Fluidized Bed Catalytic Reactor Research Articles

Experimental and CFD studies on collection efficiency of separator with arc settlers of fluidized bed catalytic reactor

Separation of catalyst dust from gas in a fluidized bed reactor is an important process. A new solid-gas separator with arc settlers was developed, in which a stable wave flow pattern of the dusty gas flow is formed. The model was based on the RANS approach using the Reynolds Stress Model for the turbulence closure and the Discrete Phase Model. Validating the simulation results with the test data showed good convergence, no more than 6% in the pressure drop and less than 15.5% in collection efficiency at different inlet gas velocities. The CFD study revealed that with a dusty gas inlet velocity of no more than 1 m/s and a catalyst particle larger than 20 μm, efficiency close to 100% is achieved with a pressure drop of less than 60 Pa. Maximum efficiency is achieved when the number of rows of the arc settlers with 40 mm diameter is 8.

Modeling of a catalytic fluidized bed reactor via coupled CFD-DEM with MGM: From intra-particle scale to reactor scale

The Computational Fluid Dynamics - Discrete Element Method (CFD-DEM) method is extended by coupling with the multi-grain model (MGM) to include particle growth due to a gas-solid reaction, as well as intra- and inter-particle phenomena such as heat and mass transfer, and reaction, next to the inter-particle and fluid-particle interactions in the reactor. This comprehensive model treats each particle individually and accounts for changes in particle properties due to both the particle growth and temporal and spatial variations of the process conditions. It also captures the impact of the change in the particles' properties on the fluidized bed reactor characteristics, such as the hydrodynamic regime. The results of the model revealed that the fluidization characteristics and solids mixing can be altered by particle growth. Particle growth also led to the formation of a particle size gradient along the height of the reactor. The coupling allows for monitoring of both external and internal mass transfer limitations. For the adopted reaction kinetics, growth rate and properties the external mass transfer limitations remained negligible, however the internal mass transfer limitation plays a significant role in the process performance.

Performance and ANN-based optimization of an advanced process for wet CO2-to-Methanol using a catalytic fluidized bed reactor integrated with separators

Large-scale green processes to produce methanol from massive industrial sources of CO2 with a certain amount of water are increasingly attractive for carbon neutralization. In this study, an advanced CO2-to-Methanol (CTM) process, consisting of a turbulent fluidized bed (TFB) reactor, separators, and other units, was developed, analyzed from start-up to steady state, and optimized for high-purity methanol production (98.5–99.9 wt%) from a wet CO2 source (1.3 MtCO2/year with 1.35 mol% H2O). A two-stage flash drum with direct feeding of wet CO2 into a flash drum was applied to the developed CTM process to remove water and enhance unconverted gas recovery. At a methanol purity of 99.9 wt%, the advanced CTM process increased the methanol yield (0.15–0.31%), production capacity (5700–10100 tMeOH/year), and net CO2 reduction (0.0009–0.0033 kgCO2/kgMeOH) but decreased production cost (3.7–7.4 $/tMeOH) compared to the conventional CTM process under various of reactor temperatures (478–538 K) and pressures (40–90 bar). During the start-up process, the CTM process indicated the peaks in the methanol molar fraction and flow rate as the TFB reactor performed the stable profile of solid temperature (548–553.75 K) and volume fraction (∼0.249). In the performance assessment, the main units (compressor, TFB reactor, and distillation column) accounted for 96, 95, and 82.5% of capital expenditure (CAPEX), operating expenditure (OPEX), and energy consumption, respectively. Meanwhile, lowering the price of the annual CO2 and H2 increased CAPEX and OPEX contributions from 10.92 (present) to 28.64% (in 2050). To optimize the process using an artificial neural network (ANN) model, three main objectives and four main operating variables were selected as features through data analysis. The ANN model precisely predicted process performances (>99% accuracy) could reduce the computational cost by 900-fold compared to the process simulation. For methanol purity of 98.5–99.9 wt%, the CTM process should be operated in the optimum domain with a reactor pressure of 57.18–75.74 bar, reactor temperature of 493.62–506.32 K, reflux ratio of 1.02–1.08, and reboiler ratio of 1.32–1.38. The results are useful for designing, operating, and decision-making processes for producing various grades of green methanol from wet CO2 sources.

