WO2000066513A1

WO2000066513A1 - Needle coke for graphite electrode and method for production thereof

Info

Publication number: WO2000066513A1
Application number: PCT/JP2000/002805
Authority: WO
Inventors: Takayuki Kawarada; Yoichi Kawano
Original assignee: Nippon Steel Chemical Co., Ltd.
Priority date: 1999-04-30
Filing date: 2000-04-28
Publication date: 2000-11-09
Also published as: JP2001011471A

Abstract

A needle coke for a graphite electrode, characterized as containing, in the coke, one or more metal components selected from among magnesium, aluminum, titanium, cobalt, manganese, sodium, and nickel, or an oxide or the like of the metal in an amount of 0.1 to 15 wt.% as an ash content; a method for producing a needle coke for a graphite electrode, characterized in that the method comprises making a solution of a compound of a metal selected from among magnesium, aluminum, titanium, cobalt, manganese, sodium, and nickel, which compound is capable of forming a metal component, an oxide of the metal component or the like by the heating with a coke, to adhere directly to the surface of a coke prior to the mixing with a binder pitch, and subjecting the coke with the compound to a heat treatment at 300 to 1500 °C, to thereby produce a needle coke having, adhered on the surface thereof, 0.1 to 15 wt.% of one or more metal components, metal oxides or the like.

Description

Description Needle coke for graphite electrode and method for producing the same

The present invention relates to a needle coke for a graphite electrode and a method for producing the same, and more particularly, to a needle coke with less puffing in a graphitization step of electrode production and a method for producing the same. Background art

Artificial graphite electrodes are produced by pulverizing coal-based coke or petroleum-based coke, adjusting it to a certain particle size distribution, kneading it with binder pitch, extruding, firing, impregnating, secondary firing, and graphitizing. Graphitization is a process of heat treatment at about 300 ° C, and is generally performed using an LWG furnace (direct energization type). However, when graphitized in this LWG furnace, the rate of temperature rise is high, the gas generation rate is high, and an abnormal expansion phenomenon called puffing is likely to occur. Puffing not only lowers the density of the electrode, but also may damage the electrode in severe cases.Therefore, a puffing inhibitor that suppresses this puffing has been required and a low puffing needle coat has been required. Was.

As the puffing inhibitor, it is thought that puffing is caused by the desorption of sulfur at a temperature of 170 to 200 ° C, at which graphitization begins, so the sulfur is trapped and iron sulfide is trapped. The desorption timing is shifted to the decomposition temperature of such compounds as iron oxide (Japanese Patent Application Laid-Open No. 55-110190) and nickels (Japanese Patent Application Laid-Open No. Japanese Patent Application Laid-Open No. 60-190491) and titanium oxide (Japanese Unexamined Patent Application Publication No. 2-51409) have been proposed and implemented.

Also disclosed is a method using iron sulfate or iron nitrate which is soluble in water or alcohol. However, it was added at the same time when the binder pitch and coke were kneaded. These methods have different effects depending on the type of raw coke, such as the fact that coal-based coke has only a slight effect.In addition, moisture or gas is generated from the inhibitor impregnated in coke, causing defects in the electrodes. There was a problem that the strength of the electrode was reduced.

In addition, as a method for producing a low-puffing needle coater, a pitch from which quinoline-insoluble matter has been removed is used to remove nitrogen or sulfur content in the raw material pitch, which is a cause of puffing, using a hydrogenation catalyst. A method of coking after hydrogenation is described below (JP-A-59-122585).

—On the other hand, after performing the first stage calcination of raw coat at a temperature lower than the normal calcination temperature, for example, around 800 ° C, it is cooled once, and then re-exposed to 1200 to 150 ° C. A method of performing the second stage calcination in the temperature range of C has also been proposed (Japanese Patent Application Laid-Open No. 53-38001).

However, these low-puffing needle cokes have difficulty in economy in any case, and have not been put to practical use, or have problems such as L which cannot always obtain a sufficient puffing reduction effect. There is.

