Liquefied Gases: What Are They, and What Are Their Important Uses?

1. What Are Liquefied Gases?

Liquefied gases are gases converted into liquid form through cooling, compression, or a combination of both.

Liquefaction reduces the volume required to store and transport gases, which makes gas handling and distribution more efficient. 

Common liquefied gases include liquefied petroleum gas (LPG), liquefied natural gas (LNG), liquid nitrogen, liquid oxygen, liquid hydrogen, liquid helium, and liquid argon.

2. How Does the Gas Liquefaction Process Work?

Gas liquefaction involves controlling temperature and pressure to convert a gas into liquid form. The process varies depending on the gas and its physical properties.

For cryogenic gases, the process typically involves three main stages:

1. Compression and initial cooling: The gas is compressed and cooled using refrigeration systems and heat exchangers.
2. Purification and further cooling: Impurities are removed when necessary, followed by additional cooling until the gas approaches its liquefaction temperature.
3. Liquefaction and storage: The gas is converted into liquid form and transferred into suitable storage systems designed to maintain the required conditions.

Learn how air is separated into industrial gases through air separation units (ASUs).

3. What Are Some Examples of Liquefied Gases?

3.1. Liquefied Petroleum Gas (LPG)

Liquefied Petroleum Gas (LPG) is a flammable mixture composed primarily of propane (C₃H₈) and butane (C₄H₁₀). It is commonly used for cooking, heating and industrial applications.

LPG can be liquefied and stored under pressure in cylinders and tanks, unlike gases that require cryogenic cooling. 

3.2. Liquefied Natural Gas (LNG)

Liquefied Natural Gas (LNG) is natural gas cooled to a liquid state to facilitate storage and transportation. It is used for energy supply and as a fuel for certain vehicles, including trucks and cars.

Unlike LPG, LNG requires cryogenic conditions to remain liquid. 

3.3. Other Cryogenic and Liquefied Gases

• Liquid nitrogen (LN₂): Supports food freezing, biological sample preservation and laboratory cooling.
• Liquid oxygen (LO₂): Supports medical oxygen supply, steelmaking and industrial manufacturing.
• Liquid hydrogen (LH₂): Supports hydrogen storage, transportation and mobility applications.
• Liquid helium (LHe): Used in specialized scientific and industrial applications requiring extremely low temperatures.
• Liquid argon (LAr): Used in industrial applications requiring an inert atmosphere.
• Liquid carbon dioxide (LCO₂): Used in food freezing and beverage carbonation, as well as in CO₂ transportation for carbon capture, utilization and storage (CCUS).

Read more about cryogenic gases and their importance

4. What Are the Applications of Liquefied Gases?

• Healthcare: Liquid oxygen supports medical gas supply. Liquid nitrogen enables cryopreservation.
• Food processing: Liquid nitrogen and carbon dioxide support rapid freezing and food preservation.
• Manufacturing: Oxygen, nitrogen and argon support metal processing and other industrial operations.
• Energy and transportation: LPG, LNG and liquid hydrogen serve different fuel, storage and transportation requirements.
• Scientific research: Cryogenic gases support specialized cooling and low-temperature applications.

5. How Do Liquefied Gases Support Sustainability?

Liquefied gases can contribute to sustainability initiatives by facilitating gas transportation, supporting low-carbon energy applications and enabling carbon dioxide management.

• Efficient transportation: Liquefaction allows larger quantities of gas to be transported per shipment, potentially reducing the number of deliveries required.
• Hydrogen mobility: Liquid hydrogen facilitates hydrogen storage and distribution for mobility applications, including heavy-duty transportation. Hydrogen produced through low-carbon pathways can support efforts to reduce transportation emissions.
• Carbon capture and storage: Liquefied CO₂ can be transported for industrial utilization or permanent geological storage, supporting carbon capture, utilization and storage (CCUS) initiatives.

With that being said, liquefaction requires energy and its overall environmental impact depends on many factors.

6. Choosing Air Liquide for Your Liquefied Gas Needs

As an industry leader in gases, technologies and services, we combine decades of experience with reliable and quality-focused solutions designed to serve as a one-stop provider for your industrial needs.

Contact us today to learn more about our solutions and how they can help you.