CN107355776A - Combustion System of Boiler Burning Fine, method and the application of ultra-low NOx emission - Google Patents

Abstract

The invention discloses an ultra-low NOx emission pulverized coal boiler combustion system, comprising a coal gasification device (2), a primary air pipe (3), a primary air nozzle (4), a secondary air pipe (5), a secondary air Spouts (6), primary overburning air spouts (7) and secondary overburning air spouts (8); the primary air spouts (4), secondary air spouts (6), primary overburning air spouts (7 ) and secondary overburning air nozzles (8) are successively arranged in layers on the water wall of the boiler furnace (1); The exhaust air nozzle (7) is connected with the secondary exhaust air nozzle (8). The invention also discloses a pulverized coal boiler combustion method with ultra-low NOx emission. The invention also discloses an ultra-low NOx emission pulverized coal boiler combustion system and application of the method. The combustion system of the present invention can realize ultra-low NOx emission of 80mg/Nm ³ -120mg/Nm ³ , directly reaching the common NOx emission standard of power plant boilers.

Description

Combustion system, method and application of pulverized coal boiler with ultra-low NOx emission

technical field

The invention belongs to pulverized coal combustion technology, and more specifically relates to a pulverized coal boiler combustion system, method and application of ultra-low NOx emission.

Background technique

Coal is still the main energy source in my country, accounting for about 70% of the energy supply. Large-scale power station pulverized coal boilers are the main equipment in my country's power industry, and the number is huge. A large amount of nitrogen oxides produced during the combustion of coal in the boiler is a harmful and difficult to deal with air pollutants. It not only stimulates the human respiratory system, damages animals and plants, directly affects the growth, destroys the ozone layer, but also causes the greenhouse effect. , one of the main substances in the reaction of acid rain and photochemical smog. With social development and technological progress, people pay more and more attention to environmental protection. In recent years, my country has put forward strict restrictions and forward-looking requirements on the emission of nitrogen oxides from power plant boilers. Large and medium-sized coal-fired boilers in the power industry have generally carried out Low-nitrogen combustion technology and denitrification transformation have played a very good role in reducing NOx emissions. With the increasingly stringent NOx control standards, many technologies have emerged to remove or reduce the generation of harmful gases, greatly reduce the discharge of harmful gases into the atmosphere, and reduce the harm to the environment.

According to research, there are three kinds of NOx that can be generated due to different NOx formation mechanisms in the process of pulverized coal combustion: ① fuel-type NOx, which is NOx directly oxidized from organic nitrogen in fuel; ② thermal-type NOx, where N ₂ in the air supply NOx formed by combining with O ₂ atoms at high temperature; ③Instantaneous NOx, hydrocarbons are produced during combustion and quickly form NOx with N ₂ , and the formation ratio in coal-fired boilers is very small, mainly the first two NOx formation. Fuel-type NOx accounts for about 70-90%, thermal-type NOx accounts for about 10-30%, and rapid-type NOx accounts for less than 5%, which are usually ignored. NOx is a general term for nitrogen oxides such as N ₂ O, NO ₂ , NO, N ₂ O ₅ and PAN. The nitrogen oxides produced during pulverized coal combustion are mainly NO and NO ₂ , of which NO accounts for more than 95%.

At present, the low-nitrogen combustion technology transformation of existing large-scale pulverized coal boilers in power plants is based on the formation mechanism of nitrogen oxides, and fuel classification and air classification are carried out in the entire boiler space, so that the entire combustion process tends to be more reasonable and effectively reduce the combustion process of pulverized coal. production of nitrogen oxides. Make the furnace form the main combustion zone, the reduction zone and the burnout zone, as shown in Figure 1. In the figure, zone I is the main combustion zone, zone II is the reduction zone, and zone III is the burnout zone. Oxygen-deficient combustion in the main combustion zone and reduction zone produces a large amount of reducing gases CO, CH ₄ , H ₂ , HCN, etc., which react with NOx to generate N ₂ , which inhibits the formation of NOx; Burn out and avoid thermal NOx formation.

