Over-temperature control system and method for platen superheater of coal-fired unit based on wall temperature prediction

Abstract

The invention discloses a screen superheater over-temperature control system and method for a coal-fired unit based on wall temperature prediction. On the one hand, the system predicts the maximum value of the screen superheater wall temperature in combination with the actual measurement signal, and combines it with the limit module and the rate-increasing speed-limiting module to realize the participation of the predicted value in the over-temperature control; on the other hand, the measured wall temperature signal of the screen superheater is also combined with the limit module and the rate-increasing speed-limiting module to realize the participation of the measured value in the control scheme; by adjusting the ember wind baffle, the first-level cooling water regulating valve and other equipment, an over-temperature control system for the screen superheater of a coal-fired unit based on wall temperature prediction is formed, and the active suppression and regulation of the screen superheater wall temperature over-temperature is realized; the invention simultaneously obtains the change trend of the predicted wall temperature and the current wall temperature, and realizes the active suppression of the advanced wall temperature over-temperature, which is of great significance to improving the operation reliability of thermal power plants, effectively reducing the risk of pipe bursts, extending the life of key equipment, and reducing maintenance and repair costs.

Description

Technical Field

[0001] The invention relates to the field of automatic control of coal-fired units, and in particular to an over-temperature control system and method for a platen superheater of a coal-fired unit based on wall temperature prediction. Background Art

[0002] With the continuous improvement of the level of thermal power units, improving power generation parameters such as steam temperature and pressure is an important way to improve the efficiency of ultra-supercritical units, but the increase in steam temperature puts higher requirements on steam pipe materials and wall temperature control. Limited by the creep strength and endurance strength of the material, temperature fluctuations must be within the safety margin. Due to the measurement deviation of the water-cooled wall temperature, the parameters cannot be adjusted in time, and the long-term over-temperature operation of the water-cooled wall will inevitably increase the risk of pipe bursting. In addition, the current domestic ultra-supercritical direct-current boilers are prone to blockage due to the lack of attention to the monitoring of the high-temperature superheater metal temperature, and are also prone to superheater pipe bursting accidents. Therefore, real-time measurement of wall temperature, advance prediction and control of wall temperature are effective ways to reduce the risk of pipe bursting.

[0003] At present, there are mainly two solutions for wall temperature measurement and control of coal-fired units:

[0004] 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.

[0005] 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 current wall temperature prediction method based on artificial neural network is mostly used, which only considers the influence of external factors on the wall temperature, and uses static network structures such as BP neural network to predict the boiler tube wall temperature. The current wall temperature historical data, upstream wall temperature historical data and the rate of change of related factors are not considered, and the time series prediction neural network structure, neural network activation function and other contents are not studied. The prediction structure is relatively backward and the calculation results are poor. In addition, the current wall temperature prediction is only in the display stage, and the prediction results are not used to participate in the closed-loop control of thermal power.

[0006] 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

[0007] In order to solve the problems existing in the above-mentioned prior art, the present invention proposes an over-temperature control system and method for a screen-type superheater of a coal-fired unit based on wall temperature prediction, and simultaneously obtains the change trend of the predicted wall temperature and the current wall temperature, thereby completing the wall temperature over-temperature control and operation guidance, and realizing the active suppression of advanced wall temperature over-temperature, which is of great significance to improving the operation reliability of thermal power plants, effectively reducing the risk of pipe burst, extending the life of key equipment, and reducing maintenance and repair costs.

[0008] In order to achieve the above object, the present invention adopts the following technical solution:

[0009] In the over-temperature control system of the platen superheater of a coal-fired unit based on wall temperature prediction, the boiler feed water flows through the low-temperature superheater 1 and is divided into two paths, the left path is connected to the left platen superheater 7 through the left-side primary cooling water regulating valve 3 and the left-side primary cooling water flow sensor 4, and the right side is connected to the right platen superheater 9 through the right-side primary cooling water regulating valve 5 and the right-side primary cooling water flow sensor 6; a plurality of low-temperature superheater wall temperature sensors 2 are arranged on the low-temperature superheater 1, a plurality of left-side platen superheater wall temperature sensors 8 are arranged on the left-side platen superheater 7, and a plurality of right-side platen superheater wall temperature sensors 10 are arranged on the right-side platen superheater 9; a left-side burnout wind damper 11 and a right-side burnout wind damper are arranged on the corresponding sides of the left-side platen superheater 7 and the right-side platen superheater 9, respectively. 12; the right side screen superheater wall temperature sensor 10 is connected to the input end of the right side screen wall temperature maximum value calculation storage module 13 and the input end of the right side screen wall temperature average value calculation storage module 14, the low-temperature superheater wall temperature sensor 2 is connected to the input end of the low-temperature superheater wall temperature average value calculation storage module 15, and the right side first-stage cooling water flow sensor 6 is connected to the input end of the right side first-stage cooling water flow differential calculation storage module 16; similarly, the left side screen superheater wall temperature sensor 8 is connected to the input end of the left side screen superheater wall temperature maximum value calculation storage module 17 and the input end of the left side screen superheater wall temperature average value calculation storage module 18, and the left side first-stage cooling water flow sensor 4 is connected to the input end of the left side first-stage cooling water flow differential calculation storage module 19.

