ISSN 0967�0912, Steel in Translation, 2010, Vol. 40, No. 9, pp. 830–832. © Allerton Press, Inc., 2010.Original Russian Text © I.S. Vokhmyakova, S.I. Pokolenko, R.A. Poluyakhtov, G.G. Bardavelidze, S.N. Gushchin, 2010, published in “Stal’,” 2010, No. 9, pp. 30–31.

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The basic raw material for ferrous metallurgy inRussia is magnetite ore. With the exhaustion of mag�netite sources and increasing processing costs, oxi�dized (hematite) ore must also be put into produc�tion. Global experience with such ore—primarily inBrazil and India—cannot always be applied to Rus�sian deposits. In the present work, we study the pel�letization of such ore for the example of Belgorodore. The content of solid fuel in the pellet batch isspecified in accordance with the subsequent require�ments: 1–2% for blast�furnace smelting and 20–30% for direct iron production using the ITmk�3system.

We consider hematite ore of the following compo�sition: 68.1% Fe, 4.5% FeO, 1.28% SiO2, 0.58% CaO,0.5% MgO, 0.17% C, 0.052% P. Samples with the fol�lowing specific surface are investigated: 640 (baseline),1870, and 2050 cm2/g. The solid fuel employed is cokefines (specific surface 2580 cm2/g), containing 83%carbon, 16% ash, and ≤1% volatiles.

As binder and slag�forming additive, we use con�centrated sulfide–alcoholic mash and milk of lime, inquantities of 1, 3, and 5%. Additives of this type arechosen on account of their low cost.

To study pelletization, we prepare batch of differentcomposition. Their preparation for the experimentsinvolves dosing of the materials, mixing, and wetting,with subsequent pelletization in a tray�type granulator.After 3�min pelletization at constant rate, the materialis screened into size classes: >5 mm, 5–3.5 mm, 3.5–2 mm, 2–1.2 mm, and <1.2 mm (State StandardGOST 27562–87).

The ease of pelletization of the batch is character�ized by the weighted mean diameter

where dmei is the mean diameter of the granules in class i,mm; wj is the relative content of the class.

The baseline adopted is concentrate with the initialspecific surface (640 cm2/g), without the addition ofbinding solid fuel; it is pelletized and screened by size.On the basis of the results, the weighted mean diame�ter (d0) of the baseline granule is calculated, anddme.we/d0 is plotted as a function of various factors.

In Fig. 1, we plot dme.we/d0 as a function of the spe�cific surface of the concentrate. Analysis shows thatincreasing the specific surface to 1870 cm2/g increasesthe proportion of large particles, regardless of thequantity of solid fuel and the additives. However, fur�ther increase to 2050 cm2/g reduces dme.we/d0 from1.18 to 0.83; in other words, the ease of pelletization ofthe batch is reduced. Analogous behavior is observedfor all the batch considered, regardless of the additivesand the content of solid fuel.

The influence of the additives on pelletization isshown in Fig. 2, where dme.we/d0 is plotted as a functionof the quantity of the additive (concentrated sulfide–alcoholic mash or milk of lime). Analysis shows thatbinders and slag�forming additives in the batch favor�ably affect its pelletization as a whole, even with 30%solid fuel.

It is evident from Fig. 2 that, with increase in addi�tive to 3%, the curves rise; dme.we/d0 is within the samerange for batch intended for different processes. Fur�ther increase to 5% has different influence on the pel�

dme.we dmeiwj,

i j=

k

∑=

Pelletization of Hematite ConcentratesI. S. Vokhmyakovaa, S. I. Pokolenkoa, R. A. Poluyakhtova,

G. G. Bardavelidzea, and S. N. Gushchinb

aOOO NPVP TOREKS, Yekaterinburg, RussiabUral Federal University, Yekaterinburg, Russia

Abstract—The pelletization of hematite concentrates from the Belgorod deposit is considered. To obtaininformation on such pelletization, experiments are conducted with batch of different composition. The solid�fuel content is specified in accordance with the requirements of subsequent processing: for blast�furnacesmelting; or for direct iron production using the ITmk�3 system. The binders and slag�forming additives areconcentrated sulfide–alcoholic mash and milk of lime. By selecting the specific surface of the concentrateand the solid fuel, as well as the type and quantity of strengthening additive, optimal conditions may beselected for batch pelletization with a large quantity of solid fuel.

