Defense Mapping School Documents

January 1978





Coal may be washed, crushed and screened in the preparation tower before being stored in the coaling tower. When required, it is charged to an individual oven by means of the charging car (approx 20 tons per charge). Indirect heat is applied by means of gas firing and the coal is baked for approx 18 hours, during which time 25% of its volume is released as gas. This is carried via the ascension pipes and crossover mains to the byproducts area, where it is cooled, scrubbed, and many valuable byproducts are extracted.

The coal which has now been converted to coke, is discharged from the oven by means of the ram car, and carried to the quenching tower by the quenching car. After quenching, it is dried and screened before being removed by either rail or conveyor to the blast furnace area. Daily coke oven production may be estimated by the following formula:

Length of the ascension pipe structures in feet, divided by the average width of a coke oven, e.g. 3.6 feet. Then multiply the answer by the average over production in tons per day, e.g., 15 tons. e.g., 820 feet X 15 / 3.6 = 3416 tons per day.

The charge for a blast furnace consists of coke, iron ore, limestone, air and water which is used as a colling agent. The layering yard and roasting and sintering areas are involved in the preparation of iron ore, limestone, and coke prior to its being charged into the blast furnace.

Various grades of iron ore, which have been previously crushed, are mixed in the layering yard prior to roasting and sintering. Coke dust may also be mixed in the layering yard or added at the sintering stage.

Limestone may be prepared for the blast furnace by either slaking or calcining. Both processes are rare at a steel plant, lime preparation normally being accomplished at the mine site.

It should be noted that all these processes are optional and will not be seen at all coke, iron, and steel works.

Layering is only required where various grades of ore are used and mixed. Roasting is used to remove impurities from low grade ores and sintering to form ore and coke fines into clinker or sinter as preparation for the blast furnace.

The raw materials are moved either by rail car or conveyor to bins under the stock trestle, from which the skip hoist moves them in measured quantities to the blast furnace. Air is fed under pressure from the blast house, via the blast main, to the hot stoves, where it is preheated and forced into the blast furnace to support combustion. Coke acts as a physical support material and combustible content of the charge. The iron content of the ore melts under extreme heat and drips through th porous coke, collecting in the bottom of the blast furnace.

The waste materials combine with the limestone, which acts as a flux, forming a slag, which floats on top of the molten iron. Both are tapped in turn, the slag being removed in slag cars, and the iron in hot metal cars.

Exhaust gases are carried away from the top of the blast furnace by the downcomer pipes, cooled, and the solid content removed in dust catchers. This dust contains iron ore, limestone, and coke, as well as waste products, and is normally recycled to the roasting and sintering area for reuse.

Average output from a modern blast furnace will be approximately 800-1000 tons per day.

Iron produced in the blast furnace is carried to the steel making area in hot metal cars. (Alternatively iron may be cast directly into pigs in a continuous pig casting machine if it is the intention to use it for the production of forged or cast iron products.

There are four main methods of steel production:
1. The Open Hearth
2. The Bessemer Converter
3. The Basic Oxygen Process
4. The Electric Furnace

In each one the carbon content of iron is reduced to a required level by the application of heat. All ingredients are added during the process to effect the properties of the finished product, which is steel.

The charge to any one of the steel-making processes will consist of approximately 50%scrap steel, and 50% molten iron, plus small quantities of alloying ingredients. The scrap steel and alloying ingredients will be prepared as a furnace charge in the charge preparation area.

Page 8 illustrates the construction and method of operation of the open hearth furnace. Page 9 shows the process stages for basic oxygen and bessemer processes. All the steel making processes are similar in basic concept, although different in application, and result in steel being poured into ingots, which are then stripped in the ingot stripping area.

The electric furnace process varies from others inasmuch as it uses electricity as a source of heat. This process is not illustrated and will be difficult to identify owing to its small size and lack of good PI features.

1. The furnace consists of a shallow bath capable of holding from 60 to 300 tons of metal at one time.

2. On each side of the bath is a set of two heating chambers. In each set there is one to preheat air...

3. ... and one to preheat gas. Chambers are filled with chequered brickworks.

4. The gas and air are led to the bath through one set of chambers, where they unite and burn with a fierce flame. The hot spent gases are vented through the other set of chambers and preheated.

5. When the first set has begun to cool, the direction of flow is reversed.

This process will produce approximately 150 tons of steel every hour.

The bessemer converter process is similar in all respects to the oxygen lance process illustrated above, with the exception of the blow (step 3), which is through the bottom of the converter.

Steel ingots are moved by rail cars to the soaking pits, where they are heated to an even temperature suitable for the initial rolling process. The rolling process is started in the blooming mill where the ingot is reduced to a bloom or billet, which may be stored before completion of the rolling process. The bloom or billet will then be reheated and the rolling process completed in the main rolling mill complex.

Not all rolling mills will have soaking pit and blooming mill areas, but may take blooms and billets from other mills and subject them to a reheat prior to the completion of the rolling process. Cold rolling is also carried out in some mills.

The finished product, which will normally b an input material for a fabrication industry (e.g., steel bars, plates, wire, or rod) will then be stored and shipped.

Photo Interpreter Keys

1. Darkest tone of installation created by coal dust
2. Conveyors connecting towers
3. Tall coaling tower over bank of long rowed ovens
4. Gasometer
5. Usually a smoke stack on each end of ovens
6. Piping from ovens to by-products area
7. Storage tanks in by-products area

Iron 1. Stockpiles of different materials result in variety of tones:

  • Coal - Dark
  • Limestone - White
  • Iron ore - Gray
    2. Stock Trestle
    3. Skip hoist running to the top of the blast furnace
    4. Blast furnace w/small building
    5. Rows of hot stoves
    6. Dorr thickener

    Steel Production 1. Open hearth

  • Pig casting area (conveyors)
  • Long building w/smoke stacks on either side
  • Possible stockpile of scrap iron
  • Stripping area (R/R/) going to soaking pits
    2. Bessemer
  • Open top building, may glow
    3. Oxygen
  • Almost impossible to recognize
  • Electrical facilities (line, transformer yard)
  • Installation close to electrical power source
  • Stockpile of scrap steel
    4. Steel Processing
    a. Rolling mills - long narrow building grouped together
    b. Cooling warehouse - vented roofs
    c. Finished product storage areas
    d. Lines of transportation
  • Rail
  • Ship
  • Highway e. Entire industry may be co-located with another - Example: ship or car manufacturing