Evaluation of Economic Performance of Co₂ Separation Process Using Mixed Matrix Membrane

A multi-stage CO₂ capture process using Mixed Matrix Membrane (MMM) could separate molecules with similar molecular diameter such as CO₂ and N₂ by dissolution and diffusion. The required energy and the membrane area were investigated based on the membrane performance such as CO₂ permeance and CO₂/N₂ selectivity. In this multi-stage CO₂ capture process, the feed gas fed into the first and second membranes. The gas permeated through the second membrane was recycled to Feed. The permeate gas from the first membrane was fed to the adsorption column to separate H₂O. The CO₂-rich dry gas was liquefied by using a compressor and a condenser. The residual gas was separated using a membrane, and the permeate gas was recycled to the dry gas. The flue gas assumed from a coal-fired power plant containing 11.6 mol% CO₂. When the CO₂ permeance of 1000 GPU and CO₂/N₂ selectivity of 50 were used for the first and second membranes of the multi-stage CO₂ capture process, the required energy was 139 MW and the membrane area was 3.6 × 10⁶ m², respectively. From these results, the operation, construction, and membrane skid costs were calculated. The CO₂ capture cost per ton of CO₂ was found to be $38/ton-CO₂. In addition, the membrane area of the second was large, and the membrane area could be reduced by using a membrane with high CO₂ permeance and low CO₂/N₂ selectivity. Therefore, a membrane with CO₂ permeance of 1000 GPU and CO₂/N₂ selectivity of 50 was used in the first. A membrane with CO₂ permeance of 3000 GPU and CO₂/N₂ selectivity of 30 was used in the second. As a result, it was clarified that the required energy was 141 MW, and the membrane area was 1.25 × 10⁶ m². The CO₂ capture cost was $29/ton-CO₂.