阅读说明：本技术 一种锅炉机组清洗方法 (Boiler unit cleaning method ) 是由 潘长龙 钟志华 于 2021-07-19 设计创作，主要内容包括：本申请提供了一种锅炉机组清洗方法,涉及锅炉机组清洗技术领域,解决目前清洗方法的除垢效果不理想的技术问题。所述锅炉机组清洗方法包括：利用碱洗药剂对锅炉机组进行碱煮处理；在所述碱煮处理之后,利用酸洗药剂对所述锅炉机组进行酸洗处理；其中,所述碱洗药剂包括碳酸钠、磷酸钠和氢氧化钠和水；所述酸洗药剂包括缓蚀剂、氢氟酸氨、硫脲、浓盐酸和水。本申请提供的锅炉机组清洗方法用于清洗锅炉机组。(The application provides a boiler unit cleaning method, relates to the technical field of boiler unit cleaning, and solves the technical problem that the descaling effect of the existing cleaning method is not ideal. The cleaning method of the boiler unit comprises the following steps: carrying out alkali boiling treatment on the boiler unit by using an alkali washing agent; after the alkaline boiling treatment, carrying out acid washing treatment on the boiler unit by using an acid washing agent; wherein the alkali washing agent comprises sodium carbonate, sodium phosphate, sodium hydroxide and water; the pickling agent comprises a corrosion inhibitor, ammonium hydrofluoric acid, thiourea, concentrated hydrochloric acid and water. The application provides a boiler unit cleaning method for cleaning a boiler unit.)

1. A boiler unit cleaning method is characterized by comprising the following steps:

carrying out alkali boiling treatment on the boiler unit by using an alkali washing agent;

after the alkaline boiling treatment, carrying out acid washing treatment on the boiler unit by using an acid washing agent;

wherein the alkali washing agent comprises sodium carbonate, sodium phosphate, sodium hydroxide and water; the pickling agent comprises a corrosion inhibitor, ammonium hydrofluoric acid, thiourea, concentrated hydrochloric acid and water.

2. The boiler unit cleaning method according to claim 1, wherein the alkaline detergent is obtained by mixing a sodium carbonate solution, a sodium phosphate solution and a sodium hydroxide solution in equal amount; wherein the mass concentration of the sodium carbonate solution is 0.3-0.6%, the mass concentration of the sodium phosphate solution is 0.5-1%, and the mass concentration of the sodium hydroxide solution is 0.8-1.2%.

3. The boiler unit cleaning method according to claim 1, wherein the pickling agent is obtained by the steps of:

adding the corrosion inhibitor, ammonium hydrofluoric acid and thiourea into water to obtain a solution A, wherein in the solution A, the mass concentration of the corrosion inhibitor is 0.3-0.4%, the mass concentration of the ammonium hydrofluoric acid is 0.1-0.3%, and the mass concentration of the thiourea is 0.4-0.6%;

and (3) adding concentrated hydrochloric acid into the solution A until the mass concentration of the concentrated hydrochloric acid is 4-7%, thus obtaining the pickling agent.

4. The boiler unit cleaning method according to claim 3, wherein the pickling treatment of the boiler unit with a pickling agent comprises:

introducing the solution A into the boiler unit;

and after the preset time, introducing concentrated hydrochloric acid into the boiler unit.

5. The boiler unit cleaning method according to claim 1, wherein after the boiler unit is acid-washed with an acid washing agent, the boiler unit cleaning method further comprises:

ammonia washing is carried out on the boiler unit by using an ammonia washing agent; wherein the ammonia washing agent is a mixed solution containing ammonia water and ammonium persulfate.

6. The boiler unit cleaning method according to claim 5, wherein in the ammonia washing agent, the mass concentration of ammonia water is 1.3% -1.5%, and the mass concentration of ammonium persulfate is 0.4% -0.5%.

7. The boiler unit cleaning method according to claim 1, wherein after the alkaline boiling treatment of the boiler unit with the alkaline detergent and before the pickling treatment of the boiler unit with the pickling detergent, the method further comprises:

cooling the boiler unit and washing with water;

and when the pH value of the discharged cleaning liquid is reduced to a target pH value and the temperature is reduced to a target temperature, emptying the cleaning liquid in the boiler unit.

8. The boiler unit cleaning method according to claim 1, wherein before the alkaline boiling treatment of the boiler unit by using the alkaline detergent, the method further comprises:

and washing the boiler unit with water.

9. The boiler unit cleaning method according to claim 5, wherein the boiler unit cleaning method further comprises:

and rinsing the boiler unit by using a rinsing liquid.

10. The boiler unit cleaning method according to claim 9, further comprising:

and passivating the boiler unit.

Technical Field

The application relates to the technical field of boiler unit cleaning, in particular to a boiler unit cleaning method.

