Mathematical modelling of a low-temperature hydrogen production process with In Situ CO2 capture

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Методологија за синтезу реактора заснована на концептима интензификације процеса и примени метода оптимизације

In this Ph.D. thesis, a new methodology for Reactor Synthesis Based on Process Intensification Concepts and Application of Optimization Methods (ReSyPIO) is presented and applied to two different cases. In Chapter 1: Introduction – Motivation and Objectives, the motive for the research is presented, and Hypotheses are formulated. The ReSyPIO methodology that rests upon these Hypotheses and consists of three consecutive stages is briefly described in this Chapter. The first stage encapsulates all present phases and phenomena inside the reactor functional building block, called module. Modules come as a direct result of a conceptual representation of the analyzed system. In the second stage, modules are further segmented if needed and interconnected, creating a reactor superstructure that is mathematically described for all desirable operating regimes. In the last stage of the ReSyPIO methodology, the optimal structure, operating conditions, and the operational regime are determined with the use of rigorous optimization. All three stages of the ReSyPIO methodology have a backflow, meaning that if analysis leads to impractical, nonfunctional or inefficient results, modifications in reactor superstructure and modules can be made. The objective is to conceptually and numerically derive the most efficient reactor structure and a set of operating conditions that would be used as a starting point in the future reactor design. Chapter 2: Literature Review is used to cover and review the most important research published in the area of Process Intensification and different Process System Engineering techniques. Different approaches and studies present in academia are highlighted and their elements compared with the presented ReSyPIO methodology with the accent on its advantages and contribution to the engineering science community.Also, in this Chapter, an array of well researched analytical and numerical approaches is presented that could be used in the future to strengthen the ReSyPIO methodology further and facilitate its easier application. In Chapter 3: Description of the ReSyPIO Methodology Reactor Synthesis based on Process Intensification and Optimization of Superstructure is explained in detail, with a graphical representation of the main building block, called Phenomenological Module. A general explanation is given on how to form a reactor superstructure and mathematically describe it with sets of material and energy balance equations that correspond to a number of present phases and components in the system. The ReSyPIO methodology is first applied to a generic case of two parallel reactions in Chapter 4, called Application of the ReSyPIO Methodology on a Generic Reaction Case. The case corresponds to two parallel reactions that could be found in the fine chemical industry. The reactions are endothermic and slow with the undesired product. After the application of the ReSyPIO methodology, an optimal reactor structure consisting of a segmented module with 17 side inlets for the reactant and heat source is obtained. It is recommended for the reactor to work in a continuous steady-state mode as the dynamic operation would not lead to a sufficient increase in reactor efficiency...