JP2008150399A - Petroleum coke and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide petroleum coke having sufficiently small thermal expansion coefficient and sufficiently suppressed puffing phenomenon and a method for producing the petroleum coke. <P>SOLUTION: The method for producing the petroleum coke comprises coking of a stock oil containing a first heavy oil obtained as a residual oil of a vacuum distillation of a prescribed stock oil and having an initial boiling point of ≥300°C, an asphalt content of ≤12 mass%, a saturated component content of ≥50 mass% and a sulfur content of ≤0.3 mass% and a second heavy oil obtained by the fluidized catalytic cracking of a prescribed stock oil and having an initial boiling point of ≥200°C, a sulfur content of ≤0.5 mass% and a nitrogen content of ≤0.2 mass%. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to petroleum coke and a method for producing the same.

  Needle coke used for the aggregate of graphite electrodes for electric steelmaking is generally manufactured using petroleum heavy oil or coal tar as a raw material. In the process of producing a graphite electrode, first, coke grains and a binder pitch are blended at a predetermined ratio, heat-combined, and then extruded to produce a raw electrode. The raw electrode is fired, graphitized, and then processed to obtain a graphite electrode product.

  Here, since the graphite electrode is used under severe conditions such as a high temperature atmosphere, it is desired that the coefficient of thermal expansion (CTE) is low. That is, the smaller the coefficient of thermal expansion, the smaller the electrode consumption during electric steelmaking, and the cost of electric steelmaking can be reduced.

  The graphitization is a process of heat treatment at about 3000 ° C., and a method using a direct current type furnace (LWG furnace) is common, but if graphitization is performed using an LWG furnace, the temperature rises. Since the speed is high, the gas generation speed increases, and an abnormal expansion phenomenon called puffing is likely to occur. When puffing occurs, the electrode is reduced in density, and in some cases, the electrode is damaged.

Therefore, methods for controlling the coefficient of thermal expansion and the quality of puffing during the manufacture of needle coke have been studied, and various methods have been proposed. For example, Patent Document 1 below discloses a method in which an oligomer whose polymerization degree is adjusted is added to a de-QI pitch from which a quinoline-insoluble component has been substantially removed from a coal tar-based raw material, and then coked by a delayed coking method. ing. In Patent Document 2 below, coal tar heavy oil and petroleum heavy oil are mixed at a ratio of a nitrogen content of 1.0 wt% or less and a sulfur content of 1.4 wt% or less. After adjusting the oil, this raw oil was charged into a delayed coker to produce raw coke, and the obtained raw coke was calcined in a temperature range of 700 to 900 ° C., once cooled, and then again 1200 to 1600. A method of calcination in the temperature range of ° C. is disclosed. Further, in Patent Document 3 below, when producing coal tar by rapid pyrolysis of coal, the thermal decomposition temperature in the reaction furnace is kept at 750 ° C. or higher, and the residence time of the thermal decomposition product in the reaction furnace is 5 A method is disclosed in which a liquid product is obtained by setting it to a second or less, and the liquid product or pitch contained therein is carbonized. Further, in Patent Document 4 listed below, oil-based heavy oil alone or a mixture of coal-based heavy oil from which quinoline insolubles have been removed in advance is subjected to delayed coking as a raw oil, and needle coke is used. A method of using a petroleum heavy oil that has been adjusted in advance so that the content of particles such as ash is in the range of 0.05% by weight to 1% by weight is disclosed.
JP-A-5-105881 JP-A-5-163491 JP-A-5-202362 Japanese Patent Laid-Open No. 7-3267

  However, even with the methods described in Patent Documents 1 to 4, the effect of reducing the coefficient of thermal expansion or suppressing puffing is not necessarily sufficient, and the quality of the obtained coke is the aggregate of the graphite electrode for electric steelmaking. The actual situation is that the required level has not yet been reached.

  The present invention has been made in view of the above-described problems of the prior art, and an object thereof is to provide a petroleum coke having a sufficiently low thermal expansion coefficient and sufficiently suppressed puffing and a method for producing the same.

