Crystallization of potassium sulfate by cooling and salting-out using 1-propanol in a calorimetric reactor

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 degreesC to test the crystallization of K2SO4 by addition of the alcohol, and from 50 to 10 degreesC 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 13degreesC 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.