Study On CO₂ Capture By Using The Triple Amine Blend Of MEA-1DMA2P-PZ

Excessive anthropogenic carbon dioxide（CO₂）emission has been considered to be the major contributor toward abnormal climate changes and global warming.In particular,the combustion of coal-fired power plants is one of the largest CO₂ emission sources.In this context,the deployment of post-combustion carbon capture and sequestration（CCS）in the coal-fired power stations is essential to reduce global CO₂emissions.The timely solution to this problem is the technology of CO₂ capture using aqueous amine solutions.However,the widespread application of this technology in the industry is confined by high energy consumption,and poor performance in absorption and desorption stages,etc.To overcome this limitation,novel triple amine blends,which contains monoethanolamine（MEA）,1-Dimethylamino-2-propanol（1DMA2P）,and piperazine（PZ）with three different 1DMA2P/PZ molar ratios,were employed to capture CO₂ from simulated flue gas.The typical processes of CO₂ capture by amine solution include two stages:the absorption and the desorption stages,in which the performance of the MEA-1DMA2P-PZ solvents and the 5M MEA solution are explored in this work and the main results are as follows:（1）The CO₂ equilibrium solubilities of the proposed blends and 5M MEA solution,which were prepared at 30,40,and 50°C with various of CO₂ partial pressures,were determined by titration using 1M HCl.The results show that the blends performed better than 5M MEA,and the solubility increased with the increase of piperazine content in the blend.During the absorption experiments,the absorption capacities and average absorption rates were obtained by the gas-phase method.Compared with the baseline solvent（e.g.5M MEA）,these two factors of the blends were improved by 25–37%,but the average absorption rates were decreased by 0.6–8.8%.For better understanding the absorption process,a quantitative study of the CO₂-derived species in the CO₂-saturated solution was carried out,which showed the blend solution with highest 1DMA2P/PZ ratio formed the largest amount of bicarbonate and the smallest amount of carbamate.The CO₂ absorption heat was calculated by the Gibbs-Helmholtz equation,and the results suggested the CO₂ absorption heat of the blends was reduced by 26–38%than 5M MEA and even lower than the similar MEA-based triple-amine solvents reported in papers.More bicarbonate with less carbamate,as well as with the lowest CO₂ absorption heat illustrated better solvent regeneration performance.This paper demonstrated that the novel tri-solvent blends,especially the blend MEA:1DMA2P:PZ=3M:1.5M:1.5M PZ could potentially be an alternative to 5M MEA solution in the flue gas CO₂ capture process.（2）The desorption process was carried out at a lower temperature range（65–90°C）focusing on the performance of amine regeneration,energy consumption,etc.The results demonstrated that all the blends performed better than 5M MEA in terms of instantaneous desorption rate,average desorption rate and cyclic capacity.Additionally,the bigger the molar ratio of 1DMA2P/PZ,the better the performance of the aforementioned aspects.The three blend solutions increased the average desorption rate by 60–140%,and enhanced the cyclic capacity by 40–120%,compared with 5M MEA solution.Especially,the blends reduce the energy penalty by 29.4–55.4%,while the MEA:1DMA2P:PZ=3M:2.5M:0.5M system was the most outstanding.Furthermore,the proposed parameter named Desorption Parameter（DP）had verified the good performance of these three blends,which could effectively evaluate the stripping performance of the amine solution and could be used as a guideline to formulate a new amine solvent.Through the analysis of the regeneration mechanism in detail,it is found that the main reason for the lower energy cost in the triple amine blend is that there are more proton provider exists in that system.Considering the energy efficiency,the MEA-1DMA2P-PZ was found a potential candidate for capturing CO₂ in industrial.