HX Fluids For Bain-Marie Boilers

punkin

Hi all, just wanted to pick some brains as to what people are using for fluid in their jacketed boilers.
I know the choices are wide, from water to oils to some extremely expensive synthetic thermal fluids, but i'd just like to gauge what people are actually using in large capacity kettles?

I have a customer who has expecting delivery of a 500l stripper and a 200l spirit still, the plan is for at least the stripper to heat the jacket up gently overnight and introduce the boiler charge once he gets in to work in the morning. Both kettles are fitted with prv on jacket and tanks.

What are all you pro's using for HX fluids and what are the positives and drawbacks you see with each fluid?

jbierling

I got your PM, I'll answer here as suggested.

I have a 500l BM with 5 ports. 3 5500W and 2 4500W. That leaves me with plenty of control just turning them on or off. You want as many high W elements as possible for even a 200l I think. I might transition to all 5500W as the 4500s die off. You could preheat the jacket as long as there was an automated shutoff.

I use tap water as the HX. It's cheap and I just dump the hot jacket and fill with cold water to help with cooling a mash. I played around with a bunch of oils but they all gave off whiffs of smoke and seemed to burn a little. Oil makes a mess out of everything it touches too. I have a 15 psi pressure release and gauge on the jacket which usually starts blowing (sounds like a fog horn)'around 12psi. You wouldn't need it with oil but water gives me a easy steam source for rehydrating barrels too.

The only downside I can see is the minerals in the water build up on the elements over time probably contributing to early death. I haven't kept track but I'd guess one dies every 25-50 runs. I can buy a lot of $7 elements for what oil HX would cost.

Kill_Devil_Spirit_Co

One guy here uses a water cycling system, heating the water with elements in line with a pump. Controls warm up that way and has the ability to hold temp which is useful.

Trent over at SD Distillery is using peanut oil in a 380L a little over the elements (uses 5x5500) and has decent control using 4 full and one adjustable.

grim

We spent a ton of time researching this before we decided to bite the bullet and go steam.

For non-HX oil, you need to manage the temperature and speed of heat up, unrefined food oils (peanut or corn being common) top out about 320F (smoke point). Refined variants are going to be better, with refined peanut or corn around 450F smoke point. Both of these are still somewhat low, and you need to manage the surface temperature of the elements (ramping), as they are prone to fouling. Just like elements can burn a wash, they can burn an oil. Elements will also die in oil if they foul.

Moving into non-food oils like mineral oil give you better performance as they are significantly more pure and have much higher temp capabilities. The HX versions of these are even better yet. A good HX mineral oil is probably good to 500-550F. You can also get non-HX food grade mineral oils that are less expensive than the dedicated HX, I assume they will perform right in the middle.

Not that you need to go 500F, but that it will remain stable and not coke or burn in a shorter period of time. In addition it will handle a more aggressive ramp time. Staying under 300F, it would probably last damn near forever. I would control these with a ramp-and-soak PID for startup, than go to manual to drive.

A high end HX oil is going to be very expensive, like $1000+ a drum. Some of the brand names here are Therminol XP, Multitherm PG-1, Paratherm NF. Why a higher end one? They are less prone to foul and burn on elements.

Water under pressure is a special situation, you need to be careful here. A pressure relief valve is not a regulator and should not be used as one. Our steam boiler has dual parallel pressure controllers on it, a PRV on the boiler, and a PRV on the still. That's 4 safety devices. Would assume at least a similar approach here with a dual active pressure control separate from a safety device. Not that I'm advocating that its a good approach.

jbierling

Yeah I should have said I don't run the jacket at pressure. Most of the time it sits at ~zero. The pressure only goes up to 12psi about 45 min after achieving a full boil only running at full power. Usually I've backed down the power well before then as my condensors can't keep up anyway.

Pressure will also go up if the pot is empty or nearly so as the heat has no where to go.

