Selective absorption of H2S from gas streams containing H2S and CO2 into aqueous solutions of N-methyldiethanolamine and 2-amino-2-methyl-1-propanol

Abstract

Selective absorption of H2S from N2 streams containing H2S and CO2 into aqueous solutions of 2-amino-2-methyl-1-propanol (AMP) as well as N-methyldiethanolamine (MDEA) was investigated in a 2.81×10−2 m o.d. stainless steel wetted-wall column at atmospheric pressure and constant feed gas ratio. In the range of gas flow rates studied (90–180×10−6 m3/s), the effect of gas-phase resistance on the absorption of H2S was significant. The rates of absorption of H2S and the selectivity factor decreased with the contact time for both alkanolamine solutions. With increasing amine concentration in the range 2.0–3.0 kmol/m3, the rates of absorption of both CO2 and H2S increased, but relatively more for CO2, resulting in a consequent decrease in the selectivity factor. In the temperature range 293–313 K, the rates of absorption of CO2 increased marginally with the increase in temperature while the rates of absorption of H2S and the selectivity factor decreased. The maximum selectivity observed in this work was 17.57 and 23.02 for AMP and MDEA, respectively. The acid gas mass transfer has been modelled using equilibrium-mass-transfer-kinetics-based combined model for CO2 and gas-phase transport equation-based approximate model for H2S considering negligible interaction between CO2 and H2S in the liquid phase. The experimental and model results have been found to be in good agreement.