Method for removing solid particles from catalytic slurry oil and method for preparing needle coke from catalytic slurry oil

Abstract

The method for removing solid particles in catalytic oil slurry and the method for preparing needle coke from catalytic oil slurry, in which catalytic cracking oil slurry is countercurrently contacted with solvent in an extraction tower, the extraction liquid rich in solvent flows out from the top of the tower, and after the solvent is recovered in a solvent recovery column, purified oil slurry is obtained, and the raffinate liquid rich in solid particles flows out from the bottom of the tower; the solvent is C6-C8 alkane. The method provided by the application makes insoluble heavy gum and asphaltene act as a coagulation agent, adsorb solid particles and accelerate the coagulation of the particles, greatly shortens the settling time, improves the solid removal efficiency, and the yield of the purified oil slurry can reach 85%. Meanwhile, the heavy gum and asphaltene are removed, the quality of the purified oil slurry is improved, and the cost and energy consumption of subsequent processing are reduced.

Description

Technical Field

[0001] The invention belongs to the field of petroleum processing, and in particular relates to a method for efficiently removing solid particles from catalytic oil slurry. Background Art

[0002] As my country's crude oil becomes increasingly heavier and inferior, the quality of oil processed by refinery catalytic cracking units (FCCs) is declining, and the amount of slurry oil produced by these units is also increasing. Currently, my country's FCC processing capacity has reached over 150 million tons per year, and slurry oil generally accounts for approximately 6% to 8% of the FCC processing volume. As a byproduct of catalytic cracking, slurry oil is rich in aromatics and low in resins and asphaltenes. It has high economic value, serving as a raw material in petrochemical production, as well as a high-quality raw material for asphalt modifiers, enhancers, and activators, and in the production of high-value-added products such as needle coke, carbon black, carbon fiber, and emulsified asphalt. Therefore, there is an urgent production demand and a huge market prospect for the comprehensive utilization of slurry oil, and research into technologies for its high-value, comprehensive utilization is of great significance. However, catalytic oil slurry usually contains 1200 to 12000 μg / g of catalyst particles, which can cause many problems such as coking, wear, and blockage in the catalytic cracking oil slurry circulation system. It is a key factor restricting the high-value comprehensive utilization of catalytic oil slurry. Removing catalyst particles from catalytic oil slurry has become an urgent problem that needs to be solved.

[0003] Existing slurry desolidification technologies primarily include natural sedimentation, filtration separation, centrifugal separation, additive sedimentation, and electrostatic separation. Natural sedimentation uses high temperatures to reduce the viscosity of the slurry to achieve particle sedimentation. However, the solid particles in the slurry are generally less than 20 μm in size and are highly dispersed within the slurry. The colloidal asphaltene in the slurry further enhances the stability of suspended particles, resulting in slow sedimentation and low desolidification efficiency. Natural sedimentation has been gradually phased out.

[0004] Filtration technology uses filter media to intercept catalyst particles in slurry oil, thereby achieving desolidification. The key to this method is selecting the appropriate filter media and an effective backwashing method. Industrialized technology is currently available. Slurry oil filtration technology utilizes simple equipment, offers high separation efficiency, and operates stably. The separation effect is minimally affected by the properties of the slurry oil. However, the initial investment is high, and the filter element and filter cloth are easily clogged by colloids, asphaltenes, and fine catalyst particles in the slurry oil, leading to a gradual decrease in throughput. Replacing or backwashing the filter media requires regular downtime, making it unsuitable for continuous operation.

[0005] Centrifugal sedimentation offers excellent separation and high solids removal efficiency, but it operates at high speeds, making maintenance difficult and requiring limited throughput. Catalytic cracking is a continuous process involving large quantities of slurry. Operating at high temperatures, centrifugal separation methods consume high energy and have low economic returns, making industrial application difficult.

[0006] The electrostatic separation method is not suitable for oil slurry with high content of colloid and asphaltene or high water content, and has unstable separation efficiency, high equipment investment and high maintenance cost, and is currently difficult to realize industrialization.

