To develop a method to predict vapor pressure from structural formula only, the vapor pressures have been predicted using the Riedel equation from parameters that have been evaluated using normal boiling point, critical temperature and critical pressure obtained by neural network theory.
Based on the stress-strain relations (Matsumoto et al., 2004; Yuu and Umekage, 2004) obtained by our Distinct Element Method calculation, particulate matter can be considered as a continuum. In this study, we simulated the flow fields of the two-dimensional bubbling fluidized bed using the Smoothed Particle Hydrodynamics (SPH) method, which gives the imaginary particle trajectory of the continuum, to calculate the equation of motion for the particulate continuum and the finite difference method for Navier-Stokes equations of the gas phase. The calculated results agree well with the experimental data. This indicates that the continuum model proposed by us and our simulation method presented in this paper including the application of the SPH method make it possible to predict correctly the flow fields in a high particle concentration gas system represented by the bubbling fluidized bed in which particulate matter exists in both quiescent and moving states.
Granules were prepared from a dispersed slurry containing binder by means of a rotational disk type of spray dryer, and the size distribution was investigated on the basis of a Balloon Model proposed in the authors' previous papers. It was experimentally confirmed that the granules exhibited broader size distribution than the initial droplets, and that this tendency was enhanced with increasing binder content. This indicated that the shrinkage ratio of the droplet size to the granule size increased with smaller initial droplet size and lower binder content. Analysis by the Balloon Model indicated that the shrinkage ratio of smaller droplets increases without being greatly affected by binder content due to the spray drying characteristics of the equipment, but the shrinkage ratio of larger droplets decreases with increasing binder content due to stronger interparticle cohesiveness.
Nanoporous TiO2 membranes (1 cm in diameter, 9 cm in length) were prepared by coating colloidal TiO2 sol solutions on the outer surface of cylindrical porous membranes (average pore diameter 1 µm) and firing at 450°C, and applied in a photocatalytic membrane reactor. In this system, a feed stream is forced through the membrane to yield a purified permeate where organic pollutants are degraded by photocatalytic reaction. Methylene blue (MB) was used as a model solute and was irradiated with blacklight lamps (BL) to promote the photocatalytic reaction. TiO2 membranes with an average pore diameter of 10 nm, yielded a normalized permeate concentration relative to feed concentration, Cp/Cf, of approximately 40% (60% rejection), based on the molecular sieving effect without BL irradiation. The normalized permeate concentration of MB decreased to 5% under BL irradiation, depending on experimental conditions such as feed concentration and applied pressure. The molecular sieving and the photocatalytic reaction can be combined to improve the selectivity. Permeate volume flux without BL irradiation decreased with an increase in feed concentration of MB, because of pore blocking by MB. On the other hand, the permeate flux increased with BL irradiation and showed approximately constant values irrespective of MB concentration. This suggested that the permeate flux was restored by photocatalytic degradation of MB which fouled the membranes.
The possibility of gas-phase conversion of tetramethoxysilane to trimethoxysilane was thermodynamically and experimentally evaluated. Tetramethoxysilane is a byproduct of a proposed process for production of polycrystalline silicon from trimethoxysilane without using chlorine compounds. It was found that a trimethoxysilane yield of more than one percent is possible under conditions of 0.1 MPa and 1023 K with a Si–Cu catalyst.
With heightened public concern about the environmental impacts (e.g. global warming, ozone layer depletion) of products and manufacturing processes, the evaluation of environmental impacts during the lifecycle of the products has become a crucial issue. Life cycle assessment (LCA) has been developed to evaluate environmental impact of existing products and existing manufacturing processes, but the current LCA tools are not suitable for the evaluation of whole product lifecycles and cannot evaluate the logistics of product lifecycles, which are crucial factor in designing feasible and efficient product lifecycles. This paper proposes a modelling and simulation environment called Green Production and Logistics Simulator (GPLS) for evaluation and design of green product lifecycles. The proposed environment employs the concepts of modular modelling, model template, Multi-Dimensional Formalism (MDF) and process inventory, and has the ability to model costs, qualities and logistics. MDF defines a paradigm for the explicit representation of physical, behavioural, and operational perspectives or dimensions of the plant, process, and product. This is the basis for the development of simulation environments in which various product lifecycle alternatives are explored with the same simulation models. The case study, in which the PET bottle resin lifecycle was modelled and simulated, was implemented as a software tool and was shown to be convenient and efficient means to evaluate various product lifecycle alternatives.
