bluuebunny/crossref_metadata_2025 huggingface dataset:
Absorption with zero and Pseudo‐Zero order chemical reaction
Authors: Prisciandaro Marina , Pepe Francesco
Published: March 2009

In this paper the equations modeling absorption accompanied by a zero order reaction and by a pseudo‐zero order reaction in the liquid phase are analytically solved by using the film theory. For the cases of both zero and pseudo‐zero order reaction the analysis leads to conclusion that three regimes of the process need to be considered; the three corresponding reactant concentration profiles are developed: for low values of the Hatta number (Ha), the reaction does not go to completion in the liquid film, and therefore the reactant concentration in the liquid bulk is not zero; for intermediate values of Ha, the concentration becomes zero at the film‐bulk interface, but its gradient is not zero so that an instantaneous reactant consumption takes place at such interface; for higher values of Ha the reactant concentration becomes zero in the liquid film. The dependence of the enhancement factor on Ha is also determined, allowing the description of transition from the slow reaction regime to the fast and instantaneous reaction regime.
Effect of process variables on scale formation in steel reheating
Authors: Ormerod R. C. , Becker H. A. , Grandmaison E. W. , Pollard A. , Sobiesiak A.
Published: March 2009

Variables affecting the high temperature oxidation of steel were investigated using an experimental design strategy. The experimental methods included continuous mass‐gain measurement to characterize the oxidation kinetics in terms of parabolic rate constants. A Morris and Mitchell (1983) eleven‐run experimental design was used to identify main effects and interactions among seven independent variables (oxidation temperature, steel grade, steel surface condition, sample history and gas composition: H2O, O2 and CO2). The levels of these variables were chosen to reflect industrial steel reheat operations. The use of this type of strategy in assessing the effect of variables at an intermediate stage in an experimental program is also demonstrated.
Étude des conditions opératoires optimales de synthèse du 2‐furyl oxirane à l'aide de modèles empiriques et mécanistiques
Authors: Uhlemann Jens , Borredon Elisabeth , Gaset Antoine
Published: March 2009

La détermination des conditions opératoires optimales de la synthèse du 2‐furyl oxirane effectuée en transfert de phase solide—liquide faiblement hydraté dans deux domaines expérimentaux différents (différentes granuloméres de la base; différents sels de sulfonium) a été realisée à l'aide de deux méthodologies d'optimisation. La première méthodologie est basée sur l'utilisation de modèles empiriques (plans d'expériences) et la seconde sur l'utilisation de modèles mécanistiques (“modélisation de tendances”). La comparaison des résultats d'optimisation permet d'apprécier les avantages et les inconvénients relatifs aux deux méthodologies. Les rendements optimaux dans les deux domaines expérimentaux sont respectivement de 89 et de 95.5%.
3‐D hydrodynamics generated in a stirred vessel by a multiple‐propeller system
Authors: Baudou C. , Xuereb C. , Bertrand J.
Published: March 2009

The aim of this study is to optimize the position and the number of propellers in a non‐standard tall vessel. Laser sheet flow visualization experiments were carried out for selected geometrical arrangements which produced stable flow patterns and good transport between the propellers. Four double‐propeller arrangements corresponding to frequent industrial cases and a three‐propeller system have been chosen. Comparison of LDA measurements in the r‐z plane, dimensionless global parameters NQp, Ntm, Np, Ep and spatial distribution of local energy dissipation rate ϵ shows that a three‐propeller system is the most efficient.
Application of random‐search algorithm for regression analysis of catalytic hydrogenations
Authors: Belohlav Zdenek , Zamostny Petr , Kluson Petr , Volf Jiri
Published: March 2009

A short review of the works concerning parameter estimation in kinetic experiments was performed. An adaptive random search algorithm was applied to evaluate the parameters and parameter confidence intervals of Langmuir‐Hinshelwood models. The kinetic parameters were determined using the Box ‐ Draper criterion. The parameter confidence regions were found by using the likelihood ratio. Three heterogeneously catalyzed hydrogenations were studied.
Power and mean flow characteristics in mixing vessels agitated by hyperboloid stirrers
Authors: Pinho F. T. , Piqueiro F. M. , Proençla M. F. , Santos A. M.
Published: March 2009

The mean flow and energy consumption in vessels powered by hyperboloid stirrers was investigated. The Newton number followed an inverse linear law for Reynolds numbers below approximately 200, which had values more than twice higher the corresponding Newton number for a standard Rushton turbine. At high Reynolds number flows the Power number varied between 0.5 for a D/T = 0.78 impeller to 0.95 for a D/T = 0.24 impeller, as compared to a value of 5 for the standard Rushton stirrer, and to values of 0.31 and 1.58 for the Chemineer and Prochern hydrofoils. The power consumption did not change with the fluid height and was double for the double‐stack configuration. The shear ribs below the impeller were the main contributor to the increased energy loss relative to a non‐shear ribbed impeller and the small clearance had no major effect upon the power consumption. For the D/T= 1/3 hyperboloid stirrer the flow in the whole tank was rather gentle, defining a circulation number of 0.57, thus leading to a circulation efficiency more than 7 times lower than that of the hydrofoils.
Exit effects in circulating fluidized bed risers
Authors: Pugsley Todd , Lapointe Diane , Hirschberg Bernd , Werther Joachim
Published: March 2009

