Flushing of boilers and heat exchangers: technology, chemicals. Chemical flushing and cleaning of boilers completely remove scale and other deposits

Cleaning, flushing of industrial boilers and repair of the circuit is one of the services that we provide to regular and new customers. Our specialists will competently perform chemical, hydrodynamic and mechanical cleaning, flushing of the boiler, heat exchanger and piping systems. Under influence high temperatures in a boiler device of any type, sooner or later, deposits and scale begin to form. Salt and scale adversely affect thermal conductivity, increase fuel consumption.

Among the services we provide - cleaning and flushing of industrial boilers:

Cleaning and flushing of heating boilers;

Cleaning and flushing of gas boilers;

Cleaning and flushing of hot water boilers;

Cleaning and flushing of steam boilers;

Cleaning and flushing of boiler heat exchangers;

Cleaning and washing of boilers dkvr.

Timely and professional service boilers - a guarantee of uninterrupted and effective work your equipment. Boiler cleaning can be done in different ways:

Chemical cleaning boiler descaling;

Hydrodynamic cleaning washing the boiler from scale and soot;

Mechanical cleaning boiler descaling.

For selection best way boiler cleaning, correct selection equipment and reagents, it is necessary to contact specialists.

Hydrodynamic cleaning boiler flushing

By contacting GLOBAL-ENGINEERING LLC, you can also order the processing of the boiler apparatus hydrodynamic method. This is a physical action on deposits in boilers using a high pressure water jet. Possibility of mechanical damage inner surface system is completely excluded here, which cannot be guaranteed in the case of using other mechanical methods. Our masters have everything necessary fixtures for pre-start purge and flushing of the steam boiler by the hydrodynamic method. This is one of the most effective ways rid the boiler of dirt and scale. Hydrodynamic cleaning Washing of boilers is carried out with water under high pressure using special equipment for washing (special pumps, attachments and other devices). To remove heavy deposits, a device is used over high pressure(ASVD).

Chemical cleaning Boiler flushing

The main condition for high performance and full-fledged functioning of boiler equipment is regular flushing of deposits. Chemical washing is usually applied to both household and industrial boilers. Minimize the corrosive effect on metal parts possible only with proper monitoring of the state of the boiler unit. If you neglect regular cleaning of the system, the heating capacity of the boiler will decrease, and scale will form on its inner surface.

Scope of work during chemical washing of the boiler:

• Preliminary diagnostics of water circuits heat exchange equipment hydraulic method overpressure. (for the tightness of the circuits)
• Chemical cleaning in place of industrial boilers, monitoring the progress of the reaction by measuring the pH level throughout the cleaning.
• Alkalinization of the boiler.
• Neutralization of the washing solution, repeated washing with water.
• Hydraulic tests (pressurization) of the boiler.

What do you get as a result of flushing or cleaning the boiler:

• Reduce fuel consumption by up to 25%;
• Decreases the likelihood of emergencies(local overheating, cracks at individual nodes, etc.) by 60%;
• Increased service life after washing.

Prevention is The best way avoid unscheduled, and therefore costly repairs or, even worse, a complete replacement of equipment.

Our staff employs qualified and experienced employees who know their business, so flushing the boiler will not be difficult for them. We are always ready to help you, so if you have any questions, you can contact our managers who will answer your questions 24/7. Entrust the boiler cleaning procedure experienced professionals. Contact a reliable engineering service company.

The boiler works properly as long as it is clean. But in the process of work, pollution is sure to appear that disrupts the work, for the removal of which chemical flushing of the boiler is necessary. Reagents and equipment are indispensable. Carbon deposits form on top of the heat exchanger, but this is a disaster, it can be easily removed mechanically during the next maintenance. But scale and deposits form inside the heat exchanger. Only flushing the boiler with chemistry will remove all this.

Typical design of a gas boiler

What happens when the boiler gets dirty

For normal operation boiler, the rate of heat exchange between the flame and the coolant (usually water) is important. If an obstacle appears in the form of soot on top of the heat exchanger, and in the form of scale inside it, then, accordingly, more energy will fly into the pipe, and not indulge in the good deed of heating the home. Also, scale inside thin tubes reduces the clearance, slows down the movement of fluid.

At the same time, the general diagnosis for the boiler does not look too confident - “it heats worse”. But the losses from this do not decrease and the house does not become warmer.

When it's time to do a chemical flush of the heat exchanger

The fact is that the exact timing for chemical cleaning The insides of the boiler do not exist, there are only general recommendations:

• for a system with water, flush every 3 years;
• for antifreeze - once every 2 years;

But often, units that are not washed for 5–20 years work tolerably and do not particularly complain about anything. But only when there is water in the system and there was no serious water exchange.

If there were leaks and there was constant make-up, then not only the radiators suffered from deposits, but first of all the boiler. Therefore, it is necessary to realistically answer for a specific heating of the house, - “Isn't it time to flush the boiler?”.

Elements of boiler equipment can be significantly contaminated

Everyone knows that Coca-Cola (from The Coca-Cola Company) cleans scale, deposits. (if you do not trust, you can experiment and pour the drink somewhere on the deposits, for example, in the toilet). But citric acid in high concentration fights scale more cheaply and more effectively. The one that is sold in bags in a culinary store, and in which everyone soaks heating elements from electric water heaters.

The same home craftsmen can do with the inside of the heat exchanger. The tank is closed to the boiler on both sides, the pump is manually turned on periodically, and “in theory” citric acid will eat up all the internal scale in the boiler system in all its nooks and crannies in a day.

Flushing with a booster

The specialists have special equipment for flushing boilers in private homes with chemical reagents. The device is called a booster, it works in the same way as described above.

Booster consists of:

• a tank with a supply of reagent;
• a pump that drives this liquid through the boiler and through this tank;
• heating ten, which is necessary to speed up the process, because when heated chemical reactions can accelerate significantly.

It remains to invite a specialist with such a device for cleaning the boiler with chemistry.

How is the boiler cleaned?

• The boiler is disconnected from the system and connected to the booster with two branch pipes, “inlet” and “outlet”.
• The booster and the boiler, combined into a small system, are filled with reagent, air is removed (the booster is above the boiler).
• The device turns on. A few hours is usually sufficient for high performance reagents.
• The liquid is drained from this system into special containers and must be sent for disposal.
• A flushing agent is poured into the system to destroy the acid. The booster system is flushed again with water.
• After turning off the booster, it is recommended to additionally drive water through the heat exchanger through the heat exchanger to remove all chemical residues, as they can be aggressive to the heating system.

The washed heat exchanger is reconnected to the heating system.

How is the boiler heat exchanger usually washed?

At the household level, concentrated water is more often used for chemical washing of the boiler. citric acid, which is not too dangerous and aggressive. But reactions take a long time (days), no one gives guarantees of complete success.

Specialists with boosters usually use more complex flushing compositions. Some of them can be dangerous, serious safety precautions are required when flushing the boiler with chemical solutions.

• Substance with adipic acid.
• Reagent based on sulfamic acid. Effective cleaner but requires flushing and care.
• Hydrochloric acid - about labor protection, and environmental protection, it is probably unnecessary to remind.

At chemical washing boilers must have overalls, goggles, rubber gloves.

Where to go for chemical cleaning of boiler equipment

In any locality, craftsmen with their know-how will be found, who will undertake to clean any boiler from anything for an inexpensive price. But here it is recommended to contact the service center that provides warranty (technical) maintenance of this boiler. True, most likely, this procedure will seem to the owners not cheap. But much here is determined by security and environmental issues, for the solution of which hard-earned hard-earned money will have to be paid ...

