Catalytic cracking slurry oil purification treatment method and system

Abstract

The invention relates to a catalytic cracking oil slurry purification treatment method and system. The system comprises a catalytic cracking oil slurry extraction unit and a fine powder recovery unit, the fine powder recovery unit comprises a tower bottom oil slurry extraction pipeline; the catalytic cracking oil slurry extraction unit comprises a liquid collecting device arranged in a main fractionating tower of the catalytic cracking device, and an oil slurry outlet of the liquid collecting device is formed in at least one layer of tower trays from the first layer to the fifth layer of tower trays from the bottom of the main fractionating tower to the top. The extracted slurry oil provided by the invention is relatively low in colloid and asphaltene content and relatively low in viscosity, so that the property of the fed slurry oil in a downstream device is improved, the slurry oil purification efficiency is improved, and the operation energy consumption is reduced; the catalyst fine powder is recycled through the catalytic cracking device, so that the influence of the catalyst fine powder on an absorption stable part of the catalytic cracking device is reduced.

Description

Technical Field

[0001] This invention belongs to the field of petrochemicals, specifically relating to a method and system for purifying catalytic cracking oil slurry. Background Technology

[0002] While producing liquefied petroleum gas and gasoline with higher hydrogen content, the catalytic cracking process of hydrocarbon oils inevitably yields slurry oil and coke with low hydrogen and high carbon content. As the processed feedstocks become increasingly heavier and of lower quality, the amount of slurry oil discharged externally is constantly increasing in order to maintain the thermal balance of the catalytic cracking unit and improve the unit's throughput, resulting in a year-on-year increase in slurry oil production.

[0003] The tricyclic and tetracyclic aromatic hydrocarbons (TAHs) in slurry oil are high-quality components for manufacturing high-value products such as carbon black, rubber fillers, needle coke, and carbon fiber, possessing extremely high economic value and application prospects. However, the high-value utilization of slurry oil places strict requirements on the content of fine catalyst particles. Due to the limitations of the separation efficiency of the cyclone separation system in catalytic cracking units, some fine catalyst particles inevitably enter the fractionation system and ultimately accumulate in the slurry oil, becoming a major factor restricting its high-value utilization.

[0004] CN1958738A provides a method for removing catalyst powder from catalytic cracking slurry. The method first mixes light solvent oil and catalytic cracking slurry to prepare a mixed oil with a density less than water. Then, an aqueous solution containing demulsifier and flocculant is preheated and mixed with the mixed oil to demulsify. The lower layer of water enriched with catalyst powder is then separated to remove fine powder from the slurry. The removal time is short and the catalyst powder removal rate is high.

[0005] In the method for removing catalyst powder from catalytic cracking slurry disclosed in CN1958735A, for light slurry with a specific gravity less than water, an aqueous solution containing demulsifier and flocculant is mixed with the catalytic cracking slurry, demulsified, and then the lower aqueous solution enriched with catalyst powder is separated; for heavy slurry with a specific gravity greater than or equal to water, substances that can increase the specific gravity of water, such as ammonium acetate, ammonium citrate, fructose, glucose, sucrose, sorbitol, or xylitol, are added to the aqueous solution as weak electrolytes or non-electrolytes.

[0006] CN112708457A discloses an oil slurry hydrotreating system, which includes an oil slurry pre-filtration system and a filtered oil hydrotreating system. The oil slurry pre-filtration system includes a filter unit and a filter aid buffer tank, with a flexible, needle-free filter bag in the filter. The filtered oil hydrotreating system includes a hydrotreating reaction zone and a gas-liquid separation zone, with the filtered oil outlet pipeline connected to the inlet of the hydrotreating reaction zone. In this oil slurry treatment method, the oil slurry is first filtered in the oil slurry pre-filtration system, and the resulting filtered oil enters the filtered oil hydrotreating system for reaction, yielding hydrotreated filtered oil. This method features low cost, long operating cycle, and good environmental performance.

[0007] The above technologies reveal that, from the perspectives of equipment investment, separation efficiency, and continuous stable filtration, the method of removing fine catalyst powder from catalytic cracking slurry by adding demulsifiers and flocculants cannot be widely applied in industrial applications.

