Measurements of capillary suction potential of mesh-type wicks have developed a capillary model, which reasonably makes it possible to predict unsaturated hydraulic conductivity by considering the dependency of tortuosity on the saturation level, as well as to deduce a dimensionless capillary suction potential. The capillary model has also been provided to predict saturation profiles observed in a wick through which liquid flows at a constant infiltration rate and draining to a liquid table. The friction factor cf determined from the observed capillary potential has been related to the Reynolds number Re by cfRe = constant, which experimentally proved independent of the mesh woven-types and mesh layers consisting of a wick. The estimated cfRe value demonstrates its availability to predict the saturated hydraulic conductivity of mesh-type wicks.
Nonlinear dynamics of the formation of mixing fields was investigated at low Reynolds numbers (Re < 100) in a disk-turbine stirred vessel with no baffle plates by means of flow-visualization. The fine structures of isolated mixing regions (IMRs) were successfully observed. It has been found that a limited number of filament structures are formed and move around the torus with a certain period depending on the rotation of the impeller and the number of turbine blades and that the number of island-shaped filaments can be determined from the number of turbine blades and the rotation number of the impeller. It has also been elucidated that the isolated filament structure can be formed, only when and where the time-period ratio of the circulating filaments to the impeller rotation becomes a certain definite integer, which is determined from the number of turbine blades and the rotation number of the impeller. As the Reynolds number is raised, the isolated mixing regions become small and finally disappear. A physical rule of bifurcation for predicting the nonlinear-dynamic mixing structure has successfully been presented in a low Reynolds number region.
Wind tunnel evaporation experiments are made to study the kinetics of evaporation of a complex hydrocarbon mixture: kerosene, and of binary and ternary mixtures of n-C7, n-C8 and n-C9. The theoretical model used is based on a mass transfer coefficient approach. For a complex mixture the use of hypothetical components is adopted. Properties of the pseudo-components are defined using a characterization procedure. The model is found to be in very good agreement with experimental data. Specific recommendations are given for further investigations on oil and oil fractions evaporation.
A novel metallic monolith support was prepared by anodization, HWT (hot water treatment) and calcination. A commercial aluminum plate was anodized to form porous alumina films in the outer surfaces of the aluminum plate. In contrast to the anhydrous and amorphous alumina formed after anodization, the alumina in the anodized film with HWT was boehmite. The calcination after HWT made the boehmite film lose its hydrate water and rearrange into γ-alumina. The HWT and calcination significantly enhanced the surface area of the support due to the formation of numerous micropores (radius <25 Å). These new micropores were superimposed on the original skeleton structure to make up a binary-pore structure. The activities of Cu-Mn-CeOx/Al2O3/Al and Pt/Al2O3/Al alumite catalysts for the SCR-HC of NO by propene were investigated under oxygen-rich conditions. At low temperatures, Pt/Al2O3/Al exhibited a higher activity for NOx removal than Cu-Mn-CeOx/Al2O3/Al. However, a higher temperature (>623 K) made the activity of Pt/Al2O3/Al inferior to that of Cu-Mn-CeOx/Al2O3/Al. In comparison with Pt/Al2O3/Al, Cu-Mn-CeOx/Al2O3/Al had a lower N2O selectivity throughout the whole temperature range. The addition of SO2 inhibited the activity of Pt/Al2O3/Al, and this activity decay was reversible. On the other hand, a dramatic promotional effect of SO2 on reducing NOx was observed over Cu-Mn-CeOx/Al2O3/Al, but this influence of SO2 on the activity was irreversible.
The cross-flow microfiltration of fine particle/macromolecule binary suspension is analyzed and modeled in this study. The filtration rate, the cake thickness and the rejection of macromolecules can be estimated from the operating variables by modeling the cake formation, the concentration polarization and the penetration of macromolecules through the filter cake. Based on the force balance model, the thickness of the filter cake formed by fine particles can be related to the operating conditions. The formed cake plays the major roles on the filtration resistances and on the rejection of macromolecules. A reversible concentration polarization layer is constructed with the macromolecules near the cake surface. The concentration profile in this layer can be calculated using the mass transfer equation once the mass transfer coefficient is obtained from the analogy analysis. The standard capture equation for depth filtration is adopted to simulate the retention and the penetration of macromolecules in the filter cake. Experiments are carried out using the binary suspensions prepared by polymethyl methacrylate (PMMA) particles and the Dextran macromolecules. The filtration rates, the rejection of Dextran and the cake properties under various operating conditions are measured and discussed. The predicted values using the proposed models agree fairly well with the experimental data under various operating conditions.
