Study On CO₂ Absorption By Organic Amines In A Rotor-Stator Reactor

With the continuous development of global economy,the demand for fossil energy is increasing in all fields,but the combustion of fossil fuels produces a large amount of CO₂,which leads to rapid increase in the level of CO₂in the atmosphere,resulting in significant changes in global climate,such as global warming and frequent extreme weather.CO₂capture technologies are important means to control CO₂emission.Conventional CO₂capture processes exhibit the disadvantages of low CO₂absorption capacity,slow CO₂absorption rate and low mass transfer efficiency.To address these issues,it is necessary to develop more efficient CO₂absorbents and reactors that have high mass transfer efficiency for the capture of CO₂in flue gas.High gravity reactors are widely used in the gas absorption field due to their advantages of high gas-liquid mass transfer efficiency and small size.The rotor-stator reactor（RSR）is a new type of high gravity reactor that features a unique rotor and stator structure.This structure solves the problem of uneven liquid circumferential distribution in the rotating packed bed（RPB）,resulting in better gas-liquid mass transfer performance compared to RPB.In this thesis,RSR was combined with three new types of absorbents to enhance the effectiveness of CO₂capture.The results are presented below.（1）The absorption of CO₂by RSR with various blended organic amine solutions was investigated,and the effects of different process conditions on the CO₂absorption efficiency（η）and overall gas-phase volumetric mass-transfer coefficient（K_Ga）were examined.The results showed that the highest CO₂absorption was achieved using a diethylenetriamine（DETA）+piperazine（PZ）solution.ηand K_Ga increased significantly with the increase of high gravity factor,liquid flow rate and liquid temperature,and decreased gradually with the increase of lean liquid CO₂loading.In addition,an artificial neural network model was developed to predictηand K_Ga in the RSR.The results showed that the predicted values ofηand K_Ga had average relative deviations within±5%and±10%,respectively,from the experimental values,which indicates that the model can predict the CO₂absorption process in the RSR satisfactorily.（2）The effects of different process conditions on theηfrom amine-activated hot K₂CO₃solution in the RSR were investigated using glycine（Gly）,N-aminoethyl piperazine（AEPZ）and PZ as promoters.The experimental results showed that PZ was the most effective promoter,followed by AEPZ,while Gly was the least effective.ηincreased gradually with the increase of high gravity factor and liquid flow rate,and decreased gradually with the increase of gas flow rate and inlet CO₂concentration.（3）Novel Choline chloride（ChCl）-DETA-H₂O deep eutectic solvents（DESs）was synthesized,and its physical properties were measured.The CO₂absorption and mass transfer properties of ChCl-DETA-H₂O in the RSR were investigated,and the effects of different process conditions onηand K_Ga in the RSR were examined.The results demonstrated that the viscosity and density of ChCl-DETA-H₂O decreased with increasing temperature and DETA molar ratios.Among the DES with different DETA ratios,1ChCl-5DETA-2H₂O had the highest CO₂absorption capacity with a value of0.250 g CO₂/g DES.ηand K_Ga increased with increasing DETA molar ratios,high gravity factor and liquid flow rate,but decreased with increasing inlet CO₂concentration.They increased first and then decreased with increasing temperature.In addition,the mechanism of CO₂absorption by1ChCl-5DETA-2H₂O was studied by FTIR and NMR.The results indicated that DETA in 1ChCl-5DETA-2H₂O first reacted with CO₂to form zwitterions,which then lost protons to form carbamates.Compared to the conventional packed columns,the K_Ga in the 1ChCl-5DETA-2H₂O/RSR process was found to be about one order of magnitude higher than that in the conventional process,suggesting that the 1ChCl-5DETA-2H₂O/RSR process has excellent CO₂absorption and mass transfer performance.（4）The effect of CO₂absorption by blended organic amine solutions,amine-activated hot potassium solution and novel DESs in the RSR was compared.The results showed that theηof 1ChCl-5DETA-2H₂O/RSR process was 26.4%higher than that of 25wt%DETA+5wt%PZ/RSR process and102.4%higher than that of 25wt%K₂CO₃+5wt%PZ/RSR process,indicating that the 1ChCl-5DETA-2H₂O/RSR process has excellent CO₂absorption performance.