A boiler combustion control method and system for ammonia-coal dual fuel blending

Abstract

The application provides a boiler combustion control method and system for ammonia-coal dual fuel blending, and belongs to the field of ammonia-coal mixed combustion control. The boiler combustion control method for ammonia-coal dual fuel blending comprises the following steps: S1: generating a boiler operation parameter in an ammonia-coal dual fuel blending process according to a boiler load and an ammonia blending ratio requirement during ammonia-coal dual fuel blending; the boiler operation parameter comprises an ammonia supply amount set value and a coal supply amount set value. The application can realize automatic adjustment control of fuel quantity, air quantity and pollutant emission in ammonia-coal dual fuel blending combustion, improve combustion efficiency, realize low pollutant emission, and improve the automatic blending level.

Description

Technical Field

[0001] This invention relates to the field of ammonia-coal combustion control technology, and in particular to a boiler combustion control method and system for ammonia-coal dual-fuel blending. Background Technology

[0002] Ammonia, as a highly efficient carrier of hydrogen, offers higher storage and transportation efficiency and safety compared to pure hydrogen. Ammonia-blended combustion in coal-fired boilers can utilize existing power plant resources to achieve large-scale carbon reduction, which is significant for helping my country's thermal power sector achieve its dual-carbon goals. However, the combustion of ammonia as a fuel still faces two challenges: firstly, ammonia has poor combustion properties, and secondly, the laminar flame velocity S of the NH3 / air premixed flame... Ｌ The peak value is only around 7 cm / s, far lower than that of CH4 and H2. Ammonia also has a narrow flammability limit range, a high auto-ignition temperature, and its adiabatic flame temperature at atmospheric pressure is much lower than that of CH4 and H2, which is unfavorable for stable combustion. Secondly, since NH3 itself contains nitrogen, it may produce a large amount of fuel-type NOx during combustion. Furthermore, because the adiabatic flame temperature of ammonia is lower than that of pulverized coal, and the composition and radiation characteristics of ammonia combustion products differ significantly from those of pulverized coal, the co-firing of ammonia and coal may cause significant changes in the furnace temperature distribution, thus affecting the boiler's heat transfer distribution. Therefore, the boiler combustion control in the ammonia-coal dual-fuel co-firing process of coal-fired boilers is quite difficult. Firstly, it is necessary to ensure that the furnace temperature field distribution is not affected; secondly, it is necessary to ensure that the NOx concentration at the furnace outlet does not exceed the standard; and thirdly, it is necessary to ensure that the ammonia is fully burned. Currently, traditional combustion control systems are unable to effectively adapt to the characteristics of ammonia combustion, and cannot monitor the furnace temperature field during the co-firing of ammonia and coal, nor can they automatically control and adjust the fuel quantity, air quantity, and furnace outlet pollutant emissions according to the ammonia blending ratio. This results in complex operation for operators, low combustion efficiency, and excessive pollutants during the co-firing of ammonia and coal.

[0003] Therefore, there is an urgent need to develop a boiler combustion control method and system for ammonia-coal dual-fuel blending. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a boiler combustion control method for ammonia-coal dual-fuel blending, which realizes automatic adjustment and control of fuel, air, and pollutant emissions during the ammonia and coal blending process, improves combustion efficiency, achieves lower pollutant emissions, and enhances the level of automation to solve the problems mentioned in the above technical background.

[0005] Accordingly, the present invention also provides a boiler combustion control system for ammonia-coal dual-fuel blending.

[0006] The present invention adopts the following technical solution:

[0007] A combustion control method for a boiler using ammonia and coal dual-fuel blending includes the following steps:

[0008] S1: Generate boiler operating parameters during the ammonia-coal dual-fuel blending process based on the boiler load and ammonia blending ratio requirements; the boiler operating parameters include ammonia feed rate setpoints and coal feed rate setpoints.

[0009] Step S1 specifically includes the following steps:

[0010] S11: Set the initial ammonia blending ratio k0, which is determined based on the boiler fuel calorific value ratio. The calculation formula is k0=(m n ×LHV n ) / (m n ×LHV n +m m ×LHV m ), where m n The mass flow rate of ammonia fuel is m. m LHV is the mass flow rate of coal fuel. n The lower heating value (LHV) of ammonia fuel is... m It has the lower calorific value of coal fuel;

[0011] S12: The fuel quantity setpoint F generated by the boiler main controller based on the load command and steam pressure deviation. total (Generated by PID control algorithm) Multiply by k0 to obtain the ammonia supply setpoint F. NH3 =k0×F total ;

[0012] S13: Set the ammonia supply rate to the set value F. NH3 The equivalent coal quantity instruction F is generated after conversion based on calorific value. coal-eq =F NH3 ×(LHV n / LHV m );

[0013] S14: Calculate the coal feed rate setpoint F coal =F total -F coal-eq .

[0014] The boiler combustion control method further includes the following steps:

[0015] S2: Real-time monitoring of NOx concentration at the furnace outlet. _NOx and unburned NH3 concentration C _NH3 The ammonia blending ratio is dynamically corrected based on the concentration deviation; new ammonia feed rate settings and new coal feed rate settings are generated based on the corrected ammonia blending ratio.

[0016] Specifically, the correction of the ammonia blending ratio is as follows:

[0017] When C _NOx>C goal_NOx When the target NOx concentration at the furnace outlet is reached, the formula k1 = k0 × [1 + 0.05 × (C)] is used. _NOx - C goal_NOx

[10] Increase the ammonia doping ratio, with a correction factor ranging from 1.05 to 1.15; where C goal_Nox The target value for NOx concentration at the furnace outlet;

[0018] When the concentration of unburned NH3 is C _NH3 >C goal_ NH3 When the target value of unburned NH3 concentration at the furnace outlet is reached, the formula k2 = k0 × [1 - 0.03 × (C)] is applied. _NH3 - C goal_ NH3

[10] Reduce the ammonia doping ratio, with a correction factor ranging from 0.85 to 0.95; where C goal_ NH3 This represents the target value for NH3 concentration at the furnace outlet.

