制焦条件和催化剂对大颗粒煤焦还原NO影响

Effect of charring condition and catalyst on NO reduction by large char particles

摘要:

为探索一种有效的工业锅炉脱硝技术,针对管式炉,研究制焦停留时间、制焦温度和担载不同催化剂对粒径1.7～2.8 mm煤焦还原NO的影响．结果表明: 900 ℃以下时,制焦停留时间越长,大颗粒煤焦对NO的还原性越差,在900 ℃时,停留时间对反应的影响则不大．随着制焦温度的升高,大颗粒煤焦-NO的反应性大体呈降低趋势,但在低温段(500～600 ℃左右)则规律相反,呈上升趋势．添加不同种类的金属催化剂对煤焦还原NO能力有不同程度的提高,平均催化活性排序为Fe>Cu>K>Na>Ca>Mg．金属元素对煤焦异相还原NO的催化效果受温度影响较大,不同实验条件下金属的催化能力不同．此外,煤焦本身的性质(包括挥发分含量、孔隙结构和微晶结构)对还原NO反应也有较大影响. 煤焦的挥发分含量越高,孔隙越发达,石墨化程度越低,对NO的还原效果就越好．

Abstract:

To find an effective way for reduction of NO_x emission, this paper made use of a tube furnace to discuss the effects of residence time, temperature, and different catalysts on char-NO reactions. The particle size of char is 1.7～2.8 mm. The results show that the extending residence time is not conducive to the reduction of NO below 900 ℃, and the residence time has a few effects on the reaction at 900 ℃. With the increase of charring temperature, the reactivity for large char tends to be decreasing. But the principle is the opposite pattern—a rising trend in the range form 500 ℃ to 600 ℃. Adding different types of metal catalysts can promote the reduction of NO, the average order of the catalytic activity is Fe>Cu>K>Na>Ca>Mg. The catalytic effect of metal elements in char is affected significantly by temperature, and the metal catalytic ability is different in different experimental conditions. Besides, the characteristics (including volatile content, pore structure and crystalline structure) of char have a great influence on the char-NO reactions. With the higher volatile content, the more developed pore and the lower degree of graphitization, the reduction effect of NO is better.