Tail gas after-treatment system, assembly and method based on full-temperature-range collaborative optimization

Abstract

The invention provides a tail gas aftertreatment system, assembly and method based on full-temperature-range collaborative optimization, and the system comprises a multi-zone wide-temperature composite reduction system which comprises at least two SCR systems; wherein the multiple SCR systems are provided with different reducing agents, so that the multiple SCR systems have multiple sections of different temperature working areas; wherein the temperature working areas corresponding to the plurality of SCR systems do not have temperature intersection and / or temperature interval, so that the temperature working areas are combined together to form a continuous full-temperature-range coverage area; and the SCR systems alternately or simultaneously carry out catalytic reduction reaction in the corresponding temperature working areas according to the exhaust temperature of the tail gas in the tail exhaust passage, so that nitrogen oxide in the tail gas is efficiently converted under the full working condition. Through the system provided by the invention, a new methanol engine post-treatment system which is more optimized and highly integrated is established, and the effectiveness of the tail gas post-treatment system under all 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] For spark-ignition methanol engines today, the exhaust gas after-treatment technology route is generally to copy the diesel after-treatment system, but there are challenges and shortcomings. On the one hand, the diesel after-treatment system is relatively complex. Since the methanol molecular formula does not contain the CC bond that produces particulate matter, it will not produce particulate matter, and the DPF is mainly used to capture particulate matter generated in the engine. Therefore, for methanol engines, the DPF in the diesel after-treatment system actually increases the complexity of the system; on the other hand, the urea reductant SCR has a high ignition temperature and the NH3 in the injected urea easily reacts with the incompletely burned methanol to produce highly toxic formamide. Therefore, the urea reductant SCR is not suitable for the exhaust gas after-treatment system of the methanol engine.

[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 the entire 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] In view of the above problems, one of the purposes of the present invention is to provide an exhaust gas after-treatment system based on full temperature range collaborative optimization, so as to establish a new more optimized and highly integrated methanol engine after-treatment system, and ensure the effectiveness of the exhaust gas after-treatment system under all operating conditions. The second purpose of the present invention is to provide a spark-ignition methanol engine assembly. The third purpose of the present invention is to provide an exhaust gas treatment method based on full temperature range collaborative optimization.

[0006] To achieve one of the objectives, in a first aspect, the present invention provides an exhaust gas aftertreatment system based on full temperature range collaborative optimization, and the technical solution adopted is: An exhaust gas aftertreatment system based on full temperature range collaborative optimization is suitable for a spark-ignition methanol engine and is arranged on the tail exhaust passage of the methanol engine. The system includes: The multi-zone wide temperature composite reduction system includes at least two SCR systems; wherein: The plurality of SCR systems are configured with different reductants, so that the plurality of SCR systems have a plurality of different temperature operating zones; wherein, The temperature working zones corresponding to the plurality of SCR systems do not have temperature intersections and / or temperature intervals, so as to be combined together to form a continuous full-temperature coverage zone; Wherein, a plurality of different SCR systems are configured as follows: According to the exhaust temperature of the exhaust gas in the tail exhaust passage, catalytic reduction reactions are performed alternately or simultaneously in the respective corresponding temperature working zones to achieve efficient conversion of nitrogen oxides in the exhaust gas under all working conditions; 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.

[0007] As one of the preferred solutions, the multi-zone wide temperature composite reduction system is a methanol-hydrogen complementary SCR system, and the methanol-hydrogen complementary SCR system 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.

[0008] As one of the preferred solutions, the system also includes: a methanol cracker, which is connected to the methanol tank and the first SCR system respectively and is located before the first SCR system, and is used to crack the methanol transmitted by the methanol tank to produce hydrogen by utilizing the exhaust temperature; 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 the cracking and distribute it to the first SCR system and the methanol engine.

[0009] As one of the preferred solutions, a bypass pipeline 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 pipeline is provided on the bypass pipeline.

[0010] As one of the preferred solutions, 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 each of the SCR system and the DOC system on the tail exhaust passage.

[0011] To achieve the second objective, in a second aspect, the present invention provides an exhaust gas aftertreatment system based on full temperature range collaborative optimization, and the technical solution adopted is: A spark-ignition methanol engine assembly, comprising: 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, 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; A methanol engine is connected to the intake system through an intake passage and to the post-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 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 arranged on the tail exhaust passage corresponding to the front and rear ends of the supercharger.

