A tail gas aftertreatment system, assembly and method based on full-temperature range collaborative optimization

Abstract

The application provides a tail gas aftertreatment system, assembly and method based on full-temperature-range collaborative optimization, the system comprising: a multi-zone wide-temperature composite reduction system comprising at least two SCR systems; wherein the multiple SCR systems are configured with different reducing agents, so that the multiple SCR systems have multiple different temperature working zones; wherein the temperature working zones corresponding to the multiple SCR systems do not have temperature intersection and / or temperature interval, to jointly form a continuous full-temperature-range coverage zone; the multiple SCR systems alternately or simultaneously perform catalytic reduction reaction in the respective corresponding temperature working zones according to the exhaust temperature of the tail gas in the exhaust passage, to realize efficient conversion of nitrogen oxides in the tail gas under full working conditions. Through the system provided by the application, a new more optimized and highly integrated methanol engine aftertreatment system is established, and the effectiveness of the tail gas aftertreatment system under full working conditions is ensured.

Description

Technical Field

[0001] The present application relates to the technical field of methanol engine after-treatment, and in particular to an exhaust gas after-treatment system, assembly and method based on full-temperature range collaborative optimization. Background Art

[0002] The existing diesel after-treatment system technology route is: DOC (Diesel Oxidation Catalyst) + DPF (Diesel Particulate Filter) + SCR (Selective Catalytic Reduction) + ASC (Ammonia Slip Catalyst), which uses urea as a reducing agent.

[0003] Today, the exhaust aftertreatment technology for spark-ignition methanol engines generally replicates diesel aftertreatment systems, but this presents challenges and drawbacks. Firstly, diesel aftertreatment systems are more complex. Methanol's molecular formula lacks the C-H bonds that contribute to particulate matter generation, and therefore does not generate it. The DPF, however, primarily captures particulate matter generated within the engine. Therefore, for methanol engines, the DPF in diesel aftertreatment systems actually increases system complexity. Secondly, the urea reductant (SCR) has a high ignition temperature, and the NH3 in the injected urea easily reacts with incompletely burned methanol to form highly toxic formamide. Therefore, urea reductant (SCR) is also unsuitable for methanol engine exhaust aftertreatment systems.

[0004] However, in the current after-treatment system of methanol engines that do not use urea SCR, although safety and health issues have been avoided to a certain extent, the temperature range of the SCR system used is single, and the catalytic reduction is limited to its own narrow temperature zone. It can only work effectively within a certain temperature range. Outside the temperature range, the conversion efficiency is low, the conversion efficiency decreases or fails, and it is impossible to achieve full nitrogen oxide purification from low-load cold start to high-load conditions, making it difficult to meet increasingly stringent emission requirements. Summary of the Invention

[0005] To address the above issues, one objective of the present invention is to provide an exhaust gas aftertreatment system based on full-temperature coordinated optimization, thereby establishing a new, more optimized and highly integrated methanol engine aftertreatment system and ensuring the effectiveness of the exhaust gas aftertreatment system under all operating conditions. A second objective of the present invention is to provide a spark-ignition methanol engine assembly. A third objective of the present invention is to provide an exhaust gas treatment method based on full-temperature coordinated optimization.

[0006] To achieve one of the objectives, in a first aspect, the present invention provides an exhaust gas after-treatment system based on full-temperature range collaborative optimization, which adopts the following technical solution:

[0007] An exhaust gas after-treatment system based on full-temperature range collaborative optimization is suitable for spark-ignition methanol engines and is installed in the exhaust passage of methanol engines. The system includes:

[0008] The multi-zone wide temperature composite reduction system includes at least two SCR systems; wherein,

[0009] The plurality of SCR systems are configured with different reducing agents, so that the plurality of SCR systems have multiple different temperature operating zones; wherein,

[0010] The temperature operating zones corresponding to the plurality of SCR systems do not have temperature intersections and / or temperature intervals, so as to be combined to form a continuous full-temperature coverage zone;

[0011] Wherein, a plurality of different SCR systems are configured as follows:

[0012] performing catalytic reduction reactions alternately or simultaneously in the respective corresponding temperature operating zones according to the exhaust temperature of the exhaust gas in the tail exhaust passage, so as to achieve efficient conversion of nitrogen oxides in the exhaust gas under all operating conditions;

[0013] The DOC system is connected to the outlet of the multi-zone wide-temperature composite reduction system and is used to oxidize other polluting components in the tail gas.

[0014] As one of the preferred solutions, the multi-zone wide temperature composite reduction system is a methanol-hydrogen complementary SCR system, which includes a first SCR system using hydrogen as a reducing agent and a second SCR system using methanol as a reducing agent;

[0015] The first SCR system and the second SCR system are connected in series along the exhaust gas flow direction;

[0016] The hydrogen is indirectly and the methanol is directly derived from a methanol tank used to supply fuel to the methanol engine.

[0017] As one of the preferred solutions, the system further includes:

[0018] a methanol cracker, connected to the methanol tank and the first SCR system respectively, and located before the first SCR system, for utilizing the exhaust gas temperature to crack the methanol transmitted from the methanol tank to produce hydrogen;

[0019] A hydrogen distribution tank is connected to the methanol cracker, the first SCR system and the methanol engine respectively, and is used to store the hydrogen generated by cracking and distribute it to the first SCR system and the methanol engine.

[0020] As one of the preferred solutions, a bypass line is provided between the first SCR system and the second SCR system, and a bypass control valve for controlling the on-off of the bypass line is provided on the bypass line.

[0021] As one of the preferred solutions, the system further includes:

[0022] The test system includes a plurality of temperature sensors and a plurality of nitrogen oxide sensors, which are respectively arranged at the inlet of the tail exhaust passage corresponding to each of the SCR system and the DOC system.

[0023] To achieve the second objective, in a second aspect, the present invention provides an exhaust gas after-treatment system based on full-temperature range collaborative optimization, which adopts the following technical solutions:

[0024] A spark-ignition methanol engine assembly, comprising:

[0025] The air intake system includes an air filter, a supercharger, an intercooler and a throttle valve which are connected in sequence;

[0026] A post-treatment system, such as the exhaust gas post-treatment system based on full-temperature range collaborative optimization as described in the first aspect of the present invention;

[0027] A methanol engine is connected to the intake system through an intake passage and to the after-treatment system through a tail exhaust passage, wherein a methanol airway nozzle and a hydrogen nozzle are provided on the intake passage, and a methanol direct injection nozzle is provided on the methanol engine;

[0028] a methanol fuel tank, which is respectively connected to the methanol gas nozzle, the methanol direct injection nozzle, the methanol cracker on the post-treatment system, and the second SCR system;

[0029] Wherein, the hydrogen nozzle is in communication with a hydrogen distribution tank on the post-processing system which is in communication with the methanol cracker;

[0030] Wherein, an exhaust gas bypass is provided on the tail exhaust passage corresponding to the front and rear ends of the supercharger.

