bluuebunny/crossref_metadata_2025_split huggingface dataset:
Devolatilization and char burning of coal particles in a fluidized bed combustor
Authors: Jia Lufei , Becker H. A. , Code R. K. 
Published: March 2009

AbstractDevolatilization and char burning were studied in an electrically heated bench‐scale fluidized‐bed reactor at 750 to 900°C bed temperature, gas oxygen mole fractions ranging from zero to 0.21, superficial gas velocities from 0.3 to 0.7 m/s and coal particle diameters 5 to 35 mm. The coals investigated include lignite, bituminous and anthracite. The coal devolatilization and char burning times, H/C ratio histories, and particle fragmentation were measured. Statistical correlations with the operating variables were developed for the devolatilization time. A mathematical model is given for the combustion of char. Most predictions of the model agree quite well with the experimental results.
Influence of tube inclination on the flow regime boundaries of condensing steam
Authors: Nitheanandan T. , Soliman H.M. 
Published: March 2009

AbstractFlow regime data of condensing steam inside an inclined 13.4 mm ID tube are presented. The effect of upward and downward inclinations within ± 10° on the different transition lines is discussed. In all test runs, complete condensation has been achieved inside the condenser, with or without full tube at exit depending on the total mass flow rate and inclination angle. It is shown that the zones occupied by the wavy and slug regimes experience significant shifts, whereas the effect on the annular flow boundary appears to be insignificant at the present small inclination angles. The present data sets are compared with adiabatic gas‐liquid flow regime maps developed analytically and experimentally for horizontal and inclined tubes. Deviations due to the condensation process are observed; however, consistent trends are identified among the two types of flow.
The effects of pressure and temperature on the catalytic oxidation of hydrogen sulfide in natural gas and regeneration of the catalyst to recover the sulfur produced
Authors: Dalai Ajay K. , Majumdar Amitabha , Chowdhury Aminul , Tollefson Eric L. 
Published: March 2009

AbstractThe influence of pressure up to 5600 kPa and temperature up to 175 °C on the oxidation of low concentrations of H2S in natural gas was studied in a fixed bed reactor over an activated carbon catalyst. Operation of this system at 5600 kPa provides higher catalyst activity (virtually 100% H2S conversion) over a longer period of time and with lower selectivity to SO2 than when operated at atmospheric pressure. The desorption of sulfur from a loaded catalyst occurs first from the macropores (> 100 nm) of the catalyst which contain a substantial portion of the sulfur load and then from the micropores (< 100 nm). This study also indicated that the sulfur recovery process is both rapid and effective at 327°C.
Hydrodynamics of a flowing gas‐solids suspension in a tube at high angles of inclination
Authors: Ginestet A. , Guigon P. , Large J. F. , Sen Gupta S. , Beeckmans J. M. 
Published: March 2009

AbstractA study was made of pneumatic transport of particles of sand suspended in air in a 31.8 mm diameter Plexiglas tube inclined at either 72 or 90 degrees with respect to the horizontal plane. The solids holdup, pressure gradient and pressure drop fluctuations over a 4.55 m test section were measured as functions of the air velocity and the solids flux. Previously observed sudden changes in slope of plots of solids holdup versus solids flux at constant gas velocity in a vertical tube (Mok et al., 1989), which were identified as transition points between dilute and dense phases, were confirmed and extended to inclined tubes. Breaks were also found in plots of pressure drop fluctuations versus solids flux at constant gas velocity.
A model for gas flow in jet spouted beds
Authors: Olazar M. , San José M. J. , Peñas F. J. , Aguyo A. T. , Arandes J. M. , Bilbao J. 
Published: March 2009

AbstractA model of general application that is based on the definition of streamlines and that is in agreement with the bed geometry has been proposed in order to describe the gas flow in a jet spouted bed in conical contactors. The model quantifies the dispersion in the direction of the streamlines by using a characteristic modulus.The validity of the model has been experimentally proven on the basis of the measurement and analytical correlation of gas velocity profiles at different radial and longitudinal positions in the contactor, and of the application of the stimulus response technique for the calculation of the residence time distribution function.
Prediction of lower/upper limiting viscosities
Authors: Kozicki W. , Kuang P. Q. 
Published: March 2009

