05-13: Evaluation into the use of Mine Drainage to Supplement Cooling Water

The Sasol petrochemical complex located in Secunda, South Africa operates the world's largest coal to synthesis gas conversion process. Expansion projects have resulted in an increase in cooling water requirements which is difficult in this water short catchment. Conversely, drainage water continuously accumulating in old coal mine workings is a growing liability. In an effort to balance the supply and demand within the complex, investigations were initiated into the use of min drainage water. The mine drainage contains amongst others, elevated concentrations of Calcium (~ 250 mg/l), Magnesium (~ 150 mg/l), and Sulphate (~ 2,955 mg/l) as well as trace quantities of iron and manganese. The addition of up to 12% of such mine drainage water to a cooling medium could tender the blend highly conducive to fouling, scaling and corrosion. Pilot scale cooling towers were operated over a twelve month period and the results including the limitations observed will be discussed.