  Therefore, in order to solve the above problems, the present invention provides an initial boiling point of 300 ° C. or higher obtained as a residual oil when a predetermined raw material oil is distilled under reduced pressure, an asphalt content of 12% by mass or less, a saturated content of 50% by mass or more and First boiling point 200 ° C. or higher obtained by fluid catalytic cracking of a first heavy oil having a sulfur content of 0.3% by mass or less and a predetermined raw material oil, sulfur content 0.5% by mass or less, nitrogen content 0.2 Provided is a method for producing petroleum coke, characterized by coking raw oil containing 2% by mass or less of a second heavy oil.

  In this way, by coking the feed oil containing the first heavy oil and the second heavy oil, it is possible to stabilize petroleum coke with a sufficiently low thermal expansion coefficient and sufficiently suppressed puffing. Can be obtained.

  In addition, the use of an anti-puffing agent (puffing inhibitor) is conventionally known as a method for suppressing puffing. In this method, the anti-puffing agent becomes an impurity and the quality of the electrode (especially thermal expansion coefficient, density, etc.) May be adversely affected. On the other hand, the petroleum coke of the present invention is very useful in that puffing can be sufficiently suppressed without using an anti-puffing agent and the thermal expansion coefficient of the petroleum coke can be sufficiently reduced.

  In the present invention, “sulfur content” means a value measured according to JIS K2541 in the case of oil, and a value measured according to JIS M 8813 in the case of coke. The “nitrogen content” in the present invention means a value measured according to JIS K 2609 in the case of oil, and a value measured according to JIS M 8813 in the case of coke. Further, “saturated content” and “asphalt content” mean values measured using a thin layer chromatograph.

  In the present invention, the raw material oil containing the first heavy oil and the second heavy oil is such that a mosaic structure of 10 μm or less gives a coke of 5% or less when heat-treated at 500 ° C. preferable.

  Moreover, this invention provides the petroleum coke characterized by being obtained by the manufacturing method of the said petroleum coke of this invention.

  Since the petroleum coke of the present invention is obtained by the above-described method for producing petroleum coke of the present invention, it is a petroleum coke having a sufficiently small thermal expansion coefficient and sufficiently suppressed puffing. Therefore, the petroleum coke of this invention is suitable for uses, such as an aggregate of the graphite electrode for electric steelmaking.

  Moreover, in the petroleum coke of this invention, it is preferable that a sulfur content is 0.3 mass% or less, and a nitrogen content is 0.1 mass% or less.

  As described above, according to the present invention, a petroleum coke having a sufficiently small thermal expansion coefficient and sufficiently suppressed puffing and a method for producing the same are provided.

  Hereinafter, preferred embodiments of the present invention will be described in detail.

  The first heavy oil according to the present invention has an initial boiling point of 300 ° C. or higher, an asphalt content of 10% by mass or less, a saturated content of 50% by mass or more, and a sulfur content obtained as a residual oil when a predetermined raw material oil is distilled under reduced pressure. It is a heavy oil of 0.3 mass% or less.

  Examples of the first heavy oil feedstock include crude oil, atmospheric distillation residue obtained by distillation of crude oil, and mixed oils thereof.

  The treatment conditions when the above raw oil is distilled under reduced pressure are not particularly limited as long as the boiling point, asphalt content, saturated content and sulfur content of the obtained first heavy oil satisfy the above conditions, but the pressure is 30 kPa or less. Preferably, the temperature is 400 ° C. or higher.

  Among the heavy oils obtained as residual oils when distilled under reduced pressure in this way, the heavy oil satisfying the above-mentioned conditions for the boiling point, asphalt content, saturated content and sulfur content is the first heavy oil according to the present invention. Used as

  That is, the initial boiling point of the first heavy oil is 300 ° C. or higher as described above, and preferably 350 ° C. or higher.

  The asphalt content of the first heavy oil is 12% by mass or less as described above, preferably 10% by mass or less, and more preferably 9% by mass or less. When the asphalt content exceeds 12% by mass, the coefficient of thermal expansion of the obtained coke becomes high.

