The process
Reheating furnaces for rolling mills burn gas or oil with preheated combustion air from a recuperator. The combustion air blower is sized for the burner pressure at the hot air temperature, and the flue fan or stack damper controls furnace pressure.
The gas at the fan
Clean air that has passed through an air heater or recuperator. Density is lower than ambient, so the fan is selected at the hot condition and checked for motor load at cold start.
Selection for this duty
| Blade form | Backward curved or aerofoil for the best efficiency on clean gas |
| Material of construction | Mild steel |
| Drive and bearings | Direct coupled or belt driven with a shaft cooling disc and bearings outside the casing |
| Density at the fan | At about 180°C the gas density is close to 0.78 kg/m³, 65% of standard air. Pressure developed and power drawn fall in the same ratio, so the selection is made at this density and the motor is checked at cold start. |
Sits at the outlet of a boiler, kiln or furnace and draws the flue gas through the plant to the stack. It handles hot, dust-laden gas at large volume, so it is sized at the hot condition and checked at cold start. Client-stated blade types for the ID Fan in general: Backward curved, backward inclined and radial tipped.
Industries
Other fans in steel reheating furnaces
ID Fan in other processes
Bagasse Fired BoilersRice Husk Fired BoilersAFBC BoilersCFBC BoilersPulverised Coal Fired BoilersOil and Gas Fired BoilersWaste Heat Recovery BoilersBiomass Fired BoilersThermic Fluid HeatersHot Air GeneratorsRotary Lime KilnsVertical Shaft Lime KilnsGypsum Calcining PlantsSponge Iron Rotary KilnsBlast Furnace Hot Blast StovesSinter PlantsCoke Oven BatteriesElectric Arc Furnace SteelmakingHeat Treatment FurnacesFerro Alloy Submerged Arc FurnacesCopper and Zinc SmeltingGlass Melting FurnacesCeramic Tunnel and Roller KilnsCeramic Body Spray Dryers
Services on this fan
Fan and System Performance TestingFan Energy AuditRetrofit of Low Efficiency FansRotor Replacement and Performance EnhancementDynamic Balancing and Vibration AnalysisCondition Monitoring and TroubleshootingInstallation, Commissioning and After-sales Support
Information needed to select or quote
- Duty point. Volume flow and static pressure at the fan inlet, with the gas density and temperature or the conditions to derive it.
- Operating conditions. Site altitude, normal operating temperature and continuous or intermittent duty.
- Gas stream. Dust loading and particle size, corrosive species, moisture, upset temperature and any tendency of the material to deposit on the impeller.
- Mechanical. Rotation viewed from the drive end, discharge orientation and motor power.