KR20210034040A - Cleaning storage method and cleaning storage device of boiler plant - Google Patents

Abstract

It is an object of the present invention to provide a cleaning storage method and a cleaning storage device for a boiler plant capable of performing rust prevention treatment on a portion to be cleaned of a boiler in a short period of time from chemical cleaning to the start of normal operation at low cost and in a short time. do. The storage method of the boiler plant of the present disclosure includes a step (S2) of neutrally cleaning a portion to be cleaned with scale adhered at room temperature with a neutral washing liquid containing a dehumidifying agent (S2), and an ammonia-based compound is included in the portion to be cleaned. A step (S4) of circulating an aqueous ammonia compound solution having a pH of 9.8 or higher at room temperature (S4) and a step (S5) of blowing an aqueous ammonia compound solution from a portion to be cleaned are provided.

Description

Cleaning storage method and cleaning storage device of boiler plant

The present disclosure relates to a cleaning storage device for cleaning and storing a boiler plant and a cleaning storage method thereof.

When a boiler plant equipped with a boiler having a drum and a heat recovery boiler (HRSG) is stored for several days due to shutdown, etc., dissolved oxygen in the feed water or boiler water becomes a corrosion factor of the boiler plant components. Therefore, during storage of the boiler plant, corrosion is prevented by using an anticorrosive agent (refer to Patent Document 1). As the anticorrosive agent, hydrazine having deoxidation ability and the like are used.

Conventionally, during storage such as stopping the operation of a boiler plant, the operating water (water supply and boiler water) in the boiler plant components is replaced with hydrazine as storage water, and when the boiler plant is restarted, the storage water, hydrazine, is operated. There are cases where the work is being done to replace it with water.

A large amount of pure water is used for the replacement of hydra water and running water. Drainage treatment is required to dispose of hydration water and running water discharged from replacement work. Therefore, the replacement of the hydration water and the running water becomes a factor that increases the load of the wastewater treatment facility.

Furthermore, hydrazine has a problem in the drainage treatment of conversion to driving water, such as a carcinogenic substance. For this reason, it is possible to convert the storage water into operation water without using hydrazine and without draining the storage water, and the use of a storage method of a boiler plant capable of preventing corrosion of plant components over several days or longer has become desirable.

As a method of preventing corrosion of boiler plant components without using hydrazine, it is known to adjust the concentration of ammonia added to feed water and boiler water, and increase the pH of feed water and boiler water as storage water (Patent Document 2). When the pH of feed water and boiler water is set to 9.8 or more, it becomes possible to prevent corrosion in plant components without adding hydrazine during storage of the boiler plant. For example, if the pH of feed water and boiler water is set to 10, the boiler plant can be stored without adding hydrazine.

In addition, Patent Document 3 discloses a cleaning method of a heat recovery boiler in which cleaning is performed at a low temperature (no heating/room temperature) using a cleaning liquid containing a neutral anti-rusting agent.

Patent Document 4 discloses a cleaning method in which a heated cleaning liquid is circulated in a heat transfer tube while the exhaust gas supply port and the exhaust gas outlet of a heat recovery boiler are closed.

Japanese Patent Laid-Open Publication No. 62-233606 Japanese Patent Publication No. 2014-159925 Japanese Patent Publication No. 2015-105786 Japanese Patent Laid-Open No. Hei 11-37405

The heat recovery boiler consists of a plurality of steam drums and evaporators. In the case of washing a plurality of parts, as shown in Fig. 12, the cleaning liquid from the cleaning facility 30 is put from the water supply system into the economizer 31, the steam drum 32, and the evaporator 33, and the cleaning is performed. There is a way to do it.

It is common for the evaporator of the heat recovery boiler to employ a fin tube with a high amount of heat dissipation. However, in the cleaning method using the heated cleaning liquid as in Patent Document 4, for example, it is difficult to maintain the temperature of the cleaning liquid at a high temperature (50°C to 90°C) due to heat radiation from the fin tube, so that the cleaning effect is lowered. do. As a countermeasure against this, in Patent Document 3, the evaporator is cleaned without heating the cleaning liquid to a high temperature by using a neutral detergent.

13 shows a process chart of a conventional chemical cleaning method. In the conventional chemical cleaning method, first, a temporary system is connected to the cleaning object (S31). Next, after chemical cleaning (S32) at a high temperature (50°C to 90°C), the cleaning solution is blown (S33), and the cleaning solution is washed with water (S34).

Because scale is removed by chemical cleaning treatment and the exposed base material easily reacts with oxygen, the inner surface of the heat transfer tube is in a state prone to rust. After washing with water, a little rust occurs, so the generated rust is washed with a rinse solution (a light-concentration acid) (S35, 20°C to 90°C). After that, the inside of the system is neutralized (S36, 20°C to 90°C), hydration is added to rust prevention treatment (S37, 80°C to 90°C) to form a rust prevention film on the inner surface of the heat transfer tube, and then blown (S38). . Finally, the hypothetical system is dismantled (S39).

In the anti-rust treatment, for the purpose of preventing rust from occurring during the period from washing to normal operation, hydration is added and the anti-rust treatment is performed at 80°C to 90°C. However, in the rust prevention treatment at a low temperature as in Patent Document 3, a sufficient rust prevention film is not formed. In an insufficient state, rust may occur on the inner surface of the heat transfer tube after the rust prevention treatment liquid is blown. The occurrence of rust on the inner surface of the heat transfer pipe is not preferable from the viewpoint of the quality of cleaning work, water quality during operation, and reliability of equipment.

It is also possible to think of anti-rust treatment in which the system is filled with storage water containing a high concentration of ammonia, but the storage water must be subtracted for the dismantling work of the temporary system. Therefore, filling water with storage water may not be desirable from the viewpoint of the degree of freedom of construction (partial separation of the system, restoration of the separated location).

