Urea injection device for diesel engine tail gas treatment

Abstract

The invention relates to the technical field of diesel engine tail gas treatment, and provides a urea injection device for diesel engine tail gas treatment, which comprises a urea tank and further comprises a decomposition box, the decomposition box is internally provided with a hollow reaction part made of a heat conduction material, and the reaction part is located in a tail gas discharge pipe path. A reaction part is arranged in the decomposition box, the two ends of the reaction part are communicated with a tail gas exhaust pipe, a spraying pipe is further arranged in the decomposition box and located over the reaction part, a plurality of electromagnetic nozzles are arranged on the spraying pipe, the urea spraying device further comprises a metering pump used for pumping a urea solution into the spraying pipe, a gas outlet is formed in the decomposition box, and the electromagnetic nozzles are communicated with the gas outlet. A gas guide pipe is arranged between the gas outlet and the tail gas discharge pipe in a communicating manner; the electromagnetic nozzle is arranged in the decomposition box and does not make contact with the tail gas, it is avoided that particulate matter in the tail gas deposits to block spraying holes of the electromagnetic nozzle, the electromagnetic nozzle is not impacted by high pressure of tail gas flow, the long-term working stability of the electromagnetic nozzle is guaranteed, and the service life is prolonged.

Description

Technical Field

[0001] The present invention relates to the technical field of diesel engine exhaust gas treatment, and specifically to a urea injection device for diesel engine exhaust gas treatment. Background Art

[0002] In a ship power system, as a core propulsion device, the exhaust gas emission treatment of a diesel engine has always been an important research topic in the environmental protection field. Currently, it has become an industry consensus to adopt the urea selective catalytic reduction (SCR) technology to reduce the nitrogen oxide (NOx) emissions in the diesel engine exhaust gas.

[0003] Currently, urea electromagnetic nozzles are usually directly installed in the exhaust gas discharge pipe. Although it is convenient for the direct injection of urea solution, on the one hand, a large amount of particulate matter rich in the exhaust gas, such as unburned soot, sulfates, etc., over time, the particulate matter deposits on the nozzle to form a stubborn carbon deposit layer, which will cause the nozzle holes to be blocked; on the other hand, diesel engines for ships have high power and high exhaust gas flow, so their exhaust gas pressure is relatively high. The electromagnetic nozzles under the impact of this high-pressure gas flow for a long time, the key components such as the internal precision electromagnetic coil, valve core and nozzle holes are easily subject to mechanical wear and thermal stress damage, accelerating the aging process of the nozzle and shortening its service life.

[0004] Therefore, the present invention proposes a urea injection device for diesel engine exhaust gas treatment to solve the above problems. Summary of the Invention

[0005] The purpose of the embodiment of the present invention is to provide a urea injection device for diesel engine exhaust gas treatment to solve the above problems.

[0006] To achieve the above purpose, the present invention provides the following technical solutions:

[0007] A urea injection device for diesel engine exhaust gas treatment includes a urea tank, and also includes a decomposition tank. A reaction part which is hollow inside and made of a heat-conducting material is arranged in the decomposition tank. The reaction part is located in the path of the exhaust gas discharge pipe, and both ends of the reaction part are communicated with the exhaust gas discharge pipe. A spray pipe is further arranged directly above the reaction part inside the decomposition tank. A number of electromagnetic nozzles are arranged in sequence on the spray pipe. The urea injection device further includes a metering pump for pumping urea solution into the spray pipe. An air outlet is arranged on the decomposition tank, and a gas guide pipe is communicated between the air outlet and the exhaust gas discharge pipe.

[0008] In an alternative embodiment: A one-way valve that only allows the gas in the decomposition tank to be discharged into the exhaust gas discharge pipe is arranged on the gas guide pipe.

[0009] In an alternative embodiment: The reaction part is in a cylindrical shape and can rotate. A bracket is arranged at one end of the reaction part, and an impeller for driving the reaction part to rotate by the impact of the exhaust gas is fixedly arranged on the bracket.

