JP7387488B2 - Chemical cleaning systems and power plants, and chemical cleaning methods - Google Patents

Description

The present disclosure relates to chemical cleaning systems and power plants, and chemical cleaning methods.

A large boiler used in a power generation plant or the like has a hollow furnace installed vertically, and a plurality of combustion burners are arranged along the circumferential direction of the furnace wall. Further, in a large boiler, a flue is connected vertically above the furnace, and a heat exchanger for generating steam is disposed in the 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.

Scale mainly composed of oxides such as iron oxide is generated in the evaporator tubes that make up the furnace wall of the boiler, and may adhere and grow on the inner surface of the evaporator tubes. For this reason, chemical cleaning (boiler cleaning or chemical cleaning) is performed by investigating the amount of scale adhesion during maintenance and inspection (for example, Patent Document 1, Patent Document 2, Patent Document 3, Patent Document 4, Patent Document 5).

Patent No. 6071856 Patent No. 6071857 Patent No. 5721888 Patent No. 6522293 Patent No. 6370651

For boiler cleaning, an acid solution such as an organic acid whose temperature is raised to about 80° C. to 90° C. may be used (acidic/high temperature cleaning). In such a case, acidic gas may be generated and combine with moisture in the atmosphere to produce acidic mist gas (fume). In addition, the base metal of the boiler evaporator tube and the acid solution may react, and hydrogen gas may be generated. For this reason, it is necessary to take safety into consideration in the working environment when cleaning the boiler. In addition, acidic and high-temperature cleaning cannot completely dissolve the hardly soluble scale (hematite) that adheres and grows in the boiler's evaporation pipes, so it is necessary to physically clean the boiler using the conveying force of the cleaning fluid. It needs to be discharged from the system, and in places such as the boiler's evaporation pipe where the flow tends to stagnate, the physical cleaning power may be reduced and scale may accumulate and remain.

In order to solve the problems of acidic and high temperature cleaning, neutral cleaning techniques have been proposed (Patent Document 1, Patent Document 2, Patent Document 3, Patent Document 4, Patent Document 5). Neutral cleaning technology can effectively remove scales containing hematite even at room temperature, and can also suppress the generation of hydrogen gas.

Although improvements to boiler cleaning have been made in this way, the properties (liquid properties) of the cleaning liquid may change depending on the environment inside the evaporation pipe of the boiler to be cleaned and the time that has passed since the start of boiler cleaning. Yes, cleaning performance may change. For example, boiler cleaning may be performed in an environment where the liquid ratio is small, i.e., by reducing the amount of cleaning liquid used for cleaning relative to the amount of scale generated on the surface of the boiler evaporation tube (or area to be cleaned). However, due to changes in the properties of the cleaning liquid, there is a possibility that the cleaning conditions will deviate from the proper cleaning conditions.

The present disclosure has been made in view of the above circumstances, and an object of the present disclosure is to provide a chemical cleaning system, a power generation plant, and a chemical cleaning method that can stably perform boiler cleaning.

In a first aspect of the present disclosure, one end is connected to an evaporation pipe of a boiler upstream of the evaporation pipe, and the other end is connected to a downstream side of the evaporation pipe, and a cleaning fluid containing a cleaning agent is passed through the boiler. A chemical cleaning system applied to a power generation plant having a chemical cleaning system that cleans the evaporation pipe using a chemical cleaning system, the chemical cleaning system comprising: a monitoring unit that monitors the properties of the cleaning fluid in the chemical cleaning system; The chemical cleaning system further includes a prediction unit that predicts an index regarding cleaning performance corresponding to the properties after a predetermined period of time has elapsed.

In a second aspect of the present disclosure, one end is connected to an evaporation pipe of a boiler on an upstream side of the evaporation pipe, and the other end is connected on a downstream side of the evaporation pipe, and a cleaning fluid containing a cleaning agent is passed through the boiler. A chemical cleaning method that is applied to a power generation plant having a chemical cleaning system that cleans the evaporation pipe by using a chemical cleaning system, the method comprising: monitoring the properties of the cleaning fluid in the chemical cleaning system; , a step of predicting an index regarding cleaning performance corresponding to the properties after a predetermined period of time has elapsed.

According to the present disclosure, there is an effect that boiler cleaning can be performed stably.

1 is a schematic configuration diagram showing a boiler according to an embodiment of the present disclosure. FIG. 1 is a schematic diagram showing a heat exchanger provided in a boiler according to an embodiment of the present disclosure. FIG. 2 is a diagram illustrating an example of a system when chemical cleaning is performed according to an embodiment of the present disclosure. It is a figure showing an example of each process performed in boiler chemical cleaning concerning one embodiment of this indication. FIG. 2 is a diagram illustrating a specific configuration example of a measurement unit according to an embodiment of the present disclosure. FIG. 1 is a diagram showing an example of a hardware configuration of a control device according to an embodiment of the present disclosure. FIG. 2 is a functional block diagram showing functions included in a control device according to an embodiment of the present disclosure. FIG. 3 is a diagram illustrating an example of the relationship between cleaning time, polarization resistance, and estimated cumulative corrosion amount according to an embodiment of the present disclosure. FIG. 3 is a diagram showing an example of a change in corrosion amount over time according to an embodiment of the present disclosure. FIG. 3 is a diagram showing an example of a change in pH over time according to an embodiment of the present disclosure. FIG. 3 is a diagram showing an example of a change in pH over time according to an embodiment of the present disclosure. FIG. 3 is a diagram illustrating an example of a change in electrical conductivity over time according to an embodiment of the present disclosure. FIG. 2 is a diagram showing an example of the relationship between Fe concentration and electrical conductivity according to an embodiment of the present disclosure. FIG. 2 is a diagram showing an example of the relationship between electrical conductivity and active ingredient concentration of a base agent according to an embodiment of the present disclosure. FIG. 3 is a diagram showing an example of the concentration dependence of a corrosion inhibitor on a change in the amount of corrosion over time according to an embodiment of the present disclosure. FIG. 3 is a diagram illustrating an example of adjusting the amount of corrosion according to an embodiment of the present disclosure. FIG. 3 is a diagram showing an example of adjusting pH according to an embodiment of the present disclosure. FIG. 2 is a flowchart illustrating an example of a procedure for adjusting the amount of corrosion according to an embodiment of the present disclosure. FIG. It is a flow chart which shows an example of the procedure of adjustment processing concerning pH concerning one embodiment of this indication. FIG. 3 is a diagram showing an example of adjusting pH according to an embodiment of the present disclosure. FIG. 3 is a diagram showing a state transition of the active ingredient concentration of a base agent according to an embodiment of the present disclosure. FIG. 3 is a diagram showing an example of the relationship between Fe concentration and electric conductivity deviation ΔEC according to an embodiment of the present disclosure. 2 is a flowchart illustrating an example of a procedure for adjusting the concentration of an active ingredient in a base agent according to an embodiment of the present disclosure.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a chemical cleaning system, a power generation plant, and a chemical cleaning method according to the present disclosure will be described below with reference to the drawings.

Preferred embodiments according to the present embodiment will be described below with reference to the accompanying drawings. It should be noted that the invention is not limited to this embodiment, and if there are multiple embodiments, it also includes a configuration in which each embodiment is combined.

FIG. 1 is a schematic configuration diagram showing a boiler 10 of this embodiment.

The boiler 10 of this embodiment uses, for example, 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 and steam. It is a coal-fired (pulverized coal-fired) boiler that can be replaced to generate superheated steam. In the following description, the words "above" and "upper" mean the upper side in the vertical direction, and "below" and "lower" mean the lower side in the vertical direction, and the vertical direction is not exact and includes errors.

In this embodiment, as shown in FIG. 1, the 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 101 that constitutes the furnace 11 is composed of a plurality of heat exchanger tubes and fins connecting these, and exchanges heat generated by combustion of pulverized fuel with water and steam flowing inside the heat exchanger tubes. This suppresses the temperature rise of the furnace wall.

The combustion device 12 is provided on the lower side of the furnace wall 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. 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 11, the number of combustion burners in one stage, the number of stages, the arrangement, etc. 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. The 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 boiler 10 by the air heater 42, heated combustion air (secondary air, oxidizing gas) is sent from the air duct 37 through the wind box 36 to each It is supplied to combustion burners 21, 22, 23, 24, and 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 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 boiler 10 provided in the boiler power generation plant 1 of the present embodiment, a steam turbine 110 that is rotationally driven by the steam generated by the boiler 10, and a steam turbine that is connected to the steam turbine 110 and that is connected to the steam turbine 110. The generator 115 generates power according to the rotation of the generator 110.

The steam turbine 110 operated by the steam generated in the boiler 10 is composed of, for example, a high pressure turbine 111, an intermediate pressure turbine 112, and a low pressure turbine 113, and after steam from a reheater, which will be described later, flows into the intermediate pressure turbine. 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 water heater 122 and the high-pressure water heater 123, and is supplied as a heat source to the high-pressure water heater 124 and the low-pressure water heater 122 via a bleed line (not shown). The water supplied to the economizer 107 is heated.

For example, a case where the boiler 10 is a once-through boiler will be explained. The economizer 107 is connected to each evaporation pipe 101a of the furnace wall 101. When the feed water heated by the economizer 107 passes through the evaporation pipe 101a of the furnace wall 101, it receives radiation from the flame in the furnace 11, is heated, and is guided to the brackish water separator 126. The steam separated in the brackish water separator 126 is supplied to the superheaters 102, 103, and 104, and the drain water separated in the brackish water separator 126 is stored in the brackish water separator drain tank 127 and connected to the drain water line. It is led to condenser 114 via 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 pipe 101a of the furnace wall 101, and as a result, the brackish water separation occurs. There may be an operating state in which a water level exists in the vessel 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 101a 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 101a of the furnace wall 101, and is then sent to the brackish water separator 126. be guided. 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. 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, in this embodiment, a case will be described in which the evaporation pipe 101a of a boiler is chemically cleaned. FIG. 3 shows an example of a system in which chemical cleaning is performed with the evaporation tube 101a as the cleaning target.

