bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence of forced cycling on the fischer‐tropsch synthesis part III. A model for forced concentration cycling over promoted iron catalyst
Authors: Feimer J. L. , Hudgins R. R. , Silveston P. L. 
Published: March 2009

AbstractA model has been developed for the forced feed concentration cycling of a Fischer‐Tropsch synthesis reactor containing an iron catalyst promoted with potassium and copper. It was based on an initiation sequence proposed by Vannice (1975) for methanation, a propagation sequence using the CO‐insertion mechanism, and termination step based on the desorption of each n‐mer, including CH4. Only surface adsorption, surface reaction and desorption steps were considered; no storage in the catalyst bulk was assumed.Agreement of the model and experimental results permits interpretation of steady‐state, as well as the cycling and step‐change rate measurements. The model shows that hydrogen is involved in the rate determining step, and further that, except for methane, the results of hydrocarbon production from steady‐state, step‐change, and periodic experiments could all be reconciled for the results from C2 to C9. Failure of the model properly to predict rates of methane formation during cycling operation is attributed to changing carbidization of the catalyst.
A new analysis of the turbulent flow of non‐newtonian fluids
Authors: Wilson Kenneth C. , Thomas Allan D. 
Published: March 2009

AbstractA new analysis has been developed for the turbulent flow of non‐Newtonian fluids. Based on enhanced viscosity effects at the small time and length scales of the dissipative micro‐eddies, the analysis predicts a thickening of the viscous sub‐layer tending to increase throughput velocity and thus promoting drag reduction. The required flow parameters can be determined directly from rheograms, without employing correlations based on pipe‐flow data. The results give good descriptions of flows of fluids with both power‐law and Bingham behaviour and explain a number of peculiarities of such flows.
Gas composition and temperature profiles in a spouted bed coal gasifier
Authors: Haji‐Sulaiman Z. , Lim C. J. , Watkinson A. P. 
Published: March 2009

AbstractVerification of scale‐up models of the spouted bed gasifier requires experimental gas composition and temperature profiles within the reactor. Radial and axial profiles are presented for key gaseous species in a 0.30‐m. dia, atmospheric pressure gasifier fed at about 30 kg coal/h. Low calorific value gases were generated at air/coal mass ratios of 2.87‐4.08, while medium calorific value gases were produced at an oxygen/coal mass ratio of 0.84 and steam/coal ratios of 2.23‐2.84. The combustion zone within the gasifier is delineated and the effects of operating conditions on gas composition and temperature profiles are illustrated for typical sub‐bituminous and bituminous coals. Recycle of char to the bed from the primary cyclone and bed depth show little effect on profile shape.
Modelling of culture kinetics and physiology for c. acetobutylicum
Authors: Yerushalmi L. , Volesky B. , Votruba J. 
Published: March 2009

AbstractA mathematical model of the batch acetone‐butanol fermentation has been proposed which reflects the process kinetics and biochemistry. The degree of importance of the key kinetic parameters has been established by a parametric sensitivity analysis. The basic model was further extended by incorporating additional culture physiological parameters such as the number of active mass transport sites and the permeability of the cellular membrane as well as the intracellular and extracellular conditions. The model assisted in studying the role of the cellular membrane in the control of the culture performance and solvent biosynthesis. The theoretical predictions were confirmed by experimental results.
Experimental study of the inverse fluidized bed biofilm reactor
Authors: Nikolov L. , Karamanev D. 
Published: March 2009

AbstractA new apparatus, the inverse fluidized bed biofilm reactor, is described. Introduction of the so called inverse fluidized bed, in which low density particles covered by a biofilm are fluidized by downflow of the liquid, allows control of the biofilm thickness and provides a high oxygen concentration in the reacting liquid. Characteristics of the reactor were studied by carrying out two important biotechnological processes: aerobic wastewater treatment by a mixed bacterial culture, and ferrous iron oxidation by the bacteria Thiobacillus ferrooxidans. The bioreaction rates per unit volume of the reactor were up to 14 times higher than those in the equivalent airlift bioreactor. The structure of the liquid flow was determined by a tracer method.
Predicting thermal conductivity of binary liquid mixtures on basis of coordination number
Authors: Tobitani Atsumi , Tanaka Tatsuo 
Published: March 2009

