Non-ideal Reactor Research Articles

A comparison of the Eulerian and particle tracking approaches for prediction of ozone contactor performance

Research Article| June 01 2011 A comparison of the Eulerian and particle tracking approaches for prediction of ozone contactor performance Jianping Zhang; Jianping Zhang 1Hatch Ltd., Mississauga, ON, Canada L5K 2R7 E-mail: jzhang@hatch.ca Search for other works by this author on: This Site PubMed Google Scholar Peter M. Huck; Peter M. Huck 2NSERC Chair in Water Treatment, Department of Civil and Environmental Engineering, University of Waterloo, ON, Canada N2L 3G1 Search for other works by this author on: This Site PubMed Google Scholar Gordon D. Stubley; Gordon D. Stubley 3Department of Mechanical and Mechatronics Engineering, University of Waterloo, ON, Canada N2L 3G1 Search for other works by this author on: This Site PubMed Google Scholar William B. Anderson William B. Anderson 2NSERC Chair in Water Treatment, Department of Civil and Environmental Engineering, University of Waterloo, ON, Canada N2L 3G1 Search for other works by this author on: This Site PubMed Google Scholar Journal of Water Supply: Research and Technology-Aqua (2011) 60 (4): 197–209. https://doi.org/10.2166/aqua.2011.061 Article history Received: October 09 2010 Accepted: March 19 2011 Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Cite Icon Cite Permissions Search Site Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAll JournalsThis Journal Search Advanced Search Citation Jianping Zhang, Peter M. Huck, Gordon D. Stubley, William B. Anderson; A comparison of the Eulerian and particle tracking approaches for prediction of ozone contactor performance. Journal of Water Supply: Research and Technology-Aqua 1 June 2011; 60 (4): 197–209. doi: https://doi.org/10.2166/aqua.2011.061 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex The Eulerian and particle tracking approaches, two commonly utilized numerical methods, were evaluated for modelling drinking water ozone disinfection systems. The Eulerian approach predicts disinfection performance by solving an advection-diffusion equation. Alternatively, the particle tracking (Lagrangian) approach calculates disinfection efficiency by numerically introducing particles into the flow and predicting their trajectories through a spatially varying field of ozone residuals. The two approaches were used for modelling two hypothetical ozone reactors and a full-scale operating ozone contactor. For ozone reactors with plug flow characteristics, the two approaches match well in evaluating disinfection efficiency (represented by the CT value). For reactors with non-ideal hydraulic performance, the particle tracking model predicted slightly lower CT values than did the Eulerian approach. This may be due to the trapping of particles in the dead zones of non-ideal reactors, and the limitation on the particle numbers that could be used for data processing. The results of a full-scale contactor study further confirmed these observations. The study also found that the effect of particle size (1–100 μm) used in this study on the particle tracking method was negligible. The Schmidt number has minor impacts on the Eulerian approach modelling results. computational fluid dynamics, disinfection, Eulerian approach, ozone contactor, particle tracking approach This content is only available as a PDF. © IWA Publishing 2011 You do not currently have access to this content.

Mejoramiento de la Enseñanza en Ingeniería a Través de Software de Dinámica de Fluidos Computacional

<p>El curso de ingeniería de las reacciones químicas, una de las piedras angulares del programa de ingeniería química, e incluso ingeniería ambiental, se ha impartido a través de cursos introductorios que no necesariamente tienen en cuenta los conceptos de reactores no ideales, los cuales son la base para el análisis de sistemas reales como los reservorios o las lagunas aireadas. En este trabajo se presenta una estrategia para optimizar la enseñanza de la Ingeniería de las reacciones químicas por medio de software de dinámica de fluidos computacional. La inclusión de dichas herramientas computacionales permite introducir conceptos de reactores no ideales en una forma más amigable, ya que es muy fácil observar perfiles de velocidad, concentración y temperatura en geometrías bidimensionales. Al mismo tiempo, la construcció del modelo garantiza el establecimiento de conexiones con otros cursos de ingeniería, tales como transferencia de calor y dinámica de fluidos, de manera que el software no se convierta en una caja negra.</p>

