CN112097244A - Wall temperature prediction-based screen type superheater overtemperature control system and method for coal-fired unit - Google Patents

Abstract

The system on one hand predicts the maximum value of the screen superheater wall temperature by combining an actual measurement signal, and combines the maximum value with an amplitude limiting module and a rate-increasing speed-limiting module to realize that a predicted value participates in overtemperature control; on the other hand, the measured wall temperature signal of the screen type superheater is combined with the amplitude limiting module and the rate-increasing speed-limiting module to realize that the measured value participates in the control scheme; the overtemperature control system of the screen type superheater of the coal-fired unit based on wall temperature prediction is formed by adjusting equipment such as an after-combustion air baffle, a primary desuperheating water adjusting valve and the like, so that the overtemperature active inhibition and adjustment of the wall temperature of the screen type superheater are realized; the method and the device simultaneously obtain the predicted wall temperature and the current wall temperature variation trend, realize the advanced wall temperature overtemperature active inhibition, and have important significance for improving the operation reliability of the thermal power plant, effectively reducing the risk of pipe explosion, prolonging the service life of key equipment and reducing the maintenance cost.

Description

Wall temperature prediction-based screen type superheater overtemperature control system and method for coal-fired unit

Technical Field

The invention relates to the field of automatic control of coal-fired units, in particular to a screen type superheater overtemperature control system and method of a coal-fired unit based on wall temperature prediction.

Background

With the continuous improvement of the grade of the thermal power generating unit, the improvement of power generation parameters such as steam temperature, pressure and the like is an important way for improving the efficiency of the ultra-supercritical unit, but the steam temperature rise puts higher requirements on steam pipeline materials and wall temperature control. The method is limited by the restriction of creep strength and endurance strength of materials, temperature fluctuation must be within a safety margin, parameter adjustment cannot be timely performed due to temperature measurement deviation of the water wall, the risk of tube explosion is inevitably increased when the water wall is operated at an overtemperature for a long time, and in addition, the scale is easy to fall off and block and the accident of tube explosion of the superheater is very easy to occur due to the fact that attention is not paid to monitoring of the metal temperature of the high-temperature superheater in the domestic ultra (supercritical) direct current boiler. Therefore, the real-time measurement of the wall temperature and the advance prediction and control of the wall temperature are effective ways for reducing the risk of pipe explosion.

At present, the coal burner group mainly adopts the following two schemes for measuring and controlling the wall temperature:

1) wall temperature measurement is realized by installing a large number of thermocouple wall temperature measuring points at the metal parts of the tube walls of the boiler superheater, the reheater, the water wall and the like, and an independent monitoring system or a DCS (distributed control system) system is directly connected for direct monitoring, so that the safety and stability of long-term operation of the boiler are improved; at present, the method has higher requirements on the environment around a measuring point, but the environment in a furnace is often severe, and has certain influence on the measuring precision and accuracy; meanwhile, the method can only measure the temperature value at the current moment, and only when the measuring points are over-temperature due to more measuring points, an alarm can be given out, so that the operating personnel can correspondingly adjust the boiler parameters according to actual experience. Therefore, operators can not judge a large number of wall temperature measuring points in real time in the process of monitoring the wall temperature overtemperature, and can not solve the overtemperature problem in time when overtemperature alarming is carried out, and adverse influence is brought to the operation safety of the boiler.

2) And establishing a wall temperature prediction model by a mechanism or mathematical analysis method, thereby realizing the calculation and prediction of the wall temperature. The method is complex, has more boundary parameters, can not give all boundary parameters for actual measuring points of the power plant, and needs to be continuously corrected under different conditions of the model, so that the method does not meet the requirement of on-line calculation and can not participate in closed-loop control of the wall temperature of the power plant in real time; based on a mathematical modeling analysis method, a wall temperature prediction method based on an artificial neural network is mostly adopted at present, only the influence of external factors on the wall temperature is considered, and static network structures such as a BP neural network and the like are adopted to predict the wall temperature of a boiler tube. The current wall temperature historical data, the upstream wall temperature historical data and the change rate of related factors are not considered, the contents of a time sequence prediction neural network structure, a neural network activation function and the like are not researched, the prediction structure is relatively backward, and the calculation result is relatively poor; and at present, the wall temperature prediction only stays in a display stage, and a prediction result is not used to participate in thermal power closed-loop control.

In summary, the existing wall temperature overtemperature countermeasures and prediction means only stop displaying alarm, so that the parameters are changed by means of the experience of operators, and closed-loop control is not realized. On the other hand, the wall temperature prediction model needs to be optimized, so that accurate prediction of the wall temperature is realized, and advanced closed-loop operation is realized to avoid overtemperature of the wall temperature.

Disclosure of Invention

In order to solve the problems in the prior art, the invention provides a screen type superheater overtemperature control system and method based on wall temperature prediction, and variation trends of the predicted wall temperature and the current wall temperature are obtained simultaneously, so that wall temperature overtemperature control and operation guidance are completed, advanced wall temperature overtemperature active inhibition is realized, and the system and method have important significance for improving the operation reliability of a thermal power plant, effectively reducing the risk of pipe explosion, prolonging the service life of key equipment and reducing the maintenance cost.

