Calculation of a Pot Still Distillation Run

[Bsnapshot]

Hi Everyone,

I was reading the section on the main sight that has the calculation of a pot still run at this link. http://homedistiller.org/calcs/husker_pot_calc_v2.php" onclick="window.open(this.href);return false;" rel="nofollow

I am having a hard time understanding how to read the chart. I understand the input pot still characteristics. If I use the amounts they give in the example and then click on calculate results the chart shows

Time Temp Collected Purity Total Collected Total Purity
20min 91C 1062 ml 60% 1062 ml 60%
40 min 92.2C 1001 ml 55% 2063 ml 58%
60 min 93.5C 938 ml 50% 3000 ml 55%
80 min 94.8 C 876 mL 43% 3875 ml 53%

Does this mean after coming up to temp at 91C I should have collected 1062 ml then in 40 min I should have 2063 ml? I know I am not a math whiz but I am confused. Maybe it is simpler that I am making it out to be..

[Husker]

Hi Everyone,

I was reading the section on the main sight that has the calculation of a pot still run at this link. http://homedistiller.org/calcs/husker_pot_calc_v2.php" onclick="window.open(this.href);return false;" rel="nofollow

I am having a hard time understanding how to read the chart. I understand the input pot still characteristics. If I use the amounts they give in the example and then click on calculate results the chart shows

Time Temp Collected Purity Total Collected Total Purity
20min 91C 1062 ml 60% 1062 ml 60%
40 min 92.2C 1001 ml 55% 2063 ml 58%
60 min 93.5C 938 ml 50% 3000 ml 55%
80 min 94.8 C 876 mL 43% 3875 ml 53%

Does this mean after coming up to temp at 91C I should have collected 1062 ml then in 40 min I should have 2063 ml? I know I am not a math whiz but I am confused. Maybe it is simpler that I am making it out to be..

Simply read this as "after 20 minutes", you should see these amounts/values/percentages. Then 20 minutes later, these are the values.

If you "reverse" observe (i.e. watch the temps, volumes, etc), then they should happen at the given elapsed time.

NOTE that all of the timings / amounts are theoretical, and depend HEAVILY upon no wattage loss due to heat loss.

H.

[Bsnapshot]

Thanks Husker for the reply,
I guess I was reading it right. If you don't mind a few more questions. I use natural gas in my kitchen and I know the power during heat up value I can just adjust until I get what it takes to bring my pot up to temp which would be 1100 W. Any hints on how I would figure my power during distillation and what my % of internal reflux would be?

[GingerBreadMan]

Hi there.

Last year I spent quite a bit of time using the calculator and comparing actual results with my still. It would seem there is theory and then there is the real world.

For my experiments I used alcohol that I already made, carefully measured the ABV and the volume and then a ran the still. I compared my actual results with the pot still calculator. There is a missing component or factor in the pot still calculator. Although it has a value for reflux there is no factor for the liquid re-vaporizing in the column. For a reflux or column still this would be the packing. But for a pot still there is no packing, but there is some re-vaporization even without packing.

My pot still has a 3/4" column that goes up 16 inches vertical and then the condenser is connected at the top and goes 45 degrees downward. From my actual data results I speculate that some of the vapors are condensing in the vertical column and then running back down the column only to re-vaporize and go back up - almost like a reflux or column still.

I think the pot still calculator assumes 1 theoretical plate while in real life my still produces about 1.3 theoretical plates.

I have no idea what the reflux % input in the calculator really is for. I can't figure out what exactly it's supposed to model. A better value in my opinion would be to able to adjust the theoretical plates of the pot still if reflux and re-vaporization is occurring.

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To calculate or approximate the watts of my stove at a certain setting - let's say 5 on the dial. I would put a wash with a known ABV, set the dial to that and wait for the boil and use the pot calculator to match the boil up time by selectively guessing the watts.

I don't know if it's totally accurate, but I think it would be a good guess.

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Anyways that's my theory, I have no idea if it's correct. Maybe someone with more knowledge can expand on this.

[Husker]

Thanks Husker for the reply,
I guess I was reading it right. If you don't mind a few more questions. I use natural gas in my kitchen and I know the power during heat up value I can just adjust until I get what it takes to bring my pot up to temp which would be 1100 W. Any hints on how I would figure my power during distillation and what my % of internal reflux would be?

About the best way is to use the "reverse" method.

i.e. run your still, observe temps, volumes, and ABV (at 5 minute intervals). Know the starting ABV of the wash. Then plug in numbers, until you get the "right" match. From that point on, you should be able to use the calc.

NOTE if you are using a detuned column, then the pot calc will not match well at all, as there still is a lot of reflux happening. If you insulate your column WELL, then it is closer to a pot, but still behaves differently.

H.

[Husker]

Hi there.

Last year I spent quite a bit of time using the calculator and comparing actual results with my still. It would seem there is theory and then there is the real world.

For my experiments I used alcohol that I already made, carefully measured the ABV and the volume and then a ran the still. I compared my actual results with the pot still calculator. There is a missing component or factor in the pot still calculator. Although it has a value for reflux there is no factor for the liquid re-vaporizing in the column. For a reflux or column still this would be the packing. But for a pot still there is no packing, but there is some re-vaporization even without packing.

The "reflux" setting in the pot calc, has a ZERO impact. All it does is slow down the takeoff. It makes an "assumption" that all reflux simply falls back into the boiler with NO revaporation.

Thus, THAT is why using the pot calc with any type of column will NOT model worth a crap. The column (unless you have "perfect" insulation), will always re-vaporize a considerable percentage of the material refluxing on the walls. Not enough to give you a "pure" product, but enough that the output will be significantly higher than the "1-plate" pot still.

I think the pot still calculator assumes 1 theoretical plate while in real life my still produces about 1.3 theoretical plates.

That is probably a very accurate statement. Yes, the pot calc DOES work with 1.0 theoretical plates. NOTE if you insulate your up column, I bet you will get very close results to the pot_calc applet.

H.