(4p) Computational Modeling and Tomographic Imaging of Fluidized Beds

Authors: 
Boyce, C. M., University of Cambridge



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.