WO2016002516A1 - Chemical washing method and chemical washing device - Google Patents

Abstract

Provided are a chemical washing method and a chemical washing device for removing hematite. A washing liquid containing a rust removal agent, which is a chelating agent, a reducing agent, or a mixture of a chelating agent and a reducing agent, is fed, through a chemical liquid feed line (102), directly to an apparatus (10) to be washed having a member on which hematite is adhered. Chemical washing is performed by immersing at least the region to which the hematite is adhered in the washing solution and maintaining the oxidation-reduction potential of the washing liquid at the value at which hematite is eluted into the washing liquid, and as a result, the hematite is eluted from the member and removed.

Description

Chemical cleaning method and chemical cleaning apparatus

The present invention relates to a chemical cleaning method and a chemical cleaning apparatus for removing hematite adhering to the inner surface of a water-cooled wall tube.

A thermal power generation system 1 illustrated in FIG. As a boiler water supply system, a condenser 20, a condensate demineralizer 21, a ground steam condenser 22, a low-pressure feed water heater 23, a deaerator 24, a high-pressure feed water heater 25, and a economizer 26 are installed. The As the steam system of the boiler, a steam separator 30, a superheater 31, a turbine 32, and a reheater 33 are installed. As the turbine 32, a high-pressure turbine, an intermediate-pressure turbine, and a low-pressure turbine may be installed.

In the thermal power generation system 1 in which oxygen treatment is applied to the boiler feedwater system, an event occurs in which the metal temperature of the water-cooled wall pipe of the once-through boiler 10 increases, and the leakage of boiler feedwater due to breakage of the water-cooled wall pipe becomes a problem. Yes. The metal temperature rise of the water-cooled wall pipe is caused by the elution of iron from the low pressure feed water heater drain system 27 or the pipe of the feed water system to produce hematite (Fe ₂ O ₃ ), and hematite adheres to and accumulates on the inner surface of the water-cooled wall pipe. This is due to poor heat conduction.

In order to prevent the above-mentioned non-conformity of the water-cooled wall tube, chemical cleaning of the water-cooled wall tube is periodically performed to remove scales composed of iron-based oxides such as hematite deposited on the inner surface of the tube. Yes. In conventional chemical cleaning, a circulation path is installed between the economizer 26 and the steam separator 30, and an acidic cleaning solution (hydrochloric acid, etc.) heated to about 60 to 80 ° C. is circulated in the circulation path. Then, the inside of the water-cooled wall pipe is cleaned (see, for example, Patent Document 1).

Patent Document 2 discloses a method for removing sludge and the like generated in a steam generator for a nuclear reactor. Patent Document 3 discloses a method for cleaning and removing iron oxide scale from a metal filter used in a thermal power plant or a nuclear power plant. In the method of Patent Document 3, the iron oxide scale is peeled off from the filter and removed by dissolving only the iron at the adhering portion of the iron oxide adhering to the filter.

JP-A-8-105602 JP-T-2004-535546 JP2013-71111A

As in Patent Document 1, in the conventional chemical cleaning, the installed circulation path needs to be filled with the cleaning liquid. Moreover, since hydrogen gas is generated during cleaning by using an acidic cleaning liquid, chemical cleaning cannot be performed in parallel with mechanical and electrical work using fire. Thus, during the chemical cleaning, there is a problem that the maintenance work cannot be performed not only on the equipment immersed in the cleaning liquid but also on other equipment, and the maintenance cannot be performed efficiently. .

In the conventional chemical cleaning method, it was necessary to circulate the cleaning liquid at a high flow rate in order to remove the scale composed of the iron-based oxide. Moreover, in order to obtain a sufficient flow rate, it is necessary to connect to a large-diameter pipe, but the upstream pipe and the downstream pipe of the once-through boiler 10 are small-diameter pipes and are not suitable for connecting a chemical cleaning device. is there. For this reason, as specifically shown in Patent Document 1, there is no choice but to connect a circulation path to the upstream side pipe of the economizer 26 and the pipe in the steam separator 30, and there are restrictions on the apparatus.

Hematite is a poorly soluble oxide, and conventional acidic cleaning liquids (for example, hydrochloric acid-based and citric acid-based) are difficult to dissolve in the cleaning liquid, and sludge is generated by chemical cleaning.
In addition, a magnetite layer that is a natural oxide scale is formed on the surface of the pipe or the metal filter disclosed in Patent Document 3. In the method of Patent Document 3, only the magnetite layer is dissolved without dissolving the attached iron oxide scale, and the scale is peeled off. Therefore, if the method disclosed in Patent Document 3 is used, sludge is generated.

Since the water-cooled wall pipe of the once-through boiler 10 in the thermal power generation system 1 has a long and complicated pipe shape, when sludge is generated, it may accumulate in a part of the pipe and close the pipe.
For this reason, in the conventional chemical cleaning, it was necessary to remove sludge from the cleaning liquid. As a method for removing sludge, a filter is provided in the middle of the portion through which the cleaning liquid passes to collect sludge floating in the cleaning liquid, or a part of the piping of the equipment to be cleaned after chemical cleaning is cut and piped. There is a method of inspecting the inside, removing it by a physical method such as suction cleaning, and then welding the pipe again.

Further, in the conventional chemical cleaning using an acidic cleaning liquid, it is necessary to heat the cleaning liquid as described above, and it is necessary to separately install a temperature raising equipment for heating the cleaning liquid. Moreover, the inside of the apparatus immersed in the acidic cleaning liquid has to be neutralized after cleaning, and a large amount of neutralized water is required.

As in the thermal power generation system shown in FIG. 20, when there is a superheater 31 having stainless steel parts on the downstream side of the steam / water separator 30, there is a risk of corrosion when the stainless steel parts come into contact with an acidic cleaning liquid such as hydrochloric acid. is there. For this reason, in conventional chemical cleaning, it is necessary to pressurize and pressurize water in the non-cleaning system adjacent to the downstream side of the equipment to be cleaned to prevent intrusion of the cleaning liquid. It was installed.

As described above, when performing conventional chemical cleaning, a large amount of cleaning liquid and water for water filling and neutralization are required, and a large-scale facility and its installation work are required, and the construction period is long. Therefore, the high maintenance cost has been a problem.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a chemical cleaning method for removing hematite and a chemical cleaning apparatus for carrying out the chemical cleaning method.

In the first aspect of the present invention, a cleaning liquid containing a chelating agent, a reducing agent, or a rusting agent that is a mixture of the chelating agent and the reducing agent is supplied to a device to be cleaned having a member to which hematite is attached. A cleaning liquid supply step, and at least a region of the member to which the hematite is adhered is immersed in the cleaning liquid, and an oxidation-reduction potential of the cleaning liquid is maintained at a value at which the hematite is eluted in the cleaning liquid. The chelating agent is one of an aminocarboxylic acid chelating agent, an oxycarboxylic acid chelating agent and an organophosphorus chelating agent, and the reducing agent is a metal ion, sulfurous acid Salt, oxalic acid, formic acid, ascorbic acid, pyrogallol, hydrazine, or hydrogen, and the pH of the cleaning solution is within the range of 4-8. That is a chemical cleaning method.

A second aspect of the present invention is a chemical cleaning apparatus for chemically cleaning a device to be cleaned having a member to which a hematite scale is attached, the chelating agent, the reducing agent, or the chelating agent and the reducing agent. The chelating agent is any one of an aminocarboxylic acid chelating agent, an oxycarboxylic acid chelating agent and an organophosphorus chelating agent, and the reducing agent is a metal ion, sulfite, oxalic acid, formic acid, A chemical solution tank containing a rust remover that is any one of ascorbic acid, pyrogallol, hydrazine, and hydrogen, containing a cleaning solution having a pH in the range of 4 to 8, and the device to be cleaned and the chemical solution tank, A chemical solution supply line for supplying the cleaning solution to the member, a pump installed in the chemical solution supply line, the device to be cleaned, and the chemical solution tank are connected. The chemical liquid discharge line for discharging the cleaning liquid from the member, means for immersing at least the region where the hematite is adhered in the member in the cleaning liquid, and the redox potential of the cleaning liquid being cleaned elutes in the cleaning liquid A chemical cleaning apparatus, wherein the chemical liquid tank, the chemical liquid supply line, and the pump supply the cleaning liquid to the member.

In the chemical cleaning method and the chemical cleaning apparatus of the above aspect, since the cleaning liquid is supplied only to the equipment to be cleaned, the amount of the cleaning liquid required for the chemical cleaning can be greatly reduced.
Furthermore, since a cleaning liquid containing a rust remover is used, even when a device having a stainless steel part is disposed downstream of the device to be cleaned, there is no need to perform water filling or the like to prevent corrosion of the member, Equipment for water filling becomes unnecessary, and the device configuration is simplified. In addition, since no hydrogen is generated during cleaning, chemical cleaning can be performed in parallel with mechanical and electrical work using fire, and inspection and maintenance work for each part can be performed in parallel. Can be shortened.
Thus, the use of the chemical cleaning method and the chemical cleaning apparatus of the present invention is advantageous because the cost required for maintenance such as equipment costs and chemical costs can be greatly reduced.

In the chemical cleaning method, the cleaning step is performed while maintaining the value within a range of −0.8 V or more and −0.4 V or less with respect to a silver-silver chloride electrode.
In the chemical cleaning method, the value may be adjusted by supplying a reducing atmosphere gas to the device to be cleaned.

The chemical cleaning apparatus includes a reducing atmosphere adjusting unit that adjusts the oxidation-reduction potential of the cleaning liquid during cleaning to a value in the range of −0.8 V or more and −0.4 V or less with respect to the silver-silver chloride electrode.
In the chemical cleaning apparatus, the reducing atmosphere adjusting unit may supply reducing atmosphere gas to the cleaning target device.

The hematite is dissolved and removed in the cleaning liquid by maintaining the reduced state as the above redox potential. The solid matter such as sludge is hardly generated by the cleaning, and even when a slight amount of solid matter is generated, it can be easily discharged from the cleaning target device together with the cleaning liquid. Further, since no equipment for removing sludge is required, the equipment cost can be reduced.

In the chemical cleaning method, it is preferable that the temperature of the cleaning liquid in the cleaning step is in a range of an ambient temperature around the member and a temperature that is 10 ° C. higher than the ambient temperature.

In the chemical cleaning apparatus, it is preferable that the temperature of the cleaning liquid supplied to the member is in a range of an ambient temperature around the member and a temperature that is 10 ° C. higher than the ambient temperature.
The chemical cleaning apparatus further includes a circulation loop that connects the chemical liquid supply line on the upstream side and the chemical liquid supply line on the downstream side across the pump, and a part of the cleaning liquid that has passed through the pump is the circulation loop. It is preferable to be conveyed to the upstream side of the pump via

According to the present invention, hematite can be removed at a lower temperature than when an acidic cleaning solution is used, and it is not necessary to positively raise the temperature of the cleaning solution, and it is extremely easy to maintain the temperature at the ambient temperature.
If the temperature of the cleaning liquid is raised to a temperature that is 10 ° C. higher than the environmental temperature, the cleaning power can be further increased. For example, the temperature of the cleaning liquid can be easily raised by using heat generated during pump operation. Since the configuration of the present invention does not actively cool, the temperature of the cleaning liquid can be maintained higher than the environmental temperature for a long time.
According to the present invention, it is possible to perform cleaning at a lower temperature than the conventional method using an acidic cleaning liquid. As a result, it is possible to reduce equipment costs and cleaning costs.

In the chemical cleaning method, the region is immersed in the cleaning liquid while the cleaning liquid is left standing.
During the cleaning, the chemical cleaning apparatus stops the supply of the cleaning liquid to the member and the discharge of the cleaning liquid from the member to allow the cleaning liquid to stand.
According to the chemical cleaning method and the chemical cleaning apparatus described above, it is not necessary to install a large circulation path for the cleaning liquid, which is advantageous because the cleaning is performed in a simple process.

The chemical cleaning method further includes a water supply step between the cleaning liquid supply step and the cleaning step, wherein a predetermined amount of the cleaning liquid is supplied to the cleaning target device in the cleaning liquid supply step, and in the water supply step A predetermined amount of water is supplied to the device to be cleaned, and the region is immersed in the cleaning liquid.
The chemical cleaning apparatus further includes a water supply unit including a water tank that stores water, a water supply line that connects the water tank and the device to be cleaned, and a water pump installed in the water supply line. Prepare.

According to this chemical cleaning method and chemical cleaning apparatus, the cleaning liquid layer and the water layer can be separated in the cleaning target device. If the area where hematite is adhered is immersed in the cleaning liquid and the other part is immersed in water, the amount of the cleaning liquid used for chemical cleaning can be greatly reduced.

