An online control method and system for NOx concentration generated by combustion in a coal-fired boiler

Abstract

The present invention discloses an online control method and system for NOx concentration generated by combustion of a coal-fired boiler, wherein the online control method for NOx concentration generated by combustion of a coal-fired boiler comprises: collecting operation data of the coal-fired boiler; performing linear modeling according to the operation data, and calculating an expected value of the total air volume of the boiler; using the difference between the expected value of the total air volume of the boiler and the total air volume of the boiler as a feedforward of a first controller, and using the difference between a set value NOxsp for NOx generation concentration control and an average NOx concentration on both sides of an inlet of an SCR denitrification device as an input of the first controller, and obtaining a total air volume offset value; adjusting the NOx concentration generated by combustion of the boiler by controlling the total air volume offset value; the present invention is helpful to optimize the operation of the SCR denitrification device, and reduce ammonia escape caused by the inability to accurately control ammonia injection when the boiler unit changes load.

Description

Technical Field

[0001] The present invention relates to the technical field of nitrogen oxide concentration control, and in particular to an online control method and system for NOx concentration generated by combustion in a coal-fired boiler. Background Art

[0002] After combustion, coal-fired boilers will generate a certain concentration of nitrogen oxides (NOx), which is detected by the flue gas analyzer at the inlet of the selective catalytic reduction (SCR) denitrification device, and serves as the basis for adjusting and controlling the reducing agent (usually ammonia NH3) of the SCR denitrification device. Due to the hysteresis of NOx concentration detection, it is difficult to control the ammonia injection of the SCR denitrification device well, especially when the NOx concentration at the inlet of the SCR denitrification device changes greatly due to variable load, there is a clear phenomenon of excessive or insufficient ammonia injection control, resulting in the net flue gas NOx concentration either exceeding the environmental protection limit or being very low, but the ammonia escape amount increases significantly, increasing the risk of air preheater blockage. Therefore, proper control of the NOx concentration generated by the combustion of coal-fired boilers under variable load will help optimize the operation of the SCR denitrification device.

[0003] At present, coal-fired boilers all adopt low-nitrogen combustion technology, which makes the NOx concentration generated by the boiler generally lower than before the adoption of low-nitrogen combustion. However, in the process of variable load, there is basically no control target value for the NOx concentration generated by boiler combustion in the operation control framework of the existing units, so that the NOx concentration generated by combustion will still change greatly. In the process of some boilers dropping from 100% rated load to 50% rated load, the NOx concentration generated by combustion may double. This change needs to be adapted by adjusting the ammonia injection amount of the SCR denitrification device. However, due to the poor operating condition of the ammonia injection regulation of the SCR denitrification device of most boilers, there are problems such as large fluctuations in the net flue gas NOx concentration and large ammonia escape. The large fluctuations in the NOx concentration at the inlet of the SCR denitrification device will reduce the precise matching of the ammonia injection regulation, aggravating the probability of ammonia escape and NOx emission concentration exceeding the standard. Summary of the invention

[0004] The object of the present invention is to provide a method for solving the problems that the ammonia spraying regulation of the SCR denitrification device of most existing boilers is poor in operation, the NOx concentration in the net flue gas ...

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions, including: collecting coal-fired boiler operation data, wherein the operation data include unit load, total boiler air volume, coal volume of each coal mill, primary air volume of each coal mill, burnout air volume and average NOx concentration on both sides of the inlet of the SCR denitrification device; performing linear modeling according to the operation data to calculate the expected value of the total boiler air volume; using the difference between the expected value of the total boiler air volume and the total boiler air volume as the feedforward of the first controller, and the difference between the set value NOxsp of the NOx generation concentration control and the average NOx concentration X on both sides of the inlet of the SCR denitrification device as the input of the first controller to obtain the total air volume offset value dQ; and adjusting the NOx concentration generated by boiler combustion by controlling the total air volume offset value dQ.

