CN111237747A - Circulating fluidized bed boiler, hearth and operation method - Google Patents
Circulating fluidized bed boiler, hearth and operation method Download PDFInfo
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- CN111237747A CN111237747A CN202010183652.9A CN202010183652A CN111237747A CN 111237747 A CN111237747 A CN 111237747A CN 202010183652 A CN202010183652 A CN 202010183652A CN 111237747 A CN111237747 A CN 111237747A
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- ultrafine powder
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- circulating fluidized
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN A CARRIER GAS OR AIR
- F23C10/00—Fluidised bed combustion apparatus
- F23C10/02—Fluidised bed combustion apparatus with means specially adapted for achieving or promoting a circulating movement of particles within the bed or for a recirculation of particles entrained from the bed
- F23C10/12—Fluidised bed combustion apparatus with means specially adapted for achieving or promoting a circulating movement of particles within the bed or for a recirculation of particles entrained from the bed the particles being circulated exclusively within the combustion zone
- F23C10/14—Fluidised bed combustion apparatus with means specially adapted for achieving or promoting a circulating movement of particles within the bed or for a recirculation of particles entrained from the bed the particles being circulated exclusively within the combustion zone the circulating movement being promoted by inducing differing degrees of fluidisation in different parts of the bed
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN A CARRIER GAS OR AIR
- F23C10/00—Fluidised bed combustion apparatus
- F23C10/18—Details; Accessories
- F23C10/20—Inlets for fluidisation air, e.g. grids; Bottoms
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN A CARRIER GAS OR AIR
- F23C10/00—Fluidised bed combustion apparatus
- F23C10/18—Details; Accessories
- F23C10/22—Fuel feeders specially adapted for fluidised bed combustion apparatus
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN A CARRIER GAS OR AIR
- F23C10/00—Fluidised bed combustion apparatus
- F23C10/18—Details; Accessories
- F23C10/28—Control devices specially adapted for fluidised bed, combustion apparatus
- F23C10/30—Control devices specially adapted for fluidised bed, combustion apparatus for controlling the level of the bed or the amount of material in the bed
Abstract
The invention discloses a circulating fluidized bed boiler, a hearth and an operation method, wherein a plurality of ultrafine powder feeding ports are arranged above an upper secondary air port and below the upper boundary line of a wear-resistant refractory covering area, the ultrafine powder feeding ports are uniformly arranged along the circumferential direction of the hearth, the ultrafine powder feeding ports are communicated with an ultrafine powder feeding device, and an ultrafine powder reburning device arranged in the hearth feeds ultrafine powder into the hearth from the feeding ports and conventional fuel fed from a coal feeding port forms graded feeding of fuel; the ultrafine powder is fed into a hearth to carry out reduction reaction with the generated NOx, so that the discharge amount of the NOx is reduced; the quantity of the ultrafine powder feeding ports is set according to the capacity of the boiler and the size of the hearth, the uniformity of distribution of the ultrafine powder after entering the hearth is guaranteed, the feeding ports are set to be high according to the coal quality characteristics of the prepared pulverized coal, the ultrafine powder can be fully burnt out before leaving the hearth, the feeding quantity proportion of conventional fuel and the ultrafine powder after burning the pulverized coal is adjusted, the variable load characteristic of the circulating fluidized bed boiler can be adjusted, and the peak regulation capacity of a boiler unit is improved.
Description
Technical Field
The invention belongs to the technical field of energy conservation and environmental protection of coal-fired circulating fluidized bed boilers, and particularly relates to a circulating fluidized bed boiler, a hearth and an operation method.
