Abstract: Method for producing soluble potassium sulfate by recrystallization of crude potassium sulfate wherein the crude potassium sulfate contains an amount of potassium, calculated as K2O, of about 15 wt % or higher, and the resulting potassium sulfate crystalline material conforms with the following characteristics: the amount of insoluble material is less than about 0.05 wt %, a 1 wt % solution of the potassium sulfate has a pH below about 6, and/or 1 pH unit lower than the pH of the crude potassium sulfate, the fraction obtained after crystallization has an average particle size within the following parameters: (i) d90<about 0.6 mm, (ii) d10>about 0.02 mm, and (iii) dust amounts to about 0.4 wt % or less, whereby the resulting potassium sulfate contains more than 51% potassium, calculated as K2O.

Abstract: The invention relates to a method for producing for producing soluble potassium sulfate by recrystallization of crude potassium sulfate wherein the crude potassium sulfate contains an amount of potassium, calculated as K2O of about 15 wt % or higher preferably about 40 wt % or higher and has either more than about 0.07 wt % insoluble material, and/or a dissolution speed wherein at 3 min dissolution of 100 gram product in 1 L cold water (20° C.