Abstract: A process of making a granulated MgO-containing potassium salt fertilizer containing potassium sulfate, and having a high abrasion resistance and high compression resistance, includes preparing a langbeinite slurry binder without an evaporation of a magnesium chloride-containing solution with heating at a temperature of from 95.degree. to 110.degree. C. with a density of from 1.6 to 1.7 g/cm.sup.3, mixing the potassium salt and recyclable fines with the langbeinite at a temperature of from 75.degree. to 100.degree. C., granulating in a granulating drum, screening to form the fertilizer and recyclable fines; and recovery and recycle of the fines. The liquid langbeinite binder can be made by mixing a mixture of magnesium sulfate and/or kieserite with potassium sulfate, schoenite and/or leonite the potassium sulfate and the magnesium sulfate being present in a mole ratio of from 1:1.5 through 1:3 and heating the mixture to a temperature of 95.degree. to 110.degree. C. with a turbidity density of 1.6 to 1.7 g/cm.

Abstract: A carnallite-containing crude salt is separated into a carnallite fraction, a sylvite fraction and an abandonable residue by grinding the salt to an average particle size of about 1.5 mm., conditioning the particles in a conventional manner with from 5-300 g/t of a conventional conditioning agent adjusting the relative humidity of the conditioned particles to 5-25%, and subjecting the resulting particles to electrostatic separation in two stages, wherein in the first stage the particles are subjected to a high voltage electric field having a field length of 0.4 to 1.2 m to separate a carnallite fraction by imparting to the carnallite fraction a high sidewards velocity relative to the initial downward velocity upon entering the field, thereby causing deflection of the carnallite away from a middlings fraction, and wherein in the second stage the first stage middling fracton is subjected to a second high voltage electric field having a field length of 1.5 to 2.

Abstract: Potassium sulfate is produced from a mixture of carnallite, potassium chloride, kieserite and residual quantities of less than 15% by weight of rock salt by treating the mixture at a temperature of 20.degree.-40.degree. C with potash magnesia liquor to form a slurry with at most 70 mole MgCl.sub.2 /1000 mole H.sub.2 O, whereafter the liquor portion of the slurry comprising a solution saturated with carnallite and rock salt is separated from the solid substance, which solid substance is then converted at temperatures of 75.degree.-110.degree. with a sulfate liquor, which contains 18-45 mole MgCl.sub.2 /1000 mole H.sub.2 O, into a mixture of langbeinite and potassium chloride, which mixture after separation from the liquor is treated at temperatures of 15.degree.-110.degree. C with a sulfate liquor containing 18-50 mole MgCl.sub.2 /1000 mole H.sub.2 O, whereupon the crystallizate is separated from the mother liquor and is converted with water to potassium sulfate.