bluuebunny/crossref_metadata_2025_split huggingface dataset:
Biological purification of exhaust air containing toluene vapor in a filter‐bed reactor
Authors: Bibeau L , Heltz M. , Kiared K. , Leroux A. , Brzezinski R. , Viel G. 
Published: March 2009

AbstractExperiments during a period of 93 days are reported on the treatment of waste air containing toluene vapor using a laboratory scale biofilter system packed with peat inoculated with specific florae (Pseudomonas type) and intermittently humidified with a nutrient solution necessary for the survival of the micro‐organisms. Design and operation parameters were regularly measured in order to check the performance of the biodegradation process.Under pseudo‐steady state conditions, a maximum elimination capacity of 70 g/m3.h was obtained for an inlet load of 190 g/m3.h. Elimination capacity data obtained agreed well with the predictions of two recognized zero order kinetic models. Also, the biofilm thickness as predicted from the Ottengraf and van den Oever model (1983) was around lmm.
A simple method of estimating surface reaction rates by moment analysis of tap reactor pulse experiments; application to benzene hydrogenation
Authors: Lafyatis David S. , Creten Glenn , Dewaele Olivier , Froment Gilbert F. 
Published: March 2009

AbstractA method of estimating the lifetime of surface reaction intermediates by moment analysis of TAP reactor pulse response curves has been developed. The average surface lifetime of the adsorbed reaction intermediate in the hydrogenation of benzene to cyclohexane over Pt/SiO2 at 140°C and 92 kPa of hydrogen is 38 ± 4 ms, as measured by a TAP pulse experiment. The steady‐state turnover frequency for this reaction under the same conditions is 1.0 ± 0.2 s−l. This implies that the surface coverage of Pt by benzene is low under the steady‐state conditions.
Evaluation of a novel self‐aerating, oscillating baffle column
Authors: Mackley M. R. , Stonestreet P. , Thurston N. C. , Wiseman J. S. 
Published: March 2009

AbstractWe describe the operation of a pilot scale oscillating baffle column using a self‐aeration system for oxygenation of water. The top baffle has a high constriction ratio and is sufficiently near to the surface of the water such that gas bubbles are generated. This aeration plate is coupled with a series of equally spaced low constriction orifice baffles, which lead to uniform dispersion of entrained air bubbles throughout the liquid volume. Flow visualisation experiments using video and still photography were used to identify two mechanisms for bubble generation: bubble formation under the water surface by surface vortex suction, and bubble generation from the collapse of a surface fountain and subsequent entrainment of bubbles into the bulk. Mass transfer measurements have shown that under most conditions a uniform oxygen concentration could be obtained throughout the column as a result of efficient mixing, and that the sole limitation to mass transfer performance was determined by the aeration mechanism. Initial comparison on the basis of aeration efficiency with other devices reveals a modest oxygen transfer rate, but with low specific power consumption of order 0.3 kW/m3.
Numerical flow simulation of viscoplastic fluids in annuli
Authors: Meuric Olivier F. J. , Wakeman Richard J. , Chiu Tak W. , Fisher Kenneth A. 
Published: March 2009

AbstractThis paper describes numerical solutions for the laminar flow of non‐Newtonian fluids in vertical annuli using the Herschel‐Bulkley model to describe the rheological behaviour of such materials. Numerical solutions have been obtained when there is both axial and tangential flows in either a concentric or eccentric annulus. The tangential flow arises from the rotation of the inner cylinder of the annulus and the axial flow from a constant axial pressure gradient. The flow is analysed by solving the momentum and continuity equation numerically using the finite element method. The dimensionless velocity, deformation and stress profiles with other quantities such as the apparent viscosity and pressure distribution have been calculated for various eccentricities, radius ratios, fluid properties and flow parameters; the results give insights into the flow behaviour in the annuli. It is shown that the inclusion of rotational effects, for a fixed pressure gradient, is likely to increase the axial volumetric flowrate over non‐rotating situations in concentric geometries. New results reveal that, in eccentric annuli, the situation is reversed and the flowrate gradually decreases as the rotation rate is increased.
A stochastic model for the simulation of the natural flow in random packed columns
Authors: Song M. , Yin F. H. , Chuang K. T. , Nandakumar K. 
Published: March 2009

