Bain-Marie Still Heating - Oil vs Steam vs Coolant

edited July 21 in General

We decided to go with oil for our 150L bain-marie kettle.

We have 60L thermal oil with 2 x 6kW elements (12kW total - we never go over 80%).

I'm curious what other folk's experiences are using oil vs steam vs coolant?

The oil works fine but I'm not convinced its the best option.

Is steam generally just a better option (yet more expensive)?

What about coolant?

I think this is not a good option as the boiling point is too low, but wanted to get some things on that.

Thanks!

Comments

  • StillDragon Bain-Maries can be thought of as built-in steam boiler. Fill enough water to keep the elements well covered but not enough to touch the kettle, and release the air from the chamber once it gets over boiling, and you are cooking with steam.

    With oil in a bain-marie, you don't get the 'steam effect' (enthalpy of evaporation that water has when you boil it and the steam comes into contact with the boiler).

    It is also more hassle draining and refilling to replace an element, and you have to buy a 2nd volume of it to have on hand if it gets fouled. I have been using water for 5 years in my 1000L and very happy..

  • Also, the expense of a "quality " oil vs 50 or 60 liters of water or so. Dead simple and fast to drain compared to the larger volume of oil.

    With the jacket at 1bar your getting 248 degrees in the jacket.

    Thing is, the SD design is set up nicely for water. Other designs are more geared toward using the oil. Got any pics? If it's not an SD kettle you may be stuck with oil.

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  • edited July 18

    Also, you will find that once your oil gets hot that your latitude for power management adjustment will be non existant. Probably not a problem once you get the hang of driving the still.

    The good news is that once you come to temp it will take very little heat input to drive the still since oil does such a nice job of holding on to it's heat. The boys in Jackson Hole run theirs with an RTD in the oil and a PID. They seem happy with what they are doing. As I recall they preheat their oil prior to the day they will run in order to minimize heat up time on distilling days. Can't say for sure but I bet the jacket stays hot for a couple days after a completed run.

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  • edited July 21

    Yep its a SD :) and we love it. The pic isnt great quality but shows how we 'plummed' an external circuit for oil circulation, there is a cooler + pump (not in pic). We have been mashing in the same vessel so cooling is a must. It is a underpowered though. Reading your feedback it sounds like cooling also would be a lot easier using water, as you can just drain it & put in cold water. We always worked on the assumption the content of the bath is 'fixed'.

    What about pressure? Is this not a concern? we have a PRV of course, but still..

    Re. oil holding its heat: we do have to continue putting in about 20 - 40% (so 4.8kw) after reaching temps - more towards the end. We use a (homegrown) PID (my partner is a bit of an MCU freak ;)

    Great answers guys, thanks a lot!

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  • edited July 21

    @Stinky said: Yep its a SD :) and we love it. The pic isnt great quality but shows how we 'plummed' an external circuit for oil circulation, there is a cooler + pump (not in pic). We have been mashing in the same vessel so cooling is a must. It is a underpowered though.

    You really do want 70 watts per liter

    @Stinky said: Reading your feedback it sounds like cooling also would be a lot easier using water, as you can just drain it & put in cold water.

    Do you mean use the jacket as your mash chiller?

    @Stinky said: We always worked on the assumption the content of the bath is 'fixed'.

    Fixed? I'm not sure I understand what you mean by fixed?

    @Stinky said: What about pressure? Is this not a concern? we have a PRV of course, but still..

    The jacket is rated for 1 bar. Without the reservoir, the design is otherwise identical to our more typical steam jacket design. It is a low pressure vessel

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  • fixed is the wrong word i guess, i just mean we approached it like "fill once and work with that".

    So if I understand correctly, when you part fill the still with water and boil that, the produced steam is what will heat the still. My concern is with pressure in the jacket when you do this (so ignore my comment about PRV, it has nothing to do with the question).

    What kind of pressures can we expect in the jacket when part-filling with water and boiling that?

    CothermanDistilling mentioned: "release the air from the chamber once it gets over boiling, and you are cooking with steam", I guess I still am not clear on the process to do this in a safe manner.

