Recovery of Mineral Salts and Potable Water from Desalting Plant Effluents by Evaporation. Part I. Evaluation of the Physical Properties of Highly Concentrated Brines

Abstract

The main theme of this study is the recovery of a salt (in particular, magnesium chloride) from rejected brines of desalination plants through the simulation of a modified Multistage Flash (MSF) evaporation system. Such a proposal is attractive for countries highly dependent on water desalination. Saudi Arabia and other Arab Gulf states are good examples. A basic assumption underlying this study (both Part I and Part II) is that desalination effluents are assumed to contain only the two most abundant salts in seawater: sodium and magnesium chlorides. In this paper and equilibrium relationship describing the solubility of NaCl in aqueous solutions of MgCl₂ is first developed. This generalized correlation is based on the solubility data available in the literature. The correlation is valid for the temperature range 15–200°C and for a concentration of MgCl₂ up to 30 g/100 g saturated solution. Next, calculations of the specific gravity and viscosity of highly concentrated brines are presented, and then compared with experimental data. Research findings presented in this paper serve as a prerequisite for the reclamation of mineral salt to be considered in Part II.