JP2001011471A - Needle coke for graphite electrode and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a needle coke for graphite electrodes and its production method which inhibit puffing of the needle coke and improve the yield and the properties of the graphite electrodes. SOLUTION: A needle coke for graphite electrodes contains 0.1-15 wt.%, based on 100 pts.wt. coke, at least one metallic component selected from magnesium, aluminum, titanium, cobalt, manganese, sodium, and nickel, its oxide or the like as the ash content. A method for producing a needle coke for graphite electrodes comprises directly adding a compound of a metal selected from magnesium, aluminum, titanium, cobalt, manganese, sodium, and nickel which produces a metallic component, its oxide or the like by heat treatment with coke to effect reaction or decomposition on to the surface of coke in a molten state before kneading with binder pitch, subjecting the resulting coke to heat treatment at 300-1,500 deg.C to allow at least one metallic component or metal oxide to attach to the coke in an amount of 0.1-15 wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a needle coke for a graphite electrode and a method for producing the same.

[0002]

2. Description of the Related Art Artificial graphite electrodes are obtained by pulverizing coal-based coke or petroleum-based coke, adjusting the particle size distribution to a predetermined value, kneading with a binder pitch, extruding, firing, impregnating, secondary firing, and graphitizing. To manufacture. Graphitization is about 300
This is a step of performing heat treatment at 0 ° C., and a method using an LWG furnace (direct energization type) is generally used. However, this LWG
When graphitized in a furnace, the rate of temperature rise is high, so the rate of gas generation is high, and an abnormal expansion phenomenon called puffing tends to occur. Puffing not only lowers the density of the electrode, but can also damage the electrode in extreme cases,
The development of a puffing inhibitor that suppresses this puffing and a low-puffing needle coke have been demanded, and development has been carried out.

As a puffing inhibitor, it is considered that puffing occurs at a temperature of 1700 to 2000 ° C. at which graphitization starts, and sulfur is desorbed. Therefore, sulfur is trapped to form a compound such as iron sulfide, and its decomposition temperature is reduced. Iron oxide (Japanese Patent Application Laid-Open No. 55-110190), nickels (Japanese Patent Application Laid-Open No. 60-190491), and titanium oxide (Japanese Patent Application Laid-Open No. 2-51409) are proposed as compounds which shift the desorption timing up to this point. Has been implemented.

Further, iron sulfate soluble in water or alcohol,
Although a method using iron nitrate is also disclosed, it was added simultaneously at the stage of kneading binder pitch and coke. However, these methods have different effects depending on the type of raw coke, such as the fact that coal-based coke has only a small effect.In addition, moisture or gas is generated from the inhibitor impregnated in coke, causing defects in the electrode, and the strength of the electrode is reduced. There was a problem that lowering.

[0005] In addition, as a method for producing low-puffing needle coke, pitch from which quinoline-insoluble components have been removed to remove nitrogen or sulfur in the raw material pitch, which is a cause of puffing, is used as a hydrogenation catalyst. A method of coking after hydrogenation and production in the presence is disclosed (JP-A-59-122585). On the other hand, after performing the first stage calcination of the raw coke at a temperature lower than the normal calcination temperature, for example, around 800 ° C., it is once cooled and then again calcined in the temperature range of 1200 to 1500 ° C. (Japanese Patent Application Laid-Open No. 53-358)
No. 01).

[0006]

However, these low puffing needle cokes are not economical in any case, and have not been put to practical use.
There is a problem that a sufficient puffing reduction effect cannot always be obtained. Therefore, from the present situation, the object of the present invention is to reduce the needle coke puffing without increasing the cost of needle coke production, and to improve the production yield and characteristics of carbon electrodes. The aim is to provide a method.

[0007]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above problems, and as a result, before kneading a metal compound used as a puffing inhibitor with a binder pitch or the like, in a solution state in advance. The present inventors have found that by directly adding to the surface of coke and performing a heat treatment, the disadvantage of the inhibitor was overcome and the effect of suppressing puffing was increased, and the present invention was completed.

That is, the needle coke for a graphite electrode of the present invention comprises one or more metal components or oxides of metal components selected from magnesium, aluminum, titanium, cobalt, manganese, sodium and nickel in the coke. Etc. are contained in an amount of 0.1 to 15% by weight as an ash content.

