dew points nr. in natural gas curve 4

[lparma]

Is it correct to say that for a natural gas mixture at a specified pressure (or temperature) selected to intersect the dew point line, one or two dew points can exist ?

 

[hans32]

That's the normal case,
however as far as I know there are examples of mixtures showing three (or perhaps more) equilibrium points on dew / bubble line, you may find an example with three dew points here

http://www.prode.com/en/dewpointnaturalgashydrocarbons.htm

 

[dcasto]

http://www.glossary.oilfield.slb.com/Display.cfm?Term=retrograde condensation

read this term definition and look up the prash for more details

 

[JLSeagull]

Some of us lack most chemical engineer details; some like dcastro may cover for us - or correct us. I will keep my head down for his corrections. ;-)

Natural gas from a gas well or especially an oil/gas well are likely saturated. A chryogenic gas plant may drop the temperature below -150 degree F to export C1 seperatly than C2 and higher yet inject sufficient C2 to maintain the BTU level etc. Some C1 gas might be sold below saturation and others not. Gas with nearly all methane often sells as natural gas; and can be blended with higher dewpoint gas from separate sellers. Or not.

 

[apetri]

you can find mixtures with critical point(s) on both sides of cricondenbar, the same for dew point line (can include or not the cricondenbar and cricondentherm), I recommend to utilize a software (see for example Prode) to calculate the phase envelope for a specific mixture.

 

[Montemayor]

Kudos to dcasto.

I appreciate the Schlumberger reference he furnishes with regards to such an important and mis-understood phenomena as retrograde condensation. The curve furnished is an excellent illustration of what can happen in a hydrocarbon reservoir.

However, I am very disappointed in the awful and inaccurate job that Schlumberger has done in its definition of terms - which goes directly to the understanding of this phase phenomena.

Here, I am not trying to apply semantics or nit picking definitions. I believe it is important to thoroughly understand all the basic engineering terms in order to understand what is happening in retrograde condensation. I list the obvious and basic errors in the given Schlumberger definition of terms for the benefit of those interested in learning more about this phenomena:

Phase = the physical state in which a substance or a fluid finds itself in – such as: vapor phase, liquid phase, solid phase, mixed phase (a combination of the previous phases). It has NOTHING to do with motion or waves in this context.

Bubblepoint = The temperature – at a given base pressure - at which the first bubble of vapor is generated from a liquid due to vaporization caused by expansion or boiling.

Dewpoint = The temperature at which the first condensate liquid comes out of solution in a gas condensate. It is NOT the pressure.

Single Phase = One phase. It has nothing to do with the quantity of components in the state under which the fluid finds itself. It is either a vapor, liquid, or solid.

Pressure = a UNIT force distributed over a surface. It is NOT just a force; that is why it is expressed as per the applied area.