An optimization control method and system for an SCR denitrification ammonia injection automatic control system

Abstract

The present invention discloses an optimization control method and system for an SCR denitration ammonia injection automatic control system, comprising: collecting hourly NOx values ​​at the denitration outlet and calculating hourly average NOx values ​​at the denitration outlet; combining the hourly average NOx values ​​at the denitration outlet with the real-time NOx values ​​at the A and B side outlets, using the start and stop of the coal mill, unit load changes, inlet NOx concentration, and inlet oxygen content as feedforwards; making corrections based on the feedforwards and adjusting the ammonia injection regulating valve. The method and system proposed by the present invention make the hourly average NOx values ​​at the outlet stable and controllable, effectively control the hourly average NOx values ​​at the denitration outlet, meet environmental protection requirements, and at the same time control ammonia slip within a normal range; when the unit starts and stops the mill, or when the denitration inlet NOx concentration fluctuates significantly, the unit load, inlet NOx concentration, inlet oxygen content, and start and stop mill signals are added to the logic as feedforwards, which can effectively adjust the ammonia injection regulating valve in advance, greatly improving the anti-disturbance capability of the denitration ammonia injection system and achieving a good automatic adjustment effect.

Description

Technical Field

[0001] The present invention relates to the technical field of denitration ammonia injection automatic control systems, and in particular to an optimization control method and system for an SCR denitration ammonia injection automatic control system. Background Art

[0002] Currently, most thermal power plants use SCR (Selective Catalytic Reduction) denitrification technology to remove NOx from flue gas. The SCR reactor is located between the economizer and the air preheater. Ammonia is mixed with dilution air and enters the inlet flue of the SCR reactor. Ammonia spray screens evenly mix the flue gas with the air. The mixed flue gas then passes through the catalyst layer within the reactor for a reduction reaction. Under the action of the appropriate temperature and catalyst, the ammonia reacts with the NOx in the flue gas to produce nitrogen (N2) and water (H2O), thereby removing NOx from the flue gas and completing the denitrification process. The denitrified flue gas then enters the air preheater for further heat exchange.

[0003] The main chemical reaction equations are as follows:

[0004]

[0005]

[0006]

[0007] At present, most denitrification automatic control systems use conventional PID control systems, and there are mainly two solutions:

[0008] 1. The set value of the controlled object is the denitrification efficiency. The ammonia demand calculated from the flue gas volume and the NOx concentration at the denitrification inlet is used as the feedforward quantity. The ammonia demand is calculated based on the current flue gas flow, the NOx concentration at the SCR inlet and the set denitrification efficiency. Finally, the actual ammonia flow is adjusted by changing the opening of the ammonia injection regulating valve through PID control, thereby realizing automatic control of denitrification.

[0009] 2. The set value of the controlled object is the NOx concentration at the SCR outlet. The ammonia demand calculated from the flue gas volume and the denitrification inlet NOx is used as the feedforward quantity. The program calculates the required ammonia injection amount based on the flue gas flow, inlet NOx concentration and the set outlet NOx concentration, and then performs PID adjustment based on the set outlet NOx concentration to ensure that the denitrification outlet NOx concentration meets the set requirements.

[0010] These two solutions provide good system control when the unit load and fuel are stable. However, in actual operation, the unit load is adjusted by the grid's AGC, resulting in rapid and large load fluctuations, significant coal flow disturbances, and significant NOx value fluctuations. This is especially true during mill startups and shutdowns, where NOx concentrations at the denitrification inlet fluctuate significantly, making it difficult to control NOx concentrations at the outlet. When the setpoint deviates significantly from the actual value, the ammonia injection control valve automatically trips. If this is not detected in time, abnormal NOx values ​​can result.

[0011] At the same time, the above two control schemes still have the following problems during operation, which makes the control quality fail to meet the requirements.

[0012] 1. The environmental protection assessment target (hourly average NOx value at the denitrification outlet) is not used as the controlled quantity, and the control target does not correspond to the assessment target.

[0013] 2. The design of PID feedforward control strategy is too simple, and the control effect on the controlled object with large lag is not ideal.

[0014] Due to the large delay of the system, it takes nearly 20 minutes from valve action to changes in NOx at the denitrification outlet, and then to changes in the hourly average NOx at the denitrification outlet according to environmental monitoring data. This is a typical large-lag controlled object, resulting in extreme instability in the denitrification ammonia injection control system.

