bluuebunny/crossref_metadata_2025 huggingface dataset:
Optimal switching policies for fixed bed catalytic reactors in series
Authors: Miertschin G. N. , Jackson R.
Published: March 2009

It frequently occurs in catalytic reforming that several fixed bed catalytic reactors are run in series. Periodically a bed must be removed and regenerated while a previously regenerated bed is used in its place. An algorithm that finds which bed to remove and how to order the remaining beds and the previously regenerated bed so that some suitable objective function is optimized is presented for the case where the catalyst decays uniformly down the length of each reactor.
A minimum time operating policy for a liquid‐liquid extraction column
Authors: Pang K. H. , Johnson A. I.
Published: March 2009

Two methods, both based on linear programming techniques, have been applied to determining the minimum time control policy for effecting a grade change in the product from a liquid‐liquid extraction column. The method was made possible by the existence of a linear dynamic model for the column derived from a previous frequency response study of the laboratory unit. Both methods predicted policies of a partial bang‐bang nature. As expected the control paths were not the same; additional control criteria such as minimum control effort or minimum number of switchings are suggested as a means of further defining a best control policy.

Suitable bounds on the controlled variables were found in the study so that physically realizable control policies were formulated.
Preparation of amorphous silica
Authors: Funnell N. A. , Sirianni A. F. , Puddington I. E.
Published: March 2009

Amorphous silica having reinforcing properties for styrene butadiene rubber (SBR) was obtained by contacting silica aquagel seed, containing 1‐3% SiO2 by weight, with a freshly prepared silica sol. Reinforcing by the isolated silica was greatly affected by the pH of the aquagel‐sol system and moderately affected by temperature and by the silica content of the aquagel seed. Maximum tensile strengths for the vulcanizates were found using the product obtained from a 2 to 2.5% silica aquagel seed‐sodium silicate system acidified with sulphuric acid to pH 3 at 85 to 95°C.
Dissolution of ferritic stainless steel scrap in hydrochloric acid
Authors: Rigg T. , Rahaman M. S.
Published: March 2009

The dissolution of a ferritic stainless steel (15.44% Cr, 0.39% Mn, 0.12% C) in hydrochloric acid has been investigated from the point of view of large scale processing. Over the range of experimental conditions employed, the rate of dissolution at 80.5°C can be represented by the equation:

where [MCl2] is the total molar concentration of divalent metal chlorides in the acid solution. The rate of dissolution is not influenced by the degree of agitation. The apparent activation energy is 21.6 K. cal. mole−1.
On the motion of gas bubbles in a viscoelastic liquid
Authors: Leal L. G. , Skoog J. , Acrivos A.
Published: March 2009

The discontinuity of terminal velocity versus bubble volume previously reported as taking place in viscoelastic liquids, was studied experimentally and theoretically. A comparison of terminal velocity data for gas bubbles and glass spheres in aqueous polymer (Separan‐AP30) solutions provides strong evidence that the discontinuity results from a change in interfacial conditions from “no‐slip” to free shear. A numerical solution of the creeping flow equations using an empirical curve fit for viscosity versus shear‐rate indicates that only a fraction of the experimentally observed velocity jump is due to the shear dependence of the viscosity alone (neglecting elastic effects). However, simple qualitative arguments seem to suggest that a relatively modest elastic contribution to the force balance on the bubble would be sufficient to account for the experimental observations.
The effect of liquid maldistribution on the performance of a packed tower absorber
Authors: Stanislav J. , Gregory G. A.
Published: March 2009

A study of the effect of liquid maldistribution on the performance of a gas absorber is reported. The experimental work was carried out using the carbon dioxide‐water system in a simulated packed column consisting of an ordered array of spheres. This device has been shown to closely approximate the behaviour of an actual column and permits the artificial manipulation of the liquid distribution. The results indicate that maldistribution causes only a small decrease in the mass transfer coefficient at low liquid flow rates, and has almost no effect at higher flows. A proposed iterative procedure for calculating the effect is presented.
La réduction de l'oxyde de nickel par l'hydrogène
Authors: Chiesa F. , Rigaud M.
Published: March 2009

L'étude cinétique de la réduction isotherme de comprimés de poudre d'oxyde de nickel par l'hydrogène a révélé l'influence de la transformation de Curie de l'oxyde sur la vitesse de réduction.

Entre 180 et 250°C, les courbes de vitesse présentent un maximum très net et l'énergie d'activation, déterminée à partir de ce maximum, est de 26.3 kcal./mole.