Simulation and Optimization of Biodiesel Production by Soybean Oil Transesterification in Non-Ideal Continuous Stirred-Tank Reactor

This research examines the transesterification reaction of soybean oil with methanol in order to model and simulate a non-ideal continuous stirred-tank reactor. A mathematical model has been developed for the reactor. The biodiesel production process was optimized by application of factorial design 25 and response surface methodology. Factorial design and response surface analysis were combined with modeling and simulation to determine the operating conditions that maximize biodiesel production and minimize reactor volume. The optimum results obtained were conversion (0.95), molar ratio alcohol/oil (6:1), temperature (60.5 oC), ? (0.75), bypass (0.10) and reactor volume (1,500 L).

Numerical investigation on new configurations for vapor-phase aerosol reactors

Non-ideal aerosol reactors for synthesizing nano- and micro-metal-oxide powders can currently be accurately designed by means of computational fluid dynamics (CFD) models instead of an expensive trial-and-error experimental technique. According to a multi-scale approach, fluid dynamics of the reacting volume is modeled by an appropriate population balance equation (PBE) coupled to momentum, energy and chemical species conservative equations. The present work refers to the modeling of non-ideal vapor-phase aerosol reactors, in particular to the numerical investigation on the effects of feeding nozzle arrangement, where the most significant gradients and aerosol phenomena occur. The described aerosol CFD model, which a priori assumes a log-normal particle size distribution (PSD), has been validated against both an experimental and an industrial case, and therefore it has been applied to the study of new reactor configurations. Numerical results show that traditional axial-symmetric and jet-opposed nozzle arrangements can be improved adopting a tangential geometry.

Mathematical Modeling and Simulation of Dispersion in a Nonideal Plug Flow Reactor

This article discusses research carried out to model and simulate a nonideal plug flow (tubular) reactor with axial dispersion. The simulated results were sufficiently close to the experimental results for the process, the mean of the deviation of the final concentration and the final conversion being 0.017 kmol/m3 and 3.07%, respectively. The dispersion number was found to be 0.0605 which implied that the dispersion in the vessel was in the range of low to intermediate dispersion. The system was further studied by simulating it for various process conditions. It was found that a conversion of 99.99% was obtained from a simulation with CA0 = 2.5075, CB0 = 6.0 kmol/m3, τ = 383 K and k = 4.074 m3/kmol·hr, suggesting these as the best values of the operational parameters for the optimization of the process. When the model was compared with a tank-in-series model for the same process conditions, it was found to be more economical than the former and hence preferable.

A semi-mechanistic model building framework based on selective and localized model extensions

In the core of many process systems engineering tasks, like design, control, optimization and fault diagnosis, a mathematical model of the underlying plant plays a key role. Such models are so important that extensive studies are available, recommending different modeling techniques to be adopted for specific processes or goals. It is usual and practical to split modeling techniques under two main groups: mechanistic methods and empirical or statistical methods. Both paradigms have been adopted, but very few frameworks were developed to combine and integrate features from both of them. In this article we describe a framework for data-driven evolution of static mechanistic models with a selective inclusion of simple empirical terms. To illustrate its practical potential, our framework is applied to the identification of a non-ideal reactor and to the optimization of the Otto–Williams benchmark reactor.

Non-ideal reactor network synthesis through IDEAS: Attainable region construction

The attainable region (AR) for non-ideal reactor networks is constructed for the first time using the Infinite DimEnsionAl State-space (IDEAS) framework. The axial dispersion model is used to represent a non-ideal reactor, and it is shown that the IDEAS framework and associated Shrink-wrap algorithm are applicable to this model. A case study demonstrates that the AR for a reactor network featuring non-ideal dispersion models is larger than the AR for a reactor network featuring only ideal CSTR/PFR models.