The relative influence of smooth and abrupt exit configurations on the axial pressure drop profile in Circulating Fluidized Bed (CFB) risers has been investigated. Experiments were performed with sand and FCC catalyst in two cold model CFBs of 0.1 metre and 0.2 metre riser diameter. The influence of the abrupt exit on the profile was observed to extend all the way to the base of the larger diameter riser for sand. However, the abrupt exit influenced only the final 1.5 to 2 metres of the riser length for the case of sand in the narrow diameter riser. When FCC catalyst was circulated, the effect of the abrupt configuration was seen only in the upper portion of the riser, irrespective of the riser diameter. A simple empirical modification to the model of Pugsley and Bermti (1996) provides a good description of the axial pressure drop profiles for the abrupt exit configurations, with the exception of the case of sand in the 0.2 metre diameter riser. This discrepancy is attributed to the lack of fully developed flow in the larger riser.
The Interaction of solute transfer, contaminants and dro break‐up in rotating disc contactors: Part II. The coupling of the mass transfer and breakage processes via interfacial tension
Authors: Cauwenberg Veerle , Degrève Jan , Slater Michael J.
Published: March 2009

In order to investigate the influence of solute transfer and of surface active agents on the drop breakage process in liquih liquid extraction columns, their effect on the interfacial tension has to be studied in detail. The difficulty encountered is that the interfacial tension during solute transfer continuously changes and that no simple apparatus is commercially available which can measure these varying interfacial tension values. An attempt has been made here to theoretically predict them. The equations developed to predict the interfacial tension variation can be combined with a model for the breakage process and hence drop size distributions can be calculated from stage to stage. Applying a new combined film mass transfer coefficient model which takes into account the effect of contaminants, single drop extraction performance has been calculated for simplified conditions of constant bulk concentration in the continuous phase. Calculated efficiencies have been compared with experimental data and a good simulation of contaminant effects and dependency on drop size has been found. The calculations were restricted to low dispersed phase hold‐up values, so that coalescence effects could be ignored. This work provides the required support for a procedure to be applied to counter‐current flow extraction columns.
Kinetics of carbon dioxide and methane hydrate formation
Authors: Malegaonkar Mahendra B. , Dholabhai Pankaj D. , Bishnoi P. Raj
Published: March 2009

Experimental data on the kinetics of carbon dioxide hydrate formation and its solubility in distilled water are reported. The experiments were carried out in a semi‐batch stirred tank reactor at nominal temperatures of 274, 276 and 278 K and at pressure ranging from 1.59 to 2.79 MPa for the kinetics experiments and at pressure ranging from 0.89 to 2.09 MPa for the solubility experiments. A minor inconsistency in the kinetic model developed by Englezos et al. (1987a) was removed and the model was modified to determine the intrinsic kinetic rate constant for carbon dioxide hydrate formation. The same model was also used to re‐determine the intrinsic kinetic rate constant for methane hydrate formation. The model is based on the crystallization theory coupled with the two‐film theory for gas absorption in the liquid phase. The Henry's constant (H) and apparent dissolution rate constant (KLa) required in the model were determined using the experimental solubility data. The kinetic model describes the experimental data very well. The kinetic rate constant obtained for the carbon dioxide hydrate formation was found to be higher than that for methane.
Gas—liauid mass transfer in three‐phase stirred tank reagors: Newtonian and non‐newtonian fluids
Authors: Rawase Yoshlnori , Araki Takae , Shimzu Kazuhiro , Miura Hideki
Published: March 2009

Gas—liquid mass transfer has been investigated in gas—liquid‐solid three‐phase stirred tank reactors with Newtonian and non‐Newtonian liquids. Volumetric mass transfer coefficients and gas hold‐ups were measured in a 0.2 m i.d. stirred tank reactor and the effects of low‐density polymeric particles (ρs, =1030 and 1200 kg/m3; up to 15 vol%) on gas—liquid mass transfer were examined. The volumetric mass transfer coefficients in water were found to decrease due to the presence of solid particles at constant impeller speed and superficial gas velocity. On the other hand, solids loading led to higher mass transfer rates in non‐Newtonian carboxymethyl cellulose aqueous solutions. Our previously proposed model for mass transfer in gas—liquid two‐phase systems was extended to gas—liquid—solid three‐phase systems. Reasonable agreement was found between the predictions of the proposed model and the experimental data.
Comments on modelling the diffusion‐controlled adsorption of surfactants
Authors: Campanelli John R. , Wang Xiaohong
Published: March 2009

In this study, dynamic interfacial tension data are obtained with a drop volume tensiometer at the mineral oil‐water interface for Triton X‐100 dissolved in the water phase, and for Span 80 dissolved in the oil phase. Surfactant adsorption is modelled under diffusion‐controlled conditions using either long or short diffusion time approximations. A dimensionless parameter relating adsorption time, ta, to a characteristic diffusion time of each surfactant, tD, is introduced in order to determine the general applicability of the diffusion approximations. In the case of Triton X‐100, the long time approximation is valid, and the ratio of ta/τD is found to be much greater than one. In the case of Span 80, the short time approximation provides a good fit to the experimental data, and the ratio ta/τD is found to be on the order of unity or less. A consideration of experimental data found in the literature for other surfactants leads to the general conclusion that the ratio ta/τD is useful in characterising diffusion‐controlled adsorption of surfactants.
Cold enzyme hydrolysis of wheat starch granules
Authors: Textor Steven D. , Hill Gordon A. , Macdonald Douglas G. , Denis Earl St.
Published: March 2009

