Objective
This article explains the default behavior and configuration options for REDOX (reduction-oxidation) reactions in OLI software, and outlines a recommended workflow for assessing their impact in simulation results. It is intended to guide users who suspect REDOX processes may be occurring in their system, particularly when working with elements like iron, sulfur, chlorine, nitrogen, or oxygen.
Understanding REDOX in OLI Software
By default, REDOX (Reduction and Oxidation) reactions are disabled in OLI software. This is because these reactions are typically rate-limited.
Common REDOX-Active Elements
Clients often investigate REDOX chemistry involving 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 your system includes one or more of these components and you suspect REDOX reactions may influence your results, we recommend the following workflow.
Recommended Workflow for REDOX Evaluation
- Initial Simulation Without REDOX
Keep REDOX reactions turned off and run your calculation or simulation. This provides a baseline for comparison. - Enable REDOX and Re-run the Simulation
Enable REDOX reactions using one of the following methods:-
In OLI Studio:
Click the "Re" button on the toolbar. This enables REDOX for transition metals by default.
To view or customize the elements included in the REDOX setting, click the arrow next to the "Re" icon, or navigate to the Menu Bar:Chemistry > Model Options > Redox
From here, you can select specific elements and allowable oxidation states. -
In OLI Flowsheet: ESP:
Navigate to:Chemistry Model tab > Redox > Include Redox Chemistry
Then, select the relevant subsystems for which REDOX reactions should be considered.
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- Compare Results
Evaluate the differences in simulation outcomes between the non-REDOX and REDOX-enabled runs. - Refine REDOX Settings
Based on your comparison, consider modifying the set of permitted half-reactions (oxidation states) in the REDOX dialog to more closely reflect your system's behavior.
Important Notes
- When using Stability Diagrams or Corrosion Rate calculations in OLI Studio, the REDOX setting is automatically enabled—typically for iron.
- When the REDOX setting is enabled in OLI Studio at the stream-level, it will also be automatically enabled for calculations added to the stream.