JPS6067590A - Pitch coke - Google Patents

Abstract

PURPOSE:A pitch coke, obtained from coal tar (pitch) containing a nitrogen-containing compound as a raw material, and capable of giving graphite electrodes with a low nitrogen content, a small pore volume and a high bulk density. CONSTITUTION:A pitch coke, obtained by removing a nitrogen-containing compound from coal tar (pitch), inserting the above-mentioned raw material into a coke drum, carbonizing the raw material at 450-500 deg.C to produce raw pitch coke, burning the raw pitch coke in a rotary kiln at 1,300-1,500 deg.C for 3-48hr, and having <0.3% nitrogen content and <=0.04cc/g pore volume at <=5,000Angstrom pore radius.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to pitch coke for producing high quality electrodes. More specifically, the present invention relates to pitch coke for producing high-quality electrodes that has special properties and is produced from coal tar and/or coal tar pitch, which are raw materials containing nitrogen compounds.

Electrode coke is generally made from coal tar and/or coal tar pitch or petroleum-based heavy oil, and is heated and carbonized in a plaid coker in a temperature range of 450°C to 500°C, and contains 5 to 1zq6 of volatile carbon. Raw pituti coke or raw petroleum coke is produced, and then the raw coke is heated to +1100°C in order to remove volatile matter and increase the degree of carbonization in a roasting furnace such as a rotary kiln, shaft furnace, or rotary hearth furnace.
It is manufactured by firing at a smoking temperature in the temperature range of ~1500°C. that time.

If a nitrogen-containing compound is contained in the coal tar and/or coal tar pitch or petroleum heavy oil as a raw material, non-nitrogen will remain in the produced electrode coke.

On the other hand, graphite electrodes are made by crushing and sieving the electrode coke produced by the method described above, adjusting the particle size to an appropriate particle size, adding binder pitch for electrodes to it, kneading it, and then molding the mixture using an extrusion molding machine or press molding machine. It is manufactured by molding and then firing to make it lead-free. However, if electrode coke contains nitrogen, sulfur, etc., gases such as nitrogen and nitrogen compounds, sulfur and sulfur compounds will be generated during the graphitization process, and the gas pressure may cause cracks in the graphite electrode. It is recognized that this causes a decrease in the strength etc. of the electrode.

2- In recent years, electric steelmaking has adopted large electric furnaces to improve productivity, and in addition,
As the operation of graphite electrodes becomes more common, the graphite electrodes used are intended to improve productivity and reduce power consumption in order to reduce manufacturing costs as electricity costs rise in the production of thick, high-quality graphite electrodes.

As graphitization furnaces, direct current furnaces have been increasingly adopted in place of the conventional Acheson furnaces. In the case of a direct current furnace, compared to the Acheson furnace, the graphitization time is 172 to 173
Therefore, the temperature gradient must be increased during graphitization. As a result, the expansion of the coke during graphitization due to the generated gas pressure increases, causing cracks in the product.

Another problem is a decrease in the strength of the electrode. Therefore, requirements regarding the quality of coke for electrodes have become increasingly strict.

The present inventors investigated in detail the properties of pitch coke for producing high-grade electrodes, which is produced from coal tar and/or coal tar pitch, and found that if the pitch coke contains nitrogen, then graphite in electrode production is possible. temperature, especially from 1300°C to 800°C
In the temperature range between nitrogen gas and nitrogen compound gas (
It was discovered that the generation of cyanide, ammonia, etc.) increased, and as a result, the electrode during graphitization expanded due to the gas pressure. At the same time, it was also found that the pore volume of pitch coke plays a large role in producing graphite electrodes with high bulk density.

Based on the above, the present inventors have completed the present invention as a result of intensive research on the properties of pinch coke suitable for manufacturing high-quality electrodes. That is, the present invention.

1. Pitch coke having a nitrogen content of less than 0.3 cm and a pore volume of 0.04 cc79 or less at a pore radius of 5000 or less.2 Pinch coke is for use in high-grade electrodes.Claim 1 Pitch coke as described.

Next, the present invention will be explained in detail.

Table 1 shows the analysis values for conventional pitch coke and also compares petroleum coke.

Figure 1 also shows a fired electrode (diameter 25mrn x 100m5) using the pitch coke and petroleum coke shown in Table 1.
The graph shows the results of measuring the longitudinal expansion of the fired electrode at each temperature during the graphitization process. This shows that there is a difference in expansion depending on the nitrogen content of coke. Table 2 shows examples of elemental analysis values when raw pitch coke is smoked at various temperatures. As you can see from this table, the temperature outside nitrogen is 1300℃.
It is shown that it is dissipated in the temperature range from 1800°C to 1800°C. At the same time, an increase in pore volume is also observed.

Table 3 shows the pitch coke A and petroleum coke A shown in Table 1 in an argon atmosphere at 1300°C to 180°C.
This is an analysis value of gas generated in the temperature range of 0°C during the graphitization process. Hydrogen gas is detected regardless of the amount of nitrogen gas, but this shows that a large amount of nitrogen and nitrogen compounds are detected in coke with a relatively large amount of nitrogen gas. From these facts, especially in the graphitization process,
Nitrogen and nitrogen compound gases play a major role in the expansion of graphite electrodes during the manufacture of graphite electrodes in the temperature range of Example 6 of analytical values of coke smoked at temperature - Heating rate: 1000°C/hr Holding time: 1 hour Table 3 Analytical values of exhaust gas generated during graphitization Note 1) N compound NH30N-, etc. Note 2) S compound C08H2SC82 etc. 7- It is easy to guess what is being performed.

