Effect of Different Cooling Modes on Crystal Size Distribution in a Batch Cooling Crystallizer for DL-Malic Acid

摘要

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 crvstallizer on crystal size distribution (CSD) as well as the mean crystal si:e have been studied for DL-malic acid.The natural cooling mode was found to yield crystals in the range of 250 to 1000 mum,whereas the linear cooling mode was found to yield larger crys-tals,in the range of 800 to 1600 mum.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 90rpm was found to yield larger mean crvstal size than agitation rates of 60 and 120 rpm.