Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
  • C25C3/00—Electrolytic production, recovery or refining of metals by electrolysis of melts
  • C25C3/06—Electrolytic production, recovery or refining of metals by electrolysis of melts of aluminium
  • C25C3/08—Cell construction, e.g. bottoms, walls, cathodes
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
  • C04B35/515—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics
  • C04B35/52—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on carbon, e.g. graphite
  • C04B35/522—Graphite
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
  • C04B35/515—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics
  • C04B35/52—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on carbon, e.g. graphite
  • C04B35/528—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on carbon, e.g. graphite obtained from carbonaceous particles with or without other non-organic components
  • C04B35/532—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on carbon, e.g. graphite obtained from carbonaceous particles with or without other non-organic components containing a carbonisable binder
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
  • C25C3/00—Electrolytic production, recovery or refining of metals by electrolysis of melts
  • C25C3/06—Electrolytic production, recovery or refining of metals by electrolysis of melts of aluminium
  • C25C3/08—Cell construction, e.g. bottoms, walls, cathodes
  • C25C3/085—Cell construction, e.g. bottoms, walls, cathodes characterised by its non electrically conducting heat insulating parts
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
  • C25C3/00—Electrolytic production, recovery or refining of metals by electrolysis of melts
  • C25C3/06—Electrolytic production, recovery or refining of metals by electrolysis of melts of aluminium
  • C25C3/16—Electric current supply devices, e.g. bus bars
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
  • C25C7/00—Constructional parts, or assemblies thereof, of cells; Servicing or operating of cells
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
  • C04B2235/02—Composition of constituents of the starting material or of secondary phases of the final product
  • C04B2235/30—Constituents and secondary phases not being of a fibrous nature
  • C04B2235/32—Metal oxides, mixed metal oxides, or oxide-forming salts thereof, e.g. carbonates, nitrates, (oxy)hydroxides, chlorides
  • C04B2235/3217—Aluminum oxide or oxide forming salts thereof, e.g. bauxite, alpha-alumina
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
  • C04B2235/02—Composition of constituents of the starting material or of secondary phases of the final product
  • C04B2235/30—Constituents and secondary phases not being of a fibrous nature
  • C04B2235/42—Non metallic elements added as constituents or additives, e.g. sulfur, phosphor, selenium or tellurium
  • C04B2235/422—Carbon
  • C04B2235/425—Graphite
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
  • C04B2235/02—Composition of constituents of the starting material or of secondary phases of the final product
  • C04B2235/30—Constituents and secondary phases not being of a fibrous nature
  • C04B2235/42—Non metallic elements added as constituents or additives, e.g. sulfur, phosphor, selenium or tellurium
  • C04B2235/428—Silicon
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
  • C04B2235/02—Composition of constituents of the starting material or of secondary phases of the final product
  • C04B2235/30—Constituents and secondary phases not being of a fibrous nature
  • C04B2235/48—Organic compounds becoming part of a ceramic after heat treatment, e.g. carbonising phenol resins
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P10/00—Technologies related to metal processing
  • Y02P10/25—Process efficiency

Definitions

• the present invention relates to a side brick for a wall in an electrolysis cell, in particular for the production of aluminum, a method for producing such a side brick and a use of such a side brick and an electrolytic cell with such a side brick.
• Electrolysis cells are used for the electrolytic production of aluminum, which is usually carried out industrially by the Hall-Heroult process.
• a melt composed of alumina and cryolite, preferably about 15 to 20% alumina and about 85 to 80% cryolite, is electrolyzed.
• the cryolite, Na 3 [AIF 6 ] serves to lower the melting point from 2,045 ° C. for pure alumina to about 960 ° C. for a mixture containing cryolite, alumina and additives such as aluminum fluoride and calcium fluoride, so that the Molten electrolysis can be carried out at a reduced temperature of about 960 ° C.
• grooves are provided on the lower sides of the cathode blocks, in each of which at least one bus bar is arranged, through which the current supplied via the anodes is removed from the electrolysis cell.
• a lining of a refractory material which thermally insulates the bottom of the steel trough from the cathode bottom.
• anode formed of individual anode blocks wherein between the anode and the surface of the aluminum, the melt containing alumina and cryolite is located.
• the aluminum formed is deposited below the melt layer due to its greater density compared to that of the melt, ie as an intermediate layer between the upper side of the cathode blocks and the melt layer.
• the aluminum oxide dissolved in the cryolite melt is split by the flow of electrical current into aluminum and oxygen.
• the layer of molten aluminum is the actual cathode because aluminum ions are reduced to elemental aluminum on its surface.
• cathode will not be used hereinafter to refer to the cathode from an electrochemical point of view, ie the layer of molten aluminum understood, but the cathode bottom forming, composed of one or more cathode blocks component.
• Modern electrolysis cells are operated at high electrolysis currents of, for example, up to 600 kA to ensure high productivity of the electrolysis cell. These high currents lead to increased heat generation during the electrolysis process.
• the thermal conditions are achieved, optimally in terms of stability and efficiency of the electrolysis and in terms of the life of the electrolytic cell are, for example, the energy efficiency of the electrolysis is reduced by excessive thermal energy losses in areas of high heat generation of the electrolysis cell.
• the unfavorable thermal conditions in the electrolysis cell affect the reliability and economy of the electrolysis operation and the service life of the electrolysis cell.
