bluuebunny/crossref_metadata_2025_split huggingface dataset:
The influence of baffle off‐bottom clearance on the solids suspension performance of pitched‐blade and high‐efficiency impellers
Authors: Myers Kevin J. , Fasno Julian B. 
Published: March 2009

AbstractAn innovative video technique indicates that the solids suspension performance of pitched‐blade impellers in flat‐bottomed tanks is improved by using a baffle off‐bottom clearance in the range of one‐fourth to one‐half of the baffle width (standard baffle width being one‐twelfth of the tank diameter). The solids suspension performance of high‐efficiency impellers is relatively unaffected by baffle off‐bottom clearances in the range of zero to one‐half of the baffle width. A baffle off‐bottom clearance equal to the baffle width is detrimental to the solids suspension performance of both pitched‐blade and high efficiency impellers.
The selective non‐catalytic reduction of nitric oxide using ammonia at up to 15% oxygen
Authors: Caton J. A. , Narney J. K. , Cariappa H. C. , Laster W. R. 
Published: March 2009

AbstractSelective non‐catalytic reduction of nitric oxide (NO) using ammonia was studied with up to 15% (by volume) oxygen at 102 kPa. The experiments were conducted in an electrically heated laminar‐flow, quartz reactor using mixtures of N2, O2, NO, and CO to simulate exhaust gas. The base case condition included 330 ppmv of NO, 495 ppmv of NH3, and 15% O2. At a reactor temperature of 1050 K, 77% of the NO was removed. For a lower oxygen concentration of 1%, the NO removal was as high as 98% at 1100 K. The degraded performance at high oxygen concentrations is attributed to increases in the oxidation reactions.A major result of this work was the quantification of the amount of N2O in the treated gases. For the base case conditions, 21 ppmv of N2O was measured for a reactor temperature of 1075 K. Increasing the ratio of NH3 to NO (by increasing the NH3 concentration) increased the maximum NO removal and decreased the temperature at which this level of NO removal was achieved. For the higher NH3 concentrations, however, the N2O concentration increased to as high as 54 ppmv. The oxidation products of ammonia (in the absence of NO) for these conditions were found to include first N2O beginning at 900 K and then NO beginning at 1050 K. Comparisons between these experimental results and predictions from the Miller and Bowman (1989) model indicate that further enhancements of the model may be necessary to incorporate the features of high oxygen conditions.
Equation of state representation of aqueous mixtures using an association model
Authors: Shinta Ali A. , Firoozabadi Abbas 
Published: March 2009

AbstractA previously proposed association equation of state (AEOS) (Anderko, 1991) for aqueous mixtures is modified to extend its applicability to a wider range of temperatures and pressures. In the AEOS, the compressibility factor is subdivided into two parts; physical and chemical. The physical part, in this work, is represented by the Peng‐Robinson (PR) (1976a) EOS for nonpolar compounds. Other cubic EOS can be used for this purpose with little effect on results. The chemical part is expressed by an empirical association model. The improved association model enables the AEOS to reproduce accurately the total compressibility of pure liquid water along the saturation line. Incorporation of the new association model in the PR‐EOS allows the combined model to calculate accurately the phase behavior of water/hydrocarbons and water/nonhydrocarbons in VLE, LLE, and VLLE regions.
Revisiting the maximum conversion of substrate in an enzymatic cstr with micromixing considerations
Authors: Malcata F. Xavier 
Published: March 2009

AbstractThe balance equations pertaining to an enzyme undergoing first order thermal deactivation and a substrate undergoing enzyme‐catalyzed transformation following Michaelis‐Menten kinetics in a CSTR are solved for the two limits of micromixing. The maximum conversions of substrate are obtained under the assumption that the space time of the reactor is infinite. The range of the maximum conversion of substrate is wider at intermediate values for the dimensionless Michaelis‐Menten constant and becomes narrower as the ratio of the time scales of the enzyme‐catalyzed reaction and the enzyme deactivation increases.
Particle cross‐flow, lateral momentum flux and lateral velocity in a circulating fluidized bed
Authors: Zhou J. , Grace J. R. , Lim C. J. , Brereton C. M. H. , Qin S. , Lim K. S. 
Published: March 2009

