Download or read book Uncertainty Analysis and Robust Optimization of a Single Pore in a Heterogeneous Catalytic Flow Reactor System written by Donovan Chaffart and published by . This book was released on 2017 with total page 132 pages. Available in PDF, EPUB and Kindle. Book excerpt: Catalytic systems are crucial to a wide number of chemical production processes, and as a result there is significant demand to develop novel catalyst materials and to optimize existing catalytic reactor systems. These optimization and design studies are most readily implemented using model-based approaches, which require less time and fewer resources than the alternative experimental-based approaches. The behaviour of a catalytic reactor system can be captured using multiscale modeling approaches that combine continuum transport equations with kinetic modeling approaches such as kinetic Monte Carlo (kMC) or the mean-field (MF) approximation in order to model the relevant reactor phenomena on the length and time scales on which they occur. These multiscale modeling approaches are able to accurately capture the reactor behaviour and can be readily implemented to perform robust optimization and process improvement studies on catalytic reaction systems. The problem with multiscale-based optimization of catalytic reactor systems, however, is that this is still an emerging field and there still remain a number of challenges that hinder these methods. One such challenge involves the computational cost. Multiscale modeling approaches can be computationally-intensive, which limit their application to model-based optimization processes. These computational burdens typically stem from the use of fine-scale models that lack closed-form expressions, such as kMC. A second common challenge involves model-plant mismatch, which can hinder the accuracy of the model. This mismatch stems from uncertainty in the reaction pathways and from difficulties in obtaining the values of the system parameters from experimental results. In addition, the uncertainty in catalytic flow reactor systems can vary in space due to kinetic events not taken into consideration by the multiscale model, such as non-uniform catalyst deactivation due to poisoning and fouling mechanisms. Failure to adequately account for model-plant mismatch can result in substantial deviations from the predicted catalytic reactor performance and significant losses in reactor efficiency. Furthermore, uncertainty propagation techniques can be computationally intensive and can further increase the computational demands of the multiscale models. Based on the above challenges, the objective of this research is to develop and implement efficient strategies that study the effects of parametric uncertainty in key parameters on the performance of a multiscale single-pore catalytic reactor system and subsequently to implement them to perform robust and dynamic optimization on the reactor system subject to uncertainty. To this end, low-order series expansions such as Polynomial Chaos Expansion (PCE) and Power Series Expansion (PSE) were implemented in order to efficiently propagate parametric uncertainty through the multiscale reactor model. These uncertainty propagation techniques were used to perform extensive uncertainty analyses on the catalytic reactor system in order to observe the impact of parametric uncertainty in various key system parameters on the catalyst reactor performance. Subsequently, these tools were implemented into robust optimization formulations that sought to maximize the reactor productivity and minimize the variability in the reactor performance due to uncertainty. The results highlight the significant effect of parametric uncertainty on the reactor performance and illustrate how they can be accommodated for when performing robust optimization. In order to assess the impact of spatially-varying uncertainty due to catalyst deactivation on the catalytic reactor system, the uncertainty propagation techniques were applied to evaluate and compare the effects of spatially-constant and spatially-varying uncertainty distributions. To accommodate for the spatially-varying uncertainty, unique uncertainty descriptions were applied to each uncertain parameter at discretized points across the reactor length. The uncertainty comparison was furthermore extended through application to robust optimization. To reduce the computational cost, statistical data-driven models (DDMs) were identified to approximate the key statistical parameters (mean, variance, and probabilistic bounds) of the reactor output variability for each uncertainty distribution. The DDMs were incorporated into robust optimization formulations that aimed to maximize the reactor productivity subject to uncertainty and minimize the uncertainty-induced output variability. The results demonstrate the impact of spatially-varying parametric uncertainty on the catalytic reactor performance. They also highlight the importance of its inclusion to adequately account for phenomena such as catalyst fouling in robust optimization and process improvement studies. The dynamic behaviour of the catalytic reactor system was similarly assessed within this work to evaluate the effects of uncertainty on the reactor performance as it evolves in time and space. For this study, uncertainty analysis was performed on a transient multiscale catalytic reactor model subject to changes in the system temperature. These results were used to formulate robust dynamic optimization studies to maximize the transient catalytic reactor behaviour. These studies aimed to determine the optimal temperature trajectories that maximize the reactor's performance under uncertainty. Dynamic optimization was also implemented to identify the optimal design and operating policies that allow the reactor, under spatially-varying uncertainty, to meet targeted performance specifications within a level of confidence. These studies illustrate the benefits of performing dynamic optimization to improve performance for multiscale process systems under uncertainty.

