A method of SCR control and apparatus therefor

Abstract

The application discloses an SCR control method and device, belonging to the technical field of tail gas treatment of large engines and industrial equipment. The method comprises the following steps: S1, detecting the working state of the SCR device in real time, judging whether the working state meets the access condition, if yes, entering the pressure building state and building pressure, and executing S2 after the pressure building is successful, otherwise, repeatedly detecting the working state, wherein the SCR device comprises a plurality of urea pumps; S2, calculating the urea demand injection amount, and performing the urea solution pressure closed-loop control according to the urea demand injection amount; S3, entering the urea injection state, continuously judging whether the injection condition is met, if yes, the urea pump keeps injecting, otherwise, the urea pump stops working, and returning to S1. The operation condition of the equipment does not need to be acquired, the calibration is easier, and the method is suitable for NOx treatment and emission reduction of large generator sets, ships, engine bench test rooms, industrial boilers and the like. x The control method is simple, has the advantages of wide adaptability, simple modification, easy implementation, convenient monitoring and the like. x ​

Description

Technical Field

[0001] This invention relates to the field of exhaust gas treatment technology for large engines and industrial equipment, and particularly to an SCR control method and device. Background Technology

[0002] NO emissions from large engines and industrial equipment x Air pollution is one of the major sources of air pollution, and the state has introduced a series of regulations to restrict its emissions. However, a large number of large engines and industrial equipment currently in use do not meet the requirements of current regulations due to factors such as their age, posing a significant threat to air pollution.

[0003] Selective catalytic reduction (SCR) technology is currently the most effective method for reducing NO. x One of the main technical means of emission reduction. Urea solution hydrolyzes into NH3 under high temperature conditions, and then reacts with NO under the action of a catalyst. x O2 undergoes a redox reaction to produce non-polluting N2 and H2O.

[0004] Large in-use engines and industrial equipment typically have characteristics such as high power, large displacement, stable operating conditions, and long working time, and existing SCR control methods and devices are difficult to meet their usage requirements. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing SCR control methods and devices, which are difficult to meet the requirements of large in-use engines and industrial equipment that require high power, large displacement, stable operation, and long working time, and to provide an SCR control method and device.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] An SCR control method includes the following steps:

[0008] S1: Real-time detection of the working status of the SCR device, and determination of whether the working status meets the access conditions. If yes, enter the pressure building state and perform pressure building. After successful pressure building, execute step S2. Otherwise, repeat the detection of the working status of the SCR device. The SCR device includes several urea pumps.

[0009] S2: Calculate the required urea injection volume and perform closed-loop control of urea solution pressure based on the required urea injection volume;

[0010] S3: Enter the urea injection state and continuously determine whether the injection conditions are met. The injection conditions are the same as the admission conditions. If they are met, the urea pump continues to inject; otherwise, the urea pump stops working and returns to step S1.

[0011] Using the above technical solution, there is no need to obtain the equipment's operating conditions, making calibration easier. This method is applicable to NO3- content in equipment such as large generator sets, ships, engine bench test laboratories, and industrial boilers. x Governance and reduction of NO x The emission control method is simple and has the advantages of wide adaptability, simple modification, easy implementation and easy monitoring.

[0012] As a preferred embodiment of the present invention, the access conditions described in step S1 include: no system faults, average temperature of upstream and downstream of SCR ≥ 200°C, urea level ≥ 20%, urea temperature ≥ 0°C, gas pressure ≥ 2 bar, and minimum injection volume ≥ 900 mg / s.

[0013] As a preferred embodiment of the present invention, step S1, which involves entering the pressure-building state and performing pressure building, includes: after entering the pressure-building state, one of the urea pumps is used for pressure building by default, a pressure-building timer is started, and a pressure threshold ≥ 2 bar, a pressure-building time threshold ≤ 30 s, a maximum pressure-building time ≤ 60 s, and a maximum number of pressure-building times are set according to actual needs. Within the maximum pressure-building time, if the actual urea solution pressure value measured by the pressure sensor reaches the set pressure threshold and meets the pressure-building time threshold, then pressure building is completed, and the urea solution pressure value at this time is recorded. The urea solution pressure value is used to determine the valve opening parameters.

[0014] If the actual urea pressure value measured by the pressure sensor does not reach the pressure threshold within the maximum pressure build-up time, the pressure build-up fails, the number of pressure build-up failures is incremented by 1, and pressure build-up is retried. When the number of pressure build-up failures exceeds the maximum number of pressure build-up attempts, a pressure build-up fault is reported, and the urea pump enters the purging state from the pressure build-up state. After the purging is completed, the pump stops.

[0015] As a preferred embodiment of the present invention, the formula for calculating the required urea injection volume in step S2 is as follows:

[0016] m=α*m b

[0017] Wherein, m b The injection volume is the base urea requirement, and α is the correction factor.

[0018] The formula for calculating the basic urea injection volume requirement is as follows:

[0019] m b =Q m *C NOx *η*γ / 34000

[0020] Among them, Q m The C is the exhaust mass flow rate. NOx NO xThe original discharge concentration, where η is the target conversion efficiency and γ is the ammonia-nitrogen ratio.

