Two-stage evaporator for tar distillation plant and distillation process method

Abstract

The application relates to the technical field of chemical equipment, and provides a two-stage evaporator of a tar distillation device and a distillation process method.The two-stage evaporator comprises a shell, an overflow plate assembly, the overflow plate assembly is sequentially and alternately provided with a first overflow plate, a second overflow plate, a third overflow plate and a fourth overflow plate from bottom to top along the inner wall of the shell to form an S-shaped rising airflow path, wherein the first overflow plate is a meniscus structure and comprises an outer arc segment fixedly connected with the inner wall of the shell and an inner arc segment recessed towards the outer arc segment, a plurality of rectangular overflow weirs are arranged on the inner arc segment and uniformly distributed along the arc line direction of the inner arc segment, the second overflow plate, the third overflow plate and the fourth overflow plate are all semicircular structures and comprise a circular arc segment fixedly connected with the inner wall of the shell and a straight line segment away from the inner wall of the shell, and a plurality of streamline overflow weirs are arranged on the straight line segment and uniformly distributed along the length direction of the straight line segment.The application solves the problems of serious coking, low separation efficiency and short operation cycle of the traditional equipment.

Description

Technical Field

[0001] This application relates to the field of chemical equipment technology, and more specifically, to a two-stage evaporator and distillation process method for a tar distillation apparatus. Background Technology

[0002] Currently, the traditional two-stage evaporators widely used in the industry suffer from severe coking, short operating cycles, and frequent maintenance. The root cause of this problem lies primarily in the unreasonable design of their internal overflow plate assembly structure. Traditional structures often lead to dead zones and liquid phase stagnation when tar and heavy components flow within the equipment, causing materials to remain in high-temperature zones for extended periods, providing conditions for thermal polymerization reactions and thus exacerbating the formation and deposition of coke. Continuous coking triggers a chain reaction of problems: first, coke slag clogs the tray channels or downcomers, causing abnormally high internal pressure drops and disrupting the distillation balance; second, it significantly reduces the effective gas-liquid contact area, decreasing the removal efficiency of light components and resulting in excessive light oil content in the final asphalt product; third, the blockage further worsens the material flow, creating a vicious cycle of "coking, blockage, and more severe coking." This forces production companies to frequently shut down for cleaning and maintenance, significantly increasing maintenance costs and severely limiting the continuous operation capacity and overall economic efficiency of the unit. Summary of the Invention

[0003] This application aims to at least address the technical problems of traditional two-stage evaporators, such as severe coking, short operating cycles, and frequent maintenance.

[0004] To solve the above-mentioned technical problems, this application is implemented as follows: In a first aspect, this application provides a two-stage evaporator for a tar distillation apparatus, comprising: a shell, wherein the shell is provided from top to bottom with a light component outlet, a reflux liquid inlet, a tar inlet, a stripping inlet, and a heavy component outlet; an overflow plate assembly, comprising multiple overflow plates disposed inside the shell and above the tar inlet, wherein the overflow plate assembly is provided with a first overflow plate, a second overflow plate, a third overflow plate, and a fourth overflow plate alternately staggered from bottom to top along the inner wall of the shell to form an S-shaped upward airflow path; and a multi-layer distillation tray, wherein... Located inside the shell, above the multi-layer overflow plate assembly and below the reflux inlet; wherein, the first overflow plate is a crescent-shaped structure, including an outer arc segment fixedly connected to the inner wall of the shell and an inner arc segment recessed towards the outer arc segment, and multiple rectangular overflow weirs evenly distributed along its arc direction are provided on the inner arc segment; the second, third, and fourth overflow plates are all semi-circular structures, including a circular arc segment fixedly connected to the inner wall of the shell and a straight segment away from the inner wall of the shell, and multiple streamlined overflow weirs evenly distributed along their length direction are provided on the straight segment.

[0005] This application provides a two-stage evaporator for a tar distillation apparatus. By optimizing the structure of the overflow plate assembly, it solves the problems of severe coking, low separation efficiency, and short operating cycle in traditional equipment. This two-stage evaporator adopts a composite structure combining a lower multi-layer overflow plate assembly with an upper multi-layer distillation tray. In the overflow anti-coking and initial separation scenario, the multi-layer overflow plate assembly is arranged alternately and staggered along the inner wall of the shell, forming an S-shaped upward airflow path. Specifically, the first overflow plate adopts a unique crescent-shaped structure, with its outer and inner arc sections working together to guide the liquid phase into a "ring-like diffusion towards the center" flow pattern, eliminating dead zones of liquid accumulation in the center of the plate. Multiple rectangular overflow weirs distributed on the inner arc section uniformly divide the liquid phase, significantly increasing the initial mass transfer area. The second to fourth overflow plates adopt a semi-circular structure with streamlined overflow weirs on their straight sections. The curved surface of these weirs facing the airflow has a smooth, convex structure, guiding the liquid phase to form a stable laminar flow, greatly reducing turbulence and localized stagnation. Combined with the specific tilt angle settings of each overflow plate layer, this achieves precise control of the liquid phase flow rate and residence time. These designs work synergistically from multiple aspects, including flow field uniformity, reduction of high-temperature stagnation, and optimization of gas-liquid contact, effectively suppressing the formation and deposition of coke slag at its source. In fine separation scenarios, the multi-layer distillation trays located above the overflow plate deeply purify the light components that have undergone preliminary separation, achieving comprehensive benefits such as extending the production cycle, reducing maintenance costs, and improving product purity.

[0006] Secondly, this application proposes a distillation process method for a two-stage evaporator in a tar distillation apparatus, applicable to the two-stage evaporator as described in the above technical solution. The distillation process method includes the following steps: S1, feeding tar material at a temperature of 340℃~400℃ and a pressure of 0.5MPa~1.2MPa tangentially into the shell through the tar inlet; S2, introducing stripping medium at a temperature not lower than 360℃ into the stripping inlet, and controlling the system pressure in the two-stage evaporator to be maintained at 0.01MPa~0.082MPa; S3, adjusting the tar... S4. Adjust the inclination angle of the first overflow plate to make the flow velocity of the tar material on the surface of the first overflow plate 0.15m / s~0.25m / s and the residence time 2s~5s; S5. Adjust the inclination angle of the second to fourth overflow plates to make the flow velocity of the heavy components on the second to fourth overflow plates 0.1m / s~0.3m / s and the residence time 2s~5s; S6. Control the material temperature at the outlet of the heavy components to 330℃~375℃ and discharge the heavy components; S7. Collect the light components from the outlet of the light components.

[0007] The distillation process method provided in this application, being used in the two-stage evaporator of the tar distillation apparatus described above, thus possesses all the beneficial effects of the two-stage evaporator of the tar distillation apparatus, which will not be elaborated further here.

[0008] Additional aspects and advantages of this application will become apparent in the following description or may be learned by practice of this application. Attached Figure Description

[0009] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 This is a schematic diagram of the structure of a two-stage evaporator according to an embodiment of this application; Figure 2 for Figure 1 A schematic diagram of the structure of the first overflow plate in the two-stage evaporator of the embodiment shown; Figure 3 for Figure 1 A schematic diagram of the structure of the second overflow plate in the two-stage evaporator of the embodiment shown; Figure 4 for Figure 2 A schematic diagram of the rectangular overflow weir in the first overflow plate of the embodiment shown; Figure 5 for Figure 3 A schematic diagram of the streamlined overflow weir in the second overflow plate of the embodiment shown; Figure 6 This is a flowchart of a distillation process method according to an embodiment of this application.

[0010] in, Figures 1 to 6 The correspondence between the reference numerals and component names in the attached drawings is as follows: 100 Two-stage evaporator, 1 shell, 11 light component outlet, 12 reflux inlet, 13 tar inlet, 14 stripping inlet, 15 heavy component outlet, 16 airflow distributor, 2 overflow plate assembly, 21 first overflow plate, 211 outer arc segment, 212 inner arc segment, 213 rectangular overflow weir, 22 second overflow plate, 23 third overflow plate, 24 fourth overflow plate, 241 circular arc segment, 242 straight segment, 243 streamlined overflow weir, 25 splash guard, 26 splash flange, 3 multi-layer distillation column tray. Detailed Implementation

[0011] To better understand the above-mentioned objectives, features, and advantages of this application, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0012] Many specific details are set forth in the following description in order to provide a full understanding of this application. However, this application may also be implemented in other ways different from those described herein. Therefore, the scope of protection of this application is not limited to the specific embodiments disclosed below.

