Primary air volume coupling and adjustment system for mixed coal volatile matter and ignition distance

Abstract

The present invention provides a primary air volume coupling and adjustment system for mixed coal volatile matter and ignition distance, relating to the field of energy conservation and environmental protection technology for power plants. The system uses a relational database interface to read the blended coal types and ratios established by the coal blending system, as well as the corresponding coal volatile matter, moisture, and ash parameters for the coal types in the coal yard, to calculate the pulverizer mixed coal fuel ratio. It also uses a real-time system database interface to read primary air volume and coal feed rate data from the SIS system and calculate the pulverizer mixed coal air-coal ratio. Based on experimental data, a fuzzy system is constructed to establish the coupling relationship between ignition distance, mixed coal volatile matter, and primary air volume. Using sliding window module technology, the system calculates the offset of the primary air volume set value in real time using a real-time weighted average, real-time primary air volume set value, and real-time ignition distance data. The system uses an external plug-in mode to interact with the original pulverizer control system, ensuring power plant safety.

Description

Technical Field

[0001] The present invention relates to the technical field of energy conservation and environmental protection of power plants, and in particular to a primary air volume coupling and adjustment system for mixed coal volatile matter and ignition distance. Background Art

[0002] Coal blending is used to meet the load capacity of the coal mill unit and ensure the safety and environmental protection of the combustion process. Coal blending must not affect the safe and stable operation of the unit and environmentally friendly emission standards, and ensure that serious incidents such as boiler fire extinguishing, severe slagging, large-scale high-temperature corrosion of heating surfaces, and fire and explosion of the pulverizing system caused by the quality of the coal entering the furnace do not occur. Thermal power generation mainly includes coal mills, boilers, steam turbines and other auxiliary equipment and adopts a DCS / PLC control system. Its operating parameters were mainly designed for a single type of coal in the early days. However, thermal power companies currently generally operate under mixed coal conditions, making the original control system operating parameters non-optimal and the equipment potential not fully utilized. Based on this, under the influence of the uncertain coal quality parameters of the blended coal every day and every shift, the adjustment and optimization of the control system of the thermal power unit is an important topic in terms of both depth and breadth.

[0003] Volatile matter, one of the parameters of mixed coal, affects the operation of both the pulverizer and boiler equipment. On the one hand, high-volatile coal mixtures require that the pulverizer outlet temperature setting value be not too high, otherwise it will cause the pulverizer to explode. On the other hand, high-volatile coal mixtures require that the boiler burner ignition distance be not too close, otherwise the burner nozzle will be easily burned and coked, which also requires that the pulverizer primary air volume setting value be not too small. However, current research on the adjustment and optimization of unit equipment control parameters by integrating the coal quality parameters of mixed coal, the pulverizer pulverization mechanism, and the boiler combustion mechanism lacks systematic and in-depth research. Domestic and foreign experts have conducted preliminary research on the primary air ignition distance. Through experiments, they have proposed empirical formulas for the relationship between volatile matter, primary air volume, and ignition distance. They have also experimentally studied the relationship between the influence of primary and secondary air on the burner recirculation zone and ignition distance. Experiments have also studied the relationship between the influence of primary and secondary air on the burner recirculation zone and ignition distance.

[0004] In summary, although valuable research results have been achieved in the coupling relationship between volatile matter, ignition distance and primary air volume, the following problems still exist: 1) At present, most coal blending and combustion companies rely basically on manual experience, and the degree of digitization is not enough, resulting in no real-time automatic calculation of mixed coal volatile matter, and no consideration of the impact of mixed coal volatile matter on the real-time performance of the unit; 2) At present, the coupling relationship between the volatile matter of a single coal type, ignition distance and primary air volume is mainly studied at a small number of discrete experimental points, and there is a lack of research on the relationship between continuous variables; 3) The current primary air volume set value of the pulverizer and the coal feed rate (equivalent to load) are adjusted by a simple function relationship, and further consideration needs to be given to the problem of automatic adjustment of the primary air volume for volatile matter and ignition distance. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to address the deficiencies of the above-mentioned existing technologies. On the basis of the previous automatic coal blending, a primary air volume coupling and adjustment system for mixed coal volatile matter and ignition distance is provided, which automatically adjusts the set value of the primary air volume of the coal mill. On the basis of existing automation, digitalization is used to promote the efficiency of the coal mill equipment and fully tap the potential of the coal mill equipment.

[0006] To solve the above technical problems, the technical solution adopted by the present invention is: a primary air volume coupling and adjustment system for mixed coal volatile matter and ignition distance, including a server, a communication module, and a software-programmed application program set on the server: a coal mill fuel ratio and air-coal ratio calculation module based on mixed coal conditions, a fuzzy system modeling module based on experimental data, a coal mill primary air volume set value bias module based on a sliding window, a relational database interface module, and a real-time database interface module; the server, as an external system, communicates with the original coal mill control system through downlink data frames from the communication module;

[0007] The relational database interface module constructs an interface between the plug-in application and the relational database, and realizes interaction with the relational database tables of the power plant coal blending system and the coal yard management system through the interface;

[0008] The real-time database interface module builds an interface between the plug-in application and the real-time database, and realizes interaction with the real-time database of the power plant SIS system through the interface;

[0009] The coal mill fuel ratio and air-coal ratio calculation module based on the mixed coal condition reads the coal type and ratio established by the coal blending system and the corresponding coal volatile matter, moisture and ash parameter information of the coal in the coal yard through the relational database interface module, and then calculates the coal mill mixed coal fuel ratio; reads the primary air volume and coal feed rate data of the SIS system through the real-time system database interface module and calculates the coal mill mixed coal air-coal ratio;

[0010] The fuzzy system modeling module based on experimental data constructs a fuzzy system based on the experimental data of the power plant to establish the coupling relationship between the ignition distance and the volatile matter of the mixed coal and the primary air volume;

[0011] The sliding window-based coal mill primary air volume set value offset module addresses the fact that current power plant primary air volume set values ​​do not consider the coupling relationship between mixed coal volatile matter and ignition distance. Based on the coupling functional relationship between ignition distance, mixed coal volatile matter, and primary air volume, the module uses sliding window technology to calculate the offset of the primary air volume set value. By adjusting the primary air volume set value, the primary air velocity entering the furnace is changed.

