Development of Continuous Freeze-Concentration Equipment: Effect of Shortening Residence Time of Ice Flakes in Centrifuge

Abstract

There is growing demand for simple freeze-concentration equipment which can operate intermittently. We have made freeze-concentration equipment consisting of an ice-making part, which continuously produces ice flakes on a rotating cooling drum, and a continuous centrifuge separating part. The purpose of this study was to evaluate the effect of shortening the residence time of ice flakes in the centrifuge part. Experiments using sea-water (Cl⁻ concentration of the mother liquor 2.04–3.02 wt%) in this equipment led to the following results. The solute recovery rate and the treated quantity of mother liquor in tests with shortened residence time(15 s) compared favorably with those of previous tests with residence time of 60 s. In the previous tests, the solute recovery rate was 0.31–0.40 when the treated quantity of mother liquor ranged from 29.9 to 32.9 kg/h. The present tests gave a solute recovery rate of 0.54–0.73 for a treated quantity of mother liquor from 56.4 to 61.1 kg/h.