JP7413009B2 - Boilers, power generation plants, and chemical cleaning methods for boilers - Google Patents

Description

TECHNICAL FIELD The present disclosure relates to a boiler, a power plant, and a method for chemically cleaning a boiler.

A large boiler such as a coal-fired boiler has a hollow furnace installed vertically, and a plurality of combustion burners are arranged along the circumferential direction of the furnace wall. In addition, in a coal-fired boiler, a flue is connected vertically above the furnace, and a heat exchanger for generating steam is arranged in this flue. Then, the combustion burner injects a mixture of fuel and air (oxidizing gas) into the furnace to form a flame, and combustion gas is generated and flows into the flue. A heat exchanger is installed in a region where combustion gas flows, and superheated steam is generated by heating water or steam flowing through heat transfer tubes that make up the heat exchanger.

In such a boiler water supply and steam system, it is known to perform chemical cleaning by circulating a cleaning liquid inside the heat exchanger tubes (for example, Patent Document 1).

In Patent Document 1, when chemically cleaning the steam water separator of the boiler and the upstream side (furnace side) thereof, after stopping the operation of the boiler, temporary piping is installed to bypass the circulation pump and valve in the circulation piping. A temporary circulation pump is installed in the temporary piping. It is also disclosed that a temporary water level gauge for detecting the water level in the superheater is installed in a connecting pipe connected from the brackish water separator to the superheater, and the superheater is filled with water.

Patent No. 6303836

When chemically cleaning the boiler's brackish water separator and the upstream side (furnace side) thereof, the heat exchanger that is connected to the brackish water separator and is not subject to chemical cleaning is filled with water. If a portion of the cleaning liquid flows into a water-filled heat exchanger system downstream of the brackish water separator that is not subject to chemical cleaning, such as a superheater system, the following problems will occur.
Scale (steam oxidation scale) generated on the inner surface of heat exchanger tubes of heat exchanger systems (for example, superheater systems) that are not subject to chemical cleaning is usually a scale that is hardly soluble in cleaning liquids. Therefore, when a portion of the cleaning liquid flows into the superheater system filled with water, the cleaning liquid is mixed non-uniformly with the water for filling and is diluted. The scale is partially dissolved by the cleaning solution that is unevenly diluted and has insufficient cleaning performance, causing cracks in the scale. When cracks occur in the scale, the cleaning liquid reaches the interface between the base metal and the scale through the cracks, dissolves part of the base material (heat exchanger tube), etc., and creates a void between the scale and the inner surface of the heat exchanger tube. may occur. When voids occur, heat transfer to the fluid (medium such as steam or water) in the heat transfer tubes is inhibited, which may reduce the heat transfer performance of the superheater.
Further, if a part of the cleaning liquid flows into the superheater system, there is a possibility that the scale will be peeled off from the cracks in the scale on the inner surface of the heat transfer tube. If the scale peels off, when the boiler is started after cleaning, the peeled scale may partially accumulate in the boiler's superheater system, potentially clogging the inside of the heat exchanger tubes. When the heat exchanger tubes become clogged, the heat exchanger tubes after the blockage become unable to exchange heat, which may result in a decrease in heat transfer performance in the superheater or damage to the heat exchanger tubes.

In order to solve the occurrence of such problems, the liquid level of the cleaning liquid in the gas-liquid separation section located upstream (furnace side) of the superheater system may be monitored and controlled using a level meter.
However, during chemical cleaning, the liquid level meter may not function properly due to sludge in the cleaning liquid or foaming of components constituting the cleaning liquid, and the liquid level may be measured incorrectly. That is, there is a possibility that the level of the cleaning liquid cannot be detected accurately. In such a case, the cleaning liquid may flow into the superheater system, potentially causing the above-mentioned problems.
Additionally, when the amount of cleaning fluid circulated is increased in order to discharge the sludge contained in the cleaning fluid from the boiler's brackish water separator and the upstream side (furnace side), the amplitude of fluctuations in the fluid level becomes large. As a result, the liquid level control operation of the cleaning liquid cannot follow up, and the cleaning liquid may flow into the superheater system, causing the above-mentioned problems.

The present disclosure has been made in view of these circumstances, and provides a boiler, a power generation plant, and a boiler chemistry system that can accurately detect cleaning liquid flowing from a gas-liquid separation section to a heat exchanger that is not subject to chemical cleaning. The purpose is to provide a cleaning method.

In order to solve the above problems, the boiler, power plant, and boiler chemical cleaning method of the present disclosure employ the following means.
A boiler according to an aspect of the present disclosure is a boiler that can be cleaned with a cleaning liquid supplied from a cleaning liquid supply device, and includes an evaporator that heats feed water to generate steam, and a steam that is generated by the feed water and the evaporator. a gas-liquid separation section that separates gas and liquid; a heat exchanger that exchanges heat with the vapor separated in the gas-liquid separation section; and a communication pipe that connects the gas-liquid separation section and the heat exchanger. In preparation, during chemical cleaning, the cleaning liquid does not flow through the heat exchanger, the cleaning liquid is supplied into the gas-liquid separation section and the evaporation section from the cleaning liquid supply device, and the communication pipe is supplied with the cleaning liquid from the cleaning liquid supply device. A detection unit is provided for detecting the cleaning liquid flowing through the communication pipe and heading towards the heat exchanger.

Further, a method for cleaning a boiler according to an aspect of the present disclosure includes: an evaporation section that heats feed water to generate steam; and a gas-liquid separation section that separates the feed water and the steam generated in the evaporation section into gas and liquid. , a method for chemically cleaning a boiler, comprising: a heat exchanger for exchanging heat with the steam separated in the gas-liquid separation section; and a communication pipe connecting the gas-liquid separation section and the heat exchanger; A supply step of supplying the cleaning liquid from the cleaning liquid supply device to the inside of the gas-liquid separation section and the evaporation section without flowing the cleaning liquid to the heat exchanger, and a detection section provided in the communication pipe to ensure the communication. and a detection step of detecting the cleaning liquid flowing inside the pipe and heading towards the heat exchanger.

According to the present disclosure, it is possible to accurately detect the cleaning liquid flowing from the gas-liquid separation unit to the heat exchanger that is not targeted for chemical cleaning.

1 is a schematic configuration diagram showing a coal-fired boiler according to a first embodiment of the present disclosure. 2 is a schematic diagram showing steam, condensate, and water supply systems in the coal-fired boiler of FIG. 1. FIG. 2 is a schematic diagram showing a steam and water supply system during chemical cleaning of the boiler in FIG. 1. FIG. FIG. 7 is a schematic diagram showing a steam and water supply system during chemical cleaning of a boiler according to a second embodiment of the present disclosure. FIG. 7 is a schematic diagram showing a steam and water supply system during chemical cleaning of a boiler according to a third embodiment of the present disclosure. FIG. 7 is a schematic diagram showing a steam and water supply system during chemical cleaning of a boiler according to a fourth embodiment of the present disclosure. FIG. 7 is a schematic diagram showing a steam and water supply system during chemical cleaning of a boiler according to a fifth embodiment of the present disclosure. FIG. 7 is a schematic diagram showing a steam and water supply system during chemical cleaning of a boiler according to a sixth embodiment of the present disclosure. FIG. 7 is a schematic diagram showing a steam and water supply system during chemical cleaning of a boiler according to a seventh embodiment of the present disclosure. FIG. 7 is a diagram showing a communication pipe and a detection unit during chemical cleaning of a boiler according to an eighth embodiment of the present disclosure. 11 is a graph showing the difference in detection time between the first ultrasonic sensor and the second ultrasonic sensor in FIG. 10.

Below, preferred embodiments of a boiler, a power generation plant, and a method for chemically cleaning a boiler according to the present disclosure will be described with reference to the drawings. Note that the present disclosure is not limited to this embodiment, and if there are multiple embodiments, the present disclosure also includes a configuration in which each embodiment is combined.

[First embodiment]
A first embodiment according to the present disclosure will be described using FIGS. 1 to 3.
FIG. 1 is a schematic configuration diagram showing a coal-fired boiler of this embodiment.

The coal-fired boiler 10 of this embodiment uses pulverized coal obtained by pulverizing coal (carbon-containing solid fuel) as pulverized fuel, combusts this pulverized fuel with a combustion burner, and transfers the heat generated by this combustion to supplied water, steam, and heat. It is a coal-fired (pulverized coal-fired) boiler that can be replaced to generate superheated steam. In the following description, the term "upper" or "upper" refers to the upper side in the vertical direction, and the term "lower" or "lower" refers to the lower side in the vertical direction.

In this embodiment, as shown in FIG. 1, a coal-fired boiler 10 includes a furnace 11, a combustion device 12, and a combustion gas passage 13. The furnace 11 has a hollow rectangular tube shape and is installed along the vertical direction. The furnace wall (heat transfer tube) 101 that constitutes the furnace 11 is composed of a plurality of evaporation tubes and fins that connect them, and the temperature of the furnace wall 101 exchanges heat generated by combustion of pulverized fuel with feed water and steam. The rise is being suppressed.

The combustion device 12 is provided on the lower side of the furnace wall 101 that constitutes the furnace 11 . In this embodiment, the combustion device 12 includes a plurality of combustion burners (for example, 21, 22, 23, 24, 25) mounted on the furnace wall 101. For example, the combustion burners 21, 22, 23, 24, and 25 are arranged at equal intervals along the circumferential direction of the furnace 11 as one set, and are arranged in multiple stages along the vertical direction. However, the shape of the furnace, the number of combustion burners in one stage, and the number of stages are not limited to this embodiment.

Each combustion burner 21, 22, 23, 24, 25 is connected to a plurality of crushers (mills) 31, 32, 33, 34, 35 via pulverized coal supply pipes 26, 27, 28, 29, 30. There is. Although not shown in the figures, each of the crushers 31, 32, 33, 34, and 35 has, for example, a rotary table supported in a housing of the crusher so as to be rotatable, and a plurality of rollers arranged above the rotary table to rotate the rotary table. They are configured to be rotatably supported in conjunction with each other. When coal is placed between multiple rollers and a rotary table, it is pulverized into a predetermined size of pulverized coal. The pulverized fuel transported to the classifier and classified within a predetermined particle size range can be supplied to the combustion burners 21, 22, 23, 24, 25 from the pulverized coal supply pipes 26, 27, 28, 29, 30. .

In addition, the furnace 11 is provided with a wind box 36 at the mounting position of each combustion burner 21, 22, 23, 24, 25, and one end of an air duct (wind path) 37 is connected to this wind box 36. There is. The air duct 37 is provided with a forced draft fan (FDF) 38 at the other end.

The combustion gas passage 13 is connected to the upper part of the furnace 11 in the vertical direction, as shown in FIG. The combustion gas passage 13 is provided with superheaters 102, 103, 104, reheaters 105, 106, and a economizer 107 as heat exchangers for recovering the heat of the combustion gas, and the combustion gas passage 13 is provided with Heat exchange occurs between the combustion gas generated in the heat exchanger and the water and steam flowing through each heat exchanger.

As shown in FIG. 1, the combustion gas passage 13 is connected to a flue 14 on its downstream side through which the combustion gas that has undergone heat exchange is discharged. An air heater (air preheater) 42 is provided between the flue 14 and the air duct 37 to exchange heat between the air flowing through the air duct 37 and the combustion gas flowing through the flue 14. , 22, 23, 24, 25 can be heated.

Further, the flue 14 is provided with a denitrification device 43 at a position upstream of the air heater 42 . The denitration device 43 supplies a reducing agent, such as ammonia or urea water, that has the effect of reducing nitrogen oxides into the flue 14, and converts the combustion gas supplied with the reducing agent into a reaction between the nitrogen oxides and the reducing agent. Nitrogen oxides in the combustion gas are removed and reduced by promoting the catalytic action of the denitrification catalyst installed in the denitrification device 43. The gas duct 41 connected to the flue 14 is provided with a dust collector 44 such as an electric dust collector, an induced draft fan (IDF) 45, a desulfurization device 46, etc. at a position downstream from the air heater 42. A chimney 50 is provided at the downstream end.

