The process
Submerged arc furnaces for ferro manganese, ferro chrome and ferro silicon produce a hot fume dense with very fine oxide dust. Semi-closed furnaces take it through a cooling system to a large bag filter, and the main ID fan on the clean side is a large volume, continuous duty. Waste heat boilers on the furnace off-gas add an ID fan of their own.
The gas at the fan
Ferro alloy furnace fume carries very fine silica and metallic dust at high temperature. Fine dust packs into blade roots, so the wheel is chosen to shed it and the fan is placed after the bag filter.
Selection for this duty
| Blade form | Radial tipped with wear liners, or straight radial where the dust is coarse |
| Material of construction | Mild steel with replaceable wear liners on the blades and the scroll at the cut-off |
| Drive and bearings | Direct coupled, shaft cooling disc, bearings in a pedestal outside the gas stream, allowance for thermal growth |
| Also specified | Hard facing or liners on the blade pressure face |
| Density at the fan | At about 250°C the gas density is close to 0.67 kg/m³, 56% 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. |
Feeds a burner with air at the pressure the burner register needs. Sized for the burner turndown range, and often fitted with an inlet silencer. Client-stated blade types for the Combustion Air Blower in general: Backward curved and radial tipped.
Industries
Other fans in ferro alloy submerged arc furnaces
Combustion Air Blower in other processes
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.