CN114053958A

CN114053958A - Braided tube type heat exchange fixed bed reactor and application

Info

Publication number: CN114053958A
Application number: CN202111504489.2A
Authority: CN
Inventors: 代玉强; 俞宁
Original assignee: Dalian Qianyi Energy Chemical Technology Co ltd; Dalian University of Technology
Current assignee: Chongqing Daowei Low Carbon Technology Co ltd; Dalian University of Technology
Priority date: 2021-12-10
Filing date: 2021-12-10
Publication date: 2022-02-18
Anticipated expiration: 2041-12-10
Also published as: CN114053958B

Abstract

A braided tube type heat exchange fixed bed reactor and application thereof belong to the technical field of reaction engineering. The heat exchange unit is woven by M, N and P groups of heat exchange tubes to form a heat exchange mat, and the heat exchange mat is coiled into scroll reels with more than two different diameters by taking a mandrel or a radial bed distributor as a center. One end of the M groups, the N groups and the P groups of heat exchange pipes of the scroll winding drum is connected to a pipe pass inlet on the first seal head, and the other end of the heat exchange pipes is connected to a pipe pass outlet on the second seal head. The structure form of the spiral winding drum of the woven mat with the heat exchange tubes is adopted, the heat transfer area is increased, the heat transfer performance is improved, meanwhile, the multi-strand heat exchange structure of the reactor is realized, heat can be timely dissipated when the reaction is carried out, and the temperature runaway phenomenon is prevented. In addition, by arranging different types of distributors inside the reactor, the heat exchange process is further optimized. For a reactor equipped with a radial bed distributor, the cross-sectional flow area is larger for the same cylinder diameter.

Description

Braided tube type heat exchange fixed bed reactor and application

Technical Field

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

The organic waste gas treatment problem is one of the important problems in environmental pollution control, and the organic waste gas treatment methods widely used at present include a liquid absorption method, an adsorption method, a thermal destruction method, a condensation method, a low-temperature plasma technology and the like. The catalytic oxidation process is used for treating organic matters in the waste gas, and is a method which has wide application range and is suitable for treating large-gas-quantity and medium-high-concentration waste gas. The patent 'catalytic oxidation device for efficiently treating VOCs (volatile organic compounds) organic waste gas' (granted publication No. 208155730U) improves the structure of a catalytic-oxidation reactor, ensures the utilization rate of a catalyst and the purification efficiency of the device to the waste gas, but the device does not have the instant reaction and instant heat dissipation process, and is easy to cause the temperature runaway phenomenon when treating high-concentration organic waste gas.

Acrylic acid and ester thereof are important chemical raw materials, can be used as a polymer monomer to synthesize thousands of polymers through homopolymerization and copolymerization, and the polymer taking the acrylic acid as the raw material has excellent performances in the aspects of chemical stability, durability, weather resistance, flexibility, hardness, solubility, miscibility and the like, and is widely applied to the fields of adhesives, synthetic coatings, leather, textiles, papermaking, detergents, plastic auxiliaries, sanitary materials, oil exploitation, super-adsorption materials and the like. The acrylic acid production method includes a chlorohydrin method, a cyanoethanol method, a ketene method, a high-pressure Reppe method, a modified Reppe method, an acrylonitrile hydrolysis method, a propylene oxidation method and the like, and the main industrial production method at present is only the propylene oxidation method. Methyl methacrylate is used as an important organic monomer in acrylic ester and is mainly applied to manufacturing organic glass, plastic modified impact-resistant auxiliary agents, lubricating oil additives, coatings, adhesives and the like. The main industrial production method of methyl methacrylate in China is an acetone cyanohydrin method, which has high production cost and serious pollution. The existing production line of the process utilizes the aldol condensation reaction of formaldehyde and acetic acid to synthesize acrylic acid, then the acrylic acid is hydrogenated and esterified with methanol to generate methyl propionate, and the methyl propionate and formaldehyde are subjected to the aldol condensation reaction to synthesize methyl methacrylate. The method is a coal-based process route different from the traditional petroleum-based route, is green and environment-friendly, has high atom utilization rate and has wide application value; however, the aldol condensation reaction is a strongly exothermic reaction and a large amount of heat of reaction is present. The patent "a method for synthesizing acrylic acid" (publication No. 111763153 a) is designed to ensure the yield of acrylic acid by devising a reaction and separation process for obtaining acrylic acid by reacting acetic acid with formaldehyde, but does not provide a reaction apparatus capable of accurately maintaining the temperature of a reaction chamber in the presence of a large amount of reaction heat.

