JPS6111991B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an improved method for producing needle coke by a delayed coking process. In particular, the present invention relates to an improved delayed coking process useful for producing high-grade needle coke used as a raw material for artificial graphite electrodes and the like. It is known to those skilled in the art to produce coke by delayed coking processes from a wide variety of raw materials.
Such processes are used to produce both the grade coke used in anode production and premium grade coke, ie, high quality coke, often referred to as needle coke. The conventional delayed coking process for the production of needle coke consists of heating a suitable coking feedstock, usually suitably pretreated, in a coke oven to the required coking temperature. The feed oil is continuously supplied to a coking drum, coking is progressed by the thermal energy of the supplied oil, and the introduction of the coking raw material is stopped after the produced coke is filled to a desired level in the coking drum. Then, the supply of the coking raw material is switched to another coking drum, and the coke in the drum where the introduction of the raw material is stopped is usually removed by steam stripping to remove residual oil immediately after being cut off, and then cut from the coking drum by jet water flow etc. The process consists of obtaining raw coke. The raw coke thus obtained is then calcined, usually at a temperature of about 1,000 to 1,400°C, and further heated to a high temperature of, generally, about 2,700 to 3,000°C to graphitize it for use in manufacturing artificial graphite electrodes. By the way, one guideline currently generally adopted for quality evaluation of needle coke is the coefficient of thermal expansion (CTE) of graphitized coke.
It is generally determined that the lower the CTE value, the better the quality of needle coke. For this reason, in the delayed coking process for the purpose of producing needle coke, CTE
Many proposals have been made to keep the value as low as possible, many of which are aimed at pre-treating coking raw materials to remove defective components and reforming them, and some are aimed at selecting processing conditions for delayed coking methods. is,
Furthermore, various combinations of the two have been proposed. For example, as an example of pretreatment of coking raw materials, US Pat.
34807) describes a method for separating and removing amorphous materials by first subjecting petroleum coking raw materials to a heat soaking treatment in the presence of sulfur and then subjecting them to controlled thermal decomposition. It has been shown that needle coke (highly crystalline petroleum coke) can be produced by delayed coking of treated coking feedstocks. As another pretreatment method to provide feedstock for needle coke production, U.S. Pat. Added sulfur to 30ppm
A not less amount of sulfur is dissolved in the pyrolyzed heavy oil, and the pyrolyzed heavy oil is heated to 450〓~600〓 (232℃
The highly unsaturated compounds present in the heavy oil are polymerized by a soaking treatment at a temperature of ~316°C), and the pyrolyzed heavy oil thus treated is heated to a temperature of ~300°C in a heating zone.
850〓~1100〓(454℃~593℃ at 600psig outlet pressure
℃), and this heating is applied to the pyrolyzed heavy oil.
Sufficient to reduce the API gravity by at least 1° based on a substance with a boiling point of 500〓 (260°C) or higher to obtain a treated pyrolyzed heavy oil with an API gravity not greater than -3° based on the material. A method is described which consists of recovering the pyrolyzed heavy oil so treated for a period of time. Furthermore, as an example of a combination of raw material pretreatment and specific delayed coking conditions, U.S. Pat. % or less of crude oil, distillation residue oil obtained from it, and sulfur content
In the first step, feedstock oil selected from cracked residue oil with a sulfur content of 0.8% by weight or less, any distillation residue oil, and cracked residue oil that has been hydrodesulfurized to a sulfur content of 0.8% by weight or less is first treated with a small proportion of alkali. hydroxides of metals or alkaline earth metals and/or
In the presence or absence of carbonates, cracking is performed by heating in a heating furnace to a temperature of 430 to 520°C under a pressure of 4 to 20 Kg/cm ² G and remaining in the heating furnace at this temperature for a period of 30 to 500 seconds. After soaking, the reactants are sent to a high-temperature flash column and subjected to high-temperature flash distillation at a pressure of 0 to 2 Kg/cm ² G and a temperature of 380 to 480°C. is continuously separated and removed from a high-temperature flash tower as a pitch, and on the other hand, light fractions such as cracked gas, gasoline, and kerosene fractions are separated from the distillate to obtain a heavy fraction. The fraction is heated to the required temperature for coking, sent to a coke drum, and subjected to delayed coking treatment for more than 30 hours at a pressure of 4 to 20 kg/cm ² G and a temperature of 430 to 460°C, and the graphite is Disclosed is a method for producing highly crystalline petroleum coke characterized by producing highly crystalline petroleum coke whose thermal expansion coefficient is 1.0×10 ^-6 /°C or less on average from 100° to 400°C. ing. Furthermore, as an example of a combination of raw material pretreatment and a modified delayed coking method, U.S. Pat.
Specification No. 4040946 (Japanese Unexamined Patent Application Publication No. 1983-44101, Publication No. 4040946)
-31482) contains low sulfur crude oil, distillation residue oil, cracked residue oil or the like in the presence or absence of small proportions of alkali metal or alkaline earth metal hydroxides and/or carbonates. The heavy oil whose amorphous carbon-forming components are separated and removed as pitch or coke by heat treatment is heated in advance to the required temperature for coking, and then a pipe equipped with a jacket heating insulation bath and an injection nozzle at the top is heated. A pressurized vertical coking crystallizer equipped with a purging steam injection nozzle at the bottom is continuously injected downward through the injection nozzle pipe, and gaseous hydrocarbons are discharged from the top of the crystallizer. The residual liquid hydrocarbons are then allowed to accumulate in the crystallizer at a predetermined coking temperature, while a small amount of heated steam is injected through the purge steam injection nozzle at a rate low enough to prevent its clogging. High purity, large crystallite coke is produced by supplying hydrogen or an inert gas and sequentially coking the liquid hydrocarbons from the bottom to the top during the residence and growing coke crystals. A method for producing high-purity large-crystalline petroleum coke using a characteristic top-injection coking method is presented. It is already recognized by those skilled in the art that apart from the issue of pre-treatment of the coking feedstock, the most important delayed coking condition for the production of needle coke with the desired low CTE value is the coking temperature. be. That is, an excessively high coking temperature has a negative effect on the CTE value of the resulting coke, and also causes premature coking in the coker furnace, creating a risk of clogging of the heating tubes. In order to avoid such disadvantages, keeping the coking temperature low reduces the amount of volatile combustible substances in the raw coke obtained due to the constraints on coking time inevitably associated with delayed coking methods.
