Fluid Catalytic Cracking Riser Research Articles

PIV investigation on the effect of gas distributor design for fluidization of Geldart A spherical particles

This is a hydrodynamics study on gas distribution during fluidization of the industrially relevant Geldart A type particles. The impact of 10 different distributor designs comprising perforated distributors (pitch and orifice arrangement pattern varied) and nozzle distributors (nozzle size varied) were studied experimentally on a bench-scale unit. Particle flow homogeneity in air was determined by a novel Particle Image Velocimetry (PIV) analysis of the freeboard velocity field. Over 50 PIV particle phase vector field images are presented and analysed. Bed expansion, Particle attrition with and without fines, velocity profiles with and without fines and effect of fines on bed expansion were ascertained. Best distributor design for a unit such as Fluid Catalytic Cracking (FCC) regenerator and FCC riser were found to be 0.8 cm and 0.6 cm nozzle plates distributors respectively. Confirmation with previous study revealed a correlation between homogeneous distribution of particulate flow and lower number of turbulence zones.

Artificial Intelligence for Hybrid Modeling in Fluid Catalytic Cracking (FCC)

This study reports a novel hybrid model for the prediction of six critical process variables of importance in an industrial-scale FCC (fluid catalytic cracking) riser reactor: vacuum gas oil (VGO) conversion, outlet riser temperature, light cycle oil (LCO), gasoline, light gases, and coke yields. The proposed model is developed via the integration of a computational particle-fluid dynamics (CPFD) methodology with artificial intelligence (AI). The adopted methodology solves the first principle model (FPM) equations numerically using the CPFD Barracuda Virtual Reactor 22.0® software. Based on 216 of these CPFD simulations, the performance of an industrial-scale FCC riser reactor unit was assessed using VGO catalytic cracking kinetics developed at CREC-UWO. The dataset obtained with CPFD is employed for the training and testing of a machine learning (ML) algorithm. This algorithm is based on a multiple output feedforward neural network (FNN) selected to allow one to establish correlations between the riser reactor feeding conditions and its outcoming parameters, with a 0.83 averaged regression coefficient and an overall RMSE of 1.93 being obtained. This research underscores the value of integrating CPFD simulations with ML to optimize industrial processes and enhance their predictive accuracy, offering significant advancements in FCC riser reactor unit operations.

Alternative Options for Ebullated Bed Vacuum Residue Hydrocracker Naphtha Utilization

The vacuum residue hydrocracker naphtha (VRHN) is a chemically unstable product that during storage changes its colour and forms sediments after two weeks. It cannot be directly exported from the refinery without improving its chemical stability. In this research, the hydrotreatment of H-Oil naphtha with straight run naphtha in a commercial hydrotreater, its co-processing with fluid catalytic cracking (FCC) gasoline in a commercial Prime-G+ post-treater, and its co-processing with vacuum gas oil (VGO) in a commercial FCC unit were discussed. The hydrotreatment improves the chemical stability of H-Oil naphtha and reduces its sulphur content to 3 ppm. The Prime-G+ co-hydrotreating increases the H-Oil naphtha blending research octane number (RON) by 6 points and motor octane number (MON) by 9 points. The FCC co-cracking with VGO enhances the blending RON by 11.5 points and blending MON by 17.6 points. H-Oil naphtha conversion to gaseous products (C1–C4 hydrocarbons) in the commercial FCC unit was found to be 50%. The use of ZSM 5 containing catalyst additive during processing H-Oil naphtha showed to lead to FCC gasoline blending octane enhancement by 2 points. This enabled an increment of low octane number naphtha in the commodity premium near zero sulphur automotive gasoline by 2.4 vol.% and substantial improvement of refinery margin. The processing of H-Oil naphtha in the FCC unit leads also to energy saving as a result of an equivalent lift steam substitution in the FCC riser.

Computational prediction of green fuels from crude palm oil in fluid catalytic cracking riser

Fluid catalytic cracking could convert crude palm oil into valuable green fuels to substitute fossil fuels. This study aimed to predict the phenomenon and green fuels yield in the industrial fluid catalytic cracking riser using computational fluid dynamics. A three-dimensional transient simulation using the Eulerian-Lagrangian with the multiphase particle-in-cell is to investigate reactive gas-particle hydrodynamics and the four-lump kinetic network model with the rare earth-Y catalyst for crude palm oil cracking behaviors. The study results show that the fluid and catalyst velocity profile increase in the middle of the riser reactor because the cracking reaction process that produces OLP and Gas products has a lighter molecular weight. The endothermic reaction causes the temperature profile to decrease because the heat of the reaction comes from the catalyst. This analysis shows that the simulation accurately predicts green fuel products from crude palm oil. As a result, the crude palm oil conversion, organic liquid product yield, and Gas yield correspond to 70 wt%, 28.8 wt%, and 27.5 wt%, respectively. Compared to the experimental study, the computational prediction of yield products showed good agreement and determined the optimal riser dimension. The methodology and results are guidelines for optimizing the FCC riser process using CPO.

