Metal powder is one of the specific materials in the metal utilization.
Powder metalluegy is wellknown since early times in the field of metallurgical processes. The particle size of the metal powder is approximately 0.1 mm.
Recently, ultra fine powder and submicron powder have been used in various industries. Precious metal powders play an important role as electric conductive materials in the electronic industry. It is desirable for metal particles to be submicron in size and spherical in shape.
This paper is a review of studies on the production of metal powder by the reduction of an aqueous solution with emphasis on hydrogen as the reductant.
The production methods discussed include reductions by other gas (SO₂) and reducible solutions as well as a disproportionation reaction that do not require a reduction agent. This review forcuses on the formation of submicron spherical particles. The formation of crystalic particles and thin film particles as well as the reduction mechanisms based on kinetic considerations are also discussed.
It can be expected that hydrogen is a clean reducing agent which does not remain in the produced powder. In relation to use of hydrogen, the future of hydrogen as secondary energy was also discussed. Technical development of the use of hydrogen will be promote the realization of idea of [Hydrogen Economy]. And the technique using hydrogen will be placed under an obligation of [Hydrogen Economy].

抄録全体を表示

It was considered that land deformation influenced on the wind shift around the development area. Statistical study was conducted on the influence of topography upon the wind directions and the wind velocity at the 60 meteorological stations (AMeDAS weather stations) in the northern Tohoku district. It was recognized that the wind were affected by the surrounding topography. It was obtained the quantitative equation (1) between the frequencies of the wind directions (F) and the deviations of inclination of the same directions (K).
F_sp = -22.8 K + 5.44 (in spring) ········· (1)
Equation (2) shows the relationship between the mean wind velocity and the variables K.
V_sp = -3.11 K + 1.98 (in spring) ········· (2)
It became possible to predict the change of the wind system around development area by the use of these equation. The case study was carried out at the quarry. As a result, it was predicted that the wind system around the quarry would change.
It was considered that cutting down trees had influence on wind velocity around the development area. Wind velocity around the development area was predicted by using effect on the windbreak forest. It was predicted that there were points where wind velocity became slow by cutting down trees at the leeward side after the development. There were points where the wind velocity fast because the effect of protection against wind was lower due to the fall of leaves.

抄録全体を表示

This paper describes quantitative evaluation of pyrite leaching with Leptospirillum ferrooxidans, an iron-oxidizing chemoautotroph without sulfur-oxidizing ability.
Leaching experiments were carried out in shaking flasks. Massive pyrite was ground and sieved to obtain the size fraction between 20 and 37 micro meters. A pure culture of L. ferrooxidans (ATCC29047) and an enrichment culture of Thiobacillus ferrooxidans were used for inoculum. Several sets of flasks containing inorganic nutrient medium, 1 % of the pyrite and the inoculum were prepared for each experiment. Every two days, one flask of the series was removed from the shaker for analysis. In the case of L. ferrooxidans, the bacterium grew in this condition and solubilized pyrite. Over 90 % of iron were dissolved from pyrite within 400 hours. With the progress of iron extraction, notable amount of sulfur particles was observed in SEM photomicrograph. Those particles attached to residual pyrite, but did not prevent pyrite dissolution. The major products of sulfur species in the pyrite degradation with L. ferrooxidans were elemental sulfur and sulfuric acid. Total amount of these two products corresponded with the amount of degraded sulfur calculated from dissolved iron in every sampling point. The molar fraction of elemental sulfur in total degraded sulfur was approximately 1 / 4 throughout the experiment. In contrast, the major product of sulfur species was sulfuric acid, and no elemental sulfur was detectable in the case of pyrite leaching by T. ferrooxidans.

抄録全体を表示

Supercritical water oxidation (SCWO) is an attractive alternative mean for treatment of organic wastes of high water contents. However, for most of organic compounds, acetic acid is a stable intermediate product, and a high reaction temperature or catalyst is required for its complete decomposition.
In this study, a new method of utilization, rather than decomposition, of residual acetic acid produced by supercritical water oxidation of beef suet was investigated. That is, the residual acetic acid was converted into (CH₃COO)₂Ca, which can be used as a deicer to reduce environmental pollution problems caused by the road deicing salts (NaCl and CaCl₂) presently available.
Results showed that acetic acid of high concentration (6,000 mg / l) and relatively high purity was obtained under the condition of 400 °C of reaction temperature, 30 seconds of reaction time and 150 % of H₂O₂ supply, and 97 % of residual acetic acid was covered to (CH₃COO) ₂Ca by adding Ca(OH)₂ or CaCO₃ in the both cases of its addition before and after the oxidation reaction. However, in the former case, when excess Ca(OH)₂ or CaCO ₃ was added, some products by thermal decomposition and hydrolysis appeared, and production of acetic acid decreased.

