A liquid-phase hydrogenation reactor and reaction process for enhancing mass transfer

Abstract

The present invention discloses a liquid-phase hydrogenation reactor for enhancing mass transfer, which comprises a reactor cylinder body. A liquid discharge port is arranged at the bottom of the reactor cylinder body, and a liquid inlet and a gas inlet are arranged on the side surface near the bottom of the cylinder body. One end of the gas inlet located inside the cylinder body is connected with a gas pre-distribution plate. A layered partition plate is arranged above the gas pre-distribution plate, and a plurality of strong dispersion bubble generators are fixedly arranged through the bottom of the layered partition plate. The present invention also discloses a reaction process using the liquid-phase hydrogenation reactor for enhancing mass transfer. The liquid-phase hydrogenation reactor and the reaction process of the present invention can enhance the full mixing of microbubbles with the catalyst and the liquid, improve the gas holdup of hydrogen in the liquid-phase hydrogenation reactor, the residence time of the microbubbles is long, and the gas-liquid contact area can be increased.

Description

Technical Field

[0001] The present invention belongs to the technical field of chemical engineering equipment, and specifically relates to a liquid-phase hydrogenation reactor for enhancing mass transfer and a reaction process. Background Art

[0002] Petroleum is the most widely used energy source in the world at present. Its liquid-phase hydrogenation technology refers to the reaction process of petroleum fractions and hydrogen under the action of a catalyst. Liquid-phase hydrogenation is an important means for refining, upgrading and heavy oil processing of petroleum products. The purpose of oil product upgrading is to remove heteroatoms such as nitrogen, oxygen, sulfur and metal impurities in the oil product, or to hydrogenate and saturate some aromatics and olefins to improve the use performance of the oil product.

[0003] Continuous liquid-phase hydrogenation technology is one of the main hydrogenation technologies applied in the process of diesel quality upgrading in China. Compared with the conventional trickle-bed hydrogenation technology, the continuous liquid-phase hydrogenation technology cancels the high-pressure recycle hydrogen system and replaces it with a recycle oil system, which can not only make the process flow of the device simpler, the operation more convenient and the inherent safety stronger, but also can greatly reduce the energy consumption and investment of the device. Compared with the traditional fluidized bed technology, the energy consumption of the device is reduced by more than 25%, and the investment is also reduced by 10%-20%. As the reaction proceeds in continuous liquid-phase hydrogenation, hydrogen is continuously consumed. In order to ensure the hydrogen replenishment rate, an efficient mass transfer method needs to be adopted to accelerate the mass transfer rate of hydrogen in the up-flow reactor. Ideally, the liquid-phase hydrogenation reactor presents a hydrogen-saturated dissolution characteristic. However, in fact, hydrogen in the up-flow liquid-phase hydrogenation reactor enters the bed in the form of bubbles, and the diameter of the hydrogen bubbles is relatively large, with an average diameter of more than 10 mm. The contact area between the gas-liquid two phases is small, resulting in high local hydrogen deficiency, high coking rate and difficult secondary oil processing, leading to problems such as high operating severity requirements of the device, poor raw material adaptability and short operation cycle, and the processing capacity and level of the device are limited; in addition, the existing reactor operates at a high temperature, which also affects the service life of the catalyst. With the upgrading of diesel quality, the scale of domestic diesel liquid-phase hydrogenation devices is continuously expanding, and it is necessary to optimize and improve the existing reactor mass transfer technology.

[0004] The hydrogenation reactor is a gas-liquid-solid three-phase reactor. At present, the hydrogenation reactor has the problem of insufficient hydrogen mass transfer. The main reason is that the bubble size cannot be small enough; the smaller the bubble, the larger the specific surface area of the bubble, and the larger the gas-liquid contact area per unit volume of the liquid, which is more conducive to gas-liquid-solid mass transfer. At the same time, the smaller the bubble, the lower the bubble rising speed. In a reactor of the same height, the residence time of microbubbles is longer, which is more conducive to gas-liquid-solid mass transfer. From the perspective of bubble coalescence analysis, the smaller the bubble, the lower the probability of bubble coalescence during the bubble rising process, so that a smaller bubble size can be further maintained, which is conducive to mass transfer. And the existence of a small number of large bubbles is beneficial to increasing the gas holdup and the overall turbulent kinetic energy of the bubbles, thereby further improving the mass transfer efficiency.

[0005] CN201644076U proposes a liquid-phase hydrogenation reactor. The reactor includes a reactor cylinder body, a catalyst bed, a reactor outlet and a reactor inlet. A mixer is arranged between the catalyst beds. The mixer has a feed inlet and a hydrogen inlet, and also has a hydrogen-dissolved mixture outlet and a gas outlet. The hydrogen-dissolved mixture outlet of the mixer is immersed in the liquid of the next catalyst bed. This mixer can effectively increase the contact surface between gas and liquid phases, has a simple structure, dissolves hydrogen in the mixed oil, promotes the reaction, and greatly improves the hydrogenation efficiency. However, it does not improve the gas-liquid reaction efficiency from the bubble scale, and the turbulent kinetic energy of this method is low, and the reaction efficiency cannot be qualitatively improved; moreover, hydrogen is likely to diffuse upward and escape, reducing the utilization rate of hydrogen.

