RU2572667C1 - Plant for metal-thermal reduction of earth metals - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: claimed plant comprises the reaction chamber its opposite ends being provided with the raw pellet loading chamber and processed pellet discharge chamber. Reaction chamber heat-insulating jacket is connected with the first container vertical displacement actuator and provided with the condenser designed to displace the condensate and to interact with the cutter with the cone arranged there under. Said cutter and cone are arranged atop the reaction chamber sidewall with condensate removal chamber abutting thereon and separated from the reaction chamber by the first vacuum gate and provided with the condensate intake bin communicated with the horizontal displacement actuator. Loading and discharge chambers are connected via the second and third vacuum gates with the first and second chambers abutting on the reaction chamber. The loading chamber is composed by the muffle kiln with its bottom communicated with the second container transfer vertical actuator. The discharge chamber is composed by vacuum chamber provided with the third container transfer vertical actuator.

EFFECT: continuous and accelerated reduction.

6 cl, 1 dwg

Description

The invention relates to metallurgy and can be used in furnaces for the production of alkaline earth metals from their oxides by metallothermic reduction.

A known installation for metallothermal production of calcium RU 2205241, B22B 20/26, published. May 27, 2003), which contains a reaction chamber in the form of a heat-resistant material retort, a condenser installed inside the chamber, a heater located outside the condenser, a metal collection tank, a loading basket placed inside the retort, as well as a vacuum and water-cooling system connected to the reaction chamber . The installation allows you to get calcium ingots grown from the gas phase, and monolithic ingots obtained by remelting the first. The operation of the installation includes the installation of a retort in a heating furnace, processing of initial briquettes from a mixture of calcium carbonate and a metal reducing agent - aluminum in the mode of a combined process of dissociation - reduction - melting, unloading a vacuum retort with the obtained solid calcium condensate and spent briquettes and cooling it in air for 15 hours, the extraction of an ingot of calcium and briquettes after air inlet into the retort.

The disadvantage of the installation for metallothermal production of calcium is associated with limited heat resistance and heat resistance of the materials of the furnace and retort heaters, which makes it impossible to produce calcium at temperatures up to 1350 ° C, providing a high calcium yield, due to a sharp decrease in the service life of the heaters and the intense oxidation of the steel retort.

In addition, the introduction of the operation of dissociation of calcium carbonate increases the duration of the process, requires continuous heating in vacuum to a temperature of recovery, the long-term use of a powerful vacuum system, which increases the cost of the recovery process.

Also known installation for metallothermal production of alkaline earth metals (RU 2339716, C22B 26/20, published. 27.11.2007). The installation includes a reaction chamber, a condenser installed inside it, a device for loading and unloading initial and spent briquettes, a vacuum system and a water cooling system. The reaction chamber is an electric furnace with a detachable bottom cover with a loading table for installing the crucible with the initial briquettes inside the heating block. The recovery process in the reaction chamber is carried out in two stages. For aluminothermic reduction of calcium oxide, first the briquettes are heated to 400 ° C for 1-2 hours under low vacuum at a gas vapor pressure of 10-10 kPa. Then, the temperature is raised to a reduction temperature of 1350 ° C and heating to a reduction temperature is carried out with continuous pumping of the working space of the chamber. Upon reaching a pressure of not higher than 10 Pa and a temperature of 1350 ° C, calcium oxide is reduced by aluminum for 5 hours. Then they turn off the heating of the chamber and inject argon to atmospheric pressure.

A disadvantage of the known installation is to increase the duration of the recovery process carried out in the reaction chamber. This is due to the time spent on preheating the briquettes to remove gases released from the load due to the decomposition of calcium carbonate present in calcium oxide with the formation of carbon dioxide.

In addition, the installation is designed for batch operation, since the loading and unloading of metal and slag is carried out in a cooled furnace.

The closest in technical essence is the installation for metallothermal production of alkaline earth metals (Mikulsky AS "Vacuum electric furnaces for the production of alkaline and alkaline earth metals", M.-L., Gosenergoizdat, 1962, pp. 40-58) .