• the removal of surplus heat produced in the electrolysis cell ie heat not required for the maintenance of the melting process
• the refractory lining arranged between the cathode bottom and the steel tub which usually consists of refractory bricks or plates, which are inserted in the steel tub and stacked on each other in the area of the bottom of the steel tub.
• the heat release over the relatively thin formed lateral wall of the formed by the cathode bottom and the side stones inner tub plays an essential role.
• the heat flows in this lateral wall are particularly relevant for the thermal conditions in the electrolytic cell, since the lateral wall is usually It may be in contact with various constituents and media in the electrolysis cell, ie in particular with the layer of liquid aluminum, the liquid melt layer arranged thereon, a layer of solidified melt or crust above the liquid melt layer and the gaseous atmosphere developing during the electrolysis cell with the various elements contained within.
• the gap between such a sidewall and a cathode block is usually filled with ramming mass of carbon and / or carbonaceous material such as anthracite or graphite, and a binder such as coal tar.
• This joint is often manually or semi-automatically tamped, whereby stamping errors can occur, which can lead to damage to the joint or, in the worst case, even to premature failure of the entire electrolysis cell. This damage often only occurs during commissioning or during operation of the electrolysis cell.
• the risk of the occurrence of the injury is the larger the wider or thicker the corresponding joint is.
• a wider or thicker joint also means a higher workload and a higher burden on the environment and the staff responsible for the electrolysis cell, as are harmful substances in conventional ramming masses.
• composite side brick Such a construction comprising a side brick and a sloping layer is hereinafter referred to as "composite side brick.”
• a composite side brick in which the silicon nitride bonded silicon carbide is bonded to the inclined layer is already used in modern electrolysis cells.
• the application of the adhesive material requires an additional work step
• the side stones of such a composite side stone consist of a uniform material and thus allow no differentiation with respect to the thermal conductivity in the side stone itself.
• the adhesive joint can have an influence on the heat flow in the electrolysis cell. Since the glue joint itself is very thin, irregularities in the cause the corresponding local heat flow.
• Carbonation of the adhesive matrix as during cell start-up may result in a reduction in its adhesion, which may weaken the bond between the oblique prebaked carbon or graphite layer and the vertical sidestring. If there is a failure of this connection, that is, that the above inclined layer and the vertical side stone are no longer connected to each other, the heat flow is degraded in an undefined manner and the necessary heat dissipation can not be sufficiently ensured. This can lead to overheating of the electrolysis cell, and in the worst case to their premature failure, ie the lifetime or life of the electrolysis cell is reduced.
• the use of adhesive material can also take place between the individual side stones, which form the side wall, in the form of a thin adhesive layer.
• DE3506200 discloses sidestones for the wall of an electrolytic cell which are a layered composite comprising an inner layer of a carbonaceous material and an outer layer of a hard ceramic material, these two layers being intimately interconnected. This allows a virtually unhindered heat flow from the inside to the outside. However, the resistance to wear, especially abrasive and / or corrosive wear is not sufficient when using such side stones. With the known electrolysis cells, therefore, no optimal process conditions can be achieved, in particular during operation with high electrolysis currents, whereby the achievable stability and economic efficiency of the electrolysis process are limited and the service life of the electrolysis cell is impaired.
• the present invention provides a side brick for the wall of an electrolytic cell, which ensures optimal process conditions and a correspondingly high efficiency and stability during the electrolysis operation and a long service life of the electrolysis cell when used in the electrolytic cell.
• the sostein should adjust the heat output through the side wall of the electrolysis cell such that prevail during the electrolysis optimal thermal conditions in the electrolytic cell and thermal losses during operation, caused by an unfavorable heat and temperature distribution, are largely avoided.
• the operating temperature of the cell during electrolysis is between 920 ° C and 1000 ° C, preferably between 950 ° C and 980 ° C.
• this side brick should have increased resistance to abrasive and / or corrosive wear, in particular to abrasive wear.
• This side brick should also be able to be produced, for example, without the use of adhesive (s).
• this side brick if it is designed as a composites side brick, also allow that the ramming mass between the side wall and the cathode block can be omitted partially or completely.
• a side brick for a wall in an electrolytic cell in particular for the production of aluminum, which is a laminated body and a layer having a lower thermal conductivity and a layer having a higher thermal conductivity, wherein the difference between lower and higher thermal conductivity at least 5 W / nrrK, measured at a temperature between 920 ° C to 1000 ° C, preferably between 950 ° C and 980 ° C, and wherein at least one of the layers with silicon (powder), an oxide ceramic material or a non- oxide material is doped.
• This laminate can be made without the use of adhesive (s), as explained later.
• side stone when used, this term may also encompass the above-mentioned composite side stones As described below, a composite side stone has a special shape.
• the terms “lower” and “higher” thermal conductivity mean that the respective layer which has this thermal conductivity has a “lower” or “higher” thermal conductivity compared to the respective other layer.
• the one layer consists of a material with a lower thermal conductivity and the other layer of a material with a higher thermal conductivity, wherein the two materials are different from each other.
• the laminated body comprises more than two layers, all the layers may have mutually different thermal conductivities, or at least two layers may have the same thermal conductivity and / or at least two groups of layers may be provided which each have the same thermal conductivity.
• the thermal conductivities of the layers differ in at least one direction of the side stone, which is preferably a direction that is in particular perpendicular to the side wall formed by the side stones.
