JP2012052476A - Exhaust emission purifying system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust emission purifying system capable of supplying ammonia serving as a reducing agent to an SCR (selective catalytic reduction) catalyst without inviting worsening of fuel consumption by a heating unit for heating a solid ammonia absorbent.SOLUTION: An exhaust manifold 12 and an exhaust pipe passage 13 are connected to an exhaust port of a diesel engine 11 as an exhaust pipe, and a front stage oxidation catalyst 16, an SCR catalyst 17, and a rear stage oxidation catalyst 18 are provided within an exhaust pipe passage 13. By arranging a tank 25 containing a solid ammonia absorbent [Sr(NH)Cl] in contact with an exhaust pipe passage 13, the solid ammonia absorbent is heated utilizing heat of an exhaust gas of a diesel engine 11, and an ammonia desorbed from the solid ammonia absorbent is supplied to the exhaust pipe passage 13 and the exhaust gas is purified by the SCR catalyst 17.

Description

  The present invention relates to an exhaust gas purification system.

  In recent years, a urea SCR system has been used as a system for purifying NOx in exhaust gas of a diesel engine. In the urea SCR system, ammonia obtained by hydrolyzing urea water is supplied to the SCR catalyst, and NOx is decomposed into harmless water and nitrogen. On the other hand, an exhaust gas purification system using a solid ammonia adsorbent as a reducing agent instead of urea water has been proposed. In Patent Document 1, ammonia, which is desorbed by heating a storage substance that has adsorbed ammonia in a heat-insulated container by heating means, is supplied to an exhaust line. Further, Patent Document 2 discloses a configuration in which ammonia is supplied by heating and desorbing an ammonia storage medium in a container with a heating device, as in Patent Document 1.

Special table 2010-513004 gazette Special table 2008-528431 gazette

  By the way, in the urea SCR system, heat is required for hydrolysis of urea water. Further, even when the solid ammonia adsorbents of Patent Document 1 and Patent Document 2 are used, a heating means is required when supplying ammonia. In these systems, since the heating means is provided and electric power is used, the fuel consumption is deteriorated. Patent Document 1 also describes that waste heat from the engine can be used as a heating means. Further, Patent Document 2 also describes that the heating means may be provided as heat from the hot exhaust gas from the combustion process. However, a specific configuration and method are not disclosed.

  The present invention has been made in view of the above problems, and the present invention provides an exhaust gas purification system that can supply ammonia, which is a reducing agent, to the SCR catalyst without deteriorating fuel consumption due to heating means for heating the solid ammonia adsorbent. The purpose is to provide a system.

  The present invention for solving the above problems includes an exhaust pipe that is connected to an exhaust port of an engine and guides exhaust gas, a reduction catalyst that is housed in the exhaust pipe and reduces NOx in the exhaust gas, adsorbs ammonia, and In an exhaust gas purification system, comprising a desorbable ammonia storage material and a tank for storing the ammonia storage material, and supplying ammonia desorbed from the ammonia storage material from the tank to an exhaust pipe upstream of the reduction catalyst. Is characterized in that it is arranged so that at least a part of it is in contact with the exhaust pipe, and the heat of the exhaust gas can be transmitted to the ammonia storage material in the tank.

  According to the present invention, the heat of the exhaust gas from the engine can be directly transmitted to the tank in contact with the exhaust pipe, and the ammonia storage material can be heated. As a result, the desorbed ammonia can be supplied to the SCR catalyst without the need to apply electric power as in the prior art, and the fuel consumption is not deteriorated.

  Further, the tank of the present invention includes a first chamber that contains a first ammonia storage material that desorbs ammonia at a first desorption temperature, and ammonia at a second desorption temperature that is higher than the first desorption temperature. It has the 2nd chamber which accommodates the 2nd ammonia storage material which remove | eliminates.

  Thereby, ammonia can be supplied at different desorption temperatures, and ammonia can be supplied from the first ammonia storage material or the second ammonia storage material in accordance with the temperature of the exhaust gas.

Also, the first chamber of the present invention is in contact with the exhaust pipe, and the second chamber is in contact with the portion of the exhaust pipe that is at the same temperature as or lower than the contact portion with the first chamber when the exhaust gas flows. Is preferred.
In addition, you may make the 1st chamber of this invention contact an exhaust pipe upstream from a 2nd chamber.
Further, the first chamber may be brought into contact with the exhaust pipe, and the second chamber may be brought into contact with the first chamber and indirectly thermally coupled to the exhaust pipe through the first chamber.

