Difference between revisions of "Modeling the Chemistry of Carbon Dioxide - Rich Phases with Impurities"
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[[User:jberthold | Author: Ron Springer (OLI), Andre Anderko (OLI), Jim Berthold (OLI, editor)]] | [[User:jberthold | Author: Ron Springer (OLI), Andre Anderko (OLI), Jim Berthold (OLI, editor)]] | ||
[[category: Thermodynamics]] | [[category: Thermodynamics]] |
Revision as of 07:15, 18 May 2020
Dense Phase CO2 Corrosion: Modeling the Chemistry of CO2 – Rich Phases with Impurities
Contents
Objectives:
- - Model the solubility of So in CO2 - rich phases in order to predict whether solid So can drop out in transmission lines
- - Predict whether So can undergo reactions in the presence of water
Chemical subsystems to be modeled
- - Pure So
- Volatility of pure So provides a baseline for its solubility in gas phase
- - So – H2O
- Solubility of So in H2O is important if an aqueous phase forms
- Model development requires considering the So – H2O system because the reference state for liquid-phase species is infinite dilution in water
- - So – CO2
- Solubility of So in CO2
- - Redox reactions of sulfur in aqueous media
- Will be important for future modeling of reactions of SOx and NOx
- - Pure So
Polymeric species of sulfur
- - Numerous sulfur species up to S20 have been detected
- - In the gas phase, eight multimers (So1 through So8) have been assumed in the model
- Thermochemical data are well established for So1 through So8
- So8 is dominant at normal and moderate conditions
- Lower multimers become prevalent at higher temperatures
- - In the pure liquid and solution phase, So8 predominates
- - In the CO2 phase, solvated So-CO2 species may appear
- Solid-vapor equilibrium transitions into liquid-vapor equilibrium at the triple point
- Calculations are supported by a large body of generally consistent data
- Pressure significantly affects the melting point
- Transition between solid-liquid equilibria and liquid-liquid equilibria at the melting point of sulfur
- Solubility is a strong function of temperature
Solubility of So in CO2: Preliminary results
- Two segments of solubility curves at each T corresponding to gas (or gas-like) and liquid (or liquid-like) CO2
- Transition is sharp for subcritical CO2 and gradual for supercritical CO2
- Fair amount of scattering in the data but the trends are clear
- In scCO2, changes due to SVE-SLE transitions are obscured by uncertainty in data
Modeling sulfur redox
- Provides a starting point for modeling reactions involving sulfur
- Redox states
- - Oxidation states range from S2- through S8+
- - Practically important states:
- S2- (sulfides, hydrogen sulfide)
- S0
- S2+ (thiosulfate)
- S4+ (sulfite)
- S6+ (sulfate)
- Thiosulfates and sulfites are usually metastable as evidenced by E-pH diagrams
- Experimental data are often kinetically constrained
- - Metastable species may be identified in addition to stable ones
Sulfur redox: Preliminary results for disproportionation
- Disproportionation reactions proceed more readily at high T
- This is not a direct comparison because measurements are kinetically constrained and calculations predict equilibria
- Therefore, only semi-quantitative agreement can be expected
- The properties of thiosulfate species (S2+) need to be reexamined
Author: Ron Springer (OLI), Andre Anderko (OLI), Jim Berthold (OLI, editor)