The content of combustible matters (hereinafter abbreviated as VCM) increases. By the way, the VCM content of raw coke has a significant influence on the subsequent calcining process. Although the increase in the porosity of the burnt coke is not large, the increase in the porosity of the burnt coke is not large, but the temperature rise rate of the raw coke is fast in a commercial-scale calciner such as the rotary kiln system that is usually used industrially. , with the increase of VCM content in raw coke, there arises a serious disadvantage that the porosity of burnt coke increases significantly (Transacticns of the
Metallurgical Society of AME, 239 , 1084~
(see page 1089, especially page 1088, July 1967). Also, as the VCM of the green coke increases, the density of the burnt coke decreases and therefore its strength decreases (Kirk-Othmer, Encyclopedia of Chemical
Technology, 3rd edition, volume 4, page 572). In particular, as mentioned above, in the industrial-scale sintering process,
Raw coke with a high VCM content has serious problems such as loss due to pulverization during its handling and sintering process, and formation of large lumps in the furnace.
On the other hand, if the VCM content of the raw coke is too low, it will naturally become extremely difficult to cut the raw coke out of the coking drum. In this way, in the production of needle coke by the delayed coking method, the CTE value of the coke and the VCM content of the raw coke have an antinomic relationship with respect to the coking temperature. The reality is that the degree of freedom regarding the selection of options is extremely limited. In fact, traditional delayed coking processes aimed at producing high-quality needle coke often produce less than the desired
The final raw coke in the coking drum is constrained by coking temperature constraints to achieve the CTE value.
VCM has to be relatively high, and is usually around 10% or slightly higher, including commercially available products. Moreover, because the heated feedstock oil is continuously conveyed to the coking drum and coked sequentially within the drum, which is a method unique to the delayed coking method, coke is generated immediately before the conveyance of the heated feedstock oil is stopped. The raw coke obtained by coking the raw material oil introduced into the coking drum, that is, the raw coke in the top layer of the coking drum, is particularly high.
It is unavoidable that the VCM content is usually around 12 to 15%, and the coke in the top layer with such a high VCM content cannot become high quality needle coke due to the problems in the calcination process mentioned above. This has been a major problem with the conventional method from the economic point of view. The main objective of the present invention is to provide improved delayed coking for the production of needle coke that can maintain both the VCM content of raw coke and the CTE value of coke at desired levels, both of which have a trade-off relationship with coking temperature. It is in providing the law. Another object of the present invention is an improved delayed coking process for producing needle coke having substantially lower CTE values than needle coke obtained by conventional delayed coking processes using the same coking feedstock. is to provide. Yet another object of the present invention is to provide a new method for adjusting the VCM of coke produced in a delayed coking process. Therefore, according to the invention, the coking feedstock is heated in a coker furnace and introduced into a coking drum, and coking proceeds until the coke is filled to the desired level in the coking drum. When producing needle coke by the delayed coking process, which consists in later cutting off the coking drum by stopping the introduction of coking feedstock and repeating the above operation for another coking drum, the coke is Coke the coking raw material in the coking drum before separating the coking drum.
in the range of 450°C to 500°C by carrying out at a temperature of 415°C to 455°C and, after separating the coking drum, passing the contents of the separated coking drum through heated non-coking steam; heating to a temperature at least 10°C higher than the coking temperature of the coke, and heating to obtain a coke having a volatile combustible material (VCM) content of at least 4% by weight and not more than 10% by weight; Provided is a method for producing needle coke by a delayed coking process characterized in that the process is carried out for a sufficient period of time. To explain the features of the present invention in more detail below, the main feature of the present invention is that the heating conditions of the coking drum are as (a) a coking temperature in the range of 415°C to 455°C; and (b)
After the subsequent separation of the coking drum, the contents of the separated coking drum should be heated to 450°C to 500°C.
range, but in combination with further heating to a temperature at least 10°C higher than the previous coking temperature. By adopting such heating conditions, according to the present invention, VCM within the above desired range can be achieved.
It is possible to obtain a higher quality raw coke with a substantially lower CTE value than if conventional delayed coking conditions were employed from the same coking feedstock, yet as previously described. 〓It is possible to prevent troubles during the baking process. The VCM content of raw coke within the range specified in the present invention corresponds to the range that has been generally accepted as a guideline for desirable VCM content for the reasons mentioned above. The coking temperature is set such that the desired coking is completed at the end of the introduction of the heated coking feedstock into the coking drum, i.e. at the time of separation of the coking drum, and therefore the coking Although the temperature is usually required to be controlled to obtain a raw coke with a desired VCM content at the point of separation, other conflicting constraints,
VCM in such a desirable range, especially because of the constraint that relatively low coking temperatures should be employed.
It is practically impossible to achieve this content, which is an inherent difficulty in delayed coking processes. While the present invention adopts delayed coking technology,
After the coking drum is separated, its contents are further heated to the specified higher temperature to produce raw coke.
By adjusting the VCM content to the desired range, it is possible to employ lower coking temperatures for the same coking feedstock than conventional delayed coking methods, i.e. coking temperatures before cutting, thereby achieving the above-mentioned This method solves the problems inherent in the delayed coking method. That is, by employing the above structure, the present invention can advantageously perform the cutting of coke from the coking drum and the subsequent calcination process, and can also advantageously perform the coke cutting process that is to be performed later, and can also perform the coke cutting process from the same coking raw material in the conventional delayed coking process. It was possible to produce needle coke with a lower CTE value than that of the previous method. The present invention therefore develops an entirely new method of adjusting the VCM of coke in a delayed coking process, thereby making it possible to employ lower coking temperatures, which are more desirable with a view to providing lower CTE values. It can be said that this is the case. Furthermore, if the delayed coking conditions that characterize the present invention are combined with various previously proposed methods of preparing coking raw materials for producing needle coke, that is, pretreatment methods, it is possible to obtain a lower CTE value. It will be clear that needle coke of improved quality can be provided. Therefore, although the present invention is applicable to a wide range of delayed coking processes for the production of needle coke,
