Split Flow EDI Apparatus for High Rate Water Purification
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Solution Overview
Problem
Existing Electro-Deionization (EDI) apparatus face limitations in achieving high product flow rates due to high pressure drops, mechanical leaks, and mechanical strength issues, particularly when dealing with single pass RO permeate water containing challenging scaling ions, which reduces system efficiency and increases costs.
Innovation Solution
A novel split-flow EDI apparatus design that splits the flow through the stack into two parts, utilizing a combination of up-flow and down-flow patterns within the dilute and concentrate chambers, reducing resin bed depth and power consumption, and incorporating a middle solid supporting rib for mechanical strength and flow distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional EDI apparatus design is used, then mechanical strength and leak prevention are maintained, but product flow rate is limited to low levels (1.5-2.0 m3/hr)
Solution Approach 1:
The apparatus is divided into multiple cell pairs (30-35 cell pairs) arranged in series, with each cell pair containing dilute chambers and concentrate chambers separated by ion exchange membranes. This segmentation allows the system to achieve high flow rates (5.0-10.0 m3/hr) while maintaining mechanical integrity through distributed stress across multiple modular units.
Solution Approach 2:
The invention transitions from traditional thin cell plate design to thick cell plate and frame construction, changing the dimensional configuration of the apparatus. This dimensional change enables higher flow rates by increasing the flow cross-section area while maintaining structural strength through the frame configuration.
2Manufacturing precision
If resin bed depth is increased to improve purification capacity, then water quality improves, but pressure drop increases and flow rate decreases
Solution Approach 1:
The resin bed is segmented into multiple chambers with multiple cell pairs in series. Each chamber contains resin media for ion removal, and the distributed arrangement across 30-35 cell pairs provides sufficient purification capacity (achieving 10-16 MOhms·cm water quality) while keeping the resin bed depth in each individual chamber moderate, thus maintaining acceptable pressure drops.
Solution Approach 2:
The invention uses thick cell plates with increased flow cross-section area, allowing the flow path to expand in the lateral dimension. This enables adequate contact time with resin media for high water quality without requiring excessive resin bed depth, thereby controlling pressure drop.
3Productivity
If number of cell pairs is increased to achieve high flow rate, then productivity improves, but device complexity and cost increase
Solution Approach 1:
The apparatus uses a modular design with 30-35 cell pairs that can be assembled in series. Each cell pair is a standardized module containing dilute chambers, concentrate chambers, and ion exchange membranes. This modular segmentation achieves high flow rates (5.0-10.0 m3/hr) while maintaining manageable complexity through repetitive standardized units.
Solution Approach 2:
The invention combines multiple functions into integrated components: the cell plate serves as both structural support and flow distribution element, the frame provides mechanical strength and sealing, and the arrangement of membranes and resin media simultaneously performs ion removal and concentrate collection. This functional integration reduces overall system complexity.
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 new design achieves product flow rates of 5.0 to 10.0 m3/hr with ultra-pure water quality (10 to 16 MOhms·cm) using 30-35 cell pairs, doubling the output of conventional EDI apparatus while maintaining low pressure drops and efficient power usage, and demonstrates flexibility in handling both single and double pass RO permeate waters.
Implementation Method 1
An Electro-Deionization apparatus (EDI) is a device that removes the dissolved impurities of reverse osmosis ('RO') permeate water with the help of resin media, ion exchange membrane and DC current
Implementation Method 2
The arrangement of ion exchange membranes, anion exchange membranes and cation exchange membrane, are very important in an EDI apparatus. They are generally arranged in alternate manner with respect to anode and cathode electrodes
Implementation Method 3
Splitting of H+ and OH− ions happens due to the electric potential generated within the dilute compartment from the H2O molecules which regenerates the corresponding resin ions continuously
Implementation Method 4
The resin media are filled in the chambers/compartments which are formed due the arrangement of anion and cation exchange membranes. This leads to the formation of dilute chambers and concentrate chambers. The dilute chambers are those in which the feed water (RO permeate) gets purified
Data Source
AI summary
We report an electro-deionization (EDI) device having split flow arrangement for the purification of second pass RO permeate water with high flow rate in which the feed water is fed through the center port and is diverted into each section of dilute chamber with equal flow rate, producing two product streams. The EDI device has concentrate chambers adjacent to dilute chambers in two sections of the stack, allowing independent flow through the separate sections. The split flow design reduces resin bed depth requirement for processing of second pass RO permeate water. This results in higher flow rate through the stack, elimination of the pressure drop limitation, and reduction of power consumption per unit volume of water.