Inferior oil hydrotreating method

Abstract

The invention relates to the technical field of light diesel oil production, in particular to an inferior oil hydrotreating method which comprises the following steps: mixing inferior oil with a hydrocracking reaction product, hydrofining, performing steam stripping desulfurization, and performing fractionation treatment to obtain light diesel oil, light cycle oil and heavy cycle oil; the hydrocracking reaction product is obtained by carrying out hydrocracking reaction on cycle oil formed by light cycle oil and heavy cycle oil, and during hydrorefining, the void ratio of a hydrorefining catalyst in a reaction system is 50-80%. According to the invention, the large-void catalyst is used as the catalyst for refining, so that the adaptability of the reaction system to the inferior oil raw material can be improved, the yield of the product can be greatly improved, and the content of impurities in the product is further reduced.

Description

Technical Field

[0001] The invention relates to the technical field of light diesel production, and in particular to a method for hydrogenating low-quality oil. Background Art

[0002] Against the backdrop of increasingly stringent global environmental protection requirements and growing pressure to reduce carbon emissions, the limitations of traditional fossil fuels are becoming increasingly prominent. At the same time, the gradual depletion of easily exploitable resources is prompting the oil and fuel industry to accelerate its transformation towards high-quality, low-carbon, and environmentally friendly products, and to actively explore the diversification of renewable raw materials. However, this diversification of raw materials also brings new challenges. Compared with traditional petroleum-based raw materials, emerging renewable and waste-derived raw materials such as waste grease, waste cooking oil, sewage oil, rancid oil, bio-asphalt, waste plastic oil, waste tire oil, waste lubricating oil, wood tar, coal tar, and heavy oil generally have high oxygen content, high acid value, enriched metal impurities, and excessive nitrogen and sulfur content, placing higher demands on processing technology and catalyst systems.

[0003] At present, when the industry uses traditional hydrotreating and cracking processes to treat the above-mentioned raw materials, low efficiency, easy coking, clogging, catalyst corrosion and contamination leading to loss of activity, and poor product quality are prone to occur. Even if cumbersome raw material pretreatment technologies such as desalination, water washing, pickling, adsorption, and filtration are used, a large amount of energy consumption and waste will be generated. It is still difficult for hydrogenation equipment to completely overcome the influence of impurities and cannot operate stably for a long period of time.

[0004] The prior art discloses a combined hydrorefining method for inferior distillate oil, which comprises hydrorefining a catalytic cracking diesel fraction and hydrorefining a coking distillate oil. The effluents from the hydrorefining and hydrorefining reactions are fed into a separation system together. This method reduces the content of impurities such as sulfur and nitrogen in the product while maintaining a high diesel yield. However, the product yield is low, the resource recovery effect is unsatisfactory, and the metal impurities in the inferior oil cannot be removed, thereby affecting the activity of the catalyst in the system. This not only results in a high impurity content in the final product, but also makes the system unable to operate stably for a long time. Summary of the Invention

[0005] Therefore, the technical problem to be solved by the present invention is to overcome the defect of low recovery rate of inferior oil in the prior art, thereby providing a hydrotreating process for inferior oil.

[0006] Another technical problem to be solved by the present invention is to overcome the defect that the prior art method for treating inferior oil cannot effectively remove impurities, especially metal impurities, in inferior oil, thereby providing a hydrogenation process for inferior oil.

[0007] To this end, on the one hand, the present invention provides a method for hydrotreating low-quality oil, comprising the following steps: mixing the low-quality oil with a hydrocracking reaction product, hydrorefining, stripping and desulfurizing, and fractionating the mixture to obtain light diesel, light cycle oil, and heavy cycle oil; the hydrocracking reaction product is a cycle oil formed by subjecting the light cycle oil and the heavy cycle oil to a hydrocracking reaction, and during the hydrorefining, the porosity of the hydrorefining catalyst in the reaction system is 50-80%.

[0008] The present invention utilizes a large void catalyst to refine low-quality oil. After the organic solid metal brought by the low-quality oil is converted into inorganic metal, it passes through a reactor and enters a fractionating tower together with the oil product. Qualified light products are separated by distillation at the top of the fractionating tower. Unqualified products are separated into two types of light and heavy circulating oils in the fractionating tower. Among them, the heavy circulating oil is filtered and separated by centrifugation to remove solid residual value and asphaltene, and then mixed with the light circulating oil to form circulating oil. After the mixed circulating oil is mixed with hydrogen, it is heated by a heating furnace and enters a cracking reactor. The cracked product is mixed with fresh raw materials, that is, untreated low-quality oil, and then enters a large void ratio hydrorefining reactor for reaction. The process provided by the present invention adopts a large void ratio solid catalyst as a refining catalyst to remove most impurities and solid pollutants. The unqualified circulating oil is further hydrocracking and mixed with the raw materials to enter a crude reaction refining, thereby realizing long-term processing of low-quality oil products such as easy coking, high oxygen content, high metal content, high sulfur and nitrogen content, improving product quality and light oil yield, and extending process service life.

