DOI
https://doi.org/10.25772/177Q-CT56
Defense Date
2022
Document Type
Dissertation
Degree Name
Doctor of Philosophy
Department
Chemical and Life Science Engineering
First Advisor
Mo Jiang
Abstract
Continuous crystallization has received increasing research interest in both academia and industry for controlling crystal qualities, including polymorphic form, size, and morphology, etc. In the field of pharmaceutical and battery industries, the highly demanding for good quality crystals lead many researchers to develop continuous manufacturing processes to overcome the problems of traditional batch manufacturing processes, such as batch-to-batch variation, scaling up problems and high capital investment. Tubular slug flow reactors are designed based on the different batch processes to generate uniform and well-controlled particles. The process parameter of slug flow reactors is the flow rate, which directly controls the slug sizes and velocity. The reactor design is based on the understanding of how the flow rate will affect the key characteristics of slug flow. The slug length/volume can be predicted by scaling law, a law that correlates the slug length to flow rate. Meanwhile, how to control the uniformity of the slug flow (i.e., narrow slug size distribution) was investigated. It was found that with tight gas control we can improve the slug uniformity. Scale-up strategies and their effect on the crystal size distribution were studied. For batch reactors, the scaling-up process results in different crystal size distribution while slug flow reactors can maintain similar crystal sizes. The volume of the microreactor can be estimated based on the developed imaging analysis, where we correlated three different slug lengths to the volume of slugs. The volume of the microreactor size can affect the crystallization process because it will affect the internal recirculation inside each slug. Hence the volume/size must be optimized and controlled. On top of a two-phase liquid/gas reactor, three-phase slug flow reactors were generated via a cross mixer and studied. The extra phase can provide a continuous film to prevent fouling and enhance the reagent addition. The scaling law for three-phase flow was brought up. And introducing a new reagent into an existing moving slug stream was realized in the three-phase xix reactor with larger injection rate tolerance and high accuracy. This can guide the design of all different kinds of chemical processes into a three-phase slug flow reactor. It is highly useful for those compounds that possess high surface energy and are easy to foul. And it can be used for the multi-step process such as chemical synthesis. The two-phase slug flow reactor was used for cooling crystallization and reactive crystallization. For cooling crystallization of glycine, the operational boundary (e.g., supersaturation) is much larger than the batch process. And the nucleation and growth process (e.g., induction time) and product quality (e.g., yield, size distribution, polymorph) were well-controlled in two-phase slug flow reactors. Reactive crystallization of glutamic acid was transferred to a single-step or a two-step slug flow process. Interestingly, the process generated completely different morphologies than the batch crystallization process. The morphologies can be controlled by supersaturation. The mechanisms of the formation of different morphologies were discussed. It was found that the supersaturation, residence time and flow rate can affect the morphology. And ultrasound had a limited effect on the final product. Three-phase slug reactors were designed for battery cathode materials synthesis. For the synthesis of nickel-cobalt-manganese hydroxide precursor, the slug flow manufacturing process can generate precursor with comparable battery performance reported before. For nickel-cobalt-manganese oxalate precursor synthesis, the slug flow can produce spherical crystals with narrow size distribution. A core-shell structure was validated by FIB-SEM and EDAX. Battery performance demonstrated that the as-synthesized precursors were improved
Rights
© The Author
Is Part Of
VCU University Archives
Is Part Of
VCU Theses and Dissertations
Date of Submission
8-30-2022