Liquid ammonia injection system and diesel engine aftertreatment system

Abstract

The invention provides a liquid ammonia injection system and a diesel engine post-treatment system. The liquid ammonia injection system comprises a liquid ammonia tank for storing liquid ammonia, an ammonia gas nozzle and an ammonia gas injection pipe for connecting the liquid ammonia tank and the ammonia gas nozzle, the liquid ammonia tank comprises a tank body, a pressure reducing and stabilizing device and an electronic control unit, the tank body and the pressure reducing and stabilizing device are both electrically connected with the electronic control unit, the tank body is connected with the pressure reducing and stabilizing device through a pipeline, the ammonia gas nozzle is connected with the pressure reducing and stabilizing device through a pipeline, and the electronic control unit is electrically connected with an engine controller; the tank body is provided with a first liquid cooling pipeline which is used for increasing the temperature of liquid ammonia and is communicated with an engine cooling system. The SCR system nitrogen oxide reduction technology has the low-temperature-section tail gas treatment capacity, the NOx conversion efficiency of the SCR system can be effectively improved, the risk that urea crystals are blocked and PM exceeds the standard is solved, a post-treatment mixer is simplified, the exhaust back pressure is reduced, and oil consumption of the whole vehicle is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of diesel engine post-processing, and in particular relates to a liquid ammonia injection system and a diesel engine post-processing system. Background Art

[0002] Conventional diesel engine post-treatment urea injection systems in the prior art include a urea tank, a urea inlet pipe, a urea return pipe, a urea pump, a urea injection pipe, and a nozzle. The working principle is that the urea pump builds pressure, draws urea from the urea tank into the urea pump through the urea inlet pipe, and fills the urea injection pipe and the nozzle. The nozzle opens according to the injection command pulse of the ECU, and urea is injected into the post-treatment under pressure through the urea injection pipe and the nozzle. Urea is hydrolyzed into ammonia (NH3) in the high-temperature exhaust gas; excess urea flows back to the urea tank through the urea return pipe.

[0003] The urea in the existing solution refers to a urea aqueous solution with a urea concentration of 32.5% and a solvent of ultrapure water. Urea can be thermally decomposed to produce ammonia (NH 3 ); One of the triggering conditions of the ECU injection command of the existing scheme is that the exhaust gas temperature is higher than 190°C (or 200°C), the purpose of which is to promote the full decomposition of urea in the exhaust gas to produce ammonia (NH 3 ) and avoid crystallization in post-treatment. Under low-speed and low-load conditions with low exhaust temperature (such as below 190°C), urea is not fully hydrolyzed, and the residual urea forms solid crystals, blocking the mixer; at the same time, less ammonia is produced, resulting in low conversion efficiency of nitrogen oxides and excessive tail emissions. Summary of the invention

[0004] The present invention provides a liquid ammonia injection system. The SCR system nitrogen oxide reduction technology has the tail gas treatment capability in the low temperature section (80-190°C), can effectively improve the NOx conversion efficiency of the SCR system, solve the risks of urea crystallization blockage and PM exceeding the standard, simplify the post-processing mixer, reduce the exhaust back pressure, and is conducive to reducing the fuel consumption of the whole vehicle.

[0005] The present invention provides a liquid ammonia injection system, comprising a liquid ammonia tank for storing liquid ammonia, an ammonia nozzle, and an ammonia injection pipe connecting the liquid ammonia tank and the ammonia nozzle; the liquid ammonia tank comprises a tank body, a pressure reducing and stabilizing device, and an electronic control unit, the tank body and the pressure reducing and stabilizing device are both electrically connected to the electronic control unit, the tank body is connected to the pressure reducing and stabilizing device through a pipeline, the ammonia nozzle is connected to the pressure reducing and stabilizing device through the ammonia injection pipe, and the electronic control unit is electrically connected to an engine controller; the tank body is provided with a first cooling pipeline for increasing the temperature of liquid ammonia and connected to an engine cooling system.

[0006] Preferably, the ammonia nozzle is provided with a second cooling pipeline for reducing the temperature and connected to the engine cooling system. In order to prevent the high-temperature exhaust gas from impacting the nozzle and causing the nozzle to be blocked or damaged, the engine cooling system is added to the ammonia nozzle for cooling protection, ensuring the working stability of the ammonia nozzle.