[0015] 3. The automatic input rate of the control system is low.

[0016] In AGC mode, the unit experienced significant load fluctuations and frequent operating adjustments, resulting in significant fluctuations in inlet and outlet NOx levels. This led to severe transient NOx exceeding standards, and the control system was unable to fully function. Manual control of the regulating valve opening was required, relying entirely on the operator's experience. This made it difficult to balance compliance with standards and economic efficiency. Operators discovered that untimely adjustments could result in excessive outlet NOx levels or excessive ammonia injection, posing a risk to the system's normal operation. Summary of the Invention

[0017] The purpose of this section is to summarize some aspects of the embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the abstract and title of this application to avoid obscuring the purpose of this section, the abstract and the title of the invention, and such simplifications or omissions should not be used to limit the scope of the present invention.

[0018] In view of the above existing problems, the present invention is proposed.

[0019] Therefore, the technical problem solved by the present invention is that the unit has large load fluctuations and frequent operating condition adjustments in AGC mode, the inlet and outlet NOx also changes significantly, and the amount of ammonia injection is large.

[0020] In order to solve the above technical problems, the present invention provides the following technical solutions: collecting the hourly value of NOx at the denitration outlet and calculating the hourly average value of NOx at the denitration outlet;

[0021] The hourly average value of NOx at the denitrification outlet is combined with the real-time value of NOx at the outlets of sides A and B, and the start and stop of the coal mill, the load change of the unit, the inlet NOx concentration and the inlet oxygen amount are used as feedforward quantities;

[0022] A correction is made based on the feedforward amount, and the ammonia injection regulating valve is adjusted.

[0023] As a preferred solution of the SCR denitration ammonia injection automatic control system optimization control method and system of the present invention, wherein: adjusting the ammonia injection regulating valve specifically includes:

[0024] When the outlet NOx hourly average value is greater than 43 mg / Nm 3 、<47mg / Nm 3 When the automatic control system takes the real-time NOx value at the outlets of sides A and B as the regulated quantity, it calculates the deviation by comparing it with the given NOx value at the outlets of sides A and B. It then corrects the ammonia dosage by combining the feedforward quantity and adjusts the ammonia injection regulating valve to make the deviation close to 0.

[0025] When the outlet NOx hourly average value is ≤40mg / Nm 3 or ≥50 mg / Nm 3 When the hourly average value of NOx at the denitrification outlet is reached, the automatic control system takes the hourly average value of NOx at the denitrification outlet as the regulated variable, and uses the function relationship F(x) to calculate the target value of the total outlet NOx required to be set for the remaining time in this hourly period, and then compares it with the real-time value of the total outlet NOx, and makes corrections based on the feedforward amount to adjust the denitrification ammonia injection regulating valves on the A and B sides respectively.

[0026] include,

[0027] When the outlet NOx hourly average value is greater than 43 mg / Nm 3 、<47mg / Nm 3 When the automatic control system takes the real-time NOx value at the outlets of side A and B as the regulated quantity;

[0028] When the deviation between the real-time NOx value at the outlet of side A and side B and the set NOx value at the outlet of side A and side B is greater than 0, open the ammonia injection regulating valve on the corresponding side to increase the amount of ammonia injection;

[0029] When the deviation between the real-time value of NOx at the outlet of side A and side B and the set value of NOx at the outlet of side A and side B is less than 0, close the ammonia injection regulating valve on the corresponding side to reduce the amount of ammonia injection. By adjusting the ammonia injection regulating valve on each side, make the deviation on each side close to 0.

[0030] include,

[0031] When the outlet NOx hourly average value is ≥50mg / Nm 3 When , the control system takes the hourly average value of outlet NOx as the regulated variable;

[0032] The target outlet total NOx value required for the remaining time of this hour is calculated based on the functional relationship F(x). The target outlet total NOx value is compared with the real-time outlet total NOx value, and instructions are issued to the A and B side regulators respectively to open the ammonia injection regulating valves on both sides until the outlet NOx hourly average value is less than 50mg / Nm 3 ;

[0033] In order to avoid the outlet NOx hourly average value exceeding the standard, a certain margin should be left for the outlet NOx hourly average value, and the outlet NOx hourly average value should be controlled at 47mg / Nm 3 ~50mg / Nm 3 between.