[0010] The output ends of the right-side screen wall temperature maximum value calculation and storage module 13, the right-side screen wall temperature average value calculation and storage module 14, the low-temperature superheater wall temperature average value calculation and storage module 15, the right-side primary desuperheating water flow differential calculation and storage module 16 and the unit load data storage module 20 are connected to the input end of the right-side screen wall temperature prediction model calculation module 21, and the output end of the right-side screen wall temperature prediction model calculation module 21 is respectively connected to the input end of the right-side screen wall temperature prediction limit module 23 and the input end of the right-side screen wall temperature prediction temperature rise rate limit module 24, and the output end of the right-side screen wall temperature prediction limit module 23 and the output end of the right-side screen wall temperature prediction temperature rise rate limit module 24 are connected to the input end of the right first or module 25 The right side screen superheater wall temperature sensor 10 is respectively connected to the input end of the right side screen wall temperature current value limiting module 26 and the input end of the right side screen wall temperature current value temperature rise rate limiting module 27, and the output end of the right side screen wall temperature current value limiting module 26 and the output end of the right side screen wall temperature current value temperature rise rate limiting module 27 are connected to the input end of the right side second or module 28; the output end of the right side first or module 25 and the output end of the right side second or module 28 are connected to the input end of the right side cooling water / burnout air control instruction bias module 35 to generate a control instruction, and the output end of the right side cooling water / burnout air control instruction bias module 35 is connected to and controls the right side first-level cooling water regulating valve 5 and the right side burnout wind damper 12; Similarly, the output ends of the left-side screen wall temperature maximum value calculation and storage module 17, the left-side screen wall temperature average value calculation and storage module 18, the low-temperature superheater wall temperature average temperature calculation and storage module 15, the left-side first-stage desuperheating water flow differential calculation and storage module 19 and the unit load data storage module 20 are connected to the input end of the left-side screen wall temperature prediction model calculation module 22; the output end of the left-side screen wall temperature prediction model calculation module 22 is respectively connected to the input end of the left-side screen wall temperature prediction limit module 29 and the input end of the left-side screen wall temperature prediction temperature rise rate limit module 30, and the input end of the left-side screen wall temperature prediction limit module 29 and the output end of the left-side screen wall temperature prediction temperature rise rate limit module 30 are connected to the left first or The left side screen superheater wall temperature sensor 8 is respectively connected to the input end of the left side screen wall temperature current value limiting module 32 and the input end of the left side screen wall temperature current value temperature rise rate limiting module 33, and the output end of the left side screen wall temperature current value limiting module 32 and the output end of the left side screen wall temperature current value temperature rise rate limiting module 33 are connected to the left second or module 34; the output end of the left first or module 31 and the output end of the left second or module 34 are connected to the input end of the left cooling water / burnout air control instruction bias module 36 to generate a control instruction, and the output end of the left cooling water / burnout air control instruction bias module 36 is connected to and controls the left first-level cooling water regulating valve 3 and the left ember wind damper 11;The right screen wall temperature average value calculation and storage module 14 and the left screen wall temperature average value calculation and storage module 18 are connected to the burnout wind control instruction bias module 37, so as to generate a burnout wind control bias instruction to control the left burnout wind damper 11 and the right burnout wind damper 12. ;

[0011] The control method of the over-temperature control system of the platen superheater of a coal-fired unit based on wall temperature prediction is:

[0012] The multiple screen wall temperature real-time data collected by the right screen superheater wall temperature sensor 10 are sent to the right screen wall temperature maximum value calculation storage module 13 to calculate the right screen wall temperature maximum value and store the historical data. At the same time, the right screen wall temperature average value calculation storage module 14 is used to obtain the right screen wall temperature average value and store the historical data. The wall temperature measured by the low-temperature superheater wall temperature sensor 2 is sent to the low-temperature superheater wall temperature average value calculation storage module 15 to calculate the real-time low-temperature superheater wall temperature average value and store the historical data. The cooling water flow rate sensor 6 on the right side measures the cooling water flow rate. The flow data is calculated by the right first-stage cooling water flow differential calculation storage module 16 to obtain the right first-stage cooling water change rate; similarly, the wall temperature measured by the left screen superheater wall temperature sensor 8 is sent to the left screen wall temperature maximum value calculation storage module 17 to calculate the left screen wall temperature maximum value and store the historical data, and the left screen wall temperature average value calculation storage module 18 is used to calculate the left screen wall temperature average value and store the historical data; the cooling water flow value measured by the left first-stage cooling water flow sensor 4 is sent to the left first-stage cooling water flow differential calculation storage module 19 to calculate the left cooling water change rate. rate; then the calculated maximum value of the right side screen wall temperature, the average value of the right side screen wall temperature, the average value of the low-temperature superheater wall temperature, the right side primary cooling water change rate and the unit load are sent to the right side screen wall temperature prediction model calculation module 21 to calculate the right side screen maximum wall temperature prediction value, and sent to the right side screen wall temperature prediction limit module 23 and the right side screen wall temperature prediction temperature rise rate limit module 24 to determine whether it exceeds the limit, and the right side first or module 25 determines that any one of them exceeds the limit, that is, sends an over-temperature signal to the right cooling water / burnout air control instruction bias module 35 to generate a burnout wind bias instruction to control the right burnout wind baffle 12 opening, thereby increasing the burnout wind in advance to reduce the right side screen wall temperature. On the other hand, the right side wall temperature measured by the right side screen superheater wall temperature sensor 10 is sent to the right side screen wall temperature current value limiting module 26 and the right side screen wall temperature current value temperature rise rate limiting module 27 for judgment. The right side second or module 28 judges that any one of them exceeds the limit, that is, sends an over-temperature signal to the right side cooling water / burnout wind control instruction bias module 35 to generate a burnout wind bias instruction and a cooling water regulating valve opening bias instruction, thereby realizing the real-time control of the right side first-level cooling water regulating valve 5 and the right side burnout wind damper 12 to avoid overheating of the screen wall temperature;

[0013] Similarly, the calculated maximum value of the left-side screen wall temperature, the average value of the left-side screen wall temperature, the average value of the low-temperature superheater wall temperature, the left-side primary cooling water change rate and the unit load are sent to the left-side screen wall temperature prediction model calculation module 22 to calculate the left-side screen wall temperature prediction value, and sent to the left-side screen wall temperature prediction limit module 29 and the left-side screen wall temperature prediction temperature rise rate limit module 30 to determine whether it exceeds the limit. The left-side first or module 31 determines that any one of them exceeds the limit, and sends an over-temperature signal to the left-side cooling water / burnout air control instruction bias module 36 to generate a burnout wind bias instruction to control the left-side burnout wind baffle 11 opening, thereby increasing the burnout wind in advance to reduce the left screen wall temperature; on the other hand, the left wall temperature actually measured by the left screen superheater wall temperature sensor 8 is sent to the left screen wall temperature current value limiting module 32 and the left screen wall temperature current value temperature rise rate limiting module 33 for judgment, and the left second or module 34 judges that any one of them exceeds the limit, that is, sends an over-temperature signal to the left cooling water / burnout wind control instruction bias module 36 to generate a burnout wind bias instruction and a cooling water regulating valve opening bias instruction, thereby realizing real-time control of the left first-level cooling water regulating valve 3 and the left burnout wind damper 11 to avoid overheating of the screen wall temperature;

[0014] Finally, the average values ​​of the left and right screen wall temperatures calculated by the right screen wall temperature average value calculation storage module 14 and the left screen wall temperature average value calculation storage module 18 are sent to the burnout wind control instruction bias module 37 for judgment. When the wall temperature deviation on both sides is greater than the protection set value, a burnout wind control bias instruction is generated to control the left burnout wind damper 11 and the right burnout wind damper 12, increase the opening of the burnout wind damper on the side with higher wall temperature, and reduce the opening of the burnout wind damper on the side with lower temperature, thereby reducing the screen wall temperature deviation on both sides.

[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, they are performing control operations and cannot solve the over-temperature problem 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. Through wall temperature prediction and wall temperature control, wall temperature over-temperature prediction and over-temperature closed-loop control can be achieved, effectively reducing the risk of over-temperature of the screen wall temperature.

[0017] (2) Due to the uneven flow of flue gas in the flue, it is very easy to cause a large difference in the wall temperature of the left and right screen superheaters, resulting in the risk of overheating on one side. At present, there is no better control method except combustion adjustment. When it is judged that there is a risk of a large difference in the wall temperature on the left and right sides, the present invention uses the adjustment function of the upper ember wind damper in a short time to achieve the purpose of auxiliary adjustment of flue gas flow, reduce the risk of overheating, and further enrich the automatic control function of the ember wind damper.

