JPH04145193A - Needle coke manufacturing method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing graphite raw material, particularly needle coke used as a raw material for graphite electrodes for electrical steel manufacturing. More specifically, by mixing petroleum-based heavy oil with coal tar-based raw material oil that does not contain quinoline-insoluble matter, CTE
The present invention also relates to a method for producing twenty-one dollar coke with low puffing and high calcined coke bulk density.

[Conventional technology]

Needle coke is mainly used as a raw material for electric steelmaking electrodes, but in the electric steelmaking industry, electric furnaces are becoming larger and UHP
(Ultra High Power) Operations and operating conditions are becoming increasingly harsh, and there is a demand for graphite electrodes with even better performance, as well as higher-grade needle coke.

In particular, the CTE (coefficient of thermal expansion) is related to thermal shock resistance during use of the electrode, and the lower the CTE, the better the electrode consumption rate, so there is a demand for electrodes and coke with a low CTE.

On the other hand, manufacturers of graphite electrodes are also trying to shorten the graphitization time to save energy during graphitization.
A problem is the irreversible thermal expansion phenomenon (puffing) that occurs when the electrode graphitizes.

Puffing becomes larger as the graphitization time becomes shorter, and in extreme cases, graphitization becomes impossible.

Further, if the puffing is large, problems such as a decrease in the bulk density of the electrode obtained after graphitization occur. Therefore, not only the CTE of the graphite electrode but also the puffing during graphitization is an important indicator of needle coke quality.

Currently, such needle coke is manufactured using coal tar-based heavy oil as a raw material and petroleum-based heavy oil as a raw material. Coal tar-based needle coke is characterized by low CTE, but has the drawback of high nitrogen compound content and high puffing. In addition, petroleum-based needle coke has a drawback of high CTE due to the low aromaticity of its raw materials.

By the way, it has been thought that puffing occurs because sulfur compounds, nitrogen compounds, etc. contained in needle coke rapidly decompose and gasify when heated to high temperatures7, forcing the coke structure to expand.

Therefore, as a measure to prevent puffing, a method has been proposed in which a metal compound (for example, iron oxide) that forms a compound with sulfur is added to trap sulfur in the temperature range where puffing occurs.

However, even though this method is effective for petroleum-based needle coke obtained from petroleum-based feedstocks with a high sulfur compound content, excessive amounts of sulfur compounds will result in high puffing, so it is necessary to select raw materials with a low sulfur content. There is.

On the other hand, this method is not effective for coal-based needle coke obtained from a coal tar-based raw material that is low in sulfur compounds and conversely high in nitrogen compounds, and is insufficient as a 1L measure to prevent puffing.

Although the sulfur content of coal-based needle coke is lower than that of petroleum-based coke, puffing is not that low.As a result of a detailed investigation into the causes of puffing in coal-based needle coke, we found that the cause of puffing was sulfur alone. It turned out that nitrogen was also the cause.

By the way, in order to produce needle coke from coal tar-based raw materials, it is necessary to remove several percent of quinoline insoluble content (hereinafter abbreviated as FQI content) contained in the coal tar-based raw materials.

Needle coke obtained from such a Ql-free coal tar-based raw material has a relatively low sulfur content, but has a high nitrogen content, so the agent has little effect on puffing prevention. For this reason,
Reducing nitrogen content in needle coke is a major issue in order to reduce puffing.

On the other hand, the CTE level of coal tar-based needle coke is lower than that of petroleum-based needle coke;
There is an inverse correlation between E and puffing, and it has been difficult to reduce CTE without reducing puffing using conventional means.

Therefore, various methods for denitrifying coal tar-based raw materials have been proposed. For example, Japanese Patent Publication No. 60149690
According to the hydrogenation method disclosed in the publication, it has been shown that it is possible to reduce CTE and puffing at the same time. This method has the disadvantage of requiring large equipment and cost.

Japanese Patent Publication No. 82-45916 proposes a method of obtaining coke in which the nitrogen content in the coke is diffused by heating the coke for a long time at a temperature range of 1430 to 1500°C, which is higher than the normal coke calcination temperature. ing. This method also has the disadvantage of requiring energy costs.

