1. All photos: Stahl-Zentrum, Düsseldorf
Primary Metals
Infrared Temperature Measurement
The steel industry provides enormous opportunities for the application if infrared temperature sensors.
The making and shaping of steel is commonly done it two types of steel mills.
The Integrated Steel Mill: These plants use enormous amounts of equipment and energy to convert the basic ingredients from the crust of the earth (iron ore, limestone and coal ) into iron and steel. These plants must produce over over 1 million tons of raw steell/year to justify the expense of the equipement, maintenance, and energy needed to serve their customers.
The Mini-Mill: These plants bypass the making of iron and steel from raw materials, and instead rely on melting and forming recycled steel scrap.
Mini-mills produce between 100 and 500 thousand tons of steel/year and are commonly located near their major markets.
Our discussion of Primary Metals will focus on the making of molten iron and steel in a typical Integrated Steel Mill.
All photos: Stahl-Zentrum, Düsseldorf

2. Overview Preparation Blast Furnace Converter Continuous Caster
Ore
Sinter
Coke
Pig Iron
Steel
Slab
Coil
Integrated Steel Mills start with basic building blocks for making iron and steel:
Iron Ore
Limestone
Coal
Preparation
Blast Furnace
Converter
Continuous Caster
Hot Rolling Mill

3. Sinter Plant
Rough mix powder of milled iron-ore, coke and lime ignited at up to 1200°C (2200°F)
Air is pulled through this mix to “cook” the sinter evenly
Allowing the right burning and ventilation in the blast furnace
Granular iron-ore from is shipped to the steel mill where it is processed by a Sintering Plant.
The sintering operation prepares the ore with the right size and consistency for use in the blast furnace.
The Sintering process forms a paste –like 9” thick mixture of iron ore, coke, lime, mill slag, and flue dust, on a continuous chain conveyor. Burners ignite the coke, which fuses the material into a solid cake.
The cake is then broken into lumps, cooled, and transported to the blast furnace.

4. Sinter Plant Very dusty environment! Coal + Iron Ore Ignition
Control Ignition vs. Conveyor Speed Multiple Sensors or Scanner
Fall Control Burning-through Check the belt spaces for clogging (air suction!) Linescanner, Thermal Camera
Sinter Cake
Fines
Infrared point sensors, line scanners, or thermal imagers are used to control the uniformity of the fusing process under the ignition hood and the sinter cake.
Linescanners and thermal imagers are also used to monitor the falling cake as it enters the breaker/cooling section.
Suction
Breaker/Cooler
Very dusty environment!

5. Sinter Plant - Ignition
up to 6 m
up to 550 mm
Linescanner
Sinter Bed
Ignition Hood
Linescanners or thermal imagers provide valuable temperature information of the ignition process.
Sinter plants can be 4-6m (12-20’ )wide and 550mm (22”) thick at temperatures of 1300°C (2350°F).

6. Sinter Plant – Fall Control
Sinter Cake
Photo: Frank Schädlich
Sinter cake must be cooled from 1300°C (2350°F) before it is transported to the blast furnace by the conveyor system.
IR thermometers, linescanners, or thermal imagers can be used to control the speed of the belt, therefore the fall rate of the sinter cake at the end of the chain conveyor.

7. Sinter Plant – Ring Cooler
Monitoring the cooling with a linescanner
The ring cooler uses IR spot sensors or scanners to ensure the lumps sinter cake are cool enough to transport on the conveyor belts to the blast furnace.
Very dusty environment!

8. Pelletizing … similar to the sinter process
Ore + water + binding agents mixed in drums plus a stepwise firing to bake pellets
Benefits of pellets: uniform size high strength and purity transportable
If the iron ore is a very fine material, it is converted into pellets, usually at or near the mine site.
Pelletized iron ore is much easier to transport and handle than the ore fines.

