An automatic control method and system for preventing ash fouling of an air preheater

Abstract

The present application relates to an automatic control method and system for preventing ash fouling in an air preheater. The method includes: during the startup phase of a thermal power unit, monitoring the flue gas temperature at the inlet of the denitration reactor on the boiler side and monitoring the opening degree of the ammonia injection valve on the boiler side; preheating through the air preheater on the boiler side according to the flue gas temperature at the inlet of the denitration reactor and the opening degree of the ammonia injection valve; during the low-load operation phase of the thermal power unit, monitoring the temperature of the cold section components of the air preheater to obtain the measured temperature value of the cold section components; controlling the opening degree of the hot primary air recirculation regulating valve of the air preheater according to the measured temperature value of the cold section components and the preset temperature value of the cold section components to prevent low-temperature corrosion of the air preheater. Through the present application, the problem of how to efficiently and accurately prevent low-temperature corrosion of the air preheater is solved, and the control of the cold section temperature of the air preheater under multiple working conditions is realized, effectively preventing the occurrence of low-temperature corrosion caused by too low temperature and the situation of affecting the economy of the unit due to too high temperature.

Description

Technical Field

[0001] The present application relates to the technical field of thermal power generation, and particularly to an automatic control method and system for preventing ash fouling of an air preheater. Background Art

[0002] Currently, the power industry is in a stage of rapid development, and unreasonable energy utilization or energy-inefficient production methods are widespread. Reducing the energy consumption of thermal power plants is of great significance for promoting sustainable economic development.

[0003] An air preheater (hereinafter referred to as "APH") is a heat exchange device for large power station boilers. It uses the heat of boiler flue gas to heat the air required for combustion, thereby improving the efficiency of the boiler. SO3 is generated by the reaction of SO2 and O2 in the boiler flue gas, and then combines with water vapor to produce H2SO4. The temperature at which the H2SO4 vapor in the flue gas begins to condense is called the acid dew point. The higher the content of H2SO4 vapor, the higher the acid dew point, which can reach 140 - 160°C. The H2SO4 liquid generated by the condensation of H2SO4 vapor will stain and corrode metals, namely low-temperature corrosion. Therefore, the acid dew point of boiler flue gas is affected by the sulfur content, ash content, and moisture content in the flue gas. If the acid dew point of the flue gas is controlled too high, the flue gas discharge temperature will increase, increasing the heat loss of flue gas discharge from the boiler and reducing the economy of the boiler; if the acid dew point of the flue gas is controlled too low, the remaining NH3, SO3 in the flue gas at the outlet of the SCR reactor will react with water to produce ammonium bisulfate, which will adhere to the surface of the heat transfer elements and adsorb a large amount of ash, causing serious ash fouling of the APH. The unbalanced flow of the medium flow surface of the APH and the uneven flue gas scouring will affect the safe and economic operation of the thermal power unit.

[0004] Among the existing solutions for preventing low-temperature corrosion of the APH in thermal power units, the main ones with low investment and significant effects are to adopt an APH hot primary air recirculation anti-ash fouling system to control the temperature of the cold section of the APH and maintain it above the safe temperature to prevent cold-end corrosion of the APH. However, this solution basically requires operators to manually control the opening of the APH hot primary air recirculation regulating valve. This manual control method has the following disadvantages: First, due to the complexity of the blending of fossil fuels, the sulfur content, ash content, and other coal qualities are different, and the actual value of the acid dew point changes. The control value of the cold section temperature of the APH should change accordingly. However, due to the lack of operation reference values, operators need to perform a large number of complex exploratory operations. Second, during the unit startup stage, when the denitration ammonia injection system is put into operation, if the operation and cooperation between the power station boiler side and the denitration system are improper and the anti-ash fouling system of this APH is not put into preheating in time, it is very likely that the activity of the SCR catalyst will decrease and the generated ammonium bisulfate will adhere to the catalyst, resulting in its failure, triggering ammonium bisulfate blockage and cold-end corrosion of the APH.

[0005] At present, no effective solution has been proposed for the problem of how to efficiently and accurately prevent low-temperature corrosion of air preheaters in related technologies. Summary of the Invention

[0006] An embodiment of the present application provides an automatic control method and system for preventing ash fouling of an air preheater to at least solve the problem of how to efficiently and accurately prevent low-temperature corrosion of an air preheater in related technologies.

[0007] In a first aspect, an embodiment of the present application provides an automatic control method for preventing ash fouling of an air preheater, and the method includes:

[0008] During the startup stage of a thermal power unit, monitor the flue gas temperature at the inlet of the denitration reactor on the boiler side and monitor the opening of the ammonia injection gate on the boiler side;

[0009] Preheat through the air preheater on the boiler side according to the flue gas temperature at the inlet of the denitration reactor and the opening of the ammonia injection gate;

[0010] During the low-load operation stage of the thermal power unit, monitor the temperature of the cold section elements of the air preheater to obtain the measured temperature value of the cold section elements;

[0011] According to the measured temperature value of the cold section elements and the preset temperature value of the cold section elements, control the opening of the hot primary air recirculation regulating valve of the air preheater to adjust the temperature of the cold section elements to prevent low-temperature corrosion of the air preheater.