[0031] To achieve the third objective, in a third aspect, the present invention provides an exhaust gas treatment method based on full-temperature range collaborative optimization, which adopts the following technical solutions:

[0032] A tail gas treatment method based on full-temperature range collaborative optimization, the method comprising:

[0033] Obtain the exhaust temperature and nitrogen oxide concentration corresponding to the inlet of each SCR system in the tail exhaust passage of the methanol engine;

[0034] determining, based on the exhaust gas temperature corresponding to the front SCR system, whether the current operating condition of the methanol engine is any one of a cold operating condition, a buffer operating condition, and a normal operating condition;

[0035] determining, based on the nitrogen oxide concentrations before and after each SCR system, an injection amount of the SCR system that needs to be injected with the reducing agent under the current operating condition;

[0036] In the cold operating condition, the exhaust temperature is increased by controlling the first execution operation, and the currently executed SCR system is controlled to start injecting the reducing agent with a first preset parameter to perform a catalytic reduction reaction with nitrogen oxides in the exhaust gas within a first wide temperature range corresponding to the reducing agent;

[0037] Under the buffer operating condition, controlling the exhaust temperature to continue to increase through a second execution operation, and controlling the corresponding SCR system to start injecting the reducing agent with a second preset parameter to perform a catalytic reduction reaction with nitrogen oxides in the exhaust gas within the corresponding second wide temperature range;

[0038] Under the normal operating condition, the operating state of the methanol engine is switched through a third execution operation, and the corresponding SCR system is controlled to start injecting the reducing agent with a third preset parameter to perform a catalytic reduction reaction with nitrogen oxides in the exhaust gas within the corresponding third wide temperature range;

[0039] Among them, the temperature ranges of the first wide temperature zone, the second wide temperature zone and the third wide temperature zone gradually increase, and the wide temperature zone is a combination of one or more sections of the multi-section temperature working zone

[0040] As one of the preferred solutions, in the cold operating condition, controlling the exhaust temperature to increase through a first execution operation, and controlling the currently executed SCR system to start injecting the reducing agent with a first preset parameter, includes:

[0041] Based on the cold operating condition, at least one of opening a hydrogen nozzle, opening a wastegate valve on an exhaust bypass, reducing a throttle opening, and opening a methanol direct injection nozzle controls the exhaust temperature to increase; and

[0042] The first SCR system is started, the bypass control valve on the bypass line is closed, and the second SCR system is closed to react within the temperature operating range of the hydrogen in the first SCR system.

[0043] As one of the preferred solutions, in the case of the buffering operating condition, controlling the exhaust temperature to continue to increase through a second execution operation, and controlling the corresponding SCR system to start injecting the reducing agent with a second preset parameter, includes:

[0044] Based on the buffering condition, the throttle opening is reduced to control the exhaust temperature to continue to increase, and,

[0045] The methanol direct injection nozzle and the first SCR system are opened, the bypass control valve on the bypass line is closed, and the second SCR system is opened to react in the composite wide temperature range formed by the hydrogen of the first SCR system and the methanol of the second SCR system.

[0046] As one of the preferred solutions, under the normal operating condition, switching the operating state of the methanol engine through a third execution operation and controlling the corresponding SCR system to start injecting the reducing agent with a third preset parameter includes:

[0047] Based on the normal operating conditions and the torque requirement of the methanol engine, controlling the operating parameters of the throttle, the methanol airway nozzle, and the methanol direct injection nozzle; and

[0048] Shut down the first SCR system, open the bypass control valve on the bypass line, and start the second SCR system to carry out the reaction within the temperature operating range of the methanol in the second SCR system;

[0049] The method of controlling the operating parameters of the throttle, the methanol airway nozzle, and the methanol direct injection nozzle based on the normal operating condition and the torque demand of the methanol engine further includes:

[0050] Determining whether the normal operating condition is a steady-state operating condition or a rapid acceleration operating condition;

[0051] In the case of the rapid acceleration condition, the hydrogen nozzle is opened at the same time to control the hydrogen to enter the methanol engine.

[0052] Compared with the prior art, this application has the following advantages:

[0053] The exhaust gas after-treatment system provided in the embodiment of the present application is a new after-treatment system suitable for spark-ignition methanol engines. It adopts a multi-zone wide-temperature composite reduction system. Based on the non-intersection and / or non-interval selection criteria, multiple SCR systems with reducing agents having continuous temperature operating zones are selected as carriers. Since the temperature operating zones of the multiple SCR systems are seamlessly connected, a continuous and efficient full-temperature coverage area is formed. The entire emission control system can maintain a high NOx level under any operating conditions (from the low temperature of cold start to the high temperature of high load). X Conversion efficiency, to meet more stringent emission standards. Especially for methanol engines, full temperature coverage can effectively improve the cold start performance of methanol engines. At the same time, due to the continuous coverage of the full temperature range, the system will not produce NO in some transition conditions of temperature changes, such as when the exhaust temperature gradually switches from cold to high temperature, and the exhaust temperature transitions from low temperature to medium and high temperature.X The significant decrease in treatment efficiency ensures the continuous stability of emission control and avoids NOx caused by changes in exhaust temperature. X The conversion rate fluctuates greatly, which improves the applicability and flexibility of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] In order to more clearly illustrate the technical solution of the present application, the following is a brief introduction to the drawings required for the description of the present application. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0055] Figure 1 This is a structural diagram of an exhaust gas after-treatment system based on full-temperature range collaborative optimization according to an embodiment of the present application;

[0056] Figure 2 This is a system architecture diagram of a spark-ignition methanol engine assembly according to an embodiment of the present application;

[0057] Figure 3 This is a flowchart of the steps of the exhaust gas treatment method based on full-temperature range collaborative optimization according to an embodiment of the present application;

[0058] Figure 4 It is a flow chart of the exhaust gas treatment method based on full-temperature range collaborative optimization described in an embodiment of the present application.

[0059] Description of reference numerals:

[0060] 1. Air filter; 2. Air pipe; 3. Turbocharger; 4. Intercooler; 5. Throttle; 6. Exhaust gas bypass valve; 7. Methanol tank; 8. Hydrogen distribution tank; 9. Methanol air duct nozzle; 10. Methanol direct injection nozzle; 11. Hydrogen nozzle; 12. Methanol cracker; 13. Hydrogen SCR nozzle; 14. Methanol nozzle; 15. First SCR system; 16. Second SCR system; 17. DOC system; 18. Front temperature sensor; 19. Middle temperature sensor; 20. Rear temperature sensor; 21. Bypass control valve; 22. Front NOx sensor; 23. Middle NOx sensor; 24. Rear NOx sensor. DETAILED DESCRIPTION

[0061] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0062] Reference Figure 1 As shown, Figure 1 The overall structure diagram of the exhaust gas after-treatment system based on full temperature range collaborative optimization shown in the present invention. Figure 1 As shown, the present invention provides an exhaust gas after-treatment system based on full-temperature collaborative optimization, which is suitable for spark-ignition methanol engines and is arranged on the tail exhaust passage of the methanol engine. The system includes: a multi-zone wide-temperature composite reduction system, including at least two SCR systems; wherein,

[0063] The multiple SCR systems are configured with different reducing agents, so that the multiple SCR systems have multiple different temperature working zones; wherein, there is no temperature intersection and / or temperature interval in the temperature working zones corresponding to the multiple SCR systems, so as to be combined together to form a continuous full-temperature coverage area; wherein, the multiple different SCR systems are configured to: perform catalytic reduction reactions alternately or simultaneously in their respective corresponding temperature working zones according to the exhaust temperature of the exhaust gas in the tail exhaust passage, so as to achieve efficient conversion of nitrogen oxides in the exhaust gas under all working conditions; the DOC system 17 is connected to the outlet of the multi-zone wide-temperature composite reduction system, and is used to oxidize other polluting components in the exhaust gas.

