A two-stage hydrocracking method for producing high-yield low-freezing diesel

Abstract

The invention discloses a two-stage hydrocracking method for producing more low-condensing diesel. The method includes a first hydrocracking reaction zone and a second hydrocracking reaction zone. The raw oil and hydrogen first enter the first hydrocracking reaction zone for reaction. The one-way conversion rate of the first hydrocracking reaction zone is controlled to be 60% to 70%. The effluent of the first hydrocracking reaction zone enters a flash separation high-pressure device. The mass ratio of hydrogen to hydrocarbons in the gas phase component obtained at the top of the flash separation high-pressure device is controlled to be 0.40 to 0.90. The liquid phase component obtained at the bottom is separated and fractionated to obtain light hydrocarbons, light naphtha, heavy naphtha, diesel and tail oil. The tail oil and the gas phase component obtained at the top of the flash separation high-pressure device enter the second hydrocracking reaction zone for reaction. The one-way conversion rate of the second hydrocracking reaction zone is controlled to be 35% to 75%. The effluent of the second hydrocracking reaction zone is separated and fractionated. The method can achieve the purpose of increasing the production of low-condensing diesel by only slightly adjusting the process, and has the advantage of long-term stable operation.

Description

Technical Field

[0001] The method of the invention relates to a two-stage hydrocracking method, in particular to a two-stage hydrocracking method for producing more low-condensation diesel. Background Art

[0002] Among the secondary processing technologies of crude oil, distillate oil hydrocracking technology has the characteristics of strong raw material adaptability, flexible production operation, diverse product solutions, and good product quality. It can directly convert various heavy and inferior raw materials into high-quality jet fuel, diesel, lubricant base oil, and chemical naphtha and tail oil steam cracking raw materials for ethylene production, which are urgently needed in the market. It plays the role of product distribution and product quality regulator in the production process of the whole plant, is the core of the combination of "oil-chemical-fiber", and has become one of the final heavy oil deep processing technologies in modern oil refining and petrochemical industries.

[0003] Among the many products of hydrocracking, diesel, as an important component, has always occupied a certain market share. Its most important use is in diesel engines for vehicles and ships. Compared with gasoline, it has high energy density, low fuel consumption rate, and low energy consumption, so some small cars and even high-performance cars have switched to diesel. For its components, according to the differences in the place and environment where it is used, the required low-temperature fluidity is different. According to the condensation point classification, light diesel has six grades of 5, 0, -10, -20, -35, and -50, and heavy diesel has three grades of 10, 20, and 30. The winter in the three northern regions of China and Tibet is long, and the demand for low-condensation diesel (low-grade light diesel) is relatively large. At present, the main means of producing low-condensation diesel is mainly based on the cutting and blending of light diesel fractions.

[0004] In the hydrocracking process, it can be divided into different types of processing techniques such as single-stage and two-stage processes. Although the two-stage hydrocracking process does not have advantages in terms of investment and structure, its high selectivity for the target product is its biggest feature. In the long run, short-term investment will bring long-term returns, so it is now increasingly used in the hydrocracking market. How to organically combine the two-stage hydrocracking process with the purpose of maximizing the production of high-quality diesel is an important research and development direction in the future and also the goal of efforts in this field.

[0005] CN103102966A discloses a high-nitrogen raw material hydrocracking method, which uses high-nitrogen heavy distillate oil as raw material and adopts a two-stage process flow. Under hydrofining conditions, the heavy distillate oil raw material and hydrogen are mixed into the first reaction zone, the first reaction zone uses a hydrofining catalyst, and the denitrification rate is controlled to be 60% to 95%. The gas phase after gas-liquid separation of the effluent of the first reaction zone is recycled after impurities are removed, and the liquid phase is fractionated to obtain light oil products and tail oil; the tail oil is mixed with hydrogen and enters the second reaction zone, the second reaction zone uses a hydrofining catalyst and a hydrocracking catalyst, and the reaction effluent of the second reaction zone enters a separation system. This method can be operated under relatively mild conditions, which is conducive to improving the operating cycle of the hydrogenation unit, but the yield increase of diesel is limited. Summary of the invention

[0006] The inventors of the present invention have found through extensive research that by adopting a two-stage hydrocracking method, the conversion depth of the hydrocracking in the first stage (i.e., the first hydrogenation reaction zone) is controlled to achieve the output of the full fraction of the hydrocracking product, and it is reasonably separated and optimized through a flash distillation, and the hydrogen-to-hydrocarbon ratio of the separated gas phase component is controlled. Due to the specific hydrogen-to-hydrocarbon ratio as well as hydrogen sulfide and ammonia contained in this gas phase component, and this gas phase component is used as the gas phase feed of the second stage (i.e., the second hydrogenation reaction zone), combined with the recycling of non-ideal components, the performance of the second hydrocracking catalyst can be improved and the concentration of the target product can be increased, and the excessive cracking of the reactants can be suppressed, thereby organically combining the first stage reactants and the second stage reaction mechanism, achieving an increase in the production of low-condensing diesel in the overall reaction effect, and being able to operate stably for a long period of time, thereby realizing the present invention. When the conventional two-stage hydrocracking method is adopted, if the existing high-fraction gas is directly used to enter the second stage as a reaction material, there is a problem that the flash separation condition does not match the high-fraction condition, and the adjustment flexibility is poor. Secondly, the high-fraction gas cannot return to the current hot high-fraction gas due to the pressure difference after going to the second stage. If a boosting device is used, the existing equipment cannot achieve direct boosting of the mixed flow and the light components after the reaction are difficult to discharge from the device. Therefore, it is difficult to achieve the connection of the processing flow by directly using high-fraction gas, and the production of the device cannot be carried out.