• the difference between lower and higher thermal conductivity - measured at a temperature between 920 ° C to 1000 ° C, preferably between 950 ° C and 980 ° C - can be between 5 W / nrrK and 80 W / nrrK, preferably between 5 and 70 W / nrrK, more preferably between 8 W / nrrK and 60 W / nrrK, and most preferably between 10 W / nrrK and 50 W / nrrK.
• the heat conduction and Abgäbe over the side stones and the course of the isotherms in the side wall can be adjusted specifically. Since the side stones are in some areas directly in contact with the layer of liquid aluminum and the melt layer in which the electrolysis takes place, thereby the local, for the stability and efficiency of the electrolysis particularly important temperature conditions can be influenced directly and with high efficiency, so that for the operation of the electrolysis cell optimal thermal conditions can be guaranteed. For example, different thermal conductivities can be provided in the areas of the side stone that are used of the side stone in the electrolysis cell come into contact with the various media of the electrolysis cell.
• the side stones can be produced with little effort and with excellent mechanical stability and in particular very good cohesion between the various layers by the side bricks are burned in one piece from a single coherent green body in which different, the layers to be produced corresponding green mixtures are contained, the Base body can correspond to a single side brick or several side stones can be separated from the fired body.
• the desired polygonal shape can be worked out, for example, from such a fired green body over the entire length of the green body at first before then individual composite sidestones are cut off like a disk. The preferred polygonal forms will be discussed later.
• grouting, elevations, recesses and roughening can be added to a composite side stone.
• the side stone formed as a layered body refers to layers having different thermal conductivity, in particular each having a thermal conductivity that differs from the thermal conductivity of at least one other layer of the side stone by 5 W / nrrK or more - measured at a temperature between 920 ° C to 1000 ° C, preferably between 950 ° C and 980 ° C - differs.
• the particular two layers can follow one another in a predetermined direction, which may correspond to a relevant for the thermal conditions in the electrolysis cell heat flow direction and may be given for example by the thickness direction of the side stone.
• the total heat flow through the side stone in this direction can be regulated in such a way that a desired isothermal course in the side stone is ensured.
• the layers can also follow one another eg in the height direction of the side stone which does not comprise composite side stone, wherein in particular the height regions of the side stone covered by the different layers when used in an electrolysis cell with different media of the electric lysezelle - such as liquid aluminum, liquid or solidified
• the heat dissipation can be adapted to the heat generation taking place in the respective medium and the respective desired thermal conditions and additionally to the chemical requirements of the individual media.
• the side brick has exactly two layers with different thermal conductivity.
• Such a layer structure also has a high stability and can be produced with little effort and high reliability and reproducibility.
• the number of different layers of the side stone is not limited to exactly two.
• the side brick may also comprise a higher number of layers, for example at least three, four, five, six or more different layers.
• the side brick comprises two to four layers, more preferably two to three layers, most preferably two layers.
• this composite sidestone may also have a higher number of layers, for example at least three , four, five, six or more different layers.
• the composite side brick comprises two to four layers, more preferably two to three layers, most preferably two layers.
• the layers can follow one another in a predetermined direction, which in particular can correspond to a thickness or height direction of the side stone, so that a variation of the thermal conductivity of the side stone in the thickness direction or the height direction of the side stone is achieved.
• the side stone may also have successive layers in different directions, so that a variation of the thermal conductivity of the side stone in different directions is achieved.
• a plurality of layers of side stone following one another in a first direction may form a first layer sequence and a plurality of other layers following one another in the first direction form a second layer sequence, wherein the two layer sequences preferably in a second direction different from the first direction and in particular perpendicular to the first direction Following each other, which would be like a checkerboard pattern.
• the laminated body has an alternating sequence of a layer with a lower thermal conductivity and a layer with a higher thermal conductivity. This alternating sequence can take place in a predetermined direction, which corresponds in particular to the thickness or height direction.
• an alternating sequence of a layer with a lower thermal conductivity and a layer with a higher thermal conductivity in a first direction may also be that an alternating sequence of a layer with a lower thermal conductivity and a layer with a higher thermal conductivity in a first direction, and an alternating sequence in a direction different from the first direction, in particular to the first direction perpendicular second direction.
• a particularly favorable heat conduction behavior is achieved when an outer layer of the laminated body represents a layer with a lower thermal conductivity and the other outer layer is a layer with a higher thermal conductivity. This effectively and directly adjusts the heat absorption, distribution and discharge across the outer surfaces of the side stone formed by the outer layers of the side stone.
• the outer layer of the laminated body, which in contact with the liquid Aluminum and / or the liquid melt layer is a layer having a lower thermal conductivity
• the other outer layer of the laminated body, which is in contact with the cathode bottom and / or the tub is a layer having a higher thermal conductivity.
• the direction in which the thermal conductivities differ is the direction which is perpendicular to the sidewall formed by the sidestones.
• the layers and / or the side stone may have any suitable shape. It should be understood that the shape is critically dependent on the intended use of the side stone, i. the adaptation of the thermal conditions in an electrolytic cell in their operation alone or the combination of this adjustment with the partial or complete replacement of the ramming mass between the cathode block and side stone.
• a particularly advantageous embodiment with regard to the heat conduction behavior and the manufacturability of the side stone is that the layers of the side stone have a block shape, in particular a cuboid shape, and are connected to one another via contact surfaces, in particular their base surfaces or via their side surfaces.
