Dirostahl boss in the climate lab: No business case for abandoning gas yet

Diro steel looks back on a company tradition spanning more than 400 years. In the 16th century, the heavy hammers of the Remscheid steel forge were powered by water power. Over time, coal and oil followed. Dirostahl now heats the workpieces, which weigh several tons, to 1200 degrees Celsius with natural gas so that they can be hammered into shape and used as gears in wind turbines. “We are certainly familiar with the idea of ​​a fuel change,” says Roman Diederichs. Nevertheless, the Dirostahl boss is at a loss. Because now a clean natural gas alternative is required, preferably green hydrogen. So far, this has only worked in the laboratory; in a real forge furnace “it is difficult,” says Diederichs in ntv’s “Climate Laboratory.” And expensive: “If you are competing internationally, these additional costs cause considerable problems.” Problems that could lead to wind turbine gearboxes soon coming from abroad – and continuing to work with gas.

ntv.de: How high is the energy consumption of Dirostahl?

Roman Diederichs: That depends heavily on capacity utilization, but we are talking about 15 gigawatt hours (GWh) of electricity and between 150 and 200 gigawatt hours of natural gas. That corresponds to the consumption of 10,000 households per year.

And now you need an alternative to natural gas.

As of now, forge furnaces are powered by natural gas. All sorts of companies in this industry are thinking about what alternative heating media could be. Some together, some individually. When the material comes out of the furnace, it must have a temperature of 1200 degrees so that it can be formed. This is not possible with every medium.

Can such high temperatures be achieved with electricity?

That depends on the dimensions of the workpieces. Automotive suppliers usually work with drop forging to produce lightweight parts in large series. The weight starts in the gram range and ends in the kilo range. These parts can be heated inductively, i.e. with electricity. But that only works up to a cross-section of around 240 millimeters. That’s about the width of a finger, something you can grasp with your hand. Larger parts can no longer be heated inductively in a reasonable amount of time with a reasonable amount of energy.

The parts you produce for the wind turbines are probably among the larger ones?

Yes, we work with an open-die forge and generally process medium-sized parts that weigh between 500 kilograms and 8 tons. The total range is from 50 to 35,000 kilograms. Often these are seamless rolled rings: first you have to shape the pre-product to create a perforated disk. This is then rolled further. Once you have this process under control, you can work with one heat or with the residual heat. If things aren’t going so well, you have to heat the piece twice.

And at the moment this is only possible with gas?

In these dimensions, yes. Of course, you can think about other technologies such as resistance heating, hydrogen or hot air. Startups, but also established companies, have various ideas. But they all have their advantages and disadvantages.

The alternative that is almost always mentioned when this question is asked is green hydrogen. Chancellor Olaf Scholz and Federal Minister of Economics Robert Habeck have traveled halfway around the world to conclude supply contracts. That doesn’t work?

You have to look at where it comes from. If you produce green hydrogen locally with green electricity, you have a massive cost disadvantage: compared to natural gas, green electricity is already relatively expensive. You then have to double this price again to get to the price of hydrogen. That is what is being rumored. It will also show whether an electrolyzer is profitable if it does not run 24 hours a day. Likewise, what import quantities of green hydrogen will ultimately reach the world market and under what conditions.

But technically would it work? You can pump green hydrogen into the same machines instead of gas? You shake your head…

There are many studies on the use of hydrogen in burners. They attempt to generate process heat using natural gas-hydrogen mixtures or by using pure hydrogen. It works on a laboratory scale – with some technical restrictions; on a large-scale scale it has so far been difficult. There are various experiments by different institutions, but also companies. You have to look at what risks and side effects the use of hydrogen has. Many components are hydrogen-capable or should be, but the approvals only allow 20 percent hydrogen by volume in natural gas. There are also technical parameters such as the adiabatic flame temperature…

… adiabatic flame temperature?

Yes (laughs)Natural gas burns at a flame temperature of around 1900 degrees, hydrogen at 2100 to 2200 degrees. This is not a big problem in the furnace. However, nitrogen in the furnace atmosphere reacts to form nitrogen oxides. At a higher adiabatic flame temperature, nitrogen formation increases massively. So you have to be careful not to produce nitrogen as a byproduct in the exhaust gas in significantly higher concentrations.

Can the nitrogen oxides be filtered out?

Once they have formed, things get difficult. That’s why you have to keep the thermal nitrogen oxide formation under control, which can be done via burner control and temperature control. So there are a few parameters to consider.

And that’s expensive?

It depends. If you work with pure oxygen, you have a more expensive feedstock than if you work with combustion air. This can also be preheated better. It’s a question of energy efficiency, and yes, if in doubt, you have to invest more money in burner technology.

But in principle, could the gas be replaced with green hydrogen?

If there is sufficient hydrogen and reliable supplies, I am sure we can get the technology under control, although some open issues such as nitrogen oxide formation will need to be addressed. Even then, however, the significant economic problems remain.

What is your current status? Are you still using green hydrogen? Are you already experimenting? Are you trying to get some for Dirostahl?

Of course, we are keeping an eye on the issue. We have also applied for a project to get these parameters under control, so that we would be ready if there were enough hydrogen. From an economic point of view, you have to consider that hydrogen currently costs about three to five times as much as natural gas. If you are in international competition – as we are with wind power products – These additional costs cause massive problems and even make production uneconomical.

Are there any plans at all as to how the hydrogen from Chile, Morocco or Oman would get to you in Remscheid? Do you need a pipeline?

There are various models. Whether there will actually be hydrogen production in Germany is beyond my horizon. At the moment we are assuming that a pipeline for the hydrogen supply must be available. This will be discussed in the Bergisches Land in the early 2030s.

That still needs to be built?

There are different models here too. It is being examined whether a natural gas pipeline can be converted and supplemented. It may also be that a new construction is required, but that is something the relevant suppliers must answer.

The Federal Ministry of Economics is working hard to cover the increased costs of the green steel industry and is providing a lot of funding. Isn’t that enough?

There are some programs that support such a transformation, but you have to see whether a medium-sized company can afford it. Thyssenkrupp has other options. You can’t subsidize everything that needs to be changed for 15 to 20 years. The budget will not be enough for that.

We have already experienced some transformations in the past decades or centuries. In the Bergisches Land there are many valleys and enough rain. In the past, the streams were dammed, water wheels built and the small forges and grinding mills were powered by water. Later, the hammers were powered by steam from coal, in the 1950s we switched to heavy oil and in the 1980s to natural gas. We are certainly familiar with the idea of ​​switching fuels. However, a positive business case is important for the changeover. There is currently none, rather noble goals. This makes it highly risky.

If the plans are implemented as they currently stand, will you end up no longer competitive?

This is a danger in energy-intensive industries if you actually back the wrong horse. Definitely. We have already lost the photovoltaic industry in Germany, and next we will certainly have to be vigilant in the wind power industry. We simply cannot afford to arbitrarily increase energy costs.

Clara Pfeffer and Christian Herrmann spoke with Roman Diederichs. The conversation has been shortened and edited for better comprehensibility. You can listen to the entire conversation in the “Klima-Labor” podcast.