A dual-jet post-processing mixing device and method

Abstract

The application provides a double-jet post-processing mixing device and method, relates to the field of post-processing systems, and aims to solve the problem of blockage caused by large crystallization amount when facing large-flow urea injection at present. Urea is injected through two nozzles, pre-mixed through two cyclone branch pipes, fully mixed with exhaust gas, and then enters a main mixing pipe for re-mixing. The mixing distance and time are increased as much as possible in limited space, the complexity inside a cyclone pipe assembly is reduced, the mixing efficiency is improved, and thus crystallization is reduced.

Description

Technical Field

[0001] This invention relates to the field of post-treatment systems, and more specifically to a dual-spray post-treatment mixing device and method. Background Technology

[0002] The SCR intake mixing structure consists of a swirl tube, a swirl tube baffle, steel wool, and an outer tube. After urea and exhaust gas are mixed, the airflow will swirl along the swirl direction and enter the SCR through the steel wool. Due to the short mixing time and high urea injection back pressure, the urea crystallization problem is serious.

[0003] Chinese patent (publication number CN113356981A) discloses a sleeve-type urea mixing device with a split-flow design. This device employs a sleeve structure, with an inner window sleeve installed inside the outer cyclone tube to enhance the splitting and crushing effect of urea, thereby improving urea decomposition efficiency. However, the added sleeve structure and inner window design make the device more complex, increasing the difficulty of production and installation. They also reduce the space within the outer cyclone tube, affecting the distribution of the internal cyclone field and increasing the probability of contact between urea and the inner window sleeve and outer cyclone tube, leading to crystallization and blockage of the urea against the tube wall. Furthermore, with increasingly stringent emission standards, the demand for urea injection volume in aftertreatment systems is gradually increasing. Under conditions of high flow rate and high back pressure injection, the crystallization problem in existing equipment becomes more severe, affecting the mixing effect of the urea mixer and causing a deterioration in the performance of the SCR system. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by providing a dual-spray post-treatment mixing device and method.

[0005] The first objective of this invention is to provide a dual-spray post-treatment mixing device, which employs the following solution:

[0006] include:

[0007] The housing has an exhaust gas chamber connected in series with the after-treatment system;

[0008] The cyclone tube assembly is located inside the exhaust gas chamber. The cyclone tube assembly includes a main mixing pipe and two cyclone branch pipes arranged symmetrically with respect to the axis of the main mixing pipe and at an angle. One end of the two cyclone branch pipes is connected to one end of the main mixing pipe to form a Y-shaped tee, and the connection point is the intersection. The end of the cyclone branch pipe away from the intersection abuts against the wall of the exhaust gas chamber and receives the injected urea. The mixture of exhaust gas and urea in the two cyclone branch pipes enters the main mixing pipe after being flushed at the intersection.

[0009] Furthermore, the axes of the two swirl branch pipes are arranged in the same plane as the axis of the main mixing pipe, and each swirl branch pipe is respectively equipped with a urea nozzle.

[0010] Furthermore, the plane containing the axes of the swirl branch pipe and the main mixing pipe is parallel to the vertical plane of the air inlet axis of the exhaust gas chamber, so that the exhaust gas input into the air inlet of the exhaust gas chamber can be transported to the swirl branch pipe.

[0011] Furthermore, an air inlet is provided on the outer circumferential surface of the swirl branch, and fins are provided on one side of the air inlet to guide the exhaust gas entering the swirl branch into the swirl branch to form a swirl.

[0012] Furthermore, the swirl branch pipe is arranged at an angle relative to the main mixing pipe, and a premixing cavity with a connecting intersection is formed inside the swirl branch pipe.

[0013] Furthermore, a main mixing chamber is formed within the main mixing pipe, which is connected to the premixing chamber via the cross section. The mixed gas in the two swirl branch pipes counteracts and reduces radial movement at the cross section.

[0014] Furthermore, the diameter of the main mixing pipe is larger than the diameter of the swirl branch pipe, and through holes are provided on the outer wall corresponding to the intersection.