Au‐dessus de 250°, la forme des courbes changent brutalement pour présenter un palier correspondant à une vitesse constante. Entre 250 et 300°C, l'énergie d'activation calculée sur la vitesse du palier, est de 11.3 kcal./mole. Au‐dessus de 300°C, la cinétique est seusiblement indépendante de la température. D'autre part, des expériences réalisées avec un mélange H2‐H2O ont mis en évidence une très forte influence inhibitrice de l'eau au‐dessus de 250°C.
A principle of equivalent states for transport properties of multicomponent liquid systems
Authors: Cullinan Harry T.
Published: March 2009

The principle of equivalent states, previously developed for binary and dilute ternary systems, is extended to concentrated multicomponent liquid systems. Inferences are drawn from absolute rate theory to allow construction of working equations for the concentration variation of transport properties. The results are tested with available data.
An evaluation of methods for determining the parameters in the BWR equation of state using volumetric and heat capacity data
Authors: Bishnoi P. R. , Robinson D. B.
Published: March 2009

The use of linear programming was compared with non‐linear least squares techniques for estimating Benedict‐Webb‐Rubin (BWR) equation of state parameters to correlate the volumetric behavior of a fluid. The techniques were extended to estimate the parameters from the volumetric and heat capacity properties of a pure component. In the non‐linear least squares technique a convergence scheme, which is a combination of the Levenberg and Marquardt algorithms, was used. The volumetric behavior of carbon dioxide, methane and their mixtures was best correlated by the parameter sets obtained by the non‐linear least squares technique when volume was chosen as the dependent variable. For the simultaneous correlation of volumetric and heat capacity properties of carbon dioxide the non‐linear least squares technique was found to be superior to the linear programming technique.
Application of numerical hill‐climbing in control of systems via Liapunov's direct method
Authors: Bennett Howard A. , Luus Rein
Published: March 2009

The procedure of determining the control effort which minimizes the forward difference of the quadratic function x(k)TQx(k) combined with improving Q by numerical hill‐climbing is investigated to determine the feasibility of establishing time sub‐optimal control policies for both linear and nonlinear systems.

For linear systems, Rosenbrock's hill‐climbing procedure is more efficient for improving Q than the method of Hooke and Jeeves; moreover it yields policies closer to the optimum when the number of state variables exceeds six. The “best” value of Q obtained by hill‐climbing depends on the initial choice of Q and the initial state of the system x(0).

The evaluation, carried out with a linear gas absorber and a nonlinear continuous stirred tank reactor, shows that the combined sub‐optimal procedure yields results close to time‐optimal control with little computational effort.
A reversed two‐environment model for micromixing in a continuous flow reactor
Authors: Chen Michael S. K. , Fan L. T.
Published: March 2009

A reversed two‐environment model which consists of a maximum mixedness environment followed by a complete segregation environment is proposed. The model may be used to explain the segregation effect which is enhanced by the viscosity increase during the reaction. Comparison between the predicted results and the experimental data for the polymerization of styrene in a stirred tank flow reactor is presented.
Viscous flow through particle assemblages at intermediate reynolds numbers — a cell model for transport in bubble swarms
Authors: Leclair B. P. , Hamielec A. E.
Published: March 2009

The fluid mechanical behaviour of a bubble swarm was simulated using a cell model. The Navier‐Stokes equations were solved numerically for the liquid flow in a uniform assemblage of circulating, spherical bubbles. Ranges of parameters studied included, Reynolds numbers, 0–1000 and porosities, 0.4–1.

The numerical calculations show the effects of variations in Reynolds numbers and porosity on: surface vorticity and pressure distributions and form and friction drag coefficients. For all Reynolds numbers investigated a standing vortex ring was absent

Predicted drag coefficients and Sherwood or Nusselt numbers agree with limiting analytical solutions for low and high Reynolds numbers. The theoretical results show good agreement with experimental data for porosity as a function of superficial gas velocity. Predicted and measured Sherwood and Nusselt Numbers were in substantial disagreement, making detailed comparison unwarranted

The calculations should also be valid for dispersions of uniform, circulating, spherical droplets for the special case where the droplet viscosity is much less than the viscosity of the continuous fluid
Flow through porous media in the presence of sound
Authors: Beeckmans J. M. , Sen‐Gupta P.
Published: March 2009

The pressure gradient at a specified flow of air through beds of randomly packed spheres was found to be increased in the presence of sound in the frequency range 500 Hz to 1100 Hz. The phenomenon was studied at several sound frequencies, sound intensities, and flow velocities. A theoretical analysis yielded predictions of the magnitude of the increased pressure drop due to sound which agreed moderately well with experiment
Longitudinal mixing of the liquid phase in packed columns with countercurrent two phase flow
Authors: Co Pham , Bibaud R.
Published: March 2009

Axial mixing of the liquid phase in trickle flow through two columns packed with Raschig rings was determined by least square fitting of the experimentally obtained F‐curve applying the Fibonacci optimal search method. The Péclet number was found to be independent of the gas flow rate and proportional to the liquid Reynolds number. The one parameter axial dispersed plug flow model was shown to be acceptable in describing axial mixing of the liquid phase. A simple correlation of the Péclet number is proposed for application in mass transfer design calculations
Expansion‐contraction behavior of dilute polymer solutions
Authors: Bilgen E.
Published: March 2009

Expansion‐contraction behavior of capillary jets of dilute polymer solutions has been studied by using small diameter capillary tubes. The test liquids were water, glycerine solution and dilute solutions of polyethylene oxide and guar gum. It has been found that polyethylene oxide molecules degraded considerably at high shear rates; however the molecular degradation had little effect on the observed expansion‐contraction behavior of capillary jets. On the other hand, the solvent viscosity had an appreciable effect on the issuing jets and on the final magnitude of the evaluated normal stresses
The kinetics of titanium dioxide agglomeration in an agitated liquid suspension
Authors: Wahl E. F. , Baker C. G. J.
Published: March 2009