[0019] Among them, the concentration target value C goal_Nox and C goal_ NH3 The determination is based on the ammonia-blended combustion test data of the corresponding power unit.

[0020] The boiler operating parameters also include an excess air coefficient; the control method further includes the following steps:

[0021] S3: Steps for controlling the excess air coefficient within a preset range;

[0022] The specific step S3 includes the following steps:

[0023] S31: Real-time monitoring of NOx concentration at furnace outlet C _NOx and unburned NH3 concentration C _NH3 Adjust the boiler air supply volume according to the concentration deviation;

[0024] S32: Based on the adjusted air supply volume, the excess air coefficient is controlled within a preset range through graded air distribution; wherein controlling the excess air coefficient within the preset range includes controlling the total excess air coefficient α of the boiler. total >1.1; and control the local excess air coefficient α in the main combustion zone of ammonia-coal co-firing. local <0.8, the graded air distribution method includes adjusting the air supply volume of the secondary air damper in the main combustion zone and the air supply volume in the burnout zone. The specific adjustments include the following:

[0025] When C _NOx The concentration exceeded the target value C for NOx concentration in the furnace outlet products. goal_NOx At the same time, reduce the secondary air volume in the main combustion zone to 40%-50% of the total air volume, and increase the SOFA damper opening in the burnout zone to 70%-80% to achieve oxygen-deficient combustion in the main combustion zone;

[0026] When the concentration of unburned NH3 is C _NH3 Exceeding the target value C for unburned NH3 concentration goal_ NH3 At that time, the oxygen concentration in the main combustion zone will be increased to 23%-25%.

[0027] The control method further includes the following steps:

[0028] S4: Real-time monitoring of furnace temperature field and furnace outlet flue gas temperature, and correction of ammonia blending ratio k0 using furnace temperature field and furnace outlet flue gas temperature;

[0029] Specifically, when the average deviation of the temperature gradient at the four corners of the furnace and / or the average deviation of the flue gas temperature at the furnace outlet ΔT > 50℃ for 30 consecutive minutes, the ammonia blending ratio correction is triggered according to the formula k3 = k0 × (1 - 0.1 × ΔT / 50), with a correction coefficient ranging from 0.9 to 1.1.

[0030] A combustion control system for a boiler using ammonia and coal dual-fuel blending, the control system comprising:

[0031] The system includes a central control module, a monitoring module, an execution module, and an alarm module; the central control module is electrically or communicatively connected to the monitoring module, the execution module, and the alarm module.

[0032] The central control module is used to generate corresponding control strategies based on the boiler load and ammonia blending ratio requirements when ammonia and coal are blended, and to adjust the control strategies based on the information from the monitoring module to generate new control strategies, and send the control strategies to the execution module; the central control module includes a fuel quantity calculation unit and an air volume distribution unit. The fuel quantity calculation unit is used to execute the control method described in any one of steps S1-S4, and the air volume distribution unit is connected to the air distribution system to execute the air distribution control strategy of step S3;

[0033] The execution module is used to adjust the boiler operating parameters during the ammonia-coal dual-fuel blending process according to the received control strategy; the execution module includes an ammonia feeding regulating valve, a coal feeder speed actuator, an air supply regulator, a secondary air damper, and an SOFA damper actuator;

[0034] The monitoring module is used to monitor in real time the NOx concentration and unburned NH3 concentration at the furnace outlet, as well as the three-dimensional temperature field of the furnace and the flue gas temperature at the furnace outlet during the ammonia-coal dual-fuel co-combustion process.

[0035] The alarm module is used to trigger an audible, visual, or vibration alarm when the ammonia escape value at the furnace outlet exceeds a threshold.

[0036] The monitoring module includes a furnace outlet NOx concentration monitoring unit, a furnace outlet unburned NH3 concentration monitoring unit, a furnace temperature field monitoring unit, and a furnace outlet flue gas temperature monitoring unit.

[0037] The furnace outlet NOx concentration monitoring unit and the furnace outlet unburned NH3 concentration monitoring unit include an online flue gas analyzer and an ammonia slip laser detector installed in the economizer outlet flue. The online flue gas analyzer is used to monitor the furnace outlet NOx concentration, and the ammonia slip laser detector is used to monitor the furnace outlet unburned NH3 concentration.

[0038] The furnace temperature field monitoring unit includes a first temperature measuring element and a data processing module; the data processing module obtains the three-dimensional temperature field of the furnace based on the measurement results of the first temperature measuring element.

[0039] The furnace outlet flue gas temperature monitoring unit measures the furnace outlet flue gas temperature value by installing a second temperature measuring element at the furnace outlet.

[0040] The first temperature measuring element is an infrared CCD camera with a spectral response range of 3-5µm, and the second temperature measuring element is a furnace infrared pyrometer.

[0041] The data processing module includes a temperature field algorithm server, a PLC controller, a communication link, a communication network, and a power supply module.

[0042] The first temperature measuring element transmits the measured data to the temperature field algorithm server via optical fiber. The temperature field algorithm server and the PLC controller are connected through a communication network and transmit data based on the TCP / IP protocol. The three-dimensional temperature field data of the furnace inverted by the temperature field algorithm server is transmitted to the PLC controller. The PLC controller is connected to the central control module through a communication link and transmits data based on the Modbus protocol. The PLC controller transmits the three-dimensional temperature field data of the furnace to the central control module.

[0043] The furnace is equipped with a first temperature measuring element in both the horizontal and vertical directions.

[0044] Two first temperature measuring elements are provided in the horizontal direction of the furnace; the two first temperature measuring elements are staggered relative to each other and are located above the burner of the ammonia-coal co-firing boiler.

[0045] And / or, two first temperature measuring elements are provided in the vertical direction of the furnace; the two first temperature measuring elements are provided on the front wall of the burner of the ammonia-coal co-firing boiler and are arranged along the height direction.

