Investigation of the Cooling System of a Membrane-based Post-combustion Process

Abstract

This paper investigates post-combustion capture in coal-fired power plants equipped with gas separation membranes. Simulations are conducted with the process engineering software, Aspen Plus®, with its Exchanger Design and Rating (EDR) tool utilized for heat exchanger design. The reference power plant chosen for the investigation is the Reference Power Plant North Rhine-Westphalia (RPP-NRW) in Germany.The Polyactive® membrane developed by the project partner, Helmholtz Zentrum Geesthacht, was used in the simulation. Because the membrane has different properties at different working temperatures in order to reach a higher degree of selectivity and less energy consumption, the flue gas should be cooled to 25°C. This results in an efficient cooling system for the capture process, which merits further development.A rigorous heat exchanger design leads to a significant increase in the pressure drops at each heat exchanger and hence the pressure ratio required by the compression machines. The energy penalty of the membrane CCS system for 57% and 76% degrees of CO2 separation was increased from 4.7%-pts to 5.3%-pts and 7%-pts to 8.3%-pts, respectively, after implementing the rigorous heat exchanger design.