bluuebunny/crossref_metadata_2025_split huggingface dataset:
Catalyst modification and process design considerations for the oxidation of low concentrations of hydrogen sulfide in natural gas
Authors: Chowdhury A. I. , Tollefson Eric L. 
Published: March 2009

AbstractLow concentrations of hydrogen sulfide (H2S) in natural gas can be selectively oxidized over an activated carbon catalyst to elemental sulfur, water and a small fraction of sulfur dioxide (SO2). Efforts to improve catalyst performance and product sulfur quality have been made by a) modification of the catalyst composition b) removal of the heavy hydrocarbons from the feed and c) choice of reaction conditions. The use of a guard bed to absorb heavy hydrocarbons and operation at elevated pressures show positive results. A preliminary flow diagram incorporating these findings has been prepared for a small commercial unit capable of processing sour natural gas containing 1.0% H2S.
Dispersed phase holdup and bubble size distributions in gas–liquid cocurrent upflow and countercurrent flow in reciprocating plate column
Authors: Sundaresan A. , Varma Y. B. G. 
Published: March 2009

AbstractDispersed phase holdup and the bubble size distribution were measured in a reciprocating plate column under cocurrent upflow and countercurrent flow of gas and liquid phases. The response of the system to a variation in design and operating conditions was found similar to that for liquid–liquid contacting; the magnitude of response, however, differed significantly between them.Taking into consideration the dominant forces encountered in gas–liquid dispersions, the experimental data are satis–factorily correlated in terms of Froude, Weber and Gallileo numbers.
Laminar mixed convection in the thermal entrance region of horizontal rectangular channels with uniform heat input axially and uniform wall temperature circumferentially
Authors: Chou Fu‐Chu 
Published: March 2009

AbstractThis paper presents a numerical study on laminar mixed convection in the thermal entrance region of horizontal rectangular channels with uniform heat input axially and uniform wall temperature circumferentially. A relatively novel numerical method of solution is developed to obtain the developing velocity and temperature fields. The values of Prandtl number are 0.7 and 7.2, corresponding to air and water, respectively. The values of Rayleigh number are 0, 104, 3 × 104 and 105. The channel aspect ratios considered are 0.2, 0.5, 1, 2 and 5. Variations in local friction factor ratios and local Nusselt numbers are presented. It is found that the circumferential boundary condition of uniform wall temperature significantly increases the value of local Nusselt number as compared to that found in earlier works under the boundary condition of uniform wall heat flux. But the boundary condition effect on the friction factor is shown to be comparatively minor. The asymptotic solutions at z → are compared to the existing numerical data with good agreement.
Influence of particle size and particle/fluid combination on particulate fouling in heat exchangers
Authors: Blöchl R. , Möller—Steinhagen H. 
Published: March 2009

AbstractThe influence of particle size on particulate fouling rates during convective sensible heat transfer to liquids has been investigated. Experiments have been carried out using aluminum oxide particles with nominal diameters ranging from 0.06 μm to 15 μm, suspended in an organic solvent for a wide range of concentrations. The observed influence of particle size on the asymptotic fouling resistance is compared with the predictions of the Watkinson–Epstein model. The results of this comparison suggest that, in addition to the changes of mass transfer coefficient with increasing particle size, reduced adhesion forces between particles and wall and increasing removal forces have to be considered as well. Additionally, the influence of different particle/fluid combinations was investigated. Experiments were performed with aluminum oxide particles suspended in isopropanol, isobutanol or water, and with kaolin particles suspended in water.
A study of liquid molar volumes for some pure halogenated hydrocarbons and their binary mixtures
Authors: Ström Krister H. U. 
Published: March 2009

AbstractLiquid volume data have been measured at compressed liquid conditions for four pure refrigerants, CCl3 F, CCl2 F2, CHClF2 and C2 Cl2 F4, and three mixtures, CCl2 F2/CCl3 F, CCl2 F2/C2 Cl2 F4, and CHClF2/C2 Cl2 F4. A comparison of measured data and data reported in the literature with calculated data by three methods is presented. The three methods are the Thomson‐Brobst‐Hankinson correlation, and two equations of state according to Carnahan‐Starling‐de Santis and Lee‐Kesler‐Plöcker. In general the Thomson‐Brobst‐Hankinson correlation shows a smaller deviation from experimental data than the two equations of state examined.
Selective formation of 2‐methyl‐2‐butene and 2‐methyl‐1‐butene: Operating conditions and kinetic analysis
Authors: Chiesa G. R. , Perez C. F. , Orio O. A. , Ardissone D. 
Published: March 2009