[0008] Filtration separation is effective due to its simple equipment, stable performance, and strong adaptability to raw materials. However, the viscosity of catalytic cracking slurry is currently high, which still leads to problems such as frequent filter switching and the inability of separation equipment to operate stably for long periods. Summary of the Invention

[0009] The purpose of this invention is to solve the problem that the device cannot operate stably for a long period of time when removing fine powder from oil slurry.

[0010] To achieve the above objectives, a first aspect of the present invention provides a catalytic cracking slurry purification system, the system comprising a catalytic cracking slurry extraction unit and a fine powder recovery unit; the fine powder recovery unit includes a bottom slurry extraction pipeline; the catalytic cracking slurry extraction unit includes a liquid collection device disposed in the main fractionation column of the catalytic cracking unit, and the slurry outlet of the liquid collection device is disposed on at least one of the 1st to 5th trays from the bottom of the main fractionation column.

[0011] Optionally, the catalytic cracking slurry extraction unit further includes a slurry buffer tank connected to the liquid collection device via a pipeline.

[0012] Optionally, the system further includes a filtration unit connected in series with the catalytic cracking slurry extraction unit; the filtration unit includes: at least one filter, and an extraction slurry inlet pipeline, a filter residue outlet pipeline, and a purified slurry outlet pipeline connected to the filter.

[0013] Optionally, the filter has an oil slurry extraction inlet at the bottom, a filter residue outlet at the bottom, and a purified oil slurry outlet at the top; a flushing medium inlet is provided at the end of the filter away from the filter residue outlet; the system also includes a flushing medium buffer tank and / or a filter residue receiving tank.

[0014] Optionally, the pore size of the filter material in the filter is 0.02-10 μm; preferably, the filter material is selected from one or more combinations of sintered metal powder filter cartridges, metal wire mesh filter cartridges, and ceramic membrane filter cartridges.

[0015] Optionally, the ratio of the flow rate of the oil slurry collected online by the liquid collection device to the flow rate of the oil slurry collected from the bottom of the main fractionation tower is 1:1-5.

[0016] Optionally, the bottom slurry extraction pipeline is connected to the slurry inlet of the catalytic cracking reactor; and / or the bottom slurry extraction pipeline is connected in parallel to the catalytic cracking slurry purification system.

[0017] A second aspect of the present invention provides a method for purifying oil slurry, the method comprising: At least one tray from the bottom to the top 5 of the main fractionation column of the catalytic cracking unit is used to extract slurry oil. Bottom oil slurry is extracted from the bottom of the main fractionation column of the catalytic cracking unit and returned to the catalytic cracking unit and / or thrown out; wherein the content of fine powder in the extracted oil slurry is 100-10000 mg / kg, preferably 150-2000 mg / kg.

[0018] Optionally, the kinematic viscosity of the extracted slurry at 100 °C is 2-70 mm. 2 / s, preferably 8-25 mm 2 / s; and / or the content of gum and asphalt in the extracted slurry is 15-30% by weight, preferably 16-28% by weight, more preferably 16-26% by weight.

[0019] Optionally, the method further includes: filtering the extracted oil slurry to obtain purified oil slurry; the filtration conditions include: a temperature of 200-350 ℃, preferably 240-320 ℃; and a pressure of 0.5-2.5 MPa, preferably 0.8-2.0 MPa.

[0020] Through the above technical solution, this invention, by extracting oil slurry from at least one of the 1-5 trays from the bottom of the fractionation tower II, can reduce the content of gum and asphaltenes in the extracted oil slurry to a low level. This improves the properties of the feed oil slurry for further downstream purification, reducing the gum and asphaltenes in the oil slurry to meet requirements while increasing the oil slurry purification efficiency and reducing operating energy consumption. The fine powder recovery unit can recover catalyst fine powder from the catalytic cracking unit, reducing the impact of catalyst fine powder on the absorption and stabilization section of the catalytic cracking unit.

