Circulating fluidized bed combustion - The technology exact for Estonian oil shale

The development of conventional bubbling fluidized bed (BFB) combustion between 1950 and 1960 led to the workout of a new type of fluid-bed process - circulating fluidized bed (CFB) combustion. The circulated fluidized bed combustion owns its name from the idea of rapid continuous circulating of ash particles in the system combustor - recycling cyclone. Due to the considerably fine particle size of fuel and high gas velocity the ash, the product of fuel burning, is carried out from the combustor with flue gases. Hot flue gases and fly ash are separated from coarse ash particles in a recycling cyclone. Coarse ash particles, the ''circulating ash'', captured by the recycling cyclone are returned into the combustor. Leadership in the development of CFB technology between 1975 and 1985 belonged to the European firms Lurgi Lentjes Babcock (LB, Germany) and Research and Development Center of Ahlstrom (Hans Ahlstrom Laboratory, Finland; since 1995 Foster Wheeler).