An evaporation–crystallization process of the type described in example 4.5-2 is used to obtain solid potassium sulfate from an aqueous solution of this salt. the fresh feed to the process contains 19.6 wt% k2so4. the wet filter cake consists of solid k2so4 crystals and a 40.0 wt% k2so4 solution, in a ratio 10 kg crystals/kg solution. the filtrate, also a 40.0% solution, is recycled to join the fresh feed. of the water fed to the evaporator, 45.0% is evaporated. the evaporator has a maximum capacity of 175 kg water evaporated/s.