Three α‐amylase enzymes were used to hydrolyze wheat starch granules suspended in water below the gelatinization temperature. The rates of hydrolysis were determined at various temperatures, pH, enzyme and starch concentrations. Barley amylase was found to be the “best” enzyme when used at pH 4.5, 45°C and starch and enzyme concentrations of 30 and 8 mg/mL respectively. It was found that under these conditions, 98% of the starch granules were hydrolyzed in 3 hours, the same amount of time used in the industrial cooking process of soluble starch. Starch particles were observed to be attacked at specific points on the surface and then hydrolyzed from the inside‐out. Some granules were hydrolyzed at a very fast rate with a first order rate constant estimated to be 40 h−1; but most granules were hydrolyzed slowly according to the Michaelis‐Menten model and the best fit parameters were found to depend on enzyme type, pH and temperature.
The marangoni effect and enhanced oil recovery Part 1. Porous media studies
Authors: Lyford Paul A. , Pratt H.R.C , Shallcross David C. , Grieser Franz
Published: March 2009

The use of partitionable solutes, e.g., aliphatic alcohols, to enhance the recovery of trapped oil in reservoir rock, has been simulated using a ballotini‐packed column initially flooded with kerosene, and subsequently lowered to an irreducible value by a water drive. Introduction of a “slug” of an alcohol effected an increased recovery, with n‐propanol and sec‐butanol giving the highest yields. Previous workers attributed such increased recovery to the formation of a “soluble front”, in which both oil and connate water are completely dissolved. However, we obtained similar recoveries using slugs with initial compositions lying on the miscibility boundary, which could not form soluble fronts. It was therefore concluded that Marangoni‐induced oscillation of the trapped drops is the more likely explanation of the enhanced recovery.
Derivation of a control oriented low order model of the dynamics of an infrared oven for the continuous drying of a thin sheet of material
Authors: Dhib Ramdhane , Thérien Normand , Broadbent Arthur Douglas
Published: March 2009

A model consisting of three partial non‐linear differential equations for describing the humidity and temperature of a thin sheet of material and of the temperature of the air flow as a function of time and position in an infrared dryer was reduced to a model more adaptable to direct digital control. To begin with the original model was discretized along the length of the dryer and then linearized. Models of orders ranging from 12 to 72 were analyzed for controllability and observability. Using Moore's method, the models thus obtained were further reduced to a controllable state space model of order 5 that produced satisfactory results and for which stability was preserved. Simulated open loop responses of the reduced model to discrete perturbations in emitter electrical power, inlet humidity and velocity of the web, produced satisfactory dynamic and steady‐state responses when compared to responses of the original model subjected to similar perturbations. The steady‐state responses showed absolute errors for humidity and temperature of the web less than 1.3% [g water/100 g] and 2.2°C, respectively.
Increase in the thermal stability during the methanation of CO2 over a Rh catalyst prepared from an amorphous alloy
Authors: Kai T. , Yamasaki Y. , Takahashi T. , Masumoto T. , Kimura H.
Published: March 2009

The hydrogenation of CO2 was investigated over a Rh catalyst prepared from an amorphous Rh20Zr80 alloy. After the reaction, the catalyst was regenerated by oxidation in air and reduction in H2. It was observed that the reaction activity increased with the repetition of regeneration. We also prepared the Rh/ZrO2 catalyst by the conventional impregnation method. The difference in the turnover frequency between the alloy‐precursor catalyst and the conventionally prepared catalyst was small. For the alloy‐precursor catalyst, however, the conversion and CH4 selectivity were stable at 723 K, whereas the conversion and CH4 selectivity decreased with time‐on‐stream even at 673 K for the catalyst prepared by the conventional impregnation method.
Design of stirred vessels with gas entrained from free liquid surface
Authors: Patwardhan Ashwin W. , Joshi Jyeshtharaj B.
Published: March 2009

In this review, the literature on surface aerators is critically analysed. In a number of studies, the critical speed for the onset of surface aeration has been correlated with the geometry of the system and the operating conditions. The studies on the rate of surface aeration, gas hold‐up, mass transfer coefficients are inadequate for the design and scale‐up. A comparison of the available designs, in terms of gas hold‐up, and mass transfer coefficient is presented. A mathematical model has been proposed for surface aeration. Guidelines have been given for the selection of impeller configuration and overall design of surface aerators. Suggestions have been made for future studies in this area.
Solids suspension with up‐pumping pitched‐blade and high‐efficiency impellers
Authors: Myers Kevin J. , Bakker André
Published: March 2009