[0012] In some embodiments, preheating through the air preheater on the boiler side according to the flue gas temperature at the inlet of the denitration reactor and the opening of the ammonia injection gate includes:

[0013] If the flue gas temperature at the inlet of the denitration reactor is greater than a preset temperature threshold and the opening of the ammonia injection gate is greater than a preset opening threshold, then open the hot primary air recirculation regulating valve of the air preheater on the boiler side for preheating.

[0014] In some embodiments, monitoring the temperature of the cold section elements of the air preheater to obtain the measured temperature value of the cold section elements includes:

[0015] Measure the temperature of the cold section elements respectively through a plurality of infrared temperature measuring devices installed in the air preheater, and select the minimum temperature value from the measured temperature values as the measured temperature value of the cold section elements.

[0016] In some embodiments, controlling the opening of the hot primary air recirculation regulating valve of the air preheater according to the measured temperature value of the cold section elements and the preset temperature value of the cold section elements includes:

[0017] When the absolute deviation between the measured temperature value and the preset temperature value of the cold section component is greater than the preset deviation threshold value, the opening degree of the hot primary air recirculation regulating valve of the air preheater is controlled through the temperature PID controller of the cold section component;

[0018] When the absolute deviation between the measured temperature value and the preset temperature value of the cold section component is not greater than the preset deviation threshold value, the opening degree of the hot primary air recirculation regulating valve of the air preheater is controlled through the differential pressure PID controller of the cold section component.

[0019] In some embodiments, controlling the opening degree of the hot primary air recirculation regulating valve of the air preheater includes:

[0020] Based on the measured temperature value of the cold section component, the NOx content of the flue gas at the inlet of the denitration reactor, and the load of the thermal power unit, the comprehensive ideal control value of the hot primary air recirculation regulating valve of the air preheater is obtained;

[0021] Based on the comprehensive ideal control value, the opening degree of the hot primary air recirculation regulating valve is controlled.

[0022] In some embodiments, based on the measured temperature value of the cold section component, the NOx content of the flue gas at the inlet of the denitration reactor, and the load of the thermal power unit, obtaining the comprehensive ideal control value of the hot primary air recirculation regulating valve of the air preheater includes:

[0023] Based on the principle of single variable, the curve formula F1 = -37.8ln(Tp) + 80.14 between the measured temperature value Tp of the cold section component and the ideal control value F1 of the hot primary air recirculation regulating valve of the air preheater is obtained;

[0024] Based on the principle of single variable, the curve formula F2 = -61.34ln(H) + 88.247 between the NOx content H of the flue gas at the inlet of the denitration reactor and the ideal control value F2 of the hot primary air recirculation regulating valve of the air preheater is obtained;

[0025] Based on the principle of single variable, the curve formula F3 = -5.946ln(P) + 11.257 between the load P of the thermal power unit and the ideal control value F3 of the hot primary air recirculation regulating valve of the air preheater is obtained;

[0026] The comprehensive ideal control value F of the hot primary air recirculation regulating valve of the air preheater is obtained as F = F1 + F2 + F3.

[0027] In some embodiments, before controlling the opening degree of the hot primary air recirculation regulating valve of the air preheater according to the measured temperature value of the cold section component and the preset temperature value of the cold section component, the method includes:

[0028] According to the comprehensive temperature at the cold end of the air preheater and the temperature characteristic curve of the cold section components, the temperature set value of the cold section components is obtained.

[0029] In some embodiments, the method includes:

[0030] During the high-load operation stage of the thermal power unit, the hot primary air recirculation shut-off door on the boiler side of the air preheater is interlocked and closed, and the hot primary air recirculation regulating door of the air preheater automatically closes to the zero position.

[0031] In some embodiments, the method further includes:

[0032] When the NOx emission concentration of the thermal power unit is lower than the preset concentration threshold, the opening of the hot primary air recirculation regulating door on the boiler side of the air preheater is switched from 0 to the preset opening.

[0033] In a second aspect, an automatic control system for preventing fouling and ash deposition of an air preheater provided by an embodiment of the present application is characterized in that the system is an automatic control system built based on a distributed control system, and the system includes a start control module and a low-load operation control module;

[0034] The start control module is used to monitor the flue gas temperature at the inlet of the denitration reactor on the boiler side and the opening of the ammonia injection door on the boiler side during the start-up stage of the thermal power unit;

[0035] The start control module is used to preheat through the air preheater on the boiler side according to the flue gas temperature at the inlet of the denitration reactor and the opening of the ammonia injection door;

[0036] The low-load operation control module is used to monitor the temperature of the cold section components of the air preheater during the low-load operation stage of the thermal power unit to obtain the measured temperature value of the cold section components;

[0037] The low-load operation control module is used to control the opening of the hot primary air recirculation regulating door of the air preheater according to the measured temperature value of the cold section components and the preset temperature value of the cold section components, and adjust the temperature of the cold section components to prevent low-temperature corrosion of the air preheater.

