Centrifugal Blowers for Steel Plants: Combustion Air, Cooling and Extraction

A steel plant runs on heat, and heat needs air. Reheating furnaces and heat-treatment lines need combustion air. Motors, drives, and electrical rooms need cooling air. Melt shops and rolling mills need ventilation. Secondary fume capture around ladles and transfer points needs extraction. Centrifugal blowers do all of this work, and this page sets out where they fit, with the honest boundary: the very largest dedusting and process-gas fans in a steel plant are multi-megawatt machines, well beyond an 800 HP blower, and that duty belongs to specialist heavy-industry fan suppliers.

Where Blowers Fit in a Steel Plant

Duty	Typical pressure	Notes
Reheating furnace combustion air	High class	Stable, pulsation-free flow across a wide firing range
Heat-treatment furnace combustion air	High class	Similar to reheating furnaces, often smaller
Motor and drive cooling	Low to medium	Forced ventilation where the motor’s own fan is not enough
Electrical and control room pressurisation	Low to medium	Filtered supply, positive pressure
Melt shop and rolling mill ventilation	Medium	Heat removal from hot bays
Secondary fume extraction	High	Capturing fume that escapes primary hoods
Cooling bed and quench zone air	Medium to high	Cooling hot product
Main EAF and BOF dedusting	Very high, very large flow	Outside our range

Worked Example: Reheating Furnace Combustion Air

A reheating furnace has a fuel input of 20 MW, about 17.2 million kcal/h. With 10% excess air:

• Stoichiometric air: 17,200 × 1.18 ≈ 20,296 Nm³/h
• With excess air: about 22,326 Nm³/h
• At 20 °C: about 23,960 m³/h, or 6.66 m³/s

If the burners and ductwork need 300 mm WC (2,942 Pa), air power is 6.66 × 2,942 ≈ 19.6 kW, and at 70% total efficiency the blower needs about 28 kW at the shaft. This sits comfortably within our range, using a backward-curved single-inlet blower. See combustion air.

Where Our Scale Ends: Melt Shop Dedusting

Melt shop fume from electric arc furnaces is captured by large canopy and direct-shell-evacuation systems feeding baghouses rated in the millions of cubic metres per hour. A baghouse of 2.4 million m³/h, for example, is roughly equivalent to six of our largest blowers running at 800 HP and 4,000 Pa. These primary dedusting fans are specialist, purpose-built machines, multi-megawatt in size, and outside our range. We are clear about that: send us the secondary extraction, cooling, and combustion air duties around the melt shop, not the primary EAF or BOF gas cleaning fan.

Cooling: Motors, Drives and Electrical Rooms

Steel plants are full of large motors, drives, and transformers that need forced-air cooling beyond their own integral fans, and control rooms need clean, cool, positive-pressure air to protect electronics from mill scale dust. A motor with 40 kW of losses and a 20 K allowed air rise needs about 5,970 m³/h. See cooling air.

Rolling Mill and Melt Shop Ventilation

Hot bays need heat removed, usually through roof extraction with make-up air, but where resistance is significant, such as filtered supply to control areas or ducted extraction, centrifugal blowers do the work that a simple roof fan cannot.

Secondary Fume Extraction

Fume that escapes the primary hoods around ladles, tundishes, and transfer points is captured by secondary extraction systems, smaller and lower-flow than the main dedusting system, and often within our range. Size for the hood’s capture requirement and the loaded-filter resistance. See dust collection system design.

Cooling Beds and Quench Zones

Product leaving a rolling mill or a heat-treatment furnace is cooled by forced air. A worked example: 2,000 kg/h of steel cooled from 300 to 100 °C removes about 55.6 kW, and with an 80 K air rise needs about 2,070 m³/h. See cooling air and furnaces, kilns and ovens.

Heat, Dust, and Scale

Mill scale and dust are abrasive and settle everywhere. Blowers near the mill need protection: filtered intakes where practical, cleanable wheels, and vibration monitoring, since deposits unbalance the wheel before they cause visible damage. See maintaining industrial blowers.

Site Altitude and Heat Together

Many steel plants sit in hot regions, and some at altitude, which compounds the density correction. A furnace combustion air blower calculated at sea level and 20 °C will under-deliver at a hot, elevated site, because both temperature and altitude reduce air density. Correct the actual pressure and airflow requirement using the site’s real density before converting to a standard-air rating, and check motor power at the coldest, densest start-up condition the site will see, not just the average summer day. See gas temperature, altitude and density correction.

Where Our Range Fits

NextAir Systems manufactures centrifugal blowers up to 800 HP (about 597 kW) and up to 500 mm WC (about 4.9 kPa) static pressure, with backward-curved and forward-curved wheels, single-inlet and double-inlet designs, and high-temperature blowers for furnaces up to 800 °C. That covers furnace combustion air, motor and electrical room cooling, rolling mill and melt shop ventilation, secondary fume extraction, and cooling-bed air. Primary EAF and BOF dedusting, and other multi-megawatt process fans, are outside our range, and we will say so early.

What to Specify

1. Furnace fuel input and required combustion air, or heat load for cooling duties.
2. System resistance, at clean and worst-case conditions.
3. Gas or air temperature, and whether the blower handles hot gas.
4. Dust and scale conditions.
5. Motor position, drive arrangement, and control approach.
6. Noise limits and site altitude.

Get a Blower Selection for Your Steel Plant

Send your duty, whether combustion air, cooling, or extraction, and site conditions, and we’ll size the blower. Contact us for a free quote.

Frequently Asked Questions