A boiler denitration control system and method under a coal economizer flue gas bypass working condition

Abstract

The application provides a boiler denitration control system and method under the economizer flue gas bypass working condition, calculates the deviation of the boiler outlet nitrogen oxide and the set value; generates PID control parameters and deviation input amplification coefficients by using an adaptive matrix according to the current state of the unit; amplifies the calculated deviation by using the deviation input amplification coefficients as the deviation input; generates a feedforward signal according to the denitration inlet nitrogen oxide content and its differential signal, the unit load and the pre-starting amount of the start-stop coal mill; generates a control output by using a PID control method under the PID control parameters based on the deviation input and the feedforward signal; and generates different amplitude limits of the control output according to the coal quality and the start-stop coal mill. The application can effectively reduce the denitration control delay, improve the control efficiency and adaptability.

Description

Technical Field

[0001] This invention belongs to the field of boiler denitrification control technology, and relates to a boiler denitrification control system and method under economizer flue gas bypass conditions. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] One of the main challenges currently limiting deep peak shaving in thermal power units is meeting the requirement for the inlet flue gas temperature of selective catalytic reduction (SCR) denitrification. The minimum operating temperature requirement for the denitrification catalyst is >300℃; below this temperature, the catalyst's effectiveness decreases, leading to adverse consequences such as NH4HSO4 deposition in downstream equipment. During deep peak shaving, as combustion weakens, the SCR denitrification inlet flue gas temperature gradually decreases until it no longer meets the requirements, causing the denitrification system to shut down and resulting in excessive NOx emissions. One solution is to add an economizer flue gas bypass. Under high boiler load conditions, the economizer flue gas bypass damper is closed; under low boiler load conditions, when the flue gas temperature is below the catalyst's minimum temperature, the bypass damper is opened, allowing the boiler flue gas to directly enter the SCR denitrification unit without passing through the economizer for cooling, thus obtaining sufficient high-temperature flue gas. This method can solve the problem of not being able to operate the SCR denitrification unit under low load conditions, and the project investment is relatively small.

[0004] During the research and development and application process, the inventors discovered the following shortcomings in boiler denitrification control under economizer flue gas bypass conditions:

[0005] High delay in denitrification control: The pure response time of denitrification control is greater than 3 minutes, and the total reaction time is about ten minutes. To achieve good control quality, it is necessary to design a control scheme with a large time lag.

[0006] The original control scheme had a simple flue gas bypass control, which was mostly manual and prone to errors. It could easily cause the differential pressure of the air preheater to deteriorate, and it required a high level of technical skills from the unit operators.

[0007] The original control scheme had poor adaptability, only considering static relationships, which made the denitrification control quality particularly poor when the unit load changed frequently and the coal mill started and stopped. Summary of the Invention

[0008] To address the aforementioned problems, this invention proposes a boiler denitrification control system and method under economizer flue gas bypass conditions. This invention can effectively reduce denitrification control delay, improve control efficiency, and enhance adaptability.

[0009] According to some embodiments, the present invention adopts the following technical solution:

[0010] A method for boiler denitrification control under economizer flue gas bypass conditions includes the following steps:

[0011] Calculate the deviation between the boiler outlet nitrogen oxide emissions and the set value;

[0012] Based on the current status of the unit, PID control parameters and deviation input amplification coefficients are generated using an adaptive matrix.

[0013] The calculated deviation is amplified using a deviation input amplification factor and used as the deviation input;

[0014] Based on the nitrogen oxide content at the denitrification inlet and its differential signal, the unit load, and the pre-start amount of the coal mill, a feedforward signal is calculated and generated.

[0015] Based on the aforementioned deviation input and feedforward signal, a control output is generated using the PID control method under the aforementioned PID control parameters.

[0016] Different amplitude limits are generated for the control output based on the quality of the coal fed into the furnace and the start and stop of the coal mill.

[0017] As an alternative implementation, the control output can also be locked out when the nitrogen oxide detection system is purged.

[0018] As an alternative implementation, it also includes: amplitude limiting control output as a tracking quantity.

