洁净煤技术

2021, v.27;No.132(02) 79-91

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富氧燃烧烟气净化工艺研究进展
Research and development on the purification technology for oxy-fuel combustion flue gas

刘敦禹;蔡雨阳;金晶;许开龙;
LIU Dunyu;CAI Yuyang;JIN Jing;XU Kailong;School of Energy and Power Engineering,University of Shanghai for Science and Technology;Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering;

摘要(Abstract):

随着工业的快速发展,化石燃料消耗与日俱增,造成了大量温室气体CO_2的排放,全球气候变化形势不容乐观。为了减少CO_2排放,需要对高浓度CO_2进行捕获、利用与封存,而富氧燃烧技术能有效实现碳捕集,是目前最具潜力的碳减排技术之一。富氧燃烧过程中,SO_x、NO_x、Hg等污染物以及惰性气体的存在不利于碳的捕集与封存。烟气中各成分浓度会对管道运输、地质储存和提高采收率(EOR)产生影响,介绍了烟气中CO_2及各种杂质浓度的不同标准,系统综述了国内外脱硫、脱硝、脱汞和惰性气体脱除以及联合脱除技术的研究进展。脱硫部分除介绍传统脱硫技术外,重点描述了富氧燃烧烟气中CO_2气氛对SO_x脱除的影响以及加压条件下SO_2的转化与去除。发现CO_2气氛下SO_2的吸收速率相比N_2气氛有所降低,且SO_2吸收过程中临界pH发生变化。脱硝部分重点描述了氧化吸收法脱硝技术以及加压条件下NO的氧化机理,并对高压下NO的氧化动力学进行阐述。随着压力的增加,NO氧化速率常数呈先下降后上升的趋势,且证明了反应器压力对液体夹带率的影响比较显著。总结了Hg脱除技术中不同烟气成分对Hg氧化的影响,HCl与Cl_2起到了明显的促进作用。对活性炭进行改性,增加孔结构比表面积以及吸附剂表面的活性位点,提高Hg的脱除效率。介绍了惰性气体的净化技术,主要采用变压吸附方法来吸附和解吸附,降低了CO_2气流中惰性气体去除的成本,实现一部分惰性气体再次循环回到锅炉中,提高CO_2的捕获。重点讨论了在烟气压缩液化系统中的联合脱除技术,有效利用压缩过程条件将SO_x、NO_x、Hg分别以硫酸、硝酸、Hg(NO_3)_2形式协同去除,随着压力的增加,SO_x与NO_x去除效率提高,有利于SO_4~(2-)、NO_3~-、HADS和HAMS(N-S化合物)的生成,同时也导致了N_2O生成量增多。证明了Hg与NO_2是气相反应,提出了高压下NO_2与Hg反应产物的不确定性。简单介绍了低温碳捕集技术,有潜力取代洗涤器和其他烟气处理方法,但目前还缺乏可行性的研究。未来需对不同压力下NO氧化速率常数的变化趋势进行解释,高压下NO_x与SO_x联合脱除的产物以及NO_2与Hg的反应产物进行分析。
With the rapid development of industry,the consumption of fossil fuels is increasing with each passing day,resulting in a large amount of greenhouse gas CO_2 emissions.The situation for global climate change is not optimistic.In order to reduce the emission of CO_2,it is necessary to capture,utilize and store the high concentration of CO_2.Oxy-fuel combustion technology can effectively achieve carbon capture,which is considered as one of the most potential carbon emission reduction technologies.In the process of oxy-fuel combustion,the existence of pollutants(including SO_x,NO_xand Hg) and inert gas is not conducive to carbon capture and storage.Since the concentration of various components in flue gas will affect pipeline transportation,geological storage,and enhanced oil recovery(EOR),the different standards of CO_2 and various impurities concentration in flue gas were introduced firstly,and the research progress of desulfurization,denitrification,mercury removal,inert gas removal,and combined removal technologies at home and abroad was systematically reviewed.In addition to the introduction of traditional desulfurization technology,the influence of CO_2 atmosphere in oxy-fuel combustion flue gas on SO_x removal and the conversion and removal of SO_2 under pressure were mainly described.It is found that the absorption rate of SO_2 in CO_2 atmosphere is lower than that in N_2 atmosphere,and the critical pH changes during the absorption process.In the denitration section,the denitration technology by oxidation absorption method and the oxidation mechanism of NO under high pressure were mainly described,and the oxidation kinetics of NO under high pressure was described.With the increase of pressure,the NO oxidation rate constant first decreases and then increases,which is proved that the effect of reactor pressure on liquid entrainment rate is significant.The effects of different flue gas components on Hg oxidation in Hg removal technology were summarized.HCl and Cl_2 play a significant role in promoting Hg oxidation.The activated carbon is modified to increase the specific surface area of pore structure and the active sites on the surface of adsorbent,so as to improve the removal efficiency of Hg.In this paper,the purification technology of inert gas was introduced.Pressure swing adsorption method is mainly used to adsorb and desorb,which reduces the cost of inert gas removal in CO_2 gas flow,realizes a part of inert gas recycling back to the boiler,and improves CO_2 capture.The combined removal technology in the flue gas compression liquefaction system is mainly discussed,which effectively uses the compression process conditions to remove SO_x,NO_x and Hg in the form of sulfuric acid,nitric acid and Hg(NO_3)_2.With the increase of pressure,the removal efficiency of SO_x and NO_x increases,which is conducive to the formation of SO_4~(2-),NO_3~-,HADS and HAMS(N-S compounds),and also leads to the increase of N_2O production.It is proved that the reaction of Hg with NO_2 is a gas phase reaction,and the uncertainty of the product of the reaction of NO_2 with Hg under high pressure is proposed.The low temperature carbon capture technology is briefly introduced,which has the potential to replace the scrubber and other flue gas treatment methods,but there is still a lack of feasibility research.In the future,it is necessary to explain the change trend of NO oxidation rate constant under different pressures,analyze the products of NO_x and SO_x combined removal and the reaction products of NO_2 and Hg under high pressure.

关键词(KeyWords): 富氧燃烧;碳捕集;烟气净化;联合脱除
oxy-fuel combustion;carbon capture;flue gas purification;simultaneous removal

Abstract:

Keywords:

基金项目(Foundation): 国家自然科学基金资助项目(51706143,51976129)

作者(Author): 刘敦禹;蔡雨阳;金晶;许开龙;
LIU Dunyu;CAI Yuyang;JIN Jing;XU Kailong;School of Energy and Power Engineering,University of Shanghai for Science and Technology;Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering;

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DOI: 10.13226/j.issn.1006-6772.CCUS20091403

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