Improving efficiency in meat processing
By Chris Little, Director, HRS Heat Exchangers
Wednesday, 06 October, 2021
Each year Australia wastes around 7.3 million tonnes of food (equal to ~300 kg per person), which accounts for more than 5% of Australia’s greenhouse gas emissions1. Not only does this waste have significant environmental impacts, but there are economic costs as well (the government estimates food waste costs the economy $20 billion each year). Australia has set itself a target to halve food waste by 2030, and all aspects of the food chain, from farmers through to consumers, have an important role to play in reducing the nation’s food waste. The processing sector is one area where some minor changes and specifying the right equipment can lead to significant economic and environmental improvements.
Food waste costs processors money in various ways. If a product is produced (or even partially processed) and then not sold, it has incurred costs including the cost of the raw material ingredients and the energy and labour that has gone into its production. It has also prevented the production of useful product which can be sold (an opportunity cost), and there may well be disposal and treatment costs associated with getting rid of the waste product. These costs can soon add up even at low levels, and each of these factors will have both a financial and an environmental (carbon) cost, so minimising or preventing waste has huge benefits for companies and the wider community.
One easy area to target is to minimise the losses of product which occur in equipment, and in an ideal world two different techniques will be used in combination. The first is to design food processing equipment, such as tubular heat exchangers, which prevents product adhering to surfaces 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 materials without fouling. Some of these units use corrugated tube designs, but in the most demanding situations, scraped surface heat exchangers are used as the scrapers continually remove residues, preventing the build-up of potential waste material. These heat exchangers can be used for numerous processes, including heating and cooling, cooking, concentrating, pasteurising and sterilising.
This scraping action provides two advantages. Firstly, as the material being treated is kept moving and 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.
However, no matter how much you avoid product build-up during operation, equipment eventually needs to be cleaned. 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 hundreds of thousands of dollars of product can be lost each year.
Traditionally ‘pigging systems’ have been used to physically push product through key parts of the system, or water, air, or a cleaning solution is used to flush product, although all these systems have their disadvantages, such as their complexity or the potential to dilute or contaminate products.
Another option is to use a heat exchanger which can empty most of the product before the cleaning cycle commences. This is possible using the HRS R Series of heat exchangers. 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 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, removing product from the heat exchanger tubes without damaging it or changing its characteristics.
The system is particularly suitable for high-value viscous products such as meat and poultry emulsions, 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.
Where product recovery is required, it is configured vertically, 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. Due to the amount of product saved, and the fact that it is often unnecessary to install additional product recovery systems, the heat exchanger can quickly pay for itself, and in the long term can be a more economic option than alternative systems which have lower capital costs.
The unique design of the R Series also provides several other benefits, such as improved mixing (and therefore improved homogeneity and more effective heat transfer) within the product. As such they are particularly useful for high-fouling products such as meat paste and meat slurry. However, because of the increased resistance within the tube, scraped surface heat exchangers (SSHEs) can create much higher pressure drops than open tube heat exchangers. A higher pressure drop means more pressure (and therefore more energy) is required to operate the equipment.
The HRS R Series of SSHEs is designed to reduce this pressure drop, using a helical screw, which resembles an auger wrapped around the scraper bar. The key to this design is the gap between the edge of the helix and the tube surface, which provides three important benefits. Firstly, the pressure drop is reduced along the heat exchanger, particularly for difficult high-viscosity products. Not only does this reduce energy consumption, but it also helps to maintain product identity and quality. The second benefit is that the gap increases turbulence at the tube wall, helping to reduce fouling and improve mixing.
The multi-tube versions of the R Series use a single motor and gearbox, helping to reduce running and installation costs, reduce operating complexity and reduce the overall footprint. Furthermore, thanks to a unique sealing system, individual tubes can be removed for cleaning or inspection, meaning that servicing is quick and parts do not need to be sent away for rechroming. Key low-cost spares can be held onsite and replaced quickly and easily. A unique gearbox design reduces operation noise, making it suitable for working environments such as food factories, while standard features include a hygienic stainless-steel construction, and units can be fully insulated and cladded.
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