In the production method of the present invention, 100 parts by weight of coke before kneading with a binder pitch is used.
A metal compound selected from magnesium, aluminum, titanium, cobalt, manganese, sodium, and nickel, which reacts or decomposes by heat treatment with coke to produce a metal component or an oxide of the metal component, etc., directly in solution, 300 added to the surface of coke
After heat treatment at 加熱 1500 ° C., it is characterized in that it is attached to coke of 0.1 to 15% by weight as one or more metal components or metal oxides.

The above metal compounds include magnesium sulfate, aluminum sulfate, titanium sulfate, cobalt sulfate,
Advantageously, it is at least one salt selected from the group consisting of manganese sulfate, sodium chloride, sodium hydroxide, and nickel sulfate.

[0011]

Embodiments of the present invention will be described below in detail. The coke used in the method for producing a needle coke for a graphite electrode of the present invention is a needle obtained by calcining raw coke produced by a delayed coking method using any one or both of petroleum-based or coal-based heavy oil as a raw material. Use coke.

The metal compound used in the present invention is a compound which reacts or decomposes by heating to produce one or more metal components or oxides (including composite oxides) of the metal components. And then heat-treated at 300 to 1500 ° C. Therefore, the metal compound serving as a puffing inhibitor may be attached to the needle coke as an aqueous solution, or if it is not soluble in water, it is dissolved in a volatile liquid such as alcohol or benzene as a solvent and then attached to the coke. Is also good.

As a specific puffing inhibitor, at least one selected from the group consisting of magnesium sulfate, aluminum sulfate, titanium sulfate, cobalt sulfate, manganese sulfate, sodium chloride, sodium hydroxide, and nickel sulfate which is easily dissolved in water. It is desirable to use one type. What is important here is that these metal compounds are directly attached to needle coke,
It is a heat treatment at 500 ° C. in advance, and as in the prior art, it is added in the form of a metal oxide when kneading the needle coke and the binder pitch, or by adding a compound that changes to a metal oxide by heating as described above. However, the effect of the present invention is small.

In the present invention, a compound which reacts or decomposes by heating to generate one or more metal components or oxides of the metal components or the like is directly attached to the surface of the needle coke in the form of a solution, and then 300 to 1500 C. and then knead the binder pitch with the raw coke, and if necessary, further add a known puffing inhibitor such as iron oxide. In particular, the addition of iron oxide is preferable in that the effects of the present invention are further enhanced, as is clear from Examples and Comparative Examples described later.

The needle coke to which the metal compound is attached is heated at 300 to 1500 ° C. to remove water of crystallization of the attached compound and to convert the compound into one or more metal oxides. If the water of crystallization is not removed by heat treatment, or if it is not converted into a metal oxide, not only does the compound generate moisture during firing in the electrode manufacturing process, causing defects in the electrode, but also the compound decomposes during firing and gas is generated. Occurs and lowers the bulk density of the electrode. For this reason, the strength of the electrode is insufficient, and the electrode may be damaged when used in an electric furnace.

Therefore, by performing a heat treatment in advance at 300 ° C. or higher, moisture and generated gas from the metal compound at the time of firing the electrode are removed, and these problems are solved.
If the heat treatment temperature is lower than 300 ° C., the water of crystallization of the compound is less likely to be eliminated, and thus the temperature is preferably 300 ° C. or higher, more preferably 500 ° C. or higher so that the compound reacts with oxygen in the air or the compound itself is decomposed. On the other hand, when the temperature exceeds 1500 ° C., graphitization of the needle coke starts during the heat treatment of the compound, and it is difficult to effectively suppress the puffing. Therefore, the temperature is preferably 1500 ° C. or lower.

The amount of the metal compound attached to coke is
The ash content (metal component or oxide of metal component, etc.) is set at 0.
It is preferably 1 to 15% by weight, more preferably 0.5 to 3% by weight. If the amount of adhesion is insufficient outside these ranges, the effect of reducing puffing is not practically sufficient, while if the amount of adhesion is excessive, the effect of increasing the amount of addition is not remarkable and the remaining ash is not preferable on the electrode product. Affect.

The thus obtained needle coke for a graphite electrode contains magnesium, aluminum,
One or more metal components selected from titanium, manganese, cobalt, sodium, and nickel, or oxides of the metal components, etc. are contained in an amount of 0.1 to 15% by weight as an ash content. The ash content here is assumed to have been obtained by the ash measurement method described later. Although the ash content of ordinary graphite electrode needle coke is suppressed to less than 0.1% by weight, in the present invention, a metal oxide or the like having an ash content of 0.1% by weight or more is contained.

