KR910004907B1 - Preparation for needle-like cokes - Google Patents

Abstract

A method for producing needle-like cokes from coal tars by two step heat treatment is characterized by rapid heating coal tars at 150-250 deg.C/min to 410-430 deg.C under pressure of 5-15 kg/ cm2G, maintaining it at this temperature for 2-5 hrs (1st heat treatment), heating it at 150-250 deg.C/min to 460-500 deg.C under pressure of 5-15 kg/cm2G, maintaining it at this temperature for 0.5-2 hrs (2nd heat treatment), and reducing the pressure to 3-5 kg/cm2G for 1-3 times before an end of the 2nd heat treatment. They have a good graphitization property, low thermal expanision coefficient, high electical conductivity, and high mechanical strength.

Description

Manufacturing method of needle coke

1, 2 and 3 are polarized light micrographs of the invention examples and comparative examples prepared by different primary and secondary heat treatment conditions.

The present invention provides a method for producing acicular coke used as a filler for graphite electrode production required for UHP (Ultra High Power) manufacturing of steel from coal tar, and more specifically, acicular coke to improve the production yield by two-stage heat treatment. It relates to a manufacturing method of. Needle coke has excellent graphitization property, low coefficient of thermal expansion, excellent electrical conductivity and mechanical strength, making it an essential raw material for producing high quality graphite electrodes required in harsh steelmaking conditions.

Currently, the liquid carbonization process for producing acicular coke is mainly used as a feedstock of various heavy oils of petroleum, and some coal tar is used as a feedstock.

However, when coal tar is used as a raw material, the carbonization yield is slightly higher than that of petroleum heavy oil. However, since it has higher QI (Quinoline Insoluble) content than petroleum heavy oil, it is necessary to efficiently purify it. There is this.

In general, a purification method using a solvent, a gravity precipitation method using a specific gravity difference with a QI component, a centrifugal separation method, a heat treatment method, and the like are known. In the present invention, a filtration method is used. However, when the heat treatment by a conventional liquid carbonization method after such purification treatment, the production yield of acicular coke remains at about 25wt%, and generally, when the yield is increased, the quality of the coke is deteriorated.

Conventional methods for producing acicular coke by improving the liquid carbonization process include heat treatment of petroleum-based heavy oil at 350-430 ° C. for 10-60 minutes, followed by petroleum coke production method with low thermal expansion coefficient and low sulfur containing crude oil. There is a method for producing amorphous coke and crystalline coke at the same time for the coking process, but this manufacturing method has the disadvantage of excellent thermal expansion coefficient but low yield of the coke produced.

On the other hand, in the method of manufacturing high quality coke by three-step heat treatment, high-quality coke having a thermal expansion coefficient of 1.7 × 10 ^-6 / ° C. can be produced up to 48-51 wt% by three-step heat treatment, but the first and second heat treatment times This draws up to 20 hours or more.

Therefore, the present invention is to improve the production yield by the two-step heat treatment of coal tar, anisotropic structure is developed, and to produce a good needle-like coke having a low coefficient of thermal expansion will be described in detail as follows.

That is, the present invention is a method for producing needle coke from coal tar by two-stage heat treatment, the coal tar is rapidly heated at a temperature increase rate of 150-250 ℃ / min at a pressure of 5-15 kg / cm ² G at 410-430 ℃ After the first heat treatment by maintaining for 2-5 hours, the temperature was rapidly increased at a heating rate of 150-250 ° C./min while maintaining the pressure at 5-15 kg / cm ² G, and the second heat treatment was completed at 460-500 ° C. for 0.5-2 hours. The present invention relates to a method for producing acicular coke, wherein the pressure drop of 3-5 kg / cm ² G is performed 1-3 times to promote coke anisotropic tissue development 10 to 60 minutes before.

Hereinafter, the reasons for limiting the general conditions of the present invention will be described.

In order to prepare acicular coke according to the present invention, the first heat treatment temperature is suitable for 410-430 ° C. In general, when the coal tar is pressurized heat-treated, when the temperature is lower than 410 ° C, the reaction proceeds slowly, Not only does it require a long time, but it also inhibits the coke's anisotropic tissue produced by secondary heat treatment.

In addition, the coke is produced when the heat treatment at a high temperature of more than 430 ℃ but the produced coke yield is less than about 40wt%.

Pressure can not inhibit the development of coke anisotropic tissue at high pressure, and in the case of normal pressure or low pressure, the production yield of coke can be lowered as the effective ingredient of coal tar flows out of the reaction, so to prevent 5-15kg / cm ² G The range of is preferable.

In addition, the secondary heat treatment temperature is in the range of 460-500 ℃ that can promote the coke and reaction of the primary heat treatment in the range of the control function, the heat treatment time is required for short time at high temperature, long time at low temperature, 1.5 -2 hours are preferred.