[0007] The auxiliary agent settling is a modification of the traditional natural settling. When the settling auxiliary agent is added in the oil slurry, the auxiliary agent and the particles wrapped in the oil slurry form strong interfacial affinity, which can reduce the dispersion stability between the particles. Under the action of the interfacial affinity, the particles are adsorbed and bridged to form large flocs, which greatly shortens the settling time and significantly improves the separation efficiency. Although the auxiliary agent settling can improve the solid removal efficiency, the settling speed is still slow, and the centrifugal equipment is needed to accelerate, which is difficult to adapt to large-scale industrial production. In addition, the introduced auxiliary agent is difficult to completely separate, and the subsequent refining operation will increase the energy consumption and cost.

[0008] The catalytic oil slurry can be pretreated by extracting normal alkane with small molecules. CN110511785A discloses a method, which first removes asphaltene from the oil slurry by mixing the oil slurry with low molecular weight normal alkane at 20-40°C, then extracts the pretreated supernatant with furfural, N-methyl pyrrolidone, etc. to obtain oil slurry rich in aromatic hydrocarbons, and finally centrifugally separates the lower layer of oil slurry rich in aromatic hydrocarbons. The method can effectively remove colloid and asphaltene from the oil slurry, but the asphaltene removal operation temperature is too low, and the mutual solubility and dispersion effect of the oil slurry and the diluent are poor, which will result in low yield of asphaltene-removed oil slurry. CN106147835A discloses a catalytic oil slurry pretreatment method, which uses C3-C5 light hydrocarbon fraction as a solvent to subcritically extract the oil slurry, and prepares purified oil slurry containing no asphaltene and solid particles, which can be used as an excellent raw material for oil-based needle coke. However, the solubility of C3-C5 light hydrocarbon is low, and the yield of purified oil is only 65%-75%.

[0009] CN102533318A discloses a method for removing catalyst powder from catalytic cracking oil slurry. The catalytic cracking oil slurry is separated from the solvent in an extraction tower, and the solvent refined oil solution flows out from the top of the tower, and after the solvent is recovered by a recovery system, the refined catalytic cracking oil slurry is obtained. The solvent refined residual oil carrying the catalytic cracking catalyst powder is discharged from the bottom of the extraction tower, and the solvent is aromatic hydrocarbon.

[0010] In summary, the key points of oil slurry solid removal are dilution and viscosity reduction of oil slurry (high temperature, solvent dissolution, etc.) and enhanced particle coagulation (auxiliary agent, centrifugation, electrostatic separation, etc.). How to achieve high processing capacity and rapid solid removal while reducing cost and energy consumption as much as possible is a problem that needs to be solved by the industry. SUMMARY

[0011] One of the technical problems to be solved by the present invention is to provide a method for removing solid particles from catalytic oil slurry, shorten the desolidification time and improve the yield of purified oil, in order to address the problems of low removal efficiency of solid particles in oil slurry, long sedimentation time and low yield of purified oil slurry.

[0012] The second technical problem to be solved by the present invention is to provide a method for preparing high-quality needle coke after desolidification of catalytic oil slurry.

[0013] In a first aspect, the present invention provides a method for removing solid particles from catalytic cracking oil slurry, wherein the catalytic cracking oil slurry and a solvent are subjected to countercurrent contact extraction in an extraction tower, the solvent-rich extract flows out from the top of the tower, enters a solvent recovery tower to recover the solvent, and then obtains a purified oil slurry; the raffinate enriched in solid particles flows out from the bottom of the tower, and the solvent is a C6-C8 alkane.

[0014] In a second aspect, the present invention provides a method for preparing needle coke from catalytic oil slurry, wherein the above-mentioned method for removing solid particles from catalytic oil slurry is used to obtain purified oil slurry, and the purified oil slurry is introduced into a delayed coking tower for a coking reaction to prepare needle coke green coke, and the obtained green coke is calcined at 1300-1500°C to obtain needle coke cooked coke.

[0015] The beneficial effects of the method for removing solid particles from catalytic oil slurry provided by the present invention are:

[0016] The method provided by the present invention uses C6-C8 alkanes as extraction solvents, allowing saturates, aromatic hydrocarbons, and light colloid components in the catalytic oil slurry to dissolve as much as possible in the extraction solvent. The insoluble heavy colloids and asphaltenes act as coagulants, adsorbing solid particles and accelerating the coalescence and sedimentation of the particles, significantly shortening the sedimentation time and improving the desolidification efficiency. Simultaneously, heavy colloids and asphaltenes are removed, improving the quality of the purified oil slurry obtained after solid particle removal.

