Sensitivity Analysis Of CO₂ Capture Process Using Aqueous Ammonia And Studies On Capacitive Separation Of Rich Solvent

With the advantages of higher CO2 absorption capacity,lower heat of absorption,no absorbent degradation and equipment corrosion problems,and simultaneous removal of CO2,SO2 and NOx in the flue gas,CO2 capture using aqueous ammonia is considered as a feasible technical route for reducing huge CO2 emissions from coal-fired power plants.Currently,for the CO2 capture process using aqueous ammonia,the comprehensive mathematical model and process simulation method need further improment,the performance evaluations of the large-scale applications are limited,the chemical reactions that play important roles in the process are not clear,and the effective way for reducing the regeneration energy is lacking,and therefore a series of studies were carried out in this dissertation for these problems.A comprehensive mathematical model and process simulation method,which simultaneously considered the hydrodynamics of the vapor and liquid phases,equilibrium between the vapor and liquid phases,rate-based heat and mass transfer,and chemical reactions with finite reaction rates,were developed for the CO2 capture process using aqueous ammonia.Based on this process simulation method,process sensitivity analyses of large-scale CO2 capture and NH3 abatement processes for a typical 500 MW coal-fired power plant were carried out,effects of the process operating parameters on the target parameters were obtained,and process optimization was further performed.Here,the NH3 abatement process adopted the carbonated aqueous ammonia solution with high CO2 loading while low NH3 concentration as the absorbent for treating the sliping NH3.For the optimized CO2 capture process using aqueous ammonia,the CO2 removal efficiency is 91.04%,and the amount of CO2 captured annually can reach 3.2167 million tonnes.Meanwhile,the optimized NH3 abatement process can achieve that the final vent NH3 meets the NH3 emission standards of many countries in the world.Reaction sensitivity analysis of the CO2 capture process using aqueousammonia was carried out.The chemical reactions that play important roles in the process under different operating conditions were identified.In the absorption process of CO2 capture using aqueous ammonia,the formation reaction of carbamate plays an important role on the CO2 absorption rate.In the regeneration process of CO2 capture using aqueous ammonia,the formation and decomposition reactions of bicarbonate both play important roles on the CO2 regenerating rate.Based on the above reaction sensitivity analysis,a novel concept for reducing the regeneration energy was proposed by directionally changing the reaction rates of the chemical reactions that play important roles in the CO2 capture process using aqueous ammonia.Simulation results showed that it can achieve the significant reduction of the regeneration energy while not affecting the CO2 removal efficiency,and the reduction of the regeneration energy can reach above 20%.The flow-by capacitive ion separation device was introduced into the CO2 capture process using aqueous ammonia for reducing the regeneration energy,and the regeneration energy analysis of the CO2 capture process using aqueous ammonia integrated with the capacitive ion separaiotn device under different properties of the rich solvent flowing out of the absorber was carried out.By choosing appropriate parameters of the capacitive ion separation device as well as reducing the flow rate of the rich solvent flowing into the stripper,simulation results showed that the significant reduction of the regeneration energy of the CO2 capture process using aqueous ammonia integrated with the capacitive ion separaiotn device can be achieved when keeping the CO2 regenerating rate unchanged,the reduction of the regeneration energy can reach above 20%.