• Such layers can be produced particularly easily and allow the targeted adaptation and variation of the thermal conductivity along the main directions of a preferably block-shaped, in particular cuboid, side stone.
• the side brick is block-shaped, in particular cuboid.
• the thickness direction of one or more layers of the side stone may in each case coincide with the thickness direction of the side stone, so that the orientation of the layers is matched to the orientation of the side stone and the corresponding main heat conduction directions in the side stone.
• Layers interconnected by their bases can accordingly follow one another in the thickness direction of the side stone and over their side surfaces interconnected layers can follow one another in the height direction of the side stone.
• a block is understood to mean a body having six rectangular surfaces, eight rectangular corners and twelve edges, each of which has at least four equal lengths and are parallel to one another. If the block represents a cuboid, four edges are the same length and parallel to each other. But it is also possible that eight of the twelve edges are the same length, in each case four edges are parallel to each other or all edges are the same length, with each four edges are parallel to each other here.
• an advantageous embodiment of the side brick is that at least one layer of the side brick has a block shape, in particular a cuboid shape, and at least one layer of the side brick has a polygonal shape.
• These layers are connected to each other via contact surfaces, in particular their base surfaces; the base of the layer having a block shape hereby has either a partial or complete contact with the base of the layer having a polygonal shape.
• the base of the layer having a block shape hereby has either a partial or complete contact with the base of the layer having a polygonal shape.
• At a complete contact of the bases both layers have the same height; lies a partial one
• the layer having a polygonal shape Before contact, the layer having a polygonal shape has a height which is 30% to less than 100%, preferably 40% to 80%, more preferably 50% to 75%, of the height of the layer having a block shape.
• Such layers can also be produced very easily and allow on the one hand a targeted adaptation and variation of the thermal conductivity along the main directions of the side stone, on the other hand is made possible with such a side stone, the partial or complete replacement of the ramming mass between side brick and cathode block.
• At least one layer of the composite sidestone has a polygonal shape.
• a polygon is understood to mean a polygon which may preferably contain three to six corners, particularly preferably three to five corners.
• a polygon with four corners for example, a rectangle, square or trapezoid understood. These polygons may be in regular or irregular form.
• a regular polygon is understood to be a polygon in which all sides have the same length and all internal angles are the same size.
• the composite side stones can be adapted to the desired electrolysis cell design; For example, more space for anodes can be created by the corresponding design of a composite side stone, ie the design of a layer in polygonal shape. Larger anode surfaces allow higher current and thus higher productivity.
• the shape of the composite side stone can be adapted to the shape of the original circumferential ramming gap joint.
• these polygons can be present with normal and / or rounded corners.
• a normal corner is the point at which two sides of the corresponding polygon meet.
• a rounded corner is understood as meaning a corner which has a concave curvature running inwards without an angular change in this curved area.
• Rounded corners have the advantage, compared to sharp corners, that a more even distribution of forces occurs at the rounded corners. This more uniform distribution of forces causes a reduction in the stresses occurring, and thus a reduced formation of cracks and / or defects at these points of the composite side stone.
• the polygon contains only normal corners, or one corner of the polygon is rounded, and the other corners represent normal corners.
• the side brick including the composite side stone, may in principle have a flat design with a relatively small thickness and in particular a significantly greater height and width, wherein the side stone may have a greater height than width.
• the thickness of the side stone may, for example, be between 50 and 700 mm when the layers are joined together over their bases, and depends on the type of use. If the side stone is used only to adapt the thermal conditions in an electrolysis cell, the thickness is preferably between 60 and 250 mm, more preferably between 80 and 150 mm, very particularly preferably between 90 and 110 mm. If, on the other hand, a composite sidestone is used in the electrolysis cell, the thickness is preferably between 150 and 600 mm, particularly preferably between 200 and 350 mm, very particularly preferably between 225 and 300 mm.
• the ratio of the thicknesses of, in particular, two layers may be for example at most 1: 3, preferably at most 1: 2 and particularly preferably 1: 1.
• the width of the side stone can be arbitrarily adapted to the length of the side wall of the electrolysis cell, that is, it can occupy either the entire length of this side wall or it is only a part of the length of the side wall.
• the length of a side wall may be, for example, either 3500 mm to 4000 mm or 10000 to 15000 mm. If the length of the side wall is 10,000 to 15,000 mm, the width of the side stone may be that length or the side wall may be covered with, for example, 2 to 3 side stones having a length of 5,000 mm.
• the width of the side stone occupies the entire length of the side wall of the electrolysis cell, on the one hand can be dispensed with such a side stone on the adhesive material may be used for the joints between the individual side bricks, on the other hand requires the simpler installation of this side stone time savings.
• the width of the side stone according to the invention is only a part of the length of the side wall, then at least two side stones according to the invention are used.
• the width of the side stone according to the invention occupies only a part of the length of the side wall, it may be between 300 and 600 mm, preferably between 400 and 600 mm, particularly preferably between 450 and 550 mm.
• the height of the side stone, including the composite side stone may for example be between 500 and 900 mm, preferably between 600 and 800 mm, particularly preferably between 600 and 750 mm.
• the length of the layer is here taken as a block having a block shape.
• one or more and in particular all layers of the side brick which represents no composite Sstein, each having a thickness of 25 to 125 mm, preferably 30 to 100 mm, more preferably 40 to 75 mm and most preferably 45 to 55 mm up.
