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Whisky Distillery Design (Masters Degree Project)

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Hello,

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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I'm assuming from your spelling of "ton" you're from either up north or way to the east and are referring to the "long" ton (tonne?) which is 2,240 pounds. A US gallon (128 oz) of etoh weighs 6.59 pounds. 40,000 long tons of etoh = 13,596,358 gallons of ethanol. You're probably posting in the wrong forum.

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United Kingdom way east. Yes the long ton 2240. I've searched high and low seems like this is the best forum and i'm hoping there's a couple of members in this line of work or who've toured an operation of this size. As a design project this doesn't have to be perfect just sensible and i'm sure there's a lot of that to go around! :)

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The dimensions you are proposing are in the right ballpark for a commercial distillery. There are members here running smaller setups, but I believe your sizes are reasonable. A useful source of information for proprietary items like mixers and pumps is the vendors themselves. They keep information on the applications they have delivered in the past and will be able to advise you on what is practical.

There are members here from all around the world. I am sure some of the more hands-on members will be able to address the rest of your questions.

As an aside, a "tonne" is an SI unit equal to 1000 kg, making it equivalent to 2204.6 lbs, not 2240.

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From a purely theoretical design perspective - at that scale why wouldn't you use jet cooking? Assuming based on your wheat/barley ratios - your wheat is unmalted, which would make it an ideal candidate for jet cooking and feeding into non-jacket or insulated tanks to be combined with malt for saccharification. This would eliminate the need for steam jacketing on the mash tuns, which would likely reduce cost and overall complexity quite significantly. Size your tanks based on the individual batch saccharification timing and the total daily production, and then size your jet cooker to assume continuous operation - filling a tank at a time, and rotating through the bank of saccharification tanks through the day. Your mash cooling could either be integral to the tanks, or a single external unit sized similarly to the jet cooking flow-rate so that your transfer to fermenters is at the same rate as the jet cooking.

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The dimensions you are proposing are in the right ballpark for a commercial distillery. There are members here running smaller setups, but I believe your sizes are reasonable. A useful source of information for proprietary items like mixers and pumps is the vendors themselves. They keep information on the applications they have delivered in the past and will be able to advise you on what is practical.

There are members here from all around the world. I am sure some of the more hands-on members will be able to address the rest of your questions.

As an aside, a "tonne" is an SI unit equal to 1000 kg, making it equivalent to 2204.6 lbs, not 2240.

Noted on the tonne. That's a relief designing something you know about through extensive recent research and seeing such large numbers can be a tad daunting. Exactly what I did with Meura for their 2001 mash filter. Sadly things like pumps/mixers I am required to design entirely as this is apparently within the scope of our necessary skills as chemical engineers, so even if I know the approximate size I have to justify data used, cite it etc, this is proving tricky.

From a purely theoretical design perspective - at that scale why wouldn't you use jet cooking? Assuming based on your wheat/barley ratios - your wheat is unmalted, which would make it an ideal candidate for jet cooking and feeding into non-jacket or insulated tanks to be combined with malt for saccharification. This would eliminate the need for steam jacketing on the mash tuns, which would likely reduce cost and overall complexity quite significantly. Size your tanks based on the individual batch saccharification timing and the total daily production, and then size your jet cooker to assume continuous operation - filling a tank at a time, and rotating through the bank of saccharification tanks through the day. Your mash cooling could either be integral to the tanks, or a single external unit sized similarly to the jet cooking flow-rate so that your transfer to fermenters is at the same rate as the jet cooking.

I have to do a mass and energy balance at some stage. My other group members are designing the rest of the downstream processes. As I suspect my values will change as I tinker with the design i'd rather changes only affect the data I've currently supplied in terms of SG, volume of wort, grain used etc minimally. Steam injection would add mass to the mixture to cook it and i'd rather keep the energy/mass bits separate. Haha this would be ideal in the real world but call me a lazy engineering student if you will!

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As a check I crunched some numbers last night to try and get the viscosity of the mash. I assumed the mixture was a slurry exhibiting Newtonian behavior (unlikely but only formula available in literature). Would the above mixture at a temperature of 60C (4l:1kg) having a viscosity of about 2cP (centipoise) seem sensible to anyone? As a reference water at 20C has a viscosity of 1cP and 0.467cP at 60C.

My aim is to size the mixers today somehow once I confirm the viscosity. Also I've run the idea of using torrified wheat or some other pre-gelatinized adjunct past my group members as I believe this is what an actual commercial distillery would do. The heating costs to cook the wheat just seem astronomical to me in the long run and money may be saved this way.

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As a check I crunched some numbers last night to try and get the viscosity of the mash. I assumed the mixture was a slurry exhibiting Newtonian behavior (unlikely but only formula available in literature). Would the above mixture at a temperature of 60C (4l:1kg) having a viscosity of about 2cP (centipoise) seem sensible to anyone? As a reference water at 20C has a viscosity of 1cP and 0.467cP at 60C.

