Why Is CO₂ Revert Gas Generated?

Dry ice is produced by expanding liquid CO₂ from its storage pressure to a lower pressure.

During this pressure reduction, only part of the liquid CO₂ forms solid CO₂ snow. The remainder becomes gaseous CO₂.

In a conventional dry ice production system without gas recovery, this low-pressure CO₂ is normally vented.

For continuous or large-volume dry ice production, the accumulated CO₂ loss can represent a significant operating cost.

YTC addresses this loss by recovering the revert gas and returning it to the liquid CO₂ production cycle.

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How the CO₂ Revert Gas Recovery System Works

Process Flow

Dry Ice Machine

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CO₂ Revert Gas Collection

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CO₂ Buffer Balloon

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CO₂ Gas Conditioning

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Oil-Free CO₂ Compression

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Cooling & Refrigeration

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CO₂ Reliquefaction

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Liquid CO₂ Return

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Liquid CO₂ Storage Tank

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Reuse for Dry Ice Production

The result is a partially closed CO₂ recycling loop between dry ice production and liquid CO₂ storage.

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Main System Components

1. CO₂ Revert Gas Collection

Low-pressure CO₂ generated by the dry ice pelletizer or block machine is collected instead of being discharged directly to atmosphere.

The gas-collection system is engineered to avoid interfering with the normal operation of the dry ice production equipment.

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2. CO₂ Buffer Balloon

The buffer balloon provides temporary gas storage between the dry ice production equipment and the CO₂ compressor.

It helps accommodate fluctuations in revert-gas generation and provides more stable gas conditions for downstream compression.

Gas reheating or conditioning can be incorporated where required by site conditions.

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3. Oil-Free CO₂ Compressor

The recovered low-pressure CO₂ must be compressed before it can be reliquefied.

YTC’s current system concept uses a water-cooled, dry-running, non-lubricated two-stage CO₂ piston compressor.

For the existing YTC configuration, the recovered CO₂ can be compressed to approximately 18–20 barg before entering the downstream liquefaction section.

Final compressor configuration is selected according to gas flow, suction conditions, required discharge pressure and project requirements.

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4. Cooling & CO₂ Reliquefaction

After compression, the recovered CO₂ is cooled and condensed using a refrigeration system.

The CO₂ liquefier removes the required heat from the compressed gas until the CO₂ returns to liquid form under the designed operating conditions.

The reliquefied CO₂ can then be returned to liquid storage.

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5. Liquid CO₂ Return

Recovered liquid CO₂ is routed back to the liquid CO₂ storage system.

From storage, it can again be supplied to the dry ice production equipment.

This completes the recovery cycle:

Liquid CO₂ → Dry Ice → Revert CO₂ Gas → Recovery → Reliquefaction → Liquid CO₂

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6. PLC Control System

The recovery process can be operated through an integrated PLC-based control system.

Depending on project scope, the control system coordinates:

• Revert-gas collection

• Buffer conditions

• Compressor operation

• Refrigeration and liquefaction

• Pressure and temperature monitoring

• Liquid CO₂ return

• Alarm and safety functions

• Start/stop sequences

The recovery plant can operate as a dedicated system or be integrated with the overall dry ice production controls.

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CO₂ Utilization in Dry Ice Production

Conventional dry ice pellet and block production typically converts only part of the supplied liquid CO₂ into solid dry ice during each pass, while the remainder becomes revert gas.

YTC’s existing engineering basis indicates conventional dry ice production may achieve approximately 40–45% direct conversion of liquid CO₂ into dry ice, with approximately 55–60% becoming gaseous CO₂.

By recovering and reliquefying a substantial portion of this revert gas, overall CO₂ utilization can be significantly increased.

Depending on system configuration and operating conditions, YTC’s integrated recovery concept is designed to achieve overall CO₂ utilization of up to approximately 90–95%.

Actual recovery and utilization performance depends on dry ice equipment, operating conditions, gas-collection efficiency and system design.

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Key Benefits

Recover Valuable CO₂

Capture process CO₂ that would otherwise be released from dry ice production.

Reduce Liquid CO₂ Consumption

Reliquefied CO₂ is returned to storage and reused, reducing the quantity of replacement liquid CO₂ required.

Improve Dry Ice Production Economics

The value of recovered CO₂ can reduce operating cost, particularly for continuous and high-volume dry ice production.

Increase Overall CO₂ Utilization

Combine conventional dry ice production with gas recovery and reliquefaction to obtain more useful dry ice from purchased or produced liquid CO₂.

Reduce Direct Process Venting

Recovering the revert stream reduces the amount of process CO₂ continuously discharged to atmosphere.

Retrofit Existing Dry Ice Plants

The recovery system can be evaluated for integration with existing dry ice pelletizers or block-making equipment, subject to the operating conditions and gas-collection arrangement of the existing plant.

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Suitable Applications

The YTC CO₂ Revert Gas Recovery System is particularly relevant for:

• Commercial dry ice producers

• Industrial gas companies

• Large dry ice production facilities

• Dry ice pellet production

• Dry ice block production

• Facilities with high liquid CO₂ costs

• Sites with continuous dry ice demand

• CO₂ plants with integrated dry ice production

The economic value of recovery depends primarily on dry ice production volume, liquid CO₂ price, operating hours, utilities and achievable gas-recovery rate.

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New-Build and Retrofit Solutions

New Dry Ice Production Plants

For new projects, YTC can engineer the revert-gas recovery system together with:

Liquid CO₂ Storage + Dry Ice Production + CO₂ Recovery + Compression + Reliquefaction + PLC Control

This allows the complete process to be optimized as one integrated system.

Existing Dry Ice Plants

For existing plants, YTC can evaluate the possibility of adding revert-gas recovery and reliquefaction equipment.

Typical engineering inputs include:

Dry ice machine capacity

Number of machines

Daily operating hours

Liquid CO₂ consumption

Existing CO₂ storage pressure

Available utilities

Current vent-gas arrangement

Project location

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Is CO₂ Revert Gas Recovery Economically Attractive?

The answer depends on the individual plant.

The main economic variables are:

Annual dry ice production

Liquid CO₂ consumption

Local liquid CO₂ price

Annual operating hours

Electricity and cooling costs

Recoverable CO₂ volume

Required investment

For larger and continuously operated dry ice plants, the value of recovered CO₂ can become substantial.

YTC can evaluate the CO₂ mass balance and provide a project-specific recovery configuration based on the customer’s actual production data.

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Turn CO₂ Loss into Reusable Liquid CO₂

A dry ice machine alone produces dry ice.

A CO₂ Revert Gas Recovery System goes one step further by recovering the gaseous CO₂ generated during production and returning it to the liquid CO₂ cycle.

With experience in CO₂ compression, refrigeration, liquefaction, storage and process integration, YTC can provide the recovery system as a standalone retrofit or as part of a complete dry ice production solution.