Method for removing hydroxyapatite in chemical cleaning of boiler of thermal power plant

Abstract

The application discloses a method for removing hydroxyapatite in chemical cleaning of a boiler of a thermal power plant, and comprises the following steps: continuously pickling until the iron oxide scale is completely removed in the cleaning system of the boiler of the thermal power plant where the hydroxyapatite scale layer exists; adding an inhibitor into the cleaning system of the boiler of the thermal power plant, then adding a hydroxyapatite scale cleaning agent, and controlling the circulation cleaning until the hydroxyapatite scale layer is completely removed; adding an EDTA rinsing solution containing the inhibitor into the cleaning system of the boiler of the thermal power plant, regularly testing the iron ion and free EDTA rinsing solution concentration of the system, adjusting the pH of the system to be alkaline by using ammonia water after the iron ion and free EDTA rinsing solution concentration are balanced, starting passivation, discharging the passivation liquid after the passivation is completed. The method has good dissolving and removing capacity for the hydroxyapatite scale layer, can effectively control the corrosion of the metal matrix, is simple in operation, high in safety, and easy to realize.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of chemical cleaning of power station thermal equipment, and particularly relates to a method for removing hydroxyapatite in chemical cleaning of a boiler in a thermal power plant. BACKGROUND

[0002] Chemical cleaning is the most commonly used method for removing corrosion and scale products inside heat exchange tubes of thermal equipment. At present, AVT(O) water treatment mode is generally used in 135MW and 300MW subcritical drum boilers in China, and phosphate is used to adjust the pH value of boiler water. In some power plants, the hardness of feed water exceeds the standard, which results in the presence of hydroxyapatite scale layer on the inner wall of the heat exchange tubes of the economizer and water-cooled wall.

[0003] At present, the chemical cleaning of boilers in thermal power plants usually adopts cleaning processes such as composite organic acid, citric acid and EDTA rinsing solution, and the removal effect of hydroxyapatite scale layer is not obvious.

[0004] Since the hydroxyapatite scale layer remains on the inner wall of the heat exchange tubes of the economizer and water-cooled wall, the metal matrix is not completely exposed, which results in that the passivation solution cannot directly contact with the metal matrix during the passivation process, and it is difficult to form a complete passivation film after passivation. At the same time, it also results in that a dense magnetite protective layer cannot be quickly formed on the inner wall of the heat exchange tubes after chemical cleaning, which causes the corrosion of the heat exchange tubes to be intensified, and seriously affects the effect of chemical cleaning.

[0005] At present, hydrochloric acid is mainly used as a cleaning medium for removing the hydroxyapatite scale layer. Since hydrochloric acid is a strong acid, it has strong acidity and exists as irritating acid mist, and has poor safety during use. At the same time, the chloride ions in hydrochloric acid can cause serious corrosion to the austenitic steel in the heat exchange tubes of the boiler superheater, and there are many disadvantages. SUMMARY

[0006] In order to solve the above-mentioned shortcomings of the prior art, the purpose of the present application is to provide a method for removing hydroxyapatite in chemical cleaning of a boiler in a thermal power plant, which is easy to implement, has good removal effect, simple process, high safety and easy to control.

[0007] In order to achieve the above-mentioned purpose, the present application adopts the following technical solutions.

[0008] The first aspect of the present application is to provide a method for removing hydroxyapatite in chemical cleaning of a boiler in a thermal power plant, which specifically comprises the following steps:

[0009] The acid pickling is continued in the boiler cleaning system of the thermal power plant with the presence of the hydroxyapatite scale layer until the iron oxide scale layer is completely removed;

[0010] The corrosion inhibitor is added to the boiler cleaning system of the thermal power plant, and then the hydroxyapatite scale layer cleaning agent is added, and the circulation cleaning is controlled until the hydroxyapatite scale layer is completely removed;

[0011] EDTA rinsing solution is added to the boiler cleaning system of a thermal power plant, the iron ion and free EDTA rinsing solution concentration of the system is tested periodically, after the iron ion and free EDTA rinsing solution concentration is balanced, ammonia is used to adjust the pH of the system to be alkaline, passivation is started, and the passivation solution is discharged after the passivation is completed.

