Showing papers in "Journal of Chemical Engineering of Japan in 1978"

TERNARY LIQUID-LIQUID AND MISCIBLE BINARY VAPOR-LIQUID EQUILIBRIUM DATA FOR THE TWO SYSTEMS n-HEXANE ETHANOL ACETONITRILE AND WATER ACETONITRILE-ETHYL ACETATE

Abstract: Liquid-liquid equilibrium data are obtained for the two ternary systems w-hexane-ethanolacetonitrile at 40°C and water-acetonitrile-ethyl acetate at 60°C. Vapor-liquid equilibria for the two miscible binaries of each ternary system are also determined. The measured ternary liquid-liquid equilibria are compared with those predicted from the constituent binary data alone by use of various activity coefficient equations.

Prediction of binary adsorption equilibria of solvent and water vapor on activated carbon

Abstract: A new method is proposed to predict adsorption equilibria of mixtures of solvent and water vapor on activated carbon. It is based on evaluating the amounts of solvent and water in the capillary condensed phase in the fine pores and in the ordinary adsorbed phase in the coarse pores, respectively. Predicted results are compared with experimental ones on two kinds of activated carbons having different pore-size distributions for water-soluble solvents (methanol and acetone) and water-insoluble solvents (benzene and toluene), respectively. Both results agree fairly well.

ABSORPTION OF DILUTE NITRIC MONOXIDE IN AQUEOUS SOLUTIONS OF Fe (II) -EOTA AND MIXED SOLUTIONS OF Fe (II) -EOTA AND Na2S03

Abstract: Absorption rates of NO in aqueous solutions of Fe(II)-EDTA chelate as well as in mixed solutions of Fe(II)-EDTA and Na2SO3 were measured using a stirred vessel with a free flat gasliquid interface and a bubble column. The rate constants of the complexing reaction of NO with Fe(II)-EDTA were determined on the basis of the theory of gas absorption accompanied by a reversible reaction. The chemical equilibrium constants were also determined at various pH values. It was found that the rate constant was of the order of 108 l/g-mol-sec and that the equilibrium constant was about 106 l/g-mol at 25°C. These values are much higher than the corresponding values of the reaction between NO and Fe(II) in the absence of EDTA. The mechanism of the absorption of NO in mixed solutions of Fe(II)-EDTA and Na2SO3 was deduced from the observation that the absorption efficiency decreased in the early stage of absorption and then increased to some steady value. The absorption rates were satisfactorily explained on the assumption that NO coordinates to Fe(II) (EDTA) (SO2-3) irreversibly. It was also found that the absorption rate of NO in the aqueous solution of Fe(II)-EDTA was much higher than those of other liquid absorbents so far investigated.

And nitric oxide in aqueous mixed solutions of sodium chlorite and sodium hydroxide

Abstract: The rates of single and simultaneous absorptions of dilute SO2 and NO in aqueous mixed solutions of NaClO2 and NaOH were measured at 25°C using a stirred vessel with a plain gas-liquid interface. In the SO2-NaClO2 system, the absorption rate exceeded the gas-film controlled rate, which implies the possibility of gas-phase oxidation of SO2 due to the evolved C1O2. In the SO2-(NaClO2+NaOH) system, the absorption rate agreed with that under gas-film controlled conditions. In the (SO2+NO)-(NaClO2+NaOH) system, the reduction of the NO absorption rate in the presence of SO2 substantially exceeded that evaluated through the decrease in interfacial concentration of NaClO2 and NaOH due to surface reaction with coexisting SO2. The rate of absorption of SO2 exceeded the gas-film controlled rate. The decomposition of NaClO2 proceeds to a greater degree during simultaneous absorption than the single absorption of SO2.

Characteristic evaluations of ici air-lift type deep shaft aerator.

Abstract: An aeration system employing a long vertical shaft of 100 m or more depth has recently been developed by ICI. The interior of the shaft is divided into two parts. Air bubbles sparged in one side of the interior flow down to the bottom and then flow up through the other side of the shaft to the surface, as liquid circulates through both sides. This liquid circulation is maintained by the gas lift action of the sparged air. In this aeration system, the flow path of the air bubbles introduced is long enough to yield high oxygen utilization. In the present paper, the authors discuss operating problems of ICI''s deep shaft aerator. The airlift type deep shaft was simulated by a mathematical model. The momentum balance equation for the fluid flow, the theoretical and empirical relations between gas velocity, liquid velocity, gas slip velocity and gas holdup, and the mass balance equation for oxygen transferred through the gasliquid interface, were all simultaneously solved to obtain the distributions of gas holdup and oxygen utilization along the shaft length. The calculated results give valuable information, such as the relations between the gas velocity, liquid circulation velocity, depth of air introduced and oxygen utilization. The power economy of the deep shaft is discussed in connection with its design and operating problems.

