Computational Modeling and Tomographic Imaging of Fluidized Beds

Fluidized beds are of great industrial importance because of their critical role in applications ranging from fluidized catalytic cracking (FCC), to drying of particulates; fluidized beds also show promise in enabling chemical looping combustion (CLC), an emerging process for burning coal and natural gas with efficient, streamlined carbon capture. In addition to being of interest to chemical engineers for practical applications, the two-phase granular flow within fluidized beds appeals to physicists because the particulate phase behaves with unique properties, to the extent that it can be considered a new state of matter. Two-phase granular flow systems, such as fluidized beds, are difficult to measure because they are three-dimensional and opaque, and thus require the use of complex tomographic techniques. These systems also present many mathematical and computational modeling challenges because they simultaneously exhibit properties of multiple states of matter and involve up to millions of particles.

My doctoral research focuses on the development of computational methods that reveal the underlying physics of fluidized beds and the validation of these methods through direct comparison with tomographic experiments. In developing my own, first-of-its-kind 3D cylindrical discrete element model with computational fluid dynamics (DEM-CFD) to simulate fluid and particle flow in fluidized beds, I have acquired skills in implementing and synthesizing novel numerical techniques to ensure accurate and stable simulation of dynamic systems. My modeling developments provide the ability to directly simulate the flow conditions of laboratory-scale fluidized beds and corresponding tomographic measurements. By simulating the acquisition process of magnetic resonance imaging (MRI) in analyzing model results, I have gained experience in comparing model and experimental results with a new level of accuracy for cross-validation. This methodology has also shed light on tomographic measurements, providing a better understanding of the complex Fourier-domain averaging and Gaussian slice excitations, necessary for MRI velocity measurements, as compared to more conventional time-averaging and slice selectivity methods. Additionally, the use of detailed computational model results validated by experiment has allowed me to find novel approaches to solve age-old questions in the field, such as the physics behind slug rise velocity and the origin of pressure fluctuations in fluidized beds.

As a research faculty member, I plan to expand upon the foundation of my doctoral work to explore the critical interplay between physics and chemistry in fluidized beds over multiple length scales. My research program will involve combining insights from multi-scale modeling and multi-scale measurement efforts to provide insights on the varying physical-chemical phenomena that occur at different length scales. This research path will also entail coupling the chemical reactions with the modeling and measurement techniques in a way such that the relationship between the physical and chemical phenomena can be better understood. Finally, my program will involve direct collaboration with researchers who build fluidized beds for applications such as combustion and catalysis, in order to aid in the design and measurement of their experiments. My ultimate aim is to enable the next generation of two-phase granular flow systems, which can offer real world solutions to the energy challenge, such as chemical looping combustion for efficient carbon capture.

I also intend to use my unique educational background, coming from a double major in physics and chemical engineering as an undergraduate at MIT to a PhD in chemical engineering as a Gates Scholar at the University of Cambridge, to enhance chemical engineering education at an American university. From my experiences, I have seen a number of ways in which the on-campus undergraduate and graduate education experience in the U.S. can be further enhanced. Firstly, as a supervisor in the education system unique to Oxford and Cambridge, I have seen the benefits of students discussing material and problems in 2-to-4-person student groups with a graduate-level supervisor in an organized yet open-ended discussion setting. Secondly, as a Gates Scholar, I have had the privilege of interacting with leading graduate students in diverse disciplines, ranging from international relations to public health to engineering; this experience has shown the exceptional and expansive nature of the graduate education that comes from discussing important research problems that cut across academic disciplines. As a faculty member, I plan to take an active role in education to ensure more chemical engineering students at my university are provided with these valuable learning opportunities.