bluuebunny/crossref_metadata_2025 huggingface dataset:
Performance studies on a high temperature thermal regenerator with radial flow geometry
Authors: Handley D. , Heggs P. J. , Stacey J. M.
Published: March 2009

This paper describes the design, construction and performance of a high temperature thermal regenerator of annular geometry with radial air flow present. This regenerator has possible application to the efficient exploitation of high temperature gas reactions and in particular to the fixation of atmospheric nitrogen for which this investigation was made. A mathematical model is formulated for the transient heat transfer between a fluid and an annular solid matrix with reversing flows and is solved numerically. The model is used to predict and analyse the operating performance of the regenerator over a range of flow rates (650 Kg/hr maximum), flow reversal periods (100 seconds maximum) and core temperatures (1431°C maximum). The model is tested by comparison of the theoretical and observed regenerator effectiveness, internal bed temperature profiles and the bed pressure drop under conditions of cyclic equilibrium. Apparent effective heat transfer coefficients for the regenerator packing are obtained and compared with an empirical correlation based on independant measurements.
Investigation of the fundamental assumptions relating compression‐permeability data with filtration
Authors: Willis M. S. , Shen M. , Gray K. J.
Published: March 2009

A recently reported investigation indicates several inaccuracies in the methodology of compression‐permeability (C‐P) testing which suggest that previously reported agreement between C‐P and filtration data may be fortuitous. Until now, there has been no separate and direct confirmation of each of the two assumptions necessary to obtain a unique correspondence between C‐P and filtration data.

The first assumption that the specific filtration resistance is a function solely of cumulative‐drag‐stress is generally accepted. Direct proof requires that the parabolic filtration equation, which is derived primarily on this assumption, describes both incompressible and compressible cake behavior. Most materials produce compressible cakes and “a priori” screening to find an incompressible cake requires identification of a material (Geon) that produces a cake with a linear axial pressure distribution. Results show that the parabolic filtration equation fits both types of cake behavior but an equation based on constant filtration resistance describes only incompressible cake behavior. To engineering accuracy and for dilute slurries, the assumption is verified.

The second assumption that the cumulative‐drag‐stress equals the cake pressure drop is a macroscopic force balance and experimental verification requires a filter chamber designed to measure both of these quantities. A theoretical development, based on integral averaging, and experimental results both indicate that the ratio of cumulative‐drag‐stress to cake pressure drop correlates extremely well with cake porosity.

A unique one‐to‐one correspondence between C‐P and filtration data is not possible without “a priori” knowledge of filter cake porosity. Previously reported agreement between C‐P and filtration data can probably be attributed to the L/D dependence of C‐P specific filtration resistances. Consequently, C‐P data can be used as a research tool to simulate filtration data but predicted filtration times based solely on C‐P data can be in considerable error.
Throughput of rotating disc contactors — a review
Authors: Landau J. , Houlihan R.
Published: March 2009

Published procedures for calculating the maximum throughput of mutually saturated phases in rotating disc contactors, based on the slip‐velocity concept, are compared against a set of experimental data from two sources. The results of the comparison are expressed as the standard relative deviation of the calculated and experimental continuous phase velocities.
Powder processing in a plasma jet: A proposed model
Authors: Boulos M. I. , Gauvin W. H.
Published: March 2009

A theoretical study is reported on the use of d.c. and r.f. plasma jets as chemical reactors for the processing of minerals in the form of a fine powder. The temperature and flow fields of the jet are calculated by solving the integral boundary layer equations. Single particles trajectories are obtained by solving the Basset‐Odar equations. A multi‐particle model is then developed for a feed of known particle size and injection velocity distributions under low loading conditions. Calculators are made on the thermal decomposition of molybdenum disulphide (5 to 30‐micron equivalent diameter). The parameters investigated are the free jet velocity, the mean injection velocity, and the reactor ambient conditions. The results are presented as the probability density distributions of the gas loading, particle temperature, and conversion at different levels downstream of the nozzle.
Kinetic study of the solid‐state reaction between phthalic anhydride and P‐nitroaniline
Authors: Ramachandran S. , Baradarajan A. , Satyanarayana M.
Published: March 2009

