RU2319091C1 - Unit of feeding mixture and reducing gas into an arc electric furnace - Google Patents

Abstract

FIELD: the invention refers to metallurgy without coking particularly to arrangements for production castings, metallic powders and granules by reduction of metals out of metal containing dispersed oxide raw materials with gaseous and dispersed reducers in plasma chemical reactors into which the main share of energy is inputted with the aid of an arc discharge.

SUBSTANCE: the unit is provided with separate pipelines for separate feeding of gas and mixture located in the cavity of the working electrode or around it so as the pipeline adjacent to the working electrode is connected to the source of reducing gas and the other, the periphery pipeline-to the mixture feeding device, at that turning to the working electrode walls of the pipeline for feeding gas are fulfilled cooled.

EFFECT: the invention allows increase efficiency of the process of production of metal and improve its quality, and also increase duration of the periods of functioning of the furnace during substitutions of the working electrodes due to reduce consumption of the material of the working electrode and possibility of using any gaseous and dispersed reducer without danger of coking of the channel of its input.

4 cl, 4 dwg

Description

The field of technology.

The invention relates to non-coke metallurgy, in particular, to devices for the production of castings, metal powders and granules by reducing metals from metal-containing dispersed oxide raw materials by gaseous and dispersed reducing agents in plasma-chemical reactors, the main share of energy which is introduced using an arc discharge.

The level of technology.

Devices for 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 Svenchansky AD M. Energoizdat, 1981, p. 251, 247). Typically, a device comprises a molten bath with metal and slag collection means, a charge and working gas supply unit, a solenoid, and a working electrode located on a central axis and made of graphite or tungsten. In some cases, the function of the charge and gas supply unit is performed by the working electrode, which has an internal cavity and is usually installed in the upper part of the device, and it is the cathode of the arc discharge, the role of the anode is played by the molten metal bath located on the bottom of the furnace.

A common disadvantage of these devices and methods is the presence of a consumable working electrode - the cathode. This requires stopping the process to replace the cathode or using a backup electrode, which is transferred to the working area using the devices provided for this (RF patents No. 1781306 and 2007463). In both cases, the technological process remains intermittent due to the need to disconnect the charge supply means from the cathode during the installation of the backup electrode, and the resulting material is contaminated by cathode erosion products.

The closest prototype of the present invention is a node for supplying reducing gas and a charge to an electric arc furnace, including a reactor located in the magnetic system, two bipolar electrodes, an upper working electrode and a lower one located on the vertical axis of the reactor connected to the source of reducing gas and the charge feeder (US Pat. RF No. 2007463).

In this device, the second electrode (anode) is a molten bath placed in a ceramic crucible, reducing gas and a charge are fed into the reactor through a hollow working electrode, a cooled pipe is installed outside this electrode, which serves to cool the working electrode and seal the chamber, the reactor and the hearth are equipped graphite and ceramic masonry, the reactor is placed in a magnetic field, and a device for moving and building is introduced to build up the working electrode.

The oxide raw material, in contact with the working electrode, is intensively restored, but the electrode material (usually graphite) is consumed, and the reduction process itself is endothermic and is accompanied by a decrease in the temperature of the working electrode, which leads to the occurrence of contracted cathode spots and electrode erosion.

When using natural gas as a reducing agent in this device, it is not possible to combine the requirements for lowering the gas temperature and maintaining the high temperature of the end of the working electrode, which is necessary to reduce its erosion associated with the presence of sedentary contracted cathode spots of the arc.

SUMMARY OF THE INVENTION

The present invention solves the technical problem of increasing the productivity of the metal production process and improving its quality.

The main technical result of the use of the invention is to increase the duration of the periods of operation of the furnace between replacements of the working electrode by reducing the consumption of material of the working electrode and the possibility of using any gaseous and dispersed reducing agent without the risk of coking of the input channel.

Additionally, the problem of reducing the contamination of the finished metal product with erosion materials of the working electrode is solved.

This result is achieved by the fact that the supply node of the reducing gas and the charge is made in the form of separate pipelines for the separate supply of gas and the charge located in the cavity of the working electrode or around it so that the pipeline adjacent to the working electrode is connected to the source of the reducing gas, and the other , peripheral, pipeline - to the charge feeder, while the walls of the pipelines for supplying gas facing the working electrode are made cooled.

In one embodiment of the invention, the pipelines are formed by two coaxial pipes, internal and external, located in the cavity of the working electrode with a ratio of its external and internal diameters of 3-5.

In another embodiment of the invention, the pipelines are formed by three coaxial pipes - internal, intermediate and external, placed outside the working electrode.

In the third embodiment of the invention, the supply unit is formed by two sets of pipes placed on circles concentric with respect to the working electrode, while the pipes of the set placed on the inner concentric circle are made cooled, radially aligned with the pipes of the set placed on the outer circumference, and connected to the source of the reducing gas, and the pipes of the set placed on the outer concentric circle are connected to the charge feeder.

