SU45304A1 - The method of obtaining sponge iron from ore by direct reduction - Google Patents

Description

It is known to obtain sponge iron from ore by direct reduction in three main ways, namely: by gas, in which the reducing agent is exclusively gas; the method of reducing with solid carbon, in which finely crushed ore is mixed with solid fuel and then heated to a temperature at which iron is reduced, and, finally, in a combined way in which recovery is achieved by mixing ore with fuel and passing some amounts of reducing gases.

The main advantages of the gas method are, firstly, the possibility of obtaining a high-quality product of coal free from harmful impurities, and, secondly, a high recovery rate in the case of the use of a high-purity reducing gas. The disadvantages of this method are the difficulty of obtaining a high-purity reducing gas, i.e. its minimum amount of water vapor and carbon dioxide (it is desirable to have gas and with a minimum nitrogen content), as well as the need to pass very large amounts of reducing gas through this mass of ore. . Therefore, for rational use of gas, it is necessary to continuously regenerate it in the gas generator and reuse it for recovery, i.e. it is necessary to produce a continuous circulation of gas from the furnace for reduction to the gas generator and back. The latter circumstance complicates the cost of equipment and leads to heat loss, resulting in very large additional costs, which increase the cost of sponge iron. The disadvantage of this method is the difficulty in providing conditions for a good homogeneous contact of reducing gases with a mass of porosha forgings, Y 45304-2. Obtaining sponge iron by reducing solid carbon 1 has the advantage of considerable simplicity of design, compared to other methods. But this method has to deal with metal contamination with sulfur, phosphorus and other harmful impurities. Therefore, high-quality metal molno receive only with pure starting materials. Impurities in fuels are especially undesirable, since they must be taken in a large excess of 50-80% by weight of ore versus a theoretical amount of the order of 20%. Moreover, a low reduction rate necessitates the use of high temperatures, approximately not less than 1000 °. Due to the poor heat transfer of the charge, the latter is difficult to heat to the required high temperature.

With the combined method, the gas volume of the reducing agent is reduced compared to the gas method, and the amount of coal or coke mixed with the ore is reduced, as compared with the second method, but here we also have to deal with large volumes of lawn. In addition, sponge iron is contaminated with sulfur, phosphorus, carbon particles from the mixed fuel. The reduction rate of this method is less than with pure gas reduction under the same temperature conditions.

The proposed method of obtaining ocyu sponge iron ectc sponge iron in two stages: the first stage is the impregnation of ore with carbon released by the Bell reaction in the temperature range of 400-600 ° C, where Bell's reaction is most developed, and the amount of released carbon should be sufficient for the subsequent stage - recovery. The second stage is the restoration of prch 900-1000 ° due to the liberated carbon in the first stage. The gas with a high content of carbon monoxide in this stage can be used in the first stage of the process. Due to the fact that the carbon released in the first stage is in a highly dispersed state, it possesses great reactivity and reacts quickly with CO2, therefore the content of carbon monoxide in the gas phase will be close to equilibrium with respect to the CO2 + 2CO reaction in the second stage. . Since carbon in the first stage is released not only on the surface, but also inside the ore, the latter is destroyed, crushed and made highly porous.

Special experiments of the author have shown that due to the highly reacted. of the precipitated carbon, the close mixing of the latter with the oxide, the crushing of the ore and the created porosity of the ore, the iron oxides are very rapidly reduced in the second stage of the process to metallic iron.

The proposed method of obtaining sponge iron, as compared with the pure gas method, allows one to obtain a high quality product free from harmful impurities of coal. In addition, the proposed method, compared with pure gas recovery, eliminates the need to use gas of high purity, replacing it with a conventional generator gas obtained from low-grade fuel. In this case, the gas flow rate is lower. With the new method 1az, it is necessary to skip only in the first stage of the process, in which the reduction of iron oxide occurs to approximately 15-20% relative to the amount of oxygen removed. The reaction to such a low recovery rate proceeds without difficulty even at low temperatures, the main task of the first stage of the process is to release carbon by the Bell reaction. The latter reaction proceeds rapidly under the influence of a negligible amount of catalysts, which spontaneously are obtained simultaneously with the reduction, and

Bell's reaction proceeds with great gas utilization. According to the author’s calculations, at about 60T) ° about 86% of carbon monoxide can decompose, while at lower temperatures, the percentage of decomposition is much higher (for example, at 500 ° above 95%) The presence of hydrogen in the reducing gas does not reduce the intensity of carbon deposition by Bell's reaction, and even it increases, as the author claims, on the basis of experiments on the reduction of iron oxides with a mixture of CO with different hydrogen content. Therefore, the presence of hydrogen in the gas is desirable.

An excess of carbon, remaining, in the sponge gland, can be easily removed by blowing cold air or by magnetic separation.

Of the further advantages of the proposed method, compared with the gas method, it is necessary to note the simplicity in the design, since there is no need for complex regeneration of the circulating gas associated with large heat losses.

Subject invention

The method of obtaining sponge iron from ore by direct reduction of iron oxides with carbon monoxide, characterized in that the ore is first exposed to a reducing gas in the furnace at a temperature of 400-600 °, in order to impregnate the ore with black carbon, after which the processed ore in another furnace or in the same furnace, but stopping the supply of reducing gas, is heated to 900-1000 °, in order to reduce iron oxides solely due to the solid coal emitted in the first stage of the process, and The carbon monoxide is directed to the first furnace for use.

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