Absorption of carbon dioxide in aqueous piperazine/methyldiethanolamine

Abstract

Abstract Carbon dioxide absorption in 0.6 M piperazine (PZ)/4 M methyldiethanolamine (MDEA) was measured in a wetted wall contactor. The data were simulated using a model that accounts for chemical reactions and transport effects with the eddy diffusivity theory. PZ/MDEA blends absorb CO 2 faster than monoethanolamine (MEA) or diethanolamine (DEA) blends with MDEA at similar concentrations. The reaction of PZ to form a monocarbamate is dominant at low loading (<0.14). The reaction of the monocarbamate to form dicarbamate is dominant at high loading. The absorption rate did not follow pseudo first‐order behavior except at very low loading. All carbamate and dicarbamate formation reactions approached instantaneous behavior at high loading. The series resistance due to pseudo first‐order reaction and instantaneous carbamate formation matched data throughout the entire loading range. A typical ammonia plant absorber was simulated at isothermal conditions using the rigorous model. Gas film limitations were dominant (>50%) only at the top of the absorber.