Refining device of crude phthalic anhydride
By combining a multi-tower distillation system with an evaporation reactor, the problem of high phthalic anhydride content in the residue of the third distillation tower was solved, thereby improving the phthalic anhydride extraction rate and reducing enterprise costs.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- KAIFENG JIUHONG CHEM CO LTD
- Filing Date
- 2025-06-09
- Publication Date
- 2026-05-15
AI Technical Summary
In the existing technology, during the crude phthalic anhydride refining process, the residue discharged from the third distillation column still contains a high concentration of phthalic anhydride, resulting in a low phthalic anhydride extraction rate and increased consumption for enterprises.
A multi-tower distillation system is adopted. By adding an evaporation reactor and a vacuum pump during the second solution reboiling cycle, the liquid flow is diverted to the evaporation reactor for heating using a booster pump. After partial evaporation of phthalic anhydride, it is then transported to the third distillation column. Combined with online chromatograph monitoring of components, the residue treatment process is optimized.
It effectively reduced the phthalic anhydride content in the residue of the third distillation column, improved the extraction rate of phthalic anhydride, reduced enterprise consumption, and improved work efficiency and economic benefits.
Smart Images
Figure CN224236100U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of equipment for refining crude phthalic anhydride, and more specifically to a refining apparatus for crude phthalic anhydride. Background Technology
[0002] Phthalic anhydride is an important basic organic chemical raw material, widely used in plasticizers, alkyd resins, unsaturated polyester resins, dyes, pharmaceuticals, and other industries. Phthalic anhydride production consists of crude phthalic anhydride production, phthalic anhydride refining, boiler feedwater treatment, and tail gas treatment. Phthalic anhydride produced from industrial naphthalene is crude phthalic anhydride and requires refining to obtain refined phthalic anhydride.
[0003] Phthalic anhydride refining involves continuous distillation processes including pretreatment, separation of light components, distillation of pure phthalic anhydride, and concentration of residues. In existing technology, the pretreated crude phthalic anhydride is fed into a first distillation column for separation of light components, yielding a first solution containing residue (the heavy component) and phthalic anhydride. This first solution is then fed into a second distillation column for further separation of the residue and phthalic anhydride. The reboiler circulation pipe at the bottom of the second distillation column continuously receives the second solution from the bottom of the column for reboiler circulation. The hot gas flow generated by this reboiler circulation serves as the rising gas flow in the second distillation column, along with the material to be refined. During this process, the reboiler circulation pipe at the bottom of the second distillation column continuously supplies a second solution to a third distillation column, where the phthalic anhydride residue in the residue is separated. The residue is then discharged from the bottom of the third distillation column. However, verification has shown that the residue discharged from the third distillation column still contains a significant amount of phthalic anhydride.
[0004] The reason is that during the reboiling cycle of the second solution entering the reboiling circulation pipeline, the unvaporized liquid substance enters the bottom of the second distillation column and merges with the first solution from the first distillation column to form the second solution, thus creating a continuous reboiling cycle at the bottom of the second distillation column. Therefore, the second solution is typically supplied from the second distillation column to the third distillation column using a level sensor installed at the bottom of the second distillation column, and the entry of the second solution into the third distillation column is continuous. Consequently, the second solution entering the third distillation column for residue and phthalic anhydride separation has a high phthalic anhydride content, resulting in a high concentration of phthalic anhydride in the residue after distillation in the third distillation column. Therefore, there is room for improvement in the existing technology, aiming to reduce the phthalic anhydride content in the distillation-treated residue, increase the extraction rate of effective intermediate products, and thereby reduce the enterprise's consumption. Summary of the Invention
[0005] To address the shortcomings of existing technologies, this invention provides a refining apparatus for crude phthalic anhydride that can reduce the phthalic anhydride content in the residue after distillation, thereby overcoming the deficiencies in existing technologies.
