降低船舶NO_x排放的紧凑型SCR实验

采用浸渍法制备铬基催化剂,在10%Cr/TiO_2基础上研究锑负载量对催化剂催化氧化NO活性的影响。结果表明,350℃焙烧的10%Cr10%Sb/TiO_2催化剂具有最佳的NO催化氧化活性,在NO体积分数为0.07%、O2体积分数为5%,空速27 000 h-1条件下,260℃时NO氧化率可达到50%,满足紧凑型SCR条件。XPS表明新鲜催化剂表面铬主要以Cr3+形式存在,经NO催化氧化反应后出现Cr6+。此外考察SO_2对催化剂的影响发现,加入体积分数为0.03%的SO_2后,350℃时10%Cr10%Sb/TiO_2催化剂经15.6 h后效率由50%缓慢下降并稳定在17%,热再生后活性完全恢复。在NO催化氧化联合SCR实验中发现,当NO氧化率为46%时促成的紧凑型SCR在高空速下仍具有很高的脱硝率。空速为300 000 h-1、200℃时紧凑型SCR脱硝率达到90%,比标准SCR提高了39.5个百分点。可有效解决船舶SCR布设空间不足的问题。

Experimental research on compact SCR for reducing NOx emission

A series of Cr-based catalysts were prepared by impregnation method.The effect of antimony loading on the catalytic oxidation of NO was investigated on 10%Cr/TiO₂.The results show that the catalyst of 10%Cr10%Sb/TiO₂ calcined at 350 ℃ has the best NO catalytic oxidation performance.The NO conversion could reach 50% at 200 ℃,with the inlet NO concentration of 0.07%,the O₂ volume ratio of 5%,and space velocity of 27 000 h^-1,which could meet the required condition of compact SCR.XPS shows that the surface chromium of fresh catalyst mainly exists in the form of Cr³⁺ and Cr⁶⁺ appeared after oxidation of NO.In addition,the influence of SO₂ was investigated.With the inlet SO₂ concentration of 0.03%,the efficiency of 10%Cr10%Sb/TiO₂ catalyst decreased slowly from 50% to around 17% after 15.6 h at 350 ℃.Catalyst activity could be recovered totally after thermal regeneration.The compact SCR was facilitated by NO catalytic oxidation combined with SCR experiments when the rate of NO oxidation was 46%.It still has high activity at high space velocity.NO removal efficiency of compact SCR can reach 90% at space velocity of 300 000 h^-1、200 ℃,which is 39.5% higher than the standard SCR.The subject process can effectively solve the problem of insufficient space for SCR layout on vessel.