March 20, 1914. THE COLLIERY GUARDIAN. 623 Mixing Plant for Coking Coals.* | By F. KORTEN. Owing to the increased production of iron, the demand for coke has grown to such an extent that it can no longer be met by coking merely the bituminous fine coal formerly almost exclusively used, and consequently the limits have been extended, to gas coals on the one hand and lean coals on the other. Since, however, not all coals are equally suitable for coking, ways and means have had to be devised so that good coke may be obtained from coals of lower quality, such means con- sisting in modifying the construction of the coke ovens, changing the character of the coal (by ramming) and finally by mixing different coals together so as to alter their composition. fl h i Fig. 1.—Baum Coal-mixing Plant. a = conveyor; b = elevator; d = worm; e — centri- fugal mill; f = dust; g = screen ; h — mill for nuts ; i - home-raised coal; j = pit for bought coal. The chief point in mixing—the object of which is to correct the deficiencies of one kind of coal by the good qualities of another kind—is to keep the components of the mixture constant in relative proportion, in order to ensure uniform coking. To attain this object, the general practice is to measure out the one class of coal, and to regulate the quantity of the other automatically by transporting the mixture with a conveyor, such as a bucket elevator, of limited carrying capacity. A number of the appliances used for this purpose are illustrated in figs. 1 to 9. Fig. 1 is a Baum mixer. The belt conveyor a feeds the elevator b with the coal from the pit, whilst the purchased coal is tipped from railway trucks into a pit c. Nuts can be reduced in a centrifugal crusher and fed to the elevator, and dry dust also can be conveyed to the latter, a worm conveyor then transporting the whole mixture to a number of centrifugal mills for mixing. A similar plant, by the same makers, is shown in fig. 2, except that here the coal from the pit is fed to the b a d c eq ■W & Fig. 2.—Baum Coal-mixing Plant. a = bought coal ; b = mill for nuts ; c = screen ; d = dust coal ; e = drainage belt for small coal; g — centrifugal mill; h = belt conveyor. crusher by a Baum drainage belt, whilst bought coal, broken nuts or dust is fed to the elevator. Both types are to be regarded less as actual coal mixers than as portions of the coal-washing plant. A plant enabling large coal to be crushed, and mixed with nuts or smalls, is illustrated in fig. 3, which repre- sents a Humboldt plant. The method of working is obvious from the drawing, only the one class of coal having to be fed to the elevator in unit time, whilst the rate of feed of the other is self-controlled. Fig. 4 shows another plant by the same makers. This enables a large quantity of bought coal to be mixed with the constant home supply (furnished, for example, by the coal-washing plant), the two together being distributed * Translated from Gluckauf. A REPORT TO THE GERMAN COKE COMMISSION. in the coking-coal tower. Here, too, the amount of bought coal introduced into the mixture per unit time can be regulated by controlling the speed of the worm conveyor, the amount conveyed being sufficient to fill up the elevator buckets. This type of plant is chiefly used in combination with a coal washery. The same remark also applies to the Meguin plant, illustrated in fig. 5. The bought coal is drawn from the storage hopper s, and conveyed by a worm and bucket elevator to the centrifugal mill, a second elevator then discharging it into a feed hopper, from which it can be discharged into the coal coming from the washery. The two are then put through a second centrifugal mill before being delivered into the coal tower. The Klbnne mixing plant (fig. 6) differs from the two just described in being independent of a coal-washing plant, and therefore suitable for cokeries proper. The classes of coal I. and II. are emptied into storage pits, from which they are fed by plate conveyors to bucket elevators delivering them to adjacently situated towers. Under each tower is a plate conveyor, which supplies a c h Fig. 3.—Humboldt Goal-mixing Plant. a — distributing worm ; b = centrifugal mill ; c = rotary distributing plate ; d - worm; e = large coal (80/200 mm.) ; f - nuts (0/80 min.) ; g = grid ; h = slide; i = breaker. Fig. 4.—Humboldt Coal-mixing Plant. a = bought coal; b — home-raised coal; c = worm ; d = centrifugal mill; e = shoot; f = belt. the coal, in accurately adjustable quantities, to centri- fugal crushers from which the finished mixture is conveyed to the coking-coal tower. Similar mixing plants are supplied by Schiichtermann und Kremer, as shown in fig. 7. The two classes of coal to be mixed are brought over the lines I. and II., and delivered by bucket elevators into mixing hoppers, from whence they are conveyed, by mixing tables, to a centrifugal crusher, the finished mixture being then elevated to the coal tower. Another type of plant by the same firm is illustrated in fig. 8. One compartment in the tower receiving coking coal from the washery is reserved for bought coal, which is brought from the self-tipping railway trucks by a bucket elevator, and distributed in measured quantities by a plate to the same belt conveyor which carries the coal from the pit to the coking-coal tower. The elevator leading to the latter has a definite maximum capacity, thus deter- mining the proportion of the home-raised coal. The plants described work in conjunction with distributing plates or centrifugal mills, or both. It is, however, possible to dispense with a special mixing plant, as is evident from the diagram, fig. 9, which illus- trates the arrangement used at the Concordia Colliery in combination with an old type of coal-washer, in which the repeated transference of the coal from one conveyor to another can be utilised for mixing. The bought coal coming from the self-tipping railway truck a is discharged at a definite rate per unit time into the pit serving the bucket elevator c, the buckets of which are filled up by home-raised coal fed through the k m m Fig. 5.—Meguin Coal-mixing Plant. c — home-raised coal; d = mill for mixed coal; e = coking-coal tower ; f — mill for bought coal ; g = bought coal ; h = plate ; k = feed hopper ; m = worm. a b T b 15 Fig. 6.—Klonne Coal-mixing. Plant. a,b = coal; g - distributing plate; h = centrifugal mill; i — worm leading to coal tower. h m Fig. 7.—Schuchtermann & Kremer Coal- mixing Plant. f — rails for mixed coal; h — mixing hopper; r = belt; n — coal tower; q = centrifugal mill. Fig. 8.—Schuchtermann & Kremer Coal- mixing Plant. n = to coking coal tower ; k = home-raised coal; p = bought coal ; o = slide ; n =• belt conveyor ; I — distributing plate. shoot b. The elevator has a capacity of 60 tons per hour. The repeated transference of the coal from the elevator c to the belt d, from this to the belt e, and finally from the latter to the coal tower, mixes the materials thoroughly. A series of samples taken at different points showed the following considerable