Electrolytic Cell Diaphragm for Chlorine Resistance

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Solution Overview

Problem

Existing electrolytic cells for producing mildly acidic solutions with active chlorine suffer from high salinity in the anodic product, leading to durability issues with anionic membranes, which are not resistant to chlorine-containing acidic solutions for extended periods, making them unsuitable for industrial applications.

Innovation Solution

A three-compartment electrolytic cell design using a cation-exchange membrane for the cathodic compartment and a diaphragm formed by a network of organic polymer fibers mechanically bound to ceramic particles for the anodic compartment, with the diaphragm arranged in layers with an anion-exchange membrane, and incorporating a decomposition catalyst in the intermediate compartment to reduce free chlorine levels, enhancing membrane durability and selectivity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If an anion-exchange membrane is used as the anodic separator, then chloride ion selectivity is improved, but membrane durability deteriorates due to chlorine attack

Engineering Contradiction:
Improvechloride ion selectivityVSAvoidmembrane durability
Core Design Contradiction:
Measurement precisionVSReliability

Solution Approach 1:

The patent applies a composite structure consisting of an anion-exchange membrane combined with a diaphragm made of chemically resistant material (such as PTFE or other fluorinated polymers). This composite separator maintains the chloride ion selectivity of the anion-exchange membrane while the chemically resistant diaphragm layer protects against chlorine attack, thereby simultaneously achieving high selectivity and durability.

Inventive Principle:
Principle #40Composite materials

Solution Approach 2:

The patent introduces a protective diaphragm layer beforehand to cushion or shield the anion-exchange membrane from direct contact with chlorine-containing acidic solutions. This preventive measure allows the membrane to maintain its selective function without being exposed to the harmful oxidizing environment that would otherwise cause rapid degradation.

Inventive Principle:
Principle #11Beforehand cushioning (Prior cushioning)

2Manufacturing precision

If a three-compartment cell is used, then product quality is improved, but device complexity increases

Engineering Contradiction:
Improveproduct qualityVSAvoidcell structure
Core Design Contradiction:
Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent divides the electrolytic cell into three separate compartments (anodic, intermediate, and cathodic chambers) separated by selective membranes. This segmentation allows independent control and optimization of each compartment's chemical environment, enabling production of high-quality oxidizing solution with controlled salinity while maintaining clear separation of reaction zones.

Inventive Principle:
Principle #1Segmentation

3Productivity

If conventional membranes are used, then initial performance is good, but maintenance costs increase due to frequent replacement

Engineering Contradiction:
Improveinitial performanceVSAvoidmaintenance time
Core Design Contradiction:
ProductivityVSLoss of time

Solution Approach 1:

The patent introduces a protective diaphragm layer beforehand to cushion or shield the anion-exchange membrane from direct contact with chlorine-containing acidic solutions. This preventive measure allows the membrane to maintain its selective function without being exposed to the harmful oxidizing environment that would otherwise cause rapid degradation.

Inventive Principle:
Principle #11Beforehand cushioning (Prior cushioning)

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 solution effectively produces a mildly acidic oxidizing solution with high chemical resistance and selectivity, maintaining efficiency and reducing membrane degradation, enabling continuous production of active chlorine solutions with low salinity and extended membrane lifespan.

Implementation Method 1

the cathodic separator, which separates the cathodic compartment from the intermediate compartment, comprises a cation-exchange membrane

Methodology Applied
Scientific EffectIon Exchange: Ion Exchange

Implementation Method 2

the anodic separator, which separates the anodic compartment from the intermediate compartment, comprises a diaphragm formed by a network of fibres of organic polymer mechanically bound to particles of ceramic material... arranged in one or more layers in intimate contact with an anion-exchange membrane

Methodology Applied
Scientific EffectIon Exchange: Ion Exchange

Implementation Method 3

where chlorine is generated

Methodology Applied
Scientific EffectElectrolysis: Electrolysis

Implementation Method 4

incorporating a decomposition catalyst in the intermediate compartment to reduce free chlorine levels

Methodology Applied
Scientific EffectCatalysis: Catalysis

Data Source

PatentEP3046879B1Electrolytic cell for the production of oxidising solutions
Publication Date: 2020.06.17 INDUSTRIE DE NORA SPA
  • EP3046879B1 patent drawingFigure 1

AI summary

The invention relates to a three-compartment electrolytic cell for production of oxidising disinfectant solutions. The intermediate compartment (300) of the cell is separated from the anodic compartment (200) by a fibrous diaphragm (321) in intimate contact with an anion-exchange membrane (320). The diaphragm (321) is formed by a network of organic polymer fibres mechanically bound to ceramic particles. The cathodic compartment (400) is separated from the intermediate compartment (300) by a cation-exchange membrane (340). Within intermediate compartment (300) a saturated solution of sodium chloride (510) is recycled. Inside tank (500) a decomposition catalyst is contained.