In particular, it can be preferably applied to producing high-grade crystalline coke from coking raw materials pretreated by heat soaking and/or pyrolysis and/or removal of amorphous materials. For example, the method of the present invention can be preferably applied to coking raw materials pretreated by the methods described in the above-cited US Pat. No. 4,108,798 or US Pat. No. 4,199,434. To explain more specifically the operating conditions of the delayed coking method of the present invention, the coking drum during operation is heated to a temperature higher than the normal coking temperature before separation, that is, by continuously introducing heated coking raw materials. Low temperature i.e. 415℃~455℃, more preferably
After operating at 420°C to 450°C and disconnecting the coking drum, i.e. after stopping the introduction of coking feedstock into the coking drum, the contents of the disconnected coking drum are heated to at least 450°C. Preferably the temperature is at least 460°C and does not exceed 500°C, preferably does not exceed 480°C, but at least 10°C below the previous coking temperature.
By passing heated non-coking steam into the contents of the coking drum at an elevated temperature of preferably at least 15°C, more preferably at least 20°C, a final concentration of at least 4% by weight is produced. , preferably for a time sufficient to obtain a coke having a volatile combustible material (VCM) content of at least 5% by weight and not exceeding 10% by weight, preferably not more than 8% by weight. After cutting off the coking drum, the time required to produce coke with a VCM content as described above will vary depending on the coke produced, the raw materials used to make such coke, and the heating temperature. . However, in many cases, such reduction in VCM content can be achieved by post-cleavage heating for periods on the order of 4 to 24 hours. As previously mentioned, post-separation heating of the coking drum contents is accomplished through the use of non-coking steam. Any of a wide variety of materials not suitable for coke production may be used for such heating. Representative examples of materials suitable for this purpose include light coker distillate, coker gas ( _C1 - _C4 hydrocarbons),
Mention may be made of water vapor, nitrogen and other non-coking gases other than oxidizing gases. The selection of suitable gases to effectuate this heating will be apparent to those skilled in the art from the description herein. The particular temperatures used in each of the coking steps and subsequent post-cutting heating steps are desired for each particular coking feedstock and final product.
It will vary depending on the CTE value. In general, using lower temperatures within the coking temperature range specified above will result in a final product with a lower CTE value, but in order to achieve a suitable reaction rate when using some coking feedstocks. It has been recognized that it is necessary to use higher temperatures within the coking temperature range specified above. The feedstocks generally used for the production of coke according to the invention are heavy petroleum feedstocks, such as distillation residues derived from crude oil, lubricating oil extracts and hydrodesulfurized lubricating oil extracts, cracking residues or distillation or cracking residues of petroleum. Hydrodesulfurization products and coal-based feedstocks such as coal tar or pitch distillate. A preferred raw material is so-called pyrolysis heavy oil or black oil, which has a boiling point higher than that of pyrolysis gasoline produced together with olefins during the pyrolysis of liquid hydrocarbon raw materials, that is, a boiling point higher than the upper limit boiling point of pyrolysis gasoline, which is approximately 187°C to 218°C. residual heavy black oil, catalytic cracking decant oil, pyrolysis tar, lubricating oil extract and its hydrodesulfurization products, coal tar or pitch distillate, etc. Generally, such raw materials have a low sulfur content, i.e. 1.5
It has a sulfur content of 0.8% by weight or less, preferably 0.8% by weight or less. Mixtures of such raw materials may also be used. Next, as a particularly preferred embodiment of the present invention,
A case in which a coking raw material is pretreated in accordance with the pretreatment method described in the specification of US Pat. No. 4,108,798 will be specifically described. The feedstock is first heat soaked in the presence of at least 300 ppm sulfur. Such sulfur is preferably provided by adding sulfur (usually in the form of at least one selected from the group consisting of elemental sulfur, mercaptans and sulfur disulfide). In most cases, the amount of added sulfur is
Do not exceed 200ppm. Heat soaking is usually for at least 5 minutes, and more commonly from 5 to 120 minutes. The heat soaking temperature is usually about 230°C to 315°C. Of course, if the required amount of sulfur is present in the feedstock, no addition of sulfur is necessary. In some cases, the desired results may be achieved by heat soaking at temperatures between 230°C and 315°C without the addition of sulfur. It is believed that the heat soaking step improves the overall effect by polymerizing the polymerizable components in the feedstock. The heat soaked feedstock is then heat treated to cause controlled pyrolysis and thereby increase aromaticity (lower API gravity). Initial heat soaking is followed by heat treatment to achieve pyrolysis, in which the raw materials are typically heated in a tubular furnace at 450°C to 595°C under pressures of the order of 4 to 50 kg/cm ² G.
This is achieved by heating to an exit temperature of approximately Pyrolysis is carried out for a sufficient time to increase aromaticity. Such pyrolysis time is usually moderate, 15 to 120 seconds. Generally, the API gravity is reduced by at least 1° (based on materials with boiling points above 260°C). After this heat treatment, the feedstock is treated to remove amorphous and non-distillable heavy components. obtain.
Such separation is usually done by high temperature flashing.
This is easily achieved by using Such high temperature flushing treatment is usually carried out at a high temperature of 380°C to 510°C under a pressure of 0.1 kg/cm ² A to 2 kg/cm ² G. In this flushing, amorphous components can be selectively removed as pitch from the flashing bottom. Materials recovered as coking raw materials are usually at 260℃
It boils in the range of ~538℃. Lighter components from feedstocks such as gas, gasoline and gas oil can be separated and recovered separately. The coking feedstock pretreated as described above is then heated according to the invention to a temperature of 415° C. to 415° C., which is lower than the coking temperatures normally used in the prior art.
Delayed coking at a temperature of 455°C. The optimum coking temperature varies depending on each feedstock. The coking pressure is usually about 2 to 10 kg/cm ² G. After the coking drum is filled, the coking drum is separated and its contents are heated to 450°C to 500°C.
