KR100898692B1 - Reactor with improved heat transfer performance, method for producing oxide using this reactor, and method for increasing heat medium flow rate of parallel flow - Google Patents

Abstract

According to the present invention, there is a first tube through which a heat medium and a first object to be transferred heat pass in an area in which a heat medium flow (parallel flow) parallel to a tube axis exists for the purpose of improving heat transfer efficiency. A multi-tube reactor or heat exchanger provided with a second tube in which the first object does not pass therein so as to be parallel to the tube axis; And using the reactor or the heat exchanger, and provides a method for producing an oxide by the catalytic gas phase oxidation reaction in the first tube through which the heat transfer medium and the first object to be transferred heat therein.

Contactor Phase Oxidation, Hot Spot, Multi-Stubber Reactor, Catalytic Reactor, Multi-Shell Catalyst Reactor, Heat Exchanger

Description

Reactor with IMPROVED HEAT TRANSFER PERFORMANCE, METHOD FOR PRODUCING OXIDE BY USING THE REACTOR, AND METHOD FOR INCREASING PARALLEL FLOW OF HEAT TRANSFER RATE}

1 is a cross-sectional view schematically showing the structure of a conventional conventional multi-tubular catalytic reactor or heat exchanger.

2 is a cross-sectional view schematically showing the structure of a reactor or a heat exchanger equipped with an unreacted tube having a constant diameter in the center according to the present invention for improving heat transfer efficiency.

Figure 3 is a cross-sectional view taken along the line X-X 'in Figure 2, to illustrate the size of the unreacted tube region, the reaction tube region, the donut-shaped baffle plate a constant diameter in the center according to one embodiment of the present invention; Sectional drawing of a reactor or heat exchanger with one unreacted tube having.

Figure 4 is a graph showing the heat transfer coefficient distribution in the reactor prepared in Comparative Example 1 and Example 1, respectively.

Figure 5 is a graph showing the temperature distribution inside the reaction tube in the reactor prepared in Comparative Example 1 and Example 1, respectively.

FIG. 6 is a cross-sectional view illustrating a structure for mounting a plurality of small diameter rod-shaped baffles or unreacted tubes that may be used instead of one unreacted tube shown in FIG. 3.

<Description of the symbols for the main parts of the drawings>

1: reactor or heat exchanger shell

2a: donut baffle plate

2b: disc baffle plate

3a, 3b, 3c: tube sheet

4: reaction tube

5a: annular conduit with heating medium

5b: annular conduit through which the heat medium is discharged

6: heating medium

7: reactive gas inlet

8: reaction gas outlet

9: unreacted tube centrally located

11: area in which the reaction tube inside the reactor or heat exchanger is located

12: inner circle of donut baffle plate

13: Internal limit of the area where the reaction tube is located

14: Heat transfer coefficient distribution in the reactor prepared in Comparative Example 1

15: Heat transfer coefficient distribution inside the reactor prepared in Example 1

16: Temperature distribution inside the reaction tube of the reactor manufactured in Comparative Example 1

17: Temperature distribution inside the reaction tube of the reactor prepared in Example 1

According to the present invention, there is a first tube through which a heat medium and a first object to be heat-transmitted exist in a region where a heat medium flow (parallel flow) parallel to the tube axis exists, and in the region parallel to the tube axis. A multi-tube reactor or heat exchanger is provided with a second tube through which the object does not pass.

In general, a multi-tube catalytic reactor in the form of a heat exchanger is a type of reactor used for the purpose of efficiently removing the heat generated by the reaction. In this type of reactor, a plurality of reaction tubes are filled with a solid catalyst, a reaction gas is supplied to the reaction tubes to cause a chemical reaction to obtain a desired component, and the heat medium is circulated in the reactor shell so that the chemical reaction can be optimally performed. Let's do it.

In multi-tubular catalytic reactors, hot spots tend to occur at localized points in the reaction tube, which causes problems such as shortening of the lifetime due to catalyst degradation and reduced selectivity for the desired product. Various methods have been tried to reduce the hot spots by efficiently transferring heat to multiple reaction tubes inside the reactor.

For example, in Korean Patent Laid-Open Publication No. 2001-0050267, the heat medium flows in an arbitrary region inside the reactor through a multi-tubular reactor provided with a circulation device for the heat medium and alternately provided with donut and disc baffles in the shell. By keeping the speed constant, the heat transfer performance was improved. It also has a circulation passage without a reaction tube in the shell between the upper and lower tube sheets and in the cross section between the periphery and the center portion of the shell, so that the heating medium flows through the circulation passage rather than through the reaction tube region in less time. Moved to the surrounding part. Therefore, the heat medium passing through the circulation passage does not make clear contact with the reaction tube but recovers the heat of reaction only in a small amount so that it can reach the surrounding parts at a relatively low temperature within a relatively short time, so that the heat medium and It was allowed to mix.