As shown in FIG. 2, the high-pressure water heater 124 is connected to the economizer 107 via a pipe P1, and the economizer 107 is connected to the evaporation pipe 101a of the furnace wall 101 via a pipe P2 (see FIG. 2). ) is connected to. Further, as shown in FIG. 3, the evaporation pipe 101a is connected to a brackish water separator 126 via a pipe P3, and the brackish water separator 126 is connected to a brackish water separator drain tank 127 via a pipe P4. When generating power, as described above, water is supplied to the economizer 107 and connected to the evaporation pipe 101a and each system located downstream thereof. In the evaporation tube 101a of the boiler, for example, scale mainly composed of oxides such as iron oxide may occur. For this reason, chemical cleaning of the boiler is carried out. In chemical cleaning work, each process is executed as shown in FIG. 4, for example. That is, before performing the cleaning process (the process within the dashed line frame in FIG. 4), a temporary circulation system (a chemical cleaning system L7, which will be described later) that connects a suitable location upstream of the cleaning target and a suitable location downstream of the cleaning target is installed. (see Figure 3) are connected. Thereafter, a cleaning process is performed, and after the cleaning process, the temporary circulation system is dismantled. Specifically, when performing chemical cleaning work on the boiler, the operation of the power plant is stopped and the chemical cleaning system L7 is connected. A circulation system consisting of the chemical cleaning system L7 and the cleaning target is configured. In the cleaning process, for example, chemical cleaning, water washing, rinsing, and rust prevention are sequentially performed. Note that each step of the cleaning step may be performed independently multiple times as necessary, or some may be omitted, and the steps and order are not limited to those described above.

The chemical cleaning system L7 has one end connected to an appropriate location upstream of the object to be cleaned (in this embodiment, the evaporation pipe 101a where scale has occurred), and the other end connected to an appropriate location downstream of the object to be cleaned. . The chemical cleaning system L7 circulates a cleaning fluid containing a cleaning agent (hereinafter referred to as "cleaning liquid") to clean the inside of the object to be cleaned. In this embodiment, specifically, as shown in FIG. 3, the chemical cleaning system L7 is a pipe whose one end is on the upstream side of the water supply flow with respect to the evaporation pipe 101a that constitutes the furnace wall 101 to be cleaned. Connected to P2 (evaporation tube inlet). Regarding the one end of the chemical cleaning system L7, if the equipment or piping is durable against the cleaning liquid, it is sufficient to connect it to the upstream side of the water supply flow to the object to be cleaned. It may also be connected to the pipe P1 (inlet of the economizer) which is on the upstream side of the water supply flow.

Moreover, the other end of the chemical cleaning system L7 is connected to the drain water line L2 (the outlet of the brackish water separator drain tank 127) which is downstream of the water supply flow with respect to the cleaning target in this embodiment. Note that the other end of the chemical cleaning system L7 may be connected to the downstream side of the water supply flow relative to the object to be cleaned, as long as the equipment or piping is durable against the cleaning liquid. may be connected to pipe P3 (evaporation pipe outlet) which is downstream of the feedwater flow, or connected to pipe P4 (evaporation pipe outlet) which is downstream of the feedwater flow to the brackish water separator 126 or to the brackish water separator 126. may be connected to a side outlet). Therefore, the connection position of one end and the other end of the chemical cleaning system L7 is limited to the configuration shown in FIG. 3 if a circulation system can be configured for equipment and piping that has a cleaning target and is durable against cleaning liquid. Not done. Further, examples of devices that are not durable against cleaning liquid include systems such as superheaters 102, 103, and 104. For example, the scale (steam oxidation scale) on the inner surface of the heat exchanger tubes of the superheaters 102, 103, 104 is hardly soluble in water, so the cleaning liquid acts unevenly and partially dissolves due to insufficient cleaning performance. Cracks may appear in the scale. When cracks occur in the scale, the cleaning liquid reaches the base material (heat transfer tube) through the crack, dissolves a portion of the heat transfer tube material, creates voids between the scale and the inner surface of the heat transfer tube, and obstructs heat transfer. Deterioration of heat transfer performance in the superheater may occur. Furthermore, if scale peels off from cracks in the scale on the inner surface of the heat exchanger tubes, it may accumulate in the superheater system of the boiler after cleaning, potentially clogging the insides of the heat exchanger tubes. Therefore, in the superheaters 102, 103, and 104, there is a possibility that the heat transfer performance of the cleaning liquid may deteriorate or the heat transfer tubes may be damaged.

By connecting the chemical cleaning system L7 in this way, a circulation system including the evaporation pipe 101a (to be cleaned) and the chemical cleaning system L7 is configured, and as the cleaning liquid circulates through the circulation system, the chemical to the cleaning target is Cleaning is performed.

Since the circulation system is configured as shown in FIG. 3, a sealing process is performed to prevent the cleaning liquid from flowing into a system other than the circulation system (non-cleaning system). For example, as shown in FIG. 3, the superheaters 102, 103, 104 are filled with water by a water sealing device 75 connected downstream of the superheaters 102, 103, 104, and the cleaning liquid is passed from the steam separator 126 to the superheated water separator 126. The water is prevented from flowing into the vessels 102, 103, and 104 (water sealing process). Further, the water-sealing process is similarly performed on the economizer 107 by filling it with water using a water sealing device (not shown), thereby suppressing the cleaning liquid from flowing into the economizer 107 from the pipe P2. Further, a water sealing process is similarly performed on the circulation line L6 by a water sealing device (not shown) to suppress the cleaning liquid from flowing into the circulation line L6 from the brackish water separator drain tank 127. Further, for the drain water line L2, a valve (not shown) suppresses the cleaning liquid from flowing into the drain water line L2 from the brackish water separator drain tank 127.

As shown in FIG. 3, the chemical cleaning system L7 includes a measuring section 71, an injection section 72, and a cleaning liquid circulation pump 73. The injection unit 72 is controlled by a control device 60, which will be described later. That is, the measurement section 71, the control device 60, and the injection section 72 constitute a chemical cleaning system. Note that the control device 60 may be a chemical cleaning system.

The measurement unit 71 measures the properties (liquid properties) of the cleaning liquid. An example of a specific configuration of the measuring section 71 is shown in FIG. As shown in FIG. 5, the measurement unit 71 extracts a part of the cleaning liquid from the chemical cleaning system L7 and measures the properties of the extracted cleaning liquid. In this embodiment, a case will be described in which different properties are measured in skid SA and skid SB, but for example, skids may be measured together. In that case, it is assumed that different properties of the skids can be measured for each of the skids SA and skid SB. Each device in the measuring section 71 is a device that is resistant to corrosion by cleaning liquids (for example, neutralized cleaning liquid, organic acids, etc.).

The cleaning liquid is mainly composed of, for example, a base agent, a reducing agent, and a corrosion inhibitor. The main agent is, for example, an organic acid, a chelating agent, etc., which has the ability to dissolve scales containing metal oxides such as rust. The reducing agent has scale component reducing properties and promotes dissolution of the scale components by its reducing action. For example, an oxygen absorber or the like. The corrosion inhibitor is, for example, a surfactant, which adsorbs to the surface of the base metal to which scale is not attached or after the scale has been removed, and improves the corrosion resistance of the base metal.

A part of the cleaning liquid is extracted by the extraction system PA connected to the chemical cleaning system L7, its properties are measured by the skid SA, and the cleaning liquid is returned to the chemical cleaning system L7. Further, a part of the cleaning liquid is extracted by the extraction system PB connected to the chemical cleaning system L7, its properties are measured by the skid SB, and the cleaning liquid is returned to the chemical cleaning system L7.

In the skid SA, a part of the cleaning liquid is drawn into the skid SA by the drawing pump 81. On the downstream side of the drawing pump 81, various measuring instruments are provided to measure the liquid state of the cleaning liquid. In this embodiment, a flow meter 83, a heater 84, and a thermometer 88 are further provided on the downstream side of the drawing pump 81, and the state of the cleaning liquid in each measuring device provided in the measuring section 71 is determined by the chemical cleaning system L7. The power of the drawing pump 81 and the output of the heater 84 may be controlled so as to be approximately equal to the state of the cleaning liquid flowing through the pump. In this way, the cleaning liquid measured by each measuring device provided in the measurement unit 71 and the cleaning liquid flowing through the chemical cleaning system L7 are set in a substantially equal environment, making it possible to measure the properties of the cleaning liquid more accurately. becomes.

The skid SA is provided with, for example, a turbidity meter 86 and a polarization resistance meter 87 as measuring instruments. Each measurement result is output to a monitoring section 61, which will be described later.

The turbidity meter 86 measures the turbidity of the cleaning liquid (the concentration of solids in the cleaning liquid). The amount of sludge generated during cleaning can be determined from the turbidity. Note that instead of the turbidity meter 86, pressure gauges may be provided before and after a predetermined position (for example, the measuring section 71), and the amount of sludge generated may be determined based on the differential pressure. The amount of sludge in the cleaning system decreases with the passage of cleaning time due to dissolution by the cleaning solution, so the progress of sludge dissolution can be confirmed by measuring the amount of sludge in the cleaning solution.

The polarization resistance meter 87 measures the polarization resistance value of the cleaning liquid. As described later, the amount of corrosion of the member through which the cleaning liquid flows is determined from the polarization resistance value.

In the skid SB, a part of the cleaning liquid is drawn into the skid SB by the drawing pump 91. On the downstream side of the drawing pump 91, various measuring instruments are provided to measure the liquid state of the cleaning liquid. In this embodiment, a flow meter 93, a heater 94, and a thermometer 99 are further provided on the downstream side of the drawing pump 91, and the state of the cleaning liquid in each measuring device of the measuring unit 71 is determined by the state of the cleaning liquid flowing through the chemical cleaning system L7. The power of the drawing pump 91 and the output of the heater 94 may be controlled so as to be approximately equal to the state of the cleaning liquid. In this way, the cleaning liquid measured by each measuring device of the measurement unit 71 and the cleaning liquid flowing through the chemical cleaning system L7 are set in an approximately equal environment, making it possible to measure the properties of the cleaning liquid more accurately. .

The skid SB is provided with measuring instruments such as a dissolved oxygen concentration meter 96, an electrical conductivity meter 97, a pH meter 98a, and an oxidation-reduction potential meter 98b. Note that measuring instruments having similar measurement principles, for example, the pH meter 98a and the oxidation-reduction potential meter 98b may be integrated. Each measurement result is output to a monitoring section 61, which will be described later.

Dissolved oxygen concentration meter 96 measures the dissolved oxygen concentration of the cleaning liquid. Leakage of oxidizer (oxygen) into the system to be cleaned can be detected based on dissolved oxygen concentration. Leakage of oxidizer (oxygen) can occur, for example, if the airtightness of pipes or equipment connections in the cleaning system is insufficient, or if a valve in an air vent installed in the cleaning system is accidentally opened during cleaning. This is thought to be caused by air from the atmosphere entering the cleaning system during operation. When cleaning using a cleaning solution containing a reducing agent, if the oxidizing agent (oxygen) leaks into the system to be cleaned, the reducing agent will be lost by the oxidizing agent (oxygen) and the reducibility of the cleaning solution will be impaired, resulting in scale dissolution. Sexuality decreases. Further, the progress of oxidation treatment in the rinsing process can be quantitatively understood from the dissolved oxygen concentration.