  • edited July 19

    With water, it is only the reservoir that gets filled. Ideally we don't want any water touching any part of the inner wall as that will reduce the amount of surface area that is exposed to steam and therefore you would lose efficiency.

    With oil it is the exact opposite. You need as much liquid contacting the surface area on the inner wall as possible

    Pressure in the jacket should not be a concern as this kettle is indeed intended to be used as a pressure vessel. Please understand that I am not at all being dismissive about the risks of working with steam. Any breaches would likely result in a pin hole sized spritz. Nothing catastrophic with a low pressure boiler properly outfitted with PRVs. For additional context, a child's bicycle tire holds 20 psi.

    The pressure in the jacket is directly related to how much heat you are throwing at the kettle. The PRV on the jacket will prevent pressure from exceeding 1 bar (14.5037738 psi). Jacket temps at 1Bar = Just under 250°F.

    Perhaps Cotherman will chime on what his typical running pressure is for various ABV charges in the kettle? I suspect he bops right along at a half bar or less depending on what he is doing?

    So there will be air in the jacket when the kettle is cold. Also a rapid cool down may also allow for air to be sucked in through the integrated vacuum break that is part of the PRV function. In any case there will be air in the jacket prior to heat up. And this air will be prevented from escaping because of the 1 bar PRV. So during heat up, having a small bleeder valve set up on your PRV tree to allow the air to escape from the jacket during heat up will ensure that all of the surface area is exposed to steam vapor. Any air in the jacket will act as an insulator/buffer and not let the steam vapor make full contact with all of the surface area. So basically, turn on the heat, crack the valve, and when you notice a bit of vapor escaping the valve you can close the valve as at that point all of the air in the jacket has been forced out by the rising vapor.

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  • I run a bm boiler and its fantastic. In a stripping run internal temperatures are normally around 115 dec c and about .45 bar. I have a pressure manomoeter. Two vacuum and manual pressure release valve. One set at +1.05 bar and the other is standard ar 1,1 or -.1 bar.

    Normally after a run i will open the manusl escape valve just to prevent any vacuum forming as the water cools down. I just love it. During the run you have excellent heat control. I used it for about 9 months without changing the water in the vapor chamber. The max I have ever gotten the pressure up to was .7bar and 125c and that was on a spirit run with a small volume of liquid. Which makes sense because as you are heating up water the stram has pressure while it is hot. When it hits the wall of the inner vessel. That temperature and therefore pressure is released.

    Oil is definitely not as forgiving. The other thing that i noticed is that when your doing this your almost never heating anypart of the wash liquid over the boiling temp. It will never turn into superheated steam. Using oil you can get well over 120 deg c

  • Many thanks guys for sharing. We will probably stick with using oil, at least for now. We aim to upgrade to 1000L in the future, this info will be invaluable.

  • While both systems are limited to how hard you can drive them (water by steam pressure, and oil by not scorching it), I am interested in some actual numbers for watts per liter per deltaT vs time.

    If you start with the heating medium at room temp and volume V, and you apply power W, you will raise the temp of the charge X degrees in Y hours. Something like kW*Hr/volume = deltaT

    Say that 30kW into a 1000L still charge to raise 90F (50C) takes 1 hour

    The math is 30,000/(1000190) takes 1 hour is 0.33 watt-hours per liter per degree F

    Or 30,000/(1000150) takes 1 hour is 0.6 watt-hours per liter per degree C

  • Well, I will go first. I ran my still pretty hard doing lots of runs and I got so familiar with it I knew it almost down to the minute when teh run was going ot start. In my garage my two 32amp circuits would feed two 4500w immersion elements that most often were only pulling about 3600 watts each element. So that is 7.2kw. It would take exactly 90 minutes to heat up to 85 degrees C from a base temperature of 20 degrees C, heating up 200l of wash with a nominal ABV of around 8%.