• the side brick has two layers which are connected to one another via their base surfaces and follow one another in the thickness direction and in particular make up 30-70%, preferably 50%, of the thickness of the side stone.
• the layers can each extend over the entire height of the side stone.
• one or more and in particular all layers of the side stone, which does not comprise a composite side stone, when these layers are interconnected via their side surfaces and follow one another in the height direction have a height of 150 to 450 mm, preferably 200 to 400 mm, more preferably from 250 to 350 mm, and most preferably from 280 to 320 mm.
• this side brick has two layers which are connected to one another via their side surfaces and follow one another in the vertical direction and in each case extend in particular over 30% -70%, preferably 50%, of the height of the side stone.
• the layers can each extend over the entire thickness of the side stone.
• the ratio of the heights of, in particular, two layers can be, for example, at most 1: 3, preferably at most 1: 2 and particularly preferably 1: 1.
• this side brick has two layers which follow one another in the thickness direction of the side brick, in particular partially or completely interconnected over their base surface, each covering 30% -70%, preferably 50%, of the thickness of the side brick and thus cover the entire thickness of the side stone. It should be understood that the percentages of the individual layer thicknesses - also below - always together make up 100%.
• a layer may extend partially or completely over the entire height of the side stone.
• the layer having a polygonal shape either extends completely over the entire height of the layer having a parallelepiped shape or extends from 30% to less than 100%, preferably from 40% to 80%, particularly preferably 50% to 75%, above the height of the layer having a cuboid shape.
• the layers each extend over the entire height of the composite side stone; if, on the other hand, there is partial contact of the bases, then the layer having a polygonal shape extends from 30% to below 100%, preferably from 40 to 80%, particularly preferably from 50% to 75%, over the height of the layer having a cuboid shape ,
• one or more rectangular layers, and in particular all parallelepiped layers of the composite side stone have a height of 500 to 900 mm, preferably of 650 to 850 mm, particularly preferably of 700 to 800 mm and one or more, and in particular All polygonal layers have a height of 150 to less than 900 mm, preferably from 200 to 720 mm, most preferably from 250 to 675 mm.
• a preferred embodiment for the use of side stone in an electrolytic cell in thermal, mechanical and chemical stability of the side stone is that at least one layer, preferably all layers, of a material selected from the group consisting of carbon, graphitic carbon, graphitized carbon or silicon carbide or any mixtures thereof or containing such material. These materials are particularly suitable for withstanding the conditions encountered in the use of the side stone in an electrolytic cell and the resulting contact of the side brick with the layer of liquid aluminum and the melt layer. Furthermore, the choice of suitable material compositions makes it possible to adapt the heat conductivity of the side brick in a favorable range of values.
• the thermal conductivity of one or more and in particular all layers of the side stone can - measured at a temperature between 920 ° C and 1000 ° C, preferably between 950 ° C and 980 ° C - for example between 4 and 120 W / nrrK, in particular between 4 and 100 W / nrrK, preferably between 5 and 80 W / nrrK, more preferably between 8 and 50 W / nrrK be.
• the production of the side stone comprises a pitch impregnation step followed by carbonization.
• the whole side stone or at least one layer of the side stone can be subjected to impregnation as described above.
• the side stone may be obtainable by firing the green block, wherein in particular carbonization and / or graphitization of the green material of the green block may take place.
• the thermal conductivity of the side stone at a temperature between 920 ° C and 1000 ° C according to DIN 51936 can be measured.
• a pulsed laser is used in measurements that exceed temperatures above 400 ° C.
• the side brick may have at least substantially homogeneous thermal conductivity.
• a transition region may be formed in which the thermal conductivity, for example at least substantially continuously, decreases from the higher to the lower value.
• Such a transition region which can be made relatively small compared to the total extent of the layers, can be regarded as part of the two layers.
• the invention further provides a process for the preparation of a side stone according to the invention as described herein which comprises the steps:
• step b) firing the green block according to step b) at a temperature of 800 to 1400 ° C, preferably 1000 to 1300 ° C.
• a green mixture comprises a carbonaceous material
• graphitization of the material can take place as a further step d).
• the carbonized or green shaped body to temperatures of more than 2000 ° C and preferably more than 2200 ° C are heated.
• a further step e) may be provided after step c) of firing and / or after a possibly provided step d) of graphitizing, which comprises impregnating the fired green block and optionally graphitized green block Bad luck covers.
• the method described above first produces a base body with a plurality of layers, from which several side stones having the desired dimensions are cut out in a step following the method steps described above, in particular by a cutting operation.
• This also applies to the production of a composite stone.
• Another object of the invention is a side stone, which is obtainable by the method described herein.
• the side stone When used in an electrolysis cell, the side stone causes an optimization of the thermal conditions in the electrolysis cell during the electrolysis operation and also has a high mechanical stability and a very strong cohesion between the various layers of the side stone.
• the side stone can be dispensed with the adhesive material between the side stones. If a composite side stone is used, it is also possible to dispense, in part or in full, with the ramming mass between the side brick and the cathode block.
• the use of the side stone according to the present invention for lining the side walls in an electrolytic cell constitutes a further independent subject matter of the present invention.
• both at least one side stone, which is used to adapt the thermal is used, is combined with at least one Kompositrichstein.
• the number of side stones or composite side stones used here can be adjusted as needed.
• Another object of the invention is an electrolytic cell, in particular for the production of aluminum, which comprises a cathode, an anode and a wall, wherein at least a portion of the wall is formed by a side stone according to the present invention.
