JP2009062860A - Engine exhaust treatment system - Google Patents

Abstract

【Task】
Urea is supplied as a reducing agent to reduce NOx discharged from the diesel engine. An object of the present invention is to provide an exhaust treatment device that efficiently supplies heater heat to urea water spray, promotes hydrolysis after vaporization, and supplies the generated ammonia gas to a denitration catalyst.
[Solution]
A shield having a reflecting portion 61 and an opening 62 in the heat transfer tube 42 in order to efficiently promote vaporization of the urea water spray 35 as a reducing agent using the heat transfer tube 42 utilizing the heat of the heater 43 and generate ammonia. A plurality of members 60 are disposed, and a hydrolysis catalyst 44 is disposed downstream thereof. Here, the inner wall surface temperature of the heat transfer tube 42 and the temperature of the shielding member 60 are set to be equal to or higher than the film boiling temperature at which the urea water spray 35 vaporizes.
[Selection] Figure 6

Description

  The present invention relates to an exhaust treatment device, and in particular, in an exhaust treatment device for efficiently removing nitrogen oxides in exhaust gas by using urea water as a reducing agent, the urea water is efficiently removed by heater heat as a heating element. It relates to technology to promote vaporization.

  As a method for removing nitrogen oxides (hereinafter referred to as NOx) contained in exhaust gas from a diesel engine or the like, a selective reduction catalyst that selectively reacts NOx with a reducing agent is disposed in a flue through which exhaust gas flows, and this upstream A technique is known in which a reducing agent (for example, hydrocarbon, ammonia or a precursor thereof) is added to the exhaust on the side, and the reducing agent is subjected to a reduction reaction with NOx on a selective reduction catalyst to reduce the NOx emission concentration. .

  A NOx reduction method using this selective reduction catalyst is called SCR (Selective Catalytic Reduction), and a method using urea as a reducing agent is called urea SCR.

  As an example of applying this urea SCR to a vehicle, there is a technique in which urea water is injected into a flue from an injection nozzle, urea is hydrolyzed using exhaust heat, and NOx is reduced using generated ammonia. It is known (for example, refer nonpatent literature 1).

  In this case, for example, the urea water is stored in a tank, the urea water supplied from the tank and the compressed air supplied from the vehicle side are mixed in the mixing chamber, and this is discharged into the exhaust from the injection nozzle in the flue. Spray. Here, the urea water amount is adjusted by controlling the drive pulse width of the solenoid valve, and the compressed air amount is regulated by electronic control.

  Further, an exhaust treatment device comprising an exhaust flue of an engine, a denitration catalyst reactor provided in the exhaust flue, and an injection valve for injecting and supplying urea water, provided with an exhaust gas diversion means, A first injection valve that injects urea water into the diverted exhaust gas is provided, and a vaporizer that heats the urea water injected from the first injection valve to form urea vapor is disposed. There is a configuration in which a second injection valve for injecting urea water is installed on the downstream side. This is because urea vapor generated from the urea water spray injected from the first injection valve is supplied to the exhaust flue at a relatively low exhaust temperature, and urea injected from the second injection valve at a high exhaust temperature. This is an engine exhaust treatment device that supplies water spray to an exhaust flue (see, for example, Patent Document 1).

JP 2006-170013 A Automotive Technology Vol.57, No.9 (2003) pp.94-99

  In the SCR device as described above, a predetermined amount of urea water commensurate with NOx discharged from the engine is added almost uniformly to the denitration catalyst, and it is rapidly hydrolyzed to produce ammonia and can react with NOx on the denitration catalyst. It is required to do so. In order to reduce NOx more efficiently, it is preferable to ammonia the urea water before reaching the denitration catalyst and to disperse the ammonia almost uniformly in the denitration catalyst.

  For example, in Non-Patent Document 1, urea water mixed with compressed air is disposed in the vicinity of the central portion of the flue upstream of the denitration catalyst at the tip of a pipe provided to extend into the flue. This improves the dispersibility of urea water in the denitration catalyst. Here, the spray sprayed hydrolyzes urea water using exhaust heat, and NOx is reduced by ammonia generated thereby. This can be said to be effective in terms of NOx reduction at high exhaust temperatures, but good at low exhaust temperatures because hydrolysis due to exhaust heat of urea water injected into the flue cannot be promoted. There is concern that no NOx reduction effect can be expected.

  Further, in Patent Document 1, urea water spray injected from the first injection valve at low exhaust temperature is supplied into the exhaust flue after the urea vapor is generated by a vaporizer, and the urea water spray is supplied at high exhaust temperature. The urea water spray injected from the injection valve 2 is directly supplied into the exhaust flue. This makes it possible to obtain high denitration performance in the entire engine operating range from the low exhaust temperature to the high exhaust temperature of the engine. The carburetor is composed of a heat transfer tube and a heater, and urea water injected from the first injection valve during the swirl flow in which the swirl flow is formed in the exhaust gas flowing into the heat transfer tube in order to promote the vaporization of urea water. Spray is being supplied. As a result, urea water droplets during the spraying of urea water are guided to the inner wall surface of the heat transfer tube, and a time for contacting the droplets on the inner wall surface of the heat transfer tube is secured to promote vaporization.

  However, there is a distribution in the spray particle size in the urea water spray injected from the first injection valve. Since spray droplets with a distribution exist from minute droplets to coarse droplets, all the spray droplets are accompanied by a swirling flow that flows through the heat transfer tube and contact the inner wall surface of the heat transfer tube to promote vaporization. It is not always done. That is, for example, a coarse droplet (a droplet having a heavy mass) in a spray injected at a predetermined pressure from the first injection valve does not accompany the swirl flow when it is injected at a predetermined flow velocity. There is a concern that it is injected substantially linearly downstream in the injection direction and passes through the vaporizer without contacting the inner wall surface of the heat transfer tube. There is a concern that urea water spray droplets that directly reach each passage on the downstream side of the heat transfer tube without contacting the inner wall surface of the heat transfer tube of the vaporizer may precipitate urea in each passage. When urea deposits in each passage, it prevents the urea water spray, which is a predetermined amount of reducing agent commensurate with the NOx emission amount discharged from the engine, for reducing NOx from being efficiently supplied to the denitration catalyst. This eventually leads to waste of urea water. In addition, when it is attempted to completely vaporize the urea water spray using the above technique, it is necessary to increase the residence time of the liquid droplets in the heat transfer tube, so there is a concern that a relatively large heat transfer tube is required. Is done.

  An object of the present invention is to efficiently hydrolyze urea water injected and supplied into a flue in all operating regions including low exhaust temperature to high exhaust temperature of an engine, and to supply ammonia to a denitration catalyst after generating ammonia. Accordingly, an object of the present invention is to provide an exhaust treatment device that ensures a high NOx reduction rate (denitration rate).

  In order to achieve the above object, the present invention mainly employs the following configurations and operations.