Currently, the existing low-nitrogen combustion technology for pulverized coal boilers in large-scale power stations generally suppresses NOx generation to around 200mg/Nm ³ (180mg/Nm ³ ～240mg/Nm ^{3 )} . For low emissions, SCR tail gas denitrification is also required. Generally, two-stage SCR selective reduction denitrification is required, and the equipment investment cost and operating cost are relatively high. Moreover, after liquid ammonia is sprayed into the flue gas, it is easy to cause corrosion blockage of the air preheater and ammonia escape. The air preheater is corroded and blocked, which affects the safe operation of the equipment; the escaped ammonia gas is discharged into the atmosphere, which will form new pollution.

After the low-nitrogen combustion technology transformation of the existing large-scale power plant pulverized coal boiler, since the combustion-supporting secondary air in the main combustion area is greatly reduced, a separate burn-out air is installed in the upper part away from the main combustion area, which is equivalent to prolonging the combustion process of pulverized coal in the furnace. It is very easy to cause the increase of fly ash combustibles, the temperature of exhaust gas at the furnace outlet, and the high temperature of superheated steam, which will lead to a large increase in the amount of desuperheating water, which will affect the thermal efficiency and safety performance of the boiler.

Contents of the invention

Aiming at the above defects or improvement needs of the prior art, the present invention provides an ultra-low NOx emission pulverized coal boiler combustion system, method and application, the purpose of which is to improve the ignition characteristics of the primary wind powder airflow in the deep anoxic state , and achieve multi-stage air classification, which can not only realize safe, stable and economical combustion of pulverized coal boilers, but also achieve ultra-low emissions of nitrogen oxides.

In order to achieve the above object, according to one aspect of the present invention, a pulverized coal boiler combustion system with ultra-low NOx emissions is provided, including: a coal gasification device, a primary air pipeline, a primary air nozzle, a secondary air pipeline, a secondary air nozzle, Primary burn-off air nozzle and secondary burn-off air nozzle;

Wherein, the primary air nozzle, the secondary air nozzle, the primary overburning air nozzle and the secondary overburning air nozzle are sequentially arranged in layers on the water wall of the boiler furnace;

The primary air pipe is connected to the primary air nozzle;

The secondary air pipe is connected to the secondary air nozzle, the primary overburning air nozzle and the secondary overburning air nozzle;

The coal gasification device is located between the end of the primary air duct and the primary air nozzle;

The primary air nozzle is used to inject primary air into the furnace, the secondary air nozzle is used to inject secondary air into the furnace, and the primary overfired air nozzle is used to inject air into the furnace The primary burn-off air, the secondary burn-off air nozzle is used to inject the secondary burn-off air into the furnace, so as to realize the ultra-low NOx emission combustion of pulverized coal.

Further, the furnace forms a pulverized coal ignition gasification zone, a main combustion reduction zone is formed between the primary air nozzle and the secondary air nozzle, and a primary combustion reduction zone is formed between the secondary air nozzle and the primary overburned air nozzle. In the reduction extension area, a primary burnout zone is formed between the primary burn-off air nozzle and the secondary burn-off air nozzle, and a secondary burn-out zone is formed between the secondary burn-off air nozzle and the furnace.

Further, the wind powder air flow entering the furnace from the primary air nozzle is arranged in a small tangential circle, and the air flow entering the furnace from the secondary air nozzle is arranged in a large tangential circle.

According to another aspect of the present invention, there is provided a pulverized coal boiler combustion method with ultra-low NOx emissions, using the pulverized coal boiler combustion system with ultra-low NOx emissions, specifically comprising the following steps:

(1) After the pulverized coal flow enters the pulverized coal gasification device, a large amount of combustible gas mainly CO will be generated after the pulverized coal gasification zone I undergoes ignition, combustion and gasification;

(2) In step (1), the pulverized coal gas flow enters the main combustion reduction zone II, forming a large amount of reducing gas and suppressing the formation of NOx;

(3) The pulverized coal gas flow in step (2) enters the reduction extension zone III, and NOx is further reduced;

(4) The pulverized coal airflow in step (3) enters the first-level burnout zone IV, and part of the burn-out air is sent from the first-level burn-out air nozzle, and the pulverized coal continues to burn under oxygen-deficient conditions, and a reducing atmosphere is still produced. difficult to generate NOx;

(5) The pulverized coal airflow in step (4) enters the secondary burnout zone V, and then is sent into part of the burnout air from the secondary burnout air nozzle. The temperature of the flue gas is already below 1100°C, and it is difficult to form thermal NOx. At the same time, the amount of fuel-type NOx generated is very small, which meets the general NOx emission standards of power plant boilers.

