Oxidation catalyst system

Abstract

To suppress heat loss of equipment provided on the down stream side from the oxidation catalyst.SOLUTION: An oxidation catalyst system includes an oxidation catalyst which is provided on an exhaust gas line from an internal combustion engine and oxidizes exhaust gas, a heat exchanger which is constituted so as to perform heat exchange between purified gas as the exhaust gas having temperature elevated by oxidation reaction by means of the oxidation catalyst and the exhaust gas flowing on the upstream side from the oxidation catalyst of the exhaust gas line, a purified gas introduction line for extracting the purified gas from the downstream side of the oxidation catalyst of the exhaust gas line and guiding the gas to the heat exchanger, a purified gas returning line for returning the purified gas to the downstream side of a first connection part as a connection part with the purified gas introduction line of the exhaust gas line from the heat exchanger, a purified gas temperature acquiring device constituted so as to acquire a temperature of the purified gas flowing through the downstream side of the oxidation catalyst of the exhaust gas line, and a purified gas flow rate adjusting device which is constituted so as to adjust a flow rate of the purified gas guided to the hat exchanger in accordance with the temperature of the purified gas obtained by the purified gas temperature acquiring device.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to an oxidation catalyst system.

Background Art

[0002] An oxidation catalyst system includes an oxidation catalyst device including an oxidation catalyst for oxidizing exhaust gas discharged from an internal combustion engine. For example, when an internal combustion engine is operated with a fuel containing unburned methane in an exhaust gas component such as liquefied natural gas, a methane oxidation catalyst may be provided downstream of the internal combustion engine in order to remove methane in the exhaust gas.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In order to improve the efficiency of the methane oxidation catalyst, the methane oxidation catalyst may be preheated. When the methane oxidation catalyst is preheated, there is a risk that the temperature of the exhaust gas passing through the methane oxidation catalyst becomes too high. If the temperature of the exhaust gas passing through the methane oxidation catalyst is too high, there is a risk of thermal damage to the equipment provided downstream of the methane oxidation catalyst in the flow direction of the exhaust gas. In particular, when a methane oxidation catalyst is additionally installed downstream of an existing internal combustion engine, the equipment provided downstream of the methane oxidation catalyst in the flow direction of the exhaust gas does not take into account the temperature rise of the exhaust gas caused by the oxidation reaction in the methane oxidation catalyst, so there is a high possibility of thermal damage to the above equipment. In order to suppress the thermal damage of the above equipment, it is necessary to control the temperature of the exhaust gas.

[0005] Patent Document 1 discloses a structure for preheating exhaust gas introduced into an oxidation catalyst by using heat generated by an oxidation reaction in the oxidation catalyst. Note that since Patent Document 1 does not describe temperature control of exhaust gas on the downstream side of the oxidation catalyst, it is not clear whether heat damage to equipment provided on the downstream side of the oxidation catalyst can be prevented.

[0006] In view of the above circumstances, at least one embodiment of the present disclosure aims to provide an oxidation catalyst system capable of suppressing heat damage to equipment provided on the downstream side in the exhaust gas flow direction of the oxidation catalyst.

Means for Solving the Problems

[0007] An oxidation catalyst system according to at least one embodiment of the present disclosure is provided in an exhaust gas line through which exhaust gas discharged from an internal combustion engine flows, and an oxidation catalyst configured to oxidize the exhaust gas; a heat exchanger configured to perform heat exchange between the purified gas, which is the exhaust gas heated by the oxidation reaction of the oxidation catalyst, and the exhaust gas flowing upstream of the oxidation catalyst in the exhaust gas line; a purified gas introduction line for extracting the purified gas from the downstream side of the oxidation catalyst in the exhaust gas line and guiding it to the heat exchanger; a purified gas return line for returning the purified gas to a downstream side of a first connection portion, which is a connection portion between the heat exchanger and the purified gas introduction line of the exhaust gas line; a purified gas temperature acquisition device configured to acquire the temperature of the purified gas flowing downstream of the oxidation catalyst in the exhaust gas line; and a purified gas flow rate adjustment device configured to adjust the flow rate of the purified gas guided to the heat exchanger according to the temperature of the purified gas acquired by the purified gas temperature acquisition device.

Advantages of the Invention

[0008] According to at least one embodiment of the present disclosure, an oxidation catalyst system is provided that can suppress thermal damage to equipment provided downstream of the oxidation catalyst in the flow direction of the exhaust gas.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0010] Hereinafter, some embodiments of the present disclosure will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the components described as embodiments or shown in the drawings are not intended to limit the scope of the present disclosure, but are merely illustrative examples.

[0011] (Internal Combustion Engine System) Each of FIGS. 1 and 2 is a schematic diagram of an internal combustion engine system 1 including an oxidation catalyst system 2 according to an embodiment of the present disclosure. As shown in FIGS. 1 and 2, the internal combustion engine system 1 includes an oxidation catalyst system 2, an internal combustion engine 11, and an exhaust gas line 12 through which the exhaust gas discharged from the internal combustion engine 11 flows. The internal combustion engine system 1 may further include a generator 15 connected to the output shaft of the internal combustion engine 11 and generating electricity by the power generated by the internal combustion engine 11. That is, the internal combustion engine 11 may be an engine for power generation. The exhaust gas line 12 forms a flow path for circulating the exhaust gas and is formed, for example, by a pipe.