In the chemical cleaning method, the cleaning liquid may be accommodated in a capsule made of a water-soluble polymer, and the capsule may be supplied to the device to be cleaned.

In the chemical cleaning apparatus, the cleaning liquid may be stored in a capsule made of a water-soluble polymer, the chemical liquid tank may store the capsule, and the capsule may be supplied from the cleaning liquid tank to the device to be cleaned.

</ RTI> By this chemical cleaning method and chemical cleaning apparatus, for example, an area where a lot of hematite is generated can be easily immersed in the cleaning liquid, so that the amount of the cleaning liquid to be used can be greatly reduced.

In the chemical cleaning method, the cleaning liquid is repeatedly discharged from the member and the discharged cleaning liquid is supplied to the member during the cleaning step, and the cleaning liquid is disposed in the vicinity of the region. Move the liquid level.

In the chemical cleaning apparatus, during cleaning, the cleaning liquid in the member is discharged toward the chemical liquid tank through the chemical liquid discharge line, and the cleaning liquid in the chemical liquid tank is supplied to the member through the chemical liquid supply line. To repeat.

According to the present chemical cleaning method and chemical cleaning apparatus, since the flow rate is given to the cleaning liquid in the region where hematite adheres and the cleaning liquid is stirred, the cleaning power is improved, which is advantageous.

In the above chemical cleaning method, during the cleaning step, the cleaning liquid passes through the member and is discharged from the upstream end of the member, and the discharged cleaning liquid is directly discharged to the downstream end of the member. Circulated.

In the chemical cleaning apparatus, the circulation line includes a circulation line that connects an upstream end and a downstream end of the member, and a circulation pump installed in the circulation line, and the circulation line is used during cleaning. Then, the cleaning liquid discharged from the front downstream end is circulated to the upstream end.

This chemical cleaning method and chemical cleaning apparatus also improve the cleaning power because a flow rate is given to the cleaning liquid and the cleaning liquid is stirred in the region where hematite is adhered. In addition, since the cleaning liquid is heated when passing through the pump and cleaning is performed in a state higher than the environmental temperature around the member, the cleaning power is improved.

The chemical cleaning method according to the first aspect further includes a measuring step in which the iron concentration in the cleaning solution is measured, and a determination step in which the removal status of the hematite from the member is determined based on the iron concentration. The cleaning liquid is discharged from the cleaning target device during the cleaning process, the iron concentration in the cleaning liquid discharged in the measurement process is measured, and the iron concentration is determined to be equal to or higher than a predetermined concentration in the determination process. In this case, or when it is determined that the amount of change in the concentration gradient is a value within a predetermined range, the cleaning step is terminated.

In the chemical cleaning apparatus according to the second aspect, while cleaning the cleaning target device while maintaining the redox potential of the cleaning liquid of the cleaning target device at a value at which the hematite is eluted in the cleaning solution, Based on the concentration of iron in the cleaning liquid discharged from the target device, the removal state in which the hematite is eluted from the member is determined, and when the iron concentration is determined to be a predetermined concentration or more, or the amount of change in the concentration gradient is When it is determined that the value is within the predetermined range, the apparatus further includes a determination unit that ends the cleaning of the cleaning target device.

In the case where hematite is unevenly distributed in the member, distribution occurs in the iron concentration in the cleaning liquid while the member is immersed in the cleaning liquid. Due to the structure of the equipment to be cleaned, it is extremely difficult to collect the cleaning liquid only from the vicinity of the region where hematite in the member is attached in order to measure the iron concentration.
Therefore, in the chemical cleaning method and the chemical cleaning apparatus of the above aspect, the end of the chemical cleaning is determined using the iron concentration in the cleaning liquid once discharged from the cleaning target device during the cleaning. This not only facilitates measurement of the iron concentration, but also improves the measurement accuracy because the cleaning solution is stirred and the iron concentration is made uniform by being discharged from the cleaning target device. According to the present invention, hematite can be reliably removed by chemical cleaning, and the effect of improving maintenance efficiency can be obtained.

In the chemical cleaning method, when the cleaning liquid is discharged from the cleaning target device at a predetermined time period in the cleaning step and the iron concentration is determined to be less than the predetermined concentration in the determination step, or the amount of change in the concentration gradient May be returned to the cleaning target device when it is determined that the value is larger than a predetermined range.

In the chemical cleaning apparatus, the determination unit may determine the removal status of the hematite using the iron concentration in the cleaning liquid discharged from the cleaning target device and stored in the chemical tank.

According to the above aspect, it is possible to perform cleaning of the cleaning target device and stirring of the cleaning liquid with a simple process and apparatus configuration.

In the chemical cleaning method according to the first aspect, during the cleaning step, the cleaning liquid passes through the member and is discharged from one end of the member, and the discharged cleaning liquid is discharged from the other end of the member. The iron concentration may be measured using a part of the cleaning liquid that is directly circulated to the end portion and discharged in the measurement step.

In the chemical cleaning apparatus according to the second aspect, a circulation unit including a circulation line that directly connects one end side end and the other end side end of the member, and a circulation pump installed in the circulation line. The cleaning liquid discharged from the one end side end portion through the circulation line during cleaning is circulated to the other end flow side end portion, an extraction portion is installed in the circulation line, and the determination portion is You may determine the removal condition of the said hematite using the said iron concentration in the said washing | cleaning liquid extract | collected from the extraction part.

In this chemical cleaning method and chemical cleaning apparatus, the flow rate is given to the cleaning liquid and the cleaning liquid is agitated in the region where hematite adheres, so that the cleaning power is improved. A part of the circulating cleaning liquid can also be used for determining the end of chemical cleaning.

In the chemical cleaning method according to the first aspect of the present invention, an observation step in which the color of the surface to which the hematite is adhered is observed during the cleaning step, and the hematite from the member based on the color A determination step in which the removal status is determined, and the surface to which the hematite is attached is the region or a portion to which the hematite in the test specimen immersed in the cleaning liquid is attached, and the determination step When it is determined that no color derived from the hematite is observed, the cleaning step is terminated.

In the chemical cleaning apparatus according to the second aspect of the present invention, the cleaning target device is cleaned while maintaining the redox potential of the cleaning solution of the cleaning target device at a value at which the hematite elutes in the cleaning solution. A determination unit that determines the removal state in which the hematite elutes on the surface on which the hematite is adhered by observing the color, and terminates the cleaning of the cleaning target device when it is determined that the color derived from the hematite is not observed The surface to which the hematite is attached is the region or the portion to which the hematite is attached in the test body immersed in the cleaning liquid.

Also in the chemical cleaning method and the chemical cleaning apparatus of this aspect, the amount of cleaning liquid required for chemical cleaning can be significantly reduced, and the maintenance work period can be shortened, so that the maintenance cost can be significantly reduced.
Furthermore, according to this aspect, it is possible to determine the end of the chemical cleaning by a simple method of determining the presence or absence of the attached hematite, so that the working efficiency is improved.

In the chemical cleaning method according to the first aspect of the present invention, a measurement step in which ultrasonic measurement or AC electrical property measurement is performed on the surface of the member opposite to the side where the region is formed during the cleaning step. And a determination step of determining a removal status of the hematite from the member based on a time change of the measurement value obtained in the measurement step, and the measurement value is equal to or less than a predetermined value in the determination step. Or when it is determined that the amount of change in the change gradient of the measured value is a value within a predetermined range.

In the chemical cleaning apparatus according to the second aspect of the present invention, the measurement is performed on the surface of the member opposite to the surface on which the hematite is formed and performs ultrasonic measurement or AC electrical property measurement on the member. And the time of the measurement value acquired by the measurement unit while cleaning the cleaning target device while maintaining the redox potential of the cleaning solution of the cleaning target device at a value at which the hematite is eluted in the cleaning solution. The removal status of the hematite from the member is determined based on the change, and when it is determined that the measurement value is equal to or less than a predetermined value, or the change amount of the change gradient of the measurement value is within a predetermined range And a determination unit that terminates the cleaning of the device to be cleaned.

In the chemical cleaning method and the chemical cleaning apparatus, it is preferable that the measured value is a thickness of the hematite attached to the member obtained by the ultrasonic measurement.

Alternatively, in the chemical cleaning method and the chemical cleaning apparatus, the measured value is preferably a reactance obtained by the AC electrical characteristic measurement.

Also in the chemical cleaning method and the chemical cleaning apparatus of this aspect, the amount of cleaning liquid required for chemical cleaning can be significantly reduced, and the maintenance work period can be shortened, so that the maintenance cost can be significantly reduced.
Further, in this embodiment, attention is paid to the fact that the measurement value obtained by performing ultrasonic measurement or AC electrical characteristic measurement from the surface opposite to the hematite adhesion surface changes corresponding to the hematite adhesion state. This embodiment has the advantage that it is not necessary to collect the cleaning liquid, and it is possible to quickly determine the end of chemical cleaning by a simple method of determining the presence or absence of the attached hematite.

In the chemical cleaning method according to the first aspect of the present invention, in the cleaning step, the cleaning liquid is discharged from the member in a state where the oxidation-reduction potential of the cleaning liquid is maintained at a value at which the hematite is eluted in the cleaning liquid. And the step of feeding at least a part of the cleaning liquid to the member is repeated, and the height of the liquid surface of the cleaning liquid is moved in the vicinity of the region, and the hematite is moved to the member. A measuring step in which the pressure of the cleaning liquid discharged from the member during the step of discharging is measured, and removal of the hematite from the member based on a change in the pressure obtained in the measuring step A determination step in which a situation is determined, and in the step of supplying, the cleaning liquid is supplied to the member while changing a supply amount at a predetermined frequency, and the determination step In this case, when it is determined that the phase difference between the waveform of the change amount of the cleaning liquid supply and the waveform of the pressure change is equal to or less than a predetermined value, or the change amount of the change gradient of the phase difference is within a predetermined range. Or when the period or amplitude of the waveform of the pressure change is determined to be less than or equal to a predetermined value, or the amount of change in the change gradient of the period or the change in the amplitude When it is determined that the change amount of the gradient is a value within the predetermined range, the cleaning process is ended.

The chemical cleaning apparatus according to the second aspect of the present invention further includes a valve installed in the chemical solution supply line, a pressure measuring unit installed in the chemical solution discharge line, and a determination unit, and the device to be cleaned While cleaning the apparatus to be cleaned while maintaining the oxidation-reduction potential of the cleaning liquid at a value at which the hematite elutes in the cleaning liquid, at least a part of the cleaning liquid in the member is passed through the chemical liquid discharge line. The discharge of the cleaning liquid in the chemical liquid tank and the supply of the cleaning liquid in the chemical liquid tank to the member through the chemical liquid supply line are repeated, and the pump or the valve supplies the cleaning liquid to the member. The supply amount is changed at a predetermined frequency, and the pressure measurement unit adjusts the pressure of the cleaning liquid flowing through the chemical liquid discharge line while cleaning the cleaning target device. The determination unit determines the removal status of the hematite from the member based on the change in the pressure, and the determination unit determines a waveform of the change in the amount of the cleaning liquid to be fed and a waveform of the change in the pressure. When the phase difference between the pressure difference and the phase difference is determined to be equal to or less than a predetermined value, or when the amount of change in the change gradient of the phase difference is determined to be within a predetermined range, or the waveform of the pressure change When it is determined that the period or amplitude is equal to or less than a predetermined value, or when it is determined that the change amount of the change gradient of the period or the change amount of the change gradient of the amplitude is a value within a predetermined range, Finish cleaning the equipment to be cleaned.

According to the chemical cleaning method and the chemical cleaning apparatus according to the above aspect, the flow rate is given to the cleaning liquid in the region where hematite is adhered by moving the liquid level by repeatedly discharging and feeding the cleaning liquid during the cleaning process. Since the cleaning liquid is agitated, the cleaning power is advantageously improved.

摩擦 The coefficient of friction between the cleaning liquid and the member changes depending on the state of hematite adhesion. When the supply amount is changed at a predetermined frequency when the cleaning liquid is supplied, the inventors vibrate the liquid level of the cleaning liquid in the member, and this vibration state is reflected in the pressure change of the cleaning liquid at the time of discharge. I found. As in this aspect, it is possible to easily determine the removal of hematite based on the phase difference between the frequency and the pressure change and the waveform of the pressure change.

According to the present invention, the amount of cleaning liquid used can be reduced as compared with the conventional chemical cleaning method, and the configuration of the chemical cleaning apparatus is simplified, so that the cost required for chemical cleaning can be greatly reduced.
Further, in the present invention, since the cleaning liquid is not supplied to other equipment and hydrogen is not generated during cleaning, it is possible to perform other operations simultaneously with chemical cleaning. For this reason, this invention has the advantageous effect that a maintenance work period is shortened compared with a prior art.
Furthermore, according to the present invention, the hematite can be reliably removed from the surface of the member because the removal status of the hematite is monitored using the parameters measured during the cleaning step to determine the timing of the end of the cleaning step.

