Integrated purification aftertreatment device for unburned ammonia and nox of ammonia fuel engine and working method

Abstract

The application provides an ammonia fuel engine unburned ammonia and NOx integrated purification aftertreatment device and working method, which comprises an ammonia fuel engine, an ammonia oxidation catalyst, an ammonia oxidation catalyst bypass valve, an ammonia oxidation catalyst bypass pipeline, a mixer and a selective catalytic reducer; the ammonia fuel engine is sequentially connected with the ammonia oxidation catalyst, the mixer and the selective catalytic reducer; one end of the ammonia oxidation catalyst bypass pipeline is connected between the ammonia fuel engine and the ammonia oxidation catalyst, and the other end is connected with the mixer, and the ammonia oxidation catalyst bypass valve is arranged on the ammonia oxidation catalyst bypass pipeline. According to the exhaust composition of the ammonia fuel engine under different working conditions, the opening degree of the ammonia oxidation catalyst bypass valve can be flexibly controlled, the ideal ammonia and NOx ratio before the selective catalytic reducer is realized, the target of integrated purification of unburned ammonia and NOx in the exhaust of the ammonia fuel engine is achieved, and additional reducing agent injection is avoided.

Description

Technical Field

[0001] This invention relates to the field of ammonia fuel engines and emission aftertreatment, specifically to an integrated purification and aftertreatment device and operating method for unburned ammonia and NOx in ammonia fuel engines. Background Technology

[0002] Traditional diesel engines typically employ a selective catalytic reduction (SCR) and an ammonia oxidation catalyst (ASC) to sequentially treat NOx emissions from the engine exhaust and a small amount of unreacted ammonia from the SCR. Ammonia-fueled engines primarily emit NOx and unburned ammonia, and the poor combustion characteristics of ammonia often result in an excess of unburned ammonia in the exhaust compared to NOx under most operating conditions. Continuing to use traditional diesel engine aftertreatment devices would lead to the re-generation of large amounts of byproducts NOx and N2O during the ASC catalytic oxidation of ammonia, making it difficult to meet emission regulations.

[0003] Patent document CN114856764A discloses an exhaust gas treatment system, engine, and ship for an ammonia fuel engine, applicable to the field of exhaust gas treatment technology. The system removes water from the engine exhaust gas using a first dehydration device. A nitrogen oxide (NOx) trap reacts the dehydrated exhaust gas with hydrogen to generate a small amount of ammonia. A portion of the exhaust gas output from the NOx trap is collected through a pipeline, and the waste heat is used to heat an ammonia synthesis device. The remaining exhaust gas and ammonia are then output to a heat exchanger. A denitrification device reduces the exhaust gas and ammonia to nitrogen and water. A liquid nitrogen heat exchanger separates the non-condensable gases and collects the ammonia. Nitrous oxide and water are then removed through a water tank and a second dehydration device. Finally, a nitrogen separation device separates nitrogen and oxygen, thus achieving ammonia collection and waste gas recovery. Patent document CN217206623U discloses an aftertreatment device for exhaust gas from a hydrogen-ammonia fuel engine, including an exhaust catalytic converter and an ammonia supply device. The exhaust catalytic converter converts ammonia (NH3) and nitrogen oxides (NOx) in the exhaust gas, and the ammonia supply device supplies ammonia (NH3) to the exhaust catalytic converter. The exhaust catalytic converter includes a first SCR catalyst, a first exhaust pipe, a second SCR catalyst, a second exhaust pipe, and an ammonia escape catalyst (ASC) connected in sequence. The inlet of the first SCR catalyst is connected to the exhaust pipe outlet of the hydrogen-ammonia fuel engine, and the end of the ammonia supply device is installed on the first exhaust pipe. Currently available exhaust gas treatment devices are complex in structure, require an additional supply of ammonia as a reducing agent, and fail to achieve integrated purification. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the purpose of this invention is to provide an integrated purification and after-treatment device and operating method for unburned ammonia and NOx in ammonia fuel engines.

[0005] According to the present invention, an integrated purification and after-treatment device for unburned ammonia and NOx in an ammonia fuel engine includes: an ammonia oxidation catalyst, an ammonia oxidation catalyst bypass valve, an ammonia oxidation catalyst bypass pipeline, a mixer, and a selective catalytic reduction device.

