FAQs about hydrogen gas generation


FAQs about hydrogen gas generation

Dr Nicole R Pendini* provides answers to several frequently asked questions collated from worldwide health, environmental, industrial, testing, medical and research laboratories regarding the safe use of hydrogen generators in the workplace.

Hydrogen is the most abundant element in the universe, although in its gaseous state it does not naturally occur on Earth and must be manufactured. In industry, H2(g) is produced on a large scale by a process called steam reforming, to separate carbon and hydrogen atoms from hydrocarbon fuels. Hydrogen is used in the laboratory for a variety of lab applications, such as gas chromatography (GC) as fuel or carrier gas; ICP-MS as a collision gas in the chemical industry to synthesise ammonia, cyclohexane and methanol; and in the food industry for hydrogenation of oils to form fats.

Significant research and development has afforded safer, efficient, greener and more cost-effective means of generating on-demand hydrogen gas for laboratories, manufacturing and industrial applications. Safety has improved so much so that hydrogen gas is now being used in some transport vehicles as a clean ‘pollution-free’ fuel, with the by-product of its combustion being water.

Why use a hydrogen gas generator?

Hydrogen gas generators are a safe, convenient and typically more cost-effective alternative to using high-pressure cylinders of H2. A hydrogen generator will provide hydrogen of a consistent purity, eliminating the risk of variation in gas quality, which can impact on analytical results.

A generator also produces gas on demand around the clock, meaning that you don’t need to worry about running out of gas at an inopportune moment. A hydrogen generator will free up more analytical time since you will not need to spend time ordering and changing out replacement cylinders.

A generator is an environmentally friendly alternative to cylinders, since once it is installed the generator will not need to leave the laboratory, providing gas for laboratory applications with all maintenance carried out in the laboratory. The generator also reduces your laboratory’s carbon footprint, since there is no need for trucks to deliver replacement cylinders and remove empty cylinders.

How can I change from cylinders to a generator with limited downtime?

The changeover is typically seamless. If you are switching from hydrogen cylinders to a generator, existing tubing can be disconnected from the cylinder and connected to the generator, using Swagelok fittings. If you are changing from helium to hydrogen, new tubing should be always be used.

How safe is the generator?

Most hydrogen generator stores less than 300cc gas, whereas cylinders store up to 9000 L at extremely high pressure (~2000–3000 psi). A hydrogen gas generator produces gas on demand, meaning only the amount needed by the gas chromatograph (GC) is produced at regulated flow (0.5 L max) and pressure (120 psi max).

Depending on your supplier, H2 gas generators are equipped with continuous internal and external leak checks in addition to an auto-shutdown features:

  • Full diagnostic checks on start-up
  • Continuous pressure-based leak check during operation
  • Automatic shutdown by isolation of the H2 generation cell
  • Audio and visual alarms
  • Forced ventilation throughout the generator
  • Low H2 gas throughout the system (<3 L max)
     

Should there be an internal leak, the generator will cease gas production and alert laboratory personnel via the HMI touchscreen, which will give a warning as well as an audible alarm. If there is a leak external to the generator, or its capacity is exceeded for 20 minutes, the generator will shut down to prevent build-up of H2 gas in the lab environment or instrument supplied. The system will also shut down if the internal pressure exceeds 120 psi.

Our safety officers are concerned about H2 gas build-up and explosion in the lab. Is this possible with a H2 gas generator?

Hydrogen is flammable between 4.1% and 78% in air. A laboratory measuring 5 x 4 x 2.5 m has a volume of 50,000 L. For the lower explosive level (LEL) of 4.1% hydrogen gas to be reached, we would need 2050 L of H2 gas released into this laboratory space in one instant.

An average ‘G’ sized H2 gas cylinder contains 9000 L of gas. Should a cylinder leak, it would need only to release 25% of its total volume to reach the LEL in this laboratory.

By contrast, the Peak Scientific Precision Hydrogen Trace 500cc generator produces 0.5 L/min. To reach the LEL with this gas generator, it would need to be in a completely sealed space, not be connected to the GC/application or severe leak and have complete failure of all safety features. Even in this scenario, the generator would need to operate for 67 hours (~three days) to reach the LEL.

Has any testing been conducted to evaluate the safety of hydrogen generators?

One should check that their generator carries CE, CSA and RCM (for use in Aus/NZ) approval for compliance and have been externally tested to IEC standards for laboratory use and safety requirements for the residual risk for an explosion hazard. Safety is evaluated by dilution tests and an unoperated fan, assuring the explosion LEL of 4.1% hydrogen is not reached under worst case conditions internally or externally to the generator.

Where should I install my generator?

The generator can reside safely in the laboratory on the bench, floor or under the GC auto-sampler. The generator should be located on a flat, level surface for operation.

Can I put the generator in a cupboard?

Adequate airflow must be maintained around the generator to allow the ventilation system to perform efficiently. If the generator is stored in an enclosed space, the environment must be controlled via an air conditioner or extraction fan. The provision must be made to allow the volume of air in the room to be changed five times per hour.

