Industrial Fluid Catalytic Cracking Unit Research Articles

Experimental study on flow characteristics of gas–solid two-phase flow in inclined pipes

In a fluid catalytic cracking unit, inclined pipes are mainly used for particle transportation and to maintain the pressure balance between the reactor and regenerator. In this experimental inclined pipe device, the characteristics of gas–solid two-phase flow were studied by measuring and analyzing the dynamic pressure and particle concentration parameters in different flow states. Corresponding relationships between pressure fluctuation and particle concentration on the one hand and flow patterns on the other were discovered. These were used for the quantitative identification of flow patterns. Measurement data from an analysis of bubble and particle velocities in an inclined pipe revealed a critical mass flow rate, Gs, in the mutual transformation of different particle flow patterns. The critical mass flow rate Gsc1 of lean-phase and dense-phase flows was 149kg/(m2·s). The critical mass flow rate Gsc2 of packed-bed and dense-phase flows was 240kg/(m2·s). This study enriches the basic theoretical knowledge on flow patterns in inclined pipes and provides a theoretical basis for the adjustment of inclined pipe operation in industrial fluid catalytic cracking units.

Servo and Regulatory Response of an Industrial Fluid Catalytic Cracking (FCC) Unit under Fuzzy Logic Supervisory Control

A self-tuning hierarchical controller in which a Fuzzy logic controller supervises the control actions of a conventional PID has been proposed, implemented and presented in this paper. The controller has been applied to a control study of Fluid Catalytic Cracking unit (FCCU) riser temperature, and regenerator temperature respectively. Comparison between the performance of the proposed Fuzzy-PID controller and the conventional PID was made in simulation studies of regulatory and servo performances of the two controller types. Six performance measures: Percent overshoot (OS), settling time (ST), integral absolute error (IAE), integral square error (ISE), integral time absolute error (ITAE) and integral time square error (ITSE) were employed as the tools for performance comparison between the conventional PID and the Fuzzy-PID controller. For the tracking of riser temperature with a set point at 524oC, the performance indicators under PID control gave the following results overshoot (14.5%); settling time (40 seconds) Integral absolute error (8.246), integral square error (3.3); integral time absolute error(1762);integral time square error (43.77) while for the same indicators under Fuzzy-PID control the following values: overshoot (3.3%); settling time (40 seconds) ;Integral absolute error (8.811); integral square error (14.5); integral time absolute error(280),;integral time square error (31.11) .The results allude to the superiority of the fuzzy-PID scheme over the PID scheme in tracking the optimal set point of riser temperature. More so, for tracking the regenerator set point temperature of 746oC, comparative study of step response under the two schemes gave the following results in six performance indicators: overshoot (PID (12.6%) / Fuzzy-PID (6%)); settling time (PID (80 seconds) / Fuzzy-PID (20seconds)); Integral absolute error (PID (14.29) / Fuzzy-PID (8.63)); integral square error (PID(6.713). Fuzzy-PID (4.506)); integral time absolute error(PID(2858)/Fuzzy-PID(305.9)), integral time square error (PID(77.55)/Fuzzy-PID(33.05)) . Moreover, the fuzzy-PID controller also showed superior performance over the conventional PID controller in terms disturbance rejection (regulatory response) of both riser and regenerator temperature. The results from this study suggest that the application of fuzzy-PID scheme to temperature control offers good promise of improved fluid catalytic cracking unit (FCCU) operations.

Processing renewable and waste-based feedstocks with fluid catalytic cracking: Impact on catalytic performance and considerations for improved catalyst design.

Refiners around the globe are either considering or are actively replacing a portion of their crude oil inputs originating from fossil sources with alternative sources, including recycled materials (plastics, urban waste, mixed solid waste) and renewable materials (bio-mass waste, vegetable oils). In this paper, we explore such replacement, specifically focusing on the fluid catalytic cracking (FCC) operation. Five pyrolysis oils, obtained from municipal solid waste (MSW) and biogenic material (olive stones/pits), were fully characterized and tested at 10% loading against a standard fluid catalytic cracking (FCC) vacuum gasoil (VGO) feed in a bench scale reactor using an industrially available fluid catalytic cracking catalyst based on ultrastable Y zeolite to simulate fluid catalytic cracking co-processing. Despite having unique feed properties, including high Conradson carbon (e.g., up to 19.41wt%), water (e.g., up to 5.7wt%), and contaminants (e.g., up to 227ppm Cl) in some cases, the five pyrolysis oils gave similar yield patterns as vacuum gasoil. Gasoline was slightly (ca. 1wt%) higher in all cases and LPG slightly (ca. 1wt%) lower. Olefinicity in the LPG streams were unchanged, bottoms and light cycle oil (LCO) showed no significant changes, while dry gas was slightly (up to -0.2wt%) lower. Coke selectivity was also unchanged (maximum -7.7wt%, relatively), suggesting minimal to no heat balance concerns when co-processing in an industrial fluid catalytic cracking unit. The results demonstrate the applicability of municipal solid waste and biogenic originating pyrolysis oils into a refinery. A catalyst design concept is explored, based on higher rare Earth oxide exchange and/or utilization of ZSM-5 zeolite, that would further minimize the impacts of replacing fossil oils with pyrolysis oils, namely one that shifts the 1% higher gasoline into LPG.