[0021] As a preferred embodiment of the present invention, the correction coefficient is calculated by the closed-loop adjustment function of the post-nitrogen oxygen concentration, including: calculating the real-time conversion efficiency based on the pre-nitrogen oxygen concentration values ​​and post-nitrogen oxygen concentration values ​​measured by the pre-nitrogen oxygen sensor and the post-nitrogen oxygen sensor respectively, setting the time for calculating the real-time conversion efficiency as t, and calculating the NO within the time period t. x The average conversion efficiency is obtained by subtracting the current conversion efficiency and taking the absolute value. When the absolute value is greater than or equal to a set threshold, the correction coefficient is equal to 1. When the absolute value is less than the set threshold, the nitrogen and oxygen concentration is adjusted in a closed loop, and the closed loop adjustment factor is calculated. At this time, the correction coefficient is equal to the closed loop adjustment factor.

[0022] The closed-loop adjustment factor is obtained by taking the deviation between the target nitrogen and oxygen concentration and the current measured nitrogen and oxygen concentration as input, and then processing it through a PI algorithm and after passing through maximum and minimum limits.

[0023] As a preferred embodiment of the present invention, the closed-loop control of urea solution pressure according to the urea demand injection amount in step S2 includes: obtaining the target urea solution pressure value by looking up the MAP according to the urea demand amount, and adjusting the urea solution pressure to the target solution pressure by controlling the return solenoid valve to control the urea injection amount.

[0024] The closed-loop control of the urea solution pressure adopts a PI algorithm, which includes: obtaining a pressure deviation by subtracting the target urea solution pressure value from the actual urea solution pressure value measured by the pressure sensor; using the pressure deviation as the input of the PI algorithm; obtaining a return solenoid valve opening coefficient through the PI algorithm; and then obtaining the valve opening.

[0025] The calculation formula for the PI algorithm is as follows:

[0026] k=kp*err(t)+ki*∑err(j) j∈[0,t]

[0027] Among them, the coefficient kp and parameter ki are obtained by looking up the urea solution pressure when the urea pump is pressure built up and the target pressure obtained by looking up the table according to the urea demand injection amount, and err(t) is the deviation value at time t.

[0028] The formula for calculating the valve opening is:

[0029] θ = k * 100% k∈[0,1]

[0030] Wherein, k is the opening coefficient of the return solenoid valve.

[0031] As a preferred embodiment of the present invention, step S3 includes: entering the urea injection state, the liquid circuit shut-off valve, the gas circuit shut-off valve, and the return liquid solenoid valve start working, and the urea solution pressure is controlled according to the required urea injection volume. In the injection state, several urea pumps operate alternately, and a single pump operating time threshold is set. When the single pump operating time exceeds the single pump operating time threshold, the pump is switched. During the pump switching period, several urea pumps operate simultaneously, and a multi-pump operating time threshold is set. When the simultaneous operating time exceeds the multi-pump operating time threshold, another pump is officially switched to operate alone. During the switching period, the liquid circuit shut-off valve, the gas circuit shut-off valve, and the return liquid solenoid valve are all closed.

[0032] As a preferred embodiment of the present invention, when performing urea injection in step S3, the urea liquid in the urea tank is replenished in real time: an upper limit and a lower limit of the urea liquid level are set respectively, the liquid level is detected in real time, and if the liquid level is lower than the lower limit, the replenishment pump works to replenish the liquid until the liquid level exceeds the upper limit, and the replenishment stops. No replenishment is performed under other conditions.

[0033] A maximum fluid replenishment time threshold is set. If the fluid replenishment time exceeds the maximum fluid replenishment time threshold during the fluid replenishment process, the fluid replenishment is stopped and a fluid replenishment failure is reported.

[0034] On the other hand, an SCR control device for implementing any of the above-described SCR control methods includes: a urea supply system, an auxiliary gas supply system, a main control system, and a packaging unit; the urea supply system and the auxiliary gas supply system are both electrically connected to the main control system.

[0035] The urea supply system includes: a replenishment pump, a urea tank, several urea pumps, a return solenoid valve, a pressure limiting valve, a liquid pressure sensor, a damper, a liquid shut-off valve, and a spray gun; the urea tank integrates a level sensor and a temperature sensor; the inlet of the replenishment pump is connected to an external replenishment tank via a first replenishment pipe, and the outlet of the replenishment pump is connected to the urea tank via a second replenishment pipe; the inlets of several urea pumps are connected to the urea tank via inlet pipes, and the outlets of several urea pumps are connected to the inlet of the liquid shut-off valve via a first outlet pipe; the liquid pressure sensor and the damper are installed in the first outlet pipe; the outlet of the liquid shut-off valve is connected to the inlet of the spray gun via a second outlet pipe; the return solenoid valve is connected in parallel with the pressure limiting valve and is disposed between the first outlet pipe and the urea tank;

[0036] The auxiliary gas supply system includes: a gas-water separator, a gas pressure sensor, and a gas shut-off valve; the gas-water separator integrates a gas pressure regulator; the gas inlet of the gas-water separator is connected to an external gas source through a first gas inlet pipe, and the gas outlet of the gas-water separator is connected to the gas inlet of the gas shut-off valve through a second gas inlet pipe; the gas pressure sensor is installed in the second gas inlet pipe; the gas outlet of the gas shut-off valve is connected to the gas inlet of the spray gun through a third gas inlet pipe.