[0010] In an alternative solution: The urea injection device further includes a scraping bar for scraping and cleaning the inner wall of the reaction part, and a vibration assembly for axially vibrating the scraping bar during scraping.

[0011] In an alternative solution: The vibration assembly includes a boss provided in the tail gas discharge pipe and a connecting rod provided on the bracket and coaxial with the reaction part. A sliding rod with a square radial cross-section is provided on the scraping bar. The sliding rod slidably penetrates through the boss, and a limiting member is provided at one end of the sliding rod away from the scraping bar. A spring is sleeved on the rod section of the sliding rod between the boss and the limiting member. A suspension rod is also hinged in the tail gas discharge pipe. An impact member capable of hitting the limiting member is provided at the lower end of the suspension rod, and the impact member is located on the side of the limiting member away from the scraping bar. One end of the connecting rod away from the bracket is located on the side of the limiting member away from the impact member, and a baffle for blocking the impact of the tail gas on the impact member is provided.

[0012] In an alternative solution: Electric heating elements are evenly distributed in the side wall of the reaction part, and a temperature sensor for sensing the temperature of the tail gas is also provided in the tail gas discharge pipe.

[0013] In an alternative solution: A gas-liquid separation membrane is also covered at the air outlet.

[0014] In an alternative solution: The urea injection device further includes a liquid scraping assembly for scraping the urea solution on the gas-liquid separation membrane. The liquid scraping assembly includes a shaft body rotatably provided in the decomposition tank and a scraping blade provided at the upper end of the shaft body and in contact with the gas-liquid separation membrane. An external gear ring is sleeved on the reaction part, and a bevel gear meshing with the external gear ring is provided on the shaft body.

[0015] In an alternative solution: The scraping blade includes a blade body and a convex portion in contact with the gas-liquid separation membrane. Liquid receiving grooves are provided on both sides of the blade body where the convex portion is located. A lower liquid channel is provided in the shaft body. The inner bottom side of the liquid receiving groove is symmetrically inclined downward towards the lower liquid channel and is communicated with the lower liquid channel.

[0016] Compared with the prior art, the beneficial effects of the embodiments of the present invention are as follows:

[0017] The diesel engine tail gas emissions pass through the reaction part. The high-temperature tail gas makes the reaction part in a high-temperature state. The urea solution in the urea tank is pumped into the spray pipe by a metering pump, and then sprayed towards the reaction part in a mist form through each electromagnetic nozzle. After the urea solution contacts the reaction part in the high-temperature state, a thermal decomposition reaction occurs to generate ammonia. The generated ammonia enters the tail gas discharge pipe through the air guide pipe and is mixed with the tail gas for subsequent reduction reactions. The electromagnetic nozzles are provided in the decomposition tank and do not come into contact with the tail gas, which not only avoids the deposition of particulate matter in the tail gas causing blockage of the spray holes of the electromagnetic nozzles, but also makes the electromagnetic nozzles not be impacted by the high pressure of the tail gas airflow, ensuring the long-term working stability of the electromagnetic nozzles and improving the service life.

[0018] It should be understood that the above general description and the following detailed description are merely exemplary and explanatory, and do not limit this application. Description of the Drawings

[0019] The drawings herein are incorporated into the specification and form a part of this specification, showing embodiments consistent with this application, and are used together with the specification to explain the principles of this application. At the same time, these drawings and the written description are not intended to limit the scope of the concept of this application in any way, but to illustrate the concept of this application to those skilled in the art by reference to specific embodiments.

[0020] Figure 1 It is a schematic structural diagram of an embodiment of the present invention.

[0021] Figure 2 It is Figure 1 an enlarged view of part A in

[0022] Figure 3 It is a front view of the baffle in an embodiment of the present invention.

[0023] Figure 4 It is Figure 1 an enlarged view of part B in

[0024] Figure 5 It is a schematic structural diagram between the scraping blade and the shaft body in an embodiment of the present invention.

