RU2724063C1 - Method of cleaning boiler equipment inner surfaces from deposits - Google Patents

Abstract

FIELD: heat power engineering.SUBSTANCE: invention relates to heat engineering and can be used for physical and chemical cleaning of internal heating surfaces of boiler equipment from deposits occurring during operation. Method involves multiple circulation of a solution containing up to 30 % orthophosphoric acid, 10–30 % citric acid, the rest is process water. Solution is heated to 100 °C by ignition of the boiler and circulates for at least 12 hours with constant maintenance of acid concentration.EFFECT: method effectively clears boilers from deposits density up to 2,500 kg/m.1 cl, 1 tbl

Description

The invention relates to a power system, and can be used for physico-chemical cleaning of the internal surfaces of the heating of boiler equipment from deposits arising during their operation.

During operation of boilers, deposits form on the inner surfaces of the water path. Subject to a regulated water regime, deposits consist mainly of iron oxides. Every year, in preparation for the new heating season, hydropneumatic cleaning of boiler equipment from scale and deposits is performed at the boiler rooms. Untimely or poor-quality cleaning of boilers leads to a decrease in the efficiency of boiler units and, consequently, to excessive consumption of fuel. According to the directory "Management of energy resources of enterprises" [Management of energy resources of mining enterprises: Textbook / Lyakhomsky A.V., Babokin G.I., - 2nd ed. - M .: Mountain Book, 2012. - 232 p .: ISBN 978-5-98672-326-6 - Access mode: http://znanium.com/catalog/product/995164)] the presence of scale on the inside of the boiler is thick 1 mm leads to an excessive consumption of fuel up to 7%. Also, the presence of scale and deposits leads to a deterioration in heat transfer, reducing the life of the equipment.

A known method of removing deposits based on 5-15% phosphoric acid when heated to 100 ° C [1].

A known method of cleaning the inner surface of the tube space of heat-exchange equipment, comprising circulating in a closed loop an aqueous solution of 20-40% phosphoric acid with heating the surface to be cleaned to 102-110 ° C and the ratio of sludge and acid 1: 5 [2].

The disadvantage of using mineral acids (in particular phosphoric acid) is the slow and incomplete dissolution of iron oxide and other deposits. In this connection, the cleaning time is extended and energy costs increase [3]. [Page 309, 310 http://elib.biblioatom.ru/text/shvedov_yadernaya-tehnologiya_1979/go,310/?bookhl=%D1%84%D0%BE%D1%81%D1%84%D0%BE%D1 % 80% D0% BD]

A mixture of inorganic (mineral) and organic acids provides high dissolving properties. Of the organic acids for chemical cleaning of equipment, citric acid is most often used, which effectively removes iron oxides. The widespread use of this mixture is also due to pronounced complexing properties. In addition, it as a water-soluble product, easy to handle [4, 5].

https://files.stroyinf.ru/Data2/1/4294816/4294816650.htmhttp://gostrf.com/normadata/1/4294817/4294817969.htm. The objective of the invention is to improve the method of cleaning the inner surface of the pipe space (heating surfaces) of heat transfer equipment, to increase the efficiency of boiler units, increase reliability and extend the life of the equipment by changing the composition of the washing solution and its temperature, which ensures the effective removal of insoluble sediment and eliminates the passivation process .

The problem is solved by the fact that the physicochemical method of cleaning the internal surfaces of the heating of boiler equipment from deposits is applied, which involves the repeated circulation of a solution containing phosphoric and citric acids, followed by washing of the equipment, according to the invention, a solution containing up to 30% phosphoric acid, 10 -30% citric acid, the rest is industrial water, heated to 100 ° C by igniting the boiler and circulating it for at least 12 hours with constant concentration of acids.

The technical result of the claimed invention is to reduce the time of removal of deposits at their high density and reducing the flow rate of the solution due to the selection of the optimal composition, which provides better dissolution and is almost completely neutralized by deposits while maintaining minimal corrosion effect on the treated surface.