The electrical conductivity meter 97 measures the electrical conductivity of the cleaning liquid. As described later, the concentration of the active ingredient in the main ingredient of the cleaning agent is determined from the electrical conductivity. Further, since the measurement result of the electrical conductivity can be obtained quickly, the pH of the cleaning liquid can be quickly estimated by performing the conversion.

The pH meter 98a measures the pH of the cleaning liquid. As described later, the cleaning performance of the cleaning liquid is determined from the pH.

The oxidation-reduction potential meter 98b measures the oxidation-reduction potential of the cleaning liquid. The maintenance status of the reducing atmosphere during cleaning in the system to be cleaned can be determined from the oxidation-reduction potential. Furthermore, when leakage of oxidizing agent (oxygen) to the system to be cleaned occurs, the deactivation effect of the reducing atmosphere can be detected.

In this embodiment, the skid SA and the skid SB are provided with measuring instruments as described above, but in order to understand the properties of the cleaning liquid, the polarization resistance meter 87, the electric At least one of a conductivity meter 97 and a pH meter 98a may be provided.

The injection unit 72 includes a tank 74 and an injection pump 76. In this embodiment, a case will be described using as an example a case where three types of regulators, a corrosion inhibitor, a reducing agent, and a base agent, are used. Therefore, each tank 74 stores a corrosion inhibitor (for example, a surfactant), a reducing agent (for example, an oxygen scavenger), and a base agent (for example, a chelating agent). An injection pump 76 is connected to each tank 74, and injects the conditioning agent stored in the tank 74 into the cleaning liquid flowing through the chemical cleaning system L7.

The configuration of the injection part 72 is not limited to the configuration shown in FIG. 3 depending on the type of cleaning agent used. Alternatively, the undiluted solution may be injected so that the active ingredients of each chemical are not diluted, or the cleaning solution may be taken out, the chemicals dissolved and added, and returned to the cleaning solution of the chemical cleaning system L7. .

The cleaning liquid circulation pump 73 pumps the cleaning liquid so that the cleaning liquid circulates within the circulation system consisting of the chemical cleaning system L7 and the object to be cleaned. That is, the cleaning liquid is circulated through the circulation system by the cleaning liquid circulation pump 73 to perform boiler cleaning.

The control device 60 monitors the properties of the cleaning liquid. Then, the cleaning liquid is managed by performing predictive control, cleaning agent injection control, etc. according to the properties. As will be described later, the control device 60 performs feedforward control. Since it may take time (for example, about 1 hour) for the properties of the cleaning system to change after each conditioning agent is injected, cleaning fluids can be managed more reliably by using feedforward control. can.

FIG. 6 is a diagram showing an example of the hardware configuration of the control device 60 according to this embodiment.
As shown in FIG. 6, the control device 60 is a computer system, and includes, for example, a CPU 160, a ROM (Read Only Memory) 131 for storing programs executed by the CPU 160, and a ROM (Read Only Memory) 131 for storing programs executed by the CPU 160. A RAM (Random Access Memory) 130 that functions as a work area, a hard disk drive (HDD) 140 as a mass storage device, and a communication section 150 for connecting to a network or the like. Note that a solid state drive (SSD) may be used as the mass storage device. These units are connected via a bus 180.

Further, the control device 60 may include an input unit such as a keyboard and a mouse, and a display unit such as a liquid crystal display device that displays data.

Note that the storage medium for storing programs and the like executed by the CPU 160 is not limited to the ROM 131. For example, other auxiliary storage devices such as a magnetic disk, a magneto-optical disk, and a semiconductor memory may be used.

A series of processing steps for realizing various functions described below are recorded in the form of a program in the hard disk drive 140, etc., and the CPU 160 reads this program into the RAM 130 etc. and executes information processing and arithmetic processing. As a result, various functions described below are realized. Note that the program may be pre-installed in the ROM 131 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.

FIG. 7 is a functional block diagram showing the functions included in the control device 60. As shown in FIG. 7, the control device 60 includes a monitoring section 61, a prediction section 62, and a control section 63.

The monitoring unit 61 monitors the properties of the cleaning liquid in the chemical cleaning system L7. Specifically, the monitoring unit 61 acquires property information of the cleaning liquid by acquiring measurement results from each measuring device in the measuring unit 71.

In addition, when grasping the properties of the cleaning liquid, it is preferable that the monitoring unit 61 preferentially acquire at least one of polarization resistance, pH, and electrical conductivity, as these have a greater influence on cleaning performance. . Furthermore, in order to grasp the properties of the cleaning liquid, the monitoring unit 61 selects at least one of the following, which has a smaller influence than those mentioned above but has a large influence on cleaning performance: turbidity, redox potential, and dissolved oxygen concentration. may be acquired as second priority. By using at least one of turbidity, redox potential, and dissolved oxygen concentration, it is possible to further improve the prediction accuracy of cleaning performance. For example, by obtaining the turbidity in the cleaning system, the amount of sludge in the cleaning liquid can be determined. The amount of sludge decreases with the passage of cleaning time because the sludge is dissolved by the cleaning liquid. Therefore, by measuring the amount of sludge in the cleaning liquid, it is possible to check the progress of sludge dissolution. Furthermore, if the amount of sludge does not decrease with the passage of cleaning time, it is possible to determine the influence of cleaning performance (decrease in cleaning performance). In addition, when cleaning using a cleaning solution containing a reducing agent, cleaning performance can be improved by measuring the oxidation-reduction potential and dissolved oxygen concentration, which can detect the occurrence of leakage of oxidizing agent (oxygen) into the system being cleaned. be able to judge the impact of

The prediction unit 62 predicts an index related to cleaning performance after a predetermined period of time has passed, based on the properties of the cleaning liquid. Indicators related to cleaning performance include, for example, the amount of corrosion of the parts to be cleaned through which the cleaning liquid flows (hereinafter referred to as parts through which the cleaning liquid flows), the pH of the cleaning liquid, and the concentration of active ingredients in the main ingredient of the cleaning agent. The index is not limited to the above as long as it is an index related to cleaning performance. In this embodiment, a case will be described in which the prediction unit 62 predicts the amount of corrosion of a member through which the cleaning liquid flows in the future, the pH of the cleaning liquid, and the concentration of the active ingredient of the main ingredient of the cleaning agent.

Regarding the processing in the prediction unit 62, in this embodiment, the case of predicting the amount of corrosion of the member through which the cleaning liquid flows, the case of predicting the pH of the cleaning liquid, and the case of predicting the concentration of the active ingredient of the main ingredient of the cleaning agent are divided respectively. This will be explained below.

(When predicting the amount of corrosion of parts through which the cleaning liquid flows based on the polarization resistance of the cleaning liquid as an index regarding cleaning performance)
First, a case will be described in which the amount of corrosion of a member through which cleaning liquid flows is predicted. In this case, the monitoring unit 61 monitors polarization resistance as a property of the cleaning liquid.

The prediction unit 62 estimates the amount of corrosion of the member through which the cleaning liquid flows based on the monitored polarization resistance of the cleaning liquid. Specifically, the corrosion rate is derived from the charge transfer resistance obtained by the AC impedance method using the Stern-Geary equation (an equation indicating that the dissolution rate of metal is proportional to the reciprocal of the polarization resistance). The Stern-Geary equation is the following equation (1).

[Number 1]
Icorr=K/Rp (1)

In the above equation (1), Icorr is the corrosion rate, Rp is the polarization resistance, and K is the Stern-Geary constant (a constant that depends on the type of metal, environment, etc.). K is set in advance.

Therefore, the corrosion rate Icorr is derived from the polarization resistance measured using equation (1). Therefore, the amount of corrosion (estimated amount of corrosion) is calculated by integrating the corrosion rate using the cleaning time. FIG. 8 is a diagram showing an example of the relationship between cleaning time, polarization resistance, and estimated cumulative corrosion amount as an example in this embodiment. As shown in FIG. 8, when the polarization resistance is measured, the amount of corrosion (estimated amount of accumulated corrosion) is derived using equation (1).

The prediction unit 62 then predicts the amount of corrosion after a predetermined period of time based on the change in the amount of corrosion over time. In this embodiment, after the predetermined period of time has passed is the end of chemical cleaning (for example, 100 hours from the start of boiler cleaning).

That is, the prediction unit 62 predicts the amount of corrosion at the end of chemical cleaning based on the change over time in the amount of corrosion calculated from the measurement results of the polarization resistance up to the present time (the time point at which the prediction is made). The method for prediction is not limited as long as it is based on changes over time in the amount of corrosion up to the present. For example, the amount of corrosion at the end of chemical cleaning may be predicted by approximately extending the change over time in the amount of corrosion to date. Further, as a similar calculation, the amount of corrosion at the end of chemical cleaning may be predicted from the concentration of the corrosion inhibitor and the change in polarization resistance over time. In this case, for example, the magnification of the change in polarization resistance value at the time of measurement may be calculated from a database of changes in polarization resistance at each predetermined concentration, and subsequent behavior may be estimated based on this. It is also possible to make predictions using machine learning from the database. In addition, we accumulate past results in a database, select those with similar change trends in polarization resistance measurement results to date, and based on examples of future trends in this data, calculate the amount of corrosion after a predetermined period of time. It may also be possible to predict.

FIG. 9 is a diagram showing an example of a change over time in the amount of corrosion calculated from the measurement results of polarization resistance. In FIG. 9, the change over time in the normal state is shown as J1. Here, for example, if the amount of corrosion has changed as shown in J2 up to now, it is predicted that the amount of corrosion will change as shown in J3 based on the change. At the end of chemical cleaning, J3 exceeds the corrosion tolerance (corrosion criteria for members through which the cleaning fluid flows). Further, J4 indicates, for example, a case where the amount of corrosion suddenly changes and the change in the amount of corrosion deviates from J1, which is the conventional normal state change over time. In this way, since changes in the amount of corrosion can be monitored during boiler cleaning, sudden changes such as J4 (when a change greater than a predetermined amount of change occurs) can also be detected.