[0012] In the following description, when simply referred to as the upstream side, it shall refer to the upstream side along the main flow direction of the fluid in the part or region related to the direction description. Similarly, in the following description, when simply referred to as the downstream side, it shall refer to the downstream side along the main flow direction of the fluid in the part or region related to the direction description.

[0013] (Oxidation catalyst system) The oxidation catalyst system 2 according to some embodiments is mounted on the internal combustion engine system 1. As shown in FIGS. 1 and 2, the oxidation catalyst system 2 includes an oxidation catalyst device 3, a catalyst casing 4, a heat exchanger 5, a purified gas introduction line 13, and a purified gas return line 14.

[0014] (Oxidation catalyst device) As shown in FIGS. 1 and 2, the oxidation catalyst device 3 includes an oxidation catalyst 31 that promotes the oxidation of at least one of the components (exhaust gas components) contained in the exhaust gas. In the illustrated embodiment, the internal combustion engine 11 is operated by a fuel that may contain unburned methane in the exhaust gas components such as liquefied natural gas. The oxidation catalyst 31 includes a methane oxidation catalyst that promotes the oxidation of methane contained in the exhaust gas. Note that the oxidation catalyst device 3 may include not only the oxidation catalyst 31 but also a catalyst carrier that supports the oxidation catalyst 31.

[0015] (Catalyst casing) As shown in FIGS. 1 and 2, the catalyst casing 4 is provided in the exhaust gas line 12 and is configured to house the oxidation catalyst device 3 including the oxidation catalyst 31. In the illustrated embodiment, the catalyst casing 4 includes a casing main body portion 41 formed in a rectangular tube shape extending along the vertical direction and having an internal space 40 through which the exhaust gas flows. The exhaust gas flowing through the inside (internal space 40) of the catalyst casing 4 flows from below to above in the vertical direction.

[0016] The oxidation catalyst device 3 is disposed in the internal space 40 and extends along a direction intersecting the flow direction of the exhaust gas flowing through the inside of the catalyst casing 4 (in the illustrated example, the horizontal direction perpendicular to the flow direction of the exhaust gas flowing through the inside of the catalyst casing 4). The internal space 40 includes two spaces 40A and 40B partitioned by the oxidation catalyst device 3. That is, the internal space 40 includes a first internal space 40A on the upstream side in the exhaust gas flow direction with respect to the oxidation catalyst device 3 and a second internal space 40B on the downstream side in the exhaust gas flow direction with respect to the oxidation catalyst device 3.

[0017] An exhaust gas inlet 42 for introducing exhaust gas from the outside of the casing main body 41 into the first internal space 40A is formed at the lower end of the casing main body 41 in the vertical direction. An exhaust gas outlet 43 for discharging exhaust gas from the second internal space 40B to the outside of the casing main body 41 is formed at the upper end of the casing main body 41 in the vertical direction.

[0018] As shown in FIGS. 1 and 2, the exhaust gas line 12 includes an upstream exhaust gas line 12A for guiding exhaust gas from the internal combustion engine 11 to the catalyst casing 4 and a downstream exhaust gas line 12B for guiding exhaust gas to the downstream side in the exhaust gas flow direction from the catalyst casing 4. The upstream exhaust gas line 12A has an upstream end connected to the internal combustion engine 11 and a downstream end connected to the exhaust gas inlet 42 of the catalyst casing 4. The downstream exhaust gas line 12B has an upstream end connected to the exhaust gas outlet 43 of the catalyst casing 4.

[0019] The exhaust gas discharged from the internal combustion engine 11 flows through the exhaust gas line 12 and is guided from the exhaust gas inlet 42 into the first internal space 40A. When the exhaust gas guided into the first internal space 40A passes through the oxidation catalyst device 3, the oxidation of at least one of the exhaust gas components (for example, methane) is promoted by the oxidation catalyst 31 included in the oxidation catalyst device 3. The exhaust gas that has passed through the oxidation catalyst device 3 is discharged from the exhaust gas outlet 43 to the outside of the casing main body 41 (downstream exhaust gas line 12B).

[0020] When the exhaust gas passes through the oxidation catalyst device 3, it is heated by the oxidation reaction of the oxidation catalyst 31. For example, when the exhaust gas flowing through the first internal space 40A in the oxidation catalyst system 2 without the heat exchanger 5 is about 400 °C, the exhaust gas flowing through the second internal space 40B after being heated by the oxidation reaction of the oxidation catalyst 31 will reach about 440 °C.

[0021] (Heat exchanger) The heat exchanger 5 is configured to perform heat exchange between the purified gas, which is the exhaust gas that has passed through the oxidation catalyst device 3 and has been heated by the oxidation reaction of the oxidation catalyst 31, and the exhaust gas flowing upstream of the oxidation catalyst device 3 in the exhaust gas line 12. The heat exchanger 5 is a heat exchanger for recovering the thermal energy of the purified gas. Through the heat exchange in the heat exchanger 5, the purified gas is cooled, and the exhaust gas flowing upstream of the oxidation catalyst device 3 in the exhaust gas line 12 is heated.