The addition reaction between the compacted powders of phthalic anhydride and p‐nitroaniline was studied. Both the reactants of equal particle size, were mixed in 1‐to‐1 molar ratio and compacted. Three particle sizes — 0.0065 cm, 0.0178 cm and 0.0376 cm and three compaction pressures — 302.0 kgf/cm2, 785.0 kgf/cm2 and 1208.0 kgf/cm2 were used for the study. Conversions were measured at 80°, 90°, 100°, 110° and 120°C for 1/2, 1, 2, 4, 8, 12, 16, 20 and 24 hours. The reaction rate changed to a constant value, after an initial phase boundary process. The mole percentage conversions increased with decrease in particle size, increase in compaction pressure corresponding to a decrease in the initial porosity of the compact. It was also observed that the final porosity of the compact increased with increase in reaction temperature. Combination of Jander's model and parabolic rate law was used to calculate the values of the reaction rate constant equivalent. The activation energy was calculated to be 14 to 34 kilocalories per gram mole.
Kinetics of reduction of solid copper sulphate by hydrogen and carbon monoxide
Authors: Van Kim Vo , Habashi Fathi
Published: March 2009

Cupric sulphate is reduced to metallic copper by H2 at 225° to 400° with formation of Cu2SO4 as an intermediate product. Under the present experimental conditions, the reduction followered the equation k = 1 — (1 — R)1/3, where R is the fraction reacted at time t and k is the velocity constant. The activation energy of the overall process in this temperature range lies between 15 and 17 Kcal/mole. Reduction by CO takes place at 400° to 650°C with formation of Cu2SO4 and Cu2O and the activation energy in this temperature range lies between 24 and 29 Kcal/mole. Reduction in both cases is exothermic.
Polymerization of butadiene with tii4‐Al(i‐Bu)3 Catalyst: Part II: Kinetic model development
Authors: Loo C. C. , Hsu C. C.
Published: March 2009

Expressions for conversions, Mn and Mw have been derived for the proposed kinetic scheme for the polymerization of butadiene using Til4 — Al(i‐Bu)3 as catalyst. The rate constants kp, kta and kd and the active sites were estimated from experimental data of conversion and molecular weight averages. The logarithm of both kp and kta are linearly related to Al/Ti ratio. On the other hand, kd and Co appear to be uncorrelated with the reaction variables studied in this investigation. The activation energy for propagation reaction was found to be 12.05 ± 1.31 which agrees well with those reported previously. The small difference in the activation energies for kp and kta accounts for the independence of the molecular weight of the polymer on the reaction temperature.
Statistical identification of the dynamic behavior of a dual input heat exchanger network
Authors: Wright J. D. , Bacon D. W.
Published: March 2009

Statistical modelling procedures proposed by Box and Jenkins are used to develop models for the transfer function and noise behaviour of a dual input pilot scale heat exchanger network. Data were collected under operating conditions closely resembling full scale industrial operation first with uncorrelated inputs and then with correlated inputs. Two modelling strategies, a superposition approach and a transformed input approach, are employed to analyze the data. Computational advantages of the transformed input procedure for correlated input situations is demonstrated and the effectiveness of both strategies in detecting nonstationarity in the system noise is also illustrated.
Comments on the prediction of liquid holdup for gas‐liquid flow in inclined pipes
Authors: Gregory G. A.
Published: March 2009

Four correlations for predicting the in situ liquid volume fraction for gas‐liquid flow in inclined pipes have been tested against available data from the literature. It is demonstrated that the commonly used correlations of Baker(4) and Flanigan(5) are subject to large errors. It is recommended that the correlation of Guzhov et al(2) be used unless it predicts values of EL less than 0.25. In the latter case, the Lockhart‐Martinelli(3) correlation should be used.
Practical significance of brinkman's extension of darcy's law: Coupled parallel flows within a channel and a bounding porous medium
Authors: Neale Graham , Nader Walter
Published: March 2009

Problems involving fluid flow past permeable surfaces have customarily been solved by matching Darcy's Law with the Navier‐Stokes equation via an empirical slip‐flow boundary condition at these surfaces. The present analysis serves to place the semi‐empirical theory proposed by Beavers and Joseph (1967) on a more rigorous physical and mathematical basis. It is demonstrated that the predictions of these workers may be derived independently, without having to formulate empirical boundary conditions, by employing Brinkman's extension of Darcy's Law within the porous medium. These predictions are in satisfactory agreement with experimental data, thereby providing a quantitative verification of Brink‐man's equation to complement its theoretical verification presented recently by several authors.
Purging calculations for cascades of mixing stages
Authors: Tomiak A.
Published: March 2009

Generalized algebraical expressions were obtained for average individual stage and final effluent concentrations in a cascade of mixing stages in series, without specifying the mixing pattern. Such expressions, combined with the knowledge of particular mining patterns, may be used for solving more complex purging problems.