In this way, by monitoring and predicting the amount of corrosion of the member through which the cleaning liquid flows based on the measured value of the polarization resistance of the cleaning liquid, it is possible to grasp the state of occurrence of corrosion. For example, if the cleaning solution contains a corrosion inhibitor (surfactant), the protection performance (polarization resistance value) of the corrosion inhibitor contained in the cleaning solution for the parts (base material) through which the cleaning solution flows is continuously monitored. , it is possible to understand the deactivation status and recovery status of the protection performance by the corrosion inhibitor. Then, as shown in FIG. 15, which will be described later, the amount and timing of addition of the corrosion inhibitor can be set based on the characteristic results.

(When predicting the pH of the cleaning solution as an index regarding cleaning performance)
Next, the case of predicting the pH of the cleaning liquid will be described. In this case, the monitoring unit 61 monitors the pH as the property of the cleaning liquid.

The prediction unit 62 predicts the pH after a predetermined period has elapsed after starting boiler cleaning based on the monitored pH change over time.

FIG. 10 is a diagram illustrating an example of the cleaning time and the pH of the cleaning liquid over time, as an example in this embodiment. As shown in FIG. 10, the pH of the cleaning solution may increase over time. For example, hydroxide ions are generated from the water in the cleaning liquid as a member through which the cleaning liquid flows corrodes, and the pH increases as the concentration of hydroxide ions increases. When the cleaning liquid is a neutral cleaning liquid, the cleaning performance, for example, the dissolution rate, may decrease due to the property shifting from neutral to basic.

Therefore, the prediction unit 62 predicts the pH at the end of the chemical cleaning based on the pH measured after a predetermined period of boiler cleaning has passed. Regarding the prediction, the method is not limited as long as it is based on the change in pH over time up to the present (time of prediction). For example, future trends may be predicted based on trends up to the present using an approximate line. In addition, by accumulating past results in a database, we select those that have a similar change trend in the pH measurement results of cleaning fluids to date, and based on examples of future trends in this data, we calculate the pH after a predetermined period of time. It may also be possible to predict.

FIG. 11 is a diagram showing an example of a change in pH of a cleaning liquid over time. In FIG. 11, the change over time in the normal state is shown as M1, which is a solid line. For example, if the pH of the cleaning solution has changed as shown by M2 shown by the broken line, it is predicted that the pH will change as shown by M3 shown by the dotted line based on the change. In addition, in FIG. 11, the change in pH in the future is predicted by approximating the change in pH over time to the present as a linear function. According to this prediction, M3 will have exceeded the pH upper limit (for example, pH=8) at the end of chemical cleaning.

By monitoring and predicting the pH of the cleaning liquid in this way, it is possible to grasp the change in the pH of the cleaning liquid, that is, the change in the cleaning performance of the cleaning liquid. Then, as shown in FIG. 17, which will be described later, by controlling the pH by adding a reducing agent, an increase in pH can be suppressed.

(When predicting the concentration of active ingredients in the main ingredient of a cleaning agent as an index regarding cleaning performance)
Next, a case will be described in which the concentration of the active ingredient in the main ingredient of a cleaning agent is predicted. In this case, the monitoring unit 61 monitors the electrical conductivity as the property of the cleaning liquid. For example, the base agent is a chelating agent. The active ingredient concentration is the concentration of the base agent that is not bound to Fe ions, and is calculated based on the amount of the base agent that is not bound to Fe ions relative to the total amount of the cleaning liquid.

As an example in this embodiment, the prediction unit 62 calculates the concentration of the active ingredient of the main ingredient of the cleaning agent as an index after the boiler cleaning has elapsed for a predetermined period of time, based on the electrical conductivity of the cleaning fluid monitored over the cleaning time. Predict. Specifically, the prediction unit 62 dilutes the cleaning liquid based on a comparison between the measured value of the electrical conductivity of the cleaning liquid through monitoring and the estimated value of the electrical conductivity of the cleaning liquid based on the iron concentration (Fe concentration) of the cleaning liquid. The rate (the rate at which the water sealing water flows into the boiler cleaning cleaning system as the boiler cleaning process progresses and the chemical concentration is diluted) is estimated, and the Fe concentration of the cleaning liquid changes over time. The concentration of the active ingredient in the main agent is predicted based on the dilution rate of the cleaning solution and the dilution rate of the cleaning solution.

First, the prediction unit 62 acquires measured values of the electrical conductivity of the cleaning liquid at predetermined time intervals. Therefore, as shown by the broken line N1 in FIG. 12, a change in the measured value of electrical conductivity over time is obtained.

On the other hand, the prediction unit 62 acquires information on the Fe concentration in the cleaning liquid. The Fe concentration is the total iron concentration, which is the sum of the Fe ion content and the iron particle content in the cleaning solution. Information on Fe concentration may be analyzed at predetermined time intervals. When analysis or the like is performed, the data is input to the prediction unit 62 by the user. Note that if it is possible to measure the Fe concentration, the measured value may be used. For example, by obtaining the relationship between the turbidity of the cleaning liquid and the Fe concentration in advance, the Fe concentration can be estimated and specified based on the turbidity measured by the turbidity meter 86.

The main agent (chelating agent) of a cleaning agent has a property that the electric conductivity decreases as the iron ions in the main agent solution increase. This is because the electrical conductivity is lower in a state in which the main material is bonded to Fe ions than in a state in which the main material is not bonded to Fe ions. Therefore, there is a negative correlation between the iron concentration (Fe concentration) in the cleaning liquid and the electrical conductivity of the cleaning liquid as shown in FIG. Based on the relationship shown in FIG. 13, the electrical conductivity of the cleaning liquid corresponding to the change in the Fe concentration in the cleaning liquid is derived. In this way, as shown by N2 in FIG. 12, a change over time in the estimated value of electrical conductivity based on the Fe concentration of the cleaning liquid is obtained.

Here, in FIG. 12, N1 is the change over time in the measured value of the electrical conductivity of the cleaning liquid, and N2 is the change over time in the estimated value of the electric conductivity derived from the Fe concentration of the cleaning liquid. As shown in FIG. 12, the measured value N1 and the estimated value N2 diverge. This is mainly due to the effect of dilution of the cleaning fluid generated during boiler cleaning. For example, to dilute the cleaning solution, the cleaning system is separated from the non-cleaning system using a water seal during boiler cleaning, but as chemical cleaning progresses, the water used for the water seal filled in the non-cleaning system becomes may enter the system to be cleaned. In such a case, the cleaning liquid will be diluted by the inflowing water. Since the influence of dilution appears in the measured value of electrical conductivity, the deviation ΔEC between N1 and N2 has a correlation with the degree of dilution of the cleaning liquid. That is, the degree of dilution can be determined from the deviation ΔEC, and the dilution rate of the cleaning liquid can be determined from the change in the deviation ΔEC.

Therefore, the prediction unit 62 estimates the electrical conductivity based on the Fe concentration at the end of the chemical cleaning from the change in the Fe concentration of the cleaning liquid up to the present. In other words, the electrical conductivity based on the Fe concentration at the end of chemical cleaning is the future transition of N2 in FIG. 12. Furthermore, the deviation ΔEC at the end of chemical cleaning is estimated based on the change in dilution rate up to the present. Then, by adding the estimated value of electrical conductivity based on the Fe concentration of the cleaning solution at the end of chemical cleaning and the estimated value of the deviation ΔEC at the end of chemical cleaning, the electrical conductivity of the cleaning solution at the end of chemical cleaning is determined. Predict the rate. The electrical conductivity calculated in this way (predicted electrical conductivity value at the end) is an electrical conductivity value that takes into consideration changes in the properties of the cleaning liquid and the effects of dilution.

Then, using the relationship between the electrical conductivity of the cleaning liquid and the active ingredient concentration of the main ingredient as shown in FIG. 14, the active ingredient concentration of the main ingredient is derived from the predicted electrical conductivity value at the end of the process. When Fe ions are not present in the cleaning solution, as shown in FIG. 14, there is a positive correlation between the concentration of the main agent and the electrical conductivity, so it is possible to derive the concentration of the active ingredient of the main agent from the electrical conductivity of the cleaning solution. can.

In this way, the status of the active ingredient concentration of the base agent can be grasped. In addition, electrical conductivity is affected by the Fe concentration of the cleaning solution and dilution due to water intrusion into the water seal used to separate the cleaning system from the non-cleaning system, but by using the Fe concentration and dilution rate, , it becomes possible to more accurately derive the active ingredient concentration of the base agent based on the electrical conductivity.

The control unit 63 performs adjustment control to add a corresponding adjusting agent to the cleaning liquid when the predicted value of the index regarding cleaning performance after a predetermined period of time has passed is outside the allowable range. That is, the control unit 63 performs control (adjustment control) to add the conditioning agent to the cleaning liquid when the predicted state at the end of the cleaning liquid is outside the allowable range. As for the conditioning agent, it is possible to use a cleaning agent contained in the cleaning liquid, or it is also possible to use a chemical for adjustment that is separate from the components of the cleaning liquid.

Regarding the adjustment control in the control unit 63, the cases of adjusting the amount of corrosion of the member through which the cleaning liquid flows, the case of adjusting the pH of the cleaning liquid, and the case of adjusting the concentration of the active ingredient of the main ingredient of the cleaning agent are explained below. explain.

(When adjusting the amount of corrosion of parts through which the cleaning liquid flows through cleaning liquid adjustment control)
First, a case will be described in which the amount of corrosion of a member through which the cleaning liquid flows is adjusted. In this embodiment, in this case, the prediction unit 62 predicts the amount of corrosion of the member through which the cleaning liquid flows at the end of the chemical cleaning of the boiler cleaning.

The control unit 63 adds a corrosion inhibitor to the cleaning liquid as an adjusting agent when the predicted value of the amount of corrosion after a predetermined period of time has passed is outside the allowable range. The upper limit of the allowable range is the upper limit value preset for the amount of corrosion (the lower limit is the amount of corrosion is zero).

As shown in Figure 9, when the amount of corrosion changes as shown in J1, the amount of corrosion does not exceed the allowable amount of corrosion at the end of chemical cleaning, so adjustment control is not performed assuming that the predicted value is within the allowable range. It won't happen. As shown in J3 in FIG. 9, when the amount of corrosion exceeds the allowable amount of corrosion at the end of chemical cleaning, the predicted value is outside the allowable range, and adjustment control is executed.

When the predicted value of the amount of corrosion at the end of chemical cleaning exceeds the allowable range, the control unit 63 controls the amount of corrosion inhibitor added as a regulating agent so that the amount of corrosion does not exceed the allowable range by the end of chemical cleaning. At least one of the addition timing and addition timing is set and adjustment control is performed. In this embodiment, a case will be described in which both the addition amount and the addition timing are set.

