At its most basic, gasification is a process that takes place in a closed system using limited oxygen and high heat to convert a carbon-containing fuel into energy. It sounds like combustion but it's not. Traditional combustion, like what happens in a wood stove, uses a lot of oxygen to produce heat. Gasification uses only a small amount of oxygen with a lot of heat in a series of stages.
The 3 stages of gasification are:
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In the first stage, heat essentially “decomposes” the wood, coal, or biomass through a process called pyrolysis – a slow, smoldering fire. As the fuel vaporizes, smoke is created that enters into the secondary combustion chamber.
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During the second stage is where the magic happens. In this chamber, the perfect amount of air is introduced creating a fire that burns up to 2,000 degrees.
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The third stage releases the energy of the smoke and produces energy that is transferred to the water stored in the boiler.
By optimizing this process, gasification uses up to 95% of the fuel energy to provide heat where you need it.
A wood furnace burns best with wood with a moisture content of around 15-30%. While wood with a higher moisture content can be burned it will cause more tar and creosote build-up. Burning well-seasoned wood will help improve the efficiency and heating performance of your wood furnace.