[0007] The present invention provides a two-stage hydrocracking method for producing more low-freezing diesel. The method can achieve the purpose of increasing the production of low-freezing diesel by only slightly adjusting the process, and has the advantage of long-term stable operation.

[0008] The present invention provides a two-stage hydrocracking method for producing high-yield low-condensate diesel, wherein the method comprises a first hydrocracking reaction zone and a second hydrocracking reaction zone, wherein the upper portion of the first hydrocracking reaction zone is a hydrocracking pretreatment zone and the lower portion is a hydrocracking zone, and the upper portion of the second hydrocracking reaction zone is a hydrocracking posttreatment zone and the lower portion is a hydrocracking posttreatment zone, and the process comprises: the feedstock oil and hydrogen first enter the first hydrocracking reaction zone for reaction, the single-pass conversion rate of the first hydrocracking reaction zone is controlled to be 60% to 70%, the effluent of the first hydrocracking reaction zone enters a flash separation high-pressure device, and the gas phase components obtained at the top of the flash separation high-pressure device are controlled to be The mass ratio of hydrogen to hydrocarbons is 0.40 to 0.90, preferably 0.41 to 0.85. The liquid phase components obtained at the bottom of the flash separation high pressure vessel are separated and fractionated to obtain light hydrocarbons, light naphtha, heavy naphtha, diesel and tail oil. The tail oil obtained by fractionation and the gas phase components obtained at the top of the flash separation high pressure vessel are introduced into the second hydrogenation reaction zone for reaction. The single-pass conversion rate of the second hydrogenation reaction zone is controlled to be 35% to 75%, preferably 60% to 70%. The effluent of the second hydrogenation reaction zone is separated and fractionated to obtain light hydrocarbons, light naphtha, heavy naphtha, diesel and tail oil.

[0009] In the above hydrocracking method, the pressure in the flash separation high pressure vessel is controlled to be lower than the reaction pressure in the first hydrogenation reaction zone, and the temperature is 185-215°C, preferably 190-210°C.

[0010] In the above hydrocracking method, the diesel obtained is low-condensing diesel.

[0011] In the above hydrocracking method, a fixed bed hydrogenation process is adopted, and both the first hydrogenation reaction zone and the second hydrogenation reaction zone adopt an upper feeding and lower discharging operation mode.

[0012] In the above hydrocracking method, the separation and fractionation of the effluent from the second hydrogenation reaction zone and the separation and fractionation of the liquid components discharged from the primary flash separation high pressure vessel can be carried out using the same separation and fractionation device.

[0013] In the above hydrocracking method, in the first hydrogenation reaction zone, the hydropretreatment section is loaded with a hydropretreatment catalyst, and the hydrocracking section is loaded with a hydrocracking catalyst; in the second hydrogenation reaction zone, the hydrocracking section is loaded with a hydrocracking catalyst, and the hydroposttreatment section is loaded with a hydroposttreatment catalyst.

[0014] In the above-mentioned hydrocracking method, the hydrogenation pretreatment catalyst loaded in the first hydrogenation reaction zone or the hydrogenation post-treatment catalyst loaded in the second hydrogenation reaction zone can be a hydrogenation pretreatment catalyst. The hydrogenation post-treatment catalyst loaded in the second hydrogenation reaction zone can be the same as or different from the hydrogenation pretreatment catalyst in the first hydrogenation reaction zone. In the present invention, the same catalyst is preferably used. The hydrogenation pretreatment catalyst includes a carrier and a hydrogenation active metal component. The hydrogenation active metal includes at least one of Group VIB and / or Group VIII in the periodic table, preferably one or more of tungsten, molybdenum, nickel, and cobalt. The carrier includes an inorganic refractory oxide, preferably one or more selected from alumina, amorphous silica-alumina, silicon oxide, and titanium oxide, and more preferably alumina. Based on the weight of the catalyst, the content of the Group VIB metal in terms of its oxide is 10% to 35%, preferably 15% to 30%, and the Group VIII metal in terms of its oxide is 1% to 7%, preferably 1.5% to 6%. The hydrogenation pretreatment catalyst may be selected from a variety of commercial catalysts or may be prepared according to the knowledge in the art. Commercial catalysts include HC-K, HC-T, HC-P developed by UOP and FF-46, FF-56 and FF-66 developed by FRIPP.

[0015] In the above hydrocracking method, the hydrocracking catalyst loaded in the first hydrogenation reaction zone or the hydrocracking catalyst loaded in the second hydrogenation reaction zone can be a commercial catalyst or can be prepared according to the prior art in the art. The hydrocracking catalyst loaded in the second hydrogenation reaction zone can be the same as or different from the hydrocracking catalyst loaded in the first hydrogenation reaction zone. In the present invention, the same hydrocracking catalyst is preferably used. The hydrocracking catalyst includes a cracking component and a hydrogenation active metal component; the hydrogenation active metal includes a Group VIB metal (such as tungsten and / or molybdenum) and a Group VIII metal (such as nickel and / or cobalt); the cracking component includes a molecular sieve, and the molecular sieve includes but is not limited to a β-type molecular sieve; the hydrocracking catalyst also contains a binder, which is usually alumina or silicon oxide. Based on the weight of the catalyst, the Group VIB metal oxide is 10% to 35%, preferably 15% to 30%, the Group VIII metal oxide is 1% to 7%, preferably 1.5% to 6%, and the content of the molecular sieve is 10% to 30%. Commercial catalysts such as FC-14 and FC-20 developed by FRIPP.