[0006] As a preferred solution of the online control method for NOx concentration generated by combustion of a coal-fired boiler according to the present invention, the linear modeling based on the operating data includes: taking the total air volume Q of the boiler as the dependent variable, linear modeling of the coal-fired boiler operating data:

[0007] Q=k 0 *P+k 1 *G A +k 2 *G B +k 3 *G C +k 4 *G D +k 5 *G E +k 6 *G F +k 7 *Q 1A +k 8 *Q 1B +k 9 *Q 1C +k

[0008] 10 *Q 1D +k 11 *Q 1E +k 12 *Q 1F +k 13 *Q 2 +k 14 *X+b

[0009] Where: Q is the total air volume of the boiler, P is the unit load, G A ~G F is the coal feeding amount of coal mills A to F, Q 1A ~Q 1F is the primary air volume of coal mills A to F, Q 2is the burnout air volume, X is the average NOx concentration on both sides of the SCR denitrification device inlet, k 0 ~k 14 is the modeling coefficient, b is the modeling constant;

[0010] The average NOx concentration X on both sides of the SCR denitrification device inlet is replaced by the set value NOxsp of NOx generation concentration control to obtain the expected value Qsp of the total boiler air volume.

[0011] As a preferred solution of the online control method for NOx concentration generated by combustion of a coal-fired boiler according to the present invention, it further includes: taking the difference between the average NOx concentration X on both sides of the inlet of the SCR denitrification device and the set value NOxsp of the NOx generation concentration control as the input of the second controller, and using the function F of the load set value Psp 2 As a feedforward of the second controller, a burnout damper command SOFAsp is output.

[0012] As a preferred solution of the online control method for NOx concentration generated by combustion in a coal-fired boiler described in the present invention, it also includes: using the deviation TL-TR of the left and right reheat steam temperatures as the input of the third controller to output the burnout damper correction instruction dSOFA.

[0013] As a preferred embodiment of the online control method for NOx concentration generated by combustion in a coal-fired boiler described in the present invention, it also includes: when the adjustment direction and control direction of the left and right burnout air on the left and right reheat steam temperatures are the same, that is, when the left burnout air door is opened or the right burnout air door is closed, the left reheat steam temperature decreases or the right reheat steam temperature increases, at this time, the sum of the burnout air door instruction SOFAsp and the burnout air door correction instruction dSOFA is used as the left burnout air door instruction SOFA_Lsp, and the difference between the burnout air door instruction SOFAsp and the burnout air door correction instruction dSOFA is used as the right burnout air door instruction SOFA_Rsp.

[0014] As a preferred embodiment of the online control method for NOx concentration generated by combustion in a coal-fired boiler described in the present invention, it also includes: when the regulation direction of the left and right burnout air on the left and right reheat steam temperatures is opposite to the control direction, that is, when the left burnout air door is opened or the right burnout air door is closed, the left reheat steam temperature increases or the right reheat steam temperature decreases, at this time, the difference between the burnout air door instruction SOFAsp and the burnout air door correction instruction dSOFA is used as the left burnout air door instruction SOFA_Lsp, and the sum of the burnout air door instruction SOFAsp and the burnout air door correction instruction dSOFA is used as the right burnout air door instruction SOFA_Rsp.

[0015] As a preferred scheme of the online control method for NOx concentration generated by combustion in a coal-fired boiler described in the present invention, it also includes: the deviation between the maximum and minimum values ​​of the unit load and the maximum and minimum loads of the unit during normal operation does not exceed 10MW, and the maximum value of the coal quantity of each pulverizer is greater than 0.

[0016] As a preferred solution of the online control method for NOx concentration generated by combustion in a coal-fired boiler of the present invention, it also includes: setting the upper limit of the total air volume offset value dQ to 0 and the lower limit to -5%.

[0017] As a preferred solution of the online control method for NOx concentration generated by combustion in a coal-fired boiler described in the present invention, it also includes: the lower limit of the outlet of the second controller is set to 10%, and the upper limit is set to 100%; the lower limit of the outlet of the third controller is set to -10%, and the upper limit is set to 10%.

