Tail gas treatment device

Abstract

The invention belongs to the technical field of automobile tail gas treatment, and discloses a tail gas treatment device. The system comprises a pipeline mixer, the front end of the pipeline mixer is connected with an outlet of an engine, a discharge pipeline is installed behind the pipeline mixer, a front-stage SCR is installed at the rear end of the discharge pipeline, a DDPF is installed at the rear end of the front-stage SCR, a rotational flow mixing assembly is installed at the rear end of the DDPF, a rear-stage SCR is installed at the rear end of the rotational flow mixing assembly, and a discharge port is formed in the rear-stage SCR. A first urea nozzle is mounted on the pipeline mixer, a second urea nozzle is mounted on the rotational flow mixing assembly, and the first urea nozzle and the second urea nozzle can spray urea into the tail gas treatment device; the problem that in the prior art, a tail gas treatment device cannot meet the requirements of national 7 emission regulations in the future is solved.

Description

Technical Field

[0001] This invention relates to the field of automotive exhaust gas treatment technology, and more particularly to an exhaust gas treatment device. Background Technology

[0002] With technological advancements, the upgrade of the China VI emission standards, and the imminent release of the China VII emission standards, diesel engine exhaust emissions are facing higher requirements. The widely adopted exhaust aftertreatment devices that meet China VI emission standards consist of four parts: DOC (Diesel Oxidation Catalyst), DPF (Diesel Particulate Filter), SCR (Selective Catalytic Reduction), and ASC (Ammonia Slip Catalyst). DOC and DPF are collectively referred to as DDPF. These four units remove harmful pollutants such as PM and NOx from diesel engine emissions, resulting in clean exhaust gases, while also ensuring that exhaust noise meets noise regulations.

[0003] With the continuous upgrading of environmental protection standards, my country's diesel engine exhaust treatment is moving towards a more stringent stage. The implementation of the China VI emission standard has significantly improved the emission control level, while the upcoming China VII emission standard will further focus on pollutant control under cold start conditions. This marks a deep extension of emission control from steady-state operation to all operating conditions, especially the low-temperature stage. China VII not only comprehensively tightens the limits of various pollutants, but more importantly, it puts forward significantly higher requirements for after-treatment emissions during the cold start stage. At the same time, the domestic emission test cycle adopts a method of monitoring and calculating cold and hot states separately. This means that the emission performance of the vehicle at the initial stage of start-up, when the after-treatment system has not yet fully reached the operating temperature, will be independently evaluated and cannot be averaged or masked by the purification effect of the subsequent high-temperature stage. Therefore, the treatment efficiency of cold-state nitrogen oxides (NOx) has become a key bottleneck to achieving the China VII standard. Summary of the Invention

[0004] The purpose of this invention is to provide an exhaust gas treatment device that solves the problem that existing exhaust gas treatment devices cannot meet the requirements of the future China VII emission regulations.

[0005] To achieve this objective, the present invention adopts the following technical solution: The present invention provides an exhaust gas treatment device, including a pipeline mixer, the front end of which is connected to the engine outlet, an exhaust pipe is installed after the pipeline mixer, a pre-stage SCR is installed at the rear end of the exhaust pipe, a DDPF is installed at the rear end of the pre-stage SCR, a swirl mixing assembly is installed at the rear end of the DDPF, a post-stage SCR is installed at the rear end of the swirl mixing assembly, and an exhaust port is installed on the post-stage SCR; The pipeline mixer is equipped with a first urea nozzle, and the swirl mixing assembly is equipped with a second urea nozzle. The first urea nozzle and the second urea nozzle can spray urea into the exhaust gas treatment device.

[0006] Preferably, the pipeline mixer includes a pipe body on which a first urea spray holder is mounted, and a first urea nozzle is mounted on the first urea spray holder.

[0007] Preferably, a first swirl fin is installed inside the tube, and the blades on the first swirl fin rotate under the drive of the exhaust gas.

[0008] Preferably, a nitrogen-oxygen sensor is also installed inside the tube, and a baffle is provided on one side of the first swirl fin, the baffle being located above the nitrogen-oxygen sensor.

