Materials Considerations in Hydrogen Production For ICHS 2007 Good afternoon ladies and gentlemen As the title of my presentation indicates I will try to sum up some of our thoughts with respect to materials and Hydrogen production based on our experience.

Highlights Our background/experience in Hydrogen Degradation of steel materials, general Other materials Knowledge – Best Practice Sum-up During the presentation I will cover the following 4 main points and summarise what we think are important conclusions. First: Our Background that naturally will colour our conclusions Secondly I will include some words on degradation of steel materials. Then I will cover some elements of other materials Finally I will give you some thoughts of Knowledge generation.

Herøya industrial site, Porsgrunn Our experience with hydrogen are from both water electrolysis and ammonia steam reforming. Hydrogen is also a by-product from chlorine production. This picture shows the island of Herøya where Hydro have built two ammonia plants (some years ago). In the background on the far side of the fjord is a chlorine plant. On the island we have this year opened a Hydrogen filling station for cars with hydrogen from the chlorine plant.

Background Hydrogen Experience Incidents Production, Handling and Storage Electrolysis, Steam reforming, Electrolysers Incidents CO2-line Ammonia plant Hydrogen out of control In our long industrial history relative few incidents are related to the effect of hydrogen gas on materials. Most hydrogen incidents are related to high temperature hydrogen, but the nasty ecperiences are not related to material damages, but to leaks of hydrogen and hydrogen out of control. In 1997 a CO2-transfer line exploded in a length of 850meters due to insufficient nitrogen purging during a plant shut down. No injuries at all were experienced. In 1985 an ammonia plant experienced a hydrogen leak in a high temperature area with the result of a fire.

Hydrogen in Porsgrunn This overview shows the area where the ammonia plant NI once was. The CO2 line went from the ammonia area down to the sign CO2 on the picture. The red line indicates the landfall of the Hydrogen line from the chlorine plant to the Hydrogen filling station.

This picture shows the Hydrogen station and one of the hydrogen cars. As mentioned the hydrogen gas comes though a linepipe from the chlorine plant. At the station, the hydrogen is compressed to 450bars in a underground storage. The plant constist of Deox/dryer unit Water absorber Compressor Storage Dispenser

Metallic Materials for Hydrogen Stress above yield Sound structure without transformation (austenite) Limited strength/stress level Design Environmental Factors (non-H2) External environment (chlorides) Production environment (lye, temperature, other..) ppm-elements (oxygen, fluorides, other..) SCC in lye Several guidelines describes material selection for hydrogen and a very short sum up for steel is: Choose an austenittic steel with a stable structure (type 316 or higher) or a carbon steel with low strength. High strength may be used but with larger margins to maximum yield stress. The brittleness does not reveal itself unless the stress level locally is above yield. Then of course the design and finishing surface of the material is important. But our experience to incidents related to hydrogen production, transportation and storage is not connected to the hydrogen-material problem, but to other factors. This indicate that it is not only important to design with hydrogen in mind, but also for other material problems. These may be: External environment, for instance chlorides in the air (coastal environment) Production environment (the picture shows stress corrosion cracking on stainless steel in lye) Important changes with respect to previous knowledge, that is the pressure and the temperature are of cource important. Ppm-elements may be extreme important for the materials evaluation. With respect to hydrogen it is reported that small amounts of oxygen in the gas will change the susceptibility of materials to hydrogen embrittlement in a positive way.

Corrosion due to environment

Other materials Composites (storage) Seals/packings Diffusion Fatigue Based on natural gas standards Seals/packings Plastic materials Rubber materials Seals and packings are also described in recommendations. To our knowledge there are no effect on plastics or elastomers from gaseous hydrogen used within the advised temperature limits. Rapid gas decompression may be detrimental to this group of materials. Of course gas diffusion should be treated seriously. The parameter window for use of composite fiber tanks is expanded. The hydrogen storage for our new hydrogen plant consists of 12 carbon fiber tanks and are certified to a pressure of 500bar. The tanks are tested according to NGV2. They are pressure tested to 750 bar and an exstensive fatigue test has been performed. After 3 year of operation further tests will be performed. Possible areas of special concern are the high pressure and the possible fatigue.

Knowledge Standards, recommendations, best practice Based on natural gas Several sources – standardisation Databases for incident reporting API – Nelson Collection of data and evaluation is important Ownership of databases, follow-up I mentioned the high temperature hydrogen problem area. This area is very good covered by API RP 941 that includes new lessons learned in the so called Nelson diagram. This diagram describes the operating limits for different steel qualities. It is important to include the same philosopy with resepect to recommended practices for hydrogen embrittlement or other possible problems experienced in the hydrogen industry. I have been studying some databases for hydrogen, and it is not always possible to find the root cause of a incident. There may be several reasons for this, but to build a good database it is important that ownership is defined and followed up. When this is said, the databases show as mentioned in the introduction concerning our experience, that hydrogen out of control is most important to safety. And the leakage is related to compressors, valves, filling nozzles and filling hoses. The reason for the leakage may be design, fabrication or installation, but as mentioned: The root cause is not always clear.

Sum-up Most incidents in the hydrogen business are not directly related to hydrogen compatibility of materials. External environment may give unexpected degradation of materials. Variations in process conditions may have large consequences upon materials selection. Focus on trace elements in production, transportation and storage of hydrogen. Be aware of established knowledge. Further develop recommended practice based on databases. This slide includes the sum-up of our experience. Most incidents in the hydrogen business are not directly related to hydrogen compatibility of materials. External environment may give unexpected degradation of materials. Variations in process conditions may have large consequences upon materials selection. Focus on trace elements in production, transportation and storage of hydrogen. Be aware of established knowledge Further develop recommended practice based on databases. Thank you for your attention.