Using Kriging surrogate model to analyze hydrogen generation with dimethyl ether in partial oxidation catalytic fluidized bed reactor

The study aimed to present a fluidized bed reactor filled with 50% platinum catalytic beads and 50% quartz sand for syngas generation via the partial oxidation of dimethyl ether (DME). For obtaining useful information, experiments were carried out using Taguchi orthogonal array method, which cut test run by 75.3%, with the results being used for constructing the Kriging surrogate model. The model was then modified to reduce the mean square error. It is validated that the model can predict the results reasonably well. The outcome shows that the proposed reactor can self-sustain the syngas reforming reaction without incurring extra heat for reactants preheating. In the operation region, the results show that the start-up temperature is most negligible in hydrogen generation. The yield rate of hydrogen increases in sync with the increase of oxygen's molar ratio and DME, thanks to higher reaction temperature. The results also suggest that the higher the molar ratio of oxygen and DME, the more significant the reverse water shift reaction. Playing a key role in the fluidized bed in the proposed reactor for hydrogen generation, the normalized velocity must be at a proper level, in order to induce bubbling fluidization without causing a lower hydrogen yield, the latter due to the short residence time of reaction caused by excessive velocity. The sensitive analysis of independent variables also proved the inference from the measured results. By comparing with the literature, the performance of the proposed reactor in the present study shows a reasonably well performance. Given focused hydrogen generation, the study's findings can be used as a basis for evaluating DME as a hydrogen carrier and the proposed fluidized bed reaction.

The CREC Fluidized Riser Simulator a Unique Tool for Catalytic Process Development

The CREC Riser Simulator is a mini-fluidized bench scale unit invented and implemented in 1992, at the CREC (Chemical Reactor Engineering Centre), University of Western Ontario The CREC Riser Simulator can be operated at short reaction times, in the 3 s to 20 s range. The present review describes and evaluates the original basic concept of the 1992-CREC Riser Simulator Unit, and the improved design of the 2019-CREC Riser Simulator. Both the initial and the enhanced units are specially engineered to allow the rigorous assessment of both catalyst performance and catalytic reaction kinetics. Kinetic parameters of relatively simple and accurate mathematical models can be calculated using experimental data from the CREC Riser Simulator. Since its inception in 1992, the CREC Riser Simulator has been licensed to and manufactured for a significant number of universities and companies around the world. Several examples of scenarios where the CREC Riser Simulator can be employed to develop fluidized bed catalytic and heterogeneous reactor simulations are reported in this review. Among others, they include (a) hydrocarbon catalytic cracking, (b) the catalytic conversion of tar derived biomass chemical species, (c) steam and dry catalytic methane reforming, (d) the catalytic oxydehydrogenation of light paraffins, (e) the catalytic desulfurization of gasoline, and (f) biomass derived syngas combustion via chemical looping. In this review, special emphasis is given to the application of the CREC Riser Simulator to TIPB (tri-iso-propyl-benzene) catalytic cracking and the light paraffins catalytic oxydehydrogenation (PODH).