The tank of the present invention covers the outer periphery of the exhaust pipe and has a separation wall that separates the first chamber and the second chamber, and the separation wall has an outer diameter of the first chamber as it goes from the upstream to the downstream of the exhaust pipe. It may be formed separately so that becomes gradually smaller.
The tank may be provided with a heater for heating the first ammonia storage material.

  According to the present invention, ammonia as a reducing agent can be supplied to the SCR catalyst without causing deterioration of fuel consumption by the heating means for heating the solid ammonia adsorbent.

1 is a schematic diagram of an exhaust gas purification system according to a first embodiment of the present invention. It is a longitudinal cross-sectional view of the tank which concerns on the 1st Embodiment of this invention. It is a longitudinal cross-sectional view of the tank which concerns on the 2nd Embodiment of this invention. It is a longitudinal cross-sectional view of the tank which concerns on the 3rd Embodiment of this invention. It is a longitudinal cross-sectional view of the tank which concerns on the 4th Embodiment of this invention. It is a longitudinal cross-sectional view of the tank which concerns on the example of a change of this invention. It is a cross-sectional view of the tank which concerns on the example of a change of this invention. It is a cross-sectional view of the tank which concerns on the example of a change of this invention. It is a cross-sectional view of the tank which concerns on the example of a change of this invention.

(First embodiment)
Hereinafter, the exhaust gas purification system according to the first embodiment will be described with reference to FIGS. 1 and 2.
The exhaust gas purification system purifies exhaust gas from the diesel engine 11, and an exhaust manifold 12 that accumulates exhaust gas in one pipe line is connected to a plurality of exhaust ports of the diesel engine 11 as exhaust pipes. Yes. An exhaust pipe 13 is connected to the exhaust manifold 12 as an exhaust pipe, and exhaust gas is discharged into the atmosphere through the exhaust pipe 13. The exhaust pipe line 13 is provided with an enlarged diameter part 13A formed to have a diameter larger than the diameter of the pipe line connected to the exhaust manifold 12, and further provided with another enlarged diameter part 13B on the downstream side. A front-stage oxidation catalyst 16 is accommodated in the expanded diameter portion 13A, and an SCR catalyst 17 and a rear-stage oxidation catalyst 18 are sequentially accommodated in the expanded diameter portion 13B.

  A supply pipe 20 for supplying ammonia as a reducing agent for reducing NOx is connected between the enlarged diameter part 13A and the enlarged diameter part 13B of the exhaust pipe line 13. The supply pipe 20 controls the supply of ammonia. An electromagnetic valve 21 is connected. The solenoid valve 21 is connected to a controller (not shown), and the opening / closing of the solenoid valve 21 is controlled by the controller determining the operating state of the diesel engine 11 and the like. The supply pipe 20 branches to the first supply pipe 20A and the second supply pipe 20B on the upstream side of the electromagnetic valve 21, and the first supply pipe 20A and the second supply pipe 20B are connected to the tank 25, respectively. A check valve 22 is provided in the second supply pipe 20B. The supply pipe 20 is provided with a pressure gauge 23.

Next, details of the tank 25 will be described.
The tank 25 stores the ammonia storage material, and is provided at a location on the upstream side of the exhaust pipe 13 and in the vicinity of the exhaust manifold 12. The tank 25 is in contact with the outer periphery of the pipeline so as to cover the upstream side of the exhaust pipeline 13. In the present embodiment, the tank 25 is partitioned into a first chamber 31 on the upstream side of the exhaust pipe 13 and a second chamber 32 on the downstream side. Since the contact portion of the second chamber 32 with the exhaust pipe 13 is downstream of the contact portion with the first chamber 31 of the exhaust pipe line 13 when the exhaust gas flows, the second chamber 32 is in contact with the first chamber 31 of the exhaust pipe line 13. It is the part where the temperature is the same as or lower than that of the contact part. Both the first chamber 31 and the second chamber 32 are formed in an annular shape. The first supply pipe 20 </ b> A is connected to the outer peripheral surface of the first chamber 31, and the second supply pipe 20 </ b> B is connected to the outer peripheral surface of the second chamber 32. In the present embodiment, the first chamber 31 and the second chamber 32 are formed with the same capacity.

  A first ammonia storage material 41 is accommodated in the first chamber 31, and a second ammonia storage material 42 is accommodated in the second chamber 32. The 1st ammonia storage material 41 and the 2nd ammonia storage material 42 are arrange | positioned at the inner peripheral side in the 1st chamber 31 and the 2nd chamber 32 which are both annular | circular shaped, and the outer periphery of a 1st chamber and a 2nd chamber On the side, a space 31A and a space 32A for deriving ammonia are secured in the first supply pipe 20A and the second supply pipe 20B, respectively.

