Three representative group contribution activity coefficient models, UNIFAC-FV, Entropic-FV and UNIFAC-r, were evaluated and compared for the prediction of the thermodynamic factor relating to the self- and the mutual-diffusion coefficients in polymer solutions using the experimental data of 40 polymer solution systems with 438 data points. The calculated results show that the three models have similar accuracy. The average absolute deviation (AAD) is around 20% for most systems, and the deviation is rather large for some systems. This work shows a potential problem in the calculation of a mutual-diffusion coefficient from the self-diffusion coefficient, that is, large uncertainty caused by the calculation of the thermodynamic factor with an existing activity coefficient model may affect significantly the predictive accuracy of the mutual diffusion coefficient even the self-diffusion coefficient model used is very accurate.

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From a new model obtained by combining the circulation model with the eddy diffusion model two dimensionless parameters were derived to correlate the mixing time with the power number and the discharge flow rate number for an agitated vessel with paddle impeller. The parameter which contained the mixing time was Y = (nt_M)(Nq_d)(d/D)³(D/H) and the one which contained the pumping efficiency number was X = {(D/d)⁴Np/Nq_d³}^1/4(H/D)^1/2. These parameters Y and X were used to correlate the mixing time measured by several researchers, who measured the mixing time, the power number and the discharge flow rate number at the same time. The mixing time correlation obtained was expressed by Y = 6.7X^-1, which was rewritten by the following expression. nt_M = 6.7(D/d)²(Np·Nq_d)^-1/4(H/D)^1/2    The mixing time estimated from the correlation well agreed with those from the empirical correlations reported before within the experimental error. The simulated result of the mixing time for a pitched blade paddle impeller by Patwardhan and Joshi (1999) was also correlated well with the obtained mixing time correlation.

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The solid-liquid mass transfer coefficients k_L in gas-liquid-solid agitated vessels with new type impellers were measured to be compared with those in vessels with conventional impellers (e.g. propeller, paddle, Rushton turbine). k_L for the new type impellers are larger than those for the conventional type impellers at a low impeller rotational speed and have the same value at the same total power consumption per unit volume. For the conventional impellers the rotational speed for the complete suspension N_JS changes with the impeller height and the gas flow rate. In the case of the new type impellers for which the aeration assists the suspension of the particles, k_L is correlated well with the sum of the power consumption per unit volume under aeration and the aeration power per unit volume. However, in the case of the Rushton turbine the aeration dose not affect the suspension, then k_L under aeration is correlated just with the power consumption per unit volume. k_Ls for the conventional impellers are affected with the impeller position for the complete suspension.

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The kinetics of membrane formation of polyurea microcapsule by interfacial polycondensation was studied both experimentally and theoretically. Diethylenetriamine (DETA) and hexamethylene-1,6-diisocyanate (HMDI) were used as a trifunctional hydrophilic monomer and a bifunctional hydrophobic monomer, respectively, so that a polymer with cross-linked structure was formed. The oil in water (O/W) emulsion was first prepared using water, cyclohexane containing HMDI, and surfactant Tween 85. The emulsion solution was then mixed with DETA aqueous solution to start the interfacial polycondensation. A mathematical model in which DETA transferred to the polymer surface in the water phase, diffused through the polymer membrane, and reacted with HMDI at an interface of the polymer and the oil phase was proposed. The size distribution of microcapsule and diffusion of DETA of both unprotonated and protonated forms were incorporated, and the relation between pH and the concentration of DETA was derived from ionic equilibrium. The calculated results explained well the time variation of the conversion of DETA at a different initial number of moles of DETA and different initial mole ratio of HMDI to DETA. The time variation of the thickness of the polymer membrane was also simulated.

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We have carried out a detailed and systematic study to derive a quantitative understanding for the mechanism of the liquid-phase reaction of methylcyclopentane on ZSM-5 catalyst in a stirred batch reactor and at five temperatures between 110 and 175°C. The rate constants (k) and catalyst deactivation (k_d) were obtained on the basis of the cyclohexane by a ring-expansion of methylcyclopentane with the selectivity of 92% or over. The rate of deactivation of ZSM-5 is as large as about 100 times of an activation rate. The activation parameters for the isomerization of methylcyclopentane are ΔH^‡ = 11.87 kcal/mol and ΔS^‡ = −55.9 cal/(mol K). As the conversion increases, the yields of 2-methylpentane and cyclohexane are linearly increased, but those of 3-methylpentane and C₅- are sharply and nonlinearly increased. The scheme of methylcyclopentane reaction over ZSM-5 is as follows: MCP → CH (main reaction) or 2-MP → 3-MP or C₅-. Higher reaction temperature favors cracking reaction (ring opening or cracked micromolecules) against the isomerization by a ring expansion.

