Energy-saving system of heat-engine unit based on low-enthalpy steam source driven feed water

Abstract

The application discloses an energy-saving system of a low-enthalpy steam source driving feed water for a thermal power unit, which comprises a boiler, a main steam turbine, a feed water pump turbine, a condensing system, a reheating system, a heat recovery system and a feed water pump turbine steam distribution system; the reheating system comprises a hot section reheating steam, a cold section reheating steam and a reheater; the i-th section extraction steam is a conventional working steam source for driving the feed water pump turbine, and the i+1-th section extraction steam is a low-enthalpy steam source for driving the feed water pump turbine; the feed water pump turbine steam distribution system comprises a working steam distribution unit, a low-enthalpy steam distribution unit and a main steam distribution unit; when the unit is in a low-load operation, the energy of the low-enthalpy steam is fully utilized to drive the feed water pump turbine to work, and the consumption of high-enthalpy steam is reduced; and by adjusting the input proportion of the low-enthalpy steam source and the conventional working steam source, efficient utilization of the steam source under a low-load condition is realized.

Description

Technical Field

[0001] This utility model belongs to the technical field of steam turbine for feedwater pumps in power generation units, specifically relating to an energy-saving system for thermal power units based on low-enthalpy steam source driving feedwater. Background Technology

[0002] In thermal power generation and combined heat and power units, feedwater pumps are key auxiliary machines for maintaining boiler feedwater pressure, and their driving power is enormous. Currently, most units use feedwater pump turbines (small turbines) to drive feedwater pumps, and their steam source is usually drawn from the fourth stage extraction of the turbine (or fourth extraction). The fourth stage extraction steam is steam with relatively high pressure and enthalpy. This design operates smoothly under the rated load of the unit and can meet the power requirements of the feedwater pumps.

[0003] With the vigorous implementation of deep peak shaving for thermal power generating units, ultra-low unit load has become the norm for thermal power generating unit operation, bringing new challenges to the stable power output of feedwater pump turbines. Chinese Patent Application No. 202422820101.5 proposes a unit load-increasing system based on a high-enthalpy steam source driving a feedwater pump turbine. Its feature is that when the unit is operating at increased load, the high-enthalpy steam source is gradually integrated into the working steam source, increasing the enthalpy of the steam entering the feedwater pump turbine, thereby increasing the power output of the feedwater pump turbine and ensuring that the unit's electrical load meets the grid requirements. The purpose is to solve the problem that excessive back pressure in summer leads to limited output of the feedwater pump turbine and thus affects the unit's load-carrying capacity.

[0004] However, when the unit load decreases, the main steam flow decreases, and the pressure and flow at each extraction port of the main turbine also decrease. At this time, in order to maintain the power required by the feedwater pump, a sufficient amount of extraction steam from all four stages is still required. This leads to two disadvantages: First, under low load, the high-quality steam that could have been used to continue expanding and generating electricity in the high and medium pressure cylinders is extracted in advance, reducing the working efficiency of the main unit and harming the overall plant economy. Second, fluctuations in extraction steam parameters may cause instability in the operating conditions of the feedwater pump turbine, thereby affecting the accuracy of feedwater flow control and posing a potential threat to the safe and stable operation of the entire unit.

[0005] The present patent aims to solve the above problems. By innovatively introducing low-enthalpy extracted steam as an auxiliary or main steam source, it jointly drives the feed water pump turbine together with four-stage extracted steam, which can significantly reduce or even completely replace the extraction amount of four-stage extracted steam under low-load working conditions. This measure retains more high-grade steam in the main turbine for full expansion to do work, reduces the overall heat consumption rate (coal consumption) of the generator set, directly improves the power generation efficiency of the main engine, and achieves remarkable energy-saving effects. At the same time, the system is equipped with an advanced steam distribution unit for cooperative regulation, which can stabilize the fluctuation of intake steam parameters caused by steam source switching or load change, ensuring that the feed water pump turbine always operates in an efficient and stable range. The significance of the present patent lies in breaking through the limitations of traditional design, and providing an efficient and energy-saving solution that can both improve operation economy and guarantee safety and stability for thermal power units, especially during wide-load peak-shaving operation. Summary of the Invention

[0006] The invention relates to an energy-saving system for thermal power units based on low-enthalpy steam source driving feed water, which provides a low-enthalpy steam source for a feed water pump turbine. The low-enthalpy steam source and a conventional working steam source can jointly drive the feed water pump turbine to do work, and the low-enthalpy steam source can also be used to independently drive the feed water pump turbine to do work, which reduces the extraction amount of high-enthalpy steam when the unit operates at low load, allows more high-quality steam to fully expand and do work for power generation in the main turbine, improves the efficiency of the main engine. Meanwhile, the cooperative regulation of the steam distribution unit can maintain the stability of the inlet steam parameters of the feed water pump turbine, avoid the operation disturbance of the turbine caused by steam source switching or flow fluctuation, and guarantee the efficient and stable operation of the unit in the low-load range.