The use of axial‐flow impellers in the up‐pumping mode has been increasing, but little performance and design information is available. Up‐pumping pitched‐blade and high‐efficiency impellers have been studied in solids suspension applications, and their performance has been compared to and contrasted with that of the more conventional down‐pumping mode. Just‐suspended speed data has been interpreted in terms of two literature correlations that can be used for design purposes. Just‐suspended torque and power requirements are presented, as well as turbulent power number and flow pattern data. In general, the just‐suspended torque and power requirements of up‐pumping pitched‐blade and high‐efficiency impellers are substantially higher than those of the down‐pumping mode. However, if a large impeller diameter is required to avoid critical speed limitations or to achieve sufficient power inputs at high solids loadings, then up‐pumping impellers may be a viable option.
Drop break‐up in intermittent turbulence: Maximum stable and transient sizes of drops
Authors: Baldyga Jerzy , Podgórska Wioletta
Published: March 2009

A multifractal method describing the fine‐scale structure of turbulence, including its intermittency, is applied to derive the drop breakage functions for drops whose diameter falls within the inertial subrange of turbulence, including effects of the viscosity of the dispersed phase. The model predicts well the transient drop size distributions of dispersions undergoing breakage at long stirring times. Concepts of quasi‐stable and asymptotically stable drop sizes are presented and discussed in relation to the exponent on the Weber number. The functions for drop break‐up in the viscous subrange are proposed and discussed.
Phase inversion studies in liquid‐liquid dispersions
Authors: Norato Michael A. , Tavlarides Lawrence L. , Tsouris Costas
Published: March 2009

A study of the phase inversion behavior of liquid‐liquid dispersions in stirred vessels is performed for liquids of various physical properties at various operating conditions. Physical parameters studied are density (867 to 1180 kg/m3), viscosity (0.00096 to 0.00378 Pa·s), and interfacial tension (0.0089 to 0.0323 N/m). Ambivalence region plots are presented and compared with results reported in the literature. Experiments are performed to examine the effects of impeller type and impeller‐to‐tank diameter ratio (D/T) on the ambivalence behavior. Also, phase inversion time experiments are performed to investigate the time required for complete phase inversion under various dynamic conditions. The traditional method of plotting the organic phase volume fraction at phase inversion against the agitation speed at that condition is compared with the method of plotting the initially dispersed phase volume fraction at phase inversion against the agitation speed at that condition. A hysteresis phenomenon is shown in phase inversion from O/W to W/O and W/O to O/W dispersions. Also, it is shown that, depending on the physical properties of the dispersed and continuous phases, phase inversion may occur when the agitation speed is increased or decreased.
Hydrodynamics of pressurized spouted beds
Authors: He Yan‐Long , Lim Choonj J. , Grace John R.
Published: March 2009

Experiments were carried out in a pressurized spouted bed with pressures up to 345 kPa. The minimum spouting velocity was found to decrease with increasing pressure. Comparison of the experimental minimum spouting velocities with the Mathur‐Gishler (1955) equation gave unsatisfactory agreement. The maximum spoutable bed height, Hm, and spout diameters increased with increasing bed pressure. The McNab and Bridgwater (1977) equation consistently overestimated Hm for large or heavy particles and underestimated Hm for small particles, with the deviations between the predicted and experimental values being greater at high bed pressures. Although the McNab (1972) equation gave good predictions of average spout diameters for beds at ambient pressure, it gave poor predictions at elevated pressures, with errors up to 66%. For a given fluid‐solid combination and column geometry the longitudinal pressure profile in the annulus was found to be independent of bed pressure. Five fairly distinct flow regimes were observed, and spoutability could be improved by increasing bed pressure.
Ion exchange equilibria in binary and ternary systems
Authors: Boyer William D. A. , Baird Malcolm H. I. , Nirdosh I.
Published: March 2009

Simple mathematical models for binary and ternary ion exchange equilibria were developed to predict selectivity coefficients and resin capacities from a simple experiment to within acceptable engineering accuracy limits. Batch equilibrium experimental investigations were undertaken to test the models for binary systems (Ni‐Na, Cu‐Na, Zn‐Na, Cd‐Na and Pb‐Na) and ternary systems (Ni‐Cu‐Na, Cd‐Ni‐Na, Cd‐Cu‐Na and Pb‐Cu‐Na) with a commercial DOWEX HCR‐W2 resin. Binary parameters were used to predict ternary equilibria. It was found that good agreement between the predicted and experimental values was obtained when the binary selectivity coefficients of the two competing heavy metal ions in the ternary system were either almost equal or differed by a factor as large as five.
Flow development in a gas‐solids downer fluidized bed
Authors: Zhang Hui , Zhu Jing‐Xu , Bergougnou Maurice A.
Published: March 2009

The development of gas and solids flow structure was studied in a 9.5 m high and 0.10 m diameter, gas‐solids cocurrent downflow circulating fluidized bed (downer). Local solids concentration and particle velocity were measured using two separate optical fibre probes at different radial positions on several axial levels along the downer. The results show that the flow development is significantly influenced by the operating conditions. For most of the conditions under which the experiments were conducted, the gas‐solids flow reaches its fully developed zone within 3 to 8 m away from the entrance. On the other hand, the development zone can extend as long as the downer itself, under certain conditions. When the solids circulation rate is over 100 kg/m2s, an increasing solids circulation rate largely extends the length of radial flow development. It is found that the flow developments in the core and at the wall are not quite simultaneous. For solids concentration, the core develops more quickly at low gas velocities and the wall region develops faster at high gas velocities. For particle velocity, higher gas velocity speeds up the development of the wall region but does not significantly affect the development of the core region. The wall region is much more sensitive to the change of superficial gas velocity than the core region. At high superficial gas velocities (> 7 m/s), a “semi‐dead” region is observed in the fully developed zone adjacent to the wall where the dilute solids are moving at a very low velocity.
Effects of the gas/solids distributor on the local and overall solids distribution in a downer reactor
Authors: Lehner Peter , Wirth Karl‐Ernst
Published: March 2009

