Processes > Mixing
Flash simulation
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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