On the other hand, when the plurality of crushers 31, 32, 33, 34, 35 are driven, the generated pulverized fuel is transferred to the pulverized coal supply pipes 26, 27, 28, 29, 30 together with the conveying gas (primary air, oxidizing gas). It is supplied to combustion burners 21, 22, 23, 24, 25 through. In addition, by exchanging heat with the exhaust gas discharged from the flue 14 of the coal-fired boiler 10 by the air heater 42, heated combustion air (secondary air, oxidizing gas) is passed from the air duct 37 through the wind box 36. and is supplied to each combustion burner 21, 22, 23, 24, 25. Then, the combustion burners 21, 22, 23, 24, 25 blow into the furnace 11 a pulverized fuel mixture in which pulverized fuel and transport gas are mixed, and blow combustion air into the furnace 11, and at this time, the pulverized fuel mixture is A flame can be formed by igniting air. A flame is generated in the lower part of the furnace 11 , and high-temperature combustion gas rises within the furnace 11 and is discharged into the combustion gas passage 13 . Note that air is used as the oxidizing gas in this embodiment. It may have a higher or lower oxygen content than air, and can be used by optimizing the fuel flow rate.

Further, the furnace 11 is provided with an additional air port 39 above the mounting position of each combustion burner 21, 22, 23, 24, 25. An end of an additional air duct 40 branched from the air duct 37 is connected to the additional air port 39. Therefore, the combustion air (secondary air, oxidizing gas) sent by the forced draft fan 38 is supplied from the air duct 37 to the wind box 36, and from this wind box 36 each combustion burner 21, 22, 23, 24, 25, and additional air for combustion sent by a forced draft fan 38 can be supplied from an additional air duct 40 to an additional air port 39.

In the lower region A of the furnace 11, a pulverized fuel mixture and combustion air (secondary air, oxidizing gas) are combusted to generate a flame. Here, the inside of the furnace 11 is maintained in a reducing atmosphere by setting the amount of air supplied to be less than the theoretical amount of air relative to the amount of pulverized coal supplied. That is, nitrogen oxides (NOx) generated by the combustion of pulverized coal are reduced in region B of the furnace 11, and then additional air is supplied from the additional air port 39 to complete the oxidative combustion of the pulverized coal. The amount of NOx generated by combustion of pulverized coal is reduced.

Thereafter, as shown in FIG. ), the second reheater 106, the first reheater 105 (hereinafter sometimes simply referred to as a reheater), and the economizer 107, and then the nitrogen oxides are reduced and removed by the denitrification device 43. After particulate matter is removed by a dust collector 44 and sulfur oxides are removed by a desulfurizer 46, the smoke is discharged into the atmosphere from a chimney 50. Note that the heat exchangers do not necessarily have to be arranged in the order described above with respect to the combustion gas flow.

Next, the superheaters 102, 103, 104, reheaters 105, 106, and energy saver 107 provided in the combustion gas passage 13 will be described in detail as heat exchangers. FIG. 2 is a schematic diagram showing a heat exchanger provided in the coal-fired boiler 10. Note that FIG. 1 does not accurately show the positions of the heat exchangers (superheaters 102, 103, 104, reheaters 105, 106, and economizer 107) in the combustion gas passage 13, but The arrangement order of the exchanger with respect to the combustion gas flow is also not limited to the description in FIG.

FIG. 2 shows a heat exchanger of the coal-fired boiler 10 provided in the boiler power generation plant 1 of this embodiment, a steam turbine 110 that is rotationally driven by the steam generated by the coal-fired boiler 10, and a steam turbine 110 connected to the steam turbine 110. and a generator 115 that generates power according to the rotation of the steam turbine 110.

A steam turbine 110 operated by steam generated in the coal-fired boiler 10 is composed of, for example, a high-pressure turbine 111, an intermediate-pressure turbine 112, and a low-pressure turbine 113, and steam from a reheater, which will be described later, flows into the intermediate-pressure turbine. It then flows into the low pressure turbine. A condenser 114 is connected to the low pressure turbine 113, and the steam that rotates the low pressure turbine 113 is cooled by cooling water (for example, seawater) in the condenser 114 and becomes condensed water. Condenser 114 is connected to energy saver 107 via water supply line L1. The water supply line L1 is provided with, for example, a condensate pump (CP) 121, a low pressure water heater 122, a boiler water pump (BFP) 123, and a high pressure water heater 124. A part of the steam that drives the steam turbines 111, 112, and 113 is extracted from the low-pressure feed water heater 122 and the high-pressure feed water heater 124, and is supplied as a heat source to the high-pressure feed water heater 124 and the low-pressure feed water heater 122 via an air extraction line (not shown). The water supplied to the economizer 107 is heated.

For example, a case where the coal-fired boiler 10 is a once-through boiler will be explained. The economizer 107 is connected to each evaporation pipe of the furnace wall 101. When the feed water heated by the economizer 107 passes through the evaporation tube of the furnace wall 101, it is heated by radiation from the flame in the furnace 11, and is led to the brackish water separator (gas-liquid separation section) 126. . The steam separated in the brackish water separator 126 is supplied to superheaters 102, 103, and 104, and the drain water separated in the brackish water separator 126 is led to a drain tank 127. Drain water discharged from the drain tank 127 is guided to the condenser 114 via the drain water line L2.

Furthermore, during startup of the once-through boiler or during low-load operation, the entire amount of feed water supplied from the economizer 107 does not evaporate when passing through each evaporation tube on the furnace wall 101, and as a result, the brackish water separator There may be an operating state in which a water level exists at 126 (wet operating state). In this wet operating state, the drain water separated by the brackish water separator 126 is merged into the water supply line L1 in the middle of the water supply line L1 through the circulation line L6 using the boiler circulation pump (BCP) 128. It may be circulated and supplied to each evaporation tube of the furnace wall 101 from there.

When the combustion gas flows through the combustion gas passage 13, the heat of the combustion gas is recovered by the superheaters 102, 103, 104, the reheaters 105, 106, and the economizer 107. On the other hand, the feed water supplied from the boiler feed pump (BFP) 123 is preheated by the energy saver 107 and then heated to steam as it passes through each evaporation tube on the furnace wall 101, and is introduced to the brackish water separator 126. It will be destroyed. The steam separated by the steam separator 126 is introduced into superheaters 102, 103, and 104, and is superheated by combustion gas. The superheated steam generated in the superheaters 102, 103, and 104 is supplied to the high-pressure turbine 111 via the steam line L3, and drives the high-pressure turbine 111 to rotate. Steam discharged from the high-pressure turbine 111 is introduced into the reheaters 105 and 106 via the steam line L4 and is superheated again. The re-superheated steam is supplied to the low pressure turbine 113 via the intermediate pressure turbine 112 via the steam line L5, and drives the intermediate pressure turbine 112 and the low pressure turbine 113 to rotate. The rotating shaft of each steam turbine 111, 112, 113 rotationally drives a generator 115 to generate electricity. The steam discharged from the low-pressure turbine 113 is cooled by the condenser 114 to become condensed water, and is sent to the energy saver 107 again via the water supply line L1.

In addition, in the combustion gas passage 13, a suit (not shown) is provided in the gaps between heat transfer tubes of each heat exchanger such as superheaters 102, 103, 104, reheaters 105, 106, and economizer 107, or in the gaps between each heat exchanger. A blower (ash removal device) may be provided. The soot blower is arranged to extend in a direction substantially perpendicular to the wall surface of the combustion gas passage 13. The soot blower is an injection device that injects steam (gas) in a direction perpendicular to the axial direction, with the axial direction being perpendicular to the wall surface of the combustion gas passage 13, and can also change the injection direction. Steam injected from the suit blower toward heat exchangers such as superheaters 102, 103, 104, reheaters 105, 106, and economizer 107 removes combustion ash accumulated on the surface of each heat transfer tube of the heat exchanger. This suppresses the decrease in heat exchange efficiency in each heat exchanger tube.

Next, the first superheater 102, the second superheater 103, the third superheater 104, the brackish water separator 126, the drain tank 127, etc. will be described in detail using FIG. 3. In addition, in FIG. 3, regarding the superheater, the brackish water separator 126, the drain tank 127, and the lines (pipes) connecting them, the upper side of the page means vertically upward, and the lower side of the page means vertically downward. Regarding the downstream side of the water supply flow to the superheater, the upper side of the paper is not vertically upward, and the lower side of the paper is not vertically downward. Note that, in FIG. 3, among the three first superheaters 102, second superheaters 103, and third superheaters 104, only the first superheater 102 is illustrated, and illustration of the other superheaters is omitted. Note that the first superheater 102 will be simply referred to as superheater 102 below.

Two brackish water separators 126 connected to the superheater 102 according to this embodiment are provided. In addition, in FIG. 3, for convenience of illustration, only one brackish water separator 126 is illustrated, and the first communication pipe 130 and subsequent parts to which the other brackish water separator 126 is connected are omitted. In addition, each of the brackish water separators 126 has substantially the same configuration, so in the following explanation, unless it is necessary to explain each, only one of the brackish water separators 126 will be explained, and the other brackish water separator 126 will be explained. Descriptions will be omitted as appropriate.

The bottom of the brackish water separator 126 and the side of the drain tank 127 are connected by a drain water line L7. Moreover, the upstream end of the above-mentioned drain water line L2 is connected to the bottom of the drain tank 127. Further, the downstream end of the steam line L8 is connected to the side of the steam water separator 126. The steam line L8 guides steam (in a gas-liquid two-phase state of steam and feed water) evaporated within the heat transfer tubes forming the furnace wall 101 to the steam separator 126.

A first communication pipe 130 that guides the steam separated by the brackish water separator 126 to the superheater 102 is connected to the ceiling of the brackish water separator 126 . That is, the first communication pipe 130 connects the brackish water separator 126 and the superheater 102. In the present embodiment, the first communication pipe 130 includes, for example, a first vertical portion 130a extending vertically upward from the ceiling of the brackish water separator 126, and a first vertical portion 130a extending approximately horizontally by bending from the upper end of the first vertical portion 130a. 1 horizontal part 130b, a second vertical part 130c that bends from the end of the first horizontal part 130b (the end opposite to the first vertical part 130a) and extends vertically downward; It has a second horizontal portion 130d that is bent from the lower end and extends substantially horizontally. Although the first horizontal part 130b has been described as a part extending in the substantially horizontal direction as an example, it may be a part that connects the first vertical part 130a and the second vertical part 130c, and does not necessarily extend in the substantially horizontal direction. It does not have to be the existing part. An end of the second horizontal portion 130d (an end opposite to the second vertical portion 130c) is connected to the superheater 102 directly or via another pipe (not shown). A first ultrasonic sensor 131 that detects the cleaning liquid present in the first communication pipe 130 is provided in the middle of the first vertical portion 130a. The cleaning liquid will be described later. The first ultrasonic sensor 131 transmits the detection result to a control device 150, which will be described later.

