WO2009139667A1

WO2009139667A1 - Method and device for the pressure production of chemically active metals

Info

Publication number: WO2009139667A1
Application number: PCT/RU2009/000223
Authority: WO
Inventors: Анатолий Евгеньевич ВОЛКОВ
Original assignee: Volkov Anatoly Evgenievich
Priority date: 2008-05-12
Filing date: 2009-05-08
Publication date: 2009-11-19
Also published as: RU2405045C2; RU2008118752A

Abstract

The invention relates to the production of chemically active metals from a crude ore and can be used for producing chemically active metals by carrying out metallothermic reactions. The method involves the metallothermic reduction of a reaction burden in a pressurised autoclave. The autoclave is placed in a sealed shaft with cooling running water. At the first stage, the autoclave body transfers the required amount of heat to the reaction burden and is used as a crystallised, at the second stage. The time for heating the reaction burden via the body and the time for cooling said body are calculated taking into account the autoclave heating time, a time for transporting, cooling and electrically igniting the reaction burden in such a way that the mechanical strength of the autoclave body wall is recovered by cooling simultaneously with a gas pressure increase. The device for carrying out the inventive method comprises the autoclave in the form of a sealed metal container with a bottom plate and a cove, an adjustment valve, an igniting system and a shaft. The container is accommodated in the sealingly closed shaft with running water and the lower part thereof is cone-shaped and is provided with oscillating devices. The invention makes the process safe, reduces costs and increases the metal output.

Description

METHOD AND DEVICE FOR AUTOCLAVE PRODUCTION OF CHEMICALLY ACTIVE METALS

Technical field

The present invention relates to the field of the production of chemically active metals from ore raw materials and other compounds and can be used for the production of metals, including chemically active and refractory metals, which can be melted due to the occurrence of metallothermic reactions.

State of the art

The method of metal reduction, the production of ceramics and other compounds, and the reactor device (autoclave) in which the metal reduction process is performed are selected as an analog. (E.A. Levashov et al. - Physicochemical and technological fundamentals of self-propagating high-temperature synthesis, - Moscow: CJSC Publishinghouse BIOM, 1999, pp. 55–156). This method involves mixing reagents (oxidizing agent and reducing agent), heating the charge, followed by loading the charge into the reactor, which is then transferred to the mine. After loading the charge, the reactor is closed and, depending on the target, vacuum or fill with inert or reaction gases, initiate the reaction. Local initiation of the process of self-propagating high-temperature synthesis (CBC) is carried out from the control panel by supplying a short-term electrical impulse to a tungsten spiral relating to the initial charge. The reaction results in the separation of metal and slag. After which spontaneous cooling occurs, the subsequent unloading of the reaction products and their mechanical separation.

This method proceeds in an enclosed space at ordinary pressures created by the reaction products. ι The course of the CBC process is controlled by the change in gas pressure in the reactor and the temperature of the cooling water. The CBC method has found great application in the production of nitrided ferroalloys for steelmaking. This is the most effective way to introduce nitrogen into steel.

The autoclave for implementing this method is made in the form of a thick-walled vessel, hermetically sealed on top with a lid, which is internally lined with refractory insulating ceramics, on the outside of which there is a water-cooling shirt. The vessel is equipped with gates.

Reactors differ in the volume of the reaction zone: from 1 to 30 liters. The internal structure of the reactor meets specific requirements, depending on the type of synthesized products. For the synthesis of carbides, borides, silicides, the inner surface of the reactor is lined with graphite. For the synthesis of nitrides, carbonitrides and hydrides, the reactor is equipped with a special device that allows filtering the reacting gases into the reaction zone. In the case of the synthesis of chalcogenides, phosphides, and magnetothermal processes, the snap-in eliminates the evaporation of charge components and condensation on the inner surface of the reactor.