[0025] Annotation of reference numerals in the drawings: 1 - urea tank, 2 - decomposition tank, 3 - reaction member, 4 - spray pipe, 5 - electromagnetic nozzle, 6 - metering pump, 7 - air outlet, 8 - gas guide pipe, 9 - check valve, 10 - impeller, 11 - electric heating member, 12 - scraping bar, 13 - vibration assembly, 1301 - convex platform, 1302 - suspension rod, 1303 - limiting member, 1304 - impact member, 1305 - sliding rod, 1306 - spring, 1307 - baffle, 1308 - connecting rod, 14 - gas-liquid separation membrane, 15 - liquid scraping assembly, 1501 - scraping blade, 15011 - blade body, 15012 - convex portion, 15013 - liquid receiving groove, 1502 - shaft body, 1503 - lower liquid channel, 1504 - bevel gear, 1505 - external gear ring, 16 - temperature sensor. Detailed Embodiments

[0026] The following further describes this application in detail with reference to the drawings. It is necessary to point out here that the following detailed embodiments are only used to further illustrate this application and should not be construed as limiting the protection scope of this application. Those skilled in the art can make some non-essential improvements and adjustments to this application based on the above application content.

[0027] Please refer to Figure 1, A urea injection device for diesel engine exhaust gas treatment, including a urea tank 1, and further including a decomposition tank 2. A reaction member 3 with a hollow interior and made of a heat-conducting material (such as copper-nickel alloy, aluminum alloy, etc.) is provided in the decomposition tank 2. The reaction member 3 is located in the path of the exhaust gas discharge pipe, and both ends of the reaction member 3 are communicated with the exhaust gas discharge pipe. A spray pipe 4 is further provided above the reaction member 3 inside the decomposition tank 2. A number of electromagnetic nozzles 5 are arranged on the spray pipe 4. The urea injection device further includes a metering pump 6 for pumping urea solution into the spray pipe 4. An air outlet 7 is provided on the decomposition tank 2, and a gas guide pipe 8 is communicated between the air outlet 7 and the exhaust gas discharge pipe.

[0028] When the diesel engine exhaust gas is discharged through the reaction member 3, the high-temperature exhaust gas makes the reaction member 3 in a high-temperature state. The urea solution in the urea tank 1 is pumped into the spray pipe 4 through the metering pump 6, and then sprayed onto the reaction member 3 in a mist form through each electromagnetic nozzle 5. After the urea solution contacts the reaction member 3 in the high-temperature state, a thermal decomposition reaction occurs to generate ammonia (and carbon dioxide gas). The generated ammonia enters the exhaust gas discharge pipe through the gas guide pipe 8 and is mixed with the exhaust gas for subsequent reduction reactions. The electromagnetic nozzles 5 are arranged in the decomposition tank 2 and do not come into contact with the exhaust gas, which not only avoids the blockage of the spray holes of the electromagnetic nozzles 5 caused by the deposition of particulate matter in the exhaust gas, but also makes the electromagnetic nozzles 5 not be impacted by the high pressure of the exhaust gas flow, ensuring the long-term working stability of the electromagnetic nozzles 5 and improving the service life.

[0029] Further, a one-way valve 9 that only allows the gas in the decomposition tank 2 to be discharged into the exhaust gas discharge pipe is provided on the gas guide pipe 8.

[0030] Please refer to Figure 1 , In an embodiment of the present invention, the reaction member 3 is cylindrical and rotatable. A bracket is provided at one end of the reaction member 3, and an impeller 10 for driving the reaction member 3 to rotate by the impact of the exhaust gas is fixedly provided on the bracket. Both ends of the reaction member 3 are rotatably connected to the exhaust gas discharge pipe and the wall of the decomposition tank 2 through sealed bearings. The reaction member 3 is driven to rotate by the impact of the exhaust gas flow on the impeller 10, so that the position where the reaction member 3 receives the mist-like urea solution changes cyclically rather than concentrating at a single landing position, ensuring that the temperature is sufficient when the urea solution contacts the reaction member 3 and enabling sufficient thermal decomposition reaction.

