A study was made on a isothermal process for the crystallization of potassium sulfate as an alternative to the cooling process. The process employs addition of 1-propanol to aqueous salt solutions to achieve the "salting-out" of the K₂SO₄. This work was carried out using an automated Mettler Toledo model RC1 reactor-crystallizer with 800 ml capacity, and controlled isothermally at 25 °C to test the crystallization of K₂SO₄ by addition of the alcohol, and from 50 to 10 °C for the cooling crystallization. In both systems, the line of nucleation points was shown to be approximately parallel to the saturation curve, with an average width of 13°C or 3 % mass for crystallization by cooling, compared with 0.2 to 1 % by salting-out. In experiments on crystallization by cooling, the K₂SO₄ crystals were 0.27 mm in mean size, showed 7 % agglomeration, and contained 8.5 % moisture. Crystals obtained by salting-out had a mean size of 0.79 mm, 28 % agglomeration, and 9-10 % moisture content. A crystal shape factor of approximately of 0.7 was obtained in both systems, apart from the agglomeration.

Keywords: salting-out crystallization, potassium sulfate, line of nucleation points

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