One of the mandatory procedures, which aims to extend the life of the boiler plant, as well as to prevent the occurrence of emergencies, is the cleaning and maintenance of hot water boilers. This equipment is constantly at risk of contamination and scale formation on all internal surfaces of the boiler due to the constant high temperatures that catalyze the formation of deposits. If scale forms in the boiler, it loses its ability to conduct heat normally and this leads to big expense electricity, and in the future to the failure of the system. In order to prevent repair or replacement of equipment, boilers should be regularly descaled.

The reason for the formation of scale in boilers is the high content of various pollutants in the water, such as dissolved iron and salt liquids, which settle on the hot surface of the boilers and this leads to the impossibility of their normal operation. In order to clean water boilers from scale, today they use different ways. The most widely used chemical and mechanical cleaning of hot water boilers, they allow you to remove most of the pollution. The choice of suitable cleaning methods for hot water boilers depends on the particular design of the boiler. For example, not suitable for soldered systems mechanical method, but at the same time, great attention should be paid to the degree of contamination of the boiler, because chemical cleaning cannot always cope with large quantity pollution. But, despite this, today, the most common method is chemical cleaning of hot water boilers, because it is this method that has the necessary efficiency and is an economically viable way to clean hot water boilers.

Chemical cleaning of hot water boilers refers to the treatment of contaminated surfaces with the help of special chemicals that destroy carbonate or any other deposits. Efficiency this method depends on two factors: on the choice of the optimal reagent for cleaning the boiler and on correct operation special equipment for cleaning boilers.

And cleaning is carried out only if there is specialized equipment for cleaning boilers, the main task of which is to supply a heated cleaning solution under a specific pressure to the system. It is necessary to control the temperature, as well as the pressure of the solution, this is due to the influence of these factors on the course of the reaction between scale and cleaning solution and on the efficiency of chemical cleaning of boilers.

For chemical cleaning of boilers, strong acids are used, which do an excellent job of dissolving most of the possible substances. For example, hydrochloric acid solutions are used to clean water-heating boilers from carbonate scale, and phosphoric acid solutions are used to remove metal oxides. Reagents for cleaning boilers are selected based on information about the composition of scale and taking into account the compatibility of reagents and the material from which certain parts of the boiler are made.

One more required condition in the chemical cleaning of hot water boilers - this is a special equipment for cleaning boilers. The main task of the equipment is to prepare, prepare and supply cleaning solutions to the system and to ensure the circulation of the solution in the system, as well as its subsequent removal. Equipment for cleaning hot water boilers consists of several elements. First of all, it includes a tank for, where the solution necessary for cleaning is located, a heating block that raises the temperature of the solution to the desired value, and a pump that supplies and removes the boiler cleaning solution from the system. In addition, it should be taken into account the importance of the fact that for high-quality cleaning of the boilers, the equipment pump must switch to the flow reverse mode, in which the waste solution will be removed from the system.

All elements of this equipment are made of chemically resistant materials because each piece of equipment is in contact with aggressive acids.

• To achieve the optimal result of boiler cleaning, complex hydrochemical and hydrodynamic, hydropower and hydroabrasive cleaning technologies are used, which are currently the most effective.
• During the work, high-quality powerful equipment is used, including hydrodynamic machines with a pressure of up to 1500 bar, installations for cleaning the internal surfaces of pipes using soft abrasive materials, hydraulic impulse equipment for cleaning pipes with diameters from 10 to 100 mm, as well as pumping stations with a capacity of up to 200 m3 / h to ensure the circulation of reagents.
• The company has implemented a quality management system ISO 9001-2008, which guarantees the accuracy of all business processes.
• The company has implemented the environmental management system ISO 14001:2004.
• The company has implemented the occupational safety and health management system OHAS 18001:2007
• For the most effective cleaning by the hydrochemical method, reagents and corrosion inhibitors with the highest efficiency are used.
• The company is a design organization and has a SRO permit for the design of works that affect the safety of facilities capital construction, for each type of work, a project for the production of work or technological regulations is developed.
• Professional specialists have all the necessary certificates and carry out work strictly according to technological maps.
• The VekFort company is responsible for the structural materials of boiler equipment and excludes their damage.
• The company employs qualified inspectors whose duty is to conduct internal control of the work performed before handing it over to the customer.

The hydrochemical method of cleaning is the process of cleaning the internal surfaces of thermal and heat exchange equipment and systems from scale-corrosion deposits by circulating working solutions of special technical detergents, mineral or organic acids with special additives along the circuit. The flushing process dissolves and removes deposits without damaging the underlying structural material. The technology is used for cleaning heating systems, non-separable boilers and heat exchangers.

Hydro-chemical flushing is very effective in removing deposits in thermal and heat exchange systems, including pipelines, as it completely dissolves and removes all deposits from the system. Deposits, as a rule, are multicomponent solid layers, which consist of iron oxides and carbonates, phosphates, sulfates, calcium oxide, magnesium, they create a large thermal resistance heat flow, which leads to a decrease in the temperature of the coolant and a decrease in the thermal conductivity of the heating system.

Hydrochemical cleaning of the internal surfaces of hot water boilers must be carried out on a regular basis, since the formation of scale-corrosive deposits on the internal surfaces of the water path of the boiler during its operation leads to a significant decrease in its operating efficiency and the entire associated system. This leads to a decrease and destabilization of the heat exchange of the system, equipment failures, damage to pipelines and increased fuel consumption.

Periodic hydrochemical cleaning of hot water boilers avoids all negative consequences associated with the formation of solid scale-corrosive deposits!

The amount of deposits on the internal surfaces of the boiler must be determined after each heating season based on the methodology for determining the density and composition of deposits given in RD 153-34.1-37.306-2001.

We carry out works on cleaning water boilers from scale-corrosion deposits in the following order:

1. Inspection of the state of the hot water boiler.

The inspection of the state of the boiler is carried out jointly with representatives of the operation service. Before starting work, it is necessary to cut a pipe sample, preferably a section of the outer coil of the convective part, as the most determining resistance, in order to determine the degree of clogging with deposits. The survey can be carried out both visually and laboratory, by analyzing the full composition of the sediments. The method of laboratory examination is carried out in specialized laboratories.

2. Washing the internal surfaces of the boiler network water.

3. Installation of the cleaning circuit.

The boiler is turned off and fittings are inserted to connect the equipment and create a flushing circulation circuit.
For organization technological process chemical cleaning of hot water boilers, a chemical cleaning scheme is mounted.

The scheme should allow organizing all technological operations necessary for chemical cleaning, namely:

• preparation of a cleaning solution;
• filling the boiler with cleaning solution;
• removal from the washing circuit of air and gases formed during the dissolution of deposits;
• circulation of washing and neutralizing solutions;
• neutralization and removal of the wash solution;
• intensive water washing of all internal surfaces of boilers.

The chemical treatment scheme may include the following equipment:

• tanks for the preparation and neutralization of the washing solution, are the capacity necessary for the stable operation of the circulation circuit;
• circulation pumps necessary for filling the boiler, displacing the flushing solution, creating circulation in the flushing circuit;
• chemical barrel pump - for supplying detergent or neutralizing reagents to the tank when preparing or neutralizing the cleaning solution.
• connecting hoses, quick-fixing and flange connections, fittings and fittings - for organizing a circulation flushing circuit, filling and emptying the boiler.
• Figure 1 shows the principle technology system chemical cleaning of the hot water boiler DKVR-10/13.

4. Alkalinization of the boiler.

Alkalinization is used to remove oily, silicic and other contaminants from the internal surfaces of the boiler, as well as some of the loose rust and scale formed during the manufacture, storage and installation of equipment. Cleaning the internal surfaces of the boiler from loose rust, oils and other contaminants is carried out by treating the boiler with a 0.5-0.8% solution of sodium hydroxide with the addition of a 0.3-0.5% solution of trisodium phosphate (alkali) in compliance with the precautionary measures .