In addition, Japanese Patent Publication No. 57-61071 aims to simultaneously produce high-grade coke (needle coke) and a raw material with a high aromatic content for carbon black production.
The use of a mixture of coal tar and thermal or catalytic cracking residual oil is disclosed. However, since this invention uses coal tar as a raw material, it contains quinoline insoluble matter that inhibits the development of flow structure during coking, resulting in a high CTE. Furthermore, as is clear from the comparative example in the example, by mixing cracking residual oil with coal tar, the sulfur content increases significantly both in the coking raw material and in the coke obtained, which leads to a decrease in puffing. It is clear that it is not connected.

In addition, Japanese Patent Publication No. 49-2648 describes a method for manufacturing needle coke in which coal-based coal tar pitch and petroleum-based heavy oil are mixed and then heated and stirred at 200 to 320°C.
This patent discloses coking a mixture obtained by separating and removing a QI-containing precipitate from the generated coal tar pitch. However, when this method is used, when a precipitate is generated by heating and stirring, heavy components such as β resin, which is the main component of the carbonization reaction in coal tar pitch, are precipitated at the same time. Not only does the carbonization component derived from coal tar pitch decrease, resulting in a decrease in coke yield, but also
The properties of the coke become similar to those obtained when petroleum-based oil is carbonized alone, resulting in a high CTE.

[Problem to be solved by the invention]

Based on the technological trends described in the conventional method, current raw materials for needle coke can be used without using hydrogenation methods that require large-scale equipment and costs, and without incurring energy costs such as high-temperature and long-term heating of coke. Measures to reduce nitrogen content are eagerly awaited.

The purpose of the present invention is to remove quinoline-insoluble content from coal tar-based raw materials, maintain the low CTE characteristic of coal tar-based needle coke, and mix it with a different type of raw material with reduced nitrogen content to form coke. By doing so, it is an object of the present invention to provide a method for producing needle coke that is excellent in both CTE and puffing.

[Means to solve the problem]

The present inventors have conducted extensive research to solve the above problems, and have found that when coal tar-based raw materials from which quinoline insoluble matter has been removed and petroleum-based heavy oil with low nitrogen content are mixed and carbonized,
The present invention was completed by focusing on the fact that the flow structure is better than when coal tar-based raw materials are carbonized alone, the nitrogen content in the raw materials is reduced compared to coal-tar-based raw materials, and the CTE is the same as that of coal-based needle coke. did.

In other words, the present invention provides (1) coal tar-based heavy oil from which quinoline-insoluble components have been removed in advance, a sulfur content of 1.2% by weight or less, and a nitrogen content of 0.5% by weight.
In the following, substantially no quinoline insoluble matter is contained, the aromatic index fa is 0.65 or more, and the Conradson residual carbon content CCR
A method for producing needle coke, characterized in that coke is produced by mixing decant oil, which is a heavy component of fluidized catalytic cracking oil of petroleum, adjusted to a concentration of 10% by weight or more, and (2) removing insoluble quinoline content in advance. Coal tar-based heavy oil with a sulfur content of 1.2% by weight or less, a nitrogen content of 0.5% by weight or less, and a quinoline-insoluble content of 1.0% or less. 02 or more,
A method for producing needle coke, characterized in that coke is produced by mixing decant oil, which is a heavy component of fluid catalytic cracking oil of petroleum, adjusted to have a Conradson residual coal ff1ccR of 10% or more, (3) ) The decant oil, which is a heavy component of fluid catalytic cracking oil of petroleum, is prepared by previously distilling the heavy components of fluid catalytic cracking under reduced pressure to cut out the light components.
) is the method for producing needle coke according to any one of the above.

The coal tar-based raw materials used in the present invention include coal tar produced when coal is carbonized, as well as high boiling point tar oil and tar pitch separated from the coal tar, and preferably tar pitch.

There are three types of tar pitch: soft pitch with a softening point of 70°C or lower, medium pitch with a softening point of 70 to 85°C, and high pitch with a softening point of 85°C or higher. It is advantageous to use Alternatively, a mixture of two or three types of cool pitch, coal tar, or high boiling point tar oil may be used.

