Study On CO₂ Absorption Into K₂CO₃/KHCO₃ Solution Intensified By Organic Phase In Rotor Stator Reactor

In recent years,due to the increasing application of gas-liquid-liquid(G-L-L)system in biochemical,homogeneous catalysis and extraction,related research on the mass transfer in G-L-L system has attracted increasing attention.In the gas-liquid mass transfer process,the addition of organic phase with a higher gas solubility can intensify the mass transfer between gas and liquid phases,and enhance the absorption efficiency of gas components.Because of the complexity and diversity,results of G-L-L studies are different and sometime contrary and sound theory is lacking.Therefore relevant researches are necessary so as to promote the industrial application of G-L-L systems.CO2 is one of the main gases causing greenhouse effect,and how to reduce CO2 emissions is the main research direction in environmental protection field,and the exploration of efficient CO2 treatment methods is of great significance.In this thesis,a HiGee device,Rotor-Stator Reactor(RSR)was employed as the reactor,CO2 absorption into K2CO3/KHCO3 solution and intensified by organic phase and sodium hypochlorite(NaCIO)respectively.Benzene,n-heptane and n-octanol with higher CO2 solubility and relative diffusion coefficient were selected as the organic phases.Firstly,the influences of benzene addition and experimental conditions on CO2 absorption percentage were investigated in a stirred tank reactor(STR).Secondly,the effects of the operating conditions,such as volume fraction of benzene,n-heptane and n-octanol,rotational speed,gas and liquid flow rate,temperature and NaClO concentration,on the CO2 absorption percentage were investigated in RSR,and the mathematical correlation between CO2 absorption percentage and operating conditions was established.The optimum operating conditions were determined and the impact of the three organics on CO2 absorption percentage and absorption rate was studied.Finally,the mass transfer of CO2 in RSR,as well as the intensification mechanism of NaCIO was deduced.The main conclusions are as follows:(1)Studies in STR revealed that benzene volume fraction,stirring intensity,gas flow rate and NaCIO concentration had significant effects on the CO2 absorption percentage.The organic phase could obviously enhance the CO2 absorption into K2CO3/KHCO3 solution.(2)Studies in RSR indicated that the viscosity,density and pH changed slightly with volume fraction of organic phases in experiment process,and the addition of organic phases could reduce the interfacial tension of the two liquid phases significantly.(3)Similar results were obtained when benzene,n-heptane and n-octanol were employed respectively as the promoters.The CO2 absorption percentage first increased and then gradually decreased with the increase of organic phase volume fraction,and increased with the increase of rotational speed,liquid flow rate and NaCIO concentration,but decreased with the increase of gas flow rate and temperature.Under the identical conditions,the intensification capacity of organic phases on CO2 absorption was:benzene>n-heptane>n-octanol.(4)Benzene,n-heptane,n-octanol experienced no chemical changes in the absorption process.The mass transfer mechanism of CO2 absorption into K2CO3/KHCO3 solution intensified by organic phases in the RSR and the intensified mechanism of NaClO were analyzed.The mathematical correlation between CO2 absorption percentage and liquid viscosity,rotational speed,liquid and gas flow rate,temperature and NaCIO concentration was established,which can be used for the calculation of the C02 absorption percentage in the system studied.This thesis studied the absorption of CO2 by K2CO3/KHCO3 solution and organics,which were intensified by the RSR.The studies indicate that the HiGee technology has a certain intensification effect on the G-L-L process and provide a new pathway for CO2 emission reduction.