The present disclosure has been made in view of the above problems, and cleaning of a boiler plant capable of storing a boiler by performing rust prevention treatment on a portion to be cleaned of a boiler at low cost and in a short time in the period from chemical cleaning to the start of normal operation. It is an object of the present invention to provide a storage method and a cleaning storage device.

In order to solve the above problems, the cleaning storage method and cleaning storage device of the boiler plant of the present disclosure employ the following means.

In the first aspect of the present disclosure, a step of neutrally washing a portion to be cleaned with scale adhered at room temperature with a neutral washing liquid containing a deodorant, and a pH of 9.8 or more containing an ammonia-based compound in the portion to be cleaned. There is provided a cleaning and storage method for a boiler plant comprising a step of circulating an aqueous ammonia compound solution at room temperature and a step of blowing the aqueous ammonia compound solution from the portion to be cleaned.

According to the first aspect, since the washing is performed at room temperature, the temperature raising facility and the preheating step of the washing liquid are unnecessary, and monitoring of the decrease in the temperature of the washing liquid due to standing cooling in the washing step becomes unnecessary. Thereby, cleaning cost and cleaning time can be reduced. In addition, "room temperature" means about room temperature, and is a temperature at which preheating or heating is not performed from the outside. Specifically, it is 5°C to 50°C, more preferably 15°C to 30°C.

After the scale is removed, an aqueous ammonia compound solution having a pH of 9.8 or higher is circulated on the surface of the base material of the area to be cleaned, and then the aqueous ammonia compound solution is blown from the area to be cleaned, and the surface is covered with an ammonia-containing water film. Thereby, it becomes possible to suppress the occurrence of rust during the period until the start of operation. The main component of the ammonia-containing water film is ammonia water, which is the same as the feed water treatment chemical used in the operation of the boiler plant. In this respect, since it is not necessary to remove the ammonia-containing water film at the start of operation, after storing the boiler plant, operation can be started as it is. Thereby, the working time can be shortened, and the cost can also be reduced. In addition, since hydrazine is not used and rust generation can be suppressed, environmental properties are excellent.

In the first aspect, in the neutral washing step, the neutral washing solution is circulated in the portion to be cleaned, and iron ions in the circulated neutral washing solution are analyzed, and the iron ion concentration change in the neutral washing solution is After confirming that the saturation tendency was exhibited, it is preferable to terminate the neutral washing.

The change in the iron ion concentration in the cleaning liquid tends to be saturated means that the scale to be cleaned is removed and the amount of scale dissolved therein is lowered. By confirming this and determining the end of cleaning, the maximum cleaning effect can be obtained in the shortest possible time.

In the first aspect, it is preferable to provide a step of acid washing at room temperature with an acidic washing liquid before the step of circulating the ammonia-based compound aqueous solution.

Depending on the operation of the plant, scale components include calcium (Ca), aluminum (Al), copper (Cu), and the like. Since Ca, Al, and Cu have low solubility in the vicinity of neutrality, in low-temperature cleaning using a neutral detergent, it may not be possible to dissolve and remove all of these scale components. The scale that could not be removed may remain in the system as sludge. The remaining sludge can be partially discharged out of the system by blowing or washing with the cleaning liquid after washing, but it is difficult to discharge the entire amount and may remain in the system. In particular, in the vertical gas flow type heat recovery boiler, the heat transfer tube is arranged horizontally, and the length is also as large as 20 m, so it is difficult to discharge sludge at the flow rate of water during washing and discharge (blow). Attention is needed. The remaining sludge becomes a factor of deterioration of the heat transfer performance of the heat transfer pipe and the occurrence of corrosion due to the sludge-containing components.

In pickling, these scale components (Ca, Al, Cu, etc.), which are difficult to dissolve in the neutral washing liquid, can be removed, and the residual amount of sludge to the portion to be cleaned can be reduced.

In the first aspect, in the acid washing step, the acidic washing solution is circulated in the portion to be cleaned, and iron ions in the circulated acidic washing solution are analyzed, and the iron ion concentration change in the acidic washing solution is After confirming that the saturation tendency was exhibited, it is preferable to complete the pickling.

In the first aspect, after the acid washing, a step of extruding and blowing the acidic washing liquid using the aqueous ammonia-based compound solution is further provided, and in the extrusion blowing step, the acidic washing liquid is After blowing about the entire amount, circulating the aqueous ammonia-based compound solution in the area to be cleaned, the pH of the aqueous ammonia-based compound solution was analyzed, and the extrusion blown and the ammonia were performed until the analyzed pH became more than a reference value. It is preferable to continue the circulation of the system compound aqueous solution.

In extrusion blow, an acidic washing solution is extruded with an aqueous ammonia compound to replace it. By judging the duration of extrusion blowing based on the pH of the blow liquid, there is no need to waste extra time.

In the first aspect, further comprising a step of extrusion-blowing the neutral washing liquid using the ammonia-based compound aqueous solution after the neutral washing, and in the extrusion blowing step, the neutral washing liquid in the extrusion blow After blowing approximately the entire amount and circulating the aqueous ammonia-based compound solution in the area to be cleaned, the component derived from the antioxidant in the aqueous ammonia-based compound solution was analyzed, and the concentration of the component derived from the analyzed antioxidant was below the reference value. It is preferable to continue the circulation of the extrusion blow and the aqueous ammonia-based compound solution until it becomes possible.

In extrusion blown, a neutral washing liquid is extruded with an aqueous ammonia-based compound to replace it. It is determined that the duration of extrusion blown is judged by the decrease in the concentration of the component derived from the deodorizing agent in the blown liquid, and there is no need to waste extra time.

In the first aspect, after the step of blowing the aqueous ammonia-based compound solution, a solid of a vaporizable ammonia compound may be introduced into a portion to be cleaned.

