高级再燃气体脱硝特性的研究

煤燃烧排放出大量有毒气体,2000年燃煤发电厂NOx排放为2.9×107 t ,预计2010年加上燃油产生的NOx,中国的NOx总排放量可能超过1×108 t1].中国酸雨污染也正在由过去的硫酸型向硫硝酸混合型转变2],这引起了政府部门的高度关注.目前,已经采取了诸如低NOx燃烧器、分级配风、火上风 (Over Fire Air) 、再燃等技术措施降低NOx排放,取得了一定的效果.其中,再燃技术是降低NOx排放最有效的措施之一.它将炉膛分为主燃区、再燃区和燃尽区.燃料分级送入炉膛,在主燃区火焰上方喷入碳氢燃料,以建立贫氧富燃料区促使主燃区生成的NOx还原为无害的N2 3,4],最后送入燃尽风以进一步燃尽燃料.国内外研究者围绕再燃脱硝运行参数、同相和异相还原机理做了大量研究4～8],而国外90年代中后期兴起的高级再燃技术,是再燃技术与氮催化射入技术的结合,是一种更有效的NOx控制技术7,9],脱硝率可达85%以上,受到了世界各国的普遍关注10～13],目前,中国对高级再燃技术的研究刚刚起步.

Study on NO reduction by advanced gas reburning

Advanced reburning (AR) is one of the novel NOx control technologies. Some primary parameters of AR have been investigated by the experiments, NOx reduction performance of two fuels is analyzed contrastively. Results show that the NO removal efficiency increases quickly with the molar ratio of gas to NO and the residence time (within 0.34s) during reburning process when the temperature is 1050℃.There exists an optimum reburning stoichiometric ratio (0.7～0.8) and a molar ratio of NH3/NO (2.0) for AR process. The optimum ratio of natural gas/NO is 3.63 at the temperature of 1200℃. The optimum reburning temperatures of natural gas and liquefied petroleum gas are about 1250℃ and 1050℃, respectively. When the residence time exceeds 0.34s, the NO reduction efficiency of advanced natural gas reburning rises slowly, but that of advanced liquefied petroleum gas reburning increases rapidly.