This paper gives the description of the recent trends in crushing and grinding field. As the remarkable topics, getting bigger of machinery, increasing application of automatic control and striking advances in autogenous grinding are described using some examples.
As for autogenous grinding, the excellent grinding mechanisms and the good effects on several succeeding extracfive processes of the improved Aerofoil mill, and some discussions on wet pebble milling are explained.
Furthermore, some essays on grinding by tumbling mill at supercritical speed or non-cataracting state, improvements in mill liners and fine grinding mi!is, and the main points of the theories and studies in comminution presented by F. C. Bond, R. T. Charles, and others are briefly introduced.

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It can be said that the progress in screening and classification is relatively noteworthy in recent years among various unit processes involved in mineral dressing and coal preparation. In this article some late developments in these phases are reviewed with special references to Mogensen Sizer, DSM Sieve Bend, and wet centrifugal classifiers, such as Denver-Morton Duplex Cyclone, Turbocyclone, and Fixed-Impeller Hydrocyclone.

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The role of the interfacial electrical condition on the adsorption of collectors on mineral surfacesis discussed with particular reference to the flotation of oxidized iron ores.From eledroklnetic measurements made on iron oxides, silica, etc., H⁺and OH^-are identified to act as potential-determining ions, thus controlling the electrical properties on these oxides. Adsorption of collectors then depends strongly on the pH of the solution; anionic collectors are adsorbed on positively charged surfaces and cationic collectors on negatively charged surfaces, which in turn defines the effective flotation range with respective collectors for a given oxide. Selectivity of flotation separation is thus demonstrated with an artificial mixture of quartz and goethite to be in good agreement with the basic floatabilities of the respective minerals. Detrimental effects of slimes in the iron ore flotation, both reagent consumption due to largespecific surface and slime coating, can also be interpreted by the interfacial electrical condition of the minerals comprising the iron ore slimes.

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The recent progress of mineral flotation reagents has been reviewed in accordance with the items; illustrated as the following:
1. Sorts and amounts of mineral flotation reagents applied annually in Japan.
2. Raw materials from which the flotation reagents are manufactured.
3. The chemical aspects of flotation reagents: Chemical studies to find a better flotation reagents. Chemical properties of flotation reagents. Analytical methods of flotation reagents.
4. Recently introduced flotation reagents. Commercial ones. Patent literatures.

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Prior to World War II radioisotopes were produced in microquantities in cyclotrons and other particle accelerators. With the construction of the nuclear reactor or “Pile” an almost unlimited source of radioisotopes was created. The majority of radioisotopes are produced in the pile by (n, γ) and (n, p) nuclear reactions induced by the thermal nutrons present in the pile.
Radioactive isotopes for scientific, medical, agricultural and industrial use constitute by far the most important contribution of atomic energy to peacetime welfare. And isotopes are already at work in hundreds of places, both in our country and abroad, adding to man's knowledge of the still largely mysterious natural forces around him and significantly to his welfare.
Today, the word “isotope” is in very wide use, particularly among those working in fields where isotopes are finding some practical application, and the techniques for using them are being increasingly understood.
In our country, studies of RI techniques are developed by the imported sources from 1947. The industrial applications of radioisotopes depend on using the radio-material either (1) as a source of ionizing radiation or (2) as a tracer or (3) as a radiation chemistry.
Gaudin lectured “Radioactivity in Mineral Dressing” in London (1952). He said, “radioactivity can be put to use in mineral dressing in three ways;(1) as a research tool;(2) for the control of nod-radioactive plant processes; and (3) as a mineral-separating tool.”
Now, l explained the outlines (67 papers) of mineral dressing, coal preparation and others sectio data from which picked up the topices problems through use of radioisotopes.
There will be an increasing use of radioisotopes in physical, chemical research and its application for industry.

