Crystallization Character of Perfect Mixed Bed-Type Crystallizer (Reverse Forced Circulation) with Apparatus of Classification

Abstract

Crystallization tests of salts with various particle size were carried out in an industrial crystallizerthat was a perfect mixed bed-type with a system of reverse forced circulation. Crystallization dataobtained were applied to crystallization theory.
Size distribution of crystals was plotted on a Rosin-Rammler diagram and straight lines wereobtained for 10 to 90 percent of cumulative weight of product crystals. Operational data wereplotted as a straight line on a diagram chart. This line was approximately parallel to line B, which was the correlation that (P/ρc·V')·l_w became constant. Here P, ρc·P', and l_w, are productionrate, density of crystal, working volume of a crystallizer, and average size of product crystaldecided at 36.8 percent on weight basis plot on Rosin-Rammler diagram, respectively. Correlationsbetween product crystal size and production rate and between suspension density of crystalbed and average crystal growth ratealso indicated that (P/ρc·V')·l_w nearly equal constant wasvalid. Points logarithmic plotted between average crystal growth rateand nucleation rate gave astraight line.
Application of operational data to crystallization theory of a perfectmixed crystallization modelindicated that our evaporating crystallizer had been similar to animproved fluidized bed-type crystallizerbecause of the effect of classification in salt leg.
The test results by using the operational line obtained from data of crystallization tests of salts suggested that the maximum mean size of crystal obtained in this crystallizer was 1.5 to 1.6 mm.