Experimental Study On CO₂ Absorption By Amine-based Multi-component Absorbents

To cope with the global climate change caused by greenhouse effect,it is imperative to develop economical,high-efficiency and large-scale CO₂ capture technology for coal-fired power plants.CO₂ capture by amine solutions is the most widely used method in today's power plants,but it has the defects of low absorption capacity and high regeneration energy consumption.In this paper,experimental study on CO₂ absorption by amine-based multi-component absorbents was carried out.Schemes for improving the performance of CO₂ capture were explored from the two paths of amine blends and amine phase change absorbents,and several amine-based multi-component absorbents with better comprehensive performance were found,which provided theoretical guidance for carbon capture process of existing power plants.Studies on CO₂ absorption properties of six common organic amines were carried out through fixed bed absorption-desorption experiments and C80 micro calorimetric experiments.Among them,two amines PZ and DETA showed excellent absorption properties.On this basis,experimental study on CO₂ absorption by amine blends was carried out.An amine blend 20%MEA+5%DETA+5%PZ which showed better comprehensive performance was obtained by adding PZ and DETA into MEA solution.Compared to traditional 30%MEA,its absorption rate and absorption capacity were respectively increased by 7%and 15%,and its regeneration energy consumption was reduced by 6%.After several cycles,its stable cycle absorption capacity increased by 15%.Besides,in order to improve the performance of the absorbent,PZ and DETA were directly mixed to obtain a new amine blend,results showed when the ratio was 10%PZ+20%DETA,its absorption capacity increased by 42%,its initial absorption rate increased by9%,its regeneration energy consumption decreased by 9%,and its stable cycle absorption capacity increased by 55%compared to 30%MEA.To further reduce the regeneration energy consumption,DETA/1-propanol/H₂O phase change absorbents were selected for CO₂ absorption experiments,which showed higher absorption capacity,absorption efficiency and lower regeneration energy consumption.Results showed that the optimum ratio of DETA/1-propanol/H₂O phase change absorbents was 30%DETA+30%1-propanol+40%H₂O.Its absorption capacity increased by 53.5%compared with 30%MEA,and its regeneration energy consumption reduced by 27%which had large potential in energy saving.After CO₂ absorption,the saturated absorption solutions were split into two phases in which more than 90%of the CO₂ was enriched in lower phase.Chemical reactions and phase transition mechanisms of CO₂ absorption by DETA/1-propanol/H₂O phase change absorbent were further clarified through experimental phenomena and ¹³C NMR characterization results.During the absorption process,CO₂reacted with DETA to form carbamate,and part of the carbamate would gradually hydrolyze to form bicarbonate.After absorption saturation,the carbamate formed was soluble in water and insoluble in 1-propanol,and its density was higher than that of1-propanol,so the carbamate would gradually enrich in lower phase,and 1-propanol would enrich in upper phase to form stratification phenomenon.