Dry ice is made by first compressing and cooling carbon dioxide (CO2) gas until it becomes liquid. This liquid CO2 is then rapidly depressurized, causing some of it to vaporize quickly, which cools the remaining liquid enough to freeze into solid CO2, forming a snow-like substance. This CO2 snow is then compressed into blocks or pellets of dry ice. The solid dry ice is extremely cold, at about -78.5 degrees Celsius, and it sublimates directly from solid to gas without becoming liquid.

Process Details

• Carbon dioxide gas, often a byproduct of industrial processes like ammonia production or fermentation, is captured and pressurized to about 150 psi.
• The gas is cooled in a condenser to become liquid CO2.
• When the pressure is suddenly reduced to atmospheric levels, some liquid CO2 vaporizes, absorbing heat and cooling the rest into dry ice snow.
• This snow is collected and compressed under high pressure to make solid blocks or extruded into pellets.
• The process produces different forms of dry ice, including large blocks and small pellets for different uses.

Applications and Safety

Dry ice is used for refrigeration, shipping, creating fog effects, and industrial cleaning. Because of its extreme cold, it must be handled with gloves to prevent frostbite. This summary covers the industrial production method widely used today and the basic scientific principle behind dry ice formation.