Hydrogen Generators & Hydrogen Cylinders: A Comparison

As a carrier gas, hydrogen gas is popular due to its several benefits like speed of analysis, resolution, and sensitivity over other gases. It works best as a fuel gas for GC-FID applications. It is quite essential to select a proper hydrogen supply source for GC-FID applications as it contributes to the reliability and usefulness of the system. There can be a number of sources of hydrogen in lab like point-of-use hydrogen cylinders, multi-cylinder configurations, and hydrogen generators. Hydrogen cylinders are the traditional sources while hydrogen generators are sophisticated sources and rapidly replacing the previous one. However a good eye on the advantages and drawbacks of both the systems will help choosing the best hydrogen supply source for a system.

Advantages of Cylinder Hydrogen Supply

• Easy control and pressure monitoring: The hydrogen delivery pressure must be alike for the best GC performance and it can be best achieved by using point-of-use cylinders. These cylinders provide the users with good control of the gas delivery system. The pressure drop in the supply can be minimized by placing the cylinder near the GC and thus provides consistent delivery pressure. Due to the proximity of the GC and gas source, the monitoring of pressure delivery becomes easier.

• Continuous gas supply: The use of multi-cylinder configurations with switchover systems gives an enhanced consistent supply of gas. It decreases the frequency of cylinder change-out requirement. During change of cylinders, GC operation is not affected because when the primary cylinder is being changed the secondary side of the switchover system keeps delivering gas. Thus this more continuous hydrogen supply enhances reliability.

Concerns of Cylinder Hydrogen Supply

• Cylinder storage and handling: The prime concern while using the hydrogen gas cylinder is that it demand frequent changing of the cylinders that interrupts the GC operation and might affect its reliability. While using the point-of-use cylinder system, it takes a lot of time in changing the cylinders. The use of multi-cylinder systems with switchover facilities are less disturbing to GC operation but they need a technician to handle multiple cylinders during changes. In both the systems there is always a threat of surrounding air contamination.
  

• Safety issues: The high pressure involved and the flammable nature of hydrogen poses serious concerns for cylinder storage and handling. During the change of cylinders the lab personnel always face a huge amount of risk due to the large size and heavy weight of these cylinders. These cylinders should be fastened to the bench top or wall using proper holders. These serious concerns are prompting many labs to replace the use of hydrogen cylinders.

• Need of additional gas delivery equipment: During the change-out of hydrogen cylinders, moisture and oxygen can't be entirely checked from entering the system. These contaminations have serious impact on GC system and to minimize these effects high purity gas handling equipment should be used. The regulators should be made of brass or stainless steel barstock construction with stainless steel diaphragms and metal-to-metal seals.

Benefits of Hydrogen Generator

• Uninterrupted gas supply: Hydrogen generators provide a continuous supply of pure hydrogen gas when installed properly and start operating. Storing and changing the cylinders are no more required, ultimately saving time and cost. Ambient air contamination is also reduced as there is no need to change the cylinders.

  

• Enhanced Safety: The gas generators are highly secure than the gas cylinders in labs. There is no need to store huge amount of highly inflammable gas. It eliminates the need of a personnel to change and handle the high pressure cylinders. Usually a gas generator contains about 100 cc of hydrogen that is far less than the contents of an average cylinder. Now-a-days some hydrogen generators come with the facility of alarm functions. The alarms alert the users or automatically shut down the system in case of any malfunctioning. Thus all these factors enhance the safety in the lab.

• Space savings: The gas generators are smaller in size compared to the cylinders and can be comfortably placed on lab benches without consuming valuable bench space.

• High purity gas supply: The purity levels of hydrogen gas supplied by the hydrogen generators touches the level of 99.9999%. This purity level is maintained all the time and provides reliability for the GC system.

Drawbacks of Hydrogen Generator

• High capital investment: Hydrogen generators require a considerable amount of money compared to the hydrogen cylinders. The cost of one hydrogen generator typically ranges from $5000-$8000 varying on the capacity. The high cost may be an obstacle for some laboratories but when this one-time capital is compared to the ongoing costs of cylinder rental, product, it will not be a bad investment at all.

• Maintenance: The gas generators require maintenance for optimal performance. Some models need the monitoring and changing of desiccant cartridges that are used to eliminate residual moisture from the hydrogen. While some of them need the addition of a caustic electrolyte solution for the production of hydrogen. Maintenance is required for generator to perform and operate properly and reliably.