Bubble formation from a submerged single orifice accompanied by pressure fluctuations in gas chamber

Abstract: An improved two-stage model is proposed to predict bubble volume and to explain the phenomena of bubble formation when bubbles are formed from a submerged single orifice accompanied by pressure fluctuations in a gas chamber. The following conclusions are reached by comparing the calculated results based on the proposed model with the experimental results: (1) The calculated bubble volumes agree well with the experimental results over a wide range of experimental conditions. (2) The change of bubble volume with bubbling time and the phenomena of pressure fluctuations in the gas chamber are well described by the model.

Safety supervision of valve operations

Abstract: For the purpose of safety control of chemical plant operations, the system of supervising valve operations is considered on the premise that all the open-or-closed information for important valves can be monitored by a computer. The algorithms consist basically of two parts: finding the particular route of a stream on specification of the starting and terminating points, and evaluating the flow state in each unit of equipment in the stream. For ease of computer processing the structure of the chemical plant is viewed as an assembly of connectors and valves as done by Rudd. In the procedure of searching routes, redundant searching and repetition of searching in loops are avoided. Once the required route is found, the flow state of each connector is evaluated with the aid of information about the topological connections among the connectors which are generated in the route-searching procedure. It is possible to determine, referring to the restrictions or requirements about the states of connectors given as the security conditions, the sequence of valve operations.

Electroosmotic dewatering of sludge under condition of constant voltage.

Abstract: Electroosmotic dewatering is very effective for sludge which is difficult to dewater by mechanical methods. Its use under condition of constant voltage was investigated. The mechanism of electroosmotic dewatering for compressible sludge under condition of constant voltage was studied by using the model of electroosmotic flow through a compressible-particle packed bed. The rate of electroosmotic dewatering and the electric power consumption were theoretically analysed. Experiments were performed by using compressible sludges such as white clay and bentonite. The equations obtained theoretically were confirmed experimentally. The theoretical equations of electroosmotic dewatering proposed in this paper are useful for the design of practical electroosmotic dewatering equipment. A few characteristics of electroosmotic dewatering under condition of constant voltage are also shown.

Reaction and transport of nitrogen oxides in nitrous acid solutions

Abstract: Depletion of nitrous acid from its aqueous solution is studied over a wide range of experimental conditions. The rate and stoichiometry of this process are determined as a function of mass transfer characteristics of gas-liquid contacting devices. It is found that the depletion of nitrous acid is brought about by three different mechanisms: 1) simultaneous hydration of N2O4 and evolution of NO, both existing in equilibrium with HNO2, 2) desorption of nitrous acid molecules and 3) decomposition of HNO2 into NO and NO2 occurring in the vicinity of the liquid surface. A quantitative analysis is made using the various rate and equilibrium constants with the oxides of nitrogen. The relative importance of the three mechanisms and, hence, the rate and stoichiometry of the whole process vary with the mass transfer characteristics of the gas-liquid contactors. The rate constants of the hydration of N2O4 and of the decomposition of nitrous acid (2HNO2→NO+NO2+H2O) as well as the solubility of N2O4 were established.

Solvent extraction of copper by benzoyl-acetone in a stirred transfer cell

Abstract: Novel separation technique using liquid surfactant membranes containing mobile carrier has recently attracted practical interest through individual ion recovery from brines and metallurgical wastes. In this paper, as a basic study of the selective separation and concentration of metal ion using liquid surfactant membranes, the extraction of copper with benzoylacetone was carried out using a stirred transfer cell. The effect of chelating complex formation on extraction rate was examined experimentally and theoretically. As a result, it became clear that the experimental results were explained by a diffusion model accompanied by the formation of chelating complex. In addition, the rate constant of complex formation and the mass transfer coefficient of benzoylacetone into aqueous phase were obtained.

