CN109869713B - Ammonia-free denitration method in circulating fluidized bed coal-fired boiler - Google Patents
Ammonia-free denitration method in circulating fluidized bed coal-fired boiler Download PDFInfo
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- 238000000034 method Methods 0.000 title claims abstract description 47
- 239000000843 powder Substances 0.000 claims abstract description 89
- 239000000463 material Substances 0.000 claims abstract description 48
- RHZUVFJBSILHOK-UHFFFAOYSA-N anthracen-1-ylmethanolate Chemical compound C1=CC=C2C=C3C(C[O-])=CC=CC3=CC2=C1 RHZUVFJBSILHOK-UHFFFAOYSA-N 0.000 claims abstract description 39
- 239000003830 anthracite Substances 0.000 claims abstract description 39
- 239000002245 particle Substances 0.000 claims abstract description 22
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 claims abstract description 21
- 229910021529 ammonia Inorganic materials 0.000 claims abstract description 10
- 239000006185 dispersion Substances 0.000 claims description 21
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Abstract
The invention provides a method for denitrating ammonia in a circulating fluidized bed coal-fired boiler, wherein the circulating fluidized bed coal-fired boiler comprises a circulating fluidized bed coal-fired boiler, a cyclone separator and a material returning device which are sequentially connected, anthracite is introduced into a boiler body from a secondary air port of the boiler body of the circulating fluidized bed coal-fired boiler, a tertiary air inlet is arranged at an inlet of the cyclone separator, and materials in the material returning device return into the boiler body of the circulating fluidized bed coal-fired boiler. According to the method, the anthracite powder with the proper particle size is selected and introduced into the circulating fluidized bed boiler at the proper position, so that the full combustion is realized in the circulating fluidized bed boiler, and the burnout rate and the combustion efficiency are improved.
Description
Technical Field
The invention belongs to the field of circulating fluidized bed boilers, and relates to a method for denitration without ammonia in a coal-fired boiler of a circulating fluidized bed.
Background
In a circulating fluidized bed boiler, NOxThe more mature removal techniques are mainly divided into two categories, i.e. control of NO during combustionxGeneration and combustion ofAnd (5) controlling after firing.
For NO during combustionxMainly using advanced low NOxThe combustion technology mainly comprises the following steps: firstly, air is combusted in a grading way; ② low oxygen combustion; thirdly, fuel staged combustion technology; fourthly, a flue gas recirculation technology; fifthly, concentration deviation combustion; sixthly, low NOxA burner.
Controlling NO after combustionxThere are two main techniques of (1) SCR (selective catalytic reduction) and SNCR (selective non-catalytic reduction).
Removal of NO in combustionxThe technology can realize higher denitration efficiency, and has the advantages of simple equipment, small occupied area and low investment cost. However, both the air staged combustion technology and the fuel staged combustion technology cause the increase of CO concentration, affect the combustion efficiency, and cause the reduction of the melting point of the coal ash due to the local oxygen-poor environment in the furnace, thereby causing furnace wall slagging, corrosion and the like
Although the SCR technology has high denitration efficiency and low consumption of the reducing agent and tail ammonia slip, the SCR technology has problems of high cost, complex system, catalyst blockage, abrasion, poisoning and deactivation and the like, and causes SO in the tail flue of the boiler3Increase in concentration with NH3Reaction to form NH4HSO4Or NH4(SO4)2Causing corrosion and coking of the tail flue of the boiler and reducing the quality of the fly ash.
SNCR also has some drawbacks, such as: firstly, the denitration efficiency is not as good as that of SCR; the reaction temperature window is narrow; consumption of the reducing agent is relatively large, and tail ammonia is easy to escape; tail portion formed similarly with (NH)4)2SO4The main ammonium salt can also cause the problems of blockage of the air preheater and the like; fifthly, the sprayed reducing agent is dissolved or atomized water is used to increase the tail smoke discharge amount and influence the boiler efficiency.
Disclosure of Invention
The invention provides a method for denitrating ammonia in a coal-fired boiler of a circulating fluidized bed, aiming at the problems that ammonia existing in the denitration of the existing circulating fluidized bed boiler escapes, anthracite is combusted in the circulating fluidized bed boiler, the carbon content of bottom slag and fly ash is higher, the combustion efficiency is low, corrosion and coking are easy to occur in the boiler and a flue, and the like. According to the method, the anthracite powder with the proper particle size is selected and introduced into the circulating fluidized bed boiler at the proper position, so that the full combustion is realized in the circulating fluidized bed boiler, and the burnout rate and the combustion efficiency are improved.
