A control method and system for sintering flue gas SCR denitration

Abstract

The present application relates to steel metallurgical sintering process technology, and in particular to a sintering flue gas SCR denitration control method and system, comprising: matching a corresponding level for the NOx concentration based on pre-set concentration size level division rules; monitoring the fluctuation value of the NOx concentration; generating a basic ammonia injection amount corresponding to the NOx concentration based on pre-set theoretical ammonia injection amounts corresponding to each concentration size level and the actual level of the NOx concentration; calculating a flow adjustment value based on pre-set fixed parameters and the fluctuation value; and outputting the sum of the basic ammonia injection amount and the flow adjustment value as an ammonia injection target value. The present application divides the NOx concentration value into different levels, each level having a different control strategy, and accurately obtains the ammonia injection flow adjustment value by analyzing the time correlation between the fluctuation values, thereby solving the problem of ammonia injection hysteresis.

Description

Technical Field

[0001] This invention relates to the field of sintering technology in iron and steel metallurgy, specifically to a control method and system for SCR denitrification of sintering flue gas. Background Technology

[0002] SCR (Selective Catalytic Reduction) denitrification of sintering flue gas is a method for controlling the concentration of NOx (nitrogen oxides) in flue gas. This method is based on SCR technology. SCR controls NOx emissions by injecting ammonia into the flue gas, where it reacts with nitrogen oxides under the action of a catalyst to reduce NOx emissions. For NOx emissions, under a baseline oxygen content of 16%, the national standard requires ≤100 mg / m³. 3 In Hebei, Shandong, and other regions, the requirement is ≤50mg / m³. 3 Furthermore, it is a key monitoring area, requiring that emission standards not be exceeded. The ammonia injection rate is related to the NOx concentration and NOx removal efficiency. It is essential to ensure that the ammonia injection rate meets the needs of NOx removal while preventing large-scale ammonia leakage. Therefore, ammonia injection rate control is the core of NOx concentration emission control. However, NOx concentration control is characterized by a large lag, with a lag time of approximately 20 minutes. Moreover, sintering flue gas is characterized by large fluctuations in flue gas volume, high moisture content, and complex dust composition, resulting in significant local fluctuations in flue gas NOx content. It is difficult to directly control NOx concentration using actual NOx content and its changing trends. Sintering flue gas NOx concentration emission control is characterized by a large lag, disturbance, fluctuation, and uncertainty.

[0003] Existing conventional control algorithms employ PID control, which sets a NOx concentration value (lower than the emission standard) and controls the emission based on the deviation from the feedback value. If the feedback value is higher than the set value, the ammonia injection rate is increased; conversely, if it is lower, the ammonia injection rate is decreased. This algorithm has the following drawbacks: First, determining the optimal NOx emission control value is difficult. If the set value is too high, it easily leads to excessive emissions; if it is too low, a large ammonia injection rate is required, wasting ammonia and resulting in significant ammonia escape. Second, control based on deviation requires small control parameters due to the system's large lag; otherwise, large fluctuations in ammonia injection flow rate lead to large NOx fluctuations. However, excessively small parameters cannot respond promptly to NOx exceedances caused by fluctuations in sintering flue gas. Third, local fluctuations lead to frequent adjustments in ammonia flow rate control, exacerbating NOx emission fluctuations. For these reasons, the conventional deviation control algorithm is far from ideal, exhibiting drawbacks such as large NOx concentration fluctuations, high risk of excessive emissions, and high ammonia consumption, failing to meet the requirements for automatic NOx concentration control.

[0004] Based on the shortcomings of the existing technology, it is necessary to design a suitable NOx concentration emission control algorithm to achieve automatic control of NOx emission concentration in sintering flue gas to meet the standards, while ensuring an appropriate ammonia injection amount to prevent excessive ammonia injection, resulting in excessive ammonia escape, secondary pollution, and waste of ammonia water. Summary of the Invention

[0005] In view of the above-mentioned shortcomings of the prior art, the present invention provides a control method and system for SCR denitrification of sintering flue gas to solve the above-mentioned technical problems.

