Flexible CO2 Removal Using Semi-Lean and Ultralean Solvents
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Solution Overview
Problem
Current CO2 removal technologies face challenges in efficiently handling high CO2 content gases, as existing methods are either economically unattractive due to high costs, energy consumption, or unable to meet stringent CO2 specifications, particularly in gas fields with variable CO2 concentrations.
Innovation Solution
A method involving sequential removal of H2S and CO2 from a hydrocarbonaceous feed gas using a semi-lean and ultralean physical solvent, with dry-air stripping for solvent regeneration, allowing for efficient CO2 capture and production of a low CO2 content product gas, suitable for CO2 sequestration and meeting stringent specifications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If membrane separators are used to separate acid gases from natural gas streams, then the system is compact and simple to operate, but membrane elements are prone to fouling and material degradation requiring periodic replacement, and single stage separators produce CO2 waste stream with high hydrocarbon content that may not meet environmental permits
Solution Approach 1:
The invention divides the CO2 removal process into multiple stages with different solvent systems. The first stage uses a physical solvent for bulk CO2 removal, and the second stage uses a chemical solvent for polishing to achieve low CO2 specifications. This segmentation allows each stage to be optimized for its specific function, improving overall reliability and performance.
Solution Approach 2:
The invention changes the operating parameters by using ultralean solvent circulation rates and specific temperature/pressure conditions in the absorber. This allows the physical solvent system to achieve high CO2 removal efficiency without the fouling and degradation issues that plague membrane systems, while maintaining operational simplicity.
2Manufacturing precision
If multiple stages of membrane separators with inter-stage recompression and recycle are used to improve membrane performance, then CO2 separation efficiency improves, but the cost and footprint of the system increase rendering membrane separation economically unattractive
Solution Approach 1:
The invention extracts the CO2 removal function from complex multi-stage membrane systems and implements it using a simplified absorber-stripper configuration with physical solvent. This extraction achieves the same CO2 separation efficiency without requiring multiple membrane stages, recompression equipment, or large system footprints.
Solution Approach 2:
The invention employs a self-regenerating solvent system where the stripper regenerates the lean solvent using heat from the absorber bottom stream. This self-service approach eliminates the need for external recompression and recycle systems, reducing both device complexity and footprint while maintaining high CO2 removal efficiency.
3Manufacturing precision
If chemical solvent systems are used to treat high CO2 content gases, then selectivity is high and product gas CO2 content can be reduced to low ppm range, but heat requirement for solvent regeneration is significant consuming substantial amounts of treated gas for heating
Solution Approach 1:
The invention performs preliminary CO2 removal using a physical solvent in the first absorption stage, which removes the bulk of CO2 at high partial pressure. This preliminary action reduces the CO2 load on the second stage, allowing the chemical solvent to achieve low ppm specifications with minimal heat requirement for regeneration.
Solution Approach 2:
The invention changes the operating parameters by using ultralean solvent circulation rates and specific temperature/pressure conditions in the absorber. This allows the physical solvent system to achieve high CO2 removal efficiency without the fouling and degradation issues that plague membrane systems, while maintaining operational simplicity.
4Productivity
If amine systems are used to treat high CO2 content gases, then CO2 removal capability is provided, but additional amine units must be added to meet sales gas specification as CO2 content increases, and equipment and piping are prone to failure from corrosion and foaming problems
Solution Approach 1:
The invention divides the CO2 removal process into multiple stages with different solvent systems. The first stage uses a physical solvent for bulk CO2 removal, and the second stage uses a chemical solvent for polishing to achieve low CO2 specifications. This segmentation allows each stage to be optimized for its specific function, improving overall reliability and performance.
Solution Approach 2:
The invention changes the operating parameters by using ultralean solvent circulation rates and specific temperature/pressure conditions in the absorber. This allows the physical solvent system to achieve high CO2 removal efficiency without the fouling and degradation issues that plague membrane systems, while maintaining operational simplicity.
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 enables effective CO2 removal from feed gases with variable CO2 content, reducing energy consumption and operational costs, while producing a dry CO2 stream suitable for reinjection or further processing, and minimizing solvent circulation and equipment corrosion.
Implementation Method 1
CO2 is then removed from the H2S depleted feed gas using a semi-lean and an ultralean physical solvent
Implementation Method 2
Pressure of the rich solvent is then reduced in a hydraulic turbine to generate work and refrigeration
Implementation Method 3
Pressure of the rich solvent is then reduced to generate work, a CO2 stream, and refrigeration
Implementation Method 4
The flashed solvent is then stripped with air in an air stripper to produce the ultralean solvent
Data Source
AI summary
A plant comprises a feed gas source, H2S removal unit, first absorber and a second, pressure reduction stages, first and second heat exchangers, stripping unit, and a conduit. The H2S removal unit selectively removes H2S from a feed gas from the feed gas source to produce an H2S depleted feed gas. The first absorber and the second absorber remove CO2 from the H2S depleted feed gas using a semi-lean and an ultralean solvent to produce a product gas and a rich solvent. The plurality of pressure reduction stages generates a cooled flashed solvent. The first heat exchanger and the second heat exchanger use the cooled flashed solvent to cool the H2S depleted feed gas and the semi-lean solvent. The stripping unit strips the flashed solvent with dried air to produce the ultralean solvent, and the conduit combines a portion of the ultralean solvent with the H2S depleted feed gas.