RU2734610C1 - Method of producing titanium-iron alloy and device for implementation thereof - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: group of inventions relates to metallurgy, particularly to electrolytic methods of producing inorganic compounds based on rare and dispersed metals, and an electrolysis cell for carrying out said method. Method of producing titanium-iron alloy containing 63–78 wt. % of titanium includes preparation of salt mixture consisting of cryolite and aluminum fluoride with cryolite ratio equal to 2.7–3.0, drying of said mixture, heating to liquid state and transfusion as electrolyte into electrolytic cell. Then melted at temperature of 1185–1200 °C. Titanium-iron alloy containing 63–65 wt. % of titanium is fed via electrolyte into molybdenum receiver of cathode. Then, through gap between anode and side wall of electrolyser to electrolyte, having temperature of 1100–1150 °C, powdered titanium oxide is loaded with excess and includes a combined source of direct and alternating current or DC and AC sources with provision of electrolyte temperature in range of 1185–1200 °C and content of titanium oxide in electrolyte 1–9 wt. %. Iron chips are introduced and finished product is unloaded in form of titanium-iron alloy. Electrolysis cell comprises graphite anode and cathode from refractory metal, at that it contains bead refractory non-electroconductive lining, corundum lining, graphite bottom, unloading pocket for unloading of finished product in form of titanium-iron alloy, having temperature of 1135–1185 °C. Said unloading channel is connected to molten metal by horizontal channel. In the upper part of the said lining between the graphite anode and the side wall of the electrolytic cell there is an armhole in the refractory lid of the said unloading pocket for supply of titanium oxide into the working space of the bath at temperature of 1100–1150 °C.

EFFECT: reduced power consumption and increased stability of electrolysis process when producing titanium-iron alloy.

3 cl, 2 dwg, 1 tbl, 1 ex

Description

The invention relates to the field of metallurgy, in particular to electrolytic methods for producing inorganic compounds based on rare and trace metals.

A known method for the production of ferrotitanium from titanium oxides and steel scrap with the simultaneous reduction of titanium oxide with excess aluminum, which is added to the molten charge (alumothermy), and carry out the reduction in an electric arc furnace [application UA, No. a200509879 A, publ. 02/15/2006, bul. 2]. The resulting melt of ferrotitanium alloy is stirred using a furnace inductor to homogenize it. Subsequently, refining is carried out in an electron beam installation with an intermediate container. The result is a high-purity ferrotitanium.

The disadvantages of this method for producing titanium-iron alloy are:

- the need to use the refining of the resulting melt of ferrotitanium from excess aluminum, which takes part in the reduction of titanium from its oxide in an electric arc furnace;

- the use of expensive, metal-intensive and difficult to maintain equipment - an installation of electron beam remelting;

- mandatory use of the device, which must ensure the transportation of the ferrotitanium melt obtained in the electric arc furnace to the vacuum installation of electron beam remelting. In this case, it takes time (from 1.2 to 1.6 hours) to pump out from the specified installation to a deep (up to 1-5⋅10 ^-5 - 5⋅10 ^-6 mm Hg) vacuum, before turning on its electronic ray cannons for refining. That is, only for remelting, powerful vacuum and diffusion pumps and, accordingly, control equipment are needed.

There is a known method of aluminothermal production of ferrotitanium, including preliminary feeding into the aggregate of metal titanium waste, loading and melting the main parts of the charge containing ilmenite concentrate, iron ore pellets, lime, aluminum in the form of a mixture of powder and granules, or a mixture of aluminum and ferrosilicon. After melting the main part of the charge, a reducing-lime mixture of an aluminum-silicon alloy and lime is introduced into the furnace, then an additional reducing part of the charge containing iron ore pellets, lime, ferrosilicon and aluminum powder is loaded and melted. The resulting ferrotitanium contains up to 6.2% silica. The method is carried out in a furnace at a temperature of at least 1700 ° C (the condition for maintaining the formation of a metal melt from titanium waste) [See. description to A.S. USSR No. 1786170, IPC S22S 33/04, publ. 07.01.93].

The disadvantages of this method for producing titanium-iron alloy are:

- This method is a furnace option for producing ferrotitanium and, therefore, involves a large consumption of electricity.

- the method provides for the disposal of titanium waste, since the amount of titanium metal waste is at least 50% of the total load.

There is a known method for producing a high-titanium ferroalloy from ilmenite (RU 2329322 C2), according to which titanium slag with a high titanium oxide content is obtained at the first stage, which includes introducing steel or cast iron scrap into an electric arc furnace, melting it and removing slag, loading after draining at the first stages of a charge of ilmenite, electrode breakage, limestone, reduction and melting of iron, discharge of slag containing titanium oxide. In the second stage, a charge is prepared, consisting of crushed slag (obtained in the first stage) and aluminum powder. The prepared mixture is placed in a metal shell and used as a consumable electrode in an electroslag melting unit, which is melted to form ferrotitanium containing wt. %: 68.00-78.70 titanium, 19.30-30.00 iron, up to 1.98 impurities containing aluminum, silicon, manganese, vanadium, sulfur.

