Download or read book CFD Simulation and Experiment of Catalyst Deactivation and Heat Transfer in a Low N Fixed bed Reactor written by Mohsen Behnam and published by . This book was released on 2011 with total page 358 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: Modeling of fluid flow, heat transfer and reaction in fixed beds is an essential part of their design. This is especially critical for highly endothermic reactions in low tube-to-particle diameter ratio (N) tubes, such as methane steam reforming (MSR) and alkane dehydrogenation as two important commercial reactions. The modeling of fixed bed reaction is available in literatures with lots of assumptions. However, there is a need for implementing the reaction conditions with diffusion aspects on a real fixed bed reactor without assuming any pseudo conditions. Computational fluid dynamics (CFD) has been found as a suitable tool by many researchers to simulate fixed beds. CFD can simulate complex geometry of randomly-packed tubes, and provides us with more fundamental understanding of the transport and reaction phenomena in reactor tubes. CFD can be used to obtain detailed three-dimensional velocity, species and temperature fields that are needed to improve engineering approaches. Previously, the geometry of 120-degree wall segment (WS) of the whole reactor tube has been studied in our group. Previous works have introduced the coupling of gas flow and resolved species and temperature gradients inside pellets by CFD for methane steam reforming (MSR) and propane dehydrogenation (PDH) without considering deactivation. The deactivation of catalysts due to carbon formation is an important problem in industry, such as steam reforming and the catalytic dehydrogenation of alkanes, which are both strongly endothermic reactions. Many researches were carried out to study the effect of carbon formation and catalyst deactivation on the reactor performance. The local carbon deposition on catalysts can cause particle breakage and strongly decrease reaction rates. Catalyst deactivation in heated tubes removes the heat sink and can result in local hot spots that weaken the reactor tube. This is particularly a problem for a low tube-to-particle diameter ratio fixed bed reactor. A 3D resolved CFD model simulation was used to study the local details of carbon deposition in which the reactions and deactivation take place inside the catalytic solid particles. CFD simulations of flow, heat transfer, diffusion and reaction were carried out using the commercial CFD code FLUENT/ANSYS 6.3 in a 3D 120-degree periodic wall segment with N=4. The mesh used boundary layer prism cells at both the inside and outside particle surfaces and at the tube wall. These reactions were represented in the solid particles using user-defined scalars to mimic species transport and reaction, with user-defined functions supplying reaction rates. Diffusion in the particles was modeled by Fick's law using an effective diffusivity, given by Hite and Jackson's approximation of the Dusty Gas Model. The transient developments of particle internal gradients and carbon accumulation have been studied for the early stages of deactivation. Carbon concentration is initially strongest close to the surface and in the high temperature regions of the catalysts and affected by the wall heat flux. Deactivation of the endothermic reactions causes a slow increase in the average catalyst temperature. The second stage of the research was the verification of our CFD reaction model with experimental data under reacting conditions. The highly endothermic commercial methane steam reforming (MSR) reaction was studied experimentally in a fixed bed reactor. The temperature contributions inside catalyst particles were measured. The MSR reaction showed strong effects on the temperature profile along the reactor. Then, a CFD model was used to predict temperature profiles under MSR reaction conditions. Comparison of CFD and experimental data showed very good qualitative as well as quantitative agreement for temperature inside catalyst particles at different inlet gas temperatures. The last stage was to develop a fundamental energy equation without introducing new adjustable parameters to study heat transfer in fixed beds. In the past, many researchers have been carried out to simulate the heat transfer in fixed bed reactors by using k[subscript r] (effective thermal conductivity) and h[subscript w] (heat transfer coefficient). But the classical model with k[subscript r] and h[subscript w] cannot give a correct T(r) near tube wall, where deactivation is strongest. Therefore we need a better model which can represent the near wall heat transfer more accurate. CFD modeling was used to develop pseudo-continuum model for T(r) using V[subscript r] (r, z) and V[subscript z] (r). To get better temperature at the wall vicinity close to the physical reality. In this model radial thermal conductivity was obtained from Zehner-Schlünder model. The convection heat transfer was calculated in the 2D flow fluid from the CFD run. Results were obtained for Reynolds numbers in the range 240-?1900. The accuracy of the new model has been validated by analytical solution. The temperature calculated by the new velocity field pseudohomogenous energy equation showed reasonable quantitative agreement with values predicted by the CFD model.