The installation includes three pressurized chambers: a reaction chamber and a briquette loading and preheating chamber adjacent to it on opposite sides and a waste briquette unloading chamber. The chambers are separated from each other by vacuum gates; a condenser is located outside the reaction chamber for vapor deposition of the reduced metal. The condenser is connected to the reaction chamber by a heated steam pipe installed in the upper part of the chamber. Rolling tables were used as means for moving briquettes through the chambers. The unit is equipped with a vacuum system. Chambers of loading and unloading have tight vacuum covers.

The preheating of the loading chamber is carried out by pendant type heaters installed on the loading boxes and connected to the contacts for current leads located on the side walls of the box.

The heating of the reaction chamber, which is an electric resistance furnace, is provided by tubular heaters.

To prevent the entry of vapors into the loading and unloading chambers during the movement of materials, an inert gas is introduced into the reaction chamber, and the recovery process is stopped. At the end of the transfer to the reaction chamber, the gas is pumped out, and the recovery process is resumed.

The disadvantage of this installation is the insufficient productivity of the installation, associated, firstly, with the time spent on the heaters not supplying electricity, and, secondly, with the forced shutdown of the process when removing solid condensate from the surface of the condenser.

The invention achieves the technical result, which consists in ensuring the continuous operation of all installation units and reducing the cost of the process.

The specified technical result is achieved as follows.

Installation for metallothermal recovery of alkaline earth metals includes a vertically mounted vacuum reaction chamber, on the opposite sides of which are located a vertical chamber for loading raw briquettes and a chamber for unloading processed briquettes.

The reaction chamber is equipped with a heating unit having a heat-insulating body, the lower part of which is connected to the first mechanism for the vertical movement of the containers and on which the heater is located. The reaction chamber also contains a capacitor configured to move the condensate and interact with the cutter, under which a guide funnel is mounted. The cutter and funnel are mounted on the upper part of the side wall of the reaction chamber, which is adjacent to the condensate removal chamber, separated from the reaction chamber by a first vacuum shutter and equipped with a condensate receiving hopper connected to the first horizontal movement mechanism.

The loading chamber and the unloading chamber are connected through the second and third vacuum gates to the first and second transport chambers adjacent to the reaction chamber. The first and second transport chambers are equipped with the second and third horizontal mechanisms for moving containers.

The loading chamber is a muffle furnace, the lower part of which is connected to the second vertical mechanism for moving containers. The unloading chamber is a vacuum chamber equipped with a third vertical mechanism for moving containers, while its body is equipped with a water cooling system.

In a particular case, the heater of the reaction chamber is made of carbon-carbon composite material.

In addition, the thermal insulation of the reaction chamber is made of a low-carbon-carbon composite material.

Also, the body of the reaction chamber is equipped with a water cooling system.

The condenser of the reaction chamber is equipped with a water cooling system.

The muffle furnace is also equipped with a resistance alloy heater, and its body is equipped with thermal insulation.

Such a constructive implementation of the installation for metallothermal recovery of alkaline earth metals will ensure continuous operation of all units of the installation while reducing the cost of the process due to:

- reducing the time of the recovery process, because the box with briquettes is moved into and out of the reaction chamber without stopping the process in the reaction chamber. The presence in the loading and unloading chambers of sealed transport chambers with moving means installed coaxially with the lower part of the thermal insulation of the reaction chamber in its lower position allows the briquettes to be moved without violating the vacuum and temperature conditions of the reaction furnace;

- reducing the time of removal and removal of solid condensate from the surface of the condenser without stopping the process. The installation inside the reaction chamber of a rotating condenser and a cutter for processing condensate into chips, as well as equipping the reaction chamber with an adjacent chamber to remove the obtained condensate with a vacuum shutter and a hopper for receiving condensate, allows the removal of solid condensate and its processing into a marketable product (chips) directly inside the reaction chamber, and removing the latter without stopping the process.

The invention is illustrated by the drawing, which shows schematically a General view of the installation for metallothermal recovery of alkaline earth metals.

The installation contains a vertically mounted reaction chamber 1 located on opposite sides of it, a briquette loading chamber 2 and a spent briquette unloading chamber 3, having vacuum gates 4, 5, a cooled condenser 6 for vapor deposition of the reduced metal, a chamber 7 for removing the obtained condensate with vacuum a shutter 8 and a movable hopper 9 for receiving condensate connected to the first horizontal movement mechanism 22.

