Evaluation of Membrane Separation Process of CO2 Recovery

Abstract

Various technologies, including CO2 geological storage and ocean storage, and CO2 utilization, have been investigated as a countermeasure to the greenhouse effect. Before they are applied to the fields of thermal power plants, cement plants, steel mills, etc., CO2 must be recovered from the exhaust flue gas from the plants. To recover CO2 from flue gas, a membrane separation processes is applicable, in which the pressure difference should be applied across the membrane as a permeation driving force. It can be done either by compressing the flue gas with a compressor or connecting a vacuum pump to the permeation side of the membrane module. The energy consumed to operate the equipment is regarded as the CO2 separation energy. A computer simulation was carried out to estimate the energy and cost for a CO2 separation process with a membrane applied to the exhaust flue gas from a 1000MW coal combustion power plant. Three types of separation processes, depending on the mode of pressure application were investigated—that is, membrane separation processes driven by decompression, compression, and compression-decompression. It was found that both the energy and cost for CO2 separation were smallest in the case of the compression-decompression mode. The membrane separation process driven by compression-decompression was the most economical among the three types of processes.