Multiphase Reactors Research Articles

Microwave heating of slurries

Selective microwave heating can significantly impact the performance of multiphase reactors, such as slurry reactors, where the dispersed (solid particles) and continuum (liquid) phases have different dielectric properties. Lack of tools to measure and predict the temperature difference between the dispersed and continuum phases hinders the understanding and optimization of microwave-heated slurry reactors. We utilize experiments, theory, and multiscale simulations to investigate microwave heating of slurries consisting of microwave absorbing solid particles dispersed in a non-polar liquid. Using controlled experiments and mathematical modeling, we propose an ideal slurry reactor and develop analytical expressions to predict the temperature evolution of the solid and liquid phases during microwave heating. Our experiments show a strong impact of the solid material and concentration on the heating rate of slurries, whereas no difference is observed in conventionally heated slurries. We also perform multiscale simulations of microwave-heated slurries employing a coarse-graining methodology to handle the large separation of length scales in slurries and compare them against experiments.

Bubble column fluid dynamics: A novel perspective for flow regimes and comprehensive experimental investigations

When a gas phase is injected into a liquid phase, it gives rise to a rich, fascinating and mysterious fluid dynamic phenomenology. The lack of knowledge regarding this phenomenology, a shortcoming in the design and operation of multi-phase reactors, is related to the absence of an unique definition of the flow regimes. To date, different studies gave different definitions of the flow patterns and, subsequently they experimentally obtained some global and local flow properties, with no physical-based description of the flow patterns. Is there a theory able to determine a-priori the boundaries of different flow regimes (and, thus, the flow regime for a given set of boundary conditions, given the phases and the system design)? Answering this question requires changing the present point of view in defining and describing the flow regimes and it is the primary motivation of this paper. To achieve this goal, a new theory has been formulated, which changes the present way of approaching bubble columns and which is based on the following statement: the fluid dynamics in gas-liquid bubble columns is interpreted by means of a general relationship―built upon five flow regime transitions―between two global fluid dynamic parameters. The strategic path to formulate this theory is, first, to go back to the pioneering studies and formulate basic relationships on the basis of a general principle. Subsequently, in order to support and verify the theory a comprehensive and multi-scale experimental investigation has been performed and coupled with previous experimental studies. The different experimental studies have been conducted in a gas-liquid large-scale bubble column (height of 5.3 m; inner diameter of 0.24 m) operated in the batch and in counter-current modes; to study all flow regimes, the bubble column was tested with five gas spargers (viz., pipe sparger in open tube and annular gap configuration, spider sparger, two different perforated plates and needle spargers) with different values of the aspect ratios and different liquid phases. It was found that, in an air-water bubble column, the gas velocity is approximately 0.03 m/s either in the case of the destabilization of the mono-dispersed homogeneous flow regimes or in the case of the destabilization of the pseudo-homogeneous flow regimes. Increasing the gas sparger opening induces a narrowing of the boundaries between the transitional flow regimes; conversely, increasing the bubble column aspect ratio destabilizes the existing flow regimes up to some critical values. Also, increasing the superficial liquid velocity in the counter-current mode destabilizes the homogeneous flow regime. Finally, it has been observed that the prevailing effect of the liquid phase, in a bubble column operated with a “coarse” gas sparger, is to change the boundary of the homogenous flow regime. It has also been discussed how the change in coordinates of the flow regime transition between the homogeneous and the heterogeneous flow regimes is caused by the changes in the size distribution. This study is intended to outline a precise definition of the flow regimes in bubble columns and it poses a rational basis for future studies.

Design and Development of Novel Continuous Flow Stirred Multiphase Reactor: Liquid–Liquid–Liquid Phase Transfer Catalysed Synthesis of Guaiacol Glycidyl Ether

Phase transfer catalysed (PTC) reactions are used in several pharmaceutical and fine chemical industrial processes. We have developed a novel stirred tank reactor (Yadav reactor) to conduct batch and continuous liquid–liquid–liquid (L-L-L) PTC reactions. The reactor had a provision of using three independent stirrers for each phase, thereby having complete control over the rate of mass transfer across the two interfaces. In the continuous mode of operation, the top and bottom phases were continuously fed into the reactor while the middle phase was used as a batch. All three stirrers were used independently, thereby having independent control of mass transfer resistances. The reactor in a batch mode showed higher conversion and selectivity compared to a conventional batch reactor. L-L-L PTC reaction in the continuous mode was successfully performed without loss of the middle catalyst phase and with steady conversion and selectivity. The reaction of guaiacol with epichlorohydrin was conducted as a model reaction, with a 76% conversion of epichlorohydrin, 85% selectivity of guaiacol glycidyl ether, and the middle catalyst phase was stable throughout the process.