It is the schematic explaining the chemical cleaning apparatus which concerns on 1st Embodiment. It is the schematic of an example of a once-through boiler. It is the schematic of an example of a once-through boiler. It is the schematic explaining the chemical cleaning method of 1st Embodiment. It is a SEM photograph of the cross section of the water-cooled wall tube before immersion of the cleaning liquid. It is a SEM photograph of the cross section of the water-cooled wall pipe after chemical cleaning. It is the schematic of the test piece used for the completion | finish determination of the washing | cleaning process based on a color change. It is a figure explaining the completion | finish determination method of the washing | cleaning process based on a color change. It is the schematic explaining the chemical cleaning apparatus for enforcing the completion | finish determination method of the washing | cleaning process based on a color change. It is a figure explaining the measuring method of an alternating current electrical property. It is a circuit diagram of the alternating current electrical property measurement shown in FIG. It is the schematic explaining the chemical cleaning apparatus which concerns on 2nd Embodiment. It is the schematic explaining the chemical cleaning apparatus which concerns on 3rd Embodiment. It is the schematic explaining the chemical cleaning apparatus which concerns on 4th Embodiment. It is the schematic explaining the chemical cleaning apparatus which concerns on 5th Embodiment. It is the schematic explaining the chemical cleaning apparatus for implementing completion | finish determination of the washing | cleaning process based on a pressure change. It is a figure explaining completion | finish determination of the washing | cleaning process based on a pressure change. It is the schematic explaining the chemical cleaning apparatus which concerns on 8th Embodiment. It is the schematic explaining the chemical cleaning apparatus which concerns on 9th Embodiment. It is the schematic of a thermal power generation system.

The cleaning liquid used in the chemical cleaning method and the chemical cleaning system of the present invention is an aqueous solution containing a neutral rust remover.
The neutral rust remover is a chelating agent, a reducing agent, or a mixed agent of a chelating agent and a reducing agent. Chelating agents include, for example, aminocarboxylic acids such as EDTA, BAPTA, DOTA, EDDS, INN, NTA, DTPA, HEDTA, TTHA, PDTA, DPTA-OH, HIDA, DHEG, GEDTA, CMGA, EDDS, and amino such as salts thereof. Carboxylic acid chelating agents, oxycarboxylic acid chelating agents such as citric acid, gluconic acid, hydroxyacetic acid and the like, and salts thereof, organic phosphoric acids such as ATMP, HEDP, NTMP, PBTC, EDTMP and their salts Organic phosphorus chelating agents such as Examples of the reducing agent include various metal ions such as Fe ²⁺ and Sn ²⁺ , sulfites such as sodium sulfite, organic compounds such as oxalic acid, formic acid, ascorbic acid, and pyrogallol, hydrazine, and hydrogen. The cleaning liquid containing a neutral rust remover has a pH of 4 to 8, and preferably a pH of 5 to 7.

腐 食 A corrosion inhibitor may be added to the neutral rust remover. In the cleaning liquid, the concentrations of the chelating agent, the reducing agent, and the corrosion inhibitor are appropriately adjusted so that a desired cleaning power and cleaning time can be obtained.

The cleaning liquid may or may not contain an antifoaming agent for preventing foaming. In this embodiment, a known antifoaming agent can be used.

Hereinafter, embodiments of the chemical cleaning method and the chemical cleaning apparatus of the present invention will be described by taking a thermal power generation system as an example. However, the present invention is not limited to a thermal power generation system, and can be applied to other devices to which hematite adheres.

[First Embodiment]
FIG. 1 is a schematic view for explaining a chemical cleaning apparatus according to the first embodiment. FIG. 1 shows a case where a chemical cleaning apparatus 100 is installed in the thermal power generation system 1 during maintenance. The configuration of the thermal power generation system 1 is the same as that shown in FIG. In the thermal power generation system 1, hematite, which is a powdery scale, adheres to the inside of the heat transfer pipe such as the water-cooled wall pipe of the once-through boiler 10, and the heat conductivity of the heat transfer pipe is lowered. Therefore, the once-through boiler 10 is a cleaning target device in order to recover the heat transfer performance.

The chemical cleaning apparatus 100 according to the first embodiment includes a chemical tank 101, a chemical supply line 102 that connects the chemical tank 101 and the once-through boiler 10, a chemical discharge line 103 that connects the chemical tank 101 and the once-through boiler 10, and a control. Part 104. The chemical tank 101 contains the above-described cleaning liquid. The control unit 104 is a computer, for example. Control unit 104 includes a determination unit.

Fig. 2 is an example of a once-through boiler. 2A is a schematic view of the once-through boiler, and FIG. 2B is an enlarged view of a portion surrounded by a circle A in FIG. 2A. The once-through boiler 10a shown in FIG. 2A includes a combustion chamber 11a surrounded by a wall surface 12a and a plurality of water-cooled wall tubes. The water-cooled wall tube 13a of the once-through boiler 10a has a straight tube extending along the wall surface 12a in a direction perpendicular to the cross section of the combustion chamber 11a. A plurality of water-cooled wall tubes 13a are arranged in the horizontal direction along the wall surface 12a. The lower header 14a is installed in the lower part of the combustion chamber 11a, and the lower ends of the plurality of water-cooled wall tubes 13a are connected to the lower header 14a. An upper header is installed in the upper part of the combustion chamber 11a, and the upper ends of the plurality of water-cooled wall tubes 13a are connected to the upper header 15a.

FIG. 3 shows another example of the once-through boiler. 3A is a schematic view of a once-through boiler, and FIG. 3B is an enlarged view of a portion surrounded by a circle B in FIG. 3A. 3 is different from the once-through boiler 10a of FIG. 2 in the shape of the water-cooled wall tube. In the once-through boiler 10b, a plurality of water-cooled wall tubes 13b are disposed along the wall surface 12b in a spiral shape below the combustion chamber 11b. The water-cooled wall pipe 13b branches into a plurality of pipes at a midway position in the vertical direction of the combustion chamber 11b (branch portion 16). The branched water-cooled wall tube 13b is straight and extends upward in the vertical direction along the wall surface 12b with respect to the cross section of the combustion chamber 11a.
The lower header 14b is installed in the lower part of the combustion chamber 11b, and the lower ends of the plurality of water-cooled wall tubes 13b are connected to the lower header 14b. An upper header is installed in the upper part of the combustion chamber 11b, and the upper ends of the plurality of water-cooled wall tubes 13b are connected to the upper header 15b.

In the chemical cleaning apparatus 100 of the first embodiment, the chemical solution supply line 102 and the chemical solution discharge line 103 are connected to the lower headers 14a, 14b of the once-through boiler 10 (10a, 10b).
The chemical solution supply line 102 is provided with a pump 105 and a valve V1. A valve V <b> 2 is installed in the chemical solution discharge line 103. The pump 105 and the valves V1 and V2 communicate with the control unit 104.

The place where hematite adheres depends on how the water-cooled wall pipe is installed. Hematite tends to adhere to a place where the flow rate of boiler feed water changes in the water-cooled wall pipe. For example, in the once-through boiler 10a of FIG. 2, hematite adheres more to the inner surface of the water-cooled wall tube 13a located below the combustion chamber 11a than the other parts. In the once-through boiler 10b of FIG. 3, hematite adheres more to the inner surface of the water-cooled wall tube 13b of the branch portion 16 than to the other portions.

The chemical cleaning apparatus 100 of the first embodiment further includes a reducing atmosphere adjusting unit. In the chemical cleaning apparatus 100 of the first embodiment, the reducing atmosphere adjustment unit is the reducing atmosphere gas supply unit 110. The reducing atmosphere gas supply unit 110 in FIG. 1 includes a reducing atmosphere gas storage unit 111 and an air supply line 112. The chemical cleaning apparatus 100 includes an exhaust line 113. Valves V3 and V4 are installed in the air supply line 112 and the exhaust line 113, respectively. The air supply line 112 and the exhaust line 113 are connected to the upper headers 15a and 15b of the once-through boiler 10 (10a and 10b). The valves V3 and V4 are connected to the control unit 104.

The reducing atmosphere gas storage unit 111 is a cylinder that stores the reducing atmosphere gas. The reducing atmosphere gas is a gas for adjusting the cleaning liquid to a reduced state. Specifically, the reducing atmosphere gas is nitrogen, argon, steam, carbon dioxide, combustion exhaust gas, or the like. The purity of the reducing atmosphere gas does not have to be a high-purity gas, and any gas can be used as long as the oxidation-reduction potential of the cleaning liquid during the cleaning process described later can be maintained within a predetermined range. When nitrogen is used as the reducing atmosphere gas, a nitrogen injection facility that is already installed in the thermal power generation system 1 can be used as the reducing atmosphere gas supply unit 110, or a nitrogen injection facility may be temporarily or newly installed. Steam or combustion exhaust gas as the reducing atmosphere gas can be steam or combustion exhaust gas generated in a boiler of another adjacent thermal power generation system.

A chemical cleaning method for cleaning and removing hematite attached in the once-through boiler using the chemical cleaning apparatus 100 of the first embodiment will be described below.
The chemical cleaning method of the present embodiment is performed, for example, during a periodic inspection of the thermal power generation system, during a process of constructing a scaffold in the furnace and a process of constructing equipment other than the equipment to be cleaned (the once-through boiler 10).
In carrying out the chemical cleaning method of the present embodiment, a valve installed in a pipe connecting the once-through boiler 10 and the economizer 26 is closed.

<Gas supply process>
The control unit 104 opens the valves V2 and V3. A reducing atmosphere gas (such as nitrogen gas) is supplied from the reducing atmosphere gas storage unit 111 to the water-cooled wall pipes 13a and 13b of the once-through boiler 10 via the air supply line 112. Air in the water-cooled wall tubes 13 a and 13 b is discharged out of the system through the chemical solution discharge line 103. By this step, the air in the water-cooled wall tubes 13 a and 13 b in the once-through boiler 10 is discharged through the chemical solution discharge line 103. By the gas supply process, the water-cooled wall tubes 13a and 13b are filled with the reducing atmosphere gas.
After a sufficient time for gas replacement has elapsed, the control unit 104 closes the valves V2 and V3.

<Cleaning liquid supply process>
The control unit 104 activates the pump 105 and opens the valve V1. The control unit 104 opens the valve V4. The cleaning liquid in the chemical liquid tank 101 is fed to the once-through boiler 10 via the chemical liquid supply line 102. As a result, the inner surfaces of the water-cooled wall pipes 13a and 13b are immersed in the cleaning liquid, and the purge gas in the water-cooled wall pipes 13a and 13b such as nitrogen having a volume corresponding to the supplied cleaning liquid is discharged out of the system through the exhaust line 113.

In this embodiment, since the valve of the pipe connecting the once-through boiler 10 and the economizer 26 is closed, the cleaning liquid supplied from the chemical liquid supply line 102 to the lower headers 14a and 14b flows into the economizer 26. There is nothing.

In this embodiment, at least the area where hematite adheres on the inner surfaces of the water-cooled wall tubes 13a and 13b is immersed in the cleaning liquid. In particular, on the inner surfaces of the water-cooled wall tubes 13a and 13b, a region where hematite is attached in a larger amount than other portions is always immersed in the cleaning liquid. For example, as shown in FIG. 4, the control unit 104 supplies the cleaning liquid so that the liquid level 18 of the cleaning liquid is located above the region 17 where hematite is attached more than the other parts. Considering the cost of chemical cleaning, the cleaning liquid is filled with the upper ends of the plurality of water-cooled wall tubes 13a and 13b (connection portions with the upper headers 15a and 15b) as the upper limit. In this embodiment, the cleaning liquid does not reach the downstream steam separator 30 beyond the once-through boiler 10. That is, in the present embodiment, the cleaning liquid is supplied only to the once-through boiler 10 that is the cleaning target device.

A region of the hematite adhering region, in particular, the region 17 where hematite adheres more than the other part is specified in advance, so that the hematite adhering region can be immersed from each size of the water-cooled wall tubes 13a and 13b. Necessary amount can be determined. The control unit 104 stores the required amount of cleaning liquid, and supplies a predetermined amount of cleaning liquid according to the required amount of steam to the once-through boiler 10 in the cleaning liquid supply process.

<Washing process>
When the region to which hematite is attached is immersed in the cleaning liquid, the control unit 104 stops the pump 105 and closes the valves V1 and V4. In a state where the cleaning liquid is allowed to stand, the hematite is immersed in the cleaning liquid and the cleaning process is performed.
The soaking time (cleaning time) depends on the amount of hematite generated, but is, for example, 24 hours or longer. During this cleaning process, the pressure in the water-cooled wall tubes 13a and 13b hardly changes and is constant.