[0007] An energy-saving system for thermal power units based on low-enthalpy steam source driving feed water comprises a boiler, a main turbine, a feed water pump turbine, a condensing system, a reheating system, a regenerative system and a steam distribution system for the feed water pump turbine. The reheating system comprises hot reheated steam, cold reheated steam and a reheater. The regenerative system comprises N stages of extracted steam, wherein the i-th stage of extracted steam is a conventional working steam source for driving the feed water pump turbine, and the (i+1)-th stage of extracted steam is a low-enthalpy steam source for driving the feed water pump turbine, with 3<i<N. The steam distribution system for the feed water pump turbine comprises a working steam distribution unit, a low-enthalpy steam distribution unit and a main steam distribution unit. The main turbine comprises a high-pressure cylinder, an intermediate-pressure cylinder and a low-pressure cylinder. Superheated steam generated by the boiler enters the main turbine to do work and then is discharged into the condensing system to be condensed into condensed water, and the condensed water passes through the regenerative system and enters the boiler to be converted into superheated steam again. The steam distribution system for the feed water pump turbine sends the conventional working steam source and the low-enthalpy steam source to the feed water pump turbine to do work, and drives the condensed water heated by the regenerative system to enter the boiler. The reheating system is connected to the high-pressure cylinder and the intermediate-pressure cylinder of the main turbine at two ends thereof, and heats the cold reheated steam discharged from the high-pressure cylinder by the reheater to generate hot reheated steam and then conveys the hot reheated steam to the intermediate-pressure cylinder.

[0008] The feedwater pump turbine can be a single feedwater pump turbine or two feedwater pump turbines arranged in parallel.

[0009] The condensing system includes a condenser, a hot well, and a condensate pump. The condensing system condenses steam into water in the condenser and then sends it to the regenerative system via the hot well and the condensate pump.

[0010] The regenerative system also includes N heaters, wherein the i-th heater is a deaerator, the 1st to i-1th heaters are high-pressure heaters, and the i+1th heater is a low-pressure heater; the i-th stage of the N-stage extraction steam enters the deaerator, the 1st to i-1th stage extraction steam enters the 1st to i-1th stage heaters respectively, and the i+1th to Nth stage extraction steam enters the i+1th to Nth heaters respectively.

[0011] The main steam distribution unit is divided into two types: external switching steam distribution and internal switching steam distribution. The main steam distribution unit of the external switching type includes a main steam distribution pipeline, a regulating valve, and a main steam valve. The main steam distribution pipeline is equipped with a main steam valve first and then a regulating valve along the direction of steam movement. The main steam distribution unit of the internal switching type includes a main steam distribution pipeline, a regulating valve, and a main steam valve. The main steam distribution pipeline is divided into two branches. Each branch is equipped with a main steam valve and a regulating valve in sequence along the direction of steam movement.

[0012] The working steam distribution unit includes a conventional working steam source distribution pipeline, a check valve, and a conventional working steam source electric valve. The conventional working steam source distribution pipeline is first equipped with the conventional working steam source electric valve and then with the check valve along the steam movement direction. One end of the conventional working steam source distribution pipeline is connected to the i-th section of extraction steam, and the other end is connected to the main steam distribution unit. The conventional working steam source electric valve can accept external power signals to perform steam cut-off and flow regulation actions.

[0013] The low-enthalpy steam distribution unit includes a low-enthalpy steam distribution pipeline, a check valve, and a low-enthalpy steam source electric valve. The low-enthalpy steam distribution pipeline is first equipped with the low-enthalpy steam source electric valve along the steam movement direction, and then with the check valve. One end of the low-enthalpy steam distribution pipeline is connected to the (i+1)th stage of steam extraction, and the other end is connected to the main steam distribution unit. The low-enthalpy steam source electric valve can accept external power signals to perform steam cut-off and flow regulation actions.

[0014] The low-enthalpy steam source can drive the feedwater pump turbine independently. Under low-load conditions, by making full use of the energy of the low-enthalpy steam to drive the feedwater pump turbine, the consumption of high-enthalpy steam can be reduced, allowing more high-enthalpy steam to perform effective work.

