Resistive Component Shifting Current in EDI Outlet
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Solution Overview
Problem
Existing electrodeionization (EDI) systems face challenges in maintaining balanced current distribution across the resin bed, leading to inefficiencies in deionization performance due to varying ion mobilities and conductivity gradients, which are not effectively addressed by prior art.
Innovation Solution
Incorporating a resistive component near the outlet region of the EDI device, either on the anion or cation membranes, to increase electrical resistance and balance current distribution between the inlet and outlet regions, thereby enhancing deionization performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the conductivity of the resin bed is uniform throughout, then the device structure is simple and easy to manufacture, but the current distribution is unbalanced leading to poor deionization performance
Solution Approach 1:
The patent applies local quality by creating zones with different resin properties within the bed. Specifically, it uses resin beads with different functional groups (strong acid cation exchange resin in the first zone, weak acid cation exchange resin in the second zone) and varies the ratio of anion-exchange to cation-exchange resin capacities across zones. This local differentiation of resin characteristics creates non-uniform conductivity distribution that optimizes current flow and deionization performance in different regions of the device.
2Manufacturing precision
If the electrical resistance of the outlet region is increased, then the current distribution is improved with more current flowing through the inlet region, but this requires additional components increasing device complexity
Solution Approach 1:
The patent implements local quality by creating distinct zones with different electrical resistance characteristics. The first zone (inlet region) is designed with lower electrical resistance through using strong acid cation exchange resin and higher anion-exchange to cation-exchange resin capacity ratios, while the second zone (outlet region) has higher electrical resistance through using weak acid cation exchange resin and lower anion-exchange to cation-exchange resin capacity ratios. This spatial variation in resistance properties naturally directs current distribution without requiring additional external components.
3Manufacturing precision
If alternating layers of ion exchange resin with different conductivity are used, then current distribution can be modified, but the manufacturing process becomes more complex requiring precise layering
Solution Approach 1:
The patent applies local quality by creating zones with different resin properties within the bed. Specifically, it uses resin beads with different functional groups (strong acid cation exchange resin in the first zone, weak acid cation exchange resin in the second zone) and varies the ratio of anion-exchange to cation-exchange resin capacities across zones. This local differentiation of resin characteristics creates non-uniform conductivity distribution that optimizes current flow and deionization performance in different regions of the device.
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 resistive component improves current distribution, reducing impurity ion penetration and enhancing the overall deionization process by shifting a greater percentage of electrical current to the inlet region, resulting in higher purity water production.
Implementation Method 1
the resistive component functions to increase the electrical resistance across the outlet region of the chamber with respect to the inlet region of the chamber
Implementation Method 2
The current passes through the bed via ion migration through both the solution and the ion-exchange beads
Implementation Method 3
ion migration through both the solution and the ion-exchange beads, with water dissociation occurring at the anion-cation, bead-bead and bead-membrane interfaces
Implementation Method 4
water dissociation occurring at the anion-cation, bead-bead and bead-membrane interfaces
Data Source
Figure 1a~1b
Figure 1c~1d
Figure 2a~2b
AI summary
An electrodeionization (EDI) apparatus (10) and method comprising an ion-depleting chamber (20) for removing ions from liquids passed therethrough, wherein a resistive component (32) is coupled proximate the outlet region of the chamber so as to increase the electrical resistance of the outlet region of the chamber with respect to the inlet region of the chamber. The resistive component may be coupled to the ion-selective membranes (22,24) bordering the diluting chamber (20) and/or the concentrate chambers (21). In an alternative embodiment, the resistive component may be coupled between the ion- exchanging media particles themselves within the ion-depleting chambers. In each embodiment, the electrical resistance of the outlet region is increased with respect to the inlet region of the chamber, with results being that electrical current is shifted from the outlet region toward the inlet region, thus enhancing overall deionization performance of the EDI device.