• This side stone can also be a composite side stone as described.
• the at least one side brick preferably forms a lateral wall of a well the layer of liquid aluminum and the melt layer are included.
• the side brick can thereby line a lateral wall of an outer steel tub of the electrolysis cell, which surrounds the inner tub formed by the side brick.
• the cathode In addition to the previously described side stones or composite side stones according to the invention and the refractory lining, which is located between the cathode and the steel trough, the cathode also has an influence on the thermal management in the electrolysis cell. If too much heat is removed from the electrolysis cell, the cryolite solidifies in the melt in excess and may extend to the cathode surface. As a consequence, the cathodic current flow is disturbed, resulting in an inhomogeneous current distribution along the cathode. denober Design, and thus leads to an increased electrical resistance and thus to reduced energy efficiency of the electrolytic cell.
• WO 02/064860 describes cathode blocks which, viewed in the direction of the cathode longitudinal side, have different layers which have different electrical resistances, i.
• different materials having different specific electrical resistances
• the flow of current through the cell should be approximated to the ideal current flow even without expensive guidance of power rails.
• Cathode blocks having different layers toward the cathode longitudinal side due to the use of different materials also have different thermal conductivities within the cathode block.
• Such cathode blocks can also be advantageously used to reduce the heat losses caused by the cathode, in particular in the direction of the cathode longitudinal side, ie towards the side walls.
• the course of the heat flow can also be controlled in the individual cathode blocks, and thus the cathode as a whole.
• the respective cathode block comprises in the direction of the cathode longitudinal axis. at least three layers, preferably three layers to seven layers, more preferably three layers to five layers, most preferably three layers.
• the cathode block may comprise at least two layers which have the same thermal conductivity, ie which consist of the same material. This may be the two outer or marginal layers of the cathode block.
• the length of a cathode block is normally 2,500 - 3,500 mm.
• the length of a single layer mentioned above - viewed in the cathode longitudinal direction - depends on the desired heat flow in the cathode block and can be selected as a function of this heat flow. Furthermore, this length of a single layer depends on the number of layers in the cathode block. For example, if there are seven layers, a single layer will have a length of 300-600 mm. If only three layers are used, the outer or marginal layers are 400 to 600 mm long and the inner layer has a length of 1700 to 2300 mm. Regardless of the number of layers, the outer or marginal layers of the cathode block have a length of 400 to 600 mm, preferably 500 mm.
• the individual layers of said cathode blocks are composed of carbon, i. made of a material containing carbon.
• the cathode block is composed of a material which is at least 50% by weight, preferably at least 80% by weight, particularly preferably at least 90% by weight, very particularly preferably at least 95 wt .-% and most preferably at least 99 wt .-% carbon.
• Said carbon may be selected from the group consisting of amorphous carbons, graphitic carbons, graphitized carbons and any mixtures of two or more of the aforementioned carbons.
• Particularly suitable materials for the green mixtures in the production of cathode blocks are all green materials which can be fired to one of the preferred materials mentioned above with respect to the finished cathode block.
• at least one green mixture may contain a material selected from the group consisting of a carbonaceous material, such as carbon black. Anthracite, a graphitic or graphitizable material, e.g. synthetic graphite and pitch, or any mixture of these materials.
• a particular carbonaceous binder such as binder pitch may be included in the mixture.
• the targeted composition of the material of the individual layers of the green block allows the heat conductivity of the various layers of the resulting cathode block to be adjusted in a targeted manner.
• FIG. 1 shows an electrolytic cell according to an embodiment of the invention in a sectional perspective view.
• FIG. 2 shows a side brick according to an embodiment of the invention in a perspective view
• FIG. 3 shows a side brick according to a further embodiment of the invention in a perspective view
• FIG. 4 shows a base body, from which several side stones according to a
• Embodiment of the invention are separable, in perspective view
• FIG. 7 shows a basic body from which a plurality of composite side bricks can be separated out according to an embodiment of the invention, as well as a separated composite side brick, in a perspective illustration;
• FIG. 8 shows a further basic body, from which a plurality of composite sidestones can be separated out according to an embodiment of the invention, in a perspective representation
• FIG. 9 shows a further base body, from which a plurality of composite side stones are detachable according to an embodiment of the invention, in cross-section.
• the current is dissipated via the cathode blocks 12 and via the busbars 22 inserted at the bottom thereof into corresponding slots of the cathode blocks 12.
• the electrolysis takes place, which leads to the elimination of elemental aluminum from the melt, which accumulates at the top of the cathode bottom to form the layer 16 of liquid aluminum.
• the electrolysis cell has a steel sump 24 serving as an outer casing, in the bottom region of which several plates 26 of a refractory material stacked on top of one another are thermally insulated from the bottom of the steel sump 24.
• the lateral walls of the steel tub 24 are lined with a plurality of cuboidal side stones 28.
• the side bricks 28 form the side walls of an inner tub, in which the layer 14 of liquid aluminum, the liquid
• Melt layer 16 and the solidified melt layer 18 are received and whose bottom is formed by the cathode bottom 12 formed by the cathode bottom.
• the joints formed between a cathode block 12 and a side brick 28 are sealed by a ramming compound 30.
• Such a ramming mass may also be provided for sealing the joints between the cathode blocks 12 and for sealing the joints between the side bricks 28.
• the side bricks 28 are formed substantially cuboid and stand upright in the steel tub 24, so that the height direction the side stones 28 is parallel to the vertical.
