JP2013124642A - Exhaust emission control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable an exhaust gas temperature on an upstream side of an SCR catalyst to rise to an ammonia production temperature, without the need for a large number of accessary facilities.SOLUTION: An urea aqueous solution spray nozzle 58 is provided in an upstream-side exhaust pipe 18 of a catalyst converter 34 with a built-in SCR catalyst 36. Condensed water c accumulated in a bend 18c of an exhaust pipe 18 is taken out from a condensed water take-out pipe 42, and stored in a condensed water storage tank 46. An electric heater 48 is provided in the condensed water storage tank 46. When an exhaust gas temperature on the upstream side of the catalyst converter 34 does not reach the ammonia production temperature, the condensed water c is heated by the electric heater 48 and turned into water vapor s, and the water vapor s is supplied to the exhaust pipe 18 near an urea aqueous solution supply unit from a water vapor spray nozzle 60 via a water vapor supply pipe 50. This makes the exhaust air temperature near the urea aqueous solution supply unit rise to the ammonia production temperature.

Description

The present invention relates to an exhaust gas purification apparatus for an internal combustion engine that is provided in an exhaust passage of the internal combustion engine and purifies NO _X present in the exhaust gas.

As a diesel engine exhaust gas purification method, an SCR (Selective Catalytic Reduction) system using an aqueous urea solution has been put into practical use. The SCR system injects a urea aqueous solution as a reducing agent into exhaust gas, and decomposes urea in the urea aqueous solution into ammonia by the retained heat of the exhaust gas. SCR catalyst is disposed downstream of the urea aqueous solution injection unit, the NO _X in the exhaust gas adsorbed by the SCR catalyst, it is reacted with ammonia, to decompose to nitrogen and water, thereby reducing the emission concentration of NOx .

This reaction process consists of the following three stages. The temperature required for the reaction in each step uses the retained heat of the exhaust.
First step: CO (NH ₂ ) ₂ aq (urea aqueous solution) → CO (NH ₂ ) ₂ (solid urea)
<Production of solid urea by evaporation of water; reaction required temperature of 100 ° C. or higher>
Second step: CO (NH ₂ ) ₂ (solid urea) → HNCO (isocyanic acid) + NH ₃
<Thermal decomposition of solid urea; reaction required temperature 130-200 ° C.>
Third step: HNCO + H ₂ O → NH ₃ + CO ₂
<Hydrolysis of isocyanic acid; reaction required temperature of 200 ° C. or higher>

  A diesel engine-equipped vehicle is provided with a DPF filter device (Diesel Particulate Filter) that removes particulate matter in the exhaust. When provided in the exhaust passage of the vehicle, the SCR purification device is generally provided under the floor of the vehicle on the downstream side of the DPF filter device from the viewpoint of the heat resistance of the catalyst and the arrangement space. For this reason, the exhaust temperature reaching the catalyst is low. On the other hand, in order to carry out the above reaction, an ammonia generation temperature (preferably 200 ° C. or higher) or a catalyst activation temperature (eg 150 ° C. or higher) that is higher than a certain temperature is required. ing. Therefore, the decomposition reaction of the injected urea aqueous solution is difficult to proceed particularly at the exhaust temperature below the ammonia generation temperature, such as during start-up and low speed / low load driving, and the urea aqueous solution is discharged downstream of the catalyst. End up.

  In order to raise the exhaust gas temperature, it is also known to perform an early temperature raising operation such as post-injection, which causes deterioration of fuel consumption and exhaust properties. As described above, the disposition position of the SCR catalyst is far from the engine, and the exhaust temperature greatly decreases. Therefore, it is not easy to raise the exhaust temperature upstream of the SCR catalyst.

  In Patent Document 1, in an exhaust gas purification apparatus using an SCR catalyst, condensed water contained in exhaust gas is collected and supplied to a storage tank of a solid reducing agent (for example, solid urea) to form a reducing agent aqueous solution. A technique for injecting an aqueous solution into an exhaust passage is disclosed. Also in Patent Document 2, in an exhaust purification apparatus using an SCR catalyst, condensed water contained in the exhaust gas is recovered, and this recovered water is used as dilution water for the high-concentration urea aqueous solution. A technique for supplying a urea aqueous solution diluted with the above to an exhaust passage is disclosed.