The injected solid of the vaporizable ammonia compound vaporizes in the area to be cleaned, diffuses rapidly, and is introduced into the ammonia-containing water film. When the portion to be cleaned is stored for a long time after the formation of the ammonia-containing water film, the ammonia component escapes from the ammonia-containing water film, but the rust-preventing effect of the water film can be maintained by introducing a solid of a vaporizable ammonia compound.

In the first aspect, at least one of the acidic washing liquid and the neutral washing liquid may be filtered during circulation.

Sludge can be removed by filtering the circulating washing liquid. As a result, since the residual amount of sludge generated during washing can be reduced, it is possible to reduce the risk of deterioration of the heat transfer performance of the heat transfer pipe due to the residual sludge and the occurrence of corrosion due to the sludge-containing components.

In the first aspect, the portion to be cleaned may be used as an evaporator of a heat recovery boiler. By limiting the portion to be cleaned to the evaporator, the amount of the cleaning liquid used can be suppressed and the amount of drainage can be reduced.

A second aspect of the present disclosure includes a circulation unit configured to circulate a fluid within a portion to be cleaned to which a scale is attached, a neutral cleaning solution supply unit supplying a neutral cleaning solution containing an anti-rusting agent to the circulation unit, and ammonia to the circulation unit. There is provided a cleaning and storage device for a boiler plant having an ammonia-based compound aqueous solution supply unit for supplying an ammonia-based compound aqueous solution containing the compound-based compound with a pH of 9.8 or higher, and a blow passage for discharging the ammonia-based compound aqueous solution from the circulation unit.

In the second aspect, the circulation portion includes a circulation flow path having both ends connected to the entrance of the portion to be cleaned, a pump provided in the middle of the circulation flow path, and a filtering device provided in the middle of the circulation flow path downstream of the pump, You may have it.

In the second aspect, one end is connected to at least one of the circulation unit and the inlet and the outlet of the portion to be cleaned, and the other end is connected to at least any of the acidic cleaning solution supply unit, the neutral cleaning solution supply unit, and the ammonia-based compound aqueous solution supply unit. You may further comprise the blown flow path which was made.

According to the second aspect, since the blown liquid can be returned to at least any of the acidic cleaning liquid supplying unit, the neutral cleaning solution supplying unit, and the ammonia-based compound aqueous solution supplying unit, the installation of the drainage tank can be omitted.

According to the present disclosure, a cleaning storage method and a cleaning storage device of a boiler plant capable of storing a boiler by performing rust prevention treatment of a portion to be cleaned of a boiler at low cost and in a short time in a period from chemical cleaning to the start of normal operation. do.

1 is a process chart of a washing storage method according to a first embodiment.
2 is a graph illustrating the amount of sludge in neutral washing.
Fig. 3 is a schematic diagram of a change in a cleaning time and a concentration of Fe ions in a neutral cleaning solution in the first embodiment.
4 is a schematic diagram of an ammonia-containing water film.
5 is a schematic diagram when washing a specific area.
6 is a process chart of the washing storage method according to the second embodiment.
7 is a graph illustrating the amount of sludge in acid washing and neutral washing in the second embodiment.
Fig. 8 is a schematic diagram of the transition of the cleaning time and the concentration of Fe ions in the cleaning liquid in the second embodiment.
9 is a process chart of a washing storage method according to a third embodiment.
10 is a schematic diagram showing an example of a washing storage device.
11 is a schematic diagram showing an example of a washing storage device.
12 is a schematic diagram at the time of washing a plurality of parts.
13 is a flowchart of a conventional chemical cleaning method.

Hereinafter, an embodiment of a cleaning storage method and a cleaning storage device for a boiler plant according to the present disclosure will be described with reference to the drawings.

In the following embodiment, the cleaning storage method of the heat recovery boiler is illustrated. In each step of the cleaning storage method according to the following embodiment, the inside of the cleaning target device (cleaning target site) is cleaned without heating using a room temperature cleaning liquid. "Room temperature" means about room temperature, and is a temperature at which preheating or heating is not performed from the outside. The "room temperature" is specifically 5°C to 50°C, more preferably 15°C to 30°C.

[First embodiment]

Fig. 1 shows a process chart of a cleaning storage method of a boiler plant according to the present embodiment. The washing storage method according to the present embodiment includes step 1 (S1) to step 6 (S6) in order.

(S1) Temporary system (cleaning storage device) connection

First, a temporary system for supplying a cleaning liquid into the device to be cleaned is connected. Thereafter, the cleaning liquid or the like is injected into the device to be cleaned through a temporary system.

(S2) neutral washing

After injecting a neutral cleaning liquid containing an anti-rusting agent from the temporary system, the inside of the device to be cleaned is filled with a neutral cleaning liquid, and the neutral cleaning liquid is circulated into the system at room temperature. While circulating, the cleaning liquid is not heated.

The pH of the neutral washing liquid containing the dedusting agent is 4 to 8. The decontamination agent is a chelating agent, a reducing agent, or a mixture of a chelating agent and a reducing agent, and is a drug capable of removing objects to be removed (e.g., scale including metal oxides or metal salts, rust bumps, etc.) adhering to the interior of the device to be cleaned. . "Rust lump" is a lump-shaped corrosion product (refer to JIS Z0103 1050) occurring on the surface of steel. In the neutral cleaning liquid, the concentrations of a chelating agent, a reducing agent, and a corrosion inhibitor are appropriately adjusted so that desired cleaning ability and cleaning time can be obtained.

