CN117070249A - Method and system for producing low-sulfur petroleum coke at low cost - Google Patents

Abstract

A low-cost method and system for producing low-sulfur petroleum coke, involving delayed coking in the field of petroleum refining to produce petroleum coke. This method divides the residual oil raw material into two parts, one part is hydrodesulfurized to obtain a heavy fraction, and the other part is deasphalted using a solvent Process treatment to obtain deoiled asphalt, and finally mix the deoiled asphalt and heavy fractions for delayed coking to produce low-sulfur petroleum coke. By optimizing the process route, the present invention combines the conventional hydrodesulfurization process with the solvent deasphalting process, thereby greatly increasing the amount of residual carbon in the raw materials entering the delayed coking unit without significantly increasing the sulfur content, thus effectively reducing the The sulfur content in the product petroleum coke significantly reduces the energy consumption of the entire process, and the vacuum residue used has a low raw material cost due to its high sulfur content, ultimately significantly reducing the production cost of low-sulfur petroleum coke. .

Description

A low-cost method and system for producing low-sulfur petroleum coke

Technical field

The present invention relates to delayed coking to produce petroleum coke in the field of petroleum refining, specifically a low-cost method and system for producing low-sulfur petroleum coke.

Background technique

Petroleum coke is the main product of the delayed coking unit, and the yield of petroleum coke is generally 25% to 30%. According to the different sulfur content of petroleum coke, it can be divided into high-sulfur coke (sulfur content above 3%) and low-sulfur coke (sulfur content below 3%). Low-sulfur coke can be used as electrode coke or metallurgical coke; while high-sulfur coke is generally used as fuel.

In recent years, the demand for low-sulfur petroleum coke has been increasing. However, petcoke products generally have high sulfur content. The high sulfur content in petroleum coke will not only limit its utilization methods, but also reduce its utilization value. The use of high-sulfur petroleum coke will also cause many problems, such as producing a large amount of sulfur-containing gases (such as sulfur dioxide), causing environmental pollution; causing corrosion of equipment, and increasing production costs of enterprises. Therefore, how to obtain low-sulfur petroleum coke is an urgent problem that relevant companies currently need to solve.

Currently, in order to obtain low-sulfur petroleum coke, one is to carry out subsequent desulfurization treatment on the existing high-sulfur petroleum coke, and the other is to control it from the source and pre-process the raw materials of the coking unit to reduce its sulfur content. The representative technology is hydrodesulfurization, which generally includes ebullating bed, fixed bed and suspended bed hydrodesulfurization technologies.

Among them, suspended bed hydrogenation has high unconverted oil ash content and is not suitable for coking process; fixed bed residual oil hydrogenation generally provides feed for catalytic cracking and produces more gasoline to maximize benefits. Fixed bed residual oil hydrogenation is delayed When coking is combined, there is a conflict between coking and catalytic cracking competing for raw materials;

The sulfur content and metal content in the unconverted oil after ebullating bed hydrotreating are reduced, but they are still higher than conventional raw materials; although considering its sulfur content, residual carbon content, and metal content, it is suitable to be processed by the delayed coking process. However, the ebullating bed hydrogenation process has high pressure and high energy consumption. Through deep hydrogenation to reduce the sulfur content of the residual oil and produce low-sulfur petroleum coke, the production cost remains high.

Contents of the invention

In order to solve the problems of high cost and large energy consumption in the production of low-sulfur petroleum coke by the existing ebullating bed hydrogenation process, the present invention provides a low-cost method and system for producing low-sulfur petroleum coke by combining ebullating bed hydrogenation with a solvent. The organic combination of deasphalting process greatly reduces the energy consumption and production cost of the entire system.

The technical solution adopted by the present invention to solve the above technical problems is: a low-cost method for producing low-sulfur petroleum coke, which includes the following steps:

1) Divide the residual oil raw material into two parts, A and B, hydrodesulfurize part A, and use 450 to 600°C as the cutting point to fractionate the heavy fraction with higher residual carbon content and the light fraction with lower residual carbon content;

2) Treat Part B using a solvent deasphalting process to obtain deasphalted oil and deoiled asphalt;

3) Mix the heavy fraction obtained in step 1) with the deoiled asphalt obtained in step 2) and perform delayed coking to obtain low-sulfur petroleum coke.

