RU2668615C2 - Side bock for electrolytic cell wall for reducing aluminum - Google Patents

Abstract

FIELD: electrical engineering.SUBSTANCE: invention relates to a side block for a wall in an electrolytic cell, in particular for producing aluminum, to a method for manufacturing such a side block, and to the use of such a side block, as well as to an electrolytic cell with such a side block. Said side block is a layered element comprising a layer with a higher thermal conductivity and a layer with a lower thermal conductivity, wherein the difference in thermal conductivity is at least 5 W/(m⋅K) at a temperature of between 920 °C and 1,000 °C, wherein at least one of the layers is doped with silicon as a powder, an oxide ceramic material, or a non-oxide material. Also, a method for manufacturing such a side block is disclosed, as well as the use of a side block for lining the side walls of an electrolytic cell for producing aluminum and an electrolytic cell for producing aluminum with a sidewall with such a side block.EFFECT: ensured the creation of optimal technological conditions to achieve high profitability and stability during electrolysis, increased life of the cell by increasing the resistance to abrasion and / or corrosion wear.16 cl, 11 dwg

Description

The present invention relates to a side block of a wall in an electrolyzer, in particular for producing aluminum, to a method for manufacturing such a side block, and to the use of such a side block, as well as to an electrolyzer with such a side block.

Electrolyzers are used for the electrolytic production of aluminum, which in industry is usually carried out according to the Hall-Hero method. In the Hall-Hero method, a melt consisting of alumina and cryolite is subjected to electrolysis, namely, preferably consisting of about 15-20% alumina and about 85-80% cryolite. In this case, cryolite, Na ₃ [AlF ₆ ], serves to reduce the melting temperature from 2045 ° C for pure alumina to about 960 ° C for a mixture containing cryolite, alumina and additional substances such as aluminum fluoride and calcium fluoride, that the electrolysis of the melt is carried out at a reduced temperature of about 960 ° C.

The electrolyzer used in this method has a bottom, which is assembled from numerous, for example, 24, adjacent to each other, forming a cathode of cathode blocks. In each case, a seam is formed between adjacent cathode blocks. The location of the cathode blocks and, if necessary, filled seams is generally indicated by the cathode bottom. The cathode bottom is surrounded by a wall formed from numerous side blocks, which together with the cathode bottom forms an inner bath containing an aluminum layer and a melt layer, which is surrounded by an outer steel bath. Seams or, respectively, gaps between adjacent cathode blocks, as well as between cathode blocks and side blocks, are usually filled with a packed mass of carbon and / or carbon-containing material, such as anthracite or graphite, and a binder material, such as coal tar pitch. It serves to seal against penetration of the components of the liquid melt and to compensate for mechanical stresses, which, for example, arise due to the expansion of the cathode blocks when heated in the commissioning mode of the cell. In order to withstand the thermal and chemical conditions prevailing during operation of the cell, the cathode blocks are usually made of a homogeneous carbon-containing material, and the side blocks are composed of a homogeneous material containing carbon or silicon carbide. In each case, grooves are provided on the lower sides of the cathode blocks, in which at least one conductive bus is placed in each case, through which an electric current supplied through the anodes is discharged. Under the cathode bottom, that is, between the cathode blocks and the bottom of the steel bath in which the cathodes are placed, a lining of refractory material is usually provided which thermally isolates the bottom of the steel bath from the cathode bottom.

At a distance of about 3 to 5 cm above the layer of molten liquid aluminum located on the upper side of the cathode, an anode made of separate anode blocks is placed, and a melt containing aluminum oxide and cryolite is located between the anode and the aluminum surface. During electrolysis carried out at a temperature of about 960 ° C, the resulting aluminum, due to its higher density compared to the melt, falls down under the melt layer, that is, acts as an intermediate layer between the upper side of the cathode blocks and the melt layer. During electrolysis, aluminum oxide dissolved in a cryolite melt decomposes into aluminum and oxygen under the influence of a flowing electric current. From the electrochemical point of view, in relation to the layer of molten liquid aluminum, we are talking about the cathode itself, since on its surface aluminum ions are reduced to elemental aluminum. However, hereinafter, the term “cathode” is understood not as a cathode from an electrochemical point of view, that is, a layer of molten liquid aluminum, but as a structural part forming a cathode bottom composed of one or many cathode blocks.

Modern electrolyzers are operated at high electrolysis currents, for example, up to 600 kA, in order to ensure high electrolysis capacity. These high currents lead to increased heat generation during the electrolysis process. Due to intense heat dissipation, it is difficult to control the heat removal from the cell in such a way that everywhere in the cell thermal conditions are reached that are optimal in terms of stability and efficiency of the electrolysis, as well as in relation to the life of the cell, and, for example, the energy efficiency of electrolysis due to excessive heat loss in areas of high heat generation in the cell. Because of this, due to adverse thermal conditions in the electrolyzer, the reliability and efficiency of the electrolysis process, as well as the durability of the electrolysis cell, are deteriorated.

True, it is possible to conduct the removal of excess, that is, unnecessary to maintain the heat melting process through the bottom of the steel bath, using a refractory lining located between the cathode bottom and the steel bath, which usually consists of refractory bricks or plates laid in a steel bath and located on top of each other in the area of the bottom of the steel bath. At the same time, a significant role for the temperature conditions in the region of the liquid aluminum layer and the melt layer in which electrolysis takes place is played by heat transfer through the relatively thin side wall of the inner bath formed by the cathode bottom and side blocks. Heat fluxes in this side wall are especially important for thermal conditions in the electrolyzer, since the side wall is usually in contact with various components and media in the electrolyzer, that is, in particular, with a layer of liquid aluminum, a layer of liquid melt located on top of it of a liquid melt layer by a solidified melt layer, or a crust, respectively, and a gaseous atmosphere formed during operation of the electrolyzer with various elements contained therein.

The released amounts of thermal energy must be partially removed in a certain way, but at the same time, too high heat losses, which mean energy losses, must be prevented, and thereby worsen the efficiency of the electrolysis process.

In the region of relatively thin side walls in known electrolyzers, due to the vertical structure of the side walls and the resulting structural requirements, no additional lining is made of stacked refractory bricks, as in the region of the bottom of the steel bath, so that the heat transfer through the side walls cannot be adjusted in the same way. in a simple manner, as in the bottom region. Uniform side walls, which usually consist of a material containing carbon or silicon carbide, are uniform in terms of thermal conductivity perpendicular to the plane of the side wall, and allow only limited control of heat fluxes and the passage of isotherms in the side wall in continuous operation. The seams between such a side wall and the cathode block are usually filled with a packed mass of carbon and / or carbon-containing material, such as anthracite or graphite, and a binder material, such as coal tar pitch. This seam is often filled manually or semi-automatically, and packing defects can occur that can damage the gap or, in the worst case, even premature failure of the entire cell. These damages often occur only during commissioning or in continuous operation of the electrolyzer. The risk of damage becomes greater, the wider or, accordingly, the corresponding seam is thicker. In addition, a wider or, correspondingly, thicker seam also means increased labor costs and an increased burden for the environment and the personnel serving the electrolyzer, since traditional packing materials contain substances harmful to health. It is known to replace a part or all necessary between the side blocks and the cathode blocks of the packed mass with an obliquely laid layer of prebaked carbon or graphite. If only a part of this packing material is replaced, then the thickness of the seam filled with the packing material is reduced by more than 50% to 99%, preferably by more than 75% to 99%, particularly preferably by more than 90 to 99% . It is also possible that this layer does not fill the entire volume of the initial packed mass layer, for example, to create space for increasing the surface of the anode. For the most part, a thin, vertically extending seam with a printed mass, for example, 50 mm thick, is still left. Using such an obliquely extending layer, vertically placed side blocks, for example, silicon carbide bonded with silicon nitride, can be connected. Such a structure, including a side block and an inclinedly extending layer, is hereinafter referred to as a “composite side block”. A composite side block, in which silicon carbide bonded by silicon nitride is glued to an inclined passage, is already used in modern electrolyzers. Usually used adhesive material may contain substances that are harmful to health, which again means a high burden on the environment and the personnel who operate the cell. In addition, the placement of the adhesive material causes an additional technological operation. If adhesion defects occur due to defective adhesive material or its incorrect application, this can lead to failure of the adhesive joints. The side blocks of such a composite side block are composed of a uniform material and thus do not allow differences in the thermal conductivity of the side block itself. The heat flux in the electrolyzer can also be influenced by the adhesive material or, accordingly, the adhesive joint. Since the adhesive joint itself is very thin, inhomogeneities in this joint can degrade the corresponding local heat flux. Carbonization of the adhesive material during commissioning of the electrolyzer can lead to a decrease in its adhesion strength, which can lead to a weakening of the bond between the oblique passing layer of pre-calcined carbon or graphite and the vertically mounted side block. If this leads to failure of this connection, that is, the aforementioned obliquely passing layer and the vertically mounted side block are no longer connected to each other, then the heat flux is deteriorated indefinitely, and the necessary heat transfer can no longer be provided sufficiently. This can lead to overheating of the electrolyzer, and in the worst case, to its premature failure, that is, the durability and, accordingly, the life of the electrolyzer are reduced. The adhesive material can also be applied between the individual side blocks that make up the side wall, in the form of a thin adhesive layer.