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(1) Deyelopment of coal washing jig.(2) A theory for coal washing by jig without preliminary sizing.(3) Devices to discharge the refuse layer from a jig.(4) Features of coal washing jigs.(5) The closing remarks.
About 120 years ago a fixed sieve jig was introduced in the field of coal washing, and then Berard, a French engineer, developed a cotinuous working, fixed sieve jig for coal washing. This is the first cotinuous workig jig in general. The Hartz jig for mineral dressing could realize an uniform pulsation over all the sieve area by giving the same area to the sieve and plunger section. The principle of the bed jig was introduced to the Hartz district from Cornwall where a movable sieve jig with an artificial bed was practiced. This principle was adapted by Luhrig to wash tine coal with success. The artificial bed is very useful to get the uniform pulsation over all the sieve area and to moderate the suction. Rittinger wrote his book in 1867. Fritz Baum invented his air pulsated jig in 1892, developed his principle to wash a raw coal without preliminary sizing in a jig, and designed the air pulsated jig with 2 cells in series which is now the conventional type. With a large jig it is very difficult to get an uniform pulsation all over the sieve area with the most ingenious device. The newly developed TACUB jig solved this long pursued and basic probrem. There are various theories proposed for the conventional practice to wash a raw coal without preliminary sizing in a jig. The author understands it as follows: at the charging end the raw coal fed is separated according to the law of falling velocity, and the larger pieces of shale are arranged at the bottom forming a sole for the coal bed. On the following way the bed flows in a mass as a whole as it is expanded moderately by the pulsion. The bed in such a state is specified by the author as a “crowding and flowing” bed. In a crowding and fiowlng bed of a raw coal the larger plecesof coal areforced to roll upword into the top byer of the bed, “reversed classification”, and the smaller pieces of shale pass through the coal bed into the bottom layer of the bed replacing the coal particles according to their sizes and specific gravities. There are various devices to discharge the bottom layer of the refuse at the discharging end. It is controlled automatically according to the thickness of the bed of the refuse. The efficiency of the work of “coal washing by jig” can be evaluated practically as high as the H. M. S. The simplicity of a plant of “coal washing by jig” must not be neglected in the field of productive engineering.

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The amounts of fine coal included in the raw coal to be washed have been, increased by reason of the adoption of mechanical coal mining method in Japan. On the one hand the demands of fine coal have been increased rapidly in the cause of the increase of the electrical power station used the low-grade coal. Therefore, it is the important problem that fine coal is recovered effectively in the coal preparation plant.
The various equipments to be.treated fine coal are classified by their use as follows:(1) separator (flotator and washing table), (2) thickener and classifier (boot of bucket elevator, Bacher tank, settling cone, thickener, wet cyclone and settling tank)(3) dewatering machine (fixed screen, vibrating screen, filter and centrifuge), (4) settling pond.
Many systems of the treatment of fine coal consist of the simple or complicated combination of the aforementioned equipments in the coal preparation plant, but the character of modern system of the treatment of fine coal includes one of the following equipments, that is, flotator, thickener, filter and centrifuge.
Both of flotation and centrifuge have been developed remarkably and adopted in our country. In this paper, therfore, the domestic status of flotation are described, on the one hand the various centrifuges are classified by their constructions and their characteristics are explained respectively.

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Industrial water from coal mine is mainly classified into 2 kinds, namely, (1) drainig water from coal mine and (2) tailing water from coal preparation plant.
Drainage water from coal mine is disposed of without treatment, so general' speaking, industrial water from coal mine means the tailing water from coal preparation plant for which the treatment is necessarily.
For the study of the treatment of the tailing water from the coal preparation plant. There are 3 items: 1. theoretical problem 2. technical problem 3. economical problem.
The three problems mentioned above are not indipended and co-related and should be solved simulaneously, in order to treat the tailing water.
This paper descibe these problems, in detail.