[0009] When traditional hydrorefining and cracking processes process raw materials, it is easy to have low efficiency, easy coking, clogging, catalyst corrosion, catalyst contamination and loss of activity, poor product quality and the like. Even if cumbersome raw material pretreatment technologies such as desalting, washing, pickling, adsorption, and filtration are used, not only a large amount of energy consumption and waste are generated, but the hydrogenation unit is still difficult to completely overcome the influence of impurities and cannot operate stably for a long period of time. The treatment method provided by the present invention effectively combines hydrorefining with circulating oil hydrocracking using a large void catalyst and optimizes the separation process. It can achieve efficient step-by-step utilization of temperature and heat, clean and separate pollutants, and continuously and stably produce clean products in a single system. This process can better solve the problem of processing inferior raw materials faced by traditional hydrogenation processes and catalysts, and achieve long-term operation while obtaining high-quality products.

[0010] In some embodiments, the hydrocracking reaction catalyst includes at least one of a cylindrical, a clover-leaf, and a spherical shape.

[0011] In some embodiments, the hydrotreating catalyst comprises at least one of a gear type, a Raschig ring type, a hollow plum blossom type, or a four-impeller type.

[0012] In some embodiments, the volume ratio of the hydrotreating catalyst to the low-quality oil is 2-5:1.

[0013] In some embodiments, the hydrotreating catalyst in the reaction system includes at least three shapes, which are arranged in the reaction system from top to bottom, and the porosity of the hydrotreating catalyst in the reaction system is 70-80%, 65-70% and 45-55% respectively. Preferably, the porosity of the hydrotreating catalyst in the reaction system is 70-80%, 65-70% and 50-55% respectively.

[0014] In some embodiments, the volume ratio of the hydrotreating catalyst with a porosity of 70-80%, the hydrotreating catalyst with a porosity of 65-70%, and the hydrotreating catalyst with a porosity of 45-55% is 10-30:30-70:10-40.

[0015] In some embodiments, the volume ratio of the hydrotreating catalyst with a porosity of 70-80%, the hydrotreating catalyst with a porosity of 65-70%, and the hydrotreating catalyst with a porosity of 50-55% is 10-30:30-70:10-40, preferably, 10-30:30-70:20-40.

[0016] In some embodiments, the hydrorefining catalysts in the reaction system are, from top to bottom, a hollow plum blossom catalyst with a porosity of 80%, a Raschig ring catalyst with a porosity of 70%, and a four-impeller catalyst with a porosity of 50%.

[0017] In some embodiments, the hydrotreating catalysts in the reaction system are, from top to bottom, a Raschig ring catalyst with a porosity of 70%, a gear-type catalyst with a porosity of 65%, and a four-impeller-type catalyst with a porosity of 55%.

[0018] In some embodiments, the heavy cycle oil obtained after fractionation treatment is subjected to solid-liquid separation and then participates in a hydrocracking reaction, wherein the solid-liquid separation includes centrifugation and filtration.

[0019] In some embodiments, the temperature of the heavy cycle oil is reduced to 100-120° C. before the solid-liquid separation process.

[0020] In some embodiments, the low-quality oil includes at least one of waste oil, waste cooking oil, hogwash oil, rancid oil, bio-asphalt, waste plastic oil, waste tire oil, waste lubricating oil, wood tar, coal tar, and heavy oil. The low-quality oil provided in the embodiments of the present invention has the characteristics of high oxygen content, high acid value, high metal impurities, high nitrogen content, and high sulfur content. The process provided in the embodiments of the present invention not only converts the low-quality oil with the above characteristics into resources, but also eliminates the need for low-quality oil pretreatment. It also increases the yield of light biodiesel, reduces impurity content, and improves the product quality rate.

[0021] In some embodiments, in the hydrocracking reaction, the volume ratio of the cycle oil to hydrogen is 300-2000:1, preferably 800-1500:1.

[0022] In some embodiments, the volume ratio of light cycle oil to heavy cycle oil in the cycle oil is 8-9:1-2.

[0023] In some embodiments, in the hydrotreating reaction, the volume ratio of hydrogen to low-quality oil is 1500-2000:1.

[0024] In some embodiments, the volume ratio of the recycled oil to the inferior oil is 1-3:1.

[0025] In some embodiments, before hydrofining, the temperature of the inferior oil is 100-250°C, the temperature of the hydrocracking reaction product is 340-420°C, and the temperature during the refining reaction is 230-390°C.

[0026] In some embodiments, before the hydrocracking reaction, the temperature of the reactants is 330-360° C., and the cracking rate is 10-70%.

[0027] In some embodiments, the metal content of the inferior oil is less than or equal to 200 ppm, the oxygen content is less than or equal to 13 vol%, the nitrogen content is less than or equal to 500 ppm, the sulfur content is less than or equal to 20,000 ppm, the water content is less than or equal to 20,000 ppm, and the phosphorus content is less than or equal to 100 ppm.

[0028] On the other hand, the present invention provides a light diesel, which is obtained by the above-mentioned light diesel oil hydrotreating method.

[0029] The invention provides an application of light diesel in renewable fuel or bio-jet fuel.

[0030] The technical solution of the present invention has the following advantages:

[0031] 1. The present invention provides a method for hydrotreating low-quality oil, comprising the steps of mixing low-quality oil with a hydrocracking reaction product, refining, desulfurizing, and fractionating to obtain light diesel, light cycle oil, and heavy cycle oil; wherein the hydrocracking reaction product is obtained by subjecting the light cycle oil and heavy cycle oil to a hydrocracking reaction, and during refining, the voidage of the catalyst in the reaction system is 50-80%. The tolerance of the hydrogenation process to raw material impurities directly affects the stability of the system, the life of the catalyst, and the quality of the product. The present invention utilizes a catalyst with large voids as a catalyst during refining, which not only improves the adaptability of the reaction system to low-quality oil raw materials, but also significantly improves the yield of the product and further reduces the impurity content in the product. In particular, the present invention uses the product of the hydrocracking reaction of the fractionated light cycle oil and heavy cycle oil as the hydrocracking reaction product, which not only improves the recovery rate of low-quality oil resources, but also effectively reduces the impurity content in the product.

