RU2326173C2 - Method of direct reduction of metals from dispersed crude ore and device for its implementation - Google Patents

Abstract

FIELD: noncoking metallurgy.

SUBSTANCE: source stock is previously reduced, the pre-reduced stock with alloying additives and reducing agent is fed into an electric arc furnace, the electric arc is excited, stock melting and final reduction are performed, the finished product and exhaust gas are discharged. The source stock is introduced into the exhaust gas flow after the final reduction, the resulting mixture is applied to the prereduction reactor, and the source stock prereduction is performed by forming the said mixture in the form of a vertically ascending flow expanding along the motion direction, and providing the recirculation of stock particles in this flow; after that, the gas and particle mixture is separated into gas and prereduced stock, which is fed into the electric furnace feeder. The solid-core prereduction reactor is designed as a vertical conical shell with the cone vertex down, with a cover; a liquid-core reactor exhaust gas pipeline, a source stock feeder is connected to this pipeline.

EFFECT: decrease in power and reducing agent consumption; use of gaseous and dispersed reducing agents, decrease in emissions of hazardous substances into atmosphere; simplification of metal production process flow.

8 cl, 5 dwg

Description

The invention relates to non-coke metallurgy, in particular to the production of iron by reducing dispersed metal-containing oxide raw materials, not only iron, such as dispersed ores, partially reduced ores, ore concentrates and metal-containing oxide waste, gaseous and dispersed reducing agents in electric arc reactors, the main share of energy into which it is introduced by means of electricity.

As is known, a method in which iron is produced by reducing iron ore bypassing blast furnace production is classified as a “direct reduction method”. Methods of direct reduction of metals and corresponding devices based on arc discharges are described in the well-known technical literature ("Industrial Electric Furnaces. Arc Furnaces and Special Heating Units." Edited by AD Svenchansky, M., Energoizdat, 1981, p. 251 , 247). Typically, the device comprises a molten bath with metal and slag collection means, feed means for supplying raw materials and a plasma-forming gas, a solenoid and a working electrode located on the central axis made of graphite or tungsten. In some cases, the source material and plasma-forming gas are supplied through a working electrode, usually located in the upper part of the device, and it is the cathode of the arc plasmatron; the role of the anode is played by the molten metal bath located on the bottom of the furnace.

Common disadvantages of these methods and devices are the high energy consumption that is lost with the exhaust gases and refrigerants of the furnace cooling system, the high material consumption of the recovery complex, the complexity of its technological structure, as well as the high electrode consumption and high consumption of the furnace lining material. Therefore, in these methods and devices, apparatuses are provided for preliminary reduction of oxide raw materials and utilization of the energy of exhaust furnace gases, for example, for generating electricity, which allows to reduce the energy intensity of the process, and by reducing the time of the final recovery of the charge in the furnace and reducing its power, reduce the consumption of electrodes and lining material (“Development of non-coke metallurgy”, under the editorship of N. Tulin, K. Mayer, M., Metallurgy, 1987, Russian Patent No. 2037524). However, these measures, due to the low productivity of the pre-recovery devices, as well as the low efficiency of recycling secondary energy resources, have not found industrial application.

The closest prototype of the present invention is a method for direct reduction of metals from dispersed ore raw materials, including preliminary reduction of the initial charge, feeding the pre-reduced charge together with alloying additives and a reducing agent to an electric arc furnace, electric arc excitation, melting and finishing reduction of the charge, output of the finished product and exhaust gas. ("The Development of Cokeless Metallurgy". Edited by N. Tulin, Mayer K. Metallurgy, M., 1987, p. 77). According to this method, a fluidized bed reactor is used for preliminary reduction of the initial charge, and gas leaving the furnace, which has significant thermal energy and has a high reduction potential, is used to generate electricity and is not used directly in the process of ore ore reduction.

The closest prototype of the invention is also a device for direct reduction of ore raw materials described in the same source, comprising a feed source feeder, a solid-state reactor for preliminary reduction of the initial charge, means for supplying a pre-reduced charge and reducing reagents to an electric arc furnace, including a furnace feeder for a pre-reduced charge, a mixer located on the central axis, a working electrode with an internal cavity, a liquid-phase reactor, a device for collecting finished products KTA molten bath with outlet system and an exhaust gas from the furnace. In this device, the working electrode is the hollow graphite cathode, and the device for collecting the finished product is the anode of the electric arc furnace connected to a DC power source.

