Apparatus for the thermal conversion of gypsum
AssigneeRhone-Poulenc Industries
InventorsAlain Charlet, Jean-Paul Coquery, Francois Mounier
Life of this patent
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Abstract
An apparatus for effecting the thermal conversion of gypsum to calcium sulfate hemihydrate includes a reactor having a series of fluidized bed compartments containing separate heat exchangers and defined by partitions each provided with an opening which is selected so that the material undergoing treatment progresses, without return movement, through the series of fluidized bed compartments. The apparatus is further constructed so as to permit recycling of fine gypsum particles from the outlet to the middle of the reactor.
Claims5
Apparatus for the progressive thermal dehydration of gypsum into a calcium sulfate hemihydrate having enhanced mechanical properties and reactivity, said apparatus comprising (i) a dehydration zone including an inlet end, an outlet end, and a plurality of distinct communicating compartments there-between, each compartment defining an individual reactor and each comprising an independent heaing element, (ii) means for feeding fluidization gas into said dehydration zone to thereby establish a homogeneous, continuously fluidized bed of heated, progressively dehydrating finely divided gypsum particles in said dehydration zone, (iii) means for heating said heating elements to thereby indirectly heat said particles to elevated temperatures of dehydration, (iv) means for ensuring that each of said heating elements remains immersed in any fluidized bed thus established, (v) means for establishing a substantially horizontal flow of fluidized gypsum particles progressively and controlledly dehydrating from the inlet end of the fluidized bed to the outlet end thereof, to and through each of the communicating compartments comprising same, without any backflow from compartment to compartment, (vi) means for continuously removing water vapor produced during the dehydration reaction, (vii) means for controlling said fluidization gas feed at a speed ranging from between that minimum theoretical rate at which fluidization is effected to about six times such minimum theoretical rate, said speed being such that an essentially constant partial pressure of water vapor is established and maintained, in conjunction with said heating means, at each point in said fluidized bed, (viii) means for effecting a temperature gradient of at least 20.degree. C. and a heat transfer coefficient ranging from about 250 to 400 kilocalories/hour/m.sup.2 /.degree. C. between each heating element and the fluidized gypsum particles in each compartment, and (ix) means for the recovery of product substantially comprised of calcium sulfate hemihydrate from the outlet end of the fluidized bed.
Apparatus for thermally treating gypsum to dehydrate it into calcium sulfate hemihydrate, comprising:
- a reactor having an inlet end and an outlet end;
- a plurality of partitions defining a series of compartments within said reactor between the inlet and outlet ends thereof;
- means for introducing gypsum into the compartment adjacent the inlet end of said reactor;
- means for continuously introducing a fluidization gas into each of said compartments at a rate such that gypsum located therein is continuously fluidized;
- a heating element disposed in at least some of said compartments so as to be immersed within the fluidized gypsum in its respective compartment;
- an opening disposed in each of said partitions, said openings being dimensioned and located such that a continuous, substantially horizontal movement of homogeneous fluidized gypsum, from the input to the output end of said reactor, is established and the flow of fluidized gypsum between two compartments in the other direction is inhibited;
- and
- means for heating said heating elements to temperatures such that the temperature of fluidized gypsum progressively increases in each compartment having a heating element from the input to the output ends of said reactor.
Dependencies are inferred from the claim text.