[0006] In a first aspect, the present invention provides a method for controlling SCR denitrification of sintering flue gas, comprising:

[0007] The NOx concentration is matched to the corresponding level based on a pre-set concentration level classification rule;

[0008] Monitor fluctuations in NOx concentration;

[0009] Based on the theoretical ammonia injection amount corresponding to each pre-set concentration level and the actual NOx concentration level, a basic ammonia injection amount corresponding to the NOx concentration is generated.

[0010] The flow regulation value is calculated based on the pre-set fixed parameters and the fluctuation value;

[0011] The sum of the basic ammonia injection rate and the flow rate adjustment value is output as the target ammonia injection rate.

[0012] In an optional implementation, the concentration level classification rules include:

[0013] Set low emission thresholds, high emission thresholds, and emission limits;

[0014] If the NOx concentration is below the low emission threshold, it is judged as a low emission level;

[0015] If the NOx concentration is above the low emission threshold and below the high emission threshold, it is classified as stable.

[0016] If the NOx concentration is above the high emission threshold but below the emission limit, it is judged as a high emission level;

[0017] If the NOx concentration is above the emission limit, it is judged as exceeding the emission level.

[0018] In an optional implementation, monitoring fluctuations in NOx concentration includes:

[0019] If the NOx concentration increases three times consecutively without fluctuation, it is considered to be an upward trend.

[0020] If the NOx concentration decreases three times consecutively and the NOx concentration does not fluctuate, it is determined to be a downward trend;

[0021] A third time threshold is set. If the NOx concentration does not fluctuate within the third time threshold, it is judged as a stable trend.

[0022] In an optional implementation, the monitoring of NOx concentration fluctuations further includes:

[0023] The NOx concentration value is rounded down to obtain the NOx usage value;

[0024] Set a first time threshold and a second time threshold;

[0025] If the NOx concentration value does not change after rounding up within the first time threshold, then the NOx value adopted is the rounded value of the current NOx concentration.

[0026] If the second time threshold is exceeded, and |NOx adopted value - actual NOx concentration rounded up| ≥ 2, then the NOx adopted value is the current actual NOx concentration rounded up.

[0027] In an optional implementation, the flow regulation value is calculated based on pre-set fixed parameters and the fluctuation value, including:

[0028] FC = (Current NOx value - NOx value before change) × K

[0029] Wherein, FC is the flow regulation value, which includes F0-F4, where F0 is the maximum regulating flow and F4 is the minimum regulating flow; K is the flow regulation amount.

[0030] In an optional implementation, the sum of the base ammonia injection rate and the flow rate adjustment value is output as the target ammonia injection rate value, including:

[0031] If the NOx concentration exceeds the emission level and shows a stable trend, an ammonia-enhancing water flow rate adjustment will be performed with an adjustment value of F0, and the steady-state time will be reset.

[0032] If the NOx concentration is at a high emission level and shows a stable trend, an ammonia-enhancing water flow rate adjustment will be performed with an adjustment value of F4, and the steady-state time will be reset.

[0033] If the NOx concentration is at a low emission level and shows a stable trend, an ammonia reduction water flow rate adjustment will be performed with an adjustment value of F4, and the steady-state time will be reset.

[0034] Secondly, the present invention provides a NOx concentration emission control system for SCR denitrification of sintering flue gas, comprising:

[0035] The matching level module is used to match the NOx concentration with a corresponding level based on a pre-set concentration level classification rule;

[0036] The fluctuation monitoring module is used to monitor the fluctuation values ​​of NOx concentration;

[0037] The basic ammonia injection module is used to generate a basic ammonia injection amount corresponding to the NOx concentration based on the theoretical ammonia injection amount corresponding to each pre-set concentration level and the actual NOx concentration level.

[0038] The flow regulation module calculates the flow regulation value based on pre-set fixed parameters and the fluctuation value;

[0039] The target ammonia injection module is used to output the sum of the basic ammonia injection quantity and the flow rate adjustment value as the target ammonia injection quantity value.