A detailed computation method was given for the specific case of countercurrent purging of a cascade under perfect mixing conditions as an example.
Some surface and kinetic effects of trace additions of selected metal oxides and halides on the thermodehydration of silica xerogel spheroids
Authors: Ross R. A. , Henry N.
Published: March 2009

A kinetic study of the sintering of silica xerogel has been carried out by following the rate of dehydration of xerogel spheroids, 2000 ‐ 841 μ, on a thermal balance in the presence of small additions, usually 5 g. ion percent of selected metal oxides and halides. First order rate constants calculated from the classical kinetic expression were in excellent agreement with those obtained from the Avrami‐Erofeev equation for nucleation and growth in the case of a monomolecular reaction. The surface areas and mercury densities of samples cooled from 900°, 850°, 800° and 500°C have been measured and X‐ray powder diffraction patterns obtained for most samples in an attempt to identify phases formed by solid‐solid interaction between the gel and the additives.

The activation energies of the dehydration for the oxide additives, (CuO, NiO, Cr2O3, BeO, ZnO and Al2O3), did not show substantial enough differences to allow any decisive analysis to be made on the basis of established properties of the oxides. CdO was the most active oxide in xerogel dehydration and it is shown that this oxide takes part readily in solid‐solid reactions with the xerogel in the vicinity of the Tamman temperature of silica. In the presence of the transition metal halides, (NiCl2, CrCl3, CuCl2 and CoCl2), hydrogen chloride was evolved from the matrix and xerogel dehydration may be accentuated by reaction of this gas with accessible surface hydroxyl groups. The addition of sodium halides showed no significant differences in dehydration rates whereas with lithium salts, the rate and amount of dehydration varied with the melting point of the additive.
A method for simplifying linear multivariable dynamic systems
Authors: Gupta Y. P. , Donnelly J. K. , Andre H.
Published: March 2009

A method for reducing the order of linear multivariable stable dynamic systems is proposed. The main advantage of this method is that the problem of determining a simplified model is reduced to few matrix manipulations and solution of a few algebraic equations which can be easily programed. The simplified model is obtained so that a quadratic functional of the difference between the output vector and that of the original model is automatically minimized for either step or impulse inputs. Applications of the method include simplification of a dynamic model of a pilot plant for the azeotropic distillation of n‐butyl acetate and n‐butanol. Very good agreement between the step responses of the original and simplified model is obtained.
Diminution du temps de préchauffage d'un réacteur isothermique
Authors: Pineault Gilles , Dekee Daniel
Published: March 2009

L'étude de la cinétique d'une réaction chimique effectuée dans un réacteur discontinu et muni d'un mécanisme de chauffage inadéquat, a conduit à la mise au point d'un systénie de préchauffage plus efficace du réacteur. Le manchon de chauffage électrique à été remplacé par un bain d'huile maintenu à température constante et muni d'un agitateur couplé au moteur électrique au moyen d'un joint d'étanchéité au mercure afin d'assurer une distribution uniforme de température à l'intérieur du bain d'huile. Le temps de préchauffage théorique de ce nouveau systéme est considérablement inférieur au temps de préchauffage du réacteur original, éliminant presque complétement les erreurs dans l'évaluation du taux de réaction chimique.
Effect of cations on the maximum yield values of a bentonite clay gel
Authors: Hu C.‐S. , Pinder K. L.
Published: March 2009

The effect of cations on the gel strength of a bentonite clay was studied by measuring the maximum yield value of clay salt mixtures.

Cations which are in large concentration as exchanged ions on the clay act very differently upon the clay strength than do cations which are only in trace concentrations in the clay. For those cations which were originally in only trace concentrations, the ability to build up the gel strength is inversely proportional to their valence.