These method and device for its implementation have the following disadvantages:

- lining of the autoclave (reactor) body with refractory insulating ceramics does not allow heating the prepared mixture directly in the autoclave before the start of the recovery reaction;

- pre-heating the powder mixture with subsequent falling asleep in the autoclave violates the safety of the process, since the heated powder is prone to spontaneous combustion;

- significant heat loss when reloading the powder from the heating tank into the autoclave and the loss of the reducing agent due to oxidation; - low yield of the desired product due to insufficient pressure in the reactor (autoclave);

- no impact on the process of the reaction due to the lack of a cooling system of the reactor,

- insufficient efficiency of the yield of a useful product, because there is no way to timely separate reaction products from the total mixture, i.e. the reaction will be reversible;

- to increase the yield of the reduced metal, termite additives are used, which leads to an increased consumption of the reducing agent per ton of the alloy obtained, and, consequently, to the high cost of the metal;

- the use of termite additives increases the amount of slag and reduces the concentration of the main reduced oxide in the melt, which worsens the conditions for the reduction of oxides and the deposition of droplets of the reduced metal;

- great difficulty in controlling the temperature to which the reaction mixture should be heated;

- significant energy costs associated with taking into account the time for transferring the autoclave from the heating furnace to the shaft, for its closure and filling with water, as well as for heating the autoclave body and its subsequent cooling.

The closest technical solution, selected as a prototype, is a metallothermic method for the reduction of molybdenum from its oxides and a sealed cylindrical steel reactor (autoclave) lined with refractory (CaO, Al ₂ O ₃ ) (A.N. Zelikman - Metallurgy of refractory rare metals, - Moscow: Publishing House “Metallurgy”, 1986, p. 185).

This method involves mixing reagents (oxidizing agent and reducing agent), heating the mixture, followed by loading the mixture into a reactor (autoclave), which is then transferred to the mine. After loading the charge, the reactor is closed and, depending on the target, vacuum or fill with inert or reaction gases, and initiate the reaction using arson. Local initiation of the process of self-propagating high-temperature synthesis (CBC) is carried out from the control panel by supplying a short-term electrical impulse to a tungsten spiral relating to the initial charge. The reaction results in the separation of metal and slag. After which spontaneous cooling occurs, the subsequent unloading of the reaction products and their mechanical separation.

This method proceeds in an enclosed space at ordinary pressures created by the reaction products.

In the case of an aluminothermic process, CaO is introduced as a flux to reduce the melting temperature of the slag (Al ₂ O ₃ ) and its viscosity in the mixture. Slag containing 20-30% CaO has a melting point of 1700-1800 ⁰ C.

An aluminum powder of optimal fineness is introduced into the charge, at which the process proceeds at a sufficient speed, but without emissions and large overheating, which ensures high extraction into the ingot. With an excess of aluminum in the charge (15–20% versus stoichiometric), the ingot extraction using MoO3 as the starting material is in the range of 91.2–93.6%. When using MoO ₂ or CaMoO _{4, the} recovery reaches 98-98.5%. Ingots contain 3-5% Al. After remelting in an electron-beam furnace, molybdenum is purified from aluminum and a number of impurities, the content of which decreases to n ^• 10 ^"3 - n -10 ^{" 4} % (n = l ÷ b).

The reactor (autoclave) for implementing this method is made in the form of a cylindrical container lined from the inside, equipped with a bottom and a lid.

The reactor is made of seamless pipes of small diameter (300-400 mm) with a height of 1100-1200 mm, to which the bottom and cover are hermetically connected.

The specified method and device have the following disadvantages: - the inability to heat the prepared mixture directly in the autoclave, because the body of the autoclave (reactor) is lined with refractory insulating ceramics, which does not allow to conduct a recovery reaction preliminary heating of the powder mixture, in addition, when falling into the autoclave, the safety of the process is impaired, since the heated powder is prone to spontaneous combustion;

- significant heat loss when reloading the powder from the heating tank into the autoclave and the loss of the reducing agent due to oxidation;

- significant energy costs associated with the time for transferring the autoclave from the heating furnace to the shaft, for its closure and filling with water, as well as for heating the autoclave body and its subsequent cooling;

- low yield of the desired product due to insufficient pressure in the reactor (autoclave);

- no impact on the process of the reaction due to the lack of a cooling system for the reactor;

- insufficient efficiency of the yield of a useful product, because there is no way to timely separate reaction products from the total mixture, i.e. the reaction becomes reversible.

