Patent EA-002758-B1 (EA)
Title: Method of producing potassium sulfate
Inventor: PHINNEY ROBIN
IPC: C01F11/18
Filed: 1999-06-15
Abstract: 1. A method of producing potassium sulfate from a source containing ammonium sulfate, characterized in that the method comprises the steps of: contacting potassium chloride and ammonium sulfate in a mixer at a temperature of between 20 degree C and 40 degree C; precipitating a first precipitate of double salt in a filtrate; mixing, in a second mixing step, said filtrate with potassium chloride; generating a second filtrate containing ammonium and potassium chloride and a second precipitate of double salt; mixing said second double salt precipitate with said first precipitate in a solution of potassium chloride; precipitating a third precipitate of potassium sulfate and a third filtrate; recirculating said third filtrate into said second mixing step; mixing said second filtrate in a mixing tank at a temperature of less than 70 degree C in a solution of less than 10% by weight sodium chloride, calcium chloride and sodium sulfate; and generating a syngenite precipitate and a fourth filtrate. 2. The method as set forth in claim 1, characterized in that said ammonium sulfate is present in an amount of less than 40% by weight. 3. The method as set forth in claim 1, characterized in that said double salt comprises K2SO4x(NH4)2xSO4. 4. The method as set forth in claim 1, characterized in that said solution of potassium chloride is a saturated solution. 5. The method as set forth in claim 1, characterized in that said third precipitate of potassium sulfate comprises a precipitate having a size distribution of between 20 mesh and 150 mesh. 6. The method as set forth in claim 1, characterized in that said second filtrate contains potassium chloride, sodium chloride and ammonium chloride. 7. A method of producing potassium sulfate from a source containing ammonium sulfate, comprising the steps of: contacting potassium chloride and ammonium sulfate in a mixer at a temperature of less than 30 degree C; precipitating a first precipitate of double salt in a filtrate; mixing, in a second mixing step, said filtrate with potassium chloride; generating a second filtrate containing ammonium and potassium chloride and a second precipitate of double salt; mixing said second double salt precipitate with said first precipitate in a solution of potassium chloride; precipitating a third precipitate of potassium sulfate and a third filtrate; recirculating said third filtrate into said second mixing step; mixing said second filtrate in a mixing tank at a temperature of less than 70 degree C in a solution of less than 10% by weight sodium chloride, calcium chloride and sodium sulfate; generating a syngenite precipitate and a fourth filtrate; mixing, in a sealed mixing tank at a temperature of about 80 degree C, said fourth filtrate with less than about 18% by weight sodium chloride, about 23.6% ammonium chloride and lime or hydrated lime; recovering ammonia from said fourth filtrate; passing said fourth filtrate into an air scrubber and further removing ammonia from calcium chloride and sodium chloride; passing said fourth filtrate into an ammonium scrubber to generate ammonium sulfate; passing said syngenite precipitate into a mixing tank at a temperature of about 70 degree C in the presence of ammonium bicarbonate; generating a calcium carbonate precipitate and a fifth filtrate containing potassium sulfate and ammonium sulfate; and recycling said fifth filtrate to at least one of the mixing steps. 8. The method as set forth in claim 7, characterized in that said ammonium sulfate is present in an amount of less than 40% by weight. 9. The method as set forth in claim 7, characterized in that said double salt comprises K2SO4x(NH4)2xSO4. 10. The method as set forth in claim 7, characterized in that said solution of potassium chloride is a saturated solution. 11. The method as set forth in claim 7, characterized in that said third precipitate of potassium sulfate comprises a precipitate having a size distribution of between 20 mesh and 150 mesh. 12. The method as set forth in claim 7, characterized in that said second filtrate contains potassium chloride, sodium chloride and ammonium chloride.