[0013] The following reference Figures 1 to 6 This application describes the distillation process of a two-stage evaporator in a tar distillation apparatus and a distillation process of a two-stage evaporator in a tar distillation apparatus, according to some embodiments of the present application.

[0014] According to the first aspect of this application, Figure 1 , Figure 2 and Figure 3 As shown, an embodiment of this application provides a two-stage evaporator 100 for a tar distillation apparatus, comprising: a shell 1, wherein the shell 1 is provided with a light component outlet 11, a reflux liquid inlet 12, a tar inlet 13, a stripping inlet 14, and a heavy component outlet 15 from top to bottom; an overflow plate assembly 2, comprising multiple overflow plates disposed inside the shell 1 and above the tar inlet 13, wherein the overflow plate assembly 2 is provided with a first overflow plate 21, a second overflow plate 22, a third overflow plate 23, and a fourth overflow plate 24 alternately and staggeredly disposed from bottom to top along the inner wall of the shell 1 to form an S-shaped upward airflow path; and a multi-layer distillation tray 3 disposed on the shell 1. Inside, and located above the multi-layer overflow plate assembly 2 and below the return liquid inlet 12; wherein, the first overflow plate 21 has a crescent-shaped structure, including an outer arc segment 211 fixedly connected to the inner wall of the shell 1 and an inner arc segment 212 recessed toward the outer arc segment 211, and multiple rectangular overflow weirs 213 evenly distributed along its arc direction are provided on the inner arc segment 212; the second overflow plate 22, the third overflow plate 23 and the fourth overflow plate 24 are all semi-circular structures, including an arc segment 241 fixedly connected to the inner wall of the shell 1 and a straight segment 242 away from the inner wall of the shell 1, and multiple streamlined overflow weirs 243 evenly distributed along its length direction are provided on the straight segment 242.

[0015] Specifically, such as Figure 1 , Figure 2 and Figure 3As shown, the alternating staggered arrangement of multiple overflow plates in the overflow plate assembly 2 forces the rising gas phase to meander along a preset S-shaped path. This not only prolongs the gas-liquid contact path and time but also makes the gas phase distribution more uniform, avoiding the problems of local short circuits or uneven airflow distribution caused by traditional direct-flow rising. Specifically, the first overflow plate 21 adopts a crescent-shaped structure. Its outer arc segment 211 guides the liquid phase to initially diffuse along the shell wall, while the inwardly concave inner arc segment 212 generates a centripetal guiding effect, jointly achieving a combined flow state of annular diffusion and central convergence of the liquid phase on the plate surface. This flow state effectively eliminates the flow dead zone and liquid accumulation at the center of the plate surface, reducing the risk of local overheating and coking due to liquid phase retention. Multiple rectangular overflow weirs 213 set on the inner arc segment 212 divide the converged liquid phase into multiple uniform fine streams, greatly increasing the contact surface area between the gas and liquid phases, thereby improving the initial removal efficiency of light components. For the second overflow plate 22 to the fourth overflow plate 24, the semi-circular arc segment 241 adheres to the shell wall, providing a stable wall-attached flow basis for the liquid phase, while the straight segment 242 defines the flow boundary of the liquid phase. The streamlined overflow weir 243 set on the straight segment 242 has a smooth, convex arc-shaped surface facing the airflow, which can guide the liquid phase flowing through the weir to transition from turbulent flow to a more stable laminar flow state, minimizing droplet splashing, mist entrainment, and material retention at the weir opening caused by violent flow disturbances or impacts, further suppressing the tendency of high-temperature coking. Among them, the second overflow plate 22, the third overflow plate 23, and the fourth overflow plate 24 are overflow plates with the same shape. The diameter of the shell 1 refers to the inner diameter of the shell 1, and the radius of the shell 1 refers to the radius of the inner diameter of the shell 1, that is, the inner radius of the shell 1.

[0016] Compared with existing technologies, the two-stage evaporator 100 provided in this application has the following advantages: The two-stage evaporator 100 adopts a composite separation structure of a lower multi-layer overflow plate assembly 2 combined with an upper multi-layer distillation tray 3. Compared with the traditional full tray design, the overflow plate assembly 2 can reduce turbulent dead zones and liquid phase retention. Combined with the tangential feed design of the shell 1 and the uniform distribution of stripping medium, it optimizes the flow field and temperature field. This synergistic design effectively reduces coking at the bottom of the column and blockage of the distillation tray, extends the production cycle, reduces the number of maintenance operations, and improves operating efficiency and equipment safety. Secondly, the first overflow plate 21 adopts a crescent-shaped structure, combined with a gradient slope and a rectangular overflow weir 213 of the inner arc section 212, to guide the liquid phase to form a "ring diffusion + central convergence" flow pattern, achieving uniform spreading, eliminating central retention, and reducing the risk of local high-temperature coking; at the same time, it increases the gas-liquid contact area, fully removes residual light components in the liquid phase, and improves the initial removal efficiency. Third, the second overflow plate 22, the third overflow plate 23, and the fourth overflow plate 24 adopt a large semi-circular structure in conjunction with a streamlined overflow weir 243. Utilizing the inclined layout of the overflow plates and the curved surface of the overflow weir, the liquid phase achieves stable laminar flow, avoiding turbulence and liquid accumulation, and shortening the high-temperature residence time. The laminar liquid film and the upward-flowing gas phase efficiently transfer mass in opposite directions, enhancing the deep removal of light components and improving separation accuracy. Fourth, the staggered arrangement of multiple overflow plates ensures that the asphalt overflowing from the upper plate falls into the receiving area of ​​the lower plate, preventing asphalt leakage and ensuring continuous gas-liquid contact and separation stability. Fifth, the use of a two-stage evaporator 100 for tar distillation reduces tar viscosity, ensuring smooth flow, weakening the high-temperature polymerization conditions of asphalt, assisting in inhibiting coking, and improving mass transfer efficiency.

[0017] In practical applications, the shell 1 serves as the main support for the two-stage evaporator 100, forming a closed distillation space inside. Its core function is to provide a stable gas-liquid separation environment for tar distillation. From top to bottom, the shell 1 is provided with a light component outlet 11 and a reflux liquid inlet 12 at the top, a tar inlet 13 in the middle, a stripping inlet 14 at the bottom, and a heavy component outlet 15, which are used to separate the light and heavy components in the tar.

[0018] Specifically, the light component outlet 11 at the top is used to discharge the remaining mixed light component gas phase with a distillation temperature of 360°C or higher after final purification by the upper distillation tray. This gas phase includes anthracene oil, naphthalene oil, wash oil, light oil, water, and stripping medium that rises with the gas phase. After being discharged, this mixed gas phase needs to be completely separated from the water and stripping medium by a subsequent oil-water separator to ensure the purity of the light component product.

[0019] Specifically, the tar inlet 13 is located on the side wall of the shell 1 below the multi-layer overflow plate assembly 2. It is preferably designed with a tangential direction, that is, the center line of the feed channel of the tar inlet 13 is consistent with the circumferential tangential direction of the side wall of the shell 1, which can make the feed spread evenly along the inner wall of the shell 1 and optimize the feed distribution effect.

[0020] Specifically, stripping inlet 14 is used to introduce stripping medium, and heavy component outlet 15 is used to remove heavy components, such as pitch, from the tar.

[0021] Specifically, the bottom stripping inlet 14 is used to introduce stripping medium to reduce the partial pressure of oil and gas in the column, promote the full vaporization and separation of light and medium fractions in coal tar, and also play a role in stirring and preventing coking, as well as supplementing heat for the distillation process. This medium will rise with the light component vapor phase into the multi-layer rectification tray 3, and finally be discharged with the final mixed light component vapor phase at the top of the column. Combined with the subsequent oil-water separation process, the steam and light components can be completely separated without introducing impurities that affect the purity of the product. For example, during atmospheric distillation, the temperature of the stripping medium does not exceed 395°C; during vacuum distillation, the operating temperature can be further reduced to meet the low-temperature requirements of the vacuum process.