  Further, as described above, the saturated content of the first heavy oil is 50% by mass or more, preferably 55% by mass or more, and more preferably 60% by mass or more. When the saturated content is less than 50% by mass, the coefficient of thermal expansion of the obtained coke is increased.

  Moreover, the sulfur content of the first heavy oil is 0.3% by mass or less as described above, preferably 0.2% by mass or less, and more preferably 0.1% by mass or less. If the sulfur content exceeds 0.2% by mass, puffing of petroleum coke cannot be sufficiently suppressed.

  In addition, the second heavy oil according to the present invention has an initial boiling point of 200 ° C. or higher, a sulfur content of 0.5% by mass or less, and a nitrogen content of 0.2% by mass or less obtained by fluid catalytic cracking of a predetermined raw material oil. Of heavy oil.

  Here, “fluid catalytic cracking” means a process of cracking a high-boiling fraction using a solid acid catalyst or the like. A fluid catalytic cracking apparatus used for such treatment is also called FCC (Fluidized Catalytic Cracking).

The second heavy oil feedstock is not particularly limited as long as it can obtain a heavy oil whose boiling point, sulfur content and nitrogen content satisfy the above conditions by fluid catalytic cracking, but the density at 15 ° C. Is preferably a hydrocarbon oil of 0.8 g / cm ³ or more. Examples of such raw material oil include atmospheric distillation residual oil, vacuum distillation residual oil, shale oil, tar sand bitumen, orinocotal, coal liquefied oil, and heavy oil obtained by hydrorefining these. In addition to the above, the raw material oil for the second heavy oil may further contain relatively light oils such as straight-run gas oil, vacuum gas oil, desulfurized gas oil, and desulfurized vacuum gas oil. In the present invention, atmospheric distillation residue and vacuum distillation residue are particularly preferably used.

The conditions for fluid catalytic cracking are not particularly limited as long as it is possible to obtain a heavy oil whose boiling point, sulfur content and nitrogen content satisfy the above conditions. For example, the reaction temperature is 480 to 550 ° C., and the total pressure is 1 to 3 kg. / Cm ² G, catalyst / oil ratio of 1 to 20, and contact time of 1 to 10 seconds are preferable.

  Examples of the catalyst used for fluid catalytic cracking include a silica / alumina catalyst, a zeolite catalyst, or a catalyst in which a metal such as platinum (Pt) is supported on these catalysts. A commercial item may be used for these catalysts.

  The initial boiling point of the second heavy oil thus obtained is 200 ° C. or higher as described above, and preferably 220 ° C. or higher. When the initial boiling point is less than 200 ° C., the coke yield at the time of coking is lowered and the thermal expansion coefficient is increased.

  Moreover, the sulfur content of the second heavy oil is 0.5% by mass or less, preferably 0.4% by mass or less, more preferably 0.3% by mass or less as described above. When the sulfur content exceeds the above upper limit value, the petroleum coke puffing cannot be sufficiently suppressed.

  Further, as described above, the nitrogen content of the second heavy oil is 0.2% by mass or less, preferably 0.15% by mass or less, and more preferably 0.1% by mass or less. If the nitrogen content exceeds the above upper limit value, the petroleum coke puffing cannot be sufficiently suppressed.

  In the present invention, by coking the raw material oil containing the first heavy oil and the second heavy oil, petroleum whose coefficient of thermal expansion is sufficiently small and puffing is sufficiently suppressed Coke can be obtained stably. Here, the mixing ratio of the first heavy oil and the second heavy oil in the raw oil is not particularly limited, but the first heavy oil is 1 to 50% by mass based on the total amount of the raw oil. It is preferably 5 to 50% by mass, more preferably 15 to 50% by mass.

  Moreover, it is preferable that the raw material oil containing the first heavy oil and the second heavy oil is such that a mosaic structure of 10 μm or less gives a petroleum coke of 5% or less when heat-treated at 500 ° C. . Here, a small proportion of the mosaic structure of 10 μm or less in petroleum coke means that the growth state of liquid crystal called mesophase is good. Mesophase is an intermediate product produced by thermal decomposition and polycondensation accompanying heat treatment of raw material oil, and a series of aromatic rings developed along the same plane. It is considered that the thermal expansion coefficient of needle coke can be reduced if this mesoface grows large and is oriented in the uniaxial direction. Therefore, it is important how to produce a mesoface with advanced crystals.

