CO2-Selective Membrane Preconcentration for Low-CO2 Exhaust Gas
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Solution Overview
Problem
Existing CO2 capture methods for low concentration exhaust gases, such as amine absorption, are inefficient and costly due to high steam requirements, leading to increased operating costs and emissions, and existing membrane-based systems like EGR have limitations such as reduced engine efficiency and additional power consumption.
Innovation Solution
Utilizing CO2-selective polymeric membranes for preconcentration of low concentration CO2 exhaust gases, which operate without steam and produce a higher concentration CO2 stream for further processing, reducing the need for large equipment and energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If amine absorption is used for CO2 capture from low concentration exhaust gases, then CO2 removal efficiency is improved, but steam consumption and operating costs increase significantly
Solution Approach 1:
The patent introduces a membrane separation unit as an intermediary component between the exhaust gas source and the amine absorption system. This membrane unit pre-concentrates CO2 from low concentration (3-4 vol.%) exhaust gas to higher concentration levels before the gas enters the amine plant, thereby reducing the steam consumption and energy requirements of the subsequent amine absorption process while maintaining effective CO2 removal efficiency
Solution Approach 2:
The membrane separation system performs a preliminary concentration action on the exhaust gas stream before it enters the amine absorption system. By pre-concentrating CO2 in a separate stage, the system prepares the gas stream in an optimized state for the amine absorption process, reducing the energy input required in the amine plant while ensuring reliable CO2 capture
2Reliability
If amine absorption is used for CO2 capture from low concentration exhaust gases, then CO2 removal efficiency is improved, but equipment size increases due to high volumetric flow
Solution Approach 1:
The membrane separation unit performs preliminary CO2 concentration on the exhaust gas stream, transforming it from a high volumetric flow low-concentration stream to a lower volumetric flow high-concentration stream. This preliminary action reduces the size of downstream equipment including the amine absorption column, regenerator, and associated infrastructure, while maintaining effective CO2 removal efficiency
Solution Approach 2:
The patent segments the CO2 capture process into two distinct stages: a membrane separation stage for pre-concentration and an amine absorption stage for final removal. This segmentation allows each stage to be optimized independently, with the membrane unit handling the volumetric reduction and the amine plant handling the efficient chemical absorption, thereby reducing overall equipment size requirements
3Volume of stationary object
If membrane-based systems like EGR are used for CO2 concentration, then equipment size is reduced, but engine efficiency decreases and power consumption increases
Solution Approach 1:
The patent extracts the CO2 concentration function from the engine exhaust recirculation system and places it in a dedicated membrane separation unit. This extraction allows the engine to operate at optimal efficiency without the burden of integrated concentration equipment, while the membrane unit independently performs the concentration function with minimal energy input compared to compression-based systems
Solution Approach 2:
The patent replaces mechanical compression systems with a membrane-based separation system for CO2 concentration. Instead of using compressors that consume significant power, the system uses selective permeation membranes that separate CO2 based on its higher permeability through the membrane material, achieving concentration with minimal energy input and no moving parts
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 membrane-based preconcentration system enhances CO2 capture efficiency and reduces costs by producing a concentrated CO2 stream suitable for further processing, while minimizing energy use and equipment size.
Implementation Method 1
feeding at least a portion of the exhaust gas stream to a membrane separation module comprising a polymeric membrane that has a perm-selectivity for CO2 over N2 and O2
Implementation Method 2
membrane-based gas separation to enhance carbon dioxide (CO2) capture
Implementation Method 3
a vacuum connected to the permeate side of the membrane separation module, and which is configured to create a pressure difference across the polymeric membrane and thereby encourage gas permeance across the polymeric membrane
Data Source
AI summary
A process of preconcentrating CO2 in an exhaust gas stream includes flowing all the exhaust gas stream from an exhaust gas source to a CO2 preconcentration system. Within the CO2 preconcentration system, at least a portion of the exhaust gas stream is fed to a membrane separation module comprising a polymeric membrane that has a perm-selectivity for CO2 over N2 and O2, to produce a CO2 rich exhaust gas. The exhaust gas stream may initially have as low as 400 ppm CO2 and may be preconcentrated to over 8 vol. % CO2, thereby generating a more optimal feed for further treatment processes.