Download or read book Measurement and Calculation of Multicomponent Diffusion and Reaction in Catalyst Particles Effect of the Catalyst Pore Structure written by Aykut Argönül and published by Cuvillier Verlag. This book was released on 2010-01-05 with total page 200 pages. Available in PDF, EPUB and Kindle. Book excerpt: A realistic diffusion system, multi-component diffusion, accompanied by a relatively simple reaction, a single reaction with simple molecules, is investigated experimentally using commercial pellets at mild conditions. The motivation was to elucidate the effect of pore structure for simultaneous diffusion/reaction systems in general. The results can be used to investigate the multi-component interactions between different components, to determine an optimum pore structure and/or to check if the whole internal surface area is utilized for reaction. Furthermore, the modeling of such systems was first shortly reviewed using a simple and a complicated pore model. Based on the conservation of mass principle, it is proven that an overall equilibrium between gas and surface phases is theoretically not possible. This has led to the development and introduction of a novel approach for modeling Knudsen flow, the projection approach. The approach is basically novel in two aspects: first, due to its architecture some commonly used assumptions can be avoided, and second, it makes use of new concepts (e.g., outer-surface) and incorporates them by a new calculation procedure. It is shown that this developed approach and modeling is convincing about its accuracy and potential. It allows for otherwise suppressed phenomena to take force and affect the behavior of the system. Moreover, it can be used to estimate the errors made in using common assumptions. It can be concluded that the results from both experimental studies and modeling stimulate the thirst for further research in this area.

Download or read book Catalyst Design written by Massimo Morbidelli and published by Cambridge University Press. This book was released on 2001-02-26 with total page 243 pages. Available in PDF, EPUB and Kindle. Book excerpt: Thorough treatment of the design, preparation, and utilization of catalytic systems for optimal performance.

Download or read book Uncertainty Analysis and Control of Multiscale Process Systems written by Shabnam Rasoulian and published by . This book was released on 2015 with total page 138 pages. Available in PDF, EPUB and Kindle. Book excerpt: Microelectronic market imposes tight requirements upon thin film properties, including specific growth rate, surface roughness and thickness of the film. In the thin film deposition process, the microscopic events determine the configuration of the thin film surface while manipulating variables at the macroscopic level, such as bulk precursor mole fraction and substrate temperature, are essential to product quality. Despite the extensive body of research on control and optimization in this process, there is still a significant discrepancy between the expected performance and the actual yield that can be accomplished employing existing methodologies. This gap is mainly related to the complexities associated with the multiscale nature of the thin film deposition process, lack of practical online in-situ sensors at the fine-scale level, and uncertainties in the mechanisms and parameters of the system. The main goal of this research is developing robust control and optimization strategies for this process while uncertainty analysis is performed using power series expansion (PSE). The deposition process is a batch process where the measurements are available at the end of the batch; accordingly, optimization and control approaches that do not need to access online fine-scale measurements are required. In this research, offline optimization is performed to obtain the optimal temperature profile that results in specific product quality characteristics in the presence of model-plant mismatch. To provide a computationally tractable optimization, the sensitivities in PSEs are numerically evaluated using reduced-order lattices in the KMC models. A comparison between bounded and distributional parametric uncertainties has illustrated that inaccurate assumption for uncertainty description can lead to economic losses in the process. To accelerate the sensitivity analysis of the process, an algorithm has been presented to determine the upper and lower bounds on the outputs through distributions of the microscopic events. In this approach, the sensitivities in the series expansions of events are analytically evaluated. Current multiscale models are not available in closed-form and are computationally prohibitive for online applications. Thus, closed-form models have been developed in this research to predict the control objectives efficiently for online control applications in the presence of model-plant mismatch. The robust performance is quantified by estimates of the distributions of the controlled variables employing PSEs. Since these models can efficiently predict the controlled outputs, they can either be used as an estimator for feedback control purposes in the lack of sensors, or as a basis to design a nonlinear model predictive control (NMPC) framework. Although the recently introduced optical in-situ sensors have motivated the development of feedback control in the thin film deposition process, their application is still limited in practice. Thus, a multivariable robust estimator has been developed to estimate the surface roughness and growth rate based on the substrate temperature and bulk precursor mole fraction. To ensure that the control objective is met in the presence of model-plant mismatch, the robust estimator is designed such that it predicts the upper bound on the process output. The estimator is coupled with traditional feedback controllers to provide a robust feedback control in the lack of online measurements. In addition, a robust NMPC application for the thin film deposition process was developed. The NMPC makes use of closed-from models, which has been identified offline to predict the controlled outputs at a predefined specific probability. The shrinking horizon NMPC minimizes the final roughness, while satisfying the constraints on the control actions and film thickness at the end of the deposition process. Since the identification is performed for a fixed confidence level, hard constraints are defined for thin film properties. To improve the robust performance of NMPC using soft constraints, a closed-form model has been developed to estimate the first and second- order statistical moments of the thin film properties under uncertainty in the multiscale model parameters. Employing this model, the surface roughness and film thickness can be estimated at a desired probability limit during the deposition. Thus, an NMPC framework is devised that successfully minimizes the surface roughness at the end of the batch, while the film thickness meets a minimum specification at a desired probability. Therefore, the methods developed in this research enable accurate online control of the key properties of a multiscale system in the presence of model-plant mismatch.

