JP2011012554A - Reforming catalyst system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reforming catalyst system efficiently recovering from poisoning of a reforming catalyst.SOLUTION: In the reforming catalyst system reforming mixed gas which is provided by mixing fuel to part of exhaust gas by the reforming catalyst, and including EGR making reformed gas re-sucked in the engine, a regulator valve regulating exhaust gas recirculation rate of exhaust gas circulated by an exhaust gas recirculation passage to exhaust gas recirculation rate at which oxygen quantity in exhaust gas supplied to the reforming catalyst gets to the maximum, based on an engine operation state. Poisoning of the reforming catalyst is efficiently recovered by this structure since the exhaust gas recirculation rate is regulated to the exhaust gas recirculation rate at which oxygen quantity in exhaust gas supplied to the reforming catalyst gets to the maximum.

Description

  The present invention relates to a reforming catalyst system that recovers poisoning of a reforming catalyst that reforms exhaust gas.

Conventionally, an internal combustion engine that can recover poisoning of a reforming catalyst is known (see, for example, Patent Document 1).
When the internal combustion engine determines that the reformed catalyst is poisoned due to the detected combustion state, the means for detecting the combustion state of the reformed gas obtained by reforming the mixed gas of exhaust gas and fuel with the reforming catalyst, And means for supplying exhaust gas containing oxygen generated by combustion to the reforming catalyst. The reforming catalyst provided in the internal combustion engine recovers from poisoning by burning poisonous substances using oxygen in the supplied exhaust gas.

JP 2006-118488 A

  However, in the internal combustion engine described in Patent Document 1, the amount of oxygen in the exhaust gas cannot be controlled because the exhaust gas air-fuel ratio for realizing lean combustion is not controlled, and the oxygen content in the exhaust gas cannot be controlled efficiently. There was a problem that the poison could not be recovered.

  Accordingly, an object of the present invention is to provide a reforming catalyst system that can efficiently recover poisoning of the reforming catalyst.

The reforming catalyst system according to the present invention reforms a mixed gas in which fuel is mixed with a part of exhaust gas with a reforming catalyst, and recirculates the reformed gas to the engine and EGR. An adjustment valve that adjusts the exhaust gas recirculation rate of the exhaust gas to an exhaust gas recirculation rate that maximizes the amount of oxygen in the exhaust gas supplied to the reforming catalyst, based on the operating state of the engine that exhausts the exhaust gas It is characterized by comprising.
According to this structure, the exhaust gas recirculation rate of the exhaust gas circulated by the EGR is adjusted to the exhaust gas recirculation rate at which the amount of oxygen in the exhaust gas supplied to the reforming catalyst is maximized. Can be efficiently recovered.

  According to the reforming catalyst system disclosed in this specification, poisoning of the reforming catalyst can be efficiently recovered.

It is a block diagram which shows one Embodiment of the reforming catalyst system of this invention. It is a block diagram showing the example of 1 structure of a control apparatus. It is a flowchart showing an example of the control processing which a control apparatus performs.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, exemplary embodiments of the invention will be described with reference to the accompanying drawings.

FIG. 1 is a configuration diagram showing an embodiment of a reforming catalyst system of the present invention.
An exhaust gas reforming system 1 shown in FIG. 1 corresponds to an example of a reforming catalyst system of the present invention. The exhaust gas reforming system 1 is mounted on a vehicle. The exhaust gas reforming system 1 includes an exhaust gas recirculation path 10, a fuel supply device 12, a cooler 14, a flow rate adjustment valve 15, a heat exchanger 20, a throttle 30, a fuel injection device 40, an introduction pipe 51, an exhaust pipe 52, an engine. 60 and a control device 70. The exhaust gas reforming system 1 recovers poisoning of a reforming catalyst that reforms a mixed gas obtained by mixing exhaust gas and fuel.

  Here, the reforming catalyst mainly generates a reformed gas containing, for example, hydrogen, carbon monoxide, and nitrogen from a mixed gas of exhaust gas and fuel by a reforming reaction that is an endothermic reaction. In this reforming reaction, for example, the reforming catalyst is poisoned by adhering substances such as by-produced carbon C and hydrocarbons CH and sulfur S contained in the fuel. Conversely, the reforming catalyst recovers from poisoning by causing poisoning substances that cause poisoning to react with oxygen and desorb by, for example, combustion. Although the reforming catalyst is described as being a rhodium-based catalyst, for example, it is not limited to this.

