A method for producing both low-sulfur coke and high-sulfur coke

Abstract

The present invention discloses a method for producing both low-sulfur coke and high-sulfur coke. Based on the original overall processing flow of the whole plant, the method starts from crude oil processing, and the atmospheric and vacuum reduction unit flexibly switches to process high-sulfur, high-metal content and low-metal content inferior crude oil according to the inventory of vacuum residue oil of different properties produced by it. By utilizing the existing process technology of the residue oil hydrogenation unit, by adjusting the raw materials, reaction parameters, etc., the production of hydrogenated residue oil with high and low residual carbon values ​​can be flexibly switched. The hydrogenated residue oil with high residual carbon value is the raw material required for the delayed coking unit to produce low-sulfur coke. The delayed coking unit utilizes the existing process flow for producing high-sulfur petroleum coke, takes high-carbon value hydrogenated residue oil as the main raw material, and produces low-sulfur coke products by adjusting the oil slurry raw material ratio. This method not only keeps the existing overall processing flow of the whole plant unchanged, but also makes full use of the existing process technology of the residue oil hydrogenation unit and the delayed coking unit to produce low-sulfur petroleum coke that meets the standards.

Description

Technical Field

[0001] The present invention relates to the technical field of petroleum refining, and relates to a method for producing both low-sulfur coke and high-sulfur coke, and specifically relates to a method for switching a constant pressure reduction unit to process high-sulfur, high- and low-metal content inferior crude oils, a method for flexibly switching a residual oil hydrogenation unit to produce high- and low-carbon residue value hydrogenated residual oils, and a method for flexibly switching a delayed coking unit to produce high- and low-sulfur petroleum cokes. Background Art

[0002] Petroleum coke is a byproduct of the petroleum refining process, produced using residual oil and heavy oil as raw materials through a delayed coking process. Petroleum coke can be classified according to its sulfur content as high-sulfur coke or low-sulfur coke. Coke with a sulfur content of less than 3.0% is considered low-sulfur coke, while coke with a sulfur content greater than 3.0% is considered high-sulfur coke.

[0003] Low-sulfur coke is primarily used in conventional graphite electrodes, which are ultimately used in short-process electric furnaces for steel production. It is also used in low- and mid-range lithium battery anodes, with the final destination being new energy vehicles and energy storage. It can also be used in high-end pre-baked anodes and other carbon products. High-sulfur coke is primarily used as a fuel and reducing agent. Its downstream fuel applications include glass factories, power plants, cement plants, and other industries. As a reducing agent, it is primarily used in silicon smelting, such as in the manufacture of calcium carbide and silicon carbide. High-sulfur coke has a high sulfur content, resulting in high SO2 emissions during the production process of electrolytic aluminum plants, easily exceeding pollution standards. Furthermore, SO2 can corrode equipment and increase anode resistivity. Therefore, high-sulfur coke is rarely used in pre-baked anodes in China.

[0004] The sulfur content of petroleum coke can be controlled during petroleum refining to reduce the sulfur content in the residual oil. However, since refining is mainly for obtaining oil and gas, it is difficult for companies to modify the process to obtain low-sulfur residual oil. Although the sulfur content of the residual oil can be reduced in theory, it is difficult for companies to implement it. At present, the delayed coking process is mostly adopted in China, which has low investment, strong raw material adaptability and mature technology. However, it is difficult to reduce the sulfur content of petroleum coke through the coking process. Petroleum coke desulfurization can also be carried out after the petroleum coke is produced. The main methods include high-temperature calcination desulfurization, hydrodesulfurization, and solvent extraction desulfurization. High-temperature desulfurization is relatively low in cost and is widely used by companies. High-temperature desulfurization requires heating the petroleum coke to above 1400℃ for the desulfurization effect to be more significant. Heating to 1700-2300℃ can produce petroleum coke with a sulfur content of about 0.1%. High-temperature desulfurization to produce low-sulfur coke requires high-temperature resistant materials, especially the production of low-sulfur coke, which is costly. In addition, the true density, porosity and reactivity of the petroleum coke after high-temperature calcination are all deteriorated. Subsequent graphitization may affect the negative electrode material produced.

[0005] CN114540059A discloses a combined process, combined system, and the needle coke produced from heavy oil. The combined process includes: a hydrogenation process, in which heavy oil is hydrogenated to remove coke-prone components to produce hydrogenated oil; a component cutting process, in which the hydrogenated oil is separated into heavy and light components; an electrostatic desolidification process, in which the light component is passed through an electrostatic desolidification device to remove ash to produce deashed oil; a solvent extraction process, in which the deashed oil is separated into an extracted oil component and a raffinate oil component; and a delayed coking process, in which the extracted oil is subjected to delayed coking to produce needle coke. The combined process of the present invention can produce high-quality needle coke with a low thermal expansion coefficient. This process is complex and can only produce needle coke products.