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Coal industry of our country is carrying out many rationalization programs with which stabilize demcnls for coal competing with other energy sources.
The coal consumption has a tendency of depending mainly upon iron manufacture and electric power generation, and inferior coal is expected to increase the demand and we must promote to expand inferior coal utilization for electric power generation at the coal field.
To cope with the situation, following methods are considered and we try to reckon the producible amount of the inferior coal with these methods in our country.
1. Reorganization coal preparation systems in order to be able to yield more inferior coal
2. Recovering suspending fine coal in waste water from the preparation plants
3. Rewashing middlings of waste piles

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We understand that there are a few underground are dressing plants in foreign countries, according to various mining journals, but the details of constructions and operations are not revealed.
Therefore, the author intends to explain the relative merits of Yatani Underground Mill which started operation in 1959. This plant is the first one of its kind in Japan entirely constructed in underground.
The tops taken up by the author are itemized as follows:
1. The difficulty of construction and its cost involved
2. The performance of mineral extraction
3. The operational running cost
4. The plant working environment or conditions
5. The general overall merits and demerits of the plant.

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In this papery is descri bed tthe progress of studies and practices in respect to iron-sand and pyrrhotite during the past ten years as follows:
1) Fundamental research of pyrrhotite.
2) Beneficiation of pyrrhotite.
3) Mechanical concentration of iron-sand.
4) Reducing roasting of iron-sand.

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This is a review on the beneficiation of some newer metal ores. Some considerations on gravity concentration, agglmerate tabling, magnetic concentration, electrostatic separation and flotation of beryllium, boron, aermanium, lithium, columbium, tantalum, vanadium, zirconium and hafnium ores are described.

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Concerning with the milling of uranium ores, the technical and economical problems were summarized First, the data, which seem to have been reasonably estimated, are presented on the inferred uranium ore reserves, and the ore production and the demands of uranium at present and in future, Second, brief explanation of are dressing and milling of the ores is given, and outline of each process-crushi ng and grinding, leaching, liquid-solids separation, uranium recovery from leach liquors, precipitation, and so on, is described mostly for the case of the sulfuric acid leaching method which is currently adopted most commonly. Third, the milling processes of Beaverlodge mill, Canada; Mary Cathleen, Australia; Kvarntorp, Sweden were explained as the examples. Finally, uranium ores in the Ningyo-toge area which has the biggest uranium ore potential in Japan, is briefly described on the ore deposits, properties of the ores, and results of the milling.

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lt is well known that mineral beneficiation is ordinarlly performed by moans of minerd drssing followed by metallurgy. in this paper, however, the author classifies some actual interesting examples of special cases other than the above mentioned combination, into the following groups and explains in outline each of them.
(1) The advantage in direct application of metallurgical processes to some kinds of ores or mill products, instead of the usual combination process, on account of difficulty in physically separating their constituent minerals.
(2) The application of any preliminary metallurgical treatment generally termed as “Metallugisches Aufbereitungsverfahren” to some kinds of ores prior to mineral dressing in order to facilitate the separation of -ore minerals by dressing.
(3) The application of any dressing process to half-finished products of metallurgy or during the course of metallurgical treatment.

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The rapid progress in dense media separators in recent years has been reviewed from the technical points of view. Dense media separators may be defined as the appliances composed of float-and-sink and medium recovery units. The treatment of both lump and fine is the primary requisite in coal preparation. On the contrary, the treatment of fine is more important in ore dressing. It must be emphasized that the density of medium should be regulated by adjusting the relative content of the medium solid, water and impurities without changing the total amount of the medium in a dense media system. The following items of interest have been discussed in detail:(a) the stability of dense media, (b) the types of separators, (c) feeding, (d) the treatment of products and waste, (e) the circulating media, and (f) the treatment of fines. The control of operation, especially the automatic control of both density and viscosity of medium in separatory vessels, the separation of medium from fine products, etc. may be the future problems.

