Ammonia injection control system and method for denitration

Abstract

This invention provides a denitrification ammonia injection control system and method, belonging to the field of flue gas treatment technology. Based on Nash equilibrium theory, the system calculates the nitrogen oxide flow rate in the flue gas section to be regulated and the preset nitrogen oxide flow rates in other flue gas sections, obtaining a proportional control coefficient. Then, under a cascade PI controller, based on the ammonia flow rate injected into the flue gas section to be regulated, the nitrogen oxide flow rate in the flue gas section to be regulated, the preset nitrogen oxide flow rates in the flue gas section to be regulated, and the proportional control coefficient, it generates an opening control command for the corresponding branch regulating valve of the flue gas section to be regulated. Finally, upon receiving the opening control command for the corresponding branch regulating valve of the flue gas section to be regulated, it adjusts the opening of the corresponding branch regulating valve of the flue gas section to be regulated. This invention not only improves the efficiency of boiler denitrification ammonia injection optimization technology but also achieves closed-loop control and can adapt to varying operating conditions.

Description

Technical Field

[0001] This invention relates to the field of flue gas treatment technology, specifically to a denitrification ammonia injection control system and a denitrification ammonia injection control method. Background Technology

[0002] High ammonia slip can lead to blockage of the air preheater by ammonium bisulfate, caking of the electrostatic precipitator, and adhesion of the induced draft fan blades. In severe cases, it can cause problems such as fan stall and unit load limitation. The main reasons for high ammonia slip include: (1) SCR outlet NOx control is too low, resulting in high ammonia slip; (2) high inlet NOx and denitrification efficiency exceeding the design value, resulting in high ammonia slip; (3) large deviation of flue flow field, resulting in local high ammonia slip. Therefore, it is necessary to reduce the amount of ammonia injected to reduce the ammonia slip and solve the series of problems caused by high ammonia slip to downstream equipment.

[0003] Currently, the main methods involve modifying the flow field of the flue gas duct, installing ammonia injection grid flow field guide plates, adding zoned ammonia injection nozzles and zoned control valves, and increasing the number of zoned NOx sampling points. The sampled flue gas is generally measured using a simultaneous measurement method, where multiple sampling devices work in conjunction with a single instrument to achieve simultaneous measurement of multiple zones. This measurement method typically includes flue gas sample extraction and holding devices, and adjusts the ammonia injection rate within each zone based on the measured zone values.

[0004] However, the existing technology has the following problems: (1) Due to the large measurement delay, the measurement value cannot always be in real-time measurement state, and the measurement instrument is affected by factors such as irregular cleaning and calibration, it is difficult to put the zone control into closed-loop control; (2) In general, the opening degree of the ammonia injection regulating valve is manually set according to the different loads of the unit, which will generate a lot of debugging time during the debugging process; (3) It has poor adaptability to changing operating conditions.

[0005] In summary, existing boiler denitrification ammonia injection control technology suffers from low efficiency, inability to achieve closed-loop control, and inability to adapt to changing operating conditions. Summary of the Invention

[0006] The purpose of this invention is to provide a denitrification ammonia injection control system and method to solve the problems of low efficiency, inability to achieve closed-loop control, and inability to adapt to changing operating conditions in existing boiler denitrification ammonia injection control technology.

[0007] To achieve the above objectives, embodiments of the present invention provide a denitrification ammonia injection control system applied to a coal-fired power unit. The coal-fired power unit includes a flue divided into multiple flue sections, the multiple flue sections including a flue section to be regulated and flue sections other than the flue section to be regulated, including:

[0008] The denitrification ammonia injection system includes a main ammonia injection line and multiple ammonia injection branches. One end of each ammonia injection branch is connected to the corresponding flue section, and the other end of each ammonia injection branch is connected to the main ammonia injection line. A main regulating valve is installed on the main ammonia injection line, and each ammonia injection branch is equipped with a branch regulating valve and an ammonia flow monitoring device to control and collect the ammonia flow rate injected into each flue section.

[0009] The nitrogen oxide flow monitoring system includes multiple measuring pipelines. One end of each measuring pipeline is connected to the corresponding flue section, and the other end of each measuring pipeline is connected to the nitrogen oxide flow monitoring device, which is used to collect the nitrogen oxide flow in the flue section to be adjusted.

[0010] The DCS control system is connected to the denitrification ammonia injection system and the nitrogen oxide flow monitoring system. It is used to calculate the nitrogen oxide flow rate in the flue section to be regulated and the nitrogen oxide flow rate in the preset flue sections other than the flue section to be regulated, based on the Nash equilibrium theory, so as to obtain the proportional control coefficient.

[0011] The DCS control system is also used to generate the opening control command of the corresponding branch regulating valve of the flue section to be regulated under the cascade PI regulating controller, based on the ammonia flow rate injected into the flue section to be regulated, the nitrogen oxide flow rate in the flue section to be regulated, the preset nitrogen oxide flow rate in the flue section to be regulated, and the proportional control coefficient.

