This gas can be burned directly in a furnace to generate process heat or it can fuel internal combustion engines, gas turbines, or fuel cells. In a fluidized bed gasifier, a gas stream passes vertically upward through a bed of inert particulate material to form a turbulent mixture of gas and solid.
Fuel is added at such a rate that it is only a few percent by weight of the bed material.
Fluidized beds are gaining favor as the reactor of choice for biomass gasification. The high thermal mass of the bed imparts a high degree of flexibility in the kinds of fuels that can be gasified, including those of high moisture content. Disadvantages include relatively high exit gas temperatures, which complicates efficient energy recovery, and relatively high amounts of impure particles in the gas due to the abrasive forces acting within the fluidized bed. Although gasifier-engine systems have been demonstrated, they can be difficult to operate, are only moderately reliable, and have lifetimes of only 10 years. They also pose a potential threat of carbon monoxide poisoning.