Background
Circulating fluidized bed boilers have certain advantages over conventional combustion methods. The circulating fluidized bed boiler adopts lower combustion temperature (850-920 ℃) and air separation and combustion, has lower NOx generation amount and certain self-desulfurization capacity (SO)2Is lower than the theoretical amount of SO2 produced, calculated as total sulfur); the circulating fluidized bed boiler can effectively remove 90 percent or more of SO by dry desulfurization in the boiler (adding a certain amount of limestone particles into the boiler)2(ii) a The circulating fluidized bed boiler has excellent fuel adaptability, and almost any fossil fuel can be designed to be used; the circulating fluidized bed boiler has good peak regulation capacity and can stably burn without oil feeding under the rated load of 30 percent. Therefore, the circulating fluidized bed boiler technology is rapidly developed in China during the last two decades, a hydraulic pressure test is completed on a built middling plastic 2 x 660MW supercritical circulating fluidized bed boiler unit, and the circulating fluidized bed boiler is planned to be put into commercial operation in 2020.
The circulating fluidized bed boiler is used as an environment-friendly combustion device to realize low-nitrogen combustion by adopting a low-temperature, low-oxygen and air classification mode, and the generation amount of NOx is lower than that of a pulverized coal boiler. According to the difference of coal types and the change of combustion conditions, the NOx emission value is generally 150-300 mg/m3In the meantime. Most circulating fluidized bed boiler units can meet the NOx emission limit without adopting flue gas denitration before new thermal power plant atmospheric pollutant emission standard is implemented in 2011The requirement of the value.
In recent years, most circulating fluidized bed boilers need to be provided with a flue gas denitration device to meet the requirement of environmental protection, and the advantage of low pollutant generation is weakened gradually. In addition, in recent years, deep peak shaving (30-40% load rate) needs to be implemented in a part of saved CFB boiler units so as to improve the economic benefit of unit operation. Under the condition of 30-40% load, due to the fact that the running temperature of a hearth is reduced, flue gas denitration cannot achieve high efficiency, NOx cannot be effectively controlled, and the circulating fluidized bed boiler achieves ultralow NOx emission in low-load running and also provides new challenges for the research of the NOx control of the circulating fluidized bed boiler.
In addition, the conventional circulating fluidized bed boiler burns coal particles with the particle size of 0-10 mm, and the burning rate is slow.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides a circulating fluidized bed boiler hearth with an ultrafine powder reburning device, the hearth with the structure can be used as conventional granular fire coal for the conventional circulating fluidized bed boiler hearth, and the ultrafine powder reburning device can also be used for inputting a certain proportion of coal powder into the hearth to realize the staged combustion of fuel, so that the generation amount of NOx is reduced, the load adjusting speed of a boiler unit is improved, and the peak regulation capacity of the unit is improved.
In order to achieve the purpose, the technical scheme adopted by the invention is that a circulating fluidized bed boiler hearth is provided with a plurality of ultrafine powder feeding ports above an upper secondary air port and below the upper boundary line of a wear-resistant refractory covering area, the ultrafine powder feeding ports are uniformly formed along the circumferential direction of the hearth, and the ultrafine powder feeding ports are communicated with an ultrafine powder feeding device.
The ultrafine powder feeding device comprises an ultrafine powder material storage device, an ultrafine powder material conveying furnace front main pipe, an ultrafine powder material distributor and an ultrafine powder material conveying branch pipe which are sequentially communicated along the material flow direction of ultrafine powder, and an ultrafine powder feeding port is communicated with the ultrafine powder material conveying branch pipe.
The superfine powder material preparation equipment adopts a steel ball coal mill, and the superfine powder material conveying equipment adopts a pneumatic conveying device.
The ultrafine powder feeding openings are 2-10 according to the boiler capacity and the size of the hearth, and 4-12 secondary air openings are uniformly formed in the lower layer of secondary air opening and the upper layer of secondary air opening along the hearth.
The bottom of the hearth is provided with an air chamber, the wall of the hearth is provided with a lower-layer secondary air port and a coal supply port, the coal supply port is positioned above the lower-layer secondary air port, the upper side of the coal supply port is provided with a circulating ash return port, the circulating ash return port is arranged below the upper-layer secondary air port, the top of the air chamber is provided with an air distribution device, and the lower-layer secondary air port is positioned above the air distribution device.
