JP2013130109A - Exhaust emission control device and method of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust emission control device and method of an internal combustion engine, capable of reducing consumption of fuel by a solid reducing agent heating means by heating a solid reducing agent using a temperature of exhaust gas.SOLUTION: A bypass flow path 14, an SCR catalyst 10, and an injection device 44 are arranged in an exhaust gas passage 2 of an engine 1. A return flow control valve 32, a solid reducing agent 38, and a coil heater 36 are arranged in the bypass flow path 14. The return flow control valve 32 is opened, the exhaust gas flows into the bypass flow path 14, and ammonium is generated from the solid reducing agent 38 when the temperature Tof the exhaust gas becomes the releasing temperature or higher. Further, the return flow control valve 32 is opened and at the same time the heating output of the coil heater 36 is lowered or the coil heater 36 is stopped. Furthermore, the urea water is injected into the exhaust gas from the injection device 44 when the temperature Tof the exhaust gas is about 200°C or higher. The urea water is hydrolyzed and the ammonium is generated.

Description

  The present invention relates to an exhaust gas purification device and a purification method for purifying NOx (nitrogen oxides) contained in exhaust gas discharged from an internal combustion engine with a reduction catalyst.

As an exhaust gas purification device that reduces NOx discharged from an internal combustion engine, particularly a diesel engine, for example, Patent Document 1 discloses a reduction catalyst provided in an exhaust gas passage of a diesel engine, and a diesel engine and a reduction catalyst. In addition, an exhaust gas purification apparatus including a bypass channel that bypasses the exhaust gas channel and a solid reducing agent provided in the bypass channel is disclosed. Part of the exhaust gas discharged from the diesel engine flows into the bypass flow path, sublimates the solid reducing agent provided in the bypass flow path to generate ammonia, and then flows into the reduction catalyst containing the ammonia To do. Thereafter, NOx contained in the exhaust gas is reduced by ammonia in the reduction catalyst, and purified as nitrogen and water.
Since this exhaust gas purifying apparatus does not include a solid reducing agent heating means such as a heater for heating and sublimating the solid reducing agent, the exhaust gas temperature is used to sublimate the solid reducing agent. Therefore, when the temperature of the exhaust gas at the time of starting or the like is low, the NOx may not be reduced because the solid reducing agent does not sublime even if the exhaust gas is allowed to pass through.
Therefore, in Patent Document 2, a reduction catalyst provided in an exhaust gas passage of a diesel engine, a bypass channel provided between the diesel engine and the reduction catalyst, bypassing the exhaust gas channel, and a bypass channel are provided. An exhaust gas purifying apparatus comprising a solid reducing agent and a solid reducing agent heating means for heating and sublimating the solid reducing agent is disclosed. In this exhaust gas purifying apparatus, a solid reducing agent is constantly heated by a solid reducing agent heating means to be sublimated to generate ammonia. That is, ammonia can always be generated regardless of the temperature of the exhaust gas. The exhaust gas that has passed through the bypass flow path contains ammonia and flows into the reduction catalyst. Thereafter, NOx contained in the exhaust gas is reduced by ammonia in the reduction catalyst, and purified as nitrogen and water.

JP 2010-65648 A JP 2001-159308 A

However, in the exhaust gas purifying apparatus described in Patent Document 2, since the solid reducing agent is constantly heated by the solid reducing agent heating means, the amount of fuel consumed for operating the solid reducing agent heating means increases. In general, the fuel for operating the solid reductant heating means is also used as the fuel supplied to the internal combustion engine. Therefore, if the fuel is consumed by the solid reductant heating means, the fuel consumption is reduced. There was a problem.
In addition, when the internal combustion engine is under a high load, the amount of exhaust gas increases, so that the amount of reducing agent required also increases. Therefore, it is necessary to sublimate a large amount of reducing agent by increasing the heating temperature of the solid reducing agent. Therefore, when the heating output of the solid reducing agent heating means is increased, the amount of fuel consumed is also increased, so that there is a problem that the fuel consumption is greatly reduced.

  Therefore, the present invention solves such a problem, and an internal combustion engine that can reduce the consumption of fuel by the solid reductant heating means by heating the solid reductant using the temperature of the exhaust gas. An object of the present invention is to provide an exhaust gas purification device and a purification method.

An exhaust gas purification apparatus for an internal combustion engine according to the present invention that solves the above-mentioned problems is provided in an exhaust gas passage connected to the internal combustion engine, and a reduction catalyst that reduces NOx contained in the exhaust gas,
One end is connected to the exhaust gas passage immediately downstream of the internal combustion engine, and the other end is connected to the exhaust gas passage between the one end and the reduction catalyst to branch a part of the exhaust gas flowing through the exhaust gas passage. Possible detour channels,
A first temperature sensor connected to the exhaust gas passage and measuring a temperature of the exhaust gas flowing into the bypass passage;
An exhaust gas adjusting means for adjusting the flow of the exhaust gas flowing into the bypass channel;
A solid reducing agent storage means for storing the solid reducing agent provided in the bypass channel;
A solid reducing agent heating means for heating the solid reducing agent to release a fluid reducing agent;
A second temperature sensor for measuring the temperature of the exhaust gas flowing through the exhaust gas passage downstream from the other end of the bypass flow path and upstream from the reduction catalyst;
A liquid reducing agent supply means for supplying a liquid reducing agent into the exhaust gas passage downstream from the second temperature sensor and upstream from the reduction catalyst;
According to the measurement result by the first temperature sensor, the exhaust gas adjusting means and the solid reductant heating means are controlled to flow the exhaust gas through the bypass flow path, and the liquid according to the measurement result by the second temperature sensor. Control means for controlling the supply of the liquid reducing agent from the reducing agent supply means into the exhaust gas.

