JP2016121547A - System and method of purifying exhaust gas of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a system and a method of purifying exhaust gas of an internal combustion engine capable of: stably supplying ammonia to a selective reduction catalyst device while taking advantage of capabilities thereof to prevent accumulation of a white product derived from urea water and to use urea water with high efficiency; reducing a slip amount of the ammonia from the selective reduction catalyst device; and improving NOx purification performance of the selective reduction catalyst device.SOLUTION: A system for purifying exhaust gas of an internal combustion engine comprises: an ammonia absorption device 30 installed on a parallel passage 31 arranged parallel to an exhaust passage 15 between a particulate matter collection device 23 and a selective reduction catalyst device 24; a flow passage switching valve 32 which guides the exhaust gas Ga flowing out of the particulate matter collection device 23 either to the exhaust passage 15 or to the parallel passage 31; and an opening and closing valve 33 which opens and closes the parallel passage 31 at a downstream side of the ammonia absorption device 30.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an exhaust gas purification system for an internal combustion engine and an exhaust gas for the internal combustion engine, which are provided with an urea water injection device, a particulate collection device, and a selective catalytic reduction device in order from the upstream side in the exhaust passage of the internal combustion engine. It relates to a purification method.

  In general, an exhaust gas purification device provided in an exhaust passage of an internal combustion engine includes a selective reduction type catalyst device (SCR catalyst device) or NOx occlusion in order to purify nitrogen oxide (NOx) contained in the exhaust gas of the internal combustion engine. A catalyst device such as a type reduction catalyst device is provided.

When this selective reduction catalyst device is used, a urea water injection device is provided in the exhaust passage upstream of the selective reduction catalyst device, and the urea water injected from the urea water injection device is hydrolyzed by the heat of the exhaust gas. By supplying ammonia (NH ₃ ) generated by decomposition as a reducing agent to the selective reduction catalyst device, nitrogen oxides contained in the exhaust gas are reduced and purified by the catalytic action of the selective reduction catalyst. .

  In the prior art, this urea water injection device is generally provided in the exhaust passage close to the inlet side of the selective catalytic reduction device, but in this configuration, biuret, cyanuric acid, etc. generated when urea water is decomposed As a result, the white products represented by (1) accumulate in the exhaust passage piping and the honeycomb structure of the selective catalytic reduction device, and the corrosion of the piping and the deterioration of the selective catalytic reduction device are accompanied by problems. Yes. Furthermore, this configuration also has a problem that the utilization efficiency of the urea water injected from the urea water injection device is poor.

  As countermeasures, an injection nozzle, a diesel particulate filter, and a selective catalytic reduction catalyst are installed in the exhaust pipe of the diesel engine in order from the exhaust gas upstream side, and urea-based liquid is discharged from the injection nozzle upstream of the diesel particulate filter. When the exhaust gas is injected into the exhaust pipe on the side and the exhaust gas is at a relatively low temperature, the produced ammonium nitrate reacts with NOx in the exhaust gas and is collected by a particulate filter provided downstream of the injection nozzle. An engine exhaust gas purification device that prevents NOx from being discharged into the atmosphere at a relatively low temperature has been proposed (see, for example, Patent Document 1).

  However, as shown in FIG. 5, the urea water injection device 27, the particulate collection device 23, and the selective catalytic reduction device 24 are arranged in this order from the upstream side in the exhaust passage 15 as in the exhaust gas purification device of this engine. In the exhaust gas purification system 1X, there is no mechanism between the particulate collection device 23 and the selective catalytic reduction device 24 that can control the amount of ammonia flowing into the selective catalytic reduction device 24. Therefore, the selective catalytic reduction catalyst The amount of ammonia reaching the device 24 depends not only on the amount of urea water U injected on the inlet side of the particulate collection device 23 but also on the degree of vaporization and decomposition of the urea water U in the particulate collection device 23. The

  Therefore, particularly when the urea water is injected into a particulate collection device of 160 ° C. or lower when the temperature is not sufficiently raised when the engine is cold, the injected urea water is not contained in the particulate collection device. Accumulated at the entrance or inside. Therefore, in this state, when the particulate collection device is heated rapidly, the accumulated urea is decomposed at a time and a large amount of ammonia is generated and supplied to the selective catalytic reduction catalyst device. Therefore, there is a possibility that a large amount of ammonia flows out downstream of the selective catalytic reduction catalyst device.

