Purifying Concentrated KOH Electrolyte via Precipitation Additives
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Solution Overview
Problem
Alkaline water electrolysis (AWE) systems face challenges in maintaining low levels of critical impurities such as dissolved transition metals, inorganic anions, and organic compounds in concentrated aqueous potassium hydroxide (KOH) solutions, which can lead to increased electrolyzer cell resistance and require frequent electrode refurbishment and electrolyte replacement.
Innovation Solution
The process involves adding precipitation additives like water-soluble salts of alkaline earth metals, nickel (II) hydroxide, and hydroxides or oxides of alkaline earth metals with high surface areas to the concentrated aqueous hydroxide solutions. These additives form insoluble compounds with the target impurities, which can then be removed by settling and filtration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If high purity potassium hydroxide and ultra-high purity water are used to prepare electrolyte, then initial electrolyte purity is improved, but impurities accumulate over time during operation causing increased cell resistance
Solution Approach 1:
The patent applies preliminary action by adding precipitation additives to the electrolyte before operation begins. These additives proactively bind to potential impurities (transition metals, alkaline earth metals, carbonates) to form insoluble precipitates that can be filtered out, preventing impurity accumulation during operation rather than dealing with it after it occurs.
Solution Approach 2:
The patent changes the chemical parameters of the electrolyte by introducing precipitation additives that alter the solubility characteristics of impurities. By adjusting the chemical environment through these additives, impurities that would normally remain dissolved are transformed into insoluble compounds that can be easily removed, thereby maintaining long-term electrolyte quality.
2Reliability
If frequent electrolyte replacement and electrode refurbishment are performed, then cell resistance is reduced, but operational continuity and productivity decrease
Solution Approach 1:
The patent enables continuity of useful action by implementing a purification system that operates continuously during electrolysis. The precipitation process occurs in-situ without requiring shutdown of the electrolyzer, allowing the system to maintain continuous operation while progressively removing impurities and maintaining low cell resistance over extended periods.
Solution Approach 2:
The patent applies self-service by enabling the electrolyte to purify itself through the addition of precipitation additives. The system uses its own operational conditions (alkaline environment, existing impurities) to drive the precipitation reaction, eliminating the need for external intervention or system shutdown for maintenance.
3Manufacturing precision
If precipitation additives are added to remove impurities, then electrolyte purity is improved, but additional chemicals and processing steps are required
Solution Approach 1:
The patent applies the extraction principle by selectively removing specific impurity classes (transition metals, alkaline earth metals, carbonates) from the electrolyte through precipitation. Each additive targets specific impurity types, allowing selective extraction of harmful substances while leaving the beneficial KOH and H2O components unchanged.
Solution Approach 2:
The patent uses precipitation additives as intermediary substances that facilitate impurity removal. These additives act as mediators by binding to target impurities to form insoluble compounds, which then can be easily separated through filtration or settling. The intermediaries enable the removal process without requiring direct manipulation of the impurities themselves.
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 process effectively reduces the levels of dissolved iron, organic compounds, carbonate anions, and sulfate anions in the KOH solutions to acceptable levels, thereby extending the life of electrolyzer cells and reducing material and logistical costs associated with frequent replacements.
Implementation Method 1
adding precipitation additives like water-soluble salts of alkaline earth metals, nickel (II) hydroxide, and hydroxides or oxides of alkaline earth metals with high surface areas to the concentrated aqueous hydroxide solutions. These additives form insoluble compounds with the target impurities, which can then be removed by settling and filtration.
Implementation Method 2
These additives form insoluble compounds with the target impurities, which can then be removed by settling and filtration.
Implementation Method 3
adding precipitation additives like water-soluble salts of alkaline earth metals, nickel (II) hydroxide, and hydroxides or oxides of alkaline earth metals with high surface areas to the concentrated aqueous hydroxide solutions
Data Source
AI summary
Disclosed are novel processes, based on precipitation, settling, and filtration for the removal of critical impurities selected from dissolved transition metals, inorganic anions and dissolved organic compounds, from highly concentrated hydroxide solutions used as electrolytes in alkaline water electrolysis (AEW) to produce hydrogen. The processes comprise adding to the solutions at least one precipitation additive selected from water-soluble salts of alkaline earth metals; nickel (II) hydroxide; and hydroxides or oxides of alkaline earth metals, provided that the surface area of the hydroxides/oxides is more than 5 m2/g, to form at least one inorganic compound (or complex) as a precipitate which is removed from the solution.