Direct impact of refrigerants

11.3.1 Design criteria for charge minimization and leak tightness

Charge minimization is one important factor for conservation of refrigerant. Minimization of the refrigerant charge would not only reduce the global consumption of refrigerants but it would also reduce their impact on climate by reducing the quantity of possible emissions that could be emitted during catastrophic leak events, during the working life of equipment and end of life of equipment. Historically, little attention has been given to minimize charge quantities. The charge amount is only specified for small equipment especially for capillary fitted units where the performance of the unit is highly affected by the charge quantity. Other systems are charged on the site and charge quantity is rarely pre-calculated or specified.

Recognizing the importance of the charge minimization, industry is paying attention to this aspect by employing designs for lower storage of refrigerant. In case of unitary air-conditioning systems with hermetic compressors, the majority of refrigerant is banked in the compressor and heat exchangers, especially in the condenser. Systems are designed with mini channel heat exchangers to reduce the internal volume of the condenser, and compressors are designed for reduced oil. Significant efforts are also being made to design and develop supermarket refrigeration equipment by using secondary loop and cascade systems that use a much smaller refrigerant charge than traditional refrigeration system. It should be noted that there may be negative effects of charge minimization: some systems may be sensitive to a charge deficit leading to an increase in energy consumption and even a system failure. Another typical trade-off situation is the choice between direct and indirect systems. The latter systems tend to minimize the direct emissions of fluids, but might increase the indirect emissions due to the increased losses. There is a balance to ensure good efficiency despite minor leakage and reduced direct emissions.

Overcharging of equipment is common, especially in systems with receivers, as the amount of refrigerant contained in refrigerant receivers is not always known. Refrigerant receivers are equipment components that contain excess refrigerant that migrates through the system as a result of changes in ambient conditions. Therefore, refrigerant receivers should be designed or selected in a proper way. On the other hand design criteria’s for varying ambient conditions and operation parameters are often not commonly known. For such equipment, field charging is often continued until the charge is considered satisfactory. Without the check of weighing the charge, the circuit could be overfilled with two harmful consequences: (1) a potential release of refrigerant, and (2) the possibility of transferring the entire charge into the receiver. The receiver-filling ratio, therefore, has to be limited during nominal operation, and an inspection tool (indicator, level, etc.) must be provided.

More detailed information has been published recently by IIR-IIF (IIR, 2014)

There is a trend in the market to move towards what is referred to a critically charged. In these systems it is very important not to charge more on the system than it is designed for. This helps not overcharging the system but it also requires more skills from the persons working on the system.

Another trend from legislation side is the move from look more on the leak potentials rather than look at the charge size. The potential leak can come from any connections, flanges, valves, compressor and motor assemblies etc. The likelihood of a pipe or a vessel should become leaky is minimal in a well-designed system. Leaks, however, tend to come when valves or flanges have been serviced. The authorities like to look at potential leak and the advantage is that you can deal with it already at the design phase. You can count the flanges and you can calculated all sealings and connections and in this way determine what leak rate you can have and where the leaks might be.

Reduction of emissions through leak tightness

Leak detection of the equipment in production or assembly is a basic element, both in constructing and servicing of cooling equipment, as it makes it possible to measure and improve conservation of refrigerant. Leak detection must take place at the end of construction by the manufacturers, at the end of assembly in the field by contractors, and during regularly scheduled maintenance of equipment by service technicians.

Beside other code of good practice and refrigeration standards covering requirements for leak testing and tightness, there are three general types of leak detection methods:

1. Global methods indicate that a leak exists somewhere, but they do not locate the leaks. They are useful at the end of construction and every time the system is opened up for repair or retrofit;

2. Local methods pinpoint the location of the leak and are the usual methods used during servicing;

3. Automated performance monitoring systems indicate that a leak exists by sensing changes in equipment performance and alerting operators.

Industry both in developed and developing countries, in recent years, have improved design for leak tightness in the air-conditioning and refrigeration equipment manufactured after the Montreal Protocol. In addition existing equipment/appliances have often been modified with new devices, such as high-efficiency purge devices for low-pressure chillers that have significantly lowered refrigerant emissions. Design changes have been made with regard to leak tightness in response to growing environmental, regulatory, and economic concerns associated with refrigerant emissions.

11.3.2 Reduction of emissions through installation, servicing and maintenance

The Montreal Protocol has globally sensitized the servicing community as well as the end-users to use good servicing practices and reduce the emissions of refrigerants through awareness programmes. Servicing practices have improved especially in some of the sectors mainly because of training of servicing personnel engaged in these sectors. Unsustainable servicing practices—such as topping-up refrigerant without repairing leaks, or leak testing with high-ODP or high-GWP refrigerants—are avoidable. Instead, refrigerant recovery, recycling, reclamation and destruction, discussed below, should be practiced.

