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廃棄物の溶融処理過程における低沸点重金属類の挙動を熱力学モデルに基づくシミュレーションにより解析し, その妥当性をコークスベッド式焼却残さ溶融炉の実証試験結果と比較し, 検討した。その結果, 溶融処理過程における低沸点重金属類の挙動に与える因子としては溶融温度, 酸素分圧等の溶融処理条件の影響が大きいことが明らかとなった。特に溶融スラグの有効利用に際して環境安全性の観点から問題となるPbの挙動については以下の知見を得た。熱力学モデルシミュレーションでは溶融処理条件として, 高温で酸素分圧が低い (強還元) 雰囲気ほどPbの揮発が促進され, 溶融スラグ中のPbの含有量が抑制されることが明らかとなった。またコークスベッド式溶融炉の実証試験ではPbの大半がガス側へ揮発し, 溶融スラグ中のPb含有量は60-70mg/kgと低いことが確認されたが, この値はシミュレーション結果によく一致した。

The simulation system for the waste melting process (SWMP) has been developed through the combination of the multi-phase equilibrium calculation method and the thermodynamic database. The SWMP can be used to simulate reactions in waste melting processes with respect to equilibrium between various phases, identify the problems experienced by the process, and help develop strategies for process optimization. Examples of the application of the SWMP to two different types of waste melting processes are presented.

Solubility of Nb2O5 and leaching behaviors of Nb and Ta from niobite in KOH solution have been investigated in order to develop an alkali hydrothermal leaching process of Nb and Ta. The solubility of Nb2O5 was measured in the range of 40 °C to 200 °C at various molar ratios of K2O to Nb2O5(n(K2O)/n(Nb2O5)). It has been found that Nb2O5 shows the maximum solubility at the solution composition of n(K2O)/n(Nb2O5)=4/3 at a given temperature; the rise of temperature increases the solubility of Nb2O5 below 120 °C, but decreases it above 120 °C. The leaching behaviors of Nb and Ta were studied in the range of 150 °C to 250 °C and 0.1 MPa to 5 MPa. With the rise of temperature, the leaching degree increases when the leaching temperature is below 200 °C, but it decreases when the leaching temperature is above 200 °C. The maximum leaching degree is about 90% at 200 °C. It was proved that the alkali hydrothermal leaching process is effective for the recovery of Nb and Ta from niobite concentrate.

Removal of cadmium and zinc ions from diluted solutions of their sulfate solutions with manganese dioxide, produced by ozone oxidation-precipitation reaction (OMD) under different conditions, has been investigated paying particular attention to correlation between the ion-uptake and the water content of OMD. Uptake of Cd2+ which is demonstrated to be an ion exchange reaction increases with an increase in the water content of OMD. The adsorbed water, which is liberated at lower temperature up to 200 °C, as well as the structural water of MnO2 takes part in the ion exchange reaction. One of the most outstanding features of OMD over both electrolytic MnO2 and chemically precipitated one is that OMD has a higher water content and shows fairly stronger ion exchanger nature than the other types of MnO2. For removal of Cd2+ with a reduced amount of Cd-contaminated MnO 2 residues, a two-stage treatment is considered to be effective. The first stage is addition of OMD in a small excess with respect to Cd2+ to uptake this ion at high efficiency and the second stage is addition of a small amount of OMD to make a high OMD / Cd2+ mole ratio to capture the remaining Cd2+ down to an adequately low concentration. Zinc ion was observed to be removed from its dilute solution by OMD addition in a similar manner to cadmium ion.

