Liquid oxygen is the liquid form of oxygen at low temperatures, with a density of about 1141kg/m³ and a light blue transparent color. As a typical cryogenic liquid, its boiling point is extremely low (-183℃), and the huge temperature difference with the surrounding environment makes it necessary to rely on efficient thermal insulation measures. In addition, although liquid oxygen is not flammable, it has strong oxidizing property, and contact with organic materials, oil and grease may cause violent reaction, which also determines that its storage and transportation need to strictly follow the safety norms.
1 liter of liquid oxygen can produce about 860 liters of gaseous oxygen after vaporization, this characteristic makes liquid oxygen show significant advantages in large-scale storage and transportation. In a medical scenario, for example, a liquid oxygen storage tank of the same capacity can satisfy the hospital’s oxygen needs for several weeks, whereas gaseous oxygen cylinders need to be replaced frequently. In addition, the purification process of liquid oxygen can make its purity over 99.5%, which provides quality assurance for precision medical and high-end industrial applications.
Cryogenic distillation: the mainstream production process
The industrialized production of liquid oxygen is mainly realized through the air separation unit (ASU), with the following process:
Air compression and purification: After the air is pressurized by the compressor, it is passed through molecular sieve and other equipments to remove water, carbon dioxide and hydrocarbons, so as to avoid crystallization and blockage of equipments at low temperature.
Cryogenic cooling and distillation: The purified air is cooled to about – 200℃ by a heat exchanger and enters a high pressure distillation tower. Due to the different boiling points of nitrogen and oxygen (nitrogen – 196℃, oxygen – 183℃), the two are separated in the tower, and “crude oxygen” with about 90% purity is obtained at the bottom of the tower, which is then purified by the low-pressure tower to medical or industrial standards.
Non-cryogenic technologies: complementary programs
For low purity oxygen needs, non-cryogenic technologies such as pressure swing adsorption (PSA) or membrane separation can be used. These methods consume less energy, but the output oxygen purity is usually lower than 95%, which is mainly used in sewage treatment, aquaculture and other scenarios.
Fullcryo provides professional liquid oxygen ASU plant construction services, 7*24 hours monitoring, the fastest response to customer needs.
1.Stationary tanks: Typical design is double-layer stainless steel structure, sandwich filled with pearlescent sand and vacuum, such as Fullcryo’s tanks with working pressure 5-37bar, designed for temperatures ranging from – 196℃ to 50℃, and the evaporation rate of liquid oxygen is controlled below 0.1% by vacuum adiabatic insulation and inert gas protection.
2.Mobile Dewar Cylinders: Suitable for small and medium scale oxygen scenarios, with vacuum jacket and polyurethane insulation, commonly used in hospital emergency transfer or laboratory oxygen.
Liquid oxygen transportation relies on professional cryogenic tankers. For example, Fullcryo’s KP9408GDYYA semi-trailer has a capacity of 27m³ and is equipped with EBS braking system and high-efficiency carburetor, which improves the unloading efficiency by 20% compared with traditional equipment. During long-distance transportation, the tanker needs to monitor the temperature and pressure in real time to ensure that the liquid oxygen is in a stable liquid state.
Coolbox is an integrated gas supply solution from Fullcryo, which provides on-demand delivery service for small and medium-sized users through remote liquid level monitoring and intelligent control system. This model can reduce the cost of gas supply by more than 30% compared to traditional cylinders, and is especially suitable for community hospitals, small factories and other scenarios.
In the medical scene, liquid oxygen is the core material for the treatment of respiratory system diseases. Whether it is oxygen therapy for COPD patients, emergency equipment in emergency rooms, or ventilator support in ICUs, high-purity liquid oxygen is converted into medical oxygen through vaporization, which directly sustains patients’ lives. during the global public health incident in 2020, liquid oxygen storage tanks became the “life support” for a number of designated hospitals due to their ability to provide a continuous and stable supply of oxygen “.
Iron and steel metallurgy: In the steel making process, liquid oxygen improves the combustion efficiency in the furnace through the oxygen blowing process, shortens the smelting time and reduces the energy consumption, so that the quality of steel can be improved in tandem with the output.
Chemical Synthesis: As a key reaction raw material or catalyst, liquid oxygen is involved in the production of methanol, ethylene and other chemicals, promoting the development of polymer materials and fine chemicals.
Aerospace: Liquid oxygen and liquid hydrogen combine to form the classic propellant for rockets, such as SpaceX’s Falcon rocket, which relies on the strong oxidizing property of liquid oxygen to ignite the fuel and realize space exploration.
Scientific research and environmental protection
In environmental management, liquid oxygen can be used in the treatment of eutrophication of water bodies to improve water quality through oxygenation.
In the hydrogen industry, liquid oxygen is involved in the preparation of raw materials for hydrogen-oxygen fuel cells, which contributes to the transformation of green energy.
In laboratory scenarios, liquid oxygen is used in low-temperature materials research, superconductivity experiments and other cutting-edge fields.
When handling liquid oxygen, you must wear low-temperature protective gloves, masks and long-sleeved overalls to avoid frostbite caused by direct skin contact. At the same time, we should be alert to the possible environmental oxygen enrichment caused by oxygen leakage, and strictly prohibit the use of open flame or flammable tools in the operation area.
Liquid oxygen storage tanks should comply with ASME standards and be installed in a well-ventilated area far away from combustible materials (safety distance ≥10 meters). Regularly check the tank pressure relief device, the integrity of the insulation layer and the sealing of pipeline connections to prevent low temperature damage and oxygen leakage.
In case of liquid oxygen leakage, immediately evacuate the surrounding people, use explosion-proof tools to enclose, and turn on forced ventilation to reduce oxygen concentration. For frostbite personnel, warm water should be used to rewarm slowly, to avoid secondary damage caused by hot compresses or friction.
New ASUs are trying to integrate renewable energy sources, such as wind power or photovoltaic power to drive air compression, to reduce carbon emissions from the production process. In addition, the introduction of heat pump technology can recover low-temperature waste heat and improve the efficiency of energy utilization. 2.
The application of vacuum insulation panels (VIP) and nano-porous materials is expected to improve the thermal insulation performance of liquid oxygen storage tanks by more than 50%. Intelligent monitoring system realizes remote warning and maintenance reminder of the storage tanks’ status through the Internet of Things (IoT) technology.
In the field of deep space exploration, scientists are studying the use of oxides in lunar soil to produce liquid oxygen, which will provide resource support for future lunar bases; in the medical field, the combination of liquid oxygen and stem cell cryopreservation technology may promote breakthroughs in the field of organ transplantation.