[0012] The denitrification ammonia injection system is also used to adjust the opening degree of the corresponding branch regulating valve of the flue section to be adjusted when it receives the opening degree control command of the corresponding branch regulating valve of the flue section to be adjusted.

[0013] Optionally, the nitrogen oxide flow monitoring system is also used to collect the nitrogen oxide flow rate in the flue section to be regulated when the nitrogen oxide flow monitoring system is not in a periodic operating state.

[0014] Optionally, the DCS control system includes: a data preprocessing module;

[0015] The data preprocessing module is used to obtain the average flow rate of nitrogen oxides in the flue section based on the nitrogen oxide flow rate in the flue section to be adjusted and the preset nitrogen oxide flow rate in the flue section other than the flue section to be adjusted. The module also replaces the preset nitrogen oxide flow rate in the flue section other than the flue section to be adjusted, which is outside the preset nitrogen oxide flow rate range, with the average flow rate of nitrogen oxides in the flue section.

[0016] Optionally, the DCS control system includes: a first non-uniformity calculation module, a second non-uniformity calculation module, and a proportional coefficient calculation module;

[0017] The first non-uniformity calculation module is used to obtain the average flow rate of nitrogen oxides in the flue section based on the nitrogen oxide flow rate in the flue section to be adjusted and the preset nitrogen oxide flow rate in the flue section other than the flue section to be adjusted, and to obtain the overall non-uniformity of the flue section based on the nitrogen oxide flow rate in the flue section to be adjusted, the preset nitrogen oxide flow rate in the flue section other than the flue section to be adjusted, and the average flow rate of nitrogen oxides in the flue section.

[0018] The second non-uniformity calculation module is used to obtain the average flow rate of nitrogen oxides in the flue section excluding the flue section to be adjusted based on the preset flow rate of nitrogen oxides in the flue section excluding the flue section to be adjusted, and to obtain the overall non-uniformity of the flue section excluding the flue section to be adjusted based on the preset flow rate of nitrogen oxides in the flue section excluding the flue section to be adjusted and the average flow rate of nitrogen oxides excluding the flue section to be adjusted.

[0019] The proportional coefficient calculation module is used to obtain the proportional control coefficient based on the overall non-uniformity of the flue section and the overall non-uniformity of the flue section excluding the flue section to be adjusted.

[0020] Optionally, the first non-uniformity calculation module is specifically used for:

[0021] Using formula (1), the flow rate of nitrogen oxides in the flue section to be regulated, the preset flow rate of nitrogen oxides in the flue sections other than the flue section to be regulated, and the average flow rate of nitrogen oxides in the flue sections are used to obtain the overall non-uniformity of the flue section.

[0022] (1);

[0023] in, C v This indicates the overall unevenness of the flue section; x i Indicates the first i Nitrogen oxide flow rate within each flue section; This represents the average flow rate of nitrogen oxides within the flue section; N This indicates the number of nitrogen oxide flow rates within the flue section.

[0024] Optionally, the second non-uniformity calculation module is specifically used for:

[0025] Using formula (2), the overall non-uniformity of the flue section excluding the flue section to be adjusted is obtained by taking the average flow rate of nitrogen oxides in the flue section excluding the flue section to be adjusted and the average flow rate of nitrogen oxides in the flue section excluding the flue section to be adjusted.

[0026] (2);

[0027] in, C v,n This indicates the overall non-uniformity of a flue section excluding the flue section to be adjusted. This represents the average flow rate of nitrogen oxides in the flue section excluding the section to be regulated; x i Indicates the first i The preset flow rate of nitrogen oxides in a flue section other than the flue section to be adjusted; N This indicates the number of nitrogen oxide flow rates in the flue sections other than the flue section to be regulated.

[0028] Optionally, the proportional coefficient calculation module is specifically used for:

[0029] Using formula (3), the proportional control coefficient is obtained for the overall non-uniformity of the flue section and the overall non-uniformity of the flue section excluding the flue section to be adjusted;

[0030] (3);

[0031] in, k Indicates the proportional control coefficient; C v,n This indicates the overall non-uniformity of a flue section excluding the flue section to be adjusted. C v This indicates the overall unevenness of the flue section.

[0032] Optionally, the DCS control system includes: a first adjustment module and a second adjustment module;

[0033] The first adjustment module is used to obtain the ammonia flow rate to be compensated in the ammonia injection branch corresponding to the flue section to be adjusted based on the nitrogen oxide flow rate in the flue section to be adjusted, the preset nitrogen oxide flow rate in the flue section to be adjusted, and the proportional control coefficient.

[0034] The second adjustment module is used to generate the opening control command of the corresponding branch adjustment valve of the flue section to be adjusted based on the ammonia flow rate to be compensated in the ammonia injection branch corresponding to the flue section to be adjusted and the ammonia flow rate injected into the flue section to be adjusted.

