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Found 8 results

  1. Hello, I have encountered an issue when running the react code I can't explain. For my research I need to run evaporation simulations well below the freezing point of pure liquid water. Therefore, I designed an extension of the Thermo_phrqpitz database down to -80oC (60, 40, 20, 0, -20, -40, -60 and -80oC). I added numerous minerals and aqueous species along with their pitzer parameters, from recent literature publications. However, when I run the code, I encounter a sudden jump in water activity between 239 and 239.1 K, which I can't explain in any way. This jump affects the water activity, the ionic activity and therefore the saturation index, generating precipitations of minerals at much higher water activity than they should (basically from 273 down to 239, the results "make sense" but not below, the water activity is way too high). I attach a figure showing such jump in water activity for a 50/50 mol% Mg(ClO3)2 / Mg(ClO4)2. Does anyone has any idea why such jump occurs? Thank you Sincerely Vincent Water_activity_Mg_ClO3-ClO4.tif
  2. Hi, I changed some of the logK's for a mineral in the thermo.dat database and realised that I didn't want to do that. How do I revert back to the original thermo.dat database? Thanks, Sam
  3. Hi everyone, After learning the tutorial about “Editing thermo”, i noticed that the range of temperature and pressure are limited. I do know how to modify the logK vaules using SUPCRT92, but i am not sure how to change the parameters of Deby-Huckel parameters/CO2activity coefficient terms and water activity coefficient terms, especially the CO2 1,2,3,4s and H2O 1,2,3,4s. Where can i find those parameters or is there a software can generate them?
  4. Hi GWB Forum, I am currently working on my thesis on corrosion and scaling in thermal waters of geothermal power stations. I hope GWB can help me analyse these reactions in geothermal brines (high pressure, high temperature). Therefore I downloaded the student version. I have the following questions. 1) Can GWB simulate corrosion? 2) As far as I know mineral precipitation can only be calculated with the standard version of GWB. Is there a way to simulate scaling/precipitation in the student version? 3) As far as I know pressure is not included in the calculation, but how can I consider pressure? Do I have to use another database of GWB to include pressure in the calculation? Do I have to use a totally different software like PhreeqC to consider high pressure? 4) Does GWB automatically calculate the amount of CO2 contained in thermal water, if I include other parameters like HCO3-, pH etc. For example I have an analysis of thermal water, where the brine was first degassed and content of CO2 was measured. Then the amount of ions like HCO3- was measured. Since I can only put either CO2 or HCO3- into the calculation, does GWB conclude CO2 content from the other values like HCO3- or in other words is one of both values sufficient? For instance I'd like to simulate scaling/precipitation of calcite in a geothermal power station, that pumps the brine from a depth of about 4350 m through pumps, heat exchangers etc. and reinjects it. If I can calculate the solubility of minerals like calcite or can simulate the precipitation for the different locations/parameters in the power station, I can estimate the extent and location of scaling. The pressure is an important parameter in this example because the brine loses pressure, which leads to degasing of CO2, which leads to precipitation. That's why I need to consider it. Thanks in advance for the answers.
  5. Hello, Is there any indication of which database was drawn from when looking at an output file? Thanks! Michael
  6. Hello, I'm looking for some help reconciling (or understanding) log K values for aqueous species with values I'm calculating from various references (Solutions, Minerals, and Equilibria - Garrels and Christ; Chemistry of Glasses - A. Paul). (As a disclaimer - my formal training is in nuclear science and I have little academic training in geochemistry, environmental chemistry or physical chemistry - and I'm hoping I'm just missing something about how these values are calculated.) For instance, the value for Zr++++ is set to log K (25°C) = -0.2385 in the thermo database, and there are no other log K's listed at other temperatures for this species (I need to simulate everything at 90°C). However, the delG0f is given as -125.350 kcal/mol (524.46 kJ/mol) in the header. Elsewhere (e.g., in Paul and in Garrels & Christ) the value is 142.0 kcal. That discrepancy aside, if I use the log K value given at 25°C in the database to back calculate the delG0f from the equation log K = -delG0f/2.303*R*T, I get a value of 1.3615 kJ/mol, which is significantly different from the other values listed. I have noticed this with a few other aqueous species; also, when I'm trying to add new species not found in the database using values I calculate, I think I'm getting skewed results in terms of activity diagrams and species not showing up or having extremely low activities when we are thinking they should be playing a larger role in the systems I'm investigating. This is especially true in terms of species that I'm adding to the database for which I'm using reference values for delG0f which yield log Ks that are significantly higher than those for other preexisting species in the database. What am I missing about how these values are determined in the file and the discrepancies between the delG0f values from the literature? Is is "ok" to back calculate the delG0f from the log K given in the database and then use that same equation to calculate values for log K at different temperatures? Please let me know when you have a chance...like I said, I feel like I'm missing a fundamental piece of knowledge here. Any help is very much appreciated.
  7. Hello, I am currently working on modeling the precipitation of seawater under evaporation. I am particularly concerned with the Iron containing phases. Which thermodynamic database should I choose to get a reliable result? "HMW" could have been an excellent choice except that it does not contain Fe. The other databases that are present include Fe as well as use B-dot equations. Generally B-dot is valid for Ionic Strengths less than 3 molal , but there were erroneous results (pg 132) cited in the book "Geochemical and Biochemical Reaction Modeling" by Craig Bethke. I am very perplexed with the choice of database. Please suggest a solution. Thank you
  8. Hi there, We at Geoscience Australia are ready to migrate from version 8 to version 10. I note that now the database format is somewhat different, though (?)backwards compatible; some of the third-party data providers suppply data in new format only (e.g., THEREDA). Where can I find the summary of these database format(s) changes? Thanks! Best regards, Evgeniy Evgeniy Bastrakov Geoscience Australia
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