У овој докторској дисертацији је представљена и примењена нова методологија за синтезу реактора заснована на концептима интензификације процеса и примени различитих оптимизационих техника (Reactor Synthesis Based on Process Intensification Concepts and Application of Optimization Methods – ReSyPIO). У поглављу Увод – Мотивација и циљеви, формиране су хипотезе на којима почива ReSyPIO методологија и дата је мотивација за истраживање. ReSyPIO методологија је укратко представљена и описана кроз три узастопне етапе. Прва етапа уоквирава све присутне фазе и феномене у реактору унутар функционалних градивних јединица, названих модули. Модули представљају резултат концептуалног приказа анализираног система. У другој етапи, модули се по потреби могу даље поделити у сегменте и међусобно повезати, креирајући суперструктуру реактора. Суперструктура је математички описана за све режиме рада реактора од интереса. У последњој етапи ReSyPIO методологије, оптимална структура, услови и режим рада реактора су одређени применом ригорозне оптимизације. Све три етапе ReSyPIO методологије имају повратни ток, што значи да уколико анализа води ка непрактичним, нефункционалним или неефикасним решењима, модификација математичког модела, суперструктуре и/или модула је могућа. Циљ примене ReSyPIO методологије је да се концептуалним и нумеричким приступом дође до оптималне препоруке за структуру реактора, оперативне услове и режим рада, која би била почетна претпоставка у будућем дизајну уређаја. Преглед литературе даје опис и приказ свих истраживања од интереса, из области Интензификације процеса и Теорије и анализе процесних система. Наглашени су различити приступи и студије присутне у истраживачкојзаједници, а њихови елементи упоређени са представљеном ReSyPIO методологијом са акцентом на предностима и научном доприносу. У овом поглављу је дат и низ добро истражених аналитичких и нумеричких приступа који би могли да буду коришћени у оквиру ReSyPIO методологије и олакшају њену примену. У поглављу Опис ReSyPIO методологије, је детаљно објашњена синтеза реактора заснована на концептима интензификације процеса и оптимизацији суперструктуре. Прво је дата процедура за графичку и концептуалну репрезентацију система, преко главних градивних јединица, феноменолошких модула. Потом је објашњено како се креира суперструктура реактора. На крају је дат уопштен поступак за математички опис суперструктуре преко скупова једначина материјалног и енергетског биланса, чији број зависи од броја присутних фаза и компонената у систему. ReSyPIO методологија је први пут примењена на случају две генеричке паралелне реакције у поглављу под називом Примена ReSyPIO методологије на случају генеричке реакције. Овај случај одговара реакцијама које се могу наћи у индустрији финих хемикалија. Реакције су ендотермне и споре, при чему је кинетички фаворизовано креирање нежељеног производа. Након примене ReSyPIO методологије, добијена је оптимална структура реактора која се састоји од сегментисаног модула са 17 улаза за извор топлоте и реактант који се дозира. Предложено је да реактор ради континуално, у стационарном режиму рада, јер би динамички режим рада резултовао недовољним повећањем ефикасности реактора..

