Ammonia-hydrogen engine aftertreatment device and control method

Abstract

The invention provides an ammonia-hydrogen engine aftertreatment device and a control method. The post-treatment device comprises an electric heater, an N2O decomposition catalyst, a selective catalytic reducer, an ammonia trapping catalyst, a sensor and a controller, the electric heater is arranged at the exhaust end of the ammonia-hydrogen engine, is powered and controlled by the controller and is used for heating exhaust of the ammonia-hydrogen engine. An N2O decomposition catalyst, a selective catalytic reducer and an ammonia trapping catalyst are sequentially arranged at the rear end of the electric heater; the sensors comprise three temperature sensors, one NOx sensor and one NH3 sensor; the controller receives a temperature signal of the temperature sensor and controls the working state of the electric heater according to the received temperature signal; and the controller receives the concentration signal of NOx and the concentration signal of NH3, and controls the working state of the electric heater according to the concentration signals. According to the invention, the decomposition efficiency of N2O can be improved, and the conversion efficiency of NOx can be improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of ammonia-hydrogen engine exhaust aftertreatment, and particularly relates to an ammonia-hydrogen engine aftertreatment device and a control method. BACKGROUND

[0002] The ammonia-hydrogen internal combustion engine is a new type of internal combustion engine technology using ammonia (NH3) and hydrogen (H2) as mixed fuel, aiming to replace traditional fossil fuels (such as gasoline and diesel) and achieve low-carbon or zero-carbon emission, especially suitable for high-energy-consumption fields such as ships and heavy trucks.

[0003] The emissions generated by ammonia / hydrogen fuel combustion contain relatively more NO and N2O, and there are also a lot of unburned NH3. The exhaust gas temperature generated by ammonia fuel combustion is relatively low, and the temperature needs to be raised compared with the original SCR catalytic reduction; at the same time, there are great differences in the working characteristics, temperature range, and selectivity of reducing agents compared with traditional SCR. Therefore, a special ammonia (or mainly ammonia) fuel internal combustion engine aftertreatment system needs to be developed for NO, N2O and NH3 emissions. SUMMARY

[0004] The purpose of the present application is to overcome the deficiencies in the prior art and provide an ammonia-hydrogen engine aftertreatment device and a control method. The ammonia-hydrogen engine aftertreatment device of the present application focuses on solving the problem of excessive unburned NH3 and N2O in the exhaust gas according to the emission characteristics of the ammonia-hydrogen engine, cooperatively controls NH3, NOx and N2O, removes N2O by using an electric heater and an N2O decomposition catalyst, realizes cooperative removal of NH3 and NOx through SCR secondary reduction, and finally oxidizes the excess unreacted NH3 by using an oxidation catalyst ASC.

[0005] To achieve the above technical purposes, the technical solutions adopted by the embodiments of the present application are as follows: In a first aspect, the embodiments of the present application provide an ammonia-hydrogen engine aftertreatment device, which comprises an electric heater, an N2O decomposition catalyst, a selective catalytic reduction device and an ammonia trapping catalyst, a sensor and a controller. The electric heater is arranged at the exhaust end of the ammonia-hydrogen engine and is powered and controlled by the controller, and is used for heating the exhaust gas of the ammonia-hydrogen engine. The N2O decomposition catalyst, the selective catalytic reduction device and the ammonia trapping catalyst are arranged in sequence at the rear end of the electric heater. The sensor comprises three temperature sensors, one NOx sensor and one NH3 sensor. The temperature sensors respectively include a first temperature sensor for measuring the front-end temperature of the electric heater, a second temperature sensor for measuring the rear-end temperature of the electric heater, and a third temperature sensor for measuring the front-end temperature of the selective catalytic reduction device, the controller is configured to receive temperature signals of the temperature sensors and control the working state of the electric heater according to the received temperature signals; The NOx sensor is configured to measure the concentration value of NOx purified by the aftertreatment system. The NH3 sensor is configured to measure the concentration value of NH3 purified by the aftertreatment system. The controller is configured to receive the concentration value signals of NOx and NH3 and control the working state of the electric heater according to the concentration signals.

[0006] Further, the NOx sensor is arranged between the selective catalytic reduction device and the ammonia trapping catalyst. The NH3 sensor is arranged at the rear end of the ammonia trapping catalyst.

