(387d) Techno-Economic Analysis of Polymeric Membrane Systems for Post-Combustion Carbon Capture

The increasing consumption of fossil fuels has resulted in immense CO₂ emissions after the Industrial Revolution. Membrane processes have been suggested as an alternative to amine absorption for post-combustion carbon capture. Despite of the tremendous research efforts, CO₂-selective polymeric membranes typically exhibit a trade-off between CO₂ permeance and CO₂/N₂ selectivity. This presentation will show how to overcome the limitations as a result of this trade-off by noval membrane process designs. In the first membrane process, called the hybrid air sweep process, the flue gas flows to a vacuum membrane stage using a membrane with high CO₂/N₂ selectivity and moderate CO₂ permeance. The retentate gas then flows to an air-sweep membrane stage employing another membrane with high CO₂ permeance but low CO₂/N₂ selectivity. The CO₂-laden sweep air is fed to a power plant boiler as combustion air. A highly selective amine-containing membrane with a CO₂ permeance of 1100 GPU (1 GPU = 10^-6 cm³ (STP)·cm^-2·s^-1·cmHg^-1) and a CO₂/N₂ selectivity >140 is used for the vacuum stage to enrich the CO₂ to >95% purity whereas a highly permeable poly(ethylene oxide)-based membrane with a CO₂ permeance of 2000 GPU and a CO₂/N₂ selectivity of 20 is employed for the air sweep stage. This hybrid membrane configuration yields a capture cost of $40.2/tonne CO₂ in the 2007 dollar basis for 90% CO₂ recovery, which nearly meets the target of the Department of Energy (DOE) set for 2025. In the second membrane process, i.e., retentate recycle process, the flue gas is passed to two stages employing the membrane with high CO₂/N₂ selectivity; these two stages are placed in an enriching cascade. A portion of the CO₂-depleted retentate of the first membrane stage is recycled as its own sweep gas. It is identified that the highly selective amine-containing membrane is needed for both stages and a 20% retentate recycle renders a capture cost of $43.1/tonne CO₂. These cost calculations in the 2007 dollar basis have included both membrane module installation cost and 20% process contingency.