Effect of Trace Additions of K-4 Structuring Agent on the Pelletizing Process of Fine-Grained Iron Ore Concentrate
Abstract Generated abstract
This paper examines the use of trace additions of the K-4 structuring agent, a partially saponified polyacrylonitrile product, to improve pelletizing of fine-grained iron ore concentrate. The authors relate pellet strength to the correspondence between maximum molecular moisture capacity and working moisture content, then assess K-4 through moisture capacity measurements and laboratory disk granulation tests on Sokolovsko-Sarbaiskii magnetite concentrate with limestone and, for comparison, bentonite. The results indicate that K-4 increases pelletizability and moisture capacity, promotes coagulation structures that strengthen green pellets, and can produce favorable size distribution and drop strength at very low addition levels. The study concludes that K-4 is promising for integration into the dewatering and pelletizing cycle and may reduce or replace bentonite, warranting pilot industrial trials.
Full Text
Effect of Microadditives of the K-4 Structuring Agent on the Pelletizing Process of Fine-Grained Iron-Ore Concentrate
V. M. Vityugin, T. G. Leont’eva, A. N. Myasoedov, I. P. Chashchin
(Presented by the scientific seminar of the Department of OKhT)
Analysis of the process of pelletizing dispersed materials shows that, in order to ensure sufficient pellet strength, strict correspondence is required between the maximum molecular moisture capacity (MMC) of the dispersed material and the working moisture content of pelletizing. As a rule, under practical conditions of pelletizing iron-ore concentrates, the optimum moisture content of the burden exceeds the MMC value. Hence there arises the need either to reduce the initial moisture content of the concentrate by increasing the efficiency of dewatering, or to increase the moisture capacity of the burden being pelletized by means of special additives. From this point of view, the use of additives of special structuring agents, which make it possible to intensify the dewatering of concentrates and simultaneously increase the moisture capacity of the burden, proves to be extremely expedient.
In the present work, the effect on the pelletizing process of additions of the K-4 structuring agent was investigated; K-4 is a product of incomplete saponification of polyacrylonitrile in an alkaline medium.
In article [1] of the present collection, the expediency of using K-4 for dewatering iron-ore concentrates is shown. Special investigations have established that the main mass of K-4 is sorbed by the concentrate and thus passes into the pelletizing process.
A preliminary assessment of the effect of K-4 on the pelletizing process of iron-ore concentrate is well illustrated by the data in Table 1. The assessment was carried out according to a method developed at the Department of ob-
Table 1
Effect of K-4 on the pelletizability of concentrates and burdens
| No. | Burden composition | MMC, % | WM, % | \(K=\dfrac{\mathrm{MMC}}{\mathrm{WM}-\mathrm{MMC}}\) |
|---|---|---|---|---|
| 1 | CCK | 5.8 | 16.0 | 0.57 |
| 2 | CCK + limestone | 6.0 | 16.0 | 0.60 |
| 3 | CCK + limestone + K-4 | 6.4 | 16.0 | 0.67 |
| 4 | CCK + limestone + bentonite | 6.5 | 16.0 | 0.69 |
| 5 | CCK + limestone + bentonite + K-4 | 6.9 | 16.0 | 0.76 |
Table 2
| No. | Charge composition, % | Moisture content of green granules, % | Size, mm | Amount, % | Porosity, % | Crushing strength of green granules, kg per pellet | Number of drops from a height of 10 mm |
|---|---|---|---|---|---|---|---|
| 1 | SSK — 92.0 Limestone — 8.0 |