According to the exhaust gas purification apparatus for an internal combustion engine, since the exhaust gas flows into the bypass flow path and the fluid reducing agent is released from the solid reducing agent using the temperature of the exhaust gas, the heating output of the solid reducing agent heating means is reduced. Or the heating by a solid reducing agent heating means can be stopped. Thereby, the fuel consumption required in order to heat a solid reducing agent heating means can be reduced. In particular, when the fuel for heating the solid reducing agent heating means is also used as the fuel supplied to the internal combustion engine, the fuel consumption of the solid reducing agent heating means is reduced, thereby reducing the fuel consumption. The influence can be reduced.
Moreover, since the bypass flow path is provided immediately downstream of the internal combustion engine, high-temperature exhaust gas can be supplied to the solid reducing agent. For example, when the solid reducing agent is provided at a position away from the internal combustion engine, the temperature of the exhaust gas is lowered, so the solid reducing agent may not be heated sufficiently. The agent can be efficiently heated.
Moreover, since the solid reducing agent heating means is provided, the fluid reducing agent can be released from the solid reducing agent even when the temperature of the exhaust gas is low. Thereby, even when the temperature of the exhaust gas is low, the fluid reducing agent can be supplied into the exhaust gas, so that NOx can be reliably purified.
Furthermore, since the liquid reducing agent supply means is provided, when the amount of reducing agent for reducing NOx is insufficient with only the fluid reducing agent that is released by heating the solid reducing agent, for example, at high load, The reducing agent can be replenished by supplying the liquid reducing agent. Thereby, NOx contained in the exhaust gas can be reliably reduced even when the internal combustion engine is under a high load.
And by adjusting the flow of the exhaust gas with the exhaust gas adjusting means, it is possible to prevent the exhaust gas from flowing into the detour channel when there is no need to take out the fluid reducing agent from the solid reducing agent, so that the exhaust pressure can be reduced. .

The control means includes
When the measurement result by the second temperature sensor is lower than the hydrolysis temperature at which the liquid reducing agent is hydrolyzed, the solid reducing agent heating means is controlled to heat the solid reducing agent and release the fluid reducing agent. Let me
When the measurement result by the second temperature sensor is equal to or higher than the hydrolysis temperature, the liquid reducing agent supply means may be controlled to supply the liquid reducing agent into the exhaust gas.

  Thus, when the liquid reducing agent is at or above the hydrolysis temperature at which it is hydrolyzed, the liquid reducing agent is supplied into the exhaust gas, so that the temperature of the exhaust gas can be used to turn the liquid reducing agent into a gas. As a result, it is possible to prevent the liquid reducing agent from flowing into the reduction catalyst as a liquid without being vaporized and being discharged into the atmosphere as a liquid without serving as a reducing agent.

The control means includes
If the measurement result by the first temperature sensor is equal to or higher than the release temperature at which the fluid reducing agent is released from the solid reducing agent, the exhaust gas adjusting means may be controlled to cause the exhaust gas to flow into the bypass channel. Good.

  In this way, when the measurement result of the temperature sensor is equal to or higher than the release temperature at which the fluid reducing agent is released by heating the solid reducing agent, the exhaust gas is caused to flow into the bypass flow path, so that the solid reduction is performed using the temperature of the exhaust gas. The fluid reducing agent can be released from the agent. Moreover, since the exhaust gas having a temperature equal to or higher than the discharge temperature of the fluid reducing agent is supplied to the solid reducing agent, the solid reducing agent heated by the solid reducing agent heating means is not cooled by the inflowing exhaust gas.

The control means includes
When the measurement result by the first temperature sensor is equal to or higher than the release temperature at which the fluid reducing agent is released from the solid reducing agent and less than a predetermined temperature value, the heating output of the solid reducing agent heating means is reduced. It is good.

  In this way, when the measurement result by the temperature sensor is equal to or higher than the release temperature of the fluid reducing agent and less than a predetermined temperature value set in advance, the exhaust gas temperature is utilized by bringing the exhaust gas into contact with the solid reducing agent. The fluid reducing agent can be released from the solid reducing agent. Thereby, since it becomes possible to reduce the heating output of a solid reducing agent heating means, the fuel consumption can be reduced. Therefore, the influence on fuel consumption can be reduced. The predetermined temperature of the exhaust gas means that when the exhaust gas at the predetermined temperature is brought into contact with the solid reducing agent, the amount of fluid reducing agent that can reduce all NOx per unit time flowing into the reduction catalyst per unit time. The temperature that can be generated is determined in advance by design or the like.

  Further, the control means may stop the heating by the solid reducing agent heating means when the measurement result by the first temperature sensor is equal to or higher than a predetermined temperature value.

  As described above, when the measurement result by the temperature sensor is equal to or higher than a predetermined temperature value set in advance, the exhaust gas is brought into contact with the solid reducing agent to release the fluid reducing agent from the solid reducing agent using the temperature of the exhaust gas. be able to. Furthermore, by contacting exhaust gas having a predetermined temperature or higher, an amount of fluid reducing agent capable of reducing all NOx contained in the exhaust gas can be released. Thereby, the heating by the solid reducing agent heating means can be stopped. That is, the fuel for heating the solid reducing agent heating means can be greatly reduced. Therefore, the influence on fuel consumption can be greatly reduced.

Further, the internal combustion engine has a turbocharger turbine driven by exhaust gas from the internal combustion engine,
The bypass flow path may be disposed in the exhaust gas passage immediately downstream of the turbine.

