A new model for estimation of just-suspension speed in a stirred tank is proposed based on the forces acting on a single stationary particle on a flat plate in the presence of a simple shear flow. We suggested that if the lift force acting on the particle is greater than the difference between gravitational force and buoyancy force, particle lifts off. However, if the lift force is smaller than the difference of these two forces, particle settles. In order to estimate the lift force component acting on the particle, a simple 3-dimensional of CFD model is generated. By simulated lift force component, the representative flow velocity subjected to the radius of the solid particle for just-suspension is determined. For estimation of the representative flow velocity, flow velocity distributions inside stirred tank is employed at the inlet of the CFD model as a customized boundary condition. The boundary condition is determined based on direct measurement of flow velocity close to the tank base using L.D.V. It is showed also that flow visualization close to the tank bottom using P.T.V. agrees well with the L.D.V. results. The representative flow velocity obtained from the CFD model is verified and compared with the experimental value at just-suspension speed for a wide range of particle densities, 0.03≦Δρ/ρl≦1.5. The results showed that the calculated value agrees reasonably well with the experimental value within the error of ±15% at a given system using a 4 bladed pitched paddle impeller. The determination of the effect of lift force acting on a solid particle for solid–liquid suspension in a stirred tank may overcome the limitation of the conventional experimental method by visual observation for characterizing the just-suspension speed. Moreover, the new proposed model also offers physical understanding in regards to explaining the mechanism of just-suspension which has not been reported by earlier workers.
In the distillation process occurring in a bioethanol production plant using waste woods for ethanol concentration and for removing organic impurities, the product quality improved when pH control is applied in the reflux tank by adding NaOH and discharging fusel oil from a side stream of the distillation column. In this study, the details of the improvements were studied from the viewpoint of the vapor–liquid equilibrium (VLE) of organic impurities present in the distillation column. The relative volatilities of the impurities to ethanol were determined by using a model mixture containing 13 organic impurities found in the plant as a function of ethanol mole fraction. The distributions of the 13 organic impurities in the distillation column were determined by the Thiele Geddes method by using the measured relative volatility data. The behavior of the 13 organic impurities in the distillation column was useful to understand the quality of the product and the effect of the fusel oil discharge from a side stream. The relative volatilities of butyric acid, 1-butanol, 2-methyl-1-butanol and 2-butanol decreased by NaOH addition.
MFI zeolite membranes were prepared by a secondary growth method on symmetric tubular supports. Adding fluoride ions to the synthesis gel significantly shortened the hydrothermal synthesis time. In addition, membranes prepared with fluoride ions showed more than ten-times higher hydrogen permeation rate than membranes prepared from conventional gel. MFI zeolite membrane showed hydrogen selectivity in hydrogen/toluene separation.
The present study aims to provide a deep insight into the cavitation intensified biodiesel synthesis under ultrasound irradiation. To reach this aim, alkaline transesterification under low-frequency high-power ultrasound irradiation was studied using an ANFIS (Adaptive Neuro-Fuzzy Inference System), which is a robust technique to identify complex input/output relationships. The changes in the reaction yield (herein output) with the operating conditions (herein inputs) were compared with the behavior of the cavitation bubbles under the same condition. Cavitation behavior was described as a function of hydrodynamic, hot-spot characteristics, oscillation velocity and capacity of cavitation bubbles using mathematical simulation of a lone cavity. Apart from these physical contributions of cavitation bubbles in the biodiesel synthesis system, the work also focused on their chemical contribution by analyzing the diffusion and condensation phenomena during the expansion and compression phases across the bubble interface and the reaction mechanism inside the cavity. The previous results in terms of physical analysis clarified the impact of cavitation on increasing local temperature, generating shock waves, and subsequently increasing the mixing quality in the system under ultrasound irradiation. Meanwhile, the latter results uncovered the equilibrium composition of the chemical compounds inside the cavitation bubbles and demonstrated the behavior of those compounds under supercritical conditions inside the cavitation bubble or the conditions the cavitation bubbles underwent (expansion and compression).
The design and preparation of heterogeneous Fenton-like nanocatalysts with high performance is an important task in the field of environmental catalysis. In this work, CuO nanowires supported on graphite film were synthesized using a facile process, and exhibited high catalytic activity and good stability in the oxidative degradation of Congo red with H2O2. At 303 K, the degradation ratio of Congo red was up to ca. 97.5% at a reaction time of 36 min, while the TOC removal reached ca. 77.0% after 80 min. The graphite film-supported CuO nanowires exhibited better stability and reusability than recently reported powdered CuO nanocatalysts. The high catalytic performance and recyclability of the graphite film-supported CuO nanowires make them a promising catalyst in the field of environmental catalysis.
Although small and medium-sized enterprises (SMEs) play an important role in the economy and use a significant amount of chemicals in their manufacturing processes, little support has been offered to improve the processes they use for chemicals management. In this series of two papers, we propose a design support framework for strategic chemicals management in SMEs, and the supporting mechanisms in the framework have been informatized as a software tool developed on the basis of a case study of metal cleaning. In Part 1, the rationale of design support for chemicals management in SMEs based on process analysis by life-cycle assessment and risk assessment is conceptually analyzed and presented as a design support framework. Supporting mechanisms required for process analysis are revealed through the analysis of existing activities toward process improvement aimed at controlling volatile organic compounds in industry. A process model for data collection and the generation of alternative candidates for risk reduction has been designed for the open-system processes employed by many SMEs.