[0006] CN103965959A proposes a liquid-phase hydrogenation method with multi-stage hydrogen dissolution. The circulating liquid material is mixed with the feed oil and enters a heating furnace for heating; hydrogen is divided into n paths and enters the heating furnace for heating; one path of hydrogen and the liquid phase material are mixed in a mixer for the first-stage hydrogen dissolution, and the remaining (n - 1) paths of hydrogen enter the reactor through the inlet of the reactor bed and are mixed with the mixture after reaction in the previous bed in the hydrogen-oil mixing component in the reactor for the second-stage hydrogen dissolution. The reaction by-products hydrogen sulfide and ammonia are stripped. A reaction pressure control system is arranged at the top of the reactor, and an exhaust system is arranged in each section of the reactor; the reaction product enters a stripping column. A hydrogen-oil mixer is arranged in the stripping column to strip the by-products hydrogen sulfide and ammonia and increase the hydrogen dissolution capacity. A part of the oil product coming out of the stripping column enters the product tank, and a part is recycled; it discharges hydrogen sulfide and ammonia from the reaction system while carrying out the catalytic hydrogenation reaction. The solid-phase catalyst contacts the liquid-phase reactants, improving the reaction efficiency. However, it combines the reaction system, the circulation system and the heating furnace system, and the reaction process is very complex, with high equipment costs and difficult operation. The equipment has a large volume, increasing the floor area. And multi-stage hydrogen dissolution increases the mass transfer reaction time, with low economic benefits. Summary of the Invention

[0007] The purpose of the present invention is to improve the above problems existing in the existing diesel liquid-phase hydrogenation reactor, so as to improve the gas-liquid mass transfer rate, improve the reaction effect of the reactor, and extend the hydrogenation reaction cycle.

[0008] To achieve the above purpose, in the first aspect of the present invention, a liquid-phase hydrogenation reactor with enhanced mass transfer is provided. The liquid-phase hydrogenation reactor includes a reactor cylinder body. A liquid discharge port is arranged at the bottom of the reactor cylinder body, and a liquid inlet and a gas inlet are arranged on the side close to the bottom of the cylinder body. One end of the gas inlet inside the cylinder body is connected with a gas pre-distribution plate, a layered partition plate is arranged above the gas pre-distribution plate, and a plurality of strong dispersion bubble generators are fixedly arranged through the bottom of the layered partition plate.

[0009] According to the present invention, the distance between the strong dispersion bubble generator and the gas pre-distribution plate is 0.5 to 2 m.

[0010] According to the present invention, the end of the gas inlet located inside the cylinder body bends upward, the gas pre-distribution plate is horizontally arranged at the end of the gas inlet, the gas pre-distribution plate includes a disc-shaped chamber and a plurality of distribution pipes uniformly distributed along the outer periphery of the disc-shaped chamber, and a plurality of exhaust holes are opened on the distribution pipes.

[0011] According to the present invention, the diameter of the exhaust hole depends on the diameter of the reactor, specifically as follows:

[0012] When the diameter of the reactor is less than 1 m, the size of the exhaust hole 43 is 1.5 to 2 mm;

[0013] When the diameter of the reactor is 1 to 2 m, the size of the exhaust hole 43 is 2 to 3 mm;

[0014] When the diameter of the reactor is 2 to 4 m, the size of the exhaust hole 43 is 2.5 to 4 mm;

[0015] When the diameter of the reactor is greater than 2 m, the size of the exhaust hole 43 is 4 to 6 mm.

[0016] According to a preferred embodiment of the present invention, the strong dispersion bubble generator is cylindrical, its top penetrates through the layered partition plate, through holes are opened at corresponding positions of the layered partition plate, and the strong dispersion bubble generator is fixed to the bottom of the layered partition plate by means of the outer wall of its cylindrical top.

[0017] Furthermore, an axial guide vane liquid inlet, a gas-liquid mixing chamber, a toothed gas-liquid outlet and a conical outlet are sequentially arranged in the strong dispersion bubble generator from bottom to top. A plurality of willow-leaf-shaped flow guides are arranged on the conical outlet, and an air inlet hole is arranged on the upper side of the gas-liquid mixing chamber. An air inlet pipe is connected to the inner side of the air inlet hole. The air inlet pipe extends to the center position of the mixing chamber and then bends downward, and a gas flow guide cone is connected to the end. One or more gas outlets in the chamber are opened at the end of the gas flow guide cone, and the gas outlets in the chamber are adjacent to the axial guide vane liquid inlet.

[0018] According to a preferred embodiment of the present invention, the axial guide vane liquid inlet is configured as a spiral rising blade, and the outer edge of the blade is fixedly connected to the inner wall of the bottom of the strong dispersion bubble generator to facilitate the liquid entering the gas-liquid mixing chamber to form a swirl.

[0019] According to a preferred embodiment of the present invention, the included angle γ between the two hypotenuses of the cross-section of the gas flow guide cone is 35° to 45°, so as to fully strengthen the swirl in the chamber.

[0020] According to the present invention, the number of the gas outlets in the cavity provided at the end of the gas guide cone depends on the gas flow rate, specifically as follows:

[0021] When the gas flow rate is greater than 5 L / min, each gas guide cone adopts 4 gas outlets in the cavity;

[0022] When the gas flow rate is between 2 and 5 L / min, each gas guide cone adopts 2 gas outlets in the cavity;

[0023] When the gas flow rate is lower than 2 L / min, each gas guide cone adopts 1 gas outlet in the cavity.

