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CentralPrayon Process H 2 SO 4 98% Phosphate Recycled acid Water Hemi Typical P 2 O 5 Yield : 98% Phos acid 32% P 2 O 5 Attack Digestion Filter Filter Steam DIHYDRATE HEMIHYDRATE Conversion Typical 3235% P 2 O 5 1% SO 3 Typical 28% P 2 O 5 8 % SO 3
A microscope study has been made of the development of crystals of calcium sulphate hemihydrate produced on, or in, sheets of the dihydrate in the form of selenite by calcining under controlled conditions. The crystal forms were shown to be strongly dependent upon both temperature and ambient water vapour pressure.
wallboard, gypsum must be partially dehydrated or calcined to produce calcium sulfate hemihydrate (CaSO4 #189;H 2O), commonly called stucco. A flow diagram for a typical gypsum process producing both crude and finished gypsum products is shown in Figure In this process gypsum is crushed, dried, ground, and calcined.
PROBLEM TO BE SOLVED: To provide a production process of regenerated hemihydrate gypsum, by which regenerated hemihydrate gypsum can be produced at a low cost so as to enable effective utilization of waste of gypsum formed bodies and application of the resulting regenerated hemihydrate gypsum to the production of a soil solidification agent.
For exploring the mechanism of butane diacid effect on crystal morphology of calcium sulfate hemihydrate in preparation from flue gas desulphurization gypsum, the crystal morphology, convert ratio, and reaction process of calcium sulfate hemihydrate were studied by scanning electron microscope observation, and crystal water testing.
The method of this invention comprises charging gypsum into a calcining kettle, heating the kettle and causing the gypsum to become a boiling, calcining mass of solids and gases by conduction of heat from the kettle, and intensifying the boiling action of the mass by contacting it with a heating element immersed therein which is emitting at least about 1, preferably from about 1 to about, British Thermal Units of
Besides these main constituents, various additives are used in small quantities. One important additive is gypsum in the form of the dihydrate (CaSO4#183;2H20) or the hemihydrate (CaSO4 #183;#189; H20). The gypsum is ground with the clinker and serves to retard the setting and hardening of the cement.
The gypsum (hydrated) forms of these materials are then processed and heated under controlled conditions to form plaster of Paris, or calcium sulfate hemihydrate (CS, CaSO 4 #183; 1/2H 2 O). Addition of water to this material, in proper quantities, causes setting of the plaster of Paris to form calcium sulfate dihydrate (CaSO 4 #183; 2H 2 O).
A process for producing alphemihydrate gypsum from dihydrate gypsum includes feeding a slurry comprising the dihydrate gypsum and water into a heating tube, heating the heating tube at a temperature effective to generate steam and pressure from the water, wherein the steam and pressure are effective to convert the dihydrate gypsum to the alphemihydrate gypsum, and withdrawing the alpha
process hemihydrate gypsum hemihydrate Prior art date Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.) Withdrawn Application number DE Other languages German (de) Other versions
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