RU2295574C2 - Method of production of metal and plant for realization of this method - Google Patents

Abstract

FIELD: metallurgy; modifying, refining and alloying of ferrous metals.

SUBSTANCE: proposed method consists in partial reduction of iron oxide materials and preliminary cooling of these materials by reducing gases escaping from melting zone at temperature of 800-1000°C. Partially reduced material is fed to melting zone for melting it at high-temperature heating for final reduction. Final reduction of iron oxide materials is performed by plasma jets at introduction of carbon-containing fuel and oxygen-containing gas. Plasma sources are mounted in form of plasmatrons which are opposite over reactor perimeter and are mounted at angle of 30-50° relative to level in way of reactor hearth. Longitudinal axes of symmetry of plasmatrons cross on reactor axis and lie in one plane with vertex of angle of plasmatron axes which is located above preset surface of metal.

EFFECT: improved quality of metal at low level of admixtures; reduced power requirements; minimization of effect on surrounding medium.

5 cl, 2 dwg, 1 ex

Description

An interrelated group of inventions relates to the field of metallurgy and foundry and can be used in the processes of modifying, refining and alloying ferrous and non-ferrous alloys.

A known method for producing ferroalloys, including burning carbonaceous materials in boilers of power plants, the slag of which contains iron oxides in an amount of 10-20%, with an excess air coefficient of 1.1-1.19, slag accumulation in the piggy bank, discharge from the boiler, cooling and isolation metal, characterized in that the slag in the boiler piggy bank is additionally heated to 1700-1800 ° C by burning fuel oil together with coal and supplying a gas torch directly to the slag surface, while additional materials are introduced into the gas torch, including oxides of alkaline earth metals and iron in an amount that provides a total input of the indicated oxides from materials of 0.01-0.1% of the mass of coal burned (AS USSR No. 1218703, decl. 07.06.83, publ. bull. No. 24, 1990).

The specified method is characterized by low productivity at high energy costs.

The closest in technical essence and the achieved result (prototype) is a method for producing iron and / or its alloys from iron oxide materials, including their partial preliminary recovery by supplying a stream of hot gas leaving the melting furnace and subjected to at least partial afterburning, separation of the partially reduced iron oxide material from the exhaust gas and feeding the separated partially reduced iron oxide material to the melting bath for melting due to the reaction with carbon-containing fuel and oxygen-containing gas, characterized in that the partial reduction of the iron oxide material is carried out simultaneously with the cooling of the gas in the vertical channel, into which the off-gas and partially burned off gas and iron oxide material are directed, and the temperature of the hot reducing gas after the iron oxide material is introduced into the vertical channel is maintained equal to 800-1000 ° C (Russian Patent No. 2077595, declared. 20.12.89, publ. bull. No. 11, 1997).

The disadvantage of this method is that as a result of its use, the obtained iron has a high content of carbon and other impurities, which does not allow the use of the obtained metal immediately after its release from the reactor for the production of high-quality products (automotive, transformer sheet, production of heat-resistant, especially durable and stainless steel, etc.). Another disadvantage is that the method cannot be carried out by plasma jets, since when the column of material is not flushed by the plasma, either the melt splashes onto the reactor wall and into the preliminary reduction zone, or the plasmatrons are damaged when they are gasdynamically locked (plasma torch burn-out, cooling water entering the melt, which are not controlled effects).

A device for producing iron and / or its alloys from iron oxide materials is known, comprising a melting furnace equipped with means for supplying carbon-containing fuel and oxygen-containing gas directly to the liquid phase and into the space below it for afterburning the gas formed as a result of melting, an outlet with an exhaust outlet pipe gas, means for introducing iron oxide material into the afterburned exhaust gas for partial reduction of the material and gas cooling, established by and therein means for separating partially reduced material from gas and means for feeding partially reduced material to the smelting furnace, characterized in that the exhaust gas pipe is installed vertically and connected to means for loading iron oxide material in its lower part and with means for separation located in the upper part of the channel or next to it (Russian Patent No. 2077595, application. 20.12.89, publ. Bulletin No. 11, 1997).

The disadvantage of this device is that the design of the reactor does not allow the use of plasmatrons for the lower purge of a solid column of a charge, and then a layer of liquid melt, since the known reactor is intended only for melting and reduction by reacting partially reduced oxide materials with a solid reducing agent.