AbstractBy applying a model of a randomly mixed packing of spheres of two sizes to binary liquid mixtures, the thermal conductivity of the mixture is related to the physical properties of each component through the number of contact points. Further, two parameters are introduced to account for the effect of the hydrogen bond and are correlated with the Lennard‐Jones (6‐12) parameters σ and ϵ, or the boiling temperature. In comparing the calculated values with the experimental data for 13 aqueous liquids and 21 non‐aqueous liquid systems, the present equation turns out to be more accurate than previous ones.
Study of an air‐lift system. Part I: Hydrodynamics of the atara piston bubble cannon mixer
Authors: Grandjean B. P. A. , Ajersch F. , Carreau P. J. , Patterson I. 
Published: March 2009

AbstractHydrodynamic studies of the two‐phase flow of air‐water mixtures were carried out in an innovative air‐lift system called the “Atara Piston Bubble Cannon Mixer”. Slug and churn flows were observed in the discharge tube. The bubble velocity in the slug flow regime and the pressure drop were measured. Bubble entrance effects, found to affect the pressure drop particular to this configuration, are explained The air‐lift pump performance is analysed and a hydrodynamic model is developed to predict the pumping capacity as a function of the gas flow rate.
Design of vertical air classifiers for municipal solid waste
Authors: Biddulph Michael W. 
Published: March 2009

AbstractA previously published diffusion‐based mathematical model is used to simulate data from two vertical air classifiers operating on shredded municipal solid waste streams. Good agreement with the model is achieved at high values of the air/solids ratio, that is, the region where interaction between solid particles would be expected to be insignificant. At lower values of the air/solids ratio the concept of a recovery efficiency is introduced to take account of interaction effects. This efficiency appears to show the expected dependence on air/solids ratio. A design method is proposed, based on feed particle size distribution and relationships between recoveries and product qualities.
Statistical assessment of a fluidized bed wood gasifier model
Authors: Wong L. A. , Bacon D. W. , Hsu C. C. 
Published: March 2009

AbstractSensitivity analyses were carried out to assess the behaviour of a fluidized bed wood gasifier simulation model in response to changes in the values of design variables, operating variables, and model coefficients. The model was originally developed using the modified Bubble Assemblage Model. Physical design specifications of the fluidized bed were found to have little influence on the quality of the product gas; in fact the composition of the gas was found to depend almost exclusively on the degree of approach to equilibrium. Overall thermal efficiency could be improved only by increasing the dry wood to oxygen ratio and reducing the moisture content in the wood feed. Because wood gasifiers produce volatiles that greatly enhance the chance of slugging, the influences of the design and operating variables on the occurrence of slugging were also investigated. The onset of slugging was found to be related most strongly to the dynamic bed height.
Control of a continuous polybutadiene polymerization reactor train
Authors: Kelly S. J. , Macgregor J. F. , Hoffman T. W. 
Published: March 2009

AbstractAn approach to controlling a continuous industrial polymerization reactor train for the production of stereoregular butadiene rubber based on the use of quality control laboratory data is presented. Empirical transfer function and disturbance models are identified directly from data collected from a designed experimental program carried out while the plant remained under operator control. The models are used to design minimum variance type control strategies for the monomer conversion and the Mooney viscosity of the final product. These controllers manipulate the flowrates of the Ziegler‐Natta catalyst components and a chemical transfer agent. The plant testing program, the development of the control strategy, and results from testing the control strategy in the plant are all described.
Effect of water on the solubilities and mass transfer coefficients of gases in a heavy fraction of fischer‐tropsch products
Authors: Karandikar B. M. , Morsi B. I. , Shah Y. T. , Carr N. L. 
Published: March 2009

AbstractThe effects of water on the solubilities, C*, and volumetric mass transfer coefficients, kLa, for CO, H2, CH4 and CO2 in a heavy fraction of Fischer‐Tropsch liquid were examined at elevated pressures and temperatures at different mixing power inputs. For these gases, higher solubilities were measured in the hydrocarbon mixture saturated with water than those obtained in the hydrocarbon free of water. The kLa values for the four gases were slightly affected by the presence of dissolved water in the hydrocarbon mixture; and they were strongly dependent on the power input per unit liquid volume. Two empirical correlations for kLa as a function of turbine speed and pressure are proposed.
Optimal design on an economic basis for continuous stirred tank reactors in series using michaelis‐menten kinetics for ping‐pong reactions
Authors: Xavier Malcata F. 
Published: March 2009