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Gold nanoparticles are prepared in titania, silica and clay suspensions by chemical reduction of tetrachroloauric ions using 1,3-aceton dicarboxylic acid. The formation rates of gold nanoparticles in titania and silica suspensions were almost the same as that in an aqueous solution. Slower formation rates were obtained in a clay gel solution, becoming slower with increasing clay concentration. Although the gold nanoparticles became large and polydispersed, due to the slow diffusion rate of tetrachroloauric ions in the clay gel, the good dispersion state of gold nanoparticles was retained even after the clay gel had dried.

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In the esterification process of long chain fatty acids with methanol, two liquid phases appear when excess methanol is added. Is this phenomenon available for the removal of water from the product mixture without any dehydrating agent and to increase the yield of the esters? The purpose of this paper is to answer the question experimentally and theoretically. The reaction and liquid-liquid distribution equilibrium have been measured at 73 ± 0.5°C for oleic acid/methanol/methyl oleate/water system with a cation exchange resin as the catalyst. Furthermore, an algorithm has been proposed for calculating the equilibrium composition of single stage extraction-coupled reaction process. The algorithm was then applied to the calculation for the esterification process of oleic acid with methanol using the reaction equilibrium constant and the interaction parameters of UNIQUAC determined from the measured data. Both experimental and calculated results showed that water produced could be well removed from the reaction product in the two-phase region. Therefore, it is possible to increase the yield of methyl oleate by using excess methanol.

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The effects of operating conditions, such as rheology of fluid, cross-flow velocity, and filtration pressure, on the cake formation and the performance of cross-flow filtration of viscoelastic slurry are studied. The viscoelastic fluid is prepared by adding a polymer, sodium polyacrylate, into de-ionized water. The results show that the viscoelastic behavior of polymeric fluid plays an important role on the performance of filtration, which results in a more compact cake but a higher filtration rate as the polymer concentration in slurry increases. Although the elastic effect of fluid increases the difficulty of filtration, and cause the filtration rate to decay quickly at the beginning of filtration, the cake mass decreases with increasing the polymer concentration due to the increase of drag force exerted on particles in the cross-flow direction. An increase in filtration pressure or a decrease in cross-flow velocity causes the filtration rate to increase. The parameter of elastic effect, E, decreases continuously during a filtration and becomes a negligible value when the filtration rate is lower than a certain value. The value of E increases with decreasing filtration pressure for a given filtration rate. The average cake porosity decreases with filtration time from the start of filtration due to the elastic effect and then increases and approaches gradually to a constant when this effect diminished. The cake porosity at pseudo-steady state decreases with increasing polymer concentration, increasing filtration pressure, and decreasing cross-flow velocity. Furthermore, the probability of particle deposition and the size distribution of particles in filter cake under various conditions are measured. The phenomenon of “selective deposition of particles” can be observed, and the size distribution of particles in the cake decreases with decreasing filtration rate or increasing polymer concentration.

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The structural change of a filter cake and its effect on permeation flux in crossflow filtration of a suspension containing particles different in size were studied. A suspension containing yeast cells (5 μm in average diameter) and polystyrene latex particles (0.5 μm) with different compositions was used as a model. The change in the structure of the filter cake formed on the membrane surface was observed by using a scanning electron microscope. When the pore size was smaller than the latex particle size, a yeast cell layer containing latex particles was formed on the membrane at the initial stage of filtration. Then, the yeast cell layer was replaced by the latex particle layer. The increase of the circulation flow rate decreased the amount of the filter cake to increase the permeation flux in this case. On the other hand, when the membrane pore size was larger than the latex particle size, a yeast cell layer was first formed on the membrane surface followed by deposition of latex particles on it. The permeation flux was relatively higher than the former case. However, the permeation flux slightly increased with the increase of the circulation flow rate although the weight of the filter cake decreased in the latter case. Thus, a small amount of the latex particles in the cell suspension considerably decreased the permeation flux in crossflow filtration of the suspension. In addition the dependence of the permeation flux on the circulation flow rate was proved to be different whether the small particles were smaller than the membrane pores. These findings including the structure of the filter cakes will be helpful to understand the permeation behaviors in the crossflow filtration of microbial broths which usually contain small particles.