The present inventors have found that there is a region where the heat transfer coefficient is significantly reduced in the reaction tube located at the center of which the heat medium flow direction is changed in a multi-tube reactor or heat exchanger in which the heat medium flows in an S-shape because the donut and disc baffle plates are alternately provided. It was. In the case of the reactor, it was found that non-ideal hot spots occur due to a decrease in heat transfer efficiency in the reaction tube in a region where the heat transfer coefficient is significantly lowered. These non-ideal hot spots increase the likelihood of shortening the life of the catalyst and reducing the selectivity for the desired product, leading to run-away reactions.

In order to solve the problems as described above, the present invention is installed in a region in which a heat medium flow (parallel flow) parallel to the tube axis is present in a multi-tube reactor or heat exchanger, the heat medium and the first object to be heat transfer therein As a method of improving the heat transfer coefficient of the first tubes passing through, it is intended to increase the heat medium flow rate of parallel flow by installing a second tube in which the first object does not pass in the parallel to the tube axis.

According to the present invention, there is a first tube through which a heat medium and a first object to be heat-transmitted exist in a region where a heat medium flow (parallel flow) parallel to the tube axis exists, and in the region parallel to the tube axis. Provided is a multi-tube reactor or heat exchanger equipped with a second tube through which an object does not pass therein.

In one embodiment of the present invention, a donut baffle plate and a disc baffle plate are alternately provided so that the flow of the heat medium is S-shaped, so that parallel flow is formed in the center of the reactor or the heat exchanger inside the donut baffle plate, and the second tube It can be installed in the center.

The diameter D1 of the second tube is preferably adjusted in the range of 5-25%, more preferably in the range of 10-20% of the inner diameter D4 of the reactor or heat exchanger shell.

The inner diameter D3 of the donut-shaped baffle plate is preferably adjusted in the range of 20-50% of the inner diameter D4 of the shell, and the inner diameter D2 of the region where the first tube is present is the distance from the central heating medium passage second tube, ie ( It is preferable to adjust the length of D2-D1) / 2 to 50 to 500 mm or 0.5 to 10% of D4, and the distance to the donut baffle plate, that is, the length of (D3-D2) / 2 to 200 to 1000 mm or It is preferable to adjust to 3-20% of D4.

In addition, the present invention is the heat transfer coefficient of the first tube through which the heat medium and the first object to be transferred heat are installed in the region where the heat medium flow (parallel flow) parallel to the tube axis is present in the multi-tube reactor or the heat exchanger. As a method for improving the temperature, the method is characterized by increasing the heat medium flow rate of parallel flow by installing a second tube in which the first object does not pass therein so as to be parallel to the tube axis.

Furthermore, the present invention provides a method for producing an oxide by using a catalytic reactor or a heat exchanger and causing a catalytic gas phase oxidation reaction in a tube through which a heat medium and a first object to be heat transferred pass therein.

Representative examples of oxides formed by contact gasification in the tubes include unsaturated aldehydes and / or unsaturated fatty acids.

Hereinafter, the present invention will be described in detail.

In the present specification, the first tube is a tube through which a heat medium and a first object to be transferred are passed therein. Chemical or physical reactions may occur in the first tube, and the reaction may be exothermic or endothermic. The first object to be heat-transferd with the heat medium may be a reactant (s) before a chemical or physical reaction, a product (s) after the reaction, or a mixture thereof, or may be a heat transfer object without a reaction.

In the present specification, the second tube is a tube through which the heat medium and the first object to be transferred are not passed therein.

The heat transfer efficiency improving method proposed in the present invention can be applied to supply or discharge a fluid such as a heat medium to a device such as a catalytic reactor or a general heat exchanger not intended for a chemical reaction, and to the reaction gas or the kind of heat medium in the reactor. It is not restricted. In particular, the process proposed in the present invention is suitable for shell-and-tube type multi-tubular reactors or heat exchangers, which can be used for catalytic gas phase oxidation reactions.

Representative examples of catalytic gas phase oxidation reactions in which a reactor or heat exchanger of the structure according to the invention can be used are processes for producing unsaturated aldehydes or unsaturated acids from olefins, non-limiting examples of which oxidize propylene or propane to acrolein and / or A process for producing acrylic acid, a process for oxidizing isobutylene, t-butyl alcohol or methyl t-butyl ether to produce methacrolein and / or methacrylic acid, oxidizing naphthalene or ortho xylene to produce phthalic anhydride or benzene And partial oxidation of butylene or butadiene to produce maleic anhydride.