AbstractA theoretical analysis of the reactant concentration profile along a given number of CSTR's in series for ping‐pong type reactions following Michaelis‐Menten kinetics (with equal initial concentrations for both substrates) has been developed. Minimising the total holding time was taken as the intermediate objective function whereas minimising the total capital investment was assumed to be the main objective function.
Characteristics of a countercurrent reciprocating plate bubble column. I. Holdup, pressure drop and bubble diameter
Authors: Rama Rao N. V. , Baird M. H. I. 
Published: March 2009

AbstractThe hydrodynamics of countercurrent air/water flow in a 5 cm diameter reciprocating plate bubble column have been studied; the plates contained 14 mm diameter perforations and had a fractional open area of 0.57. The ranges of superficial velocities of air and water were respectively 0‐0.99 cm/s and 0‐3.95 cm/s. The stroke was in most cases 4.5 cm and the reciprocation frequency was in the range 0–5 Hz.The pressure drops were measured in the absence of reciprocation for single phase and two phase flow conditions. Pressure fluctuations and time‐averaged pressure drops were measured with plate reciprocation under single and two‐phase conditions. The results were described in terms of the simple quasi‐steady state model; the effective orifice coefficients of the perforations were within the range 0.4 to 0.97 depending on the reciprocation conditions.The Sauter mean diameters of the bubbles decreased with agitation; they were about twice the values predicted from an earlier correlation developed for liquid‐liquid systems. The gas holdups were also substantially greater than predicted from correlations based on liquid‐liquid systems. Both these effects were explained as due to the tendency for bubbles to cluster in the plate region.
Characteristics of a countercurrent reciprocating plate bubble column. II. Axial mixing and mass transfer
Authors: Baird M. H. I. , Rama Rao N. V. 
Published: March 2009

AbstractOxygen absorption from air into water and axial dispersion in the aqueous phase have been measured in a 5 cm diameter reciprocating plate bubble column. The volumetric mass transfer coefficients in semi‐batch conditions were found to increase with agitation and were correlated with the specific power input and air flow rate. Under countercurrent conditions, it was found that axial mixing had little effect and conditions approached plug flow. The volumetric mass transfer coefficients were correlated with specific power input, air and water flow rates. Mass transfer coefficients were estimated using holdup and bubble diameter results. Comparison of the coefficients with the literature values indicated that the bubble surfaces were partially mobile.
Strategies for solving the chemical equilibrium problem and an efficient microcomputer‐based algorithm
Authors: Smith William R. , Missen R. W. 
Published: March 2009

AbstractGeneral strategies for solving the problem of computing the equilibrium composition of a multiphase, multispecies, chemically reacting system are discussed. An efficient new algorithm is presented based on these strategies, together with a microcomputer‐based implementation. Numerical examples show the algorithm's utility, and its advantages over other recently proposed methods in terns of a number of criteria, including speed and certainty of convergence. The range of problem types within the capability of the new algorithm, and its limitations are discussed.
Dispersive‐force modelling of turbulent suspension in heterogeneous slurry flow
Authors: Wilson K. C. , Pugh F. J. 
Published: March 2009

AbstractThe force‐balance model, originally developed for coarse‐particle slurries, has now been extended to slurries of finer particles susceptible to turbulent suspension. The analysis involves a turbulent dispersive force — an equivalent body force between the fluid and solid phases. The use of this force, together with the intergranular stresses for contact‐load particles, allows the calculation of concentration and velocity profiles which vary continuously with height. The calculated profiles are found to be in generally good agreement with experimental data from the Saskatchewan Research Council.
The inverse gaussian density function as applied to the ziegler‐natta catalysis in the oligomerization of ethylene to linear alpha‐olefins
Authors: Favis D. V. 
Published: March 2009

