CN216614470U - Light oil catalytic cracking reaction system - Google Patents
Light oil catalytic cracking reaction system Download PDFInfo
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- CN216614470U CN216614470U CN202220385872.4U CN202220385872U CN216614470U CN 216614470 U CN216614470 U CN 216614470U CN 202220385872 U CN202220385872 U CN 202220385872U CN 216614470 U CN216614470 U CN 216614470U
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Abstract
The utility model provides a light oil catalytic cracking reaction system. The system comprises a fluidized bed catalytic cracking reactor, a quenching system, a compression unit, a condensate stripping tower, a dehexanizer and a selective hydrogenation reactor which are sequentially connected, wherein an outlet of the selective hydrogenation reactor is connected with an inlet of the fluidized bed catalytic cracking reactor. According to the utility model, the selective hydrogenation reactor is additionally arranged in the light oil catalytic cracking reaction system, so that the dialkene and alkyne in the circulating material can be efficiently converted into olefin, the contents of the dialkene and alkyne in the feed of the fluidized bed catalytic cracking reactor are strictly controlled, the coking amount of the reactor system is inhibited, and the operation period of the device is prolonged.
Description
Technical Field
The utility model relates to the technical field of catalytic cracking, in particular to a light oil catalyst cracking reaction system capable of inhibiting coking of the inner wall of equipment.
Background
The technology for preparing olefins by light oil fluidized catalytic cracking is a new technology for producing low-carbon olefins, and compared with the traditional steam cracking device, the technology for preparing olefins by catalytic cracking has the advantages of higher yield of low-carbon olefins and lower energy consumption, and the development of the technology is paid more and more attention. In the flow, in order to produce more low-carbon olefins, the carbon four to carbon six produced by the device are not completely recycled to the reactor for cracking. The circulating material contains high olefin content, alkane, alkyne and dialkene, and the industrial device finds that MAPD, butadiene, cyclopentadiene and carbon hexadiene are found in the circulating material in actual operation, and the content of the dialkene is up to more than 2 wt% when the highest content is reached. The recycle stream contributes to the yield of the low-carbon olefin by catalytic cracking of the fluidized bed, but is not beneficial to the control of the coking of the fluidized bed reactor system, so that the coking of the inside of the reactor and the high-temperature oil gas quencher is caused.
The coking under the high-temperature environment comprises gas-phase coking and liquid-phase coking, wherein the gas-phase coking is mostly formed by polymerization of alkyne and dialkene, and the liquid-phase coking is formed by condensation polymerization of polycyclic aromatic hydrocarbon. The operation temperature of the light oil catalytic cracking reactor is above 600 ℃, alkyne and dialkene in gas-phase oil gas can be directly polymerized and coked, and polycyclic aromatic hydrocarbon is liquefied after being condensed to a certain molecular size in gas phase and further condensed into coke. Coking in the reaction system not only cokes on the surface of the molecular sieve catalyst, but also cokes seriously in the gas inlet and the dipleg of the cyclone separator in the settling chamber and in the heat exchange tube of the high-temperature oil gas quenching heat exchanger discharged by the reactor. The long-period efficient operation of the reaction system is influenced.
In order to effectively control coking of a reactor system for preparing olefins by catalytic cracking of light oil, the contents of dialkenes and alkynes in the feed of the reactor need to be strictly controlled, the fresh feed does not contain the dialkenes and alkynes generally, and the circulating material needs to be controlled in a critical way. The circulating material comes from the light oil catalytic cracking separation section, and the separation part is provided with a reactor for removing acetylene and oxides, so that the acetylene in the ethylene product is not overproof, and the content of the oxides in the cold box feeding is not overproof. The conversion rate of the reactor to the dialkene and MAPD is only about 50%, and a large amount of dialkene and alkyne are leaked from the discharge of the reactor and enter a circulating material to return to the catalytic cracking reactor. The practical operation of industrial plants proves that it is difficult to control the dienes and alkynes in the recycled material with high efficiency by means of the reactor for removing acetylene and oxide alone. The circulating material is an important cause of coking of a reactor system, long-period operation of the device is influenced, and an effective way for removing the dialkene and the alkyne in the device is urgently needed.
