Heterogeneous catalysis has emerged as a crucial technology to address the challenges associated with the current energy transition. In this context, the design of innovative reactors and the optimization of the existing technologies are mandatory to solve the challenges associated with the reduction of the human footprint and the sustainable use of natural resources and energy consumption, which represent a target to meet the Sustainable Development Goals posed by the United Nations. The fluidization technology, with its unique characteristics such as homogeneous reaction environment, high heat transfer rates and effective management of deactivated particles, is acknowledged as a promising route for achieving high productivity, selectivity, and energy efficiency in various catalytic processes crucial for the energy transition. Indeed, fluidized systems, particularly fluidized bed reactors, have shown promise in the context of CO2 capture and utilization technologies, valorization of natural gas to turquoise hydrogen, and integration of plastic recycling in the circular economy. A comprehensive understanding of the interactions between the fluid dynamics and homogeneous and heterogeneous reactivity is, however, required to properly design fluidized systems. Detailed multiscale modeling, coupled with selected experiments, has emerged as a promising approach to gain in-depth insights into the reactor behavior and facilitate the design, optimization, and scale-up of fluidized processes. In particular, multiscale modeling, which combines the first-principles descriptions of the phenomena occurring at the different scales from the atoms to the reactor, represents a key tool for the computational analysis of heterogeneous catalytic reactors, providing a comprehensive understanding of their performance. In this context, this Ph.D. thesis aims at fundamentally analyzing innovative fluidized technologies, relevant for the energy transition, by means of detailed multiscale numerical methods able to fully characterize mutual interactions among the phenomena in the reactive environment. Challenging issues, such as the accurate description of fluid dynamics, particle shape representation, management of chemical kinetics, and computational cost reduction, have been addressed in the development of these frameworks. For this purpose, two numerical multiscale frameworks, based on Eulerian-Lagrangian and Eulerian-Eulerian descriptions of multiphase flow, have been developed. These frameworks enable the simulation of fluidized units from lab to industrial scale, offering insights into particle shape effects, complex multiphase fluid dynamics, and detailed descriptions of chemical kinetics. On the one hand, the multiscale Euler-Lagrange framework enables the fundamental investigation of novel processes in lab-scale units and the development of engineering correlations, based on the first-principles description of the phenomena, which can improve the accuracy of less detailed numerical strategy. On the other hand, the multiscale Euler-Euler framework provides a deep knowledge of the interplay between the physical and chemical phenomena occurring in pilot or industrial units, representing a promising tool for studying the scale-up of novel fluidized processes and for optimizing the existing industrial units. The potentials of the multiscale frameworks have been finally demonstrated through fundamental investigations of novel reactor technologies, including dynamically structured fluidization, and processes, such as the Oxidative Coupling of Methane, plastic waste gasification, and the synthesis of carbon nanotubes via methane pyrolysis paving the way for the rational design of innovative fluidized technologies.
La catalisi eterogenea è emersa come una tecnologia cruciale per risolvere le sfide associate alla transizione energetica. In questo contesto, la progettazione di reattori innovativi e l’ottimizzazione delle tecnologie esistenti risulta fondamentale per risolvere le sfide associate ad un utilizzo sostenibile delle risorse naturali e del consumo energetico, in modo da raggiungere gli obiettivi posti dalle nazioni unite. La fluidizzazione, con le sue peculiari caratteristiche quali un ambiente di reazione omogeneo, l’alta velocità di scambio di energia e l’efficiente gestione di particelle disattivate, è riconosciuta come una via promettente per ottenere alte produttività, selettività ed efficienze energetiche in vari processi catalitici cruciali per la transizione energetica. Infatti, I sistemi fluidizzati, ed in particolare i letti fluidi, risultano promettenti per la cattura e l’utilizzo della CO2, la valorizzazione dei gas naturali per la produzione di idrogeno turchese e l’integrazione delle plastiche in un’economia circolare. La comprensione fondamentale delle interazioni tra la fluidodinamica e le reazioni omogenee ed eterogenee è però necessaria per poter propriamente progettare sistemi fluidizzati. I modelli multiscala, combinati con esperimenti selezionati, stanno emergendo come un promettente approccio per ottenere informazioni riguardanti il comportamento del reattore e facilitare la sua progettazione, ottimizzazione e scale-up. In particolare, i modelli multiscala, che combinano la descrizione ai principi primi dei fenomeni che avvengono a differenti scale, dall’atomica alla reattoristica, rappresentano uno strumento fondamentale per l’analisi computazionale di reattori catalitici essendo in grado di fornire una conoscenza globale delle loro performance. In questo contesto, questa tesi di dottorato ha lo scopo di analizzare sistemi fluidizzati innovativi, rilevanti per la transizione energetica, attraverso modelli mutiscala dettagliati capaci di caratterizzate le mutue interazione tra