The role of various adsorbents of special adsorbents for hydrogen production
The most important physical characteristics of adsorbents include pore volume, pore size distribution, surface area and surface properties. Different adsorbents have different adsorption capacity and adsorption capacity for each component in the mixed gas due to different pore size distribution, different specific surface area and different surface properties. Here is a special adsorbent for hydrogen production-Suzhou Jiarui gas to introduce the role of various adsorbents :
The adsorbents used in the industrial PSA-H2 device are solid particles with large specific surface area, mainly including :
Activated alumina
Activated carbon
Silica gel class
Molecular sieve adsorbent
In addition, there are special adsorption materials developed for selective adsorption of certain components, such as CO special adsorbents and carbon molecular sieves.
The adsorption performance of the adsorbent for various gases is mainly evaluated by the experimentally determined adsorption isotherms and dynamic breakthrough curves. Excellent adsorption performance and large adsorption capacity are the basic conditions for adsorption separation.
At the same time, in order to achieve effective separation in industry, it must be considered that the separation coefficient of the adsorbent to each group should be as large as possible. The so-called separation index refers to : when the adsorption equilibrium is reached, the ratio of ( the residual amount of the weak adsorption component in the dead space of the adsorption bed / the total amount of the weak adsorption component in the adsorption bed ) to ( the residual amount of the strong adsorption component in the dead space of the adsorption bed / the total amount of the strong adsorption component in the adsorption bed ). The greater the separation coefficient, the easier the separation. In general, the separation coefficient of the adsorbent in the pressure swing adsorption gas separation device should not be less than 3.
In addition, the contradiction between adsorption and desorption should also be considered in the process of industrial pressure swing adsorption. Generally speaking, the easier the adsorption, the more difficult the desorption. For strong adsorbates such as C5 and C6, relatively weak adsorbents such as silica gel should be selected to make the adsorption capacity appropriate and the desorption easier. For weak adsorbates such as N2, O2 and CO, adsorbents with relatively strong adsorption capacity should be selected, such as molecular sieves. In order to make the adsorption capacity larger and the separation coefficient higher.
In addition, in the adsorption process, since the pressure in the adsorption bed changes periodically, the adsorbent should undergo frequent erosion of the airflow, so the adsorbent should also have sufficient strength and wear resistance.
Among several adsorbents commonly used in pressure swing adsorption gas separation devices, activated alumina is a solid with strong affinity to water. It is generally prepared by thermal dehydration or thermal activation of aluminum trihydrate or gibbsite, mainly for gas drying.
Silica gel adsorbent is a kind of synthetic amorphous silica. It is a rigid continuous network of colloidal silica spherical particles. It is generally prepared by mixing sodium silicate solution and inorganic acid. Silica gel not only has a strong affinity for water, but also has a strong adsorption capacity for components such as hydrocarbon CO2.
The characteristics of activated carbon adsorbents are as follows : the oxide groups and inorganic impurities on the surface make the surface properties weak polarity or non-polarity, and the special large internal surface area of activated carbon makes activated carbon a broad-spectrum water-resistant adsorbent that can adsorb a large number of weak polar and non-polar organic molecules.
Zeolite molecular sieve adsorbent is a kind of crystalline aluminosilicate containing alkaline earth elements, which belongs to strong polar adsorbent. It has a very consistent pore structure and strong adsorption selectivity for CO, CH4, N2, Ar, O2 and so on.
Carbon molecular sieve is a kind of special adsorbent specially used to purify nitrogen in air, which is made of carbon as raw material and processed by special carbon deposition process. Its pore size distribution is very concentrated, only slightly larger than the diameter of oxygen molecules. Therefore, it is very beneficial to the separation of nitrogen and oxygen in the air.
For complex gas sources, a variety of adsorbents are often needed in practical applications. In order to achieve the purpose of separating the required product components, a composite adsorption bed is formed by layered loading according to the adsorption performance.
The above is organized and released by Suzhou Jiarui Gas, a special adsorbent for hydrogen production. Suzhou Jiarui Gas System Co., Ltd.is a science and technology company specializing in the research and development of gas separation and purification technology. The company has a science and technology development building, gas separation device assembly plant. Provide users with pressure swing adsorption hydrogen production, nitrogen production, oxygen production, purification or removal of carbon dioxide and other services, looking forward to win-win cooperation with you.