Metal-Organic Frameworks in Germany: from Synthesis to Function

Metal-organic frameworks (MOFs) are constructed from a combination of inorganic and organic units to produce materials which display high porosity, among other unique and exciting properties. MOFs have shown promise in many wide-ranging applications, such as catalysis and gas separations. In this review, we highlight MOF research conducted by Germany-based research groups. Specifically, we feature approaches for the synthesis of new MOFs, high-throughput MOF production, advanced characterization methods and examples of advanced functions and properties

110th Anniversary : carbon dioxide and chemical looping : current research trends

Driven by the need to develop technologies for converting CO2, an extraordinary array of chemical looping based process concepts has been proposed and researched over the past 15 years. This review aims at providing first a historical context of the molecule CO2, which sits at the center of these developments. Then, different types of chemical looping related to CO2 are addressed, with attention to process concepts, looping materials, and reactor configurations. Herein, focus lies on the direct conversion of carbon dioxide into carbon monoxide, a process deemed to have economic potential

A Novel Method for Pre-combustion CO2 Capture in Fluidized Bed

La comunidad internacional está realizando enormes esfuerzos para mitigar los efectos de las emisiones de gases de efecto invernadero (GEI) en el cambio climático. Aproximadamente le 25% de las emisiones globales de GEI (fundamentalmente CO2) son generados por la combustión de combustibles fósiles en el sector eléctrico. La captura y almacenamiento de CO2 se ha propuesto como una alternativa para reducir las emisiones de GEI en centrales térmicas. Numerosas tecnologías para la captura de CO2 se han desarrollado en los últimos años, fundamentalmente en tres líneas tecnológicas: postcombustión, oxicombustión y precombustión. Esta tesis presenta un nuevo método para la captura de CO2 en precombustión, produciendo hidrógeno a partir de carbón, sin emisiones de GEI. El objetivo principal de este trabajo ha sido desarrollar un modelo completo, mediante herramientas de fluido dinámica computacional (CFD), del proceso de reformado de un gas de síntesis con alto contenido en metano combinado con la captura de CO2 mediante adsorción con sorbentes sólidos regenerables. Este proceso es conocido como reformado de metano mejorado por adsorción (o SE-SMR, su acrónimo en inglés). SE-SMR representa una novedosa y eficiente energéticamente ruta para la producción de hidrógeno con captura in situ de CO2. Este proceso ha sido estudiado en un lecho fluido burbujeante, usando sorbentes sólidos de óxido de calcio como captores de CO2. Dos sorbentes sólidos han sido estudiados en laboratorio: uno natural (Dolomita) y uno sintético (CaO- Ca12Al14O33). Además, varios tratamientos han sido desarrollados para mejorar la capacidad de captura de estos sorbentes. Un completo modelo CFD del proceso de SE-SMR ha sido desarrollado. Una aproximación Euleriana-Euleriana ha sido combinada con la Teoría Cinética de Flujos Granulares para simular la fluidodinámica del lecho fluido burbujeante. Los reacciones químicas de reformado y carbonatación han sido implementadas en el modelo CFD. Se ha incluido un modelo detallado de captura de CO2 para simular el comportamiento de los diferentes sorbentes sometidos a diferentes pretratamientos para mejorar su rendimiento. Asimismo, un modelo de arrastre de partículas ha sido desarrollado para reducir el coste computacional de las simulaciones a escala semi-industrial. Se ha llevado a cabo una extensa campaña de simulaciones para validar el modelo a escala de laboratorio y semi-industrial. Las simulaciones CFD han sido combinadas con un Diseño de Experimentos Robusto, con el objetivo predecir y evaluar la sensibilidad del proceso SE-SMR a diversos factores operativos

Biporous Metal-Organic Framework with Tunable CO2/CH4 Separation Performance Facilitated by Intrinsic Flexibility.

In this work, we report the synthesis of SION-8, a novel metal-organic framework (MOF) based on Ca(II) and a tetracarboxylate ligand TBAPy4- endowed with two chemically distinct types of pores characterized by their hydrophobic and hydrophilic properties. By altering the activation conditions, we gained access to two bulk materials: the fully activated SION-8F and the partially activated SION-8P with exclusively the hydrophobic pores activated. SION-8P shows high affinity for both CO2 ( Qst = 28.4 kJ/mol) and CH4 ( Qst = 21.4 kJ/mol), while upon full activation, the difference in affinity for CO2 ( Qst = 23.4 kJ/mol) and CH4 ( Qst = 16.0 kJ/mol) is more pronounced. The intrinsic flexibility of both materials results in complex adsorption behavior and greater adsorption of gas molecules than if the materials were rigid. Their CO2/CH4 separation performance was tested in fixed-bed breakthrough experiments using binary gas mixtures of different compositions and rationalized in terms of molecular interactions. SION-8F showed a 40-160% increase (depending on the temperature and the gas mixture composition probed) of the CO2/CH4 dynamic breakthrough selectivity compared to SION-8P, demonstrating the possibility to rationally tune the separation performance of a single MOF by manipulating the stepwise activation made possible by the MOF's biporous nature

Preparation and Performance of Novel CaO-Based Sorbents for High-Temperature CO2 Removal

