Reactor

Abstract

To provide a reaction device which can reduce degradation of catalysts and can shorten a reaction vessel.SOLUTION: A reaction device in which chemical reaction involving heat generation occurs, comprises: a reaction vessel through which a raw material gas flows from an inlet toward an outlet; and catalysts that are contained in the reaction vessel, wherein the reaction device includes a first section, a second section, and a third section, in order along a direction of flow of the raw material gas. Among the first section, the second section, and the third section, the second section reduces the activation energy of the chemical reaction the least. Additionally, in the reaction device, a temperature increases in the first section, a temperature decreases in the second section, and a temperature increases in the third section.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a reaction apparatus in which a chemical reaction accompanied by heat generation occurs.

Background Art

[0002] In a reaction apparatus in which a chemical reaction accompanied by heat generation occurs when a raw material gas flows through a reaction vessel containing a catalyst, when the temperature of the reaction field rises due to the reaction heat, deterioration of the catalyst such as sintering is likely to occur. In order to reduce the deterioration of the catalyst, in the prior art disclosed in Patent Document 1, after flowing a raw material gas through reaction vessels arranged in parallel at intervals from each other and then merging them, the variation in the temperature distribution in the cross-sectional direction of the reaction vessel is reduced to prevent overheating of the catalyst.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the prior art, since the reaction vessels are arranged in parallel at intervals from each other, the volume of the reaction vessel becomes small with respect to the range where the reaction vessels are arranged. There is a problem that when ensuring the volume of the reaction vessel corresponding to the range where the reaction vessels are arranged, the overall length of the reaction vessel becomes large.

[0005] The present invention has been made to solve this problem, and an object thereof is to provide a reaction apparatus capable of reducing the deterioration of the catalyst and shortening the reaction vessel.

Means for Solving the Problems

[0006] To achieve this object, the reactor of the present invention is a reactor in which a chemical reaction accompanied by heat generation occurs, and includes a reaction vessel through which a raw material gas flows from an inlet to an outlet, and a catalyst enclosed in the reaction vessel. Along the direction of the flow of the raw material gas, it includes a first part, a second part, and a third part in order. Among the first part, the second part, and the third part, the degree of lowering of the activation energy of the chemical reaction is the smallest in the second part. Also, in the reactor, the temperature rises in the first part, decreases in the second part, and rises in the third part.

Advantages of the Invention

[0007] According to the first aspect, the reactor includes a reaction vessel enclosing a catalyst, and includes a first part, a second part, and a third part in order along the direction of the flow of the raw material gas. Among the first part, the second part, and the third part, the degree of lowering of the activation energy of the chemical reaction is the smallest in the second part, so the heat generation in the second part is smaller than the heat generation in the first part and the third part. Since the temperature that rises in the first part decreases in the second part, even if the reaction vessel is short, the temperature of the catalyst can be prevented from rising excessively. As a result, the deterioration of the catalyst can be reduced.

[0008] According to the second aspect, the reactor includes a reaction vessel enclosing a catalyst, and includes a first part, a second part, and a third part in order along the direction of the flow of the raw material gas. The temperature rises in the first part, decreases in the second part, and rises in the third part. Even if the reaction vessel is short, the temperature of the catalyst can be prevented from rising excessively, so the deterioration of the catalyst can be reduced.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0010] Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a block diagram of a reactor 10 in the first embodiment. The reactor 10 includes a reaction vessel 20 through which a raw material gas flows. A confluence pipe 17 to which two pipes 11 and 14 are connected is connected to the reaction vessel 20. Pipe 11 is a pipe to which a first raw material gas is supplied, and a control valve 12 and a check valve 13 are arranged in order from upstream to downstream. Pipe 14 is a pipe to which a second raw material gas is supplied, and a control valve 15 and a check valve 16 are arranged in order from upstream to downstream. A shut-off valve 18 is arranged in the confluence pipe 17. The first and second raw material gases are set to an optimal mixing ratio through the control valves 12 and 15 respectively, and the mixed gas (raw material gas) in which the two raw material gases are mixed is supplied to the reaction vessel 20 through the shut-off valve 18.