[0019] As an alternative implementation method, the specific process of generating PID control parameters using an adaptive matrix includes the adaptive matrix selecting the load segment calculation and the coal quality fed into the furnace through a piecewise function based on the current unit load, and obtaining the corresponding proportional coefficient Kp, integral coefficient Ki, and derivative coefficient Kd after matrix operation, which are used as PID control parameters.

[0020] A boiler denitrification control system under economizer flue gas bypass operation includes:

[0021] The parameter adaptive calculation module is configured to generate PID control parameters and deviation input amplification coefficients using an adaptive matrix based on the current state of the unit.

[0022] A deviation generation loop is configured to calculate the deviation between the boiler outlet nitrogen oxides and the set value; the calculated deviation is amplified using a deviation input amplification factor and used as the deviation input.

[0023] The feedforward generation loop is configured to calculate and generate a feedforward signal based on the nitrogen oxide content at the denitrification inlet and its differential signal, the unit load, and the pre-start amount of the start-up and shutdown of the coal mill.

[0024] The PID controller is configured to generate a control output using a PID control method based on the deviation input and the feedforward signal, under the PID control parameters.

[0025] The amplitude limiting loop is configured to generate different amplitude limits for the control output based on the quality of the coal fed into the furnace and the start / stop of the coal mill.

[0026] As an alternative implementation, the deviation generation circuit is configured to calculate the deviation between the outlet nitrogen oxides and the set value, and output it to the deviation input pin of the PID controller E after calculation of the adaptive matrix K amplification factor and the deviation dead zone.

[0027] As an alternative implementation, the feedforward generation loop is configured to take the nitrogen oxide content at the denitrification inlet, the differential nitrogen oxide content at the denitrification inlet, the unit load, the load segment calculation after selecting the load segment through a piecewise function, and the pre-start amount of the start / stop coal mill, and use them as feedforward inputs to the PID controller after calculation by an adder. When the above values ​​change, they directly act on the output of the PID controller, playing a role in pre-action, offsetting the lag effect and improving the control quality.

[0028] As an alternative implementation, the amplitude limiting loop is configured to generate different amplitude limiting values ​​through adaptive matrix operations based on different coal quality and start / stop conditions of the coal mill. These values ​​are then input to the amplitude limiting function block to limit the output command of the PID controller. When the PID output reaches the limit value, the PID operation is paused. When the start / stop of the coal mill causes a sharp change in the nitrogen oxide value, the loop limits the output, prevents integral saturation, and reduces disturbances.

[0029] As an alternative implementation, a detection system purging interlock loop is also included, which is configured such that when the detection system is purging, the output of the control system is maintained at the current value by the switch, the PID controller switches to tracking mode, and the tracked value is the current command of the denitrification control valve, which serves as a shield. When the purging ends, the shield is released and the operation resumes.

[0030] As an alternative implementation, an economizer flue gas bypass damper pre-start circuit is also included, which is configured to output a pulse signal to the PID controller and outlet switch when the unit load is less than the minimum load. The pre-start broken line function calculation based on the unit load directly outputs the command to the economizer flue gas bypass damper, thereby playing the role of pre-opening the bypass damper to increase the denitrification inlet temperature.

[0031] As an optional implementation, a denitrification inlet temperature control loop is also included, which is configured such that the deviation between the denitrification inlet temperature and the set value is calculated by a PID controller. When there is a deviation between the denitrification inlet temperature and the set value, the PID controller calculates the proportional coefficient Kp, integral coefficient Ki, and derivative coefficient Kd parameters and outputs a corresponding command to the economizer flue gas bypass damper to reduce the deviation between the denitrification inlet temperature and the set value.

[0032] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0033] (1) The PID control using the parameter adaptive matrix has strong adaptability and convergence, which can overcome the difficulty of exceeding the limit of nitrogen oxides at the outlet caused by rapid load changes and coal quality changes in the denitrification automatic control system.

[0034] (2) The multi-value input feedforward adopted can initiate the pre-action function, which can overcome the difficulties of large lag and poor control quality caused by starting and stopping the coal mill in the denitrification control system.

[0035] (3) The PID controller with adaptive matrix parameter is highly compatible and can be implemented with almost all types of distributed control systems (DCS) for power plants, saving the cost of control equipment modification and adding peripherals, and the modification cost is low.