The air chamber is internally provided with 1-8 slag discharge pipes 12, and the circulating ash return port is provided with 1-8 slag discharge pipes according to the boiler capacity and the size of the hearth.
A circulating fluidized bed boiler, comprising a separator, a tail heating surface and a hearth according to any one of claims 1 to 6, wherein a hearth outlet is communicated with a flue gas inlet of the separator, and a bottom ash particle outlet of the separator is communicated with the hearth; the outlet at the top of the separator is communicated with the flue gas inlet of the tail heating surface.
Based on the operation method of the circulating fluidized bed boiler, the fire coal burnt in the hearth is divided into two parts and fed into the hearth, and one part is conventional fuel and accounts for 50-100% of the total fuel; one part is the ultra-fine fuel, and the ultra-fine fuel is fed from the ultra-fine fuel feeding port and does not exceed 50 percent of the total fuel quantity.
The particle size of the superfine powder fuel is d50＝30～50μm，dmaxIs 100 μm.
The fine particles after combustion leave the hearth from a hearth outlet, the fine particles leaving the hearth are separated by a separator, and part of separated ash particles become circulating ash and are returned to the hearth through a circulating ash return port.
Compared with the prior art, the invention has at least the following beneficial effects: a circulating fluidized bed boiler furnace, above the upper secondary tuyere, offer several superfine powder feed openings below the upper boundary line of wear-resisting refractory material coverage area, the superfine powder feed opening is offered evenly along the circumference of the furnace, the superfine powder feed opening communicates the superfine powder feeder; the uniformity of distribution of the ultrafine powder after entering the hearth is ensured, the ultrafine powder can be fully combusted before leaving the hearth, and the ultrafine powder reburning device arranged in the hearth feeds the ultrafine powder into the hearth from the feeding port and can form graded feeding of fuel with conventional fuel fed from the coal feeding port; the ultrafine powder is fed into a hearth to carry out reduction reaction with the generated NOx, so that the discharge amount of the NOx can be reduced; the height of the feeding port is set according to the coal quality characteristic of the prepared pulverized coal, and the feeding amount proportion of conventional fuel and ultrafine powder to reburn the pulverized coal is adjusted, so that the variable load characteristic of the circulating fluidized bed boiler can be adjusted, and the peak regulation capacity of a boiler unit can be improved.
Further, setting superfine powder fuel preparation equipment, and preparing superfine powder meeting the requirement of certain granularity according to the characteristics of the superfine powder fuel and comprehensively considering factors such as burnout property of the superfine powder; adding superfine powder reburning storage equipment for storing prepared finished product superfine powder; setting superfine powder reburning conveying equipment, and conveying finished product fine powder to a stokehole main pipe according to the requirement of boiler combustion on the fine powder amount; and an ultrafine powder material distributor is arranged to uniformly distribute the fine powder to each branch distribution pipe and feed the fine powder into a hearth.
Furthermore, the feeding amount of the ultrafine powder is adjusted according to the boiler load, the NOx emission requirement and the unit variable load rate requirement.
The boiler adopting the hearth has the advantages that the outlet of the hearth is communicated with the flue gas inlet of the separator, the outlet of the ash particles at the bottom of the separator is communicated with the hearth, more fine particles can be generated, the fine particles leaving the hearth are separated by the high-temperature separator of the boiler, and part of the separated ash particles become circulating ash and are returned to the hearth through the circulating ash return port, so that the combustion condition of the hearth is stabilized, the operation temperature is adjusted, and the heat is transferred.
