TW202041812A - Method and apparatus for cleaning and maintaining boiler plant - Google Patents

Abstract

The purpose of the present invention is to provide a method and an apparatus for cleaning and maintaining a boiler plant, by which, in a period between chemical cleaning and initiation of normal operation, it is possible to subject parts of a boiler to be cleaned to a rust-proofing treatment at low cost and in a short time, and to maintain the boiler. This method for maintaining a boiler plant includes: a step (S2) for subjecting parts to be cleaned, which have scale attached thereto, to neutral cleaning at room temperature using a neutral cleaning liquid containing a rust preventive agent; a step (S4) for circulating an aqueous solution of an ammonia-based compound having a pH of 9.8 or more at room temperature to the parts to be cleaned; and a step (S5) for blowing the aqueous solution of an ammonia-based compound from the parts to be cleaned.

Description

Cleaning storage method and cleaning storage device of boiler workshop

The present disclosure relates to a cleaning storage device for cleaning and storage of a boiler factory building and a cleaning storage method thereof.

If a boiler plant with a drum holding a boiler, a heat recovery boiler (HRSG), etc., is stored for several days, such as shutting down, the dissolved oxygen in the feed water or boiler water will become a corrosive element of the boiler plant The main reason. Therefore, when storing in a boiler plant, a corrosion inhibitor is used to prevent corrosion (refer to Patent Document 1). In terms of corrosion inhibitors, hydrazine with deoxidizing energy is used.

In the past, when the operation of the boiler plant was stopped, the operating water (feed water and boiler water) in the boiler plant components was replaced with hydrazine water as storage water, and when the boiler plant was restarted, An operator who replaces hydrazine water as storage water with working water.

A large amount of pure water is used in the replacement system of hydrazine water and operating water. The waste system of the hydrazine water and operating water discharged during the replacement operation requires drainage treatment. Therefore, the replacement of hydrazine water and operating water is a factor that increases the load on wastewater treatment facilities.

In addition, hydrazine-based carcinogens, etc., have a problem in the wastewater treatment that is switched to operating water. Therefore, it is more ideal to use a storage method for boiler plants that does not use hydrazine and can be converted to operating water without even draining the storage water and can prevent corrosion of the components of the plant for more than a few days.

In terms 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 to increase the pH of the feed water and boiler water used as storage water (see patent Literature 2). If the pH of feed water and boiler water is set to 9.8 or higher, even if hydrazine is not added during storage in the boiler plant, corrosion in the components of the plant can be prevented. For example, if the pH of feed water and boiler water is set to 10, even if hydrazine is not added, the boiler building can be kept.

In addition, Patent Document 3 discloses a cleaning method of an exhaust heat recovery boiler that uses a cleaning solution containing a neutral rust remover to perform cleaning at a low temperature (unheated/normal temperature).

Patent Document 4 discloses a cleaning method in which heated cleaning liquid is circulated into the heat transfer tube in a state where the exhaust gas supply port and the exhaust gas outlet of the exhaust heat recovery boiler are closed. [Prior Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 62-233606 [Patent Document 2] JP 2014-159925 A [Patent Document 3] JP 2015-105786 A [Patent Document 4] Japanese Patent Laid-Open No. 11-37405

(The problem to be solved by the invention)

The exhaust heat recovery boiler is composed of multiple steam drums and evaporators. If the plural parts are washed, there is a method of putting the washing liquid from the washing device 30 into the economizer 31, the steam drum 32, and the evaporator 33 from the water supply system as shown in Fig. 12 to perform washing. .

In the evaporator of the exhaust heat recovery boiler, a fin tube with high heat release is generally used. However, for example, in a cleaning method using a heated cleaning solution shown in Patent Document 4, it is difficult to maintain the temperature of the cleaning solution at a high temperature (50°C to 90°C) due to heat generation from the fin tube. The net effect is reduced. As a countermeasure against this, in Patent Document 3, a neutral rust remover is used to clean the evaporator without forming the cleaning liquid to a high temperature.

FIG. 13 shows the engineering diagram of the conventional chemical cleaning method. In the conventional chemical cleaning method, first, a temporary system is connected to the cleaning target (S31). Next, after performing chemical cleaning at high temperature (50°C to 90°C) (S32), the cleaning solution is blown (S33), and the cleaning solution is rinsed with water (S34).

The base material exposed by the chemical cleaning process to remove the scale is likely to react with oxygen, so the inner surface of the heat transfer tube is in a state that is prone to rust. After washing with water, it will rust slightly, so the rust that has occurred is washed with a cleaning solution (acid with a low concentration) (S35, 20°C to 90°C). After that, neutralize the system (S36, 20°C to 90°C), put hydrazine water for rust prevention treatment (S37, 80°C to 90°C) to form an anti-rust film on the inner surface of the heat transfer tube, and blow Liquid (S38). Finally, the temporary system is dismantled (S39).

The above-mentioned anti-rust treatment is for the purpose of preventing rust during the period from after washing to normal operation. Hydrazine water is put into the anti-rust treatment at 80°C to 90°C. However, in the anti-rust treatment at low temperature as shown in Patent Document 3, a sufficient anti-rust film is not formed. In an insufficient state, there is a case where rust is formed on the inner surface of the heat transfer tube after the rust prevention treatment liquid is blown. From the viewpoint of the quality of the cleaning process, the water quality during operation, and the reliability of the equipment, rust on the inner surface of the heat transfer tube is not ideal.

The storage water containing high concentration of ammonia in the system is also considered to be filled with rust prevention treatment, but due to the dismantling of the temporary system, the storage water must be removed. Therefore, from the viewpoint of engineering freedom (partial cut-off of the system, repair of cut-off parts), the storage water becomes full water, which is not ideal.

