RU2714565C1 - Aluminum electrolytic cell with insulated onboard lining - Google Patents

Abstract

FIELD: technological processes.SUBSTANCE: invention relates to bead lining of electrolytic cell for electrolytic production of aluminum. Electrolytic cell includes metal cathode jacket, heat-insulating and refractory lining, bottom made of bottom blocks with cathode current-conducting rods, bead lining made of silicon carbide plates with an additional molded refractory layer with lower thermal conductivity, which is installed between walls of metal cathode jacket and silicon carbide plates.EFFECT: reduced operating voltage of electrolysis cell due to reduction of heat losses from onboard walls of electrolysis cell, stabilization of heat balance and increased MHD-stability of electrolysis cell.4 cl, 4 dwg

Description

Technical field

The invention relates to the field of non-ferrous metallurgy, namely, to the design of electrolytic cells for the electrolytic production of aluminum, and can be performed in all types of electrolytic cells.

State of the art

In existing designs of electrolytic cells for the electrolytic production of aluminum, the highest component of heat loss (about 35%) falls on the longitudinal side walls (Fig. 1) (see Zhaowen Wang et al., Utilization of heat from aluminum electrolytic cells. Aluminum production: Collection of reports of the IX International Congress " Non-ferrous metals and minerals. ”Krasnoyarsk: Northeastern University, 2017, 209-217). This amount of heat loss adversely affects the heat balance of the cell, and heat compensation is required due to the voltage of the cell, which entails an increased energy consumption and, consequently, an increase in the cost of aluminum produced.

Known aluminum electrolyzer with side lining (application RU 94012661, C25C 3/06, publ. 04/10/1996), which allows the formation of stable flooring and ensure a long service life of the cell. The main distinguishing feature of this design is an inclined longitudinal side wall made of onboard carbon-graphite blocks. In this case, the side lining of the cell is inclined to the horizon at an angle of 0.3-0.9 F, where F is the angle of inclination of the side wall of the cathode casing to the same plane.

Known "Cathode device of an aluminum electrolyzer" (RU 1295786, C25C 3/08, publ. 1985), where the angle of inclination of the side wall 45-66 °, "Aluminum electrolyzer" (SU 1788090, C25C 3/08, publ. 1990 g .), where the angle of inclination of the side wall is 20-45 °, "Electrolyzer for producing aluminum" (RU 94009828, publ. 04/10/1996), where the angle of inclination of the side wall is 120 °.

The disadvantage of these technical solutions is due to the fact that during the electrolysis, the force from thermal expansion of the bottom carbon graphite blocks, acting on the inclined side wall, causes a force directed perpendicular to the inclined walls of the casing. The tangential component, acting on the inclined side blocks, presses them with the flange sheet, the loads on the flange sheet increase significantly, which leads to the destruction of the side lining. Therefore, the use of inclined side walls requires an increase in the stiffness of the cathode casing, in turn, an increase in the stiffness of the casing is associated with an increase in its mass and an increase in capital costs.

Also, the disadvantage is that with this embodiment of the side lining, coal stoves are oxidized and destroyed when exposed to oxygen from the air entering through the electrolyte crust, this leads to leaking of the electrolyte melt into the lining and deterioration of the thermal insulation properties. As a result of leaks, forces arise that squeeze the coal plates from the cathode casing, which subsequently destroy the side lining.

In addition, with an inclined design of the side wall, it is possible to stabilize the heat balance of the cell by reducing heat loss from the sides only after the start-up period of the cell, i.e. after the formation of nastily and skull. Thus, the heat loss from the sides with an inclined longitudinal wall during the starting period will remain unchanged, which will require heat compensation due to the voltage of the cell.

Known lateral lining of an aluminum electrolyzer (patent RU 2072398, C25C 3/06, publ. 01/27/1997), in which a belt is made of a non-conductive ceramic material based on aluminum nitride. The belt is made of plates connected by end faces using asymmetric protrusions and recesses using glue with the addition of refractory compounds. The disadvantage of this solution is the use of expensive materials with low barrier resistance to the effects of molten electrolyte.