Many documents have already been published regarding methods for removing QI components from coal tar-based raw materials, but it is also possible to remove them using mechanical methods such as filtration and centrifugation.
Since the particle size corresponding to QI is extremely small, the separation rate is slow and the separation efficiency is low, such as LI clogging during filtration, so it cannot be implemented industrially. The same thing can be done even if a solvent is added to lower the viscosity.

As a method that can be implemented industrially, Japanese Patent Application Laid-Open No. 57-3015
As disclosed in Publication No. 9 and JP-A No. 53-669, coal tar-based raw materials are combined with aliphatic solvents such as hexane, octane, kerosene, naphtha, and butanol, and benzene, toluene, xylene, and methylnaphthalene. An effective method is to add and mix a mixed solvent with an aromatic solvent such as phenol to form an insoluble product around the QI powder particles, increase the size of the particles, and then remove the particles by sedimentation.

An important point in the present invention is that decant oil (Flu
id Catalytic Cracker Deca
nt Oil.

Commonly known as FCC-Do), it is mixed and coked.

According to the study results of the present inventors, in this case, FCC-Do
It has been found that depending on the properties of the coke, buffing may be reduced compared to the case of coal tar-based two-dollar coke content, but on the other hand, the rate of increase in CTE may be increased.

As a result of detailed study, we found that when the nitrogen content is 0.5% by weight or less and the sulfur content is 1.2% by weight or less, the aromatic index fa
FCC-D adjusted within a specific range such that CCR is 0.65 or more and Conradson residual coal amount CCR is 10% by weight or more.
It has been found that by mixing o, it is possible to reduce buffing and at the same time reduce the CTE increase rate as much as possible compared to when the raw material oil is a coal tar-based heavy oil content.

The aromatic index fa is 100 instead of 0.65 or more. If these characteristic values do not correspond depending on the quality of the FCC-DO, any value falls within the scope of the present invention.

Here, the aromatic index fa is the ratio of the number of aromatic ring carbon atoms to the total number of carbon atoms in the raw material, and is a numerical value determined by the following formula.

f a -(C-(Hα/2+Hβ/2+H7/3)
) / C However, C: Total number of carbon atoms in the raw material Ha: Number of α-position hydrogen atoms from the aromatic ring in the raw material, Hβ: Number of β-position hydrogen atoms from the aromatic ring in the raw material, Hγ; The number of hydrogen atoms at the γ-position from the aromatic ring in the raw material. FCC-Do, which is the bottom heavy oil from a fluid catalytic cracker for petroleum, usually has a nitrogen content of 0.5% by weight or less and a sulfur content of 0.5% by weight. 5 to 4% by weight, and the aromatic index fa is 0.4 to 4% by weight.
0.7, Conradson residual carbon ff1ccR is within the range of 2 to 10% by weight.

FCC-Do used in the present invention has an aromatic index fa of 0.
．． 65 or more, and the Conradson residual coal amount OCR is adjusted to be 10% by weight or more.

Even if the aromatic index fa is 0.65 or more, if the Conradson residual carbon 11CCR is less than 10% by weight, or even if the Conradson residual carbon EtCCR is 10% by weight or more, the aromatic index fa
is less than 0.65, depending on the coking conditions, the CTE may be worse than when coal tar-based heavy oil alone is used as the raw material oil.

This is because light FCC-Do, which has an aromatic index fa of less than 0.6"5 or a Conradson residual carbon ff1ccR of less than 10% by weight, has a very fast carbonization rate and cannot be mixed with coal tar-based heavy oil. Low CTE even when made into coke
This seems to be because the balance between carbonization rate and gas generation cannot be achieved to produce an anisotropic structure exhibiting .

Methods for preparing such FCC-DO include using a raw material (petroleum) with as high aromaticity as possible in the fluid catalytic cracker, increasing the cracking temperature of the fluid catalytic cracker, or using conventional fluid catalytic cracking of petroleum. It is possible to use methods such as cutting off the light components of bottom heavy oil FCC, Do from the equipment by vacuum distillation or heat treatment.

Although the FCC-DO used in the present invention does not substantially contain quinoline-insoluble matter, it is desirable to perform a treatment to remove quinoline-insoluble matter, if necessary.