  An exhaust treatment apparatus for introducing exhaust gas into a denitration catalyst reactor provided in an exhaust flue to reduce nitrogen oxides in the presence of a denitration catalyst, having an injection valve upstream of the denitration catalyst, A vaporizer with a heater for vaporizing urea water injected from the valve, and the vaporizer is configured such that a heater is disposed on an outer peripheral portion of the heat transfer tube, and urea water and exhaust gas are disposed in the heat transfer tube; In the exhaust treatment apparatus for supplying urea water vaporized by the vaporizer into the flue, a plurality of stages of shielding members are arranged in the heat transfer tube. The said shielding member has a reflection part and opening which reduce and expand the passage cross-sectional area of a heat transfer pipe axial direction perpendicular | vertical cross section. Moreover, it has the reflection part which guide | induces the spraying droplet injected in the heat exchanger tube on the inner wall surface of a heat exchanger tube, and makes it collide.

  Further, the surface temperature of the shielding member is set to be equal to or higher than the film boiling temperature that vaporizes while holding the droplets when the sprayed droplets collide. Here, the spray which collided with the reflection part has a function of reflecting the spray on the inner wall surface of the heat transfer tube while promoting vaporization while film boiling on the reflection part surface.

  Furthermore, the opening part and the reflection part of the shielding member are arranged to be inclined at a predetermined angle with respect to the vertical cross section in the axial direction of the heat transfer tube, and the respective shielding members are arranged in the opening direction of the adjacent shielding member in the axial direction of the heat transfer tube and The reflecting portions are arranged at different positions so as not to coincide with the same axis in the axial direction of the heat transfer tube.

  Furthermore, each said shielding member has a parallel part which has predetermined length in a heat exchanger tube axial flow direction, in order to expand a contact area with the heat exchanger tube inner wall surface.

  Furthermore, a hydrolysis catalyst in which a catalyst is supported on a metal base material is disposed in the heat transfer tube on the downstream side of the shielding member group or on the downstream side thereof.

  According to the present invention, it is possible to efficiently supply heater heat and exhaust heat to urea water spray droplets that pass through a heat transfer tube, which is a vaporizer, at a low exhaust temperature, and to promote vaporization of urea water spray. Therefore, since urea water vapor can be supplied to the hydrolysis catalyst disposed in the heat transfer tube or downstream thereof, the hydrolysis reaction can be promoted and ammonia can be efficiently generated. Furthermore, since the produced ammonia is supplied to the denitration catalyst, high denitration performance can be ensured at a low exhaust temperature. Therefore, a high denitration rate can be ensured in the entire operation region from the low exhaust temperature of the engine to the high exhaust temperature.

  In the present invention, the urea water injected and supplied into the flue is efficiently hydrolyzed in the entire operation region including the low exhaust temperature to the high exhaust temperature of the engine, and ammonia is generated and then supplied to the denitration catalyst. An object of the present invention is to provide an exhaust treatment device that ensures a high NOx reduction rate (denitration rate). For that purpose, it is important to secure an efficient NOx reduction rate at a low exhaust temperature. In order to ensure an efficient NOx reduction rate at low exhaust temperatures, urea water, which is a reducing agent, should not be precipitated on the inner wall of the flue, etc., and is converted to ammonia gas by a hydrolysis reaction and then supplied to the denitration catalyst. This is very important.

  For this purpose, the spraying of urea water supplied into the heat transfer tube is efficiently promoted to prevent vaporization of urea droplets that cause urea precipitation on the inner wall of the flue to the outside of the heat transfer tube. Alternatively, it is an object to efficiently promote the hydrolysis reaction of urea water spray and urea vapor by the hydrolysis catalyst disposed downstream thereof, and supply it as ammonia gas to the flue and to the denitration catalyst.

  By solving the above problem, it is possible to suppress the urea water spray droplets from flowing out of the heat transfer tube. In addition, urea deposition on the inner wall of the flue can be suppressed. Further, by allowing the hydrolysis catalyst to pass after vaporizing the urea water spray, the hydrolysis reaction can be promoted, and ammonia can be generated efficiently. Therefore, it is possible to supply the generated ammonia to the denitration catalyst, and it is possible to provide an exhaust treatment device capable of realizing a high NOx denitration performance.

  Specifically, according to the present invention, a plurality of stages of shielding members having a reflection portion, an opening portion, and a parallel portion are arranged in the heat transfer tube, and when the spray droplet collides with the surface temperature of the shielding member, An exhaust treatment apparatus having a vaporizer characterized by being a film boiling temperature or higher that vaporizes while retaining droplets, and described below by injecting urea water spray injected from an injection valve into a heat transfer tube Effect is obtained.

  (1) The spray droplets injected from the injection valve into the heat transfer tube collide with the reflecting portions of the shielding members at the respective stages heated to the film boiling temperature or more of the spray, whereby the spray is liquid on the reflecting portion surface. At the same time as vaporization is promoted while the film is boiling in the form of droplets, it becomes possible to reflect and positively impinge on the inner wall surface of the heat transfer tube, which is the heating surface. Transmission can be promoted, and vaporization of droplets can be promoted. Therefore, vaporization can be promoted while suppressing urea precipitation in the heat transfer tube. Furthermore, compared with the case where the spray is sprayed in the axial direction in the heat transfer tube of the smooth tube without the shielding member, the vaporization time until the spray droplets are completely vaporized can be greatly shortened. Downsizing (shortening of heat transfer tube length).

  (2) By arranging a plurality of shielding members in the heat transfer tube, the opening area formed by the reflection portion and the opening of each shielding member is compared with the vertical cross-sectional area in the axial direction in the case of only the heat transfer tube, Depending on the number of steps of each shielding member, the flow is repeatedly contracted and expanded. Further, in a plurality of shielding members arranged in the axial direction of the heat transfer tube, the attachment positions of the reflection portions and the opening portions of adjacent shielding members are arranged at different positions so as not to coincide with each other on the same axis. By these, compared with the case where a shielding member is not disposed in the heat transfer tube, when the shielding member is disposed, it is possible to realize a change in the exhaust flow velocity passing through the heat transfer tube and to form a swirling flow. Therefore, it is possible to create turbulence (turbulent flow) in the exhaust flow that flows in the heat transfer tube, and because the evaporation layer of the droplet that vaporizes in the heat transfer tube can be made thin, heat transfer between the exhaust and the droplet is accelerated. As a result, vaporization of the droplets can be promoted.

  (3) Furthermore, the swirl flow (number of times) of the exhaust flow and the spray droplet flow in the heat transfer tube can be realized by the number of stages in which the shielding members are arranged in the heat transfer tube. Therefore, the trace (trajectory) length of the droplets passing through the heat transfer tube due to the swirling flow in the heat transfer tube can be increased. For example, in a heat transfer tube of the same length, the flow length (trajectory) of the droplet can be increased by arranging a plurality of shielding members, so that the heat from the inner wall surface of the heat transfer tube and the exhaust droplet is sprayed. Time to give and receive can be secured, and vaporization can be promoted. Furthermore, the heat transfer tube can be downsized (the length of the heat transfer tube can be shortened).

  (4) By arranging a plurality of shielding members in the heat transfer tube, it is possible to realize the projection of the reflection member of the shielding member in the heat transfer tube, so that the reflection portion becomes a radiating fin, and the exhaust gas flows through the heat transfer tube. It is possible to raise the temperature of the liquid, and it is possible to promote vaporization of spray droplets by exhaust. Furthermore, it is possible to quickly raise the temperature of the hydrolysis catalyst in which the catalyst is supported on the metal base material disposed downstream of the shielding member to the activation temperature by raising the temperature of the exhaust gas.

