Limiting the amount of oxygen available for the reactions results in The final result is a syngas which has CO, H 2 and CH 4 as its major combustible components. The dried wood chips are fed into the gasifier and air is injected, fluidising the bed and providing oxygen for the gasification process. The turbulent flow in the fluidised bed promotes the intimate mixing required for rapid and complete conversion of the wood into syngas. The gas produced contains particulates and small amounts of tars and some impurities. The particulates, comprising bed material and particles of unburnt wood and ash, are separated out by a cyclone and recycled back to the gasifier.
Wood ash is removed from the base of the gasifier.
Step 3, Gas Cleaning. The gas produced must be cleaned of tars and impurities before it can be used in the generating plant. Tars are heavier hydrocarbons that could condense later in the process causing clogging of the pipework or damage to the gas turbine. The tars in the gas are converted in the cracker. This is a second CFB operating at a slightly higher temperature with dolomite, a naturally occurring magnesium limestone mineral, as the bed material.