Analysis of the effect of brine retention time on the scaling potential

Abstract

The overall severity of a potential scaling problem, as encountered in additive treated desalination plants, is considered through the total bulk precipitation. tendency of the brine circulating In the plant. The effects of brine circulation characteristics, retention time and supersaturation level on the degree of scale precipitation are analyzed by population balance models characterizing mixed flow and plug flow conditions, respectively. It is shown that mixing effects aggravate the scaling potential. For identical brine retention times, the degree of bulk precipitation occurring under mixed flow conditions is considerably larger than that occurring under plug flow conditions. Similarly, the induction period in a mixed flow system is shorter than that in a plug flow system. General trends on the scaling potential predicted by the proposed analysis are illustrated for a modelled vapor-compression desalination unit. The effects of brine retention time and additive concentration on the amount of scale precipitating in the brine are evaluated using roughly estimated values of kinetic coefficients for CaCO 3 retarded precipitation.