A tangentially fired boiler unit flexibility peak shaving vertical water wall temperature control method

Abstract

This invention belongs to the field of thermal power unit safety control technology, and particularly relates to a method for controlling the temperature of the vertical water-cooled wall in a tangentially circular boiler unit for flexible peak shaving. This invention is implemented in a DCS (Distributed Control System) and includes: 1) Flexibility modification of the unit's combustion system, with independent control of the burner outlet primary air flow rate in the DCS to improve the unit's low-load combustion stability; 2) During flexible peak shaving, the DCS control logic adds a boiler vertical water-cooled wall temperature monitoring module to determine if there is a local overheating trend in the boiler's vertical water-cooled wall; 3) Based on the independent control of the corresponding burner outlet primary air flow rate in the previous step, the secondary air flow rate of the boiler's air supply system is controlled, and the coal feed rate and feedwater flow rate of the corresponding pulverizing system are independently controlled; 4) The temperature of the vertical water-cooled wall of the tangentially circular combustion boiler is controlled based on the previous step. This invention allows for precise control in advance, avoiding the impact of local temperature changes in the water-cooled wall on the entire control system, ensuring safe equipment operation, and reducing workload.

Description

Technical Field

[0001] This invention belongs to the field of safety control technology for thermal power units, and particularly relates to a method for controlling the temperature of the vertical water-cooled wall in a tangential boiler unit for flexible peak shaving. Background Technology

[0002] At present, the installed capacity of new energy sources, mainly wind power, solar power, and hydropower, is increasing year by year. In order to increase the absorption capacity of new energy power, traditional thermal power generating units undertake the main peak shaving and frequency regulation work. In some areas, thermal power generating units often operate under deep peak shaving conditions. This frequent and wide-load peak shaving operation puts higher demands on the equipment status and regulation system of thermal power generating units.

[0003] Many factors limit the peak-shaving range of thermal power generating units, among which the peak-shaving capacity of boiler equipment is the main constraint on improving the deep peak-shaving capacity of most thermal power generating units. When boiler equipment deviates from the recommended operating load, both hydrodynamic and combustion states will experience adverse changes. Especially when the unit is operating at low load, many tangential boilers will experience overheating of the vertical water-cooled walls. Overheating of the boiler's vertical water-cooled walls greatly threatens the safe and stable operation of the unit and also indirectly affects the security of the regional power grid.

[0004] Ensuring the safe operation of boiler equipment in thermal power generating units while improving their peak-shaving capacity has become an urgent problem to be solved. In recent years, many domestic engineers and scholars have researched and discussed issues related to boiler metal wall overheating. For example, the Chinese patent application number 201910366592.1, "A Boiler Operation Control Method for Reducing the Influence of High-Temperature Corrosion of Water-Cooled Walls," proposes a control method that adjusts the oxygen content at the economizer outlet and the operating mode of the coal mill. The paper "Numerical Simulation and Combustion Optimization of Overheating of Water-Cooled Walls in a 300MW Wall-Type Tangential Boiler" proposes corresponding burner modification and optimization schemes through field tests and numerical simulations.

[0005] The above literature addresses the problem of boiler water-cooled wall overheating from the perspective of adjusting the unit's operating status and modifying the burner, but does not propose a control strategy for boiler vertical water-cooled wall overheating. Summary of the Invention

[0006] To address the shortcomings of the existing technology, this invention provides a method for controlling the temperature of the vertical water-cooled wall in a tangential combustion boiler unit to facilitate flexible peak shaving. The aim is to solve the safety problem of overheating that frequently occurs during the operation of the vertical water-cooled wall in existing tangential combustion boilers.

[0007] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows:

[0008] A method for controlling the temperature of the vertical water-cooled wall in a tangentially circular boiler unit for flexible peak shaving is implemented in a DCS distributed control system and includes the following steps:

[0009] Step 1: The unit's combustion system is modified for flexibility. The primary air flow rate at the burner outlet can be independently controlled by the DCS. The flexibility modification of the burner can improve the unit's combustion stability at low load.

[0010] Step 2: During the unit's flexible peak shaving process, the DCS control logic adds a boiler vertical water-cooled wall temperature monitoring module to determine if there is a local overheating trend in the boiler vertical water-cooled wall.

[0011] Step 3: Based on the local overheating trend of the vertical water-cooled wall of the boiler, independently control the primary air flow rate at the outlet of the corresponding burner, control the secondary air flow rate of the boiler air supply system, independently control the coal feed rate of the corresponding pulverizing system, and control the water feed rate.

[0012] Step 4: Control the temperature of the vertical water-cooled wall of the tangential combustion boiler by independently controlling the primary air flow and secondary air flow at the outlet of the corresponding burner, controlling the coal feed rate of the corresponding pulverizing system, and controlling the water feed rate.

[0013] Furthermore, the determination that the vertical water-cooled wall of the boiler has a local overheating trend includes:

[0014] (1) The highest wall temperature reaches the alarm value;

[0015] Its highest value The alarm value is the maximum value obtained by the high value selection module after the actual temperature of all temperature measuring points in the local area of ​​the vertical water-cooled wall to be measured is the temperature alarm value specified in the boiler manufacturer's manual.

