Water-cooled wall overtemperature control system and method for coal-fired units based on wall temperature prediction

Abstract

A water-cooled wall overtemperature control system and method for a coal-fired unit based on wall temperature prediction. On the one hand, the system combines actual measurement signals to predict the maximum wall temperature of the water-cooled wall that is prone to overheating, and combines it with a limiting module and a speed limiting module to realize the participation of the predicted value in the overtemperature control; on the other hand, the measured wall temperature signal of the water-cooled wall is also combined with the limiting module and the speed limiting module to realize the participation of the measured value in the control scheme; the present invention performs real-time measurement and monitoring of the wall temperature of the water-cooled wall that is prone to overheating, advance prediction of the wall temperature and active suppression and regulation, and effectively solves the problem of water-cooled wall overheating caused by combustion factors such as insufficient flame filling under low-load operation of the boiler and safety factors of boiler water circulation such as deviation in steam-water flow distribution in each circulation loop of the water-cooled wall through precise control of fuel air and auxiliary air of the secondary air damper and setting of the separator outlet temperature, through effectively avoiding the problem of biased burning caused by jet deviation and the risk of overheating and bursting of pipes.

Description

Technical Field

[0001] The present invention relates to the field of automatic control of thermal power units, and in particular to a water-cooled wall overtemperature control system and method for coal-fired units based on wall temperature prediction. Background Art

[0002] Faced with increasingly severe environmental pressure, the country continues to promote the adjustment of energy structure, and clean energy such as wind energy and solar energy has been continuously and rapidly developed. However, due to the randomness and intermittent characteristics of new energy such as wind energy and solar energy, large-scale grid connection is bound to have a certain impact on the safety and stability of the power grid; on the other hand, with the slowdown in economic growth and the substantial adjustment of economic structure, the overall contradiction between power supply and demand in my country has changed from shortage to relative surplus. Therefore, in order to improve the absorption capacity of new energy such as wind energy and solar energy, thermal power units are bound to bear a greater peak load load, and long-term low-load operation of units is bound to become the norm.

[0003] On the other hand, domestic units generally have the problem of actual coal deviating from the designed coal type, and the coal quality is seriously mixed. The quality of coal entering the furnace is sometimes good and sometimes bad, causing the actual coal quality to deviate from the designed coal type, which fundamentally changes the boiler design conditions. During the actual operation of the unit, there is a certain deviation in the wind and powder at the four corners of the furnace, which is easy to cause problems such as biased sintering and coking of the boiler, and the problem of water-cooled wall tube bursting.

[0004] Safety of hydrodynamic conditions. When the boiler is running under low load, the flame is less full in the furnace than when it is under high load, resulting in uneven heat load in the furnace. The increase in the deviation of steam-water flow distribution between the water-cooled wall circulation loops and adjacent tubes may cause water circulation to stop and circulation to flow back. When running under low load, due to combustion factors and safety factors of boiler water circulation, water-cooled wall overheating is prone to occur. Therefore, when running under low load, real-time measurement and monitoring of water-cooled wall temperature, and advance prediction and control of wall temperature are effective ways to reduce the risk of tube burst.

[0005] At present, there are mainly two solutions for wall temperature measurement and control of thermal power units:

[0006] 1) The wall temperature is measured by installing a large number of thermocouple wall temperature measuring points on the tube wall metal of the boiler superheater, reheater, water-cooled wall and other parts, and a separate monitoring system or direct access to the DCS system is used for direct monitoring to improve the safety and stability of the long-term operation of the boiler. At present, this method has high requirements for the environment around the measuring points, and the environment inside the furnace is often harsh, which has a certain impact on the precision and accuracy of the measurement. At the same time, this method can only measure the temperature value at the current moment. Due to the large number of measuring points, an alarm will only be issued when an over-temperature phenomenon occurs at the measuring point, so that the operating personnel can make corresponding adjustments to the boiler parameters based on actual experience. This will result in the operating personnel being unable to make real-time judgments on a large number of wall temperature measuring points during the wall temperature over-temperature monitoring process, and when an over-temperature alarm occurs, the control operation is being processed, and the over-temperature problem cannot be solved in time, which has an adverse impact on the safety of boiler operation.