In this embodiment, since the cleaning liquid is allowed to stand during the cleaning process, the temperature of the cleaning liquid during the cleaning process is approximately the same as the environmental temperature around the water-cooled wall tubes 13a and 13b. For example, the ambient temperature around the water-cooled wall tubes 13a and 13b is about 20 to 40 ° C. Since the environmental temperature is close to the outside air temperature and does not change greatly during the cleaning process, the cleaning liquid temperature is also maintained at substantially the same level as the environmental temperature.

Since the reducing atmosphere gas is filled in the space inside the water-cooled wall pipes 13a and 13b by the gas supply process, the cleaning liquid in the cleaning process is maintained in a reduced state. Specifically, the oxidation-reduction potential of the cleaning liquid during the cleaning step can be measured using, for example, an oxidation-reduction potentiometer in the middle of the chemical solution discharge line 103, and the oxidation-reduction potential is based on a silver-silver chloride electrode reference. It is maintained at 0.8V or more and −0.4V or less. According to the pH-potential diagram, by setting the oxidation-reduction potential to −0.4 V or less, the iron oxide dissolution reaction efficiency is increased and hematite is dissolved in the cleaning solution. On the other hand, Fe ⁰ occurs as the redox potential decreases. When the oxidation-reduction potential is less than −0.8 V, Fe ⁰ is generated, sludge is precipitated, and iron adheres to the water-cooled wall tubes 13a and 13b.

When the oxidation-reduction potential deviates from the predetermined range, the reducing atmosphere gas is refilled so as to maintain the oxidation-reduction potential of the cleaning liquid. Specifically, the valves V2 and V3 are opened. Thereby, the reducing atmosphere gas is supplied from the reducing atmosphere gas storage unit 111 to the once-through boiler 10, and the cleaning liquid is supplied to the chemical liquid tank 101 via the chemical liquid discharge line 103. Thereafter, the valves V2 and V3 are closed, the valves V1 and V4 are opened, and the pump 105 is started, so that the cleaning liquid in the chemical tank 101 is supplied to the once-through boiler 10. Alternatively, the valves V3 and V4 are opened while the valves V1 and V2 are closed, and the reducing atmosphere gas is supplied from the reducing atmosphere gas storage unit 111 to the once-through boiler 10 to be refilled with the reducing atmosphere gas.
When the oxidation-reduction potential deviates from a predetermined value, the above-described reducing agent may be added to the cleaning liquid. Specifically, the cleaning liquid is returned to the chemical liquid tank 101 in the same manner as described above, and after the reducing agent is added in the chemical liquid tank 101, the cleaning liquid is supplied to the once-through boiler 10.
The maintenance of the oxidation-reduction potential may be automated based on an instruction from the control unit 104 that monitors the oxidation-reduction potential, or an operator may manually detect and maintain the oxidation-reduction potential.

5 and 6 show the results of verifying the effect of the chemical cleaning method of the present embodiment using a water-cooled wall tube collected from an actual machine. A water-cooled wall tube with hematite attached was collected from the actual machine and immersed (soaked) in the above-described cleaning solution (pH 5 to 7) while maintaining at 25 ° C. The components of the cleaning liquid are appropriately selected between 3 to 5% by weight of the chelating agent and 1.5 to 2.5% by weight of the reducing agent.
The inner surface of the water-cooled wall tube before immersion in the cleaning solution was red, and an autooxidation scale (magnetite (Fe ₃ O ₄ )) and hematite were confirmed in the SEM photograph (FIG. 5). On the other hand, the inner surface of the water-cooled wall tube after the chemical cleaning was black, and only the self-oxidation scale was confirmed in the SEM photograph (FIG. 6).

Verified the cleaning effect of the cleaning liquid using hematite. A cleaning solution (pH 5 to 7) to which hematite powder was added was placed in a container, and the upper portion of the cleaning solution was purged with nitrogen and sealed. The oxidation-reduction potential during the test period was in the range of -0.8 V to -0.4 V based on the silver-silver chloride electrode. The components of the cleaning liquid are appropriately selected between 3 to 5% by weight of the chelating agent and 1.5 to 2.5% by weight of the reducing agent. As a result of keeping the washing liquid at 25 ° C. while standing for 8 hours, the washing liquid changed from opaque reddish brown to almost transparent. This means that hematite was dissolved in the cleaning liquid by soaking.

In this embodiment, the end of the cleaning step is based on one of (1) the iron concentration in the cleaning liquid, (2) the color change of the hematite adhering portion, and (3) the analysis result of the internal state from the outside of the water-cooled wall tube. Determined.

(1) Determination based on iron concentration in cleaning liquid In the cleaning process, valves V2 and V3 are opened at predetermined time intervals. The reducing atmosphere gas is supplied from the reducing atmosphere gas storage unit 111 to the water-cooled wall pipes 13a and 13b of the once-through boiler 10 through the air supply line 112, and the cleaning liquid in the water-cooled wall pipes 13a and 13b is transferred to the lower headers 14a and 14b. To the chemical liquid tank 101 through the chemical liquid discharge line 103. When all the cleaning liquid is stored in the chemical tank 101, the valves V2 and V3 are closed.

<Measurement process>
A part of the cleaning liquid collected in the chemical liquid tank 101 is collected. Using the collected cleaning liquid, the iron concentration in the cleaning liquid is measured by the quantitative analysis defined in JIS B8224. The iron concentration acquired at a predetermined time period is input to the determination unit of the control unit 104.

<Judgment process>
The numerical value of the iron concentration in the cleaning liquid increases with time, and when hematite is completely removed from the water-cooled wall tubes 13a and 13b, the concentration is saturated to a substantially constant value. A determination part determines the condition where hematite elutes and is removed from the time change of iron concentration.

It is possible to predict the iron concentration indicating that the hematite adhering to the base is sufficiently eluted by basic tests and simulations. The iron concentration obtained by the basic test or simulation may be stored in the determination unit as a predetermined concentration (determination reference concentration) indicating that hematite has been removed. In this case, when the determination unit determines that the iron concentration measured in the measurement step is equal to or higher than the determination reference concentration, the determination unit terminates the cleaning step in the control unit 104, assuming that hematite is eluted and removed. The discharge process is carried out.

Alternatively, the removal of hematite may be determined from the amount of change in iron concentration. When hematite is sufficiently eluted, the change (concentration gradient) per unit time of the difference between the measurement value of the iron concentration measured in the measurement process and the previous measurement value is gradually reduced. From this, the change amount of the concentration gradient is stored in the determination unit as a determination criterion, and when the determination unit determines that the change amount of the concentration gradient is within a predetermined range, hematite is eluted and removed. The determination unit causes the control unit 104 to end the cleaning process and to perform a discharge process described later.

For example, the iron concentration C _t at the time T _t is measured in the measurement process and input to the determination unit. Determination unit includes a iron concentration _{C t-1} in the previous (time _{T t-1),} the iron concentration _{C t-2} is also stored in the time before last (time _{T t-2).}
The determination unit determines a concentration gradient ΔC _t per unit time of iron concentration between time T _t and time T _t−1 (= (C _t −C _t−1 ) / (T _t −T _t−1 )). To get. The determination unit stores the concentration gradient ΔC _t−1 (= (C _t−1 −C _t−2 ) / (T _t−1 −T _t−2 )) per unit time of the iron concentration acquired last time. Yes.
The determination unit acquires the concentration gradient ΔC _t acquired this time and the change amount Δd _t of the concentration gradient ΔC _t−1 acquired last time. Determination unit determines if the acquired [Delta] d _t is in the range of pre-stored criteria, reaching the criteria and. For example, the criterion is ± 20%. In the case where hematite precipitates in the cleaning target device 10 is relatively uniform, the determination accuracy can be improved by setting the determination criterion to ± 10%.

When it is determined that the latest iron concentration input to the measurement unit is less than the determination criterion, or when it is determined that the amount of change in the concentration gradient is larger than the predetermined range, the determination unit causes the control unit 104 to perform a cleaning process. Let it continue. The control unit 104 supplies the cleaning liquid in the chemical liquid tank 101 to the once-through boiler 10 again in the same process as the cleaning liquid supply process.

In this embodiment, the oxidation-reduction potential of the cleaning liquid is measured simultaneously with the measurement of the iron concentration in the measurement step. By doing so, the components of the cleaning liquid may be adjusted.

(2) Determination Based on Color Change In this determination method, the determination is made by observing the color change of either (A) the test piece to which hematite has adhered or (B) the water-cooled wall tube.

(2-A) Determination using test piece A test piece to which hematite is adhered is prepared.
As shown in FIG. 7, the test piece is a water-cooled wall tube cut in two along the axial direction, and hematite is attached to the inner wall surface. This test piece (cutting test piece 120) has hematite of the same level as that of the once-through boiler 10 (device to be cleaned) being cleaned. For example, a test piece is produced by cutting a water-cooled wall tube collected from the same position during previous maintenance, or a water-cooled wall tube collected from another plant operated under similar conditions.
The test piece may be a plate material (plate-like test piece) made of the same material as the water-cooled wall tube, and hematite of the same degree as the water-cooled wall tube may be attached to one surface.
Further, the test piece may be a water-cooled wall tube (cylindrical test piece that is not cut along the axial direction like the cut test piece) collected as described above.

In this determination, the surface of the test piece to which hematite is attached is immersed in the cleaning liquid during the cleaning process.
As the dipping method, simultaneously with the start of cleaning, a plurality of cut test pieces or plate-like test pieces are immersed in the cleaning liquid stored in the chemical tank 101.
In this case, the reducing atmosphere gas can be supplied into the chemical liquid tank 101, and while the test piece is immersed, the cleaning liquid in the chemical liquid tank 101 has an oxidation-reduction potential equivalent to that of the water-cooled wall tubes 13a and 13b. It is preferable to adjust.

As another dipping method, as shown in FIG. 8, a transparent plate (for example, acrylic) 121 is disposed on the cut surface of the cutting test piece 120, and one end surface of the cutting test piece 120 is a plate material (not shown in FIG. 8). The surface having hematite attached is immersed in the cleaning liquid by injecting the cleaning liquid containing the same concentration of the rust removing agent as the cleaning liquid supplied to the once-through boiler 10 into the space 122 formed by the arrangement of Is done. The injection of the cleaning liquid is preferably performed substantially simultaneously with the start of the cleaning process.
In this case, it is preferable that the oxidation-reduction potential of the cleaning liquid injected into the cutting specimen 120 is adjusted to the oxidation-reduction potential equivalent to that of the water-cooled wall tubes 13a, 13b by the reducing atmosphere gas.

As another dipping method, as shown in FIG. 9, a bypass portion 130 is installed on the upstream side of the valve V <b> 1 of the chemical solution supply line 102, and a cylindrical test piece 132 is connected to a midway position of the bypass pipe 131 of the bypass portion 130. When the pump 105 is started and the valve V1 is opened in the cleaning liquid supply process, a part of the cleaning liquid passing through the chemical liquid supply line 102 flows into the bypass unit 130, and the inner wall surface of the cylindrical test piece 132 becomes the cleaning liquid. Soaked.
In this case, in the gas supply process, the reducing atmosphere gas is supplied so as to reach the bypass portion 130, and the cleaning liquid in the cylindrical test piece 132 is immersed in the water-cooled wall tube 13a, while the cylindrical test piece 132 is immersed. It is preferable to adjust to an oxidation-reduction potential equivalent to 13b.

<Observation process>
During the cleaning process, one of the test pieces immersed in the cleaning liquid in the chemical liquid tank 101 is taken out from the cleaning liquid at predetermined time intervals. The color of the surface of the removed specimen on which hematite is adhered is observed. The observation is performed by an operator's visual observation or using a CCD camera. In the case of visual observation, the operator inputs the determination result of the color change to the determination unit. In the case of observation by a CCD camera, measurement data is transmitted to the determination unit.

As shown in FIG. 8, when the surface on which hematite is adhered is immersed in the cleaning liquid, observation is performed visually or by a CCD camera from the transparent plate 121 side at a predetermined time period.

When the bypass unit 130 is installed as shown in FIG. 9, the inner wall surface of the cylindrical test piece 132 is observed using a CCD camera at a predetermined time period. Specifically, an observation hole is drilled in the cylindrical test piece 132, and a viewport is inserted into the observation hole so that reflected light from the observation site can enter the CCD camera, and the inner wall surface is immersed in the cleaning liquid. Is observed. The measurement data is transmitted to the determination unit.

<Judgment process>
Hematite is approximately red, but as the removal of hematite proceeds, the underlying natural oxide layer (magnetite: approximately black) or the underlying metal layer (approximately silver) is exposed, and the color changes.
The determination unit determines that hematite is removed when no color derived from hematite is observed. The determination unit causes the control unit 104 to end the cleaning process and to perform a discharge process described later. The determination unit causes the control unit 104 to continue the cleaning process when a color derived from hematite is observed.