Accordingly, in view of the above situation, an object of the present invention is to reduce the profiling of a needle coke without increasing the cost of manufacturing a needle coat, and to improve the production yield and characteristics of a graphite electrode. And a method for producing the same. Disclosure of the invention

The present inventors have conducted intensive studies in order to solve the above-mentioned problems, and as a result, before kneading the metal compound used as the puffing inhibitor with the binder-pitch etc., directly adhere it to the coke surface in a solution state in advance and heat By processing, it overcomes the drawbacks of conventional inhibitors and finds that the effect of suppressing puffing increases, The present invention has been completed.

That is, the twenty-first coke for a graphite electrode of the present invention contains, in the coke, one or more metal components or metals selected from magnesium, aluminum, titanium, konole, manganese, sodium, and nickel. It is characterized by containing 0.1 to 15% by weight of oxides and the like as ash content.

Further, as the production method of the present invention, the coke before kneading with the binder pitch is reacted or decomposed by heat treatment with coke to produce a metal component or an oxide of the metal component, magnesium, aluminum, A metal compound selected from titanium, cobalt, manganese, sodium, and nickel is directly adhered to the surface in a solution state, and after heat-treating at 300 to 150 ° C, one or more It is characterized in that it is attached to a 0.1 to 15 wt% core as a metal component or metal oxide.

It is advantageous that the metal compound is at least one salt selected from the group consisting of magnesium sulfate, aluminum sulfate, titanium sulfate, covanolate sulfate, manganese sulfate, sodium chloride, sodium hydroxide, and Nigel sulfate. . BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described in detail.

The coke used for the production of the 21 dollar coke for the graphite electrode of the present invention is a raw coke produced by a delayed coking method using either one or both of a petroleum-based or coal-based heavy oil as a raw material. Use needle coke obtained by calcining one 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 complex oxides) of the metal components, etc. After adhering to the surface of the needle coat, heat treatment is performed at 300 to 150 ° C. Therefore, the metal compound that becomes a puffing inhibitor may be attached to the needle coat as an aqueous solution, or if it does not dissolve in water, it may be dissolved. The agent may be dissolved in a volatile liquid such as alcohol or benzene and then adhered to the coater.

Specific puffing inhibitors are selected from the group consisting of magnesium sulfate, aluminum sulfate, titanium sulfate, cobalt sulfate, manganese sulfate, sodium chloride, sodium hydroxide and sodium sulfate that are easily soluble in water. It is desirable to use at least one of them. What is important here is that these metal compounds are directly adhered to $ 21 coke and then heat-treated at 300 to 150 ° C in advance. The effect of the present invention is small even if it is added in the form of a metal oxide at the time of kneading, or if a compound that changes to a metal oxide by heating as described above is added.

In the present invention, after the compound which reacts or decomposes by heating to generate one or more metal components or an oxide of the metal component, etc., is directly adhered to the surface of the needle coke in the form of a solution, the content of 300 to 100 After heating at 500 ° C., binder pitch is kneaded with the raw material coke, and if necessary, a known puffing inhibitor such as iron oxide may be further added. 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 subjected to heat treatment at 300 to 150 ° C. to remove water of crystallization of the attached compound and to remove the compound from one or more metal oxides. Change to If the water of crystallization is not removed by heat treatment or if it is not converted into a metal oxide, not only will the compound generate moisture during firing in the electrode manufacturing process, causing defects in the electrodes, but also the compound will decompose during firing, Gas is generated and the bulk density of the electrode decreases. For this reason, the strength of the electrode is insufficient, and the electrode may be damaged when used in an electric furnace.

Therefore, by previously performing a heat treatment at 300 ° C. or more, moisture and generated gas from the metal compound at the time of firing the electrode are removed, and these problems are solved. When the heat treatment temperature is lower than 300 ° C., water of crystallization of the compound is hard to be desorbed. The temperature is preferably at least o ° C, more preferably at least 500 ° C so that the compound reacts with oxygen in the air or decomposes itself. On the other hand, when the temperature exceeds 150 ° C, graphitization of the $ 21 coat begins during the heat treatment of the compound, and it is difficult to effectively suppress puffing. Preferably, there is. The amount of the metal compound adhering to the coke is 0.1 to 15% by weight, more preferably 0.5 to 3% by weight, as an ash content (metal component or metal oxide, etc.). . If the amount is outside the above range and the amount is insufficient, the effect of reducing the puffing is not practically sufficient, while if the amount is excessive, the effect of increasing the amount becomes insignificant, and the remaining ash content causes the electrode product to lose its effect. Has an unfavorable effect.

