Spent Caustic Treatment via UV Photocatalysis
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Solution Overview
Problem
Conventional methods for treating spent caustic, such as incineration and wet air oxidation, are costly and require high temperature and high pressure conditions, making them inefficient and difficult to maintain.
Innovation Solution
A method involving a mixed solution of spent caustic and an oxidizing agent passed through catalyst structures while irradiating ultraviolet rays, using a titanium oxide photocatalyst produced by wet impregnation, which oxidizes sulfide and mercaptide compounds into sulfate ions at mild temperatures and pressures, with gas and liquid separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If incineration treatment is used to remove harmful components from spent caustic, then harmful components are eliminated, but white smoke and odor containing sulfur oxides and nitric oxides occur, and sodium fouling makes maintenance difficult and costly
Solution Approach 1:
The patent converts the harmful sulfide components in spent caustic into beneficial sulfate ions through photo-oxidation. The sulfide that would normally produce harmful emissions during incineration is instead transformed into harmless sulfate using ultraviolet light and oxidizing agents, eliminating both the original harm and the secondary pollution of white smoke and odor.
Solution Approach 2:
The patent replaces the thermal incineration system with a photo-oxidation system. Instead of using high-temperature combustion to eliminate harmful components, the invention uses ultraviolet light irradiation combined with oxidizing agents to achieve the same goal without producing harmful emissions, thereby substituting a mechanical/thermal process with a photochemical process.
2Object-affected harmful factors
If wet air oxidation is used to treat spent caustic at high temperature and high pressure, then organic materials are converted to carbon dioxide and sulfur compounds are converted to thiosulfate or sulfate, but investment and operating costs become very high
Solution Approach 1:
The patent fundamentally changes the operating parameters from high temperature and high pressure conditions to ambient temperature and pressure conditions. By using photo-oxidation with ultraviolet light and oxidizing agents, the process achieves effective conversion of organic materials and sulfur compounds without requiring the extreme conditions of wet air oxidation, thereby dramatically reducing energy consumption and operating costs.
Solution Approach 2:
The patent replaces the high-energy thermal oxidation system with a low-energy photochemical oxidation system. Instead of using heat and pressure to drive the oxidation reactions, the invention uses ultraviolet light energy to activate oxidizing agents, achieving the same conversion效果 with minimal energy input and without requiring high-temperature and high-pressure equipment.
3Productivity
If wet air oxidation is used to treat spent caustic, then oxidation of sulfur compounds occurs, but the operating environment requires high temperature and high pressure resulting in very high investment and operating costs
Solution Approach 1:
The patent changes the operating parameters from high temperature and high pressure to ambient conditions. By using photo-oxidation with ultraviolet light, the process maintains high oxidation efficiency while operating at room temperature and atmospheric pressure, thereby simplifying the equipment requirements and reducing both investment and operating costs.
Solution Approach 2:
The patent introduces oxidizing agents (such as hydrogen peroxide, ozone, or persulfate) as intermediaries to facilitate the oxidation process. These intermediaries, when activated by ultraviolet light, provide the necessary oxidative power to convert sulfur compounds efficiently without requiring high temperature and high pressure conditions, thus simplifying the overall system complexity.
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 reduces chemical oxygen demand and sulfide levels significantly, is cost-effective, and operates at room temperature and atmospheric pressure, lowering energy consumption and investment costs, while being safer and simpler than traditional methods.
Implementation Method 1
oxidizing the spent caustic by passing the mixed solution through catalyst structures while irradiating ultraviolet rays
Implementation Method 2
a titanium oxide photocatalyst produced by wet impregnation of titanium dioxide
Implementation Method 3
oxidizing the spent caustic by passing the mixed solution through catalyst structures while irradiating ultraviolet rays
Data Source
AI summary
Provided are a method of treating spent caustic occurring in a refinery process, a petrochemical process, and an environmental facility, and an apparatus thereof, wherein the spent caustic may be economically treated by a Fenton-like oxidation reaction at room temperature and atmospheric pressure in a reactor in which catalyst structures are stacked as compared to conventional methods of treating spent caustic.