Dry ice plays a critical role in modern industries. It is widely used for industrial cleaning, cold chain transportation, food preservation, and medical logistics. Unlike ordinary ice, dry ice sublimates directly from a solid to a gas at –78.5°C (–109.3°F), leaving no moisture or residue.
This unique property makes it invaluable for processes where water or conductivity must be avoided.
But have you ever wondered how liquid CO₂ is transformed into solid dry ice pellets?
The answer lies in a specialized piece of industrial equipment known as a dry ice pelletizer.
In this guide, we'll take a complete look at how dry ice pelletizers work - exploring their working principles, key components, production process, and industrial applications.
What Is a Dry Ice Pelletizer?
A dry ice pelletizer is a machine designed to convert liquid carbon dioxide (LCO₂) into solid dry ice pellets through a process of rapid depressurization and mechanical compression.
Essentially, it takes liquefied CO₂ stored under high pressure and turns it into dense, cylindrical pellets ready for use in various industries.
Physical Properties of Dry Ice
Dry ice is the solid form of carbon dioxide, and it behaves very differently from water-based ice.
At –78.5°C (–109.3°F), dry ice does not melt into liquid - it sublimates directly into CO₂ gas, which means:
- It leaves no liquid residue,
- It is non-conductive, and
- It is non-toxic and safe for indirect contact with products.
This "dry" cooling behavior is why it is used in applications like precision cleaning, biomedical shipping, and cold storage.
Pellets vs. Blocks vs. Slices
Dry ice comes in several forms:
- Pellets – small cylindrical pieces (commonly 3mm, 6mm, or 9mm in diameter). These are used for dry ice blasting, cold chain logistics, and on-demand cooling.
- Blocks – large, compact pieces for long-term refrigeration or shipping bulk goods.
- Slices or slabs – flat sheets designed for food processing lines or cold displays.
Pellets are the most popular form because they're easy to handle, produce less waste, and can be made continuously using an automated pelletizer.
The Science Behind Dry Ice Formation
To understand how dry ice pelletizers work, we first need to look at the physics of CO₂ phase change.
The process involves transforming carbon dioxide gas into a liquid and then into a solid - all while skipping the liquid phase at normal pressure.
Stage 1: Liquefaction
The process begins when gaseous CO₂ is compressed and cooled to form liquid carbon dioxide (LCO₂).
This typically occurs at a pressure of about 6,250 kPa (around 900 psi) and a temperature of roughly –17°C (1°F).
The liquid is then stored in an insulated CO₂ tank, ready to be fed into the pelletizer.
Stage 2: Expansion (Rapid Pressure Drop)
Inside the pelletizer, the liquid CO₂ is released through an expansion chamber where the pressure suddenly drops.
When this happens:
- Part of the liquid instantly vaporizes (turns into gas),
- This vaporization absorbs heat,
- The remaining portion of the liquid solidifies into fine CO₂ snow - known as dry ice snow.
This "flash freezing" process is the foundation of how dry ice is created from CO₂.
Stage 3: Compaction (Solidification into Pellets)
The CO₂ snow is then compressed under high pressure - typically between 15 and 25 MPa - inside the forming chamber.
Under this pressure, the snow compacts and fuses together into dense, solid dry ice.
This solid material is then pushed through an extrusion die, forming continuous strands that are later cut into pellets.
The entire process takes advantage of dry ice's unique ability to sublimate - transition directly from solid to gas without melting.
This property makes dry ice "dry," clean, and perfect for sensitive industrial and logistics applications.
Main Components of a Dry Ice Pelletizer
A modern dry ice pelletizer is a complex system that integrates cryogenic engineering, hydraulic mechanics, and automation control.
Each component works together to ensure the CO₂ is efficiently transformed into high-density pellets.
Liquid CO₂ Storage and Delivery System
This system maintains CO₂ in its liquid state before processing.
It includes insulated tanks, pressure regulators, and delivery lines that transport the liquid CO₂ to the pelletizer.
