The National Hydrogen Strategy (NWS) adopted by the German Federal Government in 2020 is an indispensable step towards energy system transformation. It offers great potential for the German industry to maintain its strong "Made in Germany" position globally and to expand it by playing a major role in the development of these future technologies. According to the German government's target, German greenhouse gas emissions are to be reduced by 80 to 95 percent by 2050. Green hydrogen for clean energy supply is becoming the central key component of the National Hydrogen Strategy: it is produced in a climate-neutral way on the base of renewable energies, e.g. through electrolysis.
The rapid development of modern energy systems also places new demands on the pump technology used. In the production, storage and use of hydrogen, EDUR-centrifugal pumps offer some decisive product advantages that ensure reliable and efficient operation of the plants. In particular, the possibility of gas enrichment of liquids as well as the safe delivery of gas saturated liquids with the help of multiphase pumps holds great potential in the planning and development of modern energy systems. Other applications in the field of power to gas, such as methanisation, also use the advantages of multiphase pumps to dissolve hydrogen, for example.
For the production of hydrogen, electrolysis has been established as a proven process. To obtain hydrogen by electrolysis EDUR-pumps can be used in both alkaline and PEM electrolysis. The processes of electrolysis differ mainly in the medium conveyed to the stack (alkaline medium or high-purity water) and in the system pressure in which the electrolysis takes place. Both systems have their legitimacy and their own advantages and disadvantages: A high system pressure of about 30 to 40 bar reduces the effort required to further increase the pressure of the gas. A lower system pressure, on the other hand, is easier regarding the requirements of the components and is therefore usually less expensive. In both systems, however, the handling task of the pumps is similar: After gas separation, they convey the still saturated medium safely back to the stack by heat exchangers, where it is loaded with free gas again. Possible shares of residual gas or outgassing resulting from the pressure reduction in front of the pump are safely controlled and conveyed.
Figure 1: Integration of EDUR-pumps in hydrogen production by electrolysis
The medium in the stack is continuously in contact with the generated gas, which means that this liquid is 100% saturated with it. In this state of equilibrium, the smallest pressure reductions inevitably lead to outgassing. These can occur either due to installation parts such as narrow pipe bends, filters and tear-off edges in vessels or in narrow pipe sections with higher flow velocities. The saturated solution is outgassed in the suction nozzle of the pump at the latest.
EDUR pumps are usually configured with open impellers, which reliably control gas components in interaction with the ring casing. They are able to quickly disperse and release the gas bubbles due to strong shear forces of the open impellers. The pumps have also been used in flotation systems for decades, where gas contents of up to 30 percent have to be conveyed. EDUR is working on improving the special impeller technology for higher capacities. In accordance with the system pressure in electrolysis, the pumps can currently be used in pressure stages up to 40 bar.
The main advantages of EDUR-centrifugal pumps, apart from the gas conveying properties, are the low NPSH values and the high energy efficiency, e.g. through the use of lossless containment shells when using magnetic couplings. Furthermore, radial forces in the pumps are balanced by the ring housing used. Additionally, the EDUR-typical open impellers do not transmit axial forces to the shaft, so that the bearing in the magnetic coupling is only slightly loaded. Upon customer request, the pumps are designed according to ATEX.
To store or transport hydrogen, compounds with either ammonia or "liquid organic hydrogen carriers" (LOHC) are suitable. With both of these media, hydrogen can be transported to desired destinations without the use of high-pressure tanks.
Up to 600 cubic meters of hydrogen can be dissolved in one cubic meter of LOHC. For the conveyance of LOHC and ammonia, EDUR pumps can also be used. While LOHC can be transported without any risk, pumps for conveying ammonia (NH3) must be executed with a magnetic coupling. In this case, it is necessary that the pumps are hermetically sealed, as the pumped medium is hazardous to human health.
Due to their ability of handling gas contents, EDUR multiphase pumps also play a significant role in methanation for the storage of hydrogen. In this process, the hydrogen obtained is transferred into systems containing appropriate bacterial strains. By adding hydrogen, carbon dioxide (CO2) and nutrients, the gases are converted to methane (CH4). Afterwards, the synthetically produced methane can be completely fed into the natural gas grid. This is available throughout Europe and has enough capacity to store the energy source.
Further applications for the use of green hydrogen can be found e.g. in the steel industry. In this case, hydrogen is used for the direct reduction of iron ore. The amount of coal and coke required for iron ore reduction in the blast furnace can be replaced by green hydrogen. As a result, up to 95% of CO2 emissions can be reduced in the long term. The hydrogen is produced on site via electrolysis. EDUR pumps are also used in the production of artificial fuels such as aviation gasoline.
There is no standard pump solution with EDUR. Every single pump is individually selected, planned and subsequently manufactured according to the application and requirements. EDUR thus offers planners, designers and operators of modern energy storage systems unique pump solutions, optimally designed for their needs.
Well-known manufacturers of electrolysers already rely on EDUR-pump technology. The pumps from Northern Germany, for example, are already being used successfully in some serial production plants. The electrolyzers are partially pressureless, but the trend is towards higher system pressures to reduce the post-compression of the gas. Others still prefer the normal pressure range around PN 10. In whatever direction the technology will develop in the future: EDUR offers the right pump solution for both process requirements.