Pre-heating in food industry
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1. OBJECTIVE
The objective of pre-heating is to increase the energy content of a food stream before that can be further processed.
2. FIELD OF APPLICATION
Pre-heating can be applied to many food industries, e.g. in dairies for pre-heating milk before it’s processed to other milk products, in breweries for pre-heating the wort before boiling, in industries for pre-heating canned or bottled food before sterilization, in fruit and vegetable industries for heating up fruits and vegetables before blanching (BAT in the Food, Drink and Milk Industries, June 2005).
3. DESCRIPTION OF TECHNIQUES, METHODS AND EQUIPMENT
Pre-heating can be accomplished by either direct or indirect heat transfer from an auxiliary pre-heating agent, such as water or steam. In the case of liquid food streams, such as milk, pre-heating is accomplished by indirect heat transfer through conduction by the walls of a heat exchanger. In the case of bottled or canned food, pre-heating is also accomplished by indirect heat transfer through the walls of the container. In the case of fruit and vegetables or wort, pre-heating is accomplished by direct heat transfer, because the auxiliary feed (water or steam) is in direct contact with the food stream. In this case, high quality auxiliary feed should be used with the least microbiological load (BAT in the Food, Drink and Milk Industries, June 2005).
4. COMPETITIVE TECHNOLOGIES AND ENERGY SAVING POTENTIALS
- a) Changes in the process
No information is available.
- b) Changes in the energy distribution system
- Heat recovery from waste streams: (BAT in the Food, Drink and Milk Industries, June 2005)
- Pre-heating is accomplished in temperatures of approximate maximum level 80°C. Waste streams which are produced during the process and contain adequate thermal content can be recycled and re-used for preheating food streams. A system of heat exchangers will be used to allow the heat transfer between the waste streams and the food.
- Re-use of condensates: (BAT in the Food, Drink and Milk Industries, June 2005)
- Condensates produced during evaporation may be re-used in the process depending on their quality, e.g. content of organic and/or inorganic matter and SS. Steam condensate may be used for pre-heating. This leads to recovery of a considerable amount of heat and minimises the use of boiler steam. If condensate is reused this can be optimised by maximising the condensate return and avoiding losses of flash steam from condensate return.
- c) Changes in the heat supply system
No information is available.
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