Mini-TORBED Technology for Carbon Capture Adsorbent Screening

Abstract

Carbon capture (CC) via fluidized bed reactors presents a promising avenue for mitigating CO2 emissions across the energy, industrial, and transportation sectors. This research focuses on developing and evaluating a small-scale and efficient CO2 capture screening platform employing a 3D-printed toroidal fluidized bed (TORBED) reactor. A commercial sorbent, based on branched polyethyleneimine (BPEI), was screened for capturing CO2 from artificial flue gas streams under a range of conditions. The adsorption screening experiments involved the introduction of various N2/ CO2 ratios into the TORBED reactor, and breakthrough curves were collected under different operating conditions, including CO2 volume fractions, BPEI bed loads, gas flow rates, and temperatures. In the hydrodynamic study, three potential industrial materials (RTI, Sasol, and Casale materials) were screened for compatibility with the TORBED reactor. The 'desirable flow regime' was quantified through methods such as visual observations, pressure drop analysis, and standard deviation analysis of pressure drop measurements, which provided insights into particle formations, flow stability, and uniform fluidization. Key results indicated that the RTI material exhibited optimal flow regimes with minimal pressure drop and high stability, making it the most suitable candidate for further adsorption and desorption studies. This comprehensive approach ensured the selection of an effective sorbent and optimal operating conditions for the TORBED reactor, contributing to advancements in carbon capture technology. In adsorption screening experiments, artificial flue gas streams comprising various N2/CO2 ratios were introduced into the TORBED reactor. Breakthrough curves were collected under different operating conditions, including CO2 volume fractions (ranging from 2 to 20 vol%), BPEI bed loads (1–2.5 g), gas flow rates (20–35 L/min), and temperatures (40–70 °C). The breakthrough curves provided insights into the sorption behaviour of BPEI under different conditions, facilitating the characterization of its adsorption capacity and kinetics. A maximum sorbent capacity of 2.64 ± 0.06 mmol/g was measured within experiment durations lasting no longer than 10 seconds. This rapid data collection rate highlights the potential for high throughput screening. Moreover, precise temperature control within the TORBED effectively minimized the influence of heat of adsorption on kinetics. Desorption, a critical aspect of CC, was then studied given its importance in the overall process and lack of relative attention compared to adsorption in the wider literature. The desorption characteristics of the commercial BPEI adsorbent were also investigated using breakthrough experiments, with a focus on studying the influence of heat transfer effects. Experimental results revealed that higher desorption temperature (110 °C), shorter preheating time (achieved with a gas flow rate of 25 L/min), and elevated CO2 concentrations during adsorption (20 vol%) improved the desorption efficiency significantly (defined as CO2 desorbed compared to the adsorbed amount). Kinetic modelling plays a crucial role in understanding and optimizing adsorption and desorption processes. Upon analysis of the cumulative uptake curves extracted from the breakthrough data, it was found that the fractional order kinetic model best matches the behaviour of the BPEI adsorbent compared to the pseudo-1st order and pseudo-2nd order models. This implies that both physisorption and chemisorption processes are responsible for the binding of the CO2 with the BPEI surface. This work reinforced by two published papers in the Chemical Engineering Journal—provides fundamental insights and practical solutions that directly contribute to more efficient, flexible, and economically viable CCS processes. 1. Jamei et al. (2023, Chem. Eng. J. 451:138405) demonstrated rapid and intensified screening of a branched polyethyleneimine (BPEI) adsorbent, achieving breakthrough measurements in a matter of seconds. This unprecedented speed of data collection allows for the rapid assessment of multiple sorbents and conditions, ultimately reducing the time and resources required for sorbent selection and optimization. 2. Jamei et al. (2024, Chem. Eng. J., 1385894724070591) addressed challenges related to small-scale Temperature Swing Adsorption (TSA) in CCS. The study showed that by tuning temperature profiles and flow regimes within the TORBED reactor, it is possible to enhance sorbent regeneration efficiency. In summary, this research highlights the potential use of small-scale TORBED technology for screening CC materials to advance carbon capture more generally. By investigating adsorption and desorption characteristics and employing kinetic modelling, this study offers valuable insights for example optimising desirable flow regime to uniform fluidisation of sorbents in entire bed area for enhancing the efficiency of CO2 capture and mitigating industrial emissions. Keywords: TORBED, Adsorption, swirling, carbon capture, Fluidisation, BPEI