bluuebunny/crossref_metadata_2025_split huggingface dataset:
Kinetics of alkaline hydrolysis of 2‐ethylbutylformate
Authors: Chaudhuri Basab , Bhattacharjee Sekhar , Dutta Binay K. 
Published: March 2009

AbstractThe theory of mass transfer accompanied by chemical reaction has been used for studying the kinetics of alkaline hydrolysis of 2‐ethylbutylformate at different temperatures and ionic strengths of aqueous alkaline solution. Experiments have been conducted in a stirred cell having a flat liquid‐liquid interface. For aqueous phases containing 1–3 kmol/m3 sodium hydroxide, the alkaline hydrolysis conforms to the fast pseudo‐first order reaction regime. The system is of considerable practical importance and can be successfully employed for the measurement of the interfacial area of a mechanically‐agitated and flooded packed‐bed liquid‐liquid contactor.
Liquid phase residence time distribution for two phase flow in coiled tubes
Authors: Saxena A. K. , Nigam K. D. P. , Schumpe A. , Deckwer W. D. 
Published: March 2009

AbstractThe residence time distribution (RTD) of the liquid phase in air‐water flow through helical coils has been studied. Upward and downward cocurrent flows have been investigated in three coils with curvature ratios ranging from 11 to 60.7. The ranges of the Reynolds numbers for the gas and the liquid varied from 1500 to 3000 and 620 to 3200, respectively. A model has been proposed that describes the liquid phase RTD as combination of two different residence time distributions applicable for turbulent and laminar liquid flows.
Modelling of phase redistribution of horizontal annular flow divided in T‐junctions
Authors: Peng F. , Shoukri M. 
Published: March 2009

AbstractA phase redistribution model for annular flow divided in T‐junctions is developed. The model consists of two sub‐models accounting for phase distribution in the inlet to the junction and phase redistribution in the junction, respectively. In modelling phase redistribution in the junction, the dividing streamlines for each phase were determined separately assuming that the phenomena is mainly governed by the fluid inertia and pressure distribution in the junction. The overall model is capable of predicting phase redistribution in T‐junctions having horizontal inlet and any branch orientation. The predictions of this model and those of other available models are compared with experimental data. The predictions of the present model were found to be in better agreement with the experimental data than other available models and correlations.
Viscoplastic fluid flow in irregular eccentric annuli due to axial motion of the inner pipe
Authors: Hussain Quazi E. , Sharif Muhammad A. R. 
Published: March 2009

AbstractFully developed axial laminar flow of viscoplastic Herschel‐Bulkley fluids in eccentric annuli between two pipes has been investigated numerically. The pipes are closed at one end and flow is due to the axial motion of the inner pipe. The annuli may be filly open or partially blocked. General non‐orthogonal, boundary‐fitted curvilinear coordinates have been used to accurately model the irregular annular geometry due to the presence of a flow blockage. A computer code has been developed using a second‐order finite‐difference scheme. An exponential model for the shear stress, valid for both yielded and unyielded regions of the flow, is used in the computation. The effects of generalized Bingham number, flow behavior index, eccentricity, and blockage height on the pressure gradient or the surge pressure have been studied and the results are presented in dimensionless form. The pressure gradient is found to decrease with increasing eccentricity. For a partially blocked eccentric annulus the pressure gradient is found to decrease with an increase in the blockage height.
The interaction of solute transfer, contaminants and drop break‐up in rotating disc contactors: Part I. Correlation of drop breakage probabilities
Authors: Cauwenberg Veerle , Degrève Jan , Slater Michael J. 
Published: March 2009

AbstractThe breakage process of single drops in RDC liquid‐liquid extraction columns has been investigated. The breakage probability and daughter drop size distribution were the measured characteristics. Binary systems, non‐equilibrated ternary systems with mass transfer in both directions (c → d and d → c) and systems with surface active agent added were used in the experiments. A model of the breakage probability was developed based on a modified Weber number, taking into account the applied shearing stress and the resisting interfacial tension force. It is shown that breakage probability can be estimated if interfacial tension is known as a function of interfacial conditions.
In situ rheological monitoring in semi‐batch emulsification process for cosmetic lotion production
Authors: Choplin Lionel , Torandell Sandrine , Servoin Jacques 
Published: March 2009