[0018] (3) The present invention predicts the wall temperature in advance. When the over-temperature is predicted, the over-temperature of the wall is reduced in advance through the burnout air adjustment. At the same time, according to the actual temperature measurement data, real-time alarm and over-temperature prevention control are carried out. The control is completed by adjusting the cooling water and the burnout air in real time through the real data, ensuring two-level protection, thereby realizing the automatic over-temperature protection of the platen superheater, which is of great significance to solving the over-temperature problem of the platen wall temperature faced by coal-fired units. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The present invention is a schematic diagram of an over-temperature control system of a platen superheater of a coal-fired unit based on wall temperature prediction.

[0020] The reference numerals and corresponding component names in the figure are described as follows:

[0021] 1 Low temperature superheater

[0022] 2 Low temperature superheater wall temperature sensor

[0023] 3 Left primary cooling water regulating valve

[0024] 4 Left primary cooling water flow sensor

[0025] 5 Right first stage cooling water regulating valve

[0026] 6 Right first stage cooling water flow sensor

[0027] 7 Left side platen superheater

[0028] 8 Left side screen superheater wall temperature sensor

[0029] 9 Right side screen superheater

[0030] 10 Right side screen superheater wall temperature sensor

[0031] 11 Left ember wind deflector

[0032] 12 Right ember wind deflector

[0033] 13 Right side screen wall temperature maximum value calculation and storage module

[0034] 14 Right side screen wall temperature average value calculation and storage module

[0035] 15 Low temperature superheater wall temperature average value calculation and storage module

[0036] 16 Right first-stage cooling water flow differential calculation storage module

[0037] 17 Calculation and storage module for the maximum value of the left screen wall temperature

[0038] 18. Calculation and storage module for the average temperature of the left screen through the wall

[0039] 19 Left-side primary cooling water flow differential calculation storage module

[0040] 20 Unit load data storage module

[0041] 21 Right screen wall temperature prediction model calculation module

[0042] 22 Left screen wall temperature prediction model calculation module

[0043] 23 Right screen wall temperature prediction limit module

[0044] 24 Right screen wall temperature prediction temperature rise rate limit module

[0045] 25 Right first or module

[0046] 26 Right side screen through wall temperature current value limit module

[0047] 27 Right screen wall temperature current value temperature rise rate limit module

[0048] 28 Second or module on the right

[0049] 29 Left screen through wall temperature prediction limit module

[0050] 30 Left screen wall temperature prediction temperature rise rate limit module

[0051] 31 Left first or module

[0052] 32 Left side screen wall temperature current value limit module

[0053] 33 Left screen wall temperature current value temperature rise rate limit module

[0054] 34 Second or module on the left

[0055] 35 Right cooling water / burnout air control command offset module

[0056] 36 Left cooling water / burnout air control command bias module

[0057] 37 Overburn air control command bias module. DETAILED DESCRIPTION

[0058] like Figure 1 As shown, the present invention is based on the wall temperature prediction of the platen superheater over-temperature control system of the coal-fired unit. After the boiler feed water flows through the low-temperature superheater 1 for heat exchange, it is divided into two paths, the left side is connected to the left platen superheater 7 through the left-side first-level cooling water regulating valve 3 and the left-side first-level cooling water flow sensor 4, and the right side is connected to the right platen superheater 9 through the right-side first-level cooling water regulating valve 5 and the right-side first-level cooling water flow sensor 6; a plurality of low-temperature superheater wall temperature sensors 2 are arranged on the low-temperature superheater 1, a plurality of left-side platen superheater wall temperature sensors 8 are arranged on the left-side platen superheater 7, and a plurality of right-side platen superheater wall temperature sensors 10 are arranged on the right-side platen superheater 9; the left-side platen superheater 7 and the right-side platen superheater 9 are respectively arranged with a left-side burner wind baffle 11 and a right-side burner wind baffle 12 on the corresponding sides. Wind baffle 12; the right side screen superheater wall temperature sensor 10 is connected to the input end of the right side screen wall temperature maximum value calculation storage module 13 and the input end of the right side screen wall temperature average value calculation storage module 14, the low-temperature superheater wall temperature sensor 2 is connected to the input end of the low-temperature superheater wall temperature average value calculation storage module 15, and the right side first-stage cooling water flow sensor 6 is connected to the input end of the right side first-stage cooling water flow differential calculation storage module 16; similarly, the left side screen superheater wall temperature sensor 8 is connected to the input end of the left side screen superheater wall temperature maximum value calculation storage module 17 and the input end of the left side screen superheater wall temperature average value calculation storage module 18, and the left side first-stage cooling water flow sensor 4 is connected to the input end of the left side first-stage cooling water flow differential calculation storage module 19.