[0012] As a further improvement of the present application, the judging method that the ferric oxide scale layer is completely removed is that the surface of the pipe section is monitored to have no black or red scale layer, and water flushing is performed after pickling before the hydroxyapatite scale cleaning agent is added.

[0013] As a further improvement of the present application, the hydroxyapatite scale cleaning agent comprises 0.1-0.3% citric acid, 0.5% sulfamic acid and 0.2-0.4% DPTA in terms of mass percentage, and the initial pH of the hydroxyapatite scale cleaning agent is 3.5-4.0.

[0014] As a further improvement of the present application, the initial pH of the EDTA rinsing solution is 4.5-5.5, the cleaning temperature is 50-80℃, and the initial EDTA rinsing solution mass concentration is 0.5%-1% in terms of mass percentage.

[0015] As a further improvement of the present application, the judging method that the circulation cleaning is controlled to the hydroxyapatite scale is completely removed is that the surface of the pipe is monitored to have no white hydroxyapatite scale, and then water flushing is performed after emptying, and the water flushing needs to ensure that the total iron content of the system is less than 50 mg / L.

[0016] As a further improvement of the present application, the temperature for adding the hydroxyapatite scale cleaning agent is 85-95℃, and the pH value of the system is ensured to be less than 7.0 during the cleaning process.

[0017] As a further improvement of the present application, if the pH value of the cleaning system is greater than 7.0, DPTA needs to be added to adjust the pH value of the system.

[0018] As a further improvement of the present application, the corrosion inhibitor comprises 25%-40% benzotriazole, 15%-25% methyl benzotriazole, 20%-30% thiourea, 15%-20% sodium gluconate, 5%-10% defoaming agent and the rest is salt water in terms of mass percentage.

[0019] As a further improvement of the present application, the mass concentration of the corrosion inhibitor added to the system is 0.2%-0.4%.

[0020] As a further improvement of the present application, after the EDTA rinsing is completed, ammonia is used to adjust the pH of the system to be 9.0-10.5 for passivation.

[0021] Compared with the prior art, the present application has the following advantages:

[0022] The method for removing hydroxyapatite of the present application first ensures that the iron oxide scale layer is completely removed, and then removes the hydroxyapatite scale layer by adding an inhibitor and a hydroxyapatite scale layer cleaning agent; after complete removal, the hydroxyapatite scale layer is rinsed and passivated by using EDTA rinsing liquid. The method has good dissolving and removing capacity for the hydroxyapatite scale layer, can effectively control the corrosion of the metal substrate, is simple to operate, safe, and easy to implement. The method has good dissolving and removing capacity for the hydroxyapatite scale layer, and avoids the serious corrosion of the austenitic steel in the boiler superheater heat exchange tube caused by using the hydrochloric acid process. The method of the present application is safe and reliable, easy to implement, does not produce irritating acid mist during the preparation process, is safe, and easy to control. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 The test results of the inner wall of the tube sample before and after the removal process of the hydroxyapatite scale layer using the hydroxyapatite scale layer cleaning agent are shown in (a) before cleaning and (b) after cleaning. DETAILED DESCRIPTION

[0024] In order for those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be described in detail below with reference to the accompanying drawings of the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor should be within the scope of protection of the present application.

[0025] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and do not necessarily describe a specific order or sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device including a series of steps or units does not necessarily limit to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0026] The present application provides a method for removing hydroxyapatite in the chemical cleaning of a thermal power plant boiler, comprising the following steps:

[0027] Step 1. Check the cleaning condition of the monitoring tube in the acid pickling process of the boiler of the thermal power plant, if there is a hydroxyapatite scale layer in the monitoring tube, ensure that the iron oxide scale layer is completely removed, and then use a process for removing the hydroxyapatite scale layer;

[0028] Step 2. After the water flushing after the pickling is qualified, a special corrosion inhibitor is added to the cleaning system to prepare a hydroxyapatite scale cleaning agent, the initial pH of the cleaning agent is controlled to be 3.5-4.0, and the cleaning agent contains 0.1-0.3% citric acid, 0.5% sulfamic acid and 0.2-0.4% DPTA.