[0034] include,

[0035] To prevent excessive ammonia from being injected into the denitrification system, which may affect equipment safety, the ammonia-air ratio should be controlled to be less than 7;

[0036] When the ammonia-air ratio reaches 5, the standby dilution fan will be started and an audible and visual alarm will sound;

[0037] When the ammonia-air ratio reaches 6.5, the corresponding side ammonia injection regulating valve will be locked and opened, and an audible and visual alarm will sound.

[0038] When the ammonia-air ratio reaches 7 and after a delay, the interlock closes the ammonia injection regulating valve on the corresponding side, and an audible and visual alarm sounds. The ammonia injection regulating valve is not allowed to open until the ammonia-air ratio drops below 7.

[0039] To prevent excessive adjustment of the ammonia injection control valve on one side from exacerbating the disturbance of the control system, when the real-time NOx value at the outlet of side A or side B is ≤5mg / Nm 3 When the lock continues to open the corresponding side ammonia injection regulating valve, sound and light alarm;

[0040] Wait until the real-time NOx value at the outlet of side A or side B is ≥10mg / Nm 3 When the lock is released.

[0041] include,

[0042] When the outlet NOx hourly average value is ≤40mg / Nm 3 When , the control system takes the hourly average value of outlet NOx as the regulated variable;

[0043] The target outlet total NOx value required for the remaining time of this hour is calculated based on the functional relationship F(x). The target outlet total NOx value is compared with the real-time outlet total NOx value, and instructions are issued to the A and B side regulators respectively to close the ammonia injection regulating valves on both sides until the outlet NOx hourly average value is greater than 40 mg / Nm 3 ;

[0044] In order to avoid the outlet NOx hourly average value exceeding the standard, a certain margin should be left for the outlet NOx hourly average value, and the outlet NOx hourly average value should be controlled at 40mg / Nm 3 ~43mg / Nm 3 ;

[0045] The calculation of the functional relationship F(x) includes,

[0046]

[0047] Among them, F(x) represents the outlet total NOx target value required to be set for the remaining time of this hour period, S out The table shows the hourly average value of outlet NOx. 50 represents the target value for environmental assessment. The unit is mg / Nm 3 , 60 represents the time of an assessment period, unit is min, t represents the elapsed time of this hour period, unit is min, 60-t represents the remaining time of this hour period, unit is min.

[0048] Also includes,

[0049] To prevent excessive regulation of the ammonia injection regulating valve on one side from exacerbating the disturbance of the regulating system, when the real-time NOx value at the outlet of side A or side B is ≥80mg / Nm 3 When the lock continues to close the corresponding side ammonia injection regulating valve, sound and light alarm;

[0050] Wait for the real-time NOx value at the outlet of side A or side B to be ≤75mg / Nm 3 When , the lock is released;

[0051] In order to avoid frequent switching of the automatic control system, when the outlet NOx hourly average value is between 40 and 43 mg / Nm 3 Between 47 and 50 mg / Nm 3 During this time, the controlled variable of the automatic control system will not be switched, but will be adjusted according to the previously set program.

[0052] A second aspect of the present invention provides an SCR denitration ammonia injection automatic control system optimization control system, comprising:

[0053] The first unit is used to collect the hourly value of NOx at the denitration outlet and calculate the hourly average value of NOx at the denitration outlet;

[0054] The second unit is used to combine the hourly average NOx value at the denitrification outlet with the real-time NOx value at the outlets of sides A and B, and use the start and stop of the coal mill, unit load changes, inlet NOx concentration and inlet oxygen content as feedforward quantities;

[0055] The third unit is used to make corrections based on the feedforward amount and adjust the ammonia injection regulating valve.

[0056] A third aspect of the present invention provides a device comprising:

[0057] processor;

[0058] a memory for storing processor-executable instructions;

[0059] The processor is configured to call the instructions stored in the memory to execute the method described in any embodiment of the present invention.

[0060] According to a fourth aspect of the present invention, a computer-readable storage medium is provided, on which computer program instructions are stored, wherein the computer program instructions, when executed by a processor, implement the method described in any embodiment of the present invention.

