Annular centrifugal extractors have been used in spent nuclear fuel reprocessing, but the relation between the extraction rate and flow pattern in the vessel remains unclear. This study quantifies characteristics of the flow pattern to clarify this relation. An extractor produces a mixing zone around the vessel bottom and a separation zone in the rotor. The horizontal velocity of the liquid in the mixing zone was measured using particle image velocimetry at various rotor speeds and supply flow rates.

Flow behavior in the mixing zone is of three types, depending on operational conditions: Type A, Type B, and a transition regime. At lower rotor speeds and high supply flow rates, the mixing zone is fully filled with liquid from the vessel bottom up to the lower edge of the rotor: the Type A flow state. At high rotor speeds and low supply flow rates, the zone with liquid present is vertically divisible into two regions: near the vanes and around the bottom of the rotor, which is the Type B flow state. A transition regime is also observed between Type A and Type B states. In each region surrounding the two vanes on the vessel bottom and the vessel wall, the liquid flowed in the direction of rotor rotation along the vessel wall. Liquid flow altered by the vane flowed toward the center of the vessel bottom. The liquid then entered the separation zone through the orifice at the rotor bottom. For the Type A state, the horizontal velocity distribution was roughly proportional to the rotor speed. For the Type B state, the horizontal velocities around the vessel bottom were lower than those of Type A and were not proportional to the rotor speed. Presumably, the liquid fed into the vessel went directly to the rotor instead of passing between the two vanes attached to the vessel bottom.

A theoretical model describing apparent viscosity of gas–solid fluidizing particles for spherical particles in Couette flow was proposed, and the following results were obtained. 1) Estimated values of apparent viscosity as functions of Young modulus and density of particle, Coulomb’s friction factor and some adjustable parameters agreed well with the trend of earlier experimental data. 2) In the case of bimodal particle size distribution, the observed values apparent viscosity are expected to be markedly smaller than the estimated ones. 3) The proposed model supposes that rheological behavior exhibits dilatant rather than Newtonian fluid because apparent viscosity increases with particle velocity in the case of spherical particles with smooth surface in atomic and/or molecular size level.

Stirring operations in a crystallizer often induce particle abrasion caused by particle–impeller collision, resulting in numerous attrition fragments. This study developed a method for measuring the size and total number of attrition crystal fragments in a stirred vessel filled with anti-solvent, using potassium alum as the model crystal based on image-processing algorithms of SEM images of attrition fragments. The abraded volume ratio of a parent crystal was also evaluated, based on the edge length of the regular octahedron of a single potassium alum crystal. Results showed that both the number of attrition fragments and the abraded volume of parent crystals initially increased rapidly and reached saturation after about 40 h. The conical parent crystal became rounded with stirring time, although its flat surfaces did not change to any great degree. The rate of attrition fragment generation, which is correlated with the abraded ratio of the parent crystal, decreased rapidly to a few tenths as the parent crystal became rounded.

Based on earlier studies and the authors’ original idea, the IH method was proposed as a means of estimating mutual diffusion coefficients as a function of moisture content and temperature. The diffusion coefficient was determined from the coating temperature history during coating drying experiments with constant-temperature hot air. A series of computer simulations was performed for an imaginary Fick-type coating of polyvinyl alcohol–water, and the coating temperature history during drying was obtained. The diffusion coefficients estimated by the IH method showed good agreement with the cited diffusion coefficients used in the drying simulations, suggesting the validity of the IH method.

Simultaneous encapsulation of fluorescent dye molecules and crystallization of cyclodextrin-based metal-organic framework (CD-MOF) was carried out using the solution of the dye, γ-cyclodextrin (γ-CD) and KOH by vapor diffusion method of methanol. Hydrophilic fluorescein (Flu) and rhodamine B (RhB) existed in the spherical nanopores at the center of primary (γ-CD)₆ unit of CD-MOF. Isolated Flu and RhB molecules in CD-MOF emitted strong yellow and red fluorescence, respectively at the solid state due to the isolation of dye molecules in the nanopore. Optical properties of fluorescence resonance energy transfer were observed in doubel doped CD-MOF of Flu and RhB. This means Flu and RhB molecules sit close to each other in the order of nanometers.

Strong interactive forces, namely, van der Waals forces and electrical double-layer repulsion, between the particles in a fine-particle slurry result in complex changes in their state of dispersion and aggregation that make it extremely difficult to accurately understand cake formation behavior and predict the filtration characteristics of fine-particle slurry. To investigate the effect of the particle dispersion/aggregation state on the cake filtration properties of fine particle slurry, we developed a coupled DEM-CFD simulation of cake filtration and performed filtration simulations of mono-dispersed and poly-dispersed silica slurry with a nominal particle diameter of 0.5 µm with the dispersion/aggregation state adjusted by zeta potential. From the cake formation behavior obtained from the simulation, we found that there was no reduction in the filtration rate until the porosity directly above the filter medium decreased to around 0.5–0.6. In fact, the filtration rate is believed to decrease with resistance due to the pore blockage of the filter medium. However, this suggests that even if particles covered 40–50% of the surface of the filter medium, the cake would result in hardly any resistance. We found that although the variation in flow resistivity in the cake was greater for particles in the aggregated state than in the dispersed state, the flow resistivity was smaller on average. This is thought to be because the porosity of the cake is higher when particles aggregate, and because the fluid selectively permeates the parts in the cake where resistance is low. By reducing this latter flow bias, it should be possible to reduce the cake resistance.