• the sides of the sidestones 28 delimiting the tub interior are thereby formed by their base surfaces 32 parallel to the height direction and the width direction of the side bricks 28 and the side bricks 28 are connected to one another via their side surfaces 34 parallel to the height direction and the width direction.
• the side bricks 28 stand, as shown in Fig. 1, in different areas of their height with different components or media of the electrolytic cell in contact, namely with the ramming mass 30, possibly the layer 14 of liquid aluminum, the liquid melt layer 16 and solidified melt layer 18.
• the sidestones 28 of the electrolysis cell shown in Fig. 1 each have at least one layer with a lower thermal conductivity and a layer with a higher thermal conductivity, wherein the difference between lower and higher thermal conductivity is at least 5 W / nrrK.
• FIG. 2 and 3 each show a side brick 28 according to an embodiment of the invention, which is incorporated, for example, in the electrolytic cell shown in FIG. can be set.
• the side bricks 28 each have a relatively small thickness d and a width b and a height h which is greater than the width b.
• the side brick 28 shown in FIG. 2 has two cuboidal layers 36, 38, wherein the layer 36 has a lower and the layer 38 has a higher thermal conductivity.
• the layers 36, 38 are connected to each other via their parallel to the height direction and the width direction base surfaces 40, 42, each forming a contact surface, follow each other in the thickness direction of the side stone 28 and each extend over about half of the thickness d of the side stone 28th This allows the heat flows in the thickness direction and the isothermal layers within the sidestones 28 to be adjusted to optimize the thermal operating conditions in the electrolysis cell during operation.
• the side brick 28 shown in FIG. 3 likewise has two cuboidal layers 36, 38, wherein the layer 36 has a lower and the layer 38 has a higher thermal conductivity.
• the layers 36, 38 are connected to one another via their side surfaces 44, 46, which are parallel to the width direction and the thickness direction and each form a contact surface, follow one another in the height direction of the side stone 28 and each extend over approximately half the height h of FIG Side stone 28.
• the upper half of the height is preferably formed by the layer 36 with the lower thermal conductivity.
• the heat conduction via the side brick 28 can be adapted to the various constituents or media of the electrolysis cell and the thermal conditions present therein in the respective height range, thereby optimizing the thermal conditions prevailing in the electrolysis cell during electrolysis become.
• the heat is due to the good thermal contact between the lower half of Height comprising the layer 38 with the higher thermal conductivity and the cathode, which takes place via the ramming mass 30, is dissipated.
• the main body 48 is cuboidal and consists of a cuboidal layer 36 having a lower thermal conductivity and a cuboidal layer 38 having a higher thermal conductivity, which are interconnected via their base surfaces.
• a cutting process it is possible to cut off from the base body 48 a plurality of side stones forming slices which have two layers 36, 38 with different thermal conductivity.
• FIG. 5 shows a further main body 48, which substantially corresponds to the main body shown in FIG. 4.
• the main body 48 comprises two layers 36 with a lower thermal conductivity and a layer 38 arranged therebetween with a higher thermal conductivity, which are interconnected via their base surfaces.
• the base 48 for cutting the sidestones is not only cut in several planes perpendicular to the interfaces between the layers 36, 38, but additionally in a median plane of the layer 38 parallel to these interfaces, so that the resulting Side stones each have two layers 36, 38 with different thermal conductivity.
• This manufacturing process has a higher economy.
• 6 shows cross sections of various embodiments of a composite side brick 29 according to the invention, which can be used, for example, in the electrolytic cell shown in FIG.
• All the composite side stones listed in FIG. 6 have a cuboidal layer 36 and a polygonal layer 38, wherein the layer 36 has a lower thermal conductivity and the layer 38 has a higher thermal conductivity.
• the layers 36, 38 are connected to one another via their base surfaces 40, 42, which each form a contact surface, parallel to the height direction and the width direction, follow one another in the thickness direction of the composite side brick 29 and extend in each case over 30% -70%, preferably 50%, the thickness d of the composite side stone 29.
• the base surfaces 40, 42 may in this case have a partial or complete contact with each other.
• the heat flows in the thickness direction and the isothermal layers within the composite side brick 29 can be adjusted so that the thermal operating conditions in the electrolysis cell are optimized during operation, on the other hand it is also possible to use such a composite side brick 29 partially or completely dispense with the ramming mass between this composite sostein 29 and the cathode block.
• the layer 38 has a trapezoidal shape, in Fig. 6b), the layer 38 has a triangular shape and in Fig. 6c), the layer 38 has a shape of an irregular pentagon with a rounded corner.
• the base surfaces 40, 42 in complete contact.
• the base surfaces 40, 42 have only a partial contact in FIGS. 6d) and 6e), wherein in FIG. 6d) the layer 38 is a rectangle having a rounded corner and in FIG. 6e) the layer 38 is in the form of a has irregular pentagons with a rounded corner.
• a reverse arrangement of the layers may be useful in terms of their thermal conductivity.
• FIG. 7 shows a main body 48, which has been produced as an intermediate product of a method according to the invention for producing a composite side brick 29.
• This main body 48 is cuboid and consists of a cuboidal layer 36 having a lower thermal conductivity and a cuboidal layer 38 having a higher thermal conductivity, which are interconnected via their base surfaces. These layers represent horizontal layers.
