Boiler feedwater system and boiler feedwater method

Abstract

To provide a boiler feed water device and a boiler water supply method, each enabling suppression of the occurrence of water hammer due to water leakage from a feed water heater and enabling early discovery of the water leakage from the feed water heater.SOLUTION: A control device 8 measures an inlet feed water temperature Tp3 of an economizer 41 and an outlet supply water temperature of a high pressure feed water heater 3 when a first prescribed time passes from decoupling of a steam power generation facility 1, and performs circulation operation of a high pressure feed water pump 2 after a second prescribed time passes from the decoupling in the case that the inlet supply water temperature Tp3 of the economizer 41 is a predetermined temperature or more and that the outlet supply water temperature of the high pressure feed water heater increases more than when operation of the high pressure feed water pump 2 stops.

Description

Technical Field

[0001] This invention relates to a boiler water supply device and a boiler water supply method for supplying water to a boiler.

Background Art

[0002] A steam power generation facility includes a boiler, a boiler water supply device for supplying water to the boiler, a steam turbine driven by steam generated in the boiler, a generator for generating electricity by driving the steam turbine, and the like. The boiler water supply device includes a feed water pump, a feed water heater for heating the water supplied from the feed water pump and supplying it to the economizer of the boiler, a temperature sensor for measuring the feed water temperature of each part, and the like. In a steam power generation facility, in response to the decrease in power demand on weekends, a weekend start and stop (WSS) operation is performed in which the operation is stopped (hereinafter also referred to as "disconnection") on weekends and restarted at the beginning of the week (see, for example, Patent Document 1).

[0003] During the operation stop of the WSS operation, the feed water in the boiler does not flow, so the feed water temperature gradually decreases over time. However, during this operation stop, the feed water temperature in the boiler may rise, causing the feed water to flash or condense, and a water hammer may occur. When a large-scale water hammer occurs, there is a risk of damage to the boiler water pipes and the like.

[0004] When the inventor investigated the cause of the water hammer that occurred during the operation stop of the WSS operation, it was found that the feed water in the boiler flowed due to leakage from the feed water heater, and the feed water temperature increased.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] To prevent water hammer caused by leaks from feedwater heaters, the leaking feedwater heater should be repaired or replaced while the WSS (Warm Water Storage) system is shut down. However, if the leak is small, it is difficult to detect the leak because no significant changes in water level or feedwater temperature will occur during the operation of the steam power plant. Furthermore, repairing or replacing a feedwater heater takes time, which may prevent the WSS from restarting in time. Additionally, draining the feedwater from the boiler to repair or replace a feedwater heater may lower the feedwater temperature, potentially delaying the restart of operations.

[0007] Therefore, the purpose of this invention is to provide a boiler feedwater system and boiler feedwater method that can suppress the occurrence of water hammer caused by water leakage from the feedwater heater and enable early detection of water leakage from the feedwater heater. [Means for solving the problem]

[0008] To solve the above problems, the invention of claim 1 is a boiler feedwater system comprising a feedwater pump, a feedwater heater that heats the water supplied from the feedwater pump and supplies it to the boiler's economizer, a control means for controlling the feedwater pump, and a temperature sensor for measuring the feedwater temperature of each part, The economizer heats the water supplied from the feedwater heater using the waste heat from the boiler until it becomes saturated. The control means is characterized in that, when the boiler is shut down by a weekend start-up / shutdown operation and the feedwater pump is shut down, after a first predetermined time has elapsed since the boiler was shut down, the temperature sensor measures the feedwater temperature at the inlet of the economizer and the feedwater temperature at the outlet of the feedwater heater, and if the feedwater temperature at the inlet of the economizer during the first predetermined time is above a predetermined temperature and the feedwater temperature at the outlet of the feedwater heater is higher than the temperature at the time the feedwater pump was shut down, the control means causes the feedwater pump to perform a circulation operation to circulate the feedwater after a second predetermined time has elapsed since the boiler was shut down.

[0009] The invention of claim 2 is characterized in that, in the boiler feedwater device described in claim 1, if the boiler operation start time, in which the boiler operation is started by the weekend start-up-shutdown operation, is after the third predetermined time which occurs after the second predetermined time has elapsed, the control means causes the feedwater pump to perform the circulation operation after the third predetermined time has elapsed.

[0010] The invention of claim 3 is a boiler feedwater device according to claim 1 or 2, characterized in that the control means stops the circulation operation when the variation of a plurality of feedwater temperatures measured in the boiler falls within a predetermined range.

