Functions of Various Adsorbents in Special Adsorbents for Hydrogen Production
2020.12.01
As a supplier of special adsorbents for hydrogen production, Suzhou Jiarui Gas hereby introduces the functions of various adsorbents:
The adsorbents used in industrial PSA-H₂ units are all solid particles with large specific surface area, mainly including:
Activated alumina
Activated carbon
Silica gel
Molecular sieve adsorbents
In addition, there are special adsorbent materials developed for selective adsorption of specific components, such as special CO adsorbents and carbon molecular sieves.
The adsorption performance of adsorbents for various gases is mainly evaluated by experimentally measured adsorption isotherms and dynamic breakthrough curves. Excellent adsorption performance and large adsorption capacity are basic conditions for effective adsorption separation.
Meanwhile, to achieve efficient separation in industrial applications, the separation factor of the adsorbent for each component should be as large as possible. The separation index refers to the ratio of
(residual amount of weakly adsorbed component in the dead space of the adsorption bed / total amount of weakly adsorbed component in the adsorption bed)
to
(residual amount of strongly adsorbed component in the dead space of the adsorption bed / total amount of strongly adsorbed component in the adsorption bed)
at adsorption equilibrium. The larger the separation factor, the easier the separation. Generally speaking, the separation factor of adsorbents in PSA gas separation units should not be less than 3.
In addition, the contradiction between adsorption and desorption must be considered in industrial pressure swing adsorption processes. Generally speaking, the easier the adsorption, the more difficult the desorption.
For strongly adsorbed substances such as C5 and C6, adsorbents with relatively weak adsorption capacity such as silica gel should be selected to ensure appropriate adsorption capacity and easier desorption.
For weakly adsorbed substances such as N₂, O₂ and CO, adsorbents with relatively strong adsorption capacity such as molecular sieves should be selected to achieve larger adsorption capacity and higher separation factor.
Furthermore, since the pressure inside the adsorption bed changes periodically during the adsorption process, the adsorbent is subject to frequent gas scouring, so it must also have sufficient strength and abrasion resistance.
Among the commonly used adsorbents in PSA gas separation units:
Activated alumina is a solid with strong affinity for water. It is usually prepared by thermal dehydration or thermal activation of gibbsite or bauxite, and is mainly used for gas drying.
Silica gel is a synthetic amorphous silicon dioxide, consisting of a rigid continuous network of colloidal silica spherical particles, generally prepared by mixing sodium silicate solution with inorganic acid. It has a strong affinity for water and also shows high adsorption capacity for hydrocarbons, CO₂ and other components.
Activated carbon is characterized by weak polarity or non-polarity due to oxide groups and inorganic impurities on its surface, coupled with its extremely large internal surface area. It is a broad-spectrum water-resistant adsorbent capable of adsorbing large quantities of various weakly polar and non-polar organic molecules.
Zeolite molecular sieve is a crystalline aluminometasilicate containing alkaline earth elements, a strongly polar adsorbent with highly uniform pore structure and excellent adsorption selectivity. It shows high adsorption capacity for CO, CH₄, N₂, Ar, O₂, etc.
Carbon molecular sieve is a special adsorbent made from carbon raw materials through a special carbon deposition process, specially used for nitrogen purification from air. Its pore size distribution is highly concentrated, only slightly larger than the diameter of oxygen molecules, making it highly efficient for oxygen-nitrogen separation.
For gas sources with complex compositions, multiple adsorbents are often used in practical applications, layered in sequence according to their adsorption performance to form a composite adsorption bed, so as to achieve the separation of required product components.
The above information is compiled and released by Suzhou Jiarui Gas, a supplier of special adsorbents for hydrogen production.
Suzhou Jiarui Gas System Co., Ltd. is a high-tech enterprise specializing in the research and development of gas separation and purification technologies.
The company is equipped with a R&D building and a gas separation equipment assembly workshop.
It provides customers with services including PSA hydrogen, nitrogen and oxygen production, as well as carbon dioxide purification and removal.
We look forward to win-win cooperation with you.