Secondary Finishing: Energy Consumption
|
Adapted from Steel Mill Process Heating Technology Study |
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.