Essence-safe boiler feedwater oxygenation processing method

Abstract

The invention discloses an essence-safe boiler feedwater oxygenation processing method. The method comprises the following steps: 1) setting a feedwater processing mode before a thermal power unit copper-free system is oxygenized to be an ammonification processing mode; 2) closing an exhaust valve of a deaerator after meeting a certain condition; 3) carrying out oxygenation at an oxygenation point of the condensation water precision processing outlet of the unit; 4) controlling the content of water dissolved oxygen at an inlet of economizer to the range of 5-50 mu g / kg, wherein the content of master steam chromate is no obviously increased as compared with that before oxygenation; 5) controlling the cation conductivity (1.5mu S / cm and [Cl-] (125 mu g / kg) of header boiler water below a drum boiler; 6) reducing the control range of the pH of stokehole feedwater at the temperature of 25 DEG C to 8.8-9.3 before the cubic centimeter (CC) of the stokehole feedwater is reduced to 0.15 mu S / cm; 7) before the operation of the unit stops, increasing the pH of the stokehole feedwater at the temperature of 25 DEG C to 9.3-9.6; and 8) blowing out the boiler and maintaining. By using the method, accidents caused by spalling of scale cinder of a steam through-flow system after feewater oxygenation can be effectively prevented.

Description

technical field [0001] The invention relates to a process method, in particular to a method for adding oxygen to boiler feed water, and belongs to the technical field of electric power and power engineering. Background technique [0002] The purpose of adding oxygen to boiler feed water is to make use of the passivation effect of dissolved oxygen on the metal in the feed water to form a dense protective oxide film on the metal surface to reduce the iron content in the feed water and prevent flow accelerated corrosion (Flow Accelerated Corrosion, FAC for short), reduce the fouling rate of boiler tubes, slow down the rising speed of the operating pressure difference of the once-through furnace, prevent the hybrid superheater, reheater and steam turbine from salt accumulation caused by desuperheating water, prolong the period of boiler chemical cleaning and condensate cleaning Handle the operating cycle of the mixed bed. [0003] There are three main methods of boiler feed wat...

AI Technical Summary

Problems solved by technology

Main disadvantages: ①Requires pH of water supply 25℃ The value is high, resulting in a low cycle water production volume of the condensate polishing treatment mixed bed; ② Feed water iron ion content is one-third of that under the AVT(R) method, but it is not enough to eliminate FAC, and there is still a certain degree of boiler water vapor system Corrosion and Deposition Issues

Main disadvantages: ① There are certain restrictions on the material of the water supply system

OT will accelerate the corrosion and deposition of copper-containing alloys in water vapor systems, so it is not suitable for systems with copper (copper tubes for condensers and low-pressure heaters)

The so-called copper-free system is often not absolutely copper-free. For example, the material of high-pressure water supply pipelines of modern high-parameter thermal power units is generally 15NiCuMoNb5, and its copper content is 0.5% to 0.8%. Using OT will also have a certain impact; in addition, it is often used as The Stellite alloy on the hard surface of the valve, that is, the cobalt-based tungsten-chromium eutectic alloy may have abrasion-corrosion problems when DO≥50μg / L; There is a significant difference, which will increase the electrochemical potential (ECP) of the steam flow system. Under certain conditions, the chromium-rich layer of the metal multilayer oxide skin in contact with oxygen-containing steam will escape from chromium oxidation, and voids will be formed in the oxide skin. Cave defects will eventually lead to the peeling off of scale, causing accidents such as boiler superheater and reheater tube overheating or even tube explosion

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