  In other words, when the engine is cold, it is difficult to stably supply the ammonia supply to the selective catalytic reduction device, and a large amount of ammonia is instantaneously released from the particulate collection device. When supplied to the reduction catalyst apparatus, there is a problem that ammonia may slip in a large amount downstream without being consumed by the selective reduction catalyst apparatus.

  For the purpose of recovering ammonia slipped from the SCR catalyst and effectively using the recovered ammonia, an ammonia storage part is provided downstream of the SCR catalyst, and an ammonia storage tank is used as a recovery part for recovering the ammonia released from the ammonia storage part. There is proposed an exhaust gas purification device that supplies ammonia from the ammonia storage tank to the upstream side of the SCR catalyst via a flow rate adjustment valve (see, for example, Patent Document 2).

  However, in this exhaust gas purification device, in addition to the ammonia storage unit, an ammonia storage tank, a heater for heating the ammonia storage unit, an upstream exhaust valve before and after the ammonia storage unit, a downstream exhaust valve, a reducing agent recirculation Four valves, a valve and a flow rate adjustment valve, are required, and there is a problem that the configuration becomes complicated.

JP 2007-113401 A JP 2014-47721 A

  The present invention has been made in view of the above, and an object thereof is to provide a urea water injection device, a particulate collection device, and a selective catalytic reduction device in the exhaust passage of the internal combustion engine in order from the upstream side. In the exhaust gas purification system of the internal combustion engine that is configured, the selection is further made while taking advantage of the advantage that the deposition of white product derived from urea water in the selective catalytic reduction device can be suppressed and the utilization efficiency of urea water is high. Ammonia can be stably supplied to the reduction catalyst device, and the slip amount of ammonia from the selective reduction catalyst device can be reduced, so that the NOx purification performance of the selective reduction catalyst device can be improved. Another object is to provide an exhaust gas purification system for an internal combustion engine and an exhaust gas purification method for the internal combustion engine.

  In order to achieve the above object, an exhaust gas purification system for an internal combustion engine according to the present invention is provided with a urea water injection device, a particulate collection device, and a selective catalytic reduction device in order from the upstream side in the exhaust passage of the internal combustion engine. In the exhaust gas purification system of an internal combustion engine configured, a parallel passage having an ammonia adsorption device is provided in the exhaust passage between the particulate collection device and the selective catalytic reduction device, and the particulate collection device flows out of the exhaust passage. A flow path switching valve for switching the flow of exhaust gas to the flow to the exhaust passage and the flow to the parallel passage, and an on-off valve for opening and closing the parallel passage on the downstream side of the ammonia adsorption device, A first ammonia concentration sensor for detecting the ammonia concentration of the exhaust gas flowing into the selective catalytic reduction device, and the ammonia concentration of the exhaust gas flowing into the ammonia adsorption device; Configured to provide a second ammonia concentration sensor for detecting.

  According to this configuration, the ammonia amount flowing into the selective catalytic reduction catalyst device can be calculated using the ammonia concentration detected by the first ammonia concentration sensor, and the ammonia detected by the second ammonia concentration sensor Since the amount of ammonia flowing into the ammonia adsorption device can be calculated using the concentration, excess ammonia in the exhaust gas flowing out from the particulate collection device is adsorbed to the ammonia adsorption device based on these values. In addition to being able to be temporarily stored, if necessary, the ammonia adsorbed on the ammonia adsorption device can be desorbed and supplied to the selective catalytic reduction catalyst device.

  Therefore, while taking advantage of the advantage that it is possible to suppress the deposition of the white product derived from urea water in the selective catalytic reduction device and the advantage that the utilization efficiency of urea water is high, the supply of ammonia to the selective catalytic reduction device is further reduced. In addition to being able to perform stably, the amount of ammonia slip from the selective catalytic reduction apparatus can be reduced, and the NOx purification performance of the selective catalytic reduction apparatus can be improved.

  Further, in the exhaust gas purification system for an internal combustion engine, the control device for controlling the exhaust gas purification system switches the flow path switching valve to a flow to the exhaust passage and closes the on-off valve to exhaust the exhaust gas purification system. Normal control means for performing normal control for allowing gas to flow into the selective catalytic reduction device, and switching the flow path switching valve to the flow to the parallel path and opening the on-off valve to adsorb the exhaust gas to the ammonia adsorption An adsorption control means for performing adsorption control for allowing ammonia in exhaust gas to be adsorbed by the ammonia adsorbing apparatus by flowing into the apparatus, and a state in which the flow path switching valve is switched to the flow to the parallel passage and the on-off valve is opened The ammonia adsorption device is heated to a temperature higher than the ammonia desorption temperature, and the ammonia desorbed from the ammonia adsorption device is transferred to the selective reduction catalyst device. Configure a detachment control means for elimination control to enter.

