基于V-W/Ti基催化剂的NH_3选择性催化还原NO_x的试验研究

Experimental Study on Selective Catalytic Reduction of NO_x with NH_3 Based on a V-W/Ti Catalyst

针对一使用SCR技术满足欧-Ⅳ排放标准的柴油机排气特征,在连续流动固定床反应器上利用NH3作还原剂对一纳米级V-W/Ti基催化剂的选择性催化还原NO的反应进行了试验研究,分析了在不同温度、空速、NH3/NO摩尔比的情况下对DeNOx性能的影响。试验结果表明,温度对催化还原性能的影响最大,在低温下,由于催化剂活性不高,NOx的脱除效率很低,随着反应温度的升高,催化剂活性升高,NOx脱除率随之急剧升高,在300℃～450℃范围内达到较高的NOx脱除效率;随着NH3/NO摩尔比的增加,还原效率并未明显增加,但NH3的氧化和泄漏越来越严重;另外,空速对低温下还原效率也存在一定的影响。

Aiming at the SCR technology to reduce NOx emission of diesel engine, an experiment was performed in a steady-flow reactor to study the NOx reduction efficiency using ammonia （NH3） hydrolyzed from heated urea solution （（NH2）2CO） as the reducing agent based on nanometre-elass V-W/Ti catalyst. The effect of different temperatures, GHSV（gas hours space velocity） and NH3/NO mole ratio on the NOx emissions of a heavy-duty diesel engine were analyzed. Results show that the main factor affecting DeNOx efficiency is temperature, at higher temperature ammonia is oxidized while at lower temperature NOx reduction efficiency decreases, the optimal temperature range is about 300℃ -450℃. The oxidization and leakage of ammonia will become more obvious when NH3/NO mole ratio is higher than 1.0. Moreover, GHSV has an impact on overall DeNOx efficiency under lower temperature.