Extraction condensing heat supply unit operation optimization method based on heat supply safety

Abstract

The invention discloses an extraction condensing heat supply unit operation optimization method based on heat supply safety, and the method comprises the steps: adding three heat supply network heater outlet mother pipe water supply temperature measuring points, introducing the three heat supply network heater outlet mother pipe water supply temperature measuring points into a control DPU (Data Processing Unit) where a DCS (Distributed Control System) middle exhaust and extraction steam regulating valve is located, and respectively adding three middle exhaust and extraction steam pressure measuring points and three low-pressure cylinder steam inlet pressure measuring points; the intermediate exhaust steam extraction regulating valve automatically regulates the opening degree of the regulating valve by taking the water temperature of an outlet main pipe of a heater of a heat supply network as a control target, the low-pressure cylinder steam inlet regulating valve controls according to safety and economic strategies, and pulses of the intermediate exhaust steam extraction regulating valve and the low-pressure cylinder steam inlet regulating valve track primary frequency modulation large-frequency-difference disturbance optimization. An intermediate exhaust steam extraction regulating valve and a low-pressure cylinder steam admission regulating valve are automatically regulated, so that the steam admission throttling loss of a low-pressure cylinder can be reduced on the premise of ensuring the safe operation of a heat supply unit, and the heat consumption rate of a steam turbine is reduced; after a primary frequency modulation large-frequency-difference action or test instruction is sent out, a low-pressure cylinder steam inlet regulating valve is opened in a pulse mode and a middle-discharge steam extraction regulating valve is closed in a pulse mode according to a current high-pressure speed regulation valve position instruction, and the qualification rate of the primary frequency modulation large-frequency-difference action or test is increased.

Description

Technical Field

[0001] The present invention relates to the field of thermal power generation energy-saving technology, and more specifically, to a method for optimizing the operation of an extraction condensation heating unit based on heating safety. Background Art

[0002] In northern regions, winter heating is required. Currently, extraction of steam from the exhaust of the intermediate-pressure cylinder and extraction of steam through perforated pipes connecting the intermediate and low-pressure cylinders are common heating methods. The low-pressure cylinder steam inlet regulating valve uses a hydraulically controlled butterfly valve, which has poor adjustment linearity and low precision. The intermediate exhaust steam regulating valve uses an electrically (pneumatically) controlled regulating gate, which offers high adjustment precision. The steam inlet regulating valve for the heating network heater uses an electrically operated gate or an electrically controlled regulating gate, which offers high precision. The current extraction-condensation heating method has the following main problems: 1. During operation, the middle exhaust steam extraction regulating valve, the heat network heater steam inlet regulating valve, and the low-pressure cylinder steam inlet regulating valve are all manually controlled by the operating personnel. All three regulating valves or two regulating valves are throttling, resulting in large throttling losses in the low-pressure cylinder steam inlet, reduced low-pressure cylinder efficiency and low-pressure cylinder steam inlet cycle thermal efficiency, increased heat consumption rate, and a significant increase in the power generation coal consumption rate.

[0003] 2. The steam inlet regulating valve of the heat network heater is throttled, the steam inlet pressure is reduced, the flow rate is increased, and the inlet tube sheet is severely eroded, which can easily cause leakage of the heater; the operating personnel fail to monitor and adjust the pressure and temperature of the middle row, the pressure difference of the middle row last stage blades, and the low-pressure cylinder steam inlet pressure in a timely manner, which will cause the middle pressure cylinder last stage blades to be overloaded and the low pressure cylinder last stage blades to overheat, and long-term operation may cause the blades to break.

[0004] 3. Due to the low heat storage capacity of the boiler, imperfect control logic, and poor response capacity of the heating unit to the electrical load, the pass rate of the grid's large frequency deviation operation or the monthly frequency regulation large frequency difference disturbance test of the unit is low. Summary of the Invention

[0005] The object of the present invention is to provide an operation optimization method of an extraction-condensation heating unit based on heating safety.

