A method for producing low-sulfur, high-carbon residual desulfurized residual oil

Abstract

The present invention discloses a method for producing low-sulfur, high-carbon-residue desulfurized residual oil. This method increases the carbon residue value of the raw material by increasing the ratio of raw oil to the residue, improves hydrodesulfurization selectivity by maintaining a high space velocity and adjusting the bed temperature of each reactor, and improves the feedstock properties by blending catalytic diesel. This method provides high-quality low-sulfur petroleum coke feedstock for a delayed coking unit. By utilizing existing equipment and adjusting the feedstock composition and the temperature of each reactor to improve hydrodesulfurization selectivity, the method produces a low-sulfur, high-carbon-residue desulfurized residual oil that meets the requirements while maintaining the long-term operation of the equipment.

Description

Technical Field

[0001] The invention belongs to the technical field of petrochemical industry, relates to the field of production of low-sulfur petroleum coke as negative electrode raw material, and specifically relates to a method for producing low-sulfur, high-carbon residual desulfurized residual oil. Background Art

[0002] Petroleum coke is a byproduct of the petroleum refining process, produced through the delayed coking process using residual oil and heavy oil as raw materials. As crude oil quality becomes heavier and lower, petroleum coke production is increasing, with high-sulfur coke being the main component. According to sulfur content, coke with a sulfur mass fraction of 3.0% or less is considered low-sulfur coke, while coke with a sulfur mass fraction of 3.0% or less is considered high-sulfur coke. As a highly polluting product, the use of high-sulfur petroleum coke is significantly restricted, and the fuel industry's rigid demand will shift towards low-sulfur petroleum coke or alternative fuels. Downstream industries will significantly increase demand for low-sulfur coke, while demand for high-sulfur coke will shrink, leading to a situation where low-sulfur coke resources are scarce and high-sulfur coke production capacity is oversupplied. Therefore, developing a production process suitable for low-sulfur petroleum coke is crucial for resolving the issue of high-sulfur coke, improving resource utilization, and reducing environmental pollution.

[0003] The raw material processed by the traditional delayed coking process is the vacuum residue oil from the atmospheric and vacuum unit. This raw material has a high sulfur content. Relying solely on the delayed coking process cannot control the sulfur content of petroleum coke below 3.0%. Therefore, using the residue oil hydrodesulfurization process to convert the high-sulfur residue oil into desulfurized residue oil with a lower sulfur content for delayed coking to produce low-sulfur petroleum coke is a practical method.

[0004] CN101020843A discloses a hydrogenation method for catalytic cracking raw materials. The mixture of raw oil and hydrogen is sequentially contacted with a hydrogenation protective agent, a residual oil hydrodemetallization agent, and a residual oil hydrodesulfurization agent to react. The reaction product is cooled and separated to obtain a hydrogen-rich gas and a liquid product. Based on the volume of the overall catalyst, the loading volume percentages of the hydrogenation protective agent, the residual oil hydrodemetallization agent, and the residual oil hydrodesulfurization agent are 2-10% by volume, 5-70% by volume, and 20-93% by volume, respectively. This invention can blend 5-50% by weight of residual oil with gas oil to produce high-quality catalytic cracking raw materials, not only broadening the source of catalytic cracking raw materials but also improving the processing depth of the residual oil. The liquid product produced by this method has a carbon residue value of 1.65% by weight, which is a high-quality raw material for catalytic cracking. However, as a raw material for producing low-sulfur petroleum coke, the carbon residue value is far from enough.

[0005] CN113563921A discloses a method and system for producing low-sulfur petroleum coke, which comprises: (1) introducing a residual oil feedstock into a residual oil hydrogenation reaction system for hydrodesulfurization reaction to obtain hydrogenated wax oil and hydroreduced residue; (2a) introducing the hydroreduced wax oil and a portion of the hydroreduced residue into a catalytic cracking unit for catalytic cracking reaction to obtain catalytic cracking gasoline, catalytic cracking wax oil and oil slurry; (2b) introducing the remaining portion of the hydroreduced residue into a delayed coking unit for coking reaction to obtain coker wax oil and low-sulfur petroleum coke; (3) recycling the catalytic cracking wax oil, oil slurry and coker wax oil back into the residual oil hydrogenation reaction system for hydrodesulfurization reaction. This method requires a vacuum tower to be set in the fractionation part of the residual oil hydrogenation reaction system to perform vacuum fractionation on the desulfurized residual oil to obtain hydroreduced residue with high carbon residue. Since the residual oil hydrogenation reaction system with a vacuum tower is rarely used in domestic industry, the wide application of this process is limited.