The determination unit separates the RGB components of the measurement data signal and extracts only the R component or extracts the R component and the B component. The determination unit determines a state in which hematite is eluted and removed from the time change of the R component or the time change of the ratio between the R component and the B component (R component / B component).

Specifically, the determination unit determines the ratio of the R component value to the initial value (R component measurement value / R component initial value) or the ratio of the R component / B component value to the initial value ((R component / B component measurement). Value) / (R component / B component initial value)) is stored. This criterion is specifically a value within the range of 1/5 to 1/10. Since the measured values of the R component or the R component / B component differ depending on the precipitation state of hematite, it is preferable to determine the determination criteria in the basic test.
The determination unit determines that hematite-derived color is not observed when the ratio of the R component value to the initial value or the ratio of the R component / B component value to the initial value is equal to or less than the determination criterion. When the color derived from hematite is not observed, the determination unit determines that hematite is eluted and removed, and causes the control unit 104 to end the cleaning process and to perform a discharge process described later.

If the ratio of the R component value to the initial value or the ratio of the R component / B component value to the initial value is larger than the criterion, hematite remains, so the determination unit cleans the control unit 104 Continue the process.

(2-B) Determination Using Water-Cooled Wall Tube In the cleaning process, the valves V2 and V3 are opened at a predetermined time period. The reducing atmosphere gas is supplied from the reducing atmosphere gas storage unit 111 to the water-cooled wall pipes 13a and 13b of the once-through boiler 10 through the air supply line 112, and the cleaning liquid in the water-cooled wall pipes 13a and 13b is transferred to the lower headers 14a and 14b. To the chemical liquid tank 101 through the chemical liquid discharge line 103. When all the cleaning liquid is stored in the chemical tank 101, the valves V2 and V3 are closed.

<Observation process>
An observation hole is drilled in the vicinity of the region 17 where the hematite adheres to the water-cooled wall tubes 13a and 13b. The observation hole is formed on the surface of the water-cooled wall pipes 13a and 13b opposite to the fuel chambers 11a and 11b. A view port for the CCD camera is inserted into the observation hole, and the inner wall surface is observed.

<Judgment process>
In the same process as described in (2-A), the determination unit determines the hematite removal status from the color derived from hematite, and causes the control unit 104 to continue or end the cleaning process.

Note that the observation holes formed in the surfaces of the water-cooled wall tubes 13a and 13b in order to make a determination using a CCD camera are restored by filling them with welding after the chemical cleaning is completed.

(3) Determination based on analysis result of internal state from outside of water-cooled wall tube In this method, the state inside the water-cooled wall tube is analyzed by ultrasonic thickness measurement or AC electrical characteristic measurement.

(3-A) Ultrasonic measurement Before performing chemical cleaning, an ultrasonic probe is attached to the outside of the water-cooled wall tube in the area where hematite adheres. The region where hematite adheres is specified by collecting the water-cooled wall tube and observing the inner wall surface during the previous maintenance. Alternatively, it is specified by measuring the wall thickness of the water-cooled wall tube to which hematite is adhered by scanning the probe in the direction of water flow outside the water-cooled wall tube before chemical cleaning.

<Measurement process>
Ultrasonic measurement of a water-cooled wall tube is performed at predetermined time intervals during the cleaning process. The measurement value (the thickness of the water-cooled wall tube) acquired in the measurement process is transmitted to the determination unit.

<Judgment process>
When hematite is eluted and removal proceeds, the measured value decreases, and when hematite is completely removed, the ultrasonic measured value becomes constant as the wall thickness of the water-cooled wall tube without adhesion of hematite. The determination unit determines the removal status of hematite from the time change of the measurement value by the ultrasonic wave.

<Through basic tests and simulations, it is possible to predict the thickness of the water-cooled wall tube, which indicates that the attached hematite has sufficiently eluted. The wall thickness obtained by the basic test or simulation is stored in the determination unit as a determination criterion indicating that hematite has been removed. In this case, when the determination unit determines that the wall thickness measured in the measurement process is equal to or less than the determination criterion, the determination unit terminates the cleaning process in the control unit 104 as hematite is eluted and removed, which will be described later. The discharge process is carried out.

Alternatively, hematite removal may be determined from the amount of change in the measured thickness value. When hematite is sufficiently eluted, the difference between the wall thickness value obtained in the measurement process and the wall thickness value obtained in the previous measurement process is gradually reduced. From this, the change amount of the wall thickness change gradient, which is the inclination of the wall thickness change per unit time, is stored in the determination unit as a determination criterion, and the determination unit sets the change amount of the wall thickness change gradient to a value within a predetermined range. If it is determined that the hematite is eluted and removed, the determination unit causes the control unit 104 to end the cleaning process and to perform a discharge process described later.

Specific determination is performed based on the same idea as the method described in (1) Determination based on iron concentration in the cleaning liquid. Also in the case of ultrasonic measurement, the criterion is ± 20%. Moreover, when the precipitation of hematite in the apparatus 10 to be cleaned is relatively uniform, the determination accuracy can be improved by setting the determination criterion to ± 10%.

When it is determined that the wall thickness value measured in the measurement process does not reach the determination criterion, or when it is determined that the change amount of the wall thickness change gradient is larger than the predetermined range, the determination unit is a control unit In 104, the cleaning process is continued.

(3-B) AC Electrical Characteristic Measurement Before chemical cleaning, an electrical characteristic evaluation device 140 is installed outside the water-cooled wall tube in the area where hematite is adhered as shown in FIG. Two terminals 141 are installed apart from each other in the axial direction of the water-cooled wall tube 13 (13a, 13b), and an LCR meter 142 is installed between the terminals 141. The distance between the tips of the terminals 141 is set to about 1 m to 5 m so that it can be easily distinguished from the DC electric resistance of the water-cooled wall tube 13 (13a, 13b). Instead of the LCR meter 142, a network analyzer may be installed.

<Measurement process>
During the cleaning process, AC electric characteristics of the water-cooled wall tube are measured at predetermined time intervals.
FIG. 11 is a circuit diagram when the electrical property evaluation apparatus 140 is installed as shown in FIG. The water-cooled wall tube 13 and the cleaning liquid inside the water-cooled wall tube are represented as resistors R1 and R3, respectively. The region 17 to which hematite is attached is represented by resistors R2a and R2b and capacitor capacitances C1 and C2.

Hematite (oxide) is a resistance component. As hematite removal progresses, the capacitance of the hematite (C1 and C2) decreases, so the reactance of the circuit decreases. The LCR meter 141 measures the reactance of the water-cooled wall tube 13 at a predetermined time interval. The reactance value acquired in the measurement process is transmitted to the determination unit.

<Judgment process>
As the hematite removal proceeds, the measured value of the reactance decreases, and when the hematite is completely removed, the measured reactance becomes constant. The determination unit determines a removal state in which hematite is eluted from the change in reactance with time.

∙ Reactance of the water-cooled wall tube, which indicates that the attached hematite has sufficiently eluted, can be predicted by basic tests and simulations. The reactance obtained by the basic test or the simulation is stored in the determination unit as a determination criterion indicating that hematite has been removed. In this case, when the determination unit determines that the reactance measured in the measurement process is equal to or less than the determination criterion, the determination unit terminates the cleaning process in the control unit 104, assuming that hematite is eluted and removed, and will be described later. The discharge process is carried out.

Alternatively, hematite removal may be determined from the amount of change in the reactance measurement. When hematite is sufficiently eluted, the difference between the reactance obtained in the measurement process and the reactance obtained in the previous measurement process is gradually reduced. The amount of change in reactance change gradient per unit time is stored in the determination unit as a criterion, and hematite is eluted and removed when the determination unit determines that the amount of change in reactance change gradient is within a specified range. As a result, the determination unit causes the control unit 104 to finish the cleaning process and to perform a discharge process described later.

Specific determination is performed based on the same idea as the method described in (1) Determination based on iron concentration in the cleaning liquid. Even when measuring AC electrical characteristics, the criterion is ± 20%. Moreover, when the precipitation of hematite in the apparatus 10 to be cleaned is relatively uniform, the determination accuracy can be improved by setting the determination criterion to ± 10%.

When it is determined that the reactance measured in the measurement process does not reach the determination criterion, or when it is determined that the change amount of the reactance change gradient is larger than the predetermined range, the determination unit performs cleaning to the control unit 104. Continue the process.

<Discharge process>
The control unit 104 opens the valve V2. The cleaning liquid in the water-cooled wall pipes 13a and 13b is fed from the lower headers 14a and 14b to the chemical liquid tank 101 via the chemical liquid discharge line 103 and collected. Thereby, the chemical cleaning method of this embodiment is completed.
If the rust remover remains in the recovered cleaning solution, the cleaning component (the concentration of the rust remover) may be readjusted and reused for the next chemical cleaning.

According to the above method, since the cleaning liquid containing the neutral rust remover is used, the inner surfaces of the water-cooled wall tubes 13a and 13b immersed in the cleaning liquid corrode even if the cleaning process is carried out in the soaking state. Hematite can be dissolved in the cleaning solution without doing so.
As described with reference to FIGS. 5 and 6, in this embodiment, since it is not a method of separating and removing hematite by eluting a magnetite layer which is a natural oxide scale, generation of sludge is suppressed. In particular, in the thermal power generation system 1, since the pipe shape of the water-cooled wall pipe of the once-through boiler 10 is long and complicated, when sludge is generated, the sludge may accumulate in the middle of the pipe and block the inside of the pipe. If hematite is dissolved in the cleaning liquid and removed from the water-cooled wall tubes 13a and 13b as in the present embodiment, the hematite eluted with the discharge of the cleaning liquid after chemical cleaning can be discharged. Therefore, for example, in the thermal power generation system 1 adopting the present embodiment, a facility for removing sludge such as a filter is unnecessary, and a process such as another cleaning for removing sludge is also unnecessary.

[Second Embodiment]
FIG. 12 is a schematic view illustrating a chemical cleaning apparatus according to the second embodiment.
In the chemical cleaning apparatus 200 according to the second embodiment, the chemical solution supply line 202 and the chemical solution discharge line 203 are connected to the lower headers 14a and 14b of the once-through boiler 10 as in the first embodiment. The chemical solution supply line 202 and the chemical solution discharge line 203 are connected to the chemical solution tank 201. An exhaust line 213 is connected to the upper headers 15a and 15b of the once-through boiler.

The chemical cleaning apparatus 200 includes a reducing atmosphere gas supply unit 210 as a reducing atmosphere adjustment unit on the downstream side of the pump 205 of the chemical solution supply line 202. The reducing atmosphere gas supply unit 210 is connected to the control unit 204.

The reducing atmosphere gas supply unit 210 of the second embodiment is a microbubble generator. A microbubble generator is an apparatus that injects bubbles into a liquid. In the present embodiment, the gas injected into the liquid (cleaning liquid) as bubbles is the reducing atmosphere gas listed in the first embodiment.

Although not shown in FIG. 12, a reducing atmosphere gas storage section and an air supply line connected to the once-through boiler 10 may be installed as in FIG.

A chemical cleaning method using the chemical cleaning apparatus 200 of the second embodiment will be described below. Also in the present embodiment, when the chemical cleaning method is performed, a valve installed in a pipe connecting the once-through boiler 10 and the economizer 26 is closed.

<Cleaning liquid supply process / gas supply process>
The control unit 204 closes the valve V2. The control unit 204 activates the pump 205 and the reducing atmosphere gas supply unit 210 and opens the valve V1. The cleaning liquid in the chemical tank 201 is conveyed to the reducing atmosphere gas supply unit 210 via the chemical supply line 202. The reducing atmosphere gas supply unit 210 injects bubbles of the reducing atmosphere gas into the cleaning liquid. The cleaning liquid containing bubbles is supplied to the water-cooled wall tubes 13a and 13b of the once-through boiler 10 via the chemical liquid supply line 202.

Bubbles in the cleaning liquid are discharged from the cleaning liquid in the water-cooled wall pipes 13a and 13b and stored in the upper space of the cleaning liquid supplied in the water-cooled wall pipes 13a and 13b. The control unit 204 opens the valve V4, and the air in the water-cooled wall tubes 13a and 13b is discharged outside the system through the exhaust line 213. In this way, the inside of the water-cooled wall pipes 13a and 13b is replaced from the purge gas atmosphere to the reducing atmosphere gas.

Thus, in the second embodiment, an independent gas supply step is not required as in the first embodiment, and the gas replacement in the water-cooled wall tubes 13a and 13b is performed together with the cleaning liquid supply step.

