Industrial gases are often produced at high purities, particularly those separated from air in large-scale air separation units (ASUs). Yet that’s not the end of the story. Purity needs to be maintained or even enhanced, you see, as the gas molecules are moved around and then put to work.
Whether we are talking about argon for 3D printing, nitrogen for semiconductors, or hydrogen for fuel cells, to reach for three examples from hundreds, there’s a significant and growing demand for post-production purification, for high- and ultra-high-purity gases, and sometimes simply for further treatment after transportation, storage, or application has led to some contamination.
ReiCat’s pure take
Sophia Höfling, Chief Operating Officer and Authorized Signatory of ReiCat GmbH, says today purification plays a vital role in maintaining gas quality throughout the supply chain, from the moment a gas has been produced.
Industries such as electronics, transport, aerospace, and semiconductor manufacturing are pushing for increasingly stringent purity requirements today. High- or ultra-high-purity levels – 99.999% (5.0) or even 99.9999% (6.0) – are often required for sensitive applications. Hence, for industrial gas suppliers, ensuring consistent purity is very often key.
Post-production purification helps gas producers meet those stringent customer requirements and improves the commercial value of the product. “A gas of quality 5.0 can be sold at a higher price than one of quality 3.5. And for certain processes high-purity or even ultra-high-purity is simply a must.”
“Post-production is not the only application for purification along the gas supply chain. A gas might leave the plant at high purity, but by the time it reaches the end-user it could be contaminated in various ways. ” Gases can pick up impurities during storage and transport, particularly in pipelines. That’s where purification comes in again.
“New pipelines are usually moist for around two years after being built, so even a gas entering a pipeline with high-purity may need drying after pipeline delivery,” Höfling explains.
In the final step of the gas supply chain, an industrial gas is applied by an industrial end-user. In certain cases, the gas is not actually used but is still contaminated in the process. Here, gas recycling comes into play – a complex, multi-step purification process able to recover up to 98% of the gas in high-purity or ultra-high-purity.
Hydrogen purity is a challenge
High-purity or ultra-high-purity hydrogen is required for several applications. For producing flat glass, for instance, hydrogen may not contain the slightest traces of oxygen. Otherwise, the glass will turn opaque. Fuel cells also require hydrogen of high purity. If hydrogen contains, for example, residual CO2 the fuel cell will die as CO is a so-called ‘catalyst poison.’ For this reason, more regulation is coming up. In particular, the EU and North America are regions enforcing stricter rules for gas quality. An example is the SAE J2719. It is a standard of the Society of Automotive Engineers that deals with the quality of hydrogen as a fuel for fuel cell vehicles. The standard specifies the purity and maximum limit values for impurities that hydrogen must meet in order to be used safely and reliably in fuel cells – without damaging the cell or impairing its performance.
“But sensitive applications and regulations are not the only drivers for high-purity hydrogen. High-purity is essential for safe transport and storage, especially for hydrogen. If you transport wet hydrogen, you risk pipeline corrosion, and hydrogen is the smallest element. It is invisible, odourless, but highly explosive. High purity is a matter of safety,” says Höfling.
Given those industry requirements, regulations, and safety concerns, hydrogen purification is an essential step within Power-to-X, which is a growing production method for hydrogen and a cornerstone of the energy transition. “Every Power-to-X system where green hydrogen is produced requires a purification unit. There is no electrolysis technology that produces hydrogen or oxygen at the required purity levels,” Höfling explains.
Ensuring stable purity in fluctuating hydrogen production via electrolysis in Power-to-X presents a new challenge for purification technology.
“With Power-to-X, the wind is not always blowing and the sun is not always shining, so you have fluctuations in hydrogen production. We have had to adapt our purification units to cope with that while still guaranteeing high gas quality.”
Cutting the loss
Another challenge in purification is minimising gas losses. Traditional purification systems result in some volume loss, but advances in process technology are reducing this inefficiency.
“In classic temperature swing adsorption – a key technology used in many gas purification units for drying and fine purification – you lose around 3% of the gas in the process. We’ve reduced that to zero or 0.3%, which can save customers millions per year.”
This closed loop technology is key, especially when treating expensive gases and high volume flows.
Growing demand for high-purity argon and helium
Beyond hydrogen, other gases are also seeing a growing demand for purification. Argon, in particular, is seeing rising demand for high purity due to its use in 3D printing and metal powder production. Semiconductors also rely on both high-purity argon and hydrogen, making purification a crucial step in ensuring process efficiency and product quality.
And high-purity helium is required in large quantities to produce titanium for the aerospace industry within the plasma arc melting process. As this industry, as well as other high-purity helium use cases, is growing, global helium demand is rising.
The role of recycling in industrial gases
The drive for gas purification isn’t only being shaped by industrial needs but also by evolving regulations. Höfling notes that governments are enforcing stricter CO2 emissions standards which affects how the industrial gas industry operates.
Gas recycling is gaining traction as industries look for more sustainable ways to manage their resources. “The traditional gas industry model is simple: you buy gas, use it, vent it, and then buy more. But producing gas is energy-intensive and often has a high CO2 footprint,” says Höfling. “Our recycling systems let companies recover up to 98% of their process gas, which is not used up but only contaminated in the process, cutting costs and emissions.”
ReiCat develops and builds large-scale recycling systems for hydrogen, argon, helium, and nitrogen for production processes with gas volumes of up to 10,000 Nm3/h. The systems are flexibly integrated into existing production systems in which a process gas is not consumed but merely contaminated. They can recover up to 98% of the process gas using an energy-efficient process. This can reduce operating costs by up to 80% and minimises the CO2 footprint. The gas end-user at the same time becomes independent of the gas supply market.
These efforts align with the growing focus on sustainability and are also also a logical response to a geopolitical climate where gas supply might be at risk.