[0022] Specifically, a gas flow distributor 16 is provided at the stripping inlet 14 to ensure that the stripping medium is uniformly diffused along the cross-section of the shell 1, avoiding excessively high or low local medium concentrations, further improving gas-liquid contact efficiency, ensuring the removal effect of light components, and providing a uniform gas phase basis for subsequent multi-fraction separation of the distillation trays.

[0023] Specifically, the recombinant outlet 15 can be linked with the slag discharge assembly to ensure the smooth discharge of deposited coke slag and qualified recombinant liquid phase such as asphalt; wherein, the slag discharge assembly can be an automatic slag cleaning mechanism installed in the shell 1, which can discharge slag at regular intervals according to the amount of coke slag deposited, which is beneficial to extending the continuous operation cycle of the device.

[0024] Specifically, the shell 1 adopts a tower-shaped cylindrical structure, which can form a uniform flow field for the rising mixed light component gas phase, reduce the local liquid accumulation and high-temperature coking problems that may be caused by the asymmetric structure, and at the same time adapt to the precise alignment of the side stream distillate outlet and the distillation column tray level, ensuring the stability of gas-liquid separation and multi-fraction extraction.

[0025] Specifically, the shell 1 needs to withstand high temperatures of 350℃~450℃, with the highest temperature in the bottom area of ​​the tower. The temperature is lower than this range during vacuum distillation, as well as corrosion from acidic components in the tar. Corrosion-resistant and heat-resistant steel of this field can be selected as the material to ensure long-term stable operation of the equipment.

[0026] Specifically, the shell 1 is made of Q345R+Ni-based composite plate with a Ni-based alloy layer thickness of ≥3mm, which can specifically resist acidic media corrosion; the bottom wall thickness is ≥16mm to meet the requirements of high-temperature asphalt static pressure bearing, and the top wall thickness is ≥12mm to balance structural strength and economy.

[0027] Specifically, the diameter of shell 1, i.e., its inner diameter, is 1.6m to 2.0m, and its height is 4m to 6m. This size can accommodate the arrangement requirements of the multi-layer overflow plate assembly 2 and the multi-layer distillation tray 3, while balancing equipment manufacturing costs and separation efficiency. The multi-layer overflow plate assembly 2 is the core component for gas-liquid separation and anti-coking. It is located above the tar inlet 13 and below the multi-layer distillation tray 3. Along the inner wall of shell 1, from bottom to top, it is arranged as the first overflow plate 21, the second overflow plate 22, the third overflow plate 23, and the fourth overflow plate 24. Adjacent overflow plates are arranged in a circumferentially alternating staggered manner to form an S-shaped airflow channel. The specific arrangement is well known in the art. For example, the first and second layers are distributed left and right, and the third and fourth layers are distributed left and right, forming an alternating layout of left, right, left, right. This alternating staggered arrangement creates a highly efficient countercurrent separation path in which the heavy component liquid phase flows from top to bottom and the light component gas phase flows from bottom to top, meeting the requirements of gas-liquid mass transfer. The specific process is as follows: Superheated tar, such as anhydrous coal tar, enters tangentially from the middle of shell 1. Due to its high temperature, it rapidly flashes and separates into gas and liquid phases. The gas phase generated by flashing flows upward, while the remaining liquid phase falls downward to the bottom of the evaporator. Further, stripping medium is introduced into the stripping inlet 14 at the bottom of the evaporator to counter-currently contact the falling liquid phase, thereby further removing residual light components. These removed light components and the stripping medium form a secondary gas phase, which merges with the gas phase generated by flashing and flows upward together. The merged gas phase, including the flash gas phase and the stripping secondary gas phase, gradually decreases in temperature as it rises, flowing sequentially through the overflow liquid of each overflow plate for mass and heat transfer and gas-liquid separation. The gas phase continues to rise, while the liquid phase flows downward with the overflow liquid. After the gas phase flows through the fourth overflow plate, it enters the upper multi-layer distillation tray 3 for further fractionation. The liquid separated on the tray also flows downwards along the overflow plate layer by layer, and finally, together with the heavy component liquid phase after stripping at the bottom of the column, it is discharged through the heavy component outlet 15, while the high-purity light component gas phase after further separation is discharged through the light component outlet 11. Through this process of "flash evaporation initial separation, stripping further separation, overflow plate staged separation, and tray further separation", the multi-layer overflow plate assembly 2 forms a functional system of initial separation, fine separation, and droplet interception. It can not only fully remove light components to ensure separation efficiency, but also help reduce the residence time of the liquid phase in the high-temperature region and help suppress coking.

[0028] Specifically, each overflow plate is fixedly connected to the inner wall of the shell 1 by welding or flange, and the connection is rounded to reduce liquid phase retention; all overflow plates are made of heat-resistant and corrosion-resistant steel, such as ultra-low carbon austenitic stainless steel 00Cr17Ni14Mo2, and the surface is mechanically polished to reduce asphalt adhesion and inhibit coking.

[0029] Specifically, the welds connecting each overflow plate to the inner wall of the shell 1 adopt a full penetration structure, the weld surface is ground smooth, and the fillet radius is ≥5mm; the surface roughness Ra of the plate is ≤1.6μm, which is beneficial to optimizing the liquid flow characteristics. The overflow plates adopt a modular design and can be disassembled and replaced individually, reducing maintenance costs and downtime.

[0030] Specifically, the vertical spacing between two adjacent overflow plates is 20%-40% of the inner radius of shell 1, which can be adjusted according to the tar processing capacity. This spacing provides sufficient space for the liquid phase to flow from top to bottom, reducing liquid phase buildup on the walls, while also ensuring unobstructed flow of the light component gas phase from bottom to top, thus improving the gas-liquid contact effect.

[0031] Specifically, the spacing gradually increases from bottom to top, for example, by 5% to 10% of the radius of shell 1, to accommodate changes in the gas phase concentration of light components.

[0032] Specifically, each overflow plate has a splash guard 25 on its non-overflow side, i.e., the circumferential edge of the outer arc segment 211 and / or the circular arc segment 241. The splash guard 25 is arranged in the opposite direction to the overflow weir and is located at the edge of the plate body away from the overflow weir. The height of the splash guard 25 is 3% to 5% of the radius of the shell 1, which helps to reduce the entrainment of droplets caused by liquid phase splashing and ensure separation purity.

[0033] In this application, the first overflow plate 21 is the lowest layer of the multi-layer overflow plate assembly 2, located immediately above the tar inlet 13. Viewed from above, it is symmetrically distributed along the central axis with the second overflow plate 22, and is the first processing unit in the gas phase rising process. Its core function is to receive the liquid phase condensed during the gas phase rising process, achieving uniform diffusion of the liquid phase through structural design, and forming gas-liquid contact with the stripping / flash vapor phase rising from the bottom to further remove light components. After processing, the heavy component liquid phase is guided to the bottom of the shell 1, while the light component gas phase rises into the circumferentially misaligned upper plate for further processing.

[0034] In this application, the main body of the first overflow plate 21 adopts a crescent-shaped structure, including: an outer arc segment 211 adapted to the inner wall of the shell 1 and an inner arc segment 212 recessed towards the outer arc segment 211, the two forming a contour without dead angles through a smooth curve transition; the inner arc segment 212 is provided with an upwardly protruding rectangular overflow weir 213 evenly distributed along the arc, which is used to guide the liquid phase to overflow smoothly and enhance gas-liquid contact separation.

[0035] Specifically, the crescent-shaped structure enables the tar to form a composite flow pattern of "ring diffusion + central convergence". The specific process is as follows: the liquid phase formed by condensation during the rise of the gas phase flows to the first overflow plate 21. The outer arc segment 211 guides it to diffuse along the inner wall of the shell 1. Relying on the central concave structure of the inner arc segment 212, and with the gradient guiding slope of "gentle outside and steep inside", a centripetal guiding force is formed to push the liquid phase to converge towards the center, and finally spread into a uniform liquid film on the plate surface. The stripping medium introduced into the bottom of the shell 1 flows upward and forms a counter contact with the liquid film. The light components remaining in the liquid phase are rapidly vaporized and then enter the upper plate through the circumferential misalignment gap between adjacent layers. The heavy component liquid phase continues to converge towards the rectangular overflow weir 213 in the center under the action of centripetal guiding force.

