Dear All,

Please guide me how to model the below attached reboiler in Caesar ii?.

First time I am doing this system. water are important point need to consider in modelling?

Thanks in adavance

Model the piping up to the equipment nozzles. Then model the equipment nozzles with rigids like you'd do with a pump or heat exchanger, unless you have given displacements you can input.

Are you trying to capture the weight of water in the reboiler? I would think the vessel supports would handle that; but you could try to model a pipe so that the volume is approximately the same if you want.

So here's what I see:

A vessel with two (but probably 4) support clips.
4 nozzles with flanges on the walls, perhaps a 5th towards the top of the vessel in the middle of the drawing.
1 Extra Heavy Barrel on the head.
1 unflanged mitered elbow nozzle at the bottom.
An expansion joint in the middle of the vessel.
A series of internal baffles, presumably to separate heat media and process fluid (water/steam).

What I can't see:
I have no sense of scale, as I can't read diameters or thicknesses.
Exact process. I'm not exactly sure how this reboiler works. Here's my guess:
1. Liquid water enters the top nozzle on the left. It travels down the baffles (being evaporated along the way). Leftover liquid water exits the bottom nozzle on the left.
2. Heat media (superheated steam, perhaps) enters the bottom, evaporating liquid water and "medium" temperature steam exits the top.

My sense is that the lower mitered bend is selected - large diameter, low pressure means potentially high D/t ratio. I'm not certain what the rationale is for the extra heavy barrel with the extra long internal projection is.

So concerns:
1. Know what the process is.
2. Know what the purpose of the expansion joint is. Nozzle loads can move this portion of the vessel, but pressure in the vessel will move the nozzles.
3. Learn whether or not the miter joint is in your scope.
4. If High D/t ratios, you'll likely need to incorporate nozzle flexibilities as calculated in NozzlePro or similar.
5. Water will probably only impact loads from the vessel onto the structure. Unless I'm dead wrong, which should be revealed by concern number 1.

This is a strange looking reboiler, for sure. I'm having trouble wrapping my head around the disparity in size between the bottom and top nozzle on the fluid side. Usually you have a liquid level coming in the bottom and a vapor exiting the top - so the smaller nozzle would be on the bottom and the larger on top to accommodate the greater volume of the vapor flow.

That said, one of the biggest considerations is how this sits relative to the column that the reboiler is serving. Is the reboiler supported from the column? Is it on it's own structure? If it is a separate structure, you are likely going to need springs on the support lugs to allow the reboiler to be supported while it moves up/down with the column.

Nozzle Pro is going to be highly recommended for generating more realistic stiffness values at the reboiler and column connections (and subsequently more realistic loads from the Caesar run).

Particularly if you have to use springs, you are going to have to be careful running cases with the reboiler at its operating and empty weights. The springs are going to need to primarily be sized for the operating weight, which means they will be too strong for the empty/shutdown case.

The expansion joint in the reboiler is not a direct concern for pipe stress. It's most likely a fixed tubesheet design with enough difference in the tube/shell metallurgy or temperature that the differential expansion between them needs to be absorbed.

Strange reboiler design indeed. More information is needed.

I wouldn't so readily dismiss the expansion joint since even at low pressures the pressure thrust force for such a large diameter can be tremendous. But I would need to review the design in more detail. Perhaps Mr. Klein is correct and it is not a concern.

I do agree that one of the biggest considerations is the support relative to the column. I have done projects where the original design was to just "hang" the reboiler from the column nozzle. Of course, further analysis proved that it would have overstressed the column nozzle so we had to design a 4-legged structure with spring cans to support the reboiler and to prevent overload of the column nozzle. Nozzle PRO was essential in performing this check.

Hi Anubis thanks for your reply.

I need to consider weight also because for the design of the spring hanger.


I cannot consider support as fixed or simply rest reason is below nozzle is duct which is directly connected to column.
between duct and column expansion bellow also not allowed as per process requirement.

Can I model reboiler like rigd element with weight or any other option?

Dear Michael fletcher,

for your clarity see the attachment below

NAG,

No attachment was found.