Optimized operation control device for low-pressure economizer of thermal power plant

Abstract

The utility model relates to an optimized operation control device for a low-pressure economizer, the low-pressure economizer is communicated with a low-pressure heater through a circulation pipeline, and the flow and the temperature of a working medium at an inlet of the low-pressure economizer are adjusted through the optimized operation control device. The control device comprises a control system, a detection assembly and an execution mechanism. The detection assembly is connected with the control system; the executing mechanism adjusts working medium parameters of an inlet of the low-pressure economizer according to the optimal operation mode of the real-time working condition determined by the control system, so that the low-temperature economizer can always guide operation work with the optimal operation data under the real-time working condition, and the utilization level of smoke waste heat is improved.

Description

Technical Field

[0001] The utility model relates to the technical field of optimized operation of thermal power plants, in particular to a low-pressure economizer optimized operation control device. Background Art

[0002] Low-pressure economizers (LPES) are commonly installed in coal-fired power units of 300 MW and above as a waste heat recovery device for flue gas. They utilize the waste heat from the tail flue gas to heat condensate in the turbine's low-pressure heating system, which is then returned to the turbine's thermal system for exhaust steam, thereby increasing the turbine's operating capacity. However, due to the impact of low-temperature corrosion in the tail flue, the flue gas temperature after absorbing heat in the LPES typically exceeds 90°C. Therefore, there is a maximum limit to the amount of heat absorbed by the LPES under the same operating conditions. Furthermore, the amount of heat absorbed by the LPES is affected by the temperature and flow rate of the heat-releasing flue gas, as well as the temperature and flow rate of the heat-absorbing fluid. The temperature and flow rate of the heat-releasing flue gas are affected by boiler load and coal quality, and are often unadjustable. Therefore, how to adjust the flow rate and temperature of the heat-absorbing fluid entering the LPES in real time to maximize waste heat absorption while ensuring that the exhaust temperature does not fall below the low-temperature corrosion limit is crucial for energy conservation and consumption reduction.

[0003] The traditional control device determines the flow rate and temperature of the heat absorbing medium entering the low-pressure economizer at different flue gas flow rates and temperatures based on the heat exchange performance curve of the low-pressure economizer. However, the heat exchange performance curve is determined based on the status of the low-pressure economizer when it leaves the factory. Due to the influence of the on-site environment, scaling of the heat exchange surface and equipment aging, the heat exchange performance of the low-pressure economizer will change with the increase of operating time, resulting in the optimal operating mode determined in a certain period of time. After a period of operation or overhaul and cleaning, in order to achieve the best heat exchange effect, performance tests are often required to re-determine the temperature and flow of the optimal heat absorbing medium to make it consistent with the current heat exchange performance of the low-pressure economizer, which consumes a lot of manpower and material resources, and the accuracy of manual operation is not high, the risk is increased, and the optimal operating mode determined at a certain point in time cannot adapt to the changes in the heat exchange performance of the low-pressure economizer in real time. Adjustments to operating conditions during the test may also cause low-temperature corrosion and shorten the service life of the equipment.

[0004] Therefore, it is necessary to further improve the existing low-pressure economizer operation control device to maximize the absorption of flue gas waste heat. Utility Model Content

[0005] In view of the shortcomings of the existing technology, the purpose of the present invention is to provide a low-pressure economizer optimization operation control device to solve the problem that the existing optimal operation mode of the low-pressure economizer cannot adapt to the changes in the heat exchange performance of the low-pressure economizer in real time.