  According to this configuration, the normal control means, the adsorption control means, and the desorption control means are appropriately combined to supply from the urea water injection device while taking into account the amount of urea water adsorbed and released by the particulate collection device. The amount of urea water to be adjusted and the amount of ammonia desorbed from the ammonia adsorption device can be adjusted to allow ammonia to flow into the selective catalytic reduction device in an appropriate amount, improving the efficiency of using urea water, Ammonia slip can be prevented.

  Further, in the exhaust gas purification system for an internal combustion engine, the control device for controlling the exhaust gas purification system further includes ammonia detected by the first ammonia concentration sensor during injection of urea water from the urea water injection device. When it is determined that the amount of ammonia flowing into the selective catalytic reduction device calculated using the concentration is not excessive, normal control is performed by the normal control means, and urea water is being injected from the urea water injection device. When it is determined that the amount of ammonia flowing into the selective catalytic reduction device is excessive, the adsorption control means performs adsorption control, and during the injection of urea water from the urea water injection device, the second ammonia The amount of ammonia adsorbed on the ammonia adsorption device calculated using the ammonia concentration detected by the concentration sensor is set in advance. When the adsorption upper limit amount reached, the urea water injection in the urea water injection device is stopped, the desorption control means performs desorption control, and the ammonia concentration detected by the first ammonia concentration sensor and the second When the ammonia amount adsorbed on the ammonia adsorption device calculated using the ammonia concentration detected by the ammonia concentration sensor reaches a preset lower limit adsorption amount, the urea water injection in the urea water injection device is resumed. And an ammonia supply control means for performing normal control by the normal control means.

  According to this configuration, the ammonia concentration detected by the first ammonia concentration sensor and the ammonia concentration detected by the second ammonia concentration sensor are used to consider the amount of urea water adsorbed and released by the particulate collection device, Adjusting the amount of urea water supplied from the urea water injector and the amount of ammonia desorbed from the ammonia adsorber while taking into account the amount of ammonia adsorbed in the ammonia adsorber, an appropriate amount of ammonia can be converted into a selective reduction catalyst device. Since it is made to flow in, it can raise the utilization efficiency of urea water and can prevent ammonia slip. The upper limit amount of adsorption is preferably set to about 70% to 80% of the maximum amount of adsorption. The lower limit of adsorption is preferably set to about 0% to 20% of the maximum amount of adsorption.

  Further, in the exhaust gas purification system for an internal combustion engine, the ammonia adsorption device is provided with a heating device, and the ammonia adsorption device is heated by the heating device to desorb ammonia from the ammonia adsorption device. To do.

  According to this configuration, the desorption and desorption amount of ammonia from the ammonia adsorption device can be controlled more accurately by a heating device using exhaust gas or an electric heater.

  In the exhaust gas purification method for an internal combustion engine of the present invention for achieving the above object, a urea water injection device, a particulate collection device, and a selective catalytic reduction device are provided in the exhaust passage of the internal combustion engine in order from the upstream side. In an exhaust gas purification system of an internal combustion engine, a parallel passage provided with an ammonia adsorption device in the exhaust passage between the particulate collection device and the selective catalytic reduction device, and an exhaust gas flowing out from the particulate collection device A flow path switching valve for switching the flow to the flow to the exhaust passage and the flow to the parallel passage, an open / close valve for opening and closing the parallel passage on the downstream side of the ammonia adsorption device, and the selective reduction catalyst device A first ammonia concentration sensor for detecting the ammonia concentration of the exhaust gas and a second ammonia concentration sensor for detecting the ammonia concentration of the exhaust gas flowing into the ammonia adsorption device are provided. In the exhaust gas purification method of the internal combustion engine in the exhaust gas purification system of the constructed internal combustion engine, the urea concentration calculated by using the ammonia concentration detected by the first ammonia concentration sensor during the urea water injection from the urea water injection device, When it is determined that the amount of ammonia flowing into the selective catalytic reduction device is not excessive, the flow path switching valve is switched to the flow to the exhaust passage and the on-off valve is closed to reduce the exhaust gas to the selective reduction. When it is determined that the amount of ammonia flowing into the selective reduction catalyst device is excessive while the urea water injection device is injecting urea water from the urea water injection device, the flow path switching valve is set to the parallel passage. And the opening / closing valve is opened to allow the exhaust gas to flow into the ammonia adsorbing device so that the ammonia in the exhaust gas When the amount of ammonia adsorbed on the ammonia adsorbing device reaches the upper limit adsorbed in advance while the urea adsorbing device adsorbs the urea water from the urea water injecting device, the urea water in the urea water injecting device In the state where the flow path switching valve is switched to the flow to the parallel passage and the on-off valve is opened, the ammonia adsorption device is heated to an ammonia desorption temperature or higher, and the ammonia adsorption is stopped. Ammonia desorbed from the apparatus is caused to flow into the selective reduction catalyst device, and when the amount of ammonia adsorbed on the ammonia adsorption device reaches a preset lower limit of adsorption, the urea water injection in the urea water injection device is resumed. Then, the flow path switching valve is switched to the flow to the exhaust passage and the on-off valve is closed so that the exhaust gas is selectively reduced. The method is characterized in that it is caused to flow into a type catalyst device. According to this method, the same effect as the exhaust gas purification system of the internal combustion engine can be obtained.

