Abstract: A counter-current process for purifying chemicals using cyrstal purification. The unit process has a purification and recovery section which contain substantially identical stages. In operation, the unit process purifies the chemical by utilizing sequential recrystallizer. The size and purity of the crystals increases from the last recrystallizer in the recovery section through each subsequent stage to the last recrystallizer in the purification section.

Abstract: An improved freeze concentration system of the type in which a slurry of crystals and mother liquor are formed in a crystallizer and fed to the concentrated end of a gradient column. The crystals grow in size in the column as they move to the dilute end of the column. The dilute slurry is transferred to a holding tank where the crystals grow further and then to a wash column. A slurry of larger crystals from the holding tank or the column outlet are fed back to the column inlet so that crystals in the concentrated slurry dissolve and reform on the large crystals of the fed back slurry. The units can be connected in a multistage, counter-current system.

Abstract: A separator particularly useful in freeze concentration systems and apparatus, particularly multi-stage countercurrent systems for concentrating aqueous feed liquid, but useful for other kinds of separators as well. The slurry to be separated enters a vessel in which is mounted and rotated a cylindrical filter. The liquid passes through the filter to one outlet while the solids accumulate on the filter and are removed and directed to another outlet by a fixed scraper.