bluuebunny/crossref_metadata_2025_split huggingface dataset:
Gas mixing in a turbulent fluidized bed reactor
Authors: Sotudeh‐Gharebaagh Rahmat , Chaouki Jamal 
Published: March 2009

AbstractA series of experiments has been conducted to study mixing and hydrodynamic behaviour of a downward facing sparger in a turbulent fluidized bed reactor. Using pressure measurement techniques, two flow discharge modes were identified around the sparger by injecting a gas tracer into the bed. These are bubbling and jetting conditions. Experimental results show that, under bubbling conditions, bubbles tend to keep their identity, while under jetting conditions a highly turbulent heterogeneous area is formed around the injection point. Due to attrition and erosion of internal heating or cooling surfaces in industrial reactors, the dominant discharge mode is the bubbling pattern. Therefore, in this investigation, the bubbling pattern is studied by measuring the radial and axial dispersion of gas tracer injected to a hot fluidized bed reactor of 20 cm diameter of FCC and sand particles. A three‐phase model is also proposed in order to predict the mixing length. In addition, the effect of sparger configuration on tracer gas mixing was examined for FCC particles.
Fluidized state gelation of ceramic microspheres: Feasibility study of a continuous process and analysis of the chemical dehydration phenomena
Authors: Rovero Giorgio , Vanni Marco 
Published: March 2009

AbstractA continuous gelation process for producing aluminum and zirconium hydroxide microparticles was conceived and tested in a lab‐scale apparatus. Fluidized state was devised as an appropriate hydrodynamic configuration to maintain the reacting sol microdrops suspended: stable non‐coalescing spherical gel particles in a size range quite below 100 μm were produced via gelation. The microspheres produced by a subsequent calcination step showed a diameter ranging between 2 μm and 20 μm. This powder, without further size classification, was an optimal product to manufacture test specimens by sintering. Measurements on the mechanical properties, such as toughness, flexural strength and hardness, classified the test bars as a very promising ceramic material. In order to enlighten the chemical drying phenomenon and devise the main governing mechanisms acting in the gelation reaction, an extremely simplified experimental system was set. A single drop of sol was deposited into a given amount of the dehydrating liquid medium and observed by an optical microscope; image analysis permitted us to identify the gel formation, the size reduction kinetics, as well as secondary phenomena.
A model for the evaporation of water from large glass particles in pneumatic transport
Authors: Littman Howard , Day Jenn‐Yuan , Morgan Morris H. 
Published: March 2009

AbstractA model is presented for the evaporation of water from large particles in pneumatic transport. The work is relevant for estimating the coating solution feed rate and the length of the draft tube in Wurster‐type particle coaters. Specifically, the rate of evaporation of water from 1 mm glass particles in a 28.45 mm tube was calculated from the model. The rate increased with solids mass flow rate, inlet air temperature and inlet particle temperature. The heat was more rapidly removed from the particle phase than from the air phase and high inlet air temperatures are tolerated. The model presupposes that the gas and particle velocities, and voidage are known and that the water film on a particle is thin and uniformly distributed. Hydrodynamic considerations that impact on the calculations are discussed.
Enhancement of the interfacial transfer of iodine by chemical reaction
Authors: Evans Greg J. , Ling Juliette R. 
Published: March 2009

AbstractEnhancement of the air‐water interfacial transfer of I2 by reaction with I− was investigated in order to evaluate a mechanistic model. Separate systems for evaporation and absorption of I2 were studied. The overall mass transfer coefficient increased from 2 × 10−4 to 2.5 × 10−3 cm/s as I− concentration increased from 10−4 to 10−1 M. At I− concentrations greater than 10−1 M, the interfacial transfer of I2 was gas‐side limited. The model gave a good representation of these results.
Mixing of a lignin‐based slurry fuel
Authors: Posarac Dusko , Watkinson A. Paul 
Published: March 2009

AbstractLignin‐based slurry fuels are a potential alternative to fossil fuels in kraft pulp mills. Lignogels — mixtures of lignin, fuel oil, water and surfactant — are non‐Newtonian fluids, with shear‐thinning and thixotropic behaviour. Their mixing was investigated in tanks with volumes of 3 and 30 L. An A310 hydrofoil impeller was used in all experiments. Results were compared with measurements in Newtonian fluids, used to characterize the impeller over a broad range of Reynolds numbers (1–500 000). An aqueous CMC solution was also used for characterization of the impeller and estimation of the Metzner‐Otto constant. Results in the transition region were corrected by introduction of two empirical parameters.
Fluid‐Borne entities in the impeller stream of a rushton turbine
Authors: Glasgow Larry A. 
Published: March 2009