As another optimization solution for the above-mentioned low-cost low-sulfur petroleum coke production method, the residual oil raw material is vacuum residual oil, and the sulfur content in the vacuum residual oil is 0.5wt%~3wt%, and the residual carbon content is 20wt% ~50wt%.

As another optimization solution for the above-mentioned low-cost production of low-sulfur petroleum coke, the active metals of the catalyst used during hydrodesulfurization in step 1) are cobalt and molybdenum, and the mass content of cobalt oxide is 1% to 1%. 20%, the content of molybdenum oxide is 1% to 30%, and the catalyst carrier is one or more of alumina, silicon oxide, alumina-silica or titanium oxide.

As another optimization solution for the above-mentioned low-cost low-sulfur petroleum coke production method, the shape of the catalyst is an extrudate or spherical shape, the bulk density is 0.4-0.9g/cm ³ , and the extrusion diameter or spherical diameter is 0.08-1.2 mm, the specific surface area is 100~300m ² /g.

As another optimization solution for the above-mentioned low-cost low-sulfur petroleum coke production method, the reaction pressure of hydrodesulfurization in step 1) is 6-30MPa, the reaction temperature is 400-490°C, and the liquid hourly volume space velocity ratio is 0.1 ~5.0h ^-1 , the volume ratio of hydrogen to oil is 200~2000.

As another optimization solution for the above-mentioned low-sulfur petroleum coke production method, the reaction pressure of hydrodesulfurization in step 1) is preferably 15-20MPa, the reaction temperature is preferably 420-470°C, and the liquid hourly volume space velocity is preferably is 0.5 to 2.0 h ^-1 , and the hydrogen to oil volume ratio is preferably 400 to 1000.

As another optimization solution for the above-mentioned low-cost production of low-sulfur petroleum coke, the solvent used in the solvent deasphalting process in step 2) is propane, butane or pentane, the pressure is 3.0~5.0MPa, and the temperature is 120~190 ℃, solvent ratio is 4.0~6.0.

As another optimization solution for the above-mentioned low-cost production of low-sulfur petroleum coke, in step 3), the heavy fraction accounts for 75-85% of the total mass after mixing.

As another optimization solution for the above-mentioned low-cost method for producing low-sulfur petroleum coke, the temperature of delayed coking in step 3) is 450-550°C and the pressure is 150-240kPa.

As another optimization solution for the above-mentioned low-cost method for producing low-sulfur petroleum coke, the temperature of delayed coking in step 3) is preferably 490°C, and the pressure is preferably 170-180 kPa.

A low-cost production system for low-sulfur petroleum coke, including a raw material pipeline, an ebullating bed hydrogenation device, a solvent deasphalting device and a delayed coking device. The raw material pipeline delivers residual oil raw materials through a first branch pipeline and a second branch pipeline respectively. It enters the ebullating bed hydrogenation unit and the solvent deasphalting unit. The heavy oil generated by the ebullating bed hydrogenation unit is sent to the fractionation tower for cutting and fractionation through the heavy oil pipeline. The generated light fraction is discharged through the light fraction pipeline, and the heavy fraction enters the converging line. ; The deasphalted oil produced by the solvent deasphalting device is discharged through the oil and gas pipeline, and the deoiled asphalt produced is also sent to the converging line through the asphalt pipeline, and is mixed with the heavy fraction in the converging line and then sent to the delayed coking device .

The mechanism of the present invention is: based on the coking reaction mechanism and the law of sulfur transfer, it is found through experimental research that for raw materials generated by the same processing technology, the amount of sulfur in the raw materials entering the petroleum coke is roughly equivalent during the delayed coking process. Therefore, for raw materials with the same sulfur content, increasing the yield of petroleum coke can reduce the sulfur content in petroleum coke.

Through research, it was found that the petroleum coke yield is mainly affected by the residual carbon content of the raw material. The higher the residual carbon content, the higher the petroleum coke yield. Therefore, to obtain higher petcoke yields, feedstocks with high residual carbon content can be processed;

According to the coking reaction mechanism, when the sulfur content of the coking raw material is constant, increasing the residual carbon content of the raw material can reduce the sulfur content of petroleum coke.

