liquid oxygen

Physical Properties of Liquid Oxygen

Chemical Properties of Liquid Oxygen

Liquid Oxygen Supply and Procurement

Liquid oxygen (LOX) is available through industrial gas manufacturers and medical gas suppliers. In addition to liquid oxygen, these providers typically offer a range of other gases such as nitrogen, argon, and hydrogen.

In certain sectors—particularly in pharmaceuticals and advanced medical applications—there is a demand for high-purity oxygen. To ensure quality and performance, liquid oxygen must have a minimum purity level of 99.5%, verified through rigorous testing to eliminate contaminants and impurities.

When purchasing LOX, customers should consult reputable and certified suppliers. Key purchasing criteria include gas specifications, required purity, storage volume, and transportation conditions. In most cases, liquid oxygen is procured under monthly or annual contracts, depending on the client’s operational needs.

Applications of Liquid Oxygen

1. Medical Use
   Liquid oxygen is widely used in hospitals and healthcare facilities to supply oxygen therapy for patients with respiratory disorders. It plays a critical role in the treatment of conditions such as COPD (Chronic Obstructive Pulmonary Disease) and asthma, ensuring a steady and pure oxygen supply in critical care environments.
2. Aerospace Industry
   In aerospace engineering, liquid oxygen serves as a powerful oxidizer in rocket propulsion systems. Due to its high density compared to gaseous oxygen, LOX is preferred in long-range and space launch missions, enabling efficient fuel combustion in rocket engines.
3. Chemical and Steel Industries
   In the production of chemicals and steel, liquid oxygen is used as a primary oxidizing agent. It accelerates decarbonization processes, promotes metal melting, and enhances overall process efficiency in large-scale industrial operations.
4. Energy Sector
   Some power plants utilize liquid oxygen to boost the efficiency of combustion processes, generating significantly higher temperatures and improving the thermal performance of energy generation systems.

Liquid Oxygen Storage Tanks

Liquid oxygen tanks are specialized storage units engineered to maintain oxygen in its cryogenic liquid state. Given the extremely low boiling point of LOX, these tanks require advanced materials and insulation systems.

• Construction Materials: Typically made from stainless steel, aluminum, or high-strength alloys.
• Thermal Insulation: Tanks are insulated using polyurethane foam, vacuum layers, or other cryogenic-grade materials to minimize heat transfer and prevent evaporation.
• Pressure Handling: These tanks must safely withstand internal pressures between 10 to 15 bar, preventing premature phase change from liquid to gas.
• Tank Configurations: LOX tanks may be vertical (standing) for long-term storage or horizontal (lying) for mobile transportation systems.

Industrial Production Process of Liquid Oxygen

Liquid oxygen is produced industrially through Cryogenic Air Separation, which involves cooling atmospheric air and separating its components based on boiling points.

1. Air Intake & Filtration

Ambient air is drawn in using industrial compressors. Dust, moisture, and CO₂ are removed to prevent freezing in later stages.

Goal: Protect cryogenic systems and improve gas purity.

2. Air Compression

Clean air is compressed to 6–10 bar, increasing its density and preparing it for liquefaction.

3. Cooling & Liquefaction

The compressed air passes through multi-stage heat exchangers, gradually cooling to approximately -200°C, at which point it condenses into liquid form. The liquefied air is then fed into the distillation column.

4. Fractional Distillation

In the distillation tower, the major gases in air separate based on their distinct boiling points:

“Liquid oxygen is distilled at a temperature lower than argon but higher than nitrogen, and is collected from the bottom of the distillation column.”

5. Storage and Transportation

Liquid oxygen is stored in cryogenic pressure vessels, specially designed to maintain the extremely low temperatures required to keep oxygen in liquid form. Once stored, it is transported to end-users including hospitals, steel plants, and aerospace facilities.

Safety Considerations in Liquid Oxygen Production

• Liquid oxygen is a powerful oxidizer and must never come into contact with oils or greases, as such contact can lead to violent combustion or explosion.
• All equipment and pipelines must remain dry and clean to avoid contamination or unsafe reactions.
• The use of pressure gauges, safety relief valves, and alarm systems is critical to maintaining operational safety during production and storage.

Why Cryogenic Separation is the Preferred Method for LOX Production?