A continuous simulated moving bed reactor packed with solid catalyst was proposed for simultaneous high-efficiency biodiesel production and the separation of biodiesel and by-product glycerol through the transesterification of triglyceride with alcohol. Kinetic analysis for the batch transesterification between model reactants of triacetin and ethanol at 323 K using Dowex 50WX2 in the H form as catalyst was conducted to estimate the parameters of equilibrium adsorption constants and reaction rate constants intrinsic to the model reaction system used. Numerical simulations based on the mass transfer model of simulated moving bed reactor were then performed for two switching interval conditions. For the shorter switching interval, both calculated and experimental results showed that the model target product ethyl acetate was eluted from the extract port together with glycerol. On the other hand, with an adequate switching interval, both calculated and experimental results showed that triacetin completely disappeared, and ethyl acetate was continuously eluted from the raffinate port while glycerol was eluted from the extract port. The results thus showed theoretically and experimentally the effectiveness of the simulated moving bed reactor for biodiesel fuel production.

Lipase-entrapped NIPA-co-PEGMEA gels composed of amphiphilic N-isopropylacrylamide (NIPA) and hydrophilic poly(ethylene glycol) methyl ether acrylate (PEGMEA) were previously developed as a means to improve enzymatic activity and stability in organic media. This study focuses on a continuous process for the esterification of oleic acid and ethanol catalyzed by gel beads using the fixed bed method. Monodisperse millimeter-sized gel beads were prepared using a production method combining sedimentation polymerization and two-fluid atomization. The reaction rate was expressed using the ping–pong bi–bi mechanism. A continuous reaction process was successfully demonstrated. The observed values of the conversion of ethanol in the effluent were smaller than the values estimated by a mathematical analysis. This can be attributed to the accumulation of by-product water in gels.

Hydrothermal hydrolysis of rapeseed hulls to produce polyphenols was studied by treatment of aqueous slurries of 3.3 wt% rapeseed hulls at 120–220°C for 30 min–3 h. Polyphenol production, hull dissolution ratio, and total carbon yield increased with increasing temperature. The time profile of treatment at 180°C indicated that the hydrolysis proceeded rapidly in the initial 30 min and then slowed. Hydrolysis was assumed to be the main reaction pathway for polyphenol production in the initial stage of reaction, and kinetic analysis was performed. The hydrolysis rates of compounds containing ether bonds in the literature were analyzed and found to follow the enthalpy-entropy compensation rule. With the exception of phenyl ethers, the hydrolysis rates of these compounds all fell on a single line, indicating that the hydrolysis occurred through a similar reaction mechanism. Based on the enthalpy-entropy compensation rule, it is suggested that the polyphenols produced by hydrothermal hydrolysis of rapeseed hulls were derived from glycoside structures.

Pyrolysis of waste plastics in a simple facility with simple operation is required in such as developing countries. The objective product was heavy oil, which has a high boiling point, and the reactants were high density polyethylene, low density polyethylene, polypropylene, and waste low density polyethylene. Product yield for each carbon number was investigated. A high pyrolysis temperature was found to be required for heavy oil production.

This paper proposes a practical sampled-data I–P controller design for integrating processes. The controller structure, derived from model predictive control theory, is a simple I–P controller. Application to predictive functional control (PFC) is also derived. The proposed controller was obtained by converting the integrating process model to a one-step-ahead model predictive controller. In this controller, the proportional term suppresses changes in the controlled variable, and the integral term determines speed to eliminate offset. This controller is suitable mainly for sampled-data control systems with a long sampling period, because it can avoid setting excessively high proportional gain. Simulation on a typical integrating process demonstrated the effectiveness of the proposed controller. Finally, the proposed sampled-data I–P controller was successfully applied to an actual plant having an extremely slow process response.

Based on the idea that eutectic formation is a useful technology for controlling the melting points of latent heat storage materials over a wide temperature range, experimental studies were carried out on the pseudobinary mixtures of sodium carbonate decahydrate and disodium hydrogen phosphate dodecahydrate, both of which are also heat storage materials. From the distribution of melting points of the mixtures of varying composition determined from the heating curve, the phase diagram was developed as a single eutectic type, and the melting point of the eutectic was found to be 298 K. For specifying the eutectic composition, two methods were examined: one by using the empirical formula of the melting point depression, and the other by utilizing the change in the latent heat of fusion. The eutectic composition as a mole fraction of disodium hydrogen phosphate dodecahydrate was estimated to be 0.40 mol/mol by the former method and 0.37 to 0.38 mol/mol by the latter. These values closely match the 0.4 mol/mol derived from the hypothesis that the eutectic would be formed by equivalent exchange of dissociated ions in the melt of salt hydrate mixture, proposed by Watanabe and Hirasawa (2018).

PdZrNi and FePBCr amorphous metallic foils were prepared by roller quenching, and the incorporation of elemental Cu from the Cu roller into the contact surface of the metallic foil was investigated by X-ray photoelectron spectroscopy. It was found that Cu was incorporated into the surface of both metallic foils. This result suggests that the catalytic activity of the metallic alloy can be attributed to elemental Cu. This phenomenon can be used to modify the surface of an amorphous alloy to change its surface properties.