[0018] As a preferred solution of the online control system of NOx concentration generated by combustion of coal-fired boiler described in the present invention, wherein: it is used to implement the online control method of NOx concentration generated by combustion of coal-fired boiler as described in the above one, the online control system of NOx concentration generated by combustion of coal-fired boiler includes: a data acquisition module, which is configured to execute the collection of coal-fired boiler operation data, and the operation data includes unit load, total boiler air volume, coal volume of each coal mill, primary air volume of each coal mill, burnout air volume and average NOx concentration on both sides of the inlet of SCR denitrification device; a modeling module, which is configured to execute the modeling based on The linear modeling is performed according to the operation data to calculate the expected value of the total air volume of the boiler; the calculation module is configured to execute the difference between the expected value of the total air volume of the boiler and the total air volume of the boiler as the feedforward of the first controller, the difference between the set value NOxsp of the NOx generation concentration control and the average NOx concentration X on both sides of the inlet of the SCR denitrification device as the input of the first controller, and obtain the total air volume offset value dQ; the difference between the average NOx concentration X on both sides of the inlet of the SCR denitrification device and the set value NOxsp of the NOx generation concentration control is used as the input of the second controller, and the function F of the load set value Psp is used. 2 As the feedforward of the second controller, the burnout damper instruction SOFAsp is output; the deviation TL-TR between the left and right reheat steam temperatures is used as the input of the third controller, and the burnout damper correction instruction dSOFA is output; the control module is configured to execute the adjustment of the NOx concentration generated by the boiler combustion by controlling the total air volume offset value dQ, or to control the burnout damper opening through the burnout damper instruction SOFAsp or the burnout damper correction instruction dSOFA, so as to adjust the NOx concentration generated by the boiler combustion.

[0019] The beneficial effects of the present invention are as follows: through total air volume bias control and burnout damper control, proper control of NOx concentration generated by combustion in coal-fired boilers is achieved, which helps to optimize the operation of SCR denitrification devices and reduce ammonia escape caused by the inability to accurately control ammonia injection when the boiler unit changes load. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor. Among them:

[0021] Figure 1 This is a block diagram of the boiler total air volume offset control according to the first embodiment of the present invention;

[0022] Figure 2 This is a control block diagram of boiler overburnt air when the regulation direction and control direction of the overburnt air on the reheat steam temperature are the same as those described in the second embodiment of the present invention;

[0023] Figure 3 This is a control block diagram of boiler overburnt air when the regulation direction of the overburnt air on the reheat steam temperature is opposite to the control direction as described in the second embodiment of the present invention. DETAILED DESCRIPTION

[0024] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the drawings of the specification. Obviously, the described embodiments are part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary persons in the art without creative work should fall within the scope of protection of the present invention.

[0025] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0026] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0027] The present invention is described in detail with reference to schematic diagrams. When describing the embodiments of the present invention, for the sake of convenience, the cross-sectional diagrams showing the device structure will not be partially enlarged according to the general scale, and the schematic diagrams are only examples, which should not limit the scope of protection of the present invention. In addition, in actual production, the three-dimensional dimensions of length, width and depth should be included.

[0028] At the same time, in the description of the present invention, it should be noted that the directions or positional relationships indicated by the terms "upper, lower, inner and outer" are based on the directions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "first, second or third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0029] In the present invention, unless otherwise clearly specified and limited, the terms "install, connect, connect" should be understood in a broad sense, for example: it can be a fixed connection, a detachable connection or an integral connection; it can also be a mechanical connection, an electrical connection or a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0030] Example 1

[0031] Reference Figure 1 , which is the first embodiment of the present invention, provides an online control method for NOx concentration generated by combustion in a coal-fired boiler, comprising:

[0032] S1: Collect coal-fired boiler operation data, including unit load, total boiler air volume, coal volume of each pulverizer, primary air volume of each pulverizer, burnout air volume and average NOx concentration on both sides of the SCR denitrification device inlet.

[0033] Obtain the unit load P, boiler total air volume Q, and coal volume G of each coal mill from the unit's DCS (Distributed Control System) or SIS (Safety Instrumented System) system. i (i=A, B, C, D, E, F), primary air volume of each coal mill Q1 i (i=A, B, C, D, E, F), burnout air volume Q 2 , the average NOx concentration on both sides of the SCR denitrification device inlet, and continuously obtain multiple sets of data at a frequency of once per second to form a data set.

[0034] The unit load P of this data set covers the load range of the unit's normal operation, that is, the maximum and minimum values ​​of the unit load in the data set are close to the maximum and minimum loads of the unit's normal operation, and the deviation between the maximum and minimum values ​​of the unit load and the maximum and minimum loads of the unit's normal operation does not exceed 10MW; and all coal mills have been operated, that is, the coal quantity G of each coal mill in the data set is i The maximum value is greater than 0.

[0035] S2: Perform linear modeling based on the operating data and calculate the expected value of the total boiler air volume.

