4 replies to this topic

[Hoeyneroo]

Hello, everyone.

 

How I can calculate the "Column Residence Time" for a tray column.

 

I know the tray residence time, but can't find the "Total residence time of column" 

 

I appreciate your reply.

[PingPong]

Average residence time in the column will be different for the various molecules in the column feed.

 

What would be the point trying to calculate that?

[Bobby Strain]

I don't think you care about any residence time other than in the sump for control.

 

Bobby

[Hoeyneroo]

Thank you for your answers.

 

I want to know how to calculate an average residence time of homogeneous catalyst in a ethylene recovery column.

 

A dynamic simulation is the only method to calculate the residence time?? Or other equations or methods are presented??

[Pilesar]

   Average residence time is found with steady state calculations. You will probably have to use basic math and geometry skills to add up the individual tray residence times with the calculated residence time in the sumps. You will need to rate the column using the actual dimensions of the internals including weir heights and downcomer configurations. This is easiest to do with column rating software (e.g. Pro/II, AspenPlus, KGTower, FRI). Recently while trying to account for the origin of product contaminants, I calculated a downcomer residence time of several minutes per tray for an operating column which has extremely low liquid flow. If you are considering new internals, either Koch-Glitsch or Sulzer will likely be willing to model the column hydraulics using their proprietary methods if asked. They can rate your existing equipment and compare it with their proposed modifications.

   A more accurate and costly alternative method is to hire a company such as TracerCo to measure residence time using radioactive markers.