Solution of water containing boric acid

[SA8416]

I am trying to model the initial concentrations of several species in water (at high temperatures and pressures).
I am given the concentrations of Boron and Lithium in ppm, and Hydrogen in cc (STP)/kg.
Boron exists as H₃BO₃, H₄BO₄⁻, H₃B₃O₆ and H₄B₃O₇⁻ (through several equilibrium reactions)
Lithium exists as Li⁺ and LiOH
And the ionisation of water is another included reaction.

I have partially adapted this pqi file to my problem's specifications:

Code: [Select]

SOLUTION 0  Water
        units            ppm
        temp             345.0
        pressure         153.0
        pH               7.0     charge
        # pe               4.0
        pe               12.5    O2(g)   -0.68
        B                1200.0
        Li               2.0
        H(0)             1.53318         
SOLUTION 1-40  Initial solution for column
        units            mmol/kgw
        temp             25.0
        pH               7.0     charge
        pe               12.5    O2(g)   -0.68
        Na               1.0
        K                0.2
        N(5)             1.2
END
SELECTED_OUTPUT
        -file            advect.sel
        -reset           false
#        -step
        -totals          B Li
USER_PUNCH
  -heading  Temperature Pressure Hyd_K
  10 PUNCH TC, PRESSURE
  20 PUNCH CALLBACK(cell_no, 0, "HYDRAULIC_K")
END
Where SOLUTION 1-40  Initial solution for column is from the original pqi file I haven't yet adapted, as I am unsure how to proceed.

Upon running this, my output is:

Code: [Select]

------------------------------------
Reading input data for simulation 1.
------------------------------------

TITLE Example 11.--Transport and cation exchange.
SOLUTION 0  Water
        units            ppm
        temp             345.0
        pressure         153.0
        pH               7.0     charge
        pe               12.5    O2(g)   -0.68
        B                1200.0
        Li               2.0
        H(0)             1.53318         
SOLUTION 1-40  Initial solution for column
        units            mmol/kgw
        temp             25.0
        pH               7.0     charge
        pe               12.5    O2(g)   -0.68
        Na               1.0
        K                0.2
        N(5)             1.2
END
-----
TITLE
-----

 Example 11.--Transport and cation exchange.

-------------------------------------------
Beginning of initial solution calculations.
-------------------------------------------

Initial solution 0. Water

-----------------------------Solution composition------------------------------

Elements           Molality       Moles

B                 1.111e-01   1.111e-01
H(0)              1.523e-03   1.523e-03
Li                2.886e-04   2.886e-04

----------------------------Description of solution----------------------------

                                       pH  =   5.242      Charge balance
                                       pe  =   2.779      Equilibrium with O2(g)
      Specific Conductance (µS/cm, 345°C)  = 129
                          Density (g/cm³)  =   0.59444
                               Volume (L)  =   1.69386
                        Activity of water  =   0.998
                 Ionic strength (mol/kgw)  =   2.947e-04
                       Mass of water (kg)  =   1.000e+00
                 Total alkalinity (eq/kg)  =   2.886e-04
                         Temperature (°C)  = 345.00
                           Pressure (atm)  = 153.00
                  Electrical balance (eq)  =   1.665e-16
 Percent error, 100*(Cat-|An|)/(Cat+|An|)  =   0.00
                               Iterations  =  26
                                  Total H  = 1.113471e+02
                                  Total O  = 5.584150e+01

---------------------------------Redox couples---------------------------------

Redox couple             pe  Eh (volts)

H(0)/H(1)           -5.5915     -0.6858

----------------------------Distribution of species----------------------------

                                               Log       Log       Log    mole V
   Species          Molality    Activity  Molality  Activity     Gamma   cm³/mol

   H+              6.117e-06   5.728e-06    -5.213    -5.242    -0.029      0.00
   OH-             3.594e-06   3.357e-06    -5.444    -5.474    -0.030   -787.17
   H2O             5.551e+01   9.981e-01     1.744    -0.001     0.000     30.26
B             1.111e-01
   H3BO3           1.109e-01   1.109e-01    -0.955    -0.955     0.000    126.18
   H2BO3-          2.911e-04   2.718e-04    -3.536    -3.566    -0.030     (0) 
H(0)          1.523e-03
   H2              7.614e-04   7.615e-04    -3.118    -3.118     0.000     28.48
Li            2.886e-04
   Li+             2.886e-04   2.698e-04    -3.540    -3.569    -0.029   -172.02
O(0)          1.856e-03
   O2              9.282e-04   9.283e-04    -3.032    -3.032     0.000    198.68

------------------------------Saturation indices-------------------------------

  Phase               SI** log IAP   log K(618 K, 153 atm)

  H2(g)            -0.90     -3.12   -2.22  H2
  H2O(g)            2.03     -0.00   -2.03  H2O
  O2(g)            -0.68     -3.03   -2.35  O2 Pressure   0.2 atm, phi 1.000

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

Initial solution 1. Initial solution for column

-----------------------------Solution composition------------------------------

Elements           Molality       Moles

K                 2.000e-04   2.000e-04
N(5)              1.200e-03   1.200e-03
Na                1.000e-03   1.00
Where the pH is much lower than I expect it to be. How would I amend the input file to register B and Li exist as the aforementioned species?

