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PROCESSES
- Agglomeration
-
Coking
- Blast
Furnace
- Direct Reduction
- Basic Oxygen Furnace
- Electric Arc Furnace
- Heat Treating
- Ladle Metallurgy
- Continuous Casting
- Ingot Casting
- Ladle Preheating
- Secondary Finishing
- Surface
Coating
PROCESSES
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Equipment
Combustion
Technology
Energy
Consumption
Process
Description
R&D
Trends
As discussed in the overview section, 42% of the natural gas used in the
steel industry is used in heating and annealing furnaces. Fuel consumption
for reheating furnaces varies widely - from 0.3 to 4.5 MMBtu/net ton of
steel produced. Direct rolling/hot charging practice can greatly reduce
the heating requirements compared to cold charging. The theoretical energy
requirement to heat a slab from 70°F to 2200°F is 0.68 MMBtu/ton.
Current state-of-the-art practice in a continuous furnace can achieve
1.2 MMBtu/ton, an efficiency of 57%. Hot charging lowers the energy requirements
by about 25% to 35%; the industry average is about 40% hot charged slabs
(in the range of 500 to 1000°F) In the continuous strip production,
the thin cast slabs enter the roller hearth tunnel furnace with a surface
temperature of about 1900°F. Fuel consumption requirements are about
0.5 MMBtu/ton due to the lower furnace efficiencies at elevated temperatures
and the greater relative importance of holding.
Steel Mill Process Heating Technology Study, Hatch Associates, GRI-95/0106, Gas Research Institute.