Showing papers in "Journal of Chemical Engineering of Japan in 1988"
TL;DR: In this article, the fluidity of submicron powders was studied in a small-scale transparent column and the equilibrium size of agglomerates calculated from the apparent minimum fluidization velocity and the sedimentation velocity was in the range of 70-700 μm.
Abstract: The fluidity of submicron powders was studied in a small-scale transparent column. Powders of Ni, Si3N4, SiC, Al2O3 and TiO2 were smoothly fluidized when gas velocity exceeded the apparent minimum fluidization velocity. The electrical conductivity of the particles did not affect the fluidizing quality in the range of the present experiments. All the tested submicron particles formed agglomerates during fluidization. The agglomerate size and the apparent minimum fluidization velocity were dependent on species of particles and fluidizing gas. The equilibrium size of agglomerates calculated from the apparent minimum fluidization velocity and the sedimentation velocity was in the range of 70-700 μm. However, the agglomerates of CaCO3 and ZrO2 were very cohesive and could not be evaluated. The primary particle size was not a proper measure for the classification of fine particles.
154 citations
TL;DR: In this article, the statistical properties such as mean amplitude, fluctuation interval, standard deviation, skewness and flatness of pressure fluctuations have been utilized to determine the transition velocity from the bubbling to turbulent flow regimes in a fluidized bed.
Abstract: From the statistical analysis of pressure fluctuations, the hydrodynamic properties in a turbulent fluidized bed of glass beads (dp: 0.362mm) have been determined in a 0.1m-ID × 3m high Plexiglas column. The statistical properties such as mean amplitude, fluctuation interval, standard deviation, skewness and flatness of pressure fluctuations have been utilized to determine the transition velocity from the bubbling to turbulent flow regimes in a fluidized bed. The obtained transition velocities from these methods were found to have very similar values. In the turbulent flow regime, the mean amplitude, fluctuation interval, standard deviation and flatness of pressure fluctuations decreased with an increase in gas velocity. By contrast, the skewness of pressure fluctuations increased with gas velocity. The data of the present and previous studies on transition velocity from bubbling to turbulent flow regimes in terms of Reynolds number have been correlated with Archimedes number.
101 citations
73 citations
TL;DR: In this paper, a double-tubular membrane reactor equipped with a selective membrane tube as the inner tube was proposed, which makes it possible to obtain a product yield of a reversible reaction beyond its equilibrium value by continuous removal of the products during reaction.
Abstract: A membrane reactor, which is a double-tubular reactor equipped with a selective membrane tube as the inner tube, was proposed Such a reactor makes it possible to obtain a product yield of a reversible reaction beyond its equilibrium value by continuous removal of the products during reaction A microporous glass tube was employed as the selective membrane, through which gases permeate almost according to Knudsen''s law Experiments in the dehydrogenation of cyclohexane to benzene as a model reaction were carried out, using the membrane reactor under atmospheric pressure in the range of 453-493 K It was shown experimentally and theoretically that a marked increase in conversion over that at equilibrium can be achieved
70 citations
TL;DR: In this article, the optimum starting materials and catalyst loading for conversion of sewage sludge to heavy oil was investigated and the optimum kind of sludge was either raw primary sludge or raw mixed sludge.
Abstract: To investigate optimum starting materials and catalyst loading for conversion of sewage sludge to heavy oil, various kinds of sewage sludges were liquefied at a temperature of 300°C, a pressure of 12 MPa, and a catalyst (sodium carbonate) loading of 0-20 wt %. The optimum kind of sewage sludge was found to be either raw primary sludge or raw mixed sludge because average oil yields of these sludges reached 43 %-higher than those of other kinds of sludges. For most sewage sludges, oil production proceeded satisfactorily without the addition of any catalyst.
67 citations
TL;DR: In this article, an attempt was made to establish the coalescence frequency of dispersed drops in an agitated tank, where transient drop size distributions were measured during the processes of drop coalescence after a stepwise reduction of impeller speed.