DE 3506200 discloses side blocks for the cell wall, which are a layer-by-layer connecting element that comprises an inner layer of carbon-containing material and an outer layer of solid ceramic material, both of which are tightly connected to each other. This ensures a virtually unhindered heat flow from inside to outside. However, when using such side blocks, resistance to wear, in particular, abrasive and / or corrosive wear, is still insufficient.

Therefore, on known electrolyzers, in particular, when working with high values of electrolysis current, optimal technological conditions are not achieved, as a result of which achievable stability and efficiency of the electrolysis process are limited, and the life of the electrolyzer is reduced.

Therefore, the objective of the invention is to create a side block for the wall of the cell, which, when used in the cell, provides optimal technological conditions and, accordingly, high efficiency and stability during the electrolysis, as well as the long life of the cell. In particular, the side unit must regulate the heat transfer through the side wall of the electrolyzer in such a way that during the electrolysis the optimal thermal conditions prevail in the electrolysis cell and the heat losses during operation due to the unfavorable distribution of thermal energy and temperatures are most prevented. The working temperature of the electrolyzer during electrolysis is between 920 ° C and 1000 ° C, preferably between 950 ° C and 980 ° C. In addition, this side block must have increased resistance against abrasive and / or corrosion wear, in particular against abrasive wear. In addition, it is necessary that this side block can be made, for example, without the use of adhesive (s) material (s). In addition, this side block, when it is made in the form of a composite side block, should also provide the possibility of partial or complete rejection of the packing mass between the side wall and the cathode block.

According to the invention, this problem is solved by using a side block for a wall in an electrolytic cell, in particular for producing aluminum, which is a layered element, and includes a layer with lower thermal conductivity and a layer with higher thermal conductivity, the difference between lower and higher thermal conductivity is at least 5 W / m⋅K, as measured at a temperature between 920 ° C and 1000 ° C, preferably between 950 ° C and 980 ° C, and wherein at least one of the layers is doped with silicon (powder), oxide ceramics material or non-oxide material. This layered element can be - as explained below - made without the use of adhesive (s) material (s). Due to the design of the side block, it is also possible to abandon the use of adhesive (s) material (s) between the individual side blocks that form the side wall. Due to the shape of this laminate element, it is possible, as also described below, to partially or completely abandon the stuffed mass to fill the joints between the side block and the cathode block.

It was found that the execution of a side unit for an electrolyzer with layers with different thermal conductivity, at least one of the layers being doped with silicon (powder), oxide ceramic material or non-oxide material, allows a very simple way to implement and at the same time highly efficiently regulate thermal conditions in the cell during its operation in such a way that the stability and productivity of the electrolysis and the life of the cell are optimized. In addition, increased resistance to wear, in particular against abrasive and / or corrosive wear. If adhesive material is used between the individual side blocks, then thanks to the construction of this side block, this adhesive material can be completely abandoned. In addition, it was found that as a result of giving a special shape to this side block, along with this regulation of thermal conditions, it is also possible to partially or completely abandon the stuffed mass to fill the seam between the side block and the cathode block.

When the term “side block” is subsequently referred to, this term may also include the above composite side blocks. As described below, the composite side block has a special shape.

Under the concepts of "lower" and, accordingly, "higher" thermal conductivity, it should be understood that the corresponding layer that has this thermal conductivity, in comparison with the corresponding other layer has a "lower" or, accordingly, "higher" thermal conductivity. In particular, one of the layers consists of a material with lower thermal conductivity, and the other layer of a material with higher thermal conductivity, both materials being different from each other. If the layered element includes more than two layers, then all layers can have different thermal conductivities, or at least two layers can have the same thermal conductivity, and / or at least two groups of layers are provided, which in each case have the same thermal conductivity. With more than two layers, it is sufficient when the difference in thermal conductivity between at least two of the layers is at least 5 W / m⋅K - as measured at a temperature between 920 ° C and 1000 ° C, preferably between 950 ° C and 980 ° C. In particular, the thermal conductivities of the layers differ in at least one direction of the side block, and it is preferably a direction which, in particular, is perpendicular to the side wall formed by the side blocks.

The difference between lower and higher thermal conductivity - as measured at a temperature between 920 ° C and 1000 ° C, preferably between 950 ° C and 980 ° C - can be between 5 W / m⋅K and 80 W / m⋅K, preferably between 5 and 70 W / m⋅K, particularly preferably between 8 W / m⋅K and 60 W / m⋅K, and most preferably between 10 W / m⋅K and 50 W / m⋅K.

Due to the different layers of the side block with different thermal conductivity, the thermal conductivity and heat transfer through the side block and the passage of the isotherms in the side wall can be purposefully controlled. Since the side block directly in separate sections is in direct contact with the liquid aluminum layer and the melt layer in which the electrolysis takes place, it is therefore possible to directly and with high efficiency influence the prevailing temperature conditions that are especially important for the stability and productivity of electrolysis in such a way that optimal conditions for operation can be provided electrolyzer thermal conditions. For example, various thermal conductivities can be provided in the regions of the side block, which, when using the side block in the cell, are in contact with various mediums of the cell. Likewise, numerous layers with different thermal conductivities can follow one after the other along the direction of the heat flux through the side block to the outside in order to control the heat flux in the indicated direction. The achieved optimization of thermal conditions in the cell leads to a significant increase in the stability and productivity of the electrolysis process and the life of the cell. The stability and productivity of the electrolysis process and the life of the electrolyzer are also enhanced by the fact that at least one of the layers is doped with silicon (powder), oxide ceramic material or non-oxide material. Side blocks according to the invention, which also include composite side blocks, can be advantageously in the traditional way, which corresponds to known side blocks with uniform thermal conductivity, in each case with respect to a specific spatial direction, integrated into the cell and used there for lining the side wall of the steel bath, without the need to change the design of the cell and without the need to take into account the associated disadvantages, and the side wall of the cell, in particular, in a known embodiment, can be made relatively thin. Side blocks can be manufactured at low costs and with excellent mechanical stability, and, in particular, with very good adhesion between different layers, for which the side blocks are fired as a single part from a single solid raw base element, which contains various raw mixes corresponding to the manufactured layers, the base element may correspond to a separate side block, or the calcined base element may be divided into numerous shackles blocks. In the manufacture of a composite side block, for example, from such a calcined raw material preform, a desired polygonal shape may first be generated along the entire length of the raw material preform before the individual composite side block is then cut into a plate. Preferred polygonal shapes will be discussed in more detail later. During final processing, grooves, protrusions, recesses, and roughnesses may be made in the composite side block. Here it should once again be pointed out that adhesion between the various layers of the side block according to the invention is achieved without the use of adhesive (s) material (s).

Preferred embodiments of the invention are presented in the dependent claims, in the description and in the figures.

When the following description refers to one or multiple layers of the side block made in the form of a layered element, this means layers with different thermal conductivity, which, in particular, in each case have a thermal conductivity that is different from the thermal conductivity of at least one other layer of the side block 5 W / m ∙ K or more, as measured at a temperature between 920 ° C and 1000 ° C, preferably between 950 ° C and 980 ° C.

In particular, both layers can follow each other in a predetermined direction, which can correspond to the direction of the heat flux relevant to the thermal conditions in the cell, and, for example, can be set by the direction of the thickness of the side block. Due to this variation in thermal conductivity over the thickness of the side block, the total heat flux through the side block can be adjusted in this direction so that the desired passage of the isotherms in the side block is ensured. But the layers can also follow each other, for example, in the direction of the height of the side block, which does not include the composite side block, and, in particular, the height regions of the side block covered with different layers, when applied in the electrolytic cell, can come into contact with various electrolytic media - for example, such as liquid aluminum, liquid or solidified melt, gas phase. Due to the variation in thermal conductivity due to the height of the side block, the heat removal can be adjusted in accordance with the heat release occurring in the corresponding medium, and with the thermal conditions desirable there in each case, and additionally in accordance with the chemical requirements of the individual media.

