Engine tail gas aftertreatment system and method

Abstract

The invention discloses an engine tail gas after-treatment system and method, and belongs to the technical field of engine tail gas treatment.The engine tail gas after-treatment system comprises at least two pre-treatment modules connected in parallel, a shared after-treatment module, a reducing agent supply injection module and a control module; gas outlet ends of all the pre-treatment modules converge to a shared post-treatment module, the shared post-treatment module is sequentially provided with a mixing section and a selective catalytic reduction reactor, the mixing section is provided with a reducing agent injection port, and the selective catalytic reduction reactor is provided with a reducing agent injection port. The reducing agent supply injection module comprises a storage tank and an injection unit connected with the storage tank, an outlet of the injection unit is connected with the reducing agent injection port, and the control module controls the injection amount of the reducing agent according to signals monitored by a temperature sensor arranged on the shared post-processing module and a nitrogen oxide sensor arranged on the mixing section. The device is compact in structure, and efficient cooperative treatment of multi-engine tail gas can be achieved.

Description

Technical Field

[0001] This invention relates to the field of engine exhaust gas treatment technology, and specifically to an engine exhaust gas aftertreatment system and method. Background Technology

[0002] During engine operation, especially on test benches, fuel combustion produces exhaust gases containing pollutants such as nitrogen oxides, carbon monoxide, hydrocarbons, and particulate matter. To meet increasingly stringent environmental emission standards, aftertreatment devices are required in the engine exhaust system. These devices use catalytic reduction, oxidation, and filtration to convert harmful substances into harmless substances such as nitrogen and water before releasing them into the atmosphere. Common aftertreatment technologies include oxidation catalysts, particulate filters, urea injection systems, and selective catalytic reduction systems. These systems typically operate independently to achieve purification.

[0003] However, the aforementioned existing technical solutions have many shortcomings in practical applications:

[0004] Each test bench is independently equipped with a complete set of after-treatment equipment. When multiple test benches are densely arranged, the duplication of equipment construction results in a huge footprint, high initial investment costs and subsequent maintenance costs. Moreover, each module is heated independently, and the SCR catalyst heats up slowly during cold start, making it difficult to quickly reach the optimal activity temperature window. Especially under low load conditions, the exhaust gas temperature is insufficient, resulting in low nitrogen oxide conversion efficiency. In order to ensure the reaction temperature, auxiliary heaters often need to run at high power for a long time, which increases energy consumption.

[0005] Existing open-loop or semi-closed-loop urea injection strategies cannot accurately adjust the injection volume in real time according to exhaust gas flow and nitrogen oxide concentration. Excessive urea injection will cause unreacted ammonia to escape, resulting in secondary pollution. Insufficient injection will not be able to fully reduce nitrogen oxides, leading to excessive emissions. In low-temperature environments, urea solution is prone to crystallization, clogging pipelines and nozzles and affecting the normal operation of the system. At the same time, existing devices are mostly designed for specific models or fixed operating conditions. They have poor adaptability to different fuel types, displacements, or engines with variable operating conditions, requiring customized development and lacking modular and flexible configuration capabilities. Summary of the Invention

[0006] To address the problems existing in the prior art, this invention provides an engine exhaust aftertreatment system and method to solve the problems of large footprint, high cost, slow start-up and heating, low catalytic efficiency, and inaccurate urea injection control in multi-engine exhaust aftertreatment systems. It also solves the problems of urea crystallization in low-temperature environments and poor system modularity and versatility, thereby achieving the goal of exhaust purification that is compact, efficient, intelligently controlled, reliable in operation, and widely adaptable.

