Self-diffusion of a tracer particle in an electrically non-charged and charged cubic lattice with the hard-body type excluded-volume effect as a simplified structure of cross-linked network of gel is investigated by Brownian dynamics simulation. Both the excluded-volume and the electrostatic attractive interaction acting between the tracer particle and the cubic lattice result in the reduction in the self-diffusion coefficient as compared to that for the free diffusion. Reduction caused by the electrostatic attractive interaction is significant when dp/dlattice<<1 and dp/dlattice~1, where dlattice and dp denote the mesh size of the cubic lattice and diameter of the tracer particle, respectively. When dp/dlattice<<1, the reduction in the self-diffusion coefficient is mainly due to entrapment around the charged points on the cubic lattice located at the middle point of arbitrary two neighboring cross positions. When dp/dlattice~1, the entrapment time in the unit cubic lattice space is greatly enhanced due to the high potential to be overcome when the tracer particle undergoes the translation beyond the boundary of arbitrary two neighboring unit cubic lattices.
The purpose of this experimental investigation is to examine the phase separation characteristics of a two-phase gas-liquid mixture into a series of branch tubes from a header pipe. This kind of flow is encountered at, for example, an air conditioner. Three parallel branches were attached vertically downward in right angles to the horizontal inlet main tube (14 mm inside dia.) and 50 mm apart from each other. In the present experiment the flow rate of both phases in branch tubes (4 mm inside dia.) and static pressure distributions were measured. The flow pattern in the main tube is mainly slug flow. It is found that there was a maldistribution of air and water among branches.
The purpose of the study is to develop a practical catalyst for the conversion of carbon dioxide to methanol by hydrogenation. The activity and durability of a CuO-ZnO-Al2O3 catalyst and a CuO-ZnO-Al2O3-Ga2O3-MgO catalyst were investigated using a bench-scale test plant. It is found that the CuO-ZnO-Al2O3-Ga2O3-MgO catalyst shows better activity and durability than the CuO-ZnO-A1203 catalyst. Addition of Ga and Mg is effective to especially improve durability of the CuO-ZnO-Al2O3 catalyst. CO2 conversion to methanol of the CuO-ZnO-Al2O3-Ga2O3-MgO catalyst has been over 95% for 2,000 h at a pressure of 9 MPa, a temperature of 503 K and a recycle ratio of four by recycling unconverted reactants. Assuming that the CuO-ZnO-Al2O3-Ga2O3-MgO catalyst is applied to a conventional process, the optimum synthesis pressure to minimize the power consumption is estimated to be 7 MPa at a recycle ratio of 5.5 in the case of catalyst exchange after 16,000 h of use, and 10 MPa at a recycle ratio of 5 in the case of catalyst exchange after 32,000 h of use.
Selective reduction of NO with CH4 on platinum supported on cobalt phosphate was investigated. It was found that Pt/Co3(PO4)2 exhibits the high activity to NO reduction with CH4. NO conversion increased with increasing amount of Pt loading and it attained to a maximum activity at 1 wt% Pt. Conversion of NO was always higher than that of NO2 on Pt/Co3(PO4)2 under the same condition. This result suggested that the reduction of NO was proceeded not through the formation of NO2 or NO3− as intermediate species but through the direct decomposition of NO as a primary reaction. NO conversion increased with decreasing oxygen partial pressure and the high conversion of NO into N2 was exhibited when no oxygen was coexisted. Temperature programmed desorption (TPD) measurement suggested that loading Pt accelerates the dissociative adsorption of NO and weakened the adsorption of O2. Therefore, it seems that NO decomposition on Pt/Co3(PO4)2 was initiated by the dissociative adsorption of NO. Coexisting CH4 removed the formed oxygen which strongly adsorbed on the catalyst and recovered the active site. This study reveals that Pt supporting on Co3(PO4)2 is highly active for the reduction of NO with CH4.
