In recent years, the situation of light burnt magnesium powder steel industry is severe, the cost pressure before iron has increased sharply, and the quality of iron ore fines has been deteriorating. In order to stabilize the quality of sinter and further reduce the cost of ironmaking production, Shougang Jingtang Company has finally achieved natural magnesium sintering through a series of basic research. The sinter grade, strength, particle size, metallurgical properties and droplet properties have been improved and created. A considerable economic benefit.

Light burnt magnesium ball has obvious advantages in sintering magnesium

As the main charge of the blast furnace in the Asia-Pacific region, the sinter generally accounts for more than 60% of the blast furnace structure. Generally, a magnesium-containing flux such as dolomite or serpentine is added to the sintering batch to increase the MgO content in the blast furnace slag to improve the fluidity and desulfurization capacity of the slag, and to adapt to the high Al2O3 mass fraction in the slag.

Sintering is the main source of contribution to blast furnace slag MgO, and its MgO content is limited by blast furnace slag demand and blast furnace operating habits. The MgO content in the blast furnace slag of Japan and South Korea is controlled at a level of 3% to 5%, while in China, it is mostly above 7%. Affected by this, Japan's Nippon Steel, South Korea's Pohang Gwangyang and Hyundai Steel Sinter's MgO content is 0.7% to 1.2%; while domestic sinter's MgO content is mostly above 1.6%, high even at 3.0 %the above. Some researchers even believe that higher MgO content in sintering is beneficial to the quality of sintered ore.

In recent years, a large number of domestic light-burning magnesium ball sintering researchers have called for the burning of magnesium balls to reduce magnesium, and Shougang Jingtang has been at the forefront of practice. The project team carried out a series of sintering-down MgO laboratory research on the thermal equilibrium calculation of sintering process, the basic characteristics test of sintering and the in-situ observation of high temperature confocal, the study of mineral phase, the test of sintering cup and the performance test of integrated furnace droplets around Shougang Jingtang.

  The study found:

Magnesium reduction helps to improve the grade of sinter, contributes to the development of high-quality calcium ferrite, and improves the reduction of sinter. Decreasing 0.5% of MgO can increase the content of sinter TFe by more than 0.3%. Under the background of the deterioration of imported ore powder, magnesium adjustment shows the value of active sinter grade. The improvement of the grade of sinter will help to form more high-quality cement phase, acicular calcium ferrite, which is beneficial to the improvement of sinter index and reduction.

Magnesium reduction helps to reduce the heat consumption of the flux, thereby increasing the effective heat of sintering. The magnesium-containing flux decomposes heat during the sintering process, and reducing the proportion of the magnesium-containing flux helps to save energy and improve the quality of the sintered ore. The content of MgO in the sinter is reduced by 0.5%, the unit consumption of the magnesium-containing flux is reduced by 14kg/t, and the heat consumption of the decomposition process is reduced by about 1%, which is equivalent to the increase of the effective heat in the sintering process. %, which is beneficial to the improvement of the particle size composition of the sintered ore.

Magnesium reduction helps to improve the flowability of the sintering liquid phase and enhance the sintering bond effect. The sintering basic characteristics and high temperature confocal equipment test showed that the liquid phase fluidity index increased from 0.7 to 1.9 after the MgO content of the sintering mixture decreased from 2.3% to 0.3%. Compared with the MgO-containing scheme, the in-situ observation found no The MgO-containing solution has the highest liquid phase flow rate. The improvement of the fluidity of the sintering liquid phase enhances the bonding effect and is beneficial to the improvement of the grain size composition of the sintered ore.

Sintering magnesium reduction combined with pellets to improve magnesium, on the basis of ensuring the stability of the blast furnace slag system, improved the droplet performance of the integrated charge. The droplet performance test shows that the integrated charge structure is changed from sinter 1.9% MgO + pellets 0.7% MgO to sinter 1.5% MgO + pellets 1.7% MgO, the droplet interval is reduced from 64 ° C to 59 ° C, the maximum pressure difference From 1910 Pa to 1590 Pa, the S-characteristic value of the integrated charge was finally reduced from 122.2 kPa·°C to 93.8 kPa·°C.