氨/二甲醚燃料分级燃烧的排放特性

A STUDY ON EMISSION CHARACTERISTICS OF NH3/DME FLAMES IN A FUEL STAGING COMBUSTOR

由于本身含氮和氨的燃烧过程会造成高额燃料型NO_(x)排放,为了减少氨燃料利用过程释放的NO_(x),本研究采用燃料分级燃烧技术进行氨/二甲醚燃烧,通过实验探究了燃料分级方法对污染物排放特性的影响.研究发现燃料分级方法能够降低NO和NO_(2)的排放浓度,最高使得NO减少60.1%,NO_(2)减少88.7%.在进行单级燃烧时NH_(3)几乎被完全消耗,采用燃料分级方法后则会造成NH3排放,其浓度随二级氨注入量增多而增大,而NO浓度则随二级氨注入量增多而减小,当热功率为0.6 kW、局部当量比为0.85时,NH3和NO排放浓度达到3×10^(−3)左右的相同水平.实验结果表明燃料分级燃烧方式在降氮方面有良好应用前景.为了进一步了解污染物NO在分级燃烧过程中的生成和消耗特性,本研究建立了一种化学反应器网络(CRN)模型,在Chemkin软件中对本实验测试工况下的燃烧过程进行了模拟.结果表明,数值模拟准确预测了NO的排放数值,验证了CRN计算方法的准确性.敏感性分析表明二甲醚具有比常规碳氢燃料更强的活化作用,对NO生成具有显著的促进作用.产率分析表明,NO在一级燃烧区主要通过HNO路径生成,在二级反应区主要通过NH2+NO=N2+H2O和NH2+NO=NNH+OH反应被消耗.

The combustion process of ammonia causes high NO_(x) emissions.In order to reduce NO_(x) emissions,the fuel staging strategy was applied in NH3/dimethyl ether combustion.In this work,the emission characteristics of NH_(3)/DME flames were investigated in an experimental fuel staging combustor.It was found that the NO and NO_(2) concentration in exhaust decreased when the fuel staging strategy was used.The maximum reduction rates of NO and NO_(2) were 60.1%and 88.7%,respectively.NH3 was almost completely consumed under single stage combustion,but it was emitted when fuel staging method was used.The concentration of NH3 in exhaust increased with the increase of secondary NH3 injection flowrate,while the trend of the NO concentrations was opposite.The emission concentrations of NO_(x) and NH3 were observed to reach relatively low values(around 3×10^(−3))simultaneously atφpri=0.85 when the thermal power of the combustor was 0.6 kW.The experimental results showed that the globally lean-locally lean two-stage combustion strategy has a promising application prospect in NO_(x) reduction.Then,the numerical study was conducted in the chemical reactor network(CRN)to further analyze the NO emission behaviors of NH3/DME fuel staging combustion.It was showed that the CRN model captured the trend of NO emission accurately.The results of NO sensitivity analysis showed that the DME is more active than conventional hydrocarbons and has a significant promoting effect on NO production.The ROP analysis showed that NO was mainly generated through HNO pathway at the primary stage zone,and consumed through the reactions NH2+NO=N2+H2O and NH2+NO=NNH+OH at the secondary stage zone.