[0006] The technical solution adopted by this utility model is as follows: a refining device for crude phthalic anhydride, comprising a first distillation column, a first top condenser at the top of the first distillation column, a second distillation column connected to the first distillation column, a second top condenser at the top of the second distillation column, a first heating conveying pipe at the bottom of the second distillation column, and, along the direction from near to far from the second distillation column, sequentially arranged a first regulating valve, the outlet end of a liquid reflux pipe, a first booster pump, the inlet end of a first external slag discharge pipe, and a second regulating valve. A first gas delivery pipe is installed between the inlet end of the throttle valve, the first reboiler, and the gas-liquid separator, the gas phase outlet end of the gas-liquid separator, and the second distillation column. The inlet end of the liquid phase reflux pipe is connected to the liquid phase outlet end of the gas-liquid separator. A third regulating valve is installed on the liquid phase reflux pipe. A fourth regulating valve is installed on the first external slag discharge pipe. The inlet end of the evaporation reactor is installed at the outlet end of the first external slag discharge pipe. The gas phase outlet end of the evaporation reactor is connected to the first gas delivery pipe. The third distillation column is connected to the liquid phase outlet end of the evaporation reactor.
[0007] Preferably, it also includes a tail gas delivery main pipe. The top of the third distillation column is provided with a third column top condenser, and the bottom of the third distillation column is provided with a column bottom heater. The top of the cold source channel of the third column top condenser and the tail gas delivery main pipe, the top of the cold source channel of the second column top condenser and the tail gas delivery main pipe, and the top of the cold source channel of the first column top condenser and the tail gas delivery main pipe are all connected by tail gas delivery branch pipes. Each tail gas delivery branch pipe is provided with a first vacuum pump, a fifth regulating valve and a first pressure sensor in sequence along the direction from near the tail gas delivery main pipe to away from the tail gas delivery main pipe.
[0008] Preferably, the first gas delivery pipe is equipped with a one-way valve, and the one-way valve is connected to the first gas delivery pipe of the second distillation column and the gas phase outlet end of the evaporation reactor through the second gas delivery pipe. The second gas delivery pipe is sequentially equipped with a second pressure sensor, a sixth regulating valve and a second vacuum pump along the direction from near the evaporation reactor to far away from the evaporation reactor.
[0009] Preferably, the first distillation column is provided with a first baffle, a first packing layer and a second packing layer from top to bottom; the second distillation column is provided with a second baffle and a third packing layer from top to bottom; and the third distillation column is provided with a third baffle and a fourth packing layer from top to bottom. Each of the first, second and third baffles is provided with a gas lift cap. The second distillation column above the second baffle and the first distillation column between the first baffle and the first packing layer are connected by a condensate delivery pipe.
[0010] Preferably, the third distillation column below the third packing layer and the liquid phase outlet of the evaporation reactor are connected by a second external slag discharge pipe. The second external slag discharge pipe is equipped with a second booster pump and a first online chromatograph. The first distillation column above the first partition is equipped with a light component conveying pipe. The first distillation column of the first packing layer and the second packing layer is equipped with a crude phthalic anhydride conveying pipe. The second distillation column above the third partition is equipped with a refined phthalic anhydride conveying pipe.
[0011] Preferably, both the first heating delivery pipe and the first gas delivery pipe are connected to the second distillation column below the third packing layer. The first distillation column below the second packing layer is provided with a second heating delivery pipe. The inlet end and the outlet end of the second heating delivery pipe are both connected to the first distillation column. A third booster pump, the inlet end of a heavy component delivery pipe, a seventh regulating valve, and a second reboiler are sequentially arranged along the second heating delivery pipe from its inlet end to its outlet end. The outlet end of the heavy component delivery pipe is connected to the second distillation column below the third packing layer. An eighth regulating valve is provided on the heavy component delivery pipe.
[0012] The beneficial effects of this utility model are as follows: First, the liquid flow pressurized by the first booster pump is partially diverted to the evaporation reactor for heating, and the phthalic anhydride component in the liquid entering the evaporation reactor is partially evaporated before being transported to the third distillation column for further distillation. This reduces the phthalic anhydride content in the residue transported to the third distillation column, thereby reducing the phthalic anhydride content in the residue discharged from the third distillation column.
