An after-treatment method for the exhaust gas of a non-road diesel engine with fire prevention function

Abstract

The present invention provides an after-treatment method for the exhaust gas of a non-road diesel engine with a fire prevention function, which includes an exhaust gas cooling system, an exhaust gas after-treatment device system, a metering injection system, a diesel engine and a post-treatment control system; wherein, the normally closed solenoid valve in the metering injection system is connected to the coolant tank at the lower end through a coolant suction pipe, and the normally open solenoid valve is connected to the urea tank at the lower end through a urea suction pipe; the exhaust gas cooling system includes an exhaust gas air-cooled cooler, an exhaust gas water-cooled cooler and an exhaust gas connecting pipe. The present invention realizes the switching of the metering injection medium by changing the solenoid valve state and the injection strategy, so as to achieve the purpose of stopping the urea injection during the DPF active regeneration and reducing the exhaust gas temperature, and then further cools the exhaust gas through the exhaust gas cooling system to achieve the purpose of completely suppressing the formation of soot and sparks, meeting the fire prevention requirements of different types of after-treatment devices.

Description

Technical Field

[0001] The present invention relates to the technical field of diesel engine exhaust aftertreatment, and more particularly to an exhaust aftertreatment method with fire prevention function for non-road diesel engines. Background Art

[0002] Diesel engines have high thermal efficiency, good reliability and durability, and are increasingly favored by the public; non-road diesel engines in China, such as tractors, harvesting machinery, and construction machinery, have a relatively wide application market and are closely related to production and life. Therefore, the emission control system of non-road diesel engines has become a key area for energy conservation and emission reduction. Stricter emission regulations have forced diesel engine manufacturers to install particulate traps and selective catalytic reduction devices to meet the requirements of new emission regulations.

[0003] The oxidation catalytic converter DOC oxidizes carbon monoxide, hydrocarbons and nitric oxide in the exhaust gas into harmless gases through catalytic oxidation; the particulate trap DPF traps the particulates in the engine exhaust in the filter structure through the filter material; the selective catalytic reduction device SCR converts the toxic nitrogen oxides in the exhaust gas into non-toxic nitrogen and water through selective catalytic reduction reaction.

[0004] Due to the wide application range of non-road diesel engines, the matching aftertreatment devices are constantly being improved, and the most important thing is to ensure their safety during use. For non-road mobile machinery, especially harvesting machinery, its main use is to harvest mature grain crops, and the working scenario is in a flammable mature grain crop field. During the active regeneration process of the DPF in the non-road diesel engine aftertreatment device, the exhaust gas temperature at the DPF outlet reaches above 600°C, and the risk of carbon soot and sparks in the exhaust tailpipe increases rapidly. Once a fire breaks out, it will cause major safety accidents and serious economic losses; currently, the non-road diesel engine aftertreatment cooling and fire prevention device is not yet mature. To avoid the exhaust pipe from catching fire due to high temperature and solve the fire prevention problem during the regeneration of the non-road diesel engine exhaust aftertreatment device, the present application proposes an exhaust aftertreatment method with fire prevention function for non-road diesel engines. Summary of the Invention

[0005] In view of the defects and deficiencies in the prior art, the present invention proposes an exhaust aftertreatment method with fire prevention function for non-road diesel engines, which uses the switching of the injection medium in the metering injection system and the working processes of water cooling and air cooling in the exhaust gas cooling system to reduce the exhaust gas temperature, inhibit the formation of carbon soot and sparks in the exhaust gas, and improve the fire prevention function of non-road diesel engines.

[0006] The technical solution adopted by the exhaust aftertreatment method with fire prevention function for non-road diesel engines of the present invention is as follows:

[0007] (1) The exhaust gas is discharged from the diesel engine exhaust pipe and enters the DOC unit, DPF unit, and SCR unit in the exhaust gas after-treatment device system in sequence;

[0008] (2) After the exhaust gas enters the exhaust gas after-treatment device system, the metering injection system realizes the switching process of the injection medium from urea solution to coolant during the normal operation of the diesel engine and during active regeneration. The specific process is as follows: During the normal operation of the diesel engine, the normally closed solenoid valve is in the normally closed state, the normally open solenoid valve is in the normally open state, the injection pump suction pipe and the urea suction pipe between the metering injection pump and the urea tank are in a connected state. The controller collects the working conditions information of the diesel engine through the wire harness, calculates the urea solution injection amount according to the calibrated data, and then sends the corresponding injection amount signal to the metering injection pump through the wire harness. The metering injection pump injects the corresponding amount of urea solution into the exhaust connection pipe in the exhaust gas after-treatment device system through the nozzle. The urea pyrolyzes to produce ammonia, which reacts with nitrogen oxides in the exhaust gas to generate nitrogen; During the active regeneration of the diesel engine, the normally closed solenoid valve opens, the normally open solenoid valve closes, the injection pump suction pipe and the coolant suction pipe between the metering injection pump and the coolant tank are in a connected state. The controller collects the sensor information of the diesel engine and the after-treatment system through the wire harness, calculates the coolant injection amount according to the calibrated data, and then sends the corresponding injection amount signal to the metering injection pump through the wire harness. The metering injection pump injects the corresponding amount of coolant into the exhaust connection pipe in the exhaust gas after-treatment device system through the nozzle, and the atomized coolant evaporates into gas when heated;

