A urea solution atomizing device for an SCR aftertreatment system

Abstract

This utility model discloses a urea solution atomizing device for an SCR aftertreatment system, relating to the field of exhaust gas aftertreatment technology. Its structure includes a urea solution tank, an atomizing nozzle, a Venturi valve mixer, and branch connecting pipes and return connecting pipes installed on the exhaust gas pipeline. The Venturi valve mixer includes a jet head, a cylindrical mixing chamber, and a throat connected in sequence. An atomizing connecting pipe is fixed through the outer wall of the cylindrical mixing chamber. The atomizing nozzle is installed on the atomizing connecting pipe. The urea solution tank and the atomizing nozzle are connected via a high-pressure liquid supply pipeline. A liquid booster pump is installed on the high-pressure liquid supply pipeline. This utility model achieves a high urea solution decomposition rate and uniform NH3 generation through pre-decomposition via a branch pipeline, efficient mixing via a Venturi valve, enhanced mass transfer via a baffle plate, and waste heat recovery from the coolant. This reduces system energy consumption and enhances resistance to operating condition fluctuations, effectively solving the technical problems of low decomposition rate, high energy consumption, and uneven mixing in traditional SCR systems.

Description

Technical Field

[0001] This utility model belongs to the field of exhaust gas aftertreatment technology, and in particular relates to a urea solution atomization device for an SCR aftertreatment system. Background Technology

[0002] In the field of exhaust gas treatment for gas generator sets and internal combustion engines, selective catalytic reduction (SCR) technology is used to reduce nitrogen oxides (NOx). x The core method for controlling NO emissions is to inject a reducing agent (such as ammonia or urea solution) into the exhaust gas, which, under the action of a catalyst, reduces NO. x It is converted into harmless nitrogen (N2) and water (H2O). However, existing SCR systems still have the following technical defects in engineering applications, resulting in low denitrification efficiency, high energy consumption, and insufficient operational stability: low urea solution decomposition efficiency, excessive main catalyst load, and traditional SCR systems typically use a single main catalyst region to complete the decomposition of urea solution and NO. x Reduction reaction. Because the thermal decomposition of urea requires high temperatures (200-400℃) and sufficient residence time, but in actual operating conditions the exhaust gas temperature distribution is uneven and the flow rate is relatively fast, the following problems occur: Insufficient decomposition rate: Most urea is decomposed in the main catalyst region, and the remaining undecomposed urea easily crystallizes on the catalyst surface, causing pore blockage and coverage of active sites; Delayed NH3 formation: The NH3 produced by urea decomposition needs to diffuse with the exhaust gas to the catalyst surface, resulting in insufficient NH3 concentration in the initial stage of the reaction, and NO... x Conversion rate decreases by 10%-15%. Uneven mixing of exhaust gas and reducing agent leads to increased NO content. x Large fluctuations in conversion rate: The gas-liquid mixing effect after urea solution injection directly affects the performance of SCR system: Single-point injection or simple fan-shaped nozzles are difficult to cover the entire cross-section of the exhaust gas pipeline, resulting in uneven distribution of urea solution particles. Local concentrations that are too high cause crystallization, while local concentrations that are too low lead to insufficient NH3. Lack of turbulence enhancement mechanism: The exhaust gas is mostly in a laminar flow state in the pipeline. The heat exchange time between urea solution particles and high-temperature gas is short (usually <0.5 seconds), resulting in incomplete decomposition reaction, especially under low load conditions.

[0003] To address the aforementioned shortcomings, this invention proposes an SCR exhaust gas treatment device based on side-branch pipe thermal energy circulation and flow around enhancement. Utility Model Content

[0004] The purpose of this invention is to provide a urea solution atomization device for an SCR aftertreatment system. Through a side-branch pipe pre-decomposition mechanism, a venturi valve negative pressure mixing and a baffle plate to enhance mass transfer, and a closed-loop reflux and check valve design, the decomposition path of the urea solution is expanded, and the urea solution is mixed evenly with the exhaust gas in the exhaust pipe.

[0005] To solve the above-mentioned technical problems, this utility model is achieved through the following technical solution:

[0006] This utility model relates to a urea solution atomizing device for an SCR aftertreatment system, comprising a urea solution tank, an atomizing nozzle, a Venturi valve mixer, and a branch connecting pipe and a return connecting pipe installed on the exhaust gas pipeline; the Venturi valve mixer includes a jet head, a cylindrical mixing chamber, and a throat pipe connected in sequence; the atomizing connecting pipe is fixedly installed through the outer wall of the cylindrical mixing chamber; the atomizing nozzle is installed on the atomizing connecting pipe; the urea solution tank and the atomizing nozzle are connected via a high-pressure liquid supply pipeline; a liquid booster pump is installed on the high-pressure liquid supply pipeline; the throat pipe is connected to the return connecting pipe; the branch connecting pipe and the jet head are connected via a high-temperature flue gas pipeline; a high-temperature resistant axial flow fan is installed on the high-temperature flue gas pipeline.