Preferably, the excess air ratio of the pulverized coal ignition gasification zone (I) is 0.2-0.4.

Preferably, the excess air ratio of the main combustion reduction zone (II) is 0.6-0.7.

Preferably, the excess air ratio of the primary burnout zone (IV) is 0.8-0.9.

Preferably, the excess air ratio of the secondary burnout zone (V) is 1.1-1.25.

Further, the reducing gas in step (2) is one or more of CO, CH ₄ , H ₂ , HCH or CnHm.

According to another aspect of the present invention, an application of the ultra-low NOx emission pulverized coal boiler combustion system and method is provided, which is suitable for four-corner tangential combustion pulverized coal boilers, front and rear wall opposed combustion pulverized coal boilers, or W-type Flame fired pulverized coal boiler.

Generally speaking, compared with the prior art, the above technical solutions conceived by the present invention can achieve the following beneficial effects:

(1) The pulverized coal boiler combustion system of the present invention can ensure the stable ignition and combustion of pulverized coal under the condition of deep air classification, realize the ultra-low NOx emission of 80mg/Nm ³ ~ 120mg/Nm ³ , and directly reach the normal emission of NOx in power plant boilers Standard, no need to invest in the tail denitrification device.

(2) The pulverized coal boiler combustion system of the present invention requires ultra-low NOx emissions of 80mg/Nm ³ to 120mg/Nm ³ for special areas, and only a small amount of SCR denitrification device needs to be invested in the tail of the boiler to greatly reduce the input of ammonia And ammonia escape, can greatly reduce equipment investment and operating costs.

(3) In the pulverized coal boiler combustion method of the present invention, since the pulverized coal gasification device is arranged before entering the furnace, the combustion process (path and time) of the pulverized coal is substantially prolonged, which is conducive to reducing fly ash combustibles and furnace outlet smoke temperature, to avoid overheating and high air temperature resulting in a substantial increase in the amount of desuperheating water.

Description of drawings

Figure 1 is a schematic elevational view of the tangential combustion process area structure of a boiler with ultra-low NOx emissions;

Fig. 2 is a schematic plan view of the flame structure of a tangentially fired pulverized coal boiler;

Figure 3 is a schematic elevational view of the combustion area structure of the ultra-low NOx emission boiler with front and rear walls facing each other;

Fig. 4 is a schematic plan view of the flame structure of the front and rear walls opposed to the combustion boiler;

Figure 5 is a schematic elevational view of the combustion area structure of the front and rear arch W flame boiler with ultra-low NOx emissions.

In all the drawings, the same reference numerals represent the same technical features, specifically: 1-furnace, 2-coal gasification device, 3-primary air duct, 4-primary air nozzle, 5-secondary air duct, 6 -Secondary air nozzle, 601-Secondary air nozzle inside the swirl burner, 602-Outside secondary air nozzle of the swirl burner, 7-Primary burnout air nozzle, 8-Secondary burnout air nozzle. Ⅰ-Powdered coal ignition and gasification zone, Ⅱ-Main combustion reduction zone, Ⅲ-Formation reduction extension zone, Ⅳ-First-level burnout zone, V-Secondary burnout zone.

detailed description

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not constitute a conflict with each other.