[0007] The technical solution of the present invention is as follows: In a first aspect of the present invention, an engine exhaust aftertreatment system is provided, comprising: at least two pretreatment modules, a shared aftertreatment module, a reducing agent supply injection module, and a control module; The at least two pre-treatment modules are arranged in parallel. The air inlet of each pre-treatment module is used to connect to the corresponding engine exhaust source. Each pre-treatment module includes an oxidation catalyst and a particulate filter arranged sequentially along the exhaust flow direction for preliminary purification of their respective engine exhaust. The inlet of the shared aftertreatment module is connected to the outlet of all the pretreatment modules through a pipeline. The shared aftertreatment module includes a mixing section and a selective catalytic reduction reactor arranged sequentially along the exhaust flow direction. The mixing section is provided with a reducing agent injection port. The reducing agent supply injection module includes a storage tank and an injection unit connected to the storage tank, and the outlet of the injection unit is connected to the reducing agent injection port of the mixing section. The control module is communicatively connected to the temperature sensor located in the shared post-processing module, the nitrogen oxide sensor located in the mixing section, and the reducing agent supply injection module, and is used to control the injection amount of the reducing agent supply injection module according to the monitored temperature and nitrogen oxide concentration signals.

[0008] In some embodiments of the present invention, the shared post-processing module further includes a heater disposed upstream of the mixing section, the heater being communicatively connected to the control module.

[0009] In some embodiments of the present invention, the shared aftertreatment module further includes an ammonia escape catalyst disposed downstream of the selective catalytic reduction reactor.

[0010] In some embodiments of the present invention, the reducing agent supply injection module further includes a heat tracing component for heating the storage tank and its delivery pipeline.

[0011] In some embodiments of the present invention, the reducing agent supply injection module further includes a liquid level detection module for detecting the reducing agent liquid level in the storage tank.

[0012] In some embodiments of the present invention, the control module is further configured to: control the heater to start when the temperature at the air intake of the shared after-processing module is detected to be lower than a first set threshold; and control the heater to stop or reduce its power when the temperature reaches or exceeds a second set threshold.

[0013] In some embodiments of the present invention, the control module is configured to calculate and control the injection quantity of the reducing agent supply injection module based on pre-stored engine operating parameters and nitrogen oxide mapping relationship, as well as real-time monitored exhaust gas parameters.

[0014] In some embodiments of the present invention, the oxidation catalyst, particulate trap, and selective catalytic reduction reactor all adopt a modular encapsulation structure.

[0015] In some embodiments of the present invention, a flow sensor for monitoring exhaust gas flow is also included. The flow sensor is communicatively connected to the control module, and the control module is able to adjust the amount of reducing agent injected based on the monitored exhaust gas flow.

[0016] In a second aspect of the invention, an engine exhaust aftertreatment method is provided, applied to the above-described system, comprising: It receives exhaust gas from at least two engines, and each exhaust gas stream is oxidized and particulate matter captured by an independent pretreatment module. The multiple exhaust gases that have undergone pretreatment are combined and transported to a shared mixing section; Monitor the temperature and nitrogen oxide concentration of the combined exhaust gases; Based on the monitored temperature and nitrogen oxide concentration, the amount of reducing agent injected into the mixing section is controlled to mix the reducing agent with the exhaust gas. The mixed gas-liquid mixture is fed into a shared selective catalytic reduction reactor for catalytic reduction reaction.

[0017] One or more technical solutions of the present invention have the following beneficial effects: This problem is solved by using an architecture that connects at least two independent pre-treatment modules in parallel and shares a single after-treatment module. This architecture allows multiple engines to share a single downstream mixing section, selective catalytic reduction reactor, and associated heating and control unit, greatly reducing the number of redundant equipment and floor space, and significantly lowering the initial investment and long-term maintenance costs of the system.

[0018] A heater is installed upstream of the mixing section of the shared aftertreatment module, and the control module intelligently starts, stops and adjusts the power according to the intake air temperature. This can quickly increase the temperature of the collected exhaust gas, ensuring that the selective catalytic reduction reactor quickly reaches and maintains the high-efficiency operating temperature window, thereby improving the overall purification efficiency, avoiding ineffective operation of the heater, and reducing auxiliary energy consumption.

[0019] By integrating signals from temperature and nitrogen oxide sensors into the control module, closed-loop feedback control of the reductant injection quantity is achieved. This allows for precise matching of the injection quantity based on real-time exhaust gas conditions, effectively preventing excessive or insufficient reductant. While ensuring efficient nitrogen oxide conversion, it also minimizes ammonia slip. An ammonia slip catalyst added downstream of the reactor further eliminates residual ammonia, preventing secondary pollution.

