JPH0759708B2 - Method for producing coke for molded graphite - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a coke for a graphite molded body, and more specifically to a graphite molded body having good thermal shock resistance and suppressed irreversible expansion. The present invention relates to a method for producing a coke for a graphite molded body, which gives:

(Prior Art) As a coke for a graphite molded body, which is a raw material for a graphite molded body such as a graphite electrode, coke obtained by coking a heavy hydrocarbon raw material has been conventionally obtained by a delayed coking method industrially. Although coke is generally used, the coke thus obtained is generally called raw coke and contains a few% of volatile matter. This raw coke is usually used in the range of 1000 to 1500 in order to adjust the physical properties such as volatile content, true specific gravity and porosity required for the coke for a graphite molded body.
It is calcined in the temperature range of ℃ to obtain a coke for a graphite compact, which is then crushed, the particle size is adjusted, and then an appropriate amount of a binder is added to form a coke, which is then calcined and graphitized. A graphite molded body is manufactured by performing the treatment.

There is an artificial graphite electrode as a typical example of the graphite molded body manufactured in this way, but in the artificial graphite electrode,
In recent years, it has been required that the thermal shock resistance is good, that is, the coefficient of thermal expansion (CTE) is extremely low, as the conditions for using the electrodes become severer. In order to satisfy such characteristics, the raw material aggregate for the artificial graphite electrode is required. The coke for a graphite molded body, which is the above, has also been required to have a so-called needle-like structure or a developed flow structure.

On the other hand, also in the method of manufacturing the artificial graphite electrode, the power consumption is reduced by rapidly graphitizing the graphitization process that consumes a large amount of power from the viewpoint of energy saving.

(Problems to be solved by the invention) However, in such a graphitization step, particularly at a temperature of 1500 ° C. or higher, a rapid irreversible expansion, so-called puffing, often occurs during the treatment step, but especially in rapid graphitization. This tendency is remarkable, which causes problems such as reduction in product yield.

The cause of the fluffing is that heteroatoms such as sulfur in the coke are abruptly dissipated during the graphitization process. Since there is a tendency for padding to occur during the oxidization process, it is presumed that it is not solely dependent on the content of sulfur, etc., but that it has a close relationship with the coke structure of the raw material aggregate, but it has not yet been fully clarified. It has not been done.

(Means for Solving Problems) As a result of intensive investigations by the present inventors for the purpose of preventing or reducing such a hatching phenomenon, as a result of the occurrence mechanism of this phenomenon, regardless of the mechanism of occurrence of this phenomenon, a specific problem was observed in the production of coke for a graphite compact. The present inventors have found that it is possible to suppress the occurrence of puffing by carrying out stepwise heat treatment, especially in the case of coke having a well developed needle-like structure, and have reached the present invention.

That is, an object of the present invention is to obtain a coke for graphite molding which has a well-developed needle-like structure and which reduces the occurrence of puffing in the graphitization process. The object is to coke a carbonaceous raw material. 1,50 raw coke obtained
This is achieved by calcining at a temperature of 0 to 2,000 ° C., and then again subjecting the obtained calcined coke to a heat treatment at a temperature of 400 to 1000 ° C. in an oxidizing atmosphere, and the present invention will be described in detail below.

The carbonaceous raw material used in the present invention is a hydrocarbon substance containing a condensed cyclic aromatic compound, and specifically, coal tar, coal tar pitch, coal liquefaction, oil gas tar, petroleum tar or a mixture thereof. Etc., but from the viewpoint of operability and the like, coal tar and soft coal tar pitch are preferable.

Since these carbonaceous raw materials generally contain a quinoline insoluble matter (QI), it is desirable to remove the QI in advance by treating with a specific solvent as shown in, for example, JP-A-52-28501. .

Such carbonaceous raw material is coked in a delayed coker according to a conventional method. For example, the carbonaceous raw material and recycled oil are preheated to about 450 to 550 ° C.,
This is fed to a coke drum, and coking is performed at that temperature for 12 to 36 hours to obtain raw coke. The raw coke obtained usually contains 5-8% volatiles. The raw coke thus obtained is then calcined in a rotary kiln, rotary hearth or the like by a conventional method.

The calcination is usually performed at a temperature of 1000 to 1500 ° C., but in the present invention, first, a temperature range higher than the normal calcination temperature, for example, 1500
~ 2000 ° C for 0.1-3 hours, preferably 1650-2000
It is important to calcine at a temperature of ℃ for 0.5 to 2 hours.