A pulverized coal boiler combustion system with ultra-low NOx emissions, comprising a coal gasification device 2, a primary air pipe 3, a primary air nozzle 4, a secondary air pipe 5, a secondary air nozzle 6, a primary burn-off air nozzle 7 and a secondary air Level burn-off air nozzle 8. Among them, the primary air nozzle 4, the secondary air nozzle 6, the primary overburning air nozzle 7 and the secondary overburning air nozzle 8 are sequentially arranged in layers on the water wall of the boiler furnace 1; the primary air pipe 3 and the primary air nozzle 4 connected; the secondary air pipe 5 is connected with the secondary air nozzle 6, the primary overburning air nozzle 7 and the secondary overburning air nozzle 8; the coal gasification device 2 is arranged at the end of the primary air pipe 3 and the Between the primary air nozzles 4;

The primary air nozzle 4 is used to inject primary air into the furnace 1, the secondary air nozzle 6 is used to inject secondary air into the furnace 1, the primary overburning air nozzle 7 is used to inject primary overburning air into the furnace 1, and the secondary air nozzle 6 is used to inject primary air into the furnace 1. The first-stage burn-off air nozzle 8 is used to inject secondary burn-off air into the furnace 1, so as to realize ultra-low NOx emission combustion of pulverized coal.

The main combustion reduction zone II is formed between the primary air nozzle 4 and the secondary air nozzle 6, the reduction extension zone III is formed between the secondary air nozzle 6 and the primary overburning air nozzle 7, and the primary overburning air nozzle 7 and A primary burnout zone IV is formed between the secondary burnout air nozzles 8 , and a secondary burnout zone V is formed between the secondary burnout air nozzles 8 and the furnace 1 .

The wind powder air flow entering the furnace from the primary air nozzle is arranged in a small tangential circle, and the air flow entering the furnace from the secondary air nozzle is arranged in a large tangential circle.

In one embodiment of the present invention, a pulverized coal boiler combustion method with ultra-low NOx emissions, using the above-mentioned pulverized coal boiler combustion system with ultra-low NOx emissions, specifically includes the following steps:

(1) After the pulverized coal flow enters the pulverized coal gasification device, a large amount of combustible gas mainly CO will be generated after the pulverized coal gasification zone I undergoes ignition, combustion and gasification;

(2) In step (1), the pulverized coal gas flow enters the main combustion reduction zone II, forming a large amount of reducing gas and suppressing the formation of NOx;

(3) The pulverized coal gas flow in step (2) enters the reduction extension zone III, and NOx is further reduced;

(4) The pulverized coal airflow in step (3) enters the first-level burnout zone IV, and part of the burn-out air is sent from the first-level burn-out air nozzle, and the pulverized coal continues to burn under oxygen-deficient conditions, and a certain amount of reduction is still produced. Strong atmosphere, difficult to generate NOx;

(5) The pulverized coal airflow in step (4) enters the secondary burnout zone V, and then is sent into part of the burnout air from the secondary burnout air nozzle. The temperature of the flue gas is already below 1100°C, and it is difficult to form thermal NOx. At the same time, the fuel-type NOx of pulverized coal is extremely small, which meets the common NOx emission standard of power plant boilers.

In one embodiment of the present invention, the excess air coefficient of the pulverized coal ignition gasification zone (I) is 0.2-0.4.

In one embodiment of the present invention, the excess air ratio of the main combustion reduction zone (II) is 0.6-0.7.

In one embodiment of the present invention, the excess air ratio of the primary burnout zone (IV) is 0.8-0.9.

In one embodiment of the present invention, the excess air ratio of the secondary burnout zone (V) is 1.1-1.25.

In one embodiment of the present invention, the reducing gas in step (2) is one or more of CO, CH ₄ , H ₂ , HCH or CnHm.

The pulverized coal boiler combustion system of the present invention can ensure the stable ignition and combustion of pulverized coal under the condition of deep air classification, and realize ultra-low NOx emission of 80mg/Nm ³ to 120mg/Nm ³ , directly reaching the common NOx emission standard of power plant boilers, without The input of the tail denitrification device is required. It is suitable for four-corner tangential combustion pulverized coal boilers, front and rear wall opposed combustion pulverized coal boilers or W-shaped flame combustion pulverized coal boilers.

