Title of Invention	ELECTRODES USEFUL FOR MOLTEN SALT ELECTROLYSIS OF ALUMINUM OXIDE TO ALUMINUM
Abstract	The present invention provides a method of making a carbon electrode, suitable for use as an anode in an aluminum reduction cell, which comprises mixing an aggregate, comprising a mixture of particulate shot coke, and a particulate carbonaceous material other than shot coke with coal tar pitch or petroleum pitch or a combination of these pitches at an elevated temperature to form a paste wherein said aggregate comprises a combination of butts, coarse, and fine particles and said particulate shot coke may comprise a majority of said coarse particles or fine particles, and said paste comprises from about 80 to about 90%, by weight, of said aggregate and from about 10 to about 20%, by weight, of said pitch; forming said paste into a solid body; and baking said solid body at an elevated temperature to form said carbon electrode.

Title of Invention

ELECTRODES USEFUL FOR MOLTEN SALT ELECTROLYSIS OF ALUMINUM OXIDE TO ALUMINUM

Abstract

The present invention provides a method of making a carbon electrode, suitable for use as an anode in an aluminum reduction cell, which comprises mixing an aggregate, comprising a mixture of particulate shot coke, and a particulate carbonaceous material other than shot coke with coal tar pitch or petroleum pitch or a combination of these pitches at an elevated temperature to form a paste wherein said aggregate comprises a combination of butts, coarse, and fine particles and said particulate shot coke may comprise a majority of said coarse particles or fine particles, and said paste comprises from about 80 to about 90%, by weight, of said aggregate and from about 10 to about 20%, by weight, of said pitch; forming said paste into a solid body; and baking said solid body at an elevated temperature to form said carbon electrode.

