ON THE EFFECT OF LIQUID-MIXING RATE ON PRIMARY CRYSTAL SIZE DURING THE GAS-LIQUID PRECIPITATION OF CALCIUM-CARBONATE

An analysis based on gas-liquid mass transfer with chemical reaction coupled with equations describing the dynamic population balance model of crystallization and precipitation kinetics is used to predict the effect of liquid mixing rate on the transient mean crystal size of calcium carbonate precipitated in a small flat-interface gas-liquid reaction cell via the gaseous carbonation of lime water. Experimentally, small discrete calcite crystals (<1-mu-m) are formed initially in the vicinity of the gas-liquid interface during the early stages of batch precipitation followed by subsequent primary crystal growth reaching approximately 6-mu-m in the bulk. The mean crystal size increases with increasing agitation rate consistent with model predictions due to the effect of liquid agitation rate on gas-liquid mass transfer.