Heads removal : minimum power Vs higher reflux ratio

[Cletus_Spuckler]

Hi all;

Im getting a feel for my new 4" boka (SS packing) for making neutral.

During heads removal; i read somewhere that during/after equalisation if you run the still at the lowest possible power setting, you will do a better job of compressing fores/heads, because there will be less disturbance in the column. Ie; EToH is not going to be mixing in with all of the fores/heads crap.

I tried it once and sure enough, seemed to do a decent job of compressing.

The thing is, considering that I had the same take off speed as previous runs; a very low power setting would result in a low reflux ratio. Seems a little counter intuitive.

Im going to try a few different approaches during my next couple of spirit runs; so just wanted to check in and hear what people thought on the matter first.

Let me know what you think: Low power, less disturbance in the column Vs Normal/medium power, higher reflux ratio.

CS

[freefall]

During heads removal; i read somewhere that during/after equalisation if you run the still at the lowest possible power setting, you will do a better job of compressing fores/heads, because there will be less disturbance in the column. Ie; EToH is not going to be mixing in with all of the fores/heads crap.

I tried it once and sure enough, seemed to do a decent job of compressing.

The thing is, considering that I had the same take off speed as previous runs; a very low power setting would result in a low reflux ratio. Seems a little counter intuitive.

Im going to try a few different approaches during my next couple of spirit runs; so just wanted to check in and hear what people thought on the matter first.

Let me know what you think: Low power, less disturbance in the column Vs Normal/medium power, higher reflux ratio.

CS

I run mine between about 1500 and 2000 watts. Your take off is how far you open the needle valve. If you are taking off less than it takes to keep the column stacked you are ok. I have never tried to rush a run, so I can't help out on the experimenting. But I think you got it right on the last try.

[bluefish_dist]

If you reduce the power which in turn reduces velocity, the take off has to be reduced as well to hold the same reflux rate. Reduce both power and takeoff for heads removal. Then ramp up both once you get into the hearts.

The reduced power will also help get a hot break and reduce the chance of getting foam in the column.

[Cletus_Spuckler]

Thanks guy, just some further info / clarification on my post:

At one point early in my last spirit run (during fores removal) I was able to take off 96.6% ABV spirit at a rate of 1 liter per hour (twice as fast as what I achieved on my old 2" still, at a higher abv and with much less power).
Im not sure what the condenser induced reflux ratio was, but am guessing it would have been very low, as I was only using 920w (240v) of power (the boiler and column were both insulated).

My thinking is the effectiveness of my still (4" x 1.5m of tight packing sitting atop a plate) and the fact that I have very low turbulence in the column, is all I need to enable fractions to stack well and that I don't need a lot of reflux coming back down from the condenser. This is why i am able to pull high (>96%) ABV despite having a low power setting.

I figure that if I increase the power, I will cause the undesired effect of increased turbulence within the column and the mixing of fractions. That's why I like the idea of a low power setting.

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So, considering that I am already achieving around 96% ABV using bare minimum power and quite a fast takeoff; will increased reflux ratio (induced by slower takeoff / more condensate return from the condenser) really help with better compression of fores and heads?

OR

Is condenser induced reflux ratio (acknowledging reflux is constantly occurring as vapor first rises through the packing) less important if you have an effective fractionating still?

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I hope Im not rambling!

CS

[bluefish_dist]

As the column gets taller you need less reflux to hit the same abv. Also getting bigger reduces vapor speed which will further increase the ability to separate the fractions and again reduce the need for more reflux. In short, a taller, larger diameter column works better and faster in theory.

I now reduce power at the end of a run to further delay tails. I found that I could only delay tails so much by increasing reflux as the takeoff rate became much too slow. To get around that I only increase reflux to a set point, then start lowering input power which lowers vapor speed and efficiency increases.
I have observed the same thing on my column, i.e. Really low power, slow takeoff, good separation. I just could not live with that low an output rate.

[still_stirrin]

Just for clarification here, this discussion pertains to a LM column, right?

A VM would “self regulate” the reflux with power input because the vapor split would be constant regardless of the mass throughput. I don’t mean to derail this thread, just add clarification to other readers that the behavior of the LM is different from the VM. And CM’s would require coolant adjustments along with heat input changes as well, so in that regard they are somewhat like the LM in control finesse.
ss

[Cletus_Spuckler]

Yes, Ive got a LM. I dont know much about VM, but one of the advantages with VM surely has to be knowing exactly what your reflux ratio is throughout the run. With LM (and CM i guess) you are constantly guessing as vapor production will slow down as alcohol depletes from the boiler and as you move into the higher boiling point compounds.

The only way i can guess what my RR was from the last spirit run is to compare it to previous stripping runs. Using that approach, i am guessing I had a spirit run RR of 1:1 (<- is that how you write it?). That is, for every ml that i collected, another ml was returned to the column. Seems really low yet I still managed to pull +96% ABV.