C. but at least 10.degree. C. above the previous coking temperature for a period sufficient to reduce its volatile combustible content to the specified value. Although the embodiments of the present invention described above are preferred, the coking process of the present invention may be used to eliminate one or more of the raw material pretreatment steps, and even in such cases, coke Improved quality can be achieved. However, in many cases a combination of the above three pretreatment steps is a feature of the present invention due to the controlled coker furnace exit temperature and subsequent reduction of volatile combustible material content after coking drum separation. By combining this with heating, the highest quality coke can be produced. Thus, for example, the coker furnace may be operated at the specified temperature and, after the coking drum has been cut off, its contents may be heated under the specified conditions in order to obtain a coke with a volatility in the specified range. It is possible to exclude an initial soaking treatment and/or to exclude a pyrolysis treatment of the raw materials and/or to exclude a separation of amorphous components within the scope of the invention. For example, U.S. Pat. No. 4,199,434 discloses a method for pre-treating a coking feedstock comprising soaking the feedstock in the presence of sulfur at a first temperature and then heating it to a higher temperature to reduce the API gravity. is listed. Also, U.S. Patent No.
No. 3,687,840 describes a process in which coking feedstocks are pretreated in the presence of sulfur. One embodiment of the present invention will be described below with reference to the drawings. In the figure, the coking feedstock is introduced into the soaking drum 12 via a pipe 10, with sulfur being introduced simultaneously into the soaking drum 12 via a pipe 13, if required. The coking feedstock is heat soaked in the drum 12 as described above to accomplish polymerization of the highly unsaturated compounds. The heat-soaked raw material is removed from the drum 12 via tube 14 and introduced into the coil 15 of the pyrolysis furnace 16, where the raw material is pyrolyzed under the aforementioned conditions to increase its aromaticity. (Decrease API gravity). The pyrolyzed feedstock is taken out from coil 15 into tube 17, cooled by the resulting light gas oil in tube 18 as described below, and the combined stream is sent to vacuum flashing column 21 through pressure reduction valve 19. The vacuum flash column is operated at a temperature and pressure sufficient to remove amorphous materials and other heavy components from the feedstock. Generally, the flat tower is
Temperature around 380℃~510℃ and 0.1Kg/cm ² A~2Kg/
It operates at pressures on the order of cm ² G. The heavy pitch-like bottoms are transferred to column 2.
1 through tube 22. Light gas oil is recovered from column 21 through line 23, a portion of which is used as cooling oil in line 18. Naphtha and lighter gases are recovered from flash column 21 through pipe 24. The pretreated coked feedstock recovered through line 25 has components within a boiling range of approximately 260 DEG C. to 538 DEG C., and such components are then introduced into a coker combination fractionator tower 27. Coker rectifier 27, as known to those skilled in the art, recovers the coking feed from the bottom and transports light components not normally used as coking feed, such as heavy coker gas oil, through line 28 to the light coker. It is operated under conditions such that gas oil is recovered through line 29 and coker naphtha and gas are recovered through line 31. Coker fractionator 27 also receives coking drum overhead vapor through line 32, as is known to those skilled in the art. The bottom product removed from the coker rectification column 27 via tube 34 is sent to a coker furnace 35 of a type known to those skilled in the art and the heated material is introduced into a coking drum 36. The coking drum 36 is operated at the specified temperature and pressure. Overhead vapor is removed from the coking drum through line 38 and, after being cooled by a portion of the light gas oil in line 39, is introduced into coker rectification column 27 through line 32. After the coking drum has been filled to the desired level, the coking drum can be taken "off-line" as known to those skilled in the art, i.e., no longer feeding coking feedstock to the coking drum. do. The separated coking drum is shown as 36' in the drawings. According to the present invention, the separated drum 36' is heated to a higher temperature to reduce its volatile combustible content and reduce its CTE value. As shown in the drawings, superheated gas, such as light coker distillate, naphtha, coker gas, etc., is introduced into coking drum 36' through pipe 101. Such gas will normally be at a temperature and pressure sufficient to maintain the separated coking drum 36' at the specified temperature to reduce its volatile combustible content. Generally, the steam is introduced at a temperature of the order of 450<0>C to 525<0>C and a moderate pressure of 2 to 10 Kg/cm ^<2> G. The steam introduced through tube 101 and the volatile substances expelled from the drum contents are transferred to tube 102.
The coking drum 3 is removed from the coking drum 36' and separated through the coking drum 36'.
6' is introduced into a cooling tower 103 designed and operated to recover the non-coked vapor to be used in 6'. In the cooling tower 103, light components are transferred to the pipe 104.
The material to be recovered as a gas from and used as drying gas (the gas used for heating the coking drum contents after separation) is recovered as a liquid through line 105 and the heavy components are recovered as a liquid through line 10.
It is collected through 6. A portion of the material in tube 105 is passed through tube 109 into tube 107 containing condenser 108 for introduction as reflux into column 103. The remaining portion is passed through the tube 111 to the heating furnace 11.
2 and vaporized for use as a drying gas. The heated material from furnace 112 is introduced into separation column 115 to separate non-vaporized material, which is removed through tube 116. The superheated steam is separated from the separation column 115 through a conduit 101 to the coking drum 3 in order to obtain coke with a volatile combustible content as described above.
6'. In one version of the invention, the steam for the drying process can be recovered from the coker rectifier and the material removed from the separated coking drum is returned to the coker rectifier. Therefore,
In such operations, the coker rectifier is used for both the on-line (“on-line”) coking drum and the off-line (“off-line”) coking drum. . Similarly, in a preferred embodiment with reference to the drawings, (1) polymerization of unsaturated components by heat soaking treatment at low temperature, (2) increase in aromatic content (reduction in API specific gravity) by thermal decomposition treatment, and ( 3) Although the case in which pretreatment of coking raw materials by separation of pitches is employed has been described, the present invention is applicable to the case where coke is produced without such pretreatment and to one or more of such pretreatment steps. The above method can also be applied to the production of coke. Next, the present invention will be further explained with reference to Examples. Example 50 ppm of sulfur was added to decant oil having the properties shown in Table 1, and heat soaking was performed at a temperature of 260°C. The thus treated raw material was introduced into a tube with an inner diameter of 6 mm and subjected to thermal decomposition treatment at a temperature of 500° C. and a pressure of 20 Kg/cm ² G (residence time was 78 seconds based on cold oil). Next, this raw material is heated to 480℃ under atmospheric pressure.
The non-volatile substances were removed from the bottom of the column as pitch. The oil obtained by cooling the overhead distillate was used as a coking feedstock.