[0016] (2) The rate of change of the highest wall temperature exceeds the set threshold A;

[0017] The rate of change of the maximum wall temperature is defined as the change in temperature per minute of the maximum temperature of the vertical water-cooled wall. The rate of change threshold is calculated using the following formula:

[0018] (1);

[0019] In the formula, The rate of change threshold; This is the temperature alarm value; This is the highest temperature value; To adjust the system's inertial time; to adjust the system's inertial time Determined by the following formula:

[0020] (2);

[0021] In the formula, To adjust the timing of the system's step response; This is the moment when the highest temperature value in the regulated area begins to occur, and the positive change in the regulating effect begins.

[0022] (3) The expected wall temperature exceeds the set threshold B, and its expected wall temperature is defined as:

[0023] a. Calculate the sum of the first and second derivatives of the highest temperature of the vertical water-cooled wall, and denote this value as C;

[0024] b. Then calculate the product of the value C and the unit's flexibility peak-shaving coefficient, and denote this value as D;

[0025] c. Finally, calculate the sum of the maximum temperature of the vertical water-cooled wall and the value D.

[0026] Furthermore, the primary air flow rate at the burner outlet is independently controlled by the DCS. The burner body has an adjustment mechanism or the primary air-coal pulverizer outlet pipe has an adjustment mechanism. This adjustment mechanism is remotely controlled by the DCS to adjust the primary air flow rate at the burner outlet.

[0027] Furthermore, the boiler vertical water-cooled wall temperature monitoring module includes: a high-value selection module, a differential module, a rate of change calculation module, a threshold judgment module, and a piecewise linear function module. These modules perform high-value selection calculation, rate of change calculation, first-order differential calculation, second-order differential calculation, and threshold judgment on the vertical water-cooled wall temperature to determine its level, magnitude, and rate of change. They also perform piecewise linear function calculations on the unit's flexible peak-shaving load to form the unit's flexible peak-shaving coefficient.

[0028] Furthermore, the independent control of the corresponding burner is based on the pulverizing system. By controlling the adjustment mechanism of the corresponding burner, the primary air flow rate at the burner outlet is changed, the flame shape in the furnace is changed, and the radiative heat exchange of the corresponding vertical water-cooled wall is adjusted, thereby controlling the temperature of the vertical water-cooled wall. The burners in the same pulverizing system control the corresponding flame shape.

[0029] Furthermore, the independent control of the primary air flow rate at the outlet of the corresponding burner also includes the determination of the corresponding burner:

[0030] The vertical water-cooled wall of the boiler has a local overheating tendency. The burners facing this area and the lower burners facing this area are both burners that regulate the overheating tendency of the vertical water-cooled wall in this area.

[0031] The burner facing this area is the second burner in this layer, located against the direction of the flame tangency.

[0032] The lower burner facing this area is the second burner below, located in the opposite direction of the flame tangential circle.

[0033] Furthermore, the determination of the primary air flow limit for the independent control corresponding to the burner outlet is that the adjustment limit for the primary air flow at the burner outlet is the difference between the primary air flow to be adjusted and the median of the primary air flow at the outlet of other burners in the same pulverizing system is less than |±20%| of the primary air flow of this pulverizing system.

[0034] The formula for calculating the difference is as follows:

[0035] (3);

[0036] In the formula, This represents the median primary air flow rate at the outlet of other burners in the pulverizing system corresponding to this burner. This corresponds to the primary air flow rate at the burner outlet; This represents the difference between the primary air flow rate at the outlet of the corresponding burner and the median primary air flow rate at the outlet of other burners in the pulverizing system.

[0037] Furthermore, based on the local overheating trend of the vertical water-cooled wall of the boiler, the secondary air flow of the boiler air supply system is controlled: when the vertical water-cooled wall has a local overheating trend, the secondary air flow of the boiler air supply system is increased to adjust the flame shape at the burner outlet and reduce the scouring of the flame on the vertical water-cooled wall.

[0038] It also includes a limit of 3% of the actual total air volume to be increased secondary air flow when there is a local overheating trend in the vertical water-cooled wall of the boiler.

[0039] Furthermore, based on the local overheating trend of the vertical water-cooled wall of the boiler, the coal feed rate of the corresponding pulverizing system is independently controlled: when there is a local overheating trend in the vertical water-cooled wall, the coal feed rate of the pulverizing system at the horizontal position of the overheating area and the pulverizing system adjacent to the horizontal position below the overheating area is reduced. When the corresponding pulverizing system reaches the lower limit of the coal feed rate, it is prohibited to reduce the coal feed rate of the corresponding pulverizing system.

[0040] Furthermore, based on the local overheating trend of the boiler's vertical water-cooled wall, the feedwater flow rate is controlled: when the expected wall temperature exceeds the set threshold B, the boiler feedwater system is controlled to increase the feedwater flow rate, adjust the heat absorption of the boiler's vertical water-cooled wall in advance, slow down the wall temperature increase trend, and, in conjunction with other adjustment methods, ensure that the vertical water-cooled wall temperature is controlled within a reasonable range during the unit's flexible peak shaving process.

