JPS6124326B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing carbon products, and more specifically, it involves adding pitch to a specific raw retarded coke in an amount suitable for its properties, mixing it uniformly and simultaneously crushing it, and then molding it into powder according to a conventional method. , relates to a method for producing a carbon material characterized by firing or graphitizing it. Hereinafter, in this specification, raw retarded coke alone is finely pulverized to an average particle size of 100μ or less, molded according to a conventional method without adding a binder, and when fired, it foams and expands or becomes semi-molten. Raw retarded coke that sinters without deformation is referred to as raw retarded coke, and raw retarded coke is finely ground to an average particle size of 100μ or less and molded according to a conventional method without adding a binder. To differentiate, raw retarded coke that foams and expands or half-melts and deforms when fired is referred to as crude retarded coke, and raw retarded coke is referred to in general terms as raw retarded coke. . Furthermore, the term "raw coke" is used to include not only raw retarded coke but also other raw cokes obtained by coal carbonization. The feature of this method is that the raw retarded coke is used without being burned, which saves the energy and cost required for burning in the conventional method. It requires time and effort to add and knead for 1 to 2 hours while heating to 140 to 160°C.The combination process and subsequent cooling process are unnecessary.
The goal is to be able to economically produce products with properties that are equal to or better than conventional carbon products. In the production of such carbon products, in the prior art, calcined coke has been used without using live retarded coke. The reason for this is not necessarily clear, but molded products made from raw retarded coke shrink significantly during firing, resulting in deformation or frequent firing cracks, making it difficult to stably produce carbon products of a certain shape and quality at a high yield. This is thought to be due to the inability to do so. Conventionally, in an attempt to make carbon material from raw coke, it was proposed to obtain high-density carbon material by pulverizing raw coke to an average particle size of 10μ or less, molding it under high pressure, and then firing it. has been done. However, pulverizing the particles to an average particle size of 10μ or less requires considerable expense, and the pressure required for molding becomes higher as the particles become smaller, making it difficult to obtain large molded bodies. ,
Although this method can be used as a method for producing expensive high-density, high-strength carbonaceous materials, it cannot be applied to the production of inexpensive, mass-consumed aluminum electrolytic smelting electrodes, carbon bricks, graphite electrodes, etc. The inventors of the present invention have conducted extensive research over many years to determine whether it is possible to directly manufacture carbon products from raw retarded coke without going through the process of calcination, which requires a large amount of heating energy. Even raw retarded coke, which has a large firing shrinkage, is mixed with an amount of pitch suitable for its properties, mixed uniformly and pulverized at the same time, and pulverized to an average particle size of 100μ or less, molded, and sintered or graphite. It was found that the carbon material shrinks almost uniformly and that good quality carbon materials can be produced at a high yield. In other words, according to the method of the present invention, an appropriate amount of binder pitch is added to raw retarded coke of various raw materials with different sintering powers, and the average particle size is adjusted while mixing.
After crushing to 100μ or less, mold it according to the conventional method,
We have discovered that by firing or graphitizing, it is possible to inexpensively produce high-quality carbon materials with properties suitable for carbon bricks, aluminum electrolytic smelting electrodes, graphite electrodes, metallurgical materials, etc. In other words, the gist of the present invention is to finely grind raw retarded coke to an average particle size of 100μ or less, mold it according to a conventional method without adding a binder, and foam and expand or semi-melt when fired. A binder pitch with a softening point of 75 to 140°C and a fixed carbon content of 45 to 70% is added to the raw retarded coke, which sinteres without deformation, at 5 wt% of the total amount and the volatile content determined by equation (1). Add in the required amount and simultaneously crush while mixing to make a fine powder with an average particle size of 100μ or less,
