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proplene glycol

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proplene glycol

Postby stillyaakman » Fri Jan 20, 2012 9:13 pm

Does anyone have any experience or advice about using propelene glycol as an additive to a water jacketed boiler to raise the boiling temp. of the jacket?
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Re: proplene glycol

Postby pintoshine » Sat Jan 21, 2012 12:13 am

Sorry, I only have experience using it as a chilling fluid for fermenters and the control thereof. All the heat transfer fluid I have been exposed to is vegetable oil based.
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Re: proplene glycol

Postby airhill » Sat Jan 21, 2012 1:24 am

Myles is the member who can answer that, mind I think he used straight prop. There is a thread on it somewhere :) :beer: :beer:
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Re: proplene glycol

Postby myles » Sat Jan 21, 2012 4:53 am

You can add propylene glycol to the water in the jacket, but I really don't think it is worth it.

60% glycol boils at 110 deg C
80% glycol boils at just under 120 deg C

Both will still give you the problem of steam. "Problem" in the context of steam in the room. If jou have a sealed jacketed boiler this no longer is an issue and you don't need the glycol anyway.

For an open / vented doubler boiler (of the style that you can self build) I would recommend using straight 100% propylene glycol. Boiling point 180+ deg C. The point is though that it will never boil - just get hot. If you heat it to above 121 deg C it starts to degrade - slowly - but it reduces the life of the glycol.

However, chances are that you wouldn't want it too hot anyway - or why are you using the doubler boiler in the first place? Even gentle heat for distilling with solids in the boiler. I used to run mine between 120 and 130 deg C, but when I start with the new boiler it will be set to 118 deg C max.

Minimise the surface area of glycol exposed to atmosphere as some folks are irritated by the fumes. I use a submerged expansion tube open to atmosphere, so the only exposed bit is the internal surface area of the tube. Innitially warm up on low power to reduce the viscosity of the glycol, apply heat too fast and you get localised burning of the glycol. Once it has warmed up and started circulating you can put in more heat.

Don't forget the real BIG advantage of using glycol. It takes a long time to cool down. This means it is only of use on a pot still - not responsive enough to changes to use on a reflux still. Part way through the run you can turn off the power and keep going on the stored heat in the system. Excpecially with a well insulated outer boiler :D
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Re: proplene glycol

Postby jake_leg » Sat Jan 21, 2012 5:01 am

Excuse my ignorance but what are the relative merits of propylene gylcol and vegetable oil for a heating jacket?
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Re: proplene glycol

Postby stillyaakman » Sat Jan 21, 2012 1:34 pm

the reason to use oil or glycol is to raise the boiling point of the water to get greater heat transfer to the substrate.
however it seems to be a blend of glycol and water lowers the boiling point.
I am thinking about condensing the vapor of the glycol to reuse. oil is somthing I will also consider.
I may also go to a low pressure jacket.
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Re: proplene glycol

Postby stillyaakman » Sat Jan 21, 2012 1:56 pm

having done some research it looks like soy bean oil may be the way to go. with a smoke point of 495 deg. f.
It seems a temp. controled external heat source would be in order.
I repair resturant equipment and see self contained steam kettles with a heat exchanger over a gas flame piped to the kettle. the flame is controled by the pressure, temp., and water level. It seems a deep fryer thermostat and a manually re-settable high limit control in series with a gas safety valve. would do the control trick nicely with oil.
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Re: proplene glycol

Postby stillyaakman » Sat Jan 21, 2012 2:13 pm

One other thing I just thought of is some deep fryers are electricly heated it might not be too hard to have a dually heated boiler. I like having options.
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Re: proplene glycol

Postby punkin » Sat Jan 21, 2012 2:44 pm

Why not just use one of the kettles you see as is?
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Re: proplene glycol

Postby myles » Sat Jan 21, 2012 7:27 pm

I am with punkin on this one. If you can get hold of a commercially made jacketed boiler - that is the tool to use. All you need is water. Oil or glycol are alternatives for non-pressurised jacketed boilers.

You can make a non-pressurised jacketed boiler yourself, but I would never recommend anyone to build their own pressurised steam jacketed boiler. Unless that is what you do for your day job.

For the applications that we would use one for - distiling with solids in the boiler, the intention is for gentle even heat to prevent burning of the mash. Even with a jacketed boiler if you get it too hot it will still burn. That is counter-productive. If I had a propper 50psi steam boiler I would never run it that hard.