AbstractLateral and axial profiles of solids cross‐flow flux were measured in a circulating fluidized bed riser of square cross‐section with a sampling probe. The solids cross‐flow flux was found to be higher near the wall, especially near the corners, and lower in the core of the riser. The net solids horizontal flux was outwards in the lower part of the riser and inwards near the top.The lateral solids momentum flux, measured by means of a piezoelectric probe, increased with height and then decreased near the top of the riser. The lateral solids momentum flux first increased with distance from the axis and then decreased towards the wall. It was especially low near the corners.
On‐Line control of supersaturation in a continuous cooling KCL crystallizer
Authors: Redman T. P. , Rohani S. , Strathdee G. 
Published: March 2009

AbstractControl of supersaturation in a 1‐L continuous cooling KC1 crystallizer was investigated. The supersaturation was determined from on‐line measurements of the density and temperature of clear liquor samples. A cascade control scheme was used to control the supersaturation through the manipulation of the co‐saturated feed temperature set‐point while maintaining the crystallizer temperature at 303.2 K. Experimental results showed that due to the suppression of spontaneous nuclearion, a decrease in the measured supersaturation resulted in a 23% increase in the mean crystal size and a 12% decrease in the amount of NaCl impurity in the KCI crystals.
Video analysis of submerged jet microencapsulation using HEMA‐MMA
Authors: Stegemann Jan P. , Sefton Michael V. 
Published: March 2009

AbstractVideo and digital image analysis were used to understand the limiting steps in a submerged jet microencapsulation process for mammalian cells. Hydroxyethylmethacrylate‐methylmethacrylate copolymer (HEMA‐MMA) two phase droplets with an aqueous core are formed by coextrusion at a needle tip and fall through a layer of hexadecane prior to precipitation in an aqueous medium. Initial eccentricity was lowest when the capsule cores contained 20% (w/v) Ficoll and the inner needle protruded 100 m̈m past the outer needle. Capsule morphology was refined in the hexadecane over‐layer, and was strongly affected by crossing the hexadecane‐precipitation bath interface.
On the clean and efficient thermal treatment of de‐inking solid residues
Authors: Kozinski Janusz A. , Zheng Guohui , Saade Raafat , Di Lalla Sergio 
Published: March 2009

AbstractThermal treatment of contaminated de‐inking sludge in a low‐high‐low (LHL) temperature reactor was investigated. Experiments were conducted in a Cahn TGA‐171 furnace coupled with a Mattson Galaxy 5020 FTIR. Sludge samples (70 g) were heated up to 1770 K (50 K/min.), kept at that temperature for 5 min. and were then quenched (60 K/min.). During the LHL process the sludge underwent structural transformations from a mixture of fibers, through skeleton‐like structures (45–110 μm), porous particles, to compact spheres (5–30 μm). It was shown that the LHL treatment results in a safe encapsulation of heavy metals (Pb, Cd) inside the ash and in a 78.2% decrease in the amount of mutagenic polycyclic aromatic hydrocarbons. The LHL method developed could help to solve waste management and environmental protection problems.
Modelling and simulation of commercial catalytic naphtha reformers
Authors: Vathi Garimella Padma , Chaudhuri Kumar K. 
Published: March 2009

AbstractA simulation model for catalytic reforming has been developed to monitor commercial plant performance. The model consists of various modules to predict temperature and concentration profiles, catalyst deactivation and cycle length, inter stage heater duties, recycle gas composition and octane number. The lumping details of the feed and reaction scheme, parameter estimation and model validation details are given. The model numerically integrates the component and energy balance equations for the combined feed and recycle gas in each reactor and then simulates flash separator for recycle gas composition. The results of the model validated for four different commercial reactors performance are presented.
Axial and lateral dispersion of fine particles in a binary‐solid riser
Authors: Wei Fei , Cheng Yi , Jin Yong , Yu Zhiqing 
Published: March 2009

AbstractAxial and lateral mixing of fine particles in a binary‐solid riser have been investigated using a phosphor tracer method. The measured bimodal residence time distribution (RTD) demonstrated two types of axial dispersions of the fines: the dispersion of discrete particles and that of clusters. A proposed one‐dimensional, bimodal dispersion model describes the bimodal RTDs very well. The axial Peclet number of the fines is not sensitive to the fraction of coarse particles, gas velocity and solids circulation rate. Lateral solids dispersion was determined by measuring the solids RTD at different radii using a point source tracer injection. A two‐dimensional dispersion model describes the measured RTDs satisfactorily. Lateral solids mixing decreased as coarse particles were added into the riser. Correlations of the axial and lateral Peclet numbers obtained fit the experimental data well.
Representation of the concentric spherical powder reaction model in the form of linear regression analysis
Authors: Shimizu Akira , Hao Yu‐Jun , Tanaka Tatsuo 
Published: March 2009

