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25 October 2017

Possibilities for Optimising Wort Preparation – Part 5

Wort preparation geared to reducing DMS can be calculated and predicted. On that basis, the fifth part of this series of articles describes process equipment improvements in the brewhouse resulting in previously unattainable energy reduction for evaporation.

The previous parts of this series showed how existing wort preparation equipment can be operated so as to optimise driving off DMS. No equipment or technical changes have been included in these considerations. In the last part of this series of publications, procedural considerations described are used to formulate process improvements. It has thus become possible to reduce overall evaporation required to a previously unattainable minimum. Once overall evaporation goes down, so does the energy needed. Energy that is not used does not need to be recovered. Such energy savings are preferential to energy recovery as the efficiency of avoidance is 100 per cent. The efficiency of recovery is a function of equipment and always less than 100 per cent.

Presentation of Process Improvements

It was explained in the previous articles that external boiling triggers effective re-formation, and kettle boiling effective evaporation. How can these advantageous features be combined and used?

In many breweries, internal and external boilers (the principle being referred to as external boiling) are installed. In order to improve these further beyond the previously described process operations, it is necessary to combine the favourable properties of kettle boiling (good evaporation)

and the favourable properties of external boiling (good re-formation) in terms of equipment. In order to come to terms with this issue, excess heat in the wort in the boiler – something that is necessary –, causing subsequent pressure release, has to be reduced on the way to the kettle. Several possibilities exist to achieve this. The simplest method for the external and internal boiler is wort cooling by mixing it with wort that is not overheated before going into

or being depressurised in the kettle. In contrast to existing processes, this has to be done immediately after the boiler by adding wort from the kettle into the wort that has not yet been depressurised. Sufficient mixing is required to achieve the desired effect. Depending on the particular wort temperatures, the resulting pressure release is reduced though overall evaporation remains the same: instead of pressure release from 104 to 100 °C, pressure is released from e.g. 102 to 100 °C. Measuring temperatures in the kettle and boiler, the process can be kept at a constant value by controlling circulation rate (and alternatively evaporation rate).

The process has to be subdivided into two phases. Stronger re-formation takes place in phase 1. Evaporation proceeds in phase 2 during which no more (cold) wort has to be added. In order to achieve optimum DMS reduction equal to that in kettle boiling and to keep thermal load low, circulation rates have to be raised accordingly. As all DMS has now been broken down, the optimum way of evaporation can then follow.

This process with the equipment described has two positive effects. Evaporation by means of pressure release is equal to the optimum achieved in kettle boiling and temperature in the external boiler is still elevated for better re-formation. All taken together, the most efficient evaporation ever achieved by any boiling process to-date is now possible.