[0007] 2) Establish a wall temperature prediction model through mechanism or mathematical analysis methods to achieve the calculation and prediction of wall temperature. Among them, the wall temperature is calculated through the mechanism modeling analysis of water-cooled walls, superheaters and other components. This method is relatively complex and has many boundary parameters. The actual measurement points of the power plant cannot give all boundary parameters, and the model needs to be constantly corrected under different conditions. Therefore, it does not meet the requirements of online calculation and cannot participate in the real-time closed-loop control of the power station wall temperature. Based on the mathematical modeling and analysis method, the wall temperature prediction method based on artificial neural network is currently used. The static network structure such as BP neural network can realize the prediction of boiler tube wall temperature, but the current wall temperature prediction is only in the research stage and the display alarm stage, and the prediction results are not used to participate in the closed-loop control of thermal power.

[0008] In summary, the existing wall temperature over-temperature response measures and prediction methods only stop at displaying alarms, so that the parameters are changed based on the experience of the operators, and closed-loop control is not achieved. On the other hand, the wall temperature prediction model needs to be optimized to achieve accurate wall temperature prediction and achieve early closed-loop operation to avoid wall temperature over-temperature. Summary of the invention

[0009] In order to solve the problems existing in the above-mentioned prior art, the present invention proposes a water-cooled wall overtemperature control system and method for a coal-fired unit based on wall temperature prediction, which is of great significance for improving the operating reliability of thermal power plants, effectively reducing the risk of pipe bursts, extending the life of key equipment, and reducing maintenance costs.

[0010] In the water-cooled wall over-temperature control system of the coal-fired unit based on wall temperature prediction, the boiler feed water flows through the economizer 1 and the water-cooled wall lower header 2, and then flows through the spiral water-cooled wall 3 and the vertical water-cooled wall 4 in sequence, and finally converges to the water-cooled wall discharge pipe outlet header 5, thereby completing the water-cooled wall heat exchange with the steam-water separator 6. The system includes an economizer outlet temperature sensor 7 arranged at the outlet of the economizer 1, a plurality of spiral water-cooled wall wall temperature thermocouple sensors 8 evenly arranged on the spiral water-cooled wall 3, a plurality of vertical water-cooled wall wall temperature thermocouple sensors 9 evenly arranged on the vertical water-cooled wall 4, and a steam-water separator outlet temperature sensor 10 arranged at the outlet of the steam-water separator 6; the economizer outlet temperature sensor 7 is connected to the input end of an economizer outlet temperature storage module 12, a plurality of spiral water-cooled wall wall temperature thermocouple sensors 8 are connected to the input end of a spiral water-cooled wall temperature average value calculation storage module 13, and a plurality of vertical water-cooled wall wall temperature thermocouple sensors 9 are connected to the input end of a vertical water-cooled wall temperature maximum value calculation storage module 14; the output ends of the economizer outlet temperature storage module 12, the spiral water-cooled wall temperature average value calculation storage module 13, the vertical water-cooled wall temperature maximum value calculation storage module 14, the unit load data storage module 15, the coal quantity data storage module 16, the primary air pressure data storage module 17 and the secondary air volume data storage module 18 are connected to the water-cooled wall wall temperature prediction calculation model 19 The output end of the water-cooled wall temperature prediction calculation model 19 is connected to the input end of the wall temperature prediction value limiting module 20 and the wall temperature prediction value temperature rise rate limiting module 21, and the output end of the wall temperature prediction value limiting module 20 and the wall temperature prediction value temperature rise rate limiting module 21 is connected to the input end of the first or module 22; the vertical water-cooled wall temperature thermocouple sensor 9 is connected to the input end of the wall temperature current value limiting module 23 and the wall temperature current value temperature rise rate limiting module 24, and the wall temperature current value limiting module 23 and the wall temperature current value temperature rise rate limiting module The output end of the rate limiting module 24 is connected to the input end of the second or module 25; the output ends of the first or module 22 and the second or module 25 are respectively connected to the input ends of the steam-water separator outlet temperature setting value module 26 and the secondary air door control module 27, the steam-water separator outlet temperature setting value module 26 is connected to the outlet of the steam-water separator 6, and the steam-water separator outlet temperature setting value is given; the output end of the secondary air door control module 27 is connected to the secondary air door damper 11 around the boiler, and the bias instruction of the secondary air door damper 11 around the boiler is given.

