RU2167205C1 - Method for making steel of iron-containing raw material and aggregate for performing the same - Google Patents

Abstract

FIELD: ferrous metallurgy, namely, iron reduction from melt of iron-containing raw material. SUBSTANCE: method comprises steps of reducing iron from melt in drop-vortex mode realized by feeding solid reducing agent in flow of fuel combustion products to split stream of melt; completing reduction in film of melt flowing down along wall of cyclone to forehead; creating reduction atmosphere in reducing cyclone due to burning fuel with excess air factor less than 1; afterburning technological gases in lower part of melting cyclone. Aggregate for performing the method includes upper melting cyclone and lower reducing cyclone mutually separated by means of profiled diaphragm. Reducing cyclone is joined with forehead. Cyclones form water cooled hollow cylindrical column; diaphragm has lower horizontal wall. Reducing cyclone is provided with forechambers for blowing-in solid reducing agent in flow of fuel combustion products; axes of forechambers are directed tangentially relative to circle of opening of profiled diaphragm. Forehead has flat water-cooled roof with openings for feeding deoxidizing agents and carbon-containing gas. System for producing steel from iron-containing raw material in one aggregate allows to make ready steel without intermediate product - cast iron, with high degree of iron reduction from melt due to developed surface of interphase interaction in drop-vortex mode. EFFECT: minimum power consumption, high degree of iron reduction from melt. 6 cl, 2 dwg, 1 ex

Description

 The invention relates to ferrous metallurgy, and in particular to the reduction of iron from a melt of iron-containing raw materials.

 A widespread method of reducing iron in the solid phase by metallization of iron ore pellets with natural gas conversion products.

 The low rate of reduction reactions and the resulting intermediate for melting, rather than steel or cast iron, do not allow this process to compete with the domain (Voskoboinikov V.V. et al. "General Metallurgy", 1998, pp. 177-187).

 More intensively, the processes of reduction of iron from its oxides occur in the liquid phase. A liquid phase reduction furnace (ПЖВ) processes iron-containing raw materials, where coal is used as a reducing agent (Steel, N 8, 1990, p. 20-27).

 However, the product of such processing is cast iron, not steel, and with high energy costs.

 The closest in technical essence is the method of processing iron-containing material and the unit for its implementation, selected as a prototype (RF patent N 2093585 from 01.06.95 Cl. C 21 B 13/14).

 The method includes preliminary reduction and melting in a cyclone, final reduction from a melt due to injection of a solid reducing agent, separate release of slag and metal, removal of exhaust gases and their afterburning. The unit for implementing the method comprises a melting cyclone with a gas outlet upper part, means for loading, dosing and supplying charge materials, fuel and an oxidizing agent. The reduction of iron is carried out in the reduction zone, made in the form of a flowing trough, and the tuyeres for blowing the reducing agent are installed in the side walls of the trough and in a flat arch.

The disadvantages of the prototype include the following:
blowing the reducing agent into the surface layer of the metal in an oxygen stream does not provide a low carbon content metal, since there is no way to control the quality of the carbon burned in oxygen, and therefore, the amount of carbon spent on the reduction of iron from the melt. This reaction, proceeding with a high heat consumption, will take place in the volume of the melt. In that part of the melt where there is enough heat for the reaction, the reduction of iron and its carburization will occur simultaneously. In those volumes of the melt where there is not enough heat for the reaction to proceed, the reaction will not work, i.e. there will be no reduction of iron.

 The resistance of the refractory part of the flow chute should be expected to be low, as well as the material of the slag separation wall between the reduction and refining zones due to contact with the molten carbon oxides.

 The objective of the invention is to create a method for the production of steel from iron-containing raw materials and an aggregate for the production of steel with a low carbon content with minimal losses of iron with slag and minimal energy costs.

