Study Of Coupling Interaction Mechanism Of Calcium And Magnesium On Coal Ash Melt Structure

The three high-ash-fusion-temperature coals with different Si/Al ratio obtained from Anhui Huainan,Shanxi Jincheng,ZhunGeEr mining area in Inner Mongolia were selected.The mineral distribution characteristics and mineral grain size distribution in coal samples were measured by CCSEM.The effect of calcium and magnesium compound flux on coal ash fusibility,the viscosity-temperature characteristics were studied.The mineral composition,surface chemical properties,the structure of the melt and bonding characteristic were investigated under reducing atmosphere at high temperature by X-ray diffraction(XRD),scanning electron microscopy and energy dispersive X-ray spectroscopy(SEM-EDX),Raman,respectively.And the ash mineral microstructure characteristics were calculated used by FactSage software and the quantum chemistry software from the angle of molecular level.Four conclusions were summarized as follows:The total content of calcium and magnesium in ZJX coal,CP coal and BLH coal are is 1.55%,5.55%,4.52%,respectively.The main minerals in three coals are refractory minerals such as kaolinite and quartz.And the content of refractory minerals is 90.46%,76.30%,74.12%,respectively.That's why the three coal ash fusion temperatures are higher.The coupling intensity of calcium and magnesium compound flux on reducing coal ash fusion temperature was different,but both were superior to CaO and MgO.The AFTs of ZJX,CP coal increased at first and decreased subsequently as WCaO/WMgO increased.When WCaO/WMgo was equal to 1,The AFTs of ZJX,CP coal was 1289? 1279? respectively.However,The AFTs of BLH coal decreased as WCaO/WMgO increased,and When WCaO/WMgO was equal to 1,The AFTs of BLH coal was 1420?.The coal ash fusibility and ash viscosity-temperature characteristic of ZJX and CP coal added with 6%(WCaO/WMgo=1)improved significantly compared with the addition of CaO and MgO,and the range of flow temperature during 5?25Pa·s became wider.The coupling intensity of calcium and magnesium was notable,anorthite interacted with forsterite,spinel,cordierite and produced eutectic at low temperature.For the BLH coal that coupling intensity of calcium and magnesium was not notable,as the temperature reached AFTs,there was spinel with stronger stability of the lattice in coal ash slag.Ca2+ and Mg2+ electron-acceptor destroyed stable structure of kaolinite causing that coal ash fusibility,flow characteristic and viscosity-temperature characteristics changed.The calculation results implied state density of forsterite was similar to kaolinite.At the left of state density,the peak of electronic state density was the highest,which illustrated they were easier to react with electron-acceptor and lose electron.In contrast,at the left of state density,the results were opposite.Therefore,Ca2+ can be as electron-acceptor and destroy the structure of forsterite in coal ash slag,which also explained the essence of calcium and magnesium coupling was that low eutectic produced between anorthite and forsterite.