Dry ice is easily manufactured.[12][13] First, gases with a high concentration of carbon dioxide are produced. Such gases can be a byproduct of another process, such as producing ammonia from nitrogen and natural gas, oil refinery activities or large-scale fermentation.[13] Second, the carbon dioxide-rich gas is pressurized and refrigerated until it liquifies. Next, the pressure is reduced. When this occurs some liquid carbon dioxide vaporizes, causing a rapid lowering of temperature of the remaining liquid. As a result, the extreme cold causes the liquid to solidify into a snow-like consistency. Finally, the snow-like solid carbon dioxide is compressed into small pellets or larger blocks of dry ice.[14][15]
A teaching laboratory demonstration for the production of dry ice is to use a 15 lb aluminum carbon dioxide fire extinguisher with a porous fabric collecting bag over the nozzle. The Joule-Thomson expansion of the gas lowers the temperature enough to produce an approximate 50/50 mixture of CO2 gas and dry ice snow also called dust that is collected in the bag. This is an inefficient process, and unsuitable for even lab-scale production. The expansion is inefficient, fire extinguishers are an expensive way to buy carbon dioxide, especially when a signed and dated fire extinguisher certification is required. Buying CO2 in fire extinguishers, however, is no more expensive than buying CO2 in cylinders and has the added advantage of demonstrating Newton's Three Laws of Motion with a wheeled chair and increases fire safety in a laboratory when refilled promptly after use.
Dry ice is typically produced in three standard forms: large blocks, cylindrical small (5/8 or 1/2 inch diameter) pellets and cylindrical tiny (1/8 inch diameter), high surface to volume pellets that float on oil or water and do not stick to skin because of their high radii of curvature. Tiny dry ice pellets are used primarily for ice blasting, quick freezing, fire fighting, oil solidifying and...