EFFECT OF PVA AND GELATIN ADDITIVES ON BARIUM-SULFATE PRECIPITATION IN AN MSMPR REACTOR

The effect of high molecular weight additives (PVA and gelatin) on bar ium sulfate precipitation in an MSMPR reactor is investigated. The imp eller speed is varied from 0 to 1200 rpm and the additive concentratio n in the bulk solution is increased up to 5.0 g/1. As the additive con centration is increased, the particle growth rate decreases and the nu cleation rate increases. However, the particle morphology is not chang ed by the additives. The experimental results are explained qualitativ ely by supposing that the additive is adsorbed on the particle surface and inhibits the mass transfer to the surface. To explain the additiv e effect quantitatively a diffusion limitation model is developed. The diffusion limitation model predicts the effects of additives over the entire range of additive concentrations and impeller speeds set in th e experiments. The model predicts very high supersaturation levels in the reactor which is consistent with a mass transfer controlled partic le growth. Furthermore, the model results are consistent with simple t heories of polymer adsorption and diffusion in polymer solutions.