My aim is to size the mixers today somehow once I confirm the viscosity. Also I've run the idea of using torrified wheat or some other pre-gelatinized adjunct past my group members as I believe this is what an actual commercial distillery would do. The heating costs to cook the wheat just seem astronomical to me in the long run and money may be saved this way.

Vessel sizes are fine.

We've gotten samples back from the mash coming straight out of the cook. We use a grain to water ratio of roughly 3:1 ratio. This size operation I'd assume you'd want to run either 3" or 4" pipe, I certainly wouldn't go smaller than that.

I imagine a big plant would be crashing the cook temps from ~140 to fermenting temperature with a once through tube and shell exchanger.

Through a 3" line, the apparent viscosity of our mash is 7.2cP @ 140F, and 15cP @ 80F

Through a 4" line, the apparent viscosity of our mash is 13cP @ 140F, and 35cP @ 80F

I don't think 4 hour cook times are achievable with that volume without DIS. For reference, our runs are 2500 gallons, (1/5 your size) and with DIS we can run it up to 200F in about 2.5-3 hours. You can cut down on that time if you are able to recycle some of your heat from other processes.

I would run a central top mixer with props and run CIP spray on either side. CIP spray balls (the size I'm familiar with anyway), won't be getting that thing clean if you're only using one and running about 14' diameter. It also eliminates a number of problems that running from the bottom induces.

You can run without a grist hydrator without a problem as long as you're careful with you pH and temps, but I imagine it's a worthwhile time saving investment.

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It is not only the viscosity of the mash, but when "wall" viscosities through a heat exchanger become too great, you have separation of the water and a big mess on your hands.

If this is a theoretical study, I would call one of heat exchanger people like GEA (they have wide gap plate for large mash loads) or someone that does shell/tube or tube/tube exchangers.

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Vessel sizes are fine.

We've gotten samples back from the mash coming straight out of the cook. We use a grain to water ratio of roughly 3:1 ratio. This size operation I'd assume you'd want to run either 3" or 4" pipe, I certainly wouldn't go smaller than that.

I imagine a big plant would be crashing the cook temps from ~140 to fermenting temperature with a once through tube and shell exchanger.

Through a 3" line, the apparent viscosity of our mash is 7.2cP @ 140F, and 15cP @ 80F

Through a 4" line, the apparent viscosity of our mash is 13cP @ 140F, and 35cP @ 80F

I don't think 4 hour cook times are achievable with that volume without DIS. For reference, our runs are 2500 gallons, (1/5 your size) and with DIS we can run it up to 200F in about 2.5-3 hours. You can cut down on that time if you are able to recycle some of your heat from other processes.

I would run a central top mixer with props and run CIP spray on either side. CIP spray balls (the size I'm familiar with anyway), won't be getting that thing clean if you're only using one and running about 14' diameter. It also eliminates a number of problems that running from the bottom induces.

You can run without a grist hydrator without a problem as long as you're careful with you pH and temps, but I imagine it's a worthwhile time saving investment.

Firstlly thanks for the input. I guess I better get comfortsble with the use of steam injection for cooking the grain then. When I say 4 hours i'm not including the grain cooking time, just mixing, mashing, draining mixer and wort recovery. Does that still seem too short for the size of the vessels.

By props i assume you mean propeller and a single centrally mounted one? Research let me to believe an offset mixer would be the sure bet though. Mind elaborating on this?

You've got to love this non-Newtonian mash and its varying viscoscity. Any easy way you know of to predict thiis value?

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It is not only the viscosity of the mash, but when "wall" viscosities through a heat exchanger become too great, you have separation of the water and a big mess on your hands.

If this is a theoretical study, I would call one of heat exchanger people like GEA (they have wide gap plate for large mash loads) or someone that does shell/tube or tube/tube exchangers.

I'll drop them an email. I anticipated the mess of it all and figured seeing as we are using a mash filter I could getaway with cooling only the wort obtained by means of plate type heat exchangers. Also the spent grains are being dried by MVR (Mechanical Vapour Recompression), which I highly doubt is going to work now that I've seen firsthand the headaches of heating mash.

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I imagine in an industrial application a solids separator would be useful for many reasons but one is waste stream. If you could remove the grain from the liquid the fermentation, wort fluid transfer, and cooling could all be heat tranferred, and easily cooled and cleaned vs. High centipose issues at every level. Also, the main difference is you are going to want every last drop of potential alcohol out of the grain because the pencil pushers will be on your ass so things like enzymes, pressure cooking to reduce heat process time, etc come into play vs. Distilleries making beverage alcohol who are more focused on taste and cost up front.

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Also, I think you will be needing a 24 hour cleaning regime because bacteria grows fast. I don't think you will get away with 1 cleaning every 7 days. You will need a steam cleaning daily.

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