[0046] The horizontal and vertical field of view of the two first temperature measuring elements set in the horizontal direction are both at a certain angle to the boiler axis; the horizontal and vertical field of view of the two first temperature measuring elements set in the vertical direction are both at a certain angle to the boiler axis.

[0047] The horizontal field of view and the angle between the two first temperature measuring elements set in the horizontal direction and the boiler axis are 45°, and the vertical field of view and the angle between the two first temperature measuring elements set in the horizontal direction and the boiler axis are 45°.

[0048] The horizontal field of view and the angle between the two first temperature measuring elements set in the height direction and the boiler axis are 80°, and the vertical field of view and the angle between the two first temperature measuring elements set in the height direction and the boiler axis are 55°.

[0049] The monitoring module further includes:

[0050] The steam parameter monitoring unit is used to monitor the main steam parameter values ​​and reheat steam parameter values ​​of the boiler during the co-firing of ammonia and coal.

[0051] The desuperheating water monitoring unit is used to monitor the desuperheating water volume of the main steam and reheat steam in the boiler during the co-firing of ammonia and coal.

[0052] Fuel quantity monitoring unit: used to monitor the boiler coal consumption and ammonia consumption during the co-firing of ammonia and coal;

[0053] The air volume monitoring unit is used to monitor the total air volume and burnout air volume in the dual-fuel combustion of ammonia and coal, thereby monitoring the total excess air coefficient value and the excess air coefficient value of the main combustion zone of the boiler.

[0054] The central control module includes a control strategy generation unit, an adjustment strategy generation unit, and a control strategy adjustment unit.

[0055] The control strategy generation unit is used to generate boiler operating parameters during the ammonia-coal dual-fuel blending process based on the boiler load and ammonia blending ratio requirements when blending ammonia and coal.

[0056] The adjustment strategy generation unit compares the real-time measurement parameters of the monitoring module with the target values ​​of the set parameters to obtain the deviation results, calculates the required combustion reaction conditions based on the deviation results, and generates a boiler operating parameter adjustment strategy.

[0057] The control strategy adjustment unit is used to update the control strategy according to the adjustment strategy generated by the adjustment strategy generation unit, so as to obtain a new control strategy.

[0058] The alarm module includes an audible and visual alarm and a vibrator. The audible and visual alarm and the vibrator are electrically connected to the central control module. When the ammonia escape value at the furnace outlet exceeds the alarm threshold, the central control module outputs an electrical signal to the audible and visual alarm and the vibrator, causing them to activate and issue audible and visual alarms and vibration alarms.

[0059] The beneficial effects of this invention are as follows:

[0060] (1) The boiler combustion control method for ammonia-coal dual fuel blending of the present invention can generate corresponding control strategies based on the boiler load and ammonia blending ratio requirements when ammonia-coal dual fuel blending. By setting up real-time monitoring equipment for furnace temperature field, furnace outlet flue gas temperature and furnace outlet product NOx / unburned NH3 concentration, the real-time measured values ​​of furnace temperature field, furnace outlet flue gas temperature and furnace outlet product NOx / unburned NH3 concentration are obtained. The measured values ​​are compared with the target values ​​to calculate the required combustion reaction conditions and generate boiler fuel quantity and air volume parameter adjustment strategies, thereby realizing the update of the ammonia-coal dual fuel blending combustion control strategy.

[0061] (2) The present invention can realize the automatic balance of coal and ammonia in the process of ammonia-coal dual-fuel co-firing, maintain a suitable total excess air coefficient and main combustion zone excess air coefficient in boiler combustion, improve the efficiency of ammonia-coal dual-fuel co-firing, and reduce pollutant emission concentration. Attached Figure Description

[0062] Figure 1 A schematic diagram of a boiler combustion control system for ammonia-coal dual-fuel blending provided by the present invention;

[0063] Figure 2 A schematic diagram of the layout of a furnace temperature field, a furnace outlet flue gas temperature monitoring unit, and a furnace outlet NOx and unburned NH3 concentration monitoring unit provided by the present invention for a dual-fuel (ammonia and coal) boiler.

[0064] Figure 3 This is a schematic diagram of the working process of the furnace temperature field monitoring unit provided by the present invention.

[0065] In the diagram: 001-Furnace; 002-Economizer; 003-Superheater; 004-SCR device for denitrification; 005-Burnset group for ammonia-coal co-firing boiler; 100-Central control module; 110-Fuel quantity calculation unit; 120-Air volume distribution unit; 130-Temperature field algorithm server; 140-PLC controller; 200-Monitoring module; 210-Furnace temperature field monitoring unit; 220-Furnace outlet flue gas temperature monitoring unit; 230-Furnace outlet NOx concentration monitoring unit; 240-Furnace outlet unburned NH3 concentration monitoring unit. Yuan; 250-Steam parameter monitoring unit; 260-Desuperheating water monitoring unit; 270-Fuel quantity monitoring unit; 280-Air volume monitoring unit; 211-First temperature measuring element; 212-Second temperature measuring element; 231-Online flue gas analyzer; 241-Ammonia escape laser detector; 300-Actuation module; 310-Ammonia feed regulating valve; 320-Coal feeder speed actuator; 330-Air volume regulator; 340-Secondary air damper actuator; 350-SOFA air damper actuator; 400-Alarm module; 500-Power supply module. Detailed Implementation

[0066] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0067] This invention provides a boiler combustion control method for ammonia-coal dual-fuel blending, comprising the following steps:

[0068] S1: Generate boiler operating parameters during the ammonia-coal dual-fuel blending process based on the boiler load and ammonia blending ratio requirements; the boiler operating parameters include ammonia feed rate and coal feed rate.

