Purification system

Abstract

To suppress deterioration of purification performance of a catalyst.SOLUTION: A purification system S includes a catalyst 16 provided in an exhaust pipe passage 13 for discharging exhaust gas of an engine 11 to the outside and purifying the exhaust gas, a bypass pipe passage 191 branched from an intake pipe passage 12 for supplying intake air into the engine 11 and joined to the upstream of the catalyst 16 in the exhaust pipe passage 13, and an air blower 3 provided in the bypass pipe passage 191 and supplying the intake air to the upstream of the catalyst 16 in the exhaust pipe passage 13 when a temperature of the catalyst 16 is equal to or higher than a prescribed temperature higher than an activation temperature of the catalyst 16.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a purification system for purifying exhaust gas from an engine. [Background technology]

[0002] 2. Description of the Related Art Purification systems for purifying engine exhaust gas are known. Patent Document 1 discloses a purification system that is provided in an exhaust pipe line and has a catalyst that purifies nitrogen oxides in the exhaust gas. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-150872 A Summary of the Invention [Problem to be solved by the invention]

[0004] A catalyst becomes activated and purifies exhaust gas when its temperature reaches or exceeds its activation temperature. However, if the temperature of the catalyst becomes too high above its activation temperature, the purification performance of the catalyst decreases.

[0005] The present invention has been made in consideration of these points, and has an object to suppress the deterioration of the purification performance of the catalyst. [Means for solving the problem]

[0006] One aspect of the present invention provides a purification system having a catalyst provided in an exhaust pipe that discharges engine exhaust to the outside and purifies the exhaust, a bypass pipe that branches off from an intake pipe that supplies intake air to the engine and joins the exhaust pipe upstream of the catalyst, and a blower provided in the bypass pipe for supplying the intake air to the exhaust pipe upstream of the catalyst when the temperature of the catalyst is equal to or higher than a predetermined temperature that is higher than the activation temperature of the catalyst.

[0007] The bypass pipe may branch off from the intake pipe upstream of a compressor provided in the intake pipe.

[0008] The purification system may have a recirculation line that returns the exhaust gas before it reaches the catalyst to the intake pipe, the bypass pipe being composed of a first pipe in which the blower is provided and connected to the intake pipe, and a second pipe connected to the first pipe and the exhaust pipe, and the recirculation pipe being composed of a third pipe connected to the second pipe and the intake pipe, and the second pipe.

[0009] The purification system may include a valve provided in the third line capable of switching whether or not to recirculate the exhaust gas from the recirculation line to the intake line, and a valve control unit that closes the valve when the blower is operating.

[0010] When the valve is open, the blower may be stopped.

[0011] The exhaust gas may further include a cooler that is provided in the second pipe and cools the intake air that is supplied to the exhaust pipe upstream of the catalyst.

[0012] When the temperature of the catalyst is below the predetermined temperature, the blower may be stopped. Effect of the Invention

[0013] The present invention has an advantage that the deterioration of the purification performance of the catalyst can be suppressed. [Brief description of the drawings]

[0014] [Figure 1] FIG. 2 is a diagram for explaining the configuration of a purification system. [Diagram 2] FIG. 2 is a diagram for explaining a configuration of a control device. [Diagram 3] FIG. 4 is a diagram for explaining a temperature change of a catalyst. [Figure 4] 5 is a diagram for explaining a change in exhaust purification performance. FIG. [Diagram 5] 10 is a flowchart illustrating an example of a process for switching whether or not to supply intake air. [Figure 6] FIG. 1 is a schematic diagram of a purification system without a recirculation line. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] [Configuration of Purification System S] 1 is a diagram for explaining the configuration of a purification system S. The purification system S is a system that purifies the exhaust gas of an engine 11. The purification system S has a blower 3, a control device 5, a catalyst 16, and a bypass pipe 191.

[0016] The engine 11 is an internal combustion engine that generates power by burning and expanding a mixture of fuel and intake air (air). The engine 11 is, for example, a diesel engine installed in an automobile or a ship, but may also be a gasoline engine.