[0007] Further, the first temperature sensor is arranged on the exhaust pipe between the ammonia hydrogen engine and the electric heater, the second temperature sensor is arranged on the exhaust pipe between the electric heater and the N2O decomposition catalyst and is arranged close to the electric heater. The third temperature sensor is arranged on the exhaust pipe between the N2O decomposition catalyst and the selective catalytic reduction device and is arranged close to the selective catalytic reduction device.

[0008] Further, the N2O decomposition catalyst can catalytically decompose N2O into N2 and O2 at ≥450℃. The N2O decomposition catalyst adopts metal Rh / Pt and / or Fe-ZSM-5 molecular sieve. The selective catalytic reduction device is configured to catalytically convert NH3 and NOx into non-polluting N2 and water. The ammonia trapping catalyst adopts metal Pt / Pd as a catalyst to oxidize excess unburned NH3 and oxidize NH3 into N2 and water.

[0009] In a second aspect, an ammonia hydrogen engine aftertreatment control method is provided, which is suitable for the ammonia hydrogen engine aftertreatment device of the first aspect and includes the following steps: Step S1, when the engine ignition switch is turned on, the controller communicates with the control unit of the ammonia hydrogen engine to confirm the engine working state, and the controller acquires the engine operation signal from the control unit through the CAN line. Step S2, the controller acquires the temperature T1 of the first temperature sensor and the temperature T2 of the second temperature sensor, and judges whether the electric heater needs to be started to heat; at the same time, the controller acquires the temperature T3 of the third temperature sensor, and judges whether the selective catalytic reduction device is in the high-efficiency conversion efficiency interval, to determine whether the electric heater needs to be started to heat; Step S3, the controller acquires the NOx concentration signal measured by the NOx sensor in real time, the controller acquires the NH3 concentration signal measured by the NH3 sensor in real time, and performs closed-loop adjustment based on the NH3 concentration and the NOx concentration.

[0010] Further, in step S1, the engine operation signal includes the speed of the engine, the exhaust flow, the fuel consumption, the coolant temperature and the engine working mode.

[0011] Further, in step S2, the following steps are included: Step S2.1, the controller compares the acquired temperature T1, temperature T2 and temperature T3 with the configured temperature thresholds a, b, c, d, wherein a>b>c>d; Step S2.2, the controller detects whether the battery voltage is in the normal range, if the requirement is met, the next step is entered, if the requirement is not met, the heating function is not started; Step S2.3, if T1≤b and T2≤b, the heating function is started, and the controller controls the electric heater to heat at 100% power; Step S2.4, if T3≤d and T2≤a, the controller keeps heating at 100% power; Step S2.5, if d Step S2.6, if T3>c or T2>a, the controller controls the electric heater to stop heating.

[0012] Further, in step S3, when the NH3 concentration and the NOx concentration are greater than the target value, the controller controls the electric heater to heat and warm up the exhaust gas of the ammonia hydrogen engine.

[0013] Further, the temperature threshold a is configured as 450-460℃, the temperature threshold b is configured as 350-400℃, the temperature threshold c is configured as 280-300℃, and the temperature threshold d is configured as 190-220℃. The technical scheme provided by the embodiment of the application has the following beneficial effects: (1) The ammonia hydrogen engine aftertreatment device of the application can improve the decomposition efficiency of N2O and reduce N2O emission by using EHC and NDC in cooperation.

[0014] (2) The ammonia hydrogen engine aftertreatment device of the application makes full use of the reaction of unburned NH3 and NOx in the exhaust on the SCR catalyst, and the controller controls the EHC to heat the exhaust temperature, which can improve the NOx conversion efficiency.

[0015] (3) The ammonia hydrogen engine aftertreatment device of the application does not need additional NH3 injection device, which can reduce the cost and complexity of the device. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 is a structural schematic diagram of the ammonia hydrogen engine aftertreatment device in the embodiment of the application.

[0017] Figure 2 is a flow chart of temperature control in the ammonia hydrogen engine aftertreatment control method in the embodiment of the application.