The present invention is not limited to the type of end object such as (meth) acrylic acid or (meth) acrolein produced by the reactor, so long as the reactor form of the structure according to the invention is applied.

Hereinafter, the present invention will be described using a multi-tubular catalytic reactor, but the present invention is not limited to the multi-tubular catalytic reactor. In the multi-tube catalytic reactor, the reaction tube corresponds to the first tube, the unreacted tube corresponds to the second tube, and the reaction gas corresponds to the heat medium and the first object to be transferred.

A heat medium is an example of a fluid, and a non-limiting example of a heat medium is a medium having a very high viscosity, such as molten salt, which mainly consists of a mixture of potassium nitrate and sodium nitrite. Examples of other thermal media include phenyl ether media (eg "Dowtherm"), polyphenyl media (eg "Therm S"), hot oil, naphthalene derivatives (S.K. oil), mercury, and the like.

1 is a schematic cross-sectional view of a conventional multi-tubular catalytic reactor configuration having a cylindrical structure.

In FIG. 1 the reactor comprises a plurality of reaction tubes 4 fixed to a plurality of tube sheets 3a, 3b, 3c inside the cylindrical shell 1. The tube sheet 3a located at the center of the reactor separates the shell and allows the reaction temperature to be controlled by an independent heating medium. Each shell has an annular conduit 5a connected to the heat medium supply duct and an annular conduit 5b connected to the discharge duct. The heat medium 6 supplied through the annular conduit 5a connected to the supply duct flows along the S-shaped flow path formed by the donut baffle plate 2a and the disc baffle plate 2b to exchange heat with the reaction tube 4. . The reactant gas is supplied through the reactant gas supply duct 7 and is collected again after passing through the plurality of reaction tubes 4 and discharged through the outlet duct 8.

In order to describe an unreacted tube mounted at the center to improve heat transfer efficiency according to an embodiment of the present invention, an unreacted tube 9 is added to the conventional multi-tubular catalytic reactor of FIG.

2 is a cross-sectional view taken along the line X-X 'of FIG. 2. In FIG. 3, the inner diameter of the reactor shell is D4, the inner diameter of the donut baffle plate is D3, the inner diameter of the region in which the reaction tube is present is D2, and the diameter of the central unreacted tube is D1. The relationship is illustrated.

4 shows a heat transfer coefficient distribution (Example 1) in a reactor of the present invention equipped with a heat transfer coefficient distribution 14 and an unreacted tube in a conventional reactor not equipped with an unreacted tube in the center (Comparative Example 1). FIG. 15 is a graph showing a comparison along the line XX 'of FIG. 2.

In this specification, the heat transfer coefficient refers to the heat transfer coefficient at the outer surface of the tube by the heat medium passing through the shell.

As shown in FIG. 4, in the conventional reactor without an unreacted tube in the center, the heat transfer coefficient gradually increases inside the donut-shaped baffle plate diameter (D3), and when moved to the center, the heat transfer coefficient is maximized at a certain point. The value is reached and then decreases rapidly toward the center.

The reason why the heat transfer coefficient gradually increases to the inside of the donut baffle plate diameter is because the reactor or the heat exchanger is cylindrical, and thus the velocity increases as the cross-sectional area of the fluid decreases toward the center.

On the other hand, the heat transfer coefficient at the point inside the donut-shaped baffle plate diameter reaches a maximum value and then rapidly decreases toward the center part because the heat medium no longer crosses the tube due to the densely formed tube bundle. Change the direction of travel into a window flow or longitudinal flow that does not form a cross flow and flows along the tube axis, where the reaction tube is in contact with the heating medium in a flow perpendicular to the tube axis direction. This is because the heat transfer coefficient becomes smaller when contacted with the heating medium in parallel flow in the same direction as the tube axis.

At this time, if the unreacted tube of a certain size (D1) is placed at the center of the reactor, the unit area through which the heat medium flows can be reduced to increase the heat medium flow rate of parallel flow, which causes the reaction tube to be located near the center of the reactor outside the donut baffle plate. Their heat transfer coefficient can be effectively improved. The area where the unreacted tube is located is essentially a region where the flow of the heat medium is very small, so even if an unreacted tube is installed, the increase in pressure loss is very small and there is an advantage of reducing the circulation amount of the heat medium.