[0006] The ammonia fuel engine is sequentially connected to the ammonia oxidation catalyst, the mixer, and the selective catalytic reduction unit;

[0007] One end of the ammonia oxidation catalyst bypass pipeline is connected between the ammonia fuel engine and the ammonia oxidation catalyst, and the other end is connected to the mixer. The ammonia oxidation catalyst bypass valve is installed on the ammonia oxidation catalyst bypass pipeline.

[0008] Preferably, a first NOx sensor and a first ammonia sensor are provided between the ammonia oxidation catalyst and the ammonia fuel engine, a second NOx sensor and a second ammonia sensor are provided between the mixer and the selective catalytic reduction unit, and a third NOx sensor and a third ammonia sensor are provided at the end of the selective catalytic reduction unit away from the mixer.

[0009] Preferably, a reducing agent injector is provided between the selective catalytic reducer and the mixer, and the reducing agent is injected through the reducing agent injector.

[0010] Preferably, the ammonia oxidation catalyst bypass valve, the reducing agent injector, the first NOx sensor, the second NOx sensor, the third NOx sensor, the first ammonia sensor, the second ammonia sensor, and the third ammonia sensor are connected to the controller.

[0011] Preferably, the ammonia oxidation catalyst has a built-in shut-off valve at one end near the ammonia fuel engine.

[0012] Preferably, the reducing agent sprayed includes ammonia gas, ammonia water, and urea.

[0013] Preferably, the selective catalytic reducer includes: a noble metal catalyst, a metal oxide catalyst, and a molecular sieve catalyst;

[0014] The catalyst types of the noble metal catalyst include Pt / Al2O3 and Pd / Al2O3, the catalyst types of the metal oxide catalyst include V-based, Mn-based and Cu-based, and the catalyst types of the molecular sieve catalyst include Fe-based molecular sieve and Cu-based molecular sieve.

[0015] Preferably, the ammonia oxidation catalyst includes: a noble metal catalyst, a transition metal oxide catalyst, and a molecular sieve catalyst;

[0016] The catalyst types of the noble metal catalyst include Pt, Pd, Ag and Ru, the catalyst types of the transition metal oxide catalyst include V2O5, MnO2 and Fe2O3, and the types of molecular sieve catalysts include ZSM-5 molecular sieve, SAPO-34 molecular sieve and SSZ-13 molecular sieve.

[0017] Preferably, the operating modes of the ammonia fuel engine include spark ignition, diesel ignition, low-carbon / zero-carbon fuel ignition, pre-combustion chamber thermal turbulent jet ignition, and direct compression ignition.

[0018] Preferably, the catalyst of the selective catalytic reducer adsorbs and stores the reducing agent ammonia.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] This invention can flexibly control the opening of the bypass valve of the ammonia oxidation catalyst according to the exhaust gas composition under different operating conditions of the ammonia fuel engine, so as to achieve the ideal ammonia-to-nitrogen ratio (NH3 / NOx) before the selective catalytic reducer, and achieve the goal of purifying unburned ammonia and NOx in the exhaust gas of the ammonia fuel engine in an integrated manner, while eliminating the need for additional reducing agent injection. Attached Figure Description

[0021] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0022] Figure 1 Schematic diagram of an integrated purification and post-treatment device;

[0023] As shown in the figure:

[0024] Detailed Implementation

[0025] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0026] Example 1

[0027] like Figure 1As shown, this embodiment includes: an ammonia oxidation catalyst 2, an ammonia oxidation catalyst bypass valve 3, an ammonia oxidation catalyst bypass pipeline 4, a mixer 5, and a selective catalytic reduction (SCR) 6. An ammonia fuel engine 1 is sequentially connected to the ammonia oxidation catalyst 2, the mixer 5, and the SCR 6. One end of the ammonia oxidation catalyst bypass pipeline 4 is connected between the ammonia fuel engine 1 and the ammonia oxidation catalyst 2, and the other end is connected to the mixer 5. The ammonia oxidation catalyst bypass valve 3 is installed on the ammonia oxidation catalyst bypass pipeline 4. A shut-off valve is built into the end of the ammonia oxidation catalyst 2 closest to the ammonia fuel engine 1. A reducing agent injector 7 is installed between the SCR 6 and the mixer 5, and a reducing agent is injected through the reducing agent injector 7. The catalyst in the SCR 6 adsorbs and stores the reducing agent ammonia. The injected reducing agent includes ammonia gas, ammonia water, and urea.