The present disclosure was made in view of the above-mentioned problems. The purpose of this disclosure is to provide a boiler plant where the boiler can be cleaned at low cost and in a short time during the period from chemical cleaning to the start of normal operation. The cleaning storage method and cleaning storage device. (Means to solve the problem)

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

The first aspect of the present disclosure is to provide a cleaning and storage method for a boiler plant, which is provided with: the cleaning target site where the scale has adhered is carried out at room temperature with a neutral cleaning solution containing a rust remover A process of neutral cleaning; a process of circulating an ammonia-based compound aqueous solution with a pH of 9.8 or higher at the aforementioned cleaning target site; and from the aforementioned cleaning target site, the aforementioned ammonia-based compound aqueous solution Carry out the project of blowing liquid.

According to the first aspect, since the cleaning is performed at room temperature, there is no need for heating equipment and cleaning liquid preheating process, and there is no need to monitor the temperature drop of the cleaning liquid due to cooling during the cleaning process. Thereby, the cleaning cost and cleaning time can be reduced. Among them, "normal temperature" means the degree of room temperature, and is a temperature at which no external preheating or heating is performed. Specifically, it is 5°C to 50°C, more preferably 15°C to 30°C.

After removing the scale on the surface of the base material of the cleaning target part, after circulating an ammonia-based compound aqueous solution with a pH of 9.8 or higher at room temperature, if the ammonia-based compound aqueous solution is blown from the cleaning target part, the surface contains Covered with ammonia film. As a result, rust can be suppressed during the period until the operation is started. The main component of the ammonia-containing water membrane is ammonia, which is the same as the water treatment chemicals used in the operation of the boiler plant. Therefore, since it is not necessary to remove the ammonia-containing water film at the start of operation, the operation can be started directly after the boiler plant is stored. As a result, the operation time is shortened and the cost is also reduced. In addition, since rust can be suppressed without using hydrazine, it has excellent environmental performance.

In the above-mentioned first aspect, it is preferable that in the process of performing the neutral cleaning, the neutral cleaning solution is circulated in the cleaning target area, and the neutral cleaning is analyzed as the cycle. After confirming that the iron ion in the liquid has a saturation tendency in the iron ion concentration change in the neutral cleaning liquid, the neutral cleaning is completed.

The change in the concentration of iron ions in the cleaning solution becomes saturated, which means that the scale that is the object of cleaning is removed and the amount of dissolved scale is reduced. By confirming this to judge the end of the washing, the maximum washing effect can be obtained in the shortest possible time.

In the first aspect described above, it is preferable to install a process of acid cleaning at room temperature with an acidic cleaning solution before the process of circulating the aqueous ammonia compound solution.

According to the application of the plant, the scale component contains calcium (Ca), aluminum (Al), copper (Cu), etc. Ca, Al, and Cu have low solubility near neutral, so in low-temperature washing using a neutral rust remover, these scale components may not be completely dissolved/removed. The scale that cannot be removed may remain in the system as sludge. The remaining sludge can be discharged to the outside of the system by blowing the cleaning solution or washing with water after cleaning. However, it is difficult to discharge the entire amount and may remain in the system. In particular, the gas vertical flow type exhaust heat recovery boiler has a horizontally arranged heat transfer tube, and the length is as large as 20m. It is difficult to discharge the sludge at the flow rate of the water flow during cleaning and discharge (blowing). Particular attention must be paid. The remaining sludge is the main cause of the deterioration of the heat transfer performance of the heat transfer tube or the occurrence of corrosion due to the sludge content.

In the acid cleaning, the scale components (Ca, Al, Cu, etc.) that are not easily dissolved in the neutral cleaning solution can be removed, and the amount of sludge remaining on the part to be cleaned can be reduced.

In the above-mentioned first aspect, it is preferable that in the process of performing the acid cleaning, the acidic cleaning solution is circulated in the cleaning target site, and the acidic cleaning solution that is circulated is analyzed. After confirming that the iron ion concentration change in the acidic cleaning solution shows a saturation tendency, the acid cleaning is ended.

In the above-mentioned first aspect, it is preferable to additionally include: after the acid cleaning, the process of extruding and blowing the acidic cleaning solution using the aqueous ammonia compound solution, in the process of performing the extrusion blow molding In the extrusion blow molding, blow substantially the entire amount of the acidic cleaning solution, and after circulating the ammonia-based compound aqueous solution in the cleaning target part, analyze the pH of the ammonia-based compound aqueous solution, and continue the extrusion Blow molding and the circulation of the ammonia-based compound aqueous solution until the analyzed pH becomes equal to or higher than the reference value.

In extrusion blow molding, the acidic cleaning solution is extruded and replaced with an ammonia-based compound aqueous solution. According to the pH of the blowing liquid, the continuation time of the extrusion blow molding is judged, so that no extra time is spent.

In the above-mentioned first aspect, it is preferable to additionally include: after the neutral cleaning, the process of extruding and blowing the neutral cleaning solution using the aqueous ammonia compound solution, and performing the extrusion blow molding process In the process, the neutral cleaning solution is blown by extrusion blow molding, and after circulating the ammonia compound aqueous solution in the cleaning target area, the ammonia compound aqueous solution is analyzed from the rust remover Continue the cycle of extrusion blow molding and the aqueous ammonia compound solution until the analyzed concentration of the component derived from the rust remover becomes below the reference value.

In extrusion blow molding, the neutral cleaning solution is extruded and replaced with an ammonia-based compound aqueous solution. The continuation time of extrusion blow molding is judged by the decrease in the concentration of the components derived from the rust remover in the blowing liquid, so that no extra time is spent.

In the first aspect described above, after the above-mentioned ammonia-based compound aqueous solution is subjected to the process of blowing the liquid, the vaporizable ammonia compound solid may be injected into the cleaning target portion.

