WO2014203350A1

WO2014203350A1 - Exhaust gas purification device and method for thawing liquid reducing agent or precursor thereof

Info

Publication number: WO2014203350A1
Application number: PCT/JP2013/066847
Authority: WO
Inventors: 慶太郎渡邉
Original assignee: ボルボラストバグナーアクチエボラグ
Priority date: 2013-06-19
Filing date: 2013-06-19
Publication date: 2014-12-24

Abstract

Provided is an exhaust gas purification device wherein the housing for exhaust gas purification elements and the casing for a tank are formed into one body with a heat-insulating member interposed therebetween, said exhaust gas purification elements including a selective catalytic reduction (SCR) converter for purifying NO_x in exhaust gas, and said tank storing a liquid reducing agent or a precursor thereof which is to be supplied by injection to the exhaust gas upstream of the SCR converter. Then, at least a portion of the exhaust gas that has passed through the exhaust gas purification elements is introduced into the casing in order to thaw the liquid reducing agent or the precursor thereof in the tank.

Description

Exhaust purification device, method for thawing liquid reducing agent or precursor thereof

The present invention relates to an exhaust purification device that selectively reduces and purifies nitrogen oxide (NOx) in exhaust gas, and a method for thawing a liquid reducing agent or a precursor thereof used in the exhaust purification device.

SCR converter using ammonia generated by hydrolysis by injecting urea aqueous solution according to engine operating condition upstream of exhaust of selective reduction catalyst (SCR: Selective Catalytic Reduction) converter installed in engine exhaust pipe An exhaust gas purification device that purifies NOx to a harmless component by a selective reduction reaction is known. Since the urea aqueous solution freezes at about −11 ° C., as described in Japanese Patent Application Laid-Open No. 2010-19134 (Patent Document 1), exhaust is led around the tank storing the urea aqueous solution, and the heat of the exhaust is used. A technique for thawing the aqueous urea solution in the tank has been proposed.

JP 2010-19134 A

However, in the exhaust purification device, in order to prevent the urea aqueous solution in the tank from causing a chemical reaction, the exhaust purification element including the SCR converter and the tank are separated to some extent so that the heat of the exhaust purification element is not transmitted to the tank. It is necessary to. For this reason, the space occupied by the exhaust purification element and the tank tends to be large, and for example, it is difficult to secure a space for mounting other components outside the frame of the vehicle body.

Therefore, an object of the present invention is to provide an exhaust purification device and a method for thawing a liquid reducing agent or a precursor thereof that can reduce the space occupied by the exhaust purification element and the tank.

The exhaust purification device includes an exhaust purification element including an SCR converter that purifies NOx in exhaust, an injection nozzle that injects a liquid reducing agent or a precursor thereof upstream of the SCR converter, and a liquid that is supplied from the injection nozzle. A tank that stores the reducing agent or its precursor, and a casing that houses the tank so that an exhaust passage is formed between the tank and the tank. The casing of the exhaust purification element and the casing are integrated with a heat insulating member interposed therebetween, and at least a part of the exhaust gas that has passed through the exhaust purification element is introduced into the exhaust passage of the casing.

A method for thawing a liquid reducing agent or a precursor thereof stores a casing of an exhaust purification element including an SCR converter that purifies NOx in exhaust gas, and a liquid reducing agent or a precursor thereof that is supplied by injection upstream of the exhaust of the SCR converter. The casing containing the tank is integrated with a heat insulating member interposed therebetween, and at least a part of the exhaust gas that has passed through the exhaust purification element is introduced into the casing, so that the liquid reducing agent in the tank or a precursor thereof is added. Decompress.

According to the present invention, the space occupied by the exhaust purification element and the tank can be reduced, and for example, other parts can be attached to the outside of the frame of the vehicle body.

