SU1011695A1 - Process for producing iron sponge - Google Patents

Description

Ed

: o: l The invention relates to ferrous metallurgy, and that is, to methods of lhcheni sponge iron. There is a known method for reducing iron ore materials, in which a solid reducing agent in an amount is loaded into the tube furnace together with the pellets; providing iron recovery to 1-5%, then in the middle part of the furnace, the pellets are reduced by hydrocarbon gas, after which they are reduced to 90-98% by solid fuel at 10501150 С p ... The disadvantage of this method is the low productivity, due to the oxidized calcined pellets recovered in a tube furnace do not have a reducing agent inside, and at temperatures of 1050–1150 ° C the rate of reduction by solid carbon is very low. The closest to the invention to the technical essence and the achieved result is a method of obtaining sponge iron from ore-coal okatiyu on a conveyor machine, including drying, heating, reduction and cooling. According to this method, neutral gases with a temperature of 150–315 ° C are passed through and then the pellets are heated to 538–1093 s. passes are hot, not entering into the reaction, gases containing not more than 15% by weight of oxygen. Next, the mixture is heated to a temperature of not more than (1315 ° C and metallized, passing the same gas through it. Heating is carried out for a time sufficient to recover 60-90% of chemically bound iron 2. However, in this known method, the productivity and quality are low. , pellets, since the use of only carbon as a reducing agent requires a considerable consumption of carbon, which prevents the formation of pellets of high strength — and also brings with it ash and harmful impurities, in particular sulfur. lowers the production of unregulated heating, which leads to the appearance of large quantities of the liquid phase, the structure of the layer is destroyed, and, consequently, the gas permeability decreases, the purpose of the invention is to increase productivity and reduce gas consumption by increasing the process speed. According to the method of obtaining sponge iron from the ore-angled pellets of the necks on the conveyor machine, which includes drying, heating, regeneration and cooling), complex formation is first carried out Peroral 900-1150C hydrocarbon gases with a ratio of reducing agents to oxidants 18-20 and heating rates of 20-50. hail / min, and then solid carbon charge at a heating rate of 40–60 deg / min to temperatures of 1150–1350 with furnace gases with a ratio of reducing agents to oxidizers of 3-4. The essence of the method is that for different intervals of the themes. The mixtures provide an optimal ratio between indirect (gas reduction) and direct (directly solid carbon) reduction reactions. It is known that the gas reduction process has both advantages and disadvantages. The advantages include a higher initial (to the extent of 50-60%) recovery rate at relatively low temperatures. However, as the reaction products (metallic iron) increase, the reduction process is sharply slowed down, and no less (if not more) energy is required to restore the remaining blocked oxides (20-30%) and the reducing agent. Raising the temperature to higher values is not possible because of the formation of a liquid phase, which generally blocks the access of the reducing agent to the inside of the sample, and the reduction process is practically stopped. Another practically major disadvantage of gas reduction (as low-temperature) is that the resulting iron is very pyrophoric and ignites at room temperature on air. i The process of reducing the ore-coal pellets with a solid reducing agent has the disadvantages that at low temperatures (up to 11001150s) there is practically no process and that ash and sulfur applied by the fuel to the pellets deteriorate the quality of the metal produced. The advantage of this process is its high speed at 1150-1350 ° C because of the uniform distribution of the solid reducing agent in the volume of the pellet and its participation in the process of restoring the liquid phase. The invention attempts to combine both processes into one, removing or significantly weakening the shortcomings of each separately. Recovery by this method is carried out in two stages. At the first stage, in the temperature range of 900-1150C, at the rate of heating with an ore-angled pellet of 20-50 degrees / min, the oatcladium is reduced by gas with a maximum content of reducing agents, the ratio CO + H, j - K; a2., In which is 18-20. (CO + H2 content is more than 94%). Due to the fact that the material is not sintered at this stage, it possesses sufficient porosity and is readily available for gas molecules penetrating deep into it. The recovery process takes place in the kinetic region and its speed depends on the gas composition and temperature. The reduction by solid carbon at their temperatures proceeds according to the Voikov scheme with insignificant rates, since the rate of carbon gasification is insignificant. As the temperature rises, the fraction of indirect and recovery changes. When a liquid oxide phase is formed. It is established that this phase, depending on the conditions (charge composition, basicity and heating mode), participates in the reduction process. Moreover, the recovery of the liquid phase proceeds at considerably higher rates than the recovery in the solid state. This is explained by the fact that, under certain thermal conditions (temperatures above), the reduction mechanism changes — along with the Baikov scheme, the scheme for reducing the iron oxides directly to the carbon in the melt comes into play. Therefore, at temperatures above IISOC. It is advisable to create a neutral atmosphere with respect to the metallized pellets, which corresponds to the ratio .O

3-4, and the iron reduction from oxides is expediently carried out directly by solid carbon of the pellets. The method allows process management.

at maximum speeds when using gas at the first stage as a reducing agent and re-using it (at the second stage) as a heat carrier, after burning it in the following burners in the direction of the machine. Thus, the full use of both the reduction potential and the chemical energy of the gas in one unit is achieved, which significantly reduces its consumption. The use of carbon for the reduction of only part of the iron oxide can significantly reduce its consumption and thereby improve the quality of the product (strength, the content of harmful impurities).