[0006] CN109135818A discloses a residual oil desulfurization method and a petroleum coke preparation method and production equipment. The residual oil desulfurization method comprises the following steps: S1) providing residual oil as a reaction feedstock and pretreating the residual oil by mixing the residual oil with a pretreatment agent; wherein the pretreatment agent comprises a metal base and / or a metal carbonate; S2) subjecting the pretreated mixture obtained in step S1) to an electrostatic field for electrostatic adsorption desulfurization, thereby completing the desulfurization of the residual oil and obtaining a low-sulfur residual oil. This method requires subjecting the residual oil and pretreatment agent to an electrostatic field for desulfurization. Currently, most delayed coking units in refineries lack this pretreatment equipment, limiting its widespread application.

[0007] CN112745948A discloses a method and system for processing heavy feedstock oil and aromatic-rich fraction oil, comprising: (11) introducing the heavy feedstock oil into a solvent deasphalting unit for solvent deasphalting; (12) introducing the deasphalted oil into a first hydrogenation unit for hydrogenation reaction, and introducing the obtained liquid effluent into a DCC unit for reaction; (2) introducing the aromatic-rich fraction oil into a second hydrogenation unit for hydrogenation saturation and fractionation; (3) introducing the deoiled asphalt and aromatic hydrocarbon stream into a third reaction unit for hydrogenation reaction; (4) fractionating the liquid product of the third reaction unit; (51) introducing the second light component into a fourth reaction unit for reaction; and (52) introducing the second heavy component into a delayed coking unit for reaction; or using the second heavy component as a low-sulfur marine fuel oil component. This method involves a solvent deasphalting unit and a DCC unit. Currently, domestic refineries do not have industrial applications of DCC units, which limits the widespread application of this method.

[0008] In summary, the current residue oil hydrodesulfurization process reduces the sulfur content of the residue oil while greatly reducing its residual carbon value, that is, the hydrodesulfurization selectivity is not high. The desulfurized residue oil with low residual carbon value enters the delayed coking unit to produce petroleum coke. On the one hand, it is not formed and easily causes coking and blockage of the distillation system and the venting system. On the other hand, the empty tower linear velocity of the coke tower is high. Summary of the Invention

[0009] The technical problem to be solved by the present invention is: using existing equipment, by adjusting the raw material composition and the temperature of each reactor, to improve the hydrodesulfurization selectivity, so as to produce low-sulfur, high-carbon desulfurized residual oil that meets the requirements without affecting the long-term operation of the equipment.

[0010] The technical solution of the present invention is:

[0011] By increasing the slag ratio of crude oil to increase the residual carbon value of the raw material, by maintaining a high space velocity and adjusting the bed temperature of each reactor to improve the hydrodesulfurization selectivity, and by blending catalytic diesel to improve the properties of the raw material, we can provide high-quality low-sulfur petroleum coke raw materials for the delayed coking unit and ensure the long-term operation of the unit.

[0012] Specifically, the method of producing low-sulfur, high-carbon residual desulfurized residual oil of the present invention comprises the following steps:

[0013] (1) introducing atmospheric residue oil, vacuum heavy wax oil and vacuum residue oil from an atmospheric and vacuum unit and coking wax oil from a delayed coking unit into a residue oil hydrogenation reaction system for hydrodesulfurization reaction to obtain hydrogenated naphtha, hydrogenated diesel and desulfurized residue oil; the residue oil hydrogenation reaction system comprises six fixed-bed reactors, and the catalyst gradation of each reactor is as follows: the first reactor, the second reactor, the third reactor and the fourth reactor are filled with protective agent and demetallization catalyst, the fifth reactor is filled with desulfurization catalyst, and the sixth reactor is filled with carbon removal catalyst.

