Reliant on sand: Blast-furnace slag is filtered into high-quality slag sand, which is a vital product for the cement industry.
Fascinating drone images of our sites
Our August drone image
- What do we have a bird’s eye view of here?
In particular, the three breathtaking sand towers in this drone image catch the viewer’s eye. Their characteristic shape comes from the fact that the slag sand falls from the screening plant (on the left in the image) in a specific place and can reach a maximum of ten meters tall. The expansive warehouse is located at thyssenkrupp Steel’s Schwelgern plant in Duisburg, Germany.
- What is slag sand?
Slag sand is created through the fast, abrupt cooling of hot blast-furnace slag with water. Through this process of granulation, the liquid slag freezes and can be processed further in the screening plant into avaluable, highly popular by-product of pig iron production.
- Who purchases slag sand?
High-quality, finely milled slag sand is used in the cement industry and is a key component in blast-furnace cements. Concretes made from cements that contain slag sand are often identified by their light-gray, almost white coloring.
- What advantages are offered by the material?
Thanks to its physical and chemical properties, concretes made from these cements are particularly resistant to chemicals such as sulfates, for example. It also takes longer to hydrate cements containing slag sand, which leads to a lower hydration heat. In turn, this prevents cracks forming due to restraint stresses caused by thermal expansion and is important especially in large concrete constructions such as bridge piers, dams, large foundations, or locks. Last but not least, the manufacturing process of cements containing slag sand require less primary energy, meaning it generates fewer CO2 emissions than manufacturing other types.
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Our July drone image
- What can we see here?
Our drone has captured an image of Precision Steel business unit’s so-called coil rinsing facility in Hohenlimburg, Germany. The precidur®-trade mark, hot-rolled coils were first transported from the precision strip mill to the cooling system using a coil loader. Cooling the hot-rolled precision strip coils is just one production step of the many that make up the entire manufacturing process; but it is a regular one.
- How hot are the coils when they arrive for cooling?
The coils are still around 600°C when they reach the cooling unit. They are then steadily rinsed in the unit with cold water that is around 25°C in temperature, before they then level off to about room temperature over time. It generally takes 24 hours for the coils to cool down completely.
- Where does the cooling water come from?
This circulation system is fed with water that has been recycled from the precision strip mill. A certain amount evaporates naturally during the process, which is then replenished from the Lenne, a tributary of the Ruhr, the downstream section of which passes through Hohenlimburg.
- What happens with the coils after they have been cooled?
They must first be cooled down completely, so they are strung in the warehouse. Then, we either transport the coils to the next units in the process (pickling line, annealing, or the splitting plant ), or we pack them up and ship them directly to the customer, depending on their requirements.
Our June drone image
- What can be seen here?
The four cooling towers with their hexagonal, cylindrical shape are the most striking feature. The two round pools also catch the eye. These are the “circular clarifiers.”
- So what do these circular clarifiers do?
They are part of the cooling and water recycling system for the blast furnaces. To produce steel, large quantities of water are needed at various stages of production, and the quality of the water needed at each stage is different. thyssenkrupp’s steel business requires approximately one billion cubic meters of water each year – 97 percent of this being recycled water.
- That’s an impressive figure. How is this achieved?
We operate water circulation systems at all our locations, in which the water is used up to 40 times before either being evaporated or discharged as cleaned waste water. thyssenkrupp’s steel business is committed to water protection and to conserving water as a natural resource.
In addition to protecting water resources, minimizing the quantities of waste water, and disposing of waste water safely, this also means that in the plants, great importance is placed on careful handling of substances that are hazardous to water.
- The best evidence of this is living on site...
Exactly. We have wildlife taking up residence in our plant grounds. Some years ago a carp moved into one of the water pools that was no longer in use. Our colleagues christened him Kuno, and since then he has started a family. Vegetation has now taken over some parts of the pond, creating a mini-habitat for wildlife – a carp pool right next door to the pig iron production facility.
Our May drone image
- What are we looking at here?
The camera drone is located above one of the largest private inland ports in Germany, the Schwelgern Port. This is the larger of the two plant ports owned by thyssenkrupp Steel. The company uses these ports to ensure the raw materials supply for the components used to produce pig iron.
- What raw materials are these, and where are they from?
These raw materials are iron ore, coal, imported coke, and various aggregates. The ores are from Brazil, Canada, and Australia. The coal also comes from Canada and Australia – as well as from the U.S., Africa, and Asia.
- How are the raw materials transported?
They’re transported from Rotterdam to Duisburg via the Europoort harbor. The push boat fleet from the Dutch subsidiary thyssenkrupp Veerhaven is used in the process. This consists of push barges – these are transportation units that are approximately 80 meters long and can carry loads of up to 2,700 metric tons. Numerous push barges are connected with one another and pushed up and down the Rhine by a push boat.
- What stage of steel production does this represent?
The very beginning, or, more precisely, before pig iron production. From the Schwelgern Port, the raw materials are brought to the plant. Beforehand, the raw materials are mined and then temporarily stored at the seaports. After they are transported to our plant port, we store the raw materials until they are used.
Our April drone image
What is a blast furnace used for?
The blast furnace is the core component of any steel mill. Its purpose is to produce pig iron, the most important iron resource for the production of crude steel.
