JPS6259750B2 - - Google Patents

Description

[Detailed description of the invention]

This invention relates to an improved pyrolysis method for petroleum heavy oil. Conventionally, with the aim of effectively utilizing heavy petroleum oil,
Various attempts have been made to thermally decompose this to obtain gas, light cracked oil and pitch. The use of pitch, which is produced from heavy petroleum oil, which exists in large quantities, as a caking agent for the production of coke for steelmaking blast furnaces or as a substitute for caking coal means that most of the coking coal for steelmaking can be exported overseas. In Japan, which relies on imports from other countries, this is extremely meaningful for reducing imported coking coal and expanding the range of types of coking coal that can be used. In order to match the quality of the pitch produced by thermal decomposition of petroleum-based heavy oil to the above-mentioned purpose, the properties of the pitch produced should be rich in benzene-insoluble matter,
It is necessary to have a composition that has a small amount of quinoline insoluble matter, that is, a composition that has a high content of β resin and has an intermediate degree of carbonization and a degree of polycondensation. Various batch methods and continuous methods are known as methods for thermally decomposing heavy petroleum oil. However, with these conventional methods, it is difficult to obtain a pitch of quality that meets the above objectives. The applicants first conducted thermal decomposition by flowing petroleum-based heavy oil from the bottom to the top through a reactor having one or more compartmented beds with an open part in the center, and setting the residence time to 1 to 10 hours. (Special application 1986-3921) However, in general, in the thermal decomposition reaction of petroleum-based heavy oil, bubbles such as cracked gas and cracked oil vapor are generated intensely at the early stage of the reaction. In the above method, since the reaction liquid is flowed from the bottom to the top, a large amount of bubbles are generated at the bottom of the reaction tower, which increases the capacity of the reaction tower. In addition, since the reaction liquid is stirred violently by the upward flow of gas, and the entire reaction liquid approaches a mixed state, a considerable number of stages are required in order to ensure that the quality of the resulting pitch is completely compatible with the above-mentioned purpose. The present invention seeks to provide an improved method for the thermal decomposition of heavy petroleum oils that produces a residue pitch rich in β-resin components. In the petroleum heavy oil pyrolysis method of this invention, heated petroleum heavy oil is placed in the upper reaction zone of an upright cylindrical reaction tower, which is divided into an upper reaction zone and a lower reaction zone by a partition plate having openings. Oil is continuously supplied and subjected to a pyrolysis reaction, the cracked gas and oil vapor generated at this time are extracted from the upper reaction zone, and then the reaction liquid from the upper reaction zone is passed through the lower reaction zone in a form similar to a piston flow. A small amount of cracked gas and cracked oil vapor generated at this time is removed from the upper reaction zone by raising the lower reaction zone, and a residue pitch is extracted from the bottom of the lower reaction zone. It is. In this invention, the characteristics of the thermal decomposition reaction of petroleum-based heavy oil, that is, as shown in FIG. The characteristic that β-resin production from by-product pitch mainly proceeds in the latter stage of the thermal decomposition reaction is utilized. The initial reaction is carried out in the upper reaction zone under the generation of cracked gas and cracked oil vapor as described above, and most of the thermal cracking reaction is completed. The reaction liquid leaving the upper reaction zone flows from above to below in the lower reaction zone in a manner similar to a piston flow.
During this time, the β-resin production reaction progresses with some thermal decomposition reactions. The cracked gas and cracked oil vapor generated by the thermal decomposition reaction in the lower reaction zone rise in the reaction liquid and are discharged via the upper reaction zone. The lower reaction zone can be divided into two or more compartments by a partition plate having apertures such as one or more circular holes or slits. An embodiment of this invention will be described with reference to FIG. Petroleum-based heavy oil from line 1 at a pressure of 1 to 20 atm enters the heating furnace 2, is preheated to a temperature of preferably 400 to 510°C, and is introduced into the upper reaction zone 5 of the reaction column 4 via line 3. A stirrer 8 is provided within the reaction tower 4 . The upper reaction zone 5 is connected to the lower reaction zone 6 via a partition plate 7. If necessary, steam for stripping cracked oil can also be sucked into this part. The lower reaction zone 6 is further divided into four sections by similar partition plates 7', 7'', and 7. Needless to say, there is no particular restriction on the number of sections as long as it is 1 or more, but if it is 20 or more, the number of sections is The height is too small to be practical. The partition plates 7, 7', 7'' and 7 are provided with openings such as circular holes or slits, but the diameter of the circular holes or the slit width is 5 mm. It is desirable that the size is larger than that. This is because if it is less than 5 mm, the downward flow of the reaction liquid will be obstructed. The area of the opening is the cross-sectional area of the reaction tower.
It is preferably 20% or less, particularly preferably 10% or less.
When the open area ratio is 20% or more, intermixing between sections becomes large. The aperture ratio of the partition plate can also be made smaller within the above range, such as toward the lower stage. The ratio of the volume of the upper reaction zone to the volume of the lower reaction zone of the reaction tower is
It is preferably 0.5 or less. If it is 0.5 or more, the piston flow effect cannot be sufficiently obtained. The petroleum heavy oil introduced into the upper reaction zone 5 is
At this point, most of the thermal decomposition reaction is completed. A large amount of gas and oil vapor are generated as a result of the reaction, and these are discharged from the system through line 9. The reaction liquid then passes through the openings in the partition plate 7 into the lower reaction zone and flows substantially in a piston flow from above to below through the openings in each of the partition plates 7', 7'', 7. While passing through the lower reaction zone, the polymerization reaction of the reaction liquid phase progresses to produce β-resin components, quinoline insoluble components, etc. The cracked gas and cracked oil vapor generated in the lower reaction zone are small amounts;
These rise in the form of bubbles in an upward direction opposite to the flow of the reaction liquid, and are finally extracted from line 9 together with the gas generated in the upper reaction zone. In order for the reaction liquid to smoothly flow downward against the rising bubbles in the lower reaction zone, it is desirable that the porosity of the partition plate be large, but this is not preferable because it promotes mixing between the compartments. According to the results of studies conducted by the present inventors, the area of the openings is selected to be 20% or less of the cross-sectional area of the reaction tower as described above, and the flow rate of cracked gas and cracked oil vapor in the openings of the partition plate is The above conflicting demands can be satisfied by selecting the speed within the range of 1 to 10 m/sec. If the flow rate is higher than this range, the reaction liquid will not descend smoothly, and if it is lower, mixing between the compartments will be excessive and the flow will move away from the piston flow. Pitch whose content of β-resin and quinoline insoluble components has increased due to the polymerization reaction in the lower reaction zone 6 is taken out of the system through a line 10 in liquid form. According to the present invention, the content of the β-resin component in the residue pitch obtained by thermal decomposition of petroleum heavy oil is increased. Moreover, it becomes possible to make the reaction tower relatively small in size. Furthermore, since the oil is heavy, it is difficult to separate the generated gas, but in the method of the present invention, there is no problem in taking out the product because there is little gas mixed into the product. This is a very important advantage in actual operation. Example: An apparatus of the type shown in Figure 2, with an upper reaction zone diameter of 400 mm, an upper reaction zone liquid depth of 400 mm, an upper reaction zone space height of 400 mm, a lower reaction zone diameter of 300 mm, and a lower reaction zone height. 950mm, number of partition plates: 6 (including the partition plate between the upper reaction zone and lower reaction zone), partition plate spacing
A 150mm one was used. In this device, experiments were conducted with the pore ratios of the partition plates set to 3, 5, 10, and 20%, and the residence time in the device set to 2 hours. The operating conditions and results are shown in Table 1. The raw material heavy oil is all Kuwait vacuum distillation column oil, and the preheating temperature is
The temperature was 490° C., the feed rate was 50/hr, and the reaction pressure was 1.5 ATA in the upper reaction zone.

