Ash Sintering And Fusion Characteristics Of Low-grade Bituminous Coal And Mixed Burning Ash With Biomass Under O₂/CO₂ Ashing Atmosphere

Ash sintering and fusion characteristics has an important effect on the judgment of slagging characteristics and the choice of the ways of sludge discharge, which is the key factor of the normal operation of boiler. The study of foreign and domestic researchers are mostly fusing on the fusing characteristics of coal ash temperature, distribution of elements in the ash, solid sulfur ash, the deposition of fly ash and so on. The study of the ash melting and sintering characteristics on the oxygen-enriched combustion conditions is less.The paper studies on the low-grade bituminous coal, rice stem, pine sawdust, corn stalk in the Chongqing state. The ash sintering and melting properties of low-grade bituminous coal, and mixed burning ash of low-grade bituminous coal and biomass under the conditions of oxygen-enriched atmosphere are studied. The ash are analyzed by the means of ash melting point test, X-ray diffraction, TG-DSC thermal analysis and SEM morphology analysis from the view of mineralogy, thermal analysis and microscopic structure. And then the fusing and sintering characteristics of ash in different combustion conditions are obtained. The opinion of the paper is to provide reference for the selection of oxygen concentration and combustion temperature, inferior coal and biomass mixed burning technology.Experimental results show that: The change of ash melting characteristic temperature and sintering rate has no obvious regularity with the change of oxygen concentration, but which has great effect on the curves of TG-DSC. The ash weight loss and the endothermic peaks are more obvious with the decrease of the ashing oxygen concentration in the thermal analysis experiments. Higher ashing oxygen concentration can promotes the agglomeration of inherent mineral and then speed up the formation of vitreous body substance, which provides the conditions for Fe2+. Fe2+ has stronger boosting effect than other valence containing iron ore material, which can reduce the ash melting characteristics temperature. Ash fusion temperature can be reduced by increasing the ashing oxygen concentration for higher iron coal. The generation of class feldspar minerals increases with the increases of ashing temperatures. Low temperature melt is formed between the silicon oxide and silicate minerals group, which leads to lower ash melting characteristics temperature and higher sintering rates in higher ashing temperature. The ash melting characteristics temperature of mixed burning ash firstly decreases and then increases with the increas of mixing ration of biomass. The melting points of different mixed burning ash are apparently different because of the differences of biomass ash composition. The differences of biomass ash composition lead to ash sintering and melting characteristics of mixed burning ash of biomass and low-grade bituminous coal has big difference. The weight loss of mixed burning ash of corn stalk, rice stem, pine wood chips and low-grade bituminous coal increases with the increasing of biomass &coal mixing ratio. So is mixed burning ash sintering rate. The weight loss of the mixed burning ash of corn stalk and low-grade bituminous coal is the greatest with the highest alkali metal content in corn stalk ash. The weight loss of pine sawdust and inferior coal burning ash are most obviously in the TG curves. The reason is that the content of Ca O and sulfate class material is high. Much Mg CO3?Ca CO3、Ca CO3、Ca(OH)2 and sulfate class material are resolved with the increasing of temperature.