01
Characteristics and Standards of Helium
Basic Properties of Helium
Helium, a colorless, odorless, non-flammable gas, is present in the air at a concentration of about 5.2 parts per million. Although helium can be separated from the air in theory, it is often refined from natural gas containing about 0.5% helium because its content is too thin. This rare gas element plays an important role in many fields with its unique chemical properties. It is lighter than air, so it is widely used in airships and balloons, replacing highly flammable hydrogen. At the same time, liquid helium has an invaluable value in the field of cryogenics due to its extremely low boiling point.
History of Naming and Discovery of Helium
As early as 1868, French astronomer Janssen accidentally observed a unique yellow line D in the solar spectrum while observing a total solar eclipse. This discovery is significantly different from the known lines D1 and D2 of the sodium spectrum. At the same time, British astronomer Lockyer also recorded the existence of this yellow line D. At that time, astronomers generally believed that this line only existed in the sun, and they speculated that it might be an unknown metal element. Therefore, Lockyer creatively named this element Helium, which comes from the Greek "sun god" (helio) and the suffix "-ium" indicating a metal element. Its corresponding Chinese translation is "helium". In 1895, Ramsay and Travers worked together to discover an inactive gas when processing pitchblende, which was identified as helium by spectroscopy. This discovery confirmed that helium not only exists in the sun, but is also widely distributed on the earth and is a non-metallic element. Since then, helium has been widely used in various fields. Its low boiling point makes liquid helium an ideal choice for ultra-low temperature cooling, especially in the application of suspended trains and superconductors. At the same time, the chemical inactivity and lighter-than-air characteristics of helium make it an ideal choice for inflating spacecraft and advertising balloons. In addition, helium has shown a wide range of application value in many fields such as marine development, medical magnetic resonance imaging equipment, military industry, scientific research, and petrochemicals.
02
Preparation and application of helium
Preparation method of helium
Condensation method: In industry, condensation method is often used to extract helium from natural gas. This method includes the pretreatment and purification of natural gas, crude helium production and helium refining, and finally 99.99% pure helium can be produced.
Air separation method: This method usually involves extracting crude helium and neon mixed gas from air device by fractionation method. After further separation and purification, 99.99% pure helium can be obtained.
Hydrogen liquefaction method: Hydrogen liquefaction method is also used in industry to extract helium from synthetic ammonia tail gas. The process includes low-temperature adsorption to remove nitrogen, distillation to obtain crude helium, and then oxygen catalytic dehydrogenation and helium purification to finally obtain high-purity helium.
High-purity helium method: If higher purity helium is required, such as 99.9999%, 99.99% pure helium needs to be further purified by activated carbon adsorption.
It is worth noting that helium needs to be subjected to corresponding pressure during the solidification process, because it cannot solidify simply by cooling a saturated liquid to absolute zero. At 2.173K, helium will transform from a normal liquid into a fluid with unique properties, namely a superfluid. This fluid has the characteristics of zero entropy, extremely high thermal conductivity and extremely low viscosity.
Wide Application of Helium
Helium is used in scientific and technological equipment such as superconductors and nuclear magnetic resonance due to its ultra-low temperature properties, and is also widely used in aviation and military fields.
03
Safety and Risks of Helium
Risks and Prevention of Helium Inhalation
Inhaling a large amount of helium will cause oxygen in the body to be replaced by helium, causing symptoms of hypoxia, which may even be fatal in severe cases. In addition, if helium is inhaled directly from a high-pressure gas cylinder, its high flow rate may seriously damage lung tissue. Excessive inhalation of a mixture of helium and oxygen can cause high-pressure nervousness syndrome (HPNS), but a small amount of nitrogen can relieve this symptom, and nitrogen accounts for up to 78% of the air, so there is usually no need to worry. However, inhaling a large amount of helium for a long time may cause damage to the brain or even death. It is worth noting that many French fries contain a small amount of helium in their packaging, but the amount is negligible and will not cause harm.
Safety regulations for the use of helium
When using helium, it should be decompressed through a pressure reducer such as YQY-12 or 152IN-125, and the gas pipeline should be leak-free, which can be confirmed by leak detection with soapy water.
Make sure that the workplace is well ventilated to prevent helium leakage from causing a decrease in oxygen content. When the helium concentration increases to less than 19.5% oxygen content, people will experience a series of symptoms such as rapid breathing, inattention, ataxia, and in severe cases, coma and convulsions, and even death. Therefore, it is necessary to pay close attention to the use of helium to ensure safety.
When the use of helium cylinders is nearing the end, a residual pressure of at least 0.5MPa should be retained to ensure gas quality and safety of use. The bottle valve should remain closed until the residual pressure disappears.
Bottled helium must be stacked in categories during transportation, storage and use, away from open flames and heat sources. Avoid collision and rough loading and unloading during operation to ensure safety. When moving cylinders over long distances, use dangerous goods transport vehicles for transportation. In addition, the temperature of liquid helium is extremely low, and contact with the skin may cause severe frostbite, so special care is required.
[Explosion hazard] Helium itself is non-flammable, but if it is exposed to high heat, the internal pressure of the container may increase, and there is a risk of cracking and explosion. Therefore, special attention should be paid to safety during use.
[First aid measures for inhalation] If helium is accidentally inhaled, you should quickly leave the scene to a place with fresh air and keep your airway open. If you have symptoms of difficulty breathing, you should immediately give oxygen therapy. If you stop breathing, you should immediately perform artificial respiration and seek medical attention quickly.
[Fire-fighting measures] Since helium itself is non-flammable, the main thing to pay attention to in fire-fighting is the possible risks of the container when it is exposed to high heat. In the event of a fire, the container should be moved to an open area as much as possible and sprayed with water to keep the container cool until the fire is extinguished.