Multiscale CFD Simulation of an Industrial Diameter-Transformed Fluidized Bed Reactor with Artificial Neural Network Analysis of EMMS Drag Markers

Modeling of gas–solid, heterogeneously catalytic, diameter-transformed fluidized bed (DTFB) reactors is intrinsically complex and requires considering the variation of material properties and operating conditions, because of reactions and/or diameter transformation. The EMMS-matrix drag model, which correlates both operating conditions and local parameters, has been applied in computational fluid dynamics (CFD) simulation of such complex reactors by simplifying the macroscale operating conditions with one set of constant parameters. However, a complete scheme has not been reported that covers a wide range of datasets for a DTFB reactor with complex reactions. To this end, the artificial neural network (ANN), which enables exploring a multivariate relation with the contribution of a set of different parameters, is chosen to couple with EMMS drag modeling. A complete scheme of EMMS-ANN drag for hot, reactive simulation of DTFB is thereby established, with comprehensive evaluation of the contribution of drag markers successively considering the variation of gas properties and operating parameters. Both a priori tests and CFD simulations show that the voidage and slip velocity are the dominant factors in modeling of drag correction, and the effects of dynamic variation of gas properties and operating hydrodynamics are marginal; even the heterogeneous reactions and the change in bed diameter give rise to a remarkable variation in gas properties and operating parameters. The underlying mechanism is then analyzed to provide important clues for drag modeling of gas–solid, heterogeneous catalytic fluidized-bed reactors.

Power-to-gas: CO2 methanation in a catalytic fluidized bed reactor at demonstration scale, experimental results and simulation

CO2 methanation tests were carried out in a demonstration scale fluidized bed reactor (400 kWSNG capacity) to investigate its efficiency and flexibility towards operating conditions fluctuations associated with Power-to-Methane (PtM) production units. A wide range of operating conditions were explored: pressure (2–4 bara), reaction temperature (260−375 °C), H2/CO2 inlet ratio (1.5–4.8), heat released by the reaction exothermicity (13.4–32.7 kWth), and U/Umf (2.2–7.2). Whatever the operating conditions, this technology (reactor and catalyst) reached the maximum possible conversion, i.e. the thermodynamic equilibrium, in only one step. These excellent performances resulted from efficient management of methanation exothermicity (temperature gradient in the fluidized bed is lower than 20 °C) and optimized catalyst activity (even at low temperature: 280 °C). In addition to its high flexibility towards operating conditions, short stabilization time (<30 min) was required for the process to reach permanent and stable regime when the operating condition setpoints were changed. Simulations were performed to investigate different process chains efficiency for producing SNG (Substitute Natural Gas) compliant with natural gas grid standards. A process chain composed of the fluidized bed reactor studied in this article followed by a condensation step, a partial recirculation stream to the reactor inlet, and a polishing reactor was proved to be an interesting solution to produce high quality SNG with reduced equipment and compression cost. The present reactor together with the specific metal-based catalyst developed in this study appear as a very efficient and flexible solution for PtM application.

Application of Pseudohomogeneous and Heterogeneous Models in Assessing the Behavior of a Fluidized-Bed Catalytic Reactor

Comparative analysis of the steady-state and transient properties of a bubbling fluidized-bed catalytic reactor obtained according to different mathematical models of the emulsion zone was performed to verify the commonly used assumption regarding the pseudohomogeneous nature of this zone. Four different mathematical models of the fluidized-bed reactor dynamics were formulated, based on different thermal and diffusional conditions at the gas-solid interface and within the catalyst pellet, namely the model based on the assumption of pseudohomogeneous character for the emulsion zone, and a group of two-scale models accounting for the heterogeneous character of this zone. It was demonstrated that, while the pseudohomogeneous model of the emulsion zone predicts almost identical behavior of the reactor at steady-state as the proposed heterogeneous models, it may fail in the prediction of the reactor start-up behavior, especially when dealing with highly exothermic processes run at relatively high fluidization velocity.