Background

The boiler unit is a heat energy conversion system commonly used in a power plant, and in the process of long-term operation, scaling is inevitably generated at positions such as a heating surface of a boiler, so that the heat transfer effect of the boiler is influenced slightly, and safety accidents such as blasting and the like are caused seriously. Therefore, it is critical that the boiler unit be cleaned to remove the scale.

However, the scale-removing effect of the existing cleaning method is not ideal due to the complex scale-forming components.

Disclosure of Invention

The invention provides a boiler unit cleaning method which can be used for solving the technical problem that the descaling effect of the existing cleaning method is not ideal.

The embodiment of the application provides a cleaning method for a boiler unit, which comprises the following steps:

carrying out alkali boiling treatment on the boiler unit by using an alkali washing agent;

after the alkaline boiling treatment, carrying out acid washing treatment on the boiler unit by using an acid washing agent;

wherein the alkali washing agent comprises sodium carbonate, sodium phosphate, sodium hydroxide and water; the pickling agent comprises a corrosion inhibitor, ammonium hydrofluoric acid, thiourea, concentrated hydrochloric acid and water.

Alternatively, in one embodiment, the alkaline detergent is obtained by mixing a sodium carbonate solution, a sodium phosphate solution and a sodium hydroxide solution in equal amount; wherein the mass concentration of the sodium carbonate solution is 0.3-0.6%, the mass concentration of the sodium phosphate solution is 0.5-1%, and the mass concentration of the sodium hydroxide solution is 0.8-1.2%.

Optionally, in one embodiment, the acid wash reagent is obtained by:

adding the corrosion inhibitor, ammonium hydrofluoric acid and thiourea into water to obtain a solution A, wherein in the solution A, the mass concentration of the corrosion inhibitor is 0.3-0.4%, the mass concentration of the ammonium hydrofluoric acid is 0.1-0.3%, and the mass concentration of the thiourea is 0.4-0.6%;

and (3) adding concentrated hydrochloric acid into the solution A until the mass concentration of the concentrated hydrochloric acid is 4-7%, thus obtaining the pickling agent.

Optionally, in an embodiment, the performing a pickling process on the boiler unit by using a pickling agent includes:

introducing the solution A into the boiler unit;

and after the preset time, introducing concentrated hydrochloric acid into the boiler unit.

Optionally, in an embodiment, after the boiler unit is acid-washed with an acid-washing agent, the boiler unit cleaning method further includes:

ammonia washing is carried out on the boiler unit by using an ammonia washing agent; wherein the ammonia washing agent is a mixed solution containing ammonia water and ammonium persulfate.

Optionally, in an embodiment, in the ammonia washing agent, the mass concentration of ammonia water is 1.3% -1.5%, and the mass concentration of ammonium persulfate is 0.4% -0.5%.

Optionally, in an embodiment, after the alkali-boiling treatment of the boiler plant by using the alkali-washing agent and before the acid-washing treatment of the boiler plant by using the acid-washing agent, the method further includes:

cooling the boiler unit and washing with water;

and when the pH value of the discharged cleaning liquid is reduced to a target pH value and the temperature is reduced to a target temperature, emptying the cleaning liquid in the boiler unit.

Optionally, in an embodiment, before the alkali-boiling treatment of the boiler unit with the alkali-washing agent, the method further includes:

and washing the boiler unit with water.

Optionally, in an embodiment, the method for cleaning the boiler unit further includes:

and rinsing the boiler unit by using a rinsing liquid.

Optionally, in an embodiment, the method for cleaning the boiler unit further includes:

and passivating the boiler unit.

The invention has the following beneficial effects:

by adopting the boiler unit cleaning method provided by the embodiment of the application, the method comprises the following steps: carrying out alkali boiling treatment on the boiler unit by using an alkali washing agent; after the alkaline boiling treatment, carrying out acid washing treatment on the boiler unit by using an acid washing agent; wherein the alkali washing agent comprises sodium carbonate, sodium phosphate, sodium hydroxide and water; the pickling agent comprises a corrosion inhibitor, ammonium hydrofluoric acid, thiourea, concentrated hydrochloric acid and water; firstly, an alkali washing agent comprising sodium carbonate, sodium phosphate, sodium hydroxide and water is used for carrying out alkali boiling on a boiler unit, so that deposits which are difficult to remove are softened, loosened and partially shed, and then an acid washing agent comprising a corrosion inhibitor, ammonium hydrofluoric acid, thiourea, concentrated hydrochloric acid and water is used for carrying out acid washing on the boiler unit so as to further remove the deposits which are still attached to the heating surface or the pipe wall of the boiler and are difficult to remove, so that a better cleaning effect can be achieved.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on the drawings without creative efforts. In the drawings:

FIG. 1 is a schematic structural view of a boiler unit;

FIG. 2 is a schematic flow chart of a boiler unit cleaning method according to an embodiment of the present disclosure;

