tomorrow starts today.
The aim of our Carbon2Chem® initiative is to use steel mill gases from steel production as a starting material for chemical products - including the CO and CO2 they contain. In addition to today's steel mill gases, the focus is also on the future residual quantities of steel mill gases after the switch to hydrogen-based production. Surplus electricity from renewable energies is to be used as an energy source. In this way, we want to make an essential contribution to climate protection and contribute to the success of the energy transition.
In the first and second funding phases, technical solutions were developed and tested in long-term experiments in the pilot plant, which can then be scaled up.
Great importance is attached to recycling in the steel industry – and has been for a long time: Blast furnace gas was first used to generate energy for the steel mill at the end of the 19th century. Now for the first time, Carbon2Chem® is using the gases from the steelmaking process as a raw material for chemical production. Among other things this reduces CO2 emissions.
Europe’s integrated iron and steel mills now convert all their process gases. Most of them are used in power plants to generate electricity. Many mills are now autonomous and rarely have to buy in electricity.
An integrated iron and steel mill comprises coke plant, blast furnace, BOF melt shop, auxiliary equipment and processing facilities. Steel mill gases are generated in the blast furnace, the BOF melt shop and the coke plant.
In the coke plant, coke is produced by heating coal in the absence of air. Coke is harder than coal and porous, facilitating the flow of hot air in the blast furnace and stabilizing the column it forms with the iron ore.
From iron to steel
In the blast furnace iron is produced from iron ore at around 1,500 degrees Celsius. Iron is still too brittle to be made into e.g. automotive sheet, so it must first be converted into steel. This transformation takes place in the BOF melt shop. The carbon content of the iron is reduced through the addition of oxygen until steel is produced.
With Carbon2Chem® we not only want to use steel mill gases to generate electricity, we also want to produce valuable chemicals from them. The advantage is that the share of blast furnace gases used to produce chemicals will no longer be burned off and less carbon dioxide (CO2) will be generated. The carbon – including the CO2 – is used for a second time in chemical production.
Among other things, steel mill gas contains hydrogen and nitrogen. It also includes large quantities of carbon in the form of carbon monoxide (CO), carbon dioxide (CO2) and methane (CH4). Carbon, hydrogen and nitrogen form the basis for numerous chemical products.
Today, steel mill gas consists of 44 percent nitrogen, 23 percent carbon monoxide, 21 percent carbon dioxide, 10 percent hydrogen and two percent methane. In the future, the switch to direct reduction will change the composition and make it even more attractive for chemical use.
Nitrogen and hydrogen can be used to make ammonia. In turn, ammonia can be used to make mineral fertilizer – the prerequisite for feeding the majority of the world’s population. The so-called Haber-Bosch process used for this was developed in 1910. The chemical reaction takes place at a pressure of 200 to 300 bar and a temperature of 350 to 450 degrees Celsius. A catalyst accelerates the conversion.
Carbon, i.e. carbon monoxide and carbon dioxide, and hydrogen form the basis for methanol. Methanol can be used to power cars and aircraft or make other chemicals. Here again, the manufacturing process was developed in the early 20th century.
Methanol is one of the most widely produced organic chemicals. It is now mainly produced in a process involving pressures of 50 to 100 bar and temperatures of 200 to 300 degrees Celsius. Metallic catalysts are also used here to accelerate the chemical reaction. Most of the carbon needed to produce methanol is currently obtained from fossil fuels such as natural gas.
Carbon is a basic material for chemistry. The same is true of carbon dioxide. We can use a large amount of the CO2 from steelmaking in chemical production, meaning that the harmful gas is no longer emitted into the air.
Today, carbon dioxide is an unavoidable byproduct of pig iron production. In chemical terms, iron ore – the starting material for steel – is an iron oxide, i.e. a compound of iron and oxygen. To obtain iron from it, the two components must be separated. Carbon is needed to achieve this: It combines with the oxygen to form carbon monoxide and ultimately carbon dioxide, leaving the iron.
