Fluid Catalytic Cracking Riser Research Articles

Modelling and Simulation of Coking in the Riser of an Industrial Fluid Catalytic Cracking (FCC) Unit

Under normal Fluid Catalytic Cracking (FCC) conditions, coke is the most important factor that affects catalyst activity. A pseudo homogeneous two - dimensional (2D) model of an industrial FCC riser is here presented. The FCC riser models of previous researchers were mostly based on the assumption of negligible mass transfer resistance and 1D plug flow. These assumptions undermine the accuracy of the models by over-predicting the riser residence time while under-predicting the reaction time. Mass transfer resistance was incorporated in the reactor model to enhance the accuracy of the results. Finite difference was used to discretise the model equation. This investigation has advanced research into the modeling of FCC riser by predicting catalyst coke content as a function of reaction temperature. The yields of LCO, gasoline, gas and coke that were predicted by the model for industrial risers were 15.54wt%, 49.70wt%, 18.01wt% and 4.90wt% respectively. A feed stock (VGO) conversion of 79.28% was predicted by the model. An optimal operating temperature range of 786K<T<788K was predicted for the riser. http://dx.doi.org/10.4314/njt.v34i2.14

Comparison of vaporization models for feed droplet in fluid catalytic cracking risers

Vaporization of atomized feedstock is one of the critical processes in fluid catalytic cracking (FCC) risers; which is more often ignored in most of the FCC riser modelling studies. In this study, two different vaporization mechanisms of feedstock namely homogeneous mode and heterogeneous mode were studied. Different homogeneous models duly validated for various pure component droplets were applied to predict the vaporization time of the feed droplets typically expected in FCC feed vaporization zone. A new physical model for heterogeneous vaporization considering droplet–particle collision mechanics was also developed in the present study which compared well with the other existing heterogeneous modelling approaches. Comparison of the two vaporization modes indicates that under typical operating conditions of FCC riser, vaporization time of feed droplets predicted by heterogeneous mode is always lower than the homogeneous mode at least by an order of magnitude due to significant increase in heat transfer coefficient which accounts for droplet-particle contact. It is expected that actual vaporization time of feed droplets in an industrial FCC riser should lie in the range predicted by these two vaporization mechanisms which actually set the two limiting modes of vaporization. Obtained results predicted by the models could be used to aid design of the FCC feed vaporization zone.

A Computational fluid dynamics (CFD) comparison of 3-Lump and 4-Lump kinetic models for predicting gasoline, light gases and coke yield in fluid catalytic cracking (FCC) riser

In this study a comparison of 3-lump and 4-lump kinetic models predicting the yield of gasoline, light gases and coke in FCC riser has been done. Commercial CFD software with K-epsilon turbulence model is used to investigate the reactions occurrence between fluid and solids in a fluidized bed. An important feature of this model is that its kinetics includes partial differential equations. This provides accurate predictions of product yields in the FCC riser. In this simulation different process variables such as temperature and feed rate are changed to investigate the effect on product yields. Time accurate transient problem is solved with the prediction of yield profiles of gas oil, gasoline, light gas and coke. The output curves demonstrate the breaking of heavy hydrocarbon in the presence of catalyst. An approach proposed in this study shows good agreement with the experimental and numerical data available in literature.

Four – Lump Kinetic Model vs. Three - Lump Kinetic Model for the Fluid Catalytic Cracking Riser Reactor

The paper presents the research and the results obtained by the author concerning the kinetic modeling of the riser of the catalytic cracking unit. This study is structured in four parts. The first part presents the process description and the actual kinetic model existent in the special literature. The next part contains a detailed presentation of the two kinetic models developed by the author for the catalytic cracking riser reactor (four and three lump kinetic model). The final part presents the comparison results of the three and four lump kinetic model. The results reveal the 4 lump kinetic model is more appropriate to represent the kinetic model of the catalytic cracking process, in the sense that a higher gasoline yield is thus obtained, whereas a lower quantity of coke is obtained.

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.

A Comparative Study of Different Kinetic Lumps Models in the Fluid Catalytic Cracking Unit Using COMSOL Multiphysics

The COMSOL Multiphysics computational fluid dynamics software was used to simulate the fluid catalytic cracking (FCC) riser reactor of the FCC unit. The 4-, 5-, 10-, 20-, and 35-lump kinetic models were used to describe the kinetics of the cracking reactions in the riser reactor. The results of the kinetic lump models of the distributions of pressure, velocity, temperature, and yields of products were compared using practical values from the Port Harcourt Refinery Company plant. The results showed that the higher the kinetic lumps the better the accuracy of the prediction of the product yields and that the 10-, 20-, and 35-lump kinetic models could be used to predict the yield of various fractions of the riser reactor using COMSOL Multiphysics.

