Industry: Fruit and Vegetables (NAICS 3114) Dairy (NAICS 3115) Meat (NAICS 3116) Baking (NAICS 3118) Snack Foods (NAICS 3119)
Process Brief: Cooling is provided by a system in which a refrigerant is compressed and allowed to expand within a closed loop.
Energy source: Electricity
Cryogenic refrigeration uses very low temperature refrigerants, especially liquid nitrogen and solid or liquid carbon dioxide. Liquid nitrogen is produced off-site at large air separation plants and is transported to food processing plants in insulated tanks. Solid or liquid carbon dioxide is produced as a by-product of fertilizer manufacturing and is usually shipped as a solid. Liquid nitrogen has a temperature of -321°F and solid carbon dioxide sublimes at -109°F. It is estimated that 700 food processors use liquid nitrogen and 1,500 customers use carbon dioxide.
At a food manufacturing facility, the liquid nitrogen or solid carbon dioxide may be used to chill another refrigerant or will be used to directly chill the product. To chill a refrigerant, the cryogen is released into a heat exchanger where it absorbs heat from a circulating refrigerant or air. The cryogens can be used to chill products directly such as when fruits are immersed in liquid nitrogen. Because cryogenic refrigeration costs about four time as much as mechanical refrigeration, its use is limited to applications where products must be cooled far below freezing (i.e., –100°F).
Closed-Cycle Air Refrigeration (CCAR) is a new on-site cryogenic refrigeration technology that can deliver chilling temperatures of -70°F to -150°F, significantly reducing freezing times. Mechanical refrigeration is more appropriate at temperatures warmer than -70°F and existing cryogenic cooling is appropriate below -150°F. Because the CCAR achieves a lower temperature than existing mechanical systems, it can improve throughput efficiencies and enhance product safety. The CCAR design uses dry, high-pressure air as a working fluid and incorporates a reverse Brayton cycle to achieve its low temperatures. The National Institute of Standards and Technology and Air Products, Inc are developing CCAR.
Source: Overview GRI-03/0075;