[0006] In order to achieve the above purpose, the utility model adopts the following technical solutions:

[0007] A low-pressure economizer optimization operation control device, wherein the low-pressure economizer is connected to a low-pressure heater system through a flow pipeline, and the low-pressure economizer inlet working medium parameters are adjusted by the optimization operation control device, and the control device includes a control system, a detection component and an actuator;

[0008] The detection component is connected to the control system, and the detection component includes an inlet flue gas flow measurement module, an inlet flue gas temperature measurement module and an outlet flue gas temperature measurement module. The inlet flue gas flow measurement module and the inlet flue gas temperature measurement module are installed on the inlet flue of the low-pressure economizer, and the outlet flue gas temperature measurement module is installed on the outlet flue of the low-pressure economizer. The inlet flue gas flow measurement module, the inlet flue gas temperature measurement module and the outlet flue gas temperature measurement module are all communicatively connected with the control system, and are used to obtain the inlet flue gas temperature, inlet flue gas flow and outlet flue gas temperature of the low-pressure economizer when it is in real-time operating condition;

[0009] The control system is used to obtain a benchmark database of historical optimal operating modes, receive real-time operating condition data obtained by the detection component, and send adjustment instructions to the actuator by determining the optimal operating data of the real-time operating condition;

[0010] The actuator is connected to the control system. Based on the optimal operating mode of the real-time working conditions determined by the control system, the actuator adjusts the flow rate and temperature of the working medium at the low-pressure economizer inlet through an electric regulating valve installed on the low-pressure economizer inlet flow pipeline.

[0011] Furthermore, the circulation pipeline includes a first circulation pipeline, a second circulation pipeline, a mixing pipeline and a third circulation pipeline. The first circulation pipeline is connected to the outlet of the first low-pressure heater, the second circulation pipeline is connected to the outlet of the second low-pressure heater, the first circulation pipeline and the second circulation pipeline are connected and merged to connect to the mixing pipeline, the mixing pipeline is connected to the inlet of the low-pressure economizer, and the low-pressure economizer outlet is connected to the inlet of the fourth low-pressure heater via the third circulation pipeline.

[0012] Furthermore, the detection component also includes an inlet working fluid flow measurement module and an inlet working fluid temperature measurement module. The inlet working fluid flow measurement module and the inlet working fluid temperature measurement module are installed on the mixing pipeline and are communicatively connected to the control system.

[0013] Furthermore, the actuator is provided with the electric regulating valve at least on the outlet of two low-pressure heaters, respectively, for adjusting the flow rate and temperature of the working medium at the inlet of the low-pressure economizer.

[0014] Furthermore, the electric regulating valve at least includes a first electric regulating valve and a second electric regulating valve, the first electric regulating valve is installed on the first circulation pipeline, and the second electric regulating valve is installed on the second circulation pipeline.

[0015] In summary, compared with the prior art, the present invention has at least the following beneficial effects:

[0016] The present invention obtains the optimal operating mode for each operating condition from historical operating data through a control system, and uses a detection component to obtain real-time operating data of the low-pressure economizer. The control system sends real-time instructions to the actuator based on the real-time operating data to adjust the inlet working fluid flow and temperature. This solves the problem that the traditional device needs to isolate the system to determine the optimal operating mode based on performance tests, resulting in inconsistency with the actual operating conditions, as well as deviations between the performance test and the actual operating conditions. There is no need to modify the equipment, and the safety is high and the maintenance cost is low. In addition, the present invention also uses the real-time operating data of the low-pressure economizer to self-learn and update the optimal operating mode for each operating condition, overcoming the influence of the decline in the heat exchange performance of the low-pressure economizer or the influence of major and minor repairs on its heat exchange performance, so that the optimal operating mode always conforms to the actual heat exchange performance of the low-pressure economizer, thereby achieving the best state for the recovery and utilization of the waste heat of the tail flue gas. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the specific implementation methods of the utility model or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0018] Figure 1 A schematic diagram of a low-pressure economizer optimization operation control device provided in an embodiment of the present utility model.

[0019] Figure 2 A schematic diagram of a low-pressure economizer optimization operation control device according to another embodiment of the present invention.