[0013] Secondly, each exhaust gas delivery branch pipe of this utility model is sequentially equipped with a first vacuum pump, a fifth regulating valve, and a first pressure sensor along the direction from near the exhaust gas delivery main pipe to far away from the exhaust gas delivery main pipe; the installation of the first pressure sensor facilitates the feedback of pressure parameters.
[0014] Furthermore, the second external discharge slag pipe of this utility model is equipped with a second booster pump and a first online chromatograph. The installation of the first online chromatograph facilitates the feedback of component parameters.
[0015] This utility model has a simple structure, is easy to operate, and has a clever design, which greatly improves work efficiency and has good social and economic benefits. It is a product that is easy to promote and use. Attached Figure Description
[0016] Figure 1 This is a schematic diagram of the structure of this utility model.
[0017] Figure 2 for Figure 1 A magnified view of detail A.
[0018] Figure 3for Figure 1 A magnified view of detail B. Detailed Implementation
[0019] like Figures 1 to 3 As shown, a refining apparatus for crude phthalic anhydride includes a first distillation column 1, a first overhead condenser 2 at the top of the first distillation column 1, a second distillation column 3 connected to the first distillation column 1, a second overhead condenser 4 at the top of the second distillation column 3, and a first heating delivery pipe 5 at the bottom of the second distillation column 3. Along the direction from near to away from the second distillation column 3, the first heating delivery pipe 5 sequentially includes a first regulating valve 6, the outlet end of a liquid reflux pipe 7, a first booster pump 8, the inlet end of a first external slag discharge pipe 9, a second regulating valve 10, a first reboiler 11, and... A first gas delivery pipe 13 is provided between the inlet end of the gas-liquid separator 12, the gas phase outlet end of the gas-liquid separator 12, and the second distillation column 3. The inlet end of the liquid phase reflux pipe 7 is connected to the liquid phase outlet end of the gas-liquid separator 12. A third regulating valve 14 is provided on the liquid phase reflux pipe 7. A fourth regulating valve 15 is provided on the first external slag discharge pipe 9. The inlet end of the evaporation reactor 16 is provided on the outlet end of the first external slag discharge pipe 9. The gas phase outlet end of the evaporation reactor 16 is connected to the first gas delivery pipe 13. The third distillation column 17 is connected to the liquid phase outlet end of the evaporation reactor 16. This product also includes a tail gas delivery main pipe 18. The top of the third distillation column 17 is provided with a third column top condenser 19, and the bottom of the third distillation column 17 is provided with a column bottom heater 20. The top of the cold source channel of the third column top condenser 19 and the tail gas delivery main pipe 18, the top of the cold source channel of the second column top condenser 4 and the tail gas delivery main pipe 18, and the top of the cold source channel of the first column top condenser 2 and the tail gas delivery main pipe 18 are all connected by tail gas delivery branch pipes 21. Each tail gas delivery branch pipe 21 is provided with a first vacuum pump 22, a fifth regulating valve 23 and a first pressure sensor 24 in sequence along the direction from near the tail gas delivery main pipe 18 to away from the tail gas delivery main pipe 18.