A method for producing a carbon material, which comprises molding it according to a conventional method and firing or graphitizing it. VCM _(nax) = 0.39 × VCM _(gc) + 13.1 (1) [In the formula, VCM _(nax) is the upper limit (wt%) of the volatile content of the mixture of raw raw retarded coke and pituti, and VCM _{( gc)} is the volatile content (wt%) of the raw raw retarded coke, and is 7≦VCM _(gc) ≦15. The properties of raw retarded coke vary significantly depending on the manufacturer or production plant, and if it is finely ground and then molded and fired, it becomes a carbon material, so it has a certain degree of shape retention, so it should be handled with care. Although it is possible to embed it in gas coke granules (breeze) and sinter it using the usual method, the sintering force is too weak to make a good carbon material, or the adhesive force is weak and the shape retention is poor when used alone. There are various types, including those that cannot be molded. This remarkable difference in adhesive strength and sintering force is due to the difference in the amount of volatile matter in the raw retarded coke due to differences in both the retarded coking conditions and the properties of the feedstock oil, and the difference in the amount of volatile matter in the raw retarded coke, which is the main component that generates the volatile matter. This is due to the differences in the properties of the pitch-like compound and the properties of the highly coked portion, which is a large component in raw retarded coke. The adhesive force is generally stronger when the raw retarded coke has a large volatile content, but it cannot be said that the sintering force, which means the strength of sintering, is simply stronger when the volatile content is large.
The sintering force referred to here is a practical one that is expressed as the strength of the carbon material obtained by molding and firing a finely pulverized raw retarded coke. The bulk specific gravity of the fired product decreases, and if this is significant, the strength of the fired product becomes weak even if the bonding force between particles is strong. The sintering power of such raw retarded coke is practically weak. In addition, if there are bubbles in the carbon material of the product, it will be a practical limitation, and if it is deformed during firing, the yield will decrease even if it is shaped in post-processing, leading to an increase in costs. For this reason, the sintering power of raw retarded coke should be limited to a range in which it does not foam and swell to a visible degree during firing, or half-melt and deform, and within this range, the volatile content is high. Generally stronger. As mentioned above, the raw raw retarded coke that can be used as a raw material in the method of the present invention is obtained by finely pulverizing the coke to an average particle size of 100μ or less, molding and firing by a conventional method, that is, 200Kg/cm ² or more. When molded under the required pressure and fired at 1000°C or higher, it must be able to sinter into a carbon material without foaming, expanding, or melting and deforming.
As the raw retarded coke mentioned here, not only petroleum-based coke but also coal tar-based coke can be used. This expansion due to foaming during firing or deformation due to half-melting is due to the presence of too much volatile matter in the raw retarded coke, or the strong organic character of the part with a crystal structure similar to graphite, which is the main component of the raw retarded coke. etc. This is what happens because of things like. but,
Whether or not retarded coke causes the above-mentioned unfavorable phenomena during firing cannot be determined simply by the amount of volatile matter, the amount of fractionated solvent components, the average elemental analysis value, or a combination of these factors. The reason for this is that the main component in raw retarded coke that generates volatile matter is a pitch-like substance, but even if the volatile content is almost the same, the molecular weight distribution and chemical structure of the pitch-like substance depend on the properties of the feedstock oil and the retarded coke. This is because the properties of the portion having a crystal-like structure, which is the main component of raw retarded coke, vary markedly depending on the properties of the raw material oil and the retarded coking conditions. Therefore,
Not only their proportions but also the combination of their properties determine the properties of raw retarded coke, so its overall properties are influenced by a complex combination of many factors. For example, while there is crude retarded coke with a volatile content of 9.8% that causes the above-mentioned half-melting phenomenon, there is also a crude retarded coke with a volatile content of 14.5% that is suitable as raw material raw retarded coke for the method of the present invention. be. Therefore, it is necessary to determine experimentally whether a particular material can be used as raw raw retarded coke in the method of the present invention. Generally, raw retarded coke has a volatile content of 8 to 15%, some as high as 7%. The above-mentioned foaming or semi-melting is not found in those with a volatile content of 8% or less. Therefore, it goes without saying that raw retarded coke with a volatile content of 8% or less can be used as raw material raw retarded coke for use in the method of the present invention, and even raw retarded coke with a volatile content of 8 to 15% can be used in the coking drum. In many cases, the raw retarded coke collected from the lower side and near the wall surface of the coke can be directly used as the raw retarded coke used in the method of the present invention.