[0041] The present invention has the following beneficial effects and advantages:

[0042] This invention uses the tendency for localized overheating in the vertical water-cooled wall of the boiler as the trigger condition for the overheating control algorithm to participate in the control. By incorporating the wall temperature change rate and expected wall temperature value into the overheating trend judgment condition, it is possible to predict in advance that the vertical water-cooled wall of the boiler will overheat and to implement control before the overheating occurs.

[0043] This invention controls the overheating trend of the vertical water-cooled wall of the boiler by individually controlling the coal feed rate of the corresponding pulverizing system, the primary air flow rate at the outlet of the corresponding burner, the secondary air flow rate of the air supply system, and the water flow rate. This precise approach reduces the impact of local temperature changes in the water-cooled wall on the entire control system.

[0044] This invention reduces the overheating of the vertical water-cooled wall in a tangential combustion boiler by comprehensively controlling the coal feed rate of the pulverizing system, the primary air volume at the burner outlet, the secondary air volume of the air supply system, and the water flow rate, thereby ensuring the safe operation of the boiler's vertical water-cooled wall.

[0045] By implementing the above control methods, this invention automatically monitors the temperature of the vertical water-cooled wall of a tangential combustion boiler, reducing the amount of manual intervention required by operators, lowering the probability of misoperation, and reducing the workload of operators. Attached Figure Description

[0046] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0047] Figure 1 This is a flowchart of a method for controlling the temperature of a vertical water-cooled wall in a tangential circular boiler unit to achieve flexible peak shaving according to the present invention;

[0048] Figure 2 This is a control algorithm diagram for a flexible peak-shaving vertical water-cooled wall temperature control method for a tangential boiler unit according to the present invention;

[0049] Figure 3 This is a control algorithm diagram for another flexible peak-shaving vertical water-cooled wall temperature control method for tangential circular boiler units according to the present invention;

[0050] Figure 4 This is a schematic diagram of the burner arrangement in the tangential combustion boiler of the present invention.

[0051] In the diagram: Temperature alarm value A algorithm block 1, inertia time algorithm block 2, subtraction A algorithm block 3, division algorithm block 4, high limit monitoring A algorithm block 5, temperature measuring point A algorithm block 6, temperature measuring point B algorithm block 7, temperature measuring point N algorithm block 8, high selection block 9, pure delay A algorithm block 10, temperature alarm value B algorithm block 11, high limit monitoring B algorithm block 12, subtraction B algorithm block 13, OR gate A algorithm block 14, coal feed lower limit analog quantity algorithm block 15, temperature difference setpoint analog quantity setting algorithm block 16, PID regulation control algorithm block 17, analog quantity switching A algorithm block 18. Analog setpoint A algorithm block 19, Analog switching B algorithm block 20, Pulverizing system feedforward control algorithm block 21, Maximum temperature analog algorithm block 22, Temperature alarm value C algorithm block 23, Subtraction C algorithm block 24, Function A algorithm block 25, Temperature change rate threshold analog algorithm block 26, Temperature change rate analog algorithm block 27, Subtraction D algorithm block 28, Function B algorithm block 29, Addition A algorithm block 30, Actual total air volume analog algorithm block 31, Analog setpoint B algorithm block 32, Multiplication A algorithm block 33, High limit algorithm block 34, Analog setpoint C algorithm Block 35, Analog Switching C Algorithm; Block 36, Air Supply System Feedforward Control Algorithm; Block 37, Over-temperature Control Algorithm Participating in Regulation Signal Algorithm; Block 38, NOT Gate Algorithm; Block 39, SR Flip-flop Algorithm; Block 40, Analog Setpoint D Algorithm; Block 41, Analog Switching D Algorithm; Block 42, Pure Delay B Algorithm; Block 43, Pure Delay C Algorithm; Block 44, Subtraction E Algorithm; Block 45, Subtraction F Algorithm; Block 46, High Limit Monitoring C Algorithm; Block 47, High Limit Monitoring D Algorithm; Block 48, OR Gate B Algorithm; Block 49, Subtraction G Algorithm; Block 50, Function C Algorithm; Block 51, Subtraction H Algorithm; Block 52, Function D Algorithm. Block 53, Addition B algorithm block 54, Other burner flow A algorithm block 55, Other burner flow B algorithm block 56, Other burner flow C algorithm block 57, Analog quantity algorithm block for the burner to be controlled, Median algorithm block 58, Subtraction I algorithm block 69, Analog quantity algorithm block for the primary air flow of the corresponding pulverizing system, Analog quantity setpoint E algorithm block 61, Multiplication B algorithm block 62, High limit monitoring E algorithm block 63, Analog quantity switching E algorithm block 64, Analog quantity setpoint F algorithm block 65, Analog quantity switching F algorithm block 66, Analog quantity switching F algorithm block 67, Corresponding burner adjustment feedforward control algorithm 68. Detailed Implementation

[0052] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0053] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0054] The following reference Figures 1-4 The technical solutions of some embodiments of the present invention are described below.

