Energy-saving control method for driving water feeding pump turbine based on low-enthalpy-value steam source

Abstract

The invention provides an energy-saving control method for driving a feed pump turbine based on a low-enthalpy-value steam source, which comprises the following steps of: determining the power, the steam inlet pressure, the steam exhaust pressure and the steam flow of the feed pump turbine, and judging the output power of the low-enthalpy-value steam source under the maximum allowable steam extraction amount and the power of the feed pump turbine; the steam source and the extraction amount for driving the water feeding pump turbine are determined, action control over the valve is achieved through electric signal transmission, and the intelligent control method can automatically judge the steam source switching time according to the real-time working condition of a unit and accurately control the steam distribution strategy; whether the low-enthalpy-value steam source is enough to independently drive the water feeding pump turbine or not is scientifically judged, the steam flow can be reasonably distributed during combined operation of the double steam sources, and intelligent switching and optimal distribution of the steam sources of the water feeding pump turbine under the low-load working condition are achieved.

Description

Technical Field

[0001] This invention belongs to the technical field of feedwater pump turbines for power generation units, specifically relating to an energy-saving control method for feedwater pump turbines driven by low-enthalpy steam sources. Background Technology

[0002] In thermal power and combined heat and power (CHP) units, feedwater pumps are crucial auxiliary machines for maintaining boiler feedwater pressure, requiring significant driving power. Currently, most units use feedwater pump turbines to drive the feedwater pumps, with the steam source typically drawn from the fourth stage extraction steam in the main turbine, which has higher pressure and enthalpy. This design operates smoothly under rated load and meets the power requirements of the feedwater pumps. However, with the widespread implementation of deep peak shaving in thermal power units, low-load operation has become the norm. At this time, the main steam flow decreases, and the extraction steam parameters at each stage drop significantly. To maintain the required power for the feedwater pumps, a large amount of high-grade extraction steam still needs to be extracted, leading to two problems: firstly, the high-quality steam fails to fully expand and perform work within the main turbine, reducing the overall thermal efficiency; secondly, fluctuations in extraction steam parameters can easily cause instability in the feedwater pump turbine operation, affecting the accuracy of feedwater control and threatening unit safety.

[0003] Chinese patent application number 202422820101.5 proposes a unit load-increasing system based on a high-enthalpy steam source driving a feedwater pump turbine. Its characteristic is that, during unit load increase operation, the high-enthalpy steam source is gradually integrated into the working steam source, increasing the enthalpy of the feedwater pump turbine's inlet steam, thereby increasing the feedwater pump turbine's power output and ensuring the unit's electrical load meets grid requirements. The aim is to solve the problem of excessively high back pressure in summer, which limits the feedwater pump turbine's output and consequently affects the unit's load-carrying capacity. However, this system is not suitable for low-load unit operation.

[0004] In actual operation, a systematic and automated control logic has yet to be established for scientifically determining whether a low-enthalpy steam source is sufficient to drive the feedwater pump turbine alone, or for rationally allocating steam flow when dual steam sources are required to operate together. This not only affects the full realization of energy-saving effects but may also cause system disturbances due to operational delays or misjudgments.

[0005] Based on this, this invention proposes an energy-saving control method for a feedwater pump turbine driven by a low-enthalpy steam source. By introducing the Flueger formula to calculate the matching between extraction steam capacity and power, a complete steam source selection and flow regulation strategy is constructed to achieve intelligent switching and optimal allocation of the feedwater pump turbine steam source under low-load conditions. This method not only effectively improves the economic efficiency and automation level of unit operation, but also provides a reliable control guarantee for achieving high-efficiency peak shaving under wide loads in cogeneration units. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention proposes an energy-saving control method for a feedwater pump turbine driven by a low-enthalpy steam source, thereby resolving the issues raised in the background section.

[0007] The specific solution of this invention to solve the above-mentioned existing problems is as follows: an energy-saving control method for a feedwater pump turbine driven by a low-enthalpy steam source, characterized by the following steps: S1: Determine the output power G, inlet steam pressure Pj, exhaust pressure Pp, and steam flow rate L of the feedwater pump turbine; S2: Determine the extraction pressure Pd of the low-enthalpy steam source, and calculate the maximum allowable steam extraction rate and the maximum output power Gd of the low-enthalpy steam source; S3: Compare and judge; if Gd ≥ G, then execute steps S4 and S6; if... If Gd < G, then execute steps S5 and S6; S4: Calculate the actual steam extraction rate Ld of the low enthalpy steam source; S5: Calculate the actual steam extraction rate Lc of the conventional working steam source and the actual steam extraction rate Ld of the low enthalpy steam source; S6: Based on the steam extraction rate, calculate the valve opening degree and convert it into an electrical signal, which is then transmitted to the corresponding valve; S7: Based on the electrical signal, perform energy-saving regulation on the electric valves of the conventional working steam source and the electric valves of the low enthalpy steam source to achieve energy-saving control of the feedwater pump turbine driven by the low enthalpy steam source.