[0018] BRIEF DESCRIPTION OF REFERENCE NUMERALS: 1 - first temperature sensor; 2 - second temperature sensor; 3 - third temperature sensor; 4 - NOx sensor; 5 - NH3 sensor. DETAILED DESCRIPTION

[0019] In the description of the application, it should be understood that the orientation words such as "inner", "outer", "upper", "lower", "left", "right" and the like indicate the orientation or positional relationship shown in the drawings, which are only for the convenience of describing the application and simplifying the description, and do not indicate and imply that the indicated device or element must have a particular orientation or be constructed and operated in a particular orientation, therefore it cannot be understood as a limitation on the protection scope of the application.

[0020] In order to make the purpose, technical scheme and advantages of the application more clear, the application will be further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the application and not to limit the application.

[0021] Example 1 As shown in Figure 1 , an ammonia hydrogen engine aftertreatment device, comprising an electric heater (EHC), an N2O decomposition catalyst (NDC), a selective catalytic reduction device (SCR) and an ammonia trapping catalyst (ASC), a sensor and a controller (ACU); The electric heater (EHC) is arranged at the exhaust end of the ammonia hydrogen engine and is responsible for power supply and control by the controller (ACU), and is used for heating the exhaust of the ammonia hydrogen engine; The N2O decomposition catalyst (NDC), the selective catalytic reduction device (SCR) and the ammonia trapping catalyst (ASC) are arranged in sequence at the rear end of the electric heater (EHC); The sensor comprises three temperature sensors, one NOx sensor and one NH3 sensor. The three temperature sensors respectively comprise a first temperature sensor for measuring the front-end temperature of an electric heater (EHC), a second temperature sensor for measuring the rear-end temperature of the electric heater (EHC) and a third temperature sensor for measuring the front-end temperature of a selective catalytic reduction device (SCR), and the controller (ACU) is configured to receive the temperature signals of the temperature sensors and control the working state of the electric heater according to the received temperature signals. The NOx sensor is configured to measure the concentration value of NOx purified by the aftertreatment system. The NH3 sensor is configured to measure the concentration value of NH3 purified by the aftertreatment system. The controller (ACU) is configured to receive the concentration value signals of NOx and NH3 and control the working state of the electric heater according to the concentration signals.

[0022] Specifically, the NOx sensor is arranged between the selective catalytic reduction device (SCR) and an ammonia trapping catalyst (ASC); The NH3 sensor is arranged at the rear end of the ammonia trapping catalyst (ASC).

[0023] The first temperature sensor is arranged on the exhaust pipe between the ammonia hydrogen engine and the electric heater (EHC), the second temperature sensor is arranged on the exhaust pipe between the electric heater (EHC) and the N2O decomposition catalyst (NDC) and is arranged close to the electric heater (EHC); The third temperature sensor is arranged on the exhaust pipe between the N2O decomposition catalyst (NDC) and the selective catalytic reduction device (SCR) and is arranged close to the selective catalytic reduction device (SCR).

[0024] The N2O decomposition catalyst (NDC) can catalytically decompose N2O into N2 and O2 at ≥450℃.

[0025] Since the N2O decomposition catalyst (NDC) needs to be at a relatively high exhaust temperature (≥450℃) to have a relatively high conversion efficiency, when the engine exhaust temperature is relatively low, an electric heater needs to be used for auxiliary temperature raising to meet the conversion efficiency of N2O. In the medium and low load working conditions, the exhaust temperature of the ammonia hydrogen engine is difficult to reach above 450℃, and therefore the EHC needs to be used for auxiliary temperature raising to improve the N2O decomposition efficiency.

[0026] As an embodiment, the N2O decomposition catalyst (NDC) adopts metal Rh / Pt and / or Fe-ZSM-5 molecular sieve; The selective catalytic reduction device (SCR) is configured to catalytically convert NH3 and NOx into non-polluting N2 and water, and part of the unreacted NH3 is further oxidized and removed by the ASC downstream of the SCR. Ammonia slip catalyst (ASC) uses metal Pt / Pd as catalyst to oxidize excess unburned NH3, oxidizing NH3 into N2 and water.