[0024] According to a preferred embodiment of the present invention, the toothed gas-liquid outlet is formed by setting the side wall of the outlet into a sawtooth shape to facilitate the dispersion of bubbles.

[0025] According to the present invention, the willow-leaf-shaped deflector has a willow-leaf-shaped configuration with a larger middle part and tapering from the middle to both ends, and the bottom surface is a plane to facilitate fixing with the conical outlet.

[0026] Furthermore, the willow-leaf-shaped deflectors are uniformly distributed in a divergent manner on the conical outlet, presenting a Venturi form. From the toothed gas-liquid outlet outwards, a gradually reducing section and a gradually expanding section are sequentially formed between two adjacent willow-leaf-shaped deflectors.

[0027] Preferably, the angle β of the gradually reducing section is 30°, and the angle α of the gradually expanding section is 10°.

[0028] In a second aspect of the present invention, a liquid-phase hydrogenation reaction process is provided, and the reaction process uses the liquid-phase hydrogenation reactor as described above.

[0029] Furthermore, the liquid-phase hydrogenation reaction process includes the following steps:

[0030] Step 1: The raw material liquid-phase diesel and hydrogen enter a heating furnace through a raw material pump and a hydrogen compressor respectively for heating, and then enter a hydrofining reactor. In the hydrofining reactor, after passing through a gas pre-distribution plate, hydrogen is pre-dissolved in diesel. A part of the remaining hydrogen is further dissolved in a strong dispersion bubble generator, and a part generates fractal bubbles which are uniformly distributed through a bubble stratification baffle and then enter the catalyst bed layer above. A large number of fractal bubbles adhere to the surface of the catalyst to form a huge contact area, and the liquid phase follows the gas phase for further dissolution. Finally, the hydrogenation product is discharged from the top of the reactor;

[0031] Step 2: The hydrogenation product coming out of the hydrofining reactor directly enters the hot high-pressure stripping separator for gas-liquid separation. The reaction-generated gas coming out of the top of the hot high-pressure stripping separator is cooled by an air cooler and then enters the cold low-pressure separator for gas-liquid separation; the oil phase coming out of the bottom of the hot high-pressure stripping separator is divided into two paths. One path is boosted by the reaction product circulation pump and then returns to the reactor; the other path is cooled to 250 °C and then enters the hot low-pressure separator for further flashing;

[0032] Step 3: The oil phases separated from the cold low-pressure separator and the hot low-pressure separator are preheated to 250 °C together and then enter the product fractionation tower, and the gas phase is recycled.

[0033] According to the present invention, in step 1, the raw material diesel is coker diesel, catalytic diesel, straight-run diesel or a mixture thereof, wherein:

[0034] The sulfur content of the catalytic diesel is 3000-5000 μg / g, the nitrogen content is 600-1000 μg / g, and the cetane index is generally not more than 30;

[0035] The sulfur content of the coker diesel is 6000-9000 μg / g, the nitrogen content is 800-1200 μg / g, and the cetane index is 40-60;

[0036] The sulfur content of the straight-run diesel is 1000-1500 μg / g, the nitrogen content is 30-200 μg / g, and the cetane index is 60-70.

[0037] The liquid-phase hydrogenation reactor with enhanced mass transfer and the corresponding reaction process of the present invention have the following beneficial effects:

[0038] 1. The liquid-phase hydrogenation reactor of the present invention can strengthen the full mixing of fine bubbles with the catalyst and the liquid, improve the gas holdup of hydrogen in the liquid-phase hydrogenation reactor, the residence time of the microbubbles is long, and the gas-liquid contact area can be increased.

[0039] 2. The structure of the strong dispersion bubble generator increases the local pressure in the gas-liquid mixing chamber, makes hydrogen locally supersaturated, and improves the quality of diesel.

[0040] 3. The gas-liquid two phases can enter the strong dispersion microbubble generator simultaneously, the required pressure drop is low, and the energy loss is also low.

[0041] 4. The present invention improves the utilization rate of hydrogen in the liquid-phase hydrogenation reactor and improves the economic benefits.

[0042] 5. The present invention can effectively control the coking phenomenon caused by local hydrogen deficiency and extend the operation cycle of the reactor. Description of the Drawings

[0043] Figure 1 It is a partial structural schematic diagram of the liquid-phase hydrogenation reactor for enhancing mass transfer of the present invention.

[0044] Figure 2 It is a structural schematic diagram of the gas pre-distribution plate.

[0045] Figure 3 It is a structural sectional schematic diagram of the strong dispersion bubble generator.

[0046] Figure 4 It is Figure 1 The sectional view along C-C in

[0047] Figure 5 It is a schematic diagram of the conical outlet of the strong dispersion bubble generator and the willow-leaf-shaped flow guide arranged thereon.

[0048] Figure 6 It is a structural schematic diagram of the willow-leaf-shaped flow guide.

[0049] Figure 7 It is Figure 6 The sectional view along A-A in

[0050] Figure 8 It is Figure 6 The sectional view along B-B in

[0051] Figure 9 It is a schematic diagram of the reduction and expansion angles of the willow-leaf-shaped flow guide.

[0052] Figure 10 It is a process flow diagram of the liquid-phase hydrogenation reaction process for enhancing mass transfer of the present invention.

[0053] Figure 11 It is a schematic diagram of the mass transfer of the liquid phase following the gas phase on the catalyst surface.

[0054] Figure 12 It shows a schematic diagram of the liquid droplets entering the interior of the small bubbles.

