Showing papers in "Journal of Chemical Engineering of Japan in 1975"

Preparation of a generalized chart for the diffusion coefficients of gases at high pressures

Abstract: A new generalized chart analogous to that of Slattery and Bird (SB chart) was prepared from the observed values of the self- and binary-diffusion coefficients of gases at high pressures. The deviation of the values produced by the new chart from those observed is 4.1% on the average, whereas that of the values produced by the SB chart is 7.9%. In addition the new chart gives the average of the values observed, whereas the SB chart gives lower values for most of the systems.

Isothermal vapor-liquid equilibria of acetone-carbon dioxide and methanol-carbon dioxide systems at high pressures

Abstract: Isothermal vapor-liquid equilibrium data of acetone-carbon dioxide system at 25°C and 40°C and methanol-carbon dioxide system at 25°C were measured with a vapor-recirculation apparatus over a pressure range from 2 to 80 atm. Experimental results obtained are analyzed by thermodynamic procedures, and the nonidealities of vapor and liquid phases are compared between these two systems.

Ideal plug-flow properties of taylor vortex flow

Abstract: Mixing properties of Taylor vortex flow with small constant axial flow rates were investigated in an annulus between two concentric rotating cylinders by injecting a salt-solution tracer or by suspending small soluble particles. Longitudinal intermixing of fluid elements between the neighboring vortices was examined by a method of two-point measurement. Circumferential mixing in each cellular vortex was also evaluated by comparing two successive time variations of concentration at a certain point in the case of no axial flow. The modes of flow were mapped in terms of Taylor number and Reynolds number. This vortex flow has been found to be an ideal plug-flow for the range of 51.4

Modified wilson equation for vapor-liquid and liquid-liquid equilibria

Abstract: A new equation is derived explicitly based on an excess energy equation with Wilson''s local volume fractions and the Gibbs-Helmholtz correlation. The equation is expressed as the combination of the Wilson equation and a volume ratio term which has been introduced as a result of the derivation. The new equation (modified Wilson equation) contains only two parameters for a binary system, and is applicable to both miscible and partially miscible systems. The equation is readily generalized to multicomponent systems without any additional parameters. The wide applicability of the new equation is shown in representing vapor-liquid and liquidliquid equilibria for binary and ternary systems. It is also shown that the original Wilson equation is obtained without obscurity by the same derivation as for the new equation.

An improved generalized bwr equation of state applicable to low reduced temperatures

Abstract: A new equation of state applicable to lower reduced temperatures than the BWR equation of Starling and Han (BWRS equation) is proposed, adding four coefficients to their equation of eleven coefficients. Thermodynamic properties predicted by the two equations, such as density, enthalpy, isobaric heat capacity, f ngacity coefficient, vapor pressure, and vapor-liquid equilibrium, are compared to test the validity of the new equation of state. The ranges in which thermodynamic properties can be predicted, within about 10 % error, are extended down to 0.35 or below at reduced temperatures with the new equation. The limit for the prediction of saturated fugacity and vapor pressure for a pure substance, for instance, can be lowered from 0.47 with the BWRS equation to 0.32 with the new equation of state.

Effective surface diffusion coefficients of volatile organics on activated carbon during adsorption from aqueous solution

Abstract: Adsorption of fifteen kinds of volatile organics on activated carbon from aqueous solution was carried out in a batch system. It was assumed that the rate of adsorption was controlled by intraparticle surface diffusion, and the effective surface diffusion coefficient for each organic was determined by applying the concentration-time diagrams appropriated for Freundlich isotherms. The effective surface diffusion coefficients, De, thus obtained, are successfully correlated to the ratio of the boiling point of adsorbate to adsorption temperature as De=1.1×10-4exp(-5.32Tb/T) [cm2/sec]

Structure of the turbulence in pulsating pipe flows

Abstract: An experimental investigation was performed to study the dynamic process of bursting in pulsating turbulent flow. Particular emphasis is placed on the details of the process of turbulence generation and its propagation in the radial direction. The results show that the resonance in pulsating flow affects only the generation of turbulence, and that another important factor which characterizes the dynamic behaviour of turbulence is the coherency of propagation of generated turbulence: changing its frequency, the generated turbulence propagates to the centre-line of the tube with a unique propagation time which scales on the wall parameters. The propagation time in which the turbulence propagates from the position of origin to the centre-line agrees well with the mean burst period. This fact suggests that the entire cycle of the bursting phenomenon is characterized by the propagation of generated turbulence in the radial direction and that the bulk parameter dependence of burst period is attributable to the pipe radius.

