The absorption characteristics of carbon dioxide into aqueous 3DMA1P(3- Dimethylamino-1-propanol) and promoted 3DMA1P absorbent were investigated. In order to investigate the mixing effects of primary and secondary amines, MEA(Monoethanolamine), DEA(Diethanolamine), and piperazine were used as absorption rate enhancers. Vapor-liquid equilibrium of absorbent/CO2/H2O system was measured at 313 and 333 K using 30 wt.% 3DMA1P aqueous solution and promoted 3DMA1P absorbent with 3~9 wt.% MEA, DEA, piperazine. CO2 partial pressure over absorbent at arbitrary temperature, amine concentration, and CO2 loading was well predicted using the semi-empirical equation based on experimental results. 30 wt.% 3DMA1P aqueous solution has higher solubility at CO2 partial pressure of 15 kPa than 30 wt.% MEA aqueous solution which is conventionally used in post-combustion CO2 capture. At higher CO2 partial pressure, the solubility of CO2 into 3DMA1P absorbent was higher than MDEA absorbent which is commonly used in pre-combustion CO2 capture.
1. Vapor liquid equilibrium of promoted 3DA1P solution with CO2 was also measured. The solubility at CO2 partial pressure 15 kPa decreased with increasing the amount of rate enhancer, MEA, DEA, and piperazine, which can be explained by stable carbamate formation by primary and secondary amines. The change of solubility depending on the rate enhancer was in the rank of PZ < MEA < DEA.
2. Although 3DMA1P aqueous solution has excellent solubility over conventional CO2 absorbents, the rate of CO2 absorption is much lower than conventional amine solvents and this is a common challenge of tertiary amine solvent. The rate of CO2 absorption in term of overall mass transfer coefficient, KG, was measured using the wetted wall column in the range of 313~333 K. The overall mass transfer coefficient of CO2 into 30 wt.% 3DMA1P aqueous solution was only 7 %, 20 % of KG into MEA and DEA aqueous solution respectively.
3. The absorption rate of CO2 into promoted 3DMA1P absorbent with MEA, DEA and PZ was also measured, and the mixing effects of primary and secondary amines on the CO2 absorption rates were investigated. The promotion effect of 3 enhancers was in the rank of PZ > MEA > DEA, which could be expected from their rate of reaction with CO2. Overall mass transfer coefficients were correlated with the amount of rate enhancer, and the effect of rate enhancer was well described with this correlation. 3DMA1P aqueous solution blended with over 4.5 wt.% PZ showed higher CO2 absorption rate than conventional 30 wt.% MEA absorbent. Among the monoamine, primary amine was more effective rate enhancer than secondary amine, however, diamine was more effective even than primary monoamine.