Stainless steel is pickled in pickling bath with the sulfuric acid and a mixture of hydrofluoric acid and nitric acid. Suitable equipment based on speedy and accurate chemical analysis for actual production lines has not been developed yet.
The concentration of sulfuric acid can be analyzed by using the neutralization titration method. As a method of analyzing hydrofluoric acid in the mixed acid, the iron-acetylacetone complex discoloration absorbance method was adopted. For the concentration, of nitric acid, the method of subtracting the concentration of hydrofluoric acid from the total mixed acid amounts obtained by neutralization titration is adopted. Furthermore, the iron-salicylic acid complex absorbance method is adopted as a method of analyzing the iron content.
By adopting these methods, the fully automated analyzer is developed. Completing analysis work can be shortened to 40 minutes by automated sampling from the acid pipes. The fully automated acid supply and exhaust system is equipped to enable suitable pickling conditions from these results.

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In order to improve the tribological properties of magnetic tape with Co-γ-Fe₂O₃ fine particles against a magnetic head, the silica coating onto the surface of Co-γ-Fe₂O₃ particles in aqueous slurry is investigated experimentally, and the kinetic friction coefficient of magnetic tapes prepared using the coated particles is measured. By this silica coating, the amount of myristic acid absorbed on the Co-γ -Fe₂O₃ particles tends to decrease and the kinetic friction coefficient of the magnetic tapes can be reduced from 0.4 to 0.2 because of the increase of the effective amount of myristic acid working as the lubricant when the magnetic tape is moving. Since the magnetic properties and the dispersibility of Co -γ-Fe₂O₃ pigment in the magnetic lacquer are not degraded by the silica coating, this coating method is expected to result in magnetic recording media with both good magnetic and low friction properties.

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The vortex depth in an agitated vessel with paddle impeller is measured under various impeller dimensions and various baffle conditions. The vortex depth in a non-baffled vessel is correlated well by using the Froude number and the parameter n_p^0.7 (b/H) which is defined for the power correlation by Kamei et al. The difference of the vortex depth in a baffled vessel from that in a non-baffled vessel is also correlated by using the baffle condition parameter n_b^0.8 (B_w/D). The radius at the intersection of liquid free surface and static level is only affected by the ratio of the paddle impeller diameter to the vessel diameter. A new estimation method of the radius of cylindrically rotating zone from the vortex depth and the intersection radius was proposed. The radius of cylindrically rotating zone decreases with increasing baffle condition parameter (h_B/H) n_b^0.8 (B_wD) and vanishes where the baffled condition parameter is 0.24. This condition is independent of the impeller dimensions, and is weaker than the full baffle condition.

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We have developed an energy conserving regenerative rotary combustion system (RRX burner) which is combined with a regenerative type air pre-heater and can be operated continuously.
In our first report, we discussed “Heat transfer characteristics of the RRX burner” (Kagaku Kogaku Ronbunshu, 1996) and the second report discussed on “Combustion characteristics of the RRX burner” (Kagaku Kogaku Ronbunshu, 1997).
We discuss the technology of low NO_x emission when the rotary air nozzle exit areas are changed to 88°, 35° and 15°. The results show that the narrower the air exit angle combustion gets, the lower the NO_x emission. In the case of angle 15°, NO_x emission is less than 9 ppm.
We assume that the reaction speed is quite faster than the mixing speed between a fuel, air and flue gas in the furnace, and estimate a flame length and NO_x emission based on the velocity and concentration formulas of Beer and Chigier.
The estimation results coincide well with the experimental results, so it means that flue gas recirculation inside a furnace helps to attain low NO_x.

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Inferential models of product quality are very important for chemical plant operation without an on-line sensor. In this case, it is necessary to develop inferential models using measurable process variables, e. g. temperature, pressure, and flow rate. we build an inferential model for estimating the quality of petroleum products, light gas oil 90% recovered temperature, and kerosene 95% recovered temperature by using a backpropagation neural network and apply it to quality control for a topping plant in this study. It is shown that quality control can be efficiently performed by use of a neural networks model.