Side-outlet spouted bed with inner draft-tube for small-sized solid particles

Abstract: In the commonly used top-outlet spouted bed, the solid particles are restricted in size to relatively coarse ones. As suggested by Mathur and Lim, the use of coarse particles would not be advantageous for carrying out heterogeneous gas-phase reactions. This paper describes an attempt to reduce the particle size for the side-outlet spouted bed which was previously proposed. Particles as small as those used in the fluidized bed may also be used in the side-outlet spouted bed with inner draft-tube. The gas conversions have been calculated, based on the observed gas flow pattern in the annulus, for the cases of both independent and dependent of reaction rate on particle size. From the results of the calculated gas conversions, it was found that the side-outlet spouted bed with inner draft-tube gave higher gas conversions than any other spouted beds. The structure of the gas outlet has been reformed so as to be suitable for the use of small-sized particles. Instead of putting screens on the gas outlet openings, a stationary solid bed has been attached outside the openings surrounding the annnulus.

Computational studies of a chromato-graphic moving-bed reactor for consecutive and reversible reactions

Abstract: The chromatographic moving-bed reactor is a new device in which catalytic reaction and separation by adsorption take place simultaneously. In this paper, new ways of utilization of the device are investigated to make clear that the following two objects are practicable: (1) the selectivity of the intermediate products in first-order consecutive reactions can be improved compared with that in fixed-bed reactors, and (2) the conversion of products in reversible reactions can exceed the conversion at chemical equilibrium. The para-xylene production process seems to correspond to the second situation.

Creep constants in expression of compressible solid-liquid mixtures

Abstract: Increasing interest in filter-cake dewatering1>3)9) has been shown in industry. In expression of solidliquid mixtures, dewatering proceeds rather rapidly at the beginning of expression and becomes slow with elapsed time. Especially in the later period, deliquoring proceeds at a very slow speed which is mainly dependent upon the creep effects of the solid materials in the mixture. In recent studies3"6} of constant-

Abatement of nitric oxide emission in fluidized bed combustion of coal.

Abstract: Continuous combustion of coal and char particles was carried out in an experimental fluidized bed of inert particles. The experimental results indicated that the fuel nitrogen dominated the total "NO" emission. The radical reduction of "NO" emission with decreased air feed ratio below 1.0 was observed only in the case of char combustion, while the NH3 emission remained at a certain low level. The significant reductions of "NO" and NH3 emissions found in the combustion of char with reducing atmosphere suggest strongly that "NO" emission may be considerably reduced by employing staged fluidized bed combustion of char. The mechanism of this radical reduction of NO emission was studied by taking account of the steady state concentration of carbon in fluidized bed. Preliminary experiments of staged combustion were carried out, and the results obtained indicated that staged combustion of carbonized char is an effective combustion modification for the abatement of "NO" emission.

Transition to turbulence in starting pipe flows.

Abstract: An experimental investigation was performed to study the transition to turbulence in pipe flow started impulsively with a supercritical Reynolds number. The results show that a turbulentnon-turbulent interface propagates downstream by consuming the non-turbulent region where laminar boundary-layer flow is developing with time. For the startup of a completely quieted fluid, the propagation velocity is equal to the maximum velocity of the steady-state turbulent flow. For restarting the fluid flow after a brief shutoff, however, the propagation velocity is larger than the maximum velocity, and the difference increases with shorter quieting times. In the process of interface propagation, a wave of very low frequency appears ahead of the interface centring around the radial position where the smallest change in velocity is observed at the instant of propagation. A study of the mechanism of interface propagation shows that the final break of the abovementioned wave continuously triggers downstream propagation of the turbulent-flow region. In addition, random jumping of the interface in turbulence-decaying flow is concluded to be the main cause for the increase in propagation velocity for short quieting times.

Fixed-bed breakthrough curves in binary and ternary trace component adsorp-tion from aqueous solutions

Abstract: Concentration history was studied when aqueous solutions of binary and ternary component systems were fed to the fixed-bed of activated carbon granules. The systems studied were phenol-benzoic acid, benzoic acid-para-nitrophenol and phenol-benzoic acid-para-nitrophenol of several concentration ranges. Because of different adsorptivity for each component, breakthrough curves observed for less-adsorbable component showed a typical profile consisting of four parts, namely, first adsorption zone, first equilibrium-attained zone, second adsorption zone and second equilibrium-attained zone. More-adsorbable component appeared in the last two zones described above. These zones, especially the first equilibrium-attained zone and the second adsorption zone, were studied with respect to their lengths and amount adsorbed, based on simple assumptions and the constant-pattern concept. Furthermore, breakthrough curves were obtained for the ternary system to show that the above discussion is valid for the system.