[0017] The first type of prior art uses highly polar aromatic hydrocarbon solvents as extraction solvents. Due to the strong solubility of aromatic hydrocarbon solvents, they will completely dissolve the colloid asphaltene in the oil slurry. Compared with the prior art, the method provided by the present invention can remove asphaltene, heavy colloids and other impurities while removing solids, without the need for secondary removal, thus reducing costs and energy consumption. The second type of prior art uses C3-C5 light hydrocarbons as extraction solvents, which can remove colloid asphaltene and solid particles at the same time, but the purified oil slurry yield is low, only 60-75%. In contrast, the method provided by the present invention uses C6-C8 alkanes as extraction solvents, which have a higher density and stronger solubility, and the purified oil slurry yield can reach 86-93%.

[0018] The method for preparing needle coke from catalytic oil slurry provided by the present invention can prepare high-quality needle coke. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1The flow chart of the method for preparing needle coke from catalytic slurry oil is shown in the figure.

[0020] Wherein:

[0021] 1-catalytic slurry oil tank 2-solvent tank 3-slurry pump 4-solvent pump

[0022] 5-extraction column 6-solvent recovery column 7-first stripping column 8-delayed coking column

[0023] 9-second stripping column 10-asphalt vaporizer

[0024] I-slurry stream II-solvent stream III-extracted liquid IV-extracted residue liquid V-extracted residue liquid

[0025] VI-rich slurry liquid VII-clear slurry liquid VIII, X-stripping solvent

[0026] IX-residual oil X-bleached asphalt XI-coking oil gas XIII-needle coke DETAILED DESCRIPTION

[0027] The specific embodiments of the present application are described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely intended for illustration and explanation of the present application and are not intended to limit the present application.

[0028] In the present application, unless otherwise specified, the "upper part" of the container refers to 10-30% from the top to the bottom of the container; the "lower part" of the container refers to 70-90% from the top to the bottom of the container. The pressures involved are all absolute pressures.

[0029] In the first aspect, the method for removing solid particles from catalytic cracking slurry oil of the present application, the catalytic cracking slurry oil is extracted by countercurrent contact with a solvent in an extraction column, the extracted liquid rich in solvent flows out from the top of the column, and the solvent is recovered in a solvent recovery column to obtain purified slurry oil; the extracted residue liquid rich in solid particles flows out from the bottom of the column, and the solvent is a C6-C8 alkane.

[0030] In the method provided by the present application, the operating conditions of the extraction column are as follows: the extraction temperature is 5-60°C lower than the critical temperature of the solvent, preferably 20-40°C lower than the critical temperature of the solvent, the pressure is 1-5 MPa, preferably 2-4 MPa, and the mass ratio of the catalytic slurry oil to the solvent is 0.5-4:1, preferably 0.8-3:1, and more preferably 1-2.0:1.

[0031] In the method provided by the present application, the solvent recovery column is used for solvent separation under supercritical conditions, and the supercritical conditions refer to that the temperature in the solvent recovery separation column is 10-60°C higher than the critical temperature of the solvent, preferably 25-45°C higher than the critical temperature of the solvent, and the pressure is higher than the critical pressure of the solvent.

[0032] Preferably, the operating temperature of the solvent recovery tower is 180-300° C. and the pressure is 3.5-5.5 MPa.

[0033] In the method provided by the present invention, the solvent is selected from one or a mixture of n-hexane, isohexane, cyclohexane, n-heptane, isoheptane, neoheptane, n-octane and isooctane, more preferably n-hexane and / or n-heptane.

[0034] Alternatively, the resulting solids-rich raffinate is stripped and then mixed with heavy, low-quality residual oil and asphalt before entering a pitch gasification unit for partial oxidation with an oxygen-containing gas to produce synthesis gas and bottom ash. Preferably, the catalytic cracking catalyst is separated from the bottom ash and returned to the catalytic cracking unit for recycling.

[0035] In the method provided by the present invention, the volume flow rate of the raffinate enriched in solid particles discharged from the bottom of the extraction tower is 5-25%, preferably 8-15% of the volume flow rate of the catalytic oil slurry feed.

[0036] In the method provided by the present invention, the catalytic slurry has a wide application range, the solid content of the catalytic slurry is ≥1000ppm, preferably 1500-10000ppm; the asphaltene content of the slurry is ≥2%.

[0037] In the method provided by the present invention, the extraction tower is a vertical extraction tower. Preferably, a vertical extraction tower with a reduced diameter at the bottom is used.

