A post-treatment device and post-treatment control method for an ammonia internal combustion engine

Abstract

The present invention discloses a post-treatment device and a post-treatment control method for an ammonia internal combustion engine, which includes: a three-way catalytic converter and a selective catalytic reduction device connected in series downstream of the exhaust pipe of the ammonia internal combustion engine in sequence, and a reducing gas bypass valve is connected in parallel with the three-way catalytic converter. By controlling the exhaust gas diversion ratio of the reducing gas bypass valve and utilizing the oxidation heat release of NH3 and H2 in the three-way catalytic converter, the conversion efficiency of the selective catalytic reduction device is improved, so that the harmful pollutant emissions in the exhaust gas of the ammonia internal combustion engine can be treated more efficiently, and the harmful pollutant emissions in the exhaust gas can be treated more efficiently, preventing harmful pollutants from being discharged into the atmosphere; the ammonia internal combustion engine adopting the post-treatment device of the present invention can continuously operate in a lean burn mode, improving the thermal efficiency of the engine; the decoupling of the emission control of the post-treatment and the combustion control of the engine can be realized, improving the stability and robustness of the emission control, and simplifying the calibration work of the internal combustion engine and the exhaust post-treatment.

Description

Technical Field

[0001] The present invention relates to the technical field of ammonia internal combustion engines, and in particular to a post-processing device and a post-processing control method for an ammonia internal combustion engine. Background Art

[0002] According to the test results, the pollutants in the exhaust of ammonia internal combustion engines mainly include NOx and NH3, as well as some pollution-free hydrogen (H2). In the equivalent combustion mode, the emission of NOx is about 3000-8000ppm, the emission of NH3 is about 2-3 times that of NOx, and the emission of H2 is 4000-7000ppm. Moreover, the pollutants in the exhaust are also related to the combustion mode of the ammonia internal combustion engine. When the mixture in the cylinder is in lean combustion mode, the emission of NOx increases slightly, and the emission of NH3 and H2 decreases slightly; when the mixture in the cylinder is in rich combustion mode, the emission of NOx decreases slightly, and the emission of NH3 and H2 increases slightly.

[0003] Patent No. CN109162819A discloses a combined post-treatment device suitable for hydrogen fuel internal combustion engines. The NH3 generated in the device can be used to reduce NOx without adding additional NH3, thereby achieving the goal of reducing pollutants emitted by hydrogen internal combustion engines. The combined post-treatment device includes a hydrogen internal combustion engine, a TWC post-treatment device, and an SCR post-treatment device without urea injection, which are connected in sequence through pipelines. A hydrogen nozzle is arranged on the inlet pipeline of the hydrogen internal combustion engine, and a NOx sensor is arranged on the outlet pipeline of the SCR post-treatment device without urea injection. The hydrogen nozzle and the NOx sensor are respectively connected to an electronic control unit; the electronic control unit controls the hydrogen injection pulse width of the hydrogen nozzle according to the NOx content; the TWC post-treatment device and the SCR post-treatment device without urea injection are used to jointly reduce NOx in the exhaust gas; the NOx sensor measures the NOx content at the outlet of the SCR post-treatment device without urea injection and transmits it to the electronic control unit.

[0004] The combined post-treatment device disclosed in the existing invention CN109162819A is applied to ammonia internal combustion engines and will have the following problems:

[0005] 1) In the equivalence ratio combustion mode, the emission of NH3 is much greater than the emission of NOx. Under a specific temperature range, the exhaust gas can eliminate most (more than 90%) NOx after passing through the TWC, but there is still a large amount of NH3 and H2 remaining, and the downstream SCR cannot oxidize NH3 and H2, resulting in the combined after-treatment device being unable to eliminate harmful pollutants in the exhaust gas;

[0006] 2) In the lean-burn combustion mode, NOx emissions slightly increase, while NH3 and H2 emissions slightly decrease. NH3 emissions are still much greater than NOx emissions. Since the exhaust contains oxygen, only part (less than 70%) of NOx can be eliminated after the exhaust passes through the TWC within a specific temperature range. However, most of the NH3 and H2 in the exhaust are oxidized (more than 95%). At this time, the downstream SCR cannot eliminate NOx due to insufficient NH3 and H2, which also causes the combined after-treatment device to be unable to eliminate harmful pollutants in the exhaust.