  Thus, since the bypass flow path is provided immediately downstream of the turbocharger turbine, high-temperature exhaust gas can be supplied to the solid reducing agent. For example, when a solid reducing agent is provided at a position away from the turbine, the temperature of the exhaust gas is lowered, and thus the solid reducing agent may not be heated sufficiently. Can be efficiently heated.

Further, the purification method of the present invention is provided in an exhaust gas passage connected to the internal combustion engine, the reduction catalyst for reducing NOx contained in the exhaust gas, one end connected to the exhaust gas passage immediately downstream of the internal combustion engine, and The other end is connected to the exhaust gas passage between the one end and the reduction catalyst, and a detour passage capable of branching a part of the exhaust gas flowing through the exhaust gas passage, and the detour flow connected to the exhaust gas passage A first temperature sensor for measuring the temperature of the exhaust gas flowing into the passage; an exhaust gas adjusting means for adjusting the flow of the exhaust gas flowing into the bypass channel; and a solid that is provided in the bypass channel and stores a solid reducing agent A reducing agent storage means; a solid reducing agent heating means for heating the solid reducing agent to release a fluid reducing agent; and the exhaust gas downstream from the other end of the bypass channel and upstream from the reduction catalyst. Flowing through the passage A second temperature sensor for measuring the temperature of the exhaust gas, a liquid reducing agent supply means for supplying a liquid reducing agent into the exhaust gas passage downstream from the second temperature sensor and upstream from the reduction catalyst, According to the measurement result by the first temperature sensor, the exhaust gas adjusting means and the solid reductant heating means are controlled to cause the exhaust gas to flow through the bypass channel, and the liquid reduction according to the measurement result by the second temperature sensor. Control means for controlling the supply of the liquid reducing agent from the agent supply means into the exhaust gas, and a purification method using an exhaust gas purification device of an internal combustion engine comprising:
The exhaust gas is caused to flow through the bypass channel by controlling the exhaust gas adjusting means and the solid reducing agent heating means according to the measurement result by the first temperature sensor, and the liquid reduction according to the measurement result by the second temperature sensor. A liquid reducing agent is supplied into the exhaust gas from the agent supply means.

According to the purification method described above, the exhaust gas is caused to flow into the detour channel and the fluid reducing agent is released from the solid reducing agent using the temperature of the exhaust gas, so that the heating output of the solid reducing agent heating means is reduced or the heating is stopped. can do. Thereby, the fuel consumption required in order to heat a solid reducing agent heating means can be reduced. In particular, when the fuel for heating the solid reducing agent heating means is also used as the fuel supplied to the internal combustion engine, the fuel consumption of the solid reducing agent heating means is reduced, thereby reducing the fuel consumption. The influence can be reduced.
Moreover, since the bypass flow path is provided immediately downstream of the internal combustion engine, high-temperature exhaust gas can be supplied to the solid reducing agent. For example, when the solid reducing agent is provided at a position away from the internal combustion engine, the temperature of the exhaust gas is lowered, so the solid reducing agent may not be heated sufficiently. The agent can be efficiently heated.
Further, by using the solid reducing agent heating means, the fluid reducing agent can be released from the solid reducing agent even when the temperature of the exhaust gas is low. Thereby, NOx can be purified reliably.
Furthermore, by using the liquid reducing agent supply means, when the amount of reducing agent for reducing NOx is insufficient with only the fluid reducing agent that is released by heating the solid reducing agent, for example, even when the load is high, the liquid The reducing agent can be replenished by supplying the reducing agent. Thereby, NOx contained in the exhaust gas can be reliably reduced even when the internal combustion engine is under a high load.
And by adjusting the flow of the exhaust gas with the exhaust gas adjusting means, it is possible to prevent the exhaust gas from flowing into the detour channel when there is no need to take out the fluid reducing agent from the solid reducing agent, so that the exhaust pressure can be reduced. .

  ADVANTAGE OF THE INVENTION According to this invention, the exhaust gas purification apparatus and purification method of an internal combustion engine which can reduce the consumption of the fuel by a solid reducing agent heating means can be provided by heating a solid reducing agent using the temperature of waste gas. .

It is the schematic which shows the structure of the exhaust gas purification apparatus which concerns on 1st embodiment of this invention. It is the schematic which shows the apparatus connected to the exhaust gas path which concerns on this embodiment. It is the schematic which shows the relationship between the reducing agent control means which concerns on this embodiment, and its peripheral device. It is a figure which shows the exhaust gas purification | cleaning flow of the exhaust gas purification apparatus which concerns on this embodiment. It is a figure which shows the detailed flow which generates ammonia by a solid reducing agent. It is a figure which shows the detailed flow which generates ammonia with urea water. It is the schematic which shows the arrangement | positioning location of the exhaust gas purification apparatus which concerns on 2nd embodiment of this invention.

  Hereinafter, an exhaust gas purification apparatus for an internal combustion engine and a purification method using the exhaust gas purification apparatus according to the present invention will be described in detail with reference to the drawings. It should be noted that the dimensions, materials, shapes, relative arrangements, and the like of the components described in the following examples are not intended to limit the scope of the present invention unless otherwise specified, but are merely illustrative. It is just an example. Further, the case where a diesel engine is used as the internal combustion engine will be described, but the present invention is not limited to this, and the present invention can also be applied to an in-cylinder direct injection type lean burn gasoline engine or the like.