[0006] In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is as follows: a method for optimizing the operation of an extraction condensing heating unit based on heating safety, comprising the following steps: S1. Add three water supply temperature measurement points at the outlet main pipe of the heating network heater and introduce them into the DPU where the DCS exhaust steam control valve is located; S2. Increase the number of measuring points for the middle exhaust steam pressure and the low-pressure cylinder steam inlet pressure to 3 each; S3, add two calculation points: the pressure difference between the extraction steam of the first stage in the middle row and the extraction steam of the middle row, and the pressure difference between the extraction steam of the middle row and the steam inlet of the low-pressure cylinder; S4, the middle exhaust steam control valve takes the outlet main pipe water temperature of the heating network heater as the control target and automatically adjusts the opening of the control valve; S5, the low-pressure cylinder steam inlet regulating valve is controlled according to the safety and economic strategy; S6, middle exhaust steam control valve, low pressure cylinder steam inlet control valve pulse tracking primary frequency modulation large frequency difference disturbance optimization; S7. Add a control interface to control the extraction steam pressure and the opening of the above-mentioned regulating valves.

[0007] Preferably, in step S1, the parameters related to the heating network heater and the middle exhaust steam extraction regulating valve are controlled by different DPUs, and three new heating network heater outlet main pipe water supply temperature measuring points are added and connected to the DPU where the middle exhaust steam extraction regulating valve is located for control.

[0008] Preferably, in step S4, when the outlet water temperature is lower than the target value, the middle exhaust steam extraction regulating valve is automatically opened; when the outlet water temperature is higher than the target value, the middle exhaust steam extraction regulating valve is automatically closed.

[0009] Preferably, in step S5, the safety strategy is: the middle row extraction steam pressure and temperature do not exceed the limit value; the low pressure cylinder inlet steam pressure does not exceed the limit value; the pressure difference between the middle row extraction steam of the previous stage and the middle row extraction steam does not exceed the pressure difference under the designed maximum steam inlet flow condition of the turbine.

[0010] Preferably, in step S5, the economic strategy is: the low-pressure cylinder steam inlet regulating valve is automatically controlled according to the load-intermediate exhaust steam extraction pressure curve embedded in the system, the minimum intermediate exhaust steam extraction pressure limit specified in the regulations is used as the reference value, six optimized load-extraction pressure corresponding curves are set, and the other points are obtained by interpolation. Under the premise of ensuring the safety of the unit's heating parameters, the minimum difference between the intermediate exhaust steam extraction pressure and the low-pressure cylinder steam inlet pressure is used as the control target.

[0011] Preferably, the specific method of step S6 is: the pulses of the middle exhaust steam extraction regulating valve and the low-pressure cylinder steam inlet regulating valve participate in the rapid load regulation. When the frequency modulation with large frequency difference and load increase instruction is greater than A, the system quickly opens the low-pressure cylinder steam inlet regulating valve position instruction function by C% and quickly closes the steam extraction regulating valve position instruction function by D% according to the current high-pressure speed regulating valve position instruction function by B%.

[0012] Compared with the prior art, the advantages of the present invention are: The present invention realizes automatic adjustment of the middle exhaust steam extraction regulating valve and the low-pressure cylinder steam inlet regulating valve by adding some key measuring points, improving the safety monitoring means, optimizing the relevant control logic, and can reduce the throttling loss of the low-pressure cylinder steam inlet and reduce the heat consumption rate under the premise of ensuring the safe operation of the heating unit; after a large frequency difference frequency modulation action or a test instruction is issued, according to the current high-pressure speed regulating valve position instruction, the low-pressure cylinder steam inlet regulating valve is pulsed open and the middle exhaust steam extraction regulating valve is closed, thereby improving the qualified rate; solves the safety problems of the existing middle and low-pressure cylinder last-stage blade breakage caused by improper monitoring and manual operation of the operating personnel of the condensing heating unit, and frequent flushing and leakage of the heat network heater, thereby reducing the work intensity of the operating personnel. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. 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 paying any creative work.

