A post-treatment device for a hydrogen fuel internal combustion engine with a double-stage - main passive SCR coupling and its control method

Abstract

The present invention relates to a post-treatment device for a hydrogen fuel internal combustion engine with a two-stage - active and passive SCR coupling and a control method thereof. The device includes a selective hydrogen catalytic reduction catalyst (2) using H2 as a reducing agent and a selective ammonia catalytic reduction catalyst (4) using NH3 as a reducing agent, which are connected in sequence; a connecting pipeline is provided between the selective hydrogen catalytic reduction catalyst (2) and the selective ammonia catalytic reduction catalyst (4), and the connecting pipeline is connected to a urea supply source (13); one end of the selective hydrogen catalytic reduction catalyst (2) away from the connecting pipeline is provided with an intake pipeline for the exhaust gas of the hydrogen internal combustion engine to enter, and the intake pipeline is connected to a hydrogen supply source. Compared with the prior art, the present invention innovatively introduces an H2 nozzle and a urea nozzle into the post-treatment system, and supplements the reducing agent H2 or NH3 in real time according to the sensor feedback information in the electronic control unit, couples the active and passive SCR, makes full use of the NH3 reducing agent generated by the H2 - SCR device, and realizes low-cost NO x efficient emission reduction.

Description

Technical Field

[0001] The present invention relates to the field of automotive engines, and particularly to a post-treatment device for a hydrogen fuel internal combustion engine with a dual-stage - active and passive SCR coupling and a control method therefor. Background Art

[0002] Among the emissions of hydrogen fuel internal combustion engines, nitrogen oxides are the only harmful emissions. The accelerated combustion speed of rich mixtures will lead to an increase in cylinder pressure and temperature, ultimately resulting in an increase in nitrogen oxide emissions. Therefore, in order to obtain the lowest NO x emissions, hydrogen engines need to operate between an equivalence ratio of 0.5 and 0.6. Lean combustion can avoid backfire phenomena in hydrogen fuel internal combustion engines, but a leaner mixture will cause situations such as insufficient engine torque. Although reducing NO x emissions can be achieved by adjusting injection timing and intake phase, the introduction of a post-treatment device will enable a hydrogen fuel internal combustion engine to achieve low NO x emissions while ensuring power performance.

[0003] Selective catalytic reduction technology is currently the mainstream technology for treating NO x in diesel engine post-treatment systems. This technology can be further divided into NH3-SCR and H2-SCR according to the reductant used. NH3-SCR uses an aqueous urea solution or ammonia water to reduce NO x to N2 and H2O under certain temperature windows and catalytic conditions. Since NH3, as a reductant, preferentially reacts with NO x under the action of a catalyst rather than with O2, it exhibits high selectivity. NH3-SCR usually uses copper or iron or copper-iron composite molecular sieves as catalysts. And H2-SCR uses H2 as a reductant and usually uses Pd-based and Pt-based materials as catalysts.

[0004] Patent CN108678864B discloses a control method for reducing emissions and hydrogen consumption rate during the start-up of a hydrogen engine. This method realizes ultra-low NO x emissions during the start-up of a hydrogen engine by adopting a rich combustion start-up strategy and cooperating with a three-way catalytic converter; by dividing the temperature range of the catalytic converter carrier before engine start-up, and combining the influence mechanism of the hydrogen-air mixture concentration on NO x generation and the influence mechanism of temperature on the catalytic efficiency of the three-way catalytic converter, corresponding control methods are executed for different temperature ranges to reduce the hydrogen consumption rate during the start-up process. This patent not only has a complex control strategy, high requirements for sensor accuracy and control accuracy, but also is not friendly to engine economy.

[0005] Patent 201810924790.0 discloses a combined post-treatment device suitable for a hydrogen fuel internal combustion engine. The combined TWC+SCR device is used to achieve the treatment of NOx Emission control, but the TWC only achieves efficient emission reduction under stoichiometric ratio (λ = 1) conditions, while the hydrogen internal combustion engine under stoichiometric ratio has poor power performance. The hydrogen internal combustion engine has good power performance under lean burn conditions (λ > 1), but the high O2 content in its exhaust gas significantly reduces the conversion efficiency of the TWC for NO x Therefore, the TWC+SCR device provided by this invention is only applicable to hydrogen internal combustion engines under stoichiometric ratio and cannot meet the NO x emission requirements of lean burn hydrogen internal combustion engines with high power performance, resulting in low practicality. Summary of the Invention

[0006] The purpose of the present invention is to overcome the defects of the above-mentioned existing technologies and provide a post-treatment device and its control method for a hydrogen fuel internal combustion engine that can continuously and efficiently reduce NO in the exhaust gas with a wide exhaust temperature window x and solve the problem of high NO x emissions of hydrogen internal combustion engines, which is a dual-stage - active-passive SCR coupled post-treatment device for hydrogen fuel internal combustion engines.