A two‐zone model for fluid catalytic cracking riser with multiple feed injectors

Developments in modeling of the fluid catalytic cracking (FCC) process have progressed along two lines. One emphasizes composition‐based kinetic models based on molecular characterization of feedstocks and reaction products. The other relies on computational fluid dynamics. The aim is to develop an FCC model that strikes a balance between the two approaches. Specifically, we present an FCC riser model consisting of an entrance‐zone and a fully developed zone. The former has four overlapping, fan‐shaped oil sprays. The model predicts the plant data of Derouin et al. and reveals an inherent two‐zone character of the FCC riser. Inside the entrance zone, cracking intensity is highest and changes rapidly, resulting in a steep rise in oil conversion. Outside the entrance zone, cracking intensity is low and varies slowly, leading to a sluggish increase in conversion. The two‐zone model provides a computationally efficient modeling approach for FCC online control, optimization, and molecular management. © 2014 American Institute of Chemical Engineers AIChE J, 61: 610–619, 2015

Simulation of an Industrial Fluid Catalytic Cracking Riser Reactor Using a Novel 10-Lump Kinetic Model and Some Parametric Sensitivity Studies

A fluid catalytic cracking (FCC) unit has been simulated by integrating FCC riser reactor and regenerator models. This simulation uses a new10-lump riser reactor kinetic model developed in-house. The lumping scheme and reactions are based on more detailed description of the feed in terms of PNA (paraffins, naphthenes, and aromatics) in both light and heavy fractions. An artificial neural network (ANN) model, also developed in-house, relates routinely measured properties such as specific gravity, ASTM temperatures, and so on to the detailed feed composition needed for the kinetic model development. The conversion and product yields obtained by integrating the model equations were found to be in close agreement with those measured in the plant in all the cases investigated. Simulation results using the present model, when compared with results from a conventional 5-lump model, clearly brought out the improvement in prediction because of detailed feed description calculated from ANN models. A parametric sens...

An integrated methodology for the modeling of Fluid Catalytic Cracking (FCC) riser reactor

Modeling description of the riser reactor is a highly interesting issue in the development of FCC process. However, one of the challenging problems in the modeling of FCC riser reactors is that sophisticated flow-reaction models with high accuracy need long computational time, while simple flow-reaction models give rise to results with fast computation but low accuracy. This dilemma requires new type of coupled flow-reaction models. The goal of this study was to propose a novel integrated model with time-efficient computation and acceptable accuracy. The integrated model, named equivalent reactor network (ERN) model, was established based on Aspen Plus simulator with considering gas–solid hydrodynamics via built-in modules and catalytic reactions via external FORTRAN subroutines, as well as lump mixtures characterized by real components. Through comparing with pilot-scale experimental data and industrial plant data in two case studies, the developed ERN model was justified to be capable of precisely and quickly modeling FCC riser reactors. Furthermore, the proposed methodology is expected to be readily applied to studies on the dynamic simulation, optimization, and control of FCC units in future studies.

A handy method for estimating the particle concentration distribution in FCC risers using a gamma-ray transmission technique

A handy gamma-ray transmission method for estimating the particle concentration distribution in a fluid catalytic cracking (FCC) riser is proposed. The method is based on an empirical correlation , which has only one unknown parameter , hence only one single-beam experimental result is enough to estimate the particle concentration distribution in the riser. In order to verify the feasibility of this method, the particle concentrations of three cross-sections of the laboratory riser were measured and the distribution profiles were compared with those reported in the literature. Furthermore, by comparing other gamma-ray function methods applied in the measurement of risers, this method has distinct advantages, such as the device is simple and has no moving parts, the measurement is rapid, and the safety is high because only one gamma-ray beam is used. Therefore, the method has promising applications in estimating particle concentrations or monitoring operation conditions of risers.

A CFD modeling of the gas–solid two‐phase flow in an FCC riser under the electrostatic conditions

ABSTRACTElectrostatics is an inevitable phenomenon in fluidization processes and granular flow, where collisions between particulates and walls with different materials occur. In this work, a two‐dimensional computational fluid dynamics model based on the Eulerian–Eulerian approach was applied and coupled with a first‐principles electrostatic model to describe the gas–solid two‐phase flow behavior in a fluid catalytic cracking (FCC) riser reactor under the electrostatic conditions. The coupled model was used to predict the main gas–solid flow distribution parameters in the FCC riser, such as electric potential, particle volume fraction, gas‐phase temperature, and gas‐phase component fractions. The simulation results showed that the electrostatic had a significant influence on the particle distribution in the bottom dense region of the FCC riser, whereas it had a weak influence in the upper dilute region at the cold‐flow conditions. The simulation results also showed that the electrostatic had a weak influence on the particle concentration, gas‐phase temperature, and lump concentration distributions when the cracking reaction was considered. © 2014 Curtin University of Technology and John Wiley &amp; Sons, Ltd.

