Implications of crystal-size distributions in product massecuites from horizontal and vertical continuous pans

The crystal-size distribution of product massecuites from continuous pans has always been of major interest to designers of these pans. As several overseas cane factories seek to operate continuous pans with lower pressure vapour, e.g. vapour 3 or vapour 4 from the evaporators, and also to use seed with smaller crystal size in order to increase the extent of crystallisation conducted in continuous pans, a closer examination of the factors affecting the crystal size distributions of product massecuites is warranted. Both these changes tend to produce a broader spread of crystal sizes. This paper examines the influence of the seed crystal-size distribution, the residence time distribution, the number of cells in the continuous pan, and the dispersion of crystal growth rates on the product crystal-size distribution. The size distributions of both horizontal and vertical continuous pans are considered, as well as the implications for the future applications of both types of continuous pans. Measures to narrow the size distribution of the product crystals are examined. Key words crystal size distributions, continuous pans, number of cells, residence time, seed massecuite