In order to achieve the purpose, the invention adopts the following technical scheme:

the screen type superheater overtemperature control system of the coal-fired unit based on wall temperature prediction is characterized in that boiler feed water is divided into a left path and a right path after being subjected to heat exchange by a low-temperature superheater 1, the left path is connected with a left screen type superheater 7 through a left-side first-stage desuperheating water regulating valve 3 and a left-side first-stage desuperheating water flow sensor 4, and the right path is connected with a right screen type superheater 9 through a right-side first-stage desuperheating water regulating valve 5 and a right-side first-stage desu; a plurality of low-temperature superheater wall temperature sensors 2 are arranged on the low-temperature superheater 1, a plurality of left screen superheater wall temperature sensors 8 are arranged on the left screen superheater 7, and a plurality of right screen superheater wall temperature sensors 10 are arranged on the right screen superheater 9; the left screen superheater 7 and the right screen superheater 9 are respectively provided with a left burn-out air baffle 11 and a right burn-out air baffle 12 at corresponding sides; the right screen wall temperature sensor 10 is connected with the input end of a right screen superheater wall temperature maximum value calculation storage module 13 and the input end 14 of a right screen superheater wall temperature average value calculation storage module, the low-temperature superheater wall temperature sensor 2 is connected with the input end of a low-temperature superheater wall temperature average value calculation storage module 15, and the right first-stage desuperheating water flow sensor 6 is connected with the input end of a right first-stage desuperheating water flow differential calculation storage module 16; in the same way, the left screen wall temperature sensor 8 and the left screen wall temperature maximum value calculation storage module 17 and the left screen wall temperature average value calculation storage module 18 are connected, and the left one-level desuperheating water flow sensor 4 is connected with the left one-level desuperheating water flow differential calculation storage module 19.

The output ends of the right side screen wall-passing temperature maximum value calculation storage module 13, the right side screen wall-passing temperature average value calculation storage module 14, the low-temperature superheater wall-temperature average value calculation storage module 15, the right side first-stage desuperheating water flow differential calculation storage module 16 and the unit load data storage module 20 are connected with the input end of a right side screen wall-passing temperature prediction model calculation module 21, the output end of the right side screen wall-passing temperature prediction model calculation module 21 is respectively connected with the input end of a right side screen wall-passing temperature prediction amplitude limiting module 23 and the input end of a temperature rise rate speed limiting module 24, and the output end of the wall temperature prediction amplitude limiting module 23 and the output end of the temperature rise rate speed limiting module 24 are connected with the input end of a right side; the right screen type superheater wall temperature sensor 10 is respectively connected with the input end of a right screen over-wall temperature current value amplitude limiting module 26 and the input end of a right screen over-wall temperature current value temperature rise rate speed limiting module 27, and the output end of the right screen over-wall temperature current value amplitude limiting module 26 and the output end of the right screen over-wall temperature current value temperature rise rate speed limiting module 27 are connected with the input end of a 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 with the input end of the right desuperheating water/overfire air control instruction offset module 35 to generate a control instruction, and the output end of the right desuperheating water/overfire air control instruction offset module 35 is connected with and controls the right first-stage desuperheating water regulating valve 5 and the right overfire air baffle 12; similarly, the output ends of the left screen wall-passing temperature maximum value calculation storage module 17, the left screen wall-passing temperature average value calculation storage module 18, the low-temperature superheater average temperature calculation storage module 15, the left first-stage desuperheating water flow differential calculation storage module 19 and the unit load data storage module 20 are connected with the input end of the left screen wall-passing temperature prediction model calculation module 22; the output end of the left screen over-wall temperature prediction model calculation module 22 is respectively connected with the input end of a left screen over-wall temperature prediction amplitude limiting module 29 and the input end of a left screen over-wall temperature prediction temperature rise rate speed limiting module 30, and the input end of the left screen over-wall temperature prediction amplitude limiting module 29 and the output end of the left screen over-wall temperature prediction temperature rise rate speed limiting module 30 are connected with a first left OR module 31; the left screen type superheater wall temperature sensor 8 is respectively connected with the input end of a left screen over-wall temperature current value amplitude limiting module 32 and the input end of a left screen over-wall temperature current value temperature rise rate speed limiting module 33, and the output end of the left screen over-wall temperature current value amplitude limiting module 32 and the output end of the left screen over-wall temperature current value temperature rise rate speed limiting module 33 are connected with a left second or module 34; the output end of the first or module 31 on the left side and the output end of the second or module 34 on the left side are connected with the input end of the left side temperature-reducing water/over fire air control instruction offset module 36 to generate a control instruction, and the output end of the left side temperature-reducing water/over fire air control instruction offset module 36 is connected with and controls the left side first-stage temperature-reducing water regulating valve 3 and the left side over fire air baffle plate 11; the average value of the wall-passing temperature of the right side screen is calculated and stored in the module 14, and the average value of the wall-passing temperature of the left side screen is calculated and stored in the module 18, and the module 37 is connected with the over-fire air control command offset module 37, so that an over-fire air control offset command is generated to control the left over-fire air baffle plate 11 and the right over-fire air baffle plate 12.