Following polymerization, impurities composed of adduct, used solvent and catalyst remain inside the formed polymers. These aforementioned impurities should be removed by washing to improve the purity of the polymers. In this process, a model of the polymer washing process is essential for optimizing energy, resources and operating time. This study proposes a fundamental model of a polymer washing process to provide a theoretical basis for optimization. This model describes the impurity distribution inside the polymers using the pseudo-steady-state approximation with the concept of a moving boundary of diffusion. The impurity diffusion at the polymer surface is described using Fick’s law. In addition, this work reports an experimental investigation of a polymer washing process using SPAEK (sulfonated poly(aryl ether ketone)) samples. The obtained pH data are used to compute the impurity diffusion coefficient at the polymer surface. Although the computed diffusion coefficients themselves show different values for each operation as a lumped parameter, the introduction of a dimensionless number, Co, scaled by the initial concentrations for each operation, yields the same values for each operation. This result implies that the unmodeled effects that might affect the impurity diffusion are only affected by Co, even if the initial impurity concentrations inside the polymers are different for each operation. Finally, the predicted pH changes under different experimental conditions showed that the model describes the washing process well and can be applied to the process design and optimization.
Microbial flocculation is an aggregation phenomenon of bacterial cells in the form of flocs or flakes. In this study, we endowed ethanol producing E. coli KO11 cells with floc-forming ability by overexpressing a native bcsB gene (KO11/pNbcsB) without negative effect on ethanol production. Quantitative evaluation of the formed flocs was conducted on the basis of the protein amount included within floc structure. The results showed that glucose concentration and culture temperature were important parameters for E. coli floc formation. In particular, a temperature shift from 37 to 30°C suppressed the floc formation at a negligible level and the shift to 40°C doubled the amount of flocs. The sedimentation test confirmed that E. coli flocs completed sedimentation within 15 min after cessation of shaking while planktonic cells kept suspending. Finally, the repeated batch operation was performed to demonstrate the advantage of flocculating E. coli KO11. The amount of deposited cells in the culture of KO11/pNbcsB strain was about two times greater than that of original KO11 strain, thereby leading to a significant increase of ethanol productivity. In addition, the flocs lasted to be produced during the repeated batch operation, suggesting that the productivity will be enhanced in every operation.
This study is the first one to yield the controllable size of highly crystallized silicalite from rice husk ash, one of the most accessible agriculatural byproducts. Moreover, this silicalite was successfully obtained through the simplest hydrothermal method with these materials as the silica source, i.e., rice husk ash (RHA), sodium silicate and potassium silicate, prepared by dissolving RHA with NaOH and KOH. Its crystal size could be easily tuned from 3 to 23 µm by adjusting the molar ratio of NaOH : SiO2 or KOH : SiO2 in the system of SiO2–TPABr–NaOH/KOH–H2O through the synthesis process with the temperature at 187°C for 6 h. The synthesized samples were then characterized by infrared spectroscopy, X-ray powder diffraction and scanning electron microscopy. Thus, the significant outcomes of the research come in the forms of controllable size of crystallized silicalite, cost effectiveness and accessibility of its silica sources, RHA.
A mL-scale continuous crystallizer has been newly developed to produce small crystals with a narrow size distribution. The crystallizer is composed of a stainless-steel mixing vessel with an inner working volume of 7.9 mL and a high-speed agitator that can agitate the crystallization solution at up to 24,000 rpm. In a previous work, the crystallizer was used for the drowning-out crystallization of glycine and L-alanine. The crystals obtained with the novel crystallizer were small and uniform in size, comparing with those obtained with conventional beaker-scale semi-batch and continuous MSMPR type crystallizers. In this study, the cooling crystallization of L-alanine was attempted using the mL-scale crystallizer. The undersaturated hot solution of L-alanine and the water-immiscible coolant liquid were introduced into the crystallizer and were intensely agitated. The solution was dispersed as small droplets into the coolant liquid and rapidly cooled. The crystals obtained by the mL-scale cooling crystallizer are small and uniform in size as well as the drowning-out crystallization.
Lignocellulosic biomass was hydrolyzed by combining an acidic ionic liquid, 1-(1-butylsulfonic)-3-methylimidazolium hydrogen sulfate, and microwave heating, resulting in high glucose yields and short reaction times. This new approach achieved 40% glucose yield from bagasse within 12 min at 160°C; whereas, almost no glucose was yielded with a well-known method involving H2SO4 and conventional heating within 30 min at the same temperature. It was confirmed that the reaction temperature significantly affected glucose yield and reaction rate; whereas, the concentration of the acidic ionic liquid only affected the reaction rate. Three kinds of lignocellulosic biomass, including bagasse (herbaceous biomass), eucalyptus (hardwood), and Japanese cedar (softwood), were examined. Glucose yield was in the range of 30–40%, indicating that the present method effectively hydrolyzes various kinds of lignocellulosic biomasses.
August 25, 2016 Due to the system maintainance‚ some linking services on J-STAGE will be unavailable on August 27 from 10:00 to 21:00 (JST)(August 27‚ from 1:00 to 12:00(UTC)). We apologize for any inconvenience and appreciate your understanding. ※Please be noted the maintainance might not end on time.
August 05, 2016 Due to the maintenance of online payment system‚ article purchase with credit card will be unavailable as following schedule. If you may encounter the maintenance difficulties‚ please try again after the maintenance is completed. Thanks for your kind cooperation. Details
May 18, 2016 We have released “J-STAGE BETA site”.
May 01, 2015 Please note the "spoofing mail" that pretends to be J-STAGE.