Alkaline Caustic Loop for Mercaptan Removal
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Solution Overview
Problem
Current methods for treating hydrocarbon streams containing mercaptan compounds are inefficient in removing disulfide compounds without separate washing procedures, leading to increased capital, material, and energy costs.
Innovation Solution
A method involving the use of a closed-loop alkaline caustic solution system where a relatively light hydrocarbon stream is treated to remove mercaptan compounds, oxidized to disulfide compounds, and then contacted with a relatively heavy hydrocarbon stream to remove disulfide compounds, eliminating the need for separate washing apparatus and reducing the size of the physical separation system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If separate washing procedures are used to remove disulfide compounds from regenerated caustic, then disulfide compound removal is effective, but capital costs, material costs, and energy costs increase
Solution Approach 1:
The patent combines the washing function into the existing extraction column by introducing a wash zone where regenerated caustic contacts the hydrocarbon feed stream. This eliminates the need for separate washing apparatus and procedures, reducing capital costs and device complexity while maintaining disulfide compound removal efficiency.
Solution Approach 2:
The extraction column is designed to perform multiple functions: mercaptan extraction, disulfide compound removal, and caustic regeneration. By making the extraction column multi-functional, the patent eliminates the need for dedicated washing equipment, thereby reducing capital costs and material costs.
2Manufacturing precision
If separate washing procedures are used to remove disulfide compounds from regenerated caustic, then disulfide compound removal is effective, but energy costs increase
Solution Approach 1:
The washing function is merged into the extraction column operation, allowing disulfide compound removal to occur during the same process as mercaptan extraction. This integration eliminates the need for separate washing steps, thereby reducing energy consumption and energy costs.
3Manufacturing precision
If regenerated caustic is used to treat hydrocarbon streams, then mercaptan removal is effective, but disulfide compounds dissolve in the hydrocarbon stream raising sulfur content
Solution Approach 1:
The patent applies preliminary action by removing disulfide compounds from the regenerated caustic before it contacts the hydrocarbon feed stream. The wash zone is positioned upstream in the process flow, ensuring disulfide compounds are removed beforehand, preventing them from dissolving into the hydrocarbon stream and raising sulfur content.
Solution Approach 2:
The patent extracts disulfide compounds from the regenerated caustic solution in the wash zone by contacting it with the hydrocarbon feed stream. This extraction action removes the harmful disulfide compounds before the caustic is used for mercaptan removal, preventing sulfur content increase in the treated hydrocarbon stream.
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 the sulfur content in hydrocarbon streams, minimizes the presence of disulfide compounds in the treated hydrocarbon streams, and lowers overall processing costs by eliminating the need for separate washing and reducing the size of the physical separation system.
Implementation Method 1
The mercaptan compounds are preferentially dissolved in the aqueous alkaline 'caustic' solution and are thereby extracted from the hydrocarbon stream
Implementation Method 2
The mercaptan-containing caustic solution, which is referred to as a 'rich' caustic solution, is then subjected to a procedure referred to as regeneration, which includes oxidizing the mercaptan compounds to disulfide (RSSR′) compounds
Implementation Method 3
The process then continues with separating the disulfide compounds from the aqueous solution by decantation (or other physical separation means) in a phase separation vessel
Data Source
AI summary
Disclosed is a method for treating hydrocarbon streams containing mercaptan compounds including contacting a first, relatively light hydrocarbon stream including mercaptan compounds with a first alkaline caustic solution to remove the mercaptan compounds from the first hydrocarbon stream and generate a second alkaline caustic solution including mercaptan compounds and oxidizing the mercaptan compounds in the second alkaline caustic solution to generate a third alkaline solution including a first concentration of disulfide compounds. The method further includes separating a portion of the disulfide compounds in the third alkaline solution to form a fourth alkaline solution including a second concentration of disulfide compounds. Still further, the method includes contacting the fourth alkaline solution with a second, relatively heavy hydrocarbon stream including mercaptan compounds to remove the mercaptan compounds from the second hydrocarbon stream, remove the disulfide compounds from the fourth alkaline solution, and generate the first alkaline caustic solution.