Alternating Tray Heights in Extraction Columns to Reduce Axial Mixing
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Solution Overview
Problem
Liquid-liquid extraction columns experience performance variability due to axial mixing and dispersed phase entrainment in weirs, leading to reduced efficiency and increased axial dispersion, which is exacerbated by improper flow dynamics and tray design.
Innovation Solution
A liquid-liquid extraction column design with alternating perforated trays of type I and II, featuring distinct inter-tray space heights and weir cross-sections, specifically adjusting the height ratio H1/H2 between type I and II trays, and optionally increasing the central weir section S2 relative to peripheral weirs, to control hydrodynamics and minimize dispersed phase entrainment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If uniform inter-tray space heights are used in extraction columns, then the column structure is simple and easy to manufacture, but axial mixing increases and mass transfer efficiency decreases
Solution Approach 1:
The patent applies local quality by varying the inter-tray space heights to create different flow conditions in different sections of the column. Type I trays have height H1 and type II trays have height H2, creating alternating patterns that locally optimize flow distribution and reduce axial mixing while maintaining overall column functionality.
Solution Approach 2:
The extraction column is segmented into alternating type I and type II trays with different inter-tray space heights. This segmentation creates distinct flow zones that prevent uniform axial mixing and enhance mass transfer efficiency through varied hydrodynamic conditions across different sections of the column.
2Reliability
If large weir cross-sections are used to prevent dispersed phase entrainment, then axial mixing is reduced, but the column height increases and capacity decreases
Solution Approach 1:
The patent changes the geometric parameters of the weir cross-sections, creating two distinct types with different dimensions. Type I trays have weir cross-section S1 and type II trays have weir cross-section S2, allowing optimization of dispersed phase separation while controlling column height through parameter variation rather than uniform enlargement.
Solution Approach 2:
The alternating pattern of different weir cross-sections creates dynamic flow conditions that adapt to varying load conditions. The variation in weir dimensions between type I and type II trays provides flexible control over flow distribution and dispersed phase entrainment prevention without requiring uniformly large weirs throughout the column.
3Productivity
If alternating tray types with different heights are implemented, then axial mixing is reduced and mass transfer is enhanced, but device complexity increases
Solution Approach 1:
The patent implements periodic action through alternating type I and type II trays arranged in a regular sequence. This periodic variation in inter-tray space heights and weir cross-sections creates repeating patterns of flow conditions that enhance mass transfer while maintaining a manageable level of complexity through systematic repetition rather than random variation.
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
The solution maintains a sufficient coalesced layer height, reduces axial mixing, and enhances mass transfer efficiency by preventing dispersed phase entrainment, resulting in improved extraction performance with reduced column height and operational costs.
Implementation Method 1
The second dispersed phase B accumulates above the perforated tray P, forming a coalesced layer 9 above the perforated area
Implementation Method 2
The operating principle of liquid-liquid extraction columns is based on the differences in solubility of compounds in a homogeneous liquid feed in a suitable solvent
Implementation Method 3
the first and second injection points 2 and 3 being arranged to allow the first and second phases to flow counter-currently
Data Source
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AI summary
The present invention relates to a column for the liquid-liquid extraction of a feedstock by an extraction solvent, comprising perforated trays (Pi) for the passage of a dispersed phase (B), the perforated trays being spaced apart by an inter-tray space (8), and comprising spillways (6), a spillway being a hole allowing the passage of a continuous phase (A) through a perforated tray, the extraction column (1) alternately comprising perforated trays of type I having two peripheral spillways, and perforated trays of type II having a single central spillway, wherein: the height H1 of the inter-tray spaces located directly downstream of the trays of type I, in the direction of flow of the continuous phase, is greater than the height H2 of the inter-tray spaces located directly downstream of the trays of type II. The present invention also relates to a liquid-liquid extraction method using said liquid-liquid extraction column.