[0028] A first NOx sensor 801 and a first ammonia sensor 901 are installed between the ammonia oxidation catalyst 2 and the ammonia fuel engine 1. A second NOx sensor 802 and a second ammonia sensor 902 are installed between the mixer 5 and the selective catalytic reduction unit 6. A third NOx sensor 803 and a third ammonia sensor 903 are installed at the end of the selective catalytic reduction unit 6 away from the mixer 5. The ammonia oxidation catalyst bypass valve 3, the reductant injector 7, the first NOx sensor 801, the second NOx sensor 802, the third NOx sensor 803, the first ammonia sensor 901, the second ammonia sensor 902, and the third ammonia sensor 903 are connected to the controller 10.

[0029] In one embodiment, the ammonia oxidation catalyst 2 includes: a noble metal catalyst, a transition metal oxide catalyst, and a molecular sieve catalyst; the catalyst of the noble metal catalyst includes Pt, Pd, Ag, and Ru, the catalyst of the transition metal oxide catalyst includes V₂O₅, MnO₂, and Fe₂O₃, and the molecular sieve catalyst includes ZSM-5 molecular sieve, SAPO-34 molecular sieve, and SSZ-13 molecular sieve. The selective catalytic reduction catalyst 6 includes: a noble metal catalyst, a metal oxide catalyst, and a molecular sieve catalyst; the catalyst of the noble metal catalyst includes Pt / Al₂O₃ and Pd / Al₂O₃, the catalyst of the metal oxide catalyst includes V-based, Mn-based, and Cu-based catalysts, and the molecular sieve catalyst includes Fe-based molecular sieves and Cu-based molecular sieves.

[0030] In one embodiment, the operating modes of the ammonia fuel engine 1 include spark ignition, diesel ignition, low-carbon / zero-carbon fuel ignition, pre-combustion chamber thermal turbulent jet ignition, and direct compression ignition.

[0031] This embodiment also provides a method for operating the integrated purification and post-treatment device, including the following steps:

[0032] Step S1: The ammonia fuel engine 1 emits exhaust gas containing unburned ammonia and NOx. The first NOx sensor 801 and the first ammonia sensor 901 measure the NOx and unburned ammonia content in the exhaust gas, respectively, and feed the results back to the controller 10. Step S2: The exhaust gas passes through the ammonia oxidation catalyst 2 and the mixer 5 before being sent to the selective catalytic reduction reactor 6 for reaction. Step S3: When unburned ammonia is in excess compared to NOx in the reaction, the controller 10 controls the opening of the ammonia oxidation catalyst bypass valve 3 in real time based on the measurements from the second NOx sensor 802 and the second ammonia sensor 902. Part of the exhaust gas enters the mixer 5 from the ammonia oxidation catalyst bypass pipe 4 and mixes with the gas catalyzed by the ammonia oxidation catalyst 2, ensuring selective catalytic reduction. A suitable ammonia-to-nitrogen ratio (NH3 / NOx) is established before the selective catalytic reduction (SCR) unit 6. In step S4, when NOx is in excess compared to unburned ammonia in the reaction, the built-in shut-off valve of the ammonia oxidation catalyst 2 is closed, stopping the operation of the ammonia oxidation catalyst 2. Simultaneously, the controller 10 calculates the additional reducing agent requirement and controls the reducing agent injector 7 to inject additional reducing agent before the selective catalytic reduction unit 6. In step S5, the balanced unburned ammonia and NOx react in the selective catalytic reduction unit 6, thereby achieving integrated purification. In step S6, the third NOx sensor 803 and the third ammonia sensor 903 further measure the gas emitted from the selective catalytic reduction unit 6 and feed it back to the controller 10. The controller 10 confirms that the exhaust gas meets emission standards based on the measurement results.

[0033] Example 2

[0034] Example 2 is a preferred example of Example 1.

[0035] like Figure 1 As shown, this embodiment includes: an ammonia oxidation catalyst 2, an ammonia oxidation catalyst bypass valve 3, an ammonia oxidation catalyst bypass pipeline 4, a mixer 5, a selective catalytic reducer 6, a reducing agent injector 7, and a controller 10.

[0036] The ammonia oxidation catalyst 2, mixer 5, and selective catalytic reduction unit 6 are connected in sequence and are located downstream of the ammonia fuel engine 1; the ammonia oxidation catalyst bypass valve 3 and the ammonia oxidation catalyst bypass pipeline 4 are connected in sequence and in parallel with the ammonia oxidation catalyst 2. In a specific embodiment, one or more of the ammonia oxidation catalyst 2, ammonia oxidation catalyst bypass valve 3, ammonia oxidation catalyst bypass pipeline 4, and mixer 5 can be arbitrarily integrated and combined.