[0009] Preferably, the blade has a through hole.

[0010] Preferably, the swirl mixing assembly includes a housing and a second urea spray holder, the second urea spray holder is installed on the side wall of the housing, the second urea spray holder is installed on the second urea spray holder, and a second swirl fin is rotatably installed inside the housing.

[0011] Preferably, the tail end of the pre-stage SCR is coated with ASC.

[0012] Preferably, the front end of the DDPF is coated with DOC, the DDPF is detachably installed between the pre-stage SCR and the swirl mixing assembly, and a temperature sensor and / or differential pressure sensor are also installed at the front end of the DDPF.

[0013] Preferably, the pipeline mixer has a flange, and the pipeline mixer is detachably connected to the engine outlet via the flange.

[0014] Preferably, an exhaust pipe is installed on the outlet.

[0015] Beneficial effects: The system introduces ammonia gas at the front end of the exhaust gas flow through a pipeline mixer combined with a first urea nozzle, allowing the reducing agent to mix with the exhaust gas earlier and more fully, creating favorable conditions for subsequent catalytic reduction reactions. This design not only improves the uniformity of ammonia distribution but also accelerates the premixing process of reactants, facilitating the formation of a highly efficient reducing atmosphere in a short time. This effectively purifies the exhaust gas during cold starts, ensuring it meets the China VII emission standards. Secondly, this exhaust gas treatment device uses DDPF, which combines particulate matter capture and catalytic oxidation-reduction functions, simultaneously removing particulate matter and some nitrogen oxides from the exhaust gas, achieving synergistic treatment of pollutants. By adding a pre-stage SCR and placing it closer to the engine exhaust outlet, the system significantly shortens the ignition time of the exhaust gas treatment device. During cold starts, the temperature of the engine exhaust gas is high, and the pre-stage SCR near the front end of the exhaust pipe can quickly absorb heat, reaching the operating temperature required for the catalytic reaction ahead of time. This achieves immediate and efficient purification of nitrogen oxides during cold starts, effectively suppressing the emission of a large amount of pollutants at the initial stage of vehicle startup.

[0016] Meanwhile, the exhaust gas treatment device retains the post-SCR device, forming a two-stage SCR purification path of "front SCR + DDPF + post SCR". The front-stage SCR focuses on rapid ignition and high-efficiency initial conversion, while the post-stage SCR further deepens the purification, ensuring that nitrogen oxides can be fully reduced under various engine operating conditions, especially during medium and high load operation. The two-stage SCR works together to enhance low-temperature performance and ensure high-efficiency purification throughout the process, keeping exhaust emissions at an extremely low level.

[0017] In summary, this exhaust gas treatment system, through optimized mixing, the addition of a pre-engine SCR, the integration of a multi-functional DDPF, and the retention of a rear-mounted SCR, achieves significant control of emissions during the cold start phase and a comprehensive improvement in exhaust gas purification performance under all operating conditions. It not only effectively meets the stringent requirements of the China VII emission standard for cold start pollutant limits but also ensures continuous and stable ultra-low emission output throughout the vehicle's operating cycle, providing a reliable and efficient technical path for diesel vehicles to achieve clean emissions. Attached Figure Description

[0018] Figure 1 This is a main body diagram of the exhaust gas treatment device of the present invention.

[0019] In the diagram: 11. Pipeline mixer; 12. First urea nozzle; 14. Discharge pipeline; 15. Pre-stage SCR; 31. DDPF; 35. Swirl mixing assembly; 36. Second urea nozzle; 37. Post-stage SCR; 38. Exhaust pipe. Detailed Implementation

[0020] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0021] In the description of this invention, unless otherwise explicitly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0022] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0023] In the description of this embodiment, the terms "upper," "lower," "right," etc., refer to the orientation or positional relationship shown in the accompanying drawings. They are used only for ease of description and simplification of operation, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention. In addition, the terms "first" and "second" are used only for distinction in description and have no special meaning.