Abstract: An attempt was made to establish the coalescence frequency of dispersed drops in an agitated tank. In experiments, transient drop size distributions were measured during the processes of drop coalescence after a stepwise reduction of impeller speed. The transient drop size distributions were calculated from the population balance equation for dispersed drops by applying a previously proposed equation for drop breakup and assuming some different functional forms for coalescence frequency. From comparison between calculated and experimental distributions, a functional form of coalescence frequency was determined which adequately correlates transient drop size distributions with the breakup frequency equation. It was also shown that the equations for coalescence and breakup frequencies successfully predict transient drop size distributions in drop dispersion processes.
48 citations
TL;DR: In this article, the demulsification kinetics of W/O emulsion in a high A.C. electric field were investigated by using a batch cylindrical demulsifier in which a glass-sealed electrode was placed above a grounded copper disk electrode.
Abstract: The demulsification kinetics of W/O emulsion in a high A.C. electric field was investigated by using a batch cylindrical demulsifier in which a glass-sealed electrode was placed above a grounded copper disk electrode. The effects of emulsion preparation conditions (oil-phase viscosity, water drop size, water-phase holdup and surfactant concentration) and demulsifying conditions (agitation speed and temperature) on the demulsification rates were examined experimentally while keeping the applied voltage constant. The demulsification rates varied considerably with slight change of these conditions. The rate equation that expressed the above contributions in suitable functional forms gave satisfactory agreement with observed rates over a wide range of experimental conditions. Based on comparison with thermal demulsification without electric field, the accelerating effect of temperature rise was thought to be caused by the decrease of oil-phase viscosity and emulsion stability. Mixing of the demulsifier contents during the operation was found to be effective in promoting demulsification together with temperature rise.
43 citations
TL;DR: In this paper, the mass transfer coefficients between solid particles and turbulent liquids were measured in agitated vessels, and a new correlation was presented to support the postulate that fine particles may stay in and move together with microeddies.
Abstract: The mass transfer coefficients between solid particles and turbulent liquids were measured in agitated vessels. For large particles characterized by large values of the specific power group (γ1/3d4/3/v), the measured mass transfer coefficients were in good agreement with Levins and Glastonbury''s correlation. For fine particles less than 100μm, however, the mass transfer coefficient deviated below their correlation, reaching more rapidly the theoretical limiting value Sh = 2 for molecular diffusion in an infinite stagnant fluid. This lends the first quantitative support to the postulate that fine particles may stay in and move together with microeddies. A new correlation for the mass transfer coefficient is presented. The effect of particle density and vessel diameter on the mass transfer coefficients was found to be negligible. Furthermore, the effect of solid particle concentration was found to be of little importance in the range of specific surface area up to at least 3000m2/m3 of liquid.
39 citations
TL;DR: In this article, it was shown that very low frequency fluctuations in the velocity signal from several seconds to several minutes in scale are usually observed in agitated vessels and that these fluctuations result from the abrupt replacement of the flow pattern in the vessel, even in part.
Abstract: Very low frequency fluctuations in the velocity signal from several seconds to several minutes in scale are usually observed in agitated vessels. It is shown in this work that these fluctuations result from the abrupt replacement of the flow pattern in the vessel, even in part. Pattern recognition studies of the flow in the impeller region of a paddle were carried out, using high-speed VTR. The results showed that the flow between blades is characterized into five patterns which are replaced one after another. They are classified into the discharge and the cross-pass types of flow. The latter means that flow passes between impeller blades, upwardly or downwardly. The lifetime of the discharge flow type was three times that of the cross-pass flow type. The velocity distributions of the discharge and cross-pass flow types estimated from visualized pictures were quite different from each other and were different from the average distributions obtained by LDV. When the cross-pass pattern had developed over the whole region between blades, a horizontal figure-eight pattern of flow developed in the entire vessel with abrupt reduction of the torque.
37 citations
35 citations
TL;DR: In this article, the flow rate of circulating liquid was measured by the heat-pulse method and it was found that QL increased with increasing liquid viscosity and that bubble coalescence was not hindered, the gas holdup in the annulus decreased and therefore flow rate increased.
Abstract: The flow rate QL of circulating liquid was measured by the heat-pulse method. It was found that QL increased with increasing liquid viscosity. In a h''quid where bubble coalescence was not hindered, the gas holdup in the annulus decreased and therefore QL increased. Empirical equations for gas holdups in the draught tube and the pressure drop due to flow reversals, necessary for estimating QL, were proposed.
