Helium: An Introduction
Helium (He) is a chemical element with atomic number 2. It is the second lightest element in the universe, following hydrogen. As a noble gas, helium is inert, meaning it is non-reactive under normal conditions, and it is colourless, odourless, and tasteless. Its extremely low boiling point makes it invaluable in various scientific and industrial applications.
Common Applications of Helium
Inflation of Balloons
One of the most recognizable uses of helium is for inflating balloons. Due to its lower density compared to air, helium-filled balloons float. This property is utilized for decorative party balloons, as well as for scientific weather balloons. In India, the India Meteorological Department (IMD) regularly launches weather balloons filled with helium to carry instruments (radiosondes) into the upper atmosphere to collect data on temperature, humidity, and atmospheric pressure, crucial for weather forecasting.
Cryogenic Cooling in MRI Scanners
Helium’s extremely low boiling point (4.2 K or -269 °C) makes it an essential cryogen for cooling superconducting magnets. Magnetic Resonance Imaging (MRI) scanners, widely used in hospitals across India for medical diagnostics, rely on such magnets. Liquid helium maintains these magnets in a superconducting state, enabling the generation of powerful magnetic fields necessary for high-resolution imaging of the human body.
Inert Shielding Gas for Welding
In various industrial welding processes, particularly arc welding of reactive metals like aluminium and magnesium, an inert atmosphere is required to prevent oxidation and contamination of the weld joint. Helium, being an inert gas, serves as an excellent shielding gas. Its higher thermal conductivity compared to argon also allows for faster welding speeds and deeper penetration, benefiting manufacturing industries in India, including aerospace and automotive component production.
Leak Detection
The small atomic size and inert nature of helium make it ideal for detecting leaks in vacuum systems and high-pressure containers. When a component is suspected of having a leak, it can be pressurized with helium, and a helium mass spectrometer can then detect minute amounts of helium escaping from the leak points. This method is critical for ensuring the integrity of pipelines, refrigeration systems, and semiconductor manufacturing equipment.
Cryogenic Research and Specialized Applications
Beyond MRI, liquid helium is indispensable in various advanced cryogenic research applications. It is used to achieve ultra-low temperatures required for studying superconductors, quantum computing, and other fundamental physics experiments in research institutions across India. Furthermore, in specialized industrial processes, such as the production of optical fibers, helium is used to maintain a clean, inert environment.
Natural Occurrence on Earth
Helium is not readily available in large quantities in the Earth’s atmosphere; it constitutes only about 0.00052% by volume. The primary terrestrial source of helium is the radioactive decay of heavy elements like uranium and thorium within the Earth’s crust. Alpha particles emitted during this decay are essentially helium nuclei, which then capture electrons to form neutral helium atoms. This helium often becomes trapped in natural gas deposits over geological timescales. Major helium-rich natural gas fields are found in countries such as the United States, Qatar, Algeria, and Russia. India’s own natural gas reserves generally contain very low concentrations of helium, making it largely dependent on imports for its helium requirements.
Industrial Extraction and Utilization
Industrial extraction of helium primarily occurs as a byproduct of natural gas processing. Natural gas from helium-rich fields is subjected to a process called fractional distillation. This involves cooling the natural gas to extremely low temperatures. As the temperature drops, different components of the natural gas, such as methane, propane, and butane, liquefy at their respective boiling points. Since helium has the lowest boiling point of all elements, it remains a gas even when other components are liquefied. This gaseous helium is then further purified through a series of cryogenic distillation steps to achieve the desired purity levels for industrial and scientific use. The purified helium is then compressed and stored as a gas or further cooled to its liquid state for transport and distribution to users across various sectors, including those in India for medical, research, and manufacturing purposes.