bluuebunny/crossref_metadata_2025 huggingface dataset:
Robot Control Using Electromyography (EMG) Signals of the Wrist
Authors: DaSalla C. , Kim J. , Koike Y.
Published: October 2005

The aim of this paper is to design a human–interface system, using EMG signals elicited by various wrist movements, to control a robot. EMG signals are normalized and based on joint torque. A three‐layer neural network is used to estimate posture of the wrist and forearm from EMG signals. After training the neural network and obtaining appropriate weights, the subject was able to control the robot in real time using wrist and forearm movements.
Numerical Investigation for Optimal Phase Holdup of a Continuous Reactor for Hydrogenation of Nitrile Butadiene Rubber
Authors: Pan Qinmin , Rempel Garry L.
Published: October 2005

The effect of phase holdup on reactor behaviour has been investigated so that a proper reactor for a continuous process for hydrogenation of nitrile butadiene rubber can be developed. Detailed numerical analysis has been carried out, taking the coupling between the hydrogenation kinetics and reactor flow behaviours into account. The suitable liquid holdup and gas liquid mass transfer behaviour for the hydrogenation process of nitrile butadiene rubber are discussed, and the optimal reactor structure and operation conditions are suggested.
Market Demand versus Technological Development: the Future of Chemical Engineering
Authors: Charpentier Jean-Claude
Published: October 2005

In todays economy, Chemical Engineering must respond to the changing needs of the chemical process industry in order to meet market demands. The evolution of chemical engineering is necessary to remain competitive in global trade. The ability of chemical engineering to cope with scientific and technological problems is addressed in this paper. Chemical Engineering is vital for sustainability: to satisfy both the market requirements for specific end-use properties of products and the social and environmental constraints of industrial-scale processes. A multidisciplinary, multiscale approach to chemical engineering is evolving due to breakthroughs in molecular modelling, scientific instrumentation and related signal processing and powerful computational tools. The future of chemical engineering can be summarized by four main objectives: (1) Increase productivity and selectivity through intensification of intelligent operations and a multiscale approach to process control; (2) Design novel equipment based on scientific principles and new production methods: process intensification; (3) Extend chemical engineering methodology to product design and product focussed processing using the 3P Engineering molecular Processes-Product-Process approach; (4) Implement multiscale application of computational chemical engineering modelling and simulation to real-life situations from the molecular scale to the production scale.
Numerical Convection Algorithms and Their Role in Eulerian CFD Reactor Simulations
Authors: Jakobsen Hugo A.
Published: October 2005

In this paper a comparative convection algorithm study is presented. The performance of a large number of schemes is compared evaluating the predicted solutions for a standard benchmarking test problem. The nature of the errors caused by the numerical approximations to the convection term is highlighted. Although there is no algorithm that performs the best in general, several conclusions can be made. The tests performed show that the 1st order upwind scheme and several variations of this scheme are very diffusive and should be avoided. Most stable 2nd order schemes seem to be much more accurate, whereas the accuracy gained by higher order schemes (3rd order and 4th order) may be a little more costly. Implicit time integration schemes are usually not as efficient as the corresponding explicit schemes due to the computational time required on the iterative process. With larger time steps the accuracy of implicit schemes decrease rapidly. The choice of proper higher order schemes (2nd order schemes) is then seemingly determined by the trade-off between accuracy and computational time. The conservative methods like the UTOPIA, the QUICK-1D combined with a limiter, and a limited number of FCT and TVD formulations may be sufficient solving the multi-fluid model equations. For advective terms (e.g., as occur in the temperature equation) the non-flux-based modified method of characteristics is very fast, but also other higher order (2nd order) schemes performed well.
CFD Simulations of Gas Fluidized Beds Using Alternative Eulerian-Eulerian Modelling Approaches
Authors: Lettieri Paola , Cammarata Luca , Micale Giorgio D. M. , Yates John
Published: October 2005

A commercially available Computational Fluid-Dynamics code, CFX-4, has been chosen to carry out computer simulations of gas fluidized beds. In this study, the Eulerian-Eulerian granular kinetic model, which is a standard option of the code, has been used. Fluid-bed simulations of Geldart Group B materials have been performed using the granular kinetic model, spanning three hydrodynamic regimes: bubbling, slugging and turbulent fluidization. Furthermore, an alternative Eulerian-Eulerian model, the so-called "particle-bed model", has been implemented for the first time within a commercial code, and results are presented from simulations of the bubbling and slugging fluidization of a Geldart Group B material, and for the homogeneous fluidization of a Group A material. A numerical procedure has been developed to allow for a tight control of the fluid-bed voidage at maximum packing during the simulations with the particle-bed model. Results show that both the granular kinetic model approach and the particle-bed model are able to describe significant aspects of the investigated fluidization regimes.
Optimization of Styrene Reactor Design for Two Objectives using a Genetic Algorithm
Authors: Li Yue , Rangaiah Gade P , Ray Ajay Kumar
Published: October 2005

