Helium is a scarce strategic resource, especially in China, where helium resources are extremely scarce and almost entirely dependent on imports. However, helium has a wide range of applications and is an essential resource in high-end manufacturing fields such as military reconnaissance airships, industrial optical fibers, semiconductors, air conditioning, and welding. The 2017 Qatar diplomatic crisis once again severely disrupted the global helium supply, causing significant headaches for many gas companies and users. The domestic industrial sector's helium consumption has been increasing substantially year by year, yet there has been no purification and recycling in the industrial field, leading to direct emission into the atmosphere after consumptive use, resulting in tremendous waste. Therefore, research on helium purification and recycling technologies in the industrial sector has once again become a focal issue of industry concern.
[Technical Introduction]
The commonly used method for helium purification and recycling equipment is cryogenic condensation. Additionally, during the development of the equipment, numerous advanced technologies in the cryogenic field were employed, including vibration reduction for high-pressure helium compressors, specialized welding techniques for cryogenic-resistant high-pressure copper pipelines, and sealing technologies for cryogenic high-pressure quick-connect fittings, all aimed at optimizing the product. Building on this foundation, breakthroughs in membrane separation purification technology enabled the purification of low-purity helium (≥10%) to over 99.5% purity through composite purification and separation methods, achieving a system purification recovery rate of ≥60%. It is reported that a fiber-optic high-purity helium recovery and purification project by a domestic enterprise in China successfully passed acceptance in Shenzhen and was officially integrated into the user's production line for gas supply. This project successfully achieved disturbance-free gas recovery in high-temperature, high-speed, and high-dust environments, purifying feed gas with ≤50% helium content online and supplying >99.999% high-purity helium back to the process. It features 24-hour unattended automatic operation, remote monitoring, and other capabilities. The project's infrastructure, gas extraction and supply pipeline layout, and on-site construction were meticulously standardized, meeting user quality requirements and overall reducing helium consumption by over 55%, earning user recognition and praise.
[Technical Features]
The new industrial waste helium purification and recycling equipment manufactured by Chinese enterprises utilizes industrial PLCs to monitor the purity, measurement, pressure, and temperature of helium within the system. This enables fully automated monitoring of compressors, drying and purification units, purifiers, and various control valves, completing the automation of equipment operations. Fully intelligent, safe, and reliable automatic control technology is also a key feature and innovation of the project.
Helium purification is an internationally advanced research field, with methods including cryogenic condensation, membrane separation, pressure swing adsorption, and chemical adsorption. Building on cryogenic research, Chinese enterprises have overcome technical bottlenecks in cryogenic condensation separation, developed industrial helium membrane separation purification technologies and equipment, and competed with international giants in helium purification technology and equipment. They are actively researching composite helium separation methods combining membrane separation and cryogenic separation, leveraging the high recovery rate and high purity of membrane and cryogenic separation. Helium is first coarsely purified using membrane separation technology and then finely purified using cryogenic separation, meeting the dual industrial needs of energy efficiency and high purity.
[Scope of Application]
Helium is primarily used in medical, military, refrigeration, semiconductor, pipeline leak detection, high-precision welding, metal manufacturing, deep-sea diving, optoelectronic product production, balloon lifting, scientific research, and military fields. Below, an analysis of helium resource users is conducted based on its main applications.
(1) Nuclear Magnetic Resonance (Cryogenic Superconducting) Field
Magnetic Resonance Imaging (MRI) systems utilize cryogenic superconducting magnet technology that requires liquid helium for cooling. Statistics show MRI equipment accounts for 34% of global helium consumption, making it an end-use industry. Although demand for MRI systems is decreasing in developed countries, demand in developing nations continues to grow robustly, maintaining strong liquid helium requirements.
(2) Refrigeration (Household Appliances) Field
Helium is primarily used for leak detection in condensers, evaporators, and pipeline systems.
(3) Semiconductor and Optical Fiber Fields
Helium is primarily used as a protective gas in the semiconductor industry for growing germanium and silicon crystals, as well as a cooling and protective atmosphere gas in the production of optical fiber preforms and fiber drawing processes.
(4) Welding Shielding Gas
Application: To prevent certain metals from reacting with oxygen and nitrogen in the atmosphere when heated or melted, an inert atmosphere must be used for protection. A significant amount of helium is consumed in metal welding processes. In tungsten inert gas (TIG) welding, the non-consumable tungsten electrode, hot metal filler, and welding area are protected by a continuous flow of helium or a helium-argon mixture. The shielding gas mixture for welding can be prepared by blending helium and argon in varying proportions. Depending on the welding technique, filler wire, and base material being welded, the composition of the gas mixture may vary. Typically, helium content in helium-argon mixtures ranges from 15% to 70%.
(5) Cryogenic Engineering Field
Application: Due to helium's chemical inertness, extremely low liquefaction point, near-ideal gas behavior at all temperatures except extremely low ones, high specific heat capacity per unit mass, low viscosity, and high thermal conductivity, it is commonly used as the working medium in closed-cycle cryocoolers, as a cooling medium for low-temperature superconducting magnets and superconducting cavities in major scientific projects, and for research experiments in universities and institutions.
(6) Aerospace Field
Application: In rocket and spacecraft fuel systems, helium is used to purge cryogenic fuel and oxidizer tanks, as well as pressurize the ullage space above the liquid in cryogenic tanks. This provides the necessary pressure for direct transfer of liquid hydrogen and liquid oxygen or simply supplies a net positive suction head for the fuel delivery pump. Helium is commonly employed as a working medium in pneumatic control systems. Prior to rocket launches, cryogenic helium is utilized to precool upper-stage liquid hydrogen rocket engines to achieve propulsion efficiency within minutes of ignition. Liquid helium is also widely used in cryogenic radiation detectors and other specialized instruments for space exploration programs.