Direct Air Capture Membrane Pretreatment to Limit Water Co-Adsorption
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Solution Overview
Problem
Conventional direct air capture (DAC) methods face inefficiencies due to water co-adsorption with carbon dioxide sorbents, leading to high energy consumption and economic inefficiencies.
Innovation Solution
A process and system that includes a selective water removal step using a membrane permeable to water, followed by direct air capture with a sorbent, and regeneration of both the sorbent and membrane using a sweep gas derived from the DAC process, reducing water content and energy requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a sorbent is used to capture carbon dioxide from air, then carbon dioxide capture is achieved, but water co-adsorption increases energy consumption
Solution Approach 1:
The patent applies preliminary action by introducing a water removal step before the carbon dioxide capture step. The air stream is pre-treated to remove water vapor using a desiccant or condensation step, so that when the air subsequently contacts the sorbent for CO2 capture, water co-adsorption is minimized. This preliminary water removal prevents the sorbent from becoming saturated with water, thereby reducing the energy required for regeneration.
Solution Approach 2:
The patent segments the direct air capture process into two distinct stages: (1) water removal from air using a desiccant material or condensation step, and (2) carbon dioxide capture using a sorbent. This segmentation allows each step to be optimized independently, with the water removal step preparing the air stream for more efficient CO2 capture in the second step, thereby reducing overall energy consumption.
2Use of energy by moving object
If water co-adsorption is reduced by alternative sorbent regeneration, then energy efficiency improves, but process complexity increases
Solution Approach 1:
The patent merges the water removal function and carbon dioxide capture function into a single integrated process flow. By placing a water removal step (using desiccant or condensation) directly upstream of the CO2 capture sorbent, the system achieves both water reduction and CO2 capture in one continuous process, avoiding the need for separate complex regeneration systems while improving energy efficiency.
Solution Approach 2:
The patent introduces an intermediary step (water removal using desiccant or condensation) between the air intake and the CO2 capture sorbent. This intermediary treatment modifies the air stream to remove water vapor before it reaches the sorbent, thereby reducing water co-adsorption and energy requirements for regeneration without significantly increasing overall process complexity.
3Use of energy by stationary object
If a water separation device is added to reduce water co-adsorption, then energy expenditure decreases, but device complexity increases
Solution Approach 1:
The patent applies local quality by targeting water removal specifically at the inlet stage of the CO2 capture process, rather than attempting to handle water throughout the entire system. By placing a water removal device (desiccant or condensation unit) only upstream of the sorbent, the system addresses water co-adsorption locally where it has the greatest impact on energy consumption, without adding complexity to other parts of the system.
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 process achieves energy-efficient and economically feasible carbon dioxide capture, producing clean air for emission and a purified carbon dioxide stream for sequestration or chemical synthesis, with reduced energy costs and sorbent regeneration needs.
Implementation Method 1
contacting air with a membrane that is selectively permeable for water, to obtain a retentate stream of air depleted in water
Implementation Method 2
subjecting the retentate stream of step (a) to a sorbent for direct air capture, to obtain a stream of air depleted in water and carbon dioxide
Implementation Method 3
regenerating the loaded sorbent of step (b), to obtain purified carbon dioxide stream and a regenerated sorbent
Implementation Method 4
regenerating the loaded membrane of step (a) by contacting the membrane with a sweep gas at reduced pressure
Data Source
Figure 1
AI summary
The inventors developed a process for the direct air capture of carbon dioxide wherein the problem of water co-adsorption is avoided. The process according to the invention comprises: (a) contacting air with a membrane that is selectively permeable for water, to obtain a retentate stream of air depleted in water and a membrane loaded with water; (b) subjecting the retentate stream of step (a) to a sorbent for direct air capture, to obtain a stream of air depleted in water and carbon dioxide and a sorbent loaded with carbon dioxide; (c) regenerating the loaded sorbent of step (b), to obtain purified carbon dioxide stream and a regenerated sorbent; (d) regenerating the loaded membrane of step (a) by contacting the membrane with a sweep gas at reduced pressure, wherein the sweep gas comprises at least part of the stream of air depleted in water and carbon dioxide obtained in step (b) and/or at least part of the purified carbon dioxide stream obtained in step (c). The process according to the invention is economically feasible, energy efficient and affords clean air, depleted in carbon dioxide, and a purified carbon dioxide stream. The invention further concerns a system for direct air capture.