AbstractAn analysis based on steady uniform laminar flow of a non‐Newtonian fluid in a tube is presented which predicts Newtonian flow behaviour in the limits of zero and infinite shear, respectively. It is shown that an upper limiting viscosity occurs in the limit of infinite shear for a fluid with or without a yield stress, whereas a lower limiting viscosity is obtained for a fluid without a yield stress in the limit of zero shear. For a fluid with a yield stress, an infinite viscosity is found in the limit as the shear stress approaches the yield stress.
Experimental study of mixing performances using steady and unsteady jets
Authors: Simon M. , Fonade C. 
Published: March 2009

AbstractThis paper deals with the experimental study of mixing characteristics by means of steady and unsteady jets. Investigations were carried out with one and two steady jets, and with two alternate intermittent jets, supplying 0.1 m3 and 70 m3 tanks. From the data obtained from several sensors put into the tank, the signification of the mixing time as applied to the tank is discussed. A Reech‐Froude similarity appears to be a good way in scaling the results obtained on either 0.1 m3 or 70 m3 models. Combining the specific momentum of the jets and the tank characteristics, a mixing time factor M is deduced which permits the evaluation of the mixing time. The efficiency of different configurations of jets are then compared through a degree of transient inhomogeneity and required power.
Roles of ZSM‐5 modifier agents in selective toluene disproportionation
Authors: Uguina Maria A. , Sotelo Jose L. , Serrano David P. 
Published: March 2009

AbstractSelective toluene disproportionation has been studied over ZSM‐5 zeolites modified with P, Si and Cs compounds. For the P and Si modified samples, p‐xylene proportion in the primary product was 100% due to the diffusional control on the internal xylene isomerization. The number and strength of the acid sites are reduced by the three modifier agents but a relationship between para‐selectivity and the decrease of the acid strength has not been observed. The most para‐selective samples have been those modified with Si which has been related to the deposition of this agent on the external surface of the zeolite crystals avoiding the primary product isomerization.
Characterization of flooding in a wirz extraction column
Authors: Rincón‐Rubio L. M. , Kumar A. , Hartland S. 
Published: March 2009

AbstractThe flooding behaviour of a 150‐mm diameter Wirz‐II extraction column has been investigated for six different liquid‐liquid systems. Normally, flooding occurred by phase inversion but when the density difference was low could also occur by entrainment of dispersed‐phase drops at the continuous‐phase exit. Empirical expressions for flooding velocities and holdup at flooding are derived in terms of the operating variables, column geometry and physical properties of the liquid systems.
Residual oil cracking combined with hydrogen production by steam‐iron reaction
Authors: Fukase Satoshi , Suzuka Teruo 
Published: March 2009

AbstractA new residual oil upgrading process has been developed. Residual oils were cracked over an iron oxide catalyst with simultaneous generation of hydrogen. The newly‐developed iron oxide catalyst containing CaO and Cr2O3 was found to be a good catalyst for this process because it exhibited stable activity in the steam‐iron reaction in the laboratory experiment and also in a large scale pilot plant. Effects of these foreign oxides on redox cycles were investigated. The catalyst was designed so as to maintain the stoichiometric balance between the reduction of magnetite and the oxidation of wustite by adding CaO and Cr2O3.
Thermodynamics and kinetics of the kraft causticizing reaction
Authors: Wang L. , Tessier P. J.‐C. , Englezos P. 
Published: March 2009

AbstractA methodology for the calculation of the equilibrium of the causticizing reaction of pure sodium carbonate solutions at 100°C without any adjustable parameters is presented. The methodology is extended to compute the effect of sodium sulfide. The causticizing reaction was found to be slightly endothermic at 100°C. The caculated results were found to be in good agreement with experimental data. An empirical kinetic model for the causticizing reaction is also presented. The model takes into account the variations in both green liquor composition and lime quality and can yield the causticizing efficiency directly. The calculated results of the causticizing efficiency were found to be in good agreement with experimental data from several Canadian pulp mills and reflected the effect of the variation in lime quality.
Evaluation of capital cost data: Part 8: Liquid waste disposal with emphasis on biological treatment
Authors: Wright David G. , Woods Donald R. 
Published: March 2009