Reaction performance of fluidized bed catalytic reactor of Group C+ particles

Group C particles are often regarded as non-fluidizable but have proven to effectively fluidize with nanoparticle addition, which results in small bubbles and a high gas holdup in the dense phase during the experiments. Group C+ particles provide an increased surface area for gas–solid contact and improve the reaction performance, especially for gas-phase catalytic reactions. On the basis of a previous study of the ozone decomposition reaction using Group C+ particles, a two-phase model was used to evaluate the reactor contact efficiency, and was used to compare the partial oxidation performance of the n-butane to maleic anhydride reaction in fluidized-bed catalytic reactors of Group C+ and Group A particles. The reactor with Group C+ particles achieved a higher n-butane conversion and MAN yield compared with that using Group A particles, based on the identical catalyst quantity or on the same gas residence time. Therefore, the reactor with Group C+ particles can achieve the same reaction conversion and yield with fewer catalysts or a smaller reactor size, or both. Therefore, the fluidized bed catalytic reactor of Group C+ particles is expected to be of major significance in industrial processes, especially for gas-phase catalytic reactions.

Performance Enhancement of Fluidized Bed Catalytic Reactors by Going to Finer Particles

Fluidization is an important operation for multiphase reactions, especially for gas-phase catalytic reactions because it provides a large solid surface area for improved gas–solid contact efficiency. Although fine particles with small particle size (<45 μm) could be more desirable in providing larger interfacial area, their strong interparticle forces lead to poor or even no fluidization. In this project, a “nanomodification” technique has been adopted to reduce the interparticle forces so as to release the potential of fine particles in multiphase reactions. As a first attempt, “nanomodified” fine catalysts (32 μm) were used in the ozone decomposition reaction and displayed better reaction performance than regular catalysts due to larger interfacial area and more gas holdup in the bed, indicating better gas–solid contact. The reaction conversion and contact efficiency using the nanomodified fine fluid cracking catalytic (FCC) catalysts significantly increased compared to that of using regular FCC catalysts (100 μm).

Dynamic process modeling and hybrid intelligent control of ethylene copolymerization in gas phase catalytic fluidized bed reactors

AbstractBACKGROUNDPolyethylene (PE) is the most extensively consumed plastic in the world, and gas phase‐based processes are widely used for its production owing to their flexibility. The sole type of reactor that can produce PE in the gas phase is the fluidized bed reactor (FBR), and effective modeling and control of FBRs are of great importance for design, scale‐up and simulation studies. This paper discusses these issues and suggests a novel advanced control structure for these systems.RESULTSA unified process modeling and control approach is introduced for ethylene copolymerization in FBRs. The results show that our previously developed two‐phase model is well confirmed using real industrial data and is exact enough to further develop different control strategies. It is also shown that, owing to high system nonlinearities, conventional controllers are not suitable for this system, so advanced controllers are needed. Melt flow index (MFI) and reactor temperature are chosen as vital variables, and intelligent controllers were able to sufficiently control them. Performance indicators show that advanced controllers have a superior performance in comparison with conventional controllers.CONCLUSIONBased on control performance indicators, the adaptive neuro‐fuzzy inference system (ANFIS) controller for MFI control and the hybrid ANFIS–proportional‐integral‐differential (PID) controller for temperature control perform better regarding disturbance rejection and setpoint tracking in comparison with conventional controllers. © 2019 Society of Chemical Industry

Dynamic simulation and control of two-series industrial reactors producing linear low-density polyethylene

One of the leading routes for producing polyolefins is through gas-phase catalytic fluidized bed reactors. In this study, the industrial gas-phase ethylene polymerization reactor series of Jam Petrochemical Company has been dynamically analyzed, modeled and controlled. The copolymerization of ethylene with 1-butene is defined on Zeigler–Natta catalyst, assuming a double active site mechanism. To serve this purpose, pseudo-kinetic rate constants and the method of moments have been employed. The proposed model is capable of predicting the unsteady-state behavior of each reactor in addition to the properties of the product such as melt flow index (MFI), dispersion index, and molecular weight distribution (MWD). The verification of the model has been conducted with plant data to prove the accuracy of the model-estimated MWD and MFI. The controllability of the process control configuration has been examined through analyzing the dynamic behavior of the process under conventional feedback PID controllers. It has been observed that the control structure delivers a convincing performance for disturbance rejection.

