Study of the Influence of the Mineralogical Composition of Iron Ore Concentrates on the Pelletizing Process and the Quality of Roasted Pellets
Abstract Generated abstract
This study examines how the mineralogical composition of iron ore concentrates from the Sokolovskoye and Sarbaiskoye deposits affects pelletizing behavior and the quality of green and fired pellets. Laboratory drum pelletizing tests assessed concentrate properties, pelletizing coefficients, green pellet strength, drop resistance, and size, followed by firing trials at 1100 to 1300°C and oxidation measurements for selected Sarbai concentrates. The results indicate that differences in gangue content and mineral composition substantially influence pellet formation, green pellet quality, fired pellet strength, slag bond development, and oxidation behavior. Higher gangue contents were associated with changes in iron content and a lower measured degree of oxidation under the tested conditions.
Full Text
STUDY OF THE INFLUENCE OF THE MINERALOGICAL COMPOSITION OF IRON ORE CONCENTRATES ON THE PELLETIZING PROCESS AND THE QUALITY OF FIRED PELLETS
N. I. Biryukova, V. M. Vitogin, L. S. Grabko
(Submitted by the scientific seminar of the Department of GCT)
In the initial period of mastering the technology for producing green pellets at the SSGOK pelletizing plant, it was considered that the determining parameters of the pelletizing process and of the quality of green pellets were the coarseness and moisture content of the concentrate. Upon a more thorough study of the causes of disturbances in the pelletizing technology, it was observed that concentrates having different mineralogical compositions pelletize differently. Under laboratory conditions, several varieties of iron ore concentrates obtained from three types of ore from the Sokolovskoye deposit and four types of ore from the Sarbaiskoye deposits were investigated. Table 1 gives the mineralogical composition of these concentrates. In studying the quality of the concentrate, the pelletizing coefficient, granulometric composition, and specific surface area were determined.
Pelletizing of the concentrates was carried out in a laboratory batch drum pelletizer. The quality of the green granules was assessed by their crushing strength, resistance to dropping from a height of 300 mm, and the coarseness of the granules obtained. The results of the experiment are given in Table 2.
As can be seen from the results presented, the mineralogical composition of the concentrate has a substantial influence on the pelletizing process and on the quality of green pellets. The pelletizing coefficient, strength, and size of the pellets depend on the qualitative and quantitative ratio of gangue constituents in the concentrate.
In addition, firing of green pellets was carried out at temperatures of 1100, 1200, 1275, and 1300°C for 10 minutes. The strength of the fired pellets also depends on the amount of gangue in the concentrate, thus
Table 1
Mineralogical composition of concentrates
| Mineralogical constituents | Sarbaiskoye deposit, grade I | Sarbaiskoye deposit, grade II | Sarbaiskoye deposit, grade 1U | Sarbaiskoye deposit, grade U | Sokolovskoye deposit, amphibole | Sokolovskoye deposit, sokolovite vein | Sokolovskoye deposit, epidote |
|---|---|---|---|---|---|---|---|
| Magnetite | 80.0 | 93.9 | 92.0 | 81.9 | 93.3 | 93.0 | 83.5 |
| Pyrite | 1.15 | 0.07 | 0.90 | 0.80 | 0.11 | 0.09 | 0.40 |
| Hematite | 0.20 | 3.10 | 1.00 | 8.40 | 3.00 | 4.70 | 3.90 |
| Non-ore | 18.50 | 3.00 | 6.10 | 8.70 | 3.50 | 2.20 | 12.20 |
| Predominant among those presented | pyroxene | garnets | epidote, pyroxene | epidote | pyroxene, amphibole | chlorite | epidote, pyroxene |
Table 2
Quality of concentrates and green pellets
| Indicators | Sarbai deposit, ore varieties I | Sarbai deposit, ore varieties II | Sarbai deposit, ore varieties IV | Sarbai deposit, ore varieties V | Sokolov deposit, ore varieties amphibole | Sokolov deposit, ore varieties skarn-vein | Sokolov deposit, ore varieties epidote |
|---|---|---|---|---|---|---|---|
| Content of the −0.074 mm size class, % | 98.12 | 97.50 | 98.15 | 97.70 | 97.40 | 98.80 | 97.93 |
| Specific surface, cm²/g | 1305 | 1410 | 1215 | 1100 | 1045 | 1380 | 1050 |
| MV, % | 9.3 | 8.3 | 8.5 | 7.5 | 6.5 | 7.8 | 7.2 |
| KV, % | 22.0 | 21.0 | 21.5 | 21.1 | 18.1 | 18.9 | 19.0 |
| K | 0.720 | 0.653 | 0.650 | 0.550 | 0.550 | 0.700 | 0.605 |
| Strength, kg/pellet | 0.878 | 0.855 | 0.878 | 0.802 | 0.818 | 1.058 | 0.833 |
| Number of drops | 2.8 | 2.6 | 3.2 | 2.3 | 3.0 | 3.6 | 2.0 |
| Mean diameter, mm | 12.2 | 12.0 | 11.0 | 14.6 | 12.3 | 10.2 | 15.6 |
as they determine the amount and intensity of formation of the slag bond—one of the types of strengthening bonds in fired pellets (Table 3).
With an increase in the gangue content in concentrates, the iron content decreases; therefore, the degree of oxidation of pellets obtained from these concentrates will be different.
The degree of oxidation of pellets from Sarbai concentrates was studied by the change in weight on a continuous-weighing unit at a temperature of \(1000^\circ\mathrm{C}\) and an air flow rate of 10 l/min. The results obtained show that, with an increase in the gangue content from 6.1 to 13.5%, the degree of oxidation decreases from 1.75 to 1.29%.
Table 3
Strength of fired pellets as a function of gangue content in the concentrate, kg/pellet
| Firing temperature, °C | Sarbai deposit, variety I | Sarbai deposit, variety V | Sarbai deposit, variety IV | Sarbai deposit, variety II | Sokolov deposit, sk-pr. | Sokolov deposit, amphibol. | Sokolov deposit, epidot. |
|---|---|---|---|---|---|---|---|
| Gangue content, % | 18.5 | 8.7 | 6.1 | 3.0 | 2.2 | 3.5 | 12.2 |
| 1100 | 55 | 45 | 56 | 62 | 98 | 77 | 63 |
| 1200 | 102 | 88 | 95 | 87 | 121 | 98 | 89 |
| 1275 | 130 | 166 | 200 | 150 | 191 | 191 | 249 |
| 1300 | 420 | 340 | 295 | 349 | 316 | 223 | 326 |