  Conventionally, if a raw material oil contains a large amount of a saturated component, particularly an aliphatic component, a cross-linking reaction occurs in addition to the polymerization and polycondensation of aromatic components. It is believed that it does not grow and, as a result, the coefficient of thermal expansion increases. In view of this point, it is a surprising result that even if the saturated content of the first heavy oil is 60% by mass or more, a petroleum coke having a mosaic structure of 10 μm or less and 5% or less can be obtained.

  Examples of the method for coking the above-mentioned feedstock oil include a delayed coking method, a visbreaking method, a flexi coking method, a yurika process, and H-Oil. Among these, the delayed coking method is preferable.

  In the delayed coking method, petroleum coke feedstock rapidly passes through a heating pipe while being heated, and is introduced into a coke drum to cause coking. The coking conditions are not particularly limited, but the temperature is preferably 400 to 600 ° C., more preferably 450 to 550 ° C .; the time is preferably 24 to 72 hours, more preferably 36 to 60 hours.

  The coke thus obtained is preferably calcined in a rotary kiln, a shaft furnace or the like. The temperature during calcination is preferably 1000 to 1500 ° C., and the time is preferably 2 to 6 hours.

  Moreover, as a method for producing a graphite electrode product using the petroleum coke of the present invention, a raw electrode obtained by extruding and molding a raw material obtained by adding an appropriate amount of binder pitch to the petroleum coke of the present invention is manufactured. There is a method in which a raw electrode is obtained, the raw electrode is baked, graphitized, and then processed.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example at all.

[Example 1]
First, an atmospheric distillation residue (density 0.92 g / cm ³ , sulfur content 0.35 mass%) was distilled under reduced pressure under conditions of a heating furnace outlet temperature of 350 ° C. and a pressure of −100 kPa, an initial boiling point of 410 ° C., A vacuum distillation residue oil (hereinafter referred to as “vacuum distillation residue oil A”) having an asphalt content of 9% by mass, a saturation content of 61% by mass, a sulfur content of 0.1% by mass and a nitrogen content of 0.3% by mass was obtained.

  Next, the vacuum distillation residue oil A was put in a test tube and heat treated at 500 ° C. for 3 hours at normal pressure to be coke. When the produced coke was embedded in a commercially available resin and observed with a polarizing microscope, the mosaic structure of 10 μm or less was 15% by mass.

Further, desulfurized vacuum gas oil (sulfur content: 500 mass ppm, density: 0.88 g / cm ^{3 at} 15 ° C.) is subjected to fluid catalytic cracking, and fluid catalytic cracking residual oil (hereinafter referred to as “fluid catalytic cracking residual oil A”). Obtained. The initial boiling point of the obtained fluid catalytic cracking residual oil A is 210 ° C., the sulfur content is 0.1 mass%, the nitrogen content is 0.1 mass%, the asphalt content is 0 mass%, and the saturation content is 34 mass%. Met.

  Next, the fluid catalytic cracking residual oil A was put in a test tube and heat treated at 500 ° C. under normal pressure for 3 hours to be coke. When the produced coke was embedded in a commercially available resin and observed with a polarizing microscope, the presence of a mosaic structure of 10 μm or less was not recognized.

  Next, the vacuum distillation residue oil A and the fluid catalytic cracking residue oil A were mixed at a mass ratio of 1: 1 to obtain a coke raw material oil. This raw material oil was put into a test tube and heat treated at 500 ° C. under normal pressure for 3 hours to be coke. When the produced coke was embedded in a commercially available resin and observed with a polarizing microscope, the mosaic structure of 10 μm or less was 3.5% by mass.

  Next, the produced coke was fired at 1000 ° C. for 5 hours to obtain calcined coke. Table 1 shows the sulfur content, nitrogen content and bulk specific gravity of the obtained calcined coke.

