A novel circulation system of coarse solids, consisting of screw cylinders in a rotating cylinder was proposed. An experimental cylinder of transparent single screw cylinder was constructed to represent one element of the above circulation system. The cylinder was filled with rice grains, and the volume of discharged grains was measured. From the results, a theoretical equation was developed to predict the transportation rate of solids in a screw cylinder. From the equation, it was concluded that the proposed novel system can provide the same circulation capability as the Pyrox Process, and would be more convenient for a gasification plant of smaller scale.
Water vapor transfer within dried zone appearing during the falling drying rate period of non-hygroscopic porous slab was examined theoretically on the basis of a set of the non-isobaric unidirectional gas transfer equations that had been derived by using the equations for the one-dimensional gaseous transfer of the water vapor–air binary component system. The examination was performed under conditions corresponding to hot air drying, superheated steam drying with air leakage or vacuum drying with air leakage. As a result, the set of the strict non-isobaric unidirectional vapor transfer differential equations was successfully integrated and a set of approximate equations was obtained. Calculated results by five approximate equations, namely, the non-isobaric approximate equations, the isobaric unidirectional diffusion equation with or without the effect of the Knudsen flow and the vapor flow equation with or without the Knudsen, were compared with the results of the strict differential equations, and the applicable regions of the five approximations were clarified for the drying rate and the total pressure generated within the slab. The non-isobaric approximation showed an excellent agreement with the strict equations within extensive limits of the surface temperature and the pore size. The isobaric approximations were effective for pores of micron size in which little total pressure was generated. The vapor flow approximations were effective for all cases of drying in which pores were filled approximately with the vapor only. Only the non-isobaric approximation was effective for all cases of drying involving sub-micron size pores filled with both vapor and air in which considerable total pressure was generated.
The dust collection and cleaning process of a candle-type ceramic filter were tested by use of two fly ashes with different geometries and thermal properties at temperatures of 200, 500 and 800°C. The shear strength of ash samples was tested at the same temperatures as the filtration to help predict the adhesive forces between ash particles. Data from this study were compared with data from the literature in examing the influences of filtration conditions using the ash properties of the void fraction of the dust layer in order to evaluate the cleaning efficiency of ceramic filters. Four forces acting on the particles collected on the filter surface were examined as influencing factors on the structure of the dust layer. The non-dimensional packing parameter Π=FC−2FI1FV−1FG2 was found to represent the dust layer porosity, where FC is the adhesive force between particles, FI the inertial force, FV the drag force acting on a particle moving in the gas and FG the gravity force. The cleaning force σr and the adhesive force σc, acting on the particle layer, were examined as influencing factors to predict the cleaning efficiency. The force ratio Γ=σr/σc was found to describe the behavior of dust cleaning efficiency η, which increases significantly in the region 1<Γ<10. Although further detailed analysis is required, the analysis of forces acting on particles and on particle layers was found to be valid for evaluation of hot gas filtration and the cleaning characteristics of ceramic filters.
A Dual Reflux PSA (DR-PSA) is a combined process of a conventional stripping reflux PSA and an enriching reflux PSA, and it has two refluxes and an intermediate feed inlet position. In this paper, a simplified mathematical model was developed to obtain a simple semi-algebraic solution expressing the behavior of the DR-PSA process, and the effects of feed inlet position and reflux ratio on the process performance were investigated. The validity of the model was confirmed by comparing the model with existing experimental results. In addition, the model clearly described that the adsorbate concentration of the processed gas at the optimum feed inlet position is equal to that in the feed gas, and this fact has been experimentally confirmed. Also, the model could be used to derive the optimum reflux ratio to achieve a required purification/enriching performance. The proposed model provides a simple design technique for the DR-PSA process, and it is useful for the optimization of the feed inlet position and the reflux ratio, which have considerable influence on the process.
Wet flue gas desulfurization (FGD) systems that remove sulfur dioxide (SO2) from in flue gas, a cause of acid rain, operate at many power plants, but problems remain to be solved concerning the detailed behavior of these systems. Here, we experimentally studied the behaviors of O2 and CO2, which have not been fully clarified, and conducted simulations using models based on the present experimental results for O2 and CO2 and results reported for other chemical models. From the experimental results, we obtained an equation for O2 absorption as a function of superficial gas velocity, and one for CO2 desorption as a function of superficial gas velocity, pH and temperature for the oxidation tank in an FGD system. We also conducted simulations for FGD systems based on the typical chemical behaviors observed experimentally. First, we calculated the distributions of flue gas concentration, pH, and the solid phase absorbent concentration for two typical FGD methods, the limestone-gypsum method (LGM) and magnesium hydroxide method (MHM), and studied the differences in behavior between them. Next, we studied the optimum values of water depth in the oxidation tank and gas flow rate of the air compressor for oxidation and got the values of 6 m for the former, and of 2,500 m3 (STP)·h−1 (LGM); 2,700 m3 (STP)·h−1 (MHM) for the latter.
