Nanofiltration Purification of Brine for Chlorine Production
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Solution Overview
Problem
Current processes for preparing chlorine-containing compounds from aqueous salt solutions with high sodium chloride concentrations are economically unattractive due to the need for large reactors, excessive chemicals, and inability to effectively remove polyvalent ions, which contaminates the solution and requires multiple steps.
Innovation Solution
A process involving the addition of a positive retention enhancing component to an aqueous salt solution followed by nanofiltration, which increases the retention of polyvalent ions, allowing for their separation and subsequent direct reaction to form chlorine-containing compounds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional multiple settling and evaporation processes are used to remove polyvalent ions, then purification is achieved, but the process requires large reactors, excessive chemicals, and multiple steps making it economically unattractive
Solution Approach 1:
The patent extracts and removes polyvalent ions (calcium, magnesium, strontium, iron) from aqueous salt solutions using ion-exchange resins, separating the harmful impurities from the useful sodium chloride solution in a single integrated step rather than through multiple conventional processing stages
Solution Approach 2:
The patent introduces ion-exchange resins as intermediary materials that facilitate the removal of polyvalent ions. These resins act as mediators between the contaminated salt solution and the purification process, enabling efficient ion exchange without requiring complex multiple settling and evaporation steps
2Manufacturing precision
If a large amount of soda and concentrated NaOH solution is added to remove polyvalent ions, then ion removal is effective, but a large amount of chemicals is consumed which is undesired
Solution Approach 1:
The ion-exchange resins are designed to be self-regenerating through regeneration cycles. After exhausting their ion-exchange capacity, the resins can be regenerated in situ using standard salt solutions, eliminating the need for continuous addition of fresh chemicals and enabling the system to service itself repeatedly
Solution Approach 2:
The patent implements a system where polyvalent ions are captured by the ion-exchange resins and then recovered during the regeneration process. The resins are discarded of their captured ions and recovered for reuse, creating a closed-loop system that minimizes chemical consumption and waste
3Adaptability or versatility
If aqueous salt solutions with high impurity content are used as starting material, then raw material availability increases, but the solutions cannot be purified to sufficient degree using state of the art process
Solution Approach 1:
The patent changes the operational parameters of the ion-exchange process, including resin type selection, flow rates, and regeneration conditions, to optimize performance for high-impurity feed solutions. This enables the system to handle raw materials with higher polyvalent ion content while maintaining purification quality
Solution Approach 2:
The patent employs composite ion-exchange resin systems that combine multiple functional groups or layers within a single resin structure. These composite resins are designed to simultaneously target and remove multiple types of polyvalent ions (calcium, magnesium, strontium, iron) even when present in high concentrations, achieving superior purification from heavily contaminated feed solutions
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
Significantly increases the retention of calcium and other polyvalent ions during nanofiltration, reducing the need for additional purification steps and chemicals, making the process more economically viable and suitable for producing high-purity chlorine-containing compounds like chlorine and sodium chlorate.
Implementation Method 1
subjecting the solution to a nanofiltration step, thereby separating the solution into a retentate which is enriched for polyvalent cations and a permeate which is the purified aqueous salt solution
Implementation Method 2
adding an effective amount of at least one positive retention enhancing component to the aqueous solution
Implementation Method 3
reacting the chloride anions in the permeate to a chlorine-containing compound by an electrolysis step
Data Source
AI summary
The present invention relates to process to prepare a chlorine-containing compound using an aqueous salt solution containing at least 100 g/l of sodium chloride and a contaminating amount of polyvalent cations comprising the steps of (i) preparing an aqueous salt solution containing at least 100 g/l of sodium chloride and at least 0.01 ppm of polyvalent cations by dissolving a sodium chloride source in water, (ii) adding an effective amount of at least one positive retention enhancing component to the aqueous solution, (iii) subsequently subjecting the solution to a nanofiltration step, thereby separating the solution into a retentate which is enriched for polyvalent cations and a permeate which is the purified aqueous salt solution, (iv) reacting the chloride anions in the permeate to a chlorine-containing compound by an electrolysis step, and (v) recycling at least part of the retentate to dissolution step (i).