[0012] 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, and the technical solution adopted is: A tail gas treatment method based on full temperature range collaborative optimization, the method comprising: Obtaining the exhaust temperature and nitrogen oxide concentration corresponding to the inlet of each SCR system on the tail exhaust passage of the methanol engine; Based on the exhaust temperature corresponding to the front SCR system, determining whether the current operating condition of the methanol engine is any one of a cold condition, a buffer condition and a normal condition; Based on the nitrogen oxygen concentration before and after each SCR system, determining the injection amount of the corresponding SCR system that needs to perform reductant injection under the current operating condition; In the case of the cold working condition, the exhaust temperature is controlled to be increased through a first execution operation, and the currently executed SCR system is controlled 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 thereto; In the case of the buffer condition, the exhaust temperature is controlled to continue to increase through a second execution operation, and the corresponding SCR system is controlled 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; Under the normal working condition, the working 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 a third wide temperature range corresponding thereto; 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. As one of the preferred solutions, in the case of the cold working condition, controlling the exhaust temperature to increase through a first execution operation, and controlling the currently executed SCR system to start injecting the reductant with a first preset parameter, comprises: Based on the cold working condition, at least one of opening a hydrogen nozzle, opening an exhaust bypass valve on an exhaust bypass, reducing a throttle opening, and opening a methanol direct injection nozzle is performed to control the exhaust temperature to increase; and, The first SCR system is turned on, 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.

[0013] As one of the preferred solutions, in the case of the buffering condition, controlling the exhaust temperature to continue to increase through a second execution operation, and controlling the corresponding SCR system to start injecting the reductant with a second preset parameter, includes: Based on the buffering condition, the throttle opening is reduced to control the exhaust temperature to continue to increase, and, The methanol direct injection nozzle is opened, the first SCR system is 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 composed of the hydrogen of the first SCR system and the methanol of the second SCR system.

[0014] As one of the preferred solutions, under the normal working condition, switching the working 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: Based on the normal operating condition and based on the torque demand of the methanol engine, the operating parameters of the throttle, the methanol airway nozzle and the methanol direct injection nozzle are controlled; and, The first SCR system is closed, a bypass control valve on the bypass line is opened, and the second SCR system is opened to react in a temperature operating range where the methanol of the second SCR system is located; Based on the normal working condition and the torque demand of the methanol engine, the operating parameters of the throttle, the methanol airway nozzle and the methanol direct injection nozzle are controlled, and then the steps include: Determining whether the normal operating condition is a steady-state operating condition or a rapid acceleration condition; 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.

[0015] Compared with the prior art, this application has the following advantages: The exhaust gas aftertreatment system provided in the embodiment of the present application is a new aftertreatment 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 as the selection basis, multiple SCR systems with reducing agents with continuous temperature working zones as carriers are selected. 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 NO under any operating condition (from low temperature of cold start to high temperature of high load). X Conversion efficiency, 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 the process of gradually switching from cold conditions to high temperature conditions, and the exhaust temperature will transition 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

[0016] In order to more clearly illustrate the technical solution of the present application, the drawings required for use in the description of the present application will be briefly introduced below. 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 paying any creative labor.

[0017] Figure 1 It is a structural diagram of the exhaust gas after-treatment system based on full-temperature range collaborative optimization according to an embodiment of the present application; Figure 2 is a system architecture diagram of a spark-ignition methanol engine assembly according to an embodiment of the present application; Figure 3 It is a flowchart of the steps of the exhaust gas treatment method based on full temperature range collaborative optimization described in an embodiment of the present application; Figure 4It is a flowchart of an exhaust gas treatment method based on full-temperature range collaborative optimization described in an embodiment of the present application.

[0018] Description of reference numerals: 1. Air filter; 2. Air pipe; 3. Supercharger; 4. Intercooler; 5. Throttle; 6. Exhaust 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 nitrogen oxide sensor; 23. Middle nitrogen oxide sensor; 24. Rear nitrogen oxide sensor. DETAILED DESCRIPTION

[0019] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0020] Reference Figure 1 As shown, Figure 1 FIG. 1 is a diagram showing the overall structure of the exhaust gas aftertreatment system based on full temperature range collaborative optimization according to the present invention. Figure 1 As shown, the present invention provides an exhaust gas aftertreatment system based on full temperature range 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, The multiple SCR systems are configured with different reductants, 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 intersections and / or temperature intervals, 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 operating 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.

[0021] 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 gas 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.

[0022] Regarding the after-treatment system specifically for exhaust gas treatment, the embodiment of the present application proposes a new after-treatment system suitable for spark-ignition methanol engines, which realizes NO X The emission conversion covers the entire temperature range and has high efficiency. For example, the embodiment of the present application does not have a DPF, which reduces the system complexity and investment cost.