[0040] In an optional implementation, the matching level module includes:

[0041] The rating rule unit is used to set low emission thresholds, high emission thresholds, and emission limits. If the NOx concentration is below the low emission threshold, it is determined to be a low emission level; if the NOx concentration is above the low emission threshold but below the high emission threshold, it is determined to be a stable level; if the NOx concentration is above the high emission threshold but below the emission limit, it is determined to be a high emission level; and if the NOx concentration is above the emission limit, it is determined to be an over-emission level.

[0042] In an optional implementation, the monitoring fluctuation module includes:

[0043] The fluctuation detection unit is used to determine an upward trend if the NOx concentration increases three times consecutively without fluctuation; and a downward trend if the NOx concentration decreases three times consecutively without fluctuation. A third time threshold is set, and if the NOx concentration does not fluctuate within the third time threshold, it is determined to be a stable trend.

[0044] It also includes a rounding unit for rounding up the NOx concentration value to obtain the NOx adopted value; setting a first time threshold and a second time threshold; if the rounded NOx concentration value does not change within the first time threshold, then the NOx adopted value is the current rounded NOx concentration value; if the value exceeds the second time threshold and |NOx adopted value - actual NOx concentration rounded value| ≥ 2, then the NOx adopted value is the current actual NOx concentration rounded value.

[0045] In an optional implementation, the flow regulation module includes:

[0046] The flow regulation unit is used for FC = (current NOx input value - NOx input value before change) × K

[0047] Wherein, FC is the flow regulation value, which includes F0-F4, where F0 is the maximum regulating flow and F4 is the minimum regulating flow; K is the flow regulation amount.

[0048] In an optional implementation, the target ammonia injection module includes:

[0049] The target ammonia injection unit is used to adjust the ammonia injection water flow rate once if the NOx concentration is above the emission level and shows a stable trend, with an adjustment value of F0, and reset the steady-state time; if the NOx concentration is at a high emission level and shows a stable trend, it will adjust the ammonia injection water flow rate once, with an adjustment value of F4, and reset the steady-state time; if the NOx concentration is at a low emission level and shows a stable trend, it will adjust the ammonia reduction water flow rate once, with an adjustment value of F4, and reset the steady-state time.

[0050] The beneficial effects of this invention are as follows: The method and system for controlling SCR denitrification of sintering flue gas provided by this invention obtains the basic ammonia injection amount by classifying and monitoring the NOx concentration in the flue gas according to different levels, and then calculates the flow adjustment value according to preset fixed parameters and fluctuation values. Finally, the target value of the final ammonia injection amount is obtained by combining the basic injection amount and the flow adjustment, thereby completing the precise flow adjustment of ammonia water, realizing automatic control of NOx emission concentration in sintering flue gas, stabilizing emission value control, eliminating over-emission phenomenon, and reducing the number of ammonia water adjustment times by 18% through stable control. This solves the problems of large lag and local time variation.

[0051] Furthermore, the design principle of this invention is reliable, the structure is simple, and it has a very wide range of application prospects. Attached Figure Description

[0052] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0053] Figure 1 This is a schematic flowchart of a method according to an embodiment of the present invention.

[0054] Figure 2 This is a region division diagram of a method according to an embodiment of the present invention.

[0055] Figure 3 This is a NOx value curve of a method according to an embodiment of the present invention.

[0056] Figure 4 This is a feature state diagram of a method according to an embodiment of the present invention.

[0057] Figure 5 This is a process state transition diagram of a method according to an embodiment of the present invention.

[0058] Figure 6 This is a flow rate regulation function diagram of a method according to an embodiment of the present invention.

[0059] Figure 7 This is a schematic block diagram of a system according to an embodiment of the present invention. Detailed Implementation

[0060] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0061] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0062] The key terms used in this invention will be explained below.

[0063] SCR, or Selective Catalytic Reduction, is a method used to control the concentration of NOx (nitrogen oxides) in flue gas. It refers to the selective reaction of NOx in flue gas with a reducing agent (such as NH3, liquid ammonia, or urea) under the action of a catalyst, producing non-toxic and non-polluting N2 and H2O.

