Continuous Sodium Hypochlorite Bleach Production with Salt Removal
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Solution Overview
Problem
Existing continuous processes for manufacturing sodium hypochlorite bleach often result in products with high concentrations of sodium chloride and sodium chlorate, which are not efficiently removed, limiting the product's strength and stability.
Innovation Solution
A continuous process in a crystallizer tank without a skirt baffle, where fresh caustic and bleach are introduced above the bottom zone, and a high recycle rate through a heat exchanger is used to control temperature and promote crystal formation, allowing for the production of higher-strength, lower-salt bleach by continuously removing salt crystals and using a two-stage centrifuge for further processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a continuous process is used for manufacturing sodium hypochlorite bleach, then production efficiency and economy are improved, but the product contains high concentrations of sodium chloride and sodium chlorate that are not efficiently removed
Solution Approach 1:
The invention extracts and removes salt crystals from the continuous bleach manufacturing process by introducing the reaction mixture into a centrifuge that separates and removes solid salt crystals, allowing the liquid bleach to be decanted with significantly reduced salt content while maintaining continuous production
Solution Approach 2:
The invention changes the physical state parameters by controlling the reaction conditions and using centrifugal separation to remove solid salt crystals formed during the reaction, transforming the continuous liquid-phase process into a two-phase system that enables salt removal while maintaining continuous operation
2Duration of action of stationary object
If conventional continuous processes are used, then production is maintained continuously, but the bleach strength is limited and stability is reduced due to high salt content
Solution Approach 1:
The invention continuously extracts salt crystals from the reaction mixture using a centrifuge, removing the source of instability and allowing the bleach to achieve greater than 25% strength with extended half-life while maintaining continuous production
Solution Approach 2:
The invention discards the removed salt crystals as a separate solid waste stream while recovering the high-strength, low-salt bleach liquid, enabling continuous production of stable bleach product with improved reliability
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 produces a higher-strength, lower-salt sodium hypochlorite bleach with improved stability and extended half-life, achieving a sodium hypochlorite concentration of greater than 25% by weight and a NaCl/NaOCl ratio less than 0.38, with a slight excess of caustic, and effectively removes salt crystals for recovery as dry solids.
Implementation Method 1
a first portion of the withdrawn slurry forms a recycle solution that is cooled during passage through a heat exchanger
Implementation Method 2
a high recycle rate through a heat exchanger is used to control temperature and promote crystal formation
Implementation Method 3
using a two-stage centrifuge for further processing
Data Source
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AI summary
A method for continuous manufacture of higher-strength, lower-salt, aqueous sodium hypochlorite bleach from lower-strength aqueous sodium hypochlorite bleach that has some sodium hydroxide and that is essentially free of sodium chloride (salt) crystals, aqueous sodium hydroxide solution having a concentration by weight within a range from about 45% to about 51%, chlorine in gas and/or liquid phase that may or may not include inerts, and a recycle solution. Slurry is withdrawn from the tank at a level below where the lower-strength bleach, the sodium hydroxide solution, the chlorine, and the recycle solution begin to mix with slurry already in the tank. A first portion of the slurry is withdrawn and used as the recycle solution. A second portion of the slurry is withdrawn and processed to separate substantially all salt crystals from residual liquid that is recovered as the higher-strength lower-salt, aqueous sodium hypochlorite bleach.