The chelating agent is, for example, EDTA, BAPTA, DOTA, EDDS, INN, NTA, DTPA, HEDTA, TTHA, PDTA, DPTA-OH, HIDA, DHEG, GEDTA, CMGA, aminocarboxylic acids such as EDDS, and salts thereof, etc. Aminocarboxylic acid-based chelating agents, oxycarboxylic acids such as citric acid, gluconic acid, and hydroxyacetic acid, and oxycarboxylic acid-based chelating agents such as salts thereof, and organic phosphoric acids such as ATMP, HEDP, NTMP, PBTC, and EDTMP, and salts thereof And organic phosphorus-based chelating agents. Examples of reducing agents include ^{various metal ions such as Fe 2+} and Sn ²⁺ , nitrites such as sodium sulfite, organic compounds such as oxalic acid, formic acid, ascorbic acid, and pyrogallol, hydrazine, hydrogen, and the like. A corrosion inhibitor may be added to the neutral washing liquid.

(S3) extrusion blow

After analyzing the Fe ions in the circulated neutral cleaning solution and confirming that the change in the concentration of Fe ions in the solution tends to be saturated, the neutral cleaning solution is extruded and blown while injecting an aqueous ammonia compound solution at room temperature into the device to be cleaned. do. The saturation tendency means that the variation width of the Fe ion concentration in the liquid becomes 100 mg/L or less as compared with the measured value of the Fe ion iron concentration in the previous liquid. The liquid amount of the aqueous ammonia compound solution used for extrusion blowing is, for example, about 1 to 1.5 times the capacity of the device to be cleaned.

The ammonia-based compound aqueous solution contains an ammonia-based compound at a concentration of a pH of 9.8 to 11, preferably a pH of 9.8 to 10.5. The ammonia-based compound is selected from, for example, 2-amino-2-methyl-1-propanol, monoethanolamine, monoisopropanolamine, cyclohexylamine, diethylethanolamine, morpholine, 3-methoxypropylamine, and ammonia. It is a volatile amine compound.

(S4) Circulation of ammonia-based compound aqueous solution

In the above (S3), after extruding and blowing approximately the entire amount of the neutral washing liquid with the aqueous ammonia compound solution, the extrusion blowing is temporarily stopped, and the aqueous ammonia compound solution in the washing object is circulated. During the circulation of the aqueous ammonia compound solution, the aqueous ammonia compound solution is not heated.

After circulating the aqueous ammonia-based compound solution, the aqueous ammonia-based compound solution is analyzed, and components derived from the deodorizing agent in the liquid are identified.

For example, when the neutral washing liquid contains organic phosphoric acid as a chelating agent, phosphorus (P) in an aqueous ammonia compound solution is analyzed. P analysis can be performed by a molybdenum blue absorption spectrophotometric method, ion chromatography, ICP mass spectrometry, atomic absorption spectrometry, or the like described in JIS K0102 Industrial Drainage Test Method 46.3 Total Phosphorus.

The above (S3) and (S4) are repeated until the component derived from the antioxidant in the liquid becomes equal to or less than the reference value. The reference value is set in advance by a preliminary test or the like. Confirm that the component derived from the antioxidant in the liquid is below the reference value.

(S5) Ammonia-based compound aqueous solution blow

After the above (S4), an aqueous ammonia compound solution is blown from the inside of the device to be cleaned, and an ammonia-containing water film is formed on the inner surface of the device to be cleaned. This ammonia-containing water film portion has an anti-rust effect.

(S6) Dismantling of the hypothetical system

After the above (S5), the hypothetical system is disassembled.

The washing in Steps 2 to 5 may be performed only once or may be performed multiple times.

When the apparatus to be cleaned is provided with a permanent cleaning storage device, the above (S1) and (S6) are omitted.

In Fig. 2, (S2) the amount of sludge (standard value) before and after neutral washing is illustrated. In the figure, the vertical axis is the amount of sludge remaining in the equipment to be cleaned. (S2) Only neutral washing can remove about 90% of sludge.

(S2) In neutral washing, Fe scale is dissolved and removed. Fig. 3 shows a schematic diagram of the transition of the cleaning time and the concentration of Fe ions in the cleaning liquid. In the figure, the horizontal axis represents the cleaning time, the vertical axis represents the Fe ion concentration, and the broken line represents the transition during neutral cleaning. In neutral washing, when washing proceeds to a certain extent, the scale to be cleaned is removed, the amount of Fe scale dissolved therein decreases, and the change in the concentration of Fe ions in the washing liquid tends to be saturated. In the above washing storage method, by confirming the saturation tendency of the change in Fe ion concentration and ending each washing step, it is possible to perform neutral washing in the minimum necessary time, avoiding continuation of washing more than necessary. Thereby, the extension of each washing time can be suppressed.

According to the washing and storage method, after washing the neutral washing liquid, the aqueous ammonia compound solution is circulated in the system, so that a high pH (9.8 or higher) ammonia-containing water film 11 is formed on the surface of the base material 10 of the device to be cleaned. Is formed (see Fig. 4). The water film portion having a high pH has a rust-preventing effect, and this effect continues until the restoration work of the temporary piping of the cleaning facility is completed after the ammonia-based compound aqueous solution is blown. Since the pH of the ammonia-containing water film 11 is 9.8 or more, it exhibits a rust-preventing effect even without hydrazine, so that hydrazine is unnecessary and is excellent in environmental properties.

When the assembly point restoration process of the cleaning facility temporary piping is lengthened and the opening time is lengthened, the ammonia component is removed from the ammonia-containing water film 11. Therefore, (S6) during dismantling of the temporary system, a solid material of a vaporizable ammonia compound may be further introduced into the equipment to be cleaned at room temperature and pressure, and ammonia gas may be replenished. The injected ammonia compound vaporizes rapidly and generates an ammonia-based gas. The ammonia-based gas diffuses into the system and dissolves in the ammonia-containing water film. Thereby, since the pH of the ammonia-containing water film 11 can be maintained high, a decrease in the rust-preventing effect of the ammonia-containing water film 11 due to a decrease in pH can be reduced.