The injected solid of the vaporizable ammonia compound vaporizes in the cleaning target portion, rapidly diffuses, and is taken into the ammonia-containing water film. If the area to be cleaned is stored for a long period of time after the ammonia-containing water film is formed, the ammonia component will leak from the ammonia-containing water film, but the rust prevention effect of the water film can be maintained by the solid input of vaporizable ammonia compound.

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

The sludge can be removed by filtering as a circulating washing liquid. As a result, the amount of sludge remaining during cleaning can be reduced, and therefore the risk of deterioration of the heat transfer performance of the heat transfer tube due to sludge residue and the risk of corrosion caused by sludge content can be reduced.

In the first aspect described above, the part to be cleaned may be an evaporator of a waste heat recovery boiler. By limiting the area to be cleaned to the evaporator, the amount of cleaning liquid used can be suppressed, and the amount of drainage can also be reduced.

The second aspect of the present disclosure provides a cleaning and storage device for a boiler plant, which is provided with: a circulation part configured to circulate fluid in a cleaning target site where scale has adhered; A neutral cleaning solution supply part of a neutral cleaning solution of a rust remover; an ammonia-based compound aqueous solution supply part that supplies an ammonia-based compound aqueous solution with a pH of 9.8 or higher containing an ammonia-based compound to the aforementioned circulation part; and Part of the blowing channel for discharging the aforementioned aqueous ammonia-based compound solution.

In the above-mentioned second aspect, the circulation part may be provided with: a circulation flow path connected at both ends to the inlet and outlet of the cleaning target portion; a pump provided in the middle of the circulation flow path; and a pump provided more than the aforementioned pump It is a filtering device on the way of the aforementioned circulating flow path on the downstream side.

In the above-mentioned second aspect, it may additionally be provided with a blowing fluid flow path, one end of which is connected to at least any of the circulation part, the inlet and the outlet of the cleaning target part, and the other end is connected to the acidic cleaning solution At least any one of the supply unit, the neutral cleaning solution supply unit, and the ammonia-based compound aqueous solution supply unit.

According to the second aspect described above, since the blowing liquid can be returned 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, the drainage tank can be omitted. (Effect of Invention)

According to the present disclosure, during the period from chemical cleaning to the start of normal operation, the rust prevention treatment of the cleaning target part of the boiler can be performed at low cost and in a short time, and the cleaning and storage method and cleaning of the boiler building where the boiler is stored Keep the device.

Hereinafter, referring to the drawings, an embodiment of the cleaning and storage method and cleaning and storage device of the boiler plant of the present disclosure will be described.

In the following embodiments, the cleaning and storage method of the exhaust heat recovery boiler is exemplified. In each process of the cleaning and storage method of the following embodiment, a room temperature cleaning solution is used, and the inside of the cleaning target machine (the cleaning target part) is cleaned without heating. "Normal temperature" means the degree of room temperature, which is a temperature at which no preheating or heating is performed from outside. The "normal temperature" is specifically 5 to 50°C, more preferably 15 to 30°C.

[First Embodiment] Fig. 1 shows a process drawing of the cleaning and storage method of the boiler plant of the present embodiment. The cleaning and storage method of this embodiment sequentially includes step 1 (S1) to step 6 (S6).

(S1) Temporary system (cleaning storage device) connection First, connect a temporary system for supplying washing liquid to the washing target equipment. After that, the cleaning liquid and the like are injected into the cleaning target equipment through the temporary system.

(S2) Neutral wash After injecting a neutral cleaning solution containing a rust remover from the temporary system and filling the cleaning target device with the neutral cleaning solution, the neutral cleaning solution is circulated in the system at room temperature. During the period when it was circulated, the washing liquid was not heated.

The pH of the neutral cleaning solution containing the rust remover is 4-8. The rust remover is a chelating agent, a reducing agent, or a mixture of a chelating agent and a reducing agent, which can remove objects attached to the inside of the cleaning equipment (for example, scale and rust that contain metal oxides or metal salts) Removal of potions. "Rust" refers to a nodular corrosion product generated on the surface of steel (refer to JIS Z 0103 1050). The neutral cleaning solution is to appropriately adjust the concentration of chelating agent, reducing agent and corrosion inhibitor to obtain the desired cleaning ability and cleaning time.

Chelating agents such as EDTA, BAPTA, DOTA, EDDS, INN, NTA, DTPA, HEDTA, TTHA, PDTA, DPTA-OH, HIDA, DHEG, GEDTA, CMGA, EDDS and other amino carboxylic acids and their salts and other amino groups Carboxylic acid chelating agents, hydroxycarboxylic acids such as citric acid, gluconic acid, glycolic acid and their salts, organic phosphoric acids such as ATMP, HEDP, NTMP, PBTC, EDTMP, and their salts, etc. Phosphorus chelating agent. 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, and hydrogen. Corrosion inhibitors can also be added to neutral cleaning solutions.

(S3) Extrusion blow molding After analyzing the Fe ions in the circulating neutral cleaning solution, it was confirmed that the change in Fe ion concentration in the solution became saturated. Then, while injecting an ammonia-based compound aqueous solution at room temperature into the cleaning equipment, the neutral The detergent is extruded and blow molded. The saturation tendency means that the variation range of the Fe ion concentration in the liquid is 100 mg/L or less compared with the measured value of the Fe ion iron concentration in the liquid last time. The amount of the ammonia compound aqueous solution used for extrusion blow molding is, for example, about 1 to 1.5 times the capacity of the equipment to be cleaned.

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

(S4) Ammonia compound aqueous solution circulation In the above (S3), after substantially the entire amount of the neutral cleaning solution is extruded and blow molded with an ammonia compound aqueous solution, the extrusion blow molding is temporarily stopped, and the ammonia compound aqueous solution in the cleaning target equipment is circulated. During the circulation of the ammonia-based compound aqueous solution, the ammonia-based compound aqueous solution is not heated.