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The flow of liquid in a rotating cylindrical container with a rotating disc at the liquid surface is investigated using a model of the melt flow in a Czochralski crucible. The tangential velocity of the liquid was measured by using a laser Doppler velocimeter, and the effects of rotational container Reynolds number, rotational disc Reynolds number, distance between bottom of the container and the disc, and radius ratio of the disc and the container on the velocity distribution were examined. The result indicates that the radial distributions of the time-smoothed tangential velocity are independent of the vertical position from the bottom of the container, which is known as the Taylor Proudman theorem, in the cases of the container rotating and the disc being stationary, the container stationary and the disc rotating, and the container and the disc counter-rotating with small angular velocity ratio. When the container and the disc counter-rotate with a large angular velocity ratio, the effect of the disc rotation on the flow becomes remarkable in the lower part of the container.

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The time for volatile combustion and char combustion of model wastes with various shapes, sizes, materials in a fluidized bed was investigated theoretically and experimentally. The mathematical models for volatile combustion with and without char layer formation were developed to determine the time for volatile combustion. The models were validated experimentally for model wastes with various shapes and sizes over the range of Carman's shape factor Φ_s0 of 0.30.9. The time for volatile combustion with char layer formation was also examined numerically by solving a moving boundary problem. The numerical results were in good agreement with the experimental results and the times estimated by the shrinking core heat transfer model assuming the quasi-steady heat transfer rate control. It was found that the shrinking core heat transfer model is valid to estimate the time for volatile combustion with char layer formation.

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We attempt to prepare activated carbons from bean-curd refuse by chemical activation with K₂CO₃. Activated carbon with high specific surface area of 2, 656 m²/g can be prepared at a carbonization temperature of 800°C.
During an impregnation, the K₂CO₃ added reacts with bean-curd refuse and changs to KO₂ and K₂C₂O₄. Then, the bean-curd refuse is modified and the water-soluble organic components in the beancurd refuse increase. At a carbonization temperature below 500°C, the carbonization behavior of beancurd refuse is changed by the modification, and then the specific surface area of the carbonized beancurd refuse becomes larger. At temperatures above 700°C, K₂CO₃ is reduced to metal potassium. The carbon is consumed by reduction of K₂CO₃.

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In the study of modeling and control of continuous DTB crystallizers, it has been common practice to assume complete dissolution of fine crystals in an external heater (fines dissolver). However, complete dissolution of fine crystals is not always guaranteed because the dissolution rate is finite. In this work, a model of an external heater is developed by taking account of the finite dissolution rate of the crystals. The model is used to study the influence of incomplete dissolution of fine crystals on the stabilizing control of the crystal size distribution (CSD). It is found to be difficult to suppress the sustained oscillation of CSD by using the conventional SISO controllers, which regulate the amount of fines crystals by manipulating the fines flow rate. This is because when the fines flow rate is very large, an increase in the fines flow rate can reduce the amount of crystal dissolution in the external heater. It is demonstrated that instability can be avoided by imposing an upper limit on the fines flow rate. Furthermore, it is shown that the upper limit can be predicted by using the results of open-loop simulation.

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Numerical simulation and experimental studies are conducted on the dynamic characteristics of powder flow rate and particle size distribution in a closed-circuit pulverization system.
The performances of pulverizer and classifier are modeled by use of experimental data. The returning powder flow rate is taken into consideration, and material balance equations of eachsize range are numerically solved by an iterative method.
It is confirmed by simulation that product and returning powder flow rate, and product mass median particle diameter increase with time and they finally reach constant values.
The process stabilization time depends mainly on the converged value of returning powder flow rate under different operating conditions of pulverizer and classifier. Experimental data about dynamic characteristics agree with the simulational results, and the reliability of the present simulational method is confirmed.

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Noting the importance of flexible optimization for methods managing conflicts resolution of complicated and manifold problems, in this paper, we study mixed-integer programming problems (MIP) under multi-objectives. As known from the term NIMBY (Not In My Back Yard), site location problems of hazardous wastes are eligible case studies in such a situation, that is to say, associated with human, environmental and economic concerns. Showing that general formulation of such site location problems refers to MIP under multi-objective, we preliminarily discuss how to apply a genetic algorithm (GA) as a practical and effective solution method for MIP. Then we have proposed a hierarchical approach named hybrid genetic algorithm (HybGA) which is characterized by the combined use of genetic algorithm with appropriate mathematical programming. Mentioning about some promising features of the idea, we extend it to solve multi-objective mixed-integer programs, and reveal the superiority of HybGA over the conventional multiobjective methods of GA. Finally by taking a site location problem of hazardous waste disposal, we have examined numerically the effectiveness of the proposed approach through comparison both with MOGA and branch and bound methods.

