Fluidized bed reactor and process for the operation of a fluidized bed reactor

In a continuous process for the operation of a circulating, fluidized bed reactor, by which a solid particle material including a solid reactant material is introduced into a lower part of the reactor and is formed into a fast bed by means of a fluidization gas containing a gaseous reactant material introduced into the lower part of the reactor, while any non-reacted particles of said solid reactant material are continuously discharged from an upper part of the reactor and recirculated to the bed, a predetermined fraction of said solid particle material being present in the reactor is removed from at least one site of the bed positioned below said upper part of the reactor, is first subjected to substantial thermal teatment by being brought into heat-exchanging contact with heat-exchanging means in a space peripheral to the reactor, said space having confinements forming an integral part of the reactor, and said predetermined fraction including any unreacted solid particle material is then directly recirculated by continuous free gravitational fall to at least one lower positioned site of the reactor.