The agglomeration of two TiO2 pigments (0.2‐1.0μ) dispersed in an agitated 1% saline solution has been studied by a sequential count method using a Coulter counter. A model based on collision frequency due to the turbulent motion in a stirred vessel predicts the second order rate constant k to be proportional to agglomerate volume and to stirrer speed to the power 3/2. Experimental values of k were proportional to threshold volume to the power 0.79, stirrer speed to the power 1.3, and independent of TiO2 concentration
Absorption of carbon dioxide in ethylenediamine solutions i. absorption kinetics and equilibrium
Authors: Weiland R. H. , Trass Olev
Published: March 2009

The chemical absorption of carbon dioxide by a laminar jet of ethylenediamine has been studied at 25.5°C under pseudo‐first‐order kinetic conditions. The reaction was found to be second‐order with a rate constant of 1.0 x 105 1/g. mole sec. Equilibrium calculations at 18°C indicate that the partial pressure of carbon dioxide is very low, even over highly carbonated ethylenediamine solutions. The effects of amine concentration and carbonation ratio on the physical solubility and diffusivity of carbon dioxide in solution were inferred from corresponding results for nitrous oxide
Rates of reaction of SO2 with metal oxides
Authors: Deberry David W. , Sladek Karl J.
Published: March 2009

Rates of sorption of SO2 from synthetic flue gas by 14 metal oxides were determined. These oxides had been selected for their potential applicability to processes for removing SO2 from flue gas using thermal regeneration of sorbent. Measurements were performed using thermogravimetric analysis, and rates were fitted to semi‐empirical expressions; CeO2, Co3O4, Cr2O3, CuO, Fe2O3, and NiO displayed measurable rates in the range 200° to 500°C, and were converted to sulphates. Rates were immeasurably small at 25° to 800°C for Al2O3, Sb2O5, SnO2, TiO2, V2O5, WO3, ZnO, and ZrO2, CuO and CeO2 showed the highest rates
Optimisation d'un réaacteur multiéatagéa d'oxydation de l'anhydride sulfureux au moyen de trois méthodes directes (hooke et jeeves, rosenbrock, simplex).
Authors: Brusset H. , Depeyre D. , Boeda M. , Melkior R. , Staedtsbaeder J. L.
Published: March 2009

In the optimal design of multistage reactors for oxidation of sulfur dioxide, two important cost factors are considered: catalyst and heat exchange. The way to obtain the associated economic function is presented. A complete solution of the reactor train equation must be carried out to obtain each value of this implicit function of ten variables (injections of gas and temperatures in catalyst beds). To optimize the multistage reactor, three direct methods are adapted for a specific treatment of constraints on the variables. Two of these methods (Hooke and Jeeves, simplex) give satisfactory results and it appears possible to make a rational choice between exchangers and injections
The reduction of ferrous chloride with hydrogen
Authors: Miriyala V. R. R. , Bowen J. H.
Published: March 2009

Single pellet studies of the kinetics of reduction of ferrous chloride in hydrogen indicate that a significant resistance exists to diffusion of gases through the particles of which the pellets are composed. Experiments carried out at temperatures low enough for chemical reaction to be controlling enabled an activation energy of 39 k cals/g mole of ferrous chloride to be calculated
Laminar and turbulent entry flow of polymer solutions
Authors: Seyer F. A. , Catania P. J.
Published: March 2009

Entry lengths and contraction losses have been determined for 0.01, 0.2 and 0.6% aqueous solutions of Separan AP‐30. The Reynolds numbers ranged between 102 and 105 in 1/2‐in. and 2‐in. tubes. At Reynolds numbers in excess of 2100, the entry lengths and contraction losses for the polymer solutions are significantly larger than those for Newtonian fluids. These effects are shown to be related to the transitional flow phenomena which occur with drag reducing polymer solutions.

At low Reynolds number the contraction loss data show expected trends but are in quantitative disagreement with predictions based on recent studies in capillary tubes. These indicate that the analyses based on small tubes are less general than anticipated.
Drop size in power law non‐newtonian systems
Authors: Skelland A. H. P. , Raval V. K.
Published: March 2009

Drop volume studies were made by forming non‐Newtonian pseudoplastic drops in a continuous toluene phase and chlorobenzene drops in non‐Newtonian continuous phases. Combination of results for these cases enabled development of a correlation for the prediction of non‐Newtonian drop volume in a non‐Newtonian continuous phase. The development is confined to power law fluids and provides expressions for both long and short nozzles in terms of a two‐stage drop formation process. Variables included nozzle size, formation time, and rheological properties from eight non‐Newtonian systems in a program of 144 runs.
Statistical evaluation and design of an evaporator control system
Authors: Bacon David W. , Howe Gerald L.
Published: March 2009

The utility of a statistical procedure suggested by Box and Jenkins is assessed for the evaluation and modification of an industrial evaporator control system. Results, obtained from the analysis of routine unperturbed operating data, indicate that this approach is (i) readily adaptable to the analysis of the dynamic behaviour of a full scale chemical unit process, (ii) characterized by effective model form identification, and (iii) extremely useful in deriving conventional and more novel control functions to supplement existing control schemes.
Drag reduction and turbulence modification in rigid particle suspensions
Authors: Pirih R. J. , Swanson W. M.
Published: March 2009