As a result of alkalinization, i.e. treatment of the inner surface of the boiler with an alkaline-phosphate solution, occurs:
a) weakening the adhesion of the layer of rust and scale with the metal due to the penetration of the alkali solution into the cracks, its evaporation and partial dissolution of iron oxides with the formation of sodium ferrites;
b) saponification or emulsification of oily contaminants;
c) partial dissolution of silicic impurities with the formation of sodium silicates.

5. Flushing the boiler process water.

6. Preparation of the working solution of the reagent and start of the circulation circuit.

Based on the nature of the deposits, the choice and concentration of the reagent is carried out. In the form of reagents, modern highly effective technical detergents based on surfactants, a complex of acids and corrosion inhibitors or hydrochloric acid are used with the introduction of the necessary corrosion inhibitors to protect structural materials.

Technology hydrochemical washing is to ensure the circulation of the washing solution of technical detergent through closed circuit, at a given temperature. During the circulation of the washing solution, a gradual dissolution and removal of layers of accumulated deposits occurs. As the cleaning solution moves through the system, its cleaning power decreases, which is accompanied by an increase in the pH level, this indicates that the solution is reacting with deposits. During washing, the solution is adjusted. The washing solution must be circulated until the pH level does not change, this indicates that the maximum amount of deposits has been removed.

In the process of circulation of the working solution of the washing reagent, it is necessary to carry out chemical control of the cleaning ability of the reagent. Chemical control should be carried out every ½ hour - measurement of the pH of the solution. In the case of an increase in pH to 6, adjust the working solution by adding 10% of initial concentration. The control is carried out with a ph-meter or a litmus indicator.

7. Flushing the boiler with technical water.

After washing with a detergent, the boiler is washed with technical water, and then the internal surfaces of the boiler are passivated.

8. Passivation of internal surfaces of the boiler.

After graduation hydrochemical treatment, rinse the circuit with a 0.1-0.2% solution of caustic soda (sodium hydroxide) in order to neutralize and passivate the inner surface of the pipes, then rinse with industrial water to a pH level at the outlet of 6-7. The remains of the unused solution, having a pH level below 6, are neutralized with caustic soda to a pH level of 6-7, then drained into the sewer.

9. Final flushing of the circuit with network water.

During the hydrochemical cleaning of the boiler, the following indicators are monitored:

• detergent consumption;
• water consumption during water washings;
• medium pressure on the pressure and suction pipelines of the pumps, on the discharge pipeline from the boiler;
• liquid level in the tank;
• temperature of the working solution of the washing reagent;
• no accumulation of gas in the boiler circuit.

Our work experience

Over the past years, we have accumulated extensive experience in the field of hydrochemical cleaning of thermal and heat exchange equipment.

Here are some examples of our work and our clients:

• OAO Mosenergo: participation in the development and implementation of the technology for cleaning boilers PTVM-100 in Zelenograd (article in the Energy Saving magazine, 2000)
• LLC "Severgazprom" - technical diagnostics of waste heat exchangers and chemical water treatment systems at industrial sites KS-13 Urdoma and KS-16 Yubileiny. In 2000-2006, at Severgazprom LLC, we carried out chemical cleaning of more than 500 waste heat boilers of gas compressor units at 7 compressor stations located in the Komi Republic and the Arkhangelsk Region. In addition, 4 water-heating boilers ABA-4, heat exchangers of 2 central heating stations and heating systems of houses in 2 workers' settlements were cleaned
• JSC "AvtoVAZ" - development of technology and performance of works for the chemical cleaning of compressed air dryers OSV-250 manufactured by NPP ENSI LLC.
• MUP "PEUg.Skhodnya" - complex cleaning of 50 shell-and-tube heat exchangers, 10 hot water boilers, commissioning of "Complexon1" systems
• Sports complex of the Moscow Institute of Electronic Technology - complex cleaning of heat exchangers of systems air heating, heating point, cleaning of pool water preparation units
• NPO ENERGOMASH — cleaning of compressor cooling jackets, test bench heat exchangers and annealing furnaces, hot water heat exchangers workshop 429 in the amount of 140 pcs.
• Moscow Railway– development of technology for in-place cleaning of the cooling system of diesel locomotives together with MIIZhT. (Article in the journal Lokomotiv, 2001)
• Cleaning of heat exchangers (Alfa Laval, Frolling, Cetheterm, APV, SWEP) for hot water supply and heating and air conditioning installed in the ITP: Srednerussky Bank of Sberbank of Russia, Financial and Economic Department of the Complex of Perspective Development of the City of Moscow, Bank Credit Swiss First Boston, Holy Trinity Sergieva Lavra, "New Compound" - English Club, "Don-Stroy", "Atomstroyexport", "DEZ of the Kryukovo District", Central Telegraph, Mostransgaz.

In 2008-2009, we performed cleaning works: 1 Garioni Naval GPT 6000 steam boiler, 2 TVG-4r boilers, 2 KVG 4/115 boilers, 1 KV-GM-35-150 boiler, 1 Ferolli PREX 1250 boiler, 2 boilers PTVM-30, 3 boilers "Turboterm-2000", 12 heat exchangers Alfa laval - Customers - meat processing plant "Partner and K", MUP "Istra Teploset", LLC "Heat networks of Balashikha", CJSC "RIDAN", Srednerussky bank of Sberbank of Russia, Svyato Trinity Sergius Lavra. An agreement was concluded with the concern "Kurinoe Tsarstvo" (Lipetsk) for the permanent maintenance of boiler houses and ITP for this type of work.

Every cleaning project is different! If you are interested in our services, call us! Experts will advise you on all issues of their competence, help you choose optimal forms cooperation, will calculate the cost of work, will assist in solving existing problems.

RUSSIAN JOINT STOCK COMPANY
ENERGY AND ELECTRIFICATION
"UES of RUSSIA"

DEPARTMENT OF SCIENCE AND TECHNOLOGY

STANDARD INSTRUCTIONS
FOR PERFORMANCE CHEMICAL
CLEANING WATER BOILERS

RD 34.37.402-96

ORGRES

Moscow 1997

Developed JSC "Firma ORGRES"

PerformersV.P. SEREBRYAKOV, A.Yu. BULAVKO(JSC Firm ORGRES), S.F. SOLOVIEV(CJSC "Rostenergo"), HELL. Efremov, N.I. SHADRINA(JSC "Kotloochistka")

Approved Department of Science and Technology of RAO "UES of Russia" 04.01.96

Boss A.P. BERSENEV

STANDARD INSTRUCTIONS FOR OPERATIONAL CHEMICAL CLEANING WATER BOILERS

RD 34.37.402-96

Expiry date set

2. REQUIREMENTS FOR TECHNOLOGY AND CLEANING SCHEME

2.1. Washing solutions should provide high-quality cleaning surfaces, taking into account the composition and amount of deposits present in the boiler screen pipes and to be removed.

2.2. It is necessary to assess the corrosion damage to the pipe metal of the heating surfaces and select the conditions for cleaning with a cleaning solution with the addition of effective inhibitors to reduce pipe metal corrosion during cleaning to acceptable values ​​and limit the appearance of leaks during chemical cleaning of the boiler.

2.3. The cleaning scheme should ensure the efficiency of cleaning the heating surfaces, the completeness of the removal of solutions, sludge and suspension from the boiler. Cleaning of boilers according to the circulation scheme should be carried out with the speeds of movement of the washing solution and water, providing the specified conditions. In this case, the design features of the boiler, the location of convective packs in the boiler water path and the presence of a large number of horizontal pipes small diameter with multiple bends of 90 and 180°.