SUMMERY OF THE UTILITY MODEL
In order to solve the above problems, an object of the present invention is to provide a light oil catalytic cracking reaction system, which can strictly control the contents of diolefin and alkyne in the circulating material by adding a selective hydrogenation reactor, effectively inhibit coking on the inner wall of the equipment of the light oil catalytic cracking reaction system, and prolong the operation period of the apparatus.
In order to achieve the aim, the utility model provides a light oil catalytic cracking reaction system which comprises a fluidized bed catalytic cracking reactor, a quenching system, a compression unit, a condensate stripping tower, a dehexanizer and a selective hydrogenation reactor which are sequentially connected, wherein an outlet of the selective hydrogenation reactor is connected with an inlet of the fluidized bed catalytic cracking reactor.
In the reaction system, the quenching system is used for cooling and separating the discharged material of the fluidized bed catalytic cracking reactor. The quench system generally includes a reaction oil gas quench heat exchanger and a quench unit coupled to each other. The reaction oil gas quenching heat exchanger is used for cooling the discharged material of the fluidized bed catalytic cracking reactor, and the quenching unit is used for separating quenching oil, pyrolysis gasoline and process water from the cooled material. The inlet of the reaction oil gas quenching heat exchanger is used as the inlet of the quenching system and is connected with the outlet of the fluidized bed catalytic cracking reactor, and the outlet of the quenching unit is used as the outlet of the quenching system and is connected with the inlet of the compression unit.
In the above reaction system, the compression unit is used to pressurize the discharge of the quench system and separate the C3-less components from the C4-greater components. The outlet of the compression unit is generally connected to the inlet of the condensate stripper and the inlet of the dehexanizer, respectively.
In the above reaction system, the compression unit may include a compressor and a carbon-three separation column. The carbon-three separation column can also be called a depropanizer.
In the above reaction system, the inlet of the compressor as the inlet of the compression unit is generally connected to the outlet of the quenching system. When the quench system includes a reaction oil gas quench heat exchanger and a quench unit, the inlet of the compressor is typically connected to the outlet of the quench unit.
In the above reaction system, the compressor is generally a four-stage or more compressor. Each section of the compressor is provided with a gas outlet. Every section compressor all is furnished with the knockout drum, and every knockout drum is equipped with the lime set export, and the lime set export of first section to inferior end section is called the intersegmental lime set export of compressor. The separation tank of the last-stage compressor is used for carrying out cold separation on the top gas of the carbon three-separation tower and providing liquid phase reflux for the carbon three-separation tower. In a specific embodiment, a gas outlet of the second last stage of the compressor is generally connected to an inlet of the carbon-three separation column, and an interstage condensate outlet of the compressor is generally connected to an inlet of the condensate stripper column. For example, when the compressor is a four-section compressor, the interstage condensate outlet of the first to third sections of the compressor is connected with the inlet of the condensate stripping tower; a first section gas outlet of the compressor is connected with a second section inlet of the compressor, a second section gas outlet of the compressor is connected with a third section inlet of the compressor, and a third section gas outlet of the compressor is connected with an inlet of the carbon-carbon separation tower; when the compressor is a five-section compressor, the condensate outlets between the first section and the fourth section of the compressor are connected with the inlet of the condensate stripping tower, and the gas outlet of the fourth section of the compressor is connected with the inlet of the carbon separation tower.
In the reaction system, an alkaline washing tower, a dryer, a de-acetylene and oxide reactor can be sequentially connected between the gas outlet of the secondary end section of the compressor and the inlet of the carbon-three separation tower, and are used for carrying out alkaline washing, drying, de-acetylene and oxide treatment on the gas discharged by the secondary end section compressor, and then sending the treated process gas into the carbon-three separation tower.
In the above reaction system, the carbon-carbon separation column is generally provided with a top outlet and a bottom outlet. The bottom outlet of the carbon-three separation tower is generally connected with the inlet of the dehexanizer, and the top outlet of the carbon-three separation tower is generally connected with the tail inlet of the compressor.
