Lineage capitalising on new opportunities for ammonia-CO2 cascade

A new paradigm in industrial refrigeration is emerging in the United States with ammonia-CO₂ systems helping alleviate safety concerns while catering for large-scale refrigeration capacities. Accelerate America investigated the trend in the magazine’s October edition.

Read the DeCicco & Sons cover story for the October edition of Accelerate America

There are big changes looming in the North American industrial refrigeration market, as systems that use far less ammonia than conventional setups are gaining considerable traction. Add Lineage Logistics, , to the list of companies going in this direction.

Next March Lineage Logistics, one of the nation’s largest cold-storage providers, which operates 110 warehouses in the U.S. encompassing over 600 million cubic feet (182.3m³ million), plans to unveil a refrigerated warehouse in Charleston, South Carolina.

It will be Lineage’s first to employ a cascade ammonia/CO₂ refrigeration system rather than a traditional two-stage ammonia system, to blast freeze product from 30-40°F (-1.1-4.4°C) down to 0°F (-17.8°C).

The reasons for this are many – economies of scale are bringing down the cost of CO₂ systems, and facilities like Lineage’s in Charleston simply do not want to risk operating with large amounts of ammonia in their facilities. Thirdly, for facilities like Lineage’s relying on blast freezing, NH₃/CO₂ systems have proven to be very efficient in these applications.

Another large cold-storage operator, US Cold Storage (USCS), can be credited with bringing the NH₃/CO₂ system to the fore in 2005, when that technology was virtually unheard of. Since then the company has established many industry standards when it comes to NH3/CO2 installations, with 11 of its 35 public refrigerated warehouses operating this system.

Overall, there are now 53 NH₃/CO₂ cascade systems installed in industrial facilities in the U.S., eight in Canada and eight in Mexico, according to the 2015 GUIDE to Natural Refrigerants in North America.

Ten of USCS’s systems are cascade models, using low-temperature CO₂ compressors, while one, in Pennsylvania, uses a critical brine solution with CO₂ circulated as a secondary refrigerant. Its Bethlehem Pennsylvania facility has 6,400 pounds (2903 kg) of ammonia and 48,000 pounds (21,772 kg) of NH₃/CO₂ used in the cascade setup.

Lineage’s 180,262-square-foot (54,944m²) Charleston facility will contain 7,969 pounds (3,615 kg) of ammonia and 60,111 pounds (27,266 kg) of CO₂. By contrast, a traditional two-stage pump-recirculated ammonia system typically contains between 40,000 (18,144 kg) and 50,000 (22,680 kg) pounds of ammonia.

System specifications

Lineage Logistics’ NH₃/CO₂ cascade refrigeration system at its new plant in Charleston, S.C., will contain the following characteristics:

Phase 1 will have 1,698 TR capacity, with the full build-out at 2,191 TR 
One freezer space, two convertible rooms, two docks and one quick-freeze room, encompassing 647,160 cubic feet  (19,6950m³)
Two CO₂ recirculators, one at 20°F (-6.7°C) and one at -30°F  (-34.4°C)
Full build-out ammonia charge: 7,969 pounds  (3,615 kg)
CO₂ charge: 60,111 pounds  (27,266 kg)
The freezer and convertible rooms are served by mini-penthouse evaporators 
The docks are served by ceiling-hung evaporators 
The quick freeze room is served by standard penthouse evaporators 
For CO₂: Seven Sabroe high-pressure reciprocating compressors 
For NH₃: M&M high-temperature screw compressors 
For NH₃: Three rooftop hybrid condensers

Significant uptake for NH₃/CO₂

Matt Hirsch, president of Georgia-based Primus Builders, which, together with Republic Refrigeration, is installing Lineage’s NH₃/CO₂ system, has the benefit of hindsight on its side.

Primus has completed seven of US Cold Storage’s NH₃/CO₂ installations, including the most recent one in Tennessee.

“It’s true, we’ve seen a significant uptake for NH₃/CO₂ systems,” Hirsch said. “Four years ago only US Cold Storage was using the systems as well as the ice cream manufacturers like Nestle.”

Primus now has 5-6 clients - including Lineage, US Cold Storage, Americold and Valley Cold Storage – who are “seeing more and more advantages for NH₃/CO₂ systems as they move forward,” said Hirsch.

The systems are proving particularly popular for food distribution facilities eager to eliminate the use of ammonia in their facilities to improve safety and protect products. Like USCS’s Bethlehem warehouse, the Charleston facility contains a central engine room where all of the ammonia refrigeration will be confined, while CO₂ will be used as the sole cooling refrigerant in the facility.

And using under 10,000 pounds (4,536 kg) of ammonia also allows the cascade system to largely avoid federal safety and maintenance regulations such as OSHA’S PSM (Process Safety Management) program and the Environmental Protection Agency’s RMP (Risk Management Plan).

Confining the ammonia to the engine room keeps the charge low. “This is done without sacrificing efficiency and we expect to actually gain efficiency all the while using a natural refrigerant that doesn’t run the risk of phase out in the future,” noted Jim Romine, Lineage’s senior director of engineering.

“While ammonia systems are inherently safe to operate, it is an advantage to be able to lower the charge on site.”

Hirsch also points to the significant energy efficiency advantages of NH₃/CO₂ systems compared to two-stage NH₃ systems when blast freezing products in temperatures below -20°F (-6.7°C).

“The beauty of using the cascade systems is that the colder it goes, the more efficient it is,” said Hirsch. “Whereas with ammonia, the colder you go, the less efficient it becomes.”

Lower costs are also facilitating the transition to NH₃/CO₂ systems from traditional ammonia systems.

“We did evaluate this project with standard two-stage ammonia systems as well as NH₃/CO₂ systems,” said Hirsch. “There has been a cost premium attached to NH₃/CO₂ systems in the industry, but it was more significant than it is now. I would attribute that to the fact that there are many more equipment manufacturers available with CO₂ systems than there were 10 years ago.”

This change is being leveraged by Republic Refrigeration, the designer and installation contractor for the complete industrial refrigeration system in Charleston. The company sources equipment from multiple manufacturers, while supplying components of its own.

By contrast, designer/manufacturer M&M Refrigeration almost exclusively designed and supplied equipment for several of US Cold Storage’s early NH₃/CO₂ projects. But Hirsch said that practice is rare today. “M&M really used to be the only manufacturer in the U.S. designing CO₂/NH₃ systems,” he said.

“We now have a number of industrial refrigeration companies that are doing the design/builds, like Republic Refrigeration, which are able to interchange three or four equipment manufacturers. And now that we have competition in the market, the costs have come down.”

Cascade standard underway

One limitation on the growth of NH₃/CO₂ cascade systems has been the reluctance of the IIAR (International Institute of Ammonia Refrigeration) to draft a standard for cascade systems, a move that would undoubtedly impinge on the broader adoption of all-ammonia systems.

As the International Institute of Ammonia Refrigeration, “they didn’t necessarily want to promote the elimination of ammonia as a refrigerant,” Hirsch said. “However, they recognise that it’s a cascade system and it’s still using ammonia as a refrigerant.”

So in 2015 the IIAR created a sub-committee that is committed to producing a standard for NH₃/CO₂ cascade systems.

“In order for them to publish a formal standard it’s going to be a multi-year effort but it’s great that they have developed a sub-committee and a team,” said Hirsch. “A few years down the road we will see a standard similar to the IIAR’s best practice standard for ammonia refrigeration.”

Read the full article in the October issue of Accelerate America