EFFECT OF OXIDATIVE DEGRADATION OF COAL ON BALL MILLING OF BASIC SLAG

摘要

On an average the steel plants of India generate the slag about 2.5 x lO6tonnesiannum and dumped as a waste material. This slag containing P_2O_5, 2percent to 8percent and CaO, 30percent to 50percent, 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 P_2O_5 content in the Slag. The results of these investigations indicate that sample ground in presence of coal with KmnO_4 is more reactive for dissolution of P_2O_5 than the sample ground in absence of additive. The use of citric acid, gallic acid and KmnO_4 with low rank coal as additives in wet grinding, improved fumes generation to 96percent and the extraction of P_2O_5 achieved 5percent, 3percent and 23percent respectively. The possible mechanism for improving the high reactivity is due to in-situ formation of flimicacid 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.