Choi Sung-Woo, Choi Sang-Ki, Bae Hun-Kyun
a Department of Environmental Science , School of Environment, Keimyung University , Daegu , South Korea.
J Air Waste Manag Assoc. 2015 Apr;65(4):485-91. doi: 10.1080/10962247.2014.1002584.
A hybrid selective noncatalytic reduction/selective catalytic reduction (SNCR/SCR) system that uses two types of technology, low-temperature SCR process and SNCR process, was designed to develop nitrogen oxide (NOx) reduction technology. SCR was conducted with space velocity (SV)=2400 hr(-1) and hybrid SNCR/SCR with SV=6000 hr(-1), since the study focused on reducing the amount of catalyst and both achieved 98% NOx reduction efficiency. Characteristics of NOx reduction by NH3 were studied for low-temperature SCR system at 150 °C using Mn-V2O5/TiO2 catalyst. Mn-added V2O5/TiO2 catalyst was produced, and selective catalyst reduction of NOx by NH3 was experimented. NOx reduction rate according to added Mn content in Mn-V2O5/TiO2 catalyst was studied with varying conditions of reaction temperature, normalized stoichiometric ratio (NSR), SV, and O2 concentration. In the catalyst experiment according to V2O5 concentration, 1 wt.% V2O5 catalyst showed the highest NOx reduction rate: 98% reduction at temperature window of 200250 °C. As a promoter of the V2O5 catalyst, 5 wt.% Mn was added, and the catalyst showed 4790% higher efficiency even with low temperatures, 100200 °C. Mn-V2O5/TiO2 catalyst, prepared by adding 5 wt.% Mn in V2O5/TiO2 catalyst, showed increments of catalyst activation at 150 °C as well as NOx reduction. Mn-V2O5/TiO2 catalyst showed 8% higher rate for NOx reduction compared with V2O5/TiO2 catalyst in 150 °C SCR. Thus, (5 wt.%)Mn-(1 wt.%)V2O5/TiO2 catalyst was applied in SCR of hybrid SNCR/SCR system of low temperature at 150 °C. Low-temperature SCR hybrid SNCR/SCR (150 °C) system and hybrid SNCR/SCR (350 °C) showed 9195% total reduction rate with conditions of SV=24006000 hr(-1) SCR and 8501050 °C SNCR, NSR=1.5~2.0, and 5% O2. Hybrid SNCR/SCR (150 °C) system proved to be more effective than the hybrid SNCR/SCR (350 °C) system at low temperature.
NOx control is very important, since they are the part of greenhouse gases as well as the cause of acid rain and ozone hole. A technology, so-called hybrid SNCR/SCR process, was tested using Mn-V2O5/TiO2 monolithic catalyst for NOx reduction, and the method is promising. The results of this study would provide some ideas to parties such as policy makers, environmental engineers, and so on.
设计了一种结合选择性非催化还原/选择性催化还原（SNCR/SCR）两种技术的混合系统，即低温SCR工艺和SNCR工艺，以开发氮氧化物（NOx）还原技术。SCR在空速（SV）=2400 h⁻¹的条件下进行，混合SNCR/SCR在SV=6000 h⁻¹的条件下进行，因为该研究重点在于减少催化剂用量，且两者的NOx还原效率均达到98%。使用Mn-V₂O₅/TiO₂催化剂在150℃下对低温SCR系统中NH₃还原NOx的特性进行了研究。制备了添加Mn的V₂O₅/TiO₂催化剂，并对NH₃选择性催化还原NOx进行了实验。研究了在不同反应温度、归一化化学计量比（NSR）、SV和O₂浓度条件下，Mn-V₂O₅/TiO₂催化剂中添加Mn含量对NOx还原率的影响。在根据V₂O₅浓度进行的催化剂实验中，1 wt.% V₂O₅催化剂表现出最高的NOx还原率：在200250℃的温度窗口内还原率达98%。作为V₂O₅催化剂的促进剂，添加了5 wt.% Mn，该催化剂在100200℃的低温下效率也提高了4790%。在V₂O₅/TiO₂催化剂中添加5 wt.% Mn制备的Mn-V₂O₅/TiO₂催化剂在150℃时催化剂活性以及NOx还原率均有所提高。在150℃的SCR中，Mn-V₂O₅/TiO₂催化剂的NOx还原率比V₂O₅/TiO₂催化剂高8%。因此，（5 wt.%）Mn-（1 wt.%）V₂O₅/TiO₂催化剂应用于150℃低温的混合SNCR/SCR系统的SCR中。低温SCR混合SNCR/SCR（150℃）系统和混合SNCR/SCR（350℃）在SV=24006000 h⁻¹的SCR条件、8501050℃的SNCR条件、NSR=1.52.0以及5% O₂的条件下，总还原率为91~95%。事实证明，混合SNCR/SCR（150℃）系统在低温下比混合SNCR/SCR（350℃）系统更有效。
NOx控制非常重要，因为它们既是温室气体的一部分，也是酸雨和臭氧层空洞的成因。使用Mn-V₂O₅/TiO₂整体式催化剂对一种所谓的混合SNCR/SCR工艺技术进行了测试，用于还原NOx，该方法很有前景。本研究结果将为政策制定者、环境工程师等相关方提供一些思路。