[0015] Furthermore, a through hole is provided on the outer wall of the main mixing pipe, and the axis of the main mixing pipe is arranged at an equal angle to the axes of the two swirl branch pipes along the circumferential upward direction.

[0016] A second objective of the present invention is to provide a mixing method for a dual-spray post-treatment mixing apparatus as described in the first objective, comprising:

[0017] Urea is injected through two urea nozzles into two swirl branch pipes, and the waste gas enters the waste gas chamber.

[0018] The exhaust gas in the exhaust gas chamber passes through the outer wall of the swirl branch pipe and enters the swirl branch pipe, where it is premixed with urea to form a mixed gas.

[0019] The mixed gas in the two swirl tubes collide at the intersection, canceling out the radial movement along the main mixing tube, and then enters the main mixing tube axially, mixes again, and is discharged.

[0020] Furthermore, the exhaust gas enters the swirl branch pipe in a swirling manner, and then passes radially through the outer wall of the main mixing pipe into the main mixing pipe.

[0021] Compared with the prior art, the advantages and positive effects of this invention are:

[0022] (1) In response to the problem of large crystallization and blockage caused by large flow rate urea injection, urea is injected through two nozzles and premixed through two swirl branch pipes. After being fully mixed with the exhaust gas, it enters the main mixing pipe for further mixing. By increasing the mixing distance and time as much as possible in a limited space, the complexity inside the swirl tube assembly is reduced, the mixing efficiency is improved, and crystallization is reduced.

[0023] (2) A two-stage mixing method is adopted so that the exhaust gas and urea spray are fully mixed and decomposed under the action of airflow, which ensures time for urea decomposition to produce NH3. In addition, the mixed gas airflow output from the two swirl branch pipes blows against each other, which disturbs the intersection and reduces the crystallization of urea.

[0024] (3) The swirl branch pipe guides the airflow through fins. The exhaust gas and urea in the two swirl branch pipes rotate, which enhances the mixing capacity with the exhaust gas and ensures uniform swirling mixing. After passing through the swirl branch pipe, the gas enters the main mixing pipe. The airflow formed by the radial holes of the main mixing pipe prevents the urea from contacting the pipe wall of the main mixing pipe. Finally, the gas flows out of the mixer and enters the SCR, so that NH3 and exhaust gas are mixed evenly.

[0025] (4) From upstream to downstream, the waste gas is used to isolate urea from the pipe wall through the cross section to the main mixing pipe. This not only improves the operating efficiency of the dual-spray after-treatment mixing device, but also extends the service life and maintenance cycle of the device.

[0026] (5) Adapt to the current nozzle hardware and adapt to the future demand for high-flow urea injection, thereby reducing the development cost of new hardware. Attached Figure Description

[0027] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0028] Fig. 1 This is a schematic diagram of the dual-spray post-treatment mixing device in Embodiments 1 and 2 of the present invention.

[0029] Fig. 2 This is a schematic diagram of the swirl branch pipe connecting to the main mixing pipe in Embodiments 1 and 2 of the present invention.

[0030] Among them, 1. urea nozzle, 2. swirl branch pipe, 3. main mixing pipe, 4. exhaust gas chamber, 5. premixing chamber, 6. main mixing chamber, 7. intersection, 8. through hole, 9. shell. Detailed Implementation

[0031] SCR (Selective Catalytic Reduction): A technology to eliminate nitrogen oxides (NOx) in diesel engine exhaust. It utilizes ammonia (NH3) produced by the hydrolysis of urea to convert NOx in the exhaust gas into nitrogen (N2) under the action of a catalyst.

[0032] SCR mixer: A device installed between the exhaust pipe and the SCR carrier, also known as a urea mixer, mainly used to improve the uniformity of mixing between urea spray and exhaust gas, thereby increasing NOx conversion efficiency.

[0033] Example 1

[0034] In a typical embodiment of the present invention, such as Figs. 1-2 As shown, a dual-spray post-treatment mixing device is presented.