Optimization of industrial styrene reactor design for two objectives using the non-dominated sorting genetic algorithm (NSGA) is studied. Both adiabatic and steam-injected reactors are considered. The two objectives are maximization of styrene production and styrene selectivity. The study shows that styrene reactor design can be optimized easily and reliably for two objectives by NSGA. It provides a range of optimal designs, from which the most suitable design can be selected based on other considerations.
Chemical Kinetics in Dispersed-Phase Reactors
Authors: McCoy Ben J , Madras Giridhar
Published: October 2005

Many chemical engineering processes occur under conditions when a dispersed phase undergoes fragmentation (breakup) and/or aggregation (coalescence). It is of considerable interest to model a chemical process that occurs at the interface and therefore depends on the evolving size distribution of the dispersed phase. We apply distribution kinetics to represent the evolution of the dispersed-phase size distribution for simultaneous fragmentation and coalescence. The continuous phase with dissolved reactant enters and exits a continuous-flow stirred-tank reactor. When the dispersed phase contained within the vessel satisfies a similarity solution, several rate expressions, including one for interphase mass transfer, that depend on mass moments of the size distribution allow analytical or simple numerical solutions. The solutions demonstrate how chemical reaction mass balances can be combined with distribution dynamics to extend chemical reaction engineering analysis.
Influence of the Sulfur Poisoning on the Performance of a Primary Steam Reformer
Authors: Piña Juliana , Bucalá Verónica , Borio Daniel Oscar
Published: October 2005

In the present paper, the effect of sulfur on the performance of the catalyst particle and the operation of an industrial side-fired reformer is analyzed, by coupling detailed mathematical models for the reactor and the sulfur poisoning. The model predicts the transient evolution of the main variables inside the catalyst pellet (e.g., poison coverages and reaction rates) and along the axial position (e.g., gas composition, sulfur distribution, gas and tube skin temperatures). The common simplified model, which neglects the reaction rates update as the poisoning proceeds, is compared with the model proposed in this article. The deactivation phenomenon causes methane reaction rates that present maxima along the catalyst coordinate, moreover effectiveness factors higher than the unity are found close to the reactor entrance. When the poison is removed from the feedstock, non-monotonic sulfur distributions appear inside the particle and simultaneous sulfur migration towards the surface and the center of the pellet is observed. Non-isothermal deactivation conditions similar to those found in industrial reformers are simulated, i.e., the heat input is assumed constant during the poisoning. The increments in the gas and tube skin temperatures are maximum at those axial positions where the observed methane reaction rate becomes equal to its value at conditions of fresh catalyst. The proposed mathematical model is a useful tool to describe the dynamic behavior of the macroscopic reactor variables in terms of the local phenomena that take place within the catalyst particles. In practice, this model can be utilized to evaluate key variables such as: the outlet sulfur content (to minimize poisoning downstream the reformer), the maximum tube skin temperature (to extend the tube-life time) and the axial distribution of the process gas temperature and composition (to prevent carbon formation in the top section of the reactor).
Influence of Particle Properties on the Yield and Selectivity of Fast Heterogeneously Catalyzed Gas-Liquid Reactions
Authors: Raffensberger Jodi , Koynov Athanas A , Glasser Benjamin J , Khinast Johannes G
Published: October 2005

Detailed numerical results are presented that show how catalyst particles can be tailored to influence the yield and selectivity of fast, heterogeneously-catalyzed gas-liquid chemical reactions. Results from our Euler-Lagrange study demonstrate that the physical characteristics of the catalyst particle (e.g. size and density) impact where the particles concentrate in the wake of the bubble. Smaller particles concentrate in the wake, while larger particles move out of the wake. Since the dissolved gas concentration is the highest in the wake small particles will catalyze the reaction at higher concentrations than large particles. Additionally, smaller and lighter particles remain in the recirculation zone for an extended period of time, whereas the heaviest particles are removed from this region. By carefully choosing particles of a certain Stokes number, it is shown that the yield and selectivity of a fast parallel reaction network can be enhanced.
Numerical Analysis of a Reacting Gas/Solid Flow in the Riser Section of an Industrial Fluid Catalytic Cracking Unit
Authors: Benyahia Sofiane , Gonzalez Ortiz Agustin , Paz Paredes José Ignacio
Published: October 2005