[0037] NOx and unburned ammonia in the exhaust gas of ammonia fuel engine 1 are measured by the first NOx sensor 801 and the first ammonia sensor 901, respectively. NOx and ammonia after ammonia oxidation catalyst 2 are measured by the second NOx sensor 802 and the second ammonia sensor 902, respectively. NOx and ammonia after selective catalytic reduction 6 are measured by the third NOx sensor 803 and the third ammonia sensor 903, respectively.

[0038] For the condition where unburned ammonia exceeds NOx in the SCR reaction of the ammonia fuel engine 1 exhaust gas, the controller 10 controls the opening of the ammonia oxidation catalyst bypass valve 3 in real time based on the measurements from the second NOx sensor 802 and the second ammonia sensor 902. This ensures a suitable ammonia-to-nitrogen ratio (NH3 / NOx) before the selective catalytic reducer 6, achieving integrated purification of unburned ammonia and NOx in the ammonia fuel engine exhaust gas. For the same condition, the controller 10 calculates the additional reductant requirement and controls the reductant injector 7 to inject additional reductant before the selective catalytic reducer 6.

[0039] The ammonia oxidation catalyst 2 is pre-stopped by a valve that stops its operation when NOx is excessive in the exhaust gas of the ammonia-fueled engine 1, ensuring that all unburned ammonia in the exhaust gas is used for NOx reduction and minimizing additional reductant injection. The adsorption characteristics of the catalyst in the selective catalytic reduction unit 6 can be utilized to store reductant ammonia, thereby improving the overall energy efficiency of the aftertreatment system and addressing changes in exhaust composition caused by varying operating conditions.

[0040] Based on the measurements from the second NOx sensor 802, the second ammonia sensor 902, the third NOx sensor 803, and the third ammonia sensor 903, the controller 10 calculates the amount of ammonia stored in the selective catalytic reducer 6 in real time and controls the opening of the ammonia oxidation catalyst bypass valve 3 to ensure that the amount stored is maintained within the set value range.

[0041] The reducing agent injected by the reducing agent injector 7 can be ammonia, ammonia water, or urea.

[0042] The operating modes of the ammonia fuel engine 1 can be spark ignition, diesel ignition, low-carbon / zero-carbon fuel ignition, pre-combustion chamber thermal turbulent jet ignition, direct compression ignition, etc.

[0043] The selective catalytic reducer 6 can be a noble metal catalyst, a metal oxide catalyst, or a molecular sieve catalyst, etc.; the catalyst of the noble metal catalyst can be Pt / Al2O3, Pd / Al2O3, etc., the catalyst of the metal oxide catalyst can be V-based, Mn-based, and Cu-based, etc., and the molecular sieve catalyst can be Fe-based molecular sieve and Cu-based molecular sieve, etc.

[0044] The ammonia oxidation catalyst 2 can be a noble metal catalyst, a transition metal oxide catalyst, or a molecular sieve catalyst, etc.; the catalyst for the noble metal catalyst can be Pt, Pd, Ag, Ru, etc., and the catalyst for the transition metal oxide catalyst can be V2O5, MnO2, Fe2O3, etc.; the type of molecular sieve catalyst can be ZSM-5, SAPO-34, SSZ-13, etc.

