In food processing, thermal transfer is like gravity: What goes up must come down. For many liquids and solids, down is somewhere south of 5°C/40°F, making refrigeration a core process.
Freezing and cooling finished goods require energy, and better managing energy inputs is a priority. Green initiatives, lean programs and rising utility costs are prodding manufacturers and their supply partners to consider alternative approaches that boost thermal-transfer efficiencies. Whether the objective is to lock in positive attributes with freezing or preserve fresh food at refrigeration temperatures, innovative technologies are finding a receptive audience.
Hydro cooling is a case in point. Refrigerated soups, side dishes and other commissary-style products traditionally use refridgerated air at -10°F to lower the temperature of packaged foods below 40°F. Management at Lima, OH start-up Kettle Creations were inclined to go that route two years ago when local authorities ruled out an anhydrous ammonia system because of the close proximity of a heart clinic. The project engineer had a better idea: Why not leverage the superior heat-transfer of water to lower energy demand? Campbell Soup pioneered the process two years earlier at its StockPot division (see “Soup’s on at Stockpot,” Food Engineering, December 2008) when it installed four spiral coolers from Coastline Equipment Inc. Concluding what worked for soup in Everett, WA should work for mashed potatoes in Lima, Kettle’s owners opted for hydro cooling.
About 3,000 stainless steel nozzles spray cold water directly on 170°F filled containers as they wend their way down the 30-tier spiral, according to Rene Janzen, sales engineer at Bellingham, WA-based Coastline, spraying 4,000 gallons a minute. A treatment system filters, ozonates and recirculates the water. Dwell time is 90 minutes. The process is gentler on the product than frigid air, Janzen maintains, and cold air can turn the corners of the packages brittle and susceptible to cracking.
General contractor Keith Pohlman, president of All Temp Refrigeration Inc., Delphos, OH, plumbed the spiral system to a centrifugal chiller and added another energy enhancement: a heat exchanger that extracts latent heat from the containers and reuses it to heat the floors.
Pohlman’s chiller uses 134a refrigerant, the replacement for the chlorofluorocarbon (CFC) R22 (see related story below).
The ozone depletion caused by CFCs led to a worldwide ban on Freon production, and programs like the EPA’s GreenChill that encourage retailers to find replacements for CFCs and hydrochlorofluorocarbon (HCFC) are gaining steam. Critics like Bruce Badger, president of the International Institute of Ammonia Refrigeration, maintain “the new refrigerants being concocted to reduce ozone depletion are significantly less efficient” than the coolants they replace. An EPA spokesman sharply disagrees, pointing out “the energy-efficiency of a refrigeration system depends on many factors.” Hawaiian inventor Richard Maruya recently gained EPA approval for HCR188c, the first pure hydrocarbon refrigerant. In a comparison with 134a, Maruya demonstrated his refrigerant draws 48 percent less power and requires only one-fourth the charge.
Maruya targeted automotive air conditioning and home refrigerators for his blend of propane, butane and other hydrocarbons, which carries the ASHRAE designation R441A. Engineers have greeted his coolant with skepticism, particularly over flammability issues, but Maruya insists the refrigerant’s small charge “makes the risk assessment a nonfactor.” To prove the skeptics wrong, he plans to charge a 50-ton system outfitted with a safety valve to automatically lower pressure in the event of a leak at the state fairgrounds in Sacramento, CA this summer.
Big chill's go-to optionFor large spaces, mechanical refrigeration using anhydrous ammonia is the low-cost choice, with coolant costs a fraction of those for halocarbons. Safety concerns dogged installations in decades past, and while food companies are comfortable with the technology, a spate of large-scale ammonia releases and lethal accidents in recent years has put safety back in the limelight.
In the space of three months in 2009, three ammonia releases involving human fatalities occurred, including a line rupture that killed one worker and hospitalized four others at Mountaire Farms poultry plant in Lumber Bridge, NC. Within that time frame, a gas explosion and subsequent ammonia release at ConAgra’s Slim Jim plant in Garner, NC killed two and sent 38 to area hospitals, four in critical condition. Two more fatalities at a Minnesota fertilizer plant later that year made 2009 one of the worst years on record for ammonia safety.
Ammonia’s reputation received another hit in August, when a roof pipe leaked a plume of ammonia at Millard Refrigerated Services cold storage in Mobile, AL. More than 120 people were sickened and six hospitalized, at least one in intensive care.
