It is the boiler that uses a specific technology called ‘Circulating Fluidized Bed Combustion (CFBC)’.
This is one way of burning pulverised coal in electricity generation plant. The coal is burnt in a bed of hot particles maintained in flowing air. At adequately high air speed, the bed acts as a fluid resulting in rapid mixing of the particles. The fluidised action promotes complete coal combustion at relatively low temperatures, and provides a means to transfer combustion heat efficiently from the bed to the steam tubes.
Boiler in which coal is burnt in an environment of high concentration of bed material (mineral matter) derived from combustion of coal retained by using cyclone / other means. This bed material is fluidized by primary air (a part of combustion air).
The high concentration of bed material along with staged air supply ensures that bulk combustion temperatures do not exceed 950°C making it environment friendly (lesser production of NOx) means of utilizing coal.
It adopts a process different from Pulverized Fuel where coal is milled to fine powder ( similar to talcum powder) and fired. The concentration of ash is dependent of coal ash (mineral matter) content and ash (mineral matter) goes along with flue gases out of the boiler. In CFBC boiler, this ash (mineral matter) is separated using a cyclone or similar device and RECYCLED back and hence termed as CIRCULATING fluidized bed.