[0059] The output ends of the right-side screen wall temperature maximum value calculation and storage module 13, the right-side screen wall temperature average value calculation and storage module 14, the low-temperature superheater wall temperature average value calculation and storage module 15, the right-side primary desuperheating water flow differential calculation and storage module 16 and the unit load data storage module 20 are connected to the input end of the right-side screen wall temperature prediction model calculation module 21, and the output end of the right-side screen wall temperature prediction model calculation module 21 is respectively connected to the input end of the right-side screen wall temperature prediction limit module 23 and the input end of the right-side screen wall temperature prediction temperature rise rate limit module 24, and the output end of the right-side screen wall temperature prediction limit module 23 and the output end of the right-side screen wall temperature prediction temperature rise rate limit module 24 are connected to the input end of the right first or module 25 The right side screen superheater wall temperature sensor 10 is respectively connected to the input end of the right side screen wall temperature current value limiting module 26 and the input end of the right side screen wall temperature current value temperature rise rate limiting module 27, and the output end of the right side screen wall temperature current value limiting module 26 and the output end of the right side screen wall temperature current value temperature rise rate limiting module 27 are connected to the input end of the right side second or module 28; the output end of the right side first or module 25 and the output end of the right side second or module 28 are connected to the input end of the right side cooling water / burnout air control instruction bias module 35 to generate a control instruction, and the output end of the right side cooling water / burnout air control instruction bias module 35 is connected to and controls the right side first-level cooling water regulating valve 5 and the right side burnout wind damper 12; Similarly, the output ends of the left-side screen wall temperature maximum value calculation and storage module 17, the left-side screen wall temperature average value calculation and storage module 18, the low-temperature superheater wall temperature average value calculation and storage module 15, the left-side first-stage desuperheating water flow differential calculation and storage module 19 and the unit load data storage module 20 are connected to the input end of the left-side screen wall temperature prediction model calculation module 22; the output end of the left-side screen wall temperature prediction model calculation module 22 is respectively connected to the input end of the left-side screen wall temperature prediction limit module 29 and the input end of the left-side screen wall temperature prediction temperature rise rate limit module 30, and the input end of the left-side screen wall temperature prediction limit module 29 and the output end of the left-side screen wall temperature prediction temperature rise rate limit module 30 are connected to the left first or model The left side screen superheater wall temperature sensor 8 is respectively connected to the input end of the left side screen wall temperature current value limiting module 32 and the input end of the left side screen wall temperature current value temperature rise rate limiting module 33, and the output end of the left side screen wall temperature current value limiting module 32 and the output end of the left side screen wall temperature current value temperature rise rate limiting module 33 are connected to the left second or module 34; the output end of the left first or module 31 and the output end of the left second or module 34 are connected to the input end of the left cooling water / burnout air control instruction bias module 36 to generate a control instruction, and the output end of the left cooling water / burnout air control instruction bias module 36 is connected to and controls the left first-level cooling water regulating valve 3 and the left burnout air damper 11;The right screen wall temperature average value calculation and storage module 14 and the left screen wall temperature average value calculation and storage module 18 are connected to the burnout wind control instruction bias module 37, so as to generate a burnout wind control bias instruction to control the left burnout wind damper 11 and the right burnout wind damper 12. ;

[0060] like Figure 1 As shown, the control method of the over-temperature control system of the platen superheater of a coal-fired unit based on wall temperature prediction of the present invention is:

[0061] The multiple screen wall temperature real-time data collected by the right screen superheater wall temperature sensor 10 are sent to the right screen wall temperature maximum value calculation storage module 13 to calculate the right screen wall temperature maximum value and store the historical data. At the same time, the right screen wall temperature average value calculation storage module 14 is used to obtain the right screen wall temperature average value and store the historical data. The wall temperature measured by the low-temperature superheater wall temperature sensor 2 is sent to the low-temperature superheater wall temperature average value calculation storage module 15 to calculate the real-time low-temperature superheater wall temperature average value and store the historical data. The cooling water flow rate sensor 6 on the right side measures the cooling water flow rate. The flow data is calculated by the right first-stage cooling water flow differential calculation storage module 16 to obtain the right first-stage cooling water change rate; similarly, the wall temperature measured by the left screen superheater wall temperature sensor 8 is sent to the left screen wall temperature maximum value calculation storage module 17 to calculate the left screen wall temperature maximum value and store the historical data, and the left screen wall temperature average value calculation storage module 18 is used to calculate the left screen wall temperature average value and store the historical data; the cooling water flow value measured by the left first-stage cooling water flow sensor 4 is sent to the left first-stage cooling water flow differential calculation storage module 19 to calculate the left cooling water change rate. rate; then the calculated maximum value of the right side screen wall temperature, the average value of the right side screen wall temperature, the average value of the low-temperature superheater wall temperature, the right side primary cooling water change rate and the unit load are sent to the right side screen wall temperature prediction model calculation module 21 to calculate the right side screen maximum wall temperature prediction value, and sent to the right side screen wall temperature prediction limit module 23 and the right side screen wall temperature prediction temperature rise rate limit module 24 to determine whether it exceeds the limit, and the right side first or module 25 determines that any one of them exceeds the limit, that is, sends an over-temperature signal to the right cooling water / burnout air control instruction bias module 35 to generate a burnout wind bias instruction to control the right burnout wind baffle 12 opening, thereby increasing the burnout wind in advance to reduce the right side screen wall temperature. On the other hand, the right side wall temperature measured by the right side screen superheater wall temperature sensor 10 is sent to the right side screen wall temperature current value limiting module 26 and the right side screen wall temperature current value temperature rise rate limiting module 27 for judgment. The right side second or module 28 judges that any one of them exceeds the limit, that is, sends an over-temperature signal to the right side cooling water / burnout wind control instruction bias module 35 to generate a burnout wind bias instruction and a cooling water regulating valve opening bias instruction, thereby realizing the real-time control of the right side first-level cooling water regulating valve 5 and the right side burnout wind damper 12 to avoid overheating of the screen wall temperature;

