Objective
In this article, we will review the main features and capabilities of the Scale Kinetics and Inhibitor Optimization Tool (SKIT), available in V12 of OLI Studio.
Disclaimer: The user interface, calculations, and results displayed in this article are from OLI Studio Version 12.0.0.11. Other software versions may appear different or present slightly distinct results due to continual developments to the software and thermodynamic databanks.
Overview of SKIT
The Scale Kinetics and Inhibitor Optimization Tool (SKIT) is designed to align your observed scale inhibition data with OLI’s software predictions. Since scaling kinetics is a complex and largely system-dependent phenomenon, this tool tailors OLI’s outputs to your unique system. It optimizes the species’ kinetic parameters based on your experimental data of inhibitor concentration vs. observed induction time (time to see the formation of the first visible crystal).
SKIT is useful for users with scale inhibition test data, enabling the easy development of a localized scale inhibitor model and corresponding private database.
Applications
- Accurately predict scale threat in the field
- Calculate scale at a range of conditions and inhibitor concentrations/combinations to guide experimentation
Species Input Options
- Reconcile your experimental data with the software’s predictions for the species already available in OLI. The database created by SKIT will override the existing scale kinetics parameters in OLI’s standard databank.
- Create a private database with your own scaling solid and/or proprietary inhibitor, and use SKIT to optimize the scaling kinetics parameters.
OLI’s Databank
Target scaling solids available in OLI:
- Barite (BaSO₄)
- Celestine (SrSO₄)
- Gypsum (CaSO₄.2H₂O)
- Calcite (CaCO₃)
Comprehensive scaling inhibitors available in OLI:
- HEDP (1-hydroxyethane 1,1-diphosphonic acid)
- NTMP (Nitrilotris(methylenephosphoric acid))
- DTPMP (Diethylenetriamine penta(methylene phosphonic acid))
- PMLA (Poly maleic acid)
- PBTC (2-phosphono-butane-1,2,4-tricarboxylic acid)
SKIT Example in OLI Studio
In the example below, we will leverage data for a scaling solid and inhibitor already present in the standard OLI databank.
Step 1.
Add a stream with the inflows and process conditions shown below. Label it “SrCl2, Na2SO4, NaCl.”
Step 2.
Add a Single Point Isothermal calculation and label it “No BaSO4.”
In the “Specs...” window, under the Calculation Options tab, select the “Scaling Induction Time(s)” checkbox. This enables the scaling induction times for each scaling solid to be calculated and listed as outputs in the Report. The “Advanced…” window allows users to specify the scaling solids they would like to include; we will leave the default settings. (This feature can also be enabled by navigating to the Menu Bar > Tools > Options… > Calculation Options.)
Run the calculation.
Step 3.
Select the “SrCl2, Na2SO4, NaCl” stream in the Navigator Pane, add another Single Point Isothermal calculation, and label it “Add BaSO4.” Change the BaSO4 inflow to 0.1 mol. Enable the scaling induction time option with default settings. Run the calculation.
Step 4.
Select the Global Stream level in the Navigator Pane. Double-click on “Add Optimizer” in the Actions Pane. Label it “Optimizer-2-Sets-Data.”
At the top of this interface, select “No BaSO4” as the first Source Name. Add a “User Name” that provides further information as desired; here, we have simply repeated the Single Point calculation name. Leave the default Weight Factor of 1.0.
On the right-hand side, select the Scale and Inhibitor settings as shown. In the “Advanced…” window, the user can provide specifications for the thermodynamic and scaling kinetic parameters to regress; we will not change the default settings for this example.
Enter the experimental inhibitor vs. induction time data into the grid, as shown below.
Step 5.
Select “Add BaSO4” as the second Source Name at the top of the interface. Repeat the remaining instructions from Step 4 to arrive at the calculation setup below.
Step 6.
Click the “Calculate” button.
Step 7.
After the calculation has completed, navigate to the “Output Options” tab. Here, we will save the re-parametrized scaling solid and inhibitor to a private database. Enter a name for your private database and click “Save” to save this .ddb file locally.
Step 8.
In the “Plot” tab, the software will automatically plot the experimental and predicted induction times for the two Single Point sources based on inhibitor loading.
Step 9.
In the “Prediction” tab, we can evaluate the newly regressed scaling solid and inhibitor under different temperature and pressure conditions. In the plot below, we see how HEDP loading influences predicted Celestine induction time at various temperatures.
Step 10.
Employ your new private database in future scaling calculations. Private databases can be added in OLI Studio by navigating to the Menu Bar > Tools > Options… > Chemistry > Databanks tab. If this is done with the Global Stream level selected in the Navigator Pane, the private database will be enabled for all streams and calculations in the file.
Outcomes
In this article, we introduced the Scale Kinetics and Inhibitor Optimization Tool, outlined its use-cases and utility, and walked through an example with two experimental datasets of HEDP loading vs. observed Celestine induction time. The resultant private database with the re-parametrized species can be leveraged in future calculations, so users can remain confident that OLI’s scaling kinetics predictions closely model their real-life systems.