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We have analysed statistically the past data on relation of flotation results with temperature in Yoichi mill. Based on this analysis, we have made following formulas. By applicating these we have decreased variation of flotation results by controlling pulp temperature of flotation circuits.
1) Relation of Zn grade% in zinc concentrate with pulp temperature C Y=0.727X +40.220 X=1.170Y-44.150
2) Relation of Zn grade % in tailing with pulp temperature Y=0.452- 0.0112X X=24.083- 41.420Y
3) Relation of Pb extraction % in copper concentrate with pulp temperature at Cu Pb differential flotation Y=0.361X+ 6.040 X=1.642 Y-6.316

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One of the chief problems in the new UCHINOTAI project in KOSAKA division, DOWA Mining Company, is the determination of the milling tlowsheet treating “KUROMONO” (Black ore).
“KUROMONO” is a complex sulphides ore, extremely finely disseminated chalcopyrite, chalcocite, covellite, tetrahedrite, tennantite, galena, sphalerite, pyrite, gold and silver, barite and minor amount af gangue minerals.
Due to the difficulty of liberation and similar floatabilities of component minerals, this are has been known very hard to be separated by the usual flotation procedures using cyanide and/or zinc sulphate.
This article deals with the characteristics of liberation of component minerals obtained by microscopy and some flotation tests using sulphur dioxide which have given fairly better results than cyanide procedures.

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The flotation methods for oxidized lead minerals, such as anglesite, furnish galena, beaverite, were investigated by three methods mentioned below.Comparlng these methods by laboratory sfudies, foibwlng results were obtained.
1) By the soap flotation method, although the cost is low, the lead recovery is very low and the primary slime cannot be treated.
2) In the sulfidizing method using sodium sulphide and sodium phosphate dibasic, the lead recovery is satisfactory but the reagent cost is high.
3) In the modified method.using methyl xanthate and sodium phosphate dibasic, the lead recovery is quite satisfactory and the cost is lower than the sulfidizing method.
Following the third method, our plant operation has been very satisfactory.

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Kamaishi Mine has two kinds of ore dressning plant. One is a magnetic separation plant for iron ore, and the other is a flotation plant for copper ore.
ore. The magnetic separation plant treats a magnetite ore containing 21-25% magnetic iron and has a capacity of 3, 200t per day. The production of the concentrate, which has average grade is 58% iron, is 430, 000 t per year.
The kinds of ores treated at the copper plant are three as follows:
(1) The copper bearing low grade iron ore which has 13-15% magnetic iron and 0.3-0.8 copper.
(2) The mixed ore of chalcopyrite and pyrrhotite which has 7-10% iron and 1.7-2.5% copper.
(3) The wet tailing from magnetic separation plant which has 0.5-0.7% magnetic iron and 0.15-0.2% copper.
Total capacity of the copper plant is 2, 560t per day and it produces the copper concentrate of 17-18% copper and the magnetite concentrate of 57-59% iron.
Average recoveries are about 90% for copper and 90% for magnetic iron.

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The outline of the operation of Akagane concentrator which is producing copper and magnetite concentrates is dealt with. The Ore deposits of Akagane mine, Iwate Prefecture, are contact metasomatic deposits made up chiefly from pyrrhotite, magnetite, chalcopyrite and iron pyrite. Crude ore, assaying 0.7% Cu, 26.5% Fe, and 4.9% S, are crushed and ground, 800tons per day, copper concentrate (17% Cu) being produced. by flotation and magnetite being separated by magnetic separation. The magnetite concentrate is then retreated to remove pyrrhotite by flotation, leaving magnetite concentrate (65% Fe, 3.0% S) as a tailing.

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The cone type separator was installed 12 years ago to treat lump ore at Hosokura mill, but the separator was unable to treat the fine ore with satisfactory results, It was found by several tests conducted that 12-2mm size was successfully separated by cyclone type separator, using pyrite concentrate as heavy medium material.
Detail of this process and operating data is given in this paper.

