JP2006170013A - Exhaust gas processing equipment for engine and processing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To remove NOx by compact constitution and a low power consumption, in a full operation region extending from a low load region, where an exhaust gas temperature and an exhaust gas amount are low, to a high load region where an exhaust gas temperature and an exhaust gas amount are high. <P>SOLUTION: Exhaust gas processing equipment is provided with an exhaust gas flue 5 of an engine; a NOx removal catalyst reactor 6 situated in the exhaust gas flue; and an injection valve injecting urea water for feeding it. The equipment is constituted such that by-pass means for exhaust gas is situated; a first injection valve 50 to inject urea water is situated in a passage 72a for by-pass exhaust gas, carburetors 61a and 62a to heat urea water, injected by the first injection valve, into urea vapor are provided; a second injection valve 30 for injecting urea water is situated on the downstream side of the carburetor; and urea vapor produced from urea water spray injected from the first injection valve 50 when an exhaust gas temperature is low is fed to the exhaust gas flue 5 and urea water spray injected from the second injection valve 30 when an exhaust gas temperature is high is fed to the exhaust gas flue. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an exhaust treatment device and a treatment method, and more particularly, to an exhaust treatment device and a treatment method that can efficiently remove nitrogen oxides in exhaust gas using urea water as a reducing agent.

  Nitrogen oxides (hereinafter referred to as NOx) contained in exhaust gas discharged from diesel engines such as heavy trucks and buses are substances that cause photochemical smog. Since NOx emission regulations are strengthened for vehicles that discharge these, installation of exhaust denitration devices is urgently required. As a removal (denitration) method, it has been studied to use non-toxic urea as a reducing agent so that NOx can be reduced with high efficiency.

  For example, urea water is used as a reducing agent, and a NOx reduction catalyst disposed in the exhaust pipe is provided in order to obtain a high NOx reduction rate from a relatively low temperature range, and upstream of the NOx reduction catalyst In the exhaust gas purification apparatus configured to add urea water as a reducing agent, a urea decomposition catalyst is provided between the urea water addition position in the longitudinal direction of the exhaust pipe and the NOx reduction catalyst, and the urea water is decomposed in the preceding stage. The catalyst is decomposed into ammonia and carbon dioxide, and NOx is efficiently reduced by the highly reactive ammonia obtained thereby. Thus, there has been proposed an exhaust purification device capable of reducing and purifying NOx from a relatively low temperature range compared with the case of reacting urea water with NOx as it is (see, for example, Patent Document 1).

In addition, a urea SCR system has been proposed as an exhaust purification device that does not include the urea decomposition catalyst of the exhaust purification device described above (see, for example, Non-Patent Document 1).
JP 2002-161732 A Kodaka Matsuo “Challenge to Ultra Low Emission Diesel Engine” Journal of the Japan Society of Mechanical Engineers, 2002.10 Vol. 105 No. 1007, p. 23

  The conventional technique as shown in Patent Document 1 described above is a configuration in which a urea decomposition catalyst is disposed between the urea water addition position and the NOx reduction catalyst, and urea water is directly added (injected) to the urea decomposition catalyst. . Thus, urea water is decomposed into ammonia and carbon dioxide by the urea decomposition catalyst, and NOx is reacted on the NOx reduction catalyst with the decomposed ammonia, so that NOx is efficiently reduced.

  However, since urea water is directly supplied to the urea decomposition catalyst, it is difficult to uniformly distribute urea water to the urea decomposition catalyst. Further, there is a concern that it takes a relatively long time to decompose urea water on the urea decomposition catalyst. From these facts, it is preferable to supply urea water to the urea decomposition catalyst by urea vapor or the like which is easy to vaporize and promote mixing with exhaust gas.

  As a means for that, there is a method of securing a predetermined distance from the injection nozzle to the urea decomposition catalyst and heating and promoting vaporization of the urea water by exhaust heat of the exhaust gas until the urea water reaches the urea decomposition catalyst. According to their calculations, in order to vaporize the injected urea water spray, for example, when the urea water spray has a droplet diameter of about 100 μm at a predetermined flow rate of the exhaust gas, a flue length of about 1.5 m is required. When the droplet diameter is about 200 μm, a flue length of about 6.2 m is required. This leads to an increase in the size of the system and is not preferable for in-vehicle use.

  The means for obtaining the amount of heat for vaporization from the exhaust heat of the exhaust gas can be said to be an effective method in view of the fact that a large amount of NOx is generated when the exhaust gas temperature is high. Since it is low and the amount of exhaust gas is small, vaporization cannot be promoted sufficiently. Therefore, it is difficult to efficiently reduce and purify NOx at low temperatures such as at the time of starting.

  Next, when applying an exhaust treatment device using vaporized urea water and hydrolyzed ammonia as a reducing agent in a denitration catalytic reaction to a vehicle equipped with a diesel engine such as a large truck or bus, for example, in a certain operating state In order to vaporize and hydrolyze a predetermined amount of urea water (50 cc / min, 32.5 wt%, 25 ° C.), the minimum amount of heat is about 2.4 kW. It is difficult to obtain this amount of power from the vehicle battery.

  The object of the present invention is to use, for example, urea water, which is easy to handle as a reducing agent, from a low load region with a low exhaust gas temperature and a low exhaust gas amount at the time of starting, etc. It is an object of the present invention to provide an exhaust treatment device and a treatment method capable of removing NOx suitable for in-vehicle use as a low-power-consumption with a response that is compatible with the entire operation region up to the load region and a compact configuration.

In order to solve the above problems, the present invention mainly adopts the following configuration.
An exhaust flue for guiding exhaust gas of the engine, a denitration catalyst reactor provided in the exhaust flue to reduce nitrogen oxides, and urea water is injected upstream of the denitration catalyst reactor to inject the exhaust flue An exhaust treatment device comprising:
When the exhaust gas temperature is a low load region of the engine, the urea water spray injected from the injection valve is vaporized and supplied as urea vapor to the exhaust flue,
When the exhaust gas temperature is a high load region of the engine, the atomized urea water spray injected from the injection valve is supplied to the exhaust flue.

  In the exhaust treatment apparatus, urea vapor is supplied by promoting vaporization of the urea water spray by a vaporizer having a heating unit at the low exhaust temperature.

Also, an exhaust flue for guiding engine exhaust gas, a denitration catalyst reactor provided in the exhaust flue for reducing nitrogen oxides, and urea water is injected upstream of the denitration catalyst reactor to inject the exhaust An exhaust treatment device comprising an injection valve for supplying to the flue,
Providing a diversion means for diverting a part of the exhaust gas flowing through the exhaust flue;
Installing a first injection valve for injecting urea water into a passage through which the divided flow exhaust gas divided by the flow dividing means flows;
A vaporizer that heats urea water injected by the first injection valve to form urea vapor, and a hydrolysis catalyst that generates ammonia gas in the vaporizer or downstream of the diverted exhaust gas passage;
Installing a second injection valve for injecting urea water downstream of the split exhaust gas passage of the hydrolysis catalyst;
An outlet portion of urea vapor, urea water spray or ammonia gas in which the diverted exhaust gas passage communicates with the exhaust flue is disposed downstream of the second injection valve;
Supplying urea vapor and / or ammonia gas generated from urea water spray injected from the first injection valve to the exhaust flue through the outlet when the exhaust gas temperature is a low load region of the engine;
The urea water spray injected from the second injection valve is supplied to the exhaust flue through the outlet when the exhaust gas temperature is a high load region of the engine.

  According to the present invention, since the operating state of the engine can supply urea vapor and ammonia gas to the denitration catalyst from a low load region (low exhaust temperature) to a high load region (high exhaust temperature), Can efficiently remove (denitrate) nitrogen oxides (NOx) in the exhaust gas.

  Furthermore, since the vaporizer that vaporizes urea water is used only in the low load region (low exhaust temperature), the amount of urea water to be vaporized is small and it is not necessary to use wasteful power, and the power consumption is low. An exhaust treatment apparatus and an exhaust gas treatment method having a compact configuration can be provided.

  Exhaust treatment apparatuses according to first, second, and third embodiments of the present invention will be described in detail below with reference to FIGS.

“First Embodiment”
An exhaust treatment apparatus according to a first embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a diagram showing an overall configuration of an exhaust treatment apparatus according to a first embodiment of the present invention. FIG. 2 is an enlarged view of part A of the exhaust treatment apparatus shown in FIG. FIG. 3 is a diagram for explaining the operation of the exhaust treatment apparatus according to the first embodiment of the present invention. FIG. 4 is a graph showing the relationship between the denitration catalyst inlet temperature and the denitration rate in the exhaust treatment apparatus according to the embodiment of the present invention.