[0031] Please refer to Figures 1 to 3 , In an embodiment of the present invention, the urea injection device further includes a scraping strip 12 for scraping and cleaning the inner wall of the reaction member 3 (the scraping side of the scraping strip 12 contacts the inner wall of the reaction member 3) and a vibration assembly 13 for causing the scraping strip 12 to vibrate axially during scraping;

[0032] The vibration assembly 13 includes a boss 1301 disposed in the exhaust gas discharge pipe and a connecting rod 1308 disposed on the bracket and coaxial with the reaction member 3. A slide bar 1305 with a square radial cross-section is provided on the scraping strip 12. The slide bar 1305 slidably penetrates through the boss 1301, and a limiting member 1303 is provided at one end of the slide bar 1305 away from the scraping strip 12. A spring 1306 is sleeved on the rod section of the slide bar 1305 between the boss 1301 and the limiting member 1303. A suspension rod 1302 is also hinged in the exhaust gas discharge pipe. An impact member 1304 capable of hitting the limiting member 1303 is provided at the lower end of the suspension rod 1302, and the impact member 1304 is located on the side of the limiting member 1303 away from the scraping strip 12 (the width of the limiting member 1303 is relatively narrow and will not cause a large air flow blocking effect on the impact member 1304). One end of the connecting rod 1308 away from the bracket is located on the side of the limiting member 1303 away from the impact member 1304, and a baffle 1307 for blocking the impact of the exhaust gas on the impact member 1304 is provided. Preferably, the baffle 1307 is fan-shaped.

[0033] In this embodiment, when the exhaust gas flows through the inside of the reaction member 3, the particulate matter in the exhaust gas will also adhere to the inner wall of the reaction member 3. To avoid the deposition of particulate matter affecting the heat exchange efficiency between the exhaust gas and the reaction member 3, the scraping strip 12 is provided to scrape and clean the inner wall of the reaction member 3. Specifically: when the reaction member 3 rotates, a relative rotation is generated between it and the scraping strip 12, that is, the scraping strip 12 scrapes along the inner wall of the reaction member 3, thereby scraping off the particulate matter adhering to the reaction member 3 and ensuring the cleanliness of the inner wall of the reaction member 3 to avoid affecting the heat exchange efficiency with the exhaust gas; further, after the scraping strip 12 scrapes off the particulate matter on the inner wall of the reaction member 3, a part of the particulate matter will inevitably adhere to the scraping strip 12. To avoid the accumulation of particulate matter on the scraping strip 12 affecting the scraping and cleaning effect, the vibration assembly 13 is provided so that the scraping strip 12 vibrates axially while scraping, and the particulate matter adhering to the scraping strip 12 is shaken off through the vibration effect. Specifically: the rotation of the reaction member 3 drives the connecting rod 1308 to rotate, and then drives the baffle 1307 to revolve. When the baffle 1307 is misaligned with the impact member 1304, the exhaust gas flow impacts on the impact member 1304 and causes it to deflect to a certain extent, that is, the impact member 1304 stores energy by relying on gravitational potential energy. When the baffle 1307 revolves to be directly opposite to the impact member 1304, the baffle 1307 blocks the air flow in front of the impact member 1304 (explained by the flow direction of the exhaust gas). The impact member 1304 loses the driving force of the air flow and deflects downward under its own gravity to impact the limiting member 1303, causing the scraping strip 12 to vibrate, realizing the shaking off of the particulate matter on the scraping strip 12 to keep it clean and ensuring the scraping and cleaning effect on the inner wall of the reaction member 3.