The closest in technical essence and the achieved result (prototype) is a plant for the production of metals and alloys, mainly ferroalloys, containing a shaft-type reactor with refractory lining, in the upper part of which holes are made for loading coal and gas, the side walls of the reactor in the recovery zone are provided pipelines for injecting oxygen or oxygen-containing gas, and in the lower part of the reactor there are exhaust openings for metal and slag, a cyclone for separating coal particles from flue gas, the outlet end of which is connected by a pipeline to the burners, characterized in that in the side wall of the reactor there are additionally made openings connected to pipelines for blowing fine-grained oxide material located in the reduction zone above the pipelines supplying oxygen or oxygen-containing gas, and the burners are located in the side the reactor wall is higher than the pipelines for blowing oxide material, while the feed hopper with oxide material is connected to the pipeline connecting the cyclone To purify the waste gases and the burner to preheat the oxide material, the discharge end of which is connected to a conduit for injecting material into the reactor oxide (Russian Patent №1582991, appl. 10.29.87, publ. bull. No. 28, 1990).

However, such a constructive implementation of the known installation does not ensure the quality of the metal obtained due to the low intensity of metal refining in the piggy bank and the presence of harmful impurities in it, in addition, the design does not provide sufficient heat and mass transfer at the gas-melt boundary in the purge zones.

The basis of the first of the group of inventions is the task of improving the method for producing metal, in which by increasing the contact surface of the plasma jet with the iron oxide material and replacing part of the oxidizer consumption with water by introducing it into an arc discharge, as well as additional refining of the metal by blowing it with an oxidizing or with a reducing plasma jet, the processing of oxide materials and the production of them by direct means of high-quality primary iron with low ur vnem impurities, a reduced specific energy consumption and minimal impact on the environment.

The second of the group of inventions is based on the task of improving the installation for producing metal, in which, by choosing the optimal arrangement of heat sources - plasmatrons and, as a result, changing the internal temperature field of the reactor, a given temperature regime in the volume of the reaction zone, regulation of thermal power, the chemical composition of the jet and control of gas flow and thereby reduce the energy consumption of the whole process, improve the quality of the finished product and reduce emissions gases.

The first task is solved in that in a method for producing metal, comprising preliminary reduction of iron oxide materials by heating by blowing off exhaust gases from the melting zone with a temperature of 800-1000 ° C, feeding the previously reduced material into the melting zone for its melting at high temperature heating and final recovery, due to the continuous supply into the melting zone of the material, carbon-containing fuel and oxygen-containing gases, according to the invention, pr The material recovery process is carried out by plasma, into which carbon-containing fuel and oxygen-containing gas are introduced, and plasma sources are placed on the same horizon, facing each other, while the direction of the plasma jets is formed in such a way that the longitudinal axis of the jets form a central angle with a vertex on the axis of the reactor, and the apex of the angle is located above a predetermined height of the metal mirror, the reducing atmosphere for preliminary reduction of the material is supported by the supply of natural gas and / and and water vapor in the gas leaving the melting zone, whereby the plasma sources are installed at a height of 0.5-0.8 N from the hearth of the melting zone, where H is the total height of the loaded material, and the reduced metal is taken from the melting zone to the bank and is additionally blown oxidizing or reducing plasma jet.

The direction of the plasma jets of the proposed method provides an increase in the path length of the plasma jet in the melt, and as a result, an increase in the efficiency of heat and mass transfer processes.

The boundary length of plasma jets from symmetrically located sources allows them to focus only on metal reduction and prevents mixing of the finished product (metal) with molten oxides, which eliminates metal contamination and its emissions on the walls of the reactor.

The introduction of water into the arc discharge, followed by its high-temperature conversion in the arc chamber of the plasmatron to oxygen and hydrogen, reduces the total gas flow through the plasmatron, increases the enthalpy of the plasma jet, the efficiency of the plasma torch and reduces the energy consumption of the whole process.

Additional refining of the metal in the piggy bank by blowing it with an oxidizing or reducing plasma jet helps to reduce the concentration of impurities in the resulting metal.

