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Substitutes for Potent Greenhouse
Gases
4 Use of PFC substances
PFC means perfluorocarbons, i.e. substances that are
formed with basis in simple hydrocarbons, where all hydrogen
atoms are exchanged with fluoride atoms. These are
substances like CF4, C2F6, C3F8, etc.
As these substances are very stable, they have a very long
atmospheric lifetime. At the same time they are very strong
green house gases. However, only small amounts of these
substances are used in Danish industry, and the main area of
application lies within the refrigeration industry.
Abroad some PFC emission occurs in connection with aluminium
production produced from aluminium oxide (alumina) by means
of an electrolytic process. The PFC substances will only
develop if a special effect, i.e. the anode effect, occurs.
This means a rapid increase of the electric voltage during
which certain PFC substances (CF4 and C2F6) are
produced. In Norway and Sweden considerable efforts in
reducing development and emission of PFC substances have
been made during recent years.
Abroad a considerable amount of the substance C6F14 is used
within the electronic industry.
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Chemical
formula
|
R-number
|
Boiling point (C)
|
GWP
(100 yrs)
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Atmospheric
Life Time (yrs)
|
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CF4
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R-14
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-127.9
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6500
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50000
|
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C2F6
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R-116
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-78.2
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9200
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10000
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C3F8
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R-218
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-36.8
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7000
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2600
|
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C6F14
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+58
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7400
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3200
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In 1990 the global emission of CF4 was app. 15,000 tonnes,
which in 1995 decreased to app. 10,500 tonnes. In 1990 and
in 1995 the global emission of C2F6 was app. 2,000 tonnes
(personal information by Jochen Harnish, MIT).
4.1 PFC in refrigerant mixtures
According to a survey made by the Danish Environment
Protection Agency app. 8 tonnes of C3F8 (R-218) were used in
1997 as refrigerant in a special mixture.
The refrigerant is used as a drop-in substitute for CFC-12
in refrigeration plants. Consumption has been increased
heavily since 1995 and 1996, with consumption of 1.5 and 3
tonnes respectively.
The refrigerant mixtures are known under various names,
including Isceon 49 (R-413A), which consists of app. 88%
HFC-134a, 9% C3F8 and 3% Isobutane.
New mixtures occur constantly, however the industry is most
cautious about using refrigerant mixtures, as some
uncertainty about the remaining mixture after leakage
prevails. In general, transport of anymore types of
refrigerants than necessary is undesirable.
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Trade name
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R-number
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Drop-in substitute for
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Composition
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Isceon 49
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R-413A
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CFC-12
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9% of C3F8, 88% of HFC-134a, 3% isobutane
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Isceon 69L (Isceon 69S)
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R-403B R-403A
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R-502
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39% of C3F8, 56% of HCFC-22, 5% propane
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Suva 95
Forane 508A
(Arcton TP5R3)
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R-508B
(R-508A)
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R-13, R-503
(low temperatures)
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54% of C2F6 and 46% of HFC-23
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Arcton TP5R2
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R-509A
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56% of C3F8 and 44% of HCFC-22
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R-412A
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5% of C3F8, 70% of HCFC-22, 25% of HCFC-142b
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Table showing refrigerant mixtures, containing
perfluorocarbons
The mixtures may be conveniently used if extended lifetime
of a CFC-based system is required and no recycled CFC
refrigerant is available. The only reason for using these
mixtures is their capability to extend the lifetime of old
CFC based refrigeration systems. This application may be
avoided by either converting the CFC refrigeration systems
into HFC refrigerant or by maintaining tightness of system
until scrapping. It is also possible to refill with used CFC
from the KMO Recovery and Recycling Scheme.
4.2 Other applications of PFC
substances
DTI Energy has not met other types of application in
Denmark, but apparently small amounts are used in
laboratories.
In Working Report No. 20, the Danish EPA 1996: Consumption
of emissions of 8 fluoride and chloride hydrocarbons (Jan
Holmegaard Hansen, Cowi), the following is mentioned:
One of the importers informs that the company has 2
products containing perflouro combinations on the import
list. Both contain perflourohexane C6F14 as the main
component, however, none of these products have been sold
within the last year. The one product is an inactive liquid
for use in the electronic industry, whilst the other product
(an overactive product) is newly developed and thus never
sold.
It should be mentioned that attempts of selling a PFC
substance as fire extinguishant in replacement for halon has
been carried out abroad. This application of PFC is banned
in Denmark, see section 3.3.
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