Stable liquid feed ensures consistent pellet density and output.
Expansion Chamber
Here, the liquid CO₂ undergoes rapid depressurization, turning into CO₂ snow.
The expansion chamber is precisely engineered to handle the pressure drop safely and to separate gas from the newly formed solid CO₂.
Proper chamber design improves conversion efficiency and prevents CO₂ loss.
Hydraulic Compression System
This is the "heart" of the pelletizer.
The hydraulic press compresses the CO₂ snow into a dense mass under extremely high pressure.
It determines the pellet's density, shape, and hardness, directly affecting the performance of dry ice in cleaning or cooling applications.
A high-quality hydraulic system ensures stability, energy efficiency, and long service life.
Extrusion Die and Forming Head
After compression, the solid dry ice passes through a die plate with multiple holes.
These holes determine the pellet diameter - typically 3mm, 6mm, or 9mm - depending on the intended use.
The die is made of high-strength alloy steel to withstand continuous pressure and temperature fluctuations.
Cutting and Collection System
As dry ice strands exit the die, a cutting mechanism slices them into uniform pellets.
The pellets fall into an insulated collection bin, which minimizes sublimation loss.
Some systems also integrate automated packaging or conveying units for continuous operation.
Automation and Control System
Modern pelletizers are equipped with touchscreen control panels, sensors, and PLC systems.
These manage the pressure, feed rate, extrusion speed, and safety monitoring in real time.
Automation ensures stable production, reduces operator workload, and enhances overall safety.
Step-by-Step Dry Ice Pellet Production Process
Producing dry ice pellets is a continuous industrial process that combines cryogenic physics and high-pressure mechanics. Below is a simplified breakdown of the six major stages that occur inside a modern dry ice pelletizer.
CO₂ Input
The process starts with liquid CO₂ being fed from an insulated storage tank into the pelletizer through a cryogenic delivery line. Maintaining the CO₂ in a stable liquid state is crucial for consistent pellet density and production efficiency.
Rapid Pressure Drop (Flash Expansion)
Inside the expansion chamber, the liquid CO₂ undergoes a rapid pressure reduction. This sudden drop causes a portion of the CO₂ to instantly vaporize while the rest freezes into fine CO₂ "snow."
This phenomenon is known as flash freezing, forming the raw material that will become dry ice pellets.
CO₂ Snow Collection
The newly formed CO₂ snow accumulates inside a compression chamber, while excess gas is safely vented or recovered. Proper collection ensures an even feed for the compaction stage and prevents energy loss.
High-Pressure Compaction
The hydraulic system then compresses the CO₂ snow into a dense solid mass.
This process typically operates between 15–25 MPa, forming a solid column of dry ice with a density of about 1.3 – 1.45 g/cm³.
The compaction pressure determines the pellet's hardness, sublimation rate, and overall quality.
Extrusion and Cutting
The solidified dry ice column is forced through an extrusion die - a plate with multiple holes that shape the dry ice into continuous strands.
These strands are immediately cut into pellets ranging from 3 mm to 19 mm in diameter, depending on the die configuration.
The YJCO2's YJ.GB500P Dry Ice Pelletizer Machine, for instance, can produce up to 500 kg of dry ice per hour using a 15 kW hydraulic system.
Collection and Storage
The pellets fall into insulated collection containers, where they are either bagged for transport or conveyed directly to point-of-use systems such as blasting machines or cold-chain boxes.
Proper insulation minimizes sublimation loss and maintains pellet integrity for longer use.
Applications of Dry Ice Pellets
Dry ice pellets are versatile, clean, and powerful cooling media. Their compact form and uniform density make them suitable for a wide range of industrial and commercial uses.
Industrial Cleaning (Dry Ice Blasting)
3 mm pellets are commonly used in dry ice blasting systems.
Propelled by compressed air, these pellets remove oil, paint, carbon, and contaminants without abrasion or secondary waste.
They are widely adopted in automotive manufacturing, electronics, and mold maintenance.
