Void fill inside a pressure vessel

[Bilgepump]

My question concerns a polymer pilot plant.

Our problem is with the reactor vessel bottom head. Process conditions require a flat bottom. To have designed a flat bottom head for this vessel would be prohibitively expensive. This was solved by adding a false bottom over the bottom head. The false bottom is solid to prevent catalyst/gasses accumulating and causing a reaction in an undesirable location. This reactor bottom head/internal design results in a large void produced. To resolve issues of differential pressure, a balancing/equalization line was added and running to both sides of the false bottom plate. Our problem is that we are seeing this line getting clogged with polymer and the false bottom has experienced multiple failures.

We are exploring options but one of the discussion has been to eliminate the need to equalize pressure. There was a conversation had about reinforcing the false bottom to withstand design pressure but one engineer suggested maybe eliminating the void. His thought was to simply fill the cavity with some type of material that would transmit the loading from the false bottom to the bottom head. But then the question would be what to use and would it handle the compression/temperature requirements. Some type of 2 part epoxy filler, or maybe sand?

I'm interested in suggestions for filler material.

Vessel design:
Design Pressure: 35 barg (508 psig)
Design Temperature: -45C/150C (-50F/302F)

 

[TGS4]

I've run into a similar situation. Do you foresee needing to get the void filler removed? I've successfully used concrete if you don't need to the filler removed...

 

[MJCronin]

Can you post either design drawings or pictures of the vessel ?

MJCronin
Sr. Process Engineer

 

[jtseng123]

I have dealt with many kinds of reactors, but not knowing your specific reactor looks like, you may consider filling up with ceramic balls. It has all kinds of diameter. We typically use 6 mm dia up to 50 mm dia.

For "sand", yes it can be used too if that suit your need, but it shall be special treated sand so does not harm your vessel. I used sand more than 10 years ago for a drum for filtering purpose.

 

[EdStainless]

You can go to a foundry supply company and buy sand.
You can select grain size and composition (silica, Olavine MgO, Alumina, Chromite, and more) to control density and thermal properties.

Another option is to build a metal 'honeycomb' to support your flat head. This is usually done with steel plates on edge and 90deg to each other. So instead of spanning the whole width the flat head only has to span the 6" (or whatever) box sections.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[LittleInch]

If the void volume was filled with something like therminol would the volume expansion be small enough that very little polymer would enter? If you've got just gas in the void then you will be moving a lot of gas in and out during operation if you blow it down every time so not too surprising you're getting polymer in the line.

Could you route the equalisation line outside the vessel so you could clean it easier?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[HTURKAK]

The cheapest but efficient way would be , just filling with cement grout .. You may consider to speak with manufacturers ( sika grout etc )..

Another option , but better for new construction ;provide radial ribs ( one side circular to fit vessel bottom head , and the other side straight to fit false head)