Conceptual Models > Database selection and modification

Hydrogen Solubility using Pitzer database

(1/2) > >>

MMMM:
Hello
I am trying to model hydrogen solubility in brine and I am using Pitzer database but the calculated solubility is higher than the experimental values. I want to modify the parameters related to hydrogen solubility but I don't know which parameters should be modified. I would appreciate your guidance.

dlparkhurst:
I would be surprised if the solubilities are too far off from experimental; is H2 reacting with anything else in solution? Try using Hdg(g) instead of H2(g).

You can change any of the Pitzer parameters with the keyword data block PITZER. The log Ks for H2(g) and Hdg(g) (unreactive H2) are in the PHASES data block. The latest version allows for defining gas binary interaction parameters with the keyword data block GAS_BINARY_PARAMETERS.

There are quite a few posts in the forum related to hydrogen solubility if you search for "Hdg".

MMMM:
Thanks for your answer. No, at this stage only hydrogen gas and Brine (NaCl 3mol/kgw) are defined. it should be mention that for pure water and salinity under 1 mol/kgw result are match with experiments. my script is as  follow:


--- Code: ---[DATABASE C:\phreeqc\database\PITZER.DAT


SOLUTION 1
    pressure 1        # atm  Pressure
    temp 20               # degree Celsius
    -water 1
    units mol/kgw          # ppm (Resrvoir Salinity )
 Na 1
 Cl 1
END
gas_phase 1
      -fixed_pressure
      -pressure 98.69  #100 bar
     
      H2(g)  1e-20
      H2O(g) 1e-20
      CO2(g) 1e-20
      N2(g) 1e-20
      #CH4(g) 1e-20
 END

reaction 1
 H2(g) 1
 100
REACTION_PRESSURE 2
10
20
60
80
1.16E+02
1.20E+02
1.49E+02
1.92E+02
2.29E+02
2.62E+02
2.78E+02
3.87E+02
3.95E+02
4.58E+02


REACTION_TEMPERATURE 2
100
Save Solution 1

PITZER
-macinnes true
-use_etheta true
-redox true

 USE solution  1
 USE GAS_PHASE 1
 USE REACTION 1
 
  USER_GRAPH 1
-headings Time  H2 
-axis_titles "Pressure (atm)" "H2 Solubility in Water, mol/kgw"
-axis_scale x_axis auto auto auto aut
-axis_scale y_axis auto auto auto aut
initial_solutions true
-start
10 GRAPH_X pressure
20 GRAPH_Y   mol("H2")
-end/code]
--- End code ---

dlparkhurst:
The main parameters for Hdg (inert version of H2 and H2(g)) are found in SOLUTION_SPECIES, of which there is only one species, dissolved H2:

--- Code: ---Hdg = Hdg # H2
-Vm 6.52 0.78 0.12 # supcrt
-dw 5.13e-9

--- End code ---
and PHASES:

--- Code: ---Hdg(g)
Hdg = Hdg
-analytic -9.3114e+0 4.6473e-3 -4.9335e+1 1.4341e+0 1.2815e+5
-T_c 33.2; -P_c 12.8; -Omega -0.225

--- End code ---

Here is a working version of your file:


--- Code: ---#DATABASE C:\phreeqc\database\PITZER.DAT


SOLUTION 1
    pressure 1        # atm  Pressure
    temp 20               # degree Celsius
    -water 1
    units mol/kgw          # ppm (Resrvoir Salinity )
 Na 1
 Cl 1
END
gas_phase 1
      -fixed_pressure
      -pressure 98.69  #100 bar
     
      Hdg(g)  0
      H2O(g)  0
      #CO2(g) 1e-20
      #N2(g) 1e-20
      #CH4(g) 1e-20
 END

reaction 1
 Hdg(g) 1
 100
REACTION_PRESSURE 2
    10  20  60  80  116  120  149 
    192  229  262  278  387  395  458


REACTION_TEMPERATURE 2
100
Save Solution 1

PITZER
-macinnes true
-use_etheta true
#-redox true

 USE solution  1
 USE GAS_PHASE 1
 USE REACTION 1
 
  USER_GRAPH 1
-headings Time  H2
-axis_titles "Pressure (atm)" "H2 Solubility in Water, mol/kgw"
-axis_scale x_axis auto auto auto aut
-axis_scale y_axis auto auto auto aut
initial_solutions true
-start
10 GRAPH_X pressure
20 GRAPH_Y   mol("Hdg")
-end
--- End code ---

MMMM:
Thank you very much for your guidance.
I apologize for asking so many questions.
When we use Hdg, the Hdg that dissolves in water is still unreacted? How can I make it reactive?
If I want to check the solubility in the presence of MgCl2 salt, is the Pitzer database complete or does it need to be modified?

Navigation

[0] Message Index

[#] Next page