[0020] The heat source channel of the first top condenser 2 is connected to the inner cavity of the first distillation column 1. The heat source channel of the second top condenser 4 is connected to the inner cavity of the second distillation column 3. The heat source channel of the third top condenser 19 and the cold source channel of the bottom heater 20 are connected through the inner cavity of the third distillation column 17. The first distillation column 1 is provided with a first baffle 30, a first packing layer 31, and a second packing layer 32 arranged sequentially from top to bottom. The second distillation column 3 is provided with a second baffle 33 and a third packing layer 34 arranged sequentially from top to bottom. The third distillation column 17 is provided with a third baffle 35 and a fourth packing layer 36 arranged sequentially from top to bottom. Each of the first baffle 30, second baffle 33, and third baffle 35 is equipped with a gas lift cap 37. The second distillation column 3 above the second baffle 33 and the first distillation column 1 between the first baffle 30 and the first packing layer 31 are connected by a condensate delivery pipe 38. The liquid phase outlet of the third distillation column 17 below the third packing layer 34 and the evaporation reactor 16 are connected by the second external slag discharge pipe 39. The second external slag discharge pipe 39 is equipped with a second booster pump 40 and a first online chromatograph 41. The first distillation column 1 above the first partition 30 is equipped with a light component conveying pipe 42. The first distillation column 1 of the first packing layer 31 and the second packing layer 32 is equipped with a crude phthalic anhydride conveying pipe 43. The second distillation column 3 above the third partition 35 is equipped with a refined phthalic anhydride conveying pipe 44.
[0021] The first heating delivery pipe 5 and the first gas delivery pipe 13 are both connected to the second distillation column 3 below the third packing layer 34. The first distillation column 1 below the second packing layer 32 is provided with a second heating delivery pipe 45. The inlet end and the outlet end of the second heating delivery pipe 45 are both connected to the first distillation column 1. The second heating delivery pipe 45 is provided with a third booster pump 46, the inlet end of a heavy component delivery pipe 47, a seventh regulating valve 48, and a second reboiler 49 in sequence from the inlet end to the outlet end of the second heating delivery pipe 45. The outlet end of the heavy component delivery pipe 47 is connected to the second distillation column 3 below the third packing layer 34. The heavy component delivery pipe 47 is provided with an eighth regulating valve 50. The gas-liquid separator 12 is equipped with a wire mesh coalescer 51. The first heating delivery pipe 5 is connected to the gas-liquid separator 12 below the wire mesh coalescer 51, and the gas-liquid separator 12 above the wire mesh coalescer 51 is connected to the first gas delivery pipe 13. The bottom of the gas-liquid separator 12 is connected to the liquid reflux pipe 7. A liquid level sensor 52 is installed on the gas-liquid separator 12 below the wire mesh coalescer 51. A residue delivery pipe 53 is installed at the bottom of the cold source channel of the bottom heater 20. A ninth regulating valve 54 and a second online chromatograph 55 are installed on the residue delivery pipe 53.
[0022] To facilitate the merging of the gas evaporated from the evaporation reactor 16 into the vapor stream transported through the gas-liquid separator 12 to participate in the distillation process within the third distillation column 17, a one-way valve 25 is installed on the first gas delivery pipe 13 of this product. The one-way valve 25 is connected to the first gas delivery pipe 13 of the second distillation column 3 and the gas-phase outlet of the evaporation reactor 16 through a second gas delivery pipe 26. A second pressure sensor 27, a sixth regulating valve 28, and a second vacuum pump 29 are sequentially installed along the direction from near to far from the evaporation reactor 16. The installation of the second pressure sensor 27 facilitates the feedback of pressure parameters.