[0011] The invention of claim 4 is a boiler feedwater method comprising supplying water to a feedwater heater by a feedwater pump, and supplying the water heated by the feedwater heater to a boiler economizer, The economizer heats the water supplied from the feedwater heater using the waste heat from the boiler until it becomes saturated. When the boiler is shut down due to a weekend start-up / shutdown operation and the feedwater pump is shut down, the inlet feedwater temperature of the economizer and the outlet feedwater temperature of the feedwater heater are measured after a first predetermined time has elapsed since the boiler was shut down. If the inlet feedwater temperature of the economizer at the first predetermined time is above a predetermined temperature and the outlet feedwater temperature of the feedwater heater is higher than the temperature at the time the feedwater pump was shut down, the feedwater pump is made to perform a circulation operation to circulate the feedwater after a second predetermined time has elapsed since the boiler was shut down. [Effects of the Invention]

[0012] According to the inventions of claims 1 and 4, when a boiler is shut down due to weekend start-up / shutdown operation, if the feedwater temperature at the inlet of the economizer and the feedwater temperature at the outlet of the feedwater heater are higher than when the boiler is shut down, it can be estimated that there is a leak from the feedwater heater. Therefore, it is possible to detect leaks from the feedwater heater early. Furthermore, if there is a leak in the feedwater heater during the shutdown of the weekend start-up / shutdown operation, the feedwater pump can be made to circulate water, thereby equalizing the feedwater temperature in the boiler, suppressing the occurrence of water hammer, and preventing damage to the boiler water tubes.

[0013] According to the invention of claim 2, if the start time of the weekend start-up / shutdown operation is after a third predetermined time has elapsed, which occurs after a second predetermined time has elapsed, the feedwater pump can be made to perform circulation operation after the third predetermined time has elapsed. This makes it possible to further equalize the feedwater temperature in the boiler, suppress the occurrence of water hammer, and prevent damage to the boiler water tubes.

[0014] According to the invention of claim 3, the circulation operation is stopped when the variation in multiple feedwater temperatures measured inside the boiler falls within a predetermined range, so there is no need to operate the feedwater pump unnecessarily, and it is possible to suppress the occurrence of water hammer more easily. [Brief explanation of the drawing]

[0015] [Figure 1] This is a schematic diagram of a steam power generation facility according to an embodiment of the present invention. [Figure 2] This graph shows the decrease in feedwater temperature at various parts of the thermal power generation equipment when no water leakage occurs during shutdown. [Figure 3] This graph shows the decrease in water supply temperature at various parts of a thermal power generation facility when a water leak occurs while the facility is shut down. [Figure 4] This graph shows the decrease in feedwater temperature at various parts of a thermal power generation facility when water leakage and water hammer occur during shutdown. [Figure 5] This graph shows the decrease in feedwater temperature at various parts when the feedwater pump is operated in a circulating mode while the thermal power generation equipment is shut down. [Figure 6] This flowchart shows the procedure for operating a feedwater pump in a circulating manner while the thermal power generation equipment is shut down. [Modes for carrying out the invention]

[0016] The present invention will be described below based on the illustrated embodiments.

[0017] Figure 1 is a schematic configuration diagram of a steam power generation facility 1 according to an embodiment of the present invention. The steam power generation facility 1 includes a high-pressure feed water pump (feed water pump) 2, a high-pressure feed water heater (feed water heater) 3, a boiler 4, a steam turbine 5, a generator 6, a condenser 7, and a control device (control means) 8. The steam power generation facility 1 of the present embodiment performs a WSS operation in which the operation is stopped (disconnected) on weekends and restarted at the beginning of the week in response to a decrease in power demand on weekends.

[0018] The high-pressure feed water pump 2 supplies the water supplied from a water supply source (not shown) and the condenser 7 to the high-pressure feed water heater 3.

[0019] The high-pressure feed water heater 3 uses the extraction steam of the steam turbine 5 to heat the water supplied from the high-pressure feed water pump 2. The high-pressure feed water heater 3 includes a first A heater 31A and a first B heater 31B, and a second A heater 32A and a second B heater 32B as heaters for heating the feed water. The first A heater 31A and the first B heater 31B are connected in parallel to the high-pressure feed water pump 2. Also, the second A heater 32A is connected to the first A heater 31A, and the second B heater 32B is connected to the first B heater 31B. That is, the high-pressure feed water heater 3 includes a first feed water heating system that heats the feed water by the first A heater 31A and the second A heater 32A, and a second feed water heating system that heats the feed water by the first B heater 31B and the second B heater 32B.

[0020] The boiler 4 includes a economizer 41, a first water wall 42, a second water wall 43, and a superheater 44. The economizer 41 heats the water supplied from the high-pressure feed water heater 3 until it becomes saturated water using the exhaust heat of the boiler 4.

