JP2016125399A - Urea water injection device in exhaust emission control system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an urea water injection device in an exhaust emission control system capable of appropriately detecting urea water being leaked from an urea water injector while the urea water is appropriately injected from the urea water injector when the system is in an exhaust flowing state.SOLUTION: An urea water injection device is constituted in such a way that an urea water injector J for injecting urea water to an upstream side of an installed location of a selective reduction catalyst S which is installed in an exhaust passage R of an engine E, injects the urea water supplied through an urea water supply passage La, and allows the urea water not-yet injected to flow to an urea water return passage Lb. A control unit H operates a supply pump 5 when the system is in any one of an emission flowing state or an emission non-flowing state, and operates the urea water injector J when the system is in the emission flowing state, and further the control unit performs a leakage detection processing for detecting leakage of the urea water from the urea water injector J when the system is in the emission non-flowing state.SELECTED DRAWING: Figure 1

Description

The present invention stores a urea water injector that injects urea water to a location upstream of a location where a selective reduction catalyst that selectively reduces nitrogen oxides using ammonia as a reducing agent in an exhaust passage of an engine, and urea water. A urea water supply path connecting the urea water storage tank and the urea water injector, a urea water return path connecting the urea water injector and the urea water storage tank, and the urea water storage tank through the urea water supply path A supply pump that supplies the urea water stored in the urea water injector, and a control unit that controls the operation of the urea water injector and the supply pump, and
The urea water injector is configured to inject urea water supplied through the urea water supply path, and to flow uninjected urea water to the urea water return path;
When the control means is in an exhaust passage state in which exhaust from the engine flows through the exhaust passage and in an exhaust non-passage state in which exhaust from the engine does not flow through the exhaust passage. In either case, the supply pump is operated to circulate urea water through the urea water supply path and the urea water return path, and the urea water injector is operated when the exhaust gas is flowing. The present invention relates to a urea water injection device in an exhaust purification system configured to inject urea water.

  Since engine exhaust, such as lean-burn gas engines installed in cogeneration systems, contains nitrogen oxides (NOx), nitrogen oxides using ammonia as a reducing agent are added to the engine exhaust passage. Selective reduction catalyst for selective reduction is installed, and nitrogen oxides are obtained with ammonia gas obtained by hydrolyzing urea water by injecting urea water to the upstream side of the selective reduction catalyst in the exhaust passage. There is an exhaust purification system (urea SCR system) that reduces (NOx) and decomposes it into nitrogen gas and water vapor.

  The urea water injection device in the exhaust purification system according to the present invention is a device for injecting urea water to a location upstream of the installation location of the selective reduction catalyst in the exhaust passage in such an exhaust purification system, The exhaust pump from the engine is in an exhaust flow state where the exhaust passage is flowing and the exhaust pump from the engine is in a non-flow state where the exhaust from the engine is not flowing through the exhaust passage. The urea water is circulated through the urea water supply path and the urea water return path, and when the exhaust gas is flowing, the urea water injector is operated to inject the urea water (see, for example, Patent Document 1). .)

  Such a urea water injection device is configured to circulate urea water through the urea water supply path and the urea water return path in both the exhaust flow state and the exhaust non-flow state, thereby Since the damage of the injector can be suppressed, and the coagulation of the urea water and the freezing of the urea water can be suppressed, the urea water can be injected well from the urea water injector.

  That is, since the exhaust temperature of the engine is generally about 500 ° C., when the urea water injector is heated to a high temperature by the exhaust of the engine, for example, the electromagnetic actuator (electromagnetic solenoid) equipped in the urea water injector is damaged. Although there is a possibility of causing a trouble that the urea water injector is damaged, the cooling water injector can be prevented from being damaged by cooling the urea water injector with the circulated urea water.

  Moreover, since urea water tends to solidify at high temperature (for example, 300 ° C. to 650 ° C.), when urea water is retained in the urea water injector in a circulation stop state, the retained urea water is solidified, Although there is a possibility of causing trouble that the urea water cannot be injected from the urea water injector, the urea water is supplied to the urea water supply path in both the exhaust flow state and the exhaust non-flow state. And by coagulating through the urea water return path, coagulation of the urea water can be suppressed.

  In addition, since urea water tends to freeze at a low temperature (for example, −11 ° C. or less), if the urea water is left in a circulation stopped state, in winter in cold regions (for example, Tohoku and Hokkaido) The urea water staying in the injector, the urea water staying in the urea water supply path and the urea water return path, etc. may freeze, and there may be a problem that the urea water cannot be injected from the urea water injector. In both the exhaust flow state and the exhaust non-flow state, the urea water can be prevented from freezing by circulating the urea water through the urea water supply path and the urea water return path.

  Incidentally, as described in Patent Document 1, the urea water injector is provided with an internal flow path for cooling while flowing the circulating urea water, and a valve body for opening and closing the urea water injection port is provided. It is provided in a form that is opened and closed by an electromagnetic actuator (electromagnetic solenoid).