In order to achieve the purpose, the invention adopts the following technical scheme:
the invention provides a method for denitrating ammonia in a circulating fluidized bed coal-fired boiler, wherein the circulating fluidized bed coal-fired boiler comprises a circulating fluidized bed coal-fired boiler, a cyclone separator and a material returning device which are sequentially connected, anthracite is introduced into a boiler body from a secondary air port of the boiler body of the circulating fluidized bed coal-fired boiler, a tertiary air inlet is arranged at an inlet of the cyclone separator, and materials in the material returning device return into the boiler body of the circulating fluidized bed coal-fired boiler.
The circulating fluidized bed coal-fired boiler is a conventional circulating fluidized bed coal-fired boiler body in the prior art and comprises a primary air inlet and a secondary air inlet.
The invention uses anthracite as denitrifier, because Vdaf in anthracite is less than 10 wt%, carbon content is more than 70 wt%, the invention has the characteristics of low volatile component (volatile), high carbon content, high ignition temperature and burnout temperature and the like, and can reduce NO generated in the combustion processxA gas. And moreover, because of the low volatile content of the anthracite, the anthracite is ensured not to be immediately ignited after entering the hearth and to be in contact reaction with oxygen to participate in combustion, so that carbon in the coal can fully exert the denitration effect.
The invention arranges a tertiary air inlet at the inlet of the cyclone separator, which aims to improve the combustion supporting effect of the over-burning air and the over-burning rate of combustible substances in fine powder fuel and flue gas.
The following technical solutions are preferred technical solutions of the present invention, but not limited to the technical solutions provided by the present invention, and technical objects and advantageous effects of the present invention can be better achieved and achieved by the following technical solutions.
As the preferred technical scheme of the invention, the particle size of the anthracite is larger than the maximum particle size separated by the cyclone separator after the anthracite is abraded in the furnace body of the circulating fluidized bed coal-fired boiler, so that the anthracite returns to the furnace chamber after passing through the material returning device, the full combustion of the anthracite is finally realized, and the burnout rate and the combustion efficiency are improved.
Preferably, the anthracite coal has an average particle size of 500 to 800 μm, such as 500, 550, 600, 650, 700, 750, or 800 μm, but is not limited to the recited values, and other values within this range are equally applicable, preferably 500 to 600 μm.
In the invention, the particle size of the anthracite is controlled in a proper range and is sprayed from a secondary air port of the circulating fluidized bed coal-fired boiler. Because the anthracite has high carbon content and low volatile component, and the temperature of the circulating fluidized bed boiler is only about 900 ℃, the anthracite can not be fully ignited and combusted within the distance from the anthracite to the cyclone separator in the hearth. Before the anthracite enters the cyclone separator, the processes of preheating the pulverized coal, separating out volatile components and burning are finished, except that a small amount of coke participates in the burning reaction, most of the coke is used for NO in the furnacexThe reduction is realized, and CO generated by incomplete combustion can also reduce NOxReduction of NO to N2Effectively reducing the emission of nitrogen oxides.
The anthracite enters the cyclone separator and returns to the hearth to realize the complete combustion of coke, and the burnout rate is high.
As a preferred technical scheme of the invention, the anthracite is introduced into the furnace body from a secondary air port of the circulating fluidized bed coal-fired boiler through a powder dispersing and spraying system.
As the preferable technical scheme of the invention, the powder dispersing and spraying system comprises a powder fluidizing device, a high-pressure airflow dispersing device, an electrostatic dispersing device and a powder output device; the powder fluidizing device is provided with a powder feeding hole on the side wall, a gas inlet is arranged at the bottom, a material outlet is arranged at the top, and the material outlet is connected with a material inlet of the high-pressure airflow dispersing device; the material outlet of the high-pressure airflow dispersing device is connected with the material inlet of the electrostatic dispersing device, and the material outlet of the electrostatic dispersing device is connected with the material outlet of the powder output device.