Products with a volatile content of more than 15% are not commercially available, but certain parts of the delayed coking drum, such as the upper part, especially near the center, have a volatile content of more than 15%, and some contain more than 20%. There is even. A crude retarded coke containing such a large amount of volatile matter causes the above-mentioned foaming and slugging phenomena and cannot be used as it is as a raw material for the process of the present invention. This foamed and semi-melted coarse raw retarded coke can be used by mixing a small amount with a suitable raw material raw retarded coke.
Preferably, the volatile content is reduced to an appropriate amount before it is used as a raw material. The volatile content can be reduced by external heating to 400 to 500° C. in an inert atmosphere, by heating through superheated steam, or by solvent extraction. However, although the method of heating from the outside is simple, it tends to cause local heating, so it is preferable to employ the other two methods. For example, when raw retarded coke with a volatile content of 9.8% and causing the above-mentioned half-melting phenomenon is heated in superheated steam to 430°C for one hour, the volatile content drops to 8.8% and no longer exhibits the half-melting phenomenon. It has become suitable as a raw material for the method of the present invention. When the heating time was increased further or the heating temperature was increased, the volatile content further decreased and the sintering power became weaker. Also, volatile content
19.8% crude retarded coke causes a remarkable foaming phenomenon as it is, but when it is heated in 10 times the amount of xylene at 120℃
The volatile matter is heated for 2 hours to extract the soluble matter.
At 13.2%, the sintering force was strong. In addition, raw retarded coke with a volatile content of 15.0%, which has a strong sintering power as it is, was similarly extracted with xylene. The treated raw retarded coke had a volatile content of 11.0%, and its sintering power was significantly weaker than that of the untreated one. From these facts, it can be seen that there is an upper limit to the amount of volatile matter that does not cause the above-mentioned foaming or half-melting phenomenon, but the upper limit varies significantly depending on the production conditions of raw retarded coke. In the method of the present invention, binder pitch is added to the raw retarded coke that satisfies the above conditions based on the total amount.
It is an essential constituent requirement to add an amount within the range of 5wt% to the amount equivalent to the value specified by formula (1) below. VCM _(nax) = 0.39 × VCM _(gc) + 13.1 (1) [In the formula, VCM _(nax) is the upper limit (wt%) of the volatile content of the mixture of raw raw retarded coke and pituti, and VCM _{( gc)} is the volatile content (wt%) of raw raw retarded coke, and 7≦VCM _(gc) ≦15]. The upper limit of the volatile content [VCM _(nax) ] in equation (1) is determined using raw retarded coke with different volatile content and pitches with different softening points and fixed carbon contents as shown in the attached Figure 1. It is something that That is, the amount of binder pitch added to a specific raw retarded coke was gradually increased, and the value corresponding to the amount of pitch added that gave the best result was plotted. If more binder pitch is added than this, the molded product will swell due to foaming or deform due to sluggishness during firing, which is not preferable. The minimum amount of binder pitch added is 5%. If a smaller amount is added, it is not possible to expect much improvement in the strength or electrical conductivity of the product, and the product is likely to become non-uniform. One feature of the method of the present invention is that pitch is added to raw retarded coke and, while mixing, is pulverized to an average particle size of 100 μm or less to form a molding material. The raw retarded coke used in the process of the present invention is softer than burnt coke and fluidized coke and can be much more easily pulverized by grinding. Conventionally, in the production of this type of carbon product, a powder mixture having an appropriate particle size distribution has been used instead of using powder of a single particle size. Particularly in the production of electrodes for aluminum electrolytic smelting, in order to prevent the collapse phenomenon caused by thermal shock during use, it has been necessary to have a particle size distribution in a fairly wide range, and for this reason, complex The steps of crushing, sieving, and re-blending were necessary. In the method of the present invention, relatively large particles of 100 μm are used in order to obtain such an appropriate particle size distribution.
Although it can be blended into the following finely pulverized materials, in the method of the present invention, it is not necessarily necessary to blend powders with such different particle sizes, and the quality and properties of the product are mainly determined by finely pulverized particles of 100μ or less. Determined only by things. If the particle size is 100 μm or more, the bending strength and electrical conductivity will decrease, and the quality of the product will vary widely, which is not preferable. The binder pitch used in the method of the present invention preferably has a softening point of 75 to 140°C and a fixed carbon content of 45 to 70%. Originally, it is preferable to have a large amount of fixed carbon, but if it exceeds 70%, the softening point will be too high.