<Washing process>
When at least a region to which hematite has adhered (particularly region 17 to which hematite has adhered more than the other portion) is immersed in the cleaning liquid, the control unit 204 stops the pump 205 and the reducing atmosphere gas supply unit 210 and switches the valves V1 and V4. Close. In the state where the cleaning liquid is allowed to stand, the hematite is soaked and cleaned. Also in this embodiment, the cleaning liquid in the water-cooled wall tubes 13a and 13b is at the same level as the ambient temperature around the water-cooled wall tubes 13a and 13b, and the oxidation-reduction potential is −0.8 V or more on the basis of the silver-silver chloride electrode. It is maintained at 0.4V or less.

In the present embodiment, the end of the cleaning step is the same as in the first embodiment, (1) the iron concentration in the cleaning liquid, (2) the color change of the hematite adhering portion, (3) the analysis of the internal state from the outside of the water-cooled wall tube It is determined based on one of the results. When the determination unit determines that hematite is eluted and removed in the determination process, the determination unit causes the control unit 104 to end the cleaning process and to perform the discharge process.

<Discharge process>
The cleaning liquid in the water-cooled wall tubes 13a and 13b is collected in the chemical liquid tank 201 in the same process as in the first embodiment. Thereby, the chemical cleaning method of this embodiment is completed.

When a cleaning liquid that does not contain an antifoaming agent is used in the chemical cleaning methods of the first and second embodiments, the cleaning liquid is foamed by supplying the cleaning liquid to the water-cooled wall tubes 13a and 13b, and bubbles are generated in the region where hematite is generated. A sticky cleaning solution adheres. Detergency is improved by increasing the contact time between hematite and the foam-like cleaning liquid. Moreover, the usage-amount of a cleaning liquid reduces by making a cleaning liquid into foam.

[Third Embodiment]
FIG. 13 is a schematic view illustrating a chemical cleaning apparatus according to the third embodiment.
In the chemical cleaning apparatus 300 of the third embodiment, the chemical liquid supply line 302 and the chemical liquid discharge line 303 are connected to the lower headers 14a and 14b of the once-through boiler 10 as in the first embodiment. The chemical solution supply line 302 and the chemical solution discharge line 303 are connected to the chemical solution tank 301.

The chemical cleaning apparatus 300 includes a reducing atmosphere adjusting agent supply unit 310 as a reducing atmosphere adjusting unit. The reducing atmosphere adjusting agent supply unit 310 includes a reducing atmosphere adjusting agent storage unit 311 and a reducing atmosphere adjusting agent supply line 312. The reducing atmosphere adjusting agent storage unit 311 stores the reducing atmosphere adjusting agent. The reducing atmosphere adjusting agent is, for example, hydrazine, L-ascorbic acid, sulfur-based reducing agent and the like.
The reducing atmosphere adjusting agent supply unit 310 is connected to the chemical solution supply line 302 on the downstream side of the pump 305. A valve V5 is installed in the reducing atmosphere adjusting agent supply line 312. The valve V5 is connected to the control unit 304.

Although not shown in FIG. 13, a reducing atmosphere gas storage unit, an air supply line, and an exhaust line connected to the once-through boiler 10 may be installed as in FIG.

A chemical cleaning method for cleaning and removing hematite adhering to the once-through boiler using the chemical cleaning apparatus 300 of the third embodiment will be described below. In carrying out the chemical cleaning method of the present embodiment, a valve installed in a pipe connecting the once-through boiler 10 and the economizer 26 is closed.

<Cleaning liquid supply process>
The control unit 304 closes the valve V2. The control unit 304 activates the pump 305 and opens the valves V1 and V5. While the cleaning liquid in the chemical liquid tank 301 passes through the chemical liquid supply line 302, the reducing atmosphere adjusting agent is introduced into the cleaning liquid from the reducing atmosphere adjusting agent supply unit 310. The cleaning liquid charged with the reducing atmosphere adjusting agent is fed to the water-cooled wall tubes 13 a and 13 b of the once-through boiler 10.

<Washing process>
When at least the region to which hematite is attached is immersed in the cleaning liquid, the control unit 304 stops the pump 305 and closes the valves V1 and V5. In the state where the cleaning liquid is allowed to stand, the hematite is soaked and cleaned.

Also in the present embodiment, the cleaning liquid in the water-cooled wall tubes 13a and 13b is at the same level as the ambient temperature around the water-cooled wall tubes 13a and 13b. By introducing the reducing atmosphere adjusting agent from the reducing atmosphere adjusting agent supply unit 310 into the cleaning liquid, the oxidation-reduction potential of the cleaning liquid is maintained at −0.8 V or more and −0.4 V or less with respect to the silver-silver chloride electrode. The control unit 304 adjusts the opening of the valve V5 in order to obtain a reducing atmosphere adjusting agent input amount that provides a steam oxidation-reduction potential.

In the present embodiment, the end of the cleaning step is the same as in the first embodiment, (1) the iron concentration in the cleaning liquid, (2) the color change of the hematite adhering portion, (3) the analysis of the internal state from the outside of the water-cooled wall tube It is determined based on one of the results. When the determination unit determines that hematite is eluted and removed in the determination process, the determination unit causes the control unit 104 to end the cleaning process and to perform the discharge process.

<Discharge process>
In the same process as in the first embodiment, the cleaning liquid in the water-cooled wall pipes 13 a and 13 b is collected in the chemical liquid tank 301 via the chemical liquid discharge line 303. Thereby, the chemical cleaning method of this embodiment is completed.

When a large amount of hematite adheres, the oxidation-reduction potential fluctuates greatly due to the dissolution of hematite. By additionally adding a reducing atmosphere adjusting agent to the cleaning liquid as in this embodiment, the oxidation-reduction potential can be easily adjusted within the range of −0.8 to −0.4V.

[Fourth Embodiment]
FIG. 14 is a schematic view illustrating a chemical cleaning apparatus according to the fourth embodiment.
Similarly to the chemical cleaning apparatus of the first embodiment, the chemical cleaning apparatus 400 according to the fourth embodiment is a chemical tank 401, a chemical supply line 402, a chemical discharge line 403, a control unit 404, a pump 405, and a reducing atmosphere gas supply unit 410. As a reducing atmosphere gas storage unit 411, an air supply line 412, and an exhaust line 413.
In the chemical cleaning apparatus 400, a circulation loop 406 is installed across the pump 405 of the chemical solution supply line 402.
A circulation loop can also be provided for the chemical cleaning apparatuses of the second embodiment and the third embodiment.

The temperature of the cleaning liquid rises by passing through the pump 405 in the cleaning liquid supply process. Part of the cleaning liquid that has passed through the pump 405 flows into the circulation loop 406 and is conveyed to the chemical liquid sharing line upstream of the pump 405. By doing so, the heated cleaning liquid is supplied to the water-cooled wall tubes 13a and 13b of the once-through boiler 10, and the temperature is higher than that of the first to third embodiments (specifically, the water-cooled wall tube). The cleaning step is performed at a temperature higher than the ambient temperature around 13a and 13b and less than or equal to ambient temperature + 10 ° C.

The higher the temperature of the cleaning process, the more the reaction between the cleaning liquid and hematite and the dissolution in the cleaning liquid are promoted. According to this embodiment, the temperature of the cleaning liquid can be increased with a simple configuration without installing a temperature increasing facility. Further, since the temperature difference between the environmental temperature and the cleaning liquid temperature is small, the configuration of the present embodiment can maintain the temperature of the cleaning liquid higher than the environmental temperature for a long time. As a result, the cleaning power can be further increased.

Also in this embodiment, the end of the cleaning process is determined by the same method as in the first embodiment.

[Fifth Embodiment]
FIG. 15 is a schematic view illustrating a chemical cleaning apparatus according to the fifth embodiment.
Similar to the chemical cleaning apparatus of the first embodiment, the chemical cleaning apparatus 500 according to the fifth embodiment is a chemical tank 501, a chemical supply line 502, a chemical discharge line 503, a control unit 504, a pump 505, and a reducing atmosphere gas supply unit 510. As a reducing atmosphere gas storage section 511, an air supply line 512, and an exhaust line 513.
The chemical cleaning apparatus 500 further includes a water supply unit 520. The water supply unit 520 includes a water tank 521 and a water supply line 522. The water tank 521 contains water therein. A water supply pump 523 and a valve V6 are installed in the water supply line 522. The water supply line 522 is connected to the lower headers 14a and 14b.

A chemical cleaning method for cleaning and removing hematite adhered in the once-through boiler using the chemical cleaning apparatus 500 of the fifth embodiment will be described below. In carrying out the chemical cleaning method of the present embodiment, a valve installed in a pipe connecting the once-through boiler 10 and the economizer 26 is closed.

<Gas supply process>
In the same process as in the first embodiment, the reducing atmosphere gas is supplied from the reducing atmosphere gas storage unit 511 through the air supply line 512 into the water-cooled wall tubes 13a and 13b, and the water-cooled wall tubes 13a and 13b are reduced in the reducing atmosphere gas. Filled with.

<Cleaning liquid supply process>
The control unit 504 activates the pump 505 and opens the valves V1 and V4. The cleaning liquid in the chemical liquid tank 501 is supplied to the once-through boiler 10 via the chemical liquid supply line 502.

After the predetermined amount of cleaning liquid has been supplied, the control unit 504 stops the pump 505 and closes the valve V1. Next, the control unit 504 activates the water-filled pump 523 and opens the valve V6. As a result, the water in the water tank 521 is supplied to the water-cooled wall pipes 13 a and 13 b of the once-through boiler 10 through the water supply line 522.

By adjusting the flow rate of the cleaning liquid and water, the water cooling wall is in a state where the cleaning liquid layer is on the upper side in the vertical direction, the water layer is on the lower side in the vertical direction, and the cleaning liquid layer and the water layer are at least partially separated. The water level in the pipes 13a and 13b rises. In the present embodiment, the control unit 504 supplies a predetermined amount of cleaning liquid and water respectively to the chemical solution so that the region 17 where hematite adheres more than the other portions in the water-cooled wall tubes 13a and 13b is immersed in the cleaning liquid layer. The water is supplied from the tank 501 and the water tank 521 to the water-cooled wall pipes 13a and 13b.

<Washing process>
When the region 17 where hematite adheres more than the other part is immersed in the cleaning liquid, the control unit 504 stops the water-filled pump 523 and closes the valves V4 and V6. The hematite is soaked and washed in a state where the washing liquid is left still. Also in the present embodiment, the temperature of the cleaning liquid during the cleaning process is approximately the same as the ambient temperature around the water-cooled wall tubes 13a and 13b, and the oxidation-reduction potential of the cleaning liquid during the cleaning process is −0.8 V or more and −0.4 V or less. (Silver-silver chloride electrode standard).

In this embodiment, it is necessary to ensure that the cleaning liquid layer and the water layer are separated during the cleaning process. Therefore, the end of the cleaning process is determined based on either (2) color change of the hematite adhering portion described in the first embodiment, or (3) the analysis result of the internal state from the outside of the water-cooled wall tube. . When the determination unit determines that hematite is eluted and removed in the determination step, the determination unit causes the control unit 104 to end the cleaning step and cause the discharge step to be performed.

<Discharge process>
The cleaning liquid in the water-cooled wall tubes 13a and 13b is supplied to the chemical liquid tank 501 in the same process as in the first embodiment. Thereby, the chemical cleaning method of this embodiment is completed.
The cleaning liquid collected in the chemical tank 501 has a reduced rust remover concentration. Therefore, a new cleaning liquid is added and the cleaning liquid is reused, or the cleaning liquid is discharged from the chemical liquid tank 501 and discarded.

According to the method of the present embodiment, since the region 17 where hematite adheres more than the other part is immersed in the cleaning liquid and concentratedly removed, the amount of the cleaning liquid to be used can be greatly reduced. Cleaning costs can be reduced.

[Sixth Embodiment]
The chemical cleaning apparatus of the sixth embodiment has the same configuration as that of the first embodiment except that the cleaning liquid contains microcapsules.
A microcapsule is one in which the above-described cleaning liquid is packaged in a water-soluble capsule. The capsule material of the microcapsule is a water-soluble polymer such as dextrin, processed starch, gelatin, gum arabic, sodium alginate, and carrageenan. The size of the microcapsule is, for example, about 0.5 mm to 2 mm in diameter. The microcapsules are produced by, for example, a spray drying method, a spray cooling method, or the like.

In the chemical cleaning apparatus of the sixth embodiment, a microcapsule supply unit is installed on the upstream side of the pump 105 of the chemical solution supply line 102. The microcapsule supply unit has a tank that accommodates the microcapsules. The microcapsules are stored in a tank in a state of being dispersed in a transport liquid (for example, water).

