Efficiency of Liquid-liquid Extraction

In this experiment, the properties of n-nonane are a good approximation to those of the hydrocarbon mixture for equilibrium data purposes. The ternary system water/isopropanol/n-nonane exhibits Type I equilibrium behavior (there is some composition range over which phase splitting will not take place) at room temperature. The equilibrium data for this system can be found in the Appendix.

1. Operating the York-Scheibel Column

1. Fill the extractor with hydrocarbon mixture /IPA feed (if necessary) and bleed air from the feed line. Turn off the feed flow.
2. Start the mixer and keep the agitator speed constant.
3. Open the solvent, feed, extract, and raffinate ball valves; and start the flow of solvent (water) into the column.
4. If no interface is present between the solvent entrance and the raffinate exit, let the dispersed phase rise and form the upper interface.
5. When the upper interface forms, (re-)start the feed flow.
6. Control the interface level by adjusting the height of the inverted U on the extract line from the bottom of the tower.The upper interface level adjustment (inverted U) is sensitive. Movements of a fraction of an inch are often sufficient.
7. Periodically check the raffinate stream for steady state using gas chromatography. The gas chromotagraph will separate and quantify the components in the sample.
8. Use a hydrometer to measure the specific gravity of the extract stream and determine the composition. (This also can help confirm that steady state has been reached.) The extract stream composition vs. specific gravity tables can be found in Perry's Handbook.³ This data can be used to interpolate for weight percent of IPA.
9. Use a hydrometer to measure the specific gravity of the feed and raffinate for use in subsequent calculations.

2. Shutdown Procedure

1. Once the experiments are complete, turn off the agitator and main power switch.
2. Close the feed and solvent ball valves, leaving the raffinate and extract ball valves open.