2.4. It is necessary to carry out neutralization of residual acid solutions and post-flushing passivation of the heating surfaces of the boiler to protect against corrosion when the boiler is idle for 15 to 30 days or subsequent conservation of the boiler.

2.5. At the choice of technology and treatment scheme should take into account environmental requirements and provide for installations and equipment for the neutralization and disposal of waste solutions.

2.6. All technological operations should be carried out, as a rule, when washing solutions are pumped through the water path of the boiler along a closed circuit. The speed of movement of cleaning solutions during cleaning of hot water boilers should be at least 0.1 m/s, which is acceptable, as it ensures uniform distribution of the cleaning agent in the pipes of the heating surfaces and a constant supply of fresh solution to the surface of the pipes. Water washes must be carried out for discharge at speeds of at least 1.0 - 1.5 m/s.

2.7. Waste cleaning solutions and the first portions of water during water washing should be sent to the plant-wide neutralization and neutralization unit. Water is drained into these installations until a pH value of 6.5 - 8.5 is reached at the outlet of the boiler.

2.8. When performing all technological operations (with the exception of the final water washing with network water according to the standard scheme), process water is used. It is permissible to use network water for all operations, if possible.

3. CHOICE OF CLEANING TECHNOLOGY

3.1. For all types of deposits found in hot water boilers, hydrochloric or sulfuric acid, sulfuric acid with ammonium hydrofluoride, sulfamic acid, low molecular weight acid concentrate (NMA) can be used as a cleaning agent.

The choice of cleaning solution is made depending on the degree of contamination of the boiler heating surfaces to be cleaned, the nature and composition of deposits. To develop a technological regime for cleaning, samples of pipes cut out from the boiler with deposits are processed in laboratory conditions with the selected solution while maintaining the optimal performance of the cleaning solution.

3.2. Hydrochloric acid is mainly used as a detergent. This is due to its high washing properties, which allow cleaning of any type of deposits from heating surfaces, even with high specific contamination, as well as the lack of a reagent.

Depending on the amount of deposits, cleaning is carried out in one (with contamination up to 1500 g/m2) or in two stages (with greater contamination) with a solution with a concentration of 4 to 7%.

3.3. Sulfuric acid It is used to clean heating surfaces from iron oxide deposits with a calcium content of not more than 10%. In this case, the concentration of sulfuric acid, according to the conditions for ensuring its reliable inhibition during the circulation of the solution in the purification circuit, should be no more than 5%. When the amount of deposits is less than 1000 g/m2, one stage of acid treatment is sufficient, with contamination up to 1500 g/m2, two stages are required.

When cleaning is only vertical pipes(screen heating surfaces), it is permissible to use the etching method (without circulation) with a solution of sulfuric acid with a concentration of up to 10%. With the amount of deposits up to 1000 g/m2, one acid stage is required, with more contamination - two stages.

As a washing solution for removing iron oxide (in which calcium is less than 10%) deposits in an amount of not more than 800 - 1000 g / m2, a mixture of a dilute solution of sulfuric acid (concentration less than 2%) with ammonium hydrofluoride (the same concentration) can also be recommended. Such a mixture characterized by an increased rate of dissolution of deposits compared to sulfuric acid. A feature of this cleaning method is the need to periodically add sulfuric acid to maintain the pH of the solution at an optimal level of 3.0 - 3.5 and to prevent the formation of Fe (III) hydroxide compounds.

The disadvantages of methods using sulfuric acid include the formation of a large amount of suspension in the cleaning solution during the cleaning process and a lower rate of dissolution of deposits compared to hydrochloric acid.

3.4. When the heating surfaces are contaminated with deposits of carbonate-iron oxide composition in an amount up to 1000 g/m2, sulfamic acid or NMA concentrate can be used in two stages.

3.5. When using all acids, it is necessary to add corrosion inhibitors to the solution, which protect the boiler metal from corrosion under the conditions of use of this acid (acid concentration, solution temperature, presence of washing solution movement).

For chemical cleaning, as a rule, inhibited hydrochloric acid is used, into which one of the corrosion inhibitors PB-5, KI-1, B-1 (B-2) is introduced at the supplier plant. When preparing a washing solution of this acid, an inhibitor of urotropin or KI-1 must be additionally introduced.

For solutions of sulfuric and sulfamic acids, ammonium hydrofluoride, MNK concentrate, mixtures of catapine or catamine AB with thiourea or thiuram or captax are used.

3.6. If the contamination is higher than 1500 g/m2 or if there is more than 10% silicic acid or sulfates in the deposits, it is recommended to carry out alkaline treatment before acid treatment or between acid stages. Alkalinization is usually carried out between the acid stages with a solution of caustic soda or a mixture of it with soda ash. Adding 1-2% soda ash to caustic soda increases the effect of loosening and removing sulfate deposits.

In the presence of deposits in the amount of 3000 - 4000 g/m2, cleaning of heating surfaces may require successive alternation of several acidic and alkaline treatments.

To intensify the removal of solid iron oxide deposits, which are located in the lower layer, and if there are more than 8–10% silicon compounds in the deposits, it is advisable to add fluorine-containing reagents (fluoride, ammonium or sodium hydrofluoride) to the acid solution, added to the acid solution after 3–4 hours after the start of processing.

In all these cases, preference should be given to hydrochloric acid.

3.7. For post-flush passivation of the boiler, in cases where it is necessary, one of the following treatments is used:

a) treatment of the cleaned heating surfaces with 0.3 - 0.5% sodium silicate solution at a solution temperature of 50 - 60 ° C for 3 - 4 hours with the solution circulating, which will provide protection against corrosion of the boiler surfaces after draining the solution in wet conditions within 20 - 25 days and in a dry atmosphere for 30 - 40 days;

b) treatment with a solution of calcium hydroxide in accordance with the guidelines for its use for the conservation of boilers.

4. CLEANING SCHEMES

4.1. The scheme of chemical cleaning of a hot water boiler includes the following elements:

boiler to be cleaned;

a tank designed for the preparation of cleaning solutions and serving at the same time as an intermediate container when organizing the circulation of cleaning solutions in a closed circuit;

flushing pump for mixing solutions in the tank through the recirculation line, supplying the solution to the boiler and maintaining the required flow rate when pumping the solution along a closed circuit, as well as for pumping the spent solution from the tank to the neutralization and neutralization unit;

pipelines that combine the tank, pump, boiler into a single cleaning circuit and ensure the pumping of the solution (water) through closed and open circuits;

neutralization and neutralization unit, where waste cleaning solutions and contaminated water are collected for neutralization and subsequent neutralization;

hydroash removal channels (GZU) or industrial storm sewerage (PLC), where conditionally clear waters(with pH 6.5 - 8.5) when washing the boiler from suspended solids;

tanks for storing liquid reagents (primarily hydrochloric or sulfuric acid) with pumps for supplying these reagents to the purification circuit.

4.2. The rinsing tank is intended for preparation and heating of washing solutions, it is a blending tank and a place for gas outlet from the solution in the circulation circuit during cleaning. The tank must have an anti-corrosion coating, must be equipped with a loading hatch with a grid with a mesh size of 10´10 ÷ 15´15 mm or with a perforated bottom with holes of the same size, a level glass, a thermometer sleeve, overflow and drainage pipelines. The tank must have a fence, a ladder, a device for lifting bulk reagents, and lighting. Pipelines for supplying liquid reagents, steam, water must be connected to the tank. Solutions are heated with steam through a bubbling device located at the bottom of the tank. It is advisable to bring to the tank hot water from the heating network (from the return line). Process water can be supplied both to the tank and to the suction manifold of the pumps.