[0037] The main control system includes: a controller, a monitoring terminal, a differential pressure sensor, a pre-nitrogen-oxygen concentration sensor, an upstream temperature sensor of the SCR, a downstream temperature sensor of the SCR, a post-nitrogen-oxygen concentration sensor, and a cloud monitoring platform; the controller and the monitoring terminal are connected via a CAN bus; the monitoring terminal and the cloud monitoring platform are communicatively connected; the controller is electrically connected to the replenishment pump, the urea tank, several urea pumps, the return solenoid valve, the liquid circuit pressure sensor, the liquid circuit shut-off valve, the gas circuit pressure sensor, the gas circuit shut-off valve, the differential pressure sensor, the pre-nitrogen-oxygen concentration sensor, the upstream temperature sensor of the SCR, the downstream temperature sensor of the SCR, and the post-nitrogen-oxygen concentration sensor; the pre-nitrogen-oxygen concentration sensor, the upstream temperature sensor of the SCR, the downstream temperature sensor of the SCR, and the post-nitrogen-oxygen concentration sensor are respectively installed on the encapsulation unit; the differential pressure sensor is connected to the encapsulation unit via a pipeline;

[0038] The encapsulation unit includes: a bypass valve, a pre-shut-off valve, a spray gun holder, a mixer, an SCR reactor, and a post-shut-off valve; the front end of the pre-shut-off valve is connected to an air inlet pipe, and the rear end is connected to the mixer; the spray gun is mounted on the spray gun holder of the encapsulation unit; the spray gun holder is mounted on the mixer or the air inlet pipe; the rear end of the mixer is connected to the SCR reactor; the rear end of the SCR reactor is connected to the post-shut-off valve; the rear end of the post-shut-off valve is connected to an air outlet pipe; a bypass pipe is connected between the air inlet pipe and the air outlet pipe, and the bypass valve is installed in the bypass pipe.

[0039] Compared with the prior art, the advantages of this invention are: it eliminates the need to obtain the operating conditions of the equipment, making calibration easier; and this method is applicable to NO3- content in equipment such as large generator sets, ships, engine bench test laboratories, and industrial boilers. x Governance and reduction of NO x The emission control method is simple and has the advantages of wide adaptability, simple modification, easy implementation and easy monitoring. Attached Figure Description

[0040] Figure 1 This is a flowchart of an SCR control method according to Embodiment 1 of the present invention;

[0041] Figure 2 This is a schematic diagram of the overall control method of the SCR control method described in Embodiment 2 of the present invention;

[0042] Figure 3-5 This is a schematic diagram of the urea injection quantity control method of the SCR control method described in Embodiment 2 of the present invention;

[0043] Figure 6 This is a schematic diagram of the urea solution pressure control method of the SCR control method described in Embodiment 2 of the present invention;

[0044] Figure 7 This is a schematic diagram of a urea pump control method according to an SCR control method described in Embodiment 2 of the present invention;

[0045] Figure 8 This is a schematic diagram of a urea level control method according to an SCR control method described in Embodiment 2 of the present invention;

[0046] Figure 9 This is a structural block diagram of an SCR control device according to Embodiment 3 of the present invention;

[0047] Figure 10 This is a schematic diagram of an SCR control device according to Embodiment 3 of the present invention;

[0048] The diagram is labeled as follows: 01-Replenishment pump, 02-Urea tank, 03-Urea pump, 05-Return solenoid valve, 06-Pressure limiting valve, 07-Liquid circuit pressure sensor, 08-Damper, 09-Liquid circuit shut-off valve, 10-Spray gun, 11-Gas-liquid separator, 12-Gas circuit pressure sensor, 13-Gas circuit shut-off valve, 14-Controller, 15-Monitoring terminal, 16-Differential pressure sensor, 17-Pre-NOx concentration sensor, 18-Bypass valve, 19-Pre-shut-off valve, 20-Spray gun holder, 21-Mixer, 22-SCR upstream temperature sensor, 23-SCR downstream temperature sensor, 24-SCR reactor, 25-Post-shut-off valve, 26-Post-NOx concentration sensor, 27-Cloud monitoring platform. Detailed Implementation

[0049] The present invention will be further described in detail below with reference to embodiments and specific implementation methods. However, this should not be construed as limiting the scope of the above-described subject matter of the present invention to the following embodiments; all technologies implemented based on the content of the present invention fall within the scope of the present invention.

[0050] Example 1

[0051] An SCR control method, such as Figure 1 As shown, it includes the following steps:

[0052] S1: Real-time detection of the working status of the SCR device, and determination of whether the working status meets the access conditions. If yes, enter the pressure building state and perform pressure building. After successful pressure building, execute step S2. Otherwise, repeat the detection of the working status of the SCR device. The SCR device includes several urea pumps.

[0053] S2: Calculate the required urea injection volume and perform closed-loop control of urea solution pressure based on the required urea injection volume;

[0054] S3: Enter the urea injection state and continuously determine whether the injection conditions are met. The injection conditions are the same as the working state. If they are met, the urea pump continues to inject; otherwise, the urea pump stops working and returns to step S1.

