In today's mill operation, both rise of the electric power cost and lack of the land for tailing dam are serious problems. “Elimination of the gangue mineral in coarse grain sizes” can be said as an approach which solves positively the problems men-tioned above. Namely, a remarkable decrease in quantity of the gangue mineral passing a grinding circuit based on “Elimination-” brings, 1) a reduction of the electric power cost in grinding circuit, 2) a prolongation of the life of tailing dam owing to lesser formation of the slimy tailing. Moreover, by attainment of the matter mentioned above, a selling of the gangue mineral as aggregates may be expected.
In order to offer some technical informations to various trials concerned with “Elimination ”, in the second paper, this research committee has reported about the following two subjects.
1) Examples of actual operation:
Jokoku Plant (Hokkaido)
Hosokura Plant (Miyagi Pref.)
Kaneuchi Plant (Kyoto Pref.)
Yanahara Plant (Okayama Pref.)
Kuga Plant (Yamaguchi Pref.)
Kushikino Plant (Kagoshima Pref.)
2) Introduction of an important literature:
La Préconcentration (Industrie Minerale-Les Techniques, Janvier 1981)

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Mining industry is now evaluating the rock bolting as a new suppor method because of its significant advantages: reduced storage and handling requirements, improved ventilation, negligible maintenance and soon. This study has been started to reveal the advantages and disadvantages of the rock bolt support over the conventional arch support and examine its applicability to mines of Kuroko are deposit on the basis of in-situ measurement carried out at Fukazawa mine in Akita.
In this first report, the measuring system and the results at roadway supported by rock bolts are described. The rock bolts were installed in a square grid at 1 m interval, and convergence, radial extension of rock wall and axial force of rock bolt have been measured. Up to this time (200 days after installation), measured values have been continuously increasing, and some are of the considerable amount. For example, convergences are in the order of 50-70mm against the roadway of 3.3m height and 4.5m width. However, rate of increase is descreasing monotonously and no trend of roof fall or wall spalling is observed. Among others, it is most interesting that the results of convergence, extension and axial force follow the semi-log relationship, linear increase of the measured value against log time, except the axial force above its yielding point.

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This paper describes the results of an experimental research in which the fracture toughness of a granitic rock is determined by means of AE technique. ASTM standard specimens of the notched bend type having width from 30 to 508mm were tested.
The deformation and fracture behavior showed a significant nonlinearity and a stable crack growth were observed in all the tests. AE signals were detected at low load level, which indicates the occurrence of microcracking near the initial notch tip. Furthermore an analysis of the waveform and frequency spectrum of AE signals leads to a conclusion that there exists a close relationship between micro-fracture process at the crank tip and AE signals.
J-integral procedure were reasonably used because of the nonlinear deformation behavior. The relationship between the accumulated AE energy and J-integral provides a clear indication of the onset of a stable crack extension, denoted by JiAE The values of JiAE determined on the different specimens are independent of specimen size. This evidence suggests the feasibility of using a J-integral fracture criterion for this materials. A combination of non-linear fracture mechanics and AE technique provides a suitable procedure for determining the fracture toughness of rocks.

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Maintaining coals treated respectively with three surfactants (surface covering agents) in constant temperatures (90°C, 110°C, 130°C and 140°C in separate experiments), covering efficacies of each agents against incipient oxidation of coals, spontaneous combustion, are tested with quantity of oxygen deficiency and carbon monoxide produced while in 12 hours from the start of reaction.
Considerable decrease of both quantities during each reactions are observed, namely, restraining actions against coal oxidation of certain surface covering agents are recognized.
In spite of constant temperature conditions, fixed relations between validities and used concentrations, and restraining behavior of surface covering agents are not confirmed quantitatively, because of the complexity in chemical connection between oxygen deficiency and carbon monoxide produced during each reactions.

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In the course of research on the application of the Toms' effect to hydraulic tansportation of solids, it was necessary to determine the drag coefficients of sand particles in the dilute polymer solutions.
During the measurement of free-settling velocity of sands, it was observed that the drag coefficient of a particle in the dilute solutions of polyethylene oxide (PEO) is larger than the one in the fresh water.
In the range of sphere Reynolds number from 1 to 1000, as the concentration of polymer solutions and/or the molecular weight of polymer increase, the difference of the drag coefficients between in the PEO solutions and in the fresh water increase.
Using the mean square radius of gyration and the distance between molecules in the PEO solutions, the correlation of the settling velocities is formulated as follows:
v_p/v_w=0.1045 (l)/2 (S) ^3.12·(2 (S)/d) ^m
where m=0.748 log (d/2 (S))-0.2352.
v_p=settling velocity of sphere in polymer solution, v_w=settling velocity of sphere in fresh water, d=diameter of sphere, (S) =mean square radius of gyration of polymer in solution, 1=distance between molecules in polymer solution.
Therefore, the drag coefficients and the Reynolds numbers in the dilute polymer solutions can be calculated from that in Newtonian fluids and the above formula.