FIG. 1 is a schematic diagram showing a configuration of an exhaust gas purification apparatus according to the first embodiment of the present invention. Further, FIG. 2 is a schematic view showing a device connected to the exhaust gas passage according to the present embodiment. FIG. 3 is a schematic diagram showing the relationship between the reducing agent control means and its peripheral devices according to this embodiment.
As shown in FIGS. 1 to 3, an exhaust gas purification device 3 of a diesel engine (hereinafter referred to as “engine 1”) includes a DOC (Diesel Oxidation Catalyst) 6 and a DPF (Diesel Particulate Filter) 8. And an SCR (Selective Catalyst Reduction) catalyst 10, which are disposed in the exhaust gas passage 2.

In the engine 1, the fuel injection timing and the injection amount are electronically controlled by an ECU (Electronic Control Unit, not shown), and the combustion chamber 7 is connected to the fuel injection valve 5 provided for each cylinder at the injection timing and the injection amount. Fuel is injected into the inside.
The ECU includes a microcomputer including a CPU, a ROM, and a RAM (not shown). The ECU controls the operating state of the engine 1 in accordance with the operating conditions of the engine 1 and the driver's request.

  Further, the exhaust gas purifying device 3 is provided between the engine 1 and the DOC 6, and is a reducing agent that controls the bypass passage 14 that bypasses the exhaust gas passage 2, heating of a solid reducing agent 38 to be described later, injection of urea water, and the like. Control means 16.

  The bypass passage 14 has one end 14 a connected to the exhaust gas passage 2 immediately downstream of the engine 1 and the other end 14 b connected to the exhaust gas passage 2 immediately upstream of the DOC 6. Part of the exhaust gas discharged from the engine 1 flows into the bypass channel 14, passes through the bypass channel 14, and flows into the exhaust gas channel 2 again.

  A first temperature sensor 20 that measures the temperature of the exhaust gas flowing into the bypass flow path 14 is provided in the exhaust gas passage 2 immediately downstream of the engine 1. The first temperature sensor 20 is provided on the upstream side of the position where the one end 14 a of the bypass channel 14 is connected to the exhaust gas passage 2. The first temperature sensor 20 outputs the measurement result to the reducing agent control means 16 as an electrical signal.

The bypass flow path 14 is provided with a reflux control valve 32, a storage container 34 for storing the solid reducing agent 38, and a coil heater 36 for heating the solid reducing agent 38.
The reflux control valve 32 is provided at one end of the bypass flow path 14 and adjusts the flow of exhaust gas flowing into the bypass flow path 14. Opening and closing of the reflux control valve 32 is controlled by the solid reducing agent control unit 18 of the reducing agent control means 16. The solid reducing agent control unit 18 opens the reflux control valve 32 when the temperature of the exhaust gas measured by the first temperature sensor 20 is equal to or higher than the release temperature at which the fluid reducing agent can be released from the solid reducing agent 38, and is less than the release temperature. In this case, the reflux control valve 32 is closed.

  The storage container 34 is provided in the bypass flow path 14 on the downstream side of the reflux control valve 32. A solid reducing agent 38 is stored in the storage container 34. The exhaust gas that has flowed into the bypass channel 14 comes into contact with the solid reducing agent 38 in the storage container 34. As the solid reducing agent 38, an adsorbent that adsorbs ammonia or a complex that chemically contains ammonia can be used. For example, when ammonia is adsorbed on the solid reducing agent 38, the ammonia is desorbed from the adsorbent by the heat of the exhaust gas. In the case of a complex containing ammonia, ammonia is generated by the decomposition of the complex or sublimation from the complex by the heat of the exhaust gas.

  The solid reducing agent 38 is heated to come into contact with high-temperature exhaust gas to generate ammonia. The amount of ammonia generated varies with the temperature at which it is heated. Specifically, the amount of ammonia increases as the temperature increases.

  The coil heater 36 is installed so as to surround the exhaust gas passage 2 outside the storage container 34, and can release ammonia from the solid reducing agent 38 in the storage container 34 by heating. As a result, ammonia can be released from the solid reducing agent 38 even when the exhaust gas does not pass through the bypass flow path 14.

  The heating output of the coil heater 36 is controlled by the solid reducing agent control unit 18 of the reducing agent control means 16. The solid reducing agent control unit 18 adjusts the heating output of the coil heater 36 in consideration of the temperature of the exhaust gas measured by the first temperature sensor 20.

The solid reducing agent control unit 18 stops the coil heater 36 when the measurement result by the first temperature sensor 20 is equal to or higher than a predetermined temperature set in advance. The predetermined temperature of the exhaust gas is a temperature at which when the exhaust gas is brought into contact with the solid reducing agent 38, an amount of ammonia that can reduce all NOx per unit time flowing into the SCR catalyst 10 can be generated per unit time. Good, determined in advance by design and the like. The predetermined temperature is larger than the discharge temperature, and is determined based on the reducing ability of the SCR catalyst 10, the length from the first temperature sensor 20 to the storage container 34, the diameter of the bypass flow path 14, and the like.
The solid reducing agent control unit 18 reduces the heating output of the coil heater 36 when the measurement result by the first temperature sensor 20 is equal to or higher than the discharge temperature and lower than the predetermined temperature. Thereby, the fuel consumption required for heating the coil heater 36 can be reduced. In such a case, the influence on fuel consumption can be reduced.
Moreover, the solid reducing agent control part 18 stops the coil heater 36, when the measurement result by the 1st temperature sensor 20 is more than predetermined temperature. Thereby, the fuel for heating the coil heater 36 is not consumed. Since the fuel for heating the coil heater 36 is also used as the fuel supplied to the engine 1, the fuel consumption can be greatly reduced by reducing the fuel consumption.