The water film of the aqueous ammonia compound solution or the solid ammonia compound remaining at the start of operation is easily dissolved in the water for operation. In the heat recovery boiler, ammonia is used to adjust the pH of the feed water during operation. Since the ammonia-based compound aqueous solution used to form the water film in the above embodiment is mainly composed of ammonia, it is not necessary to remove it at the start of operation of the heat recovery boiler. Therefore, since the operation can be started as it is after storing the heat recovery boiler, the working time is shortened, and in addition to improving the operation rate of the plant, it is possible to reduce the cost of chemicals and wastewater treatment.

You may filter the neutral washing liquid in the middle of circulation. Thereby, since the amount of sludge remaining during washing can be reduced, it is possible to reduce the risk of deterioration of the heat transfer performance of the heat transfer pipe due to the remaining sludge and the occurrence of corrosion due to the sludge-containing components.

The cleaning storage method according to the above embodiment is suitable for cleaning the boiler water system of the exhaust heat recovery boiler. In particular, as shown in Fig. 5, specific cleaning is performed on the device to be cleaned in need of cleaning in a specific area where scale is likely to adhere (for example, a heat transfer tube of an evaporator where scale is easily adhered from temperature and pressure conditions). , It is more suitable because it is possible to reduce the amount of cleaning liquid used and the working time for cleaning.

[Second Embodiment]

6 shows a process chart of the cleaning and storage method of the boiler plant according to the present embodiment. This embodiment differs from the first embodiment in that the step of pickling is performed before neutral cleaning. The washing storage method according to the present embodiment includes step 11 (S11) to step 19 (S19) in order.

(S11) Temporary system (cleaning storage device) connection

As in (S1) of the first embodiment, first, a temporary system for supplying the cleaning liquid into the device to be cleaned is connected. Thereafter, the cleaning liquid or the like is injected into the device to be cleaned through a temporary system.

(S12) pickling

An acidic cleaning liquid is injected from the temporary system to fill the interior of the device to be cleaned with an acidic cleaning liquid, and then the acidic cleaning liquid is circulated in the device to be cleaned at room temperature. While circulating, the cleaning liquid is not heated. The acidic cleaning liquid may be an inorganic acid solution or an organic acid solution capable of dissolving Ca, Al, Cu, or the like. The pH of the acidic washing solution is preferably 4 or less, and more preferably 3 or less. For example, a 1 mass% to 10 mass% aqueous hydrochloric acid solution can be used as an acidic washing liquid.

(S13) Blowing of acidic cleaning solution

Iron (Fe) ions in the liquid of the circulated acidic cleaning liquid were analyzed, and after the saturation tendency of the change in the Fe ion concentration was confirmed, the cleaning liquid was blown to complete the pickling. The saturation tendency means that the variation width of the Fe ion concentration in the liquid becomes 100 mg/L or less as compared with the measured value of the Fe ion iron concentration in the previous liquid.

Iron ions in the liquid are phenanthroline absorption photometric method, frame atomic absorption method, electric heating atomic absorption method, or ICP emission spectroscopic analysis method, or a boiler according to JIS B8224 described in JIS K 0101 Industrial Water Test Method (60) iron (Fe). Water supply and boiler water-test method (26) 1,10-phenanthroline absorption photometric method described in iron (Fe), 2,4,6-tri-pyridyl-1,3,5-triazine (TPTZ) absorption photometric method , Frame atomic absorption method, electric heating atomic absorption method, ICP emission spectroscopy, or ICP mass spectrometry, sulfosalicil absorption photometric method, and the like. JIS is an abbreviation of Japanese Industrial Standard.

(S14) water washing

After filling the inside of the device to be cleaned with water, the water is circulated at room temperature to replace the acidic cleaning solution remaining in the device to be cleaned with water. This step may be omitted.

(S15) neutral washing

After the water in (S14) is blown, the interior of the device to be cleaned is filled with a neutral cleaning liquid containing a dehumidifying agent, and the neutral cleaning liquid is circulated in the system at room temperature. While circulating, the cleaning liquid is not heated. As the neutral washing liquid, the same thing as in the first embodiment can be used.

(S16) extrusion blow

In the same manner as in (S3) of the first embodiment, Fe ions in the solution of the circulated neutral cleaning solution were analyzed, and after it was confirmed that the change in the concentration of Fe ions in the solution tended to be saturated, an ammonia-based solution at room temperature in the apparatus to be cleaned. A neutral washing liquid is extruded and blown while injecting the aqueous compound solution. The aqueous ammonia-based compound solution may be the same as in the first embodiment.

(S17) Circulation of ammonia-based compound aqueous solution

In the same manner as in (S4) of the first embodiment, in (S16), approximately the entire amount of the neutral washing liquid is extruded and blown with an aqueous ammonia compound solution, then the extrusion blowing is temporarily stopped, and the aqueous ammonia compound solution in the device to be cleaned is removed. Cycle. During the circulation of the aqueous ammonia compound solution, the aqueous ammonia compound solution is not heated.

After circulating the aqueous ammonia-based compound solution, the aqueous ammonia-based compound solution is analyzed, and components derived from the deodorant in the liquid are identified.

The above (S16) and (S17) are repeated until the component derived from the antioxidant in the liquid becomes equal to or less than the reference value. The reference value is set in advance in a preliminary test, etc. Confirm that the component derived from the antioxidant in the liquid is below the reference value.

(S18) Ammonia-based compound aqueous solution blow

In the same manner as in (S5) of the first embodiment, after (S17), an aqueous ammonia compound solution is blown in the device to be cleaned, and a water film containing an ammonia is formed on the inner surface of the device to be cleaned. This ammonia-containing water film portion has an anti-rust effect.

(S19) Dismantling of the hypothetical system

Similar to (S6) of the first embodiment, the temporary system is dismantled after (S18).

The washing of Steps 12 to 18 of the washing storage method may be performed only once or may be performed multiple times.

When the apparatus to be cleaned is provided with a permanent storage device, the above (S11) and (S19) are omitted.