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Among the various properties required for agglomerates, strength is the most preferential common element, and related to bonding mechanism in the agglomerate.
In this study compression tests were carried out on moist agglomerates consisting of granular materials which differed in mean particle-size, particle-shape and size-distribution. Moist test-specimens were prepared by dewatering from a paste of materials in a cylindrical mold, after vibrating it.
It was confirmed that the strength of test-specimens were presented in terms of isostatic tencile-stress P_i caused by water in voids and angle of internal friction of the moist agglomerate.
P_i can be described as a function of void fraction, mean particle-diameter from permeability and degree of water saturation. The values of Pi in the funicular state, as a whole, increase linearly with saturation from the value in the pendular state (s=0.15) to the entry suction-pressure in the capillary state. But considered thisfrom a different point of view, it is recognized that experimental points show a gentle slope in the range of 0.7-0.8 saturation.

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An experimental study was carried out to examine the increase in the solid surface produced by a ball mill grinding. Samples used were silica glass, quartz, feldspar, limestone, marble and talc, and the feed size in any sample was 14-20 mesh. The pebble mill consisted of a cylinder, 12.5cm diameter and 12.5cm depth, and of porcelain balls (2.5cm dia.) of 1000g in terms of total ball weight.
The grinding was performed at the revolution speed of 87% of critical one in the feed weight range from 25 to 300g. The specific surface area was determined by the air permeability method, on assumption that the shape factor of particles was 6. And the size distribution was measured by the centrifugal particle size analyzer and micro sieving.
The results may be summarized as follows:
1) Any sample can be ground to 1-2μm in average particle size.
2) The stepwise grinding behaviors, as shown in Figs. 1 and 2, are obtained on the relationship between specific surface produced and grinding time.
3) The number of steps in the above relationship are estimated to increase with decreasing in energy per a unit mass given for sample.
4) The final specific surface produced indicates a maximum value at about 100/5 in the ratio of ball to sample weight. Taking into consideration the overall grinding efficiency, however, the greater weight of sample will give the better grinding effect.

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The activated leaching of chalcopyrite with hydrogen was investigated in this paper for the up-grading of copper concen-trates and the recovery of S as S° and of Fe as Fe₃0₄. Desulfurization of chalcopyrite with hydrogen was found to be most effective as compared to thermal decomposition under reduced pressure or in an inert gas stream. The reaction proceeds as shown below:
CuFeS₂→β-chalcopyrite→bornite+Fe_1-XS→Fe+bornite→Fe+Cu.
Coagulation of the dissociated FeS into a massive particles and formation of bornite phase surrounding it were observed under a light microscope. Also, it was found that partially reduced product was leached readily by hydrochloric acid solution with a vigorous evolution of H₂S and Cu₂S was formed. The residue with 73 to 79 per cent copper was obtained under optimum conditions. The dissolution of iron in bornite was affected significantly by nonstoichiometry of bornite and was slightly influ-enced on the acid concentration or leaching temperature.

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A set of Cu-O binary alloys with their oxygen contents being adjusted in the range 100-8, 800 ppm was prepared, and anodic dissolution experiments were carried out at 55° to determine the effect of anode oxygen level upon dissolution charac-teristics in a copper electrorefining electrolyte.
It has been found that the dissolution behavior of the Cu-O anodes is greatly affected depending upon type of the micro-structure. That is, % anode sludge formed, typically consisted of Cu°+ Cu₂O, increases with increasing oxygen content in the hypoeutectic region until a maximum is reached at the eutectic point. This then is sharply decreased, followed by the gradual increase in the hypereutectic region.
An evidence was also obtained by means of electrochemical and X-ray diffraction techniques that a Cu₂O phase present in the matrix of copper anode is partially converted to a CuO phase as a result of annealing/slow cooling process employed to this anode, and also that such heat treatment brings about a drastic change in the dissolution behavior over the entire range of oxygen level studied.

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