[0012] Preferably, the coal mill fuel ratio and air-coal ratio calculation module based on the mixed coal condition reads the coal type and ratio established by the coal blending system and the corresponding coal volatile matter, moisture and ash parameter information of the coal type in the coal yard through the relational database interface module, and then calculates the coal mill mixed coal fuel ratio; reads the coal mill primary air volume and coal feed rate parameter data of the SIS system through the real-time system database interface module and calculates the coal mill mixed coal air-coal ratio. The specific method is:

[0013] Calculate the weighted mean of coal quality parameters such as volatile matter, ash and moisture after coal mixing in the coal mill , as shown in the following formula:

[0014] (1);

[0015] Where, is the number of coal types in the coal mixture of the coal mill, Respectively Volatile matter, ash and moisture content of each blended coal, For the The proportion of coal types in the coal blending process;

[0016] Calculate the coal-fuel ratio and air-coal ratio of the coal mill;

[0017] The coal-to-fuel ratio of the pulverizer is the ratio of the coke content to the volatile content in the unit coal, as shown in the following formula:

[0018] (2);

[0019] Where, is the coal-fuel ratio of the pulverizer, Fixed carbon content of coal blend on air-dried basis;

[0020] The air-to-coal ratio of the coal mill is the ratio of the primary air volume fed into the coal mill to the amount of pulverized coal entering, as shown in the following formula:

[0021] (3);

[0022] Where, is the air-coal ratio of the coal mixture in the pulverizer, is the total amount of primary hot air and cold air of the coal mill, is the coal feeding rate of the coal mill, It is the conversion efficiency of coal at the inlet and outlet of the coal mill.

[0023] Preferably, the method for constructing the fuzzy system modeling module based on experimental data to establish a continuous functional relationship between the ignition distance, the volatile matter of the mixed coal, and the primary air volume is:

[0024] Step S1: Using the air-coal ratio and fuel ratio obtained from the power plant experiment as input vectors and the ignition distance as the output variable, a set of input and output data pairs of the fuzzy system is constructed, as shown in the following formula:

[0025] (4);

[0026] Where, Air-coal ratio and fuel ratio vector, is the ignition distance variable, is the number of sample sets;

[0027] Step S2: Set the domain interval and fuzzify the variables within the domain interval;

[0028] Set the air-coal ratio and fuel ratio vectors Distance to fire variable The domain intervals are , and , air-coal ratio and fuel ratio vector Two variables in 、 As the premise attribute of the fuzzy system, the ignition distance variable As the conclusion attribute of the fuzzy system; air-coal ratio and fuel ratio vector The domain of each variable in is evenly divided into fuzzy sets, air-coal ratio and fuel ratio vector and fire distance variables The corresponding fuzzy sets are and , Fire distance variable The number of fuzzy sets divided by the domain of discourse and the membership function assigned to each fuzzy set;

[0029] Step S3: Use a relational database table to record the data pairs of air-coal ratio, fuel ratio and ignition distance, and convert this ordinary record into a fuzzy record;

[0030] Use a relational database table to record the air-coal ratio, fuel ratio and ignition distance data pairs. Each row of the table represents a record, and each column of the table is an attribute of the record. Represents a collection of attributes, Indicates the first records, using To describe a set of Records of attribute information, namely:

[0031] (5);

[0032] use Represents premise attributes The fuzzy set of Indicates conclusion attribute The fuzzy set of and ;for The membership value attribute of Define a set of Fuzzy record of attribute information:

[0033] (6);

[0034] Where, For the The records corresponding to Membership function of attribute set;

[0035] By using the above formulas (5) and (6), The fuzzy record of attribute information is stored in another relational record table, in which the columns represent the attributes. , rows represent records with values ​​between [0,1].

[0036] Step S4: creating a fuzzy rule base using a nested algorithm;

[0037] First, through the nested double loop traversal by the premise attributes and The corresponding fuzzy set and All fuzzy subspaces composed of ;

[0038] Then, for the premise attributes and Any fuzzy subspace determined, its conclusion attribute Selected fuzzy sets, by looping through selected fuzzy sets Each fuzzy set in is calculated by the following formula:

[0039] (7);

[0040] Where, and Respectively represent The membership function value of records; Decide which fuzzy set to choose in the conclusion fuzzy subspace ;

[0041] Finally, after the fuzzy subspace is selected based on the maximum support, the following IF-THEN fuzzy rule base is constructed:

[0042] (8);

[0043] Where, For the fuzzy rules, is the number of rules in the fuzzy rule base.

[0044] Step S5: generating a fuzzy model based on the fuzzy rule base;

[0045] For step S4 Fuzzy rules, using single-value fuzzification, multiplication operation, and weighted average defuzzification, the fuzzy model can be obtained as follows:

[0046] (9);

[0047] Where, is the ignition distance calculation output of the fuzzy model, It is Rules in fuzzy membership function The corresponding maximum value Value point, that is The corresponding time value.