[0055] Using the above technical solution, there is no need to obtain the equipment's operating conditions, making calibration easier. This method is applicable to NO3- content in equipment such as large generator sets, ships, engine bench test laboratories, and industrial boilers. x Governance and reduction of NO x The emission control method is simple and has the advantages of wide adaptability, simple modification, easy implementation and easy monitoring.

[0056] Example 2

[0057] This embodiment is a specific implementation of embodiment 1;

[0058] The admission criteria include: no system malfunctions, average temperature of upstream and downstream of SCR ≥ 200℃, urea level ≥ 20%, urea temperature ≥ 0℃, gas pressure ≥ 2 bar, and minimum injection rate ≥ 900 mg / s.

[0059] Specifically, this includes the first urea pump and the second urea pump.

[0060] like Figure 2 The diagram shown is a schematic of the overall control method provided in an embodiment of the present invention. After the SCR device is powered on, the operating parameters of the SCR device are calculated and detected in real time; when the access conditions are met, the urea pump is driven to build up pressure; after the pressure is built up, the urea injection volume is controlled by controlling the urea solution pressure; during the injection process, it is detected in real time whether the injection conditions are met; if the injection conditions are not met, the urea pump stops working, and the calculation and detection of the SCR operating parameters are resumed; the injection conditions are the same as the access conditions.

[0061] like Figure 3 The diagram shown illustrates a urea injection quantity control method provided in an embodiment of the present invention. First, the required urea injection quantity is calculated. Based on the calculated required urea injection quantity, the target urea pressure is obtained by looking up the MAP. The urea solution pressure is then controlled via a return solenoid valve, thereby controlling the urea injection quantity. The required urea injection quantity *m* is derived from the basic required urea injection quantity *m0*.b The formula is as follows: (Calculated using the correction factor α)

[0062] m=α*m b

[0063] Specifically, the basic urea injection volume m b From exhaust flow rate Q m (unit: kg / h), NO x Original discharge concentration C NOx (Unit: ppm), target conversion efficiency η (unit: %), and ammonia-nitrogen ratio γ are calculated using the following formula:

[0064] m b =Q m *C NOx *η*γ / 34000

[0065] Among them, exhaust mass flow rate Q m NO x Original discharge concentration C NOx All values ​​are obtained directly or indirectly from sensor measurements; the target conversion efficiency η is obtained by referring to the MAP based on the space velocity and SCR catalyst temperature; the ammonia-to-nitrogen ratio γ is a calibration value.

[0066] like Figure 4 and 5 As shown, the correction coefficient α is calculated by the closed-loop adjustment function of the post-nitrogen and oxygen concentration. The specific method is as follows:

[0067] NO was calculated based on the NO concentration values ​​measured by the front and rear nitrogen and oxygen sensors. x Real-time conversion efficiency; set the time t for calculating real-time conversion efficiency, and calculate NO within the time period t. x Average conversion efficiency; the difference between the obtained average conversion efficiency and the current conversion efficiency is calculated and the absolute value is taken. The magnitude of the absolute value is then determined. When the absolute value is greater than or equal to the set threshold, the correction coefficient α is equal to a constant of 1. When the absolute value is less than the set threshold, the closed-loop adjustment function for nitrogen and oxygen concentration is entered, the closed-loop adjustment factor is calculated, and the correction coefficient α is equal to the closed-loop adjustment factor.

[0068] Specifically, after entering the closed-loop adjustment function for post-nitrogen and oxygen concentration, the closed-loop adjustment factor is obtained by using the target post-nitrogen and oxygen concentration and the deviation of the current post-nitrogen and oxygen measurement value as inputs, followed by a PI algorithm and maximum and minimum limits. The target post-nitrogen and oxygen concentration is determined based on the target conversion efficiency and NO... x The original discharge concentration was calculated.

[0069] The closed-loop adjustment factor is an automatically calculated value. The deviation between the target nitrogen and oxygen concentration value and the current nitrogen and oxygen sensor measurement value is used as input, and a value between 0 and 1 is calculated by the PI algorithm, which is then constrained by the maximum and minimum values.

[0070] like Figure 6 The diagram shown is a schematic of a urea solution pressure control method provided in an embodiment of the present invention. The urea solution pressure is controlled by the opening degree of the return solenoid valve, specifically as follows:

[0071] The pressure deviation, obtained by subtracting the pressure sensor measurement from the target pressure obtained from the urea injection demand table, is used as input. After processing by a PI algorithm, the valve opening coefficient k is obtained, realizing closed-loop control of the urea solution pressure. The valve opening calculation method is as follows:

[0072] θ = k * 100% k∈[0,1]

[0073] Wherein, k is the opening coefficient of the return solenoid valve.

[0074] The calculation formula for the PI algorithm is as follows:

[0075] k=kp*err(t)+ki*∑err(j)j∈[0,t]

[0076] In the PI algorithm, the coefficients kp and parameter ki are obtained by looking up the urea solution pressure when the urea pump is pressurized and the target pressure obtained by looking up the table based on the urea demand injection amount; err(t) is the deviation value at time t.

[0077] like Figure 7 The diagram shown is a schematic of the urea pump control method provided in an embodiment of the present invention. The urea pump adopts a state-flow control method, including four states: pump stop, pressure build-up, injection, and purging. The urea pump state is switched based on access conditions. The specific method is as follows:

[0078] When the controller is powered on, the urea pump is initially in the stopped state. The controller monitors the SCR's operating parameters in real time. When the access conditions are met, the urea pump (default first urea pump) begins to build up pressure. During the pressure building state, the gas circuit, liquid circuit shut-off valves, and return liquid solenoid valve are all in the closed state.