Full Text	This application has been filed as a Patent of Addition XXXXX to application No,3693/K0LNP/2006 ELECTRODES USEFUL FOR MOLTEN SALT ELECTROLYSIS OF ALUMINUM OXIDE TO ALUMINUM This patent application is a continuation-in-part of 5 U.S. Patent Application Serial No. 10/874,508, filed on June 22, 2004 in the names of Leslie Edwards, M. Franz Vogt, Richard 0. Love, J. Anthony Ross and William Morgan Jr. This application is to be incorporated herein, in toto, by this specific reference thereto. 10 The present invention relates to an electrode, e.g. an anode, for use in the manufacture of aluminum by molten salt electrolysis of aluminum oxide, e.g. in an aluminum reduction cell. More particularly, it relates to a process 15 for manufacturing an anode for use in aluminum reduction cells . It has been known to manufacture aluminum by molten salt electrolysis of aluminum oxide dissolved in a bath of 2 0 the fluorides of aluminum and sodium, or cryolite, using a carbon anode. Usually, such an electrolysis process is conducted at about 900° to 1000° Centigrade. In this process, the carbon anode is consumed by oxidation due to the oxygen produced by the decomposition of aluminum oxide 2 5 to the aluminum metal. In commercial anode production processes, calcined sponge petroleum cokes or coal tar pitch cokes, along with recycled carbon anode remnants or butts, are used to provide 3 0 an aggregate which is then separated into different size fractions. Typically, there can be anywhere between 3-6 different size fractions. A common approach is to separate 1 3502 the aggregate into three fractions: a "butts" fraction, "coarse" fraction and "fines" fraction. The different size fractions are then recombined in fixed proportions and mixed with a binder such as coal tar pitch or a combination of 5 coal- tar and petroleum pitches (combination pitch) and subsequently shaped and heated at an elevated temperature, e.g. about 1100°C, to form the commercial anode. The manufacture of such commercial anodes requires a coke that has low volatile matter, vanadium and nickel under 500ppm 10 and sulfur under 4%, by weight, and preferably under 3%, by weight. In addition, to having relatively low impurities, the cokes used in commercial anode production, are somewhat anisotropic in structure. Such coke is preferably calcined, sponge coke. In contrast to anisotropic cokes, isotropic 15 cokes are cokes with a very fine-grained structure or texture which exhibit similar properties in all directions. That is, anisotropic cokes have a coarser texture and the properties are directionally dependent. The extreme example of anisotropic coke is needle coke which has an elongated or 2 0 ribbon like structure. Delayed sponge coke used for making anodes has a heterogeneous structure with a mixture of isotropic and anisotropic structures. Shot coke is a form of isotropic coke with a very 25 unique structure. It has a fine texture with uniform directional properties, and the particles tend to be more spherical in shape and more uniform in size. Shot coke typically also has lower macro-porosity (porosity >lμm) and higher micro-porosity ( 3 0 to make anodes. 2 3502 There is a large supply of isotropic and shot coke materials in the world, and they are generally significantly lower in price than traditional anode grade green cokes. The impurity levels are typically higher than anode grade 5 cokes, particularly impurities like sulfur, vanadium and nickel and this is the primary driver of their lower cost. The aluminum industry has avoided using isotopic cokes, particularly shot cokes, to make anodes because they have 10 high coefficients of thermal expansion (CTE). Anodes made with these materials can crack catastrophically during the rapid heat-up that occurs in aluminum electrolysis cells. This creates a hazardous and costly outcome for the aluminum plant or smelter. 15 As a result, shot coke, with its higher impurity levels, more isotropic structure and higher thermal expansion coefficient when calcined, has never been successfully used for such commercial anodes. 20 In particular, carbon anodes, made from an aggregate comprising more than 5% by weight of shot coke, exhibit a propensity for thermal shock cracking due to the high coefficient of thermal expansion and the anode strength is 25 weakened due to the difficulty in binding shot coke particles with coal tar or combination pitch. Thus, the anode scrap rates from anodes prepared from shot coke are unacceptably high and anode carbon loss in the aluminum reduction cells creates a serious and unacceptable 3 0 disruption to the smelting process. 3 3502 When discussing petroleum coke, it is essential to recognize that there are three different types of coking processes and the. petroleum coke produced from each is distinctly different.. These processes - delayed, fluid and 5 flexicoking - are all effective in converting heavy hydrocarbon oil fractions to higher value, lighter hydrocarbon gas and liquid fractions and concentrating the contaminants (sulfur, metals, etc.) in the solid coke. 10 Petroleum coke from the delayed process is described as delayed sponge, shot or needle coke depending on its physical structure. Shot is most prevalent when running the unit under severe conditions with very heavy crude oil residuum containing a high proportion of asphaltenes. 15 Needle coke is produced from selected aromatic feedstocks. Although the chemical properties are most critical, the physical characteristics of each coke type play a major role in the final application of the. coke. For example, sponge coke has a relatively high macro-porosity and the pores are 20 evident from visual examination of the coke. If the quality is acceptable, it may be sold to the calcining industry as a raw material for anode coke production where it has a higher value. Shot coke looks like BB's, has a lower macro- porosity and is harder; it is almost always sold as a fuel 2 5 coke for a relatively low value. Needle coke's unique structure lends to its use for graphitized electrodes. Unlike the others, needle coke is a product (not a by- product) which the refinery intentionally produces from selected hydrocarbon feedstocks. 30 Shot coke is characterized by small round spheres of coke, the size of BB's, loosely bound together. 4 3502 Occasionally, they agglomerate into ostrich egg sized pieces. While shot coke may look like it is entirely made up of shot, most shot coke is not 100% shot. Interestingly, even sponge coke may have some measurement of embedded shot 5 coke. A low shot coke percentage in petroleum coke is preferably specified for anode grades of petroleum coke. Shot coke, while useful as a fuel, is less valuable than sponge coke which can be used to prepare the more 10 valuable carbon anodes. It is therefore desirable to find a way to use the less valuable shot coke in an application having a greater value, i.e. to manufacture carbon anodes, provided said carbon anodes do not have poor quality. 15 SUMMARY OF THE INVENTION Preferably, in accordance with the present invention, the aggregate comprises more than 5%, by weight, of shot coke, and may comprise up to 90%, by weight, of shot coke, 20 but preferably the anodes of this invention will comprise up to about 50%, e.g. from about 15% to about 5 0% shot coke. The shot coke, is preferably calcined to remove most of the volatiles prior to use in the method of the invention. 2 5 The calcined shot coke, may be screened and milled to provide particles in the correct size ranges. For the purposes of the present invention, fine particles are defined as those whereby 10 0% will pass through a 60 mesh, Tyler Sieve Size and approximately 70% or more will pass 3 0 through a 200 mesh U.S. Standard Sieve Size. 5 3502 The milling process to obtain the above fine particles is common knowledge in the art and need not be disclosed herein. 5 The particulate shot coke, may have a sulfur content of up to 8%, by weight. It is generally undesirable for the coke utilized in the manufacture of carbon electrodes for use in an aluminum reduction cell to have a sulfur content of greater than about 4%. 10 The remainder of the aggregate may comprise any particulate carbonaceous material that is suitable for preparing carbon electrodes, including recycled anode butts, for use in aluminum reduction cells. Such carbonaceous 15 materials are well known in the art. Preferably, said carbonaceous material is selected from the group consisting of sponge, needle or pitch cokes, and recycled carbon electrode remnants. 20 It has now been discovered that a satisfactory carbon electrode, suitable for use in an aluminum reduction cell may be prepared from a particulate carbonaceous, aggregate, preferably comprising more than about 5%, by weight, of a 2 5 shot coke, and more preferably said aggregate comprises from 5% to about 50%, by weight, of a shot coke. Thus, the present invention provides a method of making a carbon electrode, suitable for use as an anode in an 3 0 aluminum reduction cell, which comprises separating an aggregate into different size fractions by a combination of crushing, milling and screening whereby such an aggregate 6 3502 may comprise a mixture of a particulate shot coke, recycled anode butts, and a particulate carbonaceous material other than shot coke, with coal tar pitch or combination pitch at an elevated temperature to form a paste wherein said 5 aggregate comprises a combination of butts, coarse, and fine particles and said paste comprises up to about 90%, e.g. about 85%, by weight, of said aggregate and from about 10 to about 20%, e.g. 15%, by weight, of said coal tar pitch or combination pitch; forming said paste into a solid body; and 10 baking said solid body at an elevated temperature to form said carbon electrode. Furthermore, it has now been discovered that in the process of preparing electrodes of this invention, the 15 properties of the electrode can be influenced significantly by selecting the size of the shot coke used in the aggregate. For example, if the shot coke is added to the coarse fraction of the aggregate, the anode density can be improved but the coefficient of thermal expansion will be 20 negatively affected (higher). The anode air reactivity on the other hand, will not be significantly affected when shot coke, is added to the coarse fraction of the aggregate. When shot coke is milled and added to the fines fraction, 25 the coefficient of thermal expansion will not be significantly affected but no improvement in anode density will occur. The anode air reactivity on the other hand, will be negatively affected (increase) when the shot coke is added to the fines fraction of the aggregate. 30 7 3502 BRIEF DESCRIPTION OF THE DRAWINGS This invention will be more readily understood by reference to the drawings. 5 Figures 1-4 refer to experiments where shot coke was added to all aggregate fractions in the anode at different levels, more particularly: 10 Figure 1 shows the change in air reactivity with the percentage of shot coke in the aggregate that was used to form the carbon anode of this invention; Figure 2 shows the change in the coefficient of thermal expansion with the percentage of shot coke in the aggregate that was used to 15 form the carbon anode; Figure 3 shows the change in the CO2 reactivity residue with the percentage of shot coke in the aggregate that was used to form the carbon anode of this invention; Figure 4 shows the change in the baked apparent density with the percentage of shot coke in the aggregate 2 0 that was used to form the carbon anode of this invention; Figure 5 shows the variation of baked apparent density when shot coke was added selectively to the coarse or fines fraction; 25 Figures 6 and 7 compare the coefficient of thermal expansion wherein the shot coke is added selectively to the fines or coarse fraction of the aggregate that is used to prepare the carbon anodes of this invention; and 30 8 3502 Figure 8 shows the structure of anisotropic cokes, e.g. needle coke and sponge coke, and isotropic cokes, e.g. shot cokes. 5 DETAILED DESCRIPTION In the method of the invention, the above described aggregate is combined with a coal tar pitch binder or a combination pitch binder. 10 Coal tar pitch is a residue produced by distillation or heat treatment of coal tar. It is a solid at room temperature, consists of a complex mixture of numerous predominantly aromatic hydrocarbons and heterocyclics, and 15 exhibits a broad softening range instead of a defined melting temperature. Petroleum pitch is a residue from heat treatment and distillation of petroleum fractions. It is solid at room temperature, consists of a complex mixture of numerous predominantly aromatic and alkyl-substituted 2 0 aromatic hydrocarbons, and exhibits a broad softening range instead of a defined melting temperature. Combination pitch is a mixture or combination of coal tar pitch and petroleum pitch. 