Decode the complete set of dry stones

HowMeet, dry ice is the name given to carbon dioxide when it exists in solid state. Carbon dioxide is found in the earth's atmosphere: it is the gas that people breathe out and plants used to photosynthesize to produce chlorophyll. This chemical compound is colorless, odorless, tasteless and has 1.5 times the density of normal air.

Carbon dioxide changes from gaseous to milky solid under low pressure and temperature (minus 109 degrees F or minus 178.5 degrees C). Dry ice is produced mainly in two forms: a dry ice block weighing over 20kg or small pieces of different sizes (from the size of a grain of rice to larger pellets).

Dry ice does not dissolve, instead it will sublimate , meaning it will move from a solid state to a gaseous state (ignoring the liquid state) when the temperature begins to rise. Because of this property dry ice is often used to simulate fog or smoke in performing arts or restaurants .

Dry stone is the name given to carbon dioxide when it exists in solid state.

Dry ice itself is not toxic but the surface of dry ice is very cold and can cause "cold burn" when hand-contacted without gloves, this phenomenon occurs when human skin comes into contact with surfaces. temperatures below 0 degrees Celsius. Also, because of their heavier nature, carbon dioxide in gaseous state can be concentrated in low areas or in enclosed spaces. When the concentration of carbon dioxide in the air exceeds 5%, carbon dioxide becomes toxic. Therefore, when using carbon dioxide, the space must be airy to avoid poisoning.

To convert carbon dioxide into solid form is quite simple. Many dry stone manufacturers have been established and operated in the United States for a long time and this product is shipped to many parts of the country for many different purposes. It is important to keep cold and prevent bacteria in food from growing during transport. Dry ice used to cool or freeze food must be very clean and it is called " frozen food".

Because of the sublimation characteristics (moving from solid to gaseous) a large amount of dry ice can be put into containers without worrying about water as when using regular ice to cool food. The use of dry ice in the food sector is very diverse, including rapid freezing of foods for future use in food processing plants, slowing the growth of yeast in factories. Cake, cold storage food served the aviation industry.

Dry ice does not melt, instead it will sublimate, meaning it will move from a solid state to a gas state.

Other uses of dry ice include: slowing the growth of flower buds in nurseries to keep fresh plants for consumers, freezing quickly in the rubber manufacturing industry, limiting cold ammonia leakage and creating Smoke for the stage when performing arts. The most important application of recent dry ice is ice blasting (or cleaning), in which dry stones are thrown into the surface to be cleaned at high speed. Contaminants along with carbon dioxide will sublimate into the air and things will be cleaned. The rest is just dirt that needs to be treated later.

History

Dry stone was not invented, the properties of solid carbon dioxide were discovered in the early years of the twentieth century. Dry stone was first produced commercially in 1920 in the United States. A commercial company registered a dry stone brand in 1925 and since then it has been called solid carbon dioxide as dry stone.

Dry stone was first produced commercially in 1920 in the United States.

Prest-Air Devices Company of Long Island was the first company to successfully produce dry ice in New York in 1925. That same year, Schrafft used dry ice to keep ice cream from melting in their living room. Dry ice has been more widely used for cooling and freezing food since the mid-twentieth century to the present.

Most ice creams in the world use this way to freeze until after World War II when refrigeration equipment is cheaper and works more efficiently.

The production of dry ice has not changed much over the past decades and is a relatively simple process when we use high pressure to cool carbon dioxide. The use of dry ice has decreased somewhat due to the convenience of refrigeration. Recently, people often use dry ice to clean water, transport medical specimens, including hearts, limbs and tissues for surgery and transplantation.

Raw materials

The material used to produce dry ice is carbon dioxide . This material is a by-product of all kinds of emissions in the production process or refining other products. Most carbon dioxide used in dry ice production in the United States is derived from gas generated during screening of petroleum and ammonia gas. The carbon dioxide emitted in these processes is extracted and removed impurities (to become carbon dioxide used in food) and then the dry ice is made from this gas.

Dry ice production process

The process produces dry ice.

- Step 1: Carbon dioxide is liquefied by compression and cooling, liquefaction takes place at a pressure of 870 lb / 2 (395kg / cm ² ) at room temperature. Carbon dioxide is pumped through pipes into large tanks so that dry stone manufacturers can remove the necessary contaminants.

- Step 2: Carbon dioxide is transported in very large quantities, sometimes heavy tons. Therefore, most dry stone producers often place factories near oil or ammonia filtration facilities to reduce transportation costs. Under pressure, liquid carbon dioxide is directed directly into the tank of the dry ice factory.

- Step 3: These liquids are kept cold to maintain the liquid state in large tanks directly connected to the production site by pressure pipes to use when necessary.

- Step 4: Liquid carbon dioxide is then transported again through the pipeline from the tanks to the mold storage to produce dry ice. When transporting liquid from a high-pressure environment to an atmosphere equivalent to atmospheric pressure, it will evaporate at high speed and the liquids will turn solid at a temperature of -109 ° F (-78.3 ° C). A nozzle brings liquid into a mold that stands about 4.9 meters. This mold is specially designed with input that can withstand high pressure from the fuel. When the liquid carbon dioxide enters the dry stone mold, it immediately freezes at room temperature. Carbon dioxide now looks like snow.

- Step 5: This snow will be compressed to become dry ice. Under pressure of about 60 tons, snow is compressed into dry stone, the whole process lasts about 5 minutes. A dry stone block is usually 61cm wide, 25cm high and weighs 100kg.

- Step 6: This dry stone block is pushed out of the mold and slipped on a roller. A pneumatic saw blade cuts this dry block into two equal parts and continues to put in another sawing system to cut it out again. The original dry stone was divided into 4 equal parts, each weighing 25kg.

- Step 7: These dry ice cubes are put into containers and kept cold to their lowest level of sublimation. When transporting, dry ice blocks must be packed tightly, if removed during this time they will completely vaporize. Many manufacturers use machines to wrap paper on dry ice before delivering it to customers (if using the hand, it will be prone to cold burns).

Quality management

The issue of quality management mainly focuses on carbon dioxide materials used to produce dry ice. Recently, the US government set very strict standards for the purity of carbon dioxide used in dry ice production. The source of liquid carbon dioxide as well as the purity of the final product must pass the tests before being marketed.

Control issues also include ensuring the dry ice making system works correctly. If the pressure is not maintained properly, the product will not be produced. It is also important to move products quickly and efficiently after cutting for storage because dry ice will quickly sublimate at room temperature so it will reduce weight and cost when sold (if not well preserved. The packaging in intermediate transport must be ensured to limit sublimation.

Control issues also include ensuring the dry ice making system works correctly.

By-products / Waste treatment

No significant chemicals were created in dry ice production. When the product is sublimated, the gases will be released into the atmosphere and hardly cause any significant health and environmental impact.

Future

The use of dry ice in refrigerators and food storage may be reduced but some areas still need this dry stone. As mentioned above, dry ice can be used for cleaning, bombarding a house or something at high speed to remove dirt or other contaminants. Recently, a telephone company used dry stones as a way to safely clean sensitive electronic test equipment instead of using dangerous solvents. And there are many other uses of dry ice waiting for you to explore .