The main disadvantage of the known device is that in the technological process for the preliminary reduction of oxide raw materials to the required level by the degree of reduction, a battery of fluidized bed reactors is used, which have a low specific productivity due to significant limitations both in the temperature of the working gas and its speed, which leads to to a large consumption of reducing agent, the complication of the structural and technological scheme, the increase in capital costs when creating restoration production and the complication of its operation (General Metallurgy, V. G. Voskoboinikov, V. A. Kudrin, A. M. Yakushev, M., Metallurgy, 1985, etc.). To create the necessary operating temperature and reducing environment in such reactors, coal air gasification devices based on the low-cost fuel combustion process were used, and the use of thermal and chemical energy of the gas leaving the furnace, which has significant thermal energy and reduction potential, indirectly - through waste heat boilers, power plants - leads to inevitable significant energy losses and, as a result, to large energy intensity of metal production and low environmental Kim indicators of the overall process.

The present invention solves the technical problems of reducing energy intensity, material consumption, increasing efficiency and environmental performance of the process.

The technical result of the use of the invention is to reduce the consumption of electricity and a reducing agent, in the possibility of using any gaseous reducing agent and reducing the emission of harmful substances into the atmosphere.

Additionally, the problem of simplifying the technological scheme of metal production from dispersed ore or other metal-containing oxide raw materials is solved.

The specified result is achieved in the present invention by the fact that in the method of direct reduction of metals from dispersed ore raw materials, including preliminary restoration of the initial charge, feeding the pre-reduced charge along with alloying additives and a reducing agent to the electric arc furnace, electric arc excitation, melting and finishing the charge, the finished output product and exhaust gas, the initial mixture is introduced into the stream of exhaust gas after finishing reduction, the resulting mixture is fed to the reactor redvaritelnogo recovery and pre-reduction of the initial charge is carried out by forming the mixture into a vertically rising widening in the direction of flow and recirculating particles of the mixture in this stream are then separated mixture of gas and particles and gas predvosstanovlennuyu charge, which is fed in the electric feeder.

It is possible to control the operating temperature in the preliminary reduction reactor by mixing cold gas with the gas leaving the furnace. The values of temperature and gas velocity in the pre-reduction zone can vary over a wide range, which allows for high specific productivity, to prevent the particles of the processed charge from sticking together and to intensify the processes of heat and mass transfer, and the separation of the pre-reduced oxide raw material from the exhaust reducing gas is carried out either by gas-dynamic means - by providing the required ratio of gas-dynamic and gravitational forces acting on the particles of the mixture in solid phase m reactor or through the provision of the required ratio of gas-dynamic, inertial, gravitational and magnetic forces acting on the particle in the magnetic separator.

The problem is also solved by means of a device in which a conical high-temperature reactor is used as a solid-phase reactor, to which a line containing a mixture of hot gas leaving the reduction furnace and the initial charge is connected. The conical reactor provides turbulent movement of the mixture of the gas leaving the furnace and the initial charge and does not require separate preliminary operations to create a reducing gas to pre-restore the initial charge.

The prereduced charge supply means comprises either a pipeline with a valve connected to the lower part of the solid-phase reactor vessel, or a magnetic separator connected to the cover of this reactor.

The reducing gas supply means is divided into two branches and contains two valves. One branch of the gas main is connected to the pipeline of the gas leaving the furnace, the other to the mixer of the electric arc furnace, which ensures the mixing of the pre-restored charge and reducing gas and the supply of this mixture to the furnace. When inert gas is used as a thermoregulating agent, this gas is supplied to the pipeline of the gas leaving the furnace; in this case, the reducing gas is supplied only to the mixer of the reducing furnace.

The method and device are designed to restore dispersed oxide raw materials, the particle size of which should be 0.1-3 mm The use of raw materials with smaller particles leads to a significant increase in the height of the solid-phase reactor; with larger particles, the rates of heat and mass transfer processes both in the solid-phase reactor and in the liquid-phase finishing reduction reactor slow down. Therefore, such raw materials must be crushed.

The method and device provide for operation in two modes.

