Displacement purge cycles

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. 

Displacement-Purge Cycle This cycle, which is somewhat similar to the previous one, differs from it in that a gas or vapor which adsorbs about as strongly as the adsorbate is used to remove the adsorbate (see Figure 1) Removal is thus facilitated both by adsorbate partial-pressure reduction in the fluid around the particles and by competitive adsorption of the displacement medium. As with the inert-purge cycle, the maximum delta loading is the equilibrium loading ... 

Figure 1. Displacement-purge cycle. A, adsorbate B, less-adsorbed component and D, displacement agent.

Displacement-purge cycle. The pressure and temperature are kept essentially constant as in purge-gas stripping, but a gas or liquid is used that is adsorbed more... 

Steam stripping is often used in regeneration of solvent recovery systems using activated carbon adsorbent. This can be considered as a combination of the temperature-swing cycle and the displacement-purge cycle. 

Figure 7.11 Principle ofa displacement purge cycle operation (source Keller 1983).

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