  In FIG. 1, the diesel engine 1 determines the fuel injection amount and the injection timing based on various signals input to the control unit 2. In addition, an EGR valve (not shown) and an intake throttle for expanding the control range of the EGR rate in combination with the EGR valve are provided.

  A fine particle removal device DPF (Diesel Particulate Filter) 4 for removing fine particles such as black smoke particulate matter is connected to the flue 3 at the downstream side of the flue 3 which is a passage of the exhaust gas 8 discharged from the diesel engine 1. A denitration catalyst (SCR: Selective Catalytic Reduction: selective reduction NOx catalyst) 6 is disposed between the flue 5 and the flue 7 downstream of the flue 5. Further, a muffler or the like (not shown) is disposed downstream thereof. The flue 5 is provided with a urea vapor outlet 71, and a mixing accelerator 11 is provided downstream thereof.

  Then, the branch pipe inlet 73 is opened in the flue 5 on the downstream side of the DPF 4, and the shunt gas 9a flows in. A swirl chamber 65a is disposed on the downstream side of the diversion pipe inlet 73 via the diversion pipe 72a. A swivel member 59a is disposed in the swirl chamber 65a (see FIG. 2). On the downstream side of the swirl chamber 65a and the swivel member 59a, a passage 66 composed of the inner surface of the heat transfer tube 62a built in the heater holder 60a is disposed, and on the downstream side of the passage 66, a hydrolysis catalyst 63a is provided. It is arranged.

  Here, as the urea water 13 as the reducing agent is sprayed and supplied from the sub-injection valve 50 as the spray 58 to the passage 66 in the heat transfer tube 62a, the sub-injection valve 50 disposed in the cooling holder 52 rotates. It is arrange | positioned in the upstream of the chamber 65a and the turning member 59a. A heat insulating member 57 is disposed between the heater holder 60a and the cooling holder 52. Further, a cooling water space 53 having a predetermined space is formed in the cooling holder 52 along the outer peripheral portion of the sub injection valve 50.

  Next, a passage 67a configured inside the branch pipe 70 is disposed downstream of the hydrolysis catalyst 63a. The passage 67 a communicates with the flue 5 through the urea vapor outlet portion 71. Further, a mixing promoting material 11 is disposed in the flue 5 on the downstream side of the urea vapor outlet portion 71.

  Here, as the urea water 13 as the reducing agent is sprayed and supplied from the main injection valve 30 as the spray 38 to the passage 67a in the branch pipe 70, the main injection valve 30 disposed in the cooling holder 32 splits. Arranged upstream of the tube 70. A heat insulating member 37 is disposed between the branch pipe 70 and the cooling holder 32. The heat insulating member 37 is formed with an injection hole 36 so that a spray 38 injected from a main injection valve 30 to be described later can pass. Further, a cooling water space 33 having a predetermined space is formed in the cooling holder 32 along the outer peripheral side of the injection valve 30.

  The flow of the diverted gas 9a passing through the exhaust treatment device 120a flows in from the diversion pipe inlet 73 upstream of the flue 5 downstream of the DPF 4 and returns to the flue 5 again from the urea vapor outlet 71 downstream of the flue 5 It is. That is, through the branch pipe inlet 73 disposed in the flue 5, the branch pipe 72a, the swirl chamber 65a and the swivel member 59a, the passage 66, the hydrolysis catalyst 63a, the passage 67a, the urea vapor outlet 71, and the branch flow This is a structure communicating with the flue 5 on the downstream side of the pipe inlet 73.

  Further, the mixing promoting material 11 is disposed on the downstream side of the urea vapor outlet portion 71 in the flue 5. The mixing promoting member 11 has a shape in which a plurality of blades are formed on the outer peripheral surface of a cylindrical ring having a predetermined length in the axial direction, and the exhaust 10 flow and the mixed gas 9d flow are swirled in the flue 5. It is a member for promoting the mixing of both fluids instead of the flow.

Further, an exhaust temperature sensor 19, a NOx sensor 20, and an NH ₃ sensor 21 are disposed in the flues 5 and 7. The engine is provided with various sensors such as an engine crank sensor. Based on the output signals from these sensors, the operating conditions of the diesel engine 1 are grasped, and the optimum set temperature of the heater 61a and the injection amounts of the main injection valve 30 and the sub injection valve 50 are controlled.

  Next, the supply path of the urea water 13 supplied from the urea water tank 12 to the injection valves 30 and 50 will be described. The urea water 13 stored in the urea water tank 12 is pumped to the main injection valve 30 through the filter 15, the pump 14, the pipe 17b branched from the pipe 17a, and the urea water inlet 31. On the other hand, the urea water 13 flowing into the pipe 17 c branched from the pipe 17 a is pumped to the sub injection valve 50 via the urea water inlet 51. The urea water supply pressure to the main injection valve 30 and the sub injection valve 50 is adjusted to a predetermined urea water pressure by the regulator 16.

  On the other hand, the return urea water after being regulated by the regulator 16 passes through the pipe 18 a, flows into the cooling water space 33 from the cooling water inlet 34 formed in the cooling holder 32, and then pipes from the cooling water outlet 35. It flows out to 18b. Next, the urea water flowing out to the pipe 18b flows into the cooling water space 53 from the cooling water inlet 54 formed in the cooling holder 52, and flows out from the cooling water outlet 55 to the pipe 18c. The urea water that has flowed out to the pipe 18 c is configured to return into the tank 12. Cooling of the main injection valve 30 and the sub injection valve 50, which are electromagnetic injection valves, is promoted by the flow of the returning urea water after the pressure adjustment, and the magnetic circuits of the injection valves 30 and 50 are stably operated by exhaust heat. In addition, the urea water 13 is prevented from being precipitated in each of the injection valves 30 and 50. As a result, the urea water sprays 38 and 58 can be stably supplied into the flue 5 from the respective injection valves 30 and 50.

  FIG. 2 shows an enlarged view of part A in FIG. The detailed configuration of the exhaust treatment device 120a and the exhaust gas flow, and the mixed gas flows 9b and 9c of the urea water sprays 38 and 58 injected from the main injection valve 30 and the sub injection valve 50 and the exhaust gas flow 9a are used with reference to FIG. Etc.

  The exhaust gas 8 discharged from the diesel engine 1 passes through the DPF 4 and then flows through the branch pipe inlet 73 disposed in the upstream portion of the flue 5. Then, the exhaust gas 10 flows into the shunt gas 9 a and the flue 5. To be diverted to The diversion gas 9a passes through the diversion pipe 72a and flows into the swirl chamber 65a. Here, a swivel member 59a is disposed in the swirl chamber 65a. For this purpose, the diverted gas 9a passes through the swiveling member 59a and flows into the passage 66 disposed downstream thereof as a swirling flow.

  Further, from the sub-injection valve 50 disposed in the cooling holder 52 in accordance with the engine operating state (mainly nitrogen oxide (hereinafter referred to as NOx) emission amount, exhaust temperature, etc.), the inside of the heat transfer tube 62a. The urea water spray 58 is sprayed toward the passage 66 that is. Therefore, the urea water spray 58 passes as a swirling flow in the passage 66 on the inner surface of the heat transfer tube 62a along the flow of the diverted gas 9a. Since it passes through the inside of the passage 66 while swirling, it is possible to secure a time for contacting the inner wall surface of the passage 66, promote heat transfer from the inner wall surface of the passage 66 to the spray 58, and efficiently promote vaporization of the spray 58.

  Here, the heater 61a which is a heat generating body is arrange | positioned at the outer wall surface of the heat exchanger tube 62a. A predetermined space 64a is disposed on the outer periphery of the heater 61a in order to enhance the heat insulating effect. Further, a heater holder 60a is disposed on the outer periphery of the space 64a.

  In the present embodiment, a sheathed heater is applied to the heater 61a, and the temperature of the heater detected by a temperature sensor (not shown) is adjusted by a temperature controller. Further, the heater 61a, which is a heating element, is not limited to a sheathed heater, and may be any heating element that can generate a heat generation amount sufficient to vaporize urea water on the inner wall surface of the heat transfer tube 62a. For example, a heater such as a PTC (Positive Temperature Coefficient Thermistor) heater may be used as the heating element. This heater generates heat by applying an electric current to the electrodes. When the heater temperature exceeds a predetermined temperature, the electric resistance rapidly increases and the current decreases to keep the temperature constant. This is a ceramic heater. In this case, since the heater can adjust its own temperature, a temperature sensor for adjusting the heater temperature is unnecessary and the apparatus can be downsized.