Example 1

As shown in Figure 1 and Figure 2, the pulverized coal gasification device is installed at the position before the end of each primary air pipe enters the furnace. In the furnace, the primary tuyere and secondary tuyere of the pulverized coal gasification device are arranged in layers. The primary air powder airflow entering the furnace from the nozzle of the pulverized coal gasification device is arranged in a smaller tangential circle, and the airflow of the secondary air nozzle is arranged in a larger tangential circle. After the primary wind pulverized coal flow enters the pulverized coal gasification device, it undergoes ignition, combustion and gasification, and the formation area is the pulverized coal ignition gasification area I. Since the excess air coefficient is only 0.2 to 0.4, a large amount of combustible gas mainly composed of CO will be generated. The gas then enters the main combustion reduction zone II in the lower part of the furnace. In the main combustion and reduction zone, due to the setting method of the air-wrapped powder of the secondary air, the furnace slagging and high-temperature corrosion are prevented. A first-stage overburning air is arranged at a distance above the burner in the main combustion reduction zone, and a second-stage overburning air nozzle is arranged at a certain distance from the upper part of the first-stage overburning air nozzle. The area from the upper part of the burner in the main combustion reduction zone to the primary burn-off air nozzle is the reduction extension zone III; the area from the primary burn-off air nozzle to the secondary burn-off air nozzle is the primary burn-out zone IV ; The area between the secondary burnout air nozzle and the furnace outlet is the secondary burnout zone V.

When the flame and airflow after pulverized coal gasification enter the main combustion and reduction zone II in the lower part of the furnace, the excess air coefficient is 0.6-0.7, which is a state of deep anoxic combustion, forming a large amount of reducing gas and inhibiting the formation of NOx. After that, the flame flow enters the reduction extension zone III, and NOx is further reduced. When the flame flow enters the first-level burnout zone IV, part of the burn-out air is sent from the first-level burn-out air nozzle, so that the excess air coefficient is 0.8-0.9, and the pulverized coal continues to burn under the condition of oxygen deficiency, and a certain amount of reduction is still produced. Strong atmosphere, it is difficult to generate NOx. When the flame flow enters the secondary burnout zone V, and then part of the burnout air is sent from the secondary burnout air nozzle, so that the excess air coefficient is 1.1 to 1.25, and the flue gas temperature at this time is below 1100°C, thermal NOx It is difficult to form, and the fuel-type NOx of pulverized coal has reached a minimum.

The ultra-low NOx emission boiler combustion technology described above can achieve ultra-low NOx generation of 80mg/Nm ³ ~ 120mg/Nm ³ , directly reaching the normal NOx emission standard of power plant boilers, without the investment of tail denitrification equipment.

Example 2

As shown in Fig. 3 and Fig. 4, for boilers arranged in the way of opposing swirling burners on the front and rear walls, this ultra-low NOx generation combustion technology can also be adopted. Different from the four-corner tangential combustion boiler, the pulverized coal gasification device is set at the center of the swirl burner, and the swirl burner retains the inner secondary air and the outer secondary air. As shown in the figure, 6 is the secondary air inside the swirl burner, and 7 is the secondary air outside the swirl burner. When the primary wind pulverized coal flow enters the pulverized coal gasification device at the center of the swirl burner, it is ignited, ignited, burned, and gasified, that is, the inner center of the swirl burner is the zone I for the pulverized coal ignition and gasification area . In this area, the excess air coefficient is 0.2 to 0.4, and a large amount of combustible gas mainly composed of CO will be generated, which will be sprayed into the furnace from the center of the swirl burner. At the same time, the internal secondary air and the external secondary air of the swirl burner select different mixing points and mixing distances, and are mixed with the central primary air flame flow for combustion, and enter the main combustion reduction area II at the lower part of the furnace. The internal and external secondary air volume should not be too large, and the air excess coefficient in the main combustion and reduction zone should be maintained at 0.6 to 0.7. At a certain distance above the uppermost burner of the main combustion reduction zone in the lower part of the furnace, arrange the front and rear wall opposed first-stage overburning air nozzles; Level burn-off air nozzle. The area from the upper part of the burner in the main combustion reduction zone to the primary burn-off air nozzle is the reduction extension zone III; the area from the primary burn-off air nozzle to the secondary burn-off air nozzle is the primary burn-out zone IV ; The area between the secondary burnout air nozzle and the furnace outlet is the secondary burnout zone V.

