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Bulk Tank to Mash Tun conversion ideas?


jessicajlemmon

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Well, we jumped the gun ever so slightly and picked up a used bulk tank for use as a mash tun. 300 gallon capacity, was used to make sugar syrups prior. Pretty good shape, has the agitator but needs a new motor. Single wall, no jacket, domed bottom.

So now comes the tricky part... easiest/smartest way to turn this thing in to a cooker?

A couple contraints: We're not doing steam, so that's out and we won't likely have 3 phase power for the foreseeable future.

We're looking to cook 100% corn or a sugar wash for starters. Move on to a more standard bourbon grain bill after that. Which makes the handling of electric elements tricky with the whole scorching issues. We are open to the possiblity of strikewater if we absolutely have to.

Probably not the ideal set up but we're starting on a shoe string and this tank leaves us good room to grow (or even convert to a big pot down the line!)

Here's a pic of the new baby. (Damrow 300surg gallon dairy/food tank.)

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Look into over the side immersion heaters from companies like Wattco or Tempco.

I have a dairy tank that we use specifically for this. Get the strike up to temp and pull the elements.

It might work best to cut the top off (save for later use) and make a lid for it and wrap insulation around the tank to reduce the energy loss. You'd need about 15-20k watts of juice to heat it up in a couple hours. Having an open top will be your enemy as the BTU loss by the steam creation will be fairly substantial if you need to achieve high strike temps.

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We're doing the same thing.

However - Direct steam injection is our approach, but we've got filtered steam so it makes that easy. Can't comment on the elements, only be sure you do the math on heating before you invest the money. You don't want to be in a position where it takes you 8 hours to get to boiling. 200 gallons, from 75F to 212F, in one hour will take 80kw. That's 300 amps on a 240v service - probably beyond your service capacity. Moving down to 30kw (125 amps) - now you are going to need about 3 hours to heat. One good alternative is to use an on-demand hot water heater like a Rinnai or Noritz. They have a high btu gas-fired commercial model that will get near 170-180F output. It will probably save you hours of time every mash.

On the motor - don't look for a milk tank replacement motor, they are too small, too slow, and too expensive. Instead retrofit a washdown motor and gear reduction for the agitator, use the existing paddle. It's going to take some fabrication and welding. If you can't fab, there is a good chance you can find a nice Lightnin' mixer on the surplus market. Look for something 1/2-3/4 hp.

Another thing to keep in mind is the insulation on these milk tanks is very good, with the tops on, don't for one second think you are cooling from cook temperatures to malt temps, to pitch temps, in any reasonable amount of time - you will need some sort of active cooling. Our Mueller holds temps very well, something like 1-2F drop per hour.

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How about cut the domed bottom off on this thing and then get someone to make it a flat bottom and add a couple of Wesco round industrial heaters. They have those things at 15kw and you could easily fit two of them under this tub by the look at it. I am looking at the same problem, and I am leaning towards those big plate heaters as I want to do some moonshines and some bourbons.

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It would also make a beautiful fermenter.

I have two domestic water heater in series, to the jacketed 200 gallon tank. Roughly 20 kw and it takes hours to get to temp. We leave a temp controlled element on at night to get a head start for the morning cook. We have to improve the heat source.

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Thanks for all the suggestions, we'll definitely look in to the options. I don't think we want to cut the top off (and I think the manway is big enough I can actually fit inside if I *have to*.) Hadn't considered bringing it up to temp and pulling the elements, that's an interesting approach.

We were also wondering if we could put a hot plate type set up under it, as menitoned in one of the other options, but the domed bottom makes that a bit more tricky. Cool down is definitely going to be something we need to address as well. We had to wait half a day for a 3 gallon batch of pear wine to cool down enough to pitch yeast, I can't imagine how long this thing would take at full capacity without a little help.