The Fluid Catalytic Cracking (FCC) is an important process in a refinery used mainly to produce higher value gasoline from heavy hydrocarbons. An FCC unit can crack different type of feeds and can use different types of catalysts during its lifetime, which makes this process very flexible and profitable. In this paper, an industrial unit located in Mexico was analyzed and the computational results were compared with available design data. The FCC process involves complex reaction kinetics along with multiphase flow hydrodynamics and heat transfer. This makes it nearly impossible to model every physical phenomenon that occurs in this process. However, an interesting model should be able to predict reasonably well the yields of the cracking reactions. Cracking reactions are catalytic, and the catalyst distribution in the riser needs to be known a priori. Therefore, we modeled the physical process as a gas/solid multiphase flow with reaction. A transient Eulerian approach plus a simple 3-lumps reaction kinetic scheme (Nace et al., 1971) describe the multiphase flow model. The gas density was assumed to follow an ideal gas law, and can, thus, change with the number of moles in the system. Conservation of mass, momentum, and species (heavy oil, gasoline and gas+coke) were solved. The gas/solid hydrodynamics and the yields of the reacting species were predicted in the 2-D Riser section of the FCC unit. The results showed a dramatic effect of the change in the number of moles of the chemical species on the hydrodynamics. The increase in the number of moles due to the cracking reactions resulted in a significant increase in the gas flow rate, which changed significantly the flow regime. The reaction yields compared reasonably well with the design data for this specific unit.
Transport and Reaction Processes in Bioremediation of Organic Contaminants. 1. Review of Bacterial Degradation and Transport
Authors: Bressler David C , Gray Murray R
Published: October 2005

Bioremediation of contaminants in soil and water involves a complex interplay between transport processes and biological reactions. Equilibrium physical factors such as aqueous solubility, soil adsorption, and phase partitioning indicate the transport processes that can limit bioremediation, namely the rates of interfacial transport and availability of contaminants to microbes. The physical properties of hydrophobic contaminants and the properties of biological membranes can be considered simultaneously by constructing a simple model for flux across from the aqueous phase to the cell interior. This simple model helps to reconcile the observed maximum biodegradation rates of different priority pollutants. This flux model for bioremediation suggests that the inhibition of biotransformation by alkyl substitution of aromatics may be due to transport kinetics rather than steric hindrance at the active enzymes. This report links the solubility of contaminants to the kinetics of transport across cell membranes, and thus suggests a mechanism which can control the overall activity of bioremediation processes for complex mixtures of contaminants.
Catalytic Wet Oxidation of Acrylic Acid: Studies with Manganese-based Oxides
Authors: Silva Adrián M.T. , Marques Rita R.N. , Quinta-Ferreira Rosa M.
Published: October 2005

Development of active, stable and economical catalysts for oxidation of acrylic acid contained in industrial effluents is nowadays of great importance. Several manganese-based solids catalysts supported in Ce, Zr, Ti and Al oxides were prepared in our laboratory by incipient wetness impregnation for oxidation of acrylic acid in a batch high-pressure reactor at slurry conditions under 200°C and 15 bar of oxygen partial pressure. The Mn-Ce-O catalyst was the most active leading to high conversions (92.3%) in terms of total organic carbon (TOC) and total degradation of acrylic acid in the first 30 min of reaction. The TOC reductions were lower with Mn-Zr-O (45.6%), Mn-Ti-O (43.6%) and Mn-Al-O (28.2%) as well as acrylic acid was not completely degraded even after 180 min of reaction. The impregnation method used for catalyst preparation was compared with the co-precipitation procedure, being the last one less effective for TOC reduction (87.0%) although the same activity to oxidation of acrylic acid was observed. Acetic and formic acids were found as reaction intermediates being refractory compounds for the catalysts supported in Zr, Ti and Al. Catalyst stability was also evaluated and Mn-Ce-O prepared by impregnation showed low leaching of Mn to the liquid phase as well as carbon adsorption was not found strengthening the catalyst potentialities in the treatment of wastewaters containing acrylic acid. Since under non-catalytic conditions acrylic acid is refractory up to high temperatures (260°C), this work offers a step forward in the design of an economical catalyst able to promote acrylic acid oxidation in the liquid-phase at lower operating conditions than those used in non-catalytic systems.
Simulation of Cold Flow FCC Stripper Hydrodynamics at Small Scale Using Computational Fluid Dynamics
Authors: McKeen Tim , Pugsley Todd S.
Published: October 2005

The refining industry trend toward increased throughput of heavier feeds, accompanied by increased catalyst circulation rates in the fluid catalytic cracking (FCC) unit, has created flow problems in the FCC stripper. This has reduced stripper efficiency, leading to loss of valuable product to the regenerator. This adversely affects the FCC unit heat balance in some cases, requiring the catalyst circulation rate to be reduced, thereby limiting the flow of feed to the unit. Research on FCC strippers published in the open literature is scarce. The purpose of the present study is to model the hydrodynamics of a cold flow, laboratory scale FCC stripper using computational fluid dynamics (CFD). Simulations were performed using the two-fluid CFD code MFIX (www.mfix.org) for operating conditions of gas superficial velocities between 0.1 and 0.33 m/s and solid circulation fluxes ranging between 28 and 90 kg/m2s. A 2-D cold-flow annular FCC stripper was simulated since this study is a first step in modeling stripper hydrodynamics. The simulations were in good qualitative and quantitative agreement with the limited cold-flow stripper hydrodynamic data published in the open literature. The model was also shown to predict the onset of flooding in the baffled stripper, and the addition of downcomers to the baffles widened the stable operating envelope.
Measurement of Efficiency of Distribution of Liquid Feed in a Gas-Solid Fluidized Bed Reactor
Authors: Knapper Brian A , Gray Murray R , Chan Edward W , Mikula Randy
Published: October 2005

