As the hydrogen economy matures and production scales up, critical equipment like valves must evolve to ensure safe and optimized handling and transport
According to the Energy Transition Council, the overall share of fossil fuels is expected to decrease significantly by 2050 [1], paving the way for the widespread use of alternative energy sources, such as hydrogen. Many of hydrogen’s backers call it the perfect “green” alternative to traditional fossil fuels based on its ability to carry energy, along with the fact that, when used, its only emission is water vapor. This highlights the importance of hydrogen as a clean consumable fuel source (Figure 1) as the world transitions toward a more decarbonized future, with experts touting its massive potential for hard-to-abate sectors like heavy industry and long-haul transport.
FIGURE 1. As the hydrogen economy matures, there are many associated equipment that must evolve to meet production, handling and transport requirements
The capabilities and benefits of using hydrogen as a primary energy source have long been recognized by one significant industry: space exploration. Since humans began sending rockets into space, hydrogen has been combined with liquid oxygen to produce the exothermic reaction necessary to create the level of propulsion a rocket or space shuttle needs to break the bonds of the Earth’s atmosphere.
However, while hydrogen has established its bona fides as an energy source, mainstreaming it as a safe and reliable component in the world’s alternative fuel pool presents sizeable challenges with respect to production, safe storage and transport.
This article outlines these challenges and explains how control valves can help to ensure that large-scale hydrogen production or handling systems operate safely, reliably and efficiently.
Converting H2 from gas to liquid
The primary challenge in harnessing the potential of hydrogen as a fuel alternative is that it naturally exists in a gaseous state, which makes it more difficult to efficiently handle, transfer and store. However, once hydrogen has been converted into a liquid state, known as liquid hydrogen (LH2), it becomes more efficient to handle, transport and store. And while the large-scale production and long-distance transport of liquid hydrogen will be critical for applications in a hydrogen economy, the liquefication process for hydrogen is energy-intensive and requires specialized infrastructure.
Scottish chemist and physicist James Dewar is credited with developing the earliest methods for liquefying hydrogen in 1898. He achieved this through regenerative cooling combined with his invention, the vacuum flask (Figure 2), which later served as the basis for the modern Thermos mug. In Dewar’s experiment, the hydrogen gas was progressively cooled by its expansion, which in turn cooled additional incoming, warm hydrogen. This continually brought the temperature down while the vacuum flask maintained the new, cooler temperatures needed for conversion. Although Dewar pioneered this technique, and other methods have since followed, liquefying hydrogen is still not an easy or straightforward process like converting steam into liquid water.
FIGURE 2. The earliest liquefaction processes for gases like hydrogen and nitrogen took place in Dewar vacuum flasks, which are still used today in some industrial processes
To create LH2, hydrogen gas (H2) is first produced from feedstocks such as water or ammonia (NH3). Using water to produce LH2 involves using electrolysis to split the H2 from oxygen. The resulting gaseous H2 is then cooled and compressed in a liquefier plant. Once the liquid is condensed from the gaseous state, it is transferred to be stored in a vacuum-jacketed pressure vessel to await transport.
Due to its highly flammable nature, hydrogen must be handled with extreme care. For storage and transport, the gas is typically compressed to high pressures (up to 700 bars or 10,000 psig) or is held at cryogenic temperatures around –425°F (–254°C) and stored at pressures up to 100 psig (6.9 bars). One of the biggest challenges in handling hydrogen in its liquid form is that these extreme pressure and temperature parameters must be consistently maintained during storage and transportation. Otherwise, the LH2 will revert to its gaseous form, creating potential safety risks, as well as product loss.
As the benefits of using LH2 as a fuel have been verified and the technologies to manufacture it continue to be optimized, new companies focused on building hydrogen-liquefier plants have emerged worldwide and are steadily increasing their planned LH2 manufacturing capacity.
Larger LH2 production plants will be needed if, as some are predicting, LH2-powered heavy-duty vehicles are to become common in long-haul trucking and potentially buses, trains and ships — a realistic possibility given global decarbonization efforts.
Elevate LH2 with modern valves
To create LH2, gaseous hydrogen is pumped through a series of condensers, valves and compressors to achieve the required temperature and pressure described previously. The valves are critically important in the process, as they are used to control flow in both the LH2 production in the liquefier, as well as the transfer of the newly created LH2 to a delivery ship, barge or truck for its trip to the end-user, where it is dispensed for consumption.
For years, the preferred valve technology for the manufacturing and transportation of LH2 has been the extended-stem, vacuum-jacketed globe valve, available in either a standard T-pattern or a Y-pattern, which facilitates higher flowrates. The main benefit of this type of valve is that its design enables it to greatly reduce heat leaks, which can cause the LH2 to revert back to gaseous hydrogen.
However, recent engineering and design advancements have led to an improved variant of these globe valves, which have allowed for significant increases in size and pressure ratings.
Manufacturers have begun using larger globe valves that have been engineered for suitability in LH2 production, storage and transport, which solve some previous challenges and help make the conversion process more efficient. For example, larger valves address challenges by reducing heat ingress, enabling higher flowrates, minimizing fugitive emissions and withstanding thousands of cryogenic cycles with reduced downtime.
Such globe valves are available in manual and actuated versions, with either bellows-sealed or non-bellows designs. While vacuum-jacketing is necessary for LH2 applications, non-jacketed versions are also available.
Non-jacketed globe valves can be used for services that do not require vacuum jacketing or that can be jacketed at a later stage of construction.
As LH2 production plants become larger, their operators are starting to request greater flowrates and higher pressures, which exceed the original standards of 300 psig (21 bars). This has led to discussions within the valve industry about the types of valve designs that can handle these new production and flow parameters. As of now, larger globe valves are a likely candidate, but conversations continue regarding different valve styles (such as gate, butterfly, ball and so on) and whether they can improve upon the performance of a globe valve, but at the higher flowrates and elevated pressures that are becoming increasingly common.
In anticipation of the increasing sizes of LH2 production plants, larger globe valves are now being introduced into the market in both manual and actuated bellows-sealed designs, which support higher flowrate demands. Design work has also started to produce even larger valves that can safely accommodate even greater pressures and flow rates as LH2 production continues to ramp up.
A crucial factor in the growth of LH2 production is the design improvements of globe valves. Globe valves have historically been the go-to technology for producing and handling cryogenic liquids. Now, engineering improvements lend credence to the idea that modern globe valves can safely handle the demands of higher flowrates and pressures that are expected to be common in the LH2 ecosystem.
Although some challenges remain for production, storage, and transportation, utilizing modern globe valves provides producers with the necessary solution to handle larger flowrates and pressures as production continues to meet increased demands. ■
Edited by Mary Page Bailey
Reference
1. ETC, Fossil Fuels in Transition: Committing to the phase-down of all fossil fuels, Nov. 2023.
Author
Mike Fink is a professional engineer (P.E.) and currently is the director – Sales & Business Development for OPW Clean Energy Solutions and ACME® Cryogenics (Email: michael.fink@acmecryo.com; Phone (610) 791-7909, ext. 316). OPW Clean Energy Solutions was formed in December 2021 when OPW acquired both ACME Cryogenics and RegO® Products. Fink holds a B.S. degree in mechanical engineering from Penn State University.