Two-Stage Absorption for Mercaptan Removal
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Solution Overview
Problem
Current NGL Recovery systems face inefficiencies in removing mercaptans from high-pressure feed gases, which require additional downstream molecular sieve units, increasing capital and operating costs, and pose health, safety, and environmental risks due to high H2S partial pressures.
Innovation Solution
A two-stage absorption process is implemented, where the first stage operates at feed gas pressure for bulk H2S removal and the second stage at higher pressure for enhanced mercaptan removal, using a semi-rich solvent in the first stage and a lean solvent in the second stage, reducing the need for downstream molecular sieve units and maintaining health and safety advantages of low-pressure systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a single-stage absorption system is used for acid gas removal, then the system complexity is low, but mercaptan removal efficiency is insufficient requiring additional downstream molecular sieve units
Solution Approach 1:
The absorption process is divided into two distinct stages: a first absorber operating at feed gas pressure for bulk H2S removal, and a second absorber operating at higher pressure for enhanced mercaptan removal. This segmentation allows each stage to be optimized for its specific function, achieving high mercaptan removal efficiency while maintaining manageable system complexity through modular design
Solution Approach 2:
The invention adds a pressure dimension to the absorption process by operating the first and second absorbers at different pressures. The first absorber operates at feed gas pressure while the second absorber operates at higher pressure, creating a two-dimensional operation space that enhances mercaptan removal efficiency without simply adding more equipment at the same operational level
2Manufacturing precision
If high pressure is used for mercaptan removal, then removal efficiency improves, but health and safety risks increase due to high H2S partial pressures
Solution Approach 1:
The two-stage absorption system segments the pressure operations: the first absorber handles bulk H2S removal at the lower feed gas pressure, reducing H2S partial pressure in the gas stream before compression. The second absorber then operates at higher pressure for mercaptan removal on a gas stream with already reduced H2S content, thereby achieving high mercaptan removal efficiency while minimizing health and safety risks associated with high H2S partial pressures
3Manufacturing precision
If additional downstream molecular sieve units are added for mercaptan removal, then mercaptan removal efficiency improves, but capital and operating costs increase
Solution Approach 1:
The invention changes the operational parameters of the absorption process by implementing two stages with different pressure levels and solvent conditions. The second absorber operates at higher pressure with lean solvent to achieve enhanced mercaptan removal, eliminating or reducing the need for downstream molecular sieve units and their associated capital and operating costs
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 two-stage process significantly improves mercaptan removal efficiency, reducing the size of molecular sieve units and associated costs, while maintaining health and safety benefits, achieving over 99% methyl mercaptan removal and 71% total mercaptan removal, compared to single-stage systems.
Implementation Method 1
contacting the semi-treated gas stream with a lean solvent; removing at least a portion of the organic sulfur species and acid gas components from the semi-treated gas stream to produce a treated gas stream and a semi-rich solvent stream
Implementation Method 2
contacting the semi-treated gas stream with a lean solvent; removing at least a portion of the organic sulfur species and acid gas components from the semi-treated gas stream
Implementation Method 3
contacting a feed gas stream with the semi-rich solvent; removing at least a portion of the organic sulfur species and acid gas components from the feed gas stream to produce the semi-treated gas stream
Implementation Method 4
contacting a feed gas stream with the semi-rich solvent; removing at least a portion of the organic sulfur species and acid gas components from the feed gas stream
Implementation Method 5
compressing a semi-treated gas stream, wherein the semi-treated gas stream comprises organic sulfur species and acid gas components
Implementation Method 6
a regeneration unit configured to receive the rich solvent stream, remove acid gas components from the rich solvent stream, and produce the lean solvent stream
Data Source
AI summary
A system for processing a gas stream can include an acid gas removal unit comprising a first absorber unit, a compressor, and a second absorber unit. The first absorber unit is configured to receive a feed gas stream containing organic sulfur species and acid gas components, remove at least a portion of the organic sulfur species and acid gas components using a semi-rich solvent at a first pressure, produce a semi-treated gas stream, and produce a rich solvent stream. The compressor unit is configured to compress the semi-treated gas stream from the first pressure to a higher second pressure. The second absorber unit is configured to receive the compressed semi-treated gas stream, remove at least a portion of any organic sulfur species and acid gas components present in the compressed semi-treated gas stream using a lean solvent, produce the semi-rich solvent stream, and produce a treated gas stream.