Arcelor Mittal Georgetown Steel
Pusher Reheat Furnace
Lining Configuration: Lining Configuration: After years of service at 2150˚F, the refractory plastic roof and walls (9” Super Duty/3”Lt wt castable) were in need of repairs, along with the hearth, discharge wall and skid pipes.
Customer Need: A recommendation was made to address two (2) major challenges:
- Excessive heat loss and shell temperatures on the roof and sidewalls
- Minimal time and financial resources to completely reline the entire furnace
Engineered Approach: Using thermography and heat flow calculations,a hot face veneer was recommended to address both customer requirements. The veneer design included:
- 1” thick 12”x12” ceramic fiber squares (2300˚F temperature use limit)
- A proprietary, high emissivity hot face coating
High Emissivity Coatings: ITC manufactures a proprietary, high emissivity coating to work in concert with the furnace conditions and veneer design. Under ideal conditions, high emissivity 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 the substrate refractory
- Improved Furnace Operation – Improves the thermal efficiency of the process
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 (as indicated by thermocouples) from 2150˚F to 1840˚F.
Increased Throughput – By reflecting the energy back to the colder steel load in the furnace, the furnace throughput increased from 88 tons to as much as 120 tons per hour.
Reduced Scale/More Product – Decreased operating temperatures and increased throughput have allowed an increase in yield of approximately 2% due to a significant decrease in scale generation (scale boxes previously emptied daily are now emptied on weekends). This amounts to 9000 additional tons of saleable product per year.
Reduced Amount of Energy Required – Combining all efficiencies, the amount of energy required dropped from 1,500,000 Btu/ton to 800,000 Btu/ton.
ROOF, SIDEWALL THERMAL CALCULATIONS
Original Lining: 350˚ – 400˚F (calculated) – 350˚ – 400˚F (actual)
After Veneer/Coating: 310˚ – 350˚F (calculated) – 250˚ – 300˚F (actual)
Btu Savings: 1.9 MM Btu/hr (calculated) – 2.2 MM BTU/hr (actual)
IMPACT ON BOTTOM LINE COSTS
Fuel Savings = $1,950,000 per year (at $10 per MM Btu)
Previous: (88 tons)(1.5 MM Btu/ton) = 3168 MM Btu/day
New: (120 tons)(.8 MM Btu/ton) = 2304 MM Btu/day
Increased Production = $3,600,000 per year
(9000 additional tons/year) ($400 ton)
TOTAL IMPACT/YEAR = $5,500,000