Disclosure of invention

The technical problem of the proposed invention is to develop a method and device for its implementation, which allows to ensure the safety of the production of chemically active metals, reducing energy, economic and capital costs, as well as reducing costs and increasing the volume of metal produced.

The task is achieved in that in the autoclave production of chemically active metals, based on the inclusion of metal-thermal reduction of the reaction mixture in the autoclave under a certain (required) pressure, the autoclave is installed in a vertical hermetically sealed shaft, which functions as a direct-flow cooling pipe and ensures the safety of the process. In this case, the autoclave body transfers the required heat for the reaction mixture in the first stage (before starting the charge ignition), and in the second stage it performs mold functions. In this case, the heating time of the reaction mixture through the autoclave body and the cooling time of the body are calculated with particular accuracy, including the heating time of the autoclave, its transportation, cooling, electric ignition of the reaction mixture, so that the mechanical strength of the wall of the autoclave body due to cooling is restored simultaneously with an increase in gas pressure. At the time of the entire metallothermal reaction, oscillations of such a frequency can be superimposed on the autoclave at which maximum recovery of the reduced metal is achieved.

A device for the autoclave production of chemically active metals, contains a metal sealed container, an adjustment valve, an ignition system. The device is characterized in that the tank, designed for installation in a shaft with running water, in the lower part is made in the form of a cone with a lid to facilitate removal of reaction products. The tank can be equipped with a vibration device to create mechanical vibrations at the time of the reaction.

Brief Description of the Drawings

Figure l shows a device that implements the proposed method.

The best embodiment of the invention

The proposed method is implemented using the device shown in Fig.l. The device in the form of an autoclave is a metal sealed container with a melting chamber 1, the upper part of which is made in the form of a pipe, and the lower part is made in the form of a cone with a pallet 2, in which the reaction mixture melts due to metallothermy, which decomposes after melting into a metal ingot 3, formed on the cooled tray 2, and slag 4. To ensure cooling of the autoclave and to ensure production safety, the autoclave is installed in a vertical shaft 5. In the lower part of the shaft 5, a pipe 6 is installed for supplying a jet of water to the cooled tray 2 and cooling the autoclave body. Subsequently, the water is discharged through line 7. The top of the autoclave is closed by a lid 11, through which the electric valve 8 passes, and also the line 9 with an adjustable valve 10. The bottom of the autoclave is mounted on vibration devices 13, which during the course of the reaction condense the reaction mixture, removing as much as possible into the ingot possible mass of metal. The shaft 5 is hermetically closed by a cover 14 due to the locking mechanisms 15.

In order for autoclave metal production to achieve maximum efficiency at minimum cost, it is necessary to take into account the following features of metallothermal reactions. The most important point of the metallothermic reaction is the process temperature. Since the temperature of the process is proportional to its specific heat, the rate of aluminothermic melting also increases with the growth of the latter. In an out-of-furnace aluminothermal process, the rate of charge blending, determined by the temperature of the process, in turn, can affect the temperature level of smelting. With a decrease in the speed of the process, the fraction of heat losses proportional to the melting time increases, and, consequently, the temperature of the process decreases, and with an increase in the speed of the process, its temperature increases.

