Carbon dioxide for pH control
CO2 Clean technology
for pH reduction
airliquide.ca
food.airliquide.com
CO2 VS Acids
For many years, strong acids were used to control pH levels in water treatment facilities,
most commonly, sulfuric acid. Acid products do the job, but have many potential
problem: acids are difficult to control and are potentially dangerous to store and handle;
safety showers have to be installed and made available for operating personnel, who
must also wear special protective clothing.
Comparative neutralization curve
of mining effluent (660 mg/l CaCO3)
Corrosive acid requires special materials
for equipment and piping. Maintenance of
systems demands frequent component
repairs and replacement. Carbon dioxide
(CO2), on the other hand, is safe to handle,
easy to apply, efficient, and ecologically
safe.
H2SO4
CO2
When pH control is critical to your process
or effluent quality, you can trust the CO2
solution.
Acid added (mg/l)
Description:
When dissolved in water, CO2 forms a weak acid: carbonic acid. This substance reacts immediately with alkalis such
as caustic soda, sodium carbonate, and dissolved lime, turning them into neutral carbonates and bicarbonate salts.
CO2+H2O
H2CO3+2NaOH
H2CO3+Na2CO3
H2CO3
Na2CO3+2H2O
2NaHCO3
+
–
Carbonic acid is a mild acid present in water as ions H and HCO 3 ,
which are highly reactive. They will immediately react with the CO32-- and
OH ions that are responsible for the alkalinity of water.
Adding more CO2 forms bicarbonate ions with a pH of 8.3.
Under lower pH, free CO2 starts to form with a lower technically feasible pH of ~5.2 under pressurized conditions.
pH Control:
CO2 is introduced into high-pH water by means of a diffuser and/or venturi nozzle, which are
installed in an existing pressurized pipe, a recirculation loop, or at the bottom of a basin. Fine
CO2 bubbles are released by the diffusers and/or venturi and dissolved into the high-pH water.
A pH probe is installed downstream of the gas injection point, measuring the pH of the water
after the absorption of CO2.
A pH control manifold automatically adjusts gas flow and achieves high efficiency and reliability
with little supervision from plant personnel.
Advantages:
There is no secondary pollution introduced into the treated water by salts such as chlorides
(from HCl) or sulfates (from H2SO4).
The introduction of CO2 will contribute to the chemical equilibrium of water by forming
carbonates and bicarbonate compounds.
Supply Modes:
For small requirements, carbon dioxide can be supplied in liquid cylinders. Larger
volumes will be delivered by truck and stored on-site in a bulk CO2 storage tank
supplied by Air Liquide. Typically, CO2 is available at a pressure of up to 300 psig
and so doesn't require any pump for its transfer into your process.
Applications:
CO2 is used in various industrial waste water processes:
• Pulp and paper
• Textiles
• Cooling towers
• Food plants (cheese, dairy, slaughtering)
• Bottling
• Potable water solids removal and recarbonation
• SAGD boiler blow-down water, tailings, mining
• Dissolved air flotation
AIR LIQUIDE PROPOSES:
A pH control system that is safe for the environment
• CO2 is inert and non-corrosive
• CO2 dissipates safely into the atmosphere, leaving no residue to be neutralized
• Acid leaks must be neutralized with alkaline solutions to prevent damage to
equipment or the environment
• No special alloy or plastic distribution piping is required for the CO2 system
Regulation:
• Eliminate risk of over-acidification
No maintenance:
• Components of the system are installed and maintained by Air Liquide’s
experienced technical team
Flexibility:
• Liquid CO2 can treat streams pH as high as pH 14
These features ensure efficient control and quick reaction to any process pH change
or flow variation.
FINDING SOLUTIONS
IS IN OUR NATURE
AIR LIQUIDE CANADA INC.
Head Office
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Telephone: (514) 933-0303
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of Air Liquide
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Anjou,
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ALTEC
Group
– Environnement
H1J 1M6
Phone:
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www.food.airliquide.com / www.airliquide.ca
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Atlantic
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World leader in gases, technologies and services for Industry and Health, Air Liquide is present in 80 countries with more than 50,000 employees and
serves more than 2 million customers and patients. Oxygen, nitrogen and hydrogen have been at the core of the company’s activities since its creation in 1902.
Air Liquide’s ambition is to be the leader in its industry, delivering long-term performance and acting responsibly.
NOTE: This document is intended for general information purposes only and is not intended as a representation or warranty of any kind, or as a statement of any
terms or conditions of sale. The specifications are solely for informational purposes and shall be subject to change at the sole discretion of Air Liquide Canada Inc.
at any time. The specifications and information are believed to be correct, but are not warranted for correctness or completeness, or for applicability to any particular
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