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The solid liquid separation characteristics of activated sludge are significantly improved by a freezing and thawing treatment. This improvement is much affected by the freezing rate when using the same freezing column. In this study, the effect of the freezing column diameter (inner diameter: 16-147 mm) on the freezing and thawing treatment is investigated. This parameter is important for scale up purposes. For inner diameters greater than 40 mm and at a constant freezing rate of 2 mm/h, changes in the freezing column inner diameter had a minimal impact on both the solid liquid separation characteristics and the decreasing ratio of the biological activity. Consequently, for the freezing columns with inner diameters of 40 mm and above, scale up of the freezing and thawing equipment can be undertaken with confidence.

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Mechanically coated particles may constitute a suitable starting point in the preparation of new composite materials. The properties of the sintered materials will depend on the degree of dispersion of the constituent particles throughout the formed material block. A highly uniform particle mixture can be obtained from mechanical mixing or coating of core particles with fine ones. In this paper, cobalt, aluminum oxide and titanium carbide were used as fine particles to coat coarse tungsten carbide particles together with a binder of Carnauba wax by high-speed rotational impact blending. Uniformity of each component in both mixtures of the coated particles and the sintered composite materials was defined as the degree of mixing from the coefficient of variation of X-ray intensities measured by means of electron probe micro analyzer. Then, the degree of mixing was compared with that of the ordinary mixture prepared with a ball mill. Their differences were correlated with mechanical properties of sintered materials such as transverse rupture strength, Young's modulus, hardness and fracture toughness. As a result, it was proved that the degree of mixing by high-speed rotational impact blending was higher than that by ball mill mixing at the same initial mixing ratio due to higher level of mechanical impact and shearing forces, and that the mechanical properties by the former method were superior to those by the ordinary latter one.

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Spouted beds are often used for drying of coarse solid particles. In this study, the spherical porous solid particles of activated alumina were dried in three types of spouted beds with a draft-tube, an ordinary spouted bed, a screen-bottomed spouted bed and a top-sealed spouted bed, by using dry air at room temperature. Drying ability was defined as moisture evaporated per unit mass of solid particles per unit volume of air, being averaged during the time until moisture content reaches one-half of its initial value. The screen-bottomed spouted bed provided the highest drying ability and the ordinary spouted bed provided the lowest of all three spouted beds.

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In this study, an attempt is tried to effectively use the low-concentrated biomass ethanol. A new process for producing electric power through wet oxidation of biomass ethanol is proposed as a new efficient way of energy conservation. The process configuration is introduced and its energy efficiency is evaluated by using a simple process model. It is found that the overall thermal efficiency of the proposed system is around 24.5%, when the 20 wt% ethanol solution is adopted to react with oxygen under a pressure of 10 MPa. The advantages and disadvantages of the process are also indicated.

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The effects of vessel size and vessel aspect ratio on the formation of the air-water hollow profile under microgravity were experimentally evaluated. We investigated these parameters at various rotating speeds of vessels and variable water/vessel volume ratios using the drop towers at the Japan Microgravity Center and the National Institute of Advanced Industrial Science and Technology Hokkaido Center. The discriminate of the formation of the air-water hollow profile could be determined by the aspect ratio of the vessel, the modified Weber number and the volume ratio of water/vessel.

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In this work the effects of microwave heating on catalytic reaction systems are analyzed theoretically. In the modeling of the catalytic reaction system, the catalyst pellet was assumed to be composed of active site, support and fluid phase. Depending on the type of active sites, two cases were considered in this study: (1) a spherical active site on the flat support medium, and (2) a flat active site covered onto the flat support medium. For each case the temperature and concentration profiles within the catalyst pellet were obtained by simulation and compared with each other. When a chemical reaction was conducted with microwave heating, the reaction rate and the yield were found to be increased compared to conventional heating under the same conditions. This is due to hot spots generated by selective heating of the catalyst pellet, resulting in an increased reaction rate.

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