How do coatings contribute to advances in the hydrogen economy? Read on to discover how coatings are used in the manufacture and use of hydrogen power.
Climate change and a focus on cleaner energy are driving innovation in hydrogen powered vehicles, as well as in hydrogen production and transport. In this blog we'll discuss how SilcoTek® coatings contribute to making hydrogen a viable energy source for transportation.
In this blog post you will learn:
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Hydrogen (H2) can be found in many compounds and materials on Earth. It's quite common and literally falls from the sky in water (H2O). Unfortunately pure hydrogen is virtually non existent on Earth. H2 combines relatively easily with other elements but pure H2 can be found in only small amounts in our atmosphere. In order to produce large quantities of hydrogen, hydrogen producers are forced to extract H2 from compounds that are hydrogen rich and relatively easy to process.
Hydrogen production can be broken down into 4 basic processes.
Natural gas reforming is the predominant source of hydrogen production. Other sources of hydrogen production come from oil, coal, and water, but the primary hydrogen source currently comes from natural gas reforming. To help understand how coatings can contribute to hydrogen use and production, let's briefly review the hydrogen reforming process.
Figure 1: Diagram of a basic hydrogen production system. ("Hydrogen Fuel Quality Specifications for Polymer Electrolyte Fuel Cells in Road Vehicles", US Department of Energy, 2016)
In the reforming process, hydrogen is produced from methane (CH4) found in natural gas. Hydrogen is extracted from natural gas through a process called steam methane reforming (SMR). In the SMR process, high temperature steam (up to 1000c) is injected into the methane stream under pressure. With the help of a catalyst, the methane and steam react to produce hydrogen and carbon monoxide (see figure 1 above). The reaction looks like this:
CH4 + H20 (+heat) CO + 3H2
To increase the hydrogen yield, the carbon monoxide by-product is further processed to form additional hydrogen. That reaction looks like this:
CO + H2O (+heat) CO2 + H2
As you can see, greenhouse gases are emitted during processing but the reforming process produces about half the greenhouse gases (production to tailpipe) when compared to fossil fuels like gasoline production.
Unfortunately natural gas contains contaminants that can either poison the catalyst used in production or potentially harm distribution facilities. Additionally, hydrogen contamination can affect the performance of fuel cells or internal combustion engines that utilize hydrogen as a fuel. That's where our coatings come into the picture. Refiners and natural gas processors use our coatings to enhance the reliability and detection limits of analyzers used to detect contamination in the natural gas feedstock and in hydrogen fuels.
Figure 2: A typical gas purification system, (source: Argonne National Laboratory and "Hydrogen Fuel Quality Specifications for Polymer Electrolyte Fuel Cells in Road Vehicles", US Department of Energy, 2016)
To prevent damage to downstream systems, gas streams are purified. A typical purification system may look something like the diagram (figure 2) above. Why spend the time and money to remove contaminants from hydrogen?
Table 1 below highlights contaminants that can affect the performance of hydrogen powered systems, either in the production of hydrogen, the delivery of hydrogen, or in the efficient operation of the power system (internal combustion engines or fuel cell systems).
Some contaminants can reduce the efficiency of hydrogen production or damage catalysts which can result in catalyst poisoning and premature system failure. Contaminants can also damage hydrogen transport systems. For example water can freeze valves, regulators or filters while particulates can damage or interfere with gaskets and seal areas or clog filters.
Still other contaminants, like N2, NOx or CO2, may not directly damage the fuel delivery system or damage the fuel cell, but can reduce the overall energy density of the fuel. This can result in poor performance in fuel cells or internal combustion engines. An increase in air emissions (NOx, SOx, etc.) may also result from contamination in the fuel stream.
Table 1: Directory of limiting characteristics (maximum allowable limits of contaminants) from ISO FDIS 14687-2. ( "Hydrogen Fuel Quality Specifications for Polymer Electrolyte Fuel Cells in Road Vehicles", US Department of Energy, 2016 )
According to a study by the US Department of Energy, the contaminants that pose the greatest danger to the performance of hydrogen production, delivery, and power systems like fuel cells or internal combustion (IC) engines include:
SilcoTek inert, corrosion resistant, hydrophobic and icephobic CVD coatings benefit hydrogen use and production by improving trace detection of sulfurs, ammonia, and other reactive compounds; allowing hydrogen process facilities, transport systems, and down stream users to reliably detect potentially catastrophic damaging contaminants. SilcoTek coatings also enable users to detect emissions of target contaminants at trace levels, improving emission compliance. Need help finding the right coating for your application? Contact our Technical Service Team or try our easy to use Coating Selector Guide.
SilcoTek coatings can also boost the water repelling and ice removal properties of flow path surfaces, improving moisture management and minimizing water retention and ice formation/removal problems. Let's review some of the performance benefits of various coatings.
Stainless steel is a material commonly used in hydrogen production and transport systems. Unfortunately sulfur (one of those natural gas contaminants) is readily adsorbed onto stainless steel flow path surfaces. This makes detecting and managing sulfur poisoning more challenging. Sulfur detection is generally a manageable problem when testing at higher concentrations, usually at higher percent levels but at trace levels, detection is much more difficult.
Unfortunately, hydrogen catalysts are vulnerable to trace level sulfur poisoning. The damage from sulfur can add up quickly, resulting in reduced efficiency and shorter catalyst life. Both very expensive results. This makes testing for even trace level sulfur essential to cost efficient hydrogen production and use.