[0055] Explanation of figure numbers:

[0056] 1 - Reactor cylinder; 2 - Stratified partition; 3 - Strong dispersion bubble generator; 31 - Tooth-shaped gas-liquid outlet; 32 - Air inlet hole; 33 - Air inlet pipe; 34 - Gas flow guide cone; 35 - Gas outlet in the cavity; 36 - Axial guide vane liquid inlet; 37 - Gas-liquid mixing cavity; 38 - Conical outlet; 39 - Willow-leaf-shaped flow guide; 4 - Gas and distributor; 41 - Disk-shaped chamber; 42 - Distribution pipe; 43 - Exhaust hole; 5 - Liquid inlet; 6 - Liquid discharge port; 7 - Gas inlet. Specific embodiments

[0057] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings in specific embodiments. It should be understood that the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of the present invention.

[0058] In the following embodiments, the fixation (connection) mentioned, if not otherwise specified, is carried out in a conventional manner known in the prior art, such as welding, connection with fixing parts, etc.

[0059] Embodiment 1

[0060] As Figure 1 shown, it is a schematic diagram of the liquid-phase hydrogenation reactor for enhanced mass transfer in the liquid-phase hydrogenation of diesel. As shown in the figure, the liquid-phase hydrogenation reactor includes a reactor cylinder body 1. A liquid discharge port 6 is provided at the bottom of the reactor cylinder body 1. A liquid inlet 5 and a gas inlet 7 are provided on the side close to the bottom of the cylinder body 1. One end of the gas inlet 7 inside the cylinder body 1 is connected with a gas pre-distribution plate 4. Above the gas pre-distribution plate 4, there is a layered partition plate 2. The layered partition plate 2 is disc-shaped and is connected and fixed to the inner wall of the cylinder body 1 by means of its outer edge. A plurality of strong dispersion bubble generators 3 are fixedly arranged through the bottom of the layered partition plate 2. Preferably, the distance between the strong dispersion bubble generator 3 and the gas pre-distribution plate 4 is 0.5 - 2 m.

[0061] Further, the end of the gas inlet 7 inside the cylinder body 1 is bent upward, and the gas pre-distribution plate 4 is horizontally arranged at the end of the gas inlet 7. As Figure 2 shown, the gas pre-distribution plate 4 includes a disc-shaped chamber 41 and a plurality of distribution pipes 42 uniformly distributed along the outer periphery of the disc-shaped chamber 41. A plurality of exhaust holes 43 are opened on the distribution pipes 42. Although Figure 2 the number of the shown distribution pipes 42 is 6, those skilled in the art can easily understand that the number of the distribution pipes 42 can be adjusted according to the actual working conditions and the size of the reactor, and there is no special limitation on its number.

[0062] Further, the diameter of the exhaust hole 43 depends on the diameter of the reactor, specifically as follows:

[0063] When the diameter of the reactor is less than 1 m, the size of the exhaust hole 43 is 1.5 - 2 mm;

[0064] When the diameter of the reactor is 1 - 2 m, the size of the exhaust hole 43 is 2 - 3 mm;

[0065] When the diameter of the reactor is 2 - 4 m, the size of the exhaust hole 43 is 2.5 - 4 mm;

[0066] When the diameter of the reactor is greater than 2 m, the size of the exhaust hole 43 is 4 - 6 mm.

[0067] Preferably, the spacing between the exhaust holes 43 is controlled at 0.1 m.

[0068] Furthermore, as shown in Figure 3 Figure, the strong dispersion bubble generator 3 is cylindrical, its top penetrates through the layered partition plate 2, and through holes (not shown in the figure) are provided at corresponding positions of the layered partition plate 2. The strong dispersion bubble generator 3 is fixed in the through hole at the bottom of the layered partition plate 2 by means of the outer wall of its cylindrical top.

[0069] Inside the strong dispersion bubble generator 3, an axial guide vane liquid inlet 36, a gas - liquid mixing chamber 37, a toothed gas - liquid outlet 31, and a conical outlet 38 are successively arranged from bottom to top. A number of willow - leaf - type fluid guides 39 are provided on the conical outlet 38 ( Figure 5 ), and an air inlet hole 32 is provided on the upper side of the gas - liquid mixing chamber 37. An air inlet pipe 33 is connected to the inner side of the air inlet hole 32. The air inlet pipe 33 extends to the center position of the mixing chamber 37 and then bends downward, and a gas flow guide cone 34 is connected to the end. One or more gas outlets 35 inside the chamber are provided at the end of the gas flow guide cone 34, and the gas outlets 35 inside the chamber are adjacent to the axial guide vane liquid inlet 36.

[0070] As shown in Figure 4 Figure, the number of the strong dispersion bubble generators 3 is 4, and they are evenly distributed at the bottom of the layered partition plate 2. Those skilled in the art can easily understand that the number of the strong dispersion bubble generators 3 can be appropriately adjusted according to actual needs, such as the size of the reactor, etc.

[0071] Furthermore, the axial guide vane liquid inlet 36 is in the configuration of a spiral - rising blade, and the outer edge of the blade is fixedly connected to the inner wall of the bottom of the strong dispersion bubble generator 3 to facilitate the liquid entering the gas - liquid mixing chamber 37 to form a swirl. Preferably, the thickness of the blade of the axial guide vane liquid inlet 36 is 2 mm, and the pitch between the spiral blades is 7 mm.