[0064] Figure 1 This is a schematic flowchart illustrating a method according to an embodiment of the present invention. The order of the steps in this flowchart may be changed, and some steps may be omitted, depending on different requirements.

[0065] like Figure 1 As shown, the method includes:

[0066] Step 110: Match the NOx concentration to the corresponding level based on the pre-set concentration level classification rules;

[0067] Step 120: Monitor the fluctuation values ​​of NOx concentration;

[0068] Step 130: Based on the theoretical ammonia injection amount corresponding to each pre-set concentration level and the actual NOx concentration level, generate the basic ammonia injection amount corresponding to the NOx concentration.

[0069] Step 140: Calculate the flow regulation value based on the preset fixed parameters and fluctuation values;

[0070] Step 150: Output the sum of the basic ammonia injection rate and the flow rate adjustment value as the target ammonia injection rate.

[0071] To facilitate understanding of the present invention, the NOx concentration emission control method for sintering flue gas SCR denitrification provided by the present invention will be further described below, based on the principle of the present invention and the process of the NOx concentration emission control method for sintering flue gas SCR denitrification in the embodiments.

[0072] Specifically, the NOx emission control methods for SCR denitrification of sintering flue gas include:

[0073] S1. Match the NOx concentration to the corresponding level based on the pre-set concentration level classification rules.

[0074] The rules for classifying concentration levels include:

[0075] Set low emission thresholds, high emission thresholds, and emission limits;

[0076] If the NOx concentration is below the low emission threshold, it is judged as a low emission level;

[0077] If the NOx concentration is above the low emission threshold and below the high emission threshold, it is classified as stable.

[0078] If the NOx concentration is above the high emission threshold but below the emission limit, it is judged as a high emission level;

[0079] If the NOx concentration is above the emission limit, it is judged as exceeding the emission level.

[0080] Specifically, such as Figure 2 As shown, NOx concentration curves were plotted based on the NOx concentration values ​​of the emitted flue gas, dividing the NOx concentration values ​​into six regions, each corresponding to a specific level: Excessive emission region (excessive emission level), high emission region (high emission level), ammonia-increasing flow rate region, stable region (stable level), reduced ammonia-increasing flow rate region, and low emission region (low emission level). The ammonia-increasing flow rate region includes the excessive emission region and the high emission region; the reduced ammonia-increasing flow rate region includes the low emission ammonia region. There are five values ​​at the regional critical points: emission limit, high emission threshold, increased flow rate threshold, reduced flow rate threshold, and low emission threshold.

[0081] S2. Monitor the fluctuation value of NOx concentration.

[0082] If the NOx concentration increases three times consecutively without fluctuation, it is considered to be an upward trend.

[0083] If the NOx concentration decreases three times consecutively and the NOx concentration does not fluctuate, it is determined to be a downward trend;

[0084] A third time threshold is set. If the NOx concentration does not fluctuate within the third time threshold, it is judged as a stable trend.

[0085] Also includes:

[0086] The NOx concentration value is rounded down to obtain the NOx usage value;

[0087] Set a first time threshold and a second time threshold;

[0088] If the NOx concentration value does not change after rounding up within the first time threshold, then the NOx value adopted is the rounded value of the current NOx concentration.

[0089] If the second time threshold is exceeded, and |NOx adopted value - actual NOx concentration rounded up| ≥ 2, then the NOx adopted value is the current actual NOx concentration rounded up.

[0090] Specifically, due to the large fluctuations in flue gas volume, high moisture content, and complex dust composition of sintering flue gas, the NOx concentration in the flue gas flue gas experiences significant local fluctuations (within 1-5 minutes) and frequent local disturbances, affecting the determination of the process status. Obtaining the trend status for such signals with large local fluctuations is very difficult; therefore, the detected NOx concentration value must be processed to eliminate the influence of fluctuations. The purpose of processing the NOx concentration value is to obtain a more easily analyzed NOx value, called the NOx adoption value. The processing method is: instead of directly adopting the NOx concentration value, the NOx concentration value is rounded to eliminate local interference and reduce misjudgments of real-time NOx concentration value disturbances. In special cases, such as a malfunction in the sintering production line, the NOx adoption value changes very rapidly, and the rounded NOx concentration value may continuously increase or decrease, with the duration of each decrease being less than T1 (the first time threshold). In such cases, the system will not be able to obtain the correct NOx adoption value. T2 (the second time threshold) must be at least 1.5 times T1.