Another task is solved in that the installation for producing metal containing a reactor with a refractory lining, the side walls of which are equipped with pipelines for supplying oxygen-containing gas, heat sources, and in the lower part of the reactor there is an outlet for draining metal and slag, according to the invention, the reactor the upper part is equipped with a preliminary recovery device, made in the form of a perforated hopper placed in a lined housing, with a loading device and an outlet in the lower part with a conical locking mechanism, and the walls of the reactor in the upper part are beveled towards their inner surface with the formation of a passage section, the end surface of which is located below the conical locking mechanism, while nozzles for supplying natural gas and / or are installed along the perimeter of the passage section water vapor, and the heating sources are made in the form of plasmatrons symmetrically arranged relative to the vertical axis of the reactor, installed along the perimeter of the reactor at a height of 0.5-0.8 N from the hearth zone, where H is the total height of the loaded material, at an angle of 30-50 ° to the horizontal in the direction of the hearth, and the longitudinal axis of the plasma torch intersect on the axis of the reactor above a predetermined height of the metal mirror, and pipelines for supplying oxygen-containing gas are installed in the side walls between the plasma torches and nozzles, while opposite the outlet for metal and slag, parallel to the bottom, an additional purge-refining plasmatron is installed.

Placing the plasma torches along the perimeter of the reactor and their relative position makes it possible to increase the efficiency of heat and mass transfer processes in the reactor, to increase the path length of the plasma in the melt, and to reduce emissions and freezing of the melt on the walls of the reactor.

The proposed boundary values of the installation angles of symmetric plasmatrons obtained experimentally removed the finished metal from the interaction zone of the plasma jets of the reducing plasmatrons, since the apex of the convergence angle of the longitudinal axes of the jets is above the reduced metal zone, while a slag layer is placed between the plasma jets and the finished metal which, as the bulk of the charge is restored, less and less oxidizes the upper layer of the finished metal.

Placing the purge-refining plasmatron opposite the outlet allows warming up the notch and improves the conditions for the release of metal, and placing the plasmatron parallel to the hearth allows more uniform processing of the metal volume.

The invention is illustrated by drawings,

where figure 1 shows a General view of the installation;

figure 2 is a section aa of figure 1.

Partially reduced feedstock (charge) is loaded into the reactor. Set the plasmatrons corresponding to the technological parameters of the smelting flow of cooling water and plasma-forming gas, for example natural gas and air or oxygen. Start the plasma torches, while the supply and direction of the plasma jets, it is advisable to carry out according to the scheme below the described installation. Heated to a temperature of 3000-4000 ° C and converted to CO and H ₂ plasma-forming gas in the form of reducing plasma jets blows the charge layer. High-temperature combustible gases inside the reactor, rising up, are mixed with natural gas and / or water vapor. The resulting gas mixture at a temperature of 800-1000 ° C continuously passes through the charge layer of the feed hopper, while the charge is heated and partially restored. The solid charge in the reactor, and then the melt, intensively interact with the reducing plasma jets. The recovered metal flows into the lower part of the reactor - the money-box. The resulting metal at the bottom of the reactor is purged with an oxidizing or reducing plasma jet.

As shown in figure 1, the installation includes a reactor, the housing 1 of which is made of sheet steel. The housing 1 is lined with refractory material 2. In the lower part of the reactor is located a melting zone 3, equipped with means for supplying energy and a reducing agent through plasmatrons 4 directly to the melting zone 3. Over the layer of the melted material, nozzles 5 for supplying oxygen-containing gas are installed to burn the combustible gas leaving the melting zone . At the base of the hearth 6 there is an outlet 7 equipped with a slide gate 8. In the upper part of the reactor there is a device for preliminary reduction of oxide materials 9 located in a steel lined housing 10. Inside the housing 10 is a perforated hopper 11 made of heat-resistant steel. In the lower part of the hopper 11, an outlet 12 for supplying pre-reduced materials to the melting zone 3 is provided, equipped with a conical locking mechanism 13. In the upper part of the preliminary reduction device 9, a loading device 14 for supplying oxide materials to the reactor equipped with a sealed cover 15 is located. recovery system 16 is installed to remove exhaust gases from the reactor. The hopper 11 is closed from above by a sealed lid 17. The inner walls of the reactor form a channel 18, which is tapering in the upper part. Channel 18 connects the preliminary reduction device 9 in its lower part to the melting zone 3. In the narrowing part of channel 18 nozzles 19 are installed for additional supply of a reducing agent (for example, natural gas) and / or water vapor. Plasmatrons 4 are installed at a height of 0.5-0.8 N from the hearth of the melting zone, where N is the total height of the material loading, opposite the perimeter of the reactor at an angle of 30-50 ° to the horizontal in the direction of the hearth of the reactor so that the longitudinal axes are symmetrically located plasmatrons intersect on the axis of the reactor with the vertex of the angle of the axes located above a predetermined height of the metal mirror. The plasma torches 4 are hermetically connected to the reactor through the flanges 20 (figure 2). In the lower part of the reactor there is a repository of 21 reduced metal. At the bottom 6 of the piggy bank (reactor), opposite the outlet 7, an additional hole 22 is made, to which an additional purge-refining plasmatron 24 is connected via a slide gate 23, the longitudinal axis of which is parallel to the bottom of the piggy bank.

