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Kettle / Boiler Surface Temp for Scorching Wash?

Hi Folks.

Jacketed or BM boilers - what is the surface temp range that is prone to scorching or burning inflowing wash?

I can only assume there are many variables based on wash contents, Brix (sugar content etc), viscosity, grain in or lautered wash, boiler filling speed etc etc.

I am looking to preheat my BM boilers (thermal HX) & Wash seperately (HERMS - long retention & slow flow using thermal HX) prior to runs.

Therefore - should boiler surface temp & wash temp be pre-heated at same temp OR a have significant Delta in temp range of the jacket versus RIMS to utilise the thermal transfer from the jacket temp?

Are there general temps as a guideline or ball-park..

e.g- Jacket surface temp @ 90c with wash entering boiler @ 70 (Delta 20c) & then heated to 95c through the cycle.

Should the jacket surface temp be upwards of 110 & 120c in order for a larger Delta?

I also have in mind a RIMS tube as a variable heat source on the wash inlet to boilers OR a RIMS on the side of Boiler to boost boiler temps.

Latent Boiler or HX heat not an issue to me at this point as I want to utilise multiple runs per day.



  • I wouldn't imagine a surface temp of 120c would cause issue, but I don't understand what is going through the RIMS.

  • RIMS idea is to utilise a pre-heat option for the Wash as it is transferred from HERMS coil to Kettle.

    Basically an adjustable temp booster as the wash enters the boiler - perhaps this is just overkill & an element or KwH I would use in the RIMS is better utilised elsewhere..?

  • What a super question. One I thought only I cared about. As it should happen I've spent the last 12 months working on this and have designed a system to heat below the organic scorching threshold.

    More to come soon.



  • edited September 2016

    The surface temperature of the heating element in the RIMS tube is going to be the location with the greatest potential for scorching, due to the fact that the element sheath temperature is easily in excess of the temperatures we're talking about by 100c or more.

    If you are using electric to heat your jacket, there is nearly zero benefit to pre-heating through RIMS, as the efficiencies are likely to be similar.

    I would invest in agitators instead.

    If you want to preheat your jacket HX (as well as all the corresponding metal/thermal mass), that's fine, but don't bother taking it to these levels, preheat to 70 or 80c. If your HX fluid is oil, you may find that you hold SIGNIFICANT temperature from run to run/day to day. In fact, if you keep your still filled with the last run stillage, and dump immediately PRIOR to the next run, I bet you that achieve incredible efficiency and heat up times. The thermal mass of the stillage plus the metal, plus the oil? My insulated 1000 liter steam jacket still would probably drop 20 degrees, max, in 24 hours.

    Even better? Use a liquid to liquid heat exchanger to preheat the next batch using the old stillage.

  • edited September 2016

    Really though, preheating through RIMS sounds like it's more trouble, and more time, than it's worth. We pump over at about 30 gallons a minute, we transfer 265 gallons in less than 10 minutes.

    Sorry to switch to US terms.

    But, to get only 20F in temperature rise (pre-heat), at 30gpm I would need 300,000btu, or 88kw, of heating elements, to get this.

    That's a massive heater, to take me from 80F to 100F?

    So what next, slow it down and get a higher temp rise? Let's say I want to go from 80F to 150F, a 70F rise. Let's say I have 20kw of power (more realistic than the 16 5.5kw elements needed to get to 88kw). That means I need to pump at 2 gallons a minute to get my pre-heat. That's going to take more than 2 whole hours in my setup.

  • Oil HX jacket yes.

    Preheat wash using previous wash in a shell tube style condensor for liqud-liquid HX.. yes

    RIMS idea is fine to remove - what about thermosyphon/ calandria / shell tube HX unit to pump / agitate wash while in boiler?

    Electric - yes, my issue is making the most out of 240v 80a 3 phase I have on site..

  • Just one point. Even if you have the fluid in the jacket at 120 degrees, the inner surface in contact with the wash is NOT at 120 degrees. I have taken glycol to 130 degrees C and have never burnt the wash. Think about it.

    There is a temperature gradient through the wall of the inner pot.

    Just think about a kettle of water boiling on a gas hob. The metal surface inside the kettle is not as hot as the metal surface above the gas jets.

  • Thanks, so where is the sweet spot for Delta between boiler wall temp and wash temp to maximise heat time and temp.

    Versus kwh input and product/ run time output etc.

  • No idea because you also need to factor in agitation as this influences the disipation of heat from the wall into the bulk of the wash.

  • Agitator the best way to make use of limited power.

  • Yes - I have been looking at a external HX & pump with tangential flow in the boiler - known as 'Symphony' Wort boiling..

    I just may be batshit crazy - but such a process can also heat the wash & agitate 2 in 1..