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We have investigated the thermochemical conversion of spent grain into fuels. Spent grain with a high moisture content (77 wt % before dehydration or 67 wt % after dehydration) was reacted at a high temperature of 200°C to 350°C, and a high pressure of 7 MPa to 18 MPa through the use of nickel catalyst or alkali catalyst. When nickel catalyst was used, gaseous fuel consisting of CH₄, H₂, and CO₂ was primarily obtained. When alkali catalyst was used, the main product was a tar-like residue having a net calorific value of approximately 30 MJ/kg. However, its nitrogen content and viscosity were too high for it to be used as an alternative fuel to heavy oil. The economic evaluation of the system using thermochemical conversion suggests that the most promising method is gasification of the spent grain using nickel catalyst, with no dehydration process.

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As an approach to waste treatment and energy utilization, refuse derived fuels (RDF) have been developed as an alternative fuel for power generation. Combustion tests of RDF conducted in fluidized bed combustors and stokers have shown significantly different combustion characteristics and air pollution emission levels. To explain the differences from the view point of reaction mechanism of RDF, the combustion characteristics of a single RDF pellet (20 mm in diameter and 40 mm in length) made from municipal solid waste are investigated in an electric heating reactor (53 mm in inner diameter and 1, 000 mm in length). The weight loss and the temperature profiles of the RDF pellet were measured under two groups of heating conditions : constant heating rate condition and instantaneous heating condition.
It is found that the combustion of RDF progressed in two stages. In the first stage, volatile matters are decomposed and then burnt in gas phase, and the weight loss rate of RDF significantly depends on the heating rate. The temperature difference between the surface and the inner RDF is small and thermal decomposition is the dominant process under smaller heating rate. However, considerable temperature difference between the surface and the inner is observed, and the heat transfer in RDF is the dominant process under the instantaneous heating condition. The ignition temperature of the RDF used in this work is around 480°C. In the second stage, fixed carbon is burnt in the solid phase, and the weight loss rate and the temperature profile in RDF are strongly affected by oxygen concentrations in the ambient gas. At higher oxygen concentrations, the heat of combustion is accumulated in RDF so that a high temperature peak is observed.

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This study conducts numerical analyses and experiments on natural convection heat transfer in an eccentric horizontal annuli between a heated outer tube and a cooled inner tube with different orientation. The outer tube is an elliptical tube, and the inner tube is a cylindrical tube. Experiments are conducted with the outer tube oriented to the vertical side, and horizontal side, respectively. The numerical analyses were performed by changing the oriented angle and eccentricity parameters. Results obtained for different conditions are presented as temperature profiles, flow patterns, local Nusselt number, and total heat transfer. It is found that the heat transfer enhancement effect or heat transfer obstruction effect for the total heat transfer is changed by eccentricity and oriented angle.

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Quantitative evaluation of the composite particle layer formed with a high-speed elliptical-rotor-type mixer and the state of the composite layer are examined. Hematite particles having a median diameter of 0.48 μm were composed on the surface of glass beads having a median diameter of 107 rim. The quantity of adhesion of hematite particles was measured by ICP emission spectroscopy and the influence of operation condition of the mixer is elusidated. The state of composite particle layer was characterized by the luminosity measurement of the composite particle surface using an optical sensor.
It is found that the amount of adhesion of fine hematite particles increases with composing, however the luminosity of composite particles attains an equilibrium state. Namely, the luminosity equilibrium of the composite particles implies that the surface of the core particles is uniformly covered by hematite. The optical measurement of the composite particles is effective to characterize the composite particle layer on the core particles. A particle composing process with a high-speed elliptical-rotor-type mixer is described as the following two processes : The first is the formation process of the coating layer by collision of hematite particles, and the second is the growth process of the composite particle layer. The increment of adhered particles on the core particles is described by cumulative shearing energy subjected to the composite particles. The process with the high-speed elliptical-rotor-type mixer is the same as the composing by high shear stress.