[0022] For example, when the exhaust gas introduced into the heat exchanger 5 is about 400 °C, the exhaust gas is heated to about 410 °C by the heat exchange between the exhaust gas and the purified gas in the heat exchanger 5. Then, since the exhaust gas passing through the heat exchanger 5 is further heated by the oxidation reaction of the oxidation catalyst 31, the exhaust gas flowing through the second internal space 40B will reach about 450 °C. The purified gas is cooled from about 450 °C to about 425 °C by the heat exchange with the exhaust gas in the heat exchanger 5.

[0023] In the illustrated embodiment, the heat exchanger 5 is provided upstream of the oxidation catalyst device 3 in the exhaust gas line 12 and includes at least one heat transfer tube 51 through which the purified gas flows in the internal flow path. Around the heat transfer tube 51, the exhaust gas before being introduced into the oxidation catalyst device 3 is allowed to flow. In the embodiment shown in FIGS. 1 and 2, the at least one heat transfer tube 51 described above is arranged in the first internal space 40A, and the thermal energy of the purified gas flowing through the heat transfer tube 51 is transferred to the exhaust gas flowing through the first internal space 40A.

[0024] At one end of at least one of the above-described heat transfer tubes 51, a purification gas inlet for introducing purification gas from the outside into the heat transfer tube 51 is formed. At the other end of at least one of the above-described heat transfer tubes 51, a purification gas outlet for discharging the purification gas from the heat transfer tube 51 to the outside is formed.

[0025] (Inlet gas duct, outlet gas duct) In the illustrated embodiment, the oxidation catalyst system 2 further includes an inlet gas duct 21 attached to the outside of the catalyst casing 4 and an outlet gas duct 22 attached to the outside of the catalyst casing 4. When at least one of the above-described heat transfer tubes 51 includes a plurality of heat transfer tubes 51, each of the plurality of heat transfer tubes 51 has a purification gas inlet connected to a common inlet gas duct 21 and a purification gas outlet connected to a common outlet gas duct 22.

[0026] (Purification gas introduction line, purification gas return line) The purification gas introduction line 13 forms a flow path for extracting purification gas from a downstream side of the oxidation catalyst device 3 in the exhaust gas line 12 and guiding it to the heat exchanger 5. The purification gas return line 14 forms a flow path for returning the purification gas to a downstream side of a first connection portion P1 which is a connection portion between the heat exchanger 5 and the purification gas introduction line 13 in the exhaust gas line 12. Each of the purification gas introduction line 13 and the purification gas return line 14 is formed by, for example, piping.

[0027] In the illustrated embodiment, the purification gas introduction line 13 has an upstream end connected to the first connection portion P1 of the downstream exhaust gas line 12B and a downstream end connected to the inlet gas duct 21. The purification gas return line 14 has an upstream end connected to the outlet gas duct 22 and a downstream end connected to a second connection portion P2 which is a connection portion downstream of the first connection portion P1 of the downstream exhaust gas line 12B. The purification gas guided to at least one of the above-described heat transfer tubes 51 through the purification gas introduction line 13 is guided to a downstream side of the catalyst casing 4 in the exhaust gas line 12 through the purification gas return line 14.

[0028] (Purified Gas Temperature Acquisition Device, Purified Gas Flow Rate Adjustment Device) As shown in FIGS. 1 and 2, the oxidation catalyst system 2 according to some embodiments further includes a purified gas temperature acquisition device 6 and a purified gas flow rate adjustment device 7. The purified gas temperature acquisition device 6 is configured to acquire the temperature of the purified gas flowing downstream of the oxidation catalyst 31 in the exhaust gas line 12.

[0029] The purified gas flow rate adjustment device 7 is configured to adjust the flow rate of the purified gas guided to the heat exchanger 5 according to the measured temperature MT which is the temperature of the purified gas acquired by the purified gas temperature acquisition device 6. The purified gas flow rate adjustment device 7 increases the flow rate of the purified gas guided to the heat exchanger 5 in order to activate the oxidation catalyst 31. As the flow rate of the purified gas guided to the heat exchanger 5 increases, the temperature of the purified gas flowing downstream of the oxidation catalyst 31 becomes higher. And when the temperature of the purified gas flowing downstream of the oxidation catalyst 31 exceeds the target value, the purified gas flow rate adjustment device 7 reduces the flow rate of the purified gas guided to the heat exchanger 5 and lowers the temperature of the purified gas flowing downstream of the oxidation catalyst 31 in order to protect equipment such as piping constituting the downstream side of the second connection portion P2 of the exhaust gas line 12. Specifically, by adjusting the flow rate of the purified gas guided to the heat exchanger 5 by the purified gas flow rate adjustment device 7, the temperature of the purified gas flowing through the second internal space 40B can be lowered. Thereby, the temperature of the purified gas flowing downstream of the second connection portion P2 of the exhaust gas line 12 can also be lowered, and thermal damage to equipment such as piping constituting the downstream side of the second connection portion P2 of the exhaust gas line 12 can be suppressed. Examples of the equipment such as piping constituting the downstream side of the second connection portion P2 of the exhaust gas line 12 include a flue, a silencer, a spark arrester for preventing the scattering of fire powder and sparks, and the like.