Reactive LES-Euler/Lagrange modelling of bubble columns considering effects of bubble dynamics

Bubble columns are complex multiphase reactors producing large contact areas for mass transfer and subsequent chemical reactions. For allowing a deeper insight into this complexity and providing strategies for process optimisation, CFD (computational fluid dynamics) has become a standard tool. However, accurate models are needed to reproduce correctly such dynamic systems. Numerical computations of reactive bubble columns are conducted based on a LES-Euler/Lagrange approach. For extending this approach beyond the point-mass assumption for the dispersed elements, a bubble oscillation model based on stochastic generation of eccentricity and motion angle is proposed. The effects of bubble dynamics are modelled in the interfacial forces accounting for instantaneous eccentricity. A dynamic Sherwood number is used to consider bubble dynamics in the mass transfer. The influence of chemical reactions in species consumption within the liquid phase was modelled through the enhancement factor. Large Eddy Simulation (LES) was used for calculating the fluid flow with momentum source terms for bubbles and modelling sub-grid-scale (SGS) turbulence in the continuous phase through a transport equation for the turbulent kinetic energy. The effect of sub-grid-scale (SGS) turbulence on bubble motion, and also SGS turbulence modification by bubbles (BIT) is considered, introducing an extra source term in a kSGS equation. This source term automatically accounts for turbulence dissipation as well as enhancement (i.e. BIT). Numerical simulations of the chemisorption process for CO2 bubbles rising in highly concentrated NaOH solutions were compared with data presented in the literature. A very good agreement was only found when applying the full bubble dynamics model.

Technological characteristics of reject waters from aerobic sludge stabilization in small and medium-sized wastewater treatment plants with biological nutrient removal

Most studies on the impact of reject waters recycled from sludge processing in the multi-phase activated sludge process focus on anaerobic sludge treatment in large wastewater treatment plants, leaving apart the processes of aerobic sludge stabilization often used in smaller facilities in rural and suburban areas. The article presents the results of tests carried out in three small and medium-sized wastewater treatment plants with biological removal of biogenic compounds that use aerobic stabilization to process sludge. The research concerned the quantity and quality of reject waters generated in the process of aerobic stabilization and dewatering of sewage sludge and their impact on the multi-phase activated sludge process. The results showed that the average volume of generated reject waters ranged from 3.2 to 5% of the incoming wastewater volume. The average share of organic compounds and total nitrogen loads contained in reject waters did not usually exceed 5–10% of the loads in raw wastewater but reached almost 50% in the case of total phosphorus. Studies indicated that the composition of the supernatant from aerobic stabilization is strongly dependent on the course of the process. The best quality was obtained for cyclic operation of the aerobic stabilization tank with 16 h of aeration and 8 h of settling. The results also showed the negative impact of sudden discharges of reject waters from sludge processing to a multi-phase biological reactor, which can be reduced by using an appropriate equalization tank and pretreatment of the side stream to reduce the recirculation of phosphorus.

Prediction of fluid interface between dispersed and matrix phases by Lattice Boltzmann-adaptive network-based fuzzy inference system

ABSTRACT The integration of Lattice Boltzmann (LB) and adaptive-network-based fuzzy inference system was utilised to simulate mesoscale fluid interface in a multiphase fluid system. This method uses data generated by LB and based on the local population and density data. The interface between dispersed and matrix phases on the neural points was simulated. The neural mesh of interface was created by the ANFIS method and locally was compared by the CFD results. The results showed that there is a great agreement between ANFIS and numerical data when a particularly more number of rules are used in the learning step of simulations. Since this new overview of modelling can predict fluid flow based on existing data, less number of rules cause over prediction for the ANFIS method; however, by enhancing the number of rules, ANFIS can solve this over-prediction far from the curvature of the dispersed phase. This algorithm can be a promising tool for simulation of macroscopic parameters in the large-scale multi-phase reactors.