[0034] Please refer to Figure 2, in an embodiment of the present invention, electric heating elements 11 (the electric heating elements 11 are electric heating tubes, electric heating wires, etc. in the prior art) are evenly arranged on the side wall of the reaction member 3. A temperature sensor 16 for sensing the temperature of the exhaust gas is further provided in the exhaust gas discharge pipe. When the diesel engine is cold-started, the temperature of the discharged exhaust gas is relatively low and is not sufficient to cause the urea solution to decompose thermally. Therefore, the electric heating elements 11 are provided to assist in heating the reaction member 3 so that the urea solution can be thermally decomposed normally during the cold-start period of the diesel engine, ensuring the treatment effect of the exhaust gas. The temperature of the exhaust gas is sensed by the temperature sensor 16. When the temperature of the exhaust gas reaches the set threshold (i.e., the temperature of the exhaust gas can meet the sufficient thermal decomposition of the urea solution), the electric heating elements 11 stop working and no longer assist in heating the reaction member 3. The corresponding linkage control technology between the temperature sensor 16 and the electric heating elements 11 is the prior art and will not be elaborated here.

[0035] Based on the previous embodiment, please refer to Figure 1 , Figure 2 , Figure 4 and Figure 5 , in an embodiment of the present invention, a gas-liquid separation membrane 14 is further covered at the air outlet 7;

[0036] The urea injection device further includes a liquid scraping assembly 15 for scraping the urea solution on the gas-liquid separation membrane 14. The liquid scraping assembly 15 includes a shaft body 1502 rotatably provided in the decomposition tank 2 and a scraping blade 1501 provided at the upper end of the shaft body 1502 and in contact with the gas-liquid separation membrane 14. An external gear ring 1505 is sleeved on the reaction member 3, and a bevel gear 1504 meshing with the external gear ring 1505 is provided on the shaft body 1502;

[0037] The scraping blade 1501 includes a blade body 15011 and a convex portion 15012 in contact with the gas-liquid separation membrane 14. Liquid receiving grooves 15013 are provided on both sides of the blade body 15011 where the convex portion 15012 is located. A lower liquid channel 1503 is provided in the shaft body 1502, and the inner bottom side of the liquid receiving groove 15013 is symmetrically inclined downward towards the lower liquid channel 1503 and communicates with the lower liquid channel 1503.

[0038] It should be noted that the gas-liquid separation membrane 14 only allows ammonia and carbon dioxide gases to pass through, and the mist-like urea solution cannot pass through. Moreover, the gas-liquid separation membrane 14 is a microporous ceramic gas-liquid separation membrane with a certain rigidity, and the scraping blade 1501 will not damage it when contacting it for liquid scraping.

[0039] In this embodiment, when the ammonia gas (and carbon dioxide gas) generated by the thermal decomposition of the urea solution is discharged into the tail gas discharge pipe through the air outlet 7, a part of the atomized urea solution will be carried out by the ammonia gas and enter the tail gas discharge pipe. When the diesel engine is cold-started, the tail gas temperature is too low to fully thermally decompose the urea solution, and crystallization will occur. Therefore, the gas-liquid separation membrane 14 is provided to block the discharge of the atomized urea solution. The atomized urea solution condenses on the gas-liquid separation membrane 14. Under the meshing drive of the bevel gear 1504 and the external gear ring 1505, the reaction member 3 rotates to drive the shaft body 1502 to rotate, that is, to drive the wiper blade 1501 to rotate (the convex portion 15012 fits the gas-liquid separation membrane 14), and the urea solution condensed on the gas-liquid separation membrane 14 is scraped off. The scraped urea solution flows into the liquid receiving groove 15013, and then drips onto the reaction member 3 through the liquid passage 1503 for thermal decomposition.