Multiple use of carbon
State-of-the-art blast furnaces work at the so-called thermodynamic limit, meaning that no further reduction of the amount of carbon used in pig iron production is possible without radical technological changes. That’s why with Carbon2Chem® we have developed a strategy that enables the multiple use of carbon.
After all, carbon – and thus also CO2 – is not only the fundamental building block of all life on earth, it is also the most important raw material in organic chemistry. That’s why we recycle CO2 in ammonia and methanol production. This differentiates our solution from so-called CCS concepts (Carbon Capture and Storage) in which CO2 is separated and then stored. The advantage of Carbon2Chem®: The process is cost-effective and requires no storage facilities for CO2. And it saves fossil fuels.
New technologies for the direct reduction of iron, in which hydrogen is used instead of carbon to reduce iron, are on the rise in Europe's steel production and will become established in the long term. The advantages of this type of steel production are obvious: low CO2 emissions with consistent quality and minimal intervention in the production networks. For Carbon2Chem®, this means a changing composition of metallurgical gases over the transformation path of the steel industry up to gas compositions at the end of the transformation that cannot yet be fully predicted. However, it is already certain today that a certain amount of carbon will remain in the production process and therefore also carbon-containing gases that can be used for the transformation.
With Carbon2Chem® we need hydrogen for the chemical processes involved in ammonia and methanol production. While the hydrogen already present in the steel mill gases is sufficient for ammonia synthesis, we need to produce additional hydrogen to make methanol.
Water electrolysis with green electricity
Producing hydrogen is an energy-intensive process. Hydrogen is produced by water electrolysis, which uses electricity to separate water into oxygen and hydrogen. We want to obtain the required electricity from renewable energies – whenever there is a surplus and the cost of green electricity is particularly low. So here again Carbon2Chem® displays an excellent carbon footprint.
One challenge of the transition to renewables is the sharply fluctuating availability of electricity from wind and solar power set against the need for a reliable energy supply. By using surplus electricity for the Carbon2Chem® process we are helping to keep the electricity supply in balance.
Electricity surpluses are still a challenge for our energy system. Surplus electricity often has to be diverted to neighboring countries for a fee. Carbon2Chem® offers the opportunity to use large-scale industrial facilities like steel mills and chemical plants as energy buffers.
We then activate our chemical production when large quantities of energy are available at low prices. In this situation the steel mill gas streams are split so that part is available for steel production requirements and part for chemical production using renewables. This strategy is known as load management or demand side management. This helps stabilize the power grid and contributes toward the energy transition.
The technical challenges
However, this is also where the major technical challenges of our development project can be found. Although the chemical processes for producing ammonia and methanol are well-established, the plants which use these processes are designed for continuous operation around the clock, 365 days a year. Fluctuations in operations and changes in temperatures and pressures damage core components of these plants.
Above all, the typical catalysts are sensitive to changes in operating conditions and gas composition. So one of the central development tasks for Carbon2Chem® was to find catalysts which can cope with operating fluctuations without any impact on performance.
The project involves partners from the chemical, energy and steel industries, creating an entirely new collaboration between key national industries.
The chemical, steel and electricity industries employ more than half a million people in Germany and generate total sales of around €264 billion.
Germany is the biggest steel producer in the EU and the seventh biggest worldwide. As a basic industry, the steel sector is of great importance for value chains in Germany. The many innovations from this branch of industry and its close integration with other sectors contribute to the success of e.g. the automotive and machinery industries.
Indispensable in all areas of life
After the automotive, machinery and electrical industries, the chemical sector is the fourth largest employer in Germany. Chemical products can be found in all areas of day-to-day life and are used in 90% of all day-to-day products.
A secure supply of energy – above all electricity – at all times is of key importance for economic growth and employment. Germany is a world leader here. In the energy industry as a whole, the electricity sector is the most important. The energy industry drives innovations in the areas of energy generation, conversion, supply and use.
Contact
Mark Stagge
Head of Public & Media Relations, thyssenkrupp Steel Europe AG