The fixed bed reactor is a device for gas to react through a fixed catalyst bed layer. The reactor is mainly used for gas-solid phase catalytic reaction, has the advantages of simple structure, stable operation, convenient control, easy realization of large-scale and continuous production and the like, and is a widely used reactor structure. Conventional fixed bed reactors have the following disadvantages:

(1) the heat transfer effect is poor, and the bed temperature is easy to be distributed unevenly;

(2) when the reaction exotherm is large, the temperature rises sharply and is difficult to control;

(3) the operation process of replacing the catalyst is complicated.

Due to the defects of the traditional fixed bed reactor, in a multi-stream oxidation treatment system for high-concentration organic waste gas and a method for synthesizing acrylic acid from formaldehyde and acetic acid and synthesizing methyl methacrylate from methyl propionate and formaldehyde by using aldol condensation reaction, the existing heat exchange fixed bed reactor has the problems of poor heat exchange effect, heat release and temperature runaway of the reactor and the like. Based on the above, the invention designs a braided tube type heat exchange fixed bed reactor, develops a system for treating high-concentration organic waste gas and a method for synthesizing acrylic acid and methyl methacrylate by using aldol condensation reaction, can effectively solve the problem of temperature runaway caused by reaction heat release in the process, and simultaneously recovers the reaction heat for preheating and heating of the reaction.

Disclosure of Invention

In order to overcome the problems in the prior art, the invention provides a braided tube type heat exchange fixed bed reactor, wherein a plurality of heat exchange tubes are braided into a heat exchange mat and then wrapped on the periphery of a shaft core or a radial bed distributor, and meanwhile, through a heat exchange scheme of reasonably appointing a plurality of flows, when the heat release reaction is carried out in the reactor, the heat can be timely dissipated, so that the temperature runaway phenomenon is prevented. In addition, the cross section area of a flow passage can be increased under the same cylinder diameter through the radial bed reactor, the pressure drop of the reactor is greatly reduced, and the material inlet and outlet with large flux are realized. A system for synthesizing acrylic acid by formaldehyde and acetic acid is developed by utilizing the fixed bed reactor, the problem of temperature runaway caused by reaction heat release in the two processes can be effectively solved, the reaction temperature is controlled, and the reaction heat is recovered.

The technical scheme adopted by the invention is as follows: a braided tube type heat exchange fixed bed reactor is characterized in that a shell pass of the reactor comprises a first seal head provided with a first manhole and a shell pass outlet, a cylinder body provided with a jacket and a second seal head provided with a shell pass inlet and a second manhole, the first seal head and the second seal head are fixedly connected into a whole by adopting a first connecting flange and a second connecting flange, the jacket is provided with an inlet pipeline and an outlet casing pipeline, the first seal head is provided with inlets of a plurality of heat exchange tubes of a heat exchange unit, the second seal head is provided with outlets of a plurality of heat exchange tubes of the heat exchange unit, the heat exchange tubes comprise M groups of heat exchange tubes, N groups of heat exchange tubes and P groups of heat exchange tubes, the heat exchange unit is braided into a heat exchange mat by adopting M groups of heat exchange tubes, N groups of heat exchange tubes and P groups of heat exchange tubes, and the heat exchange mat is coiled into a scroll reel with more than two different diameters by taking a mandrel or a radial bed distributor as a center; one ends of M groups of heat exchange pipes of the scroll winding drum are connected to a first pipe pass inlet on the first end enclosure, the other ends of the M groups of heat exchange pipes are connected to a first pipe pass outlet on the second end enclosure, one ends of N groups of heat exchange pipes are connected to a second pipe pass inlet on the first end enclosure, the other ends of the N groups of heat exchange pipes are connected to a second pipe pass outlet on the second end enclosure, one ends of P groups of heat exchange pipes are connected to a third pipe pass inlet on the first end enclosure, and the other ends of the P groups of heat exchange pipes are connected to a third pipe pass outlet on the second end enclosure; the shell pass adopts an axial-flow type heat exchange structure or a radial-flow type heat exchange structure; a first distributor is arranged at the first connecting flange in the cylinder body.

The pipe diameter of the heat exchange pipe 1 is 0.1-10mm, the bending angle theta of the heat exchange pipe when the heat exchange mat 16 is woven by the heat exchange pipe is not more than 30 degrees, and the gap between the adjacent heat exchange pipes is smaller than the particle size of the catalyst.