In the sixth embodiment, the gas supply process, the cleaning liquid supply process, the cleaning process, and the discharge process are performed in the same manner as in the first embodiment. In the cleaning liquid supply process of the sixth embodiment, in the cleaning liquid in which the transport liquid including the microcapsules circulates through the chemical liquid supply line 102 by the activation of the pump installed in the flow path connecting the microcapsule supply unit and the chemical liquid supply line 102. The cleaning liquid containing the microcapsules is supplied to the water-cooled wall tubes 13a and 13b. The microcapsules move upward in the water-cooled wall tubes 13a and 13b and accumulate near the liquid surface. When the capsule of the microcapsule is dissolved in the transport liquid, the cleaning liquid is released, and a foam-like cleaning liquid layer is formed in the vicinity of the liquid surface. In particular, the dispersion concentration of the microcapsules (amount of cleaning liquid) and the liquid surface height (amount of transport liquid supplied by the control unit 104) are set so that the region 17 where hematite adheres more than the other part is immersed in the cleaning liquid layer. Adjust as appropriate.

According to the method of this embodiment, since the region where hematite is generated more than the other part can be easily immersed in the cleaning liquid, the amount of the cleaning liquid to be used can be further greatly reduced, and the cleaning cost is further increased. It is possible to reduce.

The sixth embodiment can also be applied to the chemical cleaning methods and chemical cleaning apparatuses of the second to fifth embodiments.

[Seventh Embodiment]
A chemical cleaning method according to the seventh embodiment will be described using the chemical cleaning apparatus 100 of FIG. In the chemical cleaning method of the seventh embodiment, the gas supply process, the cleaning liquid supply process, and the discharge process are performed in the same manner as in the first embodiment except for the cleaning process.

In the cleaning step of the chemical cleaning method of the seventh embodiment, when the region to which hematite is attached is immersed in the cleaning liquid, the control unit 104 stops the pump 105 and closes the valves V1 and V4.

The control unit 104 opens the valve V2. Since the cleaning liquid is fed back to the chemical liquid tank 101 via the chemical liquid discharge line 103 by opening the valve V2, the liquid level of the cleaning liquid in the water-cooled wall pipes 13a and 13b is lowered. Next, the control unit 104 closes the valve V2 and opens the valve V1 to start the pump 105. Thereby, the cleaning liquid in the chemical liquid tank 101 is supplied to the water-cooled wall pipes 13a and 13b of the once-through boiler 10 through the chemical liquid supply line 102, and the liquid level of the cleaning liquid in the water-cooled wall pipes 13a and 13b rises. The control unit 104 performs the discharge and supply of the cleaning liquid at a predetermined cycle.

The discharge amount of the cleaning liquid here may be a part or all of the cleaning liquid. If the discharge amount of the cleaning liquid is changed, the change amount of the liquid level can be changed. The discharge amount of the cleaning liquid, that is, the amount of change in the liquid level is preferably set appropriately in consideration of the size of the region where hematite adheres more than the other part, the cleaning efficiency, and the like. The control unit 104 discharges and feeds a predetermined amount of cleaning liquid according to the liquid level change amount.
Moreover, the period which repeats discharge | emission and supply of a washing | cleaning liquid, and a stationary period may be implemented alternately alternately.

When the discharge and the supply of the cleaning liquid are repeated, the cleaning liquid is agitated in the vicinity of the liquid surface in the water-cooled wall tubes 13a and 13b, and a flow rate is given to the cleaning liquid. As a result, the cleaning power is improved, and the cleaning efficiency of hematite is increased.

In the present embodiment, the end of the cleaning process is the same as in the first embodiment in (1) the iron concentration in the cleaning liquid, (2) the color change of the hematite adhering portion, and (3) the internal state from the outside of the water-cooled wall tube. The determination is made based on one of the analysis results. When the determination unit determines that hematite is removed in the determination step, the determination unit causes the control unit 104 to end the cleaning step and cause the discharge step to be performed.

Furthermore, in the present embodiment, (4) the end of the cleaning process may be determined based on the pressure change.
(4) Determination Based on Pressure Change In the determination based on the pressure change signal, as shown in FIG. 16, a pressure gauge 150 is installed in the middle of the chemical liquid discharge line 103.

During the feeding process in the above washing process, the rotational speed of the pump 105 or the opening of the valve V1 is increased or decreased at a predetermined frequency. By doing so, the feed amount of the cleaning liquid increases and decreases at a predetermined frequency, so that the liquid level of the cleaning liquid vibrates in the water-cooled wall tubes 13a and 13b.

<Measurement process>
In the discharge process in the above-described cleaning process, the pressure gauge 150 measures the pressure of the cleaning liquid passing through the chemical liquid discharge line 103. The pressure value is transmitted to the determination unit.

<Judgment process>
When the liquid level of the cleaning liquid is vibrated by the feeding process, the pressure measured by the pressure gauge 150 in the discharge process periodically changes to reflect the vibration state of the liquid level. This change in pressure varies depending on the state of hematite adhesion. That is, when the removal of hematite proceeds by cleaning, the friction coefficient between the cleaning liquid and hematite changes, so that the pressure change varies with time. When the hematite is removed from the water-cooled wall pipe, the frequency of the cleaning liquid feeding in the feeding process matches the frequency of the pressure change in the discharging process. For this reason, the difference between the phase of the periodic cleaning liquid feeding during the feeding process and the phase of the pressure change during the discharging process becomes constant.

The determination process is performed in one of the following two steps.
(Step 4-A)
As illustrated in FIG. 17, the determination unit acquires the waveform of the feeding amount during the feeding process and the waveform of the change in the pressure value acquired in the measurement process. The determination unit compares the waveform of the supply amount with the waveform of the pressure change to determine the removal state in which hematite is eluted.

Specifically, the difference (phase difference, shown in FIG. 17) between the phase of the waveform of the feeding amount and the phase of the waveform of the pressure change when the attached hematite is sufficiently eluted is predicted by basic tests and simulations. be able to. The phase difference obtained by the basic test or simulation is stored in the determination unit as a determination criterion indicating that hematite has been removed. In this case, when the determination unit determines that the phase difference measured in the measurement process is equal to or less than the determination reference, the determination unit causes the control unit 104 to finish the cleaning process and discharge the hematite, assuming that the hematite is eluted and removed. Let the process run.

Alternatively, hematite removal may be determined from the amount of change in phase difference. When hematite is sufficiently eluted, the difference between the obtained phase difference and the previously obtained phase difference gradually decreases. The change amount of the phase difference change gradient, which is the slope of the change in phase difference per unit time, is stored in the determination unit as a determination criterion, and the determination unit determines that the change amount of the phase difference change gradient has become a value within a predetermined range. In the case where the determination is made, the determination unit causes the control unit 104 to finish the cleaning process and to perform a discharge process described later.

Specific determination is performed based on the same idea as the method described in (1) Determination based on iron concentration in the cleaning liquid. Even when the determination is made using the phase difference, the determination criterion is ± 20%. Moreover, when the precipitation of hematite in the apparatus 10 to be cleaned is relatively uniform, the determination accuracy can be improved by setting the determination criterion to ± 10%.

When it is determined that the phase difference is larger than the criterion, or when it is determined that the change amount of the phase difference change gradient is larger than the predetermined range, the determination unit causes the control unit 104 to continue the cleaning process.

(Step 4-B)
The determination unit acquires a waveform of a change in pressure value acquired in the measurement process, and determines a hematite removal status from a change over time such as a period and an amplitude of the waveform.

Specifically, the period and amplitude of the pressure waveform when adhering hematite is sufficiently eluted can be predicted by basic tests and simulations. The period or amplitude obtained by the basic test or simulation is stored in the determination unit as a determination criterion indicating that hematite has been removed. In this case, when it is determined that the period or amplitude is equal to or less than the determination criterion, the determination unit causes the control unit 104 to end the cleaning process and perform the discharge process, assuming that hematite is eluted and removed.

Alternatively, the removal of hematite may be determined from the amount of change in period or amplitude. If hematite is sufficiently eluted, the difference between the period or amplitude change obtained by the measurement process and the period or amplitude change obtained last time is gradually reduced. The change amount of the periodic change gradient or the amplitude change gradient, which is the inclination of the periodic change or amplitude change per unit time, is stored as a determination criterion in the determination unit, and the determination unit determines whether the change amount of the periodic change gradient or the change amount of the amplitude change gradient is If it is determined that the value is within the predetermined range, the determination unit causes the control unit 104 to end the cleaning process and to perform a discharge process described later, assuming that hematite is eluted and removed.

Specific determination is performed based on the same idea as the method described in (1) Determination based on iron concentration in the cleaning liquid. Even in the case of determination using the period or amplitude, the determination criterion is ± 20%. Moreover, when the precipitation of hematite in the apparatus 10 to be cleaned is relatively uniform, the determination accuracy can be improved by setting the determination criterion to ± 10%.

When it is determined that the period or amplitude is larger than the determination criterion, or when it is determined that the change amount of the periodic change gradient or the change amount of the amplitude change gradient is larger than the predetermined range, the determination unit cleans the control unit 104. Continue the process.

Note that the chemical cleaning method of the present embodiment can also be applied to the case where the chemical cleaning apparatus of the second to fourth embodiments is used.

[Eighth Embodiment]
FIG. 18 is a schematic view illustrating a chemical cleaning apparatus according to the eighth embodiment.
Similar to the chemical cleaning apparatus of the first embodiment, the chemical cleaning apparatus 600 according to the eighth embodiment is a chemical liquid tank 601, a chemical liquid supply line 602, a chemical liquid discharge line 603, a control unit 604, a pump 605, and a reducing atmosphere gas supply unit 610. As a reducing atmosphere gas storage section 611, an air supply line 612, and an exhaust line 613. The chemical cleaning apparatus 600 further includes a pump 606 in the chemical solution discharge line 603. The chemical liquid discharge line 603 may be provided with a pressure gauge that measures the pressure of the cleaning liquid flowing through the chemical liquid discharge line 603.
A chemical cleaning method according to the eighth embodiment will be described with reference to FIG. In the chemical cleaning method of the eighth embodiment, the gas supply process, the cleaning liquid supply process, and the discharge process are performed in the same manner as in the first embodiment except for the cleaning process.

In the cleaning step in the chemical cleaning method of the eighth embodiment, when the region to which hematite is attached is immersed in the cleaning liquid, the control unit 604 stops the pump 605 of the chemical liquid supply line 602 and closes the valves V1 and V4.

Control unit 604 opens valves V2 and V3 and operates pump 606. When the valve V3 is opened, the reducing atmosphere gas is supplied from the reducing atmosphere gas storage unit 111 to the water-cooled wall pipes 13a and 13b of the once-through boiler 10 through the supply line 112, and the gas pressure in the space above the cleaning liquid level increases. To do. At the same time, when the valve V2 is opened and the pump 606 is activated, the cleaning liquid in the water-cooled wall pipes 13a and 13b is supplied to the chemical liquid tank 601 through the chemical liquid discharge line 603, and the liquid level of the cleaning liquid in the water-cooled wall pipes 13a and 13b. Decreases.

Next, the control unit 604 closes the valves V2 and V3 and opens the valves V1 and V4. The control unit stops the pump 606 and starts the pump 605. Thereby, the cleaning liquid in the chemical liquid tank 601 is supplied to the water-cooled wall pipes 13a and 13b of the once-through boiler 10 via the chemical liquid supply line 602, and the liquid level of the cleaning liquid in the water-cooled wall pipes 13a and 13b rises.

Since the pressurization of the cleaning liquid level with gas and the discharge of the cleaning liquid using a pump are utilized, the flow rate when the cleaning liquid is discharged is higher than that in the seventh embodiment, and the liquid level in the water-cooled wall tubes 13a and 13b The cleaning liquid is easily stirred. For this reason, a cleaning power improves rather than 7th Embodiment and the cleaning efficiency of hematite rises.

In this embodiment, the end of the cleaning process is the same as in the seventh embodiment in (1) iron concentration in the cleaning liquid, (2) color change of the hematite adhering portion, (3) internal state from the outside of the water-cooled wall tube. The determination is made based on one of the analysis result and (4) pressure change signal. When the determination unit determines that hematite is removed in the determination step, the determination unit causes the control unit 104 to end the cleaning step and cause the discharge step to be performed.

The chemical cleaning apparatus and chemical cleaning method of the present embodiment can also be applied to the case where a pump is installed in the chemical solution discharge line as compared with the second to fourth embodiments.

[Ninth Embodiment]
FIG. 19 is a schematic view for explaining a chemical cleaning apparatus according to the ninth embodiment.
Similar to the chemical cleaning apparatus of the first embodiment, the chemical cleaning apparatus 700 according to the ninth embodiment is a chemical tank 701, a chemical supply line 702, a chemical discharge line 703, a control unit 704, a pump 705, and a reducing atmosphere gas supply unit 710. As a reducing atmosphere gas storage unit 711, an air supply line 712, and an exhaust line 713. The chemical cleaning apparatus 700 further includes a circulation line 720.
A similar circulation line can be installed for the chemical cleaning apparatuses of the second to fourth embodiments.