A second communication pipe 132 that connects the drain tank 127 and the first communication pipe 130 is connected to the ceiling of the drain tank 127 . In the present embodiment, the second communication pipe 132 includes, for example, a third vertical portion 132a extending vertically upward from the ceiling of the drain tank 127, and a third vertical portion 132a bent from the upper end of the third vertical portion 132a and extending substantially horizontally. It has a horizontal part 132b and a fourth vertical part 132c that is bent from the end of the third horizontal part 132b (the end opposite to the third vertical part 132a) and extends vertically downward. Although the third horizontal portion 132b has been described as a portion extending substantially horizontally as an example, it may be a portion connecting the third vertical portion 132a and the fourth vertical portion 132c, and does not necessarily extend substantially horizontally. It does not have to be the existing part. The upper end of the third vertical section 132a is located above the upper end of the first vertical section 130a. Further, the third horizontal portion 132b is located above the first horizontal portion 130b. Note that the upper end of the third vertical section 132a may be located at the same height as the upper end of the first vertical section 130a, or may be located below the upper end of the first vertical section 130a. Similarly, the third horizontal portion 132b may be located at the same height as the first horizontal portion 130b, or may be located below the first horizontal portion 130b.
Further, the downstream end of the third vertical portion 132a is connected to a midway position of the first horizontal portion 130b of the first connecting pipe 130. A second ultrasonic sensor 133 that detects the cleaning liquid present in the second communication pipe 132 is provided at a midway position of the third vertical portion 132a. In this embodiment, the second ultrasonic sensor 133 is provided at approximately the same height level as the first ultrasonic sensor 131, and is substantially responsive to changes in the height level of the cleaning liquid. The same detection can be performed. The second ultrasonic sensor 133 transmits the detection result to a control device 150, which will be described later.

The superheater 102 includes a large number (in this embodiment, about 200 as an example) of heat exchanger tubes 102a, an inlet header 102b that extends in the width direction of the combustion gas passage 13, and to which one end of each heat exchanger tube 102a is connected. It has an outlet header 102c extending in the width direction of the combustion gas passage 13 and to which the other end of each heat transfer tube 102a is connected. The elongated heat exchanger tube 102a constituting the superheater 102 is a panel formed into a meandering planar shape that is repeatedly bent, and is formed so as to extend substantially horizontally. A large number of heat transfer tubes 102a are arranged in the width direction of the combustion gas passage 13 at predetermined intervals. The length in the furnace width direction is, for example, 15 to 30 m. The inlet header 102b distributes steam from the brackish water separator 126 to each heat transfer tube 102a. Further, the outlet header 102c causes the steam flowing through each heat transfer tube 102a to join together.
Steam is supplied to the superheater 102 from a brackish water separator 126 via a first communication pipe 130. As described above, in this embodiment, two brackish water separators 126 are provided. Steam is supplied to the superheater 102 from each brackish water separator 126 . For this reason, two first communication pipes 130 are connected to the superheater 102 (specifically, the inlet header 102b). The two first communication pipes 130 are arranged apart from each other in the width direction of the combustion gas passage 13. As a result, the connection positions between each first communication pipe 130 and the inlet header 102b are also spaced apart in the width direction of the combustion gas passage 13.
The superheater 102 superheats the steam flowing through each heat transfer tube 102a. The steam heated in the superheater 102 flows to the second superheater 103 and the third superheater 104 in order, where the steam is further superheated and is sent to the steam turbine 110 via the steam line L3, which is the main steam piping. (See Figure 2). In this embodiment, as shown in FIG. 3, in the steam line L3, two superheater side pipes L3a are connected to the second superheater 103 (see FIG. 2) and the third superheater 104 (see FIG. 2) in order. The two superheater side pipes connected to each other and led out from the third superheater 104 (see FIG. 2) are configured to merge into one turbine side pipe L3b before reaching the turbine. Therefore, there are two connection parts between the superheater side pipe L3a and the superheater 102 (specifically, the outlet header 102c). Each connection portion is spaced apart in the width direction of the combustion gas passage 13. A steam valve L3c, which is a main steam valve, is provided in the turbine side pipe L3b.

Further, a make-up water pipe 134 is connected to the turbine side pipe L3b of the steam line L3. Specifically, the make-up water pipe 134 is connected to the turbine side pipe L3b at a position closer to the superheater 102 than the steam valve L3c. The make-up water pipe 134 can supply make-up water stored in a make-up water tank (not shown) to the superheater 102, the brackish water separator 126, etc., and perform water filling as described later. The make-up water piping 134 is provided with a rust preventive agent supply section 135, a make-up water pump 134a, and a make-up water valve 134b in this order from the make-up water tank side. The rust preventive agent supply unit 135 mixes a rust preventive agent (for example, hydrazine, ammonia) into the make-up water flowing through the make-up water pipe 134 . The make-up water pump 134a circulates make-up water containing a rust preventive agent into the make-up water piping 134.

Further, the boiler 10 according to this embodiment is provided with a control device 150.
The control device 150 includes, for example, a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), a computer-readable storage medium, and the like. A series of processes for realizing various functions is stored in a storage medium, etc. in the form of a program, for example, and the CPU reads this program into a RAM, etc., and executes information processing and arithmetic processing. By doing so, various functions are realized. Note that the program may be pre-installed in a ROM or other storage medium, provided as being stored in a computer-readable storage medium, or distributed via wired or wireless communication means. etc. may also be applied. Computer-readable storage media include magnetic disks, magneto-optical disks, CD-ROMs, DVD-ROMs, semiconductor memories, and the like. Further, the control device 150 may be a part of a permanently installed control device used for operating the power plant, or may be a temporary control device for chemical cleaning of the boiler.

The control device 150 receives information from the first ultrasonic sensor 131 and the second ultrasonic sensor 133. Specifically, when the first ultrasonic sensor 131 and the second ultrasonic sensor 133 detect a cleaning liquid to be described later, a notification to that effect is received. Further, the control device 150 controls starting and stopping of the makeup water pump 134a based on information from the first ultrasonic sensor 131 and the second ultrasonic sensor 133.

In the boiler 10 according to the present embodiment, a method of chemically cleaning the heat exchanger tubes constituting the energy saver, the heat exchanger tubes constituting the furnace wall 101, the brackish water separator 126, the drain tank 127, the piping connecting these, etc. with a cleaning liquid. explain. In this embodiment, the heat exchanger connected to the brackish water separator 126 and not subject to chemical cleaning is the superheater 102.

When chemically cleaning the boiler 10, the operation of the boiler 10 is first stopped.
Next, a temporary pipe (hereinafter referred to as "temporary pipe 136") connecting the water supply line L1 and the drain water line L2 is installed. A cleaning liquid supply device 137 is provided in the temporary pipe 136. The cleaning liquid supply device 137 is provided with a cleaning liquid circulation pump (not shown) that supplies the cleaning liquid stored in a cleaning liquid storage section (not shown) to various devices via a temporary pipe 136. Examples of the cleaning liquid include acidic cleaning liquids and neutral rust preventives. Further, the temperature of the cleaning liquid may be about 30 degrees to 90 degrees. Note that if the cleaning liquid is at a high temperature, there is a possibility that the cleaning liquid will flow into the superheater system as steam. If the cleaning liquid is a cleaning liquid that exhibits chemical cleaning performance even at low temperatures, such problems will not occur because the cleaning liquid does not turn into steam.

Next, when performing chemical cleaning, the steam valve L3c is closed, and the make-up water pump 134a is driven to supply make-up water to the superheater 102 and the first communication pipe 130. At this time, the rust preventive agent is mixed with the make-up water by the rust preventive agent supply section 135. In this way, make-up water mixed with a rust preventive agent is injected into the superheater 102 and the first connecting pipe 130, and the predetermined positions of the pipes arranged vertically up and down of the superheater 102 and the first connecting pipe 130 are injected into the superheater 102 and the first connecting pipe 130. Fill the area with make-up water mixed with a rust preventive agent up to the height. Here, filling with water (filling with water) means, in other words, filling the superheater 102 and the first connecting pipe 130 with make-up water to a predetermined height, even if not all of them. Hereinafter, this state will be referred to as ``water filling'' and the height at which makeup water is filled will be referred to as ``water filling level.'' Specifically, as shown in FIG. 3, makeup water is filled so that the middle position of the second vertical portion 130c of the first communication pipe 130 is at the water surface (water level) of the makeup water.
Note that the temporary pipe 136 and the cleaning liquid supply device 137 may be installed after filling the superheater 102 and the first communication pipe 130 with makeup water.

When makeup water is filled, a cleaning liquid circulation pump (not shown) provided in the cleaning liquid supply device 137 is driven to circulate the cleaning liquid within a predetermined range. In this embodiment, the cleaning liquid is guided to the energy saver 107 and the heat transfer tubes forming the furnace wall 101 via the water supply line L1. The cleaning liquid is then led to the brackish water separator 126 via the steam line L8. The cleaning liquid discharged from the brackish water separator 126 is led to the drain tank 127 via the drain water line L7. The cleaning liquid discharged from the drain tank 127 is returned to the cleaning liquid circulation pump via the drain water line L2. As the cleaning liquid circulates in this way, various devices and piping through which the cleaning liquid passes are chemically cleaned.

During cleaning, in which the cleaning liquid circulates within a predetermined range of the boiler 10, there may be cases where the liquid level gauge installed in the drain tank 127 cannot be detected properly due to sludge in the cleaning liquid or foaming of components constituting the cleaning liquid, or when there is a problem in the cleaning liquid. In order to discharge the contained sludge from the steam water separator of the boiler and the upstream side (furnace side) of the boiler, when the amount of cleaning liquid circulated is increased, the amplitude and period of fluctuations in the liquid level become more frequent. The cleaning liquid level control operation may not be able to follow the instructions. In such a case, the cleaning liquid overflowing from the brackish water separator 126 or the drain tank 127 may flow (overflow) to the system on the superheater 102 side via the first connecting pipe 130 or the second connecting pipe 132. be. In the following, a case where the cleaning liquid overflows from the brackish water separator 126 will be described, but when the cleaning liquid overflows from the drain tank 127, the control device 150 performs the same process.
The cleaning liquid overflowing from the brackish water separator 126 flows into the first vertical section 130a of the first communication pipe 130. The level of the cleaning liquid that has flowed into the first vertical portion 130a increases as long as the overflow continues. When the level of the cleaning liquid rises to the detection target position of the first ultrasonic sensor 131, the waveform of the first ultrasonic sensor 131 changes. Thereby, the first ultrasonic sensor 131 detects the cleaning liquid. The first ultrasonic sensor 131 is, for example, a thin film ultrasonic sensor, specifically a thin film UT (Ultrasonic Testing) sensor. A thin film UT sensor is a sensor that uses ultrasonic waves, and is small and thin, so even if the pipe is covered with a heat insulating material, it will not touch the outer peripheral surface of the pipe between the pipe and the heat insulating material. It can be installed in direct contact with or in close proximity to the pipe, and changes in the liquid level in the pipe can be measured at all times even when the heat insulating material is attached to the pipe. The first ultrasonic sensor 131 transmits the detection result to the control device 150. When the control device 150 determines that the cleaning liquid has risen to the detection target position based on the information from the first ultrasonic sensor 131, it drives the make-up water pump 134a to supply new make-up water to the superheater 102 side. supply At this time, the rust preventive agent may be mixed with the make-up water from the rust preventive agent supply section 135.
The superheater 102 and the second vertical portion 130c of the first communication pipe 130 are already filled with makeup water up to a predetermined water level. Therefore, the make-up water newly supplied by the make-up water pump 134a presses the make-up water in the superheater 102 and the second vertical section 130c of the first communication pipe 130, and moves toward the brackish water separator 126 (the brackish water The make-up water that moves to the separator 126 side is also referred to as "backwash water"). As a result, when the water filling level of the second vertical section 130c rises and reaches the upper end of the second vertical section 130c, the backwash water flows into the first vertical section 130a via the first horizontal section 130b. As a result, the cleaning liquid flowing in the first communication pipe from the brackish water separator 126 toward the superheater 102 is pushed back toward the brackish water separator 126 side. Therefore, the flow of cleaning liquid into the superheater 102 is suppressed.