[0029] Step 3. After the hydroxyapatite scale layer is completely removed, water flushing is performed, and after the water flushing is qualified, EDTA rinsing liquid is prepared, the initial pH of the rinsing liquid is controlled to be 4.5-5.5, and the initial EDTA rinsing liquid concentration in the cleaning system is 0.5%-1%.

[0030] Step 4. The rinsing liquid is added to the system, the iron ion and free EDTA rinsing liquid concentration in the system are regularly tested, after the iron ion and free EDTA rinsing liquid concentration are balanced, the pH of the system is adjusted to 9.0-10.5 by using ammonia water, passivation is started, and the passivation liquid is discharged after the passivation is completed.

[0031] The method for removing the hydroxyapatite scale layer has good effect, simple process, high safety and easy control.

[0032] The judgment method for completely removing the iron oxide scale layer is that there is no black or red scale layer on the surface of the monitoring tube section, water flushing is performed after the pickling before the hydroxyapatite scale cleaning agent is added, and the water flushing needs to ensure that the total iron content in the system is less than 50 mg / L. In actual monitoring, the form is not limited, for example, visual observation or instrument testing can be used.

[0033] The judgment method for controlling the cleaning to the hydroxyapatite scale layer is that there is no white hydroxyapatite scale layer on the surface of the monitoring tube, and then water flushing is performed after the emptying, and the water flushing needs to ensure that the total iron content in the system is less than 50 mg / L. In actual monitoring, the form is not limited, for example, visual observation or instrument testing can be used.

[0034] As an optional method, the removal of the hydroxyapatite scale layer needs to be performed after the pickling is completed, it is necessary to ensure that the iron oxide scale layer has been completely cleaned, the water flushing after the pickling needs to ensure that the total iron content in the system is less than 50 mg / L, and the hydroxyapatite scale cleaning agent is prevented from being consumed due to the presence of a large amount of iron oxide scale layer in the system.

[0035] In the process for removing the hydroxyapatite scale layer, the temperature required is 85-95℃, and the pH value of the system in the cleaning process is less than 7.0. If the pH value of the cleaning system is greater than 7.0, DPTA needs to be supplemented to adjust the pH value of the system.

[0036] The main components of the corrosion inhibitor used include 25-40% benzotriazole, 15-25% methyl benzotriazole, 20-30% thiourea, 15-20% sodium gluconate, 5-10% defoaming agent, and the rest is salt water. The corrosion inhibitor is prepared according to the proportion, and is added to the system at a concentration of 0.2-0.4%.

[0037] The hydroxyapatite scale layer cleaning agent contains citric acid, sulfamic acid and DPTA. During use, the cleaning agent is prepared according to the proportion, 0.1-0.3% citric acid, 0.5% sulfamic acid and 0.2-0.4% DPTA. During use, the pH value and the temperature of the cleaning system need to be controlled. The initial pH value is 3.5-4.0. The temperature of the cleaning agent is 85-95°C, and the pH value of the system during cleaning is less than 7.0.

[0038] The specific embodiments of the present application will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present application, and are not used to limit the present application.

[0039] Example 1

[0040] A method for removing hydroxyapatite in the chemical cleaning of a boiler in a thermal power plant, specifically comprising the following steps:

[0041] 1. During the pickling process of the boiler in the thermal power plant, the cleaning condition of the monitoring tube is checked. If there is a hydroxyapatite scale layer on the monitoring tube, the process for removing the hydroxyapatite scale layer is used after the iron oxide scale layer is completely removed;

[0042] 2. After the water flushing after pickling is qualified, the corrosion inhibitor is added to the cleaning system, the hydroxyapatite scale layer cleaning agent is prepared, the initial pH value of the cleaning agent is controlled to be 3.5-4.0, and the cleaning agent contains 0.1-0.3% citric acid, 0.5% sulfamic acid and 0.2-0.4% DPTA;

[0043] 3. After the hydroxyapatite scale layer is completely removed, water flushing is performed, and EDTA rinsing solution is prepared after the water flushing is qualified. The initial pH value of the rinsing solution is controlled to be 4.5-5.5, and the initial EDTA rinsing solution concentration in the cleaning system is 0.5%-1%;

[0044] 4. The rinsing solution is added to the system, the iron ion and free EDTA rinsing solution concentrations in the system are tested regularly, and after the iron ion and free EDTA rinsing solution concentrations are balanced, the pH value of the system is adjusted to 9.0-10.5 using ammonia water, passivation is started, and the passivation liquid is discharged after the passivation is completed.

