Adsorber

An adsorber is a vessel or unit that removes one or more contaminants from a gas or liquid by adsorption, the adhesion of molecules to the surface of a solid. Feed streams pass through a bed packed with an adsorbent material, causing target species to concentrate on the surface while the rest of the fluid passes through. Adsorption is typically reversible and depends on temperature, pressure, and the specific interactions between the adsorbent and the contaminant.

Common adsorbents include activated carbon, zeolites, silica gel, alumina, molecular sieves, and various polymer resins. The choice of adsorbent depends on the contaminant, the phase of the feed, operating conditions, cost, and the desired regeneration method. Adsorption can be physical (physisorption), driven by van der Waals forces, or chemical (chemisorption), involving stronger chemical bonds.

In operation, adsorbers are often operated in fixed beds. As adsorption proceeds, the outlet concentration remains low until a breakthrough point, after which contaminants begin to appear at the effluent. To restore capacity, the bed is regenerated by heating (temperature swing), reducing pressure (pressure swing), or using a combination of methods. Some processes employ multiple adsorber beds to provide continuous operation, shifting beds from adsorption to regeneration while others handle the feed.

Applications span air purification, gas purification and separation, solvent recovery, natural gas sweetening, CO2 capture, hydrogen purification, and wastewater treatment. Performance is characterized by adsorption capacity, selectivity for specific species, breakthrough time, pressure drop, and adsorbent life. Practical design considerations include bed size, flow rates, regeneration energy, and potential issues such as channeling or fines generation.