Promoting Resource Efficiency in Small & Medium size ... - UNEP

• Chemical stability
• Compatibility
• Miscibility with lubricating oils
• Dielectric strength
• Ease of leak detection
Prior to the environmental issues of ozone layer depletion and global
warming, the most widely used refrigerants were: R 11, R 12, R 22, R
502 and ammonia. Of these, R 11 was primarily used with centrifugal
compressors in air-conditioning applications. R 12 was used primarily in
small capacity refrigeration and cold-storage applications, while the other
refrigerants were used in large systems such as large air-conditioning
plants or cold storages. Among the refrigerants used, except ammonia,
all the other refrigerants are synthetic refrigerants and are non-toxic and
non-flammable. Although ammonia is toxic, it has been very widely used
due to its excellent thermodynamic and thermo physical properties.
Since ozone layer depletion could lead to catastrophe on a global level,
it has been agreed by the global community to phase out the ozone
depleting substances (ODS). As a result, except for ammonia, all the other
refrigerants used in cold storages had to be phased-out and a search
for suitable replacements began in earnest. In view of the environmental
problems caused by the synthetic refrigerants, options differed on
replacements for conventional refrigerants. The alternate refrigerants can
be classified into two broad groups:
• Non-ODS, synthetic refrigerants based on Hydrofluorocarbons
(HFCs) and their blends
• Natural refrigerants including ammonia, carbon dioxide,
hydrocarbons and their blends
The potential for a single molecule of the refrigerant to destroy the
Ozone Layer is called ODP - The ODP or Ozone Depletion Potential. All
refrigerants use R11 as a datum reference where R11 has an ODP = 1.0.
The lower the value of the ODP - the better the refrigerant is for the ozone
layer and the environment.
Examples:
Refrigerant R11:
R11 is a single chlorofluorocarbon or CFC compound. High chlorine
content and Ozone Depletion Potential (ODP1) = 1. High Global Warming
Potential (GWP2) = 4000. The use and manufacture of R11 and similar
CFC refrigerants is now banned within the European Union even for
servicing. Non flammable, non corrosive non toxic, stable. 80
Refrigerant R12:
Difluorodichloromethane is related to the CFC group. It is characterised
by high ozone depletion potential (ODP = 1) and big global warming
potential (GWP = 8500). Clear gas with specific smell, 4.18 times as heavy
as the air. One of the most widespread and safe in operation refrigerants. 81
The effect of ammonia 82
Ammonia can safely be used as a refrigerant provided the system is properly
designed, constructed, operated and maintained. Ammonia however is toxic
and can be a hazard to human health. The Occupational Safety and Health
Administration (OSHA) Permissible Exposure Level (PEL) is 50 parts per
million (ppm), 8-hour time-weighted average. Although pure ammonia
vapours are not flammable at concentrations of less than 16%, they may
be a fire and explosion hazard at concentrations between 16 and 25%.
Mixtures involving ammonia contaminated with lubricating oil from the
system, however, may have a much broader explosive range. An important
property of ammonia is its pungent odour. The threshold concentration
at which ammonia is detectable varies from person to person; however,
ammonia can be detected usually at concentrations in the range of 5 ppm
to 50 ppm. Concentrations above 100 ppm are uncomfortable for most
people.
The effect of Volatile Organic Compounds (VOC)
Volatile organic compounds are compounds that have a high vapour
pressure and low water solubility. Many VOCs are human-made
chemicals that are used and produced in the manufacture of paints,
pharmaceuticals and refrigerants. VOCs typically are industrial solvents,
such as trichloroethylene; fuel oxygenates, such as methyl tert-butyl ether
(MTBE); or byproducts produced by chlorination in water treatment, such
as chloroform. VOCs are often components of petroleum fuels, hydraulic
fluids, paint thinners and dry cleaning agents. VOCs are common groundwater
contaminants. 83
VOCs include a variety of chemicals, some of which may have
short- and long-term adverse health effects. Concentrations of
many VOCs are consistently higher indoors (up to ten times higher)
than outdoors. VOCs are emitted by a wide array of products
numbering in the thousands. Examples include: paints and
lacquers, paint strippers, cleaning supplies, pesticides, building
materials and furnishings, office equipment such as copiers and
printers, correction fluids and carbonless copy paper, graphics and
craft materials including glues and adhesives, permanent markers
and photographic solutions.
Organic chemicals are widely used as ingredients in household products.
Paints, varnishes and wax all contain organic solvents, as do many
cleaning, disinfecting, cosmetic, degreasing and hobby products. Fuels
are made up of organic chemicals. All of these products can release
organic compounds while you are using them and, to some degree, when
they are stored. 84
The ability of organic chemicals to cause health effects varies greatly
from those that are highly toxic, to those with no known health effect.
As with other pollutants, the extent and nature of the health effect will
depend on many factors including level of exposure and length of time
exposed. Eye and respiratory tract irritation, headaches, dizziness,
visual disorders and memory impairment are among the immediate
symptoms that some people have experienced soon after exposure to
some organic chemicals. At present, not much is known about what
health effects occur from the levels of organic chemicals usually found
in homes. Many organic compounds are known to cause cancer in
animals; some are suspected of causing, or are known to cause, cancer
in humans. 85
80) The Energeering ToolBox, Refrigerants – Environmental Properties, undated
81) NBCC, Traditional Refrigerants, undated
82) EPA, Hazards of Ammonia Releases at Ammonia Refrigeration Facilities (Update), 2001
83) U.S.G.S., Volatile Organic Compounds (VOCs), undated
84) EPA – Environmental Protection Agency, An Introduction to Indoor Air Quality, undated
85) EPA – Environmental Protection Agency, An Introduction to Indoor Air Quality, undated
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