[0015] The low-enthalpy steam source can also be integrated into the conventional working steam source, and together they enter the feedwater pump turbine to drive it to do work; the input ratio of the low-enthalpy steam source and the conventional working steam source can be adjusted by the electric valve of the conventional working steam source and the electric valve of the low-enthalpy steam source. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of an energy-saving system for a thermal power unit based on a low-enthalpy steam source driving feedwater, which is one embodiment of the present patent.

[0017] Figure 2 This is a schematic diagram of an energy-saving system for a thermal power unit based on a low-enthalpy steam source driving feedwater, which is another embodiment of this patent.

[0018] Figure 3 This is a schematic diagram of an energy-saving system for a thermal power unit based on a low-enthalpy steam source driving feedwater, which is another embodiment of this patent.

[0019] Figure 4 This is a schematic diagram of a conventional thermal power unit system that does not employ this patent.

[0020] In the diagram: 1—Boiler, 2—High-pressure cylinder, 3—Intermediate-pressure cylinder, 4—Low-pressure cylinder, 5—Feedwater pump turbine, 6—Condenser, 7—Hot well, 8—Condensate pump, 9—First stage extraction steam, 10—Second stage extraction steam, 11—Third stage extraction steam, 12—Fourth stage extraction steam, 13—Fifth stage extraction steam, 14—Sixth stage extraction steam, 15—Seventh stage extraction steam, 16—Eighth stage extraction steam, 17—Hot section reheat steam, 18—No. 1 high-pressure heater, 19—No. 2 high-pressure heater, 20—No. 3 high-pressure heater, 21—Deaerator, 22—No. 5 low-pressure... Heaters, 23—No. 6 low-pressure heater, 24—No. 7 low-pressure heater, 25—No. 8 low-pressure heater, 26—shaft seal heater, 27—low enthalpy steam distribution pipeline, 28—cold section reheat steam, 29—conventional working steam source distribution pipeline, 30—main steam distribution pipeline, 31—regulating valve, 32—main steam valve, 33—check valve, 34—conventional working steam source electric valve, 35—low enthalpy steam source electric valve, 36—reheater, 37—main steam distribution unit, 38—working steam distribution unit, 39—low enthalpy steam distribution unit. Detailed Implementation

[0021] 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 this patent.

[0022] As attached Figure 1As shown, an energy-saving system for a thermal power unit based on a low-enthalpy steam source driving feedwater includes a boiler 1, a main steam turbine, a feedwater pump turbine 5, a condensing system, a reheat system, a regenerative system, and a feedwater pump turbine steam distribution system. The reheat system includes a reheater 36, hot-section reheat steam 17, and cold-section reheat steam 28. The main steam distribution unit 37 includes a main steam distribution pipeline 30, a main steam valve 32, and a regulating valve 31. The working steam distribution unit 38 includes a conventional working steam source distribution pipeline 29, a check valve 33, and a conventional working steam source electric valve 34. The low-enthalpy steam distribution unit 39 includes a low-enthalpy steam distribution pipeline 27, a check valve 33, and a low-enthalpy steam source electric valve 35.

[0023] As attached Figure 1 As shown, an energy-saving system for a thermal power unit based on a low-enthalpy steam source driving feedwater is described. Superheated steam generated by boiler 1 enters the main turbine to perform work and is then discharged into the condensing system to condense into condensate. The condensate then enters boiler 1 again via a regenerative system and becomes superheated steam once more. The main turbine includes a high-pressure cylinder 2, an intermediate-pressure cylinder 3, and a low-pressure cylinder 4. The condensing system includes a condenser 6, a hot well 7, and a condensate pump 8. The regenerative system includes eight stages of steam extraction and a No. 1 high-pressure heater 18, a No. 2 high-pressure heater 19, a No. 3 high-pressure heater 20, a deaerator 21, a No. 5 low-pressure heater 22, a No. 6 low-pressure heater 23, and a No. 7 low-pressure heater. Deaerator 24, No. 8 low-pressure heater 25, shaft seal heater 26; first stage extraction steam 9 extracts steam from high-pressure cylinder 2 to No. 1 high-pressure heater 18; second stage extraction steam 10 extracts steam from high-pressure cylinder 2 to No. 2 high-pressure heater 19; third stage extraction steam 11 extracts steam from intermediate-pressure cylinder 3 to No. 3 high-pressure heater 20; fourth stage extraction steam 12 extracts steam from intermediate-pressure cylinder 3 to deaerator 21; fifth stage extraction steam 13 extracts steam from intermediate-pressure cylinder 3 to No. 5 low-pressure heater 22; sixth stage extraction steam 14, seventh stage extraction steam 15, and eighth stage extraction steam 16 extract steam from low-pressure cylinder 4 to No. 6 low-pressure heater 23, No. 7 low-pressure heater 24, and No. 8 low-pressure heater 25, respectively.