[0011] In the present embodiment, the case where the first raw material gas is hydrogen and the second raw material gas is carbon dioxide will be described. The reaction vessel 20 is set to an appropriate pressure and heated by a heater 27 to carry out methane production (methanation) represented by the chemical reaction formula of CO2 + 4H2 → CH4 + 2H2O. The product is cooled to ice temperature by a condenser 28 connected downstream of the reaction vessel 20 and separated into a gas containing methane and water. The gas containing methane may contain hydrogen and carbon dioxide of the raw material gas.

[0012] Methanation is an example of a chemical reaction that occurs in the reactor 10, but is not limited thereto. By appropriately selecting the raw material gas, reaction conditions, and catalyst (described later), for example, the following chemical reactions can occur in the reactor 10.

[0013] Synthesis gas production by partial oxidation of methane: 2CH4 + O2 → 2CO + 4H2 Methanol synthesis: CO + 2H2 → CH3OH Methanol synthesis: CO2 + 3H2 → CH3OH + H2O Fisher-Tropsch synthesis: CO + 2H2 → -(CH2)- + H2O -(CH2)- means a straight-chain hydrocarbon Dimethyl ether synthesis: 2CO + 4H2 → CH3OCH3 + H2O

[0014] Figure 2 is a cross-sectional view of the reaction apparatus 10. The arrows shown in Figure 2 indicate the direction in which the raw material gas flows through the reaction vessel 20 (the same applies in Figures 4 to 6). The reaction vessel 20 contains catalysts 24, 26 and a low-activity catalyst 25. The reaction apparatus 10 includes a first section 21, a second section 22, and a third section 23 in order along the direction of the flow of the raw material gas (from upstream to downstream). The first section 21 and the third section 23 each contain catalysts 24, 26. The second section 22 contains a low-activity catalyst 25 whose catalytic activity is lower than that of the catalysts 24, 26. The catalysts 24, 26 and the low-activity catalyst 25 lower the activation energy of the chemical reaction and facilitate the progress of the chemical reaction. A low catalytic activity means that the degree of lowering the activation energy of the chemical reaction is small.

[0015] In this embodiment, the first section 21, the second section 22, and the third section 23 are joined to each other by tightening the flanges of tubes having the same inner diameter, in which the catalyst 24, the low-activity catalyst 25, and the catalyst 26 are respectively arranged, with bolts or the like. However, it is not limited to this. It is of course possible to provide the first section 21, the second section 22, and the third section 23 by sequentially filling a single tube with the catalyst 24, the low-activity catalyst 25, and the catalyst 26.

[0016] For the catalysts 24, 26 and the low-activity catalyst 25, catalysts suitable for various chemical reactions can be used without limitation. Examples of the catalysts 24, 26 and the low-activity catalyst 25 include powders, pellets, or porous structures in which particles are supported on a carrier. Examples of the carrier include powders, pellets, or porous structures of oxides containing one or more of alumina, silica, magnesia, titania, zirconia, niobia, silica-alumina, zeolite, and calcium phosphate. The porous structure has air permeability through which the raw material gas can pass. Also, the raw material gas passes through the gaps between the powder and the pellets.

[0017] Examples of the metal contained in the particles supported on the carrier include one or more of Fe, Co, Ni, Cu, Ru, Rh, Pd, Ag, Ir, Pt, and Au. For the catalyst, if the carrier, the material of the particles, and the particle diameter are the same, the catalytic activity is proportional to the surface area of the particles supported on the carrier. Therefore, compared with the catalysts 24 and 26, a low-activity catalyst 25 can be obtained by reducing the surface area of the particles supported on the carrier.

[0018] Also, a low-activity catalyst 25 can be obtained by mixing inert particles having no catalytic activity with the catalysts 24 and 26 and reducing the amount of the catalysts 24 and 26 contained in a fixed amount. Examples of the inert particles include powders or pellets of oxides containing one or more of alumina, silica, magnesia, titania, zirconia, niobia, silica-alumina, zeolite, and calcium phosphate.

