CN113339789A

CN113339789A - Coking-prevention pulverized coal burner with horseshoe-shaped turbulence teeth

Info

Publication number: CN113339789A
Application number: CN202110650498.6A
Authority: CN
Inventors: 王春波; 陈亮; 李顺
Original assignee: North China Electric Power University
Current assignee: North China Electric Power University
Priority date: 2021-06-11
Filing date: 2021-06-11
Publication date: 2021-09-03

Abstract

An anti-coking pulverized coal burner with horseshoe-shaped turbulence teeth. At present, the domestic electric coal has the defects of serious coking, high nitrogen oxide emission and the like due to the good and uneven quality. The utility model provides an prevent coking pulverized coal burner with horseshoe vortex tooth which characterized in that: 8 horseshoe-shaped turbulence teeth are uniformly distributed at the root of the primary air nozzle along the circumferential direction, the head area of each turbulence tooth is small, the root area is large, the total area accounts for about 15% of the area of the primary air nozzle, and the flame stabilizing and anti-coking effects are good; a strand of direct secondary air is arranged near the primary air, the air quantity is small and accounts for about 15% of the total quantity of the secondary air, and the primary air can be wrapped; the air quantity and the rotational flow strength of each air channel are respectively controlled by the air door adjusting rod and the rotational flow blade adjusting rod of each air channel so as to adjust the mixing of primary air and secondary air and reduce the generation of NOX. The invention is used for combustion equipment of a power station boiler.

Description

Coking-prevention pulverized coal burner with horseshoe-shaped turbulence teeth

Technical Field

The invention belongs to the technical field of boiler burners, and particularly relates to an anti-coking pulverized coal burner with horseshoe-shaped turbulence teeth.

Background

The thermal power plant accounts for more than 80% of the power generation share of the power industry in China. Coal fired power plant boilers are designed according to a specific coal type at the time of design. The boiler type, structure and burner selection will vary according to the type of coal being designed. The coal type according to when designing the boiler is the design coal type, is the best suitable furnace coal type. However, with the market of domestic electric coal supply and the increasing of domestic large-scale coal-fired power plants, practically all domestic power plants are burning non-designed coal. Moreover, in order to pursue the maximum economy, the mixed coal combustion of a large amount of doped poor quality coal has become the operation choice of most thermal power plants.

However, utility boilers have created a series of problems with the use of large quantities of off-design coals. The main categories are as follows:

(1) the low-volatile coal for boiler combustion can cause the coal powder burnout degree to be poor and the combustion to be unstable;

(2) when low-ash-melting-point coal is used, serious slag bonding is easy to occur on the heating surfaces of a combustor area and a screen area, and the overtemperature of a pipe wall, the rise of the exhaust gas temperature, the reduction of the boiler parameter operation, the reduction of the boiler efficiency and the like are caused;

(3) when the coal types are changed, the combustion characteristics and pollutant emission characteristics of different coals are different, and the non-ideal NOx control effect is easily caused.

These phenomena have seriously jeopardized the safe operation of the units.

The boiler burner is one of the key devices of the combustion device, and can ensure that air for coal combustion can be fully mixed when entering a hearth at a certain speed, and can timely catch fire and stably combust. In view of the current situation that non-designed coal types are generally used in domestic coal-fired power plants at present, finding a pulverized coal burner which can ensure safe operation without coking and can meet the environmental protection requirement of low NOx is an extremely urgent need. The adaptability of the boiler to coal types is greatly improved, and the operation safety and the economical efficiency of the coal-fired unit are improved.

Although the existing burner can meet the requirement of pulverized coal combustion, the problems of burner nozzle coking and the like are not considered in practical application, serious coking at the outlet of the burner can occur in practical application, the burning flow field in a furnace can be seriously changed by the burner outlet coking, the burning effect is influenced, and the running safety of a boiler can be seriously influenced by the fallen coking block.