Download or read book Mathematical Modeling of Complex Reaction Systems in the Oil and Gas Industry written by Jorge Ancheyta and published by John Wiley & Sons. This book was released on 2024-07-25 with total page 485 pages. Available in PDF, EPUB and Kindle. Book excerpt: Master the fundamentals of reaction systems modeling for the age of decarbonization Reactor design is one of the most important parts of the oil and gas industry, with reactor processes and the accompanying technologies constantly evolving to meet industry needs. A crucial component of effective reactor design is modelling complex reaction systems, which can help predict commercial performance, shape safety procedures, and more. At a time when decarbonization and clean energy transition are among the fundamental global technological challenges, it has never been more important for engineers to grasp the cutting edge of reaction system modelling. Mathematical Modeling of Complex Reaction Systems in the Oil and Gas Industry provides a systematic introduction to this timely subject. Each chapter provides a step-by-step description of the kinetic and reactor models for a particular kind of process and its accompanying systems. Backed by voluminous experimental data and incorporating extensive simulation results, the book constitutes an indispensable contribution to the global search for clean energy solutions. Mathematical Modeling of Complex Reaction Systems in the Oil and Gas Industry readers will also find: All the required tools for developing new reactor models for different reaction scales Detailed discussion of topics including hydrocracking of heavy oils, catalyst deactivation, oxidative regeneration of catalysts, and many more Extensive treatment of both steady-state and dynamic simulations Mathematical Modeling of Complex Reaction Systems in the Oil and Gas Industry is ideal for chemical and process engineers, computational chemists and modelers, catalysis researchers, and any other researchers or professionals in petrochemical engineering and the oil and gas industry.

Download or read book CFD Applications in Nuclear Engineering written by Wenxi Tian and published by Frontiers Media SA. This book was released on 2023-08-21 with total page 219 pages. Available in PDF, EPUB and Kindle. Book excerpt: High fidelity nuclear reactor thermal hydraulic simulations are a hot research topic in the development of nuclear engineering technology. The three-dimensional Computational Fluid Dynamics (CFD) and Computational Multi-phase Fluid Dynamics (CMFD) methods have attracted significant attention in predicting single-phase and multi-phase flows under steady-state or transient scenarios in the field of nuclear reactor engineering. Compared with three-dimensional thermal hydraulic methods, the traditional one-dimensional system analysis method contains inherent defects in the required accuracy and spatial resolution for a number of important nuclear reactor thermal-hydraulic phenomena. At present the CFD method has been widely adopted in the nuclear industry, across both light water reactors and liquid metal cooled fast reactors, providing an effective solution for complex issues of thermal hydraulic analysis. However, the CFD method employs empirical models for turbulence simulation, heat transfer, multi-phase interaction and chemical reactions. Such models must be validated before they can be used with confidence in nuclear reactor applications. In addition, user practice guidelines play a critical role in achieving reliable results from CFD simulations.

Download or read book 23 European Symposium on Computer Aided Process Engineering written by Fazel Moradi and published by Elsevier Inc. Chapters. This book was released on 2013-06-10 with total page 17 pages. Available in PDF, EPUB and Kindle. Book excerpt: Dimethyl ether (DME) as a clean fuel seems to be a superior candidate for high-quality diesel fuel in near future. In this study, a comprehensive three-dimensional dynamic heterogeneous model developed to simulate the flow behavior and catalytic coupling reactions for synthesis of the DME from hydrogenation of the CO and CO2, dehydration of methanol to dimethyl ether and water gas shift reaction in a fixed bed reactor. For this purpose, a CFD simulation was articulated where the standard k-ε model with 10% turbulence tolerations implemented. Then the concentration and temperature profiles along the reactor were determined. It was revealed that under conditions considered, a single phase physiochemical system under equilibrium existed for which simulations were performed. Ultimately, generated results of the model under appropriate industrial boundary conditions compared with those of others available in the open literature to verify the developed model. Then, the effects of various operating parameters including the pressure, temperature and flow rate of the feed to the reactor upon the DME production as well as; selectivity were examined. The CFD modeling results generated from the present work revealed reasonable agreement with obtained data of these authors and other experimental available in the open literature which considering the complexity of the task performed was rather satisfying.