  The first ammonia storage material 41 is a solid ammonia adsorbent that desorbs ammonia at a predetermined temperature. In this embodiment, strontium chloride [Sr (NH3) 8CL2] is used. Strontium chloride [Sr (NH3) 8CL2] is a solid that desorbs ammonia at a first desorption temperature of approximately 80 degrees, and can adsorb ammonia at a temperature of 80 degrees or less. Magnesium chloride [Mg (NH3) 6CL2] is used for the second ammonia storage material 42, and desorption is performed at approximately 170 degrees as the second desorption temperature. The first ammonia storage material 41 and the second ammonia storage material 42 are accommodated in the first chamber 31 and the second chamber 32 by sintering powder and solidifying them into pellets. In FIG. 2, although the pellet of the 2nd ammonia storage material 42 is enlarged with respect to the 1st ammonia storage material 41, the magnitude | size of each pellet can be changed suitably.

The operation of this embodiment will be described.
When the diesel engine 11 is driven, the exhaust gas is discharged to the exhaust pipe 13 through the exhaust manifold 12 and flows in the exhaust pipe 13 downstream. Upstream of the exhaust pipe line 13, the heat of the exhaust gas is transmitted to the tank 25 through the peripheral surface of the exhaust pipe line 13 at a portion where the tank 25 contacts. The exhaust gas that has transmitted heat to the tank 25 flows to the enlarged diameter portion 13A, and a part of NOx in NOx is oxidized to NO2 by the pre-stage oxidation catalyst 16, and the ratio of NO and NO2 is adjusted to 1: 1. . Then, the exhaust gas flows further to the downstream enlarged diameter portion 13B.

  In the tank 25, the first ammonia storage material 41 is heated in the first chamber 31 on the upstream side in response to heat from the exhaust gas. When the temperature of the first ammonia storage material 41 is raised to the first desorption temperature, ammonia is released as a gas, and the released ammonia flows into the first supply pipe 20A via the space 31A in the first chamber 31. Go. Also in the second chamber 32, when the temperature of the second ammonia storage material 42 is raised by the heat from the exhaust gas and reaches the second desorption temperature, ammonia is released as a gas. The ammonia released from the second ammonia storage material 42 flows to the second supply pipe 20B through the space 32A. Although the check valve 22 is provided in the second supply pipe 20B, when the pressure in the second chamber 32 becomes higher than that in the first chamber 31, ammonia is released from the second supply pipe 20B to the supply pipe 20. It flows.

  Ammonia flowing through the first supply pipe 20 </ b> A and the second supply pipe 20 </ b> B is controlled to be released to the exhaust pipe 13 by an electromagnetic valve 21 provided in the supply pipe 20. A controller (not shown) controls the opening / closing timing or opening / closing timing of the solenoid valve 21 from signals such as the pressure gauge 23 provided in the supply pipe 20 and the rotational speed, fuel injection quantity, load, etc. of the diesel engine 11 to exhaust ammonia from the exhaust pipe. Supply to path 13.

  The exhaust gas that has passed through the enlarged diameter portion 13A is mixed with ammonia supplied from the supply pipe 20 and flows to the enlarged diameter portion 13B. In the expanded diameter portion 13B, the exhaust gas is reduced by the SCR catalyst 17 by ammonia with a reduction reaction of NOx to water and nitrogen. Then, downstream downstream oxidation catalyst 18 purifies the exhaust gas by reducing ammonia and NOx that have not contributed to the NOx reduction reaction. The purified exhaust gas is discharged from the exhaust pipe 13 into the atmosphere.

Here, the starting time of the diesel engine 11 will be described.
When the diesel engine 11 is started from a state where the tank 25 is at room temperature (about 20 degrees), the heat of the exhaust gas is transmitted to the tank 25, that is, the first chamber 31 and the second chamber 32, and the first ammonia storage material 41 and the first The diammonia storage material 42 is heated. The first chamber 31 is provided on the upstream side of the exhaust pipe 13 and can absorb heat from exhaust gas discharged from the engine. Since the second chamber 32 is provided on the downstream side of the first chamber 31, the second chamber 32 absorbs heat from the exhaust gas that has passed through the inner periphery of the first chamber 31.

  Further, in the first chamber 31, the first ammonia storage material 41 is arranged on the inner peripheral side in the first chamber 31, and there are more first ammonia storage materials 41 in the vicinity of the inner peripheral surface of the first chamber 31. Absorbs heat. Then, the temperature can be raised to about 80 degrees, which is the first desorption temperature, in a short time from the start of the diesel engine 11 to release ammonia.

