Bubbling fluidized bed boilers (BFB) are often preferred in small-scale applications, with fuels having low heat value and high moisture content. Boiler efficiency figures (over LHV) are normally over 90%. Biomass fuels such as wood, wood chip and fallen leaves are fluidized in high pressure and temperature. The modern bubbling fluidized bed (BFB) CHP boilers are designed for high efficiency and availability combined with low emissions. This will give the power plant owner an excellent return on investment even using very low quality biomass with water content up to 65%. BFB power plant utilizes various materials such as wood wastes, wood chips, wood pellets, waste paper and PVC as fuels while the fuels for the current Combined Heat & Power plants on the market are limited to coal, RDF or wood pellet. It also keep the rule of European exhaust regulations known as the strictest in the world. The efficiency of the plant exceeds 90% thanks to high efficiency boiler and strong steam engines. It is an alternative solution to current powerplants.
The boiler technology is based on a modern membrane wall, natural circulation boiler with a bubbling fluidizing bed grate. The BFB grate has no moving parts and can accept impurities like metal, stones and concrete in the biomass. The impurities are removed during the operation though the grate openings. The temperature in bubbling fluidizing bed is 800~900°C high and 500–800 mm layer of natural sands or other ceramic materials are piled up at the bottom, in which fuels are fluidized with primary air from nozzles under the grates.