The recycling of waste plastics in the blast furnace has been in-vestigated with the test furnace and the commercial blast furnace. From the results of these experiments, it was found that the combustion and gasification behavior of waste plastics injected into the raceway of the blast furnace was much different from those of pulverized coal. Pulverized coal injected into raceway was consumed in the combustion zone of the raceway and converted into CO2 and H2O rapidly. On the other hand, waste plastics was mainly converted into CO and H2 by gasification with CO2 generated in the combustion zone of the raceway. Combustion and gasification efficiency of waste plas-tics was much higher than that of pulverized coal in spite of large particle. Waste plas-tics like -10mm particle can be effectively gasified due to the circulation effect of coarse particle in the raceway. Recycling effciency of waste plastics in the blast furnce was estimated to be 76%. It is considered that waste plastics injection into the blast furnace is a favorable way to realize material recycling of waste plastics and to solve environ-mental issue.

The growth ability of 12 species of phytoplankton was examined in culture media enriched with steel-making slag solution at various concentrations. Since a highly significant linear regression of the in vivo fluorescence (IVF) of cell suspension against absolute chlorophyll a concentration was established, the growth ability was determined quickly by IVF. Under the enriched conditions all the species examined showed positive growth, although in different manners. Based on the specific differences in the optimal concentration of the slag solution, 12 organisms could be divided into four groups: (I) the organisms which grow best under the highest enrichment (100%), (II) those which grow best with intermediate enrichment, but not in 100% enrichment, (114) those which grow best under enrichment lower than 60%, and (IV) those which respond inconsistently to enrichment but often grow better under enrichment. These results indicate that the slag solution has positive effects for the growth of phytoplankton, so that the slag will be utilized as nutrients in cultures for algae. On the other hand, the growth of all the four groups enhanced by the enrichment with the slag solution never exceeded the growth enhanced in an ideal culture medium, indicating that the enrichment with the slag solution can hardly be a cause of the red tide, if the enrichment is done in natural seawater.

An unsteady state boundary layer model was developed in order to analyse the combustion of single char particles in radiation fields. The model is based on the following assumptions, a spherical char particle with small diameter is combusted at atmospheric pressure, the temperature difference between the surface and the inside of the particle is negligible, particle diameter shrinks due to the reaction on the char surface, the surrounding gas is stagnant, but Stefan flow is taken into consideration and bulk gas flow is neglected. The model predicts the particle temperature increase and the distributions of gas temperature and gas components in the boundary layer. The computed distribution of gas component proves clearly that the reaction rate is mainly controlled by oxygen diffusion in the boundary layer except during the initial heating and reaction. Using the simulation model, the effects of particle size, oxygen content in bulk gas and input laser power is discussed. The results predict that smaller particles heat up faster in initial heating and higher laser input has the same effect. Further, it is shown that a higher oxygen content raises the sustained combustion temperature and shortens the combustion period.

Recovery of Samarium and Neodymium from rare earth magnet scraps which contain-30% of Sm or Nd and 50-60% of Co or Fe was examined by the fractional crystallization of their sulfates. The results are summarized as follows: 1) When H2SO4was added into the nitric acid solution containing Sm and Co, the solubility of Sm decreased and Sm sulfate hydrate preferentially crystallized. 2) Samarium sulfate hydrate of 96.5% purity with recovery rate 87.1% was obtained from Sm Co5magnet scrap by the fractional crystallization. Effective results were also obtained when Sm2 (Co, Fe, Cu, Zr) 17 was examined similarly. 3) The addition of ethanol into the sulfuric acid-nitric acid solution containing Nd and Fe was proved to be effective for the decrease of solubility and fractional crystallization of Nd. 4) Neodymium sulfate hydrate of 96.8% purity with recovery rate 97.1% was obtained from Nd-Fe-B magnet scrap by the fractional crystallization of metal sulfates with addition of ethanol as well as H2S04.