[0036] Specifically, the distance between the midpoint of the line connecting the two endpoints of the crescent-shaped structure and the center of the shell 1 is set to 25%~30% of the radius of the shell 1, ensuring that the depth of the inner arc segment 212 is adapted to the liquid phase convergence requirements, thus ensuring that there is no liquid accumulation in the central area and improving the contact between the liquid phase and the rising gas phase.

[0037] Specifically, the diameter of the circle containing the inner arc segment 212 is 60% to 70% of the diameter of the shell 1. This ratio can balance the diffusion range and convergence efficiency of the liquid phase, so that the liquid phase neither adheres excessively to the wall nor is limited to the central area, thus ensuring the uniformity of the liquid film on the plate surface.

[0038] Specifically, the radius of the rounded corner at the transition between the outer arc segment 211 and the inner arc segment 212 of the crescent-shaped structure is ≥8mm, which helps to eliminate structural dead corners, reduce the retention of liquid phase in the transition area, and suppress coking.

[0039] In addition, compared with the traditional semi-circular structure, the crescent-shaped structure in the first overflow plate 21 has significant advantages in the treatment of gas-phase condensation liquid phase. The uniformity of the liquid phase film on the plate is improved by more than 40%, which helps to avoid insufficient removal of light components due to excessively thick local liquid film, or coking on the dry wall caused by excessively thin liquid film. The moderate concave design of the inner arc section 212 avoids liquid accumulation in the center and ensures the convergence effect. At the same time, the crescent-shaped surface can optimize the fluid flow characteristics and reduce the energy loss caused by the liquid phase impacting the plate.

[0040] Specifically, such as Figure 4 As shown, the rectangular overflow weirs 213 are densely arranged along the inner arc segment 212. The number and spacing can be dynamically adjusted according to the perimeter of the inner arc segment 212. Its core function is to divide the converged heavy component-dominated liquid phase into multiple uniform liquid streams, greatly increasing the gas-liquid contact area and extending the mass transfer time, thus helping to fully remove residual light components from the liquid phase.

[0041] Specifically, such as Figure 4As shown, the rectangular overflow weirs 213 consist of 28 to 38 weirs, with a width of 12 mm to 18 mm and an adjacent spacing of 35 mm to 45 mm. This increases the gas-liquid contact area by more than 25% compared to the traditional large-spacing arrangement, improving the initial removal efficiency of light components by 15% to 20%. The weir height of the rectangular overflow weirs 213 is 10 mm to 20 mm, which can maintain a stable liquid film thickness of 8 mm to 15 mm, balancing the removal efficiency of light components with the liquid phase flow velocity. The weir opening of the rectangular overflow weirs 213 is rounded by 5 mm to 10 mm, which can reduce the turbulent impact during liquid phase flow and reduce the risk of heavy component liquid phase retention and coking.

[0042] In addition, the arc trajectory of the inner arc segment 212 is highly consistent with the direction of liquid flow, which can guide the liquid phase to overflow smoothly along the weir opening and reduce the impact turbulence caused by the traditional straight weir being perpendicular to the flow direction; at the same time, the raised structure of the rectangular overflow weir 213 is conducive to maintaining a stable liquid layer on the plate, providing a reliable guarantee for the counter-current mass transfer between the liquid phase and the rising gas phase.

[0043] Specifically, the first overflow plate 21 is inclined downwards towards the overflow weir side of the inner arc section 212. All areas of the plate have the same inclination direction, pointing downwards towards the side where the overflow weir is located. It adopts a gradient guiding slope design with a "gentle outer slope and steep inner slope." The outer arc section 211 has a smaller inclination angle and a gentler slope, while the inner arc section 212 has a larger inclination angle and a steeper slope. The inclination angle of the inner arc section 212 is 1° to 3° higher than that of the outer arc section 211, and the inclination directions are completely consistent. The gentle slope of the outer arc section 211 allows the liquid phase to diffuse slowly, ensuring sufficient contact with the rising stripping medium; the steeper slope of the inner arc section 212 facilitates the accelerated flow of the heavy component liquid phase towards the overflow weir, reducing the residence time of the liquid phase on the plate.

[0044] Specifically, the first overflow plate 21 has an angle of 15°~20° with the horizontal plane, which can stabilize the liquid phase flow velocity at 0.18m / s~0.22m / s. This not only helps to avoid the liquid droplets being entrained to the upper gas phase due to excessive flow velocity, but also reduces high-temperature coking caused by excessively slow flow velocity. Combined with the dual effects of liquid film mass transfer and gas phase flow, it achieves efficient initial removal of light components in the liquid phase.

[0045] Specifically, the second overflow plate 22, the third overflow plate 23, and the fourth overflow plate 24 are arranged sequentially from bottom to top above the first overflow plate 21, with the fourth overflow plate 24 being adjacent to the bottom of the multi-layer distillation tray 3. All three adopt a semi-circular structure, with a straight line parallel to the radial direction of the shell 1 as the diameter side and an arc conforming to the inner wall of the shell 1 as the arc side. That is, the semi-circular structure includes an arc segment 241 that fits and is fixed to the inner wall of the shell 1 and a straight line segment 242 that is away from the inner wall of the shell 1. Furthermore, the overflow plates of adjacent layers are arranged alternately around the circumference of the shell 1, meaning that adjacent layers are arranged by rotating around the central axis of the shell 1 at a certain angle, forming an alternating left-right-left-right distribution. This staggered arrangement of interlayer positions helps ensure that the liquid phase overflowing from the upper layer accurately falls into the effective receiving area of ​​the lower layer, guaranteeing the continuity of the staged processing.

[0046] Specifically, the length of the straight segment 242 is 70% to 80% of the diameter of the shell 1, the distance between the midpoint of the straight segment 242 and the center of the shell 1 is 15% to 20% of the radius of the shell 1, and the central angle corresponding to the arc segment 241 is 200° to 250°. This design allows the arc segment 241 to fit against the inner wall of the shell 1, providing sufficient diffusion space for the liquid phase, while the position of the straight segment 242 prevents excessive concentration of the liquid phase in the central region of the shell 1, ensuring the uniformity of the liquid film on the plate surface. At the same time, it reserves a smooth channel for gas phase flow, effectively balancing the needs of liquid phase diffusion and gas phase flow, and further improving the gas-liquid mass transfer efficiency.

[0047] In this application, as Figure 5 As shown, a streamlined overflow weir 243, which is a structure protruding from the surface of the overflow plate, is provided on the straight segment 242.

[0048] Specifically, each overflow plate is tilted downward toward the overflow weir side of its straight section 242, so that the liquid phase on the plate forms a unidirectional flow from the shell-attached side of the arc section 241 to the overflow weir side of the straight section 242, and finally overflows to the lower plate through the overflow weir.

[0049] Specifically, such as Figure 5As shown, the streamlined overflow weir 243 is a convex structure evenly distributed along the straight segment 242. Its cross-section along the liquid flow direction is asymmetrically arc-shaped, specifically including a curved surface facing the arc segment 241 and a curved surface facing the straight segment 242. The curved surface facing the arc segment 241 is a smooth arc-shaped surface convex towards the arc segment 241, i.e., the incoming flow side surface. Its arc profile is a continuous arc, and its core function is to actively guide the liquid phase to spread evenly to form a stable liquid film and provide a baffle structure basis for gas phase flow. The curved surface facing the straight segment 242 is a surface that smoothly transitions from the highest point of the overflow weir to the surface of the overflow plate, i.e., the back flow side surface. It connects to the surface of the overflow plate through a smooth arc, and its core function is to eliminate structural dead angles, guide the liquid phase to smoothly fall back to the overflow plate, and reduce liquid phase retention. The essential difference between the two is that the side facing the arc segment 241 is an active flow guiding arc protrusion, whose function is focused on guiding liquid flow, enhancing gas-liquid contact and deflecting droplets; the side facing the straight segment 242 is a passive transition smooth curved surface, whose function is focused on avoiding dead corners and ensuring smooth liquid overflow, without active flow guiding effect.

