Going green. It’s an environmental movement sweeping the globe. No matter whom you are, what company you work for or where you look, the call to “reduce, reuse and recycle” is impossible to miss. But “going green” is not a recent trend - in fact, some companies have been pushing this initiative for decades in an effort to improve manufacturing and industrial practices, protect the Earth’s ozone layer and offset global warming. Plant engineers have been at the vanguard of these efforts, especially as they ensure that their refrigeration systems and chillers run efficiently and environmentally friendly.
Environmental trends over the past several decades have played a large role in shaping industrial process cooling practices and the availability of various refrigerants. With the advent of the Clean Air Act (CAA) in 1970, scientists began researching the use of chlorofluorocarbons (CFCs) and their adverse effects on the stratospheric ozone. Results of these studies subsequently led to the ban on CFC use in aerosol propellants in 1978.
Almost 10 years later, the United States signed the 1987 Montreal Protocol with 190 other countries to phase out chemicals that contribute to the destruction of the stratospheric ozone. In 1992, the CAA was amended, including Title VI, which mandated that the U.S. Environmental Protection Agency (EPA) develop a “phase-out” program for the manufacture and use of ozone-depleting chemicals and promote the creation of environmentally friendly substitutes.
The 1992 CAA amendment required that CFCs be recovered, reclaimed and reused as opposed to the disposal and venting of CFCs into the atmosphere. U.S. production of ozone-depleting chemicals, including CFCs, used as refrigerants, propellants and cleaning solvents was brought to a halt in 1996, making CFCs a limited resource for refrigeration in industrial processes. Under current regulations, the EPA is now phasing out another family of chemicals, hydrochlorofluorocarbons (HCFCs), which will limit the availability of these refrigerants in the decades to come.
Engineers are left with the challenge of deciding what to do when their chillers still have a number of years of service remaining, yet the refrigerants they require are getting harder and harder to find and costs keep rising.
One solution is to commit to a total replacement of equipment and refrigerants with the latest high-efficiency models using alternative refrigerants, including hydroflourocarbons (HFCs). If the plant owners decide on this option, any regulated refrigerants must be recovered. However, the recovered refrigerants could be sold to an EPA-approved reclaimer for eventual reuse, offsetting some of the cost of the new systems.
The net capital cost of this option usually leads plant owners to decide on other alternatives to keep their systems running for their full useful lives. Sometimes chillers can be retrofitted to run on alternative refrigerants. For example, a chiller originally running on R-12, a CFC, can be retrofitted to run on R-134A, a HFC. Such conversions must be done carefully but can be an economical decision for a chiller with a long useful life.
Refrigerant Requirements in Process Cooling ApplicationsSome of the more common process cooling applications such as those used in coal and natural-gas power plants use centrifugal process chillers to liquefy steam into water. This application requires a refrigerant to operate down to, but not below, 32˚F (0˚C). Because this is not a low-temperature application, R-134A (an HFC), R-22 and R-123 (both HCFCs) are the main refrigerants used in this process.
These types of industrial systems normally contain 5,000 to 20,000 lb of refrigerant. In most cases, mechanical contractors have service agreements in place to maintain these refrigeration systems. Intensive preventive maintenance programs are performed on these chillers to ensure that they run at peak capacity and that their lifecycles are maximized.
During routine maintenance, refrigerants are replaced if any contaminants are found circulating in the systems. Contaminants such as oil, high water content, acid, metal content, mixed gases and other noncondensable particulates can erode equipment components and affect heat-transfer capacities. The contaminated supply can lead to higher energy consumption and can be detrimental to a plant’s bottom line.
The Three Rs of Green RefrigerationIt is in routine maintenance programs that plant engineers need to know the three Rs of green refrigeration: recovery, recycling and reclamation.
Recovery.Refrigerant recovery occurs when a refrigerant is completely removed from the chiller or equipment, regardless of its purity or contamination level, and is stored in temporary cylinders or containers without being tested or processed further. This method is used on a regular basis during planned outages and plant shutdowns. It also is used when a refrigerant is being phased out of the industrial process and is being replaced with another refrigerant.
Refrigerant recovery can be performed by the plant engineers, but often the equipment they use is slow in comparison to the equipment used by full-service refrigerant services providers. High-speed recovery equipment can recover refrigerant at rates above 12,000 lb/hr.
