The amount of waste plastics has gradually increased and reached around 9.5 million tons in 1997. However, only 42 % of waste plastics is utilized for a material, feedstock and thermal recycling effectively. The law for Recycling of Containers and Packaging has started since April 2000. To promote recycling of waste plastics, the development of an efficient recycling system has become an urgent issue for the environmental conservation and resources recycling.
The material recycling of waste plastics from the household is just limited because of containing the impurity in it and complex with other materials. Thus, the feed stock recycling of waste plastics such as a liquefaction, gasification and the use of blast furnace, coke oven, cement kiln have become important technology to promote the recycling of household waste plastics. Especially, to utilize polyvinyl chloride on these established process, the classification and dehydrochlorination process of PVC is the most important.
This paper is a review of the use of waste plastics as a substitute reducing agent for coke and pulverized coal in blast furnaces. In the method of using blast furnace, waste plastics can be used high efficiency with the simple processing of it due to the function of blast furnace. It is considered that waste plastics injection into the blast furnace is a favorable way to realize feedstock recycling of waste plastics and to solve environmental issue.

抄録全体を表示

In 1991, the activity was started as a subsidiary-working group in MMIJ. In 1992, the committee with financial aid by PNC was founded to develop a selecting method or an expert system for mine design and development.
At first, various mining methods were surveyed and distinctive features of them were examined and discussed. A relatively simple selecting method or chart for an appropriate mining method was proposed and implemented into a tiny expert system. The detailed data of mines were collected and test-run of the tiny expert system was carried out. It was found that the suggested mining method by the system, in most cases, coincided with the actual one. The developed system is considered to be helpful to learn the selection method for a novice and to promote mutual understanding among established mining engineers.
Special attention was paid to rock mass classification. Existing rock mass evaluation / classification systems were examined and a new provisional system, which was suggested by experienced mining engineers, was proposed and discussed.

抄録全体を表示

In 1992, the committee with financial aid by PNC was founded to develop a selecting method or an expert system for mine design and development. At first, various mining methods were surveyed and distinctive features of them were examined and discussed. A relatively simple selecting method or chart for an appropriate mining method (system A) was proposed in the previous study.
In this study, an advanced system for mine designing and development are discussed and system B is finally proposed. Additional data of mines are collected and a series of test-runs are carried out. The suggested or selected mining method by the system B, in most cases, coincides with the actual one. The developed system provided with a glossary, annotation and knowledge base concerning mining methods, design and development, is considered to be helpful for a student / novice and to promote mutual understanding among established mining engineers. The main result of the committee are compiled and recorded in CD-ROM.

抄録全体を表示

A new scheme called the Third Power Method is proposed for the quantitative analysis of water jet drilling process. The drilling speed is formulated as a function of the erosion strength : S_e of materials and the effective pressure : p of a water jet impinging on the bottom surface. The method is successfully applied to the pure water jet drilling in sedimentary rocks and fine ceramics. The attenuation of the effective pressure : p is evaluated from the measurement of the time-dependent drilling depth, as well as the erosion strength of materials which is correlative to the tensile strength of materials. As an application of the method, the chipping upon drilling is analyzed, which is a tensile fracture characteristic of brittle materials. It is clarified that the incidence of chipping increases with decreasing the tensile strength of materials, and that it occurs from the circumference of the bottom in the case that the effective pressure : p is greater than the tensile strength of materials.

抄録全体を表示

Robotic excavation and loading task have been receiving considerable attention in several fields, especially in mining and construction site. In order to realize the robotic excavation by the wheel loader, the robot has to recognize the shape of the rock pile because the excavation task is planned based on the shape of the rock pile. This paper is related to the vision system to recognize the shape of the rock pile. A CCD camera was used to obtain the image of the rock pile. The image processing procedure was proposed to detect the rock pile area from the original image.

抄録全体を表示

The Japanese government office enacted in 1994 that the effluent standard for selenium was 0.1 mg / l. This was an serious problem in the copper refineries, because they discharge a large amount of effluent containing the selenium ions higher than the standard. A provisional standard of 20 mg / l and then 1 mg / l has been applied to the industries, and the moratorium will finish within a few years. In order to clear the general standard, various methods were examined and investigated. According to the efforts, the process for the effluent containing Se(IV) is developed. The effluent containing Se(VI) is, however, difficult to fill the general standard by the practical method up to this time.
We studied the reduction of Se(VI) by TiCl₃, and the following results were obtained.
(1) Se(VI) is quickly reduced to amorphous Se at the room temperature.
(2) The reduction is of the first order.
(3) The reduction rate is depended on the excess TiCl₃.
(4) Coexisting HCl and H₂SO₄ depresses the reaction rate.
(5) H₂Se evolves when the pH is high and the excess TiCl₃ is large.

