5 replies to this topic

[Robert Charles Boyle]

Salve,

mi trovo a dover determinare la portata in una PSV installata su un separatore trifase.

la PSV va dimensionata per fire case.

il mio problema è sulla metodologia più "corretta" da utilizzare.

le API non menzionano la contemporaneità di liquid vaporization e gas expansion.

In caso di contemporanea presenza di liquid e gas come determinare la portata di relief e, soprattutto, la Design temperature delle line+psv?

vi ringrazio in anticipo

[PaoloPemi]

better to use english,

 

if you have liquid (inside separator) API method estimates (from wetted area)

heat input (energy / time) used for relief rate generation,

heat balance is then solved from difference of enthalpies (liquid and vapor) and vapor flow,

relief rate  = heat input (energy/time)  / latent heat

the procedure can be iterative or you may consider a maximum flow,

if the vessel is protected by a PSV you may utilize this procedure to estimate

initial conditions

http://prodesoftware...ns.blogspot.it/

[fallah]

Shouldn't it be included in spanish vesion of this Forum?

Edited by fallah, 02 April 2014 - 11:53 AM.

[PaoloPemi]

it's Italian.

[Robert Charles Boyle]

Thank you for your kind answers.

I'd want explain more in detail my concerns.

 

We are facing with a three phase separator with a gas phase and a liquid phase composed of produced water and crude oil.

Equipment has to be protected with a PSV sized for fire case.

 

If only liquid or only gas were present the problem is quite easy because you refer to the wetted surface and, utilizing a "dynamic" approach  to determine vapour flow (in case of liquid vaporization) or correlation in API 521 for gas expansion, relief flow rate is determined.

Problem arises when you have both: liquid and gas.

 

During the fire off course both liquid vaporization and gas expansion are present at the same time and API 521 considers or only liquid vaporization or only gas expansion.

 

In case of three phase separator described has anyone a suggestion on how to proceed in order to calculate relief flow and design temperature ?

 

Thank you so much

[PaoloPemi]

if there are two liquid phases (HC + water)

vapor phase will be in equilibrium with (all) liquid phases,

you can solve a multiphase equilibria to calculate

the different phase fractions and compositions (see my previous post)

with liquid the usual approach is to consider liquid vaporization and solve

the heat and mass balance,

you may estimate a peak flow or adopt a iterative procedure

which gives the possibility to evaluate how equilibrium temperatures

inside vessel change as light components evaporate,

you may also consider to depressurize the vessel.

Edited by PaoloPemi, 03 April 2014 - 05:16 AM.