[0050] Specifically, traditional right-angle overflow weirs, being perpendicular to the liquid flow direction and with sharp corners, easily generate strong turbulence when the liquid flows through them, resulting in a Reynolds number Re > 3000. This leads to a 2-3 times longer residence time for the liquid phase, making it highly susceptible to thermal polymerization reactions and the formation of coke residue under high-temperature distillation conditions. In contrast, the streamlined overflow weir 243 of this application, through the guiding effect of the arc-shaped curved surface facing the arc segment 241, can guide the liquid flow state to transform into a stable laminar flow, with a Reynolds number Re ≤ 2300. Experimental verification has shown that this design can reduce the amount of coke at the weir mouth by more than 60%, effectively extending the continuous operation cycle of the device.

[0051] Specifically, the fourth overflow plate 24, as the final purification unit in the gas phase rising path, undertakes the functions of droplet interception and deep purification before the light components are discharged. Under the action of the inclined slope of the overflow plate, the liquid phase flows from the shell-attached side of the arc section 241 to the streamlined overflow weir 243 of the straight section 242. Guided by the arc-shaped curved surface on the side facing the arc section 241, it spreads into a uniform liquid film and initially transfers mass with the gas phase from bottom to top. After the gas phase passes through the liquid film, it forms a natural deflection through the arc-shaped curved surface on the side facing the arc section 241. It uses inertial force to intercept the micron-sized liquid phase droplets entrained in the gas phase. After the droplets condense, they flow along the plate to the third overflow plate 23, which can improve the purity of the light components by 3% to 5%, and the droplet interception efficiency is 25% higher than that of the traditional rectangular weir.

[0052] Specifically, the third overflow plate 23 and the second overflow plate 22 serve as intermediate fine separation layers, receiving the liquid phase formed by the condensation of the upper gas phase and the liquid phase overflowing from the upper overflow plate. Under the action of the inclined slope of the overflow plate, the liquid phase flows from the shell-adhering side of the arc section 241 to the streamlined overflow weir 243 of the straight section 242, and spreads into a uniform liquid film under the guidance of the arc-shaped curved surface on the side facing the arc section 241. The stripping medium introduced at the bottom flows upward in the opposite direction, fully transferring mass with the liquid film, and efficiently removing 8% to 12% of the residual light components in the liquid phase. The light components rise with the gas phase and enter the upper plate or multi-layer distillation tray 3, while the liquid phase overflows smoothly along the weir to the lower plate. The second overflow plate 22 finally assists in the flow to converge with the first overflow plate 21.

[0053] Specifically, the second overflow plate 22 to the fourth overflow plate 24 are all inclined downwards towards the overflow weir side of their straight section 242, with an angle of 10° to 15° with the horizontal plane, and the inclination angle of adjacent layers decreases by 1° to 3° from bottom to top. The upper fourth overflow plate 24 receives a small liquid flow rate, and the gentler slope is conducive to ensuring sufficient gas-liquid mass transfer; the lower second overflow plate 22 receives a large liquid flow rate, and the steeper slope is conducive to increasing the liquid flow velocity, reducing high-temperature retention and coking, while ensuring smooth gas flow channels and maintaining the stability of gas-liquid countercurrent flow.

[0054] Specifically, the radius of curvature of the streamlined overflow weir 243 is 20mm~50mm. Here, the radius of curvature refers to the radius of curvature of the arc surface facing the arc segment 241. This radius of curvature can be adjusted according to the viscosity of the liquid phase, which is beneficial to achieving a balance between low flow resistance, avoiding stagnation, ensuring the uniformity of liquid flow, and preventing splashing.

[0055] Specifically, such as Figure 5 As shown, there are 30 to 40 streamlined overflow weirs 243, with a width of 12 mm to 18 mm. The spacing between adjacent streamlined overflow weirs 243 is 30 mm to 60 mm, and the radius of curvature is 20 mm to 50 mm. The height of the streamlined overflow weir 243 is 10 mm to 25 mm, and the thickness of the weir body is 8 mm to 12 mm. This combination of parameters can ensure the structural strength to withstand the impact of high-temperature liquid phase, while avoiding occupying too much plate space, ensuring smooth upward flow of gas phase, and maintaining the stability of gas-liquid countercurrent flow.

[0056] Specifically, a splash guard flange 26 with a height of 5mm to 8mm is added to the top of the streamlined overflow weir 243. The flange extends upward along the tangent direction of the curved surface facing the arc segment 241, and the top is a smooth arc transition, which is more conducive to enhancing the droplet interception effect and reducing the amount of liquid phase droplets entrained in the light component steam to below 0.1%. The smooth design of the flange does not interfere with the liquid phase co-flow and the gas phase through flow.

[0057] Specifically, the multi-layer distillation tray 3 is a deep separation component for tar distillation. It is located above the multi-layer overflow plate assembly 2, below the light component outlet 11, and below the top reflux inlet 12. The top reflux inlet 12 connects to the uppermost distillation tray area, allowing the reflux to flow downwards through each distillation tray. The multi-layer distillation tray 3 and the multi-layer overflow plate assembly 2 work together to form a complete separation system for overflow plate staged removal, tray-based deep separation, and fraction extraction. It receives the light component gas phase after staged processing by the overflow plate assembly 2. This gas phase consists of mixed light components with a distillation temperature above 360°C, specifically including anthracene oil, naphthalene oil, wash oil, light oil, and water. Combined with the reflux, it achieves deep purification of these light components and fraction extraction.

[0058] Specifically, the multi-layer distillation tray 3 can be selected from commonly used tray types in the field, such as floating valve trays, sieve trays, and guided sieve trays. Its core function is to deepen the gas-liquid separation of the above-mentioned mixed light components: on the one hand, it removes trace amounts of liquid droplets entrained in the gas phase to avoid heavy component impurities from being mixed into the output product; on the other hand, it utilizes the counter-current contact between the reflux liquid at the top of the column and the rising gas phase, based on the gradient characteristics of the temperature decreasing from top to bottom in the distillation column, to achieve the stratified enrichment of fractions with different boiling points, providing a basis for subsequent fraction output.

[0059] Specifically, the multi-layer distillation tray 3 is arranged in 2 to 10 layers along the height of the shell 1. The number and layout of the trays are adapted to the distillation characteristics of the mixed light components. The side stream outlet can be selectively set according to the extraction needs of the target side stream fraction, such as anthracene oil or other fractions with relatively high boiling points. It can be omitted when separate extraction is not required. The specific separation process is as follows: the mixed light components, after being treated by the multi-layer overflow plate assembly 2, enter the multi-layer distillation tray 3 from the top. The reflux liquid introduced from the top of the column flows through each tray from top to bottom, forming a counter-current contact mass transfer with the rising gas phase, removing trace liquid droplets and heavy component impurities entrained in the gas phase. Relying on the temperature gradient characteristic of decreasing temperature from top to bottom in the column, the mixed light components achieve stratified enrichment.

[0060] If a side stream distillate outlet is provided, the high-boiling-point components in the lower high-temperature tray can be condensed into liquid phase and collected through the corresponding side stream; the intermediate stage can be equipped with side streams to separate intermediate-boiling-point distillates as needed, and the remaining low-boiling-point gas phase is purified by the upper tray and then discharged from the top light component outlet 11.

[0061] If no side-stream distillate outlet is provided, all uncondensed light component gas phases are purified by the upper tray and discharged from the top light component outlet 11. The heavy component enriched liquid phase on the tray, including the captured droplets and the reflux liquid after washing, flows back to the multi-layer overflow plate assembly 2 along the overflow channel and is finally discharged from the heavy component outlet 15 at the bottom of the column along with the heavy component liquid phase.

[0062] Finally, the mixed gas phase discharged from the top light component outlet 11, containing anthracene oil, naphthalene oil, stripping medium, and water, needs to be separated into water and vapor by a subsequent oil-water separator to ensure product purity.

[0063] Specifically, the multi-layer distillation tray 3 adopts a detachable structure, which is compatible with the modular design of the multi-layer overflow plate assembly 2, making it easy to maintain and replace the equipment; the surface of the tray is treated with anti-sticking to reduce residual coking of the liquid phase, which further helps to extend the continuous operation cycle of the unit.

[0064] In some embodiments, optionally, such as Figure 1 and Figure 2 As shown, the first overflow plate 21 is inclined downwards toward the side where the rectangular overflow weir 213 of its inner arc segment 212 is located, with an angle of 15°~20° with the horizontal plane; the second overflow plate 22, the third overflow plate 23 and the fourth overflow plate 24 are all inclined downwards toward the side where the streamlined overflow weir 243 of their respective straight segments 242 is located, with an angle of 10°~15° with the horizontal plane, and the inclination angle of the second overflow plate 22, the third overflow plate 23 and the fourth overflow plate 24 decreases by 1°~3° from bottom to top.