The jacket has a PRV, thermometer and pressure gauge. Pressure and temp are obviously related and I make sure both agree (the gauge got fouled once).

grim

Yeah, same here, during a run its somewhere between 0 and 1 psi, the globe valve is barely a turn more than crack open. When we first ran a few water trials, I really wondered if people were seriously oversizing their boilers or were just used to running kettles that were seriously inefficient (no exterior insulation). Yeah yeah, heat up and all, but the difference between 7, 10, 15 psi at heatup is pretty small.

I bet you if you ran a temp controller on that, and kept it under your PRV - you wouldn't have to deal with fouling, you'd have none. Your cooling flush would keep that squeaky clean.

Smaug

@jbierling what is your heat up time with water?

Sorry if you already mentioned.

punkin

Thanks guys, really good discussion here.

jbierling

@Smaug said: jbierling what is your heat up time with water?

Sorry if you already mentioned.

About 2.5 hours completely full.

Smaug

@jbierling said: About 2.5 hours completely full.

Sorry I don't remember the size. 380L? Is that correct?

jbierling

500l.

CothermanDistilling

it seems like water would be better for a spirit run than for a stripping run, which is opposite of what would help us...

What temp is the water in the jacket when heating up? when running? is there a diff in temp during spirit and stripping (what I am kind of getting around to is - does 212F transfer so much heat to a 30-40% spirit run charge that it is too much?)

what kind of temp differential is comparable to a certain watt density of electric elements?

grim

jb - agitator?

jbierling

Yes

grim

I find that agitator cuts at least half an hour off heat up, you?

dwhuff

I've used peanut oil for several years but recently switched to soybean oil. Never had any trouble with either. Soybean oil was cheaper at Sams so switched last year.lol Only thing I don't like about using oil in the jacket is it takes a long time to cool so hard to do 2 runs in a day. I'd rather not deal with hot stillage. Now running a 200 gal pot with 5, 5500 watt elements. Heat up is about 1.5 hours

punkin

How long does a tank of oil last you?

jbierling

200 liters or 200 gallons?

Kill_Devil_Spirit_Co

I also the found the heat storing characteristics of oil to be a pain when controlling product output. Took a little tinkering to find a good balance, which was basically only partially filling the jacket just over the element ports

jacksonbrown

Soy bean will degrade quickest. If its working for you then go ahead but what's the price of rice bran oil in your area. I think it might be the best compromise for price v stability.
If there's anymore pressureisd water jacket guys I'd love to hear some first hand experience or design tips.
For the oil guys, what about controlling the oil temp instead of just the power?
The bigger the temp difference between oil and bp of the wash the faster the heat transfer.
Could be a cheap add on to your existing controllers.

dwhuff

200 gallons. I can't keep liters straight in my head. We pay tax in proof gallons and wine gallons for state so I do everything in gallons. Jacket takes about 58 gallons of oil which leaves room for expansion. I have done about 80 runs with the current fill of soybean oil and no issues yet. I also have fun getting dialed in so might try draining some oil out and running with less to see if that brings more control over the run. Never heard of rice bran oil but will look into it. As far as how long it will last I don't have an answer. I ran peanut oil for almost 2 years and only changed it once as I burnt out an element and had to drain it anyway to change so filled with new. The old oil was turning brown but I probably could have continued to use it. Just figured while I had everything drained I would start new again. Steam is in our future but we need more space. We are about a year away from outgrowing our current capacity so will make that jump then. Or at least that's the current plan. No question I would go with steam if money and space were not an issue but the oil bath method has served us well for 3 years now and as you all know, you do what you can with the resources you have till you can get something better. My biggest complaint about oil is once my run is over it takes literally an hour for the still to cool enough to stop running tails. I try to time it so I run about the tails I want but keeping the condenser cool for another hour is kind of a waste of energy and water.

jacksonbrown

The 'rubberising' that soy does has something to do with this
It's a drying oil according to Wiki and my experience cleaning out deep fryers confirms that. You'll need to circulate caustic though your jacket to get all the gum out unless some kind of stabilizer was added.
Peanut looks OK too but I think rice bran might be the best compromise between stability, low cost and high smoke point.

dwhuff

@jacksonbrown said: The 'rubberising' that soy does has something to do with this
It's a drying oil according to Wiki and my experience cleaning out deep fryers confirms that. You'll need to circulate caustic though your jacket to get all the gum out unless some kind of stabilizer was added.
Peanut looks OK too but I think rice bran might be the best compromise between stability, low cost and high smoke point.