In the present invention, the "high pressure" in the high-pressure gas stream distribution device means a pressure of 80kPa to 100kPa, for example, 80kPa, 83kPa, 85kPa, 87kPa, 90kPa, 93kPa, 95kPa, 97kPa, 100kPa, or the like, but is not limited to the recited values, and other values not recited in the range of the values are also applicable.
Because the dispersed powder particles are easy to generate secondary coagulation and agglomeration in the air flow conveying process, the system of the invention realizes the full dispersion of the powder by combining various dispersion technologies such as drying, multi-granularity fluidization, high-pressure air flow dispersion, static electricity and the like.
The invention adopts multi-component and/or multi-particle fluidization technology, utilizes coarse particle fluidization, and carries out drying, primary dispersion and feeding rate control on the superfine powder.
The invention utilizes the high-pressure airflow dispersion technology to carry out secondary dispersion on the powder, and utilizes high-pressure air to continuously dry and loosen the powder so as to reduce the liquid bridge force among powder particles and simultaneously increase the fluidity of the powder; meanwhile, the heated high-pressure airflow can heat the powder and enter the charging device together with the powder, so that the powder particles carry a large amount of static charges, the electrostatic repulsion among the charged particles is utilized to prevent the mutual agglomeration among the particles, the dispersed powder is prevented from being agglomerated before entering the furnace, the dispersed powder is in a completely uniform dispersion state and has an optimal activity state, and finally the dispersed powder is sprayed out by the most front powder output device. In the process, the charge of the powder particles to the maximum extent is the key to realize the dispersion and agglomeration resistance of the powder.
As a preferable technical scheme of the invention, a powder feeding hole of the powder fluidizing device is connected with a powder feeding device.
Preferably, the powder feeding device comprises a storage tank and a feeding component, and the storage tank is connected with a powder feeding port of the powder fluidizing device through the feeding component;
preferably, the feeding assembly comprises a screw conveyor pump and/or a chain conveyor, but is not limited to the illustrated feeding assembly, and any feeding assembly that can feed the material into the powder fluidizing device can be used in the system described herein.
Preferably, the powder fluidizing device comprises a powder fluidizing bed.
As a preferred technical scheme of the present invention, the high-pressure gas flow dispersing device includes a gas transmission pipeline, and a high-pressure gas nozzle is disposed at a tail end of the gas transmission pipeline, so as to perform high-pressure gas flow impact dispersion on the material generated from the powder fluidizing device by using the high-pressure gas flow.
Preferably, the system further comprises a gas heating and drying device, and a gas outlet of the gas heating and drying device is connected with a gas inlet of the powder fluidizing device and a gas transmission pipeline inlet of the high-pressure gas flow dispersing device.
Preferably, a pressure conveying assembly is arranged between the gas outlet of the gas heating and drying device and the inlet of the gas conveying pipeline of the high-pressure gas flow dispersing device.
Preferably, the pressure delivery assembly comprises a high pressure blower having a delivery pressure of 80kPa to 100kPa, such as 80kPa, 83kPa, 85kPa, 87kPa, 90kPa, 93kPa, 95kPa, 97kPa, or 100kPa, but is not limited to the recited values, and other unrecited values within the range are equally applicable.
As a preferred technical scheme, the electrostatic dispersion device comprises a charge needle, a charge needle support, an insulating tube, a grounding ring and a power supply, wherein the charge needle and the charge needle support are arranged in the insulating tube, the charge needle and the charge needle support are perpendicular and connected, the charge needle support is fixed in the insulating tube, the grounding ring surrounds and surrounds the insulating tube, the power supply is connected with the charge needle support, an inlet of the insulating tube is connected with a material outlet of the high-pressure airflow dispersion device, and an outlet of the insulating tube is connected with a powder output device.
In the invention, the charge needle and the charge needle support of the charging device are arranged in the insulating tube, the charge needle is connected with the power supply through the support, the power supply, the charge needle and the grounding ring form a stronger corona field, so that powder particles are charged to the maximum extent under the charge action of an electrostatic field when passing through the insulating tube, and thus, larger Coulomb repulsion force exists among the particles.
As a preferable technical scheme of the invention, the powder output device comprises a Laval nozzle.
Preferably, the powder output device is connected with a secondary air port of the circulating fluidized bed coal-fired boiler.
