A dry ice maker quickly converts liquid carbon dioxide, or CO2, into a kind of snow that the machine then compresses into a block. While there are slight variations in how each type of dry ice maker performs this process, the science of making dry ice is consistent between manufacturers and models.
Facilities that produce dry ice begin by holding liquid carbon dioxide under high pressure in special bulk storage vessels. The liquid carbon dioxide passes through an expansion chamber and into normal atmospheric pressure, where it promptly turns to gas. This transformation drops the temperature, and roughly half of the gas freezes to dry ice snow.
The remaining carbon dioxide gas subsequently enters the external atmosphere, or dry ice manufacturers re-harvest it for later use. The dry ice snow collects in another chamber, where compression of it into blocks or uniquely sized pellets per customer specification occurs.
Different dry ice makers produce different size blocks of dry ice, from approximately 10- to 220-pound solid blocks. There are also machines that produce pellets that are 1/8-inch in diameter for the purposes of dry ice blast cleaning. Dry ice blasting is a non-abrasive alternative to sandblasting that does not leave residue.
Vendors of dry ice-making equipment, such as Wickens, sell self-contained dry ice block-makers or pellet-makers as well as smaller machines that handle various aspects of the dry ice-making process.