A braided tube heat exchange fixed bed reactor and its application

Abstract

A braided tube type heat exchange fixed bed reactor and its application belong to the field of reaction engineering technology. In this braided tube type fixed bed reactor, the heat exchange unit uses M groups, N groups, and P groups of heat exchange tubes to weave into a heat exchange mat, and then the heat exchange mat is rolled into a scroll roll with two or more different circle diameters with a core shaft or a radial bed distributor as the center. One end of the M group, N group, and P group of heat exchange tubes of the scroll roll is connected to the tube side inlet on the first head, and the other end is connected to the tube side outlet on the second head. The structural form of the heat exchange tube braided mat scroll roll is adopted to increase the heat transfer area and improve the heat transfer performance. At the same time, the multi-stream heat exchange structure of the reactor is realized, which can dissipate the heat in time when the reaction is in progress to prevent the occurrence of temperature runaway. In addition, by arranging different types of distributors inside the reactor, the heat exchange process is further optimized. For a reactor with a radial bed distributor, it has a larger flow cross-sectional area under the same cylinder diameter.

Description

Technical Field

[0001] The invention relates to a braided tube type heat exchange fixed bed reactor and application thereof, belonging to the technical field of reaction engineering. Background Art

[0002] The treatment of organic waste gas is one of the important issues in environmental pollution control. Currently, the more widely used methods for treating organic waste gas include liquid absorption, adsorption, thermal destruction, condensation and low-temperature plasma technology. Using catalytic oxidation technology to treat organic matter in waste gas is a method with a wide range of applications and is suitable for treating large amounts of medium and high concentration waste gas. The patent "A catalytic oxidation device for efficiently treating VOCs organic waste gas" (authorization announcement number: 208155730U) improves the structure of the catalytic-oxidation reactor, ensures the catalyst utilization rate and the device's purification efficiency for waste gas, but the device does not achieve an immediate reaction and immediate heat dissipation process, which is prone to temperature rise when treating high-concentration organic waste gas.

[0003] Acrylic acid and its esters are an important class of chemical raw materials. As polymer monomers, they can be used to synthesize thousands of polymers through homopolymerization and copolymerization. Polymers made from acrylic acid have excellent properties in terms of chemical stability, durability, weather resistance, flexibility, hardness, solubility and miscibility. They are widely used in adhesives, synthetic coatings, leather, textiles, papermaking, detergents, plastic additives, sanitary materials, oil extraction and super-absorbent materials. The production methods of acrylic acid include chloroethanol method, cyanoethanol method, ketene method, high-pressure Reppe method, improved Reppe method, acrylonitrile hydrolysis method and propylene oxidation method. Currently, the main industrial production method is only propylene oxidation method. Methyl methacrylate, as an important organic monomer in acrylic acid esters, is mainly used in the manufacture of organic glass, plastic modified impact-resistant additives, lubricant additives, coatings, adhesives, etc. There is a process production route that uses the aldol condensation reaction of formaldehyde and acetic acid to synthesize acrylic acid, then hydrogenates acrylic acid and esterifies it with methanol to produce methyl propionate, and methyl propionate and formaldehyde undergo an aldol condensation reaction to synthesize methyl methacrylate. It is a coal-based process route that is different from the traditional petroleum-based route. It is green and environmentally friendly, has high atomic utilization, and has broad application value; however, the aldol condensation reaction is a highly exothermic reaction with a large amount of reaction heat. The patent "A method for synthesizing acrylic acid" (publication number: 111763153A) designs the reaction and separation process of obtaining acrylic acid by reacting acetic acid and formaldehyde, ensuring the yield of acrylic acid, but does not provide a reaction device that can accurately maintain the temperature of the reaction chamber in the presence of a large amount of reaction heat.

[0004] Fixed bed reactor is a device in which gas flows through a fixed catalyst bed for reaction. It is mainly used for gas-solid phase catalytic reaction and has the advantages of simple structure, stable operation, easy control, easy to achieve large-scale and continuous production. It is a widely used reactor structure. Traditional fixed bed reactors have the following disadvantages:

[0005] (1) The heat transfer effect is poor and the bed temperature is prone to uneven distribution;

[0006] (2) When the reaction releases a lot of heat, the temperature rises rapidly and is difficult to control;

[0007] (3) The operation process of replacing the catalyst is complicated.