Solids flux profiles of Geldart Group A particles in high‐velocity circulating fluidized bed risers

AbstractCirculating fluidized bed (CFB) risers using Group A particles have traditionally, mostly, been considered to operate in the fast fluidization regime, which consists of a core‐annulus flow profile with solids refluxing in the annulus layer. High gas and solids flow riser studies, however, suggest the existence of additional types of flow behaviours. Therefore, more studies are still needed to help clear uncertainties of local solids flow patterns in CFB risers of Group A particles, especially at gas and solids flow rates at or near those in commercial units. In this study, riser density and local solids flux profiles were measured in 0.3 m diameter risers of three CFB units at gas velocities of 9–16 m/s and solids fluxes of up to 700 kg/s · m2. A variety of radial solids flux profiles were obtained, including a parabolic profile with a peak flux at about the radial centre, a nearly flat profile across the riser cross‐section and an inverted parabola with peak upwards flux near the wall. At high gas velocity and solids flux, risers have no solids downflow at the wall. Multiple fluidization regimes were found to exist in the riser. The bottom dense part of the riser was in the dense suspension upflow regime, and the dilute upper part was in the dilute pneumatic transport regime. With commercial fluid catalytic cracking (FCC) risers operating at nearly similar conditions as tested here, it is likely that they also have one or both fluidization regimes and not the traditional fast fluidization regime. The data in this study fitted well on the Kim et al. fluidization regime map.

Development and application of counter‐current feed injection technology in riser reactors

AbstractA counter‐current feed injection scheme is proposed to improve the jet‐solid mixing and reaction in the injection zone of riser reactors. By analyzing the characteristics of the coupled flow field, combined with experiments and numerical simulation, the advantages of the new injection technology are investigated. Experimental results show that the particles distribute more uniformly when the feed is injected downward, which is good for the mixing and reaction of the jet with particles. By simulating the reaction in an industrial fluid catalytic cracking (FCC) riser, it is found that the yields of gasoline and liquefied petroleum gas (LPG) are increased significantly by using the counter‐current feed injection structure. Simultaneously, the formation of coke is reduced considerably. On this basis, a riser‐fluidized bed coupled reactor was designed by adopting the proposed counter‐current feed injection technology to solve the coking problem in an industrial pyridine synthesis system. Results from the side‐stream sampling show that the carbon content of the catalyst reduces significantly, indicating a decrease in coke formation. By now, the improved industrial reactor has been in stable operation for 2 years, showing good reliability.

Numerical investigation of flow, heat transfer, and kinetic reaction in a large‐difference bidisperse, circulating fluidized‐bed reactor

AbstractTo study particle bidispersity effect on the comprehensive performance of a gas–solid fluidized system, multi‐field coupling numerical research of large‐difference bidisperse circulating fluidized bed was performed. First, numerical simulation was conducted on the dynamic characteristic of a bidisperse gas–solid system that contained both Geldart A and B particles; heat transfer and reaction performances were then studied with the introduction of a propane dehydrogenation (PDH) kinetic reaction model; and finally, the concept of coupling fluid catalytic cracking (FCC) and PDH processes was proposed, and the feasibility was preliminarily discussed. The results showed that the two particle phases were hierarchically distributed with a pronounced segregation layer due to their large‐difference bidispersity characteristic, the Geldart B‐type particle was in a bubbling fluidizing state, while the Geldart A‐type particle was in a turbulent fluidizing state. With the initialized bed and regeneration temperature set to 973 K, the regenerated catalyst's final, balanced temperature could decrease to 942 K, which demonstrated that a significant decline in contact temperature between the feedstock and catalyst could be achieved in the following FCC risers. Additionally, this coupling process also achieved a nearly complete conversion of propane into propene, with a conversion efficiency of above 95%. The results showed the feasibility of this coupling process, which could optimize FCC riser reaction conditions and further achieve a higher‐valued light gas yield. This research can provide a reference for the study of the bidispersity effect on a gas–solid system, and the introduced coupling process can provide a new model for the FCC process's optimization.

