Multistage Extraction

Description

Multistage Liquid Liquid Extraction (LLE) is a process where multiple extraction steps are repeated in order to increase the recovery of a product. This process is required when, due to a small partition coefficient, the recovery in a single extraction step is insufficient.

In industrial applications, LLE is most often arranged with a “countercurrent extraction scheme” (CC-LLE) that provides the smallest consumption of extractant. In this scheme, the aqueous raffinate from one stage is fed to a former stage as a feed while the organic phase is moved in the opposite direction. Hence, even if the recovery of product in each stage is small, the overall system can achieve a high level of recovery.

In other words, with multistage extraction, selectivity of the extraction and process yield are decoupled as the yield depends on the number of extraction stages used, thus providing greater freedom to the process developer.

Important features:

• Our lab scale platform (MS-10) is the only existing tool for bench liquid-liquid counter-current extraction process development
• Minimal internal volume
• ~3ml per stage at MS-10 scale
• Easily scalable to pilot (MS-200) and production (MS-3000 or MS-40K)
• Easy to use and clean
• Simple to add/remove extraction stages
• Addresses the most difficult extractions
• High extraction efficiency
• Provides a continuous solvent extraction solution

Why is this System Helpful?

• Each extraction stage is obtained by first contacting the two phases to achieve mass transfer and then phase separation is obtained with membrane-based development scale separators or production scale separators.
• Our process implementation reaches Theoretical Efficiency

Fig 1 – Multistage extraction efficiency

• The power of multistage extraction can be seen in Fig 1 which shows the extraction efficiency of three different systems with a partition coefficient of 1 (50/50 partitioning of solute).
• As the number of stages increases, extraction efficiency increases, while still using the same amount of material that would be used if only one batch step was performed.
• Zaiput can assist you in modeling your expected extraction efficiency for different scenarios.

This system addresses 3 key challenges typically encountered in developing multi-stage LLE: lack of information, lack of material and difficulty in scale up.

• Lack of Information. In Multicomponent Systems, Equilibrium data are generally obtained by thermodynamic models (e.g. UNIQUAC, NRTL) but they are often inaccurate due to (1) lack of equilibrium data, (2) unavailable physical property data, especially for unidentified molecular species. As a result, experimental work is needed.
• Lack of material. Counter current Extraction is difficult to simulate in laboratory experiments with standard equipment; many experiments and large amounts of material are required. This platform needs 1 to 2 orders of magnitude less material per experiment than any other method.
• Difficult scale up. Scalability of CC-LLE is challenging with standard equipment (centrifuges, columns, mixer settlers); requires a lot of time and material for optimization. This platform offers seamless scalability up to production.

Technology	Mixer Settler	Columns	Centrifuges	Zaiput
Typical Internal Volume per Stage at Lab scale (ml)	25-100	150	100	3