LOOSENING UP THE CHARGE BEFORE PELLETIZING

G. B. Gritsenko, V. A. Serebrennikov, and Yu. P. Kudrin

UDC 622.785.051

A significant quantity of dense balls of charge material is formed in the pelletizing plant at the Lebedin Mining and Concentration Combine (LMCC) due to the high moisture content of the charge materials and the use of less-than-optimum equipment to discharge the materials from the feed hoppers. The macrostructure of the charge, which is determined by its moisture content and ballability, is nonuniform in this instance. The nonuniformity, in turn, desta- bilizes the pelletizing operation and adversely affects the granulometric composition of the pellets.

Some of the balls break when they drop to the bottom of the disk pelletizer, while the stronger balls help form coarse, substandard pellets. Thus, the involvement of the given material in the process of direct pelletization is impeded. This situation is facilitated by charging the charge materials by dumping them directly into the pelletizer without distrib- uting them over the surface of the disk. When the charge is thus locally introduced, the materials do not encounter pelletizing nuclei of various sizes instantly, but rather after the material has moved some distance in the disk. All of these negative factors also neces- sitate an increase in bentonite consumption.

The pellet plant is constantly searching for ways to reduce the content of coarse, sub- standard fractions in the pellets. To make the structure of the charge more uniform prior to pelletizing, in 1982 the plant reconstructed the charge chute leading to the pelletizer on one production line and installed a "squirre!'cage"-type charge disintegrator (scarifier) with its own drive.

Comparison tests were conducted before pelletizing to check the effectiveness of the charge scarification. In the control tests, the charge was not scarified or scattered over the disk. The tests were conducted on a 7.5-m-diameter disk pelletizer with constant regime parameters and a bentonite content of I.i and 1.4% in the charge. The specific surface of the concentrate, with an iron content of 66~67%, remained nearly constant at 1650-1700 cm2/g during the tests.

TABLE i. Effect of Scarifying the Charge before Pelletizing on the Quality Indices of the Raw Pellets

Pelletizing conditions

Bentonite content of charge I,I %: toUonclc soosened charge . . . . . . . . . .

enea charge . . . . . . . . . . .

Moist- ure con- tent , ~

Strength

number of Icompression, drops ] kgf/pel let

Pelletizer productivity

9,9 16,9 9,8 16,8

Pelletizer productivity

Granulometric composition (%), mm

80 tom/h

1,20 34,3 59,3 10,8 5,6 1,19 18,5 67,7 10,4 3,4

1 I0 tons/h

Bentonite content of charge 1,4 %: unloosened charge . . . . . . . . . . 9,9 18,4 1,32 18,4 71,1 7,6 3,9 loosened charge . . . . . . . . . . 9,8 18,3 1,30 11,9 77,4 6,4 3,7

Belgorod Branch of the "Mekhanobrchermet" Institute. Lebedin Mining and Concentration Combine. Translated from Metallurg, No. 12, pp. 12-13, December, 1983.

393 0026-0894/83/1112-0393507.50 �9 1984 Plenum Publishing Corporation

Ten comparison tests were conducted at a pe!letizer productivity of 80 and ii0 tons/h. In each test we took a representative sample of the raw pellets after pelletizing and deter- mined their moisture content, drop and compressive strengths, and granulometric compositon by standard methods (Table i).

The resulting data was analyzed statistically. The analysis showed that loosening the charge has almost no effect on the strength of the pellets obtained. As regards the granulo- metric composition of the raw pellets, we achieved a 5-6% improvement in their composition by the scarifying--and without an increase in bentonite consumption -- thanks to a reduction in the content of substandard +lS-mm fractions.

Thus, the study results confirm the need to loosen the charge immediately before it is charged into the pelletizer to increase the output of pellets of the standard size class. This measure is one of the reserves available for improving the granulometric composition of pellets.

UNIT FOR GUNITING THE MOUTH OF METALLURGICAL LADLES

M. I. Sharapov UDC 621.746.32:66.044.24

The units used in many shops to flame-gunite the lining of ladles contains a rotating-- lifting cantilever which supports a guniting lance that moves horizontally and vertically, a hood for covering the ladle, and a ladle rotation mechanism.

Shortcomings of such units include low productivity and their unsuitability for guniting ladles in a production line, as well as for guniting mixer-type ladles.

Another design of guniting unit consists of a platform with vertical guides, a carriage which runs in the guides, and a guniting lance attached to the carriage. This unit permits guniting of ladles in a production line, but the choice of the section of the inside surface to be gunited is made difficult by the distance of the observation platform from this surface and the need to position the lance nozzle opposite the section in question by successively actuating three lance translation drives. This lowers the productivity of the unit. Also, the guniting operation generates a great deal of dust, which makes working conditions un- healthy in the area of the unit.

To improve working conditions, increase labor productivity, and improve the quality of the guniting, the Magnitogorsk Metallurgical Combine developed and is successfully using a unit for guniting the mouth of metallurgical ladles [S. G. Dorman, T. B. Strakhova, V. N. Savochkin, et el., Inventor's Certificate No. 969452, Otkr., Izobr., Promyshl. Obr., Toy. Zn., No. 40, 48 (1982)].

The unit (Fig. i) consists of a movable platform 1 which supports vertical guides 2; horizontal annular guide 3; and vertical hood 4 equipped with rollers 5, hoisting mechanism 6, and rotation mechanism 7. The hood is flexibly joined with a ventillation duct 8. The side wall of the hood contains an opening 9. A hinge i0 fastens the guniting lance !i with its nozzle 12 to the opening. The lance is connected by flexible hoses 13 to a device 14 which feeds the gunite into the cavity of the ladle 15. The ladle is set on one of the stands 16 which are located along the path of the unit~

To control the lance, the unit is provided with stops 17, a hoisting platform 18 with an opening 19 protected by a thermally insulated jacket 20, and a mechanism 21 to raise and lower the platform. The ventilation duct is equipped with a movable flanged branch 22 which has a translation drive 23 and is situated so that it can connect with the stationary branches 24 of the ventilation system. These stationary branch pipes are located opposite each of the stands and are equipped with dampers 25 with a rotation mechanism 26. All of the stationary branches are connected to the ventilation system 27~

Magnitogorsk Metallurgical Combine. Translated from Metallurg, No. 12, pp. 13-14, December, 1983o

394 0026-0894/83/1112-0394507.50 �9 1984 Plenum Publishing Corporation