HYDROGEN: THE KEY TO A ZERO-EMISSION FUTURE?

Mr. Leitsch, how important is hydrogen for industry, and what is the significance of the different colors—gray, blue, and green?

Michael Leitsch: Hydrogen has been used since the early 20th century as a process gas for producing ammonia via the Haber-Bosch process, and today it plays a crucial role in three specific industries: as a raw material in the chemical industry (mainly for producing methanol and ammonia), in refineries for fuel desulfurization, and in hydrocracking processes, as well as in direct reduction plants for steel production. Since hydrogen occurs in nature in a bonded form, it must be produced using energy. Depending on the production process, hydrogen is categorized as gray, blue, or green.

Gray hydrogen is produced from natural gas through steam reforming, which results in corresponding CO2 emissions. Currently, 60% to 70% of hydrogen is produced from natural gas. In the case of blue hydrogen, the CO2 generated is captured and either reused or stored, meaning it doesn’t escape into the atmosphere. Additionally, hydrogen can also be produced by water electrolysis, an electrochemical process. If the electricity used for this comes from renewable energy sources, it is referred to as green hydrogen, which is CO2-neutral.

Hydrogen is being traded as an indispensable resource for climate-neutral industries. How does it contribute to reducing CO2 emissions?

Michael Leitsch: Currently, most of the hydrogen produced is derived from fossil fuels. If gray hydrogen were replaced with green hydrogen, CO2 emissions in the industry could be significantly reduced. At the same time, new opportunities are emerging, such as in power generation. Here, hydrogen as a storage medium and energy carrier could allow for an increased share and availability of renewable energy. Other sectors include transportation, especially long-haul and heavy-duty transport, as well as rail, maritime, and aviation transportation. Additionally, hydrogen has applications in heating and thermal processing, particularly in the metalworking industry. These are all promising areas of application, each of which could make a significant contribution to achieving future climate goals.

How optimistic are you about the development of green hydrogen?

Michael Leitsch: We see green hydrogen as a crucial market for the future. Avoiding CO2 is becoming increasingly important. Additionally, the generation of electricity from renewable sources will continue to expand. Worldwide, more and more governments are promoting research, innovation, and product development with national hydrogen strategies, accompanied by the corresponding scaling up of electrolysis plants. From this perspective, we find it very realistic that the green hydrogen market will grow even further. This assessment is also consistent with the feedback from our customers, whom we support in developing projects at various stages of planning. Hydrogen still plays a secondary role in the energy transition, but this could change soon.

As a rule, hydrogen must be compressed to a certain pressure after electrolysis to be used in subsequent processes. What specific features need to be taken into account?

Michael Leitsch: Hydrogen is the lightest naturally occurring element, which generally makes compression more challenging. Due to its very low energy density relative to flow (energy content per unit volume), large electrolyzers must also compress correspondingly large volumes, which impacts the scale and thus the investment costs, installation footprint, and other factors related to machinery. Additionally, hydrogen is highly reactive, meaning it is extremely flammable. Therefore, special attention must be given to the necessary explosion protection. The formation of combustible mixtures with atmospheric oxygen must be avoided at all costs. However, this also applies to other applications involving flammable or explosive gases, where AERZEN’s gas handling division has extensive experience.

Where do you see the advantages of using screw compressors compared to other compression technologies?

Michael Leitsch: Screw compressors combine the key advantages of piston and turbo compressors. Due to the displacement principle, they are also suitable for compressing very light gases—unlike turbo compressors, which can only achieve very small pressure differences per stage with gases of low molecular weight. Additionally, screw compressors are rotary machines, and compared to piston compressors, they have fewer moving parts, require significantly less space, and greatly reduce maintenance efforts and pulsation compensation in pipelines. Another important advantage is the ability to inject water into the compression chamber. On one hand, this reduces compression heat; on the other hand, water can act as a seal between the oil chamber and the gas, for example, when using water-flushed mechanical seals. Since hydrogen exits the electrolysis process in a water-saturated state, water injection is not an issue.