[0035] Optionally, the second adjustment module is further configured to convert the ammonia flow rate to be compensated in the ammonia injection branch corresponding to the flue section to be adjusted and the ammonia flow rate injected into the flue section to be adjusted into the ammonia molar amount to be compensated in the ammonia injection branch corresponding to the flue section to be adjusted and the ammonia molar amount injected into the flue section to be adjusted.

[0036] In a second aspect of the present invention, a denitrification ammonia injection control method is provided, implemented based on the above-described denitrification ammonia injection control system, comprising:

[0037] Obtain the ammonia flow rate injected into each flue section and the nitrogen oxide flow rate in the flue section to be adjusted;

[0038] Based on Nash equilibrium theory, the nitrogen oxide flow rate in the flue section to be regulated and the nitrogen oxide flow rate in the preset flue sections other than the flue section to be regulated are calculated to obtain the proportional control coefficient.

[0039] Under the cascade PI control controller, based on the ammonia flow rate injected into the flue section to be regulated, the nitrogen oxide flow rate in the flue section to be regulated, the preset nitrogen oxide flow rate in the flue section to be regulated, and the proportional control coefficient, the opening control command of the corresponding branch regulating valve of the flue section to be regulated is generated.

[0040] The opening control command of the corresponding branch regulating valve of the flue section to be adjusted is sent to the corresponding branch regulating valve of the flue section to be adjusted, so as to control the opening of the corresponding branch regulating valve of the flue section to be adjusted.

[0041] In this embodiment of the invention, the ammonia flow rate injected into each flue section and the nitrogen oxide flow rate in the flue section to be regulated are obtained. Based on Nash equilibrium theory, the nitrogen oxide flow rate in the flue section to be regulated and the preset nitrogen oxide flow rates in other flue sections are calculated to obtain a proportional control coefficient. Under a cascade PI controller, based on the ammonia flow rate injected into the flue section to be regulated, the nitrogen oxide flow rate in the flue section to be regulated, the preset nitrogen oxide flow rate in the flue section to be regulated, and the proportional control coefficient, an opening control command for the corresponding branch regulating valve of the flue section to be regulated is generated. The opening control command for the corresponding branch regulating valve of the flue section to be regulated is sent to the corresponding branch regulating valve of the flue section to be regulated to control the opening of the corresponding branch regulating valve of the flue section to be regulated. This invention not only improves the efficiency of boiler denitrification ammonia injection optimization technology but also realizes closed-loop control and can adapt to variable operating conditions.

[0042] Other features and advantages of the embodiments of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0043] The accompanying drawings are provided to further illustrate embodiments of the present invention and form part of the specification. They are used together with the following detailed description to explain the embodiments of the present invention, but do not constitute a limitation thereof. In the drawings:

[0044] Figure 1 This is a schematic diagram of the denitrification ammonia injection control system provided in an embodiment of the present invention;

[0045] Figure 2 This is a schematic flowchart of a denitrification ammonia injection control method provided in one embodiment of the present invention;

[0046] Figure 3 This is a schematic flowchart of a denitrification ammonia spraying control method provided in another embodiment of the present invention.

[0047] Explanation of reference numerals in the attached figures

[0048] 1. Flue; 2. Ammonia injection main line; 3. Ammonia injection branch lines; 4. Main regulating valve;

[0049] 5. Branch regulating valve; 6. Ammonia flow monitoring device; 7. Measuring pipeline;

[0050] 8. Nitrogen oxide flow monitoring device; 9. DCS control system; 10. Denitrification server;

[0051] 11. Flue zone to be adjusted; 12. Flue zones other than the flue zone to be adjusted. Detailed Implementation

[0052] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the scope of the present invention.

[0053] 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 application belongs; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this application.

[0054] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0055] Please refer to Figure 1 , Figure 1This is a schematic diagram of the denitrification ammonia injection control system provided in an embodiment of the present invention. The system is applied to a coal-fired power unit, which includes a flue 1 divided into multiple flue sections. These multiple flue sections include a flue section 11 to be regulated and flue sections 12 excluding the flue section to be regulated. The system includes: a denitrification ammonia injection system, comprising a main ammonia injection line 2 and multiple branch ammonia injection lines 3. One end of each branch ammonia injection line 3 is connected to the corresponding flue section, and the other end of each branch ammonia injection line 3 is connected to the main ammonia injection line 2. A main regulating valve 4 is installed on the main ammonia injection line 2, and each branch ammonia injection line 3 is equipped with a branch regulating valve 5 and an ammonia flow monitoring device 6 for controlling and collecting the ammonia flow rate injected into each flue section; and a nitrogen oxide flow monitoring system, comprising multiple measuring pipes 7. One end of each measuring pipe 7 is connected to the corresponding flue section, and the other end of each measuring pipe 7 is connected to a nitrogen oxide flow monitoring device 8 for collecting the flow rate of the flue section to be regulated. The flow rate of nitrogen oxides in flue gas section 11; the DCS control system 9, connected to the denitrification ammonia injection system and the nitrogen oxide flow monitoring system, is used to calculate the nitrogen oxide flow rate in the flue gas section 11 to be regulated and the preset nitrogen oxide flow rate in the flue gas section 12 other than the flue gas section to be regulated, based on Nash equilibrium theory, to obtain the proportional control coefficient; the DCS control system 9 is also used to generate the opening control command of the corresponding branch regulating valve 5 of the flue gas section to be regulated 11 under the cascade PI control controller, based on the ammonia flow rate injected into the flue gas section 11 to be regulated, the nitrogen oxide flow rate in the flue gas section 11 to be regulated, the preset nitrogen oxide flow rate in the flue gas section to be regulated, and the proportional control coefficient; the denitrification ammonia injection system is also used to adjust the opening of the corresponding branch regulating valve 5 of the flue gas section to be regulated 11 when it receives the opening control command of the corresponding branch regulating valve 5 of the flue gas section to be regulated 11.