[0017] The intake pipe 12 is a pipe that supplies intake air to the engine 11. A turbocharger compressor 141 is provided in the intake pipe 12. The exhaust pipe 13 is a pipe that discharges exhaust gas from the engine 11 to the outside. A turbocharger turbine 142 is provided in the exhaust pipe 13. The turbine 142 rotates when the exhaust gas passes through it. The compressor 141 is connected to the turbine 142, and rotates in conjunction with the rotation of the turbine 142 to supercharge the intake air.

[0018] A first cooler 15 for cooling the supercharged intake air is provided in the intake pipe 12. The first cooler 15 is provided downstream of the compressor 141 in the intake pipe 12. The first cooler 15 is a heat exchanger that cools the supercharged intake air by exchanging heat between the intake air and, for example, the cooling water of the engine 11 or outside air.

[0019] A catalyst 16 is provided in the exhaust pipe 13. The catalyst 16 is a catalyst that purifies exhaust gas. For example, the catalyst 16 is a selective catalytic reduction (SCR) catalyst that reacts nitrogen oxides contained in the exhaust gas with ammonia. Ammonia produced by hydrolysis of urea water injected from an injector provided in the exhaust pipe 13 immediately before the catalyst 16 by the heat of the exhaust gas is adsorbed on the surface of the catalyst 16. When the temperature of the catalyst 16 reaches or exceeds an activation temperature, the catalyst 16 becomes active and is capable of purifying exhaust gas by reacting the ammonia adsorbed on the surface of the catalyst 16 with the nitrogen oxides. The activation temperature is, for example, 250 degrees Celsius, but is not limited to this.

[0020] The temperature sensor 4 is a temperature sensor that detects the temperature of the catalyst 16. The temperature sensor 4 is, for example, an infrared thermometer, but may also be a thermocouple or a thermistor. The temperature sensor 4 in this embodiment directly detects the temperature of the catalyst 16. However, this is not limiting, and the temperature sensor 4 may detect the temperature of the exhaust gas as the temperature of the catalyst 16.

[0021] The recirculation pipe 192 is a pipe that recirculates the exhaust gas before it reaches the catalyst 16 to the intake pipe 12. The recirculation pipe 192 is composed of a second pipe 182 and a third pipe 183. The second pipe 182 is a pipe that connects the exhaust pipe 13 and the third pipe 183. The second pipe 182 is connected to a third connection point 173 of the exhaust pipe 13. The third pipe 183 is a pipe that connects the second pipe 182 and the intake pipe 12. The third pipe 183 is connected to the second pipe 182 at the second connection point 172, and is connected to the intake pipe 12 at a fourth connection point 174 upstream of the compressor 141 in the intake pipe 12.

[0022] A second cooler 184 is provided in the second pipe 182. The second cooler 184 cools the exhaust gas that is recirculated to the intake pipe 12. The second cooler 184 is a heat exchanger that cools the exhaust gas by exchanging heat between the exhaust gas and, for example, the cooling water of the engine 11 or outside air.

[0023] The third pipe 183 is provided with a second valve 22. The second valve 22 is a valve that can switch whether or not to recirculate the exhaust gas from the recirculation pipe 192 to the intake pipe 12. The second valve 22 is opened and closed under the control of the control device 5.

[0024] The bypass pipe 191 is a pipe branched from the intake pipe 12 and merges with the exhaust pipe 13 upstream of the catalyst 16. The bypass pipe 191 is composed of a first pipe 181 and a second pipe 182. The first pipe 181 is a pipe connected to the intake pipe 12, and is connected to a first connection point 171 of the intake pipe 12. The second pipe 182 is a pipe connected to the first pipe 181 and the exhaust pipe 13. That is, the second pipe 182 is shared by the bypass pipe 191 and the recirculation pipe 192. The first pipe 181 branches from the intake pipe 12 upstream of the third pipe 183. Specifically, the first pipe 181 is connected to the intake pipe 12 at the first connection point 171 upstream of the fourth connection point 174 where the third pipe 183 and the intake pipe 12 are connected. The first pipeline 181 and the second pipeline 182 are connected at a second connection point 172 .

[0025] The first pipe 181 is provided with a blower 3. The blower 3 is, for example, a fan, a blower, a pump, or the like. The blower 3 in this embodiment is a fan, but is not limited to this. The blower 3 blows out the intake air, thereby supplying the intake air upstream of the catalyst 16 in the exhaust pipe 13. Specifically, the blower 3 supplies the intake air upstream of the catalyst 16 in the exhaust pipe 13 via the second pipe 182, by blowing out the intake air at a pressure higher than the exhaust pressure.