[0038] Compared with the related art, an automatic control method and system for preventing ash fouling of an air preheater provided by an embodiment of the present application. In this method, during the startup stage of a thermal power unit, the flue gas temperature at the inlet of the denitration reactor on the boiler side is monitored, and the opening degree of the ammonia injection gate on the boiler side is monitored. According to the flue gas temperature at the inlet of the denitration reactor and the opening degree of the ammonia injection gate, preheating is carried out through the air preheater on the boiler side. During the low-load operation stage of the thermal power unit, the temperature of the cold-section elements of the air preheater is monitored to obtain the measured temperature value of the cold-section elements. According to the measured temperature value and the preset temperature value of the cold-section elements, the opening degree of the hot primary air recirculation regulating gate of the air preheater is controlled to prevent low-temperature corrosion of the air preheater, solving the problem of how to efficiently and accurately prevent low-temperature corrosion of the air preheater, and realizing the control of the cold-section temperature of the air preheater under multiple working conditions, effectively preventing low-temperature corrosion caused by too low temperature and high-temperature affecting the economy of the unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The drawings described herein are used to provide a further understanding of the present application and form a part of the present application. The schematic embodiments and descriptions thereof are used to explain the present application and do not constitute an improper limitation to the present application. In the drawings:

[0040] Figure 1 is a flowchart of the steps of the automatic control method for preventing ash fouling of the air preheater according to an embodiment of the present application;

[0041] Figure 2 is a schematic diagram of the control logic of the temperature PID controller on the A side according to an embodiment of the present application;

[0042] Figure 3 is a schematic diagram of the control logic of the differential pressure PID controller on the A side according to an embodiment of the present application;

[0043] Figure 4 is a schematic flow diagram of the automatic control method for preventing ash fouling of the air preheater according to an embodiment of the present application;

[0044] Figure 5 is a schematic diagram of the generation logic of the feedforward signal according to an embodiment of the present application;

[0045] Figure 6 is a structural block diagram of the automatic control system for preventing ash fouling of the air preheater according to an embodiment of the present application;

[0046] Figure 7 is a schematic internal structure diagram of an electronic device according to an embodiment of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0047] In order to make the objectives, technical solutions and advantages of the present application more clear and understandable, the present application will be described and explained below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application. Based on the embodiments provided in the present application, all other embodiments obtained by those of ordinary skill in the art without making creative efforts fall within the scope of protection of the present application.

[0048] Obviously, the accompanying drawings in the following description are only some examples or embodiments of the present application. For those of ordinary skill in the art, without making creative efforts, the present application can also be applied to other similar scenarios based on these drawings. In addition, it can also be understood that although the efforts made in such a development process may be complex and lengthy, for those of ordinary skill in the art related to the content disclosed in the present application, some design, manufacturing or production changes made on the basis of the technical content disclosed in the present application are only conventional technical means and should not be understood that the content disclosed in the present application is insufficient.

[0049] Referring to "embodiments" in the present application means that the specific features, structures or characteristics described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various positions in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those of ordinary skill in the art explicitly and implicitly understand that the embodiments described in the present application can be combined with other embodiments without conflict.

[0050] Unless otherwise defined, the technical terms or scientific terms involved in this application shall have the ordinary meanings understood by those with ordinary skills in the technical field to which this application belongs. The words such as "a", "an", "one kind", "the" and the like involved in this application do not indicate a quantity limitation and may represent a singular or plural number. The terms "include", "comprise", "have" and any variations thereof involved in this application are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or modules (units) is not limited to the listed steps or units, but may further include unlisted steps or units, or may further include other steps or units inherent to these processes, methods, products or devices. The words such as "connect", "be connected", "couple" and the like involved in this application are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. The "plurality" involved in this application means two or more. "And / or" describes the association relationship of associated objects and indicates that three relationships may exist. For example, "A and / or B" may represent: A exists alone, A and B exist simultaneously, and B exists alone. The character " / " generally represents an "or" relationship between the front and rear associated objects. The terms "first", "second", "third" and the like involved in this application are only used to distinguish similar objects and do not represent a specific order for the objects.