A technique has been developed to give a quantitative measure of the contacting efficiency of liquid feed onto particles in a hot fluidized bed for petroleum applications. Copper naphthenate was used as a tracer to measure the coating of atomized bitumen feed onto solid coke particles in a fluid coking pilot plant. The pilot plant consisted of a reactor vessel, where bitumen was injected into the reactor as feed, and a regeneration vessel, where coke particles were heated and circulated back to the reactor. Atomized bitumen droplets were injected through a feed nozzle into the reactor section. A small concentration of copper naphthenate tracer, pre-diluted with bitumen, was injected upstream of the nozzle, following a step function with time. As the bitumen reacted, the copper formed solid deposits on the surface of the particles, effectively labeling the particles that had been contacted by the bitumen droplets. Frequent coke samples from the solids exiting and entering the reactor were taken during and after the injection of the tracer.Two types of measurements were conducted on the coke samples; bulk copper concentration in the samples, using Inductively Coupled Plasma (ICP), and copper concentration on individual coke particles using energy-dispersive X-ray (EDX) analysis. The data for bulk copper concentration confirmed that the solids were mixed rapidly in the reactor, approximating a Continuous Stirred Tank Reactor (CSTR). The EDX analysis of individual coke particles demonstrated, however, that a significant fraction of the coke particles within the samples were not labeled with copper. This result indicated that many of the particles in the fluidized bed were not contacted by bitumen in the reactor. Consequently, the tracer technique was used to compare the coating efficiency of bitumen on coke particles by operation of different nozzle designs.
Photobioreactor Stability by Phase Plane Technique Applied to Spirulina Maxima Growth
Authors: Belkacemi Khaled , Hamoudi Safia
Published: October 2005

Spirulina maxima is a worthy multicellular filamentous micro-algae used as a food supplement and raw material for fine chemicals and biologically active compounds production. Intensive approach consisting of cultivating pure strains of this photoautotroph microorganism in photobioreactors is more desirable than extensive ones, largely incontrollable with regard to production stability. Determining the best reaction conditions to reach a steady state in the runway events is often needed in biological systems. For a biochemical engineer, knowing the system stability for an optimal bioreactor configuration is crucial to estimate the rate at which dependent variables grow or decay with the time reaction. The stability analysis becomes important in recycle processes in which possibility that these systems influence themselves exists. The aim of this work deals with the 1) description of the growth kinetics by a logistic and unstructured model based on Monod kinetics taking into account the maintenance in life of viable cells; 2) establishment of a dynamic growth model for Spirulina maxima cultivated in continuous lamellar photobioreactors using industrial manures as macro-nutrients; 3) determination of optimal culture conditions sustaining a stable growth of S. maxima in a system of two bioreactors in series; and 4) investigation of the dynamic stability of this multivariable system with nonlinear dynamics using phase plane technique (PPT). Although good mixing of the culture is essential for ensuring adequate supply of nutrients and prevention of the accumulation of toxic metabolites. Excessive agitation causes mechanical damage to Spirulina cells. An air flow rate of 2.5 L/min for airlift agitation represented a balance between the need to provide good mixing and to avoid cell damage. A stable steady state was achieved corresponding to a productivity of 10.8 g. m2/day when the system was supplied with 0.2 g N/L of minerals, at a dilution rate of 0.1 1/day, temperature of 30 °C under light intensity of 18 Klux. PPT as a powerful procedure successfully predicts the stability of such a complex system very well.
Numerical Study of the Influence of Horizontal Tube Banks on the Hydrodynamics of a Dense Gas-Solid Bubbling Fluidized Bed
Authors: Das Sharma Sanjib K. , Mohan Ratan
Published: October 2005

Numerical study of the influence of tube-bank on the hydrodynamics of a freely bubbling fluidized bed is relatively less reported in the literature. In this paper, results obtained from CFD study of a two dimensional gas-solid fluidized beds with horizontal tube-bank are compared with the published experimental data (Hull et. al., 1999). A 2-D bed, 1 m high and 0.2 m wide with tubes of diameter 0.026 m was taken for the calculations. Two different tube arrangements of staggered and inline pitch with center-to-center distance of 0.05 m were considered. Air was used as the fluidizing medium and ballotini glass (diameter: 230 mm and density: 2723 kg/m3) was the fluidized material. Air velocities used were 0.15 m/s and 0.187 m/s. The Eulerian-Eularian Two-Fluid CFD model was employed for modeling the momentum equations for both the gas and the solid phase with kinetic theory modification for the solid phase to account for the inter-particle interactions. Hydrodynamic features, such as, bubble size and bubble rise velocity and their variation with height within and outside the tube bank showed good agreement with the data of Hull et al.(1999)
Bifunctional Redox Scrubbing of Hydrogen Sulphide in Ferric Chelate Solutions - Reaction-Transport Model for Randomly Packed-Bed Scrubbers for Pulp and Paper Effluents
Authors: Iliuta Ion , Iliuta Maria , Grandjean Bernard , Larachi Faical
Published: October 2005

