RU2525033C1 - Method of maintenance cleaning and passivation of drum boiler pipe inner surface and method of maintenance cleaning and passivation of pipe inner surface of combined-cycle plant waste-heat boiler (versions) - Google Patents

Abstract

FIELD: power engineering.

SUBSTANCE: proposed method comprises processing of pipes in isolated circuit by hot detergent water-based solution containing nitrogen-bearing chemical reagent. Said nitrogen-bearing chemical reagent represents a film-forming amine while batching of detergent solution is performed at concentration of chemical reagent in the boiler of (250÷300) mcg/dm³. Cleaning is performed in one step at boiler pressure of 1.5÷2.5 MPa and working fluid temperature not exceeding 230°C to stabilisation of iron content in boiler water. Passivation is performed at boiler pressure of 2.5÷15.5 MPa and working fluid temperature equal to saturation temperature for boiler pressure to stabilisation of iron content in boiler water not exceeding 50 mcg/dm³.

EFFECT: lower costs.

2 cl, 2 tbl

Description

Area of use

The group of inventions relates to the field of power engineering and can be used for operational cleaning of deposits on the inner surfaces of boiler tubes of power boilers: drum boilers (BK) and waste heat boilers (KU) of combined cycle plants (PTU) with the subsequent passivation of these surfaces.

Deposits on the inner surface of boiler pipes during the operation of boilers are formed as a result of the ingress of raw water impurities through the leaks of the cooling system of the steam turbine condenser with the additional influence of high thermal loads of the heating surfaces. Deposits usually consist of iron and copper oxides, calcium phosphates and other impurities.

State of the art

A known method of operational cleaning and passivation of the inner surface of boiler tubes of energy BK adopted as a prototype of the first claimed invention by treating them in a dedicated circuit with a hot water-based cleaning solution with a nitrogen-containing chemical reagent introduced into it, dosed into the intake manifold of the feed pump or in the pressure line condensate pump and into the boiler drum (Guidelines for the use of hydrazine in power plants of thermal power plants RD 34.37.503-94 / VTI OJSC, Moscow, 1994, 42 pp. [1]).

According to [1], hydrazine hydrate N ₂ H ₄ · H ₂ O or hydrazine sulfate N ₂ H ₄ · H ₂ SO ₄ and ammonia are used as a chemical reagent introduced into the cleaning solution.

The disadvantages of the method [1] include:

- the chemicals listed above belong to the most environmentally hazardous first and second classes according to GOST 12.1.007-76 (Occupational safety standards system. Harmful substances. Classification and general safety requirements - [2]);

- a relatively high duration of the cleaning process (two stages with a total duration of about 100 hours);

- the need to collect and neutralize environmentally hazardous spent chemical solutions, which requires the use of special equipment and increases the complexity of the method;

When analyzing the prior art, the prototype for the second of the proposed methods is not identified.

Disclosure of invention

The technical results achieved by the group of inventions are a significant reduction in the total time of the process, increasing the strength of the protective passivating film with increasing its corrosion resistance and reducing the amount of waste that needs to be neutralized before being discharged into the environment.

The indicated technical results of the group of inventions are achieved by the fact that, in accordance with the first embodiment, in the method of operational cleaning and passivation of the inner surface of the boiler pipes of the power boiler by treating them in a dedicated circuit with a hot water-based cleaning solution with a nitrogen-containing chemical reagent introduced into it, dosed into the intake manifold feed pump or into the pressure line of the condensate pump and into the drum of the boiler, according to the invention:

- a film-forming amine is used as a chemical reagent;

- dosing of the cleaning solution is based on the achievement of the concentration of the chemical reagent in the drum of the boiler (250 ÷ 300) µg / dm ³ ;

- cleaning is carried out in one stage at a pressure in the boiler drum at a level of (1.5 ÷ 2.5) MPa and a temperature of the working medium of no more than 230 ° C until the iron content in the boiler water is stabilized no more than 500 μg / dm ³ at a concentration in it film-forming amines (PAO) not less than 50 μg / DM ³ ;

- passivation is carried out at a pressure in the boiler drum at a level of (2.5 ÷ 15.5) MPa and a working fluid temperature equal to the saturation temperature for the pressure in the boiler drum until the iron content in the boiler water is stabilized no more than 50 μg / dm ³ at a concentration in it POA is not less than 50 μg / dm ³ ;

- cleaning and passivation processes are carried out each for a period of no more than 24 hours.