[0051] An embodiment of this application provides an automatic control method for preventing ash fouling of an air preheater. Figure 1 It is a flowchart of the steps of the automatic control method for preventing ash fouling of the air preheater according to the embodiment of this application, as Figure 1 shown, and this method includes the following steps:

[0052] Step S102, during the startup stage of the thermal power unit, monitor the flue gas temperature at the inlet of the denitration reactor on the boiler side and monitor the opening degree of the ammonia injection valve on the boiler side;

[0053] Specifically for step S102, during the startup stage of the thermal power unit (such as the stage of 0% to 30% load, and the load range of the startup stage can be custom-set for specific units), through the distributed control system (DCS system, Distributed Control System), monitor the flue gas temperature at the inlet of the denitration reactor on side A and / or side B of the boiler, the opening degree of the No. 1 ammonia injection electric valve on side A and / or side B, and the opening degree of the No. 2 ammonia injection electric valve on side A and / or side B.

[0054] Step S104, preheat through the air preheater on the boiler side according to the flue gas temperature at the inlet of the denitration reactor and the opening degree of the ammonia injection valve;

[0055] Specifically, in step S104, if the flue gas temperature at the inlet of the denitration reactor is greater than the preset temperature threshold and the ammonia injection valve opening is greater than the preset opening threshold, the hot primary air recirculation regulating valve on the boiler side is opened for preheating.

[0056] Preferably, in step S104, if the flue gas temperature at the inlet of the denitration reactor on the A side and / or B side of the boiler is greater than 300 °C, the opening of the No. 1 ammonia injection electric valve on the A side and / or B side is greater than 5%, and the opening of the No. 2 ammonia injection electric valve on the A side and / or B side is greater than 5% (indicating that the denitration ammonia injection system on the A side and / or B side has been put into operation), the corresponding A side and / or B side control functions of the hot primary air recirculation anti-fouling system of the air preheater are automatically put into operation (when the denitration ammonia injection system on the A side is put into operation, the A side control function of the system is automatically put into operation; the same is true for the B side; when the denitration ammonia injection systems on both the A side and the B side are put into operation, the A side and B side control functions of the system are all automatically put into operation), that is, the hot primary air recirculation regulating valves on the A side and / or B side are interlocked and opened. The regulating valve automatically opens to the preset value X1, and the preset value X1 is customarily set according to different boilers, air preheater types and regulating valve flow characteristics. Through on-site testing and experiments, it is determined that the preset value X1 is preferably 30%. The purpose is to preheat the A / B side air preheater of the denitration ammonia injection system that has been put into operation during the boiler startup stage, prevent the reduction of the SCR catalyst activity and the attachment of ammonium bisulfate and the like generated on the catalyst, resulting in its failure, and cause blockage and cold-end corrosion of ammonium bisulfate and the like in the air preheater.

[0057] It should be noted that the air preheater (abbreviation: "APH"), and the hot primary air recirculation anti-fouling system of the air preheater mainly consists of a hot primary air pipeline, a regulating baffle valve (abbreviation: "regulating valve"), a shut-off valve, a recirculation air chamber, etc. The hot primary air recirculation regulating baffle valve of the air preheater can achieve 0-100% opening adjustment, and the shut-off valve can effectively isolate and prevent air leakage.

[0058] In step S106, during the low-load operation stage of the thermal power unit, the temperature of the cold section components of the air preheater is monitored to obtain the measured temperature value of the cold section components;

[0059] Specifically, in step S106, the temperatures of the cold section components are measured respectively by a number of infrared temperature measuring devices installed in the air preheater, and the minimum temperature value is selected from the measured temperature values as the measured temperature value of the cold section components.

[0060] Preferably, in step S106, the measured temperature value of the cold section components of the APH on the A side and / or B side of the boiler is specifically the minimum value of the measured values of three infrared temperature measuring devices of the cold section components.

[0061] The irradiation points of the light of its infrared temperature measurement device are arranged at an angle of 120° to each other inside the cold section of the air preheater, and it is representative when the closest distance from the edge of the cold section element is 200 mm (the flue gas flow field at this place is relatively stable, and the temperature difference at any position within a range of 200 mm from the surrounding is < 2°C). Three infrared temperature measurement devices are installed outside the air preheater. The installation method is as follows: Adjust the irradiation points of the infrared temperature measurement device to align them with the above three representative different positions inside the cold section of the air preheater, and then install the infrared temperature measurement device firmly.

[0062] Step S108: According to the measured temperature value and the preset temperature value of the cold section element, control the opening degree of the hot primary air recirculation regulating valve of the air preheater to adjust the temperature of the cold section element to prevent low-temperature corrosion of the air preheater.

[0063] Specifically in step S108, when the absolute value deviation between the measured temperature value and the preset temperature value of the cold section element is greater than the preset deviation value threshold, control the opening degree of the hot primary air recirculation regulating valve of the air preheater through the temperature PID controller of the cold section element;

[0064] When the absolute value deviation between the measured temperature value and the preset temperature value of the cold section element is not greater than the preset deviation value threshold, control the opening degree of the hot primary air recirculation regulating valve of the air preheater through the differential pressure PID controller of the cold section element.