[0023] 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 different reductants, and different reductants 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 NO X Therefore, by combining multiple SCR systems with different temperature operating zones, nitrogen oxide reduction in a wide temperature range can be achieved.

[0024] Exemplarily, methanol reducing agent is suitable for medium and high temperature range, and hydrogen reducing agent is suitable for low temperature range. Of course, the reducing agent can also be urea, hydrocarbon fuel, ammonia, etc. Since the embodiment of the present invention is used for a methanol engine, according to the relevant phenomena mentioned in the background technology, it is best not to use reducing agents such as urea, hydrocarbon fuel, ammonia, etc. in this embodiment, so as to avoid related problems while meeting the requirements of efficient conversion.

[0025] 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 SCR 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.

[0026] As a further explanation of this embodiment, the temperature working zones corresponding to the multiple different SCR systems selected by the present invention do not have temperature intersections and / or temperature intervals, so as to be combined together to form a continuous full-temperature coverage zone. For traditional single SCR technology or other combined forms of SCR systems, the temperature intervals are often "intermittent", and each different SCR system exhibits 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.

[0027] 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. Since there is a "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 Therefore, when the exhaust temperature is in the low temperature range, the SCR combination system cannot exert its high conversion efficiency under cold conditions.

[0028] 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 its high conversion efficiency under the medium temperature condition.

[0029] For example, hydrogen is in the low temperature zone, methanol is in the medium and 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 carrying out catalytic conversion, and there is a "partial overlap" area of ​​temperature coverage. Any one of the SCRs cannot fully exert its capacity within its temperature working zone, resulting in energy waste and leading to efficiency lows within the temperature range.

[0030] Therefore, the present application selects multiple SCR systems with reductants having continuous temperature working zones as carriers according to the selection criteria 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 under any operating condition (from low temperature of cold start to high temperature of high load). XConversion efficiency, 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 the process of gradually switching from cold conditions to high temperature conditions, and the exhaust temperature will transition 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.

[0031] In this embodiment, in order to further control emissions, multiple SCR systems are operated alternately or simultaneously in a multi-zone wide temperature composite reduction system that forms a full temperature range coverage area. It can be known that under different working conditions, the exhaust temperature will continue to change, so it is necessary to control the start and stop of each SCR system according to the real-time exhaust temperature.

[0032] For example, when the exhaust temperature is low, the SCR system in the lower temperature working area operates first; when the exhaust temperature rises to a medium-high temperature range, the SCR system in the lower temperature working area and the SCR system in the higher temperature working area operate simultaneously. When the exhaust temperature rises to a high temperature range, the SCR system in the higher temperature working area starts to work, and the SCR system in the lower temperature working area stops working.

[0033] Therefore, the alternating operation mode avoids the inefficient operation of the SCR system in the temperature working zone that does not belong to the current exhaust gas temperature range.

[0034] As the methanol engine continues to work, the exhaust temperature gradually increases. At this stage, the exhaust temperature is neither suitable for the efficient operation of the SCR system in the lower temperature working area, nor has it reached the ideal operating temperature of the SCR system in the higher temperature working area. Therefore, when the exhaust temperature gradually ends in the temperature zone corresponding to the SCR system in the lower temperature working area, the system can gradually reduce the reductant injection amount of the SCR system, and slowly increase the reductant injection amount of the SCR system in the lower temperature working area, so that the SCR system switches smoothly under different working conditions.

[0035] In some embodiments, all SCR systems can be operated simultaneously under all working conditions, but the injection amount of different SCR systems can be controlled. For example, for working conditions with high exhaust temperature, the SCR system in the lower temperature working area is controlled to continue to operate at a lower injection amount, while the SCR system in the higher temperature working area is operated at a higher injection amount. Therefore, the SCR system in the lower temperature working area can serve as an auxiliary reduction system and play a supplementary role when the SCR system in the higher temperature working area is not fully processed. The simultaneous operation mode can minimize emissions under high load and high temperature conditions.

[0036] 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.

[0037] 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 with hydrogen as the reducing agent; the SCR system in the higher temperature working zone can be a second SCR system 16 with methanol as the reducing agent.

[0038] 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.

[0039] In this embodiment, a plurality of different SCR systems can be connected in series or in parallel to the tail exhaust passage. Preferably, along the direction of exhaust gas flow, a plurality of SCR systems are connected in sequence to simplify the pipeline.