Simulation was performed to optimize a flue gas desulfurization (FGD) system, which removes sulfur dioxide (SO2) from flue gas. Optimum conditions were sought by studying the influence of various parameters on desulfurization efficiency and CaCO3 availability for the limestone-gypsum method (LGM) in comparison with the magnesium hydroxide method (MHM). When an FGD system with a cross-sectional area of 30 m2, an absorption tower of height 15 m and a water depth in the oxidation tank of 5 m was used to treat flue gas containing 1,000 ppm of SO2 at a flow rate of 500,000 m3 (STP)·h−1, we obtained the following optimum values: dissolved SO2 concentration: under 0.001 kmol·m−3 (LGM), 0.05 kmol·m−3 (MHM); diameter of droplet: 1.5 mm; pH: 6.5 (MHM), solid CaCO3 concentration: 1.0 wt% (LGM), height of absorption tower: 15 m (LGM), 10 m (MHM); and liquid flow rate of recirculation: 6,000 m3·h−1 (LGM), 4,500 m3·h−1 (MHM). Next, we studied the control system for temporary fluctuations of SO2 gas concentration and the flue gas flow rate by using the above design and operating conditions obtained for LGM. As a result, it was indicated that the stable maintenance of desulfurization performance was possible by the feed-back control using a PID controller.
The compression characteristics of consolidated deposits formed in centrifugal flotation of O/W emulsion were clarified with the aid of an analytical centrifuge which could monitor timed near-infrared (NIR) transmission profiles of samples in the centrifugal field. Compression data of the soft particles were then compared with those of the rigid particles of silicon dioxide in centrifugal sedimentation. The dependence of the local porosity on the local solid compressive pressure was determined based on the relation between the average porosity and the solid compressive pressure at the bottom of the consolidated deposit obtained from experiments conducted under various angular velocities, sample heights, and concentrations of the dispersed phase. Moreover, variations in the local porosity and the local solid compressive pressure across the consolidated deposit were evaluated from the relation between the local porosity and the local solid compressive pressure. The analysis revealed that the consolidated creaming layer of the soft particles is of much lower porosity than the consolidated sediment of the hard particles, while the solid compressive pressure is much smaller. Also, depending on conditions, the greater part of the consolidated creaming layer of oil droplets exhibited lower porosity than hexagonal close-packed undistorted spheres, because of the deformation of the oil droplets under the action of the solid compressive pressure.
We have made freeze-concentration equipment consisting of an ice-maker, which continuously produces ice flakes on a rotating cooling drum, and a continuous centrifugal separator. The purpose of this study was to evaluate the effect of screen (for solid-liquid separation) in the centrifugal separator. Experiments using sea-water (solute concentration of the mother liquor 4.6–4.9 wt%) in this equipment led to the following results. The solute recovery rate of tests with screen B (opening ratio 4.0%) compared favorably with those of tests with screen A (opening ratio 2.3%). Furthermore, a screen with an opening ratio between those of screens B and C (18.3%) is expected to give a higher separation ratio.
To develop applications of the nano-material fullerene, we examined its potential as a visible-light catalyst. Expecting the use of sun light in the future, we found that fullerene catalyzed the oxidation of phenol in aqueous solution under visible-light radiation. The decomposition rate of phenol was proportional to fullerene density, visible-light intensity, phenol concentration and partial pressure of oxygen. As pH decreased, the decomposition rate increased. We also proposed a reaction path catalyzed by fullerene excited with visible-light radiation. Experimental results were consistent with the proposed reaction path.
Nail apparatus melanoma (NAM) is a malign melanoma with relatively high incidence among Japanese compared with melanomas at other sites. The prognosis is poor because of the difficulty of diagnosis. In this study, we developed an algorithm to distinguish malign melanomas from benign melanomas based on images, captured uninvasively by dermoscopic examination. This algorithm extracts common waveform patterns in images of melanonychia striata by use of a genetic algorithm (GA), and carries out diagnosis based on common patterns by using linear discriminant analysis. In the present study, images were captured from 28 cases of NAM, including 9 malign melanomas and 19 benign melanomas by dermoscopy. The algorithm was applied to these NAM images, and the accuracy of diagnosis was found to be 80.0%. Moreover, we compared the common patterns extracted from malign and benign melanomas and confirmed that the common waveform pattern extracted from malign melanomas shows marked variations compared with that from benign melanomas.
Calcium phosphate is one of the most important inorganic constituents of cheese whey, a by-product of cheese with many nutritive constituents such as proteins, lactose, fat and inorganic salts. To recover proteins from cheese whey, membrane separation has been applied industrially. In this process calcium phosphate causes fouling by precipitating on the membrane surface. As a means to inhibit the precipitation, we studied the effect of adding chelating agents, EDTA (ethylene diamine tetraacetic acid) and citric acid. Experiments were conducted using calcium phosphate suspension as a model solution of whey and a solution of whey protein isolate (WPI) in distilled water. With the calcium phosphate suspension, calcium ions in solution were trapped by chelation, and the amount of calcium phosphate precipitation decreased. With the WPI solution, the free calcium ion concentration in solution decreased.