[0006] CN103102986A discloses a combined residue hydroprocessing and delayed coking process. Residual oil, coker gas oil, and hydrogen are mixed together and reacted in a hydroprocessing unit in the presence of a catalyst. The hydrogenated reaction products are separated. The hydrogenated residual oil and separated vacuum gas oil are mixed together or fed into a delayed coking unit along with other conventional feedstocks. The coking products are separated, and the coker gas oil is completely recycled to the residual oil hydroprocessing unit. This method improves the product structure of the combined process, eliminating the production of coker gas oil and maximizing the production of light oil products, resulting in high-quality needle coke. Furthermore, the method effectively reduces foaming within the coking tower and slows the tendency of coking in the coking furnace.

[0007] Both CN114540059A and CN103102986A relate to a combined process, method, and system for producing needle coke. The processes and methods involved are complex, technically challenging, and can only produce needle coke products. Both CN114540059A and CN103102986A obtain needle coke products by processing heavy oil, and do not mention the system balance issues related to heavy oil during the production process.

[0008] CN111892950A discloses a combined process for producing needle coke. The method involves fractionating raw oil through a vacuum distillation unit into light and heavy fractions. The heavy fraction exits the unit, and the light fraction enters a hydrotreating unit. The liquid product obtained after hydrotreating passes through a fractionating unit to separate at least a hydrogenated light fraction and a hydrogenated heavy fraction. The hydrogenated heavy fraction serves as the mesophase-forming material, which is heated in a heating furnace (A) and then enters a coke drum. Coke gas generated in the coke drum passes through a coking fractionation unit to obtain coker gas oil. The coker gas oil is mixed with the hydrogenated light fraction to form the coke-drawing material, which is heated in a heating furnace (B) and then enters the coke drum. The coke drum completes the mesophase-forming and coke-drawing stages, producing needle coke. This method enables the continuous production of high-quality needle coke with stable performance.

[0009] CN108998060A discloses a new process for producing low-sulfur coke, comprising mixing residual oil with an oxidant, subjecting it to microwave pretreatment and coking, to produce low-sulfur coke. Starting from the raw materials used to produce petroleum coke, the present invention combines the selective heating properties of chemical oxidation and microwave pretreatment to propose a new process for producing low-sulfur petroleum coke through microwave pretreatment and oxidation of residual oil. This process allows for the production of low-sulfur coke in a single step, requiring minimal investment, achieving rapid results, and ensuring clean production without pollution.

[0010] CN113122329A discloses a method and system for the co-production of needle coke and low-sulfur coke. The method comprises: hydrotreating catalytic oil slurry to obtain refined oil, which is fed to a vacuum distillation system for separation into light distillate, middle distillate, and heavy distillate. The oil and gas products of the middle distillate after coking enter a stabilizing tower for separation to produce non-condensable gas, distillate oil, and tower bottom oil. The tower bottom oil is buffered and divided into two paths: one path of tower bottom oil is returned to the stabilizing tower after temperature adjustment, and the other path of tower bottom oil enters a fractionation system. The light distillate and heavy distillate are fed to a low-sulfur petroleum coke production unit, and the reaction oil and gas products enter a fractionation system for separation to produce gas, light oil, and wax oil. The method uses some of the components in the catalytic oil slurry to produce needle coke, while the remaining components are used to produce low-sulfur petroleum coke. The production method maximizes the raw material conversion rate.

[0011] The paper "Research on the Combined Process of Residue Hydrogenation-Delayed Coking for the Production of Low-Sulfur Petroleum Coke" (Liu Tao et al., Petroleum Refining and Chemical Industry, 2021-12-12) investigated the effects of hydrogenation process conditions on the hydrodesulfurization reaction of high-sulfur residue. The results showed that increasing the reaction temperature and reducing the space velocity are beneficial to improving the activity of the hydrodesulfurization reaction; lowering the reaction temperature, reducing the hydrogen partial pressure and increasing the space velocity are beneficial to improving the hydrodesulfurization selectivity. When achieving the same desulfurization rate, increasing the reaction temperature can adopt a higher reaction space velocity, thereby reducing the processing cost of residue hydrogenation. The research results of the residue hydrogenation-delayed coking combined process show that: with the increase of the hydrodesulfurization depth, the remaining sulfur-containing compounds in the hydrogenated residue are more inclined to generate petroleum coke; the combined process can significantly reduce the sulfur mass fraction of petroleum coke to below 3.0%, meeting the index requirements of low-sulfur coke; compared with the delayed coking process alone, the combined process can produce more and better quality high-value products.

[0012] While the aforementioned methods and papers can produce low-sulfur coke, they suffer from complex processes, limited product quality, and inflexible production. In short, there is currently a lack of methods that can fully integrate low-quality crude oil processing, residue hydrotreating units, delayed coking units, heavy oil catalytic cracking units, and heavy oil inventory to enable flexible switching between low-sulfur and high-sulfur coke production. Summary of the Invention

[0013] To address the deficiencies in the prior art, the present invention provides a method for producing both low-sulfur coke and high-sulfur coke. This method, from crude oil processing to the production of petroleum coke products, does not affect the overall processing flow of the entire plant, crude oil processing and equipment operating processes and parameters, and has the advantages of flexibility, periodicity and efficient production.