As a preferred technical scheme of the invention, the circulating fluidized bed coal-fired boiler comprises a circulating fluidized bed coal-fired boiler, a cyclone separator and a material returning device which are sequentially connected, anthracite with the average particle size of 500-600 mu m is introduced into a boiler body from a secondary air port of the boiler body of the circulating fluidized bed coal-fired boiler through a powder dispersing and spraying system, a tertiary air inlet is arranged at an inlet of the cyclone separator, and materials in the material returning device return into the boiler body of the circulating fluidized bed coal-fired boiler.
Compared with the prior art, the invention has the following beneficial effects:
(1) the invention solves the problem of ammonia escape caused by SNCR and SCR denitration technology, and the problems of high carbon content of bottom slag and fly ash and low combustion efficiency caused by burning anthracite in a circulating fluidized bed boiler;
(2) the invention utilizes the characteristics of low volatile component and high ignition point of the anthracite powder, and incomplete combustion to generate a large amount of CO concentration in a short retention time in the furnace, and fully exerts the C/CO to NO under reducing atmospherexFurther realizes the reduction effect of NO in the furnacexThe denitration efficiency in the furnace can reach 30 percent;
(3) the invention selects the anthracite powder with proper grain diameter to realize full combustion in the circulating fluidized bed boiler, thereby improving the burnout rate and the combustion efficiency and leading the burnout rate of the fire coal to reach more than 96 percent.
Drawings
FIG. 1 is a schematic structural view of a system used in an ammonia-free denitration method in a circulating fluidized bed coal-fired boiler according to example 1 of the present invention;
FIG. 2 is a schematic structural view of an electrostatic dispersion apparatus described in example 1 of the present invention;
the system comprises a circulating fluidized bed coal-fired boiler 1, a cyclone separator 2, a material returning device 3, a secondary air port 4, a tertiary air inlet 5, a powder fluidizing device 6, a high-pressure airflow dispersing device 7, an electrostatic dispersing device 8, a powder output device 9, a storage tank 10, a feeding assembly 11, a gas heating and drying device 12, a pressure conveying assembly 13, a charging needle 81, a charging needle support 82, an insulating tube 83, an grounding ring 84 and a power supply 85.
Detailed Description
In order to better illustrate the present invention and facilitate the understanding of the technical solutions of the present invention, the present invention is further described in detail below. The following examples are merely illustrative of the present invention and do not represent or limit the scope of the claims, which are defined by the claims.
The embodiment of the invention provides a method for denitrating ammonia in a circulating fluidized bed coal-fired boiler, the circulating fluidized bed coal-fired boiler comprises a circulating fluidized bed coal-fired boiler 1, a cyclone separator 2 and a material returning device 3 which are sequentially connected, anthracite is introduced into the boiler body from a secondary air port 4 of the boiler body of the circulating fluidized bed coal-fired boiler, a tertiary air inlet 5 is arranged at an inlet of the cyclone separator 2, and materials in the material returning device 3 return into the boiler body of the circulating fluidized bed coal-fired boiler 1.
The following are typical but non-limiting examples of the invention:
example 1:
the embodiment provides an ammonia-free denitration method in a circulating fluidized bed coal-fired boiler, as shown in fig. 1, the circulating fluidized bed coal-fired boiler comprises a circulating fluidized bed coal-fired boiler 1, a cyclone separator 2 and a return feeder 3 which are connected in sequence, anthracite coal with the average particle size of 500-550 microns is introduced into a boiler body from a secondary air port 4 of the boiler body of the circulating fluidized bed coal-fired boiler 1 through a powder dispersing and spraying system, a tertiary air inlet 5 is arranged at an inlet of the cyclone separator 2, and materials in the return feeder 2 return to the boiler body of the circulating fluidized bed coal-fired boiler 1;
the powder dispersing and spraying system comprises a powder fluidizing device 6, a high-pressure airflow dispersing device 7, an electrostatic dispersing device 8 and a powder output 9; wherein, the side wall of the powder fluidizing device 6 is provided with a powder feeding hole, the bottom of the powder fluidizing device is provided with a gas inlet, the top of the powder fluidizing device 6 is provided with a material outlet, and the material outlet is connected with the material inlet of the high-pressure airflow dispersing device 7; a material outlet of the high-pressure airflow dispersing device 7 is connected with a material inlet of the electrostatic dispersing device 8, and a material outlet of the electrostatic dispersing device 8 is connected with a material outlet of the powder output device 9;
the powder feeding port of the powder fluidizing device 6 is connected with a powder feeding device, the powder feeding device comprises a storage tank 10 and a feeding component 11, and the storage tank 10 is connected with the powder feeding port of the powder fluidizing device 6 through the feeding component 11; wherein the feeding component 11 is a screw delivery pump, and the powder fluidizing device 6 is a powder fluidizing bed.