[0007] 3) In rich combustion mode, the situation is similar to that in equivalence ratio combustion mode;

[0008] In summary, the existing combined after-treatment device cannot efficiently treat harmful pollutants in the exhaust gas of ammonia internal combustion engines under any combustion mode, causing some harmful pollutants to be discharged into the atmosphere. Summary of the invention

[0009] The object of the present invention is to provide a post-treatment device and a post-treatment control method for an ammonia internal combustion engine to solve one or more technical problems existing in the prior art and at least provide a beneficial choice or create conditions.

[0010] The technical solutions adopted to solve the above technical problems are:

[0011] First, the present invention provides a post-treatment device for an ammonia internal combustion engine, which comprises: a three-way catalytic converter and a selective catalytic reduction device which are sequentially connected in series to the downstream of the exhaust pipe of the ammonia internal combustion engine, wherein the three-way catalytic converter is connected in parallel with a reducing gas bypass valve.

[0012] When in use, the three-way catalytic converter uses the catalyst therein to catalyze the three emissions of NH3, H2, and NOx in the exhaust gas at the same time, converting them into non-polluting N2 and H2O. However, since the exhaust gas contains O2 that does not participate in the combustion reaction, the three-way catalytic converter can oxidize most of the NH3 and H2 in the exhaust gas entering it, while the proportion of NOx in the exhaust gas being reduced is relatively low, resulting in a large amount of unreduced NOx and a small amount of reducing NH3 and H2 in the exhaust gas at the outlet of the three-way catalytic converter.

[0013] The reducing gas bypass valve provided in the present technology is in parallel with the three-way catalytic converter, which draws out a portion of the exhaust gas at the inlet of the three-way catalytic converter, and then draws this portion of the exhaust gas into the outlet of the three-way catalytic converter, where it merges with another portion of the exhaust gas flowing through the three-way catalytic converter and enters the selective catalytic reduction device. The exhaust gas of an ammonia internal combustion engine in lean-burn mode contains NH3, H2 and NOx gases of different concentrations, wherein the concentrations of NH3 and H2 are much greater than the concentration of NOx, and the concentrations of NH3, H2 and NOx in the exhaust gas drawn out through the reducing gas bypass valve meet this characteristic. However, as mentioned above, the concentrations of NH3 and H2 in the exhaust gas at the outlet of the three-way catalytic converter are much less than the concentration of NOx, and thus the opening of the reducing gas bypass valve can be controlled to control the amount of exhaust gas flowing through it, so that the concentrations of NH3, H2 and NOx in the exhaust gas entering the selective catalytic reduction device can be made reasonable;

[0014] The selective catalytic reduction device uses the catalytic effect of the catalyst in the device to make the reducing agents NH3 and H2 "selectively" react with NOx in the exhaust gas to generate non-toxic and non-polluting N2 and H2O. If the concentrations of NH3, H2 and NOx in the exhaust gas entering the selective catalytic reduction device are reasonable, most of the NOx is reduced to N2 and H2O by NH3 and H2 in the selective catalytic reduction device;

[0015] In addition, the optimal temperature range of the catalytic reaction in the selective catalytic reduction device is different depending on the type of catalyst. Except during low-temperature cold start, the low temperature will have a greater impact on the reaction rate (NOx conversion efficiency), the conversion efficiency of the selective catalytic reduction device is relatively high under most normal thermal engine conditions. The catalytic reaction of the three-way catalyst is mainly an exothermic reaction. The heat released can increase the downstream exhaust temperature, which is beneficial to the improvement of the conversion efficiency of the downstream selective catalytic reduction device, especially during the low-temperature start-up stage.

[0016] As a further improvement of the above technical solution, the catalyst of the three-way catalytic converter is a precious metal three-way catalyst or a non-precious metal catalyst. The precious metal three-way catalyst is a precious metal catalyst with platinum (Pt), palladium (Pd) and rhodium (Rh) as main components, and the non-precious metal catalyst is a perovskite catalyst.

