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ASCO CARBON DIOXIDE INC | 5409 Highway Ave. | Jacksonville, FL 32254 | T +1 904 278-6503 |
ascoco2.comVersion 3.3 (02/18)
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General Information about CO
2
O
Carbon dioxide is the combination of two atoms of oxygen joined with a single atom of carbon. Its chemical formula
CO
2
, is almost as well known as that of water, H
2
O and it is frequently referred to by its formula rather than its name.
In nature’s chain of life, themutual dependence of plant and animal life ismaintained though the link of carbon dioxide.
Every time we breathe we release thisgas, which plants need for life. Though the process of photosynthesis, the
plants separate the carbon from the oxygen. In turn, plants release the pure oxygen, which we need to survive. We
reverse the process, and by combining the oxygen with carbon from the foods we eat, produce carbon dioxide again.
CO
2
is a colourless, inert gas approximately 1½ times heavier than air and 0.03% is present in the earth’s atmos-
phere. It is odorless, has a sweet biting taste (soda water) and is highly stable (difficult to separate).
It is produced in varying amounts by the common process of combustion of fuels high in carbon content. The most
common source of fuel for combustion is oil which, when mixed with the correct proportion of air, burns to produce
around 15% CO
2
in the flue gases of a CO
2
plant. After combustion has taken place, the CO
2
can be separated
from the flue gases and, though a simple process, made available for the many commercial purposes to which it
can be applied.
CO
2
can exist in thee forms:
- in gaseous form: for the beverage and food industries
- in liquid form:
in a storage tank under pressure
- in solid form:
called dry ice (for cooling, blasting etc.)
GASEOUSCO
2
can be liquefied under pressure provided its tempera-
ture is below31 °C, this temperature being referred to as theCRITICAL
POINT. If compressed and cooled below the critical point, a colourless
fluid, approximately the same density as water, is produced.
CO
2
will remain in the liquid form as long as its temperature remains
below the critical point but will return to the gaseous state if its tem-
perature rises above this point, regardless of the pressure applied.
LIQUID CO
2
can be stored indefinitely at
High pressure
or
Low pressure
as follows:
High Pressure CO
2
High pressure liquid CO
2
is produced by compressing the gaseous CO
2
in multistage compressors to pressures in
the neighbourhood of 69bar pressure, then cooling it to around 18 °C. It is customarily filled into specially constructed
steel cylinders. Like water, liquid CO
2
can be weighed, and this is the normal form of measuring it.
Low Pressure CO
2
Low pressure liquid is an alternative method of storing CO
2
and is produced either by expanding high pressure CO
2
to a lower pressure or by refrigeration. It is held in specially constructed storage tanks, heavily insulated and equip-
ped with refrigeration units to hold the internal tank pressure at or below 21bar and -18 °C temperature. Pressure
switches are incorporated to control the refrigeration units and safety mechanism and electrical alarms are fitted to
release the tank pressure and raise an alarm in the event of refrigeration malfunction.
What is CO
2
?