[0008] Due to the above-mentioned shortcomings of traditional fixed-bed reactors, in the multi-stream oxidation treatment system for high-concentration organic waste gas and the method of synthesizing acrylic acid from formaldehyde and acetic acid and methyl methacrylate from methyl propionate and formaldehyde by aldol condensation reaction, the current heat exchange fixed-bed reactor has problems such as poor heat exchange effect and reactor exothermic temperature rise. Based on this, the present invention studies and designs a braided tube heat exchange fixed-bed reactor, and uses it to develop a system for treating high-concentration organic waste gas and a method for synthesizing acrylic acid and methyl methacrylate by aldol condensation reaction, which can effectively solve the temperature rise problem caused by reaction exotherm in the above-mentioned process, and at the same time recover the reaction heat for preheating and heating the reaction. Summary of the invention

[0009] In order to overcome the existing problems in the prior art, the present invention provides a braided tube heat exchange fixed bed reactor, which is formed by weaving a plurality of heat exchange tubes into a heat exchange mat, and then wrapped around the outer periphery of the shaft core or the radial bed distributor. At the same time, by reasonably specifying the heat exchange scheme of multiple streams, the heat can be dissipated in time when the exothermic reaction is carried out in the reactor to prevent the occurrence of temperature runaway. In addition, the radial bed reactor can increase the cross-sectional area of ​​the flow channel under the same cylinder diameter, greatly reducing the pressure drop of the reactor and realizing a large flux of material in and out. A formaldehyde acetic acid synthesis acrylic acid system was developed using the above-mentioned fixed bed reactor, which can effectively solve the temperature runaway problem caused by the reaction exothermicity in the above-mentioned two processes, control the reaction temperature, and recover the reaction heat.

[0010] The technical solution adopted by the present invention is as follows: a braided tube type heat exchange fixed bed reactor, the shell side of the reactor comprises a first head provided with a first manhole and a shell side outlet, a cylinder provided with a jacket and a second head provided with a shell side inlet and a second manhole, and the first connecting flange and the second connecting flange are used to fix and connect them into one body, the jacket is provided with an inlet pipe and an outlet sleeve pipe, the first head is provided with inlets of a plurality of heat exchange tubes of a heat exchange unit, and the second head is provided with outlets of a plurality of heat exchange tubes of the heat exchange unit, the heat exchange tubes comprise M groups, N groups and P groups of heat exchange tubes, the heat exchange unit adopts M groups, N groups and P groups of heat exchange tubes to braid into a heat exchange mat, and then the heat exchange mat is fixedly connected to form a heat exchange mat, and ... A scroll drum with more than two different diameters is rolled up as the center with a core shaft or a radial bed distributor; one end of the M group of heat exchange tubes of the scroll drum is connected to the first tube side inlet on the first head, and the other end is connected to the first tube side outlet on the second head, one end of the N group of heat exchange tubes is connected to the second tube side inlet on the first head, and the other end is connected to the second tube side outlet on the second head, one end of the P group of heat exchange tubes is connected to the third tube side inlet on the first head, and the other end is connected to the third tube side outlet on the second head; the shell side adopts an axial flow heat exchange structure or a radial flow heat exchange structure; a first distributor is arranged at the first connecting flange in the cylinder.

[0011] The diameter of the heat exchange tube 1 is 0.1-10 mm, the bending angle θ of the heat exchange tube when woven into the heat exchange mat 16 is not greater than 30 degrees, and the gap between adjacent heat exchange tubes is smaller than the particle size of the catalyst.

[0012] When an axial flow heat exchange structure is adopted, a conical porous axial bed distributor is arranged at the second connecting flange in the cylinder, and the scroll drum is positioned and fixed by a core shaft; the tube-side fluid enters from the shell-side inlet and passes through the axial bed distributor, the scroll drum and the first distributor in sequence, and is discharged from the shell-side outlet.

[0013] When a radial flow heat exchange structure is adopted, a second distributor is arranged at the second connecting flange in the cylinder, and the scroll drum is positioned and fixed by a radial bed distributor; the tube-side fluid enters from the shell-side inlet and passes through the second distributor, radial bed distributor, scroll drum and first distributor in sequence, and is discharged from the shell-side outlet.

[0014] The catalyst particles and the supporting particles are placed between the gaps of the scroll tube mats with different circle diameters of the scroll drum, or the catalyst is sprayed on the outer wall of the scroll tube mat of the scroll drum.

[0015] This braided tube type heat exchange fixed bed reactor is used for treating high concentration organic waste gas or synthesizing acrylic acid from formaldehyde and acetic acid.

[0016] The braided tube type heat exchange fixed bed reactor is applied to synthesize methyl methacrylate through aldol condensation reaction.