New insights into intraparticle transfer, particle kinetics, and gas–solid two-phase flow in polydisperse fluid catalytic cracking riser reactors under reaction conditions using multi-scale modeling

This study provides new insights into fluid catalytic cracking (FCC) riser reactor from multi-scale viewpoint. The problem of simultaneous intraparticle molecule transfer and reaction, particle kinetics, and gas–solid flow in polydisperse FCC riser reactors was considered. A multi-scale CFD method was developed for constructing a multi-scale model to solve this problem. The multi-scale model consisted of a two-phase CFD model incorporating a single-particle model and a population balance model. The main flow field distribution parameters within the catalyst particles and reactors as well as the solid particle size distribution (PSD) could be calculated simultaneously based on intraparticle transfer and reaction using these models. The single-particle and multi-scale models were first verified and evaluated. Based on the validated models, intraparticle transfer limitations and/or flow fields in two size-scale FCC riser reactors were predicted. The simulations demonstrated three different reaction zones in FCC risers, and more elaborate mass, heat, and momentum transfer behaviors could be obtained. The simulations also demonstrated that particle kinetics (i.e., breakage and aggregation) have obvious influences on the FCC flow field in FCC risers; these effects have not been observed in conventional CFD models.

Simulation Studies on Variable Cluster Size in FCC Riser Reactor

Cluster baser fluid catalytic cracking (FCC) riser models are widely used for studying the effect of operating conditions on the products yields. Cluster size is an important parameter that influences the particle residence time, heat and mass transfer coefficients, and product yields in the FCC riser. In most cluster based models a constant cluster size (6 mm) is used. In the present work, various correlations for the prediction of cluster size as a function of local flow conditions are compared. The results show significant variation in conversion, and yields of gasoline and coke for these correlations. Coke yield prediction is most influenced by the cluster size.

Advance in China fluid catalytic cracking (FCC) process

Since the first Chinese fluid catalytic cracking (FCC) unit was commercialized in 1965, these milestone innovations and developments have been achieved in the historical sequence events of zeolite catalyst-riser FCC process, residue FCC process, DCC (deep catalytic cracking) process, multi-cascade riser FCC process and the ongoing high-selective FCC process in China. In the course of the development of Chinese FCC technology, many breakthroughs have been made, such as the quantities of FCCU increased dramatically from the blank beginning, the technical level of FCCU enhanced higher and higher, the capacity of FCCU grew larger and larger, and the R&D on FCC technology was from the tracking mode to the independent innovation mode. Up to now, the total capacity of FCCU in China has been reached 150 Mt/a, in which the residue ratio of FCCU feedstock is around 40%. The outputs of FCCU are roughly taking up the components of 70%, 30% and 40% to gasoline pool, diesel pool and propylene pool respectively, as well as raw materials of alkylation units and etherificationunits. Now FCC is playing a decisive role in the aspects of heavy oil processing, higher light oil recovery, products qualification improving, and better economic benefits in the oil industry of China.

Prediction of gasoline yield in a fluid catalytic cracking (FCC) riser using k-epsilon turbulence and 4-lump kinetic models: A computational fluid dynamics (CFD) approach

Fluid catalytic cracking (FCC) is an essential process for the conversion of gas oil to gasoline. This study is an effort to model the phenomenon numerically using commercial computational fluid dynamics (CFD) software, heavy density catalyst and 4-lump kinetic model. Geometry, boundary conditions and dimensions of industrial riser for catalytic cracking unit are conferred for 2D simulation using commercial CFD code FLUENT 6.3. Continuity, momentum, energy and species transport equations, applicable to two phase solid and gas flow, are used to simulate the physical phenomenon as efficient as possible. This study implements and predicts the use of the granular Eulerian multiphase model with species transport. Time accurate transient problem is solved with the prediction of mass fraction profiles of gas oil, gasoline, light gas and coke. The output curves demonstrate the breaking of heavy hydrocarbon in the presence of catalyst. An approach proposed in this study shows good agreement with the experimental and numerical data available in the literature.

