Computation of Effectiveness Factors for Partially Wetted Catalyst Pellets using the Method of Fundamental Solution

Trickle Bed Reactors Are Widely Used in Many Process Industries. the Catalyst Particles Are Often Incompletely Wetted Especially in the Trickling Flow Regime and Hence to Design These Reactors, the Effectiveness Factor of Partially Wetted Catalyst Needs to Be Calculated Accurately. Numerical Solutions by Traditional Methods Are Time Consuming and Not Very Accurate, Especially for Some Commonly Used Complex Catalyst Shapes Such as Trilobes, Quadrilobes Etc. the Paper Presents a Novel Numerical Solution for These Problems based on the Method of Fundamental Solutions. the Advantage of the Method is that It Involves Only Boundary Collocation and Can Be Applied to Catalysts of Any Shape. Further the Method Provides an Accurate Estimate of the Gradient of the Concentration Profiles and This Information Can Be Related Directly to the Effectiveness Factor. This Accuracy of the Method is Demonstrated for Two Dimensional (2-D) and Axisymmetric Problems for a Linear Kinetics. Illustrative Results Are Presented for Some Complex Shapes under Partial Wetting Conditions. © 2003 Elsevier Science Ltd. All Rights Reserved

Fluid dynamics assessment of hydrotreating reactors of diesel oil

Orientador: José Roberto NunhezDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia QuímicaResumo: Neste trabalho, a Fluidodinâmica Computacional (CFD) foi usada para investigar o hidrotratamento de diesel (Hidrodessulfurização (HDS) e Hidrodesaromatização (HDA)) em um reator de leito fixo (TBR) em escala de laboratório. O modelo CFD utilizou uma abordagem Euleriana-Euleriana multifásica e modelos de interação interfásicos. Foram empregados, também, modelos de distribuição de porosidade para partículas trilobes, transferência de massa e reações químicas. As simulações foram realizadas em condições isotérmicas e transientes e o leito foi considerado como sendo completamente molhado. Na primeira fase do trabalho, o modelo proposto foi validado. Depois, um reator em arranjo contra-corrente foi simulado e os resultados foram comparados a um reator com fluxo paralelo. Os parâmetros analisados foram conversão, queda de pressão e holdup de líquido em função das variações de pressão, temperatura, velocidade dos fluxos de gás e líquido. A influência da porosidade sobre a velocidade do líquido, também, foi investigada. Finalmente, verificou-se a influência do Liquid Hourly Space Velocity (LHSV), temperatura, razão das vazões gás-líquido na pressão parcial de H2S. Os resultados para os dois arranjos de reatores foram similares apesar do reator em contra-corrente ter alcançado conversões mais baixasAbstract: In this work, the Computational Fluid Dynamics (CFD) was used to investigate the hydrotreating diesel (Hydrodesulfurization (HDS) and Hidrodesaromatização (HDA)) in a fixed bed reactor (TBR) in laboratory scale. The CFD model used an Eulerian-Eulerian multiphase approach and interphase interaction models. A porosity distribution models for trilobes particle mass transfer and chemical reactions were used too. The simulations were performed under isothermal and transient conditions and the bed was considered to be completely wetted. In the first phase of work, the proposed model was validated. Then a reactor in countercurrent arrangement was simulated and the results were compared to a reactor with parallel flow. The parameters analyzed were conversion, pressure drop and liquid holdup due to the pressure changes, temperature, speed of the gas and liquid flows. The influence of porosity on the velocity of the liquid also was investigated. Finally, there is the influence of the Liquid Hourly Space Velocity (LHSV), temperature, ratio of the gas-liquid outflow in the partial pressure of H2S. The results for the two arrangements reactors were similar despite the reactor in countercurrent have reached lower conversionsMestradoDesenvolvimento de Processos QuímicosMestre em Engenharia Química131239/2014-7CNP

Investigation of packed bed and moving bed reactors with benchmarking using advanced measurement and computational techniques

Trickle bed reactors (TBR), as typical packed bed reactors (PBR), are widely used in various fields. Very limited information regarding the flow behaviors, hydrodynamic, and mathematical models in extrudate catalyst shapes, such as cylinders, trilobes, and quadrilobes, can be found in literatures because the major focus was on spherical shape. Therefore, a hybrid pressure drops and liquid holdup phenomenological model for extrudate catalyst shapes was developed based on two-phase volume averaged equations, which showed high accuracy against experimental data. The maldistribution and dynamic liquid holdup were investigated in quadrilobe catalyst using gamma-ray computed tomography. A pseudo-3D empirical model was developed and compared with deep neural network predictions. Both models were in good agreement with experimental data. The accretion locations of heavy metal contaminants entrained with flow were tracked by the dynamic radioactive particle tracking technique in the packed beds of sphere, cylinder, trilobe, and quadrilobe, respectively. Kernel density estimator was used to indicate the accretion probability distribution, showing that pressure drop played an important role in heavy metal accretions. CFD simulations of random packed trilobe catalyst bed were conducted to obtain the local information and were validated by experimental data. Moving bed reactors (MBR), as a relatively new type of reactor, encounter many challenges due to the bed expansion because of the concurrent gas-liquid upflow. DEM simulation was used to generate expanded bed. A porosity distribution correlation was developed and implemented in CFD simulations to investigate the hydrodynamics --Abstract, page iv