The control method of the screen type superheater overtemperature control system of the coal-fired unit based on wall temperature prediction comprises the following steps:

sending real-time data of the wall temperatures of the multiple screens collected by the wall temperature sensor 10 of the right screen into a maximum value calculation and storage module 13 of the wall temperature of the right screen, calculating to obtain the maximum value of the wall temperature of the right screen, storing historical data, and obtaining an average value of the wall temperature of the right screen and storing the historical data through an average value calculation and storage module 14 of the wall temperature of the right screen; sending the wall temperature measured by the low-temperature superheater wall temperature sensor 2 into a low-temperature superheater wall temperature average value calculation and storage module 15 for calculation to obtain a real-time low-temperature superheater wall temperature average value and storing historical data, wherein the desuperheating water flow data measured by the right first-stage desuperheating water flow sensor 6 is calculated by a right first-stage desuperheating water flow differential calculation and storage module 16 to obtain a right first-stage desuperheating water change rate; similarly, the wall temperature measured by the left screen type superheater wall temperature sensor 8 is sent to a left screen passing wall temperature maximum value calculation and storage module 17 to calculate the left screen passing wall temperature maximum value and store historical data, and a left screen passing wall temperature average value calculation and storage module 18 calculates a left screen passing wall temperature average value and stores the historical data; the desuperheating water flow value measured by the left first-stage desuperheating water flow sensor 4 is sent to a left first-stage desuperheating water flow differential calculation storage module 19 to calculate and obtain the change rate of the left desuperheating water; then, the calculated maximum value of the wall temperature of the right side screen, the average value of the wall temperature of the low-temperature superheater, the variation rate of the first-level desuperheating water of the right side screen and the unit load are sent to a right side screen wall temperature prediction model calculation module 21 to be calculated to obtain a predicted value of the wall temperature of the maximum value of the wall temperature of the right side screen, the predicted value is sent to a right side screen wall temperature prediction amplitude limiting module 23 and a right side screen wall temperature prediction rate speed limiting module 24 to judge whether the wall temperature of the right side screen exceeds the limit, the first or the module 25 on the right side judges whether any one of the limit exceeds the limit, namely, an overtemperature signal is sent to the right side desuperheating water/overtemperature control instruction offset module 35 to generate an ember air offset instruction to control the opening of the right side ember air baffle 12, so that the overtemperature of the right side screen is reduced by increasing the ember in advance, and on When the temperature is over-temperature, the second or module 28 on the right side judges that any one of the temperature is over-limit, namely, an over-temperature signal is sent to the right side desuperheating water/burnout air control instruction offset module 35 to generate an ember air offset instruction and a desuperheating water damper opening offset instruction, so that the real-time control of the first-stage desuperheating water regulating valve 5 on the right side and the right side ember air baffle 12 is realized, and the overtemperature of the screen wall is avoided;

similarly, the calculated maximum value of the left-side screen wall-passing temperature, the calculated average value of the low-temperature superheater wall temperature, the calculated change rate of the left-side first-level desuperheating water and the unit load are sent to a left-side screen wall-passing temperature prediction model calculation module 22 to be calculated to obtain a predicted value of the left-side screen wall-passing maximum value wall temperature, the predicted value is sent to a left-side screen wall-passing temperature prediction amplitude limiting module 29 and a left-side screen wall-passing temperature prediction speed and temperature limit module 30 to judge whether the temperature exceeds the limit, the first left-side or module 31 judges that any one of the temperature exceeds the limit, namely, sends an overtemperature signal to a left-side desuperheating water/overfire air control instruction offset module 36 to generate an ember air; on the other hand, the left wall temperature actually measured by the left screen type superheater wall temperature sensor 8 is sent to a left screen over-wall temperature current value amplitude limiting module 32 and a left screen over-wall temperature current value temperature rise rate speed limiting module 33 for judgment, and a left second or module 34 judges that any one of the over-limits sending over-temperature signals is sent to a left desuperheating water/over-fire air control instruction offset module 36 to generate an over-fire air offset instruction and a desuperheating water door opening offset instruction, so that the real-time over-temperature control of the left side desuperheating air damper 3 and the left side desuperheating air damper 11 is realized, and the over-temperature control of the left side desuperheating air damper is realized;

and finally, sending the left and right side screen wall-crossing temperature average values calculated by the right side screen wall-crossing temperature average value calculation storage module 14 and the left side screen wall-crossing temperature average value calculation storage module 18 into the burnout air control instruction offset module 37 for judgment, when the wall temperature deviation of the two sides is greater than a protection set value, generating a burnout air control offset instruction to control the left burnout air baffle plate 11 and the right burnout air baffle plate 12, opening the burnout air baffle plate on the side with higher wall temperature, and reducing the burnout air baffle plate on the side with lower temperature, so as to reduce the wall temperature deviation of the two sides.