Recycling.It is possible to extract specific contaminants from refrigerants and recycle the refrigerant in the equipment without meeting all of the specified Air-Conditioning and Refrigeration Institute (ARI) requirements for reclamation. Typically cleaned using oil separation, recycled refrigerants will require one or more passes through filtration devices such as replaceable-core filter-dryers to remove common contaminants, including moisture, acidity and particulate matter. This procedure might remove some of the contaminants from the refrigerant and the chiller.
Reclamation.When a refrigerant is reclaimed, engineers can consider it as good as new. In the reclamation process, refrigerant is removed from a chiller or other equipment and placed in temporary containers. Contaminants such as oil and acid are removed by reclamation equipment, and the refrigerant is reprocessed and analyzed to purity levels outlined in the ARI Standard 700-1995 specifications for fluorocarbon refrigerants.
Typically, reclamation services require the use of specialized equipment and are performed off-site; however, some full-service refrigerant reclamation companies are equipped to do the work on-site, which saves plant engineers time and effort. Another benefit to having the work performed on-site is that the refrigerant never leaves the facility, which reduces liability to the facility owner.
In some cases, these services can be performed while the equipment is in operation, which will enable the plant to continue its manufacturing process and prevent loss of productivity. When the systems and the refrigerant are cleaned, efficiencies increase dramatically, resulting in greater production capacity and lower energy costs.
Large mobile processing systems are capable of recovering and processing low-pressure refrigerants to ARI 700-1995 standards at a rate of 2 lb/sec, or 7,200 lb/hr. High-pressure refrigerants can be processed at faster rates. Full-service refrigerant reclaimers and suppliers also can handle ultra-high-pressure refrigerants such as R-503, R-13, and R-23, which would pose greater challenges for plant engineers.
Reclamation should be done by an EPA-certified refrigerant reclaimer. Plant engineers can consult the EPA web site for a list of reclaimers approved to reprocess used refrigerant to the purity level specified in appendix A to 40 CFR part 82, subpart F (based on ARI Standard 700, “Specifications for Fluorocarbon and Other Refrigerants”). Reclamation of used refrigerant by an EPA-certified reclaimer also is required to sell used, reclaimed refrigerants.
Powerful PartnershipsOne way for plants to stay ahead of the curve and add more money to their bottom lines is to work closely with a full-service refrigerant and industrial gas supplier. Procurement of refrigerant products and services sometimes can be integrated with other industrial gases and supplies used at the plant to reduce paperwork and streamline supply chains. The range of services available will provide more options when discussing refrigerant-maintenance programs that will be cost efficient and green. Regular consultations with these suppliers in conjunction with scheduled plant maintenance shutdowns can reveal cost-saving opportunities and strengthen working relationships.
Look for companies that are aligned with credible trade associations such as the Air-Conditioning and Refrigerant Institute (ARI); the International Institute of Ammonia Refrigeration (IIAR); the Refrigerating Engineers and Technicians Association (RETA); the Refrigerant Service Engineers Society (RSES); the American Society of Heating Refrigeration Air Engineers (ASHRAE); and Heating, Air-Conditioning & Refrigeration Distributors International (HARDI).
In the near future, the challenge of reclaiming refrigerants will change. The anticipated phase-out of R-22, the most common industrial refrigerant, and other HCFCs is expected to create shortages over the next couple decades. Working with the right partners will ensure that plant engineers can keep their cool and stay "green." PC
Sidebar Case Study:In 2006, Chevron’s plant in Pascagoula, Miss., scheduled a
maintenance turnaround of two chiller trains containing R-134A, also known as
tetrafluoroethane, a long-term HFC replacement refrigerant for R-12. Chevron
asked industrial gas supplier Airgas Gulf States, one of the regional companies
within Airgas Inc., to help.
Chevron Saves Money through R-134A Reclamation
Airgas provided ten 10,000-lb recovery tanks for the used product and brought in proprietary high-speed processing equipment for recovery, analysis and reclamation to ARI 700-1995 standards. It also provided additional R-134A to top off the chillers. All work was completed on-site.
The chiller units were able to start up on schedule as originally planned under Chevron’s 2006 FCC Shutdown Plan. Using the reclamation service ultimately led to considerable cost savings.
Chevron has since used the on-site reclamation services in subsequent turnarounds of its industrial refrigeration systems, including one recovery and reclamation project that was done without taking the chillers offline.