[0021] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0022] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the following detailed description to explain the invention, but do not constitute a limitation thereof. In the drawings: Figure 1 This is a schematic diagram of a catalytic cracking slurry purification system provided in some embodiments of the present invention.

[0023] Explanation of reference numerals in the attached figures I. Catalytic cracking unit; II. Main fractionation tower; III. Filtration unit; 1. Riser reactor; 2. Main oil and gas pipeline; 3. Liquid collection device; 4. Pipeline; 5. Oil slurry buffer tank; 6. Pipeline; 7. Pipeline; 8. Outlet pipeline; 9. Pipeline; 10. Pipeline; 11. Backwash gas tank; 12. Pipeline; 13. Filter; 14. Filter; 15. Filter; 16. Pipeline; 17. Pipeline; 18. Filter residue buffer tank. Detailed Implementation

[0024] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0025] This invention provides a catalytic cracking slurry purification system, which includes a catalytic cracking slurry extraction unit and a fine powder recovery unit; the fine powder recovery unit includes a bottom slurry extraction pipeline 7; the catalytic cracking slurry extraction unit includes a liquid collection device 3 located in the main fractionation tower II of the catalytic cracking unit, and the slurry outlet of the liquid collection device 3 is located on at least one of the 1st to 5th trays from the bottom of the main fractionation tower II.

[0026] This invention reduces the content of gums and asphaltenes in the extracted slurry to a low level by extracting it from at least one of the first five trays from the bottom of the fractionation column II. The extracted slurry has a lower viscosity, improving the properties of the feed slurry for further downstream purification. This reduces the gum and asphaltenes content to acceptable levels while increasing slurry purification efficiency and reducing operating energy consumption. The fine powder recovery unit can recover catalyst fines from the catalytic cracking unit, reducing the impact of catalyst fines on the absorption and stabilization section of the catalytic cracking unit.

[0027] The aforementioned catalytic cracking unit can be a conventional reactor device in the art, such as one or more of the following: riser, constant linear velocity fluidized bed, constant diameter fluidized bed, upward conveyor line, and downward conveyor line.

[0028] In this invention, "fine powder" refers to the fine powder of catalyst in the slurry. The method for determining the content of fine powder of catalyst in the slurry adopts the enterprise standard Q / SH 0741-2018 "Determination of solid content of catalytic oil slurry by carbonization and calcination method".

[0029] The catalytic cracking slurry extraction unit also includes a slurry buffer tank connected to the collection device via a pipeline, which is used to stably transport the extracted slurry to the downstream processing unit.

[0030] Downstream of the oil slurry extraction unit, a purification unit may be provided for further reducing the amount of gum and asphalt in the oil slurry. The purification methods include, but are not limited to, sedimentation, centrifugation, electrostatic separation, and filtration. More preferably, the purification unit may be connected to a filtration device to reduce the amount of fine powder, gum, and asphalt in the oil slurry to a lower level.

[0031] The oil slurry extraction unit can be connected to a filtration device to further remove fine powder, gum, and asphalt from the extracted oil slurry.

[0032] In some specific embodiments of the present invention, the system further includes a filtration unit connected in series with the catalytic cracking slurry extraction unit; the filtration unit includes: at least one filter, and an extraction slurry inlet pipeline, a filter residue outlet pipeline and a purified slurry outlet pipeline connected to the filter.

[0033] Preferably, the filter has an oil slurry extraction inlet at the bottom, a filter residue outlet at the bottom, and a purified oil slurry outlet at the top.

[0034] The filter has a flushing medium inlet at the end away from the filter residue outlet.

[0035] Preferably, the filtration unit includes at least three filters connected in parallel. Under normal operating conditions, any two filters can be selected and switched to work alternately, and the purified slurry is output through the purified slurry outlet. When the pressure difference between the inlet and outlet of the online filter reaches the set switching pressure difference, the slurry feed is switched to the standby filter to continue filtering the slurry, and the online filter is backwashed.

