Marine LPSCR (Liquefied Petroleum Selective Catalytic Reduction) system for main engine running under low load

Abstract

According to the marine LPSCR system for operating under the low load of the main engine, a main urea path spray gun and an auxiliary urea path spray gun are arranged in an exhaust manifold and an SCR auxiliary heating device respectively, and urea injection is controlled according to different exhaust gas temperatures, so that the LPSCR system can stably operate under the low load of a T3 mode of the main engine; nitric oxide in waste gas is treated, urea is decomposed and converted sufficiently, and the risk of corrosion and crystallization is avoided.

Description

Technical Field

[0001] The invention belongs to marine exhaust gas treatment equipment, in particular to marine LPSCR nitrogen oxide removal equipment, specifically to a marine LPSCR system for main engine operation under low load. Background Art

[0002] As a highly efficient energy-saving and emission-reduction device, marine selective catalytic reduction (SCR) systems have been widely used in the shipbuilding industry. Low-pressure selective catalytic reduction (LPSCR) is a special arrangement of the SCR system, which is characterized by installing the SCR reactor after the turbocharger, reducing the restrictions on spatial layout, achieving relative independence from the main engine operation, and improving the flexibility and adaptability of the system.

[0003] However, the LPSCR system also faces some challenges, especially when the main engine T3 emission reduction mode is running at low load:

[0004] 1) Low flue gas temperature: Since the SCR reactor in the LPSCR system is located after the turbocharger, the flue gas temperature entering the SCR reactor is relatively low. When the main engine is running at low load, this low temperature condition may reduce the activity of the SCR catalyst, thereby affecting the NOx reduction efficiency.

[0005] 2) Operation stability: When a ship is sailing in a narrow channel, the main engine may be in a low-load state for a long time, resulting in a continuously low flue gas temperature. In this case, the conventional LPSCR system may stop operating because the operating conditions are not met (such as the temperature is too low). This not only affects the NOx emission reduction effect, but may also cause the crew to be forced to operate the system frequently during navigation, and the system to start and stop repeatedly. Frequent start and stop operations increase the workload of the crew and reduce their operating efficiency. At the same time, the repeated start and stop of the system may cause accelerated wear of equipment components and shorten the service life of the SCR system and components. It has a negative impact on the crew's user experience and the service life of the equipment.

[0006] In summary, although the LPSCR system provides an effective means of energy conservation and emission reduction for ships, the challenges faced when the main engine is running at low load cannot be ignored. In order to overcome these challenges, developing a more efficient and stable LPSCR system and optimizing its operation strategy are important research directions for current ship emission reduction technology. Summary of the invention

[0007] In order to solve the problem that the marine LPSCR system in the prior art cannot stably operate under the low load of the main engine T3 mode, the present invention provides a marine LPSCR system for operating under the low load of the main engine, by arranging the main urea line spray gun and the auxiliary line urea spray gun in the exhaust manifold and the SCR auxiliary heating device respectively, and controlling the injection of urea according to different exhaust gas temperatures, so as to make full use of the flue gas waste heat to decompose urea. When the ship is sailing normally, the main engine load is high, and the temperature in the exhaust manifold meets the requirements of urea evaporation and decomposition. When the LPSCR operating conditions are met, the SCR auxiliary heating system does not operate, the auxiliary line urea solenoid valve is closed, and urea is injected through the main urea line spray gun; when the ship is sailing in a narrow channel, the main engine load is low, the temperature in the exhaust manifold does not meet the requirements of urea evaporation and decomposition, the main urea line solenoid valve is closed, the SCR auxiliary heating system is operated, and the catalyst in the SCR reactor is assisted to heat up, and the auxiliary line urea solenoid valve is opened after the auxiliary heating system operates stably, and urea is injected through the auxiliary line urea spray gun.

[0008] The technical solution of the present invention is as follows:

[0009] A marine LPSCR system for operation of a main engine under low load, characterized in that it includes:

[0010] An exhaust manifold, on which a main urea spray gun is arranged;

[0011] SCR auxiliary heating system, on which an auxiliary urea spray gun is arranged;

[0012] A control unit, used for controlling the injection of urea according to different exhaust gas temperatures;

[0013] Among them, when the ship's main engine is in a high-load state and the temperature in the exhaust manifold meets the requirements of urea evaporation and decomposition, the control unit closes the auxiliary urea solenoid valve and opens the main urea solenoid valve to allow urea to be sprayed through the main urea spray gun; when the ship's main engine is in a low-load state and the temperature in the exhaust manifold does not meet the requirements of urea evaporation and decomposition, the control unit closes the main urea solenoid valve and runs the SCR auxiliary heating system. After the system runs stably, the auxiliary urea solenoid valve is opened to allow urea to be sprayed through the auxiliary urea spray gun.