抄録全体を表示

The roles of As₂O₃ and Cu²⁺ in the cementation of Co by Zn dust were studied in synthetic Zn leach solutions by polarization measurements, scanning micro-electrode technique, ESCA and EPMA analyses. It was confirmed that Co had an inherent property of not beginning to deposit at its equilibrium potential and that the potential at which Co began to deposit was polarized in Zn sulfate solution almost to reach the equilibrium potential of Zn. These properties peculiar to Co were directly responsible for the extremely small removal rate of Co in the cementation using Zn dust alone. The partial polarization curves of Co were significantly shifted to more noble direction in the presence of As₂O₃ and Cu²⁺ in Zn sulfate solution, indicating that these additives acted as a catalyst which promoted the kinetically suppressed deposition rate of Co in the presence of large amounts of Zn²⁺. Considering the fact that Cu, which began to electrodeposit at its equilibrium potential, was reduced to metallic state by Zn dust immediately, the deposited Cu on the initial Zn dust surface would offer active cathode area on which Co can deposit easily. On the other hand, As₂O₃ was also reduced by Zn dust in preference to Co and deposited in the forms of metal and oxide. The metallic As acted as an inhibitor for hydrogen evolution on the deposited Co, while As oxide worked as a catalyst to reduce the inherent deposition overpotential of Co and promoted the cementation rate of Co.

抄録全体を表示

The extraction of ruthenium (III) and rodium (III) from aqueous tartaric acid solutions have been investigated by using trioctylmethylammonium hydrogen tartarate (TOMAHTar ; R₃R'NHTar) in benzene.
The distribution ratios of both metals increase with increasing aqueous pH. The order of extraction efficiency is Ru > Rh.
At pH ≥7, the stoichiometric composition of major complex for both metals formed in the organic phase represent as R₃R'NM(Tar)₂(H₂O)₂, in which M denotes Ru and Rh. Therefore, it was deduced that although the extraction of both metals proceed according as following equilibrium equation ;
M(Tar)₂(H₂O)₂^-(a) + R₃R'NHTar_(o)⇔R₃R'NM(Tar) ₂(H₂O)₂(o) + HTar^-_(a)
where (a) and (o) represent aqueous and organic phases, respectively, the origomer species is extracted with decreasing aqueous pH.
These results were also confirmed by infrared and visible spectral measurement of the extracts.

抄録全体を表示

Cation exchange properties of K and Ca type zeolites were investigated using Na type zeolite synthesized from coal fly ash under hydrothermal conditions. The caion exchange capacity (CEC) of the Na type zeolite was about 300 meq / 100 g. The cation exchange amount of Ca type zeolite substituted from Na type zeolite was measured for NH₄⁺ and PO₄ ^3- in order to evaluate the efficiency of zeolite as a water purification agent.
Na type zeolite was exchanged with K⁺ and Ca²⁺ in the pH region of around 7. The exchanged amount of K+ did not depend on the kinds of anion in the aqueous solution, while the amount of exchanged Ca²⁺ depended on them. It was found that the substitution percentage from Na⁺ to Ca²⁺ reached to about 90 % of CEC, if the cation exchange operation was repeated.
In the cation exchange reaction for NH₄⁺, Na type zeolite exchanged much more NH₄⁺ than Ca type zeolite. In the case of PO₄^3-, Ca type zeolite removed PO₄^3- from the aqueous solution by the precipitation reaction between Ca²⁺ released from the zeolite and PO₄^3- in the solution. On the other hand, Na type zeolite could not remove PO₄ ^3- from the aqueous solution. In the adsorption behaviors of NH₄⁺ and PO₄^3- from the mixed aqueous solution with Ca type zeolite, approximately 90 % and 46 % removal was accomplished for NH₄⁺ and PO ₄^3-, respectively. The ion of PO₄ ^3- was precipitated quantitatively with Ca²⁺ released from Ca type zeolite in the solution.

抄録全体を表示

Electronic structure of ZnSb₂O₆ was investigated using the discrete variational (DV)-Xα method on the model cluster [Zn₅Sb₁₀O₅₆] ^52-. In the calculation, the band gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied MO (LUMO) was 3.80 eV. In the valence band, Sb-O and Zn-O bondings are considered to be not perfectly ionic but partially covalent because of the hybridization of O 2p orbitals with Sb 5sp and Zn 3d orbitals. Furthermore, ZnSb₂O₆ crystal is expected to have a large electron mobility because Sb 5s orbitals are dominant at the bottom of the conduction band. The calculated net charges are +1.48e for Zn, -1.20e for O and +3.02e for Sb. The bond overlap populations are calculated to be 0.09 and 0.29 for Zn-O and Sb-O bondings, respectively. These results show that Sb-O bonding is more covalent than Zn-O bonding in ZnSb₂O₆ crystal.

抄録全体を表示