[0056] It should be noted that the concept of this invention is as follows: (1) Based on the Nash equilibrium theory, with the goal of minimizing the non-uniformity of the entire flue section, the uniformity of the entire flue gas is achieved through closed-loop control of a single flue and multiple rounds of dynamic adjustment; (2) By reasonably setting the automatic and tracking states of the section controller, the ammonia injection amount can be adjusted in a timely manner after the measurement value is obtained, and the controller can also over-inject or under-inject ammonia under the control of the controller during the waiting time for other flue measurements, thus affecting the non-uniformity of the entire flue; (3) The ammonia flow rate of the branch pipe is introduced into the closed-loop control to form a cascade control, reducing the impact of pressure fluctuations in the ammonia supply pipeline on the ammonia flow rate of the section and ensuring control quality; (4) A protective setting is implemented for the abnormal values ​​measured by the nitrogen oxide monitoring device, that is, the upper and lower limits of the non-abnormal measurement values ​​of the entire flue are used to constrain the abnormal values ​​measured by the nitrogen oxide monitoring device, and the average value of the measurement values ​​measured by the nearby nitrogen oxide monitoring device is used as a temporary substitute to ensure the effective operation of this control system.

[0057] In one embodiment, the present invention divides the flue of a coal-fired unit into multiple zones, i.e., flue zones, by using a grid method.

[0058] In one embodiment, a coal-fired power unit may include multiple flues 1, each of which is divided into sections using the method provided in this embodiment of the invention. Each flue section is then connected to multiple ammonia injection branches 3, and each ammonia injection branch 3 is equipped with a branch regulating valve 5 and an ammonia flow monitoring device 6. Furthermore, each flue section is also connected to a nitrogen oxide flow monitoring device 8. It is particularly important to emphasize that each flue corresponds to one nitrogen oxide flow monitoring device 8, rather than all flues sharing a single nitrogen oxide flow monitoring device 8.

[0059] Understandably, Figure 1 The example shown is that the flue is divided into 4 flue zones. In actual application, the flue zones can be divided into more flue zones. The number of flue zones corresponds to the number of ammonia injection branches 3 and nitrogen oxide flow monitoring devices 8. In other words, the number of ammonia injection branches 3 and nitrogen oxide flow monitoring devices 8 corresponds one-to-one with the number of flue zones.

[0060] The preset nitrogen oxide flow rate in the flue section to be adjusted refers to the nitrogen oxide flow rate in the flue section to be adjusted that we need to achieve, as set in the PI controller.

[0061] Since this invention is based on wheel-side technology, the nitrogen oxide flow monitoring device 8 can only monitor the nitrogen oxide flow rate in one flue section at a time. This flue section is referred to as the flue section to be adjusted 11. Flue sections 12, excluding the flue section to be adjusted, are flue sections for which nitrogen oxide flow unevenness does not currently require adjustment. Because only the nitrogen oxide flow rate in the flue section to be adjusted 11 is measured, the nitrogen oxide flow rate in the flue sections 12 is not available. Therefore, interpolation is required, i.e., a preset nitrogen oxide flow rate is used in the flue sections 12 excluding the flue section to be adjusted. Furthermore, the nitrogen oxide flow unevenness in the flue section to be adjusted 11 is adjusted each time. In one embodiment, the measurement time of the nitrogen oxide flow monitoring device 8 is 17 seconds each time.

[0062] In one embodiment, the nitrogen oxide flow rate in flue zone 12, excluding the flue zone to be adjusted, is preset to the nitrogen oxide flow rate obtained from the previous measurement. This can keep the data more realistic and accurate, thereby improving the accuracy of closed-loop control.

[0063] Specifically, in order to eliminate the adverse effects of discontinuous measurement data caused by round-robin measurements on the closed-loop control during continuous closed-loop control, and to enable timely adjustment of the zone control valve opening upon obtaining the latest measurement data, rapid control is achieved by reasonably setting the controller action time in the control loop (i.e., ensuring effective controller control by switching between automatic and tracking states). Specifically, when the nth flue is in the process of instrument measurement, the controller for the nth flue is in tracking state, and the controlled variable is the average value of the flue. After the measurement value is completed and output to the channel, the controller for the nth flue enters automatic state, and after a 10-second delay (which can be adjusted according to actual conditions), the controlled variable switches to the measured value of the nth flue.