[0026] A first valve 21 is provided in the first pipe 181. The first valve 21 is a valve that can switch whether or not the intake air is supplied to the exhaust pipe 13. The first valve 21 is provided in the first pipe 181 between the blower 3 and the second connection point 172. The first valve 21 is opened and closed under the control of the control device 5.

[0027] When the temperature of the catalyst 16 rises, it becomes active and purifies the exhaust gas, but the ammonia adsorbed on the surface of the catalyst 16 is more likely to be desorbed from the surface of the catalyst 16 as the temperature of the catalyst 16 rises. When ammonia is desorbed from the surface of the catalyst 16, the ammonia and nitrogen oxides no longer react on the surface of the catalyst 16, making it difficult to purify the exhaust gas. In other words, when the temperature of the catalyst 16 reaches or exceeds a certain temperature that is higher than the activation temperature of the catalyst 16, the exhaust gas purification performance (purification rate) decreases.

[0028] Therefore, when the temperature of the catalyst 16 is equal to or higher than a predetermined temperature, the control device 5 cools the catalyst 16 by supplying the intake air before being supercharged to the upstream of the catalyst 16 in the exhaust pipe 13 via the bypass pipe 191. The control device 5 will be described in detail below. FIG. 2 is a diagram for explaining the configuration of the control device 5.

[0029] The control device 5 includes a storage unit 51 and a control unit 52. The storage unit 51 is a storage medium including a read only memory (ROM), a random access memory (RAM), a hard disk, etc. The storage unit 51 stores a program executed by the control unit 52.

[0030] The control unit 52 is a computational resource including a processor such as a CPU (Central Processing Unit). The control unit 52 executes a program stored in the storage unit 51 to realize functions as an acquisition unit 521, a blower control unit 522, and a valve control unit 523.

[0031] The acquisition unit 521 acquires the temperature of the catalyst 16 detected by the temperature sensor 4. The acquisition unit 521 outputs to the blower control unit 522 temperature information indicating the acquired temperature.

[0032] The blower control unit 522 controls the operation of the blower 3. For example, when the temperature of the catalyst 16 indicated in the temperature information is equal to or higher than a predetermined temperature, the blower control unit 522 operates the blower 3 to supply intake air upstream of the catalyst 16 in the exhaust pipe 13. The predetermined temperature may be appropriately determined according to the temperature at which the purification rate of the exhaust gas becomes less than a predetermined value, and a specific value of the predetermined temperature is, for example, 450 degrees Celsius, but is not limited thereto. The blower control unit 522 notifies the valve control unit 523 of status information indicating whether the blower 3 is operating or stopped.

[0033] The valve control unit 523 controls the opening and closing of the first valve 21 and the second valve 22. When the blower control unit 522 operates the blower 3 (i.e., when the status information indicates that the blower 3 is operating), the valve control unit 523 closes the second valve 22 and opens the first valve 21. As a result, the intake air sent out from the blower 3 does not pass through the third pipe 183, so that the valve control unit 523 can suppress the intake air sent out from the blower 3 from returning to the intake pipe 12, and the blower control unit 522 can supply the intake air from the second pipe 182 to the exhaust pipe 13 upstream of the catalyst 16.

[0034] The intake air sent out from the blower 3 is cooled by the second cooler 184 when passing through the second cooler 184. That is, when the intake air is supplied upstream of the catalyst 16 in the exhaust pipe 13, the second cooler 184 cools the supplied intake air. Then, the intake air cooled by passing through the second cooler 184 is mixed with the exhaust gas by being supplied upstream of the catalyst 16 in the exhaust pipe 13. The supplied intake air is cooled by the second cooler 184, so that its temperature is lower than that of the exhaust gas. Therefore, the temperature of the mixture of the intake air and the exhaust gas is lower than that of the exhaust gas. Thus, the catalyst 16 is supplied with a mixture gas having a lower temperature than the exhaust gas. As a result, the temperature of the catalyst 16 is not higher than that of the mixture gas, so that the rise in temperature is suppressed. Also, the temperature of the catalyst 16 is lowered when the temperature of the mixture gas is sufficiently low. In this way, the control device 5 can suppress the temperature rise of the catalyst 16 and can lower the temperature of the catalyst 16.

