Patent ID: 7543553

Claim:
A circulating fluidized bed boiler comprising: a furnace which combusts a fuel which is fluidized together with a bed material, a cyclone dust collector into which flue gas which is generated by a combustion in the furnace is introduced and which catches particles; a seal box into which the particles which are caught by the cyclone dust collector are introduced, an external heat exchanger which is arranged downstream of the seal box, a separation loop which separates corrosive components from said particles so as not to introduce the corrosive components to said external heat exchanger in said seal box and said separation loop comprising a duct path having an inlet through which said corrosive components which are originated by the combustion of said particles and air are carried to said furnace; and a duct which connects an upper portion of the external heat exchanger with the furnace and through which the particles are returned to the furnace, wherein said seal box is separated into a plurality of compartments, one of which is located most downstream and which contains said external heat exchanger, and including upstream of said most downstream compartment, at least two compartments with the more upstream of the two compartments receiving the particles from the dust collector and an intermediate compartment that is vertically aligned with the inlet into the duct path of the separation loop.