Development of a Two‐Fluid Hydrodynamic Model for a Riser Reactor

AbstractANSYS Fluent is used to examine the mixing of catalyst zeolite particles with petroleum feedstock and water vapor in a fluid catalytic cracking (FCC) riser. A two‐fluid model is developed for tracking catalyst particles and gas mixture in a riser, modeling the granular and gaseous phases as two interpenetrating continua. The hydrodynamic flows are analyzed with the aim to single out the principal physical effects that determine the distribution of particles. The results are compared with a study that is based on a non‐isothermal reactive model. It is demonstrated that the simplistic purely hydrodynamic model generates similar flow fields. The developed model is valuable for improvements of modern FCC risers. The model is applied for understanding the hydrodynamics of an S‐200 KT‐1/1 industrial unit.

A Review of Modelling of the FCC Unit–Part I: The Riser

Heavy petroleum industries, including the fluid catalytic cracking (FCC) unit, are useful for producing fuels but they are among some of the biggest contributors to global greenhouse gas (GHG) emissions. The recent global push for mitigation efforts against climate change has resulted in increased legislation that affects the operations and future of these industries. In terms of the FCC unit, on the riser side, more legislation is pushing towards them switching from petroleum-driven energy sources to more renewable sources such as solar and wind, which threatens the profitability of the unit. On the regenerator side, there is more legislation aimed at reducing emissions of GHGs from such units. As a result, it is more important than ever to develop models that are accurate and reliable, that will help optimise the unit for maximisation of profits under new regulations and changing trends, and that predict emissions of various GHGs to keep up with new reporting guidelines. This article, split over two parts, reviews traditional modelling methodologies used in modelling and simulation of the FCC unit. In Part I, hydrodynamics and kinetics of the riser are discussed in terms of experimental data and modelling approaches. A brief review of the FCC feed is undertaken in terms of characterisations and cracking reaction chemistry, and how these factors have affected modelling approaches. A brief overview of how vaporisation and catalyst deactivation are addressed in the FCC modelling literature is also undertaken. Modelling of constitutive parts that are important to the FCC riser unit such as gas-solid cyclones, disengaging and stripping vessels, is also considered. This review then identifies areas where current models for the riser can be improved for the future. In Part II, a similar review is presented for the FCC regenerator system.

Revisiting a large-scale FCC riser reactor with a particle-scale model

Understanding gas–solid hydrodynamics, heat and mass transfer, and multiphase reactions is of great importance to the design of a large-scale fluid catalytic cracking (FCC) riser reactor. FCC catalyst particles in a large-scale (e.g., demo-scale or industrial-scale) riser reactor are generally simulated using Eulerian methods since Lagrangian approaches are often avoided because of their high computational cost. As a result, information about the flow at the particle scale is not considered. In this study, the catalyst behaviors in a large-scale FCC riser reactor are investigated with a particle-scale model that is based on the multiphase particle-in-cell (MP-PIC) scheme. Cracking reactions are taken into account through the incorporation of an eight-lump kinetic model. Numerical predictions are found to be in very close agreement with the available plant data. Detailed particle-scale information, including the particle trajectory, residence time (i.e., internal age), and coke content of the catalysts in the large-scale riser reactor, are fully quantified. Catalyst particles may be entrapped in the diameter-enlarged section, leading to high mean residence time (i.e., 1.67 s) and coke content (more than 3.0% of 3.20% catalyst particles therein), and thereby low catalytic activities (e.g., 0.77 at the height of 2.0 m). It is believed that these findings should help better understand the particle-scale physical and chemical phenomena in large-scale FCC multi-regime riser reactors and assist the design, scale-up, and optimization of similar industrial devices.

Simulation of a kinetic model integrated with variable catalyst holdup applied in industrial fluid catalytic cracking risers

Abstract The importance of the axial catalyst holdup on the accurate prediction of reaction yields from Fluidized Catalytic Cracking Unit (FCCU) risers was explored in this study. The Kunii and Levenspiel model was incorporated in the FCCU riser simulations for predicting the solid holdup. Two approaches were compared – the popular one assuming Constant Holdup (CH) and the other incorporating Variable Holdup (VH) in the reaction kinetics models. Simulation predictions using these two approaches were fitted to the yield profiles obtained from industrial plant data reported in the literature. The kinetic parameter estimates, including frequency factors and coking parameters obtained from these two approaches, were quite similar, indicating insensitivity to catalyst holdup. However, the kinetic model incorporating VH expression could predict the plant conversion and yield to within ±10% error throughout the riser. In contrast, the CH model led to predictions that were rather erroneous (>±25%) at the riser bottom as the catalyst particle acceleration zone was neglected. Temperature, gas density, catalyst particle, and gas phase velocity profiles obtained from the VH approach were considerably different from those obtained using the CH approach. The VH approach showed that the slip factor, especially, was quite distinct as it reached a peak value before decaying exponentially. On the other hand, the CH model showed a monotonic increase in slip factor along the riser.