The disadvantage of this method for obtaining high-titanium ferroalloy is: as a reducing agent, finely ground electrode breakage with a carbon content of 86 wt. %, which leads to an increased carbon content in the intermediate product and further contamination of the final ferrotitanium with the possibility of titanium carbide formation.

The closest in technical essence and the achieved effect to the proposed invention are a method for producing titanium-iron alloy with titanium iron ore [CN 101509139 A (NORTHWEST INST NON-FERROUS METALS), 19.08.2009]. Get titanium-iron alloy in three stages, with a content of 35-45 wt. % titanium. Initial stage: preparation of the ilmenite electrode: the ilmenite raw material is subjected to crushing, uniform mixing and cold isostatic pressing. And after sintering at high temperatures, an ilmenite electrode is obtained. In the second step: the molten salt electrolysis reaction. The ilmenite electrode obtained in the first stage is used as a cathode, a graphite rod is used as the anode, the molten salt electrolysis reaction is carried out under the protection of argon. CaCl _{2 is} used as the electrolyte. The process temperature is 850-1200 ° C, and the voltage is 2.5 ÷ 3.5 V. At the third stage: Vacuum melting. The process temperature is 1350-1370 ° C, the vacuum melting density is 0.67-13.3 Pa.

The disadvantages of this method for producing titanium-iron alloy are:

- obtaining a titanium-iron alloy with a low titanium content;

- multistage technology, which complicates the process of obtaining the final product;

- CaCl _{2 is} proposed as an electrolyte. When electrolysis of molten mixtures of titanium oxide with calcium chloride, good results are not obtained: cathode deposits consist mainly of lower titanium oxides.

The technical result of the proposed invention is to reduce energy costs and increase the stability of the electrolysis process when producing titanium-iron alloy.

This is achieved by the fact that one end pocket for unloading the finished product is introduced into the design of the electrolyzer, there is a vertical hole in the anode for removing anode gases and vapors of fluoride salts, a hood for exhaust ventilation is located above the anode, there is a gap between the anode and the side wall of the electrolyzer through which iron and rutile additives, and information about the thermal state of the bath is fed to the current power source through temperature sensors and the electrolyzer balance is automatically regulated.

Along the perimeter of the anode there are vertical holes, the shape of which has a truncated cone. The holes should be spaced evenly and as far as possible from the side surface of the anode. This design should facilitate the removal of gases from under the anode.

An unloading pocket, designed to remove the finished alloy, is located on one side of the bath and is connected to the molten metal by means of a horizontal channel. The temperature of the alloy in the pocket should not be lower than in the electrolysis compartment of the bath by 15-50 ° C.

To maintain the required electrolyte temperature, there are two graphite anodes in the molten salt zone, which are supplied with alternating current. Working and heating electrodes are powered separately.

Comparison of the claimed technical result with the prototype and other solutions in this field of technology revealed the use of similar features in the process of drawing up a salt mixture, drying, heating to a liquid state and overflowing the resulting melt from the furnace into an electrolyzer containing a graphite anode, a refractory metal cathode and a lining. However, the presence in the electrolyzer of one unloading pocket, the presence of vertical holes in the anode, as well as the presence of two or more graphite anodes providing the heat balance of the electrolyzer are the hallmarks of the present invention.

The use of these differences can significantly increase the reduction in energy costs and achieve an increase in the stability of the electrolysis process.

For the normal conduct of the process of electrochemical production of an alloy containing 63-78 wt. % titanium, the electrolyte temperature in the working space of the electrolyzer should be 1185-1200 ° C. At higher melt temperatures, the fireclay lining begins to collapse, while at lower temperatures, crystals of the TiFe + β-Ti eutectic begin to precipitate and electrolysis stops. In this case, the stability of the electrolysis process is disturbed and energy costs will increase.

Titanium oxide should enter the working compartment only in a dissolved form. As a result, the resistance of the electrolyte does not increase, but, on the contrary, decreases. For this, the raw material is loaded onto the electrolyte crust. Titanium oxide heats up and dissolves in the electrolyte. A single loading of titanium oxide is determined theoretically and verified empirically. The electrolyte temperature in the gap between the anode and the side wall of the cell should be close to the temperature of the working space of the cell, i.e. 1100-1150 ° C. The difference in temperatures in the working electrolyte and in the space between the anode and the side wall of the cell is mainly due to the loss of heat through the electrolyte crust.