When an axial-flow type heat exchange structure is adopted, a conical porous axial bed distributor is arranged at a second connecting flange in the cylinder body, and the scroll cylinder is positioned and fixed by a mandrel; the tube-side fluid enters from the shell-side inlet, then sequentially passes through the axial bed distributor, the scroll reel and the first distributor, and is discharged from the shell-side outlet.

When a radial-flow heat exchange structure is adopted, a second distributor is arranged at a second connecting flange in the cylinder, and the scroll cylinder is positioned and fixed by a radial bed distributor; after entering from the shell-side inlet, the tube-side fluid sequentially passes through the second distributor, the radial bed distributor, the scroll reel and the first distributor and is discharged from the shell-side outlet.

The catalyst particles and support particles are placed between the gaps of the scroll mat of different diameters of the scroll drum or the catalyst is sprayed on the outer wall of the scroll mat of the scroll drum.

The braided tube type heat exchange fixed bed reactor is applied to the treatment of high-concentration organic waste gas or the synthesis of acrylic acid by formaldehyde and acetic acid.

The braided tube type heat exchange fixed bed reactor is applied to synthesizing methyl methacrylate by aldol condensation reaction.

The invention has the beneficial effects that: the heat exchange unit is woven by M, N and P groups of heat exchange tubes to form a heat exchange mat, and the heat exchange mat is coiled into more than two scroll reels with different diameters by taking a mandrel or a radial bed distributor as a center. One end of the M groups, the N groups and the P groups of heat exchange pipes of the scroll winding drum is connected to a pipe pass inlet on the first seal head, and the other end of the heat exchange pipes is connected to a pipe pass outlet on the second seal head. The structure form of the spiral winding drum of the woven mat with the heat exchange tubes is adopted, the heat transfer area is increased, the heat transfer performance is improved, meanwhile, the multi-strand heat exchange structure of the reactor is realized, heat can be timely dissipated when the reaction is carried out, and the temperature runaway phenomenon is prevented. In addition, the two groups of cylinder flange structures and the flange structure in the tube pass main pipe are utilized to realize the detachability of the reactor, thereby simplifying the replacement of the catalyst and facilitating the periodic maintenance of the shell pass structure. By arranging different types of distributors inside the reactor, the heat exchange process is further optimized. For the reactor provided with the radial bed distributor, the reactor has a larger flow cross section area under the same cylinder diameter, so that the pressure is reduced, and the material with large flux can pass through the reactor.

Drawings

Fig. 1 is a structural view of a woven tubular axial flow heat exchange fixed bed reactor.

FIG. 2 is a block diagram of a woven tubular radial heat exchange fixed bed reactor.

Fig. 3 is a schematic view of the structure of the heat exchange mat.

Fig. 4 is a schematic structural view of a woven mesh scroll roll of the heat exchange tube.

Fig. 5 is a block diagram of an axial bed distributor.

Figure 6 is a block diagram of a radial bed distributor.

Fig. 7 is a partially enlarged view of a in fig. 1.

Fig. 8 is a partially enlarged view of B in fig. 3.

Fig. 9 is a partial enlarged view of C in fig. 4.

FIG. 10 is a schematic fluid flow diagram of a tri-flow braided tubular heat exchange fixed bed reactor.

FIG. 11 is a schematic diagram showing the structure of a system for synthesizing acrylic acid from formaldehyde and acetic acid.

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 pass inlet, 5mo, first tube pass outlet, 5ni, second tube pass inlet, 5no, second tube pass outlet, 5pi, third tube pass inlet, 5po third tube pass outlet, 6, tube sheet, 7, flange ring, 8, shell pass outlet, 9, first distributor, 9a, second distributor, 10, first connecting flange, 10a, second connecting flange, 11, cylinder, 12, jacket, 13, shell pass inlet, 14, axial bed distributor, 15, inlet pipe, 15a, outlet pipe, 16, heat exchange mat, 17, scroll roll, 18, radial bed distributor, 41, third heat exchange tube bundle, 41a, fourth heat exchange tube bundle, 41b, fifth tube bundle, 42, third control valve, 42a, and a, A fourth control valve 42b, a fifth control valve 43, a cooling water main valve 44, a cooling liquid storage tank 45, a first heat recovery device 46, a raw material storage tank 47, a feeding pump 48, a second heat recovery device 49, a second evaporator 50, a flow control valve 51 and a second fixed bed reactor.

Detailed Description

The invention is further illustrated by the following figures and examples.

