Briefs: Sustainable fishery in Namibia

Since November 2009, Hangana Seafood has a new pre-sorting facility in Walvis Bay harbour, Namibia, which uses ammonia as a refrigerant. The 2800 m² sorting facility has a 0°C chill room for holding unsorted fish, two 16°C temperature-controlled sorting and grading rooms (one to separate hack from by-catch, the other to sort the by-catch), a flake-ice maker, a 100-tonne ice bunker, an ice raking system and a pneumatic ice conveyor system to discharge flake ice directly into the fishing vessels, a refrigeration machine room, and 2 extra blast freezers for the by-catch, among other equipment. The ammonia refrigeration plant has two Grasso screw compressors with 220 kW motors, operating at a suction temperature of -36°C and a single Grasso reciprocating compressor with a 90 kW motor operating at -8°C. A thermosiphon oil cooling system lowers the energy consumption of the compressors and allow the system to operate with a floating discharge pressure, further increasing system COP. Ammonia is used as a secondary refrigerant in the blower coils of the blast freezers, chiller holding rooms and coils of the ice bunker. It is also used in 3 surge drums, one at -36°C for the blast freezers, -8°C for the chill cold store and 1°C for the plate heat exchangers. Water cooled to 4°C thanks to an ammonia-to-water heat exchanger is used as a secondary refrigerant in the processing areas, which are equipped with a controlled atmosphere system with filtered and pressurized 100% outside air. Source: The Cold Link, March/April 2010