[0040] The multi-zone wide temperature composite reduction system is used to reduce NO in tail gas X After the conversion treatment, the DOC is located at the outlet of the last SCR system and is responsible for oxidizing other pollutants in the exhaust gas, such as hydrocarbons and carbon monoxide, to further reduce harmful substances in the exhaust gas and ensure that the exhaust emissions meet environmental standards.

[0041] This embodiment is used to illustrate the preferred combination of a multi-zone wide temperature composite reduction system. The multi-zone wide temperature composite reduction system is a methanol-hydrogen complementary SCR system, which includes 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 SCR system 15 and the second SCR system 16 are connected in series along the exhaust gas flow direction; wherein the hydrogen is indirectly and the methanol is directly derived from a methanol tank 7 used to supply fuel to the methanol engine.

[0042] 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 the 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 NO under low temperature conditions due to its low ignition temperature. X Conversion efficiency.

[0043] Therefore, for medium and high exhaust temperature conditions, the second SCR system 16 uses methanol as a reducing agent. Compared with urea SCR, the second SCR system 16 has a lower ignition temperature, which can be reduced to 200°C, and has a wider operating temperature range (280°C~500°C). When the exhaust temperature rises above 200°C, methanol begins to work as a reducing agent.

[0044] Therefore, the methanol-hydrogen complementary SCR system uses hydrogen as a reducing agent, which can be indirectly taken from the methanol tank 7. The system uses methanol as a reducing agent, which can be directly taken from the methanol tank 7. There is no need to add urea like the urea SCR, and no additional urea tank is required, which reduces the complexity and use cost of the system.

[0045] The second SCR system 16 is in the medium-high temperature range (280℃~500℃), while the first SCR system 15 is in the low temperature range (150℃ and above), and the temperature working ranges of the two are closely adjacent. Therefore, the temperature working range of the second SCR system 16 complements the first SCR system 15 to form a continuous and efficient temperature coverage range, which can effectively ensure that under all engine operating conditions, whether the exhaust temperature is low or medium-high temperature, there is a high NO X Conversion efficiency. And unlike urea SCR, it does not produce highly toxic hydrocyanic acid.

[0046] Therefore, compared with other traditional SCR technologies (such as urea, hydrocarbons, 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 to ensure 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 and realizes the full-scale utilization of a single methanol fuel.

[0047] In addition, a wider temperature range can be covered by adding different types of SCR systems. It is preferred to use two SCR systems, the first SCR system 15 and the second SCR system 16, in the methanol engine, which can not only fully utilize the multiple functions of methanol fuel, but also avoid unnecessary system redundancy, and the system is more economical and practical.

[0048] It can be seen that the embodiment of the present application comprehensively considers the multiple utilizations of the same methanol fuel source and the continuous coverage of the temperature range, and provides a more optimized and highly integrated new emission control architecture, which significantly reduces the system complexity and operating costs while improving the emission control efficiency. The embodiment of the present application further illustrates the scheme of efficient emission control through multiple reaction pathways on the same methanol fuel source: The system also includes: 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 crack the methanol transmitted by the methanol tank 7 to produce hydrogen using the exhaust temperature; 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 and distribute the hydrogen produced by cracking to the first SCR system 15 and the methanol engine.

[0049] In this embodiment, the methanol cracker 12, the first SCR system 15, the second SCR system 16 and the DOC system 17 are connected and arranged in sequence along the direction of exhaust gas circulation. Specifically, the first SCR system 15 is provided with a hydrogen SCR nozzle 13, the second SCR system 16 is provided with a methanol nozzle 14, the intake passage is provided with a methanol gas nozzle 9 and a hydrogen nozzle 11, and the engine cylinder head is provided with a methanol direct injection nozzle 10, which injects methanol into the engine cylinder to achieve high-pressure direct injection in the cylinder. The methanol direct injection nozzle 10 and the methanol gas nozzle 9 are used for composite injection to ensure the stable operation of the engine under all working conditions. Among them, the methanol tank 7 and the hydrogen distribution tank 8 are respectively connected to the nozzles of the corresponding components to transport methanol fuel and hydrogen into 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.

[0050] like Figure 2 As shown, Figure 2 The system architecture diagram of the spark-ignition methanol engine assembly. The black solid line with arrows represents the gas flow direction, the uniform dotted line with arrows represents the methanol flow direction, and the double-dotted dotted line with arrows represents the hydrogen flow direction.

[0051] 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 which are respectively supplied to corresponding positions through the corresponding four branches.

[0052] 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.

