(Heat Recovery System)
Headquartered in Naas, Co Kildare, Green Isle Foods is part of Northern Foods Frozen division. It employs over 1,300 people with operations in Naas, Portumna, Longford, and Gurteen, and produces a range of branded frozen foods. The Green Isle Food (Gurteen) plant in Sligo is the primary processing plant for the Donegal Catch range of products.
Fresh filleted fish are battered, cooked and blast frozen in a continuous production process in Gurteen. This processing is highly energy intensive and places large demands on hot water and refrigeration services. In 2009 a review of the processes identified the need to replace the refrigeration condenser. There were also concerns about the efficiency of the existing hot water generating system. Comparing hot water costs to other sister plants they realised that it was costing twice as much to produce hot water. A project scoping document for an overhaul of both refrigeration and hot water production services was prepared and a delivery plan presented to board.The upgrade received full backing to proceed to implementation.
The solution that was implemented included installing a de-super heater on the hot gas discharge pipe to generate hot water from the recovered heat. The benefit was twofold in that it produced “free” hot water but also reduced the load on the refrigeration condensers yielding some electricity savings. The hot water generation system was improved with the installation of a low pressure condensing boiler. Both systems were further enhanced with the installation of a more efficient refrigeration condenser and a modified hot water storage system to ensure maximum use of hot water generated by the heat recovery system. A modern computerised controls package was developed and installed to manage the system.
Electricity savings at the high stage side of the refrigeration plant were estimated to be 15%. A meter on LPG line for hot water production indicated that consumption was reduced by 72% in the first year of operation.
A well engineered project which required a good business case for senior management support. This project involved the rationalising of the steam and refrigeration system. The project included the installation of a high efficiency condensing hot water boiler, a heat exchanger on the hot refrigerant gas discharge pipe, a larger surface area condenser and installing float head pressure control to the refrigeration system in accordance with the local ambient conditions demanded. The project to date has reduced total site energy consumption by 30%, with greater savings to be achieved when the floating pressure head control is in full operation in the winter time. The project is being replicated on other Green Isle sites.