Technicians must study the service records to determine the history of leakage or malfunction and energy consumption trends. Technicians should also measure performance parameters to determine the operating condition of the cooling system. Fixing leaks and defects early will help avoid catastrophic failures that may contaminate or release the entire refrigerant charge. Technicians should determine the best location from which to recover the refrigerant and assure that proper recovery equipment and recovery cylinders are available. Proper maintenance documents like logbooks enable the user to monitor the frequency of repairs as well as the amount of refrigerant recovered, added and emitted.

In addition, periodical cleaning of refrigeration equipment not only enhances the proper operation of the system but also reduces the frequency of system failure.

Training of technicians is essential for the proper handling and conservation of refrigerants, the optimized operation of the equipment, the control or reduction of energy consumption, and avoids loss of stocked food when refrigerant and lubricant come in contact with it due to improper handling. Such training should include information on the environmental and safety hazards of refrigerants, the proper techniques for recovery, recycling, reclamation and leak detection, and local legislation regarding refrigerant handling. The European standard EN 13313 describes the competence developments necessary for all levels, from system design to commissioning and servicing.

11.3.3 Refrigerant recovery, recycling, reclamation and destruction

In the last few decades, there has been an increasing emphasis on conservation of refrigerants and reduction of emissions that has led the industry to develop a specific terminology which is used in this report (ISO, 1999):

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  Recover: to remove refrigerant in any condition from a system and store it in an external container.
  
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  Recycle: to clean the extracted refrigerant using oil separation and single or multiple passes through filter-driers which reduce moisture, acidity, and particulate matter. Recycling normally takes place at the field job site.
  
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  Reclaim: to reprocess used refrigerant to virgin product specifications. Reclamation removes contaminants such as water, HCl and HF reaction products, other acids, high boiling residue, particulates/solids, non-condensable gases, and impurities including other refrigerants. Chemical analysis of the refrigerant is required to determine that appropriate specifications are met. The identification of contaminants and required chemical analysis are specified by reference to national or international standards for new product specifications. Reclamation typically occurs at a reprocessing or manufacturing facility.
  
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  Destroy: to transform used refrigerant into other chemicals in an environmentally responsible manner.
  

Recovery of refrigerant, especially CFC-12 and H-CFC-22, has become an integral part of servicing practices in most of the countries, especially for systems having relatively large charge quantities. The incentives for refrigerant recovery are the cost of refrigerants and environmental protection. The regulatory framework is also a driving force for recovery of refrigerant especially in non-Article 5 countries. In developing countries, the continuing replacement of old CFC-based refrigerators in favour of new ones, many of them containing HFC as refrigerant, and the rapidly growing market of HFC-based room air conditioners, increases the importance of regulations aiming to avoid venting of refrigerants during equipment repair.

Refrigerant recovery equipment reduces emissions by providing a means of temporary storage of refrigerants that have been removed from systems undergoing service or disposal. Such equipment is used to temporarily store recovered refrigerant until the system is ready to be recharged. The recovered refrigerant may also be used in other equipment or sent for destruction. Refrigerant recovery equipment may have the added capability of recycling of refrigerants.

Refrigerant recovery equipment has been developed and is available with a wide range of features and prices. Some equipment with protected potential sources of ignition also exists for recovery of flammable refrigerant. Although liquid recovery is the most efficient, vapour recovery methods may be used alone to remove the entire refrigerant charge; however, in order to reach the vacuum levels that are required in some countries for larger systems, vapour recovery is used after liquid recovery (Clodic, 1994). Testing standards have been developed to measure equipment performance for automotive (SAE, 1990) and non-automotive (ISO, 1999) applications. Such standards, as a part of common service procedures, should be adopted by regulating authorities.

Refrigerant recycling conserves refrigerant during the service, maintenance, repair, or disposal of refrigeration and air-conditioning equipment. Refrigerant recovery and recycling equipment should be made available to service technicians in every sector. The logistic process should be easy to understand and cover all players from point of sales to the customer, and back to point of return. It may be noted that due to incompatibility issues and the array of refrigerants used that refrigerant recovery/recycling equipment intended for use with one refrigerant and/or type of air-conditioning system may not be adequate to service other refrigerants or sectors.

Recycling reduces oil, acid, particulate, moisture, and non-condensable (air) contaminants from used refrigerants. The recycling performances can be measured on standardized contaminated refrigerant samples according to test methods (AHRI, 2012). Since the quality of recycled refrigerant cannot be proven by analysis, restrictions are imposed on the use of recycled refrigerants.

