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Flash simulation

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IliasBouchkira:
Hi everyone

Is there any examples in the forum on how to carry out a Flash calculation (vapor liquid equilibrium)? The purpose is to determine phases compositions and if possible partial pressures..

Many thanks in advance

Ilias

dlparkhurst:
I'm not sure whether you want to heat of cool your solution. Here is an example of water in equilibrium with halite that is heated to 150 C (in the absence of halite solid). The solution is in contact with a 1 liter gas head space. The resulting system has a pressure of 3.6 atm due to H2O(g) in the head space, and the solution is undersaturated with halite, so no halite precipitates.


--- Code: ---SOLUTION
EQUILIBRIUM_PHASES 1
Halite 0 10
SAVE solution 1
END
USE solution 1
EQUILIBRIUM_PHASES 1
Halite 0 0
REACTION_TEMPERATURE
150
GAS_PHASE
-fixed_volume
-volume 1
H2O(g) 0
END

--- End code ---

IliasBouchkira:
Dear Dr

Many thanks for the response.

I have made this simple exemple for solubility of CO2(g) in NaCl. I am wondering if there is anyway to check vapor liquid equilibrium condition:

 φi yi fi0V = γi xi fi0L

with yi = mol fraction of i in the vapor phase, and fi0V = the vapor standard state fugacity (the fugacity of pure component vapor at T and P),  xi = mol fraction of i in the liquid phase, and fi0L = the liquid standard state fugacity.

Many thanks in advance

Ilias.




--- Code: ---
SOLUTION 1
    temp      25
    pH        7 Charge
    units     mol/kgw
    Na        1
    Cl        1   
   -water    1 # kg

GAS_PHASE 1
    -fixed_pressure
    -volume 1
    -temperature 25
    CO2(g)    1



REACTION_PRESSURE 1
    10 100 in 10 steps




--- End code ---

dlparkhurst:
The Gas phase section of the output gives the pressure and volume of the gas phase and the pressures and fugacity coefficients of the gas phase components.


--- Code: --------------------------------------Gas phase-----------------------------------

Total pressure:  1.00      atmospheres          (Peng-Robinson calculation)
    Gas volume:   3.41e-01 liters
  Molar volume:   2.43e+01 liters/mole
   P * Vm / RT:  0.99445  (Compressibility Factor Z)

                                                        Moles in gas
                                            ----------------------------------
Component         log P           P    phi     Initial       Final       Delta

CO2(g)             0.00   1.000e+00  0.994   4.110e-02   1.400e-02  -2.710e-02

--- End code ---

The Saturation indices section of the output gives the fugacity and fugacity coefficient of the gas as calculated from the solution composition.


--- Code: ---------------------------------Saturation indices-------------------------------

  Phase               SI** log IAP   log K(298 K,   1 atm)

  CH4(g)         -116.59   -119.40   -2.80  CH4
  CO2(g)           -0.00     -1.47   -1.47  CO2 Pressure   1.0 atm, phi 0.994
  H2(g)           -35.64    -38.74   -3.10  H2
  H2O(g)           -1.52     -0.02    1.50  H2O
  Halite           -1.92     -0.35    1.57  NaCl
  O2(g)           -12.05    -14.94   -2.89  O2

**For a gas, SI = log10(fugacity). Fugacity = pressure * phi / 1 atm.
  For ideal gases, phi = 1.

--- End code ---

IliasBouchkira:
Many thanks, I am wondering why I am not getting the Gas phase section in my results when using my code ?


--- Code: ---

SOLUTION 1
    temp      25
    pH        7 Charge
    units     mol/kgw
    Na        1
    Cl        1   
   -water    1 # kg

GAS_PHASE 1
    -fixed_pressure
    -volume 1
    -temperature 25
    CO2(g)    1



REACTION_PRESSURE 1
    10 100 in 10 steps





--- End code ---

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