In accordance with the second embodiment, the technical results of the group of inventions are achieved by the fact that in the method of operational cleaning and passivation of the inner surface of the boiler pipes of the power KU CCGT with at least two water-vapor circuits of different pressure, according to the invention, these surfaces are treated in a dedicated circuit with a hot water-based cleaning solution with a chemical reagent introduced into it in the form of a film-forming amine solution, moreover

- dosing of the cleaning solution is carried out in the pressure line of the condensate pump and in the drum of the boiler high pressure circuit based on the achievement of the concentration of the chemical reagent in all the drums of the boiler (250 ÷ 300) μg / dm ³ ;

- cleaning is carried out in one stage at a pressure in the drum of the boiler high pressure circuit at the level of (1.5 ÷ 2.5) MPa and the temperature of the working medium in this circuit is not more than 230 ° C until the iron content in the boiler water is stabilized not more than 200 μg / dm ³ when the concentration of POA in it is not less than 50 μg / dm ³ ;

- passivation is carried out at a pressure in the drum a high pressure circuit of the boiler at the level of (2.5 ÷ 15.5) MPa and a temperature of the working medium equal to the saturation temperature for the pressure in said boiler drum to stabilize the content of the boiler water iron not more than 50 g / dm ³ at a concentration in it POA is not less than 50 μg / dm ³ ;

- the cleaning and passivation processes are carried out each for a period not exceeding 12 hours.

The causal relationship between the distinguishing features of both variants of the group of inventions and the technical results achieved by it is as follows:

- the use of a film-forming amine as a chemical reagent, as shown by experiments, provides effective removal of operational deposits (up to 70%) while reducing the amount of waste requiring neutralization before being discharged into the environment. The improvement of the indicated characteristics of the method in both variants, compared with the use of other nitrogen-containing chemicals, can be explained by the fact that they form complexes with oxide of deposits and with a passivating oxide layer of the metal being purified.

DETAILED DESCRIPTION OF THE INVENTION

Purification and passivation based on an amine-containing reagent was performed at reduced operating parameters of the power unit or boiler with a load in the range from 30 to 50% of the nominal. The parameters of the working environment were maintained in the range from 50 to 540 ° C.

A water-based cleaning solution was prepared in a chemical reagent preparation unit with a nitrogen-containing chemical reagent octadecylamine C ₁₈ H ₃₉ N introduced into it. To clean deposits of internal heating surfaces of energy BC, including surfaces of a water economizer, this solution was injected using a metering pump into suction collector of the feed pump and directly into the drum BC. To clean the deposits of the inner surfaces of the steel pipes of the KU of the PTU power unit, the specified solution was introduced using a metering pump into the pressure line of the condensate pump and directly into the KU high-pressure drum. The pressure in the drum BK and in the drum of the high pressure circuit KU was maintained at a level of 1.5-2.5 MPa, the temperature of the working medium did not exceed 230 ° C. In both cases, the reagent content was maintained at the rate of 2 g / t of circulating water or up to a maximum of 300 μg / dm ³ in terms of POA, and the cleaning time for BC was 24 hours, for KU CCGT - 12 hours. The criterion for the completion of the treatment was the stabilization of the iron content in the boiler water at a level of not more than 500 μg / dm ³ for BC and not more than 200 μg / dm ³ for KU, and the POA content of not less than 50 μg / dm ³ for both options. The amine content was controlled by sampling from standard sampling lines of boilers.

Then, passivation of the cleaned inner surfaces of the boiler pipes BK and KU was carried out. To do this, the indicated solution was dosed into the intake manifold of the feed pump and directly into the drum of the BC, as well as into the pressure line of the condensate pump and directly into the high-pressure drum of the KU. The pressure in the drum BK and in the drum of the high pressure circuit KU was maintained at the level of (2.5 ÷ 15.5) MPa at a temperature of the working medium equal to the saturation temperature for the pressure in the drum of each of these boilers. The dosing of the solution was carried out until the content of iron in the boiler water was not more than 50 μg / dm ³ at a concentration of POA in it of at least 50 μg / dm ³ for both options. The cleaning time for BC was 24 hours, for KU vocational schools - 12 hours. The resulting protective magnetite-amine film had corrosion resistance, characterized as “highest” or having a value of more than 4 points at a corrosion rate of metal of heating surfaces not more than 0.08 mm / year (GOST 9.908-85 Unified system of protection against corrosion and aging. Metals and alloys. Methods for determination of indicators of corrosion and corrosion resistance).

The results of cleaning boiler pipes according to the proposed methods for these examples are shown in the corresponding tables 1,2.

Thus, the group of claimed inventions provides high efficiency of cleaning (at least 70%) and passivation with a significant reduction in the amount of waste requiring neutralization before being discharged into the environment and reducing the duration of these processes by more than 2 times (compared with [1]). The use of a film-forming amine or a mixture of amines allows the cleaning and passivation of boiler pipes not only for BK, but also for KU PTU pipes. In addition, as a result of passivation, a corrosion-resistant protective film is formed on the metal surface, which protects the metal from corrosion both during the further operation of the equipment, and when it is stopped for repair or in reserve.

