How heat exchangers can save on food waste and costs
21 Dec 2017
When processing viscous food product, it is inevitable that an amount will adhere to surfaces, such as the inside of vessels and pipe work, or be left in equipment after processing, explains Matt Hale.
The potential value of this lost product can soon add up, especially when handling large quantities of valuable products such as honey, syrups and purées.
One 2010 study suggested the UK figure amounted to 4.1 million tonnes. However, EU analysis has been concerned with calculating environmental impact rather than the economic costs to businesses.
The good news is that the processing and packaging part of the food chain is already the most efficient, accounting for just 4% of overall losses, according to the UN Food and Agriculture Organisation (FAO).
Management processes and equipment design are the two biggest tools food manufactures have at their disposal: Since 2009, PepsiCo has reduced food losses at its UK sites by 20% as part of a wider initiative spearheaded by the IGD.
Management processes and equipment design are the two biggest tools food manufactures have at their disposal: Since 2009, PepsiCo has reduced food losses at its UK sites by 20%
There are two ways of minimising such losses and ideally they will be used in combination. Firstly, designing equipment (such as tubular heat exchangers0 that prevents product adhering to the surface, keeping it flowing through the system. Second, using 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 use corrugated tube designs, others employed in more demanding situations use scrapers to continually remove residues from the surface of tube. These heat exchangers can be used for numerous processes, including heating and cooling, cooking, concentrating, pasteurising and sterilising.
Self-cleaning provides two advantages: As the foodstuff being treated is kept moving and does not adhere to the tube surface, losses during processing are minimised. Also, 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.
There will come a time when cleaning, usually in the form of cleaning-in-place (CIP), is required. Depending on the range of products handled and product complexity this may be necessary several times a day between production batches. If product remaining is ‘flushed’ through as part of cleaning procedures, then hundreds of thousands of pounds of product could be lost annually.
Traditionally the problem has been overcome by the use of ‘pigging’ systems that physically push product or use water or air through key parts of the system – but these involve added complexity and the potential to dilute or contaminate products.
Another option is a heat exchanger capable of emptying itself of produce before the cleaning cycle. This is possible with the HRS R Series of tube-in-tube heat exchangers that use a scraper bar within each inner tube to enhance product flow, prevent fouling and minimise pressure drop.
The unique feature of the R Series is that the scraper bar 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 particularly suitable for high value viscous products such as honey, treacle, custards and creams, where any loses of product can be economically important. The R Series can be emptied of the majority of product without the need for any additional pumps or pressure systems. This provides advantages in terms of both capital and running costs.
Matt Hale is international sales & marketing director, HRS Heat Exchangers
