Study On Improving Ash Fusibility And Fluxing Mechanism Of High Alumina Coal

High alumina and high ash melting temperature of A, B coal were selected, which from Zhungeer coal field in Inner Mongolia. By adding Chemical pure fluxes reduce the ash melting temperatures and improve viscosity temperature characteristics. The influence of SiO2, CaO and Fe2O3 on ash fusion temperature and viscosity temperature characteristics are analyzed and summarized. This paper was studied the effect of fluxes on minerals transformation, surface morphology and micro area chemical composition, slag mineral composition with the help of XRD, SEM-EDX and Thermodynamics software. The following conclusions are obtained:(1) The content of A12O3 in A, B coal ash are 53.20%,42.61%, WSiO2/WAi2O3 are 0.7 and 1.2. The main minerals in slag contained mullite, corundum, cristobalite at high temperature. These minerals played a role of skeleton supporting during ash melting, and resulted the ash flow temperature of the twos higher than 1600℃。 Increase the SiO2 content and decrease the melting temperatures of A and B coal ash. Due to the different WSiO2/WAl2O3, CaO and Fe2O3 had different effect on melting temperature of high alumina coal ash. With the increase of CaO and Fe2O3 content of coal A(WSiO2/WAl2O3<1), FT first decreased and then increased and change trends like a "V’and the order of influence is CaO>Fe2O3>SiO2-In another case, for coal B(WsiO2/WAi2O3> 1),FT has been reduced order of influence is Fe2O3> SiO2> CaO. A12# reduced the FT of A to 1321℃, B12# reduced the FT of B to 1361℃. The viscosity temperature characteristics are better, and the interval of viscosity temperatures greater than 154℃.(2) Added flux increased WSiO2/WAl2O3, CaO and Fe2O3 content. Refractory minerals mullite, corundum and quartz transformed into melilite, anorthite, cordierite and other low melting point minerals. In heating process, the slag los the skeleton of mullite, corundum and quartz and at the same time, anorthite turned eutectic with other minerals. With the increase of temperature, particle morphology of slag from the angular gradually transformed into a molten round, bond, was the mainly reason to reduce the melting temperature of high alumina coal ash. EDX results showed that Si, Al, Ca, O elements gathered in the slag at 1400℃, the anorthite existed, and the analysis results are consistent and XRD.(3) The content of mullite were higher than 50% in slag at 1400℃ of A, B form the result of FactSage. After fluxed of coal A, the mullite in slag transformed into anorthite, melilite and iolite. Anorthite, alumina, spinel and iolite transformed into eutectic when temperature higher than 1200℃. After fluxed of coal B, anorthite, quartz, iolite, leucite transformed into eutectic when temperature higher than 1100℃, The calculation results of FactSage and XRD are consistent with the analytical results of the transformation process of the crystal minerals. It is the main reason that for the decrease of melting temperature of high alumina coal ash, high melting point minerals are transformed into low temperature eutectic.(4) Using Thermodynamics software analysis the reason that CaO, Fe2O3 had different effect on reduce the A, B coal ash melting temperature.The results showed that, melilite and anorthite of A+4%CaO melted at 1300℃, anorthite, melilite and wollastonite of B+10%CaO metled at 1200℃, So the two had lower melting temperature. More flux mineral cordierite in the salg of A+4%Fe2O3, B+10% Fe2O3 that played an important role in reduced melting temperature, and the flow temperatures were lower.