[0014] (2a) In order to increase the residual carbon value of the raw material and to be more conducive to the production of low-sulfur petroleum coke raw material, the amount of vacuum residue oil added to the raw material is increased to control the residue ratio;

[0015] (2b) To improve the properties of the feedstock, some catalytic diesel was added to control the pressure drop of each reactor;

[0016] (2c) To improve the hydrodesulfurization selectivity, the residue oil hydrogenation reaction system maintains a high space velocity production, and when the fresh feed amount (i.e., the mixture of atmospheric residue oil and vacuum heavy wax oil, vacuum residue oil, catalytic diesel oil and coker wax oil) is insufficient, a certain long circulation amount is maintained;

[0017] (3) The mixed raw oil in step (2c) is pressurized (21-23 MPa) by a hydrogenation feed pump and then enters the reactor for hydrodesulfurization and carbon removal reactions.

[0018] (4) In order to further improve the hydrodesulfurization selectivity, the bed temperature of each reactor is reduced, with an emphasis on reducing the bed temperature of the decarbonization reactor to obtain low-sulfur, high-carbon desulfurized residual oil.

[0019] (5) During the cooling process, the speed of the circulating hydrogen compressor is adjusted to maintain the hydrogen-to-oil ratio between 600-1500 Nm 3 / m 3 , to prevent the hydrogen-to-oil ratio from being too low and unevenly distributed oil from generating hot spots.

[0020] In step (1) of the present invention, after the hydrodesulfurization reaction is carried out, the reaction products obtained can be separated to obtain gas, hydrogenated naphtha, hydrogenated diesel and hydrogenated slag.

[0021] Preferably, in step (2a) of the present invention, the residue ratio of the feedstock entering the residue oil hydrogenation reaction system is controlled so that the residue ratio of the mixed feedstock formed by the atmospheric residue oil, vacuum heavy wax oil, vacuum residue oil, catalytic diesel oil, and coker gas oil is greater than 50 wt%. If the residue ratio falls below this range, the feed ratio of vacuum residue oil is increased to adjust the carbon residue value of the mixed feedstock.

[0022] More preferably, the proportion of vacuum residue entering the residue hydrogenation reaction system is controlled so that the blending ratio of the mixed feed formed by the atmospheric residue and vacuum heavy wax oil, vacuum residue, catalytic diesel, and coker gas oil is 50-60 wt%, and the sulfur content of the final mixed feed is controlled to be less than 4.2 wt%, and the carbon residue value is controlled to be 11.5-13.0 wt%. When the sulfur content exceeds this range, the feed proportion of vacuum residue is reduced to control the pressure drop of each reactor, and the pressure drop of the first reactor is controlled to increase by less than 20 kPa, the pressure drop of the second reactor is controlled to increase by less than 20 kPa, the pressure drop of the third reactor is controlled to increase by less than 20 kPa, the pressure drop of the fourth reactor is controlled to increase by less than 30 kPa, the pressure drop of the fifth reactor is controlled to increase by less than 50 kPa, and the pressure drop of the sixth reactor is controlled to increase by less than 70 kPa.

[0023] Preferably, in step (2b), the proportion of the catalytic diesel is 5-10 wt %. When the proportion is above this range, the flow rate of the catalytic diesel in the mixed feed is reduced to control the temperature rise of each reactor. When the proportion is below this range, the flow rate of the catalytic diesel in the mixed feed is increased to control the pressure drop of each reactor.

[0024] Preferably, in step (2c), the residue oil hydrogenation reaction system is controlled to maintain high space velocity production so that the outlet flow rate of the hydrogenation feed pump is ≮220 t / h to improve the hydrodesulfurization selectivity.

[0025] In step (4) of the present invention, the temperature of the desulfurization reactor is appropriately lowered, with a focus on lowering the temperature of the carbon removal reactor. The fourth reactor is lowered by 3-5°C, the fifth reactor is lowered by 5-8°C, the sixth reactor is lowered by 8-10°C, and the first, second, and third reactors are lowered by 0-3°C, ultimately making the sulfur content of the desulfurized residual oil less than 0.6wt% and the carbon residue greater than 6.0wt%.