  • Once again if you've been following @HurdleCreek 's posts you will have seen his StillDragon boiler that he had designed to do the agitation with a pump. ;)

    StillDragon Australia & New Zealand - Your StillDragon® Distributor for Australia & New Zealand

  • edited September 2016

    Pumping boiling liquid can be problematic if it isn't designed well.
    Its all added complexity that adds to cost and energy consumption (pumping). It's all stuff that needs to be cleaned and more points to fail.
    Building a better mousetrap can be fun but are you going to great lengths to solve a problem that might not exist or at the very least, already has a few very simple, elegant solutions.

    The metal surface will very cool compared to the heat source.

    The wash will be sucking the heat out so it stays close to the BP.
    Making use of the heat in a spent wash or condenser water is a great idea but if you're concerned about scorching then agitation is your answer.
    CIP flowrates through your RIMS tube might help.

    I might not have a full grasp of what you're suggesting, I have a feeling there's some bastardized terms in there.

  • edited September 2016

    I never liked the concept of using a pump for agitation on a still, especially if you have any intent of running low wines. A touch too dangerous.

    On a mash tun? Doing a cereal mash? Sure, I would absolutely use my positive displacement pump, but that's a multi thousand $$ agitator.

  • edited September 2016

    @punkin said: Once again if you've been following HurdleCreek 's posts you will have seen his StillDragon boiler that he had designed to do the agitation with a pump. ;)

    We've never used the tangential return port during a run it to date. We heat a ~400lt grain wash with 2 x 28 jet duck billed burners on LPG. We've not had a serious problem with scorching. We generally get 3-4 stripping runs from a mash after which I do a quick a caustic wash and a bit of work with scrubbing brush on a pole to reclean the surface before the 1st spirit run.

    On the subject of external heating, external steam kalandrias are very common on kettles in the brewing industry. In theory, & if properly designed, once up to heat they will themosyphon but in my experience, it you want fast efficient evaporation its not uncommon keep the recircualting pump running throughout the boil. The process of wort boiling (PDF) "Symphony" is just the Briggs brand name for their external system.

    I'm thinking about adding a preheat system to use the still waste to preheat the next wash but first need to find a cheap 400lt+ insulated buffer tank to make it cost effective (+ it also has to look good as it wil be in full view outside the Stillhouse!).

  • Cheers @hurdle :)

    Surely down your way you have plenty of Dairy tanks/ vats at your fingertipsfor a preheat HERMS?

    Can I ask why the preference for the tangent port & pump install & not agitator..? What are your pro's & con's?

  • edited September 2016

    Motor outside EP zone for one. Transfer pump can just be diverted to fill or empty tank as well, or even CIP.
    Retrofitting an agitator to an existing tank can be problematic.
    We retrofitted a pump/mix setup on for a customer a while back. I can't remember why that constraint was put on us but it was a stupid idea in hindsight (for that application at least).
    What are you referring to when you use the term 'HERMS'? Just recirculating through a shell and tube?

  • Thanks.

    Herms Coil - preheat wash through a 1/2 inch copper coil inside a keg or drum with element heating.

    Inline between Fermenters & Boiler for pre-heat prior to run.

    Easily use previous wash as HX heat transfer - therefore could utilise a shell & tube condensor or a large wort chiller (thermal transfer) coil as a more of a HX concept of draining hot wash & filling boiler with new wash etc.

    All ideas are on the drawing board..

  • You're on the right track but thinking like a home brewer. A coil in a drum won't be very efficient.
    A decent sized counter current THE or PHE will be heaps better but you'll need some sort of an IBC, (obviously you can't fill and drain from the boiler at the same time :D ).
    A spare fermentor could work OK, especially if your running some backset, it could work into the process nicely.
    If you can minimize plant down down it's easier work out a continuous cycle where heat doesn't leave the system.
    Boiler to empty fermentor, fill boiler through a HEX will emptying the hot hot fermentor, leave it 20% full of backset then you'll have the next wash already pH adjusted and up to pitching temp (assuming you're not mashing).
    What are you actually running? the best answer is going to depend a lot on what you're actually trying to do/make.

  • Cheers - yes 1000L SS IBC tote fermentor will suit that nicely..

    Sorry -> T-HE OR P-HE.. HE = Heat Exchange..?

    I agree with the backset rotation & as I am in 25-30c weather all year here Down under otherwise - less 'cooling' the better from an energy balance.

    Focus is multipurpose as we can from Wine low wines for Eau De Vie/ Brandy Fortified Wines through to Rum/ Shine.

    Any grain mashing/ wash we already want to lauter & distill offgrain so this should also suit the above HX system just fine.

  • Tube Heat Exchange or Plate Heat Exchange..?

  • Tubular or Plate Heat Exchanger, yep.
    Sounds like you need a lot of flexibility which might limit options a bit. Fist fulls of cash usually fixes that though =))

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