[0027] Embodiment 2 An ammonia hydrogen engine aftertreatment control method, comprising the following steps: Step S1, the engine ignition switch is turned on, the controller (ACU) communicates with the control unit (ECU) of the ammonia hydrogen engine, and the controller (ACU) obtains engine operation signals including the engine speed, the exhaust flow, the fuel consumption, the coolant temperature and the engine working mode from the control unit (ECU) through the CAN line, and confirms the engine working state; Step S2, the controller (ACU) obtains the temperature T1 of the first temperature sensor and the temperature T2 of the second temperature sensor, and judges whether the electric heater (EHC) needs to be started; at the same time, the controller (ACU) obtains the temperature T3 of the third temperature sensor, and judges whether the selective catalytic reduction device (SCR) is in the high-efficiency conversion efficiency interval, to determine whether the electric heater needs to be started; Step S3, the controller (ACU) obtains the NOx concentration signal measured by the NOx sensor in real time and the NH3 concentration signal measured by the NH3 sensor in real time, and performs closed-loop adjustment based on the NH3 concentration and the NOx concentration; When the NH3 concentration and the NOx concentration are greater than the target value, the controller (ACU) controls the electric heater (EHC) to heat and warm up the exhaust gas of the ammonia hydrogen engine, thereby improving the SCR conversion efficiency, synchronously reducing NH3 and NOx, and improving the oxidation efficiency of the ammonia slip catalyst (ASC), oxidizing the unreacted NH3, reducing the NH3 concentration value of the tail, and meeting the emission control requirements.

[0028] As shown in Figure 2 , step S2 specifically comprises the following steps: Step S2.1, the controller (ACU) compares the obtained temperature T1, temperature T2 and temperature T3 with the configured temperature threshold values a, b, c and d, wherein a=450℃, b=400℃, c=300℃ and d=200℃; Step S2.2, the controller (ACU) detects whether the battery voltage is within the normal range, if the requirement is met, the next step is entered, if the requirement is not met, the heating function is not started; Step S2.3, if T1≤400℃ and T2≤400℃, the heating function is started, and the controller (ACU) controls the electric heater (EHC) to be fully heated at 100% power; Step S2.4, if T3≤200℃ and T2≤450℃, the controller (ACU) controls the electric heater (EHC) to heat at 100% power; Step S2.5, if 200℃<T3≤300℃, the controller (ACU) controls the electric heater (EHC) to heat at 50% power; Step S2.6, if T3>300℃ or T2>450℃, the controller (ACU) controls the electric heater (EHC) to stop heating.

[0029] In order to reduce the NH3, NOx, N2O pollutant emissions in the exhaust gas of ammonia hydrogen engine, the aftertreatment device of the present application is provided with an electric heater (EHC), an N2O decomposition catalyst (NDC), a selective oxidation catalyst (SCR) and an ammonia capture catalyst (ASC), through which the N2O in the engine exhaust gas can be removed. The catalyst needs to have a high conversion efficiency at high temperature, and when the exhaust gas temperature is insufficient, an electric heater (EHC) is used to assist in temperature raising to meet the effective working window of the N2O decomposition catalyst. The unburned NH3 in the exhaust gas reacts with NOx under the action of the SCR catalyst, further eliminating NH3 and NOx, and if NH3 is excessive, there is unreacted NH3 through the SCR system, and finally the unreacted NH3 is further oxidized by the ASC catalyst, so that the NH3, NOx, N2O pollutant emissions meet the regulatory requirements.

[0030] Finally, it should be explained that the above specific embodiments are only used to illustrate the technical solutions of the present application and not to limit it. Although the present application has been described in detail with reference to the examples, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present application, which should be covered in the scope of the claims of the present application.

Claims

1. An ammonia-hydrogen engine post-treatment device, characterized in that: Including electric heater, N2O decomposition catalyst, selective catalytic reduction device and ammonia capture catalyst, sensor and controller; The electric heater is arranged at the exhaust end of the ammonia-hydrogen engine and is powered and controlled by the controller to heat the exhaust gas of the ammonia-hydrogen engine; The N2O decomposition catalyst, the selective catalytic reduction device and the ammonia capture catalyst are sequentially arranged at the rear end of the electric heater; The sensors include three temperature sensors, a NOx sensor and an NH3 sensor; The temperature sensors include a first temperature sensor for measuring the temperature at the front end of the electric heater, a second temperature sensor for measuring the temperature at the rear end of the electric heater, and a third temperature sensor for measuring the temperature at the front end of the selective catalytic reduction device. The controller is configured to receive temperature signals from the temperature sensors and control the operating state of the electric heater according to the received temperature signals. The NOx sensor is used to measure the NOx concentration value after purification by the post-treatment system; The NH3 sensor is used to measure the NH3 concentration value after purification by the post-treatment system; The controller is used to receive a NOx concentration value signal and an NH3 concentration value signal, and control the working state of the electric heater according to the concentration signals.

