System and method for increasing drying capacity of medium-speed coal mill based on medium-temperature flue gas extraction

Abstract

The invention discloses a system and method for increasing the drying capacity of a medium-speed coal mill based on medium-temperature flue gas extraction. The system comprises a pulverized coal boiler, wherein two side walls of a flue between a low-temperature superheater and an economizer of the pulverized coal boiler are each provided with a medium-temperature flue gas extraction port, and the medium-temperature flue gas extraction ports are connected with a flue gas booster fan through a flue gas bypass; the flue gas bypass is connected with an upstream hot primary air pipeline through a hot primary air bypass pipeline, and a suction opening is formed in the upstream hot primary air pipeline; and an outlet flue of the flue gas booster fan is connected with a downstream hot primary air pipeline through a mixing structure, and an outlet of the downstream hot primary air pipeline is connected to the coal mill. The temperature of a drying medium at an inlet of the coal mill is increased to about 400 DEG C by adopting a medium-temperature flue gas extraction technology and a hot primary air bypass technology; high-temperature flue gas is not extracted, and the influence on the combustion stability of a main combustion area is small; and medium-temperature flue gas has a flue gas recirculation effect, a boiler steam temperature adjusting means is added, and the original emission of boiler nitrogen oxide can be reduced.

Description

technical field [0001] The invention belongs to the technical field of thermal power generation, and in particular relates to a system and method for increasing the drying output of a medium-speed coal mill based on extracting medium-temperature furnace smoke. Background technique [0002] The problem of coal-fired blending is common in power plant boilers in my country. Due to the shortage of coal sources, some boilers even need to carry out large-scale, cross-coal blending and even re-burning of coal. The large change in coal types has brought about drastic changes in operating conditions. , put forward higher requirements on the adaptability of the boiler and its auxiliary equipment. Boilers whose designed coal is bituminous coal face the following problems when burning high-moisture lignite and coal slime: (a) The pulverizing system cannot operate normally when burning high-moisture and high-volatile lignite Safety risks, only relying on operation adjustments cannot meet...

AI Technical Summary

Problems solved by technology

Boilers whose designed coal is bituminous coal face the following problems when burning high-moisture lignite and coal slime: (a) The pulverizing system cannot operate normally when burning high-moisture and high-volatile lignite Safety risks, only relying on operation adjustments cannot meet the requirements, and the boiler pulverizing system, combustion system, etc. must be adapted to a wide range of coal types; (b) By extracting high-temperature furnace smoke, the drying output of the pulverizing system can be greatly improved, and the drying output of the pulverizing system can be reduced. Oxygen content of the drying medium. This method needs to use the furnace smoke fan to boost the high-temperature and low-pressure furnace smoke and introduce it into the hot primary air main pipe. The current extraction furnace smoke drying technology is mainly based on the storage system of fan coal mill and steel ball coal mill. Powder system, both of which are difficult to raise the furnace smoke pressure head to a higher level

[0005] This scheme has the following disadvantages: (a) more low-temperature cold furnace smoke needs to be introduced, which reduces the quality of flue gas; (b) the layout of low-temperature cold furnace smoke pipes requires a large investment; (c) the extraction of hot furnace smoke is large, which is not conducive to Combustion stability in the main combustion area; (d) due to the introduction of more cold furnace smoke, the amount of flue gas in the flue from the boiler to the outlet of the induced draft fan has increased significantly, the wear of the heating surfaces at all levels has intensified, the resistance of the smoke and wind has increased, and the induced draft fan motor Consumption increases, electrostatic precipitator efficiency decreases; (e) Boiler efficiency decreases

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