Nucor Steel Birmingham
Pusher Reheat Furnace
Furnace: Three (3) zone, 115 tons/hr pusher type reheat furnace operating at 2350˚F, processing rebar and merchant bar products.
Customer Need: To minimize/reduce excessive BTU loss in roof, sidewalls and skid pipe.
Engineered Approach: Using thermography and heat flow calculations, a hot face veneer was recommended to address BTU loss. The veneering design included:
- 1” thick 12”x12” ceramic fiber squares on sidewalls, doors & skid pipes
- ½’ thick 12”x12” ceramic fiber squares on the roof
- A proprietary, high temperature, energy efficient ceramic hot face coating
High Temperature Energy Efficient Ceramic Coatings: ITC manufactures a proprietary, high temperature energy efficient ceramic (HTEEC) coating to work in concert with the furnace conditions and veneer design. Under ideal conditions, HTEEC coatings absorb energy from the process and re–radiate it to the furnace load, imparting the following benefits:
- Lower Heat Loss – Minimizes heat transfer through the furnace refractory walls
- Lower Maintenance Costs – Protects and prolongs the substrate refractory life
- Improved Furnace Operation – Improves the thermal efficiency of the process
- Reduction in Scale Generation – Less Fe2O3 available due to more efficient burning
- Increase Thru Put – Additional energy (Btu’s) available to heat product at an increased rate
IMPACT ON THE PROCESS
Lower Shell Temperatures – The combination of veneer and the coating significantly lowered shell temperatures.
Improved BTU Savings – Due to the thermal efficiencies, Btu savings were significantly better than the estimates.
Lower Operating Temperatures -The thermal efficiencies of the new design enabled the operators to drop normal furnace operating temperatures in the discharge zone.
ROOF, SIDEWALL & SKID PIPE THERMAL CALCULATIONS
Original Lining: 300˚ – 400˚F (calculated) – 330˚ – 430˚F (actual)
After Veneer/Coating: 250˚ – 350˚F (calculated) – 228˚ – 342˚F (actual)
BTU Savings: 50 MM BTU/hr (calculated) – 54.7 MM BTU/hr (actual)
IMPACT ON BOTTOM LINE COSTS
BTU Savings Per Year = 54.77 MM Btu/hr x 24 hr/day x 208 days/yr x $4.05/MM Btu)
TOTAL IMPACT/YEAR = $1,230,000