bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dispersion models of unsteady tubular reactors
Authors: Subramanian R. Shankar , Gill William N. , Marra Richard A. 
Published: March 2009

AbstractAxial dispersion in time‐variable laminar flow in a tubular reactor is analyzed using an exact procedure for the case of a homogenous first‐order reaction. For the first time since the Taylor Dispersion model was originally introduced for the modeling of reactors, its validity is examined over a wide range of the reaction rate parameter by comparison against an exact analysis. It is shown that a constant coefficient dispersion model can be obtained from first principles for large values of time only for initial distribution problems; however, this simple approximate model also is reasonably good for describing concentration distributions for the present inlet distribution problem for slow reactions and for axial locations sufficiently far away from the inlet. For rapid reactions, while the dispersion model is inaccurate in describing axial concentration distributions, it is surprisingly good for predicting the reactor length required for complete conversion. In contrast to the conclusion of a recent article, it will be shown that the dispersion coefficient is independent of the reaction rate constant.
Mass transfer accompanied by parallel reversible chemical reactions
Authors: Li K. Y. , Kuo C. H. , Weeks J. L. 
Published: March 2009

AbstractTheoretical effects of parallel reversible chemical reactions on the rate of mass transfer are investigated in this paper. On the basis of the film theory, an analytical equation has been derived for gas absorption accompanied by first‐order parallel rversible reactions. Analytical approximate equations have been developed and finite difference techniques applied to study the enhancement of mass transfer by second‐order complex reactions. Results of this study indicate that when the diffusion is accompanied by second‐order parallel reactions, the mass transfer rate increases with the concentration of the liquid reactant in the bulk, and approaches that of diffusion and first‐order parallel reactions if the product of the diffusivity and bulk concentration of the liquid reactant is much larger than that of the gas reactant.
An experimental investigation into uncatalyzed oxidation of toluene and pseudocumene by sulfur dioxide
Authors: Akhtar W. , Mellanby E. E. , Mathur G. P. 
Published: March 2009

AbstractThe uncatalyzed oxidation of toluene and pseudocumene by sulfur dioxide has been studied at pressures ranging from 200 to 300 atm; and at tempratures from 250 to 350°C. It was found that under these conditions, toluene is readily oxidized and that the main oxidation product is benzoic acid. Pseudocumene, however, oxidizes to mono‐ and di‐carboxylic acids rather than to trimellitic acid. Power law rate equations are proposed for the two oxidations. Activation energy for toluene oxidation is estimated to be 47.6 Kcal/gm. mole while for pseudocumene oxidation the value is 71.2 Kcal/gm. mole.
Modèle statistique généralisé pour la représentation de la distribution des temps de séjour à l'aide de la loi normale de laplace‐gauss
Authors: Pollet J.‐M. , Cholette A. 
Published: March 2009

AbstractLe modèle statistique à deux paramètres pour l'approximation au moyen de la loi normale Laplace‐Gauss en θ1/3 des distributions des temps de séjour dans les réservoirs mélangés, présente certaines imperfections surtout dans des conditions de mélange éloignées de l'idéalité.On améliore la qualité de la représentation en introduisant un troisième paramètre c, l'exposant de θ, donnant lieu à la linéarisation de la distribution des temps de séjour dans un diagramme normal.Les paramètres sont déterminés à l'aide de l'ordinateur et des points expérimentaux. Leur connaissance permet le calcul des moments de la distribution des temps de séjour et la détermination de la courbe dérivée ou distribution non cumulative.Le modèle généralisé s'applique également dans le cas d'une série de réservoirs agités ou pour des écoulements tubulaires.
Hydrogen concentration profiles and velocity distributions in a reducing argon‐hydrogen plasma
Authors: Meubus Paul 
Published: March 2009

