ABSTRACT: Mine water reuse technology takes the coal mine drainage water as water source, then reuses treated waste water for the power plant water system via technical reform and innovation process. In this technique, the fresh water demand can be greatly reduced, thus it is considered as an important approach to solve the power plant water resources scarcity. The further water treatment is crucial to the coal mine water reuse project for power plants. Due to the high salinity of brine, the pipe scaling and corrosion problems accrue constantly at high operating temperatures. Therefore, the research on pH values of the high salinity brine water is essential for studding the acidification of pipe lines during the mine water reuse project. In this paper, the pH values at a temperature from 298 to 373 K for MgCl₂ and CaCl₂ solutions with molalitis ranging from 1 to 4 mol/kg were predicted via the geochemical simulator PHREEQC(version3.7.1) based on the Pitzer activity-coefficient model with parameters taken from the literature. This study observes the pH values of the brine change into an acidic condition when calibrated with HCl (0.01 mol/kg) and an alkaline condition when calibrated with CO₃^2- and HCO₃^-(0.0025 mol/kg). In the acidic condition, the pH of solution increases with increasing temperature and decreases with increasing concentration. In the alkaline condition, the pH of solution decreases with increasing temperature and decreases with increasing concentration.
 

Mine water reuse; Pitzer Model; pH; Magnesium chloride; Calcium chloride