The global hydrogen transition

Hydrogen is one of the most talked about – and fastest growing – clean sources of fuel, and it is leading the way in the energy transition. However, while hydrogen is growing at an incredible pace as a fuel, it is not a new resource. Hydrogen production originally started more than a century ago, and has been supported for decades by Baker Hughes’ valves in the refining industry, primarily as a reactant feed to treat unrefined oil and gas products. Many of today’s wells are pulling heavy crude oil, which contains a high percentage of sulfur. However, the end customer markets are demanding improved diesel fuel with lower sulfur content. By virtue of this conflict of supply and demand, new refinery improvements have soared over recent decades, with expansions and new greenfield projects adding hydrotreating and hydrocracking units that inject hydrogen into the process to support this low sulfur content conversion. In addition, many refineries now include catalytic reforming – a chemical process used to create high octane products that generate hydrogen as a byproduct. As global demand for hydrogen increases, these proven and cost-effective methods of hydrogen production should remain a constant for many years to come.

Decades of process improvement

The oldest, but still most common hydrogen production method, is steam reforming of natural gas. This moderate pressure production technology has been around for generations and has led to many developments and improvements in hydrogen processing, including enhanced specifications such as the National Association of Corrosion Engineers (NACE), to address hydrogen embrittlement. As hydrogen has an incredibly low molecular weight, its tiny molecules can severely attack materials by easily penetrating voids, impacting castings, polymer diaphragms and other porous material surfaces if the materials are not properly specified. Further, as temperature increases, these molecules will diffuse into the steel at an even faster rate, combining with the carbon within the steel to form methane, leading to accelerated wear from corrosion. NACE hardness and radiographic quality specifications have emerged over the years to address embrittlement and corrosion from hydrogen.

Within the steam methane reformer (SMR) there are several harsh applications that require severe service valve solutions. One example is when the process condensate lines with carbon dioxide (CO2), which creates a highly-corrosive carbonic acid requiring exotic trim materials depending on the level of concentration. Other applications such as the feed gas compressor anti-surge and recycle valves, and the carbon monoxide (CO) shift converter start-up vent valves, are examples of high-pressure reduction applications where rapid gas expansion will lead to high velocity and vibration-induced damage if not properly designed with multi-stage low noise trim.

The pressure swing adsorption (PSA) plants add enhanced hydrogen purification, bringing the level to 99.99% purity – ideal for transportation and other energy uses. The greatest challenge within the PSA units is reliability due to continuous cycling, where valves are expected to exceed more than 100 000 cycles. Thorough laboratory validation is essential to ensure that the product is fit for the life cycle within these units.

Rathishkumar Sukumar and Raghavendra Mahalingam, Baker Hughes, discuss the role that specialty valves will play in delivering affordable hydrogen energy in the quest for net zero emissions.

Coal gasification, which is mostly found in countries with scarce supply of natural oil and gas resources, is another source of hydrogen production, and has several unique valve application challenges that are critical to keeping the plant running. The gasifier units produce a synthesis gas, which is processed through a series of scrubbers to remove ash or slag from the coal. This black water fluid includes highly-erosive entrained solids, which require sweep angle letdown valves coupled with tungsten carbide trim to avoid rapid failure and unit shutdown. Baker Hughes has developed proprietary, dual grade materials using additive manufacturing to blend ductile properties of stainless steel with the erosion resistance of a hardened tungsten carbide to create a custom material for longer lasting service.

Other challenging applications are the air separation units (ASU) that operate under cryogenic temperatures to separate oxygen from air. As oxygen is highly combustible, care must be taken to select materials, as having low spark tendencies, such as Alloy 625 or Monel 400/K500, followed by the removal of foreign particles, could lead to ignition. UV cleaning in a certified clean room is absolutely required to ensure safety of the plant and operators.

The transition to blue hydrogen

The adoption and transition of hydrogen as a primary fuel source is largely limited to the economic challenges when competing against gasoline. The traditional hydrocarbon-based processes remain the most efficient and cost-effective methods of hydrogen production, however their production generates CO2. As such, they are not considered a truly clean fuel source.

The use of carbon capture technologies followed by geosequestration is required to transition these processes to a carbon-free ecosystem. The capture of CO2 emissions is of critical strategic importance for sustainable large-scale production of hydrogen from natural gas or coal, without increasing greenhouse gas emissions. Present day analysis shows that producing blue hydrogen with carbon capture and sequestration can be an economical option to match the price range of gasoline or diesel fuels. However, carbon credits from government policies are still essential to offset this balance. The advancement of carbon capture technology in both greenfield construction and the retrofitting of existing assets is critical to delivering CO2 emissions reductions needed to meet global 2050 net zero emissions targets.

Present day carbon capture technologies are either amine-based or novel salt-based absorptions that rely on commodity chemicals. Baker Hughes currently has a licensing agreement in place that leverages SRI International’s Mixed-Salt Process (MSP) for CO2 capture with benefits of a low-carbon manufacturing footprint, reduced energy consumption and greater efficiency. The technology also differentiates itself from other amine-based carbon capture technologies by negligible solvent-degradation, reduced steam and water use, and low reboiler duty for solvent regeneration, and seems more promising for the future than conventional amine-based processes.