[0011] The water-cooled wall of the coal-fired unit is an evaporating heating surface composed of multiple parallel tubes laid around the furnace. The lower water-cooled wall and ash hopper use spiral tube screens, namely spiral water-cooled wall 3, and the upper water-cooled wall is a vertical tube screen, namely vertical water-cooled wall 4.

[0012] Since the spiral water-cooled wall is evenly distributed around the furnace, the spiral water-cooled wall wall temperature thermocouple sensors 8 are evenly distributed on the furnace walls around the furnace, and multiple spiral water-cooled wall wall temperature thermocouple sensors 8 are arranged on the left wall, right wall, front wall, and rear wall. Since there are relatively few vertical water-cooled wall hanging pipes on the rear wall, the vertical water-cooled wall wall temperature thermocouple sensors 9 are arranged at more measuring points on the left wall, right wall, and front wall, and fewer measuring points on the rear wall.

[0013] The control method of the water-cooled wall overtemperature control system of a coal-fired unit based on wall temperature prediction is:

[0014] The temperature signal measured by the economizer outlet temperature sensor 7 is sent to the economizer outlet temperature storage module 12 for data storage, and multiple spiral water-cooled wall temperature signals measured by the spiral water-cooled wall wall temperature thermocouple sensor 8 are sent to the spiral water-cooled wall temperature average value calculation storage module 13 for calculation to obtain the average value and store the historical value, and multiple vertical water-cooled wall temperatures measured by the vertical water-cooled wall wall temperature thermocouple sensor 9 of different furnace walls are sent to the vertical water-cooled wall temperature maximum value calculation storage module 14 for calculation to obtain the maximum value of the vertical water-cooled wall temperature of different furnace walls and store it; then the economizer outlet temperature, The average value of the spiral water-cooled wall temperature, the maximum value of the vertical water-cooled wall temperature, the unit load signal of the unit load data storage module 15, the coal quantity signal of the coal quantity data storage module 16, the primary air pressure data of the primary air pressure data storage module 17, and the secondary air volume data of the secondary air volume data storage module 18 are sent to the water-cooled wall temperature prediction calculation model 19 for prediction calculation to obtain the maximum predicted value of the water-cooled wall of each furnace wall, and then sent to the wall temperature prediction value limit module 20 and the wall temperature prediction value temperature rise rate limit module 21 to determine whether it exceeds the limit, and then sent to the first or module 22 for judgment. If any condition is met, it will trigger The signal is sent to the secondary air door control module 27, and the secondary air door control module 27 gives a smaller bias instruction. By adjusting the secondary air door baffles 11 around the boiler, the fuel air and auxiliary air volume are changed, the fuel air is strengthened at low load, the primary air powder stiffness is improved, and the biased burning caused by jet deflection is not easy to occur. At the same time, the steam-water separator outlet temperature setting value module 26 is used to reduce the intermediate point temperature setting, so that the feed water flow rate increases, the water dynamic performance in the water-cooled wall is better, and the water-cooled wall is prevented from overheating. On the other hand, the actual measurement value of the vertical water-cooled wall wall temperature thermocouple sensor 9 is sent to the wall temperature current value limit module 23 and the wall temperature current value limit module 24. The previous value temperature rise rate limit module 24 determines whether it exceeds the limit, and then sends it to the second or module 25 for logical judgment. If any condition is met, the trigger signal is sent to the secondary air door control module 27. The secondary air door control module 27 gives a larger bias instruction, and further changes the fuel wind and auxiliary air volume by adjusting the air door baffles 11 of the surrounding secondary wind boxes. The fuel wind is strengthened at low load, the primary air powder stiffness is improved, and the biased burning caused by jet deflection is not easy to occur. At the same time, the steam-water separator outlet temperature setting value module 26 is used to further reduce the separator outlet temperature setting, so that the water supply flow rate increases and the water dynamic characteristics are improved. In addition, through prediction and actual alarm, the operating personnel are reminded to make judgments in advance, and further manual adjustments can be made by adjusting the coal mill combination mode and the burner swing angle to reduce the risk of water wall burst.