AbstractThe purpose of this study is to establish a spectroscopic diagnostic of an argon‐hydrogen reducing plasma, the hydrogen being injected into the initially formed argon plasma. From calculations using the spectral line intensities measured for H(α), H(β) as well as argon lines 4,259Å and 6,965Å, information is obtained on thermal equilibrium attainment after hydrogen injection. Also, hydrogen concentration profiles are calculated, from which hydrogen counterdiffusion zones are defined allowing the use of simplified diffusion equations, so that velocity profile distributions are obtained. The hydrogen concentration profiles clearly show the mixing pattern taking place around the injection ports, while the temperature profiles for hydrogen and argon evolve toward common limiting values attained when thermal equilibrium between both gas species is accomplished. Calculations show that the error should be of the order of 20% on velocities and 15% for the concentration measurements. The method used here may conceivably be extended to high temperature chemical raections (gas‐solid reaction or pyrolysis, for instance).
A generalized vapor pressure equation for hydrocarbons
Authors: Zia Tahir , Thodos George 
Published: March 2009

AbstractA reduced vapor pressure relationship of the following form has been developed:

The optimum value of n was established to be 8.00 from vapor pressure data for n‐heptane. A method was developed for the determination of the constants A, B, C and D from one reliable vapor pressure point. By this procedure vapor pressures were calculated for 33 hydrocarbons, including saturated and unsaturated paraffins, naphthenes, and aromatics, and were compared with corresponding experimental values. For these substances the overall average deviation between calculated and actual vapor pressure was 0.38% (1879 points). This relationship was also applied to seven additional hydrocarbons not included in its development, and for these substances the resulting average deviation was 0.36% (99 points).
A discrimination among microbial iron oxidation mechanisms
Authors: Wong Chi‐Wung , Scharer Jeno M. , Reilly Park M. 
Published: March 2009

AbstractThe oxidation mechanism of ferrous ion (Fe11) by whole cells of Thiobacillus ferrooxidans was studied. Product inhibition by ferric ion (Fe111) was observed experimentally at the pH = 2.0 and initial inhibitory iron concentration of 2.58 mM ≤ Fe111 ≤ 15.0 mM. Experimental results indicated that the hyperbolic expressions (i.e. Monod type mechanisms) were valid to describe the microbial oxidation. A Bayesian statistical method for discrimination was utilized to identify the inhibition mechanism. In order to use the data efficiently the integrals of the inhibition models were taken (concentration versus time). Such analysis indicated that a non‐competitive mechanism with two inhibition parameters was superior to others describing the microbial oxidation. Not only was this the best model, it was also a good one in the sense that the errors of predictions made from it were consistent with experimental error. Estimates for the parameters of the non‐competitive inhibition model were obtained.
Variational optimization in control and time domains
Authors: Gangiah K. , Husain Asghar 
Published: March 2009

AbstractThe study has established, with the help of two typical chemical engineering models, the superiority and versatility of the functional conjugate gradient method in computing optimal control policies for continuous systems. An algorithm named as Difference Method has been developed and tested for optimization in the secondary domain of time. A computationally sound and stable scheme is presented to compute simultaneously optimum duration of time and optimal control policy for a process.
Transient deagglomeration of solid aggregates in sheared viscous liquids
Authors: Kamal Musa R. , Patterson I. 
Published: March 2009

AbstractThe model originally proposed to determine the equilibrium particle size distribution in the deagglomeration of solid aggregates in sheared viscous fluids is extended to determine the transient particle size distribution prior to equilibrium. The model requires as input data the initial size distribution of the agglomerates as well as the agglomerate strength distribution and the change in shear stress level. In this paper, a step change in stress is considered.Experiments have been performed to verify the model. The shear stress field was provided by a concentric cylinder apparatus and the analysis technique was similar to that employed in earlier work. Calculated and experimental results agree within the accuracy limits imposed by experimental and sampling errors. The results also agree with other predictions relating to the behavior of particle suspensions in liquids.
Methods of improving settling of industrial pigment slurries
Authors: Anada H. R. , Shah Y. T. , Klinzing G. E. 
Published: March 2009