[0035] FIG. 3 is a diagram for explaining the temperature change of the catalyst 16. The horizontal axis of FIG. 3 indicates time T, and the vertical axis indicates the temperature K of the catalyst 16. The temperature K of the catalyst 16 rises over time, and at time Tc, it reaches a predetermined temperature Kc that is higher than the activation temperature. The blower control unit 522 according to this embodiment operates the blower 3 at time Tc. Then, the valve control unit 523 closes the second valve 22 and opens the first valve 21, and supplies the intake air discharged by the blower 3 to the exhaust pipe 13 upstream of the catalyst 16.

[0036] A solid line A1 is a graph showing the temperature change of the catalyst 16 in this embodiment. As shown by the solid line A1, since the catalyst 16 in this embodiment is supplied with intake air that is lower in temperature than the exhaust gas after time Tc when the temperature of the catalyst 16 reaches a predetermined temperature Kc, the increase in the temperature of the catalyst 16 is suppressed. A dotted line B1 is a graph showing a comparative example in which intake air is not supplied upstream of the catalyst 16 in the exhaust pipe 13. As shown by the dotted line B1, since the comparative example does not supply intake air that is lower in temperature than the exhaust gas, the increase in temperature is not suppressed.

[0037] FIG. 4 is a diagram for explaining changes in exhaust purification performance. The horizontal axis of FIG. 4 indicates time T, and the vertical axis indicates the purification performance (purification rate P) of the catalyst 16. A solid line A2 is a graph showing changes in purification performance of the catalyst 16 in this embodiment. As shown by the solid line A2, the temperature rise of the catalyst 16 in this embodiment is suppressed, so the deterioration of the purification performance of the catalyst 16 is suppressed. A dotted line B2 is a graph showing changes in purification performance in a comparative example in which intake air is not supplied upstream of the catalyst 16 in the exhaust pipe 13. As shown by the dotted line B2, in the comparative example, the temperature of the catalyst 16 rises because intake air that is cooler than the exhaust is not supplied, so the purification performance decreases.

[0038] As described above, when the temperature of the catalyst 16 is equal to or higher than the predetermined temperature Kc, the control device 5 supplies intake air having a lower temperature than the exhaust gas to the exhaust pipe 13 upstream of the catalyst 16, thereby suppressing a rise in temperature of the catalyst 16 and lowering the temperature of the catalyst 16. In this way, the control device 5 can keep the temperature of the catalyst 16 at or below the predetermined temperature Kc, thereby suppressing desorption of ammonia from the surface of the catalyst 16 and suppressing a decrease in the purification performance of the catalyst 16.

[0039] If intake air is supplied when the temperature of the catalyst 16 is below the predetermined temperature Kc, the temperature of the catalyst 16 may drop too much and become below the activation temperature. Therefore, the blower control unit 522 stops the blower 3 when the temperature of the catalyst 16 is below the predetermined temperature Kc. This allows the blower control unit 522 to maintain the temperature of the catalyst 16 at the activation temperature. Specifically, the blower control unit 522 can suppress an increase in temperature when the temperature of the catalyst 16 is equal to or higher than the predetermined temperature Kc, and can suppress an excessive decrease in temperature of the catalyst 16 when the temperature of the catalyst 16 is below the predetermined temperature Kc. In other words, the blower control unit 522 can keep the temperature of the catalyst 16 within an appropriate range in which the catalyst 16 is activated and the purification rate is equal to or higher than a predetermined value.

[0040] When intake air is not supplied to the exhaust pipe 13 upstream of the catalyst 16, the valve control unit 523 opens and closes the second valve 22 depending on whether or not the exhaust is recirculated to the intake pipe 12. Specifically, the valve control unit 523 closes the second valve 22 when the exhaust is not recirculated to the intake pipe 12. When the exhaust is recirculated to the intake pipe 12, the valve control unit 523 opens the second valve 22 and closes the first valve 21. By closing the first valve 21, the valve control unit 523 can prevent high-temperature exhaust air from entering the blower 3.