[0019] When a raw material gas in which hydrogen and carbon dioxide are mixed flows through the reaction vessel 20, the raw material gas sequentially passes through the first section 21, the second section 22, and the third section 23, and a chemical reaction for generating methane and water proceeds.

[0020] FIG. 3 is a diagram showing the relationship between each part of the reaction apparatus 10 and the temperature. The example in FIG. 3 is the result of arranging a plurality of thermocouples along the direction in which the raw material gas flows at the center of gravity of the cross section of the reaction fields (the assembly of catalysts) of the first section 21, the second section 22, and the third section 23 and recording the temperatures detected by each thermocouple. The comparative example is the result of recording the temperature in the same manner by arranging the catalyst 24 of the first section 21 throughout the reaction vessel 20 without dividing the reaction apparatus 10 into the first section 21, the second section 22, and the third section 23.

[0021] As shown in FIG. 3, in the embodiment, the temperature rises in the first section 21, drops in the second section 22, and rises in the third section 23. In the second section 22, the catalytic activity of the low-activity catalyst 25 is lower than that of the catalyst 24, and the degree of reduction of the activation energy is smaller than that in the first section 21. Therefore, the reaction rate becomes smaller than that in the first section 21 and the temperature drops. In the third section 23, the catalytic activity of the catalyst 26 is higher than that of the low-activity catalyst 25, and the degree of reduction of the activation energy is larger than that in the second section 22. Therefore, the reaction rate becomes larger than that in the second section 22 and the temperature rises due to the heat of reaction. However, since methane and steam, which are the products of the reaction, are present in the third section 23, the heat of reaction in the third section 23 does not become so large. Further, since the second section 22 is interposed between the third section 23 and the first section 21, the heat in the third section 23 is less likely to be transmitted to the first section 21, and the temperature of the first section 21 does not become so high.

[0022] On the other hand, in the comparative example, the maximum temperature reached in the reaction field becomes higher than that in the embodiment due to the chemical reaction (exothermic reaction) that produces methane and water from the raw material gas. According to the embodiment, the temperatures of the catalysts 24, 26 and the low-activity catalyst 25 that increase with the chemical reaction can be reduced compared to the comparative example, so that the deterioration of the catalyst can be reduced. Further, since it is not necessary to arrange the reaction vessels in parallel with a space therebetween as in the prior art, the overall length of the reaction vessel 20 can be reduced while securing the volume of the reaction vessel 20.

[0023] Returning to FIG. 2 for explanation. The catalytic activity of the catalyst 24 in the first section 21 is the same as or lower than the catalytic activity of the catalyst 26 in the third section 23. The thickness of the first section 21 in the flow direction of the raw material gas is smaller than the thickness of the third section 23 in the flow direction of the raw material gas. Therefore, even if the catalytic activity of the catalyst 24 in the first section 21 is the same as the catalytic activity of the catalyst 26 in the third section 23, the temperature of the first section 21 due to the heat of reaction can be reduced compared to the case where the thickness of the first section 21 is larger than the thickness of the third section 23. Therefore, the deterioration of the catalyst 24 can be reduced. If catalysts with the same catalytic activity are arranged in the first section 21 and the third section 23, it is possible to avoid preparing two types of catalysts 24 and 26 with different catalytic activities.

[0024] The thickness of the second part 22 in the flow direction of the raw material gas is smaller than the thickness of the third part 23 in the flow direction of the raw material gas. Therefore, the overall length of the reaction vessel 20 can be reduced as compared with the case where the thickness of the second part 22 is larger than the thickness of the third part 23.

[0025] The thickness of the second part 22 in the flow direction of the raw material gas is larger than the thickness of the first part 21 in the flow direction of the raw material gas. Therefore, the heat insulation property by the low-activity catalyst 25 disposed between the first part 21 and the third part 23 can be ensured.