AbstractIn situ rheological monitoring of a semi‐batch emulsification process for the production of a simplified cosmetic lotion formulation has been realized in a rheo‐reactor (100 mL volume), which consists of a small‐scale reactor connected to a rheometer. The torque evolution as well as the mechanical spectrum evolution has been reported for two different protocols. It has been shown that the evolution of the rheological properties of the macroemulsion seems to be governed by the gelification of the continuous aqueous phase. In situ rheological characterizations of the macroemulsion at the end of the process, under controlled mechanical history mimicking somehow post‐processing “real life” of the cosmetic lotion, have shown that the stability can be significantly influenced by the process protocol.
Spout diameters in full and half spouted beds
Authors: He Ayn‐Long , Lim Choon J. , Grace John R. , Qin Shao‐Zhong 
Published: March 2009

AbstractA fiber optic probe has been used to measure spout diameters in a half‐column and a full‐column based on the significantly higher counts of output electric pulses in the spout region than in the annulus. The flat wall of a semi‐cylindrical spouted bed column was found to cause considerable distortion of spout shapes which became approximately semi‐elliptical in cross‐section. Caution must therefore be exercised when using spout diameter data from the face of half‐columns for spouted bed modelling and design. The often‐used McNab (1972) equation was found to underestimate the spout diameters in the full‐column, with an average deviation of 35.5%.
Influence of ring‐type internals on axial pressure distribution in circulating fluidized bed
Authors: Bu Jianjie , Zuh Jing‐Xu 
Published: March 2009

AbstractIn order to improve non‐uniform radial and axial flow structure of a circulating fluidized bed, the influence of ring‐type internals on the axial pressure distribution and gas—solids flow structure in a riser of 7.6 cm in diameter and 3 m in height was investigated experimentally. Four different opening areas, 70%, 80%, 90% and 95%, were used and the superficial gas velocity and solids circulation rate were in the ranges of 5 to 10 m/s and 20 to 233 kg/m2·s, respectively. With the presence of internals, the axial pressure gradient distribution shows the formation of a zigzag type profile instead of the regular exponential or S‐shape profile and the bottom acceleration region is shortened. The opening ratio of the rings plays an important role in affecting the flow structure. The optimal opening ratio is tightly related to the operating conditions. In the circulation fluidized bed used in this study, 90% open area was found to be most suitable for obtaining a more uniform gas—solids flow structure.
Effects of sparger height and orifice orientation on solids dispersion in a slurry bubble column
Authors: Gandhi Bimal , Prakash Anand , Bergougnou Maurice A. 
Published: March 2009

AbstractThe effects of gas distributor height and the orientation of its orifices are investigated on solids dispersion and gas holdup profiles in a three‐phase slurry bubble column. The height of the distributor was varied to cover locations from near column bottom to above the settled solids bed height. The orifice orientations were changed from upward facing to downwards facing directions. The measurements were conducted in a Plexiglas column of 0.15 m ID and 2.5 m height. The gas phase was oil‐free compressed air while tap water was used as liquid phase. Glass beads with an average particle diameter of 35 μm and density of 2450 kg/m3 constituted the solid phase. The settled bed height was about 0.4 m which provided an average slurry concentration of about 15% (v/v) when all solids were dispersed. Both axial and column average phase holdups were measured. Effects of sparger location, gas jets formation and liquid circulation patterns on gas holdups and solids dispersion are analyzed. Empirical correlations are developed to relate sparger location to solids dispersion as a function of gas velocity. Optimum sparger height and orifice orientation is proposed based on the measurement of this study.
Dynamic modeling of continuous evaporative cooling KCl‐NaCl crystallizers
Authors: Tadayyon Abdulsamad , Rohani Sohrab 
Published: March 2009