Fe2O3-SiO2 particles, which removes 112S and COS in hot coal gas, are prepared. The characteristics of sulfidation are studied using simulated coal gas from an air blown gasifier. In the temperature range of 623 K to 973 K, the conversion rate of Fe2O3-SiO2 particle to iron sulfide was slowest at 823 K where Fe2SiO4 is formed at reduction before sulfidation. At lower than 823 K, the stable formation is Fe3O4. The conversion rate is of first order in 112S concentration. At more than 823 K, however sulfidation does not proceed in lower 112S concentration than 1,000 ppm-2,500 ppm levels. At temperature 823 K, this concentration is lower than 2,460 ppm, which is higher than the equilibrium concentrations (175 ppm). In the temperature ranges from 673 K to 823 K and from 923 K to 973 K, sulfidation is controlled by pore diffusion under Knudsen diffusion regime. This result shows that sulfidation has the influence of the change of pore radius of Fe2O3-SiO2 particle at reduction.
The Boudouard reaction, that is, reaction of activated carbon with carbon dioxide to carbon monoxide, is carried out at 773 K in a stirred mill reactor. The mean diameter of activated carbon changes from 44 to 1.2 µm by the grinding. The reaction occurs by grinding activated carbon in the reactor and the reaction rate increases with the increase of stirring rate of ball. The reaction rate also increases by addition of iron powders as the catalyst and the catalytic activity of iron powders is changed by the kinds of ball (iron or zirconia) and the diameter of iron powders. This catalytic activity is preserved after the stirring of ball is stopped. However, the reaction rate decreases with time and the decrease rate is dependent on the kinds of ball and the diameter of iron powders. Nickel oxide powders show catalytic activity by mixing with iron ball but not with zirconia ball. To investigate the interaction between activated carbon and iron, the surfaces are observed by using a scanning electron microscope (SEM) and energy dispersive X-ray analyzer (EDX).
Magnetic iron fine-particles are industrially produced from acicular goethite fine-particles through three chemical reaction paths : goethite dehydration, hematite reduction and magnetite reduction. In this study, in order to improve the coercivity of the particles, we carried out experiments on production of magnetic iron fine-particles under various reaction conditions. Experimental results show that the coercivity of iron fine particles depends strongly on the temperature for the magnetite reduction. At the magnetite reduction temperature of 450°C, the coercivity of the products consisting of acicular primary particles reaches a maximum value of 126 kA/m. When the mole fraction of hydrogen in the supplied gas or reaction temperature for hematite reduction decreases, hematite is reduced not to iron directly but to magnetite intermediately. Particularly, when hematite is reduced to magnetite under hydrogen atmo-sphere accompanied with additional water vapor, iron fine particles compactly composed of smaller crystalline with higher coercivity are obtained after further reduction of those magnetite.
Sol-gel derived silica membranes have shown large selective permeance for hydrogen at high temperature, but the stability in hydrothermal conditions is insufficient. It is considered necessary to improve their stability against hydrothermal conditions such as the LNG reforming process, which contain high concentrations of water vapor. In this work the effects of zirconium contents in silica-zirconia composite membranes on the hydrogen permeation performance were studied. A silica-zirconia membrane with molar ratio 9/1 shows a H2 permeance of 1 x 10-5 m3 (STP) m-2 s-1 kPa-1 and H2/N2 selectivity of more than 100. An increase in zirconia content causes a decrease in the H2 permeance and the permeability ratio of H2/N2. The activation energy of H2 and He permeation increase with an increase in zirconia content, suggesting membrane densification with an increase in zirconia content.
Filters consisting of fibers with irregular cross-sections are commonly used in cigarettes. However, the influence of fiber cross-sectional shape on the filter collection performance is not well understood. In the present study, the influences of fiber cross-sectional shape on both diffusional collection efficiency and pressure drop are studied both theoretically and experimentally when the fibers were placed perpendicular to the airflow. As a result, it is found that fiber cross-sectional shape and fiber orientation have little effect on the single fiber collection efficiency, but drastically change the pressure drop. The dimensionless drag force of irregular fibers is well correlated by the width of irregular fibers projected in flow direction because the projected width of fiber determined the mutual influence of neighboring fibers. The result suggests that the use of irregular shape fiber fitter is one of the effective means to alter the pressure drop without changing collection efficiency of the filter.
