Evaporation increases capacity for drying cheese

A novel use of evaporation using heat exchanger technology from HRS Heat Exchangers has increased drying capacity for a major European processor of cheese products.

The client takes out-of-specification cheese products from production sites across Europe and converts them into high-quality protein for use in pet food and animal feed. The cheese is pasteurised and then dried to produce a powdered additive.

When the client wanted to increase production capacity, its first thought was to install an additional dryer; an expensive and energy-intensive solution. However, as the capacity of the dryer is determined by the amount of water it can remove per hour, another way to increase overall throughput would be to reduce the water content of the cheese products before drying, so that a larger volume could be dried at one time.

The client approached HRS because of its established expertise in evaporation and concentration technology. The first step was to determine if the existing dryer would cope with a more concentrated cheese solution. HRS supplied a trial evaporation system which the client used to analyse all aspects of the revised production system, the properties of the materials and the potential results. The trial unit proved that the concept was feasible, and so HRS designed an appropriate evaporation system to sit between the existing pasteuriser and dryer.

The trials and material analyses also showed how the physical and thermal properties of the cheese change as it is heated, and the water is removed. At the beginning of the process, the product is fairly liquid with good thermal transfer characteristics, but as water is removed it becomes more solid and concentrated, with less heat transfer. To provide adequate processing, a continuous treatment process would have to be designed around the ‘worst case’ thermal characteristics at the end of the process.

It was therefore decided to adopt a batch treatment approach as overall this required a smaller heat transfer surface, less equipment, and less energy, requiring a smaller evaporator, smaller ancillaries, and less energy to run. The batch system, which employs two tanks — one of which is filled while the other is being treated — is also simpler to design and operate. Employing a two-tank system with full automation also results in a continuous operational process.

Heated cheese is a high-fouling, extremely viscous, material. Therefore, an evaporator based on the HRS Unicus Series of reciprocating scraped surface heat exchangers was supplied to prevent the build-up of cheese and burnt-on cheese residue on the tube walls of the heat exchanger. To reduce energy requirements and improve operational efficiency, the evaporator operates at a vacuum of around 200 mbar, meaning that the water in the cheese solution boils off at 60°C.

HRS supplied two complete skid-mounted systems, each of which comprised the Unicus evaporator, two tanks, pumps, controls, and connections. Each skid-mounted system can process 3.6 tonnes of cheese product per hour, increasing the total solid concentration from 34 to 45%, and increasing dryer capacity by a similar amount.

More generally, the HRS Unicus Series is widely used in dairy processing and is suitable for products such as soft cheese, creams, curds, etc. The Unicus Series has been specifically designed to provide unrivalled heat transfer with a wide range of difficult dairy products which have high fouling potential (which would limit heat transfer), but which at the same time need delicate handling to preserve fragile product integrity. A process of continual improvement means that Unicus heat exchangers are available with a wide range of scraper types, providing even more choice for applications from food pasteurisation to curd processing.

The HRS Unicus series of scraped surface heat exchangers is ideal for high fouling materials like cheese and dairy products.

The Unicus Series, which is ideal for hygienic applications, is based on traditional shell and tube heat exchangers, with the addition of a patented stainless steel scraping mechanism which is hydraulically moved back and forth within each interior tube. This movement performs two key functions. Firstly, it minimises potential fouling of the product by keeping the tube wall clean. Secondly, the movement creates turbulence within the material. Both actions help to increase heat transfer rates and together, they create a highly efficient heat transfer process ideal for viscous and high fouling materials.

Designed for hygienic food industry applications, the R Series from HRS Heat Exchangers uses a rotary scraper rod which can reach velocities of 300 rpm, providing high levels of shear and mixing at the heat transfer surface which dramatically increases heat transfer rates. This makes it particularly suitable for challenging heat transfer applications, such as those where the product has the potential to crystallise during processing or where aeration is required.

The scraper rod features both a helical mixing spiral (which reduces the pressure drop in the tube) and a series of scraper blades. Together these provide a continuous scraping action which mixes highly viscous products and reduces fouling. The unique design enables high viscosity products to be pumped with reduced back pressure and lower energy use, in a compact unit which features a much smaller footprint than traditional heat exchangers for similar applications.

A unique gearbox design not only reduces noise, but also allows multiple tubes to be fitted inside a single shell from a single electrical drive, further increasing the available heat transfer area within the same shell footprint and aiding maintenance. Cleaning and maintenance are further improved by the unique sealing system used in the R Series which allows individual tubes to be removed for easy servicing and replacement if necessary.

Thanks to its helical spiral, in many applications the R Series can also be run in reverse, enabling much valuable product to be recovered before routine cleaning-in-place or product change-over without the need for additional pigging or flushing systems. Not only does this reduce costs and complexity, but saving product adds dollars to the bottom line.

Chris Little, Director for HRS Heat Exchangers

About HRS Heat Exchangers
Located in Melbourne, HRS Heat Exchangers is part of the HRS Group which operates at the forefront of thermal technology, offering innovative heat transfer solutions worldwide across a diverse range of industries. With almost 40 years’ experience in the food and drink sector, specialising in the design and manufacture of an extensive range of turnkey systems and components, incorporating our corrugated tubular and scraped surface heat exchanger technology, HRS units are compliant with global design and industry standards. HRS has a network of offices throughout the world: Australia, New Zealand, UK, Spain, USA, Malaysia and India; with manufacturing plants in the UK, India and Spain.

For further information, please email: info@anz.hrs-he.com or tel: (Australia Office): +61 3 9489 1866 or (New Zealand Office): +64 9 889 6045.