[0064] During on-site implementation, the nitrogen oxide flow monitoring device 8 may automatically and periodically operate for calibration and purging. Under these conditions, the nitrogen oxide flow rate measured by the nitrogen oxide flow monitoring device 8 generally remains the same as the previously monitored flow rate until the automatic periodic operation of the nitrogen oxide flow monitoring device 8 ends. When resuming normal operation, the measured nitrogen oxide flow rate will generate significant conflicts, which will adversely affect the closed-loop control. Therefore, in this situation, the embodiment of the present invention adopts the following handling measures:

[0065] (1) The nitrogen oxide flow monitoring system is also used to collect the nitrogen oxide flow rate in the flue section 11 to be adjusted when the nitrogen oxide flow monitoring system is not in the periodic working state.

[0066] (2) The data preprocessing module is used to obtain the average flow rate of nitrogen oxides in the flue gas partition 11 based on the nitrogen oxide flow rate in the flue gas partition 11 to be adjusted and the preset nitrogen oxide flow rate in the flue gas partition 12 other than the flue gas partition to be adjusted, and to replace the preset nitrogen oxide flow rate in the flue gas partition 12 other than the flue gas partition to be adjusted that is not within the preset nitrogen oxide flow rate range with the average flow rate of nitrogen oxides in the flue gas partition. In one embodiment, the preset nitrogen oxide flow rate range is bounded by the minimum and maximum nitrogen oxide flow rates in all flue gas partitions.

[0067] In one embodiment, the DCS control system 9 includes: a first non-uniformity calculation module, a second non-uniformity calculation module, and a proportional coefficient calculation module; the first non-uniformity calculation module is used to obtain the average flow rate of nitrogen oxides in the flue section 11 based on the nitrogen oxide flow rate in the flue section to be adjusted and the preset nitrogen oxide flow rate in the flue section 12 other than the flue section to be adjusted, and to obtain the overall non-uniformity of the flue section based on the nitrogen oxide flow rate in the flue section 11 to be adjusted, the preset nitrogen oxide flow rate in the flue section 12 other than the flue section to be adjusted, and the average flow rate of nitrogen oxides in the flue section 12. The second non-uniformity calculation module is used to obtain the average flow rate of nitrogen oxides in flue section 12 excluding the flue section to be regulated, based on the preset nitrogen oxide flow rate in the flue section 12 excluding the flue section to be regulated, and to obtain the overall non-uniformity of the flue section excluding the flue section to be regulated based on the preset nitrogen oxide flow rate in the flue section 12 excluding the flue section to be regulated and the average flow rate of nitrogen oxides excluding the flue section to be regulated 11; the proportional coefficient calculation module is used to obtain the proportional control coefficient based on the overall non-uniformity of the flue section and the overall non-uniformity of the flue section excluding the flue section to be regulated 11.

[0068] According to Nash equilibrium theory, also known as non-cooperative game equilibrium, it is an important term in game theory named after John Nash. In a game, regardless of the opponent's strategic choice, one player will choose a certain strategy, which is called the dominant strategy. If the strategic combinations of two players constitute their respective dominant strategies, then this combination is defined as a Nash equilibrium. When each player's balancing strategy maximizes their expected payoff, a strategy combination is called a Nash equilibrium. Simultaneously, all other players follow this strategy. After multiple rounds of training, measurement, and control, the overall non-uniformity of the flue will inevitably stabilize and reach a minimum value.

[0069] Specifically, the first non-uniformity calculation module is used to: use formula (1) to calculate the flow rate of nitrogen oxides in the flue section to be regulated, the flow rate of nitrogen oxides in the flue section other than the flue section to be regulated, and the average flow rate of nitrogen oxides in the flue section to obtain the overall non-uniformity of the flue section. (1); where, C v This indicates the overall unevenness of the flue section; x i Indicates the first i Nitrogen oxide flow rate within each flue section; This represents the average flow rate of nitrogen oxides within the flue section; N This indicates the number of nitrogen oxide flow rates within the flue section.

[0070] Specifically, the second non-uniformity calculation module is used to: use formula (2) to obtain the overall non-uniformity of the flue section excluding the flue section to be adjusted by using the average flow rate of nitrogen oxides in the flue section other than the flue section to be adjusted and the average flow rate of nitrogen oxides in the flue section excluding the flue section to be adjusted. (2); where, C v,n This indicates the overall non-uniformity of a flue section excluding the flue section to be adjusted. This represents the average flow rate of nitrogen oxides in the flue section excluding the section to be regulated; x i Indicates the first i The preset flow rate of nitrogen oxides in a flue section other than the flue section to be adjusted; N This indicates the number of nitrogen oxide flow rates in the flue sections other than the flue section to be regulated.