Chambers 2, 3 of loading and unloading have first and second transport chambers 10, 11, respectively, adjacent to the reaction chamber 1, and chambers 10, 11 are equipped with second and third horizontal mechanisms 19, 21 for moving containers with briquettes.

The chamber 2 is a muffle furnace with a movable upper part and contains a heat-insulating element 12. The lower part of the muffle furnace is connected to the second vertical container moving mechanism 18. The unloading chamber 3 is a vacuum chamber equipped with a third vertical container movement mechanism 20.

The reaction chamber 1 is equipped with a water cooling system. Also, the reaction chamber 1 is equipped with a heating unit 13 having a heat-insulating body, the lower part 14 of which is connected to the first vertical container movement mechanism 17. In the upper thermal insulation of the reaction chamber there is an opening for the evaporation of the reduced metal, which is deposited on a water-cooled condenser 6.

A condenser 6, a housing of the reaction chamber 1, a vacuum shutter 4 of the loading chamber 2 are connected to a water cooling system (not shown).

In the cold part (not higher than 240-400 ° C) of the reaction chamber 1, a cutter 15 for processing the condensate into chips and a guiding funnel 16 for collecting condensate chips are fixed on its side wall, to which the chamber 7 adjoins to remove the obtained condensate.

The capacitor 6 is installed inside the chamber 1 in its upper part with the possibility of rotation on an axis parallel to the axis of the heating block 13 of the reaction chamber 1.

One side of the condenser 6 is facing the hot heating unit 13, the other part of the condenser 6 is removed from the heating zone. The center distance is determined by the overall dimensions of the heating unit 13 and the possibility of dispersion of the metal vapor. To avoid noticeable heating of the condensate, the center distance between the axis of the heating unit 13 and the axis of the condenser 6 should be greater than the radius of the heating unit 13 (if the heating unit is in the form of a parallelepiped, then the center distance should be greater than the larger side of the parallelepiped). To obtain the required thickness of the metal deposited on the capacitor (the amount of metal deposited depends on the kinetics of the reduction reaction, temperature, container area and time), the rotation speed of the capacitor must be adjustable.

The mechanisms for moving the briquettes in chambers 1, 2, 3, 10, 11, as well as the mechanisms 17, 18, 19, 20, 21, 22 for moving the hopper 9 with condensate in the chamber 7 are made in the form of pushers-draggers. The temperature in the reaction chamber 1 is controlled by thermocouples 23 and 24.

The vacuum system of the installation is capable of independent pumping of the reaction chamber 1 and chambers 2, 3 and is equipped with a membrane and vacuum unit - a Roots pump with a rotary vane pump, as well as residual pressure measuring instruments and inert gas and air inlet valves.

Installation for metallothermal recovery of alkali and alkaline earth metals works as follows.

The essence of metallothermal reduction of oxides, alkaline earth metals is reduced to the course of the reduction reaction according to the scheme:

$$MeO+R\to Me\left(P\mathrm{but}R\right)+xMeO*yRO\left(t\mathrm{at}.\right)\left(\mathrm{one}\right)$$

where MeO is the oxide of the reduced metal, R is the metal reducing agent.

As follows from equations (1), the main raw materials in these processes are oxides of the corresponding metals, the natural feature of which is the relatively high moisture and carbon dioxide content. For example, in commercial calcium oxide may contain from ~ 1 to 15% of the mass. CO ₂ and from ~ 1 to 10% of the mass. moisture.

The presence of these impurities is extremely undesirable, since they complicate the process of obtaining the residual pressure necessary to restore, having a negative effect on the resistance of the heater.

Starting position - the installation is in the pumped out state, all valves and gates are in the closed position. The feedstock, for example, for metallothermic reduction of calcium are briquettes pressed from a mixture of powders of calcium oxide and aluminum in a volume ratio of 3.5: 1, and calcium oxide contains moisture, for example, up to 5% of the mass. and calcium carbonate ~ 4% of the mass.

They let air into the chamber 2. Open the lid of the chamber 2 and load the container with the initial briquettes onto the pusher mechanism 18. They close the lid, pump out and heat the chamber 2 to a temperature of 600-800 ° C, at which water vapor and carbon dioxide are removed.