[0016] In the above hydrocracking method, the operating conditions of the first hydrogenation reaction zone are as follows:

[0017] Hydrogenation pretreatment section: pressure 10.0MPa~16.5MPa, reaction temperature 280℃~435℃, liquid hourly volume space velocity 0.1h -1 ~4.0h -1, hydrogen to oil volume ratio 300:1~900:1; preferably, pressure 11.0MPa~16.0MPa, reaction temperature 290℃~410℃, liquid hourly volume space velocity 0.2h -1 ~3.5h -1 , hydrogen-oil volume ratio 400:1~800:1.

[0018] Hydrocracking section: pressure 9.9MPa~16.4MPa, reaction temperature 320℃~440℃, liquid hourly volume space velocity 0.2h -1 ~3.5h -1 , hydrogen to oil volume ratio 600:1 to 1300:1; preferably, pressure 10.9MPa to 15.9MPa, reaction temperature 330℃ to 430℃, liquid hourly volume space velocity 0.4h -1 ~3.0h -1 , hydrogen-oil volume ratio 700:1~1200:1.

[0019] In the above hydrocracking method, in the second hydrogenation reaction zone, the loading volume ratio of the hydrocracking catalyst to the hydrogenation post-treatment catalyst is 7 to 13, preferably 8 to 12, and the operating conditions of the second hydrogenation reaction zone are:

[0020] Pressure 9.0MPa~15.5MPa, reaction temperature 260℃~370℃, liquid hourly volume space velocity 0.4h -1 ~4.5h -1 , hydrogen to oil volume ratio 500:1 to 1200:1; preferably, pressure 10.0MPa to 15.0MPa a, reaction temperature 270°C to 360°C, liquid hourly volume space velocity 0.5h -1 ~3.5h -1 , the hydrogen-to-oil volume ratio is 600:1 to 1100:1. The hydrogen-to-oil volume ratio refers to the volume ratio of hydrogen gas in the mixed feed to the volume ratio of liquid feed.

[0021] In the above hydrocracking method, the feedstock oil can be selected from various distillate oils suitable as hydrocracking feedstocks, such as vacuum gas oil (VGO) (also known as vacuum wax oil), coker wax oil (CGO), heavy gas oil (HGO), catalytic cracking heavy cycle oil (HCO) obtained from petroleum, preferably vacuum gas oil. The basic properties of the feedstock have no fixed restrictions and can be one or more of cycloalkyl, intermediate or paraffinic crude oils. The properties of the feedstock oil are preferably dry point not exceeding 530°C, initial distillation point of 250-350°C, final distillation point of 450-530°C, and density not greater than 0.92g / cm 3 , generally 0.87~0.92g / cm 3The nitrogen content does not exceed 1800ug / g, generally 400-1800μg / g, the sum of Fe, Ca, Ni and V contents does not exceed 1.0μg / g, generally 0.1-1.0μg / g.

[0022] In the above hydrocracking method, the one-way conversion rate (by mass) must be controlled for both the first hydrogenation reaction zone and the second hydrogenation reaction zone, and a certain temperature point must be corresponding when the conversion rate is involved. In the present invention, the temperature point corresponding to the one-way conversion rate of the first hydrogenation reaction zone is 335°C to 365°C, preferably 345°C to 355°C, and its conversion depth can be achieved by adjusting the reaction temperature of the hydrocracking section of the first hydrogenation reaction zone; the temperature point corresponding to the one-way conversion rate of the second hydrogenation reaction zone is 330°C to 390°C, preferably 340°C to 380°C, and its conversion depth can be achieved by adjusting the reaction temperature of the hydrocracking section of the second hydrogenation reaction zone.

[0023] In the above hydrocracking method, the flash separation high pressure vessel can separate the gas and liquid phases of the logistics entering the flash separation high pressure vessel by controlling the operating conditions, i.e. adjusting the temperature and pressure. The gas phase components discharged from the upper part include light hydrocarbons, ammonia, hydrogen sulfide and hydrogen, and the liquid components mainly composed of low-condensing diesel and tail oil are discharged from the lower part. The inventors found through experimental research that the mass ratio of hydrogen to hydrocarbons in the gas phase components at the top of the flash separation high pressure vessel is controlled to be 0.40 to 0.90, preferably 0.41 to 0.85, and the gas phase components enter the second hydrogenation reaction zone as gas phase feed, which is conducive to increasing the production of low-condensing diesel and can operate stably for a long period of time. The internal pressure of the separator is between the pressure of the first hydrogenation reaction zone and the second hydrogenation reaction zone. According to the energy level difference of the normal flow of logistics, the flow of reactants can be ensured without special restrictions. The specific operating conditions of the flash separation high pressure vessel are as follows: pressure is 9.5 MPa to 16.0 MPa, preferably in the range of 10.5 MPa to 15.5 MPa, and temperature is 185°C to 215°C, preferably in the range of 190°C to 210°C.

[0024] In the above-mentioned hydrocracking method, the separation and fractionation units are common knowledge of technicians in this field and do not need to be described repeatedly. The products discharged from the system of the method of the present invention include dry gas, liquefied gas, light naphtha, heavy naphtha, and low-condensing diesel. As for the tail oil, it is discharged from the bottom of the distillation tower, recycled back to the second hydrogenation reaction zone, and processed together with the gas phase components at the top of the flash separation high-pressure vessel entering the second hydrogenation reaction zone for further reaction. The desired target product of the present invention, low-condensing diesel, is produced through further deep hydrocracking reaction.