[0065] Specifically, such as Figure 1 and Figure 2 As shown, the first overflow plate 21 is inclined at a large angle towards the central rectangular overflow weir 213, forming a guiding slope that is gentle on the outside and steep on the inside. This design allows the liquid phase diffusing along the outer arc segment 211 to spread smoothly and fully contact the rising gas phase, while simultaneously driving the liquid phase converging towards the inner arc segment 212 to obtain sufficient downward momentum and flow quickly towards the overflow weir opening. This effectively reduces the overall residence time of the liquid phase on the high-temperature plate surface and suppresses the risk of coking caused by slow flow. The second overflow plate 22 to the fourth overflow plate 24 are inclined at a relatively small angle towards the streamlined overflow weir 243 of the straight segment 242. This angle is conducive to maintaining a stable and moderately thick liquid film on the plate surface, creating ideal conditions for the gas phase to pass through the liquid layer for mass transfer. Meanwhile, the design of gradually decreasing tilt angles of 1° to 3° from bottom to top is a dynamic adaptation to the liquid flow rate and mass transfer task of different levels: the lower plate receives liquid phases with larger flow rates and higher concentrations of heavy components, and adopts a slightly steeper angle to accelerate its flow and avoid stagnation; the upper plate has a smaller liquid flow rate and higher requirements for the removal of light components, and adopts a slightly gentler angle to prolong the gas-liquid contact time and ensure separation accuracy.

[0066] In some embodiments, optionally, such as Figure 1 and Figure 2 As shown, in the first overflow plate 21, the transition between the outer arc segment 211 and the inner arc segment 212 is made with a smooth rounded corner, and the radius of the rounded corner is ≥8mm; the diameter of the circle containing the inner arc segment 212 is 60%~70% of the diameter of the shell 1.

[0067] Specifically, such as Figure 1 and Figure 2 As shown, this design ensures that the inner arc segment 212 has sufficient depth to achieve effective centripetal convergence, while avoiding the limitation of liquid phase diffusion due to an excessively small inner arc segment 212, or the excessively large inner arc segment resulting in an excessively thin liquid film or even drying out in the central region. It precisely balances the annular diffusion area of ​​the liquid phase with the central convergence efficiency, ensuring the uniformity and stability of the liquid film distribution on the plate surface. The smooth, large rounded corners and the appropriate inner arc size work together to optimize the global flow field on the surface of the first overflow plate 21, achieving efficient gas-liquid contact while minimizing the risk of coking caused by uneven flow or stagnation.

[0068] In some embodiments, optionally, such as Figure 1 As shown, in the overflow plate assembly 2, the vertical spacing between two adjacent overflow plates is 20% to 40% of the radius of the shell 1, and from bottom to top, the spacing between adjacent overflow plates increases by 5% to 10% of the radius of the shell 1.

[0069] Specifically, such as Figure 1 As shown, the vertical spacing between adjacent overflow plates is limited to 20% to 40% of the radius of shell 1. This range precisely balances the requirements for gas flow space and liquid drop height. The spacing increases progressively from bottom to top in increments of 5% to 10% of the radius of shell 1, dynamically adapting to changes in gas and liquid loads along the height of the distillation column. This achieves optimized flow field and balanced gas-liquid distribution throughout the entire column, thereby improving overall separation efficiency. Furthermore, the smooth and rational flow indirectly reduces the possibility of coking caused by flow instability or localized liquid accumulation. In some embodiments, optionally, such as Figure 1 and Figure 2 As shown, the connection between each overflow plate and the inner wall of the shell 1 is made of rounded corners with a radius of ≥5mm; the surface roughness Ra of each overflow plate is ≤1.6μm.

[0070] Specifically, such as Figure 1 and Figure 2 As shown, the connection between each overflow plate and the inner wall of the shell 1 uses a rounded transition with a radius of ≥5mm, eliminating the sharp corners and gaps inherent in traditional welding or right-angle connections. This smooth transition allows the heavy component liquid phase flowing down the shell wall to flow through the connection area without obstruction, effectively preventing the high-viscosity asphalt component from sticking, accumulating, and stagnating on the corners. At the same time, the limited roughness allows the liquid phase to flow with less resistance, spread more evenly, and is less prone to adhesion and residue when flowing on the plate surface.

[0071] In some embodiments, optionally, such as Figure 2 and Figure 3As shown, splash guards 25 are provided on the outer arc segment 211 and / or circular arc segment 241 of each overflow plate away from the overflow weir. The height of the splash guards 25 is 3% to 5% of the radius of the shell 1.

[0072] Specifically, such as Figure 2 and Figure 3 As shown, the splash guard 25 serves to forcibly confine droplets that may fly off the plate surface within the expected flow path, ensuring that the liquid phase can neatly converge along the plate surface towards the overflow weir. This significantly reduces mist entrainment losses caused by droplets being carried into the rising gas phase, thereby improving the purity of the light component gas phase. Furthermore, by suppressing splashing, it also prevents droplets from being ejected onto the high-temperature wall surface of the shell 1 or other unintended areas, thus avoiding rapid evaporation or localized solidification and eliminating a potential, randomly distributed cause of coking.

[0073] In some embodiments, optionally, such as Figure 1 As shown, the multi-layer distillation tray 3 is selected from at least one of the following: floating valve tray, sieve tray, or guided sieve tray; the multi-layer distillation tray 3 is arranged in 2 to 10 layers along the height direction of the shell 1.

[0074] Specifically, such as Figure 1 As shown, the multi-layer distillation tray 3 is selected from mature and efficient tray types in the field, such as floating valve trays, sieve trays, or guided sieve trays. This selection provides a flexible and reliable basis for deep separation of different fraction characteristics and operating conditions. Limiting the number of tray layers to 2 to 10 layers is based on precise consideration of the distillation separation process of tar light component mixtures. The setting of 2 layers meets the most basic requirements for light and heavy component separation, while the upper limit of 10 layers ensures that even for wide fractions with complex components, clear separation and high-purity recovery can be achieved through a sufficient number of theoretical plates, while avoiding excessive equipment height, excessive pressure drop, and unreasonable increase in investment costs caused by too many trays.

[0075] In some embodiments, optionally, such as Figure 1 As shown, the tar inlet 13 of the shell 1 adopts a tangential feeding design; an airflow distributor 16 is provided at the stripping inlet 14 of the shell 1.

[0076] Specifically, such as Figure 1As shown, the tar inlet 13 of the shell 1 adopts a tangential feeding design, which allows the high-temperature tar material to obtain tangential velocity when entering the shell 1, thereby forming a rotating downward liquid film flow that adheres closely to the inner wall of the shell 1. This achieves initial uniform distribution of the feed and effectively avoids direct impact of the material on internal components or local accumulation. At the same time, an airflow distributor 16 is provided at the stripping inlet 14. This distributor can disperse the incoming stripping medium into a large number of uniform and fine airflows, so that they are uniformly distributed across the cross-section of the shell 1. This avoids uneven mass transfer, temperature field fluctuations, and potential local drying or over-polymerization problems caused by excessively high local gas concentrations.

[0077] According to the second aspect of this application, such as Figure 6 As shown, embodiments of this application also propose a distillation process method for a two-stage evaporator in a tar distillation apparatus, applied to the two-stage evaporator as described in the above embodiments. The distillation process method includes the following steps: S1. Tar material with a temperature of 340℃~400℃ and a pressure of 0.5MPa~1.2MPa is fed into the shell through the tar inlet tangentially; S2. Introduce stripping medium with a temperature not lower than 360℃ into the stripping inlet, and control the system pressure in the second-stage evaporator to be maintained at 0.01MPa~0.082MPa; S3. By adjusting the tar feed rate or the tilt angle of the first overflow plate, the flow velocity of the tar material on the surface of the first overflow plate is 0.15m / s to 0.25m / s, and the residence time is 2s to 5s. S4. By adjusting the tilt angle of the second overflow plate to the fourth overflow plate, the flow velocity of the heavy components on the second overflow plate to the fourth overflow plate is 0.1m / s to 0.3m / s, and the residence time is 2s to 5s. S5. Control the material temperature at the outlet of the heavy component to 330℃~375℃, and discharge the heavy component; S6. Collect light components from the light component outlet.