[0026] Preferably, in step (4), the inlet temperature conditions of each reactor include: 330-380°C for the first reactor, 332-382°C for the second reactor, 334-384°C for the third reactor, 339-388°C for the fourth reactor, 341-387°C for the fifth reactor, and 344-389°C for the sixth reactor.

[0027] The beneficial effects of the present invention include:

[0028] This invention utilizes existing equipment without changing its production system or affecting its long-term operation. It produces desulfurized residual oil with low sulfur content and high carbon residue, thus saving investment. By selectively lowering the bed temperature in each reactor, it reduces hydrogen consumption and the load on the circulating hydrogen compressor, saving medium-pressure steam and electricity. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The present invention will be further described below with reference to the accompanying drawings.

[0030] Figure 1 It is a schematic diagram of the process flow of the present invention, Figure 1 The markings are described as follows:

[0031] 1. Mixture of atmospheric residue oil and vacuum heavy wax oil

[0032] 2. Vacuum residue

[0033] 3. Coking wax oil

[0034] 4. Catalytic diesel

[0035] 5. Circulating oil

[0036] 6. Residue oil hydrogenation reaction system

[0037] 7. First Gas

[0038] 8. Reaction liquid phase product

[0039] 9. Residue oil hydrofractionation system

[0040] 10. Second Gas

[0041] 11. Hydrotreated naphtha

[0042] 12. Hydrogenated diesel

[0043] 13. Desulfurized residual oil.

[0044] Figure 2 for Figure 1 Schematic diagram of the composition of the medium residue oil hydrogenation reaction system 6, Figure 2 The markings are described as follows:

[0045] 14. Mixed feeding

[0046] 15. Raw material buffer tank

[0047] 16. Reaction heating furnace entrance

[0048] 17. Reaction heating furnace

[0049] 18. One-way entrance

[0050] 19. A reversal

[0051] 20. Second Anti-Entrance

[0052] 21. Second Anti-Japanese War

[0053] 22. Three Anti-entry

[0054] 23. Three Antis

[0055] 24. Four Anti-Entrances

[0056] 25. Four Antis

[0057] 26. Entrance to the Five Anti-Japanese Campaign

[0058] 27. Five Antis Movement

[0059] 28. Six Anti-Entrance

[0060] 29. Six Antis

[0061] 30. Reaction effluent

[0062] 31. High and low pressure separation system. DETAILED DESCRIPTION

[0063] Example 1

[0064] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0065] Unless otherwise specified, the pressure described in the present invention is gauge pressure.

[0066] In the present invention, the slag blending ratio is expressed by the following formula: slag blending ratio = vacuum residue oil amount / (atmospheric residue oil amount+vacuum residue oil amount)*100%; the hydrogen-to-oil ratio is expressed by the following formula: hydrogen-to-oil ratio = mixed hydrogen volume flow rate*hydrogen purity / hydrogenation feed pump outlet volume flow rate.

[0067] See also Figure 1 and Figure 2 A method for producing low-sulfur, high-carbon residual desulfurized residual oil according to the present invention comprises:

[0068] (1) introducing a mixture of atmospheric residue oil and vacuum heavy wax oil 1, vacuum residue oil 2, coker wax oil 3, catalytic diesel oil 4, and circulating oil 5 into a residue oil hydrogenation reaction system 6 for hydrodesulfurization and carbon removal to obtain a first gas 7 and a reaction liquid product 8;

[0069] (2a) introducing the reaction liquid phase product into the residue oil hydrogenation reaction system fractionation system 9 for distillation and cutting to obtain a second gas 10, hydrogenated naphtha 11, hydrogenated diesel 12, and desulfurized residue 13;

[0070] (2b) introducing the desulfurized residual oil 13 into a delayed coking unit to produce low-sulfur petroleum coke;

[0071] (3) A small portion of the desulfurized residue 13 obtained in step (2a) is circulated back to the residue hydrogenation reaction system 9 as circulating oil 5 to maintain a high space velocity.