[0015] Compared with the prior art, the present invention has the following advantages:

[0016] (1) The prior art only installs a large number of thermocouple wall temperature measuring points on the tube wall metal of the boiler superheater, reheater, water-cooled wall and other parts to achieve wall temperature measurement, and uses a separate monitoring system or directly connects to the DCS system for direct monitoring; this method can only measure the temperature value at the current moment, and will only issue an alarm when an over-temperature phenomenon occurs at the measuring point. Due to the large number of measuring points, it is impossible to quickly determine the over-temperature location and over-temperature situation. On the other hand, the operating personnel cannot make real-time judgments on a large number of wall temperature measuring points during the wall temperature over-temperature monitoring process, and when an over-temperature alarm occurs, the control operation is being processed, and the over-temperature problem cannot be solved in time, which has an adverse impact on the safety of boiler operation. The present invention is developed on the basis of the existing wall temperature measuring points, without adding wall temperature measuring points for modification. By adding wall temperature prediction algorithms and wall temperature control logic, wall temperature over-temperature prediction and over-temperature closed-loop control can be achieved, effectively reducing the risk of water-cooled wall temperature over-temperature.

[0017] (2) Safety of hydrodynamic conditions. When the boiler is operating under low load, the degree of flame filling in the furnace is worse than that under high load, resulting in uneven heat load in the furnace. The increase in the deviation in steam-water flow distribution between the water-cooled wall circulation loops and adjacent tubes may cause water circulation to stop and circulation to flow back. When operating under low load, water-cooled wall overheating is prone to occur due to combustion factors and safety factors of boiler water circulation. When judging that there is a risk of water-cooled wall overheating on a certain side of the furnace wall, the present invention uses the secondary air auxiliary air and fuel air ratio adjustment in a short period of time, and increases water supply at the same time, so that the hydrodynamic conditions are optimized, the risk of water-cooled wall overheating is reduced, and the automatic control function of the secondary air is further enriched, thereby realizing automatic suppression protection of water-cooled wall overheating, which is of great significance to solving the problem of water-cooled wall overheating faced by coal-fired units. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The schematic diagram of the water-cooled wall over-temperature control system of a coal-fired unit based on wall temperature prediction of the present invention is shown.

[0019] The reference numerals and corresponding component names in the figure are described as follows:

[0020] 1 Economizer

[0021] 2 Water-cooled wall lower header

[0022] 3 Spiral water wall

[0023] 4 Vertical water wall

[0024] 5 Water-cooled wall pipe outlet header

[0025] 6. Separator

[0026] 7 Economizer outlet temperature sensor

[0027] 8 Spiral water-cooled wall temperature thermocouple sensor

[0028] 9 Vertical water-cooled wall temperature thermocouple sensor

[0029] 10. Separator outlet temperature sensor

[0030] 11 Secondary air damper around the boiler

[0031] 12 Economizer outlet temperature storage module

[0032] 13 Spiral water wall temperature average value calculation storage module

[0033] 14 Vertical water-cooled wall temperature maximum value calculation and storage module

