Method for the reduction of halite in the preparation of potassium sulphate from potassium-containing ores at high ambient temperatures

A method for the production of potassium sulphate, comprising the steps of:

• Ib) contacting an aqueous potassium and sulphate-containing composition, further comprising sodium chloride, with magnesium chloride (MgCl2), thereby precipitating halite (NaCl) and obtaining a composition that, upon evaporation, produces solids comprising kainite (KCl.MgSO4.2.75 H2O);
• IIb) concentrating and separating the kainite from the composition, obtained in step Ib by flotation, thereby producing a flotation concentrate comprising the kainite and a rest composition (flotation tailings) and controlling the concentration of sodium chloride, present in the composition comprising kainite so as to maintain the concentration of sodium chloride below about 10% by weight on dry matter basis;
• IIIb) reacting the kainite, obtained in step IIb with water, optionally comprising magnesium sulphate (MgSO4) and potassium sulphate (K2SO4), at a temperature of about 35° C. to about 70° C., so as to convert the kainite into leonite (K2SO4.MgSO4.4H2O) and separating the leonite thereof, thereby producing a rest composition (conversion liquid);
• IVb) optionally, contacting the leonite, obtained in step IIIb, with water to remove any remaining solid MgSO4 compounds;
• and
• Vb) contacting the leonite, obtained in step IIIb or IVb, with water so as to dissolve leonite and/or leach the MgSO4, contained in the leonite, and to at least substantially selectively crystallize potassium sulphate (K2SO4);
• VIb) combining at least part of the balance composition (flotation tailings) from step IIb with at least part of the balance composition (conversion liquid) from step IIIb and optionally water, to precipitate bloedite;
• characterized in that the method contains a further step II′b, situated between step IIb and IIIb, comprising contacting the flotation concentrate of step IIb with an aqueous solution of MgCl2.