Adsorption-based CO 2 capture has enjoyed considerable research attention in recent years. Most of the research efforts focused on sorbent development to reduce the energy penalty. However, the use of suitable gas−solid contacting systems is key for extracting the full potential from the sorbent to minimize operating and capital costs and accelerate the commercial deployment of the technology. This paper reviews several reactor configurations that were proposed for adsorptionbased CO 2 capture. The fundamental behavior of adsorption in different gas−solid contactors (fixed, fluidized, moving, or rotating beds) and regeneration under different modes (pressure, temperature, or combined swings) is discussed, highlighting the strengths and limitations of different combinations of gas−solid contactor and regeneration mode. In addition, the estimated energy duties in published studies and current technology readiness level of the different reactor configurations are reported. Other aspects, such as the reactor footprint, the operation strategy, suitability to retrofits, and the ability to operate under flexible loads are also discussed. In terms of future work, the key research need is a standardized techno-economic benchmarking study to calculate CO 2 avoidance costs for different adsorption technologies under standardized assumptions. Qualitatively, each technology presents several strengths and weaknesses that make it impossible to identify a clear optimal solution. Such a standardized quantitative comparison is therefore needed to focus on future technology development efforts.

Hydrodynamic simulations of a pseudo-2D bubbling fluidized bed were carried out and compared to experiments conducted over a wide range of flow conditions. The primary purpose of this study was to assess the generality of the standard 2D Two Fluid Model (TFM) closed by the Kinetic Theory of Granular Flows (KTGF) which is regularly used in the literature to simulate bubbling fluidized beds. Comparisons of the bed expansion ratio over wide ranges of fluidization velocity, bed loading and particle size showed systematic differences between simulations and experiments, indicating that the generality of this modelling approach is questionable. More detailed flow velocity measurements collected via Particle Image Velocimetry (PIV) showed that the model greatly over-predicts flow velocities in the bed. Subsequent 3D simulations showed this over-prediction to be the result of 2D simulations neglecting the wall friction at the front and back walls of the pseudo-2D bed.

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This paper experimentally demonstrates the feasibility of a novel Gas Switching Combustion (GSC) reactor as an alternative to the traditional Chemical Looping Combustion (CLC) process for power production with integrated CO2 capture. Whereas the CLC process circulates an oxygen carrier material between two fluidized bed reactors where it is exposed to separate fuel and air streams, the GSC concept employs a single dense fluidized bed reactor where the oxygen carrier is periodically exposed to fuel and air streams. A lab-scale GSC reactor was operated autothermally (without any external temperature supply) to continuously convert cold feed gasses into hot product gasses which would be suitable for driving a downstream power cycle. A parametric study was carried out to further investigate the behaviour of the GSC concept. The reactor achieved a high CO2 capture efficiency (97.2%) and purity (98.2%) even without the use of a purging stage between the oxidation and reduction stages. A small amount of carbon deposition (around 1%) had a slight negative effect on the CO2 capture efficiency. Finally, the operation of a cluster of GSC reactors capable of delivering two steady process streams to downstream process equipment was discussed. IntroductionSince the start of the second industrial revolution, fossil fuels have driven the global economy to expand by a factor of 50 (1), leading to a 500% increase in population and an 800% increase in per-capita consumption. Today, 150 years later, the global economy remains totally dependent on fossil fuels, deriving fully 87% (2) of its primary energy consumption from oil, coal and natural gas. Fossil fuel consumption is still rapidly increasing while the use of renewable energy sources (primarily hydroelectricity) still contributes only 8% to the global energy production. All major energy roadmaps (3-6) project this trend to continue up to 2030 and beyond.

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This paper reports the experimental demonstration of the novel swing adsorption reactor cluster (SARC) concept in a multistage fluidized bed reactor with inbuilt heat-transfer surfaces for postcombustion CO2 capture at a capacity up to 24 kg-CO2/day. SARC employs combined temperature and vacuum swings (VTSA), driven by heat and vacuum pumps, to regenerate the solid sorbent after CO2 capture. The laboratory-scale reactor utilized a vacuum pump and a heating oil loop (emulating the heat pump) to demonstrate 90% CO2 capture from an N2/CO2 mixture approximating a coal power plant flue gas fed at 200 NL/min. In addition, dedicated experiments demonstrated three important features required for the success of the SARC concept: (1) the polyethyleneimine sorbent employed imposes no kinetic limitations in CO2 adsorption (referred to as carbonation) and only minor nonidealities in regeneration, (2) a high heat-transfer coefficient in the range of 307–489 W/m2 K is achieved on the heat transfer surfaces inside the reactor, and (3) perforated plate separators inserted along the height of the reactor can achieve the plug-flow characteristics required for high CO2 capture efficiency. Finally, sensitivity analysis revealed the expected improvements in CO2 capture efficiency with increased pressure and temperature swings and shorter carbonation times, demonstrating predictable behavior of the SARC reactor. This study provides a sound basis for further scale-up of the SARC concept.

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