[0036] (4) The amplitude limiting circuit used can limit the output under different conditions, prevent integral saturation, and reduce disturbances.

[0037] (5) The detection system purge lockout circuit can avoid control system disturbances and enhance control quality during system purging.

[0038] (6) The economizer flue gas bypass damper adaptive circuit can adaptively adjust the control circuit according to the unit load and air preheater differential pressure signal. It can increase the denitrification inlet temperature setpoint and pre-open the economizer flue gas bypass damper according to the actual situation, avoid denitrification catalyst failure and air preheater differential pressure deterioration, and reduce unit operators' operational errors.

[0039] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0040] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0041] Figure 1 This is a structural diagram of the denitrification control in Example 1;

[0042] Figure 2 This is a structural diagram of the economizer flue gas bypass damper control in Example 2;

[0043] The block consists of: 1. PID controller block; 2. First adaptive matrix block; 3. Adder block; 4. Deviation dead zone calculation block; 5. Limiting block; 6. Switcher block; 7. First piecewise linear function block; 8. Second piecewise linear function block; 9. Third piecewise linear function block; 10. Fourth piecewise linear function block; 11. Fifth piecewise linear function block; 12. Sixth piecewise linear function block; 13. Seventh piecewise linear function block; 14. Multiplier block; 15. Second adaptive matrix block; 16. Eighth piecewise linear function block.

[0044] 1-1 PID controller block, 1-2 Dual input switcher block, 1-3 Deviation dead zone calculation block, 1-4 Piece function block, 1-5 Comparator block, 1-6 Pulse trigger block, 1-7 Subtractor block, 1-8 Adder block, 1-9 Adaptive matrix block. Detailed Implementation

[0045] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0046] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, 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.

[0047] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0048] Example 1

[0049] Figure 1 This is a structural diagram of the automatic denitrification control system involved in this embodiment. (See diagram below.) Figure 1 As shown, the denitrification control system includes a boiler outlet nitrogen oxide deviation generation loop, a parameter adaptive matrix, a feedforward generation loop, an amplitude limiting loop, and a detection system purging interlock loop.

[0050] Specifically, the boiler outlet nitrogen oxide deviation generation circuit includes an outlet nitrogen oxide deviation signal, a multiplication block 14, and a deviation dead zone block 4.

[0051] The deviation of the outlet nitrogen oxides from the set value is connected to the K coefficient output by the multiplication block 14, and the other end is connected to the deviation dead zone block 4. The other end of the deviation dead zone block 4 is connected to the deviation input E terminal of the PID controller, serving as the deviation input of the PID controller.

[0052] Specifically, the parameter adaptive matrix loop includes the unit load signal, the coal quality signal entering the furnace, the first piecewise linear function block 7, the adaptive matrix block 2, the second piecewise linear function block 8, the third piecewise linear function block 9, and the fourth piecewise linear function block 10.

[0053] The coal quality signal fed into the furnace is connected to the input terminal of the adaptive matrix block 2, and the unit load signal is connected to the input terminal of the first piecewise linear function block 7. The other end of the first piecewise linear function block 7 is connected to the input terminal of the adaptive matrix block 2. The output terminal of the adaptive matrix block 2 is connected to the input terminals of the second piecewise linear function block 8, the third piecewise linear function block 9, and the fourth piecewise linear function block 10, respectively. The output terminals of the second piecewise linear function block 8, the third piecewise linear function block 9, and the fourth piecewise linear function block 10 respectively output the proportional coefficient Kp, the integral coefficient Ki, and the derivative coefficient Kd to the PID controller as the adjustment parameters of the PID controller.

[0054] The specific feedforward generation loop includes the denitrification inlet nitrogen oxide content signal, the denitrification inlet nitrogen oxide differential signal, the unit load signal, the start-up and shutdown coal mill pre-start signal, adder block 3, fifth piecewise linear function block 11, and sixth piecewise linear function block 12.