[Table] Using the oil obtained under the above conditions, delayed coking was carried out under the conditions shown in Table 2. A coking drum with an internal diameter of about 30 cm and a height of about 50 cm was placed in the molten salt bath to provide external heating. After the coking drum was filled, it was separated and heated at the conditions listed in the table.

[Table] Operations A to C shown in Table 2 are carried out according to the method of the invention, while operations D and E are carried out under different conditions, namely in operation D the post-cutting heating temperature is used according to the method of the invention. In run E, the coking temperature was higher than that used in the process of the invention. The raw coke obtained under these conditions is heated to 1400℃ in the usual way.
The coke was roasted and the coke was crushed. Each sample of burnt coke was mixed with coal tar pitch as a binder and the mixture was extruded into rods to produce electrodes. The resulting electrode was fired at 1000°C and graphitized at 3000°C. The coefficient of thermal expansion (CTE) in the direction parallel to the extrusion direction of the graphitized electrode was measured, and the results are shown in Table 3.

[Table] The raw coke obtained in Operation D contained a large amount of pitch-like material in the upper part. It melted and foamed during the baking process and had a very unsatisfactory appearance. The raw coke obtained in Run E had a spongy appearance containing a large amount of foam. As is clear from Table 3, the coke obtained by the method of the present invention was of extremely high quality. Furthermore, among the operations A, B, and C according to the present invention, operation B, which gave the best CTE value, was compared with operation B using the same feedstock oil and various operating conditions. Each operating condition and the results obtained are shown in the following table in comparison with Operation B. The pretreatment process of the feedstock oil is the same as in each operation B.