Turbulent drag reductions on the order of 50% were obtained for pipe flow of submicron, rod‐like particle suspensions at weight concentrations of less than 0.5%. Wall Reynolds numbers as high as 40,000 were obtained for the suspensions. The suspended particle configuration was rigid and non‐elastic and was not affected by local strain rate fields. Longitudinal turbulence data are presented for two suspensions and for the Newtonian solvent at an average flow velocity of about 7 fps. Distinctly modified turbulence generation and dissipation were observed. The suspension exhibited smooth transitional flow behavior and increases in both macroscale and microscale. A particle length effect, or relaxation time effect, was observed with the larger relaxation time suspension exhibiting the more extreme flow and turbulence differences.
Aerosol particle collection in a vertical pneumatic transport line
Authors: Behie S. W. , Beeckmans J. M. , Knetting P. , Bulani W.
Published: March 2009

A vertical pneumatic transport line was found to be an efficient collector for 2.4 micron magnesium sulphate particles. Glass beads of average diameter 310 microns and 514 microns, lightly coated with a non‐volatile oil, were used as collector particles. The experimental results were in satisfactory agreement with a theoretical analysis based on an idealized single collector particle model. Electrostatic charging of the aerosol prior to entry of the collector particles did not materially alter the bead collection efficiency, with or without radial electric field in the transport line.
The effect of a uniform magnetic field on mass transfer in electrolysis
Authors: Mohanta S. , Fahidy T. Z.
Published: March 2009

By coupling uniform magnetic and electric fields, the effect of the magnetic field strength on cathode current density was studied in an experimental electrorefining cell. The increase, with respect to electrolysis in a purely electric field, in the rate of mass transfer is interpreted by an approximate mathematical model.
Multi‐component reboiled absorber modeling and parametric studies
Authors: Prowse D. R. , Johnson A. I.
Published: March 2009

The steady state operation of an industrial multi‐feed, multi‐component reboiled absorber column which was previously investigated by Petryschuk (1964) has been simulated by two alternate mathematical models — an equilibrium stage model and a tray efficiency model based on the Murphree tray efficiency concept. Development of the models required the use of a set of physical property estimation procedures which differed from those used by the previous investigator. When subjected to parametric variation studies, both new models successfully reproduce known quantitative and qualitative behavior attributed to the column. The study results demonstrate not only the sensitivity of a simulation of a multicomponent separation process upon physical property estimation procedures, but also indicates the difficulty in model discrimination when plant data of only limited range and accuracy is available.
Momentum transfer in a horizontal liquid‐jet ejector
Authors: Bhat P. A. , Mitra A. K. , Roy A. N.
Published: March 2009

The performance of a horizontal liquid‐air ejector system was greatly enhanced by creating mixing shock. Principles of macroscopic momentum and energy balances were employed to define an overall loss factor which was found to be a useful correlating parameter in the case of homogeneous bubble flow. Empirical correlations are proposed to predict mass ratio as a function of different parameters.
Holdup in vertical two and three phase flow Part I: Theoretical analysis
Authors: Bhaga D. , Weber M. E.
Published: March 2009

A general one‐dimensional theory for predicting the average holdup or column concentration in three phase flow is formulated. The analysis takes into account the local relative velocity between the phases, the non‐uniform flow and holdup distribution across the column, and the effect of the concentration of the dispersed phase on the relative velocity. The present theory is compared with the previous analyses for two phase flow reported in the literature and it is shown that all of them are special cases of the general theory proposed here.
Effect of ultrasonic waves on the activity of chromia‐alumina catalyst
Authors: Mathur Indresh , Bakhshi N. N. , Mathews J. F.
Published: March 2009

It has been found that the supported metal catalyst, chromia on alumina, prepared in the presence of ultrasonics (90 kHZ) is a more active catalyst for the decomposition of hydrogen peroxide (8N aqueous solution) than the catalyst prepared in the absence of ultrasonics. The catalyst preparation consisted of insonation for one hour during the impregnation stage and subsequent drying and calcination. The activity measurements were carried out at 25, 30, 40, 50 and 60°C in a batch reactor. The higher activity of the insonated catalyst has been explained on the basis that chromia is better dispersed on alumina in case of the insonated catalyst. The conclusion for the better dispersion of metal in the insonated case is based on BET surface areas and pore volumes and on electron microprobe analyser measurements of chromium metal distribution.
Suboptimal control of chemical engineering systems
Authors: Cormack D. E. , Luus Rein
Published: March 2009

To greatly simplify the two point boundary value problem encountered in optimization, the n‐dimensional state space is mapped into a scalar V‐domain by the quadratic transformation

as suggested by Schlossmacher and Lapidus. When Pontryagin's maximum principle is then applied to the system in this V‐domain, the two point boundary value problem contains only a single scalar adjoint equation.

A new computational form for the adjoint equation and an efficient a priori method of determining an effective Q are presented. The two point boundary value problem is solved by choosing the initial value of the adjoint variable that minimizes the performance index. A straightforward numerical minimum seeking procedure is used to locate this adjoint.