In addition, due to the characteristics of deoiled asphalt (poor fluidity and easy coking), it cannot be used as a raw material for a delayed coking device alone. It must be mixed with easily flowing heavy oil several times its own weight before it can be used as a raw material for a delayed coking device.

By optimizing the process route, the present invention uses the solvent deasphalting process to achieve a higher carbon removal rate and a lower desulfurization rate, so that the residual carbon is enriched in the deoiled asphalt, while sulfur is not enriched or is enriched in a small amount, and then the residual carbon is enriched in a small amount. Mixing it with hydrodesulfurized heavy oil as coking raw material can increase the residual carbon value of the raw material without significantly increasing the sulfur content of the raw material, ultimately effectively reducing the sulfur content in petroleum coke.

Compared with the prior art, the present invention has the following beneficial effects:

By optimizing the process route, the present invention combines the conventional hydrodesulfurization process with the solvent deasphalting process, thereby greatly increasing the amount of residual carbon in the raw materials entering the delayed coking unit without significantly increasing the sulfur content, thus effectively reducing The sulfur content in the product petroleum coke significantly reduces the energy consumption of the entire process. Moreover, the vacuum residue used has a high sulfur content and its raw material cost is also very low. This ultimately significantly reduces the production cost of low-sulfur petroleum coke. .

Description of the drawings

Figure 1 is a schematic diagram of the system structure of the present invention;

Figure 2 is a system structure diagram of Comparative Example 1;

Figure 3 is a system structure diagram of Comparative Example 2;

Reference signs: 1. Raw material pipeline, 101. First branch pipeline, 102. Second branch pipeline, 2. Ebullating bed hydrogenation unit, 201. Heavy oil pipeline, 3. Solvent deasphalting unit, 301. Oil and gas pipeline, 302. Asphalt pipeline, 4. Delayed coking unit, 401. Convergence line, 5. Fractionation tower, 501. Light fraction pipeline.

Detailed ways

The technical solutions of the present invention will be further described in detail below with reference to specific embodiments. The parts that are not explained in the following embodiments of the present invention should be understood as technologies that are known or should be known to those skilled in the art, such as ebullating bed heating. Structure of hydrogen unit, solvent deasphalting unit, delayed coking unit, fractionation tower, etc.

Example 1

A low-cost method for producing low-sulfur petroleum coke, as shown in Figure 1, includes the following steps:

1) Divide the residual oil raw material into two parts, A and B, hydrodesulfurize part A, and use 450°C as the cutting point to fractionate the heavy fraction with higher residual carbon content and the light fraction with lower residual carbon content;

The residual oil raw material is vacuum residual oil, and the sulfur content in the vacuum residual oil is 3wt%, and the residual carbon content is 25wt%;

The active metals of the catalyst used in the hydrodesulfurization are cobalt and molybdenum, and the mass content of cobalt oxide is 1%, the content of molybdenum oxide is 30%, and the carrier of the catalyst is alumina;

The shape of the catalyst is an extrudate, with a bulk density of 0.4g/cm ³ , an extrusion diameter of 0.08mm, and a specific surface area of 100m ² /g;

The reaction pressure of the hydrodesulfurization is 6MPa, the reaction temperature is 400°C, the liquid-hour volume space velocity ratio is 0.1h ^-1 , and the hydrogen-to-oil volume ratio is 200;

2) Treat Part B using a solvent deasphalting process to obtain deasphalted oil and deoiled asphalt;

The solvent used in the solvent deasphalting process is propane, the pressure is 3.0MPa, the temperature is 120°C, and the solvent ratio is 4.0;

3) Mix the heavy fraction obtained in step 1) with the deoiled asphalt obtained in step 2) and perform delayed coking to obtain low-sulfur petroleum coke;

The heavy fraction accounts for 75% of the total mass after mixing; the temperature of delayed coking is 450°C and the pressure is 150kPa.

After testing, the sulfur content in the final product petroleum coke is 2.7wt%. When processing 1 ton of raw material (relative to the delayed coking device, that is, the delayed coking device processes 1 ton of raw material), the data in the following examples and comparative examples are all used. standard), the total amount of petroleum coke produced is 529kg, the hydrogen consumption of the whole process is 90kg, and the energy consumption is 131kg of standard oil.