After circulating the ammonia-based compound aqueous solution, the ammonia-based compound aqueous solution is analyzed to confirm the components derived from the rust remover in the liquid.

For example, if a neutral cleaning solution contains organic phosphoric acid as a chelating agent, the phosphorus (P) in the aqueous ammonia compound is analyzed. The P analysis system can be implemented by the molybdenum blue absorption spectrophotometry, ion chromatography, ICP mass spectrometry, or atomic absorption method described in JIS K 0102 Industrial Drainage Test Method 46.3 Total Phosphorus.

The above (S3) and (S4) are repeated until the component derived from the rust remover in the liquid becomes below the reference value. The reference value is set in advance during preliminary tests. Confirm that the components derived from the rust remover in the liquid are below the reference value.

(S5) Ammonia compound aqueous solution blowing After the above (S4), the ammonia-based compound aqueous solution is blown from the cleaning target device to form an ammonia-containing water film on the inner surface of the cleaning target device. The part of the ammonia-containing water film has an anti-rust effect.

(S6) Temporary system disintegration After the above (S5), the temporary system will be dismantled.

The cleaning system of the above-mentioned steps 2 to 5 may be performed only once, or may be performed multiple times.

If the washing target machine has a permanent washing storage device, the above (S1) and (S6) are omitted.

Fig. 2 illustrates (S2) the amount of sludge (standard value) before and after neutral cleaning. In this figure, the vertical axis indicates the amount of sludge remaining in the cleaning target equipment. Only (S2) neutral cleaning can remove about 90% of the sludge.

In (S2) neutral washing, Fe scale is dissolved and removed. FIG. 3 shows a schematic diagram of the transition of the washing time and the Fe ion concentration in the washing liquid. In this 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 the neutral cleaning, if the cleaning progresses to a certain extent, the scale that is the cleaning target is removed, the dissolved amount of Fe scale is reduced, and the Fe ion concentration in the cleaning solution changes and becomes a saturation tendency. In the above-mentioned cleaning storage method, the saturation tendency of Fe ion concentration changes is confirmed and each cleaning process is terminated, thereby avoiding continuing cleaning more than necessary, and performing neutral cleaning in the minimum time required. Thereby, the extension of each washing time can be suppressed.

With the above-mentioned cleaning and storage method, after washing the neutral cleaning solution, the ammonia-based compound aqueous solution is circulated in the system, thereby forming a high pH (above 9.8) on the surface of the base material 10 of the cleaning target machine Ammonia-containing water membrane 11 (refer to FIG. 4). The high-pH water film has an anti-rust effect. This effect is continued after the ammonia-based compound aqueous solution is blown out until the repair work of the temporary piping of the cleaning equipment is completed. The pH of the ammonia-containing water film 11 is 9.8 or higher, and therefore even without hydrazine, the rust prevention effect is achieved, so hydrazine is not required and the environmental performance is also excellent.

If the repair work of the junction of the temporary piping of the cleaning equipment is prolonged and the open time becomes longer, the ammonia component will leak from the ammonia-containing water membrane 11. Therefore, in the dismantling of the temporary installation system (S6), the solid substance of the vaporizable ammonia compound may be additionally injected into the cleaning target equipment under normal temperature and normal pressure, and ammonia gas may be replenished. The injected ammonia compound is quickly vaporized to generate ammonia gas. The ammonia gas system diffuses in the system and dissolves in the ammonia-containing water membrane. Thereby, the pH of the ammonia-containing water film 11 can be maintained high, and therefore, the reduction in the rust prevention effect of the ammonia-containing water film 11 due to the decrease in pH can be reduced.

The water film of the aqueous ammonia compound solution or the solid substance of the ammonia compound remaining at the start of the operation is easily dissolved in the operation water. In the exhaust heat recovery boiler, ammonia is used for pH adjustment of the feed water during operation. In the above embodiment, the ammonia-based compound aqueous solution used to form the water film is mainly composed of ammonia, and therefore does not need to be removed at the start of the exhaust heat recovery boiler operation. Therefore, after storing the exhaust heat recovery boiler, it can start operation directly, so the operation time is shortened. In addition to increasing the operation rate of the plant, it is also possible to reduce the cost of medicines and waste water treatment.

It is also possible to filter the neutral detergent during the circulation. As a result, the amount of sludge remaining during cleaning can be reduced, and therefore, the risk of deterioration of the heat transfer performance of the heat transfer tube due to sludge residue or corrosion due to sludge content can be reduced.

The cleaning and storage method of the above-mentioned embodiment is suitable for cleaning the boiler water system of the exhaust heat recovery boiler. In particular, as shown in Figure 5, the cleaning target equipment that needs to be cleaned is specified at a specific location where scale is easy to adhere (for example, the heat transfer tube of an evaporator where scale is easy to adhere due to temperature and pressure conditions) , It is more suitable to cut down the usage amount of cleaning liquid and related cleaning operation time.

[Second Embodiment] Fig. 6 shows a process drawing of the cleaning and storage method of the boiler plant of the present embodiment. This embodiment is a process of performing acid cleaning before neutral cleaning, and this is different from the first embodiment. The cleaning and storage method of this embodiment sequentially includes step 11 (S11) to step 19 (S19).

(S11) Temporary system (cleaning storage device) connection As in (S1) of the first embodiment, first, a temporary system for supplying washing liquid to the washing target device is connected. After that, the cleaning liquid and the like are injected into the cleaning target equipment through the temporary system.

