1 Air compression
* Compression
of ambient air by a multi-stage turbo compressor with
intercoolers at a supply pressure of approx. 6 bar.
* Removal
of dust particles by a mechanical air filter at the inlet of the compressor. 2
Air cooling and
purification
* Cooling
of process air with water in a direct contact cooler and removal of
water-soluble air impurities.
* Chilling
of cooling water in an evaporation cooler against dry nitrogen waste gas from
the rectification process.
* Removal
of CO₂, water and hydrocarbons from the process air in
periodically loaded/regenerated molecular sieve adsorbers.
3 Cold production and
internal product compression
* Cooling
of process air in heat exchangers down to nearly liquefaction temperature by
means of counter current with gas streams from the rectification process.
* Further
compression of a side stream of process air by an air booster compressor.
Expansion and cold production of the boosted air stream in an expansion
turbine.
* Expansion
and liquefaction of a side stream of the boosted air in a liquid separator.
* Evaporation
and warming to ambient temperature of the pumped oxygen and nitrogen product in
high-pressure heat exchangers.
Cryogenic rectification of air
* Pre-separation
of the cooled and liquefied air within the pressure column into oxygen-enriched
liquid in the column sump and pure nitrogen gas at the column top.
* Liquefaction
of the pure nitrogen gas in the condenser/reboiler against boiling oxygen in
the sump of the low-pressure column. Liquefied nitrogen provides the reflux for
the pressure column and (after sub-cooling) for the low-pressure column.
* Different
types of condenser are described in detail on page 16.
* Further
separation of the oxygen-enriched liquid within the low pressure column into
pure oxygen in the sump and nitrogen waste gas at the top.
5 Cryogenic
rectification of argon
* Argon-enriched
gas from the low-pressure column is transformed into oxygen-free crude argon by
means of separation within the crude argon column.
* Pumping
back liquid oxygen from the crude argon column sump into the low-pressure
column. Removal of the remaining nitrogen in the pure argon column.
Source: Linde
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