Cathode pack for aluminium electrolytic cell and method of its production

FIELD: metallurgy.

SUBSTANCE: invention relates to a cathode pack for an aluminium electrolytic cell. The cathode pack comprises a layer of composite containing graphite and solid material such TiB2, present with single mode granulometric composition, while d50 amounts to 10 - 20 mcm, in particular to 12 - 18 mcm, preferably to 14 - 16 mcm. Method for the production of a cathode pack with the said characteristics is described as well.

EFFECT: improved wear resistance of a cathode pack and simple manufacturing.

16 cl, 1 dwg

 

The present invention relates to cathode block for aluminum electrolysis cell and method of its production.

A method of obtaining aluminum metal is the process of Hall-Heroult. In this electrolytic process, the bottom of the cell is usually formed by a surface of the cathode, which consists of separate cathode blocks. The cathodes connected from the bottom through the steel rods that are inserted into the respective elongated grooves on the bottom side of the cathode blocks.

The production of cathode blocks traditionally carried out by mixing the coke with carbon particles, such as anthracite, coal or graphite, seal and carbonation. If necessary, then do stage graphitization at higher temperatures at which carbon particles and Cox transformed, at least partially, in graphite.

However, graphitized carbon and graphite poorly wetted or not wetted by liquid aluminum. Because of this increased power consumption and, consequently, also the power consumption of the cell.

To address this problem in the prior art in the upper layer of the cathode block enter TiB2. This is described, for example, in DE 112006004078. This top layer representing the composite TiB2-graphite, is in direct contact with the aluminium is molten and therefore is crucial for the passage of current from the cathode in an aluminum melt. TiB2and similar solid materials improve the wettability of the cathode in the graphitized state and as a result provide higher energy efficiency of the electrolysis process. Moreover, the solid materials can increase bulk density and hardness of the cathodes, which provides improved wear resistance, especially with respect to aluminum and cryolite melts.

However, to work with powder TiB2and powders similar hard materials (also referred to as refractory hard material (RHM)) is difficult. Moreover, get them cathode blocks, which are fully or in its upper layer represents a layer of the composite TiB2-graphite prone to irregularities.

Therefore, the present invention is to develop a cathode composite TiB2-graphite, well wetted aluminum melts, having good properties of wear and easy to get, and how to obtain it.

The problem is solved by using the cathode block under item 1 of the claims.

The cathode unit according to the invention for aluminum electrolysis cell, which contains the layer composite, graphite and solid material, such as, for example, TiB2, characterized in that the solid material has a single-mode particle size distribution (i.e. the distribution of h is STIC size), the average particle size distribution of d50between 10 and 20 μm, in particular between 12 and 18 microns, in particular between 14 and 16 microns.

Surprisingly, within the scope of the invention it was found that when such d50the solid powder material, on the one hand, has a large active surface, providing a very good wettability of the cathode block after graphitization, and, on the other hand, has no flaws, and adversely affecting the processability (machinability) powder solid material as a component of the composite in the composite graphite-solid material. These possible disadvantages, which are not inherent in used according to the invention the powder of hard material, are as follows:

- the tendency to form dust, for example, when filling in the container for mixing or during transportation of powders;

- the formation of agglomerates, in particular, when mixed, such as, for example, a wet mixed with coke (in this regard, the wet mixing means, in particular, mixing with peck as the liquid phase);

- stratification due to the different densities of the solid material and coke.

In addition to the absence of these shortcomings is used according to the invention the solid powder material is particularly good fluidity or flowability. This makes the solid powder m the material is particularly easily transportable using a conventional conveying devices, for example, in the mixing apparatus.

Obtaining composites powder solid material for cathode blocks much easier a good processability of the powder of the solid material with d50between 10 and 20 microns and singlemode granulometric composition. The obtained cathode blocks have a very good homogeneity regarding the distribution of the powder of the solid material in the coke in green procurement and graphitized graphite cathode product.

Preferably d90refractory hard material is between 20 and 40 μm, in particular between 25 and 30 microns. The result of this is mainly that the wetting properties and technological properties of the solid powder material further improve.

Mostly d10refractory hard material is between 2 and 7 μm, in particular between 3 and 5 microns. The result of this is mainly that the wetting properties and technological properties of the solid powder material further improve.

Moreover, when the characteristic of single-mode particle size distribution width of its distribution can be described by the so-called magnitude of calculated as follows:

Span=(d90-d10)/d50

Sweep the powder of refractory hard material is preferably between 0.5 and 3,80, in particular between 1,00 and 2.25. The result of this is mainly that the wetting properties and technological properties of the solid powder material further improve.