It is a whole lineblock diagram showing an example of an exhaust-air-purification device. It is a top view which shows an example of the layout of the vehicle carrying an exhaust gas purification apparatus. It is a block diagram which shows an example of the specific structure of an exhaust gas purification apparatus. It is a flowchart which shows an example of a control program. It is a block diagram which shows the 1st modification of the specific structure of an exhaust gas purification apparatus. It is a block diagram which shows the 2nd modification of the concrete structure of an exhaust gas purification apparatus. It is a block diagram which shows the 3rd modification of the specific structure of an exhaust gas purification apparatus. It is a perspective view which shows 1st Example of the layout of an exhaust gas purification apparatus. It is a perspective view which shows 2nd Example of the layout of an exhaust gas purification apparatus. It is a perspective view which shows 3rd Example of the layout of an exhaust gas purification apparatus. It is a perspective view which shows 4th Example of the layout of an exhaust gas purification apparatus. It is a perspective view which shows 5th Example of the layout of an exhaust gas purification apparatus.

Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 shows an example of an exhaust purification device that purifies particulate matter (PM) and NOx in exhaust gas.

An intake pipe 120 connected to the intake manifold 110 of the diesel engine 100 includes an air cleaner 130 that filters dust and the like in the intake air along a direction of intake air flow, a compressor 142 of the turbocharger 140 that supercharges intake air, and a compressor 142. An intercooler 150 that cools the intake air that has passed and an intake collector 160 that smoothes the intake pulsation are arranged in this order.

On the other hand, an exhaust pipe 180 connected to an exhaust manifold 170 of the diesel engine 100 is provided with a turbine 144 of a turbocharger 140, a continuously regenerating diesel particulate filter (hereinafter referred to as “DPF”) along the exhaust circulation direction. ) Device 190, injection nozzle 200 for injecting and supplying urea aqueous solution as a reducing agent precursor, SCR converter 210 for selectively reducing and purifying NOx using ammonia generated from urea aqueous solution, and oxidizing ammonia that has passed through SCR converter 210 The oxidation catalytic converter 220 to be operated is arranged in this order. The continuous regeneration type DPF device 190 includes a DOC (Diesel Oxidation Catalyst) converter 192 that oxidizes at least NO (nitrogen monoxide) to NO ₂ (nitrogen dioxide), and a DPF 194 that collects and removes PM. Instead of DPF 194, a CSF (Catalyzed Soot Filter) having a catalyst (active component and additive component) supported on its surface can be used.

The aqueous urea solution stored in the reducing agent tank 230 is supplied to the injection nozzle 200 via a reducing agent addition unit 240 having a built-in pump and flow control valve. Here, the reducing agent addition unit 240 may be divided into a pump module with a built-in pump and a dosing module with a built-in flow control valve. In addition, the reducing agent tank 230 can be mentioned as an example of a tank.

A temperature sensor 250 for measuring the exhaust gas temperature (exhaust gas temperature) is attached to the exhaust pipe 180 located between the continuous regeneration type DPF device 190 and the injection nozzle 200 in order to grasp the active state of the SCR converter 210. Further, a temperature sensor 260 for measuring the temperature of the urea aqueous solution (urea aqueous solution temperature) is attached to the reducing agent tank 230. The output signals of the

temperature sensors

250 and 260 are input to a reducing agent addition control unit (DCU: Dosing Control Unit) 270 having a built-in computer. In addition, the DCU 270 electronically controls the diesel engine 100 via an in-vehicle network such as CAN (Controller Area Network) so that the rotation speed and load as an example of the engine operating state can be read at an arbitrary time. A unit (ECU: Engine Control Unit) 280 is communicably connected.

The DCU 270 executes a control program stored in a nonvolatile memory such as a flash ROM (Read Only Memory), thereby controlling the pump and the flow rate of the reducing agent addition unit 240 based on the exhaust temperature, the rotation speed, and the load. Electronically control the valve. Further, the DCU 270 executes a control program to execute a urea aqueous solution thawing process, which will be described later, based on the urea aqueous solution temperature.

Here, as the load of the diesel engine 100, for example, a state quantity closely related to the engine torque, such as a fuel injection amount, an intake air flow rate, an intake pressure, a supercharging pressure, and an accelerator opening degree can be used. Further, the rotational speed and load of the diesel engine 100 may be directly detected using a known sensor instead of reading from the ECU 280.