(S12) Pickling After the acidic cleaning solution is injected from the temporary system to fill the equipment to be cleaned with the acidic cleaning solution, the acidic cleaning solution is circulated in the equipment to be cleaned at room temperature. During the period when it was circulated, the washing liquid was not heated. The acidic cleaning solution may be an inorganic acid solution or an organic acid solution that can dissolve Ca, Al, Cu, etc. The pH of the acidic cleaning solution is preferably 4 or less, and more preferably 3 or less. For example, a 1% by mass to 10% by mass hydrochloric acid aqueous solution can be used as an acidic cleaning solution.

(S13) Acid cleaning liquid blowing liquid After analyzing the iron (Fe) ions in the circulating acidic cleaning solution and confirming the saturation tendency of Fe ion concentration changes, the cleaning solution is blown to complete the acid cleaning. The saturation tendency means that the variation range of the Fe ion concentration in the liquid is 100 mg/L or less compared with the measured value of the Fe ion iron concentration in the liquid last time.

The iron ions in the liquid can be used in the phenanthroline absorption spectrophotometry, flame atomic absorption method, electric heating atomic absorption method or ICP emission spectrometry method described in JIS K 0101 Industrial Water Test Method 60 Iron (Fe), or the boiler of JIS B 8224 Feed water and boiler water-test method 26 iron (Fe) described 1,10-phenanthroline absorbance method, 2,4,6-tris-pyridyl-1,3,5-triazine (TPTZ) absorbance Method, flame atomic absorption method, electric heating atomic absorption method, ICP emission spectrophotometry or ICP mass analysis method, sulfosalicylic acid absorption spectrophotometry, etc. JIS is the abbreviation of Japanese Industrial Standards.

(S14) Washing After filling the equipment to be cleaned with water, the water is circulated at room temperature, and the acidic cleaning liquid remaining in the equipment to be cleaned is replaced with water. This project can also be omitted.

(S15) Neutral wash After blowing the water of the above (S14), the equipment to be cleaned is filled with a neutral cleaning solution containing a rust remover, and the neutral cleaning solution is circulated in the system at room temperature. During the period when it was circulated, the washing liquid was not heated. The neutral cleaning liquid system can be the same as that of the first embodiment.

(S16) Extrusion blow molding In the same way as (S3) of the first embodiment, after analyzing Fe ions in the circulating neutral cleaning solution, it is confirmed that the change in Fe ion concentration in the solution has become a saturation tendency. Inject the ammonia-based compound aqueous solution at room temperature while extruding and blowing the neutral cleaning solution. The ammonia-based compound aqueous solution can be the same as in the first embodiment.

(S17) Ammonia compound aqueous solution circulation As in (S4) of the first embodiment, in the above (S16), after substantially the entire amount of the neutral cleaning solution is extruded and blow-molded with the ammonia compound aqueous solution, the extrusion blow-molding is temporarily stopped to make the cleaning target machine The aqueous ammonia compound inside is circulated. During the circulation of the ammonia-based compound aqueous solution, the ammonia-based compound aqueous solution is not heated.

After the ammonia-based compound aqueous solution is circulated, the ammonia-based compound aqueous solution is analyzed to confirm the components derived from the rust remover in the liquid.

The above (S16) and (S17) are repeated until the components derived from the rust remover in the liquid become below the reference value. The reference value is set in advance in preliminary tests, etc. Confirm that the components derived from the rust remover in the liquid are below the reference value.

(S18) Ammonia compound aqueous solution blowing As in (S5) of the first embodiment, after the above (S17), the ammonia-based compound aqueous solution is blown from the cleaning target device to form an ammonia-containing water film on the inner surface of the cleaning target device. The part of the ammonia-containing water film has an anti-rust effect.

(S19) Temporary system disintegration As with (S6) of the first embodiment, after the above (S18), the temporary system is disassembled.

The cleaning system from step 12 to step 18 of the above-mentioned cleaning storage method may be performed only once, or may be performed multiple times.

If the cleaning target machine has a permanent storage device, the above (S11) and (S19) are omitted.

According to the above-mentioned cleaning and storage method, the scales of Ca, Al, Cu, etc. that are not easily dissolved in the neutral cleaning solution are removed by acid cleaning (S12), and the sludge remaining in the equipment to be cleaned is removed by (S15) Neutral wash to remove. By using a neutral cleaning solution, the base material of the target equipment is prevented from corroding as much as possible, while the remaining scale is dissolved and removed, which can reduce the residual amount of sludge.

Fig. 7 illustrates the residual amount of sludge (standard value) in (S12) acid cleaning and (S15) neutral cleaning. In this figure, the vertical axis indicates the amount of sludge remaining in the cleaning target equipment (100 before pickling). As shown in Fig. 2, in the acid cleaning at room temperature, about 20% of the sludge remains, but about 70% of the 20% remaining due to the neutral cleaning can be removed.

In (S12) acid cleaning and (S15) neutral cleaning, Fe scale is also dissolved and removed. FIG. 8 shows a schematic diagram of the transition of the washing time and the Fe ion concentration in the washing liquid. In this figure, the horizontal axis represents the cleaning time, the vertical axis represents the Fe ion concentration, the solid line represents the transition during acid cleaning, and the broken line represents the transition during neutral cleaning. In acid cleaning and neutral cleaning, if the cleaning progresses to a certain extent, the scale that is the cleaning target is removed, the amount of Fe scale dissolved is reduced, and the Fe ion concentration in the cleaning solution changes to a saturation tendency. In the cleaning and storage method of this embodiment, the saturation tendency of Fe ion concentration changes is confirmed and each cleaning process is terminated, thereby avoiding the need to continue cleaning more than necessary, and it takes the least time to perform acid cleaning and Neutral wash. Thereby, the extension of each washing time can be suppressed.