[0020] Description of reference numerals:

[0021] 1. Control system;

[0022] 2. Detection component; 21. Inlet flue gas flow measurement module; 22. Inlet flue gas temperature measurement module; 23. Outlet flue gas temperature measurement module; 24. Inlet working fluid flow measurement module; 25. Inlet working fluid temperature measurement module;

[0023] 3. Actuator; 31. First electric regulating valve; 32. Second electric regulating valve;

[0024] 4. Low-pressure economizer; 41. First circulation pipeline; 42. Second circulation pipeline; 43. Mixing pipeline; 44. Third circulation pipeline;

[0025] 5. Low-pressure heater; 51. First low-pressure heater; 52. Second low-pressure heater; 53. Third low-pressure heater; 54. Fourth low-pressure heater. DETAILED DESCRIPTION

[0026] The following is a clear and complete description of the technical solution of the present invention in conjunction with the accompanying drawings. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0027] In the description of this utility model, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating positions or relationships, are based on the positions or relationships shown in the accompanying drawings and are intended solely to facilitate the description of this utility model and simplify the description. They do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on this utility model. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0028] In the description of this utility model, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; mechanical connections, electrical connections; direct connections, indirect connections through an intermediate medium, and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in this utility model based on the specific circumstances.

[0029] As attached Figure 1 As shown, the utility model provides a low-pressure economizer optimization operation control device. In this embodiment, the low-pressure economizer 4 is installed in the low-pressure heating system of the steam turbine of the thermal power plant. Usually, the heat-absorbing working fluid is introduced from the outlets of no less than two low-pressure heaters. For example, in this embodiment, the heat-absorbing working fluid is introduced from the low-pressure heater 51 and the low-pressure heater 52, and the heated working fluid is released at the inlet of the low-pressure heater with higher parameters. In this embodiment, the heated working fluid is released from the inlet of the low-pressure heater 54.

[0030] The low-pressure economizer optimization operation control device is located in a distributed control system (DCS). The low-pressure heater system parameters required by the operation control device, such as the low-pressure heater inlet and outlet temperatures, can be obtained from the DCS.

[0031] The low-pressure economizer optimized operation control device includes a control system 1, a detection component 2 and an actuator 3;

[0032] The detection component 2 is connected to the control system 1 and is used to obtain the inlet flue gas temperature, inlet flue gas flow rate, outlet flue gas temperature, inlet working medium temperature and flow rate of the low-pressure economizer 4 in real-time working conditions, providing the control system 1 with the basis and indicators for working condition classification;

[0033] The control system 1 is used to obtain the reference database, receive the real-time working condition information obtained by the detection component 2, compare it with the reference database, determine the optimal operating data of the real-time working condition, and send adjustment instructions to the actuator 3;

[0034] The actuator 3 adjusts the working fluid flow and inlet working fluid temperature of the low-pressure economizer 4 inlet through at least the first electric regulating valve and the second electric regulating valve according to the optimal operating mode of the real-time working conditions determined by the control system to achieve the optimal operating state.

[0035] Specifically, the control system 1 includes a reference database establishment module, which includes the following modules:

[0036] A historical data acquisition module is used to acquire historical operating data of the unit, which includes at least inlet flue gas temperature, inlet flue gas flow rate, outlet flue gas temperature, inlet working fluid flow rate and inlet working fluid temperature, and classifies historical operating data with inlet flue gas temperature within a set range and inlet flue gas flow rate within a set range as being under the same operating condition;

[0037] The steady-state operating condition judgment module is used to filter out the steady-state operating historical data of the unit under various operating conditions according to the steady-state judgment criteria. The steady-state judgment criteria are judged according to Table 1 below;

[0038] This application specifies the steady-state operating conditions of low-pressure economizers in engineering applications based on GB / T 10184-2015 "Procedure for Performance Test of Power Plant Boilers" and in combination with actual operating conditions: within 10 minutes, when the difference between the maximum and minimum values ​​of the two variables described in Table 1 is less than twice the absolute value of the fluctuation value, the unit is considered to have reached a stable state.