The capacity of the tank must be at least 1/3 of the volume of the flush circuit. When determining this value, it is necessary to take into account the capacity of the network water pipelines included in the cleaning circuit, or those that will be filled during this operation. As practice shows, for boilers with a thermal capacity of 100 - 180 Gcal / h, the volume of the tank must be at least 40 - 60 m3.

For uniform distribution and facilitating the dissolution of bulk reagents, it is advisable to lead a pipeline with a diameter of 50 mm with a rubber hose from the recirculation pipeline into the tank for mixing solutions into the loading hatch.

4.3. The pump intended for pumping the washing solution along the cleaning circuit must provide a speed of at least 0.1 m / s in the pipes of the heating surfaces. The choice of this pump is made according to the formula

Q= (0.15 ÷ 0.2) S 3600,

where Q- pump flow, m3/h;

0.15 ÷ 0.2 - the minimum speed of the solution, m/s;

S- area of ​​maximum cross section boiler water path, m2;

3600 - conversion factor.

For chemical cleaning of hot water boilers with a thermal output of up to 100 Gcal / h, pumps with a flow rate of 350 - 400 m3 / h can be used, and for cleaning boilers with a thermal output of 180 Gcal / h - 600 - 700 m3 / h. The pressure of the flushing pumps must not be less than the hydraulic resistance of the flushing circuit at a speed of 0.15 - 0.2 m/s. This speed for most boilers corresponds to a head of no more than 60 m of water. Art. For pumping cleaning solutions, two pumps are installed for pumping acids and alkalis.

4.4. The pipelines intended for organizing the pumping of cleaning solutions in a closed circuit must have diameters not less than the diameters of the suction and pressure nozzles of the washing pumps, respectively, the pipelines for draining waste washing solutions from the cleaning circuit to the neutralization tank may have diameters that are significantly smaller than the diameters of the main pressure-return ( waste) collectors.

The cleaning circuit must provide for the possibility of draining all or most of the cleaning solution into the tank.

The diameter of the pipeline intended for the removal of wash water into the industrial storm channel or the GZU system must take into account the throughput of these lines. The pipelines of the boiler cleaning circuit must be stationary. Their routing must be chosen in such a way that they do not interfere with the maintenance of the main equipment of the boiler during operation. The fittings on these pipelines should be located in accessible places, the routing of the pipelines should ensure their emptying. If there are several boilers at the power plant (heating boiler house), common pressure-return (discharge) collectors are installed, to which pipelines are connected, designed to clean a separate boiler. Shut-off valves must be installed on these pipelines.

4.5. The collection of washing solutions coming from the tank (along the overflow line, drainage line), from the sampler troughs, from pump leaks through stuffing boxes, etc., should be carried out in a pit, from where they are sent to the neutralization unit by a special pumping pump.

4.6. When carrying out acid treatments, fistulas are often formed in the heating surfaces of the boiler and pipelines of the flushing scheme. Violation of the density of the cleaning circuit can occur at the beginning of the acid stage, and the amount of washing solution loss will not allow further operation. To speed up the emptying of the defective area of ​​the heating surface of the boiler and the subsequent safe repair work to eliminate the leak, it is advisable to upper part boiler supply nitrogen or compressed air. For most boilers, the boiler vents are a convenient connection point.

4.7. The direction of movement of the acid solution in the boiler circuit must take into account the location of the convective surfaces. It is advisable to organize the direction of movement of the solution in these surfaces from top to bottom, which will facilitate the removal of exfoliated sediment particles from these elements of the boiler.

4.8. The direction of movement of the washing solution in the screen pipes can be any, since with an upward flow at a speed of 0.1 - 0.3 m / s, the smallest suspended particles will pass into the solution, which at these speeds will not be deposited in the coils of convective surfaces when moving from above down. Large sediment particles, for which the movement speed is less than the soaring speed, will accumulate in the lower collectors of the screen panels, therefore, their removal from there must be carried out by intensive water washing at a water speed of at least 1 m/s.

For boilers with convective surfaces are the outlet sections of the water path, it is advisable to organize the flow direction so that they are the first in the direction of the washing solution when pumping along a closed circuit.

The cleaning circuit must be able to change the flow direction to the opposite, for which a jumper must be provided between the pressure and discharge pipelines.

Ensuring the rate of movement of wash water above 1 m/s can be achieved by connecting the boiler to the heating main, while the scheme should provide for pumping water along a closed circuit with a constant removal of wash water from the boiler circuit while simultaneously supplying water to it. The amount of water supplied to the purification circuit must correspond to bandwidth waste channel.

In order to constantly remove gases from individual sections of the water path, the boiler air vents are combined and discharged into the flushing tank.

The connection of the pressure-return (discharge) pipelines to the water path should be made as close as possible to the boiler. To clean the sections of the network water pipeline between the sectional valve and the boiler, it is advisable to use the bypass line of this valve. In this case, the pressure in the water path must be less than in the network water pipeline. In some cases, this line can serve as an additional source of water entering the purification circuit.

4.9. To increase the reliability of the cleaning circuit and greater safety during its maintenance, it must be equipped with steel reinforcement. In order to exclude the overflow of solutions (water) from the pressure pipeline to the return pipeline through the jumper between them, to pass them into the discharge channel or the neutralization tank and to be able to install, if necessary, a plug, the fittings on these pipelines, as well as on the recirculation line to the tank, must be flanged. The principal (general) scheme of the plant for chemical cleaning of boilers is shown in fig. .

4.10. During chemical cleaning of PTVM-30 and PTVM-50 boilers (Fig. , ), the flow area of ​​the water path when using pumps with a feed rate of 350 - 400 m3 / h provides a solution velocity of about 0.3 m / s. The sequence of passage of the washing solution through the heating surfaces may coincide with the movement of network water.

When cleaning the boiler PTVM-30 Special attention it is necessary to pay attention to the organization of the removal of gases from the upper collectors of the screen panels, since the direction of the solution movement has multiple changes.

For the PTVM-50 boiler, it is advisable to supply the washing solution to the direct network water pipeline, which will allow organizing the direction of its movement in the convective package from top to bottom.

4.11. During chemical cleaning of the KVGM-100 boiler (Fig. ), the pipelines for supplying and returning cleaning solutions are connected to the pipelines of return and direct network water. The movement of the medium is carried out in the following sequence: front screen - two side screens - intermediate screen - two convective beams - two side screens - rear screen. When passing through the water path, the washing flow repeatedly changes the direction of the medium. Therefore, when cleaning this boiler, special attention should be paid to the organization of a constant removal of gases from the upper screen surfaces.

4.12. During the chemical cleaning of the PTVM-100 boiler (Fig. ), the movement of the medium is organized either according to a two- or four-way scheme. When using a two-way scheme, the speed of the medium will be about 0.1 - 0.15 m/s when using pumps with a flow of about 250 m3/h. When organizing a two-way movement scheme, the pipelines for supplying and discharging the washing solution are connected to the pipelines of the return and direct network water.

When using a four-way scheme, the speed of the movement of the medium when using pumps of the same supply is doubled. The connection of the pipelines for supplying and discharging the washing solution is organized into bypass pipelines from the front and rear screens. The organization of a four-way scheme requires the installation of a plug on one of these pipelines.