AbstractTo perform the linear regression analysis of the powder reaction rate, some kinetic equations are derived on the basis of the Hao and Tanaka's concentric spherical model (Intern. Chem. Eng. 30, 244 (1990) and Can. J. Chem. Eng. 68, 81 (1990)) assuming monodisperse particles. The applicability of the kinetic equations is examined by using the experimental data of both counterdiffusion system and uni‐directional diffusion system. This linear regression analysis enables us to decide rapidly about the suitability of the model, to predict the diffusion mode and to determine the diffusivity.
The dissolution kinetics of sand as function of particle size
Authors: Jendoubi Ferida , Mgaidi Arbi , Maaoui Mohamed El 
Published: March 2009

AbstractThe initial dissolution rate of sand into sodium hydroxide solution (12.5 mol/L) over a wide range of temperatures (150 to 220°C) and pressures (0.47 to 2.29 MPa) has been determined. A semi‐empirical equation was found to fit the dissolution data obtained at different temperatures and at different particle sizes. The influence of temperature on the reaction extent led to the activation energy of the dissolution, Ea = 74.41 kJ/mol. Six samples of sieved silica having narrow particle size distribution 38–40, 100–125, 212–200, 400–500 and 850–1000 μm were reacted with 12.5 mol/L sodium hydroxide solution at 220°C. The effect of particle size, i.e., surface area of the grains, on the initial rate of dissolution (denoted v0) has been described by an empirical equation. Evidence is given here showing that the general assumption of the simple proportionality between the rate of reaction and the exposed surface of solid is not always confirmed.
Use of velocity of sound in predicting thermodynamic properties of dense fluids from cubic equations of state
Authors: Shabani Mohammad R. , Riazi Mohammad R. , Shaban Habib I. 
Published: March 2009

AbstractIn this paper it has been shown that velocity of sound data may be used to obtain constants of a cubic equation of state and then thermodynamic properties can be accurately calculated through the constants extracted from sonic velocity data. Results are presented for estimation of heat capacities, enthalpies, vapor pressures and compressibility factors of some pure vapor and liquid compounds as well as some binary mixtures for pressures up to 100 MPa and temperatures up to 600 K for hydrocarbons from methane to hexadecane. The method will be useful for those mixtures containing heavy compounds for which accurate data on critical constants are not available, but for which the sonic velocity can be measured.
Determination of correlations to predict the minimum agitation speed for complete solid suspension in agitated vessels
Authors: Armenante Piero M. , Nagamine Ernesto Uehara , Susanto Jessyca 
Published: March 2009

AbstractExperiments were conducted to determine the effects of impeller clearance, impeller diameter, and other operating variables on the minimum agitation speed for off‐bottom solid suspension in agitated vessels, Njs, for disc turbines (DTs) and flat‐blade turbines (FBTs). Only data for which the impellers produced recirculation flows above and below the impeller (the so‐called “double‐eight” flow pattern) were considered. Regression equations for Njs were obtained, in which explicit terms for impeller clearance and vessel diameter‐to‐impeller diameter ratio (T/D) were included. Modified Zwietering equations (Zwietering, 1958) were also obtained, in which Zwietering's parameter S was mathematically expressed as a function of vessel diameter‐to‐impeller clearance ratio and T/D ratio. When used together with the correlations of Armenante and Uehara Nagamine (1998) for impellers close to the vessel bottom, the equations presented here can be used to calculate Njs for DTs and FBTs for any typical impeller clearance.
Stresses on immobilized phanerochaete chrysosporium hyphae in submerged cultures for ligninase production
Authors: Zhen Zhonming , Yu Jian 
Published: March 2009