[0069] Step S1 specifically includes the following steps:

[0070] S11: Set the initial ammonia blending ratio k0, which is determined based on the boiler fuel calorific value ratio. The calculation formula is k0=(m n ×LHV n ) / (m n ×LHV n +m m ×LHV m ), where m n The mass flow rate of ammonia fuel is m. m LHV is the mass flow rate of coal fuel. n The lower heating value (LHV) of ammonia fuel is... mIt has the lower calorific value of coal fuel;

[0071] S12: The fuel quantity setpoint F generated by the boiler main controller based on the load command and steam pressure deviation. total (Generated by PID control algorithm) Multiplied by k0, the ammonia supply setpoint F is obtained. NH3 =k0×F total ;

[0072] S13: Set the ammonia supply rate to the set value F. NH3 The equivalent coal quantity instruction F is generated after conversion based on calorific value. coal-eq =F NH3 ×(LHV n / LHV m );

[0073] S14: Calculate the coal feed rate setpoint F coal =F total -F coal-eq .

[0074] The boiler combustion control method for ammonia-coal dual-fuel blending of the present invention can automatically reduce or increase the coal feed rate as the ammonia blending ratio increases or decreases during the ammonia-coal dual-fuel blending process, thereby achieving automatic fuel balance.

[0075] In a preferred embodiment, the control method of the present invention further includes a step of correcting the ammonia blending ratio. Specifically, this includes step S2: real-time monitoring of the NOx concentration C at the furnace outlet. _NOx and unburned NH3 concentration C _NH3， The ammonia blending ratio is dynamically corrected based on the concentration deviation. Based on the corrected ammonia blending ratio, new ammonia feed rate settings and new coal feed rate settings are generated according to steps S12-S14. Specifically, the ammonia blending ratio is corrected as follows:

[0076] When C _NOx >C goal_NOx At that time, according to the formula k1=k0×[1+0.05×(C _NOx - C goal_NOx

[10] Increase the ammonia doping ratio; further, the k1 correction factor ranges from 1.05 to 1.15;

[0077] When C _NH3 >C goal_ NH3 At that time, according to the formula k2=k0×[1-0.03×(C _NH3 - C goal_ NH3

[10] Reduce the ammonia doping ratio; further, the k2 correction factor ranges from 0.85 to 0.95.

[0078] In this embodiment, the boiler operating parameters are adjusted based on the real-time monitored NOx concentration and NH3 escape concentration at the furnace outlet. The purpose is to ensure that the NOx concentration at the furnace outlet does not exceed the standard and that the ammonia is fully burned.

[0079] The specific implementation is as follows: A modified ammonia blending ratio is set. This modified ratio is multiplied by the fuel setpoint signal output by the boiler main controller to generate a modified ammonia feed command under the modified ammonia blending ratio. This modified ammonia feed command serves as the ammonia feed setpoint. The ammonia feed setpoint is then converted according to its calorific value to form an equivalent coal feed command. Fuel feed setpoint signals from the boiler main controller under different loads and ammonia blending ratios are logically subtracted from the equivalent coal feed command to generate a new coal feed setpoint. This new coal feed setpoint is then entered into the coal feed control system to replace the original coal feed setpoint. In this way, during the ammonia-coal dual-fuel blending process, the coal feed rate automatically decreases as the ammonia blending ratio increases, achieving fuel balance.

[0080] More preferably, the control method of this embodiment further includes the step of controlling the excess air coefficient; the boiler operating parameters further include the excess air coefficient; the control method further includes the step of controlling the excess air coefficient within a preset range, specifically including the following steps:

[0081] S31: Real-time monitoring of NOx concentration at the furnace outlet. _NOx and unburned NH3 concentration C _NH3 The boiler air supply volume is adjusted according to the concentration deviation; the air supply volume is also adjusted according to the comparison between the current NOx concentration of the furnace outlet product and the target value of the NOx concentration of the furnace outlet product, and the current real-time concentration of unburned NH3 and the target value of unburned NH3.

[0082] S32: Adjust the graded air distribution according to the adjusted air supply volume to keep the excess air coefficient within the preset range.

[0083] Specifically, based on the NOx concentration of the furnace outlet product and the current real-time concentration of unburned NH3, and comparing them with the target values ​​of the NOx concentration and unburned NH3 concentration of the furnace outlet product, the furnace outlet product adjustment signal value is calculated, and the corresponding combustion reaction adjustment conditions are calculated. The boiler air supply setpoint is adjusted according to the calculated combustion reaction adjustment conditions. This air supply setpoint can also be processed by cross-limiting the total fuel quantity to obtain a new air supply setpoint. This new air supply setpoint enters the air supply control system and replaces the original air supply setpoint.

[0084] Preferably, controlling the excess air coefficient within a preset range includes controlling the total excess air coefficient α of the boiler. total Greater than 1.1; and controlling the local excess air coefficient α in the main combustion zone of ammonia-coal co-firing. local Less than 0.8.

[0085] Preferably, adjusting the staged air distribution method includes adjusting the air supply volume of the secondary air damper in the main combustion zone and the air supply volume in the burnout zone. By adjusting the opening degree of the secondary air in the main combustion zone and the opening degree of the burnout damper, the local excess air coefficient in the main combustion zone of ammonia-coal co-firing is adjusted, so that the main combustion zone is in a lower reducing atmosphere, thereby reducing the formation of fuel-type NOx in ammonia-coal dual-fuel blend. Specific steps include:

[0086] When the NOx concentration exceeds the target value C for NOx concentration in the furnace outlet product goal_NOx At the same time, reduce the secondary air volume in the main combustion zone to 40%-50% of the total air volume, and increase the SOFA damper opening in the burnout zone to 70%-80% to achieve oxygen-deficient combustion in the main combustion zone;

[0087] When the concentration of unburned NH3 exceeds the target value C for unburned NH3 concentration goal_ NH3 At that time, the oxygen concentration in the main combustion zone will be increased to 23%-25%.