[0025] Compared with the prior art, it has the following beneficial effects:

[0026] The hydrocracking method of the present invention adopts a two-stage hydrocracking process, by adding a flash separation high pressure device after the first hydrocracking reaction zone, by controlling the hydrogen-hydrocarbon ratio in the gas phase obtained at the top of the flash separation high pressure device, the gas phase is used as the gas phase feed of the second hydrocracking reaction zone, and the circulating tail oil is used as the liquid phase feed of the second hydrocracking reaction zone, and the coexistence of hydrogen sulfide, ammonia, and hydrogen with a specific hydrogen-hydrocarbon ratio and light hydrocarbons in the gas phase components are used, which can not only improve the performance of the hydrocracking catalyst in the second hydrocracking reaction zone, but also because the introduction of light hydrocarbons is a non-ideal product for the second hydrocracking reaction zone, but its fraction is balanced, which can inhibit the further cracking of low-condensing diesel, and also accelerate the cracking of circulating tail oil to low-condensing diesel, so as to achieve the promotion and optimization of the hydrocracking reaction in the second hydrocracking reaction zone, thereby improving the yield of low-condensing diesel. The present invention uses existing logistics for reasonable configuration, makes full use of the characteristics of different reaction sections, can not only operate stably for a long period of time, but also achieves the increase of low-condensing diesel production, and meets the market demand for low-condensing diesel. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic diagram of the principle flow of a two-stage hydrocracking method for producing high-yield low-condensate diesel of the present invention;

[0028] Figure 2 It is a schematic diagram of the principle flow chart of the conventional two-stage hydrocracking method. DETAILED DESCRIPTION

[0029] The method of the present invention is described below in conjunction with the accompanying drawings. Some conventional unit diagrams that are not necessary for description are integrated and summarized as a separation system and a fractionation system.

[0030] In the present invention, the high-quality diesel mentioned mainly refers to wide-fraction diesel, which has a low freezing point and can be used as low freezing point diesel, with an initial distillation point of 160°C to 190°C and a final distillation point of 360°C to 380°C. Low freezing point diesel can be used as -35# diesel product.

[0031] In the present invention, the definition of conversion rate is:

[0032] Conversion rate of the first hydrogenation reaction zone (%) = [1-(unconverted oil amount / fresh feed amount)] × 100%;

[0033] The conversion rate of the second hydrogenation reaction zone (%) = {1-[circulating oil amount / (fresh feed amount+circulating oil amount)]}×100%.

[0034] like Figure 1 As shown, the process flow of the present invention is as follows:

[0035] The raw material 1 is mixed with hydrogen 17 and enters the first hydrogenation reaction zone 2 for reaction. The region contains a hydrogenation pretreatment process and a hydrocracking process. The reaction effluent 3 enters a flash separation high pressure device 4 for gas-liquid phase separation. The separated gas component 5 is discharged at the top, and the separated liquid phase component 6 enters the subsequent separation system 7 and the fractionation system 9 to obtain various gas-liquid phase products, such as light hydrocarbons 10, light naphtha 11, heavy naphtha 12, high-quality diesel 13 and tail oil 14. The tail oil 14 is mixed with the gas component 5 and enters the second hydrogenation reaction zone 15 for hydrocracking reaction. The reaction effluent 16 enters the subsequent separation system 7, and the separated gas phase 17 is used as circulating hydrogen. The separated liquid phase 8 enters the fractionation system 9 to obtain various gas-liquid phase products, such as light hydrocarbons 10, light naphtha 11, heavy naphtha 12, high-quality diesel 13 and tail oil 14. In the present invention, the tail oil 14 is not discharged as a product, thereby achieving the maximum increase in the production of high-quality diesel.

[0036] like Figure 2 The process flow of conventional two-stage hydrocracking is as follows:

[0037] The raw material 1 is mixed with hydrogen 17 and then enters the first hydrogenation reaction zone 2 for reaction. The region contains a hydrogenation pretreatment process and a hydrocracking process. The reaction effluent 3 enters the subsequent separation system 7 and the fractionation system 9 to obtain various gas-liquid products, such as light hydrocarbons 10, light naphtha 11, heavy naphtha 12, high-quality diesel 13 and tail oil 14. The tail oil 14 is mixed with circulating hydrogen 17 and then enters the second hydrogenation reaction zone 15 for hydrocracking reaction. The reaction effluent 16 enters the subsequent separation system 7, the separated gas phase 17 is used as circulating hydrogen, and the separated liquid phase 8 enters the fractionation system 9 to obtain various gas-liquid products, such as light hydrocarbons 10, light naphtha 11, heavy naphtha 12, diesel 13 and tail oil 14. In the present invention, the tail oil 14 is not discharged as a product.

[0038] The present method is further described below in conjunction with examples and comparative examples to compare and embody the effects and advantages of the two-stage hydrocracking method of the present invention for producing high-quality diesel.

[0039] In the present invention, unless otherwise specified, percentages refer to mass fractions.

[0040] In the embodiments of the present invention and the comparative examples, the conversion temperature corresponding to the first hydrogenation reaction zone is 350°C, and the conversion temperature corresponding to the second hydrogenation reaction zone is 360°C.

[0041] The embodiment of the present invention is according to Figure 1 The comparative example was operated according to the conventional two-stage hydrocracking process as shown in Figure 2The properties of the raw oil involved are shown in Table 1, the main physical properties of each catalyst are shown in Table 2, the main operating conditions are shown in Table 3 and Table 4, the comparison of their advantages and effects is shown in Table 5, and the properties of the low-condensation diesel obtained in each example are shown in Table 6.