[0034] 15 Unit load data storage module

[0035] 16 Coal quantity data storage module

[0036] 17. Primary wind pressure data storage module

[0037] 18 Secondary air volume data storage module

[0038] 19 Water-cooled wall temperature prediction calculation model

[0039] 20 Wall temperature prediction value limit module

[0040] 21 Wall temperature prediction value temperature rise rate limit module

[0041] 22 First or Module

[0042] 23 Wall temperature current value limit module

[0043] 24 Wall temperature current value temperature rise rate limit module

[0044] 25 Second or Module

[0045] 26. Steam-water separator outlet temperature setting value module

[0046] 27 Secondary air door control module. DETAILED DESCRIPTION

[0047] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0048] like Figure 1As shown, in the water-cooled wall over-temperature control system of the coal-fired unit based on wall temperature prediction of the present invention, the boiler feed water flows through the economizer 1 and the water-cooled wall lower header 2, and then flows through the spiral water-cooled wall 3 and the vertical water-cooled wall 4 in sequence, and finally converges to the water-cooled wall discharge pipe outlet header 5, thereby completing the water-cooled wall heat exchange with the steam-water separator 6. The system includes an economizer outlet temperature sensor 7 arranged at the outlet of the economizer 1, a plurality of spiral water-cooled wall wall temperature thermocouple sensors 8 evenly arranged on the spiral water-cooled wall 3, a plurality of vertical water-cooled wall wall temperature thermocouple sensors 9 evenly arranged on the vertical water-cooled wall 4, and a steam-water separator outlet temperature sensor 10 arranged at the outlet of the steam-water separator 6; the economizer outlet temperature sensor 7 is connected to the input end of an economizer outlet temperature storage module 12, a plurality of spiral water-cooled wall wall temperature thermocouple sensors 8 are connected to the input end of a spiral water-cooled wall temperature average value calculation storage module 13, and a plurality of vertical water-cooled wall wall temperature thermocouple sensors 9 are connected to the input end of a vertical water-cooled wall temperature maximum value calculation storage module 14; the output ends of the economizer outlet temperature storage module 12, the spiral water-cooled wall temperature average value calculation storage module 13, the vertical water-cooled wall temperature maximum value calculation storage module 14, the unit load data storage module 15, the coal quantity data storage module 16, the primary air pressure data storage module 17 and the secondary air volume data storage module 18 are connected to the water-cooled wall wall temperature prediction calculation model 19 The output end of the water-cooled wall temperature prediction calculation model 19 is connected to the input end of the wall temperature prediction value limiting module 20 and the wall temperature prediction value temperature rise rate limiting module 21, and the output end of the wall temperature prediction value limiting module 20 and the wall temperature prediction value temperature rise rate limiting module 21 is connected to the input end of the first or module 22; the vertical water-cooled wall temperature thermocouple sensor 9 is connected to the input end of the wall temperature current value limiting module 23 and the wall temperature current value temperature rise rate limiting module 24, and the wall temperature current value limiting module 23 and the wall temperature current value temperature rise rate limiting module The output end of the rate limiting module 24 is connected to the input end of the second or module 25; the output ends of the first or module 22 and the second or module 25 are respectively connected to the input ends of the steam-water separator outlet temperature setting value module 26 and the secondary air door control module 27, the steam-water separator outlet temperature setting value module 26 is connected to the outlet of the steam-water separator 6, and the steam-water separator outlet temperature setting value is given; the output end of the secondary air door control module 27 is connected to the secondary air door damper 11 around the boiler, and the bias instruction of the secondary air door damper 11 around the boiler is given.

[0049] As a preferred embodiment of the present invention, the water-cooled wall of the coal-fired unit is an evaporating heating surface composed of multiple parallel tubes laid around the furnace, and its lower water-cooled wall and ash hopper adopt spiral tube screens, namely spiral water-cooled wall 3, and the upper water-cooled wall is a vertical tube screen, namely vertical water-cooled wall 4.

[0050] Since the spiral water-cooled wall is evenly distributed around the furnace, the spiral water-cooled wall wall temperature thermocouple sensors 8 are evenly distributed on the furnace walls around the furnace, and multiple spiral water-cooled wall wall temperature thermocouple sensors 8 are arranged on the left wall, right wall, front wall, and rear wall. Since there are relatively few vertical water-cooled wall hanging pipes on the rear wall, as a preferred embodiment of the present invention, the vertical water-cooled wall wall temperature thermocouple sensors 9 are arranged with more measuring points on the left wall, right wall, and front wall, and fewer measuring points on the rear wall.

[0051] like Figure 1 As shown, the control method of the water-cooled wall overtemperature control system of a coal-fired unit based on wall temperature prediction of the present invention is:

[0052] The temperature signal measured by the economizer outlet temperature sensor 7 is sent to the economizer outlet temperature storage module 12 for data storage, and multiple spiral water-cooled wall temperature signals measured by the spiral water-cooled wall wall temperature thermocouple sensor 8 are sent to the spiral water-cooled wall temperature average value calculation storage module 13 for calculation to obtain the average value and store the historical value, and multiple vertical water-cooled wall temperatures measured by the vertical water-cooled wall wall temperature thermocouple sensor 9 of different furnace walls are sent to the vertical water-cooled wall temperature maximum value calculation storage module 14 for calculation to obtain the maximum value of the vertical water-cooled wall temperature of different furnace walls and store it; then the economizer outlet temperature, The average value of the spiral water-cooled wall temperature, the maximum value of the vertical water-cooled wall temperature, the unit load signal of the unit load data storage module 15, the coal quantity signal of the coal quantity data storage module 16, the primary air pressure data of the primary air pressure data storage module 17, and the secondary air volume data of the secondary air volume data storage module 18 are sent to the water-cooled wall temperature prediction calculation model 19 for prediction calculation to obtain the maximum predicted value of the water-cooled wall of each furnace wall, and then sent to the wall temperature prediction value limit module 20 and the wall temperature prediction value temperature rise rate limit module 21 to determine whether it exceeds the limit, and then sent to the first or module 22 for judgment. If any condition is met, it will trigger The signal is sent to the secondary air door control module 27, and the secondary air door control module 27 gives a smaller bias instruction. By adjusting the secondary air door baffles 11 around the boiler, the fuel air and auxiliary air volume are changed, the fuel air is strengthened at low load, the primary air powder stiffness is improved, and the biased burning caused by jet deflection is not easy to occur. At the same time, the steam-water separator outlet temperature setting value module 26 is used to reduce the intermediate point temperature setting, so that the feed water flow rate increases, the water dynamic performance in the water-cooled wall is better, and the water-cooled wall is prevented from overheating. On the other hand, the actual measurement value of the vertical water-cooled wall wall temperature thermocouple sensor 9 is sent to the wall temperature current value limit module 23 and the wall temperature current value limit module 24. The previous value temperature rise rate limit module 24 determines whether it exceeds the limit, and then sends it to the second or module 25 for logical judgment. If any condition is met, the trigger signal is sent to the secondary air door control module 27. The secondary air door control module 27 gives a larger bias instruction, and further changes the fuel wind and auxiliary air volume by adjusting the air door baffles 11 of the surrounding secondary wind boxes. The fuel wind is strengthened at low load, the primary air powder stiffness is improved, and the biased burning caused by jet deflection is not easy to occur. At the same time, the steam-water separator outlet temperature setting value module 26 is used to further reduce the separator outlet temperature setting, so that the water supply flow rate increases and the water dynamic characteristics are improved. In addition, through prediction and actual alarm, the operating personnel are reminded to make judgments in advance, and further manual adjustments can be made by adjusting the coal mill combination mode and the burner swing angle to reduce the risk of water wall burst.