Regeneration of NiAl2O4 spinel type catalysts used in the reforming of raw bio-oil

The regenerability of Ni catalysts in reforming reactions is a key factor for process viability. Accordingly, this study addresses the regeneration of two spinel NiAl2O4 type catalysts by reaction-regeneration cycles in the oxidative steam reforming (OSR) of raw bio-oil. The spinel type catalysts were prepared by different methods including a supported Ni/La2O3-αAl2O3 catalyst and a bulk NiAl2O4 catalyst. The experimental set-up consists of two units connected in series for i) the thermal treatment of bio-oil at 500 °C, in order to control the deposition of pyrolytic lignin, followed by; ii) the oxidative steam reforming (OSR) of the remaining oxygenates in a fluidized bed catalytic reactor. The conditions in the OSR reaction step were: 700 °C; oxygen/steam/carbon ratio (O/S/C), 0.34/6/1; space time, 0.75 gcatalysth/gbio-oil (for supported catalyst) and 0.15 gcatalysth/gbio-oil (for bulk catalyst). Three different strategies have been studied in the regeneration step by coke combustion, including the in situ regeneration inside the reactor at 650 °C and 850 °C, and the ex situ regeneration in an external oven at 850 °C, for 4 h in all the cases. The behavior of the fresh and regenerated catalysts has been explained according to their metallic properties, determined by different characterization techniques (temperature programmed reduction (TPR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and transmission electronic microscopy (TEM)). According to these results, the combustion ex situ of the catalyst at 850 °C is able to completely regenerate the bulk catalyst, since these regeneration conditions lead to the total recovery of the NiAl2O4 spinel phase together with negligible loss of Ni on the surface in the catalyst. These novel results are crucial for future industrial implementation of the process.

Direct route from ethanol to pure hydrogen through autothermal reforming in a membrane reactor: Experimental demonstration, reactor modelling and design

This work reports the integration of thin (∼3–4 μm thick) Pd-based membranes for H2 separation in a fluidized bed catalytic reactor for ethanol auto-thermal reforming. The performance of a fluidized bed membrane reactor has been investigated from an experimental and numerical point of view. The demonstration of the technology has been carried out over 50 h under reactive conditions using 5 thin Pd-based alumina-supported membranes and a 3 wt%Pt-10 wt%Ni catalyst deposited on a mixed CeO2/SiO2 support. The results have confirmed the feasibility of the concept, in particular the capacity to reach a hydrogen recovery factor up to 70%, while the operation at different fluidization regimes, oxygen-to-ethanol and steam-to-ethanol ratios, feed pressures and reactor temperatures have been studied. The most critical part of the system is the sealing of the membranes, where most of the gas leakage was detected. A fluidized bed membrane reactor model for ethanol reforming has been developed and validated with the obtained experimental results. The model has been subsequently used to design a small reactor unit for domestic use, showing that 0.45 m2 membrane area is needed to produce the amount of H2 required for a 5 kWe PEM fuel-cell based micro-CHP system.

Production of synthetic natural gas by CO methanation over Ni/Al2O3 catalyst in fluidized bed reactor

In order to obtain the reaction characteristics, CO methanation process is numerically investigated in fluidized bed catalytic reactor over Ni/Al2O3 catalyst. The catalysts flow behavior is analyzed, which has significant effect on the activity of catalysts. The influences of operation parameter on CO conversion and CH4 yield are evaluated. The inventory of catalysts and superficial gas velocity will not influence the output of methane but the reaction rates. Meanwhile, the performance of water-gas shift reaction on CH4 yield is taken consideration during reactions.