[0007] Preferably, the pressure reducing and stabilizing device and the ammonia injection pipe are both provided with an electric heating device, and the electric heating device is electrically connected to the electronic control unit. In order to prevent the ammonia in the liquid ammonia injection pipeline from liquefying under low temperature conditions, an electric heating device is added to the pressure reducing and stabilizing device and the ammonia injection pipeline, and whether to heat is controlled by the ambient temperature to ensure the smooth flow of the ammonia injection pipe.

[0008] Preferably, the present invention further comprises a first temperature sensor, a first pressure sensor and a liquid level sensor arranged on the tank body, the electronic control unit monitors the temperature, pressure and liquid level of the liquid ammonia in the tank body and transmits them to the engine controller, and the electronic control unit controls the output pressure of the pressure reducing and stabilizing device. The electronic control unit of the present invention monitors the temperature, pressure and liquid level of the liquid ammonia in the liquid ammonia tank and transmits them to the engine controller, and controls the output pressure of the pressure reducing and stabilizing device at the same time, the ammonia nozzle opens according to the injection instruction pulse of the ECU, and ammonia is sprayed into the post-processing under pressure through the ammonia injection pipe and the ammonia nozzle. The precise control is carried out through the signal of the sensor, and the working reliability is higher.

[0009] Specifically, the present invention further includes a second temperature sensor and a second pressure sensor disposed on the pressure reducing and stabilizing device, and the second temperature sensor and the second pressure sensor are both electrically connected to the electronic control unit. Through the temperature signal and the pressure signal, the pressure reducing and stabilizing device accurately controls the pressure of the ammonia gas, and the ammonia injection is more accurately controlled.

[0010] Preferably, the tank body is cylindrical in structure, and the pressure reducing and stabilizing device (and the electronic control unit) are integrated on the tank body. The tank body has high integration and small volume, which is convenient for vehicle layout.

[0011] Specifically, the engine cooling system heats the liquid ammonia in the liquid ammonia tank with a coolant at 70 to 90° C. through a first cooling pipeline. The liquid ammonia begins to decompose into ammonia gas at a temperature above -33° C. The pressure reducing and stabilizing device controls the gas pressure value of the ammonia gas to 2 to 6 bar by controlling the opening and closing of a water valve.

[0012] The present invention also provides a diesel engine aftertreatment system, which adopts the above-mentioned liquid ammonia injection system and also includes a DOC, a DPF and an SCR arranged in sequence along the exhaust direction, and the injection point of the ammonia nozzle is arranged at the front end of the SCR. In the aftertreatment system of the present invention, the liquid ammonia injection system directly injects ammonia (NH3) into the aftertreatment. The nitrogen oxide reduction technology of the SCR has the tail gas treatment capability in the low temperature section (80-190°C), which can effectively improve the NOx conversion efficiency of the SCR, solve the risks of urea crystallization blockage and PM exceeding the standard, simplify the aftertreatment mixer, reduce the exhaust back pressure, and help reduce the fuel consumption of the whole vehicle.

[0013] Specifically, a mixer is provided on the pipeline between the injection point of the ammonia nozzle and the SCR. The post-treatment system adopts a liquid ammonia injection system combined with a simple mixer. The liquid ammonia injection system directly injects ammonia (NH3) into the post-treatment. Only a simple post-treatment mixer is needed to adjust the uniformity of the flow field. A too complicated mixer is not required, which reduces the cost. At the same time, the simple post-treatment mixer can reduce the exhaust back pressure, which is conducive to reducing the fuel consumption of the whole vehicle.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] SCR's nitrogen oxide reduction technology has the ability to treat exhaust gas in the low-temperature range (80-190°C), which can effectively improve the NOx conversion efficiency of SCR, solve the risks of urea crystallization blockage and PM exceeding the standard, simplify the post-treatment mixer, reduce exhaust back pressure, and help reduce vehicle fuel consumption.

[0016] The circulating engine coolant is used as the heating energy for the vaporization of liquid ammonia and the cooling solution for the nozzle protection device, so the injection system has high working stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a structural schematic diagram of a liquid ammonia injection system described in the present invention.

