Difference between revisions of "Pre-heating in dairies"

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A typical Diagram of the Boiler Feed-water Preheating process:  
 
A typical Diagram of the Boiler Feed-water Preheating process:  
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[[File:Boiler_Feed-water_Preheating_Process.jpg]]
 
[[File:Boiler_Feed-water_Preheating_Process.jpg]]
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|Temperature range (°C)
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|Boiler feed water preheating
 
|Boiler feed water preheating

Revision as of 17:11, 12 March 2015

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Description

The efficiency of a boiler’s steam production may be improved by increasing the efficiency of heat transfer by the heat carrying medium. The feed-water absorbs the heat produced from combustion and steam is produced. The higher the temperature of the feed-water when it enters the boiler, the larger quantities of high quality steam will be produced, because little energy is lost to increase the feed-water temperature from ambient to evaporation conditions (EU, 2005).

Usually the boiler feed water preheating is performed by Indirect Heating using Heat Exchanger Tanks and Solar collectors depending on the requirement. Evacuated Tube Collectors (ETC) to heat the feedwater from 25 deg C to 70 deg C (avg.) are better than Flat plate collectors because of its lower cost, No scalign issues and ability to use diffusion radiation too for heating the water.


Applications

In the food industry sector, steam is generated using boilers with working pressures up to about 30bar. For power generation by steam turbines, higher pressures are needed. Steam is used for the sterilization of pipes and pipelines. Another application is UHT treatment with direct steam injection. Sometimes steam injection is used for heating the product or for adjusting the water content of the raw material. In all these cases, more or less direct contact between steam and the food product is possible, so drinking water quality is required. The quality of the boiler water is controlled by the quality of the boiler feed-water (EU, 2005).


Flowsheet

A typical Diagram of the Boiler Feed-water Preheating process:


Boiler Feed-water Preheating Process.jpg


Typical parameters of the process

Typical process Temperature range (°C) Collector based on temperature level
Boiler feed water preheating < 150 Evacuated Tube Collector / Flat plate

  • Applications

Pre-heating is typically used before further processing (e.g separation, culture adding, pasteurization, sterilization, evaporation) of intermediate milk products.



Example flowsheet


Pre-heating in dairies.jpg


Literature: Guide to Energy Efficiency Opportunities in the Dairy Processing Industry, National Dairy Council of Canada, June, 1997


Typical parameters of the process
Milk products Temperature [°C] Pressure (bar) Heat ransfer medium Residence Time Details Literature
Ice cream 30-40 BAT in Food, Drink and Milk Industries, June 2005 and Dairy science and technology, University of Guelph


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