Dry ice concept
Dry ice is solid carbon dioxide. At normal temperature and pressure of 6079.8 kPa, carbon dioxide condenses into colorless liquid, and then rapidly evaporates at low pressure, and then condenses into dense ice-like solid matter. 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, which has no residue, toxicity and odor, and has sterilization effect. Direct gasification without liquefaction after heating. 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 the carbon dioxide gas is pressurized to about 10 1325Pa, a part of the steam will freeze into snowflake volt solid carbon dioxide when it is cooled to about -56℃. The gasification heat of solid carbon dioxide is very high, which is 364.5 J/g at -60℃. During atmospheric gasification, the ambient temperature can be reduced to about -78℃ and no liquid will be produced, so it is called "dry ice".
Physical characteristics of dry ice
Molecular weight 44.0 1
Density (solid)1560kg/m3 (-78℃)
Melting point -57℃
Boiling point -78.5℃
The liquid-gas ratio is 8.726SCF (gas) /LB (liquid-17.8℃, pressure 2 1kg/cm2).
The liquid-solid ratios were 0.46 (- 17.8℃) and 0.57 (-48.3℃), respectively.
Application scope of dry ice
Dry ice is widely used in food, sanitation, industry and catering. Mainly includes:
Application of dry ice in industrial field
1. Application scope of industrial molds
Tire mold, rubber mold, polyurethane mold, polyethylene mold, PET mold, foaming mold, injection mold, alloy die-casting mold, hot core box for casting and cold core box can remove residual resin, invalid release layer, carbonizing film agent and oil stain, and can open air holes. After cleaning, the mold is as bright as new.
On-line cleaning does not need to cool and disassemble the mold, which avoids the corrosion and damage of the mold by chemical cleaning method, the mechanical damage and scratch of 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 removing the mold and waiting for the mold to cool can be omitted, and the downtime can be reduced by about 80%-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. Application scope of petrochemical industry
Clean the main fan, air compressor, fume hood, steam turbine, blower and other equipment to remove coking and carbon deposition in various heating furnaces and reactors. Clean the PVC resin on the heat exchanger; Remove oil stains, rust, hydrocarbons and dirt on the surfaces of various pressure vessels such as compressors, storage tanks and boilers; Cleaning the reaction kettle and condenser; Complex biological purification; Furnace tube cleaning, etc.
3. The application scope of food pharmacy
It can successfully remove baking residues, colloidal substances and oil stains in the oven, as well as the mixture of fresh products before baking. Effectively clean ovens, mixing and stirring equipment, conveyor belts, molded products, packaging equipment, stoves, stoves, containers, rollers, refrigerator inner walls, biscuit stoves, etc.
Benefits of dry ice cleaning: put an end to the use of harmful chemicals, and avoid production equipment contacting with harmful chemicals and generating secondary garbage; Prepare or remove bacteria such as Salmonella and Listeria, and disinfect and clean 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 accumulation of 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 harmful wastes and solutions and personal injuries caused by harmful solvents.
5. Application scope of electric power industry
Can clean electric boilers, condensers and various heat exchangers; Can directly clean indoor and outdoor transformers, insulators, power distribution cabinets, live wires and cables (below 37KV); Generator, motor, rotor, stator and other parts are clean and free from damage; Clean the rust, hydrocarbon and adhesive powder on turbines, impellers, blades and other parts, without disassembling the blades and readjusting the dynamic balance of the blades.
Benefits of dry ice cleaning: effectively decompose pollutants to be cleaned; 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; Keep the insulator intact and non-abrasive clean; More suitable for preventive maintenance.
6. Application scope of automobile industry
Cleaning the doorskin, roof, carriage, car bottom and other oil stains will not cause water pollution; Cleaning of automobile carburetor and removal of automobile surface paint; Remove carbon deposits from the engine. If the carbon deposit is treated, it will take a long time to treat it with chemical agents, at least more than 48 hours, which is harmful to human body. Dry ice cleaning can completely solve the problem of carbon deposition within 10 minute, saving time and reducing cost, and the scale removal rate reaches 100%.
7. Electronics industry
Clean the grease and dirt inside robots and automation equipment; Clean the integrated circuit board, post-welding flux, pollution coating, resin, solvent coating, protective layer and photosensitive corrosion inhibitor on the printed circuit board.