Rubberising? That doesn't sound good! lol I may have some fun in my future cleaning the jacket out. I guess the only way I will find out is when I drain it and look at the elements. I'll check into the rice bran. Thanks for the tip!

jacksonbrown

It'll be worse at the top surface where it's in contact with air.
Certainly worth keeping an eye on though, you wouldn't want to gum something important like a PRV.

jbierling

@dwhuff

I'm a bit confused how you can heat 200 gallons in 120 minutes in 1.5 hours with 27500 watts. The calculator here would seem to indicate that is not possible especially considering the jacket needs to be heated as well. Maybe our temperature rises, elevation or % alcohol are different. I'm heating 131 gallons + 35 gallons in the jacket from about 65F to 210F at 700 feet with a 8.5% wash with 25500 watts in 2.5 hours.

That calculator is pretty accurate for my still.

jbierling

@grim said: I find that agitator cuts at least half an hour off heat up, you?

I think it helps but I've been unable to quantify it. I'd suspect its quite less than a half hour though because it seems that it would only cut down on thermal loss which in my BM is probably fairly low. My kettle is insulated quite well. Is your steam kettle? Any heat not transferring into the kettle just causes the jacket to heat up more.

dwhuff

@jbierling said: dwhuff

I'm a bit confused how you can heat 200 gallons in 120 minutes in 1.5 hours with 27500 watts. The calculator here would seem to indicate that is not possible especially considering the jacket needs to be heated as well. Maybe our temperature rises, elevation or % alcohol are different. I'm heating 131 gallons + 35 gallons in the jacket from about 65F to 210F at 700 feet with a 8.5% wash with 25500 watts in 2.5 hours.

That calculator is pretty accurate for my still.

If I were heating to 210 degrees it would be longer. I'm pulling product way before 210. I'm into tails at 210. Don't know what to tell you. It takes 1.5 hours to getup to temp and have all plates going.

CothermanDistilling

I like this calculator, it validates that that is a possible time electric-heat.xls

jbierling

I guess if it's possible I'd like to know what could do better to heat my still. You've pointed out a time that's closer to two hours and it doesn't include the volume of the jacket. A boiling point of 180F is a 80% ABV mix too which most would not recommend.

My ferments are close to 68F too at the start and around 8% ABV.

Don't get me wrong, I'm just trying to make sure that apples are compared to apples.

grim

Looking back through my notes for the test runs we did without the agitator, maybe a bit less 15-20 minutes difference. But, there is absolutely a difference. One of the last water test runs we did, we were watching the jacket pressure closely. Now, the jacket pressure correlates somewhat with the amount of heating. When the liquid is cold, the jacket pressure is low, even with full steam from the boiler. The steam is condensing in the jacket as fast as we can push it in. Once the temp rises, the jacket can maintain higher pressures. One of the last test runs we did, we left the agitator off, and were slowly building pressure. As soon as we switched the agitator on, we saw the jacket pressure dip, which means more condensation and more heat transfer. At that point the temp stabilized and started moving up at a much faster clip.

That said, heating on steam is pretty fast. I can boil 1000l of water in like 30-45 minutes - this is with 15.6hp, which is like 150kw boiler input. The numbers roughly make sense, 1000 liters water, 20c starting, 100c ending, 150kw input with about 80% efficiency. 15-20 minutes on a 30-45 minute cycle is like a 50% improvement.

Our kettle is insulated, standard SD steam jacket kettle. I would say the insulation is very good, even during a long run the outer jacket temp is never too hot to touch. It's hot, but you don't get burned.

grim

@jbierling - The only other strategies are to increase the kw and to preheat your HX. I also agree that the numbers look to be too aggressive, especially given the efficiency on the bain marie can not possibly be in the mid 90s.