AbstractThe breakage or disintegration of suspended entities by energetic fluid motions in stirred tanks is an essential aspect of many operations in the chemical process industries. However, the hydrodynamic inhomogeneity of such tanks makes it extremely difficult to characterize the stresses experienced in any simple manner. This work provides a determination of both the location and the frequency of interaction of spherical fluid‐borne entities with the discharge of a Rushton turbine. These data show how both particle size and impeller speed affect the severity of the exposure, setting the groundwork for improved descriptions of the dynamic behaviour of the particle size distribution in a wide variety of dispersed‐phase processes.
Predictive models for the viscosities of multicomponent liquid n‐Alkane and regular solutions
Authors: Nhaesi Abdulghanni H. , Asfour Abdul‐Fattah A. 
Published: March 2009

AbstractThe pseudo‐binary model developed by Wu and Asfour (1992) has been used to modify some existing viscosity predictive models to that they can predict the viscosities of multicomponent liquid n‐alkane and regular mixtures. The McAllister three‐body interaction model and the Grunberg‐Nissan viscosity equation were both employed, after modification, to successfully predict the viscosity of multicomponent liquid n‐alkane and regular solutions. The modified Generalized Corresponding States Principel (MGCSP) reported by Wu and Asfour (1992), for only predicting the viscosities of n‐alkane mixtures, has been extended to predit the viscosities of multicomponent regular solutions. The predictive capabilities of several predictive models were analyzed. The obtained results showed that the pseudo‐binary McAllister model predicts the viscosity data better than the other existing predictive models.
Estimation of gas hold‐up in aerated vessels
Authors: Paglianti Alessandro , Takenaka Katsuhide , Bujalski Waldemar , Takahashi Koji 
Published: March 2009

AbstractAn attempt to produce a simple equation for gas hold‐up in stirred tank reactors has been made. This new semi‐empirical equation, based on the mass balance for the gas phase, predicts the observed effem due to the tank and impeller diameters and physical properties reasonably well. It can be used both for tanks working with a single Rushton impeller as well as with multiple Rushton impeller systems. The equation has been validated using both data found in literature and from our experiments.
Hydrodynamic behaviour of a magneto airlift column in a transverse magnetic field
Authors: Al‐Qodah Zakaria 
Published: March 2009

AbstractThe hydrodynamics of a three‐phase airlift reactor of magnetic particles has been investigated in the presence of a transverse magnetic field. Experiments were carried out in two modes: applying the magnetic field to a static bed then increasing the field flow, and applying the magnetic field to a fluidized bed then increasing the magnetic field intensity. In magnetizing the first mode and parallel to the increasing gas superficial velocity, several bed regimes were observed, including: initial packed, stabilized, and fluidized beds. On the other hand, in magnetizing last mode and while increasing the magnetic field intensity, the fluidized bed changes from a fluidized to a stabilized to frozen bed. Bed expansion before the onset of fluidization increases as the magnetic field intensity increases. Minimum fluidization velocity was found to be strongly dependent on the magnetic field intensity and the minimum stabilization intensity was also strongly dependent on the gas velocity. The magnetic field intensity also affects the bed expansion hysteresis and the liquid circulation velocity. A photocell was used to measure the water circulation rate in the downcomer of the reactor.
Gas‐liquid mass transfer in low‐ and medium‐consistency pulp suspensions
Authors: Rewatkar V. B. , Bennington C. P. J. 
Published: March 2009

