Abstract: A process for removing impurities from an oxide of titanium-bearing material such as a titania slag by treating the material with SO.sub.3 gas and subsequently leaching with a liquid. In particular a process for upgrading an ilmenite ore by preparing a titania slag therefrom and purifying the slag such that it may be used as a synthetic rutile suitable for use in a fluidized-bed chlorination reactor to produce titanium tetrachloride which can be reoxidized to TiO.sub.2.

Abstract: A process for the manufacture of calcium sulphate alpha-hemihydrate which comprises the step of interacting an aqueous solution of calcium chloride and a source of sulphate or bisulphate ions in an aqueous system at a temperature above the calcium sulphate hemihydrate/gypsum transition temperature under the reaction conditions. The preferred reagents are the waste calcium chloride/sodium chloride effluent of the ammonia soda process and sulphuric acid (e.g. impure sulphuric acid effluent) to give hydrochloric acid as a co-product. The preferred reaction temperature is at least 20.degree. C. above the transition temperature (about 70.degree. C), e.g. at 95.degree.-100.degree. C at atmospheric pressure.

Abstract: A new simplified process is described for producing pharmaceutical barium sulphate in which the barium sulphate does not require dissolution for purification.

Abstract: A process for the purification of phosphate containing impure gypsum to obtain therefrom calcium sulfate semihydrate in a purified form by digesting the phosphate containing gypsum with nitric acid at a temperature between 22.degree. and 100.degree. C, the temperature and nitric acid concentration being regulated such as to dissolve most of the phosphate impurities and to allow the recovery of calcium sulfate semihydrate.

Abstract: Alkali metal or alkaline earth metal carbonates such as calcium carbonate and magnesium carbonate found in dolomite or limestone are employed for removal of sulfur dioxide from combustion exhaust gases. The sulfated carbonates are regenerated to oxides through use of a solid-solid reaction, particularly calcium sulfide with calcium sulfate to form calcium oxide and sulfur dioxide gas. The regeneration is performed by contacting the sulfated material with a reductant gas such as hydrogen within an inert diluent to produce calcium sulfide in mixture with the sulfate under process conditions selected to permit the sulfide-sulfate, solid-state reaction to occur.

Abstract: In a process for the reaction of phosphate rock and sulfuric acid in the presence of potassium ion to form a mixture of phosphoric acid and a precipitated gypsum wherein the presence of the potassium ion causes precipitation of fluorides from the phosphate rock as potassium silicofluoride as a coprecipitate with the gypsum, and the phosphoric acid is separated from the gypsum slurry, the potassium silicofluoride is separated from the gypsum by extraction with phosphoric acid which may contain from 0-25 weight percent of sulfuric acid based on the amount of gypsum to be extracted or such phosphoric acid which may contain some fluorine. This extraction procedure provides a substantially fluoride-free gypsum product and an extraction solution containing recoverable potassium silicofluoride.

Abstract: The process for the production of synthetic anhydrite of uniform quality from the residue resulting from the production of hydrofluoric acid and containing calcium sulfate and acid, comprising suspending said residue in water with vigorous agitation, neutralizing said residue, grinding the suspension and separating water from the suspension to leave synthetic anhydrite containing less than about 50% water by weight. The product is thereafter dried after the optional addition of fillers and/or additives which accelerate subsequent hydration.

Abstract: A process for producing briquettes from wet cakes or muds containing mineral ore, including coal particles, characterized in that a wet cake or a mud is mixed with a bituminous binder selected from the group consisting of powdered bitumen, molten bitumen and a bitumen emulsion, whereafter the resltant mixture is compressed into briquettes at a temperature which is at least equal to about the Ring and Ball temperature minus 40.degree.C of the bitumen present in the binder, after which optionally the briquettes are dried.

Abstract: Heat barrier materials are prepared by forming an intimate admixture of alkaline earth sulfate and finely divided carbonaceous material into a shaped composition and subjecting said shaped composition to a high temperature to cause a surface reaction to produce a coating comprising alkaline earth sulfide on the surface of said shaped composition.