[0024] As attached Figure 1As shown, an energy-saving system for a thermal power unit driven by a low-enthalpy steam source is described. The feedwater pump turbine is installed at 100% capacity. The fourth-stage extraction steam is the conventional working steam source driving the feedwater pump turbine, and the fifth-stage extraction steam is the low-enthalpy steam source driving the feedwater pump turbine. The main steam distribution unit is an externally switched steam distribution type. The externally switched main steam distribution unit includes a main steam distribution pipeline 30, a regulating valve 31, and a main steam valve 32. The main steam distribution pipeline is installed with the main steam valve 32 first, followed by the regulating valve 31, along the steam movement direction. The working steam distribution unit includes a conventional working steam source distribution pipeline 29 and a check valve 3. 3. Conventional working steam source electric valve 34; the conventional working steam source distribution pipeline is first equipped with the conventional working steam source electric valve 34 along the steam movement direction, and then with the check valve 33; one end of the conventional working steam source distribution pipeline is connected to the fourth stage extraction steam, and the other end is connected to the main distribution pipeline 30; the low enthalpy steam distribution unit includes a low enthalpy steam distribution pipeline 27, a check valve 33, and a low enthalpy steam source electric valve 35; the low enthalpy steam distribution pipeline 27 is first equipped with the low enthalpy steam source electric valve 35 along the steam movement direction, and then with the check valve 33; one end of the low enthalpy steam distribution pipeline is connected to the fifth stage extraction steam, and the other end is connected to the main distribution pipeline 30.

[0025] As attached Figure 1 As shown, an energy-saving system for a thermal power unit based on a low-enthalpy steam source driving feedwater can adjust the enthalpy of the feedwater pump turbine inlet steam according to the unit load, unit back pressure, etc., and gradually integrate the low-enthalpy steam source into the conventional working steam source, so that they all enter the feedwater pump turbine. During normal unit operation, the fourth stage extraction steam, as the conventional working steam source, passes through the electric valve 34, check valve 33, main steam valve 32, and regulating valve 31 in sequence to drive the feedwater pump turbine 5 to do work. The regulating valve adjusts the steam inlet flow according to the boiler feedwater demand. At this time, the low-enthalpy steam source electric valve 35 is closed, and the check valve 33 on the low-enthalpy steam distribution pipeline 27 is closed, blocking the steam flow. During low-load unit operation, the low-enthalpy steam source electric valve 35 on the low-enthalpy steam distribution pipeline 27 is closed, blocking the steam flow. When the actuator valve 35 receives an electrical signal, it opens to a certain degree, and the steam flow rate in the conventional working steam source distribution pipeline 29 from the fourth-stage extraction decreases accordingly. The main steam valve 32 on the main distribution pipeline 30 ensures that the total steam volume of the feedwater pump turbine is relatively stable. At this time, the conventional working steam source electric valve 34, the low enthalpy steam source electric valve 35, and the check valves 33 on each pipeline are all open. When the unit load continues to decrease, the opening of the low enthalpy steam source electric valve 35 is gradually increased according to the boiler feedwater situation, and the power steam source of the feedwater pump turbine is completely switched to the low enthalpy steam source. At this time, the conventional working steam source electric valve 34 is closed, the check valve 33 on the conventional working steam source distribution pipeline 29 is closed, the low enthalpy steam source electric valve 35 is open, and the check valve 33 on the low enthalpy steam distribution pipeline 27 is open.

[0026] As attached Figure 2As shown, an energy-saving system for a thermal power unit based on a low-enthalpy steam source driving feedwater includes a boiler 1, a main steam turbine, a feedwater pump turbine 5, a condensing system, a reheat system, a regenerative system, and a feedwater pump turbine steam distribution system. The reheat system includes a reheater 36, hot-section reheat steam 17, and cold-section reheat steam 28. The main steam distribution unit 37 includes a main steam distribution pipeline 30, a main steam valve 32, and a regulating valve 31. The working steam distribution unit 38 includes a conventional working steam source distribution pipeline 29, a check valve 33, and a conventional working steam source electric valve 34. The low-enthalpy steam distribution unit 39 includes a low-enthalpy steam distribution pipeline 27, a check valve 33, and a low-enthalpy steam source electric valve 35.