The above is the basic implementation mode of the present invention. Further improvements, optimizations and limitations can be made on the above basis, thereby obtaining the following embodiments:

Example 2

A low-cost method for producing low-sulfur petroleum coke, as shown in Figure 1, includes the following steps:

1) Divide the residual oil raw material into two parts, A and B, hydrodesulfurize part A, and use 500°C as the cutting point to fractionate the heavy fraction with higher residual carbon content and the light fraction with lower residual carbon content;

The residual oil raw material is vacuum residual oil, and the sulfur content in the vacuum residual oil is 3wt%, and the residual carbon content is 25wt%;

The active metals of the catalyst used in the hydrodesulfurization are cobalt and molybdenum, and the mass content of cobalt oxide is 5%, the content of molybdenum oxide is 25%, and the carrier of the catalyst is silicon oxide;

The shape of the catalyst is spherical, with a bulk density of 0.5g/cm ³ , a spherical diameter of 0.2mm, and a specific surface area of 150m ² /g;

The reaction pressure of the hydrodesulfurization is 15MPa, the reaction temperature is 420°C, the liquid-hour volume space velocity ratio is 0.5h ^-1 , and the hydrogen-to-oil volume ratio is 400;

2) Treat Part B using a solvent deasphalting process to obtain deasphalted oil and deoiled asphalt;

The solvent used in the solvent deasphalting process is butane, the pressure is 3.5MPa, the temperature is 140°C, and the solvent ratio is 4.5;

3) Mix the heavy fraction obtained in step 1) with the deoiled asphalt obtained in step 2) and perform delayed coking to obtain low-sulfur petroleum coke;

The heavy fraction accounts for 80% of the total mass after mixing; the temperature of delayed coking is 460°C and the pressure is 170kPa.

After testing, the sulfur content in the final product petroleum coke is 2.8wt%. After processing 1t of raw material, the total amount of petroleum coke produced is 484kg, the hydrogen consumption is 96kg, and the energy consumption is 133kg standard oil.

Example 3

A low-cost method for producing low-sulfur petroleum coke, as shown in Figure 1, includes the following steps:

1) Divide the residual oil raw material into two parts, A and B, hydrodesulfurize part A, and use 520°C as the cutting point to fractionate the heavy fraction with higher residual carbon content and the light fraction with lower residual carbon content;

The residual oil raw material is vacuum residual oil, and the sulfur content in the vacuum residual oil is 3wt%, and the residual carbon content is 25wt%;

The active metals of the catalyst used in the hydrodesulfurization are cobalt and molybdenum, and the mass content of cobalt oxide is 10%, the content of molybdenum oxide is 20%, and the carrier of the catalyst is titanium oxide;

The shape of the catalyst is spherical, with a bulk density of 0.6g/cm ³ , a spherical diameter of 0.6mm, and a specific surface area of 200m ² /g;

The reaction pressure of the hydrodesulfurization is 20MPa, the reaction temperature is 450°C, the liquid hourly volume space velocity ratio is 1.0h ^-1 , and the hydrogen to oil volume ratio is 700;

2) Treat Part B using a solvent deasphalting process to obtain deasphalted oil and deoiled asphalt;

The solvent used in the solvent deasphalting process is pentane, the pressure is 4.0MPa, the temperature is 160°C, and the solvent ratio is 5.0;

3) Mix the heavy fraction obtained in step 1) with the deoiled asphalt obtained in step 2) and perform delayed coking to obtain low-sulfur petroleum coke;

The heavy fraction accounts for 80% of the total mass after mixing; the temperature of delayed coking is 490°C and the pressure is 180kPa.

After testing, the sulfur content in the final product petroleum coke is 2.9wt%. When 1 ton of raw material is processed, the total amount of petroleum coke produced is 491kg, the hydrogen consumption of the whole process is 107kg, and the energy consumption is 143kg of standard oil.

