Hydrogen gas is produced from a variety of different processes and in its impure form, it is considered to be a clean and flexible energy source, and finds its usage in various industrial applications and processes. To maintain and obtain a low carbon economy, the usage of raw or fossil fuel-based hydrogen needs to be cleaned and purified before being used in a wide range of these industrial applications.
Thus, the PSA or Pressure Swing Adsorber method is one of the most widely used technologies for hydrogen purification efficiently, and zeolites are the most common adsorbent material that is used in the purification process of hydrogen in the PSA systems.
When you use Molecular Sieve for PSA hydrogen purification there are low operating costs and the purification process of hydrogen is highly efficient and produces high purity and recovery rates for hydrogen as the end-product.
Molecular Sieve are commonly a type of crystalline microporous material, that contains unique absorbency characteristics that make them an ideal choice for the purification process of PSA hydrogen. Zeolites have a high rate of adsorbing capacity, and also exhibit selective separation techniques that help adsorb any impurities and contaminants from the hydrogen mixture effectively from the PSA system, thus resulting in a highly purified form of hydrogen as an end product.
The pressure swing adsorber technique is a separation method for purifying several gases, especially hydrogen, by using the selectivity adsorption technique of the molecular sieve zeolite material used during the process. Since zeolites are the primary adsorbent material used in the PSA systems, they have a uniform porous structure that is great and highly suitable for adsorbing specific gas molecules from a gas mixture.
In PSA systems that use zeolites as their primary adsorbent material, the process of adsorption is a continuous cycle that combines adsorption with desorption to obtain high-quality hydrogen. The gas mixture or stream containing hydrogen is passed through the zeolite molecular sieve bed under high pressure conditions, which leads to the purification of the hydrogen gas, making it void of any contaminants, dust, vapor, moisture, and CO2.
After the adsorption stage, the pressure in the PSA system is increased to enhance the adsorption of impurity from hydrogen gas within the zeolite 5A adsorbent material, and in the desorption phase, the pressure is decreased to release the adsorbed impurity molecules from the zeolite/adsorbent material and then pure hydrogen fragmented and processed to be used in various industrial applications.
This continuous, repetitive, and recurring cycle of adsorption, pressurization, desorption, and regeneration is what gives the pressure swing adsorber hydrogen purification process its "swing" description in its name of the pressure swing adsorption process. And, at the end of the process, since Zeolite molecular sieve has high selectivity properties for impurity like moisture, it allows for the effective separation of the present impurities in the gas mixture, resulting in a highly purified form of hydrogen.
The type of zeolite used for the purification of PSA hydrogen depends on the purpose of the application. Generally, the following are the most commonly used types of zeolites for the hydrogen purification process.
Zeolite 3A adsorbents have a high binding affinity towards water molecules, which makes it highly suitable and useful for PSA applications where you need to remove water molecules or moisture content from hydrogen and its mixtures. The zeolite 3A has selective adsorption capabilities towards water molecules thus allowing the purification of hydrogen effectively to obtain high-purity hydrogen.
Zeolite 4A molecular sieve has a high absorbency capacity for larger molecules like CO2 and sulphur compounds, thus can be widely used for various applications that require the removal of CO2 or H2S from gas mixtures, that are commonly used in natural gas purification, and different biogas applications.
Zeolite molecular sieve 5A has high adsorption and desorption capabilities, along with high mechanical strength which is very helpful in the long-term stability of the industrial equipment and products.
The ability of Zeolite 13X molecular sieve to adsorb high amounts of moisture and carbon dioxide makes it one of the most versatile and widely used materials in the pressure swing adsorber systems and is used in a wide range of applications to obtain a high level of purity.
To efficiently perform PSA hydrogen purification, you need to choose the right zeolite for your application and it depends on numerous factors.