If it becomes too high, the properties gradually become similar to raw retarded coke and differ from those of a binder such as pitch, which does not give good results. Furthermore, when the softening point is less than 75℃, the amount of fixed carbon decreases, and there is an upper limit to the amount of addition expressed by equation (1), so it is not possible to add a sufficient amount of pitch to increase the sintering force. Because of its stickiness, it tends to stick to the crusher and cause problems. It is also desirable that the required pitch be sufficiently aromatic. Otherwise, it would not have the strong sintering power mentioned here. However, in the case of materials with high aliphatic properties, when the amount of fixed carbon exceeds 45%, the softening point usually exceeds 140°C, so as a result, compositional analysis may not be necessary. If a pitch is selected with a softening point of 75-140°C and a fixed carbon content of 45-70%, it will be rich in aromaticity and therefore suitable for use in the method of the present invention. Further, it is preferable to use a grinding type pulverizer to simultaneously grind the raw raw retarded coke and pitch as described above while mixing them. This makes it easy to completely mix the pulverized materials, and at the same time, the pitch tends to soften during pulverization and adhere to the raw raw retarded coke to form a coating in the form of particles, creating a homogeneous carbon material with good shape retention. This is because it is easy. Grinding mills include edge runners and ring roll mills. Furthermore, in the method of the present invention, a small amount of calcined coke, used carbon electrodes, or various waste carbon materials can be mixed with raw retarded coke. In that case, it is inevitable that the strength will decrease as the mixing amount increases, so the mixing amount is preferably 1/4 or less of the amount of raw raw retarded coke,
More preferably, it is 1/6 or less. The upper limit of the amount of binder pitch added when this calcined carbon material is mixed and used is the value determined by equation (1) when the total weight is homogeneous raw retarded coke. That is, the amount of pitch added depends on the properties of the raw raw retarded coke used, and is not affected by the quality and quantity of the carbon product powder that is additionally blended. If you add a large amount of pitch considering that you are mixing raw materials that have already been fired, and the value exceeds the value calculated by equation (1), the amount of pitch will be too large compared to the raw raw retarded coke, which will cause problems during firing as described above. This causes swelling due to foaming or deformation due to half-melting. As mentioned above, raw retarded coke with a volatile content of 15.0% or more is known to foam and deform when fired, and the amount of binder pitch used when making carbon products from burned coke is also higher than the total amount of volatilization. When expressed in terms of quantity, the amount was in line with the above findings and was usually around 10.0%. In contrast, the method of the present invention reduces the volatile content to about 16.0% of the total amount.
A mixture containing ~19.0wt% with binder pitch gives the best results; in other words, it corresponds to the volatile content within the range that was conventionally thought to cause foaming and deformation. It specifies the amount of pitch that provides volatile content. This is understood to mean that the volatile content in the raw raw retarded coke and the volatile content in the binder pitch added as a caking agent are not equal. The firing temperature used in carrying out the method of the present invention is preferably 1100 to 1400°C, and the heating rate is 3 to 20°C.
It is preferably within the range of °C/hr. Further, as the graphitization temperature, a temperature within the range of 2500 to 3000°C is preferably adopted. The structure and effects of the present invention will be explained below using specific experimental examples, but these are merely illustrative for the convenience of explanation, and it should be understood that the present invention is limited by these. isn't it. Example 1 Softening point of raw retarded coke with volatile content of 8.2%
At 87°C, 0, 3.0, 5.0, 10.0, 19.0, 23.2, and 26.1% of coal tar pitch with a fixed carbon content of 58% was added to the total amount, and the mixture was ground to an average particle size of 35μ while being mixed with an edge runner. . The upper limit of adding pitch to this raw retarded coke is
It is 16.3% in VCM _(nax) , and the corresponding amount of pitch added is 24.0%. 2Kg of finely pulverized material
was placed in a 20×12 cm square mold and pressurized to 300 Kg/cm ² to obtain a molded product with a thickness of 7.2 to 7.4 cm. The temperature was raised at a rate of 10°C/hr in the usual manner, and after being held at 1200°C for 3 hours, it was cooled to around 300°C and taken out.
The obtained carbon material is homogeneous, and its properties are shown in Table 1.
It was like that.