Specifically, as shown in FIG. 15, the control unit 63 sets the addition amount and addition timing of the corrosion inhibitor as an adjustment agent based on information on the concentration dependence of the corrosion inhibitor on the change in the amount of corrosion over time. do. In FIG. 15, for example, a plurality of patterns (characteristics O1, O2, O3, O4, O5, O6) of changes in the amount of corrosion over time are shown for each concentration of the corrosion inhibitor. Such a pattern of changes over time in the amount of corrosion with respect to the concentration of the corrosion inhibitor can be obtained by accumulating past results in a database and organizing changes in measurement results.

If the predicted value of the amount of corrosion at the end of chemical cleaning is estimated to exceed the allowable range due to changes like J2 and J3 in Fig. Based on the characteristics shown in FIG. 15, the necessary addition amount and addition timing of the corrosion inhibitor are set by similarity calculation and DB machine learning so as not to exceed the value.

For example, the adjustment period is from now until the end of chemical cleaning, and the difference between the current amount of corrosion and the allowable corrosion amount is the allowable increase amount. Then, from the characteristics shown in FIG. 15, a change characteristic that results in an increase less than or equal to the allowable increase amount within a period corresponding to the adjustment period is specified. Then, the amount of the corrosion inhibitor added is set so that the corrosion inhibitor concentration has the change characteristic.

For example, if the amount of corrosion has been changing as J2 until now, the allowable increase amount will be ΔC (see FIG. 9) during the adjustment period T1 from now until the end of chemical cleaning. Therefore, in FIG. 15, when characteristics whose increase amount is equal to or less than the allowable increase amount ΔC in the adjustment period T1 are specified, for example, characteristics O1, O2, and O3 are selected. Since it is preferable that the amount of the corrosion inhibitor added be as small as possible, the amount of the corrosion inhibitor added is specified so that the concentration of the corrosion inhibitor becomes a concentration corresponding to the lowest characteristic O3. Regarding the addition timing, it is preferable to add the corrosion inhibitor as early as possible in order to suppress an increase in the amount of corrosion with a small addition amount. Therefore, the addition timing is set so as to add as soon as possible after setting the addition amount.

FIG. 16 shows an example in which the amount of corrosion is adjusted and controlled using a corrosion inhibitor. Before the adjustment, there was a possibility that the corrosion amount would exceed the allowable value due to the change as in J3, but as a result of the appropriate addition of corrosion inhibitors, the estimated corrosion amount has decreased from J3 before adjustment. As a result, the increase in corrosion amount is suppressed as in J5. Therefore, it is possible to prevent the amount of corrosion from exceeding the allowable amount of corrosion at the end of chemical cleaning. Incidentally, adjustment control is similarly performed for the transition like J4, and like J6, the corrosion amount is suppressed from exceeding the corrosion amount tolerance value at the end of the chemical cleaning.

In the above example, a case has been described in which the addition timing is set as soon as possible after setting the addition amount, but the addition timing can be set as appropriate in consideration of the addition amount. For example, if it is possible to set a large amount of addition, it is possible to prevent the amount of corrosion from exceeding the allowable amount of corrosion at the end of chemical cleaning even if the addition is not performed as soon as possible. Therefore, if the amount of corrosion does not reach the allowable amount of corrosion at the end of chemical cleaning, the timing of addition is not limited to the above. For example, the addition timing may be calculated backwards so that, with a predetermined addition amount, the amount of corrosion reaches the corrosion amount tolerance value (or the corrosion amount threshold value obtained by subtracting a predetermined margin from the corrosion amount tolerance value) at the end of chemical cleaning. .

(When adjusting the pH of the cleaning solution using cleaning solution adjustment control)
Next, the case of adjusting the pH of the cleaning liquid will be explained. In this case, in this embodiment, the prediction unit 62 predicts the pH of the cleaning liquid at the end of chemical cleaning in boiler cleaning.

The control unit 63 adds a reducing agent to the cleaning liquid as an adjusting agent when the predicted pH value after a predetermined period of time exceeds the allowable range. The upper limit of the allowable range is the upper limit value preset for pH (the lower limit is the lower limit value preset for pH). The tolerance range is preset based on pH-dependent cleaning performance.

When the pH changes as shown by M1 in FIG. 11, the pH does not exceed the upper limit pH at the end of chemical cleaning, and therefore no adjustment control is performed since the predicted value does not exceed the allowable range. As shown in M3 in FIG. 11, when the pH exceeds the pH upper limit at the end of chemical cleaning, the predicted value exceeds the allowable range and adjustment control is executed.

If the predicted value of pH at the end of chemical cleaning exceeds the allowable range, the control unit 63 controls at least the amount and timing of addition of the reducing agent so that the pH does not exceed the allowable range by the end of chemical cleaning. Set one or the other and perform adjustment control. In this embodiment, a case will be described in which both the addition amount and the addition timing are set.

Specifically, the pH increase characteristic of the cleaning liquid is specified based on the pH transition characteristic. For example, in the case where the change in pH of the cleaning liquid over time with the cleaning time of boiler cleaning is approximated by a linear function, the pH increase characteristic is the slope of the linear function. Then, using the slope, the addition amount and addition timing are calculated backwards so that the pH reaches the pH upper limit (or the pH threshold value obtained by subtracting a predetermined margin from the pH upper limit) at the end of chemical cleaning. For example, if the pH increases at this slope and it is predicted that the pH will reach the pH upper limit value (or the pH threshold value obtained by subtracting a predetermined margin from the pH upper limit value) at the end of chemical cleaning, the pH will change to the planned value. Specify the time when Then, this time is set as the addition timing, and the amount of addition of the pH adjuster is set to bring the pH to the planned value (for example, pH=6) at that time. Addition control is then performed at the set addition amount and addition timing.

FIG. 17 shows an example where pH adjustment control is performed using a reducing agent. Before adjustment, there was a possibility that the pH value would exceed the upper limit due to a change like M3, but by adding a reducing agent appropriately, the pH value will be lowered to the planned value, for example, M5. This suppresses the increase in pH. Therefore, it is possible to prevent the cleaning performance from decreasing beyond the allowable range at the end of chemical cleaning.

Note that, as long as the pH is below the pH upper limit at the end of chemical cleaning, the method of setting the addition amount and addition timing is not limited to the above-mentioned method.

(When adjusting the concentration of the active ingredient in the main ingredient of the cleaning agent by controlling the adjustment of the cleaning liquid)
Next, a case will be described in which the concentration of the active ingredient in the main ingredient of the cleaning agent is adjusted. In this case, in this embodiment, the prediction unit 62 predicts the active ingredient concentration of the main ingredient of the cleaning agent at the end of chemical cleaning.

The control unit 63 adds the main agent to the cleaning liquid as an adjustment agent when the predicted value of the concentration of the active ingredient of the main agent (chelating agent) of the cleaning agent after a predetermined period of time is outside the permissible range. The lower limit of the allowable range is a preset lower limit value (for example, zero) for the active ingredient concentration. The upper limit of the allowable range is the concentration of the active ingredient in the main ingredient of the cleaning solution before the start of cleaning. The permissible range is set in advance based on the cleaning performance of the cleaning liquid, which depends on the concentration of the active ingredient in the base agent.

When the predicted value of the concentration of the active ingredient in the base agent at the end of chemical cleaning is outside the allowable range, the control unit 63 controls the concentration of the active ingredient in the base agent so that the concentration of the active ingredient in the base agent does not fall outside the allowable range by the end of the chemical cleaning. Adjustment control is performed by setting at least one of the addition amount and addition timing. In this embodiment, a case will be described in which both the addition amount and the addition timing are set.

Specifically, the adjustment control of the concentration of the active ingredient in the base agent is similar to the adjustment control of the pH described above. That is, the decreasing characteristic of the active ingredient concentration of the base agent is specified based on the transition characteristic of the active ingredient concentration of the base agent. For example, in the case where the change over time in the concentration of the active ingredient in the base agent estimated after a predetermined period of boiler cleaning is approximated by a linear function, the decreasing characteristic is the slope of the linear function (particularly when the seal water is pressurized) range without adjustment). The change over time in the concentration of the active ingredient in the base agent may be determined, for example, based on the measured value of electrical conductivity, or it may be determined based on the estimated value of electrical conductivity taking into account the Fe concentration and dilution rate. good. Then, using this slope, the amount and timing of addition of the base agent is determined so that the concentration of the active ingredient in the base agent is equal to or higher than the lower limit value (or the threshold value obtained by adding a predetermined margin to the lower limit value) at the end of chemical cleaning. Count backwards. When the lower limit value is set to zero, it is preferable to use a threshold value obtained by adding a predetermined margin to zero. For example, if it is predicted that the active ingredient concentration of the base agent will decrease with this slope and that the active ingredient concentration of the base agent will be less than the lower limit value (or threshold value) at the end of chemical cleaning, the active ingredient concentration of the base agent will be the planned value ( Specify the time when the active ingredient concentration of the main agent is reached (before the start of cleaning). Then, with this time as the addition timing, the amount of addition of the base agent to bring the active ingredient concentration of the base agent to the planned value at the time, or the amount of addition of the base agent that will decrease the active ingredient concentration of the base agent with this slope and the amount of the base agent after addition. The minimum necessary amount of the base agent to be added is set so that the concentration of the active ingredient is equal to or higher than the lower limit value (or threshold value) at the end of chemical cleaning. Addition control is then performed at the set addition amount and addition timing.

Note that the method for setting the amount and timing of addition of the base agent is not limited to the method described above, as long as the active ingredient concentration of the base agent does not reach the lower limit value (zero) at the end of chemical cleaning.

(An example of a process for adjusting the amount of corrosion of parts through which the cleaning liquid flows through adjustment control of the cleaning liquid)
In the present embodiment, next, an example of an adjustment process performed by the above-mentioned control device 60 regarding the amount of corrosion of a member through which the cleaning liquid flows will be described with reference to FIG. 18. FIG. 18 is a flowchart illustrating an example of a procedure for adjusting the amount of corrosion of a member through which the cleaning liquid flows. The flow shown in FIG. 18 is repeatedly executed at a predetermined control cycle, for example, when chemical cleaning is performed.

First, the amount of corrosion (accumulated amount of corrosion) at the end of chemical cleaning is estimated based on the change over time in the amount of corrosion of the member through which the cleaning liquid flows (S101).

