Denitration system and method capable of automatically adjusting ammonia spraying strategy

Abstract

The invention discloses a denitration system capable of automatically adjusting an ammonia spraying strategy, which comprises a data sensing layer and an execution layer, the data sensing layer comprises a plurality of measuring devices arranged at an inlet and an outlet of an SCR (Selective Catalytic Reduction) reactor, the execution layer comprises a plurality of ammonia spraying grids arranged along the section of a flue in a partitioned manner, and each partition corresponds to an independent ammonia spraying branch pipe; an adjustable flow control valve is arranged on each ammonia spraying branch pipe; the control layer is in communication connection with the data sensing layer and the execution layer, and the control layer comprises an advanced controller and is configured to receive real-time data of the data sensing layer and optimize the real-time data on the basis of a preset denitration model and an optimization algorithm; calculating the distribution uniformity index of the NOx concentration at the outlet of the SCR reactor and the target ammonia gas flow required by each partition of the plurality of ammonia spraying grids; and the distributed PID controller is connected with the advanced controller and is configured to receive the target ammonia gas flow of each partition and generate a control signal to drive the corresponding flow control valve, and the total ammonia consumption can be remarkably reduced under the same denitration efficiency.

Description

Technical Field

[0001] This invention belongs to the field of denitrification technology, specifically relating to a denitrification system and method that automatically adjusts ammonia injection strategy. Background Technology

[0002] Traditional ammonia injection control strategies typically employ a simple control method: calculating the total ammonia injection rate based on the SCR reactor inlet NOx concentration and flue gas flow rate, and then using PID correction based on feedback from the outlet NOx concentration. This total quantity control mode has several problems, such as: 1) Due to deviations in the flow of flue gas within the flue, a simple ammonia injection grid cannot guarantee uniform mixing of ammonia and NOx across the flue cross-section. This results in excessive ammonia in some areas, causing ammonia escape, corrosion of downstream equipment, and increased operating costs, while insufficient ammonia in other areas leads to low denitrification efficiency and excessive emissions. 2) The SCR system is a system with large inertia and large lag. Traditional PID control has a slow response and is difficult to adapt to the drastic fluctuations in operating conditions caused by changes in unit load and coal type, which can easily lead to emission fluctuations or excessive ammonia injection. 3) The existing system cannot detect the distribution of NOx at the outlet, let alone make targeted, zoned adjustments based on the uneven distribution. Summary of the Invention

[0003] To achieve the above objectives, the present invention adopts the following technical solution: The present invention provides a denitrification system for automatically adjusting ammonia injection strategy, comprising a data sensing layer, an execution layer, and a control layer, wherein: The data sensing layer is used to collect the operating parameters of the denitrification system in real time. The data sensing layer includes multiple measuring devices installed at the inlet and outlet of the SCR reactor to measure parameters including at least NOx concentration, temperature, flue gas flow rate and oxygen content. The execution layer includes multiple ammonia injection grids arranged in sections along the flue cross-section, each section corresponding to an independent ammonia injection branch pipe, and each ammonia injection branch pipe is equipped with an adjustable flow control valve. A control layer, communicatively connected to the data perception layer and the execution layer, comprising: An advanced controller is configured to receive real-time data from the data sensing layer and, based on a preset denitrification model and optimization algorithm, calculate the distribution uniformity index of NOx concentration at the outlet of the SCR reactor and the target ammonia flow rate required for each zone of the multiple ammonia injection grids. A distributed PID controller, connected to the advanced controller, is configured to receive the target ammonia flow rate from each zone and generate control signals to drive the corresponding flow control valves.

[0004] Preferably, the data sensing layer further includes: An online laser analyzer is installed at the outlet of the SCR reactor. The online laser analyzer is configured to measure the two-dimensional NOx concentration distribution cloud map on the outlet cross section of the SCR reactor by laser scanning.