25 The hydrogen aromaticity in coal tar pitch (ratio of aromatic to total content of hydrogen atoms) varies from 0.7 to 0.9. The hydrogen aromaticity (ratio of aromatic to total hydrogen atoms) varies between 0.3 and 0.6. The aliphatic hydrogen atoms are typically present in alkyl 3 0 groups substituted on aromatic rings or as naphthenic hydrogen. 9 3502 The aggregate utilized in the method of the present invention comprises a mixture of fine, coarse and recycled anode butts particles. The mesh sizes for the fine particles are defined above. Coarse particles, which may 5 also contain recycled anode butts, will be retained on a 16 mesh Tyler screen. The aggregate is combined and mixed with the coal tar pitch or combination pitch. There are numerous mixing 10 schemes in the art. Any of them may be adapted for use in the method of this invention, simply by treating the shot coke-containing aggregate in the same way as the current aggregate is combined with the pitch. 15 It is important that the aggregate and the pitch are mixed together at an elevated temperature, e.g. greater than 150°C, in order to coat the particles with pitch, penetrate the pitch and the fine particles into the internal pores of the coarse particles and fill the interstitial aggregate 20 volume with the pitch and the fine particles. After mixing the aggregate and the coal tar pitch for 1 to 45 minutes, e.g. from 5 to 20 minutes, a paste is formed. 25 The paste may be formed into a solid body, by methods known in the art, e.g. pressing or vibroforming, prior to baking to form the electrode. The green electrode is baked at an elevated temperature 3 0 to provide a carbon electrode suitable for use in an aluminum reduction cell. Preferably, the green electrode is, baked at a temperature of from 1000°C to 1200°C, e.g. about 10 3502 1100° Centigrade for a time sufficient for the green electrode to reach a temperature within the preferred range. The baking may take place in open or closed furnaces, 5 as is well known in the art. The method of the invention provides carbon electrodes having characteristics including density, air permeability, compressive strength, modulus of elasticity, thermal 10 conductivity, coefficient of thermal expansion, air reactivity, and carboxy-reactivity which are within acceptable ranges, for use in aluminum smelters. In another aspect of the present invention, there is 15 provided a carbon electrode, suitable for use an anode in an aluminum reduction cell, which comprises (a) an aggregate comprising a mixture of particulate shot coke, and a particulate carbonaceous material other than said shot coke, and (b) a coal tar or combination pitch binder, wherein said 2 0 aggregate comprises a combination of coarse and fine particles and said particulate shot coke, comprises a majority of said coarse particulates. In said electrode, preferably said aggregate is 2 5 prepared by screening and/or milling shot coke, and a carbonaceous material other than said shot coke from a delayed coker to provide a particulate mixture comprising at least 5%, preferably about 3 0 to 4 0 percent by weight. 3 0 To this screened and/or milled aggregate may be added from about 5 to about 2 0 percent, e.g. about 15% butts. Thus, the aggregate utilized in the method of preparing the 11 3502 anodes of the invention may comprise from 5 to 60 percent, preferably about 50% coarse, from. 10 to 50 percent, preferably about 34% fine, and from 0 to 25% preferably, 16% butts. Also, in said preferred aggregate the shot coke may 5 vary from 10 to 85.0, by weight, of the aggregate. Preferably the particulate carbonaceous material in the electrode is selected from the group consisting of sponge, needle or pitch cokes, and recycled carbon electrode 10 remnants. In this aspect of the present invention, the fines may comprise shot coke, e.g., milled shot coke, or some other particulate carbonaceous material, e.g., fine particulates 15 from the delayed coking of heavy hydrocarbon oil fractions. Any of the above, novel electrodes or electrodes made by the method of the present invention may be used in a method for producing . aluminum by the molten salt 2 0 electrolysis of aluminum oxide which comprises electrolyzing aluminum oxide dissolved in a molten salt at an elevated temperature by passing a direct current through an anode to a cathode disposed in said molten salt wherein said anode is any of the above electrodes. 25 The cokes utilized in the following examples have the properties shown in Table 1, below. 12 3502 Table 1 Coke Ni% FE% V% S% ADg/cc KVBDg/cc RDg/cc SROhm-in CO2Reac.% AirReac.% permin. A 0.016 0.023 0.023 2.58 1.76 0.796 2.073 0.038 7.3 0.10 B 0.032 0. 023 0. 067 4.53 1.80 1.111 2.042 0. 042 4.3 0.36 Coke A is a regular delayed anode coke blend; and coke 5 B is a shot coke with a high percentage of BB's. The characteristics of shot cokes are as follows: • The shot cokes are significantly higher in Ni, V and 10 S. • The shot coke has a significantly higher vibrated bulk density (KVBD) and apparent density (AD). • The real density (RD) of the. shot coke was significantly lower and a specific electrical 15 resistivity significantly higher. • The air reactivity of the shot coke and isotropic coke is higher. EXAMPLE 1 20 In this example, shot coke was added to two of the aggregate size fractions - coarse and fines. Control anodes using 100% regular delayed anode coke were prepared for comparison. 25 A total of 5 different anode formulations were prepared at 3 different pitch levels (15.5, 16.0, and 16.5%) to give a 13 3502 total of 15 anodes. The mixer batch size was 9kg. Forming was done via a laboratory hydraulic press and the anodes were baked in lab mode baking furnace. The fines fraction was prepared using a laboratory ring and puck mill. A 5 standard aggregate granulometry containing 50% coarse, 34% fines and 16% butts was used for all anodes. Table 2 below, shows the different recipes tested in this Example 1. The control anodes are laboratory versions 10 of anodes that are used in commercial applications. 14 3502 TABLE 2 AnodeSeriesCode Coke Recipe % Shot Coke inAggregate S1 15% Shot/85% Regular Coke 12.5 S2 25% Shot/75% Regular Coke 21.0 S3 50% Shot/50% Regular Coke 42.0 S4 100% Shot Coke 84.0 C 100% Regular Coke 0 The results are summarized below and in Figures 1 and 2. As shown: 5 • Anode air reactivities deteriorated as the percentage of isotropic coke and shot coke increased. • Anode coefficients of thermal expansion, or CTE's, increased as the percentage of isotropic and shot coke 10 increased. • Anode densities increased as the percentage of shot coke increased. • With up to 50% shot coke in the coke recipe, most other anode properties were comparable to the control anodes. 15 Property data for all the lab anodes produced in this experiment is included in Table 3, below. 15 3502 Table 3 Lab Shot Pitch Green Koppers TC AD ER CO2 CO2 CO2 Air Air Air AP Flex CTE Code. % % Density BAD W/mK g/cc □Oms-m %Residue %Dust %Loss %Residue %Dust %Loss nPm MPa E10ˆ-6 Sll 15 14.5 1.603 1.561 2.46 1.55 87.9 96.00 0.11 3.89 76.2 7.7 16.1 2.40 3.8 4.540 S12 15 15.0 1.616 1.566 2.41 1.55 89.9 95.98 0.16 3.86 85.3 7.6 16.9 2.23 3.5 4.606 S13 15 15.5 1.633 1.581 2.44 1.57 85.0 96.70 0.11 3.19 78.0 6.5 15.6 2.60 4.0 4.314 S21 25 14.5 1.618 1.576 2.16 1.56 92.9 95.71 0.22 4.07 74.0 8.3 17.7 2.60 3.7 4.604 S22 25 15.0 1.630 1.582 . 2.31 1.57 85.0 96.34 0.11 3.55 72.0 8.8 19.2 2.45 4.3 4.484 S23 25 15.5 1.642 -1.584 2.57 1,57 81.9 96.68 0.11 3.21 74.8 7.4 17.8 2.75 5.2 4.556 S31 50 14.5 1.651 1.600 2.54 1.59 84.5 96.61 0.16 3.23 70.9 7.1 22.0 2.63 4.6 4.777 S32 50 15.0 1.661 1.615 2.55 1.60 76.3 96.94 0.11 2.95 70.3 7.7 22.0 2.30 5.6 5.012 S33 50 15.5 1.666 1.619 2.6 1.60 70.5 96.69 0.11 3.21 74.0 5.6 20.4 1.82 5.7 4.897 S41 100 14.5 1.701 1.657 2.71 1.64 58.4 97.60 0.05 2.35 67.2 5.1 27.7 2.04 7.7 5.903 S42 100 15.0 1.699 1.655 1.67 1.63 .55.2 97.37 0.10 2.52 69.3 3.5 27.2 4.05 9.3 5.622 S43 100 15.5 1.707 1.649 3.01 1.63 58.0 96.60 0.10 3.30 67.5 4.7 27.8 5.42 9.5 5.895 Lab Shot Pitch Koppers TC AD ER CO2 CO2 CO2 Air Air Air AP Flex CTE Code % % BAD W/mK g/cc □Oms-m %Residue %Dust %Loss %Residue %Dust %Loss nPm MPa E10ˆ-6 Cl 0 15.5 1.598 2.48 1.54 72 95.57 0.11 4.32 80.5 5 14.5 2.42 5.3 4.299 C2 0 16.0 1.605 2.31 1.55 75.7 94.05 0.33 5.62 82.6 4.4 13.1 1.57 6.6 4.454 C3 0 16.5 1.609 2.34 1.55 76.2 95.77 0.05 4.17 84.5 3 12.5 1.63 5.8 4.209 5 16 3502 Example 2 In the experiments described in this Example 2, the 5 shot coke was concentrated in different fractions of the aggregate. It was expected that it would be advantageous to grind the shot coke and concentrate it in the fines fraction to minimize the negative effects on CTE. Two different types of pitch were also tested in this set of experiments - 10 regular coal tar pitch and a coal tar/petroleum pitch blend. The anodes of this experiment were produced in a larger mixer batch size (17kg/mix) and a lab scale vibroformer instead of a hydraulic press was utilized. The anode baking 15 furnace was also larger, allowing up to 3 0 anodes to be baked at one time. The quantity of fines required was too large to produce in a laboratory ring and puck mill so a 70kg/hr. ball mill was used. The particle size distribution was monitored closely to make sure it matched the size 20 distribution of the ball mill utilized in commercial production of carbon anodes for aluminum smelting. Fifteen different anode formulations were tested in Example 2 at two different pitch levels giving a total of 25 thirty different mixer batches. Six lab anodes were produced from each mixer batch giving a total of one hundred eighty laboratory anodes. The different formulations tested are shown in Table 2 below. 17 3502 TABLE 4 ANODE CODE DESCRIPTION PITCH FORMING C41/C42 100% Regular CT Vibrate C51/C52 100% Regular CT Press S51/S52 25% Shot in Fines Fraction CT Vibrate S61/S62 65% shot in Fines Fraction CT Vibrate S71/S72 100% Shot in Fines Fraction CT Vibrate S81/S82 40% Shot in Coarse Fraction CT Vibrate S91/S92 75% Shot in Coarse Fraction CT Vibrate S101/S102 75% Shot in Coarse Fraction A Vibrate CT refers to coal tar pitch and A refers to Type A 5 pitch. The baked anodes were tested for density, electrical resistivity, air permeability, crush strength, flexural strength, modulus of elasticity, fracture energy, CTE, 10 thermal conductivity, air reactivity residue and CO2 reactivity residue. Results were averaged and grouped together, where possible, to determine general trends. The experiments of this Example 2 showed some 15 unexpectedly good results. A summary of key results is given below. More detailed results are included in Table 5. • Shot coke added to the fines fraction had no effect on density but when added to the coarse fraction, the 2 0 density increased significantly. • shot coke additions to the fines fraction caused a progressive deterioration in anode air reactivity. 18 3502 Anode CTE's and other mechanical properties were unaffected. • Air reactivities deteriorated only slightly when shot coke was added to the coarse fraction. 