[0072] Furthermore, the included angle γ between the two hypotenuses of the cross - section of the gas flow guide cone 34 is 35° - 45° to facilitate fully strengthening the swirl inside the chamber.

[0073] Furthermore, the number of the gas outlets 35 inside the chamber provided at the end of the gas flow guide cone 34 depends on the gas flow rate, specifically as follows:

[0074] When the gas flow rate is greater than 5 L / min, each gas flow guiding cone 34 adopts 4 gas outlets 35 inside the cavity;

[0075] When the gas flow rate is between 2 and 5 L / min, each gas flow guiding cone 34 adopts 2 gas outlets 35 inside the cavity;

[0076] When the gas flow rate is less than 2 L / min, each gas flow guiding cone 34 adopts 1 gas outlet 35 inside the cavity.

[0077] Furthermore, as Figure 5 shown, the toothed gas-liquid outlet 31 is formed by setting the side wall of the outlet into a serrated shape to facilitate the dispersion of bubbles. The willow-leaf-shaped fluid guide 39 is evenly distributed in a divergent shape on the conical outlet 38. As Figures 6 - 8 shown, the willow-leaf-shaped fluid guide 39 has a willow-leaf configuration with a larger middle part and a reduced size from the middle to both ends, and the bottom surface is a plane to facilitate fixation with the conical outlet 38; as Figure 9 shown, the willow-leaf-shaped fluid guides 39 evenly distributed in a divergent shape on the conical outlet 38 present a Venturi form. From the toothed gas-liquid outlet 31 outwards, a gradually reducing section and a gradually expanding section are successively formed between two adjacent willow-leaf-shaped fluid guides 39. Preferably, the angle β of the gradually reducing section is 30° and the angle α of the gradually expanding section is 10°.

[0078] The working principle of the liquid-phase hydrogenation reactor for intensifying mass transfer of the present invention is as follows:

[0079] 1) The liquid-phase raw material enters the bottom of the reactor from the liquid inlet 5 at the bottom of the reactor. The premixed hydrogen enters the reactor through the gas inlet 7 and passes through the exhaust holes 43 of the gas pre-distribution plate 4 into the bottom of the reactor, forming a gas-liquid mixture with the liquid-phase raw material to complete the pre-dissolution of hydrogen in diesel;

[0080] 2) The gas-liquid mixture at the bottom of the reactor forms a certain hydrogen region below the layered partition plate 4. At this time, the gas-liquid two-phase jointly enters the strong dispersed bubble generator 3. Hydrogen enters the strong dispersed bubble generator 3 from the air intake holes 32, and reaches the gas-liquid mixing cavity 37 from the gas outlet 35 inside the cavity through the air intake pipe 33; at the same time, the liquid below enters the gas-liquid mixing cavity 37 through the axial guide vane liquid inlet 36. The configuration of the spiral rising blades of the axial guide vane liquid inlet 36 causes the gas entering the mixing cavity 37 to form a swirl, which undergoes swirl shear with the gas entering the mixing cavity 37. Part of the hydrogen is supersaturated and dissolved during the swirl process, and part of the hydrogen is sheared by the liquid into fine bubbles and a small amount of large bubbles;

[0081] 3) The fine bubble and liquid mixture pass through the toothed gas-liquid outlet 31 and enter the upper part of the reactor from the conical outlet 38 under the guidance of the willow-leaf-shaped fluid guide 39. The fine bubbles and a small amount of large bubbles rise as the liquid phase rises to carry out the liquid-phase hydrogenation reaction.

[0082] Further, there is a relational expression between the bubble diameter and the cumulative number of bubbles inside the reactor:

[0083] That is, the bubble fractal dimension law, where:

[0084] The left side of the equal sign represents the number of bubbles with a size greater than or equal to λ, where λ max represents the maximum bubble size in the reactor, and D f is the fractal dimension.

[0085] Further, for the fractal bubbles generated in step 3), for reactors with different equivalent diameters of catalyst particles, the number of bubbles with different size scales is different, and thus the fractal dimension is different. For a reactor with an equivalent diameter of catalyst particles of 1 - 2 mm, the fractal dimension is 0.7 - 1.6; for a reactor with an equivalent diameter of catalyst particles of 2 - 5 mm, the fractal dimension is 1.6 - 2.9.

[0086] Example 2

[0087] As Figure 10 shown, it is a liquid-phase hydrogenation reaction device using the liquid-phase hydrogenation reactor for enhanced mass transfer in Example 1, that is, the reactor in Example 1 is used for liquid-phase hydrogenation reaction. As shown in the figure, the liquid-phase hydrogenation reaction device includes: a heating furnace F101, a hydrofining reactor R101, a hot high-pressure stripping separator C101, a hot low-pressure separator C103, an air condenser, and a cold low-pressure separator C102, where the hydrofining reactor R101 uses the liquid-phase hydrogenation reactor for enhanced mass transfer described in Example 1.

