9800kw Ammonia / Glycol plant - new frozen potato production facility

Our client is the world's largest manufacturer of frozen potato products and their existing production facility on England’s North Sea Coast was antiquated, and a major investment was necessary.

Seward Refrigeration Ltd were awarded the installation contract to install and commission a new multi-megawatt, standalone ammonia system to provide freezing and cooling duty for our customers new production facility.

The first phase of the project was to safely decommission the existing ammonia cold store refrigeration systems. Once the cold stores achieved ambient temperature the building work then commenced ready for the next phase of the project.

The scope of works for the new production facility included;

• 2 x 18 ton/hour IQF tunnel freezers
• 2 x IQF tunnel freezer refrigerated precooled sections.
• 1 x chilled glycol circuit (Coolflow DTX) feeding the batter system, Cryolator, Chilled Water & glycol evaporators.
• 1 x (ATL) Auto truck loading bay area (-18°C)
• 1 x Cold store (-18°C)
• 1 x 5 ton/hour spiral freezer (Future)
• 1 x Weighing deck area (+5°C)
• 1 x Manta deck area (+5°C)
• 1 x Coldstore outlet area (+5°C)

The design of the new plant installed caters for 4 x independent temperature zones based on;

• No1 18 tonne tunnel freezer - Operating between -28/-32°C SST (Total duty 2440 kW) Including sequential hot gas defrost load. (Two single stage economised ammonia screw compressors)
• No2 18 tonne tunnel freezer - Operating between -28/-32°C SST (Total duty 2440 Kw) Including sequential hot gas defrost load. (Two single stage economised ammonia screw compressors)
• Coldstore, ATL despatch bay and future roast product spiral freezer system - Operating between -28/-32°C SST. (total duty 945 kW) including defrost load. (One single stage economised ammonia screw compressor)
• Glycol system required for the batter cooling, weighing deck area, Manta room and Freezer outlet area – Operating at -11°C SST. (Total duty 850 kW) One single stage ammonia screw compressor.
• High temperature system required for liquid subcooling, No1 & 2 IQF tunnel freezer refrigerated precooled sections, sequential hot gas defrost load - Operating at -1°C SST. (Total duty 3062 kW) One single stage ammonia screw compressor.

Total plant duty – 9,737kw

The main plant items installed for the new refrigeration system, included;

• 5 x Mycom N280JL-VE economised screw compressors packs, inverter operated.
• 1 x Mycom N280JL-V screw compressor, inverter operated.
• 1 x Mycom N220JM-V screw compressor, inverter operated.
• 5 x Evapco ATC-935E high efficiency silent mode induced draft condensers. Wet bulb temperature +21°c, condensing temperature +30°c.
• 1 x Evapco EWSA-144-24J closed circuit glycol cooling tower for the screw compressors oil cooling system.
• 1 x closed flash flooded ammonia shell and tube economiser installed within the -1°C liquid ammonia supply line from the -1°C surge drum to the -32°C surge drum(s).
• 2 x IQF freezer, -32°C packaged surge drums, each complete with three inverter driven HRP liquid pumps, isolation valves, motorised fail safe pump suction down leg ball valve, DPRV, stand pipe, oil recovery vessel, high level cut-out switch, DPRV, level probe and isolation valves.
• 1 x satellite cold storage -32°C packaged surge drum complete with three inverter driven HRP liquid pumps, isolation valves, motorised fail safe pump suction down leg ball valve, DPRV, stand pipe, oil recovery vessel, high level cutout switch, DPRV, level probe and isolation valves.
• 1 x high temperature -1°C packaged surge drum complete with three inverter driven HRP liquid pumps, isolation valves, motorised fail safe pump suction down leg ball valve, DPRV, stand pipe, oil recovery vessel, high level cutout switch, DPRV, level probe and isolation valves.
• 5 x Witt HR4 high side floats, installed to the underside of the condensers platform at high level.
• 4 x ceiling mounted, wide fin ammonia evaporators for the new ATL dispatch bay, operating at -18°C.
• 3 x ceiling mounted Coldstore evaporators, operating at -18°C.
• 1 x flooded Vahterus plate in shell ammonia/ glycol heat exchanger, supplying chilled glycol to the Cryolator, potable water skid, weighing deck area evaporators, Manta operating room and Freezer outlet area coolers.
• Each of the two chilled glycol systems was installed with remote vertical type 304 stainless steel glycol buffer tanks complete with run and standby glycol pumps / valve stations.
• 4 x ceiling mounted coolers feeding the weighing deck area. (Coolflow DTX)
• 2 x ceiling mounted coolers feeding the Manta area. (Coolflow DTX)
• 2 x ceiling mounted coolers feeding the Freezer outlet area. (Coolflow DTX)