  (5) Since the spray droplets that do not collide with the heating surface of the inner wall surface of the heat transfer tube or the reflection portion can be drastically reduced by causing the spray droplets to collide with the reflecting part of the shielding member, It can suppress flowing out of the heat transfer tube.

  Examples of the present invention will be described below.

  An exhaust treatment apparatus according to an embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a diagram showing an overall configuration of an exhaust treatment device according to an embodiment of the present invention and its peripheral configuration, and FIG. 2 is a diagram of a urea addition device 70 shown in part A of the exhaust treatment device shown in FIG. An external perspective view is shown. FIGS. 3A and 3B are B and C direction views of the external perspective view of the urea addition device 70 shown in FIG. 2, respectively. FIG. 4 is an EE cross-sectional view of the urine addition device 70 shown in FIG. FIG. 5 is a DD cross-sectional view of the urea addition device 70 shown in FIG. FIG. 6 shows an enlarged view of a portion F of the urea addition device 70 shown in FIG. 5 and a representative flow line 55 of the shunt exhaust 14 flowing in the heat transfer tube. 7A, 7B, and 7C, respectively, the shielding member 60 disposed in the heat transfer tube 42 of the urea addition device 70, and the shielding member when the shielding member 60 is combined in four stages. 60 is a set view, and each perspective view of the heat transfer tube swirl blade 30 is shown. FIG. 8 is a diagram showing the effect of shortening the droplet evaporation time when the urea adding apparatus 70 of the present invention is applied. FIG. 11 shows the results of examining the boiling form of urea water spray droplets on the heating plate with respect to the urea water mass concentration.

  As shown in FIG. 1, the exhaust treatment apparatus of the present embodiment includes, for example, a urea addition apparatus 70 for supplying urea water as a reducing agent into a flue through which exhaust 12 discharged from the diesel engine 1 flows, A fine particle removing device DPF (Diesel Particulate Filter) 17 for removing fine particles such as black smoke particles and a urea addition device 70 disposed upstream and for treating NOx in the exhaust gas. A denitration catalyst (SCR: Selective Catalytic Reduction) 18 is provided.

  The denitration catalyst 18 has a function of accelerating the reduction reaction of NOx in the exhaust 12 and reducing the discharge amount of NOx to the outside air by urea water as a reducing agent and its vapor and ammonia generated by a hydrolysis catalytic reaction. Catalyst. In addition, on the downstream side of the denitration catalyst 18, a flue, a muffler, and the like (not shown) are disposed and communicate with the outside air.

  As shown in FIGS. 1 to 6, the urea addition device 70 is provided with two main injection valves 26 for supplying urea water 4 into the flue 10 formed therein and two sub injection valves 27. ing. The main injection valve 26 is used when injecting the urea water 4 into the flue 10, and the sub injection valve 27 injects the urea water 4 into the heat transfer pipe 42 through which the diverted exhaust gas 14, which will be described later, passes. Used when.

  The spray 34 injected from the main injection valve 26 is injected into a relatively wide space 36 formed in the flue 10.

  In addition, in the flue 10 of the urea addition device 70, a throttle 20 having a passage sectional area once reduced is formed on the downstream side of the space 36. A mainstream swirl vane 19 for generating a swirl flow in the exhaust 13 flow is disposed in the throttle 20 portion. Further, the space of the throttle 20 portion and the space 36 in the flue 10 on the upstream side thereof are communicated with each other by a diversion passage 41 that is a bypassed passage. The other end of the diversion passage 41 has an opening at the diversion passage inlet 40 so as to face the flow of the exhaust gas 13 along the axial flow direction flowing in the flue 10 on the upstream side of the throttle 20 portion. Yes. The branch passage inlet 40 communicates with the swirl chamber 33 disposed on the downstream side of the branch passage 41. A heat transfer tube swirl blade 30 is disposed in the swirl chamber 33. A heat transfer tube 42 is disposed on the downstream side of the heat transfer tube swirl blade 30, and a plurality of stages (in the present embodiment, four steps) of shielding members 60 are disposed inside the heat transfer tube 42.

  The shielding member 60 includes a reflecting portion 61 and an opening 62 that reduce and enlarge the passage cross-sectional area of the heat transfer tube 42 in the axial flow direction vertical cross section. Moreover, it has the reflection part 61 which guides the spraying droplet injected in the heat exchanger tube 42 on the inner wall surface of a heat exchanger tube, and makes it collide. Further, the reflecting portion 61 and the opening 62 of the shielding member 60 are disposed at a predetermined angle with respect to the vertical cross section in the axial direction of the heat transfer tube 42, and the shielding members 60 are adjacent to each other in the axial direction of the heat transfer tube 42. The reflection part 61 and the opening part 62 of the member 60 are arrange | positioned in a different position so that it may not correspond to the same axis | shaft in the heat exchanger tube axial flow direction. Further, each shielding plate 60 member has a parallel portion 63 having a predetermined length in the axial direction of the heat transfer tube 42 in order to increase the contact area with the inner wall surface of the heat transfer tube 42.

  Further, a hydrolysis catalyst 44 is disposed inside the heat transfer tube 42 on the downstream side of the shielding member 60 group disposed in the heat transfer tube 42. A heater 43, which is a heating element, is disposed on the outer peripheral portion of the heat transfer tube 42. The heater 43 is heated to heat the inner wall surface of the heat transfer tube 42 and promote vaporization of the spray 35 flowing inside the heater. An outer cylinder 47 is disposed on the outer peripheral portion of the heater 43 to provide a heat insulating structure in which the heater 43 is not in direct contact with the outside air. A heat insulating layer 53 that is a space is formed between the heater 43 and the inner wall of the outer cylinder 47. The heat insulating layer 53 has a structure that communicates with the inside of the outer cylinder bottom 50 described later.

  An outer cylinder bottom 50 communicating with the inside of the outer cylinder 47 is disposed on the downstream side of the hydrolysis catalyst 44 disposed inside the heat transfer tube 42, and a hydrolysis catalyst 51 is disposed at the outlet of the outer cylinder bottom 50. It is arranged.

  The outlet portion of the hydrolysis catalyst 51 communicates with the pressure regulating chamber 45 in the annular space formed by the outer wall portion of the throttle 20 and the inner wall portion of the wall 21. The pressure regulation chamber 45 has a plurality of ammonia ejection holes 46 bored in the throttle 20 part, and the pressure regulation chamber 45 and the inside of the throttle 20 part communicate with each other through the ammonia ejection hole 46. Therefore, the space 36 in the flue 10 upstream of the throttle 20 includes the branch passage inlet 40, the branch passage 41, the swirl chamber 33, the heat transfer pipe 42, the outer cylinder bottom 50, the pressure regulating chamber 45, and the ammonia ejection hole. The configuration communicates with the inside of the diaphragm 20 through 46. Here, the ammonia ejection hole 46 formed in the throttle 20 is disposed on the downstream side of the mainstream swirl vane 19.

  Next, the supply path to each part of the urea water 4 will be described. The urea water 4 stored in advance in the urea water tank 3 is sucked by the pump 6 through the filter 5, and then the urea water 4 discharged from the pump 6 is given to the main injection valve 26 and the sub injection valve 27. Supplied with pressure. Here, the pressure adjustment to the main injection valve 26 and the sub injection valve 27 is performed by the pressure adjusting valve 7 provided in the flow path branched in the flow path communicating with the tank 3 on the downstream side of the pump 6. Pressed.

