Numerical analysis on the power consumption of the PSA process for recovering CO2 from flue gas

To recover 99% CO2 from flue gas containing 10-15% CO2, a two-stage pressure swing adsorption (PSA) process is usually employed. At the first stage of the two-stage PSA, CO2 is concentrated to 40-60% and then concentrated to 99% at the second stage. Because two stages are coupled with each other, the overall optimization of the two-stage PSA process is quite a complicated task. In this paper, we only considered the first stage of the two-stage PSA process to simplify the analysis. Effects of the process configuration and operating variables such as the P/F ratio and desorption pressure on the specific power consumption were investigated. The specific power consumption at the blower was reduced with the increase of the P/F ratio. On the contrary, that at the vacuum pump was increased with the increase of the P/F ratio. Because of these two effects, there was an optimum PIF ratio, which minimized the specific power consumption. While the compression ratio is reduced with the increase of the desorption pressure, the CO2 purity is decreased and the amount of the power used to compress nitrogen is increased. As a result, the specific power consumption was insensitive to the desorption pressure within the range studied here. Employing the pressure equalization step, the CO2 purity could be increased without much increase of the specific power consumption. With the rinse step, which is often used to increase the purity of the strongly adsorbed component, the CO2 purity could be increased. However, because more gases should be pumped to produce a given amount of CO2, the specific power consumption was significantly increased at a given recovery.