(303o) Exploring Magnetically Stabilized Fluidized Bed Reactor for Enhanced Point Source CO2 Capture Using Alkali Metal Carbonate-Based Solid Sorbents

Despite the increasing use of renewable resources for power generation, natural gas and other fossil fuels will continue to have a significant role in power generation for the foreseeable future. Unfortunately, fossil fuel combustion results in carbon dioxide (CO₂) emission into the atmosphere, contributing significantly to greenhouse gas emissions. CO₂ levels have increased rapidly since the Industrial Revolution, mainly due to anthropogenic activities, resulting in harmful climate change. This issue is one of the world’s most pressing problems today, necessitating the urgent development of reliable, scalable, and cost-effective CO₂ capture technologies for Natural Gas Combined Cycle (NGCC) power plants.

CO₂ capture can be achieved through solvent-based, sorbent-based, or membrane-based approaches. Although solvent-based technologies are currently state-of-the-art for capturing carbon emissions, sorbent-based methods have potential advantages, such as being less energy-intensive, having a wider temperature range, and being easier to handle and dispose of. Alkali metal carbonate-based sorbents are commonly used due to their low cost and high CO₂ sorption capabilities, but there are issues with pressure drops and inefficient contact. Efficient and stable sorbents with good mass and heat transfer characteristics can make solid-sorbent technology competitive with solvent-based methods.

Our previous study investigated using potassium carbonate (K₂CO₃)-based solid sorbent to capture CO₂ from simulated flue gas containing 4% CO₂ and 10% water. The sorbent adsorbs between 50°C to 90°C and can be regenerated at 100°C to 150°C. Metal oxide-based supports and other support materials are used to disperse K₂CO₃ and increase the surface area. The sorbents are characterized using x-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen physisorption and diffuse reflectance infrared fourier transform spectroscopy (DRIFTS). Thermogravimetric analysis (TGA) and fixed bed experiments are conducted to test the material's recyclability, stability, and performance.

To compete with solvent-based methods, not only do we need more efficient and stable sorbents, but also an innovative technology that facilitates efficient contact between gas and solids for good mass and heat transfer. A potential solution is a magnetically stabilized fluidized bed reactor (MSFB) with a magnetically susceptible bed, which can suppress bubble formation and enhance CO₂ capture. This technology stabilizes the fluidized bed and extends the particulate fluidization regime, preventing sorbent elutriation and eliminating the need for a gas-solid separation device or cyclone. This also increases gas-solid contact, simulates a plug flow reactor-type operation, substantially reduces pressure drop, and reduces particle loss due to less particle/particle-wall collision.

In this study, a uniform magnetic field is generated in the bed using a Helmholtz coil and the effectiveness of a magnetically stabilized fluidized bed is tested. Different magnetically susceptible bed materials like ferrimagnetic Fe₃O₄ particles are used to impart magnetic properties to the bed. The pressure drops across the bed are measured with and without applying a magnetic field. Results indicate that lower pressure drops are observed when magnetic fields are applied. Detailed investigations on fluidization behavior and regimes are conducted with a comparison between magnetized and non-magnetized conditions and supplemented with computational fluid dynamics (CFD) simulations incorporating magnetism. K₂CO₃ sorbent from the previous study is impregnated onto different magnetic materials and tested for CO₂ capture performance in a fixed bed reactor. The optimized magnetic sorbent is tested under reaction conditions in a hot MSFB setup, and the results are compared to the non-magnetic K₂CO₃ sorbent by analyzing CO₂ capture efficiency, CO₂ breakthrough curves, pressure drop across the bed, and sorbent entrainment. To de-risk commercialization efforts, the project’s next phase involves designing and fabricating a bench-scale unit to study different modes of operation, including fixed bed, bubbling fluidized bed, and magnetically stabilized bed, to quantify and validate MSFB performance.

This research project can significantly contribute to both the carbon capture and fluidization fields by providing scientific and technical insights into the development of solid sorbents and innovative methods like magnetically stabilized fluidized beds for improved capture efficiency and overall CO₂ uptake. Addressing climate change by developing low-cost carbon capture technologies is the need of the hour, and this work is a promising step toward achieving this goal by capturing CO₂ from natural gas-based power plants through enhanced gas-solid contact.