  According to the exhaust gas purification system for an internal combustion engine and the exhaust gas purification method for an internal combustion engine of the present invention, a urea water injection device, a particulate collection device, and a selective catalytic reduction catalyst device are sequentially provided in the exhaust passage of the internal combustion engine from the upstream side. In the exhaust gas purification system of the internal combustion engine that is provided, while taking advantage of the advantage that the deposition of white product derived from urea water in the selective catalytic reduction device can be suppressed and the advantage that the use efficiency of urea water is high, In addition, it is possible to stably supply ammonia to the selective catalytic reduction catalytic converter and to reduce the slip amount of ammonia from the selective catalytic reduction catalytic converter, thereby improving the NOx purification performance of the selective catalytic reduction catalytic converter. Can do.

It is a figure showing typically composition of an internal-combustion engine provided with an exhaust-gas purification system of an internal-combustion engine of an embodiment concerning the present invention. It is the figure which expanded the structure of the exhaust gas purification system of the internal combustion engine of FIG. 1, and is a figure which shows the state through which exhaust gas passes a parallel passage. It is the figure which expanded the structure of the exhaust gas purification system of the internal combustion engine of FIG. 1, and is a figure which shows the state which exhaust gas does not pass a parallel channel | path. It is a figure which shows the structure of the control apparatus of the exhaust gas purification system of the internal combustion engine of embodiment which concerns on this invention. It is a figure which shows the structure of the exhaust-gas purification system of the internal combustion engine which concerns on a prior art.

  Hereinafter, an exhaust gas purification system for an internal combustion engine and an exhaust gas purification method for an internal combustion engine according to embodiments of the present invention will be described with reference to the drawings.

  First, an engine (internal combustion engine) 10 in which an exhaust gas purification system 1 for an internal combustion engine according to this embodiment is arranged will be described with reference to FIG. The engine 10 is provided with a fuel injection device 11, an intake valve 12 and an exhaust valve 13 facing a cylinder (cylinder) 10 a, and further, an intake passage 14 communicating with the intake valve 12 and an exhaust valve 13. An exhaust passage 15 and an EGR passage 16 are provided.

  The intake passage 14 is provided with an air cleaner 17, a turbocharger (turbo supercharger) 18 compressor 18 b, an intercooler 19 a, and an intake throttle valve 19 b in order from the upstream side. The turbine 18a of the turbocharger 18 and the exhaust gas purification device 20 are provided in this order from the side. The EGR passage 16 is provided by connecting an intake passage 14 downstream of the compressor 18b and an exhaust passage 15 upstream of the turbine 18a. The EGR passage 16 is provided with an EGR cooler 16a and an EGR valve 16b in this order from the upstream side. Is provided.

  The fresh air A introduced from the atmosphere is sent to the cylinder (cylinder) 10a via the intake valve 12 with the exhaust gas (EGR gas) Ge flowing into the intake passage 14 from the EGR passage 16 as necessary. It is done. Further, the exhaust gas G generated in the cylinder 10a flows into the exhaust passage 15 via the exhaust valve 13, a part of which flows as the EGR gas Ge in the EGR passage 16, and the remaining exhaust gas Ga (= G-Ge) is Then, after flowing into the exhaust gas purification device 20 via the turbine 18a and being purified, it is discharged into the atmosphere as a purified exhaust gas Gc via a muffler (not shown) and a tail pipe (not shown). Is done.