Rice. 1. Scheme of installation for chemical cleaning of the boiler:

1 - flushing tank; 2 - flushing pumps ;

Rice. 2. Scheme of chemical cleaning of the boiler PTVM-30:

1 - rear additional screens; 2 - convective beam; 3 - side screen of the convective shaft; 4 - side screen; 5 - front screens; 6 - rear screens;

Valve closed

Rice. 3. Scheme of chemical cleaning of the boiler PTVM-50:

1 - right side screen; 2 - upper convective beam; 3 - lower convective beam; 4 - rear screen; 5 - left side screen; 6 - front screen;

Valve closed

Rice. 4. Scheme of chemical cleaning of the boiler KVGM-100 (main mode):

1 - front screen; 2 - side screens; 3 - intermediate screen; 4 - side screen; 5 - rear screen; 6 - convective beams;

Valve closed

Rice. 5. Scheme of chemical cleaning of the boiler PTVM-100:

a - two-way; b - four-way;

1 - left side screen; 2 - rear screen; 3 - convective beam; 4 - right side screen; 5 - front screen;

The movement of the medium when using a two-way scheme corresponds to the direction of movement of water in the water path of the boiler during its operation. When using a four-way scheme, the passage of the heating surfaces with a washing solution is carried out in the following sequence: front screen - convective packages of the front screen - side (front) screens - side (rear) screens - convective packages of the rear screen - rear screen.

The direction of movement can be reversed when changing the purpose of the temporary pipes connected to the boiler bypass pipes.

4.13. During chemical cleaning of the PTVM-180 boiler (Fig. , ), the movement of the medium is organized either according to a two- or four-way scheme. When organizing the pumping of the medium according to a two-way scheme (see Fig. ), the pressure-discharge pipelines are connected to the pipelines of the return and direct network water. With such a scheme, it is preferable to direct the medium in convective packets from top to bottom. To create a movement speed of 0.1 - 0.15 m/s, it is necessary to use a pump with a flow rate of 450 m3/h.

When pumping the medium according to a four-way scheme, the use of a pump of such a supply will provide a speed of 0.2 - 0.3 m / s.

The organization of a four-way scheme requires the installation of four plugs on the bypass pipelines from the distributing upper network water collector to the double-light and side screens, as shown in fig. . The connection of pressure and discharge pipelines in this scheme is carried out to the return network water pipeline and to all four bypass pipes, plugged from the return network water chamber. Given that the bypass pipes have D at 250 mm and for most of its routing - turning sections, connecting pipelines to organize a four-way scheme requires a lot of labor.

When using a four-way scheme, the direction of movement of the medium along the heating surfaces is as follows: the right half of the two-light and side screens - the right half of the convective part - the back screen - the direct network water chamber - the front screen - the left half of the convective part - the left half of the side and two-light screens.

Rice. 6. Scheme of chemical cleaning of the boiler PTVM-180 (two-way scheme):

1 - rear screen; 2 - convective beam; 3 - side screen; 4 - two-light screen; 5 - front screen;

Valve closed

Rice. 7. Scheme of chemical cleaning of the boiler PTVM-180 (four-way scheme):

1 - rear screen; 2- convective beam; 3- side screen; 4 - two-light screen; 5 - front screen ;

4.14. During chemical cleaning of the KVGM-180 boiler (Fig. ), the movement of the medium is organized according to a two-way scheme. The speed of movement of the medium in the heating surfaces at a flow rate of about 500 m3/h will be about 0.15 m/s. Pressure-return pipelines are connected to pipelines (chambers) of return and direct network water.

The creation of a four-pass scheme for the movement of the medium in relation to this boiler requires significantly more alterations than for the PTVM-180 boiler, and therefore its use when performing chemical cleaning is impractical.

Rice. 8. Scheme of chemical cleaning of the KVGM-180 boiler:

1 - convective beam; 2 - rear screen; 3- ceiling screen; 4 - intermediate screen; 5 - front screen;

Valve closed

The direction of movement of the medium in the heating surfaces should be organized taking into account the change in the direction of the flow. In acidic and alkaline treatments, it is advisable to direct the movement of the solution in convective packages from the bottom up, since these surfaces will be the first in the circulation loop along a closed loop. When washing with water, it is advisable to periodically reverse the flow movement in convective packs.

4.15. Washing solutions are prepared either in portions in a washing tank with their subsequent pumping into the boiler, or by adding a reagent to the tank while circulating heated water through a closed cleaning circuit. The amount of the prepared solution must correspond to the volume of the cleaning circuit. The amount of solution in the circuit after the organization of pumping in a closed circuit should be minimal and determined necessary level for reliable operation of the pump, which is ensured by maintaining a minimum level in the tank. This allows you to add acid during processing to maintain the desired concentration or pH. Each of the two methods is acceptable for all acidic solutions. However, when performing purification using a mixture of ammonium hydrofluoride with sulfuric acid, the second method is preferred. The dosage of sulfuric acid in the cleaning circuit is best done in the upper part of the tank. Acid injection can be done either plunger pump supply of 500 - 1000 l / h, or by gravity from a tank installed at a mark above the flushing tank. Corrosion inhibitors for cleaning solution based on hydrochloric or sulfuric acid do not require special dissolution conditions. They are loaded into the tank before acid is introduced into it.

A mixture of corrosion inhibitors used for cleaning solutions of sulfuric and sulfamic acids, a mixture of ammonium hydrofluoride with sulfuric acid and NMA, is prepared in a separate container in small portions and poured into the tank hatch. The installation of a special tank for this purpose is not necessary, since the amount of the prepared mixture of inhibitors is small.

5. TECHNOLOGICAL MODES OF CLEANING

Approximate technological regimes used to clean boilers from various deposits, in accordance with Sec. are given in table. .

Table 1

	Type and amount of deposits removed	Technological operation	Solution composition	Options technological operation				Note
				Reagent concentration, %	Temperature environment, °С	Duration, h	End Criteria
1. Hydrochloric acid in circulation	With no restrictions	1.1 Water flush					Discharge water clarification
		1.2. Bucking					By time	The need for an operation is determined when choosing a cleaning technology depending on the amount and composition of deposits
		1.3. Washing with process water					The pH value of the discharged solution is 7 - 7.5
		1.4. Preparation in the circuit and circulation of the acid solution	Inhibited HCl Urotropin (or KI-1)				in contour	When removing carbonate deposits and reducing the acid concentration, periodically add acid to maintain the concentration of 2 - 3%. When removing iron oxide deposits without acid dosing
		1.5. Washing with process water					Discharge water clarification	When carrying out two or three acid stages, it is allowed to drain the washing solution with a single filling of the boiler with water and drain it
		1.6. Re-treatment of the boiler with an acid solution during circulation	Inhibited HCl Urotropin (or KI-1)				Stabilization of iron concentration	Performed when the amount of deposits is more than 1500 g/m2
		1.7. Washing with process water					Cleaning water clarification, neutral medium
		1.8. Neutralization by circulating solution	NaOH (or Na2CO3)				By time
		1.9. Drainage of alkaline solution
		1.10. Preliminary washing with technical water					Discharge water clarification
		1.11. Final washing with network water to the heating network						Carried out immediately before the boiler is put into operation
2. Sulfuric acid in circulation	<10 % при количестве отложений до 1500 г/м2	2.1. Water flush					Discharge water clarification
		2.2. Filling the boiler with acid solution and circulating it in the circuit					But no more than 6 hours	Acid free
			KI-1 (or catamine)
			Thiuram (or thiourea)
		2.3. Carrying out the operation according to
		2.4. Re-treatment of the boiler with acid during circulation					Stabilization of iron concentration	Performed when the amount of deposits is more than 1000 g/m3
		2.5. Performing operations according to paragraphs. 1.7 - 1.11
3. Sulfuric acid pickling		3.1. Water flush					Discharge water clarification
		3.2. Filling the boiler screens with mortar and pickling them					By time	It is possible to use inhibitors: katapina AB 0.25% with thiuram 0.05%. When using less effective inhibitors (1% urotropine or formaldehyde), the temperature should not exceed 45 ° C
			Thiuram (or thiourea)
		3.3. Carrying out the operation according to
		3.4. Re-treatment with acid					By time	Performed when the amount of deposits is more than 1000 g/m2
		3.5. Performing the operation according to clause 1.7
		3.6. Neutralization by filling the screens with a solution	NaOH (or Na2CO3)				By time
		3.7. Drainage of alkaline solution
		3.8. Performing the operation according to clause 1.10						It is allowed to fill and drain the boiler two or three times until a neutral reaction
		3.9. Performing the operation according to clause 1.11
4. Ammonium hydrofluoride with sulfuric acid in circulation	Iron oxide with calcium content<10 % при количестве отложений не более 1000 г/м2	4.1. Water flush					Discharge water clarification
		4.2. Preparation of the solution in the circuit and its circulation					Stabilization of iron concentration	It is possible to use inhibitors: 0.1% OP-10 (OP-7) with 0.02% captax. With an increase in pH over 4.3 - 4.4, additional dosage of sulfuric acid to pH 3 - 3.5
			Thiuram (or Captax)
		4.3. Performing the operation according to clause 1.5
		4.4. Re-treatment with cleaning solution					Stabilization of the iron concentration in the circuit at pH 3.5-4.0
			Thiuram (or Captax)
		4.5. Performing operations according to paragraphs. 1.7 - 1.11
5. Sulfamic acid in circulation	Carbonate-iron oxide in an amount up to 1000 g/m2	5.1. Water flush					Discharge water clarification
		5.2. Filling the circuit with solution and circulating it	Sulfamic acid				Stabilization of hardness or iron concentration in the circuit	No acid overdose. It is desirable to maintain the temperature of the solution by igniting one burner
			OP-10 (OP-7)
		5.3. Performing the operation according to clause 1.5
		5.4. Re-treatment with acid similar to paragraph 5.2
		5.5. Performing operations according to paragraphs. 1.7 - 1.11
6. NMC concentrate in circulation	Carbonate and carbonate-iron oxide deposits up to 1000 g/m2	6.1. Water flushing					Discharge water clarification
		6.2. Cooking in solution circuit and its circulation	NMC in terms of acetic acid				Stabilization of the iron concentration in the circuit	Acid free
		8.3. Performing the operation according to clause 1.5	OP-10 (OP-7)
		6.4. Re-treatment with acid similar to paragraph 6.2 6.5. Performing operations according to paragraphs. 1.7 - 1.11