Japanese Patent No. 3851775

  When the urea water injector does not inject urea water, the valve body closes the injection port. However, the injection port cannot be properly closed by the valve body due to the biting of foreign matter or misalignment of the valve body. There is a possibility that a closing abnormality may occur. When such a closing abnormality occurs, urea water leaks into the exhaust passage.

  If the urea water leaks into the exhaust passage when it is in the exhaust non-flowing state, the piping member forming the exhaust passage is corroded by the leaked urea water, and the piping member is perforated. Or the piping member may break.

  However, conventionally, since no countermeasure has been taken against the urea water leaking from the urea water injector to the exhaust passage, the above-mentioned abnormal situation may be caused, and an improvement is desired. .

  The present invention has been made in view of the above circumstances, and its purpose is to make urea water injected properly from the urea water injector while the urea water is injected from the urea water injector when the exhaust gas is flowing. The present invention is to provide a urea water injection device in an exhaust purification system that can appropriately detect that it is leaking from the exhaust gas.

The urea water injection device in the exhaust purification system of the present invention is a urea which injects urea water to a location upstream of a location where a selective reduction catalyst that selectively reduces nitrogen oxides using ammonia as a reducing agent in the exhaust passage of the engine. A water injector,
A urea water supply path that connects a urea water storage tank that stores urea water and the urea water injector;
A urea water return path connecting the urea water injector and the urea water storage tank;
A supply pump for supplying urea water stored in the urea water storage tank to the urea water injector through the urea water supply path;
A controller for controlling the operation of the urea water injector and the supply pump is provided,
The urea water injector is configured to inject supplied urea water supplied through the urea water supply path, and to flow uninjected urea water to the urea water return path;
When the control means is in an exhaust passage state in which exhaust from the engine flows through the exhaust passage and in an exhaust non-passage state in which exhaust from the engine does not flow through the exhaust passage. In either case, the supply pump is operated to circulate urea water through the urea water supply path and the urea water return path, and the urea water injector is operated when the exhaust gas is flowing. , Which is configured to inject urea water, and its characteristic configuration is
The control unit is configured to execute a leak detection process for detecting a leak of urea water from the urea water injector when the exhaust gas non-flow state.

  That is, the control unit executes a leak detection process for detecting a leak of urea water from the urea water injector when the exhaust from the engine is in an exhaust non-flow state where the exhaust passage does not flow. When the exhaust from the engine is in the exhaust passage state where the exhaust passage is flowing, the urea water can be injected as appropriate by not performing the leak detection process.

  In other words, when the exhaust from the engine is in an exhaust non-flow state where the exhaust passage does not flow, in other words, an exhaust non-flow state where the urea water injector is not operated to inject urea water. Sometimes, by performing the leak detection process, it is possible to appropriately detect the leakage of urea water from the urea water injector while properly injecting the urea water when the exhaust gas is in the exhaust flow state. is there.

In addition, as a leak detection process, for example, the urea water return path is switched to a closed state, and whether the urea water is flowing through the urea water supply path in a state where the urea water return path is closed. It is conceivable to execute a process of determining
If such a leak detection process is executed in the exhaust flow state, it is necessary to interrupt the injection of urea water from the urea water injector for leak detection, and urea water cannot be injected properly. However, by performing the leak detection process in the exhaust non-flowing state, the urea water can be properly injected in the exhaust flow state.

Further, as the leak detection processing, for example, the flow rate of urea water flowing in the urea water supply path and the flow rate of urea water flowing in the urea water return path are detected, and the flow rate of urea water flowing in the urea water supply path is It is conceivable to execute processing for determining whether or not the flow rate of urea water flowing through the water return path is lower.
If such a leak detection process is executed in the exhaust flow state, it is necessary to interrupt the injection of urea water from the urea water injector for leak detection, and urea water cannot be injected properly. However, by performing the leak detection process in the exhaust non-flowing state, the urea water can be properly injected in the exhaust flow state.

  In short, according to the characteristic configuration of the urea water injection device in the exhaust gas purification system of the present invention, the urea water is injected from the urea water injector while properly injecting the urea water from the urea water injector when in the exhaust flow state. It is possible to appropriately detect that it is in a leaking state.

Further, the further characteristic configuration of the urea water injection device in the exhaust purification system of the present invention is:
A supply flow rate detection sensor for detecting the flow rate of the urea water flowing through the urea water supply channel, and a return path opening / closing valve for opening and closing the urea water return path,
The control unit is configured to execute, as the leak detection process, a process for determining the presence or absence of a flow of urea water based on detection information of the supply flow rate detection sensor in a state in which the return path on-off valve is closed. It is in the point.

  That is, as the leak detection processing, the return path on-off valve is closed to switch the urea water return path to the closed state, and the detection information of the supply flow rate detection sensor is displayed in the state where the urea water return path is closed. Based on this, processing for determining whether or not urea water is flowing through the urea water supply path is performed.