In such an exhaust purification device, exhaust from the diesel engine 100 is introduced into the DOC converter 192 of the continuous regeneration type DPF device 190 through the exhaust manifold 170 and the turbine 144 of the turbocharger 140. The exhaust gas introduced into the DOC converter 192 flows to the DPF 194 while NO is oxidized to NO ₂ . In the DPF 194, PM in the exhaust gas is collected, and PM is continuously oxidized (incinerated) using NO ₂ generated by the DOC converter 192.

Further, the urea aqueous solution supplied (added) from the injection nozzle 200 according to the engine operating state is hydrolyzed using exhaust heat and water vapor in the exhaust, and converted into ammonia that functions as a reducing agent. This ammonia is known to be selectively reduced with NOx in the exhaust gas in the SCR converter 210 and purified to harmless H ₂ O (water) and N ₂ (nitrogen). At this time, NO is oxidized to NO ₂ by the DOC converter 192, and the ratio of NO to NO ₂ in the exhaust gas is improved to be suitable for the selective reduction reaction, so that the NOx purification rate in the SCR converter 210 is improved. be able to. On the other hand, the ammonia that has passed through the SCR converter 210 is oxidized by the oxidation catalyst converter 220 disposed downstream of the exhaust gas, so that it is possible to suppress the ammonia from being released into the atmosphere as it is.

FIG. 2 shows an example of the layout of a vehicle equipped with an exhaust emission control device.
A front wheel FW as a driven wheel having a steering mechanism is attached to a front portion of a ladder-shaped frame FRM extending in the front-rear direction of the vehicle body. Further, a rear wheel RW as a drive wheel to which the driving force of the diesel engine 100 is transmitted is attached to the rear portion of the frame FRM. On the right side of the frame FRM, between the front wheel FW and the rear wheel RW, there is an exhaust purification device 300 in which an exhaust purification element and a reducing agent tank 230 are integrated from the front to the rear of the vehicle, and a fuel tank FTK. Installed in order. Here, the exhaust purification element refers to an element having a function of purifying exhaust, such as the DOC converter 192, the DPF 194, the SCR converter 210, and the oxidation catalyst converter 220. On the other hand, on the left side surface of the frame FRM, between the front wheel FW and the rear wheel RW, a battery BTR, a spare tire STR, and three air reservoir tanks ARV are attached in this order from the front to the rear of the vehicle.

As shown in FIG. 3, the exhaust purification apparatus 300 includes a first casing 310 that stores an exhaust purification element, a second casing 320 that stores a reducing agent tank 230, a first casing 310, and a second casing. 320, and a heat insulating member 330 interposed therebetween. Therefore, the first casing 310 and the second casing 320 are integrated with the heat insulating member 330 interposed therebetween. Here, as the heat insulating member 330, for example, high silicate glass fiber having high temperature heat resistance can be used. In addition, while the 1st casing 310 can be mentioned as an example of another casing, the 2nd casing 320 can be mentioned as an example of a casing.

The first casing 310 includes a cylindrical first casing 312, a second cylindrical casing 314 that also has a cylindrical shape, and the far ends of the first casing 312 and the second casing 314. And a communication pipe 316 that communicates with each other. The first housing 312 and the second housing 314 are arranged side by side so that the respective axes are substantially parallel (they may be just parallel in appearance; the same applies hereinafter). The communication pipe 316 is also piped so that its axis is substantially parallel to the axis of the first casing 312 and the axis of the second casing 314.

The first casing 312 has an inlet 312A at the exhaust upstream end and an outlet 312B at the exhaust downstream end. A continuous regenerative DPF device 190, that is, a DOC converter 192 and a DPF 194 is accommodated between the inlet 312A and the outlet 312B.

The second casing 314 has an inlet 314A formed at the exhaust upstream end and an outlet 314B formed at the exhaust downstream end. The SCR converter 210 and the oxidation catalyst converter 220 are accommodated between the inlet 314A and the outlet 314B.