[0008] The feedwater pump turbine receives steam from the regenerating system to power the feedwater pump, ensuring the normal operation of the entire system.

[0009] The regenerative system includes N stages of steam extraction, where the i-th stage is the conventional operating steam source for the feedwater pump turbine, and the (i+1)-th stage is the low-enthalpy steam source for the feedwater pump turbine. <i<N。

[0010] Specifically, step S2 refers to: using the inlet steam pressure Pj, exhaust pressure Pp, and steam flow rate L of the feedwater pump turbine, as well as the extraction steam pressure Pd of the low enthalpy steam source, to calculate the maximum allowable steam extraction amount of the low enthalpy steam source using the Vlugel formula, and then calculating the maximum output power Gd of the feedwater pump turbine when the maximum allowable steam extraction amount of the low enthalpy steam source is used for the feedwater pump turbine based on the enthalpy difference.

[0011] When Gd≥G in step S3, it indicates that the low enthalpy steam source can independently provide steam to ensure normal operation under the condition that the power of the feedwater pump turbine remains unchanged. At this time, all conventional working steam sources can be shut down.

[0012] When Gd < G in step S3, it indicates that the low enthalpy steam source is insufficient to support the normal operation of the feedwater pump turbine when the power remains constant. It is necessary to combine it with the conventional working steam source to form a mixed steam source to achieve this.

[0013] Specifically, step S4 refers to: based on the extraction pressure Pd of the low enthalpy steam source, using the difference between the inlet steam pressure Pj of the feedwater pump turbine and the extraction steam pressure Pd, calculating the actual steam extraction amount Ld of the low enthalpy steam source using the Fleuger formula.

[0014] Specifically, step S5 refers to: determining the inlet steam pressure Pjd of the feedwater pump turbine at this time, and using the pressure difference between it and the extraction steam pressure Pd of the low enthalpy steam source, calculating the actual steam extraction amount Ld of the low enthalpy steam source using the Fleuger formula; and calculating the actual steam extraction amount Lc of the conventional working steam source based on the law of conservation of energy, while ensuring that the output power G of the feedwater pump turbine remains unchanged.

[0015] Specifically, step S6 refers to: calculating the valve opening corresponding to the current steam extraction rate based on the valve's flow characteristic curve, and converting it into an electrical signal according to the communication protocol and transmitting it to the corresponding conventional working steam source electric valve and low enthalpy steam source electric valve.

[0016] The energy-saving control includes remote manual control, remote automatic control, and local manual control.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: by using the power of the feedwater pump turbine, the inlet steam pressure, the outlet steam pressure, and the steam flow rate, as well as the extraction steam pressure of the low-enthalpy steam source, it is determined whether the low-enthalpy steam source can provide steam independently for the feedwater pump turbine to operate normally under the condition of maintaining constant power. It also determines the actual steam extraction amount of the conventional working steam source and the low-enthalpy steam source, forming an intelligent control method that automatically judges the timing of steam source switching and precisely controls the steam distribution strategy; it enables the scientific judgment of whether the low-enthalpy steam source can be driven alone or jointly driven with the conventional working steam source, achieving intelligent switching and optimal distribution of the feedwater pump turbine steam source under low load conditions. Attached Figure Description

[0018] Figure 1 This is a flowchart of an energy-saving control method for a feedwater pump turbine driven by a low-enthalpy steam source. Detailed Implementation

[0019] The present invention will now be described in detail with reference to the specific embodiments shown in the accompanying drawings. However, these embodiments do not limit the present invention, and any structural, methodological, or functional modifications made by those skilled in the art based on these embodiments are included within the scope of protection of the present invention.

[0020] In order to make the technical means, creative features, objectives and effects achieved by the present invention easier to understand, the present invention is further described below in conjunction with specific implementation methods.

[0021] like Figure 1As shown, the present invention provides a technical solution: an energy-saving control method for a feedwater pump turbine driven by a low enthalpy steam source, comprising the following steps.

[0022] S1: Determine the output power G, inlet steam pressure Pj, exhaust pressure Pp, and steam flow rate L of the feedwater pump turbine.

[0023] S2: Determine the extraction pressure Pd of the low enthalpy steam source. Using the inlet steam pressure Pj, exhaust steam pressure Pp, and steam flow rate L of the feedwater pump turbine, as well as the extraction pressure Pd of the low enthalpy steam source, calculate the maximum allowable steam extraction rate of the low enthalpy steam source using the Vlugel formula. Then, calculate the maximum output power Gd of the feedwater pump turbine when the maximum allowable steam extraction rate of the low enthalpy steam source is used for the enthalpy difference.