[0065] Preferably in step S108, during the operation stage of the unit from 30% to 70% load after the denitration ammonia injection system is put into operation (low load operation stage), the measured temperature value Tp of the cold section element of the air preheater on the A and / or B side of the boiler and the average differential pressure value of the air preheater within 30 seconds are used as the controlled variables for automatic control respectively: Obtain the set temperature value Ts of the cold section element of the air preheater according to the characteristic relationship curve between the comprehensive temperature x at the cold end of the A / B side air preheater and the temperature of the corresponding side cold section element. Preferably, obtain the set temperature value Ts of the cold section element of the air preheater through the formula Ts = -64.43ln(x) + 207.42 (it should be ensured that it is higher than the acid dew point value, and the operator can set the offset for it artificially).

[0066] When the absolute value deviation between the measured temperature value Tp of the cold section element of the air preheater on the A and / or B side of the boiler and the set value Ts > Y, the controlled variable is the measured temperature value Tp of the cold section element of the air preheater on the A and / or B side, the controller is the temperature PID controller of the cold section element of the air preheater on the A and / or B side, and the adjustment variable is the opening degree of the hot primary air recirculation regulating valve of the air preheater on the A and / or B side (that is, use the temperature PID controller of the cold section element of the air preheater on the A and / or B side to control the opening degree of the hot primary air recirculation regulating valve of the air preheater on the A and / or B side automatically to control the measured temperature value Tp of the cold section element of the air preheater on the A and / or B side within a predetermined range, and ensure that the temperature of the cold section element is optimized between safety and economy), Figure 2is a schematic diagram of the control logic of the A-side temperature PID controller according to an embodiment of the present application;

[0067] When the absolute value deviation between the measured value of the temperature of the cold section element of the air preheater on the A and / or B side and the set value is ≤Y, the temperature of the cold section element of the air preheater on the A and / or B side will no longer be used as the controlled variable, and the controlled variable will be switched to the average value of the air preheater differential pressure on the A and / or B side within 30 seconds, and the controller will be switched to the air preheater differential pressure PID controller on the A and / or B side, and the controlled variable will also be the opening of the hot primary air recirculation regulating door of the air preheater on the A and / or B side (that is, the air preheater differential pressure PID controller on the A and / or B side is used to automatically adjust the opening of the hot primary air recirculation regulating door of the air preheater on the A and / or B side to achieve the control of the average value of the air preheater differential pressure on the A and / or B side within the predetermined range, and the flushing of the hot primary air is used to deeply control the air preheater differential pressure). Figure 3 Schematic diagram of the control logic of the A-side pressure difference PID controller according to an embodiment of the present application.

[0068] Furthermore, in step S108, Figure 4 : is a flow chart of an automatic control method for preventing ash blockage in an air preheater according to an embodiment of the present application, such as Figure 2 As shown, the process of the temperature PID controller or pressure difference PID controller of the cold section element controlling the hot primary air recirculation adjustment door opening of the air preheater is as follows:

[0069] Step 1: Based on the single variable relationship influence quantity (i.e., the single variable principle), an experiment is conducted to obtain a curve formula between the measured temperature value Tp of the cold section element (on the boiler A and / or B side) and the ideal control value F1 of the hot primary air recirculation damper of the air preheater: F1 = -37.8ln(Tp) + 80.14;

[0070] Step 2: Based on the single variable principle, a curve formula F2 = -61.34ln(H) + 88.247 is obtained between the NOx content H of the flue gas at the denitrification reactor inlet and the ideal control value F2 of the hot primary air recirculation regulating gate of the air preheater;

[0071] Step 3: Based on the single variable principle, the curve formula between the thermal power unit load P and the ideal control value F3 of the air preheater hot primary air recirculation control door is obtained: F3 = -5.946ln(P) + 11.257;

[0072] Step 4: Obtain the comprehensive ideal control value F=F1+F2+F3 of the hot primary air recirculation regulating door of the air preheater.

[0073] Step 5: Use the comprehensive ideal control value F as the feedforward signal of the temperature PID controller and the differential pressure PID controller. Figure 5It is a schematic diagram of the feedforward signal generation logic according to an embodiment of the present application. When the measured values Tp of the cold section element temperatures of the air preheaters on the A and / or B sides of the boiler, the NOx content H of the flue gas at the denitration inlet, and the unit load P change in real time, the hot air recirculation regulating valves of the A / B side air preheaters also perform precise linkage according to the feedforward signal F.

[0074] In addition, the following special cases are also included in the anti-blocking and ash-removing of the air preheater of the thermal power unit:

[0075] First, during the high-load operation stage of the thermal power unit (such as the operation stage with a load greater than 70%), the hot primary air recirculation shut-off valves on the boiler side (A side and B side) of the air preheater are interlocked to close, and the hot primary air recirculation regulating valves of the air preheater automatically close to the zero position, and the anti-blocking and ash-removing system of the hot primary air recirculation of the air preheater is no longer put into operation.

