The Role of Refrigeration in CO₂ Liquefaction

CO₂ liquefaction requires the gas to reach specific pressure and temperature conditions. Refrigeration provides the cooling capacity necessary to remove heat from the compressed CO₂ and bring it to the required liquefaction conditions.

The refrigeration system works together with the CO₂ liquefaction section rather than operating as an independent process.

The typical process is:

Compressed CO₂ → Heat Exchange → Refrigeration → Cooling & Condensation → Gas-Liquid Separation → Liquid CO₂ Storage

Efficient thermal management and stable refrigeration control are essential for maintaining reliable liquefaction performance.

How the CO₂ Refrigeration & Liquefaction System Works

1. Compressed CO₂ Feed

Purified and dried CO₂ enters the liquefaction system under controlled pressure and flow conditions.

The CO₂ feed should meet the required moisture and impurity specifications before entering the low-temperature section.

2. Heat Exchange

The incoming CO₂ is first cooled through an integrated heat-exchange system.

Where appropriate, process-to-process heat exchange can be used to improve thermal efficiency and reduce the refrigeration duty.

3. Refrigeration

The refrigeration system removes the remaining heat required to bring the CO₂ to the target liquefaction conditions.

The refrigeration capacity is selected according to the CO₂ flow rate, inlet temperature, operating pressure, ambient conditions, and required liquid CO₂ production rate.

4. CO₂ Condensation

As the CO₂ reaches the required temperature and pressure conditions, part of the gas condenses into liquid CO₂.

The resulting two-phase stream is then transferred to the gas-liquid separation section.

5. Gas-Liquid Separation

A dedicated separator separates liquid CO₂ from the remaining gas phase.

The liquid CO₂ is transferred to the storage system, while non-condensable gases are managed through the designed vent, recycle, or purification arrangement.

6. Refrigeration Control

Automatic control regulates key refrigeration parameters such as temperature, pressure, refrigerant flow, and compressor loading.

This enables the system to adapt to variations in CO₂ production and maintain stable operating conditions.

Refrigeration System Configuration

YTC selects the refrigeration configuration according to project requirements.

The system can incorporate:

• Refrigeration compressor

• Condenser

• Expansion system

• Evaporator or process heat exchanger

• Refrigerant circulation system

• Temperature and pressure control

• Automatic protection and monitoring

The exact configuration depends on the required cooling capacity, ambient conditions, operating pressure, refrigerant selection, and plant layout.

Energy-Efficient Heat Management

Refrigeration is one of the major energy-consuming sections of a CO₂ liquefaction plant. YTC therefore considers thermal efficiency during system design.

Depending on the project, the system can incorporate:

• Optimized Heat Exchange

Efficient heat exchangers reduce unnecessary refrigeration duty and improve overall thermal performance.

• Refrigeration Capacity Control

Automatic capacity control allows the refrigeration system to adjust its operating load according to the actual CO₂ production rate.

• Cold-Energy Integration

Where suitable, available cold streams within the process can be considered for heat integration to reduce the refrigeration load.

• Automatic Operating Control

Temperature, pressure, and refrigeration parameters are continuously monitored to maintain stable operation and avoid unnecessary energy consumption.

Actual energy consumption depends on the CO₂ flow rate, inlet conditions, ambient temperature, operating pressure, refrigeration configuration, and site utilities.

Non-Condensable Gas Management

CO₂-containing gas may contain non-condensable components such as N₂, O₂, H₂, and other light gases.

During liquefaction, these components tend to remain in the gas phase rather than condense together with CO₂.

If non-condensable gases accumulate, they can increase system pressure and reduce liquefaction efficiency.

YTC can therefore incorporate appropriate venting, separation, recycle, or purification arrangements according to the feed gas composition and required CO₂ product specification.

Integration with the CO₂ Recovery Plant

The refrigeration and liquefaction unit is normally integrated with upstream and downstream process equipment:

CO₂ Pretreatment

↓

CO₂ Compression

↓

Purification & Drying

↓

Refrigeration & Liquefaction

↓

Gas-Liquid Separation

↓

Liquid CO₂ Storage

The exact process sequence depends on the source of the CO₂ and the required final product specification.

For fermentation gas, flue gas, chemical process gas, or other industrial CO₂ sources, the purification requirements may be different before the gas enters the refrigeration section.

Product Quality and Liquefaction

The refrigeration system provides the thermal conditions required for CO₂ liquefaction, but the final liquid CO₂ purity is determined by the complete purification process.

Upstream treatment may include:

• Gas washing

• Oil and aerosol removal

• Adsorption

• Dehydration

• Desulfurization

• Hydrocarbon removal

• Distillation or stripping

• Final purification

After the required impurities have been removed, the purified CO₂ can be cooled and liquefied.

Depending on the feed gas composition and overall process configuration, YTC CO₂ recovery plants can produce liquid CO₂ with purity up to 99.998%.

Flexible Capacity for Different Applications

YTC refrigeration and liquefaction systems can be engineered for different CO₂ production capacities, from smaller industrial installations to large-scale CO₂ recovery plants.

The design considers:

• CO₂ processing capacity

• CO₂ inlet pressure and temperature

• CO₂ concentration

• Required liquid CO₂ production

• Ambient conditions

• Available utilities

• Storage requirements

• Required operating flexibility

The refrigeration system can be supplied as part of a complete CO₂ recovery plant or integrated with an existing CO₂ purification and liquefaction system.

YTC CO₂ Refrigeration & Liquefaction Solution

YTC provides integrated CO₂ purification, compression, refrigeration, liquefaction, storage, and automatic control solutions for a wide range of CO₂ recovery applications.

With 16+ years of experience in CO₂ treatment and recovery and 200+ CO₂ projects completed worldwide, YTC combines process engineering, equipment manufacturing, installation, commissioning, and technical support within a complete project solution.

From refrigeration system design to final liquid CO₂ production, YTC develops each solution according to the customer’s CO₂ capacity, feed gas conditions, operating environment, energy requirements, and final product specification.