H - like Hot Liquor Tank

What is a Hot Liquor Tank?

Hot Liquor Tank is an English-language term that literally means hot water tank. This tank, which is made of stainless steel at St. Kilian Distillers, holds the hot water for the mashing-in process step. To prevent heat loss to the environment as far as possible, our hot liquor tank is provided with a thick insulating layer.

What is the hot water needed for?

For the mashing process, we need ground barley malt and hot water, which is drawn from the hot liquor tank. The two together make the mash.

What does the use of a hot liquor tank look like?

A certain amount of hot water is always stored in the Hot Liquor Tank. The hot water required for mashing is pumped into the mash tun at a temperature of about 73°C and mixed with the ground barley malt. The temperature of the water is adjusted so that the mixture with the grist reaches a final temperature of about 65°C, which is necessary for the optimal work of the starch-degrading enzymes. During mashing, the sugary wort is drained off several times via a sieve tray in the Mash Tun. At the same time, fresh water is added from the top of the Hot Liquor Tank, always at a higher temperature than before. The missing amount of water in the Hot Liquor Tank is replenished by cold water, which is previously brought to temperature in the water circuit.

How many mash waters are there at St. Kilian?

We have a total of four water additions during mashing. The temperatures are as follows:

Mash waterHot water temperatureMash temperature reached

What happens to the smooth water?

Smooth water is the term used for the last part of the drained wort. This comes from the 4th mash water, which was added to the mash tun at the end of mashing at a temperature of 95°C. The mash water contains a residual amount of extractives, but this is so small that it cannot be transferred to the mash tun together with the collected wort. Although the smooth water still contains a residual amount of extractives, it is so low that it is not transferred to the washbacks together with the collected wort. Instead, this low extract smooth water is collected separately and transferred back to the Hot Liquor Tank. From there, it is used for mashing in the next batch.

Can the heat used be recovered?

At St. Kilian Distillers, a plate heat exchanger is used to utilize the excess thermal energy of the hot wort from the mash tun. This is because this hot wort must be cooled down to a pitching temperature of 28°C on its way to our 10,800-liter fermentation vats (washbacks) for the next process step of alcoholic fermentation. This is achieved by means of a plate heat exchanger in which thermal energy is extracted from the wort in a crossflow with cold water, while at the same time the water is heated and conveyed to the hot liquor tank. In this elegant way, we recover some of the thermal energy at St. Kilian.

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