[0038] In a second aspect, the present invention provides a method for preparing needle coke from catalytic oil slurry, wherein the catalytic oil slurry is subjected to any of the above methods to remove solid particles to obtain purified oil slurry, the purified oil slurry enters a delayed coking tower for a coking reaction to obtain needle coke green coke, and the obtained needle coke green coke is calcined at 1300-1500°C to obtain needle coke cooked coke.

[0039] The delayed coking tower and operating conditions are conventional methods, and the present invention is not limited thereto. Optionally, the operating conditions of the delayed coking tower are a temperature of 450-490° C., a pressure of 0.1-2.0 MPa, and a reaction time of 12-36 hours.

[0040] A specific embodiment of the method for removing solid particles from catalytic oil slurry provided by the present invention comprises the following steps:

[0041] (1) The catalytic cracking slurry and the solvent are pumped into an extraction tower respectively, and are subjected to countercurrent contact and extraction under a subcritical state. The flow rate is controlled to obtain a solvent-rich extract and a raffinate enriched in solid particles. The extract flows out from the top of the tower and the raffinate flows out from the bottom of the tower. The solvent is a C6-C8 alkane;

[0042] (2) The solvent-rich extract obtained in step (1) is heated and subjected to solvent separation in a solvent separation tower under a supercritical state. The high-pressure solvent obtained by separation flows out from the top of the tower and enters a heat exchange network for heat exchange. The low-pressure solvent obtained after heat exchange is circulated back to the solvent tank. After the solvent is separated, a purified oil slurry is obtained; after steam stripping, it enters a delayed coking device to prepare needle coke

[0043] (3) The solid particle-rich raffinate obtained in step (1) is stripped and mixed with heavy low-quality residual oil and asphalt, and then fed into an asphalt gasification unit for partial oxidation reaction with oxygen-containing gas to produce synthesis gas and bottom ash; preferably, the catalytic cracking catalyst in the bottom ash is separated and returned to the catalytic cracking unit for recycling.

[0044] In step (1), the mixing mass ratio of the catalytic oil slurry to the solvent is 0.5 to 4:1, preferably 0.8 to 3:1, and more preferably 1 to 2.0:1. If the solvent ratio is too large, the solubility of heavy colloids and asphaltene will increase, and the quality of refined oil will be reduced; if the solvent ratio is too small, the dissolution and dispersion of the oil slurry will be poor, the solid particle sedimentation time will be too long, and the refined oil yield will be low.

[0045] The subcritical condition described in step (1) is that the extraction temperature is 5 to 60° C., preferably 20 to 40° C., lower than the critical temperature of the solvent used. In the present invention, the top temperature of the extraction tower is 50 to 180° C., preferably 80 to 150° C.; the extraction pressure is 1 to 5 MPa, preferably 2 to 4 MPa. Under subcritical conditions, the solubility of the solvent is more sensitive to changes in temperature and pressure, and can be flexibly adjusted by regulating temperature and pressure to dissolve the saturates, aromatic hydrocarbons, and light colloid components in the oil slurry in the solvent as much as possible. The insoluble heavy colloids and asphaltenes act as coagulants, adsorbing solid particles, accelerating the aggregation and sedimentation of the particles, and shortening the sedimentation time.

[0046] The flow control in step (1) is to control the volume flow of the raffinate IV enriched with solid particles at the bottom of the tower, and the control value is 5-25% of the feed volume flow, preferably 8-15% of the feed volume flow.

[0047] The supercritical state described in step (2) means that the temperature in the separation tower is 10 to 60°C higher than the critical temperature of the solvent, preferably 25 to 45°C; and the pressure is higher than the critical pressure of the solvent. In the present invention, the temperature of the separation tower is 180 to 300°C and the pressure is 3.5 to 5.5 MPa. In the supercritical state, the fluid has both the diffusivity of a gas and the fluidity of a liquid. The oil slurry is almost insoluble in the supercritical solvent, which can better achieve the purpose of solvent separation. On the other hand, the supercritical solvent can enter the heat exchange network for heat exchange, avoiding the loss of phase change latent heat caused by evaporation and gasification, while also reducing the heating energy consumption of the device and achieving a high energy recovery rate.

[0048] The heat exchange network described in step (2) can exchange heat with public works or with internal logistics, for example, it can exchange heat with extract III and oil slurry I.