[0032] 2. The present invention provides a method for hydrotreating low-quality oil, wherein the hydrorefining catalyst comprises at least one of a gear-type, Raschig ring-type, hollow plum-shaped, or four-impeller-type catalyst. The present invention selects at least one of the gear-type, Raschig ring-type, hollow plum-shaped, or four-impeller-type catalyst as the hydrorefining catalyst, which can improve the adaptability of the reaction system to low-quality oil, increase reaction efficiency, accelerate the reaction process, and effectively reduce the impurity content in the product.

[0033] 3. The present invention provides a method for hydrotreating low-quality oil, wherein the hydrorefining catalyst in the reaction system comprises at least three shapes. By selecting catalysts of different shapes, the porosity can be increased, the contact area of ​​the catalyst can be taken into account, and the utilization rate can be improved. Furthermore, the catalysts also have good strength and can improve the throughput rate of the material.

[0034] 4. The present invention provides a method for hydrotreating low-quality oil, wherein the heavy cycle oil obtained after fractionation treatment is subjected to solid-liquid separation and then to a hydrocracking reaction, wherein the solid-liquid separation includes centrifugation and filtration. The present invention separates the low-quality oil into light diesel, light cycle oil, and heavy cycle oil by reacting the low-quality oil with the hydrocracking reaction product. The light cycle oil does not contain impurities such as asphalt and metals, and relatively pure cycle oil can be obtained by solid-liquid separation of the heavy cycle oil. This not only simplifies the separation steps of impurities, especially metal impurities, but also effectively reduces the impurity content. Furthermore, by reducing the content of metal impurities in the mixed oil, the activity of the catalyst is maintained, the stability of the reaction system is improved, and the service life of the reaction system is extended.

[0035] 5. The present invention provides a method for hydrotreating low-quality oil, wherein the temperature of the heavy cycle oil is lowered to 100-120°C before solid-liquid separation. By lowering the temperature of the heavy cycle oil to 100-120°C, the present invention improves the fluidity of the heavy cycle oil, facilitating solid-liquid separation. Furthermore, the high-temperature treatment further removes water from the heavy cycle oil, further reducing impurities.

[0036] 5. The present invention provides a method for hydrotreating low-quality oil. Before hydrorefining, the low-quality oil temperature is 100-250°C, the temperature of the hydrocracking reaction product is 340-420°C, and the temperature during the refining reaction is 230-390°C. This method fully utilizes the heat from the hydrocracking reaction to heat the low-quality oil feedstock, achieving high thermal energy efficiency and effectively utilizing thermal energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0038] Figure 1 This is a process flow chart of a method for hydrotreating inferior oil provided in Example 1 of the present invention. DETAILED DESCRIPTION

[0039] The following examples are provided for a better understanding of the present invention and are not intended to limit the best mode of implementation. They do not limit the content and scope of protection of the present invention. Any product identical or similar to the present invention obtained by anyone under the guidance of the present invention or by combining the features of the present invention with other prior arts shall fall within the scope of protection of the present invention.

[0040] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in this field can be used. If the manufacturer of the reagents or instruments is not specified, they are all commercially available conventional reagents.

[0041] The catalyst in the embodiment of the present invention is the hydrogenation catalyst provided in Example 7 of the specification of publication number CN117463311A.

[0042] Example 1

[0043] See also Figure 1 As shown, this embodiment provides a method for hydrotreating low-quality oil, and the specific steps and methods are as follows:

[0044] (1) Using catering slop oil as raw oil, heating the slop oil to 150°C, mixing it with a hydrocracking reaction product at 390°C and hydrogen, and then the temperature after mixing is 245°C. The slop oil enters a large-void refining first reactor and a large-void refining second reactor for refining reaction. The catalysts in the large-void refining first reactor and the large-void refining second reactor are, in order from top to bottom, a hollow plum blossom catalyst with a void ratio of 80%, a Raschig ring catalyst with a void ratio of 70%, and a four-leaf catalyst with a void ratio of 50%. The wheel-type catalyst has 5 catalyst beds, and the volume ratio of the total catalyst loading to the sewage oil is 4:1. Among them, the volume ratio of the hollow plum blossom-type catalyst with a porosity of 80%, the Raschig ring-type catalyst with a porosity of 70%, and the four-impeller-type catalyst with a porosity of 50% is 20:40:20. The metal content in the sewage oil is 180ppm, the oxygen content is 11wt%, the sulfur content is 350ppm, the nitrogen content is 280ppm, the water content is 500ppm, and the phosphorus content is 60ppm.