A water-based commercial paint was coated on a base plate made of glass or iron. The drying rate of the coated plate was calculated by a temperature change method that uses the temperature history of the wet material measured by a radiation thermometer during drying and the difference in the mass of the material before and after drying in the case of double-sided hot air drying. Approximation of the uniform temperature within the coated plate was appropriate when the hot air temperature at each side was different. As a result, the drying rate obtained from the temperature history of the coated side closely agreed with that from the temperature histories of the coated and the reverse sides.
Hydrogenation of naphthalene and tetralin in the presence of CO was studied over alumina-supported Co, Ni, Ru, Rh, Pd and Pt catalysts. In the presence of CO, naphthalene was hydrogenated selectively without CO hydrogenation over Pd/Al2O3, whereas both naphthalene and CO were hydrogenated over Co/Al2O3, Ni/Al2O3, Ru/Al2O3 and Rh/Al2O3. The relative activity of six supported metals was dependent on the presence or absence of CO. Rh/Al2O3 showed very low activity for hydrogenation of naphthalene and tetralin with 2%CO–H2, while it showed the highest activity for hydrogenation with pure hydrogen. In contrast, Pd/Al2O3 showed the highest activity for naphthalene and tetralin hydrogenation in the presence of CO. From FTIR measurements of adsorbed CO, the high activity for naphthalene and tetralin hydrogenation over Pd/Al2O3 in the presence of CO was correlated with desorption of CO (>ca. 1950 cm−1) adsorbed on coordinatively unsaturated sites.
In recent years, abundant deposits of methane hydrate, a principal ingredient of natural gas, have been reported under the ocean floor around Japan and all over the world. Methods such as heat stimulation and decompression have been proposed for recovery of this methane hydrate, but the gas-lift method considered here has the possibility of more economical efficiency than the other recovery systems. Although the design of the bottom of the inlet pipe is important to efficiently recover hydrate from the seabed, the flow around the inlet pipe and optimal shape have not been examined. The present paper studied the flow around the inlet of recovery pipe and the indrawn particle behavior by experiments and numerical simulations. An umbrella-shaped inlet pipe was proposed in order to expand recovery area and enhance recovery efficiency compared with a normal cylinder-shaped pipe. Turbulent flow simulations were conducted for the umbrella-shaped inlet pipe with the k-ε model. The simulation results were compared with those of experiments with a recovery pipe length of 1.6 m, in which the flow near the inlet was measured by (Particle Image Velocimetry (PIV) system. The experimental results agreed well with the simulation results, and the efficiency of the umbrella-shaped inlet pipe was clarified.
The effects of water concentration in hydrogen and the composition of MmNi5-based hydrogen-absorbing alloys on their absorbing-desorbing properties were investigated. Absorption-desorption cycling tests of hydrogen containing 660 ppm and 1600 ppm H2O were carried out for two kinds of MmNi5-based hydrogen-absorbing alloys. The hydrogen absorbing-desorbing fraction of MmNi4.04Co0.60Mn0.31Al0.05 with a high content of Ce, where the fraction is defined as the amount of hydrogen undergoing absorption-desorption relative to the maximum amount, decreased significantly, because of a decrease in the rate of hydrogen absorption-desorption. On the other hand, that of MmNi4.23Co0.51Mn0.12 with a low content of Ce did not greatly decrease. Although the rate of hydrogen absorption of MmNi4.23Co0.51Mn0.12 decreased in the early cycles, it reactivated with an increase of the number of cycles. Degradation by water vapor leads to differences in the hydrogen absorbing-desorbing fraction because of the different contents of Ce. With a low content of Ce, MmNi5-based hydrogen-absorbing alloys have a high resistance to degradation by water vapor. Therefore, when MmNi5-based hydrogen-absorbing alloys are applied to electric-load leveling systems, they should be chosen according to their Mm composition.
Behaviors of dioxins in remediation of dioxin-contaminated soil by thermal desorption and relationship between the behavior and the vapor pressures were investigated. PCB-contaminated soil prepared for this study and actual contaminated soil sampled at a chemical plant were used. The performance of thermal desorption was better at higher temperature, and it changed significantly between 300°C and 400°C. A part of dioxins was decomposed in thermal desorption by catalytic action of soil. The remaining fraction correlated with the vapor pressure of each congener, and the correlation was caused by the length of reaction time with soil.
The reduction of lead sulfate was investigated in order to obtain fundamental data for developing an efficient recovery process of metallic lead from lead sulfate in a spent storage battery. Changes in lead-form distribution were followed for five systems, (1) PbSO4–C, (2) PbSO4–Na2CO3, (3) PbSO4–Na2CO3–C, (4) PbS–Na2CO3, and (5) PbS–Na2CO3–C, during heat treatment under a nitrogen stream. An optimum molar ratio of carbon to lead sulfate was obtained in the PbSO4–C system, and the yield of metallic lead decreased with excess carbon ratio, due to the production of lead sulfide as the main product. When sodium carbonate was added to the system of lead sulfate and carbon, the yield of metallic lead increased over a wide range of carbon content. It was found that sodium carbonate accelerated the formation of lead oxide from lead sulfate, and the formation of metallic lead increased with the carbon content.