Not all products are premium products and need to be treated in a direct UHT system. You have the possibility to switch between direct and indirect modes to improve energy efficiency when you choose the multimode option for the Tetra Pak® Direct UHT unit.
Direct vs indirect
“Though direct UHT technology is a star for giving the best product quality and greatest flexibility in production, as far as energy consumption goes, indirect UHT technology is better,” admits Magnus Ohlson, Commercial Leader Dairy Ambient at Tetra Pak. He has been closely involved in Tetra Pak’s biggest development in recent years in its heating platform, namely the launch of the Tetra Pak Direct UHT unit. The new unit is available with variable capacity and can be designed to run at rates from 2,000 l/h up to a mega 45,000 l/h. Magnus goes on to make a general recommendation: “If you don’t have a good reason for choosing direct UHT, choose indirect UHT instead.”
Chocolate milk is one example. Neither the colour nor the taste of most chocolate milks are sensitive to heat treatment and these milk products can therefore be processed with very good results in an indirect UHT unit and at a lower operational cost. The figures speak for themselves. The Tetra Pak Direct UHT unit has an average steam consumption of 125 kg at 7 bar per 1,000 litres of product whereas the same figure for an indirect UHT unit is just 30 kg.
Despite these figures, there are still good reasons for many companies to choose direct UHT. Indeed, about one out of every three UHT units sold by Tetra Pak is a direct system.
“Whenever a premium UHT product is required where high quality counts, direct UHT is the first choice,” says Magnus Ohlson. This explains why direct UHT remains a popular choice not just in the dairy industry but for plant-based beverages as well.
Best of both worlds
There are benefits with both systems. Magnus Ohlson has an interesting offer for those who can’t decide between a direct or indirect system – choose both in one unit! It may represent a bigger capital investment because you buy more components but you get greater flexibility and the investment can pay for itself in the long term.
One of the many options with the Tetra Pak Direct UHT unit is a combined heating solution called multimode where direct and indirect UHT are incorporated into the same unit. In this way, you can switch from one UHT system to the other or combine them both, depending on the product. This enables you to maximize the energy efficiency of your plant.
“Multimode is for when you want to have a lot of different choices within one unit between heat loads contra production costs,” Magnus Ohlson explains. “There is a balance between how much heat load your product requires or tolerates and the production costs. For some products, you want to have the least possible heat load and then direct UHT is just right. For other products, they require or tolerate more heat load, then indirect UHT would be the right choice.”
“At the other end of the spectrum, you have to consider the production costs and the energy consumption,” he continues. “Part of your portfolio may have greater margins and a lot of added value so you can charge a premium, whereas another part of your portfolio has slimmer margins so you would prefer to have a more cost-effective production method.”
The multimode option gives the customer the best of both worlds – either direct or indirect UHT from one day to the next. This solution is most attractive to food processors who produce a wide portfolio of liquid food, perhaps including both dairy and plant-based beverages.
Direct flexibility
In contrast, there are other customers who prefer to keep things simple and use direct UHT for all their products. Direct UHT is flexible enough to work for a wide product portfolio.
Reza Akbari, Product Manager at Tetra Pak, gives the example of co-packers who don’t have their own brands and are contracted to make another company’s products. “In the USA, we have sold a lot of direct UHT units to co-packers,” Reza says. “You just buy production capacity from them and you give them a recipe. So they run a lot of different products. Most of these customers choose direct UHT because they want to have the possibility to do multiple recipes in a single unit.”
Whether choosing direct mode or multimode, the good news is that there are a number of features of the Tetra Pak Direct UHT unit that improve energy efficiency and offset the higher energy consumption of the direct UHT process itself. Here we name just a couple:
Warmer cooling water from the condenser
Compared to its predecessor the Tetra Therm® Aseptic VTIS, the condenser of the Tetra Pak Direct UHT unit is separate from the flash vessel. The condenser now works with water at a higher temperature than in its predecessor. As a result, when the cooling water has done its job and is released from the condenser, it also has a higher temperature than before. The difference could be as much as 10°C. The higher the temperature, the more valuable this water is for heat recovery. The heat can be reused in the pre-production process, for example.
In addition, because the condenser can work well with water at a higher temperature, no ice water is needed in most parts of the world. As long as the cooling water is below 35°C, it is suitable.
Aseptic hibernation puts your unit to sleep
The idea of aseptic hibernation is to reduce flow when the unit goes into water circulation mode, but without losing the aseptic status of the plant. So when you switch to hibernation mode, the flow rate of water is reduced, the homogenization pressure is switched off, steam consumption is reduced to a minimum and final cooling is switched off. This enables you to cut your steam, water and electricity consumption by 60% during hibernation.
Heat pumps have great potential
We want to decrease energy losses in a Tetra Pak Direct UHT unit even more in future. That’s why we have started a joint development project to use a high temperature lift heat pump to recover heat from the cooling water leaving the condenser. In future, we see heat pumps as an efficient regeneration system to lower steam consumption in our direct UHT applications. Heat pumps represent one of the few heating technologies today that can produce steam up to 200°C, which is the temperature required for direct UHT.
In one study of a high temperature lift heat pump, 1 kW of electric power could be used to generate 2 kW of heat output. This makes a heat pump a much better heating alternative from an energy perspective than a traditional boiler. In addition, a heat pump using renewable electricity has the potential to reduce CO2 emissions significantly compared to a gas-fired or oil-fired boiler. We have high hopes for high temperature lift heat pumps.
Talking of efficiency, automating the line is the ultimate scenario. Automation and digitalization are opening up sophisticated new ways to analyze the performance of a UHT plant by sharing the data.
If a customer is willing to give us access to real-time performance data, the numbers can be crunched using our expertise to do Asset Health Monitoring. In this way, parts can be monitored for wear and replaced before they actually break down. Maintenance issues can be quickly resolved. This keeps unplanned downtime to a minimum so the plant runs more efficiently.
Magnus Ohlson encourages customers to embrace this service option:
