Dry ice is solid carbon dioxide, at room temperature and pressure of 6079.8 kPa pressure, the carbon dioxide condensed into a colorless liquid, and then evaporate rapidly under low pressure, it will be condensed into a block of ice and snow-like solid material, the temperature is minus 78.5 ° C, this is dry ice. Dry ice cold storage is more than 1.5 times the water ice, heat absorption sublimation into carbon dioxide gas, without any residue, non-toxic, odorless, sterilizing effect. It is not liquefied by heat, but directly vaporized. Dry ice is a solid state of carbon dioxide, due to the very low temperature of dry ice, the temperature of negative 78.5 degrees Celsius, so often used to keep the object to maintain the frozen or cryogenic state.
When carbon dioxide gas is pressurized to about 101,325 Pa at room temperature, a portion of the vapor freezes into snowflake volts of solid carbon dioxide when it is cooled to about -56 degrees Celsius. Solid carbon dioxide heat of vaporization is very large, at -60 ℃ for 364.5J / g, gasification at atmospheric pressure can make the surrounding temperature down to -78 ℃ or so, and does not produce liquid, so called "dry ice".
[edit]Physical Characteristics of Dry Ice
Molecular Weight 44.01
Density (solid) 1560kg/m3(-78℃)
Melting Point -57℃
Boiling Point -78.5℃
Liquid to Gas Ratio 8.726SCF(Gas)/LB (Liquid-17.8℃),Pressure 21kg/cm2 (Liquid-17.8℃),Pressure 21kg/cm2 (Liquid-17.8℃). Pressure 21kg/cm2)
Liquid to solid ratio 0.46 (-17.8 ℃) 0.57 (-48 ℃)
[Editorial]History of dry ice
The history of dry ice can be traced back to the British two called Faraday and Descartes Pittsburgh in 1823, the first liquefied carbon dioxide, and then in 1834 the German Chilolei successful production of carbon dioxide. Later in 1834, German Dr. Chilole succeeded in producing solid carbon dioxide. However, it was only used for research purposes and not for general use. Dry ice was successfully produced in industrial quantities in the United States in 1925 with the establishment of the Dry Ice Co. At that time, the finished product was called dry ice, which is now regarded as a common term, but its official name was solid carbon dioxide, and in 1928, Japan acquired the manufacturing and sales rights from Dry Ice Corporation and established Nippon Dry Ice Corporation, the predecessor of Showa Carbonic Acid Co.
[edit]Dry ice application range
Dry ice is widely used in food, health, industry, catering has a large number of applications. Mainly:
Dry ice in the industrial field of application
1. Industrial mold applications
Tire molds, rubber molds, polyurethane molds, polyethylene molds, PET molds, foam molds, injection molds, alloy die-casting molds, casting with hot core box, cold core box, can remove the remaining resin, failures of the de-filmation layer, charring film agent, oil, open the exhaust holes, after cleaning After cleaning, the mold is as bright as new.
On-line cleaning, no need to cool down and disassemble the mold, avoiding the chemical cleaning method of corrosion and damage to the mold, mechanical cleaning method of mechanical damage to the mold and scratches, as well as repeated loading and unloading lead to the decline in the accuracy of the mold and other shortcomings. The key is to eliminate the dismantling of the mold and wait for the mold to cool down the two most time-consuming steps, which can reduce the downtime of about 80% -95%.
Dry ice cleaning benefits: dry ice cleaning can reduce downtime; reduce equipment damage; extremely effective cleaning of high-temperature equipment; reduce or lower the use of solvents; improve staff safety; improve maintenance efficiency; reduce production downtime, reduce costs, improve productivity.
2. Petrochemical applications
Cleaning of the main fan, air compressor, smoke machine, turbine, blower and other equipment and various types of heating furnaces, reactors and other coking and carbon removal. Cleaning of PVC resin on heat exchangers; removal of oil, rust, hydrocarbons and their surface dirt on compressors, tanks, boilers and other types of pressure vessels; cleaning of reactors and condensers; decontamination of complex bodies; furnace pipe cleaning and so on.
3. Food and Pharmaceutical Applications
It can successfully remove baked residues, gelatinous substances and oil in the oven, as well as the mixture of fresh products before baking. Effectively clears ovens, mixing and blending equipment, conveyor belts, molded products, packaging equipment, oven racks, trays, containers, rollers, freezer interiors, cookie oven bars, etc.
Benefits of dry ice cleaning: exclude the use of harmful chemicals, avoiding exposure of production equipment to harmful chemicals and the production of a second waste; mimic or get rid of bacteria such as salmonella, listeria and other bacteria, more thoroughly disinfected, clean; exclude the damage of waterjet cleaning of electronic equipment; minimal decomposition of the equipment; reduce downtime.
4. Applications in the Printing Industry
Removing ink is difficult, and ink buildup on gears and rails can lead to poor print quality. Dry ice cleaning removes a wide range of oil and water-based inks and varnishes, cleans oil, ink and dye buildup from gears, rails and nozzles, and avoids the discharge of hazardous wastes and solutions, as well as injuries to personnel caused by hazardous solvents.