Ninety percent of ammonia produced in the US is used as fertilizer, according to an analysis of ammonia releases in the state of Minnesota over a 10-year period. Not surprisingly, agriculture accounted for almost half the period’s 459 documented releases. Refrigeration systems accounted for 27 percent, the second-leading cause and far ahead of meth labs, the third most-frequent source.
“Our customers are getting very serious about the safety of their refrigeration systems,” reflects Neil Horn, vice president-refrigeration at Stellar. Secondary fluids such as glycol are being paired with ammonia in some cases, with ammonia loops constrained to the engine room while the secondary refrigerant courses through the processing area. In a recently completed project, Horn oversaw the retrofitting of a cascading system at a supermarket distribution center, with carbon dioxide delivering cold air after exchange with ammonia.
In 2003, Stellar engineered a CO2/ammonia cascade system at Nestlé’s Jonesboro, AR Stouffers plant, a 525,000-sq.-ft. installation that was believed to be the world’s largest. The higher saturation pressure of CO2 was seen as an energy-efficiency advantage at temperatures of -40°F, an extreme seldom applied in food storage. As a result, only “a couple dozen, maybe three dozen” cascade systems have been installed in North America, he estimates. But sustainability programs add luster to cascade, and while the financial case is difficult to substantiate, Horn is convinced cascade is more energy-efficient even in partial-load situations than ammonia-only. “If you wanted to build a 100,000-sq.-ft. freezer, the CO2 cascade system will not be any more expensive than an ammonia system,” he adds. “In fact, we have found it to be 5 to 10 percent less.”
Bolstering his position is US Cold Storage, which has built six warehouses using CO2 cascade refrigeration systems in recent years. “Carbon dioxide cascade refrigeration systems are proving to be more efficient, simpler to maintain and safer to operate than typical two- or single-stage ammonia refrigeration system,” the company states on its web page. Even if initial capital requirements push out ROI a year or two, “it falls into the category of the right thing to do,” says Horn, and a growing number of companies “are willing to do the right thing and spend additional money.”
Old technology, new applicationsHigh-pressure heat pump screw compressors to capture and reuse waste heat are being commercialized by Emerson Climate Technologies’ Vilter unit, but the added expense might be better invested in boiler economizers and other heat reuse options, Horn suggests. With conventional compressors, waste heat is fairly low grade, though The Dennis Group’s John Hobden says those types of energy-efficiency projects are becoming common. Even more popular, the mechanical engineer says, are VFDs on compressors, evaporators, condensers and fans.
Tom Aurich, refrigeration group manager at Shambaugh & Son, Fort Wayne, IN, concurs. “Years ago, you never saw VFDs on compressors,” he says. Harmonic frequency issues and other concerns often were cited, but the real issue was cost. Today, VFD costs have plummeted, and paybacks are calculated in months instead of years.
Heat recovery was not part of the engine room design at a recently completed two-stage refrigeration system installed at Unilever’s Owensboro, KY plant, nor is it likely in a much larger installation at Unilever’s ice cream facility in Covington, TN, where 17 compressors and 11 evaporative condensers will power a 6,500-ton refrigeration system. “The quandary with heat recovery is storing the water until you need it,” Aurich reflects. Nonetheless, more plate and frame heat exchangers are being incorporated in designs. “Everybody wants to be green,” he says.
Among the green wannabes is WalMart, which made energy conservation a priority when engineering a 400,000-sq.-ft. perishable food distribution facility last year in the Alberta, Canada. Virginia Garbutt, director-strategic network planning and continuous improvement at WalMart Canada, called it the most ambitious sustainability-driven greenfield construction undertaken by the retailer when she recently spoke at ProMat 2011 in Chicago. “Sustainability is no longer an option; it’s part of your job description,” said Garbutt, though a solid ROI is expected. A conventional refrigerated DC was built in eastern Canada the prior year and served as a benchmark for evaluating the Balzac, Alberta DC.
Part of the DC’s energy savings will come from LED lighting that was installed in freezer areas. LED added $486,000 in incremental costs, Garbutt says, but they are 75 percent more efficient than fluorescents. “They’re durable,” she adds. “The bulbs are expected to outlast our building.” Savings of $129,000 a year on replacement bulbs alone will speed the payback.
T-5s were used throughout the previously built warehouse, and area lights are constantly on because of the delay firing the tube in extreme cold. With LED, lighting is instantaneous, and the absence of any waste heat is a plus in a freezer. The spectrum of light produced appears dull, but “it’s brighter than you think,” she says, adding insects can’t see the light and are not drawn to it.