TL;DR: In this article, the flow characteristics of the downflow bubble column with a simultaneous gas-liquid injection nozzle were experimentally investigated and the flow pattern was observed and ranges of stable cocurrent downflow operation were examined.
Abstract: Flow characteristics of the downflow bubble column with a simultaneous gas-liquid injection nozzle were experimentally investigated The flow pattern was observed and ranges of stable cocurrent downflow operation were examined Gas holdup and specific gas-liquid interfacial area were measured When the simultaneous gas-liquid injection nozzle was used in the downflow bubble column, spouting and calm sections were observed to appear in the column In the spouting section, gas holdup was higher and interfacial area was larger than those in the calm section In comparison with the results for the perforated sparger, the bubble diameter was smaller and the range of stable cocurrent downflow operation was wider In addition, it was found that, under a specified condition, the gas holdup was lower and the interfacial area was larger than those in the case of the perforated sparger, and that such differences became more marked with decreasing nozzle diameter and with increasing liquid velocity
TL;DR: A theoretical model for mean bubble size and frequency based on the collision theory with random spatial bubble distribution in freely bubbling gas-fluid id i/ed beds was developed in this paper.
Abstract: A theoretical model for mean bubble size and frequency based on the collision theory with random spatial bubble distribution in freely bubbling gas-flu id i/ed beds was developed. A hemispherical bubble velocity diagram was constructed to determine the average bubble collision frequency. The resulting theoretical equation for predicting bubble size is (U-Umf)(Db-Db0)+0.474g1/2(D3/2b-D3/2b0)=1.132(U-Umf)h Bubble characteristics such as pierced bubble length, velocity and point frequency were measured in a square (30 × 30-cm) fluidized bed by means of an electroresistivity probe. The gradient of bubble size increased linearly with bubble voidage. The bubble Froude number also increased along the bed height with bubble voidage. The bubble Froude number represents approximately a linear relationship with the average fractional change of square root of the static energy of bubble rise along the bed height. The present model of bubble size was found to represent well the data in the literature.
TL;DR: In this article, the effects of operating conditions on mechanical water entrainment into W/O emulsion drops in a (W/O)/W emulsion system were studied in a stirred tank in the absence of permeation due to osmotic pressure.
Abstract: The effects of operating conditions on mechanical water entrainment into W/O emulsion drops in a (W/O)/W emulsion system were studied in a stirred tank in the absence of permeation due to osmotic pressure. The water entrainment was influenced by surfactant concentration, water volume fraction in W/O emulsion, inner water drop size, salt concentration in the external water phase, and agitation speed in the stirred tank. There was a satisfactory correlation between the extent of water entrainment and the weight of surfactant per unit interfacial area. These observations suggested that water entrainment proceeded as a result of additional emulsification at the drop surface. This idea was confirmed by examining the water entrainment in an oil-water dispersion system where water entrainment occurred by ernulsification. The effects of the operating conditions on water entrainment in the oil-water dispersion system were quite similar to those in the (W/O)/W emulsion system. In addition, the volume of water entrained per unit surface area of dispersed oil drops was in fair agreement with that in the (W/O)/W emulsion system. These results supported the proposed mechanism of water entrainment.
TL;DR: In this article, an internal heat-integrated packed distillation column (IHIPAC) is developed on the basis of interphase mass transfer theory, and a new method for design of an IHCIPAC is proposed using the newly developed model.
Abstract: A mathematic model for an internal heat-integrated packed distillation column (IHIPAC) is developed on the basis of interphase mass transfer theory. A new method for design of an IHIPAC is proposed using the newly developed model. The binary system of methanol-water is adopted for the simulation work. The results show that an IHIPAC can be operated at a reflux ratio smaller than the minimum reflux ratio of a conventional distillation column, and that an energy saving of approximate 30% can be achieved under various operating conditions.
TL;DR: In this paper, experiments were carried out on bubble stripping of aqueous solutions of five organic solutes and oxygen dissolved at initial concentrations ranging from 0.008 to 0.04kg⋅m-3.