The main combustion and reduction zone II in the lower part of the furnace is in a state of deep anoxic combustion, forming a large amount of reducing gas and inhibiting the formation of NOx. After that, the flame flow enters the reduction extension zone III, and NOx is further reduced. When the flame flow enters the first-level burnout zone IV, part of the burn-out air is sent from the first-level burn-out air nozzle, so that the excess air coefficient is 0.8-0.9, and the pulverized coal continues to burn under the condition of oxygen deficiency, and a certain amount of reduction is still produced. Strong atmosphere, it is difficult to generate NOx. When the flame flow enters the secondary burnout zone V, and then part of the burnout air is sent from the secondary burnout air nozzle, so that the excess air coefficient is 1.1 to 1.25, and the flue gas temperature at this time is below 1100°C, thermal NOx It is difficult to form, and the fuel-type NOx of pulverized coal has reached a minimum.

The ultra-low NOx emission boiler combustion technology described above can achieve ultra-low NOx generation of 80mg/Nm ³ ~ 120mg/Nm ³ , directly reaching the normal NOx emission standard of power plant boilers, without the investment of tail denitrification equipment.

Example 3

As shown in Figure 5, for the combustion technology of the front and rear arch W flame boilers to achieve ultra-low NOx emissions, firstly, the pulverized coal gasification device is installed at the position of the primary air burner on the front and rear arches. Before, it has been ignited, burned, and gasified in the pulverized coal gasification device to generate a large amount of combustible gas flames mainly composed of CO, which are sprayed from the upper part of the double arch into the lower furnace for further combustion to form a W-shaped flame. In the combustion process of the pulverized coal gasification device, the excess air coefficient is 0.2 to 0.4. The pulverized coal gasification device on the arch is the pulverized coal ignition and gasification area in area I, and the lower furnace under the arch is the main combustion and reduction area in area II, where an appropriate amount of ejected secondary air and combustion-supporting secondary air are injected into the lower furnace. Maintain an excess air ratio of 0.6 to 0.7. At a certain distance from the upper part of the double-arched throat, a hedge type primary burnout air nozzle is set on the front and rear walls of the upper furnace, and then a hedge type secondary burnout air nozzle is set at a distance above the primary burnout air nozzle . In this way, the area from the double-arch throat to the first-level burnout air nozzle is area III, which is the reduction extension area; the area from the first-level burnout air nozzle to the second-level burnout air nozzle is area IV, which is the first-level burnout area; the area from the secondary burnout air nozzle to the furnace outlet is area V, which is the secondary burnout area.

In the main combustion reduction zone II of the lower furnace, it is in a deep anoxic combustion state, forming a large amount of reducing gas and inhibiting the formation of NOx. After that, the flame flow enters the reduction extension zone III, and NOx is further reduced. When the flame flow enters the first-level burnout zone IV, part of the burn-out air is sent from the first-level sofa burn-out air nozzle, so that the excess air coefficient is 0.8 to 0.9, and the pulverized coal continues to burn under oxygen-deficient conditions, and still produces a certain amount. Reducing atmosphere, it is difficult to generate NOx. When the flame airflow enters the secondary burnout area, and then part of the burnout air is sent into the secondary burnout air nozzle, so that the excess air coefficient is 1.1 to 1.25. At this time, the flue gas temperature is below 1100°C, and thermal NOx At the same time, the fuel-type NOx of pulverized coal has reached a minimum.

The ultra-low NOx emission boiler combustion technology described above can achieve ultra-low NOx generation of 80mg/Nm ³ ~ 120mg/Nm ³ , directly reaching the normal NOx emission standard of power plant boilers, without the investment of tail denitrification equipment.

It is easy for those skilled in the art to understand that the above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention, etc., All should be included within the protection scope of the present invention.

Claims (10)

1. A kind of 1. Combustion System of Boiler Burning Fine of ultra-low NOx emission, it is characterised in that including：Coal gasification apparatus (2), First air Pipeline (3), a wind snout (4), secondary air duct (5), overfire air port (6), one-level fire air nozzle (7) and two level after-flame Wind snout (8)；

   Wherein, a wind snout (4), overfire air port (6), one-level fire air nozzle (7) and two level fire air nozzle (8) Arranged for interval is layered successively on the water-cooling wall of boiler furnace (1)；

   The a wind pipe (3) is connected with a wind snout (4)；

   The secondary air duct (5) and the overfire air port (6), one-level fire air nozzle (7) and two level fire air nozzle (8) Connection；