[0079] The process of entering and building up pressure includes: after entering the pressure building state, the first urea pump is assumed to be building up pressure, the pressure building timer is started, and the pressure threshold is set to ≥2 bar, the pressure building time threshold is set to ≤30 s, the maximum pressure building time is set to ≤60 s, and the maximum number of pressure building times is set to 3. If the actual urea solution pressure value measured by the pressure sensor reaches the set pressure threshold and meets the pressure building time threshold within the maximum pressure building time, then the pressure building is completed, and the urea solution pressure value at this time is recorded. The urea solution pressure value is used to determine the valve opening parameters.

[0080] If the actual urea pressure value measured by the pressure sensor does not reach the pressure threshold within the maximum pressure build-up time, the pressure build-up fails, the number of pressure build-up failures is incremented by 1, and pressure build-up is retried. When the number of pressure build-up failures exceeds the maximum number of pressure build-up attempts, a pressure build-up fault is reported, and the first urea pump enters the purging state from the pressure build-up state. After the purging is completed, the pump stops.

[0081] The conditions for entering the pressure build-up state include system fault status, SCR upstream and downstream temperatures, urea level, urea temperature, gas path pressure, and minimum injection volume. The system enters the pressure build-up state once all conditions are met.

[0082] Once the pressure build-up is complete, it automatically switches to injection mode. In injection mode, the liquid circuit shut-off valve, gas circuit shut-off valve, and return solenoid valve start working, controlling the urea solution pressure and thus the urea injection volume according to the required injection volume.

[0083] During injection, the first and second urea pumps operate alternately. A single-pump operating time threshold is set, which is determined according to actual needs. When the single-pump operating time exceeds the threshold, pump switching occurs. During pump switching, the first and second urea pumps operate simultaneously. When the simultaneous operating time exceeds the set threshold, the system officially switches to sole operation of the other pump. During pump switching, all solenoid valves in the liquid path, gas path, and return liquid path are closed. When the controller is powered down or injection conditions are not met, the system enters a purging state. After purging, the system enters a pump stop state. The injection conditions are the same as the pressure build-up entry conditions.

[0084] In purging mode, the urea pump stops working, the return solenoid valve closes, and the liquid circuit shut-off valve and gas circuit shut-off valve remain open. When entering purging mode, the purging timer is started. When the purging time exceeds the set time threshold, purging is complete, and the pump transitions from purging mode to pump stop mode.

[0085] like Figure 8The diagram illustrates a urea level control method provided in an embodiment of the present invention. Upper and lower limits for the urea level are set. The level is monitored in real time. If the measured level is below the lower limit, the replenishment pump operates to replenish the urea until the measured level exceeds the upper limit, at which point replenishment stops. Replenishment is not performed under other conditions. A maximum replenishment time threshold is set, which needs to be determined based on the urea tank volume and the replenishment pump flow rate. During replenishment, if the replenishment time exceeds the set maximum replenishment time threshold, replenishment stops and a replenishment fault is reported.

[0086] The upper and lower limits of urea level need to be calibrated in advance. To prevent insufficient or excessive urea, the lower limit is generally calibrated to 10%-20%, and the upper limit is generally calibrated to 90%-95%.

[0087] Compared to existing technologies, this invention eliminates the need for extensive and meticulous calibration, making it relatively easy to modify ships, factories, and other facilities to reduce NOx emissions. x Emissions. Among them, various thresholds are based on a predetermined control logic framework and need to be calibrated according to specific application scenarios. Some thresholds can be determined based on the characteristics of the system, some can be determined based on empirical values, and some need to be determined in combination with the characteristics of the application scenario.

[0088] Example 3

[0089] This invention provides a high-flow-rate SCR device as an embodiment of the present invention. Figure 9 As shown, it includes: a urea supply system, an auxiliary gas supply system, a main control system, and a packaging unit; the urea supply system and the auxiliary gas supply system are both electrically connected to the main control system;

[0090] like Figure 10 As shown, the urea supply system includes: a replenishment pump 01, a urea tank 02, several urea pumps 03, a return solenoid valve 05, a pressure limiting valve 06, a liquid pressure sensor 07, a damper 08, a liquid shut-off valve 09, and a spray gun 10; the urea tank 02 integrates a liquid level sensor and a temperature sensor; the inlet of the replenishment pump 01 is connected to an external replenishment tank via a first replenishment pipe, and the outlet of the replenishment pump 01 is connected to the urea tank 02 via a second replenishment pipe; the inlets of the several urea pumps 03... The liquid outlet is connected to the urea tank 02 via an inlet pipe, and the outlets of several urea pumps 03 are connected to the inlet of the liquid circuit shut-off valve 09 via a first outlet pipe; the liquid circuit pressure sensor 07 and the damper 08 are installed in the first outlet pipe; the outlet of the liquid circuit shut-off valve 09 is connected to the inlet of the spray gun 10 via a second outlet pipe; the return solenoid valve 05 and the pressure limiting valve 06 are connected in parallel and are located between the first outlet pipe and the urea tank 02;

[0091] The auxiliary gas supply system includes: a gas-water separator 11, a gas pressure sensor 12, and a gas shut-off valve 13; the gas-water separator 11 integrates a gas pressure regulator; the air inlet of the gas-water separator 11 is connected to an external gas source through a first air inlet pipe, and the air outlet of the gas-water separator 11 is connected to the air inlet of the gas shut-off valve 13 through a second air inlet pipe; the gas pressure sensor 12 is installed in the second air inlet pipe; the air outlet of the gas shut-off valve 13 is connected to the air inlet of the spray gun 10 through a third air inlet pipe.