AbstractThe volumetric gas—liquid mass transfer coefficient (kLa) was measured for low‐ and medium‐consistency pulp suspensions using the cobalt‐catalyzed sulfite oxidation technique. Mass transfer rates were measured in a high‐shear mixer for a range of operating parameters, including the rotor speed (N = 10 to 50 rev/s), gas void fraction (Xg = 0.10 to 0.40) and fibre mass concentration (Cm = 0.0 to 0.10). kLa measurements were compared with the macroscale flow regime in the vessel (characterized using photographic techniques) and correlated with energy dissipation, gas void fraction and suspension mass concentration in the mixer. We found that gas‐liquid mass transfer was significantly reduced in pulp suspensions, even for low suspension concentrations. Part of this reduction was associated with dissolved components leached from the fibres into the liquid phase. This could account for reductions in kLa of up to 30% when compared with distilled water. The fibres further reduced kLa, with the magnitude of the decrease depending on the fibre mass concentration. Correlations were developed for kLa and compared with results available in the literature.
Batch kinetics and modelling of propionic acid fermentation
Authors: Goswami Vandana , Srivastava A. K. 
Published: March 2009

AbstractBatch propionic acid fermentation kinetics was studied using five different initial concentrations of lactose (i.e., 37 g/L, 45g/L, 50g/L, 57 g/L and 73 g/L) at constant temperature (30°C) and pH (6.5) under anaerobic conditions using Propionibacterium acidipropionici (ATCC 4875). When the initial substrate concentration was 37 g/L, 45 g/L, 50 g/L, 57 g/L and 73 g/L, then, correspondingly, 16 g/L, 19 g/L, 22.25 g/L, 25.3 g/L and 26.3 g/L of propionic acid was accumulated in the fermentation broth. Increasing the supply of lactose in the fermentation medium led to the accumulation of by products succinate, acetate and pyruvate. Maximum propionate yield (0.44 g/g) and comparatively lesser impurities (byproducts) were achieved with 57 g/L initial lactose concentration. The batch growth kinetics was eventually used to develop and test a mathematical model for propionic acid fermentation by P. acidipropionici at pH 6.5 and So = 57 g/L. YX/Smax was found to be the most sensitive parameter of the model. The same model also successfully simulated the batch kinetics observed at So = 37 g/L. However the model failed to simulate the fermentation kinetics observed at So = 73 g/L. The developed model can be used for process optimization studies.
Prediction of pressure fluctuations and minimum fluidization velocity of binary mixtures of geldart group b particles in bubbling fluidized beds
Authors: Leu Lii‐Ping , Wu Chih‐Nan 
Published: March 2009

AbstractA simple method was proposed to find the pressure fluctuations of binary systems of Geldart Group B particles under bubbling fluidized bed conditions. The pressure fluctuations of binary systems could be predicted from the pressure fluctuations of the individual particles component which comprised the binary systems for completely mixed and partially mixed systems. The predicted pressure fluctuations could be used to calculate the minimum fluidization velocity of the binary systems. The predicted and experimental values of pressure fluctuations and the minimum fluidization velocity of binary systems were in fairly good agreement.
Effect of temperature on gas bypassing and solids circulation rate in an internally circulating fluidized bed
Authors: Namkung Won , Guy Christophe , Boisselle Fréadéaric , Legros Robert 
Published: March 2009

AbstractThe effect of bed temperature in the annulus region on gas bypassing from annulus to riser and solids circulation rate has been determined in an internally circulating fluidized bed. The bed voidage in the annulus region increases with increasing temperature. The average fractions of gas bypassing of annulus gas are 59.4% and 87% at room temperature and high temperature (400°C to 800°C), respectively. Solids circulation rate increases with increasing annulus gas velocity, but is nearly independent of riser velocity. Solids circulation rate increases with increasing temperature.
An analysis of the use of electrical power measurements for process control in large‐scale stirred vessels
Authors: Hjorth Sven , Karlsson Lennart , Friberg Paal , Boon Lotte 
Published: March 2009

AbstractThe mechanical power that is transferred to a liquid via the shaft of an agitator is obtained from a measurement of the electrical power flowing into the electric motor within an accuracy of less than 5%. The accuracy obtained is limited by the calibration procedure. As the implementation of an electric power measurement is both simple and comparatively inexpensive, the technique is suitable for a continuous monitoring of the power used by agitators in the process industries.
Dechlorination of 1‐chlorohexadecane and 2‐chloronaphthalene in water under sub‐ and supercritical conditions
Authors: Akimoto Masamichi , Tanaka Hideharu , Watanabe Akiko 
Published: March 2009

