Sammendrag
The application of a high temperature heat pump for superheated steam drying (SSD) process was analyzed. The SSD chamber processes 10000 kg h-1 of product into dried pet food. Two different systems (“open” and “closed”), which use water as a refrigerant, were evaluated. Both systems use energy from the surplus steam, which is formed due to evaporation of moisture during drying. It was concluded that compression in three stages is required to achieve temperature of steam at 170.0 °C, when radial turbo compressors were used to fulfill the volumetric flow demand. The most efficient system is the “open” system, which provides a coefficient of performance (COP) of steam generation at 3.84. Drying efficiency (DE) is calculated at 0.19 kWh kg-1 of evaporated water. The system provides hot tap water (371.0 kW). The “open” system provides annual saving of 7.45 mln. NOK. Also low investment cost of compressor make the system beneficial