Combined reactor for preparing acrylic acid

Abstract

The utility model belongs to the technical field of chemical production equipment, and particularly relates to a combined reactor for preparing acrylic acid, which comprises a first molten salt heat exchanger, a second molten salt heat exchanger, a boiler and a tubular reactor, the second fused salt heat exchanger is connected with the boiler through a pipeline, the tubular reactor is connected with the first fused salt heat exchanger through a pipeline, the tubular reactor is connected with the second fused salt heat exchanger through a pipeline, a raw material inlet is formed in the top of the tubular reactor, a product outlet is formed in the bottom of the tubular reactor, a partition plate is arranged in the tubular reactor, and a reaction area is arranged above the partition plate. A cooling area is arranged below the partition plate. The device is uniform in heat exchange, not prone to coking, convenient to overhaul and simple in equipment.

Description

Technical Field

[0001] The utility model belongs to the technical field of chemical production equipment, and specifically relates to a combined reactor for preparing acrylic acid. Background Art

[0002] Chemical production is accompanied by chemical reactions, separation, and purification processes, among which reactions are an important link; chemical reactions may be exothermic or endothermic, and reaction heating and heat transfer are important components of the reactor. The acrylic acid production process mostly uses shell-and-tube heat exchangers, with the reaction tubes filled with catalysts. Propylene reacts to form acrylic acid, which is an exothermic reaction and requires heat exchange through a heat transfer medium to maintain the reaction temperature and reaction stability.

[0003] The acrylic acid production process is mostly a two-stage reaction. The first stage catalyst oxidizes propylene to acrolein, and the second stage reaction oxidizes acrolein to acrylic acid. After the first stage reaction is completed, rapid cooling is required to prevent over-reaction from coking, polymerization and other side reactions. The rapid cooling stage is separate and uses a fin heat exchanger for cooling. This method has uneven heat exchange, the fins are prone to coking, and it is difficult to handle. It needs to be dismantled and cleaned, and the number of equipment increases, making the control complex. Utility Model Content

[0004] The purpose of the utility model is to solve the problems of a large number of acrylic acid quenching equipment, easy coking of heat exchangers and uneven heat exchange in the above-mentioned background technology. A new combined reactor for preparing acrylic acid is proposed. The reactor combines the reaction section and the quenching section into one, so that heat exchange is carried out in the reactor, thereby avoiding the problems of coking of the fins of the external heat exchanger.

[0005] A technical solution adopted to achieve the above-mentioned purpose is a combined reactor for preparing acrylic acid, the combined reactor comprising a first molten salt heat exchanger, a second molten salt heat exchanger, a boiler and a shell-and-tube reactor, the first molten salt heat exchanger is connected to the boiler through a pipeline, the second molten salt heat exchanger is connected to the boiler through a pipeline, the shell-and-tube reactor is connected to the first molten salt heat exchanger through a pipeline, the shell-and-tube reactor is connected to the second molten salt heat exchanger through a pipeline, a raw material inlet is provided at the top of the shell-and-tube reactor, a product outlet is provided at the bottom of the shell-and-tube reactor, a partition is provided in the shell-and-tube reactor, a reaction zone is provided above the partition, and a cooling zone is provided below the partition.

[0006] In the above technical solution, the tubes in the tube reactor are lengthened, and catalysts are filled in the tubes, so that the tubes are divided into a reaction section and a rapid cooling section, which correspond to the reaction zone and the cooling zone respectively. The reaction section and the rapid cooling section both use heat transfer salt for heat exchange, and the heat transfer salt is then exchanged with boiler water, so that the heat exchange in the rapid cooling section is more uniform and no local temperature rise phenomenon occurs.

[0007] Furthermore, the side wall of the shell-and-tube reactor located in the reaction zone is provided with a first cold molten salt inlet and a first hot molten salt outlet, and the first cold molten salt inlet and the first hot molten salt outlet are respectively connected to the first molten salt heat exchanger through pipelines to form a circulation loop.

[0008] Furthermore, the first cold molten salt inlet is located below the first hot molten salt outlet.

[0009] In the above technical solution, in the reaction zone, the molten salt absorbs the heat released by the reaction, and the hot molten salt enters the first molten salt heat exchanger for heat exchange and turns into cold molten salt again, which enters the reaction zone to absorb heat. The first cold molten salt inlet is located below the first hot molten salt outlet, so that the molten salt flows in reverse and fully absorbs heat. The reaction zone is set to control a section of the reaction temperature to make the reaction temperature suitable.

