Multi-stage stratified combustion system and method for primary air and secondary air of boiler

Abstract

The invention discloses a multi-stage stratified combustion system and a multi-stage stratified combustion method for primary air and secondary air of a boiler. The multi-stage stratified combustion system comprises combustors and air after-combustion devices, which are arranged on the four corners of a furnace chamber; each combustor comprises a secondary air box, at least one primary air tube and at least one primary secondary air spray nozzle; each air after-combustion device comprises an after-combustion air box and at least one after-combustion air spray nozzle; the secondary air boxes and the after-combustion air boxes are connected with a main air duct by the respective air tubes; the primary air tube spray nozzle is divided into a thick primary air spray nozzle and a thin primary air spray nozzle; the primary secondary air spray nozzle is divided into a secondary direct-blowing air spray nozzle and a secondary deviation-blowing air spray nozzle; the after-combustion air spray nozzle is divided into an after-combustion direct-blowing air spray nozzle and an after-combustion deviation-blowing air spray nozzle; and an effect of covering powder by air is formed during the combustion process by virtue of the multi-stage stratification of the primary air and the secondary air. The multi-stage stratified combustion method and the multi-stage stratified combustion method for the primary air and the secondary air of the boiler not only can be used for ensuring the ultralow emission of NOx and improving the combustion efficiency of the pulverized coal, but also can be used for preventing the agglomeration and the high-temperature corrosion of the water-cooling wall and reducing the thermal deviation of the heating area at the outlet of the furnace chamber.

Description

technical field [0001] The invention relates to a combustion system of a boiler, in particular to a combustion system for multi-stage layering of primary and secondary air. Background technique [0002] For coal-fired boilers, four rows of burners and four rows of exhaust air devices are arranged in a tangential circle at four corners, and the combustion method is that the primary air powder and secondary air are tangent to an imaginary tangent circle at the four corners of the furnace and the center of the furnace. Spray into the furnace to realize tangential combustion of pulverized coal. The four-corner jet flame formed by the four-corner tangential direct current combustion technology can support each other, and the flue gas generated by combustion rotates and rises in the furnace. It has the characteristics of long flame stroke, good mixing in the furnace, good combustion economy, and wide adaptability to coal types. It is easy to realize staged supply of air and st...

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Problems solved by technology

[0003] However, there are also some problems in the four-corner tangential arrangement of the combustion method. One of the major features is the formation of an overall main swirling airflow in the furnace, which will deflect the jets of the primary and secondary air, that is, the jets emitted from the burner The air flow deviates from the design direction of the air flow to some extent, that is, the geometric axis of the nozzle. When the deviation is serious, it will cause the flame in the furnace to hit the wall and stick to the wall, causing slagging on the water wall and generating a reducing atmosphere. It is also prone to problems such as high-temperature corrosion of the water wall when coal is used, especially when the air depth in the furnace is graded, the main burner area is often under a low excess air coefficient, and these problems are more likely to occur; the inherent four-corner tangential combustion method The form of the airflow field in the furnace generally causes the residual rotational momentum of the flue gas at the furnace outlet to be relatively large, resulting in a large deviation of the flue gas at the furnace outlet, resulting in a large thermal deviation of the heating surface at the furnace outlet, and increasing the amount of desuperheating water; in addition, in recent years The quality of coal used in power plants in China is constantly declining, and the quality of coal in thermal power plants is variable, which makes the problem of stable combustion more prominent. The combustion system is difficult to meet the needs

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