Large pulverized coal boiler ultralow-load coal economizer switching bypass system

Abstract

The invention provides a large pulverized coal boiler ultralow-load coal economizer switching bypass system. The system mainly solves the problem of low-temperature corrosion risk of a cold end and atail flue of an air preheater. The system is characterized in that firstly, a bypass pipeline valve is opened, then a water supply pipe valve and a downcomer valve are closed, a hydrophobic valve is opened, residual boiler feedwater in a coal economizer is introduced into a boiler hydrophobic system to be recycled through a coal economizer drain pipe, the boiler feedwater enters the downcomer through a bypass pipeline, and the boiler feedwater does not absorb the flue gas heat through the coal economizer, so that the temperature of the flue gas at an outlet of the coal economizer can be increased by 60-80 DEG C. According to the system, the connecting mode is relatively simple and convenient, only certain pipeline equipment needs to be additionally arranged, the equipment investment is saved, the usability of a SCR of a ultralow-load denitration device is enhanced, the lowest load of the boiler can meet the lowest commissioning flue gas temperature condition of the SCR of the denitration device at 15% BMCR.

Description

technical field [0001] The invention relates to a switching bypass system for an ultra-low load economizer of a large pulverized coal boiler, which is applied to a pulverized coal boiler of a large thermal power unit and belongs to the technical field of large boilers. Background technique [0002] Considering environmental protection, the denitrification device SCR at the bottom of the boiler needs to be put into use when the unit is running under load. The allowable operating temperature range of the SCR catalyst of the denitrification device is generally 300 ° C ~ 410 ° C. When the operating load of the boiler decreases, the SCR flue temperature of the denitrification device at the bottom of the boiler (the smoke temperature at the outlet of the economizer) will decrease accordingly. There is a risk of operating at a temperature of 300°C. [0003] In order to deal with the commissioning of large pulverized coal boilers in ultra-low-load denitrification devices SCR, there...

AI Technical Summary

Problems solved by technology

When the operating load of the boiler decreases, the SCR flue gas temperature of the boiler tail denitrification device (the smoke temperature at the outlet of the economizer) decreases accordingly. When the boiler load is lower than 35% BMCR, the SCR flue gas temperature of the boiler tail denitrification device is usually lower than its minimum allowable The risk of operating at a temperature of 300°C

Images