Ammonia / Glycol Heat Pump - Meat packaging facility

Our client operates a meat packing facility and we were awarded the installation contract in 2014 to install a central ammonia / glycol system. During the summer of 2019 we were then awarded the installation contract to install and fully commission a brand new ammonia / glycol heat pump system, providing cooling for a factory extension, whilst heating 150m3 of mains water up to +65°c for sites wash down periods.

We proposed and installed a Grasso RedAstrum, low charge ammonia, packaged glycol chiller including high pressure screw compressor, equipped with an inverter driven 280kw motor. The pack provides 603kw of heating and 390kw of cooling capacity, supplying mono propylene glycol at -2°c / +2°c return on the cooling circuit. The package came complete with OMNI controller, which is networked back to the main refrigeration plant Trend SCADA system.

The -2°c / +2°c pressurised glycol cooling circuit is fed from a heat exchanger on the RedAstrum package, supplying mono propylene glycol at 25.3 L/s at 2.5 bar head (Run and standby pumps). The cooling circuit is linked to the existing central ammonia plants, high temperature (-2°c / +2°c return)  glycol circuit to provide the heat pump with continuous load when cooling in the new factory extension is either temperature satisfied, or surplus to requirements. The chilled glycol circuit feeds the following main plant items;

  • 2 x 181kw Lennox air handling units providing pressurised fresh air at +10°c for the new factory extension. Each requiring a flow rate of 11.68l/s (Glycol -2°c / +2°c return) Both AHU’s come complete with integral glycol heating coils.
  • 3 off glycol, low velocity, dual discharge evaporators above a mezzanine area providing conditioned air at +18°c.
  • 1 off glycol buffer tank (Pressurised)
  • 1 x temperation loop / pumping station supplying glycol at 5.6L/s onto a plate heat exchanger. The chilled water secondary side of the heat exchanger serves a buffer tank, complete with integral weir plate (Warm / cold sides). Chilled water at +5°c is supplied from three pumps (cold side) each supplying chilled water at 1.24L/s at 5.0 bar head feeding packing machines and Vacuum pumps internally to three locations throughout the facility.

The heating circuit (Heat pump), consists of a pressurised primary glycol circuit, including Run and standby pumps, supplying glycol at +70°c / +40°c return at 5.25L/s, a large buffer vessel, and 1 x plate heat exchanger. If heating on the secondary water side of the circuit is surplus to requirements or temperature satisfied, a three port diverting valve, diverts the hot glycol fluid to a 615kw JAEGGI Hybrid Blue adiabatic cooler to reject the heat.The integral PLC control monitors the fluid outlet temperature and ambient conditions. From the collected information, the optimum combination of water feed rate and fan speed are determined and controlled. The performance is assured by the integral PLC control system and variable speed fans, with each operating point being determined individually with only the necessary amount of pre-cooling water used, thus operating costs are kept to a minimum.

The secondary heating circuit (Mains water) fed from the glycol heat exchanger consists of a large buffer tank providing 150m3 of water at +65°c. The hot water generated from the heat pump provides the factory with heated water for wash down periods. This efficient process not only provides adequate cooling capacity for the new extension, it has provided significant energy savings over our customers conventional boiler system, which is still in situ for standby purposes only.

Another advantage of the system we installed is after the wash down period. Whilst the factory take advantage of the heat generated from the heat pump for their wash down, when this process has been completed the air handling units are programmed to dry out the area. This is achieved via a detailed control strategy, both cooling and heating the space via the AHU’s cooling & heating coils, drying the area out very quickly.

All new control panels were fitted with Trend controllers and HMI screens networked back to the main Trend SCADA system. The system is accessible from our offices for monitoring and fault-finding purposes.

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