[0078] Specifically, such as Figure 6As shown, in steps S1 and S2, the high-temperature, appropriately pressurized tar is tangentially fed in, achieving a uniform initial distribution. The introduction of a controlled stripping medium and maintenance of a certain system pressure create a highly efficient mass transfer driving force. In steps S3 and S4, by adjusting the feed rate or the tilt angle of a specific overflow plate, the flow rate and residence time of the tar and heavy components in key areas are actively and precisely controlled within the optimal range. This active control ensures that the liquid phase has sufficient contact time with the gas phase to guarantee separation efficiency, while also rapidly passing through the high-temperature region to minimize coking. In step S5, controlling the outlet temperature of the heavy components ensures good fluidity for smooth discharge. Finally, step S6 collects the fully separated and purified light components. The entire process systematically achieves efficient separation and long-term stable operation.

[0079] In some embodiments, optionally, such as Figure 6 As shown, the tar material is coal tar.

[0080] Specifically, such as Figure 6 As shown, the tar material is coal tar. As the main liquid byproduct generated during the thermal processing of coal, coal tar has a complex composition, high viscosity and high content of heavy components. It has significant heat sensitivity and coking tendency during the distillation process, and is the main target of the core technical problem to be solved by the two-stage evaporator of this application.

[0081] Specifically, the following are specific embodiments and comparative examples of the two-stage evaporator and distillation process method of the tar distillation apparatus provided in this application: Example 1 1. The equipment structure is as follows: like Figure 1 As shown, shell 1 has a diameter of 2000mm, is made of Q345R+Ni-based composite plate, and has a tower-type cylindrical structure. From top to bottom, it is provided with light component outlet 11, tower top reflux liquid inlet 12, tar inlet 13, stripping inlet 14, and heavy component outlet 15.

[0082] Multi-layer overflow plate assembly 2: 4 layers of overflow plates, made of 00Cr17Ni14Mo4, arranged alternately and staggered along the circumference of the shell to form an S-shaped airflow path, with a vertical spacing of 300mm between adjacent plates, increasing by 80mm from bottom to top; among which, like Figure 2As shown, the first overflow plate 21 has a crescent-shaped structure. The diameter of the circle containing the outer arc segment 211 is 2000mm. The diameter of the circle containing the inner arc segment 212 is 1800mm, which is 65% of the diameter of the shell 1. The distance between the midpoint of the line connecting the two endpoints and the center of the shell 1 is 280mm, which is 28% of the radius of the shell 1. The overall angle with the horizontal plane is 18°. The inner arc segment 212 is 2° steeper than the outer arc segment 211. The inner arc segment 212 is provided with 34 rectangular overflow weirs 213. The width of the rectangular overflow weirs 213 is 15mm, the spacing is 40mm, the weir height is 15mm, and the weir mouth is rounded by 8mm.

[0083] like Figure 3 As shown, the second overflow plate 22 to the fourth overflow plate 24 have a semi-circular structure. The straight section 242 has a length of 1600mm, which is 80% of the diameter of the shell 1. The distance between the midpoint of the straight section 242 and the center of the shell 1 is 180mm, which is 18% of the radius of the shell 1. The central angle of the arc section 241 is 230°. The straight section 242 is provided with 36 streamlined overflow weirs 243. The streamlined overflow weirs 243 have a height of 20mm, a thickness of 10mm, an adjacent spacing of 45mm, and a curvature radius of 40mm on the side facing the arc section 241. The top is provided with a 6mm high splash guard flange 26.

[0084] Multi-layer distillation trays 3:4 are floating valve trays located above the multi-layer overflow plate assembly 2 and below the light component outlet 11. The top reflux inlet 12 is connected to the uppermost tray.

[0085] Auxiliary structure: The fillet radius at the connection between the overflow plate and the inner wall of the shell 1 is 6mm, and the surface roughness Ra=1.6μm; each overflow plate is provided with a 40mm high splash guard 25 on the non-overflow side, which is 4% of the radius of the shell 1.

[0086] 2. The operating parameters are as follows: Tar feed pressure 0.2MPa, temperature 380℃; stripping medium temperature 390℃; system pressure 0.1MPa; heavy component outlet 15 temperature 395℃.

[0087] The liquid phase flows at a velocity of 0.2 m / s in the first overflow plate 21 and at a velocity of 0.2 m / s in the second overflow plate 22 to the fourth overflow plate 24.

[0088] Slag is discharged regularly every month without stopping the machine; the flow rate of the reflux liquid at the top of the tower is adjusted to 1.2 times the amount of light component produced.

[0089] 3. Key operating indicators are as follows: Continuous operation cycle: 180 days; coke deposition at the bottom of the tower: 0.8 kg / m³ 2 The total removal rate of light components was 96.5%; the entrainment of light components in gas phase droplets was 0.08%.

[0090] Example 2 The procedure is the same as in Example 1, except that only the equipment size parameters are adjusted to suit low-volume processing conditions. 1. The equipment structure is adjusted as follows: The diameter of housing 1 is 1800 mm; In the first overflow plate 21: the diameter of the circle containing the outer arc segment 211 is 1800mm, the diameter of the circle containing the inner arc segment 212 is 1170mm, which is 65% of the diameter of the shell 1, and the distance between the midpoint of the line connecting the two endpoints and the center of the shell 1 is 252mm, which is 28% of the radius of the shell 1; there are 30 rectangular overflow weirs 213, the width of the rectangular overflow weirs 213 is 15mm, and the spacing is 38mm.

[0091] Among the second overflow plate 22 to the fourth overflow plate 24: the straight section 242 has a length of 1440mm, which is 80% of the diameter of the shell 1; the distance between the midpoint of the straight section 242 and the center of the shell 1 is 162mm, which is 18% of the radius of the shell 1; there are 32 streamlined overflow weirs 243, the streamlined overflow weir 243 has a height of 18mm, a radius of curvature of 35mm, and a splash guard flange of 265mm.

[0092] The spacing between adjacent overflow plates is 225mm, increasing by 54mm from bottom to top; the height of splash guard 25 is 32mm, which is 3.6% of the radius of shell 1; the radius of the fillet at the connection between the overflow plate and the inner wall of shell 1 is 5mm.

[0093] 2. The operating parameters are adjusted as follows: Tar feed pressure 0.18MPa, temperature 370℃; stripping medium temperature 385℃; system pressure 0.1MPa.

[0094] 3. Key operating indicators are as follows: Continuous operation cycle: 175 days; coke deposition at the bottom of the tower: 0.9 kg / m³ 2 The total removal rate of light components was 96.2%; the entrainment of light components in gas phase droplets was 0.09%.

[0095] Comparative Example 1 Referring to Embodiment 1, only the structure of the first overflow plate 21 is changed, while the other equipment parameters / operation parameters remain the same.

[0096] 1. The differences in equipment structure are as follows: The first overflow plate 21 is changed to a semi-circular structure, which is consistent with the shape of the second overflow plate 22 to the fourth overflow plate 24 in Embodiment 1, and the size is the same as the projected area of ​​the first overflow plate 21 in Embodiment 1; 34 rectangular overflow weirs 213 are still provided at the corresponding positions of the inner arc segment 212, with the same parameters as in Embodiment 1.

[0097] 2. Key operating indicators are as follows: Continuous operation cycle: 95 days; coke deposition at the bottom of the tower: 2.5 kg / m³ 2The total removal rate of light components was 90.3%; the entrainment of light components in gas phase droplets was 0.22%.

[0098] 3. Analysis of the reasons for the differences: The semi-circular structure cannot form a "ring diffusion + central convergence" flow pattern, resulting in uneven liquid phase spreading, easy stagnation in the middle of the plate, and increased local high-temperature coking; the uneven liquid film leads to insufficient gas-liquid contact and a decrease in the removal rate of light components.

[0099] Comparative Example 2 The same procedure was followed as in Embodiment 1, except that the overflow weir types of the second overflow plate 22 to the fourth overflow plate 24 were changed, while the other equipment parameters / operation parameters remained the same.

