Caustic Stream Sulfur Removal via Oxidation and Adsorption
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Solution Overview
Problem
Existing methods for removing residual sulfur compounds from caustic streams are inefficient and costly, particularly in achieving low sulfur levels required by the Clean Air Act, with solvent washing and other technologies failing to effectively reduce sulfur levels below 5 ppm.
Innovation Solution
A single-step oxidation and adsorption (OAS) process using activated carbon adsorbents, which converts residual mercaptans to disulfides and adsorbs both, replacing traditional solvent washing and minimizing capital and operating costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional solvent washing is used to remove residual sulfur compounds from caustic streams, then sulfur levels can be reduced, but the process becomes costly and complex
Solution Approach 1:
The patent extracts and removes residual sulfur compounds (disulfides and mercaptans) from the caustic stream using a solid adsorbent material. The adsorbent selectively captures sulfur compounds from the liquid phase, achieving sulfur levels below 5 ppm without requiring complex solvent washing systems. This extraction approach simplifies the overall process while maintaining high removal efficiency.
Solution Approach 2:
The patent employs a porous solid adsorbent material with high surface area and porous structure to adsorb residual sulfur compounds from the caustic stream. The porous structure provides numerous active sites for sulfur compound adsorption, achieving effective polishing to below 5 ppm sulfur levels. This approach replaces complex solvent washing with a simpler adsorption-based polishing step.
2Manufacturing precision
If multiple polishing steps are used to achieve low sulfur levels, then sulfur removal is improved, but capital and operating costs increase
Solution Approach 1:
The patent combines oxidation and adsorption polishing into a single integrated process step. The oxidized caustic stream containing residual disulfides and mercaptans is directly contacted with the solid adsorbent in one operation, achieving sulfur levels below 5 ppm. This merged approach eliminates the need for multiple separate polishing steps and expensive solvent washing, significantly reducing both capital and operating costs.
Solution Approach 2:
The patent uses a relatively inexpensive solid adsorbent material that can be easily replaced or regenerated. The adsorbent provides effective sulfur removal in a single pass, and when spent, can be replaced with a new adsorbent bed or regenerated through simple thermal or solvent treatment. This approach is more economical than continuous solvent washing systems requiring expensive solvents and multiple processing units.
3Reliability
If activated carbon adsorbent is used to adsorb disulfides from caustic stream, then sulfur compounds are removed effectively, but the process requires optimization for best performance
Solution Approach 1:
The patent optimizes several process parameters to maximize adsorption effectiveness: contact time between caustic stream and adsorbent, adsorbent bed depth and configuration, caustic flow rate through the adsorbent, and pH conditions. By carefully controlling these parameters, the process achieves reliable sulfur removal below 5 ppm while maintaining simple operation. The oxidation step prior to adsorption also converts mercaptans to disulfides, enhancing overall removal efficiency.
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 sulfur levels below 5 ppm in the caustic stream, reducing the need for costly polishing steps and enabling the reuse of sulfur-free caustic for hydrocarbon treatment, with consistent performance over extended operation.
Implementation Method 1
my invention adsorbs disulfides from a caustic stream using an activated carbon adsorbent
Implementation Method 2
my invention combines both adsorption and catalytic oxidation to remove residual sulfur compounds from a caustic stream using metal phthalocyanine supported on a solid adsorbent
Implementation Method 3
the oxidation of these mercaptans to disulfides by contacting the rich caustic stream with a solid catalyst in the presence of oxygen
Data Source
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AI summary
A process for the removal of residual sulfur compounds from a liquid caustic stream is disclosed. One embodiment of my invention adsorbs disulfides from a caustic stream using an activated carbon adsorbent while another combines both oxidation and adsorption in single step to remove residual sulfur compounds from a rich caustic stream using metal phthalocyanine supported on a solid adsorbent. This process is especially useful as a polishing step in a caustic regeneration process flow scheme.