[0061] Beneficial effects of the present invention: The method and system proposed in the present invention make the hourly average value of outlet NOx stable and controllable, and the hourly average value at the hour is strictly controlled within the set value range of 45±2mg / Nm3, effectively controlling the hourly average value of denitrification outlet NOx, meeting environmental protection requirements, and at the same time, ammonia slip is also controlled within the normal range; it solves the control problem of large lag objects, and when the unit starts and stops the mill and the denitrification inlet NOx concentration fluctuates greatly, the unit load, inlet NOx concentration, inlet oxygen content, and start-stop mill signal are added to the logic as feedforward, which can effectively adjust the ammonia injection regulating valve in advance, greatly improving the anti-disturbance ability of the denitrification ammonia injection system, with a high automatic input rate and good automatic adjustment effect; it saves ammonia consumption and improves the economy of the unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive effort. Among them:

[0063] Figure 1 An optimized control method for an SCR denitration and ammonia injection automatic control system and a control logic diagram of the A-side outlet of the system provided in one embodiment of the present invention;

[0064] Figure 2An optimized control method for an SCR denitration and ammonia injection automatic control system and a control logic diagram of the B-side outlet of the system are provided in accordance with one embodiment of the present invention;

[0065] Figure 3 An optimized control method for an SCR denitration and ammonia injection automatic control system and a logic diagram for simultaneous control of the A and B side outlets of the system are provided in one embodiment of the present invention;

[0066] Figure 4 An embodiment of the present invention provides an optimization control method for an SCR denitration and ammonia injection automatic control system and a controlled object switching logic diagram of the system. DETAILED DESCRIPTION

[0067] To make the above-mentioned objects, features, and advantages of the present invention more clearly understood, the following detailed description of the specific embodiments of the present invention is given in conjunction with the accompanying drawings. It is obvious that the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary persons in this field without creative work should fall within the scope of protection of the present invention.

[0068] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0069] Secondly, the term "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in various places throughout this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive of other embodiments.

[0070] The present invention is described in detail with reference to schematic diagrams. For ease of illustration, cross-sectional views of device structures may be partially enlarged and not to scale when describing embodiments of the present invention. Furthermore, the schematic diagrams are merely illustrative and should not limit the scope of the present invention. Furthermore, in actual production, the three-dimensional dimensions of length, width, and depth should be included.

[0071] In the description of the present invention, it should be noted that the terms "upper, lower, inner, and outer" and other references to orientations or positional relationships are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limitations on the present invention. Furthermore, the terms "first, second, or third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0072] In this disclosure, unless otherwise specified or limited, the terms "mounted," "connected," and "connected" should be interpreted broadly. For example, they may refer to fixed, removable, or integral connections. They may also refer to mechanical, electrical, or direct connections, indirect connections through an intermediary, or internal communication between two components. Those skilled in the art will understand the specific meanings of these terms in this disclosure.

[0073] Example 1

[0074] Reference Figures 1 to 4 , which is an embodiment of the present invention, provides an optimization control method and system for an SCR denitration ammonia injection automatic control system, comprising:

[0075] S1: Collect the hourly value of NOx at the denitrification outlet and calculate the hourly average value of NOx at the denitrification outlet.

[0076] S2: Combine the hourly average value of NOx at the denitrification outlet with the real-time value of NOx at the outlets of sides A and B, and use the start and stop of the coal mill, unit load changes, inlet NOx concentration and inlet oxygen content as feedforward quantities.

[0077] S3: Based on the feedforward amount, the ammonia injection regulating valve is corrected and adjusted. It should be noted that:

[0078] Adjustment of the ammonia injection regulating valve specifically includes:

[0079] When the outlet NOx hourly average value is greater than 43 mg / Nm 3 、<47mg / Nm 3 When the automatic control system takes the real-time NOx value at the outlets of sides A and B as the regulated quantity, it calculates the deviation by comparing it with the given NOx value at the outlets of sides A and B. It then corrects the ammonia dosage by combining the feedforward quantity and adjusts the ammonia injection regulating valve to make the deviation close to 0.

[0080] When the outlet NOx hourly average value is ≤40mg / Nm 3 or ≥50 mg / Nm 3When the hourly average value of NOx at the denitrification outlet is reached, the automatic control system takes the hourly average value of NOx at the denitrification outlet as the regulated variable, and uses the function relationship F(x) to calculate the target value of the total outlet NOx required to be set for the remaining time in this hourly period, and then compares it with the real-time value of the total outlet NOx, and makes corrections based on the feedforward amount to adjust the denitrification ammonia injection regulating valves on the A and B sides respectively.