The coordination of thermal conditions desired in accordance with the invention in the electrolyzer during its operation can be realized even when the side block has exactly two layers with different thermal conductivities. In addition, such a layered structure has high stability and can be manufactured at low cost and high reliability and reproducibility. But in principle, the number of different layers of the side block is not limited to only two. Instead, the side block may also include a larger number of layers, for example at least three, four, five, six or more different layers. Due to this, an even more differentiated local coordination of the thermal conductivity characteristics of the side block and the thermal conditions in the cell can be achieved. The side block preferably includes two to four layers, particularly preferably two to three layers, most preferably two layers. If along with the desired coordination of thermal conditions in the electrolyzer during its operation, the goal is also to partially or completely replace the packing mass between the cathode block and the side block, that is, a composite side block is used, this composite side block can also include a larger number of layers, for example, at least three, four, five, six or more different layers. The composite side block preferably includes two to four layers, particularly preferably two to three layers, most preferably two layers.

The layers can follow each other in a predetermined direction, which may correspond, in particular, to the direction of the thickness or height of the side block, so that a variation in the thermal conductivity of the side block in the thickness direction or, accordingly, in the height direction of the side block is achieved. The side block can also have layers following in different directions one after another so that a variation in the thermal conductivity of the side block in different directions is achieved. For example, numerous side-by-side layers in a side block can form a first sequence of layers, and numerous other side-by-side layers of a side block can create a second sequence of layers, with both sequences of layers preferably following each other in a second direction, different from the first direction, and, in particular, perpendicular to the first direction, that is, in a checkerboard pattern.

According to one preferred embodiment, the laminate has an alternating sequence of a layer with lower thermal conductivity and a layer with higher thermal conductivity. This alternating sequence can be performed in a predetermined direction, which, in particular, corresponds to the direction of thickness or height. But it can also be that one alternating sequence is obtained from a layer with lower thermal conductivity and a layer with higher thermal conductivity in the first direction, and one alternating sequence is made in a second direction different from the first direction, in particular perpendicular to the first direction. Moreover, a particularly preferred thermal conductivity characteristic is achieved when the outer layer of the laminate is a layer with lower thermal conductivity, and the other outer layer is a layer with higher thermal conductivity. As a result of this, the absorption, distribution and removal of heat through the outer surfaces of the side block, which are formed by the outer layers of the side block, is effectively and directly coordinated. It is preferable that the outer layer of the layered element, which is in contact with liquid aluminum and / or the liquid melt layer, is a layer with lower thermal conductivity, and that the other outer layer of the layered element that is in contact with the cathode bottom and / or bath, was a layer with higher thermal conductivity. The direction in which the thermal conductivity is different is a direction that is oriented perpendicular to the side wall formed by the side blocks.

In principle, the layers and / or side block may have any suitable shape. It should be understood that the shape largely depends on the desired use of the side block, that is, the coordination of thermal conditions in the cell during its operation, individually or in combination of this coordination with a partial or complete replacement of the packing mass between the cathode block and the side block.

One embodiment, particularly preferred with respect to the thermal conductivity characteristics as well as the manufacturability of the side block, is that the layers of the side block have a block shape, in particular a rectangular shape, and are connected to each other by contact surfaces, in particular, their abutment surfaces , or its side surfaces. Such layers can be especially easily made and allow targeted control and variation of thermal conductivity along the main directions of the side blocks, preferably having a block shape, in particular a rectangular shape.

The side block is preferably made in block form, in particular with a rectangular shape. In this case, the thickness direction of one or many layers of the side block in each case can coincide with the direction along the thickness of the side block so that the orientation of the layers is consistent with the orientation of the side block and, accordingly, with the main directions of heat transfer in the side block. Layers interconnected by their supporting surfaces, respectively, can follow each other in the direction of the thickness of the side block, and layers interconnected by their side surfaces can follow each other in the direction of the height of the side block.

In the sense of the invention, a block is understood to mean an element that has six rectangular surfaces, eight right angles and twelve edges, of which in each case at least four are of the same length and parallel to each other. If the block is a rectangle, then in each case the four edges are equal and parallel to each other. But it is also possible that eight of the twelve ribs have the same length, and here in each case four ribs are parallel to each other, or all the ribs are of equal length, and here also in each case four ribs are parallel to each other.

If the side block is used in the electrolyzer as a composite side block, the preferred embodiment of the side block is that at least one layer of the side block has a block shape, in particular a rectangular shape, and at least one layer of the side block has a polygonal form. These layers are connected to each other by their contact surfaces, in particular, by their supporting surfaces; the supporting surface of the layer having a block shape, in this case, has either partial or full contact with the supporting surface of the layer having a polygonal shape. With full contact of the supporting surfaces, both layers have the same height; if partial contact takes place, the layer having a polygonal shape has a height that is from 30% to less than 100%, preferably from 40% to 80%, particularly preferably from 50% to 75% of the height of the layer having a block shape . Such layers can also be made in a very simple way and allow, on the one hand, to purposefully coordinate and vary the thermal conductivity along the main directions of the side block, on the other hand, using this side block, it is possible to partially or completely replace the packing mass between the side block and the cathode block.

At least one layer of the composite side block has a polygonal shape. In the sense of the invention, a polygon is understood to mean a polygon, which preferably may contain from three to six angles, particularly preferably from three to five angles. As a polygon with four corners, we mean, for example, a rectangle, square or trapezoid. These polygons can have a regular or irregular shape. Under the right polygon in the framework of the invention refers to a polygon in which all sides have the same length, and all internal angles have the same size. Using various polygonal shapes, the composite side blocks can be matched to the desired cell design; for example, due to the corresponding design of the composite side block, that is, the implementation of a layer with a polygonal shape, more space for anodes can be created. The increased area of the anodes allows the use of higher current values and thereby provide higher performance. In addition, the shape of the composite side block may be consistent with the shape of the initially passing seam with ramming mass. In addition, these polygons can have normal and / or rounded corners. A normal angle is a point at which two sides of the corresponding polygon converge with each other. A rounded corner refers to an angle that has a circular bend that extends concave inward, without having an angular or correspondingly ribbed change of direction in this curved section. Rounded corners compared with sharp corners have the advantage that a more uniform distribution of forces occurs at rounded corners. This more uniform distribution of forces causes a decrease in the stresses arising, and thereby a reduced formation of cracks and / or defects in these places of the composite side block. The polygon preferably contains only normal angles, or one vertex of the polygon is rounded, and the other angles are normal angles.

In this case, the direction in thickness of one or many layers of the composite side block in each case can coincide with the direction in thickness of the side block so that the orientation of the layers is consistent with the orientation of the side block and, accordingly, with the most important directions of heat transfer in the side block. The layers interconnected by their abutment surfaces, respectively, can follow one another in the thickness direction of the composite side block.

The side block, including the composite side block, can in principle have a flat structural shape with a relatively small thickness and, in particular, clearly greater height and width, and the side block may have a height that exceeds the width. The thickness of the side block, when the layers are interconnected by their supporting surfaces, can be, for example, between 50 and 700 mm, and depends on the application. If the side block is used only to match the thermal conditions in the cell, the thickness is preferably between 60 and 250 mm, particularly preferably between 80 and 150 mm, most preferably between 90 and 110 mm. If a composite side block is used in the cell, the thickness is preferably between 150 and 600 mm, particularly preferably between 200 and 350 mm, most preferably between 225 and 300 mm. The ratio of the thicknesses, in particular of the two layers, can be, for example, not more than 1: 3, preferably not more than 1: 2, and particularly preferably 1: 1.

The width of the side block, including the composite side block, can be in any way coordinated with the length of the side wall of the cell, that is, it can occupy either the entire length of this side wall, or it only makes up part of the length of the side wall. The length of the side wall can be, for example, either from 3,500 mm to 4,000 mm, or from 10,000 to 15,000 mm. If the length of the side wall is from 10,000 to 15,000 mm, then the width of the side block can be this length, or the side wall is covered, for example, with side blocks from 2 to 3, having a length of 5000 mm.

