21st April 2017
Benefits of Gas Generators Over Gas Cylinders : Expert opinion
The benefits of gas generators as alternatives to helium, such as the cost of gas generators, are discussed by Ed Connor. Giving his expert opinion on laboratory gas.
Dr. Ed Connor, GC Product Specialist at PEAK Scientific, speaks about the advantages for analytical laboratories adopting the use of gas generators rather than using gas stored in cylinders.
Could you please provide a brief introduction to the industry that PEAK Scientific works within and outline the key drivers?
PEAK Scientific is a manufacturer of gas generators for laboratory applications. Gas generators offer a reliable and consistent source of UHP gases which are specifically designed to produce gases at flow rates and purities specific to the requirements of the application and instrument.
The key drivers of our business are essentially the manufacturers of the analytical instruments that our gases supply and we ensure that we work closely with these companies so that they can offer cost-saving, convenient and high quality gas solutions to their customers.
Could you briefly explain how your Gas Generators work?
Nitrogen generators use a supply of dry, oil-free air to purify nitrogen via a selectively permeable membrane or carbon molecular sieve material which removes oxygen, carbon monoxide and carbon dioxide. Purified nitrogen is then stored in a buffer tank to ensure constant flow and pressure of nitrogen is supplied to the application.
Purified Air generators also require a supply of dry, oil-free compressed air which is passed through a catalyst chamber, or filtration system to remove methane, CO2 moisture and carbon monoxide. Gas is supplied to the application from a buffer tank so that flow and pressure remain constant.
Hydrogen generators electrolyse deionised water to oxygen and hydrogen via a proton exchange membrane (PEM). Hydrogen ions diffuse through the PEM membrane whereas oxygen is retained and is then vented to atmosphere. The hydrogen is then further purified using a desiccant drier or pressure swing adsorption drier before being supplied to the application.
How does this differ from conventional techniques of supplying gas, such as in cylinders?
Gas cylinders have been the traditional way to store and supply gases to applications in the lab and most gas users don’t think of using alternatives despite the potential danger and inconvenience associated with using cylinders.
Cylinders contain large quantities of gas at high pressure and therefore present a potential health and safety problem. Not only must the cylinders, which are fairly heavy, be periodically moved, but an accident can release a large volume of gas into the lab environment.
If the gas released is nitrogen, there is potential for asphyxiation of anybody unlucky enough to be in the lab. If the gas is hydrogen, there is the potential for an explosion to occur. Once the level of hydrogen in atmosphere reaches 4.1% by volume in air it can explode if there is an ignition source present.
Releasing the contents of a large hydrogen cylinder, which contains around 9000 litres of hydrogen at atmospheric pressure, rapidly into a small lab would present a major risk of explosion. Compare this with a hydrogen generator which produces 500cc/min of hydrogen and you can easily see the safety benefits of using a generator.
The other potential problem with cylinders is inconsistency in purity from cylinder to cylinder and that impurities collect at the bottom of the cylinder meaning that the last 10% of the gas is not of as good a quality and is not recommended for use. In addition to these factors, there is the transportation of cylinders which are usually transported by road and therefore add to street congestion and pollution.
What are the major advantages of using your Gas Generators over using cylinders?
The main advantages of gas generators over using cylinders are safety and convenience. Generators provide a constant supply of gas for lab applications without risking the safety for lab users.
Cylinders have the potential to release thousands of litres of gas into the lab atmosphere in a very short space of time, which could have fatal consequences
The set-up of gas generators is very straight forward and maintenance is required every 6-12 months depending on the system. The majority of PEAK gas generators require just an annual service, which can be conducted on site in only a few hours.
How are your Gas Generators unique compared to others on the market?
All PEAK products are hand-built in Scotland by our production technicians. The units are built from top to bottom by one technician to ensure that our generators meet our demands for high quality and performance.
Prior to shipping, all units are quality checked before being packaged in specially designed crates to ensure that they are not damaged in transit to our customers. PEAK generators are very simple to install and our after-sales support service is second to none.
What are the primary applications of the generators that you supply? Which industries primarily benefit from using them?
The main applications supported by our generators are analytical lab applications such as LC/MS, GC/MS, GC, TOC, FTIR as well as a variety of sample preparation techniques such as static or dynamic headspace and automated evaporation systems.