Now I don't know where the burning point is for a thick mash in the boiler, but I suspect it depends to some extent on boiler volume. Even so I suspect that you will run into trouble with a jacket temperature of over 130 degC. Too many variables to generalise but you can be sure of one thing. Get it too hot and it will still burn.
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Re: proplene glycol

Postby stillyaakman » Sat Jan 21, 2012 9:29 pm

I am very aware of how easy it is to burn things in a jacketed kettle and gentel heat is what I want.
The reasons I am planning to build are, cost, self contained steam kettles in good size ranges (15-30 gal.) are thousands, even used, and for the challenge and satisfaction of building.
Another good thing about them is heat storage for for the next batch. Lots of thermal mass in 10 or so gallons of oil. I can see stripping a couple of batches and then mashing a new batch of grain.
On with that theme I would like to figure out a good way to use the heat in my condensors to pre-heat my beer too.
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Re: proplene glycol

Postby myles » Sun Jan 22, 2012 5:22 am

stillyaakman wrote:I am very aware of how easy it is to burn things in a jacketed kettle and gentel heat is what I want.
The reasons I am planning to build are, cost, self contained steam kettles in good size ranges (15-30 gal.) are thousands, even used, and for the challenge and satisfaction of building.
Another good thing about them is heat storage for for the next batch. Lots of thermal mass in 10 or so gallons of oil. I can see stripping a couple of batches and then mashing a new batch of grain.
On with that theme I would like to figure out a good way to use the heat in my condensors to pre-heat my beer too.


In that case I would suggest ignoring water / steam completely. Instead go for an atmospheric pressure, vented jacket, using either veg oil or glycol as your thermal transfer fluid. You need to build in either an expansion chamber or leave sufficient expansion space in the jacket, with an atmospheric vent somewhere in the system. Good insulation on the outer boiler helps a lot, as does maintaining a good seal between inner and outer pots.

Drain and refil ports in the jacket for the fluid would be nice.

Easiest option for the last point is to run your warm coolant fluid from the condenser, through a secondary coil in your beer container, before it returns to the main coolant reservoir, or drain if you are not recirculating.
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Re: proplene glycol

Postby Abussive » Sun Jan 22, 2012 6:08 am

Steam generators (aka carpet cleaners, clothes steamers, wallpaper removers) are extremely cheap second-hand, if SWMBO doesn't already have one.....
Easy to control with a variac controller too. Shuts down automatically if you forget to keep it fed with water!

Why not just inject live steam from one of these into the outer jacket? Whatever configuration you decide on with steam, as long as you include a vent to atmospheric pressure somewhere, there will be no significant pressure build-up. And nothing to catch fire....... addition of a small condenser to the vent stops vapour clouds when things get hot.

As the steam gives up its latent heat, it will condense to water (at 100C unless it hits something cooler) so you need to make provision for that to be drained (overflow with u tube trap). When equalised, you'll have steam flowing into the condensed water layer, inside the outer jacket, which can be noisy unless properly catered for, be warned!
PS there's no rule that says you MUST throw the hot water away. Lots of uses for that! Even if all it does is keep your coffee pot warm as you sit beside your still for hours on end.
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Re: proplene glycol

Postby myles » Sun Jan 22, 2012 5:15 pm

Adonis, whilst I applaud your enthusiasm unless you have much bigger stuff than here in the UK this just wont be enough.

Shifting 100 litres of water from 40 deg C to 60 deg C will take 3.4 kg or more of steam. If you wish to do that in 15 minutes you are looking at 9+kW,or with inefficiencies probably about 25kW. 3kg of steam over 15 minutes is 4800 litres or about 5 litres per second.

That might be an industrial stripper, or just possibly a beer keg on a big propane burner. :)

Don't get me wrong - I would LOVE to have a steam jacketed boiler. I also really want a steam injected strip boiler. :8)
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Re: proplene glycol

Postby Abussive » Mon Jan 23, 2012 7:01 am

myles wrote:Adonis, whilst I applaud your enthusiasm unless you have much bigger stuff than here in the UK this just wont be enough.

Shifting 100 litres of water from 40 deg C to 60 deg C will take 3.4 kg or more of steam. If you wish to do that in 15 minutes you are looking at 9+kW,or with inefficiencies probably about 25kW. 3kg of steam over 15 minutes is 4800 litres or about 5 litres per second.

That might be an industrial stripper, or just possibly a beer keg on a big propane burner. :)

Don't get me wrong - I would LOVE to have a steam jacketed boiler. I also really want a steam injected strip boiler. :8)


Point taken Myles..... my own steamer delivers 2KW (about 1 gram/second steam). That -roughly speaking - would take about 3 minutes per 1C rise! That is indeed too much heating "inertia".
It would give you lots of book-reading time, I suppose!

[I've become more used to the mean heat input requirements for distilling continuously, and overlooked the huge pre-heat requirements for a pot still.]

A 100 litre pot still is quite a beast, isn't it? 9KW or more, just to bring it up to working temperature in a reasonable time.
I hope the "beast runners" who use electric heating take due care with the power capacity of their domestic wiring!
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