[0017] The beneficial effects of the present invention are as follows: in this braided tube heat exchange fixed bed reactor, the heat exchange unit uses M groups, N groups, and P groups of heat exchange tubes to weave into a heat exchange mat, and then the heat exchange mat is rolled into a scroll roll with two or more different circle diameters with the core shaft or radial bed distributor as the center. One end of the M group, N group, and P group of heat exchange tubes of the scroll roll is connected to the tube side inlet on the first head, and the other end is connected to the tube side outlet on the second head. The structural form of the heat exchange tube braided mat scroll roll is adopted to increase the heat transfer area and improve the heat transfer performance. At the same time, the multi-stream heat exchange structure of the reactor is realized, and the heat can be dissipated in time during the reaction to prevent the occurrence of the temperature runaway phenomenon. In addition, the two groups of cylinder flange structures and the flange structure in the tube side main pipe are used to realize the detachable reactor, thereby simplifying the replacement of the catalyst and facilitating the regular maintenance of the shell side structure. By arranging different types of distributors inside the reactor, the heat exchange process is further optimized. For a reactor with a radial bed distributor, under the same cylinder diameter, it has a larger flow cross-sectional area, reduces the pressure and can achieve a large flux of material passing. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a structural diagram of a braided tube type axial flow heat exchange fixed bed reactor.

[0019] Figure 2 It is a structural diagram of a braided tube radial flow heat exchange fixed bed reactor.

[0020] Figure 3 It is a structural diagram of the heat exchange seat.

[0021] Figure 4 It is a schematic diagram of the structure of the heat exchange tube braided mesh scroll drum.

[0022] Figure 5 It is a structural diagram of the axial bed distributor.

[0023] Figure 6 It is a structural diagram of the radial bed distributor.

[0024] Figure 7 yes Figure 1 A partial enlarged view of middle A.

[0025] Figure 8 yes Figure 3 A partial enlarged view of B.

[0026] Fig. 9 yes Figure 4 A partial enlarged view of C in the middle.

[0027] Fig.10 It is a schematic diagram of the fluid flow in a three-stream braided tube heat exchange fixed bed reactor.

[0028] Fig.11The schematic diagram of the structure of a system for synthesizing acrylic acid from formaldehyde and acetic acid.

[0029] In the figure: 1, heat exchange tube, 2, shaft core, 3, first manhole, 3a, second manhole, 4, first head, 4a, second head, 5mi, first tube side inlet, 5mo, first tube side outlet, 5ni, second tube side inlet, 5no, second tube side outlet, 5pi, third tube side inlet, 5po third tube side outlet, 6, tube sheet, 7, flange ring, 8, shell side outlet, 9, first distributor, 9a, second distributor, 10, first connecting flange, 10a, second connecting flange, 11, cylinder, 12, jacket, 13, shell side inlet, 14, axial bed Distributor, 15, inlet pipe, 15a, outlet pipe, 16, heat exchange mat, 17, scroll drum, 18, radial bed distributor, 41, third heat exchange tube bundle, 41a, fourth heat exchange tube bundle, 41b, fifth heat exchange tube bundle, 42, third control valve, 42a, fourth control valve, 42b, fifth control valve, 43, cooling water main valve, 44, coolant storage tank, 45, first heat recovery device, 46, raw material storage tank, 47, feed pump, 48, second heat recovery device, 49, second evaporator, 50, flow control valve, 51, second fixed bed reactor. DETAILED DESCRIPTION

[0030] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0031] Figure 1-9 The structure diagram of a braided tube type heat exchange fixed bed reactor is shown. In the figure, the shell side of the braided tube type heat exchange fixed bed reactor includes a first head 4 provided with a first manhole 3 and a shell side outlet 8, a cylinder 11 provided with a jacket 12, and a second head 4a provided with a shell side inlet 13 and a second manhole 3a, and are fixedly connected into one by a first connecting flange 10 and a second connecting flange 10a. The jacket 11 is provided with an inlet pipe 15 and an outlet sleeve pipe 15a. The first head 2 is provided with inlets of multiple heat exchange tubes 1 of the heat exchange unit, and the second head 2a is provided with outlets of multiple heat exchange tubes 1 of the heat exchange unit. The heat exchange tubes 1 include M groups, N groups, and P groups of heat exchange tubes. The heat exchange unit uses M groups, N groups, and P groups of heat exchange tubes to weave into a heat exchange mat 16 (see Figure 3 , 8 ), and then the heat exchange mat 16 is rolled around the core shaft 2 or the radial bed distributor 18 to form a scroll roll 17 with two or more different circle diameters (see Figure 4 , 9). One end of the M group of heat exchange tubes of the scroll drum 17 is connected to the first tube side inlet 5mi on the first head 2, and the other end is connected to the first tube side outlet 5mo on the second head 2a, one end of the N group of heat exchange tubes is connected to the second tube side inlet 5ni on the first head 2, and the other end is connected to the second tube side outlet 5no on the second head 2a, one end of the P group of heat exchange tubes is connected to the third tube side inlet 5pi on the first head 2, and the other end is connected to the third tube side outlet 5po on the second head 2a; the shell side adopts an axial flow heat exchange structure or a radial flow heat exchange structure; a first distributor 9 is arranged at the first connecting flange 10 in the cylinder 11.

