Development of Heated Ore Addition Technology Using Burner in Chromium Ore Smelting Reduction Converter

Abstract

In order to increase the heat efficiency of the chromium ore smelting reduction furnace, a heated ore addition technology using a burner in the converter was developed. 5 ton scale pilot converter tests were conducted. Based on the results of the pilot converter tests, this technology has been applied to the actual process. The results are summarized as follows:1) Compared with the conventional process (without burner), the amount of effective heat transfer increased by 18% with addition of heated ore using the burner in 5 ton converter.2) A decrease in the off-gas temperature and reduction of the thermal load on the refractory were also confirmed in 5 ton converter.3) The heat transfer ratio of burner combustion with addition of heated ore increased up to about 90%, depending on the increase of the ore feeding rate in 5 ton converter. 4) From the results of a numerical simulation, it was revealed that the total sensible heat of all particles increases as the ore feeding rate increases. As a result, the ore particles heated by the flame function as a medium of heat transfer from the flame to the molten metal and slag.5) This technology was applied to an actual smelting reduction furnace at JFE Steel East Japan Works (Chiba). As in the tests with 5 ton converter, the heat transfer ratio of burner combustion with addition of heated ore was about 90%. The supplied energy per unit of chromium ore added to the furnace decreased by 17%.

History and latest trends in converter practice for steelmaking in Japan

“…Therefore, to reduce the consumption of carbonaceous material used as a heat source and realise an energy-saving process, development of technology by utilising burner combustion heat as a new and efficient heat source was carried out. In this new technology, all the chromium ore, which is a powdery raw material, is heated through the burner flame and fed to the converter (Okuyama et al 2015).…”

“…This burner lance has a structure that makes it possible to feed chromium ore from the centre hole while feeding the propane-gas fuel and combustion-improving oxygen from the nozzle surrounding the centre hole. Figure 9 (Okuyama et al 2015) shows the relationship between the ratio of the feeding rate of heated ore to the burner calorific power and the efficiency of the heat transfer of burner combustion heat in the 5-t converter for experiments and 185-t actual converter. The amount of effective heat transfer increased along with an increase in the heated chromium ore feeding rate.…”

“…This result confirmed that the heated ore particles function as a medium of heat transfer for the burner combustion heat, and as a result, it is possible to efficiently transfer the burner combustion heat to the region where the chromium ore reduction reaction occurs by heating and feeding chromium ore to the converter through the burner flame. Figure 10 (Okuyama et al 2015) shows the relationship between the amount of chromium ore and the supplied thermal energy before and after the introduction of the burner lance for feeding heated chromium ore into the actual converter. The supplied thermal energy is the total of the energy of the decarburisation reaction and post-combustion by topand bottom-blown oxygen, and the burner combustion heat when the burner is used.…”

“…In this new technology, all the chromium ore, which is a powdery raw material, is heated through the burner flame and fed to the converter (Okuyama et al. 2015).…”

“…Figure9. Relationship between the ratio of the feeding rate of heated ore/burner calorific power and the efficiency of heat transfer of burner combustion heat byOkuyama et al (2015), used with permission.…”