Adsorption - Processes and applications

Adsorption processes are flexible. They can be used to fractionate a gaseous or liquid mixture containing a high proportion of adsorbable constituents (typically >10%), or to purify a mixture containing only a few percent of adsorbable constituents.

Separation by adsorption is, by nature, discontinuous, with an adsorption phase followed by a regeneration phase designed to restore the adsorbent's adsorption capacity.

On rare occasions, adsorbents are regenerated off-site or simply replaced before saturation, when several of the following factors come together: very cheap adsorbents, adsorbents that are very difficult to regenerate, or the presence of impurities requiring destruction (dioxins, for example).

In most adsorption processes, adsorbents are dynamically regenerated in situ by modulating temperature, total pressure or concentrations. These processes often operate cyclically, with the use of several fixed adsorbers (possibly accompanied by one or more storage capacities) or a rotating adsorber to ensure continuous production. Some processes, however, operate continuously, with countercurrent contact between the fluid and the adsorbents, sometimes using moving or fluidized beds, but more often simulated moving bed systems.

Adsorption can also be used for applications other than separation, such as thermal machines, gas trapping or storage, which are based solely on the adsorbents' ability to retain gases and not on selective adsorption.

In this dossier, we will look at the more practical aspects of the main adsorption processes. For more theoretical aspects of adsorption, the reader is referred to the dossier .