Sorption-Enhanced Steam Reforming process (SESR) is an auspicious technology for hydrogen (H2) production with simultaneous capture of carbon dioxide (CO2) derived from design modifications performed on the conventional Steam Reforming Process (SRP). Enhancing the reforming reaction in terms of kinetics, yield and purity through capturing in situ CO2 using high temperature solid sorbents brings advantages including reduction in energy requirements and lower investment capital. Even though SESR is a cost-effective route for energy generation based on organic volatile and gaseous feedstock including natural gas, its implementation implies overcoming challenges. Diminishing the sintering in CaO-based CO2 sorbents has become one of these challenges since the reactivity of these captors decreases significantly as the number of carbonation/calcination cycles proceeds. This research work centres its efforts in the development of novel sintering resistant CaO-based CO2 sorbents enhanced by means of the incorporation of a refractory, high surface area, polycrystalline fibrous support (Saffil), with high-Al2O3 content, acting as structural stabilizer of CaO. Four families of CaO-based CO2 sorbents were prepared using wet impregnation and precipitation methods. Different variants such as CaO precursor, precipitant agents, pH, stirring, aging time, etc. were tested to optimize the synthesis parameters. The best preparation conditions were aimed at achieving a homogeneous deposition of CaO over the Saffil support as well as a morphology in CaO that might improve the durability of CO2 acceptors. In particular, the formation of nanoflakes, and particles with an octahedral shape were found to be two of the most promising morphologies. Upon the determination of optimal synthesis parameters, the as-prepared CO2 sorbents were characterized in order to determine their physicochemical properties such as textural features (surface area and pore size distribution – N2 physisorption), real CaO content (XRF), dispersion of CaO over Saffil supports (SEM-EDX), phase identification (XRD), etc. Carrying capacities and durability of CaO-based CO2 sorbents were assessed through multicycle carbonation/decarbonation tests under controlled conditions such as temperature and atmosphere. The dynamic/isothermal experiments conducted in a TGA system confirm an enhancement in reactivity when CaO grows over the periphery of the Saffil support. In addition to the use of a support, achieving a ‘clamping effect’ (to diminish lateral mobility of CaO, thus avoiding particle densification), in conjunction with the morphology adopted by CaO, is shown to provide thermal stability. SEM-EDX techniques applied on used CaO-based sorbents (30 carbonation-calcination cycles) corroborate that the enhancement in durability is due to the outstanding sintering resistance exhibited when CaO adopted the nanoflake or octahedral structure. The viability of the as-prepared sorbents was also confirmed through a kinetic study in which kinetic parameters and mechanisms associated with both carbonation and calcination reactions were estimated. Concerning the CO2 uptake kinetics, the isothermal method was used to collect mass change data whilst model-based equations were employed to elucidate the kinetic triplet. For the calcination reaction, the kinetic study was performed using both isothermal and non-isothermal methods. Activation energies assessed for the carbonation and calcination reactions were compared among them and also in relation with other CaO-based sorbents available in the literature for reliability purposes

Enhanced hydrogen production from thermochemical processes

To alleviate the pressing problem of greenhouse gas emissions, the development and deployment of sustainable energy technologies is necessary. One potentially viable approach for replacing fossil fuels is the development of a H2 economy. Not only can H2 be used to produce heat and electricity, it is also utilised in ammonia synthesis and hydrocracking. H2 is traditionally generated from thermochemical processes such as steam reforming of hydrocarbons and the water-gas-shift (WGS) reaction. However, these processes suffer from low H2 yields owing to their reversible nature. Removing H2 with membranes and/or extracting CO2 with solid sorbents in situ can overcome these issues by shifting the component equilibrium towards enhanced H2 production via Le Chatelier's principle. This can potentially result in reduced energy consumption, smaller reactor sizes and, therefore, lower capital costs. In light of this, a significant amount of work has been conducted over the past few decades to refine these processes through the development of novel materials and complex models. Here, we critically review the most recent developments in these studies, identify possible research gaps, and offer recommendations for future research

Sorption direct air capture with CO2 utilization

Direct air capture (DAC) is gathering momentum since it has vast potential and high flexibility to collect CO2 from discrete sources as “synthetic tree” when compared with current CO2 capture technologies, e.g., amine based post-combustion capture. It is considered as one of the emerging carbon capture technologies in recent decades and remains in a prototype investigation stage with many technical challenges to be overcome. The objective of this paper is to comprehensively discuss the state-of-the-art of DAC and CO2 utilization, note unresolved technology bottlenecks, and give investigation perspectives for commercial large-scale applications. Firstly, characteristics of physical and chemical sorbents are evaluated. Then, the representative capture processes, e.g., pressure swing adsorption, temperature swing adsorption and other ongoing absorption chemical loops, are described and compared. Methods of CO2 conversion including synthesis of fuels and chemicals as well as biological utilization are reviewed. Finally, techno-economic analysis and life cycle assessment for DAC application are summarized. Based on research achievements, future challenges of DAC and CO2 conversion are presented, which include providing synthesis guidelines for obtaining sorbents with the desired characteristics, uncovering the mechanisms for different working processes and establishing evaluation criteria in terms of technical and economic aspects