5. Application scope of electric power industry
It can clean electric power boiler, condenser and all kinds of heat exchangers; it can directly clean indoor and outdoor transformers, insulators, distribution cabinets and wires and cables with electric loads (below 37KV); it can clean the parts of generators, motors, rotors and stators without damage; it can clean the parts of turbines, turbine impellers, blades and other parts of rusty scale, hydrocarbon and adhesive powder cleaning, do not need to remove the paddle, eliminating the need to re-adjust the dynamic balance of the paddle.
The benefits of dry ice cleaning: effective decomposition of the pollutants being cleaned; reduction of power losses due to the removal of these pollutants; reduction of maintenance costs for external equipment and its infrastructure; improvement of the reliability of the power system; non-abrasive cleaning, maintaining the integrity of the insulator; more suitable for preventive maintenance.
6. Applications in the automotive industry
Cleaning of door skins, roofs, carriages, underbody oil and other waterless stains, which does not lead to water contamination; automotive carburetor cleaning and automotive surface paint removal, etc.; removal of carbon deposits in the engine. If you deal with carbon deposits, it takes a long time to deal with chemicals, at least 48 hours or more, and the chemicals are harmful to the human body. Dry ice cleaning can be within 10 minutes to completely solve the problem of carbon deposits, that is, to save time and reduce costs, descaling rate of 100%.
7. Electronic industry
Cleaning robots, automation equipment, internal grease, dirt; integrated circuit boards, post-soldering flux, contamination coatings, resins, solvent coatings, protective coatings, and printed circuit boards on the removal of photosensitive anticorrosive agents.
8. Aerospace applications
Missiles, aircraft painting and general assembly of the pre-process; composite molds, special aircraft paint removal; engine carbon cleaning; maintenance cleaning (especially landing gear - wheelhouse area); aircraft shell paint removal; jet engine conversion system. Can work directly on the airframe, saving time.
9. The scope of application of the marine industry
Ship shell; seawater intake valve; seawater condenser and heat exchanger; engine room, mechanical and electrical equipment, etc., cleaner than the general use of high-pressure water jet cleaning.
10. Nuclear industry applications
Nuclear industry equipment cleaning if the use of water, sandblasting or chemical cleaning agent and other traditional cleaning methods, water, sandblasting or chemical cleaning agent and other media at the same time also contaminated by radioactive elements, the treatment of these media by the secondary contamination of time and money. The use of dry ice cleaning process, dry ice particles directly sprayed to the object to be cleaned, instant sublimation, there is no secondary pollution problems, need to deal with just be cleaned off the nuclear contamination of the scale and other waste materials.
Dry ice in the field of food applications
11, beauty industry applications
Some dermatologists use dry ice to treat acne, this treatment is the so-called cryotherapy. Because it will slightly freeze the skin.
One type of freezing material used to treat acne is a mixture of ground dry ice and acetone, sometimes mixed with some sulfur. Liquid nitrogen and solid dry ice can also be used for cryotherapy. Cryotherapy can minimize inflammation, and it was reported in the news some time ago that Liu Xiang used this type of cryotherapy to treat acne on his face. This method can reduce the production of acne scars, but is not used to remove scars.
12, dry ice in the food industry applications
a In wine, cocktails or drinks with dry ice, drinking cool and delicious, the cup of smoke, very pleasant.
b Add dry ice when making ice cream, the ice cream is not easy to melt. Dry ice is especially good for freezing take-out ice cream.
c Star hotels, restaurants produce seafood specialties, add dry ice when serving, can produce white smoke landscape, improve the banquet grade such as the production of lobster sashimi.
d Lobster, crab, shark fins and other seafood frozen frozen. Dry ice will not melt water, more clean, cleaner than water ice refrigeration, in Europe, the United States, Japan and other countries are widely used.
13, dry ice in the field of refrigerated transportation applications
a Low-temperature freezing for medical purposes and plasma, vaccines and other special medicines for low-temperature transportation.
b Electronic low-temperature materials, long and short-distance transportation of precision components.
c Fresh transportation of high-grade food such as high-grade beef and mutton.
14, in the field of entertainment in the application
Widely used in the stage, theater, film and television, weddings, celebrations, party effects such as the production of smoke, such as the National Theatre, part of the program is to use dry ice to produce the effect.
Dry ice in other areas of application
15, the application of the fire industry
Dry ice is used for fire extinguishing, such as part of the low-temperature fire extinguishers, but dry ice in this piece of the application of less, that is, the market to a lesser extent;
Notes on the use of dry ice:
Remember that every time you touch the dry ice, must be careful and use a thick woolen Gloves or other coverings should be used to touch the dry ice! If it is in the case of prolonged direct contact with the skin, it may cause cell freezing and similar to minor or extremely serious burns. Dry ice should not be used in automobiles, boats, etc. as sublimated carbon dioxide will replace oxygen and may cause shortness of breath or even asphyxiation!
1. Never leave children alone with dry ice!
2. The temperature of dry ice is extremely low, do not put it in your mouth to prevent frostbite!
3. Use thick cotton gloves, clips and other coverings (plastic gloves do not have a barrier effect!).
4. Use dry ice in a well-ventilated place, do not be in a confined space with dry ice!
5. Dry ice can not be mixed with liquid.
Warm reminder: correct, safe operation of the use of dry ice, to avoid the injury caused by it.