Next, the time when the diesel engine 11 continues to be driven will be described.
When the diesel engine 11 continues to be driven, the temperature of the exhaust gas reaches a high temperature exceeding 200 degrees, and sufficient heat is transmitted to the first chamber 31 and the second chamber 32. In the first ammonia storage material 41, not only the inner peripheral side of the first chamber 31 but also the first ammonia storage material 41 on the outer peripheral side reaches the first desorption temperature and releases ammonia. Ammonia is released beyond 170 degrees which is the second desorption temperature. The released ammonia is supplied through the supply pipe 20 in an amount sufficient for NOx purification by driving the electromagnetic valve 21 in accordance with the driving of the diesel engine 11.

Next, the case where the diesel engine 11 is stopped will be described.
When the diesel engine 11 is stopped, the electromagnetic valve 21 is closed by the controller, and high-pressure ammonia is retained in each of the space 31A, the first supply pipe 20A, the space 32A, and the second supply pipe 20B. On the other hand, since the exhaust gas does not flow through the exhaust pipe 13, the tank 25 (the first chamber 31 and the second chamber 32) is not heated, and the first ammonia storage material 41 and the second ammonia storage material 42 are gradually naturally cooled. Go. When the second ammonia storage material 42 cools below the second desorption temperature (about 170 degrees), it adsorbs ammonia gas in the second chamber and also adsorbs ammonia in the second supply pipe 20B. Here, ammonia in the supply pipe 20 and the first supply pipe 20 </ b> A does not flow into the second chamber 32 by the check valve 22 and is not adsorbed by the second ammonia storage material 42.

When the temperature of the tank 25 drops from the second desorption temperature to the first desorption temperature (approximately 80 degrees) or less, the first ammonia storage material 41 starts to adsorb ammonia, and the ammonia in the first chamber 31 and the electromagnetic valve Ammonia in the first supply pipe 20 </ b> A that is upstream from 21 is adsorbed.
Then, when the diesel engine 11 is re-driven after the tank 25 is cooled to room temperature, ammonia is supplied from the first ammonia storage material 41 heated by the exhaust gas as described above, and the exhaust gas is purified. Is done.

Next, the filling of ammonia will be described.
When the driving of the diesel engine 11 is continued, the ammonia adsorbed on the first ammonia storage material 41 and the second ammonia storage material 42 in the tank 25 is consumed. When a predetermined drive time has elapsed, the tank may be replaced with a replacement tank 25 that houses the first ammonia storage material 41 and the second ammonia storage material 42 that have sufficiently adsorbed ammonia. Further, ammonia may be filled from a filling port (not shown) provided in the first chamber 31 and the second chamber 32 without replacing the tank 25. If ammonia is repeatedly charged every predetermined driving time, the exhausted ammonia purification system functions effectively because the charged ammonia is adsorbed by the first ammonia storage material and the second ammonia storage material.

According to the first embodiment, the following effects can be obtained.
(1) A tank 25 that houses the first ammonia storage material 41 and the second ammonia storage material 42 is provided in contact with the exhaust pipe 13. Since the tank 25 is disposed so as to be thermally coupled to the exhaust pipe 13, the heat of the exhaust gas of the diesel engine 11 can be used to heat the first ammonia storage material 41 and the second ammonia storage material 42. it can. A heater for heating that has been conventionally provided is unnecessary, and power consumption can be reduced and fuel consumption can be improved.

(2) Exhaust gas by using the first ammonia storage material 41 that is a first desorption temperature that is relatively close to normal temperature and the second ammonia storage material 42 that is a second desorption temperature higher than the first desorption temperature. Immediately after the engine is started at a low temperature, ammonia can be released and the SCR catalyst 17 can purify NOx.
(3) By disposing the tank 25 in the vicinity of the exhaust manifold 12 on the upstream side of the exhaust pipe 13 having a high exhaust gas temperature, the heat of the high-temperature exhaust gas immediately after being discharged from the diesel engine 11 can be used. Therefore, the tank 25 can be sufficiently warmed.

(4) In the tank 25, the first chamber 31 that houses the first ammonia storage material 41 having a separation temperature lower than that of the second ammonia storage material 42 is disposed on the upstream side. The first chamber 31 is more easily heated than the second chamber 32 on the downstream side, and the desorption temperature of the first ammonia storage material 41 is lower than that of the second ammonia storage material 42, so that ammonia is generated quickly even when the engine is started. can do.
(5) In the first chamber 31 and the second chamber 32, the first ammonia storage material 41 and the second ammonia storage material 42 are disposed on the inner peripheral side in contact with the exhaust pipe line 13. Therefore, it heats from the whole internal peripheral surface of the tank 25, and can heat the 1st ammonia storage material 41 and the 2nd ammonia storage material 42 rapidly.

