Carrying out endothermic processes in fast fluidized reactor with conventionally fluidized holding reactor

Claim 1

In a method of carrying out an endothermic process involving a solid other than the thermal decomposition of aluminum chloride hydrate followed by calcination, wherein solids capable of endothermic reaction are treated in a fast fluidized-bed reactor supplied with secondary air introduced by an inlet at a level above a gas distributor, particles of the solids are entrained from the bed in a gas stream, and said particles are separated from the gas stream and are at least in part returned to the fast fluidized-bed reactor, the improvement which comprises: (a) introducing the gas stream together with the entrained particles from said fast fluidized-bed reactor into a holding reactor for separation in an upper position thereof; (b) fluidizing the separated particles in said holding reactor in a bed with a fluidizing gas introduced into said holding reactor at a velocity such that the solids occupy at least 35% of the volume of the bed of said holding reactor; (c) feeding particles from an overflow point of a lower portion of said holding reactor via a descending passage into said fast fluidized-bed reactor in a recirculation cycle at a rate sufficient to maintain a predetermined density of solids in said fast fluidized-bed reactor, said predetermined density of the solids in said fast fluidized-bed reactor corresponding to a solids volume of 2 to 20% of the volume of said fast fluidized-bed reactor between said gas distributor and said level and to a solids volume of 0.2 to 2% of the volume of said fast fluidized-bed reactor above the secondary-air inlet;