  In Patent Document 3, when the exhaust gas temperature or the temperature of the SCR catalyst is low, it is difficult to appropriately generate ammonia from the urea aqueous solution. When the urea aqueous solution is injected into the exhaust passage, the urea aqueous solution enters the exhaust passage. It has been found that one of the causes is that a sufficient amount of water cannot be present around the urea because it is scattered as fine droplets. For this reason, in Patent Document 3, replenishment water is injected into the upstream exhaust passage of the SCR catalyst, or a urea aqueous solution containing a large amount of water is injected into the exhaust passage, thereby providing a sufficient amount of water around the urea. The problem is solved by securing and preparing an ammonia generation environment.

Special Table 2002-510006 JP 2008-280856 A JP 2010-159893 A

  The technology disclosed in Patent Literature 1 and Patent Literature 2 relates to a method of using condensed water generated from exhaust as dilution water for a reducing agent. Therefore, it does not solve the above problem when the exhaust temperature on the upstream side of the SCR catalyst is equal to or lower than the ammonia generation temperature. Further, the technique disclosed in Patent Document 3 does not propose a means for raising the exhaust gas temperature to the ammonia generation temperature, but supplies replenishment water from the outside. Therefore, an extra facility such as a water tank is provided. Need.

  In view of the problems of the prior art, the present invention provides means for raising the exhaust temperature to the ammonia production temperature without requiring a large incidental facility when the upstream exhaust temperature of the SCR catalyst does not reach the ammonia production temperature. It aims to be realized.

In order to achieve this object, an exhaust gas purification apparatus for an internal combustion engine according to the present invention includes a NO _X selective reduction catalyst provided in an exhaust passage and a reduction agent supplying a reducing agent solution to an upstream exhaust passage of the NO _X selective reduction catalyst. agent and a supply device, a reducing agent is hydrolyzed to produce a NH _3, the internal combustion engine to harmless is reacted with NH ₃ to NO _X in the exhaust gas under the catalytic action of the NO _X selective reducing catalyst exhaust gas In the purifier, the condensed water outlet passage that opens to the condensed water storage portion of the exhaust passage, the condensed water storage tank connected to the condensed water outlet passage, the inlet side is connected to the condensed water storage tank, and the outlet end is from the SCR catalyst. Provided in the steam supply path connected to the upstream exhaust passage, the heating device for condensate stored in the condensate storage tank or the condensed water flowing in the condensate supply path to heat the steam, and the steam supply path , Drain water vapor And a pump for pumping toward the passageway.

In the present invention, the condensed water accumulated in the exhaust passage when the internal combustion engine is stopped is taken out from the condensed water outlet pipe and stored in the condensed water storage tank. During operation of the internal combustion engine, when the exhaust temperature on the upstream side of the SCR catalyst does not reach the ammonia generation temperature, for example, immediately after starting or during low speed / low load traveling, the condensate stored in the condensate storage tank is heated. To make water vapor. This water vapor is pumped from the water vapor supply passage to the exhaust passage upstream of the SCR catalyst by a water pump. As a result, the exhaust gas in the exhaust passage is set to an ammonia generation temperature or higher, preferably 200 ° C. or higher, and ammonia is generated from the reducing agent solution supplied to the exhaust passage, thereby enabling NO _X reduction reaction with the SCR catalyst.

  The heating device may be provided in the condensed water storage tank, and the condensed water stored in the condensed water storage tank may be heated into steam, or provided in the steam supply path, and the condensed water being pumped in the steam supply path is heated. And may be water vapor.