AbstractThe effect of linear gas velocity, catalyst particle size, reaction temperature, space time, etc. on the dehydration of amyl alcohols (from fusel oil) was studied, using as catalyst a pre‐treated bentonite. The analysis of the kinetic data, using Hougen‐Watson type models, gives as the best model one in which amyl alcohol is absorbed on two active sites, the reaction rate being determined by the surface reaction of absorbed species.
Gas entrainment rate and flow pattern of vertical plunging liquid jets
Authors: Kusabiraki Daisuke , Niki Hidefumi , Yamagiwa Kazuaki , Ohkawa Akira 
Published: March 2009

AbstractFor a vertical plunging liquid jet system using various liquids, the effects of the operating conditions including the nozzle length‐to‐diameter ratio on the gas entrainment rate Qg were evaluated experimentally. The differences in Qg were related to the changes in the jet shape before plunging and the velocity of the plunging liquid jet at the point where the gas sheath breaks up. Empirical relationships were also presented to predict the maximum depth Z of bubbles entrained by the diffusing jet. The changes of Z were further discussed in terms of the downward liquid velocity distribution in the submerged two‐phase region, which depends mainly on the size of entrained bubbles.
A kinetic study of pyrolysis in pitch impregnated electrodes
Authors: Kocaefe D. , Charette A. , Ferland J. , Couderc P. , Saint‐Romain J. L. 
Published: March 2009

AbstractCarbon electrodes impregnated with three different pitches have been studied and compared. The electrode samples were heated up to 893 K in a thermogravimetric analyser at different heating rates. The weight loss was recorded with respect to time and temperature. A special technique and a calculation procedure have been developed to handle the pitch dripping from the electrode at low temperatures. A kinetic model assuming a first order reaction rate was used to interpret the data. This paper presents the experimental technique and the results of the study. The model predictions are compared with the data which shows a good agreement.
Long range predictive control of a polymerization reactor
Authors: Inglis M. P. , Cluett W. R. , Penlidis A. 
Published: March 2009

AbstractThis paper examines the application of generalized predictive control (GPC), one in the class of long‐range predictive algorithms, to the control of conversion of methyl methacrylate (MMA) monomer in a simulated CSTR, and to the control of temperature in a pilot plant batch polymer reactor. The control objective is regulation in the presence of (i) stochastic disturbances due to impurities (in the case of the CSTR), and (ii) pulse disturbances from the addition of cold solvent and initiator (in the case of the batch reactor). The role of the observer polynomial as a detuning parameter for trading off performance against variability in the control action is emphasized. Also, the role of data prefiltering, prior to model parameter estimation, is examined. A frequency domain interpretation of the least squares estimation algorithm is used to clarify the role of the filter.
Nonlinear predictive control using multi‐rate sampling
Authors: Bequette B. Wayne 
Published: March 2009

AbstractA nonlinear predictive control (NLPC) strategy based on a nonlinear, lumped parameter model of the process is developed in this paper. A constrained optimization approach is used to estimate unmeasured state variables and load disturbances. Additional model/process mismatch is handled by using an additive output term which is equivalent to the Internal Model Control approach. Similar to linear predictive control methods, an optimal sequence of future control moves is determined in order to minimize an objective function based on a desired output trajectory, subject to manipulated variable constraints (absolute and velocity).Deadtime is explicitly included in the model formulation, giving NLPC the same deadtime compensation feature of linear model‐predictive techniques. The multi‐rate sampling nature of most chemical processes is also used to improve estimates of process disturbances. Infrequent composition measurements in conjunction with frequent temperature measurements are used to improve the “inferential” control of the composition in a continuous flow stirred tank reactor (CSTR).
Hydrodynamics of a vibrating perforated plate extraction column
Authors: Rao N. V. Rama , Vijayan S. , Baird M. H. I. 
Published: March 2009

