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Light burned magnesium powder can reduce magnesium by sintering, and the benefit is more beautiful

2019-07-18
Times

In recent years, the situation of light burned magnesium powder iron and steel industry is severe, the cost pressure before iron is increasing sharply, and the quality of iron ore powder is deteriorating. In order to stabilize sinter quality and further reduce ironmaking production cost, Jingtang company of Shougang finally realized natural magnesium sintering through a series of basic research, which improved sinter grade, strength, particle size, metallurgical properties and droplet properties, and created considerable economic benefits.


The advantages of reducing magnesium by sintering light burned magnesium balls are obvious


As the main burden of blast furnace in Asia Pacific region, sinter generally accounts for more than 60% of blast furnace structure. Magnesium containing fluxes such as dolomite and serpentine are usually added to the sintering ingredients to improve the MgO content in blast furnace slag, so as to improve the fluidity and desulfurization capacity of slag and adapt to the high Al2O3 mass fraction in 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 the level of 3% ~ 5%, while most of them in China are more than 7%. Affected by this, the MgO content of sinters from Nippon Steel in Japan, Pohang Guangyang in South Korea and modern iron making is at the level of 0.7% ~ 1.2%; The MgO content of domestic sinters is mostly more than 1.6%, and even more than 3.0%. Some researchers even believe that higher MgO content in sintering is conducive to the improvement of sinter quality.


In recent years, a large number of domestic researchers of light burned magnesium ball sintering have called for the reduction of magnesium by light burned magnesium ball sintering, and Shougang Jingtang is in the forefront of practice. The project team carried out a series of sintering MgO reduction laboratory studies around Jingtang of Shougang, including heat balance calculation of sintering process, basic sintering characteristic test, high temperature confocal in-situ observation, ore phase research, sintering cup test and comprehensive burden droplet performance test.


Light burned magnesia powder


Research findings:


Reducing magnesium is helpful to improve the grade of sinter, develop high-quality calcium ferrite and improve the reducibility of sinter. Reducing 0.5% MgO can increase the TFE content of sinter by more than 0.3%; Under the background of the deterioration of imported ore powder, adjusting magnesium shows the value of actively maintaining sinter grade. The improvement of sinter grade is helpful to form more high-quality binder - acicular calcium ferrite, which is beneficial to the improvement of Sinter Index and reducibility.


Magnesium reduction helps to reduce the heat consumption of flux and increase the effective heat of sintering. The decomposition heat consumption of magnesium containing flux in the sintering process and reducing the ratio of magnesium containing flux are helpful 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 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 basic characteristics of sintering and the test of high temperature confocal equipment show that the liquid phase fluidity index increases from 0.7 to 1.9 after the MgO content of sintering mixture is reduced from 2.3% to 0.3%; In situ observation showed that the scheme without MgO had the highest liquid phase flow velocity compared with the scheme with MgO. The improvement of sintering liquid phase fluidity enhances the bonding effect and is conducive to the improvement of sinter particle size composition.


Sintering magnesium reduction combined with pellet magnesium extraction can improve the droplet properties of comprehensive burden on the basis of ensuring the stability of blast furnace slag system. The droplet performance test shows that after the comprehensive charge structure changes from sinter 1.9% MgO + pellet 0.7% MgO to sinter 1.5% MgO + pellet 1.7% MgO, the droplet interval decreases from 64 ℃ to 59 ℃, the maximum differential pressure decreases from 1910pa to 1590pa, and finally the s characteristic value of the comprehensive charge decreases from 122.2kpa ·℃ to 93.8kpa · ℃.


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