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Arcelor Mittal Harriman Steel
Pusher Reheat Furnace
FURNACE DETAILS
Furnace: The furnace is rated at 75 tons/hr. and utilizes Bloom high temperature burners designed for 750˚F combustion air with and utilizing a recuperator. The maximum Btu input is 89.9 MM Btu or 1.2 MM Btu/ton. The furnace controls are minimal with the system utilizing an air lead only instead of a more precise lead lag system, and the exhaust utilizes a forced evacuation fan with manually adjustable damper blades.
Lining Configuration: Most of the existing refractory was in reasonably good shape except for the billet charge, discharge peel bar and billet discharge openings, which were badly damaged. The soak zone burner wall was also badly damaged.
Customer Need: A solution was recommended to address several major challenges:
- Excessive heat loss and shell temperatures on the roof and sidewalls
- High fuel usage
- Continual refractory maintenance with charge and discharge openings
RECOMMENDATION
Engineered Approach: ITC recommended a hot face veneer to address the customers’ 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
- Reduction in Scale Generation – Less Fe2O3 available due to more efficient burning
- Increased 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/gas savings was reduced by 20%
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 65 tons to the rated 75 tons per hour.
Reduced Scale/More Product – Decreased operating temperatures and increased throughput have allowed an increase in yield of approximately 2 ½ % due to a significant decrease in scale generation. At full production this amounts to 6,150 additional tons of saleable product per year.
Reduced Amount of Energy Required – Combining all efficiencies, the amount of energy required dropped from 1.2 MM Btu/ton to 0.96 MM Btu/ton. If the flue exhaust is restricted as is recommended and the burner control system updated, this furnace could attain 0.88 MM Btu/ton or a reduction in fuel usage of 33%
IMPACT ON BOTTOM LINE COSTS
Fuel Savings = $833,000 per year (at $8.00 per MM Btu)
Previous: (65 tons/hr.)(1.2 MM Btu/ton) = 1,872 MM Btu/day
New: (75 tons)(.8 MM Btu/ton) = 1,440 MM Btu/day
Increased Production = $2,929,500 per year
= (6,510 additional tons/year)($450 ton)
ROI = 1.33 weeks (at full production of 6,000 hours/yr. or 15 turns/wk.)
TOTAL IMPACT/YEAR = $3,762,500