[0081] A1: When the outlet NOx hourly average value is greater than 43 mg / Nm 3 、<47mg / Nm 3 When the automatic control system takes the real-time NOx value at the outlets of side A and B as the regulated quantity;

[0082] When the deviation between the real-time NOx value at the outlet of side A and side B and the set NOx value at the outlet of side A and side B is greater than 0, open the ammonia injection regulating valve on the corresponding side to increase the amount of ammonia injection;

[0083] When the deviation between the real-time value of NOx at the outlet of side A and side B and the set value of NOx at the outlet of side A and side B is less than 0, close the ammonia injection regulating valve on the corresponding side to reduce the amount of ammonia injection. By adjusting the ammonia injection regulating valve on each side, make the deviation on each side close to 0. The control logic diagram is as follows: Figure 1 、 Figure 2 shown.

[0084] A2: When the outlet NOx hourly average value is ≥50mg / Nm 3 When , the control system takes the hourly average value of outlet NOx as the regulated variable;

[0085] The target outlet total NOx value required for the remaining time of this hour is calculated based on the functional relationship F(x). The target outlet total NOx value is compared with the real-time outlet total NOx value, and instructions are issued to the A and B side regulators respectively to open the ammonia injection regulating valves on both sides until the outlet NOx hourly average value is less than 50mg / Nm 3 ;

[0086] In order to avoid the outlet NOx hourly average value exceeding the standard, a certain margin should be left for the outlet NOx hourly average value, and the outlet NOx hourly average value should be controlled at 47mg / Nm 3 ~50mg / Nm 3 between.

[0087] include,

[0088] To prevent excessive ammonia from being injected into the denitrification system, which may affect equipment safety, the ammonia-air ratio should be controlled to be less than 7;

[0089] When the ammonia-air ratio reaches 5, the standby dilution fan will be started and an audible and visual alarm will sound;

[0090] When the ammonia-air ratio reaches 6.5, the corresponding side ammonia injection regulating valve will be locked and opened, and an audible and visual alarm will sound.

[0091] When the ammonia-air ratio reaches 7 and after a delay, the interlock closes the ammonia injection regulating valve on the corresponding side, and an audible and visual alarm sounds. The ammonia injection regulating valve is not allowed to open until the ammonia-air ratio drops below 7.

[0092] To prevent excessive adjustment of the ammonia injection control valve on one side from exacerbating the disturbance of the control system, when the real-time NOx value at the outlet of side A or side B is ≤5mg / Nm 3 When the lock continues to open the corresponding side ammonia injection regulating valve, sound and light alarm;

[0093] Wait until the real-time NOx value at the outlet of side A or side B is ≥10mg / Nm 3 When the lock is released, the control logic diagram is as follows Figure 3 shown.

[0094] A3: When the outlet NOx hourly average value is ≤40mg / Nm 3 When , the control system takes the hourly average value of outlet NOx as the regulated variable;

[0095] The target outlet total NOx value required for the remaining time of this hour is calculated based on the functional relationship F(x). The target outlet total NOx value is compared with the real-time outlet total NOx value, and instructions are issued to the A and B side regulators respectively to close the ammonia injection regulating valves on both sides until the outlet NOx hourly average value is greater than 40 mg / Nm 3 ;

[0096] In order to avoid the outlet NOx hourly average value exceeding the standard, a certain margin should be left for the outlet NOx hourly average value, and the outlet NOx hourly average value should be controlled at 40mg / Nm 3 ~43mg / Nm 3 ;

[0097] The calculation of the functional relationship F(x) includes,

[0098]

[0099] Among them, F(x) represents the outlet total NOx target value required to be set for the remaining time of this hour period, S out The table shows the hourly average value of outlet NOx. 50 represents the target value for environmental assessment. The unit is mg / Nm 3 , 60 represents the time of an assessment period, unit is min, t represents the elapsed time of this hour period, unit is min, 60-t represents the remaining time of this hour period, unit is min.