[0039] Table 1 Steady-state operating condition judgment criteria

[0040] Serial number variable Fluctuation value 1 Low pressure economizer inlet flue gas temperature 2.5℃ 2 Flue gas flow at low pressure economizer inlet 5%

[0041] The module for determining the best historical operating mode is used to obtain the best operating data from all steady-state operating historical data. The best operating data are the inlet flue gas temperature, inlet flue gas flow rate, outlet flue gas temperature, inlet working fluid flow rate and inlet working fluid temperature when the outlet flue gas temperature of the low-pressure economizer 4 is greater than the low-temperature corrosion limit temperature and is closest to the low-temperature corrosion limit temperature under each operating condition. Specifically, this module is used to determine the outlet flue gas temperature corresponding to different inlet working fluid flow rates and inlet working fluid flow rates of the low-pressure economizer 4 under the same operating conditions. When the outlet flue gas temperature of the low-pressure economizer 4 is greater than the low-temperature corrosion limit temperature and is closest to the low-temperature corrosion limit temperature, the corresponding best operating data of the low-pressure economizer 4 at this time is stored in the reference database as the basis for the control system 1 to guide the low-pressure economizer 4 to optimize its operation.

[0042] The steps for establishing the benchmark database are as follows: first, the data obtained from the historical data acquisition module is filtered by the steady-state operating condition judgment module, then all stable operating conditions in the unit operation history are obtained, and finally the data of the stable operating conditions is transmitted to the historical optimal operating mode determination module, and the optimal operating data of the low-pressure economizer 4 corresponding to this time is stored in the benchmark database.

[0043] Due to the limitations of the low-pressure economizer 4 in the historical operation process, it is affected by factors such as the inlet heat-absorbing working fluid adjustment range, scaling, overhaul and cleaning, which will cause the heat exchange performance to change even under the same operating conditions. Some operating conditions have never appeared, or an operating mode that is better than the historical best operating mode stored in the historical best operating mode determination module may appear. At this time, the control system 1 also includes a benchmark database update module, which is used to update the outlet flue gas temperature in the best operating data under the corresponding operating conditions, or the inlet working fluid temperature, inlet working fluid flow rate and outlet flue gas temperature in the best operating data under the corresponding operating conditions according to the inlet flue gas temperature, inlet flue gas flow rate and outlet flue gas temperature under the real-time operating conditions, so that the best operating mode stored in the benchmark database always matches the real-time heat exchange performance of the low-pressure economizer 4.

[0044] The detection component 2 includes an inlet flue gas flow measurement module 21, an inlet flue gas temperature measurement module 22, and an outlet flue gas temperature measurement module 23. The inlet flue gas flow measurement module 21 is used to measure the inlet flue gas flow data of the low-pressure economizer 4, the inlet flue gas temperature measurement module 22 is used to measure the inlet flue gas temperature data of the low-pressure economizer 4, and the outlet flue gas temperature measurement module 23 is used to measure the outlet flue gas temperature data of the low-pressure economizer 4. The inlet flue gas flow measurement module 21, the inlet flue gas temperature measurement module 22, and the outlet flue gas temperature measurement module 23 are all communicatively connected to the control system 1 for real-time data transmission, so that the control system 1 can issue corresponding adjustment instructions to the actuator 3 based on actual operating conditions to achieve optimized operation control of the low-pressure economizer 4.

[0045] Another composition of the detection component 2 is that in addition to the above structure, it also includes an inlet working fluid flow measurement module 24 and an inlet working fluid temperature measurement module 25. The inlet working fluid flow measurement module 24 is used to measure the inlet working fluid flow data of the low-pressure economizer 4, and the inlet working fluid temperature measurement module 25 is used to measure the inlet working fluid temperature data of the low-pressure economizer 4. The inlet working fluid flow measurement module 24 and the inlet working fluid temperature measurement module 25 are both communicated with the control system 1 for real-time data transmission, so that the control system 1 can accurately detect in real time whether the current inlet working fluid flow and inlet working fluid temperature meet the requirements of the adjustment instructions. If there is a deviation, the control system 1 can quickly take corresponding adjustment measures to ensure that the system operates according to the expected settings, maintain the stability and reliability of the system, and achieve optimized operation control of the low-pressure economizer 4.

[0046] The actuator 3 includes a first electric regulating valve 31 and a second electric regulating valve 32. The first electric regulating valve 31 and the second electric regulating valve 32 are communicatively connected to the control system 1. According to the adjustment instructions sent by the control system 1, the opening of the first electric regulating valve 31 and the second electric regulating valve 32 are adjusted to make the inlet working fluid flow rate and temperature reach the inlet working fluid flow rate and temperature requirements of the optimal operating mode.

