Double-wall boiler safety/operation

[DAD300]

Trigger warning on the size issue. DSP listed.

I have two baine marie stills 50 and 170gallon, a 300 gallon mash tun, jackets filled to the 30% level with water, all closed jackets with Pressure Relief Valves (5 PSI) and Vacuum Relief Valves (0 PSI).

At best any closed jacket baine marie is about 85-90% efficient at heat transfer. Properly engineered, doesn't matter copper or stainless. So, if your putting 10,000watts into the jacket your getting ~8,800watts into the distillate pot.

While I don't know, I'd assume an open jacket baine marie is only slightly less efficient. And allowing some steam to constantly escape, may not be any safer. Where do you vent the steam and how do you keep track of water level in the outer jacket?

I try to run the stills at about 3.5 lbs pressure in the jacket. That gets a max temp in the jacket of approx 225F or 12F above water boiling. In reality, even with 170gallons, this doesn't make a great deal of difference. Several other factors can make it less or more efficient, insulation and agitation. Be careful not to spend too much effort to save 5 minutes per distillation.

I'm rarely going for a fastest, minimum heatup time. I like the slow heatup for maliardization. Look that up.

In the mash tun it is a moot point as the temps are a lot easier, I rarely see much pressure and I never attempt to maintain a temp by power. Most of my mashing is get to a temp and turn off power, coast to lower temp. The jacket does a great job of maintaining temp in the pot. This isn't beer, I'm not interested in crash cooling.

Nothing about baine marie is faster or meant to be. It is about grain in, no scorch!

A key here is to size your equipment and power for the amount of time you are willing to distill. Xgallons needs Ypower to be done in six hours. Setup and cleanup makes for an eight hour day.

Pids and running by temp...are usually conversations for people from the beer world or that don't want to be there while they distill. If you want automation, best invent a warning system for every facet you automate.

I have no power or water automation, but I have alarms for pot and water temps.

If you run your equipment a few times, make some notes, you will know the power and cooling water settings for any situation.

[shadylane]

I am not sure if I get the advantage of using vapour at 120°C instead of boiling water.

The steam jacket is a closed system, there's no need to replace and reheat the water that would boil away.
Steam @ 120c is much better at transferring heat than water boiling at atmospheric pressure.
Heat transfer fluid could be used instead of water,
but then there's the problem of overheating the oil and/or scotching the mash.
Also a jacket full of cold water makes a good wort chiller

[Birrofilo]

While I don't know, I'd assume an open jacket baine marie is only slightly less efficient. And allowing some steam to constantly escape, may not be any safer. Where do you vent the steam and how do you keep track of water level in the outer jacket?

Nothing about baine marie is faster or meant to be. It is about grain in, no scorch!

In a bain-marie technique you don't furiously boil the jacket water. You can keep it at 100°C ideally before change of state, or below that.
A PID for instance would help keeping the water at 97 °C, there is some evaporation in any case, traditionally this is all managed manually, in the modern world a system could be devised that fills the jacket with other °97 °C water to compensate the loss (for electric geeks).

I agree bain-marie is all about slowness and no scorch, and it is also associated with agitation. A still with agitator and jacket is very well suited for fruit distillates, it's the final machine.

[metalsmith]

[quote=Birrofilo post_id=7570384 time=1565305864 user_id=66317
I am not sure if I get the advantage of using vapour at 120°C instead of boiling

The only advantage I see so far would be a faster "ramping up" of temperature at the beginning of the operation.

It's also true I never operated a 100 l rig and the ramp up must be pretty boring and slow.
[/quote]

Hello, here is my 2cents. All we are doing here is move heat. It is true that the greater the differential in heat, the faster the heat moves. We know that using a double boiler, Bain Marie, or what ever you wish to call it, is good for not scorching your fruit, grain or ? That you are trying to heat. If we want speed, this may not be the method you want, sort of.

We look for efficiency. This corolates to time. The latent heat involved in phase change is very desirable. It delivers more BTU at the same temperature as the steam, than the fluid itself. A pound of water vapor (steam) has significantly more BTU than a pound of water liquid. But it all is at 100 C. Superheat it, I.e. put pressure on it, it has even more BTU content, and a higher temperature. Remember this means heat moves faster to the colder material. Ever take the lid off that pot of spaghetti? That steam burn was at atmospheric pressure, but had a lot of heat to dissipate (condense) on your skin. Ouch!

I always wondered what temperature would scorch my mash. Well, it is not 100 C. Steam even under pressure won’t do it. So I can take steam, even at modest pressure, contain my temps, and move a bunch of btu through the latent heat involved in the phase change, meaning I don’t need 12 hours to heat up my mash, not scorch the solids, and get some nice product. I do have other things to do with my day. Every one is concerned about making steam under pressure and they should be. The energy involved in rapid de pressurization (i.e. boom!). Is hard to comprehend.

Sorry, lost where I was going with this, but you get the idea. Steam can be our friend, but for some of us a very bad idea.

[DAD300]

Closed system, can result in higher temp in pot. But more importantly a more even transfer of the heat produced.

An electric element in a pot will be more efficient energy usage and only have a couple of inches of surface, while the water/steam jacket surrounding a pot would be less efficient but have a thousand times the heat transfer area.

The greater transfer area helps prevents the scorch. It doesn't have to be slower.

But the distillation may/will benefit if it is slower.