  Further, in the configuration of FIG. 1, the exhaust gas purification device 20 includes an oxidation catalyst device (DOC) 22, a particulate collection device 23, a selective catalytic reduction device (SCR) 24, an oxidation catalyst device (DOC) 25, and the like. Is done.

  A fuel injection device 26 for injecting unburned fuel into the exhaust passage 15 is disposed in the exhaust passage 15 upstream of the oxidation catalyst device 22. The unburned fuel is injected into the gas, and the exhaust gas Ga is heated by the oxidation heat of the unburned fuel oxidized by the oxidation catalyst device 22 to raise the temperature of the particulate collection device 23 to a temperature range where PM combustion is possible. ing.

  A urea water injection device 27 that injects urea water U for NOx reduction into the exhaust passage 15 is disposed in the exhaust passage 15 downstream of the oxidation catalyst device 22 and upstream of the particulate collection device 23. The urea water U injected and injected is promoted to vaporize and decompose in the particulate collection device 23 to generate ammonia, and the NOx in the exhaust gas Ga is generated by this ammonia in the selective catalytic reduction device 24 on the downstream side. Is detoxified by reducing it to water and nitrogen.

  In the present invention, in the exhaust gas purification system 1 for an internal combustion engine, as shown in FIGS. 1 and 2, an ammonia adsorption device is provided in the exhaust passage 15 between the particulate collection device 23 and the selective catalytic reduction device 24. A parallel passage 31 with 30 is provided. Further, a flow path switching valve 32 for switching the flow of the exhaust gas Ga flowing out from the particulate collection device 23 to the flow to the exhaust passage 13 and the flow to the parallel passage 31, and the parallel passage 31 on the downstream side of the ammonia adsorption device 30 are provided. Opening / closing valves 33 for opening and closing are provided.

  If the flow path switching valve 32 is formed of a three-way valve, only one valve is required, but the flow path switching valve 32 may be composed of two on-off valves. Further, the flow path switching valve 32 may be configured as a valve that selectively switches the flow to the exhaust passage 15 and the flow to the parallel passage 31, but the flow to the exhaust passage 15 and the flow to the parallel passage 31 are not limited. If the valve is configured to continuously switch the ratio of the flow from 0% to 100%, the control becomes somewhat complicated, but more fine control can be performed.

  Further, the ammonia adsorption device 30 is provided with a heating device (not shown), and the ammonia adsorption device 30 is heated by the heating device, so that ammonia is desorbed from the ammonia adsorption device 30. Thus, the desorption and desorption amount of ammonia from the ammonia adsorption device 30 can be controlled with higher accuracy by a heating device using exhaust gas or an electric heater.

  Further, a first ammonia concentration sensor 34 that detects the ammonia concentration of the exhaust gas Ga flowing into the selective catalytic reduction device 24, and a second ammonia concentration sensor 35 that detects the ammonia concentration of the exhaust gas Ga flowing into the ammonia adsorption device 30. And are configured.

  With this configuration, it is possible to calculate the amount of ammonia flowing into the selective catalytic reduction catalyst device 24 using the ammonia concentration detected by the first ammonia concentration sensor 34, and to detect it by the second ammonia concentration sensor 35. Using the ammonia concentration, the amount of ammonia flowing into the ammonia adsorption device 30 can be calculated. Based on these values, excess ammonia in the exhaust gas Ga flowing out from the particulate collection device 23 can be adsorbed to the ammonia adsorption device 30 and temporarily stored, and adsorbed to the ammonia adsorption device 30 as necessary. The released ammonia can be desorbed and supplied to the selective catalytic reduction device 24.

  Moreover, the control apparatus 40 which controls the exhaust gas purification system 1 of an internal combustion engine is provided. The control device 40 may be incorporated in an engine control module (ECM) that controls the overall operation state of the engine 10 or may be provided independently.

  And in this invention, as shown in FIG. 4, the control apparatus 40 which controls this exhaust gas purification system 1 is provided with the normal control means 41, the adsorption | suction control means 42, the desorption control means 43, and the ammonia supply control means 44. Configure.

  As shown in FIG. 3, the normal control means 41 switches the flow path switching valve 32 to the flow to the exhaust passage 15 and closes the on-off valve 33 so that the exhaust gas Ga flows into the selective reduction catalyst device 24. As shown in FIG. 2, the adsorption control means 42 switches the flow path switching valve 32 to the flow to the parallel passage 31 and opens the on-off valve 33 to open the exhaust gas Ga as shown in FIG. It is means for performing adsorption control in which ammonia in exhaust gas Ga is caused to flow into the ammonia adsorbing device 30 and adsorbed by the ammonia adsorbing device 30.