A known cell for producing aluminum and a method of maintaining a crust on the side wall and regenerating electricity (application RU 2002135593, C25C 3/06, publ. May 29, 2001), where a high-temperature, heat-resistant and heat-insulating material is located inside, on the inner part of the side walls of steel housing, characterized in that all the side walls of the cell are equipped with cooling evaporative panels. The disadvantage of the solution is that the thermal balance of the electrolyzer of the claimed design depends on the boards that are intensively formed due to cooling of the panels by the evaporation panels of the nastily and the skull, with each deviation of the technological parameters of the electrolyzer and the change in the shape of the working space, the thermal balance of the electrolyzer will be unstable. The location of the cooling evaporative panels inside the cathode casing is critical, since contacting the panels with an aggressive electrolyte environment will significantly reduce their service life, and protecting panels in a heat-resistant, heat-insulating material entails a significant increase in capital costs.

The closest in technical essence to the claimed invention is the side lining of an aluminum electrolyzer (copyright certificate SU 377419, С25С 3/08, publ. 04/17/1973), where the side lining is made in height of materials with different melt resistance, while the upper part of it is made of a material with increased resistance - graphite plates, and the lower part of a material with reduced resistance - fired coal blocks. The disadvantage of the prototype is that after sintering with an adhesive layer at a high speed of circulation of the melt, the insert is destroyed due to deformation shifts in the upper parts of the cathode casing.

Disclosure of Invention

The objective of the proposed invention is to reduce heat loss from the side walls of the cell and stabilize the heat balance of the cell, as well as the formation of a stable coating and skull, which ensures a high battery life, a stable course of electrolysis technology and can significantly reduce energy consumption due to work at a lower operating voltage electrolyzer.

The technical result is to solve the problem, reduce the operating voltage of the cell by reducing heat loss from the side walls of the cell, stabilizing the heat balance and increasing the MHD stability of the electrolyzer (MHD magnetohydrodynamic).

Due to stabilization of the heat balance of the electrolyzer, the above technical result also includes a reduction in energy consumption, due to an increase in MHD stability - an increase in current efficiency, which in turn allows to reduce the cost of aluminum produced.

The problem is solved, and the technical result is achieved due to the fact that in the electrolytic cell for the electrolytic production of aluminum, including a metal cathode casing, heat-insulating and refractory lining, a hearth made of hearth blocks with cathode current-carrying rods, side lining, the new thing is that side lining made of silicon carbide and / or carbon plates with an additional molded refractory layer with lower thermal conductivity installed between the walls of the metal cathode th shell and silicon carbide and / or carbon plates.

To implement the proposed invention, it is advisable to use carbon plates, silicon carbide materials, chamotte. Silicon carbide is a material obtained by combining powdered silicon carbide with soot, characterized by increased density, a high degree of heat resistance, electrical conductivity and resistance to the process of scale formation.

Multilayer structures can be used where the first layer is a silicon carbide plate or a cheaper carbon plate. The material of the first layer should be erosion-resistant, with low electrical and thermal conductivity, with low porosity and high density. The refractory layer may be made of chamotte material or be a multilayer structure. The dimensions of the refractory layer are determined in accordance with the design of the cathode casing, and depend on the target technological parameters of electrolysis. It is important that the first layer of silicon carbide is erosion-resistant to the aggressive environment of electrolysis (electrolyte), and the second, for example, from chamotte, is heat-resistant to reduce heat loss.

The molded refractory layer may be made of monolithic refractory plates and / or refractory bricks, may contain inserts of additional heat-insulating material located inside the masonry of refractory plates and / or refractory bricks, while the inserts may be made of molded and / or unformed heat-insulating material.

An additional refractory layer may also be made of unformed material. In this case, the installation of the side lining involves the manufacture of special equipment (frame), into which unformed material is poured for further compaction, drying and solidification in the refractory layer in the form dedicated to the equipment.

Previously, a two-layer lining was not used, i.e. there was no lining made of two different materials, either carbon (cheap, low resistance to overheating, low thermal conductivity), or silicon carbide (more expensive, but more erosion resistant, but also transmit heat strongly - high heat losses).

The invention is illustrated by drawings.