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Flow in an agitated vessel with a paddle impeller is described with the stream functions which satisfy the boundary conditions in order to understand the nature of the large scale and low frequency fluctuations of the flow. Differential equations for the stream functions are derived from the Navier-Stokes equations, which are solved numerically with a periodically changed external stream function. Non-periodic and long time fluctuations of the velocity field and the quantity related to the torque (equivalent torque) are found by frequency analysis of the time series of the velocities and the equivalent torque, the frequencies of which are clearly different from the frequency of the external input (about twentieth as low as the input frequency). The peak positions of the power spectra agree excellently with some reports of experimental analysis concerning the turbulent-flow in an agitated vessel, which shows that the results obtained by this numerical analysis are valid.

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Pressure drop and heat transfer of solid-liquid two-phase flow in which the ratio of diameter of solid particles to that of pipe is large are investigated experimentally. The solid particles used were disc plates. Measurements are made on the velocity of the solid particles, friction factor of the solid-liquid flow, and heat transfer coefficient on the pipe wall. The experimental result indicates that the ratio of mean velocity of the disc particles to that of solid-liquid flow increases with decreasing fraction of volumetric flow rate of the solid particles, and with increasing ratio of the diameter of the particles to that of the pipe. The friction factor and the heat transfer coefficient increase with increasing fraction of the volumetric flow rate of solid particles. The friction factor decreases, but the heat transfer coefficient increases with increasing ratio of diameter of particles to that of the pipe.

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A single β″-alumina tube AMTEC cell in which sodium working fluid is returned by a wick structure is designed, built and tested. The sodium which condenses in the low temperature condenser is transported to the high temperature evaporator through the wick, which generates the capillary force against the sodium vapor pressure using the fine porous structure of stainless-steel powder.
Current-voltage characteristics were measured at an operating temperature of 923 K. The cell with TiN electrode achieves a specific power output of 0.13 W/cm² initially. An electrochemical model is introduced to predict the cell performance and the calculated total resistance of the cell is 25% smaller than the measured one. The anode side current collecting resistance appears to increase the internal total resistance. Time dependent power output is also measured. Following an initial 15-30% decrease, the cell continues to generate power output in excess of 0.1 W/cm² for a period of 100 hours. The result indicates that the designed wick can return liquid sodium against the pressure difference between the low pressure condenser and the high pressure evaporator in the cell.

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It is very important to understand the curing kinetics of moisture curable one part sealants in order to design and handle them. The curing kinetics of the representative sealants are measured and their kinetic models are studied. If the quasi-steady-state is assumed, the cured time represents the quadratic equation of cured depth. Their parameters are determined, and depend upon the physical properties of the materials and their curing mechanism. The experimental cure speed agrees well with the calculated model. If the permiability of moisture through the cured film is faster, the cure speed of the sealant becomes faster. This correlation is certified by experiments and the presented kinetic model. A sealant whose cure speed is very slow in the range of low humidity, however, depends not on the permiability of moisture but on the reaction mechanism. The presented model has to be mended when the reverse reaction is taken into account on or in the region of the small cured depth where quadi-steady-state is not right.

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The conditions for production of nitrous oxide from the process of denitrification are studied by using activated sludge precultured with batch system. The activated sludge was obtained in the subsequent operations. The production of nitrous oxide was not observed in case of the sludge precultured with carbon rich substrate in spite of the change of pH and/or load of organic carbon. On the other hand, in the case of sludge precultured with TOC of less than 0.028 kg/kg-MLSS·d, nitrous oxide was produced when of pH was less than 7.0. The phenomena are recognized regardless of load of organic carbon.

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A new technique has been developed for preparing high porousity ceramics. Spray freeze drying of magnesium sulfate aqueous solution produced porous fine salt particles, which were calcined to porous particles of magnesium oxide. The oxide particles were treated to form magnesia ceramics that showed high porosity in a range of 0.50.85.
The following equation which can assess ceramics strength for high porosity is proposed.σ=σ_o (1-αε) ^m
where σ [Nm^-2] strength, ε [-] porosity and σ_o, α, m constants. The validity of the equation is confirmed by the present investigation data and also the ones published.

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