Next, it is determined whether the amount of corrosion of the member through which the cleaning liquid flows at the end of the chemical cleaning is less than the allowable amount of corrosion (S102). If the amount of corrosion of the member through which the corrosion cleaning liquid flows at the end of the chemical cleaning is less than the allowable amount of corrosion (YES determination in S102), the process ends. That is, boiler cleaning is continuously performed.

If the amount of corrosion of the member through which the cleaning liquid flows at the end of chemical cleaning is not less than the allowable amount of corrosion (NO determination in S102), the amount of corrosion at the end of chemical cleaning is not more than the allowable amount of corrosion. The amount and timing of addition of a corrosion inhibitor as a regulator is set (S103).

The corrosion inhibitor is added at the set addition amount and addition timing (S104).

In this way, the adjustment process related to the amount of corrosion of the member through which the cleaning liquid flows is performed.

(Example of adjustment process related to pH of cleaning liquid by cleaning liquid adjustment control)
Next, an example of the adjustment process related to the pH of the cleaning liquid by the above-mentioned control device 60 will be described with reference to FIG. 19. FIG. 19 is a flowchart illustrating an example of a procedure for pH-related adjustment processing. The flow shown in FIG. 19 is repeatedly executed at a predetermined control cycle, for example, when chemical cleaning is performed.

In this embodiment, first, the pH of the cleaning liquid at the end of chemical cleaning for boiler cleaning is estimated based on the change in pH over time (S201). For example, the pH at the end of chemical cleaning is estimated by linear function approximation based on the change in pH over time.

Next, it is determined whether the pH at the end of chemical cleaning is below the pH upper limit (S202). If the pH at the end of the chemical cleaning is below the H upper limit (YES determination in S202), the process ends. That is, boiler cleaning is continuously performed.

If the pH at the end of chemical cleaning is not below the pH upper limit (NO determination in S202), a reducing agent (for example, ascorbic acid) is used as an adjusting agent so that the pH at the end of chemical cleaning is below the pH upper limit. The amount and timing of addition are set (S203). For example, the addition amount and addition timing for returning the pH to the planned value are calculated backwards so that the pH at the end of chemical cleaning is below the pH upper limit.

The reducing agent is added at the set addition amount and addition timing (S204). That is, the pH is returned to the planned value at the set addition timing.

In this way, the adjustment process related to the reducing agent is performed. Regarding the adjustment process related to the reducing agent, as shown in Figure 11, the amount and timing of adding the reducing agent may be set so that the pH reaches the pH upper limit (or pH threshold) at the end of chemical cleaning. Okay, as shown in FIG. 20, the pH is lowered to the planned value by setting the addition timing as the timing when the pH is estimated to reach the pH upper limit (or pH threshold) based on the temporal change in the measured pH value. The amount of the adjusting agent added may be set so that the amount of the adjusting agent is returned.

In this way, the adjustment process related to the pH of the cleaning liquid is performed.

(Example of state transition of active ingredient concentration of main agent of cleaning liquid)
Next, the state transition of the active ingredient concentration of the base agent will be explained. FIG. 21 is a diagram showing the state transition of the active ingredient concentration of the base agent.

First, the initial charging of the base agent is completed (ST1). When ST1 is performed, the electrical conductivity of the cleaning liquid becomes the planned value. Further, since Fe is in an undissolved state in the cleaning liquid, the Fe concentration is zero (substantially zero).

As the chemical cleaning progresses, iron present in the system to be cleaned is dissolved, and the Fe concentration of the cleaning solution increases (ST2). Further, as the chemical cleaning progresses, water (for example, seal water for water sealing) flows into the cleaning liquid, causing dilution of the chemical concentration (ST3). Due to the influence of the increase in Fe concentration (ST2) and the dilution of the cleaning solution (ST3), the measured value N1 of electrical conductivity decreases over time (ST4).

On the other hand, the Fe concentration in the cleaning liquid is obtained (ST5). The Fe concentration is obtained, for example, by analysis at predetermined time intervals. As the chemical cleaning progresses, the Fe concentration of the cleaning solution increases, so the main agent combines with Fe ions, and the estimated value N2 of electrical conductivity based on the Fe concentration decreases (ST6). Here, as described above, the amount of decrease in the measured value N1 of electrical conductivity is larger than the amount of decrease in the estimated value N2 of electrical conductivity based on the Fe concentration, since the influence of dilution of the cleaning liquid is taken into account. Therefore, as shown in FIG. 22, when the Fe concentration in the cleaning liquid increases as the chemical cleaning progresses, the measured electrical conductivity value N1 and the estimated electrical conductivity value N2 based on the Fe concentration diverge. Therefore, the deviation ΔEC=N1−N2, which is the difference between the measured value N1 and the estimated value N2, increases.

By sorting out the temporal changes in the measured electrical conductivity values and the estimated electrical conductivity values based on the Fe concentration, the temporal change characteristics with cleaning time as shown in FIG. 12 are obtained (ST7).

The temporal change characteristics obtained in ST7 are used in the adjustment process related to the active ingredient concentration of the base agent, which will be described later.

(Example of adjustment process related to the concentration of active ingredient in the main ingredient of the cleaning liquid through adjustment control of the cleaning liquid)
Next, an example of the adjustment process related to the active ingredient concentration of the base agent by the above-mentioned control device 60 will be described with reference to FIG. 23. FIG. 23 is a flowchart illustrating an example of the procedure for adjusting the concentration of the active ingredient in the base agent. The flow shown in FIG. 23 is repeatedly executed at a predetermined control cycle, for example, when chemical cleaning is performed.

In this embodiment, first, the dilution rate of the cleaning liquid is estimated based on the measured value of electrical conductivity and the temporal change characteristics of the estimated value of electrical conductivity based on the Fe concentration (S301). Specifically, the dilution rate of the cleaning liquid is estimated based on the electrical conductivity deviation ΔEC in FIG. 12 .

Next, the electrical conductivity based on the Fe concentration at the end of chemical cleaning is estimated from the change in Fe concentration (S302). Then, the electrical conductivity deviation ΔEC at the end of chemical cleaning is estimated based on the dilution rate (S303). Then, the electrical conductivity at the end of the chemical cleaning is predicted by adding the estimated value of the electrical conductivity based on the Fe concentration at the end and the estimated value of the electrical conductivity deviation ΔEC at the end (S304 ).

Then, based on the predicted electrical conductivity, the concentration of the active ingredient in the base agent at the end of chemical cleaning is estimated from the relationship shown in FIG. 14 (S305).

Next, it is determined whether the active ingredient concentration of the base agent at the end of chemical cleaning is greater than zero (S306). Note that when the lower limit value is set to a value greater than zero, it is determined in S306 whether the active ingredient concentration of the base agent at the end of chemical cleaning is equal to or higher than the lower limit value. If the concentration of the active ingredient in the base agent at the end of chemical cleaning is greater than zero (YES determination in S306), the process ends. That is, boiler cleaning is continuously performed.

If the concentration of the active ingredient in the base agent at the end of chemical cleaning is not greater than zero (NO determination in S306), the concentration of the active ingredient in the base agent is added as an adjustment agent so that the concentration of the active ingredient in the base agent at the end of chemical cleaning is greater than zero. The addition amount and addition timing are set (S307). For example, the base agent may be used to return the active ingredient concentration of the base agent to the planned value so that the active ingredient concentration of the base agent is greater than zero at the end of chemical cleaning, or to perform an operation to achieve a predetermined active ingredient concentration of the base agent. The amount and timing of addition is calculated backwards.

The base ingredient is added at the set addition amount and addition timing of the base ingredient (S308). That is, at the set addition timing, the active ingredient concentration of the base ingredient is increased to the planned value or a predetermined active ingredient concentration of the base ingredient.

In this way, adjustment processing related to the active ingredient concentration of the base agent is performed. Regarding the adjustment process related to the concentration of the active ingredient in the main ingredient, the concentration of the active ingredient in the main ingredient is adjusted to the planned value by using the timing when the active ingredient concentration in the main ingredient is estimated to reach the lower limit value as the addition timing, as in Figure 20 for pH. Alternatively, the amount added may be set so as to increase the concentration of the active ingredient of the base agent to a predetermined value.

In this way, adjustment processing related to the active ingredient concentration of the base agent is performed.

In the above example, an example of setting the addition timing has been described, but the addition timing may be set in consideration of response delay. That is, it is also possible to set the addition timing based on the response delay between the position where the properties of the cleaning liquid are monitored and the position where the conditioning agent is added. If the monitoring position of the cleaning fluid properties is different from the addition position of the adjustment agent, there will be a time lag in the effect of adjustment control, so by taking the response delay into account, the cleaning liquid properties can be adjusted more effectively. This makes it possible to perform cleaning.

In addition, in the above example, a case was explained in which the properties of the corresponding cleaning liquid are individually adjusted by adding each regulator, but when adding multiple regulators, the priority order set in advance for each regulator is Each regulator may be added based on the following. When adding a plurality of adjusting agents, by adding each adjusting agent based on the order of priority, it is possible to suppress interference between the adjusting agents and to efficiently adjust the properties of the cleaning liquid. For example, when prioritizing corrosion inhibition (polarization resistance) over cleaning ability (pH, electrical conductivity), the addition of a corrosion inhibitor should be given first priority, the addition of a reducing agent should be given second priority, and the addition of a base agent should be given priority. It is effective to make this the third priority. Further, since the reducing agent and the base agent may reduce the corrosion inhibiting effect, a corrosion inhibitor may be additionally added when adding the reducing agent and the base agent. In addition, if corrosion inhibition (polarization resistance) is prioritized over cleaning performance (pH), but it is necessary to quickly recover cleaning performance (electrical conductivity) from the effects of dilution, it is necessary to add a corrosion inhibitor. It is effective to set the first priority, the addition of the base agent as the second priority, and the addition of the reducing agent as the third priority. It should be noted that by setting the order of priority for adding each adjusting agent according to the prioritized purpose, it is expected that the properties of the cleaning liquid can be adjusted more efficiently and effective cleaning can be performed.