Evaluation of this suboptimal procedure with respect to the optimization of a linear gas absorber, a nonlinear CSTR and a plug flow reactor shows that such a procedure yields results close to the optimal.
Nonlinear parameter estimation and model distinguishability of physicochemical models at chemical equilibrium
Authors: Blau G. E. , Klimpel R. R. , Steiner E. C.
Published: March 2009

The problem of estimating parameters and distinguishing between rival mathematical models describing complex chemical equilibrium systems is formulated from first principles. Using basic statistical and optimization theory, a methodology is developed for handling these systems. To illustrate its usefulness, the technique is applied to the conductivity study of solutions of alkali metal alkoxides in dimethyl sulfoxide. The method is relatively involved and its use is warranted only in complex physical systems which do not lend themselves to simplification by standard procedures.
Friction in turbulent flow of solids‐gas systems
Authors: Peters Leonard K. , Klinzing George E.
Published: March 2009

Two‐phase solids‐in‐air flow was experimentally studied in a once‐through circular tube flow system using nominal 25μ and 50μ spherical glass beads. At mass flow ratios up to 1.6, the friction factor was found to be generally higher than that for air flow alone but considerably less than that for a single‐phase fluid having a density the same as that of the mixture.

The pressure drop experienced by the 2 phase system of 25μ beads and air was found to show true drag reduction.

A continuum mechanics analysis showed the viscous stresses and Reynolds stresses to be significantly affected by solid particle addition.
A gas chromatographic method for the determination of mass‐transfer resistances in zeolite catalysts
Authors: Macdonald W. R. , Habgood H. W.
Published: March 2009

The various mass‐transfer resistances that occur in a packed bed of zeolite granules contribute to the gas chromatographic “C” terms that determine the relative width (or second moment) of a gas chromatographic peak. It was assumed that mass transport in the micropores of the crystallites was independent of the nature of the carrier gas. From measurements with hydrocarbon pulses in hydrogen and nitrogen carrier gases, it was possible by the method of Giddings and Schettler to separate the gas phase resistances from the micropore resistances. Data are given for benzene, n‐octane and (in part) n‐decane on Na × zeolite at 370, 400 and 430°C. Experimental difficulties and precautions are discussed.
Salt effects in liquid‐vapor equilibrium: A new equation for the ethanol‐water system saturated with salt
Authors: Jaques D. , Furter W. F.
Published: March 2009

A new equation for salt effect in vapor‐liquid equilibrium is presented, which correlates temperature and the liquid‐phase concentrations of all three components with equilibrium vapor composition, for isobaric systems consisting of a binary to which • salt has been added to saturation. The equation, of form

was tested successfully with literature data for 12 ethanol‐water‐salt systems, yielding a better fit for all 12 systems than the one‐constant equation of Johnson and Furter, and with the confidence level for the comparison in excess of 99.9% for six of thesystems tested.
Optimal state changeover control of a multivariable system using a minicomputer
Authors: Jarvis R. C. F. , Wright J. D.
Published: March 2009

A study of the application of the calculation and implementation of an open loop optimal changeover policy for a multivariable system on a minicomputer has been made. If the required changeover time and control time interval have been specified, a switching policy for the controls may be calculated using standard linear programming techniques. The multivariable system was an analog computer simulation of a liquid‐liquid extraction column.

By repeated use of the procedure with different overall changeover times, a “best” changeover policy could be determined. The criterion for this policy was a minimum changeover time with the restriction that the sum of squared errors between the required and actual final states was less than a specified small value. Practical as opposed to theoretical small values of this error criterion were used.
Counter‐current solid liquid extraction in a cascade of batch extractors
Authors: Plachco F. P. , Lago M. E.
Published: March 2009

An analytical solution and method of calculation is presented for a cascade of N perfectly mixed batch extractors operating counter‐currently, for spherical solid particles, with parameters which may vary for each extractor.

The results for the case of constant and equal parameters along the complete cascade are presented in dimensionless plots; N varies from 1 through 10.

The practical interest of these diagrams lies in their use in design and/or in foreseeing the behavior of a cascade when its parameters undergo variations.

A sample calculation is included.
Batch separations with tails recycle
Authors: Colbert John W.
Published: March 2009

This study develops material balance calculation techniques for repetitive batch separation processes in which the tails stream is collected in fractions which are recycled to the next batch at appropriate intervals.

Criteria for selecting the fraction sizes which minimize total separative work per unit of products are determined. In the electrolytic rectification of a D2O‐H2O mixture from 20 to 99.8% D2O at a separation factor of 11, for example, three fractions thus selected are adequate and the separative work is considerably less than that of the more conventional cascade system.
Process design considerations and steady‐state operational data for the separations of isotopes of oxygen
Authors: Wolf D. , Cohen H.
Published: March 2009

Operational data for the separation of oxygen isotopes are given on flow rates, concentrations and concentration profiles of the isotope separation plant of the Weizmann Institute of Science which has reached steady‐state operational conditions with regard to the rare and more difficult to separate oxygen‐17 isotope. This plant consists of two sections, namely packed distillation columns and thermal diffusion columns. Data on the columns and packing characteristics are given. The concentrations reached in the distillation section are up to 98% of oxygen‐18 and up to 20% of oxygen‐17. In the thermal diffusion section, concentrations of oxygen‐18 up to 99.9% and of oxygen‐17 up to 96% have been attained.
The transient behavior of an ethane dehydrogenation furnace
Authors: Li M. C. , Johnson A. I.
Published: March 2009

A mathematical model of the transient behavior of an existing ethane dehydrogenation furnace is discussed. The correlation of pressure drop with time has been found from the available data. The fractional carbon deposition and the multiplier coefficient of a pressure drop equation have been determined by the direct search optimization technique of Hooke and Jeeves.

