O3协同SCR处理船舶柴油机废气排放的试验

为提高船用柴油机低负荷下选择性催化还原(Selective Catalytic Reduction,SCR)反应器的NOx 转化率,采用O 3协同SCR进行排气处理试验研究。试验研究结果表明:柴油机在40%负荷率以下的低负荷工况,SCR反应器不工作的情况下,排气管中注入O3,NO2/NO 浓度比得以提高;柴油机在20%负荷率工况下,NO2/NO浓度比达到30%。同时,O3可有效地降低柴油机烟度( K 值)和HC的排放,其排放浓度与注入O3前相比,最高降幅分别达到51%和19.1%。柴油机在30%负荷率以下的低负荷工况,SCR反应器按氨氮比1 ∶1的标定尿素喷射量喷入尿素时,SCR反应器前的排气管注入O3与注入O3前相比,SCR反应器中NOx 转化率得以提高,最高增幅达到32.1%。主要原因在于排气管中注入O3,NO2/NO 浓度比升高,促进SCR反应器中NOx 催化还原的快速反应。排气管注入O3后,在SCR反应器工作的情况下,SCR反应器后的烟度( K 值)降低,HC排放也稍有降低。试验表明:O3协同SCR有利于柴油机在低负荷下提高SCR反应器的NOx 转化率。

Experimental Study on Treatment of Exhaust Emissions from Marine Diesel Engine by Ozonizer Synergistic SCR

The ozoner is proposed to work with the SCR(Selective Catalytic Reduction) for better treatment of exhaust gas when the diesel engine in low load operation. The experiments show that the NO2/NO concentration ratio of exhaust gas can be improved by injecting ozone into the exhaust pipe when the load of the diesel engine is below 40% when SCR reactor stops working. For instance, under the condition of diesel engine load rate of 20%, when the NO2/NO concentration ratio reaches to 30%, the smoke ( K value) and HC emissions from diesel engine can be substantially reduced by ozone injection, the maximum reduction being 51% and 19.1% respectively. Generally, Ozone injection in the exhaust pipe in front of the SCR reactor enhances the NOx conversion rate in the SCR reactor, and with 1 ∶1 ammonia to nitrogen spraying of urea, the maximum benefit reaches 32.1% when the load of the diesel engine is below 30%. The basic principle is that the increase of NO2/NO concentration ratio accelerates the reaction of NOx reduction in the SCR reactor when ozone being injected into the exhaust pipe. In doing so, the smoke ( K value) after the SCR reactor decreases, and the HC emission slightly decreases too. The experiments demonstrate that the ozone synergistic SCR design is effective to improve NOx conversion of SCR reactor for diesel engines under low load.