Gas Separation Membrane System with Recycled Permeate
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional gas separation systems for producing CH4 enriched gas from CO2 and CH4 face challenges in reducing compression power and membrane area while maintaining high recovery rates and purity, as increasing the CH4 recovery rate leads to higher gas flow rates and increased compression power, and reducing membrane area requires increased compression power.
Innovation Solution
A gas separation system comprising two gas separation membrane units with specific gas separation selectivity and membrane configurations, including a first and second gas separation membrane unit connected in series, where the second gas separation membrane unit's permeated gas is recycled back to the first unit, and the non-permeated gas from the second unit is reintroduced into the material gas feed line, with a compression means interposed in the material gas feed line and a second compression means for the permeated gas, achieving a CH4 recovery rate of 98% or higher and CO2 content of 5 mol% or less in the non-permeated gas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the CH4 recovery rate is increased, then the CH4 enriched gas purity is improved, but the gas flow rate increases and compression power increases
Solution Approach 1:
The gas separation process is divided into two distinct stages using two separate membrane units. The first unit handles bulk separation while the second unit refines the permeated gas stream, allowing optimized operation of each stage without requiring excessive compression power for the entire system.
Solution Approach 2:
The system changes operational parameters by controlling the feed flow rate ratio between the two membrane units and adjusting the compression pressure at specific stages. This allows the system to achieve high CH4 recovery (98% or higher) and purity (CO2 content ≤5 mol%) while suppressing overall compression power consumption.
2Device complexity
If the membrane area is reduced, then the system complexity is decreased, but compression power must be increased to maintain separation performance
Solution Approach 1:
By segmenting the separation function across two membrane units with different operational roles, the system achieves effective gas separation without requiring a single large membrane area. The first unit processes bulk material gas while the second unit optimizes the permeated stream, reducing total membrane area requirements.
Solution Approach 2:
The system optimizes compression power consumption by adjusting operational parameters including the feed flow rate ratio (F2/F1 ≤60%) and compression pressure at strategic points. This allows maintaining separation performance with reduced membrane area while suppressing compression power requirements.
3Productivity
If the feed flow rate ratio F2/F1 is increased, then the CH4 recovery rate is improved, but the gas flow rate increases and compression power increases
Solution Approach 1:
The system optimizes the feed flow rate ratio parameter (F2/F1) to ≤60% while adjusting compression pressure and membrane operational parameters. This parameter optimization enables achieving CH4 recovery rates of 98% or higher and CO2 content of ≤5 mol% without causing excessive compression power consumption.
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 effectively suppresses compression power and reduces membrane area while achieving high CH4 recovery rates and purity, with the gas separation selectivity of 30 or greater and a feed flow rate ratio of 60% or less, allowing for efficient production of CH4 enriched gas.
Implementation Method 1
The permeation rate—which is the volume of permeation of each of CO2 and CH4 contained in the material gas through the membrane per unit membrane area, unit time and unit partial pressure difference—can be expressed respectively as P′CO2 and P′CH4
Data Source
AI summary
A gas separation system includes: a first gas separation membrane unit; a second gas separation membrane unit; a material gas feed line connected to a gas inlet port of the unit; a first compressor interposed to the line; a first connection line connecting a permeated gas discharge port of the unit and a gas inlet port of the unit; and a second connection line connecting a non-permeated gas discharge port of the unit and the line. The unit and unit each have a gas separation selectivity of 30 or greater. The CH4 recovery rate is 98% or higher. The CO2 content in non-permeated gas of the unit is 5 mol % or less. The flow rate of gas fed to the unit is 60% or less of the flow rate of material gas fed to the unit.