Food and Cold-Chain Transport
Because dry ice contains no moisture and does not melt, it is ideal for preserving perishable foods and frozen goods during transport.
It ensures temperature stability across long distances in seafood, bakery, and ready-meal logistics.
Medical and Pharmaceutical Use
Hospitals, laboratories, and pharmaceutical companies rely on dry ice pellets to store and ship vaccines, biological samples, and reagents that require ultra-low temperatures.
The pellets' uniform shape allows precise temperature control inside medical coolers.
Manufacturing and Industrial Cooling
Dry ice is used for rapid mold cooling, deflashing rubber parts, and process temperature control in plastic and metal fabrication.
Pellets provide fast thermal transfer without introducing moisture to sensitive equipment.
Special Effects and Event Applications
In entertainment, dry ice pellets are used to create low-lying fog effects for stages, theme parks, and film sets.
When mixed with warm water, they instantly generate thick, white fog while keeping humidity low.
How to Choose the Right Dry Ice Pelletizer
Selecting the right pelletizer depends on your production scale, operational goals, and cost considerations.
Production Capacity
Determine your required output - small-scale units can produce 30 kg/h, while industrial systems reach 300 – 500 kg/h or more.
Choose a capacity that matches your daily consumption to minimize waste and cost.
Pressure and Drive System
Most industrial models use hydraulic systems for higher density and stability, while smaller mechanical types offer lower maintenance and easier setup.
Die and Pellet Size Options
If your application requires different pellet diameters (3 mm for blasting, 9 mm for cooling), choose a machine with interchangeable dies to maximize versatility.
Energy Efficiency and CO₂ Utilization
Look for machines designed with optimized gas recovery and lower power consumption, which directly reduce operating costs.
Automation and Control
Modern pelletizers feature touchscreen panels, PLC systems, and remote monitoring for safe and consistent operation.
Automation is especially valuable for 24/7 industrial production.
Cost and Maintenance Balance
While advanced models may have higher upfront costs, their durability, automation, and CO₂ efficiency typically lead to better long-term ROI.
For laboratories or small facilities, a compact semi-automatic unit might be sufficient.
Safety and Maintenance Tips
Operating a dry ice pelletizer safely requires attention to both CO₂ handling and mechanical maintenance.
Ventilation
Always ensure proper airflow in the production area. CO₂ gas can displace oxygen and pose a suffocation hazard in confined spaces.
Cold Protection
Operators must wear insulated gloves and eye protection when handling dry ice to prevent frostbite.
Equipment Inspection
Routinely check hydraulic hoses, seals, and fittings for leaks or wear. Preventive maintenance avoids costly downtime.
Electrical Safety
Ensure all equipment is properly grounded. Condensation can form on cold surfaces, so electrical components must be protected.
Pressure Relief Systems
Pelletizers should always include certified pressure-relief valves to avoid over-pressurization and ensure safe operation.
Regular cleaning of the extrusion die and hydraulic system also helps maintain optimal performance and pellet quality.
Conclusion
In simple terms, the working principle of a dry ice pelletizer is to convert liquid CO₂ into solid pellets through rapid depressurization, compression, and extrusion. Different pellet sizes are then produced by using various extrusion molds.
As industries continue to seek eco-friendly, moisture-free, and cost-effective cooling and cleaning methods, dry ice technology will remain at the forefront. If your business relies on dry ice for cleaning, cooling, or storage, consider exploring advanced pelletizing systems designed for your production scale.
About the Author
The YJCO2 brand integrates the most complete dry ice cleaning industry chain resources in China, offering a full one-stop procurement service-from raw materials to equipment. Even if customers cannot access dry ice or air compressors locally, YJCO₂ can still provide a complete solution of "dry ice + equipment + supporting systems," eliminating all operational concerns.
With its high level of automation, multi-size pellet options, and high production capacity, our YJ.GB500P dry ice pelletizer is widely favored by users and continuously supplies reliable, high-density dry ice for modern industrial needs.
Contact us now to get a free quote for our dry ice pelletizer.