I calculated the RR through the following comparison:
Maximum STRIP run take off (during fores/ early heads)

• 4400w (@240v) or 100% power
  165ml per minute takeoff (3/8 needle valve fully open)
  no reflux

Last SPIRIT run takeoff (during fores/ early heads)

• about 920w (@240v) or 20% power
  based on the above, I assume had the valve been fully open I could have produced 33ml per minute at the 20% power setting
  I actually took off 16.5ml per minute (with the needle valve partially open)
  which means, half of reflux was returned and half was collected (RR 1:1?)

On the next spirit run, Ill keep the power low but take off at a slower rate and see if the increased RR will enable improved compression.

Thanks again for you input fellas

CS

[Cletus_Spuckler]

Ive done another spirit run and this time, thought Id keep power down low and so as to keep the reflux ratio high, take off very slowly throughout the run. I had some interesting, yet slightly inconclusive results:

I had power set at 920w (@240v) and takeoff limited to a painfully slow 3 drops per second (4ml per minute / 240ml per hour). The head vapor temperature stayed between 77.5oC and 77.7oC throughout fores and heads. Sure enough, I consistently achieved my highest ever ABV.

Its hard to know for sure what the true ABV was when you consider instrument tolerances such as, alcholmeter and thermometer accuracy, the accuracy of my temperature correction formula, and my eyes ability to read 0.x from a graduated gauge! The alcometer readings were consistently 96% to 96.4% ABV, taken at a solution temperature of between 12oC and 17oC. Using a formula I ripped from an HD members spreadsheet, the temperature corrected readings came out between 97.0% and 97.8% ABV. If azeo is 97.2% ABV, there is clearly an error somewhere but despite this, Im going to call this my first ever azeo!

One weird thing happened once I hit the hearts cut and wanted to speed things up a little. Seeing the power was set so low, I thought in order to take off a a faster rate whilst maintaining the same reflux ratio, that I should also bump up the power slightly. So before opening the valve I nudged up the power. The strange thing was every time I did this (I got up to around 1400w), the head vapor temperature (probe placed under top slant plate) increased by a couple of points of a degree. It got from 77.7oC up to 78.1oC. I thought head temp would stay the same or reduce, at least until I started to increase take off.

I dropped the power back to 920w and the head vapor temp decreased (*read edit below). I then slowly opened the valve so as to quadruple my takeoff (16ml per minute), and the head temp decreased again to 77.3oC. Below what it was when I had it set to 4ml per minute!

(My instinct tells me it is better to aim for a lower temperature when extracting heads)

In summary; a low power setting with faster take off and low reflux ratio WORKED BETTER THAN a higher power setting/ slower take off/ higher reflux ratio.
Admittedly, ABV was higher (with 920w) when taking off at 4ml per minute than it was at 16ml per minute (by between 0.1% to 0.9%).

Ive got a theory as to why this might be that case. Correct me if this sounds wrong:

The still does not need much (condenser induced) reflux to hit azeo; and if in fact there is too much relux (from the condenser), this will actually cause turbulence in the column and mix up the fractions. So, once you've hit the desired ABV within the column (using the minimum amount of power possible and warmest possible reflux temperature), take off as fast as you can so as to prevent unnecessary reflux spilling back into the column.


Make sense?

CS



*BRAIN FART - Maybe head temp dropped because there was not enough concentration of vapor to allow for a correct reading? My probe is not long enough to extend beyond the thermo port, so maybe the low power / less vapor density, caused an inaccurate low temp reading?

[Cletus_Spuckler]

Did another spirit run. Couldnt hit azeo this time despite running at the same power and takeoff rate. The average hearts and heads ABV was 95.8%.

Im still trying to figure out how to best run thins thing. Again, the weird thing is based on my experiments so far, low power and high takeoff seems to be working better than anything else Ive tried to date. This fly's in face of the idea that high reflux is the primary way to increase ABV.

Can anyone explain that?

CS

[Yummyrum]

Cletus .
Just wondering if you have the reflux condenser adjusted so its over cooling the reflux which in turn upsets the equalibrium in the top of the packing and reduces the effective height of the packed section .
I suspect this is why when you run with a higher reflux ratio , you are getting worse results ..... more cold reflux causing over cooling of top packing .

Try running with the RC at critical point just before vapour escapes out the top would let it run most efficiently I believe .

[Cletus_Spuckler]

Thanks Yummy, I have considered the effect of over cooled reflux on column equilibrium, but will explore this idea some more by focusing on restricting coolant flow as much as possible.

During my last run, Im going to loosely guess that my RR through heads was 7:1; and through hearts it was 1:1 (*see below for rational). This resulted in an average ABV of 95.8% through both heads and hearts (peaking at 96.7%).
I used 920w (240v) of power throughout the run, with takeoff set to around 5ml/minute during heads and 16ml/minute for hearts.
I had the coolant set to gain around 5oC by the time it came out of the condenser. My coolant reservoir stayed around 18oC.

Does this seem right?
During my next spirit run, how much power do you think I should use?

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*Prior to equalization, I took off 500ml of fores and heads with the valve fully open. Boiler temp at the time was 84oC.
This allowed a maximum take off rate 44ml/minute during this phase of the run.
By the end of heads, my boiler temp had risen to 86.5oC and by end of hearts it was at 96.5oC
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CS

PS; Ive been referring to your youtube video and various posts of yours regarding the chemical composition of heads and tails. Ive found them really informative!