Q2 2009 / Helium conservation and recovery

In recent years, industry demand for helium and its mixtures has risen steadily, heightening the need for improved conservation and recovery methods.

Helium and its mixtures offer unique chemical and thermodynamic properties that meet the needs of many diverse industries and applications – ranging from materials research to aerospace, electronics, manufacturing and healthcare. 

Because of its chemical inertness and high thermal conductivity, helium is widely used in welding applications, lasers, heat treating, metals and glass refining, optical fiber production, plasma-arc melting, and semiconductor and flat panel display manufacturing. 

Because helium does not become 

radioactive, it is also used extensively in the nuclear industry. In addition, helium is used in medical applications ranging from magnetic resonance imaging (MRI) to diving and medical breathing mixtures.  

The nature of helium expands demand

Because helium is the second lightest element on earth and its molecule is the second smallest (after hydrogen), its properties make it ideal for leak detection applications, balloons, and other lighter-than-air applications. 

True, there have been technology improvements in mature applications such as MRI and welding that have increased the focus on helium conservation and helium-recycle technologies. This development has somewhat moderated rising demand.

However, emerging dirigible applications for heavy lifting, military, DEA, and border surveillance UAV’s (Unmanned Aerial Vehicles), plus increased use in nuclear power generation and new applications in electronics manufacturing will continue to drive the demand for helium especially in the post-recession future.

Cost and consequence

Helium is usually not a major cost driver in the manufacturing processes where it is consumed. Yet helium is an essential raw material and its absence can shut down any manufacturing process that relies on it. This could become a serious issue should a tight supply ever require rationing.

With the global economy currently in recession, all of the helium suppliers have removed supply restrictions that affected helium consumers from 2006 through most of 2008. 

However, tight helium markets may return when the global economy recovers due to the continued depletion of the “helium-rich” Hugoton Field gas wells in Texas, Oklahoma, Kansas, and the Riley Ridge area of Wyoming which today supply the majority of the world’s crude helium, impacting U.S. production. Another supply factor is that the total worldwide production capacity is expected to remain flat until new helium plants in Algeria, Qatar, and Russia start production sometime between 2012 and 2014. 

With helium being such a valuable natural resource, it is no wonder that all helium producers, refiners, and distributors practice conservation to some extent. However, the helium supply chain is extended and complex, creating many opportunities for wasting helium in practice. 

Transporting helium

Bulk helium is commonly shipped as a liquid in 11,000 gallon ISO-certified containers either over-the-road or in container ships (Figure 1). 

Figure 1: Bulk helium is shipped as a liquid to large helium end-users in 11,000 gallon ISO-certified containers.

It travels from production facilities and refineries both in the U.S. and overseas to a host of end users including industrial gas companies, distributors, and to large helium end users. 

Industrial gas companies and distributors transfill helium from the ISO container and deliver it to their customers as liquid in dewars with capacities ranging from 30 to 1,000 liters, or as high-pressure gas in cylinders and bulk tube trailers.

Typically, the vacuum- and super-insulated liquid nitrogen-shielded bulk liquid helium ISO containers and trailers allow no helium loss during shipment and storage for up to 35 days. However, the transit times for liquid helium containers vary widely depending on the point of origin and final destination. For containers originating in the U.S., the typical transit times are 10 days to Europe, 14 days to Japan, 24 days to South Africa, and over 35 days to India. 

Heat leak causes pressure to rise

Heat leak causes the pressure to rise in the container both while the container is in transit, and while it is used as a storage container at the transfill or customer site. 

Helium containers have a liquid nitrogen shield that helps reduce the rate of heat leak. However, it is not uncommon for the liquid helium container to arrive at its destination with a nearly depleted nitrogen shield. This can lead to an increase in pressure inside the container, resulting in the venting of helium through the container’s pressure relief valve. Therefore, both proper container maintenance and efficient helium container shipment logistics are crucial to reducing helium losses during transit.

Forced to vent

Despite the high value of helium, industrial gas companies and distributors are occasionally forced to vent some helium into the atmosphere. This can happen when the container arrives at the helium transfill at excessive pressure due to transit delays, or if pressure in the container rises on site due to an extended storage period. After reducing the pressure of the helium gas, transfer of the helium to other containers is less problematic.

For efficient helium decanting into dewars, the pressure in the container should ideally be maintained between 5 to 7 psig. Even with a properly pressurized container, the decanting operation always results in a significant volume of liquid flashing to gas. The vaporized gas is captured and compressed either into high-pressure ground storage or directly into the tube trailers. 

Excessive pressure in the container results in even greater gas flashing and often makes decanting impossible because the volume of evaporated gas far exceeds the storage capacity of the high-pressure vessels and gas-recompression system. 

For best results, balance the liquid and gas loads

Transfill operators should pay particular attention to properly balancing the liquid and gas loads on the transfill. If the amount of gas generated from dewar filling exceeds gas demand, helium suppliers should consider rebalancing the product mix or investing in a helium liquefier. 

Of equal importance is efficient dewar and tube trailer management. Dewars that are allowed to sit at the customer facility for too long will eventually lose all their helium and will require extensive preparation to put them back in service. 

These dewars, referred to as “hot,” must be purged with helium and evacuated to remove any air contamination before they can be refilled with liquid helium. The amount of wasted helium due to purging “hot” dewars can be significant. Dewars that contain some liquid helium or cold vapor, referred to as “cold” dewars, should be filled first to take advantage of the cold inner temperature of the dewar. 

Figure 2: A liquid dewar vent is connected to a recovery manifold during filling.