[0020] A heat tracing component for the storage tank and pipelines is installed in the reducing agent supply injection module to ensure the normal and reliable operation of the system under low temperature conditions.

[0021] The oxidation catalyst, particulate filter, and selective catalytic reduction reactor in this invention all adopt a modular packaging structure, which allows for flexible adjustment of the quantity and specifications of each module according to the specific needs of different engine types, thereby enhancing the system's versatility and deployment flexibility in the face of different fuels and operating conditions. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the composition of an engine exhaust aftertreatment system provided in Embodiment 1 of the present invention; Figure 2 This is a schematic diagram of the composition of an engine exhaust aftertreatment system provided in Embodiment 1 of the present invention for treating exhaust gas from a single engine. Figure 3 This is a schematic diagram of the composition of an engine exhaust aftertreatment system provided in Embodiment 1 of the present invention for treating exhaust gases from two engines. Figure 4 This is a schematic diagram of the composition of an engine exhaust aftertreatment system provided in Embodiment 1 of the present invention for treating exhaust gases from three engines.

[0023] In the diagram: 1. Urea tank; 2. Urea storage tank; 3. Urea pump unit; 4. Urea spray gun; 5. Engine; 6. Pretreatment module; 7. Heater; 8. Mixing section; 9. Shared aftertreatment module; 10. Oxidation catalyst; 11. Particulate trap; 12. Selective catalytic reduction reactor. Detailed Implementation

[0024] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0025] Example 1 In a typical embodiment of the present invention, such as Figure 1 As shown, an engine exhaust aftertreatment system is proposed, comprising: at least two pretreatment modules 6, a shared aftertreatment module 9, a reducing agent supply injection module, and a control module; At least two pre-treatment modules 6 are connected in parallel. The air intake of each pre-treatment module 6 is used to connect to the exhaust source of the corresponding engine 5. Each pre-treatment module 6 includes an oxidation catalyst 10 and a particulate filter 11 arranged sequentially along the exhaust flow direction, which are used to perform preliminary purification of the exhaust gas of their respective engines 5. The inlet of the shared aftertreatment module 9 is connected to the outlet of all the pretreatment modules 6 through a pipeline. The shared aftertreatment module 9 includes a mixing section 8 and a selective catalytic reduction reactor 12 arranged sequentially along the exhaust flow direction. The mixing section 8 is provided with a reducing agent injection port. The reducing agent supply injection module includes a storage tank and an injection unit connected to the storage tank. The outlet of the injection unit is connected to the reducing agent injection port of the mixing section 8. The control module is communicatively connected to the temperature sensor located in the shared post-processing module 9, the nitrogen oxide sensor located in the mixing section 8, and the reducing agent supply injection module, and is used to control the injection amount of the reducing agent supply injection module according to the monitored temperature and nitrogen oxide concentration signals.

[0026] By prepositioning and independently configuring the oxidation catalysis and particulate matter capture functions for each engine 5, while sharing the core reaction step of selective catalytic reduction and the mixing function, the system can handle multiple engines 5, such as a test bench group, without having to build a complete SCR treatment chain for each engine 5. This significantly reduces the overall footprint of the equipment, lowers the initial construction cost, and reduces the complexity of subsequent maintenance.

[0027] Secondly, the control module controls the reductant injection quantity based on signals from the temperature sensor in the shared aftertreatment module 9 and the nitrogen oxide sensor in the mixing section 8, achieving real-time monitoring and closed-loop feedback control of key parameters for exhaust gas treatment. It can dynamically and precisely adjust the injection quantity of reductants such as urea to match the real-time exhaust gas temperature and nitrogen oxide concentration entering the shared aftertreatment module 9. This avoids secondary pollution caused by ammonia escape due to excessive injection in traditional open-loop or simple operating condition control, and also prevents incomplete nitrogen oxide purification due to insufficient injection. Therefore, while ensuring emission compliance, it optimizes reductant consumption and reduces the overall system operating cost.

