GB1447281A - Crystallization apparatus - Google Patents

Abstract

1447281 Crystallisation apparatus JOH A BENCKISER GmbH 15 Aug 1973 [15 Aug 1972] 38589/73 Heading B1G A method of crystallising a substance from a solution comprises circulating the solution around a system comprising, as shown in the Fig., a crystallisation chamber 2 maintained at atmospheric pressure or slightly above, a heat exchanger 5 forming an evaporation zone located at a higher vertical level than the crystallisation chamber 2 and a vacuum chamber 1 also located at a higher vertical level than the crystallisation chamber so that the solution passes from the crystallisation chamber 2 to the heat exchanger 5, thence to the vacuum chamber 1 and back to the crystallisation chamber 2, the circulation being effected by ebullition of the solution in the heat exchanger 5 in the manner of an air lift pump. The pressure in the vacuum chamber 1 should preferably be 20-55 Ton and the solution to be crystallised fed into the upper vacuum chamber 1 or the lower crystallisation chamber 2. In order to facilitate circulation the level of liquid in the vacuum chamber 1 should be maintained at a constant level. This is preferably achieved by controlling the pressure differential between the vacuum and crystallisation chambers depending on the density of the crystal suspension. The method is suitable for crystallising substances, which cake together and/or adhere to the walls of the apparatus in solutions of water or organic solvents. Substances crystallised include organic acids e.g. citric acid, inorganic potassium and ammonium salts CuSO 4 , sodium glutamate, borax, melamine and urea.