AbstractHydrodynamic behaviour of several liquid‐liquid systems has been measured in a 5 cm diameter extraction column agitated by finely perforated plates vibrating at frequencies (f) 10–100 Hz and amplitudes (a) 0.024–1.5 mm. The Sauter mean droplet diameter is generally in the range 0.1 to 1 mm. It has been correlated empirically with af2, system properties and operating conditions. Dispersed phase holdup, when plotted against the product af, showed minimum values corresponding to the transition from mixer‐settler to emulsion regime. Holdup was also found to be affected by mass transfer and its direction. Entrainment of fine droplets in the continuous phase occurs at high agitation levels, but can be reduced by the addition of coalescence plates at the base of the column. Energy dissipation rates greatly exceed predictions from the quasi‐steady‐state model.
Impingement heat transfer under a confined slot jet. Part II: Effects of surface motion and throughflow
Authors: Polat S. , Mujumdar A. S. , Douglas W. J. M. 
Published: March 2009

AbstractLocal and average heat transfer coefficients were measured for a confined turbulent slot jet impinging on a moving surface at which there may be throughflow. Profiles of the local convective coefficient at the impingement surface were obtained using a fast responding, highly sensitive porous heat flux sensor. The decrease in average heat transfer with surface motion is not negligible, ∼20%, at values of the surface motion parameter, Mvs, comparable to those used in industry. The enhancement of heat transfer by throughflow at a moving impingement surface is linearly additive and, when expressed as δSt, is proportional to only the throughflow parameter, Mus, with a proportionality constant of 0.17 which is independent of Re, Mvs or extent of the heat transfer surface.
Salting out crystallization of sodium sulfate
Authors: Mina‐Mankarios George , Pinder Kenneth L. 
Published: March 2009

AbstractThe growth and nucleation rates of sodium sulfate crystals salted out from their solution in a 38% w/w sulfuric acid solvent by the addition of an 80:20 w/w methanol:water solution, were determined from measurements of the steady‐state crystal size distribution (CSD) generated in a continuous mixed‐suspension, mixed‐product‐removal (MSMPR) salting out crystallizer. The effects of the supersaturation, the crystal suspension density and the temperature on these rates were investigated. The effect of the Cr+++ impurity was also briefly studied.The growth rate kinetic order g was determined to be essentially unity. The nucleation rate kinetic order b was determined as 2.11. The corresponding kinetic rate constants KG and KB were fitted to an Arrhenius type temperature dependence to give.KG = 43960 exp(‐24600/RT)andKB = 0.064 exp(70900/RT)where R is in kJ/kmol · K. An increase in chromate impurity concentration caused an increase in the growth rate constant KG but had no significant effect on the nucleation kinetics.The kinetiics of crystallization as determined for this system would indicate that a high temperature, high crystal suspension density and long residence time are conditions which are favorable for the production of large sodium sulfate crystals.
On the use of approximate velocity profiles for modeling multiphase reactors
Authors: Zimmerman William H. , Bukur Dragomir B. 
Published: March 2009

AbstractThe use of an approximate axial gas velocity profile in a two‐phase reactor model has been studied. The approximate velocity was assumed to vary linearly with conversion, which reduces the number of differential equations to be solved. The approximate model was studied in systems with one or two reactions. In most cases, the approximate and rigorous solutions were in good agreement. However, when mass transfer strongly influenced the velocity profile, errors in conversion became significant (∼ 15%). Reactions with no change in the number of moles are also subject to errors if the rigorous velocity profile is not accounted for.
Deactivation of cracking catalyst in short contact time reactors: Alternative models
Authors: Kraemer D. , De Lasa H. I. , Larocca M. 
Published: March 2009

AbstractSeveral mathematical models have been used to describe the deactivation of cracking catalysts by coke. For the case of gas oil cracking under short contact times (less than 20 seconds) it was found, using data from two different experimental reactor units, that an exponential decay function or a power law function could equally represent the data. Both functions are forms of the general hyperbolic decay expression; however, the power law assumes the unrealistic limits of infinite catalyst activity at zero time‐on‐stream and requires two parameters to describe deactivation. This work shows that the simple first order decay function is an effective equation to be used in describing catalyst activity decay for short reaction times.
Nutrient and metabolite gradients in mammalian cell hollow fiber bioreactors
Authors: Piret J. M. , Devens D. A. , Cooney C. L. 
Published: March 2009