FIG. 3 is a schematic flow chart of another boiler unit cleaning method provided in the embodiment of the present application;

FIG. 4 is a schematic flow chart illustrating another method for cleaning a boiler unit according to an embodiment of the present disclosure;

FIG. 5 is a schematic flow chart illustrating a further cleaning method for a boiler unit according to an embodiment of the present disclosure;

FIG. 6 is a schematic flow chart illustrating a further cleaning method for a boiler unit according to an embodiment of the present disclosure;

FIG. 7 is a schematic flow chart illustrating another method for cleaning a boiler unit according to an embodiment of the present disclosure;

fig. 8 is a schematic flow chart of another boiler unit cleaning method according to an embodiment of the present application.

Detailed Description

In order to make the objects, technical solutions and advantages of the present application more apparent, the technical solutions of the present application will be described in detail and completely with reference to the following specific embodiments of the present application and the accompanying drawings. It should be apparent that the described embodiments are only some of the embodiments of the present application, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

As described in the background of the present application, in the process of long-term operation, scaling inevitably occurs at positions such as a heating surface of a boiler, which may affect the heat transfer effect of the boiler, and may cause safety accidents such as blasting, etc., so that the boiler unit needs to be cleaned. The boiler unit is structurally shown in fig. 1 and comprises a raw material hopper a, a coal mill b, a powder mixer c, a burner d, a steam drum e, a downcomer f, a superheater g, a cold ash hopper h, a boiler i, a reheater j, an economizer k, an air preheater l, a blower m, a dust remover n, an induced draft fan o, a chimney p and pipelines. However, the scale-forming component is complex, and besides the common oil deposit and iron salt deposit, silicate (such as SiO) is also included₂) Sulfates (e.g. CaSO)₄) Copper oxide, and the like. The existing common cleaning method (such as citric acid cleaning method) can not achieve good scale removal effect.

In view of the above, an embodiment of the present application provides a method for cleaning a boiler unit, as shown in fig. 2, the method includes the following steps:

and 102, performing alkali boiling treatment on the boiler unit by using an alkali washing agent, wherein the alkali washing agent comprises sodium carbonate, sodium phosphate, sodium hydroxide and water.

Wherein, the alkali washing agent comprises sodium carbonate, sodium phosphate, sodium hydroxide and water, and the alkali washing agent is a mixed solution comprising sodium carbonate, sodium phosphate and sodium hydroxide. Water can be added into a cleaning solution tank, and then sodium carbonate, sodium phosphate and sodium hydroxide are added and mixed to obtain the alkaline cleaning agent; the solution in the cleaning solution tank may be further heated to rapidly dissolve sodium carbonate, sodium phosphate and sodium hydroxide.

In practical application, in order to quickly obtain the alkaline washing agent and quickly clean a boiler unit, a sodium carbonate solution, a sodium phosphate solution and a sodium hydroxide solution with certain concentrations can be prepared in advance, and when the boiler unit needs to be cleaned, the sodium carbonate solution, the sodium phosphate solution and the sodium hydroxide solution can be respectively introduced into a cleaning liquid tank to be mixed to obtain the alkaline washing agent. The concentrations of the sodium carbonate solution, the sodium phosphate solution and the sodium hydroxide solution which are prepared in advance can be set according to actual conditions (such as the scaling condition of a boiler, the solution storage condition and the like), and the amount of the sodium carbonate solution, the sodium phosphate solution and the sodium hydroxide solution which are introduced into the cleaning solution tank can also be set according to the actual conditions (such as the scaling condition of the boiler and the like). In a preferred embodiment, the mass concentration of the sodium carbonate solution prepared in advance is 0.3-0.6%, the mass concentration of the sodium phosphate solution prepared in advance is 0.5-1%, and the mass concentration of the sodium hydroxide solution prepared in advance is 0.8-1.2%; the amount of the sodium carbonate solution, the sodium phosphate solution and the sodium hydroxide solution introduced into the cleaning solution tank is equal. Wherein, the amount of the sodium carbonate solution, the sodium phosphate solution and the sodium hydroxide solution which are introduced into the cleaning solution tank is equal, and can be equal in volume.

The soda boiling is also called as caustic washing, and is characterized in that a caustic washing agent is introduced into a boiler unit, and the caustic washing agent circularly flows in the boiler unit under the high-temperature condition of the boiler unit and reacts with scale so as to dissolve or drop the scale. The path of the agent circulating in the boiler unit can be a cleaning liquid tank-an economizer-a steam drum-a water-cooled wall and a water-cooled separator-a cleaning liquid tank. It should be understood that the above-mentioned circulation path is only an example, and in practical application, the path of the agent circulation flow can be set according to the equipment to be cleaned in the boiler unit; meanwhile, a plurality of circulating paths can be established according to different devices needing to be cleaned so as to clean the boiler unit in sections.