Abstract: Experiments were carried out on bubble stripping of aqueous solutions of five organic solutes and oxygen dissolved at initial concentrations ranging from 0.008 to 0.04kg⋅m-3. Little interaction was found to exist among the solutes, as far as gas holdup and overall volumetric mass transfer coefficients at low concentrations are concerned. The liquid-side and gas-side volumetric mass transfer coefficients were obtained from measured overall coefficients. Correlations for the liquid-side volumetric mass transfer coefficients were obtained in terms of liquid-phase diffusivity and gas flow rate for two types of gas spargers: single-nozzle and porous-tube spargers. Correlations for the gas-side volumetric mass transfer coefficients were also obtained for these spargers.
TL;DR: In this article, the extraction equilibrium of cerium, praseodymium and neodamium by EHPNA was investigated and was compared with that by D2EHPA.
Abstract: Solvent extraction has recently attracted major interest for industrial-scale separation of lanthanoids, alike ion exchange. It is well known that di(2-ethylhexyl)phosphoric acid (henceforth D2EHPA) is an effective extractant for the mutual separation of lanthanoids, because of its high separation factor. 2-Ethylhexylphosphonic acid mono2-ethylhexyl ester (henceforth EHPNA), which is similar in its chemical structure as D2EHPA, has a higher ability of back extraction at low acid concentration than D2EHPA. In this paper, the extraction equilibrium of cerium, praseodymium and neodymium by EHPNA was investigated and was compared with that by D2EHPA. It was found that the existence of two kinds of complexes should be considered in the region of high concentration of EHPNA, unlike the case of D2EHPA. The extraction of metals from the solution of mixed lanthanoids can be explained based on the extraction mechanism of individual elements.
TL;DR: Engineering problems in applying immobilized biocatalysts to the production of useful materials are discussed and recent developments in these subjects are reviewed.
Abstract: Engineering problems in applying immobilized biocatalysts to the production of useful materials are discussed. The scope of the review covers immobilized enzymes, immobilized microorganisms, immobilized mammalian cells, immobilized plant cells and the use of membranes for immobilization. Recent developments in these subjects are reviewed especially as to reaction analyses, mass-transfer effects, bioreactions using an organic phase and problems concerning reactor design. The future scope of research in this field is briefly described in the final section.
TL;DR: In this paper, the effect of sulfonation on the adsorption of activated carbon was investigated and the results showed that the effect was much larger when the concentration of (CH3)3N was lower in comparison with the original carbon.
Abstract: Removal of H2S, CH3SH and (CH3)3N, mixed with air in a concentration range from 10 to 800 ppm at 303 K, by use of activated carbon impregnated with NaOH or Na2CO3 (IAC) or sulfonated activated carbon (SAC) was studied to obtain the basic data useful for design of a deodorization process. For the system of IAC-H2S or CH3SH, the adsorption equilibrium was of rectangular type and adsorption capacity could be increased as much as about 40 to 60 times of that of original carbon. For the system of SAC-(CH3)3N, the adsorption equilibrium obeyed the Freundlich equation and the effect of sulfonation was much larger when the concentration of (CH3)3N was lower in comparison with the original carbon. Intraparticle effective diffusivity, Dic or Diq, was determined by curve-fitting of calculated breakthrough curves with experimental ones. The value of Dic or Diq decreased with the increase of the amount impregnated or the amount of acidic functional groups (-SO3H and -COOH) introduced by sulfonation.
TL;DR: In this paper, the wall-to-liquid mass transfer coefficient, kw, was measured for both surfaces of a coaxially immersed tube and a column wall in packed and fluidi/ed bed systems with gas-liquid concurrent upflow.
Abstract: The wall-to-liquid mass transfer coefficient, kw, was measured for both surfaces of a coaxially immersed tube and a column wall in packed and fluidi/ed bed systems with gas-liquid concurrent upflow. Supplementary measurements of kw were carried out in openpipe liquid flow, gas-liquid two-phase upflow and packed and fluidized beds with single liquid flow. The value of kw in the three-phase fluidized bed increased with increasing gas flow rate, deviating from the value in the liquid-solid fluidized bed and approaching the value in the gas-liquid two-phase upflow, while it passed through a maximum value with respect to the liquid flow rate. The value of kw in the packed-bed operation increased with increasing liquid flow rate and with increasing gas flow rate. The values of kw for the inner tube and the column wall were shown to agree with each other. The values of kw in all the gas-liquid, liquid-solid and gas-liquid-solid systems examined were correlated well by a unified equation in terms of the energy dissipation rate per unit mass of liquid. An analogy existed between wall heat transfer and wall mass transfer in all the multiphase flow systems examined.