【table】

[Table] Comparative operation B-2 is the method of the present invention and the above-mentioned U.S. Pat.
This is to compare the method described in No. 4108798 (Japanese Unexamined Patent Publication No. 53-34801) using the same raw materials and the same coking conditions, and B-2.
350 by water vapor after separation adopted in
The 3 hour treatment at 0.degree. C. generally simulates the steam stripping conditions that occur after stripping in conventional delayed coking.
Results B-2 show that without the post-cutting heating that is a feature of the present invention, the coking temperature of 435°C for this feedstock is too low to achieve the desired VCM content, and is even higher in the upper part of the coking drum. This indicates that raw coke with a VCM content is produced, which may cause problems in the calcination process, and that the CTE value of the final target, graphitized needle coke, is quite low but slightly inferior to Operation B according to the present invention. ing. Comparative run B-3 requires higher coke in a delayed coking process according to the prior art similar to comparative run B-2 to achieve the same level of green coke VCM content as obtained in inventive run B. This is the case where a coking temperature of 460 DEG C. is adopted, and the steam stripping after separation simulates the treatment after separation in the usual delayed coking process, as in the case of B-2. The result of B-3 shows that in order to achieve the desired VCM content, it is necessary to use a higher coking temperature than specified in the present invention, which results in a substantial increase in the CTE value of the target product, which is undesirable. It shows. Comparative operation B-4 shows that in operation B according to the present invention, when the coking temperature was lower than the lower limit specified by the present invention, the VCM content was reduced to that of operation B by heating to a higher temperature according to the present invention after cutting. Even if the coking rate was adjusted to the same level, the coking rate before separation was extremely low, and heating to 475℃ after separation caused a rapid coking reaction with the distillation of a significant amount of gas and evaporated matter. A considerable amount of sponge-like low-strength coke containing air bubbles is mixed into the needle coke produced, and the CTE of the needle coke obtained is
The values also show that they are substantially inferior compared to Run B. Comparative operation B-5 is a case where after coking treatment under the same conditions as operation B according to the present invention, heating after cutting was performed for 24 hours at 505 ° C., which exceeds the upper limit specified by the present invention, and the average VCM value was Although it shows 4.6% within the range specified by the present invention, coke with an abnormally low VCM is generated in the lower layer of the coke drum, causing inconvenience during cutting, and the CTE of needle coke
The value was also poor, and formation of spongy coke was observed in the upper layer. Example Decanted oil having the properties shown in Table 4 was pretreated under the conditions summarized in Table 5 to obtain a coking raw material.