According to the cleaning and storage method, scales that are difficult to dissolve in neutral cleaning solutions such as Ca, Al, and Cu are removed by (S12) pickling, and then the sludge remaining in the equipment to be cleaned is removed by (S15) neutral cleaning. By using a neutral cleaning liquid, the remaining scale can be dissolved and removed while suppressing the corrosion of the base metal of the target device as much as possible, and the residual amount of sludge can be reduced.

Fig. 7 shows the sludge residual amount (standard value) in (S12) acid washing and (S15) neutral washing. In the figure, the vertical axis is the amount of sludge remaining in the equipment to be cleaned (before pickling is set to 100). As shown in Fig. 2, about 20% of the sludge remained in the acid washing at room temperature, but about 70% of the remaining 20% of the sludge was removed by neutral washing.

In both (S12) acid washing and (S15) neutral washing, Fe scale is also dissolved and removed. Fig. 8 shows a schematic diagram of the transition of the cleaning time and the concentration of Fe ions in the cleaning liquid. In the figure, the horizontal axis represents the cleaning time, the vertical axis represents the Fe ion concentration, the solid line represents the transition during pickling, and the broken line represents the transition during neutral cleaning. In acid washing and neutral washing, when washing proceeds to a certain extent, the scale to be cleaned is removed, the amount of Fe scale dissolved therein decreases, and the change in the concentration of Fe ions in the washing liquid tends to be saturated. In the washing storage method according to the present embodiment, by confirming the saturation tendency of the change in the Fe ion concentration and ending each washing step, it is possible to avoid continuing washing more than necessary, and to perform acid washing and neutral washing in the minimum necessary time. Thereby, the extension of each washing time can be suppressed.

According to the cleaning storage method according to the present embodiment, after washing the neutral cleaning solution, an aqueous ammonia compound solution is circulated in the system, so that a high pH (9.8 or more) ammonia-containing water film on the surface of the base material 10 of the device to be cleaned (11) is formed. The water film portion having a high pH has a rust-preventing effect, and this effect continues until the restoration work of the temporary piping of the cleaning facility is completed after the aqueous ammonia-based compound solution is blown. Since the pH of the ammonia-containing water film 11 is 9.8 or more, it exhibits a rust-preventing effect even without hydrazine, so that hydrazine is not required and is excellent in environmental properties.

When the assembly point restoration process of the cleaning facility temporary piping is lengthened and the opening time is lengthened, the ammonia component is removed from the ammonia-containing water film 11. Therefore, (S19) during the dismantling of the temporary system, a solid material of a vaporizable ammonia compound may be additionally introduced into the equipment to be cleaned at room temperature and pressure, and ammonia gas may be replenished. The injected ammonia compound vaporizes rapidly and generates an ammonia-based gas. The ammonia-based gas diffuses into the system and dissolves in the ammonia-containing water film. Thereby, since the pH of the ammonia-containing water film 11 can be kept high, a decrease in the rust-preventing effect of the ammonia-containing water film 11 due to a decrease in pH can be reduced.

The water film of the aqueous ammonia compound solution or the solid ammonia compound remaining at the start of operation is easily dissolved in the water for operation. In the heat recovery boiler, ammonia is used to adjust the pH of the feed water during operation. Since the ammonia-based compound aqueous solution used to form the water film in the above embodiment is mainly composed of ammonia, it is not necessary to remove it at the start of operation of the heat recovery boiler. Therefore, after storing the heat recovery boiler, the operation can be started as it is, so that the operation time is shortened, and in addition to improving the operation rate of the plant, it is possible to reduce the cost of chemicals and wastewater treatment.

At least one of the acidic washing liquid and the neutral washing liquid may be filtered during circulation. Thereby, since the residual amount of sludge at the time of washing can be reduced, it is possible to reduce the risk of deterioration of the heat transfer performance of the heat transfer pipe due to the residual sludge and the occurrence of corrosion due to the sludge-containing components.

The cleaning storage method according to the above embodiment is suitable for cleaning the boiler water system of the exhaust heat recovery boiler. In particular, as shown in Fig. 5, cleaning specific to a specific area where scale is likely to adhere to a device to be cleaned in need of cleaning (for example, a heat transfer tube of an evaporator where scale is likely to adhere from temperature and pressure conditions), It is more suitable because the amount of cleaning liquid used and the working time for cleaning can be reduced.

[Third Embodiment]

9 shows a process chart of the cleaning storage method of the boiler plant according to the present embodiment. This embodiment differs from the first and second embodiments in that the acid washing step is performed after neutral washing. The washing storage method according to the present embodiment includes step 21 (S21) to step 28 (S28) in order.

(S21) Temporary system (storage device) connection

As in (S1) of the first embodiment, first, a temporary system for supplying the cleaning liquid into the device to be cleaned is connected. Thereafter, the cleaning liquid or the like is injected into the device to be cleaned through a temporary system.

(S22) neutral washing

In the same manner as in (S2) of the first embodiment, a neutral cleaning liquid containing a dehumidifying agent is injected from the temporary system to fill the interior of the device to be cleaned with a neutral cleaning liquid, and then the neutral cleaning liquid is circulated in the system at room temperature. While circulating, the cleaning liquid is not heated. As the neutral washing liquid, the same thing as in the first embodiment can be used.

(S23) Blow a neutral cleaning solution

Iron (Fe) ions in the liquid of the circulated neutral cleaning liquid are analyzed, and when the saturation tendency of the change in the Fe ion concentration is confirmed, the cleaning liquid is blown to complete the neutral cleaning.

(S24) pickling

After blowing the neutral cleaning liquid in the above (S23), the interior of the equipment to be cleaned is filled with an acidic cleaning liquid containing a dehumidifying agent, and the acidic cleaning liquid is circulated in the system at room temperature. While circulating, the cleaning liquid is not heated. As the acidic cleaning liquid, the same thing as in the second embodiment can be used.