[0021] The first water wall 42 and the second water wall 43 are evaporation tubes arranged around the combustion chamber of the boiler 4, and are evaporators that further heat the feed water heated to saturated water by the economizer 41 to generate saturated steam.

[0022] The superheater 44 further superheats the saturated steam generated by the primary water-cooled wall 42 and the secondary water-cooled wall 43 to a temperature above saturation to produce superheated steam. The generated superheated steam is supplied to the steam turbine 5.

[0023] The steam turbine 5 rotates its blades using superheated steam supplied from the boiler 4. The generator 6 generates electricity using the rotation of the turbine blades.

[0024] The condenser 7 cools and condenses the superheated steam used by the steam turbine 5, returns it to low-pressure saturated water, and supplies it to the high-pressure feedwater pump 2.

[0025] The steam power generation equipment 1 is equipped with temperature sensors (not shown) that measure the feedwater temperature or fluid temperature of each part. For example, the outlet feedwater temperature Tp1A of the first A heater 31A, the outlet feedwater temperature Tp1B of the first B heater 31B, the outlet feedwater temperature Tp2A of the second A heater 32A, and the outlet feedwater temperature Tp2B of the second B heater 32B, the inlet feedwater temperature Tp3 of the economizer 41, the outlet fluid temperature Tp4 of the primary water-cooled wall 42 and the outlet fluid temperature Tp5 of the secondary water-cooled wall 43, and the outlet fluid temperature Tp6 of the superheater 44 are measured by the temperature sensors, and the measurement results are transmitted to the control device 8.

[0026] The control device 8 is a device for controlling the operation of the steam power generation equipment 1 and is composed of a so-called computer. The control device 8 controls the operation of the steam power generation equipment 1 based on the measured temperatures Tp1A, Tp1B, Tp2A, Tp2B, Tp3, Tp4, Tp5, and Tp6 transmitted from the temperature sensor.

[0027] As described above, the thermal power generation facility 1 operates in WSS mode. Therefore, on weekdays, all parts of the thermal power generation facility 1 are driven to generate electricity, and on weekends, it is shut down and disconnected from the power grid.

[0028] Figure 2 is a graph showing the decrease in feedwater (fluid) temperature at each part when there is no water leakage from the high-pressure feedwater heater 3 and no water hammer occurs during the shutdown of the WSS operation. In this graph, the vertical axis represents temperature (°C) and the horizontal axis represents time. The intervals between times T1, T2, etc., are, for example, 4 hours. The steam power generation equipment 1 is disassembled at time T1, and the operation of the high-pressure feedwater pump 2 is stopped at time T1a. As can be seen from this graph, since the feedwater does not flow during the shutdown of the WSS operation, the feedwater (fluid) temperature at each part gradually decreases over time.

[0029] On the other hand, Figure 3 is a graph showing the decrease in feedwater (fluid) temperature in each part when there is a leak from the high-pressure feedwater heater 3 during the shutdown of the WSS operation, but no water hammer occurs. The steam power generation equipment 1 is disassembled at time T1, and the operation of the high-pressure feedwater pump 2 is stopped at time T1a. As can be seen from this graph, if one of the heaters of the high-pressure feedwater heater 3 leaks during the shutdown of the WSS operation, the feedwater in the boiler 4 flows (backflows), causing the feedwater temperature in the boiler 4 to become uneven, and the feedwater temperature at the economizer inlet Tp3, the outlet fluid temperature of the second A heater 32A Tp2A, and the outlet feedwater temperature of the second B heater 32B Tp2B etc. rise compared to when the high-pressure feedwater pump 2 is stopped. Specifically, the feedwater temperature Tp3 at the economizer inlet rose to 215°C 4 hours and 40 minutes after disassembly, and rose to 233°C 6 hours and 40 minutes after the high-pressure feedwater pump 2 was stopped (7 hours and 57 minutes after disassembly).

[0030] In contrast, Figure 4 is a graph showing the decrease in feedwater (fluid) temperature at each part when there is a leak from the high-pressure feedwater heater 3 and a water hammer occurs during the shutdown of the WSS operation. The steam power generation equipment 1 was disconnected at time T1 by canceling its start-up, the operation of the high-pressure feedwater pump 2 was stopped at time T1a, and a water hammer occurred at time T9a. As can be seen from this graph, when a leak occurs in one of the heaters of the high-pressure feedwater heater 3 and a water hammer occurs during the shutdown of the WSS operation, the feedwater temperature Tp3 at the economizer inlet rises to 245°C at time T2a, approximately 5 hours and 10 minutes after the high-pressure feedwater pump 2 was stopped, and the feedwater temperature Tp2B at the outlet of the second B heater 32B is significantly higher than when the high-pressure feedwater pump 2 was stopped. Furthermore, the water hammer occurs approximately 35 hours after disconnection.

