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About the sequence of calculations in Phreeqc for a RT
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Topic: About the sequence of calculations in Phreeqc for a RT (Read 389 times)
Pak
Top Contributor
Posts: 57
About the sequence of calculations in Phreeqc for a RT
«
on:
November 07, 2016, 01:03:46 PM »
Dear all,
Imagine a RT with the following blocks in Phreeqc:
Solution 0
Solution 1Ncells
Equilibrium_Phases 1Ncells
Rates
Kinetics 1Ncells
Transport
after running your simulation in Phreeqc if it has been succesfully done, you will get the output file of Phreeqc. There you can read the following sequence of calculations:
(
input, output, database
)

Reading data base

Reading input data for simulation 1
(imagine all is put together, i.e. no END block)

Beginning of initial solution
(speciation of Solution 0 and also solution 1, since solution 1 is equal to the other cells also)

Beginning of batchreaction calculations
(Reaction step 1. Using solution 0. Using pure phase assemblage 1. Using kinetics 1.)

Beginning of transport calculations
 Equilibrating initial solution > Transport step > Equilibrating > Transport
I wonder what is the purpose of the
Beginning of batchreaction calculations
step.
Thank you
«
Last Edit: November 07, 2016, 02:23:52 PM by Pak
»
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dlparkhurst
Top Contributor
Posts: 958
Re: About the sequence of calculations in Phreeqc for a RT
«
Reply #1 on:
November 07, 2016, 02:29:58 PM »
If you do not use any END statements, then PHREEQC will react the SOLUTION with the EQUILIBRIUM_PHASES and KINETICS. The resulting compositions of the equilibrium_phases and solution are not saved. The amount of kinetic reaction will change, and its change will be the only change to affect the TRANSPORT calculation.
If you place an END statement after the SOLUTION definitions, then there will be no batch reaction calculation.
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Pak
Top Contributor
Posts: 57
Re: About the sequence of calculations in Phreeqc for a RT
«
Reply #2 on:
November 07, 2016, 03:16:13 PM »
Ok thanks.
So, the solution that is used in the transport calculations continues to be the same, but the amount of the kinetic and equilibrium species for the first cell, would be different. Why is not the solution saved, but the mineral is?
Also, if I have:
Solution 0
Solution 1Ncells
END
Equilibrium_Phases 1Ncells
Rates
Kinetics 1Ncells
Transport
Where Solution 0 and Solution 1Ncells has been equilibrated with Cl.
I will get the following calculation sequence:
Beginning of initial solution calculations
Beginning of transport calculations
In the first Beginning of initial solution calculations:
I can see in the solution composition section that the solution is charge with Cl, as I have specified. (image1)
But once the transport start, the initial equilibrium (image2) and after transport steps (image3), the charge balace is related to the pH, instead of Cl. What is the reason for that?
The solution 0 has also been charged to pH, or it is still charged to Cl. And the other solution which also undergoes the process of Beginning of initial solution calculations.
Thank you again.
«
Last Edit: November 07, 2016, 04:20:12 PM by Pak
»
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dlparkhurst
Top Contributor
Posts: 958
Re: About the sequence of calculations in Phreeqc for a RT
«
Reply #3 on:
November 07, 2016, 03:49:07 PM »
I think only the amount of kinetic reactant would change. To keep the reaction calculation results, you would need to use SAVE solution and SAVE equilibrium_phases (or use RUN_CELLS, which automatically saves results).
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Pak
Top Contributor
Posts: 57
Re: About the sequence of calculations in Phreeqc for a RT
«
Reply #4 on:
November 07, 2016, 05:15:32 PM »
I have another similar question, if I have:
Solution 0
Solution 1Ncells
END
Equilibrium_Phases 1Ncells
Rates
Kinetics 1Ncells
Transport
Where Solution 0 and Solution 1Ncells has been equilibrated with Cl.
I will get the following calculation sequence:
Beginning of initial solution calculations
Beginning of transport calculations
In the first Beginning of initial solution calculations:
I can see in the solution composition section that the solution is charge with Cl, as I have specified. (image1)
But once the transport start, the initial equilibrium (image2) and after transport steps (image3), the charge balace is related to the pH, instead of Cl. What is the reason for that?
The solution 0 has also been charged to pH, or it is still charged to Cl. And the other solution which also undergoes the process of Beginning of initial solution calculations.
Thank you again.
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dlparkhurst
Top Contributor
Posts: 958
Re: About the sequence of calculations in Phreeqc for a RT
«
Reply #5 on:
November 07, 2016, 05:32:55 PM »
Charge balance adjustment with Cl (in your example) only applies to the initial solution. Once the initial solution has been calculated, with or without charge balancing, the charge of the solution is maintained; consider it an inert ion. For all subsequent reaction calculations, the pH is adjusted to maintain the charge from the initial solution calculation (or mixture of charge from multiple solutions during diffusive transport).
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About the sequence of calculations in Phreeqc for a RT