[0055] The denitrification inlet nitrogen oxide content signal and the denitrification inlet nitrogen oxide differential signal are connected to the input terminal of adder block 3. The unit load signal is connected to the input terminal of the fifth piecewise linear function block 11. The output terminal of the fifth piecewise linear function block 11 is connected to the input terminal of adder block 3. The start / stop coal mill pre-start signal is connected to the input terminal of the sixth piecewise linear function block 12. The output terminal of the sixth piecewise linear function block 12 is connected to the input terminal of adder block 3. The output terminal of adder block 3 is connected to the feedforward FF terminal of PID control block 1.

[0056] The specific amplitude limiting loops include the coal quality signal entering the furnace, the start / stop signal of the coal mill, the second adaptive matrix block 15, the seventh broken line block 13, and the eighth broken line block 16.

[0057] The coal quality signal and the start / stop signal of the coal mill are connected to the input terminal of the adaptive matrix block 15. The output terminal of the adaptive matrix block 15 is connected to the input terminals of the seventh segmented line block 13 and the eighth segmented line block 16, respectively. The output terminal of the seventh segmented line block 13 is connected to the high limit H terminal of the limiting block 5. The output terminal of the eighth segmented line block 16 is connected to the low limit L terminal of the limiting block 5. The S input terminal of the limiting block 5 is connected to the OUT output terminal of the PID controller. The output terminal of the limiting block 5 is connected to the K2 input terminal of the switch module 6. When the high and low limits of the limiting block 5 are activated, the output signal suspends the operation of the PID controller.

[0058] The specific detection system purging interlocking circuit includes the purging signal of the nitrogen oxide measuring device and switch block 6.

[0059] The purging signal of the nitrogen oxide measuring device is connected to the TS tracking switching signal of the PID control module and the SW switching input of the switch block 6. The inputs k1 and k2 of the switch block 6 are connected to the output of the switch block 6 and the output of the amplitude limiting block 5, respectively. The output of the switch block 6 is simultaneously connected to the S tracking signal of the PID control block 1 and the input k1 of the switch block 6.

[0060] In this example, the deviation of the outlet nitrogen oxides from the setpoint is calculated using an adaptive matrix K amplification factor and deviation dead zone calculation, and then output to the deviation input pin of the PID controller as the PID controller deviation input signal. The unit load is selected through a piecewise function to calculate the load segment and the coal quality entering the furnace, and then matrix operations are performed to obtain the corresponding proportional coefficient Kp, integral coefficient Ki, and derivative coefficient Kd, which serve as the control parameters for the PID controller. The nitrogen oxide content at the denitrification inlet, the derivative of the nitrogen oxides at the denitrification inlet, the unit load (selected through a piecewise function load segment calculation), and the pre-start amount of the coal mill are calculated using an adder and serve as the feedforward input for the PID controller. The coal quality entering the furnace and the coal mill start / stop signals are processed through an adaptive matrix operation to generate different amplitude limit values, which are input to the amplitude limiting function block to limit the PID output command and pause the PID operation when the PID output reaches the limit value. When the purging signal of the measuring device is triggered, the output of the control system is maintained at the current value by the switcher, and the PID controller switches to tracking mode. The tracked value is the command of the current denitrification control valve, which acts as a shield.

[0061] Example 2

[0062] Figure 2 This is a structural diagram of the economizer flue gas bypass control involved in this embodiment. Figure 2 As shown, the economizer flue gas bypass control system includes a denitrification inlet temperature deviation generation loop, an economizer flue gas bypass damper adaptive loop, and a denitrification inlet temperature PID control loop.

[0063] The specific denitrification inlet temperature deviation generation circuit includes the denitrification inlet temperature and denitrification inlet temperature setpoint number, deviation dead zone block 3, subtractor block 7, and adder block 8.

[0064] The deviation signal between the denitrification inlet temperature and the set value is connected to the input signal of the deviation dead zone block 3, and the output signal of the deviation dead zone block 3 is connected to the deviation input terminal E of the PID controller 1.

[0065] The economizer flue gas bypass damper adaptive circuit includes unit load signal, minimum load signal, air preheater differential pressure signal, adaptive matrix 9, piecewise linear function block 4, comparator block 5, pulser block 6, and switcher block 2.

