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.

Steel mill gas comprises 44% nitrogen, 23% carbon monoxide, 21% carbon dioxide, 10% hydrogen and 2% methane.

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 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.

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.

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^® is 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.