Synthesis and Soft Implementation of Supervisory Control Scheme in an Industrial Fluid Catalytic Cracking (FCC) Unit of a Nigerian Refinery

In this paper, a self-tuning hierarchical controller in which a Fuzzy logic controller supervises the control actions of a conventional PID has been proposed, implemented and presented. The controller has been applied to a control study of Fluid Catalytic Cracking (FCC) unit riser temperature, and regenerator temperature respectively. Performance comparison of the proposed Fuzzy-PID controller and the conventional PID was made in simulation studies of regulatory and servo performances of the two controller types. Six performance measures: Percent overshoot (OS), settling time (ST), integral absolute error (IAE), integral square error (ISE), integral time absolute error (ITAE) and integral time square error (ITSE) were employed as the tools for performance comparison between the conventional PID and the Fuzzy-PID controller. For the tracking of riser temperature with a set point at 524oC, the performance indicators under PID control gave the following results overshoot (14.5%); settling time (40 seconds) Integral absolute error (8.246), integral square error (3.3); integral time absolute error(1762);integral time square error (43.77) while for the same indicators under Fuzzy-PID control the following values: overshoot (3.3%); settling time (40 seconds) ;Integral absolute error (8.811); integral square error (14.5); integral time absolute error(280),;integral time square error (31.11) .The results allude to the superiority of the fuzzy-PID scheme over the PID scheme in tracking the optimal set point of riser temperature. More so, for tracking the regenerator set point temperature of 746oC, comparative study of step response under the two schemes gave the following results in six performance indicators: overshoot (PID(12.6%)/Fuzzy-PID(6%)); settling time (PID(80 seconds)/Fuzzy-PID(20seconds));Integral absolute error(PID(14.29)/Fuzzy-PID(8.63)); integral square error(PID(6.713).Fuzzy-PID(4.506)); integral time absolute error(PID(2858)/Fuzzy-PID(305.9)), integral time square error (PID(77.55)/Fuzzy-PID(33.05)).Moreover, the fuzzy-PID controller also showed superior performance over the conventional PID controller in terms disturbance rejection (regulatory response) of both riser and regenerator temperature. The results from this study suggest that the application of fuzzy-PID scheme to temperature control offers good promise of improved fluid catalytic cracking unit (FCCU) operations.

Hydrothermally stable mesoporous aluminosilicates as superior FCC catalyst: From laboratory to refinery

Well-ordered aluminosilicates (MAs) were prepared by in-situ assembly of pre-crystallized units of zeolite Y precursors at a commercial scale, and applied in an industrial fluid catalytic cracking unit for the first time. Compared with incumbent equilibrium catalyst, the surface area of trial equilibrium catalysts (30% inventory ratio) increased from 110 m2 g−1 to 120 m2 g−1. Moreover, a significant increase of the mesoporous surface area of trial equilibrium catalysts (30% inventory ratio) from 33 m2 g−1 to 40 m2 g−1 (22% increase). Furthermore, the equilibrium catalyst that contain 80% LPC-65 yields significantly lower heavy oil (0.23%) and higher total liquids (0.53%) compared with LDO-70. The industrial results demonstrated excellent hydrothermal stability and superior catalytic cracking properties, showing the promising future in the industrial units.

