Alternating Spillway Extraction Column for Lower Axial Mixing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing liquid-liquid extraction columns experience performance variability due to axial mixing and dispersed phase entrainment, leading to reduced efficiency and increased axial dispersion, which is exacerbated by continuous phase recirculation and improper weir design.
Innovation Solution
A liquid-liquid extraction column design featuring alternating type I and II perforated trays with specific weir cross-sections and inter-tray space adjustments, including larger central weirs and increased type I inter-tray spaces, to control hydrodynamics and minimize dispersed phase entrainment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional perforated trays with uniform weir sections are used, then the column structure is simple, but dispersed phase entrainment occurs and mass transfer efficiency is reduced
Solution Approach 1:
The column is segmented into alternating zones with type I and type II perforated trays, where type I trays have two peripheral weirs and type II trays have one central weir with larger cross-section. This segmentation creates different hydrodynamic conditions in alternating inter-tray spaces, preventing dispersed phase entrainment while maintaining structural feasibility.
Solution Approach 2:
Different weir configurations are applied locally to different trays based on their position and function. Type II trays with central weirs are placed where dispersed phase accumulation occurs, while type I trays with peripheral weirs are placed where continuous phase flow is dominant. The weir cross-section is locally optimized (larger for type II, smaller for type I) to control phase flow characteristics in each specific location.
2Reliability
If larger weir cross-sections are used to prevent dispersed phase entrainment, then phase separation is improved, but column height increases and cost increases
Solution Approach 1:
Instead of uniformly increasing all weir cross-sections, the column is segmented into alternating zones where only type II trays (with central weirs) have enlarged cross-sections. Type I trays maintain standard weir dimensions. This selective segmentation achieves phase separation control without proportionally increasing overall column height.
Solution Approach 2:
The invention applies excessive action partially - only to the central weir of type II trays - rather than uniformly to all weirs. The central weir cross-section is deliberately made larger than peripheral weirs to create sufficient residence time and prevent entrainment in the critical dispersed phase accumulation zone, while avoiding unnecessary height increase in other regions.
3Productivity
If alternating type I and II perforated trays are used with different weir sections, then dispersed phase entrainment is prevented, but device complexity increases
Solution Approach 1:
The column is divided into alternating segments of type I and type II trays, creating a periodic structure that is manageable and manufacturable. Each tray type maintains a relatively simple configuration (either two peripheral weirs or one central weir), avoiding the need for complex multi-component trays while still achieving the desired hydrodynamic control through the alternating pattern.
Solution Approach 2:
The column employs a periodic arrangement of type I and type II perforated trays, where the pattern repeats along the column height. This periodic structure simplifies the overall design compared to requiring different configurations for every tray, as the same tray types can be manufactured and installed in repeating sequences, reducing customization complexity while maintaining performance.
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
This design maintains a sufficient coalesced layer height, prevents dispersed phase entrainment, and enhances mass transfer efficiency by reducing axial mixing, resulting in improved extraction performance with reduced column height and cost.
Implementation Method 1
The second dispersed phase B circulates as droplets passing through the first continuous phase A in each inter-plate space 8 defined by the space between two adjacent perforated plates P
Implementation Method 2
forming a coalesced layer 9 above the perforated area
Implementation Method 3
The first continuous phase A meanders through the inter-tray spaces 8 via the weirs 6, upwards in this example of the figure 2 because the continuous phase is the light phase
Implementation Method 4
The second dispersed phase B then flows through the perforated area of the perforated tray P to feed the next perforated tray P (the lower tray if the dispersed phase is the heavy phase)
Data Source
Figure 1
Figure 2
Figure 3
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 cross-section S2 of the central spillways is larger than the cross-section S1 of the peripheral spillways, cross-section S1 corresponding to the sum of the cross-sections of the two peripheral spillways. The present invention also relates to a liquid-liquid extraction method using said liquid-liquid extraction column.