In the last few years, the downer has been proposed as a new reactor for gas/solids reactions. Compared to state‐of‐the‐art riser reactors, the cocurrent downflow of gas and solids should lead to a more uniform flow structure, close to plug flow. Experimental studies showed, that the gas/solids distributor at the top of the reactor is significantly influencing the flow pattern in a downer reactor. Local information about the solids concentration is indispensable for a thorough characterization of the flow structure in gas/solids flows. To obtain this information, x‐ray computed tomography has been used for the experimental investigations.
The NO and N2O formation mechanism under circulating fluidized bed combustor conditions: From the single particle to the pilot‐scale
Authors: Winter Franz , Löffler Gerhard , Wartha Christian , Hofbauer Hermann , Preto Fernando , Anthony Edward J.
Published: March 2009

The NO and N2O formation mechanism is studied starting from a single fuel particle burning under well‐defined conditions up to a pilot‐scale circulating fluidized bed combustor (CFBC). The fuel, petroleum coke, was the same in all tests and care has been taken to obtain chemical similarity between the different units: a formation rate unit, a laboratory‐scale and a pilot‐scale CFBC. A detailed single particle NO/N2O formation model has been developed and incorporated in a CFBC NO/N2O emission model. To thoroughly test the modeled NO/N2O mechanism, the iodine addition method has been used in all units.
The axial hydrodynamic behavior in a liquid‐solid circulating fluidized bed
Authors: Zheng Ying , Zhu Jing‐Xu , Wen Jianzhang , Martin Steve A. , Bassi Amarjeet S. , Margaritis Argyrios
Published: March 2009

Based on experimental results from a 7.6 cm I. D. and 3 m high liquid–solid circulating fluidized bed, the liquid–solid circulating fluidization regime has been separated into two zones: the initial circulating fluidization zone and the fully developed circulating fluidization zone. The distinct hydrodynamic behavior and the influence of particle properties in the two circulating fluidization zones have been studied. The overall flow structure in LSCFB, although still somewhat non–uniform, is much more uniform than that in a gas‐solid CFB. Our experimental results also show that the axial flow characteristics and the regime transition can be strongly affected by the particle density. The stable operation range of the circulating fluidization system and the influences of some associated factors, such as the solids inventory and the particle density, were also investigated for the first time.
Hydrodynamic characteristics of magnetically stabilized fluidized admixture beds of iron and copper particles
Authors: Saxena Satish C. , Wu Wei Y.
Published: March 2009

Hydrodynamic characteristics of fluidized beds of pure iron (1416 μm), copper (934 μ) and their admixture (25, 50 and 75 mass %) particles when exposed to a uniform magnetic field collinear with the gas flow are investigated. Bed pressure‐drop data taken as a function of increasing and decreasing gas velocities (up to about 8 m/s) for different values of magnetic‐field intensity over a wide range (0 to 17 272 A/m) are employed to determine the superficial minimum bubbling and fluidization gas velocities at ambient temperature and pressure. The minimum bubbling velocity is found to increase with an increase in the value of the magnetic‐field intensity, as well as with the mass fraction of magnetizable particles in the bed. These data are correlated with an empirical relation, as well as with a semi‐theoretical expression. The bed voidage data are also generated and analyzed, as also the bed quality fluidization in terms of interparticle magnetic forces. These hydrodynamic properties of magnetically stabilized fluidized‐bed reactors are useful in their design and operation for a variety of chemical and biochemical applications.
Local measurements for the study of external loop airlift hydrodynamics
Authors: Utiger Marianne , Guy Christophe , Stuber Frank , Duquenne Anne‐Marie , Delmas Henri
Published: March 2009

Hot‐film anemometry and an optical biprobe are used to measure local flow characteristics in the riser of an external loop airlift reactor. Important flow asymmetries are observed above the sparger and developing flow persists through a large part of the riser. As gas flow rate increases, radial gas hold‐up profiles change from relatively flat to parabolic while the shape of radial liquid velocity profiles remains constant and Sauter bubble diameter increases. At large gas superficial velocities, slip velocity is found to deviate considerably from the frequently used value of 0.25 m/s. Local measurements allow a better understanding of two‐phase flow in airlift reactors and can be used for CFD‐modeling development and validation.
Use of new reaction kinetics for COS formation to achieve reduced sulfur emissions from claus plants
Authors: Karan Kunal , Mehrotra Anil K. , Behie Leo A.
Published: March 2009

A simulation study of COS formation in the tubes of the waste heat boiler (WHB) located just after the reaction furnace of a Claus plant is reported. First, the kinetics of the COS forming reaction were obtained from a recently completed experimental program in our laboratory. The predictions for COS formation from the newly developed kinetic model were compared with the data from an actual industrial waste heat boiler and found to be in good agreement. The simulation results showed that up to a 50% reduction in the COS production may be achieved by operating the WHB at the maximum allowable gas mass velocity in the WHB tubes coupled with the use of a smaller diameter tube. These reductions have major implications on the overall sulfur recovery from Claus plants.
Wet oxidation of bleach plant effluent: Effects of pH on the oxidation with or without a Pd/Al2O3 catalyst
Authors: Zhang Qinglin , Chuang Karl T.
Published: March 2009