[0014] Figure 1 This is a flow chart of a method for optimizing the operation of an extraction-condensing heating unit based on heating safety according to the present invention; Figure 2 This is a framework diagram of an extraction-condensing heating unit operation optimization method based on heating safety according to the present invention applied to a DCS control system in the prior art; Figure 3 This is the curve diagram of the 660MW ultra-supercritical heating unit. DETAILED DESCRIPTION

[0015] The preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more precise definition of the protection scope of the present invention.

[0016] See Figure 1 As shown, the present invention provides an operation optimization method for an extraction condensing heating unit based on heating safety, comprising the following steps: S1. Add three water supply temperature measurement points at the outlet main pipe of the heating network heater and introduce them into the DPU where the DCS exhaust steam control valve is located; S2. Increase the number of measuring points for the middle exhaust steam pressure and the low-pressure cylinder steam inlet pressure to 3 each; S3, add two calculation points: the pressure difference between the extraction steam of the first stage in the middle row and the extraction steam of the middle row, and the pressure difference between the extraction steam of the middle row and the steam inlet of the low-pressure cylinder; S4, the middle exhaust steam control valve takes the outlet main pipe water temperature of the heating network heater as the control target and automatically adjusts the opening of the control valve; S5, the low-pressure cylinder steam inlet regulating valve is controlled according to the safety and economic strategy; S6, middle exhaust steam control valve, low pressure cylinder steam inlet control valve pulse tracking primary frequency modulation large frequency difference disturbance optimization; S7. Add a control interface to control the extraction steam pressure and the opening of the above-mentioned regulating valves.

[0017] The above-mentioned extraction-condensing heating unit operation optimization method introduces a DCS system by adding three water supply temperature measurement points at the outlet main pipe of the heating network heater. The intermediate exhaust steam control valve selects the water supply temperature to meet the automatic thermal start-up conditions. The heating network heater inlet steam control valve is fully opened, and the control logic configuration of the intermediate exhaust steam control valve and the low-pressure cylinder inlet steam control valve is optimized. While ensuring the safety of the final stage blades of the intermediate and low-pressure cylinders and preventing load oscillation, the openings of the intermediate exhaust steam control valve and the low-pressure cylinder inlet steam control valve are automatically adjusted according to the system's embedded control curve and the water supply temperature required by the heating network user. This reduces throttling losses in the low-pressure cylinder inlet steam, improves the low-pressure cylinder efficiency, and improves the thermal efficiency of the low-pressure cylinder inlet steam cycle. When a large frequency difference operation or disturbance test command is issued for the primary frequency modulation, pulse control commands are triggered for the intermediate exhaust steam control valve and the low-pressure cylinder inlet steam control valve. Based on the current high-pressure speed control valve opening, the low-pressure cylinder inlet steam control valve is automatically opened and the intermediate exhaust steam control valve is closed. This ensures that the primary frequency modulation large frequency difference operation or disturbance test passes, avoiding grid assessment.

[0018] In step S2, in the DCS (distributed control system), the DPU (distributed processing unit) where the middle exhaust steam extraction regulating valve is located is the core control node, responsible for executing the automatic control logic of the load-middle exhaust steam extraction pressure curve.

[0019] In step S3, the two calculation points are the pressure difference P1 between the extraction steam of the first stage in the middle row and the extraction steam of the middle row, and the pressure difference P2 between the extraction steam of the middle row and the low-pressure cylinder inlet steam. P1 = the extraction steam pressure of the first stage in the middle row - the extraction steam pressure of the middle row. This can reflect the pressure difference before and after the blades of the last stage in the middle row and determine whether the blades of the last stage in the middle row are overloaded. P2 = mid-row extraction steam pressure - low-pressure cylinder inlet steam pressure, which can reflect the pressure loss before and after the low-pressure cylinder inlet steam regulating valve and is used to analyze the low-pressure cylinder inlet steam throttling loss.