[0014] The overall concept of the present invention is as follows: on the basis of the original overall processing flow of the whole plant, starting from crude oil processing, the atmospheric and vacuum unit can flexibly switch to process high-sulfur, high-metal content and low-metal content inferior crude oil according to the inventory of vacuum residue oil of different properties produced by it. By utilizing the existing process technology of the residue oil hydrogenation unit, by adjusting the raw materials, reducing the reactor bed temperature, increasing the circulating hydrogen flow, reducing the new hydrogen flow, etc., it is possible to flexibly switch to produce high and low residual carbon value hydrogenated residue oil. High residual carbon value hydrogenated residue oil is the raw material required for the delayed coking unit to produce low-sulfur coke. The delayed coking unit utilizes the existing process flow for producing high-sulfur petroleum coke, uses high residual carbon value hydrogenated residue oil as the main raw material, and produces low-sulfur coke products by adjusting the oil slurry raw material ratio. This technology not only keeps the existing overall processing flow of the whole plant unchanged, but also makes full use of the existing process technology of the residue oil hydrogenation unit and the delayed coking unit to produce low-sulfur petroleum coke that meets the standards.

[0015] The technical solution of the present invention is:

[0016] A method for producing both low-sulfur coke and high-sulfur coke comprises the following steps:

[0017] S1, low-quality crude oil processing and heavy oil balance stage

[0018] S1.1: The atmospheric and vacuum unit processes low-quality crude oil with high sulfur and high metal content. The vacuum residue B produced is stored in the delayed coking unit's vacuum residue B feedstock tank. When the storage capacity reaches 90 wt.%, the atmospheric and vacuum unit switches to processing low-quality crude oil with high sulfur and low metal content. The vacuum residue A produced is stored in the vacuum residue A feedstock tank of the residue hydrotreating unit. When the storage capacity reaches 90 wt.%, the atmospheric and vacuum unit switches again to processing low-quality heavy oil with high sulfur and high metal content. The mixed heavy oil produced during the processing of low-quality crude oil in the atmospheric and vacuum unit shall always be part of the residue hydrotreating feedstock.

[0019] S1.2, the residue oil hydrotreating unit and the delayed coking unit shall be based on the inventory of the corresponding vacuum residue oil A and vacuum residue oil B respectively. If the vacuum residue oil A raw material of the residue oil hydrotreating unit is used up to 20 wt.% of the storage tank inventory, it shall be fed back to the upstream atmospheric and vacuum distillation unit to switch to processing high-sulfur, low-metal content inferior crude oil; if the vacuum residue oil B raw material of the delayed coking unit is used up to 20 wt.% of the storage tank inventory, it shall be fed back to the upstream atmospheric and vacuum distillation unit to switch to processing high-sulfur, high-metal content inferior crude oil.

[0020] Furthermore, the type of low-quality crude oil that the atmospheric and vacuum distillation unit switches to process needs to be determined based on the existing crude oil varieties, the inventory of vacuum residue raw materials in the residue hydrotreating and delayed coking units, and the processing plans of the two units.

[0021] S2, the residue oil hydrotreating unit switches to produce high and low carbon residue value hydrotreating residue oil stage

[0022] S2.1: Based on the inventory status and properties of vacuum residue A feedstock in the residue hydrotreating unit, the residue hydrotreating unit utilizes the existing process flow to switch between producing high- and low-carbon-residue hydrotreating residues. During this process, while maintaining the unit's processing capacity and the proportion of mixed heavy oil feedstock, the residue hydrotreating unit primarily controls the proportion of vacuum residue A feedstock to ultimately produce high-carbon-residue (above 5.0 wt.%) and low-carbon-residue (less than 5.0 wt.%) hydrotreating residues.

[0023] S2.2: Evaluate the carbon residue value of vacuum residue A feedstock using the analytical method specified in GB / T 17144-2021. If the carbon residue value of vacuum residue A feedstock is less than 20 wt.% and the inventory of low-carbon hydroresidue feedstock is at or below 20 wt.% of the storage tank's storage capacity, the residue hydrotreating unit will produce low-carbon hydroresidue at this stage. If the carbon residue value of vacuum residue A feedstock is greater than 20 wt.% and the inventory of high-carbon hydroresidue feedstock is at or below 20% of the storage tank's storage capacity, the residue hydrotreating unit will produce high-carbon hydroresidue at this stage.

[0024] Furthermore, in combination with the processing plan, before the delayed coking unit produces low-sulfur coke products, high-carbon-value hydrotreated residue oil is prepared in advance, and the residue oil hydrotreating unit in other stages continuously produces low-carbon-value hydrotreated residue oil as raw material for the heavy oil catalytic cracking unit.