AbstractProduct distributions taken as a function of the number of ethylene molecules per olefin fraction fit adequately a mostly two parameter inverse Gaussian distribution with a χ2goodness of fit, statistical values ranging from 0.016 to 0.037 and levels of significance α, when applicable, ranging from 0 to 0.002. The examples included typical and modified Ziegler‐Natta catalytic systems. Limited data indicate a good applicability for non Ziegler‐Natta homogeneous or heterogeneous systems. Biased reactions showed poor, if any, applicability. A typical Ziegler ethylene growth to linear alpha‐olefins mole data gave a good fit on a three parameter inverse Gaussian distribution. On a speculative basis, the results indicate a common element of underlying mechanism of most of the examined syntheses, possibly associated with a first passage time process such as that found in Brownian motion.
Kinetic modelling of the pyrolysis of biomass and biomass components
Authors: Koufopanos C. A. , Lucchesi A. , Maschio G. 
Published: March 2009

AbstractThe kinetics of the pyrolysis of lignocellulosic materials was studied with a view of providing simple kinetic models for engineering purposes. Experimental data obtained by means of thermal analysis techniques suggest that the pyrolysis of fine particles (below 1 mm) can be considered to be controlled by pyrolysis kinetics. The rate of pyrolysis of one biomass type can be represented by the sum of the corresponding rates of the main biomass components (cellulose, lignin, hemicellulose). The kinetics of each of these components was simulated by a kinetic scheme capable of predicting the pyrolysis rate and the final weight‐loss for a wide range of pyrolysis parameters including various heating conditions.
Reactor development for the ultrapyrolysis process
Authors: Berg D. A. , Briens C. L. , Bergougnou M. A. 
Published: March 2009

AbstractA new impinging‐jet reactor system has been developed for the fast pyrolysis (ultrapyrolysis) of particulate carbonaceous materials. The reactor system serves to promote rapid uniform mixing between a fine particulate heat carrier and a particulate feedstock in order to achieve the high heat transfer rates necessary for fast pyrolysis. Flow visualization experiments in a cold model testing unit indicated that the system performed effectively over a wide range of conditions. A sampling system utilizing isokinetic sampling probes was developed to investigate the small scale solids mixing. The effects of reactor geometry and operating conditions upon the solids mixing are reviewed.
Experimental laminar falling film heat transfer coefficients on a large diameter horizontal tube
Authors: Rogers J. T. , Goindi S. S. 
Published: March 2009

AbstractA test rig was designed and fabricated to measure local heat transfer coefficients from a large‐diameter, steam‐heated horizontal tube to thin falling films of water. The results of the experiments generally support the theory developed by Rogers for laminar film conditions, which were found to persist up to film Reynolds numbers of about 2000. Agreement between theoretical predictions of heat transfer coefficients and the measured values is reasonable for the thermal boundary layer development region, but measured values are about 20% lower than predicted values in the developed region. The lower values in the developed region are attributed mainly to measured film thicknesses being greater than predicted values.
Laminar start‐up flow in short pipe lengths
Authors: Patience Gregory S. , Mehrotra Anil K. 
Published: March 2009

AbstractA solution method is described for the start‐up flow of an incompressible Newtonian fluid in a short pipe. The complete Navier‐Stokes equations are solved numerically using a fragmented control volume method. The solution procedure involves a novel approach for accommodating the time‐dependent condition for pressure at the pipe inlet. It is shown that the start‐up time for short pipes is less than that for long pipes, due to kinetic head development and entrance region effects. Correlations are presented for estimating the start‐up time.
A study of bitumen recovery by gravity drainage using low temperature soluble gas injection
Authors: Dunn S. G. , Nenniger E. H. , Rajan V. S. V. 
Published: March 2009

AbstractA gravity drainage concept has been proposed and tested for in‐situ recovery of bitumen by mobilization with soluble gases at ambient reservoir temperature conditions. Experiments were done using carbon dioxide and ethane gases at ∼ 20°C to recover Athabasca bitumen from a scaled reservoir model. Thermal gravity drainage theory has been modified for the mass transfer case. The measured drainage rates were higher than those predicted by the model using molecular diffusivity data but fit the model better using an increased effective diffusivity. Lateral dispersion theory does not predict the high measured effective diffusivities. A preliminary economic evaluation of field production indicates potential application to recovery of Lloydminster heavy oil.
A study of a simulated moving bed adsorber based on the axial dispersion model
Authors: Kubota Katsuyuki , Hata Chito , Hayashi Shinya 
Published: March 2009

