The Effect Of Alkali Metal Sodium On Zhundong Coal Ash Melting Characteristic

Zhundong coalfield locates in Xinjiang region contains huge coal reserves, will become supply origin of coal resources which is extremely important and strategic significance to our country. Zhundong coal quality is good and has advantages of low pollution and good combustion activity. But alkali metal content in Zhundong coal is higher than traditional power coal, which will result in the phenomenon of heavy slag and fouling etc. in power plant boiler, which will greatly restrict ZhunDong coal promotion and utilization in xinjiang region and even nationwide. Therefore, studying the effect of alkali metal sodium on the ZhunDong coal ash melting characteristic plays an important realistic meaning.In this paper, ZhunDong Wucaiwan coal and Tianchi coal are selected as research object, study alkali metal sodium's occurrence form and content in Zhundong coal through sequential extraction experiment and microwave digestion experiment, it is found that the water soluble sodium is the main sodium,the organic sodium ranks second and the insoluble sodium is minimal. Combining TG-DTG and XRD analysis methods, study ZhunDong coal low ash and high temperature ash in different ashing temperature, it is found that main minerals in WCW are anhydrite,quartz, gehlenite and akermanite, main minerals in TC are anhydrite, larnite,akermanite and merwinite. There are a large number of fluxing minerals in Zhundong coal, and calcium containing minerals easily generate low temperature eutectic reaction and form low temperature co-melt, that will reduce the ash melting temperature and make ZhunDong coal having strong slagging.Adding different proportion of Na2 O to the low temperature ash, study the effect of sodium on ZhunDong coal ash melting temperature, and select mixed ash which added 10%,20% of Na2 O for phase analysis by XRD and for surface microscopic form by ESEM-EDX. The results show that with increasing Na2 O ratio, the ash melting temperature of Wucaiwan coal decreases at first and then increases, the reason of ash melting temperature decreasing is that there are the low melting point of newly formed hedenbergite and thenardite in coal ash, while alkali metal sodium can promote low temperature eutectic reaction between gehlenite and akermanite. With the addition of Na2 O ratio increasing further,there are the high melting point of larnite, andalusite and merwinite, so the ash melting temperature of WCW increases. With increasing Na2 O ratio, the ash melting temperature of Tianchi coal decreased at first and then became stable. The reason of ash melting temperature decreasing is that decomposition of minerals in coal ash generates CaO under high temperature, then, high content of alkali metal sodium can promote low temperature eutectic reaction forming low temperature co-melt between CaO and Na?Si?Al, and there is the low melting point of thenardite in coal ash. With the addition of Na2 O ratio increaseing further, the reason of coal ash fusion temperature remains unchanged is that mineral composition and relative content are basically unchanged in coal ash...