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dirk

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  1. Ok, sorted some out. Turns out the contaminated fluid was undersaturated with respect to Fe(OH)3 so by day 8 it has exhausted the Fe(OH)3 and that made convergence not possible for some reason that seems to be related to increase in the length of the reaction step in the first cell. So using goethite instead, seems to be working.... So I am wondering about the why of it. Fe(OH)3 is the adsorbant and is the breakdown because there is no adsorbant left , other minerals (calcite for instance) do go to 0 in the first cell, so does that mean that there has to be some adsorbant left in a cell in order for simulation to go forward?
  2. Sorry posted this on the archive thread... Hi, I am running a simulation of a flow through column experiment and slowly working up to the full rtm. I run the initial solution through for 5 days then the contaminated solution. calcite reacts based on kinetic constraints, precipitation of gypsum, gibbsite, Fe(OH)3 at equilibrium all else suppressed, adsorption using the D&M model and the FeOH database (decreased site densities of w and s sites by an order of magnitude). after adding adsorption I cannot get it to finish. current error is "Step is constrained by rate of increase in length of reaction step at node 0." after 8 days of 10 day run. Any ideas? Dirk
  3. Hi, I am running a simulation of a flow through column experiment and slowly working up to the full rtm. I run the initial solution through for 5 days then the contaminated solution. calcite reacts based on kinetic constraints, precipitation of gypsum, gibbsite, Fe(OH)3 at equilibrium all else suppressed, adsorption using the D&M model and the FeOH database (decreased site densities of w and s sites by an order of magnitude). after adding adsorption I cannot get it to finish. current error is "Step is constrained by rate of increase in length of reaction step at node 0." after 8 days of 10 day run. Any ideas? Dirk
  4. Hi Brian, yup, look like an issue with the sign, I read dissolution as positive and precipitation as negative rates based on the GWB output so I followed that convention. Getting rid of both the - sign at the front of term 1 and the minus before term 2 fixed the problem. Cheers Dirk
  5. The BCF growth theory is the Burton-Cabrera-Frank (Burton et al. 1951) is a non-linear crystal growth model that is commonly accepted (see various publications by Luttge, Arvidson, Aargaard, Hellvang amoungst others). The second term of the Q/K>1 portion is the precipitation and nucleation term derived from classical nucleation theory. It is a small number at low levels of supersaturation but increases significantly especially above lnQ/K of 4 or 5 (depending on the gamma_n term). The equation comes from Hellvang and Aagaard (2013) IJGGC, V. 15, p. 3-15. They ran it using PHREEQC and provide the PHREEQC input file. Dirk
  6. Hi Brian, see the attached. You will have to add the 2 minerals in the 'add to thermo' file to your thermo.com.V8.R6.dat file. Hutton CO2 test 4.rea add to thermo.txt
  7. I am interested in writing a simple script that incorporates the BCF crystal growth theory equation but when I run React I get fluctuating precipitation/dissolution for the precipitating mineral. The result is fluctuating positive then negative mineral mass for siderite (with initial mass = 0). This occurs when the mineral mass is very low 1e-186 but this low number is the nature of the nonlinear BCF. When left to run, the mass keeps going from positive to negative. Is there some way to write in the script something to prevent the negative numbers? It appears to be a complete transition from positive to negative to positive, ie. the next logical number in the series during the reaction can end up being the opposite sign. Any help is much appreciated. Attached is the script for siderite. Dirk Siderite1.rtf
  8. I am interested in writing a simple script that incorporates the BCF crystal growth theory equation but when I run React I get fluctuating precipitation/dissolution for the precipitating mineral. The result is fluctuating positive then negative mineral mass for siderite (with initial mass = 0). This occurs when the mineral mass is very low 1e-186 but this low number is the nature of the nonlinear BCF. When left to run, the mass keeps going from positive to negative. Is there some way to write in the script something to prevent the negative numbers? It appears to be a complete transition from positive to negative to positive, ie. the next logical number in the series during the reaction can end up being the opposite sign. Any help is much appreciated. Attached is the script for siderite. Dirk
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