The process employed in an air separation plant is called cryogenic distillation. By cooling the atmospheric air to extremely low temperatures, the component gases can be separated and harvested. Liquid forms of nitrogen or oxygen may also be harvested at some plants.
The cryogenic distillation process is a four step procedure. In the first step, atmospheric air is cleaned and compressed to a pressure range of 5 to 10 bars (4-9 atmospheres). The cleaning process removes dust and contaminants that could interfere with the cooling process. The compression process heats the air to remove traces of moisture before passing the compressed air to a heat exchanger for cooling.
When the compressed air has been cooled, the next step is purification. This process involves passing the air through a molecular sieve, which filters the air by a process called adsorption. In this process, gases or molecules are attracted to an adsorbent surface and form a layer on top of the adsorbent material. The molecular sieves are designed to remove carbon dioxide, water, and hydrocarbon gases.
After the air is purified, it can safely be passed to the cooling and distillation chamber. The cooling chamber consists of a heat exchanger and cryogenic streams. When the air is passed through this chamber, it reaches sufficiently low temperatures to enable