硅铝比对ＣａＯ－ＳｉＯ２ －Ａｌ２ Ｏ３ 熔体微观结构的影响分析

The acid-base ratio and Si-Al ratio of coal ash are the key factors affecting coal ash properties. Adding additives to coal or using mixed coal to adjust coal asli fusing characteristics by changing the ratio of Si()2 to A1203 is an important means to improve the ash and slag problems in the high temperature coal conversion process. In order to analyze the influence of the change of Si-Al ratio on the mi- crostructure of coal ash system and obtain the theoretical mechanism of the change of macroscopic properties, the radial distribution func¬tion (RDF) ,mean coordination number (CN) ,degree of polymerization,distribution of oxygen and other microstructures in Ca()-Si():- A1203 system were simulated and calculated when Si02/Al203 increased from 0.5 to 3.1 based on first principles at 1 600 °C. The results show that;when Si()2/Al203 increases from 0.5 to 3.1 ,Si-0 has a stable four coordination structure and the average bond length is 1.61 x 10 10 m; the average bond length of A1-O is 1.75x10 10 m,the coordination number of A1-0 is relatively stable,and the coordination number decreases with the increase of Si-Al ratio. Si and A1 are network formers in the silicate system of synthetic coal ash. As Si()2/ A1203 increases from 0.5 to 3.1 yQ and Q∗decrease gradually,forming Q~ and Q with low degree of polymerization. Among them, Q4 and Q∗decrease by about 23% and 10% respectively and Q∗ and Q~ increase by about 14% and 11% respectively. A large number of [Si()4]4~ and [ A104] v are destroyed,the degree of polymerization is reduced,the disorder is increased,and the network structure is destroyed,resul¬ting in the decrease of ash fusibility. With the increase of Si-Al ratio,()t and Ob decrease gradually,and ()nli increases significantly. Among them,Ob and ()t decrease by about 7% and 13% respectively,and Onb increases by about 18%. The network structure of the system is de¬stroyed, and the loose network structure makes the system more prone to collapse at high temperature. The macro performance is that the melting temperature of coal ash is reduced,and it is easier to produce low-temperature eutectic.