Regulation of ash fusion behaviors for high aluminum coal by high calcium coal addition

To meet the requirement of liquid slag tapping entrained-flow gasification, two kinds of high ash fusion temperatures (AFTs) coals with significant difference in ash chemical composition (high aluminum coal: Al2O3 > 38%, Sunjiahao coal, and Shajuzi coal; high calcium coal: CaO > 35%, Hebi coal, and Xinjiang coal) were selected. The ash fusion behaviors of blending coal were investigated. The results showed that blending coal could significantly reduce the AFTs of high-AFT coal. The formation of high melting point minerals led to the increase of AFTs (high aluminum coal: mullite, corundum, and cristobalite; high calcium coal: lime and periclase). Xinjiang coal reduced AFTs more obviously than that of Hebi coal because of the differences in the total amount of alkali oxides, Fe2O3 and MgO. The effect of CaO on AFTs was determined by the amount of CaO. CaO, Fe2O3, and MgO promoted the formation of low-melting eutectic [anorthite, gehlenite, spinel, pyrope, and ringwoodite (Fe-rich)] and made AFTs low when the mass ratios of high calcium coal were low. On the contrary, the high content of CaO increased AFTs. FactSage7.0 software is a very effective way to explore the effect of mineral transformation on AFTs.