AbstractPrevious work on the modeling of potash crystallizers has been mainly limited to the estimation of crystal size distribution (CSD) in the presence of only one solid component (KCl). In the present study, an attempt has been made to develop a model that incorporates NaCl as a second component that may co‐precipitate along with KCl under certain operating conditions. Addition of water to prevent co‐saturation or as a means of internal fines dissolution is also taken into consideration. External fines dissolution using a heat exchanger is incorporated in the model. In addition to the CSD, the model is able to predict crystal impurity resulting from co‐saturation with NaCl. The predictive capability of the model is tested using limited dynamic experimental data obtained from a 1 m3 pilot plant continuous evaporative crystallizer and the steady‐state experimental data from a two‐stage evaporative Swenson DTB industrial potash crystallizer circuit. In both cases, a good agreement between the model predictions and the experimental data was noticed.
Coprecipitation of CaCO3 and CaSO4
Authors: Sudmalis Michael , Sheikholeslami Roya 
Published: March 2009

AbstractCoprecipitation characteristics of CaCO3 and CaSO4 were studied under various operating conditions. The investigations were carried out in temperature‐controlled batch tests. Coprecipitation results were compared with our experimental results of a single salt crystallization. It was found that the induction period and kinetics of coprecipitation of these two salts follow that of pure CaCO3. However, thermodynamic concentrations of Ca in coprecipitation followed that of pure CaSO4 at all times. The relationship between the thermodynamic concentrations of Ca for pure CaCO3 and CaSO4 solutions depended on the pH of the CaCO3 solution. CaSO4 precipitated in form of gypsum and had a needle shape structure; CaCO3 had a spiral growth and precipitated in form of calcite. The precipitate structure was affected by the co‐existence of salts; the co‐precipitation resulted in CaCO3 crystals interwoven by CaSO4 crystals. This tends to result in a co‐precipitate that is stronger than pure CaSO4 and weaker than pure CaCO3 precipitate.
Gas spouting hydrodynamics of fine particles
Authors: Wang Shining , Xu Jian , Wei Weisheng , Shi Gang , Bao Xiaojun , Bi H. T. , Lim C. Jim 
Published: March 2009

AbstractHydrodynamic measurements for the spouting of fine particles were obtained in a conical‐based cylindrical bed of diameter 0.186 m, inlet orifice diameters of 6 to 14 mm, and included cone angles of 45 to 80 degrees. Four different types of fine particles with diameters ranging from 0.286 to 0.861 mm were investigated. Four different flow regimes—fixed bed, stable spouting, unstable spouting and slugging—were identified and mapped. The termination of the spouting of fine particles was caused by choking rather than by fluidization of particles in the upper bed. Stable spouting could be achieved when the ratio of the orifice diameter to mean particle diameter was less than 20. The measured minimum spouting velocities were within ±15% of those predicted by the Mathur—Gishler equation. Solids density measurements obtained by a gamma ray densitometer showed that the solid density in the spout increases with bed height and in the annulus is 3% to 10% higher than in a loosely packed bed.
Transient analysis of gas flow in a straight pipe
Authors: Hati Anindya , Verma Nishith , Chhabra Raj 
Published: March 2009

AbstractIn the present work, numerical simulation has been done to analyze transients in gas flow and pressure in a horizontal straight pipe. For a single gas pipeline, eight representative cases corresponding to different causes of transient behaviour are simulated to predict unsteady state flow and the evolution of pressure profiles. The numerical results show that depending upon the pipe dimensions and operating variables such as pressure and gas flow rate, transient effects in the pipeline may last for a long time and/or over significant length of pipe. The simulations predict an initial surge in gas flow rate greater than the final steady‐state value if the pressure drop across the pipe is increased. Similarly, initial flow rate may decrease below the final steady‐state value if the pressure drop is decreased. In case of complete closure of a valve, oscillations in both pressure and mass flow rate are observed, which gradually decay and the steady state conditions of no flow are ultimately achieved. The present results are compared with a published work from the literature. A reasonably good agreement is found between these two predictions. The present study is of practical significance in safe design and operation of a gas delivery system.
Strength development due to long term sulfation and carbonation/sulfation phenomena
Authors: Anthony Edward J. , Jia Lufei , Laursen Karin 
Published: March 2009