Currently, the automotive air-conditioning industry typically reuses recycled refrigerant without reclamation in a different owner’s system. Acceptance in other sectors depends on national regulation, recommendation of the system manufacturers, existence of reclamation services, variety and type of systems, and the preference of the service contractor and owner. Reuse of recovered refrigerant requires strict adherence to good practices including identifying the refrigerant type. Mixed refrigerants are often costly to separate which may result in the sale of cross-contaminated refrigerants. For most refrigerants there is a lack of inexpensive field instruments available to measure the contaminant levels of recycled refrigerant after processing; hence in countries where access to qualified laboratories is limited and shipping costs are prohibitive, caution is required to prevent unintentional mixing of refrigerants.

Recovery and reclamation of used refrigerants can, to a certain extent in some countries, meet the servicing requirements as well as conserve refrigerant and reduce emissions to the environment. Reclamation is the processing of used recovered refrigerant back to almost virgin specifications. Reclamation also extends the lifespan of the refrigerant as well as the equipment and decreases the dependency on virgin refrigerant by placing it back into service. Reclaimed refrigerants are tested and verified to meet specifications that are similar to newly produced refrigerants product specifications, such as those provided in (AHRI, 2012). The reclaimed refrigerants can be repacked and sold to new users.

Reclamation is essentially a market-driven industry. If there is no demand for a particular refrigerant, the costs to send recovered refrigerant to reclamation facilities will be a disincentive to reclaim. Efforts must be initiated early with refrigerant supply companies to take back refrigerant for reclamation. Many service establishments will not be able to afford storage for recovered refrigerants yet the cost of sending small quantities of recovered refrigerant to reclamation facilities is also a disincentive to reclamation efforts. Such disincentives promote venting or reuse of stockpiled refrigerant. Care should be taken by policy makers to eliminate parallel (and potentially illegal) routes to market. Such avoidance of improperly reclaimed used refrigerants requires strict auditing of the refrigerant distribution chain. Enforcement is required to insure that these refrigerants do not contain incompatible components such as R-40, methylchloride. Documented refrigerant control through its life cycle can avoid illegal trade of counterfeit refrigerants.

Small capacity portable refrigerant reclamation equipment have also been developed and are available with varying features. Such equipment is capable of reclaiming about 80 kg of refrigerant per hour.

The use of reclaimed refrigerant has the advantage of avoiding possible system breakdowns, as a direct result of contaminated refrigerant, which might lead to refrigerant emissions. As reclaimed refrigerant meets new product specifications, it may have the support of equipment manufacturers who maintain warranties on their equipment. Another advantage is that the quantification of refrigerant recovered are easily obtained. However, reclamation does require a costly infrastructure, which may only prove viable when the potential for financial return of recovered refrigerant is sufficient to overcome the initial investment of the enterprise performing reclamation.

Refrigerant destruction

There is worldwide recognition of the need for destruction of unwanted ODS refrigerants because of ozone and climate benefits from the avoided emissions of ODS. The destruction of ODS banks has the potential to earn carbon credits through global carbon markets, broadly divided into the compliance market and the voluntary market. The compliance market for GHGs is based on a legal requirement where, at an international (e.g., Clean Development Mechanism) or national and regional level (e.g., European Union Emission Trading Scheme), those participants must demonstrate that they hold the carbon credit equivalents to the amount of GHGs that they have emitted in order to meet their GHG reduction obligations. In some of these markets, the carbon credits resulting from ODS destruction are not considered for compliance generally because ODS are not included in the Kyoto Protocol and are being phased out.

The voluntary markets have also been in operation where individual organisations voluntarily commit to actions and projects to offset their GHG emissions. The voluntary carbon market also established standards for ODS destruction as carbon offset projects. Standards such as The Climate Action Reserve (CAR) and the Verified Carbon Standard (VCS) provide carbon credits for ODS destruction (CAR, 2013; VCS, 2014). Since 2010, there has been a relatively low demand for carbon credits in the voluntary markets.

Normal conditions where recovery, recycling, and reclamation under a good logistical system are prevalent should lead to fairly low requests for destruction in the refrigeration industry. This is especially the case where the demand for ODS remains high. A need for destruction facilities may be created in instances where regulations forbid the service use or export of ODS. The general method of destruction is based on incineration of refrigerants and on scrubbing combustion products that contain particularly aggressive acids, especially hydrofluoric acid. Mainly, their resistance to hydrofluoric acid limits the number of usable incinerators. CFCs and more particularly halons, burn very poorly. In order to be incinerated, they must be mixed with fuels in specific proportions.

The Parties to the Montreal Protocol, recognizing the benefits of destruction of unwanted ODS in an environment friendly manner, approved processes, through decision IV/11 as early as in 1992. Since then, the list of approved destruction processes has been updated a number of times. Presently, there are 16 destruction processes approved.

There are a number of destruction facilities based on the approved destruction processes by the Montreal Protocol, especially in non-Article 5 Parties and in some Article 5 Parties. Currently, there are limited facilities to destroy unwanted ODS refrigerants in most developing countries.