Spiral Electrodeionization Device Flow Distribution Profiling
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Solution Overview
Problem
Current electrodialysis and electrodeionization devices face challenges such as complex and costly fabrication, operational inefficiencies due to dimensional instability of membranes and beads, and issues with scaling and fouling, particularly when treating fluids with high ion concentrations or extreme pH levels.
Innovation Solution
A spiral EDI device design featuring conductive electrodes and selectively permeable membranes spirally wound around a central core, with spacers maintaining a separation between membranes to allow fluid flow, and ion exchange material in both dilute and concentrate chambers, ensuring uniform current distribution and preventing scaling through strategic flow path design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If flat plate stacks with multiple cells are used, then demineralization capacity is improved, but device complexity and fabrication cost increase
Solution Approach 1:
The patent employs a spiral winding configuration where membranes, spacers, and ion exchange materials are wound around a central collection tube in a nested manner. This allows multiple treatment cells to be integrated within a single cylindrical housing, achieving high demineralization capacity without requiring multiple separate stack assemblies. The spiral nesting reduces the number of external connections and simplifies the overall device structure.
Solution Approach 2:
The invention transitions from flat plate geometry to a curved spiral configuration. The cylindrical spiral design allows fluid to flow axially through the device while treatment occurs across radially oriented membranes. This curvature enables compact integration of multiple cells in a space-efficient manner, reducing device complexity while maintaining or enhancing productivity.
2Device complexity
If membranes and beads are used without dimensional stabilization, then device simplicity is maintained, but operational reliability deteriorates due to dimensional instability
Solution Approach 1:
The patent applies dimensional stabilization measures selectively at critical locations rather than throughout the entire device. Specifically, the spacers are provided with rigid radial support structures at their inner and outer edges to maintain precise spacing between membranes. This localized approach ensures reliable operation where dimensional stability is most critical (at membrane interfaces) while avoiding unnecessary complexity in other regions.
Solution Approach 2:
The spacers are constructed as composite structures combining flexible materials (for sealing and conformability) with rigid radial support elements (for dimensional stability). This composite construction allows the spacers to maintain precise membrane spacing and resist deformation under operating conditions, thereby improving operational reliability without requiring all components to be made from complex stabilized materials.
3Productivity
If uniform flow distribution is achieved, then demineralization efficiency is improved, but device complexity increases due to flow distribution profiling
Solution Approach 1:
The patent implements flow distribution profiling by providing the spacers with varying gap dimensions at different radial positions. The gap between adjacent spacers is made larger at the inner radius and smaller at the outer radius of the spiral winding. This local variation in spacer geometry compensates for the natural flow maldistribution in spiral configurations, achieving uniform flow distribution across all treatment cells without requiring external flow control mechanisms.
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 design enhances demineralization efficiency, reduces operational complexity, and improves cost-effectiveness by allowing for easier assembly and maintenance, while minimizing scaling and fouling through uniform current distribution and strategic flow path management.
Implementation Method 1
an electrical potential is applied across the membranes transverse to the flow to maintain an ionic current that demineralizes the feed fluid, moving ionizable species from the feed fluid in one channel, through the membranes, and into adjacent channels
Implementation Method 2
The presence of exchange material in the treatment channels or cells enhances the active fluid interaction area and the capture of ions from the feed
Implementation Method 3
The ion exchange material is continuously maintained in an at least partially regenerated (active) state by water splitting
Data Source
AI summary
EDI apparatus for demineralizing a liquid flow is assembled in a housing having a cylindrical shape, and includes two metal electrodes, and one or more leafs, each leaf comprising a pair of selectively ion-permeable membranes arranged parallel to each other and spaced apart by spacing elements that allow liquid to flow in the interstitial space between membranes, thus forming an arrangement of dilute and concentrate cells in a desired flow configuration. Spacing elements between membranes, as well as between leaves, can be formed of inert polymer material, ion exchange beads, ion exchange fibers, a combination of two or more these elements, or a porous media incorporating one or more of such elements as an intrinsic part. An inner or central electrode and an outer or perimeter electrode establish a generally uniform and radially-oriented electrical or ionic current between the inner and the outer electrodes, across the helical flow spaces defined by the membrane/spacer windings. One or both electrodes may include a pocket, and the adjacent flow cells lie parallel to the electrode and free of shadowing and field inhomogeneity around a full circumference of the electrode. Flow paths within the helical cells are defined by barrier seals, which may form a path-lengthening maze, while unfilled cell regions may disperse or collect flow within a cell and define pressure gradients promote directional flows. Impermeable barriers between membranes further prevent the feed and concentrate flows from mixing. In various embodiments, seals along or between portions of the flow path may define a multi-stage device, may define separate feed and/or concentrate flows for different stages, and/or may direct the feed and concentrate flows along preferred directions which may be co-current, counter-current or cross-current with respect to each other within the apparatus.