[0088] As a preferred embodiment, the control method of the present invention further includes a step of correcting the ammonia blending ratio using the furnace temperature field and the furnace outlet flue gas temperature. Specifically, the control method further includes the following steps: S4: Real-time monitoring of the furnace temperature field and the furnace outlet flue gas temperature, using the furnace temperature field and the furnace outlet flue gas temperature to correct the ammonia blending ratio, and generating a new ammonia feed rate setpoint and a new coal feed rate setpoint based on the corrected ammonia blending ratio. Specifically, this includes: when the average deviation of the temperature gradient at the four corners of the furnace and / or the average deviation of the furnace outlet flue gas temperature ΔT > 50℃ for 30 consecutive minutes, triggering the ammonia blending ratio correction according to the formula k3 = k0 × (1 - 0.1 × ΔT / 50), with a correction coefficient k3 = 0.9-1.1.

[0089] Accordingly, the present invention also provides a boiler combustion control system for ammonia-coal dual-fuel blending, comprising: a central control module 100, a monitoring module 200, an execution module 300, and an alarm module 400; the central control module 100 is electrically or communicatively connected to the monitoring module 200, the execution module 300, and the alarm module 400.

[0090] The central control module 100 is used to generate a corresponding control strategy based on the boiler load and ammonia blending ratio requirements when ammonia and coal are blended, and to adjust the control strategy based on the information from the monitoring module 200 to generate a new control strategy, and send the control strategy to the execution module 300; the central control module includes a fuel quantity calculation unit 110 and an air volume distribution unit 120, the fuel quantity calculation unit 110 is used to execute the control method of any one of steps S1-S4 in the claims, and the air volume distribution unit 120 is connected to the air distribution system to execute the air distribution control strategy of step S3 in the claims;

[0091] The execution module 300 is used to adjust the boiler operating parameters during the ammonia-coal dual-fuel blending process according to the received control strategy; the execution module includes an ammonia feeding regulating valve 310, a coal feeder speed actuator 320, an air supply regulator 330, a secondary air damper actuator 340, and an SOFA damper actuator 350;

[0092] The monitoring module 200 is used to monitor in real time the three-dimensional temperature field of the furnace, the flue gas temperature at the furnace outlet, and the NOx concentration and unburned NH3 concentration of the furnace outlet products during the ammonia-coal dual-fuel co-combustion process.

[0093] The alarm module 400 is used to provide audible and visual or vibration alarms when the ammonia escape value at the furnace outlet exceeds the threshold.

[0094] The information received by the central control module 100 includes the real-time monitoring data received by the monitoring module 200, such as the boiler furnace temperature field, furnace outlet flue gas temperature, and the concentrations of NOx and NH3 at the furnace outlet.

[0095] The execution module 300 is also used to adjust the boiler operating parameters in real time during the ammonia-coal dual-fuel blending combustion process according to the new control strategy.

[0096] In embodiments of the present invention, such as Figure 1 As shown, the monitoring module includes a furnace temperature field monitoring unit 210, a furnace outlet flue gas temperature monitoring unit 220, a furnace outlet NOx concentration monitoring unit 230, and a furnace outlet unburned NH3 concentration monitoring unit 240.

[0097] like Figure 2 As shown, the ammonia-coal dual-fuel boiler system includes a furnace 001, an economizer 002, a screen-type superheater 003, a denitrification SCR device 004, and an ammonia-coal burner group 005.

[0098] The furnace temperature field monitoring unit 210 monitors the two-dimensional temperature field of the furnace in the horizontal and vertical directions by means of the first temperature measuring element 211 installed in the horizontal and vertical directions of the furnace 001, and obtains the three-dimensional temperature field of the furnace by temperature field inversion and reconstruction by the algorithm server. The furnace outlet flue gas temperature monitoring unit 220 measures the furnace outlet flue gas temperature value by means of the second temperature measuring element 212 installed in the furnace outlet.

[0099] The furnace outlet NOx concentration monitoring unit 230 includes an online flue gas analyzer 231 installed in the economizer outlet flue, and the furnace outlet unburned NH3 concentration monitoring unit 240 includes an ammonia slip laser detector 241 installed in the economizer outlet flue. The online flue gas analyzer 231 is used to monitor the furnace outlet NOx concentration, and the ammonia slip laser detector 241 is used to monitor the furnace outlet unburned NH3 concentration.

[0100] In this embodiment of the invention, the first temperature measuring element 211 is an infrared CCD camera with a spectral response range of 3-5 μm, and the second temperature measuring element is a furnace infrared pyrometer; see also Figure 3 The first temperature measuring element 211 is also connected to other hardware systems, including a temperature field algorithm server 130, a PLC controller 140, and a power module 500.

[0101] The first temperature measuring element 211 transmits the measured data to the temperature field algorithm server 130 via optical fiber. The temperature field algorithm server 130 and the PLC controller 140 are connected through a communication network and transmit data based on the TCP / IP protocol. The three-dimensional temperature field data of the furnace inverted by the temperature field algorithm server 130 is transmitted to the PLC controller 140. The PLC controller 140 is connected to the central control module 100 via a communication link and transmits data based on the Modbus protocol. The PLC controller 140 transmits the three-dimensional temperature field data of the furnace to the central control module 100.

[0102] Before the formal measurement and installation, the first temperature measuring element 211 needs to be calibrated. The calibration is carried out by a blackbody furnace to obtain the quantitative relationship between image intensity and radiation intensity (1): I=A1T g +A2T w =AT0

[0103] Where I is the radiation intensity image matrix received by the first temperature measuring element; T is the actual three-dimensional temperature matrix of the furnace; T g Tw is the fourth power matrix of the temperature of the discrete unit in space; A1, A2, and A are the fourth power matrix of the temperature of the discrete unit on the wall; A1, A2, and A are the radiation intensity imaging matrices, which are mainly determined by the radiation characteristics of the medium and the wall, the number of DRESORs, the geometry of the furnace, and the camera coordinates.

[0104] During the implementation of the furnace temperature field monitoring unit, in order to ensure that the first temperature measuring element 211 receives unsaturated thermal radiation signals, a radiation temperature imaging model based on the normalization processing of the above-mentioned radiation intensity imaging matrix is ​​adopted, as shown in equation (2): A1 s T g +A2 s T w =A s T=T CCD

[0105] Among them, A1 s A2 s A sThe radiation temperature imaging matrix is ​​calculated by dividing each number in matrices A1, A2, and A by the sum of all numbers in the row containing that number; T CCD The fourth power matrix of the combustion temperature image obtained by the first temperature sensing element can be calculated using the colorimetric method based on the three primary colors of a color CCD.