[0036] Taking the total air volume Q of the boiler as the dependent variable and other parameters as independent variables, a linear model is built for the operation data of the coal-fired boiler:

[0037] Q=k 0 *P+k 1 *G A +k 2 *G B +k 3 *G C +k 4 *G D +k 5 *G E +k 6 *G F +k 7 *Q 1A +k 8 *Q 1B +k 9 *Q 1C +k

[0038] 10 *Q 1D +k 11 *Q 1E +k 12 *Q 1F +k 13 *Q 2 +k 14 *X+b

[0039] Where: Q is the total air volume of the boiler (unit: t / h or %), P is the unit load (unit: MW), G A ~G F is the coal feeding amount of coal mills A to F (unit: t / h or %), Q 1A ~Q 1F is the primary air volume of coal mills A to F (unit: t / h or %), Q2 is the burnout air volume (unit: t / h or %), X is the average NOx concentration on both sides of the inlet of the SCR denitrification device (unit: mg / m 3 ), k 0 ~k 14is the modeling coefficient, b is the modeling constant;

[0040] The average NOx concentration X on both sides of the SCR denitrification device inlet is replaced by the set value NOxsp of NOx generation concentration control. The other independent variables are online data, and the expected value Qsp of the total air volume of the boiler is obtained. Qsp is the NOx concentration generated by boiler combustion. When the set value is NOxsp, under the current boiler operating parameters, the set value of the total air volume of the boiler should be Qsp. There is a functional relationship between the two, which can be described by a linear function.

[0041] NOxsp can be a function of the load setting value, NOxsp = F1 (Psp), and the function F1 can be linear or broken line as required, as shown below:

[0042]

[0043] S3: The difference between the expected value of the total air volume of the boiler and the total air volume of the boiler is used as the feedforward of the first controller, and the difference between the set value NOxsp of the NOx generation concentration control and the average NOx concentration X on both sides of the inlet of the SCR denitrification device is used as the input of the first controller to obtain the total air volume offset value dQ.

[0044] Reference Figure 1 The difference between the expected value Qsp of the total air volume of the boiler and the current total air volume Q is used as the feedforward of the first controller (proportional integral differential controller PID1), and the difference between the set value NOxsp of the NOx generation concentration control and the average NOx concentration X on both sides of the inlet of the SCR denitrification device is used as the input of PID1. After PID1 calculation, the output is obtained, and the total air volume offset value dQ is obtained after being limited by upper and lower limits. Among them, the upper limit of the total air volume offset value dQ is set to 0, and the lower limit is set to -5%.

[0045] S4: The NOx concentration generated by boiler combustion is adjusted by controlling the total air volume offset value dQ.

[0046] The total air volume offset value dQ is sent to the original total air volume control loop of the DCS for total air volume offset control, thereby adjusting the NOx concentration generated by boiler combustion. The NOx concentration generated by boiler combustion refers to the NOx concentration in the tail flue gas after the combustion of the coal-fired boiler, that is, the NOx concentration measured at the inlet of the SCR denitrification device.

[0047] Example 2

[0048] Reference Figure 2-3 , which is the second embodiment of the present invention. This embodiment is different from the first embodiment in that it provides another online control method for NOx concentration generated by combustion in a coal-fired boiler, including:

[0049] S1: Collect coal-fired boiler operation data, including unit load, total boiler air volume, coal volume of each pulverizer, primary air volume of each pulverizer, burnout air volume and average NOx concentration on both sides of the SCR denitrification device inlet.

[0050] The average NOx concentration on both sides of the inlet of the SCR denitrification device is obtained from the DCS system (Distributed control system) or SIS system (Safety Instrumented System) of the unit, and multiple sets of data are continuously obtained at a frequency of once per second.

[0051] S2: The difference between the average NOx concentration X on both sides of the inlet of the SCR denitrification device and the set value NOxsp of the NOx generation concentration control is used as the input of the second controller (proportional integral differential controller PID2), and the function F2 of the load set value Psp is used as the feedforward of the second controller to output the burnout damper command SOFAsp.

[0052] (1) Function F2 can be a linear function of the load setting value Psp or a broken line function, as shown below:

[0053]

[0054] The lower limit of the outlet of the second controller is set to 10% and the upper limit is set to 100%.

[0055] S3: The deviation TL-TR between the left and right reheat steam temperatures is used as the input of the third controller, and the burnout damper correction instruction dSOFA is output.

[0056] The outlet lower limit of the third controller (proportional integral derivative controller PID3) is set to -10%, and the upper limit is set to 10%.

