Users of industrial refrigeration face many challenges, including selecting the best refrigerant for an application. Recently, this has become increasingly difficult when trying to comply with regulatory requirements set by the EPA, OSHA and other regulatory bodies. Increasingly tight regulations add to the already difficult selection process, which includes considerations such as safety, efficiency and maintenance costs that affect refrigerant choice. This article highlights some of the challenges and possibilities for processors to consider when choosing a refrigerant.

Refrigerant Choices. Large refrigeration system end-users have always had to consider issues such as initial costs, efficiency, facility setting and maintenance when choosing a refrigerant. In the past 100 years, the choice was made between refrigerants such as ammonia/hydrocarbons and a fluorochemical-based refrigerant such as R22.

Over time, the low toxicity and flammability of fluorochemical refrigerants made them ideal candidates for markets such as residential, light commercial and automotive. At the same time, the market for ammonia and other hazardous refrigerants has largely been identified for use in industrial refrigeration and petrochemical applications where the toxicity and flammability could be managed in an industrial setting.

Fluorochemical Refrigerant Regulations

The EPA’s Clean Air Act mandates the phase-out of production and import of ozone-depleting substances and the manufacture of equipment using these substances. Refrigerants such as R11, R12, R22 and R502 have been or are being phased-out as part of this mandate.

This has compelled processors to search for CFC and HCFC alternatives such as non-ozone-depleting HFC refrigerants like R507 and R410A. While these alternatives satisfy non-ozone-depleting requirements, many HFC refrigerants have significant global warming potential (GWP). Many environmental groups have identified this attribute as a threat to the environment, leading to heavy pressure on these refrigerants for reductions in system charge and possible future phase-out.

Ammonia Refrigerant Regulations

While ammonia refrigerant has no ozone-depleting or global-warming attributes, the health hazards of ammonia result in other regulatory issues. They include governmental oversight programs and state regulations.

EPA Oversight. The EPA’s risk management program (RMP) is required for ammonia refrigeration systems used by food processors, food distributors, refrigerated warehouses and other stationary ammonia refrigeration systems with refrigerant inventory in excess of 10,000 pounds.

OSHA Oversight. Ammonia refrigeration systems also are regulated under OSHA’s process safety management (PSM) standard, which requires compliance with and submission of PSM elements for refrigeration systems in excess of 10,000 pounds, and compliance with general duty for systems less than 10,000 pounds, whereby sufficient PSM must be in place.

State Regulations. Some states have implemented lower threshold quantities of ammonia for PSM. Check with your local regulating group for details. Many states also have additional codes and legislation for operating ammonia refrigeration systems. Local authorities, municipalities and states may review a proposed facility site plan and limit or restrict the use of certain refrigerants.

System Design Considerations

Understanding regulatory changes is one of many steps used to determine the type of refrigerant. Other considerations, including capacity, plant location, system design and compatibility, should be reviewed during the selection process.

System Capacity. Facilities requiring a significant amount of refrigeration capacity for storage or production — especially where refrigeration pipe and component sizes necessitate the use of steel — can use ammonia effectively. The operating efficiencies and installation costs of ammonia compared to other refrigerants in large, centralized refrigeration systems may offset the additional regulatory compliance cost. Users with smaller facilities may use fluorochemical-based systems where energy use is less of an issue.

Plant Location. States such as New Jersey and California, some municipalities and industrial parks limit the use of refrigerants such as ammonia. Due to increased regulations, the cost of compliance on ammonia may supersede the efficiency and cost benefits realized through the use of ammonia. In these cases, fluorochemical refrigerants should be considered as an option.

System Design. Smaller, commercial-grade systems typically will only use a fluorochemical-based refrigerant. By contrast, industrial-grade equipment may lean toward ammonia to take advantage of the efficiencies provided by this refrigerant on a larger scale.

System Compatibility. Consideration of the cooled space must be included. Safety and contamination reviews must be examined when considering toxic refrigerants such as ammonia. Processes and personnel proximity also must be reviewed to determine risks associated with refrigerant releases.

New Refrigerant Choices

Whether using ammonia, hydrocarbons or fluorochemical refrigerants, some technologies allow the end user to reduce the total charge in the facility and reduce the risk of leaks and other possible safety issues. These include secondary glycol and carbon dioxide (CO2).

Secondary Glycol. For medium temperature refrigeration, using glycol to cool the process instead of refrigerant will help to reduce the refrigerant charge by up to 90 percent of the original charge. Disadvantages to this option include the loss of efficiency and a higher capital cost for the system.

CO2. For low-temperature refrigeration, using CO2 as a secondary refrigerant to cool the process instead of refrigerant will also help to reduce the refrigerant charge by up to 90 percent of the original charge. Disadvantages to this option include the loss of efficiency and a higher capital cost for the system. However, opting for benefits that outweigh any drawbacks, many end users have made this choice, with a number of successful installations using CO2 as the secondary refrigerant.

 In conclusion, changing regulations and technologies complicate the choice of refrigerant. A poor refrigerant selection can impact facility operating costs, increase regulatory compliance requirements and increase maintenance and installation costs. Refrigerant selection and its impact on a refrigeration system will remain for the life of the system, so contacting a refrigeration professional is always a good option when evaluating the best choice for a given application. 

Is CO2 in Your Future?
Is a CO2/ammonia cascade system utilizing screw compressors the future design for cold storage warehouses in North America?