How does a blast furnace work?
Pig iron is made by melting ore, coke, sinter, pellets and other additives in the blast furnace. Hot air is required to start the chemical reaction in the furnace. This air is supplied by the hot blast stoves at up to 1300 °C. It is blown into the lower part of the blast furnace and ignites the lowest coke layer. The gases, which can reach temperatures of up to 2,200 °C, rise upwards and heat the solids that are fed from above. After about six to seven hours, the finished pig iron can be tapped off.
What material is a blast furnace made of?
The interior of the furnace vessel is lined with refractory brick. The structure is surrounded by a steel frame.
Which plant components can be seen from the air?
The two circular clarifiers in the upper right corner are easy to spot. They are used for cooling and waste water treatment in blast furnaces. The cooling tower can be seen at the right edge of the image, closer to the center. The hot blast stoves are located below the tower.
Right next to them is the hot blast stove exhaust gas stack of blast furnace 9, which is easy to find thanks to its colorful stripes. The rectangular building below it is the cast house of blast furnace 9. It is adjacent to blast furnace 9, the plant from which white steam is emerging in the image. The tall red building on the bottom left is blast furnace 8. The three circular silver buildings are the hot blast stoves of blast furnace 8. The office building, which also houses the control center for the two blast furnaces, is located directly beside the car park.
Our March drone image
- Why does thyssenkrupp Steel have its own railway operation?
The plants are supplied with raw materials by rail, and finished steel products are also transported to other thyssenkrupp locations and customers. At the Duisburg location, this amounts to around 64 million tons of material each year. The plant railway transports raw materials such as ore, coal, coke, sinter and lime to the blast furnaces and liquid pig iron from the blast furnaces to the steelworks. The slabs are then transported to the hot strip mills and the coils produced there are moved to the downstream processing units.
- What is the purpose of the ‘Grünstrasse’ marshalling yard shown here?
Wagons loaded with raw or finished materials are collected here and scheduled for onward transport to internal and external production plants and customers. The station is located at the heart of thyssenkrupp Steel’s 400-kilometer rail network and forms the hub to the ports and individual production sites.
- Where does the thyssenkrupp Steel track network end?
The thyssenkrupp track network has no clear-cut terminus since it is connected to that of Deutsche Bahn, which, in turn, interfaces with the railroad networks of neighboring countries. In practice, however, only the tracks located on the factory premises are maintained by thyssenkrupp.
- Who is responsible for operating the thyssenkrupp Steel railroad?
The Logistics business unit bears overall responsibility. The actual work, however, is performed by around 900 employees of the Railway Operations and Railway Technology departments, who ensure that everything runs smoothly. The jobs involved include locomotive drivers, wagon masters, and signalmen. By the way, at thyssenkrupp Steel you can also train to be a switchman and locomotive engineer.
It's all in the mix
- What does it show?
We are at the top of the production chain of the integrated steel mill of thyssenkrupp Steel. The view encompasses one of a total of six adjacent fine ore blending yards at the Duisburg-Schwelgern location. A so-called ‘stacker’ moves the bed on rails to fill it with raw materials for sintering.
- What is the purpose of a fine ore blending yard?
Before steel production, pig iron is produced in the blast furnace. This requires iron ore, coke, and other additives, which must be sorted and prepared accordingly. While coarser raw materials are suitable for immediate use in blast furnaces, finer material is first transported to the blending yards where it is mixed with other fine ores, fuels, and additives to form a homogeneous mixer ore of consistent quality.
- And what is the stacker used for?
Blending yards are built up in layers. The stacker ensures that the individual raw materials are ‘stacked’ one after the other in regular layers as well as in the longitudinal direction. The device needs approx. 15 minutes for one trip. Each blending yard is about 390 meters long, about 13 meters wide, and will end up being up to 13 meters high. By the time this height is reached, the stacker will have completed up to 600 trips!
- What is the lifetime of a fine ore blending yard?
A full, freshly stacked blending yard comprises 140,000 tons of ore. As a rule, after four to five days all the material is used up for sintering or pig iron production. As soon as one of the blending yards is empty, another one is ‘cut,’ and the empty blending yard is stacked again. This is why there are a total of six such blending yards on site: While two are being filled up in parallel, two can be emptied. The remaining two blending yards serve as buffers.
What a Gas!
- What are we looking at here, and where is it?
This is the Gasometer in Duisburg-Hamborn, Germany.
- What’s a gasometer, and what’s it used for?
A gasometer is a container that stores purified gases created as by-products of steel manufacturing and subsequently used to generate energy. The gasometer is used to balance out peaks in energy generation and consumption.
- How is the gas stored, and how does this system function?
Gasometers are disk-type gas holders. The disk inside the gas holder rises to the top and is filled with a certain volume of gas that is consequently stored. When the gas is removed from the gas holder, the disk is moved downwards and correspondingly reduces the stored volume. In principle, this is similar to the way that a French press for coffee works.
- What happens to the gas once it’s been removed from the Gasometer?
The gas, which has been previously purified and compressed, is removed from the gas holder using suction funs, compressed under even greater pressure, and then fed in to the energy cycle. The gas is used to heat up furnaces or to generate power in power plants.