[0032] The diameter of the heat exchange tube 1 is 0.1-10 mm, and the bending angle θ of the heat exchange tube when woven into the heat exchange mat 16 is not greater than 30 degrees (see Figure 3 ).

[0033] When the axial flow heat exchange structure is adopted, a conical porous axial bed distributor 14 is arranged at the second connecting flange 10a in the cylinder 11, and the scroll roll 17 is positioned and fixed by the core shaft 2; the tube side fluid enters from the shell side inlet 13 and passes through the axial bed distributor 14, the scroll roll 17 and the first distributor 9 in sequence, and is discharged from the shell side outlet 8 (see Figure 1 , 5 , 7).

[0034] When the radial heat exchange structure is adopted, the second distributor 9a is arranged at the second connecting flange 10a in the cylinder 11, and the scroll roll 17 is positioned and fixed by the radial bed distributor 18; the tube-side fluid enters from the shell-side inlet 13 and passes through the second distributor 9a, the radial bed distributor 18, the scroll roll 17 and the first distributor 9 in sequence, and is discharged from the shell-side outlet 8 (see Figure 2 , 6 ).

[0035] The catalyst particles and the supporting particles are placed between the gaps between the scroll tube mats of different diameters of the scroll drum 17 .

[0036] The catalyst is sprayed on the outer wall of the scroll tube mat of the scroll drum 17.

[0037] Fig.10 It is a schematic diagram of the fluid flow in a three-stream braided tube heat exchange fixed bed reactor.

[0038] Application Examples

[0039] Fig.11 The schematic diagram of the structure of a system for synthesizing acrylic acid from formaldehyde acetic acid is shown in FIG. Figure 1 or Figure 2The fixed bed reactor shown in the figure comprises a cooling liquid storage tank 44, a raw material storage tank 46, a first heat recovery device 45, a second heat recovery device 48, a second evaporator 49 and a second fixed bed reactor 51, wherein the second fixed bed reactor 51 comprises a third heat exchange tube bundle 41, a fourth heat exchange tube bundle 41a and a fifth heat exchange tube bundle 41b, and the outlet of the cooling liquid storage tank 44 is connected to the third heat exchange tube bundle 41, the fourth heat exchange tube bundle 41a and the fifth heat exchange tube bundle 41b respectively through a first control valve 42, a second control valve 42a and a third control valve 42b. The inlet of the tube bundle 41b, the outlets of the third heat exchange tube bundle 41, the fourth heat exchange tube bundle 41a, and the fifth heat exchange tube bundle 41b are connected to the inlet of the coolant storage tank 44 through the tube side of the first heat recovery device 45, and the outlet of the raw material storage tank 46 is connected to the shell side inlet of the second fixed bed reactor 51 through the feed pump 47, the shell side of the first heat recovery device 45, the shell side of the second heat recovery device 48, the second evaporator 49, and the flow control valve 50 in sequence, and the shell side outlet of the second fixed bed reactor 51 is connected to the tube side inlet of the second heat recovery device 48. A radial bed reactor is used, and the heat exchange tubes are wrapped on the radial bed distributor, and catalyst particles and support particles for catalyzing the reaction of formaldehyde and acetic acid to produce acrylic acid are filled between each layer of the heat exchange pipe network.

[0040] The method for synthesizing acrylic acid by the system of synthesizing acrylic acid from formaldehyde and acetic acid comprises the following steps:

[0041] 1. The catalyst is loaded between the gaps between the scroll tube bundles of different diameters of the woven mesh scroll roll of the heat exchange tube in the second fixed bed reactor 51 or sprayed on the outer wall of the heat exchange tube of the woven mesh scroll roll of the heat exchange tube. The shell side of the second fixed bed reactor 51 is protected by nitrogen.

[0042] 2. During the reaction process, the formaldehyde acetic acid solution in the raw material storage tank 46 is transported to the shell side of the first heat recovery device 45 and the second heat recovery device 48 in sequence by the feed pump 47 for preheating, and then enters the shell side of the second fixed bed reactor 51 through the flow control valve 50 after being gasified by the second evaporator 49, and reacts to generate acrylic acid and release a large amount of heat. The product enters the purification process after heat exchange in the tube side of the second heat recovery device 48.