5 shows a reaction tube internal temperature distribution 16 in a conventional reactor (Comparative Example 1) without an unreacted tube in the center and a reaction tube internal temperature distribution in a new reactor (Example 1) equipped with an unreacted tube (Example 1). 17) is a graph showing a comparison along the line XX 'of FIG. 2. Conventional reactors not equipped with an unreacted tube in the center have a low heat transfer coefficient region in the reaction tube located near the center of the reactor as described in FIG. 4, which generates hot spots in this region. However, in the case of a reactor equipped with an unreacted tube, the heat transfer coefficient of the reaction tube existing in all the regions inside has a minimum value that can effectively remove the internal heat of the reaction tube, so that there is almost no temperature distribution without generating a hot spot. It looks similar. As a result, the heat transfer efficiency or performance difference does not occur according to the local position where the parallel flow exists, and the overall heat transfer performance is improved in the heat exchanger, and in the case of the reactor, it is possible to suppress the occurrence of hot spots and improve the yield of the desired product. Do.

On the other hand, the diameter D1 of the unreacted tube located in the center of the reactor is preferably adjusted in the range of 5-25% of the inner diameter D4 of the shell, more preferably in the range of 10-20%.

If the diameter D1 of the unreacted tube is smaller than 5% of the inner diameter D4 of the shell, the heat transfer efficiency increase effect will be very small in the center reaction tube, and if it is larger than 25%, the space for the reaction tube will be reduced, which is inefficient. Phosphorus reactor design.

The inner diameter D3 of the donut baffle plate is preferably adjusted in the range of 20-50% of the inner diameter D4 of the shell, and the inner diameter D2 of the region where the reaction tube is present is the distance from the central unreacted tube, i.e. (D2-D1 It is preferable to adjust the length of) / 2 to 50 to 500 mm or 0.5 to 10% of D4, and the distance to the donut baffle plate, that is, the length of (D3-D2) / 2 is 200 to 1000 mm or 3 of D4. It is preferable to adjust the range to -20%.

If the length of (D2-D1) / 2 is less than 50mm or 0.5% of D4, excessive pressure loss will be required to circulate the heat medium through the shell, resulting in an increase in the heat medium circulation pump capacity and operating cost. In addition, if the length of (D2-D1) / 2 is greater than 500mm or 10% of D4, the space for the reaction tube is reduced, resulting in an inefficient reactor design.

If the length of (D3-D2) / 2 is less than 200mm or 3% of D4, even though the reaction tube can be located at the center more than enough heat transfer coefficient can be obtained, it is not possible to utilize the space inside the reactor, resulting in inefficient reactor design. If the length of (D3-D2) / 2 is greater than 1000mm or 20% of D4, it is more likely that low heat transfer coefficient region will occur in the reaction tube located near the center, and thus the advantage of mounting unreacted tube Can't get enough.

On the other hand, Figure 6 is a cross-sectional view for explaining a structure for mounting a plurality of small diameter rod-shaped baffles (9b) or unreacted tube (9b) that can be used in place of one of the unreacted tube shown in FIG. When mounting a plurality of rod-shaped baffles or unreacted tubes in this way, the area is set equal to the size of one unreacted tube described above. In addition, it is preferable to distribute symmetrically with respect to the center to prevent the disturbance of the flow.

In addition, the rod-shaped baffles or unreacted tubes are preferably arranged at a center interval of 1.2 to 1.4 times their outer diameter. If it is placed at a center spacing of 1.4 times or more, it is more likely that a low heat transfer coefficient region will occur in the reaction tube located close to the center.

The unreacted tube described above can be manufactured as in the structure described in the present invention by sealing and welding a tube of a predetermined size to the tube sheet, for example.

EXAMPLE

Hereinafter, preferred examples are provided to help understanding of the present invention, but the following examples are merely to illustrate the present invention, and the scope of the present invention is not limited to the following examples.

<Example 1>

As shown in FIG. 2, a reactor equipped with an unreacted tube was manufactured.

Length of reaction tube: 3250 mm

Inner diameter of reactor shell: 4150 mm

Inside diameter of donut baffle plate: 1600 mm

Inner diameter of the area where the reaction tube is present: 500 mm

Unreacted tube diameter in the center: 300 mm

Heat medium type: molten salt (mixture of potassium nitrate and sodium nitrite)

Thermal medium temperature: 310 ℃

Reaction gas type: mixed gas (propylene, water vapor, air mixture)

Reaction gas injection temperature: 150 ℃

Comparative Example 1

A reactor without an unreacted tube was constructed as follows.

