Controlling Boiler Temperature During Distillation

OK. You guys are going to bean me.

I got told to fuck off back to here to SD world because I couldn't understand what someone was saying on another forum. So here I am to ask what is obvious to some, but not to me, a stupid fucking question.

  • I do understand about the boiling point changing with the content of alcohol.

  • Using your SSR control kit, you manually control the temperature in the boiler. Yes or No?

  • As the ethanol evaporates the boiling point of the mixture rises. Yes or No?

  • You have to change the boiler temperature CONTINUOUSLY using the SSR as the ethanol evaporates. Yes or No?

  • Why cant a temperature controller do this for you even if you have to change the setpoint every now and then?

Sorry if I have shamed you guys for coming back here to get this answered but I am obviously missing something and no its not a fucking chromosome but the people on the other forum got very upset with me because they couldn't explain it. Or maybe I have shamed me who the fuck knows.

Mod edit to remove confusion about which other forum is involved. We like to keep our little world here peaceful.

Comments

  • As long as you are liberating alcohol you are not (really) going to be able to control the boiler temp. At least not very well.

    No you are not really controlling the boiler temp. You are controlling the input to the boiler however.

    Yes the boiler temps will naturally rise as you liberate the alcohol.

    You can adjust but that is not really needed as the boiler temps will naturally rise.

    These plated systems, when dialed in will literally shut them selves off when the usable alcohol has been collected. The collection speed may also slow down but that is a result of less and less alcohol being available to feed the column. In this instance throwing more heat at the system will reduce purity unless you bump up the reflux ratio.

    I hope I said that correctly and that others will chime to help clarify the picture for you.

    StillDragon North America - Your StillDragon® Distributor for North America

  • edited May 2014

    Bunch of jerks over there.

    Using your SSR control kit, you manually control the temperature in the boiler. Yes or No?

    The SSR control kit allows you to control the amount of power being fed into the boiler. You can control the temperature up until you hit boiling point. Once you are at boiling point, you can only lower the temperature, you can not increase it past boiling. Boiling point is a function of the percentage of alcohol and water. More alcohol, lower boiling point. Through the run, the boiling point temperature will increase as the percentage of alcohol falls.

    As the ethanol evaporates the boiling point of the mixture rises. Yes or No?

    Yes.

    You have to change the boiler temperature CONTINUOUSLY using the SSR as the ethanol evaporates. Yes or No?

    No. Once you are generating sufficient vapor to run the still, the SSR control will adjust the speed of output. Fast or slow. Although if you crank it way down, the boiler temp will fall below the boiling point and stop generating vapor. Think of it this way, once the still is running, you need ## watts to generate ## liters output. Generally though, in some cases you may need to add more power to keep flow rate high with the tails (or you might crank up the power to collect tails), likewise you may use less power during heads collection so you don't smear.

    Why cant a temperature controller do this for you even if you have to change the setpoint every now and then?

    Most temp controllers run FULL ON or FULL OFF. Depending on how large your heating elements are, when your boiler gets up to temp, this usually means that you go from generating no vapor to generating too much vapor, as the thing clicks on and off, which is extremely frustrating, and will likely create a poor product.

    The SSR controller lets you keep a constant 33% of power being fed in, for example, versus a temp controller that would provide 0% or 100%.

  • edited May 2014

    Think of the SSR controller as being the knob on a kitchen stove that controls how big or small the flame is.

    Once you get to boiling, you can make it boil more vigorously by turning the knob to high, or you can bring it down to a simmer by turning the knob towards low. Either way, you are still boiling. If you put a thermometer in the pot, you'd see that no matter if you were simmering or vigorously boiling, the temp would still be 100c. You can't make it go to 101c, no matter how high you set the flame.

    But if you start turning it to low, and the temp falls to 99c, the simmering would slow and eventually stop once the pot cooled. You'll get some whiffs of vapor, but you really aren't generating steam.

    You can use a temp controller to keep your water boiling, because if the pot is filled with nothing but water, the boiling point won't rise. With a mix of alcohol and water, you'll need to chase the boiling point upwards from 78c to 100c through the run (you'll never get to 100 realistically, why bother).

  • @grim said: Think of the SSR controller as being the knob on a kitchen stove that controls how big or small the flame is.

    Once you get to boiling, you can make it boil more vigorously by turning the knob to high, or you can bring it down to a simmer by turning the knob towards low. Either way, you are still boiling. If you put a thermometer in the pot, you'd see that no matter if you were simmering or vigorously boiling, the temp would still be 100c. You can't make it go to 101c, no matter how high you set the flame.

    But if you start turning it to low, and the temp falls to 99c, the simmering would slow and eventually stop once the pot cooled. You'll get some whiffs of vapor, but you really aren't generating steam.

    You can use a temp controller to keep your water boiling, because if the pot is filled with nothing but water, the boiling point won't rise. With a mix of alcohol and water, you'll need to chase the boiling point upwards from 78c to 100c through the run (you'll never get to 100 realistically, why bother).

    +1

    Good analogy.

    StillDragon North America - Your StillDragon® Distributor for North America

  • Indeed, Grim's analogy is excellent.

    If I may rephrase what the others have said. The purpose of the controller is to control the amount of vapor that you are sending in the column by controlling the power input. The amount of vapor is about directly proportional to the power input : i.e. at 50 % power (real power, not what you read on the knob), you are evaporating half as much as at 100%. This, and not temperature, is a the relevant parameter for your distillation.

    While you could control if water is boiling or not by using a temperature controller noone will ever do that because the rate of evaporation (how hard it is boiling) is almost always an important parameter.

    The temperature of the boiler is measured mostly to have an idea of how soon will the wash boil during the heat-up phase and to give an idea of the ABV in the boiler during operation but it would not be used for control.