[0048] Step S6: using the gradient descent method to adjust the parameters of the fuzzy model;

[0049] The fuzzy model output of formula (9) is adjusted to the following vector multiplication form:

[0050] (10);

[0051] Where, is the fuzzy model parameter vector, is the normalized vector of membership function values, where The definition is as follows:

[0052] (11);

[0053] The target error function E formed by the experimental sample data formula (4) is defined as:

[0054] (12);

[0055] Where, For the The experimental data of the ignition distance corresponding to the records, is the air-coal ratio and fuel ratio vector Take the first When the data is recorded, the ignition distance calculation data of the fuzzy model;

[0056] The gradient descent algorithm is used to minimize the target error function (12), thereby dynamically optimizing and adjusting the parameters of the fuzzy model to improve the modeling accuracy of the fuzzy model;

[0057] Fuzzy model parameters The update formula is as follows:

[0058] (13);

[0059] Where, is the number of iterations, Is a positive learning rate; the learning rate The initial value of is set to 0.02, The initial value of is determined by the fuzzy rules extracted from steps 1 to 6.

[0060] Step S7: Adjust the number of fuzzy sets in the input-output space; improve the prediction accuracy of the fuzzy model by increasing the number of fuzzy sets in the input-output space.

[0061] Preferably, the sliding window-based coal mill primary air volume set value offset module calculates the offset of the primary air volume set value based on the ignition distance, the volatile matter of the mixed coal and the primary air volume calculation data by using the sliding window technology, thereby optimizing the ignition distance and making the ignition distance reasonable; comprising:

[0062] First, by , Real-time value determines the 2*2 sliding window; , Real-time value and calculate the ignition distance through formula (9) ,if and The corresponding ignition distance The following strategy is used to calculate the offset compensation of the primary air volume set value when the sliding window is not in the range :

[0063] (14);

[0064] Where, The corresponding air-coal ratio is the maximum and minimum ignition distance in the 2*2 sliding window. The corresponding primary air volume setting value; For real-time The corresponding primary air volume setting value of the original control system; Ignition distance determined for the four test points in the 2*2 sliding window;

[0065] if and The corresponding ignition distance Within the sliding window, calculate the offset compensation of the primary air volume set value according to the following formula: :

[0066] (15);

[0067] Where, The corresponding air-coal ratio is the maximum ignition distance in the first and second rows of the 2*2 sliding window. The corresponding primary air volume setting value; They are The corresponding upper and lower bounds of the sliding window.

[0068] Preferably, the server as an external system communicates with the original coal mill control system through downlink data frames of the communication module to set the bias of the primary air volume setting value of the coal mill control system; the original coal mill control system sends a heartbeat switch request frame to the server, and the server simulates a heartbeat signal through a response of a programmed digital switch signal (0, 1), and the original coal mill control system detects whether the communication of the external system is normal through the heartbeat frame response; when the original coal mill control system fails to detect the heartbeat frame response within the set time, the external system is automatically cut off and switched to the original setting value signal of the original coal mill control system.

[0069] The beneficial effects of adopting the above technical solution are as follows: the primary air volume coupling and adjustment system for mixed coal volatile matter and ignition distance provided by the present invention is aimed at the problems of cracking, deformation, burning and coking in the operation of the burner of the current power plant hedge boiler. (1) First, considering that thermal power plants generally operate under mixed coal conditions, the mixed coal fuel ratio and air-coal ratio calculation process is given based on the mixed coal volatile matter and the primary air volume.

[0070] (2) The coupling relationship between the volatile matter of mixed coal, ignition distance and primary air volume was analyzed, revealing the irrationality of the current planning of the primary air volume set value in thermal power plants.

[0071] (3) For different mixed coal volatile matter parameters, fuzzy modeling and sliding window technology are proposed for the first time to plan the feedforward compensation of the primary air volume set value offset of the pulverizer control system, so as to optimize the ignition distance and avoid the occurrence of boiler burner burnout and coking failure.

[0072] (4) Each module proposed in the present invention is implemented on an external server, which is connected to the original coal mill primary air volume control system by means of communication. No changes are made to the original control system hardware and program. Only the original manual experience-based bias method is added and modified into an algorithm-based external computer control and adjustment implementation method. Heartbeat pulses and non-disturbance switching are used for the external server to ensure system security. Once a communication failure or other fault occurs, the original control system can also operate normally.

[0073] The proposed primary air volume coupling and adjustment system for mixed coal volatile matter and ignition distance addresses current problems with burners in power plant hedge boilers, such as cracking, deformation, burning, and coking. First, given that thermal power plants generally operate under mixed coal conditions, the calculation process for the mixed coal fuel ratio and air-to-coal ratio, as well as the causes of these problems, is presented. Then, the coupling relationship between mixed coal volatile matter, ignition distance, and primary air volume is analyzed, revealing the irrationality of current primary air volume setpoint planning in thermal power plants. Finally, under different operating conditions with mixed coal parameters, a feedforward compensation plan for the primary air volume setpoint offset in the coal mill control system using fuzzy modeling and sliding window technology is proposed for the first time, achieving the goal of optimizing the ignition distance and avoiding boiler burner burning and coking problems.

[0074] In summary, the present invention has expectedly great economic value, social value and scientific value. BRIEF DESCRIPTION OF THE DRAWINGS

[0075] Figure 1 A diagram illustrating a technical implementation route for primary air volume adjustment provided by an embodiment of the present invention;

[0076] Figure 2 A hardware process diagram of the automatic coal blending system for a power plant provided by an embodiment of the present invention;

[0077] Figure 3 This is a diagram of the software interface of the automatic coal blending system for a power plant provided by an embodiment of the present invention;

[0078] Figure 4 A schematic diagram of the primary air volume ignition distance provided by an embodiment of the present invention;

[0079] Figure 5 A diagram showing the relationship between the ignition distance, the air-to-coal ratio, and the fuel ratio provided in an embodiment of the present invention;

[0080] Figure 6 A flow chart of creating a fuzzy rule base using a nested algorithm provided in an embodiment of the present invention;

[0081] In the figure: 1. Coal bunker; 2. Coal feeder; 3. Coal mill; 4. Conveyor belt; 5. Primary air flow of burner; 6. Ignition distance; 7. Lower mixing zone; 8. Upper mixing zone; 9. Primary air center air flow; 10. Boiler furnace. DETAILED DESCRIPTION

[0082] The following embodiments of the present invention are described in further detail with reference to the accompanying drawings and examples. The following examples are used to illustrate the present invention but are not intended to limit the scope of the present invention.