AbstractCapital cost correlations are given for aeration basins, mechanical aerators, diffused aeration, conventional activated sludge process, extended aeration, contact stabilization, oxidation ditch, rotating biological contactor, trickling filter, aerobic lagoons, facultative lagoon, aerated lagoons and liners. Most of the correlations are accurate to ±30%, expressed in Canadian dollars and adjusted to a Marshall and Swift value of 1000. Details as to what components are included in the cost are given. Data are given for the labour and material costs to create a working process module. Data for oxidation ditches are accurate to ±50%.To put the current data into perspective, several hundred sources of cost data were analyzed. The major correlations are compared, on a consistent basis, with current data.
Heat transfer mechanism due to particle convection in circulating fluidized bed
Authors: Qi Chunming , Farag Ihab H. 
Published: March 2009

AbstractThe nature of heat transfer in circulating fluidized beds (CFBs) by particle convection was revealed from the experimental results of the particle flux in the lateral direction. As particles contact and rebound from the heat transfer surface because of their lateral motion, they establish a large local temperature gradient. Heat from particles is then transferred primarily through the gas to the heat transfer surface. The data of the lateral particle flux provide a basis to establish a model of heat transfer in CFBs.
Loading, draining and hold‐up in periodically operated trickle‐bed reactors
Authors: Hasokowati Wahyu , Hudgins R. R. , Szlveston P. L. 
Published: March 2009

AbstractPeriodic interruption of liquid flow in co‐current trickle beds appears to be an attractive mode of operation. For modelling these intermittent‐flow reactors, loading and draining times must be known. Experiments were undertaken using beds of activated carbon with water and air as the fluid phases. Loading time was taken as the time to water breakthrough. The gas flow was continuous while the time between the end of drainage and the start of filling was varied to simulate different periods. Drainage experiments followed the liquid flow leaving the bed as a function time. Liquid hold‐ups were determined after the filling and draining measurements. Variables considered were particle size, gas and liquid velocity. Loading closely follows the plug flow model; drainage shows tailing but does not follow literature models. Static and dynamic hold‐ups at zero gas flow agree with literature correlations for the larger particle size used. A gas velocity effect on both static and dynamic hold‐up was observed.
Coal gasification in a jet‐spouted bed
Authors: Tsuji Toshiro , Uemaki Osamu 
Published: March 2009

AbstractCoal gasification has been studied for the production of synthesis gas by use of a laboratory‐scale, two‐stage, jet‐spouted bed reactor. Tests were conducted in the dry ash mode with oxygen‐steam mixtures. The effects of operating conditions on the gasification performance were investigated at atmospheric pressure and temperatures up to 1150°C. Carbon conversions of 75% to 97% and cold gas thermal efficiencies of 62 to 78% were obtained for Taiheiyo coal. Both the carbon conversion and thermal efficiency were mainly affected by the oxygen/coal ratio. The product gases contained 36‐41% hydrogen and 30‐43% carbon monoxide.
The oxidation of valeric acid in aqueous solution
Authors: Nikolaou N. , Abatzoglou N. , Gasso S. , Chornet E. 
Published: March 2009

AbstractThe liquid phase oxidation of an aqueous solution of a lower fatty acid, valeric (pentanoic) acid, has been studied at high temperatures (240−325°C) and pressures (10.3‐10.4 MPa) in a batch autoclave reactor. The objective of the study was to develop a mechanistic understanding of the wet oxidation of industrial wastewaters contaminated with vegetable oils. Valeric acid was chosen as the prototype molecule. High performance liquid chromatography (HPLC) has been used to identify the liquid products and estimate their concentrations as a function of the extent of oxidation. Moreover the technique of GC‐MS has also been used to obtain information on specific intermediate oxidation products that could not be identified by HPLC. The gaseous products of the reaction have been also identified and quantified. A detailed reaction mechanism is proposed based on free radical reactions.
Natural convective heat transfer from open vertical tubes
Authors: Baird M. H. I. , Legree B. A. 
Published: March 2009

AbstractNatural convection heat transfer in vertical tubes is described by a one‐dimensional dispersion model similar to that used previously for fluid mixing in the presence of an unstable density gradient. Temperature profiles have been measured in air in 2 m high insulated vertical tubes (21.3, 24.5, 27.7 cm internal diameter), closed at the bottom and open at the top, and heated at the bottom with a known heat flux. The effective mixing lengths for eddy heat transport are of the same order as the tube diameters.
Cell and surfactant separation by column flotation
Authors: Husband Devon L. , Masliyah Jacob H. , Gray Murray R. 
Published: March 2009

