Oxygen plant
Oxygen plant

The capacity of the Air separation plant is 425 TPD oxygen

Air Separation Unit shall be designed for maximum efficiency, and low power consumption. The unit shall be capable for un-interrupted operation with minimum manpower, re-start after shut down should be quick with unit returning to stable operation in shortest possible time. Cold for the start-up shall be obtained from the turbo-expander.Based on the product distribution parameters, product compression by liquid pump cycle or external compression or a combination of both may be considered with emphasis on low capital cost, low maintenance as well as high reliability and optimum energy consumption.

Process Description

Air rectification is realized by using different volatility of all the components of air, i.e. by using the different vapour pressures of all the components at the same temperature to partially evaporate and condense the liquid air repeatedly to separate the each component. When the gaseous mixture of nitrogen & oxygen at the condensation temperature passes through the liquid mixture of nitrogen & oxygen at a much lower temperature, the heat & mass transfer is conducted between the liquid phase and gaseous phase. Part of the gaseous mixture is condensed into liquid and release latent heat and part of the liquid is evaporated due to the absorption of the heat. Due to the different boiling points, the evaporation sequence of nitrogen, oxygen and argon is nitrogen> argon > oxygen while the condensation sequence is oxygen > argon > nitrogen. In this system, the process is conducted on the sieve trays. When the gas passes through the sieve trays one by one from the bottom to the top, the components with lower boiling points will be concentrated continuously. If there are enough sieve trays, at the top of the column the high-purity component with lower boiling point will be obtained. At the same time, when the liquid passes through the sieve trays from the top to the bottom, the component with higher boiling point will be concentrated continuously and when a certain number of sieve trays have been passed through, the high-purity component with higher boiling point will be gained at the bottom of the column.

Because of the different boiling points of oxygen, argon and nitrogen, argon is concentrated in the middle of the upper column, from where the argon fraction for producing crude argon is extracted.


Purity %

Flow rate, Nm3/h
1 x 425 ASU

Pressure *
bar (g)

Gaseous Oxygen > 99.6% 8150 32 (internal compression,refer product distribution table)
Gaseous Oxygen > 99.6% 3300 8 (internal compression,refer product distribution table)
Liquid Oxygen(gaseous equiv.) > 99.6% 1000 ~1.5 (**)
Gaseous Nitrogen > 99.99% 1200 32 ( External compression, refer product distribution table)
Liquid Nitrogen (gaseous equiv.) > 99.99% 750 ~1.5 (**)
Liquid Nitrogen (gaseous equiv.) Impurity levels in ppm O2 < 2 ppm
N2 < 2 ppm
400 ~ 1.5 (**)

Requirement of Oxygen,Nitrogen & Argon for Integrated steel Plant




Peak Flow Rate

Pressure Kg/cm2(g)


1 Oxygen SMS Shop(EAF) pipeline designed for 100% peak flow 10800 18 Cyclic
2 Oxygen General purpose(SMS + BF + other plant) 2000 18 Fluctuation in narrow range
3 Oxygen Blast Furnace (blast enrichment) 4500 8 Continuous
4 Nitrogen BOF,CCD,CDCP,
17000 18 Cyclic
5 Argon EAF/LF VD & CCP 375 16 Cyclic

Application of Gases in steel plant

Oxygen will be mainly required for oxygen enrichment in the Blast Furnaces, blowing in the EAF, cutting of billets & blooms in the Continuous Casting Plant and for general purpose use in various units of the steel plant.Nitrogen will be mainly required as carrier gas in de-sulphurisation unit, Coal Dust Injection system, stoves & Bell Less Top equipment for Blast Furnaces, purging in GCP & EAF/LF and Coke Dry quenching Plant and also for occasional purging of fuel gas pipelines & equipment.

Argon will be required for shrouding in the continuous casting plant and for stirring in LF&VD and EAF.

Major Equipment


SI.No Major Equipments Capacity
1 Main Air Compressor 64000Nm3/hr
2 Booster Air Compressor 38500Nm3/hr
3 Nitrogen Compressor 12000Nm3/hr
4 Direct Cooler 64000Nm3/hr
5 Refrigeration Unit 66 m3/hr
6 Booster Turbo Expander 17500Nm3/hr
7 Molecular Sieve Battery 64000Nm3/hr
8 Air Separation Unit 425TPD oxygen
9 Cryogenic Pumps 170L/min
10 Liquid Storage Tanks 1000m3
11 Steam Header Water Bath Vapourizer 12000Nm3/hr
12 Buffer Tanks@32bar 250m3
13 Water Pumps 200m3/hr
14 Recirculating Water Pump 650m3/hr
15 Water Cooling Tower 2200m3/hr

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