Heat transfer to vertical gas-solid suspension flows

Abstract: Heat transfer and flow characteristics of gas-solid suspension flows in a vertical 26 mm I.D. tube were investigated using spherical glass and copper beads. Particle size ranged from 72 to 1130 microns; Reynolds number 12, 000 to 24, 000; and loading ratios of solids up to 10. The results indicated a slight increase in the wall-heat transfer coefficient for the glass beads at the higher loading ratios, and essentially no increase for the 321-micron copper beads for the range of variables covered. A new general correlation of wall-heat transfer coefficients to gas-solid suspensions is presented for uniform wall temperature conditions.

Application of particle enlargement by condensation to industrial dust collection.

Abstract: Application of the phenomena of particle growth by condensation to industrial dust collection was studied. The analysis to evaluate the extent of size enlargement was first introduced to the two essential and industrially useful methods, one of which is the mixing of hot saturated air with cold air, the other being injection of steam into air. Four typical processes are proposed for effective application to industrial exhaust gas and the procedure of using these processes is illustrated according to the various conditions of exhaust gas. The technique for size enlargement of aerosol particles by condensation was found to be essentially applicable to any industrial exhaust gas which contains submicron dust particles in low number concentration when the appropriate process shown herein is selected.

Gas-particle mixture flow in various types of convergent-divergent nozzle

Abstract: The velocity and behavior of crowded particles in the flow of gas-particle mixture as related to the shape of a convergent-divergent nozzle were investigated. Calculated values of the velocity of particles accelerated with various types of nozzle were compared with the experimental results measured by the double-flash photographic method. It was found that the calculations and experiments were in good agreement within the error of experimental measurement. On the other hand, by using the dimensional analysis method, the velocity of particles or the specific kinetic energy of particles was expressed as the function of the following parameters: particle size, particle density, nozzle geometry, and operating conditions for gas flow. It was also made clear that the velocity and behavior of particles through the nozzle strongly depend upon the mixing ratio and the nozzle geometry, particularly the geometry of inlet and throat.

On estimation of critical supercooling from waiting times measured at constant supercooling

Abstract: Waiting times were measured at supercooling of 4, 8, 10 and 12°C respectively with agitation speeds of 150, 300 and 450 rpm. Critical supercooling was also measured in the range of cooling rates from 8.08 ×10-4 to 1.56×10-2°C/sec at an agitation speed of 300 rpm. Both series are analyzed by the stochastic model in which the first nucleation is treated as a random process. The waiting times distributed exponentially. The nucleation probability, a probability of first nucleation per unit time, calculated from the waiting times is correlated to the 1.30th power of agitation speed and to the 1.38th power of supercooling. The critical supercooling is related to cooling rate by the model and this equation is compared with the similar one of Nývlt. The critical supercooling calculated by the equation of the model agrees with the experimental values. The nucleation probability is suggested to be identical with a nucleation rate.

Absorption of sulfur dioxide into aqueous ammonia and ammonium sulfite solutions

Abstract: The values of the equilibrium constants for reactions (1) and (2), Kx and K2, are 3.1xlO7 and 1.1xlO2, respectively, at 25°C and at infinite dilution. Reaction (1) may be considered to be very fast. Reaction (2) has a very muchhigher rate constant than reaction (1), since it is a proton transfer reaction. Thus, both reactions (1) and (2) may be regarded as instantaneous reactions. In aqueous ammonia solutions, reaction (1) is

Local heat transfer coefficients in scraped-film heat exchanger

Abstract: The instantaneous heat transfer coefficients in a scraped-film heat exchanger have been determined using the electrochemical technique for a two-bladed, 78.7mm I.D. exchanger. The time-averaged local heat transfer coefficients were found to agree fairly well with previous work of Azoory and Bott, though some variation in liquid flow rate was detected. The timeaveraged local Nusselt number was found to be represented by Nu=Q.15(Rer•Pr)1/2Reawwith a=(l-3.74×10-2N)/9. The variation of heat transfer coefficient with time was observed to be very different from that predicted by the accepted model for the phenomena based upon unsteady state conduction.

Stability of chemical reaction in fluid catalytic reactors.