[0045] (2) The refined product obtained after being treated in the large-void refining first reactor and the large-void refining second reactor is subjected to heat exchange treatment, and then passed through a stripping tower to remove hydrogen sulfide acid gas, and then passed into a fractionating tower. The fraction at 175-330°C in the middle of the fractionating tower is used as a light diesel product, the fraction at 330-360°C in the lower part of the fractionating tower is used as a light circulating oil, and the fraction at more than 360°C at the bottom of the fractionating tower is used as a heavy circulating oil. The temperature of the heavy circulating oil is reduced to below 120°C, and the heavy circulating oil is passed through a centrifugal separator (2500 rpm, 10 min) to remove asphaltene and metals. The heavy circulating oil is then filtered through a ceramic filter with a pore size of 5 nanometers to reduce the metal content of the heavy circulating oil to 8 ppm.

[0046] (3) Light cycle oil and heavy cycle oil are mixed to obtain mixed oil. After heat exchange treatment, the temperature of the mixed oil is 335°C. The mixed oil is mixed with hydrogen (purity of 99 vol%), wherein the volume ratio of light cycle oil to heavy cycle oil is 9:1, and the volume ratio of hydrogen to mixed oil is 800:1. The mixed oil is passed into a heating furnace and heated to 360°C. The mixed oil is then passed into a hydrocracking reactor for cracking reaction (the catalyst is a silicon-aluminum catalyst) with a cracking rate of 30%. The outlet temperature of the hydrocracking reactor is 370°C. The cracked cycle oil is mixed with the sewage oil raw material. The process comprises the following steps: combining the raw materials of the large-void refining reactor and the large-void refining reactor, adding circulating hydrogen, adding the circulating hydrogen to the hogwash oil at a volume ratio of 1500:1, and the volume of the circulating oil being twice that of the inferior oil. The temperature at the inlet of the large-void refining reactor first and the large-void refining reactor second is controlled to be 245° C., and sequentially introducing the mixture of the circulating oil, hogwash oil raw material, and hydrogen into the large-void refining reactor first and the large-void refining reactor second for refining reaction. After heat exchange treatment, the mixture is introduced into a fractionating tower after removing the hydrogen sulfide acid gas in a stripping tower to obtain light diesel. The heavy circulating oil and the light circulating oil continue to perform this step and circulate with the hogwash oil.

[0047] The yield of light biodiesel obtained in this embodiment is 84% ​​(yield of light biodiesel = mass of light biodiesel / mass of feedstock oil × 100%); the quality indicators of light biodiesel meet the test results of NB / T10897-2021 "hydrocarbon-based biodiesel" and the metal content in light biodiesel is ≤1ppm (analysis method is ICP-AES), oxygen content is ≤200ppm (analysis method is EN 17351); aromatic hydrocarbon content is <0.1wt% (analysis method is SH / T 0806), sulfur is ≤5ppm (analysis method is SH / T 0689), nitrogen content is ≤3ppm (analysis method is SH / T 0657); the stable operation cycle of the whole system can reach 2 years. The obtained light biodiesel can be used as a high-quality renewable fuel for transportation vehicles, and can also be used to produce bio-jet fuel in subsequent supporting heterogeneous depressing units.

[0048] Example 2

[0049] This embodiment provides a method for hydrotreating low-quality oil, and the specific steps and methods are as follows:

[0050] (1) Using waste plastic pyrolysis oil as raw material oil, the pyrolysis oil is heated to 200°C and mixed with a hydrocracking reaction product at 415°C. The mixed temperature is 260°C and the oil enters a large-void refining first reactor and a large-void refining second reactor for refining reaction. The catalysts in the large-void refining first reactor and the large-void refining second reactor are, from top to bottom, a Raschig ring catalyst with a void ratio of 70%, a gear catalyst with a void ratio of 65%, and a four-impeller catalyst with a void ratio of 55%. The catalyst bed is 6 The volume ratio of the total loading amount of the catalyst to the waste plastic pyrolysis oil is 2.5:1, among which the volume ratio of the Raschig ring catalyst with a porosity of 70%, the gear type catalyst with a porosity of 65% and the four-impeller type catalyst with a porosity of 55% is 20:40:20, and the metal content of the pyrolysis oil is 65ppm, the oxygen content is 1.2wt%, the sulfur content is 217ppm, the nitrogen content is 642ppm, the water content is 60ppm, the phosphorus content is 1.5ppm, the olefin content is 28%wt, and the aromatic hydrocarbon content is 13%wt.

[0051] (2) The refined product obtained after treatment in the first large-void refining reactor and the second large-void refining reactor is subjected to heat exchange treatment and removal of hydrogen sulfide acid gas, and then passed into a fractionating tower. The fraction at 175-330°C in the middle of the fractionating tower is used as light diesel product, the fraction at 330-360°C in the lower part of the fractionating tower is used as light cycle oil, and the fraction at more than 360°C at the bottom of the fractionating tower is used as heavy cycle oil. The heavy cycle oil is passed through a centrifuge (1900 rpm, 15 minutes) below 90°C to remove asphaltene and metals, and then enters a ceramic filter for filtration to reduce the metal content of the heavy cycle oil to 4 ppm.