Dewars that cannot be filled right away should be positioned on a dewar recovery manifold to capture escaping helium vapors. When filling liquid dewars, all vaporized gas should be captured. After filling, the dewars must be connected to the dewar recovery manifold until the liquid helium in the dewar settles and the dewar achieves thermal equilibrium (Figure 2). Molecules should simply not be allowed to escape into atmosphere.

First, select the right equipment, and then maintain it

To maximize helium conservation first choose the right transfill equipment. Then, institute a regular transfill equipment, dewar, and trailer fleet maintenance program. 

When it comes to selecting the right transfill equipment, look for a compressor that is properly sized to ensure that it is capable of handling the volume of gas needed both for dewar filling and for filling a jumbo tube trailer (180,000 scf capacity) in under approximately 14 hours. Selecting a compressor with insufficient capacity can create back pressure on the liquid dewar and prevent efficient decanting, add days to the time required to pump-down an over-pressurized container, or add to the time required to fill a tube trailer. 

A good compressor maintenance program is vital too. A poorly maintained compressor will not only lose its pumping efficiency, but it will also allow helium to escape past the leaking piston rings. Similarly, worn piston rings will result in higher helium contamination with compressor oil. While oil mist in helium will ultimately be removed by condensing it in moisture/gas separators and passing the helium gas through a coalescing filter and carbon bed, the compressor may have to be blown-down more frequently to expunge the oil emulsion from the separators. More frequent separator blow-down leads to higher helium losses. The compressor should be equipped with a blow-by indicator and should be regularly monitored for excessive blow-by. 

Another helium conservation measure helium transfill operators should consider is recycling the blow-down gas back to compressor inlet. 

Check for leaks

Finally, the entire transfill piping system should be regularly checked for leaks. The dewar, tube trailer valves, and pressure relief devices should be checked for leaks prior to every fill. In fact, prior to performing any maintenance that might result in helium venting into atmosphere, operators should give some thought to capturing helium for reuse. 

User guidelines

Helium users should also make every effort to conserve helium by improving operational efficiency. Users should regularly check the helium storage system, the helium distribution piping, and the process equipment for leaks. 

Even a small, hard to detect leak, may result in thousands of dollars worth of helium lost over a year’s time. Several small leaks can result in tens of thousands of dollars worth of helium lost every year. Helium users should ask their helium gas supplier to conduct an audit of their operation periodically. The supplier can help them identify leaks, and may also, where appropriate, recommend a helium recycle system that will seamlessly integrate into their manufacturing process.  

With proper equipment maintenance, regular leak checks, and a properly designed helium recycling system, the savings on helium purchases can be significant, with a financial payback measured in months rather than years.

Proven success

A number of manufacturing industries have enjoyed the benefits of helium recycling for many years. Point-of-use and centralized helium recovery solutions tailored to specific applications have been developed for leak detection, optical fiber manufacturing, vacuum heat treating, plasma melting, laser welding, superconducting magnet manufacturing, dirigible inflation, and many other applications. 

Recent advancements in helium purification  and liquefaction technologies, and the wider availability of low-cost helium purity analyzers can make helium recycle cost-effective for relatively small helium consumers.

Figure 3: A centralized helium recovery system.

A centralized helium recovery system, similar to the system shown in Figure 3 can make helium recovery economical even for average size users whose production is scattered over many points of use and over a large area. 

Today’s improved recovery economics and higher purities achievable by some helium recovery system vendors now make even semiconductor and flat panel display manufacturers (historically reluctant to employ helium recovery) reconsider helium recycling systems.

Some still drag their feet

Still, helium recycling is not as widely adopted as one would expect, given the maturity of helium recycling technology and the recent environment of tight supply, rapidly rising helium prices, and the ever increasing concern regarding helium availability. 

The reason for this resistance is that not all helium applications are conducive to helium recycling. For example, even though space shuttle and rocket launches consume very large quantities of helium, capturing and recycling this helium is impractical and uneconomical. However, even on the launch pad there are some uses of helium that easily lend themselves to helium capture and reuse. 

Figure 4: A flow diagram for helium gas recovery into high-pressure cylinders for reuse.

Likewise, many universities and R&D companies operating small MRI, NMR, cryostat, or particle accelerator facilities find helium recycling uneconomical due to their relatively low helium consumption and the relatively high cost of helium liquefaction. However, liquefaction is not a step that need be taken by the end user. Helium gas can be recovered into high-pressure cylinders and then reused for other applications at the facility. Alternatively, the reclaimed gas can be sold back to the helium supplier (Figure 4).

The future of helium recovery

As the global economy improves and helium demand growth returns, greater emphasis will be placed on helium conservation by helium producers, industrial gas companies, distributors, and end users. As a result, the economics of implementing helium recycle systems by end users will become increasingly attractive. Further improvements in helium recovery technology will allow even small helium users to reduce their helium consumption and cost. Industrial gas companies and distributors will continue to encourage helium conservation and provide financially attractive helium recovery solutions to their customers. 

Matheson Tri-Gas has a short video on Helium Recovery on its website at:

www.mathesontrigas.com/videocenter/viewmovie.aspx?clipid=4

Gary Shed is Director, Gas Applications Center, Matheson Tri-Gas. He is a Professional Engineer (PE), with a BE degree in Mechanical Engineering from The City College of The City University of New York and ME degree from The City University Graduate School of Engineering. Gary has over 25 years of business development, engineering, and project management experience (19 of which are in the industrial gases industry and 8 in helium business) with particular emphasis on process engineering and applications and industrial gas production facilities design, construction, commissioning and maintenance. 

Gary can be reached by phone at (908)-991-9264 or email at: gshed@matheson-trigas.com