According to the cleaning and storage method of this embodiment, after washing the neutral cleaning solution, the ammonia-based compound aqueous solution is circulated in the system, thereby forming a high pH (9.8 or more) on the surface of the base material 10 of the cleaning target machine )的ammonium water membrane 11. The high-pH water film has an anti-rust effect. This effect is continued after the ammonia-based compound aqueous solution is blown out until the repair work of the temporary piping of the cleaning equipment is completed. The pH of the ammonia-containing water film 11 is 9.8 or higher, and therefore even without hydrazine, the rust prevention effect is achieved, so hydrazine is not required and the environmental performance is also excellent.

If the repair work of the junction of the temporary piping of the cleaning equipment is prolonged and the open time becomes longer, the ammonia component will leak from the ammonia-containing water membrane 11. Therefore, in the dismantling of the (S19) temporary system, the solid substance of the vaporizable ammonia compound may be additionally injected into the cleaning target equipment under normal temperature and normal pressure, and ammonia gas may be replenished. The injected ammonia compound is quickly vaporized, and ammonia gas is generated. The ammonia gas system diffuses in the system and dissolves in the ammonia-containing water membrane. Thereby, the pH of the ammonia-containing water film 11 can be maintained high, and therefore, the reduction in the rust prevention effect of the ammonia-containing water film 11 due to the decrease in pH can be reduced.

The water film of the aqueous ammonia compound solution or the solid substance of the ammonia compound remaining at the start of the operation is easily dissolved in the operation water. In the exhaust heat recovery boiler, ammonia is used for pH adjustment of the feed water during operation. In the above embodiment, the ammonia-based compound aqueous solution used to form the water film is mainly composed of ammonia, and therefore does not need to be removed at the start of the exhaust heat recovery boiler operation. Therefore, after storing the exhaust heat recovery boiler, it can start operation directly, so the operation time is shortened. In addition to increasing the operation rate of the plant, it is also possible to reduce the cost of medicines and waste water treatment.

It is also possible to filter at least one of the acidic cleaning liquid and the neutral cleaning liquid in the middle of the circulation. As a result, the amount of sludge remaining during cleaning can be reduced, and therefore, the risk of deterioration of the heat transfer performance of the heat transfer tube due to sludge residue or corrosion due to sludge content can be reduced.

The cleaning and storage method of the above-mentioned embodiment is suitable for cleaning the boiler water system of the exhaust heat recovery boiler. In particular, as shown in Figure 5, the cleaning target equipment that needs to be cleaned is specified at a specific location where scale is easy to adhere (for example, the heat transfer tube of an evaporator where scale is easy to adhere due to temperature and pressure conditions) , It is more suitable to cut down the usage amount of cleaning liquid and related cleaning operation time.

[Third Embodiment] Fig. 9 shows a process drawing of the cleaning and storage method of the boiler plant of the present embodiment. This embodiment is a process of performing acid cleaning after neutral cleaning, and this is different from the first and second embodiments. The cleaning and storage method of this embodiment sequentially includes step 21 (S21) to step 28 (S28).

(S21) Temporary system (storage device) connection As in (S1) of the first embodiment, first, a temporary system for supplying washing liquid to the washing target device is connected. After that, the cleaning liquid and the like are injected into the cleaning target equipment through the temporary system.

(S22) Neutral wash As in (S2) of the first embodiment, after injecting a neutral cleaning solution containing a rust remover from the temporary system and filling the cleaning object with the neutral cleaning solution, the neutral cleaning The clean liquid circulates in the system at room temperature. During the period when it was circulated, the washing liquid was not heated. The neutral cleaning liquid system can be the same as that of the first embodiment.

(S23) Neutral detergent blowing liquid After analyzing the iron (Fe) ions in the circulating neutral cleaning solution, once the saturation tendency of Fe ion concentration changes is confirmed, the cleaning solution is blown out to complete the neutral cleaning.

(S24) Pickling In the above (S23), the neutral cleaning liquid is blown out, and the acidic cleaning liquid containing the rust remover is filled in the cleaning target equipment, and the acidic cleaning liquid is circulated in the system at room temperature . During the period when it was circulated, the washing liquid was not heated. The acidic cleaning liquid system can be the same as in the second embodiment.

(S25) Extrusion blow molding After analyzing the Fe ions in the circulating acidic cleaning solution, it was confirmed that the change in Fe ion concentration in the solution became saturated. Then, while injecting an aqueous ammonia compound solution at room temperature into the cleaning equipment, the neutral The washing liquid is extruded and blow molded. The ammonia-based compound aqueous solution can be the same as in the first embodiment.

(S26) Ammonia compound aqueous solution circulation In the above (S25), after substantially the entire amount of the acidic cleaning solution is extruded and blow molded with the ammonia compound aqueous solution with the ammonia compound aqueous solution, the extrusion blow molding is temporarily stopped, and the ammonia compound aqueous solution in the cleaning target equipment is circulated. During the circulation of the ammonia-based compound aqueous solution, the ammonia-based compound aqueous solution is not heated.

After the ammonia-based compound aqueous solution is circulated, the ammonia-based compound aqueous solution is analyzed to confirm the pH value of the ammonia-based compound aqueous solution.

The above (S25) and (S26) are repeated until the pH of the ammonia-based compound aqueous solution becomes equal to or higher than the reference value. The reference value is set in advance in preliminary tests, etc. It was confirmed that the pH of the aqueous ammonia-based compound solution was above the reference value. The reference value is pH 9.8 or more at which the anti-rust effect is achieved even without hydrazine, for example.

(S27) Ammonia compound aqueous solution blowing As in (S5) of the first embodiment, after the above (S26), the ammonia-based compound aqueous solution is blown from the cleaning target device to form an ammonia-containing water film on the inner surface of the cleaning target device. The part of the ammonia-containing water film has an anti-rust effect.

