Halocarbon Polymer Fiber Diaphragm Anolyte Flow Control
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Solution Overview
Problem
Diaphragm perforations in electrolytic cells lead to increased flow of anolyte into the catholyte compartment, resulting in lower alkali metal hydroxide concentrations and higher hypochlorite ion concentrations, increasing costs and process complexity in chlor-alkali electrolytic cells.
Innovation Solution
Introducing halocarbon polymer short fibers into the anolyte compartment to reduce the flow of anolyte through the diaphragm, thereby increasing the concentration of alkali metal hydroxide and decreasing the concentration of hypochlorite ion in the catholyte liquor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the diaphragm develops perforations, then the flow resistance decreases, but the flow of anolyte into the catholyte compartment increases excessively
Solution Approach 1:
The patent introduces a dopant material that acts as an intermediary substance within the diaphragm structure. This dopant modifies the diaphragm's properties to reduce anolyte flow through perforations without requiring complete diaphragm replacement or complex mechanical repairs, thereby addressing the reliability issue while controlling the flow rate.
Solution Approach 2:
The patent changes the chemical and physical parameters of the diaphragm by incorporating dopant materials. This modifies the diaphragm's pore structure, surface properties, or resistance characteristics, allowing it to maintain appropriate flow resistance even when perforations are present, thus balancing reliability and flow control.
2Quantity of substance
If the flow of anolyte through the diaphragm is too high, then the concentration of alkali metal hydroxide decreases, but the concentration of hypochlorite ion increases
Solution Approach 1:
The patent employs a feedback mechanism where the dopant material responds to the presence of perforations and the resulting flow conditions. By monitoring or reacting to changes in flow rate or concentration gradients, the dopant dynamically adjusts the diaphragm's resistance properties to maintain optimal concentration levels and minimize harmful byproduct formation.
Solution Approach 2:
The patent uses composite materials by combining the base diaphragm material with dopant substances. This composite structure provides both the structural integrity needed for separation and the functional properties to regulate flow and concentration, simultaneously addressing product concentration and harmful byproduct issues.
3Manufacturing precision
If process streams are recycled to work-up and purify the product, then product purity improves, but process complexity and cost increase
Solution Approach 1:
The patent applies preliminary action by incorporating the dopant material into the diaphragm before operation begins. This pre-treatment ensures that the diaphragm is already optimized for controlling flow and maintaining concentration gradients, preventing the formation of excessive harmful byproducts from the start and reducing the need for downstream purification operations.
Solution Approach 2:
The patent converts the harmful effect of diaphragm perforations into a beneficial outcome. Instead of allowing perforations to cause excessive flow and poor concentration control, the dopant material transforms this defect into an opportunity to dynamically adjust and optimize flow resistance, thereby maintaining product quality without requiring complex additional processing steps.
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 method effectively reduces the flow of anolyte through the diaphragm, restoring desired concentrations of alkali metal hydroxide and hypochlorite ion, thereby improving operational efficiency and reducing process costs by maintaining optimal product concentrations.
Implementation Method 1
introducing particulate material comprising halocarbon polymer short fiber into the anolyte compartment in amounts sufficient to lower the flow of liquid anolyte through the diaphragm into the catholyte compartment
Implementation Method 2
The microporous diaphragm is sufficiently porous to allow the hydrodynamic flow of brine through it, while at the same time inhibiting the back migration of hydroxyl ions
Implementation Method 3
The microporous diaphragm is sufficiently porous to allow the hydrodynamic flow of brine through it, while at the same time inhibiting the back migration of hydroxyl ions (during electrolysis) from the catholyte compartment into the anolyte compartment
Implementation Method 4
When direct current is applied to the cell, halogen gas is evolved at the anode, hydrogen gas is evolved at the cathode, and an aqueous alkali metal hydroxide solution is formed in the catholyte compartment
Data Source
AI summary
Described is a method for improving the operation of an electrolytic cell having an anolyte compartment, a catholyte compartment and a synthetic diaphragm separating the compartments, wherein liquid anolyte is introduced into the anolyte compartment and flows through the diaphragm into the catholyte compartment, which method involves introducing particulate material comprising halocarbon polymer short fiber, e.g., fluorocarbon polymer short fiber, into the anolyte compartment in amounts sufficient to lower the flow of liquid anolyte through the diaphragm into the catholyte compartment. In the case of an electrolytic cell wherein aqueous alkali metal chloride, e.g., sodium chloride, anolyte is introduced continuously into the anolyte compartment, thereby to produce a catholyte liquor containing alkali metal hydroxide and hypochlorite ion, the foregoing method is useful for decreasing the concentration of hypochlorite ion in the catholyte liquor and oftentimes increasing the concentration of alkali metal hydroxide in the catholyte liquor. Also describes adding at least one member chosen from halocarbon polymer microfibril, halocarbon polymer fiber, clay mineral, oxides and/or hydroxides of alkaline earth metals, and zirconium oxide/hydroxide in conjunction with the halocarbon polymer short fiber to the anolyte compartment, e.g., while the cell is operating.