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Gourmet Gardens

With their new herb processing factory at Palmwoods, Gourmet Garden wanted to explore how far they could go to achieve new benchmarks in Australia for environmentally sustainable development and it was ISECO’s task to come up with green options for refrigeration.

The factory comprises a series of medium temperature process and chiller rooms operating at design temperature in the range of 4C to 18C and one medium size coldstore with a design temperature of -25C.

ISECO Consulting Services were engaged to investigate and design a refrigeration system to address these issues, such as minimising energy consumption, reducing greenhouse gas emissions, minimising water consumption and eliminating trade wastes i.e. water treatment chemicals.

ISECO investigated the latest technologies available and how these could be applied.

Firstly, a survey all the different refrigerants available with natural refrigerants like ammonia and CO2, all the Freon and the Freon substitutes as well as a new azeotropic refrigerant blend of hydrocarbon and ammonia. The azeotropic blend was too new and Gourmet had stipulated that they did not want to use any Freon because of the ozone depletion potential and unfavourable global warming potential. Eventually, ammonia and CO2 were the preferred options, both being natural refrigerants that are readily available with system properties that provide very good energy efficiencies.

The next step was to decide what kind of plant best suited the factory, taking into account its size and future expansion.

From the energy efficiency perspective, a two-stage ammonia system was considered along with two-stage and single stage ammonia- CO2 cascade systems and the annual expected energy costs compared. The ammonia/ CO2 cascade system provided the best solution with its use of glycol as a secondary refrigerant. The glycol – a mix of anti-freeze and water, is used to transport cooling to occupied areas in the factory. Due to ammonia’s toxicity it was placed away from workers for safety reasons. Ammonia is contained in the refrigeration plant room and CO2 is used in the freezer store. Ammonia was chosen because its ozone depletion and global warning depletion potentials are zero.

The low temperature CO2 freezer system is direct expansion, and at nearly 100kWR capacity it is one of the largest CO2 direct expansion plants built.

The heat rejection equipment uses Dricon condensers, which provides savings in water consumption of 70% over equivalent cooling towers or evaporative condensers while not compromising the energy efficiency of the plant.

Also the plant incorporates a heat recovery system, where high quality heat is continuously recovered from the refrigeration plant to preheat the hot water services for the factory.

Queensland Company, Scantec Refrigeration Technologies were chosen for the refrigeration contract. Site installation commenced in September 06 and the plant was successfully commissioned in early December.