When the width of the side block occupies the entire length of the side wall of the electrolyzer, on the one hand, due to this side block, it is possible to abandon the possible use of adhesive material for the joints between the individual side blocks, on the other hand, the simplified incorporation of this side block saves time. When the width of the side block according to the invention is only part of the length of the side wall, at least two side blocks according to the invention are used. Within the scope of the invention, it is possible to use side blocks according to the invention with different widths, that is, the width of one separate side block can be adjusted according to need. When the width of the side block according to the invention, including the composite side block, occupies only a part of the length of the side wall, it can be between 300 and 600 mm, preferably between 400 and 600 mm, particularly preferably between 450 and 550 mm.

The height of the side block, including the composite side block, can be, for example, between 500 and 900 mm, preferably between 600 and 800 mm, particularly preferably between 600 and 750 mm. In this case, for the composite side block, the length of the layer having a block shape is taken as the height.

According to one preferred embodiment, the side block, which does not include the composite side block, has two consecutive ones in the thickness direction of the side block, in particular, partially or completely interconnected by their supporting surfaces of the layer, which in each case cover 30% - 70%, preferably 50%, of the thickness of the side block, and thereby cover the entire thickness of the side block. It should be understood that the values of the individual thicknesses of the layers in percent - also the following description - always together give 100%. In this case, one layer can be extended along the entire height of the side block.

Similarly, a side block, which does not include a composite side block, may have two consecutive side blocks in the direction of the height of the side block, in particular, layers connected by their side surfaces, which in each case cover 30% -70%, preferably 50%, of the height side block, and thereby cover the entire height of the side block. In this case, one layer can be extended over the entire thickness of the side block.

According to one preferred embodiment, one or more, and in particular all layers of the side block, which are not a composite side block, in each case have a thickness of from 25 mm to 125 mm, preferably from 30 to 100 mm, particularly preferably 40 to 75 mm, and most preferably 45 to 55 mm. This is particularly preferred when the side block has two layers that are interconnected by their abutment surfaces and follow each other in the thickness direction, and, in particular, in each case comprise 30-70%, preferably 50%, of the thickness of the side block. Moreover, the layers in each case can be extended along the entire height of the side block.

According to one additional preferred embodiment, one or more, and in particular all layers of the side block, which do not include the composite side block, when these layers are interconnected by their side surfaces and follow each other in the direction of height, have a height of 150 up to 450 mm, preferably from 200 to 400 mm, particularly preferably from 250 to 350 mm, and most preferably from 280 to 320 mm. This, in particular, is preferred when the side block has two layers that are interconnected by their side surfaces, and follow each other in the direction of height, and in each case are extended, in particular, 30% -70%, preferably up to 50% of the height of the side block. Moreover, the layers in each case can be extended over the entire thickness of the side block. The ratio of heights, in particular, two layers can be, for example, not more than 1: 3, preferably not more than 1: 2, and particularly preferably 1: 1.

According to one exemplary embodiment of the composite side block, this side block has two consecutive ones in the thickness direction of the side block, in particular, interconnected by their supporting surfaces of the layer, which in each case occupy 30% -70%, preferably 50%, the thickness of the side block, and thereby cover the entire thickness of the side block. It should be understood that the values of the individual layer thicknesses in percent - also in the following description - always together make up 100%. In this case, one layer may be partially or fully extended over the entire height of the side block. It may be that the layer having a polygonal shape is either completely extended over the entire height of the layer having a rectangular shape, or it occupies from 30% to less than 100%, preferably from 40% to 80%, particularly preferably from 50% to 75%, the height of the layer having a rectangular shape.

According to one additional preferred embodiment, one or more - and in particular all - layers of the composite side block in each case have a thickness of from 75 to 250 mm, preferably from 100 to 175 mm, and particularly preferably from 110 to 150 mm. This is especially preferred when the composite side block has two layers that are partially or completely interconnected by their abutment surfaces and follow each other in the thickness direction, and, in particular, in each case comprise 30-70%, preferably 50%, thickness of the composite side block. With full contact of the supporting surfaces, the layers are extended along the entire height of the composite side block; if, on the contrary, there is a partial contact of the supporting surfaces, the layer having a polygonal shape occupies from 30% to less than 100%, preferably from 40 to 80%, particularly preferably from 50% to 75%, of the height of the layer having a rectangular shape .

According to one additional embodiment, one or more layers of a rectangular shape, and, in particular, all rectangular layers of a composite side block, have a height of from 500 to 900 mm, preferably from 650 to 850 mm, particularly preferably from 700 to 800 mm, and one or several, and, in particular, all polygonal layers have a height of from 150 to less than 900 mm, preferably from 200 to 720 mm, most preferably from 250 to 675 mm.

The lateral block in its height can be in contact with various components or media of the electrolyzer, in particular, with a layer of liquid aluminum, a layer of melt, under known circumstances, with a crust of solidified melt located on top of the melt layer, as well as with the gaseous atmosphere formed during the operation of the electrolyzer with a variety of substances contained in it. In its lower region, the side block may be connected to the cathode bottom and / or the packing mass, which may be provided to provide a tight connection between the cathode bottom and the side block. The side block according to the above description may have numerous successive layers with different thermal conductivities, one after another, preferably the height regions of the side block on which the side block is in contact with different media are formed by different layers of the side block. Due to this, the absorption and removal of heat through the side unit is consistent with the existing thermal conditions and requirements in various environments. Through this alignment, the side blocks generally experience less load, which leads to higher wear resistance.

Alternatively or additionally, the side block may have multiple layers with different thermal conductivities following one after another in the thickness direction of the side block. As a result, the thermal conductivity of the side block can vary in the direction of the heat flux, which is oriented perpendicular to the side surface of the side block adjacent to the inside of the bath.

One embodiment, which is preferable with respect to the thermal, mechanical, and chemical stability of the side block that is important for the use of a side block in an electrolytic cell, is that at least one layer, preferably all layers, consists of a material selected from the group consisting of carbon , graphite carbon, graphitized carbon, or silicon carbide, or any mixtures thereof, or contains such material. These materials are particularly suitable to withstand the effects of the conditions that apply when using the side block in the cell and when the side block comes into contact with the liquid aluminum layer and the melt layer. In addition, the choice of materials with suitable compositions makes it possible to match the thermal conductivity of the side block in a preferred range of values. The thermal conductivity of one or many, and in particular all layers of the side block — as measured at temperatures between 920 ° C and 1000 ° C, preferably between 950 ° C and 980 ° C — can be, for example, between 4 to 120 W / m ⋅K, in particular between 4 to 100 W / m⋅K, preferably between 5 to 80 W / m⋅K, particularly preferably between 8 to 50 W / m⋅K.

A particularly high wear resistance of the side block and thereby a particularly long service life of the electrolyser equipped with the side block is achieved when the carbon is anthracite, preferably electrically calcined anthracite, and silicon carbide is silicon carbide bonded.

A further improvement in the thermal and mechanical characteristics of the side block can be achieved when the manufacture of the side block includes a pitch impregnation step and subsequent carbonization. In this case, the entire side block or at least one layer of the side block may be impregnated, as described above.

At least one of the layers can be doped with silicon (powder), an oxide ceramic material, for example, such as aluminum oxide or titanium dioxide, or a non-oxide ceramic material, which preferably consists of at least one metal of 4-6 Groups, and at least at least one element from the 13th or 14th group of the Periodic system of elements. Alloying is here understood to mean adding to the raw mix, the specific content of one or more alloying additives in the raw mix being 3-15% by weight, preferably 5-10% by weight. Preferably, powders are used from particles with a diameter of less than 200 microns, particularly preferably less than 63 microns. A number of these non-oxide materials include, in particular, metal carbides, metal borides, metal nitrides and metal carbonitrides, with metal from 4-6 Groups, for example, such as titanium, zirconium, vanadium, niobium, tantalum, chromium or tungsten, preferably titanium is applied. It is also possible to use any mixtures of oxide ceramic materials, any mixtures of non-oxide ceramic materials, any mixtures of oxide ceramic materials and non-oxide ceramic materials, any mixtures of oxide ceramic materials and silicon (powder), any mixtures of non-oxide ceramic materials and silicon (powder ), or any mixtures of oxide ceramic materials, non-oxide ceramic materials and (silicon) powder. As preferred non-oxide materials, titanium boride or titanium carbide can be used. If silicon (powder) is used, it is converted to silicon carbide during the firing process. It is also possible to use a precursor (precursor) for producing silicon nitride bound silicon carbide, a mixture of silicon carbide and silicon powder being used. Here, the firing process should be carried out at a controlled nitrogen content in the combustible gas at temperatures up to 1400 ° C, in order to ensure the conversion of silicon into the actual binding phase of silicon nitride. As a rule, here the heat treatment is carried out by firing, as for conventional ceramic materials, that is, at a firing temperature in accordance with the used ceramic material. Thus, it may be that in the manufacture of the laminate element, various requirements for the firing process of the individual materials used must be taken into account. In relation to this layer, we are talking, in particular, about the layer, which during operation is in contact with the surrounding steel bath and thereby exposed to an increased risk of oxidative wear.