Production equipment details

New IQF Tunnel Freezer No1 - The new tunnel freezer was designed for an operating ammonia temperature of -28/-32°C, providing a total duty of 2159 kW, and fitted with seven double mounted top feed bottom outlet connected coils. All of the coolers receive pumped ammonia from the new surge drum at -32°C with a pumping ratio at 5:1. The valve stations were installed within the access passageway between the two freezers, including extract ventilation.

New IQF Tunnel Freezer No1 Refrigerated Precooled Section - The new tunnel freezer precooled section is designed for an operating ammonia temperature of -1°C, providing a total duty of 925 kW and fitted with one double mounted top feed, bottom outlet connected stainless steel coolers. The coolers receive pumped ammonia from the new surge drum at -1°C with a pumping ratio at 5:1. The valve stations were installed within the access passageway between the two freezers, including extract ventilation.

New IQF Tunnel Freezer No2 - The new tunnel freezer was designed for an operating ammonia temperature of -28/-32°C, providing a total duty of 2159 kW, and fitted with seven double mounted top feed bottom outlet connected coils. All of the coolers receive pumped ammonia from the new surge drum at -32°C with a pumping ratio at 5:1. The valve stations were installed within the access passageway between the two freezers, including extract ventilation. To provide the duty, two Mycom single stage, economised ammonia screw compressors were installed operating between -28/-32°C (Total duty 2440 kW) Including sequential hot gas defrost load)

New IQF Tunnel Freezer No2 Refrigerated Precooled Section - The new tunnel freezer precooled section is designed for an operating ammonia temperature of -1°C, providing a total duty of 925 kW and fitted with one double mounted top feed, bottom outlet connected stainless steel coolers. The coolers receive pumped ammonia from the new surge drum at -1°C with a pumping ratio at 5:1. The valve stations were installed within the access passageway between the two freezers, including extract ventilation.

Coldstore - Three 134kw ceiling mounted, hot gas defrosting evaporators were installed in part of the old existing cold store, selected based on an high infiltration load and minimum fin spacing at 10 mm providing -18°C operating temperature.

ATL Dispatch Bay - Four 60kw ceiling mounted, hot gas defrosting coolers were installed for the new Auto Truck Loading Bay, selected based on an high infiltration load and minimum fin spacing at 10 mm providing -18°C operating temperature.

Batter Chilling and Glycol Air Coolers - One 850kw flooded Vahterus plate in shell ammonia/ CoolFlow DTX glycol heat exchanger, supplying chilled glycol to the Cryolator, potable water skid, weighing deck area evaporators, Manta operating room and Freezer outlet area coolers. The Vahterus heat exchanger is fitted with a twin system that incorporates two plates into one common shell operating on the flooded principle with ammonia evaporating at -11°C. The 0°C secondary glycol side provides a duty of 620 kW and the -6°C side provides a duty of 180 kW

Both glycol systems consisted of hot and cold side buffer tanks, vertical type with internal weir plate. The circuits include independent glycol pumps for the potable water heat exchanger, glycol coolers, recirculating pumps and valve stations.

Future - Roast Product Spiral Freezer - This will be a self-contained spiral freezer and will be connected onto the -32°C satellite packaged surge drum in the future.

Conclusion

To conclude the installation of the new refrigeration plant took just under two years to complete. The two new cold stores were commissioned first to allow product to be stored in dispatch at the required temperatures. Once the new system was partly commissioned the existing tunnel freezers were switched off individually and product was diverted to the new freezer tunnels.

When each of the new tunnel freezers were fully commissioned and in operation and the client was producing the required quantity of product, we then proceeded to decommission each of the existing tunnel freezers. In total including the existing cold stores, 29,000 KG of ammonia was safely removed from site, with the new refrigeration system being charged with 15,900Kg of ammonia in total.

The new refrigeration system is controlled via a state of the art SCADA system. Graphics and instrumentation (pressure and temperatures) are all visible on the screens which makes it ideal for site and our service engineers to diagnose issues with the system. The refrigeration plant is fully automated and requires little involvement from sites engineers to operate the system. Seward Refrigeration completed the control narrative and fully commissioned the new plant alongside software engineers.