The alkaline detergent provided by the embodiment of the application is used for alkaline boiling treatment, so that not only can oil stains and rust sediments of a boiler unit be removed, but also partial silicate sediments and sulfate sediments which are difficult to remove can be removed. The alkaline detergent provided by the embodiment of the application can chemically react with silicate sediments and sulfate sediments, so that the silicate sediments and the sulfate sediments are softened and changed into loose states, and one part of the silicate sediments and the sulfate sediments can fall off under the flowing impact of the cleaning liquid, so that the partial removal of the silicate sediments and the sulfate sediments is realized.

In order to achieve better removal effect of the sediment, the reaction time, the reaction conditions and the like of the alkaline cooking can be further set. For example, controlling the boiler unit pressure to be 30% -40% of its rated pressure can provide a greater impact force during the flow of the caustic wash agent to cause the deposits to fall off. For another example, the alkaline boiling time is controlled to be not less than 72 hours, and the contact reaction time of the alkaline detergent and the deposit is increased, thereby removing more deposit. In order to avoid the blockage of the pipeline due to the accumulation of the fallen scales, intermittent pollution discharge can be carried out at the bottom of equipment in the boiler unit, for example, the pollution discharge is carried out for 2-3 times.

And 104, after the alkaline boiling treatment, carrying out acid washing treatment on the boiler unit by using an acid washing agent, wherein the acid washing agent comprises a corrosion inhibitor, ammonium hydrofluoric acid, thiourea, concentrated hydrochloric acid and water.

Wherein, the pickling agent comprises a corrosion inhibitor, ammonium hydrofluoric acid, thiourea, concentrated hydrochloric acid and water, and the pickling agent can be understood as a mixed solution comprising the corrosion inhibitor, the ammonium hydrofluoric acid, the thiourea and the concentrated hydrochloric acid.

Corrosion inhibitors, also known as corrosion inhibitors, protect metals from the hydrochloric acid in pickling agents. The corrosion inhibitor can be inorganic corrosion inhibitor, organic corrosion inhibitor, polymer corrosion inhibitor and the like. The corrosion inhibitor may be specifically chromate, nitrite, silicate, zinc salt, polyphosphate, or the like.

Ammonium hydrofluoric acid and thiourea may be used to react with the copper oxide deposits in the scale to remove a portion of the copper oxide. The concentrated hydrochloric acid is added into the acid cleaning agent, so that the concentrated hydrochloric acid can be used for further removing silicate deposits and sulfate deposits still attached to the heating surface or the pipe wall of the boiler, and can also remove a large amount of copper oxide so as to improve the cleaning effect of a boiler unit.

The acid washing is to introduce an acid washing agent into the boiler unit, and the acid washing agent reacts with the scale in the circulating flow process in the boiler unit so as to dissolve or drop the scale. The pickling agent provided by the embodiment of the application is used for pickling, so that silicate sediments and sulfate sediments still attached to the heating surface or the pipe wall of the boiler can be further removed, copper oxide sediments are removed, and the cleaning effect of a boiler unit is further improved; and the corrosion of the metal surface by hydrochloric acid can be avoided.

In practical application, a corrosion inhibitor solution, an ammonium hydrofluoric acid solution and a thiourea solution with certain concentrations can be prepared in advance, and when the boiler unit needs to be pickled, the corrosion inhibitor solution, the ammonium hydrofluoric acid solution, the thiourea solution and concentrated hydrochloric acid can be respectively introduced into a cleaning solution box to be mixed to obtain a pickling agent. The concentrations of the corrosion inhibitor solution, the ammonium hydrofluoric acid solution and the thiourea solution which are prepared in advance can be set according to actual conditions (such as the scaling condition of a boiler, the solution storage condition and the like), and the amount of the corrosion inhibitor solution, the ammonium hydrofluoric acid solution, the thiourea solution and the concentrated hydrochloric acid which are introduced into the cleaning solution tank can also be set according to the actual conditions (such as the scaling condition of the boiler and the like). In a preferred embodiment, the pickling agent is obtained by the following steps:

adding a corrosion inhibitor, ammonium hydrofluoric acid and thiourea into water to obtain a solution A, wherein in the solution A, the mass concentration of the corrosion inhibitor is 0.3-0.4%, the mass concentration of the ammonium hydrofluoric acid is 0.1-0.3%, and the mass concentration of the thiourea is 0.4-0.6%; and (3) adding concentrated hydrochloric acid into the solution A until the mass concentration of the concentrated hydrochloric acid is 4-7%, thus obtaining the pickling agent. More preferably, in the solution A, the mass concentration of ammonium hydrofluoric acid is 0.2%, and the mass concentration of thiourea is 0.5%; based on the proportion, better cleaning effect can be achieved.