TL;DR: In this article, a comparative evaluation of on-line control techniques was made for the glucose-controlled fed-batch culture of baker''s yeast, based on the comparison of control qualities by computer simulation, two methods -moving identification combined with optimal control and programmed-PI control- were adopted for the experiments to keep the glucose concentration in the culture broth at low level.
Abstract: A comparative evaluation of on-line control techniques was made for the glucose-controlled fed-batch culture of baker''s yeast. Based on the comparison of control qualities by computer simulation, two methods -moving identification combined with optimal control and programmed-PI control- were adopted for the experiments to keep the glucose concentration in the culture broth at low level. The control variable was the feed rate of concentrated glucose. The glucose concentration in the culture broth was measured on-line every 5 min using an automatic glucose analyzer. The glucose concentration in the broth was controlled in the range of 0.1-0.2 kg/m3 with these control strategies.
TL;DR: In this article, the authors measured gas holdups and friction factors for gas-liquid parallel two-phase flow in an air-lift bubble column, and the results were correlated with dimensionless equations.
Abstract: Gas holdups and friction factors were measured for gas-liquid parallel two-phase flow in an air-lift bubble column. Velocities of gas and liquid, liquid viscosity, and surface tension were varied. The results were correlated with dimensionless equations. As to the gas holdups (eG), Akita-Yoshida''s equation1) for batchwise processes was modified to the following form to suit continuous parallel gas-liquid flow operation: eG(1-eG)-4=0.20(gD2ρL/γ)1/8(gD3/v2L)1/12(UGL/(gD)1/2) As to the friction factors (f), the following correlation was proposed. f=0.0468(UL/(gD)1/2)-1.1e0.5G These equations are useful for estimations of gas holdups, distribution of gas holdup along the column height, and liquid circulation velocities between a riser and a downcomer in an air-lift bubble column.
TL;DR: The objective of the present paper is to measure the solute permeability of commercially available dialysis membranes using 3H-water, followed by determination of structural parameters with the tortuous pore model, and to clarify the dependence of the parameters on the solutes used.
Abstract: lent method using a well-known pore model, in which solute permeability is first measured with various solutes capable of penetrating dialysis membranes. Pure water and solute permeability data allow determination of pore radius depending on the solutes used. Values for pore radius are lower with 3H-water than with 14C-urea. Wehave proposed a tortuous pore model improved from the pore model, with which structural parameters of pore radius, surface porosity and tortuosity may be determined for dialysis membranes from pure water and solute permeability and water content data. The structural parameters obtained with radioisotope-labeled urea, glucose and sucrose were almost the same for each membrane,as reported in our previous paper.3) The objective of the present paper is to measure the solute permeability of commercially available dialysis membranes using 3H-water, followed by determination of structural parameters with the tortuous pore model, and to clarify the dependence of the parameters on the solutes used.
TL;DR: Etude theorique, par la methode de l'element fini, du champ de temperature and d'ecoulement, pour la croissance cristalline de Si et Al 2 O 3 par the methode Czochralski, prevoit la distribution de temperature, le diagramme d'ECoulement en phase fondue and le cristal, and inclut notamment les formes des interfaces as discussed by the authors.
Abstract: Etude theorique, par la methode de l'element fini, du champ de temperature et d'ecoulement, pour la croissance cristalline de Si et Al 2 O 3 par la methode Czochralski. La methode prevoit la distribution de temperature, le diagramme d'ecoulement en phase fondue et le cristal, et inclut notamment les formes des interfaces
TL;DR: In this paper, the effects of particle size and liquid and gas flow rates on the solid-to-liquid mass transfer coefficient, Ks, in all the systems were investigated and the mass transfer coefficients were well correlated by the following equation proposed by Ohashi et al. in a packed bed with single liquid flow.