[0009] (3) The exhaust gas after purification and cooling is discharged from the exhaust gas after-treatment device system and enters the exhaust gas water-cooled cooler and the exhaust gas air-cooled cooler in the exhaust gas cooling system. The exhaust gas after secondary cooling is discharged from the air-cooled exhaust port;

[0010] Further, the water flow direction of the exhaust gas water-cooled cooler is opposite to the exhaust gas flow direction;

[0011] Further, a Venturi tube is arranged inside the exhaust gas air-cooled cooler.

[0012] Compared with the prior art, the present invention has the following advantages:

[0013] (1) The present invention realizes the switching of the metering injection medium by changing the solenoid valve state and the injection strategy, achieves the purpose of stopping urea injection during DPF active regeneration and reducing the exhaust gas temperature, and then further cools the exhaust gas through the exhaust gas cooling system to achieve the purpose of completely suppressing the formation of soot and sparks, meeting the fire prevention requirements of different types of after-treatment devices.

[0014] (2) During the coolant injection process of the present invention, it is equivalent to cleaning the urea injection pipeline once, which is beneficial to reducing the risk of urea crystallization. Description of the Drawings

[0015] Figure 1 It is a main system component diagram of an exhaust gas aftertreatment device with a fire prevention function for a non-road diesel engine;

[0016] Figure 2 It is a schematic structural diagram of the present invention used on a non-road diesel engine.

[0017] In the figure: 1. Exhaust gas air cooler, 2. Exhaust gas water cooler, 3. Exhaust gas connecting pipe, 4. Nozzle, 5. Injection pipe, 6. Metering injection pump, 7. Suction pipe of injection pump, 8. Normally closed solenoid valve, 9. Normally open solenoid valve, 10. Coolant suction pipe, 11. Urea suction pipe, 12. Coolant tank, 13. Urea tank, 14. Wiring harness, 15. Controller, 16. SCR unit, 17. Exhaust connection pipe, 18. DPF unit, 19. DOC unit, 20. Inlet pipe of exhaust gas water cooler, 21. Outlet pipe of exhaust gas water cooler, 22. Diesel engine, S10. Exhaust gas cooling system, S20. Exhaust gas aftertreatment device system, S30. Metering injection system, S40. Diesel engine and aftertreatment control system. Specific embodiments

[0018] In order to better understand the technical means and effects adopted by the present invention, the present invention will be further elaborated below in conjunction with the accompanying drawings and specific embodiments. The following specific embodiments are implemented based on the technical features of the present invention, and detailed implementation manners and operation steps are given, but the protection scope of the present invention is not limited to the following embodiments.

[0019] For the directional terms that appear in the following description of the specific embodiments of the present invention, the direction is specified and limited here: Taking the exhaust gas discharge order as the limiting condition, from the diesel engine along the exhaust connection pipe to the exhaust gas cooling system, the sequentially limited directional terms are from front to back. In the description of the present invention, it should also be noted that unless otherwise clearly specified and limited, the terms "set", "installed", "connected" should be understood in a broad sense; for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected or indirectly connected. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0020] Please refer to Figure 1, the main system components of an after-treatment device for non-road diesel engines with fire prevention function are as follows, including an exhaust gas cooling system S10, an after-treatment device system S20, a metering injection system S30, and a diesel engine and after-treatment control system S40; the diesel engine is connected to the after-treatment device system S20 through an exhaust connection pipe, and after the exhaust gas is discharged from the diesel engine exhaust pipe, it enters the after-treatment device system S20 for the processes of exhaust gas cooling and purification. The metering injection system S30 is connected to the after-treatment device system S20 through a nozzle, and adjusts the cooling and purification process of the after-treatment of the exhaust gas according to the actual exhaust gas emission situation. The after-treatment control system is connected by a wiring harness and controls the injection time and injection volume of the urea solution and coolant in the metering injection system S30. An exhaust gas cooling system S10 is provided behind the after-treatment device system S20, and the two are connected through an exhaust gas connection pipe. The exhaust gas is cooled by air cooling and water cooling processes in the exhaust gas cooling system S10 and then discharged.