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

When a graphite electrode is manufactured using the needle coke obtained by the above method, an ordinary method can be applied. That is, needle coke shrinkage, pulverization, sieving, particle size adjustment, kneading (kneading), extrusion, primary firing, impregnation, secondary firing, and then graphitization. Iron oxide, which is usually used as a puffing inhibitor during kneading (kneading), may be omitted from use, but if used, a further effect of reducing puffing can be obtained, so that the required quality can be reduced. The selection may be made appropriately in consideration of economic efficiency. Example

Hereinafter, the content of the present invention will be described with reference to specific examples and comparative examples. It is not limited in any way by this embodiment.

The methods for measuring puffing, graphitized bulk density (bulk density: BD) and ash used in the examples are shown below.

(1) Puffing measurement method

After crushing the coke, adjust the particle size (8-16 mesh 40%, 48-200 mesh 35%, 200 mesh or less 25%) and knead at 160 ° C with binder pitch 30% (outside split) for 20 minutes. This is molded into a size of 2 Omm0 X 100 mm. The molded test piece is fired to 900 ° C in a firing furnace, impregnated with the impregnated pitch, and fired again at 900 ° C for 2 hours. This was used as a sample for the puffing measurement. In the puffing measurement, the temperature is raised up to 2500 ° C at a heating rate of 10 ° CZmin, and the maximum elongation from 1500 ° C to 2500 ° C is expressed.

(2) Measurement method of graphitized bulk density (BD)

Calculate the volume from the diameter and length of the graphitized test piece, measure the weight, and divide the weight by the volume to calculate the bulk density (BD).

(3) Ash content measurement method

After adding the metal compound, the heat-treated coke is reduced and then powdered to 60 mesh or less to obtain an average sample. Weigh at least about lg of sample into a pre-weighed magnetic dish. Keep the sample at 800 ° C in a matsufur furnace (furnace door slightly open so that it is in 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. In the same manner, the ash content of only coke without additive was also calculated, and the amount of metal oxides and the like attached to the coke was calculated from the difference between the former and the latter. Example 1

We used $ 21 coke obtained by calcining raw coke produced by delayed coking using coal-based heavy oil as a raw material. To 3 kg of the calcined needle coke was added 7.5 g of a 6.1% by weight aqueous solution of magnesium sulfate, left for 30 minutes, dried at 150 ° C, and then further dried at 900 ° C. Heat-treated with C. Table 1 shows the results of measuring the puffing and graphitized bulk density. Examples 2 to 4

The needle coke obtained by calcining the raw coke obtained in Example 1 was used. To a 3 kg of the calcined needle coke was added 700 g of a 3.4% by weight aqueous solution of aluminum sulfate (Example 2), and 7.50 g of a 3.5% by weight aqueous solution of nickel sulfate was added. (Example 3), 750 g of an aqueous solution of titanium sulfate having a concentration of 3.0% by weight was added (Example 4), left for 30 minutes, dried at 150 ° C., and then further dried at 90 ° C. Heat treatment was performed at 0 ° C. Table 1 shows the results of measuring the puffing and graphitized bulk density.

Example 5

We used 21 dollar coke obtained by calcining raw coke produced by the delayed coking method using coal-based heavy oil as a raw material. To 3 kg of the calcined needle coke was added 75 g of a 3.4% by weight aqueous solution of aluminum sulfate, left for 30 minutes, dried at 150 ° C, and then further dried at 900 ° C. Heat treatment was performed at ° C. In an electrode preparation method according to a standard method using this as a raw coke, an electrode was prepared after adding 1 part by weight of iron oxide to 100 parts by weight of coke at the time of kneading the binder pitch. Table 1 shows the results of measuring the puffing and the graphitized bulk density. Examples 6 to 9 We used $ 21 coke obtained by calcining raw coke produced by delayed coking using coal-based heavy oil as a raw material. To 3 kg of the calcined $ 21 coke, 3.75 g of a 3.75 wt% aqueous solution of cobalt sulfate was added (Example 6), and 7.55 g of a 3.4 wt% aqueous solution of manganese sulfate were added. Addition (Example 7), addition of 750 g of a 2.0% by weight aqueous sodium chloride solution (Example 8), addition of 750 g of a 1.3% by weight aqueous sodium hydroxide solution (Example 9) Then, each was left for 30 minutes, dried at 150 ° C., and further heat-treated at 900 ° C. Table 1 shows the results of measuring the puffing and graphitized bulk density. Comparative Examples 1-3