[0035] In the aftertreatment system, urea needs to be fully heated and mixed to meet the requirements of the SCR system. Otherwise, it will not only affect the operation of the SCR system, but also produce a large amount of urea crystals, causing blockage. This embodiment is designed to address this problem by providing a dual-spray aftertreatment mixing device to solve the problem of urea crystal accumulation caused by a large amount of urea injected at a single point.

[0036] like Fig. 1 As shown, the dual-jet aftertreatment mixing device mainly includes a housing 9 and a cyclone tube assembly. The housing 9 serves as the supporting structure for the entire device, and an exhaust gas chamber 4 is located inside the housing 9. The exhaust gas chamber 4 is connected in series with the aftertreatment system and is designed to provide a flow channel and mixing environment for the exhaust gas.

[0037] The cyclone tube assembly is the core component of the device and is located within the exhaust gas chamber 4. The cyclone tube assembly consists of a main mixing pipe 3 and two cyclone branch pipes 2. The two cyclone branch pipes 2 are symmetrical about the axis of the main mixing pipe 3 and arranged at an angle, which helps to enhance the mixing effect and improve the stability of the device. One end of each of the two cyclone branch pipes 2 connects to one end of the main mixing pipe 3, forming a Y-shaped tee structure. The connection point is called the intersection 7, ensuring that the mixture of exhaust gas and urea in the cyclone branch pipes 2 can enter the main mixing pipe 3 uniformly.

[0038] The other end of the swirl branch pipe 2 abuts against the wall of the exhaust gas chamber 4. During operation, the two swirl branch pipes 2 respectively receive the injected urea, which is initially mixed with the exhaust gas in the swirl branch pipes 2. The mixed gas enters the main mixing pipe 3 after being flushed at the cross section 7, further enhancing the mixing effect. The flushing design helps to improve the dispersion and uniformity of urea, allowing the urea to be fully heated and decomposed into NH3, and can reduce the crystallization caused by the direct impact of urea on the main mixing pipe 3, thereby ensuring the effective treatment of the exhaust gas.

[0039] With its unique design and efficient mixing effect, the dual-jet aftertreatment mixing device provides stable and reliable support for the aftertreatment system, which helps to achieve effective treatment and emission of waste gas, thereby meeting environmental protection requirements.

[0040] like Fig. 2 As shown, in the dual-jet aftertreatment mixing device, the axes of the two swirl branch pipes 2 and the axis of the main mixing pipe 3 are arranged coplanarly. This ensures that the exhaust gas and urea mixture can be accurately counteracted, reducing radial movement after counteracting and minimizing contact between the urea-laden mixture and the inner wall of the main mixing pipe 3. Simultaneously, exhaust gas is introduced into the counteracting position through the through holes 8 on the outer wall corresponding to the intersection 7, using the exhaust gas to isolate the mixture from the inner wall of the intersection 7, reducing urea crystal accumulation.

[0041] A through hole 8 is provided on the outer wall of the main mixing pipe 3. The exhaust gas is also used to isolate the undecomposed urea from the inner wall of the main mixing pipe 3, thereby reducing the urea connection.

[0042] An air inlet is provided on the outer circumference of the swirl branch pipe 2, and fins are provided on one side of the air inlet to guide the exhaust gas entering the swirl branch pipe 2 to form a swirl inside the swirl branch pipe 2.

[0043] First, in the swirl branch pipe 2 section, the exhaust gas is effectively introduced into the swirl branch pipe 2 and forms a swirl by the air inlet holes and fins opened on the outer circumference.

[0044] Secondly, at the intersection 7, exhaust gas is introduced into the opposing position through the through hole 8. The exhaust gas acts as a "barrier" to isolate the urea-containing mixture from the inner wall of the intersection 7. This significantly reduces the crystallization and accumulation of urea on the inner wall of the intersection 7, thereby ensuring the smooth flow of the mixture.

[0045] Finally, in the main mixing pipe 3 section, the through holes 8 on the outer wall and the exhaust gas in the main mixing pipe 3 section also serve to isolate the undecomposed urea from the inner wall of the main mixing pipe 3, which not only reduces the adhesion and crystallization of urea, but also helps to improve the uniformity of the mixed gas in the main mixing pipe 3.

