RU2405045C2 - Method of autoclave production of chemically active materials and device to this end - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: proposed method comprises placing mix material into autoclave, heating it, initiating reduction reaction by firing mix material, its melting to produce refractory metal ingot, and unloading finished product. Reaction mix material placed in autoclave, said material is heated directly in autoclave. Autoclave is placed in tightly closed pit representing a straight flow tube with running water to cool down autoclave housing before firing reaction mix material. Mix material is heated by autoclave housing heat. Note here that heating time interval is calculated allowing for time of heating autoclave, its transportation, cooling, and firing reaction mix with due allowance for recovery of the housing mechanical strength provided by cooling the housing and increasing gas pressure. Proposed device incorporates tightly closed vertical pit representing a straight flow tube with running water to cool down autoclave housing before firing reaction mix material. Metal tight tank is arranged in aforesaid pit, while its bottom part represent a cone with cover to remove reaction products.

EFFECT: reduced costs.

5 cl, 1 dwg

Description

The present invention relates to 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.

[one]. (E.A. Levashov et al. - Physicochemical and technological fundamentals of self-propagating high-temperature synthesis, - Moscow, BINOM Publishing House, 1999, pp. 155 ÷ 156). As an analogue, you can take the method of metal reduction, production of ceramics and other compounds, which is produced in the reactor. The reactor is a thick-walled vessel made of steel 12X18H10T, with a water-cooled jacket and closures. 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 magnetothermic processes, the snap-in eliminates the evaporation of charge components and condensation on the inner surface of the reactor.

After loading the charge, the reactor is closed and, depending on the target, vacuum or fill with inert or reaction gases. Local initiation of the process of self-propagating high-temperature synthesis (SHS) is carried out from the control panel by supplying a short-term electrical impulse to a tungsten spiral relating to the initial charge.

The course of the SHS process is controlled by the change in gas pressure in the reactor and the temperature of the cooling water. The SHS method has found great application in the production of nitrided ferroalloys for steelmaking. This is the most effective way to introduce nitrogen into steel.

[2]. (A.N. Zelikman - Metallurgy of refractory rare metals, - Moscow, Metallurgy Institute, 1986, p. 185). The closest technical solution as a prototype is the reduction by a metallothermic method of molybdenum from its oxides, which is carried out in a sealed cylindrical steel reactor lined with refractory (CaO, Al ₂ O ₃ ). Reactors are 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.

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 ° 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 MoO ₃ 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 = 1 ÷ 6).

This goal is achieved by the fact that the known method of producing reactive metals by metallothermal reduction of a reaction mixture consists of reactive metal oxide and a reducing metal in an autoclave, includes preparing a reaction mixture, placing it in an autoclave, heating the mixture, initiating the reduction reaction by igniting the mixture, melting the mixture , the formation of a product in the form of an ingot of a reactive metal, unloading the finished product, characterized in that after placing the reaction mixture in a tank lava heat it directly in the autoclave and the autoclave is installed in a hermetically sealed shaft, made in the form of a cooling direct-flow pipe with running water, designed to cool the body of the autoclave before starting the ignition of the reaction charge, the charge is heated by the heat of the autoclave body, while the reaction time is heating the charges through the body and the cooling time of the body are calculated taking into account the time of heating the autoclave, its transportation, cooling, ignition of the reaction mixture with the provision of recovery the mechanical strength of the wall of the autoclave body due to cooling with a simultaneous increase in gas pressure, during restoration, mechanical vibrations are applied to the autoclave at a frequency that ensures maximum metal recovery. A device for producing chemically active metals by metallothermal reduction of a reaction mixture, consists of reactive metal oxide and a reducing metal, contains an autoclave in the form of a metal sealed container with a bottom and a lid, an adjustment valve and an ignition system, characterized in that it is equipped with a hermetically sealed vertical shaft made in the form of a direct-flow cooling pipe with running water, a metal sealed container is installed in the shaft with running water, and its lower hour s is in the shape of a cone with a lid for the removal of reaction products, metal sealed container is provided with sample catcher.

