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Get different selected output value with same script in IPHREEQC and PHREEQC

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Yongqiang:
Hi PHREEQC users and developers,

I am using IPHREEQC and PHREEQC to calculation dissolution. However, I got different results with same input. Please see the following input code:

IPHREEQC

--- Code: ---# -*- coding: utf-8 -*-
"""
Created on Tue Mar  7 09:29:09 2023

@author: che458
"""

from win32com.client import Dispatch

def result(input_str):
    db_path = 'LLNL.DAT'#'carbfix.dat'
    dbase = Dispatch('IPhreeqcCOM.Object')
    dbase.LoadDatabase(db_path)
    dbase.RunString(input_str)
    return dbase.GetSelectedOutputArray()

if __name__ == '__main__':
    a =     """
DATABASE c:\phreeqc\database\LLNL.DAT

SOLUTION 1
EQUILIBRIUM_PHASES 1
CO2(g) 3 100
SAVE SOLUTION 1
END

SELECTED_OUTPUT
    -file  selected.out
    -reset false
USER_PUNCH
    -headings pH Mol(CaCO3) Mol(CO3-2) Mol(Ca) TotalC Al An
    -start
    10 PUNCH -LA("H+")#PR_P("CO2(g)")
    20 PUNCH MOL("CaCO3")*1000
    30 PUNCH MOL("CO3-2")*1000
    40 PUNCH MOL("Ca+2")*1000
    50 PUNCH TOT("C")
    60 PUNCH -EQUI_DELTA("Albite")*1000
    70 PUNCH -EQUI_DELTA("Anorthite")*1000
    -end
END



USE SOLUTION 1
EQUILIBRIUM_PHASES 2
Albite 0 24.9
Anorthite 0 24.5
SAVE SOLUTION 2
END
 

"""
    tem = result(a)     
    print(tem)
--- End code ---


PHREEQC:


--- Code: ---DATABASE c:\phreeqc\database\LLNL.DAT

SOLUTION 1
EQUILIBRIUM_PHASES 1
CO2(g) 3 100
SAVE SOLUTION 1
END

SELECTED_OUTPUT
    -file  selected.out
    -reset false
USER_PUNCH
    -headings pH Mol(CaCO3) Mol(CO3-2) Mol(Ca) TotalC Al An
    -start
    10 PUNCH -LA("H+")#PR_P("CO2(g)")
    20 PUNCH MOL("CaCO3")*1000
    30 PUNCH MOL("CO3-2")*1000
    40 PUNCH MOL("Ca+2")*1000
    50 PUNCH TOT("C")
    60 PUNCH -EQUI_DELTA("Albite")*1000
    70 PUNCH -EQUI_DELTA("Anorthite")*1000
    -end
END



USE SOLUTION 1
EQUILIBRIUM_PHASES 2
Albite 0 24.9
Anorthite 0 24.5
SAVE SOLUTION 2
END
--- End code ---


Look forward to your insights.

Regards,
Michael

Yongqiang:
The amount of albite dissolution is different though other outputs are same. 

dlparkhurst:
Are you sure you are using the same database? Or perhaps you are using different versions of PHREEQC between the com and the batch version.

Add the log K of albite to your output file.


--- Code: ---LK_PHASE("Albite")

--- End code ---

Otherwise, print the output file and look for differences.

Yongqiang:
Hi David,

Thanks for your help.

I used your suggested method to output the logK of albite. Both of them outputted 2.6574 for albite dissolution.

I also checked the thermodynamic database. Both of them used LLNL.DAT.

The IPHREEQC and batch PHREEQC versions are 3.7.3-15968. I tried to output the file with the COM version in python. However, it seems that no output file is available for COM version in Python.

I tried to lower the pressure for CO2(g). Same results can be obtained at lower pressure, such as -3 and -1 for Equilibrium_phase command. However, deviations emerge at higher pressure.

Best Regards,
Michael

dlparkhurst:
Can you give me an example of which numbers differ? and by how much?

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