Based on the effects of the corrosion inhibitor and the ammonium hydrofluoric acid, in the embodiment of the application, the boiler unit is subjected to acid pickling treatment by using an acid pickling agent, specifically, a solution A formed by mixing the corrosion inhibitor, the ammonium hydrofluoric acid, thiourea and water is introduced into the boiler unit, so that the solution A circularly flows in a circulating path; after a preset time, concentrated hydrochloric acid is introduced into the boiler unit, mixed with the solution A and circularly flows in the circulating path. The preset time is used for forming a protective film for corrosion prevention and removing a portion of copper oxide deposits in scaling, and may be set according to the time required for forming a protective film for corrosion prevention, for example, 2 hours.

Furthermore, the reaction time and reaction conditions of acid washing can be controlled to achieve better cleaning effect. For example, before introducing the pickling agent, the temperature of a boiler unit is increased to 55-110 ℃ to ensure the reaction temperature of pickling. As another example, the pickling time is controlled within 24 hours to avoid corrosion of the boiler unit due to excessive contact with hydrochloric acid.

It can be understood that, in the boiler unit cleaning method provided by the embodiment of the application, the boiler unit is subjected to alkaline boiling by using an alkaline cleaning agent comprising sodium carbonate, sodium phosphate, sodium hydroxide and water, so that the deposits difficult to remove are softened, loosened and partially fall off, and then the boiler unit is subjected to acid cleaning by using an acid cleaning agent comprising a corrosion inhibitor, ammonium hydrofluoric acid, thiourea, concentrated hydrochloric acid and water, so that the deposits which are still attached to the heating surface or the pipe wall of the boiler and are difficult to remove are further removed, and a better cleaning effect can be achieved.

To further ensure the cleaning effect of the alkaline boiling treatment, in an embodiment, after the alkaline boiling treatment is performed on the boiler unit by using the alkaline detergent and before the acid washing treatment is performed on the boiler unit by using the acid washing detergent, as shown in fig. 3, the boiler unit cleaning method provided in the embodiment of the present application further includes step 103: and cooling the boiler unit, washing with water until the pH value of the discharged washing liquid is reduced to a target pH value, and emptying the washing liquid when the temperature is reduced to a target temperature. The target pH value and the target temperature can be set according to actual conditions. In a preferred embodiment, the target pH is 9.0 and the target temperature is 70 ℃ to 80 ℃.

During alkaline cooking, the pH value is generally about 11, the temperature is generally above 100 ℃, and the oil stains can be prevented from being adhered again by reducing the pH value to a target pH value and reducing the temperature to a target temperature, so that the cleaning effect of alkaline cooking treatment is ensured.

In order to further improve the cleaning effect of the boiler, in an embodiment, before the boiler unit is subjected to alkaline cooking treatment by using an alkaline detergent, as shown in fig. 4, the boiler unit cleaning method provided in the embodiment of the present application further includes step 101: and (5) washing the boiler unit with water.

The water washing of the boiler unit can be specifically segmented washing of each device, and the flow velocity of water flow can be controlled to be 0.8-1.2 m/s; and (4) performing alkaline boiling treatment until no obvious impurity exists in the cleaning liquid obtained by washing the boiler unit with water. When austenitic stainless steel is included in the boiler plant, the water for rinsing may be demineralized water in accordance with the GB/T12145 standard to avoid corrosion of the austenitic stainless steel.

It can be understood that through above-mentioned scheme, before utilizing the alkali wash medicament to carry out the alkali boiling to the boiler unit and handle, wash boiler unit water, can get rid of the impurity that easily is cleared up (like the impurity that adhesive force is less strong) to can improve the cleaning performance of boiler, can also practice thrift the cleaning agent of follow-up use.

In practice, a preparation before chemical cleaning may also be performed before the boiler unit is flushed with water in step 101. The preparing may specifically include: the boiler unit and the circulating cleaning system are installed, water pressure is tested, whether each pipeline is accurately installed or not is checked, a waste liquid treatment point is arranged, communication equipment is arranged at a dosing point and a pipe wall, monitoring points are arranged on a steam drum and each treatment pipe section, and if the temperature, the pressure and the like are monitored, a hearth, a tail flue and the like are sealed. Wherein, the circulation cleaning system can comprise a temporary cleaning pipeline and a cleaning pipeline of the boiler unit. Then, after the boiler unit is flushed with water in step 101, the temperature of the cleaning pipeline may be detected to detect whether each installed communication device is working normally.