Evaluation of the diffusional coefficient in the acid baking process using microwave energy to reduce phosphorus content in iron ore particles

The reduction in phosphorus content using microwave energy as a heating source has recently received remarkable attention due to the possibility of high heating rates and fracture generation in the particles. Such advantages can lead to a potential increase in productivity in the process of reducing the phosphorus content of iron ore particles, thereby increasing the reuse of large volumes of sterile with a high phosphorus content. Thus, it is highly relevant to understand how the interaction between the phosphate structure and the reaction medium occurs. Thus, this paper deals with the study of a possible kinetic model aiming at the process of reducing the phosphorus content using microwave energy to heat iron ore particles in contact with concentrated sulfuric acid (acid baking).This model treats the microwave oven as a multiphase reactor and two phases are considered simultaneously: liquid and granular or fine solids (crude or comminuted iron ore). First, a basic case consists of the ore/sulfuric acid mixture, in a ratio of 2:1. After heating, the mixture is added to a specific volume of water and then the system is stirred at a speed of 620 rpm. After the leaching process, the liquid was filtered and taken for chemical analysis, which was performed using an ultraviolet spectrometer at a wavelength of 420 nm for phosphorus and 473 nm for iron. Through the scanning electron microscopy (SEM) technique, it was possible to observe the structure of the iron ore particles after their treatment with microwave energy and leaching. Kinetic models of diffusional and chemical control were used to understand the interaction phenomena of sulfuric acid inside the particles. The mixed control kinetic model was also evaluated, in which it was possible to evaluate different parameters regarding the interaction between mineral structure and sulfuric acid as leaching medium. The obtained results indicated that the developed process has relevant utility. The kinetic modeling results contribute to a better understanding of heating phenomena using microwave energy, and also to the development of new cleaner technologies to improve the efficiency of the acid baking/leaching process to reduce particulate phosphorus content in iron ores.

Continuous Hydrogenation of Monomeric Sugars and Binary Sugar Mixtures on a Ruthenium Catalyst Supported by Carbon-Coated Open-Cell Aluminum Foam

Developing a structured catalyst was performed successfully, and carbon-coated aluminum foam-supported ruthenium catalysts were prepared. Seven different characterization techniques such as scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, temperature-programmed reduction, inductively coupled plasma-mass spectrometry, carbon monoxide chemisorption, and nitrogen physisorption were applied on the solid catalysts. The carbon-coated foams were checked for their mechanical stability, and the results indicated that the foam catalysts were mechanically stable. The Ru/C foam catalysts were used in a multiphase reactor setup, which had six tubular reactors working in parallel. Continuous hydrogenation of d-glucose, l-arabinose, and a mixture of l-arabinose and d-galactose was studied in the experimental setup. Through investigating different reaction parameters, the temperatures 100–110 °C and the liquid flow rates 0.5–1 mL/min were found to be suitable for catalyst screening and activity testing. The experiments were carried out at 20 bar hydrogen pressure. The continuous hydrogenation experiments were successful, the reproducibility was good, and the foam catalysts were stable. High selectivities of the desired products, sugar alcohols and sugar alcohol mixtures, were obtained.

Relative Effect of Additional Solid Media on Bubble Hydrodynamics in Bubble Column and Airlift Reactors towards Mass Transfer Enhancement

Many researchers have focused on multi-phase reactor development for improving mass transfer performance. However, solid particle addition in gas–liquid contactor for better oxygen mass transfer performance is still limited. Hence, this study aims to analyze the relative effect of different types of local solid media on the bubble hydrodynamic characteristics towards mass transfer enhancement in bubble columns (BCR) and airlift reactors (ALR). This was investigated by varying solid media types (ring, sphere, cylinder, and square), solid loadings (0%–15%), and superficial gas velocities (Vg) (2.6–15.3 × 10−3 m/s) in terms of the bubble hydrodynamic and oxygen mass transfer parameters. The result showed that bubble size distribution in BCR and ALR with additional plastic media was smaller than that without media addition, approximately 22%–27% and 5%–29%, respectively, due to the increase of the bubble breaking rate and the decrease of the bubble rising velocity (UB). Further, adding media in both reactors significantly decreased the UB value. Since media increased flow resistance, resulting in decreased liquid velocity, it can also be the moving bed to capture or block the bubbles from free rising. Therefore, oxygen mass transfer performance was investigated. The oxygen transfer coefficient (KLa) in BCR with solid media addition was enhanced up to 31%–56% compared to a non-addition case, while this enhancement was greater at higher solid loading due to its higher effective surface, resulting in a higher bubble break-up rate compared to the lower loading. In ALR, up to 38.5% enhanced KLa coefficient was archived after adding plastic media over the non-addition case. In conclusion, ring and cylinder media were found to be the most significant for improving KLa value in BCR and ALR, respectively, without extra energy.