[0042] Example 1

[0043] The method and process of the present invention are used as follows Figure 1 , the raw material 1 shown in Table 1 is processed, the first hydrogenation reaction zone uses the currently mature industrialized hydrogenation pretreatment catalyst FF-46 and the hydrocracking catalyst FC-20, the filling ratio of the two is 6:5, the second hydrogenation reaction zone is filled with the hydrocracking catalyst FC-20 and the hydrogenation post-treatment catalyst FF-46, the volume ratio of the two is 8:1; the reaction temperature of the pretreatment section of the first hydrogenation reaction zone is 379°C, the reaction pressure is 15.0MPa, the hydrogen-oil volume ratio is 800:1, and the liquid hourly volume space velocity is 1.0h -1 The reaction temperature of the cracking section is 385°C, the reaction pressure is 14.7MPa, the hydrogen-oil volume ratio is 1000:1, and the liquid hourly volume space velocity is 1.2h -1 The first hydrogenation reaction zone is controlled to have a conversion rate of 65% at >350℃. The reaction product enters the flash separation high pressure device for gas-liquid separation. The pressure in the device is 14.2MPa, the temperature is 200℃, and the hydrogen-to-hydrocarbon ratio in the gas phase is controlled to be 0.44. The liquid phase components discharged from the bottom enter the subsequent separation system and fractionation system. The tail oil discharged at >360℃ at the bottom of the fractionation tower is mixed with the gas phase components obtained by flash separation and then enters the second hydrogenation reaction zone to react with FC-20 and FF-46 catalysts. The reaction temperature is 342℃, the reaction pressure is 13.5MPa, the hydrogen-to-oil volume ratio is 1000:1, and the liquid hourly volume space velocity is 1.2h -1 , controlling the single-pass conversion rate at >360℃ to be 60%, the logistics after the reaction enters the above-mentioned separation system to obtain the gas phase as circulating hydrogen, and the liquid phase enters the above-mentioned distillation system to obtain various light hydrocarbons, light naphtha, heavy naphtha and low-condensing diesel products.

[0044] Example 2

[0045] The method and process of the present invention are used as follows Figure 1 , the raw material 1 shown in Table 1 is processed, the first hydrogenation reaction zone uses the currently mature industrialized hydrogenation pretreatment catalyst FF-46 and the hydrocracking catalyst FC-20, the filling ratio of the two is 6:5, the second hydrogenation reaction zone is filled with the hydrocracking catalyst FC-20 and the hydrogenation post-treatment catalyst FF-46, the volume ratio of the two is 8:1; the reaction temperature of the pretreatment section of the first hydrogenation reaction zone is 379°C, the reaction pressure is 15.0MPa, the hydrogen-oil volume ratio is 700:1, and the liquid hourly volume space velocity is 1.0h -1The reaction temperature of the cracking section is 385°C, the reaction pressure is 14.7MPa, the hydrogen-oil volume ratio is 900:1, and the liquid hourly volume space velocity is 1.2h -1 The first hydrogenation reaction zone is controlled to have a conversion rate of 65% at >350℃. The reaction product enters the flash separation high pressure device for gas-liquid separation. The pressure in the device is 14.1MPa and the temperature is 190℃. The hydrogen-to-hydrocarbon mass ratio in the gas phase components is controlled to be 0.54. The liquid phase components are discharged from the bottom for subsequent separation and fractionation systems. The tail oil discharged at >360℃ from the bottom of the fractionation tower is mixed with the gas phase components obtained by flash separation and then enters the second hydrogenation reaction zone to react with FC-20 and FF-46 catalysts. The reaction temperature is 343℃, the reaction pressure is 13.4MPa, the hydrogen-to-oil volume ratio is 900:1, and the liquid hourly volume space velocity is 1.2h -1 , controlling>360℃ single-pass conversion rate to 63%, the logistics after the reaction enters the above separation system to obtain gas phase as circulating hydrogen, and the liquid phase enters the above distillation system to obtain various light hydrocarbons, light naphtha, heavy naphtha and low-condensing diesel products.

[0046] Example 3

[0047] The method and process of the present invention are used as follows Figure 1 , the raw material 1 shown in Table 1 is processed, the first hydrogenation reaction zone uses the currently mature industrialized hydrogenation pretreatment catalyst FF-46 and the hydrocracking catalyst FC-20, the filling ratio of the two is 6:5, the second hydrogenation reaction zone is filled with the hydrocracking catalyst FC-20 and the hydrogenation post-treatment catalyst FF-46, the volume ratio of the two is 8:1; the reaction temperature of the pretreatment section of the first hydrogenation reaction zone is 381°C, the reaction pressure is 14.0MPa, the hydrogen-oil volume ratio is 700:1, and the liquid hourly volume space velocity is 1.0h -1 The reaction temperature of the cracking section is 383°C, the reaction pressure is 13.5MPa, the hydrogen-oil volume ratio is 900:1, and the liquid hourly volume space velocity is 1.2h -1 The first hydrogenation reaction zone is controlled to have a conversion rate of 60% at >350℃. The reaction product enters the flash separation high pressure device for gas-liquid separation. The pressure in the device is 12.5MPa and the temperature is 210℃. The hydrogen-to-hydrocarbon mass ratio in the gas phase components is controlled to be 0.62. The liquid phase components are discharged from the bottom for subsequent separation and fractionation systems. The tail oil discharged at >360℃ from the bottom of the fractionation tower is mixed with the gas phase components obtained by flash separation and then enters the second hydrogenation reaction zone to react with FC-20 and FF-46 catalysts. The reaction temperature is 348℃, the reaction pressure is 12.0MPa, the hydrogen-to-oil volume ratio is 900:1, and the liquid hourly volume space velocity is 1.2h -1, controlling>360℃ single-pass conversion rate to 68%, the logistics after the reaction enters the above separation system to obtain gas phase as circulating hydrogen, and the liquid phase enters the above distillation system to obtain various light hydrocarbons, light naphtha, heavy naphtha and low-condensing diesel products.