Can be advantageously provided that the layer of composite material forms the entire cathode block as a whole. The advantage of this is that to obtain the cathode block requires only one part of wet weight and, accordingly, only one stage of mixing.

Alternatively, it may be preferential to the cathode unit consisted of at least two layers, with a layer of composite forms the upper layer of the cathode block. This top layer is in the application of the cathode unit according to the invention in direct contact with the melt in the pot.

The cathode unit preferably includes at least one additional layer that contains less powder solid material than the top layer, or contains no solid powder material. This can reduce the number of costly powder solid material. This additional layer when applying the cathode in an aluminum reduction cell is not in direct contact with the aluminum melt, and therefore should not have a good wettability and durability.

Mainly the height ver the it layer can be from 10 to 50%, in particular from 15 to 45%of the total height of the cathode block. Pre-emption may be small, the height of the upper layer, such as, for example, 20%, because it requires a small amount expensive solid material.

Alternatively, priority may be high altitude of the upper layer, such as, for example, 40%, because the layer comprising solid material has high wear resistance. The higher the height of such a highly wear-resistant material in relation to the total height of the cathode block, the higher the wear resistance of the entire cathode block as a whole.

Preferably the cathode unit according to the invention produced by the method comprising the stages of availability (training) source materials including coke, a solid material such as, for example, TiB2and, if necessary, additional carbonaceous material forming the cathode block, carbonization and graphitization, and cooling. Thus according to the invention the coke includes two varieties of coke, which during the carbonization and/or graphitization, and/or cooling are various behavior change volume.

At the stage of graphitization at least part of the carbon cathode block is transformed into graphite.

Surprisingly it was found that the lifetime obtained in this way the cathode of the components is significantly more than the cathode blocks obtained by traditional methods.

Preferably obtained by the process according to the invention the cathode block has a bulk density carbon fraction, making more than 1.68 g/cm3especially preferably more 1,71 g/cm3in particular, up to 1.75 g/cm3.

Presumably a higher bulk density mainly contributes to longer service life. It may be, on the one hand, based on the fact that there is more mass per unit volume of the honeycomb unit that at a given mass flow rate per unit of time leads to a higher residual mass after a given period of spending. On the other hand, it can be assumed that the higher bulk density with the corresponding lower porosity prevents leakage of the electrolyte, which acts as a corrosive environment.

Because of the addition of RHM after graphitization, the second layer may have a bulk density comprising, for example, more than 1.80 g/cm3.

Mainly two varieties of coke include first grade coke and second grade coke, the first grade coke manifests during carbonization and/or graphitization, and/or cooling a stronger shrinkage and/or expansion than the second grade coke. While stronger shrinkage and/or expansion are you the same development of various behavior change volume, which presumably is particularly well suited to lead to a stronger seal than when mixed varieties of coke, which have the same shrinkage and/or expansion. At the same time more strong shrinkage and/or expansion related to an arbitrary temperature range. Thus, for example, during the carbonization can take place only stronger shrinkage of the first coke. On the other hand, for example, in addition to, or instead of, in the transition region between the carbonation and grafitizare may have a stronger expansion. Instead of or in addition to this different behavior volume changes can occur during the cooling process.

Preferably expressed by the volume shrinkage and/or expansion of the first grade of coke during the carbonization and/or graphitization, and/or cooling at least 10% higher than that of the second grade coke, in particular at least 25% higher, in particular at least 50% higher. Thus, for example, if 10% of the greater shrinkage of the first grade coke shrinkage from room temperature to 2000°C in the second grade coke is 1.0 vol.%, and first grade coke - 1,1 vol.%.

Predominantly expressed in volume shrinkage and/or expansion of the first grade of coke during the carbonization and/or graphitization, and/or cooling at least n is 100% higher than the second grade coke, in particular, at least 200% higher, in particular at least 300% higher. Thus, for example, in the case of 300% greater expansion of the first grade coke expansion from room temperature to 1000°C in the second grade coke is 1.0 vol.%, and first grade coke to 4.0 vol.%.

The method according to the invention also covers the case when the first grade coke is experiencing shrinkage, and second grade coke is experiencing expansion in the same temperature interval. Thus, at 300% large shrinkage and/or expansion also include, for example, the case when the second grade coke sits 1.0 vol.%, and first grade coke is expanded by 2.0%vol.