Compared with the prior art, the invention has the following advantages:

(1) in the prior art, a large number of thermocouple wall temperature measuring points are only arranged at the metal parts of the tube walls of the positions of a boiler superheater, a reheater, a water wall and the like to realize wall temperature measurement, and an independent monitoring system or a DCS (distributed control system) directly connected for direct monitoring is utilized; the method can only measure the temperature value at the current moment, and only when the over-temperature phenomenon occurs at the measuring point, the alarm can be sent out, and the over-temperature part and the over-temperature condition can not be quickly judged due to more measuring points. On the other hand, the wall temperature overtemperature monitoring process cannot judge a large number of wall temperature measuring points in real time by operators, and when overtemperature alarm occurs, control operation processing is carried out, so that the overtemperature problem cannot be solved in time, and adverse influence is brought to the operation safety of the boiler. The invention is developed on the basis of the existing wall temperature measuring point, the wall temperature measuring point is not additionally improved, the wall temperature overtemperature prediction and overtemperature closed-loop control can be realized through the wall temperature prediction and the wall temperature control, and the risk of overtemperature of the screen passing through the wall is effectively reduced.

(2) Because flue gas in the flue flows unevenly, the wall temperature difference of the left and right platen superheaters is easy to generate, so that the overtemperature risk is caused on one side, and at present, no better control method is available except for combustion adjustment. When the risk that the left and right wall temperature difference is large is judged, the purpose of auxiliary adjustment of the flow of the flue gas is achieved by means of the adjusting effect of the upper-layer burn-out air baffle in a short time, the over-temperature risk is reduced, and the automatic control function of the burn-out air baffle is further enriched.

(3) According to the invention, the wall temperature is predicted in advance, and when the overtemperature is predicted, the overtemperature of the wall is reduced in advance through the over-fire air regulation effect. Meanwhile, according to actual temperature measurement data, real-time alarm overtemperature prevention control is carried out, real data are used for adjusting desuperheating water and burning air in real time to complete control, two-stage protection is guaranteed, overtemperature automatic protection of the screen superheater is achieved, and the method has important significance for solving the problem that the screen overtemperature and overtemperature of the coal burner unit face.

Drawings

FIG. 1 is a schematic diagram of a coal-fired unit screen superheater overtemperature control system based on wall temperature prediction.

The reference numbers and corresponding component names in the figures are illustrated as follows:

1 Low-temperature superheater

2 low-temperature superheater wall temperature sensor

3 left side first-stage desuperheating water regulating valve

4 left side one-level temperature-reducing water flow sensor

5 right first-stage desuperheating water regulating valve

6 right side one-stage temperature-reducing water flow sensor

7 left screen type superheater

8 left screen type superheater wall temperature sensor

9 right screen type over heater

10 right side screen type over heater wall temperature sensor

11 left side burn-out air baffle

12 right side burn-out air baffle

Wall temperature maximum value calculation storage module is crossed to 13 right side screen

14 average value of wall temperature is crossed to right side screen calculates storage module

15 average wall temperature calculation and storage module of low-temperature superheater

16 right-side first-stage temperature-reduction water flow differential calculation storage module

17 wall temperature maximum value calculation storage module is crossed to left screen

18 left screen wall temperature average value calculation storage module

19 left-side first-stage desuperheating water flow differential calculation storage module

20 unit load data storage module

21 right side screen wall temperature prediction model calculation module

22 left screen wall temperature prediction model calculation module

23 wall temperature prediction and amplitude limiting module is crossed to right side screen

24 temperature rise rate speed-limiting module for wall temperature prediction of right side screen

25 right first or module

26 current value amplitude limiting module for wall temperature passing of right side screen

27 current temperature rise rate speed limiting module of wall temperature is crossed to right side screen

28 right second or module

29 left side screen wall temperature prediction amplitude limiting module

30 left screen wall temperature-passing prediction temperature rise rate speed-limiting module

31 left first or module

32 left side screen wall temperature-passing current value amplitude limiting module

33 temperature rise rate speed limiting module at current value of wall temperature of left screen

34 left second or module

35 right side desuperheating water/over fire air control instruction offset module

36 left side desuperheating water/over fire air control instruction offset module

The over-fire air control command biasing module is 37.

Detailed Description

As shown in fig. 1, the screen type superheater overtemperature control system based on wall temperature prediction of the invention has the advantages that boiler feed water is divided into a left path and a right path after being subjected to heat exchange by a low-temperature superheater 1, the left side of the boiler feed water is connected with a left screen type superheater 7 through a left-side first-stage desuperheating water regulating valve 3 and a left-side first-stage desuperheating water flow sensor 4, and the right side of the boiler feed water is connected with a right screen type superheater 9 through a right-side first-stage desuperheating water regulating valve 5 and a; a plurality of low-temperature superheater wall temperature sensors 2 are arranged on the low-temperature superheater 1, a plurality of left screen superheater wall temperature sensors 8 are arranged on the left screen superheater 7, and a plurality of right screen superheater wall temperature sensors 10 are arranged on the right screen superheater 9; the left screen superheater 7 and the right screen superheater 9 are respectively provided with a left burn-out air baffle 11 and a right burn-out air baffle 12 at corresponding sides; the right screen wall temperature sensor 10 is connected with the input end of a right screen superheater wall temperature maximum value calculation storage module 13 and the input end 14 of a right screen superheater wall temperature average value calculation storage module, the low-temperature superheater wall temperature sensor 2 is connected with the input end of a low-temperature superheater wall temperature average value calculation storage module 15, and the right first-stage desuperheating water flow sensor 6 is connected with the input end of a right first-stage desuperheating water flow differential calculation storage module 16; in the same way, the left screen wall temperature sensor 8 and the left screen wall temperature maximum value calculation storage module 17 and the left screen wall temperature average value calculation storage module 18 are connected, and the left one-level desuperheating water flow sensor 4 is connected with the left one-level desuperheating water flow differential calculation storage module 19.