Disclosure of Invention

The invention provides a pulverized coal burner with horseshoe-shaped turbulence teeth, which can ensure that pulverized coal is ignited and stably combusted in time, improve the burnout degree, reduce the discharge amount of NOx and effectively reduce the coking phenomenon, and is characterized in that:

the root of the primary air nozzle is provided with 8 turbulence teeth which are uniformly arranged along the radial direction, and the total area of the primary air nozzle accounts for 15 percent of the area of the primary air through flow. U-shaped turbulence tooth, characterized by: the shape is horseshoe, the head area is smaller, the bottom area is larger, and the primary air nozzle is arranged at the root of the primary air nozzle. The structure ensures that the disturbance of the flow resistance of the primary wind center is small, the disturbance to the root of the primary wind is large, the small disturbance is generated in the initial stage when the primary wind is sprayed out of the nozzle, and the disturbance is changed into large disturbance after the primary wind is sprayed out of the nozzle for a certain distance. In the initial stage of combustion, the small disturbance not only can not influence the stability of flame and can also promote the better mixture of backward flow district high temperature flue gas and buggy, and the big disturbance in later stage can strengthen the mixed intensive degree of the post secondary air of burning, promotes the burnout degree of buggy. Meanwhile, the primary air speed is improved to a certain extent due to the flow interception effect of the turbulence teeth, so that pulverized coal is not easy to flow back to a nozzle area of the combustor, the combustor is protected, and the problems of overheating, coking and the like of the combustor are avoided.

Compared with the traditional burner, the coking-prevention pulverized coal burner with the horseshoe-shaped turbulence teeth is provided with one strand of direct secondary air, and is characterized in that: a stream of direct secondary air is close to the primary air and between the primary air and the inner secondary air, and the air volume of the stream of direct secondary air is small and accounts for 15 percent of the total secondary air volume. The direct current wind has a fixed forward flow direction, plays a certain parcel effect to the primary wind when the primary wind spouts the spout, strengthens primary wind rigidity for the primary wind can not early disperse, makes the primary wind buggy concentrate in earlier stage near central backward flow district, therefore plays the steady burning effect on the one hand and has promoted the burning of catching fire of buggy, and on the other hand also avoids the outside of buggy granule to disperse, alleviates combustor spout coking. The primary air is heated in a radiation heat exchange mode after entering the hearth, the primary air is volatilized and separated out, a large amount of intermediate products such as HCN are released, and the reducibility is provided for inhibiting the generation of NOx. The direct current air solves the ignition problem caused by mixing of pulverized coal airflow and secondary air more reasonably, prevents the primary air and the secondary air from being mixed too early, reduces the probability of the premature contact of NOx and other intermediate products with oxygen, and inhibits the production of NOx in the initial stage of pulverized coal combustion more deeply.

The coking-prevention pulverized coal burner with the horseshoe-shaped turbulence teeth is characterized in that: sending four air into the hearth along the radial direction from inside to outside: primary air, direct-current secondary air, inner secondary air and outer secondary air. The primary air nozzle is arranged in the center of the combustor, the secondary air is adjusted by the inner and outer cyclone swirl vanes, and a stable ignition point is established at the throat part of the combustor. In the initial stage of a fire, a local reducing atmosphere is provided, so that the conversion of nitrogen in the coal can be reduced. The outer secondary air is gradually mixed with these combustion products and enters downstream to complete the carbon reaction while reducing NOx reformation. The combustion starting area and the burnout area are controlled by controlling the mixing of the pulverized coal and the air, and the combustion intensity and the peak temperature of the flame are reduced by a delayed combustion method, so that the peak temperature of the flame in a hearth is reduced, and the discharge amount of thermal NOx is reduced.