[0007] As a preferred embodiment of this utility model, a check valve is installed on the return connection pipe.

[0008] As a preferred embodiment of this utility model, the return connection pipe and the branch connection pipe are respectively located upstream and downstream of the exhaust gas pipeline transporting flue gas.

[0009] As a preferred embodiment of this utility model, the inner wall of the exhaust gas pipe between the return connection pipe and the branch connection pipe is provided with several interference flow plates.

[0010] As a preferred embodiment of this utility model, a coil is fixedly installed through the urea solution tank.

[0011] This utility model has the following beneficial effects:

[0012] 1. This invention uses an atomizing nozzle installed on the atomizing connection pipe on the outer wall of the cylindrical mixing chamber of a Venturi valve mixer. Urea solution is delivered to the nozzle via a high-pressure supply pipeline and a liquid booster pump. High-speed airflow in the throat section generates negative pressure, ensuring full contact between the atomized urea particles and the high-temperature exhaust gas, resulting in a high pre-decomposition rate and reduced load on the main catalyst area. The negative pressure mixing mechanism reduces dependence on external compressed air, requiring only a high-temperature resistant axial flow fan to provide exhaust gas diversion power.

[0013] 2. In this utility model, the branch connection pipe is located downstream of the exhaust gas pipeline to extract high-temperature exhaust gas, and the return connection pipe is located upstream to return the undecomposed urea solution. The two form a closed loop through a high-temperature axial flow fan and a check valve. The high-temperature exhaust gas pre-decomposes urea, and the secondary decomposition is enhanced by a baffle plate in the exhaust gas pipeline. The undecomposed urea solution particles form a spiral motion trajectory in the pipeline, increasing the heat exchange time with the high-temperature gas by 2 seconds and improving the decomposition rate.

[0014] 3. This utility model uses a urea solution tank with a fixed coil running through it, connected to a gas generator coolant storage tank via a high-temperature water pipe, and a circulating pump drives the coolant flow. The urea solution is preheated using 80-90℃ coolant, which reduces the viscosity of the urea solution, decreases the diameter of the atomized particles, and significantly increases the gas-liquid contact area.

[0015] Of course, any product implementing this utility model does not necessarily need to achieve all of the advantages described above at the same time. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of this utility model, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the urea solution atomization device used in the SCR aftertreatment system of this utility model.

[0018] Figure 2 This is a schematic diagram of a cross-section of a Venturi valve mixer.

[0019] The attached diagram lists the components represented by each number as follows:

[0020] 1-Urea solution tank, 2-Atomizing nozzle, 3-Venturi valve mixer, 31-Jet head, 32-Cylindrical mixing chamber, 33-Throat, 34-Atomizing connection pipe, 4-High-pressure liquid supply pipeline, 5-Liquid booster pump, 6-High-temperature flue gas pipeline, 7-High-temperature axial flow fan, 8-Check valve, 9-Coil, 11-Branch connection pipe, 12-Return connection pipe. Detailed Implementation

[0021] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present utility model. Specific Implementation Example 1:

[0023] Please see Figure 1-2As shown, this utility model is a urea solution atomizing device for an SCR aftertreatment system, including a urea solution tank 1, an atomizing nozzle 2, a Venturi valve mixer 3, a branch connecting pipe 11 and a return connecting pipe 12 installed on the exhaust gas pipeline. The Venturi valve mixer 3 includes a jet head 31, a cylindrical mixing chamber 32, and a throat 33 connected in sequence. An atomizing connecting pipe 34 is fixed through the outer wall of the cylindrical mixing chamber 32. The atomizing nozzle 2 is installed on the atomizing connecting pipe 34 and atomizes the urea solution into fine particles. The urea solution tank 1 and the atomizing nozzle 2 are connected by a high-pressure liquid supply pipe 4. A liquid booster pump 5 is installed on the high-pressure liquid supply pipe 4 to provide high-pressure urea solution. The throat 33 is connected to the return connecting pipe 12. The branch connecting pipe 11 and the jet head 31 are connected by a high-temperature flue gas pipe 6. A high-temperature resistant axial flow fan 7 is installed on the high-temperature flue gas duct 6 to draw high-temperature exhaust gas from the branch connection pipe 11 to the jet head 31, providing heat energy for urea decomposition.