[0010] Furthermore, a second cold molten salt inlet and a second hot molten salt outlet are provided on the side wall of the shell-and-tube reactor located in the cooling zone, and the second cold molten salt inlet and the second hot molten salt outlet are respectively connected to the second molten salt heat exchanger through pipelines to form a circulation loop.

[0011] Furthermore, the second cold molten salt inlet is located below the second hot molten salt outlet.

[0012] In the above technical solution, the principle of the solution is similar to the setting of the reaction zone. The cooling zone is set to perform rapid cooling after a reaction is completed to prevent side reactions from occurring.

[0013] Furthermore, a first water replenishment outlet and a second water replenishment outlet are provided at the bottom of the boiler, and a boiler steam production outlet is provided at the top of the boiler.

[0014] Furthermore, a first steam outlet is provided at the top of the first molten salt heat exchanger, the first steam outlet is connected to the boiler through a pipeline, and the first water replenishment outlet is connected to the first molten salt heat exchanger through a pipeline.

[0015] In the above technical solution, the first molten salt heat exchanger and the boiler form a circulation loop for heat exchange.

[0016] Furthermore, a second steam outlet is provided at the top of the second molten salt heat exchanger, the second steam outlet is connected to the boiler through a pipeline, and the second water supply outlet is connected to the second molten salt heat exchanger through a pipeline.

[0017] In the above technical solution, the second molten salt heat exchanger and the boiler form a circulation loop for heat exchange.

[0018] Furthermore, the length of the reaction zone is 2-8 m, and the length of the cooling zone is 0.5-3 m.

[0019] Furthermore, the diameter of the tubes in the tube reactor is 15-40 mm.

[0020] The advantages of the utility model are:

[0021] 1. The utility model uses a combined reactor to replace the traditional fin heat exchanger, the heat exchange is more uniform, and there is no coking of the heat exchanger fins, and the cleaning of the heat exchanger is more convenient.

[0022] 2. The utility model device is easy to maintain, and hot air is used to blow the coke out of the cooling zone. There is no need to dismantle the reactor or mechanically process it, so it takes less time and has a simple process. It can also process the coke tubes well.

[0023] 3. The utility model combines the reaction and cooling zones in the same device and uses the same heat exchange medium, so medium contamination will not occur.

[0024] 4. The utility model uses molten salt for heat exchange and then exchanges heat with boiler water to produce steam, thereby reducing the amount of steam production equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the utility model or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings in the following description are only embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0026] Figure 1 It is a structural schematic diagram of the utility model.

[0027] Illustration: 1. Raw material inlet, 2. Product outlet, 3. Partition, 4. First cold molten salt inlet, 5. First hot molten salt outlet, 6. Second cold molten salt inlet, 7. Second hot molten salt outlet, 8. First molten salt heat exchanger, 9. Second molten salt heat exchanger, 10. Boiler, 11. First steam production outlet, 12. Second steam production outlet, 13. First make-up water outlet, 14. Second make-up water outlet, 15. Boiler steam production outlet, 16. Shell and tube reactor. DETAILED DESCRIPTION

[0028] In order to enable those skilled in the art to better understand the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only embodiments of a part of the present invention rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the protection scope of the present invention.

[0029] In the description of the present invention, it should be understood that the terms "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0030] like Figure 1 As shown, a combined reactor for preparing acrylic acid is composed of a first molten salt heat exchanger 8, a second molten salt heat exchanger 9, a boiler 10 and a shell and tube reactor 16, wherein a raw material inlet 1 is provided at the top of the shell and tube reactor, a product outlet 2 is provided at the bottom, a partition 3 is provided inside, a reaction zone is above the partition, and a cooling zone is below the partition. The length of the reaction zone is 2-8m, the length of the cooling zone is 0.5-3m, and the diameter of the shell and tube reactor is 15-40mm. The reaction length and the diameter of the shell and tube can be changed and adjusted according to the actual production conditions.

[0031] A first cold molten salt inlet 4 and a first hot molten salt outlet 5 are provided on the side wall of the shell-and-tube reactor located in the reaction zone. The first cold molten salt inlet and the first hot molten salt outlet are respectively connected to the first molten salt heat exchanger through pipelines to form a circulation loop. The first cold molten salt inlet is located below the first hot molten salt outlet.

[0032] A second cold molten salt inlet 6 and a second hot molten salt outlet 7 are provided on the side wall of the shell-and-tube reactor in the cooling zone. The second cold molten salt inlet and the second hot molten salt outlet are respectively connected to the second molten salt heat exchanger through pipelines to form a circulation loop. The second cold molten salt inlet is located below the second hot molten salt outlet.

