Stripping time

[koshyeng]

I would like to know how to calculate time required to strip acetone from acetone-water solution by direct steam injection in an agitated vessel.

I have a vessel filled with 300 gallons of water and polymer solution (polymer +solvent) is pumped at 10 gpm. Steam is injected directly to strip acetone out to 1000 ppm. This is not diffusion limited (thermodynamics limited). Please help me how to calculate residence time requirements to strip solvent out.(stripped solvent and water mixture will then go to distillation for solvent recovery).

Thank You

 

[koshyeng]

Any help please...

 

[ajs1972]

What are your initial and desired acetone concentrations?
What are the conditions of your steam (temperature or pressure)?

 

[sshep]

From your statement that the process is not diffusion limited, the required residence time is not part of the calculation. Furthermore, since you already have the vessel and flow, the residence time seems like it is set(300gal/10gpm=30min).

What is sounds like you really want is to calculate the steam rate required to strip the acetone.

If you are simply sparging your steam into a vessel, then you need the equilibrium vapor pressure of acetone above the 1000ppm liquid. Using this equilibrium value and the amount of incoming acetone, you can calulate the total vapor flow that needs to be coming off the vessel. The steam rate will be the steam component of that flow plus extra steam required to heat the feed to the boiling point, so please include your feed stream temperature if you supply the feed acetone concentration data ajs1972 asks for.

If it were done countercurrent, then you would use less steam vs having the loaded acetone feed stream mixing with the stripped (1000 ppm) product.

best wishes,
sshep

 

[moltenmetal]

You won't strip ANYTHING until you get the water heated to the boiling point at your operating pressure. You need a vapour stream leaving the vessel to do any stripping whatsoever.

Once you get the bulk liquid heated to the boiling point of water, if your acetone concentrations are only modestly greater than your target concentration at the outset, you could use Henry's Law and an estimate (guess) of the approach to an equilibrium stage that your sparger-in-a-mixed-tank represents. You could then set up a finite difference or differntial equation to estimate the concentration of acetone remaining versus the volume of steam leaving the vessel. Note that Henry's Law constants are somewhat unreliable for water-miscible species like acetone.

If your concentrations are 1% or greater at the outset, Henry's is probably no longer valid. You can use a better thermo model than Henry's if you have access to a good simulation package- and someone who knows which thermo model gives the most accurate VLE data for the acetone/water system.

 

[koshyeng]

Inlet: 80% solvent and 20% solids (polymer solution)
25 gpm of water
Initial amount of water in tank is 300 gallons
Steam will be supplied at 360 deg F

Outlet: Acetone content should be 1000 ppm(w).
I would like to residence time requirements please.

Thank You

 

[sshep]

From your description you have an unknown amount of (unknown solvent composition and polymer) in 300 gallons of water with an additional flow of 25gpm of water, and no steam flow given. You might as well ask long is a piece of string.

You will never get an answer without understandable data. Consider a sketch or something.

 

[ajs1972]

Like sshep says, its necessary to know the conditions in your tank (pressure and temperature).

 

[moltenmetal]

Sorry, but I'm done here. It's obvious that the OP wants us to do their work for them rather than help them figure out how to do it for themselves.