AbstractEffects of hydraulic shear stress and oxygen starvation stress on immobilized white‐rot fungus Phanerochaete chrysosporium in submerged cultures for ligninase production were studied. The immobilized fungal hyphae formed an even mycelial mat on a rotating cylindrical stainless steel net showing little sensitivity to the shear stress. The average activity of ligninase over 24 h during a peak production period was 389 U/L at a tip velocity of 0.44 m/s and 369 U/L at a doubled tip velocity of 0.88 m/s. When the dissolved oxygen level dropped below 1 mg/L, the fungal cells responded to the oxygen starvation stress and released a considerable amount of protease. The proteolytic denaturation of ligninase was the major reason that a negligible ligninase activity was detected at a low aeration rate.
Noncatalytic and catalytic pyrolysis of toluene
Authors: Pant Kamal K. , Kunzru Deepak 
Published: March 2009

AbstractNoncatalytic and catalytic pyrolysis of toluene has been studied at atmospheric pressure in the temperature range of 1043 to 1153 K using steam or nitrogen as the diluent. The catalyst used was potassium carbonate impregnated calcium aluminate. Compared to noncatalytic pyrolysis, the conversions were significantly higher in the presence of the catalyst although the product selectivities were not affected. With nitrogen as the diluent the main products were hydrogen, methane, benzene, bibenzyl and higher hydrocarbons. When steam was used as the diluent, in addition to the above products appreciable amounts of carbon monoxide and carbon dioxide were also produced. The overall reaction of toluene could be represented by two parallel paths; one for toluene decomposition and the other for the toluene‐steam reaction. The kinetic constants of these two reactions for catalytic as well as noncatalytic pyrolysis were determined by nonlinear optimization. In the presence of the catalyst, the activation energy for toluene decompostion was significantly reduced, whereas there was only a marginal reduction in the activation energy of the toluene‐steam reaction.
Collapse of dilute suspension in different circulating fluidized bed risers with respect to different particles
Authors: Xu Guangwen , Nomura Kousuke , Nakagawa Nobuyoshi , Kato Kunio 
Published: March 2009

AbstractThe collapse of dilute suspension was studied in three different circulating fluidized bed (CFB) risers with two types of particles. The risers had the same height of 3.0 m but different inner diameters of 66 mm, 97 mm and 150 mm, respectively. FCC particles (Geldart A) and silica sand particles (Geldart B) were used. It was found that the collapse of dilute suspension is characterized by rapid accumulation of particles at the riser bottom, independent of the riser diameter and the types of particles. In accordance with the observation, an approach was developed to determine the collapsing point from experimental measurements. Then, the dilute suspension collapse was found to be dominated by an identical differential pressure drop at the riser bottom. This critical pressure drop is independent of gas velocity and riser diameter, whereas varies with the properties of particles. Riser diameter has different influences for FCC and silica sand particles upon the saturation carrying capacity, the solids circulation rate at the dilute suspension collapse. Under a given gas velocity, the collapse in a larger riser is observed to take place at a larger solids circulation rate for FCC, but at a smaller solids circulation rate for silica sand. This diversified dependence on riser diameter of the saturation carrying capacity was identified as a result of the different influences of the riser diameter on the bed density for those two types of particles.
Modeling of biomass devolatilization in a fluidized bed reactor
Authors: Difelice Renzo , Coppola Gianfilippo , Rapagna Sergio , Jand Nader 
Published: March 2009

AbstractA simple model that simulates a single biomass particle devolatilization is described. The model takes into account the main physical and chemical factors influencing the phenomenon at high temperatures (>700 K), where the production of gaseous components far outweighs that of liquids. The predictions of the model are shown to be in good agreement with published data. The model is then applied to the devolatilization of biomass in a fluidized bed, in which attention is focused on heat transfer, particle mixing and elutriation, and gas production. Predictions on the overall devolatilization time for a biomass particle are compared with experimental results obtained in a fluidized bed reactor in which the process was monitored by continuous measurement of the bed pressure. Good correspondence of predicted with calculated values was obtained, supporting the validity of the many approximations made in the derivation of the governing relationships for the pyrolysis process.
Modeling of an internally circulating fluidized bed reactor for thermal treatment of industrial solid wastes
Authors: Mukadi Lukanda , Guy Christophe , Legros Robert 
Published: March 2009

