Dynamic operation of an Integrated Direct Air Capture and CO2 Compression System

Abstract

CO2 concentration in the atmosphere has soared since the industrial era owing to the rapid and unabated increase in fossil fuel consumption globally. This has resulted in an increase in global average temperature by ≈ 1.1 C in this period; and has sparked the concern of climate disaster events across the globe. In order to tackle the issue of climate change, research into Carbon dioxide removal (CDR) technology such as Carbon Capture and Storage (CCS) and Carbon Capture and Utilization (CCU) has gained prominence.

Zero Emission Fuels (ZEF) B.V is a technology startup based in Delft, working on the CCU pathway for CDR. ZEF is developing micro plants to capture CO2 and H2O from the atmosphere using Direct Air Capture (DAC) system. The captured CO2 is then compressed to 50bar using compressors while
H2O is split electro-chemically to H2 at 50bar. This high-pressure CO2 and H2 are then used to produce methanol. The energy for the whole process is derived from the sun, making the entire process sustainable and emission-free.

ZEF’s micro-plant will derive its raw materials i.e. CO2 and H2O, from the environment. Thus, variation in the environmental conditions, i.e., humidity, temperature, and solar radiation (external disturbances
for the system), will affect the overall system output. Current work focused on the design of control scheme for the integrated DAC and CO2 compression system, which will be able to meet ZEF’s performance target. The effect of variation in solar radiation was not considered for this work.

At first, the performance parameters for the various sub-systems of the integrated DAC+FM system were identified. With this information, the operating scenarios and the process constraints for the system
were identified. Then, models for the sub-systems of the DAC and compressor system, i.e., Absorber, sump, desorber, flash tank, and compressor system were developed. Parts of the model, the desorber and flash tank, were validated using experimental setup developed by integrating the existing DAC prototype at ZEF with a representative compression system.

The main target of the experimental setup was to develop control scheme to maintain the pressure of the flash tank to the required target levels. Through multiple iterations, the final layout and control system
for the integrated setup was identified which was able to control the pressure of the flash tank at the
target level.

Finally, a control scheme for DAC production control was developed based on the steady-state output from the desorber model. Through this, the feed and power (heat) input to the desorber is varied to control the production of CO2 and H2O.

The system model developed as part of this work can be further used as a tool by ZEF to integrate different sub-systems, test the performance of different sorbents and assess the viability of different control schemes for the integrated system