[0014] Further, it includes a LPSCR system main control box for controlling a valve system, the valve system including an inlet valve, an outlet valve and a bypass valve;

[0015] When the main engine is in T2 mode and the LPSCR system is not running, the inlet valve and outlet valve are closed and the bypass valve is opened so that the exhaust gas is discharged directly without being treated;

[0016] When the host is in T3 mode and the LPSCR system is running, the inlet valve and the outlet valve are opened, the bypass valve is closed, and the SCR auxiliary heating system is used to heat the catalyst in the SCR reactor.

[0017] Furthermore, a temperature monitoring system is included, which includes:

[0018] Exhaust manifold temperature sensor, used to monitor the exhaust gas temperature in the exhaust manifold;

[0019] Post-supercharger temperature sensor, used to monitor the exhaust temperature after the supercharger;

[0020] Temperature sensors before and after the reactor are used to determine whether the SCR catalyst has been heated;

[0021] The value of the temperature monitoring system is used by the control unit to determine whether the catalyst heating is completed and whether the urea injection conditions are met, thereby controlling the operation of the SCR auxiliary heating system and the urea supply system.

[0022] The urea supply system comprises:

[0023] Urea supply unit;

[0024] A main urea solenoid valve is connected between the urea supply unit and the main urea spray gun;

[0025] An auxiliary urea solenoid valve is connected between the urea supply unit and the auxiliary urea spray gun;

[0026] Among them, when the main engine is running at high load, if the exhaust manifold temperature meets the conditions for main urea injection and the reactor inlet and outlet temperatures meet the normal working temperature of the catalyst, the main urea solenoid valve is opened, the auxiliary urea solenoid valve is closed, and urea is injected through the main urea spray gun; when the main engine is running at low load, if the exhaust manifold temperature does not meet the conditions for main urea injection, the main urea solenoid valve is closed, the SCR auxiliary heating system is operated, and when the reactor inlet and outlet temperatures meet the normal working temperature of the catalyst, the auxiliary urea solenoid valve is opened, and urea is injected through the auxiliary urea spray gun.

[0027] The SCR auxiliary heating system is started when the main engine is running at low load, and is used to assist in heating the catalyst in the SCR reactor to meet the conditions for urea injection.

[0028] The control unit controls the operation of the urea supply system, the SCR auxiliary heating system and the valve system according to the feedback from the temperature monitoring system, so as to achieve effective injection of urea and effective treatment of exhaust gas.

[0029] The working principle of the present invention is as follows:

[0030] During normal sailing (high load):

[0031] When the ship is in normal navigation, the main engine load is high, and the temperature in the exhaust manifold is sufficient to meet the requirements of urea evaporation and decomposition. At this time, if the operating conditions of the LPSCR system are met, the SCR auxiliary heating system does not operate, and the auxiliary urea solenoid valve is closed. Urea is only sprayed through the main urea line spray gun, and the high temperature in the exhaust manifold is directly used for decomposition.

[0032] When sailing in narrow channels (low load):

[0033] When the ship is sailing in a narrow channel, the load of the main engine is reduced, and the temperature in the exhaust manifold is not enough to support the evaporation and decomposition of urea. At this time, the main urea circuit solenoid valve is closed, and the injection of urea through the main urea circuit spray gun is stopped. At the same time, the SCR auxiliary heating system is started to assist in heating the catalyst in the SCR reactor to increase the temperature required for urea decomposition. When the auxiliary heating system operates stably and the temperature reaches the appropriate range for urea decomposition, the auxiliary circuit urea solenoid valve is opened, and urea is injected through the auxiliary circuit urea spray gun.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] 1) The main urea spray gun and the auxiliary urea spray gun are arranged in the exhaust manifold and the SCR auxiliary heating device respectively. The urea injection path can be flexibly adjusted according to the exhaust gas temperature and the main engine load to ensure that urea is decomposed under appropriate conditions, thereby improving the NOx reduction efficiency.

[0036] 2) Intelligently control urea injection by monitoring exhaust gas temperature, including adjusting urea injection strategy according to changes in main engine load (such as high load during normal navigation and low load in narrow waterways). Turn off the system when auxiliary heating is not needed to reduce unnecessary energy consumption.

