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Heated debate about high value product recovery

26 February 2018

Matt Hale suggests a way to reduce product losses during processing in heat exchangers. 

At a time when all forms of food waste is under increasing scrutiny, it is important that all parts of the food chain are as efficient as possible when it comes to waste. When processing even remotely viscous food product it is inevitable that a certain amount will adhere to surfaces, such as the inside of vessels and pipe work, or will be left in equipment after processing. There is relatively little data available on the amount of product lost during processing, but one European study in 2010 suggested that 4.1 million tonnes of food was lost during processing each year in the UK.

There are two ways to minimise product losses in equipment and, in an ideal situation, they will be used in combination. The first involves designing equipment, such as tubular heat exchangers, to prevent product adhering to the surface in the first place – keeping it flowing through the system. The second aspect is the use of dedicated systems to clean and recover product from equipment after processing and before full cleaning occurs.

Many modern heat exchangers are designed to handle viscous fluids without fouling. Some of these units use the corrugated tube designs, while other units, used in more demanding situations, use scrapers to continually remove residues from the surface of the tubes before they build up. These can be used for numerous processes, including heating and cooling, cooking, concentrating, pasteurising and sterilising.

This self-cleaning feature provides two advantages in use. Firstly, because the foodstuff being treated is kept moving it does not adhere to the tube surface losses during processing are minimised. Secondly, because a ‘fouling layer’ is not built up, the optimal thermal performance of the heat exchanger is maintained, increasing process efficiency and reducing energy use or treatment times.

No matter how good your equipment is at preventing product build-up, there will come a time when cleaning – usually in the form of cleaning-in-place (CIP) – needs to be carried out. Depending on the range of products handled and product complexity this may be required several times a day between production batches. If product remaining in equipment is ‘flushed’ through as part of cleaning procedures then it could result in a great deal of product being wasted.

Traditionally, the problem has been overcome by the use of ‘pigging systems’ to physically push product through key parts of the system or to use water or air to push product through, although all have certain disadvantages, and add complexity and the potential to dilute or contaminate products.

Another option is to use a heat exchanger, such as the HRS R series, which is capable of emptying itself of produce before the cleaning cycle commences. This range of tube-in-tube heat exchangers uses a scraper bar within each inner tube to enhance product flow, prevent fouling and minimise pressure drop. The scraper bar of the R series features a helical screw which rotates at high speed. When configured correctly, this screw can be run in reverse, effectively emptying the heat exchanger tubes of product without damaging it or changing its characteristics.

The system is suitable for use with high value viscous products such as honey, treacle, custards and creams, where any loses of product can be particularly costly.

The heat exchanger can be configured for both horizontal and vertical operation, so that gravity can also be used to help recover product from the tubes. Each unit can be supplied with one, three or six tubes and multiple units can be combined for larger installations.

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