Fig. 1-9 show a block diagram of a woven tubular heat exchange fixed bed reactor. In the figure, the shell pass of the braided tube type heat exchange fixed bed reactor comprises a first seal head 4 provided with a first manhole 3 and a shell pass outlet 8, a barrel 11 provided with a jacket 12 and a second seal head 4a provided with a shell pass inlet 13 and a second manhole 3a, and is fixedly connected into a whole by adopting a first connecting flange 10 and a second connecting flange 10a, the jacket 11 is provided with an inlet pipeline 15 and an outlet casing pipeline 15a, the first seal head 2 is provided with inlets of a plurality of heat exchange tubes 1 of a heat exchange unit, and the second seal head 2a is provided with outlets of a plurality of heat exchange tubes 1 of the heat exchange unit. The heat exchange tube 1 comprises M, N and P groups of heat exchange tubes, the heat exchange unit adopts M, N and P groups of heat exchange tubes to weave a heat exchange mat 16 (see fig. 3 and 8), and then the heat exchange mat 16 is coiled into more than two scroll reels 17 (see fig. 4 and 9) with different diameters by taking the mandrel 2 or the radial bed distributor 18 as the center. One end of M groups of heat exchange pipes of the scroll winding drum 17 is connected to a first pipe pass inlet 5mi on the first seal head 2, the other end of the M groups of heat exchange pipes is connected to a first pipe pass outlet 5mo on the second seal head 2a, one end of N groups of heat exchange pipes is connected to a second pipe pass inlet 5ni on the first seal head 2, the other end of the N groups of heat exchange pipes is connected to a second pipe pass outlet 5no on the second seal head 2a, one end of P groups of heat exchange pipes is connected to a third pipe pass inlet 5pi on the first seal head 2, and the other end of the P groups of heat exchange pipes is connected to a third pipe pass outlet 5po on the second seal head 2 a; the shell pass adopts an axial-flow type heat exchange structure or a radial-flow type heat exchange structure; a first distributor 9 is arranged at a first connecting flange 10 in the cylinder body 11.

The pipe diameter of the heat exchange pipe 1 is 0.1-10mm, and the bending angle theta of the heat exchange pipe when the heat exchange pipe is woven into the heat exchange mat 16 is not more than 30 degrees (see figure 3).

When an axial-flow type heat exchange structure is adopted, a conical porous axial bed distributor 14 is arranged at a second connecting flange 10a in the cylinder body 11, and the scroll winding drum 17 is positioned and fixed by the mandrel 2; the tube-side fluid enters from the shell-side inlet 13, passes through the axial bed distributor 14, the scroll wrap 17 and the first distributor 9 in sequence, and is discharged from the shell-side outlet 8 (see fig. 1, 5 and 7).

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

Catalyst particles and support particles are placed between the gaps of the scroll mat of different turns of the scroll wrap 17.

The catalyst is sprayed on the outer wall of the scroll mat of the scroll reel 17.

Application examples

FIG. 11 shows a schematic diagram of a system for synthesizing acrylic acid from formaldehyde acetic acid. In the figure, the system for synthesizing acrylic acid from formaldehyde acetic acid adopts a fixed bed reactor shown in fig. 1 or fig. 2, the system 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, 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, an outlet of the cooling liquid storage tank 44 is respectively connected with inlets of the third heat exchange tube bundle 41, the fourth heat exchange tube bundle 41a and the fifth heat exchange tube bundle 41b through a first control valve 42, a second control valve 42a and a third control valve 42b, 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 respectively connected with an inlet of the cooling liquid storage tank 44 through a tube pass of the first heat recovery device 45, and a discharge outlet of the raw material storage tank 46 sequentially passes through a feed pump 47, a feed pump, a feed, a feed, a feed, a feed, a fixed, a feed, a feed, a feed, a, 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 are connected with the shell side inlet of the second fixed bed reactor 51, and the shell side outlet of the second fixed bed reactor 51 is connected with the tube side inlet of the second heat recovery device 48. A radial bed reactor is adopted, heat exchange tubes are wrapped on a radial bed distributor, and catalyst particles and supporting particles for catalyzing the reaction of formaldehyde and acetic acid to generate acrylic acid are filled between every two layers of heat exchange tubes.

The method for synthesizing acrylic acid by using the system for synthesizing acrylic acid by using formaldehyde and acetic acid comprises the following steps:

1. the catalyst is filled in the second fixed bed reactor 51 between the gaps of the scroll bundles with different diameters of the heat exchange pipe woven mesh scroll reel or sprayed on the outer wall of the heat exchange pipe woven mesh scroll reel, and the shell pass of the second fixed bed reactor 51 is protected by nitrogen.