A hydrometallurgical procedure for the separation of copper soluble species from metallic copper of a copper converter flue dust was studied. The high content of metallic copper in the starting material made unique a procedure of such characteristics for the treatment of this secondary copper resource. The procedure consists of leaching and solvent extraction operations. Leaching was carried out under atmospheric conditions using sulphuric acid. Under various experimental conditions the metallic copper fraction remains unattacked. The solubilized copper was separated/recovered by solvent extraction using LIX 860 or MOC-55TD oximes in Iberfluid (diluent). The loaded organic solutions can be stripped using typical spent electrolyte solutions (e.g. 25 g dm–3 Cu and 180 g dm–3 H2SO4). Results obtained showed the feasibility of the operation in the treatment of a converter dust with a high content of metallic copper.
The operation of a fully thermally coupled distillation column (FTCDC) is known to be difficult, which prevents wide application of the column. By separating the main column of the FTCDC into two sections the transfer of material between the two sections is disconnected, while heat transfer is sustained by installing a heat exchanger between the sections as a substitute of a reboiler of the upper section and a condenser of the lower section. It is expected that the modification of the FTCDC improves column operability with the maintained benefit of high thermodynamic efficiency of the original FTCDC. The structural analysis and design detail of the modified column are addressed here, and the design outcome is compared with the original column. In addition, the operability of the new column is examined from the evaluation of various multivariable controllability indices. The comparison of the indices with those of the original column indicates the improved operability.
A desulfurization process for light oil has been investigated using a polymer-supported imidation agent (PI, sodium N-chloro-polystyrenesulfonamide). When n-tetradecane solution (model light oil) containing dibenzothiophene (DBT) was stirred with methanol in the presence of PI and acetic acid at a temperature of 323 K, DBT was chemically adsorbed on the PI, via the imidation of sulfur atoms on DBT by the PI, and removed successfully from the oil. The polymer obtained was insoluble to the solutions and could be recovered by filtration. The present process was found to be also effective for the desulfurization of actual light oil: the sulfur concentration of commercial light oil was decreased successfully from 400 ppm to less than 50 ppm (ultra-deep desulfurization level).
In this study, mixing of fine powders with flammable insulator liquid was conducted and continuous monitoring of the static electrification during the mixing operation was attempted by a Faraday cage and a newly developed electrostatic field sensor. The effects of operating parameters (agitation speed, particle size, powder concentration) on the electrification were investigated experimentally. The experimental results implied that the electrification increased with an increase in agitation speed and a decrease in particle size. The electrification also increased when the powder concentration increased, however, too much powder concentration greater than 30 wt% could not increase the electrification further. The electrification during mixing was also measured under various vessel sizes and the scale-up characteristics was analyzed by means of agitation power per unit volume, blade tip speed and slurry circulation velocity. It was found that the scale-up of electrification during solid mixing was well conducted by means of agitation power.
A sensor to measure the intensity of power flux on the surface of food during microwave heating has been constructed, and measurements of the power flux intensity incident from the top surface of a cylindrical container were performed using the newly constructed sensor. The container was filled with water, and the power flux estimated from the temperature increase of the water after heating was confirmed to agree with the power flux measured using the sensor. Therefore, the ability of the sensor to measure the intensity of the incident power flux was confirmed. Next, the distribution of power flux intensity was measured in the radial direction for the cases of microwaves incident at the top surface, bottom surface, and top and bottom surfaces of the cylindrical container, respectively. This distribution of power flux intensity varies greatly depending on the heating conditions, but the temperature in the interior of food calculated using this value agreed almost with the observation results using a liquid crystal sheet.