The first mode is used in the preliminary reduction of iron ore raw materials to the degree of reduction, at which the magnetite fraction is small 10-20%, or in the recovery of non-magnetic and weakly magnetic iron-free oxide minerals and non-magnetic alloying additives. The second mode is used for preliminary reduction of iron ore to magnetite.

Terms and definitions used

A solid-phase reactor is a container in which the reduction of oxide feedstock with a gaseous reducing agent is carried out without melting it.

Fluidized bed reactor - a furnace for magnetizing calcination in a reducing medium of finely divided oxide raw materials in a moving fluidized bed. The reactor contains a charge feeder, hearth devices with nozzles to which ore raw materials are supplied, and hot fluidizing reducing gas, a heat source to create the required temperature and recovery medium in the working volume, and a discharge device are blown through the nozzles.

A liquid-phase reactor is a tank in which the reduction of oxide raw materials is carried out in a liquid state. The reactor contains a cooled casing, to which the devices for collecting the product and supplying electric current to the melt are docked from below.

Feeder - a device, usually containing a hopper with raw materials and means for feeding it at a given speed.

Magnetic separator is a device for extracting iron ore raw materials with high magnetic susceptibility from a multicomponent mixture and a conveying medium. The principle of operation of the magnetic separator is based on the difference in the magnetic susceptibility of the components of the mixture.

Ore, iron ore raw materials - mineral or man-made raw materials containing one or more oxides, for example iron of various valencies.

Magnetite is a highly magnetic iron ore raw material whose magnetic susceptibility is not less than 3 · 10 ⁺⁶ m ³ / kg.

Initial charge is an initial mixture of components designed to produce metal.

Pre-restored charge is a partially restored initial charge.

Description of drawings

Figure 1 schematically shows a device operating in the first mode.

Figure 2 schematically shows a device with a magnetic separator operating in the second mode.

Figure 3 shows a longitudinal section of a solid-phase conical reactor for operation in the first mode and gas velocity diagrams (a), and also shows the change in the concentration of particles of the processed mixture in sections at different reactor heights (b).

Figure 4 shows a longitudinal section of a solid-phase conical reactor for operation in the second mode and gas velocity diagrams (a), and also shows the change in the concentration of particles of the processed mixture in sections at different reactor heights (b).

Figure 5 shows a cross section of a solid-phase conical reactor in section AA (Fig. 3.4).

A device for implementing the first recovery mode of the initial charge (Fig. 1) contains a solid-phase prereduction reactor 1 with a cover 2 and a conical body 3 connected to its lower part, a line 4 with a valve 5, through which the pre-restored charge is fed into the hopper of the feeder 6 of the arc furnace 7 including a liquid-phase reactor 8, a working electrode 9, a device for collecting the finished product 10 and a pipe 11 of the gas leaving the furnace 7 with a valve 12. The conical body 3 of the reactor 1 has an opening angle φ ° (Figs. 1, 3), about ensuring that particles of the charge from the walls of the reactor 1 are poured down to the inlet of the reactor 1. The furnace feeder 6 includes a mixer of reducing gas and a pre-restored charge, equipped with a gas shutter (not shown in the drawings). To the pipeline 11 by means of a gas mixer and a charge 13 is connected to the feeder of the original charge 14.

The diameters of the pipe 11 and the inlet of the reactor 1 - D ₁ (Fig. 3) are possibly large if the exhaust gas retains the properties of the transport medium, according to which the gas-dynamic force acting on the particles of the transported charge in the gas is much higher than the force particle severity.

The reducing gas pipeline 15 contains a mechanochemical filter 16 and is divided into two branches: one branch 17 with a valve 18 is connected to the mixer of the feeder 6 with a pre-restored charge, and the other branch 19 with the valve 20 is connected to the pipeline 11 between the reactor 8 and the mixer 13.

An exhaust gas pipe 21 with a heat exchanger 22 and a filter 23 is connected to the cover 2 of the reactor 1.

In the device for implementing the second mode (Fig. 2), the pipeline 4 and valves 5 and 12 are excluded and, in comparison with the device of Fig. 1, an additional line 24 for discharging the mixture of charge and gas from the reactor 1 with a second heat exchanger 25, an intake device 26 with a reflection plate is introduced 27 mounted on the lid 2 of reactor 1, and a magnetic separator 28, to the inlet pipe of which a line 24 is connected, and to the outlet pipe - a pipe 21. The separator 28 is mounted on the hopper of the feeder 6 and faces the outlet pipe (not shown).

