Industrial Heat Pumps

 

Pasteurization

For pasteurization a product needs to be heated above 70 °C. Afterwards the product is cooled down. The product temperature thus varies from cold before pasteurization to hot during pasteurization and back to cold again after pasteurization. In most pasteurization processes heat exchange between the cold and hot product flow is already implemented. The cold product before pasteurization is used to pre-cool the product directly after pasteurization, or looking at it the other way around: the hot product is used to pre-heat the cold product. In addition to this extra heating and cooling are needed for pasteurization. This is normally provided by, for example, steam injection and a flow of chilled water. A heat pump might be the ideal solution to extract heat from the product that needs to be cooled and supply this heat at a higher temperature to the product that needs to reach pasteurization temperature.

Conventional pasteurizer

The figure below shows an example of a well-known pasteurization process. In this case, milk will be pasteurized. Through pasteurization, organisms are killed which results in a longer durability of the milk. The example shows milk that is brought in at 10 °C and then preheated to 62 °C degrees with regenerative heat from pasteurized milk that is cooled down. After preheating the milk is heated to 72 °C with a hot water circuit powered by, for example, steam. After this desired pasteurization temperature is reached, milk needs to be cooled down back to 10 °C. At first cooling is supplied by regeneration with fresh milk. As a result the milk is cooled down to a temperature of 20 °C. To reach the desired milk temperature of 10 °C, a cold water circuit is used. This circuit is cooled with the use of mechanical cooling (a refrigeration system). The mechanical cooling system releases waste heat at its condenser site.
pasteurisation conventional EN

Pasteurization with the use of an add-on heat pump

Application of an add-on heat pump enables the opportunity to reuse the waste heat from the mechanical cooling system in the pasteurization process. If the add-on heat pump is applied, no more steam is needed for the pasteurization process. How this is realized is shown in the figure below. The principle of operation: compressed gasses from the refrigeration installation have a condensation temperature of 25 to 30 °C. The heat pump compressor increases the pressure of the gaseous refrigerant further due to which the condensation temperature becomes higher than 80 °C. Heating for pasteurization can thus be supplied by the heat released at the condenser of the refrigeration system. After condensation of the refrigerant in the refrigeration system, its pressure is reduced inside an expansion element after which the refrigerant is sent back to the original cooling cycle.
pasteurisation add-on heat pump EN

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