4 replies to this topic

[Kimbreaux]

Hello all, this is my first post but we're having issues with our process.

 

Background:

- We distill an organic peroxide using 2 columns under vacuum.  

- The first column separates the peroxide from alcohols and is running fine.

- The organic stream is then mixed with 50%NaOH & DI Water before entering the second column  (7 trays)

- The top is condensed and sent to a plain horizontal decanter.  The top layer splits into majority organic material in water (70/30) while the bottom is around 82/18 organic/water.  This bottom layer is refluxed. while the top goes further into the process.

 

Before shutting down, we were able to run maximum rates without issue.

 

When trying to restart, our vacuum pump seized and was replaced.  This has been the only major change to the process.

 

When restarting, we're unable to get past very minimum rates.  When we increase raw material flow, we end up with a small, white layer at the interface in the decanter and the top product is hazy when it is typically crystal clear.

 

The only major difference I can see is the column dP.  While it was ~30 mbar with the old pump, it's now ~18-22 mbar.  This column is typically at 140 mbar as well (decanter is under same vacuum) 

 

I can only assume it's potentially weeping and we need to increase vapor flow (more steam to reboiler), but any experience with this type of probably that could be shared would be welcome.  If there's other information that could be vital, please ask.  We increased the raw material feed to try to load the trays more, giving the vapor resistance, but this caused the entire decanter to turn white, due to mixing I assume.

[latexman]

I have no experience with this process, so a PFD or P&ID might be helpful.

[Kimbreaux]

Here's some additional info.  

 

The distillation column as well as the overheads.

Attached Files

•  Column Overheads.png   352.97KB   0 downloads
•  Column.png   100.46KB   0 downloads

[breizh]

Hi,

What about damaged equipment, let say trays? How do you explain the Pressure drop?

Probably good to review the data before and after shutdown, if not yet done.

If your operators start too quickly the column, they may have vaporized more water which could be responsible for damaged trays.

A good start up comes from a good shut down.

Breizh 

[Kimbreaux]

We pull all of the trays, inspected, passivated, and put them back in.

 

I have ordered new trays since these are 20+ years old and have been flexed multiple times by vacuum/vacuum break, etc.

 

They did, however work fine in 2025 at max rates. 

 

One reason for the pressure drop may have been fouling.  we also washed the inside of the column, and there was buildup at the dP pressure orifices in the column.  I actually need to trend back the 2nd top/bottom pressure to see if those align with the past dP, or the current one.

 

Typically on startup, we simply reflux until we've balanced and are in-spec, then push to storage, so any excess water goes to waste.