[0021] Please refer to Figure 2, the structure and connection relationship of an exhaust gas aftertreatment device with fire prevention function for non-road diesel engines are as follows: An exhaust gas aftertreatment device system S20 is arranged behind the exhaust pipe of the diesel engine. The exhaust gas aftertreatment device system S20 includes a DOC unit 19, a DPF unit 18, and an SCR unit 16 that are sequentially connected through an exhaust connection pipe 17 in the front-rear direction. One side of the exhaust connection pipe 17 between the DPF unit 18 and the SCR unit 16 is penetrated and connected with a nozzle 4, and the nozzle 4 connects the exhaust gas aftertreatment device system S20 and the metering injection system S30 together; The metering injection system S30 includes an injection pipe 5, a metering injection pump 6, an injection pump suction pipe 7, a normally closed solenoid valve 8, a normally open solenoid valve 9, a coolant suction pipe 10, a coolant tank 12, a urea suction pipe 11, and a urea tank 13. One end of the injection pipe 5 is connected to the nozzle 4 and the other end is connected to the metering injection pump 6. The inlet of the metering injection pump 6 is connected with an injection pump suction pipe 7, and the inlets of the injection pump suction pipe 7 are respectively connected with the coolant suction pipe 10 and the urea suction pipe 11. A normally closed solenoid valve 8 is arranged on the coolant suction pipe and the inlet of this coolant suction pipe is placed in the coolant tank 12. A normally open solenoid valve 9 is arranged on the urea suction pipe and the inlet of this urea suction pipe is placed in the urea tank 13; The diesel engine and the aftertreatment control system S40 include a controller 15 and a wiring harness 14. The controller 15 is connected to the normally closed solenoid valve 8, the normally open solenoid valve 9, the metering injection pump 6, and the diesel engine 22 through the wiring harness 14; Behind the exhaust gas aftertreatment device system S20, there is an exhaust gas cooling system S10. The exhaust gas cooling system S10 includes an exhaust gas air-cooled cooler 1 and an exhaust gas water-cooled cooler 2. The exhaust gas inlet of the exhaust gas water-cooled cooler 2 is connected to the SCR unit through an exhaust gas connection pipe 3, and its exhaust gas outlet is connected to the exhaust gas air-cooled cooler 1. The low-temperature fluid inlet of the exhaust gas water-cooled cooler 2 is connected to the diesel engine through an exhaust gas water-cooled cooler inlet pipe 20, and its low-temperature fluid outlet is connected to the diesel engine through an exhaust gas water-cooled cooler outlet pipe 21; Further, a venturi tube is arranged inside the exhaust gas air-cooled cooler 1.

[0022] The working process of an exhaust gas aftertreatment method with fire prevention function for non-road diesel engines according to the present invention is as follows: (1) Exhaust gas is discharged from the diesel engine exhaust pipe and sequentially enters the DOC unit 19, the DPF unit 18, and the SCR unit 16 for the purpose of removing pollutants such as carbon monoxide, hydrocarbons, solid particles, and nitrogen oxides. The technical solutions of the foregoing devices are the same as those of the existing exhaust gas purification devices and will not be elaborated here.

[0023] (2) After the exhaust gas enters the exhaust gas aftertreatment device system S20, the switching process of the injection medium of the metering injection system S30 from urea solution to coolant during the normal operation period and the active regeneration period of the diesel engine is realized through the metering injection system S30. Specifically as follows:

[0024] During the normal operation of the diesel engine, the normally closed solenoid valve 8 is in the normally closed state, and the normally open solenoid valve 9 is in the normally open state. The injection pump suction pipe 7 and the urea suction pipe 11 between the metering injection pump 6 and the urea tank 13 are in a connected state. The controller 15 collects the operating conditions information of the diesel engine through the wiring harness 14, calculates the urea solution injection amount according to the calibrated data, and then sends the corresponding injection amount signal to the metering injection pump 6 through the wiring harness 14. The metering injection pump 6 injects the corresponding amount of urea solution into the exhaust connection pipe 17 in the exhaust gas aftertreatment device system S20 through the nozzle 4. The urea pyrolyzes to generate ammonia, which reacts with the nitrogen oxides in the exhaust gas to generate nitrogen, thereby achieving the purpose of reducing the nitrogen oxides in the exhaust gas. During the active regeneration of the diesel engine, the normally closed solenoid valve 8 is opened and the normally open solenoid valve 9 is closed. The injection pump suction pipe 7 and the coolant suction pipe 10 between the metering injection pump 6 and the coolant tank 12 are in a connected state. The controller 15 collects the sensor information of the diesel engine and the aftertreatment system through the wiring harness 14, calculates the coolant injection amount according to the calibrated data, and then sends the corresponding injection amount signal to the metering injection pump 6 through the wiring harness 14. The metering injection pump 6 injects the corresponding amount of coolant into the exhaust connection pipe 17 in the exhaust gas aftertreatment device system S20 through the nozzle 4. The atomized coolant evaporates into gas when heated, thereby achieving the purpose of reducing the exhaust gas temperature.