As explained above, according to the chemical cleaning system, power generation plant, and chemical cleaning method according to the present embodiment, scale mainly composed of oxides such as iron oxide is generated in the evaporation pipe 101a of the boiler. A decrease in heat transfer efficiency in the evaporator tube may lead to a decrease in boiler performance. Therefore, when chemically cleaning the inside of the evaporation tube 101a, the properties of the cleaning liquid are monitored and an index regarding the cleaning performance after a predetermined period of time is predicted. As a result of the prediction, although it is possible to perform cleaning with the cleaning liquid, there is a possibility that the cleaning performance will deteriorate due to changes in the environment within the system through which the cleaning liquid flows, resulting in deviations from the planned values and allowable range values for each index. In such cases, the values of each index can be restored by adding the necessary amount of adjusting agent to the cleaning liquid in advance. Therefore, by predicting indicators related to future cleaning performance after a predetermined period of time has passed from the start of cleaning based on the properties of the cleaning liquid obtained by monitoring during cleaning, changes in cleaning performance can be grasped and the planned value can be calculated. In cases where the cleaning liquid is out of the allowable range, effective countermeasures can be taken, such as adding a necessary amount of adjusting agent to the cleaning liquid, if necessary. Therefore, it becomes possible to more stably take measures such as preventing a decrease in cleaning performance.

In addition, by using at least one of polarization resistance, pH, and electrical conductivity as the properties of the cleaning liquid, cleaning performance can be more greatly affected, and cleaning performance can be predicted more effectively and appropriate measures can be taken. can do. Based on the polarization resistance, it is possible to estimate the amount of corrosion on the parts through which the cleaning liquid flows, so based on the change in the amount of corrosion over time, the amount of corrosion (cumulative corrosion estimate) on the parts through which the cleaning liquid flows after a predetermined period of time from the start of cleaning amount) can be obtained. That is, as an index regarding the cleaning performance, it is possible to evaluate the corrosion occurrence potential of the member through which the cleaning liquid flows. Since the amount of corrosion after a predetermined period of time is predicted, it is also possible to take appropriate measures in advance if the corrosion rate deviates from the planned value or allowable range value. Further, from the change in pH over time, the pH after a predetermined period of time has passed from the start of cleaning can be obtained. That is, as an index regarding the cleaning performance, for example, the hydrogen ion index of the cleaning liquid, which is related to the cleaning ability, can be evaluated. Since the pH after a predetermined period of time is predicted, it is possible to take appropriate measures in advance if the pH deviates from the planned value or allowable range value. Furthermore, based on the electrical conductivity, it is possible to obtain the concentration of the active ingredient in the main ingredient of the cleaning agent after a predetermined period of time has elapsed from the start of cleaning. That is, as an index regarding the cleaning performance, for example, the concentration of the active ingredient of the base agent, which is related to the cleaning performance, can be evaluated. Since the concentration of the active ingredient in the base agent after a predetermined period of time has elapsed from the start of cleaning, it is possible to take appropriate measures in advance if the concentration deviates from the planned value or allowable range value.

In addition, if the predicted value of an index after a predetermined period of cleaning time is outside the allowable range, adjustment control is performed to add an adjustment agent corresponding to the index to the cleaning liquid, so that the index is outside the allowable range. This makes it possible to prevent this from happening in advance. By adding a necessary amount of corrosion inhibitor to the cleaning liquid when the predicted value of the amount of corrosion of the member through which the cleaning liquid flows is outside the allowable range, it becomes possible to suppress an increase in the amount of corrosion in advance. By adding a necessary amount of reducing agent to the cleaning liquid when the predicted pH value is outside the allowable range, it is possible to adjust the pH to an appropriate value in advance. For example, since pH is related to cleaning ability, it is possible to prevent a decrease in cleaning ability in advance. By adding the necessary amount of the base agent to the cleaning liquid when the predicted value of the active ingredient concentration of the base agent is outside the allowable range, it becomes possible to adjust the active ingredient concentration to an appropriate value in advance. For example, since the active ingredient concentration is related to cleaning ability, it is possible to prevent a decrease in cleaning ability in advance.

In addition, by setting at least one of the amount and timing of addition of the adjusting agent so that the index does not fall outside the allowable range by the end of the predetermined period, it is possible to add more than the necessary amount of the adjusting agent within the specified period. This makes it possible to perform cleaning more stably without having to do this.

The present disclosure is not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the invention.

In the embodiment described above, the boiler is a coal-fired boiler, but the solid fuel may be a boiler that uses biomass fuel, PC (petroleum coke) fuel generated during oil refining, petroleum residue, etc. good. 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.

It is preferable to use the measured values of the properties used for prediction in the first half of the entire cleaning process (total chemical cleaning time). Note that the first half is 50% or less, preferably 30% or less of the total cleaning time. In other words, by predicting that the index will be out of the allowable range by the end of a predetermined period at an earlier timing, the liquid properties (accumulated corrosion amount, pH, electrical conductivity) can be set at the end of chemical cleaning. The liquid properties can be adjusted to the respective planned values by adding the necessary minimum amount of the adjusting agent that is equal to or higher than the lower limit value (or threshold value) or less than the upper limit value, and the amount of the adjusting agent added can be reduced.

Although the present embodiment has mainly been described for use in chemical cleaning using a neutral chelate cleaning agent, it is also applicable to conventional chemical cleaning work using a cleaning agent such as an organic acid.

The chemical cleaning system, power generation plant, and chemical cleaning method described in each embodiment described above can be understood, for example, as follows.
The chemical cleaning system according to the present disclosure has one end connected to an evaporation pipe (101a) of a boiler upstream of the evaporation pipe (101a), and the other end connected to a downstream side of the evaporation pipe (101a). , a chemical cleaning system (L7) that cleans the evaporation pipe (101a) by circulating a cleaning fluid containing a cleaning agent, the chemical cleaning system (L7) being applied to a power plant. ); and a prediction unit (62) that predicts, based on the properties of the cleaning fluid, an index regarding cleaning performance corresponding to the properties after a predetermined period of time has elapsed. Be prepared.

According to the chemical cleaning system according to the present disclosure, scale mainly composed of oxides such as iron oxide is generated in the evaporation tube (101a) of the boiler, which deteriorates the heat transfer performance of the evaporation tube, leading to a decrease in boiler performance. Because of this possibility, chemical cleaning should be carried out by flowing a cleaning liquid through the evaporation tube. At this time, the properties of the cleaning fluid are monitored, and an index regarding the cleaning performance of the evaporation tube after a predetermined period has elapsed since the start of cleaning inside the evaporation tube is predicted. As a result, although cleaning can be performed using the cleaning fluid, there is a possibility that the index will deviate from the planned value or the allowable range value and the cleaning performance will deteriorate due to changes in the environment within the system through which the cleaning fluid flows. In some cases, the value of the index can be restored by adding a necessary amount of regulator to the cleaning fluid in advance. Therefore, by predicting an index regarding cleaning performance after a predetermined period has elapsed from the start of cleaning based on the properties of the cleaning fluid obtained by monitoring during cleaning, it is possible to grasp future changes in cleaning performance. If the predicted index deviates from the planned value or the allowable range value, effective countermeasures can be taken as necessary, such as adding a necessary amount of regulator to the cleaning fluid. Therefore, it is possible to take measures to more stably prevent the cleaning performance from deteriorating in advance (before the cleaning time has elapsed and the cleaning ends). Note that the indicators related to cleaning performance include, for example, the amount of corrosion of members through which the cleaning fluid flows, the pH of the cleaning fluid, and the concentration of active ingredients in the main ingredient of the cleaning agent.

In the chemical cleaning system according to the present disclosure, the property of the cleaning fluid may be at least one of polarization resistance, pH, and electrical conductivity.

According to the chemical cleaning system according to the present disclosure, by using at least one of polarization resistance, pH, and electrical conductivity, cleaning performance is more effectively predicted as having a greater influence on cleaning performance. can do.

In the chemical cleaning system according to the present disclosure, the property of the cleaning fluid may be at least one of turbidity, redox potential, and dissolved oxygen concentration.

According to the chemical cleaning system according to the present disclosure, at least turbidity, redox potential, and dissolved oxygen concentration have less influence than polarization resistance, pH, and electrical conductivity, but have a greater influence on cleaning performance. By using any one of them, it becomes possible to further improve the prediction accuracy of cleaning performance.

In the chemical cleaning system according to the present disclosure, the monitoring unit (61) monitors polarization resistance as a property of the cleaning fluid, and the prediction unit (62) monitors the polarization resistance of the member through which the cleaning fluid flows based on the monitored polarization resistance. The amount of corrosion may be estimated and the amount of corrosion may be predicted as the index after the predetermined period has elapsed based on a change in the amount of corrosion over time.

According to the chemical cleaning system according to the present disclosure, the amount of corrosion of the member through which the cleaning fluid flows can be estimated based on the polarization resistance, so the amount of corrosion after a predetermined period of time ( (accumulated corrosion estimate) can be obtained. That is, as an index regarding the cleaning performance, the corrosion occurrence caused by the cleaning fluid can be evaluated. Since the amount of corrosion after a predetermined period of time from the start of cleaning is predicted, it is also possible to take appropriate measures in advance.

In the chemical cleaning system according to the present disclosure, the monitoring unit (61) monitors the pH as a property of the cleaning fluid, and the prediction unit (62) determines whether the monitored pH changes over time after the predetermined period of time has elapsed. pH may be predicted as the index.

According to the chemical cleaning system according to the present disclosure, the pH of the cleaning fluid after a predetermined period of time can be obtained from the change in pH over time. That is, as an index regarding the cleaning performance, for example, the hydrogen ion index of the cleaning fluid, which is related to the cleaning ability, can be evaluated. Since the pH of the cleaning fluid after a predetermined period of time has elapsed from the start of cleaning, it is possible to take appropriate measures in advance.

In the chemical cleaning system according to the present disclosure, the monitoring unit (61) monitors electrical conductivity as a property of the cleaning fluid, and the prediction unit (62) determines the electrical conductivity during the predetermined period based on the monitored electrical conductivity. The concentration of the active ingredient in the main ingredient of the cleaning agent may be predicted as the index after the elapse of time.

According to the chemical cleaning system according to the present disclosure, it is possible to obtain the active ingredient concentration after a predetermined period has elapsed from the start of cleaning based on the electrical conductivity. That is, as an index regarding cleaning performance, for example, the concentration of active ingredients related to cleaning ability can be evaluated. Since the concentration of the active ingredient after a predetermined period of time is predicted, it is also possible to take appropriate measures in advance. The concentration of the active ingredient in the main ingredient of the cleaning agent is, for example, the concentration of the chelating agent that is not bonded to Fe ions.

In the chemical cleaning system according to the present disclosure, the prediction unit (62) determines whether the main component of the cleaning agent The concentration of the active ingredient may be predicted based on the change in iron concentration over time and the dilution rate.