[0083] In this embodiment, a primary air volume coupling and adjustment system for mixed coal volatile matter and ignition distance is provided. Figure 1 As shown, it includes a server, a communication module, and a calculation module for the coal mill fuel ratio and air-coal ratio under mixed coal conditions, a fuzzy system modeling module based on experimental data, a coal mill primary air volume setting value offset module based on a sliding window, a relational database interface module, and a real-time database interface module. The server, as an external system, communicates with the original coal mill control system through downlink data frames of the communication module to set the offset of the primary air volume setting value of the coal mill control system, eliminating the traditional manual increase of the offset. The original coal mill control system sends a heartbeat switch request frame to the server. The server simulates a heartbeat signal through a response of a programmed digital switch signal (0, 1). The original coal mill control system detects whether the communication of the external system is normal through the heartbeat frame response. When the original coal mill control system fails to detect the heartbeat frame response within a set time, the external system is automatically disconnected and switched to the set value signal of the original coal mill control system.

[0084] In this embodiment, the relational database interface module constructs an interface between the plug-in application and the relational database, and realizes interaction with the relational database tables of the power plant coal blending system and the coal yard management system through the interface;

[0085] The real-time database interface module builds an interface between the plug-in application and the real-time database, and realizes interaction with the real-time database of the power plant SIS system through the interface;

[0086] The coal mill fuel ratio and air-coal ratio calculation module based on the mixed coal condition reads the coal type and ratio established by the coal blending system and the corresponding coal volatile matter, moisture and ash parameter information of the coal in the coal yard through the relational database interface module, and then calculates the coal mill mixed coal fuel ratio; reads the primary air volume and coal feed rate data of the SIS system through the real-time system database interface module and calculates the coal mill mixed coal air-coal ratio;

[0087] The experimental data-based fuzzy system modeling module addresses the problem of the lack of quantitative description of the relationship between ignition distance, mixed coal volatile matter, and primary air volume. Based on the power plant experimental data, a fuzzy system is constructed to establish the functional relationship between ignition distance, mixed coal volatile matter, and primary air volume, laying the foundation for primary air volume adjustment.

[0088] The sliding window-based coal mill primary air volume set value offset module addresses the fact that current power plant primary air volume set values ​​do not consider the coupling relationship between mixed coal volatile matter and ignition distance. Based on the functional relationship between ignition distance, mixed coal volatile matter, and primary air volume, the module uses sliding window technology to calculate the offset of the primary air volume set value. By adjusting the primary air volume set value, the primary air velocity entering the furnace is changed. The air velocity changes the distance to the fire, preventing the ignition distance from being too close to the burner nozzle or from being too far, which results in low combustion efficiency.

[0089] In this embodiment, the primary air volume coupling and adjustment system for mixed coal volatile matter and ignition distance is implemented as follows: Figure 1 Based on the coal type parameter information provided by the coal yard coal type management system, the physical hardware and software corresponding to the power plant automatic coal blending system are as follows. Figure 2 and Figure 3 As shown, the blended coal is simultaneously delivered from the coal yard to the coal bunker 1 via two stackers and reclaimers and two conveyor belts 4. The mixed coal in the bunker 1 is then fed to the pulverizer 3 for grinding via the coal feeder 2. The coal intake of the pulverizer 2 is automatically adjusted based on the power generation load, while the primary air volume setpoint of the pulverizer 3 is automatically adjusted based on the air-to-coal ratio function. While power plants currently widely utilize blended coal blending technology, the original pulverizer control system utilizes control logic designed for a single type of coal, without considering the impact of changes in the volatile content of the blended coal on boiler combustion performance. Based on this, the present invention analyzes the coupling relationship between the volatile content of the blended coal, the ignition distance, and the primary air volume of the pulverizer, building on the automatic coal blending system, to adjust the primary air volume setpoint.

[0090] In this embodiment, based on the coal mill fuel ratio and air-coal ratio calculation module under mixed coal conditions, the specific method for calculating the coal mill mixed coal fuel ratio and air-coal ratio is as follows:

[0091] Calculate the weighted mean of coal quality parameters such as volatile matter, ash and moisture after coal mixing in the coal mill , as shown in the following formula:

[0092] (1);

[0093] Where, is the number of coal types in the coal mixture of the coal mill, Respectively Volatile matter, ash and moisture content of each blended coal, For the The proportion of coal types in the coal blending process;

[0094] Calculate the coal-fuel ratio and air-coal ratio of the coal mill;

[0095] The coal-to-fuel ratio of the pulverizer is the ratio of the coke content to the volatile content in the unit coal, as shown in the following formula:

[0096] (2);

[0097] Where, is the coal-fuel ratio of the pulverizer, Fixed carbon content of coal blend on air-dried basis;

[0098] The air-to-coal ratio of the coal mill is the ratio of the primary air volume fed into the coal mill to the amount of pulverized coal entering, as shown in the following formula:

[0099] (3);

[0100] Where, is the air-coal ratio of the coal mixture in the pulverizer, is the total amount of primary hot air and cold air of the coal mill, is the coal feeding rate of the coal mill, It is the conversion efficiency of coal at the inlet and outlet of the coal mill.