  The exhaust gas reforming system 1 includes EGR (Exhaust Gas Recirculation). EGR is realized by the exhaust gas recirculation path 10. Here, the exhaust gas recirculation path 10 circulates a part of the exhaust gas exhausted by the engine 60 and causes the engine 60 to take in again. Specifically, during the reforming operation, the exhaust gas recirculation path 10 supplies the engine 60 with the reformed gas obtained by reforming the mixed gas of the circulated exhaust gas and fuel with the reforming catalyst. During the recovery operation, the exhaust gas recirculation path 10 circulates a part of the exhaust gas containing oxygen discharged from the lean burned engine 60. Here, since the reforming catalyst is carried in the middle of the circulation path through which the exhaust gas recirculation path 10 circulates the exhaust gas, the reforming catalyst consumes oxygen in the exhaust gas circulated by the exhaust gas recirculation path 10 and is poisoned. Recover. Therefore, the exhaust gas recirculation path 10 supplies the engine 60 with the exhaust gas in which oxygen is consumed by the recovery of the reforming catalyst during the reforming operation. The exhaust gas recirculation path 10 may supply the reformed gas to the engine 60 even during the recovery operation.

Next, the configuration of the exhaust gas recirculation path 10 will be described.
The exhaust gas recirculation path 10 includes an exhaust gas introduction path 11 and a reformed gas conduit 13, and a fuel supply device 12, a cooler 14, and a flow rate adjustment valve 15 are installed.
The exhaust gas introduction path 11 is connected to the heat exchanger 20 and the exhaust pipe 52, and introduces a part of the exhaust gas that passes through the exhaust pipe 52 to the heat exchanger 20. In the exhaust gas introduction path 11, the fuel supply device 12 is installed downstream of the connection point with the exhaust pipe 52.

  The fuel supply device 12 is constituted by, for example, an injector. During the reforming operation, the fuel supply device 12 injects an amount of fuel according to the control of the control device 70 into the exhaust gas that passes through the exhaust gas introduction path 11 and a mixed gas in which the exhaust gas and the fuel are mixed. Is generated. The fuel supply device 12 does not inject fuel during the recovery operation.

Here, the heat exchanger 20 will be described once.
The heat exchanger 20 includes an exhaust passage 21 and a reforming chamber 22. The heat exchanger 20 moves the heat of the exhaust gas passing through the exhaust passage 21 to the reforming catalyst supported in the reforming chamber 22.
A part of the exhaust gas discharged from the engine 60 is supplied to the reforming chamber 22 from the exhaust gas introduction path 11. Specifically, during the reforming operation, a mixed gas of exhaust gas containing less oxygen or not containing oxygen and fuel is supplied to the reforming chamber 22, so that the reforming catalyst supported in the reforming chamber 22 The gas mixture is reformed and poisoned using the heat of the exhaust gas. Conversely, during the recovery operation, exhaust gas containing a large amount of oxygen is supplied to the reforming chamber 22, so that the reforming catalyst consumes oxygen and recovers from poisoning. A reformed gas conduit 13 is connected downstream of the reforming chamber 22.

Next, the configuration of the exhaust gas recirculation path 10 will be described continuously.
The reformed gas conduit 13 is connected to the reforming chamber 22 upstream, the cooler 14 and the flow rate adjusting valve 15 are sequentially installed in the middle stream, and merge with the introduction pipe 51 downstream. The reformed gas conduit 13 supplies the reformed gas generated in the reforming chamber 22 to the engine 60 via the introduction pipe 51 during the reforming operation. Further, during the recovery operation, exhaust gas that has consumed oxygen for combustion of poisonous substances in the reforming chamber 22 is supplied to the engine 60. The cooler 14 cools the gas passing through the reformed gas conduit 13 and increases the volume flow rate of the gas.