【table】

[Table] Steady operation impossible As is clear from Table 1, when the gas flow velocity at the opening of the partition plate was as high as 22.2 m/sec as in Experiment No. 1, the reaction liquid could not descend in the lower reaction zone, causing flattening. It will wake up and make steady operation impossible. Experiment again
When the porosity of the partition plate is 20% as in No. 4, the β-resin content in the pitch is as low as 25% by weight, which is the case in Experiment No.
It is clear that the flow is further away from the piston flow than in cases 2 and 3.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between the reaction time, the amount of gas and oil vapor generated, and the reaction temperature in the thermal decomposition reaction of petroleum-based heavy oil, and FIG. 2 is a flowchart for explaining an embodiment of the present invention. It is a sheet. 2... Heating furnace, 4... Reaction tower, 5... Upper reaction zone, 6
...lower reaction zone, 7, 7', 7'', 7...partition plate, 8
…mixer.

Claims (1)

[Claims] 1 Heated petroleum-based heavy oil is continuously supplied to the upper reaction zone of an upright cylindrical reaction tower, which is divided into an upper reaction zone and a lower reaction zone by a partition plate with openings, to initiate a thermal decomposition reaction. The cracked gas and oil vapor generated at this time are extracted from the upper reaction zone, and then the reaction liquid from the upper reaction zone is transferred from the upper part to the lower part in a form similar to a piston flow in the lower reaction zone. A small amount of cracked gas and cracked oil vapor is withdrawn from the upper reaction zone by raising the lower reaction zone.
A method for thermal decomposition of heavy petroleum oil, characterized by extracting residual pits from the bottom of a lower reaction zone.