Liquid-liquid extraction - 2014

Class date(s):	29 October 2014
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References

Please use these references to read ahead, or for extra background reading on liquid-liquid extraction. In alphabetical order:

• Ghosh, R. "Principles of Bioseparations Engineering", Chapter 7, McMaster (reserve)
• Geankoplis, C.J. "Transport Processes and Separation Process Principles", Chapter 12 in 3rd and 4th edition, McMaster Libraries (reserve)
• Perry's Chemical Engineers' Handbook, Chapter 15, Direct link (McMaster subscription)
• Richardson and Harker, "Chemical Engineering, Volume 2", 5th edition, Chapter 13 ebook
• Schweitzer, "Handbook of Separation Techniques for Chemical Engineers", Chapter 1.9, McMaster library
• Seader, Henley and Roper, "Separation Process Principles", Chapter 8 in 2nd and 3rd edition McMaster Libraries (reserve)

Date	Class number	Topic	Slides for class	Video and audio files		References and Notes
29 October	09B	Liquid liquid extraction overview	Slides	Video	Audio	A comprehensive article on liquid-liquid extraction which describes the various units available.
04 November	10A	Liquid liquid extraction theory and calculations	Slides	Video	Audio	The flowsheet for separating acetic acid from water using ethyl acetate solvent. This flowsheet has the mass flow rates, to help contrast it to distillation. click image to enlarge [reference: Seader et al., p300]
05 November	10B	Liquid liquid extraction example calculations	Slides	Video	Audio	The ternary diagram that will be used in today's class. Download and print it out for practice problems. Here's another instructor's slides on the same topic - sometimes a different point of view helps to understand.
07 November	10C	Liquid liquid extraction example calculations	Slides	Video	Audio	Web links shown in the class: Rotating disc column Karr column Scheibel column Pulsed and packed columns
11 November	11A	Liquid liquid extraction example calculations	Slides	Video	Audio	These readings seem old, but they are still relevant. For example, the same principles are used in modern bioseparations. A reading on solvent extraction principles A general article on liquid liquid extractors. An interesting reading on safety in liquid-liquid extraction plants: a further reason for counter-current operations to minimize solvent use.

Exercise

A stream of acetic acid and water (also called diluent) is being fed in a counter current manner at 1000 kg/hour, in order to extract the acetic acid. The feed composition is 30 wt% acetic acid, and 70 wt% water.

The solvent is 99% pure IPE (isopropyl ether), and contains 1% acetic acid, at an inlet flow of 2500 kg/hour.

We desire the exiting raffinate stream to contain 5 wt% acetic acid.

1. Find the number of equilibrium stages to achieve this separation (show all calculations).
2. Calculate the exiting raffinate flow, and the exiting extract flow rate.

Unfortunately, we don't have the equilibrium data, however, various samples of the 3 species were made, mixed, and when they came to equilibrium they were found to have the following compositions (each row gives the aqueous and organic phase compositions):

click image to enlarge

Feel free to download and use this empty ternary diagram.

See this YouTube video for the full solution..