Example No. 1

Table 1 Cleaning and passivation of boiler tubes of a drum boiler Name of the parameter and its unit of measurement Parameter value Specific contamination before cleaning, g / m ² 384.0 Cleaning boiler pipes with a solution of octadecylamine (C ₁₈ H ₃₉ N) introduced into it. Pressure in a drum, MPa 2.0 Medium temperature ° C 210.0 The iron content in the boiler water, μg / DM ³ 435.0 The content of POA in boiler water, μg / DM ³ 55.0 The time of circulation of the solution, h 24.0 Passivation of boiler pipes with a solution of octadecylamine (C ₁₈ H ₃₉ N) introduced into it. Pressure in a drum, MPa 10.0 Medium temperature ° C 180 The iron content in the boiler water, μg / DM ³ 44.5 The content of POA in boiler water, μg / DM ³ 51.0 The time of circulation of the solution, h 24.0 Specific contamination after cleaning, g / m ² 27.0 The level of corrosion resistance of a protective magnetite-amine film (at a corrosion rate of metal of heating surfaces not more than 0.08 mm / g), point 4 and above

Example No. 2

table 2 Cleaning and passivation of boiler pipes of the recovery boiler Name of the parameter and its unit of measurement Parameter value Specific contamination before cleaning, g / m ² 155.0 Cleaning solution with boiler tubes inserted therein octadecylamine (C ₁₈ H ₃₉ N). Pressure in a drum, MPa 2,5 Medium temperature ° C 220.00 The iron content in the boiler water, μg / DM ³ 180.0 The content of POA in boiler water, μg / DM ³ 50,0 The time of circulation of the solution, h 12.0 Passivation of boiler pipes with a solution of octadecylamine (C ₁₈ H ₃₉ N) introduced into it. Pressure in a drum, MPa 12.0 Medium temperature ° C 190.0 The iron content in the boiler water, μg / DM ³ 40.5 The content of POA in boiler water, μg / DM ³ 52.0 The time of circulation of the solution, h 12.0 Specific contamination after cleaning, g / m ² 11.0 The level of corrosion resistance of a protective magnetite-amine film (at a corrosion rate of metal of heating surfaces not more than 0.08 mm / g), point 4 and above

Claims (2)

1. The method of operational cleaning and passivation of the inner surface of the boiler tubes of an energy drum boiler by treating them in a dedicated circuit with a hot water-based cleaning solution with a nitrogen-containing chemical reagent introduced into it, dosed into the intake manifold of the feed pump or into the pressure line of the condensate pump and into the boiler drum characterized in that
- a film-forming amine is used as a chemical reagent;
- dosing of the cleaning solution is based on the achievement of the concentration of the chemical reagent in the drum of the boiler (250 ÷ 300) µg / dm ³ ;
- cleaning is carried out in one stage at a pressure in the boiler drum at a level of (1.5 ÷ 2.5) MPa and a temperature of the working medium of no more than 230 ° C until the iron content in the boiler water is stabilized no more than 500 μg / dm ³ at a concentration in it a film-forming amine of at least 50 μg / dm ³ ;
- passivation is carried out at a pressure in the boiler drum at a level of (2.5 ÷ 15.5) MPa and a working fluid temperature equal to the saturation temperature for the pressure in the boiler drum until the iron content in the boiler water is stabilized no more than 50 μg / dm ³ at a concentration in it a film-forming amine is not less than 50 μg / dm ³ ;
- cleaning and passivation processes are carried out each for a period of no more than 24 hours. 2. The method of operational cleaning and passivation of the inner surface of the boiler pipes of an energy recovery boiler of a combined cycle plant with at least two water-vapor circuits of various pressures, characterized in that these surfaces are treated in an isolated circuit with a hot water-based cleaning solution with a chemical reagent introduced into it in the form of a solution of a film-forming amine, and
- dosing of the cleaning solution is carried out in the pressure line of the condensate pump and in the drum of the boiler high pressure circuit based on the achievement of the concentration of the chemical reagent in all the drums of the boiler (250 ÷ 300) μg / dm ³ ;
- cleaning is carried out in one stage at a pressure in the drum of the boiler high pressure circuit at the level of (1.5 ÷ 2.5) MPa and the temperature of the working medium in this circuit is not more than 230 ° C until the iron content in the boiler water is stabilized not more than 200 μg / dm ³ when the concentration of the film-forming amine in it is not less than 50 μg / dm ³ ;
- passivation is carried out at a pressure in the drum of the boiler high-pressure circuit at a level of (2.5 ÷ 15.5) MPa and a working medium temperature equal to the saturation temperature for the pressure in the specified drum of the boiler, until the iron content in the boiler water is stabilized no more than 50 μg / dm ³ when the concentration of the film-forming amine in it is not less than 50 μg / dm ³ ;
- the cleaning and passivation processes are carried out each for a period not exceeding 12 hours.