A PENETRATION MODEL OF THE GAS-LIQUID REACTIVE PRECIPITATION OF CALCIUM-CARBONATE CRYSTALS

An analysis based on the coupled equations for the penetration model o f gas-liquid mass transfer, solution chemistry and the distributed dyn amic mass and population balances applied to the crystallization step is used to predict the effect of the gas-liquid mass transfer rate on the precipitation of calcium carbonate at 25 degrees C using equilibri um and kinetic data from the literature. Generally, the nucleation rat e in the region close to the gas-liquid interface is predicted to incr ease with decreasing gas-liquid mass transfer rate; at very low mass t ransfer rates, nucleation rates are, however, inhibited by the depleti on of Ca2+ ions. Under conditions of low mass transfer rates, nucleati on proceeds predominantly in the interfacial region rather than in the bulk solution. Nucleation rate, particle number density and mean part icle size are predicted to exhibit a maximum with position away from t he gas-liquid interface.