JPS6410560B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing special grade coke suitable for producing graphite electrodes for electric furnaces used in the steel industry. The electric furnace steelmaking process uses large graphite electrodes with a diameter of 0.5 to 1 m, and these electrodes are formed from a type of coke commonly labeled as "special grade" to withstand harsh service conditions. Special grade petroleum coke has been produced for many years and goes by many names. For example, special grade petroleum coke is called, for example, No. 1 coke, electrode coke, needle coke, and special grade coke. Special grade coke is crushed, calcined, mixed with a pitch of binder, extruded, and heated to form graphite electrodes. Special grade coke is distinguished from ordinary "regular coke" or "No. 2 coke" in terms of its metallic crystalline appearance and its tendency to form elongated fissures when crushed. Regular petroleum coke is somewhat amorphous and has a dark spongy appearance,
When crushed, it becomes irregularly shaped particles. Special grade coke has a low coefficient of thermal expansion (CTE).
There are various ways to measure and display coefficient of thermal expansion. The required CTE value to obtain the desired electrode is 30
When a graphite rod is measured by the optical lever method in the temperature range of ~98°C, it is 7.0×10 ^-7 /°C or lower. CTE of 5.0×10 ^-7 /℃ or less
The values are very favorable, especially for large diameter electrodes. The term "special grade coke" as used herein means delayed petroleum coke having a CTE value of 7.0x10 ^-7 /°C or less. Conventional raw materials for producing special grade coke have been petroleum fractions containing a large amount of aromatic fractions obtained by catalytic cracking. Straight-run atmospheric distillation residue is considered to be unsuitable as a raw material for producing special grade coke; in fact, the above-mentioned straight-run residue is unsuitable in most cases. US Pat. No. 2,745,794 discloses a combined catalytic and thermal cracking process. The coke obtained by this method is regular coke. US Pat. No. 2,775,549 describes a method for producing special grade coke from certain petroleum residues. In U.S. Pat. No. 2,922,755, distillation residue is mixed with hot tar, and this mixture is subjected to a delayed coking process under conditions where the distillation residue content is about 10 to 30 weight percent to produce special grade coke. . KERose's article "Hydrocarbon Processes", July 1971, pages 85-92, discusses feedstocks for special grade and regular coke in delayed coking processes. Traditionally, special grade coke has been produced by a method based on block operations. Regular Coker Hot tar obtained from gas oil is separated and fed to a special grade coker (coking equipment) based on block operation to obtain special grade coke, where most of the raw material fed to the coker is It is a hot tar obtained by thermal decomposition of regular coker light oil. A similar method for producing regular and special grade coke is disclosed in US Pat. No. 3,472,761.
A typical manufacturing method for regular coke is Kasch et al.
in his article “The oil and Journal” January 2, 1956. According to the present invention, 100% of oil is produced from atmospheric distillation residue having certain characteristics without supplying hot tar from the outside.
A method for continuously producing percent grade coke is provided. In this process, the feedstock is first mixed with the hot tar produced and then fed to the coker rectifier. The bottoms distillate from the coker rectifier is sent to a coker furnace where it heats to approximately 910-945°F (488-507°F).
heated to a coking temperature of 35 to
It is transferred to a coke drum maintained at a suitable pressure, such as 100 paig (2.50-7.03 Kg/cm ² ), where a special grade delayed coking process occurs. The steam from the coke drum containing the coker light oil is returned to the coker rectifier where approximately 400 to
Light gas oil with a boiling point of 650°F (204-343°C) and
It separates into a heavy gas oil consisting of a 650°F (343°C) fraction. The light coker gas oil is sent to the pyrolysis rectification tower,
From there, it is further sent to a light gas oil cracking furnace.
The product obtained here is returned to the pyrolysis rectification column. The heavy coker gas oil from the coker rectifier is sent to the pyrolysis rectifier, from where it is further supplied to the heavy gas oil cracker, where it is cracked and returned to the pyrolysis rectifier. The hot tar mixture from the light oil cracking furnace and the heavy oil cracking furnace is recovered from the bottom of the pyrolysis rectifier and returned to the coker rectifier where it is mixed with the atmospheric distillation residue where it is processed as described above. The series of cycles ends. The coke produced in the coke drum is recovered from the bottom of the coke drum and further processed to obtain coke suitable for electrodes for electric furnace steelmaking. All of the coke obtained by the method of the present invention is special grade coke suitable for the above-mentioned electrodes, and special grade coke and regular coke are not obtained at the same time as in the above-mentioned US Pat. No. 3,472,761. Special grade coke is significantly more expensive than regular coke, and the ability of the present invention to produce only special grade coke is highly desirable, and externally supplied raw materials are typically indispensable for the production of special grade coke. This is completely unexpected considering that it is an atmospheric distillation residue that was thought to be suitable. The object of the present invention is to provide a process in which atmospheric distillation residue is used as a fresh raw material and can produce special grade coke as a raw coke product. The raw material used in the present invention is an atmospheric distillation residue with an API specific gravity of 20 to 30, a Conradson residue carbon content (CCR) of 6.0% by weight or less, and
The boiling point distribution based on ASTM method D-1160 is as follows.