[0045] Example 1

[0046] A method for removing hydroxyapatite in the chemical cleaning of a boiler in a thermal power plant, specifically comprising the following steps:

[0047] 1. During the acid cleaning process of the boiler of a thermal power plant, the cleaning condition of the monitoring tube is checked, and if there is a hydroxyapatite scale layer on the monitoring tube, a process for removing the hydroxyapatite scale layer is used after the iron oxide scale layer is completely removed;

[0048] 2. After the water flushing after the acid cleaning is qualified, an inhibitor is added to the cleaning system, a hydroxyapatite scale cleaning agent is prepared, the initial pH of the cleaning agent is controlled to be 3.5, and the cleaning agent contains 0.1% citric acid, 0.5% sulfamic acid and 0.2% DPTA; wherein, according to the mass percentage, the inhibitor contains 25% benzotriazole, 15% methyl benzotriazole, 21% thiourea, 16% sodium gluconate, 18% defoaming agent and the balance of desalted water.

[0049] 3. After the hydroxyapatite scale layer is completely removed, water flushing is performed, and after the water flushing is qualified, an EDTA rinsing solution is prepared, the initial pH of the rinsing solution is controlled to be 4.5, and the initial EDTA rinsing solution mass concentration in the cleaning system is 0.5%;

[0050] 4. The rinsing solution is added to the system, the iron ion and free EDTA rinsing solution concentration in the system are tested regularly, after the iron ion and free EDTA rinsing solution concentration are balanced, the pH of the system is adjusted to 9.0 using ammonia water, passivation is started, and the passivation liquid is discharged after the passivation is completed.

[0051] Example 2

[0052] A method for removing hydroxyapatite in the chemical cleaning of a boiler of a thermal power plant, specifically comprising the following steps:

[0053] 1. During the acid cleaning process of the boiler of a thermal power plant, the cleaning condition of the monitoring tube is checked, and if there is a hydroxyapatite scale layer on the monitoring tube, a process for removing the hydroxyapatite scale layer is used after the iron oxide scale layer is completely removed;

[0054] 2. After the water flushing after the acid cleaning is qualified, an inhibitor is added to the cleaning system, a hydroxyapatite scale cleaning agent is prepared, the initial pH of the cleaning agent is controlled to be 3.8, and the cleaning agent contains 0.2% citric acid, 0.5% sulfamic acid and 0.3% DPTA; wherein, according to the mass percentage, the inhibitor contains 30% benzotriazole, 20% methyl benzotriazole, 22% thiourea, 16% sodium gluconate, 10% defoaming agent and the balance of desalted water.

[0055] 3. After the hydroxyapatite scale layer is completely removed, water flushing is performed, and after the water flushing is qualified, an EDTA rinsing solution is prepared, the initial pH of the rinsing solution is controlled to be 4.0, and the initial EDTA rinsing solution mass concentration in the cleaning system is 0.7%;

[0056] 4. Add the rinsing solution to the system, regularly test the system iron ion and free EDTA rinsing solution concentration, after the iron ion and free EDTA rinsing solution concentration balance, use ammonia to adjust the system pH to 10.0, start passivation, after the passivation is completed, discharge the passivation solution.

[0057] Example 3

[0058] A method for removing hydroxyapatite in a thermal power plant boiler chemical cleaning, specifically comprising the following steps:

[0059] 1. During the pickling process of the thermal power plant boiler, check the cleaning condition of the monitoring tube, if the monitoring tube has a hydroxyapatite scale layer, then ensure that the iron oxide scale layer is completely removed before adopting the process for removing the hydroxyapatite scale layer;

[0060] 2. After the water flushing after pickling is qualified, add the corrosion inhibitor to the cleaning system, prepare the hydroxyapatite scale cleaning agent, control the initial pH of the cleaning agent to be 4.0, and the cleaning agent contains 0.25% citric acid, 0.5% sulfamic acid, and 0.35% DPTA; wherein, according to the mass percentage, the corrosion inhibitor contains 40% benzotriazole, 15% methyl benzotriazole, 20% thiourea, 15% sodium gluconate, 5% defoaming agent, and the rest is desalted water.