There are a wide range of applications that require nitrogen, hydrogen and purified air and customers who are using large volumes find that they can get a very quick return on investment for the capital outlay of a generator.
Are there any environmental benefits to generating your own gas supply as and when it is needed rather than storing it in cylinders?
Once installed, a generator requires only a supply of electricity, and in the case of hydrogen generators deionised water, to produce a high purity gas suitable to supply highly sensitive analytical instruments. Therefore generators have a small carbon footprint compared with cylinders which need to be transported to and from the lab repeatedly because of their limited capacity.
A PEAK nitrogen generator supplying 32 litres per minute of nitrogen to an LC/MS will produce over 9.5 million litres of nitrogen before needing to be serviced. This volume of gas is equivalent to over 1000 nitrogen cylinders which would need to be transported to and from the cylinder depot, therefore the environmental benefits of using a generator, as well as the time and cost savings are quite clear.
There is a rising issue with the dwindling global supply of helium, with the US National Helium Reserve being sold off. Can you see this problem being overcome by switching to other carrier gases and, if so, could PEAK Scientific offer effective solutions?
There is definitely a case for analyses such as GC and GC/MS using alternatives to helium. We see a number of labs worldwide switching to nitrogen and hydrogen as alternatives to helium for GC carrier gas. Nitrogen gets some bad press as it is seen as an inferior replacement, owing to its lower optimal linear velocity relative to helium and hydrogen, however, there are a huge number of methods currently being used that would provide excellent results using nitrogen carrier gas.
Hydrogen is often cited as the best alternative to helium, although many GC users are put off using hydrogen because of its potential for reaction with analytes and its reputation as an explosive gas. In its defence, hydrogen offers potential for improved chromatography, faster sample throughput, reduced MS source maintenance and reductions in GC consumable costs and can be produced safely in the lab using a hydrogen generator. Many agree that the benefits of using hydrogen vastly outweigh the risks and we are seeing an increasing uptake of hydrogen conversion from helium for GC applications.
PEAK offers a stackable, modular space-saving range of generators aimed at supplying a total gas solution for GC applications for carrier and detector gas. The precision range offers a safe, reliable gas supply without the need to store large volumes of hydrogen in the lab.
Hydrogen is a commonly used carrier gas, how can you guarantee that the Hydrogen that your gas generators produce is high purity?
Production of hydrogen in our Precision hydrogen generators is achieved through electrolysis of deionised water via a nafion proton exchange membrane (PEM). This membrane only allows the passage of hydrogen ions.
Once hydrogen has passed through the membrane we have a further purification step using either silica gel or pressure swing adsorption (PSA) to remove any residual moisture from the gas. We also use stainless steel fittings throughout the system from cell to delivery to application to ensure that we introduce no impurities into the hydrogen gas.
How do you see the gas generation industry changing over the next 10 years?
I see the main changes being a reduction in generator footprint and size as well as increase in the range of gases available via generators. I can see new technologies coming online to further enhance gas purity whilst maintaining high volume output as well as allowing purification of trace constituents in air, allowing generator manufacturers to better compete with the range of gases offered by cylinder suppliers.
As laboratory space becomes more expensive, there will be greater consumer pressure requiring generators to fulfil these criteria as well as offering a greater variety of pure generated gases.
How will PEAK Scientific be a part of this change?
At PEAK we constantly strive to improve and update our existing generators, through state of the art technologies. We listen to our customers and industry partners so that our products deliver high purity gases at a range of volumes and flow rates.
We have a dedicated R&D team who are involved in a variety of projects looking at new product developments, as well as improvements to our existing portfolio.
About Ed Connor
Ed Connor joined PEAK Scientific in February 2013 as a GC product specialist and now functions as a Product Manager.
He has been working on a number of collaborative projects with PEAK customers and the major instrument manufacturers worldwide.
The main focus of these collaborations has been to look at conversion from helium to hydrogen or nitrogen carrier gas for GC applications but he has also worked on ELSD nitrogen gas solutions and nitrogen generators for LC-MS instruments.
Prior to joining PEAK, Ed completed his Dr.Sc. at ETH Zurich in 2007 using GC-MS to look at herbivore induced plant volatiles and their interaction with beneficial insects.
He then joined the University of Zurich where his work focused primarily on floral volatile analysis using a variety of volatile collection methods, GC-MS and GC-FID.
Enjoyed this article? Why not read our definitive guide on discarding cylinders and generating your own gas.