The circulation line 720 is connected to the lower headers 14a and 14b as one end side of the once-through boiler and to the upper headers 15a and 15b as the other end side. A circulation pump 721 is installed in the middle of the circulation line 720. The circulation line 720 and the circulation pump 721 may be temporarily installed.
An extraction portion 722 is installed on the downstream side of the circulation pump 721.

The circulation direction of the cleaning liquid is not particularly limited. In the configuration of FIG. 19, the cleaning liquid is circulated through the water-cooled wall pipes 13a and 13b from the bottom to the top. However, the cleaning liquid may be circulated from the top to the bottom.

In this embodiment, the temperature of the cleaning liquid is close to the environmental temperature, and the circulating flow rate may be a small flow rate that circulates at least once during the cleaning process. Therefore, the discharge pressure of the circulation pump 721 may be low.

A chemical cleaning method using the chemical cleaning apparatus 700 of the ninth embodiment will be described below. In the chemical cleaning method of the ninth embodiment, the gas supply process and the discharge process are performed in the same manner as in the first embodiment.

<Cleaning liquid supply process>
The control unit 704 activates the pump 705 and opens the valves V1 and V4. The cleaning liquid in the chemical liquid tank 701 is supplied to the once-through boiler 10 via the chemical liquid supply line 702. In the ninth embodiment, the cleaning liquid is supplied to all of the lower header, the water-cooled wall tube, the upper header, and the circulation line 720 in the once-through boiler 10. The control unit 704 stores an amount of cleaning liquid that can immerse all of the lower header, the water-cooled wall tube, the upper header, and the circulation line 720, and supplies a predetermined amount of cleaning liquid to the once-through boiler 10 in the cleaning liquid supply process.

Here, the valve installed in the pipe connecting the once-through boiler 10 and the steam separator 30 is closed. By doing so, the cleaning liquid can be prevented from flowing into the steam separator 30 which is a device adjacent on the downstream side of the once-through boiler 10.

<Washing process>
When a predetermined amount of cleaning liquid is supplied to the once-through boiler 10, the control unit 704 stops the pump 705 and closes the valves V1 and V4. Next, the control unit 704 activates the circulation pump 721. When the circulation pump 721 is activated, the cleaning liquid passes through the lower headers 14a and 14b, the water-cooled wall tubes 13a and 13b, the upper headers 15a and 15a, and the circulation line 720. That is, in the present embodiment, the cleaning liquid is circulated without flowing into other equipment (the economizer 26 and the steam separator 30) adjacent to the once-through boiler 10. Circulation is performed at a flow rate that allows the cleaning liquid to circulate between the once-through boiler 10 and the circulation line 720 at least once during the cleaning process.

In addition, you may increase / decrease the rotation speed of the circulation pump 721 with a predetermined period. By doing so, the flow rate of the cleaning liquid flowing through the water-cooled wall tubes 13a and 13b varies, and the cleaning performance is further improved.

Also, the temperature of the cleaning liquid is raised when passing through the circulation pump 721. For this reason, for example, as compared with the case where the cleaning liquid is allowed to stand during the cleaning process as in the first embodiment (specifically, higher than the environmental temperature around the water-cooled wall tubes 13a and 13b, the environmental temperature + 10 ° C. The cleaning step is performed in the following).

During the cleaning process, the flow path of the cleaning liquid (the lower headers 14a and 14b, the water-cooled wall pipes 13a and 13b, the upper headers 15a and 15b, and the circulation line 720) constitutes a closed space. The potential is maintained at −0.8 V or more and −0.4 V or less (silver-silver chloride electrode standard).

In the present embodiment, the end of the cleaning step is the same as in the first embodiment, (1) the iron concentration in the cleaning liquid, (2) the color change of the hematite adhering portion, (3) the analysis of the internal state from the outside of the water-cooled wall tube As a result, (4) it is determined based on one of the pressure changes.
(1) In the case of determination based on the iron concentration in the cleaning liquid, the iron concentration may be measured by collecting the cleaning liquid in the chemical tank 701 as in the first embodiment. Alternatively, a part of the cleaning liquid that passes through the circulation line 720 may be collected from the extraction unit 722 and used for iron concentration measurement.

(4) In the case of determination based on pressure change, a pressure gauge is installed in the circulation line 720 as in the seventh embodiment. The operation of increasing or decreasing the rotation speed of the circulation pump 721 at a predetermined frequency is performed, and using the pressure value measured by the pressure gauge installed in the circulation line 720, the same idea as described in the seventh embodiment, The determination unit determines a removal situation in which hematite is eluted.

When the determination unit determines that hematite has been removed in the determination step, the determination unit causes the control unit 104 to end the cleaning step and cause the discharge step to be performed.

According to this embodiment, a flow rate is given to the cleaning liquid, the cleaning liquid is stirred, and further, the cleaning liquid is heated during the cleaning process. Therefore, the cleaning power is improved as compared with the first embodiment in which no circulation line is provided, and hematite The cleaning efficiency increases.

DESCRIPTION OF SYMBOLS 1 Thermal power generation system 10,10a, 10b Through- flow boiler 11a, 11b Combustion chamber 12a, 12b Wall surface 13,13a, 13b Water-cooled wall pipe 14a, 14b Lower header 15a, 15b Upper header 16 Branch part 100,200,300,400 , 500, 600, 700 Chemical cleaning apparatus 101, 201, 301, 401, 501, 601, 701 Chemical liquid tank 102, 202, 302, 402, 502, 602, 702 Chemical liquid supply line 103, 203, 303, 403, 503 603, 703 Chemical solution discharge line 104, 204, 304, 404, 504, 604, 704 Control unit 105, 205, 305, 405, 505, 605, 606, 705 Pump 110, 210, 410, 510, 610, 710 Reducing atmosphere Gas supply part 111,411,511, 11,711 Reducing atmosphere gas storage part 112,412,512,612,712 Air supply line 113,213,413,513,613,713 Exhaust line 120 Cut specimen 121 Transparent plate 122 Space 130 Bypass part 131 Bypass pipe 132 Tube Test piece 140 Electrical characteristic evaluation device 150 Pressure gauge 310 Reducing atmosphere adjusting agent supply unit 311 Reducing atmosphere adjusting agent storage unit 312 Reducing atmosphere adjusting agent supply line 406 Circulation loop 520 Water supply unit 521 Water tank 522 Water supply line 523 Water-tight pump 720 Circulation line 721 Circulation pump 722 Extraction part

Claims (18)

1. A cleaning liquid supply step in which a cleaning liquid containing a rusting agent that is a chelating agent, a reducing agent, or a mixture of the chelating agent and the reducing agent is supplied to a device to be cleaned having a member to which hematite is attached;
   A cleaning step in which at least the region where the hematite is adhered in the member is immersed in the cleaning liquid, and the oxidation-reduction potential of the cleaning liquid is maintained at a value at which the hematite is eluted in the cleaning liquid, and the hematite is removed from the member And
   The chelating agent is any one of an aminocarboxylic acid chelating agent, an oxycarboxylic acid chelating agent and an organic phosphorus chelating agent,
   The reducing agent is any one of metal ions, sulfites, oxalic acid, formic acid, ascorbic acid, pyrogallol, hydrazine, and hydrogen;
   A chemical cleaning method wherein the pH of the cleaning liquid is within a range of 4 to 8.
2. The chemical cleaning method according to claim 1, wherein the cleaning step is performed while the value is maintained within a range of -0.8 V or more and -0.4 V or less based on a silver-silver chloride electrode.
3. The chemical cleaning method according to claim 1 or 2, wherein the value is adjusted by supplying a reducing atmosphere gas to the device to be cleaned.
4. The chemical cleaning method according to any one of claims 1 to 3, wherein a temperature of the cleaning liquid in the cleaning step is in a range from an ambient temperature around the member to a temperature not higher than 10 ° C higher than the ambient temperature. .
5. The chemical cleaning method according to any one of claims 1 to 4, wherein the region is immersed in the cleaning liquid in a state where the cleaning liquid is left standing.
6. During the cleaning step, the step of discharging the cleaning liquid from the member and the step of supplying the discharged cleaning liquid to the member are repeated to increase the level of the cleaning liquid near the region. The chemical cleaning method according to claim 1, wherein the chemical cleaning method is moved.
7. The cleaning liquid passes through the member and is discharged from the upstream end of the member during the cleaning step, and the discharged cleaning liquid is circulated directly to the downstream end of the member. The chemical cleaning method according to claim 4.
8. A measuring step in which the iron concentration in the cleaning liquid is measured;
   A determination step of determining the removal status of the hematite from the member based on the iron concentration,
   The cleaning liquid is discharged from the cleaning target device during the cleaning process, and the iron concentration in the cleaning liquid discharged in the measurement process is measured,
   The cleaning process is terminated when the iron concentration is determined to be equal to or higher than a predetermined concentration in the determination step, or when the change amount of the concentration gradient is determined to be a value within a predetermined range. The chemical cleaning method according to claim 4.
9. A chemical cleaning apparatus for chemically cleaning a device to be cleaned having a member to which a hematite scale is attached,
   A chelating agent, a reducing agent, or a mixture of the chelating agent and the reducing agent, and the chelating agent is one of an aminocarboxylic acid chelating agent, an oxycarboxylic acid chelating agent and an organophosphorus chelating agent In addition, the reducing agent contains a derusting agent that is any one of metal ions, sulfites, oxalic acid, formic acid, ascorbic acid, pyrogallol, hydrazine, and hydrogen, and contains a cleaning solution having a pH in the range of 4-8. A chemical tank,
   A chemical supply line for connecting the cleaning target device and the chemical tank and supplying the cleaning liquid to the member;
   A pump installed in the chemical supply line;
   A chemical solution discharge line for connecting the cleaning target device and the chemical solution tank, and discharging the cleaning solution from the member;
   Means for immersing at least the region of the member to which the hematite is adhered in the cleaning liquid;
   Means for maintaining the redox potential of the cleaning liquid during cleaning at a value at which the hematite elutes in the cleaning liquid;
   The chemical cleaning apparatus, wherein the chemical liquid tank, the chemical liquid supply line, and the pump are means for supplying the cleaning liquid to the member.
10. 10. The chemical cleaning apparatus according to claim 9, further comprising a reducing atmosphere adjusting unit that adjusts the value to a value within a range of −0.8 V to −0.4 V based on a silver-silver chloride electrode.
11. The chemical cleaning apparatus according to claim 9 or 10, wherein the reducing atmosphere adjusting unit supplies a reducing atmosphere gas to the cleaning target device.
12. 12. The chemical cleaning according to claim 9, wherein the temperature of the cleaning liquid supplied to the member is in a range of an ambient temperature around the member and a temperature that is 10 ° C. higher than the ambient temperature. apparatus.
13. A circulation loop connecting the upstream chemical liquid supply line and the downstream chemical liquid supply line across the pump;
    The chemical cleaning apparatus according to any one of claims 9 to 12, wherein a part of the cleaning liquid that has passed through the pump is conveyed to the upstream side of the pump through the circulation loop.
14. The chemical cleaning apparatus according to any one of claims 9 to 13, wherein during the cleaning, the supply of the cleaning liquid to the member and the discharge of the cleaning liquid from the member are stopped, and the cleaning liquid is allowed to stand still.
15. The water supply part provided with the water tank which accommodates water, the water supply line which connects the said water tank and the said washing | cleaning object apparatus, and the water supply pump installed in the said water supply line is further provided. Item 15. The chemical cleaning device according to any one of Item 14.
16. During the cleaning, the cleaning liquid in the member is discharged toward the chemical liquid tank through the chemical liquid discharge line, and the cleaning liquid in the chemical liquid tank is supplied to the member through the chemical liquid supply line. The chemical cleaning apparatus according to any one of claims 9 to 12.
17. A circulation section comprising a circulation line connecting the upstream end and the downstream end of the member, and a circulation pump installed in the circulation line;
    The chemical cleaning apparatus according to any one of claims 9 to 12, wherein the cleaning liquid discharged from the front downstream end through the circulation line is circulated to the upstream end through the circulation line.
18. The iron in the cleaning liquid discharged from the cleaning target device while cleaning the cleaning target device while maintaining the redox potential of the cleaning liquid of the cleaning target device at a value at which the hematite elutes in the cleaning solution. When the removal state in which the hematite elutes from the member is determined based on the concentration and the iron concentration is determined to be equal to or higher than the predetermined concentration, or when the change amount of the concentration gradient is determined to be a value within the predetermined range The chemical cleaning apparatus according to claim 9, further comprising a determination unit that finishes cleaning the device to be cleaned.
    
    

Images