[0028] The shared post-processing module 9 also includes a heater 7 located upstream of the mixing section 8, which is communicatively connected to the control module.

[0029] This configuration effectively enhances the system's ability to actively regulate exhaust gas temperature. Especially under conditions such as engine start-up, low-load operation, or low ambient temperature, when the collected exhaust gas temperature is insufficient to bring the SCR catalyst to its optimal activity window, heater 7 can quickly increase the gas flow temperature, ensuring that the selective catalytic reduction reaction proceeds efficiently and stably. This not only shortens the preheating time for the system to reach ideal purification efficiency but also enhances its adaptability to different operating conditions, guaranteeing the stability of emission standards across the entire operating range.

[0030] In this embodiment, heater 7 comprises a heater 7 body, an electric heater 7 control cabinet, a K-type thermocouple for temperature monitoring, and related cables and wires. Heater 7 is manually triggered and equipped with temperature sensors at both its inlet and outlet. During operation, continuous exhaust gas supply from engine 5 must be ensured. During use, heater 7 automatically adjusts its heating temperature via the heater 7 control cabinet. Requirements include a voltage of 380 / 220V, a power of 300KW, and a frequency of 50Hz. It can automatically and manually switch between starting and stopping heater 7, is equipped with an emergency stop switch, and can display the inlet and outlet exhaust gas temperatures.

[0031] The shared aftertreatment module 9 also includes an ammonia escape catalyst located downstream of the selective catalytic reduction reactor 12.

[0032] Even under closed-loop control, transient operating conditions or control deviations may still result in the release of a small amount of unreacted ammonia. An ammonia escape catalyst can further catalytically oxidize this residual ammonia into harmless nitrogen and water, completely eliminating the risk of secondary air pollution caused by ammonia escape. This results in cleaner final emissions from the system, meeting more stringent environmental protection requirements.

[0033] In this embodiment, the shared post-processing module 9 also includes a pressure ratio transmitter, an air volume transmitter, and a nitrogen oxide sensor. The CAN communication baud rate is 250kHz, the transmission cycle is 50ms, and the operating temperature range is -40℃ to 1000℃ (for exhaust gas). The temperature sensor has a measurement range of 0 to 800℃, an accuracy class of 0.5%FS, a power supply of 24VDC, and a signal output of 4-20mA. The pressure transmitter has a measurement range of 0 to 10kPa, an accuracy class of 0.25%, a power supply of 24VDC, and an output signal of 4-20mA. The air volume transmitter has a wind speed range of 0 to 50m / s, a wind pressure range of -10 to 10kPa, a temperature range of -40℃ to 800℃, a signal output of 4 mA to 20mA, a wind speed accuracy of 3%FS, and a wind pressure accuracy of 0.5%FS. It is used to monitor the NOx parameters, temperature, pressure and air volume of exhaust gas at the inlet and outlet, so as to control the amount of urea injected and realize the exhaust gas reduction reaction.

[0034] The reducing agent supply injection module also includes a heat tracing component for heating the storage tank and its delivery pipeline.

[0035] To address the issue of reducing agents, especially urea aqueous solutions, easily crystallizing and solidifying at low temperatures, the heating component can maintain the reducing agent in the storage tank and delivery pipeline within a suitable liquid temperature range, effectively preventing crystallization and blockage. This ensures the reliability and continuity of the reducing agent supply injection module in cold climates or winter conditions, improving the all-weather operation capability and reliability of the entire post-treatment system.

[0036] The reducing agent supply injection module also includes a liquid level detection module for detecting the reducing agent level in the storage tank.

[0037] This setup enables real-time monitoring of the material level in the reducing agent storage tank. Through level detection, the system can promptly warn of insufficient reducing agent reserves, reminding operators to replenish it. This prevents post-treatment malfunctions and excessive emissions due to reduced reducing agent depletion, improving the system's automation and maintainability, and ensuring long-term stable operation.