[0055] Example 1

[0056] This invention provides an embodiment of a method for controlling the temperature of the vertical water-cooled wall in a tangential combustion boiler unit to facilitate peak shaving. This invention focuses on the over-temperature control of the vertical water-cooled wall in a tangential combustion boiler, such as... Figure 1 As shown, Figure 1 This is a flowchart of a method for controlling the temperature of a vertical water-cooled wall in a tangential boiler unit to achieve flexible peak shaving according to the present invention.

[0057] This invention is based on the design of a DCS distributed control system. The implementation of the algorithm and the setting of parameters are completed in the DCS distributed control system. The specific implementation process of this invention is described below in conjunction with the DCS distributed control system.

[0058] The present invention specifically includes the following steps:

[0059] The first step is to detect a local overheating trend in the vertical water-cooled wall of the tangential combustion boiler. The overheating trend includes the highest local temperature of the vertical water-cooled wall reaching the alarm value, or the rate of change of the highest local temperature of the vertical water-cooled wall exceeding the set threshold A, or the expected local temperature of the vertical water-cooled wall exceeding the set threshold B.

[0060] The second step is to independently control the primary air flow rate at the outlet of the corresponding burner, the secondary air flow rate of the air supply system, the coal feed rate and water flow rate of the corresponding pulverizing system based on the local overheating trend of the vertical water-cooled wall, when the first step determines that there is a local overheating trend of the vertical water-cooled wall.

[0061] Third, if the local temperature overheating trend is not suppressed after the secondary air volume, coal feed rate and water flow rate of the corresponding pulverizing system are adjusted in the second step, then the primary air flow rate at the corresponding burner outlet is independently controlled.

[0062] The above methods are used to actively control the local temperature of the vertical water-cooled wall of the tangential combustion boiler.

[0063] Example 2

[0064] This invention provides another embodiment, which is a method for controlling the temperature of the vertical water-cooled wall in a tangentially circular boiler unit to facilitate flexible peak shaving. For example... Figure 2 As shown, Figure 2This is the control principle diagram of the present invention. It mainly includes three parts: over-temperature control judgment logic, corresponding pulverizing system control logic, and air supply system control logic.

[0065] The over-temperature control judgment logic includes two parts: temperature change rate judgment and temperature over-temperature judgment. The required algorithm blocks include subtraction algorithm block, division algorithm block, high selection algorithm block, pure delay algorithm block, and high limit monitoring algorithm block.

[0066] The alarm control principle for the rate of change of the highest temperature values ​​in the controlled area is as follows:

[0067] Temperature measurement points on the vertical water-cooled wall of the area to be controlled are selected. Multiple temperature measurement points in the area, including temperature measurement point A algorithm block 6, temperature measurement point B algorithm block 7, and so on up to temperature measurement point N algorithm block 8, are connected to a high-selection block 9 to select the highest value among the temperature measurement points. The output of high-selection block 9 is connected to one input of subtraction algorithm block 13 as the minuend. The output of high-selection block 9 is also connected to pure delay algorithm block 10, with a delay time set to 60 seconds. The output of pure delay algorithm block 10 is connected to the other input of subtraction algorithm block 13 as the subtrahend. This algorithm calculates the actual rate of change of the highest value at all temperature measurement points in the area to be controlled. The output of subtraction algorithm block 13 is connected to one input of high-limit monitoring algorithm block 5 and compared with a temperature change rate threshold.

[0068] The temperature change rate threshold is calculated by connecting the output of the high-limit monitoring A algorithm block 3 to one input as the subtrahend, and connecting the other input of the high-limit monitoring A algorithm block 3 to the temperature alarm value A algorithm block 1 as the minuend. This calculates the difference between the highest temperature value of the area to be controlled and the temperature alarm value of that area. The output of the subtraction A algorithm block 3 is connected to one input of the division algorithm block 4 as the dividend, and the inertial time algorithm block 2 is connected to the other input of the division algorithm block 4 as the divisor. The output of the division algorithm block 4 is the temperature change rate threshold, and its output is connected to one input of the high-limit monitoring A algorithm block 5 as the temperature change rate threshold. The other input of the high-limit monitoring A algorithm block 5 is connected to the subtraction B algorithm block 13 to compare the actual temperature change rate with the high-limit temperature change rate threshold. When the actual temperature change rate reaches or exceeds the temperature change rate threshold, the output of the high-limit monitoring A algorithm block 5 is "1". This indicates that the temperature of the area to be controlled has an over-temperature trend and requires over-temperature control algorithm intervention.