Modular Simulation of Fluidized Bed Reactors

AbstractSimulation of chemical processes involving nonideal reactors is essential for process design, optimization, control and scale‐up. Various industrial process simulation programs are available for chemical process simulation. Most of these programs are being developed based on the sequential modular approach. They contain only standard ideal reactors but provide no module for nonideal reactors, e.g., fluidized bed reactors. In this study, a new model is developed for the simulation of fluidized bed reactors by sequential modular approach. In the proposed model the bed is divided into several serial sections and the flow of the gas is considered as plug flow through the bubbles and perfectly mixed through the emulsion phase. In order to simulate the performance of these reactors, the hydrodynamic and reaction submodels should be integrated together in the medium and facilities provided by industrial simulators to obtain a simulation model. The performance of the proposed simulation model is tested against the experimental data reported in the literature for various gas‐solid systems and a wide range of superficial gas velocities. It is shown that this model provides acceptable results in predicting the performance of the fluidized bed reactors. The results of this study can easily be used by industrial simulators to enhance their abilities to simulate the fluidized bed reactor properly.

Dispersion Number Studies in CMP of Interlayer Dielectric Films

Determining the factors that cause flow nonidealities during chemical mechanical planarization (CMP) is critical for controlling and optimizing the process. This study explores aspects of the fluid dynamics of CMP on interlayer dielectric films. The residence time distribution of slurry under the wafer was experimentally determined and used to calculate the dispersion number of the fluid in the wafer-pad region based on a dispersion model for nonideal reactors. Furthermore, lubrication theory was employed to explain trends in flow behavior as operating conditions were varied. The results indicate that at low wafer pressure and high relative pad-wafer velocity, the slurry flow exhibits nearly ideal plug flow behavior. As pressure increases and velocity decreases, flow begins to deviate from ideal behavior and the slurry becomes increasingly more mixed beneath the wafer. These phenomena were found to be the result of variable slurry film thickness between the pad and the wafer, as measured by changes in the coefficient of friction between the pad and the wafer. © 2003 The Electrochemical Society. All rights reserved.

Modeling and simulation of propylene polymerization in nonideal loop reactors

AbstractA dynamic mathematical model for liquid‐phase polymerization in loop reactors was developed and implemented in language C using S‐functions in a MATLAB/SIMULINK environment. It is based on a nonideal continuous stirred‐tank reactor (CSTR) model capable of dealing with multisite copolymerization of olefins. The kinetic scheme includes a specific mechanism for hydrogen effect on rate of polymerization observed on both laboratory experiments and industrial plant trials. A nonideality due to polymer segregation at the reactor output was inserted into the model to better predict reactor slurry density. Polymer moment balances were used to compute resin properties, such as average molecular weights, polydispersity, and melt flow index. Dynamic data from an industrial polypropylene plant were used for parameter estimation and model validation.

Integration of coliform decay within a CFD (computational fluid dynamic) model of a waste stabilisation pond

CFD mathematical modelling offers the potential to predict the actual flow pattern in a pond rather than generalising its mixing and mass transport as either an ideal flow reactor or, in the case of the non-ideal flow reactor, as a single dispersion number. However, perhaps the greatest benefit that CFD offers over the previous approaches is its ability to directly account for physical influences on the pond hydraulics such as the addition of baffles for example. In addition to solving the equations of fluid flow, CFD modelling also allows incorporation of other equations. The next logical development is, therefore, the integration of a reaction model within its solution domain. This potential has been recognised by several researchers, but to date no such work has been published. The primary aim of this paper was to present a CFD model of a field pond that incorporates the first order decay equation for coliforms. Experimental monitoring of the field pond gave an average effluent concentration of 3,710 f.c./100 mL, while the CFD model predicted 4,600 f.c./100 mL. Considering the pond provides an order of magnitude decrease in faecal coliform concentration, the integrated CFD model has clearly predicted the treatment efficiency very well. The secondary aim of this paper was to demonstrate the potential application of this technique. A typical pond was designed and modelled along with two variations incorporating two baffles and six baffles respectively. As is typically found in pond systems, the standard design suffered from severe short-circuiting with the model predicting a value of 6.2 x 10(6) f.c./100 mL at the outlet. The simulations of the baffled designs illustrate how treatment efficiency was improved by reducing the short-circuiting through the pond. The model predicted values of 6.0 x 10(3) f.c./100 mL for the 2-baffle design and 5.7 x 10(2) f.c./100 mL for the 6-baffle design.