The rear of the generator will become warm to the touch during operation — a minimum clearance of 15 cm from other bodies is recommended.

The vents should not be obstructed or connected to any application. Safe, forced removal of waste gases has been engineered into the generator to prevent any internal gas or pressure build-up.

Can I place the generator outside the laboratory?

This is possible as long as the recommended environmental conditions required for normal operation are met. Reducing the length of pipework will reduce costs if not already installed and the risk of any potential leaks in the pipework going undetected, improving the safety of the installation. If possible, the generator should be placed near or close (<10 m) to the GC or application.

Do my GCs need to be ventilated?

If a customer wishes to use a fume extractor or to connect tubing between the exhaust of the generator and a fume hood, this is possible. Any hydrogen exhausted from the GC will quickly diffuse in the air and presents no danger to laboratory personnel or the environment. If tubing is attached to the exhaust ports of the generator, it is essential that this is monitored frequently, since any kinks could cause a build-up of gas and cause additional health and safety issues. The majority of laboratory environment will not be completely sealed with air conditioning in place allowing air movement and cycling, and hence will not meet the LEL of hydrogen of 4.1%. If you have concerns you should have your site evaluated, perform an installation survey and request a demonstration.

Will I need hydrogen sensors in the lab or GC oven?

In the laboratory, the amount of hydrogen generated/exhausted into the laboratory is not enough to accumulate and reach the LEL of hydrogen. The risk of a significant build-up of gas in the GC oven is also extremely low, with both the external leak safety shutdown feature of the H2 generator and the GC inlet safety shutdown feature in place.

Should your laboratory, state government or business policy require regulation, sensors or monitoring, Peak Scientific can offer both external room and in GC oven monitoring sensors for peace of mind.

How difficult are H2 gas generators to maintain?

Maintenance is very simple and cost-effective, and many generators do not require an engineer for regular maintenance. Simply refill the deionised water reservoir weekly. Preventive maintenance (PM) is typically required biannually, requiring deioniser cartridge swap-over.

Given times of social distancing, many vendors are offering online user training, Skype, tutorials, PowerPoints, detailed user manuals, 24/7 phone technical support and video support.

How many GCs can a single hydrogen generator supply?

As a typical rule of thumb, 100cc will supply two FID detectors. Of course, the required generator will depend on flow rate, carrier gas type, column, other detectors and methods used.

Will it really be more cost-effective?

Calculating the gas, delivery charges, cylinder rental charge, staff downtime time, administration, OHS measures and training, ROI is typically within 9–15 months.

Is it difficult to install a hydrogen generator?

Not at all. Simply remove packaging, connect an external UV-protected deionised water bottle (at same height or below the generator), connect to an electrical supply (10 A) and allow to reach room temperature. Connect to your GC using 1/8″ pre-cleaned (gas purged) refrigerant-grade copper or stainless steel pipe.

What piping do I need?

Supply of hydrogen should be provided through stainless steel or analytical-grade copper tubing using Swagelok compression fittings. It is important to change the tubing that was previously used to supply helium to the GC, since over time, deposits can build up on the inside of the tubing which hydrogen will carry to the application, causing higher background signal for a longer period of time.

For any connections, Swagelok compression fittings are the recommended solution to connect copper or stainless steel tubing. No chemical bonding (such as Loctite), welding or glues should ever be used, since this can introduce volatile organic compounds (VOCs) into the gas supply, which can impact on results.

When running lines >3 m, it may be necessary to use 1/4″ piping reduced to 1/8″ to supply each GC. This increases the volume considerably and can make installation more difficult. For lines >10 m between the generator and GC, please consult with your fitting specialist.

What is Tygon tubing?

Tygon tubing is used to link an external UV preventive water bottle to a gas generator. The high-purity, plasticiser-free tubing is typically used for specialist and diagnostic equipment. This tubing has low adsorption/adsorption properties, which minimises the risk of fluid retention and leaching of the material.

What water can I use for my hydrogen generator?

The recommendation is deionised water (DI) of >1 MΩ resistivity /<1 µS conductivity purity or better. If MilliQ water is available at your facility, this is preferred.

What are the benefits of hydrogen generators over cylinders?

  • Lower pressure = safer (1–100 psi at outlet)
  • Controlled flow maintains safe hydrogen levels (up to 1000cc at outlet)
  • Built-in leak sensors and automatic shutdown feature
  • On-demand production = minimal storage
  • Once installed there is no need to move
  • All maintenance carried out in the lab
  • 24/7 operation — no need to monitor supply
  • Reduce costs and admin — no repeat orders of gas
  • Lower carbon footprint — greener option for your lab
     

*Dr Nicole R Pendini works for gas generation company Peak Scientific, specialising in on-site in-laboratory nitrogen, hydrogen and zero air gas generation. She also designs complete reticulated gas systems for laboratories, food and beverage and industry from single rooms to entire building sites, ensuring the right quality, quantity and pressure of gas is supplied in a sustainable, safe and environmentally conscious manner.

Image credit: ©stock.adobe.com/au/Thomas

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