The fire coal burnt in the hearth is divided into two parts and fed into the hearth, and one part is conventional fuel and accounts for 50-100% of the total fuel amount; one part of the pulverized coal is ultrafine powder fuel, the ultrafine powder fuel is fed from an ultrafine powder feeding port, the total fuel amount is not more than 50 percent, and the particle size of the pulverized coal is smaller than that of the coal fired by a conventional circulating fluidized bed; when the load is reduced, the heat load in the boiler is rapidly reduced along with the reduction of the feeding amount and the air volume, the load lifting speed of the pulverized coal boiler can reach 10MW/min, the pulverized coal input into a hearth through the ultrafine powder reburning device can realize the staged combustion of fuel, the generation amount of NOx is reduced by 20-50%, the variable load characteristic of the circulating fluidized bed boiler can be adjusted by adjusting the feeding amount proportion of conventional fuel and ultrafine powder reburning pulverized coal, and the peak regulation capability of a boiler unit is improved.
Drawings
FIG. 1 is a schematic structural diagram of the present invention.
The system comprises an air chamber 1, an air distribution device 2, a lower-layer secondary air port 3, a coal supply port 4, an upper-layer secondary air port 5, a circulating ash return port 6, an ultrafine powder feeding port 7, an upper boundary line of a wear-resistant refractory material covering area 8, a water-cooling heating surface 9, an expansion heating surface 10, a hearth outlet 11, a slag discharge pipe 12, an ultrafine powder material preparation device 13, an ultrafine powder material storage device 14, an ultrafine powder material conveying device 15, an ultrafine powder material conveying furnace front main pipe 16, an ultrafine powder material distributor 17 and an ultrafine powder material conveying branch pipe 18.
Detailed Description
The invention is further described with reference to the following drawings and detailed description.
As shown in figure 1, the circulating fluidized bed boiler furnace chamber with the ultrafine powder reburning device is characterized in that a plurality of ultrafine powder feeding ports 7 are formed above an upper secondary air port 5 and below an upper boundary line 8 of a wear-resistant refractory covering area, the ultrafine powder feeding ports 7 are uniformly formed along the circumferential direction of the furnace chamber, and the ultrafine powder feeding ports 7 are communicated with the ultrafine powder feeding device.
The ultrafine powder feeding device comprises an ultrafine powder material storage device 14, an ultrafine powder material conveying device 15, an ultrafine powder material conveying furnace front main pipe 16, an ultrafine powder material distributor 17 and an ultrafine powder material conveying branch pipe 18 which are sequentially communicated along the material flow direction of ultrafine powder, and an ultrafine powder feeding port 7 is communicated with the ultrafine powder material conveying branch pipe 18.
The number of the ultrafine powder feeding openings is 2-10 according to the capacity of a boiler and the size of a hearth.
The bottom of the furnace is provided with an air chamber 1, the wall of the furnace is provided with a lower-layer secondary air port 3 and a coal supply port 4, the coal supply port 4 is positioned above the lower-layer secondary air port 3, the upper side of the coal supply port 4 is provided with a circulating ash return port 6, the circulating ash return port 6 is arranged below an upper-layer secondary air port 5, the top of the air chamber 1 is provided with an air distribution device 2, and the lower-layer secondary air port 3 is positioned above the air distribution device 2.
A circulating fluidized bed boiler comprises a separator, a tail heating surface and a hearth, wherein a hearth outlet 11 is communicated with a flue gas inlet of the separator, and a bottom ash particle outlet of the separator is communicated with the hearth; an outlet at the top of the separator is communicated with a flue gas inlet of the tail heating surface, and the flue gas enters a flue of the tail heating surface to exchange heat and then is discharged out of the boiler.
