Thermophysical Properties and Phase Behavior of CO₂ with Impurities: Insight from Molecular Simulations

Area of Science:

• Chemical Engineering
• Thermodynamics
• Computational Chemistry

Background:

• Experimentally determining thermophysical properties of carbon dioxide (CO2) rich mixtures is challenging.
• Accurate thermophysical data is vital for the safe and efficient design of CO2 transportation systems.

Purpose of the Study:

• To compute thermophysical properties of pure CO2 and CO2-rich mixtures with common impurities.
• To provide a comprehensive dataset for CO2 transportation system design.

Main Methods:

• Utilized Monte Carlo (MC) and Molecular Dynamics (MD) simulations.
• Calculated densities, thermal expansion coefficients, isothermal compressibilities, heat capacities, Joule-Thomson coefficients, speed of sound, and viscosities.
• Simulated mixtures of CO2 with N2, Ar, H2, and CH4 at temperatures (235–313) K and pressures (20–200) bar.

Main Results:

• Simulated properties showed good agreement with existing Equations of State (EoS).
• Impurities generally decrease gas-phase thermal expansion coefficients, isothermal compressibilities, heat capacities, and Joule-Thomson coefficients.
• Impurities increase gas-phase speed of sound while decreasing it in liquid and supercritical phases.

Conclusions:

• The study provides an extensive dataset of thermophysical properties for CO2-rich mixtures.
• Findings will aid in optimizing the design and operation of CO2 transportation infrastructure.
• Understanding impurity effects is key to ensuring the safety and efficiency of CO2 capture and transport.