(109c) Pilot Plant Testing - the Key to Solving Liquid-Liquid Extraction Challenges

The complexity of the process taking place in a liquid-liquid extraction (LLE) column (e.g. droplet breakup and coalescing, mass transfer, and axial & radial mixing), and the fact that small amounts of impurities can dramatically affect performance, make it difficult to design based upon computer models and simulations.  It remains problematic today to size LLE equipment with any reasonable degree of confidence and accuracy without some type of pilot plant testing.  This paper will focus on how pilot plant testing (1) identified potential scale up challenges, and (2) how the testing led to solutions.  The scale-up designs could only be guaranteed using the solutions gain from the pilot plant testing.  Based upon many years of experience with pilot testing LLE processes, specific challenges/solutions will be presented including emulsion formation, unfavorable density gradients, changing hydraulic behavior throughout the column, rag layer buildup at the interface, negative heat of mixing, agitation versus no agitation, transitional phase in the process, and analytical limitations.  The fact that most of these items could only be identified and solved during testing will clearly support the importance of pilot plant testing new LLE processes.