[0024] Since the implementation of the China VI emission standard, stricter requirements have been imposed on the limits of various pollutants in diesel engine exhaust. To meet the China VI emission regulations, the widely used exhaust aftertreatment system mainly consists of four core units: diesel oxidation catalyst (DOC), diesel particulate filter (DPF), selective catalytic reduction (SCR), and ammonia oxidation catalyst (ASC). These units work together to efficiently purify different pollutants in the exhaust.

[0025] DOC primarily converts carbon monoxide (CO) and hydrocarbons (HC) into carbon dioxide (CO2) and water (H2O) through oxidation reactions, while also oxidizing some nitric oxide (NO) into nitrogen dioxide (NO2), providing support for the regeneration and reaction of subsequent DPF and SCR. DPF captures and eliminates particulate matter (PM) in exhaust gas through physical filtration and periodic regeneration, significantly reducing the number and mass of particulate emissions. SCR uses urea solution as a reducing agent to convert NOx into harmless nitrogen (N2) and water (H2O) under the action of a catalyst, which is a key step in controlling NOx emissions. ASC is located after SCR and is used to oxidize escaped ammonia (NH3) to prevent secondary pollution. The integrated system consisting of the above four units (often referred to as the DOC-DPF-SCR-ASC system) can achieve good synergistic purification of PM and NOx under steady-state and hot-state conditions in the China VI emission standard stage, while also taking into account exhaust noise control and meeting current noise regulations.

[0026] However, with the imminent release of the China VII emission regulations, emission limits have become even stricter, especially placing higher demands on pollutant control under cold start conditions. The China VII regulations not only further reduce the emission limits for NOx and PM, but also strengthen the supervision of emissions during the cold start phase. The domestic emission test cycle now uses separate calculations for cold and hot states, meaning that emissions performance during the cold start phase directly affects overall compliance. During the cold start process, the engine exhaust temperature is low, and the aftertreatment system needs a certain amount of time to reach a suitable operating temperature, resulting in insufficient SCR catalyst activity, reduced urea injection and decomposition efficiency, and a significant decrease in NOx conversion rate. Traditional China VI single-stage SCR systems often cannot activate quickly under cold conditions, causing uncontrolled NOx emissions in the early stages of cold start, making it difficult to meet the stringent requirements of the China VII regulations for cold-state emissions.

[0027] In addition, the existing DOC-DPF-SCR-ASC system also faces other challenges in meeting ultra-low emission requirements. For example, the DPF regeneration process may generate additional NOx, and the oxidation efficiency of DOC on NO is limited at low temperatures, affecting the rapid activation of SCR. The conversion efficiency of SCR decreases at low temperatures and high space velocities, and the risk of urea crystallization increases. The ASC's ability to control ammonia slip is also relatively weakened at low temperatures. These factors together result in significant shortcomings in the cold start phase of the existing aftertreatment scheme, becoming a key bottleneck restricting diesel engines from meeting China VII and even higher emission standards.

[0028] Simply relying on optimizing existing single-stage SCR catalysts or adjusting system layout is no longer sufficient to achieve efficient NOx conversion during the cold start phase. Therefore, how to significantly improve NOx conversion efficiency during the cold start phase while ensuring efficient purification during the hot phase has become an important direction for technological breakthroughs in the industry.

[0029] In response to the stricter requirements for cold start emissions under the China VII emission standards, traditional aftertreatment solutions based on single-stage SCR have shown significant technical shortcomings.

[0030] To solve the above problems, such as Figure 1 As shown, the present invention provides an exhaust gas treatment device, including a pipeline mixer 11. The front end of the pipeline mixer 11 is connected to the engine outlet. An exhaust pipe 14 is installed after the pipeline mixer 11. A pre-stage SCR 15 is installed at the rear end of the exhaust pipe 14. A DDPF 31 is installed at the rear end of the pre-stage SCR 15. A swirl mixing assembly 35 is installed at the rear end of the DDPF 31. A post-stage SCR 37 is installed at the rear end of the swirl mixing assembly 35. An exhaust outlet is installed on the post-stage SCR 37. A first urea nozzle 12 is installed on the pipeline mixer 11, and a second urea nozzle 36 is installed on the swirl mixing assembly 35. The first urea nozzle 12 and the second urea nozzle 36 can spray urea into the exhaust gas treatment device.