In a mixed micellar systems of sodium bis (2-ethylhexyl) sulfosuccinate and di-2-ethylhexylamine or di-n-octylamine, the extraction of lysozyme is investigated by the phase transfer method. The extraction of lysozyme occurs at pH range between its pI and the pH where the extraction of water is observed. Lysozyme extracted into the mixed micellar systems can be successfully back-extracted with high activity yield.
Spinel lithium manganese oxide (LiMn2O4) fine particles are prepared by on ultrasonic spray pyrolysis method from an aqueous lithium nitrate and manganese acetate solution. The effect of synthesis factors, such as initial concentration of feed solution and gas flow rate, on particles morphology, composition and crystallite size is examined. The effect of axial temperature profile in the aerosol flow reactor on the morphology of prepared particles is also investigated using a tubular furnace with six independently controlled heating zones. Spinel LiMn2O4 fine particles are successfully prepared at both constant temperature distribution (1,073 K) and increasing temperature distribution (473 K-473 K -673 K-873 K-1,073 K-1,073 K) in the reactor. The particles prepared at a constant temperature profile (1,073 K) in the reactor are hollow spheres, which are formed by over ten nanometer size of crystallite, while those prepared at increasing temperature profile (473 K-473 K-673 K-873 K-1,073 K-1,073 K) are shrinking and not hollow spheres.
The effect of rotor shape on the composite process of fine particles which covers the surface of the core particles is investigated by using a high-speed elliptical-rotor-type mixer. Two kinds of different shape of rotors are used for experiments. As a result, the composite process strongly depends on the rotor shape, and it is explained by the average contact force acting between the core particles and the rotor wall which is calculated by a 3-dimensional numerical simulation (PEM) already proposed by the authors.
The characteristics of the surfactant-subtilisin Carlsberg (STC) complex are investigated on an enzymatic ester-exchange reaction in an organic solvent. The surfactant-STC complex exhibits a high enzymatic activity in various organic solvents although native STC hardly catalyzes the same reaction. The results reveal that the pH value and the surfactant concentration at the preparation stage have a prominent effect to ensure high catalytic activity of the enzyme complex in organic media. The high solubility of the surfactant-STC complex in organic media makes it possible to obtain direct information about the reaction mechanism by kinetic studies.
The kinetics of autoxidation of linoleic acid and effect of antioxidants, a-tocopherol and ascorbic acid stearate, on the reaction are investigated in a bubble column type flow reactor. The oxidation of linoleic acid is observed to have two reaction stages, which were an induction period with a slow increase of hydroperoxides and an acceleration period with their rapid increase. The results obtained are analyzed based on a reaction model with radical chain reaction. The rate equation of autoxidation of linoleic acid is formulated as a function of concentrations of linoleic acid and peroxides, partial pressure of oxygen and reaction temperature. The oxidation behavior adding a-tocopherol is found to be markedly different compared with that without a-tocopherol. Three steps during the oxidation which are induction, temporary stable, and accelerated periods are observed. In the induction period, the rate of oxidation is very slow and the maximum effect on the antioxidation is observed at a certain concentration of a-tocopherol. For more than this concentration, the rate increases with increasing in the concentration of a-tocopherol. In the stable period, appropriate formation of peroxide is interrupted and the concentration of peroxides is kept at constant. The time length and concentration of the peroxides in the period increase with increasing concentration of a-tocopherol. In the accelerated period, all of the oxidation rates are very rapid and the same with or without a-tocopherol. By the addition of both a-tocopherol and ascorbic acid stearate the oxidation is effectively suppressed.
