column reflux

[Guest Oblitze]

A column's reflux is usually controlled via controlling internal temp of the column or recycling the column's product back in to it. What I would like to know is would it be feasible to control the column's reflux by adding new product from a different run (assuming the heads had been stripped on a previous run), as opposed to recycling the column's own product back into it?

[porter]

- Column's own reflux is at/near critical temp already. Other products would take down column temp, hard to stabilize.

- Have to have some way to get rid of residual water from new introduction or it would overflow the cooker.

- I think what you are asking about is very close a continous flow distillation.

[Cutty]

Not sure I follow why you would want to implement this method, but I would think adding "new product" to enhance your reflux will disrupt the quasi-equilibrium established in the column. The distillation process is a separation (with some overlap) of the constituents of the beer (e.g. acetone, acetaldehyde, ethanol, ethyl acetate, propanol, pentanol, etc...), essentially putting all your ducks (individual chemicals) in a row. This orderly separation allows you to make your cuts. If you directly add "new product," to the still head, the orderly separation will be disrupted and making good cuts will be difficult.

If you really wanted to use this method you might try introducing the "new product" indirectly by flowing it through a coil of copper tube in the still head, which discharges into the bottom of the still. The cold "new make" will remove heat from the still head enhancing reflux without disrupting quasi-equilibrium you've established in the column. That being said I would assume the addition of the "new make" to the pot will certainly change your product distribution, which means where you make your cuts will likely change, and amount of change in the product distribution will depend on the rate of "new product" addition. It may be feasible to do it this way, but I'm missing what advantage this would give you over using a standard heat exchanger/dephlegmator, with cooling water.

[Charles@AEppelTreow]

I agree, I think you're pondering a continuous, or at least semi-continuous column.

My chem eng is rusty, so I'm sure I'm glossing over things, but the reflux isn't determined by the temperature, but by the heat flux. You're putting heat in at the bottom of the column, and taking heat out at the top. Some heat goes out the sides as loss, and some goes into the enthalpy of the separation. The reflux happens because you're taking enough heat out to convert some gas back to liquid, and it falls back down the column until it's reheated and starts moving up again. If you take enough heat out, you trap all the liquid in the column.

The temperature is just an indicator of the nature of the solution that's in flux - what you're actually controlling is heat flow.

You could inject steam into the bottom of the column. Or boil enough water in the pot to create the upward flow. And inject low wines into the middle of the column. It will fall until heated, and then work pretty normally. But then you've got to watch mass flow - the water moving down the column will eventually fill up the pot.

Hard to arrange, and while it might buy you run time, I'm skeptical that it's worth it.

[Spirit of Texas Brad]

You can pump your next batch through a coil in your column into a insulated tank waiting paitiently to cook. Yes, yes you can! I've seen and done and live the concept.

[Panama Jack]

Seems unlikely to get the same quality product from this method. Typically the big boys go the continuous route for the first second...cut, quick and cheap. When they want to pretend to make a "craft product" they do the last run with the batch method like a real artisan. Hard to imagine anything other than vodka being better from a continuous output setup.

[Spirit of Texas Brad]

Meant to type love, haha