Configure the Henry's Law options for a Fluid Type

Typically, you use Henry's Law with the thermodynamic calculations for your Fluid Type to more accurately describe the phase equilibrium when the fluid includes supercritical gases or other molecular solutes. Currently, you can use Henry's Law calculations for Fluid Types that use one of the following thermodynamic methods as their System method:

• Ideal

• Non-random two-liquid (NRTL)

• Electrolyte NRTL

• Universal Quasi-Chemical (UNIQUAC)

• Dortmund UNIQUAC Functional-group Activity Coefficient (UNIFAC)

• Wilson

Configure the Henry's Law options

1. Open the Fluid Type in the Fluid Editor if the Fluid Type is not already open.

2. Expand the Equilibrium Options section if it is not already visible.

3. (Optional) Select the Use Henry's Law checkbox to calculate the fugacity of supercritical gasses by using Henry's Law.

   The Henry's Law Data Banks box appears immediately following the Use Henry's Law checkbox, and the Henry column appears in the table in the Component List section.

   

   If your Fluid Type uses one of the liquid activity coefficient (LACT) methods as its System method, the Apply Henry's Law Pressure Correction using Brelvi O'Connell Model checkbox also appears immediately following the Henry's Law Data Banks box.

   

   If your Fluid Type uses the NRTL or Electrolyte NRTL method as its System method, the following checkboxes also appear:

   • Include activity coefficient in liquid fugacity for Henry's solutes (select for solutes in Component List)

   • Include rigorous mixing with activity coefficient and critical volumes for Henry's Law

   

   All Fluid Types use the System:SIMSCI data bank by default. This data bank includes Henry's Law coefficient data for most components commonly used in chemical process applications. However, if your process includes components that do not appear in the System:SIMSCI data bank, you can add one of the following Henry's Law data banks to your Fluid Type:

   • The System:EPA data bank installed with AVEVA Process Simulation, which includes many components that the U.S. Environmental Protection Agency (EPA) regulates and monitors.

   • The HF:HEX data bank installed with AVEVA Process Simulation, which includes components that support the hexamerization of hydrofluoric acid (HF).

   • A custom Henry's Law data bank that you created in AVEVA Thermodynamic Data Manager.

4. (Optional) Select Expand, and then add any custom Henry's Law data banks or additional system data banks that you want to use in your Fluid Type.

   See Data banks for a Fluid Type for more information on the controls for adding, removing, and moving data banks in the Fluid Type.

5. (Optional) If your Fluid Type uses one of the LACT methods as its System method, select the Apply Henry's Law Pressure Correction using Brelvi O'Connell Model checkbox to use the pressure correction for the Henry's constant calculations for all Henry's solutes.

   This adjustment to Henry's Law always uses the pure component volume data calculated from the temperature-dependent property correlations for liquid density, regardless of the Liquid Density selection in your Fluid Type. The temperature-dependent property correlations are defined by the pure component (PURECOMP) data bank that the Fluid Type uses and by the local thermodynamic data overrides specified on the Temp Dep tab in the Component Data section of the Fluid Editor. See Effects of specifying thermodynamic method overrides for more information.

6. If your Fluid Type uses the NRTL or Electrolyte NRTL method as its System method, do the following:

   1. (Optional) Select the Include activity coefficient in liquid fugacity for Henry's solutes (select for solutes in Component List) checkbox to add the activity coefficient to the vapor-liquid equilibrium (VLE) calculations for selected Henry’s solutes.

      The Henry Activity column appears in the table in the Component List section.

      The Include activity coefficient in liquid fugacity for Henry's solutes (select for solutes in Component List) checkbox is selected by default for the Electrolyte NRTL method and clear by default for the NRTL method.

   2. (Optional) Select the Include rigorous mixing with activity coefficient and critical volumes for Henry's Law checkbox to use the rigorous mixing rule to calculate the Henry's constant of the mixed solvent. Otherwise, use a simple additive mixing rule.

   Refer to the following sections for more information on how selecting these checkboxes changes the thermodynamic calculations:

   • Equations for the NRTL method

   • Equations for the eNRTL method

7. In the Component List section, in the Henry column, select the checkbox for each component that you want to treat as a Henry's solute.

   The software automatically selects the Henry checkboxes for all components with critical temperatures less than 400 K.

   

   Refer to Henry's Law for more information.

8. If your Fluid Type uses the NRTL or Electrolyte NRTL method as its System method and you selected the Include activity coefficient in liquid fugacity for Henry's solutes (select for solutes in Component List) checkbox in step 6a, in the Henry Activity column, select the checkbox for all Henry’s solutes that you want to include the activity coefficient in their VLE calculations.

   

9. (Optional) In the Method Data section, on the Henry tab, review the coefficient values that the software uses to calculate the Henry's constant for a Henry's solute (Component j) in the corresponding pure solvent (Component i), and then change the values as you desire.

   Changes that you make in the Method Data section apply only to the Fluid Type and do not propagate back to any thermodynamic libraries. See Override Henry's coefficient data for more information.