5 • Anode CTE's increased almost linearly as shot coke was added to the coarse fraction. Anode strengths also decreased. • Anode CO2 reactivities were good for all formulations tested with shot coke. 19 3502 Table 5 AnodeCode Recipe PitchType PitchLevel GAD Stdev Shrink(%) Stdev BAD Stdev ER Stdev Air Perm Stdev Crush StDev S51 25% S Fines CT Lo 1.542 0.012 1.34 0.39 1.534 0.006 76.1 3.5 2.83 1.34 35.5 0.2 S52 25% S Fines CT Hi 1.584 0.008 1.06 0.15 1.547 0.003 63.8 1.3 0.82 0.02 38.0 1.2 S61 65% S Fines CT Lo 1.533 0.006 1.32 0.07 1.512 0.011 74.5 3.8 4.24 1.45 32.6 0.5 S62 65% S Fines CT Hi 1.567 0.011 0.93 0.16 1.542 0.008 66.1 2.1 1.49 0.82 33.9 0.2 S71 100% S Fines CT Lo 1.555 0.008 1.28 0.14 1.539 0.004 70.0 0.7 1.57 0.26 39.3 1.2 S72 100% S Fines CT Hi 1.589 0.006 0.85 0.14 1.541 0.002 66.0 0.9 1.11 0.05 37.1 0.2 S81 40% S Coarse CT Lo 1.554 0.004 1.24 0.13 1.529 0.003 85.2 1.7 4.80 0.61 30.5 1.5 S82 40% S Coarse CT Hi 1.601 0.008 1.00 0,08 1.564 0.004 64.7 1.4 1.02 0.35 38.9 1.3 S91 75% S Coarse CT Lo 1.621 0.004 1.41 0:08 1.591 0.004 66.8 2.1 0.85 0.14 39.3 2.0 S92 75% S Coarse CT Hi 1.646 0.020 0.76 0.12 1.593 0.012 59.9 1.4 0.50 0.06 38.9 4.0 S101 , 75% S Coarse A Lo 1.629 0.005 0.96 0.14 1.588 0.003 65.5 1.5 1.51 0.80 40.9 0.2 S102 75% S Coarse A Hi 1.654 0.006 0.80 0.10 1.596 0.002 67.6 0.7 0.52 0.08 37.8 1.7 C41 Control CT Lo 1.537 0.008 1.16 0.11 1.514 0.007 74.1 3.0 4.05 2.73 32.7 1.7 C42 Control CT Hi 1.588 0.007 0.95 0.09 1.541 0.004 62.0 1.9 0.68 0.14 34.5 0.8 20 3502 Table 5 Continued AnodeCode Recipe MOE Stdev Flex Stdev Frac E Stdev CTE Stdev TC Stdev ARR Stdev CO2 Stdev S51 25% S Fines 1693.1 202.6 2.6 0.1 113.5 55.4 4.31 0.12 2.58 0.00 85.2 5.2 97.3 0.2 S52 25% S Fines 2191.7 127.3 4.8 0.2 157.6 16.7 4.25 0.04 2.70 0.12 83.3 1.5 97.3 0.3 S61 65% S Fines 1619.8 25.2 3.5 0.1 164.3 32.8 4.41 0.16 2.51 0.04 83.0 3.2 96.7 0.5 S62 65% S Fines 1827.3 108.3 4.7 0.5 184.4 7.9 4.28 0.04 2.56 0.09 80.2 8.0 97.4 0.2 S71 100% S Fines 2029.5 41.3 5.3 0.6 106.5 51.1 4.34 0.07 2.60 0.07 70.4 1.5 97.2 0.2 S72 100% S Fines 1834.4 352.0 6.6 1.0 132.1 59.5 4.36 0.14 2.67 0.22 74.5 1.4 97.6 0.3 S81 40% S Coarse 1511.5 233.2 1.6 0.2 59.6 5.4 4.59 0.16 2.31 0.06 92.2 1.7 95.6 1.5 S82 40% S Coarse 2265.6 168.9 3.6 0.3 94.3 27.1 4.58 0.01 2.78 0.05 89.1 2.9 94.8 1.8 S91 75% S Coarse 2007.0 187.5 3.3 0.0 120.9 1.0 4.94 0.09 2.70 0.02 88.1 0.5 96.2 1.0 S92 75% S Coarse 2193.5 37.7 6.7 1.9 144.3 73.9 5.19 0.11 2.97 0.24 87.9 1.3 95.6 1.0 S101 75% S Coarse 2292.9 269.2 4.3 0.8 248.1 0.5 5.09 0.15 2.72 0.03 84.2 2.7 97.7 0.0 S102 75% S Coarse 1945.2 40.4 3.4 0.5 244.6 2.7 4.94 0.10 2.62 0.06 82.0 0.1 96.6 0.9 C41 Control 1506.2 151.6 3.2 0.1 77.6 27.5 4.21 0.04 2.52 0.04 91.9 1.0 96.8 0.6 C42 Control 2171.2 62.7 6.4 0.1 203.7 34.7 4.37 0.02 2.73 0.01 93.0 0.4 96.7 0.3 21 3502 The results in this Example 2 show that anode properties of the carbon anodes of this invention as prepared with the addition of shot are dependent on how the shot coke is added. CTE's do not increase when the coke is 5 added to the fines fraction but anode air reactivities deteriorate. When shot cokes are added to the coarse fraction, the CTE's increase significantly but anode air reactivities are not as significantly affected. In addition, there is a major advantage of adding shot coke to 10 the coarse fraction, that is an increased anode density is obtained. Thus, the anodes prepared according to Example 2 where shot coke is selectively added to the coarse fraction, are 15 especially useful in a smelter which uses relatively small anodes at lower currents ( cells are not as susceptible to thermal shock cracking as larger anodes in higher current cells. The design of such cells is typically quite sensitive to anode airburn, 2 0 however, due to the difficulty in being able to keep the anodes well covered. As a result, any addition of shot coke to the fines fraction will exacerbate anode airburn and negatively affect cell performance. 25 EXAMPLE 3 Based on the results of Example 2, it was decided that the density gains possible by adding shot coke to the coarse fraction warranted additional optimization work. 30 In this experiment, the fines, content and pitch level of shot coke added to the coarse fraction was optimized. A 22 3502 single shot coke level was selected on the basis of the calculated anode sulfur level. At high shot coke addition rates, anode sulfur levels increase to the point where the smelter would exceed its SO2 emissions limit. The goal was to 5 keep the aggregate sulfur level under 3%. To stay within this range, shot coke additions were limited to 40% of the coarse fraction which equated to 2 0% of the total aggregate (including butts). 10 The fines content was optimized first by preparing dry aggregate mixes gave at different fines levels and measuring the vibrated bulk density. A fines content of 27% yields optimum results. 15 Pitch optimization tests were carried out at two different butts levels (16% & 18%) . Lab anodes were baked and tested and a formulation was selected for a plant trial. The main objective of the plant trial was to see if full size plant anodes could be produced with 20% shot coke 20 without production problems. It was unknown for example, how these anodes would look (deformation and cracking) after forming and anode baking. If the anodes were acceptable in appearance, i.e. not chipped or cracked or otherwise damaged, a number of such anodes would be tested in a single 25 electrolysis cell to see if thermal shock cracking would be a problem. Approximately sixty full size plant electrodes were produced and tested in a single electrolysis cell. No 3 0 significant problems were found and there was no obvious thermal shock craqking despite the higher CTE. Anode butts 23 3502 were weighed and the average butt weight was 14 7 lbs compared to the regular anode butt weight of 146 lbs. These positive results provided the incentive to move 5 to larger scale plant trial but there was a concern that the low fines level made the anodes very sensitive to small pitch level changes. Thus, a further experiment was carried out. 10 EXAMPLE 4 Additional lab experiments were undertaken at a fines level of 27% and 30%. From this work, the 30% fines shot coke anodes appeared to give the best results. A plant trial 15 was then undertaken to select the optimum pitch level and to make sure that anodes could be produced successfully on a larger scale with minimal scrap rates. The properties of the shot coke anodes baking were 20 better than expected. Anodes were produced at 3 pitch levels and the optimum level appeared to be 14.4%. This was 1.4% lower than the optimum pitch level of standard production anodes used in a representative commercial smelting process. This represents a substantial potential 25 cost saving for the smelter since pitch is significantly more expensive than calcined petroleum coke. Anode densities were also better than expected. The average density of the 14.4% pitch anodes was 1.598 g/cc 3 0 compared to a typical density of 1.555 g/cc. A sustained density increase of this magnitude would allow the 24 3502 commercial smelting process to increase anode life in the electrolysis cells. No unusual problems were reported. 5 The results from this Example 4 warranted a larger scale plant trial where anode and cell performance would be monitored closely to determined the full potential of the anode produced by the method of this invention. 10 These shot coke anodes were utilized in a commercial aluminum smelting process or pots EXAMPLE 5 15 In a larger scale plant trial 710 full scale anodes were produced and tested in 4 closely monitored cells. The shot coke anodes were used to run the four cells 2 0 through at least 3 full anode cycles. Thus, each cell completely changes out a set of shot coke anodes 3 times. This gives the cell more chance to reach steady state conditions and performance with the different anode quality. 2 5 No thermal shock cracking or anode burn-offs occurred. Although ' there has been hereinabove described a specific electrode useful for molten salt electrolysis of aluminum oxide to aluminum in accordance with the present 3 0 invention for the purpose of illustrating the manner in which the invention may be used to advantage, it should be , appreciated that the invention is not limited thereto. That 25 3502 is, the present invention may suitably comprise, consist of, or consist essentially of the recited elements. Further, the invention illustratively disclosed herein suitably may be practiced in the absence of any element which is not 5 specifically disclosed herein. Accordingly, any and all modifications, variations or equivalent arrangements which may occur to those skilled in the art, should be considered to be within the scope of the present invention as defined in the appended claims. 10 26 3502 WE CLAIM: 1. A method of making a carbon electrode, suitable for use as an anode in an aluminum reduction cell, which 5 comprises mixing an aggregate of different size fractions, comprising a mixture of particulate shot coke and a particulate carbonaceous material other than shot coke with coal tar pitch or combination pitch at an elevated temperature to form a paste, and said paste comprises from 10 about 80 to about 90%, by weight, of said aggregate and from about 10 to about 20%, by weight, of said coal tar pitch or combination pitch wherein said aggregate comprises from about 5 to 90%, by weight, shot coke; forming said paste into a solid body; and baking said solid body at an elevated 15 temperature to form said carbon electrode. 2. The method of claim 1 wherein said shot coke comprises from about 10 to 50%, by weight, of said aggregate. 20 3 . The method of claim 1 wherein said carbonaceous material is selected from the group consisting of sponge, and coal tar pitch cokes, and recycled carbon anode remnants or butts. 25 4. The method of claim 1 wherein said aggregate wherein said aggregate comprises from about 5 to 60% of coarse particles, 10 to 50% fine particles and from 0 to 30% butts. 30 5. The method of claim , 4 wherein said coarse particles comprise from 25 to 75%, by weight, of shot coke. 27 3502 6. The method of claim 4 wherein said fine particles comprise from 25 to 75%, by weight of shot coke. 5 7. The method of claim 1 wherein said solid body is subject to compressing or vibrating to form a green anode prior to baking. 8. The method of claim 1 wherein said solid body is 10 baked at a temperature of above 1000° Centigrade. 9. A method of making a carbon anode for use in an aluminum reduction cell, in which aluminum oxide is reduced to molten aluminum metal at an elevated temperature, which 15 comprises: (a) mixing an aggregate comprising a mixture of particulate shot coke, prepared by screening and milling to provide a particulate mixture comprising at least 10%, by weight and a particulate carbonaceous material other than 2 0 shot coke, and recycled carbon anode remnants or butts, with coal tar or combination pitches at an elevated temperature to form a paste wherein said aggregate comprises a combination of coarse, and fine particles and said particulate shot coke comprises a majority of said coarse 2 5 particles,, and said paste comprises from about 8 0 to about 90%, by weight, of said aggregate and from about 10 to about 20%, by weight, of said coal tar or combination pitches; (b) forming said paste into a solid body; (c) subjecting said solid body to compression or vibration to 3 0 form a green anode; and (d) baking said green anode at an elevated temperature of greater then 1000° Centigrade ,to form said carbon electrode. 28 3502 10. The product of claim 1. 11. The product of claim 9. 5 12. A carbon electrode, suitable for use as an anode in an aluminum reduction cell, which comprises (a) an aggregate comprising a mixture of particulate shot coke and a particulate carbonaceous material other than shot coke, 10 and (b) a coal tar pitch or combination pitch binder, wherein said aggregate comprises a combination of butts, coarse, and fine particles and said particulate shot coke comprises a majority of said fine particulates. 15 13. A method for producing aluminum by the molten salt electrolysis of aluminum oxide which comprises electrolyzing aluminum oxide dissolved in a molten salt at an elevated temperature by passing a direct, current through an anode to a cathode disposed in said molten salt wherein said anode is 20 the product of claim 1. 14. A method of making a carbon electrode, suitable for use as an anode in an aluminum reduction cell, which comprises mixing an aggregate, comprising a mixture of 25 particulate shot coke, and a particulate carbonaceous material other than shot coke with coal tar pitch or combination pitch at an elevated temperature to form a paste wherein said aggregate comprises a combination of butts, coarse and fine particles wherein said particulate shot coke 30 comprises more than 5%, by weight, of said aggregate, and said paste comprises from about 80 to about 90%, by weight, of said aggregate and from about 10 to about 20%, by weight, 29 3502 of said coal tar pitch or combination pitch; forming said paste into a solid body; and baking said solid body at an elevated temperature to form said carbon electrode. 30 Dated this 5th day of April. 2007. The present invention provides a method of making a carbon electrode, suitable for use as an anode in an aluminum reduction cell, which comprises mixing an aggregate, comprising a mixture of particulate shot coke, and a particulate carbonaceous material other than shot coke with coal tar pitch or petroleum pitch or a combination of these pitches at an elevated temperature to form a paste wherein said aggregate comprises a combination of butts, coarse, and fine particles and said particulate shot coke may comprise a majority of said coarse particles or fine particles, and said paste comprises from about 80 to about 90%, by weight, of said aggregate and from about 10 to about 20%, by weight, of said pitch; forming said paste into a solid body; and baking said solid body at an elevated temperature to form said carbon electrode.