Role of chlorides in reactivation of contaminant nickel on fluid catalytic cracking (FCC) catalysts

Nickel, a common contaminant in crude oil, deposits on Fluid Catalytic Cracking (FCC) catalysts and induces unwanted dehydrogenation reactions. These lead to an increase in hydrogen and coke which inhibits the FCC unit from reaching its optimal operation. Modern catalyst technologies can include nickel passivation strategies to minimize such detrimental effects, and, over time, aging of the nickel on catalyst also diminishes its deleterious activity to some extent; however, reactivation of nickel due to chemical interactions within the FCC unit can retard aging and further penalize the catalytic performance. For the first time, we attempt to demonstrate and characterize the physiochemical and catalytic effects of chloride ions on contaminant nickel in the FCC environment. Equilibrium catalyst (Ecat) samples obtained from industrial FCC units are exposed to chloride ions, and changes in physicochemical characteristics, catalytic selectivity, and the reducibility of nickel are analyzed. These changes indicate the reactivation of nickel and an increase in unwanted dehydrogenation reactions following exposure to chloride ions. Spectroscopic analyses show that the interaction with chloride ions alters the electronic environment of nickel, which makes it easier to be reduced in the FCC riser, and Advanced Cracking Evaluation (ACE) studies show equilibrium catalysts that were exposed to chloride ions gave higher coke and H2 yields. These results bridge the gap between existing literature and the FCC environment by demonstrating that chloride ions can interact and reactivate nickel contaminant on FCC catalysts.

Thermal Energy Correction Based Model Predictive Control for Fluid Catalytic Cracking Riser

A model predictive control (MPC) method optimizing the temperature distribution along the fluid catalytic cracking (FCC) riser reactor is proposed to precisely control the reactions in the FCC rise...

Validation of a filtered drag model for solid residence time distribution (RTD) prediction in a pilot-scale FCC riser

Computational fluid dynamics (CFD) is a powerful tool for prediction and analysis of complex multiphase flow hydrodynamics and residence time distribution (RTD) in chemical reactors. This study presented the validation and application of a filtered drag model for solid RTD prediction in a pilot-scale fluid catalytic cracking (FCC) circulating fluidized bed (CFB) riser with Geldart A particles. First, the filtered drag model implemented in the open-source MFiX-TFM solver was validated for flow hydrodynamics simulation in a FCC CFB riser. After that, the model was further employed to validate its ability for solid RTD prediction in the same riser by comparing the simulation results with the experimental data. The simulation with the filtered drag model well reproduced the tracer response experiment which is more accurate than that with the Gidaspow drag model. Simulations with both pulse and step tracer injection methods were compared, which reveals the limitation of solid RTD measurement using a pulse tracer injection method in the experiment.

Mixing of Jet Gas with Catalyst Particles in Fluid Catalytic Cracking Risers

The residence time distributions of upward and downward gas injections in a fluid catalytic cracking riser were investigated by large-scale cold model experiments. The tanks-in-series model was employed to describe the local mixing of feed jets with catalyst particles. The model parameter M at various axial and radial measuring points was obtained by using the helium tracer method. On this basis, M was fitted with the jet–catalyst flow momentum ratio and the axial height. By knowing M of the full mixing zone of the riser, this method calculates the influence height of jets above the injection point. Results show that the downward feed offers a fuller mixing environment for jets and catalysts in their initial contact region. Besides, the influence height above the nozzles in the downward injection scheme is over 50% shorter than that of the upward jet case. This study confirms that the downward jets can provide a more ideal environment for jet–catalyst mixing.

