In the present market scenario, Cryogenic air separation has emerged as the most cost effective technology for larger plants and for producing very high purity oxygen and nitrogen. The USP of these plants is that it is the only technology that can produce liquid products.
Cryogenic air separation is a traditional method of producing nitrogen and oxygen gases. The technology requires a large plant to cool air to several hundred degrees below zero in order to separate the component gases.
The design choice of 'Gas Process Systems' depends upon the number of products required, like, whether one needs nitrogen or oxygen, both oxygen and nitrogen, or nitrogen, oxygen and argon. The other factors that influences the choice are the gaseous product delivery pressures, required product purities and should the products be produced in liquid form.
There exists a large number of air separation systems that can be employed to manufacture Industrial Gas. Cryogenic air separation process is one of the most acceptable and popular process that is commonly used in large or medium scale plants to produce nitrogen, oxygen, and argon as gases and/ or liquid products.
Almost all cryogenic air separations begin with a similar series of steps. However, the energy required to operate them depends on the product mix and required product purities. Some designs minimize capital cost, some minimize energy usage, some maximize product recovery, and some allow greater operating flexibility. The various steps involved in every kind of Cryogenic Production Process are :
- Filtering and Compressing air
This is done by the multistage highly efficient air compressor and the Process Skid present in each plant. Condensed water is removed from the air as it is compressed and then cooled.
The compressed air is then cooled to close-to-ambient temperature by passing through water-cooled or air-cooled heat exchangers.
- Removing contaminants
The next step is removing the remaining water vapor and carbon dioxide.
- Cooling to cryogenic temperature
Further heat transfer, in brazed aluminum heat exchangers, cools the air to cryogenic temperature (which is app -300 degrees Fahrenheit or 185 degrees Celsius).
Distillation columns separate the air into desired products. This is basically done by a special kind of Air Separation Unit which commonly consists of upper & lower column and special exchangers.
- Warming gaseous products and waste
The cold gaseous products and waste streams that emerge from the air separation columns are routed back through the front end heat exchangers.
After this step we are left with the final product from a liquid Oxygen/Nitrogen that goes to the storage tank. Nitrogen and oxygen are then distributed to customers in liquid form using tanker trucks.