2. The ammonia-hydrogen engine post-treatment device according to claim 1, characterized in that: The NOx sensor is arranged between the selective catalytic reduction device and the ammonia trap catalyst; The NH3 sensor is installed at the rear end of the ammonia trap catalyst.

3. The ammonia-hydrogen engine post-treatment device according to claim 1, characterized in that: The first temperature sensor is arranged on the exhaust pipe between the ammonia hydrogen engine and the electric heater, and the second temperature sensor is arranged on the exhaust pipe between the electric heater and the N2O decomposition catalyst and is arranged close to the electric heater; The third temperature sensor is arranged on the exhaust pipe between the N2O decomposition catalyst and the selective catalytic reduction device, and is arranged close to the selective catalytic reduction device.

4. The ammonia-hydrogen engine post-treatment device according to claim 1, characterized in that: The N2O decomposition catalyst can catalytically decompose N2O into N2 and O2 at a temperature of ≥450°C; The N2O decomposition catalyst uses metal Rh / Pt and / or Fe-ZSM-5 molecular sieve; The selective catalytic reducer is used to catalyze NH3 and NOx into pollution-free N2 and water; The ammonia capture catalyst uses metal Pt / Pd as a catalyst to oxidize excess unburned NH3, oxidizing NH3 into N2 and water.

5. A post-processing control method for an ammonia-hydrogen engine, characterized in that: The ammonia-hydrogen engine after-treatment device according to any one of claims 1 to 4 comprises the following steps: Step S1: The engine ignition switch is turned on, and the controller communicates with the control unit of the ammonia-hydrogen engine to confirm that the controller obtains an engine operation signal from the control unit via a CAN line to confirm the engine operating status; Step S2: The controller obtains the temperature T1 of the first temperature sensor and the temperature T2 of the second temperature sensor, and determines whether the electric heater needs to be turned on for heating. Simultaneously, the controller obtains the temperature T3 of the third temperature sensor, and determines whether the selective catalytic reduction device is in a high-efficiency conversion efficiency range, thereby determining whether the electric heater needs to be turned on for heating. Step S3: The controller obtains a NOx concentration signal measured in real time by the NOx sensor, obtains an NH3 concentration signal measured in real time by the NH3 sensor, and performs closed-loop regulation based on the NH3 concentration and the NOx concentration.

6. The ammonia-hydrogen engine post-treatment control method according to claim 5, characterized in that: In step S1 , the engine operation signal includes engine speed, exhaust flow, fuel consumption, coolant temperature and engine operating mode.

7. The ammonia-hydrogen engine post-treatment control method according to claim 5 or 6, characterized in that: Step S2 includes the following steps: Step S2.1, the controller compares the acquired temperature T1, temperature T2 and temperature T3 with the configured temperature thresholds a, b, c and d, where a>b>c>d; Step S2.2: The controller detects whether the battery voltage is within a normal range. If so, the controller proceeds to the next step of determination. If not, the controller does not activate the heating function. Step S2.3: If T1≤b and T2≤b, start the heating function, and the controller controls the electric heater to heat at 100% power; Step S2.4: If T3≤d and T2≤a, keep the controller heating at 100% power; Step S2.5: If d<T3≤c, the controller controls the electric heater to heat at 50% power; Step S2.6: If T3>c or T2>a, the controller controls the electric heater to stop heating.

8. The ammonia-hydrogen engine post-treatment control method according to claim 5, characterized in that: In step S3, when the NH3 concentration and the NOx concentration are greater than the target values, the controller controls the electric heater to heat the exhaust gas of the ammonia-hydrogen engine.

9. The ammonia-hydrogen engine post-treatment control method according to claim 7, characterized in that: The temperature threshold a is configured to be 450-460°C, the temperature threshold b is configured to be 350-400°C, the temperature threshold c is configured to be 280-300°C, and the temperature threshold d is configured to be 190-220°C.

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