[0007] The purpose of the present invention can be achieved through the following technical solutions:

[0008] The present invention provides a post-treatment device for a hydrogen fuel internal combustion engine with dual-stage - active-passive SCR coupling. The post-treatment device for a hydrogen fuel internal combustion engine provided by the present invention includes two post-treatment devices, namely H2-SCR and NH3-SCR, and also includes an H2 nozzle and a urea nozzle. By combining H2-SCR with good low-temperature activity and NH3-SCR with good medium- and high-temperature activity, efficient conversion of NO x is achieved within a wide exhaust temperature window. At the same time, an H2 nozzle is installed upstream of the H2-SCR, and a urea nozzle is installed upstream of the NH3-SCR. According to the sensor feedback information in the electronic control unit, the reducing agents H2 or NH3 are replenished in real time, coupling active and passive SCR, and making full use of the reducing agent NH3 spontaneously generated by the system. This patent is not only applicable to hydrogen fuel internal combustion engines in a wide operating condition range, reduces the number of urea injections, and realizes low-cost efficient NO x emission reduction. The specific solution is as follows:

[0009] A post-treatment device for a hydrogen fuel internal combustion engine with dual-stage - active-passive SCR coupling, which includes a selective hydrogen catalytic reduction catalyst, abbreviated as H2-SCR, using H2 as a reducing agent, and a selective ammonia catalytic reduction catalyst, abbreviated as NH3-SCR, using NH3 as a reducing agent, which are connected in sequence;

[0010] A connecting pipe is provided between the selective hydrogen catalytic reduction catalyst and the selective ammonia catalytic reduction catalyst, and the connecting pipe is connected to a urea supply source;

[0011] One end of the described selective hydrogen catalytic reduction catalytic converter, which is far from the connecting pipe, is provided with an intake pipe for the exhaust gas of the hydrogen internal combustion engine to enter, and this intake pipe is connected to a hydrogen supply source.

[0012] Furthermore, a hydrogen nozzle connected to the hydrogen supply source, and a front gas sensor for detecting the intake gas composition and / or temperature are provided on the intake pipe.

[0013] Furthermore, the front gas sensor includes a front temperature sensor, a front NO x sensor and an H2 sensor.

[0014] Furthermore, a urea nozzle connected to the urea supply source, and a middle gas sensor for detecting the reaction gas composition and / or temperature are provided on the connecting pipe.

[0015] Furthermore, the middle gas sensor includes a middle temperature sensor, a middle NO x sensor and an NH3 sensor. Furthermore, an outlet pipe is provided on one side of the selective ammonia catalytic reduction catalytic converter far from the connecting pipe; a rear NO x for detecting the NO content in the exhaust gas is provided on the outlet pipe. x sensor.

[0016] Furthermore, the device further includes an electronic control unit for receiving and feedback signals, and this electronic control unit is signal-connected to the hydrogen nozzle, the urea nozzle, the front gas sensor, the middle gas sensor and the rear NO x sensor.

[0017] A control method for a post-treatment device for a hydrogen fuel internal combustion engine with a two-stage - main and passive SCR coupling as described above, this control method includes the following steps:

[0018] St.1 Obtain the operating condition information on the intake pipe and judge whether the exhaust gas temperature is lower than 300 °C;

[0019] St.2 Use the selective hydrogen catalytic reduction catalytic converter and the selective ammonia catalytic reduction catalytic converter to treat the exhaust gas of the hydrogen internal combustion engine;

[0020] St.3 When the current temperature sensor detects that the exhaust gas temperature is lower than 300 °C, start the hydrogen injection control step; when the exhaust gas temperature is not lower than 300 °C, start the urea injection control step.