The communication pipe 316 is the exhaust downstream side of the first housing 312, which is the far ends of the first housing 312 and the second housing 314, in other words, the far ends located on the opposite sides of each other. The exhaust port 312B is communicated with the inflow port 314A at the exhaust upstream end of the second housing 314. Therefore, the exhaust from the diesel engine 100 flows into the first casing 312 from the inlet 312A, passes through the DOC converter 192 and the DPF 194, and enters the communication pipe 316 from the outlet 312B. Then, the exhaust gas flows into the second casing 314 from the inlet 314A through the communication pipe 316, passes through the SCR converter 210 and the oxidation catalyst converter 220, and passes from the outlet 314B to the inside of the first casing 310. Discharged. That is, the exhaust passage extending from the first housing 312 to the second housing 314 via the communication pipe 316 is folded once by the communication pipe 316.

The communication pipe 316 is a straight straight pipe having bent portions formed at both ends for connection between the outlet 312B of the first casing 312 and the inlet 314A of the second casing 314. The injection nozzle 200 is attached to the bent portion with respect to the discharge port 312B, and the urea aqueous solution is injected and supplied into the linear pipe. Thereby, the linear length required for the uniform diffusion of the urea aqueous solution into the exhaust gas is secured. In order to promote uniform diffusion of the urea aqueous solution, for example, a mesh-like diffusion member may be installed in the communication pipe 316.

The first casing 310 is made of a metal material such as iron or stainless steel and has a capacity capable of exhibiting a muffler function as a muffler. A discharge port 310 </ b> A is formed in the peripheral wall of the first casing 310 to discharge the exhaust discharged inside thereof to the outside. Accordingly, the exhaust discharged into the first casing 310 from the discharge port 314B of the second housing 314 is silenced by being expanded inside the second casing 310 and discharged from the discharge port 310A. Since the discharge port 310A of the first casing 310 can be formed at any position except the surface facing the second casing 320, it is possible to avoid interference with other parts arranged around the discharge port 310A. .

The second casing 320 is made of a metal material such as iron or stainless steel and has a capacity capable of forming an exhaust passage with the outer wall of the reducing agent tank 230. The second casing 320 is communicated with the first casing 310 via a passage formed by a communication pipe 340 having a cylindrical shape. Here, since the communication pipe 340 penetrates the heat insulating member 330 and communicates the first casing 310 and the second casing 320, the overall length thereof is shortened, and for example, an increase in weight can be suppressed. it can. Therefore, at least a part of the exhaust flowing inside the first casing 310 can be guided to the exhaust passage of the second casing 320 via the communication pipe 340. For this reason, the peripheral wall of the second casing 320 is formed with a discharge port 320 </ b> A for discharging the exhaust led from the first casing 310 to the exhaust passage to the outside. Since the discharge port 320A of the second casing 320 can be formed at any position except the surface facing the first casing 310, it is possible to avoid interference with other parts arranged around the discharge port 320A. .

The communication pipe 340 is provided with a shutter 360 such as a butterfly valve that is opened and closed by a remotely operable actuator 350 such as an electric motor or an air motor in order to open and close the exhaust passage. When the DCU 270 determines that the urea aqueous solution is frozen based on the urea aqueous solution temperature measured by the temperature sensor 260, the DCU 270 outputs a valve opening signal to the actuator 350, and at least a part of the exhaust is reduced. Guide around tank 230. The exhaust led to the periphery of the reducing agent tank 230 exchanges heat with the urea aqueous solution to defrost the urea aqueous solution, and is discharged to the outside through the discharge port 320A. Here, the shutter 360 may be disposed in the discharge port 310 </ b> A of the first casing 310. The DCU 270 can be cited as an example of a control unit.

A reducing agent addition unit 240 is attached to the upper surface of the second casing 320 that houses the reducing agent tank 230. The supply pipe 370 for supplying the urea aqueous solution from the reducing agent addition unit 240 to the injection nozzle 200 is piped at least along the upper surface of the first casing 310, that is, at a position for receiving heat from the exhaust purification element. . Therefore, the supply pipe 370 can efficiently thaw the urea aqueous solution frozen inside by receiving heat of the exhaust gas from the first casing 310 without using a thawing device such as an electric heater, for example. Can do.

FIG. 4 shows an example of a control program that the DCU 270 repeatedly executes at predetermined time intervals when the ignition switch is turned on, for example.
In step 1 (abbreviated as “S1” in FIG. 4, the same applies hereinafter), the DCU 270 reads the urea aqueous solution temperature from the temperature sensor 260.