[0069] The temperature over-temperature judgment logic connects the output of temperature alarm value B algorithm block 11 to one end of high limit monitoring B algorithm block 12, and the output of the temperature selection block 9 in the controlled area to the other end of high limit monitoring B algorithm block 12. When the output temperature value of the temperature selection block 9 in the controlled area reaches or exceeds the temperature alarm value, the output of high limit monitoring B algorithm block 12 is "1", indicating that the temperature of the controlled area has an over-temperature trend and needs to be controlled by the over-temperature control algorithm. The output of high limit monitoring A algorithm block 5 and the output of high limit monitoring B algorithm block 12 are connected to the two inputs of OR gate A algorithm block 14, and the output of OR gate A algorithm block 14 serves as the enable signal for the over-temperature control algorithm.

[0070] The feedforward control of the pulverizing system includes a subtraction algorithm block, a PID control algorithm block, an analog switching algorithm block, and an analog setting algorithm block. The maximum temperature value analog algorithm block 22 is connected to one input of the subtraction C algorithm block 24. The temperature alarm value C algorithm block 23 is connected to the other input of the subtraction C algorithm block 24 to calculate the degree to which the temperature exceeds the alarm value. The output of the subtraction C algorithm block 24 is connected to the controlled variable of the PID control algorithm block 17. The setpoint of the PID control algorithm block 17 is connected to the temperature difference setpoint analog setting algorithm block 16 as the setpoint. The output of the PID control algorithm block 17 is connected to the "N" terminal of the analog switching A algorithm block 18. The output of the analog switching A algorithm block 18 is connected to its own "Y" terminal. This ensures that when the enable terminal of the analog switching A algorithm block 18 is "1", the output of this algorithm block remains unchanged. The output of the analog algorithm block 15 corresponding to the lower limit of coal feed in the pulverizing system is connected to the tracking enable terminal of the PID control algorithm block 17, serving as the tracking state trigger signal for the PID control algorithm block 17. The output of the analog algorithm block 15 is also connected to the enable terminal of the analog switching A algorithm block 18. When the coal feed in the corresponding pulverizing system reaches the lower limit, the PID control algorithm block switches to tracking mode, and the output of the analog switching A algorithm block 18 remains unchanged. The output of the analog switching A algorithm block 18 is connected to the "Y" terminal of the analog switching B algorithm block 20. The "N" terminal of the analog switching B algorithm block 20 is connected to the analog setpoint A algorithm block 19. The enable terminal of the analog switching B algorithm block 20 is connected to the output of the OR gate A algorithm block 14. Its function is that when the output of the OR gate A algorithm block 14 is "1", the pulverizing system feedforward control algorithm block 21 is activated. When the output of the OR gate A algorithm block 14 is "0", the pulverizing system feedforward control algorithm block 21 is inactive, and its output is "0".

[0071] The feedforward control of the air supply system comprises an analog quantity switching algorithm block, an analog quantity high limit algorithm block, an addition algorithm block, a function algorithm block, a subtraction algorithm block, and an analog quantity setpoint algorithm block. It controls the air supply system based on both temperature exceeding limits and temperature change rate exceeding limits. The output of the highest temperature analog algorithm block 22 is connected to one input of the subtraction C algorithm block 24 as the minuend. The output of the temperature alarm value C algorithm block 23 is connected to the other input of the subtraction C algorithm block 24 as the subtrahend. The output of the subtraction C algorithm block 24 is connected to the input of the function A algorithm block 25. The output of the function A algorithm block 25 is connected to one input of the addition A algorithm block 30. The output of the temperature change rate threshold analog algorithm block 26 is connected to one input of the subtraction D algorithm block 28 as the minuend. The output of the temperature change rate analog algorithm block 27 is connected to the other input of the subtraction D algorithm block 28 as the subtrahend. The output of the subtraction D algorithm block 28 is connected to the input of the function B algorithm block 29. The output of the function B algorithm block 29 is connected to the other input of the addition A algorithm block 30. The output of the addition A algorithm block 30 is connected to one input of the high limit algorithm block 34; the output of the actual total air volume analog quantity algorithm block 31 is connected to one input of the multiplication A algorithm block 33; the output of the analog quantity setpoint B algorithm block 32 is connected to the other input of the multiplication A algorithm block 33; and the output of the multiplication A algorithm block 33 is connected to the other input of the high limit algorithm block 34, thus completing the high limit judgment. When the output of the addition A algorithm block 30 exceeds the output value of the multiplication A algorithm block 33, the output value of the high limit algorithm block 34 is the output value of the multiplication A algorithm block 33. The output of the high limit algorithm block 34 is connected to the "Y" terminal of the analog quantity switching C algorithm block 36; the "N" terminal of the analog quantity switching C algorithm block 36 is connected to the output of the analog quantity setpoint C algorithm block 35; and the enable terminal of the analog quantity switching C algorithm block 36 is connected to the output of the OR gate A algorithm block 14. When the output of the OR gate A algorithm block 14 is "1", the air supply system feedforward control algorithm block 37 is activated. When the output of OR gate A algorithm block 14 is “0”, the feedforward control algorithm block 37 of the air supply system does not function and outputs “0”.

[0072] Example 3

[0073] This invention provides another embodiment, which is a method for controlling the temperature of the vertical water-cooled wall in a tangentially circular boiler unit to facilitate flexible peak shaving. For example... Figure 3 As shown, Figure 3 This is a control algorithm diagram for another flexible peak-shaving vertical water-cooled wall temperature control method for tangential boiler units according to the present invention.