[0100] 1. The differences in equipment structure are as follows: The streamlined overflow weirs 243 of the second overflow plate 22 to the fourth overflow plate 24 are replaced with traditional right-angle overflow weirs, that is, the corners are not rounded, the height is 20mm, the width is 15mm, the spacing is 45mm, and the rest of the structure and arrangement are the same as in Embodiment 1.

[0101] 2. Key operating indicators are as follows: Continuous operating cycle: 80 days; Coking amount at the bottom of the tower: 3.1 kg / m³ 2 Total removal rate of light components: 88.7%; Entrainment of light components in gas phase droplets: 0.35%.

[0102] 3. Analysis of the reasons for the differences: A right-angled weir is perpendicular to the direction of liquid flow, which easily forms strong turbulence, prolongs the liquid residence time, and greatly increases the risk of high-temperature coking; turbulence leads to an increase in droplet entrainment and a decrease in the purity of light components; at the same time, turbulent impacts disrupt the stability of the liquid film and reduce mass transfer efficiency.

[0103] Comparative Example 3 The same procedure was followed as in Embodiment 1, except that the overflow weir type of the first overflow plate 21 was changed, while the other equipment parameters / operation parameters remained the same.

[0104] 1. The differences in equipment structure are as follows: The 34 rectangular overflow weirs 213 of the first overflow plate 21 are replaced with streamlined overflow weirs 243 with the same parameters as the second overflow plate 22 to the fourth overflow plate 24 in Embodiment 1, namely, a radius of curvature of 40mm, a height of 15mm, and no rounding at the weir opening; the rest of the crescent-shaped structure and gradient slope are the same as in Embodiment 1.

[0105] 2. Key performance indicators: Continuous operating cycle: 120 days; Coking amount at the bottom of the tower: 1.6 kg / m³ 2 Total removal rate of light components: 93.2%; Entrainment of light components in gas phase droplets: 0.15%.

[0106] 3. Analysis of the reasons for the differences: The core flow pattern of the first overflow plate 21 is "ring diffusion + central convergence". The straight weir of the rectangular weir is more suitable for the flow trajectory of the liquid phase converging towards the center, and can divide the liquid phase into uniform streams. However, the arc structure of the streamlined weir is poorly adapted to this flow pattern, resulting in uneven liquid phase convergence, local stagnation, increased risk of coking, and reduced gas-liquid contact area, thus reducing the removal rate.

[0107] Comparative Example 4 The same procedure was followed as in Embodiment 1, except that the shapes of the second overflow plate 22 to the fourth overflow plate 24 were changed, while the remaining equipment parameters / operation parameters remained the same.

[0108] 1. Differences in equipment structure: The second overflow plate 22 to the fourth overflow plate 24 are changed to a flat plate structure, that is, without the design of the arc segment 241 and the straight segment 242. The dimensions are the same as the projected area of ​​the second overflow plate 22 to the fourth overflow plate 24 in Embodiment 1. The corresponding position of the straight segment 242 still has 36 streamlined overflow weirs 243, with the same parameters as in Embodiment 1.

[0109] 2. Key performance indicators: Continuous operation cycle: 70 days; coke deposition at the bottom of the tower: 3.8 kg / m³ 2 The total removal rate of light components was 85.1%; the entrainment of light components in gas phase droplets was 0.40%.

[0110] 3. Analysis of the reasons for the differences: The flat plate structure cannot adapt to the radial flow field distribution of the shell 1, and the liquid phase is prone to leakage along the edge of the plate, making it impossible to form a stable liquid film; at the same time, the gas phase flow channel is disordered, the mass transfer efficiency is greatly reduced, and the risk of coking and droplet entrainment increases dramatically.

[0111] In the description of this application, the term "multiple" refers to two or more. Unless otherwise expressly defined, the terms "upper," "lower," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. The terms "connection," "installation," "fixing," etc., should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection or an indirect connection through an intermediate medium. For those skilled in the art, the specific meaning of the above terms in this application can be understood according to the specific circumstances.

[0112] In the description of this specification, the terms "one embodiment," "some embodiments," "specific embodiment," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0113] The above are merely preferred embodiments of this application and are not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A two-stage evaporator for a tar distillation apparatus, characterized in that, include: The shell, from top to bottom, is provided with a light component outlet, a reflux liquid inlet, a tar inlet, a stripping inlet, and a heavy component outlet; An overflow plate assembly includes multiple overflow plates, which are disposed inside the housing and located above the tar inlet. The overflow plate assembly has a first overflow plate, a second overflow plate, a third overflow plate, and a fourth overflow plate arranged alternately and staggeredly from bottom to top along the inner wall of the housing to form an S-shaped upward airflow path. A multi-layer distillation tray is disposed inside the shell and located above the multi-layer overflow plate assembly and below the reflux inlet; The first overflow plate is a crescent-shaped structure, including an outer arc segment fixedly connected to the inner wall of the shell and an inner arc segment recessed towards the outer arc segment. Multiple rectangular overflow weirs are provided on the inner arc segment, which are evenly distributed along its arc direction. The second, third, and fourth overflow plates are all semi-circular structures, including an arc segment fixedly connected to the inner wall of the shell and a straight segment away from the inner wall of the shell. Multiple streamlined overflow weirs are provided on the straight segment and evenly distributed along its length.

2. The two-stage evaporator according to claim 1, characterized in that, The first overflow plate is inclined downward toward the side where the rectangular overflow weir of its inner arc section is located, with an angle of 15°~20° with the horizontal plane; The second, third, and fourth overflow plates are all inclined downwards toward the side where the streamlined overflow weir of their respective straight segments is located, with an angle of 10° to 15° with the horizontal plane, and the inclination angle of the second, third, and fourth overflow plates decreases by 1° to 3° from bottom to top.

3. The two-stage evaporator according to claim 1, characterized in that, In the first overflow plate, the transition between the outer arc segment and the inner arc segment is made with a smooth rounded corner, and the radius of the rounded corner is ≥8mm; The diameter of the circle containing the inner arc segment is 60% to 70% of the diameter of the shell.

4. The two-stage evaporator according to claim 1, characterized in that, In the overflow plate assembly, the vertical spacing between two adjacent overflow plates is 20% to 40% of the shell radius, and from bottom to top, the spacing between adjacent overflow plates increases by 5% to 10% of the shell radius layer by layer.

5. The two-stage evaporator according to claim 1, characterized in that, The connection between each overflow plate and the inner wall of the shell is made of rounded corners, and the radius of the rounded corners is ≥5mm; The surface roughness Ra of each overflow plate is ≤1.6μm.

6. The two-stage evaporator according to claim 1, characterized in that, Each of the overflow plates has a splash guard at the edge of the outer arc segment and / or circular arc segment away from the overflow weir, and the height of the splash guard is 3% to 5% of the radius of the shell.

7. The two-stage evaporator according to claim 1, characterized in that, The multi-layer distillation tray is selected from at least one of valve tray, sieve tray, or guided sieve tray. The multi-layer distillation trays are arranged in 2 to 10 layers along the height direction of the shell.

8. The two-stage evaporator according to claim 1, characterized in that, The tar inlet of the shell is designed with tangential feeding. An airflow distributor is provided at the stripping inlet of the shell.

9. A distillation process method for a two-stage evaporator in a tar distillation apparatus, applied to the two-stage evaporator as described in any one of claims 1 to 8, characterized in that, The distillation process includes the following steps: S1. Tar material with a temperature of 340℃~400℃ and a pressure of 0.5MPa~1.2MPa is fed into the shell through the tar inlet tangential line; S2. A stripping medium with a temperature not lower than 360°C is introduced into the stripping inlet, and the system pressure in the second-stage evaporator is controlled to be maintained at 0.01MPa~0.082MPa. S3. By adjusting the tar feed rate or the tilt angle of the first overflow plate, the flow velocity of the tar material on the surface of the first overflow plate is 0.15m / s to 0.25m / s, and the residence time is 2s to 5s. S4. By adjusting the tilt angle between the second overflow plate and the fourth overflow plate, the flow velocity of the heavy components on the second overflow plate and the fourth overflow plate is 0.1m / s to 0.3m / s, and the residence time is 2s to 5s. S5. Control the material temperature at the outlet of the heavy component to 330℃~375℃, and discharge the heavy component; S6. Collect the light component from the light component outlet.

10. The distillation process according to claim 9, characterized in that, The tar material is coal tar.

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