The secondary air from the wind box is divided into two parts which respectively enter the inner layer air regulator and the outer layer air regulator, the rotary airflow generated by the secondary air of the inner layer can entrain high-temperature flue gas to ignite the pulverized coal, and the secondary air of the outer layer is used for supplementing air required by further combustion of the pulverized coal to ensure that the pulverized coal is completely combusted. The swirl strength and the air quantity of each channel can be independently controlled by utilizing the outer secondary air swirl blade adjusting rod, the inner secondary air door adjusting rod and the inner secondary air swirl blade adjusting rod, and the rotary air flow can suck high-temperature flue gas in the hearth to a pulverized coal ignition area, ignite pulverized coal and enable the pulverized coal to be stably combusted. Meanwhile, the swirling flow strength can be changed, so that the undershoot capability of pulverized coal airflow is adjusted, the space of a lower hearth is fully and effectively utilized, and pulverized coal is effectively combusted. The burner adopts the graded air supply mode, which is not only beneficial to the ignition and stable combustion of the pulverized coal, but also beneficial to controlling the generation of nitrogen oxides in the flame.

Compared with the prior art, the invention has the following advantages:

(1) the horseshoe-shaped turbulence teeth are utilized to solve the problems of stable combustion, coking, NOx emission reduction and the like of domestic power plants, and further reduce the discharge amount of nitrogen oxides of the cyclone pulverized coal burner; (2) the basic mechanism of the coking-prevention pulverized coal burner with the horseshoe-shaped turbulence teeth is not different from that of the traditional rotational flow pulverized coal burner, can be put into use only by simple modification, and has excellent economical efficiency, adaptability and market potential; (3) the outlet area of the primary air nozzle, the positions and the sizes of the tooth root and the tooth height of the turbulence tooth can be properly adjusted according to the ignition characteristics of the pulverized coal, the primary air momentum is adjusted, the ignition time is controlled, the purposes of stable combustion and pulverized coal concentration separation are achieved, and the pulverized coal has better coal adaptability; (4) the horseshoe-shaped turbulence teeth are made of a tested wear-resistant and high-temperature-resistant material, so that the service life is long; (5) the regulation of the primary air channel baffle and the secondary air channel baffle can realize the control of a mixing point, the ignition and the burnout of another coal are regulated through the regulation of the mixing point, the local high temperature of a nozzle of the burner is effectively prevented, the control of a reduction area and an oxidation area can be realized through the control of the mixing point, and the generation of NOx is more effectively reduced.

Drawings

FIG. 1 is a schematic diagram of a spout configuration of an embodiment of the present invention;

FIG. 2 is a schematic sectional view taken along line A-A in an example of the present invention;

fig. 3 is a schematic diagram of the working principle of the embodiment of the invention.

In the figure: 1. horseshoe-shaped turbulence teeth 2, primary air 3, direct-current secondary air 4, inner secondary air 5, outer secondary air 6, outer secondary air swirl blade adjusting rods 7, inner secondary air door adjusting rods 8, inner secondary air swirl blade adjusting rods 9, a small-disturbance fire zone 10, an inner backflow zone 11 and a large-disturbance burnout zone.

