Membrane-Cryogenic CO2 Separation for High-Recovery Flue Gas Capture
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Solution Overview
Problem
Current methods for recovering CO2 from effluent gas streams are inefficient due to the lack of integration between membrane separation and distillation processes, leading to high energy requirements and limited CO2 recovery rates, especially in flue gases from coal power plants.
Innovation Solution
A method combining gas membrane separation using polymeric materials with cryogenic phase separation, where a CO2-containing gas mixture is cooled, passed through a gas separation membrane, and then subjected to cryogenic phase separation to produce a CO2-rich liquid, utilizing a sweep gas and integrated cooling to optimize energy efficiency and increase CO2 recovery rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If membrane separation and distillation are performed in isolation with temperature and pressure adjustments before each process, then CO2 separation is achieved, but energy requirements become excessive and efficiency is reduced
Solution Approach 1:
The patent combines membrane separation and distillation processes into an integrated system where the membrane unit operates at higher temperatures and pressures to produce a CO2-rich stream that is directly fed to the distillation column. This eliminates intermediate cooling and compression steps, reducing energy consumption while maintaining high CO2 recovery efficiency through the synergistic operation of both separation mechanisms.
Solution Approach 2:
The membrane separation process performs preliminary concentration of CO2 from the flue gas before the distillation step. By pre-concentrating CO2 to 40-60% through membrane separation at elevated temperature and pressure, the subsequent distillation requires less energy to achieve the desired purity, as it only needs to separate a more concentrated stream rather than dealing with dilute flue gas directly.
2Quantity of substance
If multiple separation methods are used to increase CO2 content prior to cooling, then CO2 concentration is improved, but integration of methods for energy savings is overlooked and operational complexity increases
Solution Approach 1:
The patent merges membrane separation and distillation into a single integrated flow path where the membrane permeate (CO2-rich stream) is directly fed to the distillation column without intermediate processing steps. This unified approach simplifies process control and operation while achieving high CO2 concentration (90%+ purity) through the combined separation effects of both units working in sequence.
3Quantity of substance
If flue gas from coal power plants is processed for CO2 recovery, then CO2 capture is achieved, but electricity cost increases by more than 35%
Solution Approach 1:
The patent changes the operating parameters of the membrane separation process by operating at elevated temperatures (50-150°C) and pressures (5-50 bar), which enhances CO2 permeability and selectivity. This allows the membrane unit to produce a highly concentrated CO2 stream (40-60%) that requires minimal further processing, thereby reducing the energy input needed for subsequent distillation and overall electricity consumption while achieving >90% CO2 recovery.
Solution Approach 2:
The integrated system utilizes phase transitions in the distillation column where CO2 transitions between vapor and liquid phases to achieve high-purity separation. The membrane pre-concentration reduces the amount of material requiring phase change, and the distillation efficiently completes the separation by exploiting CO2's phase behavior at controlled temperatures and pressures, minimizing energy requirements.
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 integrated method achieves greater than 90% CO2 recovery from flue gases with a less than 35% increase in electricity costs, eliminating the need for external refrigeration and reducing operational expenses.
Implementation Method 1
The cooled gas mixture is allowed to flow into a gas separation membrane module made of a polymeric material to produce a carbon dioxide-rich stream and a carbon dioxide-lean stream. The polymeric material has a CO2 solubility at 35° C. and 10 bar pressure of >0.03 [(cm3 of CO2 at STP)/(cm3 of polymeric material)(cmHg)] and a glass transition temperature of >210° C.
Implementation Method 2
The compressed carbon dioxide-rich stream is at least partially condensed through cooling. The cooled, compressed carbon dioxide-rich stream is subjected to cryogenic phase separation to produce a CO2 rich liquid and a CO2 lean vapor stream.
Implementation Method 3
The cooled, compressed carbon dioxide-rich stream is subjected to cryogenic phase separation to produce a CO2 rich liquid and a CO2 lean vapor stream.
Data Source
AI summary
Disclosed are methods of obtaining carbon dioxide from a CO2-containing gas mixture. The methods combine the benefits of gas membrane separation with cryogenic temperatures.