Journal of the Korean Society of Mineral and Energy Resources Engineers ISSN:2288-0291(Print) 2288-2790(Online) 한국자원공학회지

Although domestic coal ash contains chemical components suitable for the raw materials of cement, the direct usage of the coal ash for making clinker is restricted due to the high fusion temperature of domestic coal ash. Therefore, the fusion temperature of the ash has to be lowered down below 1450oC which is the combustion temperature of clinker by using mineralizers. The fusion temperature depressions of about 200oC were observed by 2~8 wt.% additions of mineralizers(CaO, MgO, Fe2O3 ) in earlier research. However, effects of the combinations of mineralizers and effects of small amounts of inorganic compounds(K2CO3 , Na2CO3 , TiO2 ) were not investigated on the lowering of the fusion temperature of coal ash. The fusion temperature depressions on the combined additions of mineralizers(CaO, MgO, Fe2O3) when added in 10, 20 wt.% at the ratios of CaO : MgO 0.35 : 0.65~0.65 : 0.35 or MgO : Fe2O3 0.75 : 0.25 to coal ashes from Tae-baek and Ho-nam area were observed in this study to show synergistic effects of 60oC ~ 90oC compared to the additions of single mineralizer. The tendency of CaO > MgO > Fe2O3 and the synergistic effect were observed on the fusion temperature depression by the combined use of mineralizers. Fusion temperature depressions of 150oC ~ 200oC resulting in the nearest fusion temperature to the clinker fusion temperature(1450oC) were achieved by the addition of the small amounts of inorganic compounds(K2CO3 2~5 wt.% (Fluid Temp. : 1425oC ~ 1485oC), Na2CO3 2~5 wt.%(F.T : 1374oC~1468oC)). The simulation of the fusion temperature depression was accomplished by designing a model compound whose components were similar with coal ash to build the model equation which showed the relationship between the compositions of the inorganic compounds and the fusion temperatures based on the experimental results.