[0017] As a further improvement of the above technical solution, the original gas bypass valve is an electrically controlled butterfly valve that can withstand high temperatures.

[0018] As a further improvement of the above technical solution, the catalyst of the selective catalytic reduction device is a supported precious metal catalyst, a metal oxide catalyst or a molecular sieve catalyst. The supported precious metal catalysts include Pt / Al2O3 and Pd / Al2O3, the metal oxide catalysts include vanadium-based, manganese-based and copper-based catalysts, and the molecular sieve catalysts include iron-based molecular sieve and copper-based molecular sieve catalysts.

[0019] As a further improvement of the above technical solution, the outlet of the selective catalytic reduction device is connected to an ammonia slip catalyst. In order to ensure the NOx conversion efficiency, the concentration of NH3 and H2 in the exhaust gas entering the selective catalytic reduction device often has a certain degree of surplus, so it is necessary to oxidize them before they are discharged into the atmosphere. The ammonia slip catalyst uses the catalyst in the device to catalyze the oxidation of NH3 and H2 discharged from the selective catalytic reduction device that have not participated in the reaction.

[0020] As a further improvement of the above technical solution, the catalyst of the ammonia slip catalyst is a precious metal catalyst, a metal oxide catalyst or a molecular sieve catalyst. Precious metal catalysts include Pt, Pd, silver (Ag) and ruthenium (Ru) catalysts, metal oxide catalysts include vanadium pentoxide (V2O5), manganese dioxide (MnO2) and ferric oxide (Fe2O3) catalysts, and molecular sieve catalysts include iron-based molecular sieves and copper-based molecular sieve catalysts.

[0021] As a further improvement of the above technical solution, an exhaust gas temperature sensor is provided at the inlet of the selective catalytic reduction device. The exhaust gas temperature sensor is used to detect the exhaust gas temperature at the inlet of the selective catalytic reduction device, so as to determine whether the inlet temperature of the selective catalytic reduction device is sufficient to enable the selective catalytic reduction reaction, and to determine the reaction rate of the selective catalytic reduction reaction (NOx conversion efficiency).

[0022] As a further improvement of the above technical solution, a NOx concentration sensor is provided at the outlet of the selective catalytic reduction device. The NOx concentration sensor is used to detect the NOx concentration at the outlet of the selective catalytic reduction device.

[0023] As a further improvement of the above technical solution, it also includes an electronic control unit that is simultaneously connected to the NOx concentration sensor, the exhaust temperature sensor, and the reducing gas bypass valve signal, and the electronic control unit is used to receive the signals of the NOx concentration sensor and the exhaust temperature sensor to control the opening of the reducing gas bypass valve.

[0024] The electronic control unit collects signals from the exhaust temperature sensor and the NOx concentration sensor, and generates corresponding control outputs according to the internal control logic. The control output acts on the reducing gas bypass valve, adjusts the opening of the reducing gas bypass valve, and reasonably distributes the ratio of exhaust gas flowing through the three-way catalytic converter and the reducing gas bypass valve, ensuring that the concentrations of NH3, H2 and NOx at the inlet of the selective catalytic reduction device are reasonable, so that the selective catalytic reduction device can eliminate NOx in the exhaust gas as much as possible.

[0025] In addition, the present invention also provides a post-processing control method for an ammonia internal combustion engine, which adopts the above-mentioned post-processing device, and the specific steps are as follows:

[0026] S1, ammonia internal combustion engine start;

[0027] S2, the ammonia internal combustion engine enters the operating state, and the reducing gas bypass valve is kept closed;

[0028] S3, perform a temperature determination step, compare the exhaust gas temperature at the inlet of the selective catalytic reduction device with the preset limit value: if the limit value is not reached, keep the reducing gas bypass valve fully closed; if the limit value is reached, adjust the opening of the reducing gas bypass valve according to the preset value, control the concentrations of NH3, H2 and NOx in the exhaust gas at the inlet of the selective catalytic reduction device, and enter the NOx concentration determination step;

[0029] S4. In the NOx concentration determination link, the NOx concentration at the outlet of the selective catalytic reduction device is compared with the preset limit value. If it does not meet the limit, the opening of the reducing gas bypass valve is corrected according to the NOx concentration and the exhaust temperature at the inlet of the selective catalytic reduction device, thereby realizing closed-loop control. If it meets the limit, the opening of the reducing gas bypass valve is maintained and the shutdown determination link is entered;

[0030] S5. In the shutdown determination link, if there is a shutdown request, the ammonia internal combustion engine performs a shutdown operation, otherwise it returns to the NOx concentration determination link.