After a predetermined period of time has elapsed, the control device 150 stops the make-up water pump 134a, and the make-up water that flows through the first communication pipe from the superheater 102 toward the brackish water separator 126 and becomes backwash water is stopped. The predetermined time may be determined based on, for example, the capacity of the first communication pipe 130 or the flow rate of backwash water. For example, the predetermined time may be set by multiplying the internal volume of the first connecting pipes 130 (two pipes) by the coefficient divided by the flow rate of the backwash water. At this time, the coefficient may be set to 1 to 2 in consideration of the cleaning effect.
Further, the discharge flow rate of the make-up water pump 134a may be selected in consideration of the time required for filling with water. For example, when the internal volume of the first communication pipe 130 is about 10 m ³ , the make-up water pump 134a may be driven for 12 minutes with a pump with a discharge flow rate of 100 m ³ /h. Note that in this example, the coefficient is calculated as 2. By setting the make-up water pump 134a and the predetermined time in this way, overflowing cleaning liquid can be pushed back before it reaches the superheater 102. For example, if the length of the first communication pipe is about 20 m, even if the diffusion speed due to liquid contact when the cleaning liquid comes into contact with water is about 10 m/h, the cleaning liquid will not reach the superheater 102. You can push it back before it reaches you.
Note that the predetermined time and the discharge flow rate of the make-up water pump 134a described above are merely examples, and the present invention is not limited thereto. It may be determined as appropriate depending on the internal volume of the first communication pipe 130, etc.

In this embodiment, in this way, the heat exchanger tubes constituting the energy saver 107, the heat exchanger tubes constituting the furnace wall 101, the brackish water separator 126, the drain tank 127, the piping connecting these, etc. are chemically cleaned with a cleaning liquid. . Further, it is possible to detect the cleaning liquid overflowing from the steam separator 126 or the drain tank 127 and flowing toward the superheater 102 . Furthermore, the superheater 102 connected to the brackish water separator 126 is not subjected to chemical cleaning, so that the cleaning liquid can be prevented from overflowing and flowing into the superheater 102.

This embodiment provides the following effects.

If the cleaning liquid flows into the superheater system, the following problems will occur.
When the cleaning fluid comes into contact with make-up water in the superheater system, the concentration gradient causes the cleaning fluid to diffuse into the superheater.
The scale generated in the superheater system (steam oxidation scale) is usually a scale that is hardly soluble in the cleaning solution, so if some of the cleaning solution flows into the superheater system filled with water, the cleaning solution will mix with the water for filling it. The scale is partially dissolved by the unevenly mixed and diluted cleaning solution resulting in insufficient chemical cleaning performance, causing cracks in the scale. When a crack occurs in the scale, the cleaning liquid reaches the interface between the inner surface of the heat exchanger tube 102a and the scale through the crack, melts a part of the inner surface of the heat exchanger tube 102a, and the space between the inner surface of the heat exchanger tube 102a and the scale is removed. There is a possibility of creating voids. When a gap occurs between the inner surface of the heat exchanger tube 102a and the scale, heat transfer to the fluid (medium such as steam or water) in the heat exchanger tube 102a is inhibited, resulting in a decrease in heat transfer performance in the superheater 102. there is a possibility.
Moreover, if a part of the cleaning liquid flows into the superheater system, there is a possibility that the scale will be peeled off from the cracks in the scale on the inner surface of the heat transfer tube 102a. If the scale peels off, when the boiler 10 is started up after cleaning, the peeled scale may partially accumulate in the superheater 102 system, potentially clogging the inside of the heat exchanger tubes 102a. When the heat exchanger tubes 102a are clogged, the heat exchanger tubes after the clogged point are unable to exchange heat, which may cause a decrease in the heat transfer performance of the superheater 102 and damage to the heat exchanger tubes 102a.
Incidentally, problems due to scale peeling and blockage may occur in the second superheater 103 and the third superheater 104 as well. Furthermore, there is a possibility that the scale exfoliated in the upstream superheater (for example, the superheater 102) may block the inside of the heat transfer tube of the downstream superheater (for example, the second superheater 103).
In addition, the cleaning liquid that has flowed into the superheater 102 system starts to affect the scale on the inner surface of the heat transfer tube 102a of the superheater 102 from the stage where the chemical cleaning target area is being cleaned. If this happens, prompt action is required.
Further, backwashing is performed to discharge the cleaning liquid that has entered the superheater 102 system after cleaning is completed, but when the cleaning liquid diffuses into each heat transfer tube 102a arranged in the width direction of the combustion gas passage 13, It is necessary to increase the flow rate of backwash water required for backwashing so that the backwash water reaches each heat exchanger tube 102a, which increases equipment costs such as increasing the size of makeup water pump 134a and the like. If backwashing is performed at a low flow rate, it will be difficult to backwash all of the heat exchanger tubes 102a, and there is a possibility that cracks will occur in the scale on the inner surface of the heat exchanger tubes 102a, causing the scale to peel off. In particular, it is arranged in a region far from the connection position between the outlet header 102c through which backwash water from the make-up water pipe 134 is introduced and the superheater side pipe L3a (regions A, B, C, etc. in FIG. 3). Since it is difficult for backwash water to flow into the heat exchanger tubes 102a, the effect of backwashing is reduced. Therefore, the cleaning liquid may remain even after the cleaning operation is completed, and the remaining cleaning liquid may cause deterioration of water quality after the boiler is started.
From this point of view, it is necessary to prevent the cleaning liquid from flowing into the superheater 102 system, or to quickly discharge the cleaning liquid from the superheater 102 system even if it does.

In this embodiment, ultrasonic sensors (a first ultrasonic sensor 131 and a second ultrasonic sensor 133) are provided to detect when the liquid level of the cleaning liquid has reached the first connecting pipe 130 and the second connecting pipe 132. There is. In this way, by providing an ultrasonic sensor that detects the cleaning liquid itself, it is possible to reliably detect the rise in the liquid level of the cleaning liquid in the first communication pipe 130 and the second communication pipe 132. Therefore, the cleaning liquid overflowing from the steam separator 126 or the drain tank 127 and flowing toward the superheater 102 can be detected more accurately.

Moreover, ultrasonic sensors for detecting cleaning liquid are provided at predetermined heights of the first communication pipe 130 and the second communication pipe 132 that connect the superheater 102, the brackish water separator 126, and the drain tank 127. Thereby, when cleaning liquid overflows from the brackish water separator 126 or the drain tank 127 and heads toward the superheater 102, it can be detected before the cleaning liquid reaches the superheater 102. Therefore, it is possible to prevent the cleaning liquid from reaching the superheater 102.

Furthermore, in this embodiment, when the ultrasonic sensors provided in the first connecting pipe 130 and the second connecting pipe 132 detect cleaning liquid, the make-up water pump 134a moves from the superheater 102 side to the brackish water separator 126 side. Then, backwash water is made to flow through the first communication pipe 130 and the second communication pipe 132. As a result, the cleaning liquid that is about to flow from the brackish water separator 126 or the drain tank 127 toward the superheater 102 through the first connecting pipe 130 or the second connecting pipe 132 is directed to the brackish water separator 126 side or the drain tank 127 side. being pushed back. Therefore, it is possible to suppress the cleaning liquid from flowing into the superheater 102.

Furthermore, in this embodiment, before the cleaning liquid overflows and reaches the superheater 102, the make-up water pump 134a is activated to push back the cleaning liquid with backwash water. Thereby, the inflow of the cleaning liquid can be suppressed more reliably. Therefore, it is possible to prevent a situation in which the cleaning liquid flows into the superheater 102 after the chemical cleaning operation is completed, causing blockage due to scale that has peeled off after the boiler is started, or deterioration of water quality due to residual cleaning liquid.

Further, the drive time of the make-up water pump 134a is set to a predetermined time. That is, the time for sending backwash water is set to be a predetermined time. As a result, the amount of make-up water flowing into the brackish water separator 126 side is reduced compared to the case where backwash water is continued to be sent. Therefore, dilution of the cleaning liquid by backwash water can be reduced. Therefore, it is possible to suppress a decrease in the cleaning effect due to dilution of the cleaning liquid. Furthermore, the amount of cleaning agent that is added to the diluted cleaning solution can be reduced.

Note that in this embodiment, an example has been described in which the ultrasonic sensors are provided in both the first communication pipe 130 and the second communication pipe 132, but the present disclosure is not limited thereto. An ultrasonic sensor may be provided only in either the first communication pipe 130 or the second communication pipe 132.

[Modification 1]
Note that in this embodiment, an example has been described in which the first ultrasonic sensor 131 and the second ultrasonic sensor 133 are used as sensors for detecting cleaning liquid, but the present disclosure is not limited thereto. For example, instead of each ultrasonic sensor, a pair of electrodes spaced apart from each other may be provided. When the liquid level of the cleaning liquid reaches both of the pair of electrodes, the pair of electrodes are energized, and by detecting this energization, the cleaning liquid can be detected. Even with this configuration, the same effects as in the first embodiment can be obtained.

[Modification 2]
Furthermore, for example, a temperature sensor may be used instead of each ultrasonic sensor. In this case, the temperature sensor indicates that the temperature inside the first connecting pipe 130 or the second connecting pipe 132 has risen to the temperature of the cleaning liquid or a first threshold temperature set several degrees (about 1 to 10 degrees) lower than the temperature of the cleaning liquid. When this is detected, the control device 150 drives the make-up water pump 134a to perform backwashing. Then, after a predetermined period of time has elapsed, the make-up water pump 134a is stopped, and the backwashing is completed. Note that the concept of the predetermined time is the same as in the first embodiment.
Note that the timing for stopping the make-up water pump 134a may be determined when the temperature detected by the temperature sensor falls below a predetermined second threshold temperature. In this case, the predetermined second threshold temperature is based on a temperature higher than the temperature of the supplied makeup water (or the ambient temperature of the area to be chemically cleaned) and lower than the first threshold temperature of the cleaning liquid. May be set. Note that the temperature of the cleaning liquid is obtained, for example, by a thermometer such as a thermocouple installed in the brackish water separator 126, the drain tank 127, or the cleaning liquid supply device 137, and the temperature of the makeup water is obtained, for example, by a thermometer installed in the superheater 102. It may also be obtained with a thermometer such as a pair.
Even with this configuration, the same effects as in the first embodiment can be obtained.

[Second embodiment]
Next, a second embodiment according to the present disclosure will be described using FIG. 4. In addition, in FIG. 4, the furnace wall 101, the economizer 107, the cleaning liquid supply device 137, etc. are omitted from illustration.
The boiler 10 according to the present embodiment has an electrical conductivity meter 140 instead of the first ultrasonic sensor 131 and the second ultrasonic sensor 133, and the location where the electric conductivity meter 140 is installed is different. This is different from the first embodiment. In other respects, the second embodiment is substantially the same as the first embodiment, so the same components are denoted by the same reference numerals, and detailed explanation thereof will be omitted.

The electrical conductivity meter 140 according to this embodiment is provided at the second vertical portion 130c of the first communication pipe 130, as shown in FIG. Specifically, it is provided in the second vertical part 130c of the first connecting pipe 130, which is closer to the superheater 102 than the first vertical part 130a, and is provided below the water level of the second vertical part 130c. . In other words, the electrical conductivity meter 140 is positioned in the make-up water and measures the properties of the make-up water in a state where the make-up water is filled. It is desirable that the electrical conductivity meter 140 be placed near the water filling level and below the water filling level.

If the cleaning liquid overflowing from the brackish water separator 126 or drain tank 127 overflows and reaches the make-up water filled with cleaning liquid headed for the superheater 102, the electric conductivity will increase as the make-up water and the cleaning liquid mix. Rise. When the electrical conductivity meter 140 detects an increase in the predetermined first threshold difference from the value of the electrical conductivity of the applied make-up water at the time of starting chemical cleaning, the electrical conductivity meter 140 immediately sends information to the control device 150. Send. Thereby, the control device 150 drives the make-up water pump 134a to perform backwashing. Then, after a predetermined period of time has elapsed, the make-up water pump 134a is stopped, and the backwashing is completed. Note that the concept of the predetermined time is the same as in the first embodiment.
Note that the timing for stopping the make-up water pump 134a is determined when the electric conductivity detected by the electric conductivity meter 140 decreases and is lower than the value of the electric conductivity of the make-up water at which backwashing is started, by a predetermined threshold value set in advance. It is also possible to set the timing when the value has decreased. In this case, the predetermined second threshold difference may be a value equivalent to the electrical conductivity before rising (that is, the electrical conductivity of the supplemented water before being mixed with the cleaning liquid). Further, in order to avoid hunting, the value may be set to be about 5% to 20% smaller than the threshold value.