[0041] If the first valve 21 and the second valve 22 are opened and the blower 3 is operated in an attempt to simultaneously supply intake air to the upstream of the catalyst 16 in the exhaust pipe 13 and return the exhaust gas to the intake pipe 12, the intake air that should be supplied to the upstream of the catalyst 16 in the exhaust pipe 13 may return to the intake pipe 12, or the exhaust gas may not be returned to the intake pipe 12. Therefore, only one of supplying intake air to the upstream of the catalyst 16 in the exhaust pipe 13 and returning the exhaust gas to the intake pipe 12 is performed. In other words, supplying intake air to the upstream of the catalyst 16 in the exhaust pipe 13 and returning the exhaust gas to the intake pipe 12 are not performed simultaneously.

[0042] [Process to switch whether or not to supply intake air] 5 is a flowchart showing an example of a process for switching whether or not to supply intake air. The process for switching whether or not to supply intake air is executed at a predetermined interval while the engine 11 is running. The predetermined interval is, for example, 100 milliseconds, but is not limited to this.

[0043] First, the acquisition unit 521 acquires the temperature of the catalyst 16 (step S1). Specifically, the acquisition unit 521 acquires temperature information indicating the temperature of the catalyst 16 detected by the temperature sensor 4.

[0044] The blower control unit 522 determines whether the temperature of the catalyst 16 indicated in the temperature information is equal to or higher than a predetermined temperature Kc (step S2). If the temperature of the catalyst 16 is equal to or higher than the predetermined temperature Kc (Yes in step S2), the blower control unit 522 supplies intake air upstream of the catalyst 16 in the exhaust pipe 13 (step S3). Specifically, after the valve control unit 523 opens the first valve 21 and closes the second valve 22, the blower control unit 522 operates the blower 3 to supply intake air upstream of the catalyst 16 in the exhaust pipe 13.

[0045] If the temperature of the catalyst 16 is lower than the predetermined temperature Kc (No in step S2), the blower control unit 522 does not supply intake air to the exhaust pipe 13 upstream of the catalyst 16 (step S4). In this case, the blower control unit 522 stops the blower 3. The valve control unit 523 closes the first valve 21.

[0046] (Variation 1) In the above embodiment, the bypass pipe 191 and the recirculation pipe 192 share the second pipe 182. However, this is not limited to the above, and the bypass pipe 191 and the recirculation pipe 192 may be independent of each other. In this case, the bypass pipe 191 is composed of only the first pipe 181, and the first pipe 181 is connected to the intake pipe 12 and the exhaust pipe 13. The recirculation pipe 192 is composed of only the third pipe 183, and the third pipe 183 is provided with the second cooler 184 and is connected to the third connection point 173 and the fourth connection point 174. The first pipe 181 according to the first modification is provided with the blower 3. A cooler for cooling the intake air may be provided between the connection point of the blower 3 and the exhaust pipe 13 in the first pipe 181.

[0047] (Variation 2) In the above embodiment, the purification system S has the recirculation pipe 192. However, this is not limited, and the purification system S may not have the recirculation pipe 192. FIG. 6 is a schematic diagram of the purification system S that does not have the recirculation pipe 192. As shown in FIG. 6, the purification system S according to the second modification does not have the recirculation pipe 192 shown in FIG. 1. In this case, the bypass pipe 191 is connected to the first connection point 171 and the third connection point 173 of the exhaust pipe 13. Note that a cooler may be provided between the third connection point 173 and the blower 3 in the bypass pipe 191 according to the second modification.

[0048] (Variation 3) In the above embodiment, the blower 3 is a fan, and the purification system S has the first valve 21 to prevent exhaust air from entering the blower 3. However, the blower 3 is not limited to a fan, and a positive displacement pump may be used. The positive displacement pump is, for example, a gear pump, a screw pump, a vane pump, or the like. When the blower 3 is a positive displacement pump, the exhaust air is prevented from entering the blower 3, and therefore the purification system S does not need to have the first valve 21. In this case, the purification system S does not need to be provided with the first valve 21, and therefore the configuration is simplified.

