RU2612330C2 - Method of direct reduction of materials containing metal oxides to produce melt metal and device for carrying out method - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention refers to metallurgy, in particular to the methods of producing metal by direct metal reduction from oxide-containing materials with a solid reducing agent. Metallization is performed by direct reduction of metal oxides and melting the resulting product. Oxide-containing materials in a mixture with a solid reducing agent are continuously fed through a cavity of hollow electrode into a zone of electric arc furnace located between the bottom and the hollow electrodes, and the direct reduction of metal oxides and their melting are carried out by means of Lenz-Joule heat generated in the interelectrode space of electric arc furnace comprising the bottom electrode and at least one hollow electrode mounted vertically with the possibility of lowering connected to a current source and whose inner passage is formed expanding downwardly. Oxide-containing materials and the solid reducing agent are fed into the electrode cavity in the rounded or granular state and maintained in it at a height of from 1 to 10 diameters in the electrode cavity depending on the average granules diameter.

EFFECT: invention is directed to increase the intensity of the reduction process in the high temperature zone.

6 cl, 1 dwg

Description

The invention relates to the field of metallurgy, in particular to methods for producing metal by direct reduction of metal oxides with a solid reducing agent.

A known method of reducing metal oxides by reduction with gases, for example, hydrogen, carbon monoxide. The most common recovery method is the Midrex process (N. A. Tulin, V. S. Kudryavtsev, S. A. Pchelkin and others. Development of non-coke metallurgy, M. Metallurgy, 1987, p. 230) [1]. In this method, the principle of converting natural gas into reducing gases is applied, followed by their purification and reheating before being fed into a shaft furnace loaded with pelletized oxidized pellets. The recovery process is carried out at temperatures from 800 ° C to 900 ° C. The resulting product in the form of sponge iron is cooled, packaged and sent to the consumer.

The disadvantages of this method are:

- the need for pelletizing concentrate and oxidative firing;

- the need to convert natural gas using expensive nickel catalysts and the mandatory purification of natural gas from sulfur and other harmful impurities in order to avoid poisoning of the catalyst;

- the need to clean the reducing gas from water vapor by condensation, respectively cooling;

- the need for re-heating the reducing gas;

- a relatively low temperature of the recovery process to avoid sintering;

- sintering of the recovered product in case of temperature violations.

The source [1] on page 47 also describes a method for recovering pellets with a solid reducing agent in rotary kilns, where calcined hardened and oxidized pellets are reduced with carbon-containing raw materials or coal of appropriate quality when heated with either natural gas or coal fuel [2].

The disadvantages of this method are:

- bulky equipment;

- poor process control;

- sintering of the product in the recovery zone;

- relatively low quality of the product;

- the need for preliminary pelletizing of the concentrate and hardening of the pellets by firing.

Closest to the claimed method is described on page 77 of the source [1], the recovery smelting method, namely the Elred method, which has been developed by Swedish companies since 1971 using electricity [3]. According to this method, fine ore (fraction less than 0.1 mm) and fine coal (fraction less than 0.2 mm) are introduced into the circulating fluidized bed. At a temperature of 900-1000 ° C, coal is gasified by air, and fine ore is restored by about 70%. This pre-reduced material is introduced together with slag-forming materials at a temperature of 600-700 ° C through a hollow electrode into a DC ore-reducing electric furnace. In the plasma of an electric arc arising between the electrode and the melt, the reduction and melting of the material is completed to produce cast iron containing 3–4% carbon.

The disadvantage of this method is the complexity and unreliability of the process of preliminary reduction of oxide-containing materials in a circulating fluidized bed. To prevent sticking of the metallized product, an excess supply of coal is provided, which is a full guarantee against a violation of the boiling process. In addition, this limits the performance of the process, as the process of relatively low temperature (900-1000 ° C) gas recovery is the main inhibitory factor. Another important negative factor is the need to load excess coal, for the gasification of which a significant amount of energy is spent, both in the fluidized bed system and in the electric furnace.

The objective of the invention is to increase the productivity of the metal reduction process.

The problem is achieved in that the method of direct reduction of metals from oxide-containing materials, like the known method, includes metallization by direct reduction of metal oxides and the melting of the resulting product. The claimed method is characterized in that the oxide-containing materials in a mixture with a solid reducing agent are continuously fed through the cavity of the hollow electrode into the zone of the electric arc furnace located between the bottom and hollow electrodes, and the direct reduction of metal oxides and their melting is carried out due to the Lenz-Joule heat released in the interelectrode the space of an electric arc furnace containing a bottom electrode and at least one hollow electrode, while oxide-containing materials and a solid reducing agent are fed into the cavity of the electrode and in a rounded or granular state and support in it at a height of 1 to 10 diameters of the cavity of the electrode, depending on the average diameter of the granules.