  Thus, the condensed water contained in the exhaust is taken out and the condensed water is supplied to the exhaust passage, so that it is not necessary to supply water from the outside, and no auxiliary equipment for supplying external water is required. Further, since condensed water is pumped as water vapor by a pump and injected into the exhaust passage, mixing and stirring of the exhaust gas and condensed water can be promoted, and the temperature of the exhaust gas can be easily raised. Furthermore, since the exhaust temperature can be raised without relying on an early temperature raising operation such as post injection, fuel consumption and exhaust properties are not deteriorated.

  In the present invention, a temperature sensor for detecting the temperature of the exhaust gas flowing into the supply region of the reducing agent solution, a flow rate adjustment valve provided in the condensed water supply path, and a detection value of the temperature sensor are input, and based on the detection value A control device that adjusts the heating amount of the heating device or the opening of the flow rate adjustment valve, adjusts the temperature or flow rate of water vapor flowing into the supply region of the reducing agent solution, and controls the temperature of the exhaust gas in the region to a set temperature; It is good to have. As a result, the exhaust temperature of the reducing agent solution supply region can be accurately controlled to a set temperature equal to or higher than the ammonia generation temperature. Therefore, the condensed water can be heated without excess or deficiency, and energy saving can be achieved.

  In this invention, it is good to provide the check valve which prevents the reverse flow of condensed water in a condensed water extraction path. When the condensed water in the condensed water storage tank or the condensed water flowing through the water vapor supply path is heated to become steam, the pressure in the condensed water storage tank increases. Therefore, there is a possibility that water vapor flows back to the exhaust passage through the condensed water take-out pipe, and this can be prevented by providing a check valve in the condensed water take-out pipe.

  In the present invention, a reducing agent supply device is configured, and a reducing agent spray nozzle that sprays a reducing agent solution from the wall surface of the exhaust passage to the exhaust passage, and water vapor is sprayed to the exhaust passage and is opposed to the reducing agent spray nozzle. It is good to provide the water vapor | steam spray nozzle arrange | positioned so that it may be arrange | positioned on a wall surface and a nozzle opening may face the nozzle opening of a reducing agent spray nozzle. As a result, the reducing agent solution and the water vapor collide with each other across the exhaust flow, so that the exhaust flow is disturbed by the reducing agent solution and the water vapor, and the mixing and stirring of the three-phase flow of the exhaust gas, the reducing agent solution and the water vapor is promoted. To do. Therefore, the generation of ammonia is facilitated by the synergistic effect of the mixing and stirring effect of the three-phase flow and the temperature rising effect of water vapor. If the reducing agent spray nozzle and the water vapor spray nozzle are provided on the wall surface of the exhaust passage so as not to protrude into the exhaust passage, the exhaust flow pressure loss can be suppressed without obstructing the exhaust flow.

  The reducing agent spray nozzle is disposed upstream of the steam spray nozzle in the exhaust flow direction, the spray directions of the nozzle openings of the reducing agent spray nozzle and the steam spray nozzle face each other, and both nozzles are in the exhaust flow. It is good to arrange diagonally to it. By spraying the reducing agent solution and water vapor obliquely with respect to the exhaust flow, the spray region in the cross-sectional direction of the exhaust passage can be expanded. Moreover, the mixing and stirring of the three-phase flow can be further promoted by directing the water vapor spray nozzle toward the upstream side of the exhaust flow.

  The amount of reducing agent solution sprayed from the reducing agent spray nozzle is greater than the amount of steam sprayed from the steam spray nozzle. Therefore, if the nozzle opening of the reducing agent spray nozzle is directed upstream of the exhaust flow, the flow of the exhaust is obstructed, the pressure loss of the exhaust flow increases, and the performance of the internal combustion engine is degraded. Therefore, by arranging the reducing agent spray nozzle upstream from the water vapor spray nozzle and directing the nozzle opening of the reducing agent spray nozzle to the downstream side, it is possible to suppress the pressure loss of the exhaust flow and eliminate the deterioration of the performance of the internal combustion engine. it can.

  Furthermore, it is good to arrange | position so that the axis line of the nozzle opening of a reducing agent spray nozzle and a water vapor spray nozzle may exist on the same line. As a result, the reducing agent solution and the water vapor collide from both sides of the exhaust flow with the exhaust flow sandwiched from the front, thereby further promoting the mixing and stirring of the three-phase flow.