AbstractThe separation of rehydrated Saccharomyces cerevisiae and an alkyl polyglycoside surfactant by column flotation was studied as a function of wash water flow and cation concentration. Separation of cells and surfactant was measured under steady‐state conditions. Surfactant recovery in the foam concentrate was in the range of 86–95%. Yeast cells were enriched in the foam concentration by a factor of up to 11, but the recovery only reached 55%. The use of wash water was very effective for removing the cells from the foam, giving a good separation between the cells and the surfactant. Addition of chloride salts of Na, K, Ca, and Mg at concentrations in the range of 0.05‐0.1 mol/L increased both the enrichment and the recovery of yeast in the foam. The most effective salt levels for cell flotation, less than 0.1 mol/L, were in the same range of concentration as the minimum electrophoretic mobility of the cells.
Effect of H2O2 addition mode on enzymatic removal of phenol from wastewater in the presence of polyethylene glycol
Authors: Wu Jiangning , Bewtra J. K. , Biswas N. , Taylor K. E. 
Published: March 2009

AbstractThe effect of batch and semi‐batch additions of the stoichiometric amount of H2O2 on enzymatic removal of phenol has been studied over the phenol concentration range of 1‐10 mmol/L. It is found that the ratio between the maximum H2O2 concentration during the reaction and the initial horseradish peroxidase concentration ((H2O2)max/(HRP)o) controls the rate of phenol removal by horseradish peroxidase in the presence of the additive, polyethylene glycol. An optimum range of this ratio is determined to be between 10 and 25 μmol/U. Empirical models are proposed to predict the values of (H2O2)max/(HRP)o required to treat given phenol concentrations under different modes for adding H2O2.
Phase equilibrium data on carbon dioxide hydrate in the presence of electrolytes, water soluble polymers and montmorillonite
Authors: Englezos Peter , Hall Stephen 
Published: March 2009

AbstractEquilibrium formation conditions for carbon dioxide hydrate were measured in pure water and in aqueous polymer and electrolyte solutions. The solutions that were used include: polyethylene oxide, partially (10 and 90 percent) hydrolyzed polyacrylamide, sodium chloride and calcium chloride. Experiments with solutions containing both electrolyte and polymers were also performed. It was found that the electrolytes exhibited a substantial inhibiting effect whereas the polymers only slightly altered the equilibrium hydrate formation conditions. The measured equilibrium formation pressures were compared with the predictions from existing hydrate equilibria methods and were found to be in good agreement. The effect of montmorillonite was also studied and it was found that it did not affect the equilibrium hydrate formation conditions. A total of 101 experimental measurements are reported.
Microwave assisted barking of frozen wood
Authors: Gilbert Allan F. , Turcotte Camille 
Published: March 2009

AbstractThawing pulpwood with microwave energy could be an effective means to improve winter barking operations in Canadian interior mills. Complete bark thawing requires 140 MJ per tonne of wood for average 25 cm diameter logs at 90 mass % moisture, dry basis. However, complete thawing may not be necessary, as warming both spruce and aspen bark from −20°C to −5°C, decreases the bark/wood bond strength from 2.5–4.5 MPa to room temperature values of 0.5–1.5 MPa. This improves the economics of winter operation, but the expenditure for capital which has no year‐round use is not easily justified. Also the design of safe large‐scale microwave generators and applicators remains a technical challenge.
Purification of wet process phosphoric acid by solvent extraction liquid‐liquid equilibrium at 25 and 40°C of the system water‐phosphoric acid‐methylisobutylketone
Authors: Feki M. , Fourati M. , Chaabouni M. M. , Ayedi H. F. 
Published: March 2009