[0091] like Figure 3 As shown, since the NOx values ​​used are rounded down, and the time interval between changes in each value is ≥ T1, a square curve is used for the NOx value. To facilitate control and analysis, the system automatically records the time point of each value change. Each value in this curve can be maintained for a time greater than T1, without any sharp peaks. This allows for analysis by combining four different state graphs of the most recent NOx concentration values, thereby enabling the determination of the process state of NOx concentration values.

[0092] Based on the fluctuations in NOx usage values, the NOx usage values ​​are classified into states, including: extracting characteristic states from the NOx value curve to obtain a characteristic state map; analyzing and transforming the characteristic state map to obtain a state transition map; and classifying the state transition map according to the fluctuation trigger judgment rules, including: upward trend: when the NOx usage value changes, the last three values ​​of the new state map after processing show a continuous increase without fluctuation; downward trend: when the NOx usage value changes, the last three values ​​of the new state map after processing show a continuous decrease without fluctuation; stable state: when the NOx usage value remains unchanged, and the time exceeds T3 (the third time threshold); where T3 is more than 5 times T1.

[0093] Specifically, based on the NOx value curve used, shape patterns of changes in the most recent 3-4 values ​​are extracted. There are 4 types of changes with 3 values ​​and 8 types with 4 values. For shape patterns of 4 values, if the most recent 3 values ​​are consecutive increases or decreases, they are categorized as 3-value change types. This results in a total of 8 characteristic state diagrams (see [link to relevant documentation]). Figure 4 The diagram records the magnitude and duration of each value in each state. If the NOx value changes, a transition diagram needs to be added to the existing state diagram to obtain a state transition diagram (see [link to diagram]). Figure 5 This requires analyzing and transforming the new graph. Based on the processing results, the processed state graph returns to one of the eight states, ensuring that the system continues to advance and execute in a loop.

[0094] Based on the characteristics of large system lag, disturbance, and local fluctuation, the system adopts a large trend state determination for NOx concentration control. System fluctuation triggers are divided into three types: upward trend, downward trend, and stable state.

[0095] The upward and downward trends are triggered when the NOx usage value changes. In the steady state, the NOx usage value remains unchanged. The timing is triggered when the timer reaches T3. After the trigger, the timer is reset and restarted. If the NOx usage value does not change, the steady state can be triggered multiple times. T3 is more than 5 times T1.

[0096] S3. Based on the data analysis results, adjust the ammonia injection rate. Based on the theoretical ammonia injection rate corresponding to each pre-set concentration level and the actual NOx concentration level, generate the basic ammonia injection rate corresponding to the NOx concentration.

[0097] Specifically, the magnitude of any increase or decrease in the ammonia injection flow rate must be correlated with the overall trend of the system. If the NOx concentration changes slowly, the increase or decrease should be small; conversely, it should be large. Excessive adjustment can easily lead to system oscillations, while insufficient adjustment results in slow regulation. The NOx value change trend is closely related to the duration of the NOx concentration before the change.

[0098] S4. Calculate the flow regulation value based on the preset fixed parameters and fluctuation values.

[0099] FC = (Current NOx value - NOx value before change) × K

[0100] Wherein, FC is the flow regulation value, which includes F0-F4, where F0 is the maximum regulating flow and F4 is the minimum regulating flow; K is the flow regulation amount.

[0101] For details, please see Figure 6 Since the flow rate regulation value K is closely related to the holding time before the NOx value changes, their relationship function is planned as a piecewise linear function. In the figure, IT0-IT4 represent the holding time values, and F0-F4 represent the flow rates corresponding to different holding time values. The value of IT0 is the same as the value of T1, F0 is the maximum regulating flow rate, and F4 is the minimum regulating flow rate. When the trend is upward, the ammonia flow rate regulation value is positive; otherwise, it is negative.

