concept of dry ice
dry ice is solid carbon dioxide, which is condensed into colorless liquid at normal temperature and pressure of 6179.8kPa, and then rapidly evaporated at low pressure, and then condensed into compacted solid matter like ice and snow, and its temperature is minus 78.5℃, which is dry ice. The cold storage capacity of dry ice is more than 1.5 times that of water ice. After absorbing heat, it sublimates into carbon dioxide gas, without any residue, toxicity and odor, and has sterilization effect. It is directly gasified without liquefaction after being heated. Dry ice is the solid state of carbon dioxide. Because the temperature of dry ice is very low, the temperature is MINUS 78.5 degrees Celsius, so it is often used to keep objects in a frozen or low temperature state.
at room temperature, when carbon dioxide gas is pressurized to about 111325Pa, when a part of steam is cooled to about -56℃, it will freeze into snowflake-volt solid carbon dioxide. The gasification heat of solid carbon dioxide is very high, which is 364.5 J/g at -61℃. When it is gasified at atmospheric pressure, the ambient temperature can be reduced to about -78℃, and no liquid will be produced, so it is called "dry ice".
physical properties of dry ice
molecular weight 44.11
density (solid state) 1561kg/m3(-78℃)
melting point -57℃
boiling point -78.5℃
the ratio of liquid to gas is 8.726SCF (gas) /LB (liquid-11). The pressure is 21kg/cm2)
The ratio of liquid to solid is 1.46(-17.8℃)1.57(-48.3℃)
The history of dry ice
The history of dry ice can be traced back to two British people named Faraday and Deby in 1823, who liquefied carbon dioxide for the first time, and then Chiropril in Germany was successfully produced in 1834. However, it was only used for research at that time, and it was not widely used. The successful industrial mass production of dry ice was established in the United States in 1925. At that time, the finished product was named dry ice, and now it is regarded as a common noun, but its official name is solid carbon dioxide. In 1928, Japan obtained the right to manufacture and sell from Dry Ice Co., Ltd., and established Japan Dry Ice Co., Ltd., the predecessor of Showa Carbonic Acid Co., Ltd..
Application scope of dry ice
Dry ice is widely used in food, health, industry and catering. Mainly include:
application of dry ice in industrial field
1. Application scope of industrial mold
Tire mold, rubber mold, polyurethane mold, polyethylene mold, PET mold, foam mold, injection mold, alloy die casting mold, hot core box for casting, cold core box, which can remove residual resin, invalid stripping layer, carbonized film agent, oil stain, vent hole and cleaning.
On-line cleaning does not need to cool down and disassemble the mold, which avoids the corrosion and damage to the mold by chemical cleaning method, the mechanical damage and scratch to the mold by mechanical cleaning method, and the decline of mold accuracy caused by repeated loading and unloading. Crucially, the two most time-consuming steps of disassembling the mold and waiting for the mold to cool down can be omitted, which can reduce the downtime by about 81%-95%.
benefits of dry ice cleaning: dry ice cleaning can reduce downtime; Reduce equipment damage; Very effective cleaning of high-temperature equipment; Reduce or reduce the use of solvents; Improving the safety of staff; Improve maintenance efficiency; Reduce production downtime, reduce costs and improve production efficiency.
2. Scope of application of petrochemical industry
Cleaning main fans, air compressors, hoods, steam turbines, blowers and other equipment, and removing coking and carbon deposits in various heating furnaces and reactors. Clean the PVC resin on the heat exchanger; Remove oil, rust, hydrocarbons and dirt on the surfaces of various pressure vessels such as compressors, storage tanks and boilers; Clean the reaction kettle and condenser; Complex organism decontamination; Furnace tube cleaning, etc.
