Seward Refrigeration Ltd designed, project managed and commissioned, the installation of a new pumped ammonia plant feeding a spiral freezer and transfer tunnel for a blue chip food processing manufacturer in Canada.
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 Mycom 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 Mycom 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 has been installed with a remote sump and condenser pump fitted within the compressor plantroom.