[0100] Also includes,

[0101] To prevent excessive regulation of the ammonia injection regulating valve on one side from exacerbating the disturbance of the regulating system, when the real-time NOx value at the outlet of side A or side B is ≥80mg / Nm 3 When the lock continues to close the corresponding side ammonia injection regulating valve, sound and light alarm;

[0102] Wait for the real-time NOx value at the outlet of side A or side B to be ≤75mg / Nm 3 When , the lock is released;

[0103] In order to avoid frequent switching of the automatic control system, when the outlet NOx hourly average value is between 40 and 43 mg / Nm 3 Between 47 and 50 mg / Nm 3 During this time, the controlled variable of the automatic control system will not be switched, but will be adjusted according to the previously set program.

[0104] In one embodiment, an SCR denitration ammonia injection automatic control system optimization control system is provided, comprising:

[0105] The first unit is used to collect the hourly value of NOx at the denitration outlet and calculate the hourly average value of NOx at the denitration outlet;

[0106] The second unit is used to combine the hourly average NOx value at the denitrification outlet with the real-time NOx value at the outlets of sides A and B, and use the start and stop of the coal mill, unit load changes, inlet NOx concentration and inlet oxygen content as feedforward quantities;

[0107] The third unit is used to make corrections based on the feedforward amount and adjust the ammonia injection regulating valve.

[0108] In one embodiment, a computer device is provided, comprising:

[0109] processor;

[0110] a memory for storing processor-executable instructions;

[0111] The processor is configured to call instructions stored in the memory to execute the method of any of the aforementioned embodiments.

[0112] In one embodiment, a computer readable storage medium is provided having computer program instructions stored thereon.

[0113] The computer program is used by a processor to execute the method of any one of the aforementioned embodiments.

[0114] When executed, the computer program may include the processes of the embodiments of the above-mentioned methods. Among them, any reference to memory, database or other media used in the embodiments provided by the present invention may include at least one of non-volatile and volatile memory. Non-volatile memory may include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory may include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM). The database involved in the embodiments provided by the present invention may include at least one of a relational database and a non-relational database. Non-relational databases may include, but are not limited to, distributed databases based on blockchains. The processors involved in the various embodiments provided by the present invention may be, but are not limited to, general-purpose processors, central processing units, graphics processors, digital signal processors, programmable logic devices, data processing logic devices based on quantum computing, and the like.

[0115] The method and system proposed in the present invention make the hourly average value of outlet NOx stable and controllable, and the hourly average value is strictly controlled within the set value range of 45±2mg / Nm3 at the hour, effectively controlling the hourly average value of NOx at the denitrification outlet, meeting environmental protection requirements, and at the same time controlling ammonia slip within the normal range; solving the problem of controlling objects with large lags, when the unit starts and stops the mill and when the NOx concentration at the denitrification inlet fluctuates greatly, the unit load, inlet NOx concentration, inlet oxygen content, and start-stop mill signals are added to the logic as feedforward, which can effectively adjust the ammonia injection regulating valve in advance, greatly improving the anti-disturbance capability of the denitrification ammonia injection system, with a high automatic input rate and good automatic adjustment effect; saving ammonia consumption and improving the economy of the unit.

[0116] Example 2

[0117] This embodiment is the second embodiment of the present invention. Different from the first embodiment, this embodiment provides an SCR denitrification ammonia injection automatic control system optimization control method and system verification test, in order to verify and illustrate the technical effects adopted in this method, and to compare the test results by means of scientific demonstration to verify the actual effect of this method.

[0118] Scenario 1:

[0119] The hourly average NOx value at the outlet of the denitrification system is 45 mg / Nm 3 The regulated quantity of the control system is the real-time value of NOx at the outlets of sides A and B. Assuming the unit load is 220MW, the real-time value of the total NOx at the outlet is 42mg / Nm 3 , NOx setting value at the outlet of side A is 45mg / Nm 3 , real-time value 40mg / Nm 3 , B side outlet NOx setting value 45mg / Nm 3 , real-time value 49mg / Nm 3 At this time, the ammonia injection regulating valve on the A side is closed, and the ammonia injection regulating valve on the B side is opened, and finally the deviation between the outlet NOx real-time value and the outlet NOx set value on the A and B sides is adjusted to be close to 0. Since the outlet NOx real-time value on the A and B sides has always been at 45mg / Nm 3 Therefore, the hourly average of outlet NOx is always kept at 45mg / Nm 3 about.

