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What Is Dry Ice?

Dry ice is frozen carbon dioxide (C02), the gas we exhale as we breathe. It is much denser and colder than traditional ice. Dry Ice is -109.3º F (-78.5º C). Traditional ice is 32º F (0 degrees C). In addition, dry ice doesn't melt - it sublimates. Sublimation is the process of going directly from a solid to a gas. Dry ice bypasses the liquid form, giving it its name "dry" ice.

The first step in making dry ice is to turn the carbon dioxide gas into a liquid. This is done by compressing the C02 and removing any excess heat. The C02 will liquefy at a pressure of approximately 870 pounds per square inch. Next, the pressure is reduced over the liquid carbon dioxide by sending it through an expansion valve. Part of the liquid sublimates, causing the remainder to freeze into snow flakes. The dry ice snow is then compacted together under a large press to form blocks. Dry ice is much heavier than traditional ice, weighing about the same as standard bricks.

 

Dry Ice And Its Uses...

Dry ice removes almost twice as much heat per pound as water ice. It changes directly from a solid to a gas without becoming a liquid, thus, eliminating clean-up.

These features make dry ice especially useful in food preparation, packaging, and transport. By preventing heat build-up, it protects against salmonella growth. It prevents moisture build-up in mixing and water weight loss of product during shipment. In addition, its inert carbon dioxide gas is an excellent preservative and inhibits the growth of many forms of bacteria.

Other than food applications, dry ice is extremely valuable for flash freezing, pharmaceutical packing, absorbing ammonia, refrigeration leaks, and creating fog for the entertainment industry.

As a coolant, its applications are unlimited.

Pellets are especially useful in food processing and lab applications where small nuggets can be tightly packed around items of various shapes.	Dry ice blocks serve as excellent refrigeration for food processing and transportation applications. Blocks are sliced into commercially useful shapes and sizes.

 

 

Applications For Dry Ice 

Add to Beverages Add to Pool & Jacuzzi Air Travel Baking Industry Boating Branding Cattle and Horses Broken Freezer or Refrigerator Carbonate Liquids Chemical Retardant Chemistry Pressurizing Agent Comet Project Deflashing Molded Plastics And Rubber Dents & Hail Damage Dry Food Storage Dry Ice Blast Cleaning Fog Machines Freeze Fresh Strawberries Fresh Meat Processing

Gopher Eradication Home Made Root Beer Inerting Medium Medical Industrial Uses Mosquitoes Plant Growth Power Failure Protect Sport Fish And Game Remove Floor Tile School Science Projects Shipping Table Shrink Fittings Special Effects Transporting Plants Traveling Volcano Wells Witches Brew

CAMPING AND TRAVELING WITH DRY ICE

Plan on using 10 to 20 pounds of dry ice for every 24-hour period depending upon the size of the ice chest. Dry Ice will keep everything frozen in this ice chest, including extra ice, so keep non-frozen goods to be refrigerated with regular ice in a separate ice chest. Dry Ice normally comes in 10-inch squares, 2 inches thick weighing about 10 pounds each square. Plan to put one square per each 15 inches of ice chest length. This will work out to 2 squares (20 pounds) for an average 40-quart cooler. For larger containers and longer camping or traveling times, multiply dry ice quantities by these rates. Dry Ice, at -109.0°F or -78.5°C, will freeze and keep frozen everything in its container until it is completely sublimated. These frozen items will take some extra time to thaw because they have been so cold.

HOW TO PACK DRY ICE
If the Dry Ice is placed on top of the food (cold sinks), it will work better. However it is sometimes in the way so many people prefer to keep the Dry Ice on the bottom of the ice chest for convenience. When packing items in the container fill the empty space with wadded newspaper or other filler. Any "dead air space" will cause the Dry Ice to sublimate faster. The best storage container is a three-inch thick urethane insulated box. Lining the inside of your ice chest with sheets of Styrofoam will increase the life of Dry Ice. Dry Ice sublimation (changing from a solid to a gas) will vary depending on the temperature, air pressure and thickness of insulation. The more Dry Ice you have stored in the container, the longer it will last.

TRANSPORTING BY AUTO OR VAN
Plan to pick up the Dry Ice as close to the time it is needed as possible. If possible pack insulating items such as sleeping bags around the ice chest. This will stretch the time that the Dry Ice lasts. If it is transported inside a car or van (not in the trunk) for more than 10 minutes make sure there is fresh air. After 15 minutes with Dry Ice only in its paper bag in the passenger seat next to me, I started to breathe faster and faster as though I were running a race. I couldn't figure out why I was so out of breath until I saw the car air system was set in the re-circulated position, not fresh outside air.

TRANSPORTING BY AIRPLANE
Pick up Dry Ice as close to departure time as convenient. Carry it in a well-insulated container such as an ice chest or insulated soft pack. If it is transported inside a car or van for more than 10 minutes make sure there is fresh air available. Most airlines will not let you carry more than two kilograms (4.4 pounds) of Dry Ice on the airplane without special arrangements. Because Dry Ice will sublimate continuously from the time of purchase, you can confidently declare that there is no more than two kilograms at the time you check in at the airport. Dry Ice will sublimate slightly faster due to the lower pressure that the airline maintains during flight. Make plans to refrigerate or add Dry Ice when arriving at your destination.

MANUFACTURING DRY ICE MACHINES

Dry ice manufacturing starts with liquid carbon dioxide held under pressure (300 psi) in bulk storage vessels. To begin making dry ice, the liquid C02, is sent through an expansion valve into an empty chamber where under normal atmospheric pressure it flashes into C02 gas. This change from liquid to gas causes the temperature to drop quickly. About 46% of the gas will freeze into dry ice snow. The rest of the C02 gas, 54%, is released into the atmosphere or recovered to be used again. The dry ice snow is then collected in a chamber where it is compressed into block, pellet or rice size pieces to meet customers requirements. The denser the dry ice is, the longer it will last, the easier it is to handle, and the better it will perform when blast cleaning.

There are three major types of dry ice machines. The first is a dry ice block maker. It can produce a 220 pound solid block which is usually cut into four 55 pound blocks about 11 inches cubed Newer block machines make a 50 pound or even a 10 pound block. Next there are machines that produce pellets from smaller than 1/8 inch for dry ice blast cleaning to 3/4 inch in diameter. Sometimes these machines include additional parts for blast cleaning. There are four or five major manufacturers in the world. Several additional companies manufacture small dry ice makers that connect to a CO2 tank and make 5 to 10 pound blocks of lower density dry ice.

Charles Hyde of CO2 Air Inc. has developed a machine to produce airline size dry ice blocks with a pelletizer and reformer saving many band saw cuts and associated labor.

For a low cost alternative to making dry ice blocks you can even make dry ice snow yourself with a CO2 tank. Although it is not very efficient, just open the hose into a burlap bag, and then pack the dry ice snow into a container. This can be used to fill coolers, quick freeze food products before shipment, science projects, and many of the same uses as traditional higher density blocks of dry ice without the expensive hydraulics and capitol costs of a large dry ice maker. It will also save on storage loss through sublimation as it is only used when immediately needed.

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