Even with this configuration, the same effects as in the first embodiment can be obtained.
Further, for example, even if the cleaning liquid evaporates and becomes a gas phase and flows from the brackish water separator 126 or drain tank 127 to the superheater 102 side in a gas phase state, by coming into contact with the supplementary water, The cleaning liquid in the gas phase is cooled and condensed. The condensed cleaning liquid diffuses and mixes with the make-up water, increasing the electrical conductivity of the make-up water. Therefore, even if the cleaning liquid flows to the superheater 102 in a gas phase, it is possible to drive the make-up water pump 134a to perform backwashing and suppress the cleaning liquid from flowing into the superheater 102. can.
Note that a pH sensor may be used instead of the electrical conductivity meter 140.

[Third embodiment]
Next, a third embodiment according to the present disclosure will be described using FIG. 5. In addition, in FIG. 5, the furnace wall 101, the economizer 107, the cleaning liquid supply device 137, etc. are omitted from illustration, as in FIG. 4.
The boiler 10 according to the present embodiment has a gas supply section 141 that supplies gas into the first communication pipe 130 and the second communication pipe 132, and the contents of the processing performed by the control device 150 are different from those of the first embodiment. It is different from In other respects, the second embodiment is substantially the same as the first embodiment, so the same components are denoted by the same reference numerals, and detailed explanation thereof will be omitted.

In this embodiment, when the first ultrasonic sensor 131 or the second ultrasonic sensor 133 detects the cleaning liquid overflowing from the brackish water separator 126 or the drain tank 127 and heading toward the superheater 102, the first A gas supply section 141 that supplies gas into the pipe 130 and the second communication pipe 132 is provided.

The gas supply section 141 includes a gas pipe 141a connected to the first horizontal section 130b of the first communication pipe 130 or the third horizontal section 132b of the second communication pipe 132, and a gas valve 141b provided on the gas pipe 141a. have. Examples of the gas supplied from the gas supply section 141 include nitrogen gas and air. The gas to be supplied is preferably nitrogen gas, which does not contain oxygen, in order to further reduce the influence on the performance of the cleaning liquid.

When the first ultrasonic sensor 131 or the second ultrasonic sensor 133 detects cleaning liquid, the control device 150 opens the gas valve 141b and controls the inside of the first communication pipe 130 and the second communication pipe through the gas pipe 141a. Gas is supplied into the pipe 132. As a result, gas flows into the first connecting pipe 130 and the second connecting pipe 132, and this gas causes the inside of the first connecting pipe 130 or the second connecting pipe 132 to be overheated from the brackish water separator 126 or the drain tank 127. The cleaning liquid that is about to flow toward the vessel 102 is pushed back toward the gas-liquid separation section.

After a predetermined period of time has elapsed, the gas valve 141b is closed to stop the gas supply. The predetermined time is, for example, the volume of the gas phase in the first connecting pipe 130 and the second connecting pipe 132 from the position of the first ultrasonic sensor 131 or the second ultrasonic sensor 133 to the water level x coefficient ÷ gas flow rate Determine. The coefficient may be set to 1 to 2 in consideration of the extrusion effect.

Note that instead of the first ultrasonic sensor 131 and the second ultrasonic sensor 133, a first temperature sensor and a second temperature sensor may be provided as in the second modification of the first embodiment. In this case, the gas valve 141b may be opened at a timing when the temperature detected by the temperature sensor rises above a predetermined first threshold temperature, or the gas valve 141b may be opened at a timing when the temperature detected by the temperature sensor rises above a predetermined first threshold temperature. The timing may be when the temperature detected by the temperature sensor falls below a predetermined second threshold temperature. In this case, the predetermined threshold value may be a temperature higher than the temperature of the supplied makeup water (or the ambient temperature of the area to be chemically cleaned) and lower than the temperature of the cleaning liquid.

According to this embodiment, the following effects are achieved.
In this embodiment, when the first ultrasonic sensor 131 or the second ultrasonic sensor 133 detects cleaning liquid, the gas supply section 141 supplies gas into the communication pipe. As a result, the cleaning liquid that is about to flow through the first communication pipe 130 or the second communication pipe 132 from the gas-liquid separation section toward the superheater 102 is pushed back by the gas toward the brackish water separator 126 side or the drain tank 127 side. Therefore, it is possible to suppress the cleaning liquid from flowing into the superheater 102.
Furthermore, since the cleaning liquid is pushed back by the gas, the cleaning liquid is not diluted. Therefore, deterioration of the chemical cleaning effect can be suppressed.

[Fourth embodiment]
Next, a fourth embodiment according to the present disclosure will be described using FIG. 6. In addition, in FIG. 6, the furnace wall 101, the economizer 107, the cleaning liquid supply device 137, etc. are omitted from illustration, as in FIG. 4.
The boiler 10 according to the present embodiment differs from the first embodiment in that it has a first discharge pipe (discharge section) 142 that branches from the drain water line L2, and in the processing performed by the control device 150. . In other respects, the second embodiment is substantially the same as the first embodiment, so the same components are denoted by the same reference numerals, and detailed explanation thereof will be omitted.

This embodiment includes a first discharge pipe 142 that discharges the cleaning liquid circulating in the area to be cleaned to the outside of the system when the first ultrasonic sensor 131 or the second ultrasonic sensor 133 detects the cleaning liquid. In this embodiment, the first discharge pipe 142 is provided below the drain tank 127, for example. The upstream end of the first discharge pipe 142 is connected to an intermediate position of the drain water line L2. The first discharge pipe 142 is provided with a first discharge valve 142a.

When the first ultrasonic sensor 131 or the second ultrasonic sensor 133 detects the cleaning liquid overflowing from the brackish water separator 126 or the drain tank 127 and heading towards the superheater 102, the control device 150 controls the first discharge. The valve 142a is opened, and a portion of the cleaning liquid flowing in the drain water line L2 is discharged to the outside of the system via the first discharge pipe 142. Outside the system means outside the cleaning fluid circulation system.
Furthermore, when the first ultrasonic sensor 131 or the second ultrasonic sensor 133 no longer detects the cleaning liquid, the control device 150 closes the first discharge valve 142a and stops discharging the cleaning liquid.

Note that instead of the first ultrasonic sensor 131 and the second ultrasonic sensor 133, a first temperature sensor and a second temperature sensor may be provided as in the second modification of the first embodiment. In this case, the timing at which the first exhaust valve 142a is opened may be when the temperature detected by the temperature sensor rises above a predetermined first threshold temperature; The timing for closing may be when the temperature detected by the temperature sensor falls below a predetermined second threshold temperature. In this case, the predetermined second threshold temperature may be a temperature higher than the temperature of the applied makeup water (or the ambient temperature of the area to be chemically cleaned) and lower than the temperature of the cleaning liquid.

According to this embodiment, the following effects are achieved.
In this embodiment, when the first ultrasonic sensor 131 or the second ultrasonic sensor 133 detects the cleaning liquid overflowing from the brackish water separator 126 or the drain tank 127 and heading toward the superheater 102, the drain water line L2 The cleaning liquid is discharged from inside to the outside of the system. The first discharge pipe 142 is provided below the drain tank 127. Therefore, by discharging the cleaning liquid from the first discharge pipe 142, the amount of cleaning liquid in the drain tank 127 is reduced, and the level of the cleaning liquid in the drain tank 127 is lowered. Accordingly, the cleaning liquid that is about to flow through the first communication pipe 130 and the second communication pipe 132 toward the superheater 102 is also returned to the brackish water separator 126 or the drain tank 127. Therefore, it is possible to suppress the cleaning liquid from flowing into the superheater 102.
Furthermore, since the cleaning liquid is simply discharged out of the system, the cleaning liquid is not diluted. Therefore, deterioration of the chemical cleaning effect can be suppressed.

[Fifth embodiment]
Next, a fifth embodiment according to the present disclosure will be described using FIG. 7. In addition, in FIG. 7, the furnace wall 101, the economizer 107, the cleaning liquid supply device 137, etc. are omitted from illustration, as in FIG. 4.
The boiler 10 according to the present embodiment has a second discharge pipe (discharge part) 143 that branches from the superheater 102 side from the first ultrasonic sensor 131 or the second ultrasonic sensor 133 of the first communication pipe 130. This embodiment differs from the first embodiment in the following points and the processing performed by the control device 150. In other respects, the second embodiment is substantially the same as the first embodiment, so the same components are denoted by the same reference numerals, and detailed explanation thereof will be omitted.

In this embodiment, when the first ultrasonic sensor 131 or the second ultrasonic sensor 133 detects the cleaning liquid overflowing from the brackish water separator 126 or the drain tank 127 and attempting to flow toward the superheater 102 A second discharge pipe 143 is provided for discharging the mixed fluid of make-up water and cleaning liquid in the first communication pipe 130 to the outside of the system. The upstream end of the second discharge pipe 143 is connected to a midway position of the first communication pipe 130 closer to the superheater 102 than the first ultrasonic sensor 131 or the second ultrasonic sensor 133. If the upstream end of the second discharge pipe 143 is connected to the first connecting pipe 130 at an intermediate position before reaching the second vertical section 130c, the make-up water and the cleaning liquid are connected before the cleaning liquid flows into the superheater 102. This is more preferable because the mixed fluid can be reliably discharged from the system. The second discharge pipe 143 is provided with a second discharge valve 143a.

When the first ultrasonic sensor 131 or the second ultrasonic sensor 133 detects that the cleaning liquid overflows from the brackish water separator 126 or the drain tank 127 and is about to flow toward the superheater 102, the control device 150 detects that the cleaning liquid is flowing toward the superheater 102. Then, the second discharge valve 143a is opened, and the mixed fluid of make-up water and cleaning liquid flowing through the first communication pipe 130 is discharged to the outside of the system via the second discharge pipe 143. Outside the system means outside the system through which makeup water and cleaning fluid are distributed.
Further, when the first ultrasonic sensor 131 or the second ultrasonic sensor 133 no longer detects the cleaning liquid, the control device 150 closes the second discharge valve 143a and stops discharging the mixed fluid.
Furthermore, when the first ultrasonic sensor 131 or the second ultrasonic sensor 133 detects cleaning liquid, the control device 150 may drive the make-up water pump 134a to perform backwashing at a predetermined flow rate. In this case, the predetermined flow rate is the minimum flow rate that can be set by the make-up water pump 134a, and the mixed fluid of make-up water and cleaning liquid flowing in the first communication pipe 130 is discharged from the system through the second discharge pipe 143. It may be discharged to
In addition, when the make-up water pump 134a is driven, if the first ultrasonic sensor 131 or the second ultrasonic sensor 133 no longer detects the cleaning liquid, the mixed fluid of the make-up water and the cleaning liquid flowing in the first communication pipe 130 The make-up water pump 134a may continue to be driven during the time that the water is discharged out of the system, and then the make-up water pump 134a may be stopped.

Note that instead of the first ultrasonic sensor 131 and the second ultrasonic sensor 133, a first temperature sensor and a second temperature sensor may be provided as in the second modification of the first embodiment. In this case, the second discharge valve 143a may be opened at a timing when the temperature detected by the temperature sensor rises above a predetermined first threshold temperature, or when the second discharge valve 143a is opened. The timing for closing may be when the temperature detected by the temperature sensor falls below a predetermined second threshold temperature. In this case, the predetermined second threshold temperature may be a temperature higher than the temperature of the applied makeup water (or the ambient temperature of the area to be chemically cleaned) and lower than the temperature of the cleaning liquid.
Moreover, instead of the first ultrasonic sensor 131 and the second ultrasonic sensor 133, an electrical conductivity meter may be provided in the second vertical portion 130c of the first communication pipe 130, as in the second embodiment. In this case, the timing for opening the second discharge valve 143a is determined when the electrical conductivity detected by the electrical conductivity meter is lower than the electrical conductivity of the applied make-up water at the start of chemical cleaning. The detection may also be performed when an increase in a predetermined first threshold difference that has been set in advance is detected. In addition, the timing for closing the second discharge valve 143a is such that the electrical conductivity detected by the electrical conductivity meter decreases and the electrical conductivity of the make-up water at which backwashing is started is lower than the preset value. It may also be possible that the value has fallen below the threshold. In this case, the predetermined threshold value may be a value equivalent to the electrical conductivity before rising (that is, the electrical conductivity of the supplemented water before being mixed with the cleaning liquid). Further, in order to avoid hunting, the value may be set to be about 5% to 20% smaller than the threshold value.