Gas-liquid mass transfer and hydrodynamics in a vertically-oscillating multiphase reactor

Gas-liquid mass transfer and hydrodynamics were studied experimentally and numerically in a vertically-oscillating vessel with an internal diameter of 33 mm and a height of 114 mm. The amplitude was 57 mm and frequency ranged from 2.8 to 3.7 Hz. The dissolution of pressurized oxygen into water was measured between 3 and 6 MPa. Simulations were performed using a computational fluid dynamics (CFD) model with partial interface capturing by a compressive-interface volume-of-fluid method. A new surface area reconstruction algorithm for unstructured meshes was developed and implemented into OpenFOAM. Predicted radial phase distributions were within one standard deviation of experimental values, while predicted axial distributions at high oscillation frequencies matched more closely than when approaching the onset of splashing. Mass transfer predictions performed without the use of a sub-grid model were underpredicted. Sub-grid mass transfer predictions using an eddy cell model were more scalable than a model based on penetration theory.

Experimental and modeling study on the hydrodynamics in multiphase monolith modules with different distributors

Three commonly used distributors (i.e., nozzle, packed bed, and foam) were introduced into a multiphase monolith reactor in this work to investigate the pressure drop, liquid holdup and gas–liquid distribution performance by combining experimentation and CFD simulation. The experimental results showed that the nozzle distributor exhibited the better gas-liquid phase distribution and the lowest pressure drop. However, so far, the gas and liquid velocities at the top of the monolith bed, which are crucial for the transition from a single channel to bed scale, have not been studied. Thus, a discrete phase and continuous phase coupling 3D model using CFD simulation was established for the nozzle distributor, and the magnitude and distribution of the gas and liquid velocities at the entrance of the monolith module were investigated. The simulation results showed that the droplets’ velocity reaching the monolith module was very high and had a strong influence on the gas velocity distribution. The increase in superficial gas velocity could enhance the gas distribution to some extent.

Effect of nonuniform isoflux heating on natural convection heat transfer in a prismatic modular reactor

A high temperature and pressure dual-channel facility has been designed and developed at Multiphase Reactors Engineering and Applications Laboratory (mReal) at Missouri University of Science and Technology (Missouri S&T) to investigate the thermal hydraulics of natural circulation under the loss of flow accident scenario (LOFA) in the core of a prismatic modular reactor (PMR). An advanced heat transfer measurement technique consisting of a series of heat flux foil sensors and thermocouples is adapted and implemented along the coolant flow channels (riser and downcomer channels). This study presents the effect of nonuniform isoflux heating (1.432 kW/m2 to 3.152 kW/m2, in form of stepwise-reducing and stepwise-increasing) on natural circulation heat transfer using air as a coolant at 413.7 kPa. The results showed a reversal in the direction of heat transfer and reduction in temperature fields as well as observed within the riser flow channel close to the exit (Z/L = 0.773) due to the end effect. A significant reduction of the average field temperatures along the riser channel is observed to be 24.5% and 22.4% for inner surface and air centerline temperatures, respectively for stepwise-reducing. Moreover, for stepwise-increasing, a significant reduction of the average riser channel temperature fields is observed with decreasing stepwise-increasing heating by 25.6% and 23.1% for the inner surface and air centerline temperatures, respectively. The average values of the heat transfer coefficient(h¯L) and the average Nusselt number (Nu¯L) along the riser channel were decreased with reducing the heating by 38% and 19% for stepwise-reducing heating, respectively, and by 32% and 13% for the stepwise-increasing heating, respectively.

Modeling the effects of solid particles in CFD-PBM simulation of slurry bubble columns

Prediction of gas holdup and bubble size distribution is of paramount importance for modeling mass and heat transfer and reactions in multiphase reactors. Addition of hydrophilic particles into gas-liquid systems usually decreases gas holdup and increases bubble size. Rational prediction is still difficult in view of the complex effects of solid particles on gas-liquid flows, e.g., the increase of slurry apparent density and viscosity, the reduced film drainage time during bubble coalescence, and the attenuation of liquid turbulent dissipation rate. This work attempts to construct a rational step-by-step approach to analyze these particle effects in CFD-PBM modeling. First, the EMMS-PBM approach is used to improve the BSD simulation in a solid-free system. Then for a gas-slurry system, we propose a correlation of attenuation factor for turbulent dissipation rate in PBM kernel models. Combining EMMS-PBM and the attenuation factor can well predict the gas holdup and BSD in slurry bubble columns.

