Research progress on direct capture of CO, from air

Reducing carbon emissions and promoting carbon neutralization is one of the critical ways to deal with climate change and en courage 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 C02emitted from industrial fixed sources, while the distributed sources,accounting for nearly 50% of total C()2emissions are not highly concerned.Direct air capture( DAC) technol ogy can not only capture C()2 emitted by millions of small-scale fossil fuel combustion devices and hundreds of millions of vehicles,but al so effectively reduce the concentration of C02 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 C()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 C()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 lias higher efficiency and operation time,and is expected to reduce the cost of DAC system.The cost of DAC and oth er carbon capture technologies are compared,and the technical and economic analysis is carried out.The cost of DAC mainly includes op eration and maintenance costs(^Vg&M) , adsorbent material costs(7VS ) and net cost of factory equipment(A'bop).One of the main factors lim iting 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/adsorp tion 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.