Integrated Mercaptan Extraction and Thermal Oxidation for Spent Caustic Treatment
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Solution Overview
Problem
Current processes for treating sulfidic, naphthenic, and phenolic/cresylic waste streams from hydrocarbon sweetening and extraction are inefficient and environmentally unsustainable, requiring comprehensive solutions to meet stringent regulations and reduce waste management costs.
Innovation Solution
An integrated mercaptan extraction and thermal oxidation process that operates near ambient pressure, utilizing a spent caustic surge drum and hydrocarbon surge drum to stabilize flow, reduce equipment needs, and incorporate thermal oxidation for comprehensive sulfur and nitrogen oxide treatment, with integrated control systems for seamless operation and reduced emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional liquid-liquid extraction processes are used for mercaptan removal, then mercaptans can be removed from hydrocarbon streams, but spent caustic streams containing sulfidic, naphthenic, and phenolic/cresylic contaminants are produced that require additional treatment
Solution Approach 1:
The patent combines the mercaptan extraction function with the spent caustic treatment function into a single integrated system. The extraction column and thermal oxidizer are connected such that the spent caustic from extraction is directly fed to thermal oxidation for regeneration, eliminating the need for separate waste treatment processes and enabling continuous operation.
Solution Approach 2:
The patent converts the harmful spent caustic waste stream into a beneficial regenerated caustic solution. By feeding the spent caustic containing mercaptides to a thermal oxidizer, the mercaptides are oxidized to disulfides which separate from the caustic, regenerating the caustic solution for reuse in the extraction process.
2Adaptability or versatility
If multiple separate processes are used to treat different waste streams (sulfidic, naphthenic, phenolic/cresylic), then comprehensive treatment can be achieved, but process complexity and equipment requirements increase
Solution Approach 1:
The thermal oxidizer serves multiple functions: it regenerates spent caustic from mercaptan extraction, oxidizes various sulfur compounds (H2S, mercaptans, disulfides), and can handle different types of contaminants (sulfidic, naphthenic, phenolic/cresylic) in a single unit. This multi-functional approach replaces what would traditionally require multiple separate treatment processes.
3Reliability
If traditional spent caustic treatment processes are used, then waste streams can be processed, but additional equipment such as disulfide separators, sand filters, and multiple treatment units are required
Solution Approach 1:
The patent merges the caustic regeneration function with the disulfide separation function into a single thermal oxidizer unit. The thermal oxidizer simultaneously oxidizes mercaptides to disulfides and provides the conditions for disulfide separation, eliminating the need for separate regeneration equipment and reducing overall process complexity.
4Object-affected harmful factors
If environmental regulations become more stringent, then emission standards are improved, but treatment requirements and operational costs increase
Solution Approach 1:
The patent converts potential harmful emissions into beneficial products. The thermal oxidizer completely oxidizes sulfur compounds to SO2, which is then converted to valuable sulfuric acid or sulfates that can be sold or used, rather than being released as harmful emissions. This approach simultaneously meets stringent emission standards and creates economic value.
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 integrated process effectively treats a wide range of sulfur and nitrogen-containing waste streams, reducing the need for fresh chemicals, minimizing equipment size and emissions, and ensuring compliance with environmental regulations while maintaining system uptime and efficiency.
Implementation Method 1
passing a mixed spent caustic stream from the spent caustic surge drum to a thermal oxidation and quench section of a thermal oxidation system, the mixed spent caustic stream comprising at least one sulfur compound, oxidizing the at least one sulfur compound in the thermal oxidation and quench section forming oxidized sulfur particulate and carbonate particulate in flue gas
Implementation Method 2
converting a portion of the oxidized sulfur particulate in the sulfur oxide removal section by contacting the flue gas with caustic to form sodium sulfate or sulfite particulate
Data Source
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AI summary
An integrated mercaptan extraction and/or sweetening and thermal oxidation and flue gas treatment process for a wide variety of sulfur, naphthenic, phenolic/cresylic contaminated waste streams is described. It provides comprehensive treatment for the safe disposal of sulfidic, naphthenic, phenolic/cresylic spent caustic streams, disulfide streams, spent air streams, spent mixed amine and caustic streams (also known as COS solvent streams) from sulfur treating processes. It allows the use of regenerated spent caustic in the sulfur oxide removal section of the thermal oxidation system reducing the need for fresh NaOH. It may also contain an integrated make-up water system. The integration allows the use of the liquefied petroleum gas or other hydrocarbon feeds to the respective extraction or sweetening process to offset external fuel gas requirements for the thermal oxidation system and for the push/pull system of the spent caustic surge drum and optional hydrocarbon surge drum.