In all cases, the lower ends of the pipes are placed above the lower end of the working electrode.

Terms and definitions used.

Feeder - a device, usually containing a bunker with the original ore raw materials and means for feeding it at a given speed.

Synthesis gas is a gas mixture whose main components are carbon monoxide and hydrogen.

A mixture is a mixture consisting of ore raw materials (ore, concentrate, etc.), alloying and refining additives.

Iron ore raw materials - mineral raw materials containing one or more iron oxides of various valencies.

Oxide raw materials - mineral and industrial raw materials containing metal oxides.

Description of the drawings.

Figure 1 schematically in longitudinal section shows a variant of the placement of the feed node in the cavity of the working electrode.

Figure 2 schematically in longitudinal section shows a variant of the feed node in the form of coaxial pipes surrounding the working electrode.

Figure 3 schematically in longitudinal section shows a variant of the feed node in the form of sets of pipes surrounding the working electrode.

Figure 4 shows a cross section of the device of figure 3 in the plane aa.

The device shown in Fig. 1 comprises a charge feeder 1, a reducing gas source 2, an arc furnace reactor 3 with cooled (not shown) walls 4 and a roof (cover) 5, a hollow working electrode 6, in the cavity of which a cooled external pipe 7 is placed , in which, in turn, an inner pipe 8 is installed, which together form a conduit adjacent to the electrode 6, the peripheral conduit being a pipe 8, a hearth electrode 9 on the means for collecting 10 finished products and a magnetic system in the form of a solenoid 11. The lower ends of the tr 7 and 8 b are spaced from the lower end of the electrode 6 by an amount 1-1.5 inner diameter of the electrode 6. The ratio of the outer and inner diameters of the electrode 6 is in the range 3-5. When the ratio of the diameters of the electrode 6 is less than three, the current density in it increases, which causes its increased consumption, and when the ratio of the diameters of the electrode is greater than five, the possibilities for placing pipes 7 and 8 in it are greatly reduced. The working electrode 6 is isolated from the cover 5 dielectric seal 12.

In the embodiment of the device shown in FIG. 2, the inner cooled pipe 13 and the outer pipe 14, separated by an intermediate pipe 15, are placed outside the working electrode 6, which can be both hollow and solid. In this case, the adjacent pipeline is formed by pipes 13 and 15, and the peripheral one - by pipes 15 and 14.

The pipe 14 is mounted on the cover 5 and is isolated from it by an electrically sealant 16 made of dielectric material. The lower ends of the pipes 13, 14 and 15 are placed above the lower end of the working electrode 6 and are located at a distance of 0.5-1.0 of its outer diameter.

With large transverse dimensions of the working electrode 6, the embodiment shown in FIG. 3 is preferred. The charge and reducing gas supply pipelines are formed by two sets of pipes 17 (adjacent) and 18 (peripheral) placed on circles concentric with respect to the working electrode 6 - inner 19 (pipe 17) and outer 20 (pipe 18), as shown in Fig. 4. The pipes 17 are made cooled, the pipes 17 and 18 of both sets are pairwise aligned in radial directions, but are not necessarily in contact.

Pipes 7, 13, 17 are made in the form of two connected shells (not shown in the drawing), between which refrigerant is passed.

In this case, the peripheral pipelines - pipes 8 in Fig. 1, the cavity between the pipes 14 and 15 in Fig. 2 and the pipes 18 in Figs. 3 and 4 are connected to the charge of the charge 1 and serve as a means of feeding it into the reactor 3, and adjacent pipelines - the cavity between the pipes 7 and 8 in figure 1, the cavity between the pipes 13 and 15 in figure 2 and the pipes 17 in figure 3 are connected to the gas source 2 and serve as a means of supplying it to the reactor 3.

The working electrode 6 and the hearth electrode 9 are electrodes of an electric arc furnace, their polarity can be either direct (electrode 6 serves as a cathode) or reverse (electrode 6 serves as an anode).

The implementation of the invention.

The operation of the device with the direct polarity of the electrodes of the reactor 3 is illustrated. A metal “seed” is loaded onto the electrode pad 9 of the collecting device 10, voltage is applied to the electrodes of the reactor 3 and an arc discharge is excited therein by one of the known methods, for example, by briefly touching the “working” electrode 6 with electrode 9, high-frequency breakdown, etc. At relatively low relative to the nominal values of the arc current induce on the site of the electrode 9 "swamp" of metal. Then set the operating parameters of the installation: the induction of the magnetic field of the solenoid 10, the magnitude of the arc gap between the electrode 6 and the molten metal on the site 9, the magnitude of the arc current, the flow of reducing gas through the reactor 3 from the gas source 2.

After pointing the “swamp” on the site of the electrode 9, the feeder 1 through the peripheral pipelines - pipe 8 (figure 1), through the cavity between the pipes 14 and 15 (figure 2) or through pipes 18 into the reactor 3 serves the mixture, and through adjacent pipelines - Through the cavity between the pipes 7 and 8 (FIG. 1), through the cavity between the pipes 13 and 15 (FIG. 2) or through the pipes 17, a reducing gas is supplied to the reactor 3. The mixture of charge and gas enters the melt, while the mixture is restored to metal.