[0027] As attached Figure 2 As shown, an energy-saving system for a thermal power unit based on a low-enthalpy steam source driving feedwater is described. Superheated steam generated by boiler 1 enters the main turbine to perform work and is then discharged into the condensing system to condense into condensate. The condensate then enters boiler 1 again via a regenerative system and becomes superheated steam once more. The main turbine includes a high-pressure cylinder 2, an intermediate-pressure cylinder 3, and a low-pressure cylinder 4. The condensing system includes a condenser 6, a hot well 7, and a condensate pump 8. The regenerative system includes eight stages of steam extraction and a No. 1 high-pressure heater 18, a No. 2 high-pressure heater 19, a No. 3 high-pressure heater 20, a deaerator 21, a No. 5 low-pressure heater 22, a No. 6 low-pressure heater 23, and a No. 7 low-pressure heater. Deaerator 24, No. 8 low-pressure heater 25, shaft seal heater 26; first stage extraction steam 9 extracts steam from high-pressure cylinder 2 to No. 1 high-pressure heater 18; second stage extraction steam 10 extracts steam from high-pressure cylinder 2 to No. 2 high-pressure heater 19; third stage extraction steam 11 extracts steam from intermediate-pressure cylinder 3 to No. 3 high-pressure heater 20; fourth stage extraction steam 12 extracts steam from intermediate-pressure cylinder 3 to deaerator 21; fifth stage extraction steam 13 extracts steam from intermediate-pressure cylinder 3 to No. 5 low-pressure heater 22; sixth stage extraction steam 14, seventh stage extraction steam 15, and eighth stage extraction steam 16 extract steam from low-pressure cylinder 4 to No. 6 low-pressure heater 23, No. 7 low-pressure heater 24, and No. 8 low-pressure heater 25, respectively.

[0028] As attached Figure 2As shown, an energy-saving system for a thermal power unit driven by a low-enthalpy steam source is described. The feedwater pump turbine is installed at 100% capacity. The fourth-stage extraction steam is the conventional working steam source driving the feedwater pump turbine, and the fifth-stage extraction steam is the low-enthalpy steam source driving the feedwater pump turbine. The main steam distribution unit is an internally switching type. The internally switching main steam distribution unit includes a main steam distribution pipeline 30, a regulating valve 31, and a main steam valve 32. The main steam distribution pipeline is divided into two branches, each branch having a main steam valve 32 and a regulating valve 31 sequentially along the steam movement direction. The working steam distribution unit includes a conventional working steam source distribution pipeline 29 and a check valve 33. The conventional working steam source electric valve 34 is installed first along the steam movement direction of the conventional working steam source distribution pipeline, followed by a check valve 33. One end of the conventional working steam source distribution pipeline is connected to the fourth stage extraction steam, and the other end is connected to a branch of the main distribution pipeline 30. The low enthalpy steam distribution unit includes a low enthalpy steam distribution pipeline 27, a check valve 33, and a low enthalpy steam source electric valve 35. The low enthalpy steam distribution pipeline 27 is installed first along the steam movement direction of the low enthalpy steam source electric valve 35, followed by a check valve 33. One end of the low enthalpy steam distribution pipeline 27 is connected to the fifth stage extraction steam, and the other end is connected to another branch of the main distribution pipeline 30.

[0029] As attached Figure 2 As shown, an energy-saving system for a thermal power unit based on a low-enthalpy steam source driving feedwater can adjust the enthalpy of the feedwater pump turbine inlet steam according to the unit load, unit back pressure, etc., and gradually integrate the low-enthalpy steam source into the conventional working steam source, so that they all enter the feedwater pump turbine. During normal unit operation, the fourth stage extraction steam, as the conventional working steam source, passes through the electric valve 34, check valve 33, main steam valve 32, and regulating valve 31 in sequence to drive the feedwater pump turbine 5 to do work. The regulating valve adjusts the steam inlet flow according to the boiler feedwater demand. At this time, the low-enthalpy steam source electric valve 35 is closed, and the check valve 33 on the low-enthalpy steam distribution pipeline 27 is closed, blocking the steam flow. During low-load unit operation, the low-enthalpy steam source electric valve 35 on the low-enthalpy steam distribution pipeline 27 is closed, blocking the steam flow. When the actuator valve 35 receives an electrical signal, it opens to a certain degree, and the steam flow rate in the conventional working steam source distribution pipeline 29 from the fourth-stage extraction decreases accordingly. The main steam valve 32 on the main distribution pipeline 30 ensures that the total steam volume of the feedwater pump turbine is relatively stable. At this time, the conventional working steam source electric valve 34, the low enthalpy steam source electric valve 35, and the check valves 33 on each pipeline are all open. When the unit load continues to decrease, the opening of the low enthalpy steam source electric valve 35 is gradually increased according to the boiler feedwater situation, and the power steam source of the feedwater pump turbine is completely switched to the low enthalpy steam source. At this time, the conventional working steam source electric valve 34 is closed, the check valve 33 on the conventional working steam source distribution pipeline 29 is closed, the low enthalpy steam source electric valve 35 is open, and the check valve 33 on the low enthalpy steam distribution pipeline 27 is open.

