Energy Savings for the Metals Industry
Boosting Efficiency: Advanced Controls Unlock Major Energy Savings
The steel industry is energy intensive with many opportunities to apply advanced controls to save energy. Some of the possible energy saving applications in a steel mill and the potential annual savings are illustrated in the figure below.
Energy saving systems typically use variable frequency drives, mill feedback data, and expert mill operation knowledge to precisely control and reduce the energy flows through the equipment. Some of the actual savings achieved by TMEIC on hot strip mills are shown below.
- Main Motor Cooling Fan – Energy savings through speed control of the cooling fan based on the load on the motor, winding temperature, and air temperature.
- Auxiliary Motor Cooling – Energy savings through speed control of the cooling fan based on the load on the motor, winding temperature, and air temperature.
- Fume Exhaust Fan – Energy savings through fan speed control based on the exhaust air flow.
- Cooling Water Pump – Energy savings through pump speed control based on the tank level and calculated flow of cooling water to the run out table.
- Scale Pit Pump – Energy savings through pump speed control based on position of the slab relative to the descaler.
Energy Saving Technology
| Plan | Equipment | Mechanical equipment and system technology |
|---|---|---|
| Manufacture of Pig Iron | Combustion equipment |
|
Collection of waste heat |
|
|
Other Processes |
|
|
| Steel Making | Sintering Plant |
|
Collection of waste heat |
|
|
Electrical Energy Saving |
|
|
| Rolling/ Surface Treatment | Collection of waste heat |
|
Electrical Energy Saving |
|
|
| Rod/ Shaping/ Fabrication | Heat utilization equipment |
|
Collection of waste heat |
|
|
Electrical Energy Saving |
|
|
| Other Energy Consumption Plant | Cogeneration equipment |
|
Electric power use equipment |
|
|
Lighting system |
|
Combustion equipment
- Coke oven combustion equipment
- Air heating furnace combustion equipment
Collection of waste heat
- Coke dry quenching (CDQ)
- Collection of exhaust gas heat in coke oven
- Collection of coke oven furnace gas heat
- Collection of heat from sinter cooler
- Blast Furnace dry-type TRT
- Heat collection of air heating furnace
- Material drying preheating equipment
Other Processes
- Pulverized coal injection (PCI)
- Coal moisture control equipment
- Dust collector speed control, or combustion blower
Sintering Plant
- Main Blower
- Cooling Fan
Collection of waste heat
- Material preheating equipment for electric furnace
Electrical Energy Saving
- Speed control of dust blower
- High-speed electric hoisting control, furnace cover control
Collection of waste heat
- Boiler for waste heat utilization
- Heat accumulation type regenerator
Electrical Energy Saving
- Speed control of auxiliary motor on main motor
- Speed control of roll cooling water pump
- Pressure control of de-scaling pump
Heat utilization equipment
- Speed control of furnace blower
Collection of waste heat
- Waste heat utilization
- Collection of annealing exhaust gas heat
Electrical Energy Saving
- Speed control of cooling fan motor for main motor
- Speed control of roll cooling water pump
- Change motor from DC to variable-speed AC
Cogeneration equipment
- Multiple-stage extraction steam turbine
- Back pressure turbine
Electric power use equipment
- Speed control of Fan or Pump
- Power factor improvement equipment
- High efficiency motor/ electric transformer
Lighting system
- High efficiency lighting system
- High frequency fluorescent lamp lighting
Energy Saving System for Rolling Mills and Process Lines
Features
- Providing optimal energy savings for complete rolling mills and process lines
- Providing an energy saving system which can be easily added to an existing mill
- Using a combination of PLC controllers and drives
Applications
- Energy saving using variable speed drive control
- Optimal cooling of drive motor
- Energy savings for miscellaneous power, lighting, and heaters (example: Stop while idling)
- Optimal operation using energy saving control model (example: heating furnace combustion control and mill pacing)
- Waste heat recovery
Energy Saving Controls for Hot Strip Mills
Furnace combustion control
- Improved fuel consumption using furnace combustion control model
- Reduction of material heat emission using mill control model
Improvement of power factor
- Improving efficiency and power factor by applying GCT/IEGT main drives
- Monitoring power demand for the entire mill line
- Reduction of electric power rates by improving power factor
Optimization of Ventilation cooling
- Optimal control using variable speed control
- Main motor cooling fan
- Auxiliary motor cooling fan
- Electrical room ventilation cooling fan
Applying Variable Voltage, Variable Frequency Control
- Descaler pump
- Air compressor
- Heating furnace blower
- Conveyor system
Energy saving operation
- Energy saving control of miscellaneous power, lighting and air conditioning units
Introduction of energy saving equipment
- Applying high efficiency motors
- Applying high efficiency transformers
- Replacing DC motors with AC motors and variable speed drives
Energy Saving Control System for Hot Strip Mill Main Motor Cooling Fan
In order to remove the heat generated in the main motor rotor and stator, cooling air is circulated through the unit cooler. The speed of the cooling fan motor is varied proportionally to the load of the main motor, thereby providing energy conservation.
System Configuration
Typical Change of Fan frequency and Motor Temperature. This graph shows an example of controlling the main motor cooling fan speed so the temperature rise of the motor remains constant irrespective of the main motor load. By applying this technology, large energy savings have been realized as shown in the following table.
This graph shows the power reduction by applying TMEIC’s energy saving control system in a steel company.