Full Text

This application has been filed as a Patent of Addition
XXXXX to application No,3693/K0LNP/2006
ELECTRODES USEFUL FOR MOLTEN SALT ELECTROLYSIS
OF ALUMINUM OXIDE TO ALUMINUM
This patent application is a continuation-in-part of
5 U.S. Patent Application Serial No. 10/874,508, filed on June
22, 2004 in the names of Leslie Edwards, M. Franz Vogt,
Richard 0. Love, J. Anthony Ross and William Morgan Jr.
This application is to be incorporated herein, in toto, by
this specific reference thereto.
10
The present invention relates to an electrode, e.g. an
anode, for use in the manufacture of aluminum by molten salt
electrolysis of aluminum oxide, e.g. in an aluminum
reduction cell. More particularly, it relates to a process
15 for manufacturing an anode for use in aluminum reduction
cells .
It has been known to manufacture aluminum by molten
salt electrolysis of aluminum oxide dissolved in a bath of
2 0 the fluorides of aluminum and sodium, or cryolite, using a
carbon anode. Usually, such an electrolysis process is
conducted at about 900° to 1000° Centigrade. In this
process, the carbon anode is consumed by oxidation due to
the oxygen produced by the decomposition of aluminum oxide
2 5 to the aluminum metal.
In commercial anode production processes, calcined
sponge petroleum cokes or coal tar pitch cokes, along with
recycled carbon anode remnants or butts, are used to provide
3 0 an aggregate which is then separated into different size
fractions. Typically, there can be anywhere between 3-6
different size fractions. A common approach is to separate
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the aggregate into three fractions: a "butts" fraction,
"coarse" fraction and "fines" fraction. The different size
fractions are then recombined in fixed proportions and mixed
with a binder such as coal tar pitch or a combination of
5 coal- tar and petroleum pitches (combination pitch) and
subsequently shaped and heated at an elevated temperature,
e.g. about 1100°C, to form the commercial anode. The
manufacture of such commercial anodes requires a coke that
has low volatile matter, vanadium and nickel under 500ppm
10 and sulfur under 4%, by weight, and preferably under 3%, by
weight. In addition, to having relatively low impurities,
the cokes used in commercial anode production, are somewhat
anisotropic in structure. Such coke is preferably calcined,
sponge coke. In contrast to anisotropic cokes, isotropic
15 cokes are cokes with a very fine-grained structure or
texture which exhibit similar properties in all directions.
That is, anisotropic cokes have a coarser texture and the
properties are directionally dependent. The extreme example
of anisotropic coke is needle coke which has an elongated or
2 0 ribbon like structure. Delayed sponge coke used for making
anodes has a heterogeneous structure with a mixture of
isotropic and anisotropic structures.
Shot coke is a form of isotropic coke with a very
25 unique structure. It has a fine texture with uniform
directional properties, and the particles tend to be more
spherical in shape and more uniform in size. Shot coke
typically also has lower macro-porosity (porosity >lμm) and
higher micro-porosity ( 3 0 to make anodes.
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There is a large supply of isotropic and shot coke
materials in the world, and they are generally significantly
lower in price than traditional anode grade green cokes.
The impurity levels are typically higher than anode grade
5 cokes, particularly impurities like sulfur, vanadium and
nickel and this is the primary driver of their lower cost.
The aluminum industry has avoided using isotopic cokes,
particularly shot cokes, to make anodes because they have
10 high coefficients of thermal expansion (CTE). Anodes made
with these materials can crack catastrophically during the
rapid heat-up that occurs in aluminum electrolysis cells.
This creates a hazardous and costly outcome for the aluminum
plant or smelter.
15
As a result, shot coke, with its higher impurity
levels, more isotropic structure and higher thermal
expansion coefficient when calcined, has never been
successfully used for such commercial anodes.
20
In particular, carbon anodes, made from an aggregate
comprising more than 5% by weight of shot coke, exhibit a
propensity for thermal shock cracking due to the high
coefficient of thermal expansion and the anode strength is
25 weakened due to the difficulty in binding shot coke
particles with coal tar or combination pitch. Thus, the
anode scrap rates from anodes prepared from shot coke are
unacceptably high and anode carbon loss in the aluminum
reduction cells creates a serious and unacceptable
3 0 disruption to the smelting process.
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When discussing petroleum coke, it is essential to
recognize that there are three different types of coking
processes and the. petroleum coke produced from each is
distinctly different.. These processes - delayed, fluid and
5 flexicoking - are all effective in converting heavy
hydrocarbon oil fractions to higher value, lighter
hydrocarbon gas and liquid fractions and concentrating the
contaminants (sulfur, metals, etc.) in the solid coke.
10 Petroleum coke from the delayed process is described as
delayed sponge, shot or needle coke depending on its
physical structure. Shot is most prevalent when running the
unit under severe conditions with very heavy crude oil
residuum containing a high proportion of asphaltenes.
15 Needle coke is produced from selected aromatic feedstocks.
Although the chemical properties are most critical, the
physical characteristics of each coke type play a major role
in the final application of the. coke. For example, sponge
coke has a relatively high macro-porosity and the pores are
20 evident from visual examination of the coke. If the quality
is acceptable, it may be sold to the calcining industry as a
raw material for anode coke production where it has a higher
value. Shot coke looks like BB's, has a lower macro-
porosity and is harder; it is almost always sold as a fuel
2 5 coke for a relatively low value. Needle coke's unique
structure lends to its use for graphitized electrodes.
Unlike the others, needle coke is a product (not a by-
product) which the refinery intentionally produces from
selected hydrocarbon feedstocks.
30
Shot coke is characterized by small round spheres of
coke, the size of BB's, loosely bound together.
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Occasionally, they agglomerate into ostrich egg sized
pieces. While shot coke may look like it is entirely made
up of shot, most shot coke is not 100% shot. Interestingly,
even sponge coke may have some measurement of embedded shot
5 coke. A low shot coke percentage in petroleum coke is
preferably specified for anode grades of petroleum coke.
Shot coke, while useful as a fuel, is less valuable
than sponge coke which can be used to prepare the more
10 valuable carbon anodes. It is therefore desirable to find a
way to use the less valuable shot coke in an application
having a greater value, i.e. to manufacture carbon anodes,
provided said carbon anodes do not have poor quality.
15 SUMMARY OF THE INVENTION
Preferably, in accordance with the present invention,
the aggregate comprises more than 5%, by weight, of shot
coke, and may comprise up to 90%, by weight, of shot coke,
20 but preferably the anodes of this invention will comprise up
to about 50%, e.g. from about 15% to about 5 0% shot coke.
The shot coke, is preferably calcined to remove most of the
volatiles prior to use in the method of the invention.
2 5 The calcined shot coke, may be screened and milled to
provide particles in the correct size ranges. For the
purposes of the present invention, fine particles are
defined as those whereby 10 0% will pass through a 60 mesh,
Tyler Sieve Size and approximately 70% or more will pass
3 0 through a 200 mesh U.S. Standard Sieve Size.
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The milling process to obtain the above fine particles
is common knowledge in the art and need not be disclosed
herein.
5 The particulate shot coke, may have a sulfur content of
up to 8%, by weight. It is generally undesirable for the
coke utilized in the manufacture of carbon electrodes for
use in an aluminum reduction cell to have a sulfur content
of greater than about 4%.
10
The remainder of the aggregate may comprise any
particulate carbonaceous material that is suitable for
preparing carbon electrodes, including recycled anode butts,
for use in aluminum reduction cells. Such carbonaceous
15 materials are well known in the art.
Preferably, said carbonaceous material is selected from
the group consisting of sponge, needle or pitch cokes, and
recycled carbon electrode remnants.
20
It has now been discovered that a satisfactory carbon
electrode, suitable for use in an aluminum reduction cell
may be prepared from a particulate carbonaceous, aggregate,
preferably comprising more than about 5%, by weight, of a
2 5 shot coke, and more preferably said aggregate comprises from
5% to about 50%, by weight, of a shot coke.
Thus, the present invention provides a method of making
a carbon electrode, suitable for use as an anode in an
3 0 aluminum reduction cell, which comprises separating an
aggregate into different size fractions by a combination of
crushing, milling and screening whereby such an aggregate
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may comprise a mixture of a particulate shot coke, recycled
anode butts, and a particulate carbonaceous material other
than shot coke, with coal tar pitch or combination pitch at
an elevated temperature to form a paste wherein said
5 aggregate comprises a combination of butts, coarse, and fine
particles and said paste comprises up to about 90%, e.g.
about 85%, by weight, of said aggregate and from about 10 to
about 20%, e.g. 15%, by weight, of said coal tar pitch or
combination pitch; forming said paste into a solid body; and
10 baking said solid body at an elevated temperature to form
said carbon electrode.
Furthermore, it has now been discovered that in the
process of preparing electrodes of this invention, the
15 properties of the electrode can be influenced significantly
by selecting the size of the shot coke used in the
aggregate. For example, if the shot coke is added to the
coarse fraction of the aggregate, the anode density can be
improved but the coefficient of thermal expansion will be
20 negatively affected (higher). The anode air reactivity on
the other hand, will not be significantly affected when shot
coke, is added to the coarse fraction of the aggregate.
When shot coke is milled and added to the fines fraction,
25 the coefficient of thermal expansion will not be
significantly affected but no improvement in anode density
will occur. The anode air reactivity on the other hand, will
be negatively affected (increase) when the shot coke is
added to the fines fraction of the aggregate.
30
7