[0026] The reactor 30 in the second embodiment will be described with reference to FIG. 4. In the first embodiment, the case where the low-activity catalyst 25 is disposed in the second part 22 has been described. In contrast, in the second embodiment, the case where the inert body 35 having no catalytic activity is disposed in the second part 32 will be described. The same parts as those described in the first embodiment are denoted by the same reference numerals, and the following description thereof will be omitted. FIG. 4 is a cross-sectional view of the reactor 30 in the second embodiment.

[0027] The reactor 30 includes a first part 31, a second part 32, and a third part 33 in order along the flow direction of the raw material gas. The reaction vessel 20 contains the catalysts 34, 36 and the inert body 35. The first part 31 and the third part 33 each contain the catalysts 34, 36. The catalysts 34, 36 lower the activation energy of the chemical reaction and facilitate the progress of the chemical reaction. The second part 32 contains the inert body 35 having no catalytic activity. Having no catalytic activity means that the inert body 35 has no function of lowering the activation energy of the chemical reaction.

[0028] Examples of the inert body 35 include powders, pellets, or porous structures containing one or more oxides such as alumina, silica, magnesia, titania, zirconia, niobia, silica-alumina, zeolite, and calcium phosphate. The porous structure has air permeability through which the raw material gas can pass. Also, the raw material gas passes through the gaps between the powder and the pellets.

[0029] When a raw material gas in which hydrogen and carbon dioxide are mixed flows through the reaction vessel 20, the raw material gas sequentially passes through the first section 31, the second section 32, and the third section 33, and a chemical reaction to produce methane and water proceeds. The second section 32 has no catalytic activity in the inert body 35 and the degree of lowering the activation energy is smaller than that of the first section 31, so the reaction rate becomes smaller than that of the first section 31 and the temperature decreases. In the third section 33, since the degree of lowering the activation energy by the catalyst 36 is larger than that of the second section 32, the reaction rate becomes larger than that of the second section 32 and the temperature rises due to the heat of reaction. However, since methane and water vapor are present in the third section 33, the heat of reaction in the third section 33 does not become so large. Further, since the second section 32 is interposed between the third section 33 and the first section 31, the heat of the third section 33 hardly reaches the first section 31, and the temperature of the first section 31 does not become so high. Therefore, deterioration of the catalysts 34 and 36 can be reduced.

[0030] The catalytic activity of the catalyst 34 in the first section 31 is the same as or lower than the catalytic activity of the catalyst 36 in the third section 33. The thickness of the first section 31 in the flow direction of the raw material gas is smaller than the thickness of the third section 33 in the flow direction of the raw material gas. The thickness of the second section 32 in the flow direction of the raw material gas is smaller than the thickness of the third section 33 in the flow direction of the raw material gas.

[0031] The thickness of the second section 32 in the flow direction of the raw material gas is smaller than the thickness of the first section 31 in the flow direction of the raw material gas. Therefore, the overall length of the reaction vessel 20 can be reduced as compared with the case where the thickness of the second section 32 is larger than the thickness of the first section 31.

[0032] The reaction apparatus 40 in the third embodiment will be described with reference to FIG. 5. In the first and second embodiments, the case where the thicknesses of the first sections 21 and 31 are smaller than the thicknesses of the third sections 23 and 33 has been described. In contrast, in the third embodiment, the case where the thickness of the first section 41 is the same as the thickness of the third section 43 will be described. The same parts as those described in the first embodiment will be denoted by the same reference numerals and the following description will be omitted. FIG. 5 is a cross-sectional view of the reaction apparatus 40 in the third embodiment.

[0033] The reaction device 40 includes a first section 41, a second section 42, and a third section 43 in order along the flow direction of the raw material gas. The reaction vessel 20 contains catalysts 44, 46 and a low-activity catalyst 45. The first section 41 and the third section 43 each contain a catalyst 44, 46. The catalytic activity of the catalyst 44 is lower than that of the catalyst 46. The second section 42 contains a low-activity catalyst 45 whose catalytic activity is lower than that of the catalysts 44, 46.

