04-12-2012, 06:08 PM
AIR SEPARATION UNIT
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Requirement of Nitrogen in a Hydrocarbon / Petrochemical Complex------Why
• Dry AIR is relatively uniform in composition, with primary constituents as shown below. Ambient air may have up to about 5% (by volume) water content and may contain a number of other gases (usually in trace amounts) that are removed at one or more points in the air separation and product purification system.
Chemical properties
At room temperature, nitrogen is a very inactive gas. It does not combine with oxygen, hydrogen, or most other elements. Nitrogen will combine with oxygen, however, in the presence of lightning or a spark. The electrical energy from either of those sources causes nitrogen and oxygen to form nitric oxide.
Nitrogen gas is used where an inert atmosphere is needed. An inert atmosphere is one that does not contain active elements. Ordinary air is not an inert atmosphere. It contains oxygen. Oxygen tends to react with other elements.
Introduction to Nitrogen Plant
In this chapter we shall discuss on the various aspects of conceptualization of a nitrogen plant.
The capacity of the nitrogen plant to be installed is decided based on the requirement of Nitrogen in the Units, Offsite , Packages plus keeping additional margins for future expansions.
PRINCIPLE:
PSA Based Nitrogen Plant follows the principle of Pressure swing adsorption (PSA), a technology used to separate some gas species from a mixture of gases under pressure according to the species molecular characteristics and affinity for an adsorbent material. Special adsorptive materials (e.g., zeolites) are used as a molecular sieve, preferentially adsorbing the target gas species at high pressure. The process then swings to low pressure to desorbs the adsorbent material.
Membrane Based Nitrogen plant follows the principle of differential velocity with which various gas mixture components permeates membrane substance. The driving force in the gas separation process is the difference in partial pressures on different membrane sides
Cryogenic plants operation is based on the air liquefaction and its subsequent separation with the recovery of nitrogen, oxygen, and argon. This method of gas production is called deep air freezing.