Two-Stage Membrane Separation for Low-Concentration CO2 Recovery
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Solution Overview
Problem
Integrated coal gasification combined cycle power generation faces challenges in efficiently separating CO2 from mixed gases with low CO2 concentrations, as existing separation membranes lack sufficient selectivity and increase construction and operation costs.
Innovation Solution
A method involving a two-stage membrane separation process using a first separation membrane with high H2/CO2 selectivity and a second membrane with high CO2/H2 selectivity, followed by chemical absorption in a CO2 collector to enhance CO2 recovery rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If chemical absorption using an amine absorbent is adopted to collect CO2, then CO2 collection efficiency is improved, but construction and operation costs increase and facility size increases
Solution Approach 1:
The patent replaces the mechanical/chemical absorption system (amine absorbent) with a membrane-based separation system that utilizes selective permeability properties. The membrane module separates CO2 from the mixed gas through physical membrane separation, eliminating the need for large-scale chemical absorption facilities and reducing both construction costs and operational complexity.
Solution Approach 2:
The patent employs a membrane with specific porous structure and selective permeability to separate CO2 from the mixed gas. The membrane material allows CO2 to pass through selectively while retaining other gases, enabling efficient CO2 collection without requiring large chemical absorption facilities.
2Device complexity
If air-blown gasification is used to eliminate oxygen extraction plant, then construction and operation costs are reduced, but CO2 concentration in produced gas becomes low
Solution Approach 1:
The patent replaces conventional CO2 separation methods with membrane-based separation that is specifically effective for low-concentration CO2 streams. The membrane module achieves high CO2 recovery rates even when CO2 concentration in the feed gas is low, as is the case with air-blown gasification.
Solution Approach 2:
The patent utilizes the selective permeability parameters of the membrane material to achieve separation based on gas composition differences. By optimizing membrane selection and operational parameters, the system achieves effective CO2 separation from low-concentration mixed gases produced by air-blown gasification.
3Productivity
If high-selectivity separation membranes are used to separate CO2 from low-concentration mixed gas, then CO2 separation efficiency is improved, but membrane cost and device complexity increase
Solution Approach 1:
The patent segments the CO2 separation process into multiple stages using multiple membrane modules arranged in series. Rather than requiring a single high-selectivity membrane, the system uses multiple membranes with moderate selectivity working together, which reduces individual membrane cost and complexity while achieving high overall separation efficiency.
Solution Approach 2:
The patent transitions from considering only membrane selectivity as the separation parameter to utilizing multi-stage configuration and gas recirculation as additional dimensions of separation enhancement. This multi-dimensional approach allows the use of less expensive membranes with lower individual selectivity while achieving the required overall separation performance.
4Productivity
If hydrogen separation membrane is used to separate H2 from mixed gas, then H2 recovery is improved, but CO2 permeability is inhibited and off-gas requires explosion-proof construction
Solution Approach 1:
The patent segments the gas separation process into distinct stages: first separating H2 using a hydrogen separation membrane, then separating CO2 from the off-gas using a CO2 separation membrane. This segmentation prevents CO2 from inhibiting H2 separation and eliminates explosion risks by removing H2 before CO2 collection.
Solution Approach 2:
The patent extracts H2 from the mixed gas in a first separation stage using a hydrogen-selective membrane, removing the explosive component before the gas proceeds to CO2 separation. This extraction of H2 eliminates the explosion risk in subsequent CO2 collection facilities while maintaining high H2 recovery rates.
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 efficiently separates CO2 from mixed gases with low CO2 concentrations, reducing the need for high-selectivity membranes and simplifying the CO2 collector structure, while achieving high CO2 recovery rates and lowering operational costs.
Implementation Method 1
supplying a mixed gas containing at least N2, H2, and CO2 and having a CO2 concentration of 30% or less by volume to a first separation membrane that selectively allows passage of H2
Implementation Method 2
supplying the first non-permeated gas to a second separation membrane that selectively allows passage of CO2
Implementation Method 3
supplying the second non-permeated gas to a CO2 collector that separates and collects CO2 by a separation method other than membrane separation
Data Source
AI summary
A mixed gas separation method includes supplying a mixed gas containing at least N2, H2, and CO2 and having a CO2 concentration of 30% or less by volume to a first separation membrane that selectively allows passage of H2, supplying the first non-permeated gas to a second separation membrane that selectively allows passage of CO2, and supplying the second non-permeated gas to a CO2 collector that separates and collects CO2 by a separation method other than membrane separation to collect CO2 contained in the second non-permeated gas. The first non-permeated gas has a CO2 concentration that is 5% or more by volume higher than or equal to the CO2 concentration in the mixed gas. The second non-permeated gas has an N2 concentration of 50% or more by volume and an H2 concentration of 30% or less by volume.