[0057] S4: According to the regulation direction and control direction of the left and right reheat steam temperatures by the left and right overburnt air, set the command SOFA_Lsp of the left overburnt air door and the command SOFA_Rsp of the right overburnt air door.

[0058] Reference Figure 2 When the regulation direction and control direction of the left and right burnout air on the left and right reheat steam temperatures are the same, that is, when the left burnout air valve is opened or the right burnout air valve is closed, the left reheat steam temperature decreases or the right reheat steam temperature increases. At this time, the sum of the burnout air valve command SOFAsp and the burnout air valve correction command dSOFA is used as the left burnout air valve command SOFA_Lsp, and the difference between the burnout air valve command SOFAsp and the burnout air valve correction command dSOFA is used as the right burnout air valve command SOFA_Rsp.

[0059] Reference Figure 3When the regulation direction of the left and right burnout air on the left and right reheat steam temperatures is opposite to the control direction, that is, when the left burnout air valve is opened or the right burnout air valve is closed, the left reheat steam temperature increases or the right reheat steam temperature decreases. At this time, the difference between the burnout air valve command SOFAsp and the burnout air valve correction command dSOFA is used as the left burnout air valve command SOFA_Lsp, and the sum of the burnout air valve command SOFAsp and the burnout air valve correction command dSOFA is used as the right burnout air valve command SOFA_Rsp.

[0060] S5: The burnout damper opening is adjusted by the left burnout damper command SOFA_Lsp and the right burnout damper command SOFA_Rsp, thereby adjusting the NOx concentration generated by boiler combustion.

[0061] Example 3

[0062] This embodiment provides a method for adjusting the opening of a burnout damper, comprising:

[0063] The purpose of adjusting the overburnt air door opening is to change the overburnt air ratio, thereby changing the NOx concentration generated by boiler combustion.

[0064] The overburn air ratio can also be achieved by keeping the overburn air door unchanged and changing the auxiliary air and fuel air doors of the burner, that is, by changing any one of the air volumes (overburn air volume / auxiliary air volume / fuel air volume) in the formula to change the overburn air ratio:

[0065] Burnout air ratio = burnout air volume / (burnout air volume + auxiliary air volume + fuel air volume).

[0066] Example 4

[0067] This embodiment provides an online control system for NOx concentration generated by combustion of a coal-fired boiler, including a method for implementing the online control method for NOx concentration generated by combustion of a coal-fired boiler as described above. The online control system for NOx concentration generated by combustion of a coal-fired boiler includes:

[0068] The data acquisition module is configured to collect the coal-fired boiler operation data, including the unit load, the total air volume of the boiler, the coal volume of each coal mill, the primary air volume of each coal mill, the burnout air volume and the average NOx concentration on both sides of the inlet of the SCR denitrification device;

[0069] A modeling module is configured to perform linear modeling based on the operating data to calculate an expected value of the total air volume of the boiler;

[0070] The calculation module is configured to execute the following steps: using the difference between the expected value of the total air volume of the boiler and the total air volume of the boiler as the feedforward of the first controller, and the difference between the set value NOxsp of the NOx generation concentration control and the average NOx concentration X on both sides of the inlet of the SCR denitrification device as the input of the first controller to obtain the total air volume offset value dQ; using the difference between the average NOx concentration X on both sides of the inlet of the SCR denitrification device and the set value NOxsp of the NOx generation concentration control as the input of the second controller, and using the function F of the load set value Psp 2 As the feedforward of the second controller, it outputs the burnout damper command SOFAsp; the deviation TL-TR between the left and right reheat steam temperatures is used as the input of the third controller, which outputs the burnout damper correction command dSOFA;

[0071] The control module is configured to adjust the NOx concentration generated by boiler combustion by controlling the total air volume offset value dQ, or to control the burnout damper opening through the burnout damper instruction SOFAsp or the burnout damper correction instruction dSOFA, so as to adjust the NOx concentration generated by boiler combustion.

[0072] It should be appreciated that embodiments of the present invention may be implemented or enforced by computer hardware, a combination of hardware and software, or by computer instructions stored in a non-transitory computer-readable memory. The method may be implemented in a computer program using standard programming techniques - including a non-transitory computer-readable storage medium configured with a computer program, wherein the storage medium so configured causes the computer to operate in a specific and predefined manner - according to the methods and drawings described in the specific embodiments. Each program may be implemented in a high-level procedural or object-oriented programming language to communicate with a computer system. However, if desired, the program may be implemented in an assembly or machine language. In any case, the language may be a compiled or interpreted language. In addition, the program may be run on a programmed ASIC for this purpose.

