Going green with hydrogen

The water in the inspection glass churns furiously. Gas bubbles roar past. The electrolysis plant at voestalpine’s steel works in Linz is running at full speed. In large electrolytic cells, an electric current breaks water down into its components, oxygen and hydrogen.

Voestalpine is less concerned, however, about the oxygen passing through the inspection glass. What mainly interests the steel and technology company is the up to 1,200 cubic meters of hydrogen that the cells generate each hour. In the long term, hydrogen could be used to manufacture steel with a much lower level of CO₂ emissions than now. The electrolysis technology installed by Siemens Energy is ideal for the task: It’s flexible enough to operate entirely using green power from renewable sources, so it can deliver 100-percent green hydrogen.

EU climate targets are putting the European steel industry under huge pressure to reduce its CO₂ emissions. Green hydrogen is a highly promising future option for achieving large-scale decarbonization in energy-intensive sectors like the steel industry. According to the World Steel Association, every metric ton of raw steel produced in 2018 also generated 1.85 metric tons of CO₂. Green hydrogen could significantly reduce this figure if iron could be obtained from ore using hydrogen in direct reduction plants, instead of coke and coal in blast furnaces. The sponge iron generated in this way can then be smelted into steel using electric arc furnaces. Converting the entire process to green hydrogen and electric arc furnaces running on green power would reduce the CO₂ emissions of the Linz steel works by over 80 percent in the long term.

The green hydrogen pilot plant at the voestalpine steel plant in Linz, Austria, has been in operation since November 2019. The PEM electrolyzer has a connected load of 6 MW.

The electrolysis plant produces up to 1,200 m³ of green hydrogen per hour. The oxygen produced in the process is passed through a inspection glass.

Electrolysis of water involves placing two electrodes in water and applying a DC voltage to them. This will cause hydrogen to form at the negative and oxygen at the positive electrode. The alkaline electrolysis systems most commonly used today require an electrolyte to be added to the water, which in its pure form is a poor conductor of electricity.

With the Silyzer 300 system installed in Linz, however, this is not necessary. It’s equipped with proton exchange membranes (PEM) and is therefore able to work with no additives in the water. In PEM electrolysis, electrons are drawn directly from the water molecules at the positive electrode, leaving positively charged hydrogen ions (protons) and oxygen behind. The membrane is permeable only to protons, which pass through it to the negative electrode where they combine with electrons to form hydrogen. The oxygen, which cannot pass through the membrane, remains where it was formed.

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We have set ourselves clear goals for taking direct avoidance of CO2 emissions in steel production a step further in the next few years. The world’s largest hydrogen pilot plant at our location in Linz represents an important step in driving forward research for this technology transformation.

The EU-funded H2FUTURE project brings together energy suppliers, the steel industry, technology providers and research partners, all working hand in hand on the future of energy. The partners voestalpine, VERBUND, Siemens Energy, Austrian Power Grid, K1-MET and TNO are researching into the industrial production of green hydrogen as a means of replacing fossil fuels in steel production over the long term. Furthermore, the project, which receives EUR 18 million in EU funding, will investigate the potential to provide network services, and potentially compensate for fluctuations in the power grid.

Compared to the alkaline version, there are more differences to PEM electrolysis than just the fact that it works with unadulterated water. It also doesn’t require preheating, so it can respond more quickly to changes in current. Quick starts under full load are no problem with a PEM electrolysis system. It’s also capable of operating in a very low partial load range. That means a plant like the one in Linz can consistently generate green hydrogen even with a fluctuating supply of green power.

Green hydrogen is not just of interest to steel works. Other branches of industry that require large volumes of hydrogen as a process gas, or could use it as a fuel, could also drastically reduce CO₂ emissions at their plants in this way. Refineries, chemical firms, and glass and fertilizer manufacturers are obvious examples of entities that could benefit from green hydrogen to improve their green future prospects.

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