How gas separation membrane competes with chemical absorption in postcombustion capture

This paper describes an investigation for multi-stage systems used in coal-fired power plant. The whole work was divided into two steps: energetic and economic analyses. In the first step: on the basis of a serial concept, through varying the position of compressors and vacuum pumps, recycling the retentate of the 2nd membrane to the feed side of the 1st membrane, a cascade variant was developed and analysed. In the second step: an economic model was developed to calculate the capture cost of the cascade system. The total cost is composed of investment cost, operation and maintenance (O&M) cost and electricity cost. A correlation between the membrane parameters: selectivity & permeability and capture performance: energy consumption & capture cost was built up. Using Polyactive® membrane developed by GKSS with CO2 permeance of 3 Nm3/m2hbar and CO2/N2 selectivity of 50, under the separation target of 70% degree of CO2 separation and 95 mol% CO2 purity, adopting the cascade membrane system in the 600 MW NRW-reference power plant, the specific energy consumption including CO2 compression (110 bar, 30 °C) is 256 kWh/tseparatedCO2 with 6.4%-pts efficiency loss. The capture cost is 31 euro/tseparatedCO2, which could be a promising solution as a retrofit for the existing power plants.