[0047] The opening of the electric control valve can be quantitatively determined based on the valve flow characteristic curve. For example, the optimal operating mode determined by a certain working condition control system is that the inlet working fluid flow is 35t / h and the inlet temperature is 51°C. At this time, the outlet temperature of the low-pressure heater 51 is 43°C, and the outlet temperature of the high-pressure heater 51 is 65°C. It can be calculated that the flow through the circulation pipeline 41 is 22.3t / h, and the flow through the circulation pipeline 42 is 12.7t / h. Then, according to the valve characteristic curve, that is, the opening and flow curve, the opening of the first electric control valve 31 and the second electric control valve 32 are quantitatively adjusted.

[0048] The low-pressure economizer 4 is externally connected to at least three low-pressure heaters, whose inlets and outlets communicate with the low-pressure economizer 4 via flow lines. In this embodiment, the outlet of the first low-pressure heater 51 is connected to the low-pressure economizer 4 via a first flow line 41, which is equipped with a first electric control valve 31. The outlet of the second low-pressure heater 52 is connected to the low-pressure economizer 4 via a second flow line 42, which is equipped with a second electric control valve 32. The heat-absorbing working fluid passes through the first and second electric control valves 31 and 32, respectively, and then merges at the intersection of the first and second flow lines 41 and 42, then enters the inlet of the low-pressure economizer 4 through a mixing line 43. The working fluid then passes through the low-pressure economizer heaters and enters the inlet of the fourth low-pressure heater 54 through a third flow line 44.

[0049] In this embodiment, as shown in the attached Figure 1As shown, the first electric regulating valve 31 sends the working fluid flow rate flowing out of the first low-pressure heater 51 to the control system 1, and the control system 1 obtains the working fluid temperature flowing out of the first low-pressure heater 51 from the DCS; the second electric regulating valve 32 sends the working fluid flow rate flowing out of the second low-pressure heater 52 to the control system 1, and the control system 1 obtains the working fluid temperature flowing out of the second low-pressure heater 52 from the DCS. The two working fluids flow through the first flow pipeline 41 and the second flow pipeline 42 respectively, and then mix in the mixing pipeline 45, and then flow into the low-pressure economizer 4 to absorb heat. Based on the above data, the control system 1 can calculate the inlet working fluid flow rate and the inlet working fluid temperature. This embodiment uses at least two low-pressure heaters as working fluid sources. For example, the temperature of the first low-pressure heater 51 is lower, and the temperature of the second low-pressure heater 52 is higher, and electric regulating valves are used to control the flow respectively. The inlet working fluid temperature and the inlet working fluid flow can be flexibly adjusted according to the adjustment instructions issued by the control system 1. The inlet working fluid temperature and the inlet working fluid flow can be quickly adjusted, so that the operating mode of the low-pressure economizer 4 can approach the operating mode corresponding to the optimal operating data as soon as possible, thereby quickly improving the heat exchange efficiency.

[0050] In another embodiment, as shown in the attached Figure 2 As shown, an inlet working fluid flow measurement module 24 and an inlet working fluid temperature measurement module 25 are provided on the mixing pipeline 43. After the control system 1 calculates and adjusts the inlet working fluid flow and the inlet working fluid temperature, the inlet working fluid flow and the inlet working fluid temperature are detected. If the adjustment is inaccurate, the control system 1 can quickly issue an adjustment instruction to guide the first electric control valve 31 and the second electric control valve 32 to continue to adjust, so as to ensure that the system operates according to the expected settings, maintain the stability and reliability of the system, and realize the optimized operation control of the low-pressure economizer 4.

