烧结烟气活性炭脱硝机制

Denitration mechanism of sintering flue gas on activated carbon

烧结烟气氮氧化物(NO_(x))排放占钢铁行业NO_(x)排放总量的50%以上,随着环保法规的日益严格,现有及新建烧结机只有装设烟气脱硝装置才能满足排放法规的NO_(x)排放要求。而活性炭微孔丰富、比表面积大、吸附能力强,低温时即可同时脱除烟气中的SO_(2)、NO_(x)、粉尘及其他有害气体。因此,低温烧结烟气活性炭脱硝具有显著的特点及技术优势,但活性炭脱硝易受烟气中SO_(2)和H_(2)O的影响。本工作综述了低温烟气活性炭脱硝机理,主要包括物理吸附、化学吸附及选择性催化还原反应。烟气中氧气的存在起氧化作用,能有效提高活性炭的脱硝率;而SO_(2), H_(2)O和NO存在竞争吸附作用会降低活性炭的脱硝性能,详述了SO_(2)和H_(2)O对活性炭脱硝的抑制作用及影响。阐述了活性炭负载过渡金属、稀土金属等金属氧化物化学改性对脱硝性能的促进作用及其脱硝机理,并对多元金属的负载进行了介绍;最后对烧结烟气活性炭低温脱硝技术进行了展望。要点:(1)综述了活性炭脱硝机理。(2)阐述了活性炭脱硝的影响因素。(3)详述了活性炭负载过渡金属(稀土金属)氧化物对脱硝的提高作用及机理。(4)总结并展望了低温烧结烟气活性炭脱硝技术的研发,并提出了建议。

Nitrogen oxides(NO_(x)) emission of sintering flue gas accounts for more than half of the total NO_(x) emission in the steel industry. With the increasingly stringent environmental regulations, the existed and new sintering machines equipped only with the denitration equipment of flue gas can meet the requirements of NO_(x) emission regulations. Activated carbon has an abundant microporous structure, large specific surface area, and strong absorption capacity. SO_(2), NO_(x), dust, and other harmful gases of flue gas can be removed simultaneously by activated carbon at low temperature. Therefore, denitration of sintering flue gas on activated carbon has significant technical characteristics and advantages at low temperatures. However, the poor sulfur and water resistance of activated carbon limits its wide utilization in the denitration of low-temperature flue gas. The denitration mechanism of low-temperature flue gas on activated carbon was reviewed in this work, and three denitration mechanisms were described in detail, namely physical adsorption, chemical adsorption and selective catalytic reduction(SCR) reactions. The oxidation as a result of the presence of oxygen in flue gas can effectively improve the denitration efficiency of flue gas on activated carbon. However, the competitive adsorption of SO_(2), H_(2) O, and NO in flue gas can reduce the denitration performance of activated carbon. The inhibition and influence of SO_(2) and H_(2) O on the denitration of low-temperature flue gas over activated carbon was also discussed. Chemical modification of activated carbon loading transition metal oxides and rare earth metal oxides and their effect on the activity of activated carbon were described. The mechanism of activity improvement of activated carbon loading transition metal oxides and rare earth metal oxides was also reviewed. The loading of multi-metals oxides on activated carbon and their synergistic effects on performance improvement of activated carbon were also introduced. Finally, the research direction and the industrial application of low-temperature denitration technology of sintered flue gas on activated carbon were prospected. Key learning points:(1) Denitration mechanism of activated carbon was reviewed.(2) The influencing factors of denitration on activated carbon were described.(3) The effect and mechanism of metal(rare earth metal) oxides supported over activated carbon on denitration were described in detail.(4) The research and development of low-temperature flue gas denitration technology on activated carbon were summarized and prospected, and suggestions were prospected.