[0062] Similarly, the calculated maximum value of the left-side screen wall temperature, the average value of the left-side screen wall temperature, the average value of the low-temperature superheater wall temperature, the left-side primary cooling water change rate and the unit load are sent to the left-side screen wall temperature prediction model calculation module 22 to calculate the left-side screen wall temperature prediction value, and sent to the left-side screen wall temperature prediction limit module 29 and the left-side screen wall temperature prediction temperature rise rate limit module 30 to determine whether it exceeds the limit. The left-side first or module 31 determines that any one of them exceeds the limit, and sends an over-temperature signal to the left-side cooling water / burnout air control instruction bias module 36 to generate a burnout wind bias instruction to control the left-side burnout wind baffle 11 opening, thereby increasing the burnout wind in advance to reduce the left screen wall temperature; on the other hand, the left wall temperature actually measured by the left screen superheater wall temperature sensor 8 is sent to the left screen wall temperature current value limiting module 32 and the left screen wall temperature current value temperature rise rate limiting module 33 for judgment, and the left second or module 34 judges that any one of them exceeds the limit, that is, sends an over-temperature signal to the left cooling water / burnout wind control instruction bias module 36 to generate a burnout wind bias instruction and a cooling water regulating valve opening bias instruction, thereby realizing real-time control of the left first-level cooling water regulating valve 3 and the left burnout wind damper 11 to avoid overheating of the screen wall temperature;

[0063] Finally, the average values ​​of the left and right screen wall temperatures calculated by the right screen wall temperature average value calculation storage module 14 and the left screen wall temperature average value calculation storage module 18 are sent to the burnout wind control instruction bias module 37 for judgment. When the wall temperature deviation on both sides is greater than the protection set value, a burnout wind control bias instruction is generated to control the left burnout wind damper 11 and the right burnout wind damper 12, increase the opening of the burnout wind damper on the side with higher wall temperature, and reduce the opening of the burnout wind damper on the side with lower temperature, thereby reducing the screen wall temperature deviation on both sides.