The output ends of the right side screen wall-passing temperature maximum value calculation storage module 13, the right side screen wall-passing temperature average value calculation storage module 14, the low-temperature superheater wall-temperature average value calculation storage module 15, the right side first-stage desuperheating water flow differential calculation storage module 16 and the unit load data storage module 20 are connected with the input end of a right side screen wall-passing temperature prediction model calculation module 21, the output end of the right side screen wall-passing temperature prediction model calculation module 21 is respectively connected with the input end of a right side screen wall-passing temperature prediction amplitude limiting module 23 and the input end of a temperature rise rate speed limiting module 24, and the output end of the wall temperature prediction amplitude limiting module 23 and the output end of the temperature rise rate speed limiting module 24 are connected with the input end of a right side; the right screen type superheater wall temperature sensor 10 is respectively connected with the input end of a right screen over-wall temperature current value amplitude limiting module 26 and the input end of a right screen over-wall temperature current value temperature rise rate speed limiting module 27, and the output end of the right screen over-wall temperature current value amplitude limiting module 26 and the output end of the right screen over-wall temperature current value temperature rise rate speed limiting module 27 are connected with the input end of a 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 with the input end of the right desuperheating water/overfire air control instruction offset module 35 to generate a control instruction, and the output end of the right desuperheating water/overfire air control instruction offset module 35 is connected with and controls the right first-stage desuperheating water regulating valve 5 and the right overfire air baffle 12; similarly, the output ends of the left screen wall-passing temperature maximum value calculation storage module 17, the left screen wall-passing temperature average value calculation storage module 18, the low-temperature superheater average temperature calculation storage module 15, the left first-stage desuperheating water flow differential calculation storage module 19 and the unit load data storage module 20 are connected with the input end of the left screen wall-passing temperature prediction model calculation module 22; the output end of the left screen over-wall temperature prediction model calculation module 22 is respectively connected with the input end of a left screen over-wall temperature prediction amplitude limiting module 29 and the input end of a left screen over-wall temperature prediction temperature rise rate speed limiting module 30, and the input end of the left screen over-wall temperature prediction amplitude limiting module 29 and the output end of the left screen over-wall temperature prediction temperature rise rate speed limiting module 30 are connected with a first left OR module 31; the left screen type superheater wall temperature sensor 8 is respectively connected with the input end of a left screen over-wall temperature current value amplitude limiting module 32 and the input end of a left screen over-wall temperature current value temperature rise rate speed limiting module 33, and the output end of the left screen over-wall temperature current value amplitude limiting module 32 and the output end of the left screen over-wall temperature current value temperature rise rate speed limiting module 33 are connected with a left second or module 34; the output end of the first or module 31 on the left side and the output end of the second or module 34 on the left side are connected with the input end of the left side temperature-reducing water/over fire air control instruction offset module 36 to generate a control instruction, and the output end of the left side temperature-reducing water/over fire air control instruction offset module 36 is connected with and controls the left side first-stage temperature-reducing water regulating valve 3 and the left side over fire air baffle plate 11; the average value of the wall-passing temperature of the right side screen is calculated and stored in the module 14, and the average value of the wall-passing temperature of the left side screen is calculated and stored in the module 18, and the module 37 is connected with the over-fire air control command offset module 37, so that an over-fire air control offset command is generated to control the left over-fire air baffle plate 11 and the right over-fire air baffle plate 12.

As shown in fig. 1, the control method of the screen type superheater overtemperature control system of the coal-fired unit based on wall temperature prediction of the invention comprises the following steps:

sending real-time data of the wall temperatures of the multiple screens collected by the wall temperature sensor 10 of the right screen into a maximum value calculation and storage module 13 of the wall temperature of the right screen, calculating to obtain the maximum value of the wall temperature of the right screen, storing historical data, and obtaining an average value of the wall temperature of the right screen and storing the historical data through an average value calculation and storage module 14 of the wall temperature of the right screen; sending the wall temperature measured by the low-temperature superheater wall temperature sensor 2 into a low-temperature superheater wall temperature average value calculation and storage module 15 for calculation to obtain a real-time low-temperature superheater wall temperature average value and storing historical data, wherein the desuperheating water flow data measured by the right first-stage desuperheating water flow sensor 6 is calculated by a right first-stage desuperheating water flow differential calculation and storage module 16 to obtain a right first-stage desuperheating water change rate; similarly, the wall temperature measured by the left screen type superheater wall temperature sensor 8 is sent to a left screen passing wall temperature maximum value calculation and storage module 17 to calculate the left screen passing wall temperature maximum value and store historical data, and a left screen passing wall temperature average value calculation and storage module 18 calculates a left screen passing wall temperature average value and stores the historical data; the desuperheating water flow value measured by the left first-stage desuperheating water flow sensor 4 is sent to a left first-stage desuperheating water flow differential calculation storage module 19 to calculate and obtain the change rate of the left desuperheating water; then, the calculated maximum value of the wall temperature of the right side screen, the average value of the wall temperature of the low-temperature superheater, the variation rate of the first-level desuperheating water of the right side screen and the unit load are sent to a right side screen wall temperature prediction model calculation module 21 to be calculated to obtain a predicted value of the wall temperature of the maximum value of the wall temperature of the right side screen, the predicted value is sent to a right side screen wall temperature prediction amplitude limiting module 23 and a right side screen wall temperature prediction rate speed limiting module 24 to judge whether the wall temperature of the right side screen exceeds the limit, the first or the module 25 on the right side judges whether any one of the limit exceeds the limit, namely, an overtemperature signal is sent to the right side desuperheating water/overtemperature control instruction offset module 35 to generate an ember air offset instruction to control the opening of the right side ember air baffle 12, so that the overtemperature of the right side screen is reduced by increasing the ember in advance, and on When the temperature is over-temperature, the second or module 28 on the right side judges that any one of the temperature is over-limit, namely, an over-temperature signal is sent to the right side desuperheating water/burnout air control instruction offset module 35 to generate an ember air offset instruction and a desuperheating water damper opening offset instruction, so that the real-time control of the first-stage desuperheating water regulating valve 5 on the right side and the right side ember air baffle 12 is realized, and the overtemperature of the screen wall is avoided;

similarly, the calculated maximum value of the left-side screen wall-passing temperature, the calculated average value of the low-temperature superheater wall temperature, the calculated change rate of the left-side first-level desuperheating water and the unit load are sent to a left-side screen wall-passing temperature prediction model calculation module 22 to be calculated to obtain a predicted value of the left-side screen wall-passing maximum value wall temperature, the predicted value is sent to a left-side screen wall-passing temperature prediction amplitude limiting module 29 and a left-side screen wall-passing temperature prediction speed and temperature limit module 30 to judge whether the temperature exceeds the limit, the first left-side or module 31 judges that any one of the temperature exceeds the limit, namely, sends an overtemperature signal to a left-side desuperheating water/overfire air control instruction offset module 36 to generate an ember air; on the other hand, the left wall temperature actually measured by the left screen type superheater wall temperature sensor 8 is sent to a left screen over-wall temperature current value amplitude limiting module 32 and a left screen over-wall temperature current value temperature rise rate speed limiting module 33 for judgment, and a left second or module 34 judges that any one of the over-limits sending over-temperature signals is sent to a left desuperheating water/over-fire air control instruction offset module 36 to generate an over-fire air offset instruction and a desuperheating water door opening offset instruction, so that the real-time over-temperature control of the left side desuperheating air damper 3 and the left side desuperheating air damper 11 is realized, and the over-temperature control of the left side desuperheating air damper is realized;

and finally, sending the left and right side screen wall-crossing temperature average values calculated by the right side screen wall-crossing temperature average value calculation storage module 14 and the left side screen wall-crossing temperature average value calculation storage module 18 into the burnout air control instruction offset module 37 for judgment, when the wall temperature deviation of the two sides is greater than a protection set value, generating a burnout air control offset instruction to control the left burnout air baffle plate 11 and the right burnout air baffle plate 12, opening the burnout air baffle plate on the side with higher wall temperature, and reducing the burnout air baffle plate on the side with lower temperature, so as to reduce the wall temperature deviation of the two sides.

Claims (4)

1. Coal-fired unit screen formula over temperature control system based on wall temperature prediction, its characterized in that: boiler feed water is divided into a left path and a right path after passing through a low-temperature superheater (1) for heat exchange, the left side of the boiler feed water is connected with a left screen type superheater (7) through a left-side first-stage desuperheating water regulating valve (3) and a left-side first-stage desuperheating water flow sensor (4), and the right side of the boiler feed water is connected with a right screen type superheater (9) through a right-side first-stage desuperheating water regulating valve (5) and a right-side first-stage desuperh; a plurality of low-temperature superheater wall temperature sensors (2) are arranged on the low-temperature superheater (1), a plurality of left screen superheater wall temperature sensors (8) are arranged on the left screen superheater (7), and a plurality of right screen superheater wall temperature sensors (10) are arranged on the right screen superheater (9); the left screen superheater (7) and the right screen superheater (9) are respectively provided with a left burn-out air baffle (11) and a right burn-out air baffle (12); the screen wall temperature sensor (10) on the right side is connected with the input end of a screen wall temperature maximum value calculation storage module (13) on the right side and the input end of a screen wall temperature average value calculation storage module (14), the wall temperature sensor (2) on the low temperature superheater is connected with the input end of a wall temperature average value calculation storage module (15) on the low temperature superheater, and the input end of a first-level desuperheating water flow differential calculation storage module (16) on the right side is connected with the input end of a first-level desuperheating water flow differential calculation storage module (6); in the same way, the left screen type superheater wall temperature sensor (8) and the left screen type superheater wall temperature maximum value calculation and storage module (17) are connected with the input end of the left screen type superheater wall temperature average value calculation and storage module (18), and the left first-stage desuperheating water flow sensor (4) is connected with the input end of the left first-stage desuperheating water flow differential calculation and storage module (19);