In order to produce a recombinant protein rapidly and efficiently, glucoamylase, as a recombinant protein, was produced by Escherichia coli BL21 (DE3) [pET-12-STA1] using a bioreactor with cross-flow filtration. The recombinant E. coli BL21 (DE3) [pET-12-STA1] having an overexpression system with a recombinant plasmid (pET-12-STA1) was constructed by inserting a STA1 gene (a glucoamylase gene) into an overexpression vector (pET-12). Glucoamylase activity decreased rapidly after an incubation time of 2 h due to the degradation of glucoamylase by a protease synthesized with cell growth. The molecular weights of glucoamylase and protease were about 80 kDa and 10 kDa by gel filtration chromatography. Therefore, the culture using a bioreactor with cross-flow filtration was attempted for the separation of glucoamylase from the medium containing a protease. The filtration for enzyme separation was used by ultrafiltration membrane having a nominal molecular weight cutoff of 50 kDa. The glucoamylase activity obtained using the bioreactor with cross-flow filtration reached about 20 U cm–3 and this value was much higher than that without cross-flow filtration, i.e. 6.6 U cm–3. Since the separated liquid included both glucoamylase and protease, a recycle-type bioreactor with a cross-flow filtration system was also devised for the separation of glucoamylase from the separated liquid. The glucoamylase activity obtained using a recycle-type bioreactor system was maintained at about 40 U cm–3 and this value was about 2-fold higher than that without recycling. The recycle-type bioreactor system could produce 17220 U glucoamylase in about 1 dm3 culture medium; it was about 2 times higher than that without recycling (8700 U).
The thermal performance of the capric acid and lauric acid mixture (C-L acid), in the respective composition of 65% and 35% by mole was investigated for its cooling capacity. A vertical cylindrical storage capsule was employed for the study. A supplementary simplified numerical model for the behavior analysis of the C-L acid employing the experimental design was made. The mathematical model was numerically solved using a finite difference method. The radial temperature distribution, the melting time and solidification time results performed from the charge and discharge experiments are verified to evaluate the reliability of the assumptions made on the numerical model. A two-dimensional heat transfer is represented by a one-dimensional model accounted by the effective thermal conductivity that considers both the natural convection and two-dimensional effects. The numerically estimated radial temperature distribution during melting and solidification are within the experimentally obtained ranges.
Production of tar constitutes one of the most pressing challenges in the development of low-temperature biomass gasification. As one solution to this problem, we suggest utilizing the capacitance effect of porous particles for tar-free gasification. In the present work, in order to clarify the fundamental characteristics of the capacitance effect for biomass gasification, tar yields in sawdust pyrolysis with and without porous particles were measured at 873 K and 1073 K in a lab-scale fixed bed reactor. Employment of porous particles substantially reduced the tar yield from biomass pyrolysis. Within the range studied, the tar yield without porous particles is nearly equal to the yield of carbon deposition on porous particles at 873 K. This finding indicates that porous particles can capture and hold all tar. That is, tar produced from pyrolysis is instantaneously absorbed on the surfaces of porous particles, and the residence time of tar in a gasification furnace is prolonged and then tar is pyrolyzed, carbonized and fixed on porous particles, so high tar reduction is achieved. The results of gas yield measurement show that employment of porous particles increases hydrogen yields by three times or more. There are two reasons why hydrogen yield increased. One is that the catalytic effect promotes dehydrocyclization of lower molecular weight organic gases. Another is promotion of cyclized (poly-)condensation of aromatic compounds held on porous particles. Therefore, use of porous particles is also beneficial for improving gas properties.
This work involves the treatment of model groundwater containing arsenic with the use of chemically modified zeolite. A finite volume stirred tank reactor was used to study the effects of the variables; sorbent grain fraction and sorbent dose, on arsenic reaction kinetics. The results are modelled using the pseudo-second order and second-order reversible rate equations. Equilibrium arsenic uptake and residual sum of squares evaluated from the two models are compared. From them, the arsenic sorption onto the active sites is consistent with a pseudo-second order mechanism. The initial sorption rate which drives the uptake rate was found to be in the same order of magnitude for all the grain fractions but decreased with an increase in the sorbent dose. Furthermore, based on the pseudo-second order mechanism, Thiele moduli were determined and their values suggested that intraparticle diffusion may play a significant role in arsenic uptake.
An equipment of a submerged membrane activated sludge process without sludge withdrawal was operated at three BOD loadings (0.25, 0.5 and 0.6 kg-BOD/(m3·d)) to find out its stable operational condition. The stabilized and final values of MLSS were increased with BOD loadings and the conversion ratios (0.04–0.15 kg-MLSS/kg-BOD) of substrate to biomass were much smaller than the conventional activated sludge process. The supernatant TOC in the bioreactor was low in all runs and then organic matters were not accumulated. At low BOD loadings (0.25, 0.5 kg-BOD/(m3·d)), suction pressure was constant or increased very slowly, but at the highest BOD loading (0.6 kg-BOD/(m3·d)) the pressure and total filtration resistance were increased abruptly and failed the operation rather soon. The good stable operational condition without sludge withdrawal was obtained at BOD loading below 0.5 kg-BOD/(m3·d).