In recent years gas desulfurization processes based on iron chelate chemistry have received increasing attention from both industrial and academic research groups. Utilization of ferric chelates is beneficial because hydrogen sulfide solubility is higher in these solutions. This paper discusses from a multiphase reactor engineering perspective, the design of a randomly countercurrent packed bed column by setting an exhaustive modeling framework in which are integrated both the oxidation of hydrogen sulfide in reactive ferric chelate solutions of ethylenediaminetetraacetic acid and the regeneration of ferrous chelates resulting from oxidation of hydrogen sulfide. A one-dimensional model based on the volume-average species balance equations in the gas and liquid phases coupled with the diffusion-reaction equations for the reacting species in the liquid film was developed for the description of the space evolution of the species concentration in this important class of environmental reactions. The discretization of the diffusion-reaction equations in the film and the species balance equations in the gas and liquid phases was carried out by the method of orthogonal collocation and Newton-Raphson method was employed to solve the resulting non-linear system equations.
Adsorption Competition Effects in Hydroconversion of Alkane Mixtures on Zeolites
Authors: Denayer Joeri F. , Ocakoglu Ahmet Refik , De Jonckheere Bruno A , Martens Johan A , Thybaut Joris W , Marin Guy B , Baron Gino V
Published: October 2005

In the present work, molecular competition effects in the hydroconversion of alkane mixtures in vapor and liquid phase were studied. The influence of the pore size was investigated by performing catalytic experiments with equimolar heptane/nonane mixtures on a series of bifunctional zeolite catalysts (Pt/H-Y, Pt/H-USY, Pt/H-Beta, Pt/H-MCM-22). Vapor phase catalytic experiments were performed at a total pressure of 4.5 bar, while a total pressure of 100 bar was applied in the liquid phase experiments. The experimental results were analyzed using a lumped adsorption-reaction model. In vapor phase, the longest chain is preferentially converted on all studied catalysts. In liquid phase, the differences in conversion rate were less pronounced. On Pt/H-MCM-22, with active pockets on the surface, and Pt/H-USY having large mesopores, the competition between short and long alkanes in liquid phase reflect the intrinsic reactivities of the reacting molecules. In zeolites with smaller pores (Pt/H-Y, Pt/H-Beta), an inversion of the reactivity order of alkanes of different chain length was observed when increasing the pressure from 4.5 bar and vapor phase to 100 bar and liquid phase. The inversion of apparent reactivity orders is due to changes in physisorption at high pressure, favoring uptake of the smallest molecules.
Nonlinear Bubbling Hydrodynamics in a Gas-Liquid Bubble Column with a Single Nozzle
Authors: Liu Mingyan
Published: October 2005

In this work, the chaotic bubbling mechanism in a gas-liquid bubble column with a single nozzle was investigated. The signal for the analysis was the time series of pressure fluctuations measured from a pressure transducer probe placed in the bubble column close to the nozzle. In order to study the bubbling process, statistical analysis, qualitative and quantitative non-linear analyses were carried out for the pressure fluctuations. Power spectra used as standard statistical measures provided preliminary evidence that bubbling in the middle values of gas flow rates may be chaotic in nature. Phase plots provided a qualitative means of analyzing the fine geometry structure of the attractor reconstructed from the bubbling time signal. Positive finite estimates of the Kolmogorov entropy provided a quantitative evidence of behavior consistent with chaos. Besides previous diagnostic tools, the local non-linear short-term prediction was also used as a supplement method. It was found that the bubbling process exhibits a deterministic chaotic behavior in a certain range of the gas flow rate. When increasing the gas flow rate, the sequence of periodic bubbling, primary and advanced chaotic bubbling, and jetting or random bubbling were successively observed. However, no clear period doubling sequence leading to chaotic behavior was observed. The sharp loss of the ability to predict the pressure signal successfully with the non-linear prediction method provides a strongest evidence of the presence of the chaotic bubbling. The variations of the non-linear invariants, such as the Kolmogorov entropy and the correlation dimension together with the plot of the correlation integral with the operation conditions, might be developed as potential and effective quantitative tools for flow regime identification of the bubbling process.
A Real Time Toxicity Bioassay for Activated Sludge Reactor
Authors: Pernetti Mimma , Di Palma Luca , Merli Carlo
Published: October 2005