AbstractThis work has investigated high density CRL‐1606 hybridoma cell culture in the shell‐side of ultrafiltration hollow fiber bioreactors. Oxygen depletion was measured in the recycle stream, and has been identified as the critical, axial scale‐limiting factor in these reactors. The composition of the extracapillary space has been studied by rapidly freezing these reactors in liquid nitrogen to recover samples of the shell‐side environment. The accumulation of inhibitory metabolites should have only a marginal impact on growth and product formation of this hybridoma cell line. Oxygen depletion is expected to be the major limiting factor for both the axial and radial scale‐up of hollow fiber bioreactors.
Modelling of addition polymerization processes — Free radical, ionic, group transfer, and ziegler–natta kinetics
Authors: Ray W. Harmon 
Published: March 2009

AbstractA brief review of addition polymerization processes is presented with a summary of the key characteristics classified by kinetic mechanism (free‐radical, anionic, cationic, group transfer, or Ziegler–Natta), phase behavior, and reactor type. A practical approach to modelling in the industrial R & D environment is discussed in terms of a CAD package for polymerization processes.
Hydrodynamics of disturbed flow and erosion–corrosion. Part II — Two‐phase flow study
Authors: Nešič S. , Postlethwaite J. 
Published: March 2009

AbstractErosion–Corrosion in turbulent, two‐phase liquid/particle flow with recirculation, after a sudden pipe expansion is studied by the application of a numerical flow model along with two different erosion models. The flow model, which is based on a two‐phase flow version of a standard two‐equation model of turbulence and a stochastic simulation of particle‐fluid turbulence interactions, is capable of successfully predicting local values of time averaged fluid velocities and turbulent fluctuations, as well as predicting particle dispersion and particle‐wall interaction. The erosion models used are that of Finnie (1960) and a modified version suggested by Bergevin (1984).The agreement of the predicted and measured hydrodynamic parameters, for flow through a sudden expansion, was satisfactory. Predictions of erosion rates using Bergevin's modified model were in good agreement with the stainless steel erosion measurements for a 2% water/sand slurry flow. The erosion–corrosion model was successful in predicting the overall pattern and rates of metal loss for carbon steel.
Hydrodynamics and mass transfer in an upward venturi/bubble column combination
Authors: Huynh L. X. , Briens C. L. , Large J. F. , Catros A. , Bernard J. R. , Bergougnou M. A. 
Published: March 2009

AbstractThe hydrodynamics and mass transfer characteristics of a venturi/bubble column combination were studied at high liquid superficial velocities of up to 0.35 m/s. The gas hold‐up was increased by 50% to 150% and the overall volumetric mass transfer coefficient was tripled when the venturi was used as “gas distributor” instead of a porous distributor. A correlation of the overall volumetric mass transfer coefficient (KLa) with the gas hold‐up, valid for gas hold‐ups as high as 0.3, was proposed for the cylindrical bubble column section. The energy consumption per mole of oxygen transferred was lower than with most distributors and the oxygen transfer rate per unit of reactor volume was higher than in a bubble column with a porous distributor. The venturi/bubble column combination is a compact and efficient system which does not have the operating problems of systems which require internals.
An experimental study of motion of cylinders in newtonian fluids: Wall effects and drag coefficient
Authors: Unnikrishnan A. , Chhabra R. P. 
Published: March 2009

AbstractThe terminal velocity of several cylinders (of glass, perspex and stainless steel) falling with their axis parallel to the direction of motion has been measured in a series of Newtonian fluids embracing a 40‐fold variation in liquid viscosity. The measurements have been carried out in fall tubes of four different diameters to elucidate the importance of wall effects. The experimental results encompass the following ranges of conditions: cylinder to fall tube diameter ratio: 0.08 to 0.4; length to diameter ratio: 0.05 to 2 and Reynolds number varied from 0.2 to 180.The wall effects are discussed in a manner analogous to those for spherical particles. Terminal velocity data are analysed using two approaches, namely, drag coefficient‐Reynolds number relationship and a dimensionless velocity ratio denoting the departure from the behaviour of an equivalent sphere. Predictive equations have been developed using both schemes.
Heat transfer from finned surfaces with a uniform fouling deposit
Authors: Middis J. , Möuller‐Steinhagen H. M. 
Published: March 2009