[0025] Furthermore, the proportion of vacuum residue A in the feedstock of the residue hydrotreating unit was increased to above 39.0 wt.%, and the proportion of mixed heavy oil was correspondingly reduced to below 61.0 wt.%. The two feedstocks entered the residue hydrotreating reaction system, and the reactor catalyst bed temperature was controlled at 360-375 ° C, and the circulating hydrogen flow rate was controlled at 240,000-250,000 Nm 3 / h, the flow rate of new hydrogen is controlled at 44000-48000Nm 3 / h, and obtain high carbon residue value hydrogenated residue oil with carbon residue value of more than 5.0 wt.%.

[0026] S3, the stage of switching the delayed coking unit to produce high-sulfur and low-sulfur petroleum coke products

[0027] S3.1. Based on the storage capacity of the high carbon residue hydroprocessing residue and vacuum residue B raw material storage tanks, evaluate the inventory status of high carbon residue hydroprocessing residue required for the production of low sulfur petroleum coke and vacuum residue B required for the production of high sulfur petroleum coke in the delayed coking unit.

[0028] S3.2. When the inventory of vacuum residue oil B raw material reaches 20 wt.% or less of the storage capacity of the storage tank, and the inventory of high carbon residue hydrotreated residue oil raw material reaches 90 wt.% or more of the storage capacity of the storage tank, the delayed coking unit shall produce low-sulfur petroleum coke products until the inventory of high carbon residue desulfurized residue oil drops to 20 wt.% of the storage capacity of the storage tank, and the inventory of vacuum residue oil B raw material reaches 90 wt.% or more of the storage capacity of the storage tank, and the delayed coking unit shall switch to producing high-sulfur petroleum coke products.

[0029] Preferably, the production time and output of low-sulfur coke in the delayed coking unit can be extended by controlling the ratio of high carbon residue value hydrogenated residue oil and catalytic oil slurry raw materials in the delayed coking unit.

[0030] The present invention comprises at least two types of inferior crude oil with different properties, vacuum residue oil tanks for storing two types of different properties, and desulfurized residue oil tanks for storing two types of different properties. The upper limit of the storage capacity of the storage tanks is 90 wt.%, and the lower limit is 20 wt.%. The devices and the devices and the tank farms are all connected in the system, and the switching production plan of the devices is a continuous production process.

[0031] In the present invention, the residue oil hydrotreating unit and the delayed coking unit are switched to produce products of different properties. This is based on the storage capacity of the corresponding raw material storage tanks, and it is evaluated whether the corresponding raw material inventory of the residue oil hydrotreating unit or the delayed coking unit is at the upper limit of the storage capacity of the corresponding storage tank. If the storage tank is in a state where the storage material is at the upper limit, the device producing the material must be switched to produce another material.

[0032] When the inventory of high-carbon-residue hydrotreated residue, needed for the delayed coking unit to produce low-sulfur petroleum coke, reaches the upper limit of its storage tank capacity, the delayed coking unit can switch to producing low-sulfur petroleum coke; otherwise, it cannot produce low-sulfur petroleum coke. Simultaneously, when the high-carbon-residue hydrotreated residue produced by the residue hydrotreating unit reaches the upper limit of its storage tank capacity, it must switch to producing low-carbon-residue hydrotreated residue. At this point, the atmospheric and vacuum unit must process low-quality crude oil with high sulfur and low metal content to produce vacuum residue, which provides the feedstock for residue hydrotreating to produce low-carbon-residue. If the residue hydrotreating unit switches to producing high-carbon-residue hydrotreated residue, the atmospheric and vacuum unit switches to processing low-sulfur and high-metal-residue crude oil to produce vacuum residue, which feeds the residue hydrotreating unit to produce high-carbon-residue hydrotreated residue. This high-carbon-residue hydrotreated residue is then fed back to the delayed coking unit to produce low-sulfur petroleum coke. This process is cyclical and reciprocating.

[0033] The beneficial effects of the present invention include:

[0034] The present invention can utilize the existing production processes and procedures of the residue oil hydrotreating unit and the delayed coking unit. Starting from crude oil processing, the atmospheric and vacuum distillation unit can flexibly switch to process high-sulfur, high-metal content and low-metal content inferior crude oil according to the inventory of vacuum residue oil of different properties produced by it. Utilizing the existing process technology of the residue oil hydrotreating unit, by increasing the proportion of vacuum residue oil A to above 39.0wt.%, the proportion of mixed heavy oil is correspondingly reduced to below 61.0wt.%, and at the same time, the reactor bed temperature is reduced to 360-375℃ and the circulating hydrogen flow rate is increased to 240,000-250,000Nm 3 / h, reduce the new hydrogen flow rate to 44000-48000Nm 3 / h, high-carbon-value hydrotreated residue can be produced. Otherwise, the residue hydrotreating unit will not be able to produce high-carbon-value hydrotreated residue, and the balance of the heavy oil system will be disrupted, directly resulting in the delayed coking unit lacking high-carbon-value hydrotreated residue feedstock to produce low-sulfur petroleum coke products. The delayed coking unit utilizes the existing process flow for producing high-sulfur petroleum coke, using high-carbon-value hydrotreated residue as the main feedstock. By adjusting the oil-slurry feedstock ratio, it can produce low-sulfur coke products. This method maintains the existing overall processing flow of the entire plant while fully utilizing the existing process technologies of the residue hydrotreating unit and delayed coking unit to produce low-sulfur petroleum coke that meets standards. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 Flowchart for switching the residue hydrotreating unit to produce high and low carbon residue value hydrotreating residues.