Sodium and calcium ions reacted completely differently. The clay was tolerant to a large sodium concentration but lost gel strength with the addition of only a small amount of calcium. This result is explained in the light of previously reported ion exchange properties of clay.
Scaling of enhanced heat exchanger tubes
Authors: Watkinson A. P. , Louis L. , Brent R.
Published: March 2009

The performance of inner‐fin and spirally indented heat exchanger tubes is compared with plain smooth tubes under severe scaling conditions. Artificially hardened water was recirculated through a heat exchanger which contained an enhanced tube and a plain tube in parallel and the decrease in heat transfer coefficient due to scale deposition followed with time. Inner‐fin and spirally indented tubes maintained advantages in heat transfer coefficient over plain tubes of 10 to 100% after scaling. Asymptotic fouling resistances were larger for the inner fin tubes than for plain tubes, and smaller for the spirally indented tubes at velocities above 3 ft/sec.
Dispersion models of unsteady tubular reactors
Authors: Subramanian R. Shankar , Gill William N. , Marra Richard A.
Published: March 2009

Axial 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

Theoretical 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

The 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

Le 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

The 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

A 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

The 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

The 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

The 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

An 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

The 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

The 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

The 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

The 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

The 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

The 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

This 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

Les 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

Optimal 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

With 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

This 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

A 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

The 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

The 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

Perfluorocyclic 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.
On the thermodynamics of concentrated strong electrolytes aqueous solutions the system NaNO3—NaCl—H2O
Authors: Correa H. A. , Vera J. H.
Published: March 2009

A simple analytical function is proposed for the calculation of molar excess Gibbs energy of binary solutions of strong electrolytes in water. Empirical parameters can be easily determined from experimental data reported in the literature.

The treatment is extended to ternary solutions and to solid liquid equilibria using an empirical equation. Absence of solid solutions is assumed.

The correlations are applied to the common ion ternary system NaNO3‐NaCl‐H2O in the temperature range from 0 to 100°C.

Predictions of activity coefficients of the binary systems and saturation curves of the ternary system are in good agreement with experimental data.
Identification and direct digital stochastic control of a continuous stirred tank process
Authors: Hong Huynh Man , Macgregor John F.
Published: March 2009

Several aspects associated with the identification and direct digital stochastic control of a steam‐jacketed continuous stirred tank process are investigated. Using data collected under closed‐loop conditions by an on‐line mini‐computer, statistical modelling procedures are used to identify, fit and check a discrete dynamic‐stochastic model for the process and its disturbances. Based on these models an optimal stochastic feedback controller is implemented using the minicomputer. A practical modification of this optimal controller is suggested and the modified stochastic controller is implemented and its performance is evaluated.
Optimization of multistage recycle systems by direct search
Authors: Luus Rein
Published: March 2009

Optimal operation of chemical systems with recycle is considered. An optimization procedure, whereby the control variables are obtained by direct search, is developed.

Suitability of this method for optimizing chemical engineering systems with recycle is tested by considering three systems of different complexity. Results close to the optimum were obtained in each case. For complex systems, however, care must be taken to ensure that global and not local optimum is obtained.

Due to the ease of formulation and of programming, the proposed method provides an attractive alternative to the combined use of the gradient method and Lagrange multipliers.
The rate of mass transfer at a rotating cylindrical electrode with wiper blades
Authors: Nadebaum P. R. , Fahidy T. Z.
Published: March 2009

A theoretical analysis of mass transfer at a rotating cylindrical electrode with wiper blades yields the dimensionless equation

where w is the number of the symmetrically located wiper blades, d is the wiper blade thickness and R1 is the radius of the wiped electrode. NuR, ReR and Sc are defined in terms of the cell and electrolyte parameters. Experimental evidence via the reduction of oxygen and ferrocyanide ions indicates that mass transfer rates can thus be predicted at no more than ±5% inaccuracy for Sc > 200. The two‐wiper blade system is shown to effect an increase in mass transfer rates by a factor of 7–8 with respect to a rotating cylindrical electrode without wiper blades.
Activation de la tourbe de sphaigne par le dioxyde de carbone et agglomération du charbon actif produit
Authors: Son P. N. , Khanh P. V. , Chornet E.
Published: March 2009

The physical activation of peat moss using CO2 has been investigated with respect to the operational variables and the characteristics of the active carbon produced. Peat coke is produced during carbonisation with a 30% yield. The activated carbon accounts for 25% of the initial air dried peat moss.