(6) Since the first chamber 31 and the second chamber 32 are provided with the space 31A and the space 32A on the outer peripheral side, the ammonia released from the first ammonia storage material 41 and the second ammonia storage material 42 is smoothly supplied to the first supply pipe. It is possible to flow through 20A and the second supply pipe 20B.
(7) By providing the space 31A and the space 32A, the tank 25 will not be deformed even if the first ammonia storage material 41 and the second ammonia storage material 42 expand or contract when adsorbing or releasing ammonia. .

  (8) The supply pipe 20 is provided with an electromagnetic valve 21, and when the diesel engine 11 is stopped, the electromagnetic valve 21 is closed by a controller. Therefore, the space 31A, the first supply pipe 20A, the space 32A, and the second supply pipe 20B are respectively provided. The high-pressure ammonia present in can be retained. When the first ammonia storage material 41 and the second ammonia storage material 42 are naturally cooled to the first desorption temperature or the second desorption temperature or lower, the space 31A, the first supply pipe 20A, the space 32A, the second supply The ammonia retained in each of the tubes 20B can be re-adsorbed to the first ammonia storage material 41 and the second ammonia storage material 42.

(9) Since the check valve 22 is provided in the second supply pipe 20B, even when the diesel engine 11 is stopped and the second ammonia storage material 42 is cooled below the second desorption temperature, Ammonia can be adsorbed on the first ammonia storage material 41, and ammonia can be released from the first ammonia storage material 41 when the diesel engine 11 is restarted.
(10) Since the pellets of the first ammonia storage material 41 are formed smaller than the pellets of the second ammonia storage material 42, the pellets of the first ammonia storage material 41 have less heat than the pellets of the second ammonia storage material 42. The temperature is raised at, and ammonia can be released quickly.

(Second Embodiment)
Hereinafter, an exhaust gas purification system according to a second embodiment will be described with reference to FIGS. 1 and 3.
In the second embodiment, the shapes of the first chamber and the second chamber in the tank 25 are changed. The first chamber 51 is formed on the entire inner peripheral side of the tank 25. The second chamber 52 is provided on the outer peripheral surface of the first chamber 51, that is, on the outer peripheral side of the tank 25. The second chamber 52 is separated from the exhaust pipe 13 by the first chamber 51. Therefore, the second chamber 52 is in contact with the first chamber 51 and indirectly thermally coupled to the exhaust pipe line 13 via the first chamber 51. In addition, with this configuration, the second chamber 52 is in contact with the outer peripheral portion of the first chamber 51 that has the same temperature as or lower than the contact portion with the first chamber of the exhaust pipe line 13 when the exhaust gas flows. A first ammonia storage material 41 is accommodated in the first chamber 51, and a second ammonia storage material 42 is accommodated in the second chamber 52. A space 51A and a space 52A are provided on the downstream side of the first chamber 51 and the second chamber 52, so that ammonia flows smoothly. The first supply pipe 20A is connected to the space 51A, and the second supply pipe 20B is connected to the space 52A. The other configuration is the same as that of the first embodiment.

Next, the operation of this embodiment will be described.
When the diesel engine 11 is driven and the exhaust gas flows through the exhaust pipe 13, the tank 25 is warmed by the heat of the exhaust gas and the exhaust gas flows to the enlarged diameter portion 13A. Exhaust gas adjusts the NOx ratio by the pre-stage oxidation catalyst 16, and flows to the downstream enlarged diameter portion 13B. When the first ammonia storage material 41 and the second ammonia storage material 42 reach the first desorption temperature and the second desorption temperature, ammonia is released from the tank 25 heated by the exhaust gas, and the first supply pipe 20A and It flows from the supply pipe 20 to the exhaust pipe 13 via the second supply pipe 20B.

  When the exhaust gas flows into the enlarged diameter portion 13B together with ammonia from the supply pipe 20, NOx is reduced and purified by the SCR catalyst 17 to water and nitrogen. The downstream oxidation catalyst 18 prevents ammonia slip, and the purified exhaust gas is discharged from the exhaust pipe 13 to the atmosphere.

Here, the starting time of the diesel engine 11 will be described.
When the diesel engine 11 is started from a state where the tank is at room temperature (about 20 degrees), the heat of the exhaust gas is transmitted to the first chamber 51 of the tank 25. In the first chamber 51, when the first ammonia storage material 41 is heated to a temperature equal to or higher than the first desorption temperature, ammonia is released as a gas. The released ammonia flows from the supply pipe 20 into the exhaust pipe 13 through the first supply pipe 20A.

