CO{sub}2/NH{sub}3 refrigeration replaces R-22 in large freeze-drying plant

摘要

Nestle' UK owned a relatively large, complex, low-temperature refrigeration plant that was tightly integrated into its freeze-drying process. The existing plant operated on R-22 and some system components were more than 35 years old After considering the plant's relative age, current operating costs, and the undesirable environmental nature of its refrigerant Nestle' decided to replace the plant. After a detailed examination of the options, the company concluded that the best solution was a CO{sub}2/ammonia cascade system. The company conducted a pilot test with a 100-kW, -54°C (about 30 tons at 65°F unit commissioned at the end of 1998. After successful operation of the pilot, the plant was built and began taking load off the R-22 system in early 2001. The transfer was complete by mid-year. This paper outlines the history of the project and compares actual system operation and performance with the company's original expectations.