According to this embodiment, the following effects are achieved.
In this embodiment, when the first ultrasonic sensor 131 or the second ultrasonic sensor 133 detects the cleaning liquid overflowing from the brackish water separator 126 or the drain tank 127 and attempting to flow toward the superheater 102 The mixed fluid of make-up water and cleaning liquid is discharged from the second discharge pipe 143 to the outside of the system. That is, the cleaning liquid flowing in the first communication pipe 130 toward the superheater 102 is discharged to the outside of the system. Therefore, it is possible to suppress the cleaning liquid from flowing into the superheater 102.
Furthermore, by driving the make-up water pump 134a to newly supply make-up water to the superheater 102 side, and discharging it to the outside of the system together with the mixed fluid of make-up water and cleaning liquid flowing in the first communication pipe 130, The effect of suppressing the cleaning liquid from flowing into the superheater 102 due to diffusion during discharge can be enhanced.
Furthermore, since the cleaning liquid is simply discharged out of the system, the cleaning liquid is not diluted. Therefore, deterioration of the chemical cleaning effect can be suppressed.

[Sixth embodiment]
Next, a sixth embodiment according to the present disclosure will be described using FIG. 8. In addition, in FIG. 8, the furnace wall 101, the economizer 107, the cleaning liquid supply device 137, etc. are omitted from illustration, as in FIG. 4.
The boiler 10 according to the present embodiment has a bypass pipe (bypass pipe) 144 that branches from the make-up water pipe 134 and connects to the superheater 102 side from the first ultrasonic sensor 131 or the second ultrasonic sensor 133. This embodiment differs from the first embodiment in that the rust preventive supply unit 135 has a rust preventive valve 135a, and in the processing performed by the control device 150. In other respects, the second embodiment is substantially the same as the first embodiment, so the same components are denoted by the same reference numerals, and detailed explanation thereof will be omitted.

In this embodiment, when the first ultrasonic sensor 131 or the second ultrasonic sensor 133 detects the cleaning liquid overflowing from the brackish water separator 126 or the drain tank 127 and heading toward the superheater 102, It has a bypass pipe 144 that bypasses and supplies make-up water (backwash water) into the first communication pipe 130. The upstream end of the bypass pipe 144 is located halfway along the make-up water pipe 134, and is connected between the make-up water pump 134a and the make-up water valve 134b. Further, the downstream end of the bypass pipe 144 is connected to the first communication pipe 130 closer to the superheater 102 than the first ultrasonic sensor 131 or the second ultrasonic sensor 133. If the downstream end of the bypass pipe 144 is connected to the first connecting pipe 130 at an intermediate position before reaching the second vertical section 130c, the mixed fluid of make-up water and the cleaning fluid is mixed with the cleaning fluid before the cleaning fluid flows into the superheater 102. It is even more preferable because it can reliably discharge the water out of the system. The bypass pipe 144 is provided with a bypass valve 144a.

When the first ultrasonic sensor 131 or the second ultrasonic sensor 133 detects that the cleaning liquid overflows from the brackish water separator 126 or the drain tank 127 and is about to flow toward the superheater 102, the control device 150 detects that the cleaning liquid is flowing toward the superheater 102. At the same time, the make-up water pump 134a is driven and the bypass valve 144a is opened. Moreover, when the make-up water valve 134b is in the open state, it is set in the closed state. Furthermore, when the rust preventive valve 135a of the rust preventive supply unit 135 is in the open state, it is closed. As a result, make-up water (backwash water) flows into the first communication pipe 130 via the bypass pipe 144.
Further, the control device 150 closes the bypass valve 144a after a predetermined period of time has passed, and stops backwashing. The concept of the predetermined time is the same as in the first embodiment.

Note that instead of the first ultrasonic sensor 131 and the second ultrasonic sensor 133, a first temperature sensor and a second temperature sensor may be provided as in the second modification of the first embodiment. Further, instead of the first ultrasonic sensor 131 and the second ultrasonic sensor 133, an electrical conductivity meter may be provided in the second vertical portion 130c of the first communication pipe 130, as in the second embodiment. The operation when the first temperature sensor and the second temperature sensor are provided, and the operation when the electrical conductivity meter is provided at the second vertical portion 130c of the first communication pipe 130 are the same as in the above-described embodiment.

According to this embodiment, the following effects are achieved.
In this embodiment, backwash water is made to flow through the first communication pipe 130 via the bypass pipe 144. That is, backwash water does not pass through the superheater 102. Thereby, there is no need to mix a rust preventive agent into the backwash water. Therefore, the amount of rust preventive agent used can be reduced.

[Seventh embodiment]
Next, a seventh embodiment according to the present disclosure will be described using FIG. 9. In addition, in FIG. 9, the furnace wall 101, the economizer 107, the cleaning liquid supply device 137, etc. are omitted from illustration, as in FIG. 4.
The boiler 10 according to this embodiment is different from the sixth embodiment in the processing performed by the control device 150. In other respects, this embodiment is substantially the same as the sixth embodiment, so the same components are denoted by the same reference numerals, and detailed description thereof will be omitted.

FIG. 9 also shows the brackish water separator 126, which was not shown in the above description. That is, two brackish water separators 126 are shown. In the following description, one of the brackish water separators 126 (the brackish water separators 126 described in each of the above embodiments) is referred to as a brackish water separator 126A, and the other brackish water separator 126 is referred to as a brackish water separator 126B. As shown in FIG. 9, the brackish water separator 126B is connected to the superheater 102 by a third communication pipe 145. Like the first connecting pipe 130, the third connecting pipe 145 is composed of a first vertical part 145a, a first horizontal part 145b, a second vertical part 145c, and a second horizontal part 145d. A third ultrasonic sensor 146 is provided at a predetermined position on the first vertical portion 145a. Moreover, the brackish water separator 126B is connected to the drain tank 127 by a drain water line L9.

Further, in this embodiment, in addition to the bypass pipe 144 that connects to the first communication pipe 130, a bypass pipe 144 that connects to the third communication pipe 145 is provided. In the following description, the bypass pipe 144 connected to the first communication pipe 130 will be referred to as a first bypass pipe 144A, and the bypass pipe 144 connected to the third communication pipe 145 will be referred to as a second bypass pipe 144B. Moreover, the bypass valve 144a provided in the first bypass pipe 144A is referred to as a first bypass valve 144Aa. Note that the first bypass piping 144A is substantially the same as the bypass piping 144 described in the sixth embodiment, so detailed description will be omitted. The second bypass pipe 144B branches from the first bypass pipe 144A. A downstream end of the second bypass pipe 144B is connected to a third communication pipe 145. A second bypass valve 144Ba is provided in the second bypass pipe 144B.

The control device 150 is configured such that the first ultrasonic sensor 131 , the second ultrasonic sensor 133 , or the third ultrasonic sensor 146 detects that the cleaning liquid overflowing from the brackish water separator 126 or the drain tank 127 flows toward the superheater 102 . When the cleaning liquid to be washed is detected, the make-up water pump 134a is driven. Further, the first bypass pipe 144A and/or the second bypass valve 144Ba are opened according to the detection results of each ultrasonic sensor. Note that, similarly to the sixth embodiment, when the make-up water valve 134b is in the open state, the control device 150 brings it into the closed state. Furthermore, when the rust preventive valve 135a of the rust preventive supply unit 135 is in the open state, it is closed. As a result, makeup water (backwash water) flows into the first communication pipe 130 and/or the third communication pipe 145 via the first bypass pipe 144A and/or the second bypass pipe 144B. That is, the control device 150 performs backwashing of the first communication pipe 130 and/or the third communication pipe 145 according to the detection results of each ultrasonic sensor. For example, if only the first ultrasonic sensor 131 detects the cleaning liquid, only the first bypass valve 144Aa may be opened and only the first communication pipe 130 may be backwashed.
Further, the control device 150 closes the first bypass valve 144Aa and/or the second bypass valve 144Ba after a predetermined period of time has passed, and stops backwashing. The concept of the predetermined time is the same as in the sixth embodiment.

Note that instead of the first ultrasonic sensor 131, the second ultrasonic sensor 133, and the third ultrasonic sensor 146, the first temperature sensor, the second temperature sensor, and the third A temperature sensor may also be provided. Moreover, instead of the first ultrasonic sensor 131, the second ultrasonic sensor 133, and the third ultrasonic sensor 146, the second vertical portion 130c of the first connecting pipe 130 and the third connecting pipe An electrical conductivity meter may be provided on the second vertical portion 145c of the 145. The operation when the first temperature sensor, the second temperature sensor, and the third temperature sensor are provided, and the operation when the electrical conductivity meter is provided in the second vertical section 130c and the second vertical section 145c of the first connecting pipe 130 are as follows. , similar to the previous embodiment.

According to this embodiment, the following effects are achieved.
In this embodiment, backwash water is supplied only to the connecting pipes that require backwashing. Thereby, the flow rate of backwash water can be reduced. Further, dilution of the cleaning liquid by backwash water can be suppressed, and a decrease in chemical cleaning effect due to dilution of the cleaning liquid can be suppressed. Furthermore, the amount of cleaning agent used to replenish the diluted cleaning liquid can be reduced.
Further, in this embodiment, backwash water is made to flow through the first communication pipe 130 and/or the third communication pipe 145 via the bypass pipe 144. That is, backwash water does not pass through the superheater 102. Thereby, there is no need to mix antirust agent into backwash water. Therefore, the amount of rust preventive agent used can be reduced.

[Eighth embodiment]
Next, an eighth embodiment according to the present disclosure will be described using FIGS. 10 and 11.
The boiler 10 according to this embodiment differs from the above embodiments in that each connecting pipe is provided with two ultrasonic sensors and in the processing performed by the control device 150. In other respects, this embodiment is substantially the same as each of the embodiments described above, so the same components are denoted by the same reference numerals, and detailed explanation thereof will be omitted.
Although the ultrasonic sensor provided in the first communication pipe 130 will be described below, the second communication pipe 132 and the third communication pipe 145 may be similarly configured.
As shown in FIG. 10, the first vertical portion 130a of the first communication pipe 130 according to the present embodiment contains the cleaning liquid that overflows from the brackish water separator 126 and tries to flow toward the superheater 102. A lower ultrasonic sensor (first detection unit) 147 for detection and an upper ultrasonic sensor (second detection unit) 148 that is provided above the lower ultrasonic sensor 147 and detects the cleaning liquid are provided. The lower ultrasonic sensor 147 and the upper ultrasonic sensor 148 are separated by ΔL.

As shown in FIG. 11, the control device 150 controls the time t1 when the lower ultrasonic sensor 147 detects the cleaning liquid overflowing from the brackish water separator 126 and about to flow toward the superheater 102, and the upper ultrasonic sensor 147. The time difference Δt between the time t2 when the sonic sensor 148 detects the cleaning liquid and the time difference Δt is determined, and if the time difference Δt is smaller than a predetermined value, the cleaning liquid circulation pump is stopped.
That is, the control device 150 determines the flow rate of the cleaning liquid when the cleaning liquid overflowing from the brackish water separator 126 overflows and tries to flow toward the superheater 102 based on the time difference Δt, and Determine the degree of overflow. For example, if the time is shorter than a predetermined threshold time, it is determined that a large amount of overflow has occurred, causing concern that cleaning fluid may flow into the superheater 102 even if backwashing or blowing operations are performed. Good too. When such a large amount of overflow occurs, a large flow of cleaning fluid comes into contact with the makeup water filled in the superheater 102, and the diffusion rate of the cleaning fluid into the makeup water increases, causing the superheater 102 to become overfilled. The concentration of the cleaning solution in the make-up water becomes high.

