Worts Cooling in the Whisky Production
Worts Cooling Case Study: Background
A Scottish world-leading company in the whisky production, has contacted SACOME to design and manufacture a worts cooler of 250 m3/h of worts.
The cooling of worts after cooking and prior to fermentation in the production of spirits, is an essential part of the process, since at high temperatures there is a decrease of the fermentation power, together with a loss of evaporated alcohol and aroma diminution.
With this in mind, our Technical Staff got involved to the maximum in the design of the worts coolers, paying special attention to the special design conditions, the high solids contents (grain, stones, straws etc.) suspended in the product to be cooled, the necessity of a precise final temperature of the worts at the exit of the cooler or the strict cleaning conditions of the heat exchanger after the production cycles. These factors make the tubular solution the most convenient.
In the following sections we talk about the special details in our design of tubular heat exchangers for the worts cooling with which the most important Scottish distilleries are working nowadays.
Our solution: Corrugated Tube Heat Exchangers
SACOME has designed and manufactured an important number of corrugated tube heat exchangers for the most important distilleries in Scotland and, in all cases, these units are working nowadays at full capacity.
In this particular project, a cooling from 63 ºC to 20 ºC was required prior to the fermentation process in different operating conditions and the process was divided into 4 sections according to the media used to cool the product (in this case: tower cooling water, fresh water and chilled water).
The system basically works with the worts circulating by the corrugated inner tubes along 4 sections, while the different cooling media circulate by the shell tubes of the heat exchangers. It is important to comment that the design of the heat exchanger allows the connection of the shells of the sections 1, 3 and 4, with the intention to avoid the use of chilled water in those seasons when the environmental temperature allows it, which means an important economical relief.
We have also to emphasize the important advantages of using multitubular heat exchangers with corrugated inner tubes for this kind of products as the increase of turbulence as a consequence of the corrugation results in a lower fouling, an increase of the heat transfer velocity and a better homogeneity of the product at the end of the cooling process.
Worts Coolers Thermal Calculation
On the other side, our technical staff took into account the existing restriction in the outlet temperature of the fresh water as it is used in different processes and in case of do not meet this requirement the result would be a high energy loss.
In the same way, when doing the thermal calculation of the heat exchanger, we considered that this exchanger should be working in production cycles of 30 to 45 minutes. Every 2 or 3 cycles, we made water at 85°C run through the inner tubes for cleaning and 2 or 3 times a week we repeated the same process with a hot cleaning solution.
This exchanger has been designed to process worts flows between 150 and 250 m3/h and to reach final temperatures of 20 to 22°C. Flows and temperature of the water also vary (for example, for fresh water between 120 and 150 m3/h with temperatures between 5°C and 19°C).
These variations involve a major difficulty in the calculation of the necessary number of modules (we checked more than 20 different operating conditions). Finally, this cooler consisted of 16 modules assembled in one frame with the objective to obtain an easy drainability (we included a system of drain valves). Other key element was the design of the expansion joints included on the shell of each module as we did a fatigue analysis of all the elements for 20 years.
To do the thermal calculations of this heat exchanger we used the last updated version of HTRI, in which association we are registered as a member. Regarding the mechanical design, we considered the BRITISH STANDARD 5500 Category 2 for the design pressure of 16 barg.
Process: basic stages in the whisky production
The worts cooler is required between the mashing and fermentation stages.
Worts Specifications for Whisky Production
One of the key points in the design of this kind of tubular heat exchangers for worts cooling is to know the properties of the product. In this way, from our experience in a multitude of projects for the most important distilleries in the world, in SACOME we perfectly know the behavior of the worts and, in fact, we have done some rheological tests in similar projects. Besides, we also have a lot of available references and properties of other products derived from the whisky production as, for example, the “wash”.
In this sense, it is very important to remark the nature and behavior of this product as its complexity gives it special characteristics when doing the calculations. For that reason, only a company specialized in this kind of application could be able to get the optimal solution.
On the other side, the solid content makes essential to apply certain considerations in the design of the worts coolers to avoid, for example, the risk of blockage in the inner tubes.
Corrugation of tubes in the heat exchangers
Flanged tube sheets
Self-drainability in tubeside
Thickness of inner tubes
In this way, it is very important to empty each shell while doing the cleaning at high temperatures.
Non removable tube bundle
Inlet Worts Temperature
Inlet Worts Temperature
Outlet Worts Temperature
Bigger Frame Size Dimensions