Mesoporous silica powder (SBA15) with hexagonal pore structure (pore diameter, 7.5 nm and specific surface area, 584 m2/g) was prepared in the presence of tri-block copolymer as a template. Commercial mesoporous silica MCM41 with hexagonal pore structure (pore diameter, 2.9 nm and specific surface area, 759 m2/g) and SBA15 were used as a carrier for immobilization of a hydrolytic enzyme, lipase. SBA15 immobilized a greater amount of enzyme than MCM41 because of its larger pore diameter. The hydrolysis of 2-naphthyl acetate with the lipase immobilized in mesoporous silica was examined at 25, 50 and 70°C by measuring the concentration of hydrolysis product, 2-naphthol. At 50 and 75°C, the immobilized lipase converted a greater proportion of 2-naphthyl acetate than the lipase in aqueous phase, and the conversion with MCM41 as carrier was greater than that with SBA15. On reuse of the immobilized lipase a conversion of more than 70% was obtained at 50°C. The thermal stability of lipase for the hydrolysis of 2-naphthyl acetate was increased by the immobilization of lipase in mesoporous silica.
A new method has been developed to prepare copper plates with a wettability gradient by means of electrochemical reduction and coating of the resulting surfaces with thiol self-assembled monolayers (SAMs). The wettability of the surfaces could be easily modified by varying the surface roughness according to degree of electrochemical reduction and by changing the type of thiol coating. Thiol SAM-coated copper surfaces with wettability gradient could be generated by painting the ethanolic solutions of hydrophobic perfluoroalkylthiols and hydrophilic mercaptoalcohols on the surface of the electrochemically reduced oxide-free cupper electrodes of varying roughness. The results of a simple vapor condensation test for the modified surfaces showed that numerous liquid droplets nucleate and grow by coalescence with surrounding drops, then the droplets rapidly move from the perfluoroalkylthiol SAM-covered hydrophobic side to the mercaptoalcohol SAM-covered hydrophilic side. This phenomenon could be useful for passively enhancing heat transfer including two-phase change in heat exchangers and heat pipes.
Application of an energy storage system to the LNG vaporization process can level the variation in cold energy generation rate arising from daily and seasonal fluctuations in natural gas consumption, thereby promoting LNG cold energy utilization. In order to commercialize a BOG (Boil-off Gas) re-liquefaction process with a cold energy storage system, we have conducted storage tests for LNG cold energy by freezing n-pentane as a PCM (phase-change material) in a latent heat storage unit with finned tubes, which was used in the liquefaction tests for LNG two-phase flow in our previous work. The behavior of the PCM freezing process outside the finned tube is explained from the investigation of the overall performance of the storage unit and the heat transfer characteristics around the finned tubes. It is shown that the ratio of stored cold energy to storable energy, F, is effective for correlating the experimental results in the freezing process as well as in the melting process. Furthermore, the thermal conductance of the finned tubes in the freezing process, which was smaller than that in the melting process, is represented by a simple cylindrical model.
To develop a design and operational method for a BOG (Boil-off-Gas) re-liquefaction process for the LNG cold energy storage system, we performed numerical simulation analysis on freezing and melting processes of n-pentane used as a PCM (Phase-Change Material) in the system. Based on the results of a pilot-plant test reported in our previous papers, we adopted a simplified thick-wall cylinder model in the calculation to describe the heat-transfer and phase-change phenomena around the finned tube and simplify the simulation procedure to operating commercial plants. Numerical calculations agreed well with the results obtained in the pilot-plant test and showed that the model can predict well the performance of the finned-tube latent heat storage unit with nearly the same length scale as the commercial equipment. Hence the model can be effectively used for designing a liquefaction process including a cold energy storage unit of this type and for supporting the plant operations. In addition, the analysis shows that the liquefaction time as well as the amount of discharged cold energy for the melting process decreases considerably when the length of the liquefaction zone in the finned tube exceeds the total length of the storage unit.