Techno-economic assessment of hydrogen selective membranes for CO₂ capture in integrated gasification combined cycle

In this study, the application of Pd-based H₂-selective membranes in integrated gasification combined cycle (IGCC) plants with CO₂ capture is performed from both technical and economic perspective. After a preliminary assessment, the membrane separation section is selected and designed on several membrane modules in series with adiabatic high temperature shift in between. The adoption of membrane module with 19 membrane tubes was mainly driven by techno-economics assessment and plant operation issues. Two different plant lay-outs are proposed: in the first configuration, which is more conventional, all the hydrogen is separated at high pressure and sent to the gas turbine. This lay-out achieves very high net electric efficiency (about 40%), but requires large membrane surface area with penalties from economic point of view (cost of CO₂ avoided about 50% higher than reference case). The membrane module cost accounts for more than 25% on the total investment. In the second configuration, which is an innovative part of this work, a proportion of the hydrogen is separated at low pressure and used to post-fire the heat recovery steam generator. This configuration preserves the very high efficiency of the previous case but reduces significantly the membrane surface area; the membrane cost share over the total investment drops to 15%. The resulting cost of CO₂ avoided is 36 €/tCO2, equal to the reference case, with large possibility of improvements thanks to the conservative membrane design selected.