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Oil Heated Boiler

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Oil Heated Boiler

Postby FullySilenced » Sun Sep 02, 2012 3:48 am

I have read about steam jacketed boilers and steam tubed boilers...

I was thinking of just a base that the boiler sits on or should there be a full jacket on part of the boiler.

Since distilling temperatures are well under the flash point of cooking oil i was thinking of using peanut or soybean oil ect...

This would provide a steady heat source with no hot spots in or on your kettle.

Do anyone know of anyone trying an oil heated boiler. Idea being similar to an oil filled radiator for the house.

Would also make the boiler easier to clean I imagine with no internal elements to work around...


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Re: Oil Heated Boiler

Postby nb0s » Tue Sep 04, 2012 9:52 pm

I would have thought that steam would be the best for heating the pot. The latent heat released as the steam goes back to liquid state enhances the heat transfer significantly. This is what the commercial boys do - why reinvent the wheel?
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Re: Oil Heated Boiler

Postby Zymurgy Bob » Sat Oct 06, 2012 9:49 am

nb0s wrote:I would have thought that steam would be the best for heating the pot. The latent heat released as the steam goes back to liquid state enhances the heat transfer significantly. This is what the commercial boys do - why reinvent the wheel?

Actually, excluding direct steam injection into the wash, all the phase-change energy from condensing steam does not enhance heat transfer. If you look at the heat transfer equation, and assuming constant area, metal thickness and kind of metal, only temperature difference between 100C (for the condensing steam) and whatever the wash boiling point is, changes the rate of heat transfer. As the wash ethanol depletes, the wash temperature approaches 100C, the steam/wash temperature difference approaches zero, the heat transfer approaches zero, and distilling grinds to a halt.

As Punkin pointed out, the only way to get that temperature difference high enough to reliable move serious energy, is to pressurize the steam.
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Re: Oil Heated Boiler

Postby Swede » Sat Oct 06, 2012 10:29 am

Proplene Glycol (aka RV antifreeze in north america) is a non toxic substance that will work as a hex fluid. Apparently biodiesel is another very efficient substance, as it's smoke point is quite high, and it's also non toxic. (google the msds for biodiesel and look at the toxicological effects section if you don't believe me).

I'm going to be getting a jacketed boiler in the near future, and I plan on using proplene glycol as my hex fluid....
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Re: Oil Heated Boiler

Postby rookie » Sat Oct 06, 2012 5:42 pm

Zymurgy Bob wrote:Actually, excluding direct steam injection into the wash, all the phase-change energy from condensing steam does not enhance heat transfer. If you look at the heat transfer equation, and assuming constant area, metal thickness and kind of metal, only temperature difference between 100C (for the condensing steam) and whatever the wash boiling point is, changes the rate of heat transfer. As the wash ethanol depletes, the wash temperature approaches 100C, the steam/wash temperature difference approaches zero, the heat transfer approaches zero, and distilling grinds to a halt.

As Punkin pointed out, the only way to get that temperature difference high enough to reliable move serious energy, is to pressurize the steam.


All true. Agree totally - energy transfer through a thermal conduction medium cannot occur without a temperature difference, but heating the wash through steam injection does seem pretty good to me. Steam injection cooking of corn also seems a viable proposition.

What say you?
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Re: Oil Heated Boiler

Postby FullySilenced » Sun Oct 07, 2012 4:17 am

It is used in some large scale operations in that manner but for small scale maybe to much trouble to use steam... however the small steam generators for say a sauna might work well... some of them are up to 12kw
if i member correctly

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Re: Oil Heated Boiler

Postby Zymurgy Bob » Sun Oct 07, 2012 4:45 am

I've been rattling around a design for a very compact steam generator for steam injection distilling and maybe wash cooking. My design criteria are: 1) No pressure except for liquid head backpressure from boiler and/or thumper depth. 2) Use of standard hot water heater electric element. 3) Very small water boiler volume. 4) Continuously automatically maintained water level. 5) Unvalved output, with output controlled only by power to element. 6) All of the temperature, pressure, water level, and water input pressure automatic shutdowns.

The design will probably utilize stainless pipe and fittings almost entirely.

For flavor considerations, I really want to be able to distill on the grain or fruit pulp, or anything else that imparts flavor (without sticking or scorching, of course). I've calculate how much wash dilution I'll get before the pot boils, and i can live with it just fine,
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Re: Oil Heated Boiler

Postby Zymurgy Bob » Mon Oct 08, 2012 4:24 am

What problems did you run into that made steam injection unfavorable? You may just save me a mess of time, money, and effort, here.
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Re: Oil Heated Boiler

Postby FullySilenced » Mon Oct 08, 2012 6:55 am

This whole thread started with the idea of a ss drum in a ss drum with heating elements, heating up oil which in turn would heat the mash inside the kettle... kinda like a deep fryer... you would have good control and a good return on invested energy that was put in heating the oil... I would have made it a closed system... but it is still just an idea. I got the notion from reading about steam stills of old and how they didn't burn the mash ect... and they produced exceptional product..

