Electrodialysis Electrodeionization Desalination System
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Solution Overview
Problem
The high power consumption of existing desalination technologies limits their widespread acceptance for producing potable water, especially when treating seawater, as they are inefficient in reducing energy usage and are hindered by issues like concentration polarization and elevated electrical resistance.
Innovation Solution
A desalination system comprising an electrodialysis (ED) device followed by an electrodeionization (EDI) device, with a controller to optimize the transition point between the two based on power consumption and salt removal, and the use of conductivity sensors to apply varying voltages and adjust fluid velocities to inhibit concentration polarization, thereby reducing energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional desalination technologies are used, then salt removal is achieved, but power consumption is excessively high
Solution Approach 1:
The desalination process is divided into multiple stages with different operating modes. The first stage uses electrodialysis (ED) for initial salt removal from seawater, while the second stage uses electrodeionization (EDI) for final polishing. This segmentation allows each stage to operate in its optimal efficiency range, reducing overall energy consumption while maintaining reliable salt removal.
Solution Approach 2:
The system dynamically adjusts operating parameters including voltage, current density, and flow rates based on real-time conductivity measurements. The controller modifies these parameters to optimize energy efficiency at different concentration levels, preventing excessive power consumption while ensuring complete desalination.
2Productivity
If high voltage is applied to increase salt removal rate, then productivity improves, but concentration polarization increases and electrical resistance elevates
Solution Approach 1:
The system employs dynamic control of voltage and flow rate based on real-time conductivity feedback. As salt concentration decreases during the desalination process, the controller automatically adjusts operating parameters to maintain optimal current density and prevent concentration polarization, ensuring high productivity without harmful side effects.
Solution Approach 2:
Conductivity sensors continuously monitor the salt concentration in the product stream and provide feedback to the controller. This feedback loop enables real-time adjustment of voltage and flow rate to maintain optimal operating conditions, preventing concentration polarization and electrical resistance elevation while sustaining high salt removal rates.
3Device complexity
If single-stage electrodialysis is used, then device complexity is reduced, but energy efficiency deteriorates due to concentration polarization
Solution Approach 1:
The system is segmented into two distinct devices: an electrodialysis (ED) unit for bulk salt removal and an electrodeionization (EDI) unit for final polishing. This segmentation allows the ED stage to handle high salt concentrations efficiently while the EDI stage operates at low concentrations where it is most efficient, optimizing overall energy efficiency without excessive complexity.
Solution Approach 2:
The system changes operating parameters between stages. The ED stage operates at higher voltages and flow rates suitable for bulk desalination, while the EDI stage operates at lower voltages and optimized flow rates for final polishing. This parameter optimization in each stage improves energy efficiency while maintaining manageable 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 system achieves efficient desalination of seawater with a power consumption of 1.5 kWh/m3 or less, improving current efficiency and reducing energy costs while minimizing concentration polarization and electrical resistance.
Implementation Method 1
The ED device receives a feed stream and produces a diluted stream and a concentrated stream
Implementation Method 2
an electrodialysis (ED) device, an electrodeionization (EDI) device
Implementation Method 3
an electrodeionization (EDI) device fluidly connected downstream of the ED device
Implementation Method 4
electrodeionization (EDI) device... salt removal
Implementation Method 5
at least one conductivity sensor associated with the electrical purification system
Implementation Method 6
apply a first voltage to the first ED stage and to apply a second voltage... to the second ED stage
Implementation Method 7
inhibiting concentration polarization by passing a process stream through a dilute compartment in the second ED stage at an increased velocity
Implementation Method 8
passing a process stream through a dilute compartment... at an increased velocity
Data Source
AI summary
Systems and methods for the desalination of seawater or brackish water for the purpose of obtaining potable water. Systems may include a combination of electrodialysis and electrodeionization modules. The system configuration and process controls may achieve low energy consumption and stable operation.