The proposed method implements the installation shown in the drawing. The installation in the form of an autoclave includes a body of a metal sealed container (autoclave) 1, the upper part of which is made of a pipe, and the lower part is made of a cone 17 and a cover of the cone 18, in which the reaction mixture melts due to metallothermy, which, after melting, decomposes into slag 4 and a metal ingot 3 formed on a cooled tray 2. A stream of water 16 is supplied from below to a cooled tray 2 through a conduit 6, which subsequently cools the body of the autoclave 1 and drains through a conduit 7. From above, the autoclave is closed by a lid 11, through otorrhea passes igniter 8, as well as the line 9 with an adjustable valve 10. The bottom of the autoclave was set to sample catcher 13, which during the course of the reaction, the reaction mixture was compacted by extracting a metal ingot greatest possible mass. To ensure cooling of the autoclave and to ensure the safety of production, the autoclave is installed in a vertical shaft 5, which is hermetically closed by a lid 14 due to 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.

[3] 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 aluminothermic process, the rate of charge penetration, determined by the process temperature, 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 metallothermic 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 of the aluminothermic 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 (Cr ₂ O ₃ + Al, Fe ₂ O ₃ + 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 Hg 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 proceeds 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 bar (20-40 bar). With a further increase in external pressure, the increase in speed slows down, and with a decrease in pressure to 50-100 mm Hg. the reaction rate decreases to 0.7-0.8 cm / s.

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 consumption, 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 mixture 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

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, partial replacement of aluminum with silicon, magnesium, calcium, etc.).

2. Reducing the use of thermite 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 the mechanical losses and oxidation of the metal reducing agent in the process of manufacturing the powder, the full use of all waste products of metallothermal powder production.

4. Improving the selection of the granulometric composition of the reducing agent with the aim of more complete flow of reduction reactions, reducing the burning 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 reaction under pressure, while many reduction reactions will proceed more fully with a higher efficiency in terms of metal yield. 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 more heat loss 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. Considering that a certain time is required for heating the reaction mixture in the autoclave, it is 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. The highest temperature 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, then 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 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 particularly accurately calculates the time of heating of the autoclave, the initial moment of its cooling and the moment of electric burning 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 maintain the growing gas pressure during the recovery 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 returns 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 the drawing, 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 metal recovery time 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.

Claims (4)

1. A method for producing chemically active metals by metallothermal reduction of a reaction mixture consisting of reactive metal oxide and a reducing metal in an autoclave, including preparing a reaction mixture, placing it in an autoclave, heating the mixture, initiating a reduction reaction by igniting the mixture, melting the mixture, and forming the product in in the form of an ingot of reactive metal, unloading the finished product, characterized in that after placing the reaction mixture in an autoclave, it is heated directly in the autoclave and the autoclave are installed in a hermetically sealed shaft, made in the form of a direct-flow cooling pipe with running water, designed to cool the autoclave body before ignition of the reaction mixture, the charge is heated by the heat of the autoclave body, while the reaction charge is heated through the body and the cooling time the shells are calculated taking into account the heating time of the autoclave, its transportation, cooling, ignition of the reaction mixture with the restoration of the mechanical strength of the wall of the body and by cooling the autoclave with simultaneous increase of the gas pressure. 2. The method according to claim 1, characterized in that during the restoration, mechanical vibrations are applied to the autoclave at a frequency that ensures maximum metal recovery. 3. A device for producing chemically active metals by metallothermic reduction of a reaction mixture consisting of reactive metal oxide and a reducing metal, containing an autoclave in the form of a metal sealed container with a bottom and a lid, an adjustment valve and an ignition system, characterized in that it is equipped with a hermetically sealed vertical shaft, made in the form of a cooling pipe with flowing water, a metal sealed container installed in the shaft with running water, and its lower Part I is made in the shape of a cone with a lid for the removal of reaction products. 4. The device according to claim 3, characterized in that the metal sealed container is equipped with vibration devices.

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