[0120] If the unit load drops to 170MW and the oxygen level at the denitrification system inlet increases, the control system will preemptively issue a command to increase the ammonia injection regulating valve. If the control system receives a mill stop signal, it will also preemptively issue a command to decrease the ammonia injection regulating valve. Ultimately, the hourly average outlet NOx value is controlled within the specified value.

[0121] Scenario 2:

[0122] Assume that the hourly average outlet NOx is 62 mg / Nm 3 The elapsed time t in this hour period is 40 minutes. Since the hourly average value of outlet NOx is greater than 50 mg / Nm 3 The automatic control system uses the hourly average of outlet NOx as the regulated variable. Based on the functional relationship, the automatic control system calculates that the target value of total outlet NOx needs to be set to 17mg / Nm in the remaining 20 minutes of this hour. 3 By the hour, the hourly average outlet NOx can be reduced to 47mg / Nm 3 The hourly average value of outlet NOx does not exceed the standard and remains at a relatively high value.

[0123] At this time, the automatic control system will output the total NOx at 17mg / Nm3 The target value is compared with the real-time value of the total NOx at the outlet, and instructions are sent to the A and B side regulators respectively to adjust the ammonia injection regulating valves on both sides until the hourly average value of NOx at the outlet is less than 50mg / Nm 3 .

[0124] If the real-time NOx value at the outlet of side A has dropped to 5 mg / Nm 3 , the control system locks the A-side ammonia injection regulating valve to continue to open, and at the same time sounds an audible and visual alarm to remind the operator. When the real-time value of NOx at the A-side outlet rises to 10mg / Nm 3 When the lock is released.

[0125] Scenario 3:

[0126] Assume that the hourly average outlet NOx is 30 mg / Nm 3 The elapsed time t in this hour period is 40 minutes. Since the hourly average value of outlet NOx is less than 40 mg / Nm 3 The control system uses the hourly average of outlet NOx as the regulated variable. Based on the functional relationship, the control system calculates that the target value of total outlet NOx needs to be set to 81mg / Nm in the remaining 20 minutes of this hour. 3 By the hour, the outlet NOx hourly average can reach 47mg / Nm 3 The hourly average value of outlet NOx does not exceed the standard and remains at a relatively high value.

[0127] At this time, the control system will output the total NOx of 81mg / Nm 3 The target value is compared with the real-time value of the total NOx at the outlet, and instructions are sent to the A and B side regulators respectively to adjust the ammonia injection regulating valves on both sides until the hourly average value of NOx at the outlet reaches 47mg / Nm 3 .

[0128] If the real-time NOx value at the outlet of side A has reached 80mg / Nm 3 , the control system will lock the ammonia injection regulating valve on the A side and continue to close it, and at the same time sound and light alarms to remind the operator. When the real-time value of NOx at the outlet of side A decreases to 75mg / Nm 3 When the lock is released.

[0129] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. An optimization control method for an SCR denitrification ammonia injection automatic control system, characterized in that: include: Collect the hourly value of NOx at the denitrification outlet and calculate the hourly average value of NOx at the denitrification outlet; The hourly average value of NOx at the denitrification outlet is combined with the real-time value of NOx at the outlets of sides A and B, and the start and stop of the coal mill, the load change of the unit, the inlet NOx concentration and the inlet oxygen amount are used as feedforward quantities; Correction is performed based on the feedforward amount to adjust the ammonia injection regulating valve; When the outlet NOx hourly average value is greater than 43 mg / Nm 3 、<47mg / Nm 3 When the automatic control system takes the real-time NOx value at the outlets of side A and B as the regulated quantity; When the deviation between the real-time NOx value at the outlet of side A and side B and the set NOx value at the outlet of side A and side B is greater than 0, open the ammonia injection regulating valve on the corresponding side to increase the amount of ammonia injection; When the deviation between the real-time NOx value at the outlet of side A and side B and the set NOx value at the outlet of side A and side B is less than 0, close the ammonia injection regulating valve on the corresponding side to reduce the amount of ammonia injection. Adjust the ammonia injection regulating valve on each side so that the deviation on each side is close to 0. When the outlet NOx hourly average value is ≥50mg / Nm 3 When , the control system takes the hourly average value of outlet NOx as the regulated variable; The target outlet total NOx value required for the remaining time of this hour is calculated based on the functional relationship F(x). The target outlet total NOx value is compared with the real-time outlet total NOx value, and instructions are issued to the A and B side regulators respectively to open the ammonia injection regulating valves on both sides until the outlet NOx hourly average value is less than 50mg / Nm 3 ; In order to avoid the outlet NOx hourly average value exceeding the standard, it is necessary to leave a margin for the outlet NOx hourly average value and control the outlet NOx hourly average value at 47mg / Nm 3 ~50mg / Nm 3 between; When the outlet NOx hourly average value is ≤40mg / Nm 3 When , the control system takes the hourly average value of outlet NOx as the regulated variable; The target outlet total NOx value required for the remaining time of this hour is calculated based on the functional relationship F(x). The target outlet total NOx value is compared with the real-time outlet total NOx value, and instructions are issued to the A and B side regulators respectively to close the ammonia injection regulating valves on both sides until the outlet NOx hourly average value is greater than 40 mg / Nm 3 ; In order to avoid the outlet NOx hourly average value exceeding the standard, it is necessary to leave a margin for the outlet NOx hourly average value and control the outlet NOx hourly average value at 40mg / Nm 3 ~43mg / Nm 3 ; The calculation of the functional relationship F(x) includes: ； Where F(x) represents the total outlet NOx target value required to be set for the remaining time of this hour period. The table shows the hourly average value of outlet NOx. 50 represents the target value for environmental assessment. The unit is mg / Nm 3 , 60 represents the time of an assessment period, unit is min, t represents the time elapsed in this hour period, unit is min, Indicates the remaining time of this hour, in minutes.