[0036] The system further includes a flushing medium buffer tank and / or a filter cake receiving tank; the outlet of the flushing medium buffer tank is connected to the flushing medium inlet, so that the pressurized gas in the flushing medium buffer tank can flush the filter cake on the filter element clean, and the filter cake flows through the filter cake outlet to the filter cake receiving tank, and then the soaking oil enters the filter through the pipeline to immerse the filter element.

[0037] The filter material in the filter has a pore size of 0.02-10 μm; preferably, the filter material is selected from one or more combinations of sintered metal powder filter cartridges, metal wire mesh filter cartridges, and ceramic membrane filter cartridges.

[0038] The ratio of the flow rate of the oil slurry collected online by the liquid collection device to the flow rate of the oil slurry collected from the bottom of the main fractionation tower is 1:1-5.

[0039] The bottom slurry extraction pipeline is connected to the slurry inlet of the catalytic cracking reactor, so that the catalyst fine powder in the bottom slurry is returned to the catalytic cracking unit for recovery; and / or the bottom slurry extraction pipeline is connected in parallel to the catalytic cracking slurry purification system.

[0040] A second aspect of the present invention provides a method for purifying oil slurry, the method comprising: At least one tray from the bottom to the top 5 of the main fractionation column of the catalytic cracking unit is used to extract slurry oil. Bottom oil slurry is extracted from the bottom of the main fractionation column of the catalytic cracking unit and returned to the catalytic cracking unit and / or thrown out.

[0041] The method provided by this invention can reduce the viscosity of oil slurry, improve the properties of the feed to downstream purification devices, and facilitate the long-term stable operation of the purification devices, thereby achieving efficient purification of oil slurry.

[0042] In this invention, the bottom slurry can be returned to the catalytic cracking unit for catalytic cracking reaction, or only the catalyst in the bottom slurry can be used. For example, the sludge in the bottom slurry can be mixed with the regenerated catalytic cracking catalyst and then brought together with the catalytic cracking feedstock for catalytic cracking reaction. Since the sludge in the bottom slurry contains fine catalyst powder and some heavy colloids, similar to a coking catalyst with a high hydrogen content, feeding it into the catalytic cracking reactor can reduce the catalyst activity, prevent excessive cracking of heavy oil, and thus reduce coking.

[0043] The content of fine powder in the extracted oil slurry is 100-10000 mg / kg, preferably 150-2000 mg / kg.

[0044] In some embodiments of the present invention, the kinematic viscosity of the extracted slurry at 100 °C is 2-70 mm. 2 / s, preferably 8-25 mm 2 / s.

[0045] In some embodiments of the present invention, the content of gum and asphalt in the extracted slurry is 15-30% by weight, preferably 16-28% by weight, and more preferably 16-26% by weight.

[0046] The method further includes: filtering the extracted oil slurry to obtain purified oil slurry; the filtration conditions include: a temperature of 200-350 ℃, preferably 240-320 ℃; and a pressure of 0.5-2.5 MPa, preferably 0.8-2.0 MPa.

[0047] In some specific embodiments of the present invention, after the pressure difference of the filter reaches a set value during the filtration state, a backwashing medium is used to backflush to remove the filter residue on the filter element. The backwashing medium can be a high-pressure inert gas.

[0048] Figure 1 The catalytic cracking slurry purification system of the present invention is illustrated schematically. The following is in conjunction with... Figure 1 One specific implementation of the method of this application is described, but this does not limit the scope of this application.

[0049] The slurry extraction unit includes a slurry collection device 3, a pipeline 4, a slurry buffer tank 5 and a pipeline 6, as well as other power equipment (not shown in the figure). The fine powder recovery unit includes a pipeline 7, a pipeline 9 for returning to the catalytic cracking unit, and a discharge device pipeline 8 for partially throwing out the slurry.