In the case of producing a graphite electrode using the needle coke obtained by the above method, a usual method can be applied. That is, reduction, pulverization, sieving, particle size adjustment, kneading (kneading), extrusion molding, primary firing, impregnation, secondary firing, and then graphitization of needle coke. In this case, when kneading (kneading), the use of iron oxide, which is usually used as a puffing inhibitor, may be omitted, but if it is used, a further effect of reducing puffing can be obtained. It may be appropriately selected in consideration of economic efficiency.

[0020]

The present invention will be described below with reference to specific examples and comparative examples, but the present invention is not limited to these examples. The methods of measuring puffing, graphitized BD and ash used in the examples are shown below.

(1) Puffing measurement method After coke is pulverized, the particle size is adjusted (8 to 16 mesh 40).
%, 48-200 mesh 35%, 200 mesh or less 25%), and knead at 160 ° C. with 30% binder pitch (external split) for 20 minutes. This is 20mmφ × 100m
m is molded. The molded test piece is fired in a firing furnace to 900 ° C., impregnated with the impregnation pitch, and fired again at 900 ° C. for 2 hours. This was used as a sample for puffing measurement. In the puffing measurement, the temperature was raised to 2500 ° C. at a rate of 10 ° C./min, and
Expressed by the maximum elongation from 00 ° C to 2500 ° C.

(2) Method of Measuring Graphitized BD The volume is calculated from the diameter and length of the test piece, the weight is measured, and the weight is divided by the volume to calculate the bulk density. (3) Ash content measurement method After adding the metal compound and reducing the heat-treated coke,
Grind to 60 mesh or less to obtain an average sample. Weigh at least about 1 g of sample into a pre-weighed magnetic dish. The sample is kept at a constant temperature in a muffle furnace at 800 ° C. (the door of the furnace is slightly opened so as to have an oxidizing atmosphere) until the sample is completely incinerated. After complete incineration, cool in a desiccator and weigh the entire dish to calculate the ash content. Further, in the same manner, the ash content of only the coke without addition was also calculated, and the adhesion amount of the metal oxide and the like to the coke was calculated from the difference between the former and the latter.

Example 1 A needle coke obtained by calcining a raw needle coke produced by a delayed coking method using coal-based heavy oil as a raw material was used. To 3 kg of the calcined needle coke, 750 g of a 6.1% by weight aqueous magnesium sulfate solution was added, left for 30 minutes, dried at 150 ° C., and further heated at 900 ° C. Table 1 shows the results of measuring the puffing and graphitized bulk density (bulk density; BD).

Examples 2-4 Needle coke obtained by calcining the raw needle coke obtained in Example 1 was used. 3 kg of the calcined needle coke was added to a 3.4% by weight aqueous solution of aluminum sulfate 75
0 g (Example 2), and 750 g of a 3.5% by weight nickel sulfate aqueous solution (Example 3), 3.0% by weight
750 g of an aqueous solution of titanium sulfate having a high concentration was added (Example 4).
Then, each was allowed to stand for 30 minutes, dried at 150 ° C., and further heated at 900 ° C. Table 1 shows the results of measuring the puffing and graphitized bulk density (bulk density; BD).

Example 5 A needle coke obtained by calcining a raw needle coke produced by a delayed coking method using coal-based heavy oil as a raw material was used. To 3 kg of the calcined needle coke, 750 g of a 3.4% by weight aqueous solution of aluminum sulfate was added, left for 30 minutes, dried at 150 ° C., and further heated at 900 ° C. In a conventional method of preparing an electrode using this as raw coke, the binder pitch was kneaded and 1 part by weight of iron oxide was added to 100 parts by weight of coke, and then the electrode was adjusted. The results of measuring the puffing and graphitized bulk density (bulk density; BD) are shown in Table 2.

Examples 6 to 9 Needle coke obtained by calcining raw needle coke produced by a delayed coking method using coal-based heavy oil as a raw material was used. To 3 kg of the calcined needle coke, 750 g of a 3.75 wt% aqueous solution of cobalt sulfate was added (Example 6), and 750 g of a 3.4 wt% aqueous solution of manganese sulfate were added (Example 7), and 2.0 wt. % Aqueous sodium chloride solution (750 g) (Example 8);
750 g of a 3% by weight aqueous sodium hydroxide solution was added (Example 9), and each was left for 30 minutes.
And then heat-treated at 900 ° C. Puffing and graphitized bulk density (bulk density; BD)
Table 2 shows Examples 6 to 8 and Table 3 shows Example 9 with respect to the measurement results.