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BRIEF DESCRIPTION OF THE DRAWINGS
This invention will be more readily understood by
reference to the drawings.
5
Figures 1-4 refer to experiments where shot coke was
added to all aggregate fractions in the anode at different
levels, more particularly:
10 Figure 1 shows the change in air reactivity with the
percentage of shot coke in the aggregate that was used to
form the carbon anode of this invention; Figure 2 shows the
change in the coefficient of thermal expansion with the
percentage of shot coke in the aggregate that was used to
15 form the carbon anode; Figure 3 shows the change in the CO2
reactivity residue with the percentage of shot coke in the
aggregate that was used to form the carbon anode of this
invention; Figure 4 shows the change in the baked apparent
density with the percentage of shot coke in the aggregate
2 0 that was used to form the carbon anode of this invention;
Figure 5 shows the variation of baked apparent density
when shot coke was added selectively to the coarse or fines
fraction;
25
Figures 6 and 7 compare the coefficient of thermal
expansion wherein the shot coke is added selectively to the
fines or coarse fraction of the aggregate that is used to
prepare the carbon anodes of this invention; and
30
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Figure 8 shows the structure of anisotropic cokes, e.g.
needle coke and sponge coke, and isotropic cokes, e.g. shot
cokes.
5 DETAILED DESCRIPTION
In the method of the invention, the above described
aggregate is combined with a coal tar pitch binder or a
combination pitch binder.
10
Coal tar pitch is a residue produced by distillation or
heat treatment of coal tar. It is a solid at room
temperature, consists of a complex mixture of numerous
predominantly aromatic hydrocarbons and heterocyclics, and
15 exhibits a broad softening range instead of a defined
melting temperature. Petroleum pitch is a residue from heat
treatment and distillation of petroleum fractions. It is
solid at room temperature, consists of a complex mixture of
numerous predominantly aromatic and alkyl-substituted
2 0 aromatic hydrocarbons, and exhibits a broad softening range
instead of a defined melting temperature. Combination pitch
is a mixture or combination of coal tar pitch and petroleum
pitch.
25 The hydrogen aromaticity in coal tar pitch (ratio of
aromatic to total content of hydrogen atoms) varies from 0.7
to 0.9. The hydrogen aromaticity (ratio of aromatic to
total hydrogen atoms) varies between 0.3 and 0.6. The
aliphatic hydrogen atoms are typically present in alkyl
3 0 groups substituted on aromatic rings or as naphthenic
hydrogen.
9

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The aggregate utilized in the method of the present
invention comprises a mixture of fine, coarse and recycled
anode butts particles. The mesh sizes for the fine
particles are defined above. Coarse particles, which may
5 also contain recycled anode butts, will be retained on a 16
mesh Tyler screen.
The aggregate is combined and mixed with the coal tar
pitch or combination pitch. There are numerous mixing
10 schemes in the art. Any of them may be adapted for use in
the method of this invention, simply by treating the shot
coke-containing aggregate in the same way as the current
aggregate is combined with the pitch.
15 It is important that the aggregate and the pitch are
mixed together at an elevated temperature, e.g. greater than
150°C, in order to coat the particles with pitch, penetrate
the pitch and the fine particles into the internal pores of
the coarse particles and fill the interstitial aggregate
20 volume with the pitch and the fine particles.
After mixing the aggregate and the coal tar pitch for 1
to 45 minutes, e.g. from 5 to 20 minutes, a paste is formed.
25 The paste may be formed into a solid body, by methods
known in the art, e.g. pressing or vibroforming, prior to
baking to form the electrode.
The green electrode is baked at an elevated temperature
3 0 to provide a carbon electrode suitable for use in an
aluminum reduction cell. Preferably, the green electrode is,
baked at a temperature of from 1000°C to 1200°C, e.g. about
10

3502
1100° Centigrade for a time sufficient for the green
electrode to reach a temperature within the preferred range.
The baking may take place in open or closed furnaces,
5 as is well known in the art.
The method of the invention provides carbon electrodes
having characteristics including density, air permeability,
compressive strength, modulus of elasticity, thermal
10 conductivity, coefficient of thermal expansion, air
reactivity, and carboxy-reactivity which are within
acceptable ranges, for use in aluminum smelters.
In another aspect of the present invention, there is
15 provided a carbon electrode, suitable for use an anode in an
aluminum reduction cell, which comprises (a) an aggregate
comprising a mixture of particulate shot coke, and a
particulate carbonaceous material other than said shot coke,
and (b) a coal tar or combination pitch binder, wherein said
2 0 aggregate comprises a combination of coarse and fine
particles and said particulate shot coke, comprises a
majority of said coarse particulates.
In said electrode, preferably said aggregate is
2 5 prepared by screening and/or milling shot coke, and a
carbonaceous material other than said shot coke from a
delayed coker to provide a particulate mixture comprising at
least 5%, preferably about 3 0 to 4 0 percent by weight.
3 0 To this screened and/or milled aggregate may be added
from about 5 to about 2 0 percent, e.g. about 15% butts.
Thus, the aggregate utilized in the method of preparing the
11

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anodes of the invention may comprise from 5 to 60 percent,
preferably about 50% coarse, from. 10 to 50 percent,
preferably about 34% fine, and from 0 to 25% preferably, 16%
butts. Also, in said preferred aggregate the shot coke may
5 vary from 10 to 85.0, by weight, of the aggregate.
Preferably the particulate carbonaceous material in the
electrode is selected from the group consisting of sponge,
needle or pitch cokes, and recycled carbon electrode
10 remnants.
In this aspect of the present invention, the fines may
comprise shot coke, e.g., milled shot coke, or some other
particulate carbonaceous material, e.g., fine particulates
15 from the delayed coking of heavy hydrocarbon oil fractions.
Any of the above, novel electrodes or electrodes made
by the method of the present invention may be used in a
method for producing . aluminum by the molten salt
2 0 electrolysis of aluminum oxide which comprises electrolyzing
aluminum oxide dissolved in a molten salt at an elevated
temperature by passing a direct current through an anode to
a cathode disposed in said molten salt wherein said anode is
any of the above electrodes.
25
The cokes utilized in the following examples have the
properties shown in Table 1, below.
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Table 1

Coke Ni% FE% V% S% ADg/cc KVBDg/cc RDg/cc SROhm-in CO2Reac.% AirReac.% permin.
A 0.016 0.023 0.023 2.58 1.76 0.796 2.073 0.038 7.3 0.10
B 0.032 0. 023 0. 067 4.53 1.80 1.111 2.042 0. 042 4.3 0.36
Coke A is a regular delayed anode coke blend; and coke
5 B is a shot coke with a high percentage of BB's.
The characteristics of shot cokes are as follows:
• The shot cokes are significantly higher in Ni, V and
10 S.
• The shot coke has a significantly higher vibrated
bulk density (KVBD) and apparent density (AD).
• The real density (RD) of the. shot coke was
significantly lower and a specific electrical
15 resistivity significantly higher.
• The air reactivity of the shot coke and isotropic
coke is higher.
EXAMPLE 1
20
In this example, shot coke was added to two of the
aggregate size fractions - coarse and fines. Control anodes
using 100% regular delayed anode coke were prepared for
comparison.
25
A total of 5 different anode formulations were prepared at 3
different pitch levels (15.5, 16.0, and 16.5%) to give a
13

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total of 15 anodes. The mixer batch size was 9kg. Forming
was done via a laboratory hydraulic press and the anodes
were baked in lab mode baking furnace. The fines fraction
was prepared using a laboratory ring and puck mill. A
5 standard aggregate granulometry containing 50% coarse, 34%
fines and 16% butts was used for all anodes.
Table 2 below, shows the different recipes tested in
this Example 1. The control anodes are laboratory versions
10 of anodes that are used in commercial applications.
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TABLE 2

AnodeSeriesCode Coke Recipe % Shot Coke inAggregate
S1 15% Shot/85% Regular Coke 12.5
S2 25% Shot/75% Regular Coke 21.0
S3 50% Shot/50% Regular Coke 42.0
S4 100% Shot Coke 84.0
C 100% Regular Coke 0
The results are summarized below and in Figures 1 and
2. As shown:
5
• Anode air reactivities deteriorated as the percentage
of isotropic coke and shot coke increased.
• Anode coefficients of thermal expansion, or CTE's,
increased as the percentage of isotropic and shot coke
10 increased.
• Anode densities increased as the percentage of shot
coke increased.
• With up to 50% shot coke in the coke recipe, most other
anode properties were comparable to the control anodes.
15
Property data for all the lab anodes produced in this
experiment is included in Table 3, below.
15

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Table 3

Lab Shot Pitch Green Koppers TC AD ER CO2 CO2 CO2 Air Air Air AP Flex CTE
Code. % % Density BAD W/mK g/cc □Oms-m %Residue %Dust %Loss %Residue %Dust %Loss nPm MPa E*10ˆ-6
Sll 15 14.5 1.603 1.561 2.46 1.55 87.9 96.00 0.11 3.89 76.2 7.7 16.1 2.40 3.8 4.540
S12 15 15.0 1.616 1.566 2.41 1.55 89.9 95.98 0.16 3.86 85.3 7.6 16.9 2.23 3.5 4.606
S13 15 15.5 1.633 1.581 2.44 1.57 85.0 96.70 0.11 3.19 78.0 6.5 15.6 2.60 4.0 4.314
S21 25 14.5 1.618 1.576 2.16 1.56 92.9 95.71 0.22 4.07 74.0 8.3 17.7 2.60 3.7 4.604
S22 25 15.0 1.630 1.582 . 2.31 1.57 85.0 96.34 0.11 3.55 72.0 8.8 19.2 2.45 4.3 4.484
S23 25 15.5 1.642 -1.584 2.57 1,57 81.9 96.68 0.11 3.21 74.8 7.4 17.8 2.75 5.2 4.556
S31 50 14.5 1.651 1.600 2.54 1.59 84.5 96.61 0.16 3.23 70.9 7.1 22.0 2.63 4.6 4.777
S32 50 15.0 1.661 1.615 2.55 1.60 76.3 96.94 0.11 2.95 70.3 7.7 22.0 2.30 5.6 5.012
S33 50 15.5 1.666 1.619 2.6 1.60 70.5 96.69 0.11 3.21 74.0 5.6 20.4 1.82 5.7 4.897
S41 100 14.5 1.701 1.657 2.71 1.64 58.4 97.60 0.05 2.35 67.2 5.1 27.7 2.04 7.7 5.903
S42 100 15.0 1.699 1.655 1.67 1.63 .55.2 97.37 0.10 2.52 69.3 3.5 27.2 4.05 9.3 5.622
S43 100 15.5 1.707 1.649 3.01 1.63 58.0 96.60 0.10 3.30 67.5 4.7 27.8 5.42 9.5 5.895