[0024] S3: Compare and judge. If Gd≥G, it means that the low enthalpy steam source can provide steam alone to ensure normal operation of the feedwater pump turbine under the condition that the power remains unchanged. At this time, the conventional working steam source can be shut down. Then proceed to steps S4 and S6. If Gd<G, it means that the low enthalpy steam source is not enough to support the supply of steam alone to ensure normal operation of the feedwater pump turbine when the power remains unchanged. It needs to be combined with the conventional working steam source to form a mixed steam source to achieve the same result. Then proceed to steps S5 and S6.

[0025] S4: Based on the extraction pressure Pd of the low enthalpy steam source, the actual steam extraction amount Ld of the low enthalpy steam source is calculated using the difference between the inlet steam pressure Pj of the feedwater pump turbine and the extraction steam pressure Pd, through the Vlugel formula.

[0026] S5: Determine the inlet steam pressure Pjd of the feedwater pump turbine at this time, and use the pressure difference between it and the extraction steam pressure Pd of the low enthalpy steam source to calculate the actual steam extraction amount Ld of the low enthalpy steam source using the Flügel formula; Under the condition that the output power G of the feedwater pump turbine remains unchanged, calculate the actual steam extraction amount Lc of the conventional working steam source according to the law of conservation of energy.

[0027] S6: Based on the valve's flow characteristic curve, calculate the valve opening corresponding to the current steam extraction rate, and convert it into an electrical signal according to the communication protocol, which is then transmitted to the corresponding conventional working steam source electric valve and low enthalpy steam source electric valve.

[0028] S7: Based on the electrical signal, energy-saving regulation is performed on the electric valves of the conventional working steam source and the electric valves of the low enthalpy steam source to realize energy-saving control of the feedwater pump turbine driven by the low enthalpy steam source.

[0029] Example 1 describes a 660MW supercritical unit operating at low load. The feedwater pump turbine inlet pressure Pj is 4.1 bar, the exhaust pressure Pp is 0.115 bar, the steam flow rate L is 3.22 kg / s, the steam enthalpy drop is 645 kJ / kg, and the feedwater pump turbine power G is 2.027MW. Its regenerative system includes eight extraction stages and eight heaters. The fourth extraction stage feedwater enters the deaerator. This fourth extraction stage serves as the conventional operating steam source for the feedwater pump turbine. The fifth extraction stage feedwater... The low-enthalpy steam source for the pump turbine; the maximum extraction rate of the fifth stage extraction steam in the regenerative system is 6.61 kg / s, and the output power Gd at this maximum extraction rate is 2.848 MW. At this time, Gd≥G, the fifth stage extraction steam can independently drive the feedwater pump turbine to do work. Close the check valve and the electric valve of the conventional working steam source on the feedwater pump turbine's conventional working steam source distribution pipeline, and open the check valve and the electric valve of the low-enthalpy steam source on the feedwater pump turbine's low-enthalpy steam distribution pipeline; calculate the actual extraction rate of the fifth stage extraction steam as 4.706 kg / s, and convert the flow rate into an opening power signal to transmit to the electric valve of the low-enthalpy steam source on the low-enthalpy steam distribution pipeline.

[0030] Example 2 describes a 1000MW ultra-supercritical unit. Under low-load operation, the feedwater pump turbine inlet steam pressure Pj is determined to be 3.93 bar, the exhaust steam pressure Pp to be 0.1 bar, the steam flow rate L to be 3.938 kg / s, and the feedwater pump turbine power G to be 1.976MW. Its regenerative system includes eight extraction stages and eight heaters. The fourth extraction stage feedwater pump turbine serves as the conventional operating steam source for the feedwater pump turbine. The fifth extraction stage serves as the low-enthalpy steam source for the feedwater pump turbine. The maximum extraction rate of the fifth extraction stage in the regenerative system is 5.78 kg / s. The output power G at this maximum extraction rate is... When d is 1.768MW, and Gd < G, the fourth and fifth stage extraction steam need to work together to drive the feedwater pump turbine. Open the check valve and the electric valve of the conventional working steam source distribution pipeline of the feedwater pump turbine, and open the check valve and the electric valve of the low enthalpy steam source distribution pipeline of the feedwater pump turbine. Calculate the extraction rate of the fifth stage extraction steam as 3.518kg / s and the extraction rate of the fourth stage extraction steam as 0.42kg / s. Convert the flow rate into an opening power signal and transmit it to the electric valve of the low enthalpy steam source distribution pipeline and the electric valve of the conventional working steam source distribution pipeline.