According to the present invention, the condensed water stored in the exhaust passage is stored in the condensed water storage tank via the condensed water discharge pipe, and when the exhaust temperature upstream of the SCR catalyst does not reach the ammonia generation temperature, the condensed water storage tank Since the condensed water accumulated in the water is heated and supplied to the exhaust passage as water vapor, there is no need to supply water from the outside, ammonia is generated by a simple and low-cost means, and NO in the exhaust is exhausted. _X can be purified. In addition, since water vapor is pumped by pump and injected into the exhaust passage, mixing of exhaust gas and water vapor can be promoted, and furthermore, the exhaust temperature can be raised without resorting to an early heating operation such as post injection. Fuel consumption and exhaust properties will not deteriorate.

It is a whole block diagram which shows one Embodiment of this invention apparatus. It is sectional drawing which shows the exhaust passage of the urea aqueous solution spray area | region of the said embodiment.

  Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the component parts described in this embodiment are not intended to limit the scope of the present invention to that unless otherwise specified.

  An embodiment in which the device of the present invention is applied to an in-vehicle diesel engine 10 will be described with reference to FIGS. 1 and 2. In FIG. 1, a cylinder head 14 is provided on an upper part of a cylinder block 12 of an in-vehicle diesel engine 10, and an intake pipe 16 and an exhaust pipe 18 are connected to the cylinder head 14. The exhaust pipe 18 is connected to the exhaust turbine 20 a of the supercharger 20. An oxygen concentration sensor 22 is provided in the exhaust pipe 18 on the downstream side of the exhaust turbine 20a. An oxidation catalyst 24 is provided on the downstream side of the oxygen concentration sensor 22, and a DPF filter device 26 is provided on the downstream side of the oxidation catalyst 24.

  The region of the exhaust pipe 18 where the DPF filter device 26 is provided from the exhaust turbine 20a is disposed in the vertical direction, and is disposed substantially in the horizontal direction via the bent portion 18c on the downstream side of the vertical portion 18a. Condensed water tends to accumulate in the horizontal portion 18b near the bent portion 18c, and an opening 42a of the condensed water discharge pipe 42 opens on the bottom surface of the horizontal portion 18b in the vicinity of the bent portion 18c. A check valve 44 is provided in the condensed water outlet pipe 42 in the vicinity of the opening 42a to prevent the condensed water c taken out from the bent portion 18c to the condensed water outlet pipe 42 from flowing back to the exhaust pipe 18 side.

In the horizontal portion 18b, a temperature sensor 28 for detecting the exhaust temperature, a NO _X sensor 30 for detecting the NO _X concentration in the exhaust, and a urea water supply device for supplying an aqueous urea solution to the exhaust pipe 18 in order from the upstream side in the exhaust flow direction. 32 and a catalytic converter 34 are provided. An SCR catalyst 36 is built in the catalytic converter 34. The urea aqueous solution is sprayed into the exhaust gas by the urea water supply device 32, and the urea in the sprayed urea aqueous solution is decomposed into ammonia depending on the exhaust gas temperature when the exhaust gas is equal to or higher than the ammonia generation temperature. Ammonia formed here reacts with NO _X adsorbed in the SCR catalyst 36 on the downstream side, is decomposed into nitrogen and water.

A downstream exhaust pipe 18 of the catalytic converter 34, NO _X sensor 38 for detecting the concentration of NO _X in the exhaust gas after the catalytic converter passing is provided on the downstream side of the NO _X sensor 38, the pressure control for controlling the exhaust pressure A valve 40 is provided. The pressure control valve 40 has a function of increasing the exhaust pressure by adjusting the degree of opening and closing thereof and promoting the condensation of water vapor contained in the exhaust.

