REDOX (REDduction and OXidation) reactions are off by default because on average, they are rate limited. The most common REDOX reactions used by clients are for the following elements
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Iron, Fe
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Sulfur, S
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Chlorine, Cl
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Nitrogen, N
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Oxygen, O
If you have systems with these materials and suspect that REDOX reactions will occur, then we recommend that your perform the calculation multiple times using different settings:
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First, keep REDOX off and run the calculation.
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Next, turn REDOX on and compare the two results.
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Lastly, turn REDOX on but this time, modify the allowable half-reactions in the dialog (Chemistry>Model Options>Redox). There are check boxes for each oxidation state that you can turn on and off.
Redox screen in OLI Studio
Redox screen in OLI Flowsheet: ESP
It is always good if the user has field experience, so that you can anticipate if REDOX is needed, and if so what oxidation states are dominant.