[0031] The post-processing control method of the present invention is decoupled from the combustion control of the engine, and there is no need to change the combustion mode due to emission reasons. The combustion process of the ammonia internal combustion engine is organized by maintaining a preset lean combustion degree.

[0032] The beneficial effects of the present invention are:

[0033] By controlling the exhaust gas diversion ratio of the reducing gas bypass valve and utilizing the oxidation heat release of NH3 and H2 in the three-way catalyst, the conversion efficiency of the selective catalytic reduction device can be improved, and the emission of harmful pollutants in the exhaust of an ammonia internal combustion engine can be treated more efficiently, and the emission of harmful pollutants in the exhaust can be prevented from being discharged into the atmosphere; an ammonia internal combustion engine using the post-treatment device of the present invention can continuously operate in a lean burn mode, thereby improving the thermal efficiency of the engine; using the post-treatment device of the present invention and the control method thereof, the emission control of the post-treatment can be decoupled from the combustion control of the engine, thereby improving the stability and robustness of the emission control and simplifying the calibration work of the internal combustion engine and the exhaust post-treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The present invention will be further described below in conjunction with the accompanying drawings and embodiments;

[0035] Figure 1 This is a schematic diagram of an embodiment of a post-treatment device for an ammonia internal combustion engine provided by the present invention;

[0036] Figure 2The present invention provides a post-treatment device for an ammonia internal combustion engine, and a control flow chart of one embodiment thereof. DETAILED DESCRIPTION

[0037] This section will describe in detail the specific embodiments of the present invention. The preferred embodiments of the present invention are shown in the accompanying drawings. The purpose of the accompanying drawings is to supplement the description of the text part of the specification with graphics, so that people can intuitively and vividly understand each technical feature and the overall technical solution of the present invention, but it cannot be understood as a limitation on the scope of protection of the present invention.

[0038] In the description of the present invention, it should be understood that descriptions involving orientations, such as up, down, front, back, left, right, etc., and orientations or positional relationships indicated are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0039] In the description of the present invention, if there are words such as "several", it means one or more, "more" means more than two, greater than, less than, exceed, etc. are understood as not including the number, and above, below, within, etc. are understood as including the number.

[0040] In the description of the present invention, unless otherwise clearly defined, terms such as setting, installing, connecting, etc. should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in the present invention based on the specific content of the technical solution.

[0041] At present, the commercial technology for exhaust treatment of gasoline and natural gas vehicles is to use a three-way catalytic converter (TWC) to control the emission of pollutants and control the internal combustion engine to operate near the chemical equivalent air-fuel ratio. The catalyst in the three-way catalytic converter converts the three pollutants in the exhaust gas, namely carbon monoxide (CO), hydrocarbons (HC) and nitrogen oxides (NOx), into carbon dioxide (CO2), nitrogen (N2) and water (H2O) at the same time, so that the three major pollutants are eliminated on one catalyst at the same time. In order to achieve the best pollutant conversion rate (more than 90%), it is necessary to use a closed-loop method through the electronic control system to control the air-fuel ratio of the internal combustion engine in a narrow, near-ideal area (theoretical air-fuel ratio). If the air-fuel ratio is large (lean combustion), although the conversion rates of CO and HC are slightly improved, the conversion rate of NOx drops sharply to 20%. Similarly, when the intake air of the three-way catalytic converter contains ammonia (NH3), hydrogen (H2) and NOx, under the catalytic action of the catalyst, NOx is reduced to N2 and H2O by NH3 and H2, and all of them will be eliminated in a proper ratio, with a very high conversion efficiency (conversion efficiency greater than 95%). However, when there is additional O2 in the intake air, NH3 and H2 will be oxidized by O2 first, and the NOx conversion efficiency will drop significantly.