(S25) extrusion blow

After analyzing the Fe ions in the circulated acidic cleaning solution and confirming that the change in the concentration of Fe ions in the solution tends to be saturated, the neutral cleaning solution is extruded and blown while injecting an aqueous ammonia compound solution at room temperature into the device to be cleaned. do. The aqueous ammonia-based compound solution may be the same as in the first embodiment.

(S26) Circulation of ammonia-based compound aqueous solution

In the above (S25), approximately the entire amount of the acidic washing liquid with the aqueous ammonia compound solution is extruded and blown with the aqueous ammonia compound solution, then the extrusion blowing is temporarily stopped, and the aqueous ammonia compound solution in the apparatus to be cleaned is circulated. During the circulation of the aqueous ammonia compound solution, the aqueous ammonia compound solution is not heated.

After circulating the aqueous ammonia compound solution, the aqueous ammonia compound solution is analyzed to determine the pH value of the aqueous ammonia compound solution.

The above (S25) and (S26) are repeated until the pH of the aqueous ammonia-based compound solution reaches a reference value or higher. The reference value is set in advance in a preliminary test, etc. Confirm that the pH of the aqueous ammonia-based compound solution has reached the reference value or higher. The reference value is, for example, a pH of 9.8 or more that exhibits a rust-preventing effect even without hydrazine.

(S27) Ammonia-based compound aqueous solution blow

In the same manner as in (S5) of the first embodiment, after (S26), an aqueous ammonia compound solution is blown in the device to be cleaned, and an ammonia-containing water film is formed on the inner surface of the device to be cleaned. This ammonia-containing water film portion has an anti-rust effect.

(S28) Dismantling of the hypothetical system

Similar to (S6) of the first embodiment, the temporary system is dismantled after (S27).

The washing of Step 22 to Step 27 may be performed only once or may be performed a plurality of times.

Next, cleaning in the case where the equipment to be cleaned is an evaporator of the heat recovery boiler will be described with reference to FIGS. 10 and 11.

10 is a schematic diagram of a temporary system (washing storage device 2). In FIG. 10, the device to be cleaned is a heat transfer tube of the evaporator 1. In Fig. 10, only the inlet pipe header 1a and the outlet header 1b of the heat transfer pipe to which the cleaning and storage device 2 is connected are described for simplification of the drawing. In Fig. 10, an arrow entering the inlet pipe header 1a represents a connection from the evaporator drum, and an arrow exiting the outlet pipe header 1b represents a connection to the evaporator drum.

The washing storage device 2 includes a circulation unit 3, a chemical liquid tank 4, a chemical liquid pump 5, a replenishing water tank 6, a drain tank 7, and pipes L ₁ to L ₄ connecting them. We have. The circulation part 3 is provided with a circulation flow path (pipe L ₁ ) and a pump 8.

The circulation flow path (pipe L ₁ ) has one end connected to the inlet side (inlet pipe header 1a) of the heat transfer pipe, and the other end connected to the outlet side (outlet pipe header 1b) of the heat transfer pipe. A pump 8 is provided in the middle of the circulation passage (pipe L ₁ ), and is configured to circulate a cleaning liquid or the like in the heat transfer pipe. Valves V ₁ to V ₄ are provided in the circulation passage (pipe L _{1 ).}

The chemical liquid tank 4 is connected in the middle of a circulation flow path (pipe L _{1 ) via a pipe L 2 and a chemical liquid pump 5. Valve V 5} and valve V ₆ are arranged in the pipe L ₂ so as to insert the chemical liquid pump 5. In the chemical liquid tank 4, a chemical liquid to be circulated (acid, antioxidant, or ammonia-based compound aqueous solution) may be stored. The chemical liquid tank 4 may be a tank lorry including the chemical liquid tank 4. In FIG. 10, since there is one chemical liquid tank 4, the chemical liquid in the chemical liquid tank 4 is sequentially replaced.

The replenishing water tank 6 is connected to the circulation passage (pipe L ₁ ) through a pipe L _3. Valve V ₇ and valve V ₈ are arranged in pipe L _3. The connection position of the replenishment water tank 6 may be either upstream or downstream of the circulation flow of the connection position of the chemical liquid tank 4. Water such as pure water is stored in the replenishment water tank 6.

The drainage tank 7 is connected to a connection pipe (not shown) connected to the vicinity of both ends of the circulation flow path (pipe L _{1 ) through the pipes L 4} to L _{6 and} to the inlet pipe header 1a of the heat transfer pipe or the inlet pipe header of the heat transfer pipe. It is connected. Valve V ₉ and valve V ₁₀ are arranged in pipe L _4. Valve V ₁₁ and valve V ₁₂ are arranged in pipe L _5. Valve V ₁₃ and valve V ₁₄ are arranged in pipe L _6.

In the washing storage device 2 of FIG. 10, a filtration device 9 is provided in _{a circulation flow path (pipe L 1) on the circulation flow outlet stream side of the pump 8.} The filtering device 9 is a device that removes microsolids by filter or membrane filtration. By providing the filtration device 9, since the sludge generated in the neutral washing step or the pickling step can be recovered and the amount of sludge remaining during washing can be reduced, the risk of corrosion problems due to sludge remaining can be reduced.

In the washing storage device 2 of Fig. 10, since it operates at room temperature, a means for adjusting the temperature of the fluid is not provided.

11 is a schematic diagram of a temporary system (washing storage device 20) different from that of FIG. 10. Configurations common to those of FIG. 10 are denoted by the same reference numerals. In the washing storage device 20 of Fig. 11, a plurality of chemical liquid tanks 24a to 24c are connected in parallel, and drainage (blow liquid) is supplied to any of the chemical liquid tanks 24a to 24c instead of the drain tank 7 A return blow flow path L ₂₁ is provided. L blow passage ₂₁ has a valve V ₂₇ are arranged.