[0030] According to the above configuration, by the purified gas flow rate adjusting device 7, according to the temperature MT of the purified gas acquired by the purified gas temperature acquisition device 6, by adjusting the flow rate of the purified gas led to the heat exchanger 5, an excessive increase in the temperature of the purified gas flowing on the downstream side of the oxidation catalyst 31 can be suppressed. Thereby, even if the heat-resistant temperature of equipment such as piping constituting the downstream side of the second connection portion P2 of the exhaust gas line 12 is not increased, damage to the equipment due to the heat of the purified gas can be suppressed.

[0031] In some embodiments, as shown in FIGS. 1 and 2, the above-described purified gas temperature acquisition device 6 is configured to acquire the temperature of the purified gas flowing on the downstream side of the oxidation catalyst 31 of the exhaust gas line 12 and on the upstream side of the first connection portion P1. The purified gas temperature acquisition device 6 may be provided in the second internal space 40B of the catalyst casing 4 and measure the temperature of the purified gas flowing through the second internal space 40B, or may be provided at a position upstream of the first connection portion P1 of the downstream exhaust gas line 12B and measure the temperature of the purified gas flowing through the position. The purified gas temperature acquisition device 6 may include a temperature sensor configured to measure the temperature of the purified gas.

[0032] According to the above configuration, the acquisition position of the temperature of the purified gas by the purified gas temperature acquisition device 6 is on the downstream side of the oxidation catalyst 31 of the exhaust gas line 12 and on the upstream side of the first connection portion P1. That is, the temperature of the purified gas near the second internal space 40B can be directly acquired by the purified gas temperature acquisition device 6. In the adjustment of the flow rate of the purified gas by the purified gas flow rate adjusting device 7, by using the temperature of the purified gas near the second internal space 40B acquired by the purified gas temperature acquisition device 6, the temperature of the purified gas flowing on the downstream side of the oxidation catalyst 31 of the exhaust gas line 12 and on the upstream side of the first connection portion P1 can be more reliably maintained below the above-described heat-resistant temperature. Thereby, the temperature of the purified gas flowing on the downstream side of the second connection portion P2 of the exhaust gas line 12 can be maintained below the above-described heat-resistant temperature, and damage to the equipment constituting the downstream side of the second connection portion P2 of the exhaust gas line 12 due to the heat of the purified gas can be suppressed.

[0033] (First on-off damper, suction fan) In some embodiments, as shown in FIG. 1, the above-described purified gas flow rate adjusting device 7 is provided in the purified gas introduction line 13 and includes a first on-off damper 81 that opens and closes the purified gas introduction line 13, and an induction fan 82 that is provided on the downstream side of the first on-off damper 81 of the purified gas introduction line 13 and sucks the purified gas from the exhaust gas line 12 into the purified gas introduction line 13.

[0034] The induction fan 82 is driven by being supplied with power from a generator or the like (not shown) and is configured to send the purified gas to the downstream side of the purified gas introduction line 13.

[0035] According to the above configuration, even when there is no margin in the exhaust pressure of the oxidation catalyst system 2, that is, when the pressure difference between the purified gas flowing through the purified gas introduction line 13 and the purified gas flowing downstream of the second connection portion P2, which is the connection portion between the purified gas return line 14 of the exhaust gas line 12, is small, the induction fan 82 can surely guide the purified gas to the heat exchanger 5. Further, the flow rate of the purified gas guided to the heat exchanger 5 can be adjusted by opening and closing the first on-off damper 81.

[0036] In some embodiments, as shown in FIG. 2, the above-described purified gas flow rate adjusting device 7 is provided on the downstream side of the first connection portion P1 of the exhaust gas line 12 and on the upstream side of the second connection portion P2, which is the connection portion with the purified gas return line 14, and includes a second on-off damper 83 that opens and closes the exhaust gas line 12.

[0037] According to the above configuration, when there is a margin in the exhaust pressure of the oxidation catalyst system 2, that is, when the pressure difference between the purified gas flowing through the purified gas introduction line 13 and the purified gas flowing downstream of the second connection part P2 of the exhaust gas line 12 is large, equipment such as the suction fan 82 described above for sending the purified gas to the heat exchanger 5 is not required. That is, the purified gas can be sent to the heat exchanger 5 by opening and closing the second on-off damper 83, and the flow rate of the purified gas led to the heat exchanger 5 can be adjusted. In this case, since equipment for sending the above purified gas is not required, the structure of the oxidation catalyst system 2 can be made simple.

[0038] Each of the above-described first on-off damper 81 and second on-off damper 83 may be an on-off valve whose opening degree can be adjusted between fully closed and fully open, or an opening degree adjustment valve whose opening degree can be adjusted between fully closed, fully open, and at least one intermediate opening degree therebetween.

[0039] (Adjustment of the flow rate of the purified gas) FIG. 3 is a block diagram showing an example of the opening degree control of the first on-off damper 81 in the oxidation catalyst system 2 shown in FIG. 1. FIG. 4 is a block diagram showing an example of the opening degree control of the second on-off damper 83 in the oxidation catalyst system 2 shown in FIG. 2. In some embodiments, the above-described purified gas flow rate adjustment device 7 is configured to adjust the flow rate of the purified gas led to the heat exchanger 5 so that the temperature MT of the purified gas acquired by the purified gas temperature acquisition device 6 approaches the target temperature TT of the purified gas.