[0074] Figure 3 It mainly includes four parts: dynamic judgment of temperature change rate, dynamic judgment of maximum temperature value, setting of delay time of pure delay algorithm block, and corresponding burner feedforward control logic.

[0075] Figure 3It is an independent adjustment and control system for the burner, including pure delay algorithm blocks, subtraction algorithm blocks, high-limit monitoring algorithm blocks, SR trigger algorithm blocks, NOT gate algorithm blocks, analog setpoint algorithm blocks, analog switching algorithm blocks, median algorithm blocks, function algorithm blocks, and OR gate algorithm blocks. The specific implementation is as follows:

[0076] The first part uses the dynamic change in the rate of temperature change to determine the control effect of the second step. The output of the analog algorithm block 27 for the rate of temperature change is connected to the input of the pure delay B algorithm block 43. The output of the pure delay B algorithm block 43 is connected to one input of the subtraction E algorithm block 45 as the minuend. The other input of the subtraction E algorithm block 45 is connected to the output of the analog algorithm block 27 for the rate of temperature change. The output of the subtraction E algorithm block 45 is connected to the input of the high limit monitoring C algorithm block 47. The output of the high limit monitoring C algorithm block 47 is connected to one input of the OR gate B algorithm block 49. The function of this part is to determine whether the overheating trend of the vertical water-cooled wall temperature in the controlled area has improved after the second step of the pulverizing system control and the air supply system control takes effect by changing the rate of temperature change.

[0077] The second part uses the dynamic change of the maximum temperature value to judge the control effect of the second step. The output of the analog algorithm block 22 for the maximum temperature value is connected to the input of the pure delay C algorithm block 44. The output of the pure delay C algorithm block 44 is connected to one input of the subtraction F algorithm block 46 as the minuend. The other input of the subtraction F algorithm block 46 is connected to the output of the analog algorithm block 22 for the maximum temperature value as the subtrahend. The output of the subtraction F algorithm block 46 is connected to the input of the high limit monitoring D algorithm block 48. The output of the high limit monitoring D algorithm block 48 is connected to one input of the OR gate B algorithm block 49. The function of this part is to determine whether the over-temperature trend of the vertical water-cooled wall in the controlled area has improved after the second step of the pulverizing system control and the air supply system control takes effect by using the change of the maximum temperature value.

[0078] The third part concerns the delay time settings of the pure delay algorithm blocks. The delay time settings for pure delay B algorithm block 43 and pure delay C algorithm block 44 are derived from the output value of analog quantity switching D algorithm block 42. The "Y" terminal of analog quantity switching D algorithm block 42 is connected to inertial time algorithm block 2, and the "N" terminal of analog quantity switching D algorithm block 42 is connected to the output terminal of analog quantity setpoint D algorithm block 41, which is set to "0". The enable terminal of analog quantity switching D algorithm block 42 is connected to the set output terminal of SR trigger algorithm block 40, and the set input terminal of SR trigger algorithm block 40 is connected to the over-temperature control algorithm participating in the adjustment signal algorithm block 38. The reset input terminal of SR trigger algorithm block 40 is connected to the over-temperature control algorithm participating in the adjustment signal algorithm block 38 via NOT gate algorithm block 39. This control logic sets the SR trigger when the over-temperature control algorithm participates in the adjustment. The delay time of the pure delay B algorithm block 43 and the pure delay C algorithm block 44 is the inertia time of the system. When the signal for the over-temperature control algorithm to participate in the adjustment disappears, the delay time of the pure delay B algorithm block 43 and the pure delay C algorithm block 44 is "0".

[0079] The fourth part corresponds to the burner feedforward control. The output of the maximum temperature analog algorithm block 22 is connected to one input of the subtraction G algorithm block 50 as the minuend. The output of the temperature alarm value C algorithm block 23 is connected to the other input of the subtraction G algorithm block 50 as the subtrahend. The output of the subtraction G algorithm block 50 is connected to the input of the function C algorithm block 51. The output of the function C algorithm block 51 is connected to one input of the addition B algorithm block 54. The other input of the addition B algorithm block 54 is connected to the output of the function D algorithm block 53. The input of the function D algorithm block 53 is connected to the output of the subtraction H algorithm block 52. One input of the subtraction H algorithm block 52 is connected to the temperature change rate threshold analog algorithm block 26 as the minuend. The other input of the subtraction H algorithm block 52 is connected to the temperature change rate analog algorithm block 27 as the subtrahend. This part determines how much feedforward to increase the primary airflow at the burner outlet based on the deviation between the maximum temperature value and the temperature alarm value, and the deviation between the temperature change rate and the temperature change rate threshold.