Dimethyl ether synthesis in a multi-stage fluidized bed reactor

The two-phase model with verified reaction kinetics has been implemented to study numerically dimethyl ether (DME) production in a novel multi-stage fluidized bed catalytic reactor. The single-bed configuration results show that the bifunctional catalyst composition [CuO–ZnO–Al2O3/HZSM-5] has a pronounced impact on enhancing the reactor performance. Also, the simulation results indicated that the two-bed configuration gives a substantial enhancement of DME yield of 32.67% compared to the single-bed configuration. This yield improvement is also accompanied by significantly improved DME selectivity of almost 100%. The complex interactions of the bifunctional catalyst composition, feed composition and multi-stage configuration play a central role in the extent of the synergy. Interesting two types of maximum phenomena are observed and explanations have been offered. It seems that synergistic effects have kinetics and thermodynamic strong impact on the development of these phenomena. The loci of these maxima are significant for optimal design and control of multi-bed configurations. It appears that application of multi-stage fluidized bed catalytic reactors is highly promising in DME industry.

Steady-state characteristics of autothermal structures with fluidized-bed catalytic reactors

The paper focuses on the analysis of steady-state properties of autothermal structures with a fluidized bed. The concept of autothermicity is discussed, and typical autothermal structures are presented. A method for the determination of the steady-states of such systems is described. Quantitative analysis of steady-states multiplicity is presented for two autothermal structures, that is a fluidized-bed reactor with an external heat exchanger, and with a partial recirculation of hot gases. A two-phase bubbling bed model is employed to describe quantitatively the behavior of the catalytic fluidized bed. The influence of selected design and operating parameters on steady-state characteristics is analyzed for two simple kinetic models. The effect of these parameter on the desired product yield is evaluated for the multiple-reaction process. The results obtained have both scientific and practical importance.

Speeding up heterogeneous catalysis with an improved highly reusable catalyst for the preparation of enantioenriched secondary alcohols

A new catalytic heterogeneous system, very efficient and highly reusable, for the preparation of enantioenriched secondary alcohols through the addition of diethylzinc to benzaldehyde has been developed. This system is based on a chiral bis(hydroxyamide) ligand supported on crosslinked polystyrene. The catalyst has been shown to be very efficient, leading to the corresponding secondary alcohol with an enantiomeric excess of 93% in a time as short as 2h and using just 4% of the heterogeneous catalyst and just 1.5 equivalents of the organozinc reagent. We have demonstrated that the new catalyst is very stable and can be efficiently recycled with no decrease in yield or enantioselectivity. The presented system has an unquestionable interest for the potential transfer of the reaction to the industry by using catalytic fluidized-bed reactors.

Multiple isolas in steady‐state characteristics of fluidized bed catalytic reactors

Steady‐state characteristics of a catalytic fluidized bed reactor are analyzed. A two‐phase bubbling model is used for the description of a fluidized bed of a catalyst. Particular attention is focused on the theoretical and technological consequences of a newly observed steady‐state behavior. Features of the model are presented in terms of steady‐state structures, stability, solution multiplicity, and process efficiency. The possibility of an occurrence of multiple isolas of steady states is demonstrated for two simple kinetic models. Depending on the multiplicity region they belong to, multiple isolas are referred to as first type or second type isolas. © 2016 American Institute of Chemical Engineers AIChE J, 63: 2107–2116, 2017

Computational and experimental studies on bed dynamics of a gas–solid fluidized bed using Geldart-A particle: A comparison

ABSTRACTThe bed dynamics of a two-dimensional gas–solid fluidized bed is studied experimentally and computationally using Geldart-A particles. Commercial software ANSYS FLUENT 13 is used for computational studies. Unsteady behavior of gas–solid fluidized bed is simulated by using the Eulerian–Eulerian model coupled with the kinetic theory of granular flow. The two-equation standard k−ϵ model is used to describe the turbulent quantities. The simulation predictions are compared with experimentally observed data on volume fraction, bed pressure drop and bed expansion ratio. The results of simulations are found to be in close agreement with the experimental observations, implying that computational fluid dynamics (CFD) can be used for the design of an efficient bench-scale catalytic fluidized bed reactor.