[0048] Example 4

[0049] The method and process of the present invention are used as follows Figure 1 , the raw material 2 shown in Table 1 is processed, the first hydrogenation reaction zone uses the currently mature industrialized hydrogenation pretreatment catalyst FF-46 and the hydrocracking catalyst FC-20, the filling ratio of the two is 6:5, the second hydrogenation reaction zone is filled with the hydrocracking catalyst FC-20 and the hydrogenation post-treatment catalyst FF-46, the volume ratio of the two is 11:1; the reaction temperature of the pretreatment section of the first hydrogenation reaction zone is 375°C, the reaction pressure is 15.5MPa, the hydrogen-oil volume ratio is 600:1, and the liquid hourly volume space velocity is 1.0h -1 The reaction temperature of the cracking section is 380°C, the reaction pressure is 15.0MPa, the hydrogen-oil volume ratio is 800:1, and the liquid hourly volume space velocity is 1.0h -1 The first hydrogenation reaction zone is controlled to have a conversion rate of 61% at >350℃. The reaction product enters the flash separation high pressure device for gas-liquid separation. The pressure in the device is 14.5MPa and the temperature is 195℃. The hydrogen-to-hydrocarbon mass ratio in the gas phase components is controlled to be 0.68. The liquid phase components are discharged from the bottom for subsequent separation and fractionation systems. The tail oil discharged at >360℃ from the bottom of the fractionation tower is mixed with the gas phase components obtained by flash separation and then enters the second hydrogenation reaction zone to react with FC-20 and FF-46 catalysts. The reaction temperature is 348℃, the reaction pressure is 13.9MPa, the hydrogen-to-oil volume ratio is 800:1, and the liquid hourly volume space velocity is 1.1h -1 , controlling>360℃ single-pass conversion rate to 65%, the logistics after the reaction enters the above separation system to obtain gas phase as circulating hydrogen, and the liquid phase enters the above distillation system to obtain various light hydrocarbons, light naphtha, heavy naphtha and low-condensing diesel products.

[0050] Comparative Example 1

[0051] The conventional two-stage hydrocracking method and process are as follows Figure 2 , the raw material 1 shown in Table 1 is processed, the first hydrogenation reaction zone uses the currently mature industrialized FF-46 and FC-20 catalysts, the filling ratio of the two is 6:5, the second hydrogenation reaction zone is filled with FC-20 hydrocracking catalyst and hydrogenation post-treatment catalyst FF-46, the volume ratio of the two is 8:1; the reaction temperature of the pretreatment section of the first hydrogenation reaction zone is 379°C, the reaction pressure is 15.0MPa, the hydrogen-oil volume ratio is 800:1, and the liquid hourly volume space velocity is 1.0h -1The reaction temperature of the cracking section is 385°C, the reaction pressure is 14.7MPa, the hydrogen-oil volume ratio is 1000:1, and the liquid hourly volume space velocity is 1.2h -1 The first hydrogenation reaction zone is controlled to have a conversion rate of 65% at >350°C. The generated components enter the subsequent separation system and fractionation system. The tail oil at >360°C discharged from the bottom of the fractionation tower and the circulating hydrogen enter the second hydrogenation reaction zone to react with FC-20 and FF-46 catalysts. The reaction temperature is 333°C, the reaction pressure is 14.2MPa, the hydrogen-to-oil volume ratio is 1000:1, and the liquid hourly volume space velocity is 1.2h -1 , control>360℃ single-pass conversion rate is 60%, the gas phase after the reaction enters the separation system, the gas phase is obtained as circulating hydrogen, and the liquid phase enters the fractionation system to obtain various light hydrocarbons, light naphtha, heavy naphtha and low-condensing diesel products.

[0052] Comparative Example 2

[0053] The conventional two-stage hydrocracking method and process are as follows Figure 2 , the raw material 1 shown in Table 1 is processed, the first hydrogenation reaction zone uses the currently mature industrialized FF-46 and FC-20 catalysts, the filling ratio of the two is 6:5, the second hydrogenation reaction zone is filled with FC-20 hydrocracking catalyst and hydrogenation post-treatment catalyst FF-46, the volume ratio of the two is 8:1; the reaction temperature of the pretreatment section of the first hydrogenation reaction zone is 379°C, the reaction pressure is 15.0MPa, the hydrogen-oil volume ratio is 800:1, and the liquid hourly volume space velocity is 1.0h -1 The reaction temperature of the cracking section is 385°C, the reaction pressure is 14.7MPa, the hydrogen-oil volume ratio is 1000:1, and the liquid hourly volume space velocity is 1.2h -1 The first hydrogenation reaction zone is controlled to have a conversion rate of 65% at >350°C. The generated components enter the subsequent separation system and fractionation system. The tail oil at >360°C and the circulating hydrogen discharged from the bottom of the fractionation tower enter the second hydrogenation reaction zone to react with the FC-20 catalyst. Sulfur supplementation is performed in the gas phase. The hydrogen sulfide concentration is controlled to be 800μl / l, the reaction temperature is 330°C, the reaction pressure is 14.2MPa, the hydrogen-to-oil volume ratio is 1000:1, and the liquid hourly volume space velocity is 1.1h -1 , the single-pass conversion rate is controlled at >360℃ to be 60%. The logistics after the reaction enters the separation system to obtain the gas phase as circulating hydrogen, and the liquid phase enters the distillation system to obtain various light hydrocarbons, light naphtha, heavy naphtha and low-condensing diesel products.

