为了降低空气中CO2浓度，缓解温室效应和气候变暖，直接空气捕捉(direct air capture，DAC)技术成为研究的热点，但其捕集成本较高。因此对DAC技术进行研究，得到影响CO2吸收效率的因素及其变化规律并加以优化，有利于降低CO2捕捉成本，对DAC技术的推广和实际工程应用具有重大意义。针对可用于直接空气捕捉的吸收塔，采用模拟试验的方法，搭建了逆流式机械通风吸收塔小试试验平台，通风截面积为0。6 m×0。6 m，以碱液为吸收剂，研究了碱液类型、碱液浓度、淋水密度、填料断面风速、淋水填料类型、淋水填料高度、淋水高度等对CO2吸收效率的影响。研究结果表明，在相同淋水密度下，填料高度每增加1 m，CO2吸收效率大约提高8。5%;氢氧根浓度每升高0。1 mol/L，CO2吸收效率提高约2%;CO2吸收效率随气水比的增加而减小，当气水比从500升高到2 200时，CO2吸收效率从60。33%下降到41。47%，在相同的气水比下，最大淋水密度较小时吸收效率较高;淋水高度每增加1 m，CO2吸收效率提高约1%;相同条件下，氢氧化钠碱液作为吸收液时CO2吸收效率稍高于氢氧化钾碱液。在以上研究的基础上，可对逆流式吸收塔进行设计优化，为后续CO2的捕捉和利用提供技术支持。
Study on the characteristics of countercurrent absorption tower for direct capture of CO2 in air
In order to reduce the concentration of CO2 in the air,alleviate the greenhouse effect and climate warming,direct air capture(DAC)technology has become a research hotspot.But its capture cost is relatively high.Therefore,conducting research on DAC technology and obtaining factors and their changing patterns that affect CO2 absorption efficiency is beneficial for reducing CO2 capture costs,and has significant significance for the promotion and practical engineering application of DAC technology.For absorption towers that can be used for DAC,a small-scale test platform for counter-flow mechanical ventilation absorption tower was established using simulation experiments,with a ventilation cross-sectional area of 0.6 m×0.6 m by using alkaline solution as the absorbent.The effects of alkaline solution type,alkaline solution concentration,mass water flow per unit plan area of packing,packing section wind speed,packing type,packing height,and water spraying depth on CO2 absorption efficiency were studied.The research results indicate that under the same mass water flow per unit plan area of packing,for every 1 m increase in packing height,the CO2 absorption efficiency increases by approximately 8.5%.For every 0.1 mol/L increase in hydroxide concentration,the carbon dioxide absorption efficiency increases by about 2%.The CO2 absorption efficiency decreases with the increase of the gas-water ratio.When the gas-water ratio increases from 500 to 2 200,the CO2 absorption efficiency decreased from 60.33%to 41.47%.Under the same gas-water ratio,the absorption efficiency is higher when the maximum mass water flow per unit plan area of packing is smaller;For every 1 m increase in water spraying depth,the CO2 absorption efficiency increases by about 1%.Under the same conditions,the CO2 absorption efficiency of NaOH alkaline solution as the absorption solution is slightly higher than that of KOH alkaline solution.On the basis of the research,the design optimization of the counter-flow absorption tower can be carried out to provide technical support for the subsequent capture and utilization of CO2.
direct air capturecounter-flow absorption towerpacking heightgas-water ratioabsorption efficiency
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