Comparative Examples 1 to 3 In a conventional electrode preparation method using a coal-based calcined needle coke not according to the present invention, 1 part by weight of iron oxide was added to 100 parts by weight of coke during binder pitch kneading (comparative). An electrode was prepared after Example 1), no addition (Comparative Example 2), and addition of 3.5 parts by weight of iron sulfate (Comparative Example 3). Table 3 shows the results of measuring the puffing and graphitized bulk density (bulk density; BD).

Comparative Example 4 A needle coke obtained by calcining a raw needle coke produced by a delayed coking method using coal-based heavy oil as a raw material was used. To 3 kg of the calcined needle coke was added 750 g of a 3.2% by weight aqueous copper sulfate solution,
After leaving for 0 minutes, drying at 150 ° C.
Heat treatment was performed at 0 ° C. Table 4 shows the results of measuring the puffing and graphitized bulk density (bulk density; BD).

Example 10 A needle coke obtained by calcining a raw needle coke produced by a delayed coking method using petroleum heavy oil as a raw material was used. To 3 kg of the calcined needle coke, 750 g of a 3.4% by weight aqueous solution of aluminum sulfate was added, left for 30 minutes, dried at 150 ° C., and further heated at 900 ° C. Table 4 shows the results of measuring the puffing and graphitized bulk density (bulk density; BD).

Comparative Example 5 In a conventional method for preparing an electrode using a petroleum calcined needle coke not according to the present invention, the electrode was prepared without addition of iron oxide at the time of kneading the binder pitch. Puffing and graphitized bulk density (bulk density; BD)
Are shown in Table 4.

[0031]

[Table 1]

[0032]

[Table 2]

[0033]

[Table 3]

[0034]

[Table 4]

As is clear from Tables 1, 2, 3 and 4, the puffing of each embodiment of the present invention is greatly improved as compared with the corresponding coal-based and petroleum-based comparative examples. You can see that there is. According to Comparative Example 4,
When copper sulfate was used, puffing was not significantly improved, and the specific salts of the present invention (such as magnesium sulfate)
Only one is found to be effective.

[0036]

According to the present invention, a compound which produces one or more metal oxides by heating, such as at least one of magnesium sulfate, aluminum sulfate and titanium sulfate, is adhered to the surface of needle coke and heat-treated at 300 to 1500 ° C. By using needle coke, puffing in the graphitization process of the electrode manufacturing process is effectively suppressed, the bulk specific gravity (BD) after graphitization is high, the strength characteristics are excellent, and the required characteristics in manufacturing and quality are improved. A sufficiently satisfactory needle coke for a graphite electrode can be provided. In addition, the yield of the electrodes can be improved, the product characteristics can be improved, and great industrial benefits can be provided.

Continued on the front page F term (reference) 4G032 AA02 AA09 AA22 AA23 AA24 AA41 BA05 GA11 4G046 AA02 AA05 AB01 4H012 MA01 NA01 NA05 NA08

Claims (3)

[Claims] An ash content of one or more metal components or oxides of metal components selected from magnesium, aluminum, titanium, cobalt, manganese, sodium and nickel in coke is 0.1 to 15%. Needle coke for graphite electrodes characterized by containing by weight. 2. A heat treatment with coke with respect to 100 parts by weight of coke before kneading with binder pitch to react or decompose to produce a metal component or an oxide of the metal component, magnesium, aluminum, titanium, In a solution state, a metal compound selected from cobalt, manganese, sodium, and nickel is directly added to the surface of coke, and heat-treated at 300 to 1500 ° C.
0.1 or more as one or more metal components or metal oxides
A method for producing needle coke for graphite electrodes, characterized in that the coke is attached to coke of 15 to 15% by weight. 3. The metal compound, magnesium sulfate,
The method for producing a needle coke for a graphite electrode according to claim 2, wherein at least one kind of salt selected from the group consisting of aluminum sulfate, titanium sulfate, cobalt sulfate, manganese sulfate, sodium chloride, sodium hydroxide, and nickel sulfate is used. .