Hg-CEMS烟气预处理关键问题研究与进展

Research and development of Hg-CEMS flue gas pre-treatment technology

鉴于汞在化石燃料和矿物资源中的天然禀赋以及能源与资源利用过程中汞污染物的排放与监管,研发我国自主知识产权的汞连续在线监测系统(Hg-CEMS)成为汞排放浓度监测的国家重大需求。烟气预处理技术是Hg-CEMS系统中最关键的组成部分,也是限制我国Hg-CEMS技术发展与应用的核心技术。对Hg-CEMS烟气预处理技术中的4个关键模块——稀释采样模块、Hg0/Hg^(2+)分离模块、Hg^(2+)还原模块、Hg^(2+)标气发生模块的研究进展进行全面综述。首先,介绍稀释采样技术的原理与应用,阐述音速小孔和热稀释引射器的结构和设计要点,论述数值模拟与优化设计相结合的方法。其次,针对Hg0/Hg^(2+)分离技术,综述湿法吸收、物理吸附和化学吸附的研究新进展,讨论选择性吸附剂KCl和CaO的理论和实验研究结果。第3,针对Hg^(2+)还原技术,概述湿化学还原、低温还原和高温分解还原的技术,论证低温还原技术中固态还原剂的活性成分、反应温度以及烟气成分对氧化态汞还原的影响,探讨高温分解还原技术中填充材料、酸性气体组分以及除酸剂对Hg^(2+)还原和抑制Hg0再氧化的新研究进展。最后,针对Hg^(2+)标气发生技术面临的技术难点,提出固态标气发生新技术理念并指出其工业应用的可行性。结合当前Hg-CEMS技术的研究发展和应用现状,提出上述4个关键模块的研究思路、解决方案与应用前景。

In view of the natural endowment of mercury in fossil fuels and mineral resources,as well as the mercury emission controlling and regulating in the energy and resource utilization processes,the research and development on the mercury continuous emissions monitoring system(Hg-CEMS)with proprietary intellectual property rights is the most important requirement in science and technology in China.As a critical component of the Hg-CEMS system,the flue gas pretreatment system is a core technology that limits the development and application of the Hg-CEMS technology in China.This paper presents a comprehensive review of the research progress in the four key modules of the Hg-CEMS flue gas pretreatment technology,including the dilution sampling,Hg0/Hg^(2+)separation,Hg^(2+)reduction and Hg^(2+)calibration gas generation.Firstly,the dilution sampling techniques are highlighted in their characteristics and principles.The working principles,structures,and design considerations of the critical parameters for both critical hole and thermal dilution inject-ors are summarized.Emphasis is focused on the connection of numerical simulation with the optimal design methodology for the thermal dilution injector and critical hole.Secondly,regarding the Hg0/Hg^(2+)separation technology,various parti-tioning methodologies encompassing the wet absorption separation,physical adsorption separation and chemical adsorp-tion separation are discussed.Particular attention is given to the separation and adsorption efficiency of the advanced dry chemical adsorption techniques involving the novel selective adsorbents of KCl and CaO with their updated theoretical and experimental outcomes under practical operating conditions.Thirdly,in aspect of the Hg^(2+)reduction technology,a comparative analysis of wet chemical reduction,low-temperature reduction and high-temperature reduction techniques is expatiated.Particular focus is on the active components of solid-state reducing agents,the impact of temperature on the re-duction of divalent mercury,and the detrimental influences of flue gas components on the re-oxidation of the reduced ele-mental mercury in the low-temperature reduction techniques.An in-depth investigation of the impact of filler materials,acidic gas components and acid removal techniques on the reduction of divalent mercury in the high-temperature reduction techniques is highlighted.Finally,facing the technical problems,a solid generation method of the Hg^(2+)calibration gas is invented and its industrial utilization feasibility is verified in chemistry and experiments.In conjunction with the current status of research and application of the Hg-CEMS technology,the research technical routs,the solutions to some prob-lems and development prospect for the above-mentioned four key modules are put forward.