[0052] (3) Light cycle oil and heavy cycle oil are mixed to obtain mixed oil. After heat exchange treatment, the temperature of the mixed oil is 325°C. The mixed oil is mixed with hydrogen (purity of 99 vol%), wherein the volume ratio of light cycle oil to heavy cycle oil is 9:1, and the volume ratio of hydrogen to mixed oil is 1200:1. The mixed oil is passed into a heating furnace and heated to 340°C. The mixed oil is then passed into a hydrocracking reactor for cracking reaction. The cracking rate is 60%. The outlet temperature of the hydrocracking reactor is 415°C. The cracked cycle oil is mixed with the pyrolysis oil raw material and added to the circulating oil. The volume ratio of hydrogen, circulating hydrogen and pyrolysis oil is 2000:1, the volume of circulating oil is twice the volume of the waste plastic pyrolysis oil raw material, and the temperature at the inlet of the large-void refining first reactor and the large-void refining second reactor is controlled at 260°C. The mixture of circulating oil, sewage oil raw material and hydrogen is sequentially introduced into the large-void refining first reactor and the large-void refining second reactor for refining reaction. After heat exchange treatment and removal of hydrogen sulfide acid gas, the mixture is introduced into a distillation tower to obtain light diesel. The heavy circulating oil and the light circulating oil continue to perform this step and circulate with the pyrolysis oil.

[0053] Using the detection method of Example 1, the light diesel yield obtained in this example is 92%. The metal content in the light diesel is less than 0.5 ppm, the oxygen content is less than 10 ppm, the sulfur content is less than 10 ppm, and the nitrogen content is less than 30 ppm. The entire system can maintain a stable operating cycle of up to 2.0 years. The resulting light diesel can be used as a high-quality renewable fuel for transportation vehicles.

[0054] Example 3

[0055] This embodiment provides a method for hydrotreating low-quality oil. The specific steps and methods are the same as those in Example 1, except that in step (1), the catalysts are, from top to bottom, a hollow plum blossom-shaped catalyst with a porosity of 80%, a Raschig ring-shaped catalyst with a porosity of 70%, and a four-impeller-shaped catalyst with a porosity of 50%, with a volume ratio of 30:50:30.

[0056] Using the detection method of Example 1, the yield of light biodiesel obtained in this example is 84.5%. The metal content in the light biodiesel is ≤1 ppm, the oxygen content is ≤150 ppm, the aromatics content is <0.1 wt% (analytical method SH / T 0806), the sulfur content is ≤5 ppm, and the nitrogen content is ≤2 ppm. The entire system can operate stably for 1.3 years.

[0057] Example 4

[0058] This embodiment provides a method for hydrotreating low-quality oil. The specific steps and methods are the same as those in Example 1, except that in step (1), the catalysts are, from top to bottom, a hollow plum blossom-shaped catalyst with a porosity of 80%, a Raschig ring-shaped catalyst with a porosity of 70%, and a four-impeller-shaped catalyst with a porosity of 50%, with a volume ratio of 10:30:40.

[0059] Using the detection method of Example 1, the yield of light biodiesel obtained in this example is 83.7%; the metal content in the light biodiesel is ≤1ppm, the oxygen content is ≤260ppm; the aromatics content is <0.1wt%, the sulfur content is ≤6ppm, and the nitrogen content is ≤3ppm; and the stable operation period of the entire system can reach 1.6 years.

[0060] Example 5

[0061] This embodiment provides a method for hydrotreating low-quality oil. The specific steps and methods are the same as those in Example 1, except that in step (1), the catalysts are, from top to bottom, a hollow plum blossom-shaped catalyst with a porosity of 80%, a Raschig ring-shaped catalyst with a porosity of 70%, and a four-impeller-shaped catalyst with a porosity of 50%, with a volume ratio of 20:40:10.

[0062] Using the detection method of Example 1, the yield of light biodiesel obtained in this example is 79.8%; the metal content in the light biodiesel is ≤3ppm, the oxygen content is ≤350ppm; the aromatics content is <0.1wt%, the sulfur content is ≤10ppm, and the nitrogen content is ≤5ppm; and the stable operation period of the entire system can reach 1.1 years.

[0063] Example 6

[0064] This embodiment provides a method for hydrotreating low-quality oil, and the specific steps and methods are the same as those in Example 1, except that in step (1), the void ratio of the hollow plum blossom-type catalyst is 70%, the void ratio of the Raschig ring-type catalyst is 65%, and the void ratio of the four-impeller-type catalyst is 45%, wherein the volume ratio of the hollow plum blossom-type catalyst with a void ratio of 70%, the void ratio of the Raschig ring-type catalyst with a void ratio of 65%, and the void ratio of the four-impeller-type catalyst with a void ratio of 45% is 20:40:20.

[0065] Using the detection method of Example 1, the yield of light biodiesel obtained in this example is 81.6%; the metal content in the light biodiesel is ≤2ppm, the oxygen content is ≤370ppm; the aromatic hydrocarbon content is <0.1wt%, the sulfur content is ≤15ppm, and the nitrogen content is ≤5ppm; and the stable operation period of the entire system can reach 1.0 year.

[0066] Example 7

[0067] This embodiment provides a method for hydrotreating low-quality oil. The specific steps and methods are the same as those in Example 1, except that the volume ratio of hydrogen to mixed oil in step (3) is 1500:1.

[0068] Using the detection method of Example 1, the yield of light biodiesel obtained in this example is 83.4%; the metal content in the light biodiesel is ≤1ppm, the oxygen content is ≤109ppm; the aromatics content is <0.1wt%, the sulfur content is ≤4ppm, and the nitrogen content is ≤2ppm; and the stable operation period of the entire system can reach 1.8 years.

[0069] Example 8

[0070] This embodiment provides a method for hydrotreating low-quality oil. The specific steps and methods are the same as those in Example 1, except that the volume ratio of hydrogen to mixed oil in step (3) is 300:1.

