| Summary: | Reduction of CO2 from waste gases from various industries is now desired worldwide. As a technology for separating CO2 from mixed gases, Pressure Swing Adsorption (PSA) is one of the practical processes that are widely used at present owing to the simplicity of its gas separation mechanism. In order to reduce the cost of CO2 separation, a further reduction of the running cost of CO2-PSA operation is required. Among all the utilities used in CO2-PSA, electric power consumption has the greatest impact, especially in cases where the pressure swing range between gas adsorption and gas desorption is large. Electric power consumption increases significantly when the pressure loss inside the adsorber has reached a non-negligible level. Changing the adsorbent pellet size is a convenient method for reducing pressure loss, but its effect on CO2-PSA performance was unclear. Therefore, in this work, the effects of the size of the adsorbent pellets on both the gas adsorption behavior and the electric power consumption in CO2-PSA were evaluated experimentally. From the results of laboratory-scale CO2-PSA experiments and gas adsorption rate measurements, it was observed that the effect of the pellet size appeared only in the early stage of the gas adsorption step and was not dominant when the cycle time was sufficiently long. Subsequently, pilot-scale CO2-PSA experiments with the same CO2 throughput were also conducted, and as a result, the electric power consumption of a vacuum pump was lowered by 15% in case of using d = 3.0 mm larger adsorbent pellets compared to the results with d = 1.5 mm smaller adsorbent pellets.
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