In the reaction system, the dehexanizer is used for separating C4-C6 components from pyrolysis gasoline components in components above C4. And a dehexane reflux pump is arranged in the dehexanizer and used for providing cold reflux of the dehexanizer.
In the reaction system, the selective hydrogenation reactor is used for selectively hydrogenating C4-C6 components output by the dehexanizer, so that dialkenes and alkynes in the C4-C6 components are converted into olefins and then are conveyed to flow back to the catalytic cracking reactor, thereby reducing the coking amount in the catalytic cracking reactor of the fluidized bed, increasing the olefin content in the circulating material and prolonging the operation period of the system. In some embodiments, the selective hydrogenation reactor may reduce the total content of dienes and alkynes in the C4-C6 components from 0.1-2.5 wt% to below 10 ppm.
In the above reaction system, the selective hydrogenation carried out in the selective hydrogenation reactor is generally liquid phase hydrogenation. The selective hydrogenation reactor may be loaded with a hydrogenation catalyst such as a palladium catalyst.
According to a particular embodiment of the utility model, the operating temperature of the selective hydrogenation reactor is generally between 40 and 120 ℃ and the operating pressure is generally between 2.5 and 4.5 MPaG.
The utility model has the beneficial effects that: the selective hydrogenation reactor is additionally arranged in the light oil catalytic cracking reaction system, so that the dialkene and alkyne in the circulating material can be efficiently converted into olefin, the contents of the dialkene and alkyne in the feeding material of the fluidized bed catalytic cracking reactor are strictly controlled, the coking amount of the reactor system is inhibited, and the operation period of the device is prolonged.
Drawings
Fig. 1 is a schematic view of the structure and application process of a light oil catalytic cracking reaction system of example 1.
Description of the symbols
R1-a fluidized bed catalytic cracking reactor; r2-selective hydrogenation reactor; e1-reaction oil gas quenching heat exchanger; s1-quench unit; s2-a compression unit; s21-compressor; t1-condensate stripper; t2-dehexanizer; t3-carbon three separation column.
Detailed Description
The technical solutions of the present invention will be described in detail below in order to clearly understand the technical features, objects, and advantages of the present invention, but the present invention is not limited to the practical scope of the present invention.
Example 1
The present embodiment provides a light oil catalytic cracking reaction system, and this system includes: the system comprises a fluidized bed catalytic cracking reactor R1, a quenching system, a compression unit S2, a condensate stripper T1, a dehexanizer T2 and a selective hydrogenation reactor R2.
The quenching system is used for cooling the process gas discharged from the fluidized bed catalytic cracking reactor R1, separating the process gas from quenching oil, pyrolysis gasoline and process water, and fully recovering heat. Specifically, the quench system includes a reaction oil gas quench heat exchanger E1 and a quench unit S1.
The compression unit S2 is used for pressurizing the discharge of the quenching system and separating heavy components above C4 from the materials. Specifically, compression unit S2 includes compressor S21 and carbon-three separation column T3.
The compressors are typically four-stage and higher compressors. The compressor S21 used in this embodiment is a four-stage compressor, each stage of compressor is provided with a gas outlet, and each stage of compressor is provided with a separation tank and a condensate outlet. The knockout drum of the first section to the third section S21 of the compressor S21 is used for separating condensate, the knockout drum of the fourth section (not shown in FIG. 1) of the compressor S21 is used for providing liquid phase reflux for the carbon three-separation tower T3, and the condensate outlet of the first section to the third section of the compressor S21 is called an intersegment condensate outlet.
The carbon-separation tower T3 is also called a depropanization tower and is provided with a tower top outlet and a tower kettle outlet. The carbon-three separation column is used for separating the components below C3 and the components above C4 from the process gas discharged from the second last stage (the third stage in the embodiment) of the compressor S21.
An alkaline washing tower, a dryer and a de-acetylene and oxide reactor are sequentially connected between a secondary tail section gas outlet of the compressor S21 and the carbon-separation tower T3.
