(57b) Fundamentals of Liquid-Liquid Extraction

Distillation has been the process industry workhorse for separating components in liquid mixtures.  However, there are a broad range of applications in which liquid-liquid extraction (LLE) should be the method of choice.  Unfortunately, many chemical engineers are unfamiliar with the technology and how it can be applied to separation processes.  Practical aspects of the technology are not widely known, partly because the design of extraction equipment and systems has been in the hands of equipment suppliers.  But familiarity with the basics of LLE can enable a process engineer to fully take advantage of the attractions this technique offer, and to interact effectively with those supplies.  This paper will discuss the fundamental aspects of LLE and an overview of when and how it should be applied as a separation process.  Calculation techniques will be reviewed, including generation and use of equilibrium data and applying this data to process design.  Also various aspects of LLE process development from concept formulation, to bench-top testing, to pilot plant testing will be addressed.  Simple scale-up correlations will be presented for the design of specific types of LLE columns, based upon results from pilot plant testing.  By means of flowsheets, several extraction processes will be incorporated into the presentation.