[0040] In the illustrated embodiment, as shown in FIGS. 1 to 4, the above-described purified gas flow rate adjusting device 7 further includes a control device (controller) 70 configured to control the operation of the first on-off damper 81 or the second on-off damper 83. The control device 70 is an electronic control unit for controlling the first on-off damper 81 or the second on-off damper 83. The control device 70 is configured as a microcomputer including a CPU (processor) not shown, a memory such as a ROM and a RAM, a storage device such as an external storage device, an I / O interface, a communication interface, and the like. The control device 70 may realize control in each functional unit included in the control device 70 by the CPU operating (for example, performing data calculation) according to the instructions of a program loaded in the main storage device of the memory, for example.

[0041] As shown in FIGS. 3 and 4, the control device 70 includes a purified gas temperature acquisition unit 71A, a damper opening output unit 72, a PID control unit 73, and a control value conversion unit 74. The purified gas temperature acquisition unit 71A is connected so as to be able to receive a signal (a signal related to the measured temperature MT) from the purified gas temperature acquisition device 6, and information such as a signal related to the measured temperature MT of the purified gas is sent from the purified gas temperature acquisition device 6. The PID control unit 73 performs a PID control (feedback control) operation so that the measured temperature MT of the purified gas acquired by the purified gas temperature acquisition unit 71A approaches the target temperature TT of the purified gas. The control value conversion unit 74 converts the control value output by the PID control unit 73 into an opening instruction value for the first on-off damper 81 or the second on-off damper 83. The damper opening output unit 72 is connected so as to be able to transmit a signal (a signal related to the opening instruction value) to the first on-off damper 81 or the second on-off damper 83, and sends the above opening instruction value to the first on-off damper 81 or the second on-off damper 83. The first on-off damper 81 or the second on-off damper 83 changes the opening degree to the opening degree corresponding to the opening instruction value sent from the damper opening output unit 72.

[0042] According to the above configuration, by bringing the temperature MT of the purified gas acquired by the purified gas temperature acquisition device 6 closer to the target temperature TT of the purified gas, it is possible to suppress an excessive increase in the temperature of the purified gas flowing on the downstream side of the second connection portion P2, and the exhaust gas passing through the heat exchanger 5 can raise the temperature to a level at which the oxidation catalyst 31 can exhibit its performance.

[0043] In some embodiments, the above-described purified gas flow rate adjustment device 7 is configured to reduce the flow rate of the purified gas guided to the heat exchanger 5 when the temperature MT of the purified gas acquired by the purified gas temperature acquisition device 6 is higher than the target temperature TT.

[0044] In the illustrated embodiment, when the temperature MT of the purified gas acquired by the purified gas temperature acquisition device 6 is higher than the target temperature TT, the PID control unit 73 is configured to output an output value for reducing the opening degree of the first on-off damper 81, or an output value for increasing the opening degree of the second on-off damper 83. When the temperature MT of the purified gas acquired by the purified gas temperature acquisition device 6 is lower than the target temperature TT, the PID control unit 73 is configured to output an output value for increasing the opening degree of the first on-off damper 81, or an output value for reducing the opening degree of the second on-off damper 83.

[0045] According to the above configuration, when the acquired temperature MT of the purified gas is higher than the target temperature TT, the flow rate of the purified gas guided to the heat exchanger 5 can be reduced. By reducing the flow rate of the purified gas guided to the heat exchanger 5 and reducing the thermal energy of the purified gas recovered by the exhaust gas in the heat exchanger 5, the temperature of the purified gas flowing on the downstream side of the oxidation catalyst 31 can be lowered. Thereby, an excessive increase in the temperature of the purified gas flowing on the downstream side of the oxidation catalyst 31 can be suppressed.

[0046] Depending on the type and specifications of the internal combustion engine 11, there are some cases where the load EL of the internal combustion engine 11 and the exhaust gas temperature tend as follows. That is, the exhaust gas discharged from the internal combustion engine 11 has a tendency that in the region where the load EL of the internal combustion engine 11 is below a predetermined load (for example, 75%), the exhaust gas temperature rises as the load EL increases. Also, in the region where the load EL of the internal combustion engine 11 exceeds the predetermined load, there are cases where the exhaust gas temperature decreases as the load EL increases.

[0047] (Target temperature adjustment) In some embodiments, when the load EL of the internal combustion engine 11 is higher than a predetermined load (for example, 75%), the purification gas flow rate adjustment device 7 described above is configured to increase the target temperature TT of the purification gas when the load EL increases. Note that the purification gas flow rate adjustment device 7 may gradually increase the target temperature TT of the purification gas as the load EL increases in the region where the load EL is higher than the predetermined load, or may divide the region where the load EL is higher than the predetermined load into a plurality of sections and increase the target temperature TT of the purification gas stepwise for each divided section. As shown in FIGS. 3 and 4, the purification gas flow rate adjustment device 7 may further include a load acquisition unit 71B that acquires the load EL of the internal combustion engine 11, and a target temperature adjustment unit 75 configured to adjust the target temperature TT according to the load EL acquired by the load acquisition unit 71B. The above-described control for increasing the target temperature TT accompanying the increase in the load EL of the purification gas flow rate adjustment device 7 and the control for decreasing the target temperature TT accompanying the decrease in the load EL described later may be performed by the target temperature adjustment unit 75. The load acquisition unit 71B is configured to receive information such as a signal regarding the load EL from the internal combustion engine 11, the generator 15, or the like.

