Experiment Study Of Estimate Index On Coal Reburning Of High-volatile Coal

Coal consumption holds important position in Chinese fossil energy. Coal-firedpower generation accounts for the proportion of Chinese total generating capacity ofmore than60%, this ratio will continue to be maintained at above50%in the nextthree decades. Large-scale using of coal has also brought serious environmentalproblems which caused by NO_xand other pollutants. Pulverized coal reburning is aneffective way of the combustion methood to reduce nitrogen oxide emissions. Takenthe characteristics of thermal coal in China into account reburning technology hasimportant practical significance.By of the end of2011, China has gradually built14large-scale coal bases suchas Shendong coal base and Zhundong coal base which found in Xinjiang in2008. The paper summarizes the distribution of Chinese major thermal coalresources and the characteristics of combustion and NO_xemission about three kindsof typical thermal coal have been analysised.Six kinds of high volatile coal which are yuanbaoshan lignite, Baiyinhualignite, Yimin lignite, Xiao Longtan lignite, Zhundong bituminous coal and Shenhuabituminous coal have been selected. The paper completes the work of ultimateanalysis and proximate analysis of raw coal first, and then carries out the pyrolysisprocess of true atmosphere of six high-volatile coal in a high temperature flowreactor which simulated the reducing atmosphere characteristics. At the same timesix kinds of char have been prepared and fuel-N migration characteristics have beenanalysised. The mercury porosimetry and SEM are combined to analysis the porestructure of coal char, the studies show that with the increasing of coal rank, theproportion of volatile nitrogen which converted from fuel-N in the pyrolysis processdecreased and char-N increases. The volatile-N increases as the volatile of the rawcoal added. The increasing of total char surface area which caused by the process ofvolatile releasing can effectively improve the ability of heterogeneous reductivity ofchar, the pore structure of char was positively correlated with the volatile matterunder the same reaction conditions. This article also examined the relative contentof different coal char ash of the five kinds of metal oxides (CaO+Na2O+Fe2O3+K2O+MgO) under the conditions of the real atmosphere, the metal oxides caneffectively improve the reactivity of char.The combustion and NO_xemission characteristics in the original and reburningoperating conditions of six high-volatile coal have been obtained in an entrainedflow combuster with multiple reaction segment which can be used to simulate the real boiler combustion process. The original NO_xemission is in relation to thenitrogen content and nitrogen release characteristics of coal. The high volatile coalcan burn effectively, the using of coal reburning on high volatile coal can achievereduction greatly and reach the NO_xemission concentration of180~350mg/Nm3. The correlation analysis of the physicochemical properties of high volatilecoal and coal reburning characteristics has been analyzed. The results show that it isrealized the higher efficiency with lower of nitrogen content in coal, higher of thevolatile content, greater of the total surface area in char hole and higher of metaloxides in char ash. Finally it is introduced of the comprehensive converted index [X]which is able to characterize the physical and chemical characteristics and coalreburning properties and found that the greater value of [X], the higher efficiency ofhigh volatile coal can be reached which is fiting through the data.