[0023] The usage instructions for this product are as follows: Figures 1 to 3 As shown, it includes the following steps:
[0024] S1. The pretreated crude phthalic anhydride solution is transported to the first distillation column 1 between the first packing layer 31 and the second packing layer 32 to form a first descending liquid flow. The first descending liquid flow and the first ascending gas flow exchange heat countercurrently. The light components in the first descending liquid flow are vaporized and incorporated into the first ascending gas flow. The phthalic anhydride and residue in the first ascending gas flow are liquefied and incorporated into the first descending liquid flow. The first ascending gas flow continues to rise into the first packing layer 31 and exchanges heat countercurrently with the second descending liquid flow. The phthalic anhydride and residue in the first ascending gas flow are further liquefied to form a second descending liquid flow. The light components in the second descending liquid flow are vaporized and incorporated into the first ascending gas flow. The second descending liquid flow descends into the second packing layer 32 and merges into the first descending liquid flow. The first rising gas flow is continuously liquefied to form a first rising gas-liquid mixture. After gas-liquid separation by the gas-lift cap 37 on the first partition 30, the liquid phase of the first rising gas-liquid mixture descends to form a first returning descending liquid flow, which is transported to the first packing layer 31 and merges into the second descending liquid flow. The gas phase continues to rise and is transported to the heat source channel of the first top condenser 2 and the cold source of the first top condenser 2 for heat exchange. The light components are liquefied and sent back to the first distillation column 1. The non-condensable gas in the first rising gas flow is transported to the tail gas main pipe 18 through the corresponding tail gas transport branch pipe 21. After the first descending liquid flow is delivered to the bottom of the first distillation column 1, it enters the second heating delivery pipe 45 and is pressurized by the second booster pump 40, then divided into two parts, namely the first liquid flow and the second liquid flow. The first liquid flow is delivered to the second reboiler 49 for heating and is partially vaporized to form a first gas-liquid mixture. The first gas-liquid mixture is sent back to the first distillation column 1 below the second packing layer 32. The gas phase of the first gas-liquid mixture forms a first rising gas flow, and the liquid phase of the first gas-liquid mixture is merged into the first descending liquid flow and delivered to the second heating delivery pipe 45. The second liquid flow is delivered to the second distillation column 3 through the heavy component delivery pipe 47.
[0025] S2. The second portion of the liquid flow enters the second distillation column 3 and then enters the first heating and conveying pipe 5. After being pressurized by the first booster pump 8, it is divided into two parts: a circulating liquid flow and an external discharge liquid flow. The circulating liquid flow is sent to the first reboiler 11 for heating and partial vaporization to form a second gas-liquid mixture. The second gas-liquid mixture is sent to the gas-liquid separator 12 for gas-liquid separation. The gas phase component of the second gas-liquid mixture is sent to the first gas conveying pipe 13, while the liquid phase component of the second gas-liquid mixture is temporarily stored in the gas-liquid separator 12 below the wire mesh coalescer 51. The liquid in the gas-liquid separator 12 is continuously sent to the first heating and conveying pipe 5 between the first booster pump 8 and the second distillation column 3 and merged into the second portion of the liquid flow entering the first heating and conveying pipe 5.
[0026] The discharged liquid is transported to the evaporation reactor 16 through the first discharge pipe 9. When the liquid level in the evaporation reactor 16 reaches a preset height, the discharge of the discharged liquid is stopped. The jacket of the evaporation reactor 16 receives a heat source to heat the discharged liquid in the evaporation reactor 16. The gas generated by evaporation in the evaporation reactor 16 is abnormally transported through the gas phase outlet end of the evaporation reactor 16 and the first gas delivery pipe 13 to the first gas delivery pipe 13 between the one-way valve 25 and the second distillation column 3. It merges with the gas phase components in the second gas-liquid mixture transported through the gas-liquid separator 12 to form a second rising gas flow, which is sent back to the second distillation column 3. As the second rising gas flow continues to rise, the residue in the second rising gas flow, along with a small amount of phthalic anhydride, is liquefied to form a third descending liquid flow. The second rising gas flow and the third descending liquid flow exchange heat countercurrently. The residue components in the second rising gas flow are liquefied and merged into the third descending liquid flow, which continues to descend. When the third descending liquid flow descends to the second distillation column 3... The bottom of distillation column 3 is merged into the second portion of the liquid flow that is conveyed to the second rectification column 3 via the heavy component conveying pipe 47, and then enters the first heating conveying pipe 5 together. After the second rising gas flow passes through the third packing layer 34, some components in the second rising gas flow are still continuously liquefied to form a second upward gas-liquid mixture. After gas-liquid separation by the riser cap 37 on the second baffle 33, the liquid phase component in the second upward gas-liquid mixture is enriched and forms a second return liquid flow due to gravity, which is sent back to the third packing layer. The material layer 34 is merged into the third descending liquid flow. The gas phase component in the second upward gas-liquid mixture is transported to the heat source channel of the second top condenser 4 and continuously transported to the cold source of the second top condenser 4 for heat exchange. The phthalic anhydride component is liquefied and sent back to the second distillation column 3, blocked by the second baffle 33, and continuously transported outward through the refined phthalic anhydride conveying pipe 44. The non-condensable gas component of the gas phase component in the second upward gas-liquid mixture is transported to the tail gas conveying main pipe 18 through the corresponding tail gas conveying branch pipe 21.