  Further, as shown in FIG. 2, the desorption control means 43 switches the flow path switching valve 32 to the flow to the parallel passage 31 and opens the on-off valve 33 in the state where the ammonia adsorption device 30 is opened to the ammonia desorption temperature. This is a means for performing desorption control in which the temperature is raised to the above and ammonia desorbed from the ammonia adsorption device 30 flows into the selective catalytic reduction device 24.

  As a result, the urea water injection device can be obtained by appropriately combining the normal control means 41, the adsorption control means 42, and the desorption control means 43 while taking into account the amount of urea water U adsorbed and released by the particulate collection device 23. 27, the amount of urea water U supplied from 27 and the amount of ammonia desorbed from the ammonia adsorbing device 30 can be adjusted so that an appropriate amount of ammonia can flow into the selective catalytic reduction device 24. As well as improving the efficiency of use, ammonia slip can be prevented.

  The ammonia supply control means 44 is means for performing normal control, adsorption control, and desorption control under the following conditions.

  That is, the amount of ammonia flowing into the selective catalytic reduction device 24 calculated using the ammonia concentration detected by the first ammonia concentration sensor 34 while the urea water U is being injected from the urea water injection device 27 is not excessive. When the determination is made, the normal control means 41 performs normal control.

  Further, when the urea water U is being injected from the urea water injection device 27 and when it is determined that the amount of ammonia flowing into the selective catalytic reduction device 24 is excessive, the adsorption control means 42 performs adsorption control.

  Further, during the injection of the urea water U from the urea water injection device 27, the ammonia amount adsorbed on the ammonia adsorption device 30 calculated using the ammonia concentration detected by the second ammonia concentration sensor 35 is a preset adsorption upper limit amount. Is reached, the urea water injection in the urea water injection device 27 is stopped, and the desorption control means 43 performs desorption control.

  Further, the amount of ammonia adsorbed on the ammonia adsorbing device 30 calculated using the ammonia concentration detected by the first ammonia concentration sensor 34 and the ammonia concentration detected by the second ammonia concentration sensor 35 becomes a preset lower limit of adsorption. When it reaches, the injection of the urea water U in the urea water injection device 27 is resumed, and the normal control means 41 performs the normal control.

  Thus, the ammonia concentration detected by the first ammonia concentration sensor 34 and the ammonia concentration detected by the second ammonia concentration sensor 35 are used to consider the amount of urea water U adsorbed and released by the particulate collection device 23. Then, the amount of ammonia water U supplied from the urea water injection device 27 and the amount of ammonia desorbed from the ammonia adsorption device 30 are adjusted in consideration of the ammonia adsorption amount in the ammonia adsorption device 30, and an appropriate amount of ammonia is selected. Since it flows into the reduction catalyst device 24, the utilization efficiency of the urea water U can be enhanced and ammonia slip can be prevented. The upper limit amount of adsorption is preferably set to about 70% to 80% of the maximum amount of adsorption. The lower limit of adsorption is preferably set to about 0% to 20% of the maximum amount of adsorption.

  Next, an exhaust gas purification method for an internal combustion engine according to the present invention will be described. This method is applied to the exhaust gas purification system 1 of the internal combustion engine in which the urea water injection device 27, the particulate collection device 23, and the selective reduction catalyst device 24 are provided in the exhaust passage 15 of the engine 10 in order from the upstream side. In the exhaust passage 15 between the collector 23 and the selective catalytic reduction device 24, the parallel passage 31 provided with the ammonia adsorption device 30 and the flow of the exhaust gas Ga flowing out from the particulate collection device 23 flow to the exhaust passage 15. The flow path switching valve 32 for switching to the flow to the parallel passage 31, the on-off valve 33 for opening and closing the parallel passage 31 on the downstream side of the ammonia adsorption device 30, and the ammonia concentration of the exhaust gas Ga flowing into the selective catalytic reduction device 24 A first ammonia concentration sensor 34 for detecting the ammonia concentration and a second ammonia concentration sensor 35 for detecting the ammonia concentration of the exhaust gas flowing into the ammonia adsorption device 30 are provided. An exhaust gas purification method for an internal combustion engine in the exhaust gas purification system configured internal combustion engine.

