Liquid-Liquid Extraction in HYSYS

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					Liquid-Liquid Extraction in HYSYS:
In this tutorial, you will be walked through a simple liquid-liquid extraction process in HYSYS. A liquid stream containing 60 mol percent water and 40 mol percent acetone entering at 25 C, 1 atm, and flowing at a rate of 1 kgmol/s will be extracted with a pure MIBK stream at the same exact conditions as the feed.

Initial Setup:
1. 2. 3. 4. Star Start a new case in HYSYS Select Acetone Water and MIBK for the components. Use the NRTL Fluid Package. For Liquid-Liquid Extraction cases, the binary coefficients of the components have to be checked. If some of the coefficients are not specified by HYSYS, a fatal error will occur, and the process can not be simulated. To check the Binary Coefficients, simply click the “Binary Coeffs” tab.

5. Some of the coefficients are not specified, since some of the tabs are left blank. There are a number of ways to fix this. First the coefficients can either be looked up or experimentally determined, and then entered straight into the appropriate box. Or, HYSYS can estimate the unknown coefficients using equilibrium relationships. To do that select either “UNIFAC VLE” or “UNIFAC LLE” and then clicking on the tab “Unknowns Only”. In Liquid-Liquid Extraction processes, UNIFAC LLE is the appropriate estimation to use. Close the Binary Coefficient window, and enter the simulation environment.

Setting up the Liquid-Liquid Extraction Process:
Now that the components and fluids packages are selected, HYSYS is now ready to start simulating the Liquid-Liquid Extraction process. 1. Since this is a simple Liquid-Liquid Extraction case, 4 process streams are needed; the feed, the solvent, the extracted product and the bottoms.

2. Rename the streams to Feed, Solvent, Extracted Product, and “Bottoms”. 3. Now that the process streams are in place and named, place a Liquid-Liquid Extraction column. Click on the Liquid-Liquid Extraction column button in the Simulation Toolbar, and then place it on the simulation window.

4. Double click on the Liquid-Liquid Extraction column to bring up the “Liquid-Liquid Extractor Input Expert”. Hook up the feed stream to the “Top Stage Inlet”, the solvent stream to the “Bottom Stage Inlet”, the Extracted Product to “Ovhd Light Liquid”, and the Bottoms stream to the “Bottoms Heavy Liquid” then click “Next >”.

5. Specify a constant pressure of 101.3 kPa by typing it in to the pressure columns.

6. Finally, HYSYS prompts for optional temperature estimates for the top and bottom stages. These estimates can be ignored and HYSYS will calculate them when the simulation is run. Click “Done…” to complete the Liquid-Liquid Extractor Input Expert.

7. Clicking done brings up a window displaying all of the data and options of the Liquid-Liquid Extractor. Due to the properties of this system, 10 trays are not needed to extract the acetone. Approximately 4 trays are needed to extract 99% of the acetone. Since 10 trays are specified by default, 6 trays need to be removed. Note: By default HYSYS numbers the trays in numerically ascending order, with tray 1 being at the top. 8. To remove the extra trays, click on “n = ” tab under “Num of Stages” on the drawing of the column, and simply enter in 4.

Specification of the Feed and Solvent Streams:
After completing the steps above, the Liquid-Liquid Extraction column should be fully specified for most simple extraction cases. To complete and run the simulation, the feed and solvent streams need to be specified. 1. Double click on the Feed stream, opening the specification menu. Type in the desired feed properties; a temperature of 25 C, a pressure of 101.3 kPa, a flow rate of 1 kgmol/sec, and a feed with a 40 mol % acetone and 60 mol % water

2. The solvent stream contains pure MIBK entering at 25 C, 101 kPa and flowing at 1 kg-mol/sec

Running the Simulation with a Liquid-Liquid Extractor:
Now the Liquid-Liquid Extraction column, and the feed and solvent streams are properly specified and the simulation is ready to run. 1. Click the green light for unknowns. in the upper toolbar to get HYSYS to start actively solving

2. Whenever a Liquid-Liquid Extraction column is present in a simulation, it must be started separately. Double click on the colum and click “Run”. Close the window and see that the Extracted Product and Bottoms streams have turned from turquoise to dark blue, signifying that HYSYS has successfully solved for those streams unknown properties. Note: After this stage, if any of the specifications on the Liquid-Liquid Extraction column are changed, the “Reset” button must be pressed, and then the “Run” button pressed again to rerun the distillation simulation with the new specifications.

3. If the simulation is successful, the workbook should look like this:

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