5 replies to this topic

[isjabu]

what is the reason trays falls in distillation column in methanol plant

[Pilesar]

Trays fall when they are not able to withstand the forces applied to them. Distillation trays are not generally designed for large upward forces from below. During startup, trays may experience a high vapor load without the counteracting weight of liquid on the trays which puts extra stress on the lower trays especially. Corrosion and improper installation contribute to failures. 

[isjabu]

During turnaround of our methanol plant, we found 22 trays fallen and some of them bulged as well. corrosion is one of the problem but bulging the trays is not understandable, can any one explain what is the reason of trays fallen or bulging. our column have total 83 trays. plant is designed by UHDE in 1984.
Regards

[isjabu]

we have sieve trays, your though make sence, trays was full of rust and pressure difference is one of the cause, can you please let me know the step (procedure) to calculate delta pressure, normal operating pressure is 1.2 barg and column have 83 trays. operating temperature 120 ⁰C.
Column: Total trays 83
Tray 1-22: spacing 350 mm
Tray 23-39: spacing 520 mm
Tray 40-67: spacing 74 mm
Tray 68-83: spacing 11 mm
regards

[Pilesar]

Most commercial column simulators will predict pressure drop for sieve trays. You can get a free column hydraulic simulator from Koch or Sulzer. However in this instance simulators won't be that useful and you will need measured differential pressure. If you do not have pressure transmitters at the top and bottom of this column, that is something to install while you are down to fix the internals. If you got 35 years of life from these column internals, congratulations. 

[breizh]

Hi ,

You may find pointers in the doc attached . Pilesar is right , 36 years is a lot for such equipment . 

You may consider to perform a scan at the start of the column (rebuilt)  to follow the degradation over the years .

Note : Consider to set a preventive maintenance program , with a check during turn around .

Good luck

Breizh 

Attached Files

•  Bulletin-4900.pdf   4.88MB   18 downloads