[0048] According to the above configuration, when the load EL of the internal combustion engine 11 is higher than a predetermined load and the load EL increases, the exhaust gas temperature from the internal combustion engine 11 decreases, and the efficiency of the oxidation reaction by the oxidation catalyst 31 decreases by the amount of the decrease in the exhaust gas temperature. In this case, by increasing the target temperature TT of the purified gas by the purified gas flow rate adjustment device 7 and increasing the flow rate of the purified gas led to the heat exchanger 5, the exhaust gas temperature led to the oxidation catalyst 31 can be increased, and the efficiency of the oxidation reaction by the oxidation catalyst 31 can be improved.

[0049] In some embodiments, the above-described purified gas flow rate adjustment device 7 is configured to lower the target temperature TT of the purified gas when the load EL decreases when the load EL of the internal combustion engine 11 is higher than a predetermined load (for example, 75%). Note that the purified gas flow rate adjustment device 7 may gradually lower the target temperature TT of the purified gas as the load EL decreases in a region where the load EL is higher than the predetermined load, or may divide the region where the load EL is higher than the predetermined load into a plurality of sections and lower the target temperature TT of the purified gas step by step for each divided section.

[0050] According to the above configuration, when the load EL of the internal combustion engine 11 is higher than a predetermined load and the load EL decreases, the exhaust gas temperature from the internal combustion engine 11 rises, and the efficiency of the oxidation reaction by the oxidation catalyst 31 increases by the amount of the increase in the exhaust gas temperature. In this case, by lowering the target temperature TT of the purified gas by the purified gas flow rate adjustment device 7 and reducing the flow rate of the purified gas led to the heat exchanger 5, the exhaust gas temperature led to the oxidation catalyst 31 can be lowered, and thermal damage to the equipment provided on the downstream side in the flow direction of the purified gas from the oxidation catalyst 31 can be reliably prevented.

[0051] Note that in some embodiments, the above-described purified gas flow rate adjustment device 7 may have a constant target temperature TT regardless of changes in the load EL.

[0052] In this specification, expressions indicating relative or absolute arrangements such as "in a certain direction", "along a certain direction", "parallel", "orthogonal", "center", "concentric", or "coaxial" not only strictly represent such arrangements, but also represent states where there are tolerances or relative displacements with angles or distances that can achieve the same function. For example, expressions indicating that things such as "identical", "equal", and "homogeneous" are in an equal state not only strictly represent an equal state, but also represent states where there are tolerances or differences that can achieve the same function. Also, in this specification, expressions representing shapes such as a square shape or a cylindrical shape not only represent shapes such as a square shape or a cylindrical shape in a geometrically strict sense, but also represent shapes including uneven portions, chamfered portions, etc. within a range where the same effect can be obtained. Also, in this specification, the expressions "comprising", "including", or "having" a component do not exclude the existence of other components.

[0053] The present disclosure is not limited to the above-described embodiments, and includes forms obtained by modifying the above-described embodiments and forms obtained by appropriately combining these forms.

[0054] The content described in some of the above-described embodiments can be understood as follows, for example.

[0055] 1) The oxidation catalyst system (2) according to at least one embodiment of the present disclosure is provided in an exhaust gas line (12) through which exhaust gas discharged from an internal combustion engine (11) flows, and an oxidation catalyst (31) configured to oxidize the exhaust gas; a heat exchanger (5) configured to perform heat exchange between the purified gas, which is the exhaust gas heated by the oxidation reaction of the oxidation catalyst (31), and the exhaust gas flowing upstream of the oxidation catalyst (31) in the exhaust gas line (12); a purified gas introduction line (13) for extracting the purified gas from downstream of the oxidation catalyst (31) in the exhaust gas line (12) and guiding it to the heat exchanger (5); A purified gas return line (14) for returning the purified gas to a position downstream of a first connection portion (P1), which is a connection portion between the heat exchanger (5) and the purified gas introduction line (13) of the exhaust gas line (12), A purified gas temperature acquisition device (6) configured to acquire the temperature of the purified gas flowing downstream of the oxidation catalyst (31) in the exhaust gas line (12); A purified gas flow rate adjustment device (7) configured to adjust the flow rate of the purified gas introduced into the heat exchanger (5) according to the temperature (MT) of the purified gas acquired by the purified gas temperature acquisition device (6).

[0056] According to the configuration of 1) above, the purified gas flow rate adjustment device (7) adjusts the flow rate of the purified gas introduced into the heat exchanger (5) according to the temperature (MT) of the purified gas acquired by the purified gas temperature acquisition device (6), thereby suppressing an excessive increase in the temperature of the purified gas flowing downstream of the oxidation catalyst (31). As a result, it is possible to suppress damage to the equipment downstream of the second connection portion (P2) of the exhaust gas line (12) due to the heat of the purified gas without increasing the heat-resistant temperature of the equipment.