[0080] Part 5, corresponding to the limitations of burner feedforward control. The outputs of other burner flow A algorithm block 55, other burner flow B algorithm block 56, and other burner flow C algorithm block 57 are connected to the input of median algorithm block 59. The output of median algorithm block 59 is connected to one input of subtraction I algorithm block 60 as the minuend. The other input of subtraction I algorithm block 60 is connected to the output of analog quantity algorithm block 58 of the burner to be controlled as the subtrahend. The output of subtraction I algorithm block 60 is connected to one input of high limit monitoring E algorithm block 64. The other input of high limit monitoring E algorithm block 64 is connected to the output of multiplication B algorithm block 63. One input of multiplication B algorithm block 63 is connected to the output of analog quantity setpoint E algorithm block 62. The setpoint of analog quantity setpoint E algorithm block 62 is "20%". The other input of the multiplication B algorithm block 63 is connected to the output of the analog primary air flow algorithm block 61 corresponding to the pulverizing system. The output of the high-limit monitoring E algorithm block 64 is connected to the enable terminal of the analog switching E algorithm block 65. The output of the addition B algorithm block 54 is connected to the "N" terminal of the analog switching E algorithm block 65, and the "Y" terminal of the analog switching E algorithm block 65 is connected to its own output. This part performs the function of comparing the outlet primary air flow of the burner to be controlled with the median of the outlet primary air flow of other burners in the same pulverizing system. When the deviation reaches |±20%|, the burner feedforward control output is maintained.

[0081] The output of analog quantity switching algorithm block 65 (E) is connected to the "Y" terminal of analog quantity switching algorithm block 67 (F). The "N" terminal of analog quantity switching algorithm block 67 (F) is connected to the output of analog quantity setpoint algorithm block 66 (F). The value of analog quantity setpoint algorithm block 66 (F) is set to "0". The enable terminal of analog quantity switching algorithm block 67 (F) is connected to the output of OR gate algorithm block 49 (B). This part completes the activation and deactivation of the corresponding burner regulation feedforward control algorithm 68. When the output of OR gate algorithm block 49 (B) is "1", the corresponding burner regulation feedforward control algorithm 68 is activated; when the output of OR gate algorithm block 49 (B) is "0", the corresponding burner regulation feedforward control algorithm 68 is deactivated.

[0082] Example 4

[0083] This invention provides another embodiment, which is a method for controlling the temperature of the vertical water-cooled wall in a tangentially circular boiler unit for flexible peak shaving, such as... Figure 4 As shown, Figure 4 This is a schematic diagram of the burner arrangement in the tangential combustion boiler of the present invention.

[0084] In a flexible peak-shaving vertical water-cooled wall temperature control method for a tangential boiler unit, the primary air flow rate at the burner outlet is adjusted independently, and the burner to be adjusted is determined. In the diagram, A, B, C, and D represent the four sides of the boiler furnace. a, b, c, and d represent the four burners. For example, when overheating occurs in the vertical water-cooled wall area corresponding to wall A, the primary air flow rate at the outlet of burner b, as well as the primary air flow rate at the outlet of burner b adjacent to the pulverizing system below, are adjusted.

[0085] In the description of this specification, the terms "one embodiment," "some embodiments," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0086] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for controlling the temperature of the vertical water-cooled wall in a tangentially circular boiler unit for flexible peak shaving, characterized by: In a DCS (Distributed Control System), the following steps are performed: Step 1: The unit's combustion system is modified for flexibility. The primary air flow at the burner outlet is independently controlled by the DCS. The flexibility modification of the burner improves the unit's low-load combustion stability. Step 2: During the unit's flexible peak shaving process, the DCS control logic adds a boiler vertical water-cooled wall temperature monitoring module to determine if the boiler vertical water-cooled wall has a local overheating trend, including: (1) the highest wall temperature reaches the alarm value; its highest value The alarm value is the maximum value calculated by the high-value selection module for the actual temperature of all temperature measuring points in the local area of ​​the vertical water-cooled wall to be measured. The alarm value is the temperature alarm value specified in the boiler manufacturer's manual; (2) The rate of change of the highest wall temperature exceeds the set threshold A; the rate of change of the highest wall temperature is defined as the temperature change per minute of the highest temperature of the vertical water-cooled wall. The rate of change threshold is calculated using the following formula: (1); where, The rate of change threshold; This is the temperature alarm value; This is the highest temperature value; To adjust the system's inertial time; to adjust the system's inertial time Determined by the following formula: (2); where, To adjust the timing of the system's step response; The moment when the highest temperature of the regulated area begins to change positively with the regulation effect; (3) When the expected wall temperature exceeds the set threshold B, the expected wall temperature is defined as: a. Calculate the sum of the first and second derivative values ​​of the highest vertical water-cooled wall temperature, and this value is denoted as C; b. Calculate the product of the value C and the unit flexibility peak-shaving coefficient, and this value is denoted as D; c. Finally, calculate the sum of the highest vertical water-cooled wall temperature and the value D. Step 3: Based on the local overheating trend of the vertical water-cooled wall of the boiler, independently control the primary air flow rate at the outlet of the corresponding burner, control the secondary air flow rate of the boiler air supply system, independently control the coal feed rate of the corresponding pulverizing system, and control the water feed rate. Step 4: Control the temperature of the vertical water-cooled wall of the tangential combustion boiler by independently controlling the primary air flow rate and secondary air flow rate of the corresponding burner outlet, controlling the coal feed rate of the corresponding pulverizing system, and controlling the water feed rate.