A bilevel data-driven framework for robust optimization under uncertainty – applied to fluid catalytic cracking unit

The operational optimization of refining process is facing the complex coupled state and frequently changed conditions. Especially the feed of fluid catalytic cracking (FCC) has property fluctuations which may lead to uncertainties in profit and lead to suboptimal optimization schemes from the deterministic optimization model. This study designed a bilevel data-driven robust optimization framework that optimizes the feed selection and reaction temperature of an industrial FCC unit under feed property uncertainty. Two uncertainty sets based on the feed properties data were derived from 2-year historical industrial data and simulation data. As most of the chemical reaction models are differential equations, a bilevel programming framework designed in Julia was the key point to solve the nested numerical and mathematic problems. A real-world case study is conducted to demonstrate the effectiveness of the proposed approach in protecting against uncertainties to ensure profits for FCC units.

Distributed economic model predictive control for an industrial fluid catalytic cracking unit ensuring safe operation

The economic performance of a fluid catalytic cracking (FCC) unit plays an important role in the refinery factory. In order to improve the dynamic economic performance as well as ensure safe operation, cooperative distributed economic model predictive controls (DL-EMPCs) that optimize the product yields of the FCC unit are proposed. Discrete-time Lyapunov constraints in the MPC are designed to guarantee stability and limit the MPC output such that the decrease ratio of Lyapunov function of the closed-loop system is no less than those obtained by the designed distributed auxiliary controller. The auxiliary controller is structural and designed based on a multi-model approximation of the plant due to the strong non-linearity of the FCC unit, which can keep the system’s convergence despite the unmeasurable disturbance and the model mismatch. The feasibility and stability of the proposed DL-EMPCs are discussed as well. The proposed algorithm was applied to an industrial FCC unit model based on a refinery factory in Jiujiang, China. The results show that better economic benefits are achieved compared to the set-point regulating MPC when no disturbance occurs. Additionally, the robust performance is verified that the unit with the controller can be manipulated in a safe region even if the disturbances exist.

Distributed economic model predictive control with pseudo-steady state modifier adaptation for an industrial fluid catalytic cracking unit

The fluid catalytic cracking (FCC) unit is a typical multi-timescale system. Its operational performance will make a significant difference in the overall economic benefits of the oil refining factory. Classical model-based optimization approaches may not always be completely satisfied due to unmeasurable disturbances and model-plant structure mismatch. A distributed economic MPC with pseudo-steady state modifier adaptation (DEMPC-MA) is proposed to cope with the difficulties. The strategy divides the plant into two parts, i.e., the slow dynamic part and pseudo-steady state part. The output modifier adaption is adopted to modify the model function according to the pseudo-steady state characteristics of the riser. Lyapunov stable constraints are added to the EMPC problem to guarantee a safe operation, while the feasibility of the algorithm is ensured by a set of auxiliary controllers, which are constructed offline based on the multi-model approach. The overall control optimization problem is solved in a distributed formulation through the alternating direction method of multipliers (ADMM) to improve the calculation performance. The proposed algorithm was applied to an industrial FCC unit model based on a refinery factory in Jiujiang, China. The results showed that the method obtained better economic benefits and finally reached the optimal steady-state operating point even if the model structure and parameter of the prediction model were mismatched.

Kinetic modeling for the catalytic cracking of tires pyrolysis oil

The parameters of a 6-lump kinetic model for the catalytic cracking of tire pyrolysis oil (TPO) in conditions of the industrial fluid catalytic cracking (FCC) unit have been computed. The experiments have been carried out in a riser simulator reactor, on a commercial equilibrium catalyst at the following conditions: 500–560 °C; catalyst/oil ratio (C/O), 3–7 gcat gTPO-1; and reaction time, 1–10 s. The most significant catalytic steps for conversion levels below 80% are those in which the heavy cycle oil (HCO) lump is involved, either cracked to form light cycle oil (LCO), naphtha, liquefied petroleum gases (LPG), dry gas or condensed to coke. For higher levels of conversion, LCO and naphtha lump over-crack causing exponential increases in the yields of LPG, dry gas and coke. It should be highlighted the high yield of naphtha obtained (48 wt%) for a conversion of 90% at 530 °C. It is also remarkable the low deactivation level by coke deposition, since the coke formed on the acid sites of the catalyst is not much condensed. The results are of great interest for the design or reactors ad hoc for the catalytic cracking of TPO in conditions similar to those of industrial FCC unit, as well as for its feeding to a commercial unit within the strategy involved in the Waste Refinery.