The preparation material of the heating surface of the boiler mainly comprises iron, and the oxidation of the heating surface is carried out after the pickling treatment of the boiler unit by using a pickling agentThe copper deposit is dissolved to generate copper ions, the copper ions react with iron, and the iron loses electrons and is changed into Fe²⁺The copper ions are converted into copper ions, so that the copper plating phenomenon is generated on the metal surface of the heating surface. After the heating surface is plated with copper locally, a corrosion battery with copper as a cathode and iron as an anode can be formed, so that the heating surface is continuously subjected to electrochemical corrosion, and the safety operation of a boiler is damaged. Therefore, in an embodiment, after the boiler unit is subjected to the acid washing treatment by using the acid washing agent, as shown in fig. 5, the boiler unit cleaning method provided in the embodiment of the present application further includes step 105: and carrying out ammonia washing on the boiler unit by using an ammonia washing agent, wherein the ammonia washing agent is a mixed solution comprising ammonia water and ammonium persulfate.

In a preferred embodiment, the mass concentration of the ammonia water in the ammonia washing agent is 1.3% -1.5%, and the mass concentration of the ammonium persulfate is 0.4% -0.6%. More preferably, the mass concentration of ammonium persulfate is 0.5%, based on the proportion, better removal of copper ions can be realized.

It can be understood that by performing ammonia washing after pickling, copper ions generated by pickling can be removed, so that the copper ions can be prevented from reacting with iron to become copper plated on the metal surface, and the copper plating phenomenon can be prevented from occurring.

In order to achieve a better copper ion removal effect, the reaction time, reaction conditions and the like of ammonia washing can be further set. For example, the ammonia washing temperature is controlled to 25 ℃ to 30 ℃ and the ammonia washing time is controlled to 1 to 1.5 hours.

In order to further prevent metal corrosion, after the ammonia washing is emptied of the cleaning liquid, the boiler unit can be cleaned by using a mixed solution containing sodium hydroxide and sodium phosphate, and then the cleaning liquid is emptied. In the mixed solution, the mass concentration of sodium hydroxide was 0.8%, and the mass concentration of sodium phosphate was 0.3%.

In order to slow down the corrosion rate of the metal surface during the subsequent operation of the boiler unit, in an embodiment, after the boiler unit is subjected to ammonia washing by using the ammonia washing agent, as shown in fig. 6, the boiler unit cleaning method provided by the embodiment of the present application further includes steps 106 and 107, wherein the step 106 includes: rinsing the boiler unit by using a rinsing liquid; step 107 comprises: and passivating the boiler unit.

Wherein, in step 106, the rinsing liquid comprises citric acid, corrosion inhibitor and ammonia water. Rinsing the boiler unit by using a rinsing liquid, specifically, introducing a citric acid solution with the mass concentration of 0.1-0.3% into the boiler unit, adding a corrosion inhibitor with the mass concentration of 0.1%, introducing ammonia water to adjust the pH value to 3.5-4.0, and then rinsing, wherein the circulation temperature of a cleaning liquid is controlled to be 50-80 ℃, and the circulation time is 2 hours. After the iron content in the rinsing liquid is less than 300mg/L, passivation is carried out, namely step 107 is carried out.

Step 107, passivating the boiler unit, specifically adopting a water top acid method to wash the metal in the boiler unit without contacting with air until the pH value of the washing liquid is 4.0-4.5 and the iron content is less than 50mg/L, establishing water circulation, adjusting the pH value to 8.5-9.5 in a short time, introducing free EDTA to the mass concentration of 0.5-1%, carrying out oxygenation passivation, controlling the passivation temperature to be 60-70 ℃, and stopping passivation when the oxidation-reduction potential of the solution is increased to-200 mv to-100 mv. Wherein the short time period may be 30 minutes.

Based on the boiler unit cleaning method provided by the above embodiment of the present application, an embodiment of the present application further provides a specific boiler unit cleaning method, as shown in fig. 7, the method includes:

step 201, performing pretreatment before chemical cleaning on the boiler unit.

The method specifically comprises the following steps: and (3) installing a boiler unit and a circulating cleaning system, testing whether the water pressure in each device is normal or not, checking whether each pipeline is accurately installed or not, carrying out subsequent cleaning steps after detecting no abnormality, and timely processing if the abnormality exists. And a waste liquid treatment point is arranged to ensure that the cleaning liquid can be normally discharged. Meanwhile, in order to avoid errors in control of temperature, pressure and the like in each cleaning stage of the boiler unit, corresponding communication equipment is arranged on a dosing point and the pipe wall of the pipeline, so that abnormal equipment can be warned in time; monitoring points may also be provided on the respective process pipe sections and drums to facilitate later control of the level of the liquid. In addition, the heat preservation effect of the boiler unit is realized by sealing the hearth and the tail flue. Considering that the materials of all equipment in the boiler unit are different, different circulating cleaning pipelines can be arranged aiming at different equipment to be cleaned, so that different equipment can be cleaned by different cleaning agents.

Step 202, washing the boiler unit with water.

Carry out water washing to boiler unit between alkali boils, can wash the pipeline to each circulation and carry out the operation test, whether test monitoring point, communication equipment can normally work, can also realize preliminary edulcoration (detach impurity) simultaneously, impurity can be the impurity of more easily getting rid of such as non-scale deposit class impurity.