  That is, when the urea water return path is closed, if there is no leakage in the urea water injector, the urea water will not flow through the urea water supply path, but if there is a leak in the urea water injector, the urea water return path Even in the closed state, the urea water flows through the urea water supply path. Therefore, if the urea water flows through the urea water supply path in the state where the urea water return path is closed, the urea water injector has a leak. It can be determined.

  If the urea water injector leaks with the urea water return path closed, the urea water flow in the urea water supply path immediately appears, so the urea water injector leak is detected quickly in a short time. Since the urea water circulation through the urea water supply path and the urea water return path may be temporarily stopped for the leakage detection process, it may be stopped only for a short time. In order to cool the water injector and avoid freezing and freezing of the urea water, the circulation of the urea water through the urea water supply path and the urea water return path can be continued as much as possible.

  Therefore, according to the further characteristic configuration of the urea water injection device in the exhaust purification system of the present invention, the urea water supply path and the urea water return path are provided for cooling the urea water injector and avoiding the solidification and freezing of the urea water. Leak detection processing can be performed while continuing the circulation of the urea water that has passed through as much as possible.

Further, the further characteristic configuration of the urea water injection device in the exhaust purification system of the present invention is:
A temperature sensor for detecting the temperature of the exhaust passage is provided;
When the control unit determines that the temperature of the exhaust passage is within a set temperature range based on detection information of the temperature sensor among the exhaust non-flowing states, the leak detection processing is performed. In that it is configured to run.

  That is, when performing the leak detection process in the exhaust non-flowing state, it is performed when the temperature of the exhaust passage is within the set temperature range. Even when leak detection processing is performed with the return path closed, when the temperature of the exhaust path is high and it is necessary to cool the urea water injector, or when there is a risk of solidification of the urea water, In addition, when the temperature of the exhaust passage is low and there is a risk of freezing of the urea water, the urea water circulation through the urea water supply path and the urea water return path is continued without performing the leak detection process. .

  Therefore, according to the further characteristic configuration of the urea water injection device in the exhaust purification system of the present invention, when the leak detection process is executed in the exhaust non-flowing state, the temperature of the exhaust passage is within the set temperature range. By doing so, the urea water injector can be appropriately cooled, and the coagulation and freezing of the urea water can be appropriately avoided.

Further, the further characteristic configuration of the urea water injection device in the exhaust purification system of the present invention is:
A supply flow rate detection sensor for detecting the flow rate of urea water flowing through the urea water supply path, and a return flow rate detection sensor for detecting the flow rate of urea water flowing through the urea water return path;
The control unit is configured to execute, as the leak detection process, a process of determining whether or not a detection value of the return flow rate detection sensor is lower than a detection value of the supply flow rate detection sensor. .

  That is, the control unit executes a process of determining whether or not the detection value of the return flow rate detection sensor is lower than the detection value of the supply flow rate detection sensor as the leak detection process executed when the exhaust gas non-flowing state. It will be.

  That is, when urea water is not leaking from the urea water injector, the detection value of the return flow rate detection sensor and the detection value of the supply flow rate detection sensor are the same, but when urea water is leaking from the urea water injector, the return flow rate is the same. Since the detection value of the detection sensor is lower than the detection value of the supply flow rate detection sensor, it is determined whether or not the detection value of the return flow rate detection sensor is smaller than the detection value of the supply flow rate detection sensor. It can be determined whether or not urea water is leaking.

  Such leak detection processing can detect leakage without stopping the circulation flow of urea water. Therefore, the urea water injector is appropriately cooled, and the urea water is appropriately solidified and frozen. Can be avoided.

  Therefore, according to the further characteristic configuration of the urea water injection device in the exhaust purification system of the present invention, it is possible to appropriately cool the urea water injector while performing the leak detection process, Freezing can be avoided appropriately.

Further, the further characteristic configuration of the urea water injection device in the exhaust purification system of the present invention is:
The control unit is configured to control the injection operation of the urea water injector so that the injection amount of the urea water injector becomes a set target amount based on detection information of the supply flow rate detection sensor. is there.

  That is, the control unit controls the injection operation of the injector so that the injection amount of the injector becomes the set target amount based on the detection information of the supply flow rate detection sensor that detects the flow rate of the urea water flowing through the urea water supply path. It will be.

That is, even if the flow rate of the urea water flowing through the urea water supply path changes, the urea water can be appropriately injected with the injection amount of the set target amount, and wasteful consumption of the urea water can be suppressed.
Further, the leak detection process can be performed while simplifying the configuration by performing the above-described leak detection process using the supply flow rate detection sensor provided to adjust the injection amount of the urea water to the set target amount. .

  Therefore, according to the further characteristic configuration of the urea water injection device in the exhaust purification system of the present invention, it is possible to suppress the wasteful consumption of urea water and perform the leak detection process while simplifying the configuration.