i fenomeni che avvengono nell’ambiente reattivo. Differenti problemi, come l’accurata descrizione della fluidodinamica, della rappresentazione della forma delle particelle, la gestione della chimica e la riduzione del costo computazionale, sono stati risolti nello sviluppo di questi frameworks. A tal fine, due framework multiscala, basati sulla descrizione Euleriana-Lagrangiana ed Euleriana-Euleriana dei flusso multifase, sono stati sviluppati. Questi framework consentono la simulazioni di sistemi fluidizzati dalla scala di laboratorio a quella industriale, offrendo informazioni riguardanti gli effetti della forma delle particelle, della complessa fluidodinamica multifase e della descrizione dettagliata della cinetica chimica. Da un lato, il framework multiscala Euleriano-Lagrangiano consente l’investigazione fondamentale di nuovi processi in unità di laboratorio e lo sviluppo di correlazioni ingegneristiche, basate su una descrizione ai principi primi dei fenomeni, che possono migliorare l’accuratezza di modelli numerici non dettagliati. Dall’altro lato, il framework multiscala Euleriano-Euleriano è in grado di aumentare la conoscenza riguardante le interazioni tra i fenomeni fisici e chimici che avvengono in unità pilota o industriali, rappresentando uno strumento promettente per lo scale-up di nuovi processi fluidizzati e per l’ottimizzazione di unità industriali esistenti. Le potenzialità dei framework multiscala è stata infine dimostrata attraverso l’investigazione fondamentale di nuove tecnologie reattoristiche, quali i reattori a letto fluidi dinamicamente strutturati, e processi, come l’ Oxidative Coupling of Methane, la gassificazione dei rifiuti plastici e la sintesi di nanotubi di carbonio tramite pirolisi del metano, spianando la strada per una progettazione razionale di tecnologie fluidizzate innovative.
Multiscale investigation of reactive fluidized technologies for the energy transition
MICALE, DANIELE
2022/2023
Abstract
Heterogeneous catalysis has emerged as a crucial technology to address the challenges associated with the current energy transition. In this context, the design of innovative reactors and the optimization of the existing technologies are mandatory to solve the challenges associated with the reduction of the human footprint and the sustainable use of natural resources and energy consumption, which represent a target to meet the Sustainable Development Goals posed by the United Nations. The fluidization technology, with its unique characteristics such as homogeneous reaction environment, high heat transfer rates and effective management of deactivated particles, is acknowledged as a promising route for achieving high productivity, selectivity, and energy efficiency in various catalytic processes crucial for the energy transition. Indeed, fluidized systems, particularly fluidized bed reactors, have shown promise in the context of CO2 capture and utilization technologies, valorization of natural gas to turquoise hydrogen, and integration of plastic recycling in the circular economy. A comprehensive understanding of the interactions between the fluid dynamics and homogeneous and heterogeneous reactivity is, however, required to properly design fluidized systems. Detailed multiscale modeling, coupled with selected experiments, has emerged as a promising approach to gain in-depth insights into the reactor behavior and facilitate the design, optimization, and scale-up of fluidized processes. In particular, multiscale modeling, which combines the first-principles descriptions of the phenomena occurring at the different scales from the atoms to the reactor, represents a key tool for the computational analysis of heterogeneous catalytic reactors, providing a comprehensive understanding of their performance. In this context, this Ph.D. thesis aims at fundamentally analyzing innovative fluidized technologies, relevant for the energy transition, by means of detailed multiscale numerical methods able to fully characterize mutual interactions among the phenomena in the reactive environment. Challenging issues, such as the accurate description of fluid dynamics, particle shape representation, management of chemical kinetics, and computational cost reduction, have been addressed in the development of these frameworks. For this purpose, two numerical multiscale frameworks, based on Eulerian-Lagrangian and Eulerian-Eulerian descriptions of multiphase flow, have been developed. These frameworks enable the simulation of fluidized units from lab to industrial scale, offering insights into particle shape effects, complex multiphase fluid dynamics, and detailed descriptions of chemical kinetics. On the one hand, the multiscale Euler-Lagrange framework enables the fundamental investigation of novel processes in lab-scale units and the development of engineering correlations, based on the first-principles description of the phenomena, which can improve the accuracy of less detailed numerical strategy. On the other hand, the multiscale Euler-Euler framework provides a deep knowledge of the interplay between the physical and chemical phenomena occurring in pilot or industrial units, representing a promising tool for studying the scale-up of novel fluidized processes and for optimizing the existing industrial units. The potentials of the multiscale frameworks have been finally demonstrated through fundamental investigations of novel reactor technologies, including dynamically structured fluidization, and processes, such as the Oxidative Coupling of Methane, plastic waste gasification, and the synthesis of carbon nanotubes via methane pyrolysis paving the way for the rational design of innovative fluidized technologies.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/207550