【table】

[Table] Pressure Atmospheric pressure Table 6 shows the material balance in the above pretreatment.

[Table] The coking raw material thus obtained was coked under the conditions shown in Table 7. The VCM content of the raw coke thus obtained is also listed in Table 7.

[Table] Operations F and G were carried out according to the method of the present invention,
Run H, on the other hand, was conducted at a higher coking temperature during the delayed coking operation than the present invention, and the run was conducted at a lower post-cut heating temperature than the present invention. Electrodes were prepared from coke produced under the conditions given in Table 7 and graphitized at 3000°C. Table 8 shows the CTE of the graphitized electrode.

[Table] As is clear from Table 8, the coke obtained by the method of the present invention was of extremely high quality. EXAMPLE The pyrolysis tar obtained as a by-product in the pyrolysis of gas oil was pretreated under the conditions shown in Table 9 and coke was produced from the coking feedstock thus purified.

[Table] Using this coking raw material, coking was carried out under the conditions shown in Table 10.

TABLE Runs J, L, and M were conducted according to the process of the present invention, while run K was conducted at a higher coking temperature during a delayed coking run than the process of the present invention. An electrode was produced from the obtained coke in the same manner as in the example, and the CTE of the electrode graphitized at 3000°C was measured. The measurement results are shown in Table 11.

[Table] Example A hydrodesulfurized decant oil having the properties shown in Table 12 was pretreated under the same conditions as shown in Table 5 of Examples to obtain a coking raw material.

[Table] Using this coking raw material, coking was carried out under the conditions shown in Table 13. The VCM content of the obtained raw coke is also listed in Table 13.

【table】

Table: Run N was carried out according to the process of the invention, while Run P was carried out at a higher coking temperature during the run than specified by the invention. Run O was conducted at an in-flight coking temperature of 455°C, and then after the coking drum was filled, the drum contents were purged with unsuperheated steam for 2 hours without using temperatures above the coking temperature. Electrodes were prepared from the coke obtained under the conditions given in Table 13 and graphitized at 3000°C. Table 14 shows the CTE values of the graphitized electrodes.

[Table] As is clear from Table 14, the coke obtained by the method of the present invention (operation N) was of extremely high quality. The present invention utilizes delayed coking at lower temperatures than those used in the prior art and subsequent heating of the coking drum contents to a higher temperature after the coking drum has been cut to within a specified range.
The combination of obtaining a coke with a VCM content is particularly advantageous in that the coke obtained (after its calcining and graphitization) has a lower CTE value. The coke is produced at a low temperature as in the present invention and then calcined and graphitized (after cutting off at a controlled temperature in a coking drum in order to bring the VCM content of the coke produced within the specified range before calcining). (without heating)
In some cases, the CTR value of graphitized coke is higher than according to the invention. As mentioned above, the present invention is particularly suitable for needle coke (having a CTE of 1.35×10 ^-6 /
) and super needle coke (100~400℃)
It can be applied to the production of products with an average measured CTR of 1.1×10 ^-6 /°C or less. The present invention provides (1) a heat soaking treatment, usually in the presence of sulfur (although in some cases sulfur is not required), at a temperature of 230°C to 315°C to produce coke and /or a step of reducing the tendency of the polymer to precipitate; and/or (2) 450°C to 595°C
It can be particularly advantageously applied to the coking of raw materials that have been pretreated by (3) the step of pyrolyzing to increase their aromaticity and/or (3) the step of separating amorphous substances. Although pretreatment is not required and/or only one or two of the pretreatment steps listed above may be used, best results (lowest CTE values) are obtained when the three pretreatment steps listed above are controlled. coking and subsequent
This can be achieved in combination with a post-cleavage heating step to reduce the VCM content. Example: So-called ethylene tar, which is produced as a by-product in the production of ethylene using naphtha as a raw material (its properties are 15th
As shown in the table) is operated without any preliminary treatment
and used for delayed coking according to R.

