Alternating-Height Sieve Trays for Liquid-Liquid Extraction
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Solution Overview
Problem
Liquid-liquid extraction columns experience variability in performance due to axial mixing and entrainment of dispersed phase in riser/downcomer conduits, leading to reduced extraction efficiency and increased costs.
Innovation Solution
A liquid-liquid extraction column design with alternating sieve trays of type I and type II, featuring different inter-tray space heights and riser/downcomer conduit cross sections, to control hydrodynamics and minimize axial mixing, ensuring sufficient coalesced phase layer height and continuous phase velocity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the dispersed phase is injected to increase the volume fraction, then the material transfer efficiency is improved, but the axial mixing and entrainment in riser/downcomer conduits increases, reducing extraction efficiency
Solution Approach 1:
The column is segmented into alternating compartments with different heights (H1 and H2). Type I trays have height H1 and type II trays have height H2, creating distinct zones that control dispersed phase distribution. This segmentation allows maintaining high dispersed phase volume fraction in extraction zones while preventing entrainment in separation zones.
Solution Approach 2:
Different compartments have different local characteristics - alternating heights create local variations in hydrodynamics. The higher compartments (H1) and lower compartments (H2) provide different flow conditions locally, enabling optimal dispersed phase distribution in some zones while controlling entrainment in others.
2Reliability
If the column height is increased to improve separation efficiency, then the extraction performance is improved, but the equipment cost and complexity increase
Solution Approach 1:
The system uses dynamic alternating patterns of tray types (I and II) with different heights. This creates a dynamic flow pattern where the dispersed phase experiences varying compartment heights sequentially, enhancing separation efficiency without requiring uniform increases in overall column height.
Solution Approach 2:
The alternating sequence of type I and type II trays creates a periodic structure in the column. This periodic variation in compartment height (H1, H2, H1, H2...) provides repeated cycles of enhanced mixing and separation, improving overall extraction performance while maintaining a compact column design.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Maintains a high volume fraction of dispersed phase, prevents entrainment into conduits, and enhances material transfer efficiency while reducing column height and cost.
Implementation Method 1
The principle of operation of liquid-liquid extraction columns is based on the differences in solubility of the compounds of a homogeneous liquid feedstock in an appropriate solvent
Implementation Method 2
The addition to the feedstock of a partially miscible solvent causes the appearance of a second phase to which a portion of the compounds (e.g. the aromatic compounds), which are the most soluble constituents, is preferentially transferred
Implementation Method 3
The dispersed second phase B accumulates above the sieve tray P, until it forms a coalesced layer 9 above the sieve tray
Implementation Method 4
Depending on the choice of the dispersed phase (heavy phase or light phase), the sieve tray P is designed to collect (by means of weir plates 10) the coalesced layer 9 on the upper part of the sieve tray (when the dispersed phase is the heavy phase) or on the lower part (when the dispersed phase is the light phase)
Data Source
AI summary
A column for the liquid-liquid extraction of a feedstock by an extraction solvent, containing sieve trays (Pi) for a dispersed phase (B) to pass through, the sieve trays being spaced apart by an inter-tray space (8), and riser/downcomer conduits (6), a riser/downcomer conduit being an opening that allows a continuous phase (A) to pass through a sieve tray, the extraction column (1) containing, in alternation, type-I sieve trays containing two peripheral riser/downcomer conduits, and type-II sieve trays containing a single central riser/downcomer conduit, wherein: the height H1 of the inter-tray spaces situated directly downstream of the type-I trays, in the direction of flow of the continuous phase, is greater than the height H2 of the inter-tray spaces positioned directly downstream of the type-II trays. Also, a liquid-liquid extraction method that makes use of the liquid-liquid extraction column.