Installation works as follows.

The plasmatrons 4 are installed and the flow rates of cooling water and plasma forming gas (for example, natural gas and air or oxygen) are supplied to them corresponding to the technological parameters of the smelting. Through the charging device 14, the starting oxide materials (charge) are fed into the hopper 11 and the charge is transferred to the melting zone 3 through the outlet 12, after having previously closed the outlet 7 with a slide gate 8. The outlet 12 is closed with a conical locking mechanism 13, and the charging device 14 is reloaded a predetermined mass of the initial charge into the hopper 11 and hermetically close the cover 15. Correct the required flow rates of cooling water and plasma forming gas on the plasma torches and start the plasma torches 4. Heated to medium At a temperature T _c = 3000–4000 ° С and a plasma-forming gas converted to CO and H ₂ in the form of reducing plasma jets blows through the charge layer. Under the action of plasma jets, the charge in the melting zone 3 is intensively melted, then the plasma jets purge the melt layer. The solid charge, and then the melt, intensively interact with the reducing plasma jets flowing from the plasma torches 4, and thus the metal is restored from the melt. The recovered metal flows into the liquid metal piggy bank 21.

Combustible gases leaving the process of melting and reducing oxide materials in melting zone 3 have a high temperature and a significant content of CO and H ₂ . To reduce the formation of accretions and "bridges" from an oxide material not melted in the upper layer of the charge, oxygen-containing gas (for example, oxygen) is blown through nozzles 5 in a stoichiometric ratio. The exhaust gases, when burned out, increase the temperature in the upper part of the melting zone 3, which contributes to the melting of nastily and "bridges". In the tapering part of the channel 18, nozzles 19 are installed through which natural gas and / or water vapor is blown for additional supply of a reducing agent, which, mixed with the gas leaving the melting zone, cools it. The resulting gas mixture at a temperature of 800 ... 1000 ° C, having a high reduction potential, the exhaust gas removal system 16 is “pumped” through the perforated wall of the hopper 11 into the layer of the initial charge. The initial charge is partially warmed up and restored. The temperature of the charge in the hopper is controlled by temperature sensors that automatically set the flow of natural gas and / or steam through the nozzles 19 according to a certain algorithm.

The metal obtained during the smelting process flows into the piggy bank 21, where it is blown through an additional opening 22 with a reducing or oxidizing plasma jet of a purge-refining plasmatron 24 in accordance with the requirements of the technological process. In the absence of the need for additional metal processing, the slide gate 23 does not open, the plasma torch 24 does not turn on.

After complete penetration of the solid charge in the melting zone 3, the supply of oxygen-containing gas through the nozzles 5 is stopped. The oxygen supply through the nozzles 5 during the recovery of the molten melt in zone 3 is carried out only to increase the temperature during the formation of sediments on the wall of the vertical channel 18. The formation of sediments is monitored by sensors installed in the channel wall.

After completion of the smelting and reduction process, the gate 7 opens the outlet 7, and the finished metal is drained into the ladle. After the metal is drained into the steel pouring ladle and the slag is drained, the plasma torches 4 and 24 are turned off, the natural gas supply is shut off to them, the openings 7 and 22 are closed by the slide gates 8, 22 the conical locking mechanism 13 is lowered and the partially reduced and heated oxide materials are transferred to the melting zone 3. Then the conical locking mechanism 13 is lifted, the hole 12 is closed, the lid 15 is opened, and oxide materials are fed into the pre-reduction device 9 through the charging device 14, natural gas is supplied to the plasma torches, including 4 by the plasma torches, and then the process is repeated.