In FIG. 2 a) presents the results of modeling the temperature field and the shape of the working space of an electrolyzer with a two-layer insulated side lining in comparison with the electrolyzer of the existing serial design b);

In FIG. 3 shows an electrolyzer for the electrolytic production of aluminum;

In FIG. 4 shows an additional refractory layer.

Explanations of the structural elements shown in the drawings:

1 - metal cathode casing;

2 - heat-insulating lining;

3 - refractory lining;

4 - hearth made of hearth blocks;

5 - cathode current-carrying rods;

6 - silicon carbide plates;

7 - additional molded refractory layer;

8 - insert additional thermal insulation material;

9 - refractory bricks / plates.

Until now, an on-board lining made of carbon blocks, later of silicon carbide plates, has been used in an aluminum electrolyzer. Carbon blocks are mostly cheap and have low thermal conductivity, which minimizes heat loss from the sides of the cell. At the same time, carbon blocks have a relatively low erosion resistance (weak resistance to high overheating, as well as an aggressive electrolysis environment - electrolyte), which reduces the life of the cell. On the contrary, expensive silicon carbide plates have high resistance to overheating and high resistance in the electrolyte environment. A significant drawback of silicon carbide plates is their high thermal conductivity, which entails large heat losses from the sides of the electrolyzer, which require compensation in the form of voltage to stabilize the heat balance, which leads to increased electricity consumption - an increase in the cost of aluminum.

The proposed insulated design of the side lining, consisting of silicon carbide plates adjacent to the electrolyte and an additional refractory layer between silicon carbide plates and the electrolyzer casing, combines both high resistance to overheating and high resistance to electrolyte, as well as low thermal conductivity, which ensures a high service life with stable thermal the balance of the electrolyzer, which will allow the electrolysis technology to be carried out at a lower voltage, with lower power consumption, with more izkoy cost of aluminum produced.

Below are the results of mathematical modeling of an electrolyzer with an onboard lining of the claimed design.

The calculation results showed that in order to ensure the thermal balance of the electrolytic cell with a two-layer (or more) insulated side lining, with an electrolyte temperature of 956 ° C, an MPR (interpolar distance) of 48.3 mm is necessary. Under these conditions, the total heat loss from the anode device will be 106.0 kW (42.1%), from the longitudinal walls of the cathode device 86.5 kW (21.5%), from the end walls of the cathode device 37.3 kW (14.9 %), from the bottom of the cathode device 22.8 kW (8.6%). The maximum temperature of the longitudinal wall of the cathode device will be 235 ° C, the end wall of the cathode device 155 ° C, the bottom of the cathode device 70 ° C. The length of the overlay along the longitudinal wall will be 150 mm, along the end wall - 162 mm under the anode. The minimum thickness of the skull will be 30 mm along the longitudinal wall, along the end wall - 64 mm at the level of the coal insert block. The average voltage will be 4.050 V, and the energy consumption - 12823 kWh / t.

In the framework of pilot tests of an insulated two-layer (or more) side lining, an additional refractory layer was glued to the cathode casing of the electrolyzer, and a layer of silicon carbide plates was also glued to the additional refractory layer. During the installation of the double-layer side lining, no special requirements for gluing materials, as well as for laying operations, were presented. During industrial tests on the experimental electrolyzer, due to the insulated design of the side lining, a reduction in energy consumption of 300 kWh / t was achieved relative to existing electrolyzers with silicon carbide side lining.

Claims (4)

1. An electrolytic cell for the electrolytic production of aluminum, comprising a metal cathode casing, a heat-insulating and refractory lining, a hearth made of hearth blocks with cathode current-supplying rods, an onboard lining, characterized in that the onboard lining is a multilayer structure containing silicon carbide and / or carbon plates with an additional molded at least one refractory layer with lower thermal conductivity installed between the walls of the metal cathode casing and silicon carbide and / or carbon plates. 2. The electrolyzer according to claim 1, characterized in that the molded refractory layer is made of monolithic refractory plates and / or refractory bricks. 3. The electrolyzer according to claim 1 or 2, characterized in that the molded refractory layer contains inserts of additional heat-insulating material located inside the masonry of refractory boards and / or refractory bricks. 4. The cell according to claim 3, characterized in that the inserts are made of molded or unformed thermally insulating material.

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