Two-Stage Membrane Separation for High-Purity CO2 Capture
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Solution Overview
Problem
Current methods for separating carbon dioxide from gas streams, such as those emitted by power plants or natural gas processing, are inefficient and require significant energy, particularly in achieving high CO2 purity and recovery rates.
Innovation Solution
A two-stage membrane separation process using selectively permeable membranes with specific CO2 permeance and selectivity, combined with a sweep gas and vacuum techniques, to enhance CO2 removal and purity, allowing for high CO2 recovery and reduced energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional separation methods are used to achieve high CO2 purity and recovery rates, then CO2 separation effectiveness is improved, but energy consumption increases significantly
Solution Approach 1:
The separation process is divided into two sequential membrane stages. The first membrane achieves initial CO2 enrichment from the feed gas, and the second membrane further purifies the CO2 stream. This segmentation allows each membrane to operate at optimized conditions, achieving high purity (90-99% CO2) while reducing the energy penalty compared to single-stage high-purity separation or conventional methods like amine scrubbing and cryogenic distillation
Solution Approach 2:
The system dynamically adjusts operational parameters including feed pressure (1-20 atm), permeate side pressure (0.1-5 atm), and temperature (20-100°C) to optimize the balance between CO2 permeance and selectivity. By changing these parameters, the membranes can operate in different regimes to achieve both high purity and acceptable energy consumption, avoiding the fixed high energy requirements of conventional methods
2Productivity
If conventional separation methods are used to achieve high CO2 recovery rates, then CO2 capture effectiveness is improved, but energy costs increase
Solution Approach 1:
The membrane separation process operates continuously without the intermittent cycling required by pressure swing adsorption or the thermal cycling of cryogenic distillation. The cross-flow configuration maintains continuous concentration gradients across the membranes, enabling sustained high recovery rates (80-95% CO2 recovery) with lower energy input compared to batch processes or thermally-intensive conventional methods
Solution Approach 2:
The selectively permeable membranes act as intermediaries that facilitate CO2 transfer from the feed stream to the permeate stream based on concentration gradients and membrane selectivity. This intermediary mechanism replaces energy-intensive direct separation methods with a passive diffusion-based approach enhanced by pressure and temperature optimization, achieving high recovery rates with reduced energy 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
This approach effectively captures CO2 from diverse gas streams with high purity and recovery rates, reducing energy costs and environmental impact by optimizing membrane selection and operational conditions.
Implementation Method 1
The first permeate stream is passed through a second selectively permeable membrane to produce a second retentate stream and a second permeate stream, the second permeate stream having a greater concentration of carbon dioxide than the feed gas stream
Implementation Method 2
A vacuum can be applied to generate a pressure of from 0.1 to 0.5 atm on the permeate side of the selectively permeable membrane
Data Source
AI summary
Disclosed herein are 2-stage membrane separation methods for capturing CO2 from a feed gas. The methods can employ two selectively permeable membranes, which may be the same or different. The selectively permeable membrane can have a carbon dioxide permeance of from 500 to 3000 GPU at 57° C. and 1 atm feed pressure and a carbon dioxide:nitrogen selectivity of from 10 to 1000 at 57° C. and 1 atm feed pressure. High pressure ratios across the membranes can be achieved by compressing the feed gas to a high pressure, by using vacuum pumps to create a lowered pressure on the permeate side of the membrane, by using a sweep stream, or a combination thereof. When a sweep stream is used, the sweep stream may include a portion of the retentate gas stream obtained from the retentate side of one or more of the membranes used.