FS
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Re: Oil Heated Boiler

Postby FullySilenced » Mon Oct 08, 2012 7:15 am

standard cooking oil dosen't smoke till over 450 degrees f... were only talkin 220 degrees or so max here on a boiler... so really there should not be any smoke...

FS

Whats the max temperature you have ever seen in your boiler...
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Re: Oil Heated Boiler

Postby FullySilenced » Mon Oct 08, 2012 8:07 am

OK so it was not about it working it was about the time it took to bring the kettle up to distilling temperatures...

FS
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Re: Oil Heated Boiler

Postby sweden » Tue Apr 16, 2013 4:13 am

I have done this before and I cooling with sunflower oli and its no smeel at al

Just very hard make the tempratur in the oli corekt , but its working realy good
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Re: Oil Heated Boiler

Postby myles » Tue Apr 16, 2013 9:41 am

OK time to add to the discussion.

Steam jacketed boilers are good - no doubt about that, but to get the steam temperature up to 120 to 130 deg C, you need a bit of pressure. This is why I say it is not really a good option for home build. You need to raise the temperature in the jacket to make the thermal gradient from jacket into wash more favourable. However if you go too high it will burn anyway.

If you can run the still outdoors and don't mind the steam escaping, then you can run an un-pressurised steam jacket. Would not recommend it for indoors though as your still room gets filled with steam.

So that brings us to the glycol or oil options. These are good for home build and you can get to 130 deg C with no trouble at all - at atmospheric pressure. Your thermal transfer fluid is used at a long way below its boiling point, hopefully a long way below it's smoke point also, but it is still going to give off fumes and will degrade with time.

You have to include expansion space for the fluid, and will want to minimise the exposure of vapour into your still room. I know it is more expensive but propylene glycol is a good option. Vegetable oils are cheaper and some have good properties but do think about the odour.

I have found that untreated 100% propylene glycol will start to degrade at about 121 deg C. In the future my target temperature will be 115 deg C. The fluid acts like a big heat store, and this can be used to your advantage.

My glycol boiler only heats the lower 3" or so of the inner pot. However, the new inner pot is all copper to aid the thermal transfer up the sides. Even so it is a big surface area that is getting heated.
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Re: Oil Heated Boiler

Postby sweden » Tue Apr 16, 2013 12:29 pm

If yu are bilding a steam machine you beter know what you doing- I wuld never in my life bild a machine like that becuse to much can happend and I like my life ;-)
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Re: Oil Heated Boiler

Postby myles » Tue Apr 16, 2013 8:29 pm

sweden wrote:If yu are bilding a steam machine you beter know what you doing- I wuld never in my life bild a machine like that becuse to much can happend and I like my life ;-)


I agree with you, but it is worth making a distinction between atmospheric pressure steam and pressurised steam. Unless you are qualified to build pressurised steam boilers you should not do it. It is just too dangerous.

Atmospheric steam though is something else. Personally I think it is inconvenient and would only use it outside. By definition the steam has to be able to get out of the boiler, and even if you minimise this it still gets out. It is slightly more effective than just using boiling water in the jacket. Towards the end of the run the thermal gradient is not very good, but there are ways to mitigate this.

Using some other fluid like glycol or one of the vegetable oils, is a more convenient option in my view. You can also easily lift the bath temperature a few degrees. Even running at 115 deg C is a big improvement over 100 deg C.
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Re: Oil Heated Boiler

Postby micah-jon » Sun Jun 19, 2016 9:14 pm

[quote="myles"]

I have found that untreated 100% propylene glycol will start to degrade at about 121 deg C. In the future my target temperature will be 115 deg C. The fluid acts like a big heat store, and this can be used to your advantage.

Myles, how long does your glycol last if you treat it well? And do you heat it up slowly?
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Re: Oil Heated Boiler

Postby myles » Fri Jun 24, 2016 12:15 am

micah-jon wrote:
myles wrote:
I have found that untreated 100% propylene glycol will start to degrade at about 121 deg C. In the future my target temperature will be 115 deg C. The fluid acts like a big heat store, and this can be used to your advantage.

Myles, how long does your glycol last if you treat it well? And do you heat it up slowly?


I honestly don't know as my gear is in storage, but I have not needed to change it yet. Power management is recommended - especially if you are in cold ambient temperatures. The glycol gets very thick at low temperatures and if you zap it with heat there is no circulation and it will flash burn. Warm up slowly so that it circulates in the boiler by convection and gets thinner, then increase the heat.

I used pure PG (food safe) but if I would probably recommend it with additives if you can get it. It will last longer with the additives. It really is a specialist application though.

I am building a new primary boiler that in reality is a thumper sitting INSIDE a water boiler. The wash goes in the thumper, water in the outer boiler and the steam generated by the boiling water bath, is injected into the wash. So the wash is heated by two methods. Once by sitting in a boiling water bath and also by steam injection.

I had two stainless drums manufactured, one 115 litres for the inner, and a 205 litre for the outer. They are ready and I take delivery in a few weeks. :grin:
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