The figure which shows the structure of the urea water injection apparatus of 1st Embodiment. Longitudinal side view showing schematic configuration of urea water injector The figure which shows the opening and closing control form of the urea water injector The figure which shows the structure of the urea water injection apparatus of 2nd Embodiment. The figure which shows the structure of the urea water injection apparatus of 3rd Embodiment.

[First Embodiment]
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, a first embodiment of the invention will be described with reference to the drawings.
(Overall configuration of exhaust purification system)
As shown in FIG. 1, a lean burn type gas engine E that drives a generator 1 and an exhaust path R that leads exhaust gas from the gas engine E to an exhaust heat recovery boiler B are provided. The cogeneration system which supplies the electric power to perform and the steam (heat) which the waste heat recovery boiler B produces | generates to an electric power consumption location and a steam consumption location is comprised.
Incidentally, the exhaust path R is configured by disposing a piping member 2 for forming an exhaust path.

A reactor 3 including a selective reduction catalyst S that selectively reduces nitrogen oxides using ammonia as a reducing agent is installed in the exhaust path R of the gas engine E, and is located upstream of the installation location of the selective reduction catalyst S in the exhaust path R. On the other hand, a urea water injection device F for injecting urea water is installed.
Then, using ammonia gas obtained by hydrolysis of urea water injected by the urea water injection device F as a reducing agent, nitrogen oxide (NOx) is reduced by the selective reduction catalyst S, and nitrogen gas and water vapor are reduced. An exhaust gas purification system (urea SCR system) that decomposes into two is configured.

The reactor 3 is installed in the exhaust path R in such a form that a casing 3c that houses the selective reduction catalyst S is incorporated in the middle part of the piping member 2 for forming the exhaust path.
Incidentally, in this embodiment, the case where only the selective reduction catalyst S is accommodated in the reactor 3 is exemplified, but the remaining ammonia is removed in a state where the reactor 3 is positioned downstream of the selective reduction catalyst S. It may be carried out in the form of being equipped with an oxidation catalyst.

(Configuration of urea water injection device)
The urea water injection device F includes a urea water injector J that injects urea water to a location upstream of the location where the selective reduction catalyst S is installed in the exhaust path R of the gas engine E, and a urea water storage that stores urea water. A urea water supply path La that connects the tank 4, the urea water storage tank 4 and the urea water injector J, a urea water return path Lb that connects the urea water injector J and the urea water storage tank 4, and a urea water supply path A supply pump 5 that supplies urea water stored in the urea water storage tank 4 through La to the urea water injector J, and a control unit H that controls the operation of the urea water injector J and the supply pump 5 are provided.

  The urea water injector J is configured to inject urea water supplied through the urea water supply path La and flow uninjected urea water to the urea water return path Lb. The details are described later.

The control unit H manages the operation of the gas engine E, and the exhaust flow state where the exhaust from the gas engine E flows through the exhaust path R and the exhaust from the gas engine E does not flow through the exhaust path R. An exhaust non-flow state is determined.
In other words, when the gas engine E is in operation, it is determined that the exhaust is in an exhaust passage state, and otherwise, it is determined that the exhaust gas is in a non-exhaust state.
In addition, in addition to the period during which the gas engine E is operating, the exhaust passage state is a period from when the gas engine E switches from the operating state to the stopped state until a set elapsed time (for example, several seconds) elapses. You may make it include a period.

Then, unless a special stop command is commanded from the command operation unit Ha, the control unit H operates the supply pump 5 in any of the exhaust flow state and the exhaust non-flow state to supply urea water. It is configured to circulate through the urea water supply path La and the urea water return path Lb and to actuate the urea water injector J to inject urea water when the exhaust gas is in the exhaust flow state.
The details of the injection process of operating the urea water injector J to inject urea water in the exhaust flow state will be described later.

  That is, in both the exhaust gas flow state and the exhaust gas non-flow state, the urea water injector J can be damaged by circulating the urea water through the urea water supply path La and the urea water return path Lb. The coagulation of urea water is suppressed, and the freezing of urea water is suppressed.

  That is, since the exhaust temperature of the gas engine is about 500 ° C., the urea water injector J is heated to a high temperature by the exhaust of the gas engine E, and, for example, a later-described electromagnetic solenoid JS equipped in the urea water injector J is damaged. However, the urea water injector J can be prevented from being damaged by cooling the urea water injector J with the circulated urea water.

  In addition, urea water tends to coagulate at high temperatures (for example, 300 ° C. to 650 ° C.), but urea water is circulated through urea water supply channel La and urea water return channel Lb, thereby suppressing urea water coagulation. It will be possible.

  In addition, urea water tends to freeze at a low temperature (for example, −11 ° C. or lower). In addition to being in the exhaust passage state, the urea water is also converted into the urea water in the exhaust non-flow state. By circulating through the supply path La and the urea water return path Lb, freezing of the urea water can be suppressed.