[0101] Ignition distance is a critical physical parameter in the combustion process of a hedge boiler. If the ignition point is too close to the burner nozzle, it can damage the nozzle or cause coking. If the ignition point is too far from the nozzle, the combustion process will be delayed, causing the pulverized coal to leave the furnace before it is fully burned, increasing mechanical heat losses from incomplete combustion. Furthermore, delayed ignition can cause the flame center to shift upward, potentially overheating the flue gas in the furnace outlet area and the high-temperature superheater and reheater tubes located in this area, affecting the temperature regulation of the main steam and reheat steam. Over time, this can lead to sudden accidents such as tube bursts.

[0102] like Figure 4 As shown, after the primary airflow 5 from the burner enters the furnace, a primary air center airflow 9 is formed. This airflow moves relative to the gas in the furnace 10 of the boiler. Due to the frictional entrainment, a mixing zone is formed in the area adjacent to the primary airflow and the furnace gas. This mixing zone is divided into an upper mixing zone 8 and a lower mixing zone 7. As the process expands to a certain range, the temperature in the mixing zone reaches the ignition point, causing the pulverized coal to burn, and part of the generated heat is transferred to the center of the airflow. If the ignition point requirements of the pulverized coal volatile matter and the mixture in the center of the airflow can be met, the ignition point range will rapidly expand to the entire airflow cross section. The distance between the ignition point of the entire airflow cross section and the burner nozzle is the ignition distance 6.

[0103] Ignition distance and air-coal ratio , fuel ratio The experimental simulation relationship between Figure 5 As shown in Figure 1, it is a nonlinear function. When the primary air volume remains constant, the ignition distance decreases as the volatile matter increases; when the volatile matter remains constant, the ignition distance does not decrease as the primary air volume decreases.

[0104] In this embodiment, the method for constructing the fuzzy system modeling module based on experimental data to establish a continuous functional relationship between the ignition distance, the volatile matter of the mixed coal, and the primary air volume is as follows:

[0105] Step S1: Using the air-coal ratio and fuel ratio obtained from the power plant experiment as input vectors and the ignition distance as the output variable, a set of input and output data pairs of the fuzzy system is constructed, as shown in the following formula:

[0106] (4);

[0107] Where, Air-coal ratio and fuel ratio vector, is the ignition distance variable, is the number of sample sets;

[0108] Step S2: Set the domain interval and fuzzify the variables within the domain interval;

[0109] Set the air-coal ratio and fuel ratio vectors Distance to fire variable The domain intervals are , and , air-coal ratio and fuel ratio vector Two variables in 、 As the premise attribute of the fuzzy system, the ignition distance variable As the conclusion attribute of the fuzzy system; air-coal ratio and fuel ratio vector The domain of each variable in is evenly divided into fuzzy sets, air-coal ratio and fuel ratio vector and fire distance variables The corresponding fuzzy sets are and , Fire distance variable The number of fuzzy sets divided by the domain of discourse and the membership function assigned to each fuzzy set;

[0110] Step S3: Use a relational database table to record the data pairs of air-coal ratio, fuel ratio and ignition distance, and convert this ordinary record into a fuzzy record;

[0111] Use a relational database table to record the air-coal ratio, fuel ratio and ignition distance data pairs. Each row of the table represents a record, and each column of the table is an attribute of the record. Represents a collection of attributes, Indicates the first records, using To describe a set of Records of attribute information, namely:

[0112] (5);

[0113] use Represents premise attributes The fuzzy set of Indicates conclusion attribute The fuzzy set of and ;for The membership value attribute of Define a set of Fuzzy record of attribute information:

[0114] (6);

[0115] Where, For the The records corresponding to Membership function of attribute set;

[0116] By using the above formulas (5) and (6), The fuzzy record of attribute information is stored in another relational record table, in which the columns represent the attributes. , rows represent records with values ​​between [0,1].

[0117] Step S4: creating a fuzzy rule base using a nested algorithm;

[0118] The fuzzy rule base is the basis for establishing a fuzzy system, which can be obtained through expert knowledge or experimental data. The following is the process of establishing a fuzzy rule base based on experimental data, such as Figure 6 As shown;

[0119] First, through the nested double loop traversal by the premise attributes and The corresponding fuzzy set and All fuzzy subspaces composed of ;

[0120] Then, for the premise attributes and Any fuzzy subspace determined, its conclusion attribute Selected fuzzy sets, by looping through selected fuzzy sets Each fuzzy set in is calculated by the following formula:

[0121] (7);

[0122] Where, and Respectively represent The membership function value of records; Decide which fuzzy set to choose in the conclusion fuzzy subspace ;

[0123] Finally, after the fuzzy subspace is selected based on the maximum support, the following IF-THEN fuzzy rule base is constructed:

[0124] (8);

[0125] Where, For the fuzzy rules, is the number of rules in the fuzzy rule base.

[0126] Step S5: generating a fuzzy model based on the fuzzy rule base;

[0127] For step S4 Fuzzy rules, using single-value fuzzification, multiplication operation, and weighted average defuzzification, the fuzzy model can be obtained as follows:

[0128] (9);

[0129] Where, is the ignition distance calculation output of the fuzzy model, It is Rules in fuzzy membership function The corresponding maximum value Value point, that is The corresponding time value.

[0130] Step S6: using the gradient descent method to adjust the parameters of the fuzzy model;

[0131] The fuzzy model output of formula (9) is adjusted to the following vector multiplication form:

[0132] (10);

[0133] Where, is the fuzzy model parameter vector, is the normalized vector of membership function values, where The definition is as follows:

[0134] (11);

[0135] The target error function E formed by the experimental sample data formula (4) is defined as:

[0136] (12);

[0137] Where, For the The experimental data of the ignition distance corresponding to the records, is the air-coal ratio and fuel ratio vector Take the first When the data is recorded, the ignition distance calculation data of the fuzzy model;

[0138] The gradient descent algorithm is used to minimize the target error function (12), thereby dynamically optimizing and adjusting the parameters of the fuzzy model to improve the modeling accuracy of the fuzzy model;

[0139] Fuzzy model parameters The update formula is as follows:

[0140] (13);

[0141] Where, is the number of iterations, Is a positive learning rate; the learning rate The initial value of is set to 0.02, The initial value of is determined by the fuzzy rules extracted from steps 1 to 6.