The side block is preferably made monolithic so that the layers of the side block are interconnected as a single integral part and with a material closure. Such a connection differs from the adhesive or mechanical connection in increased stability. The side block can form a composite element from separate layers. As a result of this, a particularly high thermal, mechanical and chemical stability of the side unit is obtained, and thus a particularly long service life of the cell equipped with the side unit. In particular, the side block can be obtained whole from the raw material blank, which may contain various layers of numerous different raw mixtures corresponding to the finished side block, which form the starting materials for the various layers of the side block. The side block can be obtained by firing the raw material billet, in particular, carbonization and / or graphitization of the raw material in the raw material billet can be carried out.

For example, the thermal conductivity of the side block can be measured at temperatures between 920 ° C and 1000 ° C according to DIN 51936. In this case, a pulse laser is used for measurements that exceed temperatures of 400 ° C. Inside one layer, the side block may have at least substantially uniform thermal conductivity. Between a layer which has lower thermal conductivity and a layer which has higher thermal conductivity, a transition region can be formed in which the thermal conductivity, for example, at least substantially continuously, decreases from a higher to a lower value. Such a transition region, which can be made relatively small compared to the total length of the layers, can be considered as part of both layers.

An additional subject of the invention is a method of manufacturing a side block according to the invention described above, which comprises the steps of:

a) preparing a mixture for a layer with lower thermal conductivity, a mixture for a layer with higher thermal conductivity, and, if necessary, one or many mixtures for at least one additional layer,

b) forming a raw material preform with a layered configuration from mixtures according to steps a), and

c) firing the raw material according to steps b) at a temperature of from 800 to 1400 ° C, preferably from 1000 to 1300 ° C.

By manufacturing the side block by firing a raw material billet with various raw material mixtures forming the layers for the layers, an integral side block is obtained with high stability and material closure and monolithic adhesion between the individual layers of the side block.

The formation of the raw material procurement according to step b) may provide that the raw mixes are introduced into one form. In this case, numerous layers of raw mixes can be formed in the mold according to the layered structure of the finished side block. The manufacture of the layered structure can be simple in such a way that the layers of the raw material mixtures follow each other in the direction of the disclosure of the form. In a particularly simple approach, the layers can be introduced into the form so that they are oriented essentially horizontally, mainly horizontally, and follow each other, preferably in the vertical direction.

In addition, the formation of the raw material preform according to step b) may include vibration molding and / or pressing into a block of raw materials. This can be done with or without evacuation. As a result of this, the cavities inside the material can be completely or partially eliminated, so that a universally uniform desired bulk density is achieved. In addition, a particularly high uniformity with respect to bulk density can be achieved when the formation of the raw material preform involves applying pressure sludge, respectively, compressing the raw material to compact the material.

Particularly suitable materials for raw mixes are all raw materials that can be fired to form the preferred materials with respect to the finished side block. For example, at least one raw material mixture may contain a material that is selected from the group consisting of a carbon-containing material, for example, such as anthracite, graphite or graphitized material, for example, such as synthetic graphite and pitch, or any mixture of these materials. In addition, the mixture may contain, in particular, a carbon-containing binder material, for example, such as a binder pitch. By targeted selection of the composition of the material of the individual layers of the raw material billet, the thermal conductivity of the various layers of the obtained side block can be purposefully adjusted. When the raw material mixture comprises a carbon-containing material, carbonization of the material of the raw material mixture mainly occurs during the firing of the raw material preform. In addition, as an additional step d), graphitization of the material can be performed. For this, the carbonized or raw molding product is heated at temperatures above 2000 ° C, and preferably more than 2200 ° C.

In order to further improve the thermal and mechanical properties of the side block after step c) of firing and / or after the graphitization step d) provided for in the circumstances, an additional step e) may be provided, which includes impregnating with the pitch the fired and, if necessary, graphitized raw material.

Preferably, in the manner described above, a base element with multiple layers is first manufactured, from which, in the step following the above-described steps of the method, the numerous side blocks with the desired dimensions are separated, in particular during the cutting process. This is also true for the manufacture of a composite side block.

An additional subject of the invention is a side block, which is obtained by performing the method described here. The side block, when used in the electrolyzer, optimizes the thermal conditions in the electrolyzer during electrolysis and, in addition, has high mechanical stability and very strong adhesion between the various layers of the side block. Depending on the width of the side block, it is possible to dispense with adhesive material between the side blocks. If a composite side block is used, then it is also possible to partially or completely abandon the stuffed mass between the side block and the cathode block.

The use of the side block according to the invention as described herein for lining the side walls in an electrolytic cell is an additional independent subject of the present invention. It is also possible within the scope of the invention that for lining the side wall, at least one side block, which is used to match the thermal conditions, is combined with at least one composite side block. The number of side blocks used here and, accordingly, composite side blocks can be adjusted according to need.

An additional object of the invention is an electrolytic cell, in particular for producing aluminum, which includes a cathode, anode and a wall, wherein at least one wall section is formed by the side block according to the invention in accordance with this description. This side block may also be the composite side block described above. The advantages and preferred embodiments described in relation to the side unit, its manufacture and use, and in particular its use in the electrolyzer, when used appropriately represent the advantages and preferred embodiments of the electrolyzer according to the invention. At least one side block preferably forms one side wall of the bath, which contains a layer of liquid aluminum and a layer of melt. In this case, the lateral block may be facing the side wall of the outer steel bath, which covers the inner bath formed by the side block.

As mentioned above, on the one hand, a certain part of the amount of thermal energy released in the electrolytic cell must be diverted, but, on the other hand, excessive heat loss must be prevented in order to ensure a predetermined temperature distribution in the electrolytic cell. Along with the side blocks described so far corresponding to the invention and, accordingly, the composite side blocks, and the refractory lining, which is located between the cathode and the steel bath, the cathode also affects the regulation of thermal energy in the cell. When too much heat is removed from the electrolyzer, the cryolite solidifies in the melt in an excessive amount and can reach the surface of the cathode. As a result of this, the passage of current through the cathode is disrupted, which leads to an uneven distribution of current along the cathode surface, and at the same time to increased electrical resistance and thereby reduced energy efficiency in the cell. The regulation of heat transfer from the cathode to the refractory lining located below it can be effectively performed, while the regulation of heat transfer from the cathode to the side walls is much more difficult. Typically, the cathode blocks that form the cathode consist of a uniform material, that is, these homogeneous cathode blocks have the same thermal conductivity, so that these cathode blocks are little or not able to maintain optimal regulation of heat transfer in the cell. In particular, this is true for adjusting the thermoregulation of the cathode for heat transfer to the side walls.

Document WO 02/064860 describes cathode blocks, which, when viewed in the direction of the long side of the cathode, have different layers that have different electrical resistance, that is, materials different in the direction of the long side of the cathode (having different values of specific electrical resistance). With such cathode blocks, the current flow through the electrolyzer should approach the ideal current characteristic also without the costly placement of busbars.

The cathode blocks, which in the direction of the long side of the cathode have different layers formed as a result of using different materials, also have different thermal conductivities inside the cathode block. Such cathode blocks can also be preferably used in order to reduce thermal losses due to the cathode, in particular in the direction of the long side of the cathode, that is, in the direction of the side walls. As a result, even on individual cathode blocks, and thereby for the entire cathode as a whole, the direction of the heat flux is regulated. Moreover, this cathode block in the direction of the long side of the cathode mainly includes at least three layers, preferably from three layers to seven layers, particularly preferably from three layers to five layers, and most preferably three layers. There are layers with higher thermal conductivity and layers with lower thermal conductivity, it being understood that for adjacent layers, one layer has higher thermal conductivity compared to the other layer. The difference in thermal conductivity between the layer with higher thermal conductivity and the layer with lower thermal conductivity is at least 10%, relative to the material with lower thermal conductivity, in the temperature range from 920 to 1000 ° C, measured in the direction of the long axis of the cathode block. The cathode block may include at least two layers that have the same thermal conductivity, that is, which consist of the same material. In this case, we can talk about both outer, that is, the boundary layers of the cathode block. With such a cathode block, by selecting the number of layers, the sequence of layers and selecting the thermal conductivity for each individual layer, it is possible to purposefully control the heat flux in this cathode block. For a situation where a reduced heat dissipation from the electrolyzer is preferred, a cathode block can be applied, which, for example, has three layers. Both outer layers, that is, both layers that are in direct or through thermal packing thermal contact with the side wall of the cell, are layers with lower thermal conductivity, while the third, middle layer is present as a layer with higher thermal conductivity. If, on the contrary, a more intense heat removal from the electrolyzer is desired, then in the cathode block having three layers there are both outer layers that have higher thermal conductivity compared to the third, middle layer.

