Membrane Biogas Purification Using Gas-Gas Ejector Compression
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Solution Overview
Problem
Current membrane separation technologies for biogas purification face challenges in achieving high methane yield and low cost while minimizing methane losses and electrical consumption, particularly in balancing the pressure requirements across multiple stages to optimize performance and reduce membrane module installation.
Innovation Solution
The proposed installation and process involve a three-stage membrane separation system with a gas-gas ejector to increase the pressure of the first permeate to between 2 and 6 bar, allowing for improved performance and reduced membrane surface area, thereby minimizing costs and maintaining high methane yield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the pressure of the first permeate is increased to improve the performance of the third stage membrane separation, then the productivity and methane yield are improved, but the use of energy increases due to compression requirements
Solution Approach 1:
The patent combines the compression function with the membrane separation process by using the retentate stream from an earlier stage as the driving gas for a jet compressor. This merging of functions allows the system to achieve necessary pressure increases without external electrical compression, resolving the contradiction between productivity improvement and energy consumption.
Solution Approach 2:
The system uses its own process streams (the pressurized retentate from previous stages) to provide the compression power needed for subsequent stages. The high-pressure retentate self-propels the first permeate through the jet compressor, making the system self-sufficient and eliminating external energy input for compression.
2Manufacturing precision
If a three-stage membrane system is used to improve methane purification quality, then the purity of methane is improved, but the device complexity increases
Solution Approach 1:
Each membrane stage is designed to perform multiple functions: separation of CO2 from methane, pressurization of the permeate stream, and provision of driving gas for the jet compressor. This multi-functionality reduces the need for separate dedicated components, thereby reducing overall device complexity while maintaining high methane purity.
Solution Approach 2:
The jet compressor acts as an intermediary device that couples the membrane separation stages. It uses the pressurized retentate as a mediator to transfer energy and momentum to the permeate stream, enabling the system to achieve the required pressure levels without adding complex external compression equipment.
3Ease of manufacture
If the membrane surface area is reduced to lower investment costs, then the manufacturing cost is reduced, but the separation performance deteriorates
Solution Approach 1:
The patent changes the pressure parameter of the permeate stream by using jet compression to increase it from near-atmospheric pressure to several bar. This parameter change enhances the driving force for mass transfer across the membrane, improving separation performance without requiring larger membrane surface areas, thus reducing investment costs.
Solution Approach 2:
The system employs pneumatic compression using high-pressure gas (retentate stream) to drive the compression of the permeate stream through a jet compressor. This pneumatic approach replaces traditional mechanical compression, reducing equipment complexity and cost while achieving the necessary pressure increase to maintain high separation performance with smaller membrane areas.
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 enhances methane yield and reduces investment costs by optimizing the pressure of the first permeate, allowing for efficient methane enrichment while minimizing methane losses and electrical consumption, thus achieving a more cost-effective and efficient biogas purification process.
Implementation Method 1
a first membrane separation unit (1) making it possible to receive the feed gas stream and to produce a first permeate (4) enriched in carbon dioxide and a first retentate (7) enriched in methane
Implementation Method 2
a gas-gas ejector (11) making it possible to increase the pressure of the first permeate (4) to a pressure comprised between 2 and 6 bar
Data Source
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AI summary
Installation for the treatment by membrane permeation of a feed gas stream (6) comprising at least methane and carbon dioxide to produce a methane-enriched gas stream (12) comprising: - a first membrane separation unit (1) for receiving the feed gas stream and producing a first permeate (4) enriched in carbon dioxide and a first retentate (7) enriched in methane, - a second membrane separation unit (2) for receiving the first retentate (7) and producing a second permeate (5) enriched in carbon dioxide and a second retentate (8) enriched in methane, - a gas-gas ejector (11) for increasing the pressure of the first permeate (4) to a pressure between 2 and 6 bar, more preferably between 3 and 4 bar.- a third membrane separation unit (3) allowing the first permeate (4) compressed in the ejector to be received and a third retentate (9) enriched in methane and a third permeate (10) enriched in CO2 to be produced.