Moreover, the control part H is comprised so that the leak detection process which detects the leak of the urea water injector J may be performed when it is a non-exhaust state of exhaust_gas | exhaustion, The detail is mentioned later.
Incidentally, a supply path on-off valve 6 that opens and closes the urea water supply path La is provided at a location upstream of the supply pump 5 of the urea water supply path La, and when the above stop command is commanded from the command operating section Ha. In such a case, the supply passage on-off valve 6 can be closed.

(Configuration of urea water injector)
As shown in FIG. 2, the urea water injector J is configured to have a slide type valve body 8 that opens and closes the injection port 7 a inside the main body casing 7 having the injection port 7 a formed at the tip. .
A spring 9 for biasing the valve body 8 toward the closing side and an electromagnetic solenoid JS for operating the valve body 8 toward the opening side against the biasing force of the spring 9 are provided.
FIG. 2 schematically shows the schematic configuration of the urea water injector J, and the shape of each part, the specific dimensions of each part, and the like are different from the actual configuration.

  In the main body casing 7, an internal flow path 10 surrounding the outer periphery of the valve body 8 is formed in a state communicating with the injection port 7a, and a urea water receiving section 11 to which a urea water supply path La is connected, and Each of the urea water discharge parts 12 to which the urea water return path Lb is connected is formed in a state communicating with the internal flow path 10.

Therefore, the urea water supplied to the urea water receiving unit 11 is configured to flow inside the main body casing 7 in a form in which the urea water flows through the internal flow path 10 and is discharged to the urea water discharge unit 12. By operating the valve body 8 to the open side by the solenoid JS, the urea water flowing in the internal flow path 10 is configured to be injected from the injection port 7a.
Further, the urea water injector J is cooled by the urea water supplied to the urea water receiving portion 11 flowing in the internal flow path 10 to cool the main body casing 7 and the valve body 8. ing.

(Injection process)
A supply flow rate detection sensor configured to supply the urea water at a substantially constant supply amount by being driven to rotate at a set rotational speed, and to detect the flow rate of the urea water flowing through the urea water supply path La. 13 is provided.
As shown in FIG. 3, the control unit H performs a process of intermittently opening and closing the valve body 8 in the form in which the valve body 8 is opened only during the set injection time W within the set period T, as shown in FIG. 3. Is configured to do.

  And the control part H changes and adjusts the setting injection time W based on the detection information of the supply flow rate detection sensor 13 so that the injection amount of urea water may become a setting target amount (for example, 40 cc / min). The injection process is executed in such a manner that the injection amount is adjusted by PWM control.

That is, even if the supply pump 5 is rotated at the set rotational speed, there is a possibility that the supply amount of the urea water may fluctuate. However, even if the supply amount of the urea water fluctuates, the urea water is discharged at the set target amount of injection. It can be injected.
Incidentally, when the gas engine E equipped in the cogeneration system is driven at the rated rotational speed and the load does not fluctuate greatly, the amount of nitrogen oxide (NOx) contained in the exhaust gas discharged from the gas engine E is The set target amount can be set to a fixed amount assuming that the state does not vary greatly.

  However, when the load acting on the gas engine E varies greatly, the amount of nitrogen oxide (NOx) contained in the exhaust gas discharged from the gas engine E is adjusted by adjusting the output of the gas engine E. Since it will fluctuate greatly, while estimating the amount of nitrogen oxide (NOx) contained in the exhaust gas based on engine operation information such as load information indicating the magnitude of the load acting on the gas engine E, The set target amount may be changed and set.

  Incidentally, a supply pressure detection sensor 14 for detecting the pressure of the urea water supply path La is provided, and when the controller H has an abnormal situation in which the detection value of the supply pressure detection sensor 14 falls outside the appropriate range, the gas engine E The operation is stopped, and the operation of the urea water injection device F is stopped.

(Leak detection process)
As described above, in addition to the supply flow rate detection sensor 13 for detecting the flow rate of the urea water flowing through the urea water supply channel La, as shown in FIG. 1, the return channel opening and closing for opening and closing the urea water return channel Lb. An electromagnetic return path opening / closing valve 15 is provided as a valve.
Incidentally, the return path opening / closing valve 15 is configured to be urged to return to the open state and to be closed by electromagnetic force.

Then, as a leak detection process executed when the control unit H is in an exhaust non-flowing state in which the urea water injector J is not operated, the supply flow rate detection sensor 13 in a state where the return path opening / closing valve 15 is closed. The process which determines the presence or absence of the flow of urea water based on this detection information is performed.
That is, when the return flow opening / closing valve 15 is closed, if it is detected by the supply flow rate detection sensor 13 that there is no flow of urea water, it can be determined that urea water does not leak from the urea water injector J, and the return flow If the supply flow rate detection sensor 13 detects that the urea water is flowing when the road opening / closing valve 15 is closed, it can be determined that the urea water is leaking from the urea water injector J.

