Electrodialysis Osmotic Flow Control via Concentrate Pressurization
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current electrodialysis systems face inefficiencies due to osmotic and electro-osmotic water flow from diluate to concentrate compartments, reducing the volume of purified water output and increasing energy consumption, with existing methods not effectively addressing the need to pressurize concentrate compartments to improve efficiency.
Innovation Solution
The system pressurizes the concentrate compartments relative to the diluate compartments, using specific spacers to maintain constant volume and prevent osmotic and electro-osmotic flow, combined with high electric capacitance electrodes and controlled valve operations to minimize water transfer and optimize ion movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional electrodialysis systems operate without pressurizing concentrate compartments, then the system structure is simple and easy to operate, but osmotic and electro-osmotic water flow from diluate to concentrate compartments reduces current efficiency and purified water output
Solution Approach 1:
The system pre-pressurizes the concentrate compartments before the electrodialysis process begins, establishing a pressure differential that prevents osmotic and electro-osmotic water flow from occurring. This preliminary action eliminates water loss to concentrate compartments throughout operation, improving current efficiency without requiring complex control mechanisms during the process
Solution Approach 2:
The invention extracts the water flow control function from the main electrodialysis operation by independently pressurizing concentrate compartments. This separation allows the pressure control system to operate autonomously, preventing harmful water transfer without interfering with the ion removal process, thus improving productivity while maintaining manageable system complexity
2Productivity
If higher voltage is applied to increase ion removal rate, then productivity improves, but energy consumption increases
Solution Approach 1:
The invention converts the harmful osmotic water flow into a beneficial pressure source. By allowing osmotic pressure to build up in the concentrate compartments and then utilizing this pressure to prevent further water loss, the system transforms what was previously a productivity-reducing effect into an energy-saving mechanism that maintains high current efficiency without requiring additional energy input
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 approach enhances the current efficiency of electrodialysis desalination by reducing osmotic and electro-osmotic water flow, allowing for operation at lower voltages and reduced energy consumption per unit volume of product, thereby improving the overall production rate and maintaining optimal electrolyte conductivity in electrode compartments.
Implementation Method 1
the tendency of water to enter the concentrate compartments from adjacent diluate compartments leads to pressure buildup, resulting in prevention of osmotic and electro-osmotic flow of diluted water into them
Implementation Method 2
prevention of osmotic and electro-osmotic flow of diluted water into them
Implementation Method 3
The electrodes used can also be of the capacitive type, which are capable of absorbing large amount of ions and capacitively establishing the electric field
Implementation Method 4
A typical electrodialysis cell consists of a series of diluate compartments and a concentrate compartments sequentially formed between anion exchange membranes and cation exchange membranes
Implementation Method 5
Ions are depleted from the diluate compartments and accumulated in the concentrate compartments, as is known it the art
Data Source
Figure 1
Figure 2
Figure 3
AI summary
An electrodialysis process and apparatus is presented for improving the current efficiency of salty water desalination. The process includes reducing the osmotic and the electro-osmotic flow of water from diluate compartments to concentrate compartments, and between electrode compartments and adjacent compartments, by confinement and hydraulic isolation of their contents in constant volume compartments, so that the tendency of waters entering from diluate compartments to concentrate compartments leads to pressure buildup in the concentrate compartments, reducing the transfer of product desalinated water to the concentrate waste.