AbstractA stochastic model has been developed to simulate the “natural flow” and the spatial evolution of flow patterns in the downstream direction in randomly packed beds. The natural flow is defined as the tendency of liquids flowing down a packed bed to redistribute radially in a natural fashion. A column of 0.5 m diameter with 25 mm Pall rings is selected to test the model. The simulation results of flow distributions are in good agreement with available experimental data from the literature. Unlike the existing models, our approach can simulate liquid flow distributions for different realizations of random packings.
Investigation of the mean and turbulent particle velocity fields in a spouted bed using radioactive particle tracking
Authors: Djeridane Toufik , Larachi Faïçal , Roy David , Chaovki Jamal , Legros Robert 
Published: March 2009

AbstractA non invasive experimental Radioactive Particle Tracking method (R.P.T.) was used to determine the three‐dimensional mean and turbulent particle velocity fields in a spouted bed. The local statistical properties were evaluated with approximately one million data obtained on typically 6 hours of particle tracking. Radial profiles of first and second order moments of the particle velocity field are presented in the spout, the annulus and the fountain region on several axial sections. In addition to the complete description of the solids mean flow pattern, the relevance of a strong anisotropy behavior for particle turbulence field was well established. Thus, this study constitutes an original experimental investigation needed both for a better physical understanding and refined flow modelling of gas‐solid flows in spouted beds.
Quantification of laminar mixing in the kenics static mixer: An experimental study
Authors: Jaffer Shaffiq A. , Wood Philip E. 
Published: March 2009

AbstractThe laminar flow field in a Kenics KM static mixer has been studied using laser induced fluorescence and digital image analysis. Mixing was quantified by measurement of the number average striation thickness, variance of striation widths and interfacial area, for elements of length to diameter (L/D) ratios of 0.8, 1.0, 1.5 with 90° twist per element. From flow visualisations, transitions were observed in the flow where vortices developed above the first and second elements at Reynolds numbers of 43 and 90 for L/D = 0.8 and Reynolds numbers of 55 and 105 for L/D = 1.0. It was found that these vortices did not appreciably enhance mixing based on striation thickness and variance of striation widths measurements after 4 to 5 elements. The influence of viscosity ratio showed a viscosity ratio (dyed stream/bulk stream) of I had faster interfacial area growth and created more uniform mixtures compared to a viscosity ratio of 0.2 for flow rate ratio of 0.2.
Determination of the mixing performance of sulzer SMV static mixers by laser induced fluorescence
Authors: Karoui Asma , Hakenholz Frédéric , Le Sauze Nathalie , Costes Jean , Bertrand Joël 
Published: March 2009

AbstractLocal concentrations are measured at the outlet of different configurations of Sulzer SMV static mixers placed in a tube. Laser Induced Fluorescence is the non intrusive technique used to measure mean and RMS concentrations. The two fluids mixed are miscible and the flow regime is turbulent. The influence of the number of elements, their position and the ratio between the velocities of the two compounds on the mixing is studied. The results show that these parameters are important for the quality of mixing. The velocity ratio influences the radial mixing, while the mixing length depends on the number and position of the elements.
Natural convection in a porous medium at high rayleigh numbers — application of prandtl's analogy
Authors: Rao Vedula Dharma , Naidu Sureddy V. , Sarma Pullela K. 
Published: March 2009

AbstractThe problem of natural convection heat transfer from an isothermal vertical cylinder to a saturated porous medium is solved by the integral method making use of one‐seventh profiles for velocity and temperature variation in the boundary layer. Prandtl's analogy is used to obtain the wall heat transfer coefficients. The results obtained for Rayleigh numbers greater than 109 and Prandtl numbers 4 and 0.12 are compared with experimental data from literature show satisfactory agreement. Also an approximate closed form solution is presented for the case of a flat wall to predict local Nusselt numbers.
Selective kinetic deactivation model for methanol synthesis from simultaneous reaction of CO2 and CO with H2 on a commercial copper/zinc oxide catalyst
Authors: Rahimpour Mohammad Reza , Fathikalajahi Jamshid , Jahanmiri Abdolhosein 
Published: March 2009