  Furthermore, the heater 61a disposed on the outer wall surface of the heat transfer tube 62a is not limited to one, and the temperature of the heat transfer tube 62a may be controlled using a plurality of heaters. This is because a plurality of sheathed heaters are wound around the outer wall surface of the heat transfer tube 62a, and the temperature of the heat transfer tube 62a can be partially adjusted, so that a large amount of urea water spray 58 is locally concentrated on the inner wall surface of the heat transfer tube 62a. Since an appropriate amount of heat can be supplied to a region where the amount of heat can be supplied and the spray 58 is not concentrated, the urea water spray 58 can be efficiently vaporized without supplying unnecessary amount of heat to the inner wall surface of the heat transfer tube 62a. Is.

For example, when the spray 58 is first ejected (impacted) on the inner wall surface of the passage 66, the time for the spray 58 to contact the hot shunt gas 9a and the inner wall surface of the hot passage 66 is short, and the temperature of the spray droplets has increased so much. Absent. Therefore, the temperature difference between the spray 58 and the inner wall surface of the passage 66 is large, and a relatively large amount of heat is required. However, as it goes downstream of the passage 66, the spray 58 receives heat from the diverted gas 9a and the inner wall surface of the passage 66, thereby increasing the temperature of the spray droplets and promoting vaporization. Therefore, the upstream region of the inner wall surface of the passage 66 requires a relatively large amount of heat generation, and the other regions do not require a large amount of heat generation, and an appropriate heat generation amount distribution or temperature distribution is achieved on the inner wall surface of the passage 66. It is preferable to have it.
A honeycomb hydrolysis catalyst 63a for hydrolyzing the urea water spray 58 and its vapor and supplying NH ₃ gas to the denitration catalyst 6 is disposed downstream of the heat transfer tube 62a. The hydrolysis catalyst 63a can also be heated by a heater wound around the outer periphery of the heat transfer tube 62a, so that the hydrolysis catalyst 63a can be brought to the early activation temperature or higher from the time when the diverted gas 9a is relatively low in temperature. The NOx removal rate can be improved from a relatively low exhaust temperature. Here, the hydrolysis catalyst 63a is not limited to a honeycomb shape, and may be a honeycomb-shaped or plate-shaped parallel flow type or granular.

  Further, the urea water spray 38 is directly supplied from the main injection valve 30 into the flue 5 into the branch pipe 70 downstream of the hydrolysis catalyst 63a. At that time, the urea water spray 38 is mixed with the diverted gas 9a or the mixed gas 9b, and then becomes the mixed gas 9c and passes through the urea vapor outlet 71. Thereafter, the mixed gas 9d is promoted to be mixed with the exhaust gas 10 passing through the flue 5 and flows downstream of the urea vapor outlet 71 in the flue 5. Further, the mixed gas 9d passes through the mixing promoting material 11, whereby the exhaust gas 10 and the mixed gas 9d are more uniformly mixed and promoted to become the mixed gas 22.

  Next, the operation of the exhaust treatment apparatus 120a according to the first embodiment of the present invention will be described with reference to FIG. In the diesel engine 1, the flow rate and temperature of the exhaust 8 from the engine 1 change according to the operating state. At that time, the amount of NOx discharged also changes according to the operating state. For example, in general, when the engine 1 is in a low load operation, the exhaust flow rate is relatively small, the exhaust temperature is low, and the NOx emission amount is also small. Further, when the engine 1 is in a high load operation, the exhaust flow rate is high, the exhaust temperature is high, and the NOx emission amount is also large.

  In the above-described method of operating the engine 1 and supplying (adding) urea water 13 as a reducing agent to the flue 5 in accordance with the NOx emission amount, the exhaust temperature from the engine 1 is used in the present embodiment. Is less than about 300 ° C., which is a relatively low temperature, the heater 61a disposed on the outer periphery of the heat transfer tube 62a is energized (heater ON), the heater 61a is heated, and the inner wall surface of the passage 66 in the heat transfer tube 62a Heat. At that time, a urea water spray 58 as a reducing agent corresponding to the amount of NOx discharged from the engine 1 is injected from the sub injection valve 50 into the passage 66 by a predetermined amount. Accordingly, in the passage 66, the urea water spray 58 passes through the hydrolysis catalyst 63a while being promoted to vaporize urea vapor mainly by the heater heat.

By passing through the hydrolysis catalyst 63a, the hydrolysis of the urea water spray 58 is promoted and converted to NH ₃ gas (it is not 100% converted to NH ₃ gas by the hydrolysis catalyst. Is a mixture of NH ₃ gas and urea vapor). Therefore, the urea water spray 58 is promoted to vaporize at the urea vapor outlet portion 71 and passes almost in a gas state (upper graph <vaporization region> in FIG. 3). Then, after being supplied into the diverter pipe 70 as a mixed gas 9 b of the diverted gas 9 a and NH ₃ gas, it is supplied from the urea vapor outlet portion 71 to the flue 5. Thereafter, after the mixture is promoted to be mixed with the exhaust gas 10 by the mixing accelerator 11 disposed in the flue 5, the mixed gas 22 is supplied to the denitration catalyst 6. At this time, the mixed gas 22 including the urea water spray 58 is supplied in a state where vaporization is promoted before reaching the denitration catalyst 6.

  On the other hand, when the exhaust temperature is about 300 ° C. or higher, which is a relatively high temperature, the heater 61a disposed on the outer peripheral portion of the heat transfer tube 62a is not energized (heater OFF), and the heater 61a has a heat transfer tube 62a. The inner wall surface of the passage 66 is not heated. Further, the urea water spray 58 is not supplied from the sub injection valve 50 to the passage 66. Here, urea water spray 38 which is a reducing agent commensurate with the amount of NOx discharged from the engine 1 is injected from the main injection valve 30 into the passage 67a in the branch pipe 70.

  Here, in the passage 67a, while being vaporized by the exhaust heat of the diverted gas 9a, the mixed gas 9c is supplied to the urea vapor outlet 71, but at that time, the mixed gas 9c is not completely vaporized, and the urea water spray (Upper graph <spray area> in FIG. 3). Thereafter, the mixture is promoted to be mixed with the exhaust gas 10 by the mixing accelerator 11 disposed in the flue 5 and then supplied to the denitration catalyst as a mixed gas 22. At this time, the mixed gas 22 containing the urea water spray 38 is supplied in a state where vaporization is promoted by the amount of heat of the hot exhaust gas 10 in the main passage before reaching the denitration catalyst 6.

  In this embodiment, urea water spray injection from the main injection valve 30 and the sub injection valve 50 is controlled using an exhaust temperature of about 300 ° C. as a boundary condition, but the exhaust temperature is in the vicinity of 300 ° C. and other temperature ranges. The NOx removal rate of high NOx can be obtained also by adjusting the injection amount ratio of the urea water sprays 38 and 58 injected from the injection valves 30 and 50. Therefore, it is not limited that the fuel is injected from only one of the injection valves into a certain exhaust temperature region. For example, in the exhaust temperature condition of about 250 ° C. to 300 ° C. in FIG. 3, the heater 61a disposed on the outer peripheral portion of the heat transfer tube 62a is energized and injected from the main injection valve 30 and the sub injection valve 50. It is also possible to adjust the injection amount of the urea water sprays 38 and 58 to be supplied to the urea steam outlet portion 71 at a predetermined rate so that urea steam and spray can be supplied.

  Here, the main and sub-injection valves 30 and 50 may use upstream swirl-type injection valves that swirl supply the injection fluid and supply the spray on the upstream side of the injection valve injection hole having excellent atomization characteristics of the spray. preferable. However, the injection valve is not limited to the upstream turning type injection valve. If the injection valve has excellent atomization characteristics, the present embodiment can be realized by using a multi-type injection valve.

  As described above, by spraying a predetermined amount of the spray 58 having excellent atomization characteristics according to the operating state of the engine 1, the spray 58 is swirled on the shunt gas 9a on the passage 66 in the heat transfer tube 62a. Therefore, more urea water spray 58 can be vaporized as compared with the case where the passage 66 passes through the passage 66 in the axial direction as it is. In addition, the main and sub injection valves 30 and 50 used in this embodiment apply electromagnetic valves. Therefore, the injection amount is adjusted by duty control of the solenoid valve.

