CFC's mona presentation
Transcript of CFC's mona presentation
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Presented byRani Mehmoona Sadia
MS-IRoll No:- 14
Lahore College For Women University
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What Are CFCs?CFCs is short forChlorofluorocarbons.
Commercially they are wellknown as Freons.
They are chemicals thatwere widely used by
factories (because they areeasy to store and cheap toproduce).
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Chlorofluorocarbons are
simple organiccompounds where all of
the hydrogen atoms have
been replaced with the
halogens chlorine and
fluorine (e.g. CFC-11
CFCl3 and CFC-12 CF2Cl2).
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j As solvents in Electronic industry
j In Fire extinguishers
j As dry cleaning
solvents
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Use of CFC's. Information from the US Environmental Protection Agency.
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Consequences of using CFCs
Effect on Ozone layer:-CFCs release chlorinemolecules which attackand destroy the ozonelayer and can cause ozoneholes.
Ozone holes appearedabove both the North andSouth poles and they wereincreasing in size.
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The destruction of stratospheric ozone
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Effect on Global warming
In the last 150 years, global temperatures havebeen rising and the amount of carbon dioxide inthe atmosphere has reached phenomenal levels.
The ozone layer over the Polar regions has
depleted to alarmingly low levels since the 1950s.Studies conducted by NASA have shown thatozone depletion over the Antarctic and Arcticregions will be at its worst between 2010 and2019.
Ice cover in theArctic sea hasdecreased
dramaticallydue to risingglobaltemperatures.
20051979
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Causes of global warmingCauses of global warming
Increase in greenhouse
gas emission
Due to human
activities
Sources of carbon
dioxide: Burningfossil fuels in cars,
factories and
power plants
Sources of nitrous
oxides: Vehicle
exhaust pipes,
fertilisers, livestockwastes
y Sources of CFCs: Aerosol cans,
air-conditioners, refrigerators,
plastic forms
Sources of methane:
Landfills, rice
paddies, guts of
cattle
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Greenhouse gases are gases inthe atmosphere which trap heat
from the Suns rays. Examples ofgreenhouse gases are carbondioxide, methane, nitrous oxidesand chlorofluorocarbons (CFCs).
Lu argues that the
correlation betweenglobal temperatureand CFCs is evidence
that CFCs have beenthe dominant driver of
climate over the pastcentury
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Effects on Human health
Causes the skin cancer
Melanoma, Nonmelanoma Skin Cancers,Basal Cell Carcinomas , Squamous CellCarcinomas
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Cataracts and Pterygium
Immune Suppression
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hydrochloroflourocarbons
hydroflourocarbons hydrocarbons
ammonia
helium terpenes
water and steam
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HydrochloroflourocarbonsHCFCs
break down faster (2-20years)
pose about 90% less danger to ozone layer
can be used in aerosol spray
also can be used inairconditioning
refrigeration
foam
cleaning agents
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Disadvantages are greenhouse gases
still deplete ozone when used in large quantities
health effects are largely unknown
expensive
may lower energy efficiency of appliances can be degraded to triflouroacetate(TFA)
can inhibit plant growth in wetlands
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Hydroflourocarbons Break down faster (2-20 years)
do not contain ozone destroying chlorine
can be used in
aerosol spraysrefrigeration
air conditioninginsulating foams
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Disadvantages
Are potent greenhouse gases
Expensive
Safety question about flammability and toxicity still
unresolvrd Can be degraded to TFA, which can inhibit plant growthin wetlands
May lower energy efficiency of appliances
Production of HFC-134a, a refrigerant substitute, yieldsan equal amount of methyl chloroform, a serious ozonedepleter
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HYDROCARBONS (HCS)
Such as propane and butaneCheap and readily available
Can be used in
aerosol sprays
refrigerationfoam
cleaning agents
Not patentable
Can be made locally in developing
countries
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disadvantages can be flammable and
poisonous some increase in groundlevel air pollution
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Ozone depletion potentials
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Ammonia
Simple alternative for refrigerators
Widely used before CFCs
the only honest refrigerant
Ammonia is an environmentally compatible refrigerant
because it has an ozone depletion potential (ODP) ofzero and a global warming potential (GWP) of zero. Noother refrigerant can claim such perfect statistics.
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Because of its superior thermodynamic
properties, ammonia as a refrigerantrequires less energy to produce a givenamount of cooling than otherrefrigerants.
Ammonia Safety
Ammonia refrigeration has a excellent safety record and in
spite of being by far the most widely used refrigerant on theplanet, lags behind other common refrigerants such as R22 inaccident statistics.
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This is in part due to its sharp and pungent odour which
warns of its presence even at very low concentrations, andencourages people to leave the area before any dangerexists. No other refrigerant possesses such an effective self-alarming
effect. isadvantages Toxic if inhaled
Flammable
Must be handled carefully Ammonia is hazardous at high concentrations
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Effects on human health
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Helium
D Effective coolant for
Freezers
Refrigerators
Air conditioners
In fusion power
plants
D Helium is the most favored
coolant due to its low tendency
to absorb neutrons and
become radioactive
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Disadvantages
This rare gas may become scarceif use is widespread, but verylittle coolant is needed perappliance
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Terpenes
From the rinds of lemons andother citrus fruits
Effective for cleaning electronic
parts Terpene-based formulations have been shown to bethe only viable substitutes for chlorofluorocarbons(CFCs)
Terpene-based cleaners are safe for employees and the
environment, they are effective for conventional andsurface-mount technology, and they are cost competitivewith CFCs
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Water & Steam
Effective for some cleaning operations and forsterilizing medical instrument
Disadvantages
Creates polluted water that must be treated
Wastes water unless the used water is cleaned upand reused.
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Current situation
Due to a lot of human efforts forthe past decade,inspite increasedpollution,use of CFCs has been
greatly reduced and has beensubstituted with other lessharmful compounds.
Its on us to make our
envoirnment live worthy for usbefore we have to pay the price.
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Save earth
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