Another equally important point in the metallothermic reaction is the pressure at which the reaction proceeds. The dependence of the rate of the metallothermal reaction on the magnitude of the external pressure is interesting not only from the point of view of practical smelting, but also to elucidate the mechanism of the out-of-furnace metallothermal process. This mechanism can be disclosed by the example of an aluminothermic reaction. Due to the fact that gaseous substances are not included in the stoichiometric equation of the aluminothermic reduction reaction, and also due to the high boiling points of the starting materials and reaction products, it can be assumed that the main reactions the minothermal process occur between the condensed phases. In this case, the external pressure does not significantly affect the reaction rate. Conversely, with the participation of the gas phase, the reaction rate is largely determined by the magnitude of the external pressure. With increasing pressure, the rate of gas reactions will increase due to an increase in gas density and the number of collisions of gas molecules or due to an increase in the number of impacts of gas molecules on the surface of the condensed phase at the phase boundary. For example, the dependence of the propagation velocity of the reaction front of a number of aluminothermic mixtures (CG ₂ O ₃ + Al, Fe ₂ Cb + Al, MnO ₂ + Al) on external pressure was studied by A. F. Belyaev and L. D. Komkova. As follows from the data obtained, in the interaction of chromium oxide with aluminum, an increase in pressure does not affect the reaction rate. Pressure reduction to 50-100 mm RT. Art. also does not lead to a noticeable change in the reaction rate. This suggests that the aluminothermic reduction of chromium oxide at temperatures of 1900-2100 ° K occurs without the participation of the gas phase.

In the interaction of aluminum with iron and manganese oxides, the reaction rate increases with increasing pressure. The greatest increase in speed is observed at pressures up to 20-40 atm. (20-40 bar). With a further increase in external pressure, the increase in velocity slows down, and with a decrease in pressure to 50-100 mm Hg. Art. the reaction rate decreases to 0.7-0.8 cm / sec.

It should also be noted that the conduct of metallothermal reactions in open crucibles leads to increased removal of the charge, due to the gases formed, which carry away part of the heat generated during the process from the reaction zone.

To increase the yield of the reduced metal, termite additives are used. A significant drawback of the use of termite additives is an increase in the consumption of a reducing agent per ton of the resulting alloy, which significantly increases the cost of metal and is not always economically justified. Another disadvantage of using termite additives is an increase in the amount of slag and a decrease in the concentration of the main reducible oxide in the melt, which worsens the conditions of both the reduction of oxides and the deposition of droplets of the reduced metal. Therefore, in metallothermal processes, it is necessary to strive for a minimum consumption of termite additives.

Compared to the use of thermite additives, preheating of charge materials is more effective, at which there are no costs for an expensive reducing agent.

When calorimetric the process of aluminothermic reduction of iron oxide by V. A. Bogolyubov, it was found that an increase in the temperature of the process when the charge is heated for every 100 ° is 56 °. The increase in the specific heat of the process due to physical heat introduced by the heated charge can be calculated based on the heat balance of the heat. When smelting on a heated mixture, the total heat input:

V total Vkhim ^" "^" Vphys VU

So, for example, a similar calculation for the case of aluminothermic reduction of iron oxide gives an increase in the specific heat of the process when the charge is heated by 100 ° at about 84 kJ / kg of charge. An increase in the specific heat of the process during preliminary heating of the charge cannot be a consequence of only the introduction of additional heat by the heated charge, but is combined with a decrease in heat loss due to a higher reaction rate and a more complete recovery due to an increase in the liquid mobility of the melt.

To reduce economic costs, reduce the amount of reducing agent for the smelting of metallothermal alloys due to the following:

1. The correct selection of the reducing agent necessary for the smelting of various alloys (use in some cases of secondary aluminum, the use of complex reducing agents, the partial replacement of aluminum with silicon, magnesium, calcium, etc.). 2. Reducing the use of termite additives, requiring an increased consumption of reducing agent, due to pre-heating of the mixture or other measures, which include gas pressure in the reaction products, as well as vibration processing of the substance at the time of formation of the metal ingot.

3. Reducing mechanical losses and oxidation of the metal of the reducing agent in the process of manufacturing the powder, the full use of all waste production metallothermic powder.

4. Improving the selection of the granulometric composition of the reducing agent with the aim of more complete flow of reduction reactions, reducing the fumes of the reducing agent metal during the smelting process and more complete precipitation of the reduced metal kings into the main ingot.