[0066] The unit load signal is connected to the input terminal of adaptive matrix block 9 and the input terminal 1 of comparator block 5, respectively. The air preheater differential pressure signal is connected to the input terminal of adaptive matrix block 9. The output terminal of the adaptive matrix is ​​output to the input terminals of subtractor block 8 and piecewise linear function 4, respectively. The output terminal of piecewise linear function block 4 is connected to the input terminal K1 of switcher block 2. The minimum load signal is connected to the input terminal 2 of comparator block 5. The output terminal of comparator block 5 is connected to the input terminal of pulse generator block 6, respectively. The output terminal of pulse generator block 6 is connected to the tracking switching terminal TS of PID controller 1 and the Sw terminal of switcher block 2, respectively. The output terminal of switcher block 2 is connected to the tracking quantity S terminal of PID controller block and is simultaneously output to the economizer bypass damper command.

[0067] The PID control loop for the denitrification inlet temperature includes a PID controller 1, which receives the deviation signal between the denitrification inlet temperature and the set value and performs PID adjustment according to fixed proportional coefficient Kp, integral coefficient Ki, and derivative coefficient Kd, and outputs the command to the flue gas bypass damper.

[0068] In this example, the deviation between the denitrification inlet temperature and the setpoint is calculated using a deviation dead-zone algorithm and output to the deviation input pin of the PID controller. The air preheater differential pressure signal is input to the adaptive matrix 9. When the air preheater differential pressure is too high, the adaptive matrix outputs to the adder block 8. When the unit load is less than the minimum load, a pulse signal is output to the PID controller and the outlet switch. Based on the unit load and a pre-start piecewise linear function calculation, a command is directly output to the economizer flue gas bypass damper, which pre-opens the bypass damper to increase the denitrification inlet temperature. The deviation between the denitrification inlet temperature and the setpoint is calculated by the PID module. When there is a deviation between the denitrification inlet temperature and the setpoint, the PID controller calculates parameters such as the proportional coefficient Kp, integral coefficient Ki, and derivative coefficient Kd, and outputs a corresponding command to the economizer flue gas bypass damper to reduce the deviation between the denitrification inlet temperature and the setpoint.

[0069] As can be seen from the above description, the above embodiments achieve the following technical effects:

[0070] (1) The PID control with adaptive matrix adjustment parameters has strong adaptability and convergence, which can overcome the difficulty of excessive nitrogen oxides at the outlet caused by rapid load changes and coal quality changes in the denitrification automatic control system.

[0071] (2) Multi-value input feedforward can initiate pre-action, which can overcome the difficulties of large lag and poor control quality caused by starting and stopping coal mills in the denitrification control system.

[0072] (3) The amplitude limiting loop of the adaptive adjustment matrix can limit the output under different conditions, prevent integral saturation, and reduce disturbance.

[0073] (4) The detection system purge lockout circuit can avoid control system disturbances and enhance control quality during system purging.

[0074] (5) The economizer flue gas bypass damper adaptive circuit can adaptively adjust the control circuit according to the unit load and air preheater differential pressure signal. It can increase the denitrification inlet temperature setpoint and pre-open the economizer flue gas bypass damper according to the actual situation, avoid denitrification catalyst failure and air preheater differential pressure deterioration, and reduce unit operators' operational errors.

[0075] The above embodiments are merely examples.

[0076] In other embodiments, the execution modules or their parameter setting ranges can be replaced, as long as the above functions can be achieved. It is not limited to the examples described above.

[0077] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0078] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0079] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0080] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0081] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0082] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A boiler denitration control method in a coal economizer flue gas bypass working condition, characterized in that, The method comprises the following steps: calculating the deviation of the boiler outlet nitrogen oxide and the set value; generating PID control parameters and deviation input amplification coefficients by using an adaptive matrix according to the current state of the unit; the specific process of generating PID control parameters by using an adaptive matrix comprises: the adaptive matrix selects a load section according to the current unit load through a segmented function, and calculates the corresponding proportional coefficient Kp, integral coefficient Ki, and differential coefficient Kd through matrix operation according to the coal quality fed into the furnace, as the PID control parameters; amplifying the calculated deviation by using the deviation input amplification coefficient as the deviation input; generating a feedforward signal according to the denitration inlet nitrogen oxide content and its differential signal, the unit load, and the pre-starting amount of the starting and stopping coal mill; generating a control output by using a PID control method under the PID control parameters based on the deviation input and the feedforward signal; the coal quality fed into the furnace and the starting and stopping coal mill signal are subjected to adaptive matrix operation to generate different amplitude limiting values, which are input to an amplitude limiting function block to limit the output instruction of the PID and pause the PID operation when the PID output reaches the limiting value.