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The copper dressing plant at Ashio Mine is one of the rare examples in Japan, by reason of the plant is recovering only copper concentrate, at a rate of 1, 500 tons per day treating.
This paper describes about the outline of mill operation, and some details of process data which are inquired and investiaated by the mill enaineerina. as follows-
(1) Sizing and washing operation in crushing process.
(2) Reconstruction of sink and float separation process.
(3) About the rate of consumption in ball milling, and utilization of wet cyclone to classifier which combinates with primary grinding process.
(4) Pumping up of flotation tailing with serriessetted contrifugal type sand pumps.

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It was proved at the ore dressing plant of the Ogoyq Mine that the economicql qpplication of heavy media separation by a cyclone-type separator was feasible, and its use in practical operations successfully testified by charging fine particles of ore ranging from 0.5mm to 8mm was formerly fed directly into the mill head.
head. From the results of basic tests it was determined that such factors as inlet pressure, specific gravity of the heavy media feed, and cone ratio had an important bearing on separation and that a proper combination of these factors would enable a close approach to the ideal conditions of sink and float separation. The relationship established between separation results and sharpness in separation, as obtained within the scope of these tests indicated the tendency of a very close resemblance in the relationship existing between the copper content in the waste and the percentage of discard and that between the former and the specific gravity in separation derived from Tromp's distribution curves but on the other hand showed a reverse tendency in relationship with the Terra indices. It was also ascertained that a feed inlet pressure ranging from 0.5 to 1.0kg/cm² was sufficient and that ferro-silicon as a media acted more favourably on pyrite concentrates.
concentrates. In putting this new unit, which saw initial operation in April 1960 and has been in continuous performance since, special features were devised such as the uniform and smooth circulation of the heavy medium, means for preventing contamination of the heavy media, improvements in screening efficiency, maintenance of a fixed inlet pressure to cyclone, and control of specific gravity of heavy media.
From the operational results it could be observed that the successful removal of large quantities of waste permitted a leeway of 19 percent in grinding and floating capacity leading to a possible savings in initial installation costs at the time of mass production and also reduction inflotation running cost.

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This paper gives the description of the outlines of the three plants, having total capacity of 3, 600, ton per day, at the Kamioka Mine of the Mitsui Mining & Smelting Co,
From the crude ore mined at the contact-metamorphic deposit, containing galena, sphalerite, and gangue minerals that are hedenbergite, limestone and epidote, the argentiferous lead and zinc concentrates and a small amount of the flake graphite are produced by the differential flotation process.
The grade of the milling feed is 0.41-2.3% Pb and 3.3-7.9% Zn.
Monthly production is 900 ton of lead concentrate (64-43% Pb), 6, 900ton of zinc concentrate(56-61% Zn)and 35 ton of graphite concentrate (87-92% C)

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Kohmori Mine Mill had hither adopted a milling method consisting chiefly of hand picking combined with gravity concentration but due to the recent increase in the treating amount of feed ore as well as changes in its nature of constituents, the mine has constructed a copper-pyfrhotite differential flotation plant combined with heavy media sbparation plant in 1960 and is achieving a smooth operation.
The special characteristic of this mill is that it adopts - a differential flotation combined with talc flotation and by introducing automation, it is endeavouring to attain modernization in operation.

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Our laboratory test on the dressing of the Cu-Ni bulk concentrate (Cu 4%, Ni 11%), imported from Canada, yielded following products: Cu-concentrate (Cu 25%, Ni 1.6%), Ni-concentrate (Cu 0.25-0.28%, Ni 14%) and Cu-Ni middling (Cu 2.9%, Ni 5.3%). Milling plant was built according to this results and operation was opened from 16th-Nov.-1960. Up to today, plant operating data are found nearly equal to that obtained from foregoing laboratory test.

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Flotators of SW-type, Fagergren type, Denver Sub-A type and Denver-M type are now operating at Niihama Milling plant in Bessi mine.
Because some of the flotators of SW-standard type and SW-deep cell type became to aged, they were since 1960 substituted in turn by flotators of new types and here with series of plant test comparing flotation data among new and old flotators were performed as follows.
1. The test comparing the SW (standerd type) fltator with SW large type
2. The test comparing the SW (standerd type) flotator with Fagergren flotator
3. The test comparing Denver M#30 with SW deep cell type the Results are found quite enough to answer the purpose and improve plant operating data.

