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Whisky Distillery Design (Masters Degree Project)


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As my chemical engineering masters design project I've been tasked with designing a whisky distillery. I would greatly appreciate any help anyone could give which is likely to only get more complicated over the next few weeks. Luckily I have a few group members and my section is limited to the grains receiving, milling, mashing and spent grains disposal. Onto the fun stuff then.

We are making the whisky using a 10% malted barley to 90% wheat ratio to produce 40000 tonnes of ethanol annually. I understand that the wheat will need to be precooked but I haven't looked into the design of this vessel yet. Looking at the annual production i'm sure you can appreciate we are using a lot of grain. Current details of my design are as follows.

Mashing Design

I decided to go with steam jacket heated mash mixers and mash filters. I proposed 8 mash mixers assuming a mashing time of 4 hours (filling, mashing, drain, clean, repeat) and 24 hour operation that's 6 mashes a day. I wont be sparging because a thick mash will make sizing pumps further along harder i'm assuming. Mashing 6 days a week with the 7th being a cleaning of vessels and pipelines etc. The values are as follows for one mash mixer for one mash -

Ground wheat 10054.688 kg 22120.3 pounds

Ground barley 1117.1875 kg 2457.81 pounds

Water 44687.5 kg 98312.5 pounds

Total 55859.375 kg 122891 pounds

Height 6.6 m 21.653544 feet

Base (Diameter) 4.25 m 13.94357 feet

Dish Depth 0.8 m 2.624672 feet

Volume 86.0633 m3 3039.296756 cubic feet

Liquid Level 4.2 m 13.779528 feet

Heat transfer coefficient was assumed to be 176.1090467217301 BTU(f) or 1000W/m2.K

At this stage my questions are as follows

1. Are these vessels too large for an industrial distillery?

2. Does the turnaround time of 4 hours seem sensible?

3. Does the assumed heat transfer data seem sensible?

4. How would I design a mixer for these vessels? Preferably offset and shaft from below to allow for CIP (spray balls and all from top?)

5. Following on 3 how could I obtain viscosities for mash to get calculate accurate thermodynamic data and for pump sizing.

6. Grist hydrator how do these work? I've looked at Steele's Mashers still a tad confused.

Any and all help would be immensely appreciated! Thank you in advance.

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Don't have a lot of time to answer these today, but ill give a quick stab. You stated that your are responsible for for pre and post fermentation grain handling. Are you responsible for the cooling of the mash before fermentation or is that another person? First, I would be working very closely with your team members assigned to fermentation/yeast cultivation and the actual distillation equipment, they will bottle neck you if you are mashing 6 days a week with no place for the mash to go.

1.) This is a question that needs finances involved. Being a 24 hour operation, the sky is the limit on size if you have an infinite source of heat/power and materials. But as far as total volume of your mash tuns, they are reasonable. Your "recipe" however, is off. Your grain/water ratio is very high, it will result in wasted starches which equals wasted money as well as a bad final product. Shoot for 8-12% ABV of your mash if you are making whiskey.

2.) 4 hour mashing is sensible estimate if you had the finances to buy the proper equipment.


4.) Mixers could come from top or bottom, most likely not offset however. On large mash tuns, they are almost always centered.

5.) The viscosity is always changing during mashing. For pumping, I'm assuming with those volumes you will be pumping with the grain into the fermenter, and from the fermenter with the grain into a Coffey still. So an industrial size pump capable of moving "sludge." For the post fermentation pumping, you must look at the internal components of the pumps/hoses to see if they are safe to come in contact with ethanol.

6.) Grist hydrators are simple devices. The grain is moved through the hydrator and spray with water as it falls into the mash tun "wetting" the grain so large dry pockets are not produced.

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