고리형 아민을 이용한 이산화탄소 흡수제의 흡수속도 연구

Abstract

The purpose of this study is to examine the optimal absorption characteristics depending on the temperature and the concentration of cyclic amines, which are used in CO2 Absorption process. Absorption capacity and rate are estimated as absorption characteristics of absorbents. Absorption capacity is evaluated by estimating equilibrium partial pressure and reduction in pressure with a vapor-liquid absorption equilibrium apparatus. Mass transfer rate is examined using the WWC. Speciation of the absorbents after absorption of CO2 is analyzed with 1H and 13C NMR. The results of this study on the absorption characteristics of the cyclic amines are as follows; 1. According to the absorption experiments with the amine concentrations of 15, 20, 25 and 30 wt.%, which were conducted to find absorption characteristics study on cyclic amines, it is confirmed that the absorption capacities of the absorbents increase when the amine concentrations decrease. For temperature, absorption capacity was measured at 30, 40, 50 and 60 ℃. It is found that the absorption capacities of the absorbents decrease as equilibrium partial pressures increase when temperatures are higher. Absorption capacity of 15 wt.% PZ at 30 ℃ is two times higher than that of 30 wt.% MEA at 60 ℃ (commercial process). PD, 2MPD and 2MPZ have lower absorption capacities than PZ, but higher absorption capacities than MEA.

2. The mass transfer rates of cyclic amines were calculated with amine concentrations of 15, 20, 25 and 30 wt.%. It is found that PZ is not suitable to use as a high amine concentration because of its solid-salt when the amine concentration is higher than 20 wt.% at room temperature. On the other hand, 2MPZ produced solid-salt when the amine concentration is higher than 25 wt.%. All absorbents showed increased mass transfer rate in higher temperature and amine concentration. Compared to 30 wt.% MEA, 30 wt.% PD has excellent mass transfer rate at 60 ℃. However, 2MPD is more suitable for absorption process because PD has relatively lower boiling point and higher volatility.

3. Absorbent samples with different CO2 absorption capacities were produced by a vapor-liquid absorption equilibrium apparatus, which were analyzed with NMR in order to investigate speciation. According to the analysis, PD produces carbamate at the initially step of reaction but creates bicarbonate when the amount of absorption of CO2 increases. It is expected that PZ has a high regeneration energy because its main products are carbamate and bicarbamate. 2MPD selectively creates bicarbonate. Although 2MPZ produces carbamate and bicarbonate, the percentage of bicarbonate is relatively more than the others.

As the results of this study, it is concluded that the best substitute for 30 wt.% MEA as an absorbent of cyclic amine is 20 wt.% 2MPD at 60 ℃. It is expected that the results of this study have significant effects on processing energy savings by minimizing the height of absorption tower and reducing the amount of absorbents to be circulated. In addition, it is expected that 2MPD, cyclic secondary amine is able to be used as an criterion for a future study on absorbents that reduce emission of CO2.