The temperature change in coal and graphite during heating and combustion by a CO2 laser heat source was measured using the multi-two-colour method. Laser intensity ranging up to 3.0 W mm−2 at 10.6 μm wavelength was used. The behaviour of heating particles was observed with a stereomicroscope. Graphite particles and several types of coal were used to cover the range of volatile matter from 0 to 43.3 wt%. Experiments were performed to study the influence of volatile matter, particle diameter, oxygen content in the atmosphere and laser intensity on each type of carbon particle. Volatile matter affected the initial heating stage and the ignition stage. Particle diameter had no observable effect at any stage. Laser input intensity mainly affected the heating-up in the initial stage. An increase in oxygen content gave a high heating rate in the ignition stage and raised the temperature in sustained combustion.

The dissolution rate of metallic copper plate in aqueous cupric ammine solutions was studied at 0.05-1.0 mol//CuSO4 concentration, 0-3000 rpm rotation speed and temperatures between 10-90°C. The dissolution rate was mainly controlled by chemical reaction at the temperature below 30°C, and by diffusion of cupric complex at temperatures higher than 40°C. It was found that the dissolution rate of copper increases with an increase in temperature and rotation speed, while a maximum rate was observed for increasing Cu(II) concentration. The effect of different anion showed significant results on dissolution rate of copper and iron, and carbonate ion was found to prevent the corrosion of iron. The selective dissolution of copper from iron scrap was suggested.

A new method was developed to study the preliminary surface textural change of a single coal particle heated rapidly to 500 °C with well-characterized CO2 laser under nitrogen at atmospheric pressure. The SEM observable changes of surface texture were not observed up to 485 °C with heating rates above 6300 °C s-1, even with coking coal. However, the changes were observed at about 440 °C at heating rates of ≤1800 °C s-1 even with weak-coking coal. These results suggest that the effect of heating rate on softening and melting (plasticity) of the coal particles shows that there are limited and optimum ranges of heating rate for the increase of plasticity. In addition, at heating rates of 50−240 °C s-1 for two kinds of coal, the change of surface texture (initial structural relaxation) begins around 240−260 °C, the initial softening (first melting phase) begins around 290−310 °C, the second melting phase appears around 400−410 °C, and the uniformly melting temperature is around 420−440 °C. The heating rate (

A comparative examination of existing formalisms to predict thermodynamic properties of multicomponent solutions was accomplished. All methods are based on the assumptions of discrete additivity and regularity and can be classified on heuristic and scholastic ones. A new heuristic approach to select decomposition points on verges of concentration simplex was developed; the corresponding method was named the equidistant one. To verify an accuracy of various methods experimental and calculated values of Δ mix H in the Ge-Ga-In melt and Δ ex μ Zn in the Zn-Cd-In liquid solution were compared. The equidistant method has demonstrated its advantages.

A waste-free steelmaking process, in which slags are recycled inside the steelmaking process itself by using a so-called slag regenerator, has been proposed, and its possibility was investigated by means of computer simulations.There are two kinds of discharged slags from the proposed process. One from the desiliconization furnace and another from the final dephosphorization furnace. The former slag would have no problem to be returned to a blast furnace or to a sintering process due to its low phosphorus content, while the latter could be used as fertilizer materials for its high phosphorus content such as 10 mass%.In a case that the blast furnace hot metal was of a composition of 5.04%C-0.12%P-0.50%Si-0.30%Mn on mass% base and half of the regenerated slag was recycled to the desiliconization furnace, the [P] level in the steel could be as low as 0.0087 and the total lime consumption for the whole process was approximately 20 kg/t HM. This lime consumption was about 1/2 of that in some conventional converter refining processes.

Hexagonal boron nitride was synthesized from boron oxide using super critical ammonia and solid CaO below the melting point of B 2 O 3 by the following reaction: B 2 O 3 (s)+2NH 3 (super-critical fluid) + 3CaO (s)=2BN (s)+3Ca(OH) 2 (s). The experiment was carried out at 623-753 K and the initial ammonia pressure was 3.0-40.0 MPa. The mean diameter of obtained BN particles was 0.2-0.3 μm. The yield of BN increased with increasing temperature, initial ammonia pressure and the addition of CaO. The thermochemical calculation showed that the CaO addition suppressed the decomposition loss of ammonia during the reaction.