Download or read book Catalytic Reactors written by Basudeb Saha and published by Walter de Gruyter GmbH & Co KG. This book was released on 2015-12-18 with total page 399 pages. Available in PDF, EPUB and Kindle. Book excerpt: Catalytic Reactors presents several key aspects of reactor design in Chemical and Process Engineering. Starting with the fundamental science across a broad interdisciplinary field, this graduate level textbook offers a concise overview on reactor and process design for students, scientists and practitioners new to the field. This book aims to collate into a comprehensive and well-informed work of leading researchers from north America, western Europe and south-east Asia. The editor and international experts discuss state-of-the-art applications of multifunctional reactors, biocatalytic membrane reactors, micro-flow reactors, industrial catalytic reactors, micro trickle bed reactors and multiphase catalytic reactors. The use of catalytic reactor technology is essential for the economic viability of the chemical manufacturing industry. The importance of Chemical and Process Engineering and efficient design of reactors are another focus of the book. Especially the combination of advantages from both catalysis and chemical reaction technology for optimization and intensification as essential factors in the future development of reactors and processes are discussed. Furthermore, options that can drastically influence reaction processes, e.g. choice of catalysts, alternative reaction pathways, mass and heat transfer effects, flow regimes and inherent design of catalytic reactors are reviewed in detail. Focuses on the state-of-the-art applications of catalytic reactors and optimization in the design and operation of industrial catalytic reactors Insights into transfer of knowledge from laboratory science to industry For students and researchers in Chemical and Mechanical Engineering, Chemistry, Industrial Catalysis and practising Engineers

Download or read book Theoretical Chemical Engineering Abstracts written by and published by . This book was released on 1986 with total page 954 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Product Formation Rates in Heterogeneous Catalytic Processes written by Charles Evan Sanborn and published by . This book was released on 1949 with total page 346 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Dynamic Assessment and Optimization of Catalytic Hydroprocessing Process written by Abbas Azarpour Hassankiadeh and published by . This book was released on 2021 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Among the processes in petrochemical industry, hydroprocessing is an imperative process to produce clean fuels. This process is still being improved despite its 70-year maturity. Catalyst deactivation is a key aspect in the design and operation of catalytic processes in petrochemical industry. In this research, a dynamic heterogeneous model is presented to evaluate the performance of an industrial hydropurification/hydrotreating process in the purified terephthalic acid (PTA) production plant. This process includes a trickle-bed reactor (TBR) packed with palladium supported on carbon (0.5wt.% Pd/C) catalyst. In fact, this chemical production unit represents a three-phase catalytic system where some chemical reactions take place. Therefore, an accurate and meticulous analysis is required to develop a proper mathematical model, taking into account all transport phenomena occurring in the system. The model considers the axial back-mixing, flow non-ideality, and the catalyst deactivation. Model development leads to a set of partial differential equations consisting of nonlinear equations of the reaction rates, nonlinear expression of the catalyst deactivation rate, mass balance of each component in the reaction mixture, and energy balance of each phase. The model parameters are calculated using suitable correlations. The set of partial differential equations is solved using proper numerical techniques, including method of lines and finite difference method, in MATLAB software environment. First, the model reliability is assessed through the comparison of the model results with the industrial data. The validation phase confirms that the model results are accurate, and the developed model can be used for further process evaluation. A sensitivity analysis is then implemented to assess the effects of different operating parameters on the performance of the hydropurification/hydrotreating process. The results reveal that axial dispersion model is more accurate than the plug flow model. Moreover, 4- carboxybenzaldehyde (4-CBA) impurity in the reactor feed is the most detrimental parameter, affecting the catalytic performance. It is found that reduction in the catalyst particle size can improve the catalyst performance by about 16%, and an increase in the catalyst particle porosity can enhance the catalyst lifetime by around 8%. In this condition, the catalyst bed pressure drop is maintained at an acceptable level. In addition, 13% increase in the hydrogen partial pressure enhances the catalyst lifetime by about 20%. It should be noted that pressure increase might lead to the reactor pressure fluctuation, leading to an increase in the PTA powder turbidity. Therefore, reactor operation control is a critical factor. Considering other hydrodynamic parameters, a decrease in liquid hourly space velocity and the catalyst bed porosity improves the system performance in terms of catalyst lifetime and product quality. An increase in the liquid-solid mass transfer and contacting efficiency has a slight positive impact on the catalytic system performance. Product quality control can be carried out more properly if the feed impurity concentration is managed/controlled efficiently. In this research, a practical strategy is presented to effectively mix the feed streams having varying concentrations of the impurities (e.g., high and low concentrations of 4-CBA). This can be achieved by suggesting a proper ratio control, keeping the feed composition and flowrate at normal operating conditions. This strategy can also be employed to deal with the off-spec PTA powder product. In addition, the effect of temperature on the sintering mechanism of the Pd/C catalyst deactivation is investigated. The results reveal that temperature increase can accelerate the decline rate of the Pd/C catalyst surface area. The reduced activity of Pd/C catalyst is in an acceptable agreement with the normalized ratio of reduction in the surface area of pure Pd with increasing temperature. In the last phase, an efficient methodology is proposed to assess the hydroprocessing process in terms of energy and exergy performance. The process simulation and exergy analysis are conducted using Aspen Plus® and MATLAB software packages. The results are in a satisfactory agreement with the industrial data. It is concluded that the optimal operating conditions result in 15% reduction in the exergy destruction; the optimal scenario can also reduce the operation costs and the carbon tax at 9.96% ($20.5/h) and 14.75% ($14.54/h), respectively.