【table】

Atmospheric distillation residues are obtained by distilling fresh crude oil under substantially atmospheric pressure, and this distillation is generally the first step in the crude oil refining process.
Atmospheric distillation removes the low-boiling components (approximately 400 to 650 degrees Fahrenheit) of crude oil. Only atmospheric distillation residues having the above-mentioned properties are preferably used in the process of the invention. Many atmospheric distillation residues do not have all of the above characteristics;
Therefore, the method of the present invention is not satisfied. An example of an atmospheric distillation residue having the characteristics necessary for the present invention is
It is obtained from Minas crude oil and has the following properties. Specific gravity (API) 27.9 Conradson residual carbon content 4.6

[Table] The conditions of the coking and pyrolysis steps in the present invention are the same as the conventional conditions for producing special grade coke and hot tar. Thus, the feature of the present invention lies not in the new operating conditions in the field of coking or pyrolysis, but in the combined coking and pyrolysis process for producing special coke as a coke product, in which raw materials with specific properties are externally sourced. The discovery was made that it could be used as a raw material for yutsu. A typical plant employing the method of the present invention may be described as a complete, fully equipped, fixed battery limit plant. The plant consists of a delayed coker unit, a pyrolysis unit, a gas recovery unit with product processing functions, a coke burner unit, utility equipment, and raw material and product storage tanks with shipping equipment. The present invention can produce 100% special grade coke from a raw material consisting of 100% atmospheric distillation residue, and
Up to 10% by volume of ethylene tar can optionally be added. In addition to coke, the process produces fuel gas, propane, butane, naphtha, fuel fractions, and other hydrocarbon products. Traditionally, hot tar for special grade coke production has been produced from regular coker light oil obtained from the coking process for producing regular coke. In the present invention a continuous process is adopted in which all of the feedstock fed to the system is atmospheric distillation residue and the hot tar used is externally supplied in a conventional regular coking operation. It's not manufactured, it's internally manufactured. The method of the invention will now be described with reference to the embodiment of FIG. Atmospheric distillation resid having the above-mentioned characteristics is fed via line 20 to a coker rectification column 21. Up to 10 volume percent of ethylene tar may optionally be added to the distillation residue. Ethylene tar is a residual oil obtained from conventional petrochemical processes for producing ethylene and is often used in small quantities as a premium coker feedstock. Coker rectification column 21
The light gas oil and heavy gas oil from the pyrolysis rectification tower 1
3 and cracking furnaces 17, 19 via lines 22 and 23, respectively. The light and heavy gas oils are sent from the pyrolysis rectification column 13 to a light oil cracking furnace 17 and a heavy oil cracking furnace 19, respectively, where they are respectively pyrolyzed and returned to the pyrolysis rectification column 13. The two types of light oils are transferred from the coker rectifier 21 to the cracking furnaces 17 and 19,
If desired, it may be transported directly. The tar from the cracking furnaces 17, 19 is removed from the bottom of the pyrolysis rectifier 13 and added via line 24 to the feedstock fed externally to the coker rectifier 21.
The hot tar taken out from the bottom of the coker rectification column 21 and the heavy components of the external raw materials are transferred to the coker heating furnace 5.
where it is heated to coking temperature. The material heated in the coker furnace 5 is sent to one of the coke drums 7. coke drum 7
The overhead distillate from is returned via line 25 to coker fractionator 21. High light fractions such as gasoline and gaseous products are removed from the top of the coker fractionator 21 and recovered via the separator 3. Other high and light components are removed from the top of the pyrolysis rectification column 13 and are recovered via a separator 15 and a fuel oil stripper 9. The operation of the method shown in FIG.
33901, page 4, upper left column, line 5 and below, and its typical operation is performed as follows. The atmospheric distillation residue having an API gravity of about 20-30° and the Conradson residual carbon content and boiling point distribution described above is preheated to about 815.6° C. by heat exchange and then passed to the bottom of the coker fractionator 21. The temperature at the bottom of the coker fractionator is maintained at about 842.3-898°C. 8.0~5.0°API recovered from pyrolysis rectification column 13
Hot tar having a specific gravity of 442° C. is fed to the bottom of the coker rectification column 21 together with the atmospheric distillation residual oil.
The bottom oil of the coker rectification column 21 containing the atmospheric distillation residual oil is pumped to the coker heating furnace 5, where about.
Heated to 885℃498℃. The specific gravity of the bottom oil pumped to the coker heating furnace 5 is about 14-16° API. The above-mentioned bottom oil discharged from the coker heating furnace 5 is approximately
It is passed through one of two coke drums 7 operated at a pressure of 4.57-5.28 Kg/cm ² . The two coke drums 7 are normally operated in a 24 hour cycle, with the bottom oil being passed through one drum while the coke produced and deposited is removed from the remaining drum. The overhead vapor exiting from the top of the coke strum 7 returns to the flash zone of the coker rectifier 21. After the coke produced in the coke drum is taken out, it is further processed in a baking tower. The baked coke has qualities suitable for use as electrodes and metallurgical furnaces. A heavy coker gas oil having an API gravity of approximately 14-18° and a light coker gas oil having a specific gravity of approximately 85-89° API are produced in the coker fractionator 21.
The heavy coker gas oil and the light coker gas oil are passed to the pyrolysis rectification column 13. The overhead oil from coker fractionator 21 is coker wet gas and coker naphtha. Coker rectifier 21 processes light and heavy coker gas oils to produce tar and light products. Two types of decomposition heating furnaces are used, one of which is the heavy gas oil heating furnace 19, which thermally decomposes the heavy gas oil in a gentle manner, while the light gas oil heating furnace 17 thermally decomposes the heavy gas oil under severe conditions. Decomposes thermally. The products from pyrolysis column 13 are wet gas, hot naphtha, fuel fraction, and unstripped hot tar. Decomposition heating of the above two types 17,1
The output from 9 is introduced into a fiash zone located directly below the heavy gas oil pan of the pyrolysis rectification column 13. The temperature of this flash zone is controlled to minimize the amount of gas oil in the hot tar. The raw coke from coke trum 7 is further processed in a calciner. = The yield of burned coke is about 80%. The coker furnace 5 is operated at an outlet temperature of about 496-502°C.
The coke drum 7 is operated at a pressure of about 4.57-5.28 Kg/cm ² and an outlet temperature of about 452-460°C. Another embodiment of the present invention will be described based on FIG. This example has substantially the same operating conditions as the example based on FIG. are the same. A vacuum resid fraction is removed from the bottom of the vacuum distillation column 26 and sent via line 20 to a coker rectification column 21 .
The top distillate of the vacuum distillation column 26 is fed via line 27 to the pyrolysis rectification column 13 . The use of vacuum distillation column 26 reduces the amount of material to be processed in coker fractionator 21 and coker furnace 5. As a result, the gas oil fraction of the atmospheric distillation residual oil is transferred to the coker fractionator 2.
1 and the coker heating furnace 5, and directly into the pyrolysis rectification column 13 and then the cracking furnace 1.
7 and 19, the operational efficiency can be improved. The coking and pyrolysis conditions in this example are the same as in the first example according to FIG.