[0042] At present, diesel engine aftertreatment devices use selective catalytic reduction devices (SCR). SCR technology is used to reduce NOx emissions in exhaust gas. It adds ammonia (NH3) by injecting urea and undergoes a selective reduction reaction with NOx, converting NOx into environmentally friendly N2.

[0043] Since the existing combined after-treatment device cannot effectively treat harmful pollutants in the exhaust gas of an ammonia fuel internal combustion engine under any combustion mode, some harmful pollutants are discharged into the atmosphere.

[0044] Reference Figure 1-2 The present invention provides a post-treatment device for an ammonia internal combustion engine in the following embodiments:

[0045] like Figure 1 As shown, the post-treatment device of this embodiment includes an ammonia internal combustion engine, a three-way catalyst 100 , and a selective catalytic reduction device 200 .

[0046] It will be understood by those skilled in the art that the ammonia internal combustion engine is a reciprocating piston four-stroke internal combustion engine known in the art that uses liquid ammonia or gaseous ammonia as the main fuel, and the combustion mode of the ammonia internal combustion engine in the present invention is a lean combustion mode, which can improve the thermal efficiency of the internal combustion engine and achieve higher fuel economy. At the same time, because it is a lean combustion mode, the exhaust gas of the internal combustion engine contains some O2 that does not participate in combustion.

[0047] The ammonia internal combustion engine is provided with an intake pipe and an exhaust pipe. The intake pipe is used to introduce fresh air into the internal combustion engine and participate in combustion together with the ammonia fuel, and the exhaust pipe is used to lead out the exhaust gas of the internal combustion engine. Those skilled in the art will understand that the intake pipe and the exhaust pipe are the intake pipe and the exhaust pipe of the internal combustion engine known in the art.

[0048] The three-way catalytic converter 100 and the selective catalytic reduction device 200 are connected in series in the downstream of the exhaust pipe. The three-way catalytic converter 100 uses the catalyst therein to catalyze the three emissions of NH3, H2, and NOx in the exhaust gas at the same time to convert them into non-polluting N2 and H2O, while the selective catalytic reduction device 200 uses the catalytic effect of the catalyst in the device to make the reducing agents NH3 and H2 "selectively" react with NOx in the exhaust gas to generate non-toxic and non-polluting N2 and H2O.

[0049] In addition to the three-way catalytic converter 100, a reducing gas bypass valve 300 is also provided in parallel between the exhaust pipe and the selective catalytic reduction device 200, so that part of the exhaust gas in the exhaust pipe flows through the three-way catalytic converter 100, and another part flows through the reducing gas bypass valve 300, and finally the two parts of the exhaust gas merge together and enter the selective catalytic reduction device 200.

[0050] Among them, the catalyst of the three-way catalytic converter 100 of this embodiment adopts one of a precious metal three-way catalyst or a non-precious metal catalyst. The precious metal three-way catalyst adopts a precious metal catalyst with platinum (Pt), palladium (Pd), and rhodium (Rh) as main components, while the non-precious metal catalyst adopts a perovskite catalyst.

[0051] The catalyst of the selective catalytic reduction device 200 adopts one of the supported precious metal catalysts, metal oxide catalysts or molecular sieve catalysts, wherein the supported precious metal catalysts include Pt / Al2O3 and Pd / Al2O3, the metal oxide catalysts include vanadium-based, manganese-based and copper-based catalysts, and the molecular sieve catalysts include iron-based molecular sieve and copper-based molecular sieve catalysts.

[0052] When in use, the three-way catalytic converter 100 utilizes the catalyst therein to simultaneously catalyze the reaction of the three emissions of NH3, H2, and NOx in the exhaust gas, converting them into pollution-free N2 and H2O. However, since the exhaust gas contains O2 that does not participate in the combustion reaction, the three-way catalytic converter 100 can oxidize most of the NH3 and H2 in the exhaust gas entering it, while the proportion of NOx reduced in the exhaust gas is relatively low, resulting in a large amount of unreduced NOx and a small amount of reducing NH3 and H2 in the exhaust gas at the outlet of the three-way catalytic converter 100.