Modeling fluid catalytic cracking risers with special pseudo-components

Special pseudo-components (SPCs) are proposed to be the compositional entities for characterizing the complicated mixtures of stock and product oils involved in fluid catalytic cracking risers. SPCs have invariant and definite physicochemical properties and are defined in pairs of light and heavy oil cuts of narrow boiling range. A narrow cut of true boiling point distillation of a stock or product oil is expressed with a pair of SPCs, which constitutes the basis for the characterization procedure developed in this paper. A steady state model for a prototype riser with a side feed stream is formulated where material and heat balance is strictly observed, the hydraulic behavior is considered, and the kinetic scheme of Gupta et al. (2007) is adopted. Results of tests with production data from three commercial risers show that the kinetic scheme of Gupta et al. (2007) is predictive as coupled with the suggested characterization procedure in the sense that for a given riser and given catalyst, the kinetic parameters are independent of stock oils.

In Situ Upgrading of Light Fluid Catalytic Cracking Naphtha for Minimum Loss

The key to reducing the olefin content in fluid catalytic cracking (FCC) gasoline is to upgrade the olefin-rich light FCC naphtha (LCN). To minimize the naphtha loss, several parameters were investigated in a pilot-scale riser FCC apparatus. The results indicate that, besides the reaction temperature, the catalyst-to-oil ratio, and the catalyst type, the boiling range and the olefin content of LCNs also have significant influence on the upgrading effect. Moreover, a relatively short residence time is beneficial for efficiently upgrading LCNs. In addition, the influence of the reactor structure should be brought to our attention. When a novel structurally changed reactor with a multinozzle feed system was used, significantly increased olefin conversion and decreased naphtha loss can be achieved. The calculation of hydrogen balance indicates that, because of the decrease of dry gas and coke yields, more hydrogen in the feed can be distributed into the desired products.

Conversion of low density polyethylene into fuel through co-processing with vacuum gas oil in a fluid catalytic cracking riser reactor

In this work, mixtures of vacuum gas oil and low density polyethylene, a major component of common industrial and consumer household plastics, were pyrolytically co-processed in a fluid catalytic cracking (FCC) riser reactor as a viable alternative for the energy and petrochemical revalorisation of plastic wastes into valuable petrochemical feedstocks and fuel within an existing industrial technology. Using equilibrium FCC catalyst, the oil–polymer blends were catalytically cracked at different processing conditions of temperatures between 773K and 973K and catalyst feed ratios of 5:1, 7:1 and 10:1. The influence of each of these processing parameters on the cracking gas and liquid yield patterns were studied and presented. Further analysed and presented are the different compositional distributions of the obtained liquids and gaseous products. The analysis of the results obtained revealed that with very little modifications to existing process superstructure, yields and compositional distributions of products from the fluid catalytic cracking of the oil–polymer blend in many cases were very similar to those of the processed oil feedstock, bringing to manifest the viability of the feedstock co-processing without significant detriments to FCC product yields and quality.

Evaluating the role of intraparticle mass and heat transfers in a commercial FCC riser: A meso-scale study

The paper provides new insights into the fundamental mechanism of catalytic cracking from the meso-scale viewpoint. Intraparticle mass and heat transfers were studied under fluid catalytic cracking (FCC) reaction conditions. A comprehensive single particle model was developed to characterize detailed chemical and physical phenomena occurred within catalyst particles in a commercial FCC riser from an industrial-scale refinery. This model integrates the mass, energy, and momentum balances as well as the equations for gas-state, lumped-species reaction kinetics, the multicomponent diffusion and convective heat transfer. This model is capable of predicting temperature, pressure, species mass fraction distributions, as well as the reaction rate and the effective diffusivity coefficient within the particles as a function of catalyst position in the riser. A detailed study based on the validated model demonstrated that there are three typical particle phenomena along the axial direction in the FCC riser, which leads to different catalytic and reactive operating zones under simultaneous mass and heat transfers as well as reaction. The different operating zones can be named as the transport-controlled, the reaction-controlled and the intermediate transition zones, and they have been described in detailed in this work.

Laboratory-Scale Experiments and Industrial Practice of Low-Temperature Contact and High Ratio of Catalyst to Oil in the FCC Process

Contrast experiments of fluid catalytic cracking (FCC) were conducted in a technical pilot scale riser FCC apparatus. The results showed that the use of a low-temperature regenerated catalyst and high ratio of catalyst to oil (CTO) improved the initial contact between the catalyst and feedstock. Thermal cracking was inhibited and catalytic cracking was promoted in the FCC riser, which were favorable for increasing the conversion and generation of desirable products. A modified FCC process was proposed and numerical simulation were used in the selection of the equipment structure for mixing cold and hot regenerated-catalyst streams to achieve optimal contact between the catalyst and the feedstock. A commercial unit was revamped based on the experimental results to test the modified FCC process. Results from industrial practice showed that product distributions under optimal conditions of low-temperature contact and high ratio of catalyst to oil in the modified FCC process were superior to those from routin...