The predetermined threshold time may be set based on the following formula.
Based on the time difference Δt and the like, the control device 150 calculates the time T required for the overflow cleaning liquid to reach the superheater 102 (specifically, the inlet header 102b) using the following equation (1).

T=(Δt/ΔL)×L...(1)
however,
Δt: Time difference ΔL: Distance between lower ultrasonic sensor 147 and upper ultrasonic sensor 148 L: Total length of first connecting pipe 130

Further, the control device 150 uses each ultrasonic sensor to detect cleaning fluid overflowing from the brackish water separator 126 and attempting to flow toward the superheater 102, and then drives the make-up water pump 134a to perform backwashing. The time T0 until water reaches the connecting pipe is stored in advance in the storage unit. The control device 150 compares the calculated T and T0, and if T<T0, that is, even if the make-up water pump 134a is driven to perform backwashing, the cleaning liquid will not flow into the superheater 102. If there is a concern, the cleaning liquid circulation pump is immediately stopped to stop the cleaning liquid flowing toward the superheater 102.

According to this embodiment, the following effects are achieved.
In this embodiment, the lower ultrasonic sensor 147 detects the cleaning liquid overflowing from the brackish water separator 126 and is about to flow toward the superheater 102, and then the upper ultrasonic sensor 148 detects the cleaning liquid. By measuring the time it takes for the cleaning liquid to overflow and flow toward the superheater 102, it is possible to detect the flow rate of the cleaning liquid that is about to overflow and flow toward the superheater 102. In other words, the degree of overflow can be determined.
Further, in this embodiment, when the time from when the lower ultrasonic sensor 147 detects the cleaning liquid to when the upper ultrasonic sensor 148 detects the cleaning liquid is equal to or less than a predetermined threshold time (predetermined value), the cleaning liquid circulation pump stop. As a result, the circulation speed of the cleaning liquid is increased from when the cleaning liquid that overflows and is about to flow toward the superheater 102 is detected until the make-up water pump 134a is driven and the backwash water reaches the connecting pipe. If the speed corresponding to time T0 is exceeded, the cleaning liquid circulation pump can be stopped. By stopping the cleaning liquid circulation pump, the circulation of the cleaning liquid is stopped. Therefore, the flow of the cleaning liquid from the gas-liquid separation section toward the superheater 102 in the first communication pipe is also stopped, so that the flow of the cleaning liquid into the superheater 102 can be suppressed.

Note that three or more ultrasonic sensors may be provided and the time T required for the overflow cleaning liquid to reach the superheater 102 may be determined more accurately based on information from each ultrasonic sensor.
Further, the means for pushing back the cleaning liquid may be selected based on the time difference Δt. For example, when the time difference Δt is large (when the degree of overflow is small), only backwashing may be performed as described in the first embodiment without stopping the cleaning liquid circulation pump.
Further, if the time difference Δt is smaller than a predetermined value (if the degree of overflow is large), backwashing may be performed after stopping the cleaning liquid circulation pump. By performing backwashing after stopping the flow of the cleaning liquid in this manner, the flow rate of make-up water required for backwashing can be reduced. Furthermore, since stopping the cleaning liquid circulation pump alone may not be able to suppress the inflow of cleaning liquid into the superheater 102, it is preferable to combine this with other measures such as backwashing, gas injection, and draining the cleaning liquid out of the system. It is.

Note that the present disclosure is not limited to the above embodiments, and can be modified as appropriate without departing from the gist thereof.
For example, the above embodiments may be combined as appropriate.
Further, in each of the embodiments described above, a structure for preventing the cleaning liquid from flowing into the superheater 102 has been described, but the present disclosure is not limited thereto. The present invention may be applied to a structure that prevents the cleaning liquid from flowing into another heat exchanger (for example, a reheater or an economizer) instead of the superheater 102.
Further, a means for inhibiting the flow of the cleaning liquid from the gas-liquid separation section toward the superheater 102 may be further provided, and the present invention is not limited to the above embodiments. For example, when the first ultrasonic sensor 131 or the second ultrasonic sensor 133 detects cleaning liquid, a member may be installed in the first communication pipe 130 that expands due to gas supply or the like to block the pipe. A closing part that closes off the 1-connection pipe 130 may be provided.
Further, in each of the above embodiments, an example in which the present disclosure is applied to a once-through boiler has been described, but the present disclosure may also be applied to a drum-type boiler.

In the embodiments described above, the boiler of the present invention is a coal-fired boiler, but it is also possible to use a boiler that uses biomass fuel, PC (petroleum coke) fuel generated during oil refining, petroleum residue, etc. as the solid fuel. You can. Furthermore, not only solid fuel but also liquid fuel such as heavy oil can be used as the fuel, and gaseous fuel (such as by-product gas) can also be used as the fuel. The present invention can also be applied to mixed combustion of these fuels.

The boiler, the power plant, and the chemical cleaning method for the boiler described in each of the embodiments described above can be understood, for example, as follows.

Further, the boiler (10) according to one aspect of the present disclosure is a boiler (10) that can be chemically cleaned with a cleaning liquid supplied from a cleaning liquid supply device (137), and includes an evaporation section that heats feed water to generate steam. (101, 107), a gas-liquid separation unit (126, 127) that separates the water supply and the steam generated in the evaporation unit (101, 107), and the gas-liquid separation unit (126, 127). a heat exchanger (102) that exchanges heat with the vapor separated by the chemical During cleaning, the cleaning liquid does not flow through the heat exchanger (130), and the gas-liquid separation section (126, 127) and the evaporation section (101, 107) do not flow into the cleaning liquid supply device (137). ), and the communication pipe (130) includes a detection unit (131) that detects the cleaning liquid flowing through the communication pipe (130) and heading toward the heat exchanger (102). It is provided.

In the above configuration, a detection section that detects the cleaning liquid is provided. In this way, by providing a detection section that detects the cleaning liquid itself, the cleaning liquid flowing through the communication pipe can be reliably detected. Therefore, it is possible to more accurately detect the cleaning liquid overflowing from the gas-liquid separation section and heading toward the heat exchanger.
Further, a detection section that detects the cleaning liquid is provided in a communication pipe that connects the heat exchanger and the gas-liquid separation section. Thereby, the cleaning liquid that is about to flow from the gas-liquid separation section toward the heat exchanger can be detected before it reaches the heat exchanger. Therefore, it is possible to suppress the cleaning liquid from reaching the heat exchanger.
Note that examples of the detection unit include an ultrasonic sensor, a temperature sensor, and an electrical conductivity sensor.

In addition, in the boiler (10) according to one aspect of the present disclosure, when the detection unit (131) detects the cleaning liquid, the gas-liquid separation unit (126, 127) supplies water to the heat exchanger (102). A blocking part (134a) is provided to block the inflow of the cleaning liquid.

In the above configuration, when the cleaning liquid overflows into the communication pipe, the blocking portion blocks the cleaning liquid from flowing into the heat exchanger. Thereby, it is possible to suppress the cleaning liquid from flowing into the heat exchanger.
Further, a detection section that detects the cleaning liquid is provided in a communication pipe that connects the heat exchanger and the gas-liquid separation section. Thereby, the blocking section functions before the cleaning liquid reaches the heat exchanger. Therefore, the inflow of the cleaning liquid can be suppressed more reliably.

Further, in the boiler (10) according to one aspect of the present disclosure, when the detection unit (131) detects the cleaning liquid, the blocking unit (134a) is configured to prevent the gas and liquid from flowing from the heat exchanger (102) side. It has a backwash section (134a) that allows backwash water to flow through the communication pipe (130) toward the separation section (126, 127).

In the above configuration, when the detection section provided in the communication pipe detects overflowing cleaning liquid, the backwash section causes backwash water to flow through the communication pipe from the heat exchanger side to the gas-liquid separation section side. As a result, the cleaning liquid that is about to flow through the communication pipe from the gas-liquid separation section toward the heat exchanger is pushed back toward the gas-liquid separation section. Therefore, it is possible to suppress the cleaning liquid from flowing into the heat exchanger.

Further, in the boiler (10) according to one aspect of the present disclosure, the backwash section (134a) is connected to the heat exchanger (102) side of the communication pipe (130) rather than the detection section (131). The backwash water is supplied to the communication pipe (130) via a bypass pipe (144).

When backwash water passes through a heat exchanger, a rust preventive agent may be mixed with the backwash water to prevent rust from forming within the heat exchanger. In the above configuration, the detection unit is connected to the heat exchanger side via the bypass pipe, and backwash water is made to flow through the communication pipe. That is, backwash water does not pass through the heat exchanger. Thereby, there is no need to mix a rust preventive agent into the backwash water. Therefore, since there is no need for a rust preventive agent to be mixed with the backwash water, the amount of rust preventive agent used can be reduced.

Further, in the boiler (10) according to one aspect of the present disclosure, the blocking section (134a) supplies gas into the communication pipe (130) when the detecting section (131) detects the cleaning liquid. It has a gas supply section (141).

In the above configuration, when the detection section provided in the communication pipe detects overflowing cleaning liquid, the gas supply section supplies gas into the communication pipe. As a result, the cleaning liquid that is about to flow through the communication pipe from the gas-liquid separation section toward the heat exchanger is pushed back toward the gas-liquid separation section by the gas. Therefore, it is possible to suppress the cleaning liquid from flowing into the heat exchanger.
Furthermore, since the cleaning liquid is pushed back by the gas, the cleaning liquid is not diluted by backwash water. Therefore, it is possible to suppress a decrease in the chemical cleaning effect due to dilution of the cleaning liquid.

Further, in the boiler (10) according to one aspect of the present disclosure, when the detection unit (131) detects the cleaning liquid, the blocking unit (134a) moves the cleaning liquid from the gas-liquid separation unit (126, 127). It has a discharge part (142) for discharging the cleaning liquid out of the system.

In the above configuration, when the detection unit provided in the communication pipe detects overflowing cleaning liquid, the discharge unit discharges the cleaning liquid from the gas-liquid separation unit to the outside of the system. This reduces the amount of cleaning liquid in the gas-liquid separation section. Accordingly, the cleaning liquid that is about to flow through the communication pipe from the gas-liquid separation section toward the heat exchanger is returned to the gas-liquid separation section side. Therefore, it is possible to suppress the cleaning liquid from flowing into the heat exchanger.
Furthermore, since the cleaning liquid is simply discharged to the outside of the system, the cleaning liquid is not diluted by backwash water. Therefore, it is possible to suppress a decrease in the chemical cleaning effect due to dilution of the cleaning liquid.

Further, in the boiler (10) according to one aspect of the present disclosure, the cleaning liquid is discharged from the communication pipe (130) to the heat exchanger side from the detection part (131) of the communication pipe (130) to the outside of the system. The communication pipe (130) has a discharge part (143) closer to the heat exchanger than the detection part (131).

In the above configuration, when the detection section provided in the communication pipe detects overflowing cleaning liquid, the discharge section provided on the heat exchanger side of the communication pipe discharges the cleaning liquid from the communication pipe to the outside of the system. That is, the cleaning liquid that is about to flow through the communication pipe from the gas-liquid separation section toward the heat exchanger is discharged to the outside of the system. Therefore, it is possible to suppress the cleaning liquid from flowing into the heat exchanger.
Furthermore, since the cleaning liquid is simply discharged to the outside of the system, the cleaning liquid is not diluted by backwash water. Therefore, it is possible to suppress a decrease in the cleaning effect due to dilution of the cleaning liquid.

