our country Light burned magnesium powder In recent years, the situation of light burned magnesium powder iron and steel industry is severe, the cost pressure before iron production increases sharply, and the quality of iron ore powder continues to deteriorate. In order to stabilize the sinter quality and further reduce the ironmaking production cost, Jingtang Company of Shougang has finally realized natural magnesium sintering through a series of basic research, and the sinter grade, strength, particle size, metallurgical performance and droplet performance have been improved, creating considerable economic benefits.
Light burned magnesium ball Obvious advantages of magnesium reduction in sintering
As the main burden of blast furnace in Asia Pacific region, sinter generally accounts for more than 60% of blast furnace structure. Usually, magnesium containing fluxes such as dolomite and serpentine are added in the sintering burden to increase the MgO content in the blast furnace slag, so as to improve the fluidity and desulfurization capacity of the slag and adapt to the high Al2O3 mass fraction in the slag.
Sintering is the main source of MgO contribution to blast furnace slag, and its MgO content is limited by blast furnace slag demand and blast furnace operation habits. The MgO content in blast furnace slag in Japan and South Korea is controlled at 3%~5%, while that in China is mostly above 7%. Under this influence, the MgO content of sinters from Nippon Steel (Japan), Pohang Guangyang (South Korea) and Hyundai Iron Making Co., Ltd. is 0.7%~1.2%; However, the MgO content of domestic sinters is mostly more than 1.6%, even more than 3.0%. Some researchers even believe that higher MgO content in sintering is beneficial to the improvement of sinter quality.
In recent years, a large number of domestic researchers on light fired magnesium ball sintering have called for magnesium reduction in light fired magnesium ball sintering, and Shougang Jingtang has taken the lead in practice. The project team has carried out a series of laboratory studies on reducing MgO in sintering around Shougang Jingtang on the calculation of heat balance in sintering process, testing of basic sintering characteristics, in-situ observation of high temperature confocal, mineralogy research, sintering cup test, and comprehensive furnace charge droplet performance test.
Research findings:
Reducing magnesium is helpful to improve sinter grade, develop high-quality calcium ferrite and improve sinter reducibility. Reducing 0.5% MgO can increase the TFe content of sinter by more than 0.3%; In the context of the deterioration of imported ore fines, magnesium regulation shows the value of actively maintaining sinter grade. The increase of sinter grade is conducive to the formation of more high-quality bonding phase - acicular calcium ferrite, which is beneficial to the improvement of sinter index and reducibility.
Reducing magnesium is helpful to reduce heat consumption of flux, thus increasing effective heat of sintering. The decomposition heat consumption of magnesium containing flux in the sintering process, and reducing the ratio of magnesium containing flux will help to save energy and improve the quality of sinter. The MgO content of sinter is reduced by 0.5%, the unit consumption of magnesium containing flux is reduced by 14kg/t sinter, and the decomposition heat consumption in the sintering process is reduced by about 1%, which is equivalent to that the effective heat in the sintering process is increased by 1% when the sintering heat loss is certain, which is conducive to the improvement of sinter particle size composition.
Reducing magnesium is helpful to improve the fluidity of sintering liquid phase and enhance the sintering bonding effect. The test results of basic sintering characteristics and high-temperature confocal equipment show that the liquid-phase fluidity index increases from 0.7 to 1.9 when the MgO content of sintering mixture decreases from 2.3% to 0.3%; Compared with the scheme containing MgO, the scheme without MgO has the highest liquid flow velocity by in-situ observation. The improvement of the fluidity of the sintering liquid phase enhances the bonding effect and is beneficial to the improvement of the sinter particle size composition.
The dropping of magnesium in sintering and the increasing of magnesium in pellet can improve the molten drop performance of comprehensive burden on the basis of ensuring the stability of blast furnace slag system. The molten drop performance test shows that after the comprehensive charge structure changes from 1.9% MgO+pellet 0.7% MgO to 1.5% MgO+pellet 1.7% MgO, the molten drop range decreases from 64 ℃ to 59 ℃, and the maximum pressure difference decreases from 1910 Pa to 1590 Pa, ultimately reducing the S characteristic value of the comprehensive charge from 122.2 kPa · ℃ to 93.8 kPa · ℃.
