The Role of PSA in a Refinery

The removal of other hydrocarbon gases from the hydrogen using pressure swing adsorption (PSA)  is a common practice in the refinery industry.

Purified hydrogen is produced by the PSA unit by using a molecular sieve to remove hydrocarbons other than hydrogen. After the hydrogen has been separated, pressure is used to release the hydrocarbons that have been adsorbed.

The application of pressure swing adsorption technology in the purification of hydrogen gas (H2) has received a lot of attention in recent years; however, this method can also be utilized for the separation of other gases in petroleum refineries. 

Many industrial gases can be separated and purified using the well-proven process, which uses pressure swing adsorption (PSA). We’ll take a look at the fundamental principles of PSA technology in terms of the refinery, as well as some of the design considerations that go into creating a PSA system. 

Benefits of Hydrogen Pressure Swing Adsorption

PSA technology can also be used in a variety of other petroleum refinery applications, including H2 purification, and the potential economic benefits of this approach are also discussed below. Choosing the best gas-separation technology necessitates a thorough understanding of the problem at hand.

Here are some top advantages:

• High recovery rates and the ability to produce hydrogen H2 with ultra-high purity (99,9 to 99,999 percent). Construction is simplified, project risks are minimized, and project costs are ultimately reduced when using standard process module designs.

• System performance that is safe, reliable, and guaranteed.

• PSA systems that successfully perform the intended separation by making use of adsorbents that have been proven to be commercially viable and have the ability to remove multiple contaminants from crude H2 feed streams. This includes hydrogen sulfide, hydrocarbons, carbon oxides, and water. 

The Fundamental Process

The PSA process is based on the fact that gases tend to be “adsorbed” onto solid surfaces when subjected to high pressures. The more gas that is absorbed, the higher the pressure. Desorbed gas is released when the pressure drops. It is possible to use PSA to separate different gas concentrations in a mixture so even though different gases are more or less strongly adsorbed onto a given solid surface.

It is possible to use an adsorbent that tends to attract nitrogen more strongly than oxygen to pass a gas mixture such as air through a Jalon zeolte adsorbent bed under pressure, resulting in a more oxygen-rich gas exiting the vessel. It is possible to regenerate the bed when its capacity to adsorb nitrogen exceeds its ability to do so by lowering the pressure. The oxygen-enriched air is now ready for another cycle.

Near-continuous production is possible by using two adsorbent vessels. You can use the gas that is being sucked out of the depressurized container to partially pressurize another one. This is a common industrial practice because it saves a lot of energy.

Applications of PSA

The primary oxygen source for any hospital, bulk cryogenic and otherwise compressed-cylinder storage can be replaced by PSA as a source of medical oxygen. But PSA has numerous other applications as well as shown in some of the top chemical trade show displays in Las Vegas. 

One of the main ways PSA is used is to get rid of carbon dioxide (CO2). This is the last step in the large-scale commercial production of hydrogen (H2), which is used in oil refineries and to make ammonia (NH3). 

PSA technology is frequently implemented in refineries for the purpose of removing hydrogen sulfide (H2S) from hydrogen feed and recycling streams produced by hydrotreating and hydrocracking units. If you are trying to learn how to find manufacturers in China who deal in PSA technology, make sure you know exactly where it is applied. PSA can also be used to increase the methane (CH4) to carbon dioxide (CO2) ratio in biogas. 

Biogas can be made to have a quality that is comparable to natural gas using PSA. For example, a process for upgrading landfill gas into utility-grade high purity methane gas can be included in this.

In addition, PSA is used in:

• Systems for creating low-oxygen air for use in firefighting

• Propylene dehydrogenation plants operated on purpose. This is because the selective medium they use allows methane and ethane to be adsorbed more readily than hydrogen.

• High-purity nitrogen gas can be generated from compressed air using industrial nitrogen generators based on the PSA process. They are better suited to providing intermediate levels of purity and flow, though. Standard conditions for temperature, pressure, and humidity are used to calculate the equivalent volume in liters per hour for Nm3/h capacity measurements. At 99.9 percent purity, nitrogen flows from 100 Nm3/h, up to 9000 Nm3/h; Between 88 and 93 percent purity, up to 1500 Nm3/h for oxygen.

• To reduce greenhouse gas emissions from coal-fired power plants, large quantities of CO2 are being captured prior to geosequestration in the context of carbon capture and storage (CCS).

• For spacesuit primary life support systems, PSA has been discussed as an alternative to non-renewable sorbent technology in order to save weight and extend the suit’s operating time.

• Medical oxygen concentrators used by COVID-19 and emphysema patients and others who need oxygen-enriched air for breathing use this method.

Conclusion

There are a few downsides to using PSA, which are generally safe, reliable, and affordable. PSA systems are used in the oil refining industry to turn synthesis gas, which is made by steam methane reforming (SMR), partial oxidation (POX), or gasification, into hydrogen. 

PSA technology can be used for a variety of gas separation tasks despite its reputation as an H2 purification tool. H2 and CO2 can be recovered from refinery off-gases using PSA systems. They can also be used to produce oxygen and nitric oxide.