[0142] Step S7: Adjust the number of fuzzy sets in the input-output space; improve the prediction accuracy of the fuzzy model by increasing the number of fuzzy sets in the input-output space.

[0143] In step S1, the number of fuzzy sets is generally determined based on the distribution of data samples in the corresponding domain. The initial fuzzy area is determined. Since the fuzzy model is a universal approximator, its performance can be improved by adding new fuzzy sets to the input and output spaces. After optimizing the fuzzy model parameters using step 6, the prediction accuracy of the fuzzy model still does not reach the expected prediction accuracy. Consider increasing the number of fuzzy sets in the input and output spaces to improve the prediction accuracy of the fuzzy model.

[0144] This embodiment uses the root mean square error as the performance indicator for evaluating the fuzzy model, and adjusts the number of fuzzy sets in the input and output space based on this performance indicator:

[0145] (14);

[0146] Where, is the root mean square error, is the number of input and output data pairs, For the The true output of the samples, For the The predicted output of samples.

[0147] In this embodiment, the sliding window-based coal mill primary air volume set value offset module calculates the offset of the primary air volume set value based on the ignition distance, the volatile matter of the mixed coal, and the calculated data of the primary air volume using the sliding window technology, thereby optimizing the ignition distance to make the ignition distance reasonable; including:

[0148] First, take the experimental data points in Table 1 as an example. , Real-time values ​​(such as Between 2 and 1, Between 3 and 2), the sliding window in Table 1 can be determined.

[0149] Table 1 Experimental data points of ignition distance, air-coal ratio and fuel ratio

[0150]

[0151] Depend on , Real-time value and calculate the ignition distance through formula (9) ,if and The corresponding ignition distance The following strategy is used to calculate the offset compensation of the primary air volume set value when the sliding window is not in the range :

[0152] (15);

[0153] Where, The corresponding air-coal ratio is the maximum and minimum ignition distance in the 2*2 sliding window. The corresponding primary air volume setting value; For real-time The corresponding primary air volume setting value of the original control system; The ignition distance determined for the 4 test points in the 2*2 sliding window; (as shown in Table 1 , , , );

[0154] if and The corresponding ignition distance Within the sliding window, calculate the offset compensation of the primary air volume set value according to the following formula: :

[0155] (16);

[0156] Where, The corresponding air-coal ratio is the maximum ignition distance in the first and second rows of the 2*2 sliding window. The corresponding primary air volume setting value; They are The corresponding sliding window upper and lower bounds (as shown in Table 1 , ).

[0157] The reason why the present invention selects the maximum and minimum ignition distances in the 2*2 sliding window and the corresponding air-coal ratio is The corresponding maximum set value of primary air volume The calculation takes into account that the original coal mill control system does not consider the influence of mixed coal volatile matter on the ignition distance. By appropriately increasing the primary air volume and increasing the wind speed, the ignition distance is appropriately increased, thereby reducing the coking phenomenon of volatile matter on the burner nozzle.

[0158] This embodiment takes a 350MW hedge boiler unit among the four units of a power plant as an example to illustrate the coupling and adjustment process of primary air volume for mixed coal volatile matter and ignition distance. Its technical route is as follows: Figure 1 shown.

[0159] Real-time data acquisition: Figure 1 The coal blending and combustion optimization system stores the coal blending and stoking plans for each shift and each day in the relational database SQL Server according to timestamps. Therefore, the system of the present invention can access the corresponding blended coal quality parameter information through the database interface and calculate the real-time volatile matter value and fuel ratio. Furthermore, the real-time coal quantity of the coal feeder can be obtained through the real-time database SIS system, and the real-time primary air volume set value and air-to-coal ratio can be further obtained through the air-to-coal ratio curve. Finally, based on the real-time volatile matter and real-time primary air volume set value, the fuzzy system of the present invention can be used to determine the real-time ignition distance.

[0160] Primary air volume offset calculation: First, use the obtained fuel ratio to determine the adjacent upper and lower bounds in Table 1 to determine the row position of the 2x2 sliding window. Similarly, use the obtained air-to-coal ratio to determine the adjacent upper and lower bounds in Table 1 to determine the column position of the 2x2 sliding window. Then, calculate the offset of the primary air volume setpoint and sum it with the original primary air volume setpoint of the coal mill control system through the communication module to obtain the new primary air volume setpoint.

[0161] Table 2 shows the experimental data and test results. First, by reading the mixed coal quality database, the weighted average volatile matter, moisture, and volatility of the corresponding mixed coal can be obtained, and the corresponding fuel ratios can be calculated to be 4.82 and 1.15, respectively. Then, the corresponding air-to-coal ratios can be calculated to be 1.72 and 0.65; further, the fuzzy system can be used to calculate the corresponding primary air volume ignition distances to be 3.98 and 2.06, respectively. Finally, the air-to-coal ratios corresponding to the primary air volume feedforward compensation values ​​can be calculated to be 0.28 and -0.15, respectively. The experiment shows that without changing the original air-to-coal ratio setting of the pulverizer control system, the proposed strategy automatically increases the offset compensation amount, so that the new setting not only takes into account the impact of the mixed coal volatile matter but also avoids the problem of excessive adjustment of the primary air volume and affecting combustion efficiency.