[0071] Specifically, the proportional coefficient calculation module is used to: use formula (3) to obtain the proportional control coefficient for the overall non-uniformity of the flue section and the overall non-uniformity of the flue section without the flue section to be adjusted; (3); among which, k Indicates the proportional control coefficient; C v,n This indicates the overall non-uniformity of a flue section excluding the flue section to be adjusted. C v This indicates the overall unevenness of the flue section.

[0072] In one embodiment, the algorithms contained in the first non-uniformity calculation module, the second non-uniformity calculation module, and the proportion calculation module are stored in the denitrification server 10. When the DCS control system 9 needs to perform calculations, it can obtain the algorithms from the denitrification server 10.

[0073] In one embodiment, the DCS control system 9 includes: a first adjustment module and a second adjustment module; the first adjustment module is used to obtain the ammonia flow rate to be compensated in the ammonia injection branch 3 corresponding to the flue section 11 to be adjusted based on the nitrogen oxide flow rate in the flue section 11 to be adjusted, the preset nitrogen oxide flow rate in the flue section to be adjusted, and the proportional control coefficient; the second adjustment module is used to generate the opening control command of the corresponding branch regulating valve 5 of the flue section 11 to be adjusted based on the ammonia flow rate to be compensated in the ammonia injection branch 3 corresponding to the flue section 11 to be adjusted and the ammonia flow rate injected into the flue section 11 to be adjusted.

[0074] It should be noted that the PI controller in this embodiment of the invention is a cascade controller. A PI cascade controller is a commonly used type of controller for improving system stability and response speed. It consists of two cascaded control loops, one of which is a proportional-integral (PI) controller, and the other is an outer controller. In a PI cascade controller, the inner PI controller is responsible for internal system regulation to quickly respond to and suppress system disturbances. It generates a control signal based on the difference between the measured signal and the setpoint, comprising both proportional and integral parts. The proportional part makes the control signal proportional to the error, while the integral part generates the control signal based on the cumulative history of the error to eliminate the system's steady-state error. The outer controller sits above the PI controller and is responsible for regulating the overall performance of the system. Its input is the output signal of the PI controller, i.e., the control signal of the inner controller, while its output signal is the final control signal used to drive actuators or adjust system parameters. The outer controller typically uses a proportional controller, adjusted according to the system's response speed and stability requirements.

[0075] In one embodiment, in order to better achieve the tuning of the ammonia flow rate to be compensated and the nitrogen oxide ratio parameters, the second adjustment module is further used to convert the ammonia flow rate to be compensated in the ammonia injection branch 3 corresponding to the flue section 11 to be adjusted and the ammonia flow rate injected into the flue section 11 to be adjusted into the ammonia molar amount to be compensated in the ammonia injection branch 3 corresponding to the flue section 11 to be adjusted and the ammonia molar amount injected into the flue section 11 to be adjusted.

[0076] After calculation by the PI cascade controller, an opening control command for the branch regulating valve 5 corresponding to the flue gas section 11 to be regulated is generated. This command is then sent to the branch regulating valve 5 corresponding to the flue gas section 11 to adjust the opening of the branch regulating valve 5, thereby controlling the ammonia flow rate injected into the flue gas section 11 to meet the non-uniformity of nitrogen oxide flow rate in the flue gas section 11 to be regulated. This avoids problems such as air preheater hydrogen sulfate blockage, electrostatic precipitator caking, and induced draft fan blade adhesion, which in severe cases can cause induced draft fan stall and unit load limitation.

[0077] For ease of understanding, please refer to Figure 2 The following is a specific embodiment:

[0078] First, it is determined whether the nitrogen oxide flow monitoring device 8 is in a periodic working state. If not, the nitrogen oxide flow rate in the flue section 11 to be adjusted is collected, and the nitrogen oxide flow rate in other flue sections monitored last time is used as the current nitrogen oxide flow rate in other flue sections. Then, after determining the nitrogen oxide flow rate in all flue sections, it is judged whether the nitrogen oxide flow rate in each flue section is between the minimum and maximum nitrogen oxide flow rates in all flue sections. If so, the opening control command of the corresponding branch regulating valve 5 of the flue section to be adjusted is generated through the PI cascade controller based on the ammonia flow rate injected into the flue section to be adjusted, the nitrogen oxide flow rate in the flue section to be adjusted, the preset nitrogen oxide flow rate in the flue section to be adjusted, and the proportional control coefficient (wherein, the ammonia flow rate injected into the flue section to be adjusted needs to be converted into molar quantity). Finally, the command is sent to the corresponding branch regulating valve 5 in the flue section to be adjusted 11, thereby controlling the opening of the branch regulating valve 5 and thus controlling the nitrogen oxide flow rate entering the flue section to be adjusted 11.

