System for solving overtemperature of water cooling wall of corner-tangential supercritical boiler

Abstract

The invention discloses a system for solving overtemperature of a water cooling wall of a corner-tangential supercritical boiler. The system comprises a secondary air box, a plurality of primary air branches and a plurality of lowermost primary air nozzles formed in a furnace; each primary air branch comprises a primary air bypass air pipe and a primary air pipe, and one lowermost primary air nozzle corresponds to one primary air branch; and an outlet of the secondary air box communicates with the primary air pipes through the primary air bypass air pipes, outlets of the primary air pipes communicate with the lowermost primary air nozzles, and the system can effectively solve the problem of overtemperature of the water cooling wall.

Description

technical field [0001] The invention belongs to the field of pulverized coal boilers in power stations, and relates to a system for solving the overheating of water-cooled walls of four-corner tangential circle supercritical boilers. Background technique [0002] The reasons for the local overheating of the water wall of the boiler are divided into two categories, one is the thermal deviation caused by the uneven flow distribution between the water wall tubes, and the other is the thermal deviation caused by the uneven distribution of the flame in the furnace. Among them, the influencing factors of the former are more complicated, such as the resistance deviation existing in the design of each tube, the resistance deviation caused by different cleanliness, etc., and the method of dealing with thermal deviation is also greatly limited; Uneven powder distribution, improper air distribution, improper combination of burners, etc., which can be optimized through combustion optimi...

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Problems solved by technology

Among them, the influencing factors of the former are more complicated, such as the resistance deviation existing in the design of each tube, the resistance deviation caused by different cleanliness, etc., and the method of dealing with thermal deviation is also very limited; Uneven powder distribution, improper air distribution, improper combination of burners, etc., which can be optimized through combustion optimization adjustment tests

[0003] However, due to the complexity of the supercritical hydrodynamic itself, when the supercritical unit operates at low load, the tolerance of the steam-water ratio increases. Due to the relatively reduced feedwater flow rate, the flow distribution at the inlet of the water-cooled wall is uneven, which easily causes a large steam-water mixture in each tube. Specific tolerance

Although the general supercritical boiler adopts the spiral tube water wall to increase the weight flow rate and relatively increase the flow rate, the uneven flow distribution of the water wall cannot be avoided.

According to the hydrodynamic characteristics, the flow distribution is uneven, and the working medium flow in the tube is more unstable, so the water wall of the supercritical unit boiler is prone to overheating at low load.

[0004] Generally speaking, for a supercritical unit, the heat absorption share of the lower water-cooled wall increases, the enthalpy of the working medium increases, and part of the water-cooled wall pipes generate vapor-liquid two-phase flow, which increases the pipe resistance sharply, increases the flow deviation of different tube bundles, and absorbs Due to the early evaporation of the hot tube, the resistance of the pipeline increases, the flow rate decreases, and the cooling effect deteriorates. Such a vicious cycle causes the water wall to overheat seriously.

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