The length of the cathode block is usually 2500-3500 mm. The length of one of the above individual layers — when viewed in the direction of the long side of the cathode — depends on the desired heat flux in the cathode block, and can be purposefully selected depending on this heat flux. In addition, this length of an individual layer depends on the number of layers in the cathode block. If, for example, there are seven layers, then a separate layer has a length of 300-600 mm. If only three layers are used, then the outer, that is, the edge layers have a length of 400 to 600 mm, and the inner layer has a length of 1700-2300 mm. Regardless of the number of layers, the outer, respectively, edge layers of the cathode block have a length of 400 to 600 mm, preferably 500 mm.

The individual layers of these cathode blocks are made up of carbon, that is, of a material that contains carbon. With regard to thermal conductivity, it turned out to be preferable when the cathode block consists of a material that contains at least 50% by weight, preferably at least 80% by weight, particularly preferably at least 90% by weight, most preferably at least 95% by weight, and most preferably at least 99% by weight of carbon. The specified carbon can be selected from the group consisting of amorphous carbon, graphite carbon, graphitized carbon, and any mixture of two or more of the above grades of carbon.

For the manufacture of these cathode blocks, the same method can be applied as for the side block described above according to the invention. Therefore, for the manufacture of cathode blocks in the respective above embodiments, reference is made to the manufacturing method of the side block according to the invention.

For the manufacture of cathode blocks, it is also true that by firing a raw material billet with various raw material mixtures forming the starting materials for the layers, a solid cathode block with high stability and inseparable material adhesion between the individual layers of the obtained monolithic cathode block is obtained.

In particular, all the raw materials that can be fired to form the preferred materials mentioned above with respect to the finished cathode block are also suitable as materials for raw mixtures in the manufacture of cathode blocks. For example, at least one raw material mixture may contain a material that is selected from the group consisting of a carbon-containing material, for example, such as anthracite, graphite or graphitized material, for example, such as synthetic graphite and pitch, or any mixture of these materials. In addition, the mixture may contain, in particular, a carbon-containing binder material, for example, such as a binder pitch. By targeted selection of the composition of the material of the individual layers of the raw material billet, the thermal conductivity of the various layers of the obtained side block can be purposefully adjusted.

The shape of the layers in the cathode block may be different. Along with layers that occupy the entire height H of the cathode block, there may also be layers that occupy only a portion of this height H, as, for example, shown in Figures 10 and 11. This layer formation may be performed depending on the desired heat flux in the cathode block that is, with the help of this molding, along with the choice of materials of the layers, and thereby the values of thermal conductivity, this heat flux can be purposefully controlled.

By combining the side block of the invention according to the invention with the above cathode blocks in the cell, that is, when both the side blocks of the invention and the cathode blocks described above are used in the cell, the thermal conditions in the cell can be controlled even more specifically - rather than just the side blocks corresponding to the invention. Due to this, the technological conditions in the electrolyzer are optimized, as a result of which the achievable stability and efficiency of the electrolysis process are improved, and the life of the electrolyzer is increased. It should be understood that each indicated embodiment of the side block can be combined with each indicated embodiment of the cathode blocks.

The invention will now be described by way of example of preferred embodiments with reference to the accompanying Figures, in which:

FIG. 1 is a perspective sectional view of an electrolyzer according to one embodiment of the invention;

FIG. 2 is a perspective view of a side block according to one embodiment of the invention;

FIG. 3 is a perspective view of a side block according to a further embodiment of the invention;

FIG. 4 is a perspective view of a base element from which multiple side blocks can be separated according to one embodiment of the invention;

FIG. 5 is a perspective view of an additional base element from which multiple side blocks can be separated according to one embodiment of the invention.

FIG. 6 is a sectional view of various embodiments and embodiments of a composite side block;

FIG. 7 is a perspective view of a base element from which multiple composite side blocks can be separated according to one embodiment of the invention, as well as one separated composite side block;

FIG. 8 is a perspective view of an additional base element from which multiple composite side blocks can be separated according to one embodiment of the invention;

FIG. 9 is a cross-sectional view of an additional base element from which multiple composite side blocks may be separated according to one embodiment of the invention;

FIG. 10 is a perspective view of a cathode block, and

FIG. 11 is a cathode block having various forms of layers.

In FIG. 1 shows a perspective view in partial section of an electrolyzer for producing aluminum according to one embodiment of the invention. The electrolyzer includes a cathode, which is composed of numerous cathode blocks forming the cathode bottom 12. On the upper side of the cathode is a layer of liquid aluminum 14 and a layer of liquid melt 16 on it, and on top of the liquid melt layer 16, a layer or crust 18 of solidified melt.

Above the melt layer 16, an anode is placed, which consists of numerous anode blocks 20 immersed in the melt layer 16. During operation of the electrolyzer, an electric current is supplied through the anode blocks 30 and passed through the melt layer 16 and the liquid aluminum layer 14 to the cathode blocks 12. Current is discharged through the cathode blocks 12 and through the conductive busbars 22 inserted into the corresponding grooves on the underside of the cathode blocks 12. In the melt layer 16, electrolysis occurs, which leads to the precipitation of elemental aluminum from the melt, which is collected on the upper side of the cathode bottom with the formation of liquid aluminum layer 16.

The electrolyzer has a steel bath 24 serving as the outer skin, in the bottom region of which numerous plates 26 of refractory material are placed one above the other, which thermally isolate the overlying cathode blocks 12 from the bottom of the steel bath 24.

The side walls of the steel bath 24 are lined with numerous rectangular side blocks 28. The side blocks 28 form the side wall of the inner bath, in which the liquid aluminum layer 14, the liquid melt layer 16 and the solidified melt layer 18 are enclosed, and its bottom is formed by the cathode bottom formed by the cathode blocks 12 The seams formed between the cathode block 12 and the side block 18 are sealed with a packing mass 30. Such a packing mass can also be provided to seal the seams between the cathode blocks 12 and to seal the seams between Shackle 28 blocks.

As shown in FIG. 1, the side blocks 28 are substantially rectangular and mounted vertically in the steel bath 24 so that the height direction of the side blocks 28 is parallel to the vertical. At the same time, the surfaces of the side blocks 28 bounding the inside of the bath are formed by their supporting surfaces 32 parallel to the height direction and the width direction of the side blocks 28, and the side blocks 28 are interconnected by their side surfaces 34 parallel to the height direction and the width direction. In this case, the side blocks 28, as shown in FIG. 1, in different sections of their heights are in contact with various components and, accordingly, the electrolytic medium, namely, with a packed mass of 30, and under known circumstances, with a layer 14 of liquid aluminum, a layer 16 of a liquid melt and a layer 18 of solidified melt.

During the operation of the cell in the cell, significant amounts of thermal energy are released. Typically, approximately a third of this thermal energy is absorbed by the side blocks 28 and is diverted to the outside. In this case, the main direction of the heat flux corresponds to the direction along the thickness of the side blocks 28. Approximately 15% of the thermal energy is received by the cathode bottom or, accordingly, the bars.

The side blocks 28 shown in FIG. 1 cell in each case have at least one layer with lower thermal conductivity and one layer with higher thermal conductivity, the difference between the lower and higher thermal conductivity being at least 5 W / m ∙ K. Due to this, the absorption and removal of heat through the side wall formed by the side blocks 28 is regulated in such a way that optimal thermal conditions are established everywhere in the cell during its operation, as a result of which the stability, reliability and productivity of the electrolysis process are improved, and the life of the cell increases.

In FIG. 2 and 3 show in each case a side block 28 according to one embodiment of the invention, which, for example, can be used in the embodiment shown in FIG. 1 electrolyzer. The side blocks 28 in each case have a relatively small thickness d, as well as a width b and a height h, which is larger than the width b.