[0064] Specifically, for spark-ignition methanol engines, methanol is used as fuel, which is delivered to the engine's fuel system through a fuel pump, ignited by a spark plug, and burned to generate power. The exhaust gas after combustion is discharged through the tail exhaust passage and purified by the exhaust after-treatment system on the tail exhaust passage. Usually, the harmful substances in the exhaust gas of spark-ignition methanol engines are usually NO X (nitrogen oxides), CO (carbon oxides) and HC (unburned hydrocarbons), etc.

[0065] Regarding the post-processing system specifically for exhaust gas treatment, the embodiment of the present application proposes a new post-processing system suitable for spark-ignition methanol engines, which realizes NO X Emission conversion covers the entire temperature range and is highly efficient. For example, the embodiment of the present application does not include a DPF, which reduces system complexity and investment costs.

[0066] Preferably, the present application transforms the traditional single SCR system into a multi-zone wide temperature composite reduction system. The multi-zone wide temperature composite reduction system can be more specifically understood as a composite temperature zone SCR combination system with a wide temperature coverage range composed of multiple temperature zones. It includes multiple SCR reaction systems, each SCR system is equipped with a different reducing agent, and different reducing agents have different temperature working zones due to their own characteristics. Therefore, each SCR system is different, so each SCR system has a different temperature working zone. A temperature working zone usually corresponds to an efficient temperature conversion range, and in the corresponding temperature working zone, the catalyst can maximize the promotion of the reduction reaction and efficiently convert NOX Therefore, by combining multiple SCR systems with different temperature operating zones, nitrogen oxide reduction in a wide temperature range can be achieved.

[0067] For example, methanol is suitable as a reducing agent for medium to high temperatures, while hydrogen is suitable for low temperatures. Of course, the reducing agent can also be urea, hydrocarbon fuels, ammonia, etc. Since the embodiments of the present invention are used in a methanol engine, and based on the relevant phenomena mentioned in the background technology, it is best not to use reducing agents such as urea, hydrocarbon fuels, and ammonia in this embodiment, in order to achieve efficient conversion while avoiding related problems.

[0068] Therefore, the multi-zone wide temperature composite reduction system provided by the embodiment of the present application and the temperature zone complementary mechanism of multiple SCR systems effectively solve the problem of NO in a single post-treatment system within a limited temperature range. X To solve the problem of low conversion efficiency, multiple systems complement each other in the entire operating range corresponding to different exhaust temperatures. By designing different numbers of SCR systems, it is possible to adapt to and maintain high efficiency NO conversion in a wide range or even the entire temperature range. X Conversion capability to adapt to changes in exhaust temperature under different working conditions.

[0069] As a further illustration of this embodiment, the temperature operating zones corresponding to the multiple different SCR systems selected by the present invention do not have temperature intersections and / or temperature intervals, so that they are combined to form a continuous full-temperature coverage area. For traditional single SCR technology or other combined SCR systems, the temperature ranges are often "intermittent", and each different SCR system shows a higher NO in its own specific temperature range. X conversion efficiency, but there is a "blank" area of ​​temperature coverage outside of it. Therefore, when the exhaust temperature is in the "blank" area, the NO X The conversion efficiency is significantly reduced, which can easily lead to NO X Emissions exceed standards.

[0070] Specifically, in multiple different SCR systems, for example, methanol is in the medium and high temperature zone (i.e., the temperature working zone belongs to the medium and high temperature range, the same below), and urea is in the high temperature zone. Due to the existence of temperature intervals, the combination forms an intermittent coverage area, which makes it impossible to cover the low temperature zone. Due to the "blank" area of ​​temperature coverage in front, when the temperature of the engine gradually rises during the load change process, the SCR system will not release NO before the exhaust temperature reaches its corresponding temperature zone. X The conversion rate of NO X Exceeding the standard, so when the exhaust temperature is in the low temperature range, the SCR combination system cannot exert its high conversion efficiency under cold conditions.

[0071] For example, hydrogen is in the low-temperature zone and urea is in the high-temperature zone. Due to the existence of temperature intervals, the combination forms an intermittent coverage area, which makes it impossible to cover the medium-temperature zone. Since there is a "blank" area of ​​temperature coverage in the middle, when the exhaust temperature is within the medium-temperature range, the SCR combination system cannot exert high conversion efficiency under the medium-temperature working condition.

[0072] For example, hydrogen is in the low-temperature zone, methanol is in the medium-high-temperature zone, and urea is in the high-temperature zone. Although the combination of the three covers multiple temperature zones, in the high-temperature zone, both SCR systems are performing catalytic conversion, and there is a "partial overlap" area of ​​temperature coverage. For any of the SCRs, it is impossible to fully exert its capabilities within its temperature working zone, resulting in energy waste and low efficiency within the temperature range.

[0073] Therefore, this application selects multiple SCR systems with reductants having continuous temperature working zones as carriers based on the selection principle of non-intersection and non-interval. Since the temperature working zones of multiple SCR systems are seamlessly connected, a continuous and efficient full-temperature coverage area is formed. The entire emission control system can maintain a high NOx level under any operating condition (from low temperature during cold start to high temperature during high load). X Conversion efficiency, to meet more stringent emission standards. Especially for methanol engines, full temperature coverage can effectively improve the cold start performance of methanol engines. At the same time, due to the continuous coverage of the full temperature range, the system will not produce NO in some transition conditions of temperature changes, such as when the exhaust temperature gradually switches from cold to high temperature, and the exhaust temperature transitions from low temperature to medium and high temperature. X The significant decrease in treatment efficiency ensures the continuous stability of emission control and avoids NOx caused by changes in exhaust temperature. X The conversion rate fluctuates greatly, which improves the applicability and flexibility of the system.

[0074] In this embodiment, to further control emissions, multiple SCR systems operate alternately or simultaneously within a multi-zone, wide-temperature composite reduction system that provides full temperature coverage. As will be appreciated, exhaust temperatures fluctuate continuously under different operating conditions, necessitating the activation and deactivation of each SCR system based on real-time exhaust temperatures.

[0075] For example, when the exhaust temperature is low, the SCR system in the lower temperature operating zone operates first. When the exhaust temperature rises to a medium to high temperature range, the SCR system in the lower and higher temperature operating zones operate simultaneously. When the exhaust temperature rises to a high temperature range, the SCR system in the higher temperature operating zone starts operating, while the SCR system in the lower temperature operating zone stops operating.

[0076] Therefore, the alternating operation mode avoids inefficient operation of the SCR system in a temperature operating zone that does not fall within the current exhaust gas temperature range.

[0077] As the methanol engine continues to operate, the exhaust temperature gradually rises. During this period, the exhaust temperature is neither suitable for efficient operation of the SCR system in the lower temperature operating range nor has it reached the ideal operating temperature for the SCR system in the higher temperature operating range. Therefore, as the exhaust temperature gradually reaches the end of the temperature range corresponding to the SCR system in the lower temperature operating range, the system can gradually reduce the reductant injection rate of the SCR system in that SCR system while slowly increasing the reductant injection rate of the SCR system in the lower temperature operating range, ensuring smooth transition of the SCR system under different operating conditions.

[0078] In some embodiments, all SCR systems can operate simultaneously under all operating conditions, but the injection rates of different SCR systems can be controlled. For example, under high exhaust temperature conditions, the SCR system in the lower temperature operating zone can be controlled to continue operating at a lower injection rate, while the SCR system in the higher temperature operating zone can be operated at a higher injection rate. This allows the SCR system in the lower temperature operating zone to serve as a supplementary reduction system, supplementing the incomplete treatment of the SCR system in the higher temperature operating zone. This simultaneous operation mode can minimize emissions under high-load, high-temperature conditions.