[0072] (4) The residue oil hydrogenation reaction system 6 is composed of a raw material buffer tank 15, a reaction heating furnace 17, a first reactor 19, a second reactor 21, a third reactor 23, a fourth reactor 25, a fifth reactor 27, a sixth reactor 29 and a high and low pressure separation system 31. After the mixed feed is heated in the reaction heating furnace 17, it enters the first reactor 19, the second reactor 21, the third reactor 23, the fourth reactor 25, the fifth reactor 27 and the sixth reactor 29 in sequence for hydrodesulfurization and residual carbon removal reactions. The reaction effluent 30 enters the high and low pressure separation system 31 for gas-liquid separation to obtain a first gas 7 and a reaction liquid phase product 8.

[0073] The mixed oil 1 of atmospheric residue oil and vacuum heavy wax oil used in this example has properties shown in Table 1.

[0074] The properties of vacuum residue 2 used in this example are shown in Table 2.

[0075] The properties of the catalytic diesel 4 used in this example are shown in Table 3.

[0076] The operating conditions, product yields and main product properties of the residue oil hydrogenation reaction system are shown in Table 4.

[0077] Table 1

[0078]

[0079]

[0080] Table 2

[0081] Crude oil number Vacuum residue 2 <![CDATA[Density (20 °C), kg / m 3 > 1032.6 <![CDATA[Kinematic viscosity (100 °C), mm 2 / s]]> 2164 Carbon residue, weight % 21.85 Nitrogen, weight % 0.26 Sulfur, weight % 5.32 Metal content, ppm nickel 41 vanadium 132

[0082] Table 3

[0083] Crude oil number Catalytic diesel 4 Sulfur, weight % 0.289 50％，℃ 255.1 90％，℃ 334.1 95％，℃ 347.6

[0084] Table 4

[0085]

[0086]

[0087] As can be seen from Table 4, the desulfurized residual oil produced by the method of the present invention can meet the index requirements of sulfur content <0.6wt% and residual carbon >6.0wt%.

[0088] Comparative Example 1

[0089] See also Figure 1 The method for producing low-sulfur, high-carbon residual desulfurized residual oil in this comparative example comprises:

[0090] (1) introducing a mixture of atmospheric residue oil and vacuum heavy wax oil 1, vacuum residue oil 2, coker wax oil 3, catalytic diesel oil 4, and circulating oil 5 into a residue oil hydrogenation reaction system 6 for hydrodesulfurization and carbon removal to obtain a first gas 7 and a reaction liquid product 8;

[0091] (2a) introducing the reaction liquid phase product into the residue oil hydrogenation reaction system fractionation system 9 for distillation and cutting to obtain a second gas 10, hydrogenated naphtha 11, hydrogenated diesel 12, and desulfurized residue 13;

[0092] (2b) introducing the desulfurized residual oil into a delayed coking unit to produce low-sulfur petroleum coke;

[0093] (3) A small portion of the desulfurized residual oil obtained in step (2a) is circulated back to the residual oil hydrogenation reaction system as circulating oil 5 to maintain a high space velocity.

[0094] The mixed oil 1 of atmospheric residue oil and vacuum heavy wax oil used in this example has properties shown in Table 1.

[0095] The properties of vacuum residue 2 used in this example are shown in Table 2.

[0096] The catalytic diesel 4 used in this example has properties shown in Table 3.

[0097] The feed composition, operating conditions, product yield and main product properties used in this example are shown in Table 5.

[0098] Table 5

[0099]

[0100] As can be seen from Table 5, the desulfurized residual oil produced by the method of this comparative example cannot meet the index requirement of residual carbon>6.0wt%.