抄録全体を表示

In order to utilize the residual acetic acid formed by SCWO of vegetables, the optimum reaction condition and conversion efficiency of residual acetic acid to (CH₃COO) ₂Ca were investigated. (CH₃COO)₂ Ca can be used as a deicer better than the traditional ones such as NaCl and CaCl₂ from the viewpoint of environmental protection as well as anti-corrosion.
Results showed that acetic acid of high concentration was obtained under the condition of insufficient oxygen supply. And acetic acid obtained under the condition of temperature of 400 °C, 90 s of reaction time and 50 % of H₂O₂ supply has not only the high concentration but also has the fairly high purity. By direct addition of CaCO₃ or Ca(OH)₂ into the solution after the reaction under this condition, residual acetic acid can be almost completely recovered as (CH₃COO)₂Ca. But crystallization of (CH₃COO)₂Ca does not occur when the concentration of residual intermediate products such as 2-propanone, 1-hydroxy is high.
The complete removal of residual organic materials in waste water by SCWO of garbage can be done by complete oxidation of garbage into acetic acid and its conversion into (CH₃COO)₂Ca.

抄録全体を表示

The synthesis of zeolite from coal fly ash by alkali hydrothemal reaction with NaOH was investigated under various conditions and the physical properties of the products were measured in this study. The reaction rate of cation exchange and substitution ratio of calcium ion were examined with some solutions containing calcium ion. Also, some physical properties of calcium type zeolite were measured.
Zeolite P which had large cation exchange capacity (about 500 meq / 100 g as CEC) was synthesized from coal fly ash under the particular synthesis condition; reaction temperature of 393 K, reaction time of 5 hrs, NaOH concentration of 1.5 mol / dm³ and solid-liquid ratio of 200 g / 800 cm³. The crystal type of synthesized zeolite changed from zeolite P to hydroxysodalite with an increase in concentration of NaOH. The reaction rate was obviously increased when the reaction temperature was over boiling point of water. It was confirmed that the cation exchange reaction of zeolite synthesized in this study could be almost reversible between calcium ion and sodium ion. Optimum condition for zeolite synthesis with high CEC and calcium substitution, and some factors affecting zeolite synthesis and cation exchange reaction were discussed.

抄録全体を表示

The incorporation of coexisting metal ion in the precipitates produced by ozone oxidation-precipitation in acidified MnSO₄ solutions with an added sulfate was investigated for 15 elements (18 ionic species) by chemical analysis, X-ray diffraction and discharge curve measurement of the precipitates.The precipitates were formed in the stream of O₃ - O₂ gas mixture with ozone partial pressure of 2.7 × 10 ^{- 3} atm at 70°C in the solutions of 1.0 M sulfuric acid, 0.1 M MnSO₄ and other metal sulfate. A little incorporation in the γ -MnO₂ based precipitate was detected for alkali metal ions, Mg, Cu, Co and Ni ions. Both Fe (II) and Fe (III) ions were captured in the precipitate and affected significantly the discharge curve of the precipitate. The precipitates formed in the presence of Ti, V or As showed a fairly high content of the coexisting element, X-ray diffraction peaks remarkably differing from those for γ -MnO₂ and poor discharge behavior. These suggest possibility for Ti, V or As to be precipitated as some compounds with Mn rather than to be incorporated into the MnO₂-based precipitate.

抄録全体を表示

Extraction of platinum (IV) from hydrochloric acid solutions by using dihexylsulfide (DHS) containing micro amount of trioctylmethylammonium chloride (TOMAC) was investigated under irradiation of light. Although the complex of Pt (IV) with DHS is not formed by the extraction, on this extraction system, Pt (IV) was extracted quantitatively by DHS because (TOMA)₂PtCl₆ complex activated by irradiation of ultraviolet rays acts as catalyst. The stoichiometric composition of the DHS complex formed in the organic phase was deduced to be PtCl₄DHS. Therefore, the following equilibrium equations are proposed:
PtCl₆^{2 -}_(aq) + 2TOMAC _(org) ⇔ (TOMA)₂PtCl_6(org) + 2Cl^- _(aq)
(TOMA)₂PtCl_6(org)→^hv(TOMA) ₂PtCl₆^*_(org) (activated complex)
(TOMA)₂PtCl₆^*_(org) + 2DHS_(org) ⇔ PtCl₄ · 2DHS_(org) + 2TOMAC_(org) .
In the equilibrium reactions, it was found that Pt (IV) in the complex is not reduced to Pt (II). The examination of diluent effects proved that aromatic diluents with electron-donating groups, such as m-xylene and toluene, promote the activation of TOMAC-Pt (IV) complex, whereas aromatic diluents with electron-accepting groups, such as chlorobenzene and nitrobenzene, and aliphatic diluents, such as hexane and dodecane, suppress that activation. Furthermore, it was found that from the examination of effects of high molecular-weight amine, the catalytic effect of amine-Pt (IV) complexes depends on their activated degree by irradiation of ultraviolet rays, which is promoted by electron-donating groups of amines, and ability of replacement between the chlorine atoms coordinated to Pt (IV) in the activated complex and DHS, which is affected by steric hindrance of amines.

