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# Ideal Vapor Velocity in the Column

edited April 12

Week 3 into our 5 week country shut down and my mind is all over the place.

So I am looking at ideal vapor velocity in a column depending on the process currently underway i.e. stripping, spirit run, gin run, whiskey run etc. Each run will have a different preferred velocity.

The vapor velocity in a column to me is an important element as this is derived directly from the power input to the boiler.

I am struggling to find anything out there hence the post for those whom have this answer.

For example, I had originally looked at approx 1.21 m/s for a NW 100 / 4" column. But this translates for this size to approx 12 KW which is crazy.

Have a look to the Excel chart that I am trying to put together.

Thoughts as to preferred velocities

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• edited April 12

I can see vapor velocity being important in packed or tray columns (driving column flooding), but why do you feel it's relevant in stripping?

• @grim said: I can see vapor velocity being important in packed or tray columns (driving column flooding), but why do you feel it's relevant in stripping?

Don't have a specific view other than trying to put a figure to it for a particular process / activity

• @grim ... thanks for the calculation design sheet.

But this still does not give me where to shoot for an actual preferred flow velocity number ..... looking for people whom have this number readily on hand.

• edited April 12

Wow, what an esoteric rabbit hole of variables!

Good luck extracting that kind minutia.

Notwithstanding the impact of velocity on desirable, uniform hydraulic behavior, pretty sure those data points would be identified / established after the sensory work, and on an individual basis according to interpretation.

Everybody's sensory awareness is ever so different as are stills produced by different builders. Even plate count from one system to another would surely impact any conclusions. I just don't see how an operator from over yonder, running a still from up the way is going to be able to provide to you and operational road map of optimal vapor velocity based on any number of given recipes and other variables?

I think you'll need to create your own data.

StillDragon North America - Your StillDragon® Distributor for North America

• edited April 12

Okay I have a great idea ... well I hope so :-?

Whom is going to take the lead and do the worksheet as Column Design by Gavin Duffy - School of Electrical Engineering Systems (PDF) and post at the same time the calc workings.

I think this is a brilliant exercise for the group and people will be seriously enlightened .

Me, am now too old besides I am mechanical and not chemical :-S

• Fortunately one of the coolest things about distilling is that aside from being very complex, it is also very intuitive.

After all the entire planet / weather system acts as a giant distillation apparatus.

One can observe a bird in flight and not be able to explain/diagram how flight is mathematically possible. And yet we can comprehend how it is possible by simple observation. That is my favorite part about this distilling shenanigans.

StillDragon North America - Your StillDragon® Distributor for North America

• edited April 12

Ideal vapor speed is a range, not a point. This is why you see trays as being most common. Their wider turndown ratio is far more forgiving - and when you combine this with variable power input (steam or electrical). You can find an acceptable level of overlap between all the ranges - wide enough to provide operating flexibility.

You can design for the optimal column - but that means running under very very narrow operating conditions - something that mike be more common in a refinery than in beverage distillation.

I guess in summary, trays and variable power input make big concern about vapor speed less important.

Or - the ideal top end vapor speed is the one right before you create entrainment flooding.