AbstractAn experimental study on improvement of settling of three industrial pigment slurries, with trade names chrome yellow, molybdate orange and semi‐blacktone iron blue is reported. Three methods for improvement were employed. Additions of common surfactants did not improve settling rate of any slurry. Additions of a flocculating agent with trade name Hercofloc 825.2, on the other hand, improved the settling rates of all three slurries very significantly. Settling of chrome yellow slurries was increased a phenomenally one hundred fold by additions of Hercofloc 825.2. The exposure of the slurries to low frequency (540 kHz and 765 kHz) ultrasonic radiation increased the settling rate as high as six to seven fold. The effects of ultrasonic radiation on the settling of iron blue slurry of various solids concentration, and initial slurry height were investigated. Exposure of the slurry to ultrasonic radiation appears to be a viable and practical method for improving settling of industrial pigment slurries.
Overall activation energy for parallel reactions
Authors: Giralt Francesc , Missen R. W. 
Published: March 2009

AbstractThe overall activation energy from the point of view of reactant in a kinetic scheme involving parallel reactions of the same order depends in general on whether the integrated or the differential form of the Arrhenius equation is used for the definition. Expressions are given for the two quantities (E and E', respectively), both of which are temperature‐dependent, in terms of the Arrhenius parameters (A1 and E1) of the individual steps. In the limits of low and high temperature, they become identical. At low temperature, the activation energy approaches the lowest of the Ei, non‐asymptotically for E and asymptotically for E', but at high temperature it approaches the weighted average ΣAiEi/ΣAi asymptotically in both cases. The latter result is not inconsistent with well‐known conclusions drawn from the point of view of product distribution.
Une application de l'oxydation humide à la récupération du mercure
Authors: Khanh P. V. , Chornet E. , Hudgins R. R. 
Published: March 2009

AbstractThe Canadian “Couplan Process” uses the absorptive capacity of sphagnum (peat) moss to remove heavy metal contaminants from aqueous effluents. Disposal of the peat moss is accomplished through incineration, which then permits metal recovery. Wet air oxidation (WAO) is a possible alternative to incineration for reducing the volume of peat moss wastes and recovering the metal. The objective of this study was to assess the feasibility of WAO for recovering mercury from pcat moss.Studies were performed by preparing samples of peat moss slurrics (up to 25% water added to air‐dried peat moss) and exposing them for two hours to stoichiometric excess oxygen in a stirred autoclave at temperatures reaching 500°F. Mercury‐free samples were studied, as well as those containing 3% by weight of HgS to simulate the saturated moss. The reduction in solids volume was almost 100%; about 5% by weight of the original peat moss was converted to acetic acid; ash residues amounted to 3 to 4% of the initial peat moss, and consisted of about 50% mercury by weight; about 2% of the original mercury was present in the final solution.It was concluded that wet air oxidation represents a possible alternative to incineration in the Couplan process.
H2S promoted oxidative dehydrogenation of ethylbenzene to styrene
Authors: Vadekar M. , Pasternak I. S. , Gaspar N. J. 
Published: March 2009

AbstractThe technique of using mixtures of H2S/O2 and H2S/SO2 to selectively dehydrogenate hydrocarbons in the presence of suitable catalysts has been applied to the production of styrene from ethylbenzene. The mechanism of the reaction is discussed and results are presented on the influence of different catalysts and the optimization of processing variables such as temperature, space velocity and reactant concentrations. Styrene yields as high as 75% have been achieved under optimum conditions.
H2S Promoted Oxidative Dehydrogenation of Hydrocarbons in Molten Media
Authors: Gaspar N. J. , Pasternak I. S. , Vadekar M. 
Published: March 2009

AbstractThe H2S promoted oxidative dehydrogenation of butane to butadiene can be efficiently carried out if a molten salt medium, e.g. LiCl/KCl, is used to dissipate the heat from the highly exothermic reaction. The reaction is catalyzed by the addition of soluble salts such at Tl2O3, BaCl2 or MnCl2. Optimization of reaction conditions by varying temperature, space velocity and quantity of promoter results in a 53% olefin yield (5% butenes, 48% butadiene) at 80% butane conversion. The system is also shown to be efficient for the dehydrogenation of ethane to ethylene, propane to propylene, butene to butadiene and ethylbenzene to styrene.
Optimization by distributed control of reactors with decaying catalyst Part II: First‐order catalyst deactivation
Authors: Crowe C. M. , Therien N. 
Published: March 2009