As a rule, chemical cleaning includes the following steps: 1) water washing; 2) chemical cleaning; 3) passivation. The first stage is needed only for pre-cleaning, its purpose is to remove various types of suspensions (burr, sand, etc.). The second stage is the main one and, depending on the amount and nature of the deposits, is carried out in one, two or even more stages - this is usually acid treatment. The third stage (passivation) is intended to protect the cleaned surface of the steel from subsequent corrosion exposure [6]. https://studfiles.net/preview/1190553

The main advantages of using phosphoric acid in the chemical cleaning process are the absence of secondary rusting of the cleaned surface (since the surface is covered with a protective film of iron phosphates), therefore, passivation of the metal is excluded.

Phosphoric acid, like other acids, is aggressive towards steel. Its use in high concentration requires the introduction of corrosion inhibitors into the solution, forming a protective layer on the metal surface.

The proposed physico-chemical method for cleaning the internal heating surfaces of boiler equipment from deposits is as follows:

- Fill the boiler equipment (system) with a solution containing:

phosphoric acid up to 30%, citric acid 10-30%, the rest is process water.

- Start circulation (using a boiler or network pump);

- Heat the solution to 100 ° C (by igniting the boiler);

- Carry out multiple circulation of the solution in the heat exchange equipment for at least 12 hours;

- Throughout the entire cleaning process, analytical control of the concentration of free acids and the temperature of the solution is conducted. With a decrease in the concentration of free acids, the washing solution is fed with phosphoric and citric acid;

- Drain the "contaminated" solution from the system;

- Flush the system.

As a result of cleaning occurs:

- weakening of the adhesion of the rust layer to the metal due to the penetration of the solution into cracks, evaporation of it and its partial dissolution of iron oxides;

- saponification or emulsification of oily contaminants;

- partial dissolution of silica contaminants.

In the table. the test results of the compositions of the invention are presented [7].

* Various compositions of the solution (phosphoric acid up to 30%, citric acid 10-30%, industrial water - the rest) when the solution is heated to 80 ° C. It is known that with increasing temperature of the solution to 100 ° C, its effectiveness increases.

Solution 1: phosphoric acid 10%, citric acid 30%, process water - the rest.

Solution 2: phosphoric acid 0.5%, citric acid 10%, process water - the rest;

Solution 3: phosphoric acid 30%, citric acid 10%, process water - the rest;

Solution 4: phosphoric acid 0%, citric acid 30%, process water - the rest.

The authors, experimentally established that the proposed solution under thermal and mechanical (circulation) exposure effectively cleans boiler equipment from deposits with a density of up to 2500 kg / m ³ .

Literature:

1. Chemical cleaning of heat exchange equipment. Edited by T.Kh. Margulova, M .: Energy, 1987.

2. RF patent N 1772578 MKI F28G 9/00, Bull. N 40, 1992

3. Shvedov V.P. and other Nuclear technology: [Textbook. allowance for chemical technology. specialist. universities] / V.P. Shvedov, V.M. Sedov, I.L. Rybalchenko, I.N. Vlasov; Under the total. ed. I.D. Morokhov. - M.: Atomizdat, 1979. - 336 p. Page 309-312

4. RD 34.10.407. Reagent consumption rates for pre-start and operational chemical cleanings of thermal power equipment of power plants.

5. RD 34.37.305-97. COLLECTION OF METHODS OF CHEMICAL ANALYSIS OF FLUSHING SOLUTIONS AT CHEMICAL CLEANING OF HEAT AND POWER EQUIPMENT.

6. Guzhulev EP et al. Water treatment and input-chemical regimes in the power system: Textbook. allowance / EP Guzhulev, V.V. Shalai, V.I. Gritsenko, M.A. Ram. Omsk: Publishing House of OmSTU, 2005 .-- 384 p.

7. RD 153-34.1-37.306-2001. Guidelines for monitoring the state of the main equipment of thermal power plants, determining the amount and chemical composition of deposits.

Claims (1)

A method for cleaning the inside surfaces of boiler equipment from deposits, including repeated circulation of a solution containing phosphoric and citric acids, followed by washing of equipment, characterized in that the solution contains up to 30% phosphoric acid, 10-30% citric acid, the rest is industrial water, heated to 100 ° C by igniting the boiler and circulating it for at least 12 hours with constant concentration of acids.