Dispersion Number Studies in ChemicalMechanical Planarization

AbstractThis study explores aspects of the fluid dynamics of CMP processes. The residence time distribution of slurry under the wafer is experimentally determined and used to calculate the Dispersion Number (Δ) of the fluid in the wafer-pad region based on a dispersion model for non-ideal reactors. Furthermore, lubrication theory is used to explain flow behaviors at various operating conditions. Results indicate that at low wafer pressure and high relative pad-wafer velocity, the slurry exhibits nearly ideal plug flow behavior. As pressure increases and velocity decreases, flow begins to deviate from ideality and the slurry becomes increasingly more mixed beneath the wafer. These phenomena are confirmed to be the result of variable slurry film thicknesses between the pad and the wafer, as measured by changes in the coefficient of friction (COF) in the pad-wafer interface.

Modeling compartmentalized lagoon systems under cyclic operation

Aerated lagoon systems have been widely used for municipal wastewater treatment because of their simplicity and low maintenance costs, but many have subsequently required upgrading due to increased wastewater volume and stricter environmental regulations. To improve performance and increase capacity with minimal capital infusion, Hawkins (1997, United States Patent No. 5,624,563) developed a process wherein the lagoon basin is compartmentalized and selected compartments are cycled to separate and recycle biosolids. Simulation would be useful to assess the process and to evaluate alternative plant modification schemes. The hydraulic behavior of the system is complex, however, due to the interconnected and cyclic nature of the compartments and their operation. This paper describes the development of a hydraulic modeling approach for compartmentalized lagoon systems, and discusses its implementation using AQUASIM (EAWAG, Dubendorf, Switzerland). The modeling approach was implemented for a specific configuration and several operating conditions. Simulated tracer tests indicated that the oscillatory nature of the system makes its behavior difficult to simulate with commonly used non-ideal reactor models. Biotreatment simulations using Activated Sludge Model No. 1 suggest that conversion into a compartmentalized lagoon system could effectively upgrade the performance and capacity of a conventional aerated lagoon.

UV Reactor Validation: Implications of Non-ideal Reactor Behavior

UV Reactor Validation: Implications of Non-ideal Reactor Behavior

Animal Guts as Nonideal Chemical Reactors: Partial Mixing and Axial Variation in Absorption Kinetics.

Animal guts have been idealized as axially uniform plug-flow reactors (PFRs) without significant axial mixing or as combinations in series of such PFRs with other reactor types. To relax these often unrealistic assumptions and to provide a means for relaxing others, I approximated an animal gut as a series of n continuously stirred tank reactors (CSTRs) and examined its performance as a function of n. For the digestion problem of hydrolysis and absorption in series, I suggest as a first approximation that a tubular gut of length L and diameter D comprises [Formula: see text] tanks in series. For [Formula: see text], there is little difference between performance of the nCSTR model and an ideal PFR in the coupled tasks of hydrolysis and absorption. Relatively thinner and longer guts, characteristic of animals feeding on poorer forage, prove more efficient in both conversion and absorption by restricting axial mixing. In the same total volume, they also give a higher rate of absorption. I then asked how a fixed number of absorptive sites should be distributed among the n compartments. Absorption rate generally is maximized when absorbers are concentrated in the hindmost few compartments, but high food quality or suboptimal ingestion rates decrease the advantage of highly concentrated absorbers. This modeling approach connects gut function and structure at multiple scales and can be extended to include other nonideal reactor behaviors observed in real animals.