Claims

1. A platen superheater over-temperature control system for a coal-fired unit based on wall temperature prediction, characterized in that: After passing through the low-temperature superheater (1) for heat exchange, the boiler feed water is divided into two left and right paths. The left path is connected to the left screen superheater (7) through the left first-stage desuperheating water regulating valve (3) and the left first-stage desuperheating water flow sensor (4), and the right path is connected to the right screen superheater (9) through the right first-stage desuperheating water regulating valve (5) and the right first-stage desuperheating water flow sensor (6). The low-temperature superheater (1) is provided with a plurality of low-temperature superheater wall temperature sensors (2), the left screen superheater (7) is provided with a plurality of left screen superheater wall temperature sensors (8), and the right screen superheater (9) is provided with a plurality of right screen superheater wall temperature sensors (10). The left screen superheater (7) and the right screen superheater (9) are provided with a left ember wind baffle (11) and a right ember wind baffle (12) on their respective sides. The high-temperature superheater wall temperature sensor (10) is connected to the input end of the right-side screen wall temperature maximum value calculation storage module (13) and the input end of the right-side screen wall temperature average value calculation storage module (14), the low-temperature superheater wall temperature sensor (2) is connected to the input end of the low-temperature superheater wall temperature average value calculation storage module (15), and the right-side primary cooling water flow sensor (6) is connected to the input end of the right-side primary cooling water flow differential calculation storage module (16); similarly, the left-side screen superheater wall temperature sensor (8) is connected to the input end of the left-side screen superheater wall temperature maximum value calculation storage module (17) and the input end of the left-side screen superheater wall temperature average value calculation storage module (18), and the left-side primary cooling water flow sensor (4) is connected to the input end of the left-side primary cooling water flow differential calculation storage module (19); The output ends of the right side screen wall temperature maximum value calculation and storage module (13), the right side screen wall temperature average value calculation and storage module (14), the low temperature superheater wall temperature average value calculation and storage module (15), the right side first stage desuperheating water flow differential calculation and storage module (16) and the unit load data storage module (20) are connected to the input end of the right side screen wall temperature prediction model calculation module (21), and the output end of the right side screen wall temperature prediction model calculation module (21) is respectively connected to the input end of the right side screen wall temperature prediction limit module (23) and the input end of the right side screen wall temperature prediction temperature rise rate limit module (24), and the output end of the right side screen wall temperature prediction limit module (23) is connected to the input end of the right side screen wall temperature prediction model calculation module (21). The output end of the temperature rise rate limiting module (24) is connected to the input end of the first right OR module (25); the right screen superheater wall temperature sensor (10) is respectively connected to the input end of the right screen wall temperature current value limiting module (26) and the input end of the right screen wall temperature current value temperature rise rate limiting module (27); the output end of the right screen wall temperature current value limiting module (26) and the output end of the right screen wall temperature current value temperature rise rate limiting module (27) are connected to the input end of the right second OR module (28); the output end of the right first OR module (25) and the output end of the right second OR module (28) are connected to the input end of the right desuperheating water / burnout air control instruction bias module (35). The control command is generated in succession, and the output end of the right cooling water / burnout air control command bias module (35) is connected to and controls the right primary cooling water regulating valve (5) and the right burnout air damper (12); similarly, the output ends of the left screen wall temperature maximum value calculation storage module (17), the left screen wall temperature average value calculation storage module (18), the low-temperature superheater wall temperature average value calculation storage module (15), the left primary cooling water flow differential calculation storage module (19) and the unit load data storage module (20) are connected to the input end of the left screen wall temperature prediction model calculation module (22); the output ends of the left screen wall temperature prediction model calculation module (22) are respectively connected to the left screen wall temperature prediction limit The input end of the module (29) is connected to the input end of the left screen wall temperature prediction temperature rise rate limiting module (30), and the input end of the left screen wall temperature prediction limit module (29) and the output end of the left screen wall temperature prediction temperature rise rate limiting module (30) are connected to the left first OR module (31); the left screen superheater wall temperature sensor (8) is respectively connected to the input end of the left screen wall temperature current value limit module (32) and the input end of the left screen wall temperature current value temperature rise rate limiting module (33), and the output end of the left screen wall temperature current value limit module (32) and the output end of the left screen wall temperature current value temperature rise rate limiting module (33) are connected to the left second OR module (34);The output end of the left first or module (31) and the output end of the left second or module (34) are connected to the input end of the left cooling water / burnout air control instruction bias module (36) to generate a control instruction; the output end of the left cooling water / burnout air control instruction bias module (36) is connected to and controls the left primary cooling water regulating valve (3) and the left burnout air damper (11); the right screen wall temperature average value calculation storage module (14) and the left screen wall temperature average value calculation storage module (18) are connected to the burnout air control instruction bias module (37), thereby generating a burnout air control bias instruction to control the left burnout air damper (11) and the right burnout air damper (12); The above-mentioned over-temperature control system for a platen superheater of a coal-fired unit based on wall temperature prediction comprises, on the one hand, a right-side platen over-wall temperature prediction model calculation module (21) and a left-side platen over-wall temperature prediction model calculation module (22), and in combination with the predicted temperatures, a right-side platen over-wall temperature prediction limiting module (23), a right-side platen over-wall temperature prediction temperature rise rate limiting module (24), a left-side platen over-wall temperature prediction limiting module (29), and a left-side platen over-wall temperature prediction temperature rise rate limiting module (30) are used to determine whether an over-limit alarm is issued; on the other hand, it comprises a left-side platen superheater wall temperature sensor 8 and a right-side platen superheater wall temperature sensor (10), and in combination with the measured left and right wall temperatures, a right-side platen over-wall temperature current value limiting module (26), a right-side platen over-wall temperature current value temperature rise rate limiting module (27), a left-side platen over-wall temperature current value limiting module (32), and a left-side platen over-wall temperature current value temperature rise rate limiting module (33) are used to determine whether an over-limit alarm is issued; The left-side ember wind damper (11) and the right-side ember wind damper (12) belong to the boiler secondary air system and are arranged around the boiler. The ember wind dampers located on the corresponding sides of the left-side screen superheater (7) and the right-side screen superheater (9) are respectively selected to control the problem of screen superheater overheating and the problem of large wall temperature deviation caused by uneven flue gas flow on both sides.