According to the configuration and operation described above, the form of the urea water spray supplied to the flue 5 via the urea vapor outlet 71 depending on the temperature condition of the exhaust 8 discharged from the diesel engine 1 is changed to urea vapor and NH. _{By using 3} gas or urea water spray, it is possible to always supply urea water sprays 38 and 58 as a reducing agent as urea vapor or NH ₃ gas to the denitration catalyst in the entire operation region of the engine 1. Performance can be obtained. That is, NOx discharged from the engine 1 can be greatly improved from being released to the atmosphere. Further, the power consumption for vaporizing the urea water spray is positively promoted by the heater in the operation region at the low exhaust temperature, and is vaporized by the exhaust gas heat in the temperature region at the high exhaust temperature. Therefore, low power consumption can be achieved while maintaining the denitration performance.

  Further, since the NOx emission amount is smaller in the low exhaust temperature region of the engine 1 than in the high exhaust temperature region, the addition amount of the urea water spray 58 as the reducing agent is also small. However, it is difficult to instantly vaporize the urea water spray 58 only with the exhaust heat of the diverted gas 9a in the low exhaust temperature region, and there is a concern about the increase in size and performance deterioration of the apparatus. As a countermeasure, in the present embodiment, the heater 61a heat is utilized only in the low exhaust temperature region to positively promote vaporization, thereby reducing the size and improving the performance of the apparatus.

  On the other hand, in the high exhaust temperature region of the engine 1, the amount of NOx discharged is relatively large, so the amount of urea water spray 38 that is a reducing agent is also large. However, it is possible to instantly vaporize the urea water spray only with the exhaust heat of the exhaust gas in the high exhaust temperature region. Therefore, in the present embodiment, urea water spray is directly supplied to the flue 5 in the high exhaust temperature region and is positively vaporized by the exhaust heat.

  The effect of this embodiment is demonstrated using FIG. FIG. 4 shows the relationship between the denitration catalyst inlet temperature of the mixed gas 22 on the downstream side of the flue 5 and the denitration rate during a predetermined rotation of the engine 1. The conventional specification indicated by the dotted line in the figure is a case where the urea water spray is directly supplied into the flue 5. In the present invention indicated by the solid line, the urea water spray 58 supplied from the sub-injection valve 50 at the low exhaust temperature is used as a heater. Evaporation is actively promoted by the heat of 61 a and supplied to the flue 5, and the urea water spray 38 supplied from the main injection valve 30 is directly supplied to the flue 5 in the high exhaust gas temperature region.

According to the present embodiment, according to the exhaust temperature of the exhaust 8 discharged from the engine 1, after the urea water 13 which is a reducing agent of NOx is promoted to vaporize at a low exhaust temperature, it is supplied with urea vapor and NH ₃ gas, At the time of high exhaust temperature, the urea water 13 was promoted to atomize and directly supplied to the flue 5 as the spray 38. As a result, urea water 13 as a reducing agent can be supplied to the denitration catalyst 6 as urea vapor and NH ₃ gas in the entire operation region (total exhaust temperature region) of the engine 1 (the ratio of urea vapor at a high exhaust temperature). In many cases, the low exhaust temperature passes through the hydrolysis catalyst, so the ratio of NH ₃ gas is large), and high denitration performance can be obtained. In particular, in a region where the denitration catalyst inlet temperature is low, which is a low rotation and low load region, the denitration rate can be significantly improved. For example, when the NOx removal rate is not obtained at a NOx removal catalyst inlet temperature of 200 ° C., the present invention can be improved to about 50%.

“Second Embodiment”
An exhaust treatment apparatus according to a second embodiment of the present invention will be described below with reference to FIGS. FIG. 5 is a diagram showing a detailed configuration of an exhaust treatment apparatus according to the second embodiment of the present invention. 6 is an enlarged view of a portion C of the exhaust treatment apparatus shown in FIG. FIG. 7 is a view showing the spray particle size distribution of the urea water spray used in the exhaust treatment apparatus according to the second embodiment. FIG. 8 is a diagram for explaining the operation of the exhaust treatment apparatus according to the second embodiment of the present invention.

  In FIG. 5, the main configuration and the exhaust gas flow in the second embodiment of the present invention are the same as those in the first embodiment, and a description thereof will be omitted. The difference from the first embodiment lies in the difference in configuration between the exhaust treatment apparatuses 120a and 120b in part A in FIG. In particular, the first embodiment is an exhaust treatment device 120a in which two injection valves, a main injection valve 30 and a sub-injection valve 50, are provided, whereas in the second embodiment, one injection valve 39 is provided. Only arranged. Furthermore, according to the operating state of the engine 1, the shape of the sprays 41a and 41b injected from the injection valve 39 is changed using a compressed air flow different from the exhaust flow, and the flue from the spray urea vapor outlet portion 71 is changed. The urea water 13 which is a reducing agent supplied to 5 can be supplied by urea vapor and spraying. Here, urea vapor is in a gaseous state, and spray is a group of droplets.

  In the second embodiment, the diverted gas 9a is disposed in a swirl chamber 65b disposed on the downstream side of the diverter pipe 72b through the diverter pipe inlet 73 opened on the upstream side of the flue 5 downstream of the DPF 4. It flows into the swivel member 59b and is supplied as a swirl flow in the passage 67b in the heat transfer tube 62b disposed in the heater holder 60b by the flow path structure of the swivel member 59b. Furthermore, since the downstream of the passage 67b communicates with the flue 5 via the urea vapor outlet 71, the shunt gas 9a is again supplied into the flue 5. Here, in the flue 5 on the downstream side of the urea vapor outlet portion 71, the mixing promoting material 11 is disposed. Since the configuration of the mixing promoting material 11 is the same as that of the first embodiment, description thereof is omitted. A hydrolysis catalyst 63b is disposed in the flue 5 downstream of the mixing accelerator 11.

  Further, in the heater holder 60b, there is disposed a heat transfer tube 62b that constitutes a passage 67b on its inner surface. A heater 61b is disposed on the outer periphery of the heat transfer tube 62b. Further, a space 64b for the purpose of heat insulation is disposed on the outer periphery of the heater 61b, and a heater holder 60b is disposed on the outer periphery thereof. Further, the shape of the urea vapor outlet portion 71 is the same as that of the first embodiment, and hence the description thereof is omitted.

  The passage 67b disposed in the heat transfer tube 62b is disposed in the cooling holder 32 disposed on the upstream side of the swirl chamber 65b so that urea water sprays 41a and 41b as a reducing agent can be injected and supplied. An injection valve 39 is provided. A cooling water space 33 is formed inside the cooling holder 32 on the outer periphery of the injection valve 39. In the cooling water space 33, the return urea water 13 from the regulator 16 other than the urea water 13 regulated and supplied by the regulator 16 is supplied to the urea water injection valve 39 via the urea water inlet 40 is supplied to the cooling water inlet. 34 is configured to flow in through 34. The urea water 13 that has flowed into the cooling water space 33 is configured to return to the urea water tank 12 via the cooling water outlet 35 after cooling the injection valve 39.

  An air holder 83 is disposed between the heater holder 60 b and the cooling holder 32. A pressure regulating chamber 84 is disposed in the air holder 83, and an air passage 86 is disposed inside thereof. Further, the spray 41 a. A nozzle hole 85 through which 41b can pass is formed. The air holder 83 is provided with an air introduction pipe 82 communicating with the pressure regulating chamber 84. An electromagnetic valve 80 is disposed at the other end of the air introduction pipe 82. The electromagnetic valve 80 communicates with an air tank 87 in which compressed air is stored. The electromagnetic valve 80 is opened and closed by a control signal from the control unit 2 according to the operating state of the engine 1, and is connected via an air introduction pipe 82. Thus, the compressed air flow 81 can be supplied to the pressure regulating chamber 84 in the air holder 83.

  On the other hand, the urea water spray injected from the injection valve 39 passes through the inside of the turning member 59b disposed in the turning chamber 65b through the injection hole 85 formed in the air holder 83, and is supplied to the passage 67b. It is the composition which is done.

  FIG. 6A shows an enlarged view of a portion C in FIG. FIG. 6B shows a DD cross section in FIG. The shape changing means of the sprays 41a and 41b will be described with reference to FIG. As described in the first embodiment, the NOx emission amount changes according to the operating state of the engine 1. That is, the amount of NOx discharged at a relatively low exhaust temperature is small, and at that time, the urea water 13 as a reducing agent is supplied in a state where vaporization is promoted in the urea vapor outlet portion 71, thereby obtaining a high denitration rate. Further, although the NOx emission amount at a relatively high exhaust temperature is large, the urea water 13 as the reducing agent is accelerated in the urea exhaust outlet 71 in a sprayed state in order to instantaneously promote vaporization due to the high exhaust temperature. Even when supplied, a high denitration rate can be obtained.