[0076] Second, when the NOx emission concentration of the thermal power unit is lower than the preset concentration threshold, the opening degree of the hot primary air recirculation regulating valve on the boiler side of the air preheater is switched from 0 to the preset opening degree. Preferably, when the NOx emission concentration of the thermal power unit is lower than 30 mg / Nm 3 and 20 mg / Nm 3 respectively, it indicates that the ammonia injection amount of the unit is large. At this time, on the basis of putting into PID automatic regulation, the hot air recirculation regulating valve of the air preheater is automatically opened to a position above the reasonable position, that is, the lower limit of the output instruction of the hot air recirculation regulating valve of the air preheater is changed from 0 to X2 and X3 respectively. When it is lower than 30 mg / Nm 3 it becomes X2, and when it is lower than 20 mg / Nm 3 it becomes X3.

[0077] Through steps S102 to S108 in the embodiment of the present application, under various operating conditions of the thermal power unit, the cold section temperature of the air preheater is automatically controlled within an ideal range, the cold section temperature of the air preheater is increased, the problem of air preheater blockage is effectively prevented, and at the same time, the high temperature of the cold section of the air preheater affecting the unit economy is also prevented, and the problem of how to efficiently and accurately prevent the air preheater from undergoing low-temperature corrosion is solved.

[0078] After actual production verification, after a 350 MW supercritical coal-fired unit is put into operation, although the power consumption of the primary air fan increases by about 0.2% (the coal consumption increases by 0.64 g / Kwh after conversion), it can better inhibit blockage, especially ensure the long-term operation of the air preheater in winter, the power consumption of the induced draft fan and forced draft fan is reduced by 0.15% (the coal consumption is reduced by 0.48 g / Kwh after conversion), and the warm air heater does not need to be put into operation, reducing the heat consumption of the steam turbine (the coal consumption is reduced by 1.61 g / Kwh after conversion), and the influence of the decrease in the flue gas discharge temperature and the inlet air temperature on the coal consumption is balanced. To sum up, after the system is put into operation, the coal consumption is reduced by 1.45 g / Kwh, and finally the safe and economic operation of the unit is guaranteed.

[0079] It should be noted that the steps shown in the above process or the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0080] The embodiment of the present application provides an automatic control system for preventing dust blockage in an air preheater. Figure 6 This is a structural block diagram of the air preheater anti-blocking ash automatic control system according to an embodiment of the present application. Figure 6 As shown, the system is an automatic control system based on a distributed control system (DCS system), and the system includes a startup control module 61 and a low-load operation control module 62;

[0081] The startup control module 61 is used to monitor the flue gas temperature at the inlet of the denitrification reactor on the boiler side and the opening of the ammonia injection valve on the boiler side during the startup phase of the thermal power unit;

[0082] The start-up control module 61 is used to preheat the air through the boiler side air preheater according to the flue gas temperature at the denitration reactor inlet and the ammonia injection door opening;

[0083] The low-load operation control module 62 is used to monitor the temperature of the cold section element of the air preheater during the low-load operation phase of the thermal power unit to obtain the actual temperature value of the cold section element;

[0084] The low-load operation control module 62 is used to control the opening of the hot primary air recirculation adjustment door of the air preheater according to the actual temperature value of the cold section element and the preset temperature value of the cold section element, and adjust the temperature of the cold section element to prevent low-temperature corrosion of the air preheater.

[0085] Through the startup control module 61 and the low-load operation control module 62 in the embodiment of the present application, the problem of how to efficiently and accurately prevent low-temperature corrosion of the air preheater is solved, and the temperature of the cold section of the air preheater is controlled under multiple working conditions, effectively preventing the occurrence of low-temperature corrosion caused by too low a temperature and the occurrence of too high a temperature affecting the economy of the unit.

[0086] It should be noted that the above modules can be functional modules or program modules, and can be implemented through software or hardware. For modules implemented through hardware, the above modules can be located in the same processor; or the above modules can be located in different processors in any combination.

[0087] This embodiment also provides an electronic device, including a memory and a processor. A computer program is stored in the memory, and the processor is configured to run the computer program to execute the steps in any of the above method embodiments.

[0088] Optionally, the above electronic device may further include a transmission device and an input / output device. The transmission device is connected to the above processor, and the input / output device is connected to the above processor.

[0089] It should be noted that the specific examples in this embodiment may refer to the examples described in the above embodiments and optional implementation manners, and will not be elaborated here.

[0090] In addition, in combination with the automatic control method for preventing ash fouling of the air preheater in the above embodiments, an embodiment of the present application can provide a storage medium to implement it. A computer program is stored on the storage medium; when the computer program is executed by a processor, it implements any one of the automatic control methods for preventing ash fouling of the air preheater in the above embodiments.