  • The only thing I wish to add is aimed mostly at pot distillers.

    On a simple pot still boiler you can use power management during the run. In a very limited way you can get slight control of the vapour composition leaving the pot still product condenser. For example increasing heads compression at low power input.

    Now let me stress that this is NOT changing the vapour composition that leaves the boiler. Instead by adjusting the total energy in the vapour path it allows a slight variation in the amount of natural condensation in the vapour path. That condensate is returned to the boiler, resulting in a slight change in product composition.

    It is a limited application, but many commercial pot stills do in fact use power management.

  • I gotta chime in here with my newbie question. I have seen reference online here,

    (https://www.youtube.com/watch?v=kgrJNPmFLd8&list=UU4TJceC6wVGErnoWblqafAw),

    to controlling heating input to the boiler element by using an RTD sensor in the vapor path at the top of the column. I am building a PID controller and am curious to hear feedback from you plated column veterans here as to the pros and cons of controlling the heating element this way. Is there benefit to setting up my system in this way if I want to run single malt utilizing a stripping run with no plates then a spirit run with four plates? Thanks in advance for your comments.

  • I'd control water temp/flow to the reflux condenser with the PID.

    StillDragon North America - Your StillDragon® Distributor for North America

  • I stopped watching when he advocated for letting your still run unintended.

    He loses all credibility. This is so incredibly reckless that the validity of the product is irrelevant.

  • You have to be careful about these boiler control systems. Some of them are actually just a fancy way to control the elements during the warm up period. This is intended to prevent burning of the elements by supplying too much power before the wash is circulating by convection.

    You can do this by monitoring the vapour temperature in the column, just make sure you understand WHY the boiler is being controlled, as it may have nothing to do with the product.

  • edited May 2014

    If you are looking for good discussion about automation with real-world benefits - Cotherman's post about using the Danfoss AVTA for reflux condenser water control is among the best. He may not have invented it, but the approach about as elegant as you can get. Surprised more aren't going this route. That valve is commonly found on many six figure stills. Right up there with Smaug's comment on reflex condenser control being a more interesting problem to solve.

    Thermostatic Valve Installation on Product Condenser

    I'm all for digital or mechanical control if it helps you make a more consistent product. But realize that whoever your maker is, they have you a set of sensors and a controller that would cost you hundreds of thousands of dollars to replicate with electrical parts, so don't be mislead into thinking it'll make a better product.

  • edited May 2014

    YIPPEEEEEE. Thank you everyone. I do understand temperature control on boilers, chillers etc, I do it for a living. I was just missing that tiny little link that my brain was not understanding about take off rates after the liquid is at boiling point and how it relates to boiler temps, it doesn't its just input power to the liquid to increase evaporation rate. Why the fuck I couldn't understand it last night I don't know. I get it now. THANK YOU SD USERS. I don't know who that was more painful for, me or you.

    @grim "Bunch of jerks over there". Yes some of them are and I think someone over there should stop drinking after the sun goes down, alcohol isn't everyone's friend.

  • edited May 2014

    Perhaps just being "matter of fact" came off the wrong way?

    StillDragon North America - Your StillDragon® Distributor for North America

  • Thanks to you all for perhaps the best and clearest explanation of control of power input vs temperature control that I' very read to date.

  • Hello,

    I am a new member on this forum and also greetings from Slovenija :)
    First sorry for english mistakes...

    I am looking for solutions how to control pot destiller temperature. My father uses gass burner and i was thinking to regulate flame intensity with stepper motor conected to gas valve- controled by arduino.

    As i understand as the ethanol evaporates the boiling point of the mixture rises.
    It is hard to explain my idea of program algoritm but will try- i have couple of them :

    Let say that my gas valve rotates for 270 degres. This is translated to %. So fully closed is 0% and fully open is 100%

    WARM UP phase:
    Gradualy increase flame from 30% to 80%- every 2 minutes increase by 10% - (to warm up kettle)

    PID CONTROL phase:
    PID will heat up mix to 80C, and stepper motro will adjust flame
    First set point will be 80C-boiling point of ethanol and water is higher than 80C,
    After setpoint is reached - Save position of valve (let say last position of valve was 45%)

    DESTILATION phase:
    valve on last position (45%)

    Every 30s i will check if temperature is rising or falling:

    if falling-     increase for 1%
    If rising slow- do nothing (T2-T1<1C)
    if rising fast- 1% closing (T2-T1>1C)
    if equal-       can be due to 2 reasons:
    
        reached boiling point ------------ or flame too weak //count every equal
        increase 1%                        increase 1%
        if 3x in a row temp is equal- it is boiling
                     increase 5%  - for gentle boil
    

    This is draft idea how to check if we are near boiling point- if temperature doesnt increase in 3 mesurments in a row it means that this is boiling point.

    Please let me know what do you think.

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  • In distillation, nature controls the temperature, by lowering the boiling point as alcohol is boiled off. It is not something that you can control in any way with the amount of heat applied.

    I suggest doing it by hand first, you will find that the operation you describe is far more tedious than it is worth.

    also read the manuals, you will notice there is a lack of talk controlling the boiling point...

    The StillDragon Operation Manuals

  • Don't understand the problem you are trying to solve for, or how that control approach is going to accomplish what you think it will.

  • edited October 26

    If you want to systematically check or control for boiling point, it's much easier to use two thermometers, one in the liquid, one in the headspace. Use the headspace vapor temperature in relation to the wash temperature to determine whether you've achieved boiling.

    Remember, that once you are at boiling point, you move into "power input" mode, opening or closing the valve will have no impact to the temperature, you will only change the rate of boil. Any control scheme that attempts to increase or decrease power input to determine boiling point is just going to end up cycling the boiling rate up and down.

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