REDUCTION OF EMISSIONS

Reduction of emissions must be achieved throughout the life cycle of refrigerants (production; transport; operation; management of plant; management of containers of virgin or recovered refrigerants; and recovery, recycling, regeneration and destruction when necessary); and throughout the life cycle of the plant (design, fitting, operating, decommissioning).

Reduction of initial charges normally assists in the reduction of emissions. Reduced charge can be achieved in many ways, including use of dry evaporators instead of flooded evaporator coils, low-pressure receiver systems, secondary-refrigerant systems, condensing water systems with cooling towers, etc.

However, reduction of the charge has to take into account energy consumption, given that certain solutions, such as use of a secondary refrigerant, may lead to increased energy consumption. Reduction of the charge is a field in which considerable innovation can be achieved.

In large plants and in all machine rooms, multi-probe sensing of ambient conditions normally provides the most reliable system of monitoring. Airflow patterns should be investigated in order to select sensor sites where the refrigerant, usually heavier than air, tends to concentrate. This “threshold monitoring” requires highly sensitive and accurate detectors (able to detect 1 or 2 grams/year) suitable for use with new refrigerants.

In many countries, a maintenance logbook must be available on-site at all plants larger than a specific size. This logbook enables true monitoring of the plant to be performed, and comprises servicing sheets to be filled in whenever refrigerant is added or recovered. In certain countries, an independent official inspector must check maintenance logbooks.

Reduction of emissions is important during all operations involving refrigerants: storage of large volumes at the manufacturing site, transfer into containers by distributors, charge of plant, assembly, maintenance/repair, recovery using suitable containers, and management of “heels” (seams of containers) of refrigerants, etc.

Recovery systems must be easy to use and enable the liquid and vapor phases to be recovered and pipes to be drained. For all handling operations, refrigerant charging pipes should be fitted with ball valves (or quick sealing) at each end.

The pressure thresholds at the end of the recovery process must take into account the quantity of residual refrigerant contained in the refrigerant-oil mixture.

Wherever (for technical, financial or regulatory reasons) the CFC or HCFC refrigerant recovered cannot be recycled, it must be destroyed in an approved and monitored manner.

REFRIGERANT CONTAINMENT

Achieving refrigerant containment is an important factor in preventing leaks. This involves all aspects of bringing a system on line, then maintaining it for as long as possible: the design, testing, installation, operation, maintenance, servicing and disposal of equipment. Actions required depend on the type of equipment concerned, and can be divided into broad categories including:

Household appliances such as refrigerators, freezers, small air conditioners, etc.; most of these appliances are fully brazed and tightness depends on the quality of brazing. Generally, less than one or two out of 10,000 appliances present defects.

Chillers in which all components of these systems are normally located in machine rooms, thus facilitating monitoring of tightness;

Direct-expansion systems with long refrigerant circuits used in commercial and industrial refrigeration, particularly in the food industry (such systems tend to be leak-prone); and

Vehicle air conditioning systems, which have flexible elastomer hoses and open-type, directly driven compressors. They too tend to be leak-prone. Emission levels vary according to the type of system and thus require containment policies that are appropriate to the system design.

The number of screw-on valves and fittings should be kept to a minimum in order to minimize the number of leak sites. Selection of components should be based on reliability and leakage performance.

Safety relief valves must be taken into account when defining the maximum operating pressure (MOP) in order to prevent valves from opening when the condensing pressures are too close to MOP levels. Checking the charge level has proved useful in large plants.

Information on leak rates in various types of hoses, stuffing boxes, flanges, etc., is useful at the design stage.

However, only on-site monitoring of concentrations in the air of the room, or of leak rates, makes it possible to achieve acceptable accuracy concerning tightness under real operating conditions. This has been demonstrated in other fields requiring strict tightness monitoring (vacuum, space, or nuclear systems).

Leak rate measurement is indirect. It involves measurement of the concentration in a given space (room or area around plant). In large commercial or industrial systems, it may be advisable to make a system charge-sensitive and of low charge. If signs of undercharge appear, the leak may be detected using soapy water.

Although initial tightness is achieved very effectively by most equipment manufacturers, the tightness of various components during long-term use is not well known. One example would be valves under operating conditions or pressure gauges exposed to compressor vibrations. Tightness monitoring in the field should be performed according to quality procedures, which enable Analysis of Modes of Malfunction (Analyse des Modes de Defaillance [AMDEC]) to be performed. Long term, this analysis will make it possible to modify the most critical components.