[0018] Figure 2 The present invention is a structural diagram of a diesel engine aftertreatment system.

[0019] Figure 3 The present invention is a flowchart of a diesel engine aftertreatment system working method.

[0020] In the figure: 1-liquid ammonia tank, 101-tank body, 102-pressure reducing and stabilizing device, 103-electronic control unit, 104-first temperature sensor, 105-first pressure sensor, 106-liquid level sensor, 107-second temperature sensor, 108-second pressure sensor, 2-ammonia injection pipe, 3-ammonia nozzle, 4-engine cooling system, 401-first cooling pipeline, 402-second cooling pipeline, 5-engine controller, 6-DOC, 7-DPF, 8-SCR, 9-mixer. DETAILED DESCRIPTION

[0021] The present invention will be further described below in conjunction with the accompanying drawings and specific implementation methods. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0022] Embodiment 1:

[0023] like Figure 1 and Figure 2 As shown, a liquid ammonia injection system includes a liquid ammonia tank 1 storing liquid ammonia, an ammonia nozzle 3, and an ammonia injection pipe 2 connecting the liquid ammonia tank 1 and the ammonia nozzle 3; the liquid ammonia tank 1 includes a tank body 101, a pressure reducing and stabilizing device 102, and an electronic control unit 103, the tank body 101 and the pressure reducing and stabilizing device 102 are both electrically connected to the electronic control unit 103, the tank body 101 is connected to the pressure reducing and stabilizing device 102 through a pipeline, the ammonia nozzle 3 is connected to the pressure reducing and stabilizing device 102 through the ammonia injection pipe 2, and the electronic control unit 103 is electrically connected to the engine controller 5; the tank body 101 is provided with a first cooling pipeline 401 for increasing the temperature of liquid ammonia and connected to the engine cooling system 4. In this embodiment, the first cooling pipeline 401 heats the hydraulic pressure in the tank body 101, the electronic control unit 103 controls the temperature, gasification and pressure of liquid ammonia in the liquid ammonia tank 1 by controlling the on and off of the engine coolant, and the pressure reducing and stabilizing device 102 is used to adjust the output pressure.

[0024] like Figure 1 As shown, in this embodiment, the ammonia nozzle 3 is provided with a second cooling pipeline 402 for reducing the temperature and connected to the engine cooling system 4. In order to prevent the high-temperature exhaust gas from impacting the nozzle and causing the nozzle to be blocked or damaged, the engine cooling system 4 is added to the ammonia nozzle 3 for cooling protection, ensuring the working stability of the ammonia nozzle 3.

[0025] like Figure 1As shown, in this embodiment, the pressure reducing and stabilizing device 102 and the ammonia injection pipe 2 are both provided with electric heating devices, and the electric heating devices are electrically connected to the electronic control unit 103. In order to prevent the liquefaction of ammonia in the liquid ammonia injection pipeline under low temperature environment, electric heating devices are added to the pressure reducing and stabilizing device 102 and the ammonia injection pipe 2, and the heating is controlled by the ambient temperature to ensure the smooth flow of the ammonia injection pipe 2 and prevent the ammonia from being reversely cooled into liquid ammonia.

[0026] like Figure 1 As shown, this embodiment also includes a first temperature sensor 104, a first pressure sensor 105 and a liquid level sensor 106 arranged on the tank body 101, and the electronic control unit 103 monitors the temperature, pressure and liquid level of the liquid ammonia in the tank body 101 and transmits them to the engine controller 5, and the electronic control unit 103 controls the output pressure of the pressure reducing and stabilizing device 102. The electronic control unit 103 of the present invention monitors the temperature, pressure and liquid level of the liquid ammonia in the liquid ammonia tank 1 and transmits them to the engine controller 5, the engine controller 5 is ECU, and controls the output pressure of the pressure reducing and stabilizing device 102 at the same time, and the ammonia nozzle 3 opens according to the injection instruction pulse of the ECU, and ammonia NH3 is injected into the post-processing under pressure through the ammonia injection pipe 2 and the ammonia nozzle 3. Precise control is carried out through the signal of the sensor, and the working reliability is higher.

