Two-Step CO2 Sorption Using Amine Adsorbents
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Solution Overview
Problem
Direct air capture of CO2 faces challenges due to low CO2 concentrations in the atmosphere, leading to high material costs and energy requirements, and combining it with point source capture is complicated by the need for heating and potential sorbent degradation.
Innovation Solution
A two-step sorption process where air is first captured at ambient conditions, followed by exposure to a CO2-rich flue gas stream for additional sorption, allowing for increased CO2 loading without prior heating and minimizing sorbent degradation, using amine sorbents and managing temperature and oxygen levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If direct air capture is performed using conventional amine sorbents, then CO2 can be captured from atmospheric air, but the low CO2 concentration (400 vppm) results in high material costs and high energy requirements per CO2 molecule captured
Solution Approach 1:
The sorption process is divided into two sequential stages: first capturing CO2 from air at ambient conditions to achieve partial loading, then capturing additional CO2 from a CO2-rich flue gas stream at elevated temperatures to achieve full loading. This segmentation allows each stage to operate under optimal conditions, improving overall efficiency and reducing energy consumption per CO2 molecule captured.
Solution Approach 2:
The invention changes the temperature parameter during the sorption process. The first stage operates at ambient temperature (20-25°C) to capture CO2 from air, while the second stage operates at elevated temperature (40-80°C) to capture additional CO2 from flue gas. This parameter change optimizes the sorption capacity and kinetics at different stages, reducing the energy required per CO2 molecule captured.
2Productivity
If CO2-rich flue gas is used to enhance sorbent loading, then CO2 capture efficiency increases, but heating the sorbent and exposing it to oxygen-containing gas can cause sorbent degradation
Solution Approach 1:
The sorbent is first exposed to CO2-rich flue gas at ambient or near-ambient conditions to achieve partial loading before any heating occurs. This preliminary action allows the sorbent to accumulate CO2 without thermal stress, and then subsequent heating is applied to achieve full loading while minimizing degradation by limiting the time at elevated temperatures.
Solution Approach 2:
The invention employs periodic cycling between sorption stages and regeneration stages. During sorption, CO2 is captured from air and flue gas in sequence. During regeneration, the sorbent is heated to release CO2, then cooled and reactivated. This periodic action allows the sorbent to be exposed to elevated temperatures only during brief regeneration intervals, minimizing cumulative thermal degradation while maintaining high capture efficiency.
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 CO2 capture efficiency, reduces energy consumption, and increases sorbent productivity, enabling the capture of over 100% of CO2 from point sources while minimizing sorbent degradation and operational costs.
Implementation Method 1
exposing a first gas flow containing 15 vol % to 25 vol % O2 and 100 vppm to 800 vppm CO2 to one or more amine sorbents
Implementation Method 2
one or more partially loaded amine sorbents having a first sorbent loading of CO2 sorbed
Implementation Method 3
heating the sorbent environment to a temperature of 85° C. or higher to desorb at least a portion of the CO2
Implementation Method 4
desorb at least a portion of the CO2 from the one or more additionally loaded amine sorbents
Implementation Method 5
passing a purge gas flow through the sorbent environment. Steam is an example of a purge gas flow
Data Source
AI summary
Systems and methods are provided for integrating direct air capture of carbon dioxide with capture of carbon dioxide from a point source. The systems and methods can include exposing an adsorbent to a low CO2 content gas flow (e.g., air) at conditions similar to ambient conditions to perform an initial amount of sorption of CO2. The initial sorption results in a partially loaded sorbent having a first sorbent loading. The partially loaded sorbent can then be exposed to a flue gas and/or other gas flow that contains a higher CO2 content. This allows a second sorption step to be performed using a higher CO2 content gas, resulting in an additionally loaded sorbent having a second (higher) sorbent loading. The sorbed CO2 can then be desorbed from the sorbent.