The captured CO2 is compressed (>130 bar) before delivery to storage sites, such as depleted oil reservoirs, or may be used for an enhanced oil recovery process. Injection pressures may exceed what is noted above, due to the fact that voids in oilwells gradually fill as time progresses. Compressor anti-surge recycle valves for such high-pressure drops expose the potential for CO2 icing, due to the Joule-Thomson effect, inside the active trim pressure drop stages. Multi-stage or multi-path trim designs may be needed to handle these issues in order to avoid large single step drops that can fall below the critical temperature limits.

Figure 1. The hydrogen liquefaction and transportation process.

Liquefaction and transportation

Traditional refinery production of hydrogen has often led to onsite consumption to satisfy local needs. The increased demand for this clean fuel is driving a greater need for the transportation of gas through pipelines or liquefaction of the gas followed by condensed product transportation using portable vessels such as tankers. Pipeline transportation remains attractive over long distances within a continent, and more than 4000 km of hydrogen pipeline exists worldwide today (2000+ km in the US alone). Yet even with this benefit of existing infrastructure, there remains an abundance of challenges in transporting this highly-volatile fluid.

First, the explosive nature of hydrogen must always be considered. Safety measures must be taken, and even more so when the fluid is compressed or heated, as this may lead to violent combustion or explosion. After proper safety measures are in place, additional factors must be considered, such as pipeline material selection. Hydrogen will degrade mechanical properties of most metals and leaks three times faster than natural gas. Hydrogen blending with natural gas is an alternative method to change the chemistry for transportation and reduce degradation rates. For these pipeline services, rotary valves are commonly used for isolation and control. When the hydrogen percentage of the fluid is high, the standard valve seals made from materials such as viton, nitrile rubber (NBR) or neoprene rubber will have high permeation and may later be at risk of explosive decompression (ED). Under pressure, the hydrogen atom can permeate through elastomer materials, and upon release of the pressure it can rapidly escape and cause ED. For these applications, ED-resistant materials are required to prevent a catastrophic failure.

Hydrogen liquefaction is one of the most significant and challenging processes in the entire transportation system, but it does enable more range for cross-ocean transportation by tanker. Storing hydrogen as a liquid for compact

transportation requires cryogenic temperature reduction to below -253°C (-423°F).

The use of liquid hydrogen originally started in the space industries, and it has been used as a fuel for several decades. For over 40 years, Baker Hughes has supplied cryogenic control valves for liquid hydrogen service, especially for the bench testing of cryogenic engines. The company’s long-standing relationship with the cryogenic industry is based on the use of a single-seated valve made from specially selected materials, with the packing separated from bonnet by means of an extension.

To simplify the problems of control and installations in liquid hydrogen application, valves are specially made and must meet the following industrial requirements: n Minimum material (to reduce inflow of heat by conduction) in the cold zone. n Quick and easy access to the seat area, body and plug, without having to remove the insulation located inside the cold box. n Live-load packing located remotely from the cold zone with fugitive emission standards. n Bonnet (and gasket seal) away from the cryogen cold zone to prevent any leakage into the insulated zone. n Simple assembly and ease of maintenance.

Figure 2. The Masoneilan 41005 Series is ideal for high pressure reduction, large temperature variations and cryogenic service, and is available up to 30 in. in size.

The future of green hydrogen

Today’s ongoing race is to establish a truly clean and cost-effective process to produce hydrogen through electrolysis of water. The benefit of this process is that it only produces hydrogen and oxygen, without any CO2 or methane byproducts. However, generating large volumes of hydrogen through electrolysis requires large amounts of power, which currently increases the cost of the production dramatically compared to traditional hydrocarbon-based methods.

Hydrogen production powered by renewable energy sources, such as wind or solar energy, would truly be the cleanest option available without any trace back to carbon-based output, but this currently comes at a high cost, requiring effective government subsidisation.

Present prominent electrolysis technologies use either liquid alkaline electrolyte bases or membrane technologies such as a proton exchange membrane (PEM) or solid oxide electrolysis (SOE). Despite their simplicity, these electrolysis technologies consume a large amount of power and remain very costly and uncompetitive compared to alternative methods. Typically, within moderate sized electrolysis units (PEM cells), there are approximately 100 control valves on various systems, including process water, cooling water, hydrogen purification, oxygen purification, nitrogen purging, and many others.

Alternatively, there is the high temperature electrolysis process, where heat from industrial processes, such as in a nuclear reactor, can be used to improve the efficiency of electrolysis to produce hydrogen. By increasing the temperature of the water using super-heated steam, the decomposition potential (voltage) of water is decreased. As such, less electricity is required to split it into hydrogen and oxygen, reducing the total energy required.

The current trade off for all the cases is the balance between cost and carbon-based output.

Conclusion

Though the processes for production and use of hydrogen are not something new, the global need for clean energy is growing at an unprecedented rate. The energy transition is driving the need for use of hydrogen as a cleaner fuel for vehicles and power generation, in turn driving an increased demand for hydrogen specialty valves and application-based knowledge. In petroleum refining applications, NACE standards address material selections, but new hydrogen designs within the industry still have no such standard for material selection. A considerable amount of experience is needed in this space to specify valve solutions to materials. For several decades, Baker Hughes has supplied valves for standard hydrogen applications in process industries and to the extreme cryogenic application in the aerospace industry. Today, the company continues to charter for innovation to bring energy forward, making it safer, cleaner and more efficient for people and the planet.