Download or read book CFD Studies of Reactive Flow with Thermal and Mass Diffusional Effects in a Supercritical Packed Bed Catalytic Reactor written by Samuel J. Mekala and published by . This book was released on 2018 with total page 213 pages. Available in PDF, EPUB and Kindle. Book excerpt: Packed bed reactors are widely used in various chemical processes. Fundamental understanding of the heat and mass transfer phenomena in the packed beds is essential for better modelling of these processes. Theoretical models used to describe the flow in packed beds generally assume an effectively homogeneous systems ignoring the complexities of flow in the void spaces of the packed beds. These details may however be influencing significantly the various phenomena in the system. To enhance this understanding, Computational Fluid Dynamics (CFD) is used to obtain detailed flow, temperature and concentration profiles in packed bed with multiple species undergoing heat and mass transfer with accompanying reaction in a heterogeneous catalytic reactor model. CFD is a simulation tool that through solving of momentum, mass and energy balances around complex geometries gives advanced view of fluid flow and transport mechanisms in the catalytic reactor. In this thesis work, fluid flow and heat and mass transfer phenomena in packed beds is solved using CFD codes, developing a modelling strategy to design heterogeneous reaction packed bed equipment. Supercritical transesterification reaction process, for which experimental data was available from earlier experimental work was available was taken as a reference processes for simulation models. Due to the complexity of this process which involves various transport phenomena, and extreme operating conditions, each of the transfer process occurring in the packed bed is studied distinctly. A state-of-the art and a literature review is presented for CFD applications in packed beds, supercritical fluids and transesterification reaction. The governing equations and accompanying complementary models used in the simulations are presented. Physical properties of the reaction components methanol, triolein, diglyceride, mono-glyceride, fatty acid methyl esters, and glycerol at supercritical conditions are estimated. A geometrical model of heterogeneous catalytic reactor, which is a cylindrical tube filled with cylindrical particles arranged randomly, is developed representing a laboratory pilot unit. A 120-degree segment of packed bed tube is generated and validated against a complete wall-segment bed. Mesh influence over the flow is checked for different mesh refinement and a mesh of optimal refinement, independent of the mesh is selected for further study. As the packed bed is heated from the walls, wall-to-fluid heat transfer in packed beds is analysed, and CFD obtained results are used to review the radial flow effects in packed bed flow. The results are also related with empirical correlations analysing comparable trends. Particle-to-fluid mass transfer in packed beds is also studied with the triolein diffusion from particles to analyse the diffusional effects in the bed. For an analogous energy transfer, particle-to-fluid heat transfer is also studied. CFD obtained results are compared against previously published experimental data/empirical correlations. Mixed (free + forced) convection in packed beds at high pressure is also studied. Numerical results obtained are presented and compared against experimental data on mass transfer for supercritical extraction. Applicability of available reaction kinetics for transesterification reaction is studied. Packed bed models are prepared for one-step irreversible and three-step reversible reaction kinetics, for different temperatures and space-times. Numerical results are compared against experimental results, and flow, concentration and conversion profiles are obtained and analysed. Effects of the two kinetic models is studied for different temperatures and space-times.

Download or read book The Modelling and Dynamics of Catalysts and Fixed Bed Reactors written by Klavs Flemming Jensen and published by . This book was released on 1980 with total page 358 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Modelling and Identification of a Catalytic Packed Bed Reactor written by Marvin Jay Schwedock and published by . This book was released on 1983 with total page 550 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Catalyst Deactivation and Fixed Bed Reactor Modeling written by Rustom M. Billimoria and published by . This book was released on 1979 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book CFD Study of the Intra and Inter Particles Transport Phenomena in a Fixed bed Reactor written by Alexandre Troupel and published by . This book was released on 2009 with total page 280 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: Actual models for fixed-bed reactor modeling make this assumption that temperature is uniform, or at least symmetric, within the catalytic pellets. However, if this holds true for large beds (tube-to-particle diameter ratio N greater than 10), it appears that for small N tubes (N = 3-10) that wall effects cannot be neglected anymore. A large temperature gradient appears in the near wall region. Hence for a particle at the wall a variation in temperature of up to 50\162\170C was noticed. This temperature change was investigated, and it has been noticed that the proximity to the wall, but also to a low velocity region could explain a maximum in temperature. Furthermore, species concentration discrepancies were also notice. An adiabatic run was made to show that these were not due to heated wall effects. Instead it appeared that these concentration variations are due to both their proximity to a low flow region and to a confined area. Hence incoming diffusion in these zones appeared to be lower than for the rest of the surface. We also could notice a strong impact of the flow on the temperature patterns in the near wall regions. Hence in our case, it appeared that the 4 holes geometries allowed a better flow in front the particle at the flow, and therefore better transport phenomena. On the contrary, the full cylinder geometry tend to block the flow, consequently temperature on the wall particles were hotter than what they were with the 4 holes cylinder geometry. A study of the diffusion within the catalytic particles was also conducted. Hence, the Maxwell-Stefan, the dusty gas and the binary friction models were implemented in Fluent. The goal here is to refine step by step the diffusion model used. First products and reactants molar fluxes were assumed to be proportional. The next step was to compute the actual molar fluxes; however this added one more parameter to converge; that is the diffusion coefficient. Finally the assumption of negligible pressure variation within the pellets was dropped. Unfortunately, the implementation into Fluent was not successful, and few possible reasons were given.