“WalMart is not against taking risk,” observes Bob Catone, general manager of Guth Lighting in St. Louis, and the biggest risk in LED is rapid obsolescence. “There may be a gotcha mode that nobody’s figured out yet” in the technology, but Catone believes LED soon will be dominant in freezers and elsewhere. R&D investments in metal halide and fluorescent have ended, and TV manufacturers focused on LED are taking over lighting production. “It’s the only light source that likes to be dimmed and turned on and off,” he points out, adding, “the cost differential is shrinking considerably.”
Cryogenic freezingSanitation considerations drove the design of a new cryogenic freezer from Air Liquide Industrial US, though Innovation Manager David Braithwaite points out faster clean-up also means less water use, fewer chemicals and reduced energy demand for hot water. Hydraulic lifts provide 360° access to interior components.
Instead of being conveyed, coated and sticky IQF products float on a current of liquid nitrogen through the freezer. The surrounding shell is molded fiberglass, though all the moving parts are stainless steel. “There’s not a flat surface in there,” says Braithwaite. “It’s as smooth as a bass boat.”
Whether companies are committed to sustainable manufacturing or not, “wherever you can suck out a percentage of energy cost, do it,” advises Alex Daneman, CEO of Hench Controls Inc., Hercules, CA. “Too many people have their face too close to the glass” when calculating the payback from energy-efficiency in refrigeration systems. Electricity rates have doubled in some regions in the last five years. While no one can be certain what rates will do in the next five, one certainty is that they won’t go down.
For more information:
David Braithwaite, Air Liquide Industrial, 713-624-8000
Keith Pohlman, All Temp Refrigeration Inc., 419-692-5016, firstname.lastname@example.org
Richard Maruya, A.S. Trust & Holdings, 808-235-1890, email@example.com
Rene Janzen, Coastline Equipment Inc., 360-734-8509, firstname.lastname@example.org
John Hobden, The Dennis Group, 413-787-1785
Saskia Feast, EOS Climate, 626-840-6955, email@example.com
Bob Catone, Guth Lighting, 314-566-4550
Alex Daneman, Hench Controls Inc., 510-759-7777
Tom Aurich, Shambaugh & Son, 260-487-7751, firstname.lastname@example.org
Cap-and-trade for refrigerantsMarket-based incentives to reduce greenhouse gas (GHG) emissions have, at best, an uneven track record, but proponents of an offset program targeting ozone-depleting refrigerants are cautiously optimistic about the prospects for San Francisco-based EOS Climate’s cap-and-trade program, scheduled to commence January 21, 2012.
EOS focuses on the chlorofluorocarbon (CFC) segment of the carbon-reduction market. Those refrigerants contain up to 11,000 times the ozone-depleting potency of carbon dioxide. They include CFC-11 and CFC-12, commonly known as Freon. Voluntary trading in CFC credits is off to a slow start, with 1.14 million metric tons of a potential 214 million metric tons in California over the next nine years traded, but in December, the California Air Resources Board (CARB) designated CFCs for trading in carbon credits under the cap-and-trade program established under the California climate change program. In April, Cargill Inc. became EOS’s financial and marketing partner for the tradable emission credits it will generate from destroyed CFCs.
“We needed a compliance market, and CARB has given us one,” says Saskia Feast, EOS’s vice president-business development, “and with Cargill’s strategic financing and innovations in carbon trading, we will greatly increase the removal of potent global warmers.”
“Hopefully, California will be the anchor for a much larger trading area,” says Arjun Patney, carbon market strategist with Minneapolis-based Cargill. Several Canadian provinces and a few Western states are expected to join California later in cap-and-trade under the Western Climate Initiative. In the near term, California sites generating more than 35,000 metric tons of GHG a year will have to either lower emissions or buy offsets; included in that group are 34 food facilities. One of their carbon-credit options will be those traded by EOS and Cargill.
As a result, any food or beverage company in the country will have the option of retiring a leaky Freon-based cooler and verifying its destruction through EOS, then receive cash from the buyer of the resulting credit. “A fairly limited quantity of these refrigerants gives you a large carbon credit,” Patney points out.
The intent is to give companies a financial incentive to destroy CFCs rather than turn old systems over to salvage operators, who then resell the Freon to people who need to recharge their obsolete Freon systems. It also should drive up the price for recycled CFCs.