CN-122015079-A - Hierarchical low-nitrogen combustion system and method for anthracite boiler

CN122015079ACN 122015079 ACN122015079 ACN 122015079ACN-122015079-A

Abstract

The invention discloses a grading low-nitrogen combustion system and method of an anthracite boiler, comprising a hearth body, burner groups symmetrically arranged along the periphery of the lower part of the hearth, adopting direct-current burner tangential combustion, wherein each group comprises parallel primary air nozzles and secondary air nozzles, the primary air nozzles are horizontally distributed at intervals, a grading air supply unit is provided with a main secondary air system for supplying air to a main combustion area, a compact over-fire air system above the burner groups, and a separated over-fire air system above the burner groups, the latter nozzles are at least divided into two stages along the hearth height to form a three-stage air supply structure, a fuel grading supply unit comprises a pulverizing system and a concentration separation device, can separate pulverized coal air flow and convey the pulverized coal air flow to corresponding nozzles, and an intelligent regulation module is used for regulating air supply and fuel supply through linkage of an executing mechanism according to collection parameters of a sensor group. The invention can cooperate with the organization of the furnace atmosphere and the dynamic adjustment, and solves the problem of the reduction of the combustion efficiency in deep low-nitrogen emission.

Inventors

DENG LEI
LI PEIQI
LIANG FAGUANG
WANG CHIZHONG
FANG FAN
SHAO YUNHAO
AN HONG

Assignees

西安交通大学
西安热工研究院有限公司

Dates

Publication Date: 20260512
Application Date: 20260324

Claims (10)

1. An anthracite boiler staged low nitrogen combustion system, comprising: A hearth body; The burner groups are symmetrically arranged along the wall surfaces around the lower part of the hearth body, and adopt a tangential combustion mode of a direct-current burner, each burner group comprises a plurality of primary air nozzles and secondary air nozzles which are arranged in parallel, each primary air nozzle comprises a concentrated coal powder nozzle for supplying concentrated coal powder and a light coal powder nozzle for supplying light coal powder, and the concentrated coal powder nozzles and the light coal powder nozzles are distributed at intervals along the horizontal direction of the hearth; The grading air supply unit comprises a main secondary air system for supplying air to the main combustion area, a compact type over-fire air system arranged above the burner group and a separated type over-fire air system arranged above the compact type over-fire air system, wherein the nozzle of the separated type over-fire air system is divided into at least two stages along the height direction of a hearth to form a vertical three-stage air supply structure; The fuel classification supply unit comprises a powder making system and a thick-thin separation device connected to an outlet of the powder making system, and is used for separating pulverized coal airflow into concentrated pulverized coal airflow and thin pulverized coal airflow, and respectively conveying the concentrated pulverized coal airflow and the thin pulverized coal airflow to the concentrated pulverized coal nozzle and the thin pulverized coal nozzle; The intelligent regulation and control module comprises a sensor group for collecting combustion state parameters in a hearth, a controller and an actuating mechanism connected to the classified air supply unit and the fuel classified supply unit, wherein the controller is used for carrying out linkage regulation on air supply and fuel supply through the actuating mechanism according to the parameters.
2. The hierarchical low-nitrogen combustion system of an anthracite boiler according to claim 1, wherein the secondary air nozzles of the hierarchical air supply unit comprise main secondary air nozzles with nozzle axes radially parallel to the furnace and side secondary air nozzles with nozzle axes deflected toward the furnace wall side.
3. The anthracite boiler staged low nitrogen combustion system of claim 2, wherein the nozzle axis of the side secondary air nozzle is adjustable in deflection angle in the range of 15 ° to 25 °.
4. The anthracite boiler staged low nitrogen combustion system of claim 1, wherein the split overfire air system comprises a primary split overfire air nozzle and a secondary split overfire air nozzle, the vertical distance between the primary split overfire air nozzle and the compact overfire air system nozzle is 2.5-3.0 m, and the vertical distance between the secondary split overfire air nozzle and the primary split overfire air nozzle is 3.0-3.5 m.
5. The anthracite boiler staged low nitrogen combustion system of claim 4, wherein the ratio of the air supply flow rates of the primary separated overfire air nozzle and the secondary separated overfire air nozzle is from 1:1.2 to 1:1.5.
6. The grading low-nitrogen combustion system of the anthracite boiler according to claim 1, wherein the number ratio of the concentrated coal powder nozzles to the light coal powder nozzles is 4:1, the coal powder concentration of the concentrated coal powder airflow output by the concentration separation device is 0.8-1.2 kg/kg, and the coal powder concentration of the light coal powder airflow is 0.2-0.4 kg/kg.
7. The hierarchical low-nitrogen combustion system of an anthracite boiler according to claim 1, wherein the controller of the intelligent regulation module is integrated with a fuzzy PID control algorithm, and the sensor group at least comprises a NOx concentration sensor and an oxygen content sensor which are arranged at the outlet of a hearth.
8. The anthracite boiler staged low nitrogen combustion system of claim 1, further comprising a furnace soot blowing unit and an anti-coking monitoring unit, wherein the anti-coking monitoring unit comprises an infrared temperature sensor arranged on the surface of a furnace water wall.
9. A anthracite boiler staged low nitrogen combustion system according to claim 2 or 3, wherein the side overgrate air nozzles are arranged horizontally outermost in each burner group.
10. An anthracite boiler staged low nitrogen combustion method based on the system of any of claims 1 to 9, comprising the steps of: separating the prepared coal dust into a concentrated coal dust airflow and a light coal dust airflow through a thick coal dust separation device, and sending the concentrated coal dust airflow and the light coal dust airflow into different areas of a hearth through a thick coal dust nozzle and a light coal dust nozzle respectively so as to realize the horizontal graded supply of fuel; The main and secondary air systems, the compact type over-fire air system and the separated type over-fire air system are used for sending combustion air in three stages along the height direction of the hearth, wherein the anoxic combustion condition is maintained in the main combustion area, and the subsequent over-fire of coal dust is realized through the upper-stage over-fire air system; forming a central fuel-rich area and a near-wall oxygen-rich area in the radial direction of the hearth by adjusting the air supply direction of the side secondary air nozzle; the NOx concentration at the outlet of the hearth and the parameters reflecting the boiler efficiency are monitored in real time, and the air distribution proportion of the grading air supply unit and the distribution proportion of the fuel grading supply unit are regulated in parallel to cooperatively control the NOx emission and the combustion efficiency.