Lab Shot Pitch Koppers TC AD ER CO2 CO2 CO2 Air Air Air AP Flex CTE
Code % % BAD W/mK g/cc □Oms-m %Residue %Dust %Loss %Residue %Dust %Loss nPm MPa E*10ˆ-6
Cl 0 15.5 1.598 2.48 1.54 72 95.57 0.11 4.32 80.5 5 14.5 2.42 5.3 4.299
C2 0 16.0 1.605 2.31 1.55 75.7 94.05 0.33 5.62 82.6 4.4 13.1 1.57 6.6 4.454
C3 0 16.5 1.609 2.34 1.55 76.2 95.77 0.05 4.17 84.5 3 12.5 1.63 5.8 4.209
5
16

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Example 2
In the experiments described in this Example 2, the
5 shot coke was concentrated in different fractions of the
aggregate. It was expected that it would be advantageous to
grind the shot coke and concentrate it in the fines fraction
to minimize the negative effects on CTE. Two different
types of pitch were also tested in this set of experiments -
10 regular coal tar pitch and a coal tar/petroleum pitch blend.
The anodes of this experiment were produced in a larger
mixer batch size (17kg/mix) and a lab scale vibroformer
instead of a hydraulic press was utilized. The anode baking
15 furnace was also larger, allowing up to 3 0 anodes to be
baked at one time. The quantity of fines required was too
large to produce in a laboratory ring and puck mill so a
70kg/hr. ball mill was used. The particle size distribution
was monitored closely to make sure it matched the size
20 distribution of the ball mill utilized in commercial
production of carbon anodes for aluminum smelting.
Fifteen different anode formulations were tested in
Example 2 at two different pitch levels giving a total of
25 thirty different mixer batches. Six lab anodes were
produced from each mixer batch giving a total of one hundred
eighty laboratory anodes. The different formulations tested
are shown in Table 2 below.
17

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TABLE 4

ANODE CODE DESCRIPTION PITCH FORMING
C41/C42 100% Regular CT Vibrate
C51/C52 100% Regular CT Press
S51/S52 25% Shot in Fines Fraction CT Vibrate
S61/S62 65% shot in Fines Fraction CT Vibrate
S71/S72 100% Shot in Fines Fraction CT Vibrate
S81/S82 40% Shot in Coarse Fraction CT Vibrate
S91/S92 75% Shot in Coarse Fraction CT Vibrate
S101/S102 75% Shot in Coarse Fraction A Vibrate
CT refers to coal tar pitch and A refers to Type A
5 pitch.
The baked anodes were tested for density, electrical
resistivity, air permeability, crush strength, flexural
strength, modulus of elasticity, fracture energy, CTE,
10 thermal conductivity, air reactivity residue and CO2
reactivity residue. Results were averaged and grouped
together, where possible, to determine general trends.
The experiments of this Example 2 showed some
15 unexpectedly good results. A summary of key results is given
below. More detailed results are included in Table 5.
• Shot coke added to the fines fraction had no effect on
density but when added to the coarse fraction, the
2 0 density increased significantly.
• shot coke additions to the fines fraction caused a
progressive deterioration in anode air reactivity.
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Anode CTE's and other mechanical properties were
unaffected.
• Air reactivities deteriorated only slightly when shot
coke was added to the coarse fraction.
5 • Anode CTE's increased almost linearly as shot coke was
added to the coarse fraction. Anode strengths also
decreased.
• Anode CO2 reactivities were good for all formulations
tested with shot coke.
19

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Table 5

AnodeCode Recipe PitchType PitchLevel GAD Stdev Shrink(%) Stdev BAD Stdev ER Stdev Air Perm Stdev Crush StDev
S51 25% S Fines CT Lo 1.542 0.012 1.34 0.39 1.534 0.006 76.1 3.5 2.83 1.34 35.5 0.2
S52 25% S Fines CT Hi 1.584 0.008 1.06 0.15 1.547 0.003 63.8 1.3 0.82 0.02 38.0 1.2
S61 65% S Fines CT Lo 1.533 0.006 1.32 0.07 1.512 0.011 74.5 3.8 4.24 1.45 32.6 0.5
S62 65% S Fines CT Hi 1.567 0.011 0.93 0.16 1.542 0.008 66.1 2.1 1.49 0.82 33.9 0.2
S71 100% S Fines CT Lo 1.555 0.008 1.28 0.14 1.539 0.004 70.0 0.7 1.57 0.26 39.3 1.2
S72 100% S Fines CT Hi 1.589 0.006 0.85 0.14 1.541 0.002 66.0 0.9 1.11 0.05 37.1 0.2
S81 40% S Coarse CT Lo 1.554 0.004 1.24 0.13 1.529 0.003 85.2 1.7 4.80 0.61 30.5 1.5
S82 40% S Coarse CT Hi 1.601 0.008 1.00 0,08 1.564 0.004 64.7 1.4 1.02 0.35 38.9 1.3
S91 75% S Coarse CT Lo 1.621 0.004 1.41 0:08 1.591 0.004 66.8 2.1 0.85 0.14 39.3 2.0
S92 75% S Coarse CT Hi 1.646 0.020 0.76 0.12 1.593 0.012 59.9 1.4 0.50 0.06 38.9 4.0
S101 , 75% S Coarse A Lo 1.629 0.005 0.96 0.14 1.588 0.003 65.5 1.5 1.51 0.80 40.9 0.2
S102 75% S Coarse A Hi 1.654 0.006 0.80 0.10 1.596 0.002 67.6 0.7 0.52 0.08 37.8 1.7
C41 Control CT Lo 1.537 0.008 1.16 0.11 1.514 0.007 74.1 3.0 4.05 2.73 32.7 1.7
C42 Control CT Hi 1.588 0.007 0.95 0.09 1.541 0.004 62.0 1.9 0.68 0.14 34.5 0.8
20

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Table 5 Continued

AnodeCode Recipe MOE Stdev Flex Stdev Frac E Stdev CTE Stdev TC Stdev ARR Stdev CO2 Stdev
S51 25% S Fines 1693.1 202.6 2.6 0.1 113.5 55.4 4.31 0.12 2.58 0.00 85.2 5.2 97.3 0.2
S52 25% S Fines 2191.7 127.3 4.8 0.2 157.6 16.7 4.25 0.04 2.70 0.12 83.3 1.5 97.3 0.3
S61 65% S Fines 1619.8 25.2 3.5 0.1 164.3 32.8 4.41 0.16 2.51 0.04 83.0 3.2 96.7 0.5
S62 65% S Fines 1827.3 108.3 4.7 0.5 184.4 7.9 4.28 0.04 2.56 0.09 80.2 8.0 97.4 0.2
S71 100% S Fines 2029.5 41.3 5.3 0.6 106.5 51.1 4.34 0.07 2.60 0.07 70.4 1.5 97.2 0.2
S72 100% S Fines 1834.4 352.0 6.6 1.0 132.1 59.5 4.36 0.14 2.67 0.22 74.5 1.4 97.6 0.3
S81 40% S Coarse 1511.5 233.2 1.6 0.2 59.6 5.4 4.59 0.16 2.31 0.06 92.2 1.7 95.6 1.5
S82 40% S Coarse 2265.6 168.9 3.6 0.3 94.3 27.1 4.58 0.01 2.78 0.05 89.1 2.9 94.8 1.8
S91 75% S Coarse 2007.0 187.5 3.3 0.0 120.9 1.0 4.94 0.09 2.70 0.02 88.1 0.5 96.2 1.0
S92 75% S Coarse 2193.5 37.7 6.7 1.9 144.3 73.9 5.19 0.11 2.97 0.24 87.9 1.3 95.6 1.0
S101 75% S Coarse 2292.9 269.2 4.3 0.8 248.1 0.5 5.09 0.15 2.72 0.03 84.2 2.7 97.7 0.0
S102 75% S Coarse 1945.2 40.4 3.4 0.5 244.6 2.7 4.94 0.10 2.62 0.06 82.0 0.1 96.6 0.9
C41 Control 1506.2 151.6 3.2 0.1 77.6 27.5 4.21 0.04 2.52 0.04 91.9 1.0 96.8 0.6
C42 Control 2171.2 62.7 6.4 0.1 203.7 34.7 4.37 0.02 2.73 0.01 93.0 0.4 96.7 0.3
21

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The results in this Example 2 show that anode
properties of the carbon anodes of this invention as
prepared with the addition of shot are dependent on how the
shot coke is added. CTE's do not increase when the coke is
5 added to the fines fraction but anode air reactivities
deteriorate. When shot cokes are added to the coarse
fraction, the CTE's increase significantly but anode air
reactivities are not as significantly affected. In
addition, there is a major advantage of adding shot coke to
10 the coarse fraction, that is an increased anode density is
obtained.
Thus, the anodes prepared according to Example 2 where
shot coke is selectively added to the coarse fraction, are
15 especially useful in a smelter which uses relatively small
anodes at lower currents ( cells are not as susceptible to thermal shock cracking as
larger anodes in higher current cells. The design of such
cells is typically quite sensitive to anode airburn,
2 0 however, due to the difficulty in being able to keep the
anodes well covered. As a result, any addition of shot coke
to the fines fraction will exacerbate anode airburn and
negatively affect cell performance.
25 EXAMPLE 3
Based on the results of Example 2, it was decided that
the density gains possible by adding shot coke to the coarse
fraction warranted additional optimization work.
30
In this experiment, the fines, content and pitch level
of shot coke added to the coarse fraction was optimized. A
22