  If the diesel engine 11 is continuously driven after being started, the temperature of the exhaust gas increases and the heat transfer to the tank 25 also increases. Then, all the first ammonia storage materials 41 are heated to release ammonia, and heat is applied from the first chamber 51 to the second chamber 52. In the second chamber 52, when the second ammonia storage material 42 is heated and exceeds the second desorption temperature, ammonia is released. The released ammonia flows from the supply pipe 20 to the exhaust pipe 13 to reduce NOx.

According to the second embodiment, the following effects can be obtained in addition to the effects (1), (2), (3), (8), (9), and (10) of the first embodiment.
(11) In the tank 25, the first chamber 51 is formed on the inner peripheral side where the heat of the exhaust gas is easily received, and the second chamber 52 is in contact with the outer peripheral surface of the first chamber 51. The first ammonia storage material 41 having a low temperature can be warmed first, and heat can be absorbed from the exhaust gas through a wide area, so that ammonia is supplied quickly even when the exhaust gas is at a low temperature immediately after starting the engine. be able to.

(12) Since the space 51A and the space 52A are provided on the downstream side of the first chamber 51 and the second chamber 52, the ammonia released from the first ammonia storage material 41 and the second ammonia storage material 42 is smoothly supplied to the first supply pipe. It is possible to flow through 20A and the second supply pipe 20B.
(13) By providing the space 51A and the space 52A, the tank 25 is not deformed even if the first ammonia storage material 41 and the second ammonia storage material 42 expand or contract when adsorbing or releasing ammonia. .

(14) By providing the first chamber 51 so as to be in contact with the entire inner peripheral side of the tank 25, the heat of the exhaust gas can be transmitted to a larger amount of the first ammonia storage material 41. Even at times, a sufficient amount of ammonia can be supplied quickly.
(15) Since the second chamber 52 is provided on the outer peripheral side with respect to the first chamber 51, it is easy to ensure a large volume of the second chamber 52, and many second ammonia storage materials 42 having a high desorption temperature are provided. It can be accommodated and ammonia can be reliably supplied even if the load of the diesel engine 11 continues to be high.

(Third embodiment)
Hereinafter, an exhaust gas purification system according to a third embodiment will be described with reference to FIGS. 1 and 4.
In the third embodiment, a separation wall 63 that separates the first chamber 61 and the second chamber 62 is provided in the tank 25, and the separation wall 63 increases from the upstream to the downstream of the exhaust pipe 13. The first chamber 61 and the second chamber 62 are partitioned so that the outer diameter of the first chamber 61 becomes smaller. Other configurations are the same as those of the first embodiment.

The operation of this embodiment will be described.
When the diesel engine 11 is driven, the exhaust gas flows through the exhaust pipe 13 and flows to the downstream enlarged diameter portion 13A while warming the tank 25. The exhaust gas is adjusted in the NOx ratio by the pre-stage oxidation catalyst 16 and flows to the downstream enlarged diameter portion 13A. From the tank 25 heated by the exhaust gas, ammonia is released from the first ammonia storage material 41 and the second ammonia storage material 42, and ammonia is supplied from the supply pipe 20 to the exhaust pipe line 13.

  The exhaust gas is purified with NOx in the SCR catalyst 17 of the expanded diameter portion 13B together with ammonia, and the exhaust gas purified by reducing ammonia and NOx in the post-stage oxidation catalyst 18 is released into the atmosphere.

The starting time of the diesel engine 11 will be described.
When the diesel engine 11 is started in a state where the tank is at room temperature (about 20 degrees), the heat of the exhaust gas is transmitted to the first chamber 61 of the tank 25 and the temperature is raised from the first ammonia storage material 41 on the inner peripheral side. The exhaust gas warming the first chamber 61 warms the inner peripheral side of the second chamber 62 on the downstream side in direct contact with the exhaust pipe 13 and flows downstream. In the first chamber 61, ammonia is released when the first ammonia storage material 41 reaches the first desorption temperature. The released ammonia flows from the supply pipe 20 into the exhaust pipe 13 through the first supply pipe 20A.

  If the diesel engine 11 continues to be driven thereafter, the exhaust gas temperature increases and the heat transfer to the tank 25 also increases. Then, the temperature of the first ammonia storage material 41 on the inner peripheral side is also raised and the release of ammonia is continued, and heat is transferred from the first chamber 61 to the second chamber 62 via the separation wall 63, and the second ammonia storage material. When 42 is heated from both the exhaust pipe 13 and the first chamber 61 and exceeds the second desorption temperature, ammonia is released.