A considerably improved policy for the operation of the furnace was determined by considering plant temperature profile and hydrocarbon/steam ratio as parameters for maximizing average ethylene produced per day. The effect of temperature profile on the distribution of carbon deposited along the reactor was also predicted and discussed.
Identification of one phase flow processes
Authors: Malpani S. N. , Donnelly J. K.
Published: March 2009

A method is presented for the identification of parameters in the partial differential equations describing the dynamic behaviour of a certain class of one phase flow processes. Included in this class of processes are certain types of heat exchangers and flow reactors in which axial and radial dispersion are not important. The approach employed is to reduce the partial differential equations to an extended system of ordinary differential equations with the method of characteristics. Once in this form the method of quasilinearization is employed to identify the parameters in these ordinary differential equations.
Vertical pneumatic conveying: An experimental study with particles in the intermediate and turbulent flow regimes
Authors: Capes C. E. , Nakamura K.
Published: March 2009

Vertical pneumatic conveying was studied in a 3‐inch diameter riser 30 feet in length using solids ranging in particle Reynolds number from 100 to 3500. Particle to gas mass flow ratios varied from 0 to 8 and pipeline conditions extended from dilute flow down into the choking region.

Average particle hold‐up was determined by means of a series of quick‐closing valves and particle slip velocity was often found to be greater than the calculated terminal velocity. The reasons for this are examined.

Frictional pressure losses in the riser were also determined and compared with literature data. The phenomenon of choking is considered briefly.
Statistical thermodynamics of group interactions in n‐alkanone pure liquids and solutions
Authors: Lee Tsung‐Wen , Greenkorn Robert A. , Chao Kwang‐Chu
Published: March 2009

The statistical thermodynamics of group interaction previously developed for liquids of chain molecules is extended to their mixtures. The theory is applied to pure n‐alkanone liquids, and solutions of n‐alkanone/n‐alkanone and n‐alkane/n‐alkanone systems. The interaction properties of methyl and methylene groups are taken from our previous work. The interaction properties of carbonyl group are determined and reported in this work. The calculated density and heat of vaporization of pure n‐alkanone‐2 liquids agrees with data over a wide temperature range. The calculated heats of mixing of n‐alkanone/n‐alkane and n‐alkanone/n‐alkanone solutions agree with available data.
Tracer measurements in two phase annular flow to obtain interchange and entrainment
Authors: Jagota A. K. , Rhodes E. , Scott D. S.
Published: March 2009

Experimental methods are described which yield information on entrainment and liquid interchange in two phase annular flow by using a model based on the response of the system to a steady injection of tracer in the film. Independent measurements of entrainment are also reported. The results indicate that if care is taken to ensure uniform continuous tracer injection and correct response measurement, it is possible to obtain reasonable values of the entrainment and interchange parameters. The annular flow model presented in an earlier paper1 appears to give a useful description of the interchange process.
Influence d'une agitation rotative sur le mélange en retour dans une colonne pulsée à plateaux perforés
Authors: Barame S. , Molinier J. , Angelino H.
Published: March 2009

Si l'on superpose une agitation rotative à l'agitation produite par la pulsation dans une coloune à plateaux perforés on obtient de meilleures efficacités surtout pour des valeurs du produit A.f assez faibles. Les auteurs ont mesuré experimentalement la rétention et le nombre de Péclet dans ce nouvel extracteur afin d'en déduire le coefficient de mélange en retour de la phase continue.

En comparant leurs résultats avec ceux que l'on obtient dans une colonne pulsée standard ils montrent que l'amélioration d'efficacité doit ětre attribuée à l'augmentation de rétention et non pas, comme on pouvait le penser, à la diminution du mélange en retour.
Élements de calcul des colonnes de fractionnement par moussage continu
Authors: Rovstan M. , Roqves H.
Published: March 2009

On étudie le fractionnement par inoussage consider comme une operation unitaire. Une théorie basée sur l'analyse dimensionnelle, permet de calculer le fonctiomnement des colonnes en continu. On évalue numériquement le taux de reflux interne R1 résultant de l'instabilité de la mousse. On introduit les notions de productivité spécifique P* de la colonne et d'apport énergétique spécifique E*. Une relation est établie pour corréler P* et les paramètres caractérisant la géométrie (diamètre de colonne, hauteur de mousse) et son mode opératoire (débit d'air, taux de reflux externe, débit d'alimentation, concentration d'alimentation, niveau d'alimentation).
Catalytic reduction of nitric oxide in low concentration high velocity gas streams
Authors: Lamb A. , Tollefson E. L.
Published: March 2009

