Refrigerants Ozone Depletion Potential

Montreal Protocol on Substances that Deplete the Ozone Layer. The phase-out of CFCs began on Jnly 1, 1989, and by 1997, a hydroflnorcarbon, HFC134a, with zero ozone depletion potential, became the dominant refrigerant in the United States. The phase-out of CFCs in developing countries is on a slower schedule. 

Table 1 lA presents tabulations of the safety of important refrigerants, but this list does not include aU available refrigerants. Table 11-5 summarizes a limited list of comparative hazards to life of refrigerant gas and vapor. The current more applicable refrigerants from the m or manufacturers of the CFC and HCFC refrigerants and their azeotropes/ blends/mrxtures are included, but the list excludes the pure hydrocarbons such as propane, chlorinated hydrocarbons such as methyl chloride and others, inorganics, ammonia, carbon dioxide, etc. See Table 11-6. The CFC compounds have a longer and more serious ozone depletion potential than the HCFC compounds, because these decompose at a much lower atmospheric level and have relatively short atmospheric lifetimes therefore, they do less damage to the ozone layer. Table 11-7 summarizes alternate refrigerants of the same classes as discussed previously. Table 11-8 correlates DuPont s SUVA refrigerant numbers to the corresponding ASHRAE numbers.

Haseley [2.4] differentiates between two categories of refrigerants The first group can be exchanged in compressor systems without changing the compressor itself, but changing the injection valves. The second group with no Ozone Depletion Potential (ODP). 

It is desired to find a replacement for Freon-12 as an alternative refrigerant [Duvedi Achenie (1996)]. The objective is to find replacements that have the same refrigerant related properties as Freon-12 but without the harmfull environmental properties (such as the Ozone depletion potential) - The new refrigerant must absorb heat at temperatures as low as -1.1°C and reject heat at temperatures as high as 313 K. It must also respect the following characteristics ... 

Kayukawa et al. [17] studied the PVT properties of triiluoromethyl methyl ether, because it is a possible refrigerant with zero ozone depletion potential and low global-warming potential. One series of their data is shown in Table 5.6. Calculate Z, the compressibihty factor, and the molar volume in mol m from the given data, and fit the data for Z as a function of 1 /Pm to both a linear and a quadratic equation to see whether a third virial coefficient is warranted by the data. 

OZONE-DEPLETION POTENTIAL Refrigeration and other ancillary process-related CFC-11 equivalent emission (tonnes)... 

As can be seen from Table 9.2, ozone depletion values are zero for all compounds with the exception of R12. As stated earlier, the ozone depletion potential is the relative amount of damage that the particular chemical causes to the ozone relative to R-ll (Figure 9.2). Figure 9.3 shows the global warming impact of various refrigerant... 

Hydrofluorocarbons ("HFCs") consist of molecules containing only atoms of hydrogen, fluorine and carbon and were known at the time of the Montreal Protocol to have effectively zero ozone depletion potential (ODP). Following the Montreal Protocol, many participants in the refrigerant manufacturing and end-user industries therefore looked towards HFCs as replacements for CFCs across a range of applications. R-134a is one such HFC. 

Redesign the refrigerant moleeules using the ozone depletion potential (ODP) defined for molecules having one carbon atom ... 

The major concern with fluorocarbon refrigerants is not personnel hazards but then-ozone depletion potential. Many types that were popular in the past are now banned by the Montreal Protocol or successor agreements (Section 9.1.7.2B). Handling and disposal of refrigerants with the potential for depleting the stratospheric ozone layer... 

The discussion of liquefaction of chlorine (Section 9.1.7.2B) also pointed out that new systems operate on refrigerants other than the CFCs that were the industry standard for many years. Many existing systems have also been converted to the newer materials. HCFCs, such as R-22, have much lower ozone depletion potentials than the CFCs but... 

The chemical industry responded to the crisis by developing replacement refrigerants that have a much lower ozone-depleting potential.The most prominent replacements are the hydrofluorocarbons (MFCs) and hy-drochlorofluorocarbons (HCFCs), such as the following ... 

The principal application of chloroform is the the production of the refrigerant monochlordifluormethane, HCFC 22, CHCIF2, and other chlorofluoroalkanes. Because of the ozone depletion potential of chlorofluorocarbons (CFC), their open use had been restricted for some years and afterwards prohibited by the Montreal Protocol in 1987 and subsequent international meetings. The role of CFC in stratospheric chemistry is discussed in detail in [357]. HCFCs are less active, they will be phased out about 2005. 

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