Further, the boiler (10) according to one aspect of the present disclosure includes a circulation pump that circulates the cleaning liquid between the gas-liquid separation section (126, 127) and the evaporation section (101, 107), The section (131) includes a first detection section (147) that detects the cleaning liquid heading toward the heat exchanger (102), and a first detection section (147) that is provided downstream of the first detection section (147) and that detects the cleaning liquid heading toward the heat exchanger (102). (102) includes a second detection unit (148) that detects the cleaning liquid heading toward the side, and detects the time when the first detection unit (147) detects the cleaning liquid, and the second detection unit (148) detects the cleaning liquid. The circulation pump is stopped when the time difference between the detected time and the detected time is less than a predetermined value.

In the above configuration, the detection section includes a first detection section and a second detection section provided downstream of the first detection section. With this, by measuring the time from when the first detection part detects the cleaning liquid to when the second detection part detects the cleaning liquid, the flow rate of the cleaning liquid overflowing from the gas-liquid separation part can be detected. can do. Further, in the above configuration, the circulation pump is stopped when the time from when the first detection section detects the cleaning liquid until when the second detection section detects the cleaning liquid is equal to or less than a predetermined value, which is a predetermined threshold time. Thereby, the circulation pump can be stopped when the flow rate of the overflowing cleaning liquid is equal to or higher than a predetermined rate. By stopping the circulation pump, the flow of the cleaning liquid is stopped. Therefore, the flow of the cleaning liquid from the gas-liquid separation section toward the heat exchanger in the communication pipe is also stopped, so that it is possible to suppress the cleaning liquid from flowing into the heat exchanger.

Moreover, in the boiler (10) according to one aspect of the present disclosure, the heat exchanger (102) is a superheater that can superheat steam flowing inside the heat exchanger (102).

Further, a power generation plant (1) according to an aspect of the present disclosure includes the boiler (10) according to any one of the above, and a power generation section (115) that generates power using the steam generated by the boiler (10). , is equipped with.

A method for cleaning a boiler (10) according to an aspect of the present disclosure includes: an evaporator (101, 107) that heats feed water to generate steam; and a steam generated in the feed water and the evaporator (101, 107). a heat exchanger that exchanges heat with the vapor separated in the gas-liquid separation section (126, 127); ) and a communication pipe (130) that connects the heat exchanger (102), a method for chemically cleaning a boiler (10), comprising: a cleaning liquid supply device without flowing the cleaning liquid to the heat exchanger; (137) supplying the cleaning liquid to the inside of the gas-liquid separation section (126, 127) and the evaporation section (101, 107); and a detection section (131) provided in the communication pipe (130). and a detection step of detecting the cleaning liquid flowing through the communication pipe (130) and heading toward the heat exchanger.

Further, in the boiler (10) cleaning method according to one aspect of the present disclosure, when the detection unit (131) detects the cleaning liquid, the gas-liquid separation unit (126, 127) ) for preventing the cleaning liquid from flowing into the cleaning liquid.

1: Boiler power generation plant 10: Coal-fired boiler (boiler)
11 : Furnace 12 : Combustion device 13 : Combustion gas passage 14 : Flue 21 : Combustion burner 22 : Combustion burner 23 : Combustion burner 24 : Combustion burner 25 : Combustion burner 26 : Pulverized coal supply pipe 27 : Pulverized coal supply pipe 28 : Pulverized coal supply pipe 29 : Pulverized coal supply pipe 30 : Pulverized coal supply pipe 31 : Pulverizer 32 : Pulverizer 33 : Pulverizer 34 : Pulverizer 35 : Pulverizer 36 : Wind box 37 : Air duct 38 : Forced draft fan 39 : Additional air port 40 : Additional air duct 41 : Gas duct 42 : Air heater 43 : Denitration device 44 : Dust collector 46 : Desulfurization device 50 : Chimney 101 : Furnace wall 102 : Superheater (first superheater, heat exchanger)
102a: Heat exchanger tube 103: Superheater (second superheater, heat exchanger)
104: Superheater (third superheater, heat exchanger)
105: First reheater 106: Second reheater 107: Energy saver 110: Steam turbine 111: High pressure turbine 112: Medium pressure turbine 113: Low pressure turbine 114: Condenser 115: Generator 122: Low pressure water heater 123: Boiler feed pump (BFP)
124: High pressure water supply heater 126: Brackish water separator (gas-liquid separation section)
126A: Brackish water separator (gas-liquid separation section)
126B: Brackish water separator (gas-liquid separation section)
127: Drain tank 130: First communication pipe 130a: First vertical section 130b: First horizontal section 130c: Second vertical section 130d: Second horizontal section 131: First ultrasonic sensor 132: Second communication pipe 132a: First 3rd vertical part 132b : 3rd horizontal part 132c : 4th vertical part 133 : 2nd ultrasonic sensor 134 : Makeup water pipe 134a : Makeup water pump 134b : Makeup water valve 135 : Rust preventive agent supply part 135a : Rust preventive valve 136: Temporary pipe 137: Cleaning liquid supply device 140: Electrical conductivity meter 141: Gas supply section 141a: Gas pipe 141b: Gas valve 142: First discharge pipe 142a: First discharge valve 143: Second discharge pipe 143a: Second Discharge valve 144: Bypass piping (bypass pipe)
144A: First bypass pipe 144Aa: First bypass valve 144B: Second bypass pipe 144Ba: Second bypass valve 144a: Bypass valve 145: Third communication pipe 145a: First vertical section 145b: First horizontal section 145c: Second Vertical section 145d: Second horizontal section 146: Third ultrasonic sensor 147: Lower ultrasonic sensor 148: Upper ultrasonic sensor 150: Control device A: Area B: Area C: Area L1: Water supply line L2: Drain water line L3 : Steam line L3a : Superheater side piping L3b : Turbine side piping L3c : Steam valve L4 : Steam line L5 : Steam line L6 : Circulation line L7 : Drain water line L8 : Steam line L9 : Drain water line

Claims (15)

A boiler that can be chemically cleaned with a cleaning liquid supplied from a cleaning liquid supply device,
an evaporation section that heats feed water to generate steam;
a gas-liquid separation unit that separates the water supply and the steam generated in the evaporation unit;
a heat exchanger that exchanges heat with the vapor separated in the gas-liquid separation section;
A communication pipe connecting the gas-liquid separation section and the heat exchanger,
During chemical cleaning, the cleaning liquid does not flow through the heat exchanger, and the cleaning liquid is supplied into the gas-liquid separation section and the evaporation section from the cleaning liquid supply device , and the heat exchanger and the communication Makeup water is supplied to a predetermined height inside the pipe ,
The communication pipe is provided with a detection unit that detects the cleaning liquid flowing through the communication pipe and heading towards the heat exchanger ,
The detection unit includes an electrical conductivity meter that measures the electrical conductivity of the make-up water supplied to the inside of the communication pipe or a pH sensor that measures the pH of the make-up water supplied to the inside of the communication pipe. death,
The boiler , wherein the electrical conductivity meter or the pH sensor is provided below the predetermined height . The communication pipe has a vertical portion extending in the vertical direction,
The boiler according to claim 1, wherein the electrical conductivity meter or the pH sensor is provided in the vertical section. The boiler according to claim 1 or 2, further comprising a blocking part that prevents the cleaning liquid from flowing into the heat exchanger from the gas-liquid separation part when the detection part detects the cleaning liquid. 4. The blocking section includes a backwashing section that allows backwashing water to flow through the communication pipe from the heat exchanger side to the gas-liquid separation section side when the detection section detects the cleaning liquid. boiler. The boiler according to claim 4 , wherein the backwash section supplies the backwash water to the communication pipe via a bypass pipe connected to the heat exchanger side of the communication pipe rather than the detection section. The boiler according to any one of claims 3 to 5 , wherein the blocking section includes a gas supply section that supplies gas into the communication pipe when the detection section detects the cleaning liquid. The boiler according to any one of claims 3 to 6 , wherein the blocking section includes a discharge section that discharges the cleaning liquid from the gas-liquid separation section to the outside of the system when the detection section detects the cleaning liquid. 3. The blocking part includes a discharge part that discharges the cleaning liquid from the communication pipe to the outside of the system when the detection part detects the cleaning liquid, which is closer to the heat exchanger than the detection part of the communication pipe. 8. The boiler according to claim 7 . comprising a circulation pump that circulates the cleaning liquid between the gas-liquid separation section and the evaporation section,
The detection unit includes a first detection unit that detects the cleaning liquid heading towards the heat exchanger, and a second detection unit that is provided downstream of the first detection unit and detects the cleaning liquid heading towards the heat exchanger. It has a detection part,
Claims 1 to 8, wherein the circulation pump is stopped when a time difference between a time when the first detection unit detects the cleaning liquid and a time when the second detection unit detects the cleaning liquid is a predetermined value or less. The boiler described in any of the above. A boiler that can be chemically cleaned with a cleaning liquid supplied from a cleaning liquid supply device,
an evaporation section that heats feed water to generate steam;
a gas-liquid separation unit that separates the water supply and the steam generated in the evaporation unit;
a heat exchanger that exchanges heat with the vapor separated in the gas-liquid separation section;
a communication pipe connecting the gas-liquid separation section and the heat exchanger;
a circulation pump that circulates the cleaning liquid between the gas-liquid separation section and the evaporation section,
During chemical cleaning, the cleaning liquid does not flow through the heat exchanger, and the cleaning liquid is supplied into the gas-liquid separation section and the evaporation section from the cleaning liquid supply device,
The communication pipe is provided with a detection unit that detects the cleaning liquid flowing through the communication pipe and heading towards the heat exchanger,
The detection unit includes a first detection unit that detects the cleaning liquid heading towards the heat exchanger, and a second detection unit that is provided downstream of the first detection unit and detects the cleaning liquid heading towards the heat exchanger. It has a detection part,
A boiler that stops the circulation pump when a time difference between a time when the first detection section detects the cleaning liquid and a time when the second detection section detects the cleaning liquid is equal to or less than a predetermined value. The boiler according to any one of claims 1 to 10 , wherein the heat exchanger is a superheater capable of superheating steam flowing inside the heat exchanger. The boiler according to any one of claims 1 to 11 ,
A power generation plant comprising: a power generation unit that generates power using the steam generated by the boiler. an evaporation section that heats feed water to generate steam; a gas-liquid separation section that separates the feed water and the steam generated in the evaporation section into gas and liquid; and a gas-liquid separation section that exchanges heat with the steam separated in the gas-liquid separation section. A method for chemically cleaning a boiler, comprising a heat exchanger and a communication pipe connecting the gas-liquid separation section and the heat exchanger,
a cleaning liquid supplying step of supplying the cleaning liquid from the cleaning liquid supply device to the interior of the gas-liquid separation unit and the evaporation unit without flowing the cleaning liquid to the heat exchanger;
a makeup water supply step of supplying makeup water to a predetermined height inside the heat exchanger and the communication pipe;
a detection step of detecting the cleaning liquid flowing inside the communication pipe and heading towards the heat exchanger side by a detection unit provided in the communication pipe ,
The detection step includes an electric conductivity meter that is provided below the predetermined height of the communication pipe and measures the electrical conductivity of the make-up water supplied into the communication pipe, or an electric conductivity meter installed inside the communication pipe. A chemical cleaning method for a boiler , in which the cleaning liquid is detected by a pH sensor that measures the pH of the supplied make-up water . The communication pipe has a vertical portion extending in the vertical direction,
14. The method for chemically cleaning a boiler according to claim 13, wherein in the detection step, the cleaning liquid is detected by the electrical conductivity meter or the pH sensor provided in the vertical section. The method for chemically cleaning a boiler according to claim 13 or 14, further comprising a blocking step of blocking the cleaning liquid from flowing into the heat exchanger from the gas-liquid separation unit when the detection unit detects the cleaning liquid. .

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