[0054] Comparative Example 3

[0055] The conventional two-stage hydrocracking method and process are as follows Figure 2, the raw material 1 shown in Table 1 is processed, the first hydrogenation reaction zone uses the currently mature industrialized FF-46 and FC-20 catalysts, the filling ratio of the two is 6:5, the second hydrogenation reaction zone is filled with FC-20 hydrocracking catalyst and hydrogenation post-treatment catalyst FF-46, the volume ratio of the two is 8:1; the reaction temperature of the pretreatment section of the first hydrogenation reaction zone is 379°C, the reaction pressure is 15.0MPa, the hydrogen-oil volume ratio is 800:1, and the liquid hourly volume space velocity is 1.0h -1 The reaction temperature of the cracking section is 385°C, the reaction pressure is 14.7MPa, the hydrogen-oil volume ratio is 1000:1, and the liquid hourly volume space velocity is 1.2h -1 The first hydrogenation reaction zone is controlled to have a conversion rate of 65% at >350℃. The generated components enter the subsequent separation system and fractionation system. The tail oil at >360℃ discharged from the bottom of the fractionation tower and the circulating hydrogen enter the second hydrogenation reaction zone to react with FC-20 and FF-46 catalysts. Sulfur and ammonia are supplemented in the gas phase. The hydrogen sulfide concentration is controlled to be 800μl / l, the ammonia concentration is controlled to be 250μl / l, the reaction temperature is 339℃, the reaction pressure is 14.2MPa, the hydrogen-to-oil volume ratio is 1000; 1, and the liquid hourly volume space velocity is 1.1h -1 , the single-pass conversion rate is controlled at >360℃ to be 60%. The logistics after the reaction enters the separation system to obtain the gas phase as circulating hydrogen, and the liquid phase enters the fractionation system to obtain various light hydrocarbons, light naphtha, heavy naphtha and low-condensing diesel products.

[0056] Table 1 Properties of crude oil

[0057] Source of raw materials Vacuum wax oil Vacuum wax oil serial number 1 2 <![CDATA[Density (20 °C) / g·cm -3 > 0.9104 0.9088 Distillation range / ℃ 315～519 300～489 <![CDATA[Sulfur / μg·g -1 > 13800 9800 <![CDATA[Nitrogen / μg·g -1 > 1150 980

[0058] Table 2 Main physicochemical properties of the catalysts used in each example

[0059] project FF-46 FC-20 Active metal composition Mo-Ni W-Ni <![CDATA[MoO3,wt%]]> 24.5 - NiO, wt% 4.0 7.5 <![CDATA[WO3,wt%]]> - 25.1 β molecular sieve content, wt% - 25.0 Physical properties Appearance and shape Shamrock Strips Cylindrical Bar Crushing strength, N / cm ≥150 >180 Particle diameter, mm 1.1～1.4 1.5～1.7

[0060] Table 3 Main reaction conditions for each example

[0061]

[0062] Table 4 Main reaction conditions for each example

[0063] project Comparative Example 1 Comparative Example 2 Comparative Example 3 Conversion rate of the first hydrogenation reaction zone, % 65 65 65 Hydrogen / hydrocarbon mass ratio of gaseous feed in the second hydrogenation reaction zone 1.28 1.31 1.30

[0064] Table 5 Comparison of the effects of different conditions used in each case

[0065]

[0066] Table 6 Main properties of low-freezing diesel obtained in Example

[0067]

[0068] It can be seen from Table 6 that the properties of the low-freezing point diesel obtained in the embodiment of the present invention meet the standards.

Claims

1. A two-stage hydrocracking method for producing high-yield low-condensate diesel, wherein: The method comprises a first hydrogenation reaction zone and a second hydrogenation reaction zone, wherein the upper part of the first hydrogenation reaction zone is a hydrogenation pretreatment section and the lower part is a hydrocracking section, and the upper part of the second hydrogenation reaction zone is a hydrocracking section and the lower part is a hydrogenation post-treatment section. The process comprises: the feedstock oil and hydrogen first enter the first hydrogenation reaction zone for reaction, the single-pass conversion rate of the first hydrogenation reaction zone is controlled to be 60% to 70%, the effluent of the first hydrogenation reaction zone enters a flash separation high-pressure device, and the gas phase component obtained at the top of the flash separation high-pressure device is controlled to be In the separation, the mass ratio of hydrogen to hydrocarbons is 0.40-0.90, the liquid phase components obtained at the bottom of the flash separation high pressure vessel are separated and fractionated to obtain light naphtha, heavy naphtha, diesel and tail oil, the tail oil obtained by fractionation and the gas phase components obtained at the top of the flash separation high pressure vessel are introduced into the second hydrogenation reaction zone for reaction, the single-pass conversion rate of the second hydrogenation reaction zone is controlled to be 35%-75%, and the effluent of the second hydrogenation reaction zone is separated and fractionated to obtain light naphtha, heavy naphtha, diesel and tail oil; The effluent from the second hydrogenation reaction zone is separated and fractionated using the same separation and fractionation device as the liquid components discharged from the flash separation high pressure device; The feedstock oil is selected from one or more of vacuum gas oil, coker wax oil, heavy gas oil, and catalytic cracking heavy cycle oil; The temperature point corresponding to the one-way conversion rate of the first hydrogenation reaction zone is 335°C~365°C; the temperature point corresponding to the one-way conversion rate of the second hydrogenation reaction zone is 330°C~390°C.

2. The method according to claim 1, characterized in that The mass ratio of hydrogen to hydrocarbons in the gas phase components obtained at the top of the flash separation high-pressure vessel is controlled to be 0.41~0.

85.