Animal Guts as Nonideal Chemical Reactors: Partial Mixing and Axial Variation in Absorption Kinetics

Animal guts have been idealized as axially uniform plug‐flow reactors (PFRs) without significant axial mixing or as combinations in series of such PFRs with other reactor types. To relax these often unrealistic assumptions and to provide a means for relaxing others, I approximated an animal gut as a series of n continuously stirred tank reactors (CSTRs) and examined its performance as a function of n. For the digestion problem of hydrolysis and absorption in series, I suggest as a first approximation that a tubular gut of length L and diameter D comprises $$n=L/ D$$ tanks in series. For $$n\geq 10$$, there is little difference between performance of the nCSTR model and an ideal PFR in the coupled tasks of hydrolysis and absorption. Relatively thinner and longer guts, characteristic of animals feeding on poorer forage, prove more efficient in both conversion and absorption by restricting axial mixing. In the same total volume, they also give a higher rate of absorption. I then asked how a fixed number of absorptive sites should be distributed among the n compartments. Absorption rate generally is maximized when absorbers are concentrated in the hindmost few compartments, but high food quality or suboptimal ingestion rates decrease the advantage of highly concentrated absorbers. This modeling approach connects gut function and structure at multiple scales and can be extended to include other nonideal reactor behaviors observed in real animals.

Animal guts operating as ideal and non-ideal chemical reactors

Animal guts operating as ideal and non-ideal chemical reactors

Modeling of real biological reactors for the treatment of complex substrates. Dynamic simulation

A mathematical model for the dynamic simulation of anaerobic bioreactors containing biofilm and degrading complex substrates is presented. The model allows to simulate different reactor configurations: single CSTR, multiple CSTRs and non-ideal reactors. Our simulator was developed on the basis of gPROMS, which allows to study a wide variety of problems such as optimal start-up, design under forced regimen and parameter estimations of the biofilm kinetic from experimental data. The digestion of cattle manure in different reactor configurations was selected as example to show the model and the simulator performances.

Use of linear modeling in steady-state isotopic-transient kinetic analysis of surface-catalyzed reactions: Application to plug-flow reactors

Determination of kinetic parameters from steady-state isotopic transient kinetic analysis (SSITKA) requires modeling of the reactor system and the catalyst surface. In this work, a novel application of linear-modeling methods was developed for SSITKA, using transfer functions for non-differential-length catalyst beds in non-ideal plug-flow reactors (PFR's), which are often employed in SSITKA. Various linear relationhips between the catalyst surface and the gas phase were derived - including linear convolution, which provides a new rigorous method for generating calculated isotopic transient responses from catalyst-surface and reaction-system models. Incorporation of linear convolution - which avoids a priori gas-phase behavior correction which is problematic when using non-ideal PFR's - in parametric and nonparametric kinetic analyses provides for increased accuracy in the determination of kinetic parameters in SSITKA. The linear modeling techniques developed were applied to a PFR transient-response model for an irreversible reaction occurring in a non-differential-length catalyst bed. It was determined that the dependency upon the catalyst-bed length in PFR's is unimportant if gradientless conditions - differential conversion of reactant and irreversible reaction - are maintained in a catalyst bed of non-differential length. The results illustrate how the linear modeling techniques developed can be used with SSITKA to test assumed catalyst-surface reaction models.

Dynamic modelling of pH controlled precipitation and dissolution in an aqueous solution

This paper presents a dynamic model for a chemical precipitation and dissolution process in an aqueous solution. The precipitation process is a part of the electrolyte purification section at the Falconbridge Nikkelverk in Kristiansand, Norway. The model is partly mechanistic, and partly based on first principles. The state variables in the model are chosen as a combination of linear reaction invariants and non-linear variants. The effect of dispersion and radial mixing in the non-ideal plug flow reactor (PFR), where the precipitation takes place, is modelled as a combination of ideal continuous stirred tank reactors (CSTR). The CSTR-elements can be viewed as general building blocks or objects, which may also form a larger and more complex reactor system. Easier maintenance and better chance for reuse are some of the benefits of using only one central building block when modelling reactor systems. The chemical precipitation and dissolution rates in the model are controlled by the pH value and the reduction potential. The simulation results shows a high degree of correspondence with actual measurements at the refinery, and therefore form a promising basis for design of control and operator support systems.