AbstractReactions of 1‐chlorohexadecane and 2‐chloron‐aphthalene in water under sub‐ and supercritical conditions have been investigated so as to show the possible use of water for the dechlorinations of these organic chlorides. The reactions were carried out at 275°C to 430°C in a small SUS316 batch reactor under nitrogen atmosphere at the molar organic chloride/water ratio of 1/100. Under subcritical temperatures, hydrolysis reactions occurred catalyzed by H+ ions, whereas under supercritical conditions hydrodechlorinations occurred too, in which hydrogens evolved by the reaction of HCI with the metal wall of the reactor participated. The hydrogenation and hydrogenolysis of the primary reaction products also occurred for 1‐chlorohexadecane under supercritical conditions. The dechlorination selectivity was nearly 100% for these organic chlorides irrespective of the reaction conditions employed.
Method to determine molecular diffusivities of phenol in bitumen
Authors: Tang Joseph S. , Zhang Pei Xin 
Published: March 2009

AbstractPhenols, carboxylic acids and other water‐soluble compounds in bitumen constitute a potential source of groundwater pollution. To assess the extent of damages that could result from a spill, a water extraction method was used to determine the molecular diffusion of phenol in bitumen. This method involves the diffusion of phenol through bitumen into the flowing water in a well‐stirred cell. From the phenol concentration in water, the phenol flux and hence the phenol diffusion coefficient in bitumen can be deduced. An approximate dimensionless solution was obtained by de‐coupling the diffusional flux from the concentration buildup in water. The phenol diffusion coefficient was determined to be 4.0 ± 0.3 × 10−8 m2/s at 22°C. The derivation and the properties of the dimensionless solution were also discussed in the paper.
Reductant flow control for NOX removal from lean exhaust gases
Authors: Krijnsen Henrike C. , Van Kooten Wijnand E. J. , Calis Hans Peter A. , Bleek Cor M. Van Den 
Published: March 2009

AbstractThis review article describes and discusses the literature on reducing agent control systems for NOx emission reduction in the exhaust gas of full lean‐burn engines. The literature can be classified as feedback, feedforward, feedforward‐feedback, feedforward/feedforward‐feedback and periodical dosing control systems, which can be further classified as classical, override, co‐ordinated, constrained and split systems or a combination of those.As long as reproducible, fast and cheap NOx sensors are not commercially available, the control system should be an inferential feedforward or feedforward‐feedback system supplied with constraints for environmental and economical reasons. For future applications an oxidation catalyst downstream of the deNOx catalyst should be applied to convert any inevitable reductant slip, due to modelling errors, to harmless compounds.
Simple shear, hysteresis and yield stress in biofluids
Authors: And Ning Sun , De Kee Daniel 
Published: March 2009

AbstractBiofluids such as blood, as well as other structured materials, exhibit rather complex rheological behaviour. In this paper, starting from a first‐order kinetic model, we developed a constitutive equation and studied its applicability to model biofluids. In particular, we studied the cases of simple shear flow, hysteresis and yield stress. Model predictions were successfully compared with experimental data on complex materials such as blood and a penicillin suspension.
Optimization of amino acids production from waste fish entrails by hydrolysis in sub and supercritical water
Authors: Kang Kilyoon , Quitain Armando T. , Daimon Hiroyuki , Noda Reiji , Goto Naohiro , Hu Hong‐Ying , Fujie Koichi 
Published: March 2009

AbstractA resource recovery technique using sub‐ and supercritical water hydrolysis was applied to convert waste fish entrails into amino acids. The effect of reaction parameters such as temperature and time necessary for the control of reaction towards optimum yield of amino acids was investigated. Results showed a maximum yield of total amino acids (137 mg/g dry fish) from waste fish entrails at T= 523 K (P = 4 MPa) and reaction time of 60 min in a batch reactor. Under supercritical conditions (e. g., T= 653 K, P = 45 MPa), the yield decreases due to rapid decomposition compared to production rate of amino acids. The results suggest operation of the system at short reaction time and mild temperature condition.
A new pressure drop model for flow‐through orifice plates
Authors: Liu Shijie , Afacan Artin , Masliyah Jacob H. 
Published: March 2009