[0162] Table 2 Experimental data and test data

[0163]

[0164] Take the first set of test data as an example to illustrate the calculation process. , it can be determined that the sliding window is the upper left position of Table 2, and the ignition distance at this time is Within the sliding window range, the offset of the primary air volume setting value is calculated using formula (16); and since From the upper bound of the sliding window So the maximum ignition distance test data point in the first row of the sliding window is selected for calculation (at this time With current real-time The difference is 0.28, ), that is, using the experimental data points Corresponding As the current real-time primary air volume setting value, , .

[0165] The reason for using The current real-time primary air volume setting value is based on the following considerations: 1) The corresponding time The original coal mill control system did not consider the influence of volatile matter and ignition distance, so it needed to be adjusted; 2) Test data points Corresponding It is a comprehensive setting value that adds the influence of volatile matter and ignition distance, which is relatively accurate; 3) Use within an allowable small range Alternative It is beneficial to avoid the problem of coking of the burner nozzle (increasing the primary air volume increases the primary air speed, which ignites relatively far away from the burner nozzle, solving the current problem of burner coking), and it is also beneficial to reduce the continuous fluctuation of the set value, which causes the primary air door to swing continuously and mechanical wear and tear to damage the air door prematurely.

[0166] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope defined by the claims of the present invention.

Claims

1. A primary air volume coupling and adjustment system for mixed coal volatile matter and ignition distance, characterized by: The system comprises a server, a communication module, and a calculation module for the coal mill fuel ratio and the air-coal ratio based on the mixed coal condition, a fuzzy system modeling module based on experimental data, a coal mill primary air volume setting value bias module based on a sliding window, a relational database interface module, and a real-time database interface module, which are set on the server through software programming to form an application program; the server, as an external system, communicates with the original coal mill control system through downlink data frames of the communication module; The relational database interface module constructs an interface between the plug-in application and the relational database, and realizes interaction with the relational database tables of the power plant coal blending system and the coal yard management system through the interface; The real-time database interface module builds an interface between the plug-in application and the real-time database, and realizes interaction with the real-time database of the power plant SIS system through the interface; The coal mill fuel ratio and air-coal ratio calculation module based on the mixed coal condition reads the coal type and ratio established by the coal blending system and the corresponding coal volatile matter, moisture and ash parameter information of the coal in the coal yard through the relational database interface module, and then calculates the coal mill mixed coal fuel ratio; reads the primary air volume and coal feed rate data of the SIS system through the real-time system database interface module and calculates the coal mill mixed coal air-coal ratio; The fuzzy system modeling module based on experimental data constructs a fuzzy system based on the experimental data of the power plant to establish the coupling relationship between the ignition distance and the volatile matter of the mixed coal and the primary air volume; The sliding window-based coal mill primary air volume set value offset module addresses the fact that current power plant primary air volume set values ​​do not consider the coupling relationship between mixed coal volatile matter and ignition distance. Based on the coupling functional relationship between ignition distance, mixed coal volatile matter, and primary air volume, the module uses sliding window technology to calculate the offset of the primary air volume set value. By adjusting the primary air volume set value, the primary air velocity entering the furnace is changed.

2. The primary air volume coupling and adjustment system for mixed coal volatile matter and ignition distance according to claim 1 is characterized in that: The coal mill fuel ratio and air-coal ratio calculation module based on mixed coal conditions reads the coal types and ratios established by the coal blending system and the corresponding coal volatile matter, moisture and ash parameter information of the coal types in the coal yard through the relational database interface module, and then calculates the coal mill mixed coal fuel ratio; reads the coal mill primary air volume and coal feed rate parameter data of the SIS system through the real-time system database interface module and calculates the coal mill mixed coal air-coal ratio. The specific method is as follows: Calculate the weighted mean of coal quality parameters such as volatile matter, ash and moisture after coal mixing in the coal mill , as shown in the following formula: （1）； Where, is the number of coal types in the coal mixture of the coal mill, Respectively Volatile matter, ash and moisture content of each blended coal, For the The proportion of coal types in the coal blending process; Calculate the coal-fuel ratio and air-coal ratio of the coal mill; The coal-to-fuel ratio of the pulverizer is the ratio of the coke content to the volatile content in the unit coal, as shown in the following formula: （2）； Where, is the coal-fuel ratio of the pulverizer, Fixed carbon content of coal blend on air-dried basis; The air-to-coal ratio of the coal mill is the ratio of the primary air volume fed into the coal mill to the amount of pulverized coal entering, as shown in the following formula: （3）； Where, is the air-coal ratio of the coal mixture in the pulverizer, is the total amount of primary hot air and cold air of the coal mill, is the coal feeding rate of the coal mill, It is the conversion efficiency of coal at the inlet and outlet of the coal mill.

3. The primary air volume coupling and adjustment system for mixed coal volatile matter and ignition distance according to claim 2 is characterized in that: The method for constructing the fuzzy system modeling module based on experimental data and establishing the continuous functional relationship between the ignition distance, the volatile matter of the mixed coal and the primary air volume is as follows: Step S1: Using the air-coal ratio and fuel ratio obtained from the power plant experiment as input vectors and the ignition distance as the output variable, a set of input and output data pairs of the fuzzy system is constructed, as shown in the following formula: （4）； Where, Air-coal ratio and fuel ratio vector, is the ignition distance variable, is the number of sample sets; Step S2: Set the domain interval and fuzzify the variables within the domain interval; Step S3: Use a relational database table to record the data pairs of air-coal ratio, fuel ratio and ignition distance, and convert this ordinary record into a fuzzy record; Step S4: creating a fuzzy rule base using a nested algorithm; Step S5: generating a fuzzy model based on the fuzzy rule base; Step S6: using the gradient descent method to adjust the parameters of the fuzzy model; Step S7: Adjust the number of fuzzy sets in the input-output space; improve the prediction accuracy of the fuzzy model by increasing the number of fuzzy sets in the input-output space.