[0033] A first water replenishment outlet 13 and a second water replenishment outlet 14 are provided at the bottom of the boiler, a boiler steam production outlet 15 is provided at the top of the boiler, and a first steam production outlet 11 is provided at the top of the first molten salt heat exchanger. The first steam production outlet is connected to the boiler through a pipeline, and the first water replenishment outlet is connected to the first molten salt heat exchanger through a pipeline, so that a circulation loop is formed between the boiler and the first molten salt heat exchanger.

[0034] A second steam outlet 12 is provided on the top of the second molten salt heat exchanger, and the second steam outlet is connected to the boiler through a pipeline. The second water replenishment outlet is connected to the second molten salt heat exchanger through a pipeline, and a circulation loop is formed between the boiler and the second molten salt heat exchanger.

[0035] The working principle of the utility model is as follows: acrylic acid raw material enters the tube reactor from the raw material inlet, and reacts under the action of the catalyst. The reaction is an exothermic reaction. Cold molten salt enters the tube reactor from the first cold molten salt inlet, absorbs the heat generated by the reaction, and enters the first molten salt heat exchanger from the first hot molten salt outlet for heat exchange. The first molten salt heat exchanger cools the hot molten salt through the water of the boiler, so that it re-enters the tube reactor to form a heat exchange cycle, wherein the water in the first molten salt heat exchanger absorbs heat and then vaporizes and enters the boiler. The water generated by the boiler re-enters the first molten salt heat exchanger to form a heat exchange cycle, and finally the temperature in the reactor is reduced.

[0036] The principle of the second molten salt heat exchanger is similar to that of the first molten salt heat exchanger and will not be described in detail.

[0037] In the above working principle, the acrylic acid raw material undergoes a first stage of oxidation reaction to acrolein in the reaction zone, and is rapidly cooled in the cooling zone to prevent coking and side reactions.

[0038] Finally, it should be noted that this embodiment is only used to illustrate the present invention and does not limit the scope of the present invention. In addition, it should be understood that after reading the content of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the claims attached to this application.

Claims

1. A modular reactor for preparing acrylic acid, characterized in that: The combined reactor comprises a first molten salt heat exchanger (8), a second molten salt heat exchanger (9), a boiler (10) and a shell-and-tube reactor (16), wherein the first molten salt heat exchanger is connected to the boiler via a pipeline, the second molten salt heat exchanger is connected to the boiler via a pipeline, the shell-and-tube reactor is connected to the first molten salt heat exchanger via a pipeline, the shell-and-tube reactor is connected to the second molten salt heat exchanger via a pipeline, a raw material inlet (1) is provided at the top of the shell-and-tube reactor, a product outlet (2) is provided at the bottom of the shell-and-tube reactor, a partition (3) is provided inside the shell-and-tube reactor, a reaction zone is provided above the partition, and a cooling zone is provided below the partition.

2. The combined reactor according to claim 1, characterized in that: The side wall of the tubular reactor located in the reaction zone is provided with a first cold molten salt inlet (4) and a first hot molten salt outlet (5), and the first cold molten salt inlet and the first hot molten salt outlet are respectively connected to the first molten salt heat exchanger through pipelines to form a circulation loop.

3. The combined reactor according to claim 2, characterized in that: The first cold molten salt inlet is located below the first hot molten salt outlet.

4. The combined reactor according to claim 1, characterized in that: The side wall of the tubular reactor located in the cooling zone is provided with a second cold molten salt inlet (6) and a second hot molten salt outlet (7), and the second cold molten salt inlet and the second hot molten salt outlet are respectively connected to the second molten salt heat exchanger through pipelines to form a circulation loop.

5. The combined reactor according to claim 4, characterized in that: The second cold molten salt inlet is located below the second hot molten salt outlet.

6. The combined reactor according to claim 1, characterized in that: The bottom of the boiler is provided with a first water replenishment outlet (13) and a second water replenishment outlet (14), and the top of the boiler is provided with a boiler steam production outlet (15).

7. The combined reactor according to claim 6, characterized in that: A first steam outlet (11) is provided at the top of the first molten salt heat exchanger. The first steam outlet is connected to the boiler through a pipeline, and the first water replenishment outlet is connected to the first molten salt heat exchanger through a pipeline.

8. The combined reactor according to claim 6, characterized in that: A second steam outlet (12) is provided at the top of the second molten salt heat exchanger. The second steam outlet is connected to the boiler through a pipeline, and the second water replenishment outlet is connected to the second molten salt heat exchanger through a pipeline.

9. The combined reactor according to claim 1, characterized in that: The length of the reaction zone is 2-8 m, and the length of the cooling zone is 0.5-3 m.

10. The combined reactor according to claim 1, characterized in that: The diameter of the tubes in the tube reactor is 15-40 mm.

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