[0050] The reaction oil and gas from the catalytic cracking reaction-regeneration system catalytic cracking unit I enter the main fractionation tower II of the fractionation system via the large oil and gas pipeline 2. The bottom slurry of the main fractionation tower II, enriched with fine catalyst powder, is returned to the riser reactor 1 of catalytic cracking unit I via pipelines 7 and 9, along with atomized steam from pipeline 10, or directly sent out of catalytic cracking unit I via pipeline 8. The slurry is collected by the collection device 3 and sent to the slurry buffer tank 5 via pipeline 4. The extracted slurry in the slurry buffer tank 5 is sent to the online filter 13 in the filtration unit III via pipeline 10. The purified slurry is then sent to the downstream unit via pipeline 16. After the inlet and outlet pressures of the online filter 13 reach the set pressure, the control valve switches the feed slurry to the standby filter 14, and the online filter 13 enters the backwashing working state. The high-pressure backwashing air from the backwashing air tank 11 enters the filter 13 through the pipeline 12 to wash the filter residue on the inner wall of the filter element. The filter residue enters the filter residue buffer tank 18 through the pipeline 17.

[0051] The present invention will be further described in detail below through embodiments, but the present invention is not limited to the following embodiments.

[0052] Example 1 This embodiment follows Figure 1The process shown involves drawing oil slurry from the bottom of the main fractionation column II up to the first tray, obtaining extracted oil slurry S1; oil slurry from the fine powder recovery unit is drawn from the bottom of the column, obtaining bottom oil slurry, which is then returned to the catalytic cracking unit I. The flow ratio of extracted oil slurry to bottom oil slurry is 1:1. The properties of the obtained extracted oil slurry and bottom oil slurry are shown in Table 1.

[0053] Example 2 This embodiment follows Figure 1 The process shown involves drawing oil slurry from the bottom of the main fractionation column II, up to the third tray, to obtain extracted oil slurry S2. Oil slurry from the fine powder recovery unit is drawn from the bottom of the column to obtain bottom oil slurry, which is then returned to the catalytic cracking unit I. The flow ratio of the extracted oil slurry to the bottom oil slurry is 1:1. The properties of the obtained extracted oil slurry and bottom oil slurry are shown in Table 1.

[0054] Example 3 This embodiment follows Figure 1 The process shown involves drawing oil slurry from the fifth tray above the bottom of the main fractionation column II to obtain extracted oil slurry S3; oil slurry from the fine powder recovery unit is drawn from the bottom of the column to obtain bottom oil slurry, which is then returned to the catalytic cracking unit I. The flow ratio of extracted oil slurry to bottom oil slurry is 1:1. The properties of the obtained extracted oil slurry and bottom oil slurry are shown in Table 1.

[0055] Comparative Example 1 In this comparative example, the slurry was extracted directly from the bottom of the main fractionation column II, following the existing conventional slurry extraction location, and the bottom slurry was not returned to the catalytic cracking unit for catalyst fine powder recovery. The properties of the obtained slurry D1 are shown in Table 1.

[0056] Table 1

[0057] As can be seen from the table above, compared with the conventional slurry extracted from the bottom of the main fractionation tower, the slurry extracted by the present invention has a lower content of gum and asphaltenes, and the viscosity of the extracted slurry at 100 °C is significantly reduced.

[0058] Example 4 according to Figure 1 The process shown involves feeding the extracted slurry S1 obtained in Example 1 into a filtration unit for filtration. The filtration unit includes at least three filters. The extracted slurry is fed into the filters in their filtration state, and the purified slurry obtained from filtration is sent to the downstream device. When the inlet and outlet pressures of the filters reach the set pressure values, the control valve switches the slurry feed to another filter. The filter element in each filter has a pore size of 10 μm. The filter operating conditions and the properties of the purified slurry obtained from filtration are shown in Table 2.

[0059] Examples 5-6 The process for filtering the extracted oil slurry in Examples 5-6 is the same as that in Example 4, except that the raw materials for the filtration unit are the extracted oil slurry S2 obtained in Example 2 and the extracted oil slurry S3 obtained in Example 3, respectively. The filter operating conditions and the properties of the purified oil slurry obtained by filtration are shown in Table 2.

[0060] Example 7 The process for extracting and filtering the oil slurry in this embodiment is the same as in Embodiment 4, except that the filtration temperature in the filter is 230 ℃ and the pressure is 2.1 MPa. The properties of the purified oil slurry obtained by filtration are shown in Table 2.

