As a result of modernization of mining since 1964, the output was increased, in 1970, to 6, 220 tons a day from 5, 477 tons and overall underground productivity to 19.7 tons per man-shift from 13.2 tons.
The main points of the modernization are as follows: 1. Mining a. Installation of elevator in the underground.b. Speed-up of tunnelling and raising. c. Preparation and extending use of AN-FO. d. Improvement of bits and rods for drilling. e. Increase of mining efficiency. f. Loading by larger equipments. 2. Main haulage a. Use of large-size mine cars. b. Remote control of trains. c. Introduction of automatic traffic signal system.

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In spite of the unfavourable underground conditions, Japanese coal mining industry has succeeded in increasing its output from 50, 000t/mo/face (washed coal) of 1960 to more than 100, 000t/mo/face in 1972. Such a high rate of output is made possible by the double ranging drum cutter which cuts through the whole length of a face wall in its cutting travel either way, and also by our development of the powerful shield type self-advancing support of proven safety in mining operation, which has given the indispensable help toward attaining such a mining efficiency.
Described hereunder is the circumstance leading to the development of the shield type self-advancing support by Mitsui Miike Machinery Co., Ltd. and the successful results.

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The main process of this water treatment consists of ion flotation, precipitation flotation and ultra-fine particle flotation by using NAGAHM flotation machine which was newly developed for such flotations. The characteristics of this flotation machine are as follows:
(1) Aeration rate is very great (2115l/min·m2).
(2) Air bubbles are very finely dispersed in all part of the cell.
(3) State of flowing in the cell is so smooth withont disturbance.
(4) Much froth can be taken out rapidly.
The overflow of 2700m³ per day from a zinc concentrate thickener is one of the effluents from Kamioka concentrator, containing 67ppmCu (CN) ₃^--, 14ppm CN^-, 301ppm ZnS, 1.29ppm CdS, 16.8ppm C₂H₅OCS₂^- and 18ppm frother. The trials had been made to removed copper, zinc, cadmium and cyanide from the effluent.
Sulfuric acid is added to the overflow and consequently Cu (CN) ₃^-- is decomposed into CuCN, C₂H₅OCS₂Cu and CN^-. Then, all other ingredients in the overflow than CN^- are floated and separated from the water. The treated water containing exclusively 30ppm CN^- is recycled effectively to the differential flotation circuit of lead and zinc.
This water treatment method by using NAGAHM flotation machines has remarkably improved quality of the effluent concirninig to environmental problems, bringing about a large profit to the management of the enterprise by (1) the improvement of milling recovery, (2) the recovery of copper zinc, and cadmium in the overflow, and (3) the saving of reagents consumption.

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The Saganoseki Smelter began operations in 1916 using blast furnace process and in 1966 the monthly smelting capacity had reached 20, 000 tons of copper concentrate, with two blast furnaces and five converters using oxygen enriched air. Due to rapidly increasing demand for copper in Japan, it became necessary to build a larger facility.
After studying comparative merit of various processes in their capacity, pollution control capability, construction and operation cost, etc., it was concluded that the flash smelting process would be the best, provided that it can treat 40, 000 tons of concentrate per month by one furnace. Upon having confirmed the capability through exhaustive experiments with a test furnace, the Nikko Process flash smelting furnace using high temperature oxygen enriched blast and capable of treating 40, 000 tons of concentrate per month was constructed by the end of 1969, and since then it is operating satisfactorily.

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Hachinohe Smelting Company Limited was established on February 1, 1967, as a joint smelter by six nonferrous companies in Japan. In order to treat complex lead-zinc ores, especially some concentrates from black ore in northern district of Japan and concentrates from Huanzala Mine in Peru, it was decided to construct a new smelter at the northern tip of Honshu, adopting the Imperial Smelting Process.
The entire complex was completed at the beginning of 1969, consisting of a sinter plant, acid plant, furnace plant and zinc refinery. The designed production of 4, 500 metric tons of zinc was achieved in July 1969. By expanding the furnace bottom and improving the technology, monthly output was a record 7, 101 metric tons in June 1971.
This paper gives a brief description of the plant developements and improvements. The major items of them are as follows: 1. Total control of the plant by using a supervisory computer.
2. Up draft sintering operation by adopting a process computer.
3. Separate production of dark acid from clean acid by installing a double contact acid plant.
4. Purification and decolorization of dark acid.
5. Increase of the ISF capacity.
6. Treatment of the high copper raw materials.
7. Rationalization of the cadmium process.

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This paper presents the results of the theoretical considerations concerning the experimental results for the mechanical rock cutting method combined with the thermal action by flame, which have been reported previously.
At first, the temperature distribution induced in a rock mass due to a heat source moving on the rock surface has been calculated and then, the thermal stress distribution in the rock mass due to the above temperature distribution has been analyzed.
Secondly, the range of the fissurerized zone which has been caused by either the thermal stresses or the stresses induced by the thrust of a cutting tool has been presumed.
Finally, the mechanism of the mechanical rock cutting which has been used with the preceding thermal action has been considered using the results of the above studies.

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For the purpose of clearing up the effects of structural type of crystals and surface oxidation on the flotation and magnetic separation behaviors of pyrrhotite in actual operation, an investigation was performed in regard to the Kawayama concentrator, Yamaguchi Pref.
The main results obtained are as follows:
(a) The ratio of hexagonal pyrrhotite (H. Po) and monoclinic one (M. Po) in the crude are lies between 6:4 and 5: 5.
(b) In the rougher circuit of copper flotation which is done at the first stage of separation, M. Po floats in preference to H. Po.
(c) M. Po composes approximately 80 per cent of the total pyrrhotite contained in the concentrate of magnetic separation which is followed by zinc and pyrrhotite flotation.
(d) In the flotation circuits of zinc and pyrrhotite, H. Po floats in preference to M. Po as the general tendency. The reason of this contradictive phenomenon may be based on the following two facts. 1) A protective film such as ferric hydroxide is formed on M. Po preferehtially to H. Po by oxidation in aerated solution. 2) The protective film is possible to give a harmful effect on collection of pyrrhotite in xanthate flotation attended by prior activation with copper sulphate.

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The reaction between ferric oxides and gaseous hydrogen chloride were investigated thermogravimetrically by means of a quartz glass spring thermal balance. When the reactions were carried out at temperatures below 360°C or thereabouts, the weight loss-time curves showed a sigmoid shape. The experimeotal curves could not be expressed by conventional rate equations.
On the basis of a concept of consecutive reaction, the following equation was proposed to analyze the curves:
m*=1-(1-K₁t) ³-[(1-K₂t) ³-(1-K₁t) ₃] M_Fe2Cl6/_MFe2O3where m* is the weight loss fraction, t is the reaction time, M is the molecular weight, K₁ is the apparent rate constant in the conversion of ferric oxide into solid iron chloride and K₂ is the apparent rate constant in the conversion of solid iron chloride into gaseous ferric chloride.
The values of K₁ and K₂ were obtained from the curves of the above equation and superimposed experimental curves.
It was found that the values of K₂/K₁ decreased with the lowering of the temperature and that the sigmoid shape became more pronounced in the experimental curves.

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