   The coal gasification apparatus (2) is between the end of a wind pipe (3) and a wind snout (4)；

   Wind snout (4) is used for injection primary wind and powder in the burner hearth (1), the overfire air port (6) be used for Injection Secondary Air in the burner hearth (1), the one-level fire air nozzle (7) are used for after-flame of injection into the burner hearth (1) Wind, the two level fire air nozzle (8) is used for the secondary burnout degree of injection into the burner hearth (1), so as to realize the ultralow of coal dust NOx emission is burnt.
2. A kind of 2. Combustion System of Boiler Burning Fine of ultra-low NOx emission according to claim 1, it is characterised in that the stove Thorax (1) forms coal powder ignition gasification zone (I), and primary combustion is formed also between a wind snout (4) and overfire air port (6) Former area (II), reduction zones of extensibility (III) is formed between the overfire air port (6) and the one-level fire air nozzle (7), it is described One-level burning-out zone (IV), the two level fire air nozzle are formed between one-level fire air nozzle (7) and two level fire air nozzle (8) (8) two level burning-out zone (V) is formed between burner hearth (1).
3. 3. the Combustion System of Boiler Burning Fine of a kind of ultra-low NOx emission according to claim 1, it is characterised in that described one The breeze airflow that secondary wind snout (4) enters burner hearth (1) arranges that the overfire air port (6) enters the two of burner hearth (1) for the small circle of contact Secondary general mood stream is arranged for the big circle of contact.
4. 4. a kind of coal powder boiler combustion method of ultra-low NOx emission, it is characterised in that using such as any one of claim 1-3 The Combustion System of Boiler Burning Fine of described ultra-low NOx emission, specifically comprises the following steps：

   (1) after breeze airflow enters coal dust gasification device, after in coal powder ignition gasification zone I, experience is caught fire, burns and gasified, greatly Fuel gas of the amount generation based on CO；

   (2) breeze airflow enters the experience depth anoxycausis of primary combustion reduced zone II in step (1), forms a large amount of reproducibilities Gas, suppress NOx generations；

   (3) breeze airflow in step (2) enters reduction zones of extensibility III, and NOx is further reduced；

   (4) breeze airflow in step (3) enters one-level burning-out zone IV, from one-level fire air nozzle infeed section burnout degree, coal Powder burns away under the conditions of oxygen debt, still produces reducing atmosphere, it is difficult to generates NOx；

   (5) breeze airflow in step (4) enters two level burning-out zone V, then is sent into remaining burnout degree by two level fire air nozzle, Below 1100 DEG C, thermal NO x is difficult to be formed flue-gas temperature, while the fuel type NOx of coal dust firing generation is few, meets Station boiler NOx common exhaust standard.
5. A kind of 5. coal powder boiler combustion method of ultra-low NOx emission according to claim 4, it is characterised in that the coal Powder catch fire gasification zone (I) excess air coefficient be 0.2~0.4.
6. 6. the coal powder boiler combustion method of a kind of ultra-low NOx emission according to claim 4 or 5, it is characterised in that described The excess air coefficient of primary combustion reducing zone (II) is 0.6~0.7.
7. 7. a kind of coal powder boiler combustion method of ultra-low NOx emission according to any one of claim 4-6, its feature exist In the excess air coefficient of the one-level burning-out zone (IV) is 0.8~0.9.
8. 8. a kind of coal powder boiler combustion method of ultra-low NOx emission according to any one of claim 4-7, its feature exist In the excess air coefficient of the two level burning-out zone (V) is 1.1~1.25.
9. 9. a kind of coal powder boiler combustion method of ultra-low NOx emission according to any one of claim 4-8, its feature exist In reducibility gas described in step (2) is CO, CH₄、H₂, one or more in HCH or CnHm.
10. 10. a kind of Combustion System of Boiler Burning Fine of ultra-low NOx emission as claimed in any one of claims 1-9 wherein and answering for method With, it is characterised in that fired suitable for corner tangential firing pulverized-coal fired boiler, opposed firing formula combusting coal fines boiler or W types flame Firing coal dust boiler.