  The urea addition device 70 of the present embodiment performs reduction in a relatively wide operation range from a low load region with a low exhaust temperature and a small displacement to a high load region with a high exhaust temperature and a large amount of exhaust, such as when the engine is started. In order to quickly supply a predetermined amount of urea water as an agent to the denitration catalyst 18, it is possible to change the supply form of urea water supplied from the urea addition device 70 into the flue 10.

  Details will be described below.

  The supply of the urea water spray 34 supplied from the main injection valve 26 mainly used at the high exhaust temperature to the denitration catalyst 18 will be described.

  In the exhaust treatment apparatus of the present embodiment, the exhaust 13 that has passed through the DPF 17 is supplied to a relatively wide space 36 in the flue 10 of the urea addition apparatus 70. Here, the urea water spray 34 injected from the main injection valve 26 into the space 36 in the flue 10 is promoted to be hydrolyzed together with evaporation of the droplets in the spray 34 by the transfer of heat of the exhaust gas 13, and ammonia. Generation is promoted.

  Further, the flue 10 on the downstream side of the space 36 communicates with a throttle 20 having a reduced passage cross-sectional area, and a mainstream swirl vane 19 is disposed in the throttle 20 part. Therefore, the flow rate of the exhaust 13 increases by passing through the throttle 20 part accompanying the air flow of the exhaust 13, and the flow disturbance due to the generation of the swirl flow at the throttle 20 part by passing through the mainstream swirl blade 19. As a result, mixing of the exhaust 13 and the spray 34 is promoted and vaporization is promoted.

  Due to the effects of the exhaust 13 flow, the throttle 20 and the mainstream swirl vane 19, the spray 34 injected from the main injection valve 26 is accelerated and hydrolyzed by the water contained in the high-temperature exhaust 13 and the exhaust gas. Is promoted, it is possible to supply urea spray droplets, steam and ammonia almost uniformly to the denitration catalyst 18, and high denitration performance can be obtained.

  Next, the supply of the urea water spray 34 supplied from the sub-injection valve 27 mainly used at the low exhaust temperature to the denitration catalyst 18 will be described.

  The diverted exhaust gas 14, which is a part of the exhaust gas 12 that has flowed into the diversion channel 41 from the diversion channel inlet 40, flows into the swirl chamber 33 through the diversion channel 41. A heat transfer tube swirl blade 30 is disposed in the swirl chamber 33. The heat transfer tube swirl blade 30 has a structure in which a plurality of blade 37-shaped protrusions are formed on the end face of a cylindrical ring 38 (see FIG. 7C). A space is formed between the inner wall surface of the swirl chamber 33 and the heat transfer tube swirl blade 30, and the diverted exhaust gas 14 that has flowed from the diversion passage 41 flows into the space. The diverted exhaust gas 14 flowing into the space flows into the heat transfer tube 42 while forming a swirl flow when passing through the heat transfer tube swirl blade 30. The diverted exhaust gas 14 flowing into the heat transfer tubes 42 via the heat transfer tube swirl blades 30 passes between the blades 37 formed on the heat transfer tube swirl blades 30 at a substantially uniform flow rate. The intervals are adjusted. Therefore, the diverted exhaust gas 14 flowing into the heat transfer tube 42 flows in at a substantially uniform flow rate from the circumferential direction of the inlet portion of the heat transfer tube 42 through the heat transfer tube swirl blade 30. This is important in order to supply the spray 35 uniformly in the circumferential direction of the inner wall surface of the heat transfer tube 42 and to turn the spray 35 efficiently in the heat transfer tube 42.

  Further, the urea water spray 35 is injected from the sub injection valve 27 toward the heat transfer tube 42 through the inside of the ring 38 of the heat transfer tube swirl vane 30 disposed in the swirl chamber 33.

  Here, since the shunt exhaust 14 passes through the heat transfer tube swirl blade 30 and flows while forming a swirl flow in the heat transfer tube 42, compared with the case where the flow passes through the right angle bend tube 14. Since the flow drift can be suppressed, the passage pressure loss can be reduced, and the diverted exhaust gas 14 can be efficiently introduced into the heat transfer tube. Further, the swirl flow can be efficiently formed in the heat transfer tube 42, and the spray 35 injected into the heat transfer tube 42 can be accompanied by the swirl flow, and the spray 35 is forcibly brought into contact with the inner wall surface of the heat transfer tube 42. It becomes possible. Therefore, the time for the droplets in the spray 35 to contact the inner wall surface of the heat transfer tube 42 can be extended. That is, since the trace (flow path) length in which the spray 35 droplets flow in the heat transfer tube 42 can be increased, it is possible to efficiently promote the vaporization of the spray 35.

  Furthermore, a plurality of shielding members 60 are disposed in the heat transfer tube 42 along the axial direction of the heat transfer tube 42. In the case of the present embodiment, the shielding member 60 is arranged in four stages, but is not limited to the number of stages, and depends on the amount of urea water spray 35 injected from the sub-injection valve 27, the power consumption of the heater, and the like. The number of steps of the shielding member 60 is adjusted. By adjusting the number of stages of the shielding member 60 and the like, it is possible to control the number of swirling flows of the shunt exhaust 14 and spray 35 droplets that swirl within the heat transfer tube 42. For example, in the case where the shielding members 60 of the present embodiment are arranged in four stages, the swirling flow of the diverted exhaust gas 14 in the heat transfer tube 42 is as indicated by the streamline 55 indicated by the thick dotted line in FIG. According to the study by the inventors, it was confirmed that the number of turns in the heat transfer tube 42 can be remarkably improved in comparison with the heat transfer tube (not shown) in which the shielding member 60 is not provided when the heat transfer tube swirl blade 30 is attached. did.

  The structure of the shielding member 60 includes a reflection portion 61 and an opening 62 that reduce and enlarge the passage cross-sectional area of the heat transfer tube 42 in the axial flow direction vertical cross section.

  Further, the reflection portion 61 and the opening 62 of the shielding member 60 are formed with a predetermined angle inclination with respect to the vertical cross section in the axial direction of the heat transfer tube 42, and each shielding member 60 is in the axial direction of the heat transfer tube 42. The reflection portions 61 and the openings 62 of the adjacent shielding members 60 are arranged at different positions so as not to coincide with the same axis in the axial direction of the heat transfer tube 42. Further, each shielding member 60 is formed with a parallel portion 63 having a predetermined length in the axial direction of the heat transfer tube in order to increase the contact area with the inner wall surface of the heat transfer tube 42.

  As described above, by arranging a plurality of stages of the shielding member 60 having the reflection portion 61, the opening 62, and the parallel portion 63 in the heat transfer tube 42, the passage cross-sectional area of the vertical cross section in the axial direction of the heat transfer tube 42 is set to the number of steps. Accordingly, it can be reduced and enlarged a plurality of times, and further, because the reflecting portion 61 and the opening 62 of the adjacent shielding member 60 are arranged at different positions so as not to coincide with each other on the same axis in the axial direction of the heat transfer tube 42, It is possible to change (high speed) the flow rate of the droplets 35 sprayed from the split flow exhaust 14 and the sub-injection valve 27 flowing through the heat transfer tube 42 and passing through the heat transfer tube 42. That is, the contraction and expansion of the flow in the heat transfer tube 42 can be repeated according to the number of stages of each shielding member 60. In addition, a swirl flow can be imparted to the shunt exhaust 14 and the spray 35 droplets, and the swirl flow (number of times) in the heat transfer tube 42 can be controlled according to the number of stages of the shielding member 60. By these actions, the flow of the split exhaust gas 14 flowing in the heat transfer tube 42 can be disturbed, and the spray 35 droplets injected into the heat transfer tube 42 are formed around the spray 35 droplets formed when the droplets evaporate. The evaporation layer can be made thin, heat transfer between the shunt exhaust 14 and the spray 35 droplets can be promoted, and vaporization of the spray 35 droplets can be promoted.

