The amazing benefits of ITC Coatings are seen perhaps nowhere greater than when they are used in the relining of an industrial furnace or kiln. This case study includes the issues, methods and results of a very successful reheat furnace reline we performed for a major steel producer, helping them to reach their full production potential.
• Furnace: The furnace is rated at 75 tons/hr. and utilizes Bloom high temperature burners
designed for 7500F 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: ITC recommended a solution to address several major challenges:
- Excessive heat loss and shell temperatures on the roof and sidewalls.
- High fuel consumption
- Continual refractory maintenance with charge and discharge openings
• 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-reflectivity hot face coating
• High Reflectivity Coatings: ITC manufactures a proprietary, high reflectivity coating (ITC 100HT) to work in concert with the furnace conditions and veneer design. Under ideal conditions, high reflectivity 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 throughput – 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 TEMERATURES
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