Alternatively, in at least one arbitrary temperature range of the method according to the invention instead of the first grade second grade coke coke may be stronger shrinkage and/or expansion, as described above for first grade coke.

Preferably the cathode unit according to the invention produced by the method comprising the stage of ensuring the availability of source materials, including coke, forming the cathode block, carbonization and graphitization, and cooling. While Cox preferably includes two varieties of coke, which, thanks to various behavior change volume during carbonization and/or Gras is ititaly, and/or cooling lead to compaction of the cathode block over 1.68 g/cm3. Presumably different behavior change volume two varieties of coke leads to the fact that the compaction process during the carbonization and/or graphitization, and/or cooling can be prevented adhesion (sticking) or other blocking individual coke particles to one another, which explains the similar properties of shrinkage. Presumably due to this, individual particles can be more favorable for sealing position to achieve a higher packing density of the particles of coke or received from them in the further process of the particles than traditional methods of production.

In this embodiment, the advantages of the multi-layered unit in which facing to the anode layer comprises a solid material, combined with the use of two grades of coke with different behavior change volume. Small differences in the behavior of thermal expansion during the stages of the heat treatment reduces the production time and the error rate of the cathode blocks. In addition, therefore, also preferably increases the resistance to thermal stresses and the resulting damage them in the application.

Preferably, at least one of the two varieties of coke you submitted is a petroleum or coal-pitch coke.

Preferably quantitative proportion in mass% of the second grade coke in the total amount of coke is between 50% and 90%. In such a quantitative framework of various behavior change in the volume of the first and second grades of coke has a particularly good effect on the seal during carbonization and/or graphitization, and/or cooling. Possible quantitative range of the second grade coke can range from 50 to 60%, and from 60 to 80%, as well as from 80 to 90%.

Mainly to coke add at least one carbonaceous material, and/or pitch and/or additives. This can be useful as a relatively manufacturability coke, and further properties of the obtained cathode block.

Preferably the additional carbonaceous material contains a graphite-containing material; in particular, additional carbonaceous material consists of graphite-containing material, such as, for example, graphite. Graphite may be synthetic and/or natural graphite. Due to this additional carbon-containing material is achieved that reduces the inevitable shrinkage of the cathode mass, dominated by coke.

Mainly carbonaceous material in relation to the total number of coke and carbonaceous material is from 1 to 40 wt.%, in castnet is from 5 to 30 wt.%.

Mainly, in addition to the amount of coke and, if necessary, carbonaceous material, comprising a total of 100 wt.%, can be added peck in quantities of from 5 to 40 wt.%, in particular from 15 to 30 wt.% (relative to 100 wt.% all crude mixture). Peck acts as a binder and provides a stable shape (size) of the product during carbonization.

Suitable additives can be a fluid such as oil for more spin, or stearic acid. This facilitates mixing coke and, if necessary, additional components.

Preferably coke in at least one of the two layers, i.e. in the first and/or second layer includes two varieties of coke, which, thanks to various behavior change volume during carbonization and/or graphitization, and/or cooling lead to the seal formed of graphite over 1.68 g/cm3. Therefore, depending on the desires and/or requirements of both layers or one of the two layers can be obtained according to the invention with two different varieties of coke. Thus, if necessary or desired, you can control the bulk density and the ratio of bulk density. According to the invention, for example, only the first layer can be obtained with two varieties of coke, while the second layer is obtained is only one grade of coke, but it also contains the TiB2as a solid material. Due to this, bulk density and/or expansion characteristics of the two classes are similar, which may best way to improve the durability of the joints.

Further preferential options for implementation and improvements of the invention are explained below using a preferred example of realization and shapes.

The drawing shows the granulometric composition used according to the invention powder TiB2a) in a distribution q3 bulk density and (b) in the form of a cumulative volume distribution Q3.

To obtain a cathode unit according to the invention the coke mixed with pitch, mixed with powder TiB2with single-mode particle size distribution of the particles and d5015 μm, d9030 μm and d105 μm. The magnitude of such a particle size distribution of the particles is 1,67. The weight percentage of the powder TiB2in wet weight is, for example, 10-30 wt.%, for example, 20 wt.%. The mixture is loaded into the form, mainly corresponding to the subsequent shape of the cathode blocks and compacted by vibration or pressed into blocks. The resulting green billet is heated to the final temperature in the range from 2300 to 3000°C., in particular from 2500 to 2900°C., such as, for example, 2800°C, when this happen the stage carb the organization, and then stage graphitization, and then cooled. The resulting cathode block has a very good wettability characteristics and very high wear resistance when exposed to molten aluminium and cryolite.