[0021] Furthermore, the hydrogen injection control step is: start to judge the lowest threshold C x of H2 based on the NO conversion MAP of the selective hydrogen catalytic reduction catalytic converter, and monitor whether the H2 concentration is lower than the lowest threshold C min1 by real-time collecting the H2 sensor. When the H2 concentration is less than C min1 ...min1 When it is time, turn on the hydrogen nozzle and inject hydrogen; when the H2 concentration is not less than C min1 Return to St.2

[0022] Furthermore, the urea injection control steps are as follows: Start to judge the minimum threshold C of NH3 based on the NOx conversion MAP of the selective hydrogen catalytic reduction catalyst, the NOx conversion MAP of the selective ammonia catalytic reduction catalyst, and the NH3 adsorption and desorption model min2 , by collecting the signals of the H2 sensor, temperature sensor, NO x sensor and NH3 sensor in real time, monitor the NO x conversion efficiency, and judge in real time whether the NH3 concentration is lower than the minimum threshold C min2 , when the NH3 concentration is less than C min2 , turn on the urea nozzle and inject urea; when the NH3 concentration is not less than C min2 Return to St.2

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] (1) The present invention provides a post-treatment device for a hydrogen fuel internal combustion engine with a dual-stage - active and passive SCR coupling, including two post-treatment devices: H2-SCR with good low-temperature activity and NH3-SCR with good medium- and high-temperature activity, which realizes efficient NO x conversion within a wide exhaust temperature window and is applicable to hydrogen fuel internal combustion engines in a wide operating condition range;

[0025] (2) By installing an H2 nozzle and a urea nozzle in the post-treatment device, the present invention replenishes the reducing agents H2 or NH3 in real time according to the sensor feedback information in the electronic control unit, couples the active and passive SCRs, makes full use of the NH3 reducing agent generated by the H2-SCR device, and realizes low-cost efficient NO x emission reduction;

[0026] (3) The present invention also provides an injection control strategy applicable to the dual-stage - active and passive SCR coupling post-treatment device. Based on the temperature and gas concentration signals monitored in real time, it judges whether the concentration of the reducing agent is lower than the minimum threshold, and when it is judged to be lower, the injection of the reducing agent is started. Description of the Drawings

[0027] Figure 1 It is a schematic diagram of the post-treatment device in the embodiment;

[0028] Figure 2 It is a schematic diagram of the injection strategy in the embodiment;

[0029] As shown in the figure: hydrogen nozzle 1, selective hydrogen catalytic reduction catalyst 2, urea nozzle 3, selective ammonia catalytic reduction catalyst 4, front temperature sensor 5, front NOx Sensor 6, H2 sensor 7, medium temperature sensor 8, medium NO x Sensor 9, NH3 sensor 10, rear NO x Sensor 11, electronic control unit 12, urea supply source 13. Detailed implementation mode

[0030] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented on the premise of the technical solution of the present invention, and detailed implementation methods and specific operation processes are given, but the protection scope of the present invention is not limited to the following embodiments.

[0031] Embodiment

[0032] A post-treatment device for a hydrogen fuel internal combustion engine with a dual-stage - active and passive SCR coupling and its control method, as Figure 1 shown, includes a hydrogen nozzle 1, a selective hydrogen catalytic reduction catalyst 2 using H2 as a reducing agent arranged behind the hydrogen nozzle 1, a urea nozzle 3 arranged behind the selective hydrogen catalytic reduction catalyst 2, and a selective ammonia catalytic reduction catalyst 4 using NH3 as a reducing agent arranged behind the urea nozzle 3. The air flow sequentially passes through the post-treatment devices H2-SCR and NH3-SCR, and finally is discharged into the atmospheric environment.

[0033] It further includes a front temperature sensor 5, a front NO x Sensor 6 and H2 sensor 7 installed in front of H2-SCR, a medium temperature sensor 8, a medium NO x Sensor 9 and NH3 sensor 10 installed between H2-SCR and NH3-SCR, a rear NO x Sensor 11 installed behind NH3-SCR, and an electronic control unit 12 and a urea injection control unit 13 for receiving and feedback signals.

[0034] In the post-treatment device of the hydrogen fuel internal combustion engine, the exhaust gas first passes through the post-treatment device H2-SCR. The chemical reaction process of NO x in H2-SCR includes Chemical Formula (1) and Chemical Formula (2):

[0035] Chemical Formula (1) NI + 2.5H2 → NH3 + H2O

[0036] Chemical Formula (2) NO2 + 3.5H2 → NH3 + 2H2O

[0037] Then the air flow passes through NH3-SCR. The NH3 generated by Chemical Formula (1) and Chemical Formula (2) is adsorbed by NH3-SCR and can be further used as a reducing agent to react with NO x The chemical reaction process that occurs is shown in Chemical Formula (3) to Chemical Formula (5):

[0038] Chemical formula (3): 4NO + 4NH3 + O2 → 4N2 + 6H2O

[0039] Chemical formula (4): 8NH3 + 6NO2 → 7N2 + 12H2O

[0040] Chemical formula (5): NO + 2NH3 + NO2 → 2N2 + 3H2O

[0041] At low exhaust gas temperatures, the H2-SCR aftertreatment device with good low-temperature activity will convert NO into NH3 and H2O through Chemical formula (1) and Chemical formula (2). The generated NH3 in H2-SCR enters NH3-SCR and is adsorbed. x

[0042] At medium and high exhaust gas temperatures, the NH3-SCR with good medium and high-temperature activity converts NH3 and NO into harmless N2 and H2O through Chemical formula (3), Chemical formula (4), and Chemical formula (5), ultimately achieving efficient NO emission reduction under a wide range of operating conditions for the hydrogen fuel internal combustion engine. x x emission reduction.

