The Helium Conundrum (2)
Investigators have identified three conditions, geologically, for the formation of exploitable helium reserves. First, the basement rock must be rich in uranium and/or thorium (whose decay creates helium nuclei). Secondly, the rock has to be faulted and fractured, so that the fissures function as flow channels.
But the most important factor, says the Inter-American Corporation, which specializes in helium exploration and production, “is the presence of a cap rock or seal that is impermeable enough to withstand helium leakage. This is the primary reason why we do not see more helium fields…”
Helium is being created continually beneath Earth’s surface. But, as King writes, in Geology.Com “its rate of natural production and accumulation is so slow that it must be considered a nonrenewable resource”.
Actually, most of the world’s helium is not underground, but rather, wafting through the atmosphere—in a one-to-two million year escape gambit. The American Physical Society (APS) advises though, that the 700,000 billion cubic feet (BCF) of valuable space-bound fluid is too rarefied to exploit economically.
Concurringly, Paul Lafleur, president of Canada’s Petro-Find Ltd, notes that “It is too expensive to separate helium from ambient air, because it contains only 5.4 ppm helium…”
Even to tap terrestrial sources, he adds, is costly and technically taxing: “The high price of helium, which is about 40 times that of natural gas, relates to the expensive separation and purification processes required to achieve the desired high grades”.
Helium is intermixed with methane (the most abundant natural gas) and other associated fluids—from which it needs to be separated. These include nitrogen, hydrogen, neon and argon. Each gas has a characteristic “boiling point,” below which it becomes a liquid.
Separation entails progressively reducing the temperature, until only helium (which has the lowest boiling point of any element) remains gaseous. “There are two stages in isolation of helium from natural gas,” explains an Internet posting from Gazprom VNIIGAZ, Russia’s natural gas behemoth.
“At stage one, the process of low-temperature condensation produces helium concentrate. The volume share of the target substance [i.e., helium] is at least 80 per cent in the product. Further on, helium concentrate gets cleaned from impurities – methane, nitrogen, hydrogen, neon and argon”.
Helium’s rising strategic profile stems from its light weight, low boiling point (4 K, compared with hydrogen-20 K; nitrogen-77 K and oxygen-90 K) and legendary chemical stability. It’s the most unreactive of all the noble (inert) gases, except neon—and more widely used, commercially and industrially.
“Helium is absolutely essential,” asserts APS, “to achieving the extremely cold temperatures required by many current and emerging technologies…”
Currently, the greatest use of helium, is for cooling the superconducting magnets of hospital magnetic resonance imagers (MRI scanners)—which are gaining importance, as diagnostic tools. It also prevents magnets in particle accelerators, such as CERN’s Large Hadron Collider, from overheating.
In fact, APS projects a future role for helium in rail transport systems, where high-speed magnetic levitation (MAGLEV) trains are already being introduced. These vehicles attain speeds of 500 km per hour, using superconducting magnets to rise off the track and eliminate friction.
But this noble gas has mundane applications as well. Helium helps divers to breathe. Inert and lighter than air, it is also employed for atmospheric lifting: Whether it is raising party balloons to the ceiling, buoying up weather and research craft or floating giant cargo-carrying airships.
Because of its chemical stability and extreme cryogenic properties, space agencies use helium to purge hydrogen, oxygen and other gases from the fuel tanks of their rockets. During the Space Shuttle era, Karen H. Kaplan wrote in PhysicsToday.Org, that NASA used a million cubic feet for every launch.
The Helium Conundrum (1)