[0071] Using the detection method of Example 1, the yield of light biodiesel obtained in this example is 78.7%; the metal content in the light biodiesel is ≤2ppm, the oxygen content is ≤450ppm; the aromatics content is <0.2wt%, the sulfur content is ≤7ppm, and the nitrogen content is ≤5ppm; and the stable operation period of the entire system can reach 1.0 year.

[0072] Example 9

[0073] This embodiment provides a method for hydrotreating low-quality oil. The specific steps and methods are the same as those in Example 1, except that the volume ratio of hydrogen to mixed oil in step (3) is 2000:1.

[0074] The yield of light biodiesel obtained in this embodiment is 79.2%; the metal content in the light biodiesel is ≤2ppm, the oxygen content is ≤380ppm; the aromatics content is <0.25wt%, the sulfur content is ≤6ppm, and the nitrogen content is ≤4ppm; and the stable operation period of the entire system can reach 1.2 years.

[0075] Example 10

[0076] This embodiment provides a method for hydrotreating low-quality oil, and the specific steps and methods are as follows:

[0077] (1) Using catering slop oil as raw oil, the slop oil is heated to 100°C, mixed with a hydrocracking reaction product at 415°C and hydrogen, and the temperature after mixing is 330°C. The slop oil enters a large-void refining first reactor and a large-void refining second reactor for refining reaction. The catalysts in the large-void refining first reactor and the large-void refining second reactor are, in order from top to bottom, a hollow plum blossom catalyst with a void ratio of 80%, a Raschig ring catalyst with a void ratio of 70%, and a four-leaf catalyst with a void ratio of 50%. The wheel-type catalyst has 5 catalyst beds, and the volume ratio of the total catalyst loading to the sewage oil is 2:1. Among them, the volume ratio of the hollow plum blossom-type catalyst with a porosity of 80%, the Raschig ring-type catalyst with a porosity of 70%, and the four-impeller-type catalyst with a porosity of 50% is 20:40:20. The metal content in the sewage oil is 180ppm, the oxygen content is 11wt%, the sulfur content is 350ppm, the nitrogen content is 280ppm, the water content is 500ppm, and the phosphorus content is 60ppm.

[0078] (2) The refined product obtained after being treated in the large-void refining first reactor and the large-void refining second reactor is subjected to heat exchange treatment, and then passed through a gas stripping tower to remove hydrogen sulfide acid gas, and then passed into a fractionating tower, and the fraction at 175-330°C in the middle of the fractionating tower is used as a light diesel product, the fraction at 330-360°C in the lower part of the fractionating tower is used as a light circulating oil, and the fraction at more than 360°C at the bottom of the fractionating tower is used as a heavy circulating oil. The temperature of the heavy circulating oil is reduced to below 120°C, and the heavy circulating oil is passed through a centrifugal separator (2000 rpm. 20 min) to remove asphaltene and metals, and then filtered through a ceramic filter with a pore size of 5 nanometers to reduce the metal content of the heavy circulating oil to 8 ppm.

[0079] (3) Light cycle oil and heavy cycle oil are mixed to obtain mixed oil. After heat exchange treatment, the temperature of the mixed oil is 320°C. The mixed oil is mixed with hydrogen (purity of 99 vol%), wherein the volume ratio of light cycle oil to heavy cycle oil is 8:2 and the volume ratio of hydrogen to mixed oil is 800:1. The mixed oil is passed into a heating furnace and heated to 360°C. The mixed oil is then passed into a hydrocracking reactor (the catalyst is a silicon-aluminum catalyst) for cracking reaction. The cracking rate is 40%. The outlet temperature of the hydrocracking reactor is 415°C. The cycle oil after cracking treatment is a hydrocracking product. The product is mixed with hogwash oil feedstock, and circulating hydrogen is added. The volume ratio of circulating hydrogen to hogwash oil is 2000:1. The volume of circulating oil is three times that of inferior oil. The temperature at the inlet of the first and second large-void refining reactors is controlled at 330°C. The mixture of circulating oil, hogwash oil feedstock, and hydrogen is sequentially introduced into the first and second large-void refining reactors for refining reaction. After heat exchange treatment to remove hydrogen sulfide acid gas, the mixture is introduced into a fractionating tower to obtain light diesel. The heavy circulating oil and light circulating oil continue to perform this step and circulate with the hogwash oil.

[0080] Using the detection method of Example 1, the yield of light biodiesel obtained in this example is 80.2%; the metal content in the light biodiesel is ≤1ppm, the oxygen content is ≤110ppm; the aromatics content is <0.12wt%, the sulfur content is ≤4ppm, and the nitrogen content is ≤2ppm; and the stable operation period of the entire system can reach 1.7 years.