We had planned on picking up ye old standard dairy tank, but this one popped up for a fair price and we just couldn't resisit. My better half has good sourcing for all the pieces and parts, it's more the question of what we need to look for. I think this gives us good direction in general.

We do have access to both electric and gas, the on demand water heater might be a good way to go. As of right now we're aiming for 100 gallon still, but we're thinking of maybe cooking 2 batches at a time (2/3 capacity of the tank) just to keep things efficient.

A side debate regarding this thing is building a platform for it to go on so we can gravity feed from it and elminiate the need for a pump at that part. Has anyone tried jacking one of their milk tanks up to accomplish this?

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  • 4 weeks later...

I have a suggestion. You could wrap the outside of the tank with flexible silicone rubber heating pads. This would work similar to a steam setup in that the entire outer surface area of the tank would be evenly heated. The heat then conducts through the wall of your tank into your mash. You'd need a layer of insulation on top of the heating pads. These pads are usually designed for 2.5, 5, or 10 W/in^2. Just estimating the size of your tank I'd say it was 4 feet in diameter by 3 feet tall of surface area, which works out to almost 300 gallons. If you wrapped the outer surface with a heating pad at 5 W/in^2, you would have at least 25,000 W of heating, or 50,000 W if you use a higher watt density heater. The electric service will be your most expensive thing if it can't already handle this capacity.

I'm not a representative of this company, but I have used them before on a project in my former professional life as an engineer. There are certainly more manufacturers out there that make these type heaters. They have on their website an example used in food processing for holding a constant temperature of very viscous liquids at a constant temperature, almost what you are doing in mashing.

http://www.michaelsenterprises.com/custom-heating-solution-food-processing.html

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Im heating 150 gallons of h2o in about an hour to hour and a half with 7 - 5,500 elements.

Covered the outside of my tank with spray foam insulation, helped tremendously.

I tried an adjustable element placed in the mash, it scourched the grain.

Cooking corn inside your tank IMHO will not work unless you double wall it.

Gravity feed will be a disaster (take a long time to drain) if cooked corn is in it.

Hope this helped

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Cooling a wash can be done by pumping through a external plate exchanger plus either city water or a closed loop chiller (I can send photos of the chiller system commonly used for your size loads).

Mike G

MG Thermal

www.mgthermalconsulting.com

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County Seat- Heat up time will be entirely dependent on the surface area that gets covered in heaters and the watt density of the heating pad, the volume of liquid being heated, amd the efficiency of the heating. Generally these style of heaters are designed for 2.5, 5, or 10 W/sq. In. If you had a 36" diameter tank, and had heating pads over the entire circumference that was 36" tall, the surface area would be about 4000 sq. In, so you could possibly have 40,000 W of heating. A 36" diameter tank that is 36" tall is about 150 gallons.If the tank was 4' tall it would hold 200 gallons. A good rule of thumb is 1000 BTU of heating per gallon of mash to get your still boiling in one hour. 40,000 W is equivalent to about 136,000 BTU/hr. If the heating was only about 80% efficient, the example outlined above might take an hour and a half to get the still boiling. That's a rough napkin calculation anyway on an estimated heating time.

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  • 3 weeks later...

Fell through the rabbit hole for a while, working on the building paperwork and such.

The heating pad thing intrigues me. How much of an energy hog is that sytem? Our tank can go up to 300 gallon, but the still we have on order is only 100 gallon, so in theory the heating pad would be able to cover the lower half of the tank and do a standard mash, posisbly.

I may have access to some fire insulation type materials that could be good to wrap the unit in. And a picture of the chiller wouldn't hurt :)

(We were out of campden tablets, thus we were poorly trying to pasturize the perry.... lesson learned.)

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  • 3 weeks later...

I have attached a photo of a mash tank that I have used for three years and am selling for $800.00. Motors not included. I'm getting too old to get in and out of it and going to a small unit. I do 300 gallons at a time with a conversion of 10%. call me if interested: 608-335-2461.

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