[0073] Furthermore, the operations of the processes described herein may be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The processes described herein (or variations and / or combinations thereof) may be performed under the control of one or more computer systems configured with executable instructions, and may be implemented as code (e.g., executable instructions, one or more computer programs, or one or more applications) that is executed collectively on one or more processors, by hardware, or a combination thereof. The computer program includes a plurality of instructions that may be executed by one or more processors.

[0074] Further, the method can be implemented in any type of computing platform that is operably connected to a suitable computer, including but not limited to a personal computer, a minicomputer, a mainframe, a workstation, a network or distributed computing environment, a separate or integrated computer platform, or in communication with a charged particle tool or other imaging device, etc. Aspects of the present invention can be implemented in machine-readable code stored on a non-transitory storage medium or device, whether removable or integrated into a computing platform, such as a hard disk, an optical read and / or write storage medium, a RAM, a ROM, etc., so that it can be read by a programmable computer, and when the storage medium or device is read by the computer, it can be used to configure and operate the computer to perform the process described herein. In addition, the machine-readable code, or part thereof, can be transmitted via a wired or wireless network. When such media includes instructions or programs that implement the steps described above in conjunction with a microprocessor or other data processor, the invention described herein includes these and other different types of non-transitory computer-readable storage media. When programmed according to the methods and techniques described in the present invention, the present invention also includes the computer itself. The computer program can be applied to input data to perform the functions described herein, thereby converting the input data to generate output data stored in a non-volatile memory. The output information can also be applied to one or more output devices such as a display. In a preferred embodiment of the present invention, the converted data represents a physical and tangible object, including a specific visual depiction of the physical and tangible object produced on a display.

[0075] As used in this application, the terms "component", "module", "system", etc. are intended to refer to a computer-related entity, which can be hardware, firmware, a combination of hardware and software, software, or software in operation. For example, a component can be, but is not limited to: a process running on a processor, a processor, an object, an executable file, a thread in execution, a program, and / or a computer. As an example, an application running on a computing device and the computing device can both be components. One or more components can exist in a process and / or thread in execution, and a component can be located in a computer and / or distributed between two or more computers. In addition, these components can be executed from various computer-readable media having various data structures thereon. These components can communicate in a local and / or remote process manner, such as according to a signal having one or more data packets (e.g., data from a component that interacts with another component in a local system, a distributed system, and / or interacts with other systems in a signal manner through a network such as the Internet).

[0076] 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 preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. An online control method for NOx concentration generated by combustion in a coal-fired boiler, characterized in that: include: Collecting coal-fired boiler operation data, including unit load, total boiler air volume, coal volume of each coal mill, primary air volume of each coal mill, burnout air volume, and average NOx concentration on both sides of the inlet of the SCR denitrification device; Perform linear modeling based on the operating data to calculate the expected value of the total air volume of the boiler; The difference between the expected value of the total air volume of the boiler and the total air volume of the boiler is used as the feedforward of the first controller, and the difference between the set value NOxsp of the NOx generation concentration control and the average NOx concentration on both sides of the inlet of the SCR denitrification device is used as the input of the first controller to obtain the total air volume offset value dQ; The NOx concentration generated by boiler combustion is adjusted by controlling the total air volume offset value dQ; The linear modeling based on the operating data includes: Taking the total air volume Q of the boiler as the dependent variable, a linear model is built for the operation data of the coal-fired boiler: Q=k0*P+k1*GA+k2*GB+k3*GC+k4*GD+k5*GE+k6*GF+k7*Q1A+k8*Q1B+k9*Q1C+k10*Q1D+k11*Q1E+k12*Q1F+k13*Q2+k14*X+b Where: Q is the total air volume of the boiler, P is the unit load, GA~GF is the coal feed volume of pulverizers A~F, Q1A~Q1F is the primary air volume of pulverizers A~F, Q2 is the burnout air volume, X is the average NOx concentration on both sides of the inlet of the SCR denitrification device, k0~k14 are modeling coefficients, and b is the modeling constant; The average NOx concentration X on both sides of the inlet of the SCR denitrification device is replaced by the set value NOxsp of the NOx generation concentration control to obtain the expected value Qsp of the total air volume of the boiler; The difference between the average NOx concentration X on both sides of the inlet of the SCR denitrification device and the set value NOxsp of the NOx generation concentration control is used as the input of the second controller, and the function F2 of the load set value Psp is used as the feedforward of the second controller to output the burnout damper command SOFAsp; The difference TL-TR between the left and right reheat steam temperatures is used as the input of the third controller, which outputs the burnout damper correction instruction dSOFA.