[0079] In some embodiments, for the plurality of SCR systems, the number of SCR systems in the higher temperature operating zone and the number of SCR systems in the lower temperature operating zone may be the same or different, and may be selected within a wide range.

[0080] In some embodiments, for ease of understanding, when the multi-zone wide-temperature composite reduction system is two SCR systems, the SCR system in the lower temperature working zone can be a first SCR system 15 using hydrogen as a reducing agent; and the SCR system in the higher temperature working zone can be a second SCR system 16 using methanol as a reducing agent.

[0081] It can also be understood that the exhaust gas condition can be monitored in real time through temperature sensors and nitrogen oxide sensors, and the feedback can be fed back to the vehicle ECU for control execution. The ECU can automatically adjust multiple different SCR systems to work alternately or simultaneously within the full operating range, thereby achieving efficient purification of nitrogen oxides and optimizing energy consumption.

[0082] In this embodiment, multiple different SCR systems can be connected in series or in parallel to the tail exhaust passage. Preferably, multiple SCR systems are connected in sequence along the direction of exhaust gas flow to simplify the piping.

[0083] The NO in the exhaust gas is reduced by a multi-zone wide temperature composite reduction system XAfter conversion treatment, the DOC is located at the outlet of the last SCR system, responsible for oxidizing other pollutants in the exhaust gas, such as hydrocarbons and carbon monoxide, further reducing harmful substances in the exhaust gas and ensuring that exhaust emissions meet environmental protection standards.

[0084] This embodiment illustrates a preferred configuration for a multi-zone, wide-temperature composite reduction system. The multi-zone, wide-temperature composite reduction system is a methanol-hydrogen complementary SCR system comprising a first SCR system 15 using hydrogen as a reducing agent and a second SCR system 16 using methanol as a reducing agent. The first and second SCR systems 15, 16 are connected in series along the exhaust gas flow direction. The hydrogen is indirectly and the methanol is directly sourced from a methanol tank 7 used to supply fuel to the methanol engine.

[0085] Specifically, a methanol-hydrogen complementary SCR system is proposed for the exhaust after-treatment system of the spark-ignition methanol engine. Because the fuel of the methanol engine has a high latent heat of vaporization, the cold start and low-temperature operation time are relatively long. The first SCR system 15 uses hydrogen as a reducing agent. Hydrogen has a high activity and can ensure that the conversion efficiency of SCR is improved at a lower temperature. The ignition temperature of the first SCR can be reduced to 150°C. Therefore, the first SCR system 15 is particularly suitable for methanol engines to maintain a high NOx under low temperature conditions due to its low ignition temperature. X Conversion efficiency.

[0086] Therefore, for medium to high exhaust temperature conditions, the second SCR system 16 uses methanol as the reducing agent. Compared to urea SCR, the second SCR system 16 has a lower light-off temperature, down to 200°C, and a wider operating temperature range (280°C to 500°C). When the exhaust temperature rises above 200°C, methanol begins to function as a reducing agent.

[0087] Therefore, the methanol-hydrogen complementary SCR system uses hydrogen as a reducing agent, which can be indirectly taken from the methanol tank 7. Using methanol as a reducing agent, methanol can be directly taken from the methanol tank 7. There is no need to add urea like urea SCR, and no additional urea tank is required, which reduces the complexity and use cost of the system.

[0088] The second SCR system 16 operates in the medium-high temperature range (280°C to 500°C), while the first SCR system 15 operates in the low temperature range (150°C and above). The temperature operating ranges of the two systems are closely adjacent. Therefore, the temperature operating range of the second SCR system 16 complements that of the first SCR system 15, forming a continuous and efficient temperature coverage range, which can effectively ensure high NOx reduction under all engine operating conditions, regardless of whether the exhaust temperature is low or medium-high. XConversion efficiency. And unlike urea SCR, it does not produce highly toxic hydrocyanic acid.

[0089] Therefore, compared with other traditional SCR technologies (such as urea, hydrocarbons, and ammonia) that have insufficient temperature range coverage or temperature breakpoints, the methanol-hydrogen complementary SCR system can not only achieve efficient conversion under all operating conditions through continuous coverage of the temperature range, ensuring emission control effects under all operating conditions, but also rely on the same energy source (methanol tank 7) on the methanol engine. The first SCR system 15 and the second SCR system 16 are closely integrated with the methanol engine, further simplifying the fuel supply chain and making the system structure more compact and efficient. It is particularly suitable for the optimization and improvement of the methanol engine, realizing the full-scale utilization of a single methanol fuel.

[0090] In addition, a wider temperature range can be covered by adding different types of SCR systems. Preferably, the use of two SCR systems, the first SCR system 15 and the second SCR system 16, in the methanol engine can fully utilize the multiple functions of methanol fuel, avoid unnecessary system redundancy, and make the system more economical and practical.

[0091] As can be seen, the embodiment of the present application comprehensively considers the multiple utilization of the same methanol fuel source and the continuous coverage of temperature ranges, providing a more optimized and highly integrated new emission control architecture, which significantly reduces system complexity and operating costs while improving emission control efficiency. The embodiment of the present application further illustrates the solution of efficient emission control through multiple reaction pathways on the same methanol fuel source:

[0092] The system also includes:

[0093] The methanol cracker 12 is connected to the methanol tank 7 and the first SCR system 15 respectively, and is located before the first SCR system 15, and is used to use the exhaust temperature to crack the methanol transmitted from the methanol tank 7 to produce hydrogen; the hydrogen distribution tank 8 is connected to the methanol cracker 12, the first SCR system 15 and the methanol engine respectively, and is used to store the hydrogen produced by cracking and distribute it to the first SCR system 15 and the methanol engine.

[0094] In this embodiment, a methanol cracker 12, a first SCR system 15, a second SCR system 16, and a DOC system 17 are sequentially connected along the exhaust gas flow direction. Specifically, a hydrogen SCR nozzle 13 is installed in the first SCR system 15, a methanol nozzle 14 is installed in the second SCR system 16, a methanol gas nozzle 9 and a hydrogen nozzle 11 are respectively provided in the intake passage, and a methanol direct injection nozzle 10 is installed in the engine cylinder head. The methanol direct injection nozzle 10 injects methanol into the engine cylinder, achieving high-pressure direct injection. The combined injection of the methanol direct injection nozzle 10 and the methanol gas nozzle 9 ensures stable operation of the engine under all operating conditions. The methanol tank 7 and the hydrogen distribution tank 8 are respectively connected to the nozzles of the corresponding components to deliver methanol fuel and hydrogen to the nozzles. The reducing agent hydrogen in the first SCR system 15 is injected by the hydrogen SCR nozzle 13; the reducing agent methanol in the second SCR system 16 is injected by the methanol nozzle 14.

[0095] like Figure 2 As shown, Figure 2 This is a system architecture diagram of the spark-ignition methanol engine assembly. The solid black line with an arrow represents the gas flow direction, the uniform dashed line with an arrow represents the methanol flow direction, and the double-dotted dashed line with an arrow represents the hydrogen flow direction.

[0096] The methanol tank 7 is divided into four branches which are respectively connected to the methanol cracker 12, the second SCR system 16 and the intake passage and cylinder head of the methanol engine, and the methanol is divided into four streams and supplied to the corresponding positions through the corresponding four branches.

[0097] Among them, the hydrogen distribution tank 8 is divided into three branches, which are respectively connected to the methanol cracker 12, the first SCR system 15 and the intake passage of the methanol engine. After the hydrogen flows from the methanol cracker 12 to the hydrogen distribution tank 8, it is divided into two streams and supplied to the corresponding positions through the remaining two branches.

