Ice water cooling in dairy plants

Use of our efficient BUCO ice water systems in dairy plants

Our BUCO ice water systems are more efficient than the coil-in-tank-systems  available on the market. If the old, existing coil-in-tank systems only worked with T0= -12°C, it is possible to get about 30% more power out of the compressor with the same compressor and direct cooling by means of a falling film chiller at T0= -2°C. The energy consumption of the compressor motors, however, only increases by 5%. Therefore, the existing motors can often continue to be used. Only the evaporation condensers that are predominantly used today must be enlarged.

In dairies, the first treatment of the milk (i.e. preheating, pasteurisation, etc.) is mainly carried out with plate heat exchangers. Subsequently, 2 cooling stages take place. The first stage is carried out with normal city water, the second with ice water. In many cases in the past, coil-in-tank-systems were used as ice storage for the ice water systems. The entire day‘s output was stored in ice on the pipes and defrosted when needed. Load peaks of the dairy products are thus absorbed. Nowadays, the process in a dairy looks different. There is usually a constant base load over 24 hours plus one or two longer operating phases with high power requirements.

Coil-in-tank-systems have the disadvantage of a large space requirement, a low evaporation temperature (T0= 10°C to T0= -15°C) and a large refrigerant content. The heat transfer coefficient (K-value) of these systems is very low and decreases further the thicker the ice layer grows on the pipe. Manufacturers of plate heat exchangers sell their higher evaporation temperatures (0°C) with smaller temperature differences between ice water and evaporation temperatures as an advantage of their systems. However, problems with ice formation in the channel bends of the plate heat exchangers occur time and again, especially with contaminated process water in these closed units. From experience, we know about the degree of contamination of dairy process water in most plants, especially if they are older. A high degree of control with flow switches and hot gas injection make the system complex and susceptible to permanently safe operation in order to eliminate or minimise the risk of freezing in the plate heat exchangers.

In steps of optimisation of ice water plants, a combination of direct cooling and ice storage in one plant is designed today. A combination of direct cooling using falling film chillers and ice production using ice bank silos is a proven and more energy-efficient solution. Depending on the space available on site, both rectangular containers and cylindrical silos with small space can be used. An alternative combination of direct cooling by means of a falling film chiller and ice production by means of ice bank silos is also a proven and more energy-efficient solution by building a falling film chiller on top of existing ice storage as a pre-cooler to increase the capacity of the ice water system.

The main part of the load profile (kWh per hour over a 24-hour day) is gradually handled more favourably in terms of energy by a falling film chiller, which is switched on and off. Only the peak loads are met by the ice bank system or ice bank silo, which is also operated more favourably (T0= -8°C) than a conventional coil-in-tank ice storage (T0= -10°C to -15°C). The advantage of BUCO falling film chillers, ice bank systems and ice bank silos is their open design, which is accessible for cleaning, and is made entirely of stainless steel. No seals need to be replaced, as is the case with plate heat exchangers, and should unforeseeable control fluctuations in the refrigeration system nevertheless occur, ice freezes on the Buco evaporators, which then defrosts again during control operation without mechanically destroying the evaporators.  Fouling also does not have a serious effect with an increased risk of mechanical destruction as with the use of plate heat exchangers.

Conclusion

Experience has shown that if conventional coil-in-tank-systems of higher capacity are easily operated with refrigerant volumes of 4-5 tonnes of NH3 in circulation, this volume can be reduced by up to 80% when converting to BUCO ice water systems. In addition, the energy costs of the agitators installed in the pipe coil systems can also be reduced by 70%.

We have always assimilated engineering science and thermodynamics optimally in the various manufacturing processes.

Thermodynamicists,mechanical engineers and welding engineers define the dimensioning, design and construction of customised heat exchanger panels and systems in materials ranging from mild and austenitic steels through to titanium, and ensure successful distribution of their work worldwide.

In doing so they fall back on production engineering expertise and calculations developed in the course of the past hundred years that are still being continuously optimised in an ongoing process.

In the perception of our customers, the Buco product stands for:

Technical and process-oriented consulting
Thermodynamic efficiency
Quality and longevity