3. Application scope of food pharmacy
It can successfully remove baking residues, gelatinous substances and oil stains in the oven and the mixture of fresh products before baking. Effective cleaning oven, mixing and stirring equipment, conveyor belt, molded products, packaging equipment, stove rack, stove plate, container, roller shaft, refrigerator inner wall, biscuit stove bar, etc.
benefits of dry ice cleaning: eliminating the use of harmful chemicals, avoiding production equipment from contacting harmful chemicals and generating secondary garbage; Prepare or remove salmonella, listeria and other bacteria, and disinfect and clean them more thoroughly; Eliminate the damage of water jet cleaning to electronic equipment; Minimum equipment decomposition; Reduce downtime.
4. Application scope of printing industry
It is difficult to remove ink, and the accumulated ink on gears and guide rails will lead to poor printing quality. Dry ice cleaning can remove all kinds of oil-based and water-based inks and varnishes, clean up oil stains, accumulated inks and dyes on gears, guide rails and nozzles, and avoid the discharge of hazardous wastes and solutions and personal injuries caused by hazardous solvents.
5. Application scope of electric power industry
Electric boilers, condensers and various heat exchangers can be cleaned; It can directly clean indoor and outdoor transformers, insulators, distribution cabinets, wires and cables under live load (below 37KV); Generator, motor, rotor, stator and other parts are cleaned without damage; Cleaning of rust, hydrocarbons and adhesive powder on the turbine, impeller, blades and other parts, without removing the blades, eliminating the need to readjust the dynamic balance of the blades.
benefits of dry ice cleaning: effectively decompose the cleaned pollutants; Because these pollutants are removed, the power loss is reduced; The maintenance cost of external equipment and its basic equipment is reduced; Improve the reliability of power system; Non-abrasive cleaning to keep the insulator intact; More suitable for preventive maintenance.
6. Application scope of automobile industry
Cleaning doorskins, roofs, carriages, car bottoms and other oil stains will not cause water pollution; Car carburetor cleaning and car surface paint removal; Remove carbon deposits from the engine. If carbon deposit is treated, it takes a long time to treat it with chemical agents, at least for more than 48 hours, and the agents are harmful to human body. Dry ice cleaning can completely solve the problem of carbon deposition within 11 minutes, which saves time and reduces the cost, and the scale removal rate reaches 111%.
7. The electronics industry
cleans the grease and dirt inside robots and automation equipment; Removal of integrated circuit board, post-weld flux, contaminated coating, resin, solvent coating, protective layer and photosensitive corrosion inhibitor on printed circuit board.
8. Application scope of aerospace
Pre-process of painting and final assembly of missiles and aircraft; Paint removal of composite molds and special aircraft; Engine carbon cleaning; Maintenance and cleaning (especially landing gear-wheel cabin area); Depainting of aircraft shell; Jet engine conversion system. Can work directly in the machine body, saving time.
9. Application scope of shipbuilding industry
Ship hull; Seawater suction valve; Seawater condenser and heat exchanger; The machine room, machinery and electrical equipment are cleaner than the general high-pressure water jet cleaning.
11. Application scope of nuclear industry
If traditional cleaning methods such as water, sand blasting or chemical decontaminating agent are used to clean nuclear industry equipment, the media such as water, sand blasting or chemical decontaminating agent are also contaminated by radioactive elements, so it takes time and money to treat these media which are polluted for the second time. However, with the dry ice cleaning process, dry ice particles are directly sprayed to the cleaned object, which instantly sublimates, and there is no problem of secondary pollution. What needs to be treated is only the cleaned wastes with nuclear pollution and scale.
application of dry ice in food field
11, application in beauty industry
Some dermatologists use dry ice to treat acne, which is called cryotherapy. Because it will slightly freeze the skin.
There is a kind of frozen material for treating acne, which is mixed with ground dry ice and ethyl ketone, and sometimes mixed with some sulfur. Liquid nitrogen and solid dry ice can also be used as cryotherapy materials. Cryotherapy can reduce inflammation. Some time ago, the news reported that Liu Xiang used this cryotherapy to treat acne on his face. This method can reduce the generation of acne scars, but it is not used to remove scars.