✅ Achieves oxygen purity levels up to 99.5%
✅ Simultaneous recovery of nitrogen and argon
✅ Ideal for medical, industrial, and research applications
✅ Ensures stable temperature and pressure control

Technical Specifications of Liquid Oxygen Tanks

• Tank Capacity:
  Tank sizes vary depending on application. Domestic LOX tanks may hold just a few liters, whereas industrial tanks can range from 100 liters up to 50,000 liters.
• Pressure Resistance:
  To prevent the vaporization of liquid oxygen, these tanks must withstand high internal pressure as well as extreme cryogenic conditions.
• Thermal Insulation:
  Proper insulation is critical. Vacuum jackets and specialized foam insulation are commonly used to minimize heat transfer and avoid boil-off losses.

Manufacturing and Transport of LOX Tanks

Manufacturing:
The design and fabrication of LOX tanks require precise calculations of internal pressure, volume, and thermal stresses. These tanks are produced in industrial gas manufacturing facilities, using advanced welding techniques and high-pressure testing protocols.

Transportation:

• Cryogenic Tankers:
  LOX is transported using specially designed insulated tankers capable of maintaining the cryogenic temperature. These tankers are constructed from heat-resistant materials to prevent temperature rise during transit.
• Safety Precautions:
  Transporting liquid oxygen comes with risks such as explosion and fire hazards. It’s essential to maintain appropriate temperature and pressure levels and to use pressure-relief valves, heat-resistant nozzles, and real-time gas monitoring systems.

Safety Considerations When Handling Liquid Oxygen

If you’re planning to purchase or use liquid oxygen from a certified supplier or trusted manufacturer, it’s important to know that liquid oxygen is non-toxic. However, two critical hazards must be carefully managed: extremely low temperatures and rapid vaporization.

• Extremely Low Temperature:
  Liquid oxygen boils at -297.3°F (-183°C) and is extremely cold. Components like valves, lines, or couplings exposed to liquid oxygen can cause severe frostbite or cryogenic burns upon contact with unprotected skin or clothing. Skin can freeze to cold surfaces, increasing the risk of injury.
• Rapid Expansion on Vaporization:
  When warmed to room temperature at atmospheric pressure, one volume of liquid oxygen expands to approximately 860 volumes of gaseous oxygen. If this gas is trapped in a closed system, the pressure buildup can lead to explosive rupture of containers, pipelines, or transfer lines.

Potential Hazards During Liquid Oxygen Transfer:

• Strong oxidizing nature of oxygen
• Cryogenic temperatures of both liquid and vapor (classified as a cryogenic fluid)
• Pressure build-up due to vaporization and/or liquid expansion

In oxygen-enriched environments, materials that are normally flammable in air can ignite more easily, burn more intensely, and reach significantly higher temperatures. Even substances not typically considered combustible may catch fire in such conditions. Examples of items commonly found near patients in healthcare settings that may pose a fire risk include:

• Hair oils, oil-based lubricants, skin lotions, facial tissues, clothing, bedding
• Alcohols, acetone, certain plastics
• Powered devices: electric wheelchairs, electric razors, bed remotes, hair dryers, remote controls, TVs, radios, computers, air conditioners, phones, and fans

For example, absorbent materials like fabric or bedding can become saturated with oxygen, and in the presence of an ignition source, can ignite violently.

Fire and Explosion Risk from Contamination:

If oxygen-handling equipment becomes contaminated with oil or grease, it can pose a significant fire hazard. It is crucial to keep oxygen systems away from ignition sources.

One vital safety rule: do not smoke in areas where liquid oxygen is stored or used, as it can lead to dangerous fires or explosions.

Health Considerations with High Oxygen Concentrations

While atmospheric air contains about 21% oxygen and is non-toxic, exposure to elevated oxygen levels can be harmful over time. Studies show that:

• 50% oxygen for more than 24 hours, or
• 80% oxygen for more than 12 hours
  can irritate the respiratory system.

Breathing pure oxygen at pressures above 2–3 atmospheres may also result in observable neurological effects, such as:

• Nausea, dizziness, vomiting
• Fatigue, lightheadedness
• Mood changes, euphoria, confusion
• Poor coordination, muscle twitching
• Tingling sensations (especially in fingers and toes)
• In severe cases: loss of consciousness