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28 Feb 2016

Five amazing liquid CO2 uses in our lives which were unknown to us

Liquid CO2

    Anyone with basic science knowledge is well aware of Carbon dioxide (CO2). Animals and plants exhale CO2 in gaseous form during respiration process and plants uses CO2 from atmosphere to produce food during photosynthesis process. It is a greenhouse gas and due to its excessive production from industry and automobiles, it is always thought to be dangerous and harmful to humans. It can be easily liquefied by established industrial methods and there are some amazing daily uses of liquid CO2 while many of us are unaware of these. First of all I will briefly describe CO2 properties and production method.

liquid CO2 storage

Properties of CO2:

   CO2 is naturally present is air at the concentration of 0.04%. It is a colorless gas with no smell in pure condition. Its molecular weight is 44 g/mol and it stays in gaseous form at ambient temperature and pressure conditions. Its boiling/sublimation temperature is -78.45 C. Liquid CO2 temperature depends upon its pressure and saturation conditions

Liquid CO2 Production:

   Now I will concisely explain how liquid CO2 is made. It is liquefied industrially by first purifying then increasing its pressure and decreasing temperature. Depending upon source of raw CO2, impurities are removed by absorption with amine solutions, scrubbing with water, drying with different bed dryers and stripping/distillation to remove non condensing impurities. After purification with above methods, CO2 pressure is increased about 270-280 psi by using compressors and then its temperature is decreased up to -28 C by using ammonia or Freon based refrigeration systems. Purity of 99.90% is achieved to make it food grade. Liquid CO2 is stored in insulated and pressurized storage tanks.

Liquid CO2 uses:

  Liquid CO2 is cryogenic in nature and has wide industrial applications in beverage industry, laboratories, medicines, chemical production, water treatment and metal industry. Most of us know CO2 as firefighting media in fire extinguishers but here are few amazing uses of liquefied CO2 in industry and daily life

Production of carbonated beverages like Coca Cola and Pepsi:

Whenever you open your soda cane you see bubbles of gas coming out, this is CO2 which was added during production process. Liquid CO2 is first vaporized and then added to carbonated beverages. Small quantity of CO2 is very necessary to make your drink really tasty. Without CO2, it is just a cane filled of sugared water. Moreover, CO2 produces carbonic acid with the water, which plays a vital role in digestion process. I am not staying that drink carbonate beverages is very healthy but their special taste depends upon CO2

Liquid CO2 in Carbonated beverages

Food preservation especially in airline kitchens:

Liquid CO2 possess a very unique and useful property. When it is flashed from high pressure to atmospheric pressure, it is converted in solid form usually known as dry ice. As name shows, it is just like ice but without any moisture and with much lower temperature (-78 C) then regular water ice. This makes it a very excellent food preservative agent. This technique of keeping food cold and preserved is usually used in airline kitchens. So when you enjoy your chilled drink on a flight, it was most probably due to dry ice produced from liquid CO2

Liquid CO2 as food preservative

Liquid CO2 as refrigerant in super markets:

Liquid CO2 is a good refrigerant with very less environmental concerns as compare to other synthetic refrigerants (like CFCs and HCFCs). It has applications in refrigeration industry since 1920 but later due to development of clorofloro carbons its use decreased. Now supermarkets are using liquid CO2 based refrigeration systems and replacing their conventional systems. CO2 based systems include expansion and evaporation of liquid CO2 by absorbing heat of the system and  then again compression and condensation of vapor CO2 to  produce liquid.

Use of Supercritical CO2 in coffee production:

So you are thinking what is connection between liquid CO2 and your Coffee? This is due to super critical property of CO2. It is the state of CO2 at which it behaves both as liquid and gas. At this state it can expand like a gas and has density like a liquid. It behaves as supercritical fluid at temperature above 31.10 C and pressure above then 1071 psi. 
CO2 at supercritical state is used as decaffeinating solvent during coffee manufacturing. It is passed from fresh green beans of coffee and water is sprayed to remove caffeine and then further processing is carried out to produce coffee

supercritical co2 in coffee production

PH control agent in swimming pools:

As we know, when CO2 is mixed with water it produces a week acid named as carbonic acid. This reaction makes it a good PH controlling agent especially in swimming pools and waste water treatment units. 99.9% pure Liquid CO2 is supplied in cylinders and this is injected in swimming pool on a controlled rate to maintain PH for superior water quality. It has edge over conventional PH control agents due to its lower costs and negligible environmental impacts.

Above uses of liquid CO2 are just few one from a long list. Its industrial applications are numerous like preservation of human and animal organs, production of medicines, as a mixture with Oxygen for respiratory stimulation. in paper and pulp industry, as a firefighting media and production of chemicals. 
In the end, as a safety precaution always consult Liquid CO2 MSDS if you ever have to work with it.