Step 202, performing water washing on the boiler unit, which may specifically include: and (3) washing with clear water, and when a plurality of circulating cleaning pipelines exist, performing sectional washing, and controlling the flow rate of water flow to be 1m/s (+ -0.2 m/s) until no obvious impurities exist in the washed cleaning liquid. For austenitic stainless steel equipment, the austenitic stainless steel structure may be protected by flushing with demineralized water conforming to the GB/T12145 standard. After cleaning, heating operation detection is carried out on the cleaning pipeline, and the pressure in the boiler unit is raised to a proper pressure so as to simulate the operation condition during subsequent cleaning and timely process the abnormal condition.

And 203, performing alkali boiling treatment on the boiler unit by using an alkali washing agent, wherein the alkali washing agent comprises sodium carbonate, sodium phosphate, sodium hydroxide and water.

The alkali washing agent is obtained by mixing a sodium carbonate solution, a sodium phosphate solution and a sodium hydroxide solution in equal amount (equal volume). Wherein, the mass concentration of the sodium carbonate solution is 0.3 to 0.6 percent, the mass concentration of the sodium phosphate solution is 0.5 to 1 percent, and the mass concentration of the sodium hydroxide solution is 0.8 to 1.2 percent.

The alkali boiling treatment of the boiler unit by using an alkali washing agent specifically comprises the following steps: and respectively introducing a sodium carbonate solution, a sodium phosphate solution and a sodium hydroxide solution into the cleaning solution tank. Each solution can be intermittently introduced into the cleaning solution tank as one cycle with the cleaning solution circulating once in the cleaning circulation line. For example, a sodium carbonate solution, a sodium phosphate solution and a sodium hydroxide solution are introduced into the cleaning liquid tank to obtain an alkaline cleaning agent, and the sodium carbonate solution, the sodium phosphate solution and the sodium hydroxide solution are introduced into the cleaning liquid tank for the second time when the alkaline cleaning agent is discharged from the cleaning liquid tank and returns to the cleaning liquid tank again. The sodium carbonate solution, the sodium phosphate solution and the sodium hydroxide solution are uniformly pumped into the cleaning solution box in equal quantity, so that the components are fully mixed. In order to ensure the descaling effect of the alkali cleaning agent, the pressure of the boiler unit is controlled to be 30-40% of the rated value, the alkali boiling time is controlled to be more than 72 hours, and then large scales can fall off. In order to avoid the blockage of pipelines by the falling scales in the circulating process and to facilitate the cleaning of the falling scales, the pollution discharge is carried out from the bottom of the equipment in the alkali boiling process, and the pollution discharge can be carried out for 2-3 times regularly. And (3) after the alkali cooking is finished, introducing water for cleaning, and completely discharging the cleaning solution when the pH value of the discharged cleaning solution is reduced to 9.0 and the temperature is reduced to 70-80 ℃.

And 204, after the alkaline boiling treatment, carrying out acid washing treatment on the boiler unit by using an acid washing agent, wherein the acid washing agent comprises a corrosion inhibitor, ammonium hydrofluoric acid, thiourea, concentrated hydrochloric acid and water.

In order to ensure the descaling effect of acid pickling, the boiler unit is heated to 55 ℃ in advance after alkali boiling and before acid pickling. The boiler unit is subjected to acid washing treatment by using an acid washing agent, and the method specifically comprises the following steps: adding water into a cleaning solution tank, then adding a corrosion inhibitor, wherein the mass concentration of the corrosion inhibitor is 0.3-0.4%, and then adding ammonium hydrofluoric acid and thiourea, wherein the mass concentration of the ammonium hydrofluoric acid is 0.2%, and the mass concentration of the thiourea is 0.5%; after the solution is circularly cleaned for a certain time, adding concentrated hydrochloric acid until the mass concentration of the concentrated hydrochloric acid is 4-7%. Within the certain time, the corrosion inhibitor can form a protective film on the metal surface to prevent the metal surface from being corroded by hydrochloric acid; the ammonium hydrofluoric acid and the thiourea can react with the copper oxide to remove part of the copper oxide; hydrochloric acid can remove scale still attached to the metal surface which is difficult to remove, and can also remove a large amount of copper oxide. The concentrated hydrochloric acid may be added uniformly according to the rate of circulation of the solution. The time for cleaning the boiler unit by the cleaning solution (solution A) without hydrochloric acid is controlled within 24 hours, the time for cleaning the superheater is not more than 48 hours, and the time for cleaning the boiler unit by the cleaning solution containing hydrochloric acid is not more than 10 hours. And after the acid washing is finished, draining the cleaning solution.

And step 205, performing ammonia washing on the boiler unit by using an ammonia washing agent, wherein the ammonia washing agent is a mixed solution comprising ammonia water and ammonium persulfate.

