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 apparatus for separating a mixture of solid and liquid components including a tank for the mixture with at least one inlet for the mixture under pressure and at least one outlet. One or more separators are provided within the tank and including one or more circular-cylindrical filter elements within the tank. Each of the filters includes a wall portion which is permeable to the liquid component of the mixture. Further, a helical transporting and scraping element is mounted within the circular-cylindrical wall of the filter and is sized so as to scrape the solid component of the mixture as cake from the inner wall of the filter and return it to the mixture within the tank.