[0025] (3) The exhaust gas after purification and cooling is discharged from the exhaust gas aftertreatment device system S20 and enters the exhaust gas water-cooled cooler 2 and the exhaust gas air-cooled cooler 1 in the exhaust gas cooling system S10. The exhaust gas after secondary cooling is discharged from the air-cooled exhaust port. The water flow direction of the exhaust gas water-cooled cooler 2 is opposite to the exhaust gas flow direction, which can better reduce the exhaust gas temperature. There is a Venturi tube in the internal structure of the exhaust gas air-cooled cooler 1. When the exhaust gas flow passes through, since the air pressure at the Venturi tube outlet is less than the external environmental pressure, the external cold fresh air is introduced into the exhaust pipe to mix with the exhaust gas, achieving the effect of further cooling the exhaust gas.

[0026] During the active regeneration of the exhaust gas aftertreatment device system in the present invention, by switching the solenoid valve state and the injection strategy, the switching of the injection media urea solution and coolant is realized, achieving the purpose of reducing the exhaust gas temperature and suppressing the formation of soot and sparks in the exhaust gas. Moreover, the exhaust gas is further cooled by the exhaust gas cooling system, thereby achieving the purpose of completely suppressing the formation of soot and sparks. In addition, during the coolant injection process, it is equivalent to cleaning the residual urea solution in the pipeline, thereby greatly reducing the risk of urea crystallization during the urea solution injection process.

[0027] The present invention may have other forms of embodiments based on the above device, and will not be enumerated one by one. Therefore, any person skilled in the art, without departing from the scope of the technical solution of the present invention, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. An aftertreatment method for the exhaust gas of a non-road diesel engine with a fire prevention function, characterized in that: (1) The exhaust gas is discharged from the diesel engine exhaust pipe and enters the DOC unit, DPF unit, and SCR unit in the exhaust gas aftertreatment device system in sequence. (2) After the exhaust gas enters the exhaust gas aftertreatment device system, the switching process of the injection medium of the metering injection system from urea solution to coolant during the normal operation of the diesel engine and during active regeneration is realized through the metering injection system, as follows: During the normal operation of the diesel engine, the normally closed solenoid valve is in the normally closed state, the normally open solenoid valve is in the normally open state, the injection pump suction pipe and the urea suction pipe between the metering injection pump and the urea tank are in a connected state. The controller collects the working condition information of the diesel engine through the wire harness, calculates the urea solution injection amount according to the calibrated data, and then sends the corresponding injection amount signal to the metering injection pump through the wire harness. The metering injection pump injects the corresponding amount of urea solution into the exhaust connection pipe in the exhaust gas aftertreatment device system through the nozzle. The urea pyrolyzes to generate ammonia, which reacts with nitrogen oxides in the exhaust gas to generate nitrogen; During the active regeneration of the diesel engine, the normally closed solenoid valve opens, the normally open solenoid valve closes, the injection pump suction pipe and the coolant suction pipe between the metering injection pump and the coolant tank are in a connected state. The controller collects the sensor information of the diesel engine and the aftertreatment system through the wire harness, calculates the coolant injection amount according to the calibrated data, and then sends the corresponding injection amount signal to the metering injection pump through the wire harness. The metering injection pump injects the corresponding amount of coolant into the exhaust connection pipe in the exhaust gas aftertreatment device system through the nozzle, and the atomized coolant evaporates into gas when heated. (3) The exhaust gas after purification and cooling is discharged from the exhaust gas aftertreatment device system and enters the exhaust gas water-cooled cooler and the exhaust gas air-cooled cooler in the exhaust gas cooling system. The exhaust gas after secondary cooling is discharged from the air-cooled exhaust port.

2. The aftertreatment method for the exhaust gas of a non-road diesel engine with a fire prevention function according to claim 1, characterized in that The water flow direction of the exhaust gas water-cooled cooler is opposite to the exhaust gas flow direction. The low-temperature fluid inlet of the exhaust gas water-cooled cooler is connected to the diesel engine through the exhaust gas water-cooled cooler inlet pipe, and its low-temperature fluid outlet is connected to the diesel engine through the exhaust gas water-cooled cooler outlet pipe.

3. The aftertreatment method for the exhaust gas of a non-road diesel engine with a fire prevention function according to claim 1, characterized in that A venturi tube is arranged inside the exhaust gas air-cooled cooler.

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