[0043] 3. The coolant in the coolant storage tank 44 enters the tube side of the second fixed bed reactor 51 through the third heat exchange tube bundle 41, the fourth heat exchange tube bundle 41a, and the fifth heat exchange tube bundle 41b. After heat exchange, it enters the tube side of the first heat recovery device 45 to preheat the raw materials and then returns to the coolant storage tank 44.

[0044] The heat exchange process can be optimized by changing the properties of the heat exchange medium in different streams, so that the reactor can dissipate a large amount of heat in a timely manner through the heat exchange tube bundle during the strong exothermic reaction process. The shell side is always maintained at the most suitable temperature of 360℃-380℃ for the reaction.

Claims

1. A braided tube type heat exchange fixed bed reactor, wherein the shell side of the reactor comprises a first end cap (4) provided with a first manhole (3) and a shell side outlet (8), a cylinder (11) provided with a jacket (12), and a second end cap (4a) provided with a shell side inlet (13) and a second manhole (3a), and the reactor is fixedly connected into one body by a first connecting flange (10) and a second connecting flange (10a), the jacket (12) is provided with an inlet pipe (15) and an outlet pipe (15a), the first end cap (4) is provided with inlets of a plurality of heat exchange tubes (1) of a heat exchange unit, and the second end cap (4a) is provided with outlets of a plurality of heat exchange tubes (1) of the heat exchange unit, wherein: The heat exchange tubes (1) include M groups, N groups, and P groups of heat exchange tubes; the heat exchange unit uses the M groups, N groups, and P groups of heat exchange tubes to weave into a heat exchange mat (16); the heat exchange mat (16) is then rolled around a core shaft (2) or a radial bed distributor (18) to form a scroll roll (17) having two or more different circle diameters; one end of the M group of heat exchange tubes of the scroll roll (17) is connected to a first tube side inlet (5mi) on a first end cap (4), and the other end is connected to a first tube side outlet (5mo) on a second end cap (4a). , one end of the N group of heat exchange tubes is connected to the second tube side inlet (5ni) on the first head (4), and the other end is connected to the second tube side outlet (5no) on the second head (4a); one end of the P group of heat exchange tubes is connected to the third tube side inlet (5pi) on the first head (4), and the other end is connected to the third tube side outlet (5po) on the second head (4a); the shell side adopts an axial flow heat exchange structure or a radial flow heat exchange structure; a first distributor (9) is provided at the first connecting flange (10) in the cylinder (11); The diameter of the heat exchange tube (1) is 0.1-10 mm, and the bending angle θ of the heat exchange tube when it is woven into a heat exchange mat (16) is no greater than 30 degrees.

2. A braided tube heat exchange fixed bed reactor according to claim 1, characterized in that: When an axial flow heat exchange structure is adopted, a conical multi-porous axial bed distributor (14) is arranged at the second connecting flange (10a) in the cylinder (11), and the scroll drum (17) is positioned and fixed by a core shaft (2); the tube-side fluid enters from the shell-side inlet (13) and passes through the axial bed distributor (14), the scroll drum (17) and the first distributor (9) in sequence, and is discharged from the shell-side outlet (8).

3. The braided tube type heat exchange fixed bed reactor according to claim 1, characterized in that: When a radial flow heat exchange structure is adopted, a second distributor (9a) is arranged at the second connecting flange (10a) in the cylinder (11), and the scroll drum (17) is positioned and fixed by a radial bed distributor (18); the tube-side fluid enters from the shell-side inlet (13) and passes through the second distributor (9a), the radial bed distributor (18), the scroll drum (17) and the first distributor (9) in sequence, and is discharged from the shell-side outlet (8).

4. The braided tube type heat exchange fixed bed reactor according to claim 1, characterized in that: The catalyst particles and the supporting particles are placed between the gaps between the scroll tube mats of different diameters of the scroll drum (17).

5. The braided tube type heat exchange fixed bed reactor according to claim 1, characterized in that: The catalyst is sprayed onto the outer wall of the scroll tube mat of the scroll drum (17).

6. The braided tube type heat exchange fixed bed reactor according to claim 1 is used for synthesizing acrylic acid from formaldehyde acetic acid.

7. The braided tube heat exchange fixed bed reactor according to claim 1 is used for synthesizing methyl methacrylate by aldol condensation.

8. The braided tube heat exchange fixed bed reactor according to claim 1 is used for treating high-concentration organic waste gas.

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