[0102] S5. The sum of the basic ammonia injection rate and the flow rate adjustment value is output as the target ammonia injection rate.

[0103] If the NOx concentration exceeds the emission level and shows a stable trend, an ammonia-enhancing water flow rate adjustment will be performed with an adjustment value of F0, and the steady-state time will be reset.

[0104] If the NOx concentration is at a high emission level and shows a stable trend, an ammonia-enhancing water flow rate adjustment will be performed with an adjustment value of F4, and the steady-state time will be reset.

[0105] If the NOx concentration is at a low emission level and shows a stable trend, an ammonia reduction water flow rate adjustment will be performed with an adjustment value of F4, and the steady-state time will be reset.

[0106] Specifically, based on the NOx emission levels in the region, corresponding control strategies are formulated. Ammonia flow rate adjustment is only implemented when the process state trigger conditions are met; otherwise, the ammonia injection flow rate remains unchanged. In high-emission areas, even if NOx emission levels are stable, the reason for increasing the ammonia flow rate is that NOx levels are close to exceeding emission limits. If the sintering flue gas suddenly fluctuates, there is a risk of exceeding emission limits. Therefore, increasing the ammonia injection rate is necessary to reduce NOx concentration and mitigate the risk of exceeding emission limits. Similarly, in low-emission areas, timely reduction of the ammonia injection flow rate reduces ammonia usage, lowers ammonia consumption, prevents significant ammonia escape, and saves ammonia costs.

[0107] In this embodiment, the NOx concentration emission control system 700 for sintering flue gas SCR denitrification can be divided into multiple functional modules according to its functions, such as... Figure 7 As shown. The functional modules may include: a matching level module 710, a fluctuation monitoring module 720, a basic ammonia injection module 730, a flow regulation module 740, and a target ammonia injection module 750. The module referred to in this invention is a series of computer program segments that can be executed by at least one processor and perform a fixed function, and are stored in memory. In this embodiment, the functions of each module will be described in detail in subsequent embodiments.

[0108] The matching level module is used to match NOx concentrations to corresponding levels based on pre-set concentration level classification rules;

[0109] The fluctuation monitoring module is used to monitor the fluctuation values ​​of NOx concentration;

[0110] The basic ammonia injection module is used to generate the basic ammonia injection amount corresponding to the NOx concentration based on the theoretical ammonia injection amount corresponding to each pre-set concentration level and the actual NOx concentration level.

[0111] The flow regulation module calculates the target ammonia injection value based on pre-set fixed parameters and fluctuation values. The ammonia injection module outputs the sum of the basic ammonia injection quantity and the flow regulation value as the target ammonia injection quantity.

[0112] Optionally, as an embodiment of the present invention, the matching level module includes:

[0113] The rating rule unit is used to set low emission thresholds, high emission thresholds, and emission limits. If the NOx concentration is below the low emission threshold, it is determined to be a low emission level; if the NOx concentration is above the low emission threshold but below the high emission threshold, it is determined to be a stable level; if the NOx concentration is above the high emission threshold but below the emission limit, it is determined to be a high emission level; and if the NOx concentration is above the emission limit, it is determined to be an over-emission level.

[0114] Optionally, as an embodiment of the present invention, the fluctuation monitoring module includes:

[0115] The fluctuation detection unit is used to determine an upward trend if the NOx concentration increases three times consecutively without fluctuation; and a downward trend if the NOx concentration decreases three times consecutively without fluctuation. A third time threshold is set, and if the NOx concentration does not fluctuate within the third time threshold, it is determined to be a stable trend.

[0116] It also includes a rounding unit for rounding up the NOx concentration value to obtain the NOx adopted value; setting a first time threshold and a second time threshold; if the rounded NOx concentration value does not change within the first time threshold, then the NOx adopted value is the current rounded NOx concentration value; if the value exceeds the second time threshold and |NOx adopted value - actual NOx concentration rounded value| ≥ 2, then the NOx adopted value is the current actual NOx concentration rounded value.