  A condensed water storage tank 46 is provided in the condensed water outlet pipe 42 on the downstream side of the check valve 44. On the inner peripheral surface of the condensed water storage tank 46, an electric heater 48 for heating the condensed water stored in the condensed water storage tank 46 is provided, and a temperature sensor 49 for detecting the temperature of the heated condensed water is provided. It has been. In addition, a steam supply pipe 50 is connected to the condensed water storage tank 46, and the other end of the steam supply pipe 50 is immediately downstream of the urea aqueous solution supply unit and is connected to the upstream exhaust pipe 18 of the catalytic converter 34. It is connected. The steam supply pipe 50 is provided with a pump 52 that pumps the condensed water in the condensed water storage tank 46 to the exhaust pipe 18, and a flow rate adjusting valve 54 is provided downstream of the pump 52.

  The detection value of each sensor is input to the control device 56. Based on these detected values, the control device 56 controls the power supply device 48a of the electric heater 48, adjusts the heating amount of the electric heater 48, controls the flow rate of the pump 52, or controls the flow rate adjusting valve 54 or The opening degree of the pressure control valve 40 is adjusted.

In this configuration, the exhaust e is discharged from the cylinder head 14 by the operation of the on-board diesel engine 10, and the exhaust e exhausted to the exhaust pipe 18 is downstream of the exhaust pipe 18 by the exhaust turbine 20 a of the supercharger 20. Sent. NO in the exhaust gas is converted into NO ₂ by the oxidation catalyst 24, and the particulate matter captured by the DPF filter device 26 is burned and removed by the oxidation action of NO ₂ . In the catalytic converter 34 provided on the downstream side of the DPF filter device 26, NO _X adsorbed on the SCR catalyst 36 is reduced by ammonia and rendered harmless.

  While the vehicle-mounted diesel engine 10 is stopped, the condensed water c flowing down from the vertical portion 18a of the exhaust pipe 18 and stored in the bent portion 18c is taken out from the opening 42a opened on the lower surface of the bent portion 18c to the condensed water outlet pipe 42. . Since the condensed water outlet pipe 42 is arranged in the vertical direction, the condensed water c falls on the condensed water outlet pipe 42 by the action of gravity and is stored in the condensed water storage tank 46. When the in-vehicle diesel engine 10 is started or when running at a low speed / low load, the exhaust gas upstream of the catalytic converter 34 may not reach the ammonia generation temperature.

  Therefore, the exhaust gas temperature is detected by the temperature sensor 28, and when the detected value does not reach the ammonia generation temperature, the electric heater 48 is turned on by the controller 56, and the condensed water c stored in the condensed water storage tank 46 is removed. Heat to steam. Next, the flow control valve 54 is opened by the control device 56 and the condensed water pump 52 is operated. As a result, steam is supplied from the steam supply pipe 50 to the upstream exhaust pipe 18 of the catalytic converter 34.

  The configuration of the exhaust pipe 18 in the vicinity of the urea water supply device 32 will be described with reference to FIG. The urea water supply device 32 includes a urea water spray nozzle 58 provided in the exhaust pipe 18, and the urea aqueous solution is sprayed into the exhaust gas by the urea water spray nozzle 58. A steam spray nozzle 60 is provided on the wall portion of the exhaust pipe 18 slightly downstream of the urea water spray nozzle 58, and the steam supply pipe 50 is connected to the steam spray nozzle 60. Water vapor s is sprayed into the exhaust gas from the water vapor spray nozzle 60. The urea water spray nozzle 58 is mounted on the upper wall of the horizontal portion 18b and is disposed obliquely toward the exhaust downstream side. On the other hand, the water vapor spray nozzle 60 is mounted on the bottom wall of the horizontal portion 18b and is disposed obliquely toward the exhaust upstream side.

  That is, the urea water spray nozzle 58 and the water vapor spray nozzle 60 face each other with the exhaust passage between the upper wall and the bottom wall of the horizontal portion 18b. Further, the positions and directions of the nozzle openings are set so that the axes x of the nozzle openings of both nozzles coincide. For this reason, the urea aqueous solution and the water vapor sprayed in the exhaust gas collide with each other while entraining the exhaust gas flow from both sides. Accordingly, mixing and stirring of the exhaust gas, the urea aqueous solution, and the three-phase flow of water vapor are promoted. As a result, the temperature of the exhaust near the urea water spray nozzle 58 and the downstream thereof rapidly rises to reach the ammonia generation temperature.