In the first part of the paper, various attempts on the development of new ironmaking processes in Japan are briefly reviewed.The decade of 80's is assumed to be the third period of the intensive R & D on new ironmaking and is featured by an anticipation of an appreciable structure change in crude iron supplying system. The blast furnace system itself is changing by introduction of extensive use of coal injection as a possible alternative of cokemaking on which blast furnace process is inevitably based.The differentiation of the functions of blast furnace and their proper recombination would be the second route of new ironmaking processes, which are called smelting reduction processes (SRP)In the second part, smelting reduction processes under development in the world are briefly reviewed.SC, Corex and XR are classified into the shaft type processes and Corex is the only SRP which has been developed to the commercial level. So called in-bath type SRP should be classified in two groups, iron bath and slag bath type.HIsmlt process has characteristics of iron bath type and DIOS and LPR have features of typical slag bath type process.

A computer program system was developed to simulate the smelting reduction ironmaking process. This system, combining the database MALT with the phase equilibrium calculation software ChemSage-derived from the widely well-known SOLGASMIX, can be expected to deal with problems encountered in metallurgical processes. As an example, the behaviors of some recycling elements, such as Na, K, Zn and S, in the smelting reduction process have been investigated from the thermodynamic point of view in case of the dust being recycled. The simulation results indicate that Zn is most influential on sulphur behavior among Zn, Na and K, and ZnS is the prevailing form of the deposited sulphur when there is zinc existing in the system. Zn can effectively prevent sulphur from entering the outlet gas. Alkaline components, especially potassium K, accumulate as carbonates in the system. At a high post combustion ratio of the gas generating from the smelting reduction furnace, or at a lower temperature of Cooler 1, FeS deposition takes place and results in an appreciable amount of sulphur leaving the system in the outlet gas.

The simulation analysis of material and heat flow in coal packed bed type smelting reduction process, such as COREX process, was conducted by use of the computer model developed based on the heat and material balance. The simulation was conducted by focusing on the amount of volatile material in coal used in the process and the operation condition of the fluidized bed melter gasifier where the reducing gas used in the reduction shaft is generated. The coal consumption decreases with decrease amount of the volatile material in coal. By increasing the oxidation degree of off-gas from the fluidized bed melter gasifier, the coal consumption decreases but the increasing amount is limited by the requirements of reduction shaft. The simulation results show that it is important for efficient process to control the volume and temperature of off-gas from the fluidized melter gasifier to be matched with the requirement of reduction shaft, which is necessary for reducing the amount of gas scrubbed and cooled as much as possible. It can be accomplished by using the low volatile coal and by increasing the oxidation degree of off-gas from the fluidized melter gasifier within the allowable range.

A computer program system was developed to simulate the smelting reduction ironmaking process. In this study, the effects of zinc, temperature, and post combustion ratio of the gas generated from the smelting reduction furnace on the behaviour of sulphur in the iron bath smelting reduction process were investigated from the thermodynamic point of view. The simulated results indicated that even a very small amount of zinc could introduce sulphur into the dust in the form of ZnS, which would effectively prevent the sulphur from entering the outlet gas. Moreover the deposited ZnO would accumulate continuously in the system in case of all dust being recycled

For the purpose of developing an alkali leaching-solvent extraction directly from alkali solution process, the extraction of niobium from alkali solution by long-chain alkyl quternary ammonium salt (methyltrioctylammonium chloride R4NCl) in toluene was investigated. The experiments were carried out under conditions of 25 °C, Nb(V) concentration 0.01 mol/L, pH 10.7–13.8, R4NCI concentration 0.02–0.14 mol/L. It has been found that the distribution ratio of niobium increases with increasing R4NCl concentration and with decreasing KCl concentration, but it shows maximum value at pH value of about 12 and decreases below or above this pH value. Distribution ratio of niobium goes up to over 1 000 in appropriate conditions, and so it has been proved that R4NCl is an effective extractant for extraction of niobium from alkali solution.