the output ends of a right-side screen wall-passing temperature maximum value calculation storage module (13), a right-side screen wall-passing temperature average value calculation storage module (14), a low-temperature superheater wall-passing temperature average value calculation storage module (15), a right-side primary desuperheating water flow differential calculation storage module (16) and a unit load data storage module (20) are connected with the input end of a right-side screen wall-passing temperature prediction model calculation module (21), the output end of the right-side screen wall-passing temperature prediction model calculation module (21) is respectively connected with the input end of a right-side screen wall-passing temperature prediction amplitude limiting module (23) and the input end of a temperature rise rate speed limiting module (24), and the output ends of the wall-temperature prediction amplitude limiting module (23) and the temperature rise rate speed limiting module (24) are connected with the input end of a right-; the right screen type superheater wall temperature sensor (10) is respectively connected with the input end of a right screen over-wall temperature current value amplitude limiting module (26) and the input end of a right screen over-wall temperature current value temperature rise rate speed limiting module (27), and the output end of the right screen over-wall temperature current value amplitude limiting module (26) and the output end of the right screen over-wall temperature current value temperature rise rate speed limiting module (27) are connected with the input end of a 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 with the input end of the right desuperheating water/over-fire air control instruction offset module (35) to generate a control instruction, and the output end of the right desuperheating water/over-fire air control instruction offset module (35) is connected with and controls the right first-stage desuperheating water regulating valve (5) and the right over-fire air baffle plate (12); similarly, the output ends of a left screen wall-passing temperature maximum value calculation and storage module (17), a left screen wall-passing temperature average value calculation and storage module (18), a low-temperature superheater average temperature calculation and storage module (15), a left first-stage desuperheating water flow differential calculation and storage module (19) and a unit load data storage module (20) are connected with the input end of a left screen wall-passing temperature prediction model calculation module (22); the output end of the left screen over-wall temperature prediction model calculation module (22) is respectively connected with the input end of a left screen over-wall temperature prediction amplitude limiting module (29) and the input end of a left screen over-wall temperature prediction temperature rise rate speed limiting module (30), and the input end of the left screen over-wall temperature prediction amplitude limiting module (29) and the output end of the left screen over-wall temperature prediction temperature rise rate speed limiting module (30) are connected with a first or module (31) on the left side; the left screen type superheater wall temperature sensor (8) is respectively connected with the input end of a left screen over-wall temperature current value amplitude limiting module (32) and the input end of a left screen over-wall temperature current value temperature rise rate speed limiting module (33), and the output end of the left screen over-wall temperature current value amplitude limiting module (32) and the output end of the left screen over-wall temperature current value temperature rise rate speed limiting module (33) are connected with a left second or module (34); the output end of the first left OR module (31) and the output end of the second left OR module (34) are connected with the input end of a left desuperheating water/over-fire air control instruction offset module (36) to generate a control instruction, and the output end of the left desuperheating water/over-fire air control instruction offset module (36) is connected with and controls a left first-stage desuperheating water regulating valve (3) and a left burn-out air baffle plate (11); the average value of the wall-crossing temperature of the right side screen is calculated and stored by the module (14) and the average value of the wall-crossing temperature of the left side screen is calculated and stored by the module (18) and is connected with the over-fire air control instruction offset module (37), so that an over-fire air control offset instruction is generated to control the left over-fire air baffle plate (11) and the right over-fire air baffle plate (12).

2. The coal-fired unit screen superheater overtemperature control system based on wall temperature prediction as claimed in claim 1, characterized in that: the screen type superheater overtemperature control system based on wall temperature prediction comprises a right side screen overtemperature prediction model calculation module (21) and a left side screen overtemperature prediction model calculation module (22), and judges whether overtemperature alarm is carried out or not through a right side screen overtemperature prediction amplitude limiting module (23), a right side screen overtemperature prediction temperature rate speed limiting module (24), a left side screen overtemperature prediction temperature limiting module (29) and a left side screen overtemperature prediction temperature rate speed limiting module (30) in combination with the predicted temperature; on the other hand contains left side screen formula over heater wall temperature sensor 8, right side screen formula over heater wall temperature sensor (10) to pass through wall temperature current value amplitude limiting module (26), wall temperature current value temperature rise speed limit module (27), wall temperature current value temperature limit module (32), wall temperature current value temperature rise speed limit module (33) are crossed to the left side screen to the left side wall temperature of combining its actual measurement, and whether the alarm is carried out to transfinite in the wall temperature current value temperature rise speed limit module (33) is crossed to the left side screen.

