Simultaneous Removal of SO2 and NOX by a Combination of Red Mud and Coal Mine Drainage

Simultaneous removal of sulfur dioxide (SO2) and nitrogen oxides (NOX) is an important research field in air pollution control. The combination application of red mud (RM) with coal mine drainage as absorbent in simultaneous desulfurization and denitrification is an innovative attempt. In this study, a series of bubbling and spray tower tests were conducted to improve desulfurization and denitration abilities. Effects of RM concentration, gas flow, liquid-gas ratio, and SO2 concentration were investigated in the test. Our results indicated that SO2 removal efficiency depends primarily on RM concentration, gas flow, and the liquid-gas ratio. In the denitration test, the denitration characteristics of the absorbent were not consistent with industrial requirements, but denitration ability could be improved by the addition of an oxidant. In addition, influence of interactions between SO2 and NOX was observed, and low concentrations of SO2 could enhance NOX absorption, whereas high SO2 concentrations inhibit NOX absorption. Meanwhile, NOX concentration has a negligible effect on SO2 removal. Under optimized conditions, such as with RM concentration of 12%, gas flow of 40 L/min, liquid-gas ratio of 20 L/m(3), absorbent renewal rate of 15%, and a sodium chlorite concentration of 1.9%, desulfurization efficiency is >99.0%, and denitration efficiency ranges from 45.0% to 47.0%. RM and mine water slurry show strong potential as a novel absorbent for the simultaneous removal of SO2 and NOX. This study provides a potential feasible technology for reusing RM and coal mine drainage with low cost instead of conventional method.