8 replies to this topic

[panoska]

If I know the packing height of my column. How can I calculate the number of the equilibrium stages in order to use them in my Aspen simulation?

Thank you in advance!

[Pilesar]

Column efficiency varies for packed columns as well as for trayed columns. The composition and flow rates for the vapor and liquid matter as well as the type of packing. Stages are usually shorter than 2 feet of height. There are lots of variables so you may want to consult the column designer or the packing manufacturer if you do not have access to the design calcs. If you have an existing column, you can use simulation to back-calculate the column efficiency using historical data.

[panoska]

Hi Pilesar, I thought that with the equilibrium model if you use trays or packing, the effect is on hydraulics of column and not really on the compositions. The compositions are result of number of trays and reflux ratio.

[Pilesar]

Here is a link to an article which seems a good summary of some of the parameters affecting tower efficiency: https://chempedia.in...ked_hetp_value/

[breizh]

Hi,

You may want to study this material .

Breizh 

[panoska]

Thank you both! I am going to read the documents and I will come to you if I have any questions!!!

[SilverShaded]

Hi Pilesar, I thought that with the equilibrium model if you use trays or packing, the effect is on hydraulics of column and not really on the compositions. The compositions are result of number of trays and reflux ratio.

Your talking about theoretical stages of seperation not real world trays with efficiencies, 2 trays with 50% efficency are equivalent to 1 theoretical stage.

 

Real trays can vary between 0% and 120+% efficiency.

Edited by SilverShaded, 26 February 2023 - 12:26 PM.

[panoska]

Hi Silver, I am refering to theoretical stages!! Do you might have any view on my question?

[SilverShaded]

Hi Silver, I am refering to theoretical stages!! Do you might have any view on my question?

Yes, guess the number of stages and adjust the effciency of your trays to match whatever data you have be it design or operational.  If you have no data, get the HETP from the vendor.