Towards understanding of phenolic compounds impact on Ni- and V-USY zeolites during bio-oils co-processing in FCC units

In this work, the n-heptane transformation was carried out in absence and presence of 1.2 wt% of guaiacol over Ni- and V-impregnated zeolites at 450 °C, to evaluate the influence of these metals on the poisoning effect of phenolic molecules during bio-oils and traditional Fluid Catalytic Cracking (FCC) feedstocks co-processing. Impregnation of the metals slightly decreased the Brønsted acid sites, but importantly increased the Lewis acidity. Notably, guaiacol was found to be less poisonous at shorter time-on-streams when Ni or V were present on the zeolite, as the metal-induced Lewis acidity seems to promote guaiacol transformation, which slows down coke formation from n-heptane. Simultaneously, unconverted guaiacol molecules adsorb mainly on the Lewis acid sites, resulting in a higher number of Brønsted acid sites available for the cracking reactions. Influence of Ni on the attenuation of the guaiacol deactivating effect was more important owing to the generation of a higher amount of metal-induced Lewis acid sites. Hence, taking into account the short contact times in the FCC riser, the presence of metal contaminants, such as Ni and V, on the FCC catalysts appears to be beneficial for the co-processing, being possibly one of the explanations for the lower impact of the phenolic compounds on the FCC equilibrium catalyst when compared to pure ultra-stable Y zeolites.

Two-fluid model with variable particle–particle restitution coefficient: application to the simulation of FCC riser reactor

In most gas–solid fluidized bed reactors, particle–particle interactions vary as a result of the physical and/or chemical process. However, a constant value for the particle–particle restitution coefficient, a modeling parameter that can significantly affect the predicted hydrodynamics, is normally used to describe the particle–particle interaction in the simulation with the two-fluid model (TFM). Therefore, an advanced TFM with variable particle–particle restitution coefficient was developed to simulate the complex hydrodynamics and reaction behavior in the gas–solid fluidized bed reactor. The fluid catalytic cracking (FCC) riser reactor, in which the particle–particle restitution coefficient tends to decrease during catalytic cracking reactions because of the formation of cohesive coke under high temperature, was taken as an example to illustrate the application of the advanced TFM. Simulation results indicate that the advanced TFM can successfully describe the variation of the particle–particle restitution coefficient in the computational fluid dynamics (CFD) simulation of FCC riser reactor.

Parameter estimation of a six-lump kinetic model of an industrial fluid catalytic cracking unit

In this work a simulation of detailed steady state model of an industrial fluid catalytic cracking (FCC) unit with a newly proposed six-lumped kinetic model which cracks gas oil into diesel, gasoline, liquefied petroleum gas (LPG), dry gas and coke. Frequency factors, activation energies and heats of reaction for the catalytic cracking kinetics and a number of model parameters were estimated using a model based parameter estimation technique along with data from an industrial FCC unit in Sudan. The estimated parameters were used to predict the major riser fractions; diesel as 0.1842 kg-lump/kg-feed with a 0.81% error while gasoline as 0.4863 kg-lump/kg-feed with a 2.71% error compared with the plant data. Thus, with good confidence, the developed kinetic model is able to simulate any type of FCC riser with six-lump model as catalyst-to-oil (C/O) ratios were varied and the results predicted the typical riser profiles.

Numerical investigation of influence of treatment of the coke component on hydrodynamic and catalytic cracking reactions in an industrial riser

A three dimensional gas-solid reactive flow model based on the Eulerian-Eulerian approach was used to simulate the hydrodynamic, heat transfer and catalytic cracking reaction within in a conventional Fluid Catalytic cracking (FCC) riser. A 12-lump kinetic model was used to represent the catalytic cracking reaction network. It was proposed a catalyst deactivation model as a function of the weight percentage of coke amount on the catalyst to replace the deactivation model dependent of the residence time. It was compared the effects of novel treatment for coke component (coke produced in the solid phase) with common treatment (coke produced in the gas phase) on the fluid dynamic and catalytic cracking. The results showed that the treatment for coke component affects radial distribution of coke mass flow. It also showed that the treatment for coke plays an important role in simulation with catalyst deactivation as a function of coke amount on catalyst.

Modeling a FCC Riser with the RBF Neural Network

A radial basis function(RBF) neural network model has been proposed for predicting production yields and reducing simulation times of a modified special pseudo-components(SPCs) fluid catalytic cracking riser. Subsequently, a modified special pseudo-components riser, served as the source of reliable data for artificial neural network(ANN) model training and testing. The ANN model experimental results show a substantial reduction of computation time and good match compared to special pseudo-components fluid catalytic cracking riser mechanism model. Its potential use for modeling optimize and control of the riser is enormous.