重型燃气机铂/铑/钯基三元催化器N_(2)O排放特性

N_(2)O emission characteristics of Pt/Rh/Pd three-way catalyst for heavy duty gasengine

以采用当量比燃烧+EGR+铂/铑/钯基TWC技术路线、且满足国六排放标准的重型燃气机为研究对象,基于全球统一瞬态实验循环(WHTC)工况对燃气机瞬态条件下不同燃气组分、排气温度、尾气组分的N_(2)O排放特性进行定量研究。结果表明:N_(2)O排放主要集中在冷态WHTC城市工况前140 s,热态WHTC总排放量约是冷态的1%;燃料组分对N_(2)O生成有一定影响,含N_(2)高的低热值G25燃气冷、热态N_(2)O排放浓度均高于LNG、CNG,加权比排放量分别为15.3 mg·kWh^(-1)、9.6 mg·kWh^(-1)、7.5 mg·kWh^(-1);N_(2)O生成与温度密切相关,主要生成区间为160~350℃,高温会抑制N_(2)O生成;N_(2)O与NH3的生成存在竞争关系,高于400℃时NH3生成量增加。本研究可为重型燃气机污染物N_(2)O的源头控制提供参考。

Taking a heavy-duty gas engine using equivalent ratio combustion EGR Pt/Rh/Pd three-way Catalyst and meeting the National VI emission standards as the research object,this study quantitatively investigated the N_(2)O emission characteristics of the gas engine under transient conditions with different gas compositions,exhaust temperatures,and tail gas compositions based on the global transient cycle WHTC.The results showed that N_(2)O emissions were mainly concentrated in the first 140 seconds of the cold WHTC urban cycle,and the total N_(2)O emissions of the hot WHTC are about 1%of the cold cycle.The fuel composition had a certain influence on N_(2)O generation.The cold and hot N_(2)O emission concentrations of G25 gas with high N_(2)content were higher than those of LNG and CNG,and the weighted specific emission was 15.3 mg·kWh^(-1),9.6 mg·kWh^(-1),and 7.5 mg·kWh^(-1),respectively.N_(2)O generation was closely related to temperature,and the main generation interval was between 160~350℃.High temperature inhibited N_(2)O generation.There was a competitive relationship between N_(2)O and NH3 generation,and the NH3 generation increased when the temperature was higher than 400℃.This study can provide data reference for the source control of N_(2)O pollution in heavy-duty gas engine.