5. Combustion in high-calorific mixtures of metal oxides with reducing agents and non-metals is accompanied by a strong spread of the melt and proceeds in an explosive mode. The increased gas pressure (argon, nitrogen, air) suppresses the spread and puts combustion in a controlled stationary mode. To keep the gas pressure in the reaction products and prevent the mechanical release of the substance, closed containers are used, called reactors or autoclaves. On the other hand, in the present invention, the completeness of the yield of the reduced metal in the ingot can be controlled by all of the above process control capabilities.

Based on the foregoing, it should be noted that the method of the proposed autoclave melting is designed to fulfill all the necessary conditions that contribute to the maximum recovery of the recoverable metal with minimal use of the metal reducing agent, and, therefore, is designed to minimize the cost of production. Increased efficiency in metal yield is ensured due to the fact that the normal release of a substance that occurs in open containers is prevented. So, for example, autoclave melting can provide a flow stocks under pressure, while many recovery reactions will proceed more fully with a higher metal yield efficiency. The gases formed during the course of the reaction in the autoclave, without leaving its inner space, thereby do not cool the reaction products and do not inhibit the recovery process, while these same gases create the necessary pressure, contributing to a more complete course of the recovery process. Therefore, due to this, capital costs are reduced. In order for the reaction products to be cleaner from gas inclusions, the autoclave can be evacuated before reduction and inert gases can be pumped into the interior.

In contrast to the analogue and prototype, where the bodies of the autoclaves (reactors) are lined with refractory insulating ceramics, in the present invention the body of the autoclave is metal without an inner lining. This feature allows you to heat the prepared mixture directly in the autoclave before starting the recovery reaction. This allows you to very accurately control the heating temperature, to conduct heating in a vacuum or inert gas environment. If you pre-heat the powder mixture and then pour it into the autoclave, then the safety rules will be violated, since the heated powder is more prone to spontaneous combustion. In addition, there will be greater heat losses during powder overloading from the heating tank into the autoclave, the loss of a reducing agent due to oxidation, as well as greater difficulties in adjusting the temperature to which the reaction mixture should be heated. The proposed autoclave without an internal heat-insulating lining, can be heated with great accuracy for a certain time in resistance shaft furnaces, induction or plasma-gas furnaces. The longer the heating period of the reaction mixture, the more accurately you can achieve the required temperature for its heating.

From the point of view of energy costs, the heating time should be optimal so as not to expend unnecessary energy. Given the fact that it takes a certain time to warm up the reaction mixture in an autoclave, it is also necessary to take into account the time to transfer the autoclave from the heating furnace to the shaft, as well as the time to close and fill it with water. Most of the heat will be absorbed by the body of the autoclave and then due to radiation, convection of gases and thermal conductivity will be gradually transferred to the inside of the autoclave. When heating the reaction mixture, it is necessary to calculate the heating of the autoclave body in such a way as to take into account the thermal energy that will enter the charge during the transportation of the autoclave from the heating furnace to the shaft and the time before ignition of the reaction mixture. That is, during this time, the autoclave body will transfer part of the missing thermal energy to the reaction mixture to a theoretically calculated temperature. In order for the autoclave body to regain its mechanical strength, since it will decrease due to its heating, it will need to be cooled with water before the moment of ignition. It should be noted that if the autoclave body is cooled for a long time, the reaction mixture inside the autoclave will be cooled. From an energy point of view, this will cause significant losses to the metal reduction process. Therefore, the technological process when implementing the proposed method for the autoclave production of chemically active metals takes into account the time required to cool the body of the autoclave, which must withstand the pressure created by the reaction products. In addition, it is necessary to take into account the time required to initiate the reaction and achieve the working pressure at which the process proceeds optimally. That is, the operator calculates with particular accuracy the moment of heating of the autoclave, the initial moment of its cooling and the moment of electric ignition of the reaction mixture, so that the mechanical strength of the wall of the autoclave body due to cooling is restored to such an extent as to keep the increasing gas pressure during the course of the reduction reaction. Mechanical strength should be restored at the same time as the gas pressure increases. The upper limit of this pressure is constant, as it is regulated by a valve mounted on the top cover of the autoclave.