Wet oxidation of acidic bleach plant effluent was carried out at 423K and 1.5 MPa in a slurry reactor. The influence of pH of the bleach plant effluent was evaluated for both catalytic and non‐catalytic oxidation in the liquid phase. The stability of the heterogeneous catalysts was investigated by measuring the extent of metal leaching into the solution. The pH of wastewater solution was found to influence significantly both the rate of total organic carbon (TOC) removal and the stability of the Pd/Al2O3 catalyst. Leaching of palladium and alumina occurred mostly at pH 2 and pH 11 under experimental conditions. With Pd/Al2O3, comparable rates of TOC removal were obtained in the pH range of 5 to 9 without significant leaching of both palladium and alumina. No metal leaching was observed using the Pd‐Pt/Al2O3 catalyst at an initial pH value of 7. Implications of these experimental results for designing a catalytic wet oxidation process are discussed. A novel approach has been proposed for the treatment of effluents from softwood Kraft pulp mills.
Estimation of phase velocities at flooding point in packed columns for any gas/liquid system
Authors: Kuźniewska‐lach Irena
Published: March 2009

A method for the estimation of gas velocity at the flooding point of various packings, based on such fundamental parameters as the porosity and specific surface of the packing itself, has been developed and introduced herein. The proposed relationships can be applied to the computation of rectification and absorption towers alike, within a wide range of physical/chemical properties of the gas and liquid phases. The method presented in this paper should be particularly useful for estimating the flooding‐point gas velocity of new packing elements, mostly, because it needs no empirical constants to be determined.
Methanol‐based pulping of eucalyptus globulus
Authors: Gilarranz M. A. , Oliet M. , Rodriguez F. , Tijero J.
Published: March 2009

The autocatalyzed pulping of Eucalyptus globulus wood with methanol‐water mixtures was studied. A surface response design was employed to develop mathematical models describing the pulp properties as a function of cooking time, cooking temperature and methanol concentration. The ranges studied for these variables were 40–120 min, 170‐200°C and 30‐70% (w/w), respectively. The pulp properties modeled were kappa number, total yield, screenings content, screened yield and viscosity. Under the optimum cooking conditions pulps with low kappa number and acceptable viscosity can be obtained with a high yield.
Sunflower protein precipitation in a tubular precipitator
Authors: Raphael Matheo , Rohani Sohrab
Published: March 2009

Isoelectric precipitation of sunflower protein was carried out in a 20 m long, 6 mm internal diameter glass tubular precipitator. Effects of feed flow rate, protein concentration in the feed stream, and mean residence time on particle size distribution (PSD) were studied. The population balance equation (PBE) for the tubular precipitator was solved using the orthogonal collocation multiple shooting method. A simulated annealing method was used to determine the precipitation kinetic parameters for the nucleation rate, growth rate, aggregation rate, and breakage rate from the experimental data. Due to the lack of experimental data on the kinetics of sunflower protein precipitation in the literature, the extracted kinetics from our experiments were used to evaluate the predictive capability of the present model for experiments whose results had not been used to derive the kinetics. The model predictions of the particle size distribution along the tubular precipitator showed better agreement with the experimental data for large particles in comparison to the small particles (< 10 μm).
Developmental studies of an adaptive on‐line softsensor for biological wastewater treatments
Authors: Jose L. , Sanchez Garcia , Campbell Robinson W. , Budman Hector
Published: March 2009

Efficient monitoring and automatic control systems for biological wastewater treatment processes, especially those dealing with bioinhibitory pollutants, such as phenol, are urgently required in order to meet increasingly stringent environmental regulations. Practical on‐line sensors of variables that describe water quality, such as BOD or individual toxic pollutants such as phenol, are not commercially available; e.g. phenol is generally monitored off‐line by spectrofluorometry. Inference software sensors could be an attractive alternative for on‐line monitoring of these variables. As a first step towards the development of inferential sensors for biological wastewater treatment processes, we consider in this study, a simplistic version of such a process which consists of a continuous culture of Pseudomonas putida Q5 degrading phenol. In this work, we propose a neural network based inferential sensor for phenol monitoring using on‐line biomass concentration measurements by spectrophotometry. The network was built with wavelets as the basis functions and the adaptive algorithm for the weights was based on a Lyapunov stability analysis. Predicted phenol output of the network showed good agreement with experimental data, over fairly broad ranges of inlet phenol concentration and dilution rate step changes. Simulations were conducted to find convergence conditions and to investigate possible sources for errors in phenol estimates.
Transfert photonique dans un photoréacteur à écoulement tourbillonnaire
Authors: Pruvost Jérémy , Legrand Jack , Legentilhomme Patrick
Published: March 2009

