Novel single-bed and twin-bed pressure swing adsorption systems

Abstract

Pressure swing adsorption (PSA) is one of the promising technologies for separation of gas mixtures. Multi-bed (poly-bed) PSA units are used to get both raffinate and extract products of high purities. Any multi-bed PSA cycle can be carried out in a single bed (or in multiple beds connected in parallel to a common header) with a requisite number of holding tanks and a single set of compressors and vacuum pumps. The performances of single-bed systems have been studied operating on the molecular gate, duplex, modified and moving-bed emulation of 3-bed PSA cycles, which are known to yield both products of high purities and to have potential for process intensification. The sizes of holding tanks were found to be unwieldy for commercial applications. Twin-bed systems have been proposed in which an additional complementary bed replaced the holding tanks. The twin-bed system facilitates also the scale-up of molecular-gate PSA, which was considered difficult to scale up to commercial units. A process-intensification index has been used to compare the performance of different configurations. The studies show that the performances of the 3-bed and modified duplex PSA configurations are far superior to the other two for CO2 capture from flue gas.