Air Blowers for the Steel & Metallurgy Industry: Aeration, Vacuum Degassing and Furnace Gas Handling

In steelmaking, gases and vacuum are involved at many process stages. Air blower applications can be divided into two groups: vacuum generation (secondary metallurgy, steel degassing) and process gas transport/compression (direct reduction lines, furnace gas handling). Each group has its own technical requirements, but both demand oil-free dry-compression equipment.

The common requirement across all three: equipment must withstand continuous operation for years and must prevent oil contamination of the process gas stream — a factor that directly determines finished steel quality.

In high-quality steelmaking, dissolved gases such as argon, carbon monoxide (CO), oxygen, and carbon dioxide (CO₂) must be removed because they adversely affect mechanical properties. In particular, dissolved hydrogen causes steel embrittlement — extracting hydrogen under vacuum helps reduce this phenomenon and improves purity. This is why secondary metallurgy is closely associated with vacuum systems.

According to Aerzen documentation, typical processes include: RH (Ruhrstahl-Heraeus) — drawing a portion of molten steel into a vessel through two snorkels and injecting argon for decarburisation and degassing; RH-OB — an upgraded version adding oxygen for higher-grade steel; as well as VD (Vacuum Degassing) and VOD (Vacuum Oxygen Decarburisation). Dry-compression blowers handle the safe extraction of these harmful gases under vacuum conditions.

This type of vacuum system applies to new steel plants, modernisation projects replacing old steam ejectors, and mini mills / micro mills processing scrap steel. Flow rates for large blowers range from approximately 10,000–97,000 m³/h, while canned motor models serve lower flow rates — these figures are illustrative and depend on the specific model and operating conditions.

Beyond vacuum applications, steel plants also need to compress and transport process gas. In direct reduction of iron (DRI – Direct Reduction of Iron) lines, process gas blowers handle the compression of process gas, cooling gas, and sealing gas. Furnace gas streams such as coke oven gas and blast furnace gas are also handled by dedicated process gas blowers.

The critical requirement here is a gas-tight, oil-free construction: lubricating oil must be completely isolated from the compression chamber to prevent contamination of the process gas. Aerzen uses submerged mechanical seals combined with purgeable labyrinth seals, permanently separating the oil chamber from the gas chamber. The GQ process gas series covers a wide range of flow rates and differential pressures (model-dependent), designed for long-term continuous operation.

Air blowers generate low pressure ≤1 bar at high flow rates, distinct from high-pressure air compressors. There are three main technologies, with selection depending on flow rate, differential pressure, and energy-saving requirements:

For process gas and vacuum applications in metallurgy, gas-tight construction and oil-free dry compression capability are the priority criteria. For auxiliary aeration applications (e.g. plant wastewater treatment), the focus shifts to energy efficiency — where screw blowers and control systems offer advantages. For high-pressure oil-free compressed air requirements, Aerzen also offers an oil-free screw air compressor range compliant with ISO 8573-1 Class 0.

Compressed air and aeration are among the largest electricity consumers in a plant. Control optimisation is typically the primary area of energy savings, especially for multi-blower stations running in parallel. Aerzen provides three control layers:

For auxiliary aeration applications, AERsmart coordinates multiple air blowers according to dissolved oxygen (DO) demand, avoiding operation at excess capacity. Actual energy savings depend on system configuration and the load profile of each plant.