[0040] In addition, it should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A urea injection device for treating diesel engine exhaust, comprising a urea tank (1), characterized in that: The invention also comprises a decomposition box (2), wherein a reaction piece (3) having a hollow interior and made of a heat-conducting material is provided in the decomposition box (2), wherein the reaction piece (3) is located in the path of the exhaust gas discharge pipe, and both ends of the reaction piece (3) are connected to the exhaust gas discharge pipe. A spray pipe (4) is also provided in the decomposition box (2) directly above the reaction piece (3), wherein a plurality of electromagnetic nozzles (5) are arranged on the spray pipe (4), and the urea injection device further comprises a metering pump (6) for pumping urea solution into the spray pipe (4). The decomposition box (2) is provided with an air outlet (7), and an air guide pipe (8) is provided between the air outlet (7) and the exhaust gas discharge pipe.

2. The urea injection device for treating diesel engine exhaust according to claim 1, characterized in that: The air guide pipe (8) is provided with a one-way valve (9) which only allows the gas in the decomposition box (2) to be discharged into the tail gas discharge pipe.

3. The urea injection device for treating diesel engine exhaust according to claim 1, characterized in that: The reaction piece (3) is cylindrical and rotatable. A bracket is provided at one end of the reaction piece (3). An impeller (10) is fixed on the bracket and is used for exhaust gas impact to drive the reaction piece (3) to rotate.

4. The urea injection device for treating diesel engine exhaust according to claim 3, characterized in that: The urea injection device further comprises a scraper bar (12) for scraping and cleaning the inner wall of the reaction piece (3) and a vibration component (13) for causing the scraper bar (12) to vibrate axially when scraping the dirt.

5. The urea injection device for treating diesel engine exhaust according to claim 4, characterized in that: The vibration assembly (13) comprises a boss (1301) arranged in the exhaust pipe and a connecting rod (1308) arranged on a bracket and coaxial with the reaction member (3); a sliding rod (1305) having a square radial cross section is arranged on the scraper (12); the sliding rod (1305) slides through the boss (1301); and a stopper (1303) is arranged at one end of the sliding rod (1305) away from the scraper (12); the sliding rod (1305) is located on the rod section between the boss (1301) and the stopper (1303). A spring (1306) is sleeved therein, and a suspension rod (1302) is hingedly arranged in the exhaust gas emission pipe, and an impact piece (1304) capable of impacting a limiting piece (1303) is arranged at the lower end of the suspension rod (1302), and the impact piece (1304) is located on a side of the limiting piece (1303) away from the scraper (12), and an end of the connecting rod (1308) away from the bracket is located on a side of the limiting piece (1303) away from the impact piece (1304), and a baffle (1307) is arranged to prevent the exhaust gas from impacting the impact piece (1304).

6. The urea injection device for treating diesel engine exhaust according to claim 3, characterized in that: Electric heating elements (11) are evenly distributed in the side wall of the reaction element (3), and a temperature sensor (16) for sensing the temperature of the exhaust gas is also provided in the exhaust gas exhaust pipe.

7. The urea injection device for treating diesel engine exhaust according to claim 6, characterized in that: The gas outlet (7) is also covered with a gas-liquid separation membrane (14).

8. The urea injection device for treating diesel engine exhaust according to claim 7, characterized in that: The urea injection device further comprises a scraping assembly (15) for scraping off urea solution on the gas-liquid separation membrane (14), the scraping assembly (15) comprising a shaft (1502) rotatably arranged in the decomposition box (2) and a scraper (1501) arranged at the upper end of the shaft (1502) and in contact with the gas-liquid separation membrane (14), the reaction member (3) being sleeved with an outer gear ring (1505), and the shaft (1502) being provided with a bevel gear (1504) meshing with the outer gear ring (1505).

9. The urea injection device for treating diesel engine exhaust according to claim 8, characterized in that: The scraper (1501) comprises a sheet body (15011) and a raised portion (15012) in contact with the gas-liquid separation membrane (14); the sheet body (15011) is provided with liquid receiving grooves (15013) at both sides of the raised portion (15012); a lower liquid channel (1503) is provided in the shaft body (1502); the inner bottom side of the liquid receiving groove (15013) is symmetrically inclined downward toward the lower liquid channel (1503) and is connected to the lower liquid channel (1503).

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