[0088] The corresponding reaction process includes the following steps:

[0089] Step 1: The raw material liquid-phase diesel and hydrogen enter the heating furnace through a raw material pump P101 and a hydrogen compressor K101 respectively for heating, and then enter the hydrofining reactor R101. Inside the hydrofining reactor R101, after passing through the gas pre-distribution plate 4, hydrogen is pre-dissolved in diesel. A part of the remaining hydrogen is further dissolved in the strong dispersion bubble generator 3, and a part generates fractal bubbles, which are evenly distributed through the bubble stratification partition plate 2 and then enter the catalyst bed layer at the upper part of the reactor. As Figure 11 shown in the mass transfer schematic diagram, a large number of fractal bubbles attach to the catalyst surface to form a huge contact area, and the liquid phase follows the gas phase for further dissolution, and finally the hydrogenation product is discharged from the top of the reactor;

[0090] Step 2: The hydrogenation product coming out of the hydrofining reactor directly enters the hot high-pressure stripping separator C101 for gas-liquid separation. The reaction-generated gas coming out of the top of the hot high-pressure stripping separator C101 is cooled by an air cooler and then enters the cold low-pressure separator C102 for gas-liquid separation therein; the oil phase coming out of the bottom of the hot high-pressure stripping separator C101 is divided into two paths. One path is boosted in pressure by the reaction product circulation pump P102 and then returns to the reactor R101 again; the other path is cooled to 250 °C and then enters the hot low-pressure separator C103 for further flashing;

[0091] Step 3: The oil phases separated from the cold low-pressure separator C102 and the hot low-pressure separator C103 are preheated to 250 °C together and then enter the product fractionating column, and the gas phases are recycled and utilized.

[0092] The liquid-phase hydrogenation reaction process of this embodiment is applicable to diesel hydrogenation reactions with a reaction pressure of 8 - 12 MPa, a reaction temperature of 350 - 420 °C, a liquid hourly space velocity of 1.5 - 2.5 h -1 , a recycle ratio of 1.2:1 - 3:1, and a hydrogen-oil volume ratio of 1:1 - 1:20. The reaction conditions can be determined and optimized according to the raw material properties. For example, when a mixture of straight-run diesel and coker diesel is selected, with a sulfur content of 6300 μg / g, a nitrogen content of 170 μg / g, and a cetane index of 69, the total pressure at the reactor inlet is 10 MPa, the space velocity is 2.0 h -1 , the reaction temperature is 352 °C, and the gas-liquid ratio is 1:5.

[0093] Further, in Step 1, the raw material diesel is coker diesel, catalytic diesel, straight-run diesel or a mixture thereof. The sulfur content of catalytic diesel is 3000 - 5000 μg / g, the nitrogen content is 600 - 1000 μg / g, and the cetane index is generally not more than 30; the sulfur content of coker diesel is 6000 - 9000 μg / g, the nitrogen content is 800 - 1200 μg / g, and the cetane index is 40 - 60; the sulfur content of straight-run diesel is 1000 - 1500 μg / g, the nitrogen content is 30 - 200 μg / g, and the cetane index is 60 - 70.

[0094] Further, in Step 1, the liquid-phase hydrofining reactor uses a strong dispersion bubble generator to simultaneously generate a small amount of large bubbles and a large amount of fine bubbles. After entering the catalyst bed layer, the large and small bubbles completely cover the surface of the catalyst particles. The equivalent diameter of the catalyst for diesel hydrogenation is 1 - 5 mm, the diameter of the large bubbles is 2 - 5 times the equivalent diameter of the catalyst, the diameter of the small bubbles is 0.02 - 0.1 times the equivalent diameter of the catalyst. The small amount of large bubbles provides enhanced turbulence for the fine bubbles, and the small bubbles provide a large gas-liquid contact area, reduce the rising speed, and improve the mass transfer rate.

[0095] Further, in Step 1, under the reaction conditions, the equilibrium solubility of hydrogen is 0.3 - 0.4 mol·kg -1 , the equilibrium solubility of hydrogen increases with the increase of pressure. The liquid-phase diesel generates a swirl in the strong dispersion bubble generator, forming a pressure gradient field in the swirl chamber, enhancing the local pressure in the chamber. When the pressure in the chamber reaches 15 MPa, the equilibrium solubility of hydrogen reaches 0.6 mol·kg -1 , making the liquid phase reach local hydrogen supersaturated dissolution.

[0096] Further, in Step 1, the rising speed of the microbubbles is 0.05 - 0.1 m / s, and the liquid flow rate is 0.1 - 0.2 m / s. In the reactor, the liquid phase rises following the gas phase. As Figure 12 shown, the liquid velocity is relatively high, and the liquid droplets are likely to enter the interior of the small bubbles. Due to the high internal pressure and surface tension of the small bubbles, hydrogen penetrates into the liquid phase, resulting in liquid supersaturation and enabling hydrogen supersaturated dissolution.

[0097] Further, in Step 2, the temperature of the thermal high-pressure gas-liquid separator is the same as that of the reactor, which is 320 - 370 °C.

[0098] Further, in Step 3, the gas in the cold low-pressure gas-liquid separator is recycled, and part of the hydrogen can be recycled.

[0099] Example 3

[0100] A certain petrochemical plant uses the liquid-phase hydrogenation reactor with enhanced mass transfer of Example 1, and compares the liquid-phase hydrogenation reaction method of Example 2 with the original device. The properties of the raw material liquid-phase diesel in this example are shown in Table 1, the reaction conditions of this example and the original device are shown in Table 2, and the product properties of this example and the original device are shown in Table 3.

