Adsorption pressure swing cycle

Steps. A pressure-swing cycle has at least three steps adsorption, blowdown, and repressurization. Although not always necessary, a purge step is normally used. In finely tuned processes, cocurrent depressurization and pressure-equalization steps are frequendy added. 

Regenerative adsorption units can be operated by a thermal-swing cycle, pressure-swing cycle, displacement-purge cycle, or inert-purge cycle. Combinations of these are frequently employed. 

A pressure-swing adsorption (PSA) process cycle is one in which desorption takes place at a pressure much lower than adsorption. Reduction of pressure is used to shift the adsorption equilibrium and affect regeneration of the adsorbent. Figure 16-39 depicts a simplified pressure-swing cycle. Feed fluid containing an adsorbate at a molar concentration of y i = pi /Pi is passed through an adsorbent at conditions... 

Pressure-Swing Cycle. In a gas-adsorption cycle, the partial pressure of an adsorbate can be reduced by reducing the total pressure of the gas This change can be used to effect a desorption. The lower the total pressure of the desorbing step, the greater the maximum delta loading will be ... 

As with temperature, the most convenient pressure for adsorption is that of the feed. When a mage of pressure is available, the highest pressure should be chosen so that the adsorptive londing is maximized. The comments above on condensation are applicable to pressure selection also. For pressure-swing cycles, the adsorption premure must be arrived at from economic irode-offB. since larger swinga in pressure yield better ndsorbent utilization hat require more compression power. 

Repressurization of the adsorber to feed pressure completes the steps of a pressure-swing cycle. Pressurization can be done with product and/or i. When piquet is used, it should be applied countercurrent to adsorption to continue put png of the effluent end. Pressurization with feed should be carried out cocurrent to adsorption to prevent contamination of the effluent end. 

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