Absorption Performance And Corrosion Behavior For CO₂ Capture Process Using Amino Acid Ionic Liquids-Potassium Carbonate Aqueous Solution

In recent decades,the global climate change and environmental problems caused by the emission of carbon dioxide(CO2)seriously impacted the sustainable development of the economy.Development of affordable yet technically feasible separation technologies for CO2 capture is attracting more and more attention.Coal-fired power plant is the largest source of CO2 emissions in China,and the capture of low partial pressure CO2 in flue gas has caused increasing concern for the sustainable economic development.Chemical absorption technologies based on potassium carbonate solution have good application potential in the field of CO2 capture duo to their advantages of simple process,low cost and high absorption capacity.However,low absorption rate and high corrosion to equipment restrict their application in coal-fired power plants.Considering the low partial pressure of CO2,it is very necessary to construct a new and efficient absorption system to increase the absorption rate,reduce the energy consumption for rich phase regeneration and poor phase cooling,and decrease the corrosion to equipment.In this thesis,new absorbents were developed by blending potassium carbonate(K2CO3)and amino acid ionic liquids(AAILs)including tetramethylammonium glycinate([N1111][Gly]),1-butyl-3-methylimidazolium glycinate([Bmim][Gly])and 1-butyl-3-methyl-imidazolium lysinate([Bmim][Lys]).To verify the absorption capacity of the proposed new absorbents,the time-dependent CO2 absorption capacities in K2CO3-[N1111][Gly],K2CO3-[Bmim][Gly]and K2CO3-[Bmim][Lys]aqueous solutions under series of temperatures and solution concentrations were measured in a self-designed absorption equipment.The equilibrium absorption amount and CO2 loading were determined.The effects of temperature,K2CO3 concentration and AAILs concentration on the absorption capacity were demonstrated.Moreover,simulated flue gas with CO2 partial pressure ranging from 10 to 90 kPa was prepared,and the absorption performance of CO2 in K2CO3-AAILs aqueous solution was measured.The CO2 partial pressure dependence of absorption performance was also illustrated.To verify the enhancement of AAILs on absorption rate,the apparent absorption rates of CO2 in K2CO3-AAILs aqueous solutions were determined based on the time-dependent absorption amount under series of CO2 partial pressures,temperatures,K2CO3 concentrations and AAILs concentrations.The effects of operation conditions on apparent absorption rate were illustrated.Moreover,the viscosities of both CO2-unloaded and CO2-loaded K2CO3-AAILs aqueous solutions were measured and then correlated by using thermodynamic models.The effects of temperature and solution concentrations on viscosities were illustrated.On the basis of the investigation of viscosity and apparent absorption rate,the competitive effect of the solution concentration and solution viscosity on apparent absorption rate was clarified.To verify the corrosion behavior of carbon steel in carbonated K2CO3-AAILs aqueous solutions,an electrochemical experimental platform was designed.The pH values of C02 loaded K2CO3-[N1111][Gly],K2CO3-[Bmim][Gly]and K2C03-[Bmim][Lys]aqueous solutions and the corresponding corrosion polarization curves of carbon steel were measured under a series of temperatures,A AIL type/concentrations and CO2 loadings.The variations of corrosion voltage and corrosion current were analyzed.From the corrosion polarization curves,the corrosion rates were determined,and the effects of temperature,K2CO3 concentration,AAILs type/concentration,CO2 loading,pH value and H+concentration on corrosion rate were clarified.The corrosion mechanism of carbon steel in K2CO3-AAILs aqueous solutions was analyzed,and the competitive effect of heteroatoms in AAILs molecular structure and HCO3-/H+ concentration on corrosion rate was demonstrated.Based on the study of absorption capacity,apparent absorption rate,solution viscosity and corrosion rate,a high efficient absorbent was determined and the CO2 removal efficiency was verified in a self-made tray column.The effects of inlet gas flow rate,inlet liquid flow rate and plate number on the removal efficiency and total volumetric mass transfer coefficients were illustrated.Compared with the traditional K2CO3 and K2CO3-DEA(Diethanolamine)absorbents,the AAILs promoted K2CO3 aqueous solutions take the advantages of higher CO2 absorption capacity,higher absorption rate and lower corrosivity.Moreover,the CO2 removal efficiency in tray column is satisfactory.The new absorbents are promising to improve the CO2 capture efficiency and reduce cost and energy consumption,thus have good application potential in CO2 capture from coal-fired power plants.