[0046] In summary, the comprehensive urea-pipe wall isolation design, utilizing waste gas from upstream to downstream through the swirl branch pipe 2, the cross section 7, and the main mixing pipe 3, not only improves the operating efficiency of the dual-spray aftertreatment mixing device but also extends the device's service life and maintenance cycle. This is of great significance for improving the performance of the aftertreatment system and meeting environmental protection requirements.

[0047] Among them, such as Fig. 2 As shown, multiple through holes 8 are distributed circumferentially upward at the intersection 7. At the same time, the through holes 8 are arranged in an array circumferentially upward at the main mixing pipe 4, supplying exhaust gas to the intersection 7 and the main mixing pipe 4 from multiple circumferential positions.

[0048] Each swirl branch pipe 2 is equipped with a corresponding urea nozzle 1, allowing urea to be precisely injected into the swirl branch pipe 2. Furthermore, the plane containing the axes of the swirl branch pipe 2 and the main mixing pipe 3 is set perpendicular to the axis of the exhaust gas chamber 4 inlet. This ensures that exhaust gas can be smoothly input from the inlet and guided to the swirl branch pipe 2, helping to improve exhaust gas treatment efficiency and reduce internal resistance of the device.

[0049] The coplanar arrangement simplifies the structure of the device, making production and installation easier compared to a nested structure. Simultaneously, the more uniform mixing of exhaust gas and urea helps improve the overall performance and stability of the aftertreatment system. This design also helps reduce exhaust emissions, thereby minimizing environmental impact.

[0050] like Fig. 2 As shown, the swirl branch pipe 2 is arranged at an angle relative to the main mixing pipe 3. A premixing cavity 5 with a connecting intersection 7 is formed inside the swirl branch pipe 2. The axis of the main mixing pipe 3 and the axes of the two swirl branch pipes 2 are arranged at equal angles along the circumferential upward direction, both being 120°.

[0051] The equiangular arrangement of the two swirl branches 2 and the main mixing pipe 3 forms a stable triangular structure, which helps to enhance the stability of the device and reduce vibration problems that disturb the swirl tube assembly when exhaust gas enters the tail gas chamber. At the same time, the inclined arrangement increases the distance and time for the exhaust gas and urea to mix within a limited space, ensuring that the exhaust gas and urea spray are fully mixed and decomposed under the action of airflow.

[0052] A main mixing chamber 6 is formed within the main mixing pipe 3, connecting to the cross section 7. The main mixing chamber 6 is connected to the premixing chamber 5 via the cross section 7. The mixed gas in the two swirling branch pipes 2 counteracts and reduces radial movement at the cross section 7. The diameter of the main mixing pipe 3 is larger than the diameter of the swirling branch pipes 2, and through holes 8 are provided on the outer wall corresponding to the cross section 7. This helps to enhance the dispersion and uniformity of the mixed gas and reduce the deviation of the mixed gas during the flow process.

[0053] The swirl branch 2 guides the airflow through fins. The exhaust gas and urea inside the two swirl branch 2 rotate, enhancing their mixing ability and ensuring uniform swirling mixing. After passing through the swirl branch 2, the gas enters the main mixing pipe 3. The airflow formed by the radial holes in the main mixing pipe 3 prevents the urea from contacting the pipe wall of the main mixing pipe 3. Finally, the gas flows out of the mixer and enters the SCR, ensuring uniform mixing of NH3 and exhaust gas.

[0054] Example 2

[0055] In another typical embodiment of the present invention, such as Figs. 1-2 As shown, a mixing method for a dual-spray post-treatment mixing device is presented.

[0056] Using the dual-spray post-treatment mixing device as described in Example 1, the following steps are included:

[0057] Urea is injected through two urea nozzles 1 and enters two swirl branch pipes 2 respectively, and the waste gas enters the waste gas chamber 4;

[0058] The exhaust gas in the exhaust gas chamber 4 passes through the outer wall of the swirl branch pipe 2 and enters the swirl branch pipe 2, where it is premixed with urea to form a mixed gas.

