Coal cleaning through removal of phosphorus mineral from morupule main seam coal

Phosphorus is critical for the strength of metals; however, in excess it makes the metal product fragile. This leads to quality complaints and financial losses. Phosphorus is finely disseminated in coal and forms part of the coal structure. Despite the use of a coal facility at Morupule, the final product surpasses the maximum limit of 0.02% phosphorus. Reduction of the phosphorus by convectional coal cleaning processes is a challenge due to the mineral associations with the coal structure. Selective mining is the current implemented option at Morupule to attain the low phosphorus production but it is costly and time-consuming. Hence, the aim of the research to investigate coal leaching as a primary method for phosphorus reduction. Hydrochloric acid at 1 Mol concentration was used for 4 hours at room temperature. Sixty-four percent phosphorus removal was achieved resulting in 0.012% residual phosphorus. To improve the rate of reaction, microwave pretreatment was conducted to further reduce the amount of phosphorus in the coal. The effect of phosphorus reduction using 1000 W single-mode cavity was compared to that of the multimode cavity. The optimum processing parameters were 2 minutes and 3 hours leaching time to yield a residual phosphorus of 0.008%.