By mixing FCC-Do with coal tar-based heavy oil, the coke produced from this feedstock has a nitrogen content of 0.4% by weight or less and a sulfur content of 1.0% by weight.
The following are preferred as they greatly reduce puffing.

In addition, when the above-mentioned FC (, -Do) is used alone as a coke feedstock oil, it contains a lot of sulfur which causes puffing of petroleum-based needle coke, and only a coke with a higher CTE can be obtained than coal-based needle coke.

In the present invention, puffing and CTE can be simultaneously lowered by mixing such petroleum-based heavy oil with de-Qlt-removed coal tar-based heavy oil and coking this as a raw material oil. .

In the present invention, FCC for coal tar-based heavy oil
-The mixing ratio of Do is coal tar-based heavy oil 90~20w1
, 1, FCC-DO is 10 to 80 w+N, preferably coal tar heavy oil 80 to 501,
FCC-Do is 20-501. If the mixing ratio of FCC-Do is lower than io=+h, puffing will be high in coal tar-based needle coke, and if the mixing ratio of FCC-Do is higher than 8O-=N, the CTE will be as high as petroleum-based needle coke. turn into.

Further, when coal tar-based heavy oil and FCC-DO are mixed and carbonized, the content of nitrogen and sulfur remaining in the needle coke is almost additive with respect to the mixing ratio. Therefore, the nitrogen content, which causes puffing, can be reliably reduced compared to coal tar-based raw materials. Although the sulfur content increases compared to coal tar-based raw materials, the amount of increase is within 0.5% by weight, and since anti-puffing agents are effective against puffing caused by sulfur, this increase is a problem. do not become.

In addition, in the present invention, FC (FC) with specific properties that does not substantially contain QI is added to coal tar-based heavy oil from which QI has been removed.
, -Do are mixed, so the compatibility between the two is very good,
No insoluble precipitates are formed during mixing.

Based on these facts, CTE can be achieved by mixing coal tar-based heavy oil from which the QI content has been removed with FCC-DO adjusted to specific properties and coking it.

It has become possible to produce needle coke with excellent puffing properties.

After QI removal, a known method can be used for mixing with FCC-DO adjusted to specific properties and then forming coke. For example, under pressure (1 to 20 kg/+) in a delayed coker.
JG), produce raw coke at 450-550℃, and then heat the raw coke in a rotary kiln, shaft furnace, etc.
It is calcined at 200 to 1500°C to produce needle coke.

Needle coke obtained by the method of the present invention can be crushed,
After adjusting the particle size, it is mixed with binder pitch and molded. If this is fired and then fired at a temperature of 2500°C or higher, a graphite electrode with excellent performance can be efficiently obtained.

That is, the graphite electrode made from the needle coke obtained by the method of the present invention has a small CTE, and also has excellent strength because it is difficult to cause puffing during manufacturing.

[For production]

In the present invention, by coking by mixing heavy oils with different carbonization rates and gas generation states during coking,
Needle coke with an optically anisotropic structure exhibiting a low CTE can be produced by changing the carbonization rate and gas generation state during coking. At the same time, the nitrogen content and sulfur content, which cause puffing, are reduced, making it possible to reduce puffing.

〔Example〕

The present invention will be explained in more detail below with reference to Examples, but the present invention is not limited to these Examples in any way.

(Example 1) Coal tar pitch (CTP) from which Q1 was removed in advance had a nitrogen content of 0.1% by weight, a sulfur content of 0.67% by weight, fa
FCC decant oil adjusted to O,73, CCR11,3% by weight is heated to a temperature of 100°C and mixed at a mixing ratio of 7/3 to 3/7, and the resulting pitch is heated to 480 to 4% by weight in a small reactor.
Coke was made at 85° C. for 8 hours to produce cow coke, and then baked at 1450° C. for 1 hour in an argon atmosphere.

Regarding the obtained coke, KPIs were determined for NOx, sulfur content, puffing, CTE, etc. in the coke. Results first
Shown in the table. The measurement of puffing was carried out by adding 1% of Fe2O3 as a puffing inhibitor.

(Example 2) FCC-Do used was fa-0,68, CCR=1.
1.1wt5+ was treated in the same manner as in Example 1, except for
The results are shown in Table 1.