9. Coke Plant - Chamber 900 to 1400°C (1652 to 2552°F)
24 h coke baking process
Heating and degasing the coke for a cleaner burning
Coke temperature corresponds to its quality
Installations: a) on top at chamber roof b) from the side looking through holes in the pusher guide
Top View
3 pyrometers each side vertically installed at 10 m distance looking through 100 mm holes
Wagon
Pusher
Metalurgical coke provides the carbon source and fuel used in the blast furnace.
Coal is crushed and heated in pressurized coke ovens for approximately 24 hours at temperatures up to 1400C (2552°F).
Because of the long processing time, a coke plant may have up to 100 ovens to provide a continuous supply of fuel for the blast furnace.
Chambers

10. Coke Plant - Quenching Hot spots of several hundred degrees
Extinguish hot spots with a minimum quantity of water to ensure the coke quality
Avoid the damage of the conveyor belt
Multiple linescanners installed along the long wharf
Monitoring while dumping the coke
Linescanner
Infrared sensors, scanners and/or thermal imagers are used to measure the coke temperature as it is pushed from each oven, where it is quenched with fresh water, then transferred by conveyor belt to the blast furnace.
Infrared sensors, linescanners and/or thermal imagers are used to monitor the quality of the coke, and ensure it is cool enough for transporting on the conveyor system.
Photos: Corus

11. Coke Plant – Conveyor
Detection of remaining hot spots to avoid damage on the rubber conveyor belt
Extreme dusty environment
Defocused optic allows to cover whole conveyor width (typ. D:S < 2:1)
Controlling the cooling sprayers
Point Sensor
Cooling Spray
Hot Spot
The conveyor system is further protected by using 8-14 micron point sensors with a wide field-of-view.
These allow the activation of water sprays in the event a hot ember is detected.
DZA

12. Use shortest possible wavelength for maximized hot spot sensitivity!
Coke Plant – Conveyor
A large field-of-view allows the IR sensor to view the width of the conveyor belt.
Use the shortest possible wavelength for maximum hot-spot sensitivity.
Hot Spot, 500°C (932°F)
Measured Spot
Use shortest possible wavelength for maximized hot spot sensitivity!
50°C
(122°F)

13. Blast Furnace Iron Ore  Iron Slag Flue Gas Iron Ore Coke Coke Layer
Pellet Layer
Smoke Outlet
Iron ore (pellets or sinter cake) + coke + lime are fed into the top of the blast furnace. Hot combustion air from the stove domes is forced into the furnace through the tuyeres. The tuyeres are water-cooled copper nozzles delivering oxygen through the incandescent coke.
The bottom of the furnace is tapped for slag and pig iron.
A portion of the pig iron is sent to foundries, where it is further processed into cast iron.
The major portion of the pig iron is transported by torpedo cars to the Steelmaking shop.
Slag
Air Feed
Raw Iron (1450°C/2642°F)
Air Heater (Cowper)

14. Blast Furnace
Up to 6 Stove Domes per millbricks at 1300 to 1350°C (2372 to 2462°F)
Tuyere introducing fuel to the furnace
Stove domes are designed to store heat energy from the blast furnace.
These are large vessels filled with stacks of refractory brick.
The brick is heated by the hot exhaust from the blast furnace. Once the bricks reach 1300°C (2350°F), the combustion air to the tuyeres is drawn through the stove, thus pre-heating the combustion air.
Blast furnaces are usually served by 3 stove domes. 2 are being “charged” with hot exhaust, and 1 is providing the heated combustion air.
Tapping Hole

15. Stove Dome Pre-heating the feeding air
Preventing of overheating and damage to refractory bricks
Very high pressure inside with up to 6 bar
Ratio pyrometer with Quartz window, shutter, air purge and isolation ball valve
Pyrometer
Quartz window
Ball valve
Refractory
Infrared sensors are used to monitor the refractory brick in the stoves.
The temperature data is used to optimize the heating of the combustion air, while maximizing the service life of the refractory.
The incoming exhaust gas creates high temperature and pressure within the dome, requiring the use of a special stove-dome thermometer mounting assemblies.
The stove dome assembly includes a sight tube, gate valve, pressure window, and a 2-color IR sensor.
Refractory
honeycomb