Download or read book Heterogeneous Catalysis in Microreactors written by Xiaotong Zhan and published by . This book was released on 2018 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This study presents the preparation and the evaluation of performance of a new monolithic catalyst in microreactor. The transfer hydrogenation of p-nitrophenol by formic acid is chosen as the model reaction for the comparison of the monolith with a traditional packed-bed microreactor containing commercial catalyst.This thesis includes an important experimental part. On the one hand, experimental set-up and protocols involving on-line analysis have been developed in order to study quantitatively the model reaction; On the other hand, the conditions of preparation of functionalized silica monolith in a stainless steel tube with the inner wall pre-coated by glass were optimized, and the palladium nanoparticles were immobilized by a continuous flow method. The monolith possesses the flow-through macropores, typical hexagonal organization of mesopores and micropores, and scarcely any shrinkage. The comparison of the two types of catalysts mainly focuses on the activity of catalysts in the model reaction, their kinetic model and their dynamic behavior in the start-up phase of the flow microreactor. In the theoretical part, the modelisation of reactor has been investigated both under stationary conditions for kinetics determination and under transient conditions for the rationalization of experimental observations. Pd@silica monolith and commercial Pd@alumina powder have different behavior and gives different kinetic laws. A reaction model with change in the catalytic surface properties could explain the unusual profile of concentrations observed with commercial catalyst. The superior performance of monolithic catalyst is demonstrated, which also exhibits particular industrial interests.

Download or read book Robust Control System Design for a Fixed bed Catalytic Reactor written by Jorge Anibal Mandler and published by . This book was released on 1987 with total page 518 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book APPLICATION OF UNCERTAINTY ANALYSIS OF IGNITION PERFORMANCE TO THE ENGINEERING TEST REACTOR written by S.K. HO and published by . This book was released on 1988 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Studies on a Heterogeneous Catalytic Reactor in the Transient State written by Gilles Henri Denis and published by . This book was released on with total page 362 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Preparation of Catalysts IV written by and published by . This book was released on 1987 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Optimization of Activity Distributions in Heterogeneous Catalysts written by Richard Charles Dougherty and published by . This book was released on 1985 with total page 230 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book American Chemical Society Directory of Graduate Research 1987 written by American Chemical Society, Committee on Professional Training Staff and published by . This book was released on 1987 with total page 1390 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Chemical Reactor Analysis and Design written by Gilbert F. Froment and published by . This book was released on 1990-01-16 with total page 706 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is the Second Edition of the standard text on chemical reaction engineering, beginning with basic definitions and fundamental principles and continuing all the way to practical applications, emphasizing real-world aspects of industrial practice. The two main sections cover applied or engineering kinetics, reactor analysis and design. Includes updated coverage of computer modeling methods and many new worked examples. Most of the examples use real kinetic data from processes of industrial importance.

Download or read book Kinetics of Heterogeneous Catalytic Reactions written by Michel Boudart and published by Princeton University Press. This book was released on 2014-07-14 with total page 241 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is a critical account of the principles of the kinetics of heterogeneous catalytic reactions in the light of recent developments in surface science and catalysis science. Originally published in 1984. The Princeton Legacy Library uses the latest print-on-demand technology to again make available previously out-of-print books from the distinguished backlist of Princeton University Press. These editions preserve the original texts of these important books while presenting them in durable paperback and hardcover editions. The goal of the Princeton Legacy Library is to vastly increase access to the rich scholarly heritage found in the thousands of books published by Princeton University Press since its founding in 1905.