An ammonia supply pump 40 for supplying exhaust gas containing ammonia to the downstream side and a check valve 42 are provided on the other end side of the bypass flow path 14 on the downstream side of the storage container 34.
Since the ammonia supply pump 40 is provided, the exhaust gas containing the generated ammonia can be reliably supplied to the exhaust gas passage 2. The operation and stop of the ammonia supply pump 40 are controlled by the solid reducing agent control unit 18. The solid reducing agent control unit 18 opens the reflux control valve 32 and simultaneously operates the ammonia supply pump 40 and closes the reflux control valve 32 and simultaneously stops the ammonia supply pump 40.

  The check valve 42 is provided on the downstream side of the ammonia supply pump 40. The check valve 42 prevents the exhaust gas from flowing from the exhaust gas passage 2 into the other end of the bypass passage 14, and the exhaust gas containing ammonia supplied from the ammonia supply pump 40 side to the exhaust gas passage 2. It has a function to feed.

  The exhaust gas containing ammonia supplied from the ammonia supply pump 40 passes through the check valve 42 and flows into the exhaust gas passage 2, merges with the exhaust gas that has passed through the exhaust gas passage 2, and flows into the DOC 6.

  An oxygen concentration sensor 26 is provided in the exhaust gas passage 2 between the junction 14 of the other end 14 b of the bypass channel 14 and the exhaust gas passage 2 and the DOC 6. The oxygen concentration sensor 26 outputs the measurement result to the reducing agent control means 16 as an electrical signal. The urea water control unit 45 of the reducing agent control means 16 estimates the amount of ammonia contained in the exhaust gas based on the oxygen concentration in the exhaust gas by the oxygen concentration sensor 26.

In Doc6, NO contained in the exhaust gas is oxidized NO ₂ is generated. The exhaust gas containing NO ₂ after passing through the DOC 6 subsequently flows into the DPF 8. The DPF 8 captures PM (Particulate Matter) contained in the exhaust gas. The DOC 6 and the DPF 8 are accommodated in one case 9. Thereby, when the amount of PM trapped in the DPF 8 exceeds a predetermined amount, the exhaust gas temperature can be increased by post-injection of fuel or the like, and PM can be burned.
The temperature of the exhaust gas entering the DPF 8 is measured by a second temperature sensor 22 attached to the case 9 upstream of the DPF 8.

The exhaust gas that has passed through the DPF 8 flows into the SCR catalyst 10. A third temperature sensor 24 for measuring the temperature of the exhaust gas is provided in the exhaust gas passage 2 between the DPF 8 and the SCR catalyst 10. Thereby, the temperature of the exhaust gas flowing into the SCR catalyst 10 can be accurately grasped.
The second temperature sensor 22 and the third temperature sensor 24 each output a measurement result as an electric signal to the reducing agent control means 16.

The exhaust gas passage 2 between the DPF 8 and the SCR catalyst 10 is provided with a first NOx concentration sensor 28 that measures the concentration of NOx contained in the exhaust gas. Further, a second NOx concentration sensor 30 that measures the concentration of NOx contained in the exhaust gas is provided in the exhaust gas passage 2 downstream of the SCR catalyst 10. The first NOx concentration sensor 28 and the second NOx concentration sensor 30 each output the measurement result as an electric signal to the reducing agent control means 16.
As described above, since the first NOx concentration sensor 28 and the second NOx concentration sensor 30 are provided on the upstream side and the downstream side of the SCR catalyst 10, the concentration of NOx contained in the exhaust gas flowing into the SCR catalyst 10 and the SCR catalyst 10. The concentration of NOx contained in the exhaust gas after passing through can be accurately grasped. Thereby, the NOx purification rate (NOx concentration measured by the first NOx concentration sensor 28 / NOx concentration measured by the second NOx concentration sensor 30) can be calculated.

  Further, the exhaust gas purification device 3 includes an injection device 44 that injects urea water, which is a liquid reducing agent, immediately upstream of the SCR catalyst 10. The injection device 44 includes an injection nozzle 46 provided in the exhaust gas passage 2 located between the first NOx concentration sensor 28 and the SCR catalyst 10, a urea water supply pump 47 for supplying urea water to the injection nozzle 46, urea A urea water tank 48 for storing water.

The urea water supply pump 47 has a variable mechanism capable of adjusting the supply amount of urea water. The variable mechanism of the urea water supply pump 47 is controlled by the urea water control unit 45 of the reducing agent control means 16.
The urea water supplied from the urea water supply pump 47 is injected into the exhaust gas from the injection nozzle 46.

  Generally, when the temperature of the exhaust gas passing through the DPF 8 is less than about 200 ° C., the decomposition reaction of the injected urea water is difficult to proceed, and ammonia slip may occur. Therefore, when the temperature of the exhaust gas measured by the third temperature sensor 24 is about 200 ° C. or higher, the urea water control unit 45 operates the urea water supply pump 47 to inject urea water. The urea water sprayed on the exhaust gas is decomposed to produce ammonia.

  The exhaust gas containing ammonia generated by the decomposition of urea water and ammonia generated by sublimating the solid reducing agent 38 flows into the SCR catalyst 10. In the SCR catalyst 10, NOx contained in the exhaust gas is reduced by ammonia. The exhaust gas that does not contain NOx is discharged into the atmosphere through the exhaust gas passage 2.