[Table] The experiments with pitch addition amounts of 0, 3.0, and 26.1 are for comparison. Example 2 Coal tar pitch with a softening point of 87°C used in Example 1 was added to raw retarded coke with a volatile content of 8.9% at 20% of the total amount (total volatile content 15.5%, VCM _(nax) 16.6
%) was added and ground to various average particle sizes by grinding while mixing, and carbon materials were prepared in the same manner as in Example 1. Its characteristics are shown in Table 2.

[Table] Note that the experiment with a particle size of 150μ is for comparison. Example 3 Pitch with a softening point of 87°C and a fixed carbon content of 58% was added to 14.5% and 20.0% of the total amount of raw retarded coke with volatile content (A) 14.5% and (B) 8.9% [of both retarded cokes] The VCM _(nax) were 18.8% and 16.6%, respectively, and the total volatile content of the pitch additive was 18.5% and 15.5%, respectively], and were simultaneously crushed in the same manner as in Example 1 to obtain a fine powder with an average particle size of 35μ. A carbon material was produced in the same manner as in Example 1. The properties of the obtained carbon material were as shown in Table 3. For comparison, conventional products and standard values are also shown.

【table】

[Table] Example 4 Raw retarded coke with a volatile content of 14.5% is mixed with (A) coal tar pitch with a softening point of 80°C and a fixed carbon content of 50% and (B) petroleum pitch with a softening point of 138°C and a fixed carbon content of 69%. An amount corresponding to the upper limit of 18.8% of the volatile content was added, and the mixture was pulverized in the same manner as in Example 1 to an average particle size of 35 μm. The amount of both added is 12.1% each of the total amount.
and 26.1%. A carbon material was produced from the finely pulverized material in the same manner as in Example 1. Its characteristics were as shown in Table 4.

[Table] Example 5 Adding various types of coal tar pitch to raw raw retarded coke with a volatile content of 12.1% at the upper limit of the total volatile content
VCM _(nax) was added and finely pulverized to an average particle size of 35μ in the same manner as in Example 1, to produce a carbon material in the same manner as in Example 1. The results were as shown in Table 5.

[Table] Example 6 Raw retarded coke with a volatile content of 8.2% is added with 1/6 part by weight of coarsely crushed waste carbon material based on the coke, and the softening point of the mixture is 23% at 87°C. , Pitch containing 58% fixed carbon was added and ground to an average particle size of 30μ while mixing. A carbon material was produced from this pulverized product in the same manner as in Example 1. The obtained carbon material has a bulk specific gravity of 1.44 and a bending strength of 420.
Kg/cm ² and a specific resistance of 4400 μΩ-cm.

[Brief explanation of the drawing]

FIG. 1 is a graph of the amount of volatile matter that gives optimal results, where the vertical axis is the percentage of volatile matter relative to the total amount of the raw material composition, and the horizontal axis is the percentage of volatile matter in the raw raw retarded coke.

Claims (1)

[Scope of Claims] 1 Raw retarded coke alone is finely pulverized to an average particle size of 100μ or less, molded according to a conventional method without adding a binder, and when fired, it foams and expands or becomes semi-molten. Raw retarded coke, which is sintered without deformation, has a softening point of 75 to 140℃ and a fixed carbon content of 45 to 70.
% binder pitch with 5wt% of the total amount (1)
Add the amount necessary to give the volatile content determined by the formula, and grind simultaneously while mixing to determine the average particle size.
A method for manufacturing carbon materials, which consists of making a fine powder of 100μ or less, molding it according to a conventional method, and firing or graphitizing it.VCM _(nax) = 0.39 × VCM _(gc) + 13.1 (1) [In the formula _{7 _} ≦VCM _(gc) ≦15]. 2 The volatile content of raw raw retarded coke is 8 to 15wt
%. 3. The method according to claim 1 or 2, wherein the pulverization is carried out by grinding. 4. The method according to any one of claims 1 to 3, wherein the firing temperature is 1100 to 1400°C. 5. The method according to any one of claims 1 to 4, wherein the graphitization temperature is 2500 to 3000°C. 6. The method according to any one of claims 1 to 5, wherein the temperature for firing is increased at an average rate of 3 to 20°C/hr. 7 Raw retarded coke that is finely pulverized to an average particle size of 100μ or less, molded according to a conventional method without adding a binder, and foams and expands or semi-melts and deforms when fired. By using retarded coke as a crude raw material and reducing its volatile content, raw retarded coke that foams and expands under the above conditions or half-melts and does not deform is produced, and this is given a softening point.
Add binder pitch at 75 to 140°C and with a fixed carbon content of 45 to 70% in the range of 5 wt% to the total amount and the amount necessary to give the volatile content determined by equation (1),
A method for producing a carbon material, which consists of mixing and simultaneously pulverizing the powder to a fine powder with an average particle size of 100μ or less, molding it according to a conventional method, and firing or graphitizing it. VCM _(nax) = 0.39 × VCM _(gc) + 13.1 (1) [In the formula, VCM _(nax) is the upper limit (wt%) of the volatile content of the mixture of raw raw retarded coke and pituti, and VCM _{( gc)} is the volatile content (wt%) of raw raw retarded coke, and 7≦VCM _(gc) ≦15]. 8. The method according to claim 7, wherein the operation for reducing the volatile content is external heating. 9. The method according to claim 7, wherein the operation for reducing the volatile content is internal heating with an inert gas. 10. The method according to claim 7, wherein the operation for reducing the volatile content is solvent extraction.