Side Stream Subsystem for Impurity Removal in Electrolysis
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Solution Overview
Problem
In chlor-alkali and chlorate electrolysis systems, the conventional treatment processes are ineffective in removing silicon and aluminum species from brine solutions, leading to their accumulation in recycling circuits, which increases effluent and capital costs, and existing methods for removal in main lines are not economical or suitable for side streams.
Innovation Solution
A side stream subsystem is introduced in the electrolysis system, which includes the addition of alkali metal hydroxide and magnesium chloride to form complexes with silicon and aluminum species, allowing for their precipitation and filtration, reducing the need for extensive filtration systems and raw material consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional secondary treatment process using cationic chelating resins is used, then brine purification is achieved, but aluminum and silica impurities cannot be effectively removed
Solution Approach 1:
The patent changes the chemical parameters of the brine by adding magnesium ions and adjusting pH to alkaline conditions. This transforms the brine chemistry to enable precipitation of aluminum and silica impurities as magnesium-containing compounds, which can then be effectively filtered. The parameter change from acidic/neutral to alkaline conditions is the key to enabling impurity removal.
Solution Approach 2:
Magnesium ions serve as an intermediary substance that mediates the removal of aluminum and silica impurities. The magnesium ions form insoluble complex compounds with aluminum and silica under alkaline conditions, acting as a bridge that enables the precipitation and subsequent filtration of these impurities from the brine stream.
2Quantity of substance
If continuous purging of brine from the recirculation line is used to remove impurities, then aluminum and silicon species can be removed, but salt loss occurs which is not economical
Solution Approach 1:
Instead of removing brine through purging, the patent changes the chemical parameters by adding magnesium chloride and adjusting pH. This enables in-situ precipitation of impurities within the recirculation system, allowing continuous operation without salt loss while still achieving effective impurity removal through chemical transformation rather than physical removal.
Solution Approach 2:
The patent converts the harmful accumulation of aluminum and silica impurities into a beneficial process by inducing controlled precipitation. The impurities, which would otherwise accumulate and cause problems, are transformed into removable precipitates through chemical reaction with magnesium ions, turning a harmful accumulation into a controllable and reversible process.
3Reliability
If treatment of the full flow of brine in the recirculation line is used, then impurities can be removed, but raw material and capital costs increase
Solution Approach 1:
The patent extracts only a side stream portion of the brine flow for treatment rather than treating the entire recirculation flow. This side stream approach allows impurity removal in a controlled, smaller-volume system, reducing the scale and complexity of required filtration equipment while maintaining effective impurity removal through the chemical precipitation process.
Solution Approach 2:
The brine treatment system is segmented into a main recirculation line and a separate side stream treatment line. The side stream is diverted for chemical treatment with magnesium chloride and pH adjustment, then the treated portion is returned to the system. This segmentation allows independent optimization of treatment conditions without affecting the entire brine circulation system.
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 effectively reduces raw material and capital costs by allowing a substantial portion of the brine to be treated in a side stream, achieving efficient removal of impurities with lower operating and capital expenses, and minimizing effluent discharge.
Implementation Method 1
the addition of alkali metal hydroxide and magnesium chloride to form complexes with silicon and aluminum species
Implementation Method 2
allowing for their precipitation and filtration
Implementation Method 3
allowing for their precipitation and filtration
Data Source
AI summary
A side stream subsystem can be used to remove impurity species from the recirculating alkali metal chloride solution in certain electrolysis systems. Silicon and/or aluminum species can be removed via precipitation after introducing an alkali metal hydroxide and magnesium chloride in a side stream line in the subsystem. The invention can allow for a substantial reduction in raw material and capital costs.