In Step 2, the DCU 270 determines whether or not the urea aqueous solution stored in the reducing agent tank 230 is frozen. Specifically, the DCU 270 determines whether the urea aqueous solution temperature is equal to or lower than the freezing temperature of the urea aqueous solution. Here, since the urea aqueous solution freezes at about −11 ° C., for example, the freezing temperature of the urea aqueous solution can be set slightly higher than −11 ° C. in consideration of the possibility of freezing by running wind or the like. If the DCU 270 determines that the urea aqueous solution is frozen, the process proceeds to step 3 (Yes), whereas if it determines that the urea aqueous solution is not frozen, the process proceeds to step 4 (No).

In step 3, the DCU 270 outputs a valve opening signal to the actuator 350, thereby opening the shutter 360 and causing the first casing 310 and the second casing 320 to communicate with each other. In this way, a part of the exhaust gas that has passed through the exhaust purification element is guided from the first casing 310 to the second casing 320 through the communication pipe 340. Then, the exhaust gas guided to the second casing 320 contacts the peripheral wall of the reducing agent tank 230 to exchange heat with the urea aqueous solution, and thaws the urea aqueous solution frozen by the heat. At this time, since the exhaust temperature changes depending on the load, for example, even immediately after the diesel engine 100 is started, the urea aqueous solution frozen in the reducing agent tank 230 can be thawed in a short time. The exhaust gas that has not been introduced from the first casing 310 into the second casing 320 is exhausted to the outside through the first casing outlet 310A, and the exhaust gas that has been introduced into the second casing 320 is 2 is discharged to the outside through the outlet 320A of the casing 320.

In step 4, the DCU 270 outputs a valve closing signal to the actuator 350, thereby closing the shutter 360 and blocking communication between the first casing 310 and the second casing 320. In this way, since exhaust gas is not introduced from the first casing 310 to the second casing 320, the urea aqueous solution stored in the reducing agent tank 230 does not excessively rise in temperature. It can suppress chemical reaction.

According to the exhaust gas purification apparatus 300, whether or not the urea aqueous solution is frozen is determined based on the temperature of the urea aqueous solution stored in the reducing agent tank 230. When the urea aqueous solution is frozen, a part of the exhaust gas is introduced from the first casing 310 to the second casing 320, and heat exchange is performed with the urea aqueous solution in the reducing agent tank 230. Thaw the frozen urea solution.

Since the first casing 310 and the second casing 320 are integrated with the heat insulating member 330 interposed therebetween, the occupied space in the frame FRM can be reduced as shown in FIG. For this reason, it becomes possible to arrange | position other parts around it, and can promote the effective utilization of vehicle space. At this time, since the heat insulating member 330 makes it difficult for heat of the exhaust to be transmitted from the first casing 310 to the second casing 320, no problem occurs even if the exhaust purification element and the reducing agent tank 230 are arranged close to each other.

As the exhaust purification element of the exhaust purification apparatus 300, it is only necessary to include at least the SCR converter 210 among the DOC converter 192, the DPF 194, the SCR converter 210, and the oxidation catalyst converter 220 as shown in FIGS. When the exhaust purification device 300 includes only the SCR converter 210, as shown in FIG. 5, the first casing 312 is accommodated in the first casing 310, and the second casing 314 and the communication pipe are accommodated. 316 becomes unnecessary. In the example illustrated in FIG. 6, one of the DPF 192 and the DOC converter 194 is accommodated in the first housing 312.

Further, at least one of the first casing 310 and the second casing 320 in the exhaust purification apparatus 300 is not limited to the configuration in which the first casing 310 and the second casing 320 are arranged in the horizontal direction, as shown in FIGS. Thus, it can also be arranged in the vertical direction. In the example shown in FIGS. 9 and 11, the communication pipe 316 that communicates the first housing 312 and the second housing 314 is the proximal end of the first housing 312 and the second housing 314. The parts communicate with each other.

As shown in FIG. 12, the exhaust purification apparatus 300 includes a first casing 312 (which may be the second casing 314 or both) in which the exhaust purification element is accommodated, and a second casing 320, and a heat insulating member 330. May be integrated. In this case, the 1st housing | casing 312 can be mentioned as an example of a casing.