AbstractOn the basis of the axial dispersion model, the concentration profiles for a simulated moving bed adsorber were theoretically predicted. Experimentally, an apparatus consisting of four sections was employed. Glucose and sorbitol were separated from the liquid dissolved with these components both co‐currently and counter‐currently. The experimental results seemed to support the predicted curves.
Rheology of oil in water emulsions with added solids
Authors: Pal Rajinder , Masliyah Jacob 
Published: March 2009

AbstractThe effect of added solids on the rheology of oil in water emulsions was investigated. The range of the oil concentration, solids free basis, was (0‐70%) and the solids volume fraction was (0‐0.16). The solids mean diameter was 45 μm and it was about four times larger than the oil droplets. In the absence of added solids, non‐Newtonian behaviour was observed for oil concentrations above 40%. The added solids increased the emulsion viscosity in a manner similar to the addition of solids to a homogeneous fluid.The rheological data of all the emulsion‐solids mixtures investigated were correlated as relative viscosity versus solids volume fraction, where the relative viscosity is defined as the ratio of the emulsion‐solids mixture viscosity to the solids‐free emulsion viscosity. In the case of non‐Newtonian systems, the emulsion‐solids mixture viscosity and the solids‐free emulsion viscosity were calculated at the same shear stress. The Barnea and Mizrahi viscosity correlation was found to fit the data well.
Bubble size distribution in bubble columns
Authors: Saxena A. C. , Rao N. S. , Saxena S. C. 
Published: March 2009

AbstractThe bubble size distributions are measured for the air‐water system as a function of air velocity at room temperature in two bubble columns. High speed cinephotography and fiber optic probe techniques are used to measure the bubble size. Our limited measurements suggest that the bubble size may be independent of gas velocity in the range 3.6 to 9.2 cm/s and may be dependent on column diameter with smaller bubbles for narrower columns. The bubble size appears to be smaller at the column wall than at distances away from the wall.
Reaction kinetics over iron catalysts used for the fischer‐tropsch synthesis
Authors: Zimmerman William H. , Bukur Dragomir B. 
Published: March 2009

AbstractThe kinetics of the Fischer‐Tropsch (FT) and water‐gas shift (WGS) reactions were studied in a stirred tank slurry reactor, using a 100 Fe/0.3 Cu/0.2 K catalyst and a commercial catalyst, Ruhrchemie LP 33/81. The 100 Fe/0.3 Cu/0.2 K catalyst was more active than the Ruhrchemie catalyst for both reactions. FT kinetics which accounted for water inhibition was the best of the rate forms considered for the 100 Fe/0.3 Cu/0.2 K catalyst. First order in H2 kinetics was sufficient for the Ruhrchemie catalyst, probably due to the low conversions obtained during the test of this catalyst. WGS kinetics, which included product inhibition, were also studied for each catalyst.
Effect on surface charges of bubbles and fine particles on air flotation process
Authors: Okada Kenji , Akagi Yasuharu , Kogure Masahiko , Yoshioka Naoya 
Published: March 2009

AbstractThe adhesion of fine particles onto bubbles in flotation was studied on the basis of surface charge measurements of the bubbles and particles.The surface charges of the bubbles were measured by the use of a micro‐electropheresis apparatus devised in our previous study and the mechanism of the bubble charging was studied under various experimental conditions. In distilled water, the bubbles were negatively charged and the iso‐electric point appeared at pH = 2.5. The surface charges of the bubbles in the surfactant solution were determined by the surfactant molecules adsorbed at the surface and depend strongly on the values of pH.The flotation efficiency of latex particles (0.923 μm) was found to be strongly influenced by the surface charges of both the particles and the bubbles. The force between the particle and the bubble was estimated from the observation of the particle attachment to the bubble surface, and a simple equation including the effects of the hydrodynamic and surface charge interactions was proposed to determine the floatability limit.