The flow properties and mixing characteristics of a submerged gas jet near the injection point were measured using an isokinetic sampling probe in a water model. The radial and axial profiles of gas velocity, water velocity, and void fraction were measured. Since the gas velocity was always larger than that of the water, the existence of a slip velocity between gas and water was confirmed. A one-dimensional mathematical model was developed using the dimensionless slip velocity as a parameter. The dimensionless slip velocity (S) was estimated to be 0.3 to 0.6 for the nitrogen-water system. TheS of the He-water system was slightly larger than that of the nitrogen-water system. When the model was applied to calculate the gas fraction in the jet for the nitrogen-mercury system,S was estimated to be 0.95 to 0.97. A large slip velocity between gas and liquid is expected for gas-metal systems.

An application of the alkaline hydrothermal process to the extraction of rare earth elements from complex ores was studied. A typical rare earth ore, bastnaesite, was reacted with NaOH solution under a high temperature and pressure to produce a mixture of rare earth hydroxides. The recovery of rare earth elements was measured as a function of temperature (373-723K) and NaOH concentration (1-5 mol/l). The results obtained were as follows;1. The optimum conditions for this process were 523-573K and 4-5 mol/l NaOH.2. Fluorine and silica in the are where extracted into the alkaline solution.3. The recovery of rare earth was decreased when the temperature exceeded 573K, which was assumed to be caused by the formation of cerium and praseodymium oxides.

Iron is no doubt the most fundamental element to materialize the human society. Present production of iron and steel is about 800 million t in the world and about 100 million t, including 7 million t of cast iron, in Japan. Regarding to recycling, 30% of crude steel is produced utilizing scrap as a secondary sourse of iron. Since the accumulation of the steel in Japan is becoming 1 billion t, the amount of scrap iron will become much larger in the future. Thus, effective smelting and steel making technologies with converter or energy saving electric furnace should be applied to the scrap. On the other hand, the quality of scrap in terms of chemical composition is becoming poorer as the products being needed light and small-sized and having lots of value added. Then the application of precise physical separation becomes important, as well as the development of technological and political system from the view point of the facility of recycling.

In the development of a continuous decomposition process of rare earth ores, the decompositionrate of bastonaesite by the alkaline hydro-thermal reaction was measured at 373-723K. The reaction was described by the dissolving core model. The apparent reaction rate constant, k', was proportional to the 3.9 power of NaOH concentration, which is given by the following equation.k'=2.79×107·exp(-1.41×104/T)·C3.9NaOH

The penetrating behavior of a single particle impinged on liquid surface has been studied with cold model experiments.The velocity of a polystyrene particle at impact on distilled water or glycerin liquid was obtained by detectors consisted of laser diode photo sensors. The behavior of the particle, entrained gas bubbles and liquid flow were observed by using a high speed video and camera and analyzed by a mathematical model.At impact of the particle on liquid surface, a cavity was formed and gas was entrained as a columnar bubble, when the particle impact velocity (Vpo) exceeded a critical velocity.Although the penetrating length of the particle (Lp) increased with increasing Vpo, the rate of increase of Lp gradually decreases with increasing Vpo.A mathematical model was developed to predict how the initial kinetic energy of the particle was distributed and consumed by several energy dissipation mechanisms.It was inferred that most of the kinetic energy was consumed as dissipation works, mainly spitting and heat generation in a higher region of Vpo and hence the attainment of a higher particle velocity could not be an effective means to increase penetration length into the liquid. The effect of reduction of the apparent liquid density by increasing gas holdup in the liquid with entrained gas or gas jet was discussed as an effective way to obtain deep penetration of powders into the liquid.

This study describes the temperature determination method with sufficient accuracy even in the case that the emissivity of surface is significantiy dependent on the wavelength.