Activated sludge reactor is commonly employed for the secondary treatment of industrial wastewater, showing a high purification yield, operating simplicity and cost-effectiveness. Nevertheless, industrial wastewater generally contain numerous organic and inorganic compounds which are not biodegradable; heavy metals are often found in effluents from electroplating and metal-processing industries, manufacturing of paints, plastics, scientific instruments, salts are found in wastewater from production of pesticides, pharmaceutical and food industry, waste-dump percolating water. Primary treatments are often designed to reduce heavy metal and salt contents in wastewater, nevertheless trace concentrations persist and may reach the biological reactor, resulting in biomass inhibition and dramatic loss in purification efficiency. Respirometry through Oxygen Uptake Rate measurement is one of the most rapid and reliable methods to assess the inhibition of activated sludge. In previous studies toxicity tests for specific compounds have been performed following different procedures and attaining heterogeneous results. In this work a simple modification of the configuration is proposed, in order to assess in real time the toxicity and the inhibiting effect of the incoming wastewater before it reaches the reactor. A sample is drawn from the influent and a respirometric test is performed on mixed liquor collected from the reactor itself. If the inhibition exceeds the limit, the influent is sent to storage and to an alternative treatment. Preliminary experiments were carried out with bench-scale CSTR, supplied with synthetic wastewater. Copper sulphate and sodium chloride were chosen as inhibiting compounds, supplied separately to batch samples of activated sludge in shock load at different concentrations. Copper concentration in the mixed liquor was measured by atomic absorption and salt concentration was determined through conductance measures. Inhibition up to 90% was evaluated by OUR test with short response time, demonstrating the suitability of this tool to a real time toxicity bioassay for activated sludge reactor.
2D and 3D CFD Simulations of Bubbling Fluidized Beds Using Eulerian-Eulerian Models
Authors: Cammarata Luca , Lettieri Paola , Micale Giorgio D. M. , Colman Derek
Published: October 2005

This paper reports on CFD simulations of freely bubbling gas fluidized beds using CFX-4, a commercial code developed by CFX Ltd. (formerly AEA Technology). Two Eulerian-Eulerian modelling approaches, the granular kinetic model and the particle-bed model (Gibilaro, 2001), have been investigated. The particle bed model has been recently implemented in CFX-4 for 2D simulations and a numerical procedure was developed to allow for a tight control of the fluid-bed voidage at maximum packing during the simulations, see Lettieri et al. (2003). The work has now been extended to 3D simulations and qualitative and quantitative results are presented in this paper for both the 2D and 3D simulations of the bubbling fluidization of a Geldart Group B material. Results on bed expansion, bubble size and bubble hold-up are reported. In particular, simulated bubble size is compared with predictions given by the Darton et al. (1977) equation at different bed heights. The paper shows that the bubble size predicted by both the granular kinetic model and the particle-bed model is in good agreement with the Darton's equation.
Theoretical Analysis of Fluidized-Bed Reactor for Dimethyl Ether Synthesis from Syngas
Authors: Lu Wen-Zhi , Teng Li-Hua , Xiao Wen-De
Published: October 2005

Dimethyl ether (DME) is regarded as an environmentally benign fuel for vehicles. Two kinds of reactor technologies for DME synthesis have been proposed by previous researchers: the fixed-bed and the slurry reactor. As the reactions are highly exothermic and the temperature window of the catalyst is very narrow, the fixed-bed reactor provides a limited heat removal capability and a low conversion of the syngas. The slurry reactor can provide an effective temperature control but a very high inter-phase mass transfer resistance is added by the liquid medium. The Fluidized bed reactor can be an ideal reactor for DME synthesis as it possesses both high heat and mass transfer efficiencies. In this paper, a two-phase model is used to theoretically analyze the DME synthesis in a fluidized bed reactor, with both phases assumed to be in plug flow and taking into account the changes in bubble diameter resulting from the reaction. Three reactions take place simultaneously when DME is manufactured from the syngas (H2 + CO): a) CO+2H2 = CH3OH; b) 2CH3OH = DME+H2O; and c) CO+H2O = CO2+H2. The simulation shows that, at the reactor outlet, the equilibrium approaches of the three reactions are 0.32, 0.1, and 0.61, respectively. When H2/CO=1.0, the CO conversion and DME selectivity in a fluidized bed reactor are 62% and 95%, while those in a fixed-bed reactor are 9% and 86%. In a slurry reactor, the CO conversion and DME selectivity are 17% and 70%, respectively. Therefore, the fluidized-bed is the most promising candidate reactor for conducting the DME synthesis from syngas. Effects of the operating conditions on the performance of DME synthesis in the fluidized-bed reactor are discussed in details. The optimal H2/CO ratio is between 1.0-1.5, and increasing the pressure is shown to improve the reactor performance.
Catalytic Drying of Digested Sludge
Authors: Chaouki Jamal
Published: October 2005