[0034] When a raw material gas in which hydrogen and carbon dioxide are mixed flows through the reaction vessel 20, the raw material gas passes through the first section 41, the second section 42, and the third section 43 in order, and a chemical reaction to produce methane and water proceeds. In the second section 42, since the catalytic activity of the low-activity catalyst 45 is lower than that of the catalyst 44 and the degree of lowering of the activation energy is smaller than that of the first section 41, the reaction rate becomes smaller than that of the first section 41 and the temperature decreases. In the third section 43, since the degree of lowering of the activation energy by the catalyst 46 is larger than that of the second section 42, the reaction rate becomes larger than that of the second section 42 and the temperature rises due to the reaction heat. However, since methane and water vapor are present in the third section 43, the reaction heat of the third section 43 does not become so large. Further, since the second section 42 is interposed between the third section 43 and the first section 41, the heat of the third section 43 is difficult to be transmitted to the first section 41, and the temperature of the first section 41 does not become so high. Therefore, deterioration of the catalysts 44, 46 and the low-activity catalyst 46 can be reduced.

[0035] The thickness of the first section 41 in the flow direction of the raw material gas is the same as the thickness of the third section 43, but since the catalytic activity of the catalyst 44 in the first section 41 is lower than that of the catalyst 46 in the third section 43, it is possible to prevent the reaction heat in the first section 41 from becoming excessive.

[0036] Referring to FIG. 6, the reactor 50 in the fourth embodiment will be described. In the first to third embodiments, the case where the low-activity catalyst 25, 45 or the inert body 35 is disposed in the second parts 22, 32, 42 has been described. In contrast, in the fourth embodiment, the case where the pipe 55 is provided in the second part 52 will be described. The same parts as those described in the first embodiment are denoted by the same reference numerals, and the following description thereof will be omitted. FIG. 6 is a cross-sectional view of the reactor 50 in the fourth embodiment.

[0037] The reactor 50 includes a first part 51, a second part 52, and a third part 53 in this order along the flow direction of the raw material gas. The first part 51 and the third part 53 each include a catalyst 54, 57. The second part 52 includes a pipe 55 connecting the first part 51 and the third part 53 and a condenser 56 disposed in the pipe 55. The first part 51 and the third part 53 are set to an appropriate pressure and heated by a heater (not shown). A heater is not disposed around the condenser 56.

[0038] When a raw material gas in which hydrogen and carbon dioxide are mixed is supplied to the first part 51, the raw material gas passes through the first part 51, the second part 52, and the third part 53 in this order, and a chemical reaction for generating methane and water proceeds. Since the second part 52 has no catalyst disposed therein and the degree of lowering the activation energy is smaller than that of the first part 51, the reaction rate becomes smaller than that of the first part 51 and the temperature decreases. In the third part 53, since the degree of lowering the activation energy by the catalyst 57 is larger than that of the second part 52, the reaction rate becomes larger than that of the second part 52 and the temperature rises due to the reaction heat. However, since methane is present in the third part 53, the reaction heat of the third part 53 does not become so large. Further, since the second part 52 is interposed between the third part 53 and the first part 51, the heat of the third part 53 hardly reaches the first part 51, and the temperature of the first part 51 does not become so high. Therefore, deterioration of the catalysts 54, 57 can be reduced.

[0039] Particularly, since the condenser 56 is disposed in the pipe 55 and no heater is disposed around the condenser 56, the second part 52 can be cooled as compared with the second parts 22, 32, 42 in the first to third embodiments.

[0040] The catalytic activity of the catalyst 54 in the first section 51 is the same as or lower than the catalytic activity of the catalyst 57 in the third section 53. The thickness of the first section 51 in the direction of the flow of the raw material gas is smaller than the thickness of the third section 53 in the direction of the flow of the raw material gas. Therefore, even if the catalytic activity of the catalyst 54 in the first section 51 is the same as the catalytic activity of the catalyst 57 in the third section 53, the temperature of the first section 51 due to the reaction heat can be reduced compared to the case where the thickness of the first section 51 is larger than the thickness of the third section 53. Thus, deterioration of the catalyst 54 can be reduced.