[0106] Therefore, based on the combustion temperature image detected by the first temperature measuring element, the actual temperature distribution T inside the furnace can be solved by the inversion algorithm using equation (2).

[0107] In one embodiment, see Figure 2 A first temperature measuring element 211 is installed in both the horizontal and vertical directions of the furnace chamber 001.

[0108] Furthermore, the two first temperature measuring elements 211 arranged horizontally in the boiler are respectively installed on the left and right walls of the furnace 001 of the four-corner tangential ammonia-coal co-fired boiler, and are both located 8m above the burner group 005 of the ammonia-coal co-fired boiler in the height direction. Furthermore, the direction of the first temperature measuring element in the horizontal direction is at a certain angle to the boiler axis, with a horizontal field of view of 55° and a vertical field of view of 45°. The two elements are staggered, and the projected cross-sectional dimensions of the horizontal field of view that can be covered are 15717m × 11790m (width × depth).

[0109] Furthermore, the two first temperature measuring elements 211 arranged vertically in the boiler are located at two observation holes along the height direction on the front wall of the furnace 001 of the four-corner tangential ammonia-coal co-fired boiler. The height direction ensures that the vertical field of view of the two first temperature measuring elements can cover the entire burner area of ​​the furnace. The direction of the first temperature measuring elements in the vertical direction is at a certain angle to the boiler axis, with a horizontal field of view of 80° and a vertical field of view of 55°. The longitudinal field of view projection cross-section size that can be covered is 11790m × 14628 (depth × height).

[0110] In this embodiment, the second temperature measuring element 212 is arranged at the furnace outlet to measure the flue gas temperature at the furnace outlet and provide feedback on changes in the heat absorption distribution of the furnace. When the furnace outlet temperature rises, it indicates that the radiative heat absorption of the furnace has decreased; when the flue gas temperature at the upper furnace outlet decreases, it indicates that the radiative heat absorption of the furnace has increased.

[0111] Based on the combustion characteristics of ammonia (ammonia has a lower adiabatic flame temperature, and ammonia combustion competes with pulverized coal for oxygen, causing delayed pulverized coal ignition) and the characteristics of combustion products (complete combustion produces N2 and H2O, with only gaseous radiation and no carbon soot or fly ash radiation), the furnace flame center temperature may decrease or the furnace flame center may shift upwards, leading to changes in the heat flow distribution within the furnace and affecting boiler steam parameter regulation. By combining the three-dimensional furnace temperature field measurement and furnace outlet flue gas temperature measurement in this embodiment, changes in the furnace temperature field and furnace outlet flue gas temperature during ammonia-coal dual-fuel blending combustion can be monitored in real time. This allows for the determination of changes in the heat flow distribution within the furnace during ammonia-coal dual-fuel blending combustion, enabling corresponding adjustments to the boiler's steam-water parameters on the boiler side and the combustion parameters on the furnace side, ensuring boiler combustion stability during the ammonia-coal dual-fuel blending process.

[0112] In an embodiment of the present invention, see Figure 1 The monitoring module 200 further includes:

[0113] Steam parameter monitoring unit 250 is used to monitor the main steam parameter value and reheat steam parameter value of the boiler during the dual-fuel co-firing of ammonia and coal.

[0114] The desuperheating water monitoring unit 260 is used to monitor the desuperheating water volume of the main steam and reheat steam in the boiler during the ammonia-coal dual-fuel co-firing process.

[0115] Fuel quantity monitoring unit 270: used to monitor the boiler coal feed rate and ammonia consumption during the co-firing of ammonia and coal;

[0116] The air volume monitoring unit 280 is used to monitor the total air volume and burnout air volume in the dual-fuel combustion of ammonia and coal, thereby monitoring the total excess air coefficient value and the excess air coefficient value of the main combustion zone of the boiler.

[0117] In this embodiment, the central control module generates an adjustment strategy based on the real-time monitored values ​​of boiler furnace temperature field, furnace outlet flue gas temperature, furnace outlet NOx concentration, unburned NH3 concentration, total boiler fuel and air volume, total boiler excess air coefficient, and excess air coefficient of the boiler main combustion zone.

[0118] In this embodiment, the central control module 100 includes a control strategy generation unit, an adjustment strategy generation unit, and a control strategy adjustment unit;

[0119] The control strategy generation unit is used to generate boiler operating parameters during the ammonia-coal dual-fuel blending process based on the boiler load and ammonia blending ratio requirements when blending ammonia and coal.

[0120] The adjustment strategy generation unit compares the boiler furnace temperature field, furnace outlet flue gas temperature, and furnace outlet product NOx concentration and unburned NH3 concentration values ​​measured in real time by the monitoring module with the set target values ​​for the boiler furnace temperature field, furnace outlet flue gas temperature, and furnace outlet product NOx concentration and unburned NH3 concentration, obtains the deviation results, calculates the required combustion reaction conditions based on the deviation results, and generates a boiler operating parameter adjustment strategy based on the calculated combustion reaction conditions.

[0121] The control strategy adjustment unit is used to update the control strategy according to the adjustment strategy generated by the adjustment strategy generation unit, so as to obtain a new control strategy.

[0122] The control strategy generated by the control strategy generation unit is based on the original combustion optimization of coal-fired boilers, and focuses on realizing the automatic balance control of coal and ammonia quantities during the ammonia-coal dual-fuel blending process. The control strategy includes adjustment methods and control parameters corresponding to different loads and different ammonia-coal blending ratios.

[0123] The strategy generation unit optimizes the total excess air coefficient and local excess air coefficient (main combustion zone) based on the NOx and unburned NH3 products at the furnace outlet during the co-firing of ammonia and coal.