When the circulating fluidized bed boiler furnace with the superfine powder reburning device is in operation, primary air enters the furnace from the air chamber 1 through the air distribution device 2 and is used for normal fluidization air and partial coal combustion air of materials on the air distribution device 2; the overfire air is fed from the lower layer of the overfire air port 3 and the upper layer of the overfire air port 5 in two layers and is used for staged combustion of the overfire air and air of the coal, 4-12 air ports are arranged in each layer according to the size of the hearth, the combustion efficiency is ensured, and the emission of pollutants such as NOx is reduced. Coal particles meeting the combustion requirement of a coal-fired unit enter a hearth from a coal feeding port 4 and are combusted in the hearth to release heat, and the number of the coal feeding ports 4 is set to be 2-12 according to the size of the hearth; the fine particles after combustion leave the hearth from a hearth outlet 11 at the top of the hearth, and the number of the hearth outlets 11 is 1-6 according to the boiler capacity; the burned coarse particles are discharged out of the hearth through a hearth slag discharging pipe 12 at the bottom of the hearth, and the number of the slag discharging pipes 12 is set to be 1-8 according to the boiler capacity and the size of the hearth; separating fine particles leaving the hearth by a high-temperature separator of the boiler, returning part of separated ash particles into circulating ash to the hearth through a circulating ash returning port 6, and setting 1-8 circulating ash returning ports 6 according to the capacity of the boiler and the size of the hearth; the circulating ash plays a role in stabilizing the combustion condition of the hearth, adjusting the operation temperature and transferring heat. Because the material concentration of the lower part of the hearth is high and the operation temperature is high, the hearth of the area is covered with the wear-resistant refractory material to the upper boundary line 8; more than 5 in upper strata secondary air mouths, setting up superfine powder feed inlet 7 below wear-resisting refractory material footprints upper boundary line 8, the buggy that accords with the requirement of superfine powder granule gets into furnace from superfine powder feed inlet 7, realizes the fractional combustion of fuel, reduces NOx's formation volume to adjust the variable load characteristic of boiler, superfine powder feed inlet sets up 2 ~ 10 according to the size of boiler capacity and furnace. The water-cooling heating surface 9 and the expansion heating surface 10 absorb heat generated after fuel combustion to heat working media flowing inside the heating surface.
The fire coal burnt in the hearth is fed into the hearth in two parts, one part is fed from the coal feeding port 4 and accounts for 50-100% of the total fuel quantity, and the other part is fed from the ultrafine powder feeding port 7 and accounts for 0-50% of the total fuel quantity.
The ultrafine powder material preparing apparatus 13 is used for preparing ultrafine powder particles meeting the requirement of reburning granularity, and the granularity is d50＝30～50μm，dmaxIs 100 μm; the ultrafine powder material preparation device 13 prepares qualified fine powder particles and stores the fine powder particles in an ultrafine powder material storage device 14; during the operation of the boiler, fine powder is conveyed to the front of the boiler by the ultrafine powder material conveying equipment 15 according to the operation working condition requirement and is conveyed into a hearth through the ultrafine powder material distributor 17, the ultrafine powder material conveying branch pipe 18 and the ultrafine powder feeding port 7.
The ultrafine powder reburning nozzle 7 is arranged at a position which can ensure that the pulverized coal has enough time for ignition and combustion after entering the hearth and before leaving the hearth, so as to ensure the combustion efficiency.
The operation mode of the ultrafine powder reburning device has good flow regulation characteristic according to the requirements of low-nitrogen combustion of a boiler, variable load characteristics of the boiler and peak regulation capacity of a unit, and meets the regulation requirements of the boiler on the feeding amount of ultrafine powder under different loads and combustion working conditions.
The principle of reducing the NOx generation amount by reburning the ultrafine powder is as follows: since the generated NO encounters hydrocarbon radical CHiAnd incomplete combustion products CO, H2C and CnHmThen, a reduction reaction of NO occurs, and the overall reaction equation is:
2NO+2CO→N2+CO2
2NO+2H2→N2+2H2O
2NO+C→N2+2CO
the superfine powder reburning technology utilizes the NO destruction principle to reduce the emission of NOx, the superfine powder reburning is used as a low-nitrogen combustion technology, the influence on the combustion efficiency is small through the control of the granularity of the superfine powder and the optimized design of the nozzle position, the generation amount of the NOx is effectively reduced compared with a hearth with a conventional structure, and the comprehensive economy is high.
