LOW TEMP DISTILLATION

[vino-tinto]

I have been working on 23L stripping runs using a Grainfather/T500 and homemade pot still, in particular boiler temperatures. After several tests I have found some interesting things out.
As some know I have an ALVA controller which enables me to run programs as set out below.

OK, standard science, water boils at 100C at sea level and lower at higher altitudes, and in doing so water vapour (steam) is created.

Alcohol boils at anything from 57C to 97C, so why do we heat up a wash to boiling point, as doing so causes spirit and water vapours to be created at the same time.

Instead, bring the wash up to 88C and hold it there. This will cause a low temp rolling boil which is required to give the vapour some pressure so it will climb the column.
At this temp it should create a better separation of the alcohol vapour, this in turn causes a much higher proportion of spirit than water (higher ABV) to go through the condenser.
When mixing alcohol and water together it isn't easily separated so you'll always get a mixture of both.

As the spirit flow ABV decreases it means the alcohol to water ratio has also decreased and as I said earlier water boils at 100C so more water means more energy is required to keep it in the same state of rolling boil.

The answer is to slowly ramp up the boiler temp in increments of 1C at a time, taking off spirit as you go until 93C is reached, at this point the spirit will have dropped to approx 20% ABV.

Another thing I tried was adding 60 grams of natural sea salt to the wash which in turn increases the boiling point of water so in doing so, increases the alcohol content over not using salt. Apparently salt is non volatile so always remains in the wash, but beware salt can attack stainless steel in the same way as bleach causing small pits on the surface, so thorough cleaning is required after.

This does not refer to the use of a reflux still, refluxing causes water vapour to drop down the column first as it has a higher boil temp.

So now we can debate the pros & cons, someone must have an idea

[Anavrin]

Hi vino-tinto

I agree with you that alcohol boils at a lower temperature, however in order to boil a mixture of alcohol and water, you cannot simply heat above the boiling point of alcohol and expect the alcohol to boil.

It won't, nothing will boil until the boiling point of the entire mixture is reached, and that will depend on the concentration of how much alcohol is in the water.

The guys who have been designing digital parrots like YHB amongst others, have already done the maths on this, and from any given boiler temperature could probably tell you the products %ABV and how much alcohol is left in your boiler.

I don't think increasing the temp setpoint in small steps will produce the effect your looking for but I can see a use for it if you knew from some trial and error, what the boiler temp is at the point when your hearts cut starts, this could be done and automated to stop boiling any further once the heads are out of the way, this could work for both pot and reflux still as the boiling point would be the same in both cases.

[vino-tinto]

Hi vino-tinto

I agree with you that alcohol boils at a lower temperature, however in order to boil a mixture of alcohol and water, you cannot simply heat above the boiling point of alcohol and expect the alcohol to boil.

It won't, nothing will boil until the boiling point of the entire mixture is reached, and that will depend on the concentration of how much alcohol is in the water.

The guys who have been designing digital parrots like YHB amongst others, have already done the maths on this, and from any given boiler temperature could probably tell you the products %ABV and how much alcohol is left in your boiler.

I don't think increasing the temp setpoint in small steps will produce the effect your looking for but I can see a use for it if you knew from some trial and error, what the boiler temp is at the point when your hearts cut starts, this could be done and automated to stop boiling any further once the heads are out of the way, this could work for both pot and reflux still as the boiling point would be the same in both cases.

I think what I should have made clearer is that this is what I have actually tested on my pot still setup and it works for a stripping run, not making cuts. All I did was program my ALVA to bring the temp up to 88C and hold it there. I did this by programming the quantity of wash, the ABV of the wash and the amount I wanted to extract in litres per hour. The PID controller then took over after 88C had been maintained, increasing 1C in timed steps according to the amount I programmed to extract.

[Anavrin]

So you have a PID controlling an SSR or similar to provide varying yet constant power to your boilers element, to achieve a rolling boil like you say, I then assume as the output flow or ABV decreases, the temperature is increased in 1°c steps to maintain it.

I must admit I assumed your method wasn't that clever, and that the temp controller would switch off the power once the set temperature had been reached.