However, such a process is impossible without thermal regulation, which consists in holding a certain heating rate of the ore pellets, both at the first stage and at the second. At the first stage it is necessary to maintain the heating rate in the range of 20-50 degrees / min. The lower limit is due to productivity (low), the upper limit is due to the violation of the layer structure. The fact is that at high heating rates (ZO S / min) a large amount of ferrous oxide gets into the high temperature region (and above), which, interacting with the empty rock of the pellet, forms a liquid phase, the amount of which exceeds the critical value and HRP The WITHO is to melt the layer and practically stop the restoration.

In the second stage, the heating rate must be kept within 40 bOS / min, which is explained by the same reasons. Moreover, if in the first stage the heating rate was ZO S / min, then in the second it is necessary to maintain it at 40 ° C / min, if at the first stage it was equal to ZO C / MHH, then at the second - 60 s / min.

The speed interval at the first stage .e (20-5o C / min) depends on the composition of the mixture of pellets. It is known that the rate of reduction of fluxed pellets is higher than the rate of reduction of non-fluxed ones. If the pellets containing a lot of ferrous oxide (low rate of reduction), fall into high temperatures, then the layer will melt. Therefore, non-fluxed pellets heat at a rate of 20 C / min, and fluxed to basicity 1.2 at a rate of 50 s / min.

Example. The mixture consisting of 83% SevGOK concentrate, 7% coke and 10% return of metallized pellets is mixed for 3 minutes, pelletized until reaching a size of 8-14 mm, and loaded onto the grate of a conveyor machine with a height of 25 iO mm Then the pellets are dried at при50s by sucking the products of combustion of natural gas through a layer of pellets. The ltration rate is 1.2-c. Drying time 5 min. The pellets entering the preheating zone are heated to flue gases, the filtration rate of which is 1.0. Heating time 10 min. In the first part of the restoration zone, in the temperature range of 900–1150 ° C, the heating rate is 20 degrees / min. The reduction is carried out by sucking natural gas conversion products, the ratio CO + ti2 / CO + Pur in which is 18. The gas consumption in this area is 0, 65 sec. In the second part of the reduction zone, the pellet is heated to the gases from the first half of the zone by afterburning them in the burners. In this part of the recovery zone, the heating rate is maintained at O deg / min. The ratio of CO + Hj / CO + Hj O is 3-4 and ensures gas neutrality with respect to the metallized pellets. The gas filtration rate is 1.04. Recovery time 16 min. The final degree of metallization is 90%. Then the oxides are cooled in a mixture of nitrogen and cooled gas to OOC. The filtration rate is 2.0, the cooling time is 10 minutes. Example 2. From a mixture consisting of 78% of SevGOK concentrate, 5.5% limestone, 6.5% of coke, and 10% of return of metallized yachts, prepared for oats, is dried and heated according to the technology described in example one. . In the first part of the reduction zone, in the temperature range 900IISO C-, the heating rate is 35 ° C / min. The ratio of CO + U-2 / CO is t + H 0 20. The consumption of reducing gases in this area is 0.7. In the second part of the zone, the rakatyshes are heated to the gases leaving the first part of the zone by afterburning them in the burners. The heating rate is maintained at a ratio of CO + Pu / COU + P O 3. Filtration speed 1.0. nm vm with The recovery time is 14 min. The degree of metal ionization is 90%. Cooling is carried out as in Example 1. I Example H. From a charge consisting of 72% SevGOK concentrate, 12% limestone, 6% coke, and 10% return of mechanical okatey, prepare oats, dry and heat them according to the technology described in example 1. In the first part of the recovery zone, in the temperature range 900-1150 ° C, the heating rate is 50 ° C / min. The ratio is 20. The consumption of reducing gases in this area is 0.7 tl. In the second part of the zone, the octane is heated to the gases emitted from the first part of the zone by afterburning them in the burners, the heating rate is maintained at 40 C / min. Attitude. + HiO 3. Filtering speed 1.0. The recovery time is 13 missions. The degree of metallization 88%. Cooling is carried out. Also, as in Example 1. According to laboratory data, the recovery time for the proposed method is reduced from 30 to 15 minutes (on average), and the total time from 60 to 45 minutes, which is 25% of the increase in production. With an annual production of 1 million tons of metallized pellets, the economic effect is 175,000 rubles.

Claims (1)

METHOD FOR PRODUCING FINGERIRE IRON from ore-carbon pellets on a conveyor machine, including drying, heating, restoring and cooling, with the exception of the fact that, in order to increase productivity and reduce gas consumption by increasing speed The process of reduction is first carried out at a temperature of 900–1150 ° C with hydrocarbon gases, with them, with a ratio of reducing agents to oxidizing agents of 18–20 and a heating rate of 20–50 deg / min, and then with solid carbon of the charge at a heating rate of 40–60 deg / min to temperatures 1150-1350 * With furnace gases with a ratio reductants to oxidants 3-4.