[0030] As attached Figure 3As shown, an energy-saving system for a thermal power unit driven by a low-enthalpy steam source includes a boiler 1, a main steam turbine, a feedwater pump turbine 5, a condensing system, a reheat system, a regenerative system, and a feedwater pump turbine steam distribution system. The reheat system includes a reheater 36, hot-section reheat steam 17, and cold-section reheat steam 28. The main steam distribution unit 37 includes a main steam distribution pipeline 30, a main steam valve 32, and a regulating valve 31. The working steam distribution unit 38 includes a constant-temperature steam distribution system. The boiler 1 includes a standard working steam source distribution pipeline 29, a check valve 33, and a standard working steam source electric valve 34; the low enthalpy steam distribution unit 39 includes a low enthalpy steam distribution pipeline 27, a check valve 33, and a low enthalpy steam source electric valve 35; the superheated steam generated by boiler 1 enters the main turbine to do work and is then discharged into the condensing system to condense into condensate. The condensate then enters boiler 1 again through the regenerative system and becomes superheated steam again; the main turbine includes a high-pressure cylinder 2, an intermediate-pressure cylinder 3, and a low-pressure cylinder 4; the condensing system includes a condenser 6, a hot well 7, and a condensate pump 8; the regenerative system includes eight stages of extraction steam and high-pressure heaters 18, 19, 20, 21, 22, 23, 24, 25, and 26; the first stage extraction steam 9 extracts steam from high-pressure cylinder 2 to high-pressure heater 18; the second stage extraction steam 10 extracts steam from... Steam is extracted from high-pressure cylinder 2 to high-pressure heater 19; steam is extracted from intermediate-pressure cylinder 3 to high-pressure heater 20; steam is extracted from intermediate-pressure cylinder 3 to deaerator 21; steam is extracted from intermediate-pressure cylinder 3 to low-pressure heater 22; steam is extracted from intermediate-pressure cylinder 3 to low-pressure heater 23, 24, 25, and 25 respectively from low-pressure cylinder 4.

[0031] As attached Figure 3As shown, an energy-saving system for a thermal power unit driven by a low-enthalpy steam source is disclosed. Two feedwater pump turbines operate at 50% capacity and are arranged in parallel. The fourth extraction stage serves as the conventional working steam source for driving the feedwater pump turbines, while the fifth extraction stage serves as the low-enthalpy steam source. The main steam distribution unit is an internally switching type. This internally switching main steam distribution unit includes a main steam distribution pipeline 30, a regulating valve 31, and a main steam valve 32. The main steam distribution pipeline is divided into two branches, each with a main steam valve 32 and a regulating valve 31 installed sequentially along the steam movement direction. The working steam distribution unit includes a conventional working steam source distribution pipeline 29. The system includes a check valve 33 and a conventional working steam source electric valve 34. The conventional working steam source distribution pipeline is first equipped with the conventional working steam source electric valve 34 along the steam movement direction, followed by the check valve 33. One end of the conventional working steam source distribution pipeline connects to the fourth stage extraction steam, and the other end connects to a branch of the main distribution pipeline 30. The low enthalpy steam distribution unit includes a low enthalpy steam distribution pipeline 27, a check valve 33, and a low enthalpy steam source electric valve 35. The low enthalpy steam distribution pipeline 27 is first equipped with the low enthalpy steam source electric valve 35 along the steam movement direction, followed by the check valve 33. One end of the low enthalpy steam distribution pipeline 27 connects to the fifth stage extraction steam, and the other end connects to another branch of the main distribution pipeline 30.