2. The method for controlling the temperature of the vertical water-cooled wall in a tangential boiler unit for flexible peak shaving according to claim 1, characterized in that: The primary air flow rate at the burner outlet is independently controlled by the DCS. The burner body has an adjustment mechanism or the primary air-coal pulverizer outlet pipeline has an adjustment mechanism. This adjustment mechanism is remotely controlled by the DCS to adjust the primary air flow rate at the burner outlet.

3. The method for controlling the temperature of the vertical water-cooled wall in a tangential boiler unit for flexible peak shaving according to claim 1, characterized in that: The boiler vertical water-cooled wall temperature monitoring module includes: a high-value selection module, a differential module, a rate of change calculation module, a threshold judgment module, and a piecewise linear function module. It performs high-value selection calculation, rate of change calculation, first-order differential calculation, second-order differential calculation, and threshold judgment on the vertical water-cooled wall temperature to determine the temperature level, magnitude, and rate of change of the vertical water-cooled wall. It also performs piecewise linear function calculation on the unit's flexible peak-shaving load to form the unit's flexible peak-shaving coefficient.

4. The method for controlling the temperature of the vertical water-cooled wall in a tangential boiler unit for flexible peak shaving according to claim 1, characterized in that: The independent control of the corresponding burner is based on the pulverizing system. By controlling the adjustment mechanism of the corresponding burner, the primary air flow rate at the burner outlet is changed, the flame shape in the furnace is changed, and the radiative heat exchange of the corresponding vertical water-cooled wall is adjusted, thereby controlling the temperature of the vertical water-cooled wall. The burners in the same pulverizing system control the corresponding flame shape.

5. The method for controlling the temperature of the vertical water-cooled wall in a tangential boiler unit for flexible peak shaving according to claim 1, characterized in that: The independent control of the primary air flow rate at the outlet of the corresponding burner also includes the determination of the corresponding burner: The vertical water-cooled wall of the boiler has a local overheating tendency. The burners facing this area and the lower burners facing this area are both burners that regulate the overheating tendency of the vertical water-cooled wall in this area. The burner facing this area is the second burner in this layer, located against the direction of the flame tangency. The lower burner facing this area is the second burner below, located in the opposite direction of the flame tangential circle.

6. The method for controlling the temperature of the vertical water-cooled wall in a tangential boiler unit for flexible peak shaving according to claim 1, characterized in that: The determination of the primary air flow limit for the independent control corresponding to the burner outlet is that the adjustment limit for the primary air flow at the burner outlet is that the difference between the primary air flow to be adjusted and the median of the primary air flow at the outlet of other burners in the same pulverizing system is less than |±20%| of the primary air flow of this pulverizing system. The formula for calculating the difference is as follows: （3）； In the formula, This represents the median primary air flow rate at the outlet of other burners in the pulverizing system corresponding to this burner. This corresponds to the primary air flow rate at the burner outlet; This represents the difference between the primary air flow rate at the outlet of the corresponding burner and the median primary air flow rate at the outlet of other burners in the pulverizing system.

7. The method for controlling the temperature of the vertical water-cooled wall in a tangential boiler unit for flexible peak shaving according to claim 1, characterized in that: Based on the local overheating trend of the vertical water-cooled wall of the boiler, control the secondary air flow of the boiler air supply system: when the vertical water-cooled wall has a local overheating trend, control the boiler air supply system to increase the secondary air flow to adjust the flame shape at the burner outlet and reduce the flame's scouring of the vertical water-cooled wall. It also includes a limit of 3% of the actual total air volume to be increased secondary air flow when there is a local overheating trend in the vertical water-cooled wall of the boiler.

8. The method for controlling the temperature of the vertical water-cooled wall in a tangential boiler unit for flexible peak shaving according to claim 1, characterized in that: Based on the local overheating trend of the vertical water-cooled wall of the boiler, the coal feed rate of the corresponding pulverizing system is independently controlled: when there is an overheating trend in the vertical water-cooled wall, the coal feed rate of the pulverizing system at the horizontal position of the overheating area and the pulverizing system adjacent to the horizontal position below the overheating area is reduced. When the corresponding pulverizing system reaches the lower limit of the coal feed rate, it is prohibited to reduce the coal feed rate of the corresponding pulverizing system.

9. The method for controlling the temperature of the vertical water-cooled wall in a tangential boiler unit for flexible peak shaving according to claim 1, characterized in that: Based on the local overheating trend of the boiler's vertical water-cooled wall, the feedwater flow rate is controlled as follows: when the expected wall temperature exceeds the set threshold B, the feedwater flow rate of the boiler feedwater system is increased to adjust the heat absorption of the boiler's vertical water-cooled wall in advance, slow down the wall temperature increase trend, and, in conjunction with other adjustment methods, ensure that the vertical water-cooled wall temperature is controlled within a reasonable range during the unit's flexible peak shaving process.

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