Sulfuric Acid → Aluminum Sulfate

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A method of making sintered aluminous abrasives from uncalcined bauxite. The uncalcined bauxite is mixed with sulphuric acid and dissolved. This forms aluminum sulfate hydrate as a major product. The aluminum sulphate hydrate is then dried to form aluminum sulphate which is then calcined to form gamma alumina and sulphur trioxide. The sulphur trioxide is mixed with water to form sulphuric acid and is then recycled for further use as additional dissolving material. A slurry of the gamma alumina is prepared, poured into a container and then dried to form a cake known as an unfired body. The unfired body is then broken into particles and screened to size. Following this, the particles are sintered. The sintered particles are finally cooled, then screened into the various desired abrasive grit sizes. Alternate methods for forming the unfired body include: (1) extrusion of a paste made up of gamma alumina and water followed by drying of the extruded material; and (2) pressing the dry gamma alumina into compacted cakes.

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