Symptoms of frostbite and treatment measures:
Definition of frostbite
Frostbite refers to the prolonged exposure of a part of the body to the cold environment, the skin and tissues are thus injured.
Symptoms:
The skin feels very cold and is a little red before frostbite.
The skin first loses its color, but as the frostbite develops, it turns white or yellow with a grayish tinge, or white with blotches.
Blisters may form. It may hurt a little, or you may not even know you have frostbite
The initial symptom of frostbite (frostnip) is tingling, followed by numbness and stiffness, with the affected area appearing pale in color; at this point, if it is warmed up, it can be fully recovered. If the initial frostnip is not dealt with, it will progress to superficial frostnip, at this time the skin and subcutaneous tissue has been necrotic, the skin is still pale or slightly gray, touch cold but soft; thawing will be red, pain, one to a few days after the formation of large blisters as second-degree burns; and then a few days after the blisters dry to form a black scorched scab (eschar), such as the absence of concurrent infections, and finally will be replaced by the newborn skin.
The blisters dry to form black scabs (eschar) after a few days.
Frostbite treatment measures:
Move to a warm place, maintain the affected part in warm, dry air. Remove restraints to prevent swelling and prevent removal. Place in gradually adjusted warm water (38.8~40.5 degrees Celsius) to keep warm
Do not expose to cold, elevate the affected part to reduce pain and swelling, and then wrap the affected part with clean gauze and send it to the hospital; the purpose of first aid is to normalize the body fluids of the cold knot. Therefore, if the area around the affected part can be warmed, it can be cured quickly. It is forbidden to soak the affected part directly into hot water or to roast the affected part with fire, as this will aggravate the frostbite. As massage can cause, remember not to do massage on the affected area.
Note - Do not massage, bake, and puncture the blisters to prevent the affected area from becoming infected.
[edit]Is there dry ice on Mars?
Scientists have succeeded in the first discovery of flowing material in the deep valleys of Mars, Dr. Nick Hoffman, a geologist at the University of Melbourne, Australia, found signs of active processes of action flowing in valleys, gullies, and channels of the polar regions in the photographs taken by the Mars Global Surveyor of the surface of Mars. Although most scientists believe this is liquid water flow, Dr. Hoffman believes it is mostly frozen carbon dioxide. If his estimate is correct, NASA's attempt to discover liquid water and life on Mars will be doomed to failure.
Dr. Hoffman presents his new evidence in the new issue of Astrobiology that what flows in the gullies during the Martian spring at temperatures of minus 130 degrees Celsius is full of ice and snow composed of carbon dioxide, and that even the acid in the batteries turns cobblestones at such cold, low temperatures. Water simply cannot flow at such low temperatures, so it is mostly carbon dioxide that flows in Martian gullies. But liquid carbon dioxide could not exist on Mars, because carbon dioxide would be converted directly from a solid to a gas (so-called sublimation). Obviously, the "fluid" is an avalanche or ice avalanche of "boiling" dry ice with sand, dust, and rocks.
Dr. Hoffman noted, "This discovery dispels any illusions about life on Mars, as NASA's claims of life near the Martian surface would be impossible if all the young gullies on Mars formed by the same mechanism. There will be no liquid water on Mars, and NASA has not found liquid water either, despite numerous reports of large amounts of water ice found on Mars in the recent past."
Dr. Hoffman argued that the discovery of active "fluids" on Mars was itself an epochal discovery, because until then the planet had been absolutely static, if one didn't notice its dust storms. The gullies on Mars are considered to be the most likely candidate for the discovery of liquid water on Mars today, and many NASA experts have focused their attention on the search for mechanisms that would explain the formation of gullies by erosion, but no one has been able to see the gullies "flowing" before now.
Dry ice is carbon dioxide in a solid state, and is often used to keep objects frozen or cryogenic because it has a very low temperature of minus 78.5 degrees Celsius. Dry ice is capable of freezing objects and lowering temperatures in a hurry and has been used extensively. When dry ice is dissolved, it is not converted from solid to liquid, but sublimated directly from solid to gas, so its melting does not produce any water or liquid, which is why we call it "dry ice".
American scientists announced in 2006 that they had discovered "dry ice fountains" on Mars that could spray dry ice hundreds of feet into the air.
The scientists said that through a camera mounted on the Mars rover Odyssey, they found dry ice spewing like a geyser from the south pole of Mars at speeds of up to 100 miles per hour.
According to the BBC, the photos show that the dry ice spewing out of the Martian interior is picking up a lot of dust and leaving various black marks on the ice cap.
Scientists explained that the surface of Mars warmed by the sun, melting the dry ice, which was originally frozen, to form a high-pressure gas that was ejected at high speed.
Dr. Christensen of Arizona State University said, "If you're there, you're standing on a thick layer of dry ice. And all around you, the dry ice is still spewing out of the ground, spewing hundreds of feet above the ground, picking up a lot of dust."
Christensen said, "A similar phenomenon does not exist on Earth."