AbstractA kinetic model for the deactivation of copper/zinc oxide catalyst during the methanol synthesis has been developed. This model is of the Langmuir‐Hinshelwood‐Hougen‐Watson type and considers two types of active sites for the deactivation of catalyst. One of the site types on copper is allocated for the deactivation of the catalyst due to carbon dioxide while another type is assigned for the deactivation of the catalyst due to carbon monoxide. The parameters of the deactivation rate equations based on the above concept have been determined using the experimental data of Hoffmann (1993). The validity of the deactivation model has been checked by comparing the results predicted by the model with experimental data different than of those used to evaluate the parameters of the model. The good agreement that noticed in this comparison confirmed the idea that CO and CO2 are responsible at different extent for the deactivation of Cu/ZnO catalyst during methanol synthesis.
A method of evaluating limestone reactivity with SO2 under fluidized bed combustion conditions
Authors: Mattisson Tobias , Lyngfelt Anders 
Published: March 2009

AbstractThe reactivity of limestone with sulphur dioxide has been evaluated during conditions similar to those existing in a fluidized bed combustor using a fixed‐bed quartz reactor. The reactivity of up to 11 particle sizes of 2 limestones were evaluated, and an exponential decay function was found to best describe the rate behaviour versus conversion of CaO to CaSO4. The two constants in the exponential decay approximation could both be expressed as functions of particle size. Subsequently, the limestone reactivity as a function of both size and conversion could be reasonably well described by a total of 4 to 6 constants. An analytical sulphur capture model for fluidized bed boilers (FBB) that incorporates this type of reactivity function is proposed.
Faradaic processes on activated carbon particles: Example of sulfite anodic oxidation
Authors: Balduf Torsten , Valentin GÉRard , Lapicqve François 
Published: March 2009

AbstractActivated carbon has often been reported as a suitable material for numerous applications e.g. energy storage, batteries and pollution control, due its high adsorption capacity allowed by its high surface area. Besides, activated carbon can also be used for the chemical transformation of matter through faradaic processes. This paper deals with the performance of activated carbon (AC) particles as an electrode material for the anodic oxidation of sulfite and bisulfite species into sulfate. The oxidation was carried out at the surface of a packed‐bed of AC particles (volume 170 cm3); the main operating conditions, namely potential and solution pH were varied. The sulfate production was shown to be controlled by the electrode kinetics and the internal transfer in the carbon pores. Interactions between the capacitive phenomena, occurring in the electrical pretreatment, and the faradaic processes were discussed.
Batch reactor control using a multiple model‐based controller design
Authors: Krishnan Arun , Kosanovich Karlene A. 
Published: March 2009

AbstractThis work presents the development of a model‐based controller design called Multiple Model Predictive Control (MMPC) based on a set of linear, time‐varying, state space models to regulate batch processes according to multiple, pre‐specified reference profiles. Sufficient conditions for stability and boundedness of the dynamic evolution of the forced nonlinear system are provided. The performance of the MMPC design is demonstrated on a model of a batch reactor that represents the production of a polymer product.
Kinetics and reaction mechanism of catalytic oxidation of low concentrations of hydrogen sulfide in natural gas over activated carbon
Authors: Dalai Ajay K. , Tollefson Eric L. 
Published: March 2009

AbstractThe kinetics of the hydrogen sulfide oxidation process, producing mostly sulfur and water, was studied using 0.25 to 1.0 g Hydrodarco activated carbon catalyst and varying the O2/H2S ratio (molar basis) in the feed gas between 0.5 to 0.6 in the temperature, and pressure ranges from 125 to 200°C and 225 to 780 kPa. SO2 was obtained as an undesirable by‐product during H2S oxidation reaction or as a product during regeneration of the catalyst. The feed gas contained 0.9 — 1.3 mol% H2S with approximately 80 mol% CH4. In this paper, the factors affecting the H2S conversion and SO2 formation are presented. The rate expressions for (a) H2S conversion and (b) SO2 formation were developed from the Langmuir‐Hinshelwood surface control reaction model. The experimental data were well correlated by the rate equations. Also, the rate parameters were evaluated and correlated with temperature. The activation energies for H2S oxidation and SO2 production reactions were calculated to be 34.2 and 62.5 kJ/mol, respectively. Partial pressures of oxygen and H2S were found to influence H2S conversion whereas, the presence of water in the feed gas up to 10.5 mol% did not affect H2S conversion significantly. Heats of adsorption for various species on the active sites were calculated. SO2 production was, as expected, enhanced at higher temperature, and its rate was much smaller than the oxidation rate of H2S under the reaction conditions used.
Fabrication of amperometric biosensors by entrapment of enzymes in functionalized polypyrrole films
Authors: Cosnier Serge 
Published: March 2009

