Demister critical DP

[AndreChE]

Hello

We are facing a severe problem in our ethylene plant.
We have a demister in a knock-out drum with 800 mbar of differential pressure. The design values normally are 30-50 mbar. It is severelly fouled and we know that.

My question is: what is the maximum DP we can handle?before mechanical destruction or critical flow across it?

If we have, for instance, 70% fouled, the flow regime is much higher than the normal and the plates should be severilly eroded.

How can I calculate this maximum DP?

Thanks
AndreChE

 

[siretb]

This would depend a lot on the material of construction of the plates, and the thickness.
Process wise, 800 mbar pressure drop is unacceptable. I would consider 150 mbar as a maximum, but the mecanical damage will come from impaction, or vibrations.
If the mist load is important and the velocity is important, you are at risk.
What kind of front velocity do you have? (I agree that if some part is blocked, locally you'll have higher velocities)
I do not know of a method that will allow you to calculate the maximum allowable DP. Ask the supplier.

 

[AndreChE]

Yes, it is unacceptable.

The velocity at the drum inlet is like 2,9 m/s.

The supplier...I'm still waiting!