process and installation for the preparation of a simple solution based on the solution composition.

摘要

A continuous process for obtaining a solution of a single component having a negative heat of solution, wherein a compound solution containing said component and others is evaporated under sub-atmospheric pressure so that crystals of the required component are formed; both the vapours and the crystals being withdrawn from the evaporator and introduced into a direct-contact condenser in which a solution of said single component is circulating, and from which PICT:0655084/III/1 part of said circulating solution is continuously withdrawn. The heat of condensation of the vapours is thus utilized for dissolving the crystals. The solution obtained by digesting raw phosphate with dilute nitric acid is introduced through pipe 3 into a circulating system comprising pump 4, evaporator 1, and crystallizer 2. A 50 per cent solution of calcium nitrate is circulated by pump 7 through cooler 8, direct-contact condenser 5, and reservoir 6. The entire system is evacuated by steam-ejector 9. The evaporator 1 is maintained at 4.3 mm. whereby the digestion-liquor evaporates at 15 DEG C. and deposits crystals of calcium nitrate; these crystals are separated from mother-liquor in centrifuge 11 and then introduced in reservoir 6. The vapours from the evaporator pass to the condenser through pipe 10. The temperature of the solution circulating in the condenser is maintained at 3.2 DEG C. by cooler 8; and the solution is maintained at the required concentration by adding water through pipe 14. Part of the solution is continuously withdrawn through line 15.