[0092] The main control system includes: a controller 14, a monitoring terminal 15, a differential pressure sensor 16, a pre-nitrogen oxygen concentration sensor 17, an upstream temperature sensor 22 of the SCR, a downstream temperature sensor 23 of the SCR, a downstream nitrogen oxygen concentration sensor 26, and a cloud monitoring platform 27; the controller 14 and the monitoring terminal 15 are connected via a CAN bus; the monitoring terminal 15 and the cloud monitoring platform 27 are communicatively connected; the controller 14 is connected to the replenishment pump 01, the urea tank 02, several urea pumps 03, the return solenoid valve 05, the liquid circuit pressure sensor 07, and the... The liquid circuit shut-off valve 09, the gas circuit pressure sensor 12, the gas circuit shut-off valve 13, the differential pressure sensor 16, the upstream nitrogen and oxygen concentration sensor 17, the upstream temperature sensor 22 of the SCR, the downstream temperature sensor 23 of the SCR, and the downstream nitrogen and oxygen concentration sensor 26 are electrically connected; the upstream nitrogen and oxygen concentration sensor 17, the upstream temperature sensor 22 of the SCR, the downstream temperature sensor 23 of the SCR, and the downstream nitrogen and oxygen concentration sensor 26 are respectively installed on the packaging unit; the differential pressure sensor 16 is connected to the packaging unit through a pipeline;

[0093] The encapsulation unit includes: a bypass valve 18, a front shut-off valve 19, a spray gun holder 20, a mixer 21, an SCR reactor 24, and a rear shut-off valve 25; the front end of the front shut-off valve 19 is connected to an air inlet pipe, and the rear end is connected to the mixer 21; the spray gun 10 is mounted on the spray gun holder 20 of the encapsulation unit; the spray gun holder 20 is mounted on the mixer 21 or the air inlet pipe; the rear end of the mixer 21 is connected to the SCR reactor 24; the rear end of the SCR reactor 24 is connected to the rear shut-off valve 25; the rear end of the rear shut-off valve 25 is connected to an air outlet pipe; a bypass pipe is connected between the air inlet pipe and the air outlet pipe, and the bypass valve 18 is installed in the bypass pipe.

[0094] The aforementioned device comprises a replenishment pump 01, a urea tank 02, a urea pump 03, a return solenoid valve 05, a pressure limiting valve 06, a liquid pressure sensor 07, a damper 08, a liquid shut-off valve 09, and a spray gun 10, forming a urea supply system. Specifically, the replenishment pump 01 replenishes the urea tank; the urea tank 02 stores the urea solution and provides feedback on the urea level and temperature; the urea pump 03 and the return solenoid valve 05 jointly control the urea solution pressure; the pressure limiting valve 06 is a manually adjustable valve that limits the urea solution pressure; the liquid pressure sensor 07 measures the urea solution pressure; the damper 08 stabilizes the liquid pressure within the urea pipeline; the liquid shut-off valve 09 controls the opening and closing of the urea pipeline; and the spray gun 10 sprays the urea solution.

[0095] In the above-mentioned device, the gas-water separator 11, the gas pressure sensor 12, and the gas shut-off valve 13 together constitute the auxiliary gas supply system. Among them, the gas-water separator 11 is used to separate the moisture in the auxiliary gas and set the pressure of the auxiliary gas; the gas shut-off valve 13 is used to control the opening and closing of the gas path of the spray gun 10; and the gas pressure sensor 12 is used to measure the pressure of the auxiliary gas.

[0096] In the above-mentioned device, the controller 14 is the control center of the entire device, realizing functions such as sensor signal acquisition and processing, execution of control logic, driving of actuators, and fault diagnosis.

[0097] In the aforementioned device, the monitoring terminal 15 is used to display and monitor the device's operating parameters, including temperature, pressure, urea injection rate, nitrogen and oxygen concentration, conversion efficiency, and fault codes. This monitoring information is acquired through communication with the controller 14 and then wirelessly transmitted to the cloud monitoring platform 27 for display and storage.

[0098] The monitoring terminal 15 also has positioning and remote calibration functions. Specifically, parameter calibration is performed through the cloud monitoring platform 27; the cloud monitoring platform 27 transmits the calibration results to the monitoring terminal 15 for parsing and processing via wireless communication; the monitoring terminal 15 sends the processed calibration results to the controller 14 for storage and execution via the CAN bus, thereby realizing the remote calibration function.

[0099] In the aforementioned device, the front nitrogen and oxygen concentration sensor 17 and the rear nitrogen and oxygen concentration sensor 26 are used to measure NO. x The original discharge concentration and the concentration after treatment; the upstream temperature sensor 22 and the downstream temperature sensor 23 of the SCR are used to measure the tail gas temperature at the inlet and outlet of the SCR reactor 24, respectively.