2. The boiler denitration control method in the economizer flue gas bypass working condition according to claim 1, characterized in that, It also comprises: the amplitude limiting control output as a tracking quantity.

3. A boiler denitration control system in a coal economizer flue gas bypass working condition, characterized in that, It comprises: a parameter adaptive calculation module configured to generate PID control parameters and deviation input amplification coefficients by using an adaptive matrix according to the current state of the unit; the specific process of generating PID control parameters by using an adaptive matrix comprises: the adaptive matrix selects a load section according to the current unit load through a segmented function, and calculates the corresponding proportional coefficient Kp, integral coefficient Ki, and differential coefficient Kd through matrix operation according to the coal quality fed into the furnace, as the PID control parameters; a deviation generation loop configured to calculate the deviation of the boiler outlet nitrogen oxide and the set value; and amplify the calculated deviation by using the deviation input amplification coefficient as the deviation input; a feedforward generation loop configured to generate a feedforward signal according to the denitration inlet nitrogen oxide content and its differential signal, the unit load, and the pre-starting amount of the starting and stopping coal mill; a PID controller configured to generate a control output by using a PID control method under the PID control parameters based on the deviation input and the feedforward signal; an amplitude limiting loop configured to generate different amplitude limiting values by adaptive matrix operation on the coal quality fed into the furnace and the starting and stopping coal mill signal, which are input to an amplitude limiting function block to limit the output instruction of the PID and pause the PID operation when the PID output reaches the limiting value.

4. The boiler denitration control system under the economizer flue gas bypass working condition according to claim 3, characterized in that, The deviation generation loop is configured to calculate the deviation of the outlet nitrogen oxide and the set value, which is subjected to adaptive matrix K amplification coefficient and deviation dead zone operation and then output to the E deviation input pin of the PID controller.

5. The boiler denitration control system in the economizer flue gas bypass working condition according to claim 3, characterized in that, The feedforward generation loop is configured to perform adder operation on the denitration inlet nitrogen oxide content, the denitration inlet nitrogen oxide differential, the unit load subjected to segmented function selection of the load section, and the pre-starting amount of the starting and stopping coal mill, as the feedforward input of the PID controller, which directly acts on the output of the PID controller when the feedforward input value of the PID controller changes.

6. The boiler denitration control system in the economizer flue gas bypass working condition according to claim 3, characterized in that, The amplitude limiting loop is configured to generate different amplitude limiting values according to different coal qualities and start-stop coal mill conditions, input the amplitude limiting values to the limiting function block, limit the output instruction of the PID controller, and pause the PID operation when the output of the PID controller reaches the limiting value.

7. The boiler denitration control system in the economizer flue gas bypass working condition according to Claim 3, characterized in that, The detection system purge locking loop is further included, which is configured to keep the output of the control system at the current value by the switcher, and switch the PID controller to the tracking mode when the detection system is purged, and the tracked value is the current denitration control valve instruction.

8. The boiler denitration control system in the economizer flue gas bypass working condition according to claim 3, characterized in that, The economizer flue gas bypass damper pre-starting loop is further included, which is configured to output a pulse signal to the PID controller and the outlet switcher when the unit load is less than the minimum load, directly output the unit load to the economizer flue gas bypass damper instruction through the pre-starting fold line function operation.

9. The boiler denitration control system in the economizer flue gas bypass working condition according to Claim 3, characterized in that, The denitration inlet temperature control loop is further included, which is configured to perform PID controller operation on the deviation of the denitration inlet temperature from the set value, and output corresponding instructions to the economizer flue gas bypass damper when there is a deviation between the denitration inlet temperature and the set value through the proportional coefficient Kp, the integral coefficient Ki, and the differential coefficient Kd parameters.

Images