AbstractSolubility and liquid‐liquid phase equilibrium data are presented for the ternary system water‐phosphoric acid‐methyl isobutyl ketone at 25 and 40°C. Binodal curves, tie lines and distribution curves have been determined. Hand's method has been used to correlate tie lines and to calculate coordinates of plait points. The heterogeneous region at 40°C appeared to be slightly broader than that at 25°C, and the slopes of tie lines somewhat higher: the solubility of this system increases with decreasing temperature. The distribution curves indicated that methyl isobutyl ketone was an effective extractant for concentrated phosphoric acid solutions only.
Application of inductive heating to granular media: Modelling of electrical phenomena
Authors: Duquenne P. , Deltour A. , Lacoste G. 
Published: March 2009

AbstractA model is examined in order to predict the behaviour of a granular bed made with conductive particles subjected to an inductive electromagnetic field. The model shows how heat generated in the bed can be described by its electric impedance for the high‐frequency generator required for inductive heating. Once the relationship between electrical characteristics and power dissipation has been established, comparisons between experimental and theoretical results are presented and the validity of the model is discussed.
A general procedure for the estimation of diffusivities in sonas
Authors: Doví V. G. , Reverberi A. P. , Meshalkin V. P. 
Published: March 2009

AbstractA method for overcoming the difficulty of using realistic interface adsorption kinetics in mass sorption experiments for the estimation of diffusivities in solids is described in this paper. The method is shown to possess three important advantages:

Complex kinetics are allowed for interface adsorption processes
Analytical solutions can be obtained for arbitrary interface kinetics
No additional parameter is introduced in the estimation problem

An important special case is worked out in detail.
Modeling of grid region heat transfer in a shallow gas‐solid fluidized bed
Authors: Wang Rong‐Chi , Cho Wei‐Chang , Ho T. C. 
Published: March 2009

AbstractHeat transfer coefficients between the bed and an immersed horizontal tube in the grid‐region of a shallow gas‐solid fluidized bed were experimentally and theoretically studied. Experiments were carried out in two fluidized bed columns with inside diameters of 88 and 137 mm, respectively. The fluidized particles tested were sand, limestone and glass beads. Experimental parameters also included particle size, superficial gas velocity, tube diameter, tube location and distributor design. A mechanistic model considering the contributions of jet phase, emulsion phase and dead phase was derived for estimating the grid‐region heat transfer coefficients. Most of the model predictions were found to be within 25% of the experimentally observed data.
A simplified couette flow solution of non‐newtonian power‐law fluids in eccentric annuli
Authors: Yang Liao , Chukwu Godwin A. 
Published: March 2009

AbstractFlow of non‐Newtonian fluids in both the concentric and eccentric annuli is of great importance in extruders for molten plastics and wellbore fluid circulation for the removal of drilling cuttings. The steady laminar couette flow of non‐Newtonian power‐law fluids in eccentric annulus is employed in this study to analyze the problems of surge or swab pressures encountered when running or pulling tubular goods (pipes) in a liquid filled borehole. This is similar to the annular space created by two long co‐axial cylinders with the inner cylinder in motion at a steady velocity, and a stationary outer cylinder.The solutions of the equations of motion are presented in both dimensionless form and as a family of curves for different pipe/borehole eccentricity ratios and power‐law fluid index values for a more general application. The expected error in surge computation for concentric annulus as a result of eccentricity is evaluated.
Adaptive time stepping strategy for solidification processes based on modified local time truncation error
Authors: Chao Long‐Sun , Peng Hsiun‐Chang 
Published: March 2009

AbstractAdaptive time step methods provide a computationally efficient means of simulating transient problems with a high degree of numerical accuracy. However, choosing appropriate time steps to model the transient characteristics of solidification processes is difficult. The Gresho–Lee–Sani predictor–corrector strategy, one of the most commonly applied adaptive time step methods, fails to accurately model the latent heat release associated with phase change due to its exaggerated time steps while the apparent heat capacity method is applied. Accordingly, the current study develops a modified local time truncation error‐based strategy designed to adaptively adjust the size of the time step during the simulated solidification procedure in such a way that the effects of latent heat release are more accurately modeled and the precision of the computational solutions correspondingly improved. The computational accuracy and efficiency of the proposed method are demonstrated via the simulation of several one‐dimensional and two‐dimensional thermal problems characterized by different phase change phenomena and boundary conditions. The feasibility of the proposed method for the modeling of solidification processes is further verified via its applications to the enthalpy method. Copyright © 2009 John Wiley & Sons, Ltd.