In this study, rat primary hepatocytes were cultured on a non-woven PTFE fabric coated with a copolymer of poly (amino acid) -urethane (PAU) to examine the expression of their original functions. In the culture dish, ammonium metabolic activity of hepatocytes cultured using the fabric coated with PAU is higher than that using collagen-coated polystyrene. It is also indicated that it is possible for hepatocytes to maintain the functions for long-term culture in the circulatory culture equipment with the fabric coated with PAU.
The treatment of soil contaminated with trichloroethylene (TCE) is demonstrated. In the present study, electric osmosis was applied to the removal/decomposition of TCE. First, the behavior of water and TCE in electrolyte (KN03) solution was examined with electricity supply. The permeation rate of electrolyte (KN03) solution through a cylindrical unglazed plate was increased with increased voltage and concentration of electrolyte. On the other hand, the diffusion rate of TCE without electricity was increased with addition of electrolyte, while the rate was negligibly small. The TCE added to the inside solution (anode side) mostly stayed inside and was completely decomposed. Based on the above results, the decomposition of TCE in soil was tried. The contaminated soil at the outside of the cylinder was moved and decomposed in the initial stage, however, the rates were reduced and its concentrations in both solutions were increased with the decrease in current density. Therefore, the electrolyte was added periodically, which increased current density, leading to the decomposition of TCE in both sides. Finally more than 99.9% decomposition of TCE added to the soil was demonstrated by 10 h electric osmosis with a 10 voltage.
We attempted to design a capsule type heat storage system, which can store heat with warm water 333 K and can produce warm water (over 320 K) directly from the heat storage tank. We developed a new PCM with melting point 323 K and heat of fusion 205 kJ/kg. This PCM was obtained by adding sodium nitrate to sodium acetate trihydrate. It is found that this PCM melted with warm water of 333 K and crystallized at 321 K. Also, it was found that heat quantity and melting point of this PCM didn't change even if freezing and melting was repeated 1,100 times. We carried out characteristics evaluation of this system. It was found that this system could store heat with warm water (333 K) within 10 hours. So, this system is able to use off peak discount electric power. The theoretical heat storage quantity of this system is 322 MJ and the experimental value was 305 MJ in this evaluation. So, it is understood that this system could store heat almost equal to the theoretical value. Also, it was found that this system could produce warm water over 320 K, which is required space heating, and can release almost stored heat.
This paper describes a study on combustion of livestock wastes for development of a power generation system using them. Broiler, layer and swine excrements are used as fuel. The relationship between calorific value and moisture content is examined. Although moisture content of the prepared livestock wastes shows sufficient fluctuations (10-80 wt%), it does not strongly affect the lower calorific values on a dry basis. The livestock wastes are burned using an established test fluidized-bed furnace. Because moisture content of the swine excrement is very high (80 wt%), swine excrement is mixed with other livestock wastes to decrease the moisture in the fuel. The combustion efficiency, which is defined as the ratio of the heat generation in the fluidized bed to the calorific value of the supplied fuel, is evaluated using a heat balance in the fluidized bed. On the basis of the results, an empirical equation for estimating the combustion efficiency is presented. The fluidized-bed temperatures estimated using the empirical equation and the heat balance almost agree with the experimental ones.
Pyrolysis and gasification of wastes supposed to be in an entrained gasifier were analyzed by thermogravimetry under a constant heating rate of 2 K/min. Ordinary plastics PE, PP, PS, and PET are rapidly decomposed in the temperature range of 600-750 K, and PVC and rubber are decomposed in the range of 500-800 K. Sawing tip and cellulose are pyrolyzed in the range of 550-800 K, and municipal waste and waste plastics are in the range of 500-800 K. Gasification of char with CO2 and/or H2O proceeds in the temperature range of 1,000-1,500 K and the TG curves are dependent on the char components. It is shown that the degradation processes of PVC and rubber are divided into two or three stages. The respective TG curves of individual materials are well simulated by modified volume reaction model equations. The reaction rate constants and the related activated energies and pre-exponential factors are determined from model equations. TG curves of the waste plastic and municipal waste are well simulated by adding the reaction ratios of individual components.
