What is the use of air compressors in steel mills?

In steel mills, air compressors, as the core power equipment, provide stable power sources and media for multiple process links through compressed air. Their application runs through the entire process of steel smelting. The specific uses are as follows:

1. Sintering process: pneumatic conveying and power execution

1. sintering pneumatic conveying
   • function: Sintered iron ore, coke and other raw materials are transported to the blast furnace through compressed air to achieve efficient and dust-free material transfer.
   • parameters: The pressure is usually 0.5MPa, and the air consumption is large but the quality requirements are low. Oil injection screw air compressors are generally used without post-processing equipment.
   • advantages: Compared with electric drive, compressed air is more reliable and safe, and can adapt to the harsh environment with heavy dust in the sintering workshop.
2. power actuator
   • application: Drive the ash unloading device, cooperative actuator and other equipment to complete sintering ore unloading, screening and other operations.
   • case: The sintering workshop of a 2500m³ iron-making blast furnace requires multiple screw air compressors to work together to ensure stable transportation of sinter ore.

2. Iron-making blast furnace: blast combustion and pulverized coal transportation

1. blast furnace blast
   • function: Compressed air is blown into the blast furnace through a high-pressure fan (pressure 0.2MPa) to support combustion of coke, maintain the high temperature in the furnace (about 1500℃), and accelerate iron ore smelting.
   • device: Large-scale axial flow compressor with a flow rate of more than 10000m³/min and a power of over 70000kW.
2. pulverized coal injection
   • application: Use compressed air (pressure 1.2MPa) to inject pulverized coal into the blast furnace to replace part of the coke and reduce smelting costs.
   • parameters: A single blast furnace requires 4 40m³/min screw air compressors (3 in use and 1 in standby) to ensure uniform injection of pulverized coal.

3. Steelmaking and continuous casting: Pneumatic control and cooling

1. converter bottom blowing
   • function: Oxygen is blown into the bottom of the converter by compressed air to strengthen the smelting reaction and improve the purity of molten steel.
   • parameters: The pressure needs to be stable at 0.8-1.2MPa, which requires extremely high stability of the air compressor.
2. Continuous casting steam spray cooling
   • application: Use compressed air to drive a steam spray device to cool the continuous cast billet and prevent cracking.
   • case: The continuous casting line of a steel plant uses multiple oil-free screw air compressors to ensure that the oil content of the compressed air is less than 0.01mg/m³ to avoid polluting the molten steel.

4. Auxiliary system: instrument control and cleaning maintenance

1. Pneumatic instrument valve
   • function: Drive instrument valves of blast furnace and converter to achieve precise control of pressure, flow and other parameters.
   • parameters: A non-thermal regenerative dryer and oil removal filter need to be equipped to ensure that the quality of compressed air reaches ISO 8573-1 Class 2 standard (solid particles ≤1μm, oil content ≤0.01mg/m³).
2. Pulse bag filter purging
   • application: Regularly clean the filter with compressed air to prevent dust clogging and extend equipment life.
   • parameters: The purging pressure is 0.5-0.7MPa, and the pulse frequency is adjustable to adapt to different working conditions.

5. Special scenario: residual pressure recovery and energy conservation

1. Blast furnace gas residual pressure recovery turbine power generation device (TRT)
   • function: Use the pressure energy of the blast furnace top gas to drive the turboexpander to generate electricity, and the recovered energy accounts for about 30% of the energy required by the blast furnace blower.
   • parameters: The turbine rotor is a 2-3 stage axial flow type, with a power of tens of thousands of kilowatts, significantly reducing energy consumption.

6. Air compressor configuration and management

1. Distributed air compressor station
   • layout: There are multiple independent air compression stations in the steel plant, which serve sintering, ironmaking, steel-making and other areas respectively, making it easy for management, transformation and expansion.
   • advantages: Different qualities of compressed air can be configured according to different process requirements (for example, instrument air needs to be dry and oil-free, and power air requirements can be relaxed appropriately).
2. Trend of energy-saving renovation
   • technology: Adopt frequency conversion screw air compressors, waste heat recovery devices, etc. to reduce energy consumption by 10%-30%.
   • case: A steel factory has saved more than 10 million yuan in annual electricity bills through energy-saving renovation of air compressors.