Shown in FIG. 2, the side block 28 has two rectangular layers 36, 38, the layer 36 having a lower layer and the 38 having higher thermal conductivity. The layers 36, 38 are interconnected by their parallel direction in height and in the direction of the width of the supporting surfaces 40, 42, which in each case form contact surfaces, are connected to each other, follow each other in the thickness direction of the side block 28 and in each case are approximately half the thickness d of the side block 28. As a result, the heat fluxes in the direction of the thickness and the position of the isotherms inside the side blocks 28 can be coordinated so that the thermal conditions in ktrolizere during operation.

Shown in FIG. 3, the side block 28 also has two rectangular layers 36, 38, the layer 36 having a lower layer and the 38 having higher thermal conductivity. The layers 36, 38 are interconnected by their parallel direction in width and direction in thickness of the side surfaces 44, 46, which in each case form contact surfaces, are connected to each other, follow each other in the direction of height of the side block 28 and in each case are approximately half the height h of the side block 28. Moreover, relative to the location in the cell, the upper half of the height is preferably formed by a layer 36 with lower thermal conductivity. As a result of this, the thermal conductivity through the lateral block 28 can be coordinated with various components located in the corresponding height region in contact with the lateral block 28 or, respectively, the electrolytic medium and the thermal conditions there, thereby optimizing the thermal conditions prevailing during the electrolysis in the electrolytic cell. Thus, in the case described above, the heat is removed through good thermal contact between the lower half of the height, including the layer 38 with higher thermal conductivity and the cathode that occurs through the packing mass 30.

For other thermal parameters in the electrolyzer, it may be appropriate to re-arrange the layers with respect to their thermal conductivity.

In FIG. 4 shows a base element 48, which was manufactured as a semi-finished product of the inventive method for manufacturing a side block. The base element 48 is made with a rectangular shape and consists of a rectangular layer 36 with lower thermal conductivity and a rectangular layer 38 with higher thermal conductivity, which are connected to each other by their supporting surfaces. During the cutting process, numerous plates forming side blocks that have two layers 36, 38 with different thermal conductivity can be separated from the base element 48. For this, the base element 48, as indicated by dashed lines in FIG. 4, is cut along several cut planes that extend perpendicular to the boundary surface located between both layers 36, 38.

In FIG. 5 shows an additional base element 48, which essentially corresponds to that shown in FIG. 4 to the base element. True, the base element 48 includes two layers 36 with lower thermal conductivity and a layer 38 with higher thermal conductivity disposed between them, which are connected between their abutment surfaces. As shown in FIG. 5, the base element 48 for manufacturing the side blocks is cut not only in several planes perpendicular to the boundary surfaces between the layers 36, 38, but also additionally along the median plane of the layer 38, parallel to these boundary surfaces, so that the resulting side blocks in each case have two layer 36, 38 with different thermal conductivity. This manufacturing method has a higher profitability.

In FIG. 6 shows, in cross-section, various embodiments of the composite side block 29 according to the invention, which, for example, can be used in FIG. 1 electrolyzer.

All shown in FIG. 6, the composite side blocks have a rectangular layer 36 and a polygonal layer 38, the layer 36 having lower thermal conductivity and the layer 38 having higher thermal conductivity. The layers 36, 38 are interconnected by their parallel direction in height and in the direction of the width of the supporting surfaces 40, 42, which in each case form contact surfaces, are connected to each other, follow each other in the direction of the thickness of the composite side block 29, and are extended in each case, from 30% to 70%, preferably 50%, of the thickness d of the composite side block 29. The supporting surfaces 40, 42 can have partial or full contact with each other. Using such various designs of composite side blocks, on the one hand, the heat fluxes in the direction of thickness and the position of the isotherms inside the composite side block 29 can be adjusted so that the thermal conditions in the cell during operation are optimized, on the other hand, it is also possible with such a composite side block 29 partially or completely abandon the stuffed mass between this composite side block 29 and the cathode block.

In FIG. 6 (a), the layer 38 has a trapezoidal shape, in FIG. 6 (b), the layer 38 has a triangular shape, and in FIG. 6 (c), the layer 38 has the shape of an irregular pentagon with a rounded corner. In these embodiments, the support surfaces 40, 42 are in full contact. In contrast, in FIG. 6 (d) and 6 (e), the supporting surfaces 40, 42 have only partial contact, with FIG. 6 (d), the layer 38 is a rectangle having one rounded corner, and in FIG. 6 (e), the layer 38 has the shape of an irregular pentagon with one rounded corner.

For other thermal parameters in the electrolyzer, it may be appropriate to re-arrange the layers with respect to their thermal conductivity.

In FIG. 7 shows a base element 48, which was manufactured as a semi-finished product of the method for manufacturing the composite side block 29. This base element 48 is rectangular in shape and consists of a rectangular shape layer 36 with lower thermal conductivity and a rectangular shape layer 38 with higher thermal conductivity which are interconnected by their supporting surfaces. These layers are horizontal layers. The layer 36 is machined so that this layer takes the desired polygonal shape along the entire length of the base element 48. Then, in the next step, plates with the desired width are cut from this base element 48. Thus, it is possible to use the grain orientation that occurs during the manufacture of the base element and the properties that are different in the horizontal and vertical directions, for example, such as thermal conductivity, and adjust it in the side block, for which, when processing the base element, the supporting surfaces are selected accordingly.

In FIG. 8 shows a base element 48, which was manufactured as a semi-finished product of the method for manufacturing the composite side block 29. This base element 48 is rectangular in shape and consists of two rectangular layers 36 with lower thermal conductivity and one rectangular layer 38 with a higher thermal conductivity, which are interconnected by their supporting surfaces. These layers are vertical layers, with layers 36 representing both outer layers. Here, numerous plates can be cut off from the base member 48, which have two outer layers 36 and one inner layer 38 with different thermal conductivities. In a subsequent step, the layer 38 is cut so that two blocks are obtained, of which in an additional step, the layer 38 is cut so as to obtain the desired polygonal shape. Alternatively, first, the longitudinal direction is divided into two halves, a polygon is produced, and then, according to the circumstances, the plates of the desired length are cut off.

Here, by orienting the layers in the manufacture of the corresponding base element, either in horizontal or vertical form, it is possible to influence various properties, for example, such as thermal conductivity. The reason for this is the different orientation of the grains during the molding process and the resulting dependence of the physical properties on the direction.

In FIG. 9 also shows a base element 48, which was manufactured as a semi-finished product of the method of the invention for manufacturing the composite side block 29. This base element 48 is rectangular and consists of the base element 48 in FIG. 8, from two rectangular-shaped layers 36 with lower thermal conductivity and one rectangular-shaped layer 38 with higher thermal conductivity, which are interconnected by their abutment surfaces. These layers are vertical layers, with layers 36 representing both outer layers. Here, also, numerous plates can be cut off from the base element 48, which have two outer layers 36 and one inner layer 38 with different thermal conductivity. Then, in a subsequent step, by appropriate cutting, two composite side blocks 29 having the same shape can be cut out of such a separate cut fragment. An advantage of this method is the processing sequence, which ensures that almost no material loss occurs.

In FIG. 10 shows a cathode block 12 having three layers, both outer layers consisting of the same material A, and the middle layer consisting of material B. The individual layers here extend over the entire height of the cathode block.

In FIG. 11 a) and b) shows the various forms of layers in the cathode block 12, and in these cathode blocks in each case two materials are used, that is, material A and material B. In this case, both layers of material A in each case occupy only part of the height H and the length L of the cathode block.

Examples of execution:

Execution example 1:

The side block is made of a mixture A containing 58 weight percent (% by weight) of electrically calcined anthracite, 9% by weight of synthetic graphite, 17% by weight of binder pitch, 8% by weight of silicon, and 8% by weight of alumina, and mixture B containing 77% by weight of synthetic graphite and 23% by weight of binder pitch. For this, the vibroform for the manufacture of the raw material preform is filled with both mixtures so that in the raw material preform, two layers following from each other in the direction of the height of the manufactured side block from mixture A and mixture B follow each other. In this case, the height of the layers in the vibration form is selected taking into account the target bulk density, which is obtained by following the filling of the raw material billet seal, so that after compaction both layers occupy half the height of the raw material billet in each case. After this, the raw material is fired in a ring furnace at a temperature of 1200 ° C for the manufacture of the base element.