[0027] S3. After the liquid in the evaporation reactor 16 is heated to a preset time, the second booster pump 40 is turned on. The residual liquid in the evaporation reactor 16 is then transported to the third distillation column 17 through the second external slag discharge pipe 39. After entering the third distillation column 17, the residual liquid is transported to the cold source channel of the bottom heater 20 and the heat source continuously supplied to the bottom heater 20 for heat exchange. The phthalic anhydride component in the residual liquid is further evaporated to form a third rising gas flow, which is sent back to the third distillation column 17. The third rising gas flow continues to rise, and the residue in the third rising gas flow is gradually liquefied to form a fourth descending liquid flow. The third rising gas flow adjacent to the fourth descending liquid flow undergoes countercurrent heat exchange. The phthalic anhydride component in the fourth descending liquid flow is vaporized and merged into the third rising gas flow adjacent to the fourth descending liquid flow. The residue component in the third rising gas flow is liquefied and merged into the fourth descending liquid flow. The fourth descending liquid flow continues to descend and is transported to the cold source channel of the bottom heater 20.
[0028] After passing through the fourth packing layer 36, some components of the third upward gas stream continue to liquefy, forming a third upward gas-liquid mixture. After passing through the riser cap 37 of the third baffle 35, the liquid phase component of the third upward gas-liquid mixture is enriched and forms a third return liquid stream due to gravity. This third return liquid stream is transported to the fourth packing layer 36 and merges into the fourth downward liquid stream. The gas phase component of the third upward gas-liquid mixture is transported to the heat source channel of the third top condenser 19 for heat exchange with the continuously supplied cold source. The phthalic anhydride component is liquefied and transported through the condensate delivery pipe 38 to the first distillation column 1 between the first baffle 30 and the first packing layer 31, merging into the first return downward liquid stream. When the liquid medium in the cold source channel of the bottom heater 20 is heated to a preset time, it is transported outward through the residue delivery pipe 53, during which time the components are detected by the second online chromatograph 55.
[0029] In this embodiment, the liquid flow pressurized by the first booster pump 8 is partially diverted into the evaporation reactor 16 for heating. After the phthalic anhydride component in the liquid entering the evaporation reactor 16 is partially evaporated, it is then transported to the third distillation column 17 for further distillation. This reduces the phthalic anhydride content in the residue transported to the third distillation column 17, thereby reducing the phthalic anhydride content in the residue discharged from the third distillation column 17.
[0030] The embodiments described above are merely preferred embodiments of this utility model and are not intended to limit the scope of implementation of this utility model. Therefore, all equivalent changes or modifications made to the structure, features and principles described in the patent claims of this utility model should be included within the scope of the patent application of this utility model.
Claims
1. A refining apparatus for crude phthalic anhydride, characterized in that: The system includes a first distillation column (1), a first top condenser (2) at the top of the first distillation column (1), a second distillation column (3) connected to the first distillation column (1), a second top condenser (4) at the top of the second distillation column (3), a first heating delivery pipe (5) at the bottom of the second distillation column (3), and the first heating delivery pipe (5) sequentially includes a first regulating valve (6), the outlet end of a liquid reflux pipe (7), a first booster pump (8), the inlet end of a first external slag discharge pipe (9), a second regulating valve (10), a first reboiler (11), and a gas-liquid separator along the direction from near to far from the second distillation column (3). (12) The inlet end of the gas-liquid separator (12) is connected to the gas phase outlet end of the gas-liquid separator (12) and the second distillation column (3). The inlet end of the liquid phase reflux pipe (7) is connected to the liquid phase outlet end of the gas-liquid separator (12). The liquid phase reflux pipe (7) is equipped with a third regulating valve (14). The first external slag discharge pipe (9) is equipped with a fourth regulating valve (15). The outlet end of the first external slag discharge pipe (9) is connected to the inlet end of the evaporation reactor (16). The gas phase outlet end of the evaporation reactor (16) is connected to the first gas conveying pipe (13). The liquid phase outlet end of the evaporation reactor (16) is connected to the third distillation column (17).