2. In the reaction process, the formaldehyde-acetic acid solution in the raw material storage tank 46 is sequentially conveyed to the shell passes of the first heat recovery device 45 and the second heat recovery device 48 through the feed pump 47 for preheating, then is gasified through the second evaporator 49 and enters the shell pass of the second fixed bed reactor 51 through the flow control valve 50, acrylic acid is generated through reaction and releases a large amount of heat, and the product enters the purification process after heat exchange through the tube pass of the second heat recovery device 48.

3. The cooling liquid in the cooling liquid 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, and enters the tube side of the first heat recovery device 45 after heat exchange to preheat the raw material and then returns to the cooling liquid storage tank 44.

The heat exchange process can be optimized by changing the properties of the heat exchange media in different streams, so that a large amount of heat can be timely emitted by the heat exchange tube bundle in the strong heat release reaction process of the reactor. The shell side is always kept at the temperature of 360-380 ℃ which is most suitable for reaction.

Claims

1. A braided tubular heat exchange fixed bed reactor, the shell side of the reactor comprises a first head (4) provided with a first manhole (3) and a shell side outlet (8), a jacket ( 12) of the cylinder (11) and the second head (4a) provided with the shell side inlet (13) and the second manhole (3a), and the first connecting flange (10), the second connecting flange (10a) is fixedly connected as a whole, the jacket (11) is provided with an inlet pipe (15), an outlet pipe (15a), and a plurality of heat exchange tubes (1) of the heat exchange unit are provided on the first head (2). ) and the outlet of a plurality of heat exchange tubes (1) of the heat exchange unit on the second head (2a), characterized in that: the heat exchange tubes (1) include M groups, N groups, and P groups Heat exchange tubes, the heat exchange unit is made of M groups, N groups, and P groups of heat exchange tubes braided into heat exchange mats (16), and then the heat exchange mats (16) are connected with mandrels (2) or radial bed distributors (18) A scroll drum (17) with more than two different circle diameters is wound around the center; one end of the M group heat exchange tubes of the scroll drum (17) is connected to the first head (2) The first tube side inlet (5mi) on the upper end is connected to the first tube side outlet (5mo) on the second head (2a), and one end of the N groups of heat exchange tubes is connected to the first head (2) The second tube-side inlet (5ni) of the heat exchanger, the other end is connected to the second tube-side outlet (5no) on the second head (2a), and one end of the P group heat exchange tubes is connected to the first head (2). The third tube side inlet (5pi), 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 provided at the first connecting flange (10) in the cylindrical body (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 weaving it into a heat exchange mat (16) is not more than 30 degrees.

2. A braided tubular heat exchange fixed bed reactor according to claim 1, characterized in that: when an axial flow heat exchange structure is adopted, the second connection method in the cylinder (11) A conical porous axial bed distributor (14) is arranged at the flange (10a), and the scroll reel (17) is positioned and fixed with the mandrel (2); the tube side fluid enters from the shell side inlet (13) in sequence It is discharged from the shell side outlet (8) through the axial bed distributor (14), the scroll wrap (17) and the first distributor (9).

3. A braided tubular heat exchange fixed bed reactor according to claim 1, characterized in that: when a radial heat exchange structure is adopted, the second connecting flange in the cylinder (11) A second distributor (9a) is provided at (10a), and the scroll roll (17) is positioned and fixed with a radial bed distributor (18); the tube side fluid enters from the shell side inlet (13) and passes through the second Distributor (9a), radial bed distributor (18), scroll wrap (17) and first distributor (9), discharged from shell side outlet (8).

4. A braided tube type heat exchange fixed bed reactor according to claim 1, wherein the catalyst particles and the supporting particles are placed on the scroll tube sheets of different diameters of the scroll drum (17). between the gaps.

5 . The braided tube heat exchange fixed bed reactor according to claim 1 , wherein the catalyst is sprayed on the outer wall of the scroll tube sheet of the scroll roll ( 17 ). 6 .

6. A kind of braided tubular heat exchange fixed bed reactor according to claim 1 is applied to formaldehyde acetic acid synthesizing acrylic acid.

7. A kind of braided tubular heat exchange fixed bed reactor according to claim 1 is applied to aldol condensation to synthesize methyl methacrylate.

8. A braided tubular heat exchange fixed bed reactor according to claim 1 is applied to the treatment of high-concentration organic waste gas.