CO<sub>2</sub>Capture Performance Comparisons of Polyamines at Practical Concentrations for Use as Activators for Methyldiethanolamine for Natural Gas Sweetening
Bander Jaffary, Laila Jaafari, Raphael Idem
Abstract
High-performance polyamines, namely, branched polyethylenimine (PEI-B), tetraethylenepentamine (TEPA), and piperazine (PZ), at concentrations of 0.1, 0.3, and 0.5 M were studied for use as activators for methyldiethanolamine (MDEA) for natural gas sweetening, particularly for CO2 removal. The natural gas was mimicked by a gas stream containing 50% CO2 (balance N2). Performance comparison was in terms of rich loading, lean loading, cyclic capacity, absorption rate, desorption rate, and heat duty. Results showed that PEI-B exhibited the best performance in all evaluation parameters. Also, 13C NMR analysis performed at equilibrium rich loadings on 0.1 M polyamines showed that PEI-B formed and desorbed the largest amounts of CO2 products as compared with those from PZ. Additionally, two pseudo-first-order models with respect to CO2 and amine for the absorption process were developed. In both models, although PZ exhibited the highest rate constant per amino group, the overall rate constant of PEI-B was the highest. Furthermore, first-order exponential rise and decay expressions were developed to adequately describe the absorption and desorption processes, respectively.