Electrolyzer Feed Stream Ion Separation
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Solution Overview
Problem
Current electrochlorination systems face inefficiencies in generating sodium hypochlorite from seawater due to precipitate formation and limited concentration of hypochlorite production, primarily caused by divalent ions like Mg2+ and Ca2+, which impair cell performance and reduce product strength.
Innovation Solution
The system employs nanofiltration and electrodialysis units to adjust the feed stream composition by reducing divalent ion concentrations and increasing monovalent ion concentrations, thereby preventing precipitate formation and enhancing hypochlorite production. This involves separating seawater into retentate and permeate using nanofiltration, and using monovalent selective membranes in electrodialysis to transport monovalent ions, ensuring optimal electrolyzer feed stream conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If seawater is directly fed to the electrochlorination cell, then the system operates continuously without pre-treatment, but precipitate formation occurs due to divalent ions reducing cell performance and product strength
Solution Approach 1:
The patent applies preliminary action by implementing nanofiltration and electrodialysis units before the electrochlorination cell to pre-treat the feed stream. These units remove divalent ions (Ca2+, Mg2+) and adjust the ion composition in advance, preventing precipitate formation during electrolysis and enabling higher hypochlorite production concentrations without performance degradation
2Reliability
If divalent ion concentrations are reduced through nanofiltration and electrodialysis, then precipitate formation is prevented and hypochlorite concentration increases, but the system complexity and equipment requirements increase
Solution Approach 1:
The patent segments the pre-treatment process into two distinct functional units: nanofiltration for removing divalent ions and electrodialysis for adjusting monovalent ion concentrations. This segmentation allows each unit to perform its specific function efficiently, with nanofiltration membranes targeting Ca2+ and Mg2+ removal while electrodialysis membranes regulate Na+ and Cl- levels, together ensuring stable cell performance without excessive overall 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
This approach significantly increases the concentration of hypochlorite produced, mitigates precipitate formation, and improves the overall performance of the electrochlorination system by maintaining optimal pH and ion ratios, achieving higher product strengths and operational efficiency.
Implementation Method 1
separating seawater into retentate and permeate using nanofiltration
Implementation Method 2
using monovalent selective membranes in electrodialysis to transport monovalent ions
Implementation Method 3
Electrochemical devices used to produce a product solution from a feed stream by chemical reactions at electrodes
Implementation Method 4
Reaction at anode: 2Cl−→Cl2+2e−
Data Source
AI summary
An electrochlorination system includes an electrolyzer fluidically connectable between a source of feed fluid and a product fluid outlet, and a sub-system configured to one of increase a pH of the feed fluid, or increase a ratio of monovalent to divalent ions in the feed fluid, upstream of the electrolyzer.