THERMAL STABILITY ANALYSIS OF IRON-ORE PELLETS PRODUCED USING THE TECHNOLOGY OF HEAT-SPRAYING OF WET CHARGE

The article presents the results of the study of thermal stability of wet iron-ore pellets obtained by heat-spraying technology of wet charge on charge pelletizer skull, as well as on the clumping off-grade pellets. The experiments involve the pellets obtained by the technology of nucle-
ation by spraying and additional clumping and the technology of nucleation, pelletizing and spraying. These pellets have structural heterogeneity on the moisture content. The former has the reduced moisture content in the center of the pellet; the second one has lower moisture content
in the coat of the formed pellets. It is established that the cracking temperature and shock fracture increase signifi cantly with the decrease of moisture content in the center (nucleation by spraying and additional clumping) and in the coat (the technology of nucleation, pelletizing and spraying) of pellets as compared with the conventional technology. It was found out that in case of equality of the total moisture content of the pellets obtained by the technology of nucleation by spraying and additional clumping and the technology of nucleation, pelletizing and spraying, their fracturing temperatures differ signifi cantly. The boundaries of the moisture ratio of the surface layer and the central part of the pellet, achieved by each of the offered technologies and affect directly the heat
resistance parameters are also different from each other. In particular, the structural heterogeneity of the pellets according to the moisture content at which a minimum amount of moisture is contained in the central area of the pellet (the technology of nucleation by spraying and additional
clumping), has the largest interval of the moisture ratio. For the pellets, obtained according to the technology of nucleation by spraying and additional clumping in the interval of the moisture ratio, it is possible to raise the cracking temperature at 240 °C compared to pellets formed according to the technology of nucleation, pelletizing (560 °C). The pellets, obtained according to the technology of nucleation, pelletizing and spraying, have the boundaries of the moisture ratio in the surface and
central parts, which are signifi cantly less. Within these boundaries the change in heat resistance according to the criterion of crack formation does not exceed 40 °C.

1. Bokovikov B.A., Klein V.I., Malkin V.M., Nevolin V.N., Soloukhin A.A., Yaroshenko Yu.G. The formation mechanism of the overwetting area in the drying zone of the burning conveyor machine. Stal’. 2003, no. 9, pp. 20–23. (In Russ.).

2. Isaev E.A., Chernetskaya I.E. To the approach of intensifi cation of iron-ore pellet production. Metally. 1997, no. 6, pp. 8–13. (In Russ.).

3. Yusfi n Yu.S., Kamenov A.D., Butkarev A.P. Upravlenie okuskovaniem zhelezorudnykh materialov [Control of agglomeration of iron-ore materials]. Moscow: Metallurgiya, 1990. 280 p. (In Russ.).

4. Yusfi n Yu.S., Pashkov N.F., Antonenko L.K. Intensifi katsiya proizvodstva i uluchshenie kachestva okatyshei [Intensifi cation of production and pellet quality improvement]. Moscow: Metallurgiya, 1994. 240 p. (In Russ.).

5. Maerchak Sh. Proizvodstvo okatyshei [Pellet production]. Moscow: Metallurgiya, 1982. 232 p. (In Russ.).

6. Sulimenko E.I. Proizvodstvo okatyshei [Pellet production]. Moscow: Metallurgiya, 1988. 128 p. (In Russ.).

7. Timofeeva V.S., Nikitchenko T.V., Fedina V.V. Analysis of thermal stability of pellets. Stal’. 2012, no. 12, pp. 12–14. (In Russ.).

8. Pavlovets V.M. Principals of forced nucleation in the idle zone of a palletizing disk. Izvestiya vuzov. Chernaya metallurgiya = Izvestiya – Ferrous Metallyrgy. 2009, no. 4, pp. 3–6. (In Russ.).

9. Pavlovets V.M. Comparison of methods of combined pellet obtaining by spraying charge with low-temperature compressed air jets. Izvestiya vuzov. Chernaya metallurgiya = Izvestiay – Ferrous Metallyrgy. 2005, no. 6, pp. 11–17. (In Russ.).

10. Pavlovets V.M. Sposob polucheniya okatyishei [Pellet process]. Patent RF no. 2402619 and 2464328. Byul. Izobretenii. 2010, no. 30 and 2012, no. 29. (In Russ.).