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The dense-medium cyclone washery has been put into operation since October 1959 at Toyosato colliery, Hokkaido, for the purpose of upgrading fine clean coal from the existent jig washery. In this article its operation and performances are described, including flowsheets, dense-medium. cyclone unit, screens, medium recovery system, and the sharpness of separation. The plant is characterized in that (1) the flotation tailing is used as a dense medium, (2) the cyclone is upgrading the cleaned coal from jig washery, and (3) the size of the cyclone feed is 0.5/4 and 4/24mm respectively.

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Part of the reconstruction program of the Pombetsu coal preparation plant for intensive operations, has Tecently been completed, with a new capacity of 400 tons per hour.
Instead of the old hand-picking method for lump coal, dense-media process has been introduced, i. e. two WEMCO separators, one single drum and the other double-drum, with a total capacity of 250t/h, are used to clean 200-25mm raw coal. At the same time, in addition to the two old Baum jigs, a TACUB jig and flotation machines have been installed.

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According to the increasing output plan, construction of the new coal preparation plant of 400 tons per hour in capacity had been projected at Mitsubishi-Bibai Colliery, Hokkaido. The new plant construction was started in February 1960 and was put in operation in June 1961. For the purpose of high efficiency in cleaning and accurate stability in coal quality, the new plant adopted Drewboy dense-medium separators for, coarse coal and a feldspar bed-jig for fine coal.
This paper describes chiefly the fundamental elements and some problems involved in the design of the new plant as well as its outlines.

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In this article the outline of the new coal preparation plant completed in August 1960 at Horonai Colliery. Hokkaido, is described. The plant consists of main and auxiliary Drewboy dense-medium separators imported from PIC, France, having the capacity of 250 tons and 110 tons per hour respectively, together with its medium reclamation system. It is expected that the plant will produce approximately 4000 tons of cleaned coal per day by 1963.

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The coal seam in a Nakayama Colliery of Yamagata Prefecture consists of a lignite and a coaly shale, but this Nakayama lignite is inferior somewhat to other lignite in the washability chracteristics.
A piston jig was installed in this coal preparation plant seven years ago for the purpose of washing The minus 80mm lignite, but the performance of the separation of this separator was unsatisfactory.
Therefore, a drum type separator using copper slag ds medium was installed in October 1960 at the same preparation plant.About 10tons of minus 80mm plus 6mm lignite per hour is continuously run through the plant with this separator in about 4 hours per day.When the performances of separation of minus 80mm plus 6mm lignite with a drum type separator were compared with the results of separation of minus 80mm lignite with a jig separator during the past halfayear, it was found that (1) the washed coal increased in the yield from 10 to 15 percent, (2) the ash content of washed coal was same, (3) the sharpness of the separation and the separating effectivness were both satisfactory.But the several problems of the reclamation of medium, the purification of medium, the defacement of machine and the freezing of wash water in the winter season would be solved in future.

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Brief description is made in this article on the Iwaki-West coal preparation plant, Joban colliery, Fukushima Prefecture, which was completed in March 1961.
After being sorted by Bradford breaker, 120/28mm run-of-mine coal goes to PIC-Drewboy dense-medium baths (a 2100 main washer and a 115t/h rewasher) using magnetite medium, while 28/0mm raw fines are washed by Baum jigs (a 240t/h main washer and a 120t/h rewasher).Slurries are treated in the circuit which consists of settling tanks, a thickener, and centrifuges.Jig washery refuse is retreated by a verticaltype Drewboy separator (28/8mm) and a densemedium cyclone (8/1mm) to recover low-grade boiler coals.
Automatic control systems relating to dense-medium density and to jig operating variables are shortly mentioned.

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