The high-pressure airflow dispersing device comprises a gas transmission pipeline, and the tail end of the gas transmission pipeline is provided with a high-pressure air nozzle;
the system also comprises a gas heating and drying device 12, wherein a gas outlet of the gas heating and drying device 12 is connected with a gas inlet of the powder fluidizing device 6 and a gas transmission pipeline inlet of the high-pressure gas flow dispersing device 7; a pressure conveying assembly 13 is arranged between the gas outlet of the gas heating and drying device 12 and the inlet of the gas conveying pipeline of the high-pressure gas flow dispersing device 7, and the pressure conveying assembly 13 is a high-pressure fan;
as shown in fig. 2, the electrostatic dispersion device 8 includes a charge needle 81, a charge needle support 82, an insulating tube 83, a grounding ring 84 and a power supply 85, wherein the charge needle 81 and the charge needle support 82 are disposed in the insulating tube 83, the charge needle 81 and the charge needle support 82 are perpendicular and connected, the charge needle support 82 is fixed in the insulating tube 83, the grounding ring 84 surrounds and surrounds the insulating tube 83, the power supply 85 is connected with the charge needle support 82, an inlet of the insulating tube 83 is connected with a material outlet of the high-pressure airflow dispersion device 7, and an outlet of the insulating tube 83 is connected with the powder output device 9;
the powder output device 9 comprises a Laval nozzle, and the powder output device 9 is connected with the secondary air port 4 of the circulating fluidized bed coal-fired boiler.
By adopting the method of the embodiment, the denitration efficiency of the circulating fluidized bed boiler can reach 34%, and the burnout rate of the fire coal can reach more than 96%.
Example 2:
the embodiment provides an ammonia-free denitration method in a circulating fluidized bed coal-fired boiler, the circulating fluidized bed coal-fired boiler comprises a circulating fluidized bed coal-fired boiler, a cyclone separator and a return feeder which are sequentially connected, anthracite with the average particle size of 570-600 mu m is introduced into a boiler body from a secondary air port of the boiler body of the circulating fluidized bed coal-fired boiler through a conventional injection means (such as a Laval nozzle), a tertiary air inlet is arranged at an inlet of the cyclone separator, and materials in the return feeder return into the boiler body of the circulating fluidized bed coal-fired boiler.
By adopting the method of the embodiment, the denitration efficiency of the circulating fluidized bed boiler can reach 26%, and the burnout rate of the fire coal can reach more than 94%.
Comparative example 1:
this comparative example provides a process for ammonia-free denitration in a circulating fluidized bed coal-fired boiler, which is comparable to the process of example 2 except that: the secondary air inlet of the circulating fluidized bed coal-fired boiler is not anthracite, but other coal types such as lignite and the like.
Comparative example 2, the denitration efficiency of the circulating fluidized bed boiler was only about 10% by the method of this comparative example.
Comparative example 2:
this comparative example provides a process for ammonia-free denitration in a circulating fluidized bed coal-fired boiler, which is comparable to the process of example 2 except that: the grain diameter of the anthracite is more than 800 mu m.
Comparative example 2, the denitration efficiency of the circulating fluidized bed boiler was only 18% and the burnout of the coal was 90% by the method of this comparative example.
It can be seen from the above examples and comparative examples that the present invention utilizes the characteristics of low volatile matter content, high ignition point of anthracite powder, incomplete combustion in a furnace for a short residence time to generate a large amount of CO concentration, and fully utilizes C/CO to NO under reducing atmospherexFurther realizes the reduction effect of NO in the furnacexThe denitration efficiency can reach 30 percent;
the invention selects the anthracite powder with proper grain diameter to realize full combustion in the circulating fluidized bed boiler, thereby improving the burnout rate and the combustion efficiency and leading the burnout rate of the fire coal to reach more than 96 percent.
The applicant states that the present invention is illustrated by the above examples to show the detailed process equipment and process flow of the present invention, but the present invention is not limited to the above detailed process equipment and process flow, i.e. it does not mean that the present invention must rely on the above detailed process equipment and process flow to be implemented. It should be understood by those skilled in the art that any modification of the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.