Modeling long-time behaviors of industrial multiphase reactors for CO2 capture using CFD-based compartmental model

Pilot- and industrial-scale mineral carbonation plants to remove CO2 through a reaction with Ca(OH)2 were built in South Korea to address concerns related to global warming. To simulate mineral carbonation reactors with complex gas–liquid–solid interacting flow patterns, a computational fluid dynamics (CFD)-based compartmental model was developed. In the model, the reactors were divided into hundreds of zones, and each zone was assumed to be a single homogeneous reactor. Mass and heat balance equations were formulated for each zone and the entire reactor, separately. The mass flow rates between adjacent zones and initial CO2 holdup at each zone were calculated from CFD simulations, and a kinetic model, which included all the involved reactions, was built in MATLAB. The total CO2 removal efficiency, pH, and temperature changes as well as concentration profiles of CO2 and other species were predicted during batch operations. To validate the performance of the model, the simulated results were compared with the real operation data from the pilot- and industrial-scale plants. The errors at steady states were within 7% without any adjustable parameters. Furthermore, the model was used to predict the performances of reactors 2.5 and 10 times larger than the industrial-scale reactor.

Optimisation of interaction parameters for CFD modelling of multiphase flow using NR method

Accurate modelling of fluid and particle flow is essential for reliable predictions of gas–solid reactions in the multiphase reactor. Due to the promising features such as short contact time, less back mixing of solids and low residence time, downer column has been used in industries than conventional riser configuration. However, the effective simulation and validation of the hydrodynamic characteristics have been scarce. A RANS model with an appropriate Eulerian-Eulerian approach poses a challenging task of choosing the hydrodynamic simulation parameters, such as i) particle-particle restitution coefficient, ii) particle-wall restitution coefficient and iii) specularity coefficient. The objective of the present study was to optimise these model parameters to obtain close validation with experimental data so that accurate downer hydrodynamics can be predicted. The error obtained from validating the experimental data with the CFD simulation output is our function which needs to be minimised. Newton Raphson multi-parameter root finding method was used for this purpose. The Jacobian evaluation required multiple CFD simulations at each iteration. A 61% reduction in error was achieved after 3 iterations. Thus, the optimised model parameters of hydrodynamics used for further modelling study in predicting hydrodynamic characteristics of a 200 mm diameter 8 m column. Highlights Validation of hydrodynamics of multiphase flow in downer employing Eulerian-Eulerian Approach Optimisation of hydrodynamic interactive model parameters viz., Restitution and Specularity coefficient coupled with Newton Raphson multi-parameter root finding and Jacobian Method. Agreement between experimental and simulation with optimised modelling parameters

Machine learning based position‐rendering algorithms for radioactive particle tracking experimentation

AbstractRadioactive particle tracking (RPT) is one of the most widely used non‐intrusive velocimetry technique for multiphase reactors. The large volume of interrogation and the presence of internals limit the application of RPT in large‐scale real‐world systems. The main challenge lies in having fast reconstruction algorithms applicable to conventional (i.e., bubble columns, fluidized beds, etc.) as well as new vessels. In this contribution, a reconstruction methodology is proposed based on machine learning. Three machine‐learning algorithms, namely, artificial neural network (ANN), support vector regression (SVR), and relevance vector regression (RVR), have been employed for RPT reconstruction. The results show that the position reconstruction accuracy of SVR was best for all cases and that the accuracy of RVR was comparable to SVR for large training datasets. Whereas, in terms of reconstruction speed, RVR outperforms SVR significantly, owing to sparser RVR model. SVR and RVR based reconstruction algorithms expedite the position reconstruction.

Bubble dynamics and mass transfer characteristics from an immersed orifice plate

AbstractBACKGROUNDBubble dynamics plays an important role in performance enhancement of multiphase reactor. The formation of the bubbles at the orifice is critical for the dynamics of bubbles and the mass transfer process during the rising stage. However, few studies have focused on the detailed changing characteristic of bubble formation and its relationship with mass transfer.RESULTSThe evolution of the bubble dynamics from millimeter to micrometer‐sized immersed orifice plates is in situ visualized. Bubble inrush is observed from the orifices with diameters below 421 μm, resulting in significant fluctuation on the gas–liquid interface. The base of the leading bubble varies with the orifice diameter. Smaller orifice is preferred to produce more trailing bubbles with smaller size. The inrush time of the trailing bubble is prolonged with decreasing orifice diameter and increasing gas velocity. The inrush time and diameter of the latter trailing bubble are higher than the former at a certain gas velocity. The volumetric mass transfer coefficient (KLa) is obtained by measuring the bubble volume during the rising process using chemical absorption of carbon dioxide (CO2) with sodium hydroxide (NaOH). Increasing gas velocity, decreasing orifice diameter and bubble inrush make an apparent positive impact on the KLa.CONCLUSIONSThe bubble inrush happens at micrometer orifice. Decreasing orifice diameter and increasing gas velocity are important to intensify oscillation of the leading bubble and increase the frequency of bubbles with high specific interfacial area, which are conducive to the enhancement of the volumetric mass transfer coefficient. © 2020 Society of Chemical Industry

