商用SCR催化剂对单质汞(Hg~0)的氧化作用研究
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摘要
为开发对烟气NO_x和汞等多种污染物具有良好联合脱除效用的一体化新型催化剂,研究了目前商用SCR脱硝催化剂对单质汞(Hg~0)的氧化作用及其影响因素,探求Hg~0氧化反应机理。实验结果表明:SCR催化剂对烟气中的Hg~0具有一定的氧化作用,但在催化剂最佳反应温度250～300℃时,其对Hg~0的最大氧化效率仍低于50%。在低浓度NO和5%O_2同时存在的情况下,催化剂对Hg~0有相对较高的氧化效率;SO_2存在时,Hg~0的氧化明显被抑制,SO_2对催化剂的毒性基本不可逆转;NH_3与Hg~0在吸附过程中存在竞争关系,因而NH_3的存在降低了催化剂对Hg~0的氧化效率;H_2O对Hg~0的氧化有十分明显的负面影响。
In order to develop a novel integrated catalyst with better joint removal effects on various pollutants such as NO_x and mercury in the flue gas, the oxidation effects of commercial SCR denitration catalyst on elemental mercury(Hg~0) and its influencing factors were studied in this paper. The oxidation reaction mechanism of Hg~0 was also explored. The experimental results show that the SCR catalyst has some certain oxidation effects on Hg~0 in flue gas. However, its maximum oxidation efficiency on Hg~0 is still below 50% even at the optimum reaction temperature of 250～300 °C. In the presence of low concentration of NO and 5% O~2, the catalyst has a relatively high oxidation efficiency for Hg~0. While in the presence of SO_2, the oxidation of Hg~0 was apparently inhibited, and the toxicity of SO_2 to the catalyst was basically irreversible. Moreover, there exists a competitive relationship between NH_3 and Hg~0 in the adsorption process. So the presence of NH_3 reduces the oxidation efficiency of Hg~0 by the catalyst. It also appears that the presence of H_2 O has significant negative impact on the oxidation of Hg~0.
In order to develop a novel integrated catalyst with better joint removal effects on various pollutants such as NO_x and mercury in the flue gas, the oxidation effects of commercial SCR denitration catalyst on elemental mercury(Hg~0) and its influencing factors were studied in this paper. The oxidation reaction mechanism of Hg~0 was also explored. The experimental results show that the SCR catalyst has some certain oxidation effects on Hg~0 in flue gas. However, its maximum oxidation efficiency on Hg~0 is still below 50% even at the optimum reaction temperature of 250～300 °C. In the presence of low concentration of NO and 5% O~2, the catalyst has a relatively high oxidation efficiency for Hg~0. While in the presence of SO_2, the oxidation of Hg~0 was apparently inhibited, and the toxicity of SO_2 to the catalyst was basically irreversible. Moreover, there exists a competitive relationship between NH_3 and Hg~0 in the adsorption process. So the presence of NH_3 reduces the oxidation efficiency of Hg~0 by the catalyst. It also appears that the presence of H_2 O has significant negative impact on the oxidation of Hg~0.
引文
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[19] WANG Zhen, LIU Jing, ZHANG Bingkai, et al. Mechanism of heterogeneous mercury oxidation by HBr over V2O5/TiO2 catalyst[J].Environmental Science&Technology, 2016, 50(10):5398-5404.
[20] GUO Pan, GUO Xin, ZHENG Chuguang. Computational insights into interactions between Hg species andα-Fe2O3(001)[J]. Fuel,2011,90(5):1840-1846.
[21]姜烨,高翔,吴卫红,等.选择性催化还原脱硝催化剂失活研究综述[J].中国电机工程学报,2013, 33(14):18-31.JIANG Ye, GAO Xiang, WU Weihong, et al. Review of the deactivation of selective catalytic reduction De NOx catalysts[J].Proceedings of the CSEE,2013, 33(14):18-31.
[2]王书肖,张磊,吴清茹,等.中国大气汞排放特征、环境影响及控制途径[M].北京:科学出版社,2016.
[3]刘发圣,夏永俊,徐锐,等.燃煤电厂污染控制设备脱汞效果及汞排放特性试验[J].中国电力,2017, 50(4):162-166.LIU Fasheng, XIA Yongjun, XU Rui, et al. Experimental study on mercury removal effect and mercury emission characteristics of pollution control equipment in coal-fired power plants[J]. Electric Power, 2017, 50(4):162-166.
[4]杨立国,段钰锋,杨祥花,等.燃煤电厂汞排放特性实验研究[J].东南大学学报(自然科学版),2007, 37(5):817-821.YANG Liguo, DUAN Yufeng, YANG Xianghua, et al. Mercury emission characteristics from coal-fired power plants[J]. Journal of Southeast University(Natural Science), 2007, 37(5):817-821.
