CO2化学吸收系统污染物排放与控制研究进展

CO₂化学吸收技术因其捕集效率高、技术相对成熟和适应性好,是目前最具工业应用潜力的CO₂捕集技术,然而,CO₂化学吸收系统在使用吸收剂捕集烟气中CO₂的同时,部分吸收剂及其降解产物随烟气排出,不仅增加吸收剂损耗,且在大气中进一步反应生成强致癌物硝胺和亚硝胺。因此,有必要对CO₂化学吸收系统污染物排放进行有效控制。目前,通常通过调节系统运行参数、使用污染物控制手段对污染物进行控制,但缺乏普适性的控制方法,还未建立污染物排放的控制目标值。介绍了CO₂化学吸收系统污染物的3类排放形式,包括物理夹带、气体和气溶胶,其中气溶胶具有较高的排放量且难以被传统方式控制;梳理了研究机构测量到的排放情况,不同规模的CO₂化学吸收系统普遍具有较高的排放量;分析了气溶胶生成生长机理,气溶胶排放主要通过非均相成核产生,依赖于凝结核的存在和过饱和的环境;基于试验和模拟2种方法综述了烟气凝结核、贫液进口温度、贫液负荷、烟气CO₂含量等因素对气溶胶主导的有机胺排放影响。简要介绍了对降解产物排放的研究,包括氧化降解和热降解;最后对当前污染物排放控制手段的控制效果及优缺点进行了总结。传统水洗方法能有效控制有机胺气态排放,传统除雾器对大粒径气溶胶颗粒控制效果好,但对小颗粒脱除效率低。湿式电除尘、蒸汽注入、干床等方法虽有一定脱除效果,但成本较高。酸洗能解决氨气排放问题,但难以回收有机胺。胶质气体泡沫法对气溶胶脱除效率高,但缺乏工业级研究。未来对于污染物的排放需要开发新型控制手段,这一手段既要有效减少气相和气溶胶形式的污染物排放,又要控制工业投资成本,这将成为建立先进碳捕集工艺系统的关键环节。

Research progress on pollutant emission and control from CO2 chemical absorption system

Due to its high capture efficiency,relatively mature technology and good adaptability,CO₂ chemical absorption technology is cur?rently the most potential CO₂ capture technology for industrial application.However,in CO₂ chemical absorption system,absorbent is used to capture CO₂ in the flue gas,and part of the absorbent and its degradation products are discharged with the flue gas,which not only in?creases the loss of absorbent,and further reacts in the atmosphere to form strong carcinogen nitrate amine and nitrosamines.Therefore,it is necessary to effectively control the pollutant emission from CO₂ chemical absorption system.At present,pollutants are usually controlled by adjusting the operating parameters of the system and using pollutant control means,but there is no universal control method and the pollu?tant emission control target value has not been established.In this paper,three emission forms of pollutants in CO₂ chemical absorption sys?tem were introduced,including physical entrainment,gas and aerosol.The aerosol has high emission and is difficult to be controlled by tra?ditional methods.According to the emissions measured by the research institutions,CO₂ chemical absorption systems of different scales generally have higher emissions.The mechanism of aerosol generation and growth was analyzed.The aerosol emission is mainly pro?duced through heterogeneous nuclei,which depends on the existence of condensation nuclei and the supersaturated environment.Based on the experimental and simulation methods,the effects of condensation core of flue gas,inlet temperature of lean liquid,lean liquid load and CO₂ content of flue gas on the emission of organic amine dominated by aerosols were reviewed.The research on the emission of degradation products,including oxidative degradation and thermal degradation,was briefly introduced.Finally,the control effect,advantages and disad?vantages of the current pollutant emission control methods were summarized.The traditional water washing method can effectively control the gaseous emission of organic amines.The traditional mist eliminator has a good control effect on large-size aerosol particles,but the re?moval efficiency of small particles is low.Although wet electric dust removal,steam injection,dry bed and other methods have certain re?moval effect,but the cost is high.Acid pickling can solve the problem of ammonia emission,but it is difficult to recover organic amines.Colloid gas foam method has high efficiency for aerosol removal,but there is a lack of industrial research.In the future,it is necessary to develop new control methods for pollutant emission,which can effectively reduce the emission of pollutants in the form of gas phase and aerosol,and control the industrial investment cost.This method will be the key link for the establishment of advanced carbon capture process system.