The device operates as follows. In both modes, the metal “seed” is first loaded onto the collecting device 10 of the final product of the furnace 7. Between the "seed" and the hollow working electrode 9, an arc discharge is excited. The operating parameters of the installation are established: the value of the arc current, the value of the arc gap, the flow rate of the reducing gas through the reactors of the liquid-phase reactor 8 of the final reduction of the furnace 7 by means of valve 18 and the solid-phase conical reactor 1 of preliminary reduction by means of valve 20.

After the melt bath is guided in the liquid-phase reactor 8 by the feeder 14, the initial charge is fed into the mixer 13, which is mixed with the reducing gas and fed through the pipe 11 to the solid-phase reactor 1, after which the pre-reduced charge is mixed with the reducing gas in the mixer of the furnace feeder 6 and fed to the mirror bath melt through the cavity of the electrode 9.

In stationary mode, the exhaust gas from the furnace 7 is fed into the pipeline 11, into which the initial charge from the feeder 14 is also introduced, and the mixture is fed to the top of the cone of the reactor 1.

Consider a stationary process in a conical reactor 1. In the active phase of the first mode (Figs. 1 and 3), the batch particles are carried by the gas flow to the upper, wider part of the reactor 1, where the flow naturally expands, with the distance from the axis of the reactor 1, the rising gas-dynamic flow force gas decreases (figa) and, when it becomes less than the gravity of the particles of the mixture, the latter fall along the walls 3 of the reactor 1 to its top. Since the mixture flow entering through the apex of the cone draws the mixture into its upward movement from the adjacent reactor space 1, the dropping particles of the charge again move upward, but, being already at some distance from the center of the stream, are under the action of a lower lifting force and rise to a lower height . The height of the reactor 1 exceeds the height of the lifting of the mixture (Fig.1, 3). Therefore, the gas leaving the furnace 7, having given its energy to the partial reduction of the charge, leaves the reactor 1 at the same rate as it was introduced, and the partially restored charge accumulates in the reactor 1, constantly being in the process of recirculation, and the path length, which determines the degree recovery of newly incoming particles of the mixture is becoming less. At the same time, charge particles circulate for a long time in the working volume and are absent in the exhaust gas. The residence time of particles in the reactor 1 is determined empirically for each type of charge by a given degree of reduction of the charge oxides, the upper value of which is determined by the limit value of the concentration of particles in the reactor 1, at which the rate of reduction of the oxide begins to slow down significantly and the process of particle adhesion and pelletization develops significantly.

Then, with the closed valves 18, 20, 12 and the open valve 5, the pre-restored charge is fed into the hopper of the furnace feeder 6 (passive phase of the reactor 1). After emptying the reactor 1, the valves 18, 20 and 12 are re-opened, and the valve 5 is closed. This ends the passive phase of reactor 1 and again begins its active phase. All this time, the arc burning process does not stop and the molten bath is maintained in a liquid state.

Gas from the reactor 1 through a pipe 21 is fed into the heat exchanger 22, after which through the filter 23 the gas enters to utilize its thermal and chemical energy or is released into the atmosphere.