[0053] The reducing gas bypass valve 300 provided in the present technology is in parallel with the three-way catalyst 100, which draws out a part of the exhaust gas at the inlet of the three-way catalyst 100, and then draws the part of the exhaust gas into the outlet of the three-way catalyst 100, and merges with another part of the exhaust gas flowing through the three-way catalyst 100 to enter the selective catalytic reduction device. The exhaust gas of the ammonia internal combustion engine using the lean combustion mode contains different concentrations of NH3, H2 and NOx gases, wherein the concentrations of NH3 and H2 are much greater than the concentration of NOx, and the concentrations of NH3, H2 and NOx in the exhaust gas drawn out through the reducing gas bypass valve 300 meet this feature, but as mentioned above, the concentrations of NH3 and H2 in the exhaust gas at the outlet of the three-way catalyst 100 are much less than the concentration of NOx, and thus the concentrations of NH3, H2 and NOx in the exhaust gas entering the selective catalytic reduction device 200 can be made reasonable by controlling the opening of the reducing gas bypass valve 300 and controlling the amount of exhaust gas flowing through it.

[0054] Since the selective catalytic reduction device 200 utilizes the catalytic effect of the catalyst in the device to make the reducing agents NH3 and H2 "selectively" react with NOx in the exhaust gas to generate non-toxic and non-polluting N2 and H2O, as mentioned above, the concentrations of NH3, H2 and NOx in the exhaust gas entering the selective catalytic reduction device 200 are reasonable, and most of the NOx is reduced to N2 and H2O by NH3 and H2 in the selective catalytic reduction device 200.

[0055] In addition, the optimal temperature range of the catalytic reaction in the selective catalytic reduction device 200 is different depending on the type of catalyst. Except during low-temperature cold start, the reaction rate (NOx conversion efficiency) will be greatly affected due to the low temperature. Under most normal thermal engine conditions, the conversion efficiency of the selective catalytic reduction device 200 is relatively high. The catalytic reaction of the three-way catalyst 100 is mainly an exothermic reaction. The heat released can increase the downstream exhaust temperature, which is beneficial to the improvement of the conversion efficiency of the downstream selective catalytic reduction device 200, especially during the low-temperature start-up stage.

[0056] In addition, in this embodiment, an exhaust temperature sensor 500 is installed at the inlet of the selective catalytic reduction device 200. The exhaust temperature sensor 500 is used to detect the exhaust temperature at the inlet of the selective catalytic reduction device 200, so as to determine whether the inlet temperature of the selective catalytic reduction device 200 is sufficient to enable it to perform a selective catalytic reduction reaction, and at the same time determine the reaction rate of the selective catalytic reduction reaction (NOx conversion efficiency).

[0057] Furthermore, in order to ensure the conversion efficiency of NOx, the concentration of NH3 and H2 in the exhaust gas entering the selective catalytic reduction device 200 is often surplus to a certain extent, so it is necessary to oxidize them before they are discharged into the atmosphere. The downstream of the selective catalytic reduction device 200 of this embodiment is provided with an ammonia slip catalyst 400. At present, the diesel engine aftertreatment device also uses an ammonia slip catalyst (ASC, Ammonia Slip Catalyst). ASC technology is an emerging technology that can effectively convert ammonia into nitrogen. It is used as the final unit of the diesel vehicle aftertreatment system at this stage to treat the leaked NH3. The ammonia slip catalyst 400 of this embodiment uses the catalyst in the device to catalytically oxidize the NH3 and H2 that have not participated in the reaction discharged from the selective catalytic reduction device 200.

[0058] The catalyst of the ammonia slip catalyst 400 uses a precious metal catalyst, a metal oxide catalyst or a molecular sieve catalyst. Precious metal catalysts include Pt, Pd, silver (Ag) and ruthenium (Ru) catalysts, metal oxide catalysts include vanadium pentoxide (V2O5), manganese dioxide (MnO2) and ferric oxide (Fe2O3) catalysts, and molecular sieve catalysts include iron-based molecular sieve catalysts and copper-based molecular sieve catalysts.

[0059] A NOx concentration sensor 600 is installed between the selective catalytic reduction device 200 and the ammonia slip catalyst 400. The NOx concentration sensor 600 is used to detect the NOx concentration at the outlet of the selective catalytic reduction device 200.

