Hydrate formation in piping bends

[djwright]

I am looking at wet natural gas piping system.

An expert has advised that hydrate crystals have a tendency to accumulate at piping bends (radius < 3d).

Intuitively, this does not seem right. Also I have been unable to find any references to the phenomenum on the internet.

Has anyone got any knowledge about this?

Regards,

djwright

 

[MortenA]

Why should this not be the case? The way i see it the hydrate may form as a mist of particles while in a straight section. When the pipe then bends the particles hit the pipewall and stick to it.

Best regards

Morten

 

[steveen]

DJwright,
I have a lot of experience with hydrates, most occuring around 4 am in a cold windy place. Early models predicted hydrate formation based on bulk fluid temperature. This proved to be incorrect. It is the pipe wall temperature that drives the formation of crystals. Most references will state free water has to be present. THIS IS INCORRECT. The temperature of the pipe wall has to be below the water condensation temperature and the temperature of hydrate formation. Pipe bends seem to be a good place for these crystals to accumulate.
An excellent reference source is Dendy Sloan's book "clanthrate Hydrates". I can help with resolution of your hydrate problems. 713-204-3615.

 

[MortenA]

Steveen

I have not read the book that you reference (but i have started pestering my manager to buy it for me ) - so i have one question: If your water dewpoint is say -10 deg C and your gas temperature might drop to a lower temperature - but your pipewall stays warmer than -10 deg C because its uninsulated and submerged in water - will Hydrates then form?

Best regards

Morten

 

[djwright]

Thanks for your advice.

My original post was I think slighly misleading. A reinterpretation of the expert's view is that turbulent flow regimes can promote hydrate growth.

Typically, a production well has xmas tree, pipework with choke, NRV connected to a manifold by means of a tee.

Our flow stream is susceptible to hydrate formation during start-up and designers have now suggested we can minimuse turbulent flow and reduce the risk of hydrate formation by eliminating the NRV and replacing the conventional tee with a swept tee.

Sounds sensible?

Regards,

djwright