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Modifications to thermo database


Eva Stueeken
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We have made several modifications to the thermo database, specifically to carbon and nitrogen, and are now having trouble with getting it to work. We changed the basis species to CO(aq) and NO(aq) and then redefined various redox couples, aqueous species and gases. However, when we now try to run a model in REACT, for example, and we add anything to do with redox reactions, an error message appears saying that the model did not converge. Our modified database is attached. If anyone can spot a mistake, please let us know. 

Thanks!

thermo_StA-CES 8 (1).tdat

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  • 2 weeks later...

Hello Eva,

Taking a quick look at your thermo database, I believe the issue might be caused by the log K values for the new reactions. They seem to be either incredibly large or small values (e.g. 3984175, -4005773). I would suggest checking these values against the source and make sure that they are in the correct units. If this doesn't help, can you please attach your input file along with the modified thermo dataset so we can directly troubleshoot? 

Hope this helps,
Jia Wang

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  • 3 weeks later...

Hi Jia,

 

Thanks a lot for your help, and sorry for my slow reply!

We have finally found an error in our calculations of the equilibrium constants and were able to get something to work. However, we still seem to have a problem with the equilibrium between NOx gas phases and aqueous phases. I'm attaching our modified database, along with a REACT script. In the script, I created a model where 10mmol of NO(g) are reacted with a liter of water. I am able to plot up aqueous NOx species that form as a result of this reaction, but for some reason the gas phases (NO, N2O, NO2, etc.) are all zero. REACT is unable to calculate the equilibrium gas fugacities for all N-gases. I tested the same model with H2S gas, and here the calculation of the H2S(g) fugacity works fine. Something must still be wrong with our NOx gas species in the database. Do you have any idea what could be going on? Any advice you can provide would be extremely helpful.

Best regards,

Eva

 

thermo_StA-CES.tdat NOx and H2S anoxic.rea

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Hello Eva,
 
My apologies for the delayed response. After taking a closer look at your dataset, I noticed that all the factors for calculating the new gas species' fugacities are filled in with zeros. This happens when you view a gas entry in TEdit and then save the dataset. This is a bug found earlier this year and a fix will be available later this year. The default fugacity model set for this dataset is Tsonopoulos type, as indicated in the Header pane or the header lines at the top of the dataset. This method uses the critical point pressure, temperature, and accentric factors for the fugacity calculations for more species. For polar or hydrogen bonding gases, like H2O(g), the model may also extend to include factors a and b. If you do not provide values in these fields (leaving them blank), then the software will assume ideal gas conditions for calculating the fugacity and pressure model. For now, you can change the gas model to default or off or delete them using a text editor like Notepad.
 
For more information on fugacity methods used, please take a look at section 2.3 Thermodynamic datasets in the GWB Essentials User's Guide and section 3 Thermo Datasets in the GWB Reference Guide.
 
Hope this helps,
Jia Wang
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