Detailed Description

In the embodiment shown in fig. 1-3: the U-shaped turbulence teeth 1 are 8 bosses which are uniformly arranged at the root part of the primary air nozzle along the circumferential direction, are U-shaped, have small head area and large bottom area, have small flow disturbance to the primary air center and large disturbance to the primary air root, and account for 15 percent of the flow area of the primary air 2. When primary wind blows coal powder, the primary wind speed can be improved to a certain degree due to the intercepting effect of the turbulence teeth 1, so that the coal powder is not easy to flow back in a nozzle area of the combustor. The secondary air is divided into three strands, namely direct-current secondary air 3, inner secondary air 4 and outer secondary air 5 from inside to outside. The air volume of the direct-current secondary air 3 is small and accounts for 10-15% of the total secondary air volume, a certain wrapping effect can be achieved on primary air, on one hand, pulverized coal is better concentrated in a central backflow area to promote ignition and combustion of the pulverized coal, on the other hand, outward diffusion of pulverized coal particles can be avoided, and meanwhile, the pulverized coal is prevented from being mixed with the inner secondary air 4 and the outer secondary air 5 too early, so that the purpose of reducing NOx is achieved. The inner secondary air can generate rotary airflow to suck high-temperature flue gas to ignite the coal powder, and the outer secondary air is used for supplementing air required by further combustion of the coal powder to ensure that the coal powder is completely combusted. The outer secondary air swirl blade adjusting rod 6, the inner secondary air door adjusting rod 7 and the inner secondary air swirl blade adjusting rod 8 are utilized to realize independent control of swirl strength and air quantity of each channel, and the rotary air flow can suck high-temperature flue gas in a hearth to a pulverized coal ignition area to ignite pulverized coal and enable the pulverized coal to be stably combusted. Meanwhile, the swirling flow strength can be changed, so that the undershoot capability of pulverized coal airflow is adjusted, the space of a lower hearth is fully and effectively utilized, and pulverized coal is effectively combusted. The burner adopts the graded air supply mode, which is not only beneficial to the ignition and stable combustion of the pulverized coal, but also beneficial to controlling the generation of nitrogen oxides in the flame.

According to the ignition characteristics of different pulverized coals, the outlet area of the primary air nozzle 2 and the positions and the sizes of the tooth root and the tooth height of the turbulence tooth 1 can be properly adjusted, the adaptability of the burner to coal quality change is enhanced, the primary air momentum is adjusted, the ignition time is controlled, and the purposes of safe, efficient and low-pollution combustion are achieved.

Claims

1. The utility model provides an prevent coking pulverized coal burner with horseshoe vortex tooth, its constitution includes: u-shaped turbulence tooth, characterized by: the shape is horseshoe, the head area is smaller, the bottom area is larger, and the primary air nozzle is arranged at the root of the primary air nozzle.

2. The anti-coking pulverized coal burner with horseshoe-shaped turbulator teeth as claimed in claim 1, wherein: the root of the primary air nozzle is provided with 8 turbulence teeth which are uniformly arranged along the radial direction, and the total area accounts for 15 percent of the primary air through-flow area.

3. The anti-coking pulverized coal burner with horseshoe-shaped turbulator teeth as claimed in claim 1, wherein: the outer part of the primary air is provided with three secondary air streams, namely direct-current secondary air, inner secondary air and outer secondary air from inside to outside along the radial direction.

4. The anti-coking pulverized coal burner with horseshoe-shaped turbulator teeth as claimed in claim 1, wherein: near the primary air, there is a stream of direct secondary air, the air quantity of which accounts for 15% of the total quantity of the secondary air.

5. The anti-coking pulverized coal burner with horseshoe-shaped turbulator teeth as claimed in claim 1, wherein: the swirl strength and the air volume of each channel can be independently controlled by the adjusting rod of the outer secondary air swirl vane, the adjusting rod of the inner secondary air door and the adjusting rod of the inner secondary air swirl vane.

6. A method of combustion using the anti-coking pulverized coal burner with horseshoe-shaped turbulator teeth of claim 1, characterized in that: the method comprises the following steps: the primary air pulverized coal airflow from the coal mill passes through the horseshoe-shaped turbulence teeth at the primary air nozzle, so that the wind speed is improved, meanwhile, beneficial disturbance is generated on a primary air flow field, the pulverized coal airflow enters a hearth to be combusted under the wrapping of direct-current secondary air, the outward diffusion of pulverized coal particles is reduced, the coking of a nozzle of a combustor is reduced, inner secondary air generated by rotational flow timely rolls up high-temperature hot flue gas and supplements required air timely, the ignition of pulverized coal is facilitated, the oxygen amount of a combustion area is controlled to inhibit the generation of nitrogen oxides, and finally, the outer secondary air and the pulverized coal are mixed to promote the burnout of the pulverized coal.