Effect of flow patterns in the recirculation catalyst standpipe on the performance of FCC high-efficiency regenerator

In this work, the flow patterns of the recirculation catalyst standpipe in an industrial fluid catalytic cracking unit (FCCU) were investigated based on the dynamic pressure, and their effects on the regeneration process were analyzed. First, the dynamic pressure along the standpipe was systematically measured and used to determine the flow patterns. The results demonstrated that the frequency, amplitude, and standard deviation of the dynamic pressure were correlated with various fluid patterns. Meanwhile, gas leakage was detected near the slide valve. Based on the dynamic pressure behavior, two flow pattern models, which involved bubbling fluidized flow, transitional packed bed flow and packed bed flow, were established to interpret the impacts on the regeneration parameters. The results indicated that the developed model was consistent with precious observations regarding an industrial FCCU. This work contributes to a deeper understanding of the flow patterns in industrial luid catalytic cracking standpipes.

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.

Upgrading of heavy coker naphtha by means of catalytic cracking in refinery FCC unit

The upgrading of heavy coker naphtha under conditions of the industrial fluid catalytic cracking (FCC) unit has been investigated, with the aim of obtaining light olefins and a gasoline fraction suitable to be used in the blending of motor fuels. The experiments have been conducted in a riser simulator reactor at: 500 and 550 °C; catalyst to oil mass ratio, 6 gcat goil−1; and, contact time, 3 to 12 s. Moreover, the effect of the properties of two commercial equilibrium catalysts on the products has been also assessed. Products have been grouped in: dry gas, liquefied petroleum gases, gasoline, light cycle oil and coke. The presence of strong acid sites in the catalyst favors the formation of light olefins, yielding a 5 and 3.3 wt% of propylene and butenes, respectively, at 550 °C and 6 s. A higher content of zeolite (with moderate acid strength sites) and a bigger size of the mesopores of the matrix promote the formation of a commercially interesting gasoline fraction with a yield of 90 wt% under the same conditions, with a concentration of aromatics, naphthenes, n-paraffins, olefins and iso-paraffins of 25, 10, 28, 21 and 15 wt%, respectively, and a RON of 84.

Co-cracking of high-density polyethylene (HDPE) and vacuum gasoil (VGO) under refinery conditions

The co–cracking of a 5 wt% of high–density polyethylene (HDPE) dissolved in vacuum gasoil (VGO) under conditions similar to those of the industrial fluid catalytic cracking (FCC) unit has been studied. The main goal has been to assess the effect of the co–feeding of waste plastic on attained conversion, as well as on the yield and composition of the products, given its interest for the subsequent refinery processes focused on the production of fuels. The products have been grouped in fractions: dry gas (C1-C2); liquefied petroleum gas (C3-C4), naphtha (C5-C12), light cycle oil (C13−C20), heavy cycle oil (C20+) and coke. Obtained results expose a significant synergy in the co–cracking, obtaining with the HDPE/VGO blend a higher conversion at 560 °C, together with higher yield of naphtha and concentration of light olefins. The synergy is based on the fast formation of intermediate alkylcarbenium ions at high temperature. Naphtha has been extensively characterized obtaining higher contents of n–paraffins and olefins and lower of iso–paraffins and aromatics in the cracking of the HDPE/VGO blend. This last characteristic increases the interest of the naphtha obtained in the co–cracking to be included in the gasoline pool of the refinery.

Surrogate-model-based, particle swarm optimization, and genetic algorithm techniques applied to the multiobjective operational problem of the fluid catalytic cracking process

This article provides a concise multiobjective optimization methodology for an industrial fluid catalytic cracking unit (FCCU) considering stochastic optimization techniques, genetic algorithms (GA) and particle swarm optimization (PSO), based on surrogates or meta-models in order to approximate the objective function. A FCCU was considered and simulated in an AspenONE process simulator. In addition the article examines the claim that PSO has the same effectiveness (finding the optimal global solution) as GA, but with significantly better computational efficiency (fewer function evaluations). The optimization results obtained with the PSO technique, based on the evaluation of less functions and adjustment of less parameters, showed a 3% increase in yield of naphtha as compared to results obtained with the GA technique. Finally, the results of the optimization obtained with the stochastic optimization techniques were compared and analyzed with a deterministic one. The performance targets of the multiobjective operational optimization supported the FCCU design and production planning to ensure refinery profitability and a regulatory environment.