[0098] Furthermore, when the engine is operating normally, the methanol cracker 12 receives the methanol fuel transmitted from the methanol tank 7, and uses the heat from the high exhaust temperature in the engine tail exhaust passage to perform thermal cracking of the methanol to produce hydrogen. The methanol cracker 12 is also connected to the hydrogen distribution tank 8, and transmits the hydrogen produced by the cracking to the hydrogen distribution tank 8 for storage. The hydrogen stored in the hydrogen distribution tank 8 has two uses: (1) as a reducing agent for the first SCR system 15, so that the methanol fuel at least realizes the indirect supply of hydrogen to the first SCR system 15, and is injected through the hydrogen SCR nozzle 13 to convert NO in the exhaust gas. X (2) By injecting hydrogen into the intake pipe as an auxiliary fuel, it can not only achieve rapid warm-up of the methanol engine and rapid increase in exhaust temperature under cold start or cold operating conditions, but also increase the combustion rate under rapid acceleration of the methanol engine, thereby achieving simultaneous improvement in power and thermal efficiency.

[0099] When the engine is in low load or cold working condition, the exhaust temperature is too low to support the normal operation of the methanol cracker 12. X The emission level is low. At this time, most of the hydrogen in the hydrogen tank 8 is used to promote engine combustion, and a small part is used by the first SCR system 15 to treat NO X As the engine exhaust temperature rises, the methanol cracker 12 starts to work, and the hydrogen generated fills the hydrogen distribution tank 8 and then stops working.

[0100] It can be understood that the ratio of hydrogen and methanol in the intake passage can be adjusted in terms of injection amount, injection timing and mixing ratio under different working conditions, and this embodiment does not limit this.

[0101] For the spark-ignition methanol engine assembly, the methanol tank 7 itself feeds the methanol engine through two channels and then feeds the second SCR system 16 through one channel. At the same time, the methanol cracker 12 and the engine share a methanol tank 7. The heat in the exhaust gas of the methanol engine is used to crack the methanol into hydrogen, which is then stored and distributed to the engine's intake passage as part of the fuel. It is also used in the first SCR system 15 in the exhaust gas post-treatment to participate in the treatment of NO X Therefore, the post-treatment system of the embodiment of the present application is highly integrated with the fuel system of the methanol engine. It uses the same methanol fuel to simultaneously supply the methanol engine and the exhaust gas post-treatment systems, completing the integration of dual-temperature zone SCR technology and achieving full life cycle resource optimization from engine combustion to exhaust gas post-treatment. There is no need to rely on external reducing agents or other chemicals throughout the process, optimizing the overall structure of the system and constructing an integrated SCR solution based on methanol fuel.

[0102] In a further technical solution, a bypass line is provided between the first SCR system 15 and the second SCR system 16. A bypass control valve 21 is provided on the bypass line to control the on / off state of the bypass line. The inlet of the bypass line is located before the inlet of the first SCR system 15, and the outlet is connected to the inlet of the second SCR system 16. Therefore, the first SCR system 15 and the second SCR system 16 can be directly connected, or the first SCR system 15 can be bypassed via the bypass line using the bypass control valve 21.

[0103] When the exhaust temperature is low, the bypass control valve 21 is closed, and the engine exhaust gas passes through the first SCR system 15, the second SCR system 16 and the DOC system 17 respectively, thereby reducing emissions; as the exhaust temperature rises, the NO X The reduction effect is reduced, and the NO XThe conversion effect is improved, the bypass control valve 21 is opened, and the engine exhaust gas passes through the second SCR system 16 and the DOC system 17 respectively, thereby reducing emissions.

[0104] In a further technical solution, the test system includes multiple temperature sensors and multiple nitrogen oxide sensors, respectively positioned at the inlet of each of the SCR systems and the DOC system 17 in the exhaust passage. In this embodiment, the test system includes a front temperature sensor 18, a middle temperature sensor 19, a rear temperature sensor 20, a front nitrogen oxide sensor 22, a middle nitrogen oxide sensor 23, and a rear nitrogen oxide sensor 24. In the aftertreatment test system, the front temperature sensor 18 and the front nitrogen oxide sensor 22 are located before the first SCR system 15 and are used to measure the exhaust temperature entering the first SCR system 15 and the concentration of nitrogen oxides in the exhaust gas. The middle temperature sensor 19 and the middle nitrogen oxide sensor 23 are located before the second SCR system 16 and are used to measure the exhaust temperature entering the second SCR system 16 and the concentration of nitrogen oxides in the exhaust gas. The rear temperature sensor 20 and the rear nitrogen oxide sensor 24 are located before the DOC system 17 and are used to measure the exhaust temperature entering the DOC system 17 and the concentration of nitrogen oxides in the exhaust gas.

[0105] The nitrogen oxide concentration values ​​are collected by the front nitrogen oxide sensor 22 and the middle nitrogen oxide sensor 23, and the nitrogen oxide conversion efficiency of the first SCR system 15 is calculated, thereby determining the amount of hydrogen injected by the hydrogen SCR nozzle 13; the nitrogen oxide concentration values ​​are collected by the middle nitrogen oxide sensor 23 and the rear nitrogen oxide sensor 24, and the nitrogen oxide conversion efficiency of the second SCR system 16 is calculated, thereby determining the amount of methanol injected by the methanol nozzle 14.

[0106] The exhaust temperature before the first SCR system 15 is measured by the front temperature sensor 18. When the exhaust temperature is lower than 250°C, the exhaust temperature is at a low level and the engine exhaust passes through the first SCR system 15 for NO removal. X conversion;

[0107] The exhaust gas temperature before the second SCR system 16 is measured by the intermediate temperature sensor 19. When the exhaust gas temperature is higher than 250°C, it has reached the temperature working range of the second SCR system 16. At this time, the bypass control valve 21 is opened, and the engine exhaust gas reaches the second SCR system 16 through the bypass pipe to perform NO X efficient conversion.

[0108] When the engine exhaust temperature detected by the current temperature sensor 18 is lower than 200° C., the engine is started to execute the thermal management control strategy.

[0109] In some embodiments, hydrogen is generated by the methanol cracker 12 for use in the first SCR system 15, and unburned methanol can be used in the second SCR system 16. By controlling the injection amount of methanol and hydrogen in the aftertreatment system and / or the engine combustion system, the emission requirements under different operating conditions are met, thereby simplifying the control strategy of the system.

[0110] In summary, the new exhaust gas after-treatment system proposed by the present invention is not only highly integrated with the fuel system of the methanol engine, but also can improve the cold start performance of the methanol engine through full temperature coverage. Figure 2 The present invention also provides a spark-ignition methanol engine assembly, which includes: an intake system, including an air filter, a supercharger 3, an intercooler 4 and a throttle valve 5 connected in sequence; an after-treatment system, such as the exhaust gas after-treatment system based on full-temperature range collaborative optimization provided in the first aspect; a methanol engine connected to the intake system through an intake passage and connected to the after-treatment system through a tail exhaust passage, the intake passage being provided with a methanol air nozzle 9 and a hydrogen nozzle 11, and the methanol engine being provided with a methanol direct injection nozzle 10; a methanol fuel tank 7 connected to the methanol air nozzle 9, the methanol direct injection nozzle 10, a methanol cracker 12 and a second SCR system 16 on the after-treatment system respectively; wherein the hydrogen nozzle 11 is connected to a hydrogen distribution tank 8 on the after-treatment system connected to the methanol cracker 12; wherein an exhaust gas bypass is provided on the tail exhaust passage corresponding to the front and rear ends of the supercharger 3.