In the second mode of operation of the device (figure 2, 4,), the process of preliminary recovery and selection of partially restored mixture with exhaust gas in the reactor 1 is conducted continuously. At the beginning of his work, the concentration of particles in the reducing gas in the working volume of the solid-state reactor 1 is less than in the region of its inlet in the region D ₁ (Fig. 4), and the mass gas velocities at the inlet and outlet of the reactor 1 are equal, and the mass velocities of the charge different: the mass velocity of the charge at the inlet exceeds the mass speed at the outlet of the reactor 1. This leads to the accumulation of the charge in the reactor 1 and, therefore, to increase its concentration in the gas. When the concentration of raw materials in the gas in the region of the intake hole D ₂ reaches a value that ensures the equality of the mass velocities of the discharge and introduction of the charge into the reactor 1, the increase in the concentration of the charge in the reactor 1 stops and the process goes into a stationary mode. The speed of the upward movement of the mixture (and lifting force) is high enough to transport the charge up to the separator 28, therefore, a reflector 27 is installed in the upper part of the reactor 1, after which the gas movement becomes turbulent, the charge particles move to the walls 3 of the reactor 1, where the lifting force of the gas stream is significantly less (Fig. 4a) and part of the gas stream even changes the direction of motion, dragging the charge along to the base of the cone. There, the particles of the charge are again picked up by the upward flow. The conical shape of the reactor 1 ensures that the charge particles descending along the walls 3 of the reactor 1 will certainly be captured by the upward flow of gas and the formation of a fixed mass of the mixture will not occur. Such a vortex movement the batch particle performs repeatedly until it enters the intake device 26. This makes it possible to vary within a wide range the residence time of the batch particles in the reactor and, therefore, to vary within a wide range the degree of their recovery. The pre-reduced charge in the form of magnetite enters the heat exchanger 25, where the magnetite is cooled to a temperature below the Curie point (627 ° C). After that, the magnetite is transferred by a gas stream to a magnetic separator 28, in the magnetic field of which magnetite is separated from the gas and supplied to the furnace feeder 6. Gas from the magnetic separator through a pipe 21 enters the heat exchanger 22 and the filter 23, and then it is utilized or released into the atmosphere .

The height of the reactor N is made equal to the height of the particles in the reactor 1 (Fig.2, 4). At a higher altitude, the volume of reactor 1 is underutilized; at a lower altitude, the productivity of reactor 1 decreases.

The amount of penetration of the intake device 26 into the reactor 1 h determines the residence time of the charge in the reactor 1 and the degree of its recovery (conversion to magnetite). With an increase in the depth, the residence time and the degree of recovery of the charge decrease and vice versa.

The plasma arc current is set such that the thermodynamically necessary thermal conditions are provided in the reaction volume of the liquid-phase reactor 8. For example, when reducing iron ore concentrate in a collecting device 10 in the form of a copper crystallizer, the specific heat flux to the melt pool mirror should be about 5 MW / m ² , that with a mold diameter of 100 mm corresponds to a current value of 1200 A. With a smaller heat flux, iron does not recover, with a larger one, excessive evaporation of the metal occurs.

The flow rate of the reducing gas through the liquid phase reactor 8 is determined by calculation and set equal to 1-1.5 of the thermodynamically necessary flow rate. The flow rate of the reducing gas or inert gas supplied to the line 11 by means of a valve 20 (inert gas supply is not shown in the drawing) is set such that the average temperature of the gas and the charge in the reactor 1 as a result of mixing the gases and the charge is within 1000-1500 ° FROM. At lower temperatures, the speed of the recovery process decreases. At higher temperatures, the particles of iron oxide stick together.

The use of a conical high-temperature solid-state reactor 1 in the process of metal reduction allowed solving several technical problems, namely, reducing the energy and material consumption of metal production from oxide raw materials, reducing the consumption of reducing agent, and reducing the environmental impact due to at least three factors:

- reducing the energy intensity of the metal recovery process, due to the utilization of the recovery and energy potentials of the gas leaving the furnace 7 directly in the recovery process of the device;

- reducing the consumption of reducing gas due to an increase in its use;

- improving the environmental performance of the process, which is directly related to the decrease in energy and material consumption of the process.

The gas velocity in the reactor 1, depending on the technological requirements of the recovery process, in contrast to the fluidized-bed reactor, can be varied in a wide range: the lower speed limit is determined from the conditions for ensuring the pneumatic conveying of the charge in the gas lines, and the upper limit of the gas velocity through the reactor 1 has no limitation and determined from the conditions of the recovery process of the charge under optimal conditions in the reactor 1 (optimal dimensions of the reactor, the degree of recovery, the degree of use restored carrier, temperature and other factors). Due to the high velocity of the gas flow, which prevents the particles from sticking together, the pre-reduction process is carried out at a relatively high, 1000-1500 ° C, operating temperature in the reactor 1.