  Further, 30% by mass of a coal-based binder pitch was added to calcined coke, and a cylindrical piece was produced with an extruder. This piece was fired at 1000 ° C. for 1 hour using a muffle heating furnace, and the thermal expansion coefficient after firing was measured. Furthermore, the piece was heat-treated from room temperature to 2800 ° C., and the degree of expansion in this process was measured as puffing. The obtained results are shown in Table 1.

[Example 2]
The reduced pressure distillation residue oil A and the fluid catalytic cracking residue oil A were mixed at a mass ratio of 1: 5 to prepare a coke raw material oil. A coke feedstock was prepared. Next, the obtained raw material oil was put in a test tube and heat-treated at normal pressure and 500 ° C. for 3 hours to be coke. When the produced coke was embedded in a commercially available resin and observed with a polarizing microscope, the mosaic structure of 10 μm or less was 2.5% by mass.

  Next, the produced coke was fired at 1000 ° C. for 5 hours to obtain calcined coke. Table 1 shows the sulfur content, nitrogen content and bulk specific gravity of the obtained calcined coke.

  Further, 30% by mass of a coal-based binder pitch was added to calcined coke, and a cylindrical piece was produced with an extruder. This piece was fired at 1000 ° C. for 1 hour using a muffle heating furnace, and the thermal expansion coefficient after firing was measured. Furthermore, the piece was heat-treated from room temperature to 2800 ° C., and the degree of expansion in this process was measured as puffing. The obtained results are shown in Table 1.

[Example 3]
The vacuum distillation residue oil A and the fluid catalytic cracking residue oil A were mixed at a mass ratio of 1: 3 to prepare a coke raw material oil. A coke feedstock was prepared. Next, the obtained raw material oil was put in a test tube and heat-treated at normal pressure and 500 ° C. for 3 hours to be coke. When the produced coke was embedded in a commercially available resin and observed with a polarizing microscope, the mosaic structure of 10 μm or less was 3.0% by mass.

  Next, the produced coke was fired at 1000 ° C. for 5 hours to obtain calcined coke. Table 1 shows the sulfur content, nitrogen content and bulk specific gravity of the obtained calcined coke.

  Further, 30% by mass of a coal-based binder pitch was added to calcined coke, and a cylindrical piece was produced with an extruder. This piece was fired at 1000 ° C. for 1 hour using a muffle heating furnace, and the thermal expansion coefficient after firing was measured. Furthermore, the piece was heat-treated from room temperature to 2800 ° C., and the degree of expansion in this process was measured as puffing. The obtained results are shown in Table 1.

[Comparative Example 1]
The vacuum distillation residue oil A was put into a test tube and heat-treated at normal pressure and 500 ° C. for 3 hours to be coke. Next, the produced coke was fired at 1000 ° C. for 5 hours to obtain calcined coke. Table 1 shows the sulfur content, nitrogen content and bulk specific gravity of the obtained calcined coke.

  Further, 30% by mass of a coal-based binder pitch was added to calcined coke, and a cylindrical piece was produced with an extruder. This piece was fired at 1000 ° C. for 1 hour using a muffle heating furnace, and the thermal expansion coefficient after firing was measured. Furthermore, the piece was heat-treated from room temperature to 2800 ° C., and the degree of expansion in this process was measured as puffing. The obtained results are shown in Table 1.

[Comparative Example 2]
Fluid catalytic cracking residual oil A was put in a test tube and heat-treated at normal pressure and 500 ° C. for 3 hours to be coke. Next, the produced coke was fired at 1000 ° C. for 5 hours to obtain calcined coke. Table 1 shows the sulfur content, nitrogen content and bulk specific gravity of the obtained calcined coke.

  Further, 30% by mass of a coal-based binder pitch was added to calcined coke, and a cylindrical piece was produced with an extruder. This piece was fired at 1000 ° C. for 1 hour using a muffle heating furnace, and the thermal expansion coefficient after firing was measured. Furthermore, the piece was heat-treated from room temperature to 2800 ° C., and the degree of expansion in this process was measured as puffing. The obtained results are shown in Table 1.