According to the present embodiment, the following effects can be obtained in addition to the effects of the first embodiment.
(16) Since the tank 25 is provided with the separation wall 63 for separating the first chamber 61 and the second chamber 62 so that the outer diameter of the first chamber 61 becomes smaller from the upstream to the downstream of the exhaust pipe 13. The area where the first chamber 61 contacts the exhaust pipe 13 is increased, the heat of the exhaust gas is easily transmitted to the first ammonia storage material 41, and the first ammonia storage material 41 can be quickly transferred even when the exhaust gas temperature is low, such as immediately after the engine is started. The temperature can be raised to the desorption temperature.

(Fourth embodiment)
Hereinafter, an exhaust gas purification system according to a fourth embodiment will be described with reference to FIGS. 1 and 5.
In the fourth embodiment, a heater 70 is provided in the first chamber 61 of the tank 25 in the third embodiment. The heater 70 is inserted from the upstream end face of the first chamber 61 to the vicinity of the separation wall 63. The heater 70 is controlled by a controller (not shown). Other configurations are the same as those of the third embodiment.

The operation of this embodiment will be described.
When the diesel engine 11 is driven, the exhaust gas flows through the exhaust pipe 13 and flows to the downstream enlarged diameter portion 13A while warming the tank 25. The exhaust gas is adjusted in the NOx ratio by the pre-stage oxidation catalyst 16 and flows to the downstream enlarged diameter portion 13A. From the tank 25 heated by the exhaust gas, ammonia is released from the first ammonia storage material 41 and the second ammonia storage material 42, and ammonia is supplied from the supply pipe 20 to the exhaust pipe line 13.

  The exhaust gas is purified with NOx in the SCR catalyst 17 of the expanded diameter portion 13B together with ammonia, and the exhaust gas purified by reducing ammonia and NOx in the post-stage oxidation catalyst 18 is released into the atmosphere.

The starting time of the diesel engine 11 will be described.
When the diesel engine 11 is started in a state where the tank is at room temperature (about 20 degrees), the heat of the exhaust gas is transmitted to the first chamber 61 of the tank 25 and is heated from the first ammonia storage material 41 on the inner peripheral side. Go. The exhaust gas warming the first chamber 61 warms the inner peripheral side of the second chamber 62 on the downstream side in direct contact with the exhaust pipe 13 and flows downstream. In the present embodiment, when the controller (not shown) detects the start of the diesel engine 11, the heater 70 is energized to directly heat the first ammonia storage material 41. In the first chamber 61, ammonia is released when the first ammonia storage material 41 reaches the first desorption temperature. The released ammonia flows from the supply pipe 20 into the exhaust pipe 13 through the first supply pipe 20A.

  If the diesel engine 11 continues to be driven thereafter, the exhaust gas temperature increases and the heat transfer to the tank 25 also increases. Then, the temperature of the first ammonia storage material 41 on the inner peripheral side is also raised and the release of ammonia is continued, and heat is transferred from the first chamber 61 to the second chamber 62 via the separation wall 63, and the second ammonia storage material. When 42 is heated from both the exhaust pipe 13 and the first chamber 61 and exceeds the second desorption temperature, ammonia is released. At this time, if the controller determines that the diesel engine 11 is continuously driven for a predetermined time or longer, the controller stops energization of the heater 70.

According to the present embodiment, in addition to the effects of the first embodiment and the effects of the third embodiment, the following effects can be obtained.
(17) Since the heater 70 is provided in the first chamber 61 of the tank 25 and the first ammonia storage material 41 is directly heated when the diesel engine 11 is started, ammonia can be supplied more quickly from the start of the diesel engine 11. it can.
(18) Since the first ammonia storage material 41 is also heated from the exhaust pipe 13 by the heat of the exhaust gas, the usage time of the heater 70 can be shortened, and fuel consumption deterioration due to power supply can be suppressed.

The present invention is not limited to the above-described embodiment, and modifications of the present invention will be described below.
Although the tank 25 is provided on the upstream side of the enlarged diameter portion 13A of the exhaust pipe 13, it may be provided so as to be in contact with the exhaust manifold 12. The upstream side where the exhaust gas is hot is preferable, and either the exhaust line 13 or the exhaust manifold 12 may be contacted. The exhaust pipe of the present invention is composed of the exhaust manifold 12 and the exhaust pipe line 13.

  As shown in FIG. 6, in the tank 25 of the first embodiment, the first chamber 31 may have a tapered shape whose diameter decreases toward the upstream side. The first chamber 81 is tapered so that the amount of the first ammonia storage material 41 on the upstream side of the exhaust gas is reduced and the heat capacity is partially lowered to make it easier to warm, thereby increasing the temperature of the exhaust gas more efficiently. Can be used for Thereby, the time for the first ammonia storage material 41 to reach the first desorption temperature can be shortened.