A reflux pump is arranged in the dehexanizer T2, and a reflux pump outlet is arranged at the top of the dehexanizer T2.
The selective hydrogenation reactor R2 is packed with a palladium-based catalyst. The selective hydrogenation reactor R2 in this example is an adiabatic fixed bed selective hydrogenation reactor.
As shown in fig. 1, the connection relationship of each part in the light oil catalytic cracking reaction system is as follows: an inlet of the fluidized catalytic cracking reactor R1 for receiving light oil and a recycle stream; the outlet of the fluidized bed catalytic cracking reactor R1 is connected with the inlet of a reaction oil gas quenching heat exchanger E1, and the outlet of the reaction oil gas quenching heat exchanger E1 is connected with the inlet of a quenching unit S1; the outlet of the quenching unit S1 is connected with the inlet of the compressor S21; an intersegment condensate outlet of the compressor S21 is connected with an inlet of a condensate stripping tower T1; a secondary end section gas outlet of the compressor S21 is connected with an inlet of the carbon-three separation tower T3; the tower top outlet of the carbon-three separation tower T3 is connected with the fourth section inlet of the compressor S21; an outlet of the condensate stripping tower T1 and an outlet of the carbon-three separation tower T3 are respectively connected with an inlet of a dehexanizer T2; the outlet of the dehexanizer T2 is connected to the inlet of the selective hydrogenation reactor R2; the outlet of the selective hydrogenation reactor R2 is connected with the inlet of the fluid catalytic cracking reactor R1.
In this embodiment, the condensate outlet of the fourth stage of compressor S21 may be connected to the inlet of carbon triseparator T3 for providing a liquid phase reflux to carbon triseparator T3.
The present embodiment also provides a light oil catalytic cracking reaction process method performed in the light oil catalytic cracking reaction system, where the process method includes:
1. conveying light oil to a fluidized bed catalytic cracking reactor R1 for catalytic cracking, and conveying the formed process discharge to a reactor oil gas quenching heat exchanger E1 from an outlet of the fluidized bed catalytic cracking reactor R1;
2. the process discharge of the fluidized bed catalytic cracking reactor R1 is cooled in a reactor oil gas quenching heat exchanger E1, and then enters a quenching unit S1 to separate the process gas from quenching oil, pyrolysis gasoline and process water, and sufficient heat recovery is carried out;
3. the process gas discharged from the quenching unit S1 enters a compressor S21 of a compression unit S2 for pressurization, an intersegment separation tank from a first section to a third section of the compressor S21 separates condensate, the condensate takes components above C4 as main components, and a small amount of light components below C3 are dissolved in the condensate; the condensate enters a condensate stripping tower T1 to separate components above C4 from components below C3, and the components above C4 are discharged from a tower kettle of the condensate stripping tower T1 and enter a dehexanizer T2;
the process gas discharged from a gas outlet of the second tail section of the compressor S21 is subjected to alkali washing, drying, acetylene removal and deoxidization treatment and then enters a carbon separation tower T3, the process gas is separated in a carbon separation tower T3, components above C4 discharged from the tower bottom of the carbon separation tower T3 enter a dehexanizer T2, gas (mainly components below C3) discharged from the tower top of the carbon separation tower T3 enters a fourth section of the compressor S21 and is compressed and then enters a compression tank for cold separation, a part of condensate discharged from a condensate outlet of the fourth section of the compressor returns to the carbon separation tower T3 to serve as liquid phase reflux, and the rest condensate and the gas are extracted as light components.
4. The tower bottom discharge of the condensate stripping tower T1 and the tower bottom discharge of the carbon three separation tower T3 enter a dehexanizer T2 to separate C4-C6 components from pyrolysis gasoline, and C4-C6 component materials enter a selective hydrogenation reactor R2 from a reflux pump outlet at the top of a dehexanizer T2.
