of wood gasification. To that end it has been successful. However, the design of the system was largly determined by the materials that were available and certainly does not represent an optimun design.
The gasifier illustrated is suitable for an engine of 250 to 350 cubic inches displacement. However, anyone interested in a wood gas system for anything other than a hobby or as a curiosity should not copy this system but refer to the thechnical literature or contact a firm specializing in this equipment. A list of such firms and a bibliography of selected gasifier articles is included (not included in this online version).
Copyright belongs to original authors.
Copyright 2007, all rights reserved.