We conducted gasification tests for municipal waste plastic recycling by using a 2 ton/day entrained partial combustion plant, and show that the recovery gases are applicable for fuel for a gas turbine. The properties of recovery gases and their dependency on the operational conditions, feed rate of plastics and applied oxygen ratio, are clarified. We also developed a mathematical model to simulate the chemical process in the entrainment gasifier, assuming that the gas and particulate solids are in one-dimensional steady state flow and flammable volatiles from the waste plastics can be characterized just by ethylene in pyrolysis process. We show that the constituents of the recovery gases can be predicted in fairly close relation with those from the results of gasification test. The rateconstants related to pyrolysis and char gasificationreactions were determined by previous thermogravimetric studies and the rate constants for the reaction between volatile and CO2 and/or H2O are determined by a data fitting with the results of gasification tests.
The possibility of enlargement in water absorption ability of bauxite for its practical use as newinorganic water absorbent was studied. (1) Absorbed water by calcined bauxite is possibly utilized for plant growth. High possibility wasdemonstrated for material. (2) Rapid heating in calcination in fluidized bed (F. B.) was fond to be more effective than mufflecalcination to increase water absorption ability of bauxite. Water amount of uncalcinatedbauxite was 35 to 38%. More than half of total moisture (20%) was fond to distribute on thesurface of bauxite, which is expected to be utilized for plant growth. The other part of moisturewas structured (combined) water in bauxite particles. (3) Rapid calcination bauxite at 700°C in F. B. indicated the highest values of water absorption,specific surface area and total pore volume, respectively which relate to water absorption andwater preservation ability of bauxite particles. The temperature of 700°C was found as optimumcalciantion temperature.
In order to explain the de-hydrochloric (de-HCI) phenomena in densified refuse-derived fuel (RDF) combusted in a fluidized bed, experiments under combustion and pyrolysis conditions for some laboratorial model RDFs and RDF made from municipal solid waste are carried out in an electric furnace. The combustion characteristics of each single RDF pellet under similar combustion conditions as those in fluidized bed combustion (FBC) or stoker combustion are studied. The emission of HC1 through the flue gas, and the capture of chlorine by Ca additive in the RDF during the combustion are measured. It is found that the fraction of Cl captured by the residual ash increases from 0 to nearly 70% under similar combustion conditions as in FBC when the molar ratio of Ca/(S+0.5 Cl) is increased from 0 to 12.6. It is also found that the fraction of CI captured by the residual ash apparently decreases with increasing oxygen concentration under ambient cenditions. The devolatilization process of RDF is verified to take a very important part of de-HC1 process. Moreover, the effect of temperature profile in the RDF pellet, which is varied with the heating rate of RDF and the ambient oxygen concentration, on the de-HC1 is discussed. Accordingly FBC has been verified to be beneficial for de-HCI reaction.
We propose a new method for producing ice by winter air in cold regions, and perform tests with an apparatus assembled as trial. The apparatus consists of two parts, a heat exchanger and an ice making part, to get high thermal efficiency. The tests yield the following results: 1) The production rate of ice is estimated to be 2---19 kg-h-' from the heat intake ability of the ice maker, which was obtained by the tests carried out at refrigerant (25 wt% calcium chloride) tempera-tures of -4.4- -14.5°C at the inlet of the ice maker and at refrigerant flow rates of 1. 0- 5.6 1-min-'. 2) The production rate of ice is 3.5-6.8 kg-h-' in the proof tests, which were carried out at outdoor temperatures of - 5 - -10°C (refrigerant temperatures of 3-8°C at the inlet of the ice maker) and refrigerant flow rates of 1.3-5.2 1-min-1.