[0049] The purified slurry oil obtained in step (2) can be used to prepare needle coke, or as a high-quality raw material for impregnating asphalt or asphalt softener, preferably as a raw material for preparing needle coke by delayed coking.

[0050] The ratio of the solid particle-enriched raffinate oil and the inferior slag and asphalt blended in step (3) is 5% to 50%, preferably 10% to 30%. After blending, the viscosity of the slag and asphalt flow can be reduced, the pipeline transmission fluidity can be improved, and the pipeline heating energy consumption can be reduced.

[0051] The preferred embodiment of the method for removing solid particles from catalytic oil slurry provided by the present invention is to mix the catalytic oil slurry with C6-C8 alkanes and then perform subcritical extraction in an extraction tower. The temperature and pressure are controlled so that the saturated components, aromatic hydrocarbons, and light colloid components in the oil slurry are dissolved in the solvent as much as possible. The insoluble asphaltene acts as a coagulant, which can adsorb solid particles, accelerate the aggregation and sedimentation of the particles, and enter the bottom of the extraction tower for separation and removal. The purified oil solution after desolidification flows out from the top of the extraction tower and enters the supercritical recovery tower. The solvent is recovered under a supercritical state. The recovered high-pressure solvent can be recovered through the heat exchange network for energy recovery, reducing energy consumption. The solid content of the purified oil slurry after desolidification is <100ppm, and the content of colloid and asphaltene is low. It is preferably used as a high-quality raw material for needle coke. The prepared needle coke meets the standards of premium needle coke. The residual liquid enriched with catalyst particles is discharged from the bottom of the tower and can be mixed with heavy residual oil and asphalt to enter the asphalt gasification device to recover the catalyst.

[0052] In the method provided by the present invention, C6-C8 alkanes are used as solvents, and their ability to dissolve oil slurry is significantly stronger than that of C3-C5 solvents. The solubility of catalytic oil slurry in the solvent is about 85-95%, and the purified oil yield is significantly improved compared with C3-C5. The remaining insoluble matter is mainly asphaltenes and heavy colloids, which will be adsorbed on solid particles, increase the particle size, and accelerate particle coagulation. At the same time, since C6-C8 alkanes are used as solvents, the dissolving ability is enhanced, the corresponding extraction temperature increases, the viscosity and density of the mixed system are reduced, and the sedimentation rate of the solid particles increases, which can effectively shorten the sedimentation time and improve the desolidification efficiency. Using C6-C8 alkanes as solvents can also reduce the amount of solvent used and reduce costs.

[0053] The following further describes the specific embodiments of the method for removing solid particles from catalytic oil slurry provided by the present invention with reference to the accompanying drawings, but the present invention is not limited thereto.

[0054] Attachment Figure 1This is a schematic flow diagram of an embodiment of the method for preparing needle coke from catalytic oil slurry provided by the present invention. Figure 1 As shown, slurry I from catalytic slurry storage tank 1 flows through slurry pump 3 and enters extraction tower 5 from the top of the tower. C6-C8 solvent II from solvent storage tank 2 flows through solvent pump 4 and enters extraction tower 5 from the bottom of the tower, where it comes into countercurrent contact with the catalytic slurry and undergoes extraction and solid removal under subcritical conditions. After extraction and separation, solvent-rich extract III flows out of the top of extraction tower 5, while solids-rich raffinate IV flows out of the bottom of extraction tower 5. Extract III enters solvent recovery tower 6 for solvent separation under supercritical conditions. The resulting high-pressure solvent V flows out of the top of the tower and enters the heat exchange network for heat exchange. The resulting low-pressure solvent is then recycled back to solvent storage tank 2. The oil-rich slurry VI, after solvent separation, enters the first stripping tower 7 for steam stripping, producing purified slurry VII and stripping solvent VIII. After cooling, the solvent is recycled back to solvent tank 2. The purified slurry VII enters delayed coking tower 8 for coking, producing coker gas XII and needle coke XIII.

[0055] The solid particle-enriched raffinate IV enters the second stripping tower 9 for steam stripping to obtain residual oil IX and stripping solvent X. The solvent is cooled and circulated back to the solvent tank 2. The residual oil can be mixed with inferior residue and asphalt XI and then enter the asphalt gasification device 10 to recover the catalyst.

[0056] The method for removing solid particles from catalytic oil slurry and its technical effects of the present invention are described below with reference to the examples, but the present invention is not limited thereto.