[5]蔡兴飞,牛天文,张玉斌,等.燃煤烟气低温SCR脱硝领域研究进展[J].锅炉技术,2014,45(2):77-80.CAI Xingfei, NIU Tianwen, ZHANG Yubin, et al. Progress in the field of low-temperature SCR of flue gas denitrification Technology[J]. Boiler Technology, 2014, 45(2):77-80.
[6]许月阳,薛建明,王宏亮,等.燃煤烟气常规污染物净化设施协同控制汞的研究[J].中国电机工程学报,2014,34(23):3924-3931.XU Yueyang, XUE Jianming, WANG Hongliang, et al. Research on mercury collaborative control by conventional pollutants purification facilities of coal-fired power plants[J]. Proceedings of the CSEE,2014, 34(23):3924-3931.
[7]陶莉,张旭楠,李彩亭,等.选择性催化还原催化剂氧化脱除烟气中单质汞[J].环境工程学报,2015, 9(6):2925-2932.TAO Li, ZHANG Xunan, LI Caiting, et al. Oxidation and capture of elemental mercury over SCR catalyst in simulated flue gas[J].Chinese Journal of Environmental Engineering, 2015,9(6):2925-2932.
[8]郑逸武,段钰锋,汤红健,等.燃煤烟气污染物控制装置协同脱汞特性研究[J].中国环境科学,2018, 38(3):862-870.ZHENG Yiwu, DUAN Yufeng, TANG Hongjian, et al.Characteristics of the existing air pollutant control devices on Hg synergistic removal in a coal-fired power plant[J]. China Environmental Science, 2018, 38(3):862-870.
[9]张旭楠.CeO2改性SCR催化剂同时脱除烟气中Hg0和NO的实验研究[D].长沙:湖南大学,2015.
[10] YANG Jian, YANG Qiang, SUN Jian, et al. Effects of mercury oxidation on V2O5-WO3/TiO2 catalyst properties in NH3-SCR process[J]. Catalysis Communications, 2015, 59:78-82.
[11] SUAREZ NEGREIRA A, WILCOX J. DFT study of Hg oxidation across vanadia-titania SCR catalyst under flue gas conditions[J]. The Journal of Physical Chemistry C,2013, 117(4):1761-1772.
[12] YE Z, LAUMB J, LIGGETT R, et al. Impacts of acid gases on mercury oxidation across SCR catalyst[J]. Fuel Processing Technology, 2007, 88(10):929-934.
[13]赵莉,刘宇,吴洋文,等.燃煤烟气中零价汞的催化氧化理论研究进展[J].中国电力,2018,51(3):170-176.ZHAO Li, LIU Yu, WU Yangwen, et al. Review on theoreticalresearch of the catalytic oxidation of Hg0 in coal-fired flue gas[J].Electric Power, 2018, 51(3):170-176.
[14]曲立涛,李超,于洪海,等.燃煤机组深度调峰对环保设施的影响分析及对策[J].东北电力技术,2016, 37(10):38-40, 44.QU Litao,LI Chao, YU Honghai, et al. Impact analysis and countermeasures on coal fired units in-depth peak regulation of environmental protection facilities[J]. Northeast Electric Power Technology, 2016, 37(10):38-40, 44.
[15] LI Hailong, LI Ying L, WU Changyu, et al. Oxidation and capture of elemental mercury over SiO2-TiO2-V2O5 catalysts in simulated lowrank coal combustion flue gas[J]. Chemical Engineering Journal,2011, 169(1/2/3):186-193.
[16] LI Hailong, WU Changyu, LI Ying, et al. Superior activity of MnOxCeO2/TiO2 catalyst for catalytic oxidation of elemental mercury at low flue gas temperatures[J]. Applied Catalysis B:Environmental,2012, 111/112:381-388.
[17] YAN Naiqiang, CHEN Wanmiao, CHEN Jie, et al. Significance of RuO2 modified SCR catalyst for elemental mercury oxidation in coalfired flue gas[J]. Environmental Science&Technology, 2011,45(13):5725-5730.
[18] PUDASAINEE D, KIM J H, YOON Y S, et al. Oxidation,reemission and mass distribution of mercury in bituminous coal-fired power plants with SCR, CS-ESP and wet FGD[J]. Fuel, 2012, 93(1):312-318.
[19] WANG Zhen, LIU Jing, ZHANG Bingkai, et al. Mechanism of heterogeneous mercury oxidation by HBr over V2O5/TiO2 catalyst[J].Environmental Science&Technology, 2016, 50(10):5398-5404.
[20] GUO Pan, GUO Xin, ZHENG Chuguang. Computational insights into interactions between Hg species andα-Fe2O3(001)[J]. Fuel,2011,90(5):1840-1846.
[21]姜烨,高翔,吴卫红,等.选择性催化还原脱硝催化剂失活研究综述[J].中国电机工程学报,2013, 33(14):18-31.JIANG Ye, GAO Xiang, WU Weihong, et al. Review of the deactivation of selective catalytic reduction De NOx catalysts[J].Proceedings of the CSEE,2013, 33(14):18-31.