ENGINEERING
From woodchips to woodgas
Wood gasification devices utilize a pyrolytic process to convert woodchips to a combustible gas called wood gas, generator gas or producer gas. This gas can be fed to an internal combustion engine, which delivers mechanical energy for driving an electric generator.
The benefit of it: electric energy can be gained economically by cogeneration power plants, this high efficiency can be reached even with very small devices of only a few kilowatts.
The gasification pyroloytic process is based on the principal of the incomplete combustion, i. e. substoichiometry or deficiency of oxygen.
In case of adding oxygen to it, wood can burn as in a boiler. The result of the gasification process is a gas mixture including the following combustible components: carbon monoxide, hydrogen and methane.
Four processes form a flowing transition from woodchips to wood gas in the wood gas reactor.
1. Drying
In the drying zone the water content of the wood evaporates at a temperature of over 100 ° C.
2. Oxidation zone
Preheated air is added into the oxidation zone, the heat rises up to approximately 400 – 500 ° C, the light volatile components of the wood chips escape and start burning, rising up temperature to the maximum of 1300°C
3. Pyrolysis zone ( Reduction zone)
When the whole amount of oxygen is used up no further rise in temperature is possible. The consequence of high temperatures with no oxygen is a pyrolysis process which cracks charcoal and long chained hydrocarbon products as wood tar. Here, charcoal is largely consumed and the desired combustible gases like carbon monoxide (CO) methane and oxygen are formed.
At the end of this zone tar-free wood gas is the result, this is important because tar elements damage the engine.
4. Relaxation zone
The gas velocity is lowered and the temperature decreases to save the grate from overheating.
The so obtained dusty gases are then freed of dust, are cleaned, accordingly cooled and fed into the block heat and power plant.
You can send a message around the world in one-fifth of a second, yet it may take years for it to get from the outside of a man's head to the inside.