4. The primary air volume coupling and adjustment system for mixed coal volatile matter and ignition distance according to claim 3 is characterized in that: The step S2 sets the air-coal ratio and fuel ratio vector Distance to fire variable The domain intervals are , and , air-coal ratio and fuel ratio vector Two variables in 、 As the premise attribute of the fuzzy system, the ignition distance variable As the conclusion attribute of the fuzzy system; air-coal ratio and fuel ratio vector The domain of each variable in is evenly divided into fuzzy sets, air-coal ratio and fuel ratio vector and fire distance variables The corresponding fuzzy sets are and , Fire distance variable The number of fuzzy sets divided by the domain of discourse is determined, and a membership function is assigned to each fuzzy set.

5. The primary air volume coupling and adjustment system for mixed coal volatile matter and ignition distance according to claim 4 is characterized in that: Said step S3 uses a relational database table to record the data pairs of air-coal ratio, fuel ratio and ignition distance, wherein each row of the table represents a record and each column of the table serves as an attribute of the record; Represents a collection of attributes, Indicates the first records, using To describe a set of Records of attribute information, namely: （5）； use Represents premise attributes The fuzzy set of Indicates conclusion attribute The fuzzy set of and ;for The membership value attribute of Define a set of Fuzzy record of attribute information: （6）； Where, For the The records corresponding to Membership function of attribute set; By using the above formulas (5) and (6), The fuzzy record of attribute information is stored in another relational record table, in which the columns represent the attributes. , rows represent records with values ​​between [0,1].

6. The primary air volume coupling and adjustment system for mixed coal volatile matter and ignition distance according to claim 5 is characterized in that: The specific method of step S4 is: First, through the nested double loop traversal by the premise attributes and The corresponding fuzzy set and All fuzzy subspaces composed of ; Then, for the premise attributes and Any fuzzy subspace determined, its conclusion attribute Selected fuzzy sets, by looping through selected fuzzy sets Each fuzzy set in is calculated by the following formula: （7）； Where, and Respectively represent The membership function value of records; Decide which fuzzy set to choose in the conclusion fuzzy subspace ; Finally, after the fuzzy subspace is selected based on the maximum support, the following IF-THEN fuzzy rule base is constructed: （8）； Where, For the fuzzy rules, is the number of rules in the fuzzy rule base.

7. The primary air volume coupling and adjustment system for mixed coal volatile matter and ignition distance according to claim 6 is characterized in that: The step S5 is for the step S4 obtained Fuzzy rules, using single-value fuzzification, multiplication operation, and weighted average defuzzification, the fuzzy model can be obtained as follows: （9）； Where, is the ignition distance calculation output of the fuzzy model, It is Rules in fuzzy membership function The corresponding maximum value Value point, that is The corresponding time value.

8. The primary air volume coupling and adjustment system for mixed coal volatile matter and ignition distance according to claim 7 is characterized in that: The step S6 adjusts the fuzzy model output of formula (9) into the following vector multiplication form: （10）； Where, is the fuzzy model parameter vector, is the normalized vector of membership function values, where The definition is as follows: （11）； The target error function E formed by the experimental sample data formula (4) is defined as: （12）； Where, For the The experimental data of the ignition distance corresponding to the records, is the air-coal ratio and fuel ratio vector Take the first When the data is recorded, the ignition distance calculation data of the fuzzy model; The gradient descent algorithm is used to minimize the target error function (12), thereby dynamically optimizing and adjusting the parameters of the fuzzy model to improve the modeling accuracy of the fuzzy model; Fuzzy model parameters The update formula is as follows: （13）； Where, is the number of iterations, Is a positive learning rate; the learning rate The initial value of is set to 0.02, The initial value of is determined by the fuzzy rules extracted from steps 1 to 6.

9. The primary air volume coupling and adjustment system for mixed coal volatile matter and ignition distance according to claim 8, characterized in that: The sliding window-based coal mill primary air volume set value offset module calculates the offset of the primary air volume set value based on the ignition distance, the volatile matter of the mixed coal, and the primary air volume calculation data using the sliding window technology, thereby optimizing the ignition distance and making the ignition distance reasonable; comprising: First, by , Real-time value determines the 2*2 sliding window; , Real-time value and calculate the ignition distance through formula (9) ,if and The corresponding ignition distance The following strategy is used to calculate the offset compensation of the primary air volume set value when the sliding window is not in the range : （14）； Where, The corresponding air-coal ratio is the maximum and minimum ignition distance in the 2*2 sliding window. The corresponding primary air volume setting value; For real-time The corresponding primary air volume setting value of the original control system; Ignition distance determined for the four test points in the 2*2 sliding window; if and The corresponding ignition distance Within the sliding window, calculate the offset compensation of the primary air volume set value according to the following formula: : （15）； Where, The corresponding air-coal ratio is the maximum ignition distance in the first and second rows of the 2*2 sliding window. The corresponding primary air volume setting value; They are The corresponding upper and lower bounds of the sliding window.

10. The primary air volume coupling and adjustment system for mixed coal volatile matter and ignition distance according to claim 1, characterized in that: The server, as an external system, communicates with the original coal mill control system via downlink data frames from the communication module to set the offset of the primary air volume set value of the coal mill control system; the original coal mill control system sends a heartbeat switch request frame to the server, and the server simulates a heartbeat signal by responding with a programmed digital switch signal (0, 1). The original coal mill control system detects whether the communication of the external system is normal through the heartbeat frame response; When the original coal mill control system fails to detect a heartbeat frame response within a set time, the external system is automatically cut off and switched to the set value signal of the original coal mill control system.

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