  Furthermore, by forming a swirl flow in the droplets of the urea water spray 35 and the diverted exhaust 14 in the heat transfer tube 42, the trace (flow path) of the spray 35 droplets can be expanded, and the droplets of the spray 35 In addition, it is possible to increase the time for transferring the heat of the diverted exhaust 14 and the heater 43 and to promote vaporization.

  Furthermore, since the reflection part 61 of the shielding member 60 is formed with a predetermined angle inclination with respect to the vertical cross section in the axial direction of the heat transfer tube 42, the spray 35 droplets are vaporized by colliding with the reflection part 61. While being promoted, it is reflected and actively induced and collides with the inner wall surface of the heat transfer tube 42 of the heating surface which is a hot wall. Since the sprayed 35 droplets positively collide with the wall of the heat transfer tube 42 of the heating surface which is a hot wall, the heater 43 can actively transfer heat through the inner wall surface of the heat transfer tube 42 and vaporize. Promotion is achieved, and the evaporation time of the spray 35 droplets can be greatly shortened.

  Furthermore, by arranging the shielding member 60 in a plurality of stages in the heat transfer tube 42, the sprayed 35 droplets reflected at the first stage of the reflecting portion 61 of the shielding member 60 collide with the inner wall surface of the heat transfer tube 42, and thereafter Each of the shields collides with the inner wall surface of the heat transfer tube 42 a plurality of times by colliding with the second, third and fourth reflecting portions 61 and reflecting each time toward the inner wall surface of the heat transfer tube 42. It moves in the downstream direction in the heat transfer tube 42 through the opening 62 of the member 60. Therefore, the spray 35 can actively collide with the inner wall surface of the heat transfer tube 42 that is the heating surface, and the heat generated by the heater 43 disposed on the outer wall surface of the heat transfer tube 42 is transmitted through the inner wall surface of the heat transfer tube 42. In addition, since heat can be transferred effectively to the droplets of the spray 35 colliding with the inner wall surface of the heat transfer tube 42, the vaporization of the spray 35 by the heat of the heater 43 can be realized. In addition, it is possible to suppress the coarse droplets in the spray 35 that are not exposed to the airflow from flowing out of the heat transfer tube 42.

  In this embodiment, the heat transfer tube swirl blade 30 is disposed at the inlet of the heat transfer tube 42, and the swirl flow is formed in the divided exhaust 14 at the inlet of the heat transfer tube 42. This is provided in order to form a swirl flow more effectively in the heat transfer tube 42. However, in this embodiment, even if the heat transfer tube swirl blade 30 is not disposed, the shunt exhaust 14 and the spray are sufficiently provided. The 35 droplets can be swirled in the heat transfer tube 42 and the spray 35 droplets can be guided to the inner wall surface of the heat transfer tube 42, and the vaporization of the spray 35 droplets can be promoted. Therefore, the heat transfer tube swirl blade 30 is not an essential component in the present embodiment.

  Here, the spray 35 injected from the sub-injection valve 27 collides with the reflecting portion 61 of the shielding member 60 in a relatively concentrated manner. Moreover, in the reflection part 61 to which heat is supplied from the inner wall of the heat transfer tube 42 by heat conduction compared to the heat transfer tube 42 that is directly heated by the heater 43 that is a heating element, when the spray 35 collides, In comparison, the surface temperature of the reflective portion 61 tends to decrease. If the surface temperature of the reflecting portion 61 is significantly reduced, there is a concern that the urea water spray 35 droplets become a liquid flow on the surface of the reflecting portion 61 and flow out to the downstream hydrolysis catalyst 44 or downstream thereof. Here, in the reflection part 61 and the hydrolysis catalyst 44, or in the downstream thereof, the urea water that has become a liquid flow may vaporize only the water in the urea water, and urea may be deposited. As a result, urea precipitation occurs in the passages of the respective parts or the like, and clogging due to urea precipitation occurs, so that it is impossible to smoothly supply ammonia gas, which is a reducing agent that should be supplied, and its vapor to the denitration catalyst 18. Concerned. Therefore, a point to be considered is that, in the shielding member 60 (particularly the reflection portion 61) disposed in the heat transfer tube 42, the boiling form of the spray 35 droplets is not a nucleate boiling form but a film boiling form. is there. A predetermined amount of heat is supplied from the heater 43 to the shielding member 60, and an axial flow of the heat transfer tube 42 in the reflection portion 61 of the shielding member 60 and the opening 62 so as to smoothly convey the spray 35 droplets in the reflection portion 61 of the shielding member 60. The mounting angle with respect to the vertical cross section in the direction, the opening ratio of the reflecting portion 61 and the opening portion 62, the mounting interval of each shielding member 60, and the contact area between the shielding member 60 and the inner wall surface of the heat transfer tube 42 are expanded and shielded from the heater 43. In order to promote the transfer of the heat supplied to the member 60, it is realized by optimizing the parallel portion 63 having a predetermined length along the inner wall surface of the heat transfer tube 42 in the axial direction of the heat transfer tube 42. Here, when the spray 35 droplets are nucleate boiled on the inner wall surface of the heat transfer tube 35 and the reflecting portion 61 surface of the shielding member 60, heat transfer between the inner wall surface of the heat transfer tube 42 and the urea water is promoted, The temperature of the inner wall surface of the heat transfer tube 42 is rapidly reduced, and urea is deposited on the inner wall surface. However, if the form of boiling of the spray 35 droplets on the inner wall surface of the heat transfer tube 42 and the surface of the shielding member 60 is the film boiling form, the heat transfer coefficient from the heater 43 is lower than that in the case of the nucleate boiling form. Although vaporization promotion is impaired, urea precipitation can be prevented by vaporizing the sprayed 35 droplets in the heat transfer tube 42 in the form of droplets.

  Here, the result of having examined the boiling form of the urea water spray droplet on the heating plate with respect to the urea water mass concentration is shown in FIG. This figure has been examined by the inventor in carrying out the present invention. In the examination method, the temperature of the heating plate (made of stainless steel) can be arbitrarily adjusted, and droplets (urea water) were dropped on the heating plate at a predetermined temperature, and the evaporation form of the droplets was observed. The purpose is to find an appropriate temperature for preventing urea precipitation by grasping the evaporation form of the urea water spray 35 at the set wall temperature of the heat transfer tube 42 and the reflecting portion 61 of the shielding member 60 and the like. The horizontal axis represents the urea water mass concentration (wt%), and the vertical axis represents the heating plate temperature (° C.). A region above the heating plate temperature of the dotted line in FIG. 11 (region above the dotted line in the drawing) indicates a film boiling (droplet vaporization) region in which the urea water droplets dropped on the heating plate are vaporized in the state of droplets. . And in the area below the heating surface temperature of the dotted line (area below the dotted line in the figure), the urea water droplet dripped on the heating plate is instantaneously destroyed, and a liquid film is formed on the heating plate, The nucleate boiling region promoting vaporization is shown. In the film boiling region where the hot plate temperature is high (the region above the dotted line in the figure), there is an air layer between the droplet and the hot plate, and vaporization is promoted in a droplet state, so the evaporation time is relatively long. Tend to be. However, the surface of the heated plate after evaporation is very clean, and there is almost no precipitation of urea.

  On the other hand, in the nucleate boiling region where the hot plate temperature is low (the region below the dotted line in the figure), when the temperature of the nucleate boiling region is relatively high, when a urea droplet is dropped on the hot plate, a relatively fast time The droplets disappeared and the evaporation time was found to be very short. In the case of a relatively low temperature in the nucleate boiling region, a droplet dropped on the heating plate forms a liquid film on the heating plate, and bubbles are generated in the liquid film, evaporating in a relatively long time. The time turned out to be long. Here, it has been found that urea precipitates on the surface of the heating plate in any case in the nucleate boiling region on the heating plate (region below the dotted line in the figure). Moreover, it was clarified that the film boiling and nucleate boiling temperature change as shown in the figure depending on the mass concentration of urea water as a reducing agent.

  Based on these examination results, the heating plate is replaced with the inner wall surface of the heat transfer tube 42 and the shielding member 60, so that urea precipitation does not occur on the inner wall surface of the heat transfer tube 42 of the present invention and the shielding member 60 disposed therein. For this, the surface temperature needs to be present in the film boiling (droplet vaporization) region shown in FIG. For example, in the case of a urea water mass concentration of 32.5 wt%, which is a urea water mass concentration used in a general urea SCR, the surface temperature of the inner wall surface of the heat transfer tube 42 and the shielding member 60 disposed therein is about 235. It is preferable to set it as ° C or more.

  As a result of application to the heat transfer tube 42 of the present invention, urea deposition on the inner wall surface of the heat transfer tube and the surface of the shielding member can be prevented, and the heat transfer tube 42 capable of realizing vaporization of the urea water spray 35 has been developed.

  Since the shielding member 60 is formed with the parallel portion 63 along the inner wall surface of the heat transfer tube 42, the contact area between the inner wall surface of the heat transfer tube 42 and the parallel portion 63 is enlarged, and the heat of the heater 43 is shielded. The reflection part 61 of the member 60 has a structure in which heat is easily input, and a temperature drop due to vaporization of the spray 35 droplets in the reflection part 61 is suppressed.

  Further, a hydrolysis catalyst 44 having a cylindrical shape along the inner wall surface of the heat transfer tube 42 and having a lattice-like vertical cross section is disposed at the most downstream side of the shielding member 60 inside the heat transfer tube 42. The hydrolysis catalyst 44 is preferably one in which the base material is a metal and the hydrolysis catalyst is supported so that heat from the heater 43 can be easily transferred. By disposing the hydrolysis catalyst 44, vaporization can be promoted even when there are 35 spray droplets that could not be vaporized by the shielding member 60 disposed upstream thereof. Then, the vaporized urea vapor and urea droplets can be hydrolyzed to produce ammonia. Further, by providing the hydrolysis catalyst 44 in the heat transfer tube 42 in which the heater 43 is provided on the outer periphery of the heat transfer tube 42, the temperature of the hydrolysis catalyst 44 is directly increased to the activation temperature by the heat of the heater 43. Even if the temperature of the exhausts 12 and 14 is equal to or lower than the activation temperature of the hydrolysis catalyst 44, the temperature of the hydrolysis catalyst 44 disposed in the heat transfer tube 42 can be raised to the activation temperature by the heat of the heater 43. The ammonia gas 15 can be generated efficiently.

  Further, by arranging the shielding member 60 in a plurality of stages in the heat transfer tube 42, the reflection portion 61 of the shielding member 60 protrudes into the heat transfer tube 42. The temperature of the diverted exhaust gas 14 flowing through the fuel can be increased, and the vaporization of the spray 35 droplets by the exhaust heat can be promoted. Furthermore, the hydrolysis catalyst disposed downstream of the shielding member 60 can be quickly heated to the activation temperature by raising the temperature of the divided exhaust 14.

  Furthermore, since the shielding member 60 is provided in a plurality of stages in the heat transfer tube 42, the vaporization of the urea water spray 35 in the heat transfer tube 42 can be promoted, so that the heat transfer tube 42 can be reduced in size. Since the heat transfer tube 42 can be miniaturized, the heat radiation area to the outside (outside air) can be reduced, so that the amount of heat radiation loss from the heater 43 to the outside air can be reduced.

  In the present embodiment, when the shielding member 60 is disposed in the heat transfer tube 42, the disposition position in the axial flow direction in the heat transfer tube 42 is determined by the length of the parallel portion 63 in the axial flow direction. That is, the end on the downstream side in the axial direction of the parallel part 63 of the shielding member 60 is in contact with the end on the upstream side in the axial direction of the shielding member 60, and the respective axial direction in the heat transfer tube 42. The position of is determined. Further, the downstream end of the parallel part 63 of the shielding member 60 located on the most downstream side is fixed in the heat transfer tube by contacting the hydrolysis catalyst 44. Here, the hydrolysis catalyst 44 is fixed in contact with the heat transfer tube 42.

  The urea vapor that has been vaporized in the heat transfer tube 42 is promoted to undergo hydrolysis by the heat of the divided exhaust 14 and the heat supplied from the heater 43, which is a heating element, into the heat transfer tube 42. Furthermore, the hydrolysis reaction is further promoted by passing through hydrolysis catalysts 44 and 51 arranged downstream of the plurality of stages of shielding members 60 arranged inside the heat transfer tube 42, and ammonia water is converted into ammonia gas. Can be planned. The ammonia gas 15 that has promoted the ammonia gasification of the spray 35 flows into the pressure regulating chamber 45 disposed downstream of the hydrolysis catalyst 51, and enters the mainstream exhaust 13 from the plurality of ammonia ejection holes 46 formed in the throttle 20. It is attracted and supplied into the diaphragm 20. This is because the throttle 20 through which the main flow exhaust 13 passes increases the pressure loss of the heat transfer tube 42, so that the pressure regulation on the throttle 20 side decreases, and the flow rate of the split exhaust 14 in the heat transfer tube 42 is ensured.

  By passing through the throttle 20, the main flow exhaust 13 has a higher flow rate than the flow rate of the exhaust 12. Further, by passing through the disposed mainstream swirl vane 19, the mainstream exhaust 13 flow downstream of the mainstream swirler 19 is locally disturbed to form a swirl and promote mixing with the ammonia gas 15. By supplying the mixed gas 16 to the denitration catalyst 18, high denitration performance can be obtained.

  As described above, in the present embodiment, the urea water supply form supplied from the urea addition device 70 into the flue 10 and the throttle 20 is changed in accordance with the operation state of the engine, so that it is high in the entire operation region of the engine. Denitration performance can be secured.

  Here, the temperature of the exhaust 12 from the engine 1 changes depending on the load of the engine 1, and when the temperature of the exhaust 12 is high, the urea water is vaporized and hydrolyzed by the heat obtained from the exhaust 12 even if the urea water is directly injected. The decomposition reaction proceeds rapidly, and a necessary amount of ammonia gas as a reducing agent is supplied to the denitration catalyst 18, but when the temperature of the exhaust 12 is low, the hydrolysis reaction of urea water is not promoted, and ammonia gasification proceeds. First, the reduction reaction at the denitration catalyst 18 does not proceed sufficiently. For this reason, generally, when the temperature of the exhaust 12 is low, the NOx reduction rate (denitration rate) deteriorates.

  Next, FIG. 8 shows the result of studying the effect of shortening the droplet evaporation time in the heat transfer tube 42 when the present embodiment is applied.

  The horizontal axis represents time, and the vertical axis represents the droplet evaporation rate. The specification of the “conventional example” indicated by the thick dotted line in FIG. 8 is a case where a predetermined amount of spray 35 is injected into the heat transfer pipe 42 of the straight pipe, and the specification of the “present invention” indicated by the thick solid line is The shielding member 60 is arranged in four stages in the heat pipe 42. The droplet evaporation rate on the vertical axis indicates the evaporation rate of droplets in the spray 35 at the outlet of the heat transfer tube 42. A thin dotted line (complete vaporization) in FIG. 8 shows a case where the droplets in the spray 35 are completely vaporized.

  From FIG. 8, as one means for improving the evaporation rate of the droplets (for example, complete vaporization), it is possible to increase the time during which the sprayed 35 droplets stay in the heat transfer tube. By increasing the residence time of the sprayed 35 droplets, the amount of heat transferred to the sprayed 35 droplets can be increased from the amount of heat generated by the heater 43 and the amount of heat of the diverted exhaust 14, and evaporation can be promoted and complete vaporization is realized. (“Conventional example” in FIG. 8, point C on the thick dotted line). However, when the urea water spray injected into the straight heat transfer tube 42 is completely vaporized as in the conventional example, the flying speed and the heat transfer surface temperature of the spray 35 droplets passing through the heat transfer tube 42 From the relationship of the diverted exhaust temperature, it is estimated that an unrealistic heat transfer tube length is required when considering installation on an actual machine.

  In addition, in consideration of the ease of mounting on an actual machine, the evaporation rate of the 35 droplets of the spray 35 is very low when it is of a predetermined size (heat transfer tube length) (point B on the thick dotted line in the “conventional example” in FIG. 8). There is concern about a large amount of spray droplets that are not vaporized out of the heat tube 42, and it is estimated that it is difficult for the urea addition apparatus 70 to obtain the desired high denitration performance.

  On the other hand, in the case of the specification of the present invention, four stages of shielding members 60 are arranged in the heat transfer tube 42, thereby forming a swirl flow in the shunt exhaust 14 and the spray 35 droplet flow passing through the heat transfer tube 42. The flow (flow path) length of the spray 35 droplets can be increased several times as compared with the case of the straight pipe, so that the time for transferring heat from the shunt exhaust 14 and the inner wall surface of the heat transfer pipe 42 Vaporization can be promoted. Further, the swirling flow can be generated by arranging the shielding member 60 in a plurality of stages in the heat transfer tube 42, and the vertical cross section in the axial direction of the heat transfer tube 42 can be reduced a plurality of times by the reflecting portion 61 and the opening 62 of the shielding member 60. Because it is possible to realize enlargement and to increase the passage speed of the shunt exhaust 14 and the spray 35 droplets in the heat transfer tube, it is possible to form turbulence in the flow and to thin the evaporation layer around the spray 35 droplets. The vaporization of the sprayed 35 droplets can be promoted. Further, since the reflection portion 61 of the shielding member 60 is disposed at a predetermined angle with respect to the vertical cross section in the axial direction of the heat transfer tube 42, the sprayed 35 droplets that collide with the reflection portion 61 are transferred to the outer periphery of the heat transfer tube 42. Since the gas is positively guided to and collided with the inner wall surface of the heat transfer tube 42 heated by the heater disposed in the, the vaporization of the spray 35 droplets and the inner wall surface of the heat transfer tube 42 can be promoted. Further, since the coarse droplets that are not in the airflow in the spray 35 ejected from the injection valve 27 collide with the reflecting portion 61 of the shielding member 60, the coarse droplets can be promoted to be vaporized, and the heat transfer tube 42 can be moved outside. The outflow of 35 droplets of spray can be suppressed.

  Due to the above effects, the urea water spray 35 injected into the heat transfer tube 42 can be completely vaporized in the heat transfer tube 42, and the droplet evaporation time can be shortened. 42 can be realized. Further, since the urea water spray 35 can be completely vaporized, the hydrolysis reaction can be promoted on the hydrolysis catalysts 44 and 51, so that ammonia gas can be generated efficiently. Therefore, since ammonia gas can be supplied to the denitration catalyst 18, high denitration performance can be maintained.

  Next, a second embodiment will be described. FIGS. 9A and 9B are perspective views of a set of the shielding member 64 and the shielding member 64 disposed in the heat transfer tube of the second embodiment of the present invention.

  The difference from the first embodiment is the difference in the shape of the shielding member 64, and the other shapes, configurations, and operational effects are substantially the same as those of the first embodiment, and thus the description thereof is omitted.

  The difference between the first embodiment and the second embodiment is the attachment position of the reflection portion and the opening of the shielding member.

  That is, in the shielding member 60 of the first embodiment, the reflecting portion 61 and the opening 62 have a predetermined angle with respect to the vertical cross section in the axial direction of the heat transfer tube 42 (represented by the shielding member 60). The reflecting portion 61 and the parallel portion 62 are inclined at a predetermined angle with respect to the parallel portion 63 of the shielding member 60). Further, an end portion shared by the reflecting portion 61 and the opening portion 62 is formed in parallel to the tilt direction. On the other hand, in the shielding member 62 of the second embodiment, the reflecting portion 65 and the opening 66 are inclined at a predetermined angle with respect to the parallel portion 67 and the reflecting portion 65 and the opening portion 66 are orthogonal to the inclined direction. An end shared by the opening 66 is formed. And when it arrange | positions in the heat exchanger tube 42, it arrange | positions so that the edge part which the reflection part 65 of the adjacent shielding member 64 and the opening part 66 share may be orthogonal.

  By applying the shielding member 64 having the above configuration, the same operation and effect as the first embodiment can be obtained.

  The shape of the opening 66 and the mounting position of the shielding member 64 are not limited to this, and the opening 66 may be any shape that has an opening as well as a semicircular shape. Further, it is only necessary that the openings of the plurality of shielding members arranged in the heat transfer tube do not coincide with the openings of the adjacent shielding members in the axial direction of the heat transfer tube.

  Next, a third embodiment will be described. 10 (a) and 10 (b) are perspective views of a combined view of the shielding member 72 and the shielding member 72 disposed in the heat transfer tube of the third embodiment of the present invention.

  The difference from the first embodiment is the difference in the shape of the shielding member 72, and the other shapes, configurations, and operational effects are substantially the same as those of the first embodiment, and the description thereof will be omitted.

  The difference between the first embodiment and the third embodiment is the attachment position of the reflection portion and the opening of the shielding member.

  That is, in the shielding member 60 of the first embodiment, the reflecting portion 61 and the opening 62 are disposed with a predetermined angle with respect to the vertical cross section in the axial direction of the heat transfer tube 42 (represented only by the shielding member 60). The reflecting portion 61 and the parallel portion 62 are inclined at a predetermined angle with respect to the parallel portion 63 of the shielding member 60). On the other hand, in the shielding member 72 of the third embodiment, the reflecting portion 73 and the opening 74 are formed perpendicular to the parallel portion 75. And when it arrange | positions in the heat exchanger tube 42, it arrange | positions so that the edge part which the reflection part 73 and the opening part 74 of the adjacent shielding member 72 share may each orthogonally cross.

  By applying the shielding member 72 having the above configuration, the reflecting portion 73 is arranged in parallel to the vertical cross section in the axial direction of the heat transfer tube 42 as compared with the first embodiment. Although the effect of causing the spray 35 droplets to be reflected and colliding with the inner wall surface of the heat transfer tube 42 is reduced, the trapping effect of the spray 35 droplets in the reflecting portion 73 is enhanced, so that the vaporization performance of the urea water spray 35 is not much. The same effect as the first embodiment can be obtained without change.

1 is a diagram illustrating an overall configuration of an engine exhaust treatment apparatus according to a first embodiment of the present invention. It is an external appearance perspective view of the urea addition apparatus of the exhaust gas processing apparatus shown in FIG. FIG. 3 is a B direction arrow view and a C direction arrow view of the external perspective view shown in FIG. 2. It is a figure which shows EE sectional drawing in FIG. It is a figure which shows DD sectional drawing in FIG. It is a figure which shows the F section enlarged view in FIG. The perspective view of "the shielding member" arrange | positioned in the heat exchanger tube of 1st Example of this invention, and the "assembly figure of a shielding member", and the perspective view of the "swirl blade" arrange | positioned in the heat exchanger tube upstream step part FIG. It is a figure which shows the effect which shortened the droplet evaporation time of the exhaust processing apparatus which concerns on this invention. It is a perspective view of "the shielding member" arrange | positioned in the heat exchanger tube of the 2nd Example of this invention, and the "combination drawing of a shielding member". It is a perspective view of "the shielding member" arrange | positioned in the heat exchanger tube of the 3rd Example of this invention, and the "combination drawing of a shielding member". It is a figure which shows the result of having examined the boiling form of the urea water spray droplet on the heating plate with respect to urea water mass concentration.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Diesel engine 3 Urea water tank 4 Urea water 5 Filter 6 Pump 7 Pressure control valve 12, 13, 16 Exhaust 14 Divided exhaust 15 Ammonia gas 17 DPF
18 DeNOx catalyst 19 Main flow swirl 26 Main injection valve 27 Sub injection valve 30 Heat transfer tube swirl 40 Split flow passage inlet 41 Split flow passage 42 Heat transfer tube 43 Heater 44 Upstream hydrolysis catalyst 45 Pressure regulation chamber 46 Ammonia gas injection hole 51 Water Decomposition catalyst 60, 64, 72 Shield member 61, 65, 73 Reflection part 62, 66, 74 Opening part 63, 67, 75 Parallel part 70 Urea supply device

Claims (6)

An exhaust treatment device for reducing nitrogen oxides in exhaust gas, having an injection valve for injecting urea water into exhaust gas, and a heater for promoting vaporization of urea water spray injected from the injection valve The vaporizer is provided with a heater disposed on the outer periphery of the heat transfer tube, urea water spray and exhaust gas pass through the heat transfer tube, and the urea water spray vaporized by the vaporizer In an exhaust treatment device for an engine that supplies gas into a flue,
An apparatus for converting the axial velocity direction component in the heat transfer tube of the spray droplet supplied into the heat transfer tube into the heat transfer tube a plurality of times toward the inner wall surface of the heat transfer tube and causing the spray droplet to collide with the inner wall surface of the heat transfer tube An exhaust treatment apparatus for an engine comprising: a heat transfer tube inner wall surface and a device that collides with the heat transfer tube inner wall surface at a temperature equal to or higher than a temperature at which spray droplets boil. An exhaust treatment device for reducing nitrogen oxides in exhaust gas, having an injection valve for injecting urea water into exhaust gas, and a heater for promoting vaporization of urea water spray injected from the injection valve The vaporizer is provided with a heater disposed on the outer periphery of the heat transfer tube, urea water spray and exhaust gas pass through the heat transfer tube, and the urea water spray vaporized by the vaporizer In an exhaust treatment device for an engine that supplies gas into a flue,
A plurality of shielding members having a reflecting portion and an opening are disposed in the heat transfer tube, and the heat transfer tube inner wall surface and the shielding member are set to a temperature equal to or higher than the temperature at which the urea water spray droplets boils,
The shielding member reduces and enlarges the passage cross-sectional area of the vertical cross section in the axial direction of the heat transfer tube, and vaporizes a part of the spray droplet group supplied into the heat transfer tube by colliding with the reflection part of the shield member at each stage. An exhaust treatment apparatus for an engine, characterized in that spray droplets that are reflected together and do not flow in the airflow passing through the heat transfer tube always collide with the inner wall surface of the heat transfer tube or the reflection part of the shielding member. An exhaust treatment device for reducing nitrogen oxides in exhaust gas, having an injection valve for injecting urea water into exhaust gas, and a heater for promoting vaporization of urea water spray injected from the injection valve The vaporizer is provided with a heater disposed on the outer periphery of the heat transfer tube, urea water spray and exhaust gas pass through the heat transfer tube, and the urea water spray vaporized by the vaporizer In an exhaust treatment device for an engine that supplies gas into a flue,
A plurality of shielding members having a reflecting portion and an opening are disposed in the heat transfer tube, and the heat transfer tube inner wall surface and the shielding member are set to a temperature equal to or higher than the temperature at which the urea water spray droplets boils,
The reflective portion and the opening of the shielding member reduce and enlarge the passage cross-sectional area of the vertical cross section in the axial direction of the heat transfer tube, and the reflective portion and the opening that are inclined at a predetermined angle with respect to the vertical cross section in the axial direction of the heat transfer tube. Have
The respective shielding members are arranged at different positions where the reflection portions and openings of adjacent shielding members in the axial direction of the heat transfer tube do not coincide with the same axis in the axial direction of the heat transfer tube. An exhaust processing apparatus for an engine, characterized in that a swirling flow is formed in passing exhaust gas, and spray droplets are reflected by a reflecting portion and can collide with an inner wall surface of a heat transfer tube. The engine exhaust treatment apparatus according to any one of claims 1 to 3,
An exhaust treatment apparatus for an engine, wherein a surface temperature of the inner wall surface of the heat transfer tube and the shielding member is 235 ° C or higher. The engine exhaust treatment apparatus according to any one of claims 1 to 4,
The shield member has a parallel portion having a predetermined length in the axial direction of the heat transfer tube as it comes into contact with the inner wall surface of the heat transfer tube, and fixes the shield member in the heat transfer tube by the parallel portion, An exhaust processing apparatus for an engine, wherein a contact area between a wall surface and the shielding member is enlarged. The engine exhaust treatment apparatus according to any one of claims 1 to 5,
An exhaust treatment apparatus for an engine, wherein a hydrolysis catalyst having a catalyst supported on a metal base material is disposed in the heat transfer tube downstream of the shielding member or downstream thereof.

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