RU2557155C1 - Method of steam and chemical cleaning and passivation of surfaces of metal pipes - Google Patents

Abstract

FIELD: power industry.

SUBSTANCE: in the method of steam and chemical cleaning and passivation of surfaces of metal pipes which is characterized by their purging with water vapour with oxidizer and activators of cleaning process into the water vapour flow during their purging first the reagent is added which emits carbon oxide - water solution of formic acid, then hydrogen and at the end of the process oxygen is added.

EFFECT: improvement of efficiency of cleaning and passivation of internal surfaces of heat exchange pipes due to performing the process in three stages at consecutive dosing in the flow of steam of reagent of the formic acid decayed with release of carbon oxide in the following sequence: formic acid, hydrogen and oxygen.

Description

The invention relates to energy, in particular to methods for cleaning heat exchangers from deposits and their subsequent passivation, and can be used in energy, engineering, petrochemical and other fields of national economy.

A known method of cleaning and passivation of the path of the working environment of steam boilers by treating the specified path with a vapor-oxygen mixture (Copyright certificate SU No. 976761, 3 F22B 37/48, 1980). The disadvantages of this method is the low efficiency when removing deposits formed during operation, in particular iron oxide compounds.

There is a method of steam-chemical cleaning from operating deposits of surfaces of metal pipes, characterized by their purging with water vapor, into which a two-substituted sodium salt of ethylenediaminetetraacetic acid is introduced during purging (Polevich AN Steam-chemical cleaning from operating deposits of internal heating surfaces of a PTVM-180 boiler. Energy saving and Water Treatment No. 2, 2009, pp. 25-27). The disadvantages of this method are the high degree of corrosion of metal wear during the cleaning process, the inability to conduct cleaning at high temperatures.

There is a method of steam chemical cleaning and passivation of the surfaces of metal pipes, characterized by blowing water vapor with an oxidizing agent and activators of the cleaning process, while gaseous reactants are introduced into the steam stream during the purge process, and carbon dioxide is first introduced, a reagent emitting during thermal decomposition of carbon monoxide, then hydrogen and oxygen is added to complete the process. (Patent for invention RU No. 2514569 with priority dated 02/03/2013, published on 04/27/2014. Bull. No. 12, IPC F28G 9/00), selected by the authors as a prototype.

The disadvantages of this method are the low efficiency in the removal of deposits at the first stage, since the carbon dioxide supplied to the vapor medium in the temperature range from 200 to 650 ° C is not decomposed into carbon monoxide in an insufficient amount, which reduces the efficiency of the process and further the reliability of the equipment.

The aim of the proposed method is to increase the efficiency of cleaning the internal surfaces of heat transfer pipes from deposits, reduce corrosion losses from the surface of the boiler steel to be cleaned, and increase the reliability of equipment in subsequent operation.

The technical result achieved by the use of the invention is to increase the efficiency of cleaning and passivation of the inner surfaces of heat transfer pipes by carrying out the process in three stages with successive dosing of a reagent - formic acid, decomposing at temperatures from 200 to 650 ° C with the release of carbon monoxide, in next priority: formic acid, hydrogen and oxygen.

The goal is achieved, and the technical result is achieved by the fact that in the method of vapor-chemical cleaning and passivation of the surfaces of metal pipes, characterized by blowing them with steam with an oxidizing agent and activators of the cleaning process, moreover, the reagent emitting carbon monoxide is firstly introduced into the stream of water vapor during their purging process , then hydrogen and oxygen are introduced at the end of the process, in order to intensify the cleaning process and increase reliability, a reagent is first introduced into the water vapor stream - an aqueous solution of m ravinoy acid, then hydrogen and finally the process oxygen is injected.

The method is as follows.

Formic acid is dosed into the vapor medium in the temperature range from 200 to 650 ° C. Operational cleaning with a steam-gas mixture (ASG) based on formic acid of heat exchange tubes from operational deposits consisting of 98% of iron oxide deposits occurs according to the following reactions:

Example. Superheated steam with a pressure of 2.5 MPa and a temperature of 450 ° C was fed into a metal heat exchange tube (TOT) with a flow rate of 300 kg / h and at a speed of 50-60 m / s. Before the superheated steam enters the HTF, an aqueous solution of formic acid was supplied to the injection device from the dosing unit.

Example

Purification by a gas-vapor mixture based on carbon monoxide obtained by thermal decomposition of formic acid.

Parameters of gas-vapor mixture:

- temperature 450 ° C;

- pressure 2.5 MPa;

- speed 50 ÷ 60 m / s;

- consumption of 300 kg / h;

- the concentration of carbon monoxide in the vapor medium 1 g / kg

The high efficiency of the method was confirmed by testing samples at the experimental stand of the All-Russian Heat Engineering Institute OJSC.

Claims (1)

The method of steam chemical cleaning and passivation of the surfaces of metal pipes, characterized by their purging with water vapor with an oxidizing agent and activators of the cleaning process, moreover, the reagent emitting carbon monoxide is firstly introduced into the stream of water vapor during their purging process, then hydrogen and oxygen are added at the end of the process, characterized in that in order to intensify the process, a reagent is first introduced into the water vapor stream - an aqueous solution of formic acid.