Study On The Capture Mechanism Of Modified Fly Ash To The Gas Phase Alkali Metal During The Combustion Of Zhundong Coal

In this study,fly ash was used as raw material,and after water washing and acid modification,two modified fly ash were obtained.The microstructure was analyzed by SEM,BET and so on.Then,the melting characteristics of the original fly ash and the modified fly ash were analyzed.The XRD material analysis and XRF elemental analysis were used to analyze the melting temperature change of the fly ash.HSC Chemistry software was used to study the thermodynamic properties of six additives such as SiO₂,Al₂O₃,kaolin,raw fly ash,washed fly ash and pickled fly ash to capture the gas phase alkali metal.Based on the thermodynamic properties,the above six kinds were studied.The additive was studied for further reaction characteristics.The research results are as follows:?1?The original fly ash has a large particle size distribution in the range of more than 100?m and less than 37?m,and the microstructure is spherical,and the specific surface area of the fly ash is increased after modification.?2?Fly ash with particle size less than 37?m,the melting characteristic parameters are basically unchanged after washing,and the melting characteristic temperature after pickling is reduced by about 30°C;the melting characteristic temperature after washing with fly ash in the range of 37?m⁶5?m The temperature is increased by about 30°C.After pickling,the fly ash is increased by about 20°C except for FT.The other melting characteristic temperatures are basically unchanged.The fly ash of more than 100?m has a constant melting characteristic temperature after washing,and is melted after pickling.The characteristic temperature rises above100°C.The content of O,Al,Mg and K in the washing and pickling of fly ash did not change much,the content of Ca and Na decreased,and the content of Fe increased.?3?After washing with fly ash with particle size less than 37?m,the peaks of CaSO₄ and CaO decrease,and further decrease after pickling;the diffraction intensity of CaFeO₅ decreases,but the intensity of diffraction peak of Fe_1.5Ca_0.5?SiO₃?₂increases.The melting point of the coal ash is reduced after pickling.The main crystalline phase materials present after pickling of fly ash having a particle size larger than 100?m are SiO₂ and iron-aluminum spinel.?4?The six additives have the ability to capture the gas phase NaCl at 600°C-1000°C,and the kaolin captures the gas phase NaCl best.?5?Both the washing and pickling of fly ash enhance the ability of fly ash to capture gas phase NaCl,and the acid-modified fly ash captures the best effect of gas phase alkali metal compound.Modified fly ash is more likely to combine with Na to form aluminosilicates,and it also reduces the formation of gaseous Na₂Cl₂.?6?Comparing the weight loss rate of the six additives with the solid NaCl reaction,it is concluded that the pickled fly ash captures the gaseous NaCl best when the working condition is 1000°C and the burning is 90 min.