As part of this Institute of Refrigeration Ireland (IRI) award-winning project, Powertech Refrigeration were approached with the view of designing and installing an ammonia refrigeration system that would incorporate existing plant equipment to introduce stability and reliability, whilst also expanding the overall capacity of the system.
Through early-stage discussions Powertech identified several key areas for adding value to the design, namely changing from the proposed pumped ammonia system to a critically charged ammonia system; thus, allowing for the quantity of refrigerant within the system to be greatly reduced.
The new system would utilise a bank of two new Sabroe screw compressors, each combining to produce a cooling capacity of 1600kW, alongside two existing Sabroe reciprocating compressors with each pair serving a Vahterus plate heat exchanger. The two plate heat exchangers would then combine to chill production water from +7°C to +2°C within a single 80m3 weir tank.
The overall efficiency of the system was improved through the introduction of a de-super heater on the common ammonia discharge to pre-heat water going to the boilers of another system, allowing for reduced condenser load and fossil fuel usage, whilst smart variable speed KSB pumps were also used to optimise the pumped water efficiency in conjunction with the cycling of lead and follower pumps to add both longevity and control to the system.