[0101] Table 1. Properties of Liquid-Phase Diesel

[0102] Source Straight-run diesel + coker diesel Ratio 80 / 20 Fraction range / °C 180～365 <![CDATA[Density (20 °C) / (g·cm -3 )]]> 0.8254 <![CDATA[Sulfur / (μg·g -1 )]]> 6350 <![CDATA[Nitrogen / (μg·g -1 )]]> 180 Cetane index * 49

[0103] Table 2. Reaction Conditions of This Example and the Original Device

[0104]

[0105]

[0106] Table 3. Product Properties of the Example and the Original Device

[0107] Item This example Original unit <![CDATA[Density (20 °C) / (g·cm -3 )]]> 0.830 0.831 <![CDATA[Sulfur / (μg·g -1 )]]> 35 46 <![CDATA[Nitrogen / (μg·g -1 )]]> 14 22 Cetane index * 58 54.5

[0108] From the data analysis in Table 3, it can be seen that the desulfurization and denitrification efficiency of this example is improved compared with the original device, and the cetane index is also improved.

[0109] Example 4

[0110] A certain petrochemical plant uses the liquid-phase hydrogenation reactor with enhanced mass transfer in Example 1, and compares the liquid-phase hydrogenation reaction method in Example 2 with the original device. The properties of the raw material liquid-phase diesel in this example are shown in Table 4, the product requirements are shown in Table 5, the reaction conditions of this example and the original device are shown in Table 6, and the energy consumption of this example and the original device are shown in Table 7.

[0111] Table 4. Properties of Liquid-phase Diesel

[0112] Source Straight-run diesel Fraction range / °C 171～364 <![CDATA[Density (20 °C) / (g·cm -3 )]]> 0.8512 <![CDATA[Sulfur / (μg·g -1 )]]> 3400 <![CDATA[Nitrogen / (μg·g -1 )]]> 100 Cetane index * 48

[0113] Table 5. Product Requirements

[0114] <![CDATA[Sulfur / (μg·g -1 )]]> ≤40 <![CDATA[Nitrogen / (μg·g -1 )]]> ≤10 Cetane index * ≥55

[0115] Table 6. Reaction Conditions of This Example and the Original Device

[0116] Item Example 4 Original unit Total pressure at reactor inlet / MPa 9 9 Number of catalyst beds 3 3 Average reaction temperature / °C 352 352 Recycle ratio 1.5：1 1.5：1 Chemical hydrogen consumption / % 0.45 0.45 <![CDATA[Space velocity per hour -1 > 2.0 2.0

[0117] Table 7. Energy Consumption of This Example and the Original Device

[0118] Item Example 4 Original unit <![CDATA[Electricity / (kW·t -1 )]]> 15.25 18.27 <![CDATA[Circulating water / (t·t -1 )]]> 1.25 1.57 <![CDATA[Fuel gas / (Nm 3 ·t -1 )]]> 0.21 0.25 Condensate / (t·t-1) 0.0019 0.0023 <![CDATA[Unit energy consumption / (kg standard oil·t -1 )]]> 4.58 6.34 Engineering cost / billion yuan ～2.6 ～2.8

[0119] From the data analysis in Table 7, it can be seen that under the same product requirements, the energy consumption of this example is lower than that of the original device, and the unit energy consumption is reduced by 27%. Moreover, the engineering cost of using the liquid-phase hydrogenation reactor and reaction method is reduced by 0.2 billion yuan.

[0120] Example 5

[0121] The liquid-phase hydrogenation reactor and reaction method of the present invention are industrially applied in a 2.6 million tons / year diesel liquid-phase hydrogenation unit in Shijiazhuang. On the basis of ensuring the operation cycle of the pre-transformation device, the proportion of secondary oil blending can be increased to 30%; the secondary oil is mainly the crude diesel produced by the fluid catalytic cracking unit, which contains a large amount of unsaturated hydrocarbons and has a very high chemical reaction hydrogen consumption, usually more than 5 times that of straight-run diesel.

[0122] During the diesel hydrocracking process, the hydrogen replenishment rate is greatly increased, and it has very good hydroconversion and anti-coking performance. The hydrogen partial pressure is reduced from 12 MPa to 8 MPa, the reaction conversion rate is increased by two percentage points, and the operation cycle of the diesel hydrogenation reaction device is extended.

Claims

1. A liquid-phase hydrogenation reactor for enhancing mass transfer, characterized in that, The liquid-phase hydrogenation reactor includes a reactor cylinder body. A liquid discharge port is provided at the bottom of the reactor cylinder body. A liquid inlet and a gas inlet are provided on the side surface near the bottom of the cylinder body. One end of the gas inlet located inside the cylinder body is connected with a gas pre-distribution plate. A layered partition plate is provided above the gas pre-distribution plate. A number of strong dispersion bubble generators are fixedly arranged through the bottom of the layered partition plate. The strong dispersion bubble generator is cylindrical. Its top penetrates into the layered partition plate. Through holes are opened at corresponding positions of the layered partition plate. The strong dispersion bubble generator is fixed in the through holes at the bottom of the layered partition plate by means of the outer wall of its cylindrical top. Inside the strong dispersion bubble generator, an axial guide vane liquid inlet, a gas-liquid mixing chamber, a toothed gas-liquid outlet and a conical outlet are successively arranged from bottom to top. A number of willow-leaf-shaped fluid guides are arranged on the conical outlet. And an air inlet hole is provided on the upper side surface of the gas-liquid mixing chamber. An air inlet pipe is connected to the inner side of the air inlet hole. The air inlet pipe extends to the center position of the mixing chamber and then bends downward, and a gas guide cone is connected at the end. One or more gas outlets inside the cavity are opened at the end of the gas guide cone. The gas outlets inside the cavity are adjacent to the axial guide vane liquid inlet. The axial guide vane liquid inlet is configured as a spiral rising blade. The outer edge of the blade is fixedly connected to the inner wall of the bottom of the strong dispersion bubble generator to facilitate the liquid entering the gas-liquid mixing chamber to form a swirl. The included angle γ between the two hypotenuses of the cross-section of the gas guide cone is 35°-45° to facilitate fully strengthening the swirl inside the cavity. The willow-leaf-shaped fluid guide has a willow-leaf shape with a larger middle part and tapering from the middle to both ends, and the bottom surface is flat to facilitate fixing with the conical outlet.

