Nanofiltration Salt Purification Process
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Solution Overview
Problem
Current processes for preparing salt from aqueous salt solutions with high sodium chloride concentrations struggle to effectively remove polyvalent ions and organic contaminants, leading to scaling issues and contamination in the final product, especially when using surface water, which disrupts flocculation and precipitation steps and results in high Total Organic Carbon levels, making it unsuitable for electrolysis.
Innovation Solution
A process involving the addition of a positive retention enhancing component to the aqueous salt solution followed by nanofiltration, which significantly increases the retention of polyvalent ions like calcium, allowing for the production of purified salt with reduced sulphate content and lower organic contamination, enabling direct concentration to produce high-quality salt.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple flocculation and precipitation steps are used to remove polyvalent ions, then purification effectiveness is improved, but process complexity and chemical usage increase
Solution Approach 1:
The patent extracts and removes the need for multiple complex flocculation and precipitation steps by implementing a single nanofiltration step that directly removes polyvalent ions (Ca2+, Mg2+, Sr2+) and sulphate ions from the brine solution, achieving effective purification with simplified process equipment and reduced chemical consumption
Solution Approach 2:
The patent replaces the mechanical-chemical system of multiple flocculation and precipitation steps with a membrane-based nanofiltration system that uses pressure-driven separation to achieve ion removal, thereby reducing process complexity and chemical usage while maintaining purification effectiveness
2Manufacturing precision
If multiple flocculation and precipitation steps are used to remove polyvalent ions, then purification effectiveness is improved, but chemical consumption increases
Solution Approach 1:
The patent eliminates the need for large amounts of chemicals (soda and concentrated NaOH solution) by using nanofiltration membrane technology that physically separates polyvalent ions and sulphate ions from the brine through size-exclusion and charge-based mechanisms, achieving effective purification with minimal chemical input
3Quantity of substance
If surface water is used as water supply, then cost savings are achieved, but organic contamination increases
Solution Approach 1:
The patent applies nanofiltration as a preliminary treatment step before evaporation to remove organic contaminants (fulvic acids, humic acids, microorganisms, cell debris) and polyvalent ions from brine prepared with surface water, preventing these contaminants from interfering with subsequent processing and ensuring product quality while maintaining the cost advantage of using surface water
4Quantity of substance
If organic materials are present in water supply, then cost savings are achieved, but flocculation and precipitation steps are disrupted
Solution Approach 1:
The patent replaces the unreliable flocculation and precipitation process (which is disrupted by organic materials) with a robust nanofiltration membrane system that reliably removes polyvalent ions and organic contaminants through physical separation mechanisms that are not affected by the presence of organics, ensuring consistent purification performance while maintaining cost savings from surface water usage
5Stability of the object's composition
If conventional purification process is used, then scaling is prevented, but heat transfer capacity decreases
Solution Approach 1:
The patent performs preliminary removal of polyvalent ions (Ca2+, Mg2+, Sr2+) and sulphate ions through nanofiltration before the evaporation process, preventing the formation of scale deposits on heat transfer surfaces during evaporation, thereby maintaining high heat transfer capacity and energy efficiency throughout the salt production process
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 process achieves a substantial increase in polyvalent ion retention during nanofiltration, reducing sulphate content and organic contaminants, resulting in salt of desired quality that can be directly concentrated, improving energy efficiency and reducing purge flow, while being economically attractive by minimizing the need for large reactors and chemical usage.
Implementation Method 1
subjecting the solution to a nanofiltration step, thereby separating the solution into a retentate which is enriched for the 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 salt solution
Implementation Method 3
concentrating the permeate to produce salt
Data Source
AI summary
The present invention relates to a process to prepare salt comprising the following steps: (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 industrial water, (ii) adding an effective amount of at least one positive retention enhancing component to the aqueous salt solution, (iii) subsequently subjecting the solution to a nanofiltration step, thereby separating the solution into a retentate which is enriched for the polyvalent cations and a permeate which is the purified aqueous salt solution, and (iv) concentrating the permeate to produce salt.