Incidentally, in the present embodiment, since the supply pump 5 is equipped with a relief mechanism for adjusting the discharge pressure to a set value or less, the supply pump 5 is driven even when the return path opening / closing valve 15 is closed. Is configured to continue.
When the supply pump 5 is not equipped with a relief mechanism, the drive of the supply pump 5 is stopped when the return path opening / closing valve 15 is closed.

In the present embodiment, as shown in FIG. 1, a temperature sensor 16 for detecting the temperature of the exhaust passage is provided.
When the control unit H determines that the temperature of the exhaust passage R is within the set temperature range based on the detection information of the temperature sensor 16 among the exhaust non-flowing states, the leak detection process is performed. Is configured to run.
Incidentally, the above-mentioned set temperature range is, for example, a range of 50 to 100 ° C.

  That is, even when the exhaust gas is not flowing, immediately after the gas engine E is stopped, the temperature of the exhaust passage R is high, so that the urea water injector J is cooled and the urea water is not solidified. It is necessary to circulate the water through the urea water supply path La and the urea water return path Lb, and even in the exhaust non-flow state, when the temperature of the exhaust path R is low due to winter or the like, the urea water is frozen. In order to avoid this, it is necessary to circulate the urea water through the urea water supply path La and the urea water return path Lb, so that the leakage detection process is executed when the temperature of the exhaust path R is within the set temperature range. It is configured.

The leak detection process is preferably executed every time the exhaust flow state is switched to the exhaust non-flow state. However, it is not always necessary to execute the leak detection process every time the exhaust flow state is switched to the exhaust non-flow state. For example, it may be executed with a frequency of about once every several days.
Incidentally, when the gas engine E shifts from the stopped state to the operating state during execution of the leak detection process, the leak detection process is interrupted and the above-described injection process is performed.

Moreover, in this embodiment, although the case where only one temperature sensor 16 for detecting the temperature of the exhaust passage is provided at the downstream side of the reactor 3 is illustrated, the temperature sensor 16 is provided at the upstream side of the reactor 3. For example, a plurality of temperature sensors 16 may be provided.
In this case, when the detection value for detecting the maximum temperature and the detection value for detecting the minimum temperature among the plurality of temperature sensors 16 are in the above-described set temperature range, the leak detection process may be executed.

(Summary of the first embodiment)
As described above, the urea water injection device F in the exhaust purification system of the first embodiment can appropriately perform urea water injection in the exhaust flow state by executing the leak detection process when the exhaust gas is not in the flow state. While doing so, leakage of urea water from the urea water injector J can be accurately detected.

  In addition, when the leak detection process is executed in the exhaust non-flow state, it is performed when the temperature of the exhaust passage R is within the set temperature range, so the urea water injector J is appropriately cooled. Moreover, coagulation and freezing of urea water can be avoided.

  In addition, since the leakage detection process is executed while using the detection information of the supply flow rate detection sensor 13 that is provided to adjust the injection amount of urea water to the set target amount, the configuration is simplified. Leak detection processing can be performed.

[Second Embodiment]
Next, a second embodiment will be described. This second embodiment shows another embodiment of the leak detection process, and the other configuration is the same as that of the first embodiment. Only a different part from a form is demonstrated, about the structure similar to 1st Embodiment, the same code | symbol as 1st Embodiment is attached | subjected and detailed description is abbreviate | omitted.

As shown in FIG. 4, in addition to the supply flow rate detection sensor 13 for detecting the flow rate of the urea water flowing through the urea water supply channel La, the return flow rate detection sensor for detecting the flow rate of urea water flowing through the urea water return channel Lb. 17 is provided.
In the second embodiment, the return path opening / closing valve 15 provided in the first embodiment is omitted.

  As a leak detection process executed when the control unit H is in the exhaust non-flow state, a process of determining whether or not the detection value of the return flow rate detection sensor 17 is smaller than the detection value of the supply flow rate detection sensor 13 is executed. Is configured to do.

  That is, when urea water is not leaking from the urea water injector J, the detection value of the return flow rate detection sensor 17 and the detection value of the supply flow rate detection sensor 13 are the same, but urea water is leaking from the urea water injector J. Sometimes, the detection value of the return flow rate detection sensor 17 is lower than the detection value of the supply flow rate detection sensor 13, so it is determined whether or not the detection value of the return flow rate detection sensor 17 is less than the detection value of the supply flow rate detection sensor 13. By doing so, it can be determined whether urea water is leaking from the urea water injector J.

(Summary of the second embodiment)
As described above, the urea water injection device F in the exhaust purification system of the second embodiment performs the leak detection process when the exhaust gas non-flowing state, similarly to the urea water injection device F in the exhaust purification system of the first embodiment. By executing, the urea water leakage from the urea water injector J can be accurately detected while the urea water injection in the exhaust flow state can be appropriately performed.