[0031] Taking into consideration the fluctuations in feedwater temperature due to leakage from the high-pressure feedwater heater 3 while the system is shut down, in the steam power generation equipment 1 of this embodiment, after a first predetermined time (for example, 5 hours) has elapsed since disassembly, the control device 8 measures the feedwater temperature Tp3 at the economizer inlet, the feedwater temperature Tp1A at the outlet of the first A heater 31A, the feedwater temperature Tp1B at the outlet of the first B heater 31B, the feedwater temperature Tp2A at the outlet of the second A heater 32A, and the feedwater temperature Tp2B at the outlet of the second B heater 32B.

[0032] Furthermore, the control device 8 checks if the measured economizer inlet water temperature Tp3 is above a predetermined temperature (for example, 215°C), and if the outlet water temperature Tp1A of the 1st A heater 31A, the outlet water temperature Tp1B of the 1st B heater 31B, the outlet water temperature Tp2A of the 2nd A heater 32A, and the outlet water temperature Tp2B of the 2nd B heater 32B have risen above the temperature at which the high-pressure water supply pump 2 is stopped. In this case, the high-pressure water supply pump 2 is started after a second predetermined time (for example, 20 hours) has elapsed since disconnection, and a circulation operation is performed to circulate the water supply.

[0033] Furthermore, if the WSS operation shutdown period is, for example, two days (48 hours) on Saturday and Sunday, the high-pressure feedwater pump 2 is started after a third predetermined time (for example, 40 hours) has elapsed since disconnection, and a circulation operation is performed to circulate the feedwater. As a result, the feedwater temperature in the boiler 4 is made uniform, so flashing and condensation due to variations in feedwater temperature do not occur, and the occurrence of water hammer can be effectively suppressed.

[0034] Next, the operation of the above embodiment will be explained based on the graph shown in Figure 5 and the flowchart shown in Figure 6. The steam power generation equipment 1 performs WSS operation, which disconnects the circuit at time T1 (step S1), and stops the operation of the high-pressure feedwater pump 2 at time T1a (step S2).

[0035] When a first predetermined time has elapsed since disconnection and time T2a has arrived (YES in step S3), the control device 8 measures the economizer inlet feedwater temperature Tp3, the outlet feedwater temperature Tp1A of the first A heater 31A, the outlet feedwater temperature Tp1B of the first B heater 31B, the outlet feedwater temperature Tp2A of the second A heater 32A, and the outlet feedwater temperature Tp2B of the second B heater 32B (step S4).

[0036] If the measured economizer inlet water temperature Tp3 is above a predetermined temperature, and the outlet water temperature Tp1A of the first A heater 31A, the outlet water temperature Tp1B of the first B heater 31B, the outlet water temperature Tp2A of the second A heater 32A, and the outlet water temperature Tp2B of the second B heater 32B have risen above the temperature at which the high-pressure water pump 2 was stopped (YES in step S5), and a second predetermined time has elapsed since the disconnection (YES in step S6), the control device 8 will operate the high-pressure water pump 2 in a circulating operation between times T4a and T4b (step S7).

[0037] Furthermore, if a third predetermined time has elapsed since disconnection (YES in step S8), the control device 8 causes the high-pressure water supply pump 2 to operate in a circulating manner between times T8a and T8b (step S9).

[0038] Furthermore, it is preferable that the circulation operation is stopped when the feedwater (fluid) temperature in each part of the boiler 4 is monitored by the control device 8 and the variation in these temperatures falls within a predetermined range, that is, when the feedwater (fluid) temperature in each part of the boiler 4 becomes approximately uniform.

[0039] As explained above, according to the steam power generation equipment 1 of this embodiment, when the equipment is shut down by WSS operation, if the inlet feedwater temperature Tp3 of the economizer 41 is above a predetermined temperature, and the outlet feedwater temperatures Tp1A of the first A heater 31A, Tp1B of the first B heater 31B, Tp2A of the second A heater 32A, and Tp2B of the second B heater 32B are higher than when the high-pressure feedwater pump 2 is shut down, it can be estimated that there is a leak from the high-pressure feedwater heater 3. Therefore, it is possible to detect the leaking heater from among the multiple heaters constituting the high-pressure feedwater heater 3 at an early stage. Furthermore, if the high-pressure feedwater heater 3 is leaking during the shutdown of the WSS operation, the high-pressure feedwater pump 2 can be made to perform circulation operation, thereby equalizing the feedwater temperature in the boiler 4, suppressing the occurrence of water hammer, and preventing damage to the boiler water tubes.

