Modeling the Chemistry of Carbon Dioxide - Rich Phases with Impurities

Dense Phase CO2 Corrosion: Modeling the Chemistry of CO₂ – Rich Phases with Impurities

• Objectives:

  - Model the solubility of S^o in CO₂ - rich phases in order to predict whether solid S^o can drop out in transmission lines

  - Predict whether S^o can undergo reactions in the presence of water

• Chemical subsystems to be modeled

  - Pure S^o

  Volatility of pure S^o provides a baseline for its solubility in gas phase

  - S^o – H₂O

  Solubility of S^o in H₂O is important if an aqueous phase forms

  Model development requires considering the S^o – H₂O system because the reference state for liquid-phase species is infinite dilution in water

  - S^o – CO₂

  Solubility of S^o in CO₂

  - Redox reactions of sulfur in aqueous media

  Will be important for future modeling of reactions of SOx and NOx

• Polymeric species of sulfur

  - Numerous sulfur species up to S₂₀ have been detected

  - In the gas phase, eight multimers (S^o₁ through S^o₈) have been assumed in the model

  Thermochemical data are well established for S^o₁ through S^o₈

  S^o₈ is dominant at normal and moderate conditions

  Lower multimers become prevalent at higher temperatures

  - In the pure liquid and solution phase, S^o₈ predominates

  - In the CO₂ phase, solvated S^o-CO₂ species may appear

Vapor pressure of S^o

• Solid-vapor equilibrium transitions into liquid-vapor equilibrium at the triple point
• Calculations are supported by a large body of generally consistent data