In this invention, it should be noted that the autoclave body plays a large technological role in carrying out the reduction reaction, both at the preparation stage and at the subsequent stage of recovery. That is, through the autoclave body at the preparation stage, the reaction mixture is warming up. At the time of increasing gas pressure, the body cools and restores mechanical strength, holding gas pressure. When a metal ingot is formed, the body of the autoclave, and in particular its cooled copper tray, removes thermal energy from the ingot, thereby increasing the volume of metal produced, since the reduction reaction will shift to the right.

As can be seen in Fig. L, the autoclave is mounted on vibration devices 13, which operate due to pneumatics, electric motors, electromagnets, etc. drives. Creating a high-frequency or low-frequency vibration (the frequency is selected based on its efficiency in extracting the metal to be recovered, to one or another autoclave), during the course of the recovery reaction, favorable conditions are created that increase the efficiency of the process. So, for example, vibration will reduce the viscosity of the melt and make heavier the droplets of the reduced metal, which will allow them to stand out from the slag in a larger volume and form into an ingot. Due to vibration, mixing of the reaction mixture will increase, which will increase the fluidity and the reaction rate. Due to this, the reaction temperature will increase, the reduction time of the metal will decrease, which will reduce the metal consumption of the reducing agent, reduce the initial heating temperature of the charge (therefore, reduce the energy consumption of the process) and increase the yield.

In connection with the foregoing, the proposed method and device for the autoclave production of chemically active metals can be widely used in production. LITERATURE

[one]. E.A. Levashoe et al. - Physicochemical and technological fundamentals of self-propagating high-temperature synthesis, - Moscow: CJSC Publishing House BIOM, 1999, pp.94., Pp.l55 ÷ 156

[2]. A.N. Zelikman - Metallurgy of refractory rare metals, - Moscow: Publishing House "Metallurgy", 1986, p. 185, pg. 343.

[3]. Yu.L. Pliner, S. I. Suchilnikov, E. A. Rubinshtein - Aluminothermic production of ferroalloys and alloys, - Moscow: State Scientific and Technical Publishing House of Literature on Ferrous and Non-Ferrous Metallurgy)), 1963, (pg. .31 ÷ 32, 152 ÷ 157).

Claims

CLAIM

1. The method of autoclave production of reactive metals, based on the metallothermic reduction of the reaction mixture in an autoclave at the required pressure, including preparing the mixture, heating it, placing the latter in an autoclave, which is installed in the mine, initiating the reaction, unloading the finished product, characterized in that heating the charge is produced directly in the autoclave, which is then installed in a hermetically sealed shaft, which serves as a cooling direct-flow pipe, where the autoclave is cooled before the beginning of ignition of the charge, the charge is heated due to the heat of the autoclave body, while the time of heating the reaction mixture through the body and the cooling time of the body is calculated taking into account the time of heating the autoclave, its transportation, cooling, electric ignition of the reaction mixture, with the possibility of restoring the mechanical strength of the wall of the autoclave for cooling due to a simultaneous increase in gas pressure, in addition, after the start of the formation of an ingot of pure product, the pan is cooled.

2. The method for the autoclave production of chemically active metals according to claim 1, characterized in that at the time of the entire metallothermal reaction, mechanical vibrations can be superimposed on the autoclave with a frequency that ensures the maximum recovery of the metal being recovered.

3. The method of autoclave production of reactive metals according to claim 1, characterized in that the autoclave is installed in a vertical shaft, hermetically sealed by a lid due to locking mechanisms.

4. A device for the autoclave production of chemically active metals, containing a metal sealed container with a bottom and a cover, an adjustment valve, an ignition system, characterized in that the lower part of the tank, installed in a hermetically sealed shaft with running water, is made in the form of a cone.

5. A device for the autoclave production of chemically active metals according to claim 4, characterized in that the container can be equipped with vibration devices.