The temperature in the unloading pocket is 1135-1185 ° C, i.e. lower than in the electrolysis bath. Lowering the temperature lower than in the working space of the electrolyzer leads to the release of intermetallic compounds at the bottom of the pocket. They are periodically removed using a special device. If the composition of the metal alloy does not change, then the composition of the intermetallic compounds remains constant. The temperature range of the unloading pocket 1135-1185 ° C is due to the fact that at a temperature below 1135 ° C, the alloy will completely solidify in the unloading zone, and at a temperature below 1185 ° C, the first intermetallic compounds will precipitate. In both cases, unloading of the iron-titanium alloy will be impossible, which negatively affects the stability of the process.

To maintain a constant temperature or for variability of the thermal regime, the installation contains a combined power source or two sources of direct and alternating current. In this case, the working density of the direct current on the electrodes is 0.3 ÷ 0.6 A / cm ² , and the density of the alternating current can be no more than 1.0 A / cm ² . The range of DC density 0.3-0.6 A / cm ² is due to the fact that at a DC density below 0.3 A / cm ² titanium is recharged and the electrolysis process is ineffective, and at a DC density above 0.6 A / cm ² , aluminum begins to precipitate at the cathode.

The thermal regime of the electrolyzer is maintained and regulated by means of alternating current sources and temperature sensors. Feedback allows you to adjust the balance of the bath automatically.

FIG. 1 shows an electrolyzer for producing a titanium-iron alloy containing 63-78 wt. % titanium. The electrolyzer consists of a graphite anode 1, an onboard refractory non-conductive lining 2, a cathode metal 3, a cathode made of a refractory metal 4, a corundum lining 5, a refractory cover for a pocket for removing alloy 6, a graphite hearth 7, tapered holes for removing gases 8, an armhole for feeding titanium oxide 9, bell device for gas collection 10, anode frame 11, sources of alternating and direct current 12.

FIG. 2 shows a diagram of the implementation of obtaining an alloy iron - titanium. After drying and melting the cryolite in the chamber furnace 13, the molten electrolyte is poured into the bath 14. Then the anode is lowered into the electrolyzer. The anode and cathode are connected to a combined AC and DC power supply 12 by means of current leads, and an electric current is supplied. In this case, the interelectrode distance and the supplied current must be maximum. The cathode alloy melted in the chamber furnace is introduced through the pocket to remove the alloy 6. The temperature sensor is in the electrolyte and provides feedback to the power source. If the electrolyte temperature is lower than the set one, then the current is increased and, conversely, if the temperature is higher, then the supplied current is reduced. When the required melt temperature is reached, rutile is loaded in the required amount through the aperture 9 between the anode and the side wall of the electrolyzer, and the rated current is set using a power source. Iron is also added through the armhole between the anode and the sidewall of the cell. When insoluble deposits form in the cathode alloy, they are discharged through a pocket to remove alloy 6.

For the production of titanium-iron alloy, with a titanium content of 63-78 wt. %, make up a salt mixture containing cryolite and aluminum fluoride with c.o. equal to 2.7-3.0, dried and heated to a liquid state. The resulting melt is poured into an electrolyzer, consisting of a steel lined casing with a conductive hearth, a refractory metal cathode placed on the hearth, a graphite anode suspended on a steel rod and an end pocket for unloading the finished product. Through the armhole between the anode and the side wall of the electrolytic cell, titanium oxide is fed into the working space of the bath into the electrolyte having a temperature of 1100-1150 ° C. Using a combined source of combined power or two sources of direct and alternating current, electrical energy is supplied to the electrodes. With the introduction of the electrolysis process, the operating density of the direct current is in the range of 0.3 ÷ 0.6 A / cm ² , and the density of the variable does not exceed 1.0 A / cm ² . The electrolyte temperature is in the range 1185-1200 ° C. After the appearance of the first crystals of intermetallic compounds of the titanium-iron system in the discharge pocket at a temperature of 1135-1185 ° C, iron shavings are introduced through the armhole between the anode and the side wall of the electrolyzer and the finished product is unloaded.

Salt melt, consisting of cryolite and aluminum fluoride from to about. equal to 2.7-3.0. A decrease in the cryolite ratio less than 2.7 leads to a decrease in the rate of dissolution of rutile in the molten melt. Increasing the cryolite ratio above 3.0 decreases the amount of titanium oxide dissolution. Therefore, the required rate and volume of dissolved rutile will be in the electrolyte in the above range.

The range of titanium content is 63-78 mass. % of the resulting alloy is due to the fact that when the titanium content in the titanium-iron alloy is less than 63 wt. % or more than 78 wt. %, within the indicated temperatures, the titanium-iron alloy is in a solid state and cannot be effectively pumped out of the unloading pocket.