AbstractThe concept and potentialities of an original electrochemical procedure of enzyme immobilization are described. This two‐step method consists of the adsorption of an aqueous amphiphilic pyrrole monomer‐enzyme mixture on an electrode surface followed by the electropolymerization of the adsorbed monomers. This procedure is compared with the conventional electrochemical methods of biosensor construction. Several bienzyme electrodes devoted to the improvement of the biosensor selectivity or to the amplification of the biosensor sensitivity are described. In addition, examples of organic phase enzyme electrode and the electrical wiring of immobilized enzymes are presented.
The efficiency of short airlift pumps operating at low submergence ratios
Authors: Lawniczak Fabrice , Francois Pierre , Scrivener Olivier , Kastrinakis Eleftherios G. , Nychas Stavros G. 
Published: March 2009

AbstractAn airlift pump operating at submergence ratios between 0.2 and 0.6 and using water as the pumping liquid, has been investigated. Circular pipes of constant short length of 1 m and inner diameters of 3 and 5 cm were used as riser tubes. The water flow rate measurements for various air flow rates allowed the study of the pumping efficiency as a function of the air flow rate, submergence ratio and certain geometrical parameters (riser tube diameter and injector design). The efficiency curves start from a zero efficiency at a minimum air flow rate, then increase rapidly with the air flow rate up to an efficiency maximum. For higher air flow rates, the efficiency decreases exponentially. Diagrams showing the influence of the riser tube diameter and injector design, are presented. Additionally, based on the experimental data, two equations are presented, which allow the prediction of the maximum efficiency and the corresponding water and air flow rates inside the experimental range.
The influence of particle size and density on the radial gas mixing in the dilute region of the circulating fluidized bed
Authors: Mastellone Maria Laura , Arena Umberto 
Published: March 2009

AbstractA cold model of a CFB, having a 0.120m ID, 5.75m high riser, was operated at a superficial gas velocity of 6m/s and at average solids mass fluxes varying in the range between 16 and 55kg/sm2. A stream of carbon dioxide was injected continuously at a fixed position along the riser axis and used as tracer gas. Three solids, belonging to groups A and B of Geldart's classification, were selected in order to investigate separately, the effect of particle size and density on the radial mixing of the gas phase. The intensity of radial gas dispersion reduced when larger or heavier particles were used. The differences in the values of radial dispersion coefficient and Peclet number were explained, taking into account the role of the particle size with respect to the scale of gas turbulence.
Chaotic characteristics of local voidage fluctuation in a circulating fluidized bed
Authors: Ohara Hiroaki , Ji Hongshen , Kuramoto Koji , Tsutsumi Atsushi , Yoshida Kunio , Hirama Toshimasa 
Published: March 2009

AbstractLocal voidage fluctuations have been measured by using an optical transmittance probe at various axial and radial positions in a circulating fluidized bed riser with a 0.1 m i. d. and 10 m height. The chaotic time series analysis of the local voidage fluctuations has been adopted to characterize the nonlinear dynamics of the circulating fluidized bed riser. The variations of the correlation dimension and the Kolmogorov entropy of the voidage fluctuation were found to depend on the local time‐average voidage. The axial and radial distributions of the correlation dimension and the Kolmogorov entropy were strongly affected by the solids flow structures (e.g. core‐annulus flow) in various operating conditions. The correlation dimension of local voidage fluctuations increases along the riser, except the position near the distributor. Both, the correlation dimension and the Kolmogorov entropy of local voidage fluctuations near the wall, were found to be smaller than those at the center of the riser, independent of the solids circulation rate and the axial position.
Kinetics and mechanism of the reaction between ozone and hydrogen peroxide in aqueous solutions
Authors: Kuo Chiang‐Hai , Zhong Li , Zappi Mark E. , Hong Andrew P. 
Published: March 2009

