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there are a few values published by developer,

"http://www.prode.com/en/hydrate.htm"

I have verified some of these points (ask Prode for the list),
with simplified model for hydrate formation pressure you may expect an error in the range 3-15% (depending from structure and temperature),
errors in hydrate formation temperature are in the range 1-2 K

the complex model is more accurate,

when adding methanol as inhibitor erros are about the same (with the specific parameters provided for CPA PR Cubic Plus Association or other models,
however I suggest to contact Prode for more accurate figures...

Tags: formation, gas, hydrate, inhibition, methanol

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Uncategorized

I have found several papers discussing this topic, one is "Improved control valve sizing for multiphase flow" from Hydrocarbon Processing March 200, the authors say "HNE-DS method basically assumes that the flow pattern in the control valve is homogeneous but gas and liquid are not in equilibrium – a non-equilibrium factor N represents the boiling delay"
your comment agrees with this statement.
By the way I found also an interesting thread comparing API PSV formulation for gas flow here

'http://www.cheresources.com/invision/topic/16104-psv-discharging-temperature'

the author has provided a Excel page to compare different procedures

Discharging temperature (PSV outlet)
1) calculated with isentropic + adiabatic flash (the default in nozzle.xls)
2) calculated with adiabatic flash
3) calculated with isentropic flash

Calculated Area
1) rigorous numerical solution of isentropic nozzle
2) API formulation for gas and vapors, ideal cp/cv
3) API formulation for gas and vapors, real cp/cv
4) API formulation for gas and vapors, real cp/cv, Zv = 1

all the required properties are calculated by Prode library , for personal/academic use you can download a free -with limited number of components- copy from 'www.prode.com'

I recommend to read this thread to everyone interested in PSV sizing.
psvcompare1.xls

Tags: flow, gas, hem, liquid, psv

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Uncategorized

Hydrate formation curve in Excel

Prode Properties 1.19 includes a utility which allows to calculate the hydrate formation curve directly in Microsoft Excel,
the distribution files include a Excel page hydrate.xls , from this page one can define composition including all common hydrate formers
C1 Methane,
C2 Ethane,
C3 Propane,
C4 n Butane
C4 i Butane
N2 Nitrogen
CO2 Carbon Dioxide
H2S Hydrogen Sulfide

plus inhibitors as Methanol, Ethanol, Glycol and salts (salts require the electrolyte package)

Hydrates modeled according van der Waals and Plateeuw (rigorous, statistical approach) and Cubic Plus Association (CPA) for vapor, liquid phases
A free students version is available from Prode WEB Site

Tags: gas, hydrate, natural, pressure, temperature

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Oil And Gas Process

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