Electrodeionization Apparatus with Barrier Cells for Scale Inhibition
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Solution Overview
Problem
Electrically-motivated separation apparatuses, such as electrodialysis and electrodeionization devices, face challenges in reducing scale formation, particularly when treating water with high hardness or silica content, which limits their effectiveness and increases operational costs due to the need for additional pretreatment processes.
Innovation Solution
The electrodeionization apparatus incorporates a depleting compartment and concentrating compartment configuration with layered media and mixed anion and cation exchange resins, along with barrier cells and an acidic solution, to inhibit scale formation by trapping precipitable species and controlling pH, thereby reducing the likelihood of scale formation and eliminating the need for pre-treatment processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electrodeionization apparatus is used to treat water with high hardness or silica content, then scale formation occurs, but additional pretreatment processes are required which increases device complexity and operating costs
Solution Approach 1:
The electrodeionization apparatus is divided into multiple compartments including depleting compartments, concentrating compartments, barrier cells, and electrode compartments. This segmentation allows different regions to perform specialized functions: depleting compartments remove ions, concentrating compartments collect precipitable species, and barrier cells control pH gradients, collectively preventing scale formation without external pretreatment
Solution Approach 2:
Barrier cells act as intermediary compartments between depleting and electrode compartments. These barrier cells contain acidic solutions that mediate pH control, preventing the formation of scale by maintaining appropriate pH conditions in adjacent compartments while allowing ion transport
2Quantity of substance
If electrodeionization apparatus treats water with high hardness content, then scale formation increases, but treatment effectiveness decreases
Solution Approach 1:
The apparatus extracts and concentrates precipitable species (such as calcium, magnesium, and silica) from the feed water into dedicated concentrating compartments. By removing these scale-forming substances from the main water stream and concentrating them in separate compartments, the system maintains high treatment capacity while preventing scale formation in the product water
Solution Approach 2:
Different compartments are designed with locally optimized properties: depleting compartments use ion-exchange media for ion removal, concentrating compartments are designed to accommodate precipitate accumulation, and barrier cells maintain specific pH conditions. This local optimization allows each region to handle specific aspects of hardness removal while preventing overall scale formation
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 configuration effectively treats water with high hardness and silica content without additional pretreatment, reducing capital and operating costs while improving treatment reliability and capacity, and maintains water quality comparable to systems using two-pass reverse osmosis.
Implementation Method 1
a first depleting compartment disposed between the anode compartment and the cathode compartment, a concentrating compartment in ionic communication with the depleting compartment
Implementation Method 2
electrically-motivated separation apparatus including, but not limited to, electrodialysis as well as electrodeionization devices
Data Source
AI summary
An electrochemical treating device having low scale potential is disclosed. The device has a variety of configurations directed to the layering of the anionic exchange and cationic exchange. The treatment device can also comprise unevenly sized ion exchange resin beads and/or have at least one compartment that provides a dominating resistance that results in a uniform current distribution throughout the apparatus.