Thus, the present invention allows:

- reduce the consumption of the reducing agent for the production of metal from dispersed ore raw materials by using the recovery potential of the exhaust gas from the furnace in the recovery process and increasing the degree of use of the reducing gas by increasing the operating temperature and gas velocity in the conical solid-state reactor 1 by about two times compared with the reactor with fluidized bed;

- reduce the energy consumption of metal production from dispersed oxide raw materials through the use of thermal and chemical energy of the gas leaving the furnace in the recovery process, reduce the consumption of reducing agent and increase the degree of pre-recovery;

- reduce the material consumption of metal production from dispersed oxide raw materials by increasing the specific productivity of the process of pre-restoration of the initial charge in the reactor 1 and reducing the installed capacity of the furnace due to the increase in the degree of pre-reduction;

- reduce harmful effects on the environment by reducing the emission of carbon monoxide and carbon dioxide into the atmosphere due to the reduction of the reducing agent consumption and the elimination of heat sources based on fuel combustion from the process;

- to simplify the technological scheme of metal production from dispersed ore raw materials through the use of more productive reactors 1 of preliminary reduction and reduction of their number, as well as the elimination of heat sources based on fuel combustion from the recovery process;

- use any gaseous reducing agent.

The invention can be used at the enterprises of metallurgy and mechanical engineering for direct production of metal from dispersed ore raw materials using gaseous and dispersed reducing agents, including natural gas and hydrogen.

The industrial applicability of the invention is determined by the widespread use in industry of individual elements of the invention, as follows from the description of the above analogues, but in other combinations and with other technical results.

The possibility of realizing all the effects accompanying the use of a conical high-temperature solid-phase reactor in the process of metal reduction for preliminary reduction of dispersed oxide raw materials was established by us for the first time and has not been published anywhere.

The terms of reference have been prepared and an agreement has been concluded with a metallurgical complex enterprise for the development and manufacture of an industrial plant in accordance with the invention, its design has been completed.

Claims (8)

1. A method for the direct reduction of metals from dispersed ore raw materials, including preliminary reduction of the initial charge, feeding the pre-reduced charge together with alloying additives and a reducing agent to an electric arc furnace, initiating an electric arc, melting and finishing the charge, outputting the finished product and exhaust gas, characterized in that the initial charge is introduced into the stream of gas leaving after the final reduction, the resulting mixture is fed into the preliminary reduction reactor, and The initial charge is completely restored by forming the above mixture in the form of a vertically ascending flow expanding along the direction of motion and ensuring the charge particles to recirculate in this flow, then mix the gas and particle mixture into gas and the pre-reduced charge, which is fed to the electric furnace feeder. 2. The method according to claim 1, characterized in that the separation of the mixture of gas and particles of the pre-restored mixture is performed by gas-dynamic forces. 3. The method according to claim 1, characterized in that the separation of the mixture of gas and particles of the pre-restored mixture is performed by magnetic separation. 4. The method according to any one of claims 1 to 3, characterized in that in the process of preliminary reduction of the original mixture to the exhaust gas is mixed with reducing and / or inert gases. 5. A device for the direct reduction of metals from dispersed ore raw materials containing a feeder of the initial charge, a solid-phase prereduction reactor, means for supplying a pre-reduced charge and reducing reagents to an electric arc furnace, including a furnace feeder with a pre-reduced charge, a mixer placed on its central axis a working electrode with an internal cavity, liquid-phase reactor for final reduction, device for collecting the finished product, system for removing the effluent from the liquid-phase reactor gas, characterized in that the solid-phase reactor is made in the form of a vertically arranged cone-shaped body, facing down with the top of the cone, with a lid, a pipeline of gas leaving the liquid-phase reactor is connected to the top of the cone, the source charge feeder is connected to this pipeline, and the furnace furnace feeder is mounted on the mixer . 6. The device according to claim 5, characterized in that a pipeline with a valve is connected to the pre-restored charge supply means, connected at one end to the bottom of the cone body of the solid-phase reactor, the other end to the electric furnace feeder, and the gas exhaust system is installed on the cover of the same reactor . 7. The device according to claim 5, characterized in that the means of supplying the pre-restored charge is equipped with a magnetic separator, including the input and output pipelines and the outlet pipe of the output of the pre-restored charge, mounted on the furnace feeder, while the input pipe of the separator is connected to the cover of the solid-state reactor by a pipeline, and to The outlet pipe of the separator is connected to a gas exhaust system. 8. A device according to any one of claims 5 to 7, characterized in that a source of reducing and / or inert gas is connected to the exhaust gas pipeline.

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