[0111] In this embodiment, each component of the intake system is connected via corresponding pipelines. For example, the air filter, supercharger 3, intercooler 4, and throttle 5 are all located on the air pipe 2. The throttle 5 then connects to the multiple cylinders via the intake pipe and intake manifold. In conjunction with the above embodiments, the methanol nozzle 9 and hydrogen nozzle 11 are both located in the corresponding locations of the intake pipe.

[0112] The methanol gas nozzle 9 is used to inject gaseous methanol during the intake process to provide a uniform mixture of methanol and air. By selecting high-pressure direct injection in the cylinder through the methanol direct injection nozzle 10, the exhaust temperature of the engine can be quickly increased through the methanol long-lasting injection strategy during the cold start phase or cold working condition of the methanol engine. By injecting the fuel late, the afterburning ratio of the fuel is increased, which is conducive to the rapid increase of the exhaust temperature; the unburned methanol fuel enters the aftertreatment system, which can further reduce NO X emission.

[0113] As described in the first aspect, the system is an exhaust gas after-treatment system based on full-temperature collaborative optimization, adopting a multi-zone wide-temperature composite reduction system, including at least two SCR systems, which can operate alternately or simultaneously to cover the full temperature range. The system can efficiently convert NO in the exhaust gas within the different exhaust temperature ranges from the cold state to the normal working state of the engine. X .

[0114] In the tail exhaust passage, exhaust gas bypasses are provided at the front and rear ends of the turbine of the supercharger 3, allowing the exhaust gas to partially bypass the supercharger 3, thereby regulating the exhaust pressure and temperature.

[0115] Correspondingly, for the third aspect, please refer to Figure 3 As shown, Figure 3 This is a flowchart of the steps of an exhaust gas treatment method based on full-temperature collaborative optimization. The present invention also provides an exhaust gas treatment method based on full-temperature collaborative optimization, which is utilized in the exhaust gas after-treatment system based on full-temperature collaborative optimization provided by the first aspect of the present invention, and / or the spark-ignition methanol engine assembly provided by the second aspect of the present invention. The method comprises the following steps:

[0116] S1. Obtaining the exhaust temperature and nitrogen oxide concentration corresponding to the inlet of each SCR system in the tail exhaust passage of the methanol engine;

[0117] A temperature sensor and a nitrogen oxide sensor are installed at the inlet of each SCR system to collect exhaust temperature and nitrogen oxide concentration information in real time, and then transmit the information to the vehicle ECU to determine the current operating conditions.

[0118] S2. Based on the exhaust gas temperature corresponding to the front SCR system, determining whether the current operating condition of the methanol engine is any one of a cold operating condition, a buffer operating condition, and a normal operating condition;

[0119] The exhaust temperature reflects the current operating conditions. For example, a lower exhaust temperature usually occurs when the methanol engine is just started or running at low load. At this time, if the exhaust temperature is lower than the first preset value, the system will judge it as a cold operating condition; the exhaust temperature begins to rise with the continuous operation of the methanol engine. When the temperature gradually rises but does not reach the temperature required for normal operating conditions, it is usually in the early stage of acceleration or high load stage of the methanol engine. At this time, if the exhaust temperature is higher than the first preset value but lower than the second preset value, the system will judge it as a transitional operating condition; when the exhaust temperature reaches the third preset value where the normal operating condition is, it is judged to be a normal operating condition.

[0120] The determination is made by comparing the exhaust temperature with preset temperature thresholds for each operating condition. For example, the first preset value is set to less than 200°C, the second preset value is set to 200-300°C, and the third preset value is set to greater than 300°C. Of course, the specific temperature range can be adjusted according to actual application.

[0121] In this embodiment, for a plurality of SCR systems connected in series, only the exhaust temperature information collected by the temperature sensor at the inlet of the front SCR system can be used as a basis for determining the current operating condition.

[0122] S3. Determining, based on the nitrogen oxide concentrations before and after each SCR system, an injection amount of the SCR system that requires reductant injection under the current operating condition;

[0123] The number and order of executing multiple SCR systems that need to execute reducing agent injection may be determined based on the current operating conditions.

[0124] After determining the number of executions, the multiple SCR systems corresponding to a specific number are usually at least two SCR systems with adjacent temperature working zones to form a continuous full-temperature coverage zone, starting from the low-temperature zone and ending at the high-temperature zone. The requirements for exhaust gas treatment are different under different working conditions, so the number of executions of the SCR systems can be flexibly adjusted to avoid a certain SCR system working at an unsuitable temperature or to avoid excessive or insufficient injection of reducing agent. Therefore, by determining the number of SCR systems that need to participate in the work under the current operating conditions, the catalytic capacity of the system can be fully utilized to avoid overloading a single system or mutual interference between multiple systems, thereby improving the overall performance of the system.

[0125] Each SCR system has a different temperature operating range. Therefore, under the exhaust temperature condition, the temperature operating range of each SCR system can be compared and the exhaust temperature can be used to determine which SCR systems can currently operate at that temperature.

[0126] In different temperature ranges, the system selects the order in which the currently active SCR systems are executed based on the current operating conditions. For example, in cold conditions, the SCR systems in the lower temperature operating zone take priority. As the temperature gradually rises, the SCR systems in the higher temperature operating zone gradually take over, allowing the SCR systems to operate alternately. When the exhaust temperature is in the transition zone between different SCR systems, multiple SCR systems operate simultaneously.

[0127] After determining the number and order of SCR systems requiring reductant injection under the current operating conditions, the corresponding reductant injection amount for each SCR system is determined based on the detected NOx concentration and exhaust temperature. For example, if the NOx conversion efficiency falls below a preset target, the reductant injection amount will need to be increased to provide more reductant. If the NOx conversion efficiency reaches or exceeds the target, the current hydrogen injection amount can be maintained or fine-tuned based on actual needs.

[0128] Among them, the ECU dynamically adjusts the power-on time of the corresponding nozzle according to the data of each sensor to adjust the injection amount.

[0129] S4. In the cold operating condition, controlling the exhaust temperature to increase through a first execution operation, and controlling the currently executed SCR system to start injecting a reducing agent with a first preset parameter to perform a catalytic reduction reaction with nitrogen oxides in the exhaust gas within a first wide temperature range corresponding to the reducing agent;

[0130] S5. Under the buffer operating condition, controlling the exhaust temperature to continue to increase through a second execution operation, and controlling the corresponding SCR system to start injecting a reducing agent with a second preset parameter to perform a catalytic reduction reaction with nitrogen oxides in the exhaust gas within the corresponding second wide temperature range;

[0131] S6. Under the normal operating condition, the operating state of the methanol engine is switched through a third execution operation, and the corresponding SCR system is controlled to start injecting the reducing agent with a third preset parameter to perform a catalytic reduction reaction with nitrogen oxides in the exhaust gas within its corresponding third wide temperature range.

[0132] The temperature ranges of the first wide temperature zone, the second wide temperature zone and the third wide temperature zone gradually increase, and the wide temperature zone is a combination of one or more sections of the multi-section temperature working zone.

[0133] In steps S4-S6, the ECU performs a series of actions on the SCR system or related components of the combustion system under different operating conditions to adjust exhaust temperature and activate the appropriate SCR system. These actions include adjusting the air-fuel ratio, adjusting the EGR rate, increasing engine load, adjusting ignition timing, adjusting engine operating parameters, or opening the wastegate valve 6. Dynamically adjusting these actions to suit the engine's operating conditions facilitates efficient operation of the SCR system.