When a large amount of ammonia is supplied when the concentration of NOx is low, ammonia slip occurs, so the urea water control unit 45 adjusts the injection amount of urea water according to the concentration of NOx.
Specifically, the urea water control unit 45 estimates the amount of ammonia contained in the exhaust gas from the oxygen concentration by the oxygen concentration sensor 26. Subsequently, in consideration of the ammonia amount and the temperature of the exhaust gas by the third temperature sensor 24, the exhaust gas contains an amount of ammonia necessary for reducing NOx in the exhaust gas (hereinafter referred to as a predetermined amount). If it is determined, the urea water is not injected. On the other hand, the urea water control unit 45 takes into account the amount of ammonia contained in the exhaust gas and the temperature of the exhaust gas from the oxygen concentration sensor 26, and when the predetermined amount of ammonia is not contained in the exhaust gas and the ammonia is insufficient. If it is determined, the supply amount of urea water necessary to generate the shortage of ammonia is calculated. Then, the urea water control unit 45 operates the urea water supply pump 47 and controls the urea water supply pump 47 so as to supply the calculated urea water to discharge the necessary amount of urea water into the exhaust gas. Supply inside.

  Since the exhaust gas flowing into the SCR catalyst 10 contains ammonia, NOx contained in the exhaust gas is reduced in the SCR catalyst 10. Then, the purified exhaust gas that does not contain NOx passes through the exhaust gas passage 2 and is released into the atmosphere.

Next, an exhaust gas purification flow of the exhaust gas purification apparatus 3 having the above configuration will be described with reference to FIG.
As shown in FIG. 4, first, when the temperature of the exhaust gas is relatively low, such as immediately after the engine 1 is operated, the solid reducing agent 38 is heated to generate ammonia (step S1). Thereafter, when the engine 1 is warmed and the temperature of the exhaust gas is high, ammonia is generated by supplying urea water (step S20).

A detailed flow for generating ammonia by the solid reducing agent 38 will be described with reference to FIG.
As shown in FIG. 5, first, when the solid reductant control unit 18 of the reductant control means 16 detects that it is in the cold operation state (step S2), the solid reductant 38 is heated by the coil heater 36 (step S2). Step S4). Subsequently, the ammonia supply pump 40 is operated. When the solid reducing agent 38 is heated by the coil heater 36, ammonia is generated. The generated ammonia is supplied to the exhaust gas passage 2 by the ammonia supply pump 40, merges with the exhaust gas that has passed through the exhaust gas passage 2, and flows into the DOC 6, DPF 8, and SCR catalyst 10. Thereby, NOx contained in the exhaust gas is purified.

Then, the solid reductant control unit 18, upon detecting that the cold-operating condition has ended the engine 1 is warm (step S6), and the temperature T ₁ of the exhaust gas obtained from the first temperature sensor 20 is more than the release temperature Is determined (step S8).

Solid reductant control unit 18 determines, in step S8, if the temperature T ₁ of the exhaust gas is less than the discharge temperature, and flowing the exhaust gas to the bypass passage 14 is not possible (step S10). In such a case, all the exhaust gas is allowed to flow into the exhaust gas passage 2.
On the other hand, the solid reductant control unit 18 determines, in step S8, and the temperature T ₁ of the exhaust gas is not less than release temperature, it is possible to flow the exhaust gas to bypass flow path 14 (step S12). In such a case, the solid reducing agent control unit 18 opens the reflux control valve 32 (step S14). Further, the ammonia supply pump 40 is operated. Thereby, a part of the high-temperature exhaust gas discharged from the engine 1 flows into the bypass channel 14. When the high-temperature exhaust gas passes through the bypass channel 14, ammonia is generated by heating the solid reducing agent 38. The generated ammonia is fed to the exhaust gas passage 2 by an ammonia supply pump 40.

Then, the solid reductant control unit 18 determines the temperature T ₁ of the exhaust gas, whether preset the predetermined temperature or higher (step S16).
Solid reductant control unit 18, in step S16, if it is determined that the temperature T ₁ of the exhaust gas is higher than a predetermined temperature, stopping the heating by the coil heater 36 (step S18). Thereby, the consumption of the fuel for operating the coil heater 36 can be reduced significantly.

Meanwhile, in step S16, the solid reductant control unit 18, the temperature T ₁ of the exhaust gas is determined to be lower than the predetermined temperature, to reduce the heating output of the coil heater 36 (step S17). Thereby, the consumption of the fuel for operating the coil heater 36 can be reduced.

Next, a detailed flow for generating ammonia with urea water will be described with reference to FIG.
As shown in FIG. 6, firstly, to measure the temperature _{T 3} of the exhaust gas by the third temperature sensor (Step S21). Subsequently, the urea water control unit 45 determines the temperature _{T 3} of the exhaust gas is hydrolyzable temperature, whether for example 200 ° C. or higher (step S22).

Urea water control unit 45 determines in step S22, and if the temperature _{T 3} of the exhaust gas is below 200 ° C., injection of the urea water is not possible (step S24).
On the other hand, urea water control unit 45 determines in step S22, and if the temperature _{T 3} of the exhaust gas is more than 200 ° C., injection of the urea water is possible (step S26). If it is determined that the urea water injection is possible, the urea water control unit 45 then estimates the amount of ammonia flowing through the exhaust gas passage 2 based on the oxygen concentration acquired from the oxygen concentration sensor 26 (step S28).

Next, the urea water control unit 45 determines whether or not the ammonia amount estimated in step S28 is less than the predetermined amount (step S30).
If the urea water control unit 45 determines in step S30 that the amount of ammonia is less than the predetermined amount, the urea water supply pump 47 is operated to inject the urea water in an amount necessary for reducing NOx. (Step S32). Thereby, NOx contained in the exhaust gas can be efficiently reduced by the SCR catalyst.
Moreover, if the urea water control part 45 determines with the quantity of ammonia being more than predetermined amount in step S30, it will not use urea water (step S34). Thereby, ammonia slip can be prevented.