Directly irradiated fluidized bed reactor for thermochemical energy storage and solar fuels production

The path toward a greener economy is leading the world energy scenario to an ever-increasing use of renewable energy sources. Concentrating Solar Thermal (CST) systems are typically based on technologies in which solar energy, concentrated by means of optical sun tracking mirrors, is exploited to drive power cycles or sustain chemical processes. Integration of CST technologies with relatively inexpensive energy storage systems decouples the collection of solar radiation from its use, and thus greatly increases the dispatchability of thermal energy production. Huge research efforts are currently devoted to the study of ThermoChemical Energy Storage (TCES) systems, in which solar energy is used to perform endothermal chemical reactions featuring large latent heat, so as to store solar energy in the noble and stable form of chemical bonds and/or produce solar fuels. Since most TCES processes involve gas/solid chemical reactions, multiphase chemical reactors own a key role for the success of the TCES technology. In this study, a novel batch lab-scale fluidized bed reactor for TCES of concentrated solar power and solar fuels production was designed. The reactor targets at maximizing the collection of solar energy, withstanding the highly-concentrated flux typical of high-temperature CST applications and ensuring uniform temperature distribution of the reactive materials. An experimental campaign consisting in hydrodynamical and thermal characterization of the system under inert conditions was performed. Moreover, reactive tests aimed at TCES of solar energy were performed using limestone calcination/carbonation as model reversible reaction. Heating of the system was performed by means of a simulator of concentrated solar energy made of a 7 kWe short-arc Xe lamp coupled with an elliptical reflector. The hydrodynamical characterization disclosed the main features of the reactor and the possibility of establishing different regimes of operation. Thermal characterization revealed that reactor can be safely operated at temperature of over 1000 °C. Reactive tests proved the feasibility and reliability of the designed reactor toward chemical reactions aimed at TCES of concentrated solar energy and encourage future studies toward solar fuels production.

Mass transfer modeling and simulation of a transient homogeneous bubbly flow in a bubble column

Bubble columns have wide applicability in the industry as contactors such as absorbers, strippers, and multiphase reactors. Despite their simple construction and operation, the success in the design of bubble columns requires deep knowledge of transport phenomena applied to multiphase flow. Modeling and simulating the fluid dynamics through numerical methods may circumvent the high cost of empirical methods when analyzing key parameters for the design and scale-up of bubble columns. The main objective of this work is to model and simulate the interfacial mass transfer in a bubble column, for both steady-state and transient analysis. The equations of mass, momentum, and species conservation are described in a Euler-Euler framework using a one-dimensional Two-Fluid Model (TFM), taking adequate closure relations for modeling interfacial transport phenomena. The equations are integrated by the Finite Volume Method (FVM) in an algorithm developed by the authors and the numerical results obtained are compared with experimental data found in the literature. The simulations are predictive and run with no need for matching experimental data, which is the main contribution of this work. The results obtained showed good agreement when compared with experimental data. Additionally, a high-order in space (TVD) and time (Crank-Nicolson) is developed to capture the gradients of gas fraction and composition, providing a remarkable tool for transient analysis.

Kinetic study of the toluene oxidation in homogeneous liquid phase

To better understand the interplay of fluid dynamics, mass transport, and chemical reactions in multi-phase reactors, each of these effects needs to be studied separately. In particular, reactions are hard to study separately from mass transport. In this work, using a new reactor concept a macroscopic reaction kinetics of the oxidation of toluene is determined in homogeneous liquid-phase. By operating at elevated pressure, mass transport limitations are avoided. The reactor concept requires the measurement of the oxygen concentration within the organic liquid phase, which further allows to setup an atomic oxygen balance. Running experiments at different oxygen flow rates, a kinetic model was parameterized, which describes the experimental results for oxygen flow rates in an industrially relevant range. Since the developed model has no mass transport limitations, it can be used in processes where independent modelling of mass transport and chemical reactions are combined, such as with computational fluid dynamics.