 The problem is solved by preliminary reduction of iron from a melt of its oxides in a drop-vortex mode, organized by supplying a solid reducing agent in a stream of fuel combustion products to a melt stream draining from a melting cyclone, and the final metal reduction is carried out in a melt film flowing down the wall of a reducing cyclone in the piggy bank. The release of metal from the piggy bank is carried out periodically, and deoxidants are constantly fed to the surface of the slag. At the same time, a reducing atmosphere is created in the recovery cyclone by burning fuel in oxygen with an excess air coefficient of less than unity. The afterburning of process gases is carried out in the lower part of the melting cyclone. The unit for implementing the method is a melting cyclone with a gas outlet upper part, equipped with means for supplying charge materials, fuel and an oxidizing agent, and equipped with a reducing cyclone located under the melting cyclone with means for creating a reducing atmosphere and a piggy bank connected to it. In this case, the melting and reducing cyclones are separated from each other by means of a profiled diaphragm having a horizontal lower wall, and form a hollow cylindrical column made water-cooled. The recovery cyclone is equipped with pre-chambers for injecting a solid reducing agent in the flow of fuel combustion products, the axes of which are directed tangentially to the circumference of the hole in the profiled diaphragm. The melt piggy bank is equipped with a flat water-cooled arch, in which openings are made for the supply of deoxidizing agents and carbon-containing gas.

 The invention meets the criteria of patentability: it has novelty, which follows from a comparison with the prototype and analogues; inventive step, as it clearly does not follow from the current level of technology; practically feasible with minimal energy costs.

 In FIG. 1 shows a longitudinal section of an aggregate in which a method for producing steel is carried out; in FIG. 2 - section along aa.

 The method for the production of steel from iron-containing raw materials consists of the processes of melting the charge, reducing iron from the melt, and refining.

 The process of melting the mixture is carried out in a melting cyclone. The mixture is blown into the melting space in the stream of products of combustion of fuel in oxygen. The melt moves along the wall of the cyclone and through the outlet it enters a recovery cyclone, where it is crushed into droplets by jets of fuel combustion products carrying a powdery reducing agent. Preliminary reduction of iron from the melt takes place in the vortex-droplet mode, and the final one continues and ends in the film of the melt moving along the cyclone wall into the piggy bank. Process gases from the recovery cyclone enter the smelter, where they are burned in oxygen.

 The refining process is carried out by the supply of slag-forming and deoxidizing agents and by purging the metal with gases. In this case, the slag is removed continuously through the slag notch.

 Metal is produced periodically.

 The unit for implementing the method of producing steel from iron-containing raw materials is a water-cooled hollow cylindrical column 1, divided by a profiled diaphragm 2 into a melting cyclone 3 with a water-cooled cover 4 and a recovery cyclone 5 connected to the money box 18.

 The diameter of the opening of the profiled diaphragm 2 is the calculated value of the aerodynamics of cyclone 3. Its profile ensures the constancy of the thickness of the film of the melt flowing down the wall of the melting cyclone 3, as well as the separation of the film from the wall when flowing into the recovery cyclone 5. Therefore, the lower wall of the profiled diaphragm 2 is horizontal.

 In the melting cyclone, a pipe 6 is made for the removal of flue gases to the waste heat boiler. In the side walls of the melting cyclone, pre-chambers 7 are installed for preheating the powdered charge materials. Each prechamber is equipped with a nozzle 8 for supplying a ground charge and an oxy-fuel burner 9. The axes of the prechambers 7 are directed tangentially to the circumference of the smoke outlet 6. Lances 10 for supplying oxygen are installed in the lower part of the wall of the melting cyclone.

 In the side walls of the recovery cyclone, prechambers 11 are installed to create gases in the cyclone of the reducing atmosphere containing particles of a solid reducing agent. Each prechamber is equipped with a pipe 12 for supplying a solid carbon-containing reducing agent and a gas-oxygen burner 13, into which fuel is supplied through the pipe 14 and oxygen is supplied through the pipe 15.

 The axis of the prechambers 11 are directed tangentially to the circumference of the hole in the profiled diaphragm. Water-cooled wall 16 of the unit with the stuffed mass 17 provides the conditions for the formation of a skull. The recovery cyclone 5 is connected to the piggy bank 18. The piggy bank is equipped with a water-cooled arch 19 in which a hole 20 for supplying deoxidizers and a hole 21 for supplying carbon-containing gas are made. The bottom of the piggy bank tilts to the outlet 23. In the bottom of the piggy bank in front of the outlet there is a porous plug 24 through which metal is blown with argon to remove non-metallic inclusions. Under the vault of the piggy bank there is a notch 25 for the release of slag.