[0057] 2) In some embodiments, the oxidation catalyst system (2) described in 1) above, The purified gas flow rate adjustment device (7) is configured to adjust the flow rate of the purified gas introduced into the heat exchanger (5) such that the temperature (MT) of the purified gas acquired by the purified gas temperature acquisition device (6) approaches the target temperature (TT) of the purified gas.

[0058] According to the configuration of 2) above, by bringing the temperature (MT) of the purified gas acquired by the purified gas temperature acquisition device (6) closer to the target temperature (TT) of the purified gas, it is possible to suppress an excessive increase in the temperature of the purified gas flowing downstream of the second connection portion (P2), and at the same time, the exhaust gas passing through the heat exchanger (5) can raise the temperature of the oxidation catalyst (31) to a temperature at which its performance can be exhibited.

[0059] 3) In some embodiments, the oxidation catalyst system (2) described in 2) above, the purified gas flow rate adjusting device (7) is configured to reduce the flow rate of the purified gas led to the heat exchanger (5) when the temperature (MT) of the purified gas acquired by the purified gas temperature acquisition device (6) is higher than the target temperature (TT).

[0060] According to the configuration of 3) above, when the acquired temperature (MT) of the purified gas is higher than the target temperature (TT), the flow rate of the purified gas led to the heat exchanger (5) can be reduced. By reducing the flow rate of the purified gas led to the heat exchanger (5) and reducing the heat energy of the purified gas recovered by the exhaust gas in the heat exchanger (5), the temperature of the purified gas flowing downstream of the oxidation catalyst (31) can be lowered. Thereby, an excessive rise in the temperature of the purified gas flowing downstream of the oxidation catalyst (31) can be suppressed.

[0061] 4) In some embodiments, the oxidation catalyst system (2) described in 2) or 3) above, the purified gas flow rate adjusting device (7) is configured to raise the target temperature (TT) of the purified gas when the load (EL) of the internal combustion engine (11) is higher than a predetermined load and the load (EL) increases.

[0062] According to the configuration of 4) above, when the load (EL) of the internal combustion engine (11) is higher than a predetermined load and the load (EL) increases, the exhaust gas temperature from the internal combustion engine (11) drops, and the efficiency of the oxidation reaction by the oxidation catalyst (31) decreases by the amount of the decrease in the exhaust gas temperature. In this case, by raising the target temperature (TT) of the purified gas by the purified gas flow rate adjusting device (7) and increasing the flow rate of the purified gas led to the heat exchanger (5), the exhaust gas temperature led to the oxidation catalyst (31) can be raised, and the efficiency of the oxidation reaction by the oxidation catalyst (31) can be improved.

[0063] 5) In some embodiments, the oxidation catalyst system (2) described in 2) or 3) above, The purification gas flow rate adjusting device (7) is configured such that: when the load (EL) of the internal combustion engine (11) is higher than a predetermined load, the target temperature (TT) of the purification gas is decreased when the load (EL) decreases.

[0064] According to the configuration of 5) above, when the load (EL) of the internal combustion engine (11) is higher than a predetermined load and the load (EL) decreases, the exhaust gas temperature from the internal combustion engine (11) rises, and the efficiency of the oxidation reaction by the oxidation catalyst (31) increases by the amount of the rise in the exhaust gas temperature. In this case, by decreasing the target temperature (TT) of the purification gas by the purification gas flow rate adjusting device (7) and reducing the flow rate of the purification gas led to the heat exchanger (5), the exhaust gas temperature led to the oxidation catalyst (31) can be decreased, and heat damage to the equipment provided on the downstream side in the flow direction of the purification gas from the oxidation catalyst (31) can be reliably prevented.

[0065] 6) In some embodiments, the oxidation catalyst system (2) according to any one of 1) to 5) above, wherein the purification gas flow rate adjusting device (7) includes: a first on-off damper (81) provided in the purification gas introduction line (13) for opening and closing the purification gas introduction line (13); and a suction fan (82) provided on the downstream side of the first on-off damper (81) in the purification gas introduction line (13) for sucking the purification gas from the exhaust gas line (12) into the purification gas introduction line (13).

[0066] According to the configuration of 6) above, even when there is no margin in the exhaust pressure of the oxidation catalyst system (2), the suction fan (82) can reliably lead the purification gas to the heat exchanger (5). Further, the flow rate of the purification gas led to the heat exchanger (5) can be adjusted by opening and closing the first on-off damper (81).

[0067] 7) In some embodiments, the oxidation catalyst system (2) according to any one of 1) to 5) above, wherein the purification gas flow rate adjusting device (7) is configured such that: It is provided on the downstream side of the first connection part (P1) of the exhaust gas line (12) and on the upstream side of the second connection part (P2) which is the connection part with the purified gas return line (14), and includes a second on-off damper (83) for opening and closing the exhaust gas line (12).

[0068] According to the configuration of 7) above, when there is a margin in the exhaust pressure of the oxidation catalyst system (2), equipment such as the above-described suction fan (82) for sending purified gas to the heat exchanger (5) is not required. That is, the purified gas can be sent to the heat exchanger (5) by opening and closing the second on-off damper (83), and the flow rate of the purified gas led to the heat exchanger (5) can be adjusted. In this case, since equipment for sending the purified gas is not required, the structure of the oxidation catalyst system (2) can be made simple.

