Single-Column Oxidation Process for Caustic Desulfurization
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Solution Overview
Problem
Current methods for removing sulfur compounds, specifically mercaptans and disulfides, from caustic streams are inefficient, leading to residual sulfur contamination in regenerated caustic, which affects hydrocarbon extraction efficiency and requires multiple costly unit operations.
Innovation Solution
A single-column three-phase catalytic oxidation process using vertical hanging fibers, where mercaptans are oxidized to disulfide oils within a gas continuous phase, effectively reducing sulfur compounds to less than 7.5 ppm in the regenerated caustic, eliminating the need for additional vessels and unit operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional oxidation reactor followed by gravity separator is used, then mercaptans are converted to disulfides, but substantial mercaptans and DSO remain in regenerated caustic causing loss of extraction efficiency
Solution Approach 1:
The patent combines the oxidation reactor and gravity separator into a single integrated column system where hanging fibers serve dual functions as both catalyst support and separation medium. This merging eliminates the need for separate vessels and achieves both high conversion and complete separation in one unit, resolving the contradiction between reliability and manufacturing precision.
Solution Approach 2:
The patent employs hanging fibers with high surface area and porous structure that provide numerous active sites for catalytic oxidation while simultaneously acting as a separation medium. The porous nature of the fibers enables efficient contact between gas-liquid phases and facilitates complete separation of DSO from regenerated caustic, achieving both high conversion and complete sulfur removal.
2Manufacturing precision
If multiple unit operations including solvent washing are used to achieve complete sulfur removal, then sulfur compounds are reduced to below 5 ppm, but capital and operating costs increase significantly
Solution Approach 1:
The patent merges oxidation and separation functions into a single integrated column, eliminating the need for multiple separate unit operations such as oxidation reactors, gravity separators, and solvent washing units. This single-vessel design achieves complete sulfur removal while dramatically reducing device complexity and capital costs.
Solution Approach 2:
The hanging fibers in the integrated column serve multiple functions simultaneously: they act as catalyst support for oxidation, provide gas-liquid contact surface area, and function as a separation medium for DSO removal. This multi-functionality eliminates the need for separate specialized equipment for each function, reducing overall device complexity.
3Productivity
If oxidation reactor with multiple vessels is used, then mercaptan conversion is achieved, but land space and equipment costs increase
Solution Approach 1:
The patent consolidates multiple vessels (oxidation reactor, gravity separator, and potentially solvent washing units) into a single integrated column. This merging of functions into one compact unit maintains high mercaptan conversion efficiency while dramatically reducing the land space and equipment footprint required.
Solution Approach 2:
The patent employs vertical hanging fibers that extend through the column height, utilizing the vertical dimension to maximize surface area for catalysis and separation within a compact footprint. This vertical arrangement allows high productivity in a small land area by exploiting the third dimension rather than requiring large horizontal space.
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 process achieves significant reduction of sulfur compounds in the regenerated caustic, enhancing hydrocarbon extraction efficiency and reducing capital and operating costs by integrating into existing processes, ensuring a lean caustic stream suitable for reuse.
Implementation Method 1
oxidizing the rich caustic to convert mercaptans to disulfides (typically referred to as disulfide oils ("DSO"))
Implementation Method 2
oxidizing the rich caustic to convert mercaptans to disulfides
Implementation Method 3
using a gravity separator to separate the DSO from the oxidized caustic solution
Data Source
Figure 1~4
Figure 2
Figure 3
AI summary
A process for the removal of residual sulfur compounds from rich liquid caustic is disclosed where a single column containing two reaction zones catalytically oxidizes mercaptans to disulfide oils. The second reaction zone utilizes a bundle of vertical hanging fibers and is maintained as a gas continuous phase comprising from about 20% to about 100% by volume vapor. This process is especially useful as part of a hydrocarbon desulfurization process flow scheme.