Cryogenic Freezer – Cryogenic, Carbon Dioxide
Industry: Fruit and Vegetables (NAICS 3114) Meat (NAICS 3116)
Process Brief: The product is rapidly chilled by using liquid carbon dioxide
Energy source: Electricity/ some Natural Gas
Energy Intensity: 250-1,700 Btu/lb of product
Cryogenic freezing incorporates straight belt, spiral, and immersion designs with liquid carbon dioxide. These freezers have a very high heat transfer rate; and meats, vegetables, and fruits can be frozen in less than a minute. Carbon dioxide does not contaminate the product, although careful venting of the process is essential. Cryogenic process lines can be much smaller and cheaper than chilled air or liquid systems. Rapid cooling improves quality for most products but care must be given because the surface of some products may crack.
An important difference from other chilling technologies is that cryogenic freezing usually does not incorporate on-site refrigeration equipment. In almost all cases the carbon dioxide is produced off-site and is shipped to the food plant in a pressurized, insulated tank.
Carbon dioxide does not exist as a liquid at atmospheric pressure. When high-pressure liquid carbon dioxide is released, it cools to -110°F as half of it becomes a vapor and half of it becomes dry-ice snow. The design of the freezer generally attempts to keep the dry-ice snow from attaching to the product or by allowing sufficient time for the snow to sublimate.
Source: Overview GRI-03/0075;