[0057] The catalytic slurry used in the examples and comparative examples was obtained from a catalytic cracking unit of the Fujian Branch of Sinopec, and its properties are listed in Table 1.

[0058] in,

[0059]

[0060] Table 1

[0061] Fujian FCC slurry <![CDATA[20℃密度(kg / m 3 )]]> 1141.9 <![CDATA[80℃粘度(mm 2 / s)]]> 302.4 Viscosity at 100°C (mm2 / s) 55.91 Carbon residue (wt%) 13.8 Solid content (μg / g) 1600 C content (wt%) 91.68 H content (wt%) 6.81 S content (wt%) 0.88 N content (mg / kg) 1400 Saturates content (wt%) 4.7 Aromatics content (wt%) 74.5 Gel content (wt%) 15.8 Asphaltene content (wt%) 5

[0062] Example 1

[0063] The catalytic oil slurry listed in Table 1 was fed from the top of the extraction column, while n-hexane was fed from the bottom for countercurrent contact and extraction. The catalyst-to-oil mass ratio was 1.5:1, the residence time was 30 minutes, the extraction column top temperature was 160°C, the column bottom temperature was 150°C, and the pressure was 4 MPa. The supercritical solvent separation column temperature was 260°C and the pressure was 4.0 MPa. The solvent-rich extract and solids-rich raffinate exited the top and bottom of the extraction column, respectively, with the volumetric flow rate of the extraction column bottom stream controlled at 92% of the feed rate. After desolidification, the oil-rich slurry was subjected to supercritical solvent separation and steam stripping to remove the solvent. The resulting purified oil slurry had a mass yield of 86%. The solids content and properties of the four components are shown in Table 2. The purified oil slurry obtained was fed into a delayed coking tower for coking reaction. The tower feeding conditions were a temperature of 480°C, a pressure of 0.7 MPa, and a reaction time of 36 h. The obtained needle coke was calcined at 1400°C to obtain cooked coke, the properties of which are shown in Table 3.

[0064] Example 2

[0065] The Fujian catalytic oil slurry listed in Table 1 was fed from the top of the extraction column, while n-heptane was introduced from the bottom of the column for countercurrent contact and extraction. The solvent-to-oil mass ratio was 1.0:1, the residence time was 60 minutes, the extraction column top temperature was 180°C, the column bottom temperature was 170°C, and the pressure was 4 MPa. The supercritical solvent separation column temperature was 280°C and the pressure was 3.5 MPa. The solvent-rich extract and solids-rich raffinate exited the top and bottom of the extraction column, respectively, with the volume flow rate of the extraction column bottom stream controlled at 94% of the feed rate. After desolidification, the oil-rich slurry was subjected to supercritical solvent separation and steam stripping to remove the solvent. The resulting purified oil slurry had a yield of 90%. The solids content and properties of the four components are shown in Table 2. The purified oil slurry obtained was fed into a delayed coking tower for coking reaction. The tower feeding conditions were a temperature of 460°C, a pressure of 0.5 MPa, and a reaction time of 24 h. The obtained needle coke was calcined at 1350°C to obtain cooked coke, the properties of which are shown in Table 3.

[0066] Example 3

[0067] The Fujian catalytic oil slurry listed in Table 1 was fed from the top of the extraction column, while n-octane was introduced from the bottom of the column for countercurrent contact and extraction. The solvent-to-oil mass ratio was 1.0:1, the residence time was 60 minutes, the extraction column top temperature was 200°C, the column bottom temperature was 190°C, and the pressure was 4 MPa. The supercritical solvent separation column temperature was 300°C and the pressure was 3.5 MPa. The solvent-rich extract and solids-rich raffinate exited the top and bottom of the extraction column, respectively, with the volume flow rate of the extraction column bottom stream controlled at 95% of the feed rate. After desolidification, the oil-rich slurry was subjected to supercritical solvent separation and steam stripping to remove the solvent. The resulting purified slurry yield was 92%. The solids content and properties of the four components are shown in Table 2. The purified oil slurry obtained was fed into a delayed coking tower for coking reaction. The feeding conditions were a temperature of 450°C, a pressure of 0.3 MPa, and a reaction time of 18 h. The obtained needle coke was calcined at 1300°C to obtain cooked coke, the properties of which are shown in Table 3.

