CN113440883A

CN113440883A - Refining distillation tower for preparing acrylic acid by circulating propylene oxidation method

Info

Publication number: CN113440883A
Application number: CN202111007922.1A
Authority: CN
Inventors: 李金江; 王兵杰; 荣洪杰
Original assignee: Shandong Lanwan New Material Co Ltd
Current assignee: Shandong Lanwan New Material Co Ltd
Priority date: 2021-08-31
Filing date: 2021-08-31
Publication date: 2021-09-28
Anticipated expiration: 2041-08-31
Also published as: CN113440883B

Abstract

The invention relates to a refined distillation tower in the preparation of acrylic acid by a cyclic propylene oxidation method, which relates to the technical field of chemical equipment and comprises a shell, an upper interlayer, a lower interlayer, a sleeve, an air passage and a flow passage, wherein the shell is of a hollow columnar structure, the upper interlayer is fixedly connected to the upper part of an inner cavity of the shell, and the lower interlayer is fixedly connected to the lower part of the inner cavity of the shell so as to divide the shell into three cavities, namely a light component removal area, an acetic acid removal area and a refined area from top to bottom, wherein the light component removal area is communicated with the acetic acid removal area, and the acetic acid removal area is communicated with the refined area; a plurality of sleeves are fixedly connected in the shell below the lower interlayer at intervals, and heating pipes are penetrated in the sleeves; the invention has the advantages that crude purification and fine purification of acrylic acid can be completed by only one distillation tower, a plurality of groups of distillation towers are not needed, the occupied area of a factory is saved, and in addition, energy can be saved.

Description

Refining distillation tower for preparing acrylic acid by circulating propylene oxidation method

Technical Field

The invention relates to the technical field of chemical equipment, in particular to a refining distillation tower for preparing acrylic acid by a cyclic propylene oxidation method.

Background

In recent years, with the increase of the use amount of the super absorbent resin and the washing assistant, the market demand of acrylic acid products is further pulled, the application of the acrylic acid is greatly expanded, the acrylic acid products which are originally widely applied are favored, and the updating development of the industrial production method and the process of the acrylic acid is promoted. The production process of acrylic acid has undergone the cyanoethanol process, REPPE (REPPE) process (oxo process), ketene process, acrylonitrile hydrolysis process and propylene oxidation process, and the former 4 processes have been gradually eliminated for technical and economic reasons. The acrylic acid devices newly built and expanded after the 80 s in the 20 th century all adopt a propylene oxidation method. The propylene oxidation process has sufficient raw material sources (propylene, air and steam), and the core of the process is the selection of the catalyst and the optimized combination of the process. Through many years of exploration, the propylene oxidation method is improved in the aspects of catalysts and processes, the one-step method and the two-step method are mainly used for producing acrylic acid through propylene oxidation, and the two-step method is the current main acrylic acid production method due to the fact that the two-step method is reliable in technology, high in product yield, stable in product quality and high in economic benefit.

The key to the industrial scale-up of the mature production method is the device. Propylene oxidation catalysts and process modifications are also increasingly demanding on production facilities, particularly how to increase thermal efficiency without increasing energy consumption. The distillation tower is generally used when the thermal efficiency is low, although the distillation tower can heat and vaporize the required materials to achieve the purpose of purification, much heat does not really participate in the endothermic vaporization of the materials in the heating process, so that more energy is lost, and the thermal efficiency is reduced. And a plurality of distillation towers are arranged on the whole production line for purifying different materials, and the single distillation tower has low heat efficiency, so that the energy loss caused by the plurality of distillation towers is very large.

Therefore, in view of the above-mentioned disadvantages, it is desirable to provide a purification distillation column for recycling acrylic acid produced by the oxidation of propylene.

Disclosure of Invention

Technical problem to be solved

The invention aims to solve the technical problem of low thermal efficiency of the existing distillation tower.