(S28) Temporary system disintegration As in (S6) of the first embodiment, after the above (S27), the temporary system is disassembled.

The cleaning system of steps 22 to 27 described above may be performed only once, or may be performed multiple times.

Next, referring to Figs. 10 and 11, the cleaning when the cleaning target equipment is used as the evaporator of the exhaust heat recovery boiler will be described.

Fig. 10 is a schematic diagram of a temporary installation system (washing storage device 2). In FIG. 10, the equipment to be cleaned is the heat transfer tube of the evaporator 1. In FIG. 10, in order to simplify the illustration, only the inlet pipe header 1a and the outlet pipe header 1b connected to the heat transfer pipes of the washing storage device 2 are described. In FIG. 10, the arrow entering the inlet header 1a indicates the connection from the evaporator drum, and the arrow exiting from the outlet header 1b indicates the connection to the evaporator drum.

The washing and storage device 2 is provided with a circulation part 3, a chemical liquid tank 4, a chemical liquid pump 5, a replenishing water tank 6, a drainage tank 7, and pipes L ₁ to L _{4 connecting these} . The circulation part 3 is provided with a circulation flow path (piping L ₁ ) and a pump 8.

The circulation flow path (pipe L ₁ ) is connected at one end to the inlet side of the heat transfer tube (inlet tube header 1a), and the other end is connected to the outlet side of the heat transfer tube (outlet tube header 1b). A pump 8 is provided in the middle of the circulation flow path (piping L ₁ ), and it is configured to circulate cleaning liquid and the like in the heat transfer tube. Valves V ₁ to V ₄ are arranged in the circulation flow path (piping L ₁ ).

The liquid medicine tank 4 is connected to the middle of the circulation flow path (piping L ₁ ) through the pipe L ₂ and the liquid medicine pump 5. A valve V ₅ and a valve V ₆ are arranged in the pipe L _{2 so} as to sandwich the liquid chemical pump 5. In the chemical liquid tank 4, the chemical liquid (acid, rust remover, or ammonia compound aqueous solution) to be circulated can be stored. The liquid medicine tank 4 may also be a tanker containing the liquid medicine tank 4. In FIG. 10, the number of the liquid medicine tank 4 is one, so the liquid medicine in the liquid medicine tank 4 is sequentially replaced.

A makeup water tank 6 is connected to the circulation flow path (piping L ₁ ) through a pipe L ₃ . A valve V ₇ and a valve V ₈ are arranged in the piping L ₃ system. The connection position of the replenishing water tank 6 may be either upstream or downstream of the circulating flow of the connection position of the medicinal solution tank 4. Water such as pure water is stored in the make-up water tank 6 system.

The drain groove 7 is connected to the vicinity of both ends of the circulation flow path (piping L ₁ ) and the inlet pipe header 1a of the heat transfer pipe or the connection pipe connected to the inlet pipe header 1a of the heat transfer pipe through the pipes L ₄ to L ₆ ( Not shown) connected. A valve V ₉ and a valve V ₁₀ are arranged in the pipe L ₄ system. A valve V ₁₁ and a valve V ₁₂ are arranged in the piping L ₅ series. A valve V ₁₃ and a valve V ₁₄ are arranged in the piping L ₆ system.

In the washing storage device 2 of FIG. 10, a filter device 9 is provided in the circulation flow path (piping L ₁ ) on the outlet flow side of the circulation flow of the pump 8. The filtering device 9 is a device that removes fine solids through a filter or membrane filtration. With the filter device 9, the sludge generated in the neutral cleaning process or the acid cleaning process can be recovered, and the amount of sludge remaining during cleaning can be reduced, thus reducing the risk of corrosion problems caused by sludge remaining .

Since the washing and storage device 2 of FIG. 10 operates at room temperature, no means for adjusting the temperature of the fluid is provided.

FIG. 11 is a schematic diagram of another temporary system (washing storage device 20) different from FIG. 10. The components common to FIG. 10 are indicated by the same symbols. In the washing and storage device 20 of FIG. 11, a plurality of chemical liquid tanks 24a to 24c are connected in parallel, and a device is provided instead of the drain tank 7 to send drain (blowing liquid) back to any of the chemical liquid tanks 24a to 24c. Blowing liquid flow path L ₂₁ . A valve V ₂₇ is arranged in the blowing liquid flow path L ₂₁ system.

In FIG. 11, the replenishment water tank 6, the chemical liquid tank 24a, the valve V _25a , the valve V _26a , the chemical liquid pump 5, the piping L ₂ and the valve V ₆ are the acid detergent supply part, the replenishment water tank 6, the chemical liquid tank 24b , Valve V _25b , valve V _26b , chemical liquid pump 5, piping L ₂ and valve V ₆ are the neutral detergent supply parts, supply water tank 6, chemical liquid tank 24c, valve V _25c , valve V _26c , chemical liquid pump 5. The pipe L ₂ and the valve V ₆ are the ammonia compound aqueous solution supply part.

Acid is stored in the chemical liquid tank 24a. A neutral rust remover is stored in the chemical tank 24b. The ammonia-based compound aqueous solution is stored in the chemical liquid tank 24c.

By setting the chemical liquid tanks 24a to 24c for each chemical liquid, the blowing liquid of each process of acid cleaning liquid blowing, water washing, extrusion blowing, and ammonia compound aqueous solution blowing is sent back to the chemical liquid tanks 24a to 24c Any one of.

Among them, the cleaning storage devices 2 and 20 of FIGS. 10 and 11 may also be an attachable and detachable type that can be installed on the cleaning target machine when in use, and can be removed from the cleaning target machine when not in use, or Any one of the permanent type.