[0053] Furthermore, when the engine is operating normally, the methanol cracker 12 receives the methanol fuel transmitted by the methanol tank 7, and utilizes the heat from the high exhaust temperature in the engine tail exhaust passage to thermally crack 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 indirectly supplies 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.

[0054] When the engine is in a low-load condition or in a cold condition, the exhaust temperature is low and is insufficient 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 increases, the methanol cracker 12 starts to work, and the hydrogen produced fills the hydrogen tank 8 and then stops working.

[0055] 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.

[0056] For the spark-ignition methanol engine assembly, the methanol tank 7 itself supplies the methanol engine through two routes and then supplies the second SCR system 16 through one route. 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 intake passage of the engine 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 XTherefore, 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 supply the two major systems of the methanol engine and the exhaust gas post-treatment at the same time, completing the integration of the dual-temperature zone SCR technology and realizing the 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.

[0057] In a further technical solution, a bypass pipeline is provided between the first SCR system 15 and the second SCR system 16, and a bypass control valve 21 for controlling the on-off of the bypass pipeline is provided on the bypass pipeline. The inlet of the bypass pipeline is provided before the inlet of the first SCR system 15, and the outlet is provided before the inlet of the second SCR system 16. Therefore, the first SCR system 15 is directly connected to the second SCR system 16, or the first SCR system 15 can be bypassed through the bypass pipeline by the bypass control valve 21.

[0058] 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 increases, the NO X The reduction effect is reduced, and the NO X The 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 achieving emission reduction.

[0059] In a further technical solution, the test system includes a plurality of temperature sensors and a plurality of nitrogen oxide sensors, which are respectively arranged at the entrance of each of the SCR system and the DOC system 17 on the tail 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 post-treatment 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.

[0060] The nitrogen oxide concentration value is 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 value is 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.

[0061] 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 exhaust temperature is at a relatively low level. The engine exhaust passes through the first SCR system 15 for NO removal. X conversion; The exhaust temperature before the second SCR system 16 is measured by the intermediate temperature sensor 19. When the exhaust temperature there is higher than 250°C, the temperature working area of ​​the second SCR system 16 has been reached. At this time, the bypass control valve 21 is opened, and the engine exhaust gas reaches the second SCR system 16 through the bypass pipeline to perform NO X efficient conversion.

[0062] 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.

[0063] 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. Then, 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.

[0064] In summary, the new exhaust gas aftertreatment 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 with full temperature coverage. Figure 2The 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 5 which are connected in sequence; an after-treatment system, such as the exhaust after-treatment system based on full-temperature range collaborative optimization provided in the first aspect; a methanol engine, which is connected to the intake system through an intake passage and to the after-treatment system through an exhaust passage, wherein a methanol airway nozzle 9 and a hydrogen nozzle 11 are provided on the intake passage, and a methanol direct injection nozzle 10 is provided on the methanol engine; a methanol tank 7, which is respectively connected to the methanol airway nozzle 9, the methanol direct injection nozzle 10, a methanol cracker 12 and a second SCR system 16 on the after-treatment system; wherein the hydrogen nozzle 11 is connected to a hydrogen distribution tank 8 on the after-treatment system which is connected to the methanol cracker 12; wherein an exhaust gas bypass is provided on the exhaust passage corresponding to the front and rear ends of the supercharger 3.

[0065] In this embodiment, each component in the intake system is connected through corresponding pipelines, for example, the air filter, the supercharger 3, the intercooler 4 and the throttle 5 are all arranged on the air pipe 2, and the throttle 5 is then connected to multiple cylinders through the intake pipe and the intake manifold. In combination with the above embodiments, the methanol gas nozzle 9 and the hydrogen nozzle 11 are both correspondingly arranged at the location of the intake pipe.

[0066] 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-post 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 post-treatment system, which can further reduce NO X emission.

[0067] The system is as described in the first aspect, based on the exhaust gas after-treatment system of full temperature range collaborative optimization, adopts a multi-zone wide temperature composite reduction system, including at least two SCR systems, which can be operated alternately or simultaneously, covering the full temperature range, and 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 .

[0068] In the tail exhaust passage, the exhaust gas bypass is arranged 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.

[0069] Correspondingly, for the third aspect, please refer to Figure 3 As shown, Figure 3The present invention also provides an exhaust gas treatment method based on full temperature range collaborative optimization, which is used in the exhaust gas post-treatment system based on full temperature range 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, and the method comprises the following steps: S1. Obtaining the exhaust temperature and nitrogen oxide concentration corresponding to the inlet of each SCR system on the tail exhaust passage of the methanol engine; 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.

