Why Final CO₂ Purification Is Important

CO₂ recovered from fermentation, industrial processes, or other gas sources may contain trace impurities that cannot be completely removed during initial gas treatment.

Depending on the source, these impurities may include:

• Oxygen

• Nitrogen

• Hydrogen

• Hydrocarbons

• Alcohol or other volatile compounds

• Moisture

• Other light and non-condensable components

Even at low concentrations, these impurities can affect CO₂ liquefaction, storage stability, and final product quality.

The purification reboiler provides an additional separation stage before liquefaction, helping reduce residual volatile and non-condensable impurities.

How the CO₂ Purification Reboiler Works

The purification reboiler uses controlled heating and gas-liquid separation to selectively remove components with different boiling and condensation characteristics from the CO₂ stream.

1. Purified CO₂ Feed

After compression, preliminary purification, and dehydration, the CO₂-rich gas enters the purification section under controlled pressure and temperature conditions.

The exact inlet conditions depend on the CO₂ source and upstream process configuration.

2. Controlled Heating

The CO₂ stream enters the reboiler system, where controlled heat input creates the required temperature conditions for further separation.

Heating is carefully controlled to maintain stable operation while avoiding unnecessary energy consumption.

3. Stripping and Separation

The reboiling process promotes the separation of CO₂ from more volatile and non-condensable components.

Light gases and other components with different phase-equilibrium characteristics are preferentially removed from the CO₂ stream, while the purified CO₂ remains available for downstream processing.

4. Gas-Liquid Separation

The generated gas and liquid phases are separated within the purification system.

Proper control of temperature, pressure, residence time, and liquid level helps maintain stable separation performance.

5. Removal of Non-Condensable Components

Components such as N₂, O₂, H₂, and other light gases may remain in the gas phase under CO₂ liquefaction conditions.

The purification reboiler and associated separation system can therefore reduce the concentration of these components before the CO₂ enters the liquefaction stage.

6. Purified CO₂ Output

The treated CO₂ leaves the purification section under controlled conditions and is transferred to the drying and/or liquefaction stage according to the overall plant configuration.

Purification for Different CO₂ Sources

The required purification process depends strongly on the source of the recovered CO₂.

Brewery & Ethanol CO₂

Fermentation CO₂ may contain alcohol, moisture, fermentation aerosols, and other volatile substances. The purification system can be configured to remove these contaminants before liquefaction.

Flue Gas CO₂

Flue gas-derived CO₂ requires extensive pretreatment and capture before final purification. After capture and concentration, the purification system can be configured to control residual oxygen, nitrogen, moisture, and other process-specific contaminants.

Chemical & Petrochemical CO₂

Chemical and petrochemical gas streams may contain hydrocarbons, sulfur compounds, hydrogen, carbon monoxide, and other process-specific impurities.

The purification sequence is therefore customized according to the actual feed gas composition.

Integration with CO₂ Drying and Liquefaction

The purification reboiler normally works as part of a complete CO₂ recovery and liquefaction system.

A typical process may be arranged as:

CO₂ Pretreatment

↓

CO₂ Compression

↓

Preliminary Purification

↓

Adsorption & Drying

↓

Purification Reboiler

↓

CO₂ Liquefaction

↓

Final Purification / Separation

↓

Liquid CO₂ Storage

The actual process sequence may vary according to the CO₂ source and required product specification.

The purification reboiler should therefore be considered as one component of the complete purification system rather than a standalone device that determines final CO₂ purity.

Controlled Heating and Energy Management

The reboiler requires controlled heat input to achieve the required separation conditions.

YTC optimizes the heating system according to the process pressure, CO₂ flow rate, feed composition, impurity load, and required purification performance.

Depending on the project, the system can incorporate:

• Automatic temperature control

• Optimized heat transfer

• Insulated process equipment

• Controlled heating duty

• Pressure and liquid-level control

• Integration with plant heat sources where appropriate

These measures help maintain stable purification performance while controlling energy consumption.

Automatic Operation and Process Control

The purification reboiler can be integrated into the plant’s PLC or DCS control system.

Key operating parameters can include:

• Temperature

• Pressure

• Liquid level

• Gas flow

• Heating duty

• Differential pressure

• Purification operating status

Automatic control helps maintain stable operating conditions and coordinate the purification section with upstream compression, drying, and downstream liquefaction systems.

Product Quality

The purification reboiler contributes to the removal of residual impurities before CO₂ liquefaction.

However, final CO₂ purity is determined by the complete recovery and purification process, including pretreatment, compression, adsorption, drying, stripping, liquefaction, and final separation.

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

For applications requiring tighter impurity specifications, such as electronic-grade CO₂, additional purification and monitoring stages can be incorporated according to the customer’s requirements.

Designed for Reliable Continuous Operation

The purification reboiler is engineered for continuous industrial operation and can be customized according to:

• CO₂ processing capacity

• Feed gas composition

• CO₂ concentration

• Operating pressure

• Impurity concentration

• Heating conditions

• Required product specification

• Downstream liquefaction requirements

The system can be supplied as part of a complete YTC CO₂ recovery plant or integrated into an existing CO₂ purification system.

YTC CO₂ Purification Solution

YTC provides integrated CO₂ recovery, purification, drying, stripping, liquefaction, storage, and automatic control solutions for different CO₂ sources and product requirements.

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.

Each purification system is engineered according to the customer’s feed gas composition, impurity profile, processing capacity, operating conditions, and required CO₂ specification.

From recovered CO₂ gas to high-purity liquid CO₂, YTC provides a complete process solution designed for stable operation, effective impurity control, and reliable product quality.