Alternatively, instead of a single grade of coke use two varieties of coke with different behavior change volume. The different behavior change volume two varieties of coke leads to high bulk density of graphite in the composite and, therefore, to an even higher resistance of the cathode blocks than when using only one powder TiB2.

According to the following variant form is first partially filled with a mixture of coke, graphite and TiB2and, if appropriate, compacted by vibration. Then formed on the initial layer, which in the future the cathode is a top layer facing the anode, and therefore come into direct contact with the aluminum melt, pour the mixture of coke and graphite and re-condense. The resulting initial upper layer represents the future of the cathode bottom layer facing away from the anode side. Such two-layer "brick" (block) carbonothioyl and graphicsyou in the same manner as in the first example implementation.

The following alternative as coke lower the Loya use two varieties of coke with different behavior change volume. The wear resistance of the thus obtained cathode block under the influence of aluminum is particularly high. This is due to the smaller difference in bulk density between the upper and lower cathode layers than in the case of traditional composite blocks with TiB2.

All listed in the description, examples and claims the signs can contribute to the invention in any combination. However, the invention is not limited to the described examples, but may also be implemented with modifications not specifically described here. In particular, in addition to the TiB2can also be used powders of other solid materials, such as, for example, ZrB2, HfB2or other borides of transition metals.

1. Cathode block for aluminum electrolysis cell comprising a layer of composite which contains graphite and solid material, such as, for example, TiB2, characterized in that the solid material is present with a single-mode particle size distribution, with d50between 10 and 20 μm, in particular between 12 and 18 microns, mostly between 14 and 16 microns.

2. Cathode block under item 1, characterized in that the d90solid material is between 20 and 40 μm, in particular between 25 and 30 microns.

3. The cathode unit according to any one of paragraphs.1 or 2, characterized in that the d10solid material is IU the Doo 2 and 7 μm, in particular between 3 and 5 microns.

4. Cathode block under item 3, characterized in that the range=(d90-d10)/d50particle size distribution of the powder of the solid material is between 0,65 and of 3.80, in particular between 1,00 and 2.25.

5. Cathode block under item 4, characterized in that the layer of composite material forms the entire cathode block as a whole.

6. Cathode block under item 5, wherein the cathode unit includes at least two layers, with a layer of composite forms the upper layer of the cathode block.

7. Cathode block under item 6, characterized in that the cathode unit includes at least one additional layer that contains less powder solid material than the top layer, or contains no solid powder material.

8. Cathode block under item 7, characterized in that the thickness of the upper layer is from 10 to 50%, in particular from 15 to 45%of the total thickness of the cathode block.

9. Cathode block under item 8, characterized in that the bulk density in at least one layer of the cathode block related to carbon fraction is more than 1.68 g/cm3.

10. Cathode block under item 9, characterized in that the bulk density is more than 1,71 g/cm3.

11. The method of obtaining the cathode block for aluminum electrolysis cell according to any one of paragraphs.1-10, including the stage of ensuring the availability of raw materials, on the expectation Cox and if necessary, additional carbonaceous material, and a powder of a hard material, such as powder TiB2mixing starting materials, forming the cathode block, carbonization, graphitization and cooling, using a solid powder material, which has a single-mode particle size distribution and d50which is between 10 and 20 μm, in particular between 12 and 18 microns, mostly between 14 and 16 microns.

12. The method according to p. 11, characterized in that use solid powder material, which has d90between 20 and 40 μm, in particular between 25 and 30 microns.

13. The method according to p. 11 or 12, characterized in that use solid powder material, which has d10between 2 and 7 μm, in particular between 3 and 5 microns.

14. The method according to p. 13, characterized in that use powder solid material, granulometric composition which has a span=(d90-d10)/d50between 0,65 and of 3.80, in particular between 1,00 and 2.25.

15. The method according to p. 14, characterized in that the coke includes two varieties of coke, which have different behavior volume changes during carbonization and/or graphitization, and/or cooling.

16. The method according to p. 15, characterized in that the gain of the cathode block with bulk density carbon fractions over 1.68 g/cm3in particular over 1,71 g/cm3.



 

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6 cl, 7 dwg, 1 tbl

FIELD: metallurgy; production of graphitic cathodes.

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2 cl, 2 dwg

Aluminum cell // 2256009

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EFFECT: improved resistance of carbon containing component against rupture at operation of electrolysis cell.

