10 replies to this topic

[engeng]

Hello to All

 

Please how much can I take the efficiency of crude oil distillation trays, and how can I calculate it for each tray?

 

Best Reagards

 

engeng

 

[shan]

When liquid and vapor reach equilibrium on a distillation tray, the tray efficiency is 100%. 

[engeng]

_{But liquid and vapour never reach equilibrium on tray, in this case how can calculate the efficiency?}

[Propacket]

"Distillation Design" by Henry Z Kister has a full chapter of tray efficiency. Get a copy of this book. 

Edited by Propacket, 07 May 2013 - 08:00 AM.

[Robert Montoya]

There are methods to calculate the efficiency of a distillation column are theoretical methods and finally determines the effciency of trays in column l is the manufacturer. Effciency of the trays must be greater than 65% thus to early stages of this project is usually placed efficiency. You can determine the efficiency and the diameter of the tower using programs such KOSH and  SULZER manufacturers; in fact these programs take balance data directly from HYSYS or PRO II and so you can determine the arrangement according to the  standars of your company.

Edited by Robert Montoya, 08 May 2013 - 02:59 PM.

[Propacket]

There are methods to calculate the efficiency of a distillation column are theoretical methods and finally determines the effciency of trays in column l is the manufacturer. Effciency of the trays must be greater than 65% thus to early stages of this project is usually placed efficiency. You can determine the efficiency and the diameter of the tower using programs such KOSH and  SULZER manufacturers; in fact these programs take balance data directly from HYSYS or PRO II and so you can determine the arrangement according to the  standars of your company.

 

Why greater than 65% efficiency? What is the basis for that? 

[Robert Montoya]

Propacket estimated, as elemental namely internal efficiency in a column directly affects the height of the distillation column, is not economically feasible to design a column operating with very low efficiency. In this case you should change the type of internal or change the manufacturer.

[engeng]

Thank you very much, I take a copy of Distillation design book, I Will read it and tell you later.

 

Best regards

[Himanshu Sharma]

Dear All

 

Apologies for joining late in topic but i had an observation.

 

For Crude Distillation efficiency of Trays are usually in the range of 50% for Overflash/wash zone and gets even worst at Heavy gas oil-RCO section.

 

Design of internals is one part but another part is the service in which trays are put in,here in the section below i have tried to summarize some of the Physical factors known to me, which have an impact on tray efficiency.

 

Liquid Viscosity: General trend ,as liquid viscosity increases, efficiency decreases.

 

Relative Volatility: General trend ,When relative volatility increases, efficiency decreases.

 

Vapor Diffusivity: General Trend,Increased diffusivities will increase efficiency. Keep in mind, as pressure increases,
vapor diffusivities decrease.

 

Liquid Diffusivity: General Trend is that higher liquid diffusivities will result in higher efficiencies. Liquid diffusivities generally increase withpressure which countervail the change in vapor diffusivity. However, in most distillation systems the influence of the vapor diffusivity will dominate the influence of the liquid diffusivity.

 

Liquid Surface Tension: Debatable but decrease in surface tension appears to be resulting in increase in efficiency.This effect is not visible for high pressure distillation column.

[a.aryan]

A simple empirical method is to use the O'Connel correlation:

 

H E O’Connell

Plate Efficiency of Fractionation Columns and Absorbers

Trans AIChE, Vol 46, p-741-755, 1946

 

E_o    =   0.492 (α µ) ^-0.245          

 

  

          ^{E_o         Overall Plate Efficiency                      (fraction)}

 

          ^{α            Relative Volatility of Key Components being separated}

 

          ^{μ            Viscosity of Feed                            cP}

                        ^{Average Column Conditions}

 

[Vinayak Chavan]

Dear

 

Recommended tray efficiency in crude distillation column for fractionation section is about 66% and for pump arround section is 33%