H – as in Hot Liquor Tank

What is a Hot Liquor Tank?

A Hot Liquor Tank is a vessel, which at St. Kilian Distillers is made of stainless steel, that holds the hot water for the mashing process step. To largely avoid heat loss to the environment, our Hot Liquor Tank is equipped with a thick insulation layer.

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What is the hot water needed for?

For mashing, we need milled barley malt and hot water, which is drawn from the Hot Liquor Tank. Together, these two components form the mash.

How is a Hot Liquor Tank used?

A certain amount of hot water is always stored in the Hot Liquor Tank. The hot water needed for mashing is conveyed into the Mash Tun at a temperature of approximately 73°C and mixed with the milled barley malt. The water temperature is adjusted so that the mixture with the grist reaches a final temperature of approximately 65°C, which is necessary for the optimal activity of the starch-degrading enzymes. During mashing, the sugary wort is drained several times through a sieve bottom in the Mash Tun. Simultaneously, fresh water from the Hot Liquor Tank, at a progressively higher temperature, is added from above. The missing water volume in the Hot Liquor Tank is replenished with cold water, which is first brought to temperature in the water circuit.

How many mashing waters are used at St. Kilian?

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

What happens to the sparge water?

Sparge water refers to the last part of the run-off wort. This comes from the 4th mashing water, which was added to the Mash Tun at a temperature of 95°C at the end of mashing. Although the sparge water still contains a residual amount of extract, it is so small that it is not transferred to the washbacks along with the collected wort. Instead, this low-extract sparge water is collected separately and returned to the Hot Liquor Tank. From there, it is used for mashing 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 from the hot wort from the Mash Tun. This hot wort must be cooled down to a pitching temperature of 28°C on its way to our 10,800-liter fermentation vessels (washbacks) for the next process step of alcoholic fermentation. This is achieved by means of a plate heat exchanger, where the thermal energy is removed from the wort in a cross-flow with cold water, simultaneously heating the water and conveying it to the Hot Liquor Tank. In this elegant way, we recover some heat energy at St. Kilian.