AbstractThe change in thermal efficiency when a uniform fouling deposit is added to an extended surface was determined by two‐dimensional numerical analysis. Calculations were done over a wide range of parameters such as fin length, fin thermal conductivity and deposit thermal conductivity. The results were compared with two previously reported analytical models, namely, a Series Model and a Parallel Model. Owing to simplifications used in the models, major discrepancies exist between the analytical and the numerical results for most relevant situations, especially in the case of the Parallel Model.
Distribution of volatile sulphur containing products during fixed bed pyrolysis and gasification of coals
Authors: Furimsky Edward , Palmer Allan D. , Cheng Meng 
Published: March 2009

AbstractThree sub‐bituminous and two bituminous coals from Western Canada were used to study the evolution of H2S, COS and SO2 during the pyrolysis and gasification processes in a fixed bed reactor. For all types of coals, most of H2S and SO2 were released during the devolatilization stage. COS was formed only during the gasification stage in the presence of CO2. The mineral matter of coal may have played a role during the gasification stage. Some observations made during this latter stage in CO2 and/or steam were interpreted in terms of the equilibrium effects.
An inverted cup reciprocating plate for gas absorption
Authors: Baird M. H. I. , Rama Rao N. V. 
Published: March 2009

AbstractThe characteristics of a novel type of reciprocating plate have been investigated. The plate is in the form of an inverted cup, 13.8 cm outside diameter and 7 cm deep, reciprocated on a central shaft in a 15 cm internal diameter water‐filled column. Reciprocation stroke length was 2.9 cm and the frequency was in the range 0–4.5 Hz. Air or oxygen is supplied steadily to the space beneath the cup and escapes from 1 mm diameter holes drilled around the side of the cup. At high reciprocation frequencies, this arrangement produces very fine gas bubbles of less than 1 mm diameter. Measurements have been made of Sauter mean bubble diameter, gas holdup and volumetric mass transfer coefficient for the oxygen‐water system.
Correlation and prediction of the viscosity of defined and undefined hydrocarbon liquids
Authors: Allan Juliet Mcclatchey , Teja Amyn S. 
Published: March 2009

AbstractA new method based on the effective carbon number is presented for the correlation and prediction of the viscosity of liquid hydrocarbons and hydrocarbon mixtures. It is proposed that the effective carbon number for the substance of interest be obtained from a single viscosity datum in the liquid range. The viscosity‐temperature relationships of sixty‐nine hydrocarbons, eleven defined hydrocarbon mixtures and eight crude oil fractions were studied in the present work. In general, calculated viscosities compared favorably with experimental data for all the systems studied. The calculated viscosities were also found to compare favorably with the results of the widely‐used TRAPP method.
A new four‐parameter cubic equation of state for fluids
Authors: Jan Dong‐Syau , Tsai Fuan‐Nan 
Published: March 2009

AbstractA simple cubic equation of state of the van der Waals type has been developed and successfully applied to both nonpolar and polar fluids. It contains four parameters and only one parameter is temperature‐dependent. The parameters have been determined by using reliable data of vapour pressure and saturated liquid volume, and correlated in terms of critical properties and acentric factor. The P‐V‐T relationships, vapour pressures, volumes, and enthalpies of vapourization were calculated for a variety of substances. Comparison of the calculated results with experimental data and with results obtained from other equations shows that the proposed equation is a superior one in overall performance.
Upgrading of tall oil to fuels and chemicals over HZSM‐5 catalyst using various diluents
Authors: Sharma R. K. , Bakhshi N. N. 
Published: March 2009

AbstractThe upgrading of crude tall oil (CTO) to fuels and chemicals was studied at atmospheric pressure and in the temperature range 370 to 440°C in a fixed bed microreactor containing HZSM‐5. The oil was co‐fed with diluents such as tetralin, methanol and steam. High oil conversions of the order of 80–90 wt. % were obtained using tetralin and methanol as diluents but with steam the conversion only ranged between 36 to 70 wt. %. The maximum concentration of gasoline range aromatic hydrocarbons in the liquid product was 52 and 57 wt. % with tetralin and steam but only 39 wt. % with methanol. The amount of gas product in most of the runs was 1–4 wt.%. A reaction scheme is postulated based on the results.