[0038] The reducing agent supply injection module consists of a urea tank 1, a urea storage tank 2, a urea level sensor, a urea temperature sensor, an electric heat tracing heating component, an external insulation part for the urea tank, a urea pump unit 3, a urea metering unit, urea inlet and outlet pipes, and a urea spray gun 4. This enables automatic urea replenishment, prevents urea crystallization in cold environments, controls the amount of urea injected, and performs secondary atomization during injection.

[0039] The control module is also configured to: start the heater 7 when the temperature at the intake of the shared after-treatment module 9 is detected to be lower than the first set threshold; and stop or reduce the power of the heater 7 when the temperature reaches or exceeds the second set threshold.

[0040] The start-up and power of heater 7 are controlled by comparing the inlet temperature of shared post-processing module 9 with the set threshold, realizing intelligent and energy-saving heating process. The control module starts heating only when the temperature is lower than the required threshold, and stops or reduces power after reaching or exceeding the target temperature, avoiding continuous ineffective operation of heater 7, ensuring that the reaction temperature requirement is met while minimizing auxiliary energy consumption.

[0041] The control module is configured to calculate and control the amount of reducing agent supplied to the injection module based on the pre-stored engine operating parameters and the mapping relationship between nitrogen oxides and exhaust gas parameters monitored in real time.

[0042] This setup combines feedforward and feedback control, improving the predictability and accuracy of the control module. The pre-stored mapping relationship provides a basic injection quantity estimate based on the engine 5's operating status, while real-time sensor signals are used for fine-tuning and correction to address actual variables such as individual differences in engine 5, fuel changes, and catalyst aging. This makes the control of the reducing agent injection quantity more precise and adaptive, further optimizing the balance between purification efficiency and reducing agent consumption.

[0043] The oxidation catalyst 10, the particulate trap 11, and the selective catalytic reduction reactor 12 all adopt a modular encapsulation structure.

[0044] The modular packaging structure improves the system's standardization, maintainability, and versatility, allowing the oxidation catalyst 10, particulate filter 11, and selective catalytic reduction reactor 12 to be quickly disassembled, replaced, or upgraded as independent modules, facilitating maintenance. Furthermore, the number of oxidation catalysts 10, particulate filter 11, and selective catalytic reduction reactor 12, as well as catalyst specifications such as pore density and precious metal loading, or carrier type, can be flexibly adjusted according to the specific engine 5's displacement, power, fuel type (e.g., diesel or gas engine), and emission targets, without requiring a complete system redesign. This significantly enhances the system's adaptability and deployment flexibility in diverse application scenarios.

[0045] It also includes a flow sensor for monitoring exhaust gas flow. The flow sensor is connected in communication with the control module, which can adjust the amount of reducing agent injected based on the monitored exhaust gas flow.

[0046] By setting up a flow sensor for flow monitoring, the control of the reductant injection quantity becomes more comprehensive. The control module can integrate three key parameters—temperature, nitrogen oxide concentration, and exhaust gas flow rate—to more scientifically calculate the required reductant stoichiometric ratio, achieving more precise injection based on quality and quantity. This further improves control accuracy, ensuring that high nitrogen oxide conversion efficiency is maintained and ammonia escape is minimized under different engine loads.

[0047] In a second aspect of the invention, an engine exhaust aftertreatment method is provided, applied to the above-described system, comprising: It receives exhaust gas from at least two engines 5, and allows each exhaust gas stream to undergo oxidation and particulate matter capture through an independent pre-treatment module 6. The pre-treated exhaust gases are combined and transported to the shared mixing section 8. Monitor the temperature and nitrogen oxide concentration of the combined exhaust gases; Based on the monitored temperature and nitrogen oxide concentration, the amount of reducing agent injected into mixing section 8 is controlled to mix the reducing agent with the exhaust gas; The mixed gas-liquid mixture is fed into a shared selective catalytic reduction reactor 12 for catalytic reduction reaction.