Le transfert photonique est évalué pour deux conditions hydrodynamiques différentes dans un photoréacteur annulare: un écoulement tourbillonnaire non entretenu généré par une entrée tangentielle et un écoulement axial généré par une entrée radiale. Le coefficient de transfert photonique est déterminé graCce à la photoréduction homogène du ferri‐oxalate de potassium. La comparaison des deux types d'écoulement est réalisée pour une solution aqueuse et pour une suspension de noir animal dans un milieu de faible pénétration de la lumière. Cette étude met en évidence l'intérět des écoulements tridimensionnels pour l'augmentation de l'efficacité des photoréacteurs.
The development of a medium for the in vitro expansion of mammalian neural stem cells
Authors: Sen Arindom , Behie Leo A.
Published: March 2009

A new medium, PPRF‐m2, has been developed for the in vitro expansion of murine neural stem cells. Neural stem cells (NSC) are primitive cells that have the capability to give rise to all of the cells that comprise the central nervous system (CNS). PPRF‐m2 was developed in part by examining key aspects of a commercial NSC medium used in our laboratory, and includes the basal media combination RPMI/DMEM/F12 in a 1:1:1 volumetric ratio supplemented with a hormone mixture, sodium bicarbonate (21.4 g/L), Hepes (4.3 g/L), glucose (1.75 g/L), glutamine (0.14 g/L), epidermal growth factor (20 μg/L) and basic fibroblast growth factor (10 μg/L). Cells inoculated into PPRF‐m2 effectively doubled 4 times in 5 days to achieve a maximum viable cell density of 1.2 × 106 cells/mL in stationary culture. This was approximately 650% higher than the maximum cell density achieved in the commercial NSC medium. In addition, the PPRF‐m2 cultures were observed to contain less cellular debris, and the cells were less granular and exhibited a lower degree of attachment. Immunocytochemistry revealed that cells grown in PPRF‐m2 retained the ability to generate neurons, astrocytes, and oligodendrocytes.
Mixing of miscible liquids with density differences: Effect of volume and density of the tracer fluid
Authors: Gogate Parag R. , Pandit Aniruddha B.
Published: March 2009

The effect on the mixing time of the density difference between the tracer fluid and the bulk, the type and geometry of the impeller, and the amount of the fluid added as a tracer, has been investigated in a tank with diameter of 0.31 m. The amount of tracer pulse has been varied in the range of 2 to 8% of the bulk volume and the density difference between two fluids has been varied in the range of 54 to 145 kg/m3. A generalized correlation has been developed for the prediction of dimensionless mixing time (Nθ) in terms of amount of the tracer fluid, density differences between the bulk and the tracer liquid and the pumping effectiveness of the impeller. A pitched blade downflow turbine with diameter as small as possible is the most energy efficient among the impellers studied in this work.
Dissolution reaction of potash fertilizer with moisture
Authors: Peng Shi‐Wen , Strathdee Graeme , Besant Robert W.
Published: March 2009

This paper presents the solubility analysis of potash fertilizer at thermodynamic equilibrium. The Pitzer equations applicable to a KCl‐NaCl‐MgCl2‐H2O system are developed to describe the interaction between the aqueous ions. The equilibrium constant method is used to analyze the dissolution reaction equilibrium. A critical relative humidity around 52% is obtained which characterizes the moisture‐potash interaction mechanism as adsorption or condensation. Three distinct stages of dissolution exist for typical potash products that depend on moisture and temperature, with surface brine saturated with three salts (sylvite, halite and carnallite), two salts (sylvite and halite), and single salt (sylvite), respectively. At high relative humidities (i.e., RH > 75%), dissolution depends on the temperature, and moisture content may exceed 3% and dissolution of sylvite can increase without a limit.
Pyrolysis of kraft lignin in the presence of molten ZnCl2‐KCl mixture
Authors: Kudsy Mahally , Kumazawa Hidehiro
Published: March 2009

Pyrolysis of kraft lignin was carried out using small reactors with an added ZnCl2‐KCl mixture at three levels of temperature, 500°C, 550°C and 600°C, and three levels of salt‐to‐lignin ratio (SR), 1, 2 and 3. Nineteen kinds of phenolic compound were identified and their quantitative determinations were made by gas chromatography. The yield of gaseous products determined gravimetrically exhibited a strong dependence on the added amount of salt mixture, and its lowest value was obtained at SR of 1. The formation of gaseous products, apparently stemming from decomposition of liquid products and tar, was observed at reaction times longer than 30 min. At SR of 1 and a temperature of 550°C, all phenolic compounds attained their maximum yields almost synchronously at a reaction time of 15 min. Cresol's formation was slightly increased with the amount of added salt mixture. At a temperature of 550°C, cresols and guaiacols decomposed according to a pseudo‐first‐order lumping model, while catechols did not follow the similar model.
Effect of sound on the fluidization of group B particles
Authors: Leu Lii‐Ping , Yen Yung Song
Published: March 2009

