With temperatures rising over the summer, it's hard to stay away from ice-cold beverages and ice cream to cool down. But did you know that there is a type of ice that turns directly into vapor? Let's dig deeper and discover what is dry ice and what it's mostly used for.
What Is Dry Ice?
What is dry ice made of? Dry ice is basically solid carbon dioxide that changes directly from a solid to a gaseous phase through the process of sublimation. Carbon dioxide in its gaseous state is a chemical compound that is odor-free, colorless and tasteless. Under pressure and at low temperatures, carbon dioxide becomes an opaque white solid. Dry ice also has a lower temperature compared to water ice, making it an effective cooling agent when other methods of cooling are inefficient or unavailable.
Solid carbon dioxide molecules are made up of a single carbon atom which is bonded to two oxygen atoms. Solid carbon dioxide is non-flammable, colorless and has a sour odor. Because dry ice has lower temperatures compared to water ice, touching the surface of dry ice can cause frost burns. When dissolved in water, solid carbon dioxide forms carbonic acid.
The existence of solid carbon dioxide was first observed by French inventor Adrien-Jean-Pierre Thilorier in 1835. In 1924, an American by the name of Thomas B. Slate patented solid carbon dioxide for commercial sale and succeeded in manufacturing dry ice and turning it into an industry. By 1925, a company called DryIce Corporation of America trademarked the name “dry ice,” which has since been recognized as the common name for solid carbon dioxide. Dry ice was sold commercially for the first time that same year by DryIce Co.
During the mid-twentieth century, dry ice was used extensively to refrigerate and freeze foods in the absence of affordable and efficient refrigeration. The invention of electric refrigeration after World War II led to the decline of its use.
How Is Dry Ice Manufactured?
1. Production of Gases
First, gases with a high concentration of carbon dioxide are produced. Carbon dioxide-rich gases are acquired during the refinement process of ammonia and petroleum. The carbon dioxide is suctioned off during the refinement process. Impurities from the carbon dioxide are then removed to ensure that it is “food grade” before being turned into its solid form.
2. Liquefaction of Gases
Carbon dioxide-concentrated gases are then pressurized and refrigerated to turn them into liquid form. Carbon dioxide liquefies at a pressure of approximately 870 lbs. per square inch at room temperature. The pressurized and liquified carbon dioxide is then pumped into holding tanks and shipped in large quantities by tank trucks to dry ice manufacturers.
3. Transfer of Liquified Carbon Dioxide to Tank Trucks
The liquid carbon dioxide is transferred by the tank trucks to the dry ice manufacturer's plant. After the liquid carbon dioxide has been transferred to the huge tanks, it is kept refrigerated and under pressure so it will remain in its liquid state. 4. The pressure is reduced to allow some liquid carbon dioxide to vaporize and to lower the temperature rapidly.
4. Release to the Dry Ice Press
The liquid carbon dioxide is released from the tanks through the pipes and into the dry ice press. The movement of the liquid carbon dioxide from a highly pressurized environment to atmospheric pressure causes it to expand and evaporate quickly, cooling it to its freezing point (-109 degrees Fahrenheit) in the process. Extremely low temperatures solidify the remaining carbon dioxide into a snow-like consistency.
5. Compression Into Blocks
The solidified carbon dioxide is compressed into large blocks of dry ice. A pressure of about 60 tons squashes the snow-like carbon dioxide into a large block of dry ice for about five minutes. The resulting block of dry ice measures about 2 feet wide and 10 inches tall and weighs about 220 lbs.
6. Cutting Into Smaller Blocks
Each block of dry ice is then cut into four smaller blocks and stored in containers at extremely cold temperatures. Using a pneumatic saw, the large block of dry ice is then cut into four parts with each weighing about 55 lbs. Then it is stored in containers in freezing temperatures to prevent sublimation.
The final step is wrapping the blocks in paper for safe handling. Through the use of a machine, the blocks of dry ice are wrapped in paper, as any human contact with the dry ice during handling can cause freezer burn. The blocks of dry ice are now ready for shipping to wholesalers and distributors.
Manufactured dry ice also comes in several forms: as a block, as small and cylindrical pellets about 13 or 16 millimeters in diameter, or as tiny cylindrical pieces measuring about one-eighth of an inch in diameter.
What Is Dry Ice Used for?
Storage and Transport
So what is dry ice typically used for? Because of its very cold temperature, dry ice is particularly helpful when it comes to freezing and preserving items that need to be kept cold for longer periods, such as meat, ice cream, and other perishable frozen food. Dry ice is also used when shipping food items that need to be kept at safe temperatures. Additionally, airline industries use dry ice to keep catering food chilled.
However, dry ice has several other benefits that go beyond just freezing and preserving food. Because dry ice sublimates, there is no liquid residue or standing water left after evaporation. This unique property prevents the growth of bacteria and makes cleaning up a lot easier.
When it comes to industrial cleaning, dry ice blasting is especially useful in removing contaminants while preventing water from getting into important mechanisms. Small pellets of dry ice are sprayed on the intended target or surface. Extremely cold temperatures shrink dirt and make cleaning effortless. Dry ice blasting is often used to clean manufacturing die tools, electrical motors, and printing presses.
What is dry ice in terms of other functions? Dry ice may also be used for:
Now that you're aware of the properties and uses of dry ice, it's also important to know and practice safety precautions when handling it. As useful as it may be, dry ice can also cause carbon dioxide poisoning and potential injuries such as freezer burn. Here are some safety practices to keep in mind when using dry ice:
Do Not Ingest
Never taste nor ingest dry ice. Dry ice will burn your tongue and your mouth. When ingested, it is capable of damaging and killing cells in your body because of the extreme cold temperature. Sublimation of dry ice inside your body can cause adverse effects to your digestive system.
Do Not Store in a Sealed Container
Do not store dry ice in a sealed container. Dry ice constantly sublimates into carbon dioxide in gas form. If you store dry ice in a sealed container, the gas released will cause pressure to build up and may cause the container to explode.
Do Not Put in a Freezer
Do not store dry ice in a freezer. Doing so will cause your freezer's thermostat to shut off because it will detect the very cold temperature from the dry ice.
Always Keep Ventilated
Use dry ice in well-ventilated areas only. Dry ice is constantly releasing carbon dioxide in the air, so it's important to use it in a well-ventilated space only, as it can become a suffocation hazard. Carbon dioxide sinks to the floor, so make sure that the area you're using is properly aerated so as to prevent carbon dioxide poisoning.
As a final tip, remember that summer can also be a season of power outages, so you might find dry ice handy when you have a lot of frozen food in the refrigerator that needs to be kept cold. Just don't forget to remove it from the freezer when the power goes back on!