[0061] Comparative Example 2 according to Figure 1 The process shown involves feeding the extracted slurry obtained in Comparative Example 1 into a filtration unit for filtration. The filtration unit includes at least three filters. The extracted slurry is fed into the filters in their filtration state, and the purified slurry obtained from filtration is sent to the downstream device. When the inlet and outlet pressures of the filters reach the set pressure values, the control valve switches the slurry feed to another filter. The operating conditions and properties of the purified slurry are shown in Table 2.

[0062] Table 2

[0063] As can be seen from the data in the table above, compared with the bottom slurry extracted from the conventional extraction position, the extraction slurry provided by the present invention has a longer filter switching interval when used for filtration, and the total content of gum and asphaltenes in the purified slurry is lower, resulting in better filtration effect. The filtration device can operate stably for a long period of time, avoiding frequent filter switching and reducing the formation of aging mesophase, which is beneficial to improving the quality of needle coke products.

[0064] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0065] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0066] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A catalytic cracking slurry oil purification treatment system characterized by comprising: The system comprises a catalytic cracking slurry extraction unit and a fine powder recovery unit; the fine powder recovery unit comprises a bottom slurry extraction pipeline; the catalytic cracking slurry extraction unit comprises a liquid collecting device arranged in a main fractionating tower of a catalytic cracking device, and an oil slurry outlet of the liquid collecting device is arranged on at least one of the first to fifth trays from the bottom of the main fractionating tower upward.

2. The system of claim 1, wherein, The catalytic cracking slurry extraction unit further comprises an oil slurry buffer tank in communication with the liquid collecting device through a pipeline.

3. The system of claim 1, wherein, The system further comprises a filtering unit in series with the catalytic cracking slurry extraction unit. The filtering unit comprises at least one filter, and an extracted oil slurry inlet pipeline, a filter residue outlet pipeline and a purified oil slurry outlet pipeline in communication with the filter.

4. The system of claim 3, wherein, The filter is provided with an extracted oil slurry inlet at the lower part, a filter residue outlet at the bottom and a purified oil slurry outlet at the upper part; an end of the filter away from the filter residue outlet is provided with a flushing medium inlet; the system further comprises a flushing medium buffer tank and / or a filter residue receiving tank.

5. The system of claim 3 or 4, wherein, The pore size of the filter material in the filter is 0.02-10 μm. Preferably, the filter material is selected from one or a combination of two or more of sintered metal powder filter cartridges, metal wire mesh filter cartridges and ceramic membrane filter cartridges.

6. The system of claim 1, wherein, The ratio of the flow rate of the online extracted oil slurry to the flow rate of the bottom extracted oil slurry of the main fractionating tower is 1:1-5.

7. The system of claim 1, wherein, The bottom slurry extraction pipeline is in communication with an oil slurry inlet of a catalytic cracking reactor; and / or the bottom slurry extraction pipeline outputs the catalytic cracking slurry purification treatment system in parallel through a pipeline.

8. A method for slurry oil purification treatment, characterized by, The method comprises: extracting oil slurry from at least one of the first to fifth trays from the bottom of a main fractionating tower of a catalytic cracking device upward to obtain extracted oil slurry; extracting bottom slurry from the bottom of the main fractionating tower of the catalytic cracking device, and returning the bottom slurry to the catalytic cracking device and / or discharging the bottom slurry; wherein the content of fine powder in the extracted oil slurry is 100-10000 mg / kg, preferably 150-2000 mg / kg.

9. The method of claim 8, wherein, The 100°C kinematic viscosity of the extracted slurry is 2-70 mm 2 / s, preferably 8-25 mm 2 / s; and / or the content of gum and asphaltenes in the extracted slurry is 15-30 wt%, preferably 16-28 wt%, more preferably 16-26 wt%.

10. The method of claim 8, wherein, The method further comprises: filtering the extracted oil slurry to obtain purified oil slurry; the filtering conditions comprise: a temperature of 200-350 ℃, preferably 240-320 ℃; a pressure of 0.5-2.5 MPa, preferably 0.8-2.0 MPa.

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