抄録全体を表示

The electrokinetic characteristics were investigated in the solutions containing a supporting electrolyte for magnetite particles produced at ambient temperature and those of magnetite of commercial chemical reagent. For this purpose, the variation in the zeta (ζ)-potential with pH and the corresponding isoelectric point (i.e.p.) were determined for magnetite particles suspended in diluted solution of a supporting electrolyte, KNO₃, K₂SO₄, Ca(NO₃)₂ or Al(NO₃)₃. The ζ-potential in KNO₃ solution for the fine particles of magnetite produced at ambient temperature showed values similar to those of magnetite of chemical grade and for the both magnetite the isoelectric point was 6.5. In the presence of K₂SO₄, a shift of the i.e.p. toward pH 4 was attributed to the specific adsorption of SO₄^2- . In an Al(NO₃)₃ solution, the i.e.p. of 9.35 is considered to be brought by presence of Al(OH)₂⁺. Furthermore, in a solution containing calcium ion, the i.e.p. appeared in acidic environment probably due to non-equivalent exchange of proton on the particle surface with calcium ion in the solution. In all the cases under the conditions of this work the fine particles of magnetite prepared by ambient-temperature synthesis yields the almost same electrokinetic behavior as the chemical-grade magnetite which was treated at an elevated temperature.

抄録全体を表示

This report reviews recent production technologies for the extra heavy oil reserves such as Athabasca oil sands. The extra heavy oils (bitumen) in Canada and Venezuela represent a huge amount of recovery oil resources, about 300 billion barrels respectively. Recently, economical and technical conditions for operation and production of heavy oils have been turned for the better. More and more new projects for in situ production have been planed and some of them are on going using advanced well architecture such as horizontal wells technology and improved recovery methods. It is predicted that the amount of bitumen and synthetic oil productions will be quickly increased until 2005. For last ten years, the steam assisted gravity drainage (SAGD) method have been developed as an improved in situ production method at Alberta, Canada. It provides economic means to produce a part of the huge reserves of Athabasca oil sands. This report also focuses on the recent SAGD projects including the Japan Canada Oil Sands (JACOS) Project and introduces author's experimental studies.

抄録全体を表示

As for the development of methane hydrate that exists under bottom of the sea, the safety measures are most important. The methane hydrate development system using artificial block and prop system was proposed to prevent the landslide and the sudden fall. Artificial block system is a method of improving strength of the sediment by injecting carbon dioxide into the sediment.
It was assumed to form carbon dioxide hydrate in the bottom of the sea stratum to achieve this purpose, and so we examined the properties of formation / dissociation, and the influence of the particle. The results obtained are as follows;
(1) The formation condition approaches the estimated equilibrium value by mixing the particle, and the level of the shift depends on the correlation of the heat conductivity of the particle and water. It can be suggested that carbon dioxide hydrate be formed easily at the case without the stratum particle when the carbon dioxide bubble rises as a result within the space of the particle in the sediment. It is considered that the dissociation condition of carbon dioxide hydrate almost agrees to the estimated equilibrium value in any case, and is not influenced by the presence of the stratum particle.
(2) It has been understood that the supercooling phenomenon be comes smaller with increasing the particle diameter, and that the particle diameter has close relation to the formation condition of carbon dioxide hydrate. This shows that the formation condition changes according to the particle diameter of the sediment.
(3) The initial formation rate varies from the range of 0.2 to 0.6 ml / (min · g), and the dissociation rate varies from 1 to 1.5 ml / (min · g) in case of carbon dioxide hydrate. The rates increase with the presence of the particle, and also increase with the particle diameter.
We will continue to achieve the methane hydrate development system by the experiment that uses similar particles to the strata of the sea sediment in the future.

抄録全体を表示

Coalbed Methane (CBM) is a natural gas recovered from coal seams. It is sometimes called Coal Mine Gas (CMG), when the gas is recovered related to coal mining activities. This report summarizes the recent topics on recovery and utilization technology of CBM and CMG. The topics include gas recovery by CO₂ injection, CO₂ sequestration into coal seams, power generation by small sized IC-engine fueled by methane, synthetic oil production from coal mine gas and heat recovery from methane of very low concentration (mine ventilation air). This report focused on the importance of the international projects on CMG projects in considering the emission trade of global warming gases.

抄録全体を表示