In a conventional electrode adjustment 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 kneading of binder pitch (Comparative Example 1). , No additive (Comparative Example 2), and 3.5 parts by weight of iron sulfate (Comparative Example 3), and then an electrode was prepared. Table 1 shows the results of measuring the puffing and graphitized bulk density. Comparative Example 4

Needle coke obtained by calcining raw coke produced by the delayed coking method using coal-based heavy oil as a raw material was used. To 3 kg of the calcined needle coat was added 75 g of a 3.2% by weight aqueous copper sulfate solution, left for 30 minutes, dried at 150 ° C., and then further dried at 900 ° C. Heat treatment was performed at ° C. Table 1 shows the results of measuring the puffing and graphitized bulk density. Example 10

Needle coke obtained by calcining raw coke produced by the delayed coking method using petroleum heavy oil as a raw material was used. 3 Kg of calcined needle coke 3. 750 g of a 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 1 shows the results of measuring the puffing and graphitized bulk density. Comparative Example 5

In an ordinary method for preparing an electrode using petroleum calcined needle coke not according to the present invention, the electrode was prepared without kneading iron oxide at the time of kneading the binder pitch. Table 1 shows the results of measuring the puffing and graphitized bulk density.

Table 1 (Continued) Difficult 5 5 6 6 7 8 Needle Coal Coal Coal Coal Lime Thread Yield Aluminum sulfate Cobalt sulfate Manganese sulfate Sodium chloride Coke 100 parts by weight 1.2 1.0 Amount per 2 1.8 (%)

[Ash content]

Puffy added during kneading

Nginhibitor type Iron oxide None None None and coke 100 weight 1 weight part

Addition amount per part

Puffing 0.90 1.05 1.09 L. 19 Graphitized BD 1.584 1.596 1.568 1.536 (Continued)

Table 1 (continued)

As is evident from Table 1, the puffing of each of the examples of the present invention is significantly improved as compared with the comparative examples corresponding to the respective coal-based and petroleum-based ones. In addition, according to Comparative Example 4, when copper sulfate was used, puffing was not significantly improved, indicating that only the specific salts (such as magnesium sulfate) of the present invention were effective. Industrial applicability

The needle coke of the present invention, which is obtained by adhering a compound that generates one or more metal oxides by heating to the surface of the needle coke and heat-treated at 300 to 150 ° C., is a graphite in the electrode manufacturing process. It can be used for the production of graphite electrodes that can effectively suppress puffing during the carbonization process, have a high bulk specific gravity (BD) after graphitization, have excellent strength characteristics, and sufficiently satisfy the required characteristics in production and quality. It can increase electrode yield, improve product characteristics, and provide significant industrial benefits.

Claims

The scope of the claims

1. One or more metal components or metal oxides selected from magnesium, aluminum, titanium, ruthe, manganese, sodium and nickel in the coke are 0.115% by weight as ash. Dolks for graphite electrodes, characterized by containing.

2. Magnesium, Aluminum, Titanium, Noreto, Manganese, Sodium, and the like before kneading with binder pitch, react or decompose by heat treatment with coke to produce metal components or oxides of metal components. A metal compound selected from Nigel is attached in a solution state to the surface of the matrix directly and heat-treated at 300 ° C. at a temperature of 300 ° C., and then 0 or more as one or more metal components or metal oxides, etc. A method for producing a doltas for a graphite electrode, wherein the doltas is attached to a 115 wt% core.

3. The method according to claim 2, wherein the metal compound is at least one salt selected from the group consisting of magnesium sulfate, aluminum sulfate, titanium sulfate, cobalt sulfate, manganese sulfate, sodium chloride, sodium hydroxide and nigel sulfate. Method for manufacturing doltas for graphite electrodes.