Claims (16)
1. A method for denitrating ammonia in a circulating fluidized bed coal-fired boiler is characterized in that the circulating fluidized bed coal-fired boiler comprises a circulating fluidized bed coal-fired boiler, a cyclone separator and a material returning device which are sequentially connected, anthracite is introduced into a boiler body from a secondary air port of the boiler body of the circulating fluidized bed coal-fired boiler, a tertiary air inlet is arranged at an inlet of the cyclone separator, and materials in the material returning device return into the boiler body of the circulating fluidized bed coal-fired boiler;
the particle size of the anthracite is larger than the maximum particle size separated by the cyclone separator after the anthracite is abraded in the boiler body of the circulating fluidized bed coal-fired boiler;
the average grain diameter of the anthracite is 500-800 mu m.
2. The method according to claim 1, wherein the anthracite coal has an average particle size ranging from 500 μm to 600 μm.
3. The method according to claim 1, wherein the anthracite coal is passed into the furnace body from the secondary tuyere of the circulating fluidized bed coal-fired boiler through a powder dispersion and injection system.
4. The method of claim 3, wherein the powder dispersion and injection system comprises a powder fluidization device, a high pressure gas stream dispersion device, an electrostatic dispersion device, and a powder output device; the powder fluidizing device is provided with a powder feeding hole on the side wall, a gas inlet is arranged at the bottom, a material outlet is arranged at the top, and the material outlet is connected with a material inlet of the high-pressure airflow dispersing device; the material outlet of the high-pressure airflow dispersing device is connected with the material inlet of the electrostatic dispersing device, and the material outlet of the electrostatic dispersing device is connected with the material outlet of the powder output device.
5. The method of claim 4, wherein a powder feed inlet of the powder fluidizing device is connected to a powder feeding device.
6. The method of claim 5, wherein the powder feed device comprises a storage tank and a feed assembly, and the storage tank is connected with a powder feed inlet of the powder fluidizing device through the feed assembly.
7. The method of claim 6, wherein the feed assembly comprises a screw conveyor pump and/or a chain conveyor.
8. The method of claim 6, wherein the powder fluidization device comprises a powder fluidization bed.
9. The method of claim 4, wherein the high pressure air stream dispersing device comprises a gas pipeline, and a high pressure air nozzle is arranged at the tail end of the gas pipeline.
10. The method as claimed in claim 4, wherein the system further comprises a gas heating and drying device, and the gas outlet of the gas heating and drying device is respectively connected with the gas inlet of the powder fluidizing device and the gas pipeline inlet of the high-pressure gas flow dispersing device.
11. The method according to claim 10, wherein a pressure delivery assembly is provided between the gas outlet of the gas heated drying apparatus and the gas delivery conduit inlet of the high pressure gas flow dispersion device.
12. The method of claim 11, wherein the pressure delivery assembly comprises a high pressure blower having a delivery pressure of 80kPa to 100 kPa.
13. The method according to claim 4, wherein the electrostatic dispersion device comprises a charge needle, a charge needle support, an insulating tube, a grounding ring and a power supply, wherein the charge needle and the charge needle support are arranged in the insulating tube, the charge needle and the charge needle support are vertical and connected, the charge needle support is fixed in the insulating tube, the grounding ring surrounds and surrounds the insulating tube, the power supply is connected with the charge needle support, an inlet of the insulating tube is connected with a material outlet of the high-pressure airflow dispersion device, and an outlet of the insulating tube is connected with the powder output device.
14. The method of claim 4, wherein the powder output device comprises a Laval nozzle.
15. The method of claim 4, wherein the powder output device is connected to a secondary tuyere of a circulating fluidized bed coal-fired boiler.
16. The method according to claim 4, wherein the circulating fluidized bed coal-fired boiler comprises a circulating fluidized bed coal-fired boiler, a cyclone separator and a material returning device which are connected in sequence, anthracite with the average particle size of 500-600 μm is introduced into the boiler body from a secondary air port of the boiler body of the circulating fluidized bed coal-fired boiler through a powder dispersing and spraying system, a tertiary air inlet is arranged at the inlet of the cyclone separator, and materials in the material returning device return into the boiler body of the circulating fluidized bed coal-fired boiler.
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