富氧燃烧条件下燃煤NO_x排放的实验研究

Experimental study of NO_x emissions from coal combustion under oxy-fuel conditions

以神华（SH）烟煤和晋城（JC）无烟煤为研究对象,利用一维沉降炉（DTF）开展了煤粉在O_2/N_2、O_2/Ar、O_2/CO_2和O_2/RFG 4种气氛下燃烧时的NO_x排放特性实验,研究了温度和氧浓度对NO_x排放特性的影响,探讨了富氧燃烧条件下导致NO_x排放降低的各个因素的贡献率的变化。结果表明：温度上升会导致燃料氮向NO_x的转化率增大;氧浓度的上升同样会导致转化率的增加,SH烟煤由于挥发分含量较大,受氧浓度影响较大;定量分析结果表明,富氧燃烧条件下导致NO_x排放降低的主要因素是循环NO_x的还原,占整体的50%以上;其次是高浓度CO_2气氛对NO_x的还原,约占20%～30%;而热力型和快速型NO_x的缺失对降低NO_x排放的贡献率不及20%。温度的上升对JC无烟煤各因素贡献率有较大影响;氧浓度的增加会导致SH烟煤各因素贡献率有明显变化。

NO_x emission characteristics during coal combustion were studied in a one-dimensional drop-tube furnace（ DTF） under O_2/ N_2,O2/ Ar,O_2/ CO_2,and O_2/ RFG atmospheres to determine the effects of temperature and oxygen concentration on the characteristics of conversion of fuel nitrogen to NO_x and to investigate the changes in contribution ratios of the individual factors reduced NO_x emissions under oxy-fuel combustion. The Shenhua（ SH） bituminous coal and Jincheng（ JC） anthracite were selected for this study. The results show that the conversion rates of fuel nitrogen to NO_x increase with increasing temperature. The increased oxygen concentration enhances the fuel-nitrogen conversion rates. The nitrogen conversion rates of SH bituminous coal are more sensitive to oxygen concentration due to its higher volatile contents. Quantitative analysis shows that the contribution of recycled-NO_x reduction is dominant,accounting for more than 50% of the total NO_x reduction. The high CO2 concentration in the furnace accounted for 20% to 30%,while the elimination of atmospheric nitrogen accounted for less than 20%. For JC anthracite,higher temperatures significantly change the contribution ratios of the individual factors. For SH bituminous coal,the contribution ratios of the factors are sensitive to oxygen concentration.