Download or read book Computational Fluid Dynamics CFD Simulation of a Gas Solid Fluidized Bed Residence Time Validation Study written by Baru Debtera and published by GRIN Verlag. This book was released on 2021-11-29 with total page 26 pages. Available in PDF, EPUB and Kindle. Book excerpt: Academic Paper from the year 2021 in the subject Physics - Mechanics, , language: English, abstract: In this study, numerical simulations of a gas-solid fluidized bed reactor involving a two-fluid Eulerian multiphase model and incorporating the Kinetic Theory of Granular Flow (KTGF) for the solids phase have been performed using a commercial Computational Fluid Dynamics (CFD) software. The fluidized bed setup consists of 1,5 m height and 0,2 m diameter in which a series of experiments were performed using Helium tracer to determine the Residence Time Distribution (RTD) at various normalized velocities i.e., with different degrees of gas-solids mixing. Both 2D and 3D simulations of the fluidized bed reactor are performed. The main purpose of this study is to understand the hydrodynamic behavior of a gas-solid fluidized bed reactor through a framework of Eulerian multiphase model and to analyze hydrodynamic behavior of the gas-solids mixing.

Download or read book Modeling Chemistry and Flow in Catalytic Fixed bed Reactors with Detailed Geometry written by Ying Dong and published by . This book was released on 2018 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this work, three-dimensional CFD models were developed and applied to simulate catalytic fixed bed reactors with different types of packing configuration and reactions. A spatially resolved profile measurement technique was applied in this work to critically validate the simulation results, and to calibrate parameters required in the model. This work demonstrates that detailed reactor modeling and profile measurements are useful tools for achieving an in-depth understanding of the interactions between flow, heat and mass transfer and catalytic reactions in fixed bed reactors. Furthermore, with the comprehensive knowledge gained from both methods, a knowledge-based reactor optimization approach can be put forward.

Download or read book Power to Gas Technology and Business Models written by Markus Lehner and published by Springer. This book was released on 2014-07-18 with total page 99 pages. Available in PDF, EPUB and Kindle. Book excerpt: Increased production of energy from renewable sources leads to a need for both new and enhanced capacities for energy transmission and intermediate storage. The book first compares different available storage options and then introduces the power-to-gas concept in a comprehensive overview of the technology. The state of the art, advancements, and future requirements for both water electrolysis and methanation are described. The integration of renewable hydrogen and methane into the gas grid is discussed in terms of the necessary technological measures to be taken. Because the power-to-gas system is very flexible, providing numerous specific applications for different targets within the energy sector, possible business models are presented on the basis of various process chains taking into account different plant scales and operating scenarios. The influence of the scale and the type of the integration of the technology into the existing energy network is highlighted with an emphasis on economic consequences. Finally, legal aspects of the operation and integration of the power-to-gas system are discussed.

Download or read book An Introduction to Chemical Engineering Kinetics Reactor Design written by Charles G. Hill and published by Рипол Классик. This book was released on with total page 603 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book CFD Studies of Wall region Fluid Flow and Heat Transfer in a Fixed Bed Reactor written by Michiel Nijemeisland and published by . This book was released on 1998 with total page 14 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Measurement and Calculation of Temperature and Conversion in Fixed bed Catalytic Reactors written by Jørgen Kjær and published by . This book was released on 1958 with total page 220 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Structured Catalysts and Reactors written by Andrzej Cybulski and published by CRC Press. This book was released on 2005-11-02 with total page 828 pages. Available in PDF, EPUB and Kindle. Book excerpt: Interest in structured catalysts is steadily increasing due to the already proven, as well as potential, advantages of these catalysts. Updating the comprehensive coverage of the first edition published in 1998 with the latest science and applications, Structured Catalysts and Reactors, Second Edition gives detailed information on all aspect

Download or read book Advances in Catalyst Deactivation written by Calvin H. Bartholomew and published by MDPI. This book was released on 2018-10-01 with total page 312 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is a printed edition of the Special Issue "Advances in Catalyst Deactivation" that was published in Catalysts