AbstractThe problem of optimally choosing the temperature T(z, t) as a function of time t and position z in a tubular fixed bed chemical reactor, so as to minimize the total yield of product over a fixed time period for a reaction‐deactivation system with a slow decaying catalyst has been formulated for the case where the rate of catalyst decay is linearly dependent upon activity.Several characteristics of extremal control policies which supplement the theoretical characterization obtained for the case of general reaction‐deactivation kinetics using Sirazetdinov and Degtyarev's maximum principle are indicated. Results are that the supplementary properties of the extremal controls for linear catalyst deactivation kinetics may be used to advantage to reduce the computational dimensionality in synthesizing the control policies.Numerical calculations are presented to illustrate this fact in the case of initial catalyst activity profiles which are not uniform nor continuous along the reactor bed.
Generalized drying curves for porous solids
Authors: Kisakurek Bilgin , Peck Ralph E. , Çlakaloz Temel 
Published: March 2009

AbstractThe purpose of this study is to obtain generalized drying curves which can be used in the prediction of drying times of porous solids in the falling‐rate period. The drying model introduced assumes that the movement of moisture in the solid body is by capillary motion, and that the major resistance to heat and mass transfer lies on the boundary layer at the solid surface. It has been applied to the drying of gypsum particles of various sizes in a rotary dryer at different feed rates and gas temperatures. The results show that the deviation between the experimental data and the ones predicted from theory is very small. The deviation increases at low moisture concentrations which may indicate that internal resistance to moisture flow starts to dominate the drying phenomena.
Mathematical models for the drying of rigid porous materials
Authors: Novak Lawrence T. , Coulman George A. 
Published: March 2009

AbstractThis paper presents a resume of literature on theories and mathematical models for drying of rigid porous materials. Key work on drying by soil physicists has been neglected in the engineering drying literature. We have included these works here to bring this literature to the attention of engineers.A new and general model for moisture and energy transport in rigid porous media during drying is presented. It is demonstrated that under certain simplifying assumptions, the general model reduces to less general models which have previously been proposed.Experimental and simulation results are given for the drying of Valentine sand. Under the drying conditions studied, the drying rate during the falling rate period is controlled by the capillary flow of water to an evaporation zone in the porous media.The models simulated here are of varying complexity and rigor. The capabilities and limitations of these models are discussed.
Propriétés physico‐chimiques et thermodynamiques du système binaire hexamethylphotriamide + eau
Authors: Jose Jacques , Philippe Robert , Clechet Paul 
Published: March 2009

AbstractLes auteuts présentent les densités, les constantes diélectriques, les indices de réfraction, les volumes d'excès, les enthalpies de mélange et les enthalpies libres d'excès des mélanges hexaméthylphosphotriamide (HMPT) + eau. Les fonctions thermodynamiques d'excès sont negatives et présentent leur plus grande déviation par rapport à l'idéalité pour une fraction molaire en HMPT voisine de 0,3. Ces résultats indiquent de fortes interactions entre l'HMPT et l'eau et laissent supposer l'existence de complexes du type: HMPT – n H2O.
Optimal two point control of a binary distillation column
Authors: Chan Alan L. , Talbot Frank D. 
Published: March 2009

AbstractOptimal two point control and operating policies have been developed for a semi‐works scale 10 tray distillation column separating methanol and water. Two controllers, based on different control philosophies were synthesized. They are:

The controller that will bring the product compositions to their desired values while keeping off‐specification products to a minimum.
The controller that will bring the product compositions to their desired values while maintaining the average product composition of the control period at the desired level.

