Process Optimization of a Fixed Bed Reactor System for Direct Air Capture

Michel Schellevis,Tim Van Schagen,Wim Brilman

doi:10.2139/ssrn.3821508

Abstract

The extraction of CO2 directly from the atmosphere (Direct Air Capture) is commonly employed using supported amine sorbents. This adsorption technology is under rapid development with novel sorbents materials emerging and with processes being demonstrated on increasingly larger scale. Optimization of such processes require accurate knowledge on sorbent characteristics and knowledge on how operational variables change process performance. This study is primarily focused on the latter, where we aim to quantify the influence of operational parameters on the energy duty and CO2 productivity. In addition, we examined the influence of weather conditions on the adsorption rate. For this, we developed a dynamic model of the complete temperature-pressure swing adsorption cycle (TPSA). The model is validated by experimental results on a kg-scale direct air capture system. The impact of selected operational variables is assessed by two-dimensional sensitivity analyses. We show that desorption temperature is preferably high, limited by the chemical stability of the sorbent material in this particular case. In addition, the sorbent working capacity should be large when opting for an optimization towards energy duty, whereas it reaches a clear optimum in terms of CO2 productivity. Finally, we conclude that weather conditions and diurnal variations can significantly affect the performance of a direct air capture process and should certainly be considered during design and operation. With these insights and the developed model, this study provides a sound basis for further process development and optimization of direct air capture using fixed bed technology combined with solid amine sorbents.

Highlights

Direct Air Capture (DAC), the extraction of CO2 directly from the atmosphere, is considered an important technology in climate change mitigation (Breyer et al, 2019; Lackner et al, 2012; Beuttler et al, 2019)
Two major technologies are considered for DAC on commercial scale: absorption using alkaline so lutions and adsorption using amine-functionalized solid sorbents (Keith et al, 2018; Zeman, 2007; Socolow, 2011; Gebald et al, 2011; Fasihi et al, 2019; Goeppert et al, 2012; Bajamundi et al, 2019)
Treated air is released back into the laboratory. This leads to a slight decrease in CO2 concentration of the ingoing air in the early stage of adsorption when the released air is very lean in CO2

Summary

Introduction

Direct Air Capture (DAC), the extraction of CO2 directly from the atmosphere, is considered an important technology in climate change mitigation (Breyer et al, 2019; Lackner et al, 2012; Beuttler et al, 2019). DAC is a technology that enables zero or negative emission technologies, because a sustainable carbon source is acquired. These carbon sources are necessary to produce limitless products, food, feed and materials of our everyday life (Speight, 2011). Two major technologies are considered for DAC on commercial scale: absorption using alkaline so lutions and adsorption using amine-functionalized solid sorbents (Keith et al, 2018; Zeman, 2007; Socolow, 2011; Gebald et al, 2011; Fasihi et al, 2019; Goeppert et al, 2012; Bajamundi et al, 2019). Absorption with alkaline solutions was the proposed technology by Lackner et al (1999). Sorbent development is domi nating research efforts in this research area (Choi et al, 2009; D’Ales sandro et al, 2010; Gelles et al, 2020; Sanz-Perez et al, 2016; Singh et al, 2020)

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Results

Conclusion