The Key to the entire Air separation Process lies within the Air Separation Unit (A.S.U). Here, the mixture of Oxygen and Nitrogen is separated by virtue of the difference in their liquefication temperatures.

The design and efficiency of the A.S.U determines the quality of the final product i.e. Oxygen and Nitrogen in terms of quantity and quality. The Boschi design A.S.U features highly efficient fin type aluminium heat exchangers and column, wherein the entire upper column is a packed column thus reducing the operational pressure and increasing the Oxygen, Nitrogen and Argon recovery.

Argon is recovered by a revolutionary technique employing full rectification without using the Hydrogen and De-Oxo unit thus saving further on power costs, operational costs and investment. This makes the Boschi design machines highly versatile and economical thanks to all the research and development done over the years.


TURBO EXPANDER

The Turbo expander is a gas or oil bearing expansion refrigeration turbine that is much more efficient than any other expansion device.
It works on the technique of induced cooling via expansion due to which the operational pressure of the plant is further reduced and the performance of the distillation column is stabilized for constant production and high purity.

1. Compression

Air is compressed at a very pressure of 5-7 bar (kg/cm2). Air can be compressed at such low pressure by trouble free rotary compressor (Screw / Centrifugal Type advanced technology is employed in lieu of old bulky piston compressor)

2. Pre Cooling System

The second stage of the process uses a low pressure refrigerant for precooling the processed air to temperature around 12 deg C before it enters the purifier.

3. Purification of Air BY Purifier

The air enters a purifier consisting of twin Molecular Sieve driers, working alternatively. The Molecular Sieves remove the Carbon dioxide & moisture from the processed air before the air enters Air Separation Unit.

4. Cooling of Air By Expander (turbo)

The air has to be cooled to sub zero temperatures for liquification & the cryogenic refrigeration & the cooling is provided by highly efficient turbo expander, which cools the air to temperature almost below -165 to-170 deg C

5. Separation

Oil free, moisture free and Carbon Dioxide free air enters into low pressure aluminium brazed fin type HEAT EXCHANGER where the air is cooled below sub zero temperatures by air expansion process in the turbo expander.
Air gets liquefied when it enters the air separation column & gets separated into oxygen & nitrogen by the process of rectification. Argon can be recovered successfully in plants above 1000m3/hr as the percentage in air is below 1%.

6. Withdrawal

The final product in the form of Gas Oxygen/Nitrogen goes to the storage tank