In Fig. 11, the replenishing water tank 6, the chemical liquid tank 24a, the valve V _25a , the valve V _26a , the chemical liquid pump 5, the pipe L ₂ and the valve V ₆ are an acid washing liquid supply part, the replenishing water tank 6, Chemical liquid tank (24b), valve V _25b , valve V _26b , chemical liquid pump (5), piping L ₂ and valve V ₆ are neutral washing liquid supply, replenishing water tank (6), chemical liquid tank (24c), valve V _25c , valve V _26c , the chemical liquid pump 5, the pipe L ₂ and the valve V ₆ are the ammonia-based compound aqueous solution supply units.

Acid is stored in the chemical liquid tank 24a. Neutral detergent is stored in the chemical liquid tank 24b. In the chemical liquid tank 24c, an aqueous ammonia compound solution is stored.

By providing the chemical liquid tanks 24a to 24c for each chemical liquid, the blown liquid in each step of the acidic washing liquid blowing, water washing, extrusion blowing, and the ammonia-based compound aqueous solution blowing can be returned to any of the chemical liquid tanks 24a to 24c.

In addition, the cleaning and storage devices 2 and 20 of FIGS. 10 and 11 can be used by being attached to a cleaning target device when in use, and a detachable type that can be separated from the cleaning target device when not in use, or It may be of any permanent type.

10 is applicable to the cleaning and storage method of the boiler plant of the first to third embodiments. 11 is applicable to the cleaning and storage method of the boiler plant of the first to third embodiments. Fig. 11 is particularly suitable for the cleaning and storage method of the boiler plant of the second and third embodiments.

1: evaporator
1a: inlet pipe header
1b: outlet pipe header
2: cleaning storage device
3: circulation part
4, 24a, 24b, 24c: chemical liquid tank
5: chemical liquid pump
6: fill water tank
7: drain tank
8: pump
9: Filtration device
10: base material
11: Ammonia-containing water film

Claims (12)

A step of neutrally cleaning the area to be cleaned with scale adhered to it at room temperature with a neutral cleaning solution containing a dehumidifying agent;
A step of circulating an ammonia-based compound aqueous solution at room temperature of pH 9.8 or higher containing an ammonia-based compound to the portion to be cleaned, and
A method for cleaning and storing a boiler plant, comprising a step of blowing the aqueous ammonia-based compound solution from the portion to be cleaned. The method according to claim 1, wherein in the neutral washing step,
Circulating the neutral cleaning solution in the area to be cleaned,
Analyze the iron ions in the circulated neutral washing liquid,
The cleaning storage method of a boiler plant, wherein the neutral cleaning is terminated after confirming that the change in the iron ion concentration in the neutral cleaning liquid exhibits a saturation tendency. The cleaning and storage method of a boiler plant according to claim 1 or 2, comprising a step of acid washing at room temperature with an acidic washing liquid before the step of circulating the aqueous ammonia compound solution. The method according to claim 3, wherein in the acid washing step,
Circulating the acidic cleaning solution in the area to be cleaned,
Analyze the iron ions in the circulated acidic washing solution,
The washing storage method of a boiler plant, wherein the acid washing is terminated after confirming that the change in the iron ion concentration in the acidic washing liquid exhibits a saturation tendency. The method according to claim 3 or 4, further comprising a step of extruding and blowing the acidic washing liquid using the aqueous ammonia-based compound after the acid washing,
In the extrusion blowing process,
In the extrusion blow, approximately the entire amount of the acidic cleaning solution is blown, and after circulating the aqueous ammonia compound solution in the area to be cleaned, the pH of the aqueous ammonia compound solution is analyzed,
A method for cleaning and storing a boiler plant, wherein circulation of the extrusion blow and the aqueous ammonia compound solution is continued until the analyzed pH becomes equal to or higher than a reference value. The method according to any one of claims 1 to 4, further comprising a step of extruding and blowing the neutral washing liquid using the aqueous ammonia-based compound after the neutral washing,
In the extrusion blowing process,
In the extrusion blow, approximately the entire amount of the neutral washing liquid is blown, and after circulating the aqueous ammonia-based compound solution in the area to be cleaned, the component derived from the antioxidant in the aqueous ammonia-based compound is analyzed,
A method for cleaning and storing a boiler plant in which the extrusion blow and the circulation of the aqueous ammonia compound are continued until the analyzed concentration of the component derived from the dehumidifying agent becomes equal to or less than a reference value. The cleaning and storage method of a boiler plant according to any one of claims 1 to 6, wherein after the step of blowing the aqueous ammonia-based compound solution, a solid of a vaporizable ammonia compound is introduced into the portion to be cleaned. The cleaning storage method for a boiler plant according to any one of claims 1 to 7, wherein at least one of the acidic cleaning liquid and the neutral cleaning liquid is filtered during circulation. The cleaning storage method for a boiler plant according to any one of claims 1 to 8, wherein the portion to be cleaned is used as an evaporator of a heat recovery boiler. A circulation unit configured to circulate a fluid within the area to be cleaned to which the scale is attached,
A neutral cleaning liquid supplying part for supplying a neutral cleaning liquid containing an anti-rusting agent to the circulation part,
An ammonia-based compound aqueous solution supplying unit for supplying an ammonia-based compound aqueous solution having a pH of 9.8 or higher containing an ammonia-based compound to the circulation unit;
Blow passage for discharging the aqueous ammonia compound solution from the circulation unit
A cleaning storage device of a boiler plant provided with a. The method of claim 10, wherein the circulation unit,
A circulation passage having both ends connected to the entrance of the portion to be cleaned,
A pump provided in the middle of the circulation flow path,
Filtration device provided in the middle of the circulation flow path downstream from the pump
A cleaning storage device of a boiler plant provided with a. 13. A cleaning storage device of a boiler plant connected to at least any one.

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