[0041] By means of the condenser 56 disposed in the pipe 55 of the second section 52, the product of the reaction in the first section 51 is cooled to ice temperature and water is separated. Since the water vapor supplied to the third section 53 through the second section 52 can be reduced, the reaction rate in the third section 53 can be increased.

[0042] Although the present invention has been described based on the embodiments, it is easily conceivable that the present invention is not limited to the above embodiments at all, and various improvements and modifications are possible without departing from the spirit of the present invention.

[0043] In the embodiments, the case where the inner diameters of the first sections 21, 31, 41, the second sections 22, 32, 42, and the third sections 23, 33, 43 are the same has been described, but it is not necessarily limited thereto. It is of course possible to make the inner diameters of the first sections 21, 31, 41, the second sections 22, 32, 42, and the third sections 23, 33, 43 different.

[0044] In the fourth embodiment, the case where no heater is disposed around the condenser 56 provided in the second section 52 has been described, but it is not necessarily limited thereto. When the cooling capacity of the condenser 56 is large, since the temperature rise of the second section 52 by the heater can be reduced, a heater may be disposed around the condenser 56.

[0045] In the fourth embodiment, the case where the second part 52 includes the condenser 56 has been described, but it is not necessarily limited to this. It is of course possible to omit the condenser 56. This is because by connecting the first part 51 and the third part 53 with the pipe 55, the reaction rate in the second part 52 can be made smaller than the reaction rates in the first part 51 and the third part 53.

[0046] In the fourth embodiment, the case where the condenser 56 is arranged in the pipe 55 provided in the second part 52 has been described, but it is not necessarily limited to this. Instead of the condenser 56, it is of course possible to arrange in the pipe 55 a low-activity catalyst having a lower catalytic activity than the catalysts 54 and 57, or an inert body having no catalytic activity.

Explanation of Reference Numerals

[0047] 10, 30, 40, 50 Reactor 20 Reaction vessel 21, 31, 41, 51 First part 22, 32, 42, 52 Second part 23, 33, 43, 53 Third part 24, 26, 34, 36, 44, 46, 54, 57 Catalyst 25, 45 Low-activity catalyst 35 Inert body

Claims

1. A reaction apparatus comprising a reaction vessel through which a raw material gas flows from an inlet to an outlet, and a catalyst contained within the reaction vessel, in which a chemical reaction accompanied by heat generation occurs, wherein the chemical reaction is a reaction for synthesizing methane from the raw material gas containing hydrogen and carbon dioxide, wherein the catalyst is disposed in the reaction vessel along the flow direction of the raw material gas and includes, in order, a first part, a second part, and a third part, and wherein the degree of reduction of the activation energy of the chemical reaction among the first part, the second part, and the third part is the smallest in the second part.

2. A reaction apparatus comprising a reaction vessel through which a raw material gas flows from an inlet to an outlet, and a catalyst contained within the reaction vessel, in which a chemical reaction accompanied by heat generation occurs, wherein the chemical reaction is a reaction for synthesizing methane from the raw material gas containing hydrogen and carbon dioxide, wherein the catalyst is disposed in the reaction vessel along the flow direction of the raw material gas and includes, in order, a first part, a second part, and a third part, and wherein the temperature rises in the first part, decreases in the second part, and rises in the third part.

3. The reaction apparatus according to claim 1, wherein the second part includes an inert body having no catalytic activity or a low-activity catalyst having a lower catalytic activity than the catalytic activity of the catalyst contained in the first part and the third part.

4. The reaction apparatus according to claim 1 or 3, wherein the first part includes a catalyst having a lower catalytic activity than the catalytic activity of the catalyst contained in the third part.

5. The reaction apparatus according to claim 1 or 3, wherein the thickness of the first part in the flow direction is smaller than the thickness of the third part in the flow direction.

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