US 4,076,796 AGranted

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

AssigneeMetallgesellschaft Aktiengesellschaft

InventorsLothar Reh, Hans-Werner Schmidt, Ludolf Plass

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Abstract

Endothermic processes are carried out in a fluidized-bed reactor which is connected to a holding reactor, solids being recirculated between the two reactors. The primary fluidized-bed reactor uses a fast-fluidized bed system in which the solids concentration decreases continuously from the bottom to the top of the reactor. After the necessary residence time in the holding reactor, solids are discharged. Solids are entrained with the gas stream from the primary reactor and are separated therefrom to be delivered to the holding reactor. The reaction is controlled by regulating the rate of recirculation of solids from the holding reactor to the fast fluidized bed reactor.

Claims11

Dependent claims

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;
(d) withdrawing particles from the cycle formed by said fluidized-bed reactor and said holding reactor in a partial stream;
(e) maintaining the particles in said holding reactor for a residence time in excess of the residence time of the solids in said fast fluidized-bed reactor;
and
(f) maintaining a substantially constant temperature in both said reactors by regulating the rate at which particles are fed in step (c) from said holding reactor to said fast fliuidized-bed reactor, said rate being regulated by varying the flow cross section of said passage between said overflow point and a low point of said fluidized-bed reactor.

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Abstract

(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;
(d) withdrawing particles from the cycle formed by said fluidized-bed reactor and said holding reactor in a partial stream;
(e) maintaining the particles in said holding reactor for a residence time in excess of the residence time of the solids in said fast fluidized-bed reactor;
and
(f) maintaining a substantially constant temperature in both said reactors by regulating the rate at which particles are fed in step (c) from said holding reactor to said fast fliuidized-bed reactor, said rate being regulated by varying the flow cross section of said passage between said overflow point and a low point of said fluidized-bed reactor.

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