(II) technical scheme

In order to solve the technical problem, the invention provides a refining distillation tower for preparing acrylic acid by a cyclic propylene oxidation method, which comprises a shell, an upper interlayer, a lower interlayer, a sleeve, an air passage and a flow passage, wherein the shell is of a hollow columnar structure, the upper interlayer is fixedly connected to the upper part of an inner cavity of the shell, and the lower interlayer is fixedly connected to the lower part of the inner cavity of the shell, so that the shell is divided into three cavities which are respectively a light removal area, an acetic acid removal area and a refining area from top to bottom, the light removal area is communicated with the acetic acid removal area, and the acetic acid removal area is communicated with the refining area; a plurality of sleeves are fixedly connected in the shell below the lower interlayer at intervals, and heating pipes are penetrated in the sleeves; the air flue links firmly under on the interlayer, and the air flue top extends to the interlayer lower part, and spiral helicine runner links firmly in the air flue outside, and the runner outer wall and shell inner wall butt.

As a further description of the present invention, it is preferable that the sleeve is a hollow metal tube, the heating tube is preferably an infrared heating tube, and lubricating grease is filled between the sleeve and the heating tube.

As a further explanation of the present invention, preferably, the housing on one side of the upper portion of the upper partition is fixedly connected with a transfer pipe, the transfer pipe is connected with a pump body and a detection device, and the outlet end of the transfer pipe extends into the acetic acid removing area and is located right above the flow channel.

As a further explanation of the invention, preferably, the top of the shell is fixedly connected with a feed inlet, the shell on one side above the upper interlayer is fixedly connected with an entrainer injection port, and one side of the feed inlet is fixedly connected with an exhaust port.

As a further description of the present invention, preferably, the air passage is a cylindrical structure, the bottom of the air passage is communicated with the refining area, the axial direction of the air passage coincides with the axial direction of the casing, the caliber of the top of the air passage is contracted and bent, and the length direction of the bent portion of the air passage is perpendicular to the axial direction of the casing and extends out of the casing.

As a further illustration of the invention, preferably the airway outer diameter satisfies:

whereinDIs the inner diameter of the shell;

dis the outer diameter of the air passage;

the wall thickness of the air channel is not more than 5 mm.

As a further illustration of the invention, the pitch of the flow channels preferably satisfies:

whereinLIs the length of the acetic acid removing area;

is the pitch of the flow channel;

the number of spiral turns of the flow channel is not less than 4.

As a further explanation of the present invention, it is preferable that the upper and lower partition layers are hollow in the middle, wherein the hollow area of the upper partition layer is a heating chamber, the hollow area of the lower partition layer is a heat insulation chamber, the heating chamber is filled with distilled water, and heat insulation bricks are inserted into the heat insulation chamber at intervals.

As a further explanation of the present invention, it is preferable that the casing at one side of the heating chamber is fixedly connected with a water injection pipe, and the water injection pipe is communicated with the heating chamber; a shell on one side of the heat insulation cavity is provided with a detection hole, a plurality of groups of temperature sensors are inserted in the detection hole, and the temperature sensors stretch into the middle of the heat insulation cavity.

As a further explanation of the present invention, it is preferable that the spiral inner ring of the flow channel is fixedly connected with a spiral mounting ring, and the thickness of the mounting ring is greater than that of the flow channel.

(III) advantageous effects

The technical scheme of the invention has the following advantages:

the invention combines the actual production requirements, can realize the purification of the acrylic acid by one distillation tower by improving the structure of the traditional distillation tower, adopts the heat conduction principle, and can realize the separation of materials with different boiling points without using an additional heating device. And effectively improve the area of contact of liquid and surrounding environment, improve heat exchange efficiency, and then can further improve purification efficiency, kill many birds with one stone.

Drawings

FIG. 1 is a front elevational view of the final assembly of the present invention;

FIG. 2 is a rear elevational view of the present invention;

FIG. 3 is a partial cross-sectional view of the present invention;

FIG. 4 is a side view of the present invention;

fig. 5 is a diagram of the airway connection location of the present invention.

In the figure: 1. a housing; 11. a feed inlet; 12. a discharge port; 13. an entrainer injection port; 14. an exhaust port; 15. an air outlet channel; 16. a light component removal area; 17. a de-acetic acid zone; 18. a refining zone; 2. an upper interlayer; 21. a heating cavity; 22. a transfer tube; 23. a water injection pipe; 3. a lower interlayer; 31. a thermal insulation cavity; 32. a flow changing pipe; 33. a detection hole; 4. a sleeve; 41. a base; 5. an airway; 51. an exhaust pipe; 6. a flow channel; 61. and (7) installing a ring.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.

