Lesson 4 - Wort Boiling Technology and Process Control

As we saw in the last section, forming a thin film of wort makes it easier to evaporate volatiles. The Merlin wort boiling system achieves this throughout the boil.

The figure below shows the setup used in the Merlin wort boiling system.

Figure: Merlin wort boiling and stripping system

Wort from the lauter tun is collected in the whirlpool via a pre-heater that raises its temperature to 96°C. Once the whirlpool is full, the wort is pumped up to the Merlin and distributed over the cone. Flow over the cone is at high velocity and turbulence so heat transfer is enhanced. The wort returns to the whirlpool by gravity and is distributed inside to ensure the temperature is uniform throughout the vessel.

This process of recirculating the wort from the whirlpool/wort collection vessel and back over the conical surface is continued until the wort in the whirlpool reaches boiling temperature. Hops are then dosed into the whirlpool. The wort is then boiled before the whirlpool is left to stand to form the trub cone. The stand is usually around 10 minutes. After this, the wort is pumped back over the heating cone en route to the wort cooler to strip out any DMS that may have formed during the whirlpool stand. The times, flowrates, steam pressures and temperatures of each step in the process are shown in the table below.

Table: Step parameters for Merlin operation

The total evaporation is just above four percent. The system was reported to use less energy than conventional kettles, to reduce thermal load and to give improved hop utilisation. Krones Steinecker no longer supply Merlin systems but some are still in use.