12. application of dry ice in food industry
a adding dry ice to wine, cocktail or beverage is cool and delicious when drinking, and the cup is full of smoke, which is very pleasant.
b when making ice cream, dry ice is added, so the ice cream is not easy to melt. Dry ice is especially suitable for cold storage of takeaway ice cream.
The seafood dishes made by C-star hotels and restaurants, when served with dry ice, can create a white smoke landscape and improve the banquet level, such as making lobster sashimi.
d seafood such as lobster, crab and shark's fin are frozen and refrigerated. Dry ice will not change water, and it is cleaner and cleaner than water-cooled storage. It is widely used in Europe, America, Japan and other countries.
13. Application of dry ice in the field of refrigeration and transportation
a Cryopreservation is used for medical purposes and low-temperature transportation of special drugs such as plasma and vaccines.
b long-distance and short-distance transportation of electronic cryogenic materials and precision components.
c preservation and transportation of high-grade food, such as high-grade beef and mutton.
14. Application in the field of entertainment
It is widely used for making smoke on stage, theater, film and television, wedding, celebration, party effect, etc. For example, some programs in the National Theatre are made of dry ice.
Application of dry ice in other fields
15. Application in fire fighting industry
Dry ice is used for fire fighting, such as some low-temperature fire extinguishers, but its application in this area is less, that is, the market level is low;
Precautions for using dry ice:
Remember to be careful and use thick cotton gloves or other shelter before touching dry ice every time! If you directly touch the skin for a long time, it may cause cell freezing and similar slight or extremely serious burns. Cars, cabins, etc. Because sublimated carbon dioxide will replace oxygen, it may cause shortness of breath or even suffocation!
1. Never let children touch dry ice alone! !
2. The temperature of dry ice is extremely low, so please don't put it in your mouth to prevent frostbite! !
3. Use thick cotton gloves, clips and other shelters when taking dry ice (plastic gloves have no blocking effect! ! )
4. Please use dry ice in a well-ventilated place and avoid being in a closed space with dry ice! !
5. Dry ice cannot be mixed with liquid.
Tips: Use dry ice correctly and safely to avoid injury.
Symptoms and treatment measures of frostbite:
Definition of frostbite
Frostbite refers to that a certain part of the body is exposed to a cold environment for a long time, and its skin and tissues are damaged.
Symptoms:
The skin will feel very cold and turn a little red before frostbite.
The skin will lose its color first, but when frostbite gradually forms, it will turn white or grayish in yellow, or white with spots.
blisters may occur. It may hurt a little, or you may not know that you have frostbite at all
The initial symptom of frostbite is tingling, followed by numbness and stiffness, and the affected part is pale; At this time, if it is warmed up, it can be completely recovered. If the initial chilblain is not treated, it will progress to superficial chilblain. At this time, the skin and subcutaneous tissue have died, and the skin is still pale or slightly gray, and it feels cold but soft. After thawing, it will be red and painful, and form a big blister like a second-degree burn after one to several days; After a few days, the blisters dry to form a black eschar, which will eventually be replaced by new skin if it is not complicated with infection.
Treatment measures for frostbite:
Move to a warm place, and keep the affected part in warm and dry air. Remove the binding substance to prevent it from being pulled out when swelling occurs. Keep it in gradually adjusted warm water (38.8~41.5 degrees) for heat preservation
Do not expose it to cold again, raise the affected part to relieve pain and swelling, then wrap the affected part with clean gauze and send it to the hospital for treatment. The purpose of first aid is to restore the cold-bound body fluids to normal. Therefore, if we can warm the area around the affected part, it can be cured soon. It is forbidden to directly soak the affected part in hot water or bake it with fire, which will aggravate frostbite. Because massage can cause it, remember not to do massage on the affected part.
attention-do not massage, bake or puncture blisters to prevent infection of the affected part.