Evaluation of effectiveness of highly concentrated alkanolamine solutions for capturing CO2 in a rotating packed bed

Abstract

The capture of CO2 by single and mixed alkanolamine solutions of monoethanolamine (MEA), 2-methyl-amino-ethanol (MMEA) and piperazine (PZ) with total alkanolamine concentrations from 30 to 100wt% was conducted in a rotating packed bed (RPB). The effects of rotational speed, gas flow rate and composition of the absorbent were investigated. Experimental results showed that increasing the alkanolamine concentration and the rotational speed up to 1800rpm effectively improved the CO2 removal efficiency. However, the removal efficiency decreased as the gas flow rate increased. MMEA solutions exhibited a higher removal efficiency than MEA because MMEA reacts faster with CO2 than MEA. The alkanolamines that were mixed with PZ were more effective in capturing CO2 than single alkanolamine solutions. The height of transfer unit (HTU) decreased as the alkanolamine concentration and rotational speed increased, but increased with the gas flow rate. A CO2 removal efficiency of 99.4% and an HTU of 0.74cm were obtained using absorbent that contained 80wt% MMEA and 20wt% PZ at a rotational speed of 600rpm, a liquid flow rate of 0.1L/min, a gas flow rate of 30L/min and a temperature of 313K. The high removal efficiency and low HTU value reveal that an RPB has great potential for CO2 capture from a gas stream using an absorbent with a high alkanolamine concentration.