Estimating the rate of generation of acid drainage products in coal storage heaps

The rate of oxidation of iron sulphides contained in reject coal from a coal washery was measured in small scale reactors designed to simulate the conditions in a storage heap. The results from such tests compared well with the measured levels of oxidation products generated in acid waste streams emanating from large scale columns (scale-up factor of 200), indicating the value of the procedure in predicting some of the variables necessary for the design of a treatment facility. As previous studies have shown, the rate of oxidation was found to be constant up to a critical point when the oxidation rate dropped noticeably. During this period, the oxidation rate varied from 61.4 - 206.4 mg Fe/day/kg of coal for temperatures ranging from 25°C to 37°C