2. The liquid-phase hydrogenation reactor according to claim 1, characterized in that, The distance between the strong dispersion bubble generator and the gas pre-distribution plate is 0.5-2 m.

3. The liquid-phase hydrogenation reactor according to claim 1, characterized in that, The end of the gas inlet located inside the cylinder body bends upward. The gas pre-distribution plate is horizontally arranged at the end of the gas inlet. The gas pre-distribution plate includes a disc-shaped chamber and a number of distribution pipes evenly distributed along the outer circumference of the disc-shaped chamber. A number of exhaust holes are opened on the distribution pipes.

4. The liquid-phase hydrogenation reactor according to claim 3, characterized in that, The diameter of the exhaust holes depends on the diameter of the reactor, specifically as follows: When the diameter of the reactor is less than 1 m, the size of the exhaust hole 43 is 1.5-2 mm. When the diameter of the reactor is 1-2 m, the size of the exhaust hole 43 is 2-3 mm. When the diameter of the reactor is 2-4 m, the size of the exhaust hole 43 is 2.5-4 mm. When the diameter of the reactor is greater than 2 m, the size of the exhaust hole 43 is 4-6 mm.

5. The liquid-phase hydrogenation reactor according to claim 1, characterized in that, The number of gas outlets inside the cavity provided at the end of the gas guide cone depends on the gas flow rate, specifically as follows: When the gas flow rate is greater than 5 L / min, each gas guide cone uses 4 gas outlets inside the cavity. When the gas flow rate is 2-5 L / min, each gas guide cone uses 2 gas outlets inside the cavity. When the gas flow rate is less than 2 L / min, each gas guide cone uses 1 gas outlet inside the cavity.

6. The liquid-phase hydrogenation reactor according to claim 1, characterized in that, The toothed gas-liquid outlet is formed by setting the side wall of the outlet into a serrated shape to facilitate dispersing bubbles.

7. The liquid-phase hydrogenation reactor according to claim 1, characterized in that, The willow-leaf-shaped fluid guide body is uniformly distributed in a divergent shape on the conical outlet, presenting the form of a Venturi. From the toothed gas-liquid outlet outwards, a converging section and a diverging section are sequentially formed between two adjacent willow-leaf-shaped fluid guide bodies.

8. The liquid-phase hydrogenation reactor according to claim 7, characterized in that, The angle β of the converging section is 30°, and the angle α of the diverging section is 10°.

9. A liquid-phase hydrogenation reaction process, characterized in that, The reaction process uses the liquid-phase hydrogenation reactor described in any one of claims 1 to 8.

10. The liquid-phase hydrogenation reaction process according to claim 9, characterized in that, It includes the following steps: Step 1: The raw material liquid-phase diesel and hydrogen enter a heating furnace through a raw material pump and a hydrogen compressor respectively for heating, and then enter a hydrofining reactor. In the hydrofining reactor, after passing through a gas pre-distribution plate, hydrogen is pre-dissolved in the diesel. A part of the remaining hydrogen is further dissolved in a strong dispersion bubble generator, and a part generates fractal bubbles. After being evenly distributed through a bubble stratification partition plate, it enters the catalyst bed layer above. A large number of fractal bubbles adhere to the catalyst surface to form a huge contact area. The liquid phase follows the gas phase for further dissolution, and finally a hydrogenation product is discharged from the top of the reactor. Step 2: The hydrogenation product coming out of the hydrofining reactor directly enters a hot high-pressure stripping separator for gas-liquid separation. The reaction-generated gas coming out of the top of the hot high-pressure stripping separator is cooled by an air cooler and then enters a cold low-pressure separator for gas-liquid separation. The oil phase coming out of the bottom of the hot high-pressure stripping separator is divided into two paths. One path is boosted by a reaction product circulation pump and then returns to the reactor again; the other path is cooled to 250 °C and then enters a hot low-pressure separator for further flashing. Step 3: The oil phases separated from the cold low-pressure separator and the hot low-pressure separator are preheated to 250 °C together and then enter a product fractionating tower, and the gas phase is recycled.

11. The liquid-phase hydrogenation reaction process according to claim 10, characterized in that, In Step 1, the raw material diesel is coking diesel, catalytic diesel, straight-run diesel or a mixture thereof, wherein: The sulfur content of the catalytic diesel is 3000 - 5000 μg / g, the nitrogen content is 600 - 1000 μg / g, and the cetane index is not more than 30. The sulfur content of the coking diesel is 6000 - 9000 μg / g, the nitrogen content is 800 - 1200 μg / g, and the cetane index is 40 - 60. The sulfur content of the straight-run diesel is 1000 - 1500 μg / g, the nitrogen content is 30 - 200 μg / g, and the cetane index is 60 - 70.

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