[0005] Preferably, the advanced controller is configured as follows: Based on the two-dimensional NOx concentration distribution cloud map, the relative standard deviation of the outlet NOx concentration is calculated as the distribution uniformity index. When the relative standard deviation exceeds the first preset threshold, it is determined that the uniformity of ammonia injection is poor, and an ammonia injection leveling strategy is initiated. The ammonia injection leveling strategy includes: adjusting the target ammonia flow rate of the corresponding ammonia injection branch pipe in reverse according to the concentration level of each region in the two-dimensional NOx concentration distribution cloud map, that is, increasing the ammonia injection amount in high concentration areas and decreasing the ammonia injection amount in low concentration areas.

[0006] Preferably, the denitrification model preset in the advanced controller is a data-driven model, which is trained using historical operating data. The historical operating data includes the mapping relationship between inlet NOx, flue gas flow rate, temperature, ammonia injection rate and outlet NOx concentration. The optimization algorithm is a model predictive control algorithm, which is used to solve the optimal target ammonia flow rate sequence for each zone in the future period, with the goal of minimizing ammonia consumption and / or optimizing the uniformity of outlet NOx distribution, under the premise of meeting the total NOx emission limit at the outlet.

[0007] Preferably, the advanced controller is further configured to: Based on the real-time collected flue gas flow rate and inlet NOx concentration, calculate the theoretical total ammonia injection amount required by the system; Based on the deviation between the average NOx concentration at the outlet of the SCR reactor and the set value, the theoretical total ammonia injection rate is corrected by PID to obtain the global ammonia injection set value. The global ammonia injection setting value is allocated to each partition according to the optimization results of the advanced controller.

[0008] Preferably, it further includes: The ammonia slip monitoring module includes multiple ammonia slip monitors installed at the outlet of the SCR reactor to measure the ammonia slip concentration in different areas; The advanced controller is also configured to: receive the ammonia escape concentration data, and when the ammonia escape concentration in any region exceeds a second preset threshold, reduce the ammonia injection rate of the corresponding zone until the ammonia escape concentration returns to a safe range.

[0009] Preferably, a denitrification method for automatically adjusting the ammonia injection strategy of the system includes the following steps: S1 collects the operating parameters of the denitrification system in real time through the data sensing layer, including the NOx concentration, temperature, flue gas flow rate at the inlet and outlet of the SCR reactor, and the NOx concentration distribution at the outlet section. S2, the advanced controller, performs the following calculations based on the collected data, using a built-in denitrification model and optimization algorithm: Calculate the distribution uniformity index of NOx concentration at the outlet; With the goal of reducing total ammonia consumption and / or improving the uniformity of NOx distribution at the outlet, the target ammonia flow rate for each ammonia injection zone is calculated. S3, the distributed PID controller receives the target ammonia flow rate of each zone and drives the corresponding flow control valve to achieve independent and precise control of the ammonia injection amount of each zone. S4. Repeat steps S1 to S3 to form a closed-loop control.

[0010] Preferably, in step S2, the calculation of the distribution uniformity index of the outlet NOx concentration includes calculating its relative standard deviation based on the two-dimensional NOx concentration distribution cloud map measured by the laser online analyzer; when the relative standard deviation is greater than a first preset threshold, an ammonia injection leveling strategy is executed, and the ammonia injection amount of each zone is adjusted inversely according to the concentration distribution.

[0011] Preferably, in step S2, the optimization algorithm is model predictive control, which specifically includes: Establish a system dynamic model with inlet parameters as input and outlet NOx as output; An optimization function is defined with the objectives of minimizing total ammonia consumption and achieving optimal uniformity of NOx distribution at the outlet over a future period. In each control cycle, based on the current system state, the optimization function is solved continuously to obtain the sequence of optimal ammonia injection rates for each zone in the future control time domain, and the first value in the sequence is used as the target ammonia flow rate for each zone at the current moment.

[0012] Preferably, it also includes an ammonia slip protection step: Real-time monitoring of ammonia slip concentration at the SCR reactor outlet; When the ammonia escape concentration of a certain zone is detected to exceed the second preset threshold, the target ammonia flow rate of that zone is overridden first, and the ammonia injection rate is forcibly reduced.