[0036] Figure 2 Flow chart for switching the delayed coking unit to produce high- and low-sulfur petroleum coke products.

[0037] Figure 3 is a flow chart of the method of the present invention.

[0038] Figure 4 Schematic diagram of the method of the present invention.

[0039] The symbols in the accompanying drawings are described as follows:

[0040] 1. Low-quality crude oil with high sulfur content and low metal content;

[0041] 2. Atmospheric and vacuum device;

[0042] 3. Pipeline for vacuum residue A to feed residue hydrogenation feed tank;

[0043] 4. Pipeline for mixed heavy oil to feed residual oil hydrogenation raw material tank;

[0044] 5. Vacuum residue oil B enters delayed raw material tank pipeline;

[0045] 6. Delayed coking unit vacuum residue oil B raw material tank;

[0046] 7. Vacuum residue oil A raw material tank of residue oil hydrogenation unit;

[0047] 8. Residue oil hydrotreating unit mixed heavy oil raw material tank;

[0048] 9. Inlet of residue oil hydrogenation reaction system;

[0049] 10. Residue oil hydrogenation reaction system;

[0050] 11. Pipeline for low carbon residue value hydrogenated residue oil to feed heavy oil catalytic cracking tank;

[0051] 12. Pipeline for high carbon residue value hydrogenated residue oil to enter delayed coking raw material tank;

[0052] 13. Low carbon residue value hydrogenated residue oil tank area;

[0053] 14. High carbon residue value hydrogenated residue oil tank area;

[0054] 15. Pipeline for low carbon residue hydrotreated residue oil to enter heavy oil catalytic cracking unit;

[0055] 16. Pipeline for high carbon residue value hydrogenated residue oil to enter delayed coking unit;

[0056] 17. Low-quality crude oil with high sulfur and high metal content;

[0057] 18. Catalytic slurry raw materials;

[0058] 19. Delayed coking reaction system inlet;

[0059] 20. Coking unit reaction system;

[0060] 21. Low sulfur petroleum coke;

[0061] 22. High sulfur petroleum coke. DETAILED DESCRIPTION

[0062] Example 1

[0063] Step 1

[0064] S1.1, based on the inventory of vacuum residue A and B raw materials of different properties, low-quality crude oil 1 with high sulfur and low metal content enters atmospheric vacuum unit 2. The production mixed heavy oil enters the residue oil hydrogenation feed tank pipeline 4 and enters the mixed heavy oil feed tank 8 of the residue oil hydrogenation unit. The production vacuum residue A enters the residue oil hydrogenation feed tank pipeline 3 and enters the residue oil hydrogenation unit vacuum residue A feed tank 7. Low-quality crude oil 17 with high sulfur and high metal content enters atmospheric vacuum unit 2. The production vacuum residue B enters the vacuum residue B delayed feed tank pipeline 5 and enters the delayed coking unit vacuum residue B feed tank 6.

[0065] S1.2. Based on the inventory of hydrotreated residue oil raw materials of different properties, evaluate the switching of production of high and low carbon value hydrotreated residue oil. The low carbon value hydrotreated residue oil produced will enter the low carbon value hydrotreated residue oil tank area 13 via the low carbon value hydrotreated residue oil into heavy oil catalytic cracking raw material tank pipeline 11. Subsequently, the low carbon value hydrotreated residue oil will enter the heavy oil catalytic cracking unit pipeline 15 for processing.

[0066] Step 2

[0067] S2.1, the high carbon value hydrogenated residue oil produced by the residue oil hydrogenation unit enters the high carbon value hydrogenated residue oil tank area 14 through the high carbon value hydrogenated residue oil into delayed coking raw material tank pipeline 12, and then the high carbon value hydrogenated residue oil is supplied to the delayed coking unit for processing through the high carbon value hydrogenated residue oil into the delayed coking unit pipeline 16.

[0068] S2.2: Increase the proportion of vacuum residue A in the feedstock of the residue hydrotreating unit to above 39.0 wt.%, and correspondingly reduce the proportion of mixed heavy oil to below 61.0 wt.%. The two feedstocks enter the residue hydrotreating reaction system 10, and control the reactor catalyst bed temperature at 360-375°C and the circulating hydrogen flow rate at 240,000-250,000 Nm 3 / h, new hydrogen flow control 44000-48000Nm 3 / h (the control temperature of low carbon residue hydrotreating residue oil is 371-386℃, and the circulating hydrogen flow rate is 235000-248000Nm 3 / h, new hydrogen flow control 44500-56500Nm 3 / h) to obtain high carbon residue value hydrogenated residue oil (carbon residue value above 5.89 wt.%), which enters the high carbon residue value hydrogenated residue oil tank area 14 and is used as a raw material for the coking unit to produce low sulfur petroleum coke.