  In addition, since the leakage detection process is executed while using the detection information of the supply flow rate detection sensor 13 that is provided to adjust the injection amount of urea water to the set target amount, the configuration is simplified. Leak detection processing can be performed.

  Furthermore, since the leak detection process can detect leaks without stopping the circulation flow of urea water, it is possible to appropriately cool the urea water injector J and avoid coagulation and freezing of urea water. Become.

[Third Embodiment]
Next, a third embodiment will be described. This third embodiment shows another embodiment of the leak detection process, and other configurations are the same as those of the first embodiment. Only a different part from a form is demonstrated, about the structure similar to 1st Embodiment, the same code | symbol as 1st Embodiment is attached | subjected and detailed description is abbreviate | omitted.

As shown in FIG. 5, in addition to the electromagnetic return path opening / closing valve 15 being provided as a return path opening / closing valve for opening / closing the urea water return path Lb, the upstream side of the supply pressure detection sensor 14 in the urea water supply path La. In addition, an electromagnetic supply path opening / closing valve 18 serving as a supply path opening / closing valve for opening / closing the urea water supply path La is provided at a location corresponding to the downstream side of the supply pump 5.
Incidentally, the supply passage opening / closing valve 18 is configured to be urged to return to the open state and to be closed by electromagnetic force.

Then, as a leak detection process executed when the control unit H is in the exhaust non-flow state, the supply pressure detection sensor 14 detects the leakage while the supply path on / off valve 18 and the return path on / off valve 15 are closed. It is configured to execute processing for determining whether or not the detected value decreases.
That is, if the detection value of the supply pressure detection sensor 14 does not decrease when the supply path opening / closing valve 18 and the return path opening / closing valve 15 are closed, it can be determined that urea water is not leaking from the urea water injector J. If the detection value of the supply pressure detection sensor 14 decreases when the path opening / closing valve 18 and the return path opening / closing valve 15 are closed, it can be determined that urea water is leaking from the urea water injector J.

Incidentally, in the present embodiment, as in the first embodiment, since the supply pump 5 is equipped with a relief mechanism for adjusting the discharge pressure to a set value or less, the return path opening / closing valve 15 is closed. Sometimes, it is configured to continue driving the supply pump 5.
When the supply pump 5 is not equipped with a relief mechanism, the drive of the supply pump 5 is stopped when the return path opening / closing valve 15 is closed.

Further, as shown in FIG. 5, in the present embodiment, a temperature sensor 16 for detecting the temperature of the exhaust passage is provided as in the first embodiment.
When the control unit H determines that the temperature of the exhaust passage R is within the set temperature range based on the detection information of the temperature sensor 16 among the exhaust non-flowing states, the leak detection process is performed. Is configured to run.
Incidentally, the above-mentioned set temperature range is, for example, a range of 50 to 100 ° C.

  That is, even when the exhaust gas is not flowing, immediately after the gas engine E is stopped, the temperature of the exhaust passage R is high, so that the urea water injector J is cooled and the urea water is not solidified. It is necessary to circulate the water through the urea water supply path La and the urea water return path Lb, and even in the exhaust non-flow state, when the temperature of the exhaust path R is low due to winter or the like, the urea water is frozen. In order to avoid this, it is necessary to circulate the urea water through the urea water supply path La and the urea water return path Lb, so that the leakage detection process is executed when the temperature of the exhaust path R is within the set temperature range. It is configured.

The leak detection process is preferably executed every time the exhaust flow state is switched to the exhaust non-flow state. However, it is not always necessary to execute the leak detection process every time the exhaust flow state is switched to the exhaust non-flow state. Instead, for example, it may be executed as frequently as once per several days.
Incidentally, when the gas engine E shifts from the stopped state to the operating state during execution of the leak detection process, the leak detection process is interrupted and the above-described injection process is performed.

Moreover, in this embodiment, although the case where the temperature sensor 16 which detects the temperature of an exhaust passage is provided in the downstream location of the reactor 3 is illustrated, the temperature sensor 16 is provided also in the upstream location of the reactor 3. For example, a plurality of temperature sensors 16 may be provided.
In this case, when the detection value for detecting the maximum temperature and the detection value for detecting the minimum temperature among the plurality of temperature sensors 16 are in the above-described set temperature range, the leak detection process may be executed.

(Summary of the third embodiment)
As described above, the urea water injection device F in the exhaust purification system of the third embodiment performs the leak detection process when the exhaust water non-flowing state, similarly to the urea water injection device F in the exhaust purification system of the first embodiment. By executing, the urea water leakage from the urea water injector J can be accurately detected while the urea water injection in the exhaust flow state can be appropriately performed.

In addition, when the leak detection process is executed in the exhaust non-flow state, it is performed when the temperature of the exhaust passage R is within the set temperature range, so the urea water injector J is appropriately cooled. Moreover, coagulation and freezing of urea water can be avoided.