3. The method according to claim 1, characterized in that The single-pass conversion rate of the second hydrogenation reaction zone is controlled to be 60%~70%.

4. The method according to claim 1, characterized in that The pressure controlled in the flash separation high pressure vessel is lower than the reaction pressure of the first hydrogenation reaction zone, and the temperature is 185-215°C.

5. The method according to claim 4, characterized in that The pressure controlled in the flash separation high pressure vessel is lower than the reaction pressure of the first hydrogenation reaction zone, and the temperature is 190-210°C.

6. The method according to claim 1 or 4, characterized in that: The pressure of the flash separation high pressure vessel is 9.5MPa~16.0MPa.

7. The method according to claim 6, characterized in that The pressure of the flash separation high pressure vessel is 10.5 MPa to 15.5 MPa.

8. The method according to claim 1, characterized in that In the first hydrogenation reaction zone, the hydrogenation pretreatment section is loaded with a hydrogenation pretreatment catalyst, and the hydrocracking section is loaded with a hydrocracking catalyst; in the second hydrogenation reaction zone, the hydrocracking section is loaded with a hydrocracking catalyst, and the hydrogenation posttreatment section is loaded with a hydrogenation posttreatment catalyst.

9. The method according to claim 1 or 4, characterized in that: The raw material oil is vacuum gas oil.

10. The method according to claim 1, characterized in that The properties of the raw oil are as follows: dry point not exceeding 530°C, density not exceeding 0.92 g / cm 3 , nitrogen content does not exceed 1800μg / g.

11. The method according to claim 8, characterized in that The hydrogenation pretreatment catalyst loaded in the first hydrogenation reaction zone or the hydrogenation post-treatment catalyst loaded in the second hydrogenation reaction zone has a content of 10% to 35% of Group VIB metals in terms of their oxides, and 1% to 7% of Group VIII metals in terms of their oxides, based on the weight of the catalyst.

12. The method according to claim 8, characterized in that The hydrogenation pretreatment catalyst loaded in the first hydrogenation reaction zone or the hydrogenation post-treatment catalyst loaded in the second hydrogenation reaction zone has a content of 15% to 30% of Group VIB metals in terms of their oxides, and 1.5% to 6% of Group VIII metals in terms of their oxides, based on the weight of the catalyst.

13. The method according to claim 8, characterized in that The hydrocracking catalyst loaded in the first hydrogenation reaction zone or the hydrocracking catalyst loaded in the second hydrogenation reaction zone comprises a cracking component and a hydrogenation active metal component; the cracking component comprises a molecular sieve, and the molecular sieve comprises a β-type molecular sieve; based on the weight of the catalyst, the content of the VIB group metal oxide is 10% to 35%, the content of the VIII group metal oxide is 1% to 7%, and the content of the molecular sieve is 10% to 30%.

14. The method according to claim 8, characterized in that The hydrocracking catalyst loaded in the first hydrogenation reaction zone or the hydrocracking catalyst loaded in the second hydrogenation reaction zone comprises a cracking component and a hydrogenation active metal component; the cracking component comprises a molecular sieve, and the molecular sieve comprises a β-type molecular sieve; based on the weight of the catalyst, the content of the VIB group metal oxide is 15% to 30%, the content of the VIII group metal oxide is 1.5% to 6%, and the content of the molecular sieve is 10% to 30%.

15. The method according to claim 1, characterized in that The operating conditions in the first hydrogenation reaction zone are: Hydrogenation pretreatment section: pressure 10.0MPa~16.5MPa, reaction temperature 280℃~435℃, liquid hourly volume space velocity 0.1h -1 ~4.0h -1 , hydrogen-oil volume ratio 300:1~900:1; Hydrocracking section: pressure 9.9MPa~16.4MPa, reaction temperature 320℃~440℃, liquid hourly volume space velocity 0.2h -1 ~3.5h -1 , hydrogen-oil volume ratio 600:1~1300:

1.

16. The method according to claim 15, characterized in that The operating conditions in the first hydrogenation reaction zone are: Hydrogenation pretreatment section: pressure 11.0MPa~16.0MPa, reaction temperature 290℃~410℃, liquid hourly volume space velocity 0.2h -1 ~3.5h -1 , hydrogen-oil volume ratio 400:1~800:1; Hydrocracking section: pressure 10.9MPa~15.9MPa, reaction temperature 330℃~430℃, liquid hourly volume space velocity 0.4h -1 ~3.0h -1 , hydrogen-oil volume ratio 700:1~1200:

1.

17. The method according to claim 1, characterized in that In the second hydrogenation reaction zone, the loading volume ratio of the hydrocracking catalyst to the hydrogenation post-treatment catalyst is 7-13, and the operating conditions of the second hydrogenation reaction zone are: pressure 9.0MPa-15.5MPa, reaction temperature 260°C-370°C, liquid hourly volume space velocity 0.4h -1 ~4.5h -1 , hydrogen-oil volume ratio 500:1~1200:

1.

18. The method according to claim 17, characterized in that In the second hydrogenation reaction zone, the loading volume ratio of the hydrocracking catalyst to the hydrogenation post-treatment catalyst is 8-12, and the operating conditions of the second hydrogenation reaction zone are: pressure 10.0MPa-15.0MPa a, reaction temperature 270°C-360°C, liquid hourly volume space velocity 0.5h -1 ~3.5h -1 , hydrogen-oil volume ratio 600:1~1100:

1.

19. The method according to claim 1, characterized in that The temperature point corresponding to the one-way conversion rate of the first hydrogenation reaction zone is 345°C~355°C; the temperature point corresponding to the one-way conversion rate of the second hydrogenation reaction zone is 340°C~380°C.

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