Property Packages
Property packages define the thermodynamic models used to calculate phase equilibrium, enthalpies, and densities in Rigorous mode. Select a package via the property method selector in the toolbar.
Available Packages
Ideal
Simple property calculations assuming ideal gas and ideal liquid behavior.
| Aspect | Detail |
|---|---|
| VLE model | Raoult's Law: Ki = Psat,i(T) / P |
| Vapor phase | Ideal gas |
| Liquid phase | Ideal solution |
| Best for | Light gases, similar-molecule mixtures, screening studies |
Use Ideal for initial flowsheet debugging. It converges fastest and helps isolate topology issues from thermodynamic issues.
SRK (Soave-Redlich-Kwong)
Cubic equation of state with Soave's alpha function.
| Aspect | Detail |
|---|---|
| EOS | P = RT/(V-b) - a(T)/[V(V+b)] |
| Vapor phase | SRK EOS |
| Liquid phase | SRK EOS |
| Best for | Hydrocarbons, natural gas processing, refinery applications |
SRK handles non-ideal vapor behavior well and is the standard choice for hydrocarbon systems at moderate pressures.
PR (Peng-Robinson)
The industry-standard cubic EOS for oil and gas applications.
| Aspect | Detail |
|---|---|
| EOS | P = RT/(V-b) - a(T)/[V(V+b) + b(V-b)] |
| Vapor phase | PR EOS |
| Liquid phase | PR EOS |
| Best for | Oil & gas, high-pressure systems, supercritical fluids |
PR provides better liquid density predictions than SRK, particularly near the critical point. It is the default choice for most industrial hydrocarbon simulations.
NRTL (Non-Random Two-Liquid)
Activity coefficient model for non-ideal liquid mixtures.
| Aspect | Detail |
|---|---|
| Liquid phase | NRTL activity coefficients |
| Vapor phase | Ideal gas (or PR for high pressure) |
| Parameters | Binary interaction parameters (alpha, tau) |
| Best for | Polar mixtures, alcohol-water systems, azeotropes |
NRTL requires binary interaction parameters for each component pair. If parameters are unavailable for your system, the solver falls back to Ideal.
UNIQUAC (Universal Quasi-Chemical)
Activity coefficient model based on local composition theory with surface area and volume parameters.
| Aspect | Detail |
|---|---|
| Liquid phase | UNIQUAC activity coefficients |
| Vapor phase | Ideal gas (or PR for high pressure) |
| Parameters | Binary interaction parameters, molecular r and q values |
| Best for | Complex mixtures, polymer solutions, systems with molecules of very different sizes |
Falls back to Ideal if binary interaction parameters are not available for the selected component pair.
eNRTL (Electrolyte NRTL)
Extended NRTL model for systems containing ionic species.
| Aspect | Detail |
|---|---|
| Liquid phase | eNRTL activity coefficients (ion-molecule, ion-ion interactions) |
| Vapor phase | Ideal gas |
| Parameters | Electrolyte binary interaction parameters |
| Best for | Acid gas treating (CO2/H2S in amine), saline solutions, electrolyte systems |
Falls back to Ideal if electrolyte interaction parameters are not available.
Selection Guide
| System Type | Recommended Package |
|---|---|
| Light hydrocarbons, natural gas | SRK or PR |
| Heavy hydrocarbons, refinery | PR |
| High-pressure / supercritical | PR |
| Alcohol-water, polar organics | NRTL |
| Azeotropic distillation | NRTL |
| Polymer solutions, mixed-size molecules | UNIQUAC |
| Amine gas treating | eNRTL |
| Screening / debugging | Ideal |
How to Select
- Open the editor toolbar above the flowsheet canvas.
- Click the property method selector.
- Choose a property package.
- Press Run.
The property package applies globally to the entire flowsheet. All unit operations and streams use the same thermodynamic model.
The property method selector only appears when Rigorous mode is active. Quick mode always uses the Ideal package.
Component Database
Rigorous mode provides 70+ validated components sourced from:
- NIST — National Institute of Standards and Technology
- DIPPR — DIPPR 801 Database
- Perry's Chemical Engineers' Handbook — critical properties, heat capacity correlations
- RPP (Reid, Prausnitz, Poling) — equation of state parameters, interaction coefficients
Each component includes: molecular weight, critical temperature, critical pressure, acentric factor, heat capacity coefficients, Antoine coefficients, and (where available) binary interaction parameters for NRTL/UNIQUAC.