2. The refining apparatus for crude phthalic anhydride according to claim 1, characterized in that: It also includes a tail gas delivery main pipe (18), a third top condenser (19) is provided at the top of the third distillation column (17), a bottom heater (20) is provided at the bottom of the third distillation column (17), the top of the cold source channel of the third top condenser (19) and the tail gas delivery main pipe (18), the top of the cold source channel of the second top condenser (4) and the tail gas delivery main pipe (18), and the top of the cold source channel of the first top condenser (2) and the tail gas delivery main pipe (18) are all connected by tail gas delivery branch pipes (21). Each tail gas delivery branch pipe (21) is provided with a first vacuum pump (22), a fifth regulating valve (23) and a first pressure sensor (24) in sequence along the direction from near the tail gas delivery main pipe (18) to away from the tail gas delivery main pipe (18).
3. The refining apparatus for crude phthalic anhydride according to claim 1, characterized in that: The first gas delivery pipe (13) is equipped with a one-way valve (25). The one-way valve (25) is connected to the first gas delivery pipe (13) of the second distillation column (3) and the gas phase outlet end of the evaporation reactor (16) through the second gas delivery pipe (26). The second gas delivery pipe (26) is equipped with a second pressure sensor (27), a sixth regulating valve (28) and a second vacuum pump (29) in sequence along the direction from near the evaporation reactor (16) to away from the evaporation reactor (16).
4. The refining apparatus for crude phthalic anhydride according to claim 1, characterized in that: The first distillation column (1) is provided with a first partition (30), a first packing layer (31) and a second packing layer (32) from top to bottom. The second distillation column (3) is provided with a second partition (33) and a third packing layer (34) from top to bottom. The third distillation column (17) is provided with a third partition (35) and a fourth packing layer (36) from top to bottom. Each of the first partition (30), the second partition (33) and the third partition (35) is provided with a gas lift cap (37). The second distillation column (3) above the second partition (33) and the first partition (30) and the first packing layer (31) are connected by a condensate delivery pipe (38).
5. The refining apparatus for crude phthalic anhydride according to claim 4, characterized in that: The liquid phase outlet of the third distillation column (17) below the third packing layer (34) and the evaporation reactor (16) are connected by the second external slag discharge pipe (39). The second external slag discharge pipe (39) is equipped with a second booster pump (40) and a first online chromatograph (41). The first distillation column (1) above the first partition (30) is equipped with a light component conveying pipe (42). The first distillation column (1) of the first packing layer (31) and the second packing layer (32) is equipped with a crude phthalic anhydride conveying pipe (43). The second distillation column (3) above the third partition (35) is equipped with a refined phthalic anhydride conveying pipe (44).
6. The refining apparatus for crude phthalic anhydride according to claim 4, characterized in that: The first heating delivery pipe (5) and the first gas delivery pipe (13) are both connected to the second distillation column (3) below the third packing layer (34). The first distillation column (1) below the second packing layer (32) is provided with a second heating delivery pipe (45). The inlet end of the second heating delivery pipe (45) and the outlet end of the second heating delivery pipe (45) are both connected to the first distillation column (1). Along the second heating delivery pipe (45) from the inlet end to the outlet end, the third booster pump (46), the inlet end of the heavy component delivery pipe (47), the seventh regulating valve (48), and the second reboiler (49) are sequentially provided. The outlet end of the heavy component delivery pipe (47) is connected to the second distillation column (3) below the third packing layer (34). The heavy component delivery pipe (47) is provided with an eighth regulating valve (50).