• the layer 36 is machined so that this layer assumes the desired polygonal shape over the entire length of the base 48.
• discs of the desired width are then cut off from this base body 48. It is thus possible to exploit the grain orientation which occurs in the production of the base body and thus different properties occurring in the horizontal or vertical direction, such as the thermal conductivity, and to adjust it in the side stone by selecting the base areas accordingly during machining of the base body.
• FIG. 8 shows a main body 48, which has been produced as an intermediate product of a method according to the invention for producing a composite side brick 29.
• This main body 48 is cuboidal and consists of two cuboidal layers 36 having a lower thermal conductivity and a cuboidal layer 38 having a higher thermal conductivity, which are interconnected via their base surfaces. These layers represent vertical layers, with the layers 36 representing the two outer layers.
• a plurality of disks can be cut off from the main body 48, the two outer layers 36 and an inner layer 38 with different chen sauceleitzuen have.
• the layer 38 is cut so that two blocks are obtained, from which in a further step the layer 38 is cut so that the desired polygonal shape is obtained.
• FIG. 9 likewise shows a main body 48, which has been produced as an intermediate product of a method according to the invention for producing a composite side stone 29.
• This main body 48 is cuboid and, like the main body 48 in FIG. 8, consists of two parallelepipedal layers 36 with a lower thermal conductivity and a cuboidal layer 38 with a higher thermal conductivity, which are interconnected via their bases. These layers represent vertical layers, with the layers 36 representing the two outer layers.
• Fig. 1 a) and b) show different forms of the layers in a cathode block 12, wherein in these cathode blocks in each case two materials, ie material A and material B, is used. In this case, the two layers of the material A take only a part of the height H and the length L of the cathode block.
• Exemplary Embodiment 1 A side brick is made from a mixture A containing 58% by weight (% 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. % Alumina, and a blend B containing 77% by weight of synthetic graphite and 23% by weight of binder pitch.
• a vibrating mold for producing a green block is filled with the two mixtures in such a way that two successive layers of mixture A and mixture B follow one another in the green block in the height direction of the sidestones to be produced.
• the height of the layers in the Ganttelform is taking into account a target density, which results from a subsequent filling on the following densification of the green block, chosen so that after compaction both layers each extend over half the height of the green block. This is followed by burning of the green block in a ring furnace at 1200 ° C to produce a body.
• the material A has a thermal conductivity of approximately 8 W / nRrK measured at room temperature in one direction of the side stone, while the Material B in the same direction of the side stone, in the grain orientation of the materials A and B, has a thermal conductivity of about 45 W / nrrK.
• the thermal conductivity at room temperature can be measured according to ISO 12987, in a given direction, in the case of pressurization of the starting material during the production of the side-brick, e.g. perpendicular or parallel to the direction of pressurization, i. against or in the grain orientation.
• the thermal conductivity measured at a temperature between 920 ° C to 1000 ° C is about 9 W / nrrK for material A and about 37 W / nrrK for material B.
• the measurement of the thermal conductivity can be done here in grain alignment according to DIN 51936 using a pulsed laser.
• Embodiment 2 is a diagrammatic representation of Embodiment 1:
• a composite sidestone is made from a 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 a 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.
• a vibrating mold for producing a green block is filled with the two mixtures so that successive layers of mixture A and mixture B follow one another in the green block in the height direction of the combo stones to be produced.
• the height of the layers in the Ganttelform is taking into account a target density, which results from a subsequent filling on the following densification of the green block, chosen so that after compaction both layers each extend over half the height of the green block. This is followed by burning of the green block in a ring furnace at 1300 ° C for producing a base body. Thereafter, the layer containing material A is processed so that it assumes the desired polygonal shape over the entire length of the green block. In a next step, then slices of a thickness of 50 cm are cut off from this basic body.
• An exemplary finished composite stone has a width of 500 mm, a height of 700 mm and a thickness of 250 mm.
• the material A has a thermal conductivity of about 8 W / nrrK measured at room temperature in one direction of the side brick, while the material B in the same direction of the side stone, in the grain orientation of the materials A and B, has a thermal conductivity of about 45 W / nrrK ,
• the thermal conductivity at room temperature can be measured according to ISO 12987, in a particular direction, in the case of pressurization of the starting material during the production of the side brick, e.g. perpendicular or parallel to the direction of pressurization, i. against or in the grain orientation.
• the thermal conductivity measured at a temperature between 920 ° C to 1000 ° C is about 9 W / nrrK for material A and about 37 W / nrrK for material B.
• a cathode block as shown in Fig. 10 is prepared by filling in a vibrating mold, the height of which is considered as a finished height of the green body, first with a mixture A, then with a mixture B and then again with a mixture A.
• the mixture A is composed as follows:
• the height of the layers in the Rüttelform is taking into account a target density, which results from a subsequent filling on the following densification of the green block, chosen so that after compaction both layers each extend over half the height of the green block. This is followed by burning of the green block in a ring furnace at 1200 ° C to produce a body.
• the material A has a thermal conductivity of about 15 W / nrrK measured at room temperature in one direction of the cathode block, while the material B has a heat conductivity of about 40 W / nrrK in the same direction of the cathode block, in grain alignment of the materials A and B ,
• the thermal conductivity at room temperature can be measured according to ISO 12987, in a certain direction, in the case of pressurization of the starting material during manufacture of the cathode block, eg perpendicular or parallel to the direction of pressurization, ie against or in the grain orientation.

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