Vapor-liquid equilibrium relations for the system accompanied by hypothetical chemical reaction containing salt

Abstract: In a system accompanied by hypothetical chemical reaction vapor-liquid equilibrium ratio, Ki, of component i has been expressed by logKi=-Ai/T+Biwhere T is the absolute temperature, Ai is a constant determined by reaction system and component i, and Bi is a constant determined from vapor-liquid equilibrium data for the liquid composition at conversion 0 and/or 1. The object of this paper is to show that the equation mentioned above can also be applied to the system including salt. Following two systems are herein discussed: i-propanol-M-propanoI-calcium chloride methanol-ethanol-water-calcium chloride In these systems Ai implies the salt effect, but its behavior was not definitely observed.

Intraparticle diffusivities in liquid-phase adsorption with nonlinear isotherms

Abstract: Diagrams showing concentration change in an agitated tank adsorber are presented to estimate intraparticle diffusivities under nonlinear isotherms, where either pore or surface diffusion is assumed to be controlling. The adsorption kinetics of DBS and phenol from dilute aqueous solutions onto two kinds of activated carbon are measured, and the intraparticle diffusivities are estimated with diagrams. An approximation method for the case where surface diffusion is controlling, which is a modification of the Dryden and Kay method, is also proposed. This method gives good agreement with the diagrams obtained numerically.

Isothermal vapor-liquid equilibrium data of isopropanol-water system

Abstract: Total pressure for the system of isopropanol and water was measured in a temperature range from 35 to 75°C by using a modified Othmer recirculation still. The vapor-liquid equilibrium was calculated from the total pressure-composition data by using the numerical method of Barker. Simultaneous fitting of the excess Gibbs energy and the excess enthalpy data was successfully done by using the Wilson equation.

A study of cake filtration

Abstract: Continuity equations and Darcy''s law are utilized to obtain a basic equation for cake filtration. The boundary condition at the moving surface is newly derived, and the cake filtration is formulated in a Stefan problem. A similarity variable is introduced to transform the governing equation into an ordinary one, which in turn is solved numerically. The moment method is shown to offer good initial values to start the numerical computation. Satisfactory agreement is observed between experimental data of Shirato et al. and computed values of some physical properties.

A definition of quality of mixedness

Abstract: To express the degree of mixing in chemical process equipment, a new, generally applicable definition of quality of mixedness is presented by making use of the entropy in information theory. The newly defined quality of mixedness varies from zero for the complete separate state or "piston flow" to values approaching unity for the final mixing state or the complete mixing state. The application of the newly defined quality of mixedness is explained with two types of examples.

Heats of mixing for binary systems and data reduction based on a triplet model of guggenheim

Abstract: Heat of mixing data for 12 binary systems are obtained using a calorimeter designed previously by Nagata, et al. (1972). Experimental data are well correlated by a modification of Guggenheim''s equation derived for a system of triplets. The proposed equation is applied for a simultaneous fit of the excess Gibbs free energy and heat of mixing data for three binary systems.

The burning rate of coke deposited on zeolite catalyst

Abstract: Burning rate of coke deposited on zeolite catalyst is evaluated under conditions of chemical reaction control and compared with experimental data reported previously by other investigators. The rate equation obtained in this paper is first order with respect to both coke concentration and oxygen partial pressure. Its activation energy is 26.2 kcal/g-mol, slightly lower than those of other works. Burning rate is approximately independent of the source of coke, but is affected by a certain kind of cation in zeolite.

Behavior of various impurities in simple distillation of aqueous solution of ethanol

Abstract: Equilibrium ratios of 29 impurities in aqueous solution of ethanol are expressed as functions of the concentration of ethanol. The constants of these functions have been determined by use of the vapor-liquid equilibrium data in the literature. A mathematical model of a pot-still is presented, in which open-steam heating, partial condensation and the passing of live steam are taken into consideration. The simultaneous differential equations are solved numerically and the distillation curves of the impurities are obtained. It is shown that the curves have characteristic shapes according to the type of minor component and are affected mostly by the concentration of ethanol in the charge. The calculated distillation curves are compared with the observed ones, which were obtained from papers on the production of distilled spirit.

Salt effects on vapor-liquid equilibrium of isopropanol-water system

Abstract: Effects of LiCI, LiBr and CaCI2 on vapor-liquid equilibrium of isopropanol-water system were measured by the dynamic method at constant temperature and constant solvent composition. From these equilibrium data, the activity coefficients of isopropanol and water and the relative change of chemical potentials of both solvents by salt addition, Δμ, were exactly determined. Linearity of Δμ with respect to salt concentration assumed by Johnson and Furter was observed in low salt concentration region.

Minimum wetting rate on wetted-wall column

Abstract: Minimum wetting rates were obtained for glass and stainless steel tubes by using glycerolwater mixtures of various compositions. Results show that the wetting behavior of the liquid in the range of high viscosity is sharply different from what has been reported previously by several workers. To account for this phenomenon, the model proposed to date, in which only the inertia force is taken into account, is modified for addition of the viscous force. As a result, the following semiempirical equation is obtained:K(Γ/μ)2/3+2•35/3/15(Γ/μ)5/3=A(ρσ3/μ4g)1/3where K and A are the numerical constants to be evaluated appropriately. It has been demonstrated that the proposed equation gives good correlation in a wide range of (ρσ3/μ4g).