[0031] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. It will be apparent to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and that the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, the embodiments should be regarded as exemplary and non-limiting in all respects. The scope of the present invention is defined by the appended claims rather than the foregoing description. Therefore, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention, and no reference numerals in the claims should be regarded as limiting the scope of the claims.

[0032] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. An energy-saving control method for a feedwater pump turbine driven by a low-enthalpy steam source, characterized in that... The steps include: S1: Determine the output power G, inlet steam pressure Pj, exhaust pressure Pp, and steam flow rate L of the feedwater pump turbine; S2: Determine the extraction pressure Pd of the low enthalpy steam source, and calculate the maximum allowable steam extraction rate and the maximum output power Gd of the low enthalpy steam source. S3: Compare and determine if Gd≥G, then execute steps S4 and S6; if Gd<G, then execute steps S5 and S6. S4: Calculate the actual steam extraction rate Ld from the low enthalpy steam source; S5: Calculate the actual steam extraction rate Lc of the conventional working steam source and the actual steam extraction rate Ld of the low enthalpy steam source; S6: Based on the steam extraction rate, calculate the valve opening degree, convert it into an electrical signal, and transmit it to the corresponding valve; S7: Based on the electrical signal, energy-saving regulation is performed on the electric valves of the conventional working steam source and the electric valves of the low enthalpy steam source to realize energy-saving control of the feedwater pump turbine driven by the low enthalpy steam source.

2. The energy-saving control method for a feedwater pump turbine driven by a low-enthalpy steam source according to claim 1, characterized in that: The feedwater pump turbine receives steam from the regenerating system to power the feedwater pump, ensuring the normal operation of the entire system.

3. The energy-saving control method for a feedwater pump turbine driven by a low-enthalpy steam source according to claim 2, characterized in that: The regenerative system includes N stages of steam extraction, where the i-th stage is the conventional operating steam source for the feedwater pump turbine, and the (i+1)-th stage is the low-enthalpy steam source for the feedwater pump turbine. <i<N。 4. The energy-saving control method for a feedwater pump turbine driven by a low-enthalpy steam source according to claim 1, characterized in that, Specifically, step S2 refers to: using the inlet steam pressure Pj, exhaust pressure Pp, and steam flow rate L of the feedwater pump turbine, as well as the extraction steam pressure Pd of the low enthalpy steam source, to calculate the maximum allowable steam extraction amount of the low enthalpy steam source using the Vlugel formula, and then calculating the maximum output power Gd of the feedwater pump turbine when the maximum allowable steam extraction amount of the low enthalpy steam source is used for the feedwater pump turbine based on the enthalpy difference.

5. The energy-saving control method for a feedwater pump turbine driven by a low-enthalpy steam source according to claim 1, characterized in that, When Gd≥G in step S3, it indicates that the low enthalpy steam source can independently provide steam to ensure normal operation under the condition that the power of the feedwater pump turbine remains unchanged. At this time, all conventional working steam sources can be shut down.

6. The energy-saving control method for a feedwater pump turbine driven by a low-enthalpy steam source according to claim 1, characterized in that, When Gd < G in step S3, it indicates that the low enthalpy steam source is insufficient to support the normal operation of the feedwater pump turbine when the power remains constant. It is necessary to combine it with the conventional working steam source to form a mixed steam source to achieve this.

7. The energy-saving control method for a feedwater pump turbine driven by a low-enthalpy steam source according to claim 1, characterized in that, Specifically, step S4 refers to: based on the extraction pressure Pd of the low enthalpy steam source, using the difference between the inlet steam pressure Pj of the feedwater pump turbine and the extraction steam pressure Pd, calculating the actual steam extraction amount Ld of the low enthalpy steam source using the Fleuger formula.

8. The energy-saving control method for a feedwater pump turbine driven by a low-enthalpy steam source according to claim 1, characterized in that, Specifically, step S5 refers to: determining the inlet steam pressure Pjd of the feedwater pump turbine at this time, and using the pressure difference between it and the extraction steam pressure Pd of the low enthalpy steam source, calculating the actual steam extraction amount Ld of the low enthalpy steam source using the Fleuger formula; and calculating the actual steam extraction amount Lc of the conventional working steam source based on the law of conservation of energy, while ensuring that the output power G of the feedwater pump turbine remains unchanged.

9. The energy-saving control method for a feedwater pump turbine driven by a low-enthalpy steam source according to claim 1, characterized in that, Specifically, step S6 refers to: calculating the valve opening corresponding to the current steam extraction rate based on the valve's flow characteristic curve, and converting it into an electrical signal according to the communication protocol and transmitting it to the corresponding conventional working steam source electric valve and low enthalpy steam source electric valve.

10. The energy-saving control method for a feedwater pump turbine driven by a low-enthalpy steam source according to claim 1, characterized in that: The energy-saving control includes remote manual control, remote automatic control, and local manual control.

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