[0061] 3. After the hydroxyapatite scale layer is completely removed, perform water flushing, and after the water flushing is qualified, prepare the EDTA rinsing solution, control the initial pH of the rinsing solution to be 5.0, and the initial EDTA rinsing solution mass concentration in the cleaning system is 0.8%;

[0062] 4. Add the rinsing solution to the system, regularly test the system iron ion and free EDTA rinsing solution concentration, after the iron ion and free EDTA rinsing solution concentration balance, use ammonia to adjust the system pH to 10.0, start passivation, after the passivation is completed, discharge the passivation solution.

[0063] Example 4

[0064] A method for removing hydroxyapatite in a thermal power plant boiler chemical cleaning, specifically comprising the following steps:

[0065] 1. During the pickling process of the thermal power plant boiler, check the cleaning condition of the monitoring tube, if the monitoring tube has a hydroxyapatite scale layer, then ensure that the iron oxide scale layer is completely removed before adopting the process for removing the hydroxyapatite scale layer;

[0066] 2. After the water rinsing after the acid washing is qualified, the corrosion inhibitor is added into the cleaning system, the hydroxyapatite scale layer cleaning agent is prepared, the initial pH of the cleaning agent is controlled to be 3.9, the cleaning agent contains 0.28% citric acid, 0.5% sulfamic acid, 0.38% DPTA; wherein, according to the mass percentage, the corrosion inhibitor contains 25% benzotriazole, 25% methyl benzotriazole, 30% thiourea, 10% sodium gluconate, 8% defoaming agent and the rest is desalted water.

[0067] 3. After the hydroxyapatite scale layer is completely removed, water rinsing is carried out, and after being qualified, the EDTA rinsing solution is prepared, the initial pH of the rinsing solution is controlled to be 5.0, and the initial EDTA rinsing solution mass concentration in the cleaning system is 0.8%;

[0068] 4. The rinsing solution is added into the system, the iron ion and free EDTA rinsing solution concentration in the system are regularly tested, after the iron ion and free EDTA rinsing solution concentration are balanced, the pH of the system is adjusted to 10.2 by using ammonia water, passivation is started, and the passivation liquid is discharged after the passivation is completed.

[0069] Application example

[0070] The chemical cleaning of a certain 135MW subcritical boiler adopts composite organic acid cleaning, the water-cooled wall monitoring tube is checked in the later cleaning stage, and it is found that there is a large area of white hydroxyapatite scale layer on the inner wall of the monitoring tube, the acid washing step is stopped after the black iron oxide scale layer is completely removed by continuing cleaning. After the acid washing, water rinsing is carried out, and the rinsing end point is that the pH value is 5.1 and the total iron in the system is 15mg / L. The corrosion inhibitor is added into the cleaning system, the hydroxyapatite scale layer cleaning agent is prepared, 0.2% citric acid, 0.5% sulfamic acid and 0.2% DPTA are added, the pH value is adjusted to 3.8 by using ammonia water, the circulating temperature is controlled to be 85-95℃, and after six hours of circulating cleaning, the hydroxyapatite scale layer is completely removed. After being emptied, water rinsing is carried out until the pH value is 4.2 and the total iron in the system is 25mg / L, the system is switched to carry out rinsing, the EDTA rinsing solution is prepared, the pH value of the rinsing solution is 4.9, the EDTA rinsing solution concentration is 0.5%, and the system temperature is controlled to be 50-80℃. After four hours of rinsing, the total iron in the system and the free EDTA rinsing solution are balanced, ammonia water is added into the system to convert passivation, the passivation pH value is 9.5, and after four hours of passivation, the passivation liquid in the system is discharged. After the cleaning, the monitoring tube is checked, the passivation film is complete, there is no pitting and secondary rust.