[0101] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A method for producing low-sulfur, high-carbon desulfurized residual oil, wherein the sulfur content of the low-sulfur, high-carbon desulfurized residual oil is less than 0.6 wt% and the carbon residue is greater than 6.0 wt%; characterized in that: The method comprises the following steps: (1) introducing a mixed oil of atmospheric residue oil and vacuum heavy wax oil from an atmospheric and vacuum unit, vacuum residue oil, and coker wax oil into a residue oil hydrogenation reaction system for hydrodesulfurization reaction to obtain gas, hydrogenated naphtha, hydrogenated diesel, and desulfurized residue oil; the residue oil hydrogenation reaction system comprises six fixed-bed reactors, and the catalyst gradation of each reactor is as follows: the first reactor, the second reactor, the third reactor, and the fourth reactor are filled with a protective agent and a demetallization catalyst, the fifth reactor is filled with a desulfurization catalyst, and the sixth reactor is filled with a carbon removal catalyst; (2a) increasing the amount of vacuum residue added to the raw material to control the residue ratio, so as to increase the residual carbon value of the raw material and thus be more conducive to the production of low-sulfur petroleum coke raw material; (2b) To improve the properties of the feedstock, some catalytic diesel was added to control the pressure drop of each reactor; (2c) To improve the hydrodesulfurization selectivity, the residue oil hydrogenation reaction system maintains a high space velocity production. When the feed amount of the mixed oil of atmospheric residue oil and vacuum heavy wax oil, vacuum residue oil, coker wax oil and catalytic diesel oil is insufficient, the desulfurized residue oil is used as the circulating oil to maintain a certain long circulation amount; (3) The mixed feed oil in step (2c) is pressurized to 21-23 MPa by a hydrogenation feed pump and then enters the reactor for hydrodesulfurization and carbon removal reaction; (4) Lower the bed temperature of the carbon removal reactor to obtain low-sulfur, high-carbon desulfurized residual oil; during the cooling process, adjust the speed of the circulating hydrogen compressor to maintain the hydrogen-to-oil ratio between 600 and 1500 Nm 3 / m 3 , used to prevent uneven oil distribution and hot spots caused by too low hydrogen-to-oil ratio; In step (2a), the proportion of vacuum residue oil entering the residue oil hydrogenation reaction system is controlled so that the residue blending ratio of the mixed feed formed by the atmospheric residue oil, vacuum heavy wax oil, vacuum residue oil, catalytic diesel oil, and coker wax oil is 50-60wt%, and the sulfur content of the final mixed feed is controlled to be less than 4.2wt%, and the residual carbon value is controlled to be 11.5-13.0wt%; the residue blending ratio = vacuum residue oil amount / (atmospheric residue oil amount+vacuum residue oil amount)*100%; In step (2b), the proportion of the catalytic diesel is 5-10 wt%; In step (2c), the residue oil hydrogenation reaction system is controlled to maintain high space velocity production so that the outlet flow rate of the hydrogenation feed pump is ≮220 t / h to improve the hydrodesulfurization selectivity; In step (4), lowering the bed temperature of the carbon removal reactor includes lowering the temperature of the desulfurization reactor and lowering the temperature of the carbon removal reactor; In step (4), the temperature of each reactor is reduced by 3-5°C for the fourth reactor, 5-8°C for the fifth reactor, 8-10°C for the sixth reactor, and 0-3°C for the first, second, and third reactors respectively; The inlet temperature conditions of each reactor are: 330~380℃ for the first reactor, 332~382℃ for the second reactor, 334~384℃ for the third reactor, 339~388℃ for the fourth reactor, 341~387℃ for the fifth reactor, and 344~389℃ for the sixth reactor.

2. The method according to claim 1, wherein: When the residue blending ratio is higher than 60wt%, the feed ratio of vacuum residue oil is reduced to control the pressure drop of each reactor, and the pressure drop of the first reactor is controlled to increase by <20KPa, the pressure drop of the second reactor is controlled to increase by <20KPa, the pressure drop of the third reactor is controlled to increase by <20KPa, the pressure drop of the fourth reactor is controlled to increase by <30KPa, the pressure drop of the fifth reactor is controlled to increase by <50KPa, and the pressure drop of the sixth reactor is controlled to increase by <70KPa.

3. The method according to claim 1 or 2, characterized in that: When the proportion of the catalytic diesel is higher than 10wt%, the flow rate of the catalytic diesel in the mixed feed is reduced to control the temperature rise of each reactor; when it is lower than this range, the flow rate of the catalytic diesel in the mixed feed is increased to control the pressure drop of each reactor.

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