Example 4

A low-cost method for producing low-sulfur petroleum coke, as shown in Figure 1, includes the following steps:

1) Divide the residual oil raw material into two parts, A and B, hydrodesulfurize part A, and use 550°C as the cutting point to fractionate the heavy fraction with higher residual carbon content and the light fraction with lower residual carbon content;

The residual oil raw material is vacuum residual oil, and the sulfur content in the vacuum residual oil is 3wt%, and the residual carbon content is 25wt%;

The active metals of the catalyst used in the hydrodesulfurization are cobalt and molybdenum, and the mass content of cobalt oxide is 15%, and the content of molybdenum oxide is 10%, and the carrier of the catalyst is alumina-silica;

The shape of the catalyst is an extrudate, with a bulk density of 0.7g/cm ³ , an extrusion diameter of 0.8mm, and a specific surface area of 250m ² /g;

The reaction pressure of the hydrodesulfurization is 25MPa, the reaction temperature is 470°C, the liquid hourly volume space velocity ratio is 2.0h ^-1 , and the hydrogen to oil volume ratio is 1000;

2) Treat Part B using a solvent deasphalting process to obtain deasphalted oil and deoiled asphalt;

The solvent used in the solvent deasphalting process is butane, the pressure is 4.5MPa, the temperature is 170°C, and the solvent ratio is 5.5;

3) Mix the heavy fraction obtained in step 1) with the deoiled asphalt obtained in step 2) and perform delayed coking to obtain low-sulfur petroleum coke;

The heavy fraction accounts for 80% of the total mass after mixing; the temperature of delayed coking is 520°C and the pressure is 200kPa.

After testing, the sulfur content in the final product petroleum coke is 2.9wt%. When 1 ton of raw material is processed, the total amount of petroleum coke produced is 495kg, the hydrogen consumption of the whole process is 121kg, and the energy consumption is 156kg standard oil.

Example 5

A low-cost method for producing low-sulfur petroleum coke, as shown in Figure 1, includes the following steps:

1) Divide the residual oil raw material into two parts, A and B, hydrodesulfurize part A, and use 600°C as the cutting point to fractionate the heavy fraction with higher residual carbon content and the light fraction with lower residual carbon content;

The residual oil raw material is vacuum residual oil, and the sulfur content in the vacuum residual oil is 3wt%, and the residual carbon content is 25wt%;

The active metals of the catalyst used in the hydrodesulfurization are cobalt and molybdenum, and the mass content of cobalt oxide is 20%, the content of molybdenum oxide is 1%, and the carrier of the catalyst is alumina;

The shape of the catalyst is spherical, with a bulk density of 0.9g/cm ³ , a spherical diameter of 1.2mm, and a specific surface area of 300m ² /g;

The reaction pressure of the hydrodesulfurization is 30MPa, the reaction temperature is 490°C, the liquid-hour volume space velocity ratio is 5.0h ^-1 , and the hydrogen-to-oil volume ratio is 2000;

2) Treat Part B using a solvent deasphalting process to obtain deasphalted oil and deoiled asphalt;

The solvent used in the solvent deasphalting process is propane, the pressure is 5.0MPa, the temperature is 190°C, and the solvent ratio is 6.0;

3) Mix the heavy fraction obtained in step 1) with the deoiled asphalt obtained in step 2) and perform delayed coking to obtain low-sulfur petroleum coke;

The heavy fraction accounts for 85% of the total mass after mixing; the temperature of delayed coking is 550°C and the pressure is 240kPa.

After testing, the sulfur content in the final product petroleum coke is 3.0wt%. When 1 ton of raw material is processed, the total amount of petroleum coke produced is 501kg, the hydrogen consumption of the whole process is 145kg, and the energy consumption is 180kg standard oil.

Example 6

A low-cost low-sulfur petroleum coke production system, as shown in Figure 1, includes a raw material pipeline 1, an ebullating bed hydrogenation device 2, a solvent deasphalting device 3 and a delayed coking device 4. The raw material pipeline 1 passes through the first branch respectively. The pipeline 101 and the second branch pipeline 102 send the residual oil raw material to the ebullating bed hydrogenation unit 2 and the solvent deasphalting unit 3. The heavy oil generated by the ebullating bed hydrogenation unit 2 is sent to the fractionation tower 5 for cutting and fractionation through the heavy oil pipeline 201. , the light fraction produced is discharged through the light fraction pipeline 501, and the heavy fraction enters the converging line 401; the deasphalted oil produced by the solvent deasphalting device 3 is discharged through the oil and gas pipeline 301, and the produced deoiled asphalt is also sent through the asphalt pipeline 302 into the converging line 401, mixed with the heavy fraction in the converging line 401, and then sent to the delayed coking device 4.