Hats off to you sir, I'll have to put my thinking hat on, I'd be interested to know how your PID is wired and programmed, I have an Omron PID that I liberated from a job at work, always wanted to find a project for it.

[gaza the instructor]

VT
Does this mean on a striping run there is
no point in collecting anything after 93oC.

[vino-tinto]

VT
Does this mean on a striping run there is
no point in collecting anything after 93oC.

On my setup I will probably have stopped before it gets to 93C. This is boiler temp and not vapour temp which is probably higher than the 93.

On my tests 20% ABV was coming off at 92C boiler temp. I am at present waiting for a new temp probe to fit in the vapour path to get some additional info. This is where a parrot is necessary so you can compare temps with ABV

[Easydrinker]

This is all very interesting and bumps along with the fact that I can safely go to bed and leave my reflux still running, knowing that the thing will stop producing and the tails will still be sitting in the boiler in the morning.
Low temp./Power used here also.
And just a little bit of magic.
Because it was never intended, it just happens.

Robert.

[gaza the instructor]

Ok so temp at bottom of column
not the top.Its a shame they did away with
the bottom thermo on the T500.
Thanks VT your help appreciated.

[vino-tinto]

I'd be interested to know how your PID is wired and programmed, I have an Omron PID that I liberated from a job at work, always wanted to find a project for it.

I’m not completely sure how best to explain it as the ALVA was built by an electronics wizard from Portugal named Merlin. He programmed the operating system and algorithms. It could be based on the Arduino board or even a Raspberry Pi, I’ve never opened the case, from what I can see it’s all circuit board, no doubt there is an SSR in it somewhere.

Before I could use it I had to program in the specifications of my Grainfather boiler and carry out some tests to set some constants.

The distilling program is quite simply although doing a complicated job. After I start the distill program, it requests I input the amount of wash, the ABV of that wash and the flow rate of the spirit in L/Hr that I want. After this is done it requests I add the wash to the boiler and press SET, it then goes onto full power until the low rolling boil temp and maintains it.

This is the point at which the PID takes over according to the parameters I inputted. It works out the amount of alcohol produced, subtracts it from the initial wash quantity and ramps up the temp as necessary as the alcohol to water ratio changes.

I am able to set the ALVA to Brew, Distil and Ferment, all I have to do now that it’s all set up, is write a program sequence using a set of given variables that can be up to 48 lines long, I’ve even set it up to do a Grainfather cleaning routine after beer brewing.

[Anavrin]

Hi vino-tinto

I found a link for the Alva http://www.alva-control.eu/index.html

It doesn't say how much it is but looking at it, I'm pretty sure it's Arduino based, I see it connects directly to the element of the Grainfather, if that's the case how do you also have a PID connected?

[vino-tinto]

Hi vino-tinto

I found a link for the Alva http://www.alva-control.eu/index.html

It doesn't say how much it is but looking at it, I'm pretty sure it's Arduino based, I see it connects directly to the element of the Grainfather, if that's the case how do you also have a PID connected?

The PID is an integral part of the ALVA, run by an auto tuning PID algorithm. All I know is that I would need a 5 pin programmer and a lot more knowledge than I have to change anything.
I've just been youtubing and it looks as if everyone using a system like the ALVA is using an Arduino board of some sort.

The cost before the Brexit vote was approx £320 delivered.

[Anavrin]

Wow, pricy but looks very tempting, it's a nice bit of kit with many uses.

I bet the PID is doing most of the work, they are stand alone units that can monitor an input such as temperature and in turn, proportionaly control a heating element via an SSR.

For any one reading this who is unfamiliar with PID's, I say proportionally because they look at the difference between the set temp and the actual temp, as the temperature aproches the set temp there output will decrease in proportion until the set temp is reached in order to maintain it.

The perfect rolling boil without any unessesary additional power in this case

[vino-tinto]

If anyone wants to know more about PID controllers, I would recommend this guy's videos on brewing and distilling controls. Very informative and down to earth terminology.


https://www.youtube.com/channel/UCatCieEI4cPNteKXzBomVMQ/videos