Chlorine Purification via Stream Segmentation
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Solution Overview
Problem
Conventional chlor-alkali processes produce chlorine gas contaminated with bromine, which is a health hazard and costly to purify, especially in water treatment and organic compound production, due to the energy-intensive and expensive methods currently employed.
Innovation Solution
A method involving the separate handling of chlorine produced during electrolysis and from depleted brine in the primary dechlorination step, with optional secondary dechlorination and further purification steps, including pH adjustment and recycling, to achieve a low bromine content chlorine product.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional chlor-alkali processes are used to produce chlorine from brine electrolysis, then chlorine gas is produced efficiently, but the chlorine is contaminated with bromine which is a health hazard and requires costly purification
Solution Approach 1:
The process segments chlorine production into two separate streams: (1) chlorine from direct electrolysis of brine, and (2) chlorine from acidification of depleted brine. By keeping these streams separate and not combining them, the patent prevents bromine contamination from the depleted brine stream from mixing with the pure electrolysis chlorine stream, thus maintaining high chlorine purity while preserving production efficiency.
2Manufacturing precision
If distillation or other purification methods are used to remove bromine from chlorine, then chlorine purity is improved, but the process becomes energy intensive and costly
Solution Approach 1:
The patent applies preliminary action by separating the chlorine streams at the source before bromine contamination can occur. Instead of purifying contaminated chlorine through energy-intensive distillation, the process prevents contamination by directing depleted brine to acidification for separate chlorine generation, thereby producing high-purity chlorine directly from electrolysis without requiring subsequent purification energy.
3Object-affected harmful factors
If alkali metal bromide is removed from brine before electrolysis, then bromine contamination in chlorine is reduced, but the process becomes more complex and costly
Solution Approach 1:
The patent extracts the bromine-containing depleted brine stream from the main electrolysis process and directs it to a separate acidification pathway. This extraction prevents bromine from entering the chlorine production stream without requiring complex pre-electrolysis brine purification systems, as the separation occurs naturally after electrolysis when the brine is depleted.
4Object-affected harmful factors
If oxidation of bromine species in brine to bromate is performed, then chlorine with low bromine content is produced, but the process becomes costly and complex
Solution Approach 1:
The patent converts the harmful effect of bromine contamination into a benefit by using the acidification of depleted brine (which contains bromine) to generate a separate chlorine stream. This contaminated chlorine can be used for applications where purity is less critical, while the pure electrolysis chlorine stream remains available for high-purity applications, thereby eliminating the need for costly oxidation processes.
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 reduces bromine content in chlorine gas, achieving over 60% improvement in purity by separating and purifying the chlorine streams, and allows for the utilization of contaminated chlorine in less demanding applications, while being more cost-effective and energy-efficient.
Implementation Method 1
separating gaseous chlorine from the electrolyte (anolyte in the case of the membrane process)
Implementation Method 2
electrolyzing brine to produce gaseous chlorine, alkali metal hydroxide and hydrogen
Data Source
AI summary
Chlorine with a low bromine content is produced by electrolyzing brine to produce gaseous chlorine, alkali metal hydroxide and hydrogen, separating the gaseous chlorine from the electrolyte (anolyte in the case of the membrane process), directing electrolyte (anolyte in the case of the membrane process) to a primary dechlorination step using hydrochloric acid to remove gaseous chlorine therefrom, optionally directing depleted electrolyte (anolyte in the case of the membrane process) from the primary dechlorination step to a secondary dechlorination step using a reducing agent for chlorine and oxychlorine species, and recycling dechlorinated depleted electrolyte (anolyte in the case of the membrane process) to salt dissolvers to prepare brine for electrolysis. At least part of the gaseous chlorine generated in the primary dechlorination step is not combined with gaseous chlorine generated in the electrolysis step.