Recently, we patented an efficient process for the drying of digested sludge with zero liquid emission. The main components of this drying system are a conical spouted bed dryer and a natural gas combustion chamber that burns the Volatile Organic Compounds (VOC) in the drying gases. The proposed integrated spouted bed drying process is simple and safe. It is also robust and easy to maintain since there is no moving mechanical part in the set-up. Although the system is quite thermally efficient, the operating and the investment costs are still relatively high. In order to avoid the combustion chamber and its accessories operating at high temperature and to reduce the energy consumption, a catalytic fluidized bed dryer may replace these units. It is proposed, then, to produce in situ the energy for the drying by catalytic oxidation of hydrocarbons and to destroy catalytically the VOCs generated by the drying. The purpose of this paper is to show the feasibility of this new process, called the catalytic drying of digested sludge. Based on the experimental work, advantages and limitations of this process are also discussed.
Towards Improved Reaction Runaway Assessment Methods I. Simple Calorimetric Method Of Evaluation Of Heat Transfer Coefficient And Reactor Thermal Mass
Authors: Papadaki Maria , Nawada Hosadu Parameswara
Published: October 2005

The use of reaction calorimetry in the chemical industry is constantly growing. Its use aims at the assessment and subsequent reductions of the risks arising from reaction thermal runaways in the event of cooling system malfunction or agitation failure and at optimum process design.A reaction calorimeter is a small-scale automated jacketed reactor equipped with a precise temperature controller, which is capable of heat balancing. The reactor contents may be heated or cooled by heat-transfer oil and they are continuously agitated. A powerful thermostatic bath allows rapid adjustment of jacket temperature to maintain the desired reactor temperature-profile. The reactor and jacket temperatures as well as a number of other quantities are continuously measured. A heat balance, based on a number of assumptions, is used for the evaluation of the heat of reaction and its global kinetics. The evaluation of the overall heat transfer coefficient and the accumulated heat are achieved by means of calibrations. Their measurement is, in the main, long. Also it is very often lacking sufficient accuracy.In the present approach, a simple method for the accurate evaluation of the overall heat transfer coefficient is presented. It is also shown how the analysis of the heat-balance equations in different stages can be used for the simultaneous evaluation of a number of quantities and constants of the reaction calorimeter using a single set of calibration experiments.
Tertiary Butyl Mercaptan Adsorption in Soils. Determination of Kinetic and Transport Parameters from Experimental Data
Authors: Eberhardt Andrea , Lopez Eduardo , Bucalá Verónica , Damiani Daniel E
Published: October 2005

The present paper addresses the importance of the adsorptive properties of argentinean soils in the odor fade odor problem that is faced in the presence of odorized natural gas leakages. Samples of soils were subjected to stimulus-response experiments in which the soils were exposed to a step change in odorant concentration. A typical S shaped breakhrough curve was obtained at the soil bed exit. The adsorption characteristics of each soil is associated to its composition. The results confirm that clay based soils adsorb the gas odorant (tert butyl mercaptan) more strongly than sand based soils or soils with high organic carbon content. The adsorption process was modeled. The model takes into account the following mass-transfer processes: plug flow of TBM along the solid bed, external resistances to the mass transfer, diffusion within the particle and adsorption/desorption of TBM between the gas phase of the intraparticle pore space and the particle surface. The model reproduces quite well the experimental data. The results suggest that the odorant adsorption process is controlled by the mass transfer steps.
Disinfecting E.coli Bacteria In Drinking Water Using A Novel Fluidized Bed Reactor.
Authors: Kabir Mohammad F , Haque Farzana , Vaisman Elena , Langford Cooper H. , Kantzas Apostolos
Published: October 2005

Disinfecting microorganisms such as E.coli is a great concern in drinking water supply facilities around the world. Photocatalysis became an attractive technology to disinfect microorganisms due to its ability to degrade very low concentration of microorganisms without producing any harmful by-products. The use of optical fibre mesh reactors and slurry type photocatalytic reactors has been investigated by researchers around the world. It was shown that such reactors have low potential to be scaled up. An annular type fluidized bed reactor has been constructed and tested to disinfect E.coli bacteria. A specially prepared catalyst (TiO2 + Glass Bead + Zeolite) was used for this purpose. The proposed catalyst offered better degradation of E.coli compared to existing technology. Fluidization enhances the degradation of E-coli by moving the catalyst particles to the illuminated zone. E.coli degradation is tested in a similar arrangement in small scale with 100cm3 of contaminated water with the 106 E-coli/cm3. Repeated experiments were done with/without the presence of catalyst along with UV irradiation. With the presence of catalyst in the fluidized condition, the E-coli count is reduced to only 100/cm3 whereas the E-coli count after 30 minutes of UV irradiation only became 1800/cm3. The efficiency of E.coli removal is increased to 99.99% from 99.82% by using the proposed technology. Results of small scale prompted a construction of a pilot plant scale reactor and effectiveness of this reactor is being tested. Use of supported catalyst and the effective illumination of catalyst by fluidization help faster disinfection of microorganisms by this reactor. It has been found that the pilot scale is capable of degrading 84% of E.coli within 80minutes compared with 77.3% by using UV only which has capacity of handling 46 litre/min. E.coli degradation in larger scale is being tested for the first time and its result compared with only UV destruction is promising. The potential to use this method on a continuous reactor increases the potential for scale up.
Analysis of the Microscopic Flow Structure of a CFB Downer Reactor Using Solids Concentration Signals
Authors: Manyele Samwel V , Zhu Jesse , Zhang Hui
Published: October 2005