Concrete example

Four plasma torches with a power consumption of 0.3 MW each were installed in the melting zone, and 0.1 MW in the piggy bank. The thermophysical parameters of plasma jets with a given mass average temperature and speed provide a purge of the column height of the material to be melted equal to 1.3 m. For a given cross-sectional area of the reactor and specific power Р _у = 2 kW per 1 kg of finished metal, the weight of the charge loaded into the reactor was one ton, those. one ton into zone 3 and one ton into hopper 11. At a melting time of 1 hour, 0.5 tons of molten metal with an average chemical composition,%: Fe = 99.8; C = 0,000; Mn = 0,000; Si = 0.002; S = 0.02; P = 0.004; Cr = 0.07; Ni = 0.03; Cu = 0.01; Al = 0,000; Mo = 0,000; V = 0.09; Ti = 0,000; As = 0,000. The consumption of natural gas per 1 ton of finished metal is 300-400 kg.

The quality of the obtained metal can be used as a starting matrix for the production of high-quality alloyed high-strength and heat-resistant steels, as well as a finished product for the production of electrical steel or other products. In addition, the claimed method and device allows to obtain high-quality metal, bypassing many stages of remelting (blast furnace, converter, vacuum arc furnace). The claimed method of metal smelting has high environmental performance, since all dust emissions practically remain in the charge layer in the partial recovery hopper, and therefore it has an extremely low environmental impact.

Since the claimed method for producing metal and the installation have high specific energy indicators, the relatively small dimensions of the installation - all this makes it possible to use them with a shortage of production space.

At the moment, the method for producing metal has passed experimental tests on the installation for its implementation. Positive results form the basis of the industrial design construction project.

Claims (5)

1. A method of producing a metal, including partial reduction of iron oxide materials and preliminary heating by blowing off of reducing gases leaving the melting zone with a temperature of 800-1000 ° C, supplying partially reduced material to the melting zone for its melting at high temperature heating and final recovery due to continuous supply to melting zone of carbon-containing fuel and oxygen-containing gases, characterized in that the final reduction of the material is carried out by plasma jets into which carbon-containing fuel and oxygen-containing gas are introduced, while the plasma sources are placed on the same horizon with the direction of the plasma jets towards each other with the formation of their longitudinal axes at a central angle with a vertex on the axis of the reactor located above a predetermined height of the metal mirror, in this case natural gas and / or water vapor is blown from the melting zone to partially recover materials. 2. The method according to claim 1, characterized in that the input of the plasma jets is carried out at a height of 0.5-0.8 N from the hearth of the melting zone, where H is the total material loading height. 3. The method according to claim 1, characterized in that the reduced metal is removed from the melting zone to the piggy bank and is additionally blown with an oxidizing or reducing plasma jet. 4. Installation for producing metal, containing a reactor with a lined casing, in the upper part of which is placed a means of partial reduction of iron oxide materials, made in the form of a perforated hopper with a loading device and an outlet with a conical locking mechanism in the lower part for feeding partially reduced materials to the smelter zone, a pipeline of exhaust gases from the melting zone, connecting the melting zone with the lower part of the partial recovery means and made in the upper narrowed parts, heating sources located in the side wall of the reactor, and an outlet for metal and slag in the lower part of the reactor, characterized in that the melting zone is equipped with oxygen-containing gas supply pipelines, heating sources are made in the form of symmetrically located plasmatrons installed below the oxygen-containing supply pipelines gas along the perimeter of the reactor at a height of 0.5-0.8 N from the hearth of the melting zone, where N is the total height of the loaded materials, at an angle of 30-50 ° to the horizontal in the direction of the hearth pa, with the intersection of the longitudinal axes of the plasma torches of the reactor axis a predetermined height above the mirror metal, and a constricted portion of the pipeline installed flue gas injector for supplying gas and / or steam. 5. Installation according to claim 4, characterized in that opposite the outlet for metal and slag, an additional purge-refining plasmatron is installed parallel to the hearth.

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