Two-Stage Low-Temperature Membrane Separation for CO2 Capture
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Solution Overview
Problem
Current membrane separation technologies for capturing carbon dioxide from gas mixtures face limitations in achieving high purity and high recovery rates while requiring substantial cooling energy, with existing low-temperature processes only achieving a carbon dioxide purity of about 68% and consuming significant cooling energy.
Innovation Solution
A low-temperature membrane separation device and method involving a two-stage process with a first membrane unit and a second membrane unit, where the second separation step is performed at a lower temperature than the first, utilizing a membrane-cooling device and feed-gas-cooling device to adjust temperatures and enhance carbon dioxide selectivity, thereby reducing cooling energy and increasing purity and recovery rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a low-temperature process is used to increase the purity of separated carbon dioxide, then the purity is improved, but substantial cooling energy is required
Solution Approach 1:
The membrane separation process is divided into two sequential stages: a first membrane unit that performs initial separation at higher temperature, and a second membrane unit that performs final separation at lower temperature. This segmentation allows the system to achieve high purity carbon dioxide (95% or higher) while minimizing total cooling energy requirements, as only the second stage requires substantial cooling.
Solution Approach 2:
The invention changes the temperature parameter across different stages of separation. The first membrane unit operates at higher temperature (requiring minimal or no cooling), while the second membrane unit operates at lower temperature (requiring substantial cooling). This parameter change optimizes the balance between purity achievement and energy consumption.
2Manufacturing precision
If a single-stage membrane separation is used, then the device complexity is reduced, but the carbon dioxide purity is limited to about 68%
Solution Approach 1:
The separation system is segmented into two distinct membrane units with different functional roles. The first membrane unit handles the bulk separation at higher temperature, while the second membrane unit performs fine-tuning separation at lower temperature. This segmentation enables the system to achieve 95% or higher purity, overcoming the 68% purity limitation of single-stage systems.
3Productivity
If cooling is applied to the entire gas mixture before separation, then the separation efficiency is improved, but the cooling energy consumption increases substantially
Solution Approach 1:
Cooling is segmented and applied only to the permeate stream from the first membrane unit before it enters the second membrane unit, rather than cooling the entire feed gas mixture. This approach maintains high separation efficiency while substantially reducing cooling energy consumption, as only a portion of the gas stream requires cooling.
Solution Approach 2:
The first membrane unit performs preliminary separation at higher temperature, concentrating carbon dioxide in the permeate stream. This preliminary action prepares the gas for more efficient low-temperature separation in the second unit, reducing the overall cooling energy required compared to cooling the entire feed stream from the beginning.
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 method effectively captures high-purity carbon dioxide at a high recovery rate by optimizing temperature differences between the two membrane units, significantly reducing cooling energy requirements and improving overall separation efficiency.
Implementation Method 1
passing the mixed gas, which is provided through the first feed gas line, through the first membrane unit
Implementation Method 2
a second separation step of providing the permeation gas, which is released through the first permeate gas line of the first membrane unit, through the second feed gas line into the second membrane unit, followed by passing the provided gas through the second membrane unit, is performed. The membrane separation device according to the present invention may be controlled so that the second separation step is performed at a temperature that is lower than the temperature at which the first separation step is performed
Data Source
AI summary
The present invention relates to a low-temperature membrane separation device and method for capturing carbon dioxide at a high concentration, in which a gas mixture is passed through a membrane unit to thus separate carbon dioxide. The membrane unit includes a membrane for capturing carbon dioxide and is connected to a feed gas line, a retentate gas line and a permeate gas line. The method includes a first separation step of passing the gas mixture through a first membrane unit and a second separation step of passing the permeation gas, which is discharged to the permeate gas line connected to the first membrane unit, through a second membrane unit. The second separation step is performed at a temperature that is lower than a temperature at which the first separation step is performed.