Study On Using X-ray Diffraction Assisted Coal Ash Composition To Prevent Slag Blockage

19typical coal samples from different regions of china were studied. The coal ashes made in low temperature and high temperature were tested respectively by X-ray diffraction (XRD) and the qualitative and quantitative analysis was carried out. The relationship between crystal minerals in coal ash and the ash fusion characteristics was explored, which was used to change ash composition and then prevent slag block. The following conclusions are obtained:1、Through the qualitative and quantitative analysis of XRD, kaolinite, quartz, calcite, pyrite, rutile, ankerite, siderite and muscovite are mainly contained in low temperature ashes. Crystalline minerals in high temperature ashes are mainly quartz, hematite, calcite, lime, anhydrite, muscovite. It has little difference between oxides transformed from crystal minerals in the high temperature ash and ash chemical composition.2、Crystal minerals in19kinds of coal ash samples was used to predict the coal ash flowing temperature, and a prediction equation was take out. Checking the equation and absolute deviation is less than50℃. Taking use of grey correlation to calculate the correlation of crystal mineral in coal ash and coal ash flowing temperature, the result is as following:r muscovite> r quartz> r hematite>r calcite>r anhydrite.3、6kinds of coal samples slag viscosity was analyzed, the melting slag viscosity temperature characteristic curve has close contact with content of Fe2O3and CaO in coal ash. The form of slag with low iron calcium ratio will be "glass slag". The form of slag with high iron calcium ratio will be "crystalline slag". In the crystalline slag, the lower iron calcium ratio, the viscosity temperature curve changes obviously around critical temperature point. The coal ash viscosity can be improved due to the increase of iron calcium ratio.4、Combining the example of slag blocking of Shell gasifier in actual industry process, the main reason of slag blockage of gasifier is the precipitation of anorthite in the melting slag. The critical temperature of viscosity temperature curve is higher than melting slag temperature at25pa·s. Using the second and third conclusion proposed to adjust the coal ash chemical composition. Increasing iron calcium ratio in coal ash and then analyze the adjusted coal slag. Anorthite content in melting slag was decreased. The critical temperature is lower than melting slag temperature in25pa·s. The melting slag viscosity is improved.