[0117] Optionally, as an embodiment of the present invention, the flow regulation module includes:

[0118] The flow regulation unit is used for FC = (current NOx input value - NOx input value before change) × K

[0119] Wherein, FC is the flow regulation value, which includes F0-F4, where F0 is the maximum regulating flow and F4 is the minimum regulating flow; K is the flow regulation amount.

[0120] Optionally, as an embodiment of the present invention, the target ammonia injection module includes:

[0121] The target ammonia injection unit is used to adjust the ammonia injection water flow rate once if the NOx concentration is above the emission level and shows a stable trend, with an adjustment value of F0, and reset the steady-state time; if the NOx concentration is at a high emission level and shows a stable trend, it will adjust the ammonia injection water flow rate once, with an adjustment value of F4, and reset the steady-state time; if the NOx concentration is at a low emission level and shows a stable trend, it will adjust the ammonia reduction water flow rate once, with an adjustment value of F4, and reset the steady-state time.

[0122] Therefore, the technical effects of the sintering flue gas SCR denitrification control method and system of the present invention can be referred to the above description, and will not be repeated here.

[0123] Those skilled in the art will clearly understand that the techniques in the embodiments of the present invention can be implemented using software and necessary general-purpose hardware platforms. Based on this understanding, the technical solutions in the embodiments of the present invention, or the parts that contribute to the prior art, can be embodied in the form of a software product. This computer software product is stored in a storage medium such as a USB flash drive, a portable hard drive, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk, or any other medium capable of storing program code. It includes several instructions to cause a computer terminal (which may be a personal computer, a server, or a second terminal, a network terminal, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention.

[0124] The same or similar parts between the various embodiments in this specification can be referred to mutually. In particular, the terminal embodiments are basically similar to the method embodiments, so the description is relatively simple, and the relevant parts can be referred to the description in the method embodiments.

[0125] In the embodiments provided by this invention, it should be understood that the disclosed systems and methods can be implemented in other ways. For example, the system embodiments described above are merely illustrative. For instance, the division of modules is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple modules or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between systems or modules may be electrical, mechanical, or other forms.

[0126] The modules described as separate components may or may not be physically separate. The components shown as modules may or may not be physical modules; that is, they may be located in one place or distributed across multiple network modules. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs.

[0127] In addition, the functional modules in the various embodiments of the present invention can be integrated into one processing module, or each module can exist physically separately, or two or more modules can be integrated into one module.

[0128] Although the present invention has been described in detail with reference to the accompanying drawings and preferred embodiments, the invention is not limited thereto. Various equivalent modifications or substitutions can be made to the embodiments of the invention by those skilled in the art without departing from the spirit and essence of the invention, and such modifications or substitutions should all be within the scope of the invention. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the invention should also be covered within the protection scope of the invention. Therefore, the protection scope of the invention should be determined by the scope of the claims.