AbstractCFBC boilers firing high sulfur, low ash fuels can produce deposits consisting of almost pure CaSO4. Test work has shown that if sorbents or bed materials are sulfated for long times (several days or more), they develop compositions similar to those deposits. Sulfation increases with temperature from 650°;C to 900°C, and strength increases continuously in the temperature range of 650°C to 950°C. When sulfation occurs under conditions where CaCO3 is stable, the overall strength of the deposit increases but the degree of sulfation diminishes. Finally, this work suggests that pellet tests using crushed and calcined sorbents can give misleading information and should be used with caution to study the phenomena described here.
Effect of temperature and concentration in catalytic deactivation of a parallel (competitive) reaction system: Application to hydrotreating of vacuum gas oil
Authors: Bruzzanese Adriana , Galiasso Roberto 
Published: March 2009

AbstractThe temperature‐time sequences to maintain constant the concentration of one product in a two‐parallel (competitive) exothermic reaction system undergoing catalyst deactivation are analyzed. Kinetics is described by a power law model and linear particle deactivation. A computational algorithm and a parametric study for adiabatic packed bed reactors are presented. It is found that temperature‐time trajectories are strongly influenced by mean activity, and the selectivity. Experimental information for Hydrotreating of vacuum gas oil was obtained keeping constant desulfurization, while hydrocracking and denitrogenation are function of time. Trajectories and final operating temperature are predicted with error below 2% compared to real operation.
Transition velocities and phase holdups at minimum fluidization in gas–liquid–solid systems
Authors: Lee Donghyun , Macchi Arturo , Epstein Norman , Grace John R. 
Published: March 2009

AbstractHydrodynamic experiments were performed using a 127‐mm diameter column with 3.2‐mm porous alumina, 3.3‐mm polymer blend, 5.5‐mm polystyrene and 6.0‐mm glass spheres, with water, aqueous glycerol solution and silicone oil as liquids, and air as the gas. The voidage at minimum fluidization fell initially to a minimum, then rose gradually with increasing superficial gas velocity, and was lower for three‐phase systems than for corresponding two‐phase (liquid–solid) fluidized beds. The compaction appears to be due to agitation by gas bubbles near the minimum liquid fluidization condition. The gas holdups agree reasonably well with the correlation of Yang et al. (1993). Curves of minimum liquid fluidization velocity, Ulmf, vs. superficial gas velocity, Ug always show Ulmf decreasing as Ug increases, initially in a concave‐downward manner, but sometimes concave‐upward.
Relationship between the colloidal and rheological properties of mineral suspensions
Authors: Cerpa Arisbel , García‐González Maria T. , Serna Carlos J. , Tartaj Pedro 
Published: March 2009

AbstractThe electrokinetic and rheological behaviour of lateritic aqueous suspensions has been analyzed as a function of samples chemical composition, pH of suspensions, and nature and concentration of electrolyte added to the aqueous suspensions. First, it was determined that the isoelectric point (IEP) of suspensions in the presence of non‐adsorbing electrolytes is a function of the ratio serpentine/ goethite present in samples. The flow properties of the suspensions are strongly dependent on pH, reaching the highest values of apparent viscosity at values around the isoelectric point. Specific adsorption of silicate and magnesium species on particles surface was revealed by a shift in the IEP. In particular, silicate anions shifted the IEP value to acidic pH whilst magnesium cations shifted the value to basic pH. A similar trend was displayed in the rheological behaviour of suspensions where the highest viscosity values were shifted to the same direction.
Trickle‐bed scrubbing of flue gas SO2 using non‐aqueous solvents
Authors: Panthaky Mahiyar A. , Vladeas Radu V. , Lohi Ali , Hudgins Robert R. , Silveston Peter L. 
Published: March 2009