[Another embodiment]
Next, another embodiment is listed.
(1) In the said 1st-3rd embodiment, although the gas engine E was illustrated as an engine, various engines, such as a diesel engine and a gasoline engine, are applicable as an engine.

(2) In the first to third embodiments, the urea water injection device F of the exhaust purification system equipped in the cogeneration system is exemplified. However, the urea water injection device F of the present invention is, for example, a large bus or a large size. The present invention can be applied to an exhaust purification system installed in various facilities and equipment, such as an exhaust purification system mounted on a vehicle such as a truck.

(3) In the first to third embodiments, the control unit H that controls the operation of the urea water injector F manages the operation of the gas engine E. However, the operation of the gas engine E is managed. The engine control unit may be separately provided.

(4) In the first to third embodiments, the form in which urea water is injected from one urea water injector J is illustrated. However, a plurality of urea water injectors J are connected to a urea water supply path La and a urea water return path. You may implement in the form provided in a serial state or parallel state between Lb.

(5) In the said 1st-3rd embodiment, although the thing of the form equipped with the valve body 8 opened and closed intermittently as the urea water injector J was illustrated, the valve body by which an opening degree is adjusted is illustrated. Various configurations of the urea water injector J, such as those equipped, can be changed.

(6) As the leak detection process, in addition to the forms described in the first to third embodiments, for example, a storage amount detection sensor for detecting the urea water storage amount of the urea water storage tank is provided to store the urea water. If the amount decreases in the exhaust non-flowing state, various forms such as determining that the urea water injector J has leaked can be adopted.

  The configuration disclosed in the above embodiment (including another embodiment, the same shall apply hereinafter) can be applied in combination with the configuration disclosed in the other embodiment, as long as no contradiction occurs. The embodiment disclosed in this specification is an exemplification, and the embodiment of the present invention is not limited to this. The embodiment can be appropriately modified without departing from the object of the present invention.

4 Urea water storage tank 5 Supply pump 13 Supply flow rate detection sensor 15 Return path opening / closing valve 16 Temperature sensor 17 Return flow rate detection sensor E Engine H Control unit J Urea water injector La Urea water supply path Lb Urea water return path R Exhaust path S selection Reduction catalyst

Claims (5)

A urea water injector that injects urea water to a location upstream of the location of the selective reduction catalyst that selectively reduces nitrogen oxides using ammonia as a reducing agent in the exhaust passage of the engine;
A urea water supply path connecting the urea water storage tank for storing urea water and the urea water injector;
A urea water return path connecting the urea water injector and the urea water storage tank;
A supply pump for supplying urea water stored in the urea water storage tank to the urea water injector through the urea water supply path;
A controller for controlling the operation of the urea water injector and the supply pump is provided,
The urea water injector is configured to inject urea water supplied through the urea water supply path, and to flow uninjected urea water to the urea water return path;
When the control unit is in an exhaust passage state in which exhaust from the engine flows through the exhaust passage and in an exhaust non-passage state in which exhaust from the engine does not flow through the exhaust passage. In either case, the supply pump is operated to circulate urea water through the urea water supply path and the urea water return path, and the urea water injector is operated when the exhaust gas is flowing. A urea water injection device in an exhaust purification system configured to inject urea water,
A urea water injection device in an exhaust gas purification system configured to execute a leak detection process for detecting leakage of urea water from the urea water injector when the control unit is in the exhaust non-flow state. A supply flow rate detection sensor for detecting the flow rate of the urea water flowing through the urea water supply channel, and a return path opening / closing valve for opening and closing the urea water return path,
The control unit is configured to execute, as the leak detection process, a process for determining the presence or absence of a flow of urea water based on detection information of the supply flow rate detection sensor in a state in which the return path on-off valve is closed. The urea water injection device in the exhaust gas purification system according to claim 1. A temperature sensor for detecting the temperature of the exhaust passage is provided;
When the control unit determines that the temperature of the exhaust passage is within a set temperature range based on detection information of the temperature sensor among the exhaust non-flowing states, the leak detection processing is performed. The urea water injection device in the exhaust purification system according to claim 2, wherein the urea water injection device is configured to be executed. A supply flow rate detection sensor for detecting the flow rate of urea water flowing through the urea water supply path, and a return flow rate detection sensor for detecting the flow rate of urea water flowing through the urea water return path;
The said control part is comprised so that it may perform the process which determines whether the detection value of the said return flow rate detection sensor is smaller than the detection value of the said supply flow rate detection sensor as the said leak detection process. A urea water injection device in the exhaust purification system described.   The control unit is configured to control an injection operation of the urea water injector based on detection information of the supply flow rate detection sensor so that an injection amount of the urea water injector becomes a set target amount. The urea water injection apparatus in the exhaust gas purification system according to any one of 2 to 4.

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