Two types of disturbances were studied, namely disturbances in the feed stream and changes in product specifications.The column operation was represented by a linearized dynamic mathematical model based on a component material balance. The solution of the problem was obtained by application of the minimum principle of Fontryagin and the modified Riccati transformation technique. Simplified optimal control schemes can be developed from the results of this work. These control schemes are simple enough to be used for direct digital computer control.
The hydrodynamics of spherical capsules
Authors: Ellis H. S. , Kruyer Jan , Roehl A. A. 
Published: March 2009

AbstractWith water as the conveying liquid the pressure gradient of a train of spheres is comprised of a basic pressure gradient due to shear of the surrounding liquid, to which has to be added a very small density‐dependent increment due to solid friction, and a further increment due to any irregularity of the spheres. With viscous liquids the pressure gradient generally rises rapidly with specific gravity and with increase of viscosity.Even at the low specific gravity of 1.25 the power require‐nients of cast spheres conveyed by water are generally lower than those of smooth cylinders, and the advantage increases with increase of specific gravity. However, the lower power require‐uient has to be weighed against the possibly greater cost of forming spheres, and the cost of larger pipe that would be neces‐sary to secure a given throughput, particularly if the spheres were run at low velocities to secure very low pressure gradients.
Natural convective heat transfer from a horizontal cylinder in the presence of nearby walls
Authors: Marsters C. F. 
Published: March 2009

AbstractThis work deals with thc influence of unheated vertical walls, symnietrically placed with respect to a single heated horizontal cylinder, upon the natural convection heat transfer froni a heated cylinder. The study is experimental. By using air, water and Frecon 113 as working flnids, a Rayleigh number range of 10 to 500,000 lias been investigated. Various conibiuations of wall spacing and wall height have been examined. Empirical correlations of Nussclt number with Rayleigh nnmber and geometric parameters are presented. The presence of walls enhances heat transfer froni the cylinder for certain geometries. Wall spacings smaller than two diameters have not been investigated.
Crystallization in a dispersed phase
Authors: Shiloh K. , Sideman S. , Resnick W. 
Published: March 2009

AbstractA study of a non‐conventional dispersed phase crystallizer, whereby the mother liquor feed is dispersed in an immiscible continuous phase and product withdrawn continuously from the agitated 3‐phase slurry is presented. A nucleation mechanism is suggested and relationships which enable an estimate of crystal size, growth rate and segregation effects are proposed. Continuous bench scale experiments indicated that no particular operational difficulties arise, provided the feed is properly dispersed, and verified the anticipated theoretical results.
New thermochemical cycles for hydrogen production
Authors: Soliman M. A. , Carty R. H. , Conger W. L. , Funk J. E. 
Published: March 2009

AbstractThe ease of decomposing some metal sulfates to oxides and sulfur trioxide is employed in the search for efficient closed cycle thermochemical methods for water splitting. The main features of the new processes are the production of O2 through the decomposition of SO2 and/or SO3, the production of hydrogen by the decomposition of H2S, reaction of H2S with a metal, reaction of water with a metal, and/or reaction of water with sulfides.
The disinfection of sewage treatment plant effluents using ultraviolet light
Authors: Oliver Barry G. , Cosgrove Ernest G. 
Published: March 2009

AbstractThe discharge of chlorinated wastewaters may result in acute toxicity to the aquatic ecosystem. This toxicity is due to chlorine residuals and to chlorinated organics formed during chlorination. An alternative method to chlorination for effluent disinfection is ultraviolet light irradiation. Kills of more than 99% have been obtained for coliform, fecal coliform, fecal streptococci and heterotrophic bacteria by irradiating secondary effluents from conventional activated sludge sewage treatment plants with ultraviolet light (254nm). Laboratory scale treatment studies of ultraviolet sterilization as a method of reducing the toxicity of municipal effluents and producing effluents of acceptable bacterial quality is reported.
Hydrocarbon‐propionitrile systems
Authors: Kikic I. , Alessi P. 
Published: March 2009

AbstractPerfluorocyclic oxide is proposed as an antisolvent for studying the behaviour of binary systems by liquid‐liquid equilibrium. The experimental results, obtained for the ternary systems perfluorocyclic oxide — hydrocarbon — propionitrile, are correlated with the NRTL equation. The values of NRTL parameters allow the prediction of the behaviour of ternary systems hydrocarbon A — hydrocarbon B — propionitrile. The use of liquid‐liquid extraction with mixed solvent (perfluorocyclic oxide and propionitrile) is suggested for the separation of hydrocarbon mixtures.