A tightness-of-components standard remains to be implemented. When such a standard does come into effect, it must take sufficiently accurate leak-tightness and measurement methods into consideration.

POLITICAL, ECONOMIC, AND COMMERCIAL ASPECTS

Although many technological measures described above have been available for years, rate of adoption tends to be slow. How can barriers to implementation be removed?

Suitable recovery equipment and, where possible, recycling equipment must be available on-site when recovery needs to be performed. The staff must be familiar with this equipment and trained in its use. If the recovered refrigerant cannot be recycled, means of destruction must be available.

Emissions reductions will become widespread only if such reductions are in the interests of each user concerned: fitters, plant managers, refrigerant distributors, etc. Containment and recovery involve additional expense, staff training and incentives, implementation of monitoring and approval or sanctions, communication with customers, and the taking into account of recycling or even destruction. In order for the companies concerned to recover these additional expenses, containment must lead to reduced use of refrigerant fluid and, where possible, recycling should produce reusable refrigerant fluid.

Other factors should provide financial incentives for companies to comply with regulations. Customers may impose special clauses concerning emissions in delivery and/or maintenance contracts. The seeking of an “ecological” image or label must be granted only under well-defined conditions.

However, benefits do not necessarily offset costs, particularly where:

Recycling is not possible for regulatory (where reuse or resale is illegal) or practical reasons;

If inexpensive illegal refrigerants are available; or

If the recovered refrigerant fluid must be destroyed.

In these situations, structural measures will then be required to promote emission reductions.

According to the context, cultural factors, and common practice in each country, state and professional organizations will play more or less important roles, which must in all cases converge.

Some reasons:

To curb the black market and ensure that all recovered refrigerant fluid controlled by regulations (and which is not to be recycled) is in fact destroyed;

To ensure, more generally, that regulations are complied with without disturbing competition; and

To promote standardization for instances of recovered refrigerant fluids, labeling, as well as inter-professional agreements, promoting remuneration of recovered refrigerant fluid at a sufficiently high price level, and packaging guidelines, etc.

Where necessary, the following aspects should be taken into account:

Promote appropriate incentives (such as tax reductions) and international assistance for purchase of specific recovery, recycling, regenerating, and destruction equipment when required.

Avoid unnecessary red tape. Recovered refrigerant fluids do not need to be subjected to all the regulations applying to more-dangerous products.

In certain countries, the reuse or resale of recovered refrigerant or CFC-containing equipment is illegal now or will become illegal. Such regulations are a deterrent for the black market, promote the updating of industrial plants, and expand markets for equipment and new refrigerants.

However, it is important to ensure that the refrigerant is destroyed (despite the cost involved) and will not be leaked (either accidentally or deliberately) into the atmosphere, when in fact it could have been reused or contained in a plant. Certain countries levy taxes on new refrigerants or envision doing so. If this solution is adopted, it will require additional efforts to curb the black market and must not disturb competition.

Reducing emissions implies radical changes in maintenance and operating methods, and even attitudes, and requires significant initial training and continuing education. This training and compliance with good practice procedures has more impact where certification of staff and companies is achieved.

Developing countries consume small quantities of CFCs and HCFCs at present and have the right to “consume” CFCs until 2010 and HCFCs until 2040. They can speed up this process by entering into particular agreements, and this has become an important recommendation since global warming has begun to be taken into account.

Regeneration and destruction may be more difficult, for instance, because refrigeration plants are widely dispersed across countries. Before implementing a subsidized recovery plant, a thorough financial study must be performed in order to ensure that the use of such a plant is profitable for everyone involved.

Regulations adopted anywhere in the world concerning the phaseout of equipment using CFCs and HCFCs create an incentive to export new or second-hand CFC and HCFC equipment to developing countries. This may contribute to the short-term development of refrigeration in these countries, but simply shifts the environmental problem and is likely to cause major retrofitting problems in the future.

Containmen technology transfer towards developing countries can help protect the ozone layer and fight global warming.

Billiard is director of the International Institute of Refrigeration, based in Paris, France. This information was made available at the Purdue University Compressor-Refrigeration-Natural Working Fluids joint conferences in West Lafayette, IN.

Publication date: 12/04/2000