[0013] The advantages of this invention compared to existing technologies are as follows: 1) By using zoned control and leveling based on distribution cloud maps, the mixing uniformity of ammonia and flue gas is greatly improved, and the total ammonia consumption can be significantly reduced under the same denitrification efficiency. 2) Through zoned control and ammonia escape interlock protection, excessive ammonia injection in local areas can be directly prevented, fundamentally reducing the risk of ammonia escape, protecting downstream air preheaters and other equipment, and extending their maintenance cycle. 3) The system realizes a fully automated closed loop from perception and decision-making to execution, reducing reliance on the experience of operators, reducing labor intensity, and realizing the intelligent operation of the denitrification system. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the denitrification process for automatically adjusting the ammonia injection strategy described in this invention. Detailed Implementation

[0015] The present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0016] Example: Figure 1 As shown, this embodiment adopts the following technical solution: This invention provides a denitrification system that automatically adjusts the ammonia injection strategy, including a data sensing layer, an execution layer, and a control layer, wherein: The data sensing layer is used to collect the operating parameters of the denitrification system in real time. The data sensing layer includes multiple measuring devices installed at the inlet and outlet of the SCR reactor to measure parameters including at least NOx concentration, temperature, flue gas flow rate and oxygen content. The execution layer includes multiple ammonia injection grids arranged in sections along the flue cross-section, each section corresponding to an independent ammonia injection branch pipe, and each ammonia injection branch pipe is equipped with an adjustable flow control valve. A control layer, communicatively connected to the data perception layer and the execution layer, comprising: An advanced controller is configured to receive real-time data from the data sensing layer and, based on a preset denitrification model and optimization algorithm, calculate the distribution uniformity index of NOx concentration at the outlet of the SCR reactor and the target ammonia flow rate required for each zone of the multiple ammonia injection grids. A distributed PID controller, connected to the advanced controller, is configured to receive the target ammonia flow rate from each zone and generate control signals to drive the corresponding flow control valves.

[0017] Furthermore, the data perception layer also includes: An online laser analyzer is installed at the outlet of the SCR reactor. The online laser analyzer is configured to measure the two-dimensional NOx concentration distribution cloud map on the outlet cross section of the SCR reactor by laser scanning.

[0018] Furthermore, the advanced controller is configured to: Based on the two-dimensional NOx concentration distribution cloud map, the relative standard deviation of the outlet NOx concentration is calculated as the distribution uniformity index. When the relative standard deviation exceeds the first preset threshold, it is determined that the uniformity of ammonia injection is poor, and an ammonia injection leveling strategy is initiated. The ammonia injection leveling strategy includes: adjusting the target ammonia flow rate of the corresponding ammonia injection branch pipe in reverse according to the concentration level of each region in the two-dimensional NOx concentration distribution cloud map, that is, increasing the ammonia injection amount in high concentration areas and decreasing the ammonia injection amount in low concentration areas.

[0019] Furthermore, the denitrification model preset in the advanced controller is a data-driven model, which is trained using historical operating data. The historical operating data includes the mapping relationship between inlet NOx, flue gas flow rate, temperature, ammonia injection rate and outlet NOx concentration. The optimization algorithm is a model predictive control algorithm, which is used to solve the optimal target ammonia flow rate sequence for each zone in the future period, with the goal of minimizing ammonia consumption and / or optimizing the uniformity of outlet NOx distribution, under the premise of meeting the total NOx emission limit at the outlet.

[0020] Furthermore, the advanced controller is also configured to: Based on the real-time collected flue gas flow rate and inlet NOx concentration, calculate the theoretical total ammonia injection amount required by the system; Based on the deviation between the average NOx concentration at the outlet of the SCR reactor and the set value, the theoretical total ammonia injection rate is corrected by PID to obtain the global ammonia injection set value. The global ammonia injection setting value is allocated to each partition according to the optimization results of the advanced controller.

[0021] Furthermore, it also includes: The ammonia slip monitoring module includes multiple ammonia slip monitors installed at the outlet of the SCR reactor to measure the ammonia slip concentration in different areas; The advanced controller is also configured to: receive the ammonia escape concentration data, and when the ammonia escape concentration in any region exceeds a second preset threshold, reduce the ammonia injection rate of the corresponding zone until the ammonia escape concentration returns to a safe range.