Although the content of volatile substances such as sulfur compounds and nitrogen compounds in the coke can be reduced by calcining above this specific temperature, it may lead to a decrease in the bending strength of the graphite molded product that is the product. The calcined coke obtained by the above calcining is again in an oxidizing atmosphere at a temperature of 400 to 1000 ° C., preferably 600 to 800 ° C. for 1 to 20 hours, preferably 2 to
Heat treatment for 6 hours.

The oxidizing atmosphere is not particularly limited as long as it is a compound that oxidizes the calcined coke, such as oxygen, but it is preferably carried out in air for operation.

The heat treatment in an oxidizing atmosphere can be performed in either a flow system or a closed system. In the closed system, air or the like is previously supplied to the heat treatment zone to perform the heat treatment.
From the viewpoint of equipment and operation, it is preferable to perform the heat treatment while supplying air or the like to the heat treatment zone continuously or intermittently, and further to make the oxygen concentration in the gas phase in the heat treatment zone uniform. It is preferable to supply air or the like.

It is industrially preferable to use a furnace such as a rotary kiln or a multi-story furnace as the heating furnace, and the heat treatment may be performed in a reaction zone independent of the calcination treatment zone, but the thermal atmosphere in the calcination treatment is used. However, the heat treatment may be performed subsequent to the calcination treatment.

The obtained coke for a graphite molded body was crushed, the particle size was adjusted, and the mixture was mixed and kneaded with a binder to perform molding.
By firing at a temperature of 0 to 1000 ° C. and further performing graphitization treatment in a temperature range of 2500 to 3000 ° C., a graphite compact having good thermal shock resistance can be obtained.

(Effect) When the coke for a graphite molded body obtained by the method of the present invention is used, it is possible to effectively suppress the puffing that occurs in the graphitization step, but although the cause is not fully clear, calcination It is performed at a temperature higher than the normal calcination temperature, and the calcinated coke obtained is again subjected to 400
By heat-treating again at a temperature of ~ 1000 ° C, the content of volatile substances is reduced, and the fine pores present in the calcined coke are increased compared to before reheat treatment. It is presumed that it has a buffering effect on the generated gas or generated stress, suppresses the occurrence of puffing, enhances the bond between the coke and the binder, and increases the bending strength of the graphite molded product as a product.

In any case, the occurrence of padding is usually a low level of about several percent, but the graphite molded product as a product is manufactured through time and the number of steps and consumes high energy, so the loss rate is extremely serious. Since it is possible to improve it even a little, a great industrial advantage is realized, and therefore, the method of the present invention capable of suppressing the puffing and thus forming a high-performance graphite molded body is an advance in the state of the art. It greatly contributes to.

(Examples) Hereinafter, the present invention will be described more specifically with reference to Examples.
The present invention is not limited to the following examples unless it exceeds the gist.

Example 1 Coal tar and kerosene were mixed at a ratio of 1: 0.4-0.6 to 260-2.
The quinoline insoluble matter was allowed to settle and settle under heating at 90 ° C to prepare a raw material. Next, the above raw materials and recycled oil are preheated to about 450 to 550 ° C. and put in a coke drum, and coke is obtained for 24 hours to obtain raw coke, which is calcined for 15 minutes at 1650 ° C. under argon flow in an electric furnace. Done,
A calcined coke was produced. The calcined coke thus obtained was again heat-treated in an air atmosphere at 600 ° C. for 3 hours to produce a coke for a graphite compact.

This coke for a graphite compact was crushed and mixed with 70% of powder particles larger than 200mesh and 30% of powder particles smaller than 200mesh and mixed with 100 parts of the binder pitch (softening point 92
℃) was mixed with 30 parts, heated and bonded, then molded and fired at 1000 ℃ from the test piece (80 m long)
m, diameter 20 mm) was sampled and graphitized at 2700 ° C. for 30 minutes. The bending strength was measured after graphitization. The results are shown in Table 1.

Comparative Examples 1-2 Coke obtained in the same manner as in Example 1 was calcined in an electric furnace under argon flow under the conditions shown in Table 1, and was carried out without heat treatment in an oxidizing atmosphere. It was crushed, molded, fired and graphitized in the same manner as in Example 1. The results are shown in the table.

Claims (1)

[Claims] 1. Raw coke obtained by coking a carbonaceous raw material is calcined at a temperature of 1,500 to 2,000 ° C., and then the calcined coke obtained is heated again at a temperature of 400 to 1,000 ° C. in an oxidizing atmosphere. A method for producing a coke for a graphite molded body, which comprises treating the coke.