A catalytic micro‐reacting system and a gas chromatographic analytical method were used to investigate the effectiveness of metal alloys in the catalytic reduction of nitric oxide by hydrogen. Oxidative pretreatment significantly increased the catalytic activity. The rate of nitric oxide removal was directly proportional to hydrogen concentration but independent of nitric oxide concentration. Temperatures were 378 — 500°C, space velocities 42,000 — 54,000 hr−1 and hydrogen and nitric oxide concentrations 400 — 55,000 ppm and 600 — 6,800 ppm, respectively. The data support a mechanism involving adsorbed nitric oxide and hydrogen molecules, the rate determining step being the collision of the latter with the catalyst surface. Some selectivity towards nitric oxide reduction in the presence of oxygen was observed.
The multicomponent solubility of hydrocarbons in water
Authors: Leinonen Paul J. , Mackay Donald
Published: March 2009

The aqueous solubility of six binary hydrocarbon systems consisting of benzene and cyclohexane with each of 2‐methyl‐pentane, n‐hexane, and l‐hexene, have been measured at 25d'C. The solubility of each hydrocarbon component is greater by from 6 to 35% than the value expected by prediction on the basis of the solubility of the hydrocarbon component being proportional to its mole fraction in the hydrocarbon phase. This positive deviation is partly attributable to the activity coefficient of the hydrocarbon in the hydrocarbon phase being slightly greater than unity. There is, however, additional solubility enhancement of from 1 to 25% with an average of 10.7% apparently due to the reduction of the hydrocarbon activity coefficients in the aqueous phase by the presence of the other hydrocarbon. The implications of these effects in calculating the solubility of complex hydrocarbon mixtures in water is considered.
Production of mono‐dispersed drops by forced vibration of a liquid jet
Authors: Rajagopalan R. , Tien Chi
Published: March 2009

The production of mono‐dispersed liquid drops by controlled vibration of a liquid jet issuing from a capillary has been investigated experimentally. The variables studied are the physical properties of the liquid, the dimensions of the capillary and the frequency and amplitude of the vibration. Stainless steel hypodermic needles of various sizes (22G to 30G) were used as capillary and the test liquids were water, aqueous solutions of human serum albumin (HSA) and aqueous solutions of glycerol. The experimental results reveal conditions under which drops of good mono‐dispersity can be produced.
Permeation of hydrocarbon gases through polymer membranes
Authors: Chung T. S. , Howell J. A.
Published: March 2009

Experimental results are presented for the permeation of propane and ethylene through polyethylene membranes and for the permeation of propane through “Saran” in the temperature range from —10 to 20°C and the pressure range from 20.0 to 50.0 psig. The flux of propane through polyethylene exhibits a minimum as the temperature approaches the condensation temperature. No such minimum was observed either for the flux of ethylene through polyethylene or for propane through “Saran”.

The permeability coefficients for propane through polyethylene are compared with those predicted on the assumption of a diffusion coefficient exponentially dependent on the concentration of permeability.
Measurement of residence times, and film and drop velocities in two phase annular flow
Authors: Jagota A. K. , Rhodes E. , Scott D. S.
Published: March 2009

The development of tracer pulse techniques for measuring mean film and droplet velocities (film and droplet residence times) in vertical two phase annular flow is described. Results of experiments are discussed, and compared to a computer simulation of a tracer pulse in annular flow as described by the interchange model. The experiments show that the mean film velocity can be determined accurately, but not the droplet velocity. The computer simulation supports the experimental results. The effect of interchange is also shown to be sufficiently large in much of the annular flow region to give average film and droplet residence times which are not greatly different.
Solids entrainment in a large gas fluidized bed
Authors: Fournol A. B. , Bergougnou M. A. , Baker C. G. J.
Published: March 2009

Entrainment from a gas fluidized bed of cracking catalyst in a 2‐ft diameter column equipped with continuous solids recycle has been studied. Radial profiles of entrainment rate and mean particle size were relatively flat. The entrainment rate decreased rapidly with increasing height above the bed and with decreasing fluidizing velocity. The existence of a transport disengaging height above which the entrainment rate and mean particle size become essentially constant was confirmed experimentally. This may be taken as the height above the bed surface at which the inverse Froude number becomes equal to 1000.
Friction reduction by chemical additives in the turbulent flow of fibre suspensions
Authors: Bilgen E. , Boulos R.
Published: March 2009

The effect of friction reducing additives on the turbulent flow characteristics of fibre suspensions have been studied experimentally by using a small diameter straight tube and a free rotating disk. The fibre concentration varied between 0.1 and 5.0%. The friction reducing additives were polyethylene oxide and guar gum. The optimum conditions for friction reduction and effects of temperature, aging and mechanical degradation have been determined; the viscoelastic behaviour of fibre suspensions with and without additives have also been studied. It is shown that the use of friction reducing additives in the turbulent flow of paper making fibre suspensions results in a friction reduction comparable to that in water and the quality of fibre suspensions can be improved.
Oxidation of propane over a diesel exhaust catalyst
Authors: Wanke Sieghard E.
Published: March 2009