Table: Run Q follows the method of the present invention, while Run R has the temperature conditions of a conventional delayed coking process selected to give the same level of VCM content in the green coke as Run Q. Table 16 shows a comparison of the operating conditions and results obtained for operations Q and R.

[Table] The above results demonstrate that the process of the present invention provides a significant improvement in CTE values compared to conventional delayed coking processes even when applied to coking feedstocks without pretreatment. . Example This example illustrates the case where the method of the present invention is applied to a coal-based coking feedstock. That is, operation S is an example in which coal tar is used as a starting material, while operation T is an example in which hydrotreated coal tar is used as a starting material. Run U is a comparative example that follows a prior art process that uses the same coal tar as feedstock used in Run S, and the coking temperature was adjusted to give a VCM content at the same level as that of the raw coke obtained in Run S. The following is the case when selected. Table 17 shows the properties of the raw materials used in these operations, and Table 18 shows the operating conditions and results.

【table】

[Table] Volume percentage

[Table] Ash content, weight percent 0.01 0.01

【table】 [Brief explanation of the drawing]

The drawings are schematic process diagrams showing a preferred embodiment of the present invention. 12... Soaking drum, 16... Pyrolysis furnace, 21... Vacuum flashing column, 27... Coker rectification column, 35... Coker heating furnace, 36,3
6'...coking drum, 103...cooling tower,
112... Heating furnace.

Claims (1)

[Claims] 1. Coking raw materials are heated in a coker heating furnace and introduced into a coking drum, and after coking proceeds and coke is filled into the coking drum to a desired level, coking is performed. When producing needle coke by the delayed coking process, which consists of disconnecting the coking drum by stopping the introduction of raw materials and repeating the above operation for another coking drum, The coking of the coking feedstock in the coking drum before separation is carried out at a temperature of 415° C. to 455° C. and after the separation of the coking drum the contents of the separated coking drum are heated to non-coking. 450℃~ by passing steam
500°C, at least 10°C above the coking temperature of the coke, and the heating is carried out to a temperature of at least 4% by weight and with a volatile combustible material content not exceeding 10% by weight. A method for producing needle coke by a delayed coking process, characterized in that the process is carried out for a sufficient period of time to obtain needle coke. 2. The method of claim 1, wherein the heating temperature after cutting off is at least 15°C higher than the coking temperature before cutting off. 3. The method according to claim 2, wherein the coking temperature is 420 to 450°C. 4 The heating temperature is at least 460°C and 480°C
4. The method according to claim 3, wherein the temperature does not exceed . 5. The method of claim 1, wherein the coking raw material is pretreated by heat soaking at a temperature of 230°C to 315°C to polymerize unsaturations in the raw material. 6. The method of claim 5, wherein the heat soaking is carried out in the presence of at least 30 ppm dissolved sulfur. 7. The method of claim 1, wherein the coking feedstock is pretreated by heating it to a final temperature of 450°C to 595°C to cause its thermal decomposition. 8 Following heat soaking, the coking raw material is heated to 450 ml.
A method according to claim 1, characterized in that the pretreatment is carried out by heating to a final temperature of between 595°C and pyrolysis thereof. 9 Heat-soaking the coking raw material at a temperature of 230°C to 315°C to polymerize unsaturated components; heating the heat-soaked coking raw material to a final temperature of 450°C to 595°C to cause its thermal decomposition. amorphous substances and heavy components are separated from the heat-treated product to obtain a pitch-free coking feedstock, which is heated in a coker heating furnace and introduced into a coking drum, where it is heated at 415°C to coking at a temperature of 455° C.; disconnecting the coking drum by stopping the introduction of the coking feedstock after coke has been filled to the desired level in the coking drum; The contents of the coking drum are finally heated to a temperature in the range of 450°C to 500°C, at least 10°C above the coking temperature of the coking drum, by passing heated non-coking steam through it. A process according to claim 1, comprising heating for a period sufficient to obtain a coke having a volatile combustible material content of 4% by weight and not exceeding 10% by weight. 10 Claims 1 to 9, wherein the coking raw material is pyrolysis heavy oil, lubricating oil extract, hydrodesulfurized lubricating oil extract, catalytic cracking decant oil, pyrolysis tar, or a mixture thereof. Any method described.