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assumes a high importance when it comes to provide a direct and representative interpretation of the adsorption process. An evaluation of the amount adsorbed, the influence of other species and the interval required by each step (adsorption and desorption) can be obtain through the analysis of the breakthrough curve [13]. Due to the importance played by the adsorbent material in the adsorption process, the knowledge of the thermodynamics and the kinetics of a given adsorbate/adsorbent system is therefore necessary and can be acceded through the equilibrium adsorption isotherms and breakthrough experiments, respectively [32]. 2.9 Pressure Swing Adsorption for Hydrogen Purification Numerous PSA processes for the purification of hydrogen are found in literature with different configurations. These configurations may vary in the number of beds put to use, the number of steps, number of equalization steps, the adsorbents employed as well as the number of layers of adsorbent and the disposition of it, along with others. Also, the equations used in the models and the equations employed for the calculation of some parameters may vary. In 2003, Baksh et al. compared recoveries and purities obtained in processes with 2 beds – 12 steps, with and without product pressurization. Beds had three adsorbent layers: alumina, activated carbon and zeolite. Results demonstrate that product pressurization increases purity from 99.9 to 99.991% but decreases recovery from 80 to 77.81%. It was also suggested a 4 bed – 12 steps process with a purity of 99.99999% and recovery of 77.5% [33]. Later, Gittleman et al. (2005) examined the performance of the separation in a system with 9 beds, 3 simultaneously in adsorption steps and 2 equalizations for the same inlet stream, but with different feed pressures. Results showed that increasing the inlet pressure increases also the recovery. This process was performed at a temperature of 60°C [34]. In 2006, Sircar and T.C. Golden studied the two most used PSA processes for hydrogen purification. The process patented by Union Carbide Corporation of U.S.A. named as Polybed consists in a cycle with 11 steps. This process allows recoveries of 86.0% and purities of 99.999 %. The other process, named as Lofini process and patented by Toyo Engineering Corporation of Japan, consisted in 9 steps and 4 beds. With this process recoveries of 86.3 % and purities of 99.96 % are achievable. Multilayer beds for the two processes were used with a first layer of activated carbon and the other layer with zeolite 5A [15]. A comparison between a complete and reduced model was studied by Ana M. Ribeiro et al. 2008. While the complete model comprises three equations for the mass balance (gas phase balance, solid-phase macropore balance and the solid-phase micropore balance), one momentum balance equation and three energy balance equations (gas-phase balance, solid- Pressure Swing Adsorption for Hydrogen Purification Contextualization and state of art 8PDF Image | PRESSURE SWING ADSORPTION FOR THE PURIFICATION OF HYDROGEN
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