Detection values of the temperature sensor 28 and the temperature sensor 49 are input to the control device 56. The control device 56 adjusts the heating amount of the condensed water in the condensed water storage tank 46 or the opening degree of the flow rate adjusting valve 54 so that the detected value of the temperature sensor 28 becomes a set value of 200 ° C. or more, and the exhaust pipe 18. Adjust the temperature or flow rate of water vapor sprayed on As a result, the exhaust temperature in the vicinity of the urea aqueous solution supply unit is maintained at the set value, so that ammonia is reliably generated from urea. Therefore, the NO _X reduction reaction in the catalytic converter 50 can be promoted to make NO _X harmless.

  According to the present embodiment, the condensed water contained in the exhaust is taken out, and this condensed water is supplied to the exhaust pipe 18, so there is no need to supply water from the outside, and no external water supply facility is required. it can. Further, since this condensed water is heated and supplied as water vapor to the exhaust pipe 18 in the vicinity of the urea aqueous solution supply section, the exhaust can be heated to the ammonia production temperature. Therefore, even when the exhaust temperature does not reach the ammonia generation temperature, ammonia can be generated by raising the exhaust temperature. As a result, ammonia can always be reliably generated during operation of the in-vehicle diesel engine 10. Furthermore, since the exhaust temperature can be raised without relying on an early temperature raising operation such as post injection, fuel consumption and exhaust properties are not deteriorated.

  Further, the temperature or flow rate of water vapor sprayed on the exhaust pipe 18 is adjusted by the control device 56 based on the detected values of the temperature sensors 28 and 49, and the exhaust temperature near the urea aqueous solution supply unit becomes a set value of 200 ° C. or more. Therefore, it is possible to heat the condensed water without excess and deficiency and achieve energy saving. Further, since the check valve 44 is provided in the condensed water take-out pipe 42 on the upstream side of the condensed water storage tank 46, there is no possibility that the condensed water that has become water vapor flows back to the horizontal portion 18b.

  Further, since the water vapor of the condensed water is pumped to the water vapor spray nozzle 60 by the pump 52, the water vapor can be sprayed from the water vapor spray nozzle 60 at a high pressure, and mixing and stirring with the exhaust e and the urea aqueous solution can be promoted. In addition, the nozzle opening of the urea water spray nozzle 58 and the nozzle opening of the water vapor spray nozzle 60 are arranged so as to face each other across the exhaust flow, and the axes x of both nozzle openings coincide with each other. And steam collide head-on across the exhaust stream. This facilitates mixing and stirring of the exhaust gas, the urea aqueous solution, and the three-phase flow of water vapor.

Further, since the urea water spray nozzle 58 and the water vapor spray nozzle 60 are disposed on the wall surface of the exhaust passage and do not protrude into the exhaust passage, and spray a urea aqueous solution having a large spray amount toward the downstream side of the exhaust flow, It is not necessary to greatly disturb the exhaust flow. Thereby, the pressure loss of the exhaust flow can be suppressed. Further, since the urea aqueous solution and the water vapor s are sprayed in an oblique direction with respect to the exhaust flow, the spray region in the exhaust can be expanded, and the water vapor spray nozzle 60 is directed toward the upstream side of the exhaust flow. Therefore, the three-phase mixing and stirring effect can be improved. Due to the synergistic effect of the mixed stirring effect and the temperature rise of the exhaust gas by spraying water vapor, the urea aqueous solution spray area and the exhaust gas downstream thereof can be rapidly heated to 200 ° C. or higher. Therefore, it is possible to reliably perform NO _X purification in the generation of ammonia and the SCR catalyst 36.

