Members of he Champlain Valley Chapter pose during the tour.
By Bill Atkinson, P.E., and Tom Zoller, P.E.
BURLINGTON, Vt.—What's summer without a cool cone of Ben and Jerry's "Cherry Garcia" or "Chunky Monkey" ice cream?
And what's ice cream without ASHRAE and ammonia refrigeration?
The Champlain Valley Chapter recently got a special tour of the Ben and Jerry's ice cream facility in Waterbury, Vt. Matt Lillis, P.E., Member ASHRAE, engineering services manager for the plant, took chapter members through the ice cream manufacturing process and explained how an ammonia refrigeration system is used to help Ben and Jerry's make its unique ice cream.
Although this plant offers daily tours, the chapter received a behind-the-scenes tour of the main production plant and the engine room that houses the refrigeration system for the facility. Because of the low temperatures required to freeze the ice cream, ammonia is the preferred refrigerant. Lillis discussed the advantages and disadvantages of ammonia as a refrigerant, and provided an overview of the system and components used in the plant.
Rotary screw compressors are used, using 23,000 lb (10 400 kg) of ammonia refrigerant and capable of producing about 1,000 tons (3500 kW) of refrigeration. The ammonia is compressed in two stages in the plant design, providing an efficient system as well as intermediate temperatures used for coolers and building HVAC needs. Chilled glycol is used as a heat transfer medium for these intermediate temperature processes. The second stage of compression is then completed on the ammonia to create a –40°F (–40°C) refrigerant that is used in the multiple freezers during production. One of these is a 40 ft (12 m) tall spiral freezer in which the freezing process is completed, where the pints experience temperatures of –40°F (–40°C) (–70°F [–57°C] with wind chill from the fans). The ice cream is then palletized and moved to a storage freezer that is kept at –25°F (–32°C) until shipment.
Due to the properties of ammonia, the plant is configured to minimize the amount of ammonia piping that is inside the plant. Glycol solutions are used whenever possible and valves are located in strategic locations. There is also constant monitoring inside the plant, and many protocols are in effect to maintain a safe working environment.