AbstractA predictive mathematical model is developed to describe and characterize the key design variables of a novel Internal Circulating Fluidized Bed Combustor. The model is based on fundamental principles of heat transfer, mass transfer, hydrodynamics and reaction kinetics. Under justifiable assumptions unsteady state mathematical equations are written and solved. The input parameters of the model are gas and solid flowrates, solid circulation flux, as well as physical properties of gas and solids. The model allows to predict and to investigate the temperature, the combustible conversion, the oxygen concentration, the residence time, the voidage and the solid velocity in the riser. Experiments with spent foundry sand are undertaken in order to assess the validity of the model. The predictions for the transition period of heating clean sand and the treatment of waste compare satisfactorily to the experimental data.
Leaching of uranium and 226ra from low‐level radioactive waste from port hope, ontario
Authors: Nirdosh Inderjit 
Published: March 2009

AbstractUranium and radium were leached from a low‐level radioactive soil sample neutralized with limestone from Port Hope, ON, in single stage and multistage leaching tests. The leachants used were alkaline EDTA, sodium citrate, sodium potassium tartrate, acidic ferric chloride, hydrochloric acid, nitric acid and hydrochloric or nitric acid plus boric acid mixtures. All leaching tests except the two‐stage acid leachings proved ineffective in yielding leach residues with low residual 226Ra concentrations of < 100 pCi/g. Leaching with 4 mol/L HNO3 in the first stage followed by treatment with 4 mol/L HNO3 plus 0.05 mol/L boric acid in the second stage proved effective and gave a leach residue with 85 pCi/g 226Ra and 16 ppm uranium.
Influence of geometry and solids concentration on the hydrodynamics and mass transfer of a rectangular airlift reactor for marine sediment and soil bioremediation
Authors: Tobajas Montserrat , Siegel Marc H. , Apitz Sabine E. 
Published: March 2009

AbstractHydrodynamics and mass transfer characteristics of a three‐phase airlift reactor were studied in a rectangular split‐vessel reactor and using an air‐seawater‐marine sediment system. Experiments were conducted over a range of downcomer to riser cross‐sectional area ratios (AD/AR = 0.65 to 1.0) for two‐phase systems and for five sediment concentrations (5 to 25% w/v) using marine sediments. The influence of higher sediment concentrations (30 to 50% w/v) was examined for AD/AR = 1. The presence of fine sediment particles in the system had little effect on hydrodynamic and mass transfer parameters compared to the two‐phase systems up to 25% loading, decreasing at higher loadings. The airlift reactor was found to meet the dissolved oxygen demand needed for a contaminated sediment treatment process. Axial distribution of the particles was uniform along the riser and the downcomer. Correlations were developed that described the hydrodynamic and mass transfer behaviour for all experimental conditions examined.
Onset of pulsing in trickle beds: Evaluation of current tools and state‐of‐the‐art correlation
Authors: Larachi F. , Iliuta I. , Chen M. , Grandjean B. P. A. 
Published: March 2009

AbstractThe transition between trickle flow and pulse flow regimes in cocurrent trickle‐bed reactors is not properly predicted by existing phenomenological, semi‐theoretical and empirical tools. Based on the most complete flow regime transition data base (700 measurements, 30 gas–liquid systems, 18 columns diameters, 38 packing materials, high pressure conditions, coalescing, non‐coalescing and pseudoplastic non‐Newtonian aqueous and organic liquids), a state‐of‐the‐art explicit correlation of trickle‐to‐pulse flow changeover was derived relying on neural network modeling. Robustness of the proposed correlation was verified, and the limitations of the literature correlations and models were demonstrated through systematic statistical testing over the constructed data base. The overall result was a net improvement in predicting the trickle‐to‐pulse flow regime transition.
Numerical correlation for thermal conduction in packed beds
Authors: Lund Kurt O. , Nguyen Huy , Lord Stephen M. , Thompson Chrystal 
Published: March 2009

AbstractThe numerical conduction of heat in packed beds of particles is investigated, including the effects of inter‐particle microasperity gaps and deformation contacts. A detailed numerical model of two half spheres in contact with interstitial fluid is constructed, including asperity (roughness) gaps and deformation contacts on the respective orders of 5 μm and 100 μm for 1 mm particle diameters. The resulting heat flux distributions at the diametrical planes of the particles are integrated to yield the overall thermal conductance, K, or resistance, R = 1/K, between the two diametrical planes. The results show K to be strongly dependent on the interstitial fluid gap and the deformation contact diameter, as well as on fluid and solid conductivities. The effective bed conductivity, ke, is determined as a function of K and the void fraction, and correlated in terms of bed parameters. The resulting ke correlation agrees well with published experimental data over a wide range of substances and temperatures.