[0051] Based on the above two embodiments, when the inlet flue gas flow and inlet flue gas temperature of the low-pressure economizer 4 are judged to belong to operating condition 1 based on the fluctuation range of Table 1, and at the same time in accordance with the steady-state operating condition rules, the control system 1 adjusts the first electric regulating valve 31 and the second electric regulating valve 32 in real time based on the optimal operating data of the operating condition recorded in the benchmark database, and adjusts the flow of the working fluid through the first flow pipeline 41 and the second flow pipeline 42, so as to control the inlet working fluid temperature and inlet working fluid flow flowing into the low-pressure economizer 4 in real time, thereby making full use of the waste heat of the flue gas and improving the energy-saving effect of the unit.

[0052] The working medium after absorbing heat in the low-pressure economizer 4 is discharged from the inlet of the fourth low-pressure heater 54 through the third flow pipeline 44, thereby returning the absorbed flue gas waste heat to the turbine thermal system to achieve effective utilization of the waste heat.

[0053] The above-mentioned embodiments are only preferred embodiments of the present invention and cannot be used to limit the scope of protection of the present invention. Any non-substantial changes and replacements made by technicians in this field on the basis of the present invention fall within the scope of protection required by the present invention.

Claims

1. A low-pressure economizer optimization operation control device, wherein the low-pressure economizer is connected to a low-pressure heater (51, 52, 53, 54) system through a flow pipeline, and the low-pressure economizer inlet working medium parameters are adjusted by the optimization operation control device, characterized in that: The control device comprises a control system (1), a detection component (2) and an actuator (3); The detection component is connected to the control system (1), and the detection component (2) includes an inlet flue gas flow measurement module (21), an inlet flue gas temperature measurement module (22), and an outlet flue gas temperature measurement module (23). The inlet flue gas flow measurement module (21) and the inlet flue gas temperature measurement module (22) are installed on the inlet flue of the low-pressure economizer, and the outlet flue gas temperature measurement module (23) is installed on the outlet flue of the low-pressure economizer. The inlet flue gas flow measurement module (21), the inlet flue gas temperature measurement module (22), and the outlet flue gas temperature measurement module (23) are all connected to the control system for communication and are used to obtain the inlet flue gas temperature, inlet flue gas flow, and outlet flue gas temperature of the low-pressure economizer in real-time operating conditions. The control system (1) is used to send adjustment instructions to the actuator (3); The actuator (3) is connected to the control system (1), and the actuator (3) adjusts the flow rate and temperature of the working medium at the inlet of the low-pressure economizer through the electric regulating valves (31, 32) installed on the flow pipeline of the inlet of the low-pressure economizer based on the optimal operating mode of the real-time working conditions determined by the control system (1); The circulation pipeline includes a first circulation pipeline (41), a second circulation pipeline (42), a mixing pipeline (43) and a third circulation pipeline (44), wherein the first circulation pipeline (41) is connected to the outlet of the first low-pressure heater (51), the second circulation pipeline (42) is connected to the outlet of the second low-pressure heater (52), the first circulation pipeline (41) and the second circulation pipeline (42) are connected and merged to connect to the mixing pipeline (43), the mixing pipeline (43) is connected to the inlet of the low-pressure economizer, and the outlet of the low-pressure economizer is connected to the inlet of the fourth low-pressure heater (54) through the third circulation pipeline (44).

2. The low-pressure economizer optimized operation control device according to claim 1, characterized in that: The detection assembly further includes an inlet working fluid flow measurement module (24) and an inlet working fluid temperature measurement module (25), wherein the inlet working fluid flow measurement module and the inlet working fluid temperature measurement module are installed on the mixing pipeline (43) and are communicatively connected to the control system (1).

3. The low-pressure economizer optimized operation control device according to claim 1, characterized in that: The actuator is provided with the electric regulating valve at the outlet of at least two low-pressure heaters (51, 52), respectively, for regulating the flow rate and temperature of the working medium at the inlet of the low-pressure economizer.

4. The low-pressure economizer optimized operation control device according to claim 3, characterized in that: The electric regulating valve comprises at least a first electric regulating valve (31) and a second electric regulating valve (32), wherein the first electric regulating valve (31) is installed on a first circulation pipeline (41), and the second electric regulating valve (32) is installed on a second circulation pipeline (42).

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