34 cl, 1 dwg, 4 tbl, 7 ex

FIELD: non-ferrous metallurgy; electrolytic production of aluminum; cathode units of aluminum electrolyzers.

SUBSTANCE: proposed side lining includes interconnected members - plates and blocks made from non-metallic refractory compounds possessing high resistance and interconnected by means of end faces in form of inversed symmetrical projections and recesses and adhesive or cementing mix. Plates and blocks are made from silicon carbide. Angular blocks are made in form of strip, 70 mm thick and 600-800 mm long which is bent at center around longitudinal axis at angle of 90° relative to vertical whose end faces are inclined at angle of 18° relative to vertical and are narrowing downward by 219 mm each. End faces are made in form of inversed symmetrical projections and recesses at radius of 14-15 mm which are parallel to vertical axis of walls of aluminum electrolyzer.

EFFECT: increased service life; enhanced strength and reliability; saving of lining material; increased useful volume of electrolyzer; increased yield of aluminum.

4 dwg

FIELD: aluminum cells, namely cathode facing for them.

SUBSTANCE: cathode facing includes carbon blocks, heat insulation layer and refractory part having two protection layers, upper layer adjoining to carbon blocks and lower layer made of powder materials. Upper protection layer includes alumosilicate composition resistant against action of electrolyte components containing 27 -35% of Al2 O3 with fraction size no more than 2.5 mm and with thickness consisting 10 - 50% of height of refractory part. Lower protection layer is made at least of one sealed metallic vessel filled with refractory material including carbon-containing composition resistant against action of melt aluminum and electrolyte components and having heat conductivity factor no more than 0.1 Wt/(mK). In lower protection layer vessels are filled with carbon black; thickness of said layer consists 50 - 90% of height of refractory part.

EFFECT: increased useful life period, improved operational characteristics of cell.

3 cl, 7 dwg, 1 tbl

FIELD: aluminum production electrolyzers of all types.

SUBSTANCE: proposed method includes mounting the heat-insulating and refractory components of electrolyzer and applying protective material on base of covalent nitrides to surface of side lining. Used as protective material is boron nitride-based material which ensures reduction of after-start period, increases electrolyzer service life, enhances aluminum grade, increases yield by current and daily productivity of electrolyzer; protective material is applied flush with top in continuous layer. Lower boundary of coat is located below "electrolyte-metal" interface. Thickness of coat is maintained within 0.1-1 mm. Open surface porosity is maintained within 2-3%. Consistency of material of coat changes from fluid to viscous-flow state. Application of coat is performed by spraying, painting or concrete-spraying method.

EFFECT: increased service life of electrolyzer; increased daily productivity of electrolyzer.

4 cl, 2 dwg, 1 tbl

FIELD: installation of aluminum electrolyzer hearth.

SUBSTANCE: proposed method includes preliminary estimation of quality of hearth modules by proximate ultrasonic inspection, mounting of complete set of hearth modules and forming of hearth; electrolyzer is equipped with hearth modules at inhomogeneity index not exceeding 0.65 relative units according to ultrasonic inspection; inhomogeneity index is determined by the following formula Iinhom = (tmax/tmin-1), where Iinhom is inhomogeneity index according to ultrasonic inspection; tmax is maximum magnitude of index of ultrasonic inspection for definite electrolyzer; tmin is minimum magnitude of index of ultrasonic inspection for definite electrolyzer; hearth is formed in such way that adjacent modules with close indices of ultrasonic inspection are mounted in longitudinal and transversal directions; modules with minimum indices of ultrasonic inspection are mounted in center of hearth at smooth increase of this index toward end faces of electrolysis bath.

EFFECT: increased service life of hearth; reduced yield of low-grade metal; reduced power requirements.

3 dwg, 1 ex

FIELD: mounting aluminum electrolyzers at major repair or in capital construction.

SUBSTANCE: current-supply metal rod is placed in slot of carbon block on layer of carbon-containing conducting material. Surface of carbon block slot is preliminarily coated with carbon-based surfactant and layer of carbon-containing conducting material is compacted by vibration applied on current-supply metal rod, thus ensuring reliable electromechanical "conducting rod-carbon block" contact and reducing probability of penetration of aluminum melt into hearth body. At application of vibration in local zone on side of flush area, maximum reduction of voltage drop is ensured in contact layer between rod and block slot. Maximum thickness of layer of carbon-containing conducting material before vibration is equal to optimal magnitude determined by definite formula.

EFFECT: enhanced efficiency.

4 cl, 4 dwg, 1 tbl

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