16. Tuyeres Ring-shaped die for feeding the blast furnace with hot air
Measuring through the tuyeres inside to get the flame temperature (2200°C/3992°F) to control the fuel
Early detection of die blockages due to pulverized coal  no risk of explosions
View Port Standard glass to be exchanged with Quartz!
The Tuyere is a water-cooled copper nozzle through which the hot combustion air from the stove dome is injected into the incandescent coke.
2-color IR sensors are used to measure the internal temperature of the blast furnace, as well as detecting blockages in the feed die.
Too high temperature indicates die with isolating problem
Monitoring via pan/tilt linescanner (system and photo by Selmatec)

17. Tuyeres Typically 4 ratio sensors installed on each 90° Fuel saving
Blockage detection via attenuation alarm
Process temperature controls furnace efficiency
Hot Air
Wall
The attenuation alarm on a 2-color IR sensor can alert the plant personnel of a blockage in the tuyere.
Inside Furnace
Cooling
Die
Pyrometer

18. Sensor with closed-end sighting tube
Tapping Hole
Measuring the molten iron (1450°C/2642°F) at the tapping hole to get information about the inside temperature
A lot of slag at that location!
Better measurements during torpedo car loading (slag already removed)
Alternative: IR sensor with closed-end sighting tube dipped into the molt iron
Slag is removed from the top of the liquid iron in the upper hearth section of the blast furnace.
The tap hole for the molten iron is located near the bottom of the hearth.
Measuring the iron stream as it pours into the transfer ladle or torpedo car with a 2-color IR sensor will avoid the interference from the slag.
Sensor with closed-end sighting tube

19. Torpedo Car
Measuring the iron pouring during loading and unloading to calculate temperature losses
Monitoring the outside refractory temperature to check for wear and cracks
Extends the refractory life time
Avoids accidents and production stops due to hot breakouts
The health and integrity of torpedo cars is vitally important.
These refractory-lined railroad vessels often contain up to 300 tons of 1500°C (2732°F) molten iron which is often transported great distances.
Linescanners or thermal imaging cameras can be used to keep a thermal history of each torpedo car.
Refractory monitoring ideally with automatic car identification via software pattern recognition for trending analysis

20. Ladle
Measuring the iron pouring during loading and unloading to calculate temperature losses
Monitoring the outside refractory temperature to check for wear and cracks
Extends the refractory life
Avoids accidents/production stops due to breakouts
Linescanner for moving ladle
Camera for pausing ladle
Refractory-lined ladles are used to transport liquid metal within the plant.
Infrared sensors and thermal imaging cameras can provide important information on the health of the ladle refractory.
This is a major safely concern in steel mills.

21. Pre-Heatings
Pre-heating required to avoid damage to the refractory by thermal shock from the molten metal
Checking temperatures for fuel saving
Big burner flame!
1-color pyrometer
Burner
Pyrometer
Torpedo Car
Ladle
Torpedo cars and ladles require pre-heating to avoid thermal shock from 1500°C (2732°F) molten metal.
A 3.9 micron sensor is ideal for measuring the refractory and controlling the gas or oil fired burner used in this process.
The 3.9 micron wavelength is immune from luminous flames and assures the refractory is heated to the correct temperature to receive the liquid metal.
Burner ON
Temp.

22. Benefits of Noncontact Temperature Measurement
Measure moving products from a distance
Quickly identify temperature gradients on refractory
Better temperature control of the entire process
Less production downtime
Increased throughput
Integrated steel mills provide numerous opportunities for infrared temperature measurement.
High temperatures, dangerous environments, and targets inaccessible or impossible to measure with contact devices make IR technology the ideal solution in the metals industryl

23. Primary Metals Thank you for your attention!
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