Reducing the pressure of liquid carbon dioxide, one part of liquid carbon dioxide evaporates and absorbs a lot of heat, so that the other part of carbon dioxide cools into a snow-like solid. Compacting snow-like solid carbon dioxide to obtain dry ice. (Or liquid carbon dioxide can be cooled to -2 1. 1℃ and the pressure is 0.4 15MPa, or solid carbon dioxide can be formed. )
The simple method is to put a canvas bag on the mouth of the container containing liquid carbon dioxide, and then open the container to release carbon dioxide, so that some dry ice can be collected in the pocket.
Mass production needs a special dry ice maker.
Dry ice should be stored in high-pressure steel cylinders. If there is no high-pressure steel cylinder, it can be stored in the freezer of the refrigerator for 5 ~ 10 days.