Effect of different cooling modes on crystal size distribution in a batch cooling crystallizer for DL-malic acid

The effects of various cooling modes such as natural cooling mode, linear cooling mode, and controlled cooling modes type A and B in a batch cooling crystallizer on crystal size distribution (CSD) as well as the mean crystal size have been studied for DL-malic acid. The natural cooling mode was found to yield crystals in the range of 250 to 1000 mu m, whereas the linear cooling mode was found to yield larger crystals, in the range of 800 to 1600 mu m. The mean crystal size was found to increase in the order of natural cooling mode, controlled cooling mode A, controlled cooling mode B, and linear cooling mode. Since linear cooling mode was found to yield larger mean crystal size, the effect of operating parameters such as the seed concentration and agitation rates on CSD was assessed using the linear cooling mode. The increase in seed concentration from 0.5 to 1% resulted in a larger mean crystal size; while an increase from 1 to 2% reduced the mean crystal size. An agitator rate of 90 rpm was found to yield larger mean crystal size than agitation rates of 60 and 120 rpm.