Figure 2 shows the smoking temperature of raw pittichoke at -200℃,
By changing the temperatures to 1400℃, 160'0℃, and 1800℃, we used smoked pitch coke with a higher nitrogen content, and the electrode (
Make a diameter of 25mm and a length of lOOmm.

The results of measuring the expansion in the longitudinal direction are shown. This figure shows that as the nitrogen content decreases, the expansion decreases. Therefore, denitrification of coke requires high-temperature smoldering.

However, if the smoldering temperature is changed for the purpose of denitrifying the coke, the pore volume of the coke will differ as described above. Figure 3 shows the results of measuring the pore volume using a mercury porosimeter when raw pitchcoke was smoked at various smoldering temperatures in an argon atmosphere to avoid the formation of pores due to oxidation.

The horizontal axis represents the radius of the pores in the coke, and the vertical axis represents the cumulative volume of those pores. As shown in Figure 3, the pore radius of coke smoked at high temperature is 50.
It can be seen that the number of pores below 00X is increasing. Therefore, the bulk specific gravity of 8-coke smoked at high temperatures becomes small, and the bulk specific gravity of graphite electrodes made using such coke becomes small.
This leads to a decrease in the strength of the electrode.

Therefore, the pitch coke for manufacturing high-quality electrodes must have a nitrogen content of less than 0.3q6 and a pore volume of 0.04 cC/y or less with a pore radius of 5oooi or less. Preferably 0.03cc/
y or less.

If the nitrogen content is 0.3 or more, the expansion of the electrode becomes large during graphitization during electrode manufacture. In addition, the pore volume of coke with a pore radius of 5oooi or less is 0604cc/y
If it is more than that, the bulk density of the electrode becomes small, which is not preferable.

In order to produce pitch coke having the properties of the present invention, the present inventors investigated how to denitrify raw pitch coke from coal tar and/or coal tar pitch, which are raw materials containing nitrogen compounds, and at the same time
We conducted research on how to prevent the generation of pores of 0X or lower as much as possible. As a result, we found that the denitrification setting is not only related to the smoking temperature, but also to the holding time at the smoking temperature. It has also been found that the volume of pores generated at the same time, especially the volume of pores with a pore radius of 5000X or less, is related to the smoldering temperature. That is, if the smoldering temperature is relatively low, the pore volume below the pore radius of 5000' will be small, and if it is high, it will be large.

To produce the pitch coke of the present invention from coal tar and/or coal tar pitch containing nitrogen-containing compounds,
First, components that adversely affect the production of high-quality electrodes are removed from coal tar and/or coal tar pitch, which are raw materials. The components can be removed by any known method, for example, by solvent purification or filtration.

Insert the prepared raw material into a coke drum.

Therefore, it is carbonized at a temperature range of 450 to 500°C to produce raw pitch coke. The mixture is then combusted in a rotary kiln by maintaining the smoking temperature at 1,300°C to 1,500°C and holding time for 3 to 48 hours.

At a smoldering temperature of 1,300°C or lower, nitrogen components contained in the coke will dissipate. At a calcination temperature of 1,500°C or higher, the nitrogen components will dissipate. This is unfavorable because the occurrence of pores increases. Further, the holding time in the temperature range may be within 48 hours. The longer the retention time, the better the results, but the retention time may be determined in consideration of economic efficiency. Preferably it is 3 hours to 24 hours. When the holding time is 3 hours or less, it is difficult to reduce the nitrogen component mentioned above, although it depends on the 1M firing temperature.

Next, an explanation will be given using an example.

Example Raw pitch coke obtained by coking coal tar soft pitch in which the quinoline soluble content was adjusted to 0.2 or less in a derate coker was used to produce smoldered coke under the temperature conditions listed in Table 4. Next, the smoked coke is crushed, and 2
50% by weight of the pulverized material having 0 to 70 meshes and 50% by weight of the pulverized material having 100 meshes or less are mixed well together with the binder pitch, and a molded product (diameter 25wn - length) is formed by extrusion molding.
-00mm) was created. Next, using a graphitizing crucible, each molded body was fired at 900°C for 6 hours, and further heated at 260°C.
Graphitization was carried out at 0° C. for 5 minutes. The results are shown in Table 4.

As can be seen from this table, it is difficult to reduce the nitrogen content of pitch coke calcined at a temperature of +1300°C for a short holding time.

Furthermore, it is possible to reduce the nitrogen content by smoking at a temperature higher than the temperature conditions of the present invention.

When the pore volume is 0.04 QC/f or more, the graphite compact made from such coke has a small bulk density, which leads to a decrease in the performance of the electrode, making it undesirable.

As explained above, the present invention relates to pitch coke for manufacturing high-quality electrodes, and the present invention relates to pitch coke having the properties of the present invention.
The most balanced electrodes can be produced using Tsuticoke.

Table 4

[Brief explanation of drawings]

Figure 1 shows the coefficient of thermal expansion during graphitization of graphite compacts using various types of coke. Figure 2 shows the coefficient of thermal expansion during graphitization of graphite compacts using pitch coke at different smoking temperatures. Figure 3 shows the first closed graphite pores of pitch coke smoked at various temperatures.

Claims (1)

[Claims] 1. Nitrogen content is less than 0.3 inches and pore radius is 5000
Pitch coke 2 having a pore volume of 0.04 cc/y or less at X or less, the pitch coke according to claim 1, characterized in that the pitch coke is used for high-grade electrodes.