[0060] In order to realize automatic control, the present embodiment further includes an electronic control unit 700, which is connected to the NOx concentration sensor 600 via a data line, and collects a signal representing the NOx concentration output by the NOx concentration sensor 600. The electronic control unit 700 is connected to the exhaust temperature sensor 500 via a data line, and collects a signal representing the exhaust temperature output by the exhaust temperature sensor 500. The electronic control unit 700 is connected to the reducing gas bypass valve 300 via a data line, and the electronic control unit 700 outputs a control signal to control the opening of the reducing gas bypass valve 300.

[0061] The electronic control unit 700 collects signals from the exhaust temperature sensor 500 and the NOx concentration sensor 600, and generates corresponding control outputs according to the internal control logic. The control output acts on the reducing gas bypass valve 300, adjusts the opening of the reducing gas bypass valve 300, and reasonably distributes the ratio of the exhaust gas flowing through the three-way catalytic converter 100 and the reducing gas bypass valve 300, ensuring that the concentrations of NH3, H2 and NOx at the inlet of the selective catalytic reduction device 200 are reasonable, so that the selective catalytic reduction device 200 can eliminate NOx in the exhaust gas as much as possible.

[0062] Preferably, the reducing gas bypass valve 300 is a butterfly valve capable of withstanding high temperatures. Those skilled in the art will appreciate that the reducing gas bypass valve 300 may be any valve known in the art capable of achieving flow control.

[0063] Using the post-treatment device of the present invention, the corresponding emission control method is as follows:

[0064] S1. The ammonia internal combustion engine starts to start. The starting method can use any known control method, which will not be described in detail in the present invention.

[0065] S2, the ammonia internal combustion engine enters the operating state, and according to the pre-setting of the electronic control system, the reducing gas bypass valve 300 is controlled to remain fully closed. At this time, the internal combustion engine is in the gradual warm-up process, and the exhaust gas of the exhaust pipes of all internal combustion engines passes through the three-way catalytic converter 100, so that the three-way catalytic converter 100 is heated up as quickly as possible to reach the working state. Next, the temperature determination link is carried out.

[0066] S3, in the temperature determination link, the electronic control unit 700 compares the temperature signal value output by the exhaust temperature sensor 500 with the preset limit value, and determines whether the exhaust temperature at the inlet of the selective catalytic reduction device 200 reaches the limit value. If the limit value is not reached, the reducing gas bypass valve 300 is still kept fully closed. If the limit value is reached, the opening of the reducing gas bypass valve 300 is adjusted according to the preset setting of the electronic control unit 700 to control the concentrations of NH3, H2 and NOx in the exhaust gas at the inlet of the selective catalytic reduction device 200, and enter the NOx concentration determination link.

[0067] S4, in the NOx concentration determination link, the electronic control unit 700 compares the NOx concentration signal value of the exhaust NOx concentration sensor 600 with the preset limit value to determine whether the NOx concentration at the outlet of the selective catalytic reduction device 200 meets the standard, that is, whether the selective catalytic reduction device 200 efficiently processes NOx in the exhaust gas. If it does not meet the standard, the electronic control unit 700 corrects the opening of the reducing gas bypass valve 300 according to the NOx concentration and the temperature signal of the exhaust temperature sensor, thereby realizing closed-loop control. If it meets the standard, the opening of the reducing gas bypass valve 300 is maintained, and the shutdown determination link is entered.

[0068] S5, in the shutdown determination link, determine whether there is an engine shutdown request. If there is a shutdown request, the engine is shut down, otherwise it returns to the NOx concentration determination link.

[0069] According to the above emission control method and the working process of the ammonia internal combustion engine, the output of the emission control method (the opening of the reducing gas bypass valve 300) is limited to the after-treatment device, and there is no need to adjust the lean combustion degree of the internal combustion engine to increase the concentration of NH3 and H2 in the exhaust gas, that is, the emission control method is decoupled from the combustion control of the engine.