[0031] The engine outlet directly discharges the exhaust gas that needs treatment. The exhaust gas enters the pipeline mixer 11 directly. After entering, the exhaust gas is mixed with ammonia in the pre-stage SCR 15 through the first urea injector 12. An oxidation-reduction reaction occurs on the carrier of the pre-stage SCR 15. During the process of the exhaust gas passing through the entire pre-stage SCR 15 carrier, the unreacted ammonia mixed in is oxidized to N2 and H2O by ASC. This is the first round of exhaust gas purification treatment. Because it is close to the engine exhaust port, it can treat the exhaust gas emitted during cold starts. Afterwards, the exhaust gas continues to flow to DDPF 31, where HC in the exhaust gas is oxidized. DDPF 31 has a high-efficiency filtration capacity. After a long period of carbon accumulation, the engine injects HC. In DDPF31, DOC can oxidize HC to release heat, which is used for the regeneration reaction of DPF in DDPF31. At this time, particulate matter in the hot start exhaust gas can be filtered out. DDPF31 can improve the exhaust gas standard so that it can meet the subsequent China VII emission standard. After that, the exhaust gas passes through the swirl mixing assembly 35 and enters the tail stage SCR37. The urea solution sprayed from the second urea nozzle 36 in the swirl mixing assembly 35 can catalyze the unreacted ammonia gas to be oxidized into N2 and H2O after vaporization and decomposition.

[0032] The pipeline mixer 11 includes a pipe body, on which a first urea spray holder is mounted, and on which a first urea nozzle 12 is mounted. The first urea spray holder is mounted on the pipe body by welding. The urea water sprayed from the first urea nozzle 12 mixes with the exhaust gas inside the pipe body and undergoes a catalytic reduction reaction on the carrier of the pre-stage SCR 15.

[0033] In the exhaust gas treatment system of this patent, the innovative design of the first swirling fin inside the pipe is the core element for achieving efficient urea decomposition and uniform mixing. This fin is not a fixed structure; its blades can rotate under the impetus of the high-speed exhaust gas. The rotating swirling fin greatly enhances the flow field disturbance and mixing efficiency. When the exhaust gas flows through the rotating blades, it is cut and forms high-intensity, multi-scale turbulence. This not only breaks and refines the urea water spray from the first urea nozzle, making it into smaller droplets and significantly increasing the surface area of ​​gas-liquid contact, but also promotes the intense mixing of exhaust gas and atomized urea. The above mixing process directly accelerates the decomposition and hydrolysis of urea. The refined urea droplets are more likely to evaporate moisture in the high-temperature exhaust gas, and the intense turbulent mixing ensures that the droplets can quickly and uniformly absorb the heat of the exhaust gas. The vortex formed by the rotating fin prolongs the effective residence time of urea in the high-temperature region, allowing urea to undergo pyrolysis and hydrolysis dehydrogenation more quickly and thoroughly, generating the key reducing agent required for the catalytic reduction reaction—ammonia (NH3).

[0034] After pretreatment by swirl fins, the mixture of exhaust gas and ammonia has reached a highly homogeneous state. When this mixed gas flow enters the SCR catalyst support at the rear end, the ammonia can undergo a more complete and faster catalytic reduction reaction with nitrogen oxides on the support surface.

[0035] In summary, the dynamic rotation design of the first swirl fin utilizes the kinetic energy of the exhaust gas itself to achieve passive and efficient mixing and heat transfer. In particular, it provides an efficient and stable reaction precursor for the pre-stage SCR during the cold start phase, and is a key component in improving the performance of the entire exhaust gas aftertreatment system.

[0036] A nitrogen-oxygen sensor is also installed inside the tube. A baffle is provided on one side of the first swirl fin, positioned above the nitrogen-oxygen sensor. This baffle prevents urea solution from being directly sprayed onto the sensor. The first and second swirl fins are manufactured through stamping and welding, reducing weight and simplifying the welding process. Through holes are provided on the blades of both swirl fins to ensure complete hydrolysis of the urea solution, producing ammonia. The first swirl fin also guides the flow, preventing urea from adhering to the inner wall of the tube.

