Large-scale Air Separation Unit for Steel Mill
Introduction
The large-scale air separation equipment supporting steel mills is the "second blast furnace" of the steel industry, providing essential oxygen, nitrogen, and argon gases. The core features of this type of equipment are ultra large scale, ultra-high reliability, and customized design around the pace of steel production.
Operating principle: customized cycle for steel "breathing"
The principle can be summarized as "deep freezing, distillation separation, flexible output", and the entire process is designed closely around the characteristics of large gas consumption, multiple pressures, and periodic peaks in steel production.
1. Air compression and purification:
A large amount of ambient air is compressed to about 0.5 MPa by a high-power centrifugal air compressor, and then purified by a molecular sieve purification system to remove water, carbon dioxide, and hydrocarbons, providing clean raw materials for low-temperature separation.
2. Deep freezing and heat exchange:
The purified air is cooled to a temperature close to the liquefaction temperature (about -172 ℃) by the product cold gas flowing back in the main heat exchanger. The expansion machine provides the vast majority of the cooling capacity required by the system.
3. Core distillation separation: Liquid air enters the two-stage distillation tower system.
Lower tower: Perform preliminary separation to produce oxygen rich liquid air and pure liquid nitrogen.
Upper tower: Perform final precision separation to obtain high-purity liquid oxygen at the bottom and high-purity nitrogen at the top of the upper tower. The argon fraction is extracted from the middle of the upper tower and sent to the complete distillation argon production system for further purification.
4. Product processing and flexible blending (customized core for steel mills):
Oxygen: According to the requirements of steel technology, oxygen of different pressure levels (such as low-pressure for blast furnace and high-pressure for converter) is produced through internal compression process (liquid oxygen pump+high-pressure heat exchange) or external compression process (oxygen compressor), and transported to large spherical tanks for storage to balance the instantaneous huge consumption of oxygen blowing in the converter.
Nitrogen/argon: extracted from different parts of the distillation tower, pressurized to various pressure levels by a compressor, forming a pipeline network covering the entire plant.
Parameter
Oxygen
|
Output |
Purity |
Pressure |
|
Single set 20000-100000+Nm ³/h |
≥ 99.6% |
Oxygen consumption for blast furnace:~0.8-1.6 MPa Oxygen for converter: 2.5-3.5 MPa |
Nitrogen
|
Output |
Purity |
Pressure |
|
About 2-3 times the oxygen production |
99.999% (≤ 10 ppm O₂) |
Multiple types: from low-pressure blowing to medium pressure spraying. |
Argon
|
Output |
Purity |
|
Approximately 5% -12% of oxygen production |
≥ 99.999% |
Operation and energy consumption
|
Unit oxygen consumption |
Annual operating time |
|
0.35 – 0.45 kWh/Nm³ O₂ |
≥ 8,300 hours |
(For reference only)
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