An analysis of limited crystal growth in the crystallizer with inner suspension circulation has been studied. The new exhaustively theoretical analysis of crystal attrition sources, pumping effect and power input requirements, as well as the experimental investigations in concentrated suspensions have been done, respectively. In the light of collected theoretical and experimental evidence, in the Draft Tube Magma (DTM) crystallizers there are no significant possibilities for improvement of crystal size. The new constructional modification of DTM crystallizer was proposed for achieving better crystal quality. The new apparatus, with two coaxial draft tubes and partially hydraulic magma classification, makes possible to increase the mean crystal size up to 33%. The product efficiency from unit volume in this case is comparable with a DTM vessel. Moreover, the favorable conditions of crystal growth in a new crystallizer enable one to extend the residence time to 8 h, and because of that, to produce the crystals of the average size up to 1000 mum.