It should be noted that the above embodiments are only used to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: it still The technical solutions described in the foregoing embodiments can be modified, or some or all of the technical features can be equivalently replaced; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to depart from the scope of the technical solutions of the embodiments of the present invention. .

In order to verify the advantages of the present invention and the existing technology, the following comparative experiments were conducted:

Experimental example 1

As shown in Figure 1, the process flow of this experimental example is described in detail as follows: the vacuum residue raw material is divided into two parts, and one part is pressurized and mixed with hydrogen and enters the ebullating bed hydrogenation reactor 2. By contacting with the hydrogenation catalyst, the decompression residue is separated into two parts. Remove some metals, sulfur, nitrogen and other impurities in the residual oil, while reducing the carbon residue value of the raw material, and try to meet the feed requirements of the downstream catalytic cracking and delayed coking unit 4; the heavy oil generated at the outlet of the ebullating bed hydrogenation reactor 2 enters the fractionation tower 5. Cut into light fractions and heavy fractions; the light fractions go to the downstream catalytic cracking unit;

Another part of the vacuum residue raw material enters the solvent deasphalting device 3 to generate deasphalted oil and deoiled asphalt. The deoiled asphalt is mixed with the heavy fraction and then enters the delayed coking device 4 to produce petroleum coke.

In the experimental example, the composition of the residual oil and the process conditions are the same as those in Example 3. The sulfur content in the final product petroleum coke is 2.9wt%. When 1 ton of raw material is processed, the total amount of petroleum coke produced is 491kg. The entire process Hydrogen consumption is 107kg, and energy consumption is 143kg standard oil.

Comparative example 1

The same residual oil raw material as in Experimental Example 1 is used, and the process flow is shown in Figure 2. The residual oil raw material is pressurized and mixed with hydrogen and enters the ebullating bed hydrogenation reactor 2. The generated heavy oil enters the fractionation tower 5 and is cut into light fractions and The heavy fraction enters the delayed coking unit 4 to produce petroleum coke. The process conditions of the ebullating bed hydrogenation reactor 2, the process conditions of the fractionating tower 5, and the process conditions of the delayed coking device 4 are all the same as Experimental Example 1.

The sulfur content in the final product petroleum coke is 3.2wt%. When 1 ton of raw material is processed, the total amount of petroleum coke produced is 318kg, the hydrogen consumption is 120kg, and the energy consumption is 140kg standard oil.

Comparative example 2

The same residual oil raw material as Experimental Example 1 is used. The process flow is shown in Figure 3. The vacuum residual oil raw material is divided into two parts. A part of the residual oil raw material is passed through the solvent deasphalting device 3 to generate deasphalted oil and deoiled asphalt. The oil asphalt is mixed with another part of the residual oil raw material (the mixing ratio is 20% of the deoiled asphalt and 80% of the residual oil raw material) and enters the ebullating bed hydrogenation reactor 2. The generated heavy oil enters the fractionation tower 5 and is cut into light fractions and heavy fractions. The fraction enters the delayed coking unit 4 to produce petroleum coke. The process conditions of the solvent deasphalting device 3, the process conditions of the ebullating bed hydrogenation reactor 2, the process conditions of the fractionating tower 5, and the process conditions of the delayed coking device 4 are all the same as Experimental Example 1.

The sulfur content in the final product petroleum coke is 2.7wt%. When 1 ton of raw material is processed, the total amount of petroleum coke produced is 477kg, the hydrogen consumption of the whole process is 133kg, and the energy consumption is 170kg standard oil.

It can be seen from the above comparative experimental results that the sulfur content of Experimental Example 1 is 2.8wt%, which meets the standard of low-sulfur petroleum coke. The sulfur content of Comparative Example 1 is 3.2wt%, which does not meet the standard of low-sulfur petroleum coke. Comparative Example 2 The sulfur content is 2.7wt%, which also meets the standard of low-sulfur petroleum coke, and is not much different from the sulfur content of Example 1. However, the hydrogen consumption and energy consumption of Comparative Example 2 are much greater than Experimental Example 1;

To sum up, the solution of the present invention can produce low-sulfur petroleum coke that meets standard requirements with the lowest energy consumption, thereby reducing production costs.

