DESIGN CHARTS FOR THE FINES-DISSOLVING CRYSTALLIZER

The principle of particle size increase in continuous crystallization processes is to remove fine particles at a faster rate than large ones. Two technologies based on this principle are the double draw-off (DDO) and the fines-dissolving (FD) crystallizer configurations. Design charts were developed for the FD crystallizer. It was found that the particle size increase passes through a maximum value as the fines classification cut size is increased. Based on this information, a design protocol was suggested for the FD crystallizer. A limited amount of data are required for this method of design. Particle size increase was demonstrated in the laboratory for sodium chloride crystallization in caustic liquor using an FD crystallizer. A fines/feed flow modification as well as actual fines dissolution was used in the FD experiments. Significant size increase was observed in both cases. These experiments indicate that appreciable dissolution cost would be involved in FD operation. Experimental results were in good agreement with values predicted from design charts.