[Brief explanation of drawings]

FIG. 1 is a flow sheet of one embodiment of the present invention, and FIG. 2 is a flow sheet of another embodiment. 21... Coker rectification column, 5... Coker heating furnace,
7... Coke drum, 13... Pyrolysis rectification column, 17
...Light gas oil cracking furnace, 19...Heavy gas oil cracking furnace, 26
...Vacuum distillation column.

Claims (1)

[Scope of Claims] 1 (a) A step of supplying a raw material consisting of 90 to 100% by volume of atmospheric distillation residual oil and 10% by volume or less of ethylene tar to a coker rectification column (provided that the above-mentioned atmospheric distillation The residual oil has an API gravity of 20-30, a Conradson residual carbon content of less than 6.0%, and has the following boiling point distribution); Volume Percent Temperature (°C) 5 232-371 10 260-399 20 299-438 30 332-471 40 354-504 50 382-532 60 482+ (b) Transferring the bottom distillate from the coker rectifier to a coker heating furnace and heating the bottom distillate to the coking temperature; ( c) A step of supplying the heated bottom distillate to a coke drum maintained under special coking conditions to produce special coke therein; (d) Transferring the top distillate vapor from the coke drum to the above coke drum. (c) Recovering light oil from the coker rectification tower, supplying it to a pyrolysis unit, and pyrolyzing this light oil in the pyrolysis furnace means to contain hot tar. (f) supplying the effluent from said pyrolysis furnace means to a pyrolysis rectifier; (g) recovering hot tar from said pyrolysis rectifier;
and a step of combining this hot tar with the upper atmospheric distillation residue; (h) a step of recovering special grade coke, which is the only coke product obtained through each of the above steps, from the coke drum; In a method for producing special grade coke from oil; before the step (a) above, the atmospheric distillation residue is first fed to a vacuum distillation column, where it is separated into a vacuum distillation residue fraction and a light oil fraction. , the vacuum distillation residue fraction is supplied to the coker rectification column, and the gas oil fraction is supplied to the thermal cracking unit. 2. The method according to claim 1, wherein the gas oil comprises light gas oil and heavy gas oil. 3. The method of claim 2, wherein said light and heavy gas oils are fed to said pyrolysis rectifier before being fed to said pyrolysis furnace means. 4. The method according to claim 3, wherein the pyrolysis furnace means comprises a light gas oil cracking furnace and a heavy gas oil cracking furnace. 5. The method according to claim 4, wherein the gas oil fraction from the vacuum distillation column is supplied to the pyrolysis rectification column.