[0079] In this embodiment of the invention, the ammonia flow rate injected into each flue section and the nitrogen oxide flow rate in the flue section 11 to be regulated are obtained. Based on Nash equilibrium theory, the nitrogen oxide flow rate in the flue section 11 to be regulated and the preset nitrogen oxide flow rate in the flue section 12 (excluding the flue section to be regulated) are calculated to obtain a proportional control coefficient. Under the cascade PI control controller, based on the ammonia flow rate injected into the flue section 11 to be regulated, the nitrogen oxide flow rate in the flue section 11 to be regulated, the preset nitrogen oxide flow rate in the flue section to be regulated, and the proportional control coefficient, an opening control command for the corresponding branch regulating valve 5 of the flue section 11 to be regulated is generated. The opening control command for the corresponding branch regulating valve 5 of the flue section 11 to be regulated is sent to the corresponding branch regulating valve 5 of the flue section 11 to control the opening degree of the corresponding branch regulating valve 5 of the flue section 11 to be regulated. This invention not only improves the efficiency of boiler denitrification ammonia injection optimization technology but also realizes closed-loop control and can adapt to variable operating conditions.

[0080] Based on the same inventive concept, and referring to Figure 2 This invention also provides a denitrification ammonia injection control method, based on the above-mentioned denitrification ammonia injection control system, which includes the following steps:

[0081] S100, obtain the ammonia flow rate injected into each flue section and the nitrogen oxide flow rate in the flue section to be adjusted;

[0082] S200, based on Nash equilibrium theory, calculates the nitrogen oxide flow rate in the flue section to be regulated and the nitrogen oxide flow rate in the preset flue sections other than the flue section to be regulated, and obtains the proportional control coefficient.

[0083] S300, under the cascade PI control controller, generates the opening control command of the corresponding branch control valve of the flue section to be adjusted based on the ammonia flow rate injected into the flue section to be adjusted, the nitrogen oxide flow rate in the flue section to be adjusted, the preset nitrogen oxide flow rate in the flue section to be adjusted, and the proportional control coefficient.

[0084] S400 sends the opening control command of the corresponding branch regulating valve of the flue section to be adjusted to the corresponding branch regulating valve of the flue section to control the opening of the corresponding branch regulating valve of the flue section to be adjusted.

[0085] The specific structure of the denitrification ammonia injection control system is as described in the above embodiments. Since the denitrification ammonia injection control method adopts all the technical solutions of all the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be elaborated here.

[0086] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0087] The above are merely embodiments of this application and are not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

Claims

1. A denitrification ammonia injection control system, applied to a coal-fired power unit, the coal-fired power unit including a flue divided into multiple flue sections, the multiple flue sections including a flue section to be regulated and flue sections other than the flue section to be regulated, characterized in that, include: The denitrification ammonia injection system includes a main ammonia injection line and multiple ammonia injection branches. One end of each ammonia injection branch is connected to the corresponding flue section, and the other end of each ammonia injection branch is connected to the main ammonia injection line. A main regulating valve is installed on the main ammonia injection line, and each ammonia injection branch is equipped with a branch regulating valve and an ammonia flow monitoring device to control and collect the ammonia flow rate injected into each flue section. The nitrogen oxide flow monitoring system includes multiple measuring pipelines. One end of each measuring pipeline is connected to the corresponding flue section, and the other end of each measuring pipeline is connected to the nitrogen oxide flow monitoring device, which is used to collect the nitrogen oxide flow in the flue section to be adjusted. The DCS control system is connected to the denitrification ammonia injection system and the nitrogen oxide flow monitoring system. It is used to calculate the nitrogen oxide flow rate in the flue section to be regulated and the nitrogen oxide flow rate in the flue sections other than the flue section to be regulated based on the Nash equilibrium theory, so as to obtain the proportional control coefficient. The DCS control system is also used to generate the opening control command of the corresponding branch regulating valve of the flue section to be regulated under the cascade PI regulating controller, based on the ammonia flow rate injected into the flue section to be regulated, the nitrogen oxide flow rate in the flue section to be regulated, the nitrogen oxide flow rate in the flue sections other than the flue section to be regulated, and the proportional control coefficient. The denitrification ammonia injection system is also used to adjust the opening degree of the corresponding branch regulating valve of the flue section to be adjusted when it receives the opening degree control command of the corresponding branch regulating valve of the flue section to be adjusted.

2. The denitrification ammonia injection control system according to claim 1, characterized in that, The nitrogen oxide flow monitoring system is also used to collect the nitrogen oxide flow rate in the flue section to be regulated when the nitrogen oxide flow monitoring device is not in regular working condition.

3. The denitrification ammonia injection control system according to claim 1, characterized in that, The DCS control system includes: a data preprocessing module; The data preprocessing module is used to obtain the average flow rate of nitrogen oxides in the flue section based on the nitrogen oxide flow rate in the flue section to be adjusted and the nitrogen oxide flow rate in the flue sections other than the flue section to be adjusted. It also replaces the nitrogen oxide flow rate in the flue sections other than the flue section to be adjusted that is not within the preset nitrogen oxide flow rate range with the average flow rate of nitrogen oxides in the flue section.