7.11 | 10 | 18.0 | 25 | 686 | 8 |
| 1 | SSK — 92.0 Limestone — 8.0 |
7.11 | 7–10 | 30.0 | 25 | 686 | 8 |
| 1 | SSK — 92.0 Limestone — 8.0 |
7.11 | 5–7 | 26 | 25 | 686 | 8 |
| 1 | SSK — 92.0 Limestone — 8.0 |
7.11 | 3–5 | 25.7 | 25 | 686 | 8 |
| 1 | SSK — 92.0 Limestone — 8.0 |
7.11 | 3–0 | 0.3 | 25 | 686 | 8 |
| 2 | SSK — 91.0 Bentonite — 1.0 Limestone — 8.0 |
8.86 | 10 | 50.0 | 26 | 760 | 9 |
| 2 | SSK — 91.0 Bentonite — 1.0 Limestone — 8.0 |
8.86 | 7–10 | 25.0 | 26 | 760 | 9 |
| 2 | SSK — 91.0 Bentonite — 1.0 Limestone — 8.0 |
8.86 | 5–7 | 16.3 | 26 | 760 | 9 |
| 2 | SSK — 91.0 Bentonite — 1.0 Limestone — 8.0 |
8.86 | 3–5 | 7.9 | 26 | 760 | 9 |
| 2 | SSK — 91.0 Bentonite — 1.0 Limestone — 8.0 |
8.86 | 3–0 | 0.3 | 26 | 760 | 9 |
| 3 | SSK — 91.99 K-4 — 0.01 Limestone — 8.0 |
9.2 | 10 | 70.5 | 30 | 740 | 11 |
| 3 | SSK — 91.99 K-4 — 0.01 Limestone — 8.0 |
9.2 | 7–10 | 27.8 | 30 | 740 | 11 |
| 3 | SSK — 91.99 K-4 — 0.01 Limestone — 8.0 |
9.2 | 5–7 | 0.7 | 30 | 740 | 11 |
| 3 | SSK — 91.99 K-4 — 0.01 Limestone — 8.0 |
9.2 | 3–0 | — | 30 | 740 | 11 |
[[unclear: end of preceding word]] Chemical Technology of the Tomsk Polytechnic Institute. The pelletizability \((K)\) was determined from the equation:
\[ K=\frac{\mathrm{MMB}}{\mathrm{MKB}-\mathrm{MMB}}, \tag{1} \]
where \(\mathrm{MMB}\) is the maximum molecular moisture capacity, %;
\(\mathrm{MKB}\) is the maximum capillary moisture capacity, %.
The pelletizability of the concentrate and of its mixtures with limestone and bentonite in the presence of K-4, as was to be expected, increases noticeably. As is known, [2] the addition of K-4 in an amount of 0.05–1.4 causes strong structure formation as a result of coagulation of the colloidal fractions.
The formation of coagulation structures arising under the action of molecular bonding forces between the colloidal and coarser solid particles of the iron-ore concentrate contributes to strengthening of the pellets. Along with high plasticity, the aggregative stability of the resulting coagulation structures is comparatively low, which has a positive effect on the dynamics of the pelletizing process.
For a more detailed assessment of the effect of K-4 on the pelletizing process of Sokolovsko-Sarbaiskii magnetite concentrate, laboratory pelletizing experiments were carried out on a disk granulator with a diameter of 1 m. The following materials were used for the studies: concentrate of Sokolovsko-Sarbaiskii ores, with a particle size of less than 0.1 mm and containing 67% iron; Azkamar bentonite, with a particle size of less than 0.1 mm; limestone from the Kzylzhar deposit, with a particle size of less than 0.5 mm. The experimental results are given in Table 2.
Analysis of the results of the study shows that the use of the K-4 structure-forming agent in the dewatering—pelletizing cycle is fully justified, and in this connection it is necessary to continue the studies at the pilot-industrial pelletizing plant of SSGOK in order to accelerate the introduction of these results into production. The introduction of the K-4 structure-forming agent into the pelletizing process will make it possible to remove ballast bentonite from this process.
REFERENCES
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V. M. Vityugin, S. A. Babenko, A. V. Voznyak. Intensification of the dewatering process of fine-grained iron-ore concentrates by means of microadditives of the K-4 structure-forming agent. The present collection.
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Colloid Chemistry of Palygorskite. Edited by Academician F. D. Ovcharenko, Kiev, 1963.