Info

' OSHA - US Occupational Safety and Health Administration (1986). b NIOSH - US National Institute of Occupational Safety and Health (1997). c ACGIH - American Conference of Governmental Industrial Hygienists.

' OSHA - US Occupational Safety and Health Administration (1986). b NIOSH - US National Institute of Occupational Safety and Health (1997). c ACGIH - American Conference of Governmental Industrial Hygienists.

cloud not only because of the high concentration of CO2 but also because of the danger of frostbite.

Hydrates, or ice plugs, can form in the piping of CO2 facilities and flowlines, especially at pipe bends, depressions and locations downstream of restriction devices. Temperatures do not have to fall below 0oC for hydrates to form; under elevated pressures this can occur up to a temperature of 11oC.

AI.2.4 Established uses for CO2

A long-established part of the industrial gases market involves the supply of CO2 to a range of industrial users (source: Air Liquide). In several major industrial processes, CO2 is manufactured on site as an intermediate material in the production of chemicals. Large quantities of CO2 are used for enhanced oil recovery. Other uses of CO2 include:

- Carbon dioxide is used in synthesis chemistry and to control reactor temperatures. CO2 is also employed to neutralize alkaline effluents.

- The main industrial use of CO2 is in the manufacture of urea, as a fertilizer.

- Large amounts of CO2 are also used in the manufacture of inorganic carbonates and a lesser amount is used in the production of organic monomers and polycarbonates.

- Methanol is manufactured using a chemical process which makes use of CO2 in combination with other feedstocks.

- CO2 is also used in the manufacture of polyurethanes.

• Pharmaceuticals

- CO2 is used to provide an inert atmosphere, for chemical synthesis, supercritical fluid extraction and for acidification of waste water and for product transportation at low temperature (-78oC).

• Food and Beverage

- CO2 is used in the food business in three main areas: Carbonation of beverages; packaging of foodstuffs and as cryogenic fluid in chilling or freezing operations or as dry ice for temperature control during the distribution of foodstuffs.

- Intra-abdominal insufflation during medical procedures to expand the space around organs or tissues for better visualization.

• Metals industry

- CO2 is typically used for environmental protection; for example for red fume suppression during scrap and carbon charging of furnaces, for nitrogen pick-up reduction during tapping of electric arc furnaces and for bottom stirring.

- In non-ferrous metallurgy, carbon dioxide is used for fume suppression during ladle transfer of matte (Cu/ Ni production) or bullion (Zn/Pb production).

- A small amount of liquid CO2 is used in recycling waters from acid mine drainage.

Pulp and paper

- CO2 enables fine-tuning of the pH of recycled mechanical or chemical pulps after an alkaline bleaching. CO2 can be used for increasing the performance of paper production machines.

Electronics

- CO2 is used in waste water treatment and as a cooling medium in environmental testing of electronic devices. CO2 can also be used to add conductivity to ultra-pure water and, as CO2 snow, for abrasive cleaning of parts or residues on wafers; CO2 can also be used as a supercritical fluid for removing photoresist from wafers, thus avoiding use of organic solvents.

Waste treatment

- Injection of CO2 helps control the pH of liquid effluents.

Other applications

- CO2 snow is used for fire extinguishers, for pH control and for regulation of waste waters in swimming pools.

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