AbstractA kinetic model has been developed, taking into account both decomposition of ozone molecules and interactions between ozone and hydrogen peroxide for formation of hydroxyl radical and subsequent reactions. Experiments were carried out at 25°C in the pH range of 3 to 13, indicating that the depletion rate of ozone increases with the concentrations of ozone, hydrogen peroxide and hydroxyl ion, as predicted by the kinetic model. Adverse scavenging reactions, however, also play significant roles at sufficient concentration ratios of hydrogen peroxide to ozone and high concentrations of hydroxyl ion in reducing the depletion rate. Results of this research suggest, that it is most desirable to conduct the peroxone oxidation for pollutant destruction by the hydroxyl radical reaction in alkaline solutions of pH below 11, while maintaining about the same concentration of ozone and hydrogen peroxide.
Assessing the precision of model predictions and other functions of model parameters
Authors: Quinn Shannon L. , Bacon David W. , Harris Thomas J. 
Published: March 2009

AbstractModels fitted to data are used extensively in chemical engineering for a variety of purposes, including simulation, design and control. In any of these contexts it is important to assess the uncertainties in the estimated parameters and in any functions of these parameters, including predictions from the fitted model. Profiling is a likelihood ratio approach to estimating uncertainties in parameters and functions of parameters. A comparison is made between the optimization and reparameterization approaches to determining likelihood intervals for functions of parameters. The merits and limitations of generalized profiling are discussed in relation to the linearization approach commonly used in engineering. The benefits of generalized profiling are illustrated with two examples. A geometric interpretation of profiling is used to elucidate its value, and cases are identified for which the numerical algorithm fails. An alternative approach is suggested for these cases.
Effect of the grid‐velocity on attrition in gas fluidized beds
Authors: Wu Shu‐Yii , Baeyens Jan , Chu Chen‐Yeon 
Published: March 2009

AbstractChanges in particle size distribution play an important role in fluidized bed processes, and these changes are dominated by elutriation and carryover of fines and by attrition or agglomeration. In this study on attrition in gas‐fluidized beds, we found that the attrition is a function of the particle size distribution, the jet velocities and the overall superficial gas velocity. Empirical equations have been developed to predict the attrition rate.
On the scaling‐up of a two‐stage air blown entrained flow coal gasifier
Authors: Chen Caixia , Miyoshi Takahiro , Kamiya Hidehiro , Horio Masayuki , Kojima Toshinori 
Published: March 2009

AbstractA two‐stage air blown entrained flow gasifier is being developed in Japan for the IGCC process. However, its scale‐up up faces significant difficulties because of ash/slag deposition problems. The ash/slag deposition in the gasifier depends on both the ash properties and entrainment produced by the swirling gas flow. Therefore, the flow hydrodynamics are critical issues for the control of the ash behavior. In this paper, a comprehensive simulation model is used to examine the effects of the gasifier geometry and jet configuration on the flow hydrodynamics in order to control the ash deposition on the gasifier walls. A swirl number for the multi‐stage injection swirling gas flow is defined and proved to be the most important hydrodynamic scaling law for the entrained flow gasifier.
Experimental study on the simultaneous adsorption of carbon dioxide and moisture from nitrogen in linde 5 a molecular sieves
Authors: Ghosal Aloke K. , Samanta Amar N. , Maiti Binoy R. 
Published: March 2009

AbstractExperimental data for the simultaneous adsorption of CO2 and moisture with variations of some process variables, such as inlet adsorbate concentration, particle Reynolds number, and bed diameter to bed length ratio, have been generated to see their effects on the efficiency of adsorption of CO2 and moisture. Presence of moisture strongly affects the CO2 adsorption behaviour leading to roll up of CO2 concentration breakthrough curves, whereas the presence of CO2 has an insignificant effect on the moisture adsorption behaviour.
An explicit approximation for the wetted angle in two‐Phase stratified pipe flow
Authors: Biberg Dag 
Published: March 2009

AbstractIn two‐phase stratified pipe flow the wetted angle relates the flow geometry to the holdup. The relation linking the holdup to the wetted angle does not, however, have a simple explicit solution and is therefore often solved numerically. This analysis yields simple explicit approximations for the wetted angle for a given holdup, which constitute a convenient alternative to a numerical solution.