Claims

1. A method for controlling SCR denitrification of sintering flue gas, characterized in that, include: NOx concentrations are matched to corresponding levels based on pre-set concentration level classification rules; Monitor fluctuations in NOx concentration; Based on the theoretical ammonia injection amount corresponding to each pre-set concentration level and the actual NOx concentration level, a basic ammonia injection amount corresponding to the NOx concentration is generated. The flow regulation value is calculated based on the pre-set fixed parameters and the fluctuation value; The sum of the basic ammonia injection rate and the flow rate adjustment value is output as the target ammonia injection rate value. Monitoring fluctuations in NOx concentrations, including: If the NOx concentration increases three times consecutively without fluctuation, it is considered to be an upward trend. If the NOx concentration decreases three times consecutively and the NOx concentration does not fluctuate, it is determined to be a downward trend; A third time threshold is set. If the NOx concentration does not fluctuate within the third time threshold, it is judged as a stable trend. The monitored NOx concentration fluctuation values ​​also include: The NOx concentration value is rounded down to obtain the NOx usage value; Set a first time threshold and a second time threshold; If the NOx concentration value does not change after rounding up within the first time threshold, then the NOx value adopted is the rounded value of the current NOx concentration. If the second time threshold is exceeded, and |NOx adopted value - actual NOx concentration rounded up| ≥ 2, then the NOx adopted value is the current actual NOx concentration rounded up. Calculating the flow regulation value based on pre-set fixed parameters and the fluctuation value includes: FC = (Current NOx usage - NOx usage before change) × K Wherein, FC is the flow regulation value, which includes F0-F4, where F0 is the maximum regulating flow and F4 is the minimum regulating flow; K is the flow regulation amount; The sum of the basic ammonia injection rate and the flow rate adjustment value is output as the target ammonia injection rate, including: If the NOx concentration exceeds the emission level and shows a stable trend, an ammonia-enhancing water flow rate adjustment will be performed with an adjustment value of F0, and the steady-state time will be reset. If the NOx concentration is at a high emission level and shows a stable trend, an ammonia-enhancing water flow rate adjustment will be performed with an adjustment value of F4, and the steady-state time will be reset. If the NOx concentration is at a low emission level and shows a stable trend, an ammonia reduction water flow rate adjustment will be performed with an adjustment value of F4, and the steady-state time will be reset.

2. The method according to claim 1, characterized in that, The concentration level classification rules include: Set low emission thresholds, high emission thresholds, and emission limits; If the NOx concentration is below the low emission threshold, it is judged as a low emission level; If the NOx concentration is above the low emission threshold and below the high emission threshold, it is classified as stable. If the NOx concentration is above the high emission threshold but below the emission limit, it is judged as a high emission level; If the NOx concentration is above the emission limit, it is judged as exceeding the emission level.

3. A NOx concentration emission control system for sintering flue gas SCR denitrification, applicable to the control method for sintering flue gas SCR denitrification as described in any one of claims 1-2, characterized in that, include: The matching level module is used to match NOx concentrations to corresponding levels based on pre-set concentration level classification rules; The fluctuation monitoring module is used to monitor the fluctuation values ​​of NOx concentration; The basic ammonia injection module is used to generate a basic ammonia injection amount corresponding to the NOx concentration based on the theoretical ammonia injection amount corresponding to each pre-set concentration level and the actual NOx concentration level. The flow regulation module calculates the flow regulation value based on pre-set fixed parameters and the fluctuation value; The target ammonia injection module is used to output the sum of the basic ammonia injection quantity and the flow rate adjustment value as the target ammonia injection quantity value.

4. The system according to claim 3, characterized in that, The rules for classifying concentration levels include: The rating rule unit is used to set low emission thresholds, high emission thresholds, and emission limits. If the NOx concentration is below the low emission threshold, it is judged as a low emission level; If the NOx concentration is above the low emission threshold and below the high emission threshold, it is classified as stable. If the NOx concentration is above the high emission threshold but below the emission limit, it is judged as a high emission level; If the NOx concentration is above the emission limit, it is judged as exceeding the emission level.

5. The system according to claim 3, characterized in that, The monitoring fluctuation module includes: The fluctuation detection unit is used to determine an upward trend if the NOx concentration increases three times consecutively without fluctuation; and a downward trend if the NOx concentration decreases three times consecutively without fluctuation. A third time threshold is set, and if the NOx concentration does not fluctuate within the third time threshold, it is determined to be a stable trend. It also includes a rounding unit for rounding up the NOx concentration value to obtain the NOx adopted value; setting a first time threshold and a second time threshold; if the rounded NOx concentration value does not change within the first time threshold, then the NOx adopted value is the current rounded NOx concentration value; if the value exceeds the second time threshold and |NOx adopted value - actual NOx concentration rounded value| ≥ 2, then the NOx adopted value is the current actual NOx concentration rounded value.

6. The system according to claim 5, characterized in that, The flow regulation module includes: Flow regulation unit, used for FC = (current NOx input value - NOx input value before change) × K Wherein, FC is the flow regulation value, which includes F0-F4, where F0 is the maximum regulating flow and F4 is the minimum regulating flow; K is the flow regulation amount.

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