[0059] The mixed gas in the two swirl tubes collide at the intersection 7, canceling out the radial movement along the main mixing tube 3, and then enters the main mixing tube 3 axially, mixes again, and is discharged.

[0060] The exhaust gas enters the swirl branch pipe 2 in a swirling manner, and then passes radially through the outer wall of the main mixing pipe 3 into the main mixing pipe 3. The exhaust gas acts as a "barrier", isolating the urea-containing mixture from the inner wall of the swirl pipe assembly.

[0061] The two-stage mixing method ensures that the exhaust gas and urea spray are fully mixed and decomposed under the action of airflow, providing sufficient time for urea decomposition to produce NH3. In addition, the mixed gas flow output from the two swirl branch pipes 2 blows against each other, causing disturbance to the intersection 7 and reducing the crystallization of urea.

[0062] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A dual-spray post-treatment mixing device, characterized in that, include: The housing has an exhaust gas chamber connected in series with the after-treatment system; The cyclone tube assembly is located inside the exhaust gas chamber. The cyclone tube assembly includes a main mixing pipe and two cyclone branch pipes arranged symmetrically with respect to the axis of the main mixing pipe and at an angle. One end of the two cyclone branch pipes is connected to one end of the main mixing pipe to form a Y-shaped tee, and the connection point is the intersection. The end of the cyclone branch pipe away from the intersection abuts against the wall of the exhaust gas chamber and receives the injected urea. The mixture of exhaust gas and urea in the two cyclone branch pipes enters the main mixing pipe after being flushed at the intersection. The urea is injected through two urea nozzles into two swirl branch pipes respectively, and the waste gas enters the waste gas chamber. The waste gas in the waste gas chamber passes through the outer wall of the swirl branch pipe and enters the swirl branch pipe, where it is premixed with the urea to form a mixed gas. The mixed gas in the two swirl pipes collide at the intersection, canceling the radial movement along the main mixing pipe, and then enters the main mixing pipe axially, where it is mixed again and discharged.

2. The dual-spray post-treatment mixing device as described in claim 1, characterized in that, The axes of the two swirl branch pipes are arranged in the same plane as the axis of the main mixing pipe, and each swirl branch pipe is respectively equipped with a urea nozzle.

3. The dual-spray post-treatment mixing device as described in claim 2, characterized in that, The plane containing the axes of the swirl branch pipe and the main mixing pipe is parallel to the vertical plane of the air inlet axis of the exhaust gas chamber, and the exhaust gas input into the air inlet of the exhaust gas chamber can be transported to the swirl branch pipe.

4. The dual-spray post-treatment mixing device as described in claim 1, characterized in that, An air inlet is provided on the outer circumference of the swirl branch pipe, and fins are provided on one side of the air inlet to guide the exhaust gas entering the swirl branch pipe to form a swirl inside the swirl branch pipe.

5. The dual-spray post-treatment mixing device as described in claim 1, characterized in that, The swirl branch pipe is arranged at an angle relative to the main mixing pipe, and a premixing cavity with a connecting intersection is formed inside the swirl branch pipe.

6. The dual-spray post-treatment mixing device as described in claim 5, characterized in that, The main mixing pipe forms a main mixing chamber with a connecting cross section. The main mixing chamber is connected to the premixing chamber through the cross section. The mixed gas in the two swirl branch pipes counteracts and reduces radial movement at the cross section.

7. The dual-spray post-treatment mixing device as described in claim 1, characterized in that, The diameter of the main mixing pipe is larger than the diameter of the swirl branch pipe, and through holes are provided on the outer wall corresponding to the intersection.

8. The dual-spray post-treatment mixing device as described in claim 7, characterized in that, The main mixing pipe has a through hole on its outer wall, and the axis of the main mixing pipe is arranged at an equal angle to the axes of the two swirl branch pipes along the circumferential direction.

9. The dual-spray post-treatment mixing device as described in claim 1, characterized in that, The exhaust gas enters the swirl branch pipe in a swirling manner, and then passes radially through the outer wall of the main mixing pipe into the main mixing pipe.

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