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ItemRechargeable Zn-Based Batteries for Large Scale Energy Storage: Operando Imaging, Material Designing and Device Engineering(Georgia Institute of Technology, 2020-11-19) Wu, YutongEnergy storage technologies have the potential to change the energy infrastructure from relying heavily on fossil fuels to mostly using temporally intermittent renewable energy sources. Lithium-ion battery is the dominant energy storage solution for portable electronics, but have safety concerns stemming from flammable organic electrolytes, which is more severe when batteries are scaled up for applications in electric vehicles and utilities. And due to the stacked powder-film-on-current-collector geometry, lithium-ion batteries have limitations in scalability and maintainability. Batteries using aqueous electrolyte (e.g. Zn-air) are intrinsically safe, and flow batteries (e.g. Zn-Br) are attractive choice for large scale energy storage. However, these two technologies (Zn-air and Zn-Br) have problems such as rechargeability, self-discharge, and power density. This research identifies the limiting factors of both portable and large-scale batteries, especially zinc-based ones, and innovate at the material and device levels to overcome these limitations. Specifically, Section 1 introduces the background and motivation of this research. Section 2 identifies the root cause for irreversible electrochemical reaction of Zn anode, namely passivation and dissolution, and leverage nanoscale materials design to address these problems. Section 3 develops an in situ visualization platform for studying Br electrochemistry in Zn-Br batteries. Phenomena such as phase separated Br2 formation, self-discharge, and phase change of Br2 product will be imaged, to bridge the gap between electrolyte composition and electrochemical performance. Section 4 uses a hollow fiber based flow battery geometry design to significantly enhance the volumetric power density. The device is universal, scalable, and not limited to electrolyte types. Section 5 provides a conclusion to this research and provides future directions. The outcomes of this research (e.g. in operando imaging platform, design principle of reversible metal anode, high power density electrochemical reactor) provides insights for portable scale and grid scale energy storages and other electrochemical flow devices. To note that the videos in this work is in .avi format.
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ItemHybrid fiber sorbents for odorant removal from pipeline natural gas(Georgia Institute of Technology, 2017-06-27) Chen, GracePipeline natural gas is typically odorized with about 10 ppm of mercaptans for safety purposes in case of a leak. However, when burned in air inside of gas turbines, these sulfur compounds react with alkali material present in air to form a corrosive combustion product which corrodes the inside of the turbine and reduces its efficiency and lifetime. It is therefore of interest to remove mercaptan odorants from pipeline natural gas before introduction into combustion turbines for the purposes of preventing or delaying corrosion associated with SOx production. The overall goal of the current project was to investigate several metal organic frameworks (MOFs) and zeolites for the removal of a common odorant, t-butyl mercaptan (TBM), from natural gas and to evaluate their ability to be practically and economically integrated into a cyclic adsorption system in a fiber module configuration. Several MOFs were synthesized and characterized for TBM adsorption capacity, selectivity, cyclic regenerability, and stability, and compared to benchmark zeolites using gravimetric sorption methods. These aspects are important to the economic viability of a TBM removal system. Results showed that MOFs can be advantageous over zeolites for this application, and the highest performing materials were chosen for further studies with fiber spinning. The materials were incorporated into hybrid cellulose acetate polymer fibers and their adsorption performances were reevaluated gravimetrically and in an automated temperature swing adsorption (TSA) system. Both MOF and zeolite hybrid fibers were successfully fabricated with high sorbent loadings, and continued to exhibit high sorption capacities and selectivities to TBM in the model natural gas flow, while remaining stable to multiple temperature swing regeneration cycles. Different operating conditions were varied in the TSA system to determine their effects on the breakthrough curve, adsorption capacity, and mass transfer. The overall results demonstrate a proof of concept that fiber sorbent creation and implementation is feasible and worth further investigation for odorant removal from pipeline natural gas in an industrial setting. This research ties together to the two major challenges in adsorption applications: materials design and system implementation, which pushes forward the development of an industrial scale system for odorant removal from natural gas.
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ItemFiber adsorbents for tert-butyl mercaptan removal from pipeline grade natural gas(Georgia Institute of Technology, 2013-08-12) Chen, GraceThe purpose of this thesis study is to assess the feasibility of using a fiber sorbent module system to remove t-butyl mercaptan (TBM), a common odorant, from pipeline grade natural gas. Odorants such as mercaptans are added to natural gas for safety reasons, but their combustion products are corrosive and decrease the lifetime of the turbines in which they are combusted. Therefore, it is desirable to remove the odorants to extend this lifetime. A TBM removal system attached to a 840 MW natural gas-fueled combined cycle power plant unit such as the one at Plant McDonough-Atkinson (Smyrna, GA) must process gas at a flow rate of approximately 180,000 standard cubic feet per minute. A single 85 MW GE 7EAQ gas turbine has a flow rate of approximately 15,000 standard cubic feet per minute, and will serve as the basis for a system design and process analysis study. The concentration of odorants in natural gas is typically 10 ppm or less. For the purposes of this study, the upper limit of 10 ppm TBM will be used. Zeolite 13X was selected as the model adsorbent for this study due to its high sorption capacity for mercaptans and its ease of incorporation into both fibers and pellets. Design calculations were performed to optimize and determine the feasibility of fiber modules for TBM removal, as well as assess their advantages over conventional pellet packed beds. An understanding of how critical parameters such as heat and mass transfer resistances, pressure drop, and capital and operating costs are affected by design specifications such as sorbent and bed dimensions, allows an optimal design for the needs of the model turbine to be found. Based on these design equations, a fiber sorbent module configuration that selectively and continuously removes TBM from natural gas is developed
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ItemThree applications of green chemistry in engineering: (1) silylamines as reversible ionic liquids for carbon dioxide capture; (2) carbon dioxide as protecting group in chemical syntheses; (3) mitigating the thermal degradation of polyvinyl chloride(Georgia Institute of Technology, 2013-06-17) Switzer, Jackson ReevesGreen chemistry principles served as a guide for three industrially-relevant projects. In the first project, silylamines were applied as reversible ionic liquids for carbon dioxide capture from post-combustion flue gas streams. The effect of silylamine structure was thoroughly researched to develop a comprehensive library of silylamines and an accompanying set of structure-property relationships. The proposed solvent systems have the potential to present significant energy savings, as design has focused on their use in a non-aqueous, solvent-free environment. The second project also dealt extensively with carbon dioxide capture, as a reversible, in-situ protecting group for amines. Three strategies for the reversible protection of amines using carbon dioxide were developed and evaluated. Further, a chemoselective reaction was performed using carbon dioxide to protect a reactive amine and consequentially direct reactivity elsewhere within the same molecule. The carbon dioxide-protection technology developed has significant impact in multi-step industrial syntheses, as reversible, in-situ protection with carbon dioxide could eliminate the need for separate protection and deprotection unit operations. Lastly, a study was performed on the thermal degradation and stabilization of PVC in the presence of both plasticizers and thermal stabilizers. The study combined both model compound experiments as well as work with bulk PVC blends to gain a holistic understanding of the processes that take place during the degradation and stabilization of PVC. A bio-based plasticizer was investigated as a replacement for petroleum-based phthalate plasticizers. Additionally, two novel thermal stabilizers for PVC were presented and evaluated.