[0037] 3) Enhance system adaptability: Enable the SCR system to adapt to operation under different host loads and exhaust temperature conditions, and improve overall performance and reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 Schematic diagram of a marine LPSCR system for operation of a main engine under low load according to an embodiment of the present invention

[0039] In the figure:

[0040] 1. Exhaust manifold

[0041] 2. Supercharger

[0042] 3. Control unit

[0043] 4.LPSCR Reactor

[0044] 5.SCR auxiliary heating system

[0045] 6. Urea supply system: 6.1 Urea supply unit 6.2 Main urea spray gun 6.3 Auxiliary urea spray gun 6.4 Main urea solenoid valve 6.5 Auxiliary urea solenoid valve

[0046] 7.SCR control system: 7.1 Inlet valve 7.2 Outlet valve 7.3 Bypass valve

[0047] 8. Temperature monitoring system: 8.1 Exhaust manifold temperature sensor 8.2 Supercharger rear temperature sensor 8.3 SCR reactor front temperature sensor 8.4 SCR reactor rear temperature sensor DETAILED DESCRIPTION

[0048] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments, but this should not limit the protection scope of the present invention.

[0049] See also Figure 1 , Figure 1 Schematic diagram of a marine LPSCR system for operation of a main engine under low load according to an embodiment of the present invention. As shown in the figure, a marine LPSCR system for operation of a main engine under low load includes:

[0050] An exhaust manifold 1 is connected to the engine cylinder and the supercharger 2, and a main urea spray gun 6.2 is arranged on the exhaust manifold;

[0051] Supercharger 2, after the exhaust gas flows out from the exhaust manifold 1, it passes through the supercharger to do work, the pressure is reduced, and the temperature is reduced; the intake air passes through the supercharger to increase the pressure, and then flows to the subsequent system.

[0052] A control unit 3, used to control the injection of urea according to different exhaust gas temperatures, and to control the start and stop of the auxiliary heating system 5;

[0053] LPSCR reactor 4, where urea is mixed with exhaust gas and reacts under the action of catalyst to reduce NOx to N2 and H2O.

[0054] The SCR auxiliary heating system 5 is equipped with an auxiliary urea spray gun. When the exhaust gas temperature is not enough to support the decomposition of urea, the auxiliary heating system is started to increase the temperature in the LPSCR reactor 4 to ensure that the urea can be fully decomposed and reacted. It is controlled by the control unit 3 and determines whether to start according to the values ​​of each temperature sensor in the temperature monitoring system;

[0055] The urea supply system 6 stores and supplies urea solution, and injects the urea solution into the exhaust gas through the main urea path or the auxiliary urea path. It is controlled by the control unit 3, including the timing and amount of urea injection. Its components include:

[0056] The urea supply unit 6.1 is used to store and supply urea solution.

[0057] The main urea spray gun 6.2 and the auxiliary urea spray gun 6.3 are respectively located after the exhaust manifold and the SCR auxiliary heating system (or connected thereto), and are used to spray urea solution into the exhaust gas.

[0058] The main urea solenoid valve 6.4 and the auxiliary urea solenoid valve 6.5 control the injection of urea solution.

[0059] The valve system 7 includes an inlet valve 7.1, an outlet valve 7.2 and a bypass valve 7.3, which are used to control the flow direction and temperature regulation of the exhaust gas. The bypass valve 7.3 is particularly used to bypass the SCR reactor and discharge the exhaust gas directly when the SCR system needs maintenance or fails.

[0060] The temperature detection and monitoring system 8 includes an exhaust manifold temperature sensor 8.1, a supercharger rear temperature sensor 8.2, an SCR reactor front temperature sensor 8.3 and an SCR reactor rear temperature sensor 8.4, which are used to monitor the temperature of the exhaust gas at different positions in real time and provide data support for system control.

[0061] Exhaust gas flows out of the engine exhaust manifold and is pressurized by the supercharger. According to the exhaust gas temperature and system control strategy, the urea supply system injects urea solution into the exhaust gas through the main urea or auxiliary urea line. In the LPSCR reactor, urea reacts with NOx in the exhaust gas under the action of the catalyst to generate N2 and H2O. When the exhaust gas temperature is low, the SCR auxiliary heating system starts to increase the temperature in the SCR reactor to ensure that urea can be fully decomposed and reacted. The temperature detection and monitoring system monitors the exhaust gas temperature in real time, provides data support for system control, and ensures that the system can operate stably under different working conditions.

[0062] When the main engine is in T2 mode, that is, the LPSCR system is not running, the inlet valve 7.1 and the outlet valve 7.2 are closed and the bypass valve 7.3 is opened. At this time, the exhaust gas is directly discharged without being treated;

[0063] When the host is in T3 mode, the LPSCR system starts to operate, opens the inlet valve 7.1 and the outlet valve 7.2, closes the bypass valve 7.3, uses the flue gas to heat the SCR catalyst, and opens the SCR auxiliary heating system 5. to heat the catalyst in the SCR reactor. The values ​​of each temperature sensor in the temperature monitoring system 8 are used to determine whether the catalyst heating is completed and whether the urea has the injection conditions, thereby controlling the operation of the SCR auxiliary heating system 5. and the urea supply system 6. The exhaust manifold temperature sensor 8.1 is used to monitor whether the exhaust gas temperature in the exhaust manifold meets the urea injection temperature, the post-supercharger temperature sensor 8.2 is used to monitor the exhaust temperature after the supercharger, and the reactor front and rear temperature sensors 8.2 and 8.3 are used to determine whether the SCR catalyst has been heated.