    So that is 7200*1.5/(200/65) which equals 0.83. I had about 25 litres of water in the vapor chamber. In my house I had the problem that my still has 3 entrances for heating elements but my basic control panel would only heat up two. And pulling 7 kw would put me at the limit of the power supply for my barrio, and you could tell as the volts would drop from 220 down to 205 when I was sucking all the juice at maximum amps of about 19 amps per circuit. If I had a wash with a low abv, like a triticale or Rye wash it could take longer. A high malt high barley content could be a bit sooner but it was pretty close to 90 minutes almost every time.

    I just found some 9kw immersion elements on Amazon which use a 2" tri clamp and 220v so I am very keen to get some of those and I should be able to put in about 6kw from each one of those so my heat up is a lot faster. As well too I need to say thats on the stripping run which after the run started would run for about 4 hours with a wash with an ABV of around 7.5 to 8%.

    On the spirit run I would put in 4 batches of low wines at around 30% abv and dilute to 20% but increasing teh volume up to about 220l. Then the heat up would last about 65 minutes, but the run would go for about 6 to 7 hours and I would get about 80 to 85l of spirit at 50% final abv and it would go straight in the barrel at 50%. I am still working on my shed as everyone knows. Was this what you were after @CothermanDistilling mate.

  • @DonMateo said: Well, I will go first. I ran my still pretty hard doing lots of runs and I got so familiar with it I knew it almost down to the minute when teh run was going ot start.

    Well, it does change sounds..... :))

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  • @punkin actually funny you should say that. I had a kitchen timer with a really fucking annoying and loud alarm on it. So I would load up the still for 60 mins and set it running, keeping the top open. Then do it again for 20 mins. The last 10 mins I would wait in front of the still as I would button up at the last minute. So there were sound changes. This way I could be distilling and keep working on my consulting jobs. Last year I made the best money I ever have and also made about 2000 litres of great whiskey.

  • 0.85 is perfect, @DonMateo I will calculate my 380 direct and my 1000BM when i get a chance, the numbers I gave are my estimate of my 1000L... then we need an oil user...

  • To be honest I cant imagine using oil. Steam is so good and easy to use. You just have a lot more control. The funny story was when my tank maker mate was testing this boiler he called me up and said how do I test this. So I told him dont fill it up to the top and fill it up with water. Just put enough in the bottom to cover the elements. So what did he do. He filled it up to teh top of the vapor chamber and filled the inner tank up to the neck and started the run. It took about 4 hours to heat up with 5kw and he got the inner chamber up to 120 degrees and blowing about 1.5bar. He calls me up and said the pressure is really high what do I do. I was screaming noooooooo. Dont do that. So he turned it off dumped the liquid out and the next day did it properly. They only thing that has pissed me off is working in my garage I havent had enough power to be able to put in 10kw or more. Still I will be in my shed soon.

  • I had high pressure until I learned to vent the air off every time I heated the still, I did install a steam trap on a valve to make it a bit more automated, but I close the valve once it is bled of air.

    when you need high temps for a process, oil can be better, because it takes REALLY high pressure steam to match, but we don't need that... the only thing I would like it knowledge on reasonable boiler additives that may help the inside with regards to corrosion for my RO water I add...

  • edited July 27

    Why not just use an automatic steam air vent valve on the kettle?

    Hoffman, Watts and others make them, they are commonly seen on steam radiators. We have them on all our kettles. At startup they will vent air and steam for a bit, and close up automatic. If we shut down heat and the kettle pulls a vacuum, it will vent the air again when the kettle is turned back on.

    Easy peasy - you’ll normally see these always installed next to the vacuum breaker in large scale steam kettle setups. They should be located at the highest point possible.

  • @grim said: Why not just use an automatic steam air vent valve on the kettle?

    I have one but I put a ball valve before it and shut it off once bled of air, because they (the one I have) is temp based, and therefore cools with ambient air and has to re-release steam to heat up, so it makes an annoying leaking sound in my otherwise quiet area... I even stopped using the agitator... I like tranquility.... even @Smaug's latest video of the continuous has me rethinking parts of mine...

  • BM water/steam FTW.

    A thermostatic steam trap should be standard on every BM. You can put a valve on its output if you want to close it entirely off once at temperature.

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