PhreeqcUsers Discussion Forum

Beginners => PHREEQC basics => Topic started by: gpflach on August 22, 2020, 11:14:05 PM

Title: Use previous SOLUTION and EQUILIBRIUM_PHASES but not REACTIONS in TRANSPORT?
Post by: gpflach on August 22, 2020, 11:14:05 PM
In this toy problem I prepare for a transport simulation by creating 1) 'salty' Portlandite cement by reacting CaO and NaNO3 with water, and 2) an acidic solution by equilibration with gaseous CO2. The solutions and equilibrium_phases from simulations 1 and 2 are as intended and saved. Transport simulation 3) uses the results from simulations 1) and 2).
Code: [Select]
DATABASE C:\Program Files\USGS\phreeqc-3.6.2-15100-x64\database\llnl.dat

SOLUTION 1-3 #Portlandite cement made by mixing dry CaO with NaNO3 solution
    pH        7 charge
    -water    1000 #kg
EQUILIBRIUM_PHASES 1-10
    Portlandite 0 0
REACTION 1-3
    CaO   1000 #mol
    NaNO3 1000  #mol
    1 moles of above reaction in 1 steps
SAVE SOLUTION 1-3
SAVE EQUILIBRIUM_PHASES 1-3
END

SOLUTION 4 #Acidic water for one boundary condition
    pH        7 charge
    -water    1000 #kg
EQUILIBRIUM_PHASES 4
    CO2(g)    -2 10
SAVE SOLUTION 4
SAVE EQUILIBRIUM_PHASES 4
END

USE REACTION NONE #has no apparent effect
TRANSPORT #Portlandite exposed to acidic solution on one boundary
    -cells 3
    -shifts 2
    -time_step 1 yr
    -flow_direction diffusion_only
    -boundary_conditions closed constant
    -lengths 3*1
    -diffusion_coefficient 1.e-9
END
In simulation 3 the 'Equilibrating initial solutions' step reproduces the simulation 1 and 2 results as expected. The problem comes here:
Code: [Select]
Transport step   1. Mixrun   1.

Using mix 1.
Using pure phase assemblage 1. Pure-phase assemblage after simulation 3.
Using reaction 1.
The REACTIONS from simulations 1) and 2) are applied in each TRANSPORT shift, even though they were not saved. How should the transport simulation be defined such that it uses the saved equilibrated solutions and phase assemblages but not the (unsaved) reactions, which were intended to be one-time?
Title: Re: Use previous SOLUTION and EQUILIBRIUM_PHASES but not REACTIONS in TRANSPORT?
Post by: dlparkhurst on August 23, 2020, 05:25:25 AM
You have a couple options. (1) You can number the reaction outside the range of the tranport column, say 100. (2) You can delete the reaction. Here is a slightly modified version of the beginning of your file that more closely describes the way cells 1-3 are defined.


Code: [Select]
SOLUTION 1 #Portlandite cement made by mixing dry CaO with NaNO3 solution
    pH        7 charge
    -water    1000 #kg
END
EQUILIBRIUM_PHASES 1
    Portlandite 0 0
END
REACTION 1
    CaO   1000 #mol
    NaNO3 1000  #mol
    1 moles of above reaction in 1 steps
END
USE solution 1
USE equilibrium_phases 1
USE reaction 1
SAVE SOLUTION 1-3
SAVE EQUILIBRIUM_PHASES 1-3
END
DELETE
-reaction 1
END