[0064] 1) When the main engine is running at high load, the inlet and outlet temperatures of the reactors 8.3 and 8.4 meet the normal working temperature of the catalyst, the exhaust manifold temperature 8.1 meets the conditions for main urea line injection, the urea supply system is running, the auxiliary urea solenoid valve is closed, the main urea solenoid valve is opened, and 6.4 urea is injected through the main urea spray gun 6.2.

[0065] 2) When the main engine is running at low load, when the exhaust manifold temperature does not meet the conditions for main urea line injection, the main urea solenoid valve 6.4 is closed, and urea stops being injected from the main urea line. At this time, the SCR auxiliary heating system 5 is operated. When the reactor inlet and outlet temperatures meet the normal operating temperature of the catalyst, the auxiliary urea solenoid valve 6.5 is opened, and urea is injected through the main urea spray gun 6.2.

Claims

1. A marine LPSCR system for main engine operation under low load, characterized in that: include: An exhaust manifold, on which a main urea spray gun is arranged; SCR auxiliary heating system, on which an auxiliary urea spray gun is arranged; A control unit, used for controlling the injection of urea according to different exhaust gas temperatures; Among them, when the ship's main engine is in a high-load state and the temperature in the exhaust manifold meets the requirements of urea evaporation and decomposition, the control unit closes the auxiliary urea solenoid valve and opens the main urea solenoid valve to allow urea to be sprayed through the main urea spray gun; when the ship's main engine is in a low-load state and the temperature in the exhaust manifold does not meet the requirements of urea evaporation and decomposition, the control unit closes the main urea solenoid valve and runs the SCR auxiliary heating system. After the system runs stably, the auxiliary urea solenoid valve is opened to allow urea to be sprayed through the auxiliary urea spray gun.

2. The marine LPSCR system for main engine operation under low load according to claim 1, characterized in that: It also includes the LPSCR system main control box, which is used to control the valve system: When the main engine is in T2 mode and the LPSCR system is not running, the inlet valve and outlet valve are closed and the bypass valve is opened so that the exhaust gas is discharged directly without being treated; When the host is in T3 mode and the LPSCR system is running, the inlet valve and the outlet valve are opened, the bypass valve is closed, and the SCR auxiliary heating system is used to heat the catalyst in the SCR reactor.

3. The marine LPSCR system for main engine operation under low load according to claim 1, characterized in that: Also included is a temperature monitoring system comprising: Exhaust manifold temperature sensor, used to monitor the exhaust gas temperature in the exhaust manifold; Post-supercharger temperature sensor, used to monitor the exhaust temperature after the supercharger; Temperature sensors before and after the reactor are used to determine whether the SCR catalyst has been heated; The value of the temperature monitoring system is used by the control unit to determine whether the catalyst heating is completed and whether the urea injection conditions are met, thereby controlling the operation of the SCR auxiliary heating system and the urea supply system.

4. The marine LPSCR system for main engine operation under low load according to claim 3, characterized in that: The urea supply system comprises: Urea supply unit; A main urea solenoid valve is connected between the urea supply unit and the main urea spray gun; An auxiliary urea solenoid valve is connected between the urea supply unit and the auxiliary urea spray gun; Among them, when the main engine is running at high load, if the exhaust manifold temperature meets the conditions for main urea injection and the reactor inlet and outlet temperatures meet the normal working temperature of the catalyst, the main urea solenoid valve is opened, the auxiliary urea solenoid valve is closed, and urea is injected through the main urea spray gun; when the main engine is running at low load, if the exhaust manifold temperature does not meet the conditions for main urea injection, the main urea solenoid valve is closed, the SCR auxiliary heating system is operated, and when the reactor inlet and outlet temperatures meet the normal working temperature of the catalyst, the auxiliary urea solenoid valve is opened, and urea is injected through the auxiliary urea spray gun.

5. The marine LPSCR system for main engine operation under low load according to claim 3, characterized in that: The SCR auxiliary heating system is started when the main engine is running at low load, and is used to assist in heating the catalyst in the SCR reactor to meet the conditions for urea injection.

6. The marine LPSCR system for main engine operation under low load according to any one of claims 2 to 5, characterized in that: The control unit controls the operation of the urea supply system, the SCR auxiliary heating system and the valve system according to the feedback from the temperature monitoring system, so as to achieve effective injection of urea and effective treatment of exhaust gas.

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