|Working Group III: Mitigation|
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184.108.40.206 HFC-23 Emissions from HCFC-22 Production
HFC-23 is generated as a by-product during the manufacture of HCFC-22 and emitted through the plant condenser vent. There are about 20 HCFC-22 plants globally. Additional new plants are expected in developing countries as CFC production plants are converted to comply with the Montreal Protocol and demand for refrigeration grows. Although HCFC-22 is an ozone-depleting chemical and production for commercial use will be phased out between 2005 and 2040, production as a feedstock chemical for synthetic polymers will continue.
Technologies available to reduce emissions of HFC-23 have been reviewed by the Research Triangle Institute (RTI, 1996; Rand et al., 1999) and March Consulting Group (March Consulting, 1998). Two emission reduction options were identified.
220.127.116.11 Emissions of SF6 from the Production, Use and Decommissioning of Gas Insulated Switchgear
SF6 is used for electrical insulation, arc quenching, and current interruption in electrical equipment used in the transmission and distribution of high-voltage electricity. SF6 has physical properties that make it ideal for use in high-voltage electric power equipment, including high dielectric strength, excellent arc quenching properties, low chemical reactivity, and good heat transfer characteristics. The high dielectric strength of SF6 allows SF6-insulated equipment to be more compact than equivalent air-insulated equipment. An SF6-insulated substation can require as little as 10% of the volume of an air-insulated substation. Most of the SF6 used in electrical equipment is used in gas-insulated switch gear and circuit breakers. SF6 in electric equipment is the largest use category of SF6 with global estimates of over 75% of SF6 sales going to electric power applications (SPS, 1997). Options to reduce emissions include upgrading equipment with low emission technology, and improved handling during installation maintenance and/decommissioning (end-of-life) of SF6-insulated equipment, which includes the avoidance of deliberate release and systematic recycling. Guidelines on equipment design to allow ease of gas recycling, appropriate gas handling and recycling procedures, features of gas handling and recycling equipment, and the impact of voluntary emission reduction programmes are contributing to the reduction of emissions from this sector (Mauthe et al, 1997; Causey, 2000).
Significant emissions may also occur during the manufacturing and testing of gas-insulated switch gear when the systems are repeatedly filled with SF6 and re-evacuated (Harnisch and Hendriks, 2000). Historically these emissions have been in the range of 30%-50% of the total charge of SF6. The existence and appropriate use of state-of-the art recovery equipment can help to reduce these emissions down to at least 10% of the total charge of SF6.
18.104.22.168 Emissions of SF6 from Magnesium Production and Casting
In the magnesium industry, a dilute mixture of SF6 with dry air and/or CO2 is used as a protective cover gas to prevent violent oxidation of the molten metal. It is assumed that all SF6 used is emitted to the atmosphere. 7% of global SF6 sales is estimated to be for magnesium applications (SPS, 1997). Manufacturing segments include primary magnesium production, die casting, gravity casting and secondary production (i.e., scrap metal recycling). Because of differing production processes and plant scale, emission reduction potential varies across manufacturing segments. Emissions of SF6 in magnesium casting can potentially be reduced to zero by switching to SO, a highly toxic and corrosive chemical used over20 years ago as a protective cover gas. Harnisch and Hendriks (2000) estimate that net costs of switching from SF6 to SO2-based cover gas systems are about US$1/tCeq, but as a result of the high toxicity and corrosivity of SO2 much more careful handling and gas management is required. In many cases the specific usage of SF6 can be reduced by operational changes, including moderate technical modifications (Maiss and Brenninkmeijer, 1998). Companies may also reduce SF6 emissions and save money by carefully managing the concentration and application of the cover gas (IMA, 1998). A study is currently beingundertaken to identify and evaluate chemical alternatives to SF6 and SO2 for magnesium melt protection (Clow and Hillls, 2000).
22.214.171.124 Some Smaller Non-CO2 Emission Reduction Options
There are a number of small emission sources of SF6, some of which are considered technically unnecessary. For example, SF6 has been used as a substitute for air, hydrogen or nitrogen in sport shoes and luxury car tyres to extend the lifetime of the pressurized system. SF6 in sport shoes has been used by a large global manufacturer for over a decade under a patented process. Soundproof windows have been manufactured with SF6 in several countries in Europe.
Small quantities of SF6 are used as a dielectric in the guidance system of radar systems like the airborne warning and control system (AWACS) aircraft and as a tracer gas for pollutant dispersion studies. Small quantities of PFCs and SF6 are used in medical applications such as retina repair, collapsed lung expansion, and blood substitution (UNEP, 1999).
126.96.36.199 Summary of Manufacturing Industry GHG Emission Reduction Options
An overview of greenhouse gas emission reduction options in manufacturing industry due to fuel switching, carbon dioxide removal, material efficiency improvements, and reduction of non-CO2 greenhouse gases emissions practices is presented in Table 3.21, which complements information from Table 3.19.
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