Trends in use of large scale plate freezers in Australia

According to a paper of the Australian Institute of Refrigeration, Air Conditioning and Heating (AIRAH), a simplified comparison of energy required to freeze meat for an automated air blast freezer and plate freezer, assuming a continuous production, shows a saving of 26% for the plate freezer. The main difference in the comparative energy to freeze product is related to air circulation fans. There is also the effect of the higher heat transfer rate for plate freezing, which results in a 24-hour freezing cycle for a typical meat carton compared to a 48-hour cycle in an air blast.

As a result, for a typical mid range export beef plant freezing 4,000 cartons per day the annual energy savings based on this comparison are approximately 600 MWh.

Current trends and opportunities in large plate freezer technology

While the use of plate freezers already saves a considerable amount of energy compared to other technologies such as air blast freezers, there are ways to further improve the energy efficiency. Currently, two main trends in relation to the energy efficiency improvement of plate freezers in Australia include naked block freezing and single station opening. These are both ongoing projects; however, they have been proceeding slowly at present.

• Naked block freezing: Bare product freezing allows for lower energy use, minimal packaging requirements and avoidance of plastic inclusions in the frozen product.
• Single station opening: In a single station opening unit only the station being loaded is open – all other stations remain closed with the plates in full contact with the product. The short lifting stroke in this design results in an increase in the stacking density of the freezer and leads to a smaller enclosure volume for a given product capacity.

Large refrigerant charge size for plate freezers and limitations in freezing multiple package sizes are two of the main challenges limiting the wider adoption of plate freezers. Nevertheless the industry is advancing in finding solutions:

• Refrigerant charge reduction: Compared to an air blast freezer evaporator, a plate freezer would require a large ammonia charge for the same product quantity. However, a number of heat transfer fluids are available allowing the use of a reduced ammonia charge, which is confined to the plant room and heat exchangers. The work on introducing heat transfer fluids to large-scale plate freezers continues.
• Multiple package sizes: Work on the single station opening plate freezer design has shown the possibility of adapting the design to accommodate multiple package sizes in a large-scale plate freezer. The development of plate freezers able to accommodate a range of carton sizes will make the energy and carbon reduction benefits of plate freezers available to a wider range of processors.

Large plate freezers in use since 1980s in Australia

Whilst small plate freezers have been in use extensively for decades, large plate freezers were pioneered only in early 1980s. Designed by Klaas Visser, the first large plate freezer in Australia was constructed at Tancred Brothers meat plant in Queensland. Visser was assisted by Professor Gustav Lorentzen with the plate circuit design. The installation provided the critical proof of concept experience which lead to the wide spread adoption of plate freezers by the Australian export meat industry. Australia is unique in the use of large-scale plate freezers for 27,2 kg meat cartons, typically 150 to 170 mm thickness. Currently, there are over 100 large scale plate freezers in Australia with over 15,000 kg capacity. One beef plant has ten Milmeq plate freezers, which were installed in stages between 1993 and 2009, all with the same basic design with a combined daily freezing capacity of 670,000 kg of boneless meat in 27.2 kg cartons.

DSI vertical plate freezers

The Danish company DSI, a leader in the designing and manufacturing of manually-operated and automatic plate freezers, is currently doing joint investigations in order to show the Australian meat industry the obvious benefits of freezing meat in Vertical Plate Freezers. Australian processors have shown a high degree of interest in how the European meat industry has developed automated systems. DSI has partnered with Milmeq, an international company delivering specialist capital plant equipment to food processing operations, to deliver robust vertical plate freezing technologies.