[0027] like Figure 1 As shown, this embodiment further includes a second temperature sensor 107 and a second pressure sensor 108 disposed on the pressure reducing and stabilizing device 102, and the second temperature sensor 107 and the second pressure sensor 108 are both electrically connected to the electronic control unit 103. Through the temperature signal and the pressure signal, the pressure reducing and stabilizing device 102 accurately controls the pressure of the ammonia gas, and the ammonia injection is more accurately controlled.

[0028] like Figure 2 As shown, in this embodiment, the tank body 101 is cylindrical, and the pressure reducing and stabilizing device 102 and the electronic control unit 103 are both integrated on the tank body 101. The integration is high, the volume is small, and the whole vehicle layout is convenient.

[0029] In this embodiment, the engine cooling system 4 heats the liquid ammonia in the liquid ammonia tank 1 with a coolant at 70 to 90° C. through the first cooling pipeline 401, and the pressure reducing and stabilizing device 102 controls the gas pressure value of the ammonia gas to 2 to 6 bar.

[0030] Embodiment 2:

[0031] like Figure 2As shown, a diesel engine aftertreatment system adopts the liquid ammonia injection system in the above embodiment 1, and also includes DOC6, DPF7 and SCR8 arranged in sequence along the exhaust direction, and the injection point of the ammonia nozzle 3 is set at the front end of SCR8.

[0032] In this embodiment, DOC refers to an oxidation catalyst, SCR refers to a selective catalytic reducer, and DPF refers to a particulate filter.

[0033] like Figure 1 As shown, specifically, a mixer 9 is provided on the pipeline between the injection point of the ammonia nozzle 3 and the SCR 8. The post-treatment system adopts a liquid ammonia injection system combined with a simple mixer 9. The liquid ammonia injection system directly injects ammonia (NH3) into the post-treatment. Only a simple post-treatment mixer 9 is needed to adjust the uniformity of the flow field. A too complicated mixer 9 is not required, which reduces the cost. At the same time, the simple post-treatment mixer 9 can reduce the exhaust back pressure, which is conducive to reducing the fuel consumption of the whole vehicle.

[0034] like Figure 3 As shown, the specific working steps of this embodiment are as follows:

[0035] Step 1: The engine cooling system 4 is connected to the first cooling pipeline 401 to heat the liquid ammonia in the liquid ammonia tank 1 to raise the temperature of the engine coolant to 70-90° C.;

[0036] Step 2: The liquid ammonia in the liquid ammonia tank 1 is heated to above -33°C, and the liquid ammonia is decomposed into ammonia gas by heat;

[0037] Step 3: The ammonia gas is transported to the pressure reducing and stabilizing device 102, and the pressure reducing and stabilizing device 102 controls the gas pressure at 2 to 6 bar;

[0038] Step 4: the pressure reducing and stabilizing device 102 outputs ammonia gas and fills the ammonia injection pipe 2;

[0039] Step 5: The electronic control unit 103 monitors the liquid ammonia temperature, pressure and liquid level of the liquid ammonia tank 1 and transmits the information to the engine controller 5 . Meanwhile, the electronic control unit 103 controls the output pressure of the pressure reducing and stabilizing device 102 .

[0040] Step 6: The ammonia nozzle 3 is opened according to the injection instruction pulse of the engine controller 5, and ammonia is injected into the aftertreatment system under pressure through the ammonia nozzle 3.

[0041] Specifically, in step 1 of this embodiment, by opening the coolant valve of the first cooling pipeline 401, the coolant at 70-90° C. flows in the pipeline of the liquid ammonia tank 1, and in step 2 of this embodiment, the high-temperature coolant heats the liquid ammonia to above -33° C. and decomposes ammonia gas;

[0042] Specifically, in step 3 of this embodiment, the ammonia pressure in the liquid ammonia tank 1 is controlled at 2 to 6 bar by controlling the circulation and closing of the coolant; the decomposed ammonia is transported to the pressure reducing and stabilizing device 102, and the pressure of the ammonia in the pressure reducing and stabilizing device 102 is controlled at a certain pressure value by the regulation on the electronic control unit 103, and the pressure fluctuation range is ±5%;

[0043] In this embodiment, the electronic control unit 103 in the liquid ammonia tank 1 controls the gasification and pressure of the liquid ammonia in the liquid ammonia tank 1 by controlling the on and off of the engine coolant;

[0044] In order to prevent the ammonia in the liquid ammonia injection pipeline from liquefying under low temperature conditions, an electric heating device is added to the pressure reducing and stabilizing device 102 and the ammonia injection pipe 2 to control heating according to the ambient temperature to prevent the ammonia from cooling back to liquid ammonia.