Examples and Comparative Examples Table 1 Carbonization temperature: 480 to 485° C. (Comparative Example 1) The same treatment as in Example 1 was carried out except that FCC-Do was not mixed. The results are shown in Table 2.

(Comparative Example 2) Example 1 except that coal tar pinch was not mixed.
The same process was carried out. The results are shown in Table 1. The puffing measurement results are also shown at the same time (7).

(Comparative Example 3) FCC-Do used was fa-0.63, CCR=1
．． 0. The treatment was carried out in the same manner as in Example 1 except for 6WT$1, and the results are shown in Table 2.

(Comparative Example 4) FCC-Do used was fa-0.68, CCR=7.
The processing was performed in the same manner as in Example 1 except for 0wrx, and the results are shown in Table 2.

Table 2 Carbonization temperature 480-485°C (Example 3) Various FCs with different CCRs adjusted by the distillation cut rate of light boiling point bones were added to coal tar pitch from which Q1 was removed in advance.
C-Do (however, fa>0.65, d4>1.02
0) at a mixing ratio of 1/1 and mixed at a temperature of 100°C.
The resulting pitch was heated to 480-490°C in a small reactor to make coke for 8 hours, and then calcined at 1450°C for 1 hour in an argon atmosphere.

The CTE and puff ink of the obtained coke were measured. The results are shown in Table 3. Figure 1 also shows the amount of increase in CTE compared to the CTE of coal tar pitch alone.
Plotted against CH.

Due to this relationship, when CCR becomes 1.0WT% or less,
It can be seen that puffing causes a sudden increase in CTE without much change.

Further, when the CCR is 10 wt or more than 1, the amount of increase in CTE is maintained at a nearly constant level.

(Example 4) CCR is 1. , 1 wTx and different fa were used, but the same process as in Example 1 was performed.

The FCC-Do used here is Ta.

The results are shown in Table 4. Further, in Table 2, the amount of increase in CTE is plotted against fa.

From this relationship, when fa becomes less than 0.65, CT suddenly increases.
It can be seen that E increases.

Table 3 Table 4 [Effects of the Invention] According to the method of the present invention, energy consumption can be achieved in hydrogenation of coal tar-based feedstock oil, high-temperature long-time baking of coke, etc.
FCC adjusted to specific properties without any cost
- Low CT by mixing with Do and coking
E. Needle coke with low buffing can be produced at low cost. This invention greatly contributed to the coke industry.

[Brief explanation of drawings]

Figure 1 shows FCC-D O/CT P-1,/1
It is a graph showing the relationship between CCR of FCC-Do and CTE of coke at the time of . Figure 2 shows FCC-Do/CTP-1/1 and FCC-Do/CTP-1/1.
It is a graph showing the relationship between fa of Do and CTE of coke. Application agent Hiroshi Fujimoto Figure 1 Figure 2 fat illusion

Claims (3)

[Claims] (1) Coal tar-based heavy oil from which quinoline insoluble matter has been removed in advance, sulfur content 1.2% by weight or less, nitrogen content 0.5% by weight
In the following, substantially no quinoline insoluble matter is contained, the aromatic index fa is 0.65 or more, and the Conradson residual carbon content CCR
1. A method for producing needle coke, which comprises mixing decant oil, which is a heavy component of fluidized catalytic cracking oil of petroleum with a concentration of 10% by weight or more, to form coke. (2) Coal tar-based heavy oil from which quinoline insoluble matter has been removed in advance, sulfur content 1.2% by weight or less, nitrogen content 0.5% by weight
Below, substantially no quinoline insoluble matter is contained, and 10
Specific gravity at 0℃ (d_4^1^0^0) is 1.02 or more,
A method for producing needle coke, which comprises mixing decant oil, which is a heavy component of fluid catalytic cracking oil of petroleum with a Conradson residual carbon content CCR adjusted to 10% by weight or more, to form coke. (3) The decant oil, which is a heavy component of fluid catalytic cracking oil of petroleum, is prepared by previously distilling the heavy components of fluid catalytic cracking under reduced pressure and cutting off the light components. 2
) The method for producing needle coke according to any one of the above.