[0081] Example 11

[0082] This embodiment provides a method for hydrotreating low-quality oil, and the specific steps and methods are as follows:

[0083] (1) Using catering slop oil as raw oil, heating the slop oil to 250°C, mixing it with a hydrocracking reaction product at 350°C and hydrogen, and then the temperature after mixing is 280°C. The slop oil enters a large-void refining first reactor and a large-void refining second reactor for refining reaction. The catalysts in the large-void refining first reactor and the large-void refining second reactor are, in order from top to bottom, a hollow plum blossom catalyst with a void ratio of 80%, a Raschig ring catalyst with a void ratio of 70%, and a four-leaf catalyst with a void ratio of 50%. The wheel-type catalyst has 5 catalyst beds, and the volume ratio of the total catalyst loading to the sewage oil is 5:1. Among them, the volume ratio of the hollow plum blossom-type catalyst with a porosity of 80%, the Raschig ring-type catalyst with a porosity of 70%, and the four-impeller-type catalyst with a porosity of 50% is 20:40:20. The metal content in the sewage oil is 180ppm, the oxygen content is 11wt%, the sulfur content is 350ppm, the nitrogen content is 280ppm, the water content is 500ppm, and the phosphorus content is 60ppm.

[0084] (2) The refined product obtained after being treated in the large-void refining first reactor and the large-void refining second reactor is subjected to heat exchange treatment, and then passed through a gas stripping tower to remove hydrogen sulfide acid gas, and then passed into a fractionating tower. The fraction at 175-330°C in the middle of the fractionating tower is used as a light diesel product, the fraction at 330-360°C in the lower part of the fractionating tower is used as a light circulating oil, and the fraction at more than 360°C at the bottom of the fractionating tower is used as a heavy circulating oil. The temperature of the heavy circulating oil is reduced to below 120°C, and the heavy circulating oil is passed through a centrifugal separator (2500 rpm, 10 min) to remove asphaltene and metals. The heavy circulating oil is then filtered through a ceramic filter with a pore size of 5 nanometers to reduce the metal content of the heavy circulating oil to 8 ppm.

[0085] (3) Light cycle oil and heavy cycle oil are mixed to obtain mixed oil. After heat exchange treatment, the temperature of the mixed oil is 340°C. The mixed oil is mixed with hydrogen (purity of 99 vol%), wherein the volume ratio of light cycle oil to heavy cycle oil is 8:2, and the volume ratio of hydrogen to mixed oil is 800:1. The mixed oil is heated to 360°C in a heating furnace and then enters a hydrocracking reactor for cracking reaction (the catalyst is a silicon-aluminum catalyst). The cracking rate is 38%, and the outlet temperature of the hydrocracking reactor is 350°C. The cycle oil after cracking treatment is a hydrocracking product. The product is mixed with a hogwash oil feedstock, and circulating hydrogen is added. The volume ratio of circulating hydrogen to hogwash oil is 2000:1, and the volume of circulating oil is 1 times that of the inferior oil. The temperature at the inlet of the large-void refining reactor (1) and the large-void refining reactor (2) is controlled at 280°C. The mixture of circulating oil, hogwash oil feedstock, and hydrogen is sequentially introduced into the large-void refining reactor (1) and the large-void refining reactor (2) for refining reaction. After heat exchange treatment to remove hydrogen sulfide acid gas, the mixture is introduced into a fractionating tower to obtain light diesel. The heavy circulating oil and light circulating oil continue to perform this step and circulate with the hogwash oil.

[0086] Using the detection method of Example 1, the yield of light biodiesel obtained in this example is 81.3%; the metal content in the light biodiesel is ≤2ppm, the oxygen content is ≤160ppm; the aromatics content is <0.14wt%, the sulfur content is ≤4ppm, and the nitrogen content is ≤3ppm; and the stable operation period of the entire system can reach 1.5 years.

[0087] Comparative Example 1

[0088] This comparative example provides a method for hydrotreating inferior oil, and the specific steps and methods are as follows:

[0089] (1) Catering slop oil was used as raw oil, the slop oil was heated to 245°C, and entered into the first large-void refining reactor and the second large-void refining reactor for refining reaction. The catalysts in the first large-void refining reactor and the second large-void refining reactor were, in order from top to bottom, a hollow plum blossom catalyst with a porosity of 80%, a Raschig ring catalyst with a porosity of 70%, and a four-impeller catalyst with a porosity of 50%. The number of catalyst beds was 5, and the volume ratio of the total loading amount of the catalyst to the slop oil was 4:1. Among them, the volume ratio of the hollow plum blossom catalyst with a porosity of 80%, the Raschig ring catalyst with a porosity of 70%, and the four-impeller catalyst with a porosity of 50% was 20:40:20. The metal content in the slop oil was 180 ppm, the oxygen content was 11 wt%, the sulfur content was 350 ppm, the nitrogen content was 280 ppm, the water content was 500 ppm, and the phosphorus content was 60 ppm.

[0090] (2) The refined product obtained after being treated in the large-void refining first reactor and the large-void refining second reactor is subjected to heat exchange treatment, and then passed through a gas stripping tower to remove hydrogen sulfide acid gas, and then passed into a fractionating tower. The fraction at 175-330°C in the middle of the fractionating tower is used as a light diesel product, the fraction at 330-360°C in the lower part of the fractionating tower is used as a light circulating oil, and the fraction at more than 360°C at the bottom of the fractionating tower is used as a heavy circulating oil. The temperature of the heavy circulating oil is reduced to below 120°C, and the heavy circulating oil is passed through a centrifugal separator (2500 rpm, 10 min) to remove asphaltene and metals. The heavy circulating oil is then filtered through a ceramic filter with a pore size of 5 nanometers to reduce the metal content of the heavy circulating oil to 8 ppm.

