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It's cheaper and safer using co2 pellets propelled with ordinary air than liquid nitrogen. It gets sufficiently cold, and sufficiently abrasive to freeze, shatt

It's cheaper and safer using co2 pellets propelled with ordinary air than liquid nitrogen. It gets sufficiently cold, and sufficiently abrasive to freeze, shatter, and disperse the sap and plant fats and other sticky stuff. Co2 cleaners are used in high end auto cleaning and detailing, so there's established use, safety, and equipment out there. The use is novel, the tech is decades old.

arcticbull 4y ago
The temperature alone - dry ice is only like -109F and sold at most Safeways for a few bucks a pound (and safe enough to ship via all standard postal carriers with nothing more than an optional sticker) while LN2 is -320F. That requires a completely different storage and handling protocol.
- robbedpeter 4y ago
  Interesting rabbit hole, I can't find any detailed reasons why co2 is better or not to use LN2. LN2 might also then be too cold and affect the temper of the steel, or it might evaporate too quickly, requiring a lot more mass than co2. Or maybe it could be a perfectly fine alternative but the co2 pellet systems have market advantage.
  - flaviut 4y ago
    CO2 density: 1562 kg/m^3 Sand density: 1520-1680 kg/m^3 LN2: 806 kg/m^3 CO2 is just disappearing sand as far as these systems are concerned. They probably use the same equipment that they use for sand. Plus LN2 is way colder and harder to handle and also it's a liquid.
- adhesive_wombat 4y ago
  Temperature and injuries aside, a dewar of LN spilled in a room temperature enclosed space will boil and evaporate into an asphyxiating cloud very, very quickly. A box of dry ice dumped on the floor will take quite a bit longer to sublimate enough, partly because the phase change temperature is much higher, and also because thermal contact between a very low viscosity liquid and surfaces is very much higher than a solid pellet sitting on the surface. Nitrogen will also kill you silently, while you will definitely know when CO2 levels are getting high (because it really really hurts).

arcticbull 4y ago

The temperature alone - dry ice is only like -109F and sold at most Safeways for a few bucks a pound (and safe enough to ship via all standard postal carriers with nothing more than an optional sticker) while LN2 is -320F. That requires a completely different storage and handling protocol.

robbedpeter 4y ago
Interesting rabbit hole, I can't find any detailed reasons why co2 is better or not to use LN2. LN2 might also then be too cold and affect the temper of the steel, or it might evaporate too quickly, requiring a lot more mass than co2. Or maybe it could be a perfectly fine alternative but the co2 pellet systems have market advantage.
- flaviut 4y ago
  CO2 density: 1562 kg/m^3 Sand density: 1520-1680 kg/m^3 LN2: 806 kg/m^3 CO2 is just disappearing sand as far as these systems are concerned. They probably use the same equipment that they use for sand. Plus LN2 is way colder and harder to handle and also it's a liquid.
adhesive_wombat 4y ago
Temperature and injuries aside, a dewar of LN spilled in a room temperature enclosed space will boil and evaporate into an asphyxiating cloud very, very quickly. A box of dry ice dumped on the floor will take quite a bit longer to sublimate enough, partly because the phase change temperature is much higher, and also because thermal contact between a very low viscosity liquid and surfaces is very much higher than a solid pellet sitting on the surface. Nitrogen will also kill you silently, while you will definitely know when CO2 levels are getting high (because it really really hurts).