Abstract: Effect of the freeboard and the transition region on stability of fluid catalytic reactors is presented. Wall heat transfer coefficient and solid circulation rate have a significant effect on stability. These properties were measured. Both decrease as bed density decreases in the dilute phase (freeboard) and transition region. On the premise that non-catalytic violent reactions are induced due to temperature rise initiated by catalytic reactions in the dilute phase and/or the transition region, an approach to instability of the reaction system is presented by calculations. If the noncatalytic reactions are highly exothermic and their activation energies are large, the system can easily run awayat any level of solid circulation. Thus, the possibility of these non-catalytic reactions, e. g. combustion or polymerization, should be avoided by such meansas control of inlet compositions or close control of temperature in the dilute phase.

Mixing effect on irreversible second order reaction in batch stirred tank reactor

Abstract: The mass exchange type "micromixing" model in a flow system is extended to batch mixing rate process accompanying a second-order reaction between miscible reactive fluids A and B. The performance of batch mixing rate process accompanied by reaction and the dimensionless parameter q=krCb0/km are obtained from theoretical analysis of the model. When the value of q becomes less than about 0.1, the mixing effect is negligible on the course of reaction. Through analysis of the mixing characteristics of the model, the mass exchange coefficient km can be correlated with mixing time as follows. km=ln(l/δ)/t(δ)M:δ=1-F=√IS¥=ΔC/ΔC0Theoretical studies mentioned above are confirmed through experimental studies of the alkaline hydrolysis of ethyl chloroacetate, for which the reaction rate is comparable to the rate of mixing and the infinitely rapid reaction of ammonium hydroxide and acetic acid. The experimental values of km determined in each experiment show that macromixing due to circulation of the fluid element has a dominant effect on the course of reaction in the experimental condition of 300 < Re < 5000.

Numerical analysis of flow behaviour of highly viscous fluid in agitated vessel

Abstract: A numerical algorithm of two-dimensional laminar flow in an agitated vessel is established and the numerical results of the power input, the stream line and the velocity profiles for paddle and anchor impellers of various sizes are compared with the experimental ones. Both results are in good agreement with each other and it is concluded that the flow pattern in an agitated vessel with large-width impeller is almost two-dimensional. It is also shown that the characteristic velocity and length defined for the analogy expression of the transport phenomena at the agitated vessel wall by the authors are very useful for the local similarity of momentum transfer at and near the vessel wall for small-size impeller of d/D<0.6 in high ReG range.

Restrictions on patterns of residue curves around heterogeneous azeotropes.

Abstract: The definition of the residue curve is extended to heterogeneous systems by use of the mean liquid composition to analyze characteristics of heterogeneous azeotropes. The analysis of patterns of residue curves around heterogeneous azeotropes shows that the number of possible types for n-component heterogeneous azeotropes is given by (n-m+1), where m is the number of coexisting liquid phases, and that when n=m, in particular, the only possible type is a minimum azeotrope.

Effects of desorption and absorption of surface tension-lowering solutes on liquid-phase mass transfer coeffi-cients at a turbulent gas-liquid interface

Abstract: Effects of desorption and absorption of surface tension-lowering solutes through a turbulent gas-liquid interface on liquid-phase mass transfer coefficients were studied experimentally by the use of oxygen as a tracer component. A stirred contactor was used in the experimental work. Water and nitrogen were used as the liquid and gas phases, and acetone and methanol were chosen as the solutes. The results revealed that the coefficients increased with an increase in desorption rate, and that they decreased with an increase in absorption rate. The difference between the desorption and the absorption lies in the fact that the surface tension-driven force induced by the transfer of the solutes promotes the original turbulence near the interface in desorption, while it inhibits turbulence in absorption.

A definition of separation efficiency.

Abstract: By using the entropy of information theory, a more reasonable separation efficiency can be defined from the point of view of statistics. This newly defined separation efficiency varies from zero for the case of non-separation, in which the mass fractions of valuable component in both product and residuum take the same values as that in feed, to unity for the case of ideal separation, in which the valuable material and useless material in the feed leave the separator as the product and the residuum, respectively, and has sufficient detection sensitivity for even a small change of mass fraction of components in the product or in the residuum. The newly defined separation efficiency, which satisfies the fundamental requirements described above and has clear physical meaning on the basis of its definition, may be useful to evaluate the performance of separation processes.