  The flow rate adjusting valve 15 controls an exhaust gas recirculation rate (hereinafter simply referred to as an EGR rate) of the exhaust gas circulated by the exhaust gas recirculation path 10. Here, the EGR rate refers to a ratio obtained by dividing the EGR amount by the sum of the amount of air taken in by the engine 60 and the amount of exhaust gas circulated by the exhaust gas recirculation path 10 (hereinafter simply referred to as the EGR amount). Specifically, the flow rate adjusting valve 15 controls the EGR rate by controlling the amount of gas passing through the reformed gas conduit 13 according to the control of the control device 70. That is, the flow rate adjusting valve 15 controls not only the amount of exhaust gas supplied to the reforming chamber 22 but also the amount of exhaust gas recirculated to the engine 60.

The throttle 30 is connected to an accelerator sensor (not shown). The throttle 30 opens and closes the introduction pipe 51 according to the accelerator operation detected by the accelerator sensor. That is, the throttle 30 controls the amount of air taken in by the engine 60 by opening and closing the introduction pipe 51. The throttle 30 can also be connected to the control device 80 and adopt a configuration in which the EGR rate is controlled by controlling the amount of air taken in by the engine 60 according to the control of the control device 80.
The fuel injection device 40 is composed of, for example, an injector. The fuel injection device 40 injects an amount of fuel controlled by the control device 80 into the introduction pipe 51.

The introduction pipe 51 is connected to the throttle 30 upstream, and is connected to the intake port of the engine 60 downstream. Further, the introduction pipe 51 joins the reformed gas conduit 13 in the middle stream, and the fuel injection device 40 is installed at a point between a point where the reformed gas conduit 13 joins and a point connected to the engine 60. The introduction pipe 51 includes an amount of air controlled by the throttle 30, an amount of gas controlled by the flow rate adjusting valve 15 provided in the reformed gas conduit 13, and an amount of fuel injected by the fuel injection device 40. The air-fuel mixture is introduced into the engine 60.
The exhaust pipe 52 is connected upstream with the exhaust port of the engine 60 and discharges the exhaust gas discharged by the engine 60 to the atmosphere outside the vehicle. Further, the exhaust pipe 52 branches off from the exhaust gas recirculation path 10 downstream, and the heat exchanger 20 is installed downstream of the branch point.

The engine 60 is provided with a detection device 60a. The detection device 60a is composed of, for example, an NE sensor (Number of Engine speed), detects the rotational speed of the engine 60, and outputs an NE signal representing the detected rotational speed to the control device 80.
The engine 60 is composed of, for example, a gasoline engine. The engine 60 generates power for running the vehicle by burning the air-fuel mixture introduced from the introduction pipe 51. Specifically, during the reforming operation, the engine 60 is supplied from the introduction pipe 51 with an air-fuel mixture that is substantially the same as the fuel-rich or theoretical air-fuel ratio obtained by mixing the reformed gas, air, and fuel. On the other hand, during the recovery operation, the engine 60 is supplied with a weak lean air-fuel mixture in which exhaust gas containing little oxygen or no oxygen, air, and fuel are mixed from the introduction pipe 51. This is because exhaust gas containing excess oxygen that has not been consumed by combustion is supplied to the poisoned reforming catalyst.

  Specifically, the total amount of non-combustible gas calculated from the amount of air supplied to the engine 60 (oxygen gas amount) and the amount of exhaust gas recirculated to the engine 60 (EGR amount) includes the combustion in the engine 60. There is a supply limit to prevent misfire. In the present embodiment, the total amount of incombustible gas is described as being a predetermined value determined by the traveling state of the vehicle on which the engine 60 is mounted, but is not limited thereto. In addition, since the predetermined value determined by the running state of the vehicle differs depending on the design of the vehicle, those skilled in the art can specify it by experiments.

  For this reason, even if the amount of oxygen gas supplied to the engine 60 is increased, the total amount of the oxygen gas amount and the EGR amount needs to be equal to or less than a predetermined value, so that the EGR amount decreases. Therefore, even if the amount of surplus oxygen that does not contribute to combustion is increased by increasing the amount of oxygen gas supplied to the engine 60, the amount of exhaust gas supplied to the reforming catalyst is reduced, so that it is supplied to the reforming catalyst. The amount of oxygen in the exhaust gas may decrease. Conversely, even if the amount of exhaust gas supplied to the reforming catalyst is increased by increasing the EGR amount, the amount of oxygen in the exhaust gas supplied to the reforming catalyst is reduced by reducing the surplus oxygen amount. May decrease.