[dlparkhurst]

If you want those boron species you either need a database that defines those species, or you need to define the species in a SOLUTION_SPECIES data block. You also have to consider the the temperature is beyond the range of many of the databases and that the O2 concentration that you specify is inconsistent with the H(0) concentration.

If you know the appropriate pH, then you should specify it rather than using charge balance.

If you can ignore redox and substitute Cl- for NO3-, I would use the pitzer.dat database. Otherwise, maybe sit.dat, but to be honest, I would be pretty skeptical of redox calculations at 345 C in high ionic strength water.

[SA8416]

Thanks for the reply!

I have included the pitzer.dat database and finshed adapting my .pqi file, which is given as:

Code: [Select]

TITLE Example 01.--Test
SOLUTION $id
        units   ppm
        pH      7.0 charge
        temp    345.0
        pressure  153.0
        B               1200.0 ppm
        Li              2.0 ppm
        H(0)            2.5 ppm
    END
SOLUTION_MASTER_SPECIES
        #element    species        alk     gfw_formula  element_gfw

        #B   B(OH)3  0   B   10.811
        #B(3)    B(OH)3  0   B   -36.44179
        LiBO2(s) LiBO2(s) 0.0 LiBO2

SOLUTION_SPECIES
        ######## IW
        H2O = H+ + OH-
        #-analytic
        -gamma 1E5 0
        ######## BA
        B(OH)3 + OH- = B(OH)4-
        -analytic 28.6059, 0,012078, 1573.21, 13.2258, 0.0, 0.0
        2B(OH)3 + OH- = B2O(OH)5- + H2O
        -analytic -18.7322, -0.00033, 2756.1, 5.835, 0.0, 0.0
        3B(OH)3 + OH- = B3O3(OH)4- + 3H2O
        -analytic -7.85, 0.00033, 3339.5, 1.497, 0.0, 0.0
        # 3B(OH)3 = B3O3(OH)3 + 3H2O
        # -analytic 0.54558, 0.0, -2248.91, 0.0, 0.0
        ######## LB
        # Li+ + B(OH)4- = LiB(OH)4
        -analytic -862.0372, 0.1272792, -37623.67, 136.9755, 0.0, 0.0
        ######## LD
        # LiOH  + H+  = Li+ + H2O
        # Li+ + H2O = H+ + LiOH
        -analytic -12.5311, 0.0, 3839.08, 0.0, -1.22243E+06, 0.0
        ######## PT
        LiBO2(s) + H2O + H+ = Li+ + B(OH)3
        # Li+ + B(OH)3 = LiBO2 (s) + H2O + H+
        -analytic -11.19885, 0.0, 2531.538, 5.1128, 0.0, 0.0
        ######## LV
        # B(OH)3 (l) = B(OH)3 (g)
        # H2 (l) = H2 (g)
        # O2 (l) = O2 (g)
        ######## RD
        # 2OH = H2O2
        # OH + e- = OH-
        # OH + H = H2O
        # OH + HO2 = O2 + H2O
        # OH + O2- = O2 + OH-
        # OH + H2O2 = HO2 + H2O
        # OH + H2 = H + H2O
        # OH + OH- = H2O + O-
        # OH + HO2- = HO2 + OH-
        # OH + O- = HO2-
        # O- + H2O = OH + OH-
        # 2e- + 2H2O = H2 + 2OH-
        # e- + H + H2O = H2 + OH-
        # e- + O2- + H2O = HO2- + OH-
        # e- + HO2 = HO2-
        # e- + H2O2 = OH + OH-
        # e- + O2 = O2-
        # e- + H+ = H
        # e- + H2O = H + OH-
        # e- + HO2- = O- + OH-
        # H + H = H2
        # H+ + O2- = HO2-
        # H + HO2 = H2O2
        # H + H2O2 = OH + H2O
        # H + O2 = HO2
        # H + OH- = e- + H2O
        # HO2 + HO2 = H2O2 + O2
        # HO2 + O2- = HO2- + O2
        # HO2 = H+ + O2-
        # H+ + O2- = HO2
        # H2O2 + OH- = HO2- + H2O
        # HO2- + H2O = H2O2 + OH-
        # H2O2 = H2O + O
        # O + O = O2
        # H2O = H+ + OH-
        # H+ + OH- = H2O
        # O2- + O2- + H+ = HO2- + O2
    END

But I receive an error:

Code: [Select]

ERROR: ERROR: Elements in species have not been tabulated, LiBO2(s).
ERROR: Reaction for species has not been defined, LiBO2(s).
ERROR: Calculations terminating due to input errors.

Where LiBO2 is a product of a precipitation/dissolution reaction. I have not found it in any other database available to me, and I am unsure how to manually tabulate this species.

Many thanks!!

[dlparkhurst]

SOLUTION_MASTER_SPECIES and SOLUTION_SPECIES are used to define dissolved species. Association reactions are used for dissolved species, with the new species defined as the first entity on the right-hand-side of the equation.

If LiBO2(s) is a solid, it should be defined in a PHASES data block with a dissociation reaction (first entity on the left-hand-side of the equation).