An example of the method of production of steel from iron-containing raw materials
After heating the unit, including heating the masonry of the piggy bank with portable burners, smelting and reducing cyclones with stationary gas-oxygen burners 9 and 13, they begin to feed the mixture through the pipe 8 into the pre-chamber 7.

 The mixture is a mixture of sludge from steelmaking, lime and fluorspar. The ratio of the components of the mixture is calculated on the basis of data on the chemical composition of the components of the mixture. The mixture heated in the prechamber 7 is carried out by the combustion products into the working volume of the cyclone 3 and enters the wall 16. At the moment of touching the skull lining 17, the charge particle has a temperature that ensures its adhesion to the wall. Heat supplied to the wall due to the vortex of the products of fuel combustion from the burners 9 and from the afterburning of the process gases with oxygen entering through the tuyeres 10 ensures the melting of the charge particles adhering to the cyclone wall, reaching the temperature of the liquid-mobile state and the melt film swelling down the melting cyclone wall. Falling through the opening of the profiled diaphragm 2 into the recovery cyclone 5, the flowing melt is divided into droplets by jets coming tangentially to the cylindrical surface of the melt film from the prechambers 11. The jets emanating from the prechambers carry a solid carbon-containing reducing agent (coal) with fraction sizes 0 ... 0, 5 mm. The recovery process proceeds under favorable conditions - the contact of each droplet volume with a reducing agent (coal) during intensive heat supply provided by the vortex mode of gas flow in the recovery cyclone. The recovery process takes place in each microvolume (drop) of the melt, which ensures complete recovery of iron, that is, the process proceeds with small losses of iron in slag.

 The final reduction takes place in a film of melt flowing down the walls of the cyclone, onto the surface of which a solid reducing agent enters and which is washed by reducing technological gases due to the combustion of gas supplied through pipe 14 in oxygen supplied through pipe 15 with an excess air coefficient of 0.9 .

Process gases coming from the piggy bank 18 and recovery cyclone 5 and containing CO and H ₂ are burned at the inlet of the melting cyclone 3 with oxygen supplied through tuyeres 10. The heat of these gases is used to melt the charge, which reduces the energy costs of production. The flowing melt from the reducing cyclone 5 is a mixture of iron with slag, which, falling into the piggy bank 18, is divided into metal and slag in accordance with the density of these materials. Preliminary deoxidation is carried out by feeding deoxidizing agents through the opening 20. Natural gas is introduced through the openings 21 to reduce heat loss from the surface of the slag. Slag is continuously removed through a notch 25.

Claims (6)

 A method of producing steel from iron-containing raw materials, including melting the charge in a cyclone, reducing iron from the melt by introducing solid reduction, removing exhaust gases, afterburning and separate release of metal and slag, characterized in that the reduction of iron from the melt is carried out in two stages located under a melting cyclone and a recovery cyclone separated from it by means of a profiled diaphragm, while preliminary recovery is carried out in the drop-vortex mode of feeds minutes the solid reductant in the stream of combustion products in the melt stream coming from the melting cyclone and a final reduction of iron - in the film melt, flowing along the wall in the reduction cyclone forehearth, the tapping is carried out periodically and continuously on the surface of the removed slag deoxidizing yield.  2. The method according to claim 1, characterized in that in the recovery cyclone support a reducing atmosphere by burning fuel with a coefficient of excess air less than one.  3. The method according to claim 1, characterized in that the afterburning of the process gases is carried out in the lower part of the melting cyclone.  4. A unit for the production of steel from iron-containing raw materials, containing a melting cyclone with a gas outlet upper part, equipped with means for supplying charge materials, fuel and an oxidizing agent, characterized in that the unit is equipped with a recovery cyclone located under the melting cyclone with means for creating a reducing atmosphere and connected to a piggy bank, while the melting and reducing cyclones are separated from each other by means of a profiled diaphragm having a horizontal lower enku and form a cylindrical column made water-cooled.  5. The assembly according to claim 4, characterized in that the means for creating a reducing atmosphere are made in the form of prechambers for injecting a solid reducing agent in the stream of fuel combustion products, the axes of which are directed tangentially to the circumference of the hole in the profiled diaphragm.  6. The unit according to claim 4, characterized in that the melt bank is equipped with a flat water-cooled arch, in which openings are made for the supply of deoxidizers and carbon-containing gas.

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