Subambient CO2 Separation With Membrane-Based Adsorber Regeneration
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Solution Overview
Problem
Current methods for purifying oxycombustion flue gases at subambient temperature are inefficient, particularly in regenerating adsorption units and recycling permeate, leading to suboptimal energy usage and CO2 recovery.
Innovation Solution
Recycling permeate into the feed gas compressor at an inter-stage and using multiple membrane separators in series to improve energy efficiency and CO2 recovery, with specific temperature control and heat management strategies to enhance the process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the adsorption unit is regenerated by sending dry gas through the bed, then the accumulated humidity is eliminated, but significant energy is consumed for heating and cooling cycles
Solution Approach 1:
The patent changes the temperature parameter by operating the membrane separator at subambient temperatures (below ambient temperature) instead of conventional temperatures. This parameter change allows the system to condense water vapor during regeneration without requiring extensive heating, thereby reducing the energy consumption for heating and cooling cycles while maintaining effective adsorption unit regeneration
Solution Approach 2:
The patent utilizes phase transitions of water vapor by operating at subambient temperatures where water vapor condenses into liquid form during the regeneration process. This phase transition from vapor to liquid occurs naturally at the lower operating temperature, eliminating the need for additional heating steps and reducing overall energy consumption in the adsorption unit regeneration cycle
2Reliability
If permeate is recycled to the boiler or environmental island, then impurities are handled efficiently, but the pressure of the permeate is wasted
Solution Approach 1:
The patent applies self-service by having the permeate stream perform dual functions: it regenerates the adsorption unit (removing impurities) and simultaneously provides pressure energy to drive part of the compression process. The high-pressure permeate from the membrane separator is routed to drive a compressor, allowing the system to utilize its own pressure energy rather than discarding it, thereby reducing external energy requirements
Solution Approach 2:
The patent merges two functions into a single integrated system: the permeate stream simultaneously serves for adsorption unit regeneration and as a power source for compression. By combining the regenerative function with the energy recovery function in one unified process flow, the system eliminates the waste of permeate pressure while maintaining effective impurity handling
3Productivity
If low temperature operation is used in membrane system, then CO2 recovery efficiency is improved, but the system complexity increases
Solution Approach 1:
The subambient temperature membrane separator performs multiple functions simultaneously: it separates CO2 from the gas stream, condenses water vapor for adsorption unit regeneration, and produces high-pressure permeate for driving the compressor. By making the membrane system multi-functional, the patent achieves high CO2 recovery efficiency without proportionally increasing system complexity, as one piece of equipment accomplishes several critical tasks
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 energy efficiency, maintains high CO2 recovery rates, and reduces the need for ASU production by valorizing permeate pressure and optimizing the use of light components, while improving the overall thermodynamic efficiency of the system.
Implementation Method 1
The separated stream is sent to a membrane separator (21) to produce a permeate stream (25) and a non-permeate stream (23)
Implementation Method 2
The dried stream (11) is cooled in a heat exchanger (13)
Implementation Method 3
The dried flue gas is sent from the adsorption unit to the separation unit to be separated by subambient temperature distillation using at least one phase separator
Data Source
Figure 1
Figure 2
AI summary
In a process for the separation of a stream containing carbon dioxide, water and at least one light impurity including a separation step at subambient temperature, the feed stream (1, 3) is compressed in a compressor (C1, C2, C3) comprising at least two stages to form a compressed feed stream (7), the compressed feed stream is purified in an adsorption unit (A1, A2) to remove water and form a dried compressed stream (9, 11), the dried compressed stream or a stream derived therefrom is cooled to a subambient temperature and separated by partial condensation and/or distillation in a separation apparatus (19, 31), liquid enriched in carbon dioxide (37, 43) is removed from the separation apparatus, the adsorption unit is regenerated using a regeneration gas (25, 53) and the regeneration gas is formed by separating,by permeation in a permeation unit (21, 51), the dried compressed stream (9) or a gas (19) derived therefrom, the permeate of the permeation unit constituting the regeneration gas.