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

1: Evaporator 1a: inlet pipe header 1b: outlet pipe header 2: washing storage device 3: circulation part 4, 24a, 24b, 24c: liquid tank 5: liquid pump 6: supply water tank 7: drainage tank 8: Pump 9: Filtering device 10: Base material 11: Ammonia-containing water film 30: Cleaning equipment 31: Economizer 32: Steam drum 33: Evaporator L ₁ ~ L ₆ : Piping L ₂₁ : Blowing liquid flow path V ₁ ~V ₁₄ ,V _25a ,V _25b ,V _25c ,V _26a ,V _26b ,V _26c ,V ₂₇ : Valve

[Figure 1] is an engineering drawing of the cleaning and storage method of the first embodiment. [Figure 2] A graph illustrating the amount of sludge cleaned by neutral cleaning. Fig. 3 is a schematic diagram showing the transition of the washing time and the Fe ion concentration in the neutral washing liquid in the first embodiment. [Figure 4] A schematic diagram of an ammonia-containing water membrane. [Fig. 5] is a schematic diagram of washing specific parts. [Fig. 6] is an engineering drawing of the cleaning and storage method of the second embodiment. [Fig. 7] A graph illustrating the amount of sludge in the acid cleaning and neutral cleaning in the second embodiment. Fig. 8 is a schematic diagram showing the transition of the washing time and the Fe ion concentration in the washing liquid in the second embodiment. [Figure 9] is an engineering drawing of the cleaning and storage method of the third embodiment. [Fig. 10] is a schematic diagram showing an example of the washing and storing device. [Fig. 11] is a schematic diagram showing an example of a washing storage device. [Fig. 12] A schematic diagram of the cleaning of plural parts. [Figure 13] The engineering drawing of the conventional chemical cleaning method.

Claims (12)

A cleaning and storage method for boiler workshop, which has: Perform a neutral cleaning process at room temperature with a neutral cleaning solution containing a rust remover on the part to be cleaned with attached scale; A process of circulating an ammonia-based compound aqueous solution with a pH of 9.8 or higher at the aforementioned cleaning target site; and From the area to be cleaned, the ammonia-based compound aqueous solution is blown into liquid. Such as the cleaning and storage method of the boiler plant in claim 1, where in the aforementioned neutral cleaning process, Circulate the neutral washing liquid in the washing target area, Analyze the iron ions in the aforementioned neutral cleaning solution used for circulation, After confirming that the iron ion concentration change in the neutral cleaning solution shows a saturation tendency, the neutral cleaning is ended. For example, the cleaning and storage method of the boiler plant of claim 1 or 2, wherein, before the process of circulating the aforementioned ammonia-based compound aqueous solution, there is a process of performing acid cleaning at room temperature with an acidic cleaning solution. Such as the cleaning and storage method of the boiler plant in claim 3, in which, in the above-mentioned acid cleaning process, In the area to be cleaned, the acidic cleaning solution is circulated, Analyze the iron ions in the aforementioned acidic cleaning solution used for circulation, After confirming that the iron ion concentration change in the acidic cleaning solution shows a saturation tendency, the acid cleaning is ended. For example, the cleaning and storage method of the boiler plant of claim 3, which additionally includes: after the acid cleaning, the process of extruding and blowing the acidic cleaning liquid using the aqueous ammonia compound solution, In the aforementioned extrusion blow molding process, In the extrusion blow molding, substantially 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, The circulation of the extrusion blow molding and the aqueous ammonia compound solution is continued until the analyzed pH becomes equal to or higher than the reference value. Such as the cleaning and storage method of the boiler plant of claim 1, which additionally includes: after the neutral cleaning, the neutral cleaning solution is extruded and blow molded using the aqueous ammonia compound solution, In the aforementioned extrusion blow molding process, Blow roughly the entire amount of the neutral cleaning solution by the extrusion blow molding, and circulate the ammonia-based compound aqueous solution in the cleaning target area, and then analyze the ammonia-based compound aqueous solution for the rust remover The ingredients, Continue the cycle of the extrusion blow molding and the aqueous ammonia compound solution until the analyzed concentration of the component derived from the rust remover becomes below the reference value. The cleaning and storage method of a boiler plant according to claim 1, wherein after the ammonia-based compound aqueous solution is subjected to a liquid blowing process, a vaporizable ammonia compound solid is introduced into the cleaning target portion. The cleaning and storage method of a boiler plant in claim 1, wherein at least one of the acidic cleaning liquid and the aforementioned neutral cleaning liquid is filtered during the circulation. Such as the cleaning and storage method of the boiler plant of claim 1, wherein the cleaning target part is the evaporator of the exhaust heat recovery boiler. A cleaning and storage device for boiler workshops, which is equipped with: It is constituted as a circulation part that circulates fluid in the cleaning target part where the scale has adhered; A neutral cleaning solution supply part that supplies a neutral cleaning solution containing a rust remover to the aforementioned circulation part; An ammonia-based compound aqueous solution supply unit that supplies an ammonia-based compound aqueous solution with a pH of 9.8 or higher containing an ammonia-based compound to the aforementioned circulation unit; and A blowing flow path for discharging the ammonia-based compound aqueous solution from the circulation part. For example, the cleaning and storage device of the boiler plant in claim 10, in which the aforementioned circulation part is equipped with: The two ends are connected to the circulation flow path of the inlet and outlet of the aforementioned cleaning target part; A pump located on the way of the aforementioned circulating flow path; and A filter device provided in the middle of the circulation flow path downstream of the pump. The cleaning storage device of a boiler plant of claim 10 or 11, wherein one end of the blowing liquid flow path is connected to at least any one of the circulation part, the inlet and the outlet of the cleaning target part, and the other end is connected to the middle At least any one of the aqueous cleaning solution supply unit and the aforementioned ammonia-based compound aqueous solution supply unit.

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