Effect of Preliminary Vibration Treatment on the Agglomeration of Iron Ore Concentrates
Abstract Generated abstract
This study examines whether preliminary vibration treatment can improve preparation of fine iron ore concentrates for sintering by enhancing pelletizing and bed permeability. Laboratory cup sintering tests compared conventional drum pelletizing with a sequence in which moistened charge mixtures received vibration treatment at 100 Hz and 0.6 mm amplitude for one minute before drum pelletizing, using burdens with 10 to 40 percent return. The vibration treatment increased bulk density, raised sintering rates and maximum temperatures, reduced average vacuum, and modestly increased the yield of usable agglomerate. Its relative effect was strongest at lower return contents, since higher return levels already improved granulation and gas permeability.
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PROCEEDINGS
OF THE TOMSK ORDER OF THE OCTOBER REVOLUTION
AND ORDER OF THE RED BANNER OF LABOR
POLYTECHNIC INSTITUTE named after S. M. KIROV
Vol. 234 1974
EFFECT OF PRELIMINARY VIBRATION TREATMENT
ON THE AGGLOMERATION OF IRON-ORE CONCENTRATES
V. L. TROFIMOV, V. M. VITYUGIN
(Presented by the scientific seminar of the Department of General Chemical Technology)
Solving the problem of intensifying the sintering of fine iron-ore concentrates of deep beneficiation while maintaining the level is one of the main tasks of modern agglomerate production. The agglomeration process can be successful only with intensive admission of air into the combustion zone. A layer of loose material can acquire high gas permeability only provided that all fine and finest particles are converted into aggregate granules. This problem is solved most successfully by moistening and subsequent pelletizing of the agglomeration charge. However, the pelletizing process, owing to the nonuniform size composition of the charge and the short pelletizing time, proves insufficiently effective. In this connection, improvement of the pelletizing cycle in the general scheme of preparing charge materials for agglomeration becomes especially important.
Earlier we reported [1] that preliminary vibration treatment substantially intensifies the process of pelletizing iron-ore concentrates. Taking this into account, we carried out laboratory studies to determine this effect in the process of preparing the charge for agglomeration. The work was performed on a laboratory agglomeration unit (a cup 90 mm in diameter and 370 mm high) using two methods of preparing the charge materials. In the first method, after mixing, the charge was subjected to vibration treatment on the plane of an electromagnetic stand at a frequency of 100 Hz and an amplitude of 0.6 mm for 1 min. After this, the sample was pelletized in a drum mixer for 2 min, followed by loading into the sinter cup. According to the second scheme, the initial charge, after moistening and mixing, was pelletized in the drum for 2 min and then loaded into the sinter cup. Four types of charges were investigated, containing 10, 20, 30, and 40% return. To prepare the charges, the following were taken: Sokolovsko-Sarbaiskii deep-beneficiation iron-ore concentrate, limestone of 3–0 mm size, and coke of 3–0 mm size. The return was prepared in advance. In all cases, preliminary vibration treatment promoted an increase in bulk weight in comparison with the untreated charge. Moreover, this increase was more noticeable in the charge with a lower return content. In both cases the charge was loaded into the sinter cup in a 300 mm layer. After ignition, the exhauster was switched on. At time intervals of 1 min, readings were taken of the temperature of the air being drawn off beneath the charge layer, the total vacuum under the layer, and the conditional velocity of the air being drawn through. The end of sintering was determined by a sharp drop in temperature and a decrease in the vacuum of the system. After the cup had cooled, the yield of usable agglomerate (+10 mm) was determined during discharge—
when dropping the sintered product from a height of 1 m onto a cast-iron plate, the sintering rate in mm/min, and also the average vacuum over 1 min. The results are presented in Table 1.
As can be seen from the table, preliminary vibration treatment of the burden markedly intensifies the sintering process of fine-grained iron-ore
Table 1
Sintering-process indices
| Amount of return in the burden, % | Sintering in a drum: sintering rate, mm/min | Sintering in a drum: average furnace vacuum, mm water column | Sintering in a drum: maximum temperature, °C | Sintering in a drum: yield of suitable agglomerate, % | Preliminary vibration treatment: sintering rate, mm/min | Preliminary vibration treatment: average furnace vacuum, mm water column | Preliminary vibration treatment: maximum temperature, °C | Preliminary vibration treatment: yield of suitable agglomerate, % |
|---|---|---|---|---|---|---|---|---|
| 10 | 12 | 1480 | 220 | 41.5 | 14.5 | 1340 | 340 | 49 |
| 20 | 14.3 | 1395 | 320 | 50 | 16.6 | 1310 | 380 | 56 |
| 30 | 16.5 | 1300 | 380 | 57 | 17.1 | 1250 | 400 | 59 |
| 40 | 17.2 | 1240 | 395 | 60.5 | 18 | 1190 | 420 | 63.5 |
concentrates. As the content of return in the burden increases, the effectiveness of vibration treatment decreases, since the presence of a larger amount of return in the burden already by itself substantially improves the aggregate properties of the burden and increases the gas permeability of the bed. Owing to the more intensive course of the sintering process, the yield of suitable agglomerate increases somewhat.
REFERENCES
- V. A. Trofimov, V. M. Vityugin, M. P. Talkhaev. Influence of preliminary vibration treatment on the pelletizing of iron-ore concentrates. Izv. VUZov, Chernaya metallurgiya, No. 6, 1968.