2. The control method of the over-temperature control system of the platen superheater of a coal-fired unit based on wall temperature prediction according to claim 1 is characterized by: The real-time data of multiple screen wall temperatures collected by the right screen superheater wall temperature sensor (10) are sent to the right screen wall temperature maximum value calculation and storage module (13) to calculate the right screen wall temperature maximum value and store the historical data. At the same time, the right screen wall temperature average value calculation and storage module (14) is used to obtain the right screen wall temperature average value and store the historical data. The wall temperature measured by the low-temperature superheater wall temperature sensor (2) is sent to the low-temperature superheater wall temperature average value calculation and storage module (15) to calculate and obtain the real-time low-temperature superheater wall temperature average value and store the historical data. The cooling water flow rate measured by the right primary cooling water flow sensor (6) is used to calculate the cooling water flow rate. The flow data is calculated by the right first-stage cooling water flow differential calculation storage module (16) to obtain the right first-stage cooling water change rate; similarly, the wall temperature measured by the left screen superheater wall temperature sensor (8) is sent to the left screen wall temperature maximum value calculation storage module (17) to calculate the left screen wall temperature maximum value and store the historical data; the left screen wall temperature average value calculation storage module (18) is used to calculate the left screen wall temperature average value and store the historical data; the cooling water flow value measured by the left first-stage cooling water flow sensor (4) is sent to the left first-stage cooling water flow differential calculation storage module (19) to calculate the left cooling water change rate ; Subsequently, the calculated maximum value of the right side screen wall temperature, the average value of the right side screen wall temperature, the average value of the low temperature superheater wall temperature, the right side first stage cooling water change rate and the unit load are sent to the right side screen wall temperature prediction model calculation module (21) to calculate and obtain the right side screen wall temperature prediction value, and sent to the right side screen wall temperature prediction limit module (23) and the right side screen wall temperature prediction temperature rise rate limit module (24) to determine whether it exceeds the limit. If any one of them exceeds the limit, the over-temperature signal is sent to the right side cooling water / burnout air control command bias module (35) to generate a burnout air bias command to control the right side burnout air damper (12). opening, thereby increasing the burnout wind in advance to reduce the right screen wall temperature. On the other hand, the right side wall temperature measured by the right screen superheater wall temperature sensor (10) is sent to the right side screen wall temperature current value limiting module (26) and the right side screen wall temperature current value temperature rise rate limiting module (27) for judgment. If any one of them exceeds the limit, it is judged by the right side second or module (28) that an over-temperature signal is sent to the right side cooling water / burnout wind control command bias module (35) to generate a burnout wind bias command and a cooling water regulating valve opening bias command, thereby realizing real-time control of the right side first-stage cooling water regulating valve (5) and the right side burnout wind damper (12) to avoid over-temperature of the screen wall temperature. Similarly, the calculated maximum value of the left screen wall temperature, the average value of the left screen wall temperature, the average value of the low-temperature superheater wall temperature, the left primary cooling water change rate and the unit load are sent to the left screen wall temperature prediction model calculation module (22) to calculate the left screen maximum wall temperature prediction value, and sent to the left screen wall temperature prediction limit module (29) and the left screen wall temperature prediction temperature rise rate limit module (30) to determine whether it exceeds the limit. If any one of them exceeds the limit, the left first or module (31) is used to determine that the over-temperature signal is sent to the left cooling water / burnout air control command bias module (36) to generate a burnout air bias command to control the left burnout air damper (11 ) opening, thereby increasing the burnout wind in advance to reduce the left screen wall temperature; on the other hand, the left wall temperature actually measured by the left screen superheater wall temperature sensor (8) is sent to the left screen wall temperature current value limiting module (32) and the left screen wall temperature current value temperature rise rate limiting module (33) for judgment, and the left second or module (34) judges that any one of them exceeds the limit, that is, sends an over-temperature signal to the left cooling water / burnout wind control instruction bias module (36) to generate a burnout wind bias instruction and a cooling water regulating valve opening bias instruction, thereby realizing real-time control of the left first-level cooling water regulating valve (3) and the left burnout wind damper (11), thereby avoiding overheating of the screen wall temperature; Finally, the average values ​​of the left and right screen wall temperatures calculated by the right screen wall temperature average value calculation storage module (14) and the left screen wall temperature average value calculation storage module (18) are sent to the burnout wind control instruction bias module (37) for judgment. When the wall temperature deviation on both sides is greater than the protection set value, a burnout wind control bias instruction is generated to control the left burnout wind damper (11) and the right burnout wind damper (12), increase the opening of the burnout wind damper on the side with higher wall temperature, and reduce the opening of the burnout wind damper on the side with lower temperature, thereby reducing the screen wall temperature deviation on both sides.

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