[0020] In this embodiment, in step S1, the relevant parameters of the heating network heater and the middle exhaust steam extraction regulating valve are controlled by different DPUs, and three new heating network heater outlet main pipe water supply temperature measuring points are added and connected to the DPU where the middle exhaust steam extraction regulating valve is located.

[0021] In this embodiment, in step S4, when the outlet water temperature is lower than the target value, the middle exhaust steam extraction regulating valve is automatically opened; when the outlet water temperature is higher than the target value, the middle exhaust steam extraction regulating valve is automatically closed.

[0022] In this embodiment, in step S5, the safety strategy is: the middle row extraction steam pressure and temperature do not exceed the limit value; the low pressure cylinder inlet steam pressure does not exceed the limit value; the pressure difference between the middle row extraction steam of the previous stage and the middle row extraction steam does not exceed the pressure difference under the designed maximum steam inlet flow condition of the turbine.

[0023] In this embodiment, in step S5, the economic strategy is: the low-pressure cylinder steam inlet regulating valve is automatically controlled according to the load-intermediate exhaust steam extraction pressure curve embedded in the system, and the minimum intermediate exhaust steam extraction pressure limit specified in the regulations is used as the reference value. Six optimized load-extraction pressure corresponding curves are set, and the other points are obtained by interpolation. Under the premise of ensuring the safety of the unit's heating parameters, the difference between the intermediate exhaust steam extraction pressure and the low-pressure cylinder steam inlet pressure is minimized as the control target to reduce the low-pressure cylinder steam inlet throttling loss.

[0024] Through precise control, it is possible to avoid overload and breakage of the last stage blades of the intermediate pressure cylinder; avoid excessive low steam pressure in the low pressure cylinder, which may cause overheating and breakage of the last stage blades of the low pressure cylinder; and avoid scouring and leakage of the tube bundle caused by throttling of the steam inlet regulating valve of the heat network heater.

[0025] Take a 660MW ultra-supercritical heating unit as an example (see Figure 3 ), the horizontal axis is the load, and the vertical axis is the middle exhaust steam pressure.

[0026] Grid companies require units to meet their primary frequency regulation (PFR) tracking capabilities for large frequency deviation disturbances. Failure to meet these requirements will result in a power assessment. Testing standards for large deviation disturbances in primary frequency regulation vary across provincial grids. For example, in the Shandong PFR, each month when a major frequency disturbance occurs, the actual operation of each unit is used to calculate the primary frequency regulation power contribution index (Q%). In the absence of major frequency disturbances, each unit's primary frequency regulation power contribution index (Q%) and the unit's comprehensive primary frequency regulation assessment index (K0) are calculated through remote primary frequency regulation disturbance testing. If the primary frequency regulation power contribution index (Q%) is less than 40%, a power assessment of twice the rated capacity is applied. Due to the poor ability of heating units to quickly respond to electrical loads, the pass rate for large deviation primary frequency regulation operations is low.

[0027] In order to increase the qualified rate of the large deviation action of the primary frequency modulation, in this embodiment, the pulses of the middle exhaust steam extraction control valve and the low-pressure cylinder steam inlet control valve participate in the rapid load regulation. When the primary frequency modulation with large frequency difference and load instruction is greater than A, the system will quickly open the low-pressure cylinder steam inlet control valve position instruction function by C% and quickly close the extraction steam control valve position instruction function by D% according to the current high-pressure speed regulating valve valve position instruction function B%.

[0028] like Figure 2 As shown, the optimization method of the present invention is introduced into the existing DCS control system. Figure 21 in the middle is the intermediate pressure cylinder of the steam turbine, 2 is the low pressure cylinder of the steam turbine, 3 is the low pressure cylinder steam inlet regulating valve, 4 is the connecting pipe between the intermediate and low pressure cylinders, 5 is the steam supply pipe for the middle row, 6 is the electric door for the steam extraction of the middle row, 7 is the steam extraction regulating valve for the middle row, and 8 is the steam extraction pipe for the first stage of the middle row; Through the control button in the display window, in manual mode, you can manually change the "set pressure" to change the extraction pressure; in automatic mode, the opening of the low-pressure cylinder steam inlet regulating valve is automatically controlled according to the load-mid-exhaust extraction pressure corresponding curve, and more precise automatic control can be achieved by manually changing the "pressure bias".