8. Application scope of aerospace
Pre-coating treatment and final assembly of missiles and aircraft; Paint removal of composite molds and special aircraft: engine carbon cleaning; Maintenance and cleaning (especially the landing gear-wheel well area); Depainting of aircraft shells: jet engine conversion system. Can work directly in the body, saving time.
9. Scope of application of shipbuilding industry
Hull; Seawater suction valve; Seawater condenser and heat exchanger; The machine room, machinery and electrical equipment are cleaner than ordinary high-pressure water jet cleaning.
10. Application scope of nuclear industry
If the nuclear industry equipment is cleaned by traditional cleaning methods such as water, sand blasting or chemical detergent, the media such as water, sand blasting or chemical detergent will also be polluted by radioactive elements, so it takes time and money to treat these secondary polluted media. In the process of dry ice cleaning, dry ice particles are directly sprayed on the object to be cleaned, which instantly sublimates, and there is no problem of secondary pollution. All that needs to be treated is the cleaned waste with nuclear pollution and scale.
Application of dry ice in food field
1 1, 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 frozen substance for treating acne, which is made of ground dry ice and ethyl ketone, and sometimes some sulfur is added. 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.
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, and the ice cream is not easy to melt. Dry ice is especially suitable for cold storage of takeaway ice cream.
Seafood dishes made in C-star hotels and restaurants, with dry ice, can create a white smoke landscape and improve the banquet level, such as making lobster sashimi.
D lobster, crab, shark fin and other seafood are frozen and refrigerated. Dry ice will not change water, and it is cleaner than water-cooled storage. Widely used in Europe, America, Japan and other countries.
13, Application of dry ice in refrigerated transportation field
Cryopreservation and transportation of special drugs for medical use, such as plasma and vaccines.
B. Long-distance and short-distance transportation of electronic cryogenic materials and precision parts.
C. preservation and transportation of high-grade foods such as high-grade beef and mutton.
14, application in entertainment field
Widely used in stage, theater, film and television, wedding, celebration, party effect and so on. For example, some programs in the National Theatre are made of dry ice.
Application of dry ice in other fields
15, Application in Fire Protection Industry
Dry ice is used for fire fighting, such as some low-temperature fire extinguishers, but the application of dry ice in this respect is less, that is, the market level is low;
Precautions for using dry ice:
Remember to be careful every time you touch dry ice. Touch dry ice with thick cotton gloves or other shelter! If it is in direct contact with the skin for a long time, it may cause cell freezing and similar minor 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, please don't put it in your mouth to prevent frostbite! !
3. When taking dry ice, be sure to use thick cotton gloves, clips and other shelter (plastic gloves have no shelter! ! )
4. Please use dry ice in a well-ventilated place and avoid in a closed space with dry ice! !
5. Dry ice cannot be mixed with liquid.
Tip: Use dry ice correctly and safely to avoid injury.
Symptoms and treatment of frostbite:
Definition of frostbite
Frostbite means that a part of the body is exposed to cold environment for a long time, and its skin and tissue are damaged.
Symptoms:
You will feel cold and a little red before frostbite.
The skin will lose its color first, but when frostbite gradually forms, it will turn white or grayish yellow, or white with spots.
There may be blisters. It may hurt a little, or you may not even know you have frostbite.
The first symptom of frostbite (chilblain) is tingling, followed by numbness and stiffness, and the affected part is pale; At this time, if it is heated, it can be completely restored. The initial chilblain will develop into superficial chilblain if it is not treated. 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, swollen and painful, and form a big blister similar to second-degree burn after one to a few days; After a few days, the blisters dry to form a black eschar, which will eventually be replaced by new skin if there is no concurrent infection.
Frostbite treatment measures:
Move to a warm place and keep the affected part in warm and dry air. Remove the binding substance to avoid being unable to pull it out when it is swollen. Keep warm in gradually adjusted warm water (38.8~40.5 degrees).
Don't catch cold, raise the affected area to relieve pain and swelling, then wrap the affected area with clean gauze and send it to hospital for treatment; The purpose of first aid is to restore the body fluids bound by cold to normal. Therefore, if we can warm the area around the affected area, it can be cured soon. It is forbidden to directly soak the affected area with hot water or bake it with fire, which will aggravate frostbite. Because massage can cause it, remember not to do massage in the affected area.
Caution-Do not massage, bake or puncture blisters to prevent infection.