4. The denitrification ammonia injection control system according to claim 1, characterized in that, The DCS control system includes: a first non-uniformity calculation module, a second non-uniformity calculation module, and a proportional coefficient calculation module; The first non-uniformity calculation module is used to obtain the average flow rate of nitrogen oxides in the flue section based on the nitrogen oxide flow rate in the flue section to be adjusted and the nitrogen oxide flow rate in the flue sections other than the flue section to be adjusted, and to obtain the overall non-uniformity of the flue section based on the nitrogen oxide flow rate in the flue section to be adjusted, the nitrogen oxide flow rate in the flue sections other than the flue section to be adjusted, and the average flow rate of nitrogen oxides in the flue section. The second non-uniformity calculation module is used to obtain the average flow rate of nitrogen oxides in the flue section excluding the flue section to be regulated based on the nitrogen oxide flow rate in the flue section excluding the flue section to be regulated, and to obtain the overall non-uniformity of the flue section excluding the flue section to be regulated based on the nitrogen oxide flow rate in the flue section excluding the flue section to be regulated and the average flow rate of nitrogen oxides in the flue section excluding the flue section to be regulated. The proportional coefficient calculation module is used to obtain the proportional control coefficient based on the overall non-uniformity of the flue section and the overall non-uniformity of the flue section excluding the flue section to be adjusted.

5. The denitrification ammonia injection control system according to claim 4, characterized in that, The first non-uniformity calculation module is specifically used for: Using formula (1), the flow rate of nitrogen oxides in the flue section to be regulated, the flow rate of nitrogen oxides in the flue sections other than the flue section to be regulated, and the average flow rate of nitrogen oxides in the flue sections are calculated to obtain the overall non-uniformity of the flue section. （1）； in, C v This indicates the overall unevenness of the flue section; x i Indicates the first i Nitrogen oxide flow rate within each flue section; This represents the average flow rate of nitrogen oxides within the flue section; N This indicates the number of flue sections.

6. The denitrification ammonia injection control system according to claim 4, characterized in that, The second non-uniformity calculation module is specifically used for: Using formula (2), the average flow rate of nitrogen oxides in the flue section other than the flue section to be regulated and the average flow rate of nitrogen oxides without the flue section to be regulated are calculated to obtain the overall non-uniformity of the flue section without the flue section to be regulated. （2）； in, This indicates the overall non-uniformity of a flue section excluding the flue section to be adjusted. This represents the average flow rate of nitrogen oxides excluding the flue section to be regulated; Indicates the first i The flow rate of nitrogen oxides in each flue section except for the flue section to be regulated; n This indicates the number of flue zones other than the flue zone to be adjusted.

7. The denitrification ammonia injection control system according to claim 4, characterized in that, The proportional coefficient calculation module is specifically used for: Using formula (3), the overall non-uniformity of the flue section and the overall non-uniformity of the flue section without the flue section to be adjusted are calculated to obtain the proportional control coefficient. （3）； in, k Indicates the proportional control coefficient; This indicates the overall non-uniformity of a flue section excluding the flue section to be adjusted. C v This indicates the overall unevenness of the flue section.

8. The denitrification ammonia injection control system according to claim 1, characterized in that, The DCS control system includes: a first adjustment module and a second adjustment module; The first adjustment module is used to obtain the ammonia flow rate to be compensated in the ammonia injection branch corresponding to the flue section to be adjusted based on the nitrogen oxide flow rate in the flue section to be adjusted, the nitrogen oxide flow rate in the flue sections other than the flue section to be adjusted, and the proportional control coefficient. The second adjustment module is used to generate the opening control command of the corresponding branch adjustment valve of the flue section to be adjusted based on the ammonia flow rate to be compensated in the ammonia injection branch corresponding to the flue section to be adjusted and the ammonia flow rate injected into the flue section to be adjusted.

9. The denitrification ammonia injection control system according to claim 8, characterized in that, The second adjustment module is also used to convert the ammonia flow rate to be compensated in the ammonia injection branch corresponding to the flue section to be adjusted and the ammonia flow rate injected into the flue section to be adjusted into the ammonia molar amount to be compensated in the ammonia injection branch corresponding to the flue section to be adjusted and the ammonia molar amount injected into the flue section to be adjusted.

10. A method for controlling ammonia injection during denitrification, implemented based on the ammonia injection control system for denitrification according to any one of claims 1-9, characterized in that, include: Obtain the ammonia flow rate injected into each flue section and the nitrogen oxide flow rate in the flue section to be adjusted; Based on Nash equilibrium theory, the nitrogen oxide flow rate in the flue section to be regulated and the nitrogen oxide flow rate in the flue sections other than the flue section to be regulated are calculated to obtain the proportional control coefficient. Under the cascade PI control controller, based on the ammonia flow rate injected into the flue section to be regulated, the nitrogen oxide flow rate in the flue section to be regulated, the nitrogen oxide flow rate in the flue sections other than the flue section to be regulated, and the proportional control coefficient, the opening control command of the corresponding branch control valve of the flue section to be regulated is generated. The opening control command of the corresponding branch regulating valve of the flue section to be adjusted is sent to the corresponding branch regulating valve of the flue section to be adjusted, so as to control the opening of the corresponding branch regulating valve of the flue section to be adjusted.

Images