[0100] In the aforementioned apparatus, the mixer 21, SCR reactor 24, spray gun holder 20, bypass valve 18, pre-shutdown valve 19, and post-shutdown valve 25 constitute the main encapsulated parts of the apparatus. The mixer 21 is the site for the decomposition and mixing of the urea solution; the SCR reactor 24 is for the reduction of NO. x The catalytic converter; bypass valve 18 and shut-off valves 19 and 25 respectively control the opening and closing of the tail gas bypass passage and the SCR reactor passage.

[0101] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An SCR control method, characterized in that, Includes the following steps: S1: Real-time detection of the working status of the SCR device, and determination of whether the working status meets the access conditions. If yes, enter the pressure building state and perform pressure building. After successful pressure building, execute step S2. Otherwise, repeat the detection of the working status of the SCR device. The SCR device includes several urea pumps. The process of entering and building up pressure includes: after entering the pressure building state, one of the urea pumps is used for pressure building by default. A pressure building timer is started, and a pressure threshold of ≥2 bar, a pressure building time threshold of ≤30 s, a maximum pressure building time of ≤60 s, and a maximum number of pressure building attempts are set according to actual needs. If the actual urea solution pressure value measured by the pressure sensor reaches the set pressure threshold and meets the pressure building time threshold within the maximum pressure building time, then the pressure building is completed, and the urea solution pressure value at this time is recorded. The urea solution pressure value is used to determine the valve opening parameters. If the actual urea pressure value measured by the pressure sensor does not reach the pressure threshold within the maximum pressure build-up time, the pressure build-up fails, the number of pressure build-up failures is incremented by 1, and the pressure build-up is retried. When the number of pressure build-up failures exceeds the maximum number of pressure build-up attempts, a pressure build-up fault is reported, and the urea pump enters the purging state from the pressure build-up state. After the purging is completed, the pump stops. S2: Calculate the required urea injection volume and perform closed-loop control of urea solution pressure based on the required urea injection volume; S3: Enter the urea injection state and continuously determine whether the injection conditions are met. If yes, the urea pump continues to inject; otherwise, the urea pump stops working and returns to step S1. The injection conditions are the same as the admission conditions. Entering the urea injection state includes: the liquid circuit shut-off valve, the gas circuit shut-off valve, and the return liquid solenoid valve starting to work; urea solution pressure control according to the required urea injection volume; during the injection state, several urea pumps operate alternately; a single pump operating time threshold is set; when the single pump operating time exceeds the single pump operating time threshold, pump switching occurs; during the pump switching period, several urea pumps operate simultaneously; a multi-pump operating time threshold is set; when the simultaneous operating time exceeds the multi-pump operating time threshold, another pump is officially switched to operate alone; during the switching period, the liquid circuit shut-off valve, the gas circuit shut-off valve, and the return liquid solenoid valve are all closed.

2. The SCR control method according to claim 1, characterized in that, The access conditions mentioned in step S1 include: no system faults, average temperature of upstream and downstream of SCR ≥200℃, urea level ≥20%, urea temperature ≥0℃, gas pressure ≥2bar, and minimum injection rate ≥900mg / s.

3. The SCR control method according to claim 1, characterized in that, The formula for calculating the required urea injection volume in step S2 is as follows: Wherein, m b The injection volume is the base urea requirement, and α is the correction factor. The formula for calculating the basic urea injection volume requirement is as follows: Among them, Q m The C is the exhaust mass flow rate. NOx NO x The original discharge concentration, where η is the target conversion efficiency and γ is the ammonia-nitrogen ratio.

4. The SCR control method according to claim 3, characterized in that, The correction coefficient is calculated by the closed-loop regulation function of the post-nitrogen and oxygen concentration, including: calculating the real-time conversion efficiency based on the pre-nitrogen and oxygen concentration values ​​measured by the pre-nitrogen and oxygen sensors and the post-nitrogen and oxygen sensors, respectively, setting the time for calculating the real-time conversion efficiency as t, and calculating the NO within the time period t. x The average conversion efficiency is obtained by subtracting the current conversion efficiency and taking the absolute value. When the absolute value is greater than or equal to a set threshold, the correction coefficient is equal to 1. When the absolute value is less than the set threshold, the nitrogen and oxygen concentration is adjusted in a closed loop, and the closed loop adjustment factor is calculated. At this time, the correction coefficient is equal to the closed loop adjustment factor. The closed-loop adjustment factor is obtained by taking the deviation between the target nitrogen and oxygen concentration and the current measured nitrogen and oxygen concentration as input, and then processing it through a PI algorithm and after passing through maximum and minimum limits.