[0070] This embodiment improves the conversion efficiency of the selective catalytic reduction device 200 by controlling the exhaust gas diversion ratio of the reducing gas bypass valve 300 and utilizing the oxidation heat release of NH3 and H2 in the three-way catalyst 100, which can more efficiently treat the emission of harmful pollutants in the exhaust gas of the ammonia internal combustion engine and prevent harmful pollutants from being discharged into the atmosphere; the ammonia internal combustion engine using the after-treatment device of the present invention can continuously operate in the lean burn mode, thereby improving the thermal efficiency of the engine; the after-treatment device and the control method thereof of the present invention can achieve decoupling of the emission control of the after-treatment and the combustion control of the engine, thereby improving the stability and robustness of the emission control and simplifying the calibration work of the internal combustion engine and the exhaust after-treatment.

[0071] The preferred embodiments of the present invention are specifically described above, but the invention is not limited to the embodiments. Those skilled in the art may make various equivalent modifications or substitutions without violating the spirit of the invention. These equivalent modifications or substitutions are all included in the scope defined by the claims of this application.

Claims

1. A post-treatment control method for an ammonia internal combustion engine, applicable to a post-treatment device of an ammonia internal combustion engine, characterized in that: The post-treatment device of an ammonia internal combustion engine comprises: a three-way catalytic converter (100) and a selective catalytic reduction device (200) which are sequentially connected in series to the downstream of an exhaust pipe of the ammonia internal combustion engine, wherein the three-way catalytic converter (100) is connected in parallel to a reducing gas bypass valve (300); The outlet of the selective catalytic reduction device (200) is connected to an ammonia slip catalyst (400); An exhaust temperature sensor (500) is provided at the inlet of the selective catalytic reduction device (200); The outlet of the selective catalytic reduction device (200) is provided with a NOx concentration sensor (600); It also includes an electronic control unit (700) connected to the NOx concentration sensor (600), the exhaust temperature sensor (500), and the reducing gas bypass valve (300) signals at the same time, the electronic control unit (700) being used to receive signals from the NOx concentration sensor (600) and the exhaust temperature sensor (500) to control the opening of the reducing gas bypass valve (300); The post-treatment control method of an ammonia internal combustion engine has the following specific steps: S1, ammonia internal combustion engine start; S2, the ammonia internal combustion engine enters the operating state, and the reducing gas bypass valve (300) is kept closed; S3, performing a temperature determination step, comparing the exhaust gas temperature at the inlet of the selective catalytic reduction device (200) with a preset limit value: if the limit value is not reached, keeping the reducing gas bypass valve (300) fully closed; if the limit value is reached, adjusting the opening of the reducing gas bypass valve (300) according to the preset value, and controlling the exhaust gas temperature at the inlet of the selective catalytic reduction device (200). and , NOx concentrations, and enter the NOx concentration determination link; S4. In the NOx concentration determination link, the NOx concentration at the outlet of the selective catalytic reduction device (200) is compared with a preset limit value. If the limit value is not reached, the opening of the reducing gas bypass valve (300) is corrected according to the NOx concentration and the exhaust gas temperature at the inlet of the selective catalytic reduction device (200), thereby realizing closed-loop control. If the limit value is reached, the opening of the reducing gas bypass valve (300) is maintained, and the shutdown determination link is entered; S5. In the shutdown determination link, if there is a shutdown request, the ammonia internal combustion engine performs a shutdown operation, otherwise it returns to the NOx concentration determination link.

2. The post-treatment control method of an ammonia internal combustion engine according to claim 1, characterized in that: The catalyst of the three-way catalytic converter (100) is a precious metal three-way catalyst or a non-precious metal catalyst.

3. The post-treatment control method of an ammonia internal combustion engine according to claim 1, characterized in that: The primary gas bypass valve (300) is an electrically controlled butterfly valve capable of withstanding high temperatures.

4. The post-treatment control method of an ammonia internal combustion engine according to claim 1, characterized in that: The catalyst of the selective catalytic reduction device (200) is a supported precious metal catalyst, a metal oxide catalyst or a molecular sieve catalyst.

5. The post-treatment control method of an ammonia internal combustion engine according to claim 1, characterized in that: The catalyst of the ammonia slip catalyst (400) is a precious metal catalyst, a metal oxide catalyst or a molecular sieve catalyst.

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