  After the cold operation state ends, while the engine 1 is operating, the above-described steps S8 to S34 are repeatedly performed to continue supplying ammonia into the exhaust gas.

As described above, according to the exhaust gas purifying device 3 according to the present embodiment, the measurement result by the first temperature sensor 20, that is, if the temperature T ₁ of the exhaust gas is higher release temperature of the solid reductant 38, bypass flow exhaust gas In order to be able to flow into the passage 14, ammonia can be released from the solid reducing agent 38 using the temperature of the exhaust gas. Since ammonia is released from the solid reducing agent 38 using the temperature of the exhaust gas, the heating output from the coil heater 36 can be reduced. Thereby, the fuel consumption required in order to heat the coil heater 36 can be reduced. Since the fuel for heating the coil heater 36 is used together with the fuel supplied to the internal combustion engine, the consumption of the fuel for the coil heater 36 can be reduced to reduce the influence on the fuel consumption. .
When the temperature T ₁ of the exhaust gas is equal to or higher than the predetermined temperature value, to stop the coil heater 36, it is possible to greatly reduce the consumption of fuel. Thereby, the influence on a fuel consumption can be reduced significantly.

  Further, since the bypass flow path 14 is provided immediately downstream of the engine 1, high-temperature exhaust gas can be supplied to the solid reducing agent 38. When the solid reducing agent 38 is provided at a position away from the engine 1, the temperature of the exhaust gas is lowered, so that the solid reducing agent 38 may not be heated sufficiently. The agent 38 can be heated efficiently.

  Further, since the ammonia supply pump 40 is provided in the bypass flow path 14, ammonia can be reliably supplied to the exhaust gas passage 2. This is effective when ammonia cannot be supplied to the exhaust gas passage 2 due to the pressure difference due to the pressure loss of the exhaust gas or the pulsation of the exhaust gas.

  Further, since the coil heater 36 for heating the solid reducing agent 38 is provided, the solid reducing agent 38 can be heated to release ammonia even if the temperature of the exhaust gas is lower than the discharge temperature. Thereby, the NOx purification efficiency by the SCR catalyst 10 can be improved. Then, by adjusting the heating output of the coil heater 36, it is possible to adjust the amount of animonia generated.

  Further, since the first NOx concentration sensor 28 and the second NOx concentration sensor 30 are provided on the upstream side and the downstream side of the SCR catalyst 10, respectively, the NOx purification rate can be calculated. Furthermore, since the oxygen concentration sensor 26 is disposed in the exhaust gas passage 2, the amount of ammonia contained in the exhaust gas can be grasped. When the NOx purification rate is lower than a preset value (poor purification rate), the NOx purification rate is increased by adjusting the heating output of the coil heater 36 to adjust the amount of ammonia contained in the exhaust gas. can do.

  By adjusting the flow of the exhaust gas with the reflux control valve 32, it is possible to prevent the exhaust gas from flowing into the bypass channel 14 when it is not necessary to take out the ammonia from the solid reducing agent 38, so that the exhaust pressure can be reduced.

  Then, when all of the NOx cannot be reduced only with ammonia generated from the solid reducing agent 38, ammonia can be replenished by injecting urea water. Thereby, all NOx contained in the exhaust gas can be reduced even when the engine 1 is under a high load. Thereby, the NOx purification efficiency by the SCR catalyst 10 can be improved.

  Next, a second embodiment of the present invention will be described. In the following description, portions corresponding to the above-described embodiment are denoted by the same reference numerals, description thereof is omitted, and differences are mainly described. The engine of the second embodiment has a turbocharger.

FIG. 7 is a schematic view showing an arrangement location of the exhaust gas purifying apparatus 3 according to the second embodiment of the present invention.
As shown in FIG. 7, a turbine 4 a of the turbocharger 4 is disposed in the exhaust gas passage 2 immediately downstream of the engine 11. Further, a bypass flow path 14 that bypasses the exhaust gas passage 2 is provided between the turbine 4 a of the turbocharger 4 and the DOC 6.

  The detour passage 14 has one end 14 a connected to the exhaust gas passage 2 immediately downstream of the turbine 4 a and the other end 14 b connected to the exhaust gas passage 2 immediately upstream of the DOC 6. Part of the exhaust gas that has passed through the turbine 4 a flows into the bypass channel 14, passes through the bypass channel 14, and joins the exhaust gas channel 2 again.

  A first temperature sensor 20 that measures the temperature of the exhaust gas is provided in the exhaust gas passage 2 immediately downstream of the turbine 4a. The first temperature sensor 20 is provided on the upstream side of the position where one end of the bypass channel 14 is connected. Thereby, the temperature of the exhaust gas flowing into the detour channel 14 can be grasped.

  Similarly to the first embodiment, the bypass flow path 14 includes a reflux control valve 32, a storage container 34 for storing the solid reducing agent 38, and a coil heater 36 for heating and sublimating the solid reducing agent 38. And are provided.

  As described above, according to the present embodiment, the bypass channel 14 is provided immediately downstream of the turbine 4 a, so that high-temperature exhaust gas can be supplied to the solid reducing agent 38. When the solid reducing agent 38 is provided at a position away from the turbine 4a, the temperature of the exhaust gas is lowered, and thus the solid reducing agent 38 may not be heated sufficiently. The reducing agent 38 can be efficiently heated. Moreover, according to the exhaust gas purification apparatus 3, the effect demonstrated by 1st embodiment can also be acquired.

