Pressure swing adsorption abbreviated as PSA is the method that is applied to separate a gaseous mixture under pressure based on the gas’s molecular characteristics and its affinity to the adsorbent. In simple terms, it is a method applied for gas separation. An adsorbent is a material that adsorbs the target gas at the right pressure. Once the adsorbent absorbs the gas, a method called de-adsorption is employed to get the adsorbed material from the adsorbent. Many different adsorbents are available in the market like zeolite, molecular sieves, activated carbon, alumina, resin and silica gel just to name a few. Based on your need, you get to choose the appropriate one.
How does PSA work?
The concept behind pressure swing adsorption is that at high pressure gases get adsorbed (attracted to) by solid surfaces. Every gas gets adsorbed at a different pressure and this is what is used in the process of adsorption. At different pressures different gases are absorbed by the adsorbent. The first step usually is carbon capture where different carbon products are removed. One of the most popular applications of this method is biogas extraction. Biogas, also known as natural gas usually is contaminated with unwanted materials and pressure swing adsorption is extensively used to extract biogas from the contaminated mixture. There are different variations done to the pressure swing adsorption method. Two of the variations are rapid PSA and double stage PSA.
Getting a gas in its pure form is almost impossible. There is always a contaminant or other gas mixed with it and hence there is a high demand for adsorption. Many industries like healthcare, petro chemical plants, refineries and nuclear industries require adsorption in order to extract a particular gas from a mixture. Usually, the gas passes through many different stages and at each stage we remove one particular gas. For example, if we consider zeolite as our adsorbent and air as our gaseous mixture, then when air is passed over zeolite at a particular pressure, then the zeolite adsorbs the nitrogen and the mixture that comes out of the stage is richer in oxygen.
Advancements in this field
Much advancement has been made in this field. Vacuum pressure swing adsorption is now being extensively used as it highly effective. Similarly, many new adsorbents are being used that increase the chances of extracting a pure gas. Currently, pressure swing adsorption techniques are being researched to reduce the emission of green house gases into the atmosphere especially form coal mines and power plants. Researchers are making great strides in this field and are coming up with new and innovative techniques that are proving to be boon to the industry.
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