Air Separation plant in Steel production industry

Large capacity steel production industries consume three industrial gases, namely nitrogen, oxygen and argon. These are produced in air separation plant present in the utilities section. Each of these gases are used for performing typical operation, like for blowing and heating operation in LD converter oxygen is used. In case of blast furnace top cleaning and coke cooling nitrogen is used and finally argon is used for agitation of molten liquid form steel and for steel homogenization.

Continuous column operation in air separation plant:

Column of air separation plant

Oxygen consumption:
On ideal base calculation for a 3 MT steel industry oxygen consumption on daily basis is done in the following operations;

CONSUMERS 3.0 MT STAGE REQUIREMENTS
 Yearly106 N cum Daily103Ncum
LD Converters blowing & LD Vessels heating 189.20 540.60
General purpose uses of SMS 9.46 27.00
Rolling Mills 2.00 4.94
Blast Furnace 1.01 3.60
Repair shops and others 1.59 5.14
TOTAL 203.6 581.28

Nitrogen consumption:
For purging of pipelines and LD converter gas cleaning system and pressurization of top charging systems of bell-less blast furnace, dry quenching of coke, and for are done by using nitrogen.

CONSUMERS 3.0 MT STAGE REQUIREMENTS
 Yearly 106 N cum Daily 103 N cum
Blast furnace 321.46 919.20
LD Gas cleaning plant & Continuous casting dept 22.68 64.80
Pipe line purging & others 51.485 420.012
TOTAL 395.625 1404.012

Argon consumption:
Argon is used for welding in the repair shops and stirring of liquid steel in the teeming ladles.

CONSUMERS 3.0 MT STAGE REQUIREMENTS
 Yearly 106 N cum Daily 103 N cum
CCD of SMS 0.252 0.72
Miscellaneous like repair shops, in site repairs etc., 0.02 0.05
TOTAL 0.272 0.77

A typical standard air separation plant performance at below condition would be
Pressure : 760 mm Hg
Ambient temperature : 45.3° C max, 10.5° C min
Design temperature : 36° C
Relative humidity (%) : 100 (max), 4 (min)
Design humidity : 59 %

Production rate for the air flow rates (Nm3/hr):

Flows: Mixed Run Gaseous Run
100% 110% 100% 110%
Treated air flow (Nm3/hr) 95000 105000 88400 97300
Oxygen Purity Flow (Nm3/hr)- gas %- liquid%

99.5

12750985 140251072 14800110 16280110
Pressure (kg/cm2abs)

1.533

Temperature (° C)

25

Nitrogen Purity %Flow (Nm3/hr)- gas %- liquid%

99.9

25500100 28050110 29600- 32560-
Pressure (kg/cm2abs)

1.07

Temperature (° C)

25

Liquid Argon Purity %Flow (Nm3/hr)

99.99

100

110

100

110

Air compressor flowsheet in control panel of air separation plant