The mass concentration of ammonia water in the ammonia washing agent is 1.3-1.5%, the mass concentration of ammonium persulfate is 0.5%, the ammonia washing temperature is controlled at 25-30 ℃, and the washing time is controlled at 1-1.5 h. The ammonia washing agent can react with the residual copper ions in the boiler unit to remove the copper ions. After ammonia washing, the washing liquid is discharged, and then the mixed solution containing 0.8 percent of sodium hydroxide and 0.3 percent of sodium phosphate is used for washing, and then the washing liquid is discharged.

And step 206, rinsing the boiler unit by using the rinsing liquid.

Rinsing the boiler unit by using the rinsing liquid, which specifically comprises the following steps: firstly introducing a citric acid solution with the mass concentration of 0.1-0.3% into a boiler unit, then adding a corrosion inhibitor with the mass concentration of 0.1%, then introducing ammonia water to adjust the pH value to 3.5-4.0, and then rinsing, wherein the circulation temperature of the cleaning solution is controlled to be 50-80 ℃, and the circulation time is 2 hours. After the iron content in the rinsing liquid is less than 300mg/L, passivation is performed, that is, step 207 is performed.

And step 207, passivating the boiler unit.

The passivating treatment of the boiler unit specifically includes: adopting a water top acid method to wash the metal in the boiler unit without contacting with air until the pH value of the cleaning solution is 4.0-4.5 and the iron content is less than 50mg/L, establishing water circulation, adjusting the pH value to 8.5-9.5 in a short time, introducing free EDTA to the mass concentration of 0.5-1%, carrying out oxygenation passivation, controlling the passivation temperature to be 60-70 ℃, and stopping passivation treatment when the oxidation-reduction potential of the solution is increased to-200 mv to-100 mv. Wherein the short time period may be 30 minutes.

It can be understood that, according to the scheme, firstly, the boiler unit is subjected to alkali boiling by using an alkali washing agent comprising sodium carbonate, sodium phosphate, sodium hydroxide and water, so that deposits which are difficult to remove are softened, loosened and partially fall off, and then, the boiler unit is subjected to acid washing by using an acid washing agent comprising a corrosion inhibitor, ammonium hydrofluoric acid, thiourea, concentrated hydrochloric acid and water, so that the deposits which are still attached to the heating surface or the pipe wall of the boiler and are difficult to remove are further removed, and a better cleaning effect can be achieved. On the other hand, under the condition that more copper ions remain after acid washing, ammonia washing is carried out, so that the copper plating phenomenon can be effectively avoided, and the safe operation of the boiler unit can be ensured.

In practical applications, in order to save cleaning cost and cleaning time under the conditions that copper ions remaining after pickling are few and a copper plating phenomenon is not easy to occur, an embodiment of the present application further provides a specific boiler unit cleaning method, as shown in fig. 8, the method includes:

step 301, performing pretreatment before chemical cleaning on the boiler unit.

Step 302, washing the boiler unit with water.

And 303, performing alkali boiling treatment on the boiler unit by using an alkali washing agent, wherein the alkali washing agent comprises sodium carbonate, sodium phosphate, sodium hydroxide and water.

And 304, after the alkaline boiling treatment, carrying out acid washing treatment on the boiler unit by using an acid washing agent, wherein the acid washing agent comprises a corrosion inhibitor, ammonium hydrofluoric acid, thiourea, concentrated hydrochloric acid and water.

The specific implementation manners of step 301, step 302, step 303 and step 304 may refer to the above embodiments, and are not described herein again.

Step 305, the boiler unit is flushed with water and nitrogen is introduced.

Injecting water into the circulating cleaning pipeline to discharge residual pickling solution, introducing nitrogen with the purity of more than 97 percent into the circulating cleaning pipeline to eject the waste acid solution, and repeatedly flushing until the pH value of the discharged cleaning solution is 4.0-4.5. And finally, manually cleaning residues which are difficult to clean in the steam drum and the cleaning solution tank.

And step 306, rinsing the boiler unit by using the rinsing liquid.

And 307, passivating the boiler unit.

The specific implementation manner of step 306 and step 307 may refer to the above embodiments, and is not described herein again.

It can be understood that, according to the scheme, firstly, the boiler unit is subjected to alkali boiling by using an alkali washing agent comprising sodium carbonate, sodium phosphate, sodium hydroxide and water, so that deposits which are difficult to remove are softened, loosened and partially fall off, and then, the boiler unit is subjected to acid washing by using an acid washing agent comprising a corrosion inhibitor, ammonium hydrofluoric acid, thiourea, concentrated hydrochloric acid and water, so that the deposits which are still attached to the heating surface or the pipe wall of the boiler and are difficult to remove are further removed, and a better cleaning effect can be achieved.

It should also be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.

Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.