Intrinsically-safe water-feeding and oxygen-adding treatment method of once-through boiler

Abstract

The invention discloses an intrinsically-safe water-feeding and oxygen-adding treatment method of a once-through boiler, comprising the following steps of: (1) adopting independent ammonia-adding treatment as a water-feeding treatment mode before adding oxygen of a copper-free system of a thermal power unit and adjusting the pH value at 25DEG C of water fed before the boiler to be 9.3-9.6 by adding ammonia; (2) closing an exhaust valve of a deaerator after meeting certain conditions; (3) adding oxygen at an oxygen adding point of a condensed water precision treatment outlet of the unit; (4) controlling that the content of dissolved oxygen at an inlet of a coal economizer is in the range of 5-50mu g/L and the oxygen content of main steam is not remarkably increased compared with the before adding oxygen; (5) reducing the control range of the pH value at 25DEG C of water fed before the boiler to be 8.8-9.3 after the electrical conductivity (CC) of anions of water fed before the boiler is reduced to be less than 0.15mu S/cm; (6) improving the pH value at 25DEG C of water fed before the boiler before the unit stops to be 9.3-9.6 until the unit halts; and (7) stopping the operation of the boiler and maintaining. The treatment method can be used for enhancing the buffer capacity of the water-feeding and oxygen-adding treatment and reducing the fluctuation of the dissolved oxygen content of the fed water and other parameters.

Description

technical field [0001] The invention relates to a process method, in particular to a method for adding oxygen to feed water of a once-through boiler. It 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 (FAC) in the furnace front system. , referred to as FAC), 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 and reheater and steam turbine from salt accumulation caused by desuperheating water, prolong the period of boiler chemical cleaning and condensate The operating cycle of the fine treatment mixed bed. [0003] For once-throu...

AI Technical Summary

Problems solved by technology

Main disadvantages: ①Requires pH of water supply 25℃ The value is high, resulting in low cycle water production of condensate polishing treatment mixed bed, and it is not suitable for systems with copper; ② Feed water iron ion content is one-third of that in AVT(R) mode, but it is not enough to eliminate FAC, The boiler water vapor system still has some corrosion and deposition problems

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 15Ni CuMoNb5, and its copper content is 0.5% to 0.8%. Using OT will also have a certain impact; in addition, commonly used The Stellite alloy used as the hard surface of the valve, that is, the cobalt-based tungsten-chromium eutectic alloy may have abrasion-corrosion problems when DO≥50μg / L; ② DO and AVT(O) in steam when the feed water DO is high There is a significant difference in the way, which will increase the electrochemical potential (ECP) of the steam flow system, which will affect the steam flow system, especially the scale in the boiler superheater and reheater, causing it to fatigue, fall off, and cause Metal overheating or even pipe burst accidents

Images