Claims (11)

1. A low-cost method for producing low-sulfur petroleum coke, which is characterized by including the following steps: 1) Divide the residual oil raw material into two parts, A and B, hydrodesulfurize part A, and use 450 to 600°C as the cutting point to fractionate the heavy fraction with higher residual carbon content and the light fraction with lower residual carbon content; 2) Treat Part B using a solvent deasphalting process to obtain deasphalted oil and deoiled asphalt; 3) Mix the heavy fraction obtained in step 1) with the deoiled asphalt obtained in step 2) and perform delayed coking to obtain low-sulfur petroleum coke. 2. A low-cost method for producing low-sulfur petroleum coke according to claim 1, characterized in that: the residual oil raw material is vacuum residual oil, and the sulfur content in the vacuum residual oil is 0.5wt%~3wt%. , the residual carbon content is 20wt% ~ 50wt%. 3. A low-cost method for producing low-sulfur petroleum coke according to claim 1, characterized in that: the active metals of the catalyst used during hydrodesulfurization in step 1) are cobalt and molybdenum, and the oxide of cobalt is The mass content of molybdenum oxide is 1% to 20%, the content of molybdenum oxide is 1% to 30%, and the catalyst carrier is one or more of alumina, silicon oxide, alumina-silica or titanium oxide. 4. A low-cost method for producing low-sulfur petroleum coke according to claim 3, characterized in that: the shape of the catalyst is extrudate or spherical, the bulk density is 0.4-0.9g/cm ³ , and the extrusion diameter is Or the spherical diameter is 0.08~1.2mm, and the specific surface area is 100~300m ² /g. 5. A low-cost method for producing low-sulfur petroleum coke according to claim 1, characterized in that: the reaction pressure of hydrodesulfurization in step 1) is 6-30MPa, the reaction temperature is 400-490°C, and the liquid The hourly volume airspeed ratio is 0.1~5.0h ^-1 , and the hydrogen-oil volume ratio is 200~2000. 6. A low-cost method for producing low-sulfur petroleum coke according to claim 5, characterized in that: the reaction pressure of hydrodesulfurization in step 1) is 15-20MPa, the reaction temperature is 420-470°C, and the liquid The hourly volume space speed is 0.5~2.0h ^-1 , and the hydrogen-to-oil volume ratio is 400~1000. 7. A low-cost method for producing low-sulfur petroleum coke according to claim 1, characterized in that: the solvent used in the solvent deasphalting process in step 2) is propane, butane or pentane, and the pressure is 3.0 to 5.0 MPa, the temperature is 120~190℃, and the solvent ratio is 4.0~6.0. 8. A low-cost method for producing low-sulfur petroleum coke according to claim 1, characterized in that in step 3), the heavy fraction accounts for 75-85% of the total mass after mixing. 9. A low-cost method for producing low-sulfur petroleum coke according to claim 1, characterized in that the temperature of delayed coking in step 3) is 450-550°C and the pressure is 150-240kPa. 10. A low-cost method for producing low-sulfur petroleum coke according to claim 1, characterized in that the temperature of delayed coking in step 3) is 490°C and the pressure is 170-180kPa. 11. A low-cost low-sulfur petroleum coke production system, including a raw material pipeline (1), an ebullating bed hydrogenation device (2), a solvent deasphalting device (3) and a delayed coking device (4), characterized by: The raw material pipeline (1) sends the residual oil raw material to the ebullating bed hydrogenation unit (2) and the solvent deasphalting unit (3) through the first branch pipeline (101) and the second branch pipeline (102) respectively. The heavy oil generated by the hydrogen device (2) is sent to the fractionation tower (5) for cutting and fractionation through the heavy oil pipeline (201), the light fraction produced is discharged through the light fraction pipeline (501), and the heavy fraction enters the converging line (401); The deasphalted oil produced by the solvent deasphalting device (3) is discharged through the oil and gas pipeline (301), and the produced deoiled asphalt is also sent to the converging line (401) through the asphalt pipeline (302), and is connected with the converging line (401) The heavy fractions in the mixture are mixed and sent to the delayed coking device (4).