[0069] The residue oil hydrotreating unit switches from producing low carbon residue value hydrotreating residue oil to high carbon residue value hydrotreating residue oil. The switching production process is adjusted in a step-by-step manner under the premise of maintaining stable production of the unit. That is, under the premise of maintaining the feed rate of the unit unchanged, by reducing the mixed heavy oil and correspondingly increasing the vacuum residue A, the proportion is finally adjusted to produce high carbon residue hydrotreating residue oil. The changes in the properties of the raw materials during the switching process are shown in Table 1.

[0070] Step 3

[0071] S3.1 Assess the inventory status of high carbon residue hydroprocessing residue and vacuum residue raw materials.

[0072] S3.2, when the delayed coking unit is in accordance with the production plan and the vacuum residue B raw material is in a high inventory state, the vacuum residue B (proportion 78 wt.%) and the catalytic oil slurry raw material 18 (proportion 22 wt.%) enter the coking unit reaction system 20 through the delayed coking reaction system inlet 19 to obtain high sulfur petroleum coke 22.

[0073] S3.3, the delayed coking unit uses high carbon value hydroresidue oil as the main raw material for producing low sulfur petroleum coke. When the high carbon value hydroresidue oil raw material is in a high inventory state, the delayed coking unit uses the high carbon value hydroresidue oil raw material (proportion of 58 wt.% or more) from the high carbon value hydroresidue oil tank area 14 and the catalytic oil slurry raw material 18 (proportion of 42 wt.% or less) to enter the coking unit reaction system 20 through the delayed coking reaction system inlet 19 to obtain low sulfur petroleum coke 21.

[0074] The delayed coking unit switches from producing high-sulfur petroleum coke 22 to low-sulfur petroleum coke 21. The switching production process is adjusted in a step-by-step manner under the premise of maintaining stable production of the unit. That is, under the premise of maintaining the feed rate of the unit unchanged, the vacuum residue is reduced until it is completely stopped, and the catalytic oil slurry feedstock 18 and high carbon residue value hydrogenated residue are correspondingly increased to meet the production requirements of low-sulfur petroleum coke 21. The main properties of the raw materials of the delayed coking unit are shown in Table 2. The changes in the properties of the raw materials when switching from high-sulfur petroleum coke 22 to low-sulfur petroleum coke 21 are shown in Table 3.

[0075] Based on the raw material inventory of the residue hydrotreating unit and delayed coking unit, the switching of different crude oil processing plans was evaluated. In the process of switching to the production of high- and low-carbon value hydrotreated residue oil and switching to the production of high- and low-sulfur petroleum coke products, the raw material inventory of mixed heavy oil, vacuum residue oil, high-carbon value hydrotreated residue oil, low-carbon value hydrotreated residue oil and catalytic oil slurry was always sufficient to meet the normal production of the catalytic cracking unit, residue hydrotreating unit and delayed coking unit. The heavy oil inventory balance is shown in Table 4.

[0076] Table 1 Changes in properties of residue oil hydroprocessing feedstock adjustment

[0077]

[0078] Table 2 Main properties of delayed coking unit raw materials

[0079]

[0080] Table 3 Changes in raw material ratios and sulfur content of petroleum coke in delayed coking units

[0081]

[0082] Table 4 Heavy oil inventory balance

[0083]

[0084] Comparative Example

[0085] The overall production process of this comparative example is basically consistent with the overall production process in the implementation, and the focus is on explaining the impact of changes in a certain link on the entire process.

[0086] Step 1

[0087] S1.1, the atmospheric and vacuum unit processes low-quality crude oil with high sulfur and low metal content, and the residue oil hydrogenation unit increases the proportion of vacuum residue oil A in the feedstock to below 30 wt.%, and correspondingly reduces the proportion of mixed heavy oil to above 70 wt.%. The two feedstocks enter the residue oil hydrogenation reaction system 10, and the obtained low-carbon hydrogenated residue oil (carbon value below 4.0 wt.%) enters the low-carbon hydrogenated residue oil tank area 13 as the feedstock for the heavy oil catalytic cracking unit.

[0088] Step 2

[0089] S2.1. During this process, the proportion of vacuum residue A in the residue hydrotreating unit decreases, causing the inventory of vacuum residue A to remain in an increasing state until the inventory reaches the upper limit of the storage tank capacity. The atmospheric and vacuum distillation unit switches to processing low-quality crude oil with high sulfur and high metal content. At this time, the residue hydrotreating unit needs to switch to producing high-carbon value hydrogenated residue. Vacuum residue B still needs to be sent to the residue hydrotreating unit for processing. The residue hydrotreating unit maintains the ratio of vacuum residue B to mixed heavy oil feedstock unchanged. The properties of the produced hydrogenated residue are shown in Table 5 below.

