Seward Refrigeration have designed a new pumped ammonia plant feeding a spiral freezer currently being installed for a food processing site In Canada. The project is being project managed by Seward Refrigeration over the coming months including commissioning on completion.
The spiral freezer is designed to freeze five metric tonnes of product per hour, with the product entering the spiral freezer at +90°C and is frozen down to -18°C. The spiral freezer is designed to operate continuously for a 21 day period and to achieve this there are five sequential defrosting ammonia evaporators each with a duty of 418 kW, operating with pumped ammonia at -32°C. Four of the coils are continually in use with the fifth coil defrosting with hot gas.
A split surge drum will provide -32/-5°C ammonia. Connected to the -32°C dry suction line, are two open flash economised screw compressors each operating at 3600 RPM and directly driven by 530 kW, 4100 volt high-efficiency inverter operated motors. The -5°C surge drum section offers liquid sub cooling and connection onto the new retrograde product drier and 0°C transfer tunnel. The compressor on this section is A screw compressor operating at 3600 RPM and directly driven by a 350 kW, 4100 volt high-efficiency inverter operated motor.
A high-efficiency condenser suitable for operation in the extreme winter conditions of Canada will be installed with a remote sump and condenser pump fitted within the compressor plantroom.