[0032] As attached Figure 3 As shown, an energy-saving system for a thermal power unit based on a low-enthalpy steam source driving feedwater can adjust the enthalpy of the feedwater pump turbine inlet steam according to the unit load, unit back pressure, etc., and gradually integrate the low-enthalpy steam source into the conventional working steam source, so that they all enter the feedwater pump turbine. During normal unit operation, the fourth stage extraction steam, as the conventional working steam source, passes through the electric valve 34, check valve 33, main steam valve 32, and regulating valve 31 in sequence to drive the feedwater pump turbine 5 to do work. The regulating valve adjusts the steam inlet flow according to the boiler feedwater demand. At this time, the low-enthalpy steam source electric valve 35 is closed, and the check valve 33 on the low-enthalpy steam distribution pipeline 27 is closed, blocking the steam flow. During low-load unit operation, the low-enthalpy steam source electric valve 35 on the low-enthalpy steam distribution pipeline 27 is closed, blocking the steam flow. When the actuator valve 35 receives an electrical signal, it opens to a certain degree, and the steam flow rate in the conventional working steam source distribution pipeline 29 from the fourth-stage extraction decreases accordingly. The main steam valve 32 on the main distribution pipeline 30 ensures that the total steam volume of the feedwater pump turbine is relatively stable. At this time, the conventional working steam source electric valve 34, the low enthalpy steam source electric valve 35, and the check valves 33 on each pipeline are all open. When the unit load continues to decrease, the opening of the low enthalpy steam source electric valve 35 is gradually increased according to the boiler feedwater situation, and the power steam source of the feedwater pump turbine is completely switched to the low enthalpy steam source. At this time, the conventional working steam source electric valve 34 is closed, the check valve 33 on the conventional working steam source distribution pipeline 29 is closed, the low enthalpy steam source electric valve 35 is open, and the check valve 33 on the low enthalpy steam distribution pipeline 27 is open.

[0033] As attached Figure 4The diagram shows a conventional thermal power unit system not implemented using this patent. The feedwater pump turbine is at 100% capacity, with one unit. The system includes a boiler 1, a main turbine, a feedwater pump turbine 5, a condensing system, a reheat system, a regenerative system, and a feedwater pump turbine steam distribution system. The reheat system includes a reheater 36, hot-section reheat steam 17, and cold-section reheat steam 28. The main steam distribution unit 37 includes a main steam distribution pipeline 30, a main steam valve 32, and a regulating valve 31. The working steam distribution unit 38 includes a conventional working steam source distribution pipeline 29, a check valve 33, and a conventional working steam source electric valve 34. The feedwater pump turbine 5 relies on four-stage extraction steam 12 as its steam source. The steam drives the feedwater pump turbine to perform work after passing through the conventional working steam source distribution pipeline 29 and the main steam distribution pipeline 30. When the unit load changes, the steam source of the feedwater pump turbine cannot be adjusted, and the feedwater pump turbine has a single drive method.

[0034] The structures, proportions, and sizes depicted in the accompanying drawings are solely for illustrative purposes and to aid those skilled in the art in understanding and reading the content disclosed herein. They are not intended to limit the scope of this patent's implementation and therefore have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to size, provided they do not affect the efficacy or purpose of this patent, should still fall within the scope of the technical content disclosed in this patent. Furthermore, terms such as "upper," "lower," "left," and "right" used in this specification are merely for clarity and not intended to limit the scope of this patent's implementation. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of this patent's implementation.

[0035] The foregoing has shown and described the basic principles, main features, and advantages of this patent. It is obvious to those skilled in the art that this patent is not limited to the details of the above exemplary embodiments, and that this patent can be implemented in other specific forms without departing from the spirit or basic features of this patent. Therefore, the embodiments should be regarded as exemplary and non-restrictive in all respects. The scope of this patent is defined by the appended claims rather than the foregoing description. Therefore, it is intended to encompass all variations falling within the meaning and scope of equivalents of the claims. No reference numerals in the claims should be regarded as limiting the scope of the claims.

[0036] 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 system for a thermal power unit based on a low-enthalpy steam source driving feedwater, comprising a boiler, a main steam turbine, a feedwater pump turbine, a condensing system, a reheat system, a regenerative system, and a feedwater pump turbine steam distribution system; characterized in that: The reheat system comprises hot reheat steam, cold reheat steam, and a reheater; the regenerative system comprises N sections of extraction steam, wherein the i-th section of extraction steam is a conventional working steam source for driving the feed water pump turbine, and the (i+1)-th section of extraction steam is a low-enthalpy steam source for driving the feed water pump turbine, where 3<i<N; the steam distribution system of the feed water pump turbine comprises a working steam distribution unit, a low-enthalpy steam distribution unit, and a main steam distribution unit; the main steam turbine comprises a high-pressure cylinder, an intermediate-pressure cylinder, and a low-pressure cylinder; the superheated steam generated by the boiler enters the main steam turbine to do work, and is then discharged into the condensing system to be condensed into condensed water, and the condensed water enters the boiler through the regenerative system and turns into superheated steam again; the steam distribution system of the feed water pump turbine sends the conventional working steam source and the low-enthalpy steam source to the feed water pump turbine to do work, driving the condensed water heated by the regenerative system into the boiler; the reheat system connects the high-pressure cylinder and the intermediate-pressure cylinder of the main steam turbine front and rear, heats the cold reheat steam discharged from the high-pressure cylinder through the reheater, generates hot reheat steam, and then delivers it to the intermediate-pressure cylinder.