AbstractExperiments were carried out on the performance of several ketone solvents for the scrubbing of dilute SO2 from a gas stream and its conversion to sulfuric acid in a trickle‐bed reactor packed with activated carbon. Using a bench‐scale trickle bed packed with a structured packing based on Sulzer static mixers coated with CentaurTM activated carbon and a Teflon binder, measurements of SO2 removal, conversion to acid and catalyst productivity showed that all were considerably greater than levels achieved with water flushing. The combination of Teflon‐coated Centaur activated carbon with a non‐aqueous solvent as the flushing agent provided from 10 to 100 times higher catalyst productivity than those obtained with water alone and other activated carbons. Also, the productivities obtained by this combination were up to 40 times higher than the productivity of typical vanadium pentoxide catalyst operating at 350°C to 400°C.
Measurement and correlation of the activity coefficients of individual ions in aqueous electrolyte solutions of Na2So4 and K2So4
Authors: Rodil Eva , Vera Juan H. 
Published: March 2009

AbstractIon selective electrodes have been used to measure the activity coefficients at 298.2 K of individual Na+ions in aqueous solutions of Na2SO4 up to 3 molal, and of individual K+ ions in aqueous solutions of K2SO4 up to 0.69 molal. The activity coefficients of the sulfate anion were calculated using values of the mean ionic activity coefficients of the salts. Contrary to the behavior found in 1:1 electrolyte aqueous solutions, the activity coefficients of both cations have been found to be larger than the activity coefficient of the sulfate anion. A model proposed by Khoshkbarchi and Vera was used to correlate the data and model parameters are reported.
Periodic behaviour of a class of unstructured kinetic models for continuous bioreactors
Authors: Ajbar Abdelhamid 
Published: March 2009

AbstractThe periodic behaviour of a large dass of unstructured kinetic models for continuous bioreactors is analyzed using elementary concepts of singularity theory and continuation techniques. The class consists of models for which the utilization rate of the limiting substrate is linearly related to the rates of cell growth and product formation. The model kinetics are allowed, on the other hand, to depend on substrate, biomass and product. The stability analysis allows the derivation of general analytical conditions for the occurrence of periodic behaviour in these models. It is shown that for a number of important cases, the occurrence of oscillatory behaviour is conditioned mainly by the kinetics of product formation. The singularity theory also allows the construction of a useful picture in the multidimensional parameter space delineating the different behaviour these models can predict including bistability and stable oscillatory behaviour.
Multi‐controller scheme for load rejection and set‐point tracking
Authors: Guo Bingjun , Jutan Arthur 
Published: March 2009

AbstractTo acheive complete compensation for loads, a novel multi‐controller scheme with feedforward control is proposed. This scheme has four controllers, a set‐point controller, two load controllers, and a feedforward controller. This results in the separation of the load response from the set‐point response in a closed‐loop system. These four controllers can then be designed independently to achieve good system performance for both set‐point tracking and load rejection. One of the load controllers can be chosen as a proportional controller; this guarantees physical realizability and provides excellent compensation. The results of simulation and real time control show that the proposed multi‐controller scheme is superior to a double‐controller system and a Smith predictor in the presence of large uncertainty in process dynamics especially for load disturbances.
Photolysis of o‐Nitrobenzaldehyde in the Gas Phase: A New OH. Formation Channel
Authors: Cheng Shi‐Bo , Zhou Can‐Hua , Yin Hong‐Ming , Sun Ju‐Long , Han Ke‐Li 
Published: March 2009

AbstractNew route to gas‐phase OH.: UV photolysis of gaseous o‐nitrobenzaldehyde forms OH radicals via the transformation into the ketene or o‐nitrosobenzoic acid intermediate (see figure). The OH. product is monitored by single‐photon laser‐induced fluorescence (LIF).magnified imagePhotolysis of gaseous o‐nitrobenzaldehyde (o‐NBA) with selected different excitation wavelengths (355‐400 nm) is investigated, and the nascent OH radical is detected by the single‐photon laser‐induced fluorescence (LIF) technique. The relative quantum yield and rotational excitation of OH formation are found to be dependent on the excitation energy. The distributions of rotational, spin–orbit, and Λ‐doublet states are obtained at 355–400 nm by analyzing the experimental data. The OH radicals are found to be vibrationally cold at all photolysis wavelengths. The spin–orbit and Λ‐doublet states have nonstatistical distributions. To understand the dissociative process involved in the OH‐generating channel, DFT calculations are performed. Based on both experimental and theoretical results, possible photolysis channels of o‐NBA leading to the OH fragment are proposed and discussed.