A refined distillation tower for preparing acrylic acid by cyclic propylene oxidation is disclosed, which is combined with a figure 1 and a figure 3 and comprises a shell 1, an upper interlayer 2, a lower interlayer 3, a sleeve 4, an air passage 5 and a flow passage 6, wherein the shell 1 is of a hollow columnar structure, the upper interlayer 2 is fixedly connected to the upper part of an inner cavity of the shell 1, the lower interlayer 3 is fixedly connected to the lower part of the inner cavity of the shell 1, so that the shell 1 is divided into three cavities, a light component removal area 16, an acetic acid removal area 17 and a refining area 18 are respectively arranged from top to bottom, the light component removal area 16 is communicated with the acetic acid removal area 17, and the acetic acid removal area 17 is communicated with the refining area 18. Wherein, each cavity is internally provided with an adjusting device to maintain the pressure constant and reduce the accident rate. A plurality of sleeves 4 are fixedly connected in the shell 1 below the lower interlayer 3 at intervals, and heating pipes penetrate through the sleeves 4; air flue 5 links firmly on interlayer 3 down, and 5 tops of air flue extend to 2 lower parts of interlayer, and spiral helicine runner 6 links firmly in 5 outsides of air flue, and 6 outer walls of runner and 1 inner wall butt of shell.

With reference to fig. 1 and 4, a feed inlet 11 is fixedly connected to the top of the housing 1, and the feed inlet 11 is communicated with a lightness removing area 16; the feed port 11 is provided to inject the chemically reacted liquid into the housing 1. The bottom of the material shell 1 is fixedly connected with a discharge port 12, and the discharge port 12 is communicated with a refining area 18 and used for discharging waste materials out of the shell 1. An entrainer injection port 13 is fixedly connected to the shell 1 on one side above the upper interlayer 2, and liquid toluene is introduced into the entrainer injection port 13. One side of the feed inlet 11 is fixedly connected with an exhaust port 14 for discharging azeotropic gas. The shell 1 below the upper interlayer 2 is fixedly connected with an air outlet channel 15 for discharging gas containing acetic acid.

With reference to fig. 2 and 4, the upper interlayer 2 and the lower interlayer 3 are formed by welding two circular iron sheets at intervals on the inner wall of the shell 1, the two circular iron sheets have a distance so that the middle parts of the upper interlayer 2 and the lower interlayer 3 are hollow, wherein the hollow area of the upper interlayer 2 is a heating cavity 21, the hollow area of the lower interlayer 3 is a heat insulation cavity 31, the heating cavity 21 is filled with distilled water, and heat insulation bricks are inserted into the heat insulation cavity 31 at intervals. The upper interlayer 2 and the lower interlayer 3 with fillers are arranged and used for layering the distillation tower and also used for insulating temperature and adjusting heat conduction amount, so that the temperature of each area of the shell 1 can reach the design temperature, a heating component is not required to be additionally added, and energy is saved. A water injection pipe 23 is fixedly connected to the shell 1 at one side of the heating cavity 21, and the water injection pipe 23 is communicated with the heating cavity 21; the shell 1 on one side of the heat insulation cavity 31 is provided with a detection hole 33, a plurality of groups of temperature sensors are inserted in the detection hole 33, and the plurality of groups of temperature sensors are distributed at intervals along the axial direction of the detection hole 33 until the temperature sensors stretch into the middle of the heat insulation cavity 31.

Referring to fig. 2 and 4, the water injection pipe 23 is provided to inject or extract deionized water into or from the heating chamber 21, and the heating chamber 21 is filled with deionized water, so that even if the temperature in the acetic acid removing region 17 is decreased in a short time, the large specific heat capacity of water can be used to ensure that the temperature fluctuation range in the light removing region 16 is small, thereby maintaining the normal and continuous azeotropic operation in the light removing region 16. The heat insulation cavity 31 is arranged to prevent high heat emitted by the sleeve 4 from being directly conducted to the acetic acid removing area 17 to cause the vaporization of both acetic acid and acrylic acid, and the purification work of the acrylic acid is influenced. And set up multiunit temperature sensor moreover, not only be used for monitoring and conduct to the heat that removes acetic acid district 17, can also monitor the homogeneity that the heat gived off, in case the temperature gived off inhomogeneous then shut down at once and overhaul, avoid producing the accident.