[0069] 8) In some embodiments, it is the oxidation catalyst system (2) described in any one of 1) to 7) above, wherein the purified gas temperature acquisition device (6) is configured to acquire the temperature of the purified gas flowing on the upstream side of the first connection part (P1) of the exhaust gas line (12).

[0070] According to the configuration of the above (8), the acquisition position of the temperature of the purified gas by the purified gas temperature acquisition device (6) is downstream of the oxidation catalyst (31) in the exhaust gas line (12) and upstream of the first connection part (P1). That is, the purified gas temperature acquisition device (6) can directly acquire the temperature of the purified gas near the second internal space (40B). In the adjustment of the flow rate of the purified gas by the purified gas flow rate adjustment device (7), by using the temperature of the purified gas near the second internal space (40B) acquired by the purified gas temperature acquisition device (6), the temperature of the purified gas flowing downstream of the oxidation catalyst (31) in the exhaust gas line (12) and upstream of the first connection part (P1) can be more reliably maintained below the heat-resistant temperature described above. Thereby, the temperature of the purified gas flowing downstream of the second connection part (P2) of the exhaust gas line (12) can be maintained below the heat-resistant temperature described above, and damage to the purified gas due to heat of the equipment constituting the downstream side of the second connection part (P2) of the exhaust gas line (12) can be suppressed.

Explanation of Signs

[0071] 1 Internal combustion engine system 2 Oxidation catalyst system 3 Oxidation catalyst device 4 Catalyst casing 5 Heat exchanger 6 Purified gas temperature acquisition device 7 Purified gas flow rate adjustment device 11 Internal combustion engine 12 Exhaust gas line 12A Upstream exhaust gas line 12B Downstream exhaust gas line 13 Purified gas introduction line 14 Purified gas return line 15 Generator 21 Inlet gas duct 22 Outlet gas duct 31 Oxidation catalyst 40 Internal space 40A First internal space 40B Second internal space 41 Casing main body part 42 Exhaust gas inlet 43 Exhaust gas outlet 51 Heat transfer tube 70 Control device 71A Purified gas temperature acquisition unit 71B Load acquisition unit 72 Damper opening output unit 73 PID control unit 74 Control value conversion unit 75 Target temperature adjustment unit 81 First on-off damper 82 Induced draft fan 83 Second on-off damper EL Load of internal combustion engine MT Measured temperature of purified gas P1 First connection part P2 Second connection part TT Target temperature

Claims

1. An oxidation catalyst provided in an exhaust gas line through which exhaust gas discharged from an internal combustion engine flows, and configured to oxidize the exhaust gas; A heat exchanger configured to perform heat exchange between the purified gas, which is the exhaust gas heated by the oxidation reaction of the oxidation catalyst, and the exhaust gas flowing upstream of the oxidation catalyst in the exhaust gas line; A purified gas introduction line for extracting the purified gas from downstream of the oxidation catalyst in the exhaust gas line and guiding it to the heat exchanger; A purified gas return line for returning the purified gas to a position downstream of a first connection portion, which is a connection portion between the heat exchanger and the purified gas introduction line in the exhaust gas line; A purified gas temperature acquisition device configured to acquire the temperature of the purified gas flowing downstream of the oxidation catalyst in the exhaust gas line; A purified gas flow rate adjustment device configured to adjust the flow rate of the purified gas guided to the heat exchanger according to the temperature of the purified gas acquired by the purified gas temperature acquisition device. The oxidation catalyst system is provided with: The purified gas flow rate adjustment device is: When the temperature of the purified gas acquired by the purified gas temperature acquisition device is higher than a target temperature, it is configured to decrease the flow rate of the purified gas guided to the heat exchanger within a range where the flow rate is not reduced to zero. An oxidation catalyst system.

2. The purified gas flow rate adjustment device is: Configured to adjust the flow rate of the purified gas guided to the heat exchanger so that the temperature of the purified gas acquired by the purified gas temperature acquisition device approaches the target temperature of the purified gas. The oxidation catalyst system according to claim 1.

3. The purified gas flow rate adjustment device is: When the load of the internal combustion engine is higher than a predetermined load, it is configured to increase the target temperature of the purified gas when the load increases. The oxidation catalyst system according to claim 1 or 2.

4. The purified gas flow rate adjustment device is: When the load of the internal combustion engine is higher than a predetermined load, it is configured to lower the target temperature of the purified gas when the load decreases. The oxidation catalyst system according to claim 1 or 2.

5. The purified gas flow rate adjustment device is: A first on-off damper provided in the purified gas introduction line and configured to open and close the purified gas introduction line. Provided downstream of the first on-off damper of the purified gas introduction line, and including an induction fan for sucking the purified gas from the exhaust gas line into the purified gas introduction line. The oxidation catalyst system according to claim 1 or 2.

6. The purified gas flow rate adjustment device Provided downstream of the first connection part of the exhaust gas line and upstream of a second connection part which is a connection part with the purified gas return line, and including a second on-off damper for opening and closing the exhaust gas line. The oxidation catalyst system according to claim 1 or 2.

7. The purified gas temperature acquisition device Configured to acquire the temperature of the purified gas flowing upstream of the first connection part of the exhaust gas line. The oxidation catalyst system according to claim 1 or 2.

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