[0022] Furthermore, a denitrification method for automatically adjusting the ammonia injection strategy of the system includes the following steps: S1 collects the operating parameters of the denitrification system in real time through the data sensing layer, including the NOx concentration, temperature, flue gas flow rate at the inlet and outlet of the SCR reactor, and the NOx concentration distribution at the outlet section. S2, the advanced controller, performs the following calculations based on the collected data, using a built-in denitrification model and optimization algorithm: Calculate the distribution uniformity index of NOx concentration at the outlet; With the goal of reducing total ammonia consumption and / or improving the uniformity of NOx distribution at the outlet, the target ammonia flow rate for each ammonia injection zone is calculated. S3, the distributed PID controller receives the target ammonia flow rate of each zone and drives the corresponding flow control valve to achieve independent and precise control of the ammonia injection amount of each zone. S4. Repeat steps S1 to S3 to form a closed-loop control.

[0023] Further, in step S2, the calculation of the distribution uniformity index of the outlet NOx concentration includes calculating its relative standard deviation based on the two-dimensional NOx concentration distribution cloud map measured by the laser online analyzer; when the relative standard deviation is greater than a first preset threshold, an ammonia injection leveling strategy is executed, and the ammonia injection amount of each zone is adjusted inversely according to the concentration distribution.

[0024] Further, in step S2, the optimization algorithm is model predictive control, which specifically includes: Establish a system dynamic model with inlet parameters as input and outlet NOx as output; An optimization function is defined with the objectives of minimizing total ammonia consumption and achieving optimal uniformity of NOx distribution at the outlet over a future period. In each control cycle, based on the current system state, the optimization function is solved continuously to obtain the sequence of optimal ammonia injection rates for each zone in the future control time domain, and the first value in the sequence is used as the target ammonia flow rate for each zone at the current moment.

[0025] Furthermore, it also includes ammonia slip protection steps: Real-time monitoring of ammonia slip concentration at the SCR reactor outlet; When the ammonia escape concentration of a certain zone is detected to exceed the second preset threshold, the target ammonia flow rate of that zone is overridden first, and the ammonia injection rate is forcibly reduced.

[0026] It should be noted that the above content merely illustrates the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. For those skilled in the art, various improvements and modifications can be made without departing from the principle of the present invention, and all such improvements and modifications fall within the scope of protection of the claims of the present invention.

Claims

1. A denitrification system that automatically adjusts ammonia injection strategy, characterized in that, include: The data sensing layer is used to collect the operating parameters of the denitrification system in real time. The data sensing layer includes multiple measuring devices installed at the inlet and outlet of the SCR reactor to measure parameters including at least NOx concentration, temperature, flue gas flow rate and oxygen content. The execution layer includes multiple ammonia injection grids arranged in sections along the flue cross-section, each section corresponding to an independent ammonia injection branch pipe, and each ammonia injection branch pipe is equipped with an adjustable flow control valve. A control layer, communicatively connected to the data perception layer and the execution layer, comprising: An advanced controller is configured to receive real-time data from the data sensing layer and, based on a preset denitrification model and optimization algorithm, calculate the distribution uniformity index of NOx concentration at the outlet of the SCR reactor and the target ammonia flow rate required for each zone of the multiple ammonia injection grids. A distributed PID controller, connected to the advanced controller, is configured to receive the target ammonia flow rate from each zone and generate control signals to drive the corresponding flow control valves.

2. The denitrification system with automatic ammonia injection strategy adjustment according to claim 1, characterized in that, The data perception layer also includes: An online laser analyzer is installed at the outlet of the SCR reactor. The online laser analyzer is configured to measure the two-dimensional NOx concentration distribution cloud map on the outlet cross section of the SCR reactor by laser scanning.

3. The denitrification system with automatic ammonia injection strategy adjustment according to claim 2, characterized in that, The advanced controller is configured to: Based on the two-dimensional NOx concentration distribution cloud map, the relative standard deviation of the outlet NOx concentration is calculated as the distribution uniformity index. When the relative standard deviation exceeds the first preset threshold, it is determined that the uniformity of ammonia injection is poor, and an ammonia injection leveling strategy is initiated. The ammonia injection leveling strategy includes: adjusting the target ammonia flow rate of the corresponding ammonia injection branch pipe in reverse according to the concentration level of each region in the two-dimensional NOx concentration distribution cloud map, that is, increasing the ammonia injection amount in high concentration areas and decreasing the ammonia injection amount in low concentration areas.