The microflow structure in a downer reactor was studied by measuring the solids concentration fluctuations at various elevations and radial positions, using an optical fiber probe, at a sampling rate of 970 Hz. The downer reactor (0.1 m i.d. and 10 m high) was operated at gas velocities ranging from 3.5 to 10.0 m/s and solids flux from 50 to 200 kg/m2s, with spent FCC catalyst of Sauter mean diameter of 67 mm and density of 1500 kg/m3. The analysis of solids concentration time series was performed using statistical, spectral and chaos techniques. Results from these analyses were compared and related to the operating conditions (gas velocity and solids circulation rate) as well as to the spatial locations (radial and axial positions) in the downer reactor. Different techniques of time series analysis gave similar results but with different sensitivity to changes in the dynamics. A combination of the three signal analysis techniques proved to be more useful in providing more insight understanding of the microflow structure.
Nonlinear Dynamic Analysis of the Local Heat Transfer Rate in Three-Phase Reactors
Authors: Chen Wei , Tsutsumi Atsushi , Shigaki Yoshiki , Otawara Kentaro
Published: October 2005

In this present work, nonlinear dynamic analysis was performed to the fluctuation signals of the local heat transfer rate measured in three-phase reactors of different scales to characterize the dynamics of three-phase reactors. The results of nonlinear test with surrogate data give evidence of nonlinear determinism in heat transfer rates series. The chaotic nature of the local heat transfer rate was further characterized in terms of the correlation dimension and Kolmogorov entropy. It was found that the correlation dimensions were in the range between 2.0 and 4.0 and Kolmogorov entropies were varied with the change of measurement positions and the operating conditions. With the increase of column scale or the addition of solids, Kolmogorov entropies decrease significantly. The dependence of chaotic parameters on the column scale is considered to be closely related to the different macroscopic flow structures observed in three-phase reactors of different scales.
Digital X-ray Imaging Technique to Study the Horizontal Injection of Gas-Liquid Jets into Fluidized Beds
Authors: Ariyapadi Siva , Holdsworth David W. , Norley Chris J.D. , Berruti Franco , Briens Cedric
Published: October 2005

Gas-liquid jets injected into fluidized beds of particles/catalyst find applications in many industrial processes. The effective distribution and mixing of the feed droplets with the entrained bed particles is vital in improving the process efficiency. The present study utilizes a sophisticated digital X-ray imaging system to study the internal flow structure of jets injected into fluidized beds. The system is equipped with an X-ray image intensifier (XRII) and optical detectors, which convert the transmitted X-ray photons into digital images of up to 60 frames s-1. The imaging technique provides useful information such as the jet expansion angle and the penetration distance. These are functional quantities in optimizing the performance of feed nozzles, and in modeling the jet-fluidized bed interactions.In this work, the horizontal injection of gas, gas-liquid, and liquid jets into fluidized beds is investigated. The results indicate that the jet expansion (half-angle) is considerably reduced for a gas-liquid jet (5-7 degrees) when compared to that of a gas jet (10-15 degrees). The gas-liquid jet also appears to penetrate more than a gas jet with the same momentum. When a liquid feed is introduced into a fluidized bed of particles, the particles may agglomerate if they are wet-enough to form liquid bridges. Improper feed distribution may be a direct contributor to enhanced agglomeration. In this regard, radio-opaque tracers mixed with the feed liquid are injected to track the formation and the movement of agglomerates. The tracer experiments show that the agglomerates are generated at the end of the jet region, close to its maximum penetration distance. A brief discussion on the modifications required to achieve improved contrast for the acquired images, and the effect of some important X-ray parameters are also included in the present study.
Optimal Catalyst Distribution in Catalytic Plate Reactors
Authors: Baratti Roberto , Tronci Stefania , Zanfir Monica , Gavriilidis Asterios
Published: October 2005

Steam reforming of methane taking place in a Catalytic Plate Reactor (CPR) having as heat source catalytic methane combustion is studied. The CPR thermal behaviour is maintained in an operating range that provides maximum conversions and at the same time is not detrimental to the catalyst. A non-uniform catalyst distribution on either channel, provides a degree of flexibility to control the reactor thermal behaviour. Optimisation is employed in order to obtain optimal non-uniform catalyst distribution having as objective the minimisation of the difference between the temperature along the reactor and its inlet value. In this way, the reactor operates close to isothermal conditions avoiding formation of hot or cold spots and high conversions are achieved. Two types of catalyst distributions are presented. First, a non-uniform distribution along the catalytic plate which can maintain the temperature along the reactor within +/- 2.5 K from the inlet value. A two-step catalyst distribution, which can be easier to implement in practice, is further considered. This type of catalyst distribution maintains the reactor temperature in a wider range, +/-19 K if it is used in the endothermic channel, and +/-38 K if it is used in the exothermic one.