[0091] Using the detection method of Example 1, the yield of light biodiesel obtained in this comparative example is 58.3%; the metal content in the light biodiesel is ≤15ppm, the oxygen content is ≤1200ppm; the aromatics content is <0.3wt%, the sulfur content is ≤15ppm, and the nitrogen content is ≤8ppm; and the stable operation period of the entire system can only reach 0.8 years.

[0092] Comparative Example 2

[0093] This comparative example provides a method for hydrogenating low-quality oil. The specific steps and methods are the same as those in Example 1, except that the catalyst in step (1) only contains a hollow plum blossom-shaped catalyst with a porosity of 90%.

[0094] Using the detection method of Example 1, the yield of light biodiesel obtained in this comparative example is 63.4%; the metal content in the light biodiesel is ≤21ppm, the oxygen content is ≤800ppm; the aromatics content is <0.4wt%, the sulfur content is ≤22ppm, and the nitrogen content is ≤9ppm; and the stable operation period of the entire system can only reach 0.9 years.

[0095] Comparative Example 3

[0096] This comparative example provides a method for hydrogenating low-quality oil. The specific steps and methods are the same as those in Example 1, except that the catalyst in step (1) only contains a hollow plum blossom-shaped catalyst with a porosity of 40%.

[0097] The yield of light biodiesel obtained in this comparative example is 83.4%; the metal content in the light biodiesel is ≤10ppm, the oxygen content is ≤190ppm; the aromatics content is <0.2wt%, the sulfur content is ≤6ppm, and the nitrogen content is ≤3ppm; the stable operation period of the entire system can only reach 0.4 years.

[0098] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will readily appreciate that other variations or modifications based on the above descriptions are possible. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A method for hydrotreating low-quality oil, characterized in that: The following steps are included: The low-quality oil is mixed with the hydrocracking reaction product, and then subjected to hydrorefining, stripping, desulfurization and fractionation treatment to obtain light diesel, light cycle oil and heavy cycle oil; The hydrocracking reaction product is a cycle oil formed by light cycle oil and heavy cycle oil, which is obtained through a hydrocracking reaction. During hydrotreating, the porosity of the hydrotreating catalyst in the reaction system is 50-80%.

2. The low-quality oil hydrotreating method according to claim 1, characterized in that: The hydrotreating catalyst comprises at least one of a gear type, a Raschig ring type, a hollow plum blossom type or a four-impeller type; and / or, The volume ratio of the hydrorefining catalyst to the inferior oil is 2-5:

1.

3. The low-quality oil hydrotreating method according to claim 2, characterized in that: The hydrorefining catalyst in the reaction system includes at least three shapes, which are arranged in the reaction system from top to bottom, and the void ratios of the catalyst in the reaction system are 70-80%, 65-70% and 45-55% respectively; The volume ratio of the catalyst with a void ratio of 70-80%, the catalyst with a void ratio of 65-70%, and the catalyst with a void ratio of 45-55% is 10-30:30-70:10-40, preferably 10-30:30-70:20-40.

4. The method for hydrotreating low-quality oil according to claim 3, wherein: The hydrorefining catalysts in the reaction system are, from top to bottom, a hollow plum blossom catalyst with a porosity of 80%, a Raschig ring catalyst with a porosity of 70%, and a four-impeller catalyst with a porosity of 50%. The hydrorefining catalysts in the reaction system are, from top to bottom, a Raschig ring catalyst with a porosity of 70%, a gear type catalyst with a porosity of 65%, and a four-impeller type catalyst with a porosity of 55%.

5. The method for hydrotreating low-quality oil according to claim 1, wherein: The heavy cycle oil obtained after fractionation treatment is subjected to hydrocracking reaction after solid-liquid separation, wherein the solid-liquid separation includes centrifugation and filtration; and / or, Before solid-liquid separation, the temperature of the heavy cycle oil is reduced to 100-120°C; and / or, The inferior oil includes at least one of waste grease, waste kitchen grease, sewage oil, rancid oil, bio-asphalt, waste plastic oil, waste tire oil, waste lubricating oil, wood tar, coal tar, and thick oil.

6. The method for hydrotreating low-quality oil according to claim 1, wherein: In the hydrocracking reaction, the volume ratio of circulating oil to hydrogen is 300-2000:1, preferably 800-1500:

1. The volume ratio of light cycle oil to heavy cycle oil in the cycle oil is 8-9:1-2; and / or, In the hydrorefining reaction, the volume ratio of hydrogen to inferior oil is 1500-2000:

1. The volume ratio of circulating oil to inferior oil is 1-3:

1.

7. The method for hydrotreating low-quality oil according to claim 1, characterized in that: Before hydrorefining, the temperature of the inferior oil is 100-250℃, the temperature of the hydrocracking reaction product is 340-420℃, and the temperature during the refining reaction is 230-390℃.

8. The method for hydrotreating low-quality oil according to claim 1, wherein: Before the hydrocracking reaction, the temperature of the reactants is 330-360°C and the cracking rate is 10-70%; and / or, The inferior oil has a metal content of less than or equal to 200 ppm, an oxygen content of less than or equal to 13 vol%, a nitrogen content of less than or equal to 500 ppm, a sulfur content of less than or equal to 20,000 ppm, a water content of less than or equal to 20,000 ppm, and a phosphorus content of less than or equal to 100 ppm.

9. A light diesel, characterized in that: The light diesel is obtained by the oil hydrotreating method according to any one of claims 1 to 8.

10. Use of the light diesel according to claim 9 in renewable fuel or bio-jet fuel.

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