At the same time, the reaction chamber 1 is pumped out and its heating is turned on to a predetermined working temperature, which, for example, for aluminothermic reduction of calcium oxide is 1350 ° C. After degassing is completed in chamber 2 (as judged by the pressure gauge), the pressure in the chambers 1 and 2 is equalized and the water-cooled shutter 4 and the movable heat-insulating element 12 of the chamber 2 are opened, designed to equalize the temperature field in this chamber and reduce the temperature pressure on the shutter 4 , lower the movable lower part 14 of the block 13 and using the mechanisms 18, 19 move the container with briquettes to the lower part 14. Then close the heat-insulating element 12 and the shutter 4. The chamber 2 is ready for loading the next container but according to the described algorithm.

Using the mechanism 17, the container with the initial briquettes is transferred to the heating unit 13 of the reaction chamber 1, in which the metal recovery-evaporation processes and the vapor of the reduced metal are deposited on the water-cooled condenser 6. The power supplied to the heater is controlled by the signal of thermocouple sensors 23 and 24.

Produce pumping chamber 7 to remove the resulting condensate. After reaching a pressure in the chamber of not higher than 10 Pa, open the shutter 8 and move the hopper 9 to receive condensate under the guide funnel 16.

After turning the condenser 6, the condensate is removed by the cutter 15. The condensate removed through the funnel 16 enters the hopper 9. After filling the hopper 9 through the shutter 8, it is returned to the chamber 7. Then the shutter 8 is closed, an inert (neutral) gas is introduced into the chamber 7, and the hopper is removed 9 and set the next. Then the chamber 7 is again pumped out and at a residual pressure of no higher than 10 Pa, the shutter 8 is opened, the installed hopper 9 is moved under the guide funnel 16. The collection of condensate continues.

After completion of the recovery (in time depending on the temperature of the process), the lower part 14 of the reaction chamber 1 with the container of spent briquettes using the mechanism 17 is moved from the heating unit 13 of the chamber 1.

To unload spent briquettes, the unloading chamber 3 is pumped out to a pressure of no higher than 10 Pa, the shutter 5 is opened. Using mechanisms 21, 20, they are transferred to the unloading chamber. Then close the shutter 5, let in air and remove the briquettes through the bottom cover. For the next discharge, the chamber 3 is closed and pumped out.

Since the recovery time is hours, and the opening and closing times of shutters and movement using pushers is tens of seconds, a noticeable “loss” of the reduced metal is eliminated.

All processes are repeated. The algorithm is easy to formalize; a computer can control the operation of the furnace.

The proposed installation for metallothermal recovery of alkaline earth metals in comparison with the known ones will allow to ensure continuous operation of all units of the installation while reducing the cost of the process.

Claims (6)

1. Installation for metallothermal recovery of alkaline earth metals, containing a vertically mounted vacuum reaction chamber, on the opposite sides of which there is a vertical chamber for loading raw briquettes and a chamber for unloading treated briquettes, the reaction chamber is equipped with a heating unit having a heat-insulating casing, the lower part of which is connected to the first a mechanism for the vertical movement of the containers and on which the heater is located, with a capacitor configured to condensate movement and interaction with the cutter, under which a guide funnel is mounted, the latter being mounted on the upper part of the side wall of the reaction chamber, adjacent to the condensate removal chamber, separated from the reaction chamber by a first vacuum shutter and equipped with a condensate receiving hopper connected to the first mechanism horizontal movement, while the loading chamber and the unloading chamber are connected through the second and third vacuum locks with the first and second transport chambers, adjacent to the reaction chamber, the first and second transport chambers equipped with a second and third horizontal mechanisms for moving containers; the loading chamber is a muffle furnace, the lower part of which is connected to the second vertical mechanism for moving containers, the discharge chamber is a vacuum chamber equipped with a third vertical mechanism for moving containers, while its body is equipped with a water cooling system. 2. Installation according to claim 1, in which the heater of the reaction chamber is made of carbon-carbon composite material. 3. Installation according to claim 1, in which the thermal insulation of the reaction chamber is made of a low-density carbon-carbon composite material. 4. The apparatus of claim 1, wherein the reaction chamber body is provided with a water cooling system. 5. Installation according to claim 1, in which the condenser of the reaction chamber is equipped with a water cooling system. 6. Installation according to claim 1, in which the muffle furnace is equipped with a resistance alloy heater, and its body is equipped with thermal insulation.