Spirit Still ml per minute take off speed

[Sudzie]

We have always run our spirit stills slow.  When we had a 60 gal Spirit still our take off speed was 170 -190 ml per minute. We then went to a 100 gallon spirit still and settled at 295 - 350 mlpm.  Now we have a 250 gallon spirit still and run it at 1150 -1350 mlpm.  I was having a conversation with a couple of other distiller friends and they run faster and think I’m wasting time.  So I haven’t seen anything on the forum referencing this question. 
So what is the proper takeoff speed in Millimeters per minute (mlpm) based on the volume of the still.  I understand there will be variables to this question based on condenser, BTU input and the diameter surface area of the stIll.   So I toss a pebble into the pond to see if it creates any ripples.......  Thanks in advance. 

[JustAndy]

Unfortunately I think it really depends on the equipment and objective; the column size, heat input, condenser capacity, as well as how much active or passive reflux you are looking for are bigger factors than the pot size. On our 200 L 3 plate bain marie still, the flow rate obviously varies considerably based on how much water is flowing to the deplg. When i worked places with a more simple pot still, flow rate had a bigger impact on the flavor of the spirit but each of the 4 stills had a sweet spot which seemed more driven by the design of the still rather than just the size. If you already have a solid protocol setup, try doing some runs faster and see if you feel there is a difference.

In general, in visiting around it seems like a lot of the folks running slowly have badly designed/under built stills, and a lot of other folks are running too fast and condensing too hot.    

[DrDistillation]

I'd pretty much agree that you could just try running it a bit faster and see if it degrades the spirit and if so back off and go back to what was working.  If you can run it faster then just keep trying a bit faster each run to find your sweet spot.

Just doing some back of the napkin calcs real quick.

If the still is 250 and you charge the spirit still with 225 gallons at 30% you have 67.5% pure alcohol in there. 

Assuming it's a whiskey run that will average 65% ABV off the still you have 67.5/.65=103.8 gallons to take off.

103.8 gallons is 393 liters.

If you are pulling off 1.25 liters per minute it will take 393/1.25=314 minutes or 5.25 hours which doesn't sound bad at all.

So I'd say you're already in the "ball park" and you just want to play with speeds to see what speed comes out with the best product.

[PeteB]

I have heard of stills being run slowly while doing cuts then run faster the rest of the time.

Basic science tells me that shouldn't cause much smearing of compounds.

[Alex_Sor]

On 6/4/2020 at 4:21 PM, Sudzie said:

We have always run our spirit stills slow.  When we had a 60 gal Spirit still our take off speed was 170 -190 ml per minute. We then went to a 100 gallon spirit still and settled at 295 - 350 mlpm.  Now we have a 250 gallon spirit still and run it at 1150 -1350 mlpm.

 

The rate of distillation (alcohol yield) depends on what you want to get out: pure 90+% ethanol or alcohol suitable for drinks (35-55% strength).

The size of the tank does not really matter, it is the area of the evaporation surface, that is, the "evaporation mirror" (the tank should be very wide, not high), and the power input that matter.
You can use vacuum distillation, then you will accelerate the yield of alcohol and get high purity from impurities (no fusel oils, tailings).
So for example, the actually achievable rate of alcohol release when using a vacuum (-80kPa) is 1.5 liters per hour, with an area of the "evaporation mirror" = 0.28 m2. Linear dependence (on the "evaporation mirror").

If you need even higher distillation rates, you need to switch to the use of stripping columns, for example, a 4 "column with 5-7 kilowatts of steam generator power will be able to distill up to 45-56 liters of input mixture per hour (this corresponds to 3.2 ... 4.5 liters of ethanol output 35 -55% per hour if the strength of the input mixture is 8%).