Abstract: Methods of processing an aqueous solution comprising potassium sulfate and magnesium sulfate include crystallizing K2SO4, crystallizing recycle crystals, and mixing at least a portion of the recycle crystals with the aqueous solution. Systems for processing potassium sulfate and magnesium sulfate include a first crystallizer and a second crystallizer in fluid communication with the second mix tank. The second crystallizer is structured and adapted to precipitate recycle crystals from the concentrated liquor to form a potassium-depleted recycle brine. The recycle crystals precipitated in the second crystallizer have a composition suitable to be recycled to the first crystallizer to increase the production of SOP.

Abstract: Methods of processing an aqueous solution comprising potassium sulfate and magnesium sulfate include crystallizing K2SO4, crystallizing recycle crystals, and mixing at least a portion of the recycle crystals with the aqueous solution. Systems for processing potassium sulfate and magnesium sulfate include a first crystallizer and a second crystallizer in fluid communication with the second mix tank. The second crystallizer is structured and adapted to precipitate recycle crystals from the concentrated liquor to form a potassium-depleted recycle brine. The recycle crystals precipitated in the second crystallizer have a composition suitable to be recycled to the first crystallizer to increase the production of SOP.

Abstract: Methods of forming potassium sulfate include calcining polyhalite ore particles to convert the polyhalite ore particles to a water-soluble composition. At least a portion of the water-soluble composition is dissolved in an aqueous medium to form an aqueous solution comprising K+, Mg2+, and SO42? ions and a calcium-containing solid. The calcium-containing solid is separated from the aqueous solution to form a filtrate comprising K+, Mg2+, and SO42? ions. A potassium-containing salt is dissolved in the filtrate to increase the concentration of K+ and SO42? ions to from a concentrated liquor, and K2SO4 is crystallized from the concentrated liquor. A system for processing polyhalite ore includes a countercurrent leaching apparatus, a first mix tank, an evaporator, and at least one crystallizer.

Abstract: Methods of forming potassium sulfate include calcining polyhalite ore particles to convert the polyhalite ore particles to a water-soluble composition. At least a portion of the water-soluble composition is dissolved in an aqueous medium to form an aqueous solution comprising K+, Mg2+, and SO42? ions and a calcium-containing solid. The calcium-containing solid is separated from the aqueous solution to form a filtrate comprising K+, Mg2+, and SO42? ions. A potassium-containing salt is dissolved in the filtrate to increase the concentration of K+ and SO42? ions to from a concentrated liquor, and K2SO4 is crystallized from the concentrated liquor. A system for processing polyhalite ore includes a countercurrent leaching apparatus, a first mix tank, an evaporator, and at least one crystallizer.