The village of Mankota in the Canadian province of Saskatchewan has around 240 inhabitants and one motel with 18 rooms. Apart from that, it’s mostly grassland. A lot of flat grassland. With the next major town a three-hour car ride away, anyone travelling here should not expect to be overwhelmed by the sights. And yet, since the summer, this small village has a technological attraction that cannot be found anywhere else in the world. Six kilometres from the centre of the village, US company the Weil Group is recovering high-purity helium from nitrogen-rich natural streams using a new process developed by Linde Engineering that does not rely on cryogenic gas separation. This makes it cheaper and more energy-efficient than conventional processes in many cases. It also produces a very high helium yield.
For almost a century, making money with helium was a difficult business. After the First World War, the US government started extracting helium from natural gas. At that time, helium was in demand primarily as a lifting gas for airships. To meet this growing need, the US created helium reserves that exceeded annual global demand several times over. And it was these stockpiles that kept prices low.
From lifting gas to coolant
Today, liquid helium is primarily used as a coolant to generate extremely low temperatures. In the fields of medicine and research, for example, it is used to cool superconductive magnets in magnetic resonance imaging systems. In addition, helium is used in the semiconductor industry as a shielding gas during chip fabrication. It is also needed in aerospace. Now, however, the US government is exiting the helium business and aims to sell its entire reserve by 2021 at the latest. As a result, the price of this sought-after gas is rising – along with the need for new producers.
The Weil Group is keen to capitalise on emerging market opportunities for private helium developers. Its plant in Mankota processes over 250,000 standard cubic metres of raw gas per day, delivering helium with an extremely high purity of 99.999 percent. The helium yield is above 95 percent. Previously, this kind of quality could only be achieved with cryogenic methods, in other words, by distilling the different components at their respective boiling points. “Now, for the first time, we are combining new, highly efficient and selective membranes with a pressure swing adsorption plant in Mankota,” explains project manager Sebastian Zimmermann from Linde Engineering. “These highly selective membranes make our plants more cost effective to buy and to operate, plus they are more efficient than competitor plants. They are thus paving the way for the cost-effective development of smaller helium sources,” adds Zimmermann.
The picture shows membranes - a part of the helium purification facility in Mankota, Canada.
How Linde’s new helium process works
Linde sources the membranes for this new process from its technology partner and specialty chemicals expert Evonik. At the heart of the system are hollow fibres made of high-performance polymers that Evonik embeds in cylindrical stainless steel cartridges. The pre-treated raw gas is fed into the membrane cartridge under high pressure. Small molecules in the gas mixture (for example, helium and hydrogen) and molecules with a high specific rate of diffusion (for example, gaseous water or carbon dioxide) can pass through the membrane faster than larger molecules and leave the membrane module as permeate on the low-pressure side (first exit). Larger molecules such as methane and nitrogen diffuse through the membrane at a much slower rate. As a result, the majority of these leave the hollow fibres again as retentate gas from the module’s second exit (high-pressure side). The technical name for this process is the principle of selective permeation. Depending on the gas composition and the size of the plant, any number of cartridges can be combined in one or more membrane stages to optimise the yield.
To obtain the actual high-purity helium, the concentrated gas from the membranes is fed into a pressure swing adsorption (PSA) plant. Here, remaining impurities are adsorbed under high pressure by the surface of a highly porous material – leaving behind a very high-purity helium.A key challenge in designing these plants lies in choosing the right pre-treatment process for the raw natural gas to remove the components that could damage the membrane. Linde Engineering has a broad spectrum of gas purification processes to choose from here, giving customers optimum flexibility.
Assembly of industrial tent in Mankota
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Protection against extreme cold
In Mankota, the inner technical workings are hidden behind the white canvas of a double-walled industrial tent that is heated with propane gas. “The membranes are extremely sensitive to liquids and so we can’t allow the gas components to condense,” says Linde project manager Zimmermann. “We have to protect the plant because temperatures of minus 20 degrees Celsius are not unusual during the Mankota winter.”
Over the coming years, further helium recovery plants could be built in Canada along the same lines as the Mankota facility. A number of the country's natural gas reserves would be well suited to this production model. In recent years, the largest new extraction plants have been concentrated in Qatar, Algeria and Russia. However, Linde’s new hybrid process combining membrane and pressure swing adsorption technologies is now opening up new opportunities for smaller plants in other regions of the world.
Interview with Jeffrey Vogt, Managing Director and founder of Weil Group Resources.
What makes the Mankota project so special?
Well, we are operating a relatively small plant here, but it’s the technology that sets it apart – it is not being used anywhere else in the world. So we are creating a reference model for the entire industry. We are the first company to extract helium with this level of purity from natural gas using a combination of membrane and pressure swing adsorption technologies.
What made you choose this technology from Linde Engineering?
We evaluated the different processes and the cost-benefit trade-offs. At the end of the day, we chose the technology that would deliver high-purity helium as cost-effectively as possible under the conditions we have here, given this particular gas composition.
What were the greatest challenges in this project?
Some months of Mankota's harsh climate and its isolated location were of course difficult to deal with. But the biggest challenge came from the banks. At the beginning, they were reluctant to provide project finance as there was no precedent in this approach. Now that we are operating, we are seeing increasing interest from the banking community for these unique projects.
How do you see the future of the helium business?
Helium is unique. It is irreplaceable and cannot be manufactured artificially. It is needed in semiconductor, superconductor and many other key applications. As the US government's helium reserve shrinks, opportunities for other providers will keep growing. We believe that demand will rise significantly as this unique element is applied to more high tech applications.
Does this mean that are you planning to build other plants with Linde technology?
We have several other similarly situated projects, and are in discussions about that now with Linde where this technology may be suitable for the given gas composition and project context.