[0070] S2. judging whether the current operating condition of the methanol engine is any one of a cold condition, a buffer condition and a normal condition based on the exhaust temperature corresponding to the front SCR system; 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 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 condition; when the exhaust temperature reaches the third preset value of the normal operating condition, it is judged as a normal operating condition.

[0071] The determination is made by comparing the exhaust temperature with the preset temperature thresholds of each operating condition. For example, the first preset value is set to be less than 200°C, the second preset value is set to be 200-300°C, and the third preset value is set to be greater than 300°C. Of course, the specific temperature range can be adjusted according to actual application.

[0072] 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 the basis for determining the current operating condition.

[0073] S3, based on the nitrogen oxygen concentration before and after each SCR system, determining the injection amount of the SCR system corresponding to the reductant injection that needs to be performed under the current operating condition; The number and order of execution of multiple SCR systems that need to perform reductant injection may be determined based on the current operating conditions.

[0074] After determining the number of executions, the corresponding specific number of multiple SCR systems 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 SCR systems executed can be flexibly adjusted to avoid a certain SCR system working at an inappropriate temperature or to avoid excessive or insufficient injection of reductant. 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. Each SCR system has a different temperature operating zone. Therefore, under the exhaust temperature condition, the temperature operating zone of each SCR system can be compared, and which SCR systems can currently operate at this temperature can be determined based on the exhaust temperature.

[0075] In different temperature ranges, the system can select the execution order of the currently executed number of SCR systems according to the current operating conditions. For example, in cold conditions, the SCR system in the lower temperature working area is executed first, and when the temperature gradually rises, the SCR system in the higher temperature working area gradually takes over, so that the SCR system operates alternately. When the exhaust temperature is in the transition zone of different SCR systems, multiple SCR systems work simultaneously.

[0076] After determining the number and order of SCR systems that need to perform reductant injection under the current operating conditions, the reductant injection amount corresponding to each SCR system is determined according to the detected nitrogen oxide concentration and exhaust temperature. For example, if the nitrogen oxide conversion efficiency is lower than the preset target value, the reductant injection amount needs to be increased to provide more reductant. If the nitrogen oxide conversion efficiency reaches or exceeds the target value, the current hydrogen injection amount can be maintained or fine-tuned according to actual needs.

[0077] 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.

[0078] S4, in the case of the cold working 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, so as to perform a catalytic reduction reaction with nitrogen oxides in the exhaust gas within a first wide temperature range corresponding thereto; S5. Under the buffer 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, so as to perform a catalytic reduction reaction with nitrogen oxides in the exhaust gas within the corresponding second wide temperature range; S6. Under the normal operating condition, the working 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.

[0079] 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.

[0080] In step S4-step S6, the ECU performs a series of actions on the SCR system or related components of the combustion system under different working conditions to adjust the exhaust temperature and start the appropriate SCR system. The execution operation includes adjusting the air-fuel ratio, adjusting the EGR rate, increasing the engine load, adjusting the ignition timing, adjusting the engine operating parameters, or opening the exhaust bypass valve 6, etc. The dynamic adjustment execution operation is adapted to the operating conditions of the engine, which facilitates the efficient operation of the SCR system.

[0081] Under different working conditions, the working parameters of the multiple SCR systems are also different, wherein the first preset parameter, the second preset parameter and the third preset parameter may include at least one of the reductant injection amount, the injection start temperature, the injection timing and the injection frequency. The injection start temperature threshold can be obtained by the temperature sensor at the inlet of each SCR system to obtain the exhaust gas temperature entering the corresponding SCR system, and compared with its own injection start temperature, when the exhaust gas temperature at the inlet reaches the injection start temperature, the corresponding SCR system can be turned on.

[0082] In combination with 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 the SCR systems that need to perform the 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 started.

[0083] 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.

[0084] 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 corresponding to each working condition, and multiple single-stage wide temperature ranges jointly cover NO under all working conditions. X Conversion.

[0085] In some embodiments, each wide temperature range 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 range can cover two temperature segments, the low temperature segment processes NO during cold start. X The second wide temperature zone and the third wide temperature zone may also cover multiple temperature ranges.

[0086] 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 in 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 in the first wide temperature zone, the second wide temperature zone, and the third wide temperature zone may be partially the same or different.

[0087] The combination of one or more sections of the first, second and third wide temperature zones can be determined according to the specifications and volume of the methanol engine. For example, a large-displacement methanol engine can be started and injected by multiple SCR systems with lower temperatures under cold working conditions.

