(565e) A Techno-Economical Analysis of Membranes, Amine Absorption and Membranes-Amine Hybrid Process for CO2 Removal From Flue Gases

In this study, a technical and economic analysis of CO₂ removal from flue gases with competing technology such as membranes, amine absorption and their hybrid process has been conducted. Polymer membranes have found applications in variety of gas separation processes. However, there exists considerable confusion and argument about the preferential use of membranes over alternative processes. Amine absorption is still considered a state of the art technology for acid gas removal. However, amine units use more energy when the CO₂ concentration increases. Membranes, on the other hand, use partial pressure as the driving force and are most effective at high concentrations of CO₂. Membranes can easily be combined with amine absorption to yield hybrid processes with cost/performance advantages that neither process could achieve individually. Membrane/absorption hybrid systems take the advantage of bulk CO₂ removal properties of membranes with a relatively small area while the amine is used for the final cleanup to achieve the required specification. Several cascade configurations of cellulose acetate based asymmetric hollow fiber membranes, and amine absorption with MEA and DEA as solvents were studied individually for a target recovery and purity, both for the product value of CO₂ (e.g., enhanced oil/coal bed methane recovery) and for environmental reasons (reducing the greenhouse effect). A mathematical model was first developed for multicomponent gas separation by high-flux asymmetric hollow fiber membranes which takes into account the permeate pressure build up inside the fiber bore, and also considers cross flow with respect to the membrane skin, irrespective of the flow direction of the bulk permeate stream outside of the porous layer. Amine unit was simulated in AspenPlus^® and membrane model was later incorporated into AspenPlus^® to study the hybrid process. The developed membrane model was incorporated into AspenPlus^® as a user-model for an overall membrane process study and for the design and simulation of hybrid processes for CO₂ removal. The study was conducted to find the extent of optimal conditions for which the aforementioned technologies are best suited, and to evaluate the capital investment and processing cost.