[0037] The swirl mixing assembly 35 of the present invention includes a housing and a second urea spray holder. The second urea spray holder is installed on the side wall of the housing, and a second urea nozzle 36 is installed on the second urea spray holder. A second swirl fin is rotatably installed inside the housing.

[0038] The tail end of the pre-stage SCR15 is coated with ASC. ASC can catalyze the oxidation of ammonia, and can catalyze the undecomposed ammonia to N2 and H2O.

[0039] The DDPF31 of this invention has a DOC coating on its front end. The DDPF31 is detachably installed between the pre-stage SCR15 and the swirl mixer assembly 35 for easy cleaning, maintenance, and disassembly. A temperature sensor and / or differential pressure sensor are also installed at the front end of the DDPF31, allowing the system to detect the DDPF31's status. If abnormal data is detected, disassembly and cleaning maintenance can be performed. A flange is formed on the pipeline mixer 11, which is detachably connected to the engine outlet via the flange.

[0040] An exhaust pipe 38 is installed on the exhaust outlet, which is connected to the pipeline mixer 11 at the engine outlet. The front and rear ends of the exhaust gas treatment device have the same connection method as the China VI standard, which can reduce the modification cost of the bottom of the car.

[0041] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art will be able to make various obvious changes, readjustments, and substitutions without departing from the scope of protection of the present invention. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A tail gas treatment device, characterized in that, Includes a pipeline mixer (11), the front end of which is connected to the engine outlet, a discharge pipeline (14) is installed after the pipeline mixer (11), a pre-stage SCR (15) is installed at the rear end of the discharge pipeline (14), a DDPF (31) is installed at the rear end of the pre-stage SCR (15), a swirl mixing assembly (35) is installed at the rear end of the DDPF (31), a post-stage SCR (37) is installed at the rear end of the swirl mixing assembly (35), and an outlet is installed on the post-stage SCR (37). The pipeline mixer (11) is equipped with a first urea nozzle (12), and the swirl mixing assembly (35) is equipped with a second urea nozzle (36). The first urea nozzle (12) and the second urea nozzle (36) can spray urea into the exhaust gas treatment device.

2. The exhaust gas treatment device according to claim 1, characterized in that, The pipeline mixer (11) includes a pipe body on which a first urea spray holder is mounted, and a first urea nozzle (12) is mounted on the first urea spray holder.

3. The exhaust gas treatment device according to claim 2, characterized in that, The tube is equipped with a first swirl fin, and the blades on the first swirl fin rotate under the push of the exhaust gas.

4. The exhaust gas treatment device according to claim 3, characterized in that, A nitrogen-oxygen sensor is also installed inside the tube, and a baffle is provided on one side of the first swirl fin, the baffle being located above the nitrogen-oxygen sensor.

5. The exhaust gas treatment device according to claim 4, characterized in that, The blade has through holes.

6. The exhaust gas treatment device according to claim 1, characterized in that, The swirl mixing assembly (35) includes a housing and a second urea spray holder. The second urea spray holder is installed on the side wall of the housing, and a second urea nozzle (36) is installed on the second urea spray holder. A second swirl fin is rotatably installed inside the housing.

7. The exhaust gas treatment device according to claim 1, characterized in that, The tail end of the pre-stage SCR (15) is coated with ASC.

8. The exhaust gas treatment device according to claim 1, characterized in that, The front end of the DDPF (31) is coated with DOC. The DDPF (31) is detachably installed between the pre-stage SCR (15) and the swirl mixing assembly (35). The front end of the DDPF (31) is also equipped with a temperature sensor and / or a differential pressure sensor.

9. The exhaust gas treatment device according to claim 1, characterized in that, A flange is formed on the pipeline mixer (11), and the pipeline mixer (11) is detachably connected to the engine outlet via the flange.

10. The exhaust gas treatment device according to claim 1, characterized in that, An exhaust pipe (38) is installed on the outlet.

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