How much liquid CO₂ a tonne of dry ice takes

A pelletizer turns less than half of the liquid it receives into dry ice — the rest flashes off as gas. What that means for the raw material bill, the tank size and the pressure at the inlet.

Dry ice is solid carbon dioxide, and it is made from the same liquid CO₂ that a brewery or a welding shop buys. The surprise for anyone planning a workshop is the conversion ratio: you do not get a kilogram of pellets from a kilogram of liquid.

Why less than half of it becomes ice

Liquid CO₂ arrives at the pelletizer at about 20 bar and −20 °C. When it is released to atmospheric pressure, part of it flashes into gas, and the heat that evaporation removes freezes the rest into snow at −78.5 °C. The snow is then pressed into pellets or blocks.

The physics fixes the split at roughly 40–45% snow and 55–60% flash gas. In practice that means 2.2–2.5 kg of liquid CO₂ per kilogram of dry ice if the flash gas is simply vented. Plants that return the flash gas to a liquefaction unit bring the figure down towards 1.1–1.2, but that requires a recovery system, not just a pelletizer.

The numbers on the right are why a dry ice workshop is a heavy consumer even at modest output. A 50 m³ tank holds about 48 tonnes — under two weeks of supply for a 200 kg/h line running full shifts. Storage here is sized around the delivery schedule far more tightly than in most other applications.

Pressure is the parameter that breaks first

A pelletizer needs liquid delivered within a narrow pressure band, typically around 18–21 bar. Continuous heavy draw-off cools the tank contents and the pressure drops — and a pelletizer fed below its band starts producing soft, low-density pellets that sublimate faster in the customer's box.

• A pressure building coil, sized for the continuous flow rather than the average.
• Insulated liquid lines kept as short as the layout allows.
• A vent line for the flash gas, routed outdoors — this is a large, continuous gas flow, not a trickle.
• Gas detection in the workshop, because both the pelletizer and the stored product release CO₂ continuously.

Purity: the ice inherits it from the liquid

Dry ice used for food cooling, transporting pharmaceuticals or blasting food equipment is in contact with the product, so the liquid CO₂ behind it has to be food grade to ISBT. Nothing in the pelletizing process removes contamination — whatever is in the liquid ends up in the pellet and then sublimates directly onto the product. Incoming inspection belongs at the tank, before the liquid reaches the machine.

In Ukraine dry ice is produced industrially by, among others, IceLab — plants in Kyiv and Lviv with an output of up to 400 kg/h and a 60-tonne raw material store. That store is the point: at that capacity the CO₂ supply has to be sized as a continuous industrial feed, not as a periodic purchase.

What to work out before ordering a pelletizer

1. The pellet output you actually need per shift, including seasonal peaks.
2. Liquid CO₂ demand at 2.2–2.5 kg per kilogram of ice, unless you are also buying recovery.
3. Storage volume that takes one full tanker delivery with a working reserve.
4. Continuous flow rate and the pressure building capacity that holds the inlet band.
5. Ventilation and gas detection for the workshop and the storage room.