3502
single shot coke level was selected on the basis of the
calculated anode sulfur level. At high shot coke addition
rates, anode sulfur levels increase to the point where the
smelter would exceed its SO2 emissions limit. The goal was to
5 keep the aggregate sulfur level under 3%. To stay within
this range, shot coke additions were limited to 40% of the
coarse fraction which equated to 2 0% of the total aggregate
(including butts).
10 The fines content was optimized first by preparing dry
aggregate mixes gave at different fines levels and measuring
the vibrated bulk density. A fines content of 27% yields
optimum results.
15 Pitch optimization tests were carried out at two
different butts levels (16% & 18%) . Lab anodes were baked
and tested and a formulation was selected for a plant trial.
The main objective of the plant trial was to see if full
size plant anodes could be produced with 20% shot coke
20 without production problems. It was unknown for example,
how these anodes would look (deformation and cracking) after
forming and anode baking. If the anodes were acceptable in
appearance, i.e. not chipped or cracked or otherwise
damaged, a number of such anodes would be tested in a single
25 electrolysis cell to see if thermal shock cracking would be
a problem.
Approximately sixty full size plant electrodes were
produced and tested in a single electrolysis cell. No
3 0 significant problems were found and there was no obvious
thermal shock craqking despite the higher CTE. Anode butts
23

3502
were weighed and the average butt weight was 14 7 lbs
compared to the regular anode butt weight of 146 lbs.
These positive results provided the incentive to move
5 to larger scale plant trial but there was a concern that the
low fines level made the anodes very sensitive to small
pitch level changes. Thus, a further experiment was carried
out.
10 EXAMPLE 4
Additional lab experiments were undertaken at a fines
level of 27% and 30%. From this work, the 30% fines shot
coke anodes appeared to give the best results. A plant trial
15 was then undertaken to select the optimum pitch level and to
make sure that anodes could be produced successfully on a
larger scale with minimal scrap rates.
The properties of the shot coke anodes baking were
20 better than expected. Anodes were produced at 3 pitch
levels and the optimum level appeared to be 14.4%. This was
1.4% lower than the optimum pitch level of standard
production anodes used in a representative commercial
smelting process. This represents a substantial potential
25 cost saving for the smelter since pitch is significantly
more expensive than calcined petroleum coke.
Anode densities were also better than expected. The
average density of the 14.4% pitch anodes was 1.598 g/cc
3 0 compared to a typical density of 1.555 g/cc. A sustained
density increase of this magnitude would allow the
24

3502
commercial smelting process to increase anode life in the
electrolysis cells.
No unusual problems were reported.
5
The results from this Example 4 warranted a larger
scale plant trial where anode and cell performance would be
monitored closely to determined the full potential of the
anode produced by the method of this invention.
10
These shot coke anodes were utilized in a commercial
aluminum smelting process or pots
EXAMPLE 5
15
In a larger scale plant trial 710 full scale anodes
were produced and tested in 4 closely monitored cells.
The shot coke anodes were used to run the four cells
2 0 through at least 3 full anode cycles. Thus, each cell
completely changes out a set of shot coke anodes 3 times.
This gives the cell more chance to reach steady state
conditions and performance with the different anode quality.
2 5 No thermal shock cracking or anode burn-offs occurred.
Although ' there has been hereinabove described a
specific electrode useful for molten salt electrolysis of
aluminum oxide to aluminum in accordance with the present
3 0 invention for the purpose of illustrating the manner in
which the invention may be used to advantage, it should be ,
appreciated that the invention is not limited thereto. That
25

3502
is, the present invention may suitably comprise, consist of,
or consist essentially of the recited elements. Further,
the invention illustratively disclosed herein suitably may
be practiced in the absence of any element which is not
5 specifically disclosed herein. Accordingly, any and all
modifications, variations or equivalent arrangements which
may occur to those skilled in the art, should be considered
to be within the scope of the present invention as defined
in the appended claims.
10
26

3502
WE CLAIM:
1. A method of making a carbon electrode, suitable
for use as an anode in an aluminum reduction cell, which
5 comprises mixing an aggregate of different size fractions,
comprising a mixture of particulate shot coke and a
particulate carbonaceous material other than shot coke with
coal tar pitch or combination pitch at an elevated
temperature to form a paste, and said paste comprises from
10 about 80 to about 90%, by weight, of said aggregate and from
about 10 to about 20%, by weight, of said coal tar pitch or
combination pitch wherein said aggregate comprises from
about 5 to 90%, by weight, shot coke; forming said paste
into a solid body; and baking said solid body at an elevated
15 temperature to form said carbon electrode.
2. The method of claim 1 wherein said shot coke
comprises from about 10 to 50%, by weight, of said
aggregate.
20
3 . The method of claim 1 wherein said carbonaceous
material is selected from the group consisting of sponge,
and coal tar pitch cokes, and recycled carbon anode remnants
or butts.
25
4. The method of claim 1 wherein said aggregate
wherein said aggregate comprises from about 5 to 60% of
coarse particles, 10 to 50% fine particles and from 0 to 30%
butts.
30
5. The method of claim , 4 wherein said coarse
particles comprise from 25 to 75%, by weight, of shot coke.
27

3502
6. The method of claim 4 wherein said fine particles
comprise from 25 to 75%, by weight of shot coke.
5 7. The method of claim 1 wherein said solid body is
subject to compressing or vibrating to form a green anode
prior to baking.
8. The method of claim 1 wherein said solid body is
10 baked at a temperature of above 1000° Centigrade.
9. A method of making a carbon anode for use in an
aluminum reduction cell, in which aluminum oxide is reduced
to molten aluminum metal at an elevated temperature, which
15 comprises:
(a) mixing an aggregate comprising a mixture of
particulate shot coke, prepared by screening and milling to
provide a particulate mixture comprising at least 10%, by
weight and a particulate carbonaceous material other than
2 0 shot coke, and recycled carbon anode remnants or butts, with
coal tar or combination pitches at an elevated temperature
to form a paste wherein said aggregate comprises a
combination of coarse, and fine particles and said
particulate shot coke comprises a majority of said coarse
2 5 particles,, and said paste comprises from about 8 0 to about
90%, by weight, of said aggregate and from about 10 to about
20%, by weight, of said coal tar or combination pitches;
(b) forming said paste into a solid body; (c)
subjecting said solid body to compression or vibration to
3 0 form a green anode; and (d) baking said green anode at an
elevated temperature of greater then 1000° Centigrade ,to
form said carbon electrode.
28

3502
10. The product of claim 1.
11. The product of claim 9.
5
12. A carbon electrode, suitable for use as an anode
in an aluminum reduction cell, which comprises (a) an
aggregate comprising a mixture of particulate shot coke and
a particulate carbonaceous material other than shot coke,
10 and (b) a coal tar pitch or combination pitch binder,
wherein said aggregate comprises a combination of butts,
coarse, and fine particles and said particulate shot coke
comprises a majority of said fine particulates.
15 13. A method for producing aluminum by the molten salt
electrolysis of aluminum oxide which comprises electrolyzing
aluminum oxide dissolved in a molten salt at an elevated
temperature by passing a direct, current through an anode to
a cathode disposed in said molten salt wherein said anode is
20 the product of claim 1.
14. A method of making a carbon electrode, suitable
for use as an anode in an aluminum reduction cell, which
comprises mixing an aggregate, comprising a mixture of
25 particulate shot coke, and a particulate carbonaceous
material other than shot coke with coal tar pitch or
combination pitch at an elevated temperature to form a paste
wherein said aggregate comprises a combination of butts,
coarse and fine particles wherein said particulate shot coke
30 comprises more than 5%, by weight, of said aggregate, and
said paste comprises from about 80 to about 90%, by weight,
of said aggregate and from about 10 to about 20%, by weight,
29

3502
of said coal tar pitch or combination pitch; forming said
paste into a solid body; and baking said solid body at an
elevated temperature to form said carbon electrode.
30
Dated this 5th day of April. 2007.

The present invention provides a method of making a
carbon electrode, suitable for use as an anode in an
aluminum reduction cell, which comprises mixing an
aggregate, comprising a mixture of particulate shot coke,
and a particulate carbonaceous material other than shot coke
with coal tar pitch or petroleum pitch or a combination of
these pitches at an elevated temperature to form a paste
wherein said aggregate comprises a combination of butts,
coarse, and fine particles and said particulate shot coke
may comprise a majority of said coarse particles or fine
particles, and said paste comprises from about 80 to about
90%, by weight, of said aggregate and from about 10 to about
20%, by weight, of said pitch; forming said paste into a
solid body; and baking said solid body at an elevated
temperature to form said carbon electrode.

Documents:

http://ipindiaonline.gov.in/patentsearch/GrantedSearch/viewdoc.aspx?id=4t5D7XgCD9RdEQSnkPFyZQ==&loc=wDBSZCsAt7zoiVrqcFJsRw==

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Patent Number

270493

Indian Patent Application Number

1205/KOLNP/2007

PG Journal Number

01/2016

Publication Date

01-Jan-2016

Grant Date

28-Dec-2015

Date of Filing

05-Apr-2007

Name of Patentee

CII CARBON LLC

Applicant Address

2021 LAKESHORE DRIVE, SUITE 200, NEW ORLEANS, LA

Inventors:

#	Inventor's Name	Inventor's Address
1	VOGT, M, FRANZ	2021 LAKESHORE DRIVE, SUITE 200, NEW ORLEANS, LA 70122,
2	EDWARDS, LESLIE, C	2021 LAKESHORE DRIVE, SUITE 200, NEW ORLEANS, LA 70122
3	LOVE, RICHARD, O	P.O. BOX 98, ROUTE 2, SOUTH RAVENSWOOD WV 26164
4	ROSS, J ANTHONY	P.O. BOX 98, ROUTE 2, SOUTH RAVENSWOOD WV 26164
5	MORGAN, WILLIAM, ROGERS, JR.	1627 STATE ROUTE 271N, POST OFFICE BOX 500 HAWESVILLE, KY 42348

PCT International Classification Number

N/A

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	11/540,419	2006-09-29	U.S.A.