2. The method for online control of NOx concentration generated by combustion of a coal-fired boiler according to claim 1, characterized in that: Also includes: When the regulation direction and control direction of the left and right burnout air on the left and right reheat steam temperatures are the same, that is, when the left burnout air valve is opened or the right burnout air valve is closed, the left reheat steam temperature decreases or the right reheat steam temperature increases. At this time, the sum of the burnout air valve command SOFAsp and the burnout air valve correction command dSOFA is used as the left burnout air valve command SOFA_Lsp, and the difference between the burnout air valve command SOFAsp and the burnout air valve correction command dSOFA is used as the right burnout air valve command SOFA_Rsp.

3. The method for online control of NOx concentration generated by combustion of a coal-fired boiler according to claim 2, characterized in that: Also includes: When the regulation direction of the left and right burnout air on the left and right reheat steam temperatures is opposite to the control direction, that is, when the left burnout air valve is opened or the right burnout air valve is closed, the left reheat steam temperature increases or the right reheat steam temperature decreases. At this time, the difference between the burnout air valve command SOFAsp and the burnout air valve correction command dSOFA is used as the left burnout air valve command SOFA_Lsp, and the sum of the burnout air valve command SOFAsp and the burnout air valve correction command dSOFA is used as the right burnout air valve command SOFA_Rsp.

4. The method for online control of NOx concentration generated by combustion of a coal-fired boiler according to claim 2 or 3, characterized in that: Also includes: The deviation between the maximum and minimum values ​​of the unit load and the maximum and minimum loads of the unit during normal operation shall not exceed 10MW, and the maximum value of the coal quantity of each pulverizer shall be greater than 0.

5. The method for online control of NOx concentration generated by combustion of a coal-fired boiler according to claim 4, characterized in that: Also includes: The upper limit of the total air volume bias value dQ is set to 0, and the lower limit is set to -5%.

6. The method for online control of NOx concentration generated by combustion in a coal-fired boiler according to claim 5, characterized in that: Also includes: The lower limit of the outlet of the second controller is set to 10% and the upper limit is set to 100%; The lower limit of the outlet of the third controller is set to -10% and the upper limit is set to 10%.

7. An online control system for NOx concentration generated by combustion of a coal-fired boiler, used to implement the online control method for NOx concentration generated by combustion of a coal-fired boiler as claimed in any one of claims 1 to 6, wherein the online control system for NOx concentration generated by combustion of a coal-fired boiler comprises: A data acquisition module is configured to collect coal-fired boiler operation data, wherein the operation data includes unit load, total boiler air volume, coal volume of each coal mill, primary air volume of each coal mill, burnout air volume, and average NOx concentration on both sides of the inlet of the SCR denitrification device; A modeling module is configured to perform linear modeling based on the operating data to calculate an expected value of the total air volume of the boiler; The calculation module is configured to execute the following steps: using the difference between the expected value of the total air volume of the boiler and the total air volume of the boiler as the feedforward of the first controller, and the difference between the set value NOxsp of the NOx generation concentration control and the average NOx concentration X on both sides of the inlet of the SCR denitrification device as the input of the first controller to obtain the total air volume offset value dQ; using the difference between the average NOx concentration X on both sides of the inlet of the SCR denitrification device and the set value NOxsp of the NOx generation concentration control as the input of the second controller, and using the function F2 of the load set value Psp as the feedforward of the second controller to output the burnout damper instruction SOFAsp; using the deviation TL-TR of the left and right reheat steam temperatures as the input of the third controller to output the burnout damper correction instruction dSOFA; The control module is configured to adjust the NOx concentration generated by boiler combustion by controlling the total air volume offset value dQ, or to control the burnout damper opening through the burnout damper instruction SOFAsp or the burnout damper correction instruction dSOFA, so as to adjust the NOx concentration generated by boiler combustion.

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