  In this method, the amount of ammonia flowing into the selective catalytic reduction device 24 calculated using the ammonia concentration detected by the first ammonia concentration sensor 34 while the urea water U is being injected from the urea water injection device 27 is calculated. When it is determined that the flow rate is not excessive, the flow path switching valve 32 is switched to the flow to the exhaust passage 15 and the on-off valve 33 is closed to allow the exhaust gas Ga to flow into the selective catalytic reduction device 24.

  When it is determined that the amount of ammonia flowing into the selective catalytic reduction device 24 is excessive during the injection of the urea water U from the urea water injection device 27, the flow path switching valve 32 is changed to the flow to the parallel passage 31. At the same time, the on-off valve 33 is opened, and the exhaust gas Ga is caused to flow into the ammonia adsorption device 30 so that the ammonia in the exhaust gas Ga is adsorbed to the ammonia adsorption device 30.

  Further, during the injection of the urea water U from the urea water injection device 27, when the amount of ammonia adsorbed on the ammonia adsorption device 30 reaches a preset adsorption upper limit amount, the urea water U injection in the urea water injection device 27 is stopped. In the state where the flow path switching valve 32 is switched to the flow to the parallel passage 31 and the on-off valve 33 is opened, the ammonia adsorption device 30 is heated to the ammonia desorption temperature or higher and desorbed from the ammonia adsorption device 30. The prepared ammonia is caused to flow into the selective reduction catalyst device 24.

  Further, when the amount of ammonia adsorbed on the ammonia adsorbing device 30 reaches a preset lower limit amount of adsorption, the urea water U injection in the urea water injecting device 27 is resumed, and the flow of the flow path switching valve 32 to the exhaust passage 15 is resumed. And the on-off valve 33 is closed to allow the exhaust gas Ga to flow into the selective catalytic reduction device 24.

  Then, according to the exhaust gas purification system 1 for an internal combustion engine and the exhaust gas purification method for the internal combustion engine having the above-described configuration, the urea water injection device 27 and the particulate collection device 23 are sequentially provided in the exhaust passage 15 of the engine 10 from the upstream side. In the exhaust gas purification system 1 for an internal combustion engine configured by providing the selective reduction catalyst device 24, the advantage of being able to suppress the deposition of the white product derived from the urea water U in the selective reduction catalyst device 24 and the urea water While taking advantage of high utilization efficiency of U, it is possible to stably supply ammonia to the selective catalytic reduction device 24 and to reduce the slip amount of ammonia from the selective catalytic reduction device 24. Thus, the NOx purification performance of the selective catalytic reduction device 24 can be improved.

1, 1X Exhaust gas purification system for internal combustion engine 10 Engine (internal combustion engine)
11 Fuel injection device 14 Intake passage 15 Exhaust passage 20 Exhaust gas purification device 22 Oxidation catalyst device (DOC)
23 Fine particle collector 24 Selective reduction type catalytic device (SCR)
25 Oxidation catalyst equipment (DOC)
26 Fuel injection device 27 Urea water injection device 30 Ammonia adsorption device 31 Parallel passage 32 Flow path switching valve 33 On-off valve 34 First ammonia concentration sensor 35 Second ammonia concentration sensor 40 Control device 41 Normal control means 42 Adsorption control means 43 Desorption Control means 44 Ammonia supply control means A Fresh air G Generated exhaust gas Ga Exhaust gas Gc passing through exhaust gas purification device Purified exhaust gas Ge EGR gas U Urea water

Claims (5)

