Gas flow equations use for Flare Stack calculation

[pyMorty]

Hi,

Can gas flow equations formulas like Weymouth, Pandhandle, AGA, General flow, be used to calculate the flow capacity of a vertical flare just by having P1 and assuming P2 being atmospheric pressure? I mean, it looks to me I can, since at the end it is gas flow through a pipe, but am I missing something that could prevent me from getting a good approach from the flare flow capacity?

The example is a flare of 18" diamater, required to verify if good for 30 MMSCFD, flare height 40', gas pressure 20 psig.

Is it the flare exit considered to be at atmospheric pressure or a little backpressure has to be accounted for due to the flaring?

What is the max recommended velocity at the flate tip?

 

[1503-44]

Not all of them. Weymouth, Panhandle A, Panhandle B were developed to avoid iterative solutions for many miles of length and large diameter pipelines >= 20". Better to reserve those for pipeline use. I am not sure if IGT, AGA or General flow can be used for flare design. I would simply use Colebrook-White, if you like iteration, or Churchill if you don't.

“What I told you was true ... from a certain point of view.” - Obi-Wan Kenobi, "Return of the Jedi"

 

[pyMorty]

Thank you ax1e.

I found some interesting books on the subject and realiced there are several specific issues to take into account while sizing flare diameter.

 

[1503-44]

Then you know infinitely more about flare design than myself. I didn't answer some of your questions, because I never designed a flare stack. I always asked the equipment supplier to include design of those bits.

“What I told you was true ... from a certain point of view.” - Obi-Wan Kenobi, "Return of the Jedi"

 

[gwalkerb]

I would start with API 521 section 5.7 - 'Disposal to Flare'.