  Therefore, in the second embodiment of the present invention, when the exhaust gas temperature is relatively low, the electromagnetic valve 80 is closed, and the compressed air 81 from the air tank 87 is not supplied into the air holder 83, and the fine particles are produced by the injection valve 39. The spray 41b that has been promoted is supplied directly to the passage 67b through the nozzle hole 85 formed in the air holder 83. The spray angle (θw1) of the spray 41b injected from the injection valve 39 at that time is a spray that collides with the upstream end of the passage 67b. Furthermore, since the diverted gas 9a forms a swirling flow in the passage 67b by the swirling chamber 65b and the swirling member 59b, the spray 41b swirls in the passage 67b along the swirling flow. Pass while. At this time, the heater 61b disposed on the outer periphery of the passage 67b is energized to generate heat. Therefore, since the spray 41b injected from the injection valve 39 through the heated passage 67b passes along the swirl flow, vaporization can be promoted by the heater and can be supplied to the urea vapor outlet 71 as urea vapor.

  Next, at a relatively high exhaust temperature, since the spray 41a can be instantly accelerated by exhaust heat, it is not necessary to positively promote vaporization by the heater heat of the heater 61b, and it is allowed to collide with the inner wall surface of the passage 67b. (If the urea water spray collides with the inner wall surface of the passage, there is a risk that urea precipitates may adhere to the wall surface under the temperature condition that no heater heat is applied to the wall surface. Because it becomes difficult to control the supply of urea water to the amount of NOx due to changes in the path diameter). Therefore, the spray 41a is preferably a narrow-angle (θn1) spray. For this purpose, the solenoid valve 80 is opened and the compressed air 81 from the air tank 87 is supplied to the air introduction pipe 82, and then the cylindrical space in the air holder 83 is used. The air is supplied into a certain pressure regulating chamber 84, and the compressed air 81 a is uniformly supplied from the entire circumferential direction of the nozzle hole 85 through the air passage 86 and then supplied from the nozzle hole 85 to the passage 67 b. At that time, since the spray 41b and the compressed air 81a injected from the injection valve 39 pass through the same injection hole 85, the angle of the spray 41a can be narrowed.

  In this way, when the exhaust of the engine 1 is at a low exhaust temperature, it is possible to supply urea vapor that has been vaporized at the urea steam outlet 71, and at a high exhaust temperature, it is possible to supply a narrowed spray. .

  Further, atomization of the spray 41a can be promoted by supplying compressed air to the spray 41a. FIG. 7 shows the result of atomization of the spray. The spray B in FIG. 7 is a particle size distribution of the spray when compressed air is not supplied to the spray, and in this injection valve, the Sauta average particle size is about 60 μm. On the other hand, the spray A is a particle size distribution when compressed air is supplied to the spray. The average particle diameter of the spray A is about 10 μm, and atomization of the spray is very promoted. The fact that the spray 41a is supplied after being promoted to atomize means that the contact area between the spray droplet group and the exhaust increases, so that the heat transfer from the exhaust to the spray can be promoted, and the vaporization of the spray is further promoted. I can plan. Therefore, as compared with the large spray droplet group (spray B), the small droplet group (spray A) can instantaneously promote vaporization.

  Next, the operation of the exhaust treatment apparatus 120b according to the second embodiment of the present invention will be described with reference to FIG. As in the first embodiment of the present invention, in the diesel engine 1, the flow rate and temperature of the exhaust 8 from the engine 1 vary depending on the operating state. At that time, the amount of NOx discharged also changes according to the operating state. For example, in general, when the engine 1 is in a low load operation, the exhaust flow rate is relatively small, the exhaust temperature is low, and the NOx emission amount is also small. Further, when the engine 1 is in a high load operation, the exhaust flow rate is high, the exhaust temperature is high, and the NOx emission amount is also large.

  In the operation state of the engine 1 as described above, in the present embodiment, the exhaust temperature from the engine 1 is relatively low in the method of adding the urea water 13 as the reducing agent to the flue 5 in accordance with the NOx emission amount. When the temperature is less than about 300 ° C., the heater 61b disposed on the outer peripheral portion of the heat transfer tube 62b is energized (fourth stage in FIG. 3: heater ON), the heater 61b is heated, and the passage in the heat transfer tube 62b The inner wall surface 67b is heated. At that time, a urea water spray 41b, which is a reducing agent, corresponding to the amount of NOx discharged from the engine 1 is injected from the injection valve 39 into the passage 67 by a predetermined amount. Therefore, in the passage 67, the urea water spray 41b is promoted to vaporize urea vapor mainly by the heater heat. Therefore, the urea water spray 41b is promoted to vaporize at the urea vapor outlet portion 71 and passes in a substantially gas state (second stage in FIG. 3: <vaporization region>).

  And it is supplied to the flue 5 from the urea vapor outlet 71. Thereafter, mixing with the exhaust gas 10 is promoted by the mixing promoting material 11 disposed in the flue 5, and after passing through the hydrolysis catalyst 63 b, the mixed gas 24 is supplied to the denitration catalyst 6. At this time, the mixed gas 24 containing the urea water spray 41 b is supplied in a state where vaporization is promoted before reaching the denitration catalyst 6.

  On the other hand, when the exhaust temperature is about 300 ° C. or higher, which is a relatively high temperature, the heater 61b disposed on the outer periphery of the heat transfer tube 62b is not energized (fourth stage in FIG. 8: heater OFF). The heating of the inner wall surface of the passage 67 in the heat transfer tube 62b by 61b is not performed. A predetermined amount of urea water spray 41a, which is a reducing agent commensurate with the amount of NOx discharged from the engine 1, is injected from the injection valve 39 into the passage 67b in the heater holder 60b. Here, by supplying the compressed air 81a from the entire circumference of the spray 41a sprayed from the injection valve 39 (third stage in FIG. 3: air assist ON), the spray 41a can be narrowed and atomized. Promotion (Sauta average particle diameter of about 10 μm) can be achieved. Here, in the passage 67b, vaporization is promoted by the exhaust heat of the diverted gas 9a, and the mixed gas 9e is supplied to the urea vapor outlet 71. At that time, the mixed gas 9e is not completely vaporized and is in a state of spraying urea water (second stage in FIG. 8: <spraying area>).

  Thereafter, mixing with the exhaust gas 10 is promoted by the mixing promoting material 11 disposed in the flue 5, hydrolysis is promoted by the hydrolysis catalyst 63 b, and then the mixed gas 24 is supplied to the denitration catalyst. At this time, since the average particle size of the sprayed urea water spray is about 10 μm, the atomization is promoted very much. Therefore, the vaporization time is longer than that of the sprayed Sauta average particle size of 60 μm supplied from the main injection valve 30 of the first embodiment. Therefore, the apparatus can be further reduced in size as compared with the first embodiment. Further, the mixed gas 24 including the urea water spray 41a is supplied in a state where vaporization is accelerated by the amount of heat of the high-temperature exhaust gas 10 before reaching the denitration catalyst 6.

“Third Embodiment”
An exhaust treatment apparatus according to a third embodiment of the present invention will be described below with reference to FIGS. 9 and 10. FIG. 9 is a diagram showing a detailed configuration of an exhaust treatment apparatus according to the third embodiment of the present invention. FIG. 10 is a diagram for explaining the operation of the exhaust treatment apparatus according to the third embodiment of the present invention.

  FIG. 9A is a configuration diagram of an exhaust treatment device 120c according to the third embodiment of the present invention. The configuration of only the portion C in FIG. 5 of the second embodiment is different, and the detailed configuration thereof is shown. Is shown. FIG. 9B is a cross-sectional view taken along the line E-E in FIG. FIG. 9C is a cross-sectional view taken along the line FF in FIG.

  The main configuration and the exhaust gas flow in the third embodiment are the same as those in the second embodiment, and a description thereof will be omitted. The difference from the second embodiment is the difference in the configuration of part C in FIG. In particular, depending on the operating state of the engine 1, the shape of the sprays 42 a and 42 b injected from the injection valve 39 is changed using a compressed air flow different from the exhaust flow, and the flue 5 from the spray steam outlet 71. This is characterized in that urea water, which is a reducing agent supplied to the water, can be supplied by urea vapor and spraying. Here, urea vapor is in a gaseous state, and spray is a group of droplets.