Analysis of the active carbon has revealed a surface area up to 600 m2/g and a chemical reactivity similar to commercial active carbon as measured by the iodine, phenazone and phenol indexes.

The active carbon thus produced is a powdered material, with a weak abrasive resistance. Agglomeration of the carbon and subsequent pelletization has been done with ammonium ligno‐sulfonate, water, and the application of pressure. Resistant pellets can be obtained using 15–20% lignosulfonate and 3000 psi.
Thorium as a nuclear fuel for CANDU reactors
Authors: Banerjee S. , Critoph E. , Hart R. G.
Published: March 2009

The reasons for the attractiveness of thorium as a fuel for CANDU reactors are discussed. By the use of thorium fuels it is shown that the amount of energy that can be extracted from nuclear fuel resources can be increased substantially. Cumulative savings in nuclear fuel requirements are estimated for a number of situations.

The thorium fuel cycle is shown to be relatively insensitive to the cost of natural resources. The conditions under which fuelling costs for the thorium cycle will become competitive with the present natural uranium fuel cycle are discussed.
Règies de construction et d'extrapolation des réacteurs auto‐agités par jets gazeux
Authors: David R. , Matras D.
Published: March 2009

An analysis is made of the agitation mechanism in a spherical reactor which is self‐stirred by means of gas jets; it is made on the double assumption of an internal recycling and of a turbulent free jet.

Extrapolation laws have been developed and verified experimentallly by means of the residence time distribution in several reactors of volumes varying between 501 and several cubic centimeters, the passage times varying from 0.6 to 7.5 seconds: the experiments involved several gases and different temperatures.
Vapor liquid equilibrium constants through a non‐equation of state approach: Methane‐free aliphatic binary systems
Authors: Hsiung Thomas H. , Thodos George
Published: March 2009

Using vapor liquid equilibrium measurements available in the literature for the three binaries of the system ethane—n‐butane—n‐heptane, correlations have been developed that predict K‐constants for other aliphatic binary mixtures, not containing methane. This approach does not involve the use of an equation of state, but utilizes fundamental properties associated with the pure state components and the critical pressure of the mixture.

This method produces for seven additional binary systems, K‐values that are in good agreement with experimental measurements, and particularly in the vicinity of the critical point.
An improved group solution model for the prediction of excess free energies of liquid mixtures
Authors: Ronc M. , Ratcliff G. A.
Published: March 2009

An improved analytical group solution model has been developed and applied to mixtures containing the groups methylene and hydroxyl. The new model predicts molecular activity coefficients for alcohol/n‐alkane and alcohol/water systems with an accuracy of about 5%. Predictions are equally good for systems of alcohols and n‐alkanes of the same chain length; earlier models give poor predictions for these newly‐measured systems.
Uni‐directional spreading of one liquid on the surface of another
Authors: Huh C. , Inoue M. , Mason S. G.
Published: March 2009

The spreading rate of a thin film of a liquid on the horizontal surface of an immiscible liquid substrate is calculated by an approximate quasi‐steady analysis. Spreading is assumed to be driven by the combination of gravity and interfacial forces. Dimetryl siloxane fluids of various viscosities were permitted to spread uni‐directionally on the surface of water in a rectangular channel. The measured rates were in reasonably good agreement with the theoretical values.
Relationship between capsule pulling force and pressure gradient in a pipe
Authors: Kruyer Jan , Snyder William T.
Published: March 2009

A method is presented for predicting the pressure gradient required to transport a cylindrical capsule through a liquid‐filled pipeline. It is based upon a coefficient of lubricated friction which is obtained experimentally by pulling a capsule by a string through the liquid‐filled pipe. A simplified method for measuring this coefficient and relating it to the capsule pressure gradient is proposed.
Experimental studies of incipient vapor nucleation
Authors: Schultz R. R. , Kasturirangan S. , Cole R.
Published: March 2009

Experimental investigations of the vapor nucleation characteristics of single cavities under conditions of both uniform and non‐uniform superheat of the adjacent liquid are described and discussed.