Temperature Probe Location

I am making a controller to regulate the temperature of a heating element inside of a keg on my column still. Where would be the best place to put the temperature gauge. My first thought would be at the head of the column, after the dephlegmator. My second option is obviously in the keg.

Answers

  • It would depend on what you are trying to accomplish. The two places you mentioned for placement would be places to monitor to control two different processes. I monitor in the boiler to control the heating element. Also monitor the vapor temp to control the reflux. Controlling the element is not accomplished by measuring vapor temps.

  • Hi @cbastian81 and welcome.
    I'm not sure I understand what you are trying to accomplish. Are you trying to automate the ramp up to boiling and then dial back to running power?
    I'm not aware of any way to regulate the power going to the element based on any temperature readings because, as you probably already know, more power does not increase the vapor temp or the charge inside the boiler once it is boiling - it just increases the vapor speed or makes the pot boil more vigorously.

  • I am using the controller (PID) to heat the boiler to running temp and then maintain a set temp as i make my run. You guys answered my question, thanks!

  • To help as best as I can...
    We typically dial in the heat to the boiler that we think the column can be happy with and that is a bit of trial and error (call it experience if you will) and push it to find your limit.
    The PID adjustment as far as running goes is to control the dephlegmator and that is based on either the vapor temp or the dephlegmator exit water temp. After trials I prefer the dephlegmator temp vs the vapor temp for system stability. Your mileage may vary and if you differ from me I'd sure like to hear about it as this is all new science.
    Also, a separate PID for the product condenser is very cool and an over-temp alarm here is handy here since a cooling water input failure here could be catastrophic. A product temp PID that sets the product output at a given temperature of, say, 20C is just so great as the alcoholmeter in the parrot reads perfect. The alarm is great because should you turn your back to the still to take a pee and you lose water pressure to the still then you get an alarm that flammable alcohol vapors are about to spew.

    Never leave a running still unattended. Never collect below 30% on the parrot. Never say never :) and the exception will bite you on your ass.

  • you could use your PID's alarm functions to have a 2nd element powered for heat-up(or be full-on, then switch to max duty cycle once reached... but you really want steady power to the boiler, not necessarily a steady temp in or above the boiler... Like Lloyd said, the thing you want to control is water flow, to both save water, and provide just enough reflux to keep your ABV where you want to increase hearts..

  • @cbastian81 said: I am using the controller (PID) to heat the boiler to running temp and then maintain a set temp as i make my run. You guys answered my question, thanks!

    You cannot set a boiler temp and still take off product, you could only set the temp below the boiling point of the binary mixture, not above it.

    It just doesn't work like that.

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

  • I am a little confused as to what you mean by steady power to your still/boiler. Is there not a temp that you try and maintain in your still so that you don't have to continually make adjustments to your water flow? Or is it just balls to the wall and managed by the water flow? Couldn't I use the PID to maintain a temp in the still to say around 90c and use the dephlegmator to increase the ABV?

  • Take 2 pots of water on the stove.

    Just simmer the first pot of water, it will give off a little bit of steam- aka vapour in our terms.

    Turn the power all the way up on the second one. It will boil and bubble heaps, it will give lots of steam- aka vapour.

    Q. Now what temp are both pots of water?
    A. The same.

    Thats why everyone says you can use a pid or whatever to assist to bring the boiler up to temp only, once its hot you need a power level that produces the amount of vapour the still can handle only.

    After producing steam - vapour - the temp of the wash increases as we draw off alcohol and more water remains, I dont know the maths or precise numbers, but that is the way it works.

    Most off all the boiler controls is to maintain a power level to suit the run, lots of power for stripping, or warm up then wind back for spirit runs, more power during tails run out etc.

    I can use 2 elements flat out at 7200w on heatup, and for stripping. I can only use between 2400w- 3600w on spirit runs otherwise its too much vapour for my still to handle, floods and produces crap results.

    The boiler temp will be the same however, so if I used a PID to control temp, it will heat using whatever elements are connected, then turn off, cool down, elements back on full, etc it would be a nightmare to run the still itself.

    I really want to join the semi-auto control system as well, but they are based on water control on the still, boiler is manual in most cases.

    fadge

  • edited June 2014

    Exactly what Fadge said. More technical detail on this page about half way down, past the Raoults Law discussion.

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

  • yep, you put in power at a stable rate to put out steam(alcohol vapor) at a stable rate... so for the boiler, you want a controller that does variable power. This can be done with the SD DIY controller, a PID and SSR with a 'manual' mode, something more simple like different elements of voltages, or something more complicated like a PLC-type controller

  • edited June 2014

    I seem to remember the boiler control question being explained to me on another thread. Maybe if he goes here for the boiler control question and here for an excellent discussion on the sensor locations.

  • Thanks mate.

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

  • I use a PID, but only for heat up or if I am going to leave the building. Lets say I want to skip heat up in the morning, I set the PID in timer function to turn on a certain amount of time before I arrive for work(100 minutes before as this is my heat up time), and to only let it get to a certain temperature(in case I am late). Likewise if I want to leave during the heat up I just set it to a temperature so it doesn't get to boiling point. When I return in either case I switch the PID to manual mode and give it whatever percentage I want, the PID function has no use when you are pulling product. I have my RTD temp probe in one of my element ports with a triclamp/npt adapter, I am only using 4 out of my 5 element ports for elements, I found 22kw on my 500 liter to be enough power. If you ever look at swede's stuff at distillerycontrols.com he has a dial where you can switch to percentage, this is basically the exact same as switching to manual mode on your PID. I worked at a custom ski mfg for a while where we used PIDs and PLRs on various equipment and got comfortable around them, there are really quite simple.

  • There is a lot of discussions relating to boiler power management, but a lot of this is aimed at POT stills, where you do use power management during the run. On a pot still you can use different power levels during the different phases, although many folks don't bother. They just find a "sweet spot" for their own still and consistently use that power level.

    On the column you also use power management, but this is mostly to do with maintaining a constant vapour speed throughout the run, as the plates or packing are optimised for a specific range of vapour speeds.

    Power management during warm up can be used on any boiler.

  • I find on a bubble column that I tend to increase the power a dab through the run.
    A bit lower power than at collection speed to load the column and drive as much heads out of the boiler as possible during equalization - thus needing less cooling water to the dephlegmator during that 1/2 hour or so.
    Once firmly into hearts I bump the power up a bit to increase production.
    If I sense tails creeping in I have 2 choices; lower the power (and take off rate) or increase the reflux cooling flow which also lowers the take off rate. I typically do a little of both, but that's just me.

    All of that has recently been mitigated by using a PID controller for the dephlem coolant water as the controller can more accurately respond to column conditions than I possibly can by fiddling with valves. Instead of bumping power I raise the temp on the PID controller and it adjusts the water flow to precisely maintain the desired vapor temperature. Product flow slowly tapers off and when it really slows then I'm into tails.

    I've run my Dash without ANY temperature sensors at all and got great product. I added thermometers here and there and was able to get more repeatable results. I added PID controls and find I don't need to do very much still tending. I get better results with much less effort but somehow I miss "winging" it. PID adds a high degree of accuracy but removes the tactile enjoyment to constantly monitoring the still.
    After adding computer control to my still I probably will never go back but having "winged" it for so long gave me a deeper understanding.

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