[0091] In one embodiment, a computer device is provided. The computer device may be a terminal. The computer device includes a processor, a memory, a network interface, a display screen, and an input device connected through a system bus. The processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system and a computer program. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The network interface of the computer device is used to communicate with an external terminal through a network connection. When the computer program is executed by the processor, it implements an automatic control method for preventing ash fouling of an air preheater. The display screen of the computer device may be a liquid crystal display screen or an electronic ink display screen. The input device of the computer device may be a touch layer covering the display screen, or a button, a trackball, or a touchpad provided on the housing of the computer device, or an external keyboard, a touchpad, or a mouse, etc.

[0092] In one embodiment, Figure 7 is a schematic internal structure diagram of an electronic device according to an embodiment of the present application. As Figure 7 shown, an electronic device is provided. The electronic device may be a server, and its internal structure diagram may be as Figure 7As shown. The electronic device includes a processor, a network interface, an internal memory, and a non-volatile memory connected through an internal bus. Among them, the non-volatile memory stores an operating system, a computer program, and a database. The processor is used to provide computing and control capabilities. The network interface is used to communicate with external terminals through a network connection. The internal memory is used to provide an environment for the operation of the operating system and the computer program. The computer program, when executed by the processor, implements an automatic control method for preventing ash fouling of an air preheater. The database is used to store data.

[0093] Those skilled in the art can understand that Figure 7 the structure shown in is only a block diagram of some structures related to the solution of this application, and does not constitute a limitation on the electronic device to which the solution of this application is applied. The specific electronic device may include more or fewer components than those shown in the figure, or combine some components, or have different component arrangements.

[0094] Those of ordinary skill in the art can understand that all or part of the processes in the methods of the above embodiments can be completed by instructing relevant hardware through a computer program. The computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it may include the processes of the embodiments of the above methods. Among them, any reference to a memory, storage, database, or other medium used in the various embodiments provided in this application may include non-volatile and / or volatile memories. Non-volatile memory may include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), or flash memory. Volatile memory may include random access memory (RAM) or an external cache. By way of illustration and not limitation, RAM is available in many forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDR SDRAM), enhanced SDRAM (ESDRAM), synchronous link (Synchlink) DRAM (SLDRAM), memory bus (Rambus) direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM), etc.

[0095] Those skilled in the art should understand that the technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered to be within the scope described in this specification.

[0096] The above-described embodiments merely represent several implementation manners of the present application. The description thereof is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all fall within the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the appended claims.

Claims

1. An automatic control method for preventing ash fouling of an air preheater, characterized in that, The method includes: During the startup phase of a thermal power unit, monitoring the flue gas temperature at the inlet of the denitration reactor on the boiler side and monitoring the opening degree of the ammonia injection valve on the boiler side; According to the flue gas temperature at the inlet of the denitration reactor and the opening degree of the ammonia injection valve, preheating is carried out through the air preheater on the boiler side; During the low-load operation phase of the thermal power unit, monitoring the temperature of the cold section components of the air preheater to obtain the measured temperature value of the cold section components; When the absolute value deviation between the measured temperature value of the cold section components and the preset temperature value is greater than the preset deviation threshold value, through the temperature PID controller of the cold section components, based on the principle of single variable, the curve formula between the measured temperature value Tp of the cold section components and the ideal control value F1 of the hot primary air recirculation regulating valve of the air preheater is obtained as F1 = -37.8ln(Tp) + 80.14; based on the principle of single variable, the curve formula between the NOx content H of the flue gas at the inlet of the denitration reactor and the ideal control value F2 of the hot primary air recirculation regulating valve of the air preheater is obtained as F2 = -61.34ln(H) + 88.247; based on the principle of single variable, the curve formula between the load P of the thermal power unit and the ideal control value F3 of the hot primary air recirculation regulating valve of the air preheater is obtained as F3 = -5.946ln(P) + 11.257; the comprehensive ideal control value F of the hot primary air recirculation regulating valve of the air preheater is obtained as F = F1 + F2 + F3; When the absolute value deviation between the measured temperature value of the cold section components and the preset temperature value is not greater than the preset deviation threshold value, through the differential pressure PID controller of the cold section components, based on the principle of single variable, the curve formula between the measured temperature value Tp of the cold section components and the ideal control value F1 of the hot primary air recirculation regulating valve of the air preheater is obtained as F1 = -37.8ln(Tp) + 80.14; based on the principle of single variable, the curve formula between the NOx content H of the flue gas at the inlet of the denitration reactor and the ideal control value F2 of the hot primary air recirculation regulating valve of the air preheater is obtained as F2 = -61.34ln(H) + 88.247; based on the principle of single variable, the curve formula between the load P of the thermal power unit and the ideal control value F3 of the hot primary air recirculation regulating valve of the air preheater is obtained as F3 = -5.946ln(P) + 11.257; the comprehensive ideal control value F of the hot primary air recirculation regulating valve of the air preheater is obtained as F = F1 + F2 + F3; Then, based on the comprehensive ideal control value, controlling the opening degree of the hot primary air recirculation regulating valve to adjust the temperature of the cold section components to prevent low-temperature corrosion of the air preheater.