[0043] When the electronic control unit 12 detects through the feedback information of the front temperature sensor 5, the front NO sensor 6, the H2 sensor 7, the middle temperature sensor 8, the middle NO sensor 9, and the NH3 sensor 10 that the reducing agent H2 or NH3 needs to be supplemented, the hydrogen nozzle 1 and the urea nozzle 3 can inject H2 and urea that generates NH3 into the system respectively. Finally, the efficient emission reduction effect of NO is monitored through the post NO sensor 11, further achieving efficient NO emission reduction. x x x x x emission reduction.

[0044] When NH3-SCR realizes efficient conversion of NO only relying on the generated NH3 of H2-SCR, it is called passive NH3-SCR. When NH3-SCR cannot achieve complete conversion of NO only relying on the generated NH3 of H2-SCR, it is necessary to control the urea nozzle 3 to inject urea into the system to supplement the reducing agent NH3 through the urea injection control unit 13, which is called active SCR. x x

[0045] As Figure 2 shown, the embodiment adopts the following injection control strategy. By collecting the signals of the front temperature sensor 5 and the front NO sensor 6 in real time, it is judged in real time whether the exhaust gas temperature is lower than 300 °C. When it is judged that the exhaust gas temperature is lower than 300 °C, the NO conversion MAP based on H2-SCR is started to judge the lowest threshold C of H2 x x min1 ​​​​​​​​​​, monitor whether the H2 concentration is lower than the minimum threshold C by collecting the signal of the H2 sensor 7 in real time min1 , when it is less than, turn on the hydrogen nozzle to inject hydrogen.

[0046] When it is judged that the exhaust gas temperature is higher than 300 °C, start the NO conversion MAP based on H2-SCR and the NO conversion MAP of NH3-SCR x and the NH3 adsorption and desorption model to judge the minimum threshold C of NH3 x , monitor the NO conversion efficiency by collecting the signals of the H2 sensor 7, the medium temperature sensor 8, the medium NO sensor 9 and the NH3 sensor 10 in real time, and judge in real time whether the NH3 concentration is lower than the minimum threshold C min2 , by collecting the signals of the H2 sensor 7, the medium temperature sensor 8, the medium NO sensor 9 and the NH3 sensor 10 in real time x sensor 9 and NH3 sensor 10 signals, monitor NO x conversion efficiency, and judge in real time whether the NH3 concentration is lower than the minimum threshold C min2 , when it is less than, turn on the urea nozzle to inject urea.

[0047] In summary, at present, with the clarification of China's dual-carbon goal, hydrogen internal combustion engines, as power devices with zero carbon emissions, have received extensive attention. However, the contradiction between their power performance and NO x emissions has not been solved. This aftertreatment device innovatively combines H2-SCR with good low-temperature activity and NH3-SCR with good medium- and high-temperature activity to achieve efficient NO x conversion within a wide exhaust gas temperature window, and is applicable to hydrogen fuel internal combustion engines with a wide operating condition range. The present invention innovatively introduces both an H2 nozzle and a urea nozzle into the aftertreatment system, and replenishes the reducing agents H2 or NH3 in real time according to the sensor feedback information in the electronic control unit, couples the active and passive SCR, makes full use of the NH3 reducing agent generated by the H2-SCR device, and realizes low-cost NO x efficient emission reduction, and has broad application prospects.

