Effect of Chemical Pretreatment on the Desulfurization of Coal by Selective Oil Agglomeration

摘要

An experimental investigation was carried out to improve selective oil agglomeration as a method for separating coal and mineral particles. The effectiveness of a special chemical pretreatment for enhancing the rejection of inorganic sulfur and ash by subsequent agglomeration was studied. The special treatment used hot alkaline solutions containing dissolved oxygen to oxidize pyrite, reducing its tendency to agglomerate with finely divided coal particles. Sodium carbonate was a very effective alkali for use in the pretreatment reaction. There appeared to be an optimum sodium carbonate concentration (1 or 2 wt %) for the rejection of inorganic sulfur by oil agglomeration. By pretreating coal containing 4.96% inorganic sulfur and 15.7% ash with a 2.0 wt % sodium carbonate solution at 80 exp 0 C for 15 min, 87.9% of the inorganic sulfur and 63.6% of the ash were removed by selective agglomeration with a heavy fuel oil mixture. Chemical pretreatment was more effective in reducing the inorganic sulfur content of minus 400 mesh coal than of minus 100 mesh coal. The chemical pretreatment reaction leaches only small portions of the pyrite from the coal and serves mainly to develop a hydrophilic surface on the pyrite particles. The method of chemical pretreatment followed by selective oil agglomeration was not equally effective on all of the kinds of coal tested. Chemical pretreatment was a very effective method of suppressing the agglomeration of relatively pure, finely divided pyrite. (ERA citation 04:012001)