[0071] The inner wall photos of the tube sample before and after the hydroxyapatite scale layer cleaning agent removal process of the monitoring tube are shown as Figure 1 (a) is before cleaning, and (b) is after cleaning. It can be seen that after the use of the embodiment, the passivation film is complete, there is no pitting and secondary rust.

[0072] After the chemical cleaning of the embodiment, the deposits on the inner surface of the water cooling wall tube are all cleaned, and the passivation film is formed completely; the average descaling rate of the water cooling wall tube to the fire side is 97.6%, and the average descaling rate of the back fire side is 98.0%; the total amount of SA-210C material corrosion is 7.00g / m 2 , and the average corrosion rate is 0.32g / (m 2 ·h); all indexes reach the excellent standard stipulated in DL / T794-2012 "Guidelines for Chemical Cleaning of Boilers in Thermal Power Plants".

[0073] The optional embodiments of the application are described in detail above in combination with the drawings, but the application is not limited thereto. Within the technical concept of the application, the technical solutions of the application can be subjected to various simple modifications. Each specific technical feature is combined in any suitable manner. In order to avoid unnecessary repetition, the application will not be described again for various possible combination manners. However, these simple modifications and combinations should also be regarded as the disclosed content of the application, and all belong to the protection scope of the application.

Claims

1. A method for removing hydroxyapatite in a chemical cleaning of a boiler of a thermal power plant, characterized by: Specifically comprising the following steps: continuing pickling to completely remove the iron oxide scale layer in the boiler cleaning system of the thermal power plant with the hydroxyapatite scale layer; adding the corrosion inhibitor to the boiler cleaning system of the thermal power plant, then adding the hydroxyapatite scale layer cleaning agent, and controlling the circulation cleaning until the hydroxyapatite scale layer is completely removed; adding the EDTA rinsing solution to the boiler cleaning system of the thermal power plant, regularly testing the iron ion and free EDTA rinsing solution concentrations of the system, adjusting the pH of the system to alkaline by using ammonia water after the iron ion and free EDTA rinsing solution concentrations are balanced, and starting passivation, and discharging the passivation solution after the passivation is completed; the hydroxyapatite scale layer cleaning agent comprises 0.1-0.3% citric acid, 0.5% sulfamic acid, and 0.2-0.4% DPTA in terms of mass percentage; the initial pH of the hydroxyapatite scale layer cleaning agent is 3.5-4.0; the initial pH of the EDTA rinsing solution is 4.5-5.5, the cleaning temperature is 50-80°C, and the initial EDTA rinsing solution mass concentration is 0.5%-1% in terms of mass percentage; the corrosion inhibitor comprises 25%-40% benzotriazole, 15%-25% methyl benzotriazole, 20%-30% thiourea, 15%-20% sodium gluconate, 5%-10% defoaming agent, and the rest is desalted water in terms of mass percentage; the mass concentration of the corrosion inhibitor added to the system is 0.2%-0.4%; the temperature for adding the hydroxyapatite scale layer cleaning agent is 85-95°C, and the pH of the system is ensured to be less than 7.0 during the cleaning process; if the pH of the cleaning system is greater than 7.0, DPTA needs to be added to adjust the pH of the system.

2. The method for removing hydroxyapatite in a thermal power plant boiler chemical cleaning according to claim 1, characterized in that: the judgment method for completely removing the iron oxide scale layer is to monitor that there is no black or red scale layer on the surface of the pipe section, and water flushing needs to be performed after pickling before adding the hydroxyapatite scale layer cleaning agent, and the water flushing needs to ensure that the total iron content of the system is less than 50 mg / L.

3. A method for removing hydroxyapatite in a chemical cleaning of a boiler of a thermal power plant according to claim 1, characterized in that: the judgment method for completely removing the hydroxyapatite scale layer by controlling the circulation cleaning is to monitor that there is no white hydroxyapatite scale layer on the surface of the pipeline, and then water flushing is performed after emptying, and the water flushing needs to ensure that the total iron content of the system is less than 50 mg / L.

4. The method for removing hydroxyapatite in a thermal power plant boiler chemical cleaning according to claim 1, characterized in that: after the EDTA rinsing solution rinsing is completed, the pH of the system is adjusted to 9.0-10.5 by using ammonia water for passivation.

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