Internally insulated reaction vessels ?

[someguy2]

We have a reaction that we would like to occur at high temperatures, preferable around 1000C. This creates a problem in that most (all ?) alloy design pressure must be derated due to creep rupture issues.

Is there a spec or has anyone designed an internally insulated pressure vessel wherein the vessel shell is kept considerably cooler than the contents due to a combination of internal insulation keeping the heat away from the shell and external cooling keeping the shell cool ?

I'm thinking something like spraying the interior of the shell with alumina.

Thanks.

 

[someguy2]

Further to this point, what about cooling the shell ?

What if we put a pressurized water jacket around the shell and kept the exterior temperature of the shell at 1000F. (Say we ran the process at 1600F). One could even go so far as to make the water jacked pressure the same as the internal pressure, thus removing a large load from the shell.

The reason I consider this is because the design stress for 316H is 11,000 PSI as 1100F versus 1300 PSI at 1500F.

If one could control the shell temp and keep it at 1100F through the use of insulation and cooling, one could run a hotter process temperature as well as use a much thinner shell.

Is this feasible ? Is there a design spec that covers it ?

 

[metengr]

You have several options. Here is what I would do in your situation - generate a request for proposal (RFP) and send it to various ASME U-Stamp pressure vessel fabricators with emphasis on pressure vessel design capability. Describe your process in detail and constraints, and let them provide you with recommended vessel designs. This is really the best way to handle this type of a test or prototype pressure vessel.

 

[EdStainless]

Look at how a vacuum furnace is built. What if you have a small high temperature chamber inside a larger (water cooled) high pressure chamber. As long as you inner chamber sees little pressure difference then it can be very weak at temp.
You can pressurize between the two with an inert gas, Ar has poor heat transfer. You could even insulate the outside of your reaction chamber to minimize heat loss.

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[someguy2]

I agree. I was thinking the space between the outer shell and the inner shell could be filled with a castable insulating refractory material.

As long as the refractory shrinkage isn't too great, as soon as the inner shell gets pressure on it, it will press on the refractory, which will push on the outer shell. If the outer shell is kept cool, less than 1100F, it has pretty good design strength, 11,000 PSI.

As an added bonus, the vessel could be double shelled. If the inner shell ever failed, the outer shell would contain the contents.

The insulating refractory could be cooled if necessary.

Anyone see a problem with this approach ?

 

[metengr]

No, but why not simply line the primary vessel internal surface with refractory to keep the mean wall metal temperature below 1100 deg F?? I really don't see any benefit with such a complex, double wall design if all you are trying to do is to keep the mean wall metal temperature at or below 1100 deg F.

 

[unclesyd]

I was starting a response very similar to metengr's and stopped just to add that it quite common to take this approach in things like hot gas lines on H2 plants. We also have a couple of reactors that are refractory lined operating in you temperature range at 60 psig.

Just remember that there are still some design caveats on material compatibilities that need to be addressed.

 

[EdStainless]

I presumed that there are reasons why you can't use insulation inside of the reaction vessel.
I also thought that I would rather have high pressure inert gas carrying my pressure load than insulation material.
Now that you mention it, I have also seen vessels with castable liners, even with water cooling in the insulation.

= = = = = = = = = = = = = = = = = = = =
Rust never sleeps
Neither should your protection

http://www.trent-tube.com/contact/Tech_Assist.cfm

 

[someguy2]

The only concern I have to the inner insulation is that we are dealing with some steam (water vapor) in the reaction and I am unsure how the <castable> liner would handle that. That if the temperature dropped and pressure was maintained and the steam condensed ?

BTW: the operating pressure of the vessel is 2000 PSI.

Where in the ASME standard is the liner or double wall insulated construction handled ? Or would this be an "outside the standard" design ?

Thanks... your replies have been most helpful.

 

[metengr]

Review UG-27 (f) and also UG-47 (c) in ASME Section VIII, Div 1. These sections deal with a stayed jacketed shell.