  Further, since the pressure control valve 40 is provided in the exhaust pipe 18 on the downstream side of the catalytic converter 34, when the amount of condensed water accumulated in the bent portion 18c is small, the opening degree of the pressure control valve 40 is adjusted and the exhaust pipe 18 is not provided. By increasing the pressure, the condensation of water vapor in the exhaust can be promoted and the condensed water can be increased. Thereby, the amount of condensed water sent to the exhaust pipe 18 can be secured.

  In this embodiment, instead of providing the electric heater 48 in the condensed water storage tank 46, the electric heater 48 or other heating device is provided in the steam supply pipe 50 to heat the condensed water flowing through the steam supply pipe 50. Steam may be used.

According to the present invention, in an internal combustion engine equipped with an SCR purifying device, even when the exhaust temperature upstream of the SCR catalyst is low, no extra incidental equipment is required, and the exhaust temperature can be increased to the ammonia generation temperature. _X purification reaction can be maintained.

DESCRIPTION OF SYMBOLS 10 Vehicle-mounted diesel engine 12 Cylinder block 14 Cylinder head 16 Intake pipe 18 Exhaust pipe 20 Supercharger 20a Exhaust turbine 22 Oxygen concentration sensor 24 Oxidation catalyst 26 DPF device 28, 49 Temperature sensor 30, 38 NO _X sensor 32 Urea water supply device 34 Catalytic Converter 36 SCR Catalyst 40 Pressure Control Valve 42 Condensed Water Extraction Pipe 42a Opening 44 Check Valve 46 Condensed Water Storage Tank 48 Electric Heater 48a Power Supply Device 50 Steam Supply Pipe 52 Pump 54 Flow Control Valve 56 Control Device 58 Urea Water Spray Nozzle 60 Steam spray nozzle c Condensate e Exhaust

Claims (4)

A NO _X selective reduction catalyst provided in the exhaust passage, and a reducing agent supply device that supplies a reducing agent solution to the upstream exhaust passage of the NO _X selective reduction catalyst, hydrolyzing the reducing agent to generate NH ₃ An exhaust gas purifying apparatus for an internal combustion engine that renders NO _X in exhaust gas to be harmless by reacting with NH ₃ under the catalytic action of a NO _X selective reduction catalyst,
A condensate outlet that opens to the condensate reservoir in the exhaust passage;
A condensate storage tank connected to the condensate outlet,
A water vapor supply path having an inlet side connected to the condensed water storage tank and an outlet end connected to an exhaust passage upstream of the NO _X selective reduction catalyst;
A heating device that heats the condensed water stored in the condensed water storage tank or the condensed water flowing through the water vapor supply path into water vapor; and
A pump provided in the water vapor supply path, for pumping the water vapor toward the exhaust passage,
An exhaust gas purification apparatus for an internal combustion engine, characterized in that the steam is supplied to an upstream exhaust passage of the NO _X selective reduction catalyst. A temperature sensor for detecting the temperature of the exhaust gas flowing into the supply region of the reducing agent solution;
A flow rate adjusting valve provided in the water vapor supply path;
The detection value of the temperature sensor is input, and based on the detection value, the heating amount of the heating device or the opening of the flow rate adjustment valve is adjusted to adjust the temperature or flow rate of water vapor flowing into the supply region of the reducing agent solution. The exhaust emission control device for an internal combustion engine according to claim 1, further comprising a control device that controls the temperature of the exhaust gas in the region to a set temperature.   The exhaust gas purification apparatus for an internal combustion engine according to claim 1 or 2, wherein a check valve for preventing a reverse flow of the condensed water is provided in the condensed water outlet passage. Constituting the reducing agent supply device, reducing agent spray nozzle for spraying the reducing agent solution from the wall surface of the exhaust passage to the exhaust passage;
A water vapor spray nozzle that sprays water vapor on the exhaust passage and is disposed on the wall surface facing the reducing agent spray nozzle, and the nozzle opening is disposed so as to face the nozzle opening of the reducing agent spray nozzle. The exhaust gas purification apparatus for an internal combustion engine according to any one of claims 1 to 3, wherein the exhaust gas purification apparatus is an internal combustion engine.

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