Furthermore, the liquid reducing agent or its precursor is not limited to an aqueous urea solution, and an ammonia aqueous solution, a light oil mainly composed of hydrocarbons, or the like is used depending on the function of the exhaust purification element that purifies exhaust harmful substances. You can also. In this case, the freezing temperature for determining whether or not the liquid reducing agent or its precursor is frozen may be appropriately selected according to the characteristics.

192 DOC Converter 194 DPF
200 Injection nozzle 210 SCR converter 220 Oxidation catalytic converter 230 Reductant tank 260 Temperature sensor 270 DCU
DESCRIPTION OF SYMBOLS 300 Exhaust gas purification device 310 1st casing 312 1st housing | casing 314 2nd housing | casing 320 2nd casing 330 Heat insulation member 340 Communication pipe 350 Actuator 360 Shutter 370 Supply piping

Claims

An exhaust purification element including a selective reduction catalytic converter that purifies nitrogen oxides in the exhaust;
An injection nozzle for injecting and supplying a liquid reducing agent or a precursor thereof upstream of the exhaust of the selective catalytic reduction converter;
A tank for storing a liquid reducing agent sprayed from the spray nozzle or a precursor thereof;
A casing that houses the tank so that an exhaust passage is formed between the tank and the tank;
Have
The casing of the exhaust purification element and the casing are integrated with a heat insulating member interposed therebetween, and at least a part of the exhaust gas that has passed through the exhaust purification element is introduced into the exhaust passage of the casing.
An exhaust purification device characterized by that.
A remotely operable shutter that opens and closes a passage for introducing a portion of the exhaust that has passed through the exhaust purification element into the exhaust passage of the casing;
A temperature sensor for measuring the temperature of the liquid reducing agent or its precursor stored in the tank;
A control unit that opens and closes the shutter based on the temperature measured by the temperature sensor;
The exhaust emission control device according to claim 1, further comprising:
The control unit determines whether the liquid reducing agent or its precursor stored in the tank is frozen based on the temperature measured by the temperature sensor, and the liquid reducing agent or its precursor is Open the shutter when it is determined that it is frozen,
The exhaust emission control device according to claim 2.
It further has another casing for housing the exhaust purification element casing,
The casing and the other casing are integrated with the heat insulating member interposed therebetween,
The exhaust emission control device according to any one of claims 1 to 3, wherein:
The exhaust purification element has a diesel oxidation catalytic converter that oxidizes at least carbon monoxide in the exhaust into carbon dioxide upstream of the exhaust of the selective catalytic reduction converter.
The exhaust emission control device according to any one of claims 1 to 4, wherein:
The exhaust purification element has a diesel particulate filter that collects particulate matter in the exhaust between the selective reduction catalytic converter and the diesel oxidation catalytic converter.
The exhaust emission control device according to claim 5.
The exhaust purification element has an oxidation catalytic converter that oxidizes a liquid reducing agent or a precursor thereof that has passed through the selective catalytic reduction converter downstream of the selective catalytic reduction converter.
The exhaust emission control device according to any one of claims 1 to 6, wherein:
A passage for introducing a part of the exhaust gas that has passed through the exhaust purification element into the casing penetrates the heat insulating member.
The exhaust emission control device according to any one of claims 1 to 7, wherein:
A supply pipe for supplying a liquid reducing agent or a precursor thereof from the tank to the injection nozzle is piped to a position for receiving heat from the exhaust purification element.
The exhaust emission control device according to any one of claims 1 to 8, wherein
The liquid reducing agent or a precursor thereof is an aqueous urea solution.
The exhaust emission control device according to any one of claims 1 to 9, wherein
A casing for housing a casing for an exhaust purification element including a selective reduction catalytic converter for purifying nitrogen oxide in exhaust gas, and a tank for storing a liquid reducing agent to be injected and supplied upstream of the selective reduction catalytic converter or a precursor thereof. Are integrated with a heat insulating member interposed therebetween, and at least a part of the exhaust gas that has passed through the exhaust purification element is introduced into the casing to defrost the liquid reducing agent or the precursor thereof in the tank. ,
A method for thawing a liquid reducing agent or a precursor thereof.