3. The coal-fired unit screen superheater overtemperature control system based on wall temperature prediction as claimed in claim 1, characterized in that: burn out air baffle (11) and right side and burn out air baffle (12) in left side belong to boiler overgrate air system, arrange around the boiler, select respectively to be located the burn out air baffle of the corresponding side of left side screen superheater (7) and right side screen superheater (9) and come the problem that screen superheater overtemperature problem and both sides flue gas flow unevenness lead to the wall temperature deviation is big.

4. The control method of the coal-fired unit screen superheater overtemperature control system based on wall temperature prediction of any one of claims 1 to 3 is as follows: the method is characterized in that:

sending real-time data of the wall temperatures of a plurality of screens collected by a wall temperature sensor (10) of a right screen into a maximum wall temperature calculation and storage module (13) of the right screen, calculating to obtain the maximum wall temperature of the right screen, storing historical data, and obtaining the average wall temperature of the right screen through an average wall temperature calculation and storage module (14) of the right screen and storing the historical data; the wall temperature measured by the low-temperature superheater wall temperature sensor (2) is sent to a low-temperature superheater wall temperature average value calculation and storage module (15) for calculation to obtain a real-time low-temperature superheater wall temperature average value, historical data are stored, and the desuperheating water flow data measured by the right-side first-stage desuperheating water flow sensor (6) is calculated by a right-side first-stage desuperheating water flow differential calculation and storage module (16) to obtain the change rate of the right-side first-stage desuperheating water; similarly, the wall temperature measured by the left screen type superheater wall temperature sensor (8) is sent to a left screen overtall temperature maximum value calculation and storage module (17) to calculate the left screen overtall temperature maximum value and store historical data, and the left screen overtall temperature average value calculation and storage module (18) calculates the left screen overtall temperature average value and stores the historical data; sending the flow value of the desuperheating water measured by the left first-stage desuperheating water flow sensor (4) into a left first-stage desuperheating water flow differential calculation storage module (19) to calculate and obtain the change rate of the left desuperheating water; then sending the calculated maximum value of the wall temperature of the right screen, the average value of the wall temperature of the low-temperature superheater, the change rate of the first-level desuperheating water of the right side and the unit load into a calculation module (21) of a prediction model of the wall temperature of the right side screen for calculation to obtain a predicted value of the wall temperature of the maximum value of the wall temperature of the right side screen, sending the predicted value into a prediction amplitude limiting module (23) of the wall temperature of the right side screen and a prediction temperature rise rate speed limit module (24) of the wall temperature of the right side screen for judgment whether the predicted value exceeds the limit, sending an overtemperature signal into a bias module (35) of the desuperheating water/overfire air control command for generating an overfire air bias command to control the opening of a right side air baffle (12) through a first module (25) on the right side, increasing the overfire air in advance to reduce the wall temperature of the right side screen, sending the actually measured right side wall temperature of a screen type The temperature rise rate speed limit module (27) at the current temperature value judges that any one of the temperature rise rate speed limit modules exceeds the limit, namely an overtemperature signal is sent to the right desuperheating water/overfire air control instruction offset module (35) to generate an ember air offset instruction and a desuperheating water damper opening offset instruction through the second or module (28) on the right side, so that the real-time control of the first-stage desuperheating water adjusting valve (5) on the right side and the ember air damper (12) on the right side is realized, and the overtemperature of the wall is avoided;

similarly, the calculated maximum value of the left-side screen over-wall temperature, the calculated average value of the low-temperature superheater wall temperature, the calculated change rate of the left-side first-level desuperheating water and the unit load are sent to a left-side screen over-wall temperature prediction model calculation module (22) to calculate to obtain a predicted value of the left-side screen over-maximum wall temperature, the predicted value is sent to a left-side screen over-wall temperature prediction amplitude limiting module (29) and a left-side screen over-wall temperature prediction temperature rise rate speed limiting module (30) to judge whether the temperature exceeds the limit, and a first or module (31) on the left side judges that any one of the temperature exceeds the limit, namely, an overtemperature signal is sent to a left-side desuperheating water/overfire air control instruction offset module (36) to generate an overfire air; on the other hand, the left wall temperature actually measured by the left screen type superheater wall temperature sensor (8) is sent into a left screen over-wall temperature current value amplitude limiting module (32) and a left screen over-wall temperature current value temperature rise rate speed limiting module (33) for judgment, and a left second or module (34) judges that any over-limit sent over-temperature signal is sent into a left desuperheating water/over-fire air control instruction offset module (36) to generate an over-fire air deviation instruction and a left side over-fire air temperature control instruction offset module (11) so as to avoid the fact that the left side over-fire air deviation instruction and the left side over-fire air temperature control door (the left side over-fire air temperature control door) adjust the temperature in real time, and therefore the left side over;

and finally, sending the left and right side screen over-wall temperature average values calculated by the right side screen over-wall temperature average value calculation storage module (14) and the left side screen over-wall temperature average value calculation storage module (18) into an over-fire air control instruction offset module (37) for judgment, and when the two side wall temperature deviations are greater than a protection set value, generating an over-fire air control offset instruction to control the left side over-fire air baffle (11) and the right side over-fire air baffle (12), opening the over-fire air baffle on the side with the higher wall temperature, and reducing the over-fire air baffle on the side with the lower temperature, so that the two side screen over-wall temperature deviation is reduced.

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