2. The energy-saving system for a thermal power unit based on a low-enthalpy steam source driving feedwater as described in claim 1, characterized in that: The feed water pump turbine is a single feed water pump turbine or two parallel feed water pump turbines.

3. The energy-saving system for a thermal power unit based on a low-enthalpy steam source driving feedwater as described in claim 1, characterized in that: The condensing system comprises a condenser, a hot well, and a condensate pump; the condensing system condenses steam into water in the condenser, and then sends the water to the regenerative system through the hot well and the condensate pump.

4. The energy-saving system for a thermal power unit based on a low-enthalpy steam source driving feedwater as described in claim 1, characterized in that: The regenerative system further comprises N heaters, wherein the i-th heater is a deaerator, the 1st to (i-1)-th heaters are high-pressure heaters, and the (i+1)-th heater is a low-pressure heater; the i-th section of extraction steam in the N sections of extraction steam enters the deaerator, the 1st to (i-1)-th sections of extraction steam respectively enter the 1st to (i-1)-th heaters, and the (i+1)-th to N-th sections of extraction steam respectively enter the (i+1)-th to N-th heaters.

5. The energy-saving system for a thermal power unit based on a low-enthalpy steam source driving feedwater according to claim 1, characterized in that: The main steam distribution unit is divided into two types: external switching steam distribution and internal switching steam distribution; the main steam distribution unit of the external switching steam distribution type comprises a main steam distribution pipeline, a regulating valve, and a main steam valve; along the steam movement direction, a main steam valve is arranged first on the main steam distribution pipeline, and a regulating valve is arranged after that; the main steam distribution unit of the internal switching steam distribution type comprises a main steam distribution pipeline, a regulating valve, and a main steam valve; the main steam distribution pipeline is divided into two branches, and a main steam valve and a regulating valve are sequentially arranged on each branch along the steam movement direction.

6. The energy-saving system for a thermal power unit based on a low-enthalpy steam source driving feedwater according to claim 1, characterized in that: The working steam distribution unit comprises a conventional working steam source steam distribution pipeline, a check valve, and a conventional working steam source electric valve; along the steam movement direction, the conventional working steam source electric valve is arranged first on the conventional working steam source steam distribution pipeline, and the check valve is arranged after that; one end of the conventional working steam source steam distribution pipeline is connected to the i-th section of extraction steam, and the other end is connected to the main steam distribution unit; the conventional working steam source electric valve can receive external power signals to perform steam cut-off and flow regulation actions.

7. The energy-saving system for a thermal power unit based on a low-enthalpy steam source driving feedwater according to claim 1, characterized in that: The low-enthalpy steam distribution unit comprises a low-enthalpy steam distribution pipeline, a check valve, and a low-enthalpy steam source electric valve; along the steam movement direction, the low-enthalpy steam source electric valve is arranged first on the low-enthalpy steam distribution pipeline, and the check valve is arranged after that; one end of the low-enthalpy steam distribution pipeline is connected to the (i+1)-th section of extraction steam, and the other end is connected to the main steam distribution unit; the low-enthalpy steam source electric valve can receive external power signals to perform steam cut-off and flow regulation actions.

8. The energy-saving system for a thermal power unit based on a low-enthalpy steam source driving feedwater according to claim 1, characterized in that: The low-enthalpy steam source can drive the feedwater pump turbine independently. Under low-load conditions, by making full use of the energy of the low-enthalpy steam to drive the feedwater pump turbine, the consumption of high-enthalpy steam can be reduced, allowing more high-enthalpy steam to perform effective work.

9. The energy-saving system for a thermal power unit based on a low-enthalpy steam source driving feedwater according to claim 1, characterized in that: The low-enthalpy steam source can also be integrated into the conventional working steam source and jointly enter the feedwater pump turbine to drive it to do work; The input ratio of low-enthalpy steam source to conventional working steam source can be adjusted by the electric valve of conventional working steam source and the electric valve of low-enthalpy steam source.

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