Experimental study on CO₂ absorption by aqueous ammonia solution at elevated pressure to enhance CO₂ absorption and suppress ammonia vaporization

Abstract

Abstract The low CO 2 absorption rate and high ammonia volatile loss rate are two major issues for the ammonia‐based CO 2 capture technology. In this work, we investigated the effect of total pressure on CO 2 absorption and ammonia vaporization in ammonia solutions on a wetted‑wall column. We found that the elevated pressure absorption process was an effective way to increase CO 2 absorption rate and suppress ammonia vaporization at the same time. We also studied the mass transfer mechanism at elevated pressure and found the overall mass transfer coefficients of CO 2 absorption in both ammonia and MEA solutions at elevated pressures were lower than that under atmospheric pressure. The overall mass transfer coefficients of CO 2 absorption in 3 M NH 3 (298 K) at 1, 1.5, 2, 2.5 bar were 0.723 × 10 −6 , 0.652 × 10 −6 , 0.591 × 10 −6 , 0.555 × 10 −6 mol/(s m 2 Pa) and the corresponding gas side mass transfer coefficients were 13.8 × 10 −6 , 4.52 × 10 −6 , 2.61 × 10 −6 , 2.03 × 10 −6 mol/(s m 2 Pa), respectively. We also found the gas side mass transfer coefficient in the wetted‐wall column was not only dependent on the hydrodynamic conditions of the column but also influenced by the total pressure. © 2014 Society of Chemical Industry and John Wiley & Sons, Ltd