[0049] (Variation 4) The purification system S in the above embodiment has the first valve 21 to prevent exhaust air from entering the blower 3. However, the present invention is not limited to this, and the purification system S may have a check valve instead of the first valve 21. The check valve passes the intake air from the blower 3 toward the exhaust pipe 13 and blocks the exhaust air from the exhaust pipe 13 toward the blower 3. The purification system S using the check valve does not need to open and close the valve to switch between supplying the intake air sent out by the blower 3 to the exhaust pipe 13 and preventing the exhaust air from entering the blower 3, and therefore the control is simplified.

[0050] [Effects of Purification System S] As described above, the purification system S includes the catalyst 16 provided in the exhaust pipe 13 that discharges the exhaust of the engine 11 to the outside and purifies the exhaust, the bypass pipe 191 that branches off from the intake pipe 12 that supplies intake air to the engine 11 and joins the exhaust pipe 13 upstream of the catalyst, and the blower 3 provided in the bypass pipe 191 that supplies the intake air to the exhaust pipe 13 upstream of the catalyst 16 when the temperature of the catalyst 16 is equal to or higher than a predetermined temperature Kc that is higher than the activation temperature of the catalyst. With the above configuration, the purification system S can supply the catalyst 16 with a mixture of intake air and exhaust gas that is lower than the temperature of the exhaust when the temperature of the catalyst 16 reaches the predetermined temperature Kc (for example, 450 degrees Celsius or higher at which the purification performance of the catalyst 16 falls below a predetermined value). In this way, the catalyst 16 is supplied with a mixture gas that is lower in temperature than the exhaust gas. As a result, the purification system S can suppress the temperature of the catalyst 16 from reaching the predetermined temperature Kc or higher, thereby suppressing a decrease in the purification performance of the catalyst.

[0051] Although the present invention has been described above using the embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments, and various modifications and changes are possible within the scope of the gist of the present invention. For example, all or part of the device can be configured by distributing or integrating functionally or physically in any unit. In addition, new embodiments resulting from any combination of multiple embodiments are also included in the embodiments of the present invention. The effect of the new embodiment resulting from the combination combines the effect of the original embodiment. [Explanation of symbols]

[0052] 11 Engine 12 Intake pipe 13 Exhaust pipe 14 Turbocharger 141 Compressor 142 Turbine 15 1st cooler 16 Catalyst 171 First Connection Point 172 Second Connection Point 173 Third Connection Point 174 4th Junction 181 1st pipeline 182 2nd pipeline 183 3rd pipeline 184 2nd cooler 191 Bypass Pipe 192 Recirculation line 21 First valve 22 Second valve 3. Blower 4 Temperature Sensor 5. Control device 51 Storage section 52 Control section 521 Acquisition Department 522 Blower control unit 523 Valve control section

Claims

1. a catalyst provided in an exhaust pipe that discharges engine exhaust to the outside and purifies the exhaust; a bypass pipe branching off from an intake pipe for supplying intake air to the engine and joining the exhaust pipe upstream of the catalyst; a blower provided in the bypass pipe and configured to supply the intake air to an upstream of the catalyst in the exhaust pipe when the temperature of the catalyst is equal to or higher than a predetermined temperature that is higher than an activation temperature of the catalyst; A purification system having:

2. The bypass pipe is branched off from the intake pipe upstream of a compressor provided in the intake pipe. The purification system of claim 1 .

3. a recirculation pipe that recirculates the exhaust gas before it reaches the catalyst to the intake pipe, the bypass pipe includes a first pipe in which the blower is provided and which is connected to the intake pipe, and a second pipe which is connected to the first pipe and the exhaust pipe, The recirculation line is composed of a third line connected to the second line and the intake line, and the second line. The purification system of claim 1 .

4. a valve provided in the third pipe line and capable of switching whether or not to recirculate the exhaust gas from the recirculation pipe line to the intake pipe line; a valve control unit that closes the valve when the blower is operating; having The purification system of claim 3.

5. When the valve is open, the blower is stopped. The purification system of claim 4.

6. a cooler provided in the second pipe to cool the intake air supplied to the exhaust pipe upstream of the catalyst; The purification system according to claim 4 or 5.

7. When the temperature of the catalyst is lower than the predetermined temperature, the blower is stopped. The purification system of claim 1 .

Images