Two-Stage Membrane Cooling for Methane-Enriched Gas Recovery
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Solution Overview
Problem
Existing gas separation systems for producing high-purity methane from a mixed gas containing CO2 and CH4 are inefficient and costly due to the trade-off between membrane area and operating pressure, and they do not achieve optimal recovery rates and selectivity.
Innovation Solution
A gas separation system comprising a first and a second gas separation membrane unit, where the second unit operates at a lower temperature than the first, with a higher CO2 permeation rate, connected in series, and includes a cooling mechanism to optimize the operating conditions for enhanced selectivity and recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a membrane with high gas separation selectivity is used, then the recovery rate is improved, but the permeation rate decreases requiring larger membrane area or higher operating pressure
Solution Approach 1:
The gas separation system is divided into multiple stages with different membrane units. The first stage uses a membrane with high permeation rate to achieve initial separation, while subsequent stages use membranes with different characteristics to progressively improve purity. This segmentation allows the system to achieve both high recovery rate and high purity without requiring excessively large membrane area in a single stage.
Solution Approach 2:
The invention changes operating parameters (temperature, pressure) and membrane selection across different stages. By adjusting these parameters and selecting appropriate membranes for each stage, the system optimizes the balance between permeation rate and separation selectivity, achieving high recovery rate without requiring disproportionately large membrane area.
2Reliability
If a membrane with high gas separation selectivity is used, then the recovery rate is improved, but the operating pressure must be increased
Solution Approach 1:
The separation process is segmented into multiple stages, each handling a portion of the separation task. This distributes the pressure requirements across stages rather than requiring high pressure throughout the entire system, reducing overall operating pressure while maintaining high recovery rate.
Solution Approach 2:
The system changes pressure parameters across different stages, using appropriate pressure levels for each separation step. This allows achieving high recovery rate without subjecting the entire system to high operating pressure.
3Area of stationary object
If a membrane with high permeation rate is used, then the membrane area and operating pressure can be reduced, but the gas separation selectivity decreases
Solution Approach 1:
Different membrane units with different selectivity characteristics are used in sequence. The first unit may use a membrane with higher permeation rate and moderate selectivity, while subsequent units use membranes with progressively higher selectivity. This segmentation allows the system to achieve high overall selectivity without requiring any single membrane to have both high permeation rate and high selectivity.
Solution Approach 2:
The system changes membrane selection and operating parameters across stages to achieve the desired separation. By appropriately selecting membranes and adjusting parameters for each stage, the system achieves high gas separation selectivity without requiring excessively large membrane area.
4Reliability
If multiple gas separation membrane units are used in series, then the purity and recovery rate are improved, but the system complexity and cost increase
Solution Approach 1:
The system is segmented into a specific number of stages (typically 2-4 stages) which provides optimal balance between performance and complexity. Each stage is relatively simple in design, but their series combination achieves high purity and recovery rate without excessive overall complexity.
Solution Approach 2:
By optimizing the number of stages and the parameters of each stage, the system achieves high purity and recovery rate with minimal necessary complexity. The parameter optimization ensures that adding more stages beyond the optimal number does not provide sufficient benefit to justify the increased complexity and cost.
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 system achieves high-purity methane production at a reduced cost by minimizing membrane area and power consumption, while maintaining high recovery rates and selectivity through controlled temperature differences between the units.
Implementation Method 1
a membrane separation method based on the difference between the gas permeation rates of the gases through a membrane
Implementation Method 2
a gas separation membrane having gas permselectivity
Implementation Method 3
a cooling part for lowering an operating temperature of the second gas separation membrane unit, T2, below an operating temperature of the first gas separation membrane unit, T1
Data Source
Figure 1~3
Figure 4~6
AI summary
A gas separation system 10 for producing a CH4-enriched gas from a feedstock gas containing CO2 and CH4, comprising a first gas separation membrane unit 11 and a second gas separation membrane unit 12, wherein the gas separation system 10 comprises: a feedstock gas supply line 26 connected to a gas inlet 11a of the first gas separation membrane unit 11; a compression part 21 disposed in the feedstock gas supply line 26; a first line 14 connecting the retentate gas outlet 11b of the first gas separation membrane unit 11 and the gas inlet 12a of the second gas separation membrane unit 12; a second line 17 connecting the permeate gas outlet 12c of the second gas separation membrane unit 12 and the feedstock gas supply line 26; and a cooling part 22 for lowering the operating temperature of the second gas separation membrane unit below the operating temperature of the first gas separation membrane unit.