Wood gas generator

A wood gas generator often known as a gasifier, is a wood-fueled gasification reactor mounted on an internal combustion engine, to provide a wood gas, a form of syngas. These devices are also known as gas producers.

History

Shortages of petroleum-based fuels during World War II resulted in very large numbers of such generators, often improvised. Commercial generators were in production before and after the war, for use in special circumstances or in distressed economies. Production skyrocketed during the war.

Gasification was an important and familiar 19th century technology, and its potential and practical applicability to internal combustion engines were well-understood from the earliest days of their development. Town gas was produced as a local business, and experience in the trade was very widespread; most practicing technical people would know a good deal about it. When stationary internal combustion engines became available, they were commonly fueled by town gas during the early 20th century.

By the time World War II arrived, town gas production had been displaced by petroleum gas, but older people remembered both town gas and gas-fueled engines, and wood gas generators were in active production.

World War II era wood gas generators were of the "Imbert" type. They was designed around 1920 by French inventor Georges Imbert.Usually, wood gas generators burn wood, but improvements to efficiency and energy-density are possible, by using charcoal instead.

Modern generators

With rising oil prices, wood gas generators are coming back. The US Federal Emergency Management Administration published a book, " [http://www.global-greenhouse-warming.com/support-files/wood_gas_generator.pdf "Construction of a Simplified Wood Gas Generator for Fueling Internal Combustion Engines in a Petroleum Emergency"] ", in March 1989, describing a different design called the "stratified downdraft gasifier". It solves several drawbacks of earlier types.

The FEMA wood gas generator is (by definition of the FEMA manual) an emergency gasifier. It is designed to be rapidly assembled in a true fuel crisis. While this simplified design and departure from the standard European design does have some distinct benefits (ease of refueling and construction), it also has a host of new problems. The lack of a fixed oxidization zone allows the oxidization zone to creep to a larger area, causing a drop in temperature. The lower temperatures lead to tar production. It also lacks a true reduction zone further increasing this designs propensity to produce tar. Tar in the wood gas stream is considered a dirty gas and tar will gum up a motor quickly, possibly leading to stuck valves, and rings. The FEMA unit does not have a proven track record of being a reliable unit. In fact most successful wood gas generators in use in Europe and the United States are some variation of the imbert. The United Nations produced the FOA 72 document " [ftp://ftp.fao.org/docrep/fao/t0512e/t0512e00.pdf] ". It has a wealth of information on wood gas generators design and construction.

A project about the energy future of Europe was begun in 2005 in Güssing, Austria with contribution of European Union research furtherance. The project consisted of a power plant with a wood gas generator and a gas engine to convert the wood gas into 2 MW electric power and 4.5 MW heat. At the wood gas power plant are also two containers for experiments with wood gas. In one container is an experiment to convert wood gas, using the Fischer-Tropsch process, to a diesel-like fuel. By October 2005, it was possible to convert 5 kg wood into 1 litre fuel.

Disadvantages

The disadvantages of wood gas generators are: large size, slow to start (build a fire), and the batch-burn operation (of some designs). When not carefully designed and used, deaths have occurred because wood gas contains a large percentage of deadly carbon monoxide (CO) gas.

Carbon monoxide is one of the primary fuel-gases produced during gasification: it is an intentional fuel-product, and is subsequently burned in the engine (or other application) along with the other fuel-gases.

Media coverage

In 2008, an example of designing and constructing a working wood gas generator powered truck was shown on the National Geographic Channel's "Planet Mechanics" in the eighth episode, "Tree Powered Car".cn

ee also

* "Holzbrenner Strength through Joy Wagon" (Volkswagen Beetle, 1940-1945)

External links

* [http://www.woodgas.net Woodgas powered trucks and cars in the United States]
* [http://youtube.com/watch?v=jwR18kILPWQ Intro of the Planet Mechanics episode 'Tree Powered Car' on You tube describing how to make wood gas generator]
* [http://live.pege.org/2005-wood Wood gas generator power plant in Güssing Austria]
* [http://car.pege.org/2005-wood Experiment to make a Diesel like liquid fuel out of wood gas]