Green hydrogen has almost unlimited potential as a replacement for fossil fuels and will be an essential contributor to getting to net zero.
Nickel-containing stainless steel is a sustainable companion on the path to a climate-neutral future. Hydrogen is 14 times lighter than air, non-toxic, colorless and odorless, does not self-ignite and burns without residue with a colorless flame. It is gaseous down to -253 °C, after which it liquefies. It is a very reactive element that only occurs in a bound form, for example as a hydrogen molecule, in water with oxygen, or in methane with carbon.
Hydrogen itself is energy intensive to produce. Worldwide annually, 30 million tonnes of “grey” hydrogen are produced from fossil fuels such as natural gas or oil, mostly by steam reforming. This is a process that converts water and methane into hydrogen and carbon dioxide (CO2). And every tonne of hydrogen produces ten tonnes of CO2.
The more climate-friendly alternative is “green” hydrogen, produced in a climate-neutral manner from 100% renewable energies. The most common production process for green hydrogen is electrolysis of water where hydrogen is separated from oxygen.
Hydrogen is an important raw material for the chemical and petrochemical industries to produce basic chemicals such as green ammonia or green methanol. More than half of hydrogen production is processed into ammonia for the manufacture of fertilisers. Hydrogen can also be used directly for building heating, industrial furnaces and in fuel cells to drive electric motors for transportation. It is so attractive because its only exhaust emission is water.
The specific properties of hydrogen place the highest demands on the materials used for its generation, cryogenic storage, transport and use of electrolysers, high-pressure compressors, tanks, valves, pipes and fittings. The high diffusibility of hydrogen requires reliable gas tightness of all components to avoid losses and mitigate the risk of explosion or fire due to escaping hydrogen.
With many metals, hydrogen atoms can penetrate the material (permeation) and significantly impair their mechanical properties. Even at a hydrogen concentration of a few ppm, in susceptible material, degradation can occur resulting in the formation of cracks and brittle fractures and therefore representing an unacceptable safety risk. Components made of nickel-containing stainless steel, on the other hand, permanently resist both permeation and degradation thanks to their microstructure. Thus, they prevent the gradual escape of gas and protect the components from embrittlement, maintaining consistently high strength, ductility and homogeneity.
For components that come into contact with hydrogen, austenitic stainless steel Types 316L (UNS S31603) and 304L (S30403) are used as standard. Types 317LMN (S31726), 2205 (S32205) and 2507 (S32750) are tried and tested for particularly critical applications.
Looking forward to a sustainable future, ways and means of producing, using and distributing green hydrogen are being expanded around the world. Many grades of stainless steel will play a key role in the process, from start to finish.
Hydrogen is an element that exists primarily in molecular forms such as water and organic compounds. Hydrogen gas can be produced from various sources or processes. To identify these different sources or processes the hydrogen is identified by a colour code.
Green hydrogen is produced through water electrolysis, which uses renewable electricity to split water into hydrogen and oxygen gas. The reason it is called green is that there is no CO2 emission during the production process.
Grey, brown and black hydrogen is produced using fossil fuel, natural gas, lignite coal and bituminous coal, respectively. However, these options all emit CO2 to differing degrees.
Blue hydrogen is derived from natural gas. However, the CO2 is captured and stored underground (carbon sequestration). As no CO2 is emitted, the blue hydrogen production process is categorised as carbon neutral.
Pink, purple and red hydrogen. Hypothetically, hydrogen can be produced by the use of nuclear power. Pink hydrogen is generated through electrolysis of water by using electricity from a nuclear power plant. Purple hydrogen is made though using nuclear power and heat through combined chemo thermal electrolysis splitting of water. Red hydrogen is produced through the high-temperature catalytic splitting of water using nuclear power thermal as an energy source.