5. The total content of dialkene and alkyne in the feed of the selective hydrogenation reactor R2 (namely C4-C6 components discharged from a dehexanizer T2) is 0.1-2.5 wt%, under the conditions that the operation temperature is 40-120 ℃ and the operation pressure is 2.5-4.5MPaG, the feed is subjected to liquid phase selective hydrogenation in the selective hydrogenation reactor R2, the dialkene and alkyne in the feed are converted into olefin, the content of the dialkene and alkyne in the discharge of the selective hydrogenation reactor R2 is less than 10ppm, and the discharge returns to the fluidized bed catalytic cracking reactor R1 for cyclic cracking.
When the diene and alkyne content in the feed to selective hydrogenation reactor R2 is high (e.g. above 2.5 wt%), the diene and alkyne content in the discharge from selective hydrogenation reactor R2 is above 10 ppm. The process also comprises the steps of conveying the discharged material of the selective hydrogenation reactor R2 as a feed to the selective hydrogenation reactor R2 for liquid phase selective hydrogenation until the content of dialkene and alkyne in the discharged material is less than 10ppm, and returning the discharged material to the fluidized bed catalytic cracking reactor R1 for circular cracking.
The light oil feeding amount of a process for preparing olefin by fluidized catalytic cracking of certain light oil is 40 ten thousand tons per year, a selective hydrogenation reactor is additionally arranged in the system, the process is operated, and the change condition of the coking amount of the system before and after the selective hydrogenation reactor is additionally arranged is shown in table 1.
TABLE 1
As can be seen from the results in Table 1, by adding the selective hydrogenation reactor in the system, the content of dialkene and alkyne in the circulating material of the light oil catalytic cracking reactor is greatly reduced and is less than 10ppm, the coking rate of the catalytic cracking reactor system is obviously reduced, and the operation period of the reactor is prolonged from 12 months to 24 months.
It should be understood that the above-mentioned embodiments of the present invention are only examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention, and it will be obvious to those skilled in the art that other variations or modifications may be made on the basis of the above description, and all embodiments may not be exhaustive, and all obvious variations or modifications may be included within the scope of the present invention.
Claims (10)
1. The utility model provides a light oil catalytic cracking reaction system, its characterized in that, the system is including the fluidized bed catalytic cracking reactor, quench system, compression unit, condensate stripping tower, dehexanizer, the selective hydrogenation ware that connect gradually, the export of selective hydrogenation ware with the entry linkage of fluidized bed catalytic cracking reactor.
2. The light oil catalytic cracking reaction system of claim 1, wherein the quenching system comprises a reaction oil gas quenching heat exchanger and a quenching unit which are connected with each other, an inlet of the reaction oil gas quenching heat exchanger is connected with an outlet of the fluidized bed catalytic cracking reactor, and an outlet of the quenching unit is connected with an inlet of the compression unit.
3. The light oil catalytic cracking reaction system according to claim 1, wherein an outlet of the compression unit is connected to an inlet of the condensate stripper and an inlet of the dehexanizer, respectively.
4. The light oil catalytic cracking reaction system of claim 1, wherein the compression unit includes a compressor and a carbon three separation column.
5. The light oil catalytic cracking reaction system according to claim 4, wherein the compressor is a four-stage or higher compressor.
6. The light oil catalytic cracking reaction system according to claim 5, wherein an interstage condensate outlet of the compressor is connected to an inlet of the condensate stripping tower, and a penultimate gas outlet of the compressor is connected to an inlet of the carbon separation tower.
7. The light oil catalytic cracking reaction system of claim 6, wherein an alkaline washing tower, a dryer, a de-acetylene and oxide reactor are sequentially connected between the gas outlet of the secondary end section of the compressor and the inlet of the carbon three-separation tower.
8. The light oil catalytic cracking reaction system of claim 4, wherein the carbon-three separation tower is provided with an overhead outlet and a kettle outlet, the overhead outlet of the carbon-three separation tower is connected with the last inlet of the compressor, and the kettle outlet of the carbon-three separation tower is connected with the inlet of the dehexanizer.
9. The light oil catalytic cracking reaction system according to claim 1, wherein a dehexane reflux pump is provided inside the dehexanizer.
10. The light oil catalytic cracking reaction system according to claim 1, wherein the selective hydrogenation reactor is loaded with a palladium-based catalyst.
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