Description

Hierarchical low-nitrogen combustion system and method for anthracite boiler Technical Field The invention belongs to the technical field of thermal power generation equipment and control, and particularly relates to a hierarchical low-nitrogen combustion system and method for an anthracite boiler. Background Nitrogen oxides (NOx) generated during the combustion of pulverized coal boilers are one of the main atmospheric pollutants. To control NOx emissions, low nitrogen combustion technology is widely used as a solution to control from the source of combustion due to its relatively low cost. Currently, low nitrogen combustion technology applied to utility boilers is mainly developed around two ideas, air classification and fuel classification. The air classification technology forms a preliminary anoxic-oxygenized combustion stage by arranging an overfire air nozzle (such as compact overfire air, CCOFA) above the main combustion zone, and can inhibit the generation of NOx to a certain extent. However, for anthracite type fire-resistant coal, the gas has low volatile matter and difficult ignition burnout, if air classification is adopted, the oxygen content of a main combustion area is excessively pressed for pursuing lower NOx emission, so that insufficient coal dust combustion and high fly ash carbon content are easily caused, and the boiler efficiency is reduced. Conversely, if the main combustion region oxygen concentration is increased to ensure combustion efficiency, the NOx production increases greatly. The above contradiction is particularly pronounced in anthracite combustion. In addition, to further reduce NOx, the prior art has also attempted to introduce fuel staging techniques, i.e., injecting a portion of the fuel into a specific area within the furnace to form a strong reduction zone to reduce the NOx that has been produced. However, in practical applications, especially in tangential firing boilers, it is a technical difficulty how to accurately feed and stabilize the reburn fuel in the desired spatial region and to form an effective fit with the air classification, rather than simply mixing with the main fuel. If the pure fuel classification lacks a matched space burning structure, the denitrification effect is limited and unstable. Accordingly, the prior art lacks a combustion system capable of systematically organizing the combustion atmosphere in the furnace space in a coordinated manner and having dynamic adjustment capability to cope with the problem of reduced combustion efficiency faced by anthracite boilers when achieving deep low nitrogen emissions. Disclosure of Invention Aiming at the problems in the prior art, the invention provides a grading low-nitrogen combustion system and method for an anthracite boiler, which aim to systematically and cooperatively organize the space combustion atmosphere in the boiler, have dynamic adjustment capability, and solve the problem of combustion efficiency reduction faced by the anthracite boiler when deep low-nitrogen emission is realized. In order to solve the technical problems, the invention is realized by the following technical scheme: according to a first aspect of the present invention, there is provided an anthracite boiler staged low nitrogen combustion system comprising: A hearth body; The burner groups are symmetrically arranged along the wall surfaces around the lower part of the hearth body, and adopt a tangential combustion mode of a direct-current burner, each burner group comprises a plurality of primary air nozzles and secondary air nozzles which are arranged in parallel, each primary air nozzle comprises a concentrated coal powder nozzle for supplying concentrated coal powder and a light coal powder nozzle for supplying light coal powder, and the concentrated coal powder nozzles and the light coal powder nozzles are distributed at intervals along the horizontal direction of the hearth; The grading air supply unit comprises a main secondary air system for supplying air to the main combustion area, a compact type over-fire air system arranged above the burner group and a separated type over-fire air system arranged above the compact type over-fire air system, wherein the nozzle of the separated type over-fire air system is divided into at least two stages along the height direction of a hearth to form a vertical three-stage air supply structure; The fuel classification supply unit comprises a powder making system and a thick-thin separation device connected to an outlet of the powder making system, and is used for separating pulverized coal airflow into concentrated pulverized coal airflow and thin pulverized coal airflow, and respectively conveying the concentrated pulverized coal airflow and the thin pulverized coal airflow to the concentrated pulverized coal nozzle and the thin pulverized coal nozzle; The intelligent regulation and control module comprises a sensor group for collecting combustion state parameters in a hearth,