The oxidation of propane, over a concentration range of 0.30 to 1.04 mole % in air was investigated over a commercial diesel exhaust catalyst consisting of CuO, Cr2O3and Pd supported on Al2O3. The rate of reaction was correlated by a first order, irreversible rate function; the resulting pre‐exponential factor and activation energy were 3.15 × 107cc/g‐sec and 21.3 kcal/gmole, respectively. At high temperatures the reaction rate became influenced by pore diffusion. A temperature of 675°K was required to obtain 50% propane conversion. It was concluded that this catayst is unsuitable for catalytic mufflers on diesel buses since the measured value of diesel exhaust temperatures at the cataytic muffler inlet is significantly less than 675°K.
Identification of a packed absorption column
Authors: Malpani S. N. , Donnelly J. K.
Published: March 2009

A method is presented for the identification of parameters in the partial differential equations describing the dynamic behaviour of a certain class of two phase flow processes. This method is an extension of a procedure for the identification of single phase flow processes which were introduced in a previous paper. The method is applied to the identification of two parameters in the five simultaneous partial differential equations describing the behaviour of a packed absorption column being used to remove carbon dioxide from air with an aqueous solution of monoethanolamine. These parameters were determined from a single experimental step response. The approach employed was to reduce the partial differential equations to two coupled systems of ordinary differential equations by the method of characteristics. Once in this form the identification problem could be formulated as two coupled boundary value problems and solved with the use of quasilinearization.
The optimization of serial processing systems
Authors: Bundgaard‐Nielsen M. , Rono P. E.
Published: March 2009

The literature on applications of dynamic programming in the chemical processing industries is quite comprehensive. However, only a few studies have been conducted in which the strategy of dynamic programming has been compared with efficient optimization algorithms not utilizing the structural properties of the optimization problem in question. The purpose of this short note is to report on the results of such a comparative study and to suggest some general guidelines as to the proper choice of optimization strategy when dealing with serial processing systems in the chemical industry.
Drag coefficients and pressure drops for hydrodynamically suspended spheres in a vertical tube with and without polymer addition
Authors: Latto B. , Round G. F. , Anzenavs R.
Published: March 2009

The pressure drops associated with the suspension velocities for single, hydrodynamically suspended spheres were measured for a range of steel spheres in a 5.3 cm diameter vertical glass tube. Nineteen different sphere to tube diameter ratios (d/D) were investigated ranging from 0.191 to 0.967. Three different liquid media were used: pure water, and two polyacrylamide solutions of concentration 25 wppm and 50 wppm of Reten 423.

In the range 0 < (d/D) < 0.7 polymer addition increased the drag coefficient. For d/D > 0.7 the drag coefficient was not affected. The available data for air, water and polymer solution were correlated with an equation explicit in pressure drop, and the agreement between theory and experiment was found to be excellent.
Exact solutions for a class of heat and mass transfer problems
Authors: Davis E. James
Published: March 2009

A number of heat and mass transfer problems of chemical engineering interest involve the convective diffusion equation of the form

where θ = θ(X1, X2). Exact solutions for such problems are developed in terms of well‐known functions which have been thoroughly studied in recent years. Several problems which have appeared in the literature, solved by completely numerical methods, are re‐examined and new problems are discussed and solved. The results of the present analysis are compared with those obtained by other methods where possible. The problem of axial diffusion of heat or mass is solved in terms of known functions.

The present formulation is shown to be particularly useful in the analysis of conjugated boundary value problems, i. e. for problems involving heat or mass transfer across an interface where the interfacial boundary condition is not known a priori but is related to the temperature or concentration fields in the adjacent phases.
Interpretation of experimental rates of reaction for multiple step chemical reaction systems: Part I: A general modelling procedure
Authors: Lana I. G. Dalla , Myint A. , Wanke S. E.
Published: March 2009

Experimental kinetic data in a form equivalent to concentration‐time trajectories (or the corresponding rates of reaction) may be decomposed into rate data for the individual chemical reaction steps defining a chemical reaction network. When kinetic models are fitted to each set of single‐step rate data, the resulting single‐step kinetic models may be combined to formulate an overall kinetic model for the network. Such network‐kinetic models may exhibit consistency with both the apparent chemistry and the observed rate behaviour.
Symposium on application of pulse techniques to kinetic measurements: Étude d'une réaction homogène rapide d'ordre deux en phase gazeuse par des méthodes transitoires dans un réacteur autoagité
Authors: David Et Rene , Villermaux Jacques
Published: March 2009

The determination of the kinetics of butadiene dimerization, a second‐order rapid and homogeneous reaction, could be determined in a continuous reactor which was thoroughly stirred in a gas phase by jets from nozzles. The above reaction was studied between 500°C and 600°C by means of a transient method based on the deformation of a concentration pulse signal while crossing the reactor.

A study was also made of a modification of the transient method which consisted in superimposing a small pulse to a continuous feed of reactant. The linearization permitted to bring the reaction back to an apparent first order one with respect to the butadiene concentration.

The concentration signals were measured by means of a mass spectrometer and stocked in actual time on an IBM 1800 computer.

The results found in both cases agreed well with those described in the literature and with those of the conventional method in a steady system.

The following expression of the kinetics constant was obtained.