Liquid CO2 Storage Pressure: Key Facts and Safety Standards

Liquid carbon dioxide (CO₂) is a versatile industrial commodity used in food processing, beverage carbonation, firefighting, welding, and enhanced oil recovery. To store CO₂ in its liquid form, it must be kept under specific pressure and temperature conditions. This article explains the liquid CO₂ storage pressure requirements, the science behind CO₂ liquefaction, relevant safety standards, and practical guidelines for industrial operations.

Understanding the Basics: How CO₂ Becomes Liquid

Carbon dioxide exists naturally as a gas at atmospheric pressure. To transform it into a liquid, both temperature and pressure must be carefully controlled. The CO₂ phase diagram shows that CO₂ becomes liquid only when pressure is above its triple point (5.18 bar / 75 psi) and temperature is below 31.1°C (88°F), known as the critical temperature.

In industrial storage, liquid CO₂ is typically kept at pressures between 12–22 bar (174–319 psi), depending on the storage design and ambient temperature. Below these pressures, the CO₂ would revert to a gas; above them, storage vessel stress and safety become major concerns.

Why Pressure Matters in Liquid CO₂ Storage

• Preventing Phase Change: Maintaining adequate pressure ensures CO₂ remains in liquid state during storage and transport.
• Equipment Safety: Pressure controls reduce risks of vessel rupture or valve damage.
• Operational Efficiency: Stable pressure ensures consistent CO₂ delivery for applications like beverage carbonation or dry ice production.

Typical Pressure Ranges for Different Storage Systems

Liquid CO₂ can be stored in various container types, each with its own pressure requirements:

• High-Pressure Gas Cylinders: 50–60 bar (725–870 psi), often used for small-scale distribution.
• Low-Pressure Refrigerated Tanks: 12–22 bar (174–319 psi), common for bulk CO₂ storage in food processing plants.
• Transport ISO Tanks: 17–22 bar (246–319 psi), designed for safe shipment over long distances.

Temperature and Pressure: The Critical Link

In liquid CO₂ storage, pressure and temperature are directly related by CO₂’s vapor pressure curve. For example:

• At -18°C (0°F), liquid CO₂ has a pressure of around 12 bar (174 psi).
• At 0°C (32°F), pressure increases to about 17 bar (246 psi).
• At 20°C (68°F), pressure rises to approximately 57 bar (827 psi), which is unsuitable for low-pressure storage tanks.

This is why many bulk CO₂ tanks are equipped with refrigeration systems to keep temperatures low, thus reducing internal pressure.

International Safety Standards for Liquid CO₂ Storage

To ensure safety and compliance, liquid CO₂ storage systems must meet recognized industry and governmental standards, such as:

• ASME Boiler and Pressure Vessel Code – Governs design and construction of pressure vessels in the U.S.
• ISO 9809 – Specifies design for gas cylinders and vessels used worldwide.
• EN 13445 – European standard for unfired pressure vessels.
• DOT Regulations – U.S. Department of Transportation rules for CO₂ transport containers.

Safety Risks of Improper Pressure Management

Storing liquid CO₂ outside its recommended pressure range can result in serious hazards:

• Overpressure Explosions: Excessive pressure can rupture tanks, causing life-threatening accidents.
• Rapid Phase Change: Sudden depressurization can cause CO₂ to expand violently, creating dry ice or a gas cloud.
• Asphyxiation Hazards: Escaping CO₂ gas displaces oxygen in enclosed areas.

Best Practices for Liquid CO₂ Pressure Control

• Install pressure relief valves to prevent overpressure incidents.
• Use automatic pressure monitoring systems with alarms.
• Maintain regular inspection and certification of vessels according to national regulations.
• Train operators on emergency venting procedures.

Liquid CO₂ Storage Solutions by Cryo-Tech

Cryo-Tech offers a full range of CO₂ storage and transport solutions engineered to meet stringent safety and performance standards. Their products include:

• ISO Tanks for long-distance CO₂ transport.
• Refrigerated Bulk Tanks for stable low-pressure storage.
• Portable Liquid Cylinders for on-site use in food, beverage, and welding applications.

With global certifications, custom design capabilities, and robust after-sales service, Cryo-Tech ensures CO₂ storage systems are both compliant and operationally efficient.

Future Developments in CO₂ Storage Pressure Technology

Emerging trends in CO₂ storage include improved insulation materials to reduce heat ingress, AI-powered monitoring for predictive maintenance, and hybrid vessels capable of handling multiple cryogenic gases. These innovations will further improve safety, reduce energy costs, and expand CO₂ applications in industries such as carbon capture and utilization (CCU).

Conclusion

Liquid CO₂ storage pressure is a critical parameter that determines operational safety, equipment lifespan, and product quality. By understanding the relationship between pressure, temperature, and CO₂ phase behavior—and by complying with international safety standards—industries can safely harness the benefits of liquid CO₂. With advanced solutions from companies like Cryo-Tech, businesses can achieve both safety and efficiency in CO₂ storage and transport.