[0068] Comparative Example 1

[0069] Solvent extraction was used to remove solid particles from the catalytic oil slurry, using toluene as the extraction solvent. The Fujian catalytic oil slurry listed in Table 1 was introduced from the top of the extraction column, and toluene was introduced from the bottom. The solvent-to-oil ratio was 1.0:1, the residence time was 30 minutes, the tower top temperature was 170°C, the tower bottom temperature was 160°C, and the pressure was 4.5 MPa. Evaporation was used for solvent separation at 250°C. The solvent-rich extract and the solids-rich raffinate exited the top and bottom of the extraction column, respectively, with the bottom flow rate controlled at 92% of the feed rate. After desolidification, the oil-rich slurry was subjected to supercritical solvent separation and steam stripping to remove the solvent. The resulting purified slurry yield was 88%. The solids content and properties of the four components are shown in Table 2.

[0070] From the comparison between Comparative Example 1 and Example 1, it can be seen that the use of aromatic hydrocarbon solvent toluene almost completely dissolves the slurry oil, and has almost no removal effect on asphaltenes and heavy colloids; the lack of the coagulation process of asphaltenes and heavy colloids slows the sedimentation rate of solid particles. Within a short residence time of 30 minutes, the yield of purified slurry oil is similar, and the solid content of the obtained purified slurry oil is much higher than that of Example 1. This shows that when toluene is used, due to the complete dissolution of asphaltenes, the tiny catalyst particles lack the coagulation effect, are in a highly dispersed state, have a slow sedimentation rate, and have a poor sedimentation effect.

[0071] Comparative Example 2

[0072] The solid particles in the catalytic oil slurry are removed by solvent extraction, and the extraction solvent is n-butane.

[0073] The Fujian catalytic oil slurry listed in Table 1 was introduced from the top of the extraction column, and n-butane was introduced from the bottom. The catalyst-to-oil mass ratio was 2.5:1, the residence time was 60 minutes, the extraction column top temperature was 110°C, the column bottom temperature was 100°C, and the pressure was 4.3 MPa. The supercritical solvent separation column temperature was 200°C and the pressure was 4.0 MPa. The solvent-rich extract and solids-rich raffinate exited the top and bottom of the extraction column, respectively, with the volume flow rate of the extraction column bottom stream controlled at 75% of the feed rate. After desolidification, the oil-rich slurry was subjected to supercritical solvent separation and steam stripping to remove the solvent. The resulting purified oil slurry yield was 67%. The solids content and properties of the four components are shown in Table 2.

[0074] Comparative Example 3

[0075] The solid particles in the catalytic oil slurry are removed by solvent extraction, and the extraction solvent is isopentane.

[0076] The Fujian catalytic oil slurry listed in Table 1 was introduced from the top of the extraction column, and isopentane was introduced from the bottom. The catalyst-to-oil mass ratio was 2.0:1, and the residence time was 60 minutes. The extraction column top temperature was 140°C, the column bottom temperature was 130°C, and the pressure was 4.5 MPa. The supercritical solvent separation column temperature was 220°C and the pressure was 4.0 MPa. The solvent-rich extract and solids-rich raffinate exited the top and bottom of the extraction column, respectively, with the volume flow rate of the extraction column bottom stream controlled to be 80% of the feed rate. After desolidification, the oil-rich slurry was subjected to supercritical solvent separation and steam stripping to remove the solvent. The resulting purified oil slurry yield was 75%. The solids content and properties of the four components are shown in Table 2.

[0077] From the comparison between Comparative Examples 2 and 3 and Examples 2 and 3, it can be seen that the use of n-butane and isopentane has better desolidification and deasphalting effects, and the asphaltene content in the purified slurry is lower than that using C6-C8 solvents, but the purified slurry yield is low, at 67% and 75% respectively; while using n-heptane as the solvent, the purified slurry yield can be greatly increased to 90%.

[0078] Table 2

[0079]

[0080] As can be seen from the data in Table 2, the purified slurries obtained in Examples 1-3 all had solids contents below 80 μg / g and asphaltene contents below 2.1 wt%, making them suitable as high-quality feedstock for needle coke production with high mass yield and excellent solids removal efficiency. The process flow is simple and suitable for large-scale industrialization with high throughput.