With reference to fig. 3 and 4, the shell 1 on one side of the upper part of the upper partition layer 2 is fixedly connected with a transfer pipe 22, the transfer pipe 22 is connected with a pump body and a detection device, the outlet end of the transfer pipe 22 extends into the acetic acid removing area and is positioned right above the flow channel 6, and the transfer pipe 22 is arranged for guiding the liquid in the light removing area 16 into the acetic acid removing area 17 for secondary extraction. The shell 1 on one side of the upper part of the lower interlayer 3 is fixedly connected with a flow changing pipe 32, the flow changing pipe 32 is also connected with a detection device of a pump body, and the outlet end of the flow changing pipe 32 extends into the refining area 18 so as to guide the liquid in the acetic acid removing area 17 into the refining area 18.

Referring to fig. 3 and 4, the sleeve 4 is a hollow metal tube, the heating tube is preferably an infrared heating tube, and lubricating grease is filled between the sleeve 4 and the heating tube. The heating pipe is provided for heating the refining zone 18 to vaporize the acrylic acid and discharge it out of the housing 1 through the gas passage 5, thereby purifying the acrylic acid. In addition, the sleeve 4 is arranged, so that the heating pipe can be prevented from being corroded by reactants, and heat can be better transferred by combining lubricating grease.

With reference to fig. 4 and 5, the gas duct 5 is a cylindrical structure, the bottom of the gas duct 5 is communicated with the refining area 18, the axial direction of the gas duct 5 coincides with the axial direction of the housing 1, the caliber of the top of the gas duct 5 is contracted and bent, and the length direction of the bent part of the gas duct 5 is perpendicular to the axial direction of the housing 1 and extends out of the housing 1 for discharging acrylic acid gas. The runner 6 is the metal sheet of bolt form, 6 spiral inner circles of runner have linked firmly spiral helicine collar 61, collar 61 thickness is greater than 6 thicknesses of runner, set up collar 61 and not only can improve 6 structural strength of runner, still be convenient for weld 6 regular in the runner on air flue 5, and then when follow-up in 1 interior assembly air flue 5 of shell and

runner

6, 6 outer wall surfaces of runner can laminate on 1 inner wall of shell, avoid appearing clearance fit or interference fit and cause great assembly degree of difficulty.

Referring to fig. 4 and 5, the reacted material enters the light component removal zone 16 through the feed inlet 11, then flows to the acetic acid removal zone 17 through the transfer pipe 22, then enters the refining zone 18 through the flow change pipe 32, after the liquid capacity in the refining zone 18 reaches two thirds of the total volume of the refining zone 18, the heating pipe in the sleeve 4 is started to make the temperature in the refining zone 18 reach about 160 ℃, at this time, acrylic acid, acetic acid and the like in the liquid are vaporized into gas, and the gas flows out of the shell 1 through the gas passage 5 and the gas exhaust pipe 51, the gas initially passing through the gas exhaust pipe 51 enters the condenser for condensation and then is discharged into the light component removal zone 16 through the feed inlet 11, the main purpose is to make the heat in the refining zone 18 be transferred to the acetic acid removal zone 17 and the light component removal zone 16, and raw materials are not wasted.

Referring to fig. 4 and 5, the heat transfer between the refining zone 18 and the acetic acid removal zone 17 depends primarily on the heat exchange between the gas in the gas duct 5 and the space in the acetic acid removal zone 17. Wherein the outer diameter of the air passage 5 satisfies:

whereinDIs the inner diameter of the shell 1;

dthe outer diameter of the air passage 5;

the wall thickness of the air duct 5 is not more than 5 mm.

