循环流化床喷射混合还原剂的脱硝反应试验研究

随着大气污染形势日趋严峻,控制NOx排放的相关环保标准也日益严格。选择性非催化还原技术(SNCR)可以有效降低NOx排放,但受限于反应温度窗口狭窄,在流化床中的脱硝效率有限。研究表明H2、碳氢化合物和CO作为添加剂时,可以拓宽SNCR的反应温度窗口,促使低温下的脱硝反应得以进行;但在循环流化床热态试验系统上,鲜有使用工业副产品如煤气化合成气作为添加剂,分析H2、碳氢化合物和CO共存时对SNCR产生的影响效果。为了探究合成气与氨构成的混合还原剂对脱硝反应的影响,在循环流化床热态试验系统上,对比了合成气与氨水构成的混合还原剂和氨水的脱硝效果,同时考虑了反应温度、NSR、添加剂浓度、添加剂喷射位置等影响因素。结果表明:在840℃低温下,使用氨还原剂的SNCR反应已经失效,还会增加NOx排放量。混合还原剂可大幅提高低温区的脱硝效率,添加合成气能促使SNCR反应在此较低温度下进行。840℃时,脱硝效率从0提升至44%~62%。在氨氮摩尔比较低的情况下,如NSR=0.5或1.0、合成气为120×10^-6时,合成气喷射位置的不同对NOx排放量影响不大;但当氨过量时(NSR>1.0),将合成气喷射至分离器前温度较低的烟气管道中,能增强氨的选择性,进一步降低NOx排放量。当NSR=1.5时,NOx的排放量达到了最低101~110 mg/m^3,相比炉膛出口处喷射降低了约60 mg/m^3。独立喷射氨水与合成气使其在炉内混合的方式,比氨气与合成气预混后喷射方式好,NOx排放量会降低60 mg/m3左右。合成气添加剂与氨存在很强的相互协同、相互促进作用,合成气可以提高氨还原剂的选择性。

Experimental study on denitration reaction of injectingmixed reductant in circulating fluidized bed

With the increasingly severe situation of air pollution,the relevant environmental protection standards for controlling NO x emissions have become increasingly strict.Selective non-catalytic reduction(SNCR)can effectively reduce NO x emissions,but the denitration efficiency in fluidized bed is limited due to the narrow reaction temperature window.Previous studies have proved that when H 2,hydrocarbon and CO are used as additives,the reaction temperature window of SNCR can be can widened and the denitration reaction at low temperature can be carried out.However,in the thermal test system of circulating fluidized bed,few studies have been carried out to analyze the effect of coexisting H 2,hydrocarbon and CO on SNCR by using industrial by-products such as coal gasification syngas as additives.In order to study the influence of the mixture reducing agent composed of syngas and ammonia on the denitrification reaction,the denitrification effects of ammonia water and the mixed reductant composed of syngas and ammonia water were compared in a combustion experimental system of circulating fluidized bed.At the same time,the factors such as reaction temperature,molar ratio of ammonia to NOx(NSR),additive concentration and injection location were considered.The experimental results show that at low temperature of 840℃,the SNCR reaction using ammonia reducing agent not only fails,but also the NO x emission increases.The denitrification efficiency in the low temperature zone can be greatly improved by mixing reductants,and the addition of syngas can promote the SNCR reaction to be carried out at a lower temperature.At 840℃,the denitration efficiency increases from 0 to 44%-62%.When the NSR is relatively low,such as NSR=0.5 or 1.0,and the syngas is 120×10^-6,the different syngas injection positions have little impact on NO x emissions.However,when ammonia is in excess(NSR>1.0),the syngas is injected into the flue gas pipe with a low temperature in front of the separator to enhance ammonia selectivity and further reduce NOx emissions.When NSR=1.5,NOx emissions reaches a minimum of 101-110 mg/m^ 3,which is about 60 mg/m^3 lower than injection at the outlet of the furnace.The way of injecting ammonia water and syngas to independently mix in the furnace has a better denitration effect than the way of injecting premixed ammonia and syngas.NOx emissions are about 60 mg/m^ 3 lower than that of premixed injection.Syngas additive and ammonia have a strong synergistic and promoting effect on each other.Synthesis gas can improve the selectivity of ammonia reducing agent.