Abstract
This thesis concerned the capture of CO2 from the atmosphere, which is also referred to as Direct Air Capture, in a steam-assisted temperature-vacuum swing adsorption process (S-TVSA). Harvesting CO2 from air is a method to acquire a sustainable carbon source to be used as raw material in a net zero CO2 emissions scenario. The objective of this thesis is the design and optimization of a DAC process using supported-amine sorbents.
The dilute nature of CO2 concentration in the atmosphere means that a huge amount of air must be processed. Efficient gas-solid contacting is therefore essential, which stands or falls with the design and operation of the gas-solid contactor. First, we compared and evaluated two operation modes of such a contactor: batch wise operation in a fixed bed or continuous operation in a cross-flow moving bed. The moving bed configuration showed a reduced capture efficiency compared to the fixed bed configuration.
The design of a Direct Air Capture pilot unit with a design capacity of 1 kgCO2/d was an important objective within this thesis. Fixed bed technology with multiple parallel adsorption beds was chosen to achieve semi-continuous operation. For the pilot unit under optimized constant operating conditions, a productivity of 0.27 kgCO2/kgs/d with an energy duty of 14.5 MJ/kgCO2 was obtained. A dynamic model of this process was developed and validated with experimental data. This model is subsequently used for process optimization.
Process optimization aims to minimize the cost of CO2 capture. Ambient conditions play an important role, because temperature and relative humidity influence the properties of the adsorbent. Therefore, the main objective of the optimization study is to evaluate the impact of climate conditions on the cost of CO2 capture. It was shown that climates with a higher average temperature are more beneficial for Direct Air Capture. Furthermore, varying seasonal conditions in temperate and continental climates require dynamic process control to minimize cost of Direct Air Capture.
The dilute nature of CO2 concentration in the atmosphere means that a huge amount of air must be processed. Efficient gas-solid contacting is therefore essential, which stands or falls with the design and operation of the gas-solid contactor. First, we compared and evaluated two operation modes of such a contactor: batch wise operation in a fixed bed or continuous operation in a cross-flow moving bed. The moving bed configuration showed a reduced capture efficiency compared to the fixed bed configuration.
The design of a Direct Air Capture pilot unit with a design capacity of 1 kgCO2/d was an important objective within this thesis. Fixed bed technology with multiple parallel adsorption beds was chosen to achieve semi-continuous operation. For the pilot unit under optimized constant operating conditions, a productivity of 0.27 kgCO2/kgs/d with an energy duty of 14.5 MJ/kgCO2 was obtained. A dynamic model of this process was developed and validated with experimental data. This model is subsequently used for process optimization.
Process optimization aims to minimize the cost of CO2 capture. Ambient conditions play an important role, because temperature and relative humidity influence the properties of the adsorbent. Therefore, the main objective of the optimization study is to evaluate the impact of climate conditions on the cost of CO2 capture. It was shown that climates with a higher average temperature are more beneficial for Direct Air Capture. Furthermore, varying seasonal conditions in temperate and continental climates require dynamic process control to minimize cost of Direct Air Capture.
| Original language | English |
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| Qualification | Doctor of Philosophy |
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| Award date | 21 Apr 2023 |
| Place of Publication | Enschede |
| Publisher | |
| Print ISBNs | 978-90-365-5584-5 |
| Electronic ISBNs | 978-90-365-5585-2 |
| DOIs | |
| Publication status | Published - 21 Apr 2023 |