[Comparative Example 3]
Low-sulfur crude oil with a sulfur content of 0.2% by mass, nitrogen content of 0.3% by mass and saturation content of 40% by mass is distilled under reduced pressure, initial boiling point 410 ° C., asphalt content 12% by mass, saturation content 40% by mass, sulfur content A vacuum distillation residue oil (hereinafter referred to as “vacuum residue oil B”) having 0.2 mass% and nitrogen content of 0.3 mass% was obtained. This vacuum residue oil was put in a test tube and heat-treated at normal pressure and 500 ° C. for 3 hours to be coke. When the produced coke was embedded in a commercially available resin and observed with a polarizing microscope, the mosaic structure of 10 μm or less was 18%.

  Next, the produced coke was fired at 1000 ° C. for 5 hours to obtain calcined coke. Table 1 shows the sulfur content, nitrogen content and bulk specific gravity of the obtained calcined coke.

  Further, 30% by mass of a coal-based binder pitch was added to calcined coke, and a cylindrical piece was produced with an extruder. This piece was fired at 1000 ° C. for 1 hour using a muffle heating furnace, and the thermal expansion coefficient after firing was measured. Furthermore, the piece was heat-treated from room temperature to 2800 ° C., and the degree of expansion in this process was measured as puffing. The obtained results are shown in Table 1.

[Comparative Example 4]
The vacuum distillation residue oil B and the fluid catalytic cracking residue oil A were mixed at a mass ratio of 1: 1 to prepare a coke raw material oil. This raw material oil was put into a test tube and heat-treated at normal pressure and 500 ° C. for 3 hours to be coke. When the produced coke was embedded in a commercially available resin and observed with a polarizing microscope, the mosaic structure of 10 μm or less was 5%.

  Next, the produced coke was fired at 1000 ° C. for 5 hours to obtain calcined coke. Table 1 shows the sulfur content, nitrogen content and bulk specific gravity of the obtained calcined coke.

  Further, 30% by mass of a coal-based binder pitch was added to calcined coke, and a cylindrical piece was produced with an extruder. This piece was fired at 1000 ° C. for 1 hour using a muffle heating furnace, and the thermal expansion coefficient after firing was measured. Furthermore, the piece was heat-treated from room temperature to 2800 ° C., and the degree of expansion in this process was measured as puffing. The obtained results are shown in Table 1.

[Comparative Example 5]
The reduced pressure residual oil A and fluid catalytic cracking residual oil A were mixed at a mass ratio of 1: 5 to prepare a coke raw material oil. This raw material oil was put into a test tube and heat-treated at normal pressure and 500 ° C. for 3 hours to be coke. Next, the produced coke was fired at 1000 ° C. for 5 hours to obtain calcined coke. Table 1 shows the sulfur content, nitrogen content and bulk specific gravity of the obtained calcined coke.

  Further, 30% by mass of a coal-based binder pitch was added to calcined coke, and a cylindrical piece was produced with an extruder. This piece was fired at 1000 ° C. for 1 hour using a muffle heating furnace, and the thermal expansion coefficient after firing was measured. Furthermore, the piece was heat-treated from room temperature to 2800 ° C., and the degree of expansion in this process was measured as puffing. The obtained results are shown in Table 1.

Claims (4)

  A first heavy oil having an initial boiling point of 300 ° C. or higher, an asphalt content of 12% by mass or less, a saturated content of 50% by mass or more, and a sulfur content of 0.3% by mass or less obtained as a residual oil when a predetermined raw material oil is distilled under reduced pressure. Oil and a second heavy oil having an initial boiling point of 200 ° C. or higher obtained by fluid catalytic cracking of a predetermined raw material oil, a sulfur content of 0.5% by mass or less, and a nitrogen content of 0.2% by mass or less. A method for producing petroleum coke, characterized by coking raw material oil to be coke.   The raw material oil containing the first heavy oil and the second heavy oil is characterized in that a mosaic structure of 10 μm or less gives a coke of 5% or less when heat-treated at 500 ° C. The method for producing petroleum coke according to claim 1.   A petroleum coke obtained by the method for producing petroleum coke according to claim 1. The petroleum coke according to claim 3, wherein the sulfur content is 0.3 mass% or less and the nitrogen content is 0.1 mass% or less.