Here, with reference to FIG. 2, the relationship between the oxygen amount supplied to the reforming catalyst and the EGR rate determined by the oxygen gas amount (air amount) supplied to the engine 60 and the EGR amount will be described. FIG. 2 is a diagram illustrating a relationship between the EGR rate and the amount of oxygen supplied to the reforming catalyst in a predetermined traveling state of the vehicle on which the engine 60 is mounted.
In FIG. 2A, the vertical axis represents the amount of oxygen supplied to the reforming catalyst, and the horizontal axis represents the EGR rate. As shown in FIG. 2A, when the EGR rate is larger than the optimum EGR rate Rmax that maximizes the amount of oxygen supplied to the reforming catalyst, the amount of non-combustible gas is constant, so that the oxygen can be supplied to the engine 60 The amount of oxygen decreases, and as a result, the amount of oxygen supplied to the reforming catalyst decreases. When the EGR rate is smaller than the optimum EGR rate Rmax, the amount of oxygen gas supplied to the engine 60 can be increased, but the amount of oxygen supplied to the reforming catalyst is increased because the EGR rate recirculating to the reforming catalyst decreases. I can't. The relationship between the EGR rate and the amount of oxygen supplied to the reforming catalyst varies depending on the design of the exhaust gas reforming system 1, but can be determined by experiments by those skilled in the art.

Returning now to FIG. 1, the exhaust gas reforming system 1 will be described.
The control apparatus 70 is comprised by ECU (Electronic Control Unit), for example. The control device 70 controls each device and device to be connected so that the amount of oxygen in the exhaust gas supplied to the reforming catalyst is maximized by executing a control process that is a software process.
Here, with reference to FIG. 2B, the hardware configuration used by the control device 70 to execute software processing will be described. FIG. 2B is a hardware configuration diagram illustrating a configuration example of the control device 70.
2A includes, for example, an execution unit 70a configured by a CPU (Central Processing Unit), a storage unit 70b configured by a RAM (Random Access Memory), and an AD converter, for example. An input / output unit 70c configured by (Analog-to-Digital) is provided. The software processing is realized by the execution unit 70a reading the program stored in the storage unit 70b and performing calculations according to the execution procedure of the software processing represented by the read program. In addition, the calculation result which the arithmetic unit performed is written in the memory | storage part 70b. Further, as necessary, the input / output unit 70c inputs a signal input by the detection device 60a as a calculation target and outputs a calculation result to the flow rate adjusting valve 15 and the like.

Next, with reference to FIG. 2C, the configuration of the control device 70 will be described focusing on the function. FIG. 2C is a functional block diagram illustrating a configuration example of the control device 70.
The control device 70 includes an acquisition unit 71, a traveling state identification unit 72, an optimum EGR rate storage unit 73, an EGR rate determination unit 74, and an EGR rate control unit 75.

The acquisition unit 71 is realized by the execution unit 70a executing the acquisition process. The acquisition unit 71 acquires an NE signal from the detection device 60a.
The traveling state specifying unit 72 is realized by the execution unit 70a executing the traveling state specifying process. The traveling state specifying unit 72 specifies the traveling state of the vehicle on which the engine 60 is mounted. Specifically, the traveling state specifying unit 72 specifies the traveling state of the vehicle based on the operating state of the engine 60. More specifically, the traveling state of the vehicle is specified based on the rotational speed and load (torque) of the engine 60 represented by the NE signal acquired by the acquisition unit 71.

  The optimum EGR rate storage unit 73 is configured by, for example, a storage unit 70b. The optimum EGR rate storage unit 73 stores the traveling state of the vehicle equipped with the engine 60 and the EGR rate (hereinafter referred to as the optimum EGR rate) at which the amount of oxygen supplied to the reforming catalyst is the largest in the traveling state. To do. The optimum EGR rate depends on the design of the vehicle, but can be determined by experimentation by those skilled in the art.

