Scale up distillation column 6

[pmoneysh]

Hello experts,

I am now involved in a project to design a distillation column for PF5 generator. This project is a scale up of existing plant. Existing design of distillation column is:

Bottom part of the column is a reactor and there is a re-circulation pump. There is only 1 outlet from the top. However, there is required spec of impurity at the top ( less than 10 ppm- for the new project). Existing plant has impurity of around 100 ppm. How effective would it be if we increase the column height? I am thinking of using an additional tail column but the operating cost is quite high. It is the 1st time I am seeing a distillation tower with only one outlet.

I am just wondering how it has been possible to operate this tower with no any major issue for years. I need to learn more on distillation

Any of your suggestion and experience sharing is appreciated.

 

[georgeverghese]

Distillation is a complex skill and many companies keep their distillation technology know how confidential.
Going from 100ppm to 10ppm impurity in overhead product is a big step change.
What is PF5? Is this a multicomponent mix ? What is the coolant at the overheads condensor ? Sometimes, a HP column and a LP column in series is used when higher purity is required for overhead product.
Work out what the key components are in the bottoms and overheads and see if you can use the Fenske Underwood, Smith Brinkley or the Kremser Brown method to get some estimate on the additional column height required to go down to 10ppm.
Adding an extraction solvent can also help to increase the relative volatility, but it adds complication when the extraction solvent is stripped out.

 

[Latexman]

Phosphorus pentafluoride (nasty stuff) is a colorless, poisonous, nonflammable, compressed gas with a pungent odor. It is extremely irritating to skin, eyes and mucus membranes. It is very toxic by inhalation and can cause pulmonary edema. Toxic and corrosive fumes are generated when this material is exposed to water or steam. It is used as a source of Phosphorus in semi-conductors and as a catalyst in ionic polymerization.

Good Luck,
Latexman

 

[EdStainless]

Scaling up a distillation column is all of Chemical Engineering in one go.
Nothing scales linearly; flow, heat transfer, reaction rates, separation times, will each have their own scale factors.
This is big time engineering.
I hope that you have a very experienced team.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[MJCronin]

Ed Stainless gives good advice ... Distillation column design and rework is the big leagueof Chemical Engineering

I strongly suggest paying the money for an experienced consultant to develp a detailed report. This sounds like a unique distillation column and associated equipment ...

Mistakes in hardware can be very, very costly and can follow you through your career !!!

Wisdom is knowing when you are at the limits of your individual effort .. Scaling up a process is not for beginners ...

Or, as Harry Callahan (Clint Eastwood) said in Magnum Force:

"A man's gotta know his limitations"

MJCronin
Sr. Process Engineer