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    空气中直接捕集CO2技术研究进展

    Research progress on direct capture of CO_2 from air

    • 摘要: 减少碳排放并推动碳中和是应对气候变化、促进经济社会绿色转型的重要途径之一,碳中和技术已成为工业界和学术界的关注焦点。目前碳捕集与封存主要对工业固定源排放的CO2进行处置捕集,而对占CO2总排放近50%的分布源CO2关注度不高。直接空气捕集(Direct air capture, DAC)技术不仅可对数以百万计的小型化石燃料燃烧装置以及数以亿计的交通工具等分布源排放的CO2进行捕集处理,还可有效降低大气中CO2浓度。笔者介绍了DAC的发展历史、研究现状以及发展趋势,综述了已有DAC技术的工艺流程以及反应装置,分析了DAC吸收/吸附材料的作用原理以及吸附效果,对比了DAC与其他碳捕集技术的成本并进行了技术经济性分析,指出目前限制DAC工业化应用的主要因素之一在于吸收/吸附材料和相关工艺成本过高。全面探究吸收/吸附材料稳定性、动力学、吸附容量、选择性、再生能量损失等综合性能,研发利于快速装载和卸载吸附剂的相关装置,开发成本低廉的工艺系统是目前DAC领域的发展方向和迫切需求。

       

      Abstract: Reducing carbon emissions and promoting carbon neutralization is one of the critical ways to deal with climate change and encourage the green transformation of economy and society. Carbon neutralization technology has become the focus of industry and academia.At present,carbon capture and storage technology(CCS) is mainly used to treat and capture CO_2 emitted from industrial fixed sources,while the distributed sources,accounting for nearly 50% of total CO_2 emissions are not highly concerned. Direct air capture(DAC) technology can not only capture CO_2 emitted by millions of small-scale fossil fuel combustion devices and hundreds of millions of vehicles,but also effectively reduce the concentration of CO_2 in the atmosphere. The development history,research status,and development trend of DAC were introduced. The existing DAC technology process flow and reaction equipment were summarized. The air capture module,absorbent or adsorbent regeneration module and CO_2 storage module involved in DAC current process were described. The advantages and disadvantages of several processes,adsorbent types and regeneration methods were compared. It was pointed out that the key to the development of DAC technology lied in developing high-efficiency and low-cost absorption and adsorption materials and equipment. The functional principle and adsorption effect of DAC absorption/adsorption material was analyzed. The raw material cost of alkaline solution is relatively low,but the energy consumption is high in the regeneration process of alkaline solution. Although the regeneration energy consumption of molecular sieve and metal-organic framework adsorbent is low,the adsorption capacity and adsorption selectivity of CO_2 in air are average. However,amine adsorbents show good adsorption capacity,and industrial waste heat or a small amount of heat energy is used to supply energy for the system because of its low regeneration temperature. In addition,when amine adsorbents are used,adsorption and desorption gradually occur in one unit,which has higher efficiency and operation time,and is expected to reduce the cost of DAC system. The cost of DAC and other carbon capture technologies are compared,and the technical and economic analysis is carried out. The cost of DAC mainly includes operation and maintenance costs(N_(Q&M)),adsorbent material costs(N_S) and net cost of factory equipment(N_(bop)). One of the main factors limiting the industrial application of DAC is the high cost of absorption/adsorption materials and related processes. With the emergence of new adsorbents such as anion exchange resin and the development of technology,the cost of DAC will decrease year by year. It is the current development directions and urgent needs of the DAC field: to comprehensively explore the comprehensive properties of absorption/adsorption materials such as stability,kinetics,adsorption capacity,selectivity,regeneration energy loss,and develop related devices that facilitate rapid loading and unloading of adsorbents,and develop low-cost process systems. DAC technology will provide important technical support for reducing global carbon emissions and achieving carbon neutrality.

       

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