COMPRESSORS


Three liquid cooling systems individually employ a Bitzer OSKA95103-K ammonia screw compressor, each delivering 1,100kW. The fourth system is equipped with two Bitzer OSKA8591-K ammonia screw compressors, each delivering 500kW, with a high performance OAHC oil separator. This latter plant has been optimised to cover periods of part-load demand, particularly at the weekend when production is much reduced. Each screw compressor is equipped with its own frequency inverter, with mains operation ranging from 30 Hz to 70 Hz to precisely match output to load. To further enhance efficiency, the systems feature an economiser, while the Alfa Laval plate heat exchangers used in the glycol system operate with an ammonia thermosiphon system.


Cooling is distributed around the factory via a liquid coolant circuit made of welded stainless steel pipe, which contains some 85,000ltrs of coolant (Coracon WT EKO F-14, –8/–4°C). An automatic pressure monitoring system with refill ensures additional safety.


To further enhance energy efficiency, waste heat from the refrigeration system is used to defrost the air coolers, as well as heat and dry the factory floors after cleaning. Waste heat that cannot be used – particularly in summer – is discharged via a heat exchanger.


In addition to the ammonia systems, two CO2 refrigeration plants are used to meet the facility’s


low temperature requirements.


One uses two Bitzer 4CSL-12K compressors operating on twin circuits to produce flake ice. This brine-cooled, subcritical CO2


system uses


liquid coolant from the distribution grid in the first stage.


A second CO2 refrigeration system generates


cooling for a low temperature storage room. BITZER reciprocating compressors are also used in the compound system – three 2FSL-4K compressors with a combined cooling capacity of 75 kW.


Heat rejection is handled by four V-shaped stainless steel condensers and a heat exchanger with EC fan motors installed on the roof. Three of the units are equipped with a water spray system to increase capacity, while one unit has an additional adiabatic system to extend headroom and further increase efficiency. To fine-tune control and optimise performance, the air coolers have two-way volume flow control valves with integrated Delta T control and adaptive, electronic return temperature limit. The cooling capacity required is supplied via the valve and bus system. Two large displays at the facility show detailed technical information on refrigeration,


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distribution circuit and evaporators, as well as wiring diagrams, key figures, parameters and alarm notifications. This ensures that service staff and onsite technicians have a clear, real-time view of operating conditions and system status at all times.


The detailed read-out is also available online to the factory’s monitoring specialists, located 250 km away, enabling issues to resolved remotely, eliminating the need for on-site visits. If a more serious problem occurs requiring intervention at the factory, the refrigeration plant has sufficient resilience built in to maintain critical cooling until investigations have been carried out and the situation remedied. Overall, we believe high performance, high efficiency ammonia systems offer a highly attractive zero-GWP solution for industrial and large commercial applications. Our range of factory-built Ammonia Compressor Packs (ACP) have the added benefits of factory-controlled production, and modular plug-and-play design for ease and speed of installation and servicing. With a modern, ultra-reliable system design and careful application, this long-established refrigerant offers a solution to one of the most pressing environmental challenges of our time.


X www.bitzer.de/gb/en/ www.acr-news.com • November 2021 23


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