Claims

1. A control method for a water-cooled wall overtemperature control system of a coal-fired unit based on wall temperature prediction, characterized in that: In the control system, boiler feed water flows through an economizer (1) and a water-cooled wall lower header (2), then flows through a spiral water-cooled wall (3) and a vertical water-cooled wall (4) in sequence, and finally converges to a water-cooled wall discharge pipe outlet header (5), thereby completing water-cooled wall heat exchange with a steam-water separator (6); the system comprises an economizer outlet temperature sensor (7) arranged at the outlet of the economizer (1), a plurality of spiral water-cooled wall wall temperature thermocouple sensors (8) evenly arranged on the spiral water-cooled wall (3), a plurality of vertical water-cooled wall wall temperature thermocouple sensors (9) evenly arranged on the vertical water-cooled wall (4), and a steam-water separator outlet temperature sensor (10) arranged at the outlet of the steam-water separator (6). 0); the economizer outlet temperature sensor (7) is connected to the input end of the economizer outlet temperature storage module (12); a plurality of spiral water-cooled wall temperature thermocouple sensors (8) are connected to the input end of the spiral water-cooled wall temperature average value calculation storage module (13); a plurality of vertical water-cooled wall temperature thermocouple sensors (9) are connected to the input end of the vertical water-cooled wall temperature maximum value calculation storage module (14); the economizer outlet temperature storage module (12), the spiral water-cooled wall temperature average value calculation storage module (13), the vertical water-cooled wall temperature maximum value calculation storage module (14), the unit load data storage module (15), the coal quantity data storage module (16), a The output ends of the wind pressure data storage module (17) and the secondary air volume data storage module (18) are connected to the input end of the water-cooled wall temperature prediction calculation model (19), the output end of the water-cooled wall temperature prediction calculation model (19) is connected to the input end of the wall temperature prediction value limiting module (20) and the wall temperature prediction value temperature rise rate limiting module (21), the output ends of the wall temperature prediction value limiting module (20) and the wall temperature prediction value temperature rise rate limiting module (21) are connected to the input end of the first or module (22); the vertical water-cooled wall temperature thermocouple sensor (9) is connected to the input end of the wall temperature current value limiting module (23) and the wall temperature current value temperature rise rate limiting module (24) , the output ends of the wall temperature current value limiting module (23) and the wall temperature current value temperature rise rate limiting module (24) are connected to the input end of the second OR module (25); the output ends of the first OR module (22) and the second OR module (25) are respectively connected to the input ends of the steam-water separator outlet temperature setting value module (26) and the secondary air door control module (27); the steam-water separator outlet temperature setting value module (26) is connected to the outlet of the steam-water separator (6) to provide the steam-water separator outlet temperature setting value; the output end of the secondary air door control module (27) is connected to the secondary air door dampers (11) around the boiler to provide the bias instructions of the secondary air door dampers (11) around the boiler; The control method comprises: sending the temperature signal measured by the economizer outlet temperature sensor (7) to the economizer outlet temperature storage module (12) for data storage, sending multiple spiral water-cooled wall temperature signals measured by the spiral water-cooled wall wall temperature thermocouple sensor (8) to the spiral water-cooled wall temperature average value calculation storage module (13) for calculation, obtaining the average value and storing the historical value, sending multiple vertical water-cooled wall temperatures measured by the vertical water-cooled wall wall temperature thermocouple sensors (9) of different furnace walls to the vertical water-cooled wall temperature maximum value calculation storage module (14) for calculation to obtain the maximum values ​​of the vertical water-cooled wall temperatures of different furnace walls and storing them; then storing the economizer outlet temperature and the spiral water-cooled wall temperature average value. , the maximum value of the vertical water-cooled wall temperature, the unit load signal of the unit load data storage module (15), the coal quantity signal of the coal quantity data storage module (16), the primary air pressure data of the primary air pressure data storage module (17), and the secondary air volume data of the secondary air volume data storage module (18) are sent to the water-cooled wall temperature prediction calculation model (19) for prediction calculation to obtain the maximum predicted value of the water-cooled wall of each furnace wall, and then sent to the wall temperature prediction value limit module (20) and the wall temperature prediction value temperature rise rate limit module (21) to determine whether it exceeds the limit, and then sent to the first or module (22) for judgment. If any condition is met, the trigger signal is sent to the secondary air door control module (27), and the secondary air door control The module (27) gives a smaller bias instruction, and changes the fuel air and auxiliary air volume by adjusting the secondary air dampers (11) around the boiler, strengthens the fuel air at low load, improves the stiffness of the primary air powder, and is less likely to cause biased burning caused by jet deflection. At the same time, the steam-water separator outlet temperature setting value module (26) is used to reduce the intermediate point temperature setting, so that the feed water flow rate increases, the hydrodynamic performance in the water-cooled wall is better, and the water-cooled wall is prevented from overheating. On the other hand, the actual measurement value of the vertical water-cooled wall wall temperature thermocouple sensor (9) is sent to the wall temperature current value limit module (23) and the wall temperature current value temperature rise rate limit module (24) to determine whether it exceeds the limit, and then sent to the second or module (25) for logical judgment, and any When the conditions are met, a trigger signal is sent to the secondary air door control module (27). The secondary air door control module (27) gives a larger bias instruction. By adjusting the air door baffles (11) of the secondary air boxes on all sides, the fuel air and auxiliary air volume are further changed. The fuel air is strengthened at low load, the primary air powder stiffness is improved, and the biased burning caused by jet deflection is not easy to occur. At the same time, the steam-water separator outlet temperature setting value module (26) is used to further reduce the separator outlet temperature setting, so that the water feed flow rate increases and the water dynamic characteristics are improved. In addition, through the prediction and actual alarm, the operating personnel are reminded to make judgments in advance, adjust the coal mill combination mode, and further manually adjust the burner swing angle to reduce the risk of water wall burst.

2. The control method of the water-cooled wall over-temperature control system of a coal-fired unit based on wall temperature prediction according to claim 1 is characterized by: The water-cooled wall of a coal-fired unit is an evaporation heating surface composed of multiple parallel tubes laid around the furnace. The lower water-cooled wall and ash hopper adopt spiral tube screens, namely spiral water-cooled walls (3), and the upper water-cooled wall is a vertical tube screen, namely vertical water-cooled wall (4).

3. The control method of the water-cooled wall over-temperature control system of a coal-fired unit based on wall temperature prediction according to claim 1 is characterized in that: Since the spiral water-cooled wall is evenly distributed around the furnace, the spiral water-cooled wall wall temperature thermocouple sensors (8) are evenly distributed on the furnace walls around the furnace, with multiple sensors arranged on the left wall, the right wall, the front wall, and the rear wall; since there are fewer vertical water-cooled wall hanging pipes on the rear wall, more vertical water-cooled wall wall temperature thermocouple sensors (9) are arranged on the left wall, the right wall, and the front wall, and fewer measurement points are arranged on the rear wall.

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