[0081] Table 3 Properties of needle coke obtained by delayed coking

[0082]

[0083]

[0084] From the data in Table 3, it can be seen that the purified oil slurry obtained by the method provided by the present invention has a low solid content and a high aromatic hydrocarbon content. The obtained needle coke has an ash content of 0.2 wt%, a volatile matter content of 0.4 wt%, and a true density of >2.13 g / cm 3 , resistivity ≯600μΩ·m, both reaching the standard of superior needle coke.

Claims

1. A method for removing solid particles from catalytic oil slurry, characterized in that: The catalytic cracking oil slurry and the solvent are subjected to countercurrent contact extraction in an extraction tower. The solvent-rich extract flows out from the top of the tower and enters a solvent recovery tower to recover the solvent to obtain a purified oil slurry. The raffinate enriched in solid particles flows out from the bottom of the tower. The solvent is a C7-C8 alkane. The operating conditions of the extraction tower are as follows: the extraction temperature is 5-60°C lower than the critical temperature of the solvent, the pressure is 1-5 MPa, the mass ratio of the catalytic oil slurry to the solvent is 0.5-4:1, the solid content of the catalytic oil slurry is ≥1000 ppm, and the asphaltene content is ≥2%.

2. The method for removing solid particles from catalytic oil slurry according to claim 1, characterized in that: The operating conditions of the extraction tower are: the extraction temperature is 20-40°C lower than the critical temperature of the solvent, the pressure is 2-4 MPa, and the mass ratio of the catalytic oil slurry to the solvent is 0.8-3:

1.

3. The method for removing solid particles from catalytic oil slurry according to claim 1 or 2, characterized in that: The solvent recovery tower performs solvent separation in a supercritical state, wherein the supercritical state means that the temperature in the solvent recovery tower is 10-60° C. higher than the critical temperature of the solvent and the pressure is higher than the critical pressure of the solvent.

4. The method for removing solid particles from catalytic oil slurry according to claim 3, characterized in that: The operating temperature of the solvent recovery tower is 25-45° C. higher than the critical temperature of the solvent.

5. The method for removing solid particles from catalytic oil slurry according to claim 4, characterized in that: The operating temperature of the solvent recovery tower is 180-300° C., and the pressure is 3.5-5.5 MPa.

6. The method for removing solid particles from catalytic oil slurry according to any one of claims 1-2, 4-5, characterized in that: The solvent is one or a mixture of n-heptane, isoheptane, neoheptane, n-octane and isooctane.

7. The method for removing solid particles from catalytic oil slurry according to any one of claims 1-2, 4-5, characterized in that: The solid particle-rich raffinate obtained is stripped and mixed with heavy low-quality residual oil and asphalt, and then fed into the asphalt gasification unit for partial oxidation reaction with oxygen-containing gas to obtain synthesis gas and bottom ash.

8. The method for removing solid particles from catalytic oil slurry according to claim 7, characterized in that: The catalytic cracking catalyst is separated from the bottom ash and returned to the catalytic cracking unit for recycling.

9. The method for removing solid particles from catalytic oil slurry according to any one of claims 1-2, 4-5, characterized in that: The volume flow rate of the solid particle-enriched raffinate discharged from the bottom of the extraction tower is 5-25% of the volume flow rate of the catalytic oil slurry feed.

10. The method for removing solid particles from catalytic oil slurry according to claim 9, characterized in that: The volume flow rate of the solid particle-enriched raffinate discharged from the bottom of the extraction tower is 8-15% of the volume flow rate of the catalytic oil slurry feed.

11. The method for removing solid particles from catalytic oil slurry according to claim 1, characterized in that: The solid content of the catalytic oil slurry is 1500-10000 ppm.

12. The method for removing solid particles from catalytic oil slurry according to claim 1, characterized in that: The extraction tower is a vertical extraction tower with a reduced diameter at the bottom.

13. A method for preparing needle coke from catalytic slurry oil, characterized in that: Purified slurry oil is obtained by the method for removing solid particles from catalytic slurry oil according to any one of claims 1 to 12, and the purified slurry oil is introduced into a delayed coking tower for coking reaction to prepare needle coke green coke, and the obtained green coke is calcined at 1300-1500° C. to obtain needle coke cooked coke.

14. The method for preparing needle coke from catalytic slurry oil according to claim 13, characterized in that: The operating conditions of the delayed coking tower are a temperature of 450-490° C., a pressure of 0.1-2.0 MPa, and a reaction time of 12-36 hours.

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