Waldir Pedro Martignoni

Three-dimensional modeling of fluid catalytic cracking industrial riser flow and reactions

Abstract A three-dimensional and two-phase flow model to predict the dynamic behavior of a fluid catalytic cracking (FCC) industrial reactor was developed in this work. The study took into account heat transfer and chemical reactions. A four-lump model was proposed to represent the catalytic cracking reactions in which the heavy oil (gas oil) is converted into gasoline and light hydrocarbon gases. Gas acceleration inside the reactor due to molar expansion and a model to describe undesirable catalyst deactivation by coke deposition on its surface were also considered. An Eulerian description of the phases was used to represent the two-phase flow. A commercial CFD code (Ansys CFX version 11.0) was used to obtain the numerical data. Appropriate functions were implemented inside the CFX code to model the heterogeneous kinetics and catalyst deactivation. Results show nonuniform tendencies inside the reactor, emphasizing the importance of using three-dimensional models in FCC process predictions.

CFD Study of Industrial FCC Risers: The Effect of Outlet Configurations on Hydrodynamics and Reactions

Fluid catalytic cracking (FCC) riser reactors have complex hydrodynamics, which depend not only on operating conditions, feedstock quality, and catalyst particles characteristics, but also on the geometric configurations of the reactor. This paper presents a numerical study of the influence of different riser outlet designs on the dynamic of the flow and reactor efficiency. A three-dimensional, three-phase flow model and a four-lump kinetic scheme were used to predict the performance of the reactor. The phenomenon of vaporization of the liquid oil droplets was also analyzed. Results showed that small changes in the outlet configuration had a significant effect on the flow patterns and consequently, on the reaction yields.

Analysis of Process Variables via CFD to Evaluate the Performance of a FCC Riser

Feedstock conversion and yield products are studied through a 3D model simulating the main reactor of the fluid catalytic cracking (FCC) process. Computational fluid dynamic (CFD) is used with Eulerian-Eulerian approach to predict the fluid catalytic cracking behavior. The model considers 12 lumps with catalyst deactivation by coke and poisoning by alkaline nitrides and polycyclic aromatic adsorption to estimate the kinetic behavior which, starting from a given feedstock, produces several cracking products. Different feedstock compositions are considered. The model is compared with sampling data at industrial operation conditions. The simulation model is able to represent accurately the products behavior for the different operating conditions considered. All the conditions considered were solved using a solver ANSYS CFX 14.0. The different operation process variables and hydrodynamic effects of the industrial riser of a fluid catalytic cracking (FCC) are evaluated. Predictions from the model are shown and comparison with experimental conversion and yields products are presented; recommendations are drawn to establish the conditions to obtain higher product yields in the industrial process.

Fluid dynamic modelling and simulation of circulating fluidized bed reactors: importance of the interface turbulence transfer

The main objective of this work is to analyze the importance of the gas-solid interface transfer of the kinetic energy of the turbulent motion on the accuracy of prediction of the fluid dynamic of Circulating Fluidized Bed (CFB) reactors. CFB reactors are used in a variety of industrial applications related to combustion, incineration and catalytic cracking. In this work a two-dimensional fluid dynamic model for gas-particle flow has been used to compute the porosity, the pressure, and the velocity fields of both phases in 2-D axisymmetrical cylindrical co-ordinates. The fluid dynamic model is based on the two fluid model approach in which both phases are considered to be continuous and fully interpenetrating. CFB processes are essentially turbulent. The model of effective stress on each phase is that of a Newtonian fluid, where the effective gas viscosity was calculated from the standard k-e turbulence model and the transport coefficients of the particulate phase were calculated from the kinetic theory of granular flow (KTGF). This work shows that the turbulence transfer between the phases is very important for a better representation of the fluid dynamics of CFB reactors, especially for systems with internal recirculation and high gradients of particle concentration. Two systems with different characteristics were analyzed. The results were compared with experimental data available in the literature. The results were obtained by using a computer code developed by the authors. The finite volume method with collocated grid, the hybrid interpolation scheme, the false time step strategy and SIMPLEC (Semi-Implicit Method for Pressure Linked Equations - Consistent) algorithm were used to obtain the numerical solution.

