Selenium Removal via Sorbent Inhibitor Conditioning
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Solution Overview
Problem
Current selenium removal techniques from aqueous streams, particularly in oil refining and coal processing, are inefficient in removing oxidized selenium species and often fail to meet regulatory discharge standards, leading to suboptimal treated water quality for reuse.
Innovation Solution
A method and system that involve reducing the concentration of selenium sorption inhibitors like oils, soluble organic compounds, and thiosulfate in the aqueous stream, followed by passing the treated stream through a support impregnated with sulfur, selenium, or tellurium to absorb selenium, and using a reducing agent to precipitate selenium, thereby enhancing removal efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional adsorption techniques are used to remove selenium, then some selenium can be removed, but the ability to remove oxidized selenium species is relatively weak
Solution Approach 1:
The treatment process is divided into multiple sequential stages: (1) removal of sorption inhibitors (oils, soluble organics, thiosulfate), (2) oxidation of selenium to oxidized species, (3) adsorption of oxidized selenium onto sulfur-impregnated activated carbon. This segmentation allows each stage to optimize for its specific function, with the oxidation step specifically enhancing the removal of oxidized selenium species while the adsorption step handles total selenium removal.
Solution Approach 2:
The patent changes the oxidation state parameter of selenium from reduced forms (selenide, selenocyanate) to oxidized forms (selenite, selenate) through chemical oxidation. This parameter change enhances the affinity for the sulfur-impregnated activated carbon sorbent, significantly improving removal effectiveness for oxidized species while maintaining overall selenium removal capability.
2Reliability
If conventional selenium removal techniques are applied, then selenium can be removed to some extent, but treated water fails to meet criteria for reuse
Solution Approach 1:
The patent performs preliminary removal of sorption inhibitors (oils, soluble organic compounds, and thiosulfate) from the aqueous stream before the selenium adsorption step. This preliminary action prevents these inhibitors from interfering with the selenium removal process and ensures that the treated water meets quality criteria for reuse in applications such as boiler feed and desalting units.
Solution Approach 2:
The treatment process maintains continuous effective action through multiple sequential steps that build upon each other: inhibitor removal → oxidation → adsorption. This continuous multi-stage action ensures consistent achievement of regulated selenium levels and water quality criteria for reuse, rather than relying on a single step that may be insufficient.
3Reliability
If longer sorbent beds are used to improve selenium removal, then removal efficiency increases, but system complexity and cost increase
Solution Approach 1:
The patent changes the chemical parameters of the aqueous stream by removing sorption inhibitors and oxidizing selenium before contact with the sorbent. This parameter change enhances the effectiveness of the sorbent material, allowing for shorter sorbent bed lengths to achieve the same removal efficiency, thereby reducing system complexity while maintaining performance.
Solution Approach 2:
The patent uses sulfur-impregnated activated carbon as a modeled effective sorbent that replicates the high removal efficiency of longer, more complex sorbent beds but in a simplified configuration. The sulfur impregnation creates active sites that enhance selenium adsorption, allowing shorter beds to achieve the same treatment effectiveness.
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 selenium concentrations in aqueous streams, improving the efficiency of selenium removal and enabling treated water to meet regulatory standards for discharge and reuse, particularly by extending sorbent life and reducing the length of sorbent beds required.
Implementation Method 1
passing the aqueous stream from which the concentration of the sorption inhibitor has been reduced into contact with a support impregnated with at least one of sulfur, selenium and tellurium to absorb the selenium
Implementation Method 2
Adding a reducing agent to the aqueous stream removed from the sorbent bed and containing some of the selenium in a positive oxidation state causes the selenium to form a precipitate
Implementation Method 3
Adding a reducing agent to the aqueous stream removed from the sorbent bed and containing some of the selenium in a positive oxidation state causes the selenium to form a precipitate
Data Source
AI summary
Methods and apparatus relate to treating fluid to at least reduce selenium content within the fluid. The treating includes conditioning stages to alter a composition of the fluid prior to removal of the selenium content from the fluid. The composition of the fluid after the conditioning stages facilitates the removal of the selenium content or at least limits detrimental impact to selenium removal efficiency.