After that, plates with a thickness of 10 cm are cut off from the calcined and pre-treated base element, which are further processed in the next step and, for example, can be impregnated with pitch. An exemplary finished side block has a width of 475 mm, a height of 640 mm and a thickness of 100 mm, and with respect to the mounting situation of the side block in the cell, in which it is placed vertically along the direction of its height, the upper 320 mm of the height of the side block is formed by material A obtained from the mixture A and the lower 320 mm are made up of material B obtained from mixture B.

In this case, material A has a thermal conductivity measured at room temperature in one direction of the side block of about 8 W / m ∙ K, while material B in the same direction of the side block, in the grain orientation of materials A and B, has a thermal conductivity of about 45 W / m ∙ TO.

The thermal conductivity at room temperature can be measured according to ISO 12987, namely, in a certain direction, in the case of pressure loading of the starting material during manufacture of the side block, for example, perpendicularly or parallel to the direction of loading by pressure, i.e., against or in accordance with the orientation of the grains.

The thermal conductivity measured at a temperature between 920 ° C to 1000 ° C is about 9 W / m ∙ K for material A and about 37 W / m ∙ K for material B. The thermal conductivity measurement here can be carried out according to the orientation of the grains according to DIN 51936 using a pulsed laser.

Execution example 2:

The composite side block is made from mixture A containing 58% by weight of electrically calcined anthracite, 9% by weight of synthetic graphite, 17% by weight of binder pitch, 8% by weight of silicon, and 8% by weight of alumina, and mixture B, containing 65% by weight of synthetic graphite, 5% by weight of alumina, 10% by weight of silicon powder and 20% by weight of binder pitch. For this, the vibroform for the manufacture of the raw material preform is filled with both mixtures so that in the raw material preform two layers following from each other in the direction of the height of the manufactured composite block from mixture A and mixture B follow each other. In this case, the height of the layers in the vibration form is selected taking into account the target bulk density, which is obtained by following the filling of the raw material billet seal, so that after compaction both layers occupy half the height of the raw material billet in each case. After that, the raw material is fired in an annular furnace at a temperature of 1300 ° C for the manufacture of the base element.

After that, the layer containing material A is processed so that it takes the desired polygonal shape along the entire length of the raw material preform. Then, at a subsequent stage, plates with a thickness of 50 cm are cut from this base element. An exemplary finished composite side block has a width of 500 mm, a height of 700 mm and a thickness of 250 mm.

In this case, material A has a thermal conductivity measured at room temperature in one direction of the side block of about 8 W / m⋅K, while material B in the same direction of the side block, in the grain orientation of materials A and B, has a thermal conductivity of about 45 W / m⋅ TO. The thermal conductivity at room temperature can be measured according to ISO 12987, namely, in a certain direction, in the case of pressure loading of the starting material during manufacture of the side block, for example, perpendicularly or parallel to the direction of loading by pressure, i.e., against or in accordance with the orientation of the grains.

The thermal conductivity measured at a temperature between 920 ° C to 1000 ° C is about 9 W / m⋅K for material A and about 37 W / m⋅K for material B.

Execution Example 3:

A cathode block is made as shown in FIG. 10, for which a vibroform, the height of which is considered as the height of the finished raw material molding product, is first filled with mixture A, then with mixture B, and then again with mixture A.

In this mixture A has the following composition:

- 57% by weight of anthracite

- 24% by weight of graphite, and

- 19% by weight of binder pitch.

In addition, the mixture has the following composition:

- 80% by weight of graphite, and

- 20% by weight of binder pitch.

The height of the layers in the vibration form is selected taking into account the target bulk density, which is obtained by following the filling of the raw material seal, so that after compaction both layers occupy half the height of the raw material in each case. After this, the raw material is fired in a ring furnace at a temperature of 1200 ° C for the manufacture of the base element. In this case, material A has a thermal conductivity measured at room temperature in one direction of the cathode block of about 15 W / mK, while material B in the same direction of the cathode block, in the grain orientation of materials A and B, has a thermal conductivity of about 40 W / m⋅ TO. The thermal conductivity at room temperature can be measured according to ISO 12987, namely, in a certain direction, in the case of pressure loading of the starting material during the manufacture of the cathode block, for example, perpendicularly or parallel to the direction of pressure loading, i.e., against or in accordance with the orientation of the grains.

The cathode block thus manufactured can have a width of 420 mm, a height of 400 mm and a length of 3100 mm, and can be used to make a cathode bottom having, for example, 24 cathode blocks. Such cathode blocks together with the side blocks of the invention can be used in an electrolytic cell.

Legend List

12 Cathode block

14 Layer of liquid aluminum

16 layer of liquid melt

18 hardened melt layer

20 Anode block

22 Busbar

24 Steel bath

26 fireproof plate

28 Side block

29 Composite side block

30 Stuffed mass

32 abutment surface

34 side surface

36 Layer with lower thermal conductivity

38 Layer with higher thermal conductivity

40, 42 bearing surface

44, 46 Side surface

48 Base element

b Width

h Height

d Thickness

H Cathode block height

L The length of the cathode block

Claims (45)

1. The lateral block for the wall of the cell, in particular for the production of aluminum, and the side block (28) is a layered element, comprising a layer (36) with lower thermal conductivity and a layer (38) with higher thermal conductivity, the difference between the lower and higher thermal conductivity being at least 5 W / m⋅K - as measured at a temperature between 920 ° C and 1000 ° FROM, characterized in that at least one of the layers (36, 38) is doped with silicon in the form of a powder, oxide ceramic material, or non-oxide material. 2. The side block according to claim 1, characterized in that the layered element is made with an alternating sequence of a layer (36) with lower thermal conductivity and a layer (38) with higher thermal conductivity. 3. The side block according to claim 2, characterized in that the outer layer of the laminate is a layer (36) with lower thermal conductivity, and the other outer layer is a layer (38) with higher thermal conductivity. 4. The side block according to one of paragraphs. 1-3, characterized in that the layers (36, 38) have a block shape, in particular a rectangular shape, and are interconnected by contact surfaces, in particular their supporting surfaces (40, 42) or their side surfaces (44, 46). 5. The side block according to one of paragraphs. 1-3, characterized in that one of the layers (36, 38) has a block shape, in particular a rectangular shape, and the other layer (36, 38) has a polygonal shape, both layers being interconnected by contact surfaces, in particular, their supporting surfaces (40, 42). 6. The side block according to claim 5, characterized in that the layer (36, 38) having a polygonal shape is made in the form of a polygon with the number of angles from three to six. 7. The side block according to claim 4, characterized in that when the layers (36, 38) are joined together by their supporting surfaces (40, 42), the thickness of the layered element is from 50 to 700 mm. 8. The side block according to claim 6, characterized in that when the layers (36, 38) are joined together by their supporting surfaces (40, 42), the thickness of the layered element is from 50 to 700 mm. 9. The side block according to claim 4, characterized in that when the layers (36, 38) are connected to each other by their lateral surfaces (44, 46), the height of the layers is from 150 to 450 mm. 10. The side block according to one of paragraphs. 1-3, characterized in that at least one layer (36, 38) consists of, or contains, a material selected from the group consisting of carbon, graphite carbon, graphitized carbon, or silicon carbide, or any mixtures of them. 11. The side block according to one of paragraphs. 1-3, characterized in that the difference between the lower and higher thermal conductivity of the layer is from 5 to 80 W / m⋅K, preferably from 5 to 70 W / m⋅K, particularly preferably from 8 to 60 W / m⋅K, and most preferably between 10 W / m⋅K and 50 W / m⋅K. 12. A method of manufacturing a side block (28) according to one of claims. 1-11, comprising the following steps: a) preparing a mixture for a layer (36) with lower thermal conductivity, a mixture for a layer (38) with higher thermal conductivity, and, if necessary, one or more mixtures for at least one additional layer, b) forming a raw material preform with a layered configuration from mixtures according to step a), c) firing the raw material preform according to step b) at a temperature of from 1100 to 1400 ° C., preferably 1200 ° C. 13. The method according to p. 12, characterized in that the formation according to step b) comprises a vibration molding. 14. The use of the side block (28) according to one of paragraphs. 1-11 for lining the side walls of the cell. 15. The electrolyzer, in particular, to obtain aluminum, which contains the cathode (12), the anode (20) and the side wall, while at least one wall section is formed by the side block (28) of at least one of paragraphs. 1-11. 16. The electrolyzer according to claim 15, in which the cathode is formed of cathode blocks, each of which is a layered element comprising layers with lower thermal conductivity and layers with higher thermal conductivity.

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