[0134] Under different operating conditions, the operating parameters of the multiple SCR systems vary. The first, second, and third preset parameters may include at least one of a reductant injection amount, an injection activation temperature, an injection timing, and an injection frequency. The injection activation temperature threshold may be determined by comparing the exhaust gas temperature entering the corresponding SCR system with the corresponding injection activation temperature, obtained by a temperature sensor at the inlet of each SCR system. The corresponding SCR system may be activated when the exhaust gas temperature at the inlet reaches the injection activation temperature.

[0135] In the above embodiments, the current operating condition is determined by the temperature information at the inlet of the foremost SCR system, and the number and order of SCR systems that need to perform reductant injection under the current operating condition are determined. When the exhaust temperature reaches the injection start temperature of a certain SCR system, the SCR system is activated.

[0136] For example, the exhaust temperature before the first SCR system 15 is measured by the front temperature sensor 18. When the exhaust temperature there is lower than 250°C, the first SCR system 15 is started and executed; the exhaust temperature before the second SCR system 16 is measured by the middle temperature sensor 19. When the exhaust temperature there is higher than 250°C, the first SCR system 15 is started and it is decided whether to continue to execute the first SCR system 15.

[0137] In this embodiment, the wide temperature ranges under the three working conditions are different, and each working condition can also correspond to at least one SCR system, and at least one SCR system forms a single-stage wide temperature range and multiple-stage coordinated wide temperature ranges. In some embodiments, a single-stage wide temperature range formed by an SCR system can be set for each working condition, and multiple single-stage wide temperature ranges can jointly cover NO X conversion.

[0138] In some embodiments, each wide temperature zone can be composed of multiple temperature segments, that is, each operating condition is jointly executed by multiple SCR systems. For example, the first wide temperature zone can cover two temperature segments, the low temperature segment processes the NO during cold start. X The second wide temperature zone and the third wide temperature zone can also cover multiple temperature segments.

[0139] In some embodiments, the number of temperature segments covered by the first wide temperature zone, the second wide temperature zone, and the third wide temperature zone may be the same or different. In some embodiments, the types of temperature segments covered by each of the first wide temperature zone, the second wide temperature zone, and the third wide temperature zone may be the same or different. In some embodiments, the types of temperature segments covered by the first wide temperature zone, the second wide temperature zone, and the third wide temperature zone may be partially the same or different.

[0140] The combination of one or more sections in the first, second, and third wide temperature ranges can be determined based on the specifications and volume of the methanol engine. For example, a large-displacement methanol engine can be started and injected by multiple SCR systems at lower temperatures under cold conditions.

[0141] Therefore, the setting of the first, second and third wide temperature zones ensures the exhaust gas treatment capacity in different temperature ranges, from cold start to normal operation, and the NO X Emissions can be effectively converted.

[0142] See also Figure 4 , Figure 4 This is a flowchart of a tail gas treatment method based on full-temperature collaborative optimization configured with a methanol-hydrogen complementary SCR system. The following methanol-hydrogen complementary SCR system is used as an example to specifically illustrate steps S4 to S6 of this application.

[0143] Furthermore, step S4 includes:

[0144] Based on the cold operating condition, at least one of opening the hydrogen nozzle 11, opening the exhaust bypass valve 6 on the exhaust bypass, reducing the opening of the throttle valve 5 and opening the methanol direct injection nozzle 10 is performed to control the exhaust temperature increase; and, opening the first SCR system 15, closing the bypass control valve 21 on the bypass line, and closing the second SCR system 16 to react within the temperature working zone where the hydrogen of the first SCR system 15 is located.

[0145] In this embodiment, the engine exhaust temperature before the first SCR system 15 is collected by the front temperature sensor 18. If the temperature is less than 200°C, it means that the engine is in a cold state and the engine enters the thermal management control stage. In this stage, the engine operation is mainly aimed at quickly raising the exhaust temperature.

[0146] Specifically, the hydrogen nozzle 11 is turned on, and the hydrogen in the hydrogen distribution tank 8 is controlled to be sprayed into the intake pipe. Then, it is distributed into multiple engine cylinders through the intake manifold along with fresh air. Due to the high activity of hydrogen and the lower ignition temperature, it is helpful to solve the problem of cold starting. The high flame propagation speed is conducive to accelerating combustion, thereby achieving a rapid increase in exhaust temperature under cold engine conditions.

[0147] Open the wastegate valve 6 on the exhaust bypass to allow the engine exhaust to bypass the turbine. At this time, the turbine of the supercharger 3 does not work, which helps to reduce the amount of fresh air entering the cylinder and increase the exhaust temperature.

[0148] Control the opening of the throttle valve 5. By reducing the opening of the throttle valve 5, the amount of air entering the cylinder is reduced, thereby achieving the effect of increasing the exhaust temperature;

[0149] The methanol direct injection nozzle 10 is turned on and the injection time is during the expansion stroke or exhaust stroke. At this time, the combustion of the fuel injected into the cylinder is mainly concentrated in the second half of the combustion stage, which is not only conducive to increasing the exhaust temperature, but also allows the unburned methanol to enter the post-treatment system and convert NO in the exhaust gas. X emission.

[0150] The conversion efficiency of the first SCR system 15 is calculated based on the nitrogen oxide concentrations measured by the front nitrogen oxide sensor 22 and the middle nitrogen oxide sensor 23, thereby obtaining the amount of hydrogen injected. The amount of hydrogen injected is controlled by adjusting the power-on time of the hydrogen SCR nozzle 13. Since the temperature at this time does not reach the temperature working range of the second SCR system 16, the methanol nozzle 14 is closed, and only the methanol direct injection nozzle 10 is required to inject the methanol that has not been burned in the cylinder and enters the post-treatment system for NO X conversion;

[0151] The bypass control valve 21 is closed, and the engine exhaust gas flows through the first SCR system 15 , the first SCR system 15 , and the DOC system 17 in the following order.

[0152] Furthermore, step S5 includes:

[0153] Based on the buffering operating condition, the opening of the throttle valve 5 is reduced, the exhaust temperature is controlled to continue to increase, and the methanol direct injection nozzle 10 is opened, the first SCR system 15 is opened, the bypass control valve 21 on the bypass line is closed, and the second SCR system 16 is opened to react in the composite wide temperature range composed of the hydrogen in the first SCR system 15 and the methanol in the second SCR system 16.

[0154] In this embodiment, the engine exhaust temperature before the first SCR system 15 is collected by the front temperature sensor 18. If the temperature is less than 300°C, the engine enters the thermal management maintenance stage, in which the engine is aimed at optimizing both economy and exhaust temperature.

[0155] Control the opening of the throttle valve 5. By reducing the opening of the throttle valve 5, the amount of air entering the cylinder is reduced, thereby achieving the effect of increasing the exhaust temperature;

[0156] The methanol direct injection nozzle 10 is opened, and the injection timing is during the expansion stroke or the exhaust stroke.

[0157] The conversion efficiency of the first SCR system 15 is calculated based on the nitrogen oxide concentrations measured by the front nitrogen oxide sensor 22 and the middle nitrogen oxide sensor 23, thereby obtaining the injection amount of hydrogen; the injection amount of hydrogen is controlled by adjusting the power-on time of the hydrogen SCR nozzle 13;

[0158] At this point, the temperature has entered the temperature operating range of the second SCR system 16. The methanol injection rate of the second SCR system 16 is calculated based on the nitrogen oxide concentrations measured by the middle nitrogen oxide sensor 23 and the rear nitrogen oxide sensor 24. The methanol injection rate is controlled by adjusting the power-on time of the methanol nozzle 14.