[0088] 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.

[0089] See also Figure 4 , Figure 4 The flowchart of the tail gas treatment method based on full temperature range collaborative optimization configured with a methanol-hydrogen complementary SCR system is shown below. The following methanol-hydrogen complementary SCR system is taken as an example to specifically describe steps S4 to S6 of the present application.

[0090] Further, step S4 includes: 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 5 and opening the methanol direct injection nozzle 10 is used 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 operating range where the hydrogen of the first SCR system 15 is located.

[0091] 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 a thermal management control stage. In this stage, the engine works mainly for the purpose of quickly raising the exhaust temperature.

[0092] Specifically, the hydrogen nozzle 11 is turned on, and the hydrogen in the hydrogen tank 8 is controlled to be sprayed into the intake pipe, and then enters into multiple engine cylinders through the intake manifold along with fresh air. Since hydrogen has the characteristics of high activity and lower ignition temperature, it is helpful to solve the problem of cold starting, and the high flame propagation speed is helpful to accelerate the combustion, so as to achieve a rapid increase in exhaust temperature under the cold working condition of the engine; Open the waste gas bypass valve 6 on the waste gas bypass to allow the engine exhaust to bypass the turbine. At this time, the turbine of the supercharger 3 does not work, which is beneficial to reduce the fresh air entering the cylinder and increase the exhaust temperature; 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; The methanol direct injection nozzle 10 is turned on and the injection time is during the expansion stroke or the 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.

[0093] The conversion efficiency of the first SCR system 15 is calculated according to the nitrogen oxide concentration measured by the front nitrogen oxide sensor 22 and the middle nitrogen oxide sensor 23, so as to obtain the injection amount of hydrogen; the injection amount of hydrogen is controlled by adjusting the power-on time of the hydrogen SCR nozzle 13; since the temperature does not reach the temperature working range of the second SCR system 16 at this time, the methanol nozzle 14 is closed, and only the methanol direct injection nozzle 10 is needed to inject the methanol that has not been burned in the cylinder and enters the post-treatment system for NO X conversion; 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.

[0094] Further, step S5 includes: Based on the buffering 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 of the first SCR system 15 and the methanol of the second SCR system 16.

[0095] 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 simultaneously.

[0096] 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; The methanol direct injection nozzle 10 is opened, and the injection timing is during the expansion stroke or the exhaust stroke.

[0097] The conversion efficiency of the first SCR system 15 is calculated according to the nitrogen oxide concentration 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; At this time, the temperature has entered the temperature working area of ​​the second SCR system 16. The methanol injection amount of the second SCR system 16 is calculated according to the nitrogen oxide concentration measured by the middle nitrogen oxide sensor 23 and the rear nitrogen oxide sensor 24. The methanol injection amount is controlled by adjusting the power-on time of the methanol nozzle 14. 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 .

[0098] If the temperature measured by the medium temperature sensor 19 is less than 300° C., the process continues to cycle through step 5 ; if it exceeds 300° C., the process proceeds to step 6 .

[0099] Further, step S6 includes: 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.

[0100] 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 greater than 300°C, the engine enters the normal operation stage, in which the engine is optimized for economic efficiency. The normal operating condition also includes a steady-state operating condition and a rapid acceleration condition.

[0101] Under steady-state operating conditions, based on the engine torque demand, the opening of the throttle valve 5 and the methanol airway nozzle 9 are controlled in real time; based on the engine torque acceleration demand, the methanol direct injection nozzle 10 is opened in real time to achieve oil replenishment.

[0102] In the case of 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 in the rapid acceleration state of the methanol engine, thereby achieving a simultaneous improvement in power and thermal efficiency.

[0103] The bypass control valve 21 is open. At this time, the engine exhaust temperature is relatively high, and only the second SCR system 16 is needed to remove NO in the exhaust gas. X Just do the processing and close the hydrogen SCR nozzle 13; Calculate the methanol injection amount of the second SCR system 16 according to the nitrogen oxide concentration measured by the middle nitrogen oxide sensor 23 and the rear nitrogen oxide sensor 24; and control the methanol injection amount by adjusting the power-on time of the methanol nozzle 14; The methanol cracker 12 starts to work, and the generated hydrogen enters the hydrogen distribution tank 8 for storage.

[0104] 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.

[0105] 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.

[0106] 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 or similar parts between the various embodiments can be referenced to each other.