[0040] Furthermore, according to the steam power generation equipment 1 of this embodiment, if the start time of WSS operation is after the third predetermined time which occurs after the second predetermined time, the high-pressure feedwater pump 2 can be made to circulate after the third predetermined time has elapsed. This makes it possible to further equalize the feedwater temperature in the boiler 4, suppress the occurrence of water hammer, and prevent damage to the boiler water tubes. That is the case.

[0041] Furthermore, according to the steam power generation equipment 1 of this embodiment, the circulation operation is stopped when the variation in multiple feedwater temperatures measured in the boiler 4 falls within a predetermined range. Therefore, there is no need to operate the high-pressure feedwater pump 2 unnecessarily, making it easier to suppress the occurrence of water hammer.

[0042] Although embodiments of this invention have been described above, the specific configuration is not limited to the embodiments described above, and any design changes, etc., that do not depart from the gist of this invention are also included. For example, although the above embodiments were described using a thermal power generation facility 1 as an example, it is also possible to apply it to a combined cycle power generation facility. In addition, although the high-pressure feedwater pump 2 is circulated twice, the circulation operation may be performed once or three or more times if the occurrence of water hammer can be suppressed. Furthermore, if the operation of the thermal power generation facility 1 is restarted before the timing for circulation operation arrives, the circulation operation may be omitted.

[0043] Furthermore, if a leak in the high-pressure feedwater heater 3 is detected based on the measurement results of the feedwater temperature Tp3 at the inlet of the economizer 41, the control device 8 may notify the repair department of the organization responsible for maintaining the steam power generation equipment 1. This would allow for early repair or replacement of the high-pressure feedwater heater 3, effectively suppressing the occurrence of water hammer. [Explanation of symbols]

[0044] 1. Steam power generation equipment 2. High-pressure water supply pump (water supply pump) 3. High-pressure feedwater heater (feedwater heater) 4 Boiler 41 Economizer 42 Primary water cooling wall 43 Secondary water cooling wall 44 Superheater 5 Steam Turbine 6 Generators 7. Condenser 8. Control device (control means)

Claims

1. A boiler feedwater system comprising a feedwater pump, a feedwater heater that heats the water supplied from the feedwater pump and supplies it to the boiler's economizer, control means for controlling the feedwater pump, and temperature sensors for measuring the feedwater temperature of each part, The economizer heats the water supplied from the feedwater heater using the waste heat from the boiler until it becomes saturated. The control means is When the boiler is shut down due to a weekend start-up / shutdown operation and the feedwater pump is shut down, the temperature sensor measures the feedwater temperature at the inlet of the economizer and the feedwater temperature at the outlet of the feedwater heater after a first predetermined time has elapsed since the boiler was shut down. If the inlet feedwater temperature of the economizer is above a predetermined temperature during the first predetermined time, and the outlet feedwater temperature of the feedwater heater is higher than the temperature at the time the feedwater pump is stopped, the feedwater pump is made to perform a circulation operation to circulate the feedwater after a second predetermined time has elapsed since the boiler was stopped. A boiler feedwater system characterized by the following features.

2. The boiler feedwater device according to claim 1, characterized in that, if the boiler operation start time, which is the time when the boiler operation is started by the weekend start-up / shutdown operation, is after the third predetermined time which occurs after the second predetermined time has elapsed, the control means causes the feedwater pump to perform the circulation operation after the third predetermined time has elapsed.

3. The boiler feedwater device according to claim 1 or 2, characterized in that the control means stops the circulation operation when the variation of a plurality of feedwater temperatures measured in the boiler falls within a predetermined range.

4. A boiler feedwater method comprising supplying water to a feedwater heater by a feedwater pump, and supplying the water heated by the feedwater heater to a boiler economizer, The economizer heats the water supplied from the feedwater heater using the waste heat from the boiler until it becomes saturated. When the boiler is shut down due to a weekend start-up / shutdown operation and the feedwater pump is shut down, the inlet feedwater temperature of the economizer and the outlet feedwater temperature of the feedwater heater are measured after a first predetermined time has elapsed since the boiler was shut down. If the inlet feedwater temperature of the economizer is above a predetermined temperature during the first predetermined time, and the outlet feedwater temperature of the feedwater heater is higher than the temperature at the time the feedwater pump is stopped, the feedwater pump is made to perform a circulation operation to circulate the feedwater after a second predetermined time has elapsed since the boiler was stopped. A boiler feedwater method characterized by the following features.

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