6. CONTROL OF THE TECHNOLOGICAL PROCESS OF CLEANING

6.1. To control the technological process of cleaning, instrumentation and sampling points made in the cleaning circuit are used.

6.2. During the cleaning process, the following indicators are monitored:

a) the consumption of cleaning solutions pumped through a closed circuit;

b) the flow rate of water pumped through the boiler in a closed circuit during water washing;

c) pressure of the medium according to pressure gauges on the pressure and suction pipelines of the pumps, on the discharge pipeline from the boiler;

d) the level in the tank on the index glass;

e) the temperature of the solution according to the thermometer installed on the pipeline of the purification circuit.

6.3. The absence of gas accumulation in the purification circuit is controlled by periodically closing all the valves on the boiler air vents, except for one.

6.4. The following scope of chemical control over individual operations is organized:

a) when preparing cleaning solutions in the tank - the acid concentration or pH value (for a solution of a mixture of ammonium hydrofluoride with sulfuric acid), the concentration of caustic soda or soda ash;

b) when treated with an acid solution - the concentration of the acid or the pH value (for a solution of a mixture of ammonium hydrofluoride with sulfuric acid), the iron content in the solution - 1 time in 30 minutes;

c) when treated with an alkaline solution - the concentration of caustic soda or soda ash - 1 time in 60 minutes;

d) with water washes - pH value, transparency, iron content (qualitatively, for the formation of hydroxide during alkaline treatment) - 1 time in 10 - 15 minutes

7. CALCULATION OF THE QUANTITY OF REAGENTS FOR PURIFICATION

7.1. To ensure the complete cleaning of the boiler, the consumption of reagents must be determined based on the data on the composition of deposits, the specific contamination of individual sections of heating surfaces, determined from pipe samples cut before chemical cleaning, and also on the basis of obtaining the required concentration of the reagent in the washing solution.

7.2. The amount of caustic soda, soda ash, ammonium hydrofluoride, inhibitors and acids when washing iron oxide deposits is determined by the formula

where Q is the amount of reagent, g;

V is the volume of the purification circuit, m3 (the sum of the volumes of the boiler, tank, pipelines);

Ср is the required concentration of the reagent in the washing solution, %;

γ - specific gravity of the washing solution, t/m3 (assumed to be 1 t/m3);

a - safety factor equal to 1.1 - 1.2;

7.3. The amount of hydrochloric and sulfamic acid and NMC concentrate to remove carbonate deposits is calculated by the formula

where Q- amount of reagent, t;

BUT- the amount of deposits in the boiler, t;

P- the amount of 100% acid required to dissolve 1 ton of deposits, t / t (when dissolving carbonate deposits for hydrochloric acid n = 1.2, for NMK P= 1.8, for sulfamic acid P= 1,94);

7.4. The amount of deposits to be removed during cleaning is determined by the formula

A \u003d g f 10-6,

where A is the amount of deposits, t;

g - specific contamination of heating surfaces, g/m2;

f - surface to be cleaned, m2.

With a significant difference in the specific contamination of convective and screen surfaces, the amount of deposits present on each of these surfaces is determined separately, then these values ​​are summed up.

The specific contamination of the heating surface is found as the ratio of the mass of deposits removed from the surface of the pipe sample to the area from which these deposits were removed (g/m2). When calculating the amount of deposits located on the screen surfaces, the value of the surface should be increased (approximately twice) compared to that indicated in the boiler passport or in the reference data (where data are given only for the radiation surface of these pipes).

Data on the surface area of ​​pipes to be cleaned and their water volume for the most common boilers are given in Table. . The actual volume of the cleaning circuit may differ slightly from that indicated in the table. and depends on the length of the return and direct network water pipelines filled with a cleaning solution.

7.5. Consumption of sulfuric acid to obtain a pH value of 2.8 - 3.0 in mixtures with ammonium hydrofluoride is calculated based on the total concentration of the components at their ratio by weight of 1: 1.

From stoichiometric ratios and based on the practice of purification, it was found that about 2 kg of ammonium hydrofluoride and 2 kg of sulfuric acid are spent per 1 kg of iron oxides (in terms of Fe2O3). When cleaning with a solution of 1% ammonium hydrofluoride with 1% sulfuric acid, the concentration of dissolved iron (in terms of Fe2O3) can reach 8–10 g/l.

8. MEASURES SAFETY COMPLIANCE

8.1. When preparing and carrying out work on the chemical cleaning of hot water boilers, it is necessary to comply with the requirements of the “Safety Rules for the Operation of Thermal Mechanical Equipment of Power Plants and Heating Networks” (M.: SPO ORGRES, 1991).

8.2. Technological operations of chemical cleaning of the boiler begin only after the completion of all preparatory work and the removal of repair and installation personnel from the boiler.

8.3. Before carrying out chemical cleaning, all personnel of the power plant (boiler house) and contractors involved in chemical cleaning undergo a safety briefing when working with chemical reagents with an entry in the briefing log and the signature of the instructed.

8.4. An area is organized around the boiler to be cleaned, the flushing tank, pumps, pipelines and appropriate warning posters are hung out.

8.5. Enclosing handrails are made on the tanks for the preparation of reagent solutions.

8.6. Good lighting of the boiler to be cleaned, pumps, fittings, pipelines, stairs, platforms, sampling points and the workplace of the shift on duty is provided.