The density of the cathode alloy is 4.4-4.6 g / cm ³ , and the electrolyte is 2.1-2.5 g / cm ³ . The difference in density leads to the formation of an immiscible two-layer phase system. At the bottom, a titanium-iron alloy is formed and accumulates, and an oxide-fluoride electrolyte at the top. The range of electrolyte densities is explained by the content of rutile, which varies from 1 to 9 mass%, and the electrolyte by the content of aluminum fluoride, i.e. cryolite ratio 2.7-3.0.

The graphite anode burns out during electrolysis to form CO and _CO2 . The anode has vertical holes for collecting gases. Above the anode, there is a steel cap for the removal of anode gases and vapors of fluoride salts.

An example of the invention

The starting materials (chemically pure grade) are dried in an oven at a temperature of 280-300 ° C for 3 hours to remove moisture. After drying, the salt mixture is melted in a chamber furnace at a temperature of 980-1000 ° C, then the resulting electrolyte is poured into a bath. The electrolyte temperature was measured using a platinum-platinum-rhodium thermocouple with a Fluke 177 digital multimeter. The starting titanium-iron alloy containing 63-65 wt. % titanium is also melted in a Nabertherm KC 2/15 muffle furnace at a temperature of 1185-1200 ° C and, through an electrolyte, is directed to a molybdenum cathode receiver. After that, through the gap between the anode and the side wall of the electrolyzer, powdered titanium oxide is loaded in excess and two sources of direct current GW PSW7 30-72 and alternating current AKIP-1134A-30-50 are switched on. In this case, the working density of direct current at the electrodes is 0.3 ÷ 0.6 A / cm ² , and the alternating current is not limited and can reach 50 A. At the beginning of the experiment, the alternating current should be maximum. The current and voltage are monitored using an ES9P ammeter (0-50 A) and a voltmeter (0-30 V). Then, when the titanium content reaches 75-78 wt. %, iron is added to the alloy in the form of shavings 0.2-1.0 mm in size. The duration of each experiment is 8 hours. The titanium oxide content ranges from 1 to 9 wt. %. During electrolysis, the evolution of hydrocarbons and fluorinated gases was not detected.

The results are shown in Table 1.

Claims (3)

1. A method of obtaining a titanium-iron alloy containing 63-78 wt.% Titanium, characterized in that a salt mixture consisting of cryolite and aluminum fluoride with a cryolite ratio equal to 2.7-3.0 is made, said mixture is dried, heated to a liquid state and poured as an electrolyte into an electrolyzer, after which the titanium-iron alloy melted at a temperature of 1185-1200 ° C, containing 63-65 wt.% titanium, is fed through the electrolyte into the molybdenum cathode receiver, then through the gap between the anode and the side the wall of the electrolytic cell into the electrolyte having a temperature of 1100-1150 ° C is loaded with an excess of powdered titanium oxide and a combined source of direct and alternating current or sources of direct and alternating current with a working density of direct current in the range 0.3 ÷ 0.6 A / cm ² and with an alternating current density not exceeding 1.0 A / cm ² , ensuring the electrolyte temperature in the range 1185-1200 ° C and the titanium oxide content in the electrolyte 1-9 wt.%, After the appearance of ne open crystals of intermetallic compounds of the titanium-iron system in the unloading pocket of the electrolyzer at a temperature of 1135-1185 ° C through the armhole between the anode and the side wall of the electrolyzer, iron shavings are introduced and the finished product is discharged in the form of a titanium-iron alloy. 2. An electrolyzer for producing a titanium-iron alloy containing 63-78 wt% titanium, containing a graphite anode and a cathode, characterized in that it contains an onboard refractory non-conductive lining, corundum lining, a graphite hearth, an unloading pocket for unloading the finished product in the form titanium-iron alloy having a temperature of 1135-1185 ° C, while the said discharge channel is connected to the molten metal by a horizontal channel, while the graphite anode and cathode are connected by means of current leads to a combined AC and DC power supply or to AC and DC power supplies current with the provision of electrolysis at a working DC density in the range of 0.3 ÷ 0.6 A / cm ² and an AC density not exceeding 1.0 A / cm ² , while the cathode is made of refractory metal and placed on a graphite hearth , and the graphite anode is suspended on the anode frame with the possibility of lowering it into the electrolyte with a temperature of 1185-1200 ° C, while m, vertical holes are made in the graphite anode, having the shape of a truncated cone, and a steel cap is placed above the anode to remove anode gases and vapors of fluoride salts, while in the upper part of these linings between the graphite anode and the side wall of the electrolyzer, an armhole is made in the refractory cover of the said discharge pocket for feeding titanium oxide into the working space of the bath at a temperature of 1100-1150 ° C. 3. The electrolyzer according to claim 2, characterized in that to stabilize the temperature regime of the electrolyzer, the AC power of the AC power supply reaches 50 A.

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