[0090] Step 3

[0091] S3.1, the hydrogenated residue oil produced by the above-mentioned S2.1 residue oil hydrogenation unit is used as the feedstock of the delayed coking unit. While the delayed coking unit maintains the ratio of raw material for producing low-sulfur petroleum coke, the hydrogenated residue oil feedstock (ratio of 58 wt.% or more) and the catalytic oil slurry feedstock 18 (ratio of 42 wt.% or less) enter the coking unit reaction system 20 through the delayed coking reaction system inlet 19. The main properties of the delayed coking unit raw materials are shown in Table 6, and the properties of the obtained petroleum coke product are shown in Table 7.

[0092] The delayed coking unit uses S2.1 hydrotreated residue as raw material to produce petroleum coke. This part of hydrotreated residue was originally processed as raw material for the heavy oil catalytic cracking unit. During this stage, the inventory of hydrotreated residue raw material of the heavy oil catalytic cracking unit continued to decline until it reached a relatively low level. In order to maintain the normal production of the heavy oil catalytic cracking unit, the residue hydrogenation unit needs to always maintain the production of hydrotreated residue raw material required for heavy oil catalytic cracking and cannot switch to producing hydrotreated residue with a high residual carbon value, otherwise the heavy oil catalytic cracking unit will not be able to produce normally.

[0093] Table 5 Changes in properties of residue oil hydroprocessing feedstock adjustment

[0094]

[0095] Table 6 Main properties of delayed coking unit raw materials

[0096]

[0097] Table 7 Changes in raw material ratios and sulfur content in petroleum coke in delayed coking units

[0098]

[0099] Table 8 Balance of heavy oil system before and after the delayed coking unit produces low sulfur coke

[0100]

[0101] The above examples and comparative examples demonstrate that the residue hydroprocessing unit in the examples switches to producing high-carbon-value hydroprocessed residue (carbon value 5.89 wt.% or higher) based on its vacuum residue feedstock inventory and properties, while the low-carbon-value hydroprocessed residue feedstock inventory also meets the needs of the heavy oil catalytic cracking unit for normal production. The delayed coking unit produces low-sulfur petroleum coke (sulfur content 1.4 wt.%) using high-carbon-value hydroprocessed residue as its primary feedstock. Before and after the delayed coking unit switches to producing low-sulfur petroleum coke, the atmospheric and vacuum units switch to processing low-quality crude oils of different properties based on the vacuum residue feedstock inventory. During this process, the inventory of hydroprocessed residue, vacuum residue, and other feedstocks can meet the needs of the residue hydroprocessing unit, delayed coking, and heavy oil catalytic cracking units for normal production.

[0102] In a comparative example, the residue hydroprocessing unit reduced the proportion of vacuum residue A to produce a low-carbon residue (carbon residue value below 4.0%). Vacuum residue B, produced by processing low-quality crude oil with high sulfur and metal content in the atmospheric and vacuum units, was then processed in the residue hydroprocessing unit. The resulting hydrogenated residue had a maximum carbon residue value of 3.98 wt.%, with a nickel and vanadium content of 12.3 wt.%. The hydrogenated residue produced in this stage was then processed in a delayed coking unit, resulting in a petroleum coke product with a sulfur content of 2.06 wt.%, which did not meet the standard for low-sulfur petroleum coke and, therefore, could not be produced.

[0103] In the comparative example, since the residue oil hydrotreating unit cannot produce high-carbon-value hydrotreating residue oil, the inventory of high-carbon-value hydrotreating residue oil has always remained at zero inventory, while the inventory of vacuum residue oil A has continued to increase. The balance of the entire heavy oil system cannot be maintained at a normal state, prompting the atmospheric and vacuum unit, the residue oil hydrotreating unit, and the delayed coking unit to continue to maintain the original production plan, and it is impossible to flexibly switch to produce high-sulfur and low-sulfur petroleum coke products.