A circulating fluidized bed boiler furnace with a superfine powder reburning device calculates the sectional area of the furnace according to the fuel characteristics, arranges a water-cooling heating surface and an expansion heating surface, and meets the requirement of boiler heat exchange; selecting the proportion of primary air and secondary air according to the calculated total air quantity requirement meeting the fuel combustion requirement, and determining the total amount of primary air and the total amount of secondary air; determining the areas of the air chamber and the air distribution device according to the fluidization speed of the materials on the air distribution device; according to the burnout characteristics of the fuel and the requirements of low-nitrogen combustion on air classification, the feeding amount of upper and lower secondary air is further determined, and the number and the positions of upper and lower secondary air ports are determined; determining the proportion and the quality of fly ash and low slag under the rated working condition of the boiler according to the coal quality characteristics; determining the height and width of a hearth outlet flue and the number of high-temperature separators corresponding to the hearth outlet according to the fly ash amount, the flow velocity of flue gas at the hearth outlet and other parameters; a circulating ash return port is arranged below each high-temperature separator, and circulating ash separated by the separator is returned to the hearth, so that on one hand, the hearth material amount required by the normal operation of the boiler is maintained, and on the other hand, the normal operation temperature of the hearth is adjusted; and a certain number of slag discharge pipes are arranged according to the generation amount of the low slag, and the slag discharge amount is adjusted in the operation of the boiler to maintain the material amount of the hearth so as to ensure the normal operation of the boiler.
And (2) ultrafine powder feeding ports are arranged in an area above the upper secondary air port and below the upper boundary of the coverage area of the wear-resistant refractory material, the number of the feeding ports is given according to the maximum amount of the pulverized coal for boiler combustion, the allowance is considered, and 2-10 feeding ports are arranged according to the sectional area of the hearth, so that the uniformity of mixing of the pulverized coal and the flue gas after the pulverized coal is sprayed into the hearth is ensured. The height of the feeding port is set according to burnout of the fine coal powder and the time needed for participating in NOx reduction reaction, so that sufficient time for the NOx reduction reaction is ensured, and the coal powder can be fully burnt out before leaving the hearth.
The fuel is fed into furnace, and the superfine powdered fuel is sprayed over the flame in dense-phase combustion zone over the air distributor to create a fuel-rich zone to produce NOxConversion to HCN and eventual formation of harmless N2For example, about 80% of fuel is fed into a dense-phase combustion zone (main combustion zone) from a coal feeding port 4 as conventional fuel (primary fuel), about 20% of fuel (as secondary fuel and reburning fuel) is fed into a secondary combustion zone (reburning zone), a strong reducing atmosphere is formed under the condition that α is less than 1, α is an excess air coefficient, and the average ratio is calculated according to the oxygen measurement value of a tail flue of a boiler, wherein α is 21/(21-O)2) NO produced in the main combustion zonexIs reduced while inhibiting new NOxAnd (4) generating.
The ultrafine powder reburning device adjusts the variable load characteristic of the boiler, and as the granularity of the conventional fire coal for burning the circulating fluidized bed boiler is generally not more than 10mm, the boiler finishes burning after a series of processes such as heat absorption → water separation → volatile analysis → volatile combustion → coal particle explosion → coke combustion, and the like after the coal particles enter a hearth when the load is increased. Generally, after entering a hearth, coal particles need to be circularly combusted for many times to ensure the complete combustion of fuel. The load rises slowly at the initial stage of the load-up, and the load-up rate increases rapidly when newly added coal particles are ignited and burned. When the load is reduced, because a large amount of bed materials exist in the furnace, in order to ensure the operation safety and prevent risks such as coking, the reduction rate of primary air is lower than that of the coal feeding amount, so the reduction rate of the load is slower. The load lifting speed of a common circulating fluidized bed boiler is 1.5-3 MW/min.
