Crystallizer filter

The present invention resides in an improved method and apparatus for the crystallization and filtration of a crystallizable material from a solution in which the crystallizable material is dissolved. The solution is supersaturated with the crystallizable material. The solution is fed through a filter having a layer of seed material thereon. The depth of the layer of seed material and the rate of flow of solution through the seed layer allow the crystallization of the crystallizable material to take place within the layer of seed material. The crystallization is allowed to proceed until a bed of crystals of the crystallizable material is formed on the filter surface. A preferred filter material is a thin, flexible, polymeric material which is essentially two-dimensional. The filter is back-flushed removing the bed of the crystallizable material from the filter surface. Enough crystals remain on the filter surface to function as a seed layer for the formation of a new bed of crystals of the crystallizable material with the flow of additional solution through the filter.