Evaluation of the Performance of the Riser in the Fluid Catalytic Cracking Process

In a 3D model simulating in the riser of the fluid catalytic cracking (FCC) was studied feedstock conversion and yield products. Computational fluid dynamics (CFD) and Eulerian-Eulerian approach with a 12-lump model was used to predict the hydrodynamic and kinetic behavior, respectively. All the equations and conditions were solved using a solver Ansys CFX 14.0. The different operation variables and hydrodynamic effects of the riser are evaluated. Predictions from the model are shown and comparison with experimental data is presented; recommendations are drawn to establish the conditions to obtain higher product yields in the industrial process.

MODELAGEM CFD DE UM REATOR RISER-FCC USANDO O MODELO CINETICO DE LUMPING CONTINUO

RESUMO Sabe-se que os efeitos da hidrodinâmica sobre a seletividade e conversao dos produtos devem ser considerados na descricao cinetica das reacoes do craqueamento catalitico fluidizado (FCC). Embora, os testes experimentais sejam bastante desejados, seu custo e tempo muitas vezes os tornam inviaveis, especialmente em equipamentos de escala industrial. Desse modo, a fluidodinâmica computacional (CFD) considera-se uma ferramenta util no projeto e otimizacao desses processos. Nao obstante, a modelagem das reacoes FCC nao e uma tarefa facil, ja que, envolve um alto numero de reacoes e componentes, por isso frequentemente tem-se utilizado abordagens cineticas baseadas em pseudo-componentes para representar as reacoes, porem existem algumas limitacoes na descricao precisa destes pseudo-componentes. Neste trabalho propoe-se a utilizacao de uma abordagem inovadora em que funcoes de distribuicao da especie quimica sao aplicadas para descrever a cinetica das reacoes FCC sendo considerada a mistura reativa como continua. No estudo pretende-se avaliar a implementacao do modelo cinetico de lumping continuo em juncao com a hidrodinâmica associada de um leito fluidizado circulante (CFB) para predizer o rendimento dos produtos de uma unidade FCC industrial. Resultados preliminares mostraram uma adequada concordância com dados experimentais reportados na literatura, sendo possivel desse modo, descrever reacoes em misturas complexas com um numero reduzido de parâmetros cineticos alem de maior detalhamento das reacoes de craqueamento.

The influence on products yield and feedstock conversion of feedstock injection position along the industrial riser

The fluid catalytic cracking (FCC) process is at the heart of a modern refinery oriented toward maximum gasoline and diesel production. Within the entire refinery process, this process offers the greatest potential for increasing profitability; even a small improvement in the gasoline yield it implies a substantial economical profit when dealing with a production of millions of barrels of gasoline a day. There are several articles published in the last two decades focusing the attention on 2-D and 3-D computational fluid dynamic models of the industrial riser of a circulating fluidized bed. Nevertheless, there are few research works published in the literature that include studies on how the localization of feedstock along the riser affects the yield products. A 3D hydrodynamic model coupled with a 12 lump kinetic model is presented in this work. Four different injection points in an FCC industrial riser were considered in order to evaluate the hydrodynamic behavior and their effect in the gas oil conversion and products yield. The equations were solved numerically by finite volume method using the Eulerian-Eulerian approach and a commercial CFD code, CFX version 14.0. Appropriate functions were implemented in the model via user defined functions considering the heterogeneous kinetics and catalyst deactivation. The results from the model were validated against the experimental industrial results and it was found that the conversion of gas oil and the production yield significantly change with the feedstock localization.

Effect of Injection Zone on Catalyst and Gas Homogenization in FCC Riser

In the fluid catalytic cracking (FCC) process, the riser is the most important equipment where the reaction taken place. In the riser operation, the feedstock is fed through injectors and mixed with catalyst and steam. A good design and localization of the injectors to ensure rapid evaporation of the feedstock and a good contact of the droplets with the catalyst is important to improve the process efficiency due to a better reagent distribution which ensures a good feedstock conversion and product yields. Hydrodynamic modelling, heat transfer and cracking reactions were studied in this paper using Computational Fluid Dynamic (CFD) in order to evaluate the effect of nozzles design and configuration on the homogeneity of the gas-solid distribution. A 3D model was solved with the Eulerian – Eulerian approach using ANSYS/CFX version 14.0 as calculation tool. The simulation results showed that the distribution of gas-solid depends significantly on the configuration of the feedstock injectors.