4. The denitrification system with automatic ammonia injection strategy adjustment according to claim 1, characterized in that, The advanced controller's preset denitrification model is a data-driven model, trained using historical operating data, which includes the mapping relationship between inlet NOx, flue gas flow rate, temperature, ammonia injection rate, and outlet NOx concentration. The optimization algorithm is a model predictive control algorithm, used to solve the optimal target ammonia flow rate sequence for each zone over a future period, with the goal of minimizing ammonia consumption and / or achieving optimal uniformity of outlet NOx distribution, while meeting the total outlet NOx emission limit.

5. The denitrification system with automatic ammonia injection strategy adjustment according to claim 1, characterized in that, The advanced controller is also configured to: Based on the real-time collected flue gas flow rate and inlet NOx concentration, calculate the theoretical total ammonia injection amount required by the system; Based on the deviation between the average NOx concentration at the outlet of the SCR reactor and the set value, the theoretical total ammonia injection rate is corrected by PID to obtain the global ammonia injection set value. The global ammonia injection setting value is allocated to each partition according to the optimization results of the advanced controller.

6. The denitrification system with automatic ammonia injection strategy adjustment according to claim 1, characterized in that, Also includes: The ammonia slip monitoring module includes multiple ammonia slip monitors installed at the outlet of the SCR reactor to measure the ammonia slip concentration in different areas; The advanced controller is also configured to: receive the ammonia escape concentration data, and when the ammonia escape concentration in any region exceeds a second preset threshold, reduce the ammonia injection rate of the corresponding zone until the ammonia escape concentration returns to a safe range.

7. A denitrification method based on the system of any one of claims 1 to 6, characterized in that, Includes the following steps: S1 collects the operating parameters of the denitrification system in real time through the data sensing layer, including the NOx concentration, temperature, flue gas flow rate at the inlet and outlet of the SCR reactor, and the NOx concentration distribution at the outlet section. S2, the advanced controller, performs the following calculations based on the collected data, using a built-in denitrification model and optimization algorithm: Calculate the distribution uniformity index of NOx concentration at the outlet; With the goal of reducing total ammonia consumption and / or improving the uniformity of NOx distribution at the outlet, the target ammonia flow rate for each ammonia injection zone is calculated. S3, the distributed PID controller receives the target ammonia flow rate of each zone and drives the corresponding flow control valve to achieve independent and precise control of the ammonia injection amount of each zone. S4. Repeat steps S1 to S3 to form a closed-loop control.

8. The denitrification method for automatically adjusting ammonia injection strategy according to claim 7, characterized in that, In step S2, the calculation of the distribution uniformity index of NOx concentration at the outlet includes calculating the relative standard deviation based on the two-dimensional NOx concentration distribution cloud map measured by the laser online analyzer; when the relative standard deviation is greater than a first preset threshold, an ammonia injection leveling strategy is executed, and the ammonia injection amount of each zone is adjusted inversely according to the concentration distribution.

9. The denitrification method for automatically adjusting ammonia injection strategy according to claim 7, characterized in that, In step S2, the optimization algorithm is model predictive control, which specifically includes: Establish a system dynamic model with inlet parameters as input and outlet NOx as output; An optimization function is defined with the objectives of minimizing total ammonia consumption and achieving optimal uniformity of NOx distribution at the outlet over a future period. In each control cycle, based on the current system state, the optimization function is solved continuously to obtain the sequence of optimal ammonia injection rates for each zone in the future control time domain, and the first value in the sequence is used as the target ammonia flow rate for each zone at the current moment.

10. The denitrification method for automatically adjusting ammonia injection strategy according to claim 7, characterized in that, It also includes ammonia escape protection steps: Real-time monitoring of ammonia slip concentration at the SCR reactor outlet; When the ammonia escape concentration of a certain zone is detected to exceed the second preset threshold, the target ammonia flow rate of that zone is overridden first, and the ammonia injection rate is forcibly reduced.

Images