The particle size of the micropowder is generally: d50＝30～50μm，dmaxThe particle size of the coal is 100 mu m, which is smaller than that of the coal fired by a conventional circulating fluidized bed, so that the fine coal powder can be quickly ignited and combusted after entering a hearth along with the increase of the feeding amount and the air volume when the load of the boiler is increased, and the heat load of the boiler can be quickly increased; when the load is reduced, the heat load in the furnace is rapidly reduced along with the reduction of the feeding amount and the air volume. Generally, coal dustThe rate of the load lifting of the boiler can reach 10 MW/min.
Therefore, the variable load characteristic of the circulating fluidized bed boiler can be adjusted by adjusting the feeding amount proportion of the conventional fuel and the ultrafine powder to reburn the fine coal powder, and the peak regulation capacity of the boiler unit is improved.
According to the requirements of maximum feeding quantity and granularity of the ultrafine powder required by the ultrafine powder reburning, ultrafine powder reburning preparation equipment, ultrafine powder reburning storage equipment, ultrafine powder reburning conveying equipment, ultrafine powder conveying furnace front main pipe, distributor, conveying branch pipe and other equipment, pipelines and pipeline accessories are designed.
The method for determining the operating parameters of the hearth of the circulating fluidized bed boiler with the ultrafine powder reburning device comprises the following steps: (1) obtaining the mathematical relation of the change of the NOx emission value along with the feeding amount of the ultrafine powder under different load conditions by the experimental study of the actual furnace; in the normal operation of the boiler, the feeding amount of the superfine powder reburning device with different loads is adjusted according to the experimental data of the real boiler, so as to achieve the purpose of controlling the generation of NOx. (2) Obtaining the mathematical relation between the fine powder feeding amount and the variable load rate of the boiler through the experimental study of the real boiler; in the normal operation of the boiler, according to the experimental data of the real furnace, the feeding amount of the ultrafine powder reburning device is adjusted in real time according to the requirement of the variable load rate of the unit, and the rate requirements of the variable load rate and the peak shaving rate of the unit are met. (3) The system comprises an ultrafine powder material preparation device, an ultrafine powder material storage device, an ultrafine powder material conveying main pipe, an ultrafine powder material distributor and an ultrafine powder material conveying branch pipe, wherein the ultrafine powder material distributor and the ultrafine powder material conveying branch pipe are adjusted in real time in the combustion process of the boiler, and the requirement of boiler combustion on the feeding amount of ultrafine powder is met.
In conclusion, the circulating fluidized bed boiler furnace with the ultrafine powder reburning device can be used as conventional granular coal for burning of the conventional circulating fluidized bed boiler furnace, and can also realize the staged combustion of fuel by the pulverized coal input into the furnace by the ultrafine powder reburning device, so that the generation amount of NOx is reduced by 20-50%. The load adjusting speed of the boiler unit and the peak shaving capacity of the boiler unit are improved.
Claims (10)
1. The circulating fluidized bed boiler hearth is characterized in that a plurality of ultrafine powder feeding openings (7) are formed above an upper secondary air port (5) and below an upper boundary line (8) of a wear-resistant refractory covering area, the ultrafine powder feeding openings (7) are uniformly formed along the circumferential direction of the hearth, and the ultrafine powder feeding openings (7) are communicated with an ultrafine powder feeding device.
2. The circulating fluidized bed boiler furnace according to claim 1, wherein the ultrafine powder feeding device comprises an ultrafine powder material storage device (14), an ultrafine powder material conveying device (15), an ultrafine powder material conveying furnace front mother pipe (16), an ultrafine powder material distributor (17) and an ultrafine powder material conveying branch pipe (18) which are communicated in sequence along the material flow direction of the ultrafine powder, and the ultrafine powder feeding port (7) is communicated with the ultrafine powder material conveying branch pipe (18).
3. The circulating fluidized bed boiler furnace according to claim 1, characterized in that the ultrafine powder material preparation device (13) adopts a steel ball mill, and the ultrafine powder material conveying device (15) adopts a pneumatic conveying device.
4. The circulating fluidized bed boiler furnace according to claim 1, characