a fluidized bed reactor and a method of operating same in which a bed of particulate material is supported on a grate in an enclosure . air is passed through the grate to fluidize the particulate material and promote the combustion of the fuel . at least one separating unit is disposed adjacent each of two walls forming the enclosure for receiving the mixture of air , the gaseous products of combustion and the relative fine particulate material entrained by the air and gaseous products of combustion . each separating unit operates to separate the particulate material from the mixture , and a distributor unit is associated with each separating unit for receiving the separated particulate material and distributing it to the bed at multiple locations .