8.7. Water is supplied by hoses to the reagent preparation unit, to the place of work of personnel for flushing spilled or spilled solutions through leaks.

8.8. Means are provided for neutralizing washing solutions in case of violation of the density of the washing circuit (soda, bleach, etc.).

8.9. The duty shift workplace is provided with a first aid kit with medicines necessary for first aid (individual packages, cotton wool, bandages, tourniquet, boric acid solution, acetic acid solution, soda solution, weak potassium permanganate solution, vaseline, towel).

8.10. It is not allowed to be present in hazardous areas near the equipment to be cleaned and the area where flushing solutions are dumped by persons who are not directly involved in chemical cleaning.

8.12. All work on receiving, transferring, draining acids, alkalis, preparing solutions is carried out in the presence and under the direct supervision of technical managers.

8.13. Personnel directly involved in chemical cleaning work are provided with woolen or canvas suits, rubber boots, rubberized aprons, rubber gloves, goggles, and a respirator.

8.14. Repair work on the boiler, reagent tank is allowed only after their thorough ventilation.

Appendix

CHARACTERISTICS OF REAGENTS USED IN CHEMICAL CLEANING OF WATER BOILERS

1. Hydrochloric acid

Technical hydrochloric acid contains 27 - 32% hydrogen chloride, has a yellowish color and a suffocating odor. Inhibited hydrochloric acid contains 20 - 22% hydrogen chloride and is a liquid from yellow to dark brown (depending on the introduced inhibitor). PB-5, V-1, V-2, katapin, KI-1, etc. are used as inhibitors. The inhibitor content in hydrochloric acid is in the range of 0.5 ÷ 1.2%. The dissolution rate of St 3 steel in inhibited hydrochloric acid does not exceed 0.2 g/(m2 h).

The freezing point of a 7.7% hydrochloric acid solution is minus 10 ° C, 21.3% - minus 60 ° C.

Concentrated hydrochloric acid smokes in air, forms a mist, which irritates the upper respiratory tract and the mucous membrane of the eyes. Diluted 3-7% hydrochloric acid does not smoke. The maximum permissible concentration (MAC) of acid vapors in the working area is 5 mg/m3.

Skin exposure to hydrochloric acid can cause severe chemical burns. If hydrochloric acid gets on the skin or in the eyes, it must be immediately washed off with a plentiful stream of water, then the affected area of ​​the skin should be treated with 10% sodium bicarbonate solution, and the eyes with 2% sodium bicarbonate solution and contact the first-aid post.

Personal protective equipment: coarse wool suit or acid-resistant cotton suit, rubber boots, acid-resistant rubber gloves, goggles.

Inhibited hydrochloric acid is transported in non-gummed steel rail tank cars, tank trucks, containers. Tanks for long-term storage of inhibited hydrochloric acid should be lined with diabase tiles on acid-resistant silicate putty. The shelf life of inhibited hydrochloric acid in an iron container is not more than one month, after which additional administration of the inhibitor is required.

2. Sulfuric acid

Technical concentrated sulfuric acid has a density of 1.84 g/cm3 and contains about 98% H2SO4; It mixes with water in any proportions with the release of a large amount of heat.

When sulfuric acid is heated, sulfuric anhydride vapors are formed, which, when combined with air water vapor, form an acid fog.

Sulfuric acid, when it comes into contact with the skin, causes severe burns, which are very painful and difficult to treat. Inhalation of sulfuric acid vapors irritates and cauterizes the mucous membranes of the upper respiratory tract. Contact with sulfuric acid in the eyes threatens with loss of vision.

Personal protective equipment and first aid measures are the same as when working with hydrochloric acid.

Sulfuric acid is transported in steel rail tank cars or tank trucks and stored in steel tanks.

3. Caustic soda

Caustic soda is a white, very hygroscopic substance, highly soluble in water (1070 g / l dissolves at a temperature of 20 ° C). The freezing point of a 6.0% solution is minus 5 ° C, 41.8% - 0 ° C. Both solid sodium hydroxide and its concentrated solutions cause severe burns. Contact with alkali in the eyes can lead to serious eye diseases and even loss of vision.

If alkali gets on the skin, it is necessary to remove it with dry cotton wool or pieces of cloth and wash the affected area with a 3% solution of acetic acid or a 2% solution of boric acid. If alkali gets into the eyes, rinse them thoroughly with a stream of water, followed by treatment with a 2% solution of boric acid and contact the first-aid post.

Personal protective equipment: cotton suit, goggles, rubberized apron, rubber gloves, rubber boots.

Caustic soda in solid crystalline form is transported and stored in steel drums. Liquid alkali (40%) is transported and stored in steel tanks.

4. Concentrate and condensate of low molecular weight acids

The purified NMC condensate is a light yellow liquid with the smell of acetic acid and its homologues and contains at least 65% C1 - C4 acids (formic, acetic, propionic, butyric). In water condensate, these acids are contained in the range of 15 ÷ 30%.

The purified NMC concentrate is a combustible product with a self-ignition temperature of 425 °C. Foam and acid fire extinguishers, sand, felt mats should be used to extinguish a product on fire.

NMC vapors cause irritation of the mucous membrane of the eyes and respiratory tract. MPC of vapors of the purified NMC concentrate in the working area is 5 mg/m3 (in terms of acetic acid).

In case of contact with the skin, NMC concentrate and its dilute solutions cause burns. Personal protective equipment and first aid measures are the same as when working with hydrochloric acid, in addition, a brand A gas mask should be used.

Non-inhibited purified NMC concentrate is supplied in railway tanks and steel drums with a capacity of 200 to 400 liters, made of high-alloy steels 12X18H10T, 12X21H5T, 08X22H6T or bimetals (St3 + 12X18H10T, St3 + X17H13M2T), and is stored in containers made of the same steel or in tanks made of carbon steel and lined with tiles.

5. Urotropin

Urotropin in its pure form is a colorless hygroscopic crystals. The technical product is a white powder, highly soluble in water (31% at 12°C). Easily ignited. In a hydrochloric acid solution, it gradually decomposes into ammonium chloride and formaldehyde. The dehydrated pure product is sometimes referred to as dry alcohol. When working with urotropin, strict compliance with the requirements of fire safety rules is necessary.

If it comes into contact with the skin, urotropine can cause eczema with severe itching, which quickly passes after the cessation of work. Personal protective equipment: goggles, rubber gloves.

Urotropin is supplied in paper bags. Must be stored in a dry place.

6. Wetting agents OP-7 and OP-10

They are neutral yellow oily liquids, highly soluble in water; when shaken with water, they form a stable foam.

If OP-7 or OP-10 gets on the skin, they must be washed off with a stream of water. Personal protective equipment: goggles, rubber gloves, rubberized apron.

Supplied in steel drums and can be stored outdoors.

7. Captax

Captax is a yellow bitter powder with an unpleasant odor, practically insoluble in water. Soluble in alcohol, acetone and alkalis. It is most convenient to dissolve captax in OP-7 or OP-10.

Prolonged exposure to Captax dust causes headache, poor sleep, bitter taste in the mouth. Skin contact may cause dermatitis. Personal protective equipment: respirator, goggles, rubberized apron, rubber gloves or silicone protective cream. At the end of work, you must thoroughly wash your hands and body, rinse your mouth, and shake out the overalls.

Captax is supplied in rubber bags with paper and polyethylene liners. Stored in a dry, well-ventilated area.

8. Sulfamic acid

Sulfamic acid is a white crystalline powder, highly soluble in water. When dissolving sulfamic acid at a temperature of 80 ° C and above, it is hydrolyzed with the formation of sulfuric acid and the release of a large amount of heat.

Personal protective equipment and first aid measures are the same as when working with hydrochloric acid.