Promoted Aqueous Ammonia Based Carbon Dioxide Capture

Exceed emission of carbon dioxide(C02)to atmosphere is the major contribute to the global warming.Aqueous ammonia based solvents have received increasingly attention because of its key advantages on CO2 capture such as higher CO2 absorption removal capacity,and lower regeneration energy.In spite of its advantages,aqueous NH3-based PCC faces two major challenges:low CO2 absorption rate and high volatility.Accordingly,future research should focus on these areas to make improvement and accelerate the commercialization process of aqueous NH3-based PCC.In this work,the influence of operating conditions of ammonia loss rate within the wetted-wall column and a bubble column was investigated,including ammonia concentration,CO2 loading and temperature.The focus of this work is to identify a potential promoter to enhance the C02 absorption into aqueous ammonia based solvents as well as investigate the reaction mechanism between CO2 and the mixture of ammonia and rate promoter.The influence of rate promoter on ammonia loss rate was also studied.The main results are as the followings:First,the wetted-wall column and bubble column revealed that the operating conditions that favored CO2 absorption can increase ammonia loss rate,such as increase in ammonia concentration and operating temperature and decrease in CO2 loading.By comparing the overall mass transfer of ammonia to that of CO2,a conclusion could be drawn that the ammonia desorption is a relative fast process and need further attention.Secondly,the second-order rate constant of NH3 react with CO2 was calculated based on the wetted-wall column results and show good agreements with published values.The kinetic results from wetted-wall column apparatuses proved that the addition of a small amount of additive can enhance CO2 absorption to a large extend.Also,the screening test results revealed that PZ is the best rate promoter,among all the additives tested,for aqueous ammonia based CO2 capture process.Thirdly,the second-order rate constant of PZ react with CO2 agreed very well with published values,which calculated based on the absorption kinetics that generated from wetted-wall column.Addition of a small amount of PZ can enhance CO2 absorption to a large extend especially with high CO2 loadings.The C02 absorption rate increases with the rises of PZ concentration added to aqueous ammonia solutions.The addition of PZ can increase the ammonia loss rate as well.Finally,the stopped flow technique test reveals that there is no catalytic effect of PZ on the reaction mechanism between CO2 aqueous ammonia solutions.