According to the chemical cleaning system according to the present disclosure, the dilution rate of the base agent can be estimated based on the measured value of electrical conductivity through monitoring and the estimated value of electrical conductivity based on the iron concentration of the cleaning fluid. . For example, when water for filling enters the cleaning solution from outside the closed circuit consisting of the evaporation pipe (101a) and the cleaning system (L7) (for example, water sealing), the main agent is diluted. This indicates that cleaning performance is affected. Based on the dilution rate and the change in iron concentration over time, the concentration of the active ingredient in the base agent can be predicted.

In the chemical cleaning system according to the present disclosure, the prediction unit (62) may predict the index after the predetermined period has passed, based on past performance data regarding the index.

According to the chemical cleaning system according to the present disclosure, based on past performance data, it is possible to more efficiently predict the index after a predetermined period of time has passed from the start of cleaning.

The chemical cleaning system according to the present disclosure includes a control unit ( 63).

According to the chemical cleaning system according to the present disclosure, when the predicted value of the index after a predetermined period of time has passed is out of the allowable range, by performing adjustment control to add a conditioning agent corresponding to the index to the cleaning fluid, It becomes possible to prevent the index from falling outside the permissible range in advance.

The chemical cleaning system according to the present disclosure includes a control unit ( 63).

According to the chemical cleaning system according to the present disclosure, it is possible to prevent an increase in the amount of corrosion in advance by adding a corrosion inhibitor to the cleaning fluid when the predicted value of the amount of corrosion is outside the allowable range. .

The chemical cleaning system according to the present disclosure includes a control unit ( 63).

According to the chemical cleaning system according to the present disclosure, by adding a reducing agent to the cleaning fluid when the predicted pH value is outside the allowable range, it is possible to adjust the pH to an appropriate value in advance. For example, since pH is related to cleaning ability, it is possible to prevent a decrease in cleaning ability in advance.

The chemical cleaning system according to the present disclosure performs adjustment control to add a main ingredient of the cleaning agent as an adjustment agent to the cleaning fluid when the predicted value of the concentration of the active ingredient after the predetermined period is out of the allowable range. It is also possible to include a control section (63).

According to the chemical cleaning system according to the present disclosure, it is possible to adjust the active ingredient concentration to an appropriate value in advance by adding a base agent to the cleaning fluid when the predicted value of the active ingredient concentration is outside the allowable range. becomes. For example, since the active ingredient concentration is related to cleaning ability, it is possible to prevent a decrease in cleaning ability in advance.

In the chemical cleaning system according to the present disclosure, if the predicted value of the index after the predetermined period is out of the allowable range, the control unit (63) controls the control unit (63) to Adjustment control may be performed by setting at least one of the amount and timing of addition of the adjusting agent so that it falls within an allowable range.

According to the chemical cleaning system according to the present disclosure, at least one of the amount and timing of addition of the adjuster is set so that the index does not fall outside the allowable range after the elapse of the predetermined period. It becomes possible to perform cleaning more stably.

In the chemical cleaning system according to the present disclosure, the control unit (63) may set the addition timing based on a response delay between a position for monitoring the properties of the cleaning fluid and a position for adding the conditioning agent. .

According to the chemical cleaning system according to the present disclosure, if the position for monitoring the properties of the purified fluid and the position for adding the adjustment agent are different, there will be a time lag in the effect of adjustment control. , it becomes possible to perform cleaning more effectively.

In the chemical cleaning system according to the present disclosure, when adding a plurality of conditioning agents, the control unit (63) adds each conditioning agent based on a priority order set in advance for each conditioning agent. It may also be added.

According to the chemical cleaning system according to the present disclosure, when adding a plurality of conditioning agents, each conditioning agent is added based on the order of priority, thereby suppressing interference between the conditioning agents, etc., and efficiently adjusting. It becomes possible to do so.

The power plant according to the present disclosure has one end connected to an evaporation pipe (101a) of a boiler on the upstream side of the evaporation pipe (101a), and the other end connected to the downstream side of the evaporation pipe (101a), A chemical cleaning system (L7) for chemically cleaning the evaporation tube (101a) by flowing a cleaning fluid containing a cleaning agent, and the chemical cleaning system described above are provided.

In the chemical cleaning method according to the present disclosure, one end is connected to an evaporation pipe (101a) of a boiler upstream of the evaporation pipe (101a), and the other end is connected to a downstream side of the evaporation pipe (101a). , a chemical cleaning system (L7) that cleans the evaporation pipe (101a) by flowing a cleaning fluid containing a cleaning agent, the chemical cleaning method being applied to a power plant, the chemical cleaning system (L7) ), and a step of predicting, based on the properties of the cleaning fluid, an index regarding the cleaning performance corresponding to the properties after a predetermined period of time has elapsed.

1 : Boiler power generation plant 10 : 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 60: Control device 61: Monitoring unit 62: Prediction Section 63: Control section 71: Measurement section 72: Injection section 73: Cleaning liquid circulation pump 74: Tank 75: Water seal device 76: Injection pump 81: Retraction pump 83: Flow meter 84: Heater 86: Turbidity meter 87: Polarization resistance Total 88: Thermometer 91: Drawing pump 93: Flow meter 94: Heater 96: Dissolved oxygen concentration meter 97: Electrical conductivity meter 98a: pH meter 98b: Oxidation-reduction potential meter 99: Thermometer 101: Furnace wall 101a: Evaporation tube 102: First superheater 103: Second superheater 104: Third superheater 105: First reheater 106: Second reheater 107: Energy saver 110: Steam turbine 111: High pressure turbine (steam turbine)
112: Intermediate pressure turbine (steam turbine)
113: Low pressure turbine (steam turbine)
114: Condenser 115: Generator 122: Low pressure water heater 123: Boiler feed water pump 124: High pressure water heater 126: Brackish water separator 127: Brackish water separator drain tank 130: RAM
131: ROM
140: Hard disk drive 150: Communication section 160: CPU
180: Bath L1: Water supply line L2: Drain water line L3: Steam line L4: Steam line L5: Steam line L6: Circulation line L7: Chemical washing system PA: Extraction system PB: Extraction system SA: Skid SB: Skid

Claims (17)

One end is connected to an evaporation pipe of a boiler on an upstream side of the evaporation pipe, and the other end is connected on a downstream side of the evaporation pipe, and a cleaning fluid containing a cleaning agent is passed through to clean the evaporation pipe. A chemical cleaning system applied to a power generation plant having a cleaning system,
a monitoring unit that monitors the properties of the cleaning fluid in the chemical cleaning system;
a prediction unit that predicts an index regarding cleaning performance corresponding to the properties after a predetermined period of time based on the properties of the cleaning fluid;
Chemical cleaning system with. The chemical cleaning system according to claim 1, wherein the property of the cleaning fluid is at least one of polarization resistance, pH, and electrical conductivity. 3. The chemical cleaning system according to claim 2, wherein the property of the cleaning fluid is at least one of turbidity, redox potential, and dissolved oxygen concentration. The monitoring unit monitors polarization resistance as a property of the cleaning fluid,
The prediction unit estimates the amount of corrosion of a member through which the cleaning fluid flows based on the monitored polarization resistance, and predicts the amount of corrosion as the index after the predetermined period of time based on a change in the amount of corrosion over time. The chemical cleaning system according to any one of Items 1 to 3. The monitoring unit monitors pH as a property of the cleaning fluid,
The chemical cleaning system according to any one of claims 1 to 4, wherein the prediction unit predicts pH as the index after the predetermined period has elapsed based on a monitored change in pH over time. The monitoring unit monitors electrical conductivity as a property of the cleaning fluid,
The chemical according to any one of claims 1 to 5, wherein the prediction unit predicts the active ingredient concentration of the main ingredient of the cleaning agent as the indicator after the predetermined period of time has passed, based on the monitored electrical conductivity. cleaning system. The prediction unit estimates the dilution rate of the main agent of the cleaning agent based on the measured value of electrical conductivity by monitoring and the estimated value of electrical conductivity based on the iron concentration of the cleaning fluid, and calculates the change in iron concentration over time. 7. The chemical cleaning system according to claim 6, wherein the active ingredient concentration is predicted based on: and the dilution rate. The chemical cleaning system according to any one of claims 1 to 7, wherein the prediction unit predicts the index after the predetermined period has elapsed based on past performance data regarding the index. 9. Any one of claims 1 to 8, further comprising a control unit that performs adjustment control to add an adjustment agent corresponding to the index to the cleaning fluid when the predicted value of the index after the predetermined period of time is out of an allowable range. The chemical cleaning system according to item 1. The chemical cleaning according to claim 4, further comprising a control unit that performs adjustment control to add a corrosion inhibitor to the cleaning fluid as an adjustment agent when the predicted value of the amount of corrosion after the predetermined period of time is out of an allowable range. system. The chemical cleaning according to claim 5, further comprising a control unit that performs adjustment control to add a reducing agent to the cleaning fluid as an adjusting agent when the predicted pH value of the cleaning fluid after the predetermined period is out of an allowable range. system. 7. The method according to claim 6, further comprising a control unit that performs adjustment control to add the main ingredient of the cleaning agent to the cleaning fluid as an adjustment agent when the predicted value of the concentration of the active ingredient after the predetermined period of time is out of an allowable range. chemical cleaning system. The control unit controls the adjusting agent so that, when the predicted value of the index after the predetermined period is out of the permissible range, the index falls within the permissible range by the end of the predetermined period. The chemical cleaning system according to any one of claims 9 to 12, wherein at least one of an addition amount and an addition timing is set and adjustment control is performed. 14. The chemical cleaning system according to claim 13, wherein the control unit sets the addition timing based on a response delay between a monitoring position of the properties of the cleaning fluid and an addition position of the conditioning agent. The chemical cleaning system according to claim 13, wherein, when adding a plurality of the conditioning agents, the control section adds each conditioning agent based on a priority order set in advance for each conditioning agent. boiler evaporation tube,
a chemical cleaning system that has one end connected to an upstream side of the evaporation pipe and the other end connected to a downstream side of the evaporation pipe, and that flows a cleaning fluid containing a cleaning agent to chemically clean the evaporation pipe;
A chemical cleaning system according to any one of claims 1 to 15,
A power generation plant equipped with One end is connected to an evaporation pipe of a boiler on an upstream side of the evaporation pipe, and the other end is connected on a downstream side of the evaporation pipe, and a cleaning fluid containing a cleaning agent is passed through to clean the evaporation pipe. A chemical cleaning method applied to a power generation plant having a cleaning system, the method comprising:
monitoring the properties of the cleaning fluid in the chemical cleaning system;
a step of predicting an index regarding cleaning performance corresponding to the properties after a predetermined period of time based on the properties of the cleaning fluid;
A chemical cleaning method with

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