2. The SCR denitration ammonia injection automatic control system optimization control method according to claim 1, characterized in that: include, To prevent excessive ammonia from being injected into the denitrification system, which may affect equipment safety, the ammonia-air ratio should be controlled to be less than 7; When the ammonia-air ratio reaches 5, the standby dilution fan will be started and an audible and visual alarm will sound; When the ammonia-air ratio reaches 6.5, the corresponding side ammonia injection regulating valve will be locked and opened, and an audible and visual alarm will sound. When the ammonia-air ratio reaches 7 and after a delay, the interlock closes the ammonia injection regulating valve on the corresponding side, and an audible and visual alarm sounds. The ammonia injection regulating valve is not allowed to open until the ammonia-air ratio drops below 7. To prevent excessive adjustment of the ammonia injection control valve on one side from exacerbating the disturbance of the control system, when the real-time NOx value at the outlet of side A or side B is ≤5mg / Nm 3 When the lock continues to open the corresponding side ammonia injection regulating valve, sound and light alarm; Wait until the real-time NOx value at the outlet of side A or side B is ≥10mg / Nm 3 When the lock is released.

3. The SCR denitration ammonia injection automatic control system optimization control method according to claim 2, characterized in that: Also includes, To prevent excessive regulation of the ammonia injection regulating valve on one side from exacerbating the disturbance of the regulating system, when the real-time NOx value at the outlet of side A or side B is ≥80mg / Nm 3 When the lock continues to close the corresponding side ammonia injection regulating valve, sound and light alarm; Wait for the real-time NOx value at the outlet of side A or side B to be ≤75mg / Nm 3 When , the lock is released; To avoid frequent switching of the automatic control system, when the outlet NOx hourly average value is between 40 and 43 mg / Nm 3 Between 47~50mg / Nm 3 During this time, the controlled variable of the automatic control system will not be switched, but will be adjusted according to the previously set program.

4. An SCR denitration ammonia injection automatic control system optimization control system, using the SCR denitration ammonia injection automatic control system optimization control method according to any one of claims 1 to 3, characterized in that: include: The first unit is used to collect the hourly value of NOx at the denitration outlet and calculate the hourly average value of NOx at the denitration outlet; The second unit is used to combine the hourly average NOx value at the denitrification outlet with the real-time NOx value at the outlets of sides A and B, and use the start and stop of the coal mill, unit load changes, inlet NOx concentration and inlet oxygen content as feedforward quantities; The third unit is used to make corrections based on the feedforward amount and adjust the ammonia injection regulating valve.

5. A device, characterized in that include: processor; a memory for storing processor-executable instructions; The processor is configured to call the instructions stored in the memory to execute the method according to any one of claims 1 to 3.

6. A computer-readable storage medium having computer program instructions stored thereon, characterized in that: When the computer program instructions are executed by a processor, the method according to any one of claims 1 to 3 is implemented.

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