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<報文>テーブル浮游選炭法の基礎的試験

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  • <Original Papers>Fundamental Testing of Agglomerate Tabling of Coal

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The rapid development of the dense-media coal cleaning in our country brought about the problem of effective treatment of finer undersize coals from dense-media separation. The problem is an important one because raw coals now mined in our country are relatively low in rank, high in ash content, and liable to disintegrate. The concentrating table seems to be the most adequate device for treating intermediate sizes between dense-media separation and flotation, but the capacity of the table is limited. The authors and their collaborators carried out previously tabling tests to separate undersize coals from dense-media ones, and found that the separation was satisfactory. In the present tests, the process of agglomerate tabling was tried to examine whether 8 to 100 mesh samples of coal from the Iwasaki Pit, Iwaki Coal Mine, Joban Coal Mining Co. were effectively separated under increased feed capacity or not. The coal used for tests contained 40.44% fixed carbon on the dry, mineral-matter-free basis, exhibited the heating value of 12,339 B.T.U. per pound on the moist, mineral-matter-free basis, and was nonagglomerating. It may be classified as subbituminous A coal according to the American Society for Testing Materials' standards. The thin sections of coal were prepared and examined under Leitz's Ultropak ore dresssing microscope and it was found that the coal showed the banded structure of vitrain and durain including minute particles (mostly under 10 microns in diameter) of pyrite scattered or in streaks or aggregates. The reagent used for agglomerating coal was prepared by fractionating kerosene between 180° and 210℃. The specific gravity of the fraction was 0.827 and the refractive index was 1.4618 at 15℃. The apparatus consisted of the Wilfley table, 954 mm×407 mm in size, the conditioner, remodeled 500g Fahrenwald type flotator, and the constant head tank. The effectiveness of separation was expressed by the magnitude of imperfection I, proposed by Charbonnages de France. The results obtained may be summarized as follows : - The process of agglomerate tabling was satisfactorily applied to the separation of ash content of coal of intermediate size and it was found that the separation was better than that by the ordinary tabling at the same feed capacity or the feed capacity was larger at the same magnitude of imperfection. Under varying conditions of operation it was found that (1) the air inlet to the impeller of the conditioner should be opened ; (2) the quantity of wash water should be between 3.5 to 4.0 l/min ; (3) as the qnuantity of reagent added was increased, the value of I decreased exponentially and became nearly constant at about 300g/t ; (4) the optimum separation was obtained for feed sizes ranging from -14+28 to -28+48 mesh ; and (5) as the feed rate was increased, the value of I increased hyperbolic and attained rapidly to higher values at the feeding time of less than 45 sec. In the present tests the sulphur content of clean coal was not lowered appreciably. When the values of probable error of separation obtained in the present tests were plotted against the values of the corresponding partition density, the points distributed between the straight lines representing I=0.1 and 0.25,but the points for the ordinary tabling centre around the line of I=0.2 and those for agglomerate tabling around the line of I=0.15.

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