Length of reaction tube: 3250 mm

Inner diameter of reactor shell: 4150 mm

Inside diameter of donut baffle plate: 1600 mm

Inner diameter of the area where the reaction tube is present: 500 mm

Heat medium type: molten salt (mixture of potassium nitrate and sodium nitrite)

Thermal medium temperature: 310 ℃

Reaction gas type: mixed gas (propylene, water vapor, air mixture)

Reaction gas injection temperature: 150 ℃

<Consideration>

According to Comparative Example 1, a reactor in which a donut-type baffle plate and a disc-shaped baffle plate are alternately mounted without installing an unreacted tube in the center thereof has a heat transfer coefficient at a reaction tube located at the center where the heating medium travel direction is changed as shown in FIG. 4. There was a region where remarkably decreased. Accordingly, as shown in FIG. 5, non-ideal hot spots are generated due to a decrease in heat transfer efficiency in the reaction tube in a region where the heat transfer coefficient is significantly lowered. These non-ideal hot spots increase the likelihood of shortening the life of the catalyst and reducing the selectivity for the desired product, leading to run-away reactions.

According to Example 1, a reactor equipped with an unreacted tube in the center has an improved heat transfer efficiency because the internal heat transfer coefficient distribution 15 has a larger heat transfer coefficient distribution than a reactor without an unreacted tube according to Comparative Example 1. . Through this, hot spots in the reaction tube located in the center of the reactor generated in the conventional reactor structure no longer occurred in the reactor equipped with the unreacted tube in the center.

In short, according to the present invention, if a non-reacted tube having a certain size is installed at the center of the reactor, a hot spot occurs due to a decrease in heat transfer efficiency according to the local position of the reaction tube in the conventional reactor, resulting in a difference in performance in FIGS. 4 and 5. As shown, all reaction tubes have heat transfer coefficients above a certain value, so that no hot spots occur, so there is no difference in heat transfer efficiency or performance depending on the local location.

According to the present invention, a reactor or heat exchanger equipped with a second tube, such as an unreacted tube, in a region in which the heat medium flows in parallel flow, for example, in the center of a cylindrical device, is provided with a first tube, such as a reaction tube, located in or near the region without significant pressure loss increase. Since the heat transfer efficiency of the tube can be improved, all tubes have a heat transfer coefficient of a predetermined value or more, so that a hot spot does not occur, so that a heat transfer efficiency or a performance difference according to a local position does not occur. This improves the overall heat transfer performance in the heat exchanger, and suppresses the occurrence of hot spots in the reactor and improves the yield of the desired product.

Therefore, in the reactor having the structure proposed in the present invention, (meth) acrylic acid and / or (meth) acrolein are more stable in operation by catalytic gas phase oxidation of a gas containing propylene or isobutylene, and with a smaller amount of heat medium circulation. In addition, lower yields can lead to improved yields and longer catalyst life.

Claims (13)

The donut-shaped baffle plate and the disc-shaped baffle plate are alternately provided so that the heat medium flow is S-shaped, so that the heat medium flow (parallel flow) parallel to the tube axis is formed inside the donut baffle plate, and the heat medium and A multi-tube reactor having a first tube through which a first object to be transferred heat passes, and having a second tube in which the first object does not pass in parallel to the tube axis, The inner diameter D2 of the region where the first tube is present is the distance from the second tube, the length of (D2-D1) / 2 ranges from 0.5 to 10% of the inner diameter D4 of the reactor shell, the distance from the donut baffle plate, Reactor characterized in that the length of (D3-D2) / 2 ranges from 3-20% of D4, where D1 is the diameter of the second tube and D3 is the inner diameter of the donut baffle plate. The reactor according to claim 1, wherein the parallel flow is formed at the center of the reactor, and a second tube is installed at the center of the reactor. delete The reactor of claim 1, wherein the diameter D1 of the second tube is in the range of 5-25% of the inner diameter D4 of the reactor shell. The reactor according to claim 1, wherein the inner diameter D3 of the donut-shaped baffle plate is in the range of 20-50% of the inner diameter D4 of the reactor shell. delete The reactor of claim 1, wherein at least two second tubes are installed in one region in which parallel flow exists. The reactor of claim 7, wherein the two or more second tubes are installed symmetrically with respect to the center point of one region in which the parallel flow exists. The reactor of claim 8, wherein the second tubes are disposed at center intervals of 1.2 to 1.4 times their outer diameter. 10. The method according to any one of claims 1, 2, 4, 5, and 7-9, wherein the heat medium and the first object to be heat transferred are reactant (s) prior to chemical or physical reactions. , Reactor or product after the reaction. Claims 1, 2, 4, 5 and 7 to 9, wherein the heat medium and the first object to be heat-transfer, the agent passing through the inside A method of producing an oxide by causing a catalytic gas phase oxidation reaction in one tube. The method according to claim 11, wherein the oxide is unsaturated aldehyde or unsaturated fatty acid. delete

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