5. The SCR control method according to claim 1, characterized in that, Step S2, which describes closed-loop control of urea solution pressure based on the required urea injection volume, includes: obtaining the target urea solution pressure value by looking up the MAP based on the required urea volume, and adjusting the urea solution pressure to the target solution pressure by controlling the return solenoid valve, thereby controlling the urea injection volume. The closed-loop control of the urea solution pressure adopts a PI algorithm, which includes: obtaining a pressure deviation by subtracting the target urea solution pressure value from the actual urea solution pressure value measured by the pressure sensor; using the pressure deviation as the input of the PI algorithm; obtaining a return solenoid valve opening coefficient through the PI algorithm; and then obtaining the valve opening. The calculation formula for the PI algorithm is as follows: k=kp*err(t)+ki*∑err(j)j∈[0,t] Among them, the coefficient kp and parameter ki are obtained by looking up the urea solution pressure when the urea pump is pressure built up and the target pressure obtained by looking up the table according to the urea demand injection amount, and err(t) is the deviation value at time t. The formula for calculating the valve opening is: Wherein, k is the opening coefficient of the return solenoid valve.

6. The SCR control method according to claim 1, characterized in that, Step S3, when performing urea injection, also includes real-time replenishment of urea solution in the urea tank: setting an upper limit and a lower limit for the urea solution level, detecting the solution level in real time, and if the solution level is lower than the lower limit, the replenishment pump will work to replenish the solution until the solution level exceeds the upper limit, at which point replenishment will stop. No replenishment will be performed under other conditions. A maximum fluid replenishment time threshold is set. If the fluid replenishment time exceeds the maximum fluid replenishment time threshold during the fluid replenishment process, the fluid replenishment is stopped and a fluid replenishment failure is reported.

7. An SCR control device for implementing the SCR control method according to any one of claims 1-6, characterized in that, include: Urea supply system, auxiliary gas supply system, main control system, and packaging unit; The urea supply system and the auxiliary gas supply system are both electrically connected to the main control system; The urea supply system includes: a replenishment pump (01), a urea tank (02), several urea pumps (03), a return solenoid valve (05), a pressure limiting valve (06), a liquid pressure sensor (07), a damper (08), a liquid shut-off valve (09), and a spray gun (10); the urea tank (02) integrates a liquid level sensor and a temperature sensor; the inlet of the replenishment pump (01) is connected to an external replenishment tank through a first replenishment pipe, and the outlet of the replenishment pump (01) is connected to the urea tank (02) through a second replenishment pipe; several urea pumps (03) The inlet of the urea pump (03) is connected to the urea tank (02) through an inlet pipe, and the outlets of several urea pumps (03) are connected to the inlet of the liquid shut-off valve (09) through a first outlet pipe; the liquid pressure sensor (07) and the damper (08) are installed in the first outlet pipe; the outlet of the liquid shut-off valve (09) is connected to the inlet of the spray gun (10) through a second outlet pipe; the return solenoid valve (05) is connected in parallel with the pressure limiting valve (06) and is located between the first outlet pipe and the urea tank (02); The auxiliary gas supply system includes: a gas-water separator (11), a gas pressure sensor (12), and a gas shut-off valve (13); the gas-water separator (11) integrates a gas pressure regulator; the air inlet of the gas-water separator (11) is connected to an external gas source through a first air inlet pipe, and the air outlet of the gas-water separator (11) is connected to the air inlet of the gas shut-off valve (13) through a second air inlet pipe; the gas pressure sensor (12) is installed in the second air inlet pipe; the air outlet of the gas shut-off valve (13) is connected to the air inlet of the spray gun (10) through a third air inlet pipe. The main control system includes: a controller (14), a monitoring terminal (15), a differential pressure sensor (16), a pre-nitrogen oxygen concentration sensor (17), an SCR upstream temperature sensor (22), an SCR downstream temperature sensor (23), a post-nitrogen oxygen concentration sensor (26), and a cloud monitoring platform (27); the controller (14) and the monitoring terminal (15) are connected via a CAN bus; the monitoring terminal (15) and the cloud monitoring platform (27) are connected via a communication connection; the controller (14) is connected to the replenishment pump (01), the urea tank (02), several urea pumps (03), the return solenoid valve (05), and the liquid circuit pressure sensor (06), respectively. 7) The liquid circuit shut-off valve (09), the gas circuit pressure sensor (12), the gas circuit shut-off valve (13), the differential pressure sensor (16), the upstream nitrogen and oxygen concentration sensor (17), the upstream temperature sensor (22) of the SCR, the downstream temperature sensor (23) of the SCR, and the downstream nitrogen and oxygen concentration sensor (26) are electrically connected; the upstream nitrogen and oxygen concentration sensor (17), the upstream temperature sensor (22) of the SCR, the downstream temperature sensor (23) of the SCR, and the downstream nitrogen and oxygen concentration sensor (26) are respectively installed on the packaging unit; the differential pressure sensor (16) is connected to the packaging unit through a pipeline; The encapsulation unit includes: a bypass valve (18), a front shut-off valve (19), a spray gun holder (20), a mixer (21), an SCR reactor (24), and a rear shut-off valve (25); the front end of the front shut-off valve (19) is connected to an air inlet pipe, and the rear end is connected to the mixer (21); the spray gun (10) is mounted on the spray gun holder (20) of the encapsulation unit; the spray gun holder (20) is mounted on the mixer (21) or the air inlet pipe; the rear end of the mixer (21) is connected to the SCR reactor (24); the rear end of the SCR reactor (24) is connected to the rear shut-off valve (25); the rear end of the rear shut-off valve (25) is connected to an air outlet pipe; a bypass pipe is connected between the air inlet pipe and the air outlet pipe, and the bypass valve (18) is installed in the bypass pipe.

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