The supply of reducing gas through pipelines adjacent to the working electrode 6, prevents the mixture fed through the peripheral pipelines and containing oxide raw materials to the working electrode 6 and reduces its wear.

Cooling the walls of adjacent pipelines (pipes 7, 13 or 17) allows the supply of natural gas to the reactor 3 at a temperature below the gas pyrolysis temperature, which does not require its conversion. Moreover, due to the fact that the charge supplied to the reactor 3 does not interact with the material of the working electrode 6, and the areas of thermal contact of the pipes 7, 13, and 17 with the electrode 6 can be located far enough from the lower end of the electrode 6 or be completely absent, the temperature of the latter can be maintained a significant amount (about 3000 ° C), sufficient for the formation on the end of the electrode 6 of a diffuse arc spot, providing a uniform and, therefore, reduced output of the electrode 6.

Placing the lower ends of the tubes 7 and 8 at a distance from the lower end of the electrode 6, greater than 1.5 of the diameter of its cavity, and the lower ends of the tubes 13-15, 17 and 18 at a distance greater than 1 of the outer diameter of the electrode 6, leads to a significant hit of the charge on working electrode, located at high temperature (about 3000 ° C), and its increased wear. When removing the lower ends of the tubes 7 and 8, less than 1.0 of the diameter of the cavity of the electrode 6, and the lower ends of the tubes 13-15, 17 and 18, less than 0.5 of the outer diameter of the electrode 6, the probability of a jump arc discharge to these pipes and their destruction.

The axial magnetic field of the solenoid 10 provides azimuthal rotation of the arc and the molten bath, which leads to uniform heating and active interaction with the reducing gas of the entire mass of the incoming charge and to obtain a homogeneous metal.

Thus, the present invention allows:

- reduce erosion of the working electrode 6 by eliminating its contact with the charge when it is fed into the working space of the reactor 3 and the formation of a diffuse cathode spot by increasing the temperature of the end face of the electrode 6;

- use any gaseous reducing agents: synthesis gas, hydrogen, unconverted natural gas by supplying gas through cooled metal pipes 17 or cavities with cooled walls (pipes 7 or 13);

- to obtain a homogeneous metal with a low content of impurities (for example, carbon) due to the reduction of erosion of the electrode 6, the use of gaseous reducing agents and the elimination of the use of coke and to increase the productivity and continuous operation of the arc furnace by reducing the consumption of the electrode 6.

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

The environmental indicators of the proposed method and device are significantly higher than that of analogues: coke is not consumed, agglomeration and pelletizing of ore raw materials are not required, it is possible to work on hydrogen and on raw natural gas.

The possibility of realizing all the effects accompanying the process of supplying reducing gas to the reactor through cooled pipes and cavities with the prevention of contact of the charge with the material of the working electrode, was established by us for the first time and has not been published anywhere.

Claims (4)

1. A node for supplying a reducing gas and a charge to an electric arc furnace, including a reactor located in the magnetic system, two bipolar electrodes - an upper working electrode and a lower one located on the vertical axis of the reactor, a reducing gas source and a charge feeder, characterized in that the node is equipped with a set of pipelines adjacent and peripheral with respect to the surface of the working electrode, and the pipelines of the adjacent sets are made cooled, and the lower ends of all pipelines are placed above the lower end of the working electrode. 2. The node according to claim 1, characterized in that the pipelines are formed by two coaxial pipes - external and internal, located in the cavity of the working electrode, made with a ratio of its external and internal diameters of 3-5, the outer pipe is made cooled, while to the adjacent pipeline formed by the outer and inner pipes, a source of reducing gas is connected, and a charge feeder is connected to the peripheral pipe formed by the inner pipe, the lower ends of both pipes being separated from the lower end of the work electrode by an amount 1-1.5 diameter of its cavity. 3. The assembly according to claim 1, characterized in that the pipelines are formed by three coaxial pipes - external, intermediate and internal, installed outside the working electrode, the inner pipe is made cooled, while a source of reducing gas is connected to an adjacent pipe formed by the intermediate and internal pipes and the charge feeder is connected to the peripheral pipeline formed by the intermediate and external pipes, and the lower ends of all pipes are separated from the lower end of the working electrode by an amount 0.5-1.0 outer diameter of the working electrode. 4. The assembly according to claim 1, characterized in that it has two sets of pipes located on two circles concentric with respect to the working electrode - internal and external, and the pipes of the adjacent set placed on the internal concentric circle are made cooled, aligned in radial directions with pipes of the peripheral set located on the outer circumference and are connected to the source of reducing gas, and pipes of the peripheral set are connected to the charge feeder, and the lower ends of the pipe sets are separated from the lower the end of the working electrode by a value of 0.5-1.0 of the outer diameter of the working electrode.

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