Oxide-containing materials and a reducing agent are fed into the electrode cavity in a ground state.

Oxide-containing materials and a reducing agent are supplied in a heated state.

Slag-forming materials are added to the mixture of oxide-containing materials and a reducing agent.

15-20% of slag-forming materials are added to the mixture of oxide-containing materials and a reducing agent.

A device for the direct reduction of metals from oxide-containing materials, like the known device, contains a high-temperature electric arc furnace, a device for feeding oxide-containing material or its concentrates mixed with a solid reducing agent, and the discharge of metal and slag melts. The claimed device is characterized in that the electric arc furnace is made in the form of a refractory container containing a bottom electrode and at least one hollow electrode, made with the possibility of continuous supply through its cavity of oxide-containing materials or their concentrates in a mixture with a solid reducing agent, the internal channel of the hollow the electrode is made expanding downward, the hollow electrode is mounted vertically and connected to a current source with the possibility of vertical movement.

The invention consists in the following. In the claimed method, oxide-containing materials mixed with a solid reducing agent are fed into the zone of the highest temperatures of the electric arc furnace, which occurs between the end face of the hollow electrode and the bottom electrode, which is either under a layer of liquid slag or under a layer of liquid metal. Under liquid slag, the process proceeds in a current mode at a temperature of 1900-2000 ° C (Lenz-Joule heat), and in the presence of liquid metal or when approaching the bottom carbon electrode at a certain distance, an arc is ignited, which is supported by the furnace automation, as a rule current, which ensures a high temperature of 5000 ° C and higher in the zone of arc burning inside the tubular electrode. In the high temperature zone, oxide particles with sizes up to 0.1-0.5 mm are restored in 0.001-0.01 seconds due to the carbon of the reducing agent (coal) and at the same time it is melted to the degree of liquid molten metal and slag. Subsequently, settling liquid products are discharged from the electrodes and removed for further redistribution.

The reduction of metal oxides will occur not only due to the supplied solid reducing agent - coal, but also partially due to the carbon of the hollow electrode, since oxide-containing material goes directly to the heat release zone. Loading oxide-containing materials allows to obtain liquid metal - cast iron in one operation. The supply of crushed oxide-containing material and solid reducing agent allows you to ensure maximum speed recovery process.

The supply of oxide-containing materials and a reducing agent in rounded or granular form will allow for partial reduction of oxides in the process of lowering them through the hollow electrode due to rising reducing gases in the layer between the pellets or granules. Maintaining a certain layer of pellets or granules will allow the efficient use of reducing gases leaving the furnace through a hollow electrode. A layer of one cavity diameter corresponds to smaller granules based on the hydraulic resistance of the layer, and a layer of 10 cavity diameters corresponds to standard, industrially produced pellets. When using finely granulated or finely dispersed materials, the gas-dynamic resistance of the layer to gas movement increases, so the layer of the column of oxide-containing materials should be much smaller - at the level of one diameter of the electrode channel, which will allow more efficient use of the arc energy potential.

When heating oxide-containing materials, especially due to the heat of the exhaust gases of the electric arc furnace, a higher process efficiency is achieved by reducing the energy consumption, as a more expensive energy source. The addition of slag-forming materials in an amount of 15-20% will ensure the production of a molten metal with a lower content of harmful impurities. Amounts of slag-forming substances outside this limit can lead to an excessive consumption of electricity and lack of competitiveness.

The implementation of the device for the recovery of materials containing metal oxides to obtain a molten metal in the form of a refractory vessel type, containing at least one hollow electrode placed in the tank with the ability to work in the resistance furnace under a layer of slag with continuous supply of the mixture oxide-containing materials with a solid reducing agent in the cavity of the electrode, allows you to instantly, in one operation to obtain a molten metal, such as cast iron, from iron ore concentrate with the purity of the original meta and obtain subsequently high quality steel after removal of carbon in the unit, for example, a ladle furnace or converter. The implementation of the inner channel of the electrode conical with the expansion downward will reduce or eliminate the risk of karpeniya oxide-containing material inside the cavity of the electrode, which under certain conditions is not excluded with a cylindrical or tapering channel.

A new technical result achieved by the invention is a multiple increase in the intensity of the metal reduction process in the high temperature zone exceeding the usual temperatures used in known metallization systems (700 ÷ 1000 ° C) two to three times (2000-5000 ° C), as well as the use of fine concentrate (without pelletizing) or simply enriched and crushed ore, the production of liquid metal - cast iron in one redistribution without preliminary recovery.