By adopting the above calculation formula, the air passage 5 can be adjusted in size according to the shells 1 of different specifications, so that not only can the faster heat exchange be realized, but also the heat in the air passage 5 can be more quickly dissipated to the acetic acid removing area 17 to heat the liquid in the acetic acid removing area 17. But also avoids the problems that the volume of the acetic acid removing area 17 is insufficient due to the overlarge volume of the air channel 5, the quantity of the acrylic acid supplied to the refining area 18 is insufficient, and the subsequent yield of the acrylic acid gas is insufficient, so that the heat exchange efficiency is reduced. In addition, in order to improve the productivity and the heat exchange efficiency, a spiral flow channel 6 is arranged outside the air channel 5, so that the liquid entering the acetic acid removing area 17 can flow downwards in a spiral mode, wherein the pitch of the flow channel 6 meets the following requirements:

whereinLThe length of the acetic acid removal zone 17;

is a stream6, the pitch is achieved;

the number of spiral turns of the flow channel 6 is not less than 4.

By adopting the design, the liquid can be slowly flowed in the acetic acid removing area 17, so that the liquid can fully exchange heat with gas in the air passage 5, the air passage 6 is not fully loaded on the air passage 5, the gas can heat the surrounding environment of the acetic acid removing area 17, the failure of the acetic acid removing work caused by condensation in the acetic acid removing area 17 after the acetic acid is vaporized is avoided, and in addition, the light removing area 16 can be heated. And the number of turns of the runner 6 is controlled, the manufacturing difficulty and the assembling difficulty of the runner 6 are reduced, and the practicability of the device is improved.

With reference to fig. 4 and 5, the reasonable structural design of the outer shell 1, the upper partition layer 2 and the lower partition layer 3 and the temperature control of the heating pipe can make the temperature in the refining zone 18 reach about 160 ℃, and the acrylic acid with the boiling point of 140.9 ℃ can be vaporized. The temperature in the acetic acid removing area 17 can be maintained at 122 +/-3 ℃ by heat exchange, so that the acetic acid with the boiling point of 117.9 ℃ is vaporized. The temperature in the light component removal zone 16 can be maintained at 103 +/-3 ℃ through heat exchange, so that the acetic acid added with the toluene and the water are subjected to azeotropic vaporization to realize the primary separation of the acetic acid. Wherein the inner cavity of the shell 1 is decompressed during the whole distillation process.

The materials continuously enter the shell 1, and after the temperature of the acetic acid removing area 17 and the light removing area 16 rises, the valves of the exhaust port 14 and the exhaust passage 15 are opened to prepare for absorbing distilled gas. Then the entrainer injection port 13 is opened to inject liquid toluene into the light component removal zone 16, most of acetic acid, water and toluene are mixed to form an azeotrope, the azeotrope is vaporized and evaporated at about 100 ℃, and tower bottom liquid containing a small amount of acetic acid is left after being pumped out through an exhaust port. Then the liquid in the light component removing area 16 is pumped into the acetic acid removing area 17 through the transfer pipe 22, at this time, the liquid slowly flows on the flow passage 6, and exchanges heat with the gas in the air passage 5, a small amount of acetic acid in the liquid is also vaporized again, and the liquid is pumped out of the shell 1 through the air outlet passage 15. Finally, the liquid flows into the refining area 18, acrylic acid is vaporized and evaporated by high-temperature heating, enters a condenser through an exhaust pipe 51 and is condensed into liquid, and then enters an acrylic acid storage area, so that the extraction of acrylic acid is completed.

In conclusion, the invention adopts the integrated distillation tower, can realize the purification of the acrylic acid, adopts the heat conduction principle and can realize the separation of materials with different boiling points without using an additional heating device. And the contact area of the liquid and the surrounding environment is effectively improved by designing the air passage 5 and the flow passage 6, the heat exchange efficiency is improved, compared with the existing distillation purification time, the time for distilling one ton of raw materials can be shortened by about 3h, the amount of the finally produced acrylic acid liquid is only about 1kg less than that of the existing acrylic acid liquid, the purity is the same, and the production efficiency is greatly improved in comparison. In addition, the use of a plurality of groups of distillation towers is reduced, the equipment purchase and use cost is reduced, the occupied area is reduced, and the spare area can be provided with a plurality of safety equipment for improving the production safety of the whole production line.

Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.