[0159] The bypass control valve 21 is closed. At this time, the engine exhaust gas undergoes three purification steps. First, it is processed by the first SCR system 15 , then by the second SCR system 16 , and finally the unburned components are oxidized in the DOC system 17 .

[0160] If the temperature measured by the medium temperature sensor 19 is less than 300° C., the process continues to loop to step 5; if it exceeds 300° C., the process proceeds to step 6.

[0161] Furthermore, step S6 includes:

[0162] Based on the normal operating conditions and the torque demand of the methanol engine, the operating parameters of the throttle valve 5, the methanol air nozzle 9 and the methanol direct injection nozzle 10 are controlled; and the first SCR system 15 is closed, the bypass control valve 21 on the bypass line is opened, and the second SCR system 16 is opened to react within the temperature operating range of the methanol in the second SCR system 16.

[0163] In this embodiment, the engine exhaust temperature before the first SCR system 15 is measured by the front temperature sensor 18. If the temperature is greater than 300°C, the engine enters a normal operating phase, which aims to optimize engine fuel economy. Normal operating conditions also include steady-state operating conditions and rapid acceleration conditions.

[0164] Under steady-state operating conditions, the opening of the throttle valve 5 and the methanol airway nozzle 9 are controlled in real time based on the engine torque demand; based on the engine torque acceleration demand, the methanol direct injection nozzle 10 is opened in real time to achieve oil replenishment.

[0165] Under the rapid acceleration condition, the hydrogen nozzle is opened at the same time, and hydrogen enters the methanol engine through the hydrogen nozzle. Hydrogen, as a supplementary fuel, can increase the combustion rate under the rapid acceleration operation state of the methanol engine, thereby achieving a simultaneous improvement in power and thermal efficiency.

[0166] The bypass control valve 21 is open. At this time, the engine exhaust temperature is high and only the second SCR system 16 is needed to remove NO in the exhaust gas. X Just do the treatment and close the hydrogen SCR nozzle 13;

[0167] Calculating the amount of methanol injected into the second SCR system 16 based on the nitrogen oxide concentrations measured by the middle nitrogen oxide sensor 23 and the rear nitrogen oxide sensor 24; and controlling the amount of methanol injected by adjusting the power-on time of the methanol nozzle 14;

[0168] The methanol cracker 12 starts working and the generated hydrogen enters the hydrogen distribution tank 8 for storage.

[0169] It should be noted that, for the method embodiments, the embodiments of the present application are not limited by the described order of actions, because according to the embodiments of the present application, certain steps can be performed in other orders or simultaneously.

[0170] As for the above method embodiment, since it is basically similar to the system embodiment, the description is relatively simple, and the relevant parts can continue to refer to the partial description of the system embodiment.

[0171] It should be noted that the various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same and similar parts between the various embodiments can be referenced to each other.

[0172] It should also be noted that, in this article, the directions or positional relationships indicated by the terms "upper", "lower", "left", "right", "inside", "outside", etc. are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, relational terms such as "first" and "second" are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations, nor can they be understood as indicating or implying relative importance. Moreover, the term "comprises" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or terminal device that includes a series of elements includes not only those elements, but also includes other elements that are not explicitly listed, or also includes elements that are inherent to such process, method, article or terminal device.

[0173] The above is a detailed introduction to the exhaust gas after-treatment system, assembly and method based on full-temperature range collaborative optimization provided by this application. Specific examples are used herein to illustrate the principles and implementation methods of this application. The description of the above embodiments is only used to help understand this application, and the content of this specification should not be understood as limiting this application. At the same time, for those of ordinary skill in the art, according to this application, there will be different forms of changes in the specific implementation methods and application scopes. It is not necessary and impossible to list all implementation methods here, and the obvious changes or modifications derived therefrom are still within the scope of protection of this application.

Claims

1. An exhaust gas after-treatment system based on full temperature range collaborative optimization, characterized in that: Applicable to spark-ignition methanol engines, installed on the tail exhaust passage of methanol engines, the system includes: Multi-zone wide temperature composite reduction system, including two SCR systems; The two SCR systems are configured with different reducing agents, so that the two SCR systems have multiple different temperature operating zones; wherein, The temperature operating zones corresponding to the two SCR systems do not have temperature intersections and / or temperature intervals, so as to be combined to form a continuous full-temperature coverage zone; Wherein, the two different SCR systems are configured as follows: performing catalytic reduction reactions alternately or simultaneously in the respective corresponding temperature operating zones according to the exhaust temperature of the exhaust gas in the tail exhaust passage, so as to achieve efficient conversion of nitrogen oxides in the exhaust gas under all operating conditions; A DOC system is connected to the outlet of the multi-zone wide temperature composite reduction system and is used to oxidize other pollutants in the exhaust gas; Wherein, the multi-zone wide temperature composite reduction system is a methanol-hydrogen complementary SCR system, which includes a first SCR system using hydrogen as a reducing agent and a second SCR system using methanol as a reducing agent; The first SCR system and the second SCR system are connected in series along the exhaust gas flow direction; The hydrogen is indirectly and the methanol is directly derived from a methanol tank used to supply fuel to the methanol engine.

2. The exhaust gas after-treatment system based on full-temperature range collaborative optimization according to claim 1, characterized in that: The system also includes: a methanol cracker, connected to the methanol tank and the first SCR system respectively, and located before the first SCR system, for utilizing the exhaust gas temperature to crack the methanol transmitted from the methanol tank to produce hydrogen; A hydrogen distribution tank is connected to the methanol cracker, the first SCR system and the methanol engine respectively, and is used to store the hydrogen generated by cracking and distribute it to the first SCR system and the methanol engine.

3. The exhaust gas after-treatment system based on full-temperature range collaborative optimization according to claim 1, characterized in that: A bypass line is provided between the first SCR system and the second SCR system, and a bypass control valve for controlling the on-off of the bypass line is provided on the bypass line.

4. The exhaust gas after-treatment system based on full-temperature range collaborative optimization according to any one of claims 1 to 3, characterized in that: The system also includes: The test system includes a plurality of temperature sensors and a plurality of nitrogen oxide sensors, which are respectively arranged at the inlet of the tail exhaust passage corresponding to each of the SCR system and the DOC system.

5. A spark-ignition methanol engine assembly, characterized in that: The assembly includes: The air intake system includes an air filter, a supercharger, an intercooler and a throttle valve which are connected in sequence; A post-treatment system, an exhaust gas post-treatment system based on full-temperature range collaborative optimization according to any one of claims 1 to 4; A methanol engine is connected to the intake system through an intake passage and to the after-treatment system through a tail exhaust passage, wherein a methanol airway nozzle and a hydrogen nozzle are provided on the intake passage, and a methanol direct injection nozzle is provided on the methanol engine; a methanol fuel tank, which is respectively connected to the methanol gas nozzle, the methanol direct injection nozzle, the methanol cracker on the post-treatment system, and the second SCR system; Wherein, the hydrogen nozzle is in communication with a hydrogen distribution tank on the post-processing system which is in communication with the methanol cracker; Wherein, an exhaust gas bypass is provided on the tail exhaust passage corresponding to the front and rear ends of the supercharger.

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