Study On Mechanism Of Alkali Metal Capture By High Alkali Coal Liquid Slag

Zhundong coal is a good power coal with huge reserves,but excessive alkali metal content leads to serious adhesion and slagging.In this paper,the idea of capturing alkali metal in coal by liquid slag discharge is proposed,and Na in coal is captured by high alkali slag itself.The core problem of the study is the influencing factors and reaction mechanism of Na capture by high alkali coal slag.Firstly,for the common zhundong coal species,the experiment of Na in coal captured by slag was carried out,and the influencing factors of Na captured by slag were explored by combining the ash content of different coal species and the occurrence form of Na.The results show that the Na capture rate of different coal slag varies greatly,and the insoluble Na in coal mainly exists in the form of silicoaluminate compound.The higher the insoluble Na content is,the more easily Na is captured in coal,while the more water-soluble Na is,the more difficult it is to be captured.On the basis of this choice Zhun Dong coal and shenhuo coal for the experiment of Na of the modified slag capture coal,ash respectively,SiO₂,CaO and kaolin is added to the change of coal ash composition after capturing Na experiment was carried out under the melting temperature,research has shown that adding SiO₂ content or kaolin in coal ash content is higher,the slag’s ability to capture the Na stronger,but CaO content is higher,is not conducive to capture Na slag.In order to further study the mechanism of alkali metal capture by slag,simulated coal ash（SiO₂-Al₂O₃-Fe₂O₃-CAO-NaCl）was used to replace the east coal ash for fusing test.Then solid NUCLEAR magnetic resonance test and phase analysis were conducted on the samples to explore the influence of the main components of coal ash on Na capture rate,and the capture mechanism was analyzed in combination with the changes of slag structure.The results showed that Na was captured and entered the si-AL network structure of slag.The more Si and Al content in coal ash,the higher Na is captured.Ca and Na compete for coordination in the si-AL network structure and inhibit Na capture.The higher Si/Al ratio is,the better Na capture effect will be.Combined with Material Studio,the liquid slag network structure was calculated,and the DMol³ module was selected for calculation.Due to the amorphous nature of the liquid slag,the structural units of silicon tetrahedron and aluminum tetrahedron were selected to calculate the bond length and Fukui function.On this basis,the calculation of the combination of the two tetrahedron structural units was done.The results showed that the tetrahedron structure of Si played a role in capturing the alkali metal in the liquid slag,which mainly depended on the coordination of Si to the alkali metal.After Si captures Na,the structure of Qn will constantly change.The more Na captures,the more bridged oxygen bonds will be broken.