Research On Combustion And Slgging Characteristics Of Zhundong Coal

As the most important status of national economic development in China, coal willbe in a dominant position for a long time in the energy structure of China. With thegradual increase of electricity consumption, coal consumption has increasedsignificantly. So coal-fired boilers in power plant can not burn a single designed coal,which have to be burned with new coal, resulting in a series of negative effects, such asslagging. Zhundong coal has large reserves, which is high quality, such as lowash(Aad=5.5%). Because of its high moisture, low ash melting point, high content ofiron and alkali metal in coal ash, the output of boiler will be reducing, furnace slagging,heated area fouling and other issues occur during running.In this paper, the research on prevention measures and status of boiler slagging isevaluated in detail, the combustion characteristics of Zhundong coal were investigated,especially slagging. Firstly, comprehensivly analyzing the based characteristics oftypical Zhundong coal, the Entrained Flow Combuster with Multiple Reaction Segmentwas used to study the slagging characteristics, the influence of furnace temperature(1150℃、1250℃、1350℃) and excess air coefficient(0.7、0.8、0.9、1.0) in primarycombustion zone on slagging and burnout characteristics was studied, which is inair-staged combustion conditions.The results show that Zhundong coal is flammable coal, which is fired easily, andthe ignition temperature is610.15K, when the temperature is above1150℃, the burningrate is more than98%. Without air-staged combustion conditions, with the temperatureincreasing the slagging increases significantly. In the main combustion zone of airstaged combustion conditions, the slagging characteristic increases as the excess aircoefficient reducing in main combustion zone. In the conditions that the temperature is1150℃, α=0.9/1.0and is1250℃, α=1.0, slagging appears lighter characteristicphenomenon, however when the temperature rises to1350℃, there will be severeslagging characteristic whatever the excess air coefficient is. Appropriately reducing the furnace temperature, increasing the excess air coefficient, enable boilers burningZhundong coal safely, at the same time ensure combustion efficiency.By XRD and SEM-EDX analysis, obtaining the melting characteristics of mineralsin Zhundong coal under high temperature conditions. Because the Fe2O3content in ashis higher, low temperature eutectic phenomenon of Fe and silicate minerals is obvious.The result of XRD analysis shows, the minerals in slagging are mainly anorthite, mullite,quartz，albite, nepheline and hematite. Without air-staged combustion conditions, withthe temperature rising, the content of mullite and hematite decreases, the vitreous issignificantly increased. In the main combustion zone of air staged combustionconditions, with the excess air coefficient decreasing, mullite content decreases, thevitreous was significantly increased, which are important reasons aggravating slagging.When the temperature rises to1350℃, the minerals species is detected, vitreousincreases significantly, crystalline phase minerals is mainly mullite. SEM-EDX analysisresults are consistent with the XRD analysis results, The result of EDX analysis showsthat the Si, Fe, Na are enrich in slagging, the content of Al is lower, Fe is mainly enrichin some irregular spherical particles.