How can I size a seal tank for a elevated flare?

[Saver2008]

Hi everybody!

I want to know the steps to size a seal tank for a elevated flare. This seal will be vertical position, at flare stack base. I already know the diameter of the flare stack, but I require to size a seal tank (diamenter and length). or where can I get that info?

Pls Pls Pls help.

Thank you very much.

 

[Saver2008]

In my last question about seal tank , I mean water seal drum. The question is for a water seal drum sizing...how can I do it?

Thanks

 

[gr2vessels]

Try the link below.

http://www.gba.com/ancilliaries1.htm

gr2vessels

 

[Flareman]

Saver2008
There are a variety of conditions you need to consider when sizing a water seal. Some of the basics are outlined in my download at

http://www.geocities.com/flareman_xs

navigate to main index|downloads.
When preparing a design think about ALL the pressure features of the vessel and make the best practical calculations you can to determine how it will work and where the water goes at each stage.
When there is NO flow, what pressure do you need to hold up in the incoming line?
When there is maximum flow, what pressure drop, or inlet back pressure is tolerable?
Is that compatible with the break pressure?
Do you expect the water to stay in the vessel at high rate or be lost into the flare line. 2-phase flow rules will tell you at which velocities to expect mist flow entrainment or bubble flow in the drum etc.
Include the down stream back pressure in the calculations and deliberations. Suppose the flare back pressure at 100% design is 4 psig and the water seal breaks at 3 psig. Then the flare "sees" an instantaneous surge flow of sqrt(3/4) = 87% design rate (reducing as the system bleeds down). Is that OK?
Is there enough water left to reseal the incoming line when the seal just breaks and displaces water but then the flow stops again?
Where does the displaced water go? Does it come back or stay lost? How quickly does it come back? Can the speed of return cause a surging (pulsing) problem when the gas flow is miniscule? Do changes in the stored water affect the break pressure?
Are your sizing decisions based on the economic considerations of making a sale (in which case your design is too small) or on a bundle of theoretical design conditions (in which case it is probably too big).
Are you designing a seal which assumes no water loss when the gas temperature is well above 212degF (????) Make a calculation of the thermal/mass transfer case and see what really happens. How does all that extra downstream steam affect your pressure assumptions?
Is there enough water to permit a negative in the upstream system without breaking the seal (in reverse)?
Do any gases dissolve in water?
What are the relative corrosion issues?
Are you disposing of or reusing water?

All that will keep you busy for a couple of days. If you do it well, you'll be the expert.

Good luck
Happy New Year
David