[0048] First, oxidation and particulate matter capture are performed separately through independent pre-treatment modules 6, enabling parallel treatment of carbon monoxide, hydrocarbons, and particulate matter in the exhaust gases of each engine 5. This reduces the pollution load in subsequent shared stages and avoids potential problems caused by direct mixing of untreated exhaust gases. Second, the multiple exhaust gases are combined and transported to a shared mixing section 8 for unified reducing agent injection and mixing. A single injection and mixing device serves multiple engines 5, simplifying the system. Finally, injection is controlled based on real-time monitoring of temperature and nitrogen oxide concentration, and the mixture is fed into a shared SCR reactor. This achieves precise response and efficient purification of the combined exhaust gas characteristics, resulting in compact, efficient, intelligent, and reliable exhaust gas purification.

[0049] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. An engine exhaust aftertreatment system, characterized in that, include: It includes at least two pre-processing modules, one shared post-processing module, one reducing agent supply and injection module, and one control module. The at least two pre-treatment modules are arranged in parallel. The air inlet of each pre-treatment module is used to connect to the corresponding engine exhaust source. Each pre-treatment module includes an oxidation catalyst and a particulate filter arranged sequentially along the exhaust flow direction for preliminary purification of their respective engine exhaust. The inlet of the shared aftertreatment module is connected to the outlet of all the pretreatment modules through a pipeline. The shared aftertreatment module includes a mixing section and a selective catalytic reduction reactor arranged sequentially along the exhaust flow direction. The mixing section is provided with a reducing agent injection port. The reducing agent supply injection module includes a storage tank and an injection unit connected to the storage tank, and the outlet of the injection unit is connected to the reducing agent injection port of the mixing section. The control module is communicatively connected to the temperature sensor located in the shared post-processing module, the nitrogen oxide sensor located in the mixing section, and the reducing agent supply injection module, and is used to control the injection amount of the reducing agent supply injection module according to the monitored temperature and nitrogen oxide concentration signals.

2. The engine exhaust aftertreatment system according to claim 1, characterized in that, The shared post-processing module also includes a heater located upstream of the mixing section, and the heater is communicatively connected to the control module.

3. The engine exhaust aftertreatment system according to claim 2, characterized in that, The shared aftertreatment module also includes an ammonia escape catalyst located downstream of the selective catalytic reduction reactor.

4. The engine exhaust aftertreatment system according to claim 1, characterized in that, The reducing agent supply injection module also includes a heat tracing component for heating the storage tank and its delivery pipeline.

5. The engine exhaust aftertreatment system according to claim 1, characterized in that, The reducing agent supply injection module also includes a liquid level detection module for detecting the reducing agent liquid level in the storage tank.

6. The engine exhaust aftertreatment system according to claim 2, characterized in that, The control module is also configured to: control the heater to start when the temperature at the air intake of the shared after-treatment module is detected to be lower than a first set threshold; and control the heater to stop or reduce its power when the temperature reaches or exceeds a second set threshold.

7. The engine exhaust aftertreatment system according to claim 1, characterized in that, The control module is configured to calculate and control the injection quantity of the reducing agent supplied to the injection module based on the pre-stored engine operating parameters and the mapping relationship between nitrogen oxides and the real-time monitored exhaust gas parameters.

8. The engine exhaust aftertreatment system according to claim 1, characterized in that, The oxidation catalyst, particulate trap, and selective catalytic reduction reactor all adopt a modular encapsulation structure.

9. The engine exhaust aftertreatment system according to claim 1, characterized in that, It also includes a flow sensor for monitoring exhaust gas flow rate, the flow sensor being communicatively connected to the control module, the control module being able to adjust the reductant injection amount based on the monitored exhaust gas flow rate.

10. An engine exhaust aftertreatment method, applied to an engine exhaust aftertreatment system as described in any one of claims 1 to 9, characterized in that, include: It receives exhaust gas from at least two engines, and each exhaust gas stream is oxidized and particulate matter captured by an independent pretreatment module. The multiple exhaust gases that have undergone pretreatment are combined and transported to a shared mixing section; Monitor the temperature and nitrogen oxide concentration of the combined exhaust gases; Based on the monitored temperature and nitrogen oxide concentration, the amount of reducing agent injected into the mixing section is controlled to mix the reducing agent with the exhaust gas. The mixed gas-liquid mixture is fed into a shared selective catalytic reduction reactor for catalytic reduction reaction.

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