[0107] It should also be noted that, in this article, the orientation or position relationship indicated by the terms "upper", "lower", "left", "right", "inside", "outside", etc. is based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention. In addition, relational terms such as "first" and "second" are only 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 "include" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or terminal device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or terminal device.

[0108] The above is a detailed introduction to the exhaust gas after-treatment system, assembly and method based on full-temperature coordinated optimization provided by the present application. Specific examples are used in this article to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the present application, and the content of this specification should not be understood as a limitation on the present application. At the same time, for those of ordinary skill in the art, according to the present 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 the implementation methods here, and the obvious changes or modifications derived from this are still within the scope of protection of the present application.

Claims

1. An exhaust gas aftertreatment 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: The multi-zone wide temperature composite reduction system includes at least two SCR systems; wherein: The plurality of SCR systems are configured with different reductants, so that the plurality of SCR systems have a plurality of different temperature operating zones; wherein, The temperature working zones corresponding to the plurality of SCR systems do not have temperature intersections and / or temperature intervals, so as to be combined together to form a continuous full-temperature coverage zone; Wherein, a plurality of different SCR systems are configured as follows: According to the exhaust temperature of the exhaust gas in the tail exhaust passage, catalytic reduction reactions are performed alternately or simultaneously in the respective corresponding temperature working zones to achieve efficient conversion of nitrogen oxides in the exhaust gas under all working conditions; 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.

2. The exhaust gas after-treatment system based on full temperature range collaborative optimization according to claim 1, characterized in that: 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.

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

4. The exhaust gas after-treatment system based on full temperature range collaborative optimization according to claim 2 is characterized in that: A bypass pipeline 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 pipeline is provided on the bypass pipeline.

5. An exhaust gas after-treatment system based on full temperature range collaborative optimization according to any one of claims 1 to 4, 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 each of the SCR system and the DOC system on the tail exhaust passage.

6. 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 as claimed in any one of claims 1 to 5; A methanol engine is connected to the intake system through an intake passage and to the post-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 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 arranged on the tail exhaust passage corresponding to the front and rear ends of the supercharger.

7. A tail gas treatment method based on full temperature range collaborative optimization, characterized in that the method include: Obtaining the exhaust temperature and nitrogen oxide concentration corresponding to the inlet of each SCR system on the tail exhaust passage of the methanol engine; Based on the exhaust temperature corresponding to the front SCR system, determining whether the current operating condition of the methanol engine is any one of a cold condition, a buffer condition and a normal condition; Based on the nitrogen oxygen concentration before and after each SCR system, determining the injection amount of the corresponding SCR system that needs to perform reductant injection under the current operating condition; In the case of the cold working condition, the exhaust temperature is controlled to be increased through a first execution operation, and the currently executed SCR system is controlled 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 thereto; In the case of the buffer condition, the exhaust temperature is controlled to continue to increase through a second execution operation, and the corresponding SCR system is controlled 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; Under the normal working condition, the working 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 a third wide temperature range corresponding thereto; 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.

8. The exhaust gas treatment method based on full temperature range collaborative optimization according to claim 7 is characterized in that: In the cold working condition, controlling the exhaust temperature to increase through a first execution operation, and controlling the currently executed SCR system to start injecting the reductant with a first preset parameter, includes: Based on the cold working condition, at least one of opening a hydrogen nozzle, opening an exhaust bypass valve on an exhaust bypass, reducing a throttle opening, and opening a methanol direct injection nozzle is performed to control the exhaust temperature to increase; and, The first SCR system is turned on, 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.

9. The exhaust gas treatment method based on full temperature range collaborative optimization according to claim 7, characterized in that: In the case of the buffering condition, controlling the exhaust temperature to continue to increase through a second execution operation, and controlling the corresponding SCR system to start injecting the reductant with a second preset parameter, includes: Based on the buffering condition, the throttle opening is reduced to control the exhaust temperature to continue to increase, and, The methanol direct injection nozzle is opened, the first SCR system is 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 composed of the hydrogen of the first SCR system and the methanol of the second SCR system.

10. The exhaust gas treatment method based on full temperature range collaborative optimization according to claim 7, characterized in that: In the case of the normal working condition, switching the working 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: Based on the normal operating condition and the torque demand of the methanol engine, the operating parameters of the throttle, the methanol airway nozzle and the methanol direct injection nozzle are controlled; and, The first SCR system is closed, a bypass control valve on the bypass line is opened, and the second SCR system is opened to react in a temperature operating range where the methanol of the second SCR system is located; 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 comprises: Determining whether the normal operating condition is a steady-state operating condition or a rapid acceleration condition; 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.

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