In the exhaust gas purification system of an internal combustion engine configured by providing a urea water injection device, a particulate collection device, and a selective catalytic reduction device in order from the upstream side in the exhaust passage of the internal combustion engine,
A parallel passage provided with an ammonia adsorption device is provided in the exhaust passage between the particulate collection device and the selective catalytic reduction device,
A flow path switching valve for switching the flow of the exhaust gas flowing out from the particulate collection device to the flow to the exhaust passage and the flow to the parallel passage, and an on-off valve for opening and closing the parallel passage on the downstream side of the ammonia adsorption device Provided,
Furthermore, a first ammonia concentration sensor that detects the ammonia concentration of the exhaust gas flowing into the selective reduction catalyst device and a second ammonia concentration sensor that detects the ammonia concentration of the exhaust gas flowing into the ammonia adsorption device are provided. An exhaust gas purification system for an internal combustion engine, characterized in that it is configured. A control device for controlling the exhaust gas purification system;
Normal control means for performing normal control for switching the flow path switching valve to the flow to the exhaust passage and closing the on-off valve to allow exhaust gas to flow into the selective catalytic reduction device;
Adsorption control for switching the flow path switching valve to the flow to the parallel passage and opening the on-off valve to allow exhaust gas to flow into the ammonia adsorption device and to adsorb ammonia in the exhaust gas to the ammonia adsorption device Adsorption control means for performing
Ammonia desorbed from the ammonia adsorbing device by switching the flow path switching valve to the flow to the parallel passage and raising the temperature of the ammonia adsorbing device to an ammonia desorption temperature or more with the open / close valve opened. The exhaust gas purification system for an internal combustion engine according to claim 1, further comprising a desorption control unit that performs desorption control for causing the gas to flow into the selective catalytic reduction device. A control device for controlling the exhaust gas purification system;
When it is determined that the amount of ammonia flowing into the selective catalytic reduction catalyst device calculated using the ammonia concentration detected by the first ammonia concentration sensor during injection of urea water from the urea water injection device is not excessive. The normal control means performs normal control,
During the injection of urea water from the urea water injection device, when it is determined that the amount of ammonia flowing into the selective reduction catalyst device is excessive, adsorption control is performed by the adsorption control means,
During the injection of urea water from the urea water injection device, the amount of ammonia adsorbed on the ammonia adsorption device calculated using the ammonia concentration detected by the second ammonia concentration sensor reached a preset upper limit of adsorption. Sometimes, the urea water injection in the urea water injection device is stopped, the desorption control means performs desorption control,
The amount of ammonia adsorbed on the ammonia adsorption device calculated using the ammonia concentration detected by the first ammonia concentration sensor and the ammonia concentration detected by the second ammonia concentration sensor has reached a preset lower limit of adsorption. 3. The exhaust gas purification system for an internal combustion engine according to claim 2, further comprising ammonia supply control means for resuming urea water injection in the urea water injection device and performing normal control by the normal control means.   The internal combustion engine according to any one of claims 1 to 3, wherein a heating device is provided in the ammonia adsorption device, and the ammonia adsorption device is heated by the heating device to desorb ammonia from the ammonia adsorption device. Exhaust gas purification system. An exhaust gas purification system for an internal combustion engine in which an urea water injection device, a particulate collection device, and a selective reduction catalyst device are provided in the exhaust passage of the internal combustion engine in this order from the upstream side, the particulate collection device and the selective reduction catalyst A parallel passage provided with an ammonia adsorption device in the exhaust passage between devices, and a flow path switching for switching the flow of exhaust gas flowing out from the particulate collection device to the flow to the exhaust passage and the flow to the parallel passage A valve, an on-off valve that opens and closes the parallel passage on the downstream side of the ammonia adsorption device, a first ammonia concentration sensor that detects the ammonia concentration of the exhaust gas flowing into the selective catalytic reduction device, and the ammonia adsorption device The exhaust gas of the internal combustion engine in the exhaust gas purification system of the internal combustion engine, which is provided with a second ammonia concentration sensor for detecting the ammonia concentration of the inflowing exhaust gas In the purification method,
When it is determined that the amount of ammonia flowing into the selective catalytic reduction catalyst device calculated using the ammonia concentration detected by the first ammonia concentration sensor during injection of urea water from the urea water injection device is not excessive. , Switching the flow path switching valve to the flow to the exhaust passage and closing the on-off valve to flow the exhaust gas into the selective catalytic reduction device,
When it is determined that the amount of ammonia flowing into the selective reduction catalyst device is excessive during the injection of urea water from the urea water injection device, the flow path switching valve is switched to the flow to the parallel passage and the Opening the on-off valve, allowing the exhaust gas to flow into the ammonia adsorbing device and adsorbing ammonia in the exhaust gas to the ammonia adsorbing device;
During the injection of urea water from the urea water injection device, when the amount of ammonia adsorbed on the ammonia adsorption device reaches a preset adsorption upper limit amount, the urea water injection in the urea water injection device is stopped, and the flow In a state where the path switching valve is switched to the flow to the parallel passage and the on-off valve is opened, the ammonia adsorption device is heated to an ammonia desorption temperature or higher, and the ammonia desorbed from the ammonia adsorption device is Flow into the selective catalytic reduction device,
When the amount of ammonia adsorbed on the ammonia adsorbing device reaches a preset adsorbing lower limit amount, the urea water injection in the urea water injection device is restarted, and the flow path switching valve is switched to the flow to the exhaust passage. An exhaust gas purification method for an internal combustion engine, wherein the on-off valve is closed to allow exhaust gas to flow into the selective catalytic reduction device.

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