In addition, the present invention allows the processing of complex ores into the corresponding alloys, for example, from nickel ores, ferronickel can be obtained in one action. Experimental data show that Norilsk Nickel concentrate with a nickel content of 7.2% produces ferronickel with a nickel content of 19.2%, iron 78.8%, cobalt 1.06% and copper 0.82%. Also, pig iron with a metal content of 99.9%, including 4.36% carbon, was obtained from the Lebedinsky concentrate with an iron content of about 66%. These results indicate a sufficiently high purity of the obtained metal.

The method is illustrated in the figure, where in FIG. 1 shows a device for implementing a method with one hollow electrode.

The device comprises a reactor vessel 1, a hollow tubular electrode 2 with a holder 3, a loading funnel 4, a metering feeder 5, a slag taphole (window) 6, a bottom electrode 7, a cooler 8, and a cast iron taphole 9. When the reactor is designed as a U-shaped vessel with two hollow electrodes 2 connected to a direct current source, the reactor 1 is equipped with a skimmer 10, separating the electrodes in the upper part. Skimmer 10 has a window 11 for the flow of slag to the notch 6.

The claimed method and device work as follows. At the initial start-up, a certain amount of coke is loaded into the housing 1 of the prepared device to prevent the lower electrode 7 from heating up. By lowering the electrode 2 with a special mechanism (not shown), the arc in the reactor 1 is ignited and the recovery zone is heated. If necessary, through the slag window (tap hole) 6 toss and throw liquid slag or liquid metal from the scrap. After the appearance of a liquid melt — the so-called “swamp” —the prepared mixture of concentrate and reducing agent (charge) begins to be fed through the cavity of the electrode 2 through the funnel 4 and the metering feeder 5. When the prepared charge enters the reactor’s high temperature zone, the oxides are reduced by carbon of the solid reducing agent inside the hollow electrode and while melting, the metal, passing through a slag layer, settles on the bottom of the reactor. Upon reaching the metal level to the level of notch 9, the metal begins to flow out and is poured either into ingots or granulated. A variant of processing in a ladle furnace unit in a liquid state is possible.

Slag is also maintained at a certain level by draining the excess through the window-notch 6. Long-term operation of the reactor is ensured by cooling the lower electrode and the bottom cooler 8.

The use of the claimed invention will significantly increase the intensity of the recovery process in the zone of high temperatures exceeding the usual temperatures used in known metallization systems (700 ÷ 1000 ° C) two to three times (2000-5000 ° C), as well as use fine concentrate (without rolling ) or simply enriched and ground ore, and the production of liquid metal - cast iron in one redistribution without preliminary reduction.

Claims (6)

1. A method of direct reduction of metals from oxide-containing materials, comprising metallization by direct reduction of metal oxides and melting of the obtained product, characterized in that the oxide-containing materials in a mixture with a solid reducing agent are continuously fed through the cavity of the hollow electrode into the zone of the electric arc furnace located between the bottom and hollow electrodes and direct reduction of metal oxides and their melting is carried out due to the Lenz-Joule heat released in the interelectrode space of the electron an arc furnace containing a bottom electrode and at least one hollow electrode, while oxide-containing materials and a solid reducing agent are fed into the electrode cavity in a rounded or granular state, maintaining their layer at a height of 1 to 10 diameters of the electrode cavity, depending on the average the diameter of the granules. 2. The method according to p. 1, characterized in that the oxide-containing materials and a reducing agent are fed into the electrode cavity in a ground state. 3. The method according to p. 1 or 2, characterized in that the oxide-containing materials and the reducing agent are served in a heated state. 4. The method according to any one of paragraphs. 1-3, characterized in that in the mixture of oxide-containing materials and a reducing agent add slag-forming materials. 5. The method according to any one of paragraphs. 1-4, characterized in that in the mixture of oxide-containing materials and a reducing agent add 15-20% of slag-forming materials. 6. A device for the direct reduction of metals from oxide-containing materials, containing a high-temperature electric arc furnace, a device for feeding oxide-containing material or its concentrates mixed with a solid reducing agent, the discharge of metal and slag melts, characterized in that the electric arc furnace is made in the form of a refractory tank containing a bottom electrode and at least one hollow electrode, made with the possibility of continuous supply through its cavity of oxide-containing materials or their concentrates in a mixture with Verdi reducing agent, wherein the inner passage of the hollow electrode is made extended downward and mounted vertically hollow electrode can be lowered and connected to a current source.

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