[0045] In order to prevent the high-temperature exhaust gas from impacting the nozzle and causing the nozzle to be blocked or damaged, an engine cooling system 4 is added to the ammonia injection pipe 2 for cooling protection.

[0046] In this embodiment, the nitrogen oxide reduction technology of SCR8 has the exhaust gas treatment capability in the low temperature section (80-190°C), which can effectively improve the NOx conversion efficiency of SCR8, solve the risks of urea crystallization blockage and PM exceeding the standard, simplify the post-treatment mixer 9, reduce the exhaust back pressure, and help reduce the fuel consumption of the whole vehicle.

Claims

1. A liquid ammonia injection system, characterized in that The invention comprises a liquid ammonia tank (1) for storing liquid ammonia, an ammonia nozzle (3), and an ammonia injection pipe (2) connecting the liquid ammonia tank (1) and the ammonia nozzle (3); the liquid ammonia tank (1) comprises a tank body (101), a pressure reducing and stabilizing device (102), and an electronic control unit (103); the tank body (101) and the pressure reducing and stabilizing device (102) are both electrically connected to the electronic control unit (103); the tank body (101) is connected to the pressure reducing and stabilizing device (102) through a pipeline; the ammonia nozzle (3) is connected to the pressure reducing and stabilizing device (102) through the ammonia injection pipe (2); and the electronic control unit (103) is electrically connected to an engine controller (5); the tank body (101) is provided with a first cooling pipeline (401) for increasing the temperature of liquid ammonia and connected to an engine cooling system (4).

2. A liquid ammonia injection system according to claim 1, characterized in that: The ammonia nozzle (3) is provided with a second cooling pipeline (402) for reducing the temperature and connected to the engine cooling system (4).

3. A liquid ammonia injection system according to claim 1, characterized in that: The pressure reducing and stabilizing device (102) and the ammonia injection pipe (2) are both provided with electric heating devices, and the electric heating devices are electrically connected to the electronic control unit (103).

4. A liquid ammonia injection system according to claim 1, characterized in that: The invention also comprises a first temperature sensor (104), a first pressure sensor (105) and a liquid level sensor (106) arranged on the tank body (101); the electronic control unit (103) monitors the temperature, pressure and liquid level of the liquid ammonia in the tank body (101) and transmits the information to the engine controller (5); the electronic control unit (103) controls the output pressure of the pressure reducing and stabilizing device (102).

5. A liquid ammonia injection system according to claim 1, characterized in that: It also includes a second temperature sensor (107) and a second pressure sensor (108) arranged on the pressure reducing and stabilizing device (102); the second temperature sensor (107) and the second pressure sensor (108) are both electrically connected to the electronic control unit (103).

6. A liquid ammonia injection system according to claim 1, characterized in that: The tank body (101) is of cylindrical construction, and the pressure reducing and stabilizing device (102) and the electronic control unit (103) are both integrated and arranged on the tank body (101).

7. A liquid ammonia injection system according to claim 1, characterized in that: The engine cooling system (4) heats the liquid ammonia in the liquid ammonia tank (1) with a coolant at 70 to 90° C. through a first cooling pipeline (401).

8. A liquid ammonia injection system according to claim 1, characterized in that: The pressure reducing and stabilizing device (102) controls the gas pressure value of ammonia gas to be between 2 and 6 bar.

9. A diesel engine aftertreatment system, using the liquid ammonia injection system according to any one of claims 1 to 8, characterized in that It also includes a DOC (6), a DPF (7) and an SCR (8) which are arranged in sequence along the exhaust direction, and the injection point of the ammonia nozzle (3) is arranged at the front end of the SCR (8).

10. A diesel engine aftertreatment system according to claim 9, characterized in that: A mixer (9) is provided on the pipeline between the injection point of the ammonia nozzle (3) and the SCR (8).

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