The EGR rate determination unit 74 is realized by the execution unit 70a executing the EGR rate determination process. The EGR rate determination unit 74 controls the flow rate adjustment valve 15 to determine an EGR rate that is realized. Specifically, the EGR rate determination unit 74 searches for the optimum EGR rate stored in the optimum EGR rate storage unit 73 in association with the running state of the vehicle specified by the running state specifying unit 72. Next, the EGR rate determining unit 74 substantially matches the searched optimum EGR rate with the EGR rate of the exhaust gas circulated by the exhaust gas recirculation path 10 (hereinafter simply referred to as the EGR rate of the exhaust gas recirculation path 10). Thus, the EGR rate as the control target is determined.
According to this configuration, the exhaust gas recirculation rate of the exhaust gas to be circulated is controlled to the exhaust gas recirculation rate that maximizes the amount of oxygen in the exhaust gas supplied to the reforming catalyst. The poison can be recovered reliably and efficiently.

  The EGR rate control unit 75 is realized by the execution unit 70a executing the EGR rate control process. The EGR rate control unit 75 controls the EGR rate of the exhaust gas circulated by the exhaust gas recirculation path 10 so that the EGR rate determined by the EGR rate determining unit 74 is obtained. Specifically, the EGR rate control unit 75 controls the flow rate adjustment valve 15 so that the EGR gas passes through the reformed gas conduit 13 by the amount of gas that realizes the EGR rate determined by the EGR rate determination unit 74. Note that the EGR rate control unit 75 may control the throttle 30 so that air is introduced into the introduction pipe 51 by the amount of gas that realizes the EGR rate determined by the EGR rate determination unit 74.

Next, control processing executed by the control device 70 will be described with reference to FIG. FIG. 3 is a flowchart illustrating an example of a control process executed by the control device 70.
First, the control device 70 acquires an NE signal representing the engine speed from the detection device 60a (step S01). Next, the control device 70 specifies the traveling state of the vehicle equipped with the engine 60 based on the acquired NE signal as described above (step S02). Thereafter, the control device 70 determines the optimum EGR rate as described above based on the identified traveling state of the vehicle (step S03). Next, the control device 70 controls the flow rate adjusting valve 70 so as to realize the determined optimum EGR rate (step S04). Thereafter, the control device 70 ends the execution of the control process.

  In FIG. 3, step S01 corresponds to an example of an acquisition process for realizing the acquisition unit 71, and step S02 corresponds to an example of a driving state specifying process for realizing the driving state specifying unit 72. Corresponds to an example of an EGR rate determination process for realizing the EGR rate determination unit 74, and step S04 corresponds to an example of an EGR rate control process for realizing the EGR rate control unit 75.

  Part or all of the functions realized by executing software processing by the control device 70 can be realized by using a hardware circuit.

  A program describing a processing procedure executed by the control device 70 can be provided by being stored and distributed in a magnetic disk, optical disk, semiconductor memory, or other recording medium, or distributed via a network.

  Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to the specific embodiments, and various modifications, within the scope of the gist of the present invention described in the claims, It can be changed.

1 ... Exhaust gas reforming system 10 ... Exhaust gas recirculation path
11 ... Exhaust gas introduction path 12 ... Fuel supply device
13 ... reformed gas conduit 14 ... cooler
15 ... Flow control valve 20 ... Heat exchanger
21 ... Exhaust passage 22 ... Reforming chamber
30 ... Throttle 40 ... Fuel injection device
51 ... Introduction pipe 52 ... Exhaust pipe
60 ... Engine 60a ... Detection device
70 ... Control device 70a ... Execution unit
70b: Storage unit 70c: Input / output unit
70f ... Bus 71 ... Acquisition part
72 ... Traveling state specifying unit 73 ... Optimal EGR rate storage unit
74 ... EGR rate determination unit 75 ... EGR rate control unit

Claims (1)

In a reforming catalyst system equipped with EGR that reforms a mixed gas obtained by mixing a part of exhaust gas with a fuel using a reforming catalyst and reintakes the reformed gas into the engine.
The amount of oxygen in the exhaust gas supplied to the reforming catalyst is maximized based on the exhaust gas recirculation rate of the exhaust gas circulated by the EGR based on the operating state of the engine exhausting the exhaust gas. A reforming catalyst system comprising an adjusting valve for adjusting an exhaust gas recirculation rate.

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