  ○ The tank 25 may not be annular. As shown in FIG. 7, the tank 25 of the second embodiment may be formed as a tank 90 (first chamber 91, second chamber 92) so as to cover a part of the exhaust pipe 13 while being opened. Further, the tank may be formed so that a part (first chamber) of the tank is in contact with the exhaust pipe line 13 and not to cover the exhaust pipe line 13.

  ○ The shape and size of the first chamber and the second chamber can be appropriately changed. The tank 25 in the second embodiment may be an elliptical tank 93 as shown in FIG. The first chamber 94 and the second chamber 95 are also elliptical, and the size may be adjusted as appropriate. In the first embodiment, the first chamber 31 and the second chamber 32 have the same capacity, but the first chamber 31 may be a short ring and the second chamber 32 may be changed to a long ring.

  The first chamber and the second chamber may be connected in parallel to the same location on the exhaust path flowing from the upstream to the downstream of the exhaust pipe. For example, as shown in FIG. 9, the tank 96 is disposed so as to cover the entire outer periphery of the exhaust pipe line 13, the first chamber 97 is formed in a semicircular shape in the tank 96, and the second chamber 98 is further formed in the tank 96. You may form in the semicircle shape symmetrical with the 1st chamber 97. FIG. Thereby, heat from the exhaust gas can be similarly transmitted to the first chamber 97 and the second chamber 98 via the exhaust pipe 13.

  The heater 70 provided in the tank 25 in the fourth embodiment may be similarly provided in the first chamber in the other embodiments. Heating by the heater 70 makes it possible to supply ammonia even when the exhaust gas is at a low temperature. By heating the tank 25 in contact with the exhaust manifold 12 and the exhaust pipe 13, the energization time of the heater 70 can be shortened, and the fuel consumption is reduced. Can be prevented from worsening.

  In the present invention, strontium chloride [Sr (NH3) 8CL2] is used as the first ammonia storage material 41, and magnesium chloride [Mg (NH3) 6CL2] is used as the second ammonia storage material 42. May be used. For example, calcium chloride [Ca (NH3) 8CL2] may be used, and the first separation temperature and the second separation temperature can be appropriately changed according to the displacement of the diesel engine 11 or the place where the tank 25 is brought into contact with the exhaust pipe 13. The solid ammonia adsorbent may be changed according to the desorption temperature.

11 Diesel Engine 12 Exhaust Manifold 13 Exhaust Pipe 13A Expanded Part 13B Expanded Part 16 Pre-stage Oxidation Catalyst 17 Reduction Catalyst 18 Subsequent Oxidation Catalyst 20 Supply Pipe 20A First Supply Pipe 20B Second Supply Pipe 21 Electromagnetic Valve 22 Check Valve 23 Pressure gauge 25 Tank 31 First chamber 31A Space 32 Second chamber 32A Space 41 First ammonia storage material 42 Second ammonia storage material

Claims (7)

An exhaust pipe connected to the exhaust port of the engine to guide the exhaust gas,
A reduction catalyst housed in the exhaust pipe and reducing NOx in the exhaust gas;
An ammonia storage material capable of adsorbing and desorbing ammonia;
A tank for storing the ammonia storage material,
In the exhaust gas purification system for supplying ammonia desorbed from the ammonia storage material to the exhaust pipe upstream of the reduction catalyst from the tank,
The exhaust gas purification system, wherein the tank is disposed so that at least a part thereof is in contact with the exhaust pipe, and heat of the exhaust gas can be transmitted to the ammonia storage material in the tank. The tank
A first chamber containing a first ammonia storage material from which ammonia is desorbed at a first desorption temperature;
2. The exhaust gas purification system according to claim 1, further comprising a second chamber containing a second ammonia storage material from which ammonia is desorbed at a second desorption temperature higher than the first desorption temperature. .   The first chamber is in contact with the exhaust pipe, and the second chamber is in contact with a portion of the exhaust pipe that is at the same temperature as or lower than the contact portion with the first chamber when the exhaust gas flows. The exhaust gas purification system according to claim 2, wherein   The exhaust gas purification system according to claim 3, wherein the first chamber is in contact with the exhaust pipe upstream of the second chamber.   The first chamber is in contact with the exhaust pipe, the second chamber is in contact with the first chamber, and is indirectly thermally coupled to the exhaust pipe through the first chamber. The exhaust gas purification system according to claim 3. The tank covers the outer periphery of the exhaust pipe,
A separation wall separating the first chamber and the second chamber;
The exhaust gas purification system according to claim 4, wherein the separation wall is separated and formed so that the outer diameter of the first chamber gradually decreases from the upstream to the downstream of the exhaust pipe.   The exhaust gas purification system according to any one of claims 2 to 6, wherein the tank is provided with a heater for heating the first ammonia storage material.

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