Air Separation Unit / Cold Box consists of Distillation Column with Heat Exchangers for heat transfer between the incoming air and the out going cold Nitrogen and Oxygen. It is equipped with Expansion valves for controlling the operation of the plant. Control panel for the cold box is provided with the plant. Defrost heater for thawing plant is also provided on the cold box. It is also equipped with liquid oxygen pump which is a single cylinder equipment and delivers Bone-dry Oxygen up to pressure of 165 Kg/Cm2. Cold box is insulated with perlite for minimizing cold losses and reducing power consumption.

Oxygen was first extracted from the atmosphere by a chemical process. This was superseded over 80 years ago by the cryogenic (low temperature) process involving the liquefaction and distillation of air.

The cryogenic air separation process is still by far the most widely used. However, non cryogenic techniques first developed during the 1970s -- pressure swing adsorption (PSA), and membrane diffusion -- are becoming increasingly significant for smaller or less demanding on-site applications.

There are several factors influencing the choice of separation technology. The best supply option for each customer depends upon the following:

• Volume required - Cryogenic separation is economical for large tonnage users.
• Low temperature applications - Only cryogenic systems provide the liquefied gases essential for low temperature applications such as food freezing
• Purity required - Non cryogenic systems are generally unable to achieve high purities economically, but less pure products may be adequate for some applications.
• Continuity of supply - Fluctuating demand is best satisfied from liquid storage tanks filled by road tanker or an on-site plant. If a gas supply is an essential process requirement, perhaps for safety reasons, a non cryogenic system would usually need to be backed up with liquid storage for emergency use.
• Customer location - Some places are too remote for economical delivery of liquid supplies by road tanker or may be out of reach altogether, such as on board a ship.

Technical Details of Air Separation Plants as follows :