Claims

1. A refined distillation tower in the preparation of acrylic acid by a cyclic propylene oxidation method is characterized in that: the device comprises a shell (1), an upper interlayer (2), a lower interlayer (3), a sleeve (4), an air passage (5) and a flow passage (6), wherein the shell (1) is of a hollow columnar structure, the upper interlayer (2) is fixedly connected to the upper part of an inner cavity of the shell (1), the lower interlayer (3) is fixedly connected to the lower part of the inner cavity of the shell (1) so that the shell (1) is divided into three cavities which are respectively a light component removal area (16), an acetic acid removal area (17) and a refining area (18) from top to bottom, the light component removal area (16) is communicated with the acetic acid removal area (17), and the acetic acid removal area (17) is communicated with the refining area (18); a plurality of sleeves (4) are fixedly connected in the shell (1) below the lower interlayer (3) at intervals, and heating pipes penetrate through the sleeves (4); air flue (5) link firmly under on interlayer (3), and air flue (5) top extends to interlayer (2) lower part, and spiral helicine runner (6) link firmly in air flue (5) outside, and runner (6) outer wall and shell (1) inner wall butt.

2. The recycle propylene oxidation process acrylic acid finishing distillation column as claimed in claim 1, wherein: the sleeve (4) is a hollow metal pipe, the heating pipe is preferably an infrared heating pipe, and lubricating grease is filled between the sleeve (4) and the heating pipe.

3. The recycle propylene oxidation process acrylic acid finishing distillation column as claimed in claim 1, wherein: a transfer pipe (22) is fixedly connected to the shell on one side of the upper part of the upper interlayer (2), a pump body and a detection device are connected to the transfer pipe (22), and the outlet end of the transfer pipe (22) extends into the acetic acid removing area (17) and is positioned right above the flow channel (6).

4. The recycle purification distillation column for acrylic acid production by oxidation of propylene as claimed in claim 3, wherein: the top of the shell (1) is fixedly connected with a feed inlet (11), the shell (1) on one side above the upper interlayer (2) is fixedly connected with an entrainer injection port (13), and one side of the feed inlet (11) is fixedly connected with an exhaust port (14).

5. The recycle propylene oxidation process acrylic acid finishing distillation column as claimed in claim 1, wherein: air flue (5) are cylinder tubular structure, and air flue (5) bottom communicates with each other with refined district (18), and air flue (5) axis direction and shell (1) axis direction coincidence, and air flue (5) top bore shrink and buckle, and air flue (5) kink length direction is perpendicular shell (1) axis and is stretched out outside shell (1).

6. The recycle purification distillation column for acrylic acid production by oxidation of propylene as claimed in claim 5, wherein: the outer diameter of the air passage (5) satisfies the following conditions:

whereinDIs the inner diameter of the shell (1);

dis the outer diameter of the air passage (5);

the wall thickness of the air channel (5) is not more than 5 mm.

7. The recycle purification distillation column for acrylic acid production by oxidation of propylene as claimed in claim 6, wherein: the pitch of the flow channel (6) meets the following requirements:

whereinLThe length of the acetic acid removing area (17);

is the screw pitch of the flow passage (6);

the number of spiral turns of the flow channel (6) is not less than 4.

8. The recycle propylene oxidation process acrylic acid finishing distillation column as claimed in claim 1, wherein: the middle parts of the upper interlayer (2) and the lower interlayer (3) are hollow, wherein the hollow area of the upper interlayer (2) is a heating cavity (21), the hollow area of the lower interlayer (3) is a heat insulation cavity (31), distilled water is filled in the heating cavity (21), and heat insulation bricks are inserted in the heat insulation cavity (31) at intervals.

9. The recycle purification distillation column for acrylic acid production by oxidation of propylene as claimed in claim 8, wherein: a water injection pipe (23) is fixedly connected to the shell (1) at one side of the heating cavity (21), and the water injection pipe (23) is communicated with the heating cavity (21); a detection hole (33) is formed in the shell (1) on one side of the heat insulation cavity (31), a plurality of groups of temperature sensors are inserted into the detection hole (33), and the temperature sensors extend into the middle of the heat insulation cavity (31).

10. The recycle propylene oxidation process acrylic acid finishing distillation column as claimed in claim 7, wherein: the spiral inner ring of the flow channel (6) is fixedly connected with a spiral mounting ring (61), and the thickness of the mounting ring (61) is larger than that of the flow channel (6).