That is, if the secondary heat treatment temperature is 500 ° C. or longer or the heat treatment is performed for a long time, the primary heat treated material is rapidly decomposed or polycondensed, thereby making it difficult to control the anisotropic tissue of coke and inhibiting anisotropic tissue development or decreasing carbonization yield. The pressure is also the same as for the first heat treatment.

On the other hand, the reason for the pressure increase of 3-5kg / cm ² G 1-3 times before each reaction is finished is to forcibly release the volatiles generated in the secondary heat treatment and remain in the reaction system to the outside of the reaction system and they are discharged. This is because the effect of improving the coke's anisotropic tissue orientation can be obtained.

Example 1

Coal tar was treated in the primary and secondary heat treatment conditions of Table 1 to measure the coke structure and carbonization yield is shown in Table 1 below, and also the tissue photograph of each specimen is shown in FIG.

TABLE 1

As can be seen in FIG. 1, in the case of FIG. 1a showing the comparative example (a) in which coal tar was heated at a heating rate of 150 ° C./min under a pressure of 8 kg / cm ² G and maintained at 430 ° C. for 5 hours. In the case of FIG. 1b showing the comparative example b in which the reaction was carried out at about 550 ° C. and maintained at 550 ° C. for 5 hours and 1 hour before the end of the reaction, 5 kg / cm ² G was intensified. This lack of manufacturing yield is only 35.76wt% as shown in Table 1.

However, in the case of Fig. 1c showing Inventive Example 1 manufactured by the present invention, the anisotropic tissue development is good, and as shown in Table 1 (Inventive Example 1), the yield of coke production is also high as 56.6 wt%.

Example 2

Coal tar was treated in the first and second heat treatment conditions in Table 2 to measure the coke structure and the carbonization yield is shown in Table 2 below, and also the tissue photograph of each specimen is shown in FIG.

TABLE 2

As can be seen in FIG. 2, the tissue of Comparative Example c produced by primary heat treatment in which coal tar was heated at a heating rate of 200 ° C./min under a pressure of 8 kg / cm ² G and maintained at 470 ° C. for 5 hours. In the case of FIG. 2a, the anisotropic tissue development is good, but the production yield is only 47.9 wt% as shown in Table 2 above.

However, in the case of FIGS. 2b and c showing the tissues of Inventive Examples 2 and 3 produced by the present invention, the anisotropic tissue alignment was excellent, and as shown in Table 2, the yield of coke production was 62.2 wt. % And Inventive Example 3 were 63.1 wt%, showing a considerably higher yield than Comparative Example.

Example 3

Coal tar was treated in the first and second heat treatment conditions of Table 3 to measure the anisotropic structure, the coefficient of thermal expansion and the carbonization yield is shown in Table 3 below, and the tissue photograph for each is shown in FIG.

TABLE 3

* Coefficient of thermal expansion (CIE): Measured temperature range of 100-200 ℃ from bulk green coke

As can be seen in Figure 3, the tissue of Comparative Example d prepared by primary heat treatment in which coal tar is heated at a temperature increase rate of 250 ° C./min under a pressure of 8 kg / cm ² G and maintained at 500 ° C. for 5 hours. In the case of FIG. 3a, the anisotropic tissue development is good, but the production yield is only 40.8 wt% as shown in Table 3 above.

However, in the case of Figs. 3b and c, respectively, showing the tissues of Inventive Examples 4 and 5 produced by the present invention, the anisotropic tissue orientation is good, and as shown in Table 3, the yield of coke is 53.7 wt% (Inventive Example 4). ) And 60.4 wt% (Inventive Example 5), showing very high values.

In particular, in the coefficient of thermal expansion, Comparative Example d showed 8.8 × 10 ⁻⁷ / ° C., while Examples 4 and 5 produced by the present invention showed 1.1-1.2 × 10 ^{−7, which} was very low.

As described above, the present invention has the effect that the production yield is increased, the anisotropic structure is developed, and the fine needle-shaped coke having a low coefficient of thermal expansion can be produced.

Claims (1)

In the method for producing needle coke from coal tar by ^two- stage treatment, coal tar is rapidly heated at a heating rate of 150-250 ° C./min under a pressure of 5-15 kg / cm ² G for 2-5 hours at 410-430 ° C. After maintaining the primary heat treatment, while maintaining the pressure at 5-15kg / cm ² G, the temperature is raised rapidly at a heating rate of 150-250 ℃ / min and secondary heat treatment at 460-500 ℃ for 0.5-2 hours, the end of secondary heat treatment 10 A method for producing acicular coke, characterized in that a pressure drop of 3-5 kg / cm ² G is performed 1-3 times before -60 minutes.

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