Behavior of single air bubbles held stationary in downward flows

Abstract: The behavior of single air bubbles was studied by holding them stationary by downward flows Two series of experiments, involving undisturbed flow and disturbed flow by an immersed cylinder, respectively, were conducted in the Reynolds number range 2000-5000 and at the equivalent spherical diameter of bubble 04-2 cm In the disturbed flow, the intensity of turbulence was 013 and the integral scale was of the same order of magnitude as bubble diameter And although the bubble shape was changed considerably from time to time by the effect of turbulence, the relative velocity of bubbles was almost the same as in the undisturbed flow The averaged ratio of the wake region volume to the bubble volume for the two cases was 47

Heat-transfer in a taylor vortex flow

Abstract: The characteristics of heat transfer affected by Taylor vortex motion were investigated experimentally by the use of electrochemical method and theoretically with the aid of the nonlinear theory suggested by J. T. Stuart. The present non-linear theory, which considers the effect of the fundamentals of disturbances on heat transfer, especially in the wide gap problem, is also applicable to the heat-transfer problem in the range of 1

Mass transfer in adsorption on bidisperse porous materials

Abstract: Considering pore size distribution of adsorbent particles to be bidispersed and assuming diffusion within the particles in series from macro- to micro-pores and vice versa, theoretical equations of fixed-bed breakthrough curves for a linear adsorption isotherm system are derived and intraparticle diffusion resistance for two cases is given. Adsorption of Kr-85 on activated carbon of several particle sizes with different amounts of FeCl3 deposition was studied to assertain the applicability of the derived equations and resistances of both macro- and micro-pore diffusion were also evaluated. The difference of diffusion resistances from steady-state and from dynamic method is discussed.

The start-up response of pipe flow to a step change in flow rate

Abstract: The start-up response of pipe flow to a step input of constant flow rate given by an automatic solenoid valve has been studied experimentally by the use of electrochemical technique. The variation of velocity distribution and velocity gradient at the pipe wall with the passage of time has been measured far downstream from the inlet section, where flow becomes fully developed in the steady state. The velocity profiles of the start-up flow development show a trend essentially different from those of steady-state flow development at different distances in the entrance region of a circular pipe: they show a minimum at the axis and a maximum in the intermediate region between the axis and the wall as the result of non-uniformity of acceleration in the central core (annular jet effect). The development of the laminar boundary layer with time could be regarded as that of the constant-stress layer near the wall. Still, the velocity profiles in the laminar boundary layer at different times are similar to each other.

Oxygen transfer within fungal pellet

Abstract: Oxygen transfer to and within fungal pellet is discussed on the assumption that oxygen is supplied to the pellet interior by simple molecular diffusion. The assumption was found to be invalid under some operational conditions; the oxygen uptake rate for pellets of Aspergillus niger, measured in an agitated vessel, depended on operating conditions. Diffusional resistance around the pellet was negligible and the mass transfer rate within the pellet under ordinary agitation was enhanced from the rate by molecular diffusion. Estimated values of effective diffusivity within the pellet were more than twice the molecular diffusivity of oxygen. The oxygen uptake rate could be correlated with pellet diameter, agitation speed, impeller diameter and liquid viscosity.

Settling velocity of floc

Abstract: Buoyant density of floe can be obtained by simultaneous use of Oden balance method and photoextinction method, provided that the relationship between size and settling velocity of floe is known, and that flocculation and redispersion of floes do not occur significantly during settling. By use of this method the following result is obtained. Settling velocity of activated sludge and floe formed by bentonite and alum can be represented by a settling velocity equation for solid spheres.

Minimum transport velocity for horizontal pneumatic conveying

Abstract: The minimum transport velocity, that is, the mean air velocity required to prevent the settling of particles on the bottom of a horizontal pipe, was experimentally studied for granular particles. Two pipe sizes were used, 26 mm and 49 mm diameter, and 14 groups of solid particles ranging from 0.3 mm to 2 mm diameter were used. A general correlation for minimum transport velocity was obtained including density and size of solid particles and pipe diameter. The saltation point, at which the flow pattern changed from suspension flow to sliding flow, was also correlated on the basis of a simple theoretical consideration.

Liquid-liquid extraction in a multistage vibrating disk column

Abstract: Mass transfer characteristics of a multistage vibrating disk column are studied for the extraction of methyl isobutyl ketone-acetic acid-water system. The disk vibration definitely increases the mass transfer rate, and in the high vibration range the over-all mass transfer capacity coefficient becomes nearly three times that in the absence of disk vibration. The increase in mass transfer rate by disk vibration is mainly caused by the increase in dispersed-phase holdup and the decrease in droplet size, and the resulting remarkable increase in interfacial area.