On substances that deplete the ozone layer
Options for existing equipment
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- 5.4.1 Conversion to HFC blends
- 5.4.2 Conversion to R-744
- 5.4.3 Conversion to R-717
- 5.4.4 Conversion to hydrocarbon
- 5.5 Service requirements
- 5.6 Concluding remarks
5.4 Options for existing equipmentSystems using HCFC-22 have been converted to zero ODP refrigerants, but it is difficult to replicate the operating conditions of HCFC-22 and so conversions often involve an element of equipment replacement. Before committing to any large scale retrofit project consideration should be given to the age of the plant, the cost of replacement with a modern, more efficient system and the risks to continued operation of retrofit. 5.4.1 Conversion to HFC blendsThere are numerous blends for the replacement of HCFC-22 in DX (superheat controlled) systems, but there is none that replicates the pressure temperature relationship of HCFC-22 without significant glide, and so these blends are much less common in flooded systems where fractionation of the blend is a concern. Where industrial systems are converted to a blend it may also be necessary to change from mineral or alkyl benzene lubricant to a synthetic ester. Some blends are formulated with hydrocarbons in the mix so that, although still non-flammable, the lubricant is more miscible and less likely to accumulate in the evaporator of the system. For a large flooded system it might be appropriate to convert the compressors and condensers to an HFC blend, but convert the low pressure side to a secondary fluid, or even R-744 as a volatile secondary. Retrofitting of HCFC-22 plant in Article 5 countries is very uncommon to date. 5.4.2 Conversion to R-744The high operating pressure of R-744 systems makes it highly unlikely that an existing HCFC-22 system could be converted to operate on R-744. Conversion to a cascade system is possible, greatly reducing the inventory of fluorocarbon refrigerant in the system. It may even be possible to reuse the low pressure pipework and evaporators in the system if they are suitably rated. A cold storage or freezing system operating as a cascade on R-744 could be limited to an allowable pressure of 25 bar gauge, however this is a complex retrofit and it may well be more economic to replace the whole plant, especially if it is already more than ten years old. 5.4.3 Conversion to R-717In a very few cases a pumped HCFC-22 plant has been converted to R-717 (Jensen, 1996). In some cases the compressors and evaporative condensers are suitable for either refrigerant, and pipework is probably welded steel in large applications. If the evaporators are copper tube then they need to be replaced. It is imperative that the system is carefully cleaned during the conversion because any residual traces of HCFC-22, for example in lubricant will react with R-717 to produce a solid foam which can block all the internal components. Triple evacuation with nitrogen purging is probably necessary – this is time-consuming and expensive and again plant replacement should be considered. In the majority of cases, in all countries, equipment using HCFC-22 is not suitable for this conversion. 5.4.4 Conversion to hydrocarbonUnlike R-744 and R-717 it is technically feasible to remove HCFC-22 from existing systems and replace it with HC-290, however it is highly likely that the resultant system will not comply with safety codes on the use of hydrocarbons because the refrigerant quantity will not comply with charge restrictions and the electrical infrastructure will not be suitably protected. A conversion of this type is believed to have been responsible for a fatal accident in New Zealand in 2008 (NZFS, 2008). A consequence of rapid phase out of HCFCs in Article 5 countries might be an increase of this type of conversion without adequate controls. There is however a case for a controlled conversion from HCFC-22 to HC refrigerant (HC-290 or HC-1270) where the system efficiency can be improved. In this case it is essential that suitable safety measures are ensured. 5.5 Service requirementsGiven the difficulty of converting from HCFC-22 to zero ODP refrigerants, many users with multiple systems have planned a replacement strategy to conserve their stock of refrigerant. Setting priorities for which system to replace or convert first includes consideration of age of the plant, likelihood of leakage and ease of conversion. Refrigerant which is recovered from converted systems can be recycled and stored on site to be used in the remaining plants. In Europe, where service with “virgin” HCFC-22 was prohibited from the beginning of 2010, some users have banked additional refrigerant by overcharging their plants with new HCFC- 22 prior to the end of 2009 and then recovering the excess refrigerant, which is then classed as recycled. This practice is not strictly outside the law, but it is not in the spirit of the regulation. It probably accounted for some additional sales of HCFC in the two years leading up to the prohibition, keeping sales artificially high at a time when many plants were being converted or decommissioned. If other regions implement similar regulations for the phase out of HCFCs they should consider ways to plug this loophole, for example by limiting the time that recovered HCFC can be stored before it is used, and requiring it to be sent for destruction or reprocessing if it is not used within the timeframe. This was done in Ireland, and greatly improved the effectiveness of the restriction on virgin HCFC-22. 5.6 Concluding remarksThe majority of large industrial systems in some parts of the world use R-717 as the refrigerant. When R-717 is not acceptable in direct systems in these countries, options include R-744 or glycol in secondary systems or HCFCs or HFCs in direct systems. In countries where R-717 has not been the preferred solution, or in market segments with smaller systems, the transition from HCFC-22 is not straightforward. It requires acceptance of higher cost fluorocarbons in systems similar to the types used with HCFC-22 or the adoption of more expensive systems with the cheaper refrigerants R-717 and R-744. This transition is slow and is constrained by a lack of trained personnel and lack of experience of the local end-users. It has been facilitated by corporate policy from multinational food and beverage manufacturers exemplified by the policy statement from the Consumer Goods Forum (CGF, 2010). The industrial sectors covered by this chapter are too diverse to facilitate the level of development expenditure required to bring a new fluid to market. It therefore follows that if any new development gains market share in industrial systems it will be a fluid developed for some other purpose, either as a refrigerant in smaller mass-market systems or as a foam-blowing agent, solvent or other specialty chemical. Apart from absorption systems there is no significant growth of other not-in-kind cooling or heating solutions. Directory: meeting meeting -> Program description meeting -> Iea shcp/pvps working Group on pv/t solar Systems meeting -> Office of the collector: jagatsinghpur (st & sc development Section) meeting -> World meteorological organization meeting -> WG/hwsor action item summary (Current as of 28 Feb 2013) meeting -> Review of the past hurricane season meeting -> Review of the past hurricane season reports of hurricanes, tropical storms, tropical disturbances and related flooding during meeting -> Town of seabrook island meeting -> World meteorological organization Download 1.63 Mb. Share with your friends:
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