2. The method according to claim 1, wherein According to the flue gas temperature at the inlet of the denitration reactor and the opening degree of the ammonia injection valve, preheating through the air preheater on the boiler side includes: If the flue gas temperature at the inlet of the denitration reactor is greater than the preset temperature threshold value and the opening degree of the ammonia injection valve is greater than the preset opening degree threshold value, then open the hot primary air recirculation regulating valve of the air preheater on the boiler side for preheating.

3. The method according to claim 1, wherein Monitoring the temperature of the cold section components of the air preheater to obtain the measured temperature value of the cold section components includes: The temperatures of the cold-section components are respectively measured by a number of infrared temperature measuring devices installed in the air preheater, and the minimum temperature value is selected from the measured temperature values as the actual measured value of the temperature of the cold-section components.

4. The method according to claim 1, wherein Before controlling the opening degree of the hot primary air recirculation regulating valve of the air preheater according to the actual measured value of the temperature of the cold-section components and the preset temperature value of the cold-section components, the method includes: Obtaining the temperature set value of the cold-section components according to the comprehensive temperature at the cold end of the air preheater and the temperature characteristic curve of the cold-section components.

5. The method according to claim 1, characterized in that, The method includes: During the high-load operation stage of the thermal power unit, the hot primary air recirculation shut-off valve on the boiler side of the air preheater is interlocked and closed, and the hot primary air recirculation regulating valve of the air preheater is automatically closed to the zero position.

6. The method according to claim 5, wherein The method further includes: When the NOx emission concentration of the thermal power unit is lower than the preset concentration threshold, the opening degree of the hot primary air recirculation regulating valve on the boiler side of the air preheater is switched from 0 to the preset opening degree.

7. An automatic control system for preventing ash fouling of an air preheater, characterized in that, The system is an automatic control system built based on a distributed control system, and the system includes a start control module and a low-load operation control module; The start control module is used to monitor the flue gas temperature at the inlet of the denitration reactor on the boiler side and the opening degree of the ammonia injection valve on the boiler side during the start-up stage of the thermal power unit; The start control module is used to preheat through the air preheater on the boiler side according to the flue gas temperature at the inlet of the denitration reactor and the opening degree of the ammonia injection valve; The low-load operation control module is used to monitor the temperature of the cold-section components of the air preheater during the low-load operation stage of the thermal power unit to obtain the actual measured value of the temperature of the cold-section components; The low-load operation control module is used when the absolute value deviation between the actual measured value of the temperature of the cold-section components and the preset temperature value is greater than the preset deviation value threshold, and based on the principle of single variable, the curve formula F1 = -37.8ln(Tp) + 80.14 between the actual measured value Tp of the temperature of the cold-section components and the ideal control value F1 of the hot primary air recirculation regulating valve of the air preheater is obtained through the temperature PID controller of the cold-section components; Based on the principle of single variable, the curve formula F2 = -61.34ln(H) + 88.247 between the NOx content H of the flue gas at the inlet of the denitration reactor and the ideal control value F2 of the hot primary air recirculation regulating valve of the air preheater is obtained; Based on the principle of single variable, the curve formula F3 = -5.946ln(P) + 11.257 between the load P of the thermal power unit and the ideal control value F3 of the hot primary air recirculation regulating valve of the air preheater is obtained; the comprehensive ideal control value F of the hot primary air recirculation regulating valve of the air preheater is obtained as F = F1 + F2 + F3; When the absolute value deviation between the actual measured value of the temperature of the cold-section components and the preset temperature value is not greater than the preset deviation value threshold, based on the principle of single variable, the curve formula F1 = -37.8ln(Tp) + 80.14 between the actual measured value Tp of the temperature of the cold-section components and the ideal control value F1 of the hot primary air recirculation regulating valve of the air preheater is obtained through the differential pressure PID controller of the cold-section components; Based on the principle of single variable, the curve formula between the flue gas NOx content H at the inlet of the denitration reactor and the ideal control value F2 of the hot primary air recirculation regulating valve of the air preheater is obtained as F2 = -61.34ln(H) + 88.247; Based on the principle of single variable, the curve formula between the load P of the thermal power unit and the ideal control value F3 of the hot primary air recirculation regulating valve of the air preheater is obtained as F3 = -5.946ln(P) + 11.257; The comprehensive ideal control value F of the hot primary air recirculation regulating valve of the air preheater is obtained as F = F1 + F2 + F3; Based on the comprehensive ideal control value, the opening of the hot primary air recirculation regulating valve is controlled to adjust the temperature of the cold section components to prevent low-temperature corrosion of the air preheater.

Images