Abstract: Mass transfer from solid particles to liquid in gas-liquid-solid fluidization was experimentally investigated by means of an electrochemical method with 7-9 particle electrodes fixed at various radial positions in a column of 82.9 mm i.d. Supplementary measurements were also conducted for the solid-to-liquid mass transfer in single liquid flow, gas-liquid two-phase upflow and liquid-solid fluidization. The effects of particle size and liquid and gas flow rates on the solid-to-liquid mass transfer coefficient, Ks, in all the systems were investigated and the mass transfer coefficient was well correlated by the following equation proposed by Ohashi et al. for Ks in a packed bed with single liquid flow. Shs = 2 + O.51(E1/3dp4/3/V1)0.06Sc1/3where E is the energy dissipation rate per unit mass of liquid, dp the particle diameter, vl the kinematic viscosity of liquid, Shs the Sherwood number and Sc the Schmidt number. The value of E was expressed by the sum of the kinetic energy supply terms due to viscous drag force across a particle and to gas agitation.
TL;DR: In this article, the bubble volumes formed in both non-Newtonian and highly viscous Newtonian liquids are compared to those formed in relatively low-viscosity Newtonian liquid.
Abstract: Bubble formation at a submerged orifice was studied experimentally for non-Newtonian liquids (aqueous CMC solutions) and highly viscous Newtonian liquids (aqueous glycerol solutions). The bubble volumes formed in both non-Newtonian and highly viscous Newtonian liquids are large compared to those formed in relatively low-viscosity Newtonian liquids. The formation regime of the constant-pressure condition, usually found for low-viscosity Newtonian liquids as reported by Tadaki et al., 12) was not observed. Using an extended two-stage bubble-formation model, the bubble volumes formed at a submerged orifice in non-Newtonian and highly viscous Newtonian liquids are considered. The predicted bubble volumes compare satisfactorily with the experimental data over a wide range of parameters of power law liquid (m n > 0.57) and viscosities of Newtonian liquids (5.05 Pa. s > μl > 0.439Pa s) including the results of the present work and that of Tsuge et al.13, 15)
TL;DR: In this article, the flow structure and mixing mechanism of high-viscosity fluid in an agitated thin-film evaporator were experimentally and numerically investigated, and the results showed that most of the fluid flows down in a fillet and that mixing between fillets and film is extremely suppressed.
Abstract: The flow structure and mixing mechanism of the high-viscosity fluid in an agitated thin-film evaporator were experimentally and numerically investigated. Film thickness, holdup and power consumption were measured, and velocity distributions were numerically calculated using a finite element method. The results show that most of the fluid flows down in a fillet and that mixing between fillet and film is extremely suppressed. This also suggests that usual thin-film evaporators are not always effective.
TL;DR: In this article, the authors show that the mixing time of pseudoplastic liquids with a helical ribbon impeller increases with an increase in the apparent Reynolds number in the laminar flow region, but starts to decrease with the Reynolds number above a certain critical Reynolds number.
Abstract: A huge number of data prove that the dimensionless mixing time of pseudoplastic liquids with a helical ribbon impeller increases with an increase in the apparent Reynolds number in the laminar flow region, but starts to decrease with the Reynolds number above a certain critical Reynolds number. The mixing time is strongly affected by the liquid shear-thinning property, increasing as the liquid shear-thinning property increases. The mixing time in the laminar-flow region is correlated with liquid properties, impeller geometry and operational conditions. The optimum impeller geometry for the mixing of pseudoplastic liquids is predicted.
TL;DR: In this paper, the effects of salt solution on water-absorbing temperature-sensitive poly(vinylmethylether) gel (PVMEG) prepared by γ-ray irradiation were experimentally studied.
Abstract: The effects of salt solution on water-absorbing temperature-sensitive poly(vinylmethylether) gel (PVMEG) prepared by γ-ray irradiation were experimentally studied. The swelling and shrinking behavior of PVMEG were affected solely by the kind and concentration of anion group independently of relevant cation. The equilibrium volume of gel in a salt solution was determined by both the valency and radius of the anion group. The transition temperature of PVMEG, below and above which the gel swells and shrinks, respectively, was 310 K independently of the kind and concentration of salt.