When testing for sulfur using materials like stainless steel, metal alloys, or even glass, the sulfur is adsorbed in the flow path and never reaches the sulfur detector. This results in reduced sulfur response at the detector and a false negative test; when in fact the feedstock stream may be poisoning the catalyst.
The flow test plot below demonstrates how various surfaces perform in trace sulfur analysis. The coated surfaces provide fast response and result in a higher detection signal when compared to uncoated stainless steel.
SilcoNert® radically improves sulfur response over uncoated stainless steel in analytical systems. This helps to maintain consistent and reliable detection, keeping hydrogen processing and fuel cell catalysts safe from poisoning.
Like sulfur contamination detection, improved ammonia detection can also contribute to preventing damage to catalysts. SilcoNert improves test reliability and lowers the detection limit of ammonia, helping to detect ammonia contamination before catalysts are damaged.
A University of Helsinki study found that SilcoNert improves the trace detection of ammonia by 95% when compared to uncoated 316L stainless steel. Improved detection will enable refiners and users to better manage hydrogen fuel quality and maintain high efficiency in production and use.
As noted earlier, some gases may not physically harm production, transport, or use but can reduce the energy density of hydrogen fuels. Reliable detection of nitrogen, N2, or other contaminants assures hydrogen powered systems run at peak efficiency.
Advances in instrumentation and test procedures help, but inert surfaces like SilcoNert® and Dursan® enable testing agencies to repeatably detect part-per-million and part-per-billion levels of NOx and sulfurs and other emissions.
The California Energy Commission conducted a study comparing SilcoNert® (noted as Silcosteel® in the study) to other materials commonly used in sampling systems. The results show the SilcoNert coated surface reduces surface reactivity with NOx, sulfurs and other common emissions, enabling more reliable testing of trace emissions.
Hydrophobic coatings, like Notak®, repel water and ice to help to maintain a water free surface. This helps to control moisture contamination in hydrogen production, fuel delivery, and use. Notak prevents moisture carryover by preventing trace water from attaching to hydrogen flow path surfaces and hydrogen sampling flow paths. This allows the user to detect moisture before it becomes a problem in hydrogen manufacturing and transport flow paths.
Goniometer water contact evaluation (below) compares hydrophobicity data of various SilcoTek coatings. The water repelling properties of Notak, evident in the water droplet and 143 degree contact angle, prevent wetting and water retention of the stainless steel substrate. For reference, an uncoated stainless steel water droplet surface contact angle ranges from 30 to 40 degrees, making stainless steel a wettable surface that can retain water in tubing, valves, filters and other flow path surfaces.
Ice formation and removal is also a problem in hydrogen storage and transport. Surfaces with ice repelling or icephobic properties help operators to manage the accumulation and removal of ice. The ice repelling and removal properties of Notak® coated stainless steel are compared in the photo and table below. The frozen Notak droplet has the highest contact angle when compared to other coated and uncoated surfaces, indicating an icephobic surface.
Notak also made ice removal easier. After freezing coated and uncoated metal coupon samples, a metal pick was inserted at the point of ice attachment to the coupon. Gradual increasing force was applied laterally to the ice sample until the ice dislodged from the surface. The effort required (1 = easy, 10 = difficult) to remove the ice and associated observations are listed in the table below.
316 SS Coupon Surface |
Effort (1-10) |
Observations |
Notak® |
2 |
complete removal with little effort |
Dursan® |
6 |
partial removal from surface with effort |
Silcolloy® 1000 |
7 |
partial removal from surface with greater effort |
Dursox® |
8 |
difficult, bulk chipped with minimal surface separation |
Uncoated |
8 |
difficult, bulk chipped with minimal surface separation |
The ice and water repelling property tests demonstrate how SilcoTek coatings can improve the moisture detection, reduce the accumulation of water in flow paths and help to make ice removal from surfaces easier.
SilcoTek corrosion resistant barrier coatings prevent flow path surface interaction with corrosives; extending component life while preventing hydrogen contamination. Our corrosion resistant coatings, Silcolloy®, Dursox® and Dursan®, are particularly useful for fighting corrosion in high purity or otherwise sensitive processes found in hydrogen production, transport and use. (see graph below)
In addition to extending the usable life of precision stainless steel parts, SilcoTek coatings prevent nano-scale corrosive reactions that can cause metal ion leaching and contamination, ultimately increasing process yield and reducing failure rates.
Because hydrogen reacts with most elements, hydride formation may be a concern in hydrogen production, transport and in downstream power systems. SilcoTek coatings act as a barrier to reduce or prevent ion leaching and interaction of flow path substances with the metal substrate.
In the example graph below, methanol (CH3OH) extracted metal ions from uncoated alloy surfaces. Metal ion extraction can contaminate flow path fluids and may result in system system corrosion.
SilcoTek® coatings contribute to the hydrogen economy by enhancing contaminant detection, improving system reliability, and system operation. Overall coating contributions to the hydrogen economy include:
The overall value of using coatings in the hydrogen economy result in reduced cost and improved efficiency of hydrogen use and production.
Interested in using SilcoTek® coatings in your process? Our Research and Development Team are here to help you select, evaluate, and use our coatings in your application. Contact our Technical Service Team to learn more. To keep in touch with the latest in coating development, subscribe to our blog, or follow us on LinkedIn.
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Geoff White contributed to this blog post.