Modelling and simulation of an industrial RFCCU-riser reactor for catalytic cracking of vacuum residue

A one-dimensional adiabatic mathematical model was developed for the riser reactor of an industrial residue fluid catalytic cracking unit (RFCCU). A seven-lump kinetic model was presented for the catalytic cracking of vacuum residue, taking cognisance of diffusion resistance, which is a departure from the general norm in the literature. Also, heat transfer resistance between the fluid and solid phases was incorporated into the energy balances for instantaneous and one-dimensional vaporization of feedstock. The developed model was a set of twelve coupled, highly non-linear and stiff ordinary differential equations, ODEs, which was numerically solved with an implicit MATLAB built-in solver, ode23t, designed deliberately for handling stiff differential equations to circumvent the problem of instability associated with explicit methods. An excellent agreement was achieved between the industrial RFCCU plant data and the simulated results of this study, with average absolute deviation being < ± 5% for instantaneous vaporization of feedstock in all cases investigated. Moreover, the simulated results revealed that half of the reactor was relatively redundant as this accounted for only 3% of the conversion. Hence, the findings of this study could be useful to the production practice for the Khartoum Refinery Company.

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.

Study on the integration of fluid catalytic cracking unit in refinery with solvent-based carbon capture through process simulation

Fluid catalytic cracking unit (FCCU) is an important refinery process by cracking heavy hydrocarbons to form lighter valuable products, including gasoline and diesel oil. However, the FCCU also generates the largest amount of CO2 emissions among all the refinery units. To solve this problem, solvent-based carbon capture can be introduced to capture CO2 in the flue gas from FCCU, but the energy consumption from the reboiler of the carbon capture plant will undoubtedly reduce the economic benefits of the refinery. In this paper, solvent-based carbon capture for an FCCU in a real life refinery is studied through process simulation. This study takes into account the process design and heat integration. An industrial FCCU with a feed capacity of over 1.4 million tons vacuum gas oil per year was modelled, and the process model was validated according to industrial operating data. A carbon capture plant model with MEA solvent was also developed in Aspen Plus® at pilot scale, and scaled up to match the capacity of the FCC unit. Case studies were performed to analyze the integration of the FCCU with commercial scale carbon capture plant, in which different heat integration options were discussed to reduce the energy consumption. The simulation results indicated that a proper design of heat integration will significantly reduce the energy consumption when the carbon capture plant is integrated with an industrial FCCU.

Seventeen-lump model for the simulation of an industrial fluid catalytic cracking unit (FCCU)

A 17-lump kinetic model has been developed for the riser–reactor cum regenerator of a fluid catalytic cracking unit (FCCU). This accounts for cracking, hydrogen transfer, aromatization, isomerization, alkylation and dimerization, as well as catalyst deactivation due to the coke deposition in its pores. A model for the industrial combustor–regenerator unit is also developed. The lumping scheme includes the detailed characterization in terms of the paraffins, naphthenes and aromatics (PNAs) for the VGO feed and also the detailed compositions of the two important products: gasoline and LPG. A total of 199 kinetic parameters for the riser–reactor cum regenerator have been fitted (tuned) using 192 sets of plant data (under different operating conditions) from an industrial FCC unit. The tuned model of the integrated FCCU was run for 15 additional operating conditions. The match was found to be quite good.

Maximization of Gasoline in an Industrial Fluidized Catalytic Cracking Unit

The riser of a fluid catalytic cracking (FCC) unit cracks gas oil to make fuels such as gasoline and diesel. However, changes in quality, the nature of crude oil blends feedstocks, environmental changes, and the desire to obtain higher profitability lead to many alternative operating conditions of the FCC riser. The production objective of the riser is usually the maximization of gasoline and diesel. Here, an optimization framework is developed in gPROMS to maximize the gasoline in the riser of an industrial FCC unit (reported in the literature) while optimizing mass flow rates of catalyst and gas oil. A detailed mathematical model of the process developed is incorporated in the optimization framework. It was found that concurrent use of the optimal values of mass flow rates of catalyst (310.8 kg/s) and gas oil (44.8 kg/s) gives the lowest yield of gases, but when these optimum mass flow rates are used one at a time, they produced the same and better yield of gasoline (0.554 kg of lump/(kg of feed)).

Model Optimization for an Industrial Fluid Catalytic Cracking Riser-regenerator Unit by Differential Evolution Algorithm

A differential evolution (DE) algorithm for determining 16 advanced turning model parameters of a 1.2 million industrial fluid catalytic cracking (FCC) unit modeling by HYSYS 8.4 is presented. Industrial data from a Chinese petroleum refinery were used to develop, train and check the model. Due to FCC complexity, the proposed model is capable of predicting the yield of products based on main operating conditions. The optimized FCC model is used for further optimized analysis of the FCC unit operating conditions based on the maximum of economic benefits. Prediction of the economic benefit of FCC unit increases 917 yuan/h at the optimized operating conditions.