[0029] Although the embodiments of the present invention are described in conjunction with the accompanying drawings, the patent owner may make various changes or modifications within the scope of the appended claims. As long as they do not exceed the scope of protection described in the claims of the present invention, they should be within the scope of protection of the present invention.

Claims

1. A method for optimizing the operation of an extraction-condensing heating unit based on heating safety, characterized in that: The following steps are involved: S1. Add three water supply temperature measurement points at the outlet main pipe of the heating network heater and introduce them into the DPU where the DCS exhaust steam control valve is located; S2. Increase the number of measuring points for the middle exhaust steam pressure and the low-pressure cylinder steam inlet pressure to 3 each; S3, add two calculation points: the pressure difference between the extraction steam of the first stage in the middle row and the extraction steam of the middle row, and the pressure difference between the extraction steam of the middle row and the steam inlet of the low-pressure cylinder; S4, the middle exhaust steam control valve takes the outlet main pipe water temperature of the heating network heater as the control target and automatically adjusts the opening of the control valve; S5, the low-pressure cylinder steam inlet regulating valve is controlled according to the safety and economic strategy; S6, middle exhaust steam control valve, low pressure cylinder steam inlet control valve pulse tracking primary frequency modulation large frequency difference disturbance optimization; S7. Add a control interface to control the extraction steam pressure and the opening of the above-mentioned regulating valves.

2. The method for optimizing the operation of an extraction-condensation heating unit based on heating safety according to claim 1, characterized in that: In step S1, the parameters related to the heating network heater and the middle exhaust steam extraction regulating valve are controlled by different DPUs, and three new water supply temperature measuring points of the heating network heater outlet main pipe are added and connected to the DPU where the middle exhaust steam extraction regulating valve is located for control.

3. The method for optimizing the operation of an extraction-condensation heating unit based on heating safety according to claim 1, characterized in that: In step S4, when the outlet water temperature is lower than the target value, the middle exhaust steam extraction regulating valve is automatically opened; when the outlet water temperature is higher than the target value, the middle exhaust steam extraction regulating valve is automatically closed.

4. The method for optimizing the operation of an extraction-condensation heating unit based on heating safety according to claim 1, characterized in that: In step S5, the safety strategy is: the middle row extraction steam pressure and temperature do not exceed the limit value; the low pressure cylinder inlet steam pressure does not exceed the limit value; the middle row extraction steam pressure difference between the previous stage extraction steam and the middle row extraction steam does not exceed the pressure difference under the design turbine maximum steam inlet flow condition.

5. The method for optimizing the operation of an extraction-condensation heating unit based on heating safety according to claim 1, characterized in that: In step S5, the economic strategy is as follows: the low-pressure cylinder steam inlet regulating valve is automatically controlled according to the load-intermediate exhaust steam extraction pressure curve embedded in the system, and the minimum intermediate exhaust steam extraction pressure limit specified in the regulations is used as a reference value. Six optimized load-extraction pressure corresponding curves are set, and the other points are obtained by interpolation. Under the premise of ensuring the safety of the unit's heating parameters, the minimum difference between the intermediate exhaust steam extraction pressure and the low-pressure cylinder steam inlet pressure is set as the control target.

6. The method for optimizing the operation of an extraction-condensation heating unit based on heating safety according to claim 1, characterized in that: The specific method of step S6 is: the pulses of the middle exhaust steam extraction regulating valve and the low-pressure cylinder steam inlet regulating valve participate in the rapid load regulation. When the large frequency difference frequency modulation and load increase instruction is greater than A, the system quickly opens the low-pressure cylinder steam inlet regulating valve position instruction function by C% and quickly closes the extraction steam regulating valve position instruction function by D% according to the current high-pressure speed regulating valve position instruction function B%.

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