Most people outside the industrial gas industry are familiar
with Carbon Dioxide, CO2, as the bubbles in soft drinks and as the
chemical in fire extinguishers. CO2
is used in more forms than any other gas in the industrial gas market making it
one of the most versatile products sold.
CO2 was discovered in the early 1600’s as the off
gas of burning wood by Jan Baptista von Helmont, a scientist in Finland. In the mid 1700’s a chemist in England,
Joseph Priestly, found that mixing water and CO2 being expended from
a fermentation process created sparkling water which gave the water a different
taste and became the basis for the soft drink industry.
One of the properties of the gas that was discovered was how
easily it could be liquefied. This
resulted in it becoming the first commercial industrial gas to be supplied as a
packaged gas. As more was understood, CO2
became the only gas supplied and used in all three of its phases – gas, liquid
Most of us in the industry associate CO2 with
welding as a shielding gas and as a refrigerant in the food industry. Other characteristics make it unique.
The best example is when CO2 comes in contact
with water and it forms carbonic acid. Although it is a weak acid, it is an acid nonetheless and can be used to
adjust the pH in some processes where the pH is an important system
parameter. This is evident in different
industries such as paper production, textiles, and water treatment
processes. An additional benefit is that
carbonic acid is not stored as an acid (such as sulfuric or hydrochloric
acids). As mentioned, the CO2 needs
water to form the acid so it remains CO2 until needed and is not
considered hazardous like other acids.
CO2 is stored as a liquid regardless of the
container. The pressure in an
uninsulated CO2 cylinder is somewhere around 800 psig depending on
the ambient temperature. This means that
any application using liquid CO2 has to be under pressure. Workers in the oil industry are aware of CO2
replacing water in enhanced oil recovery (EOR) where the liquid is mixed
with sand or sand like substance (proppant) and pumped down an oil well to
recover oil that is trapped inside the rock layers. EOR is a blanket term to describe different
applications but the most common is fracking. Here the proppant is forced into the oil rich rock through man made
fissures. This forces the rock to
fracture and release trapped oil. When CO2
is used instead of water, its natural expansion of volume from liquid to
gas helps enlarge the fissure and recover an additional amount of oil.
It’s not common knowledge that liquid CO2 is also
used in the dry cleaning industry. In a
special high pressure washer, liquid CO2 is introduced with a stain
remover. The laundry is treated as in a
regular washing machine using turbulence to clean the wash. When the cycle is done, the dirt, grime and
stain remover are separated from the liquid CO2. The liquid CO2 is then removed for
reuse and the laundry is removed clean and dry since no water was used.
Every chemical (element or compound) has a state in which
the three phases (gas, liquid and solid) have the same properties and is
attained adjusting the pressure and temperature; this is called the supercritical state. The supercritical state of CO2 can
be produced in a specially designed processor. The fluid phase of supercritical CO2 is an exceptional
solvent and is used to extract fragrances and color from flowers and plants. The process is, of course, performed under high
pressure and requires highly specialized equipment.
Solid CO2 or dry ice is used as a coolant in
several ways and forms. When liquid CO2
is transported through a high pressure line and discharged through
special nozzles, it immediately turns to CO2 snow and is used in the
refrigeration or freezing of food. Dry
ice pellets replace regular ice in tubs that hold perishables for long over-the-road
Dry ice in very small form (about the size of a grain of
rice) is used as an abrasive to remove coatings from surfaces without harming
the surface itself by shooting the rice size pellets through a blasting lance. This is popular in the aircraft industry
where an airplane’s body has to maintain its integrity and cannot tolerate any
damage that would occur with sand blasting. An additional benefit is that the removed coating does not have to be
separated from the abrasive as the pellets sublimate to CO2 gas
leaving the residue particles for easy cleanup.
Calling CO2 a super-gas may be overstepping the
bounds of the definition, but it is definitely the most versatile product
available in the industrial gas market.
About the Author
John Segura is a licensed Professional Engineer and a
seasoned executive in the industrial gas industry. He has over 30 years of experience covering
sales, marketing and operations both domestic and international. He has led teams of engineers and technicians
as an R & D manager for major gas companies. His work directed him to lead the marketing
efforts of technology worldwide for industrial gas suppliers. He now consults to the industry on the
business specializing in operations, applications and marketing.