Membrane-Cryogenic CO2 Separation for Low-Energy Flue Gas Recovery
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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, especially in flue gases from pulverized coal power plants, where no technology effectively removes at least 90% of CO2 with less than a 35% increase in electricity costs.
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 to produce a carbon dioxide-rich stream, and then subjected to cryogenic phase separation, utilizing a sweep gas and integrated cooling to enhance efficiency, with the option to compress and condense the stream to produce a CO2-rich liquid and lean vapor, while using the carbon dioxide-lean stream for further cooling and energy recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
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 process efficiency decreases
Solution Approach 1:
The patent combines membrane separation and distillation processes into an integrated hybrid system where the membrane unit operates at lower temperatures and pressures to pre-concentrate CO2, and the distillation unit completes the separation. This merging eliminates the need for separate temperature and pressure adjustments between isolated processes, reducing overall energy consumption while maintaining high CO2 recovery efficiency.
Solution Approach 2:
The membrane separation process performs preliminary concentration of CO2 from the flue gas before the distillation step. By using the membrane to pre-enrich the CO2 stream at milder conditions, the subsequent distillation requires less energy to achieve the final separation, thereby reducing total energy requirements while improving overall productivity.
2Loss of energy
If multiple separate methods are used for CO2 removal, then separation is achieved, but integration for energy savings is overlooked and costs increase
Solution Approach 1:
The patent integrates membrane separation and distillation into a unified hybrid process system with coordinated operation. The membrane unit and distillation column are coupled such that the membrane permeate feeds directly into the distillation feed, creating an integrated flow path that recovers energy internally and reduces external energy inputs while achieving effective CO2 separation.
Solution Approach 2:
The hybrid system design allows the same process configuration to handle varying CO2 concentrations in flue gas from different sources. The membrane-distillation integration provides multi-functionality by adapting to different feed conditions while maintaining energy efficiency, reducing the need for separate specialized processes for different applications.
3Productivity
If conventional CO2 removal technologies are applied to pulverized coal power plants, then some CO2 is removed, but less than 90% recovery is achieved with more than 35% increase in electricity costs
Solution Approach 1:
The patent changes the operating parameters of the separation process by using membrane separation at lower temperatures and pressures to pre-concentrate CO2 before distillation. This parameter optimization allows the system to achieve greater than 90% CO2 recovery from pulverized coal flue gas while keeping the electricity cost increase below 35%, as the membrane step reduces the energy burden on the distillation unit.
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 energy consumption by utilizing the carbon dioxide-lean stream for cooling, thereby improving the overall efficiency and cost-effectiveness of the process.
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
Implementation Method 2
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.