1 Engine 2 Exhaust gas passage 3 Exhaust gas purification device 4 Turbocharger 4a Turbine 5 Fuel injection valve 6 DOC
7 Combustion chamber 8 DPF
9 Case 10 SCR catalyst 11 Engine 14 Bypass flow path 14a One end 14b Other end 16 Reductant control means 18 Solid reductant controller 20 First temperature sensor 22 Second temperature sensor 23 Exhaust gas purifier 24 Third temperature sensor 26 Oxygen concentration sensor 28 First NOx concentration sensor 30 Second NOx concentration sensor 32 Reflux control valve 34 Storage container 36 Coil heater 38 Solid reducing agent 40 Pump 42 Check valve 44 Injection device 45 Urea water control unit 46 Injection nozzle 47 Urea water supply pump 48 Urea water tank

Claims (7)

A reduction catalyst provided in an exhaust gas passage connected to the internal combustion engine for reducing NOx contained in the exhaust gas;
One end is connected to the exhaust gas passage immediately downstream of the internal combustion engine, and the other end is connected to the exhaust gas passage between the one end and the reduction catalyst to branch a part of the exhaust gas flowing through the exhaust gas passage. Possible detour channels,
A first temperature sensor connected to the exhaust gas passage and measuring a temperature of the exhaust gas flowing into the bypass passage;
An exhaust gas adjusting means for adjusting the flow of the exhaust gas flowing into the bypass channel;
A solid reducing agent storage means for storing the solid reducing agent provided in the bypass channel;
A solid reducing agent heating means for heating the solid reducing agent to release a fluid reducing agent;
A second temperature sensor for measuring the temperature of the exhaust gas flowing through the exhaust gas passage downstream from the other end of the bypass flow path and upstream from the reduction catalyst;
A liquid reducing agent supply means for supplying a liquid reducing agent into the exhaust gas passage downstream from the second temperature sensor and upstream from the reduction catalyst;
According to the measurement result by the first temperature sensor, the exhaust gas adjusting means and the solid reductant heating means are controlled to flow the exhaust gas through the bypass flow path, and the liquid according to the measurement result by the second temperature sensor. An exhaust gas purification apparatus for an internal combustion engine, comprising: control means for controlling supply of the liquid reducing agent from the reducing agent supply means into the exhaust gas. The control means includes
When the measurement result by the second temperature sensor is lower than the hydrolysis temperature at which the liquid reducing agent is hydrolyzed, the solid reducing agent heating means is controlled to heat the solid reducing agent and release the fluid reducing agent. Let me
2. The liquid reductant is supplied into the exhaust gas by controlling the liquid reductant supply means when the measurement result by the second temperature sensor is equal to or higher than the hydrolysis temperature. An exhaust gas purification device for an internal combustion engine. The control means includes
When the measurement result by the first temperature sensor is equal to or higher than the release temperature at which the fluid reducing agent is released from the solid reducing agent, the exhaust gas adjusting means is controlled to cause the exhaust gas to flow into the bypass flow path. The exhaust gas purification apparatus for an internal combustion engine according to claim 1 or 2, characterized in that The control means includes
When the measurement result by the first temperature sensor is equal to or higher than a release temperature at which the fluid reducing agent is released from the solid reducing agent and less than a predetermined temperature value, the heating output of the solid reducing agent heating means is reduced. The exhaust gas purification device for an internal combustion engine according to any one of claims 1 to 3, wherein the exhaust gas purification device is an internal combustion engine.   The said control means stops heating by the said solid reducing agent heating means, when the measurement result by the said 1st temperature sensor is more than predetermined temperature value, The heating means by any one of Claims 1-4 characterized by the above-mentioned. An exhaust gas purification apparatus for an internal combustion engine as described. The internal combustion engine has a turbocharger turbine driven by exhaust gas from the internal combustion engine,
The exhaust gas purification apparatus for an internal combustion engine according to any one of claims 1 to 5, wherein the bypass flow path is disposed in the exhaust gas passage immediately downstream of the turbine. A reduction catalyst provided in an exhaust gas passage connected to the internal combustion engine, for reducing NOx contained in the exhaust gas, one end connected to the exhaust gas passage immediately downstream of the internal combustion engine, and the other end of the one end and the reduction catalyst Connected to the exhaust gas passage, and a bypass channel capable of branching a part of the exhaust gas flowing through the exhaust gas channel, and a temperature of the exhaust gas flowing into the bypass channel connected to the exhaust gas channel. A first temperature sensor to be measured; an exhaust gas adjusting means for adjusting a flow of exhaust gas flowing into the bypass flow path; a solid reducing agent storage means provided in the bypass flow path for storing a solid reducing agent; and the solid reduction A solid reducing agent heating means for heating the agent to release the fluid reducing agent, and measuring the temperature of the exhaust gas flowing through the exhaust gas passage downstream of the other end of the bypass channel and upstream of the reduction catalyst. 2 temperature sensors, liquid reducing agent supply means for supplying a liquid reducing agent into the exhaust gas passage downstream from the second temperature sensor and upstream from the reduction catalyst, and the measurement results by the first temperature sensor. Accordingly, the exhaust gas adjusting means and the solid reducing agent heating means are controlled to flow the exhaust gas through the bypass flow path, and from the liquid reducing agent supply means into the exhaust gas according to the measurement result by the second temperature sensor. A control means for controlling the supply of the liquid reducing agent, and a purification method using an exhaust gas purification device of an internal combustion engine comprising:
The exhaust gas is caused to flow through the bypass channel by controlling the exhaust gas adjusting means and the solid reducing agent heating means according to the measurement result by the first temperature sensor, and the liquid reduction according to the measurement result by the second temperature sensor. A purification method, wherein a liquid reducing agent is supplied from the agent supply means into the exhaust gas.

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