[0124] The main adjustment measures for fuel balance are based on the boiler coordination control system and the coal feed control system, and are implemented as follows: A set ammonia blending ratio is established. This set ammonia blending ratio is multiplied by the fuel setpoint signal output by the boiler main controller to generate an ammonia feed command under the set ammonia blending ratio. The ammonia feed command is then corrected using the furnace outlet product and the concentration of unburned NH3. The corrected ammonia feed command serves as the ammonia feed setpoint. This ammonia feed setpoint is then converted according to its calorific value to form an equivalent coal feed command. For different loads and ammonia blending ratios, the fuel feed setpoint signal from the boiler main controller is logically subtracted from the equivalent coal feed command to generate a new coal feed setpoint. This new coal feed setpoint is then entered into the coal feed control system to replace the original coal feed setpoint. In this way, during the ammonia-coal dual-fuel blending process, the coal feed rate automatically decreases as the ammonia blending ratio increases, achieving fuel balance.

[0125] Secondly, the optimization measures for the excess air coefficient are based on the boiler air supply control system and the graded air distribution control system, specifically described as follows: Based on the real-time NOx concentration and unburned NH3 concentration of the furnace outlet products, and comparing them with the target values ​​of the NOx / O2 concentration and unburned NH3 concentration of the furnace outlet products, the furnace outlet product adjustment signal value is calculated. The corresponding combustion reaction adjustment conditions are then calculated. Based on these calculated combustion reaction adjustment conditions, the boiler air supply setpoint is adjusted. This setpoint can also undergo cross-limiting processing of the total fuel quantity to obtain a new air supply setpoint. This new setpoint enters the air supply control system and replaces the original setpoint, thereby adjusting the overall excess air coefficient of the boiler (generally greater than 1.1). By adjusting the secondary air opening and burnout damper opening in the main combustion zone, the local excess air coefficient in the ammonia-coal co-firing main combustion zone is adjusted (generally less than 0.8), ensuring the main combustion zone is in a lower reducing atmosphere and reducing the generation of fuel-type NOx in the ammonia-coal dual-fuel blend.

[0126] In an embodiment of the present invention, the central control module further includes a user interface for inputting the target values ​​of the ammonia blending ratio, main steam pressure, furnace outlet flue gas temperature, and furnace outlet product NOx / unburned NH3 concentration.

[0127] In an embodiment of the present invention, the alarm module 400 includes an audible and visual alarm and a vibrator. The audible and visual alarm and the vibrator are electrically connected to the central control unit 100. When the ammonia escape concentration value at the furnace outlet exceeds the alarm threshold, the central control unit 100 outputs an electrical signal to the audible and visual alarm and the vibrator to activate them and issue an audible and visual alarm and a vibration alarm.

[0128] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0129] The parts of this invention not described in detail are well-known in the art. The above embodiments are provided merely for the purpose of describing the invention and are not intended to limit the scope of the invention. The scope of the invention is defined by the appended claims. All equivalent substitutions and modifications made without departing from the spirit and principles of the invention should be covered within the scope of the invention.

Claims

1. A method of ammonia-coal dual fuel blended boiler combustion control, the method comprising: The method comprises the following steps: ​ S1: generating boiler operation parameters in the ammonia-coal dual fuel blending process according to the boiler load and ammonia blending ratio requirements during ammonia-coal dual fuel blending; the boiler operation parameters include ammonia supply set value, coal supply set value, and excess air coefficient; S2: monitoring the concentration C of NOx at the furnace outlet in real time _NOx and the concentration C of unburned NH3 _NH3 , dynamically correcting the ammonia blending ratio according to the concentration deviation; generating a new ammonia supply setting value and a new coal supply setting value according to the corrected ammonia blending ratio; S3: controlling the excess air coefficient within a preset range; S4: real-time monitoring of the furnace temperature field and the flue gas temperature at the furnace outlet, and correcting the ammonia blending ratio k0 using the furnace temperature field and the flue gas temperature at the furnace outlet; The step S1 specifically comprises the following steps: S11: set an initial ammonia blending ratio k0, which is determined according to a boiler fuel heat value ratio, and a calculation formula is k0=(m n ×LHV n ) / (m n ×LHV n +m m ×LHV m ), wherein m n is an ammonia fuel mass flow, m m is a coal fuel mass flow, LHV n is a low heat value of the ammonia fuel, and LHV m is a low heat value of the coal fuel; S12: The boiler master controller generates a fuel quantity set value F based on the load command and the steam pressure deviation total = k0 x F NH3 = k0 x F total ; S13: Set the ammonia supply amount set value F NH3 The equivalent converted coal amount command F is formed after conversion according to the calorific value coal-eq =F NH3 × (LHV n / LHV m ); S14: Calculate the coal feed set value F coal = F total - F coal-eq ; The correction of the ammonia blending ratio in step S2 is specifically: When C _NOx > C goal_NOx , the ammonia doping ratio is increased according to the formula k1=k0x[1+0.05x(C _NOx -C goal_NOx ) / 10], with the correction coefficient ranging from 1.05 to 1.

15. When the unburnt NH3 concentration C _NH3 > C goal_ NH3 , the ammonia doping ratio is reduced according to the formula k2=k0x[1-0.03x(C _NH3 - C goal_ NH3 ) / 10], with a correction factor ranging from 0.85 to 0.

95. Specifically, step S3 comprises the following steps: S31: Real-time monitoring of the NOx concentration C at the furnace outlet _NOx and the unburned NH3 concentration C _NH3 adjusting the boiler air supply according to the concentration deviation; S32: controlling the excess air coefficient in the preset range by the staged air distribution control according to the adjusted air supply amount; wherein the control of the excess air coefficient in the preset range comprises control of the total excess air coefficient α of the boiler total >1.1; and control of the local excess air coefficient α of the main combustion zone of the ammonia-coal mixed combustion local <0.8, and the staged air distribution mode comprises adjustment of the air supply amount of the secondary air door of the main combustion zone and the air supply amount of the burnout zone.

