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A sludge drying heat pump with CO2 and ammonia as natural refrigerants.

Author(s) : FLAGA-MARYANCZYK A., SCHNOTALE J.

Summary

A heat pump system for sewage sludge drying can be an energy efficient alternative for the traditional methods, that also avoids emissions from the drying installation. In this system sludge is dried by closed loop circulating air, treated in the heat pump. Natural working fluid in a heat pump and refrigeration equipment is increasingly important in view of the HFC (hydrofluorocarbons) phase out. In the paper two natural fluids are considered: CO2 and ammonia, each of them requiring different cycle arrangements. Due to the critical parameters of CO2: T(c)= 304.13 K and p(c)= 7.38 MPa, the process in the CO2 heat pump is the transcritical cycle with high compressor discharge temperature. It provides additional hygienization of dried product which becomes sanitary safe and environmentally sound. For ammonia being a toxic and flammable refrigerant a secondary fluid loop system is considered. The article investigates the heat pump dryer for sewage sludge drying and presents energetic evaluation and optimization of the working parameters of the transcritical CO2 heat pump and a secondary loop ammonia cycle. The influence of the isentropic efficiency of the compressor on specific moisture extraction rate is discussed. Impact of the internal heat exchanger and gas cooler pressure on energy efficiency of the heat pump and the whole drying system have also been analyzed.

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Pages: 2009-6

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Details

  • Original title: A sludge drying heat pump with CO2 and ammonia as natural refrigerants.
  • Record ID : 2009-2512
  • Languages: English
  • Source: Compressors 2009: 7th International Conference on Compressors and Coolants
  • Publication date: 2009/09/02

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