Effect of oxidative degradation of coal on ball milling of basic slag

Abstract

On an average the steel plants of India generate the slag about 2.5 x 10(6) tonnes/annum and dumped as a waste material. This slag containing P2O5, 2% to 8% and CaO, 30% to 50%, is suitable after comminution to d(95), 0.063 mm for soil conditioner and nutrition for plants. Since grinding is an energy intensive process, in this paper an attempt is made to use of chemicals in the grinding to improve the mill performance as well as the reactivity of P2O5 content in the slag. The results of these investigations indicate that sample ground in presence of coal with. KMnO4 is more reactive for dissolution of P2O5 than the sample ground in absence of additive. The use of citric acid, gallic acid and KMnO4 with low rank coal as additives in wet grinding, improved fines generation to 96% and the extraction of P2O5 achieved 5%, 3% and 23% respectively. The possible mechanism for improving the high reactivity is due to in-situ formation of fumicacid by degradation of coal during wet milling of slag. During this process, a typical honey comb structure develops in the slag structure, which favours for faster rate of grinding and increase the finness.