[0045] In the description of this application, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0046] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A method for operating an integrated purification and after-treatment device for unburned ammonia and NOx in an ammonia-fueled engine, characterized in that, The integrated purification and after-treatment device for unburned ammonia and NOx in the ammonia fuel engine includes: an ammonia oxidation catalyst (2), an ammonia oxidation catalyst bypass valve (3), an ammonia oxidation catalyst bypass pipeline (4), a mixer (5), and a selective catalytic reduction device (6). The ammonia fuel engine (1) is connected in sequence to the ammonia oxidation catalyst (2), the mixer (5) and the selective catalytic reducer (6); One end of the ammonia oxidation catalyst bypass pipeline (4) is connected between the ammonia fuel engine (1) and the ammonia oxidation catalyst (2), and the other end is connected to the mixer (5). The ammonia oxidation catalyst bypass valve (3) is provided on the ammonia oxidation catalyst bypass pipeline (4). A first NOx sensor (801) and a first ammonia sensor (901) are provided between the ammonia oxidation catalyst (2) and the ammonia fuel engine (1), a second NOx sensor (802) and a second ammonia sensor (902) are provided between the mixer (5) and the selective catalytic reducer (6), and a third NOx sensor (803) and a third ammonia sensor (903) are provided at the end of the selective catalytic reducer (6) away from the mixer (5). A reducing agent injector (7) is provided between the selective catalytic reducer (6) and the mixer (5), and a reducing agent is injected through the reducing agent injector (7); The ammonia oxidation catalyst bypass valve (3), the reducing agent injector (7), the first NOx sensor (801), the second NOx sensor (802), the third NOx sensor (803), the first ammonia sensor (901), the second ammonia sensor (902), and the third ammonia sensor (903) are connected to the controller (10). The working method includes the following steps: Step S1, the ammonia fuel engine (1) emits exhaust gas containing unburned ammonia and NOx, and the first NOx sensor (801) and the first ammonia sensor (901) measure the content of NOx and unburned ammonia in the exhaust gas and feed it back to the controller (10). In step S2, the exhaust gas passes through the ammonia oxidation catalyst (2) and the mixer (5) before being sent to the selective catalytic reducer (6) for reaction. In step S3, when unburned ammonia is in excess compared to NOx in the reaction, the controller (10) controls the opening of the ammonia oxidation catalyst bypass valve (3) in real time according to the measured values ​​of the second NOx sensor (802) and the second ammonia sensor (902). Part of the tail gas enters the mixer (5) from the ammonia oxidation catalyst bypass pipeline (4) and mixes with the gas catalyzed by the ammonia oxidation catalyst (2) to ensure a suitable ammonia to NOx ratio before the selective catalytic reducer (6). Step S4: When NOx is in excess relative to unburned ammonia in the reaction, close the built-in shut-off valve of the ammonia oxidation catalyst (2) near the ammonia fuel engine (1) to stop the ammonia oxidation catalyst (2) from working. Meanwhile, the controller (10) calculates the additional reducing agent requirement and controls the reducing agent injector (7) to inject additional reducing agent in front of the selective catalytic reducer (6); In step S5, the balanced unburned ammonia and NOx react in the selective catalytic reducer (6) to achieve integrated purification; In step S6, the third NOx sensor (803) and the third ammonia sensor (903) further measure the gas emitted by the selective catalytic reducer (6) and feed it back to the controller (10). The controller (10) confirms that the exhaust gas meets the emission standards based on the measurement results.

2. The operating method of the integrated purification and after-treatment device for unburned ammonia and NOx in an ammonia-fueled engine according to claim 1, characterized in that: The ammonia oxidation catalyst (2) has a built-in shut-off valve at one end near the ammonia fuel engine (1).

3. The operating method of the integrated purification and aftertreatment device for unburned ammonia and NOx in an ammonia-fueled engine according to claim 1, characterized in that: The sprayed reducing agent includes ammonia, ammonia water, and urea, and the catalyst of the selective catalytic reducer (6) adsorbs and stores the reducing agent ammonia.

4. The operating method of the integrated purification and after-treatment device for unburned ammonia and NOx in an ammonia-fueled engine according to claim 1, characterized in that, The selective catalytic reducer (6) includes: a noble metal catalyst, a metal oxide catalyst, and a molecular sieve catalyst; The catalyst types of the noble metal catalyst include Pt / Al2O3 and Pd / Al2O3, the catalyst types of the metal oxide catalyst include V-based, Mn-based and Cu-based, and the catalyst types of the molecular sieve catalyst include Fe-based molecular sieve and Cu-based molecular sieve.

5. The operating method of the integrated purification and after-treatment device for unburned ammonia and NOx in an ammonia-fueled engine according to claim 1, characterized in that, The ammonia oxidation catalyst (2) includes: a noble metal catalyst, a transition metal oxide catalyst, and a molecular sieve catalyst; The catalyst types of the noble metal catalyst include Pt, Pd, Ag and Ru, the catalyst types of the transition metal oxide catalyst include V2O5, MnO2 and Fe2O3, and the types of molecular sieve catalysts include ZSM-5 molecular sieve, SAPO-34 molecular sieve and SSZ-13 molecular sieve.

6. The operating method of the integrated purification and after-treatment device for unburned ammonia and NOx in an ammonia-fueled engine according to claim 1, characterized in that: The operating modes of the ammonia fuel engine (1) include spark ignition, diesel ignition, low-carbon / zero-carbon fuel ignition, pre-combustion chamber thermal turbulent jet ignition, and direct compression ignition.

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