Membrane CO2 Separation Recycle Loop
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Solution Overview
Problem
Membrane-based CO2 separation systems face challenges in maintaining performance and efficiency when dealing with varying CO2 concentrations in gas streams, leading to increased auxiliary loads and reduced power plant efficiency due to the need for compression and limited driving force for separation.
Innovation Solution
A process involving a membrane-based separation system with a recycle loop that recycles a part of the CO2-rich permeate stream back into the feed stream to stabilize CO2 concentration, reducing the incremental auxiliary load and improving performance by adjusting the CO2 concentration dynamically.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If compression is used to increase the overall pressure of the feed to improve separation performance, then the driving force for separation is improved, but parasitic auxiliary loads increase and power plant efficiency is reduced
Solution Approach 1:
The patent changes the concentration parameter of the feed stream by recycling CO2-rich permeate back to the feed stream inlet. This increases the CO2 concentration in the feed without requiring compression, thereby maintaining the driving force for separation while avoiding the energy penalty of compressing the entire gas stream.
Solution Approach 2:
The patent implements a feedback loop where a portion of the CO2-rich permeate stream is recycled back to the feed stream inlet. This feedback mechanism dynamically adjusts the feed composition to maintain optimal separation performance without requiring additional compression energy.
2Force
If vacuum is used to decrease the pressure on the permeate side to improve separation performance, then the driving force for separation is improved, but the improvement is limited since permeate pressure can only be reduced about 1 atmosphere
Solution Approach 1:
Instead of relying on vacuum to improve the driving force, the patent changes the feed composition parameter by recycling CO2-rich permeate. This approach provides a more versatile and scalable method to enhance the driving force without being constrained by the 1 atmosphere limitation of vacuum systems.
3Quantity of substance
If retentate is recirculated to increase CO2 concentration in the feed, then the CO2 concentration is increased, but the system complexity increases and the ability to achieve target levels of CO2 removal is compromised
Solution Approach 1:
Instead of recycling retentate as in conventional EGR systems, the patent recycles permeate back to the feed stream inlet. This inverted approach simplifies the system by eliminating the need for complex retentate recirculation infrastructure while still achieving the goal of increasing CO2 concentration in the feed to membrane stages.
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 stabilizes CO2 concentration in the feed stream, reduces energy requirements, and maintains high CO2 recovery rates while minimizing the need for compression, thus enhancing the overall efficiency of the CO2 separation process.
Implementation Method 1
membrane-based separation system comprising one or more membrane stages in-line, each membrane stage would obtain a CO2-depleted retentate stream and a CO2-rich permeate stream
Data Source
AI summary
The invention relates to gas separation, particularly to a process for separating CO2 from a CO2 containing gas stream with varying CO2 concentration using a membrane-based separation system. The process for separating CO2 comprises: (i) feeding the CO2 containing gas stream into a membrane-based separation system comprising one or more membrane stages in-line, each membrane stage producing a CO2-depleted retentate stream and a rich CO2 permeate stream, and (ii) recycling a part of the CO2-rich permeate stream from at least one membrane stage as a recycled stream, into a preceding feed stream of one or more membrane stages in the membrane-based separation system to adjust the CO2 concentration of the feed stream. The process could stabilize the CO2 concentration in the feed steam by recirculation of a fraction of the high purity CO2 permeate to the feed of the membrane system, which would result in a lower incremental auxiliary load than other options such as compression of the entire gas stream.