GB613207A - Improvements in and relating to the dehydration of gypsum - Google Patents

Abstract

In the dehydration of gypsum, a bed of particulate gypsum is maintained in a fluidised state by the upward passage therethrough of a gas at elevated temperature, particulate gypsum being continuously fed to and dehydrated gypsum being continuously removed from the bed and the particulate solids being constrained to flow in a horizontal direction. The horizontal flow may be effected by arranging the exit or exits for the solid to be remote in a horizontal direction from the inlet or inlets. The gas may be introduced into the bottom of the vessel through a series of jets or through a perforated plate. Alternatively, a layer or layers of granular material having a weight such that they remain undisplaced by the gas stream may be placed on the perforated bottom. Preferably the granules of the upper layers are smaller than those of the lower layers. The particulate gypsum may be contacted successively in separate steps with gas, the temperature of which varies from step to step, either in a series of interconnected vessels through which the solid material flows by gravity, by entrainment in a stream of gas or in a single vessel of elongated horizontal cross-section divided by a number of vertical partitions. The dehydrating gas may be air or flue gas and may enter the apparatus at a temperature of 230 DEG C., heating the bed of particulate gypsum to a temperature of 120-140 DEG C.