AbstractThis study was carried out to seek a suitable model to describe flow through orifices. The model of developing flow through short ducts was found to be adequate. There were two free parameters in the model equation involving the normalized pressure drop and Reynolds number. Experiments were performed using two Plexiglas tanks separated by an orifice. The liquid level height variation with time was recorded. A unique parametric estimation technique was used to determine the two free parameters from the dynamic liquid level data. It was found that direct use of the experimental data (liquid level heights) is the best option in correlating the experimental data with the model. The correlation fits well with the present and literature experimental data quite well. It was found that the variation of the pressure drop with the flow rate is linear when the flow is weak, where the orifice Reynolds number is less 10. When the flow is strong, the ratio of the pressure drop to the flow rate becomes linearly related to the flow rate. These two limits are identical to those for flow in porous media.
Hydrodynamic modelling of the axial density profile in the riser of a low‐density circulating fluidized bed
Authors: Smolders Kathleen , Baeyens Jan 
Published: March 2009

AbstractThe axial density profile is an important characteristic of the CFB riser and a key parameter in the CFB design. A simple, but reliable model is needed to predict the density profiles. Elutriation‐based models treat the dense phase at the bottom of the riser as a dense bubbling bed whereas the dilute phase higher up can be looked upon as the entrainment zone above the dense bed. The elutriation model, as originally presented by Rhodes et al. (1986) and based on Wen et al. (1982) is extensively studied and modified. In spite of the modifications, the use of entrainment models has certain clear limitations due to a wide range of predictions as evident from Table 1. Elutriation rates are calculated based on the hydrodynamic phenomena in the dense bed and a fitting procedure for the entrainment decay constant (σ) was performed.
Fluidization regimes in two‐ and three‐phase fluidized beds: Comparison between measurement techniques
Authors: Barghi Shazad , Briens Cedric L. 
Published: March 2009

AbstractFluidization regimes were studied in liquid‐solid and gas‐Liquid‐solid fluidized beds. The liquid velocities at which regime transitions occur in liquid‐solid and gas‐liquid‐solid systems were obtained for monosize and multicomponent systems. Minimum fluidization, complete fluidization and complete mixing velocities of particles were obtained from pressure drop measurements, a collision technique or a conductivity method. The collision technique provided accurate complete fluidization and complete mixing velocities by measuring directly the particle motion. The conductivity technique, which is easier to implement, gave similar but less accurate results.
Heat transfer between an isolated bubble and the dense phase in a fluidized bed
Authors: Hartman George , Wu Wenyuan , Chen Zumao , Agarwal Pradeep K. 
Published: March 2009

AbstractHeat transfer between the bubble and dense phases of a bubbling fluidized bed plays a very important role in the system performance, especially for applications involving solids drying and gas‐phase combustion. However, very few experimental data are available on this subject in the literature. An experimental and modelling investigation on the heat transfer behaviour of isolated bubbles injected into an incipiently fluidized bed is reported in this paper. A new single‐thermocouple technique was developed to measure the heat transfer coefficient. The effects of bed particle type and size, and bubble size on the heat transfer coefficient were examined. The heat transfer coefficient was found to exhibit a maximum as the bubble size increased in the bubble size range investigated. The bed particle size had a comparatively small effect on the heat transfer coefficient. A simple mathematical model was developed which provides good agreement with experimental data.
Enhancement of the overall volumetric oxygen transfer coefficient in a stirred tank bioreactor using ethanol
Authors: Bi Yonghong , Hill Gordon A. , Sumner Robert J. 
Published: March 2009

AbstractEthanol was observed to improve the oxygen mass transfer rate into a well‐mixed bioreactor. The effects of impeller speed and ethanol concentration on the oxygen transfer from air to the water phase and on the average bubble diameter in a stirred tank bioreactor are reported and modelled. The results show that the oxygen mass transfer coefficient (kLa) increases from 0.002 to 0.017 s−1 (for distilled water) due to the increase of impeller speed from 135 to 600 rpm. With increasing ethanol concentration from 0 to 8 g/L, the oxygen mass transfer coefficients increase from 0.015 to 0.049 s−1 and from 0.017 to 0.076 s−1, for impeller speeds of 450 and 600 rpm, respectively. The average bubble diameter decreased from 7.0 mm to 1.7 mm in pure distilled water as the impeller speed was increased from 135 to 600 rpm. When ethanol was present in the aqueous phase, the bubble diameter fell from 6.0 mm to 0.6 mm as the impeller speed was similarly increased.