The behaviour of several kinds of group B particles ranging from 100 μm to 600 μm was studied in a sound wave vibrated fluidized bed (SVFB). The fluidized bed consists of a transparent Plexiglas tube that is 54 mm i.d. × 1 m high. A speaker mounted at the top of the bed was supplied by a function generator with square waves and was used to generate the sound as the source of vibration of the fluidized bed. The influence of the particle size, density of particles and sphericity of particles on the minimum fluidization velocity, pressure fluctuations and bubble rise velocity in the SVFB was investigated. The minimum fluidization velocity decreased as the sound energy increased. When the sound energy was strong enough and greater than the critical power, the minimum fluidization velocity would approach the same value regardless of the degree of resonance (DOR) value if the particles were in spherical shape. For non‐spherical shape particles the minimum fluidization velocity was the function of the DOR value if the power was greater than the critical power. For the middle particle size range, the standard deviation of pressure fluctuations in an SVFB became lower than the one without the effect of sound in high superficial gas velocity range, but the result was reverse for the low superficial velocity; for the large particle size range, the standard deviation of pressure fluctuations in an SVFB was larger than the one without the effect of sound. The sound could also reduce the bubble rise velocity in an SVFB.
Testing a mathematical model for initial chemical reaction fouling using a dilute protein solution
Authors: Rose Ian C. , Watkinson A. Paul , Epstein Norman
Published: March 2009

A 1 wt% lysozyme solution was used as a model fluid to test a previously formulated mathematical model for the initial chemical reaction fouling rate of a heat transfer surface. The experimental results showed that, at a given wall temperature, a maximum initial fouling rate existed over a range of fluid velocities. The maximum rate and the fluid velocity at which it occurred both increased as the wall temperature increased. These observations were consistent with the model. Quantitatively, the average absolute percent deviation between the experimental results and the optimum model predictions was 23,3%. The decrease in initial fouling rate with increasing velocity at high fluid velocities was even greater than predicted by the model.
The effect of surface properties on CaSO4 scale formation during convective heat transfer and subcooled flow boiling
Authors: Müller‐Steinhagen Hans , Zhao Qi , Helali‐Zadeh Abbas , Ren Xiao‐Guang
Published: March 2009

In this paper the effects of surface energy and surface roughness on the deposition of calcium sulphate during convective and subcooled flow boiling heat transfer to aqueous CaSO4 solutions are studied. The surfaces of several test heaters have been treated by Ion Beam Implantation, Unbalanced Magnetron Sputtering, Mixed Sputtering and Plasma Arc Deposition to reduce surface energy. One heater was electropolished to reduce surface roughness and one heater was etched by an electrochemical method to increase surface roughness. Fouling runs with these heaters, and with an untreated surface as control, were carried out at different heat fluxes, flow velocities and salt concentrations. The results show that heat transfer surfaces with low surface energy experienced significantly reduced fouling, while electropolishing did not have a notable beneficial effect. The combined effect of reduced surface energy and flow velocity on fouling reduction is considerably stronger than previously reported for pool boiling.
The control of biofilms in tubes using wire‐wound inserts
Authors: Wills Amanda , Bott T. Reg , Gibbard Ian J.
Published: March 2009

As a possible alternative to the use of biocides in industrial water systems, studies have been made on the effectiveness of wire‐wound tube inserts for biofilm control. Comparisons of data obtained at two different empty tube velocities of 0.86 m/s and 1.27 m/s and a Reynolds number of 14 000 with and without inserts, show that a biofilm accumulation reduction approaching 50% can be achieved by the use of inserts under certain circumstances. Further work is required to establish the optimum design of insert for maximum effectiveness.
Lateral mixing of shallow liquid pools by air bubbling
Authors: Baird Malcolm H. I. , Rao Nadella V. Rama
Published: March 2009

The lateral mixing of water in a shallow rectangular tank (length 225 cm, width 56.5 cm, depth 15 cm) under the action of bottom‐stir plugs has been studied. The process has been measured and video‐recorded, using an acid‐base reaction with indicator to show the flow patterns. It is concluded that in spite of the very low depth/width ratio in the tank, lateral mixing can be achieved quite efficiently using certain configurations of plugs which promote lateral circulation. With the best configuration, a mixing time of about 3.5 min could be achieved using either 4 or 6 plugs. The specific power dissipation rate was very low (0.0044 W/kg). The mixing time was essentially the same with 4 or 6 plugs provided the total gas flow to the plugs was the same in the two cases. Tests with intermittent blowing of the plugs did not show any improvements over steady operation.
Flow patterns and oil—water dispersion in a 0.38 m diameter oscillatory baffled column
Authors: Ni Xiongwei , Nelson Greig , Mustafa Imtiaz
Published: March 2009

We report our experimental flow visualization observations of flow patterns and experimental oil‐water dispersion measurements in an oscillatory baffled column (OBC) of an internal diameter 380 mm. Both types of experiments were carried out covering an identical range of oscillation frequencies, amplitudes, orifice diameters and baffle spacings. The flow visualization observations show that eddy mixing has been achieved in the pilot OBC and the intensity of which is largely dependent on the operational and geometrical parameters tested, which is similar to that in a smaller scale OBC. The scale‐up correlation was found to be linear. The oil‐water dispersion measurements show that the degree of the dispersion depends significantly on the oscillation frequency and amplitude with an increase in either leading to an increase in dispersion. The effect of the orifice diameter on the oil—water dispersion is also evident, but the effect of the baffle spacing is much weaker. Based on the experimental data we have established a correlation relating the degree of oil—water dispersion to the power input to the system. We have also compared the power requirement to achieve a complete dispersion in the pilot OBC with that in a bench scale OBC of 50 mm diameter and found that the energy dissipation is more economical in the large scale application.