[0024] A branch connection pipe 11 and a return connection pipe 12 are installed on the exhaust gas pipeline to work with a high-temperature axial flow fan 7 to extract the high-temperature exhaust gas from the exhaust gas pipeline. The atomizing nozzle 2 atomizes the urea solution into fine atomized particles. In the Venturi valve mixer 3, a high-speed airflow through the throat 33 section generates negative pressure, which can efficiently mix the gas and liquid. The whole system constitutes a urea solution atomization and decomposition pre-reaction system on the side branch pipe of the exhaust gas pipeline to generate NH3, which participates in the SCR after-treatment system of the exhaust gas.

[0025] To ensure the stable operation of the entire exhaust gas pipeline side branch line, the return connection pipe 12 and the branch connection pipe 11 are located upstream and downstream of the exhaust gas pipeline, respectively. To prevent interference from air intake from one end of the exhaust gas pipeline, a check valve 8 is installed on the return connection pipe 12.

[0026] In order to improve the residual thermal decomposition efficiency of undecomposed urea solution in the exhaust pipe, a few turbulence plates are provided on the inner wall of the exhaust pipe between the return connection pipe 12 and the branch connection pipe 11 to enhance the thermal decomposition of undecomposed urea solution.

[0027] A coil 9 is fixedly installed through the urea solution tank 1. Both ends of the coil 9 are connected to the gas generator coolant storage tank through high-temperature water pipes, and a circulation pump is installed on the high-temperature water pipes to heat the urea solution in the urea solution tank 1 using the generator coolant (temperature 80-90℃), thereby reducing the energy consumption of electric heating.

[0028] A specific implementation process of this embodiment:

[0029] For exhaust gas diversion and heat energy utilization, the high-temperature axial flow fan 7 extracts high-temperature exhaust gas (200-400℃) from the downstream of the exhaust gas pipeline through the branch connection pipe 11, and then transports it to the jet head 31 through the high-temperature flue gas pipeline 6. The exhaust gas mixes with urea solution particles sprayed from the atomizing nozzle 2 in the cylindrical mixing chamber 32, and the high-speed airflow generated in the throat section 33 generates negative pressure to achieve efficient gas-liquid mixing.

[0030] Urea pre-decomposition and circulation: The mixed urea solution is pre-decomposed into NH3 and CO2 under the action of high-temperature exhaust gas. The incompletely decomposed solution is returned to the upstream of the exhaust gas pipeline through the return connection pipe 12, where secondary thermal decomposition is enhanced by the baffle plate. The check valve 8 ensures unidirectional flow of the return gas, avoiding interference with the upstream exhaust gas diversion. The decomposed NH3 participates in the SCR aftertreatment system to reduce nitrogen oxides.

[0031] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0032] The preferred embodiments of this utility model disclosed above are merely illustrative of the present utility model. These preferred embodiments do not exhaustively describe all details, nor do they limit the utility model to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of this utility model, thereby enabling those skilled in the art to better understand and utilize it. This utility model is limited only by the claims and their full scope and equivalents.

Claims

1. A urea solution atomizing device for an SCR aftertreatment system, characterized in that: Includes a urea solution tank (1), an atomizing nozzle (2), a venturi valve mixer (3), a branch connection pipe (11) and a return connection pipe (12) installed on the exhaust gas pipeline; The Venturi valve mixer (3) includes a jet head (31), a cylindrical mixing chamber (32) and a throat (33) connected in sequence; an atomizing connecting pipe (34) is fixed through the outer wall of the cylindrical mixing chamber (32); the atomizing nozzle (2) is installed on the atomizing connecting pipe (34); The urea solution tank (1) and the atomizing nozzle (2) are connected by a high-pressure liquid supply pipe (4); a liquid booster pump (5) is installed on the high-pressure liquid supply pipe (4); the throat pipe (33) is connected to the return connection pipe (12); The branch connecting pipe (11) is connected to the jet head (31) through a high-temperature flue gas pipe (6); a high-temperature resistant axial flow fan (7) is installed on the high-temperature flue gas pipe (6).

2. The urea solution atomizing device for the SCR aftertreatment system according to claim 1, characterized in that, A check valve (8) is installed on the return connection pipe (12).

3. The urea solution atomizing device for the SCR aftertreatment system according to claim 1, characterized in that, The return connection pipe (12) and the branch connection pipe (11) are located upstream and downstream of the exhaust gas pipeline, respectively.

4. The urea solution atomizing device for the SCR aftertreatment system according to claim 1, characterized in that, The inner wall of the exhaust pipe between the return connection pipe (12) and the branch connection pipe (11) is provided with several interference flow plates.

5. The urea solution atomizing device for the SCR aftertreatment system according to claim 1, characterized in that, A coil (9) is fixedly installed through the urea solution tank (1).

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