2. The ammonia-coal dual fuel blended boiler combustion control method of claim 1, wherein: Step S32 specifically adjusts as follows: When C _NOx When the concentration exceeds the target value C goal_NOx of the product NOx concentration at the furnace outlet, the secondary air volume in the main combustion zone is reduced to 40-50% of the total air volume, and the SOFA damper opening in the burnout zone is increased to 70-80%. When the unburnt NH3 concentration C _NH3 exceeds the unburnt NH3 concentration target value C goal_ NH3 the main combustion zone oxygen concentration is raised to 23-25%.

3. The ammonia-coal dual fuel blended boiler combustion control method of claim 1, wherein: Step S4 is specifically: when the average value of the temperature gradient deviation of the four corners of the furnace and / or the average value of the flue gas temperature deviation at the furnace outlet ΔT is greater than 50℃ for 30 consecutive minutes, the ammonia blending ratio correction is triggered according to the formula k3=k0×(1-0.1×ΔT / 50), and the correction coefficient ranges from 0.9 to 1.

1.

4. A dual fuel ammonia-coal blended boiler combustion control system, characterized by, The control system is used to execute the ammonia-coal dual fuel blending boiler combustion control method of any one of claims 1 to 3, and the control system comprises: a central control module, a monitoring module, an execution module, and an alarm module; the central control module is electrically connected or communicatively connected with the monitoring module, the execution module, and the alarm module; the central control module is used to generate a corresponding control strategy according to the boiler load and ammonia blending ratio requirements during ammonia-coal dual fuel blending, to adjust the control strategy according to the information of the monitoring module to generate a new control strategy, and to send the new control strategy to the execution module; the central control module comprises a fuel quantity calculation unit and an air quantity distribution unit, the fuel quantity calculation unit is used to execute the control method of any one of steps S1-S4, and the air quantity distribution unit is connected with an air distribution system to execute the air distribution control strategy of step S3; the execution module is used to adjust the boiler operation parameters in the ammonia-coal dual fuel blending process according to the received control strategy; the execution module comprises an ammonia adjusting valve, a coal feeder speed executor, an air supply quantity regulator, a secondary air door, and a SOFA air door executor; the monitoring module is used to real-time monitor the NOx concentration and unburned NH3 concentration at the furnace outlet, and the three-dimensional temperature field of the furnace and the flue gas temperature at the furnace outlet during the ammonia-coal dual fuel blending combustion process; the alarm module is used to perform audible and visual or vibration alarm when the ammonia escape value at the furnace outlet exceeds a threshold value.

5. The ammonia-coal dual fuel blended boiler combustion control system in accordance with claim 4, wherein, The monitoring module comprises a furnace outlet NOx concentration monitoring unit and a furnace outlet unburned NH3 concentration monitoring unit, a furnace temperature field monitoring unit, and a furnace outlet flue gas temperature monitoring unit; the furnace outlet NOx concentration monitoring unit and the furnace outlet unburned NH3 concentration monitoring unit comprise an online flue gas analyzer and an ammonia escape laser detector installed at the economizer outlet flue; the online flue gas analyzer is used to monitor the NOx concentration at the furnace outlet, and the ammonia escape laser detector is used to monitor the unburned NH3 concentration at the furnace outlet; the furnace temperature field monitoring unit comprises a first temperature measuring element and a data processing module; the data processing module obtains the three-dimensional temperature field of the furnace according to the measurement results of the first temperature measuring element. The furnace outlet flue gas temperature monitoring unit measures the flue gas temperature at the furnace outlet by a second temperature measuring element installed at the furnace outlet.

6. The ammonia-coal dual fuel blended boiler combustion control system in accordance with claim 5, wherein, The first temperature measuring element is an infrared CCD camera, and the second temperature measuring element is an infrared pyrometer.

7. The ammonia-coal dual fuel blended boiler combustion control system in accordance with claim 5, wherein, The data processing module comprises a temperature field algorithm server, a PLC controller, a communication link, a communication network and a power module. The first temperature measuring element transmits the measured data to the temperature field algorithm server through an optical fiber, the temperature field algorithm server and the PLC controller are connected through a communication network and transmit data based on a TCP / IP protocol, and the PLC controller transmits the three-dimensional temperature field data of the furnace to the central control module.

8. The ammonia-coal dual fuel blended boiler combustion control system in accordance with claim 5, wherein, The first temperature measuring element is arranged in the horizontal and vertical directions of the furnace.

9. The ammonia-coal dual fuel blended boiler combustion control system in accordance with claim 8, wherein, Two first temperature measuring elements are arranged in the horizontal direction of the furnace, the two first temperature measuring elements are arranged in opposite positions, and the two first temperature measuring elements are arranged above the burner of the ammonia-coal mixed combustion boiler. And / or, two first temperature measuring elements are arranged in the vertical direction of the furnace, and the two first temperature measuring elements are arranged on the front wall of the burner of the ammonia-coal mixed combustion boiler and in the height direction.

10. The ammonia-coal dual fuel blended boiler combustion control system of claim 9, wherein, The horizontal and vertical field angles of the two first temperature measuring elements arranged in the horizontal direction are both at a certain angle with the axis of the boiler; the horizontal and vertical field angles of the two first temperature measuring elements arranged in the height direction are both at a certain angle with the axis of the boiler.

11. The ammonia-coal dual fuel blended boiler combustion control system of claim 10, wherein, The angle between the horizontal field angle of the two first temperature measuring elements arranged in the horizontal direction and the axis of the boiler is 45°, and the angle between the vertical field angle of the two first temperature measuring elements arranged in the horizontal direction and the axis of the boiler is 45°. The angle between the horizontal field angle of the two first temperature measuring elements arranged in the height direction and the axis of the boiler is 80°, and the angle between the vertical field angle of the two first temperature measuring elements arranged in the height direction and the axis of the boiler is 55°. The field angle ensures that the furnace cross-section coverage is greater than 95%.

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