Emblem Cranberry (Emblème Canneberge), a major processor and distributor of cranberries and blueberries based in Sainte-Eulalie, Quebec, Canada, recently completed an expansion that comprises one of the largest transcritical CO2 systems in the world.

Emblem’s facility, which opened in 2016, has undergone a three-stage development that was completed in November. It now houses six blast/storage freezers, one IQF (individual quick freezing) tunnel, two production areas for fruit sorting, cleaning and packaging, one cooler and two refrigerated dock areas. This can accommodate over 55 million lbs (25 million kg) of cranberries, and 16 million lbs (7.3 million kg) of blueberries.

To generate the freezing and cooling, Emblem installed nine CO2 racks, which supplies 1,500TR (5,300kW) of capacity.

Thus far, the CO2 system has “worked quite well for us,” said Vincent Godin, President of Emblem Cranberry. Maintenance has been “normal,” with a few compressor changes and a few CO2 leaks addressed in the CO2/glycol heat exchangers.

Godin talked about the installation of the system and evolution of the facility during an end-users  presentation at the ATMOsphere America conference, held online November 3. (ATMOsphere America was organized by ATMOsphere, formerly shecco, publisher of R744.com.)

Godin acknowledged that ammonia is more widely used as an industrial refrigerant than CO2 in Quebec. But Emblem chose a CO2 system because an ammonia leak would be more damaging to its food products than a CO2 leak. “That is one of the main reasons we went with a CO2 system,” he said.

Another incentive was that Emblem received a grant from the Quebec government for purchasing the CO2 system.

The nine CO2 racks were provided by Saint-Bruno, Quebec-based Zero-C, which also has a plant in Switzerland. Zero-C has supplied about 60 CO2 systems, as well as ammonia systems, to a variety of customers, including supermarkets, cold storage and food facilities, arenas and pharmaceutical plans, said Valentin Delate Zero-C’s Sales Manager .

Emblem’s racks include six medium-temperature (transcritical) circuits with a maximum pressure rating of 1,740psi (120bar), and three low-temperature (subcritical) circuits with a maximum pressure rating of 650psi (45bar). The medium- temperature circuits deliver final temperatures of 40°F (4.4°C). The low-temperature circuits,with suction temperatures ranging from -20°F to -40°F (-29°F to -40°F) and a discharge temperature of around 20°F (-6.7°C), produce blast/storage freezer temperatures of 0°F (-17.8°C) and -13°F (-25°C) for the IQF tunnel.

Unlike many commercial CO2 systems, which utilize direct expansion, Emblem’s system pumps the CO2 to the evaporators. This improves efficiency, said Godin. “The pumped system allows us to have more tonnage of refrigeration with less compressor horsepower.”

In pumped systems, “suction pressure is constant, superheat is constant, liquid return to the compressor is almost impossible, and the load is more stable,” noted David Bastrash, Engineering & Manufacturing Manager for Zero-C. “This means minimizing the use and cycling of compressors, fans and valves, making the systems more efficient, stable and reliable.”

Pumped systems are also simpler and easier to maintain, with no need for an expansion device on every evaporator and no need for a suction accumulator, said Bastrash.  “In other words, we can gain the very best advantages of using CO2, combined with pumped industrial ammonia system advantages, but without the ammonia disadvantages.”

According to Zero-C, Emblem’s CO2 system saves 20-30% on energy costs compared to an ammonia pumped unit with screw compressors and a cooling tower.  “We think it’s more efficient than a traditional system,” said Godin.

Emblem’s energy provider, Hydro-Québec, pays the company for reducing its energy consumption during the daily three-hour period of peak demand. Emblem programs its Micro Thermo controls to leave only one compressor per rack operating during this time period. “When we do that, there is a small change of temperature in the [storage] freezer, not even a decimal of Fahrenheit, because of the insulation and the huge mass of frozen product,” explained Godin.

Emblem has a maintenance contract with CO2 system provider Zero-C, which can monitor the system remotely and send technicians to make repairs. Godin acknowledges that the complexity of the system makes it challenging for Emblem employees to fully understand. For example, cranberries bring in a lot of humidity, which means that “we have to adjust the number of defrosts per evaporator each day,” said Godin.

Cranberries are harvested from October through December. After they are cleaned and stored in bins, the cranberries are blast-frozen in the freezers over 45-60 days, until they reach 0°F, and then are stored at that temperature for the rest of the year.

The CO2 technology has aligned with Emblem’s expectations in terms of the time it takes for the fruit to reach 0°F after being received from the field, said Godin. In addition, the IQF tunnel has exceeded the production capacity expectations that Emblem had for it.

In 2016, the first phase of its development, Emblem installed three 0°F blast/storage freezers, a 40°F production area, a 40°F cooler and a 40°F dock area cooler. These are served by two CO2 refrigeration racks that include subcooling.

In 2017 (phase two), Emblem deployed another 0°F blast/storage freezer which is served by two CO2 racks, with subcooling and a Refplus Opti-Mist adiabatic gas cooler.

This year (phase three), Emblem installed the IQF tunnel with a suction temperature of -40°F for processing wild blueberries. The blueberries are first hydrocooled by CO2-cooled water; they then enter the tunnel – supplied by U.S.-based Advanced Food Equipment (AFE) – which freezes up to 25,000lbs (11,340kg of blueberries per hour to -13°F; the fruit is then stored in a new -13°F blast/storage freezer.

Emblem also added another 0°F blast/storage freezer for cranberries this year, along with another 40°F production area where 6,000cfm of makeup air is provided, and another 40°F dock area. Five additional CO2 racks were installed, including parallel compression and a Güntner HydroBLU adiabatic gas cooler.

Godin noted that waste heat produced by the CO2 racks is carried via glycol to production floors for radiant heating, as well as to freezer floors to prevent ice build-up and to evaporators and the IQF tunnel for defrosting. It’s also used for make-up air treatment and office space heating. In addition, Emblem sanitizes its production areas and IQF tunnel with hot water heated by the glycol.

While Emblem has a 100kW furnace to heat its building when the CO2 compressors don’t generate enough waste heart, the company has only used the furnace once for about a day during a very cold period since it opened in 2016. “We practically don’t have to pay anything for heating because of the heat recovery,” Godin said.

“The pumped system allows us to have more tonnage of refrigeration with less compressor horsepower.”

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