Claims

1. A method for producing both low-sulfur coke and high-sulfur coke, characterized in that: The following steps are involved: S1, inferior crude oil processing and heavy oil balance: The atmospheric and vacuum unit obtains information on inferior crude oil of different properties and outputs vacuum residue of corresponding properties; S2, the residue hydrotreating unit switches to produce high- and low-carbon residue hydrotreating residues: The residue hydrotreating unit processes vacuum residues of different properties, outputs hydrotreating residues of corresponding properties, and simultaneously feeds back vacuum residue raw material inventory data of different properties, including: Based on the inventory status of vacuum residue A raw material in the residue hydrotreating unit, the properties of vacuum residue A raw material, and the unit's processing plan, the residue hydrotreating unit utilizes the existing process flow to switch between producing high- and low-carbon-residue-value hydrotreating residues. During the process of switching between producing high- and low-carbon-residue-value hydrotreating residues, the residue hydrotreating unit switches to producing high-carbon-residue-value hydrotreating residues by adjusting the raw materials, lowering the reactor bed temperature, increasing the circulating hydrogen flow rate, and reducing the fresh hydrogen flow rate, while maintaining the same processing volume and mixed heavy oil ratio. The high-carbon-residue-value hydrotreating residue enters the high-carbon-residue-value hydrotreating residue tank area and serves as a feedstock for producing low-sulfur petroleum coke in the coking unit. Evaluate the carbon residue value of vacuum residue A raw material. When the carbon residue value of vacuum residue A raw material is low and the inventory of low carbon residue hydroresidue raw material is low, the residue hydrotreating unit will produce low carbon residue hydroresidue in this stage. When the carbon residue value of vacuum residue A raw material is high and the inventory of high carbon residue hydroresidue raw material is low, the residue hydrotreating unit will produce high carbon residue hydroresidue in this stage. S3, delayed coking unit switches to produce high and low sulfur petroleum coke products, including: S3.1 Assess the inventory status of high carbon residue hydroprocessing residue and vacuum residue raw materials; S3.2, when the delayed coking unit is in accordance with the production plan and the vacuum residue B feedstock is in a high inventory state, a ratio of 78.0 wt.% vacuum residue B and 22.0 wt.% catalytic slurry feedstock is introduced into the coking unit reaction system through the delayed coking reaction system inlet to produce high-sulfur petroleum coke; S3.3, the delayed coking unit uses high carbon value hydroresidue oil as the main raw material for producing low-sulfur petroleum coke. When the high carbon value hydroresidue oil raw material is in a high inventory state, the delayed coking unit uses high carbon value hydroresidue oil raw material of more than 58.0wt.% from the high carbon value hydroresidue oil tank area and catalytic oil slurry raw material of less than 42.0wt.% to enter the coking unit reaction system through the inlet of the delayed coking reaction system to obtain low-sulfur petroleum coke.

2. The method according to claim 1, characterized in that In step S2: Increase the proportion of vacuum residue A in the feedstock of the residue hydrotreating unit to above 39.0 wt.%, and correspondingly reduce the proportion of mixed heavy oil to below 61.0 wt.%. The two feedstocks enter the residue hydrotreating reaction system, and then control the reactor catalyst bed temperature at 360-375 ° C, and the circulating hydrogen flow rate at 240,000-250,000 Nm 3 / h, the flow rate of new hydrogen is controlled at 44000-48000Nm 3 / h, and obtain high carbon residue value hydrogenated residue oil with carbon residue value of more than 5.0 wt.%.

3. The method according to claim 1, characterized in that Step S1 includes: The atmospheric and vacuum unit processes low-quality crude oil with high sulfur and high metal content. When the vacuum residue B produced is stored in the raw material tank of the delayed coking unit until the storage tank is full of vacuum residue, the atmospheric and vacuum unit switches to processing low-quality crude oil with high sulfur and low metal content. When the vacuum residue A produced is stored in the raw material tank of the residue oil hydrogenation unit until the storage tank is full of vacuum residue, the atmospheric and vacuum unit switches again to processing low-quality heavy oil with high sulfur and high metal content.

4. The method according to claim 3, characterized in that Step S1 includes: The mixed heavy oil produced during the processing of low-quality crude oil in the atmospheric and vacuum units is always used as part of the residue hydroprocessing feed.

5. The method according to claim 4, characterized in that Step S1 specifically includes: (1) According to the specific processing volume or processing plan of the delayed coking unit and the residue oil hydrotreating unit, if the vacuum residue oil B raw material of the delayed coking unit is used up to a low inventory state, it is necessary to switch the atmospheric vacuum process to process high sulfur, high metal content inferior crude oil; if the vacuum residue oil A raw material of the residue oil hydrotreating unit is used up to a low inventory state, it is necessary to switch the atmospheric vacuum process to process high sulfur, low metal content inferior crude oil; (2) The choice of low-quality crude oil to be processed by the atmospheric and vacuum units needs to be based on the existing crude oil varieties, the inventory of vacuum residue raw materials in the residue hydrotreating and delayed coking units, and the processing plans of the two units.

6. The method according to claim 1, wherein: The residual carbon value of the vacuum residue oil A raw material is evaluated using the GB / T 17144-2021 analysis method.

7. The method according to claim 1, characterized in that In step S3: By controlling the ratio of high carbon residue value hydrogenated residue oil and catalytic oil slurry raw materials in the delayed coking unit, the production time and output of low-sulfur coke in the delayed coking unit can be extended.

8. The method according to any one of claims 1 to 7, characterized in that: It contains at least two kinds of inferior crude oil with different properties, two kinds of vacuum residue oil tanks with different properties, and two kinds of desulfurized residue oil tanks with different properties. The system is connected between devices and between devices and tank areas. The switching production plan of the devices is a continuous production process.

9. The method according to any one of claims 1 to 7, characterized in that In step S2: Evaluate the residual carbon value of the vacuum residue A raw material. When the residual carbon value of the vacuum residue A raw material is low and the inventory of low-carbon-value hydroresidue raw material is in a low inventory state, the residue hydrotreating unit will produce low-carbon-value hydroresidue at this stage; when the residual carbon value of the vacuum residue A raw material is high and the inventory of high-carbon-value hydroresidue raw material is in a low inventory state, high-carbon-value hydroresidue will be produced at this stage.

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