DOI: 10.3103/S0967091210090135

STEEL IN TRANSLATION Vol. 40 No. 9 2010

PELLETIZATION OF HEMATITE CONCENTRATES 831

letization: the ease of pelletization rises sharply insome cases and slightly in others. For blast�furnacebatch, 3–5% is optimal.

The maximum dme.we/d0 is observed for batch con�taining milk of lime. In that case, it is logical to assumethat a large quantity of moisture accounts for thehigher dme.we/d0 than for concentrated sulfide–alco�holic mash. (The residual moisture content after filtra�tion is 10%, and extra water is supplied with the milkof lime.) This tends to increase the adhesive strengthbetween the particles, which will ultimately affect theease of pelletization [1].

It is found that the quantity of solid fuel has littleinfluence on the ease of pelletization. With 3–5%binder (concentrated sulfide–alcoholic mash andmilk of lime), increasing the content of solid fuel (to2%) has little influence on the ease of pelletization,except in cases where the specific surface of the con�

centrate is 2050 cm2/g. We may assume that, since thisis close to the specific surface of coke fines, conditionsfor better adhesion of particles of different batch com�ponents and hence for pelletization are created [3].

In the pelletization of batch with 20 and 30% solidfuel, we find that increase in the content of coke finesreduces the ease of pelletization in the presence of 1and 5% concentrated sulfide–alcoholic mash. With3% binder (for all values of the concentrate’s specificsurface and all types of additives), boosting the solid�fuel content increases the ease of pelletization. This isevidently associated with the phase interactions in thesystem and requires additional study.

1.3

1.1

0.9

0.7

0.5

0.32100170013001100900700500

dme.we/d0

19001500

1.5

1.2

0.9

0.6

0.32100170013001100900700500 19001500

Specific surface, cm2/g

20%, 1%

30%, 1%

20%, 3%

30%, 3%

20%, 5%

30%, 5%

(a)

(b)

1%, 1%

2%, 1%

1%, 3%

2%, 3%

1%, 5%

2%, 5%

Fig. 1. Influence of the specific surface of the concentrateon batch pelletization: (a) for a blast furnace (with addi�tions of concentrated sulfide–alcoholic mash); (b) for theITmk�3 process (with added milk of lime); the first figureis the content of solid fuel, %; the second is the content ofthe additive, %.

Fig. 2. Influence of the quantity of additives on batch pel�letization: (a) for a blast furnace (with additions of concen�trated sulfide–alcoholic mash); (b) for the ITmk�3 process(with added milk of lime); S1, S2, S3 are values of the spe�cific surface for the concentrate—640 (baseline), 1870,and 2050 cm2/g, respectively; the second figure is the con�tent of solid fuel, %.

1.3

1.1

0.9

0.7

0.5

0.35.53.52.51.50.5

dme.we/d0

4.5

S1, 1%

S1, 2%

S2%, 1%

S2%, 2%

S3%, 1%

S3%, 2%

1.5

1.3

0.9

0.7

0.5

0.35.53.52.51.50.5 4.5

1.1

S1, 20%

S1, 30%

S2, 20%

S2, 30%

S3, 20%

S3, 30%

(a)

(b)

Quantity of binder, %

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VOKHMYAKOVA et al.

Thus, by selecting the specific surface of the con�centrate and the solid fuel and also the type and quan�tity of strengthening additive, we may select the opti�mal pelletization conditions for batch with a largecontent of solid fuel.

On the basis of the experimental data we concludethat optimal pelletization of Belgorod hematite con�centrate requires the following conditions.

(1) The specific surface of the hematite concen�trate must not exceed ~1900 cm2/g.

(2) The batch for pellets used in a blast furnacemust contain 3–5% of any specific additive; the

choice of binder depends on the requirements on theperformance and cost of the product.

(3) The content of solid fuel in the pellets for theITmk�3 process must be 30% (this is consistent withthe requirements of the process) with the addition of3% strengthening additives.

REFERENCES

1. Korotich, V.I., Osnovy teorii i tekhnologii podgotovkisyr’ya k domennoi plavke (Theoretical and Technologi�cal Principles in Preparing Raw Materials for Blast�Furnace Smelting), Moscow: Metallurgiya, 1978.