[0048] The above are only the preferred embodiments of the present invention, and are not intended to limit the present invention in other forms. Any person skilled in the art may use the disclosed technical content to make changes or modifications into equivalent embodiments with equivalent changes. However, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the technical solution content of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A post-treatment device for a hydrogen fuel internal combustion engine with a dual-stage - primary and secondary SCR coupling, characterized in that, The device includes a selective hydrogen catalytic reduction catalytic converter (2) using H2 as a reducing agent and a selective ammonia catalytic reduction catalytic converter (4) using NH3 as a reducing agent, which are connected in sequence; A connecting pipe is provided between the selective hydrogen catalytic reduction catalytic converter (2) and the selective ammonia catalytic reduction catalytic converter (4), and the connecting pipe is connected to a urea supply source (13); One end of the selective hydrogen catalytic reduction catalytic converter (2) away from the connecting pipe is provided with an intake pipe for the exhaust gas of the hydrogen internal combustion engine to enter, and the intake pipe is connected to a hydrogen supply source; A hydrogen nozzle (1) connected to the hydrogen supply source and a front gas sensor for detecting the intake gas composition and / or temperature are provided on the intake pipe; The front gas sensor described above includes a front temperature sensor (5), a front NO x sensor (6) and an H2 sensor (7); A urea nozzle (3) connected to the urea supply source (13) and a middle gas sensor for detecting the reaction gas composition and / or temperature are provided on the connecting pipe; The medium gas sensor described above includes a medium temperature sensor (8), a medium NO x sensor (9) and an NH3 sensor (10); The control method of the device includes the following steps: St.1 Obtain the working condition information on the intake pipe and judge whether the exhaust gas temperature is lower than 300 °C; St.2 Use the selective hydrogen catalytic reduction catalytic converter (2) and the selective ammonia catalytic reduction catalytic converter (4) to treat the exhaust gas of the hydrogen internal combustion engine; St.3 When the current temperature sensor (5) detects that the exhaust gas temperature is lower than 300 °C, start the hydrogen injection control step; when the exhaust gas temperature is not lower than 300 °C, start the urea injection control step; The described hydrogen injection control steps are as follows: Start the NO conversion MAP based on the selective hydrogen catalytic reduction catalyst (2) x to determine the minimum threshold C of H2 min1 , and monitor whether the H2 concentration is lower than the minimum threshold C by real-time collecting the H2 sensor (7) min1 . When the H2 concentration is less than C min1 , open the hydrogen nozzle (1) to inject hydrogen; when the H2 concentration is not less than C min1 , return to St.2; The urea injection control steps are as follows: Start the NO conversion MAP based on the selective hydrogen catalytic reduction catalyst (2), the NO conversion MAP of the selective ammonia catalytic reduction catalyst (4), and the NH3 adsorption and desorption model to determine the minimum threshold C of NH3. By collecting the signals of the H2 sensor (7), the medium temperature sensor (8), the medium NO sensor (9), and the NH3 sensor (10) in real time, monitor the NO conversion efficiency and judge in real time whether the NH3 concentration is lower than the minimum threshold C. When the NH3 concentration is less than C, open the urea nozzle (3) to inject urea; when the NH3 concentration is not less than C, return to St.

2. x conversion MAP, the NO conversion MAP of the selective ammonia catalytic reduction catalyst (4), and the NH3 adsorption and desorption model to determine the minimum threshold C of NH3. x By collecting the signals of the H2 sensor (7), the medium temperature sensor (8), the medium NO sensor (9), and the NH3 sensor (10) in real time, monitor the NO conversion efficiency and judge in real time whether the NH3 concentration is lower than the minimum threshold C. min2 When the NH3 concentration is less than C, open the urea nozzle (3) to inject urea; when the NH3 concentration is not less than C, return to St.

2. x conversion efficiency and judge in real time whether the NH3 concentration is lower than the minimum threshold C. x When the NH3 concentration is less than C, open the urea nozzle (3) to inject urea; when the NH3 concentration is not less than C, return to St.

2. min2 When the NH3 concentration is less than C, open the urea nozzle (3) to inject urea; when the NH3 concentration is not less than C, return to St.

2. min2 When the NH3 concentration is less than C, open the urea nozzle (3) to inject urea; when the NH3 concentration is not less than C, return to St.

2. min2 When the NH3 concentration is not less than C, return to St.

2.

2. The post-treatment device for a hydrogen fuel internal combustion engine with a double-stage - master-slave passive SCR coupling according to claim 1, characterized in that, On one side of the selective ammonia catalytic reduction catalytic converter (4) far from the connecting pipe, an air outlet pipe is provided; on the air outlet pipe, a post-NO x sensor (11) for detecting the NO x content in the tail gas is provided.

3. The post-treatment device for a hydrogen fuel internal combustion engine with a double-stage - master-slave passive SCR coupling according to claim 2, characterized in that, The device further includes an electronic control unit (12) for receiving and feeding back signals, and the electronic control unit (12) is signal-connected to the hydrogen nozzle (1), the urea nozzle (3), the front gas sensor, the middle gas sensor, and the rear NO x sensor (11).

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