  In the third embodiment, the diverted gas 9a is disposed in a swirl chamber 65c disposed downstream of the diverter pipe 72b via the diverter pipe inlet 73 opened upstream of the flue 5 downstream of the DPF 4. It flows into the swivel member 59c and is supplied as a swirl flow in the passage 67c in the heat transfer tube 62c disposed in the heater holder 60c by the flow path structure of the swivel member 59c. Furthermore, since the downstream of the passage 67 c communicates with the flue 5 via the urea vapor outlet 71, the shunt gas 9 a is again supplied into the flue 5. Here, in the flue 5 on the downstream side of the urea vapor outlet portion 71, the mixing promoting material 11 is disposed. Since the configuration of the mixing promoting material 11 is the same as that of the first embodiment, description thereof is omitted. A hydrolysis catalyst 63b is disposed in the flue 5 downstream of the mixing accelerator 11.

  Further, in the heater holder 60c, a heat transfer tube 62c is disposed that constitutes a passage 67c on its inner surface. A heater 61c is disposed on the outer periphery of the heat transfer tube 62c. Furthermore, a space 64c for the purpose of heat insulation is disposed on the outer periphery of the heater 61c, and a heater holder 60c is disposed on the outer periphery. Further, the shape of the urea vapor outlet portion 71 is the same as that of the first embodiment, and hence the description thereof is omitted.

  The passage 67c disposed in the heat transfer tube 62c is disposed in the cooling holder 32 disposed on the upstream side of the swirl chamber 65c so that urea water sprays 42a and 42b as a reducing agent can be injected and supplied. An injection valve 39 is provided. A cooling water space 33 is formed inside the cooling holder 32 on the outer periphery of the injection valve 39. In the cooling water space 33, the return urea water 13 from the regulator 16 other than the urea water 13 regulated and supplied by the regulator 16 is supplied to the urea water injection valve 39 via the urea water inlet 40 is supplied to the cooling water inlet. 34 is configured to flow in through 34. The urea water 13 that has flowed into the cooling water space 33 is configured to return to the urea water tank 12 via the cooling water outlet 35 after cooling the injection valve 39.

  Air holders 94 and 98 are disposed between the heater holder 60 c and the cooling holder 32. Pressure regulating chambers 95 and 99 are disposed in the air holders 94 and 98, respectively, and a groove 101 and an air passage 96 are disposed inside thereof. Further, injection holes 97 and 102 are formed inside the groove 101 and the air passage 96 and through which the sprays 42a and 42b injected from the injection valve 39 can pass.

  The air holders 94 and 98 are provided with air introduction pipes 90 and 92 that communicate with the pressure regulating chamber. At the other end of each of the air introduction pipes 90 and 92, an electromagnetic valve (not shown) is provided. Each solenoid valve communicates with an air tank 87 (not shown) in which compressed air is stored, and opens and closes each solenoid valve by a control signal from the control unit 2 in accordance with the operating state of the engine 1 to introduce air. The compressed air 91 and 93 can be supplied to the pressure regulating chambers 95 and 99 in the air holders 94 and 98 through the pipes 90 and 92.

  On the other hand, the urea water spray injected from the injection valve 39 passes through the inside of the swivel member 59c disposed in the swirl chamber 65c through the nozzle holes 97 and 102 bored in the air holders 94 and 98, It is the structure supplied to the channel | path 67c.

  Here, the shape changing means of the sprays 42a and 42b will be described. As described in the first embodiment, the NOx emission amount changes according to the operating state of the engine 1. That is, the amount of NOx discharged at a relatively low exhaust temperature is small, and at that time, the urea water 13 as a reducing agent is supplied in a state where vaporization is promoted in the urea vapor outlet portion 71, thereby obtaining a high denitration rate. Further, although the NOx emission amount at a relatively high exhaust temperature is large, the urea water 13 as the reducing agent is accelerated in the urea exhaust outlet 71 in a sprayed state in order to instantaneously promote vaporization due to the high exhaust temperature. Even when supplied, a high denitration rate can be obtained.

  Therefore, in the third embodiment of the present invention, at a relatively low exhaust temperature (for example, less than 300 ° C.), an electromagnetic valve connected to the air introduction pipe 90 (not shown) is opened and the electromagnetic valve connected to the air introduction pipe 92 is opened. The air holder 94 is supplied with the compressed air 91 from the air tank 87, and the compressed air 93 is not supplied, so that the spray 42 b injected from the injection valve 39 is pierced in the air holders 94, 98. It is supplied to the passage 67b through the nozzle holes 97 and 102. At that time, the swivel member 100 (intervened between the air holders 94 and 98) disposed in the air holder 98 has the injection hole 97 so that the spray injected from the injection valve 39 can be supplied to the passage 67c. , 102 and a hole 103 whose center axis is coaxial. Further, a plurality of grooves 101 having a predetermined passage cross-sectional area are formed along the circumferential tangent direction of the hole 103.

  As a result, when the spray 42b passes through the swivel member 100 via the nozzle hole 97, the compressed air 93a is supplied from the spray outer peripheral tangential direction of the spray injection direction vertical cross section, so that the spray has a wide angle (θw2). Can be realized and the atomization is promoted by the compressed air 93a while passing through the nozzle hole 102 and injected into the passage 67c.

  The spray angle (θw2) of the spray 42b injected from the injection valve 39 is spray that collides with the upstream end of the passage 67c. Further, since the diverted gas 9a forms a swirling flow in the passage 67c by the swirling chamber 65c and the swirling member 59c, the spray 42b swirls in the passage 67c along the swirling flow. Pass while. At this time, the heater 61b disposed on the outer periphery of the passage 67c is energized to generate heat. Therefore, since the spray 41b injected from the injection valve 39 through the heated passage 67c passes along the swirl flow, vaporization can be promoted by the heater and can be supplied to the urea vapor outlet 71 as urea vapor.

  Next, when the exhaust temperature is relatively high (for example, 300 ° C. or higher), the spray 42a can be instantly accelerated by exhaust heat, so it is necessary to positively promote vaporization by the heater heat of the heater 61b. It is preferable to supply without causing a collision with the inner wall surface of the passage 67c. Therefore, the spray 42a is preferably a narrow-angle (θn2) spray. Therefore, an electromagnetic valve connected to an air introduction pipe 90 (not shown) is closed, and an electromagnetic valve connected to the air introduction pipe 92 is opened to open an air tank in the air holder 94. By supplying the compressed air 93 from 87 and not supplying the compressed air 91, the spray 42a injected from the injection valve 39 is supplied to the passage 67b via the injection holes 97, 102 formed in the air holders 94, 98. To do. At that time, the swivel member 100 disposed in the air holder 98 has a hole 103 having a central axis coaxial with the nozzle holes 97 and 102 so that the spray injected from the injection valve 39 can be supplied to the passage 67c. It is worn.

  Therefore, after supplying the compressed air 93 to the air introduction pipe 92, the compressed air 93 is supplied into the pressure regulating chamber 99, which is a cylindrical space in the air holder 94, and uniformly from the circumferential direction of the nozzle hole 102 through the air passage 101. After supplying the compressed air 93a, the compressed air 93a is supplied to the passage 67c through the nozzle hole 97, the hole 103, and the nozzle hole 102. At that time, since the spray 42 b and the compressed air 91 a injected from the injection valve 39 pass through the same injection hole 97, the angle of the spray 42 a can be reduced.

  As described above, when the engine 1 has a low exhaust temperature, urea vapor that has been vaporized at the urea steam outlet 71 can be supplied, and when the exhaust temperature is high, a narrow-angled spray can be supplied. Further, atomization of the sprays 42a and 42b can be promoted by supplying compressed air to the sprays 42a and 42b. Further, the sprays 42a and 42b are supplied with the atomization promoted, which means that the contact area between the spray droplet group and the exhaust increases, so heat transfer from the heat of the exhaust and the heater 61c to the spray can be promoted. Further, the vaporization of the spray can be further promoted. Therefore, vaporization of a small droplet group can be instantaneously promoted compared to a large spray droplet group.

  Next, the operation of the exhaust treatment apparatus 120c according to the third embodiment of the present invention will be described with reference to FIG. As in the first embodiment of the present invention, in the diesel engine 1, the flow rate and temperature of the exhaust 8 from the engine 1 vary depending on the operating state. At that time, the amount of NOx discharged also changes according to the operating state. For example, in general, when the engine 1 is in a low load operation, the exhaust flow rate is relatively small, the exhaust temperature is low, and the NOx emission amount is also small. Further, when the engine 1 is in a high load operation, the exhaust flow rate is high, the exhaust temperature is high, and the NOx emission amount is also large.

  In the operation state of the engine 1 as described above, the exhaust temperature from the engine 1 is compared in the third embodiment in the method of adding the urea water 13 as the reducing agent to the flue 5 in accordance with the NOx emission amount. When the temperature is low, for example, less than about 300 ° C., the heater 61b disposed on the outer periphery of the heat transfer tube 62b is energized (fifth stage in FIG. 10: heater ON) to heat the heater 61b and heat transfer tube The inner wall surface of the passage 67c in 62c is heated. At that time, a predetermined amount of urea water spray 42b, which is a reducing agent commensurate with the amount of NOx discharged from the engine 1, is injected from the injection valve 39 into the passage 67c. Further, the compressed air 93a is supplied as if turning from the tangential direction of the vertical section of the spray 42b (third stage in FIG. 3: turning air assist ON).

  As a result, widening and atomization of the urea water spray 42b can be promoted. Further, in the passage 67c, the urea water spray 42b is promoted to be vaporized into urea vapor mainly by the heater heat. Therefore, at the urea vapor outlet portion 71, the urea water spray 42b is promoted to vaporize and passes almost in a gas state (second stage in FIG. 10: <vaporization region>). And it is supplied to the flue 5 from the urea vapor outlet 71. Thereafter, mixing with the exhaust gas 10 is promoted by the mixing promoting material 11 disposed in the flue 5, and after passing through the hydrolysis catalyst 63 b, the mixed gas 24 is supplied to the denitration catalyst 6. At this time, the mixed gas 24 containing the urea water spray 42 b is supplied in a state where vaporization is promoted before reaching the denitration catalyst 6.

  On the other hand, when the exhaust temperature is about 300 ° C. or higher, which is a relatively high temperature, the heater 61c disposed on the outer periphery of the heat transfer tube 62b is not energized (fifth stage in FIG. 10: heater OFF). The inner wall surface of the passage 67c in the heat transfer tube 62c is not heated by 61c. A predetermined amount of urea water spray 42a, which is a reducing agent corresponding to the amount of NOx discharged from the engine 1, is injected from the injection valve 39 into the passage 67c in the heater holder 60c. Here, by supplying the compressed air 91a from the entire circumference of the spray 42a sprayed from the injection valve 39 (fourth stage in FIG. 10: collision air assist ON), the spray 42a can be narrowed and finely divided. Can be promoted (Sauta average particle size of about 10 μm). Here, in the passage 67c, the vaporized gas is promoted by the exhaust heat of the diverted gas 9a and supplied to the urea vapor outlet 71 as a mixed gas 9e. At that time, the mixed gas 9e is not completely vaporized and is in a state of spraying urea water (second stage in FIG. 10: <spraying area>).

  Thereafter, mixing with the exhaust gas 10 is promoted by the mixing promoting material 11 disposed in the flue 5, hydrolysis is promoted by the hydrolysis catalyst 63 b, and then the mixed gas 24 is supplied to the denitration catalyst. At this time, since the average particle size of the sprayed urea water spray is about 10 μm, the atomization is promoted very much. Therefore, the vaporization time is longer than that of the sprayed Sauta average particle size of 60 μm supplied from the main injection valve 30 of the first embodiment. Therefore, compared with the first embodiment, the apparatus can be further reduced in size, and the mixed gas 24 including the urea water spray 41a reaches the denitration catalyst 6 until the denitration catalyst 6 is reached. It is supplied in a state where vaporization is promoted by the amount of heat of the high-temperature exhaust 10 (first stage in FIG. 10: <spraying area>).

In the above description, urea vapor obtained by vaporizing urea water spray at a low exhaust temperature lower than 300 ° C. as an example is generated and supplied (NH ₃ gas by a hydrolysis catalyst is a further specific example), and is supplied. Although it has been disclosed that urea water spray is supplied when the exhaust gas temperature is higher than that, for example, the exhaust gas temperature in the engine operating state is 200 ° C. to 350 ° C. Within the range of ° C., a mixture of urea vapor from the sub-injection line and urea water spray from the main injection line shown in FIG. 2 may be supplied. At this time, the mixing ratio of the mixture is, for example, a temperature close to 350 ° C. while the temperature range described above is detected by the exhaust temperature sensor, and the urea water spray ratio is increased if the temperature is close to 200 ° C. The ratio of urea vapor is increased. Further, in the above description, it has been disclosed that the urea water is sprayed into the split gas of the engine exhaust gas, but this carrier gas and urea vapor and / or urea water spray are used by using an appropriate carrier gas instead of the exhaust gas. May be mixed and supplied to the flue 5 (the mixing promoting material 11 and the upstream side of the denitration catalyst 6).

  As described above, the main features of the exhaust treatment apparatus according to the embodiment of the present invention have the following concept, function, and action. That is, the atomization of urea water is attempted and the exhaust gas of the engine is used as a carrier gas for urea water. Further, according to the operating state of the engine, urea water can be supplied into the flue by either gas or spray, or gas and spray at a predetermined ratio. Here, when urea water injected from the injection valve becomes urea vapor and ammonia gas and reaches the denitration catalyst, compared with the case where it reaches the denitration catalyst as urea water spray, the nitrogen oxide discharged from the engine It is known that there is a difference in denitration performance. Also, when the exhaust temperature is low (for example, the exhaust temperature is less than 300 ° C.), which is a low load region, the vaporization of urea water is promoted by the exhaust heat compared to when the exhaust temperature is high (for example, the exhaust temperature is 300 ° C. or more). Denitration performance is clearly inferior at low exhaust temperatures compared to high exhaust temperatures. In order to obtain high denitration performance, it may be preferable to supply urea water as urea vapor and ammonia gas to the denitration catalyst.

  Therefore, in the present embodiment, urea water is vaporized mainly by heater heat in an operation region where the exhaust amount and the exhaust temperature are low, such as at the time of starting. At this time, since a small amount of NOx is generated, the amount of urea water to be processed is small, and the heater can be vaporized with the minimum necessary power consumption. Also, when the exhaust temperature of the engine is high and a large amount of NOx is generated, the heater heat is not used to vaporize the urea water, but the urea water is directly injected into the exhaust, and the vaporization is accelerated by the exhaust heat of the exhaust. Plan.

  Further, in order to effectively use the heat of the exhaust gas, the exhaust gas and a shunt gas that is a part of the exhaust gas are used as a carrier fluid for spraying urea water injected into the vaporizer and downstream thereof. In addition, a plurality of heaters are arranged so that the evaporation surface of the vaporizer has a predetermined temperature or higher and a predetermined temperature distribution can be formed on the evaporation surface, and each heater is controlled.

  Therefore, according to the present embodiment, when the exhaust temperature is low, the atomized spray injected from the injection valve to the flue is positively promoted by the vaporizer to supply urea vapor. When the exhaust temperature is high, atomized spray injected from the injection valve is supplied to the flue. At that time, since the exhaust temperature in the flue is high, the atomized urea water spray is instantaneous. Vaporization is promoted to urea vapor in the flue in a short time. For this reason, urea vapor can be supplied to the denitration catalyst from the low load region (low exhaust temperature) to the high load region (high exhaust temperature), so when urea water spray is supplied to the denitration catalyst in the entire operation region of the engine. Compared with, high denitration performance can be obtained.

  Further, by arranging a hydrolysis catalyst for promoting urea hydrolysis in the carburetor on the downstream side of the injection valve or in the downstream passage or flue thereof, the urea vapor is more efficiently brought into contact with the hydrolysis catalyst. Ammonia gas is generated and can be supplied to the denitration catalyst. Therefore, it is possible to obtain higher denitration performance than when the denitration catalyst is supplied with urea vapor.

  After all, according to the present invention, it is possible to remove NOx at a high NOx removal rate from the low temperature range to the high temperature range of the exhaust gas temperature while having a low power consumption and a compact device. Therefore, it can be said that the possibility of use in industries that develop and use diesel engines including the automobile industry is very high.

1 is a diagram illustrating an overall configuration of an exhaust treatment apparatus according to a first embodiment of the present invention. It is an enlarged view of the A section of the exhaust treatment device shown in FIG. It is a figure explaining operation | movement of the exhaust-gas treatment apparatus which concerns on the 1st Embodiment of this invention. It is a figure which shows the relationship between the denitration catalyst inlet temperature and the denitration rate in the exhaust treatment apparatus which concerns on embodiment of this invention. It is a figure which shows the detailed structure of the exhaust-gas treatment apparatus which concerns on the 2nd Embodiment of this invention. It is an enlarged view of the C section of the exhaust treatment device shown in FIG. It is a figure which shows the spray particle size distribution of the urea water spray used in the exhaust gas processing apparatus which concerns on 2nd Embodiment. It is a figure explaining operation | movement of the exhaust gas processing apparatus which concerns on the 2nd Embodiment of this invention. It is a figure which shows the detailed structure of the exhaust-gas treatment apparatus which concerns on the 3rd Embodiment of this invention. It is a figure explaining operation | movement of the exhaust gas processing apparatus which concerns on the 3rd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Diesel engine, 2 ... Control unit, 3 ... Flue, 4 ... DPF, 5 ... Flue, 6 ... Denitration catalyst, 7 ... Flue, 8 ... Exhaust, 9a ... Shunt gas, 9d ... Mixed gas, 10 ... exhaust, 11 ... mixing promoting material, 12 ... tank, 13 ... urea water, 14 ... pumps, 15 ... filter, 16 ... regulator, 19 ... exhaust gas temperature sensor, 20 ... NOx sensor, 21 ... NH ₃ sensor, 30 ... main injection Valve 38, urea water spray, 50 ... sub-injection valve, 58 ... urea water spray, 59a ... rotating member, 60a ... heater holder, 61a ... heater, 62a ... heat transfer tube, 63a ... hydrolysis catalyst, 70 ... shunt tube, 71 ... Urea vapor outlet, 81 ... Compressed air flow, 81a ... Compressed air flow, 100 ... Swivel member, 101 ... Groove, 102 ... Injection hole, 120 ... Urea addition device

Claims (9)

An exhaust flue for guiding exhaust gas of the engine, a denitration catalyst reactor provided in the exhaust flue to reduce nitrogen oxides, and urea water is injected upstream of the denitration catalyst reactor to inject the exhaust flue An exhaust treatment device comprising:
When the exhaust gas temperature is a low load region of the engine, the urea water spray injected from the injection valve is vaporized and supplied as urea vapor to the exhaust flue,
An exhaust treatment apparatus that supplies atomized urea water spray injected from the injection valve to the exhaust flue at a high exhaust temperature that is a high load region of an engine. In claim 1,
An exhaust treatment apparatus characterized by supplying urea vapor by promoting vaporization of the urea water spray by a vaporizer having a heating means at the low exhaust temperature. In claim 2,
An exhaust treatment apparatus characterized in that, at the low exhaust temperature, the urea vapor is supplied to the exhaust flue as ammonia gas by passing through a hydrolysis catalyst. In claim 1, 2 or 3,
The exhaust gas treatment is characterized in that the fluid for supplying and transporting the urea vapor, the urea water spray, or the ammonia gas to the exhaust flue is a shunt gas that diverts a part of the exhaust gas flowing through the exhaust flue. apparatus. An exhaust flue for guiding exhaust gas of the engine, a denitration catalyst reactor provided in the exhaust flue to reduce nitrogen oxides, and urea water is injected upstream of the denitration catalyst reactor to inject the exhaust flue An exhaust treatment device comprising:
Providing a diversion means for diverting a part of the exhaust gas flowing through the exhaust flue;
Installing a first injection valve for injecting urea water into a passage through which the divided flow exhaust gas divided by the flow dividing means flows;
A vaporizer that heats urea water injected by the first injection valve to form urea vapor, and a hydrolysis catalyst that generates ammonia gas in the vaporizer or downstream of the diverted exhaust gas passage;
Installing a second injection valve for injecting urea water downstream of the split exhaust gas passage of the hydrolysis catalyst;
An outlet portion of urea vapor, urea water spray or ammonia gas in which the diverted exhaust gas passage communicates with the exhaust flue is disposed downstream of the second injection valve;
Supplying urea vapor and / or ammonia gas generated from urea water spray injected from the first injection valve to the exhaust flue through the outlet when the exhaust gas temperature is a low load region of the engine;
An exhaust treatment apparatus, wherein a urea water spray injected from the second injection valve is supplied to the exhaust flue through the outlet when the exhaust gas temperature is a high load region of an engine. An exhaust flue for guiding exhaust gas of the engine, a denitration catalyst reactor provided in the exhaust flue to reduce nitrogen oxides, and urea water is injected upstream of the denitration catalyst reactor to inject the exhaust flue An exhaust treatment device comprising:
Providing a diversion means for diverting a part of the exhaust gas flowing through the exhaust flue;
Installing a vaporizer with a heat transfer surface having a heating means in a passage through which the divided flow exhaust gas divided by the flow dividing means flows;
An injection valve for spraying urea water toward the heat transfer surface of the vaporizer is provided,
Installing a shape changing means for reducing the outer diameter shape of the spray by colliding an air flow from the outer periphery of the urea water spray injected from the injection valve;
An outlet of urea vapor or urea water spray is provided downstream of the injection valve, the diverted exhaust gas passage communicating with the exhaust flue,
At low exhaust temperature, which is a low load area of the engine, urea water spray injected from the injection valve is converted to urea vapor by heating on the heat transfer surface of the carburetor, and the urea vapor is passed through the outlet portion to the exhaust smoke. Supply to the road,
The urea water spray injected from the injection valve when the exhaust gas temperature is a high load region of the engine is reduced by reducing the outer diameter shape of the spray by the shape changing means and contacting the heat transfer surface. An exhaust treatment apparatus, wherein the exhaust flue is supplied to the exhaust flue through a section. An exhaust flue for guiding exhaust gas of the engine, a denitration catalyst reactor provided in the exhaust flue to reduce nitrogen oxides, and urea water is injected upstream of the denitration catalyst reactor to inject the exhaust flue An exhaust treatment device comprising:
Providing a diversion means for diverting a part of the exhaust gas flowing through the exhaust flue;
Installing a vaporizer with a heat transfer surface having a heating means in a passage through which the divided flow exhaust gas divided by the flow dividing means flows;
An injection valve for spraying urea water toward the heat transfer surface of the vaporizer is provided,
Narrowing means for narrowing the spray by supplying an airflow toward the spray center direction of the vertical cross section of the urea water spray injected from the injection valve, and the spray circumscribing circle tangential direction of the spray direction vertical cross section And widening means to widen the spray by supplying airflow toward
An outlet of urea vapor or urea water spray is provided downstream of the injection valve, the diverted exhaust gas passage communicating with the exhaust flue,
The urea water spray injected from the injection valve at the low exhaust temperature, which is a low load region of the engine, is heated on the heat transfer surface of the carburetor by the operation of the widening means to form urea vapor, and the urea Supplying steam to the exhaust flue through the outlet,
The urea water spray injected from the injection valve at a high exhaust temperature, which is a high load region of the engine, does not come into contact with the heat transfer surface of the carburetor by the operation of the narrowing means, and passes through the outlet portion. An exhaust treatment apparatus that supplies the exhaust flue. An exhaust flue for guiding exhaust gas of the engine, a denitration catalyst reactor provided in the exhaust flue to reduce nitrogen oxides, and urea water is injected upstream of the denitration catalyst reactor to inject the exhaust flue In an exhaust treatment method for removing nitrogen oxides in exhaust gas by providing an injection valve to
First, at the time of a low exhaust temperature that is a low load region of the engine, the urea water spray injected from the injection valve is vaporized to supply this urea vapor to the exhaust flue as urea vapor,
Next, when the exhaust gas temperature is a high load region of the engine, the atomized urea water spray injected from the injection valve is directly supplied to the exhaust flue. An exhaust flue for guiding exhaust gas of the engine, a denitration catalyst reactor provided in the exhaust flue to reduce nitrogen oxides, and urea water is injected upstream of the denitration catalyst reactor to inject the exhaust flue An exhaust treatment device comprising:
Providing a diversion means for diverting a part of the exhaust gas flowing through the exhaust flue;
Installing a first injection valve for injecting urea water into a passage through which the divided flow exhaust gas divided by the flow dividing means flows;
A vaporizer for heating urea water injected by the first injection valve to form urea vapor;
Installing the second injection valve for injecting urea water downstream of the diverted exhaust gas passage of the vaporizer;
An outlet portion for spraying urea vapor or urea water, wherein the diverted exhaust gas passage communicates with the exhaust flue on the downstream side of the second injection valve;
When the exhaust temperature of the exhaust gas is within a predetermined temperature range, urea vapor generated from the urea water spray injected from the first injection valve, and urea water spray injected from the second injection valve; The exhaust gas treatment apparatus is characterized in that the mixed urea vapor and the urea water spray are supplied to the exhaust flue through the outlet portion by appropriately changing the mixing ratio.

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