A colorless, liquefied, high-pressure gas which is slightly acidic and is shipped at its vapor pressure of 830 psi at 70°F. It is relatively nonreactive and nontoxic. It will not burn, and it will not support combustion or life. Solid carbon dioxide (dry ice) at atmospheric pressure transforms directly to a gas without passing through the liquid phase.
Gaseous carbon dioxide is used to carbonate soft drinks, for pH control in water treatment, in chemical processing, as a food preservative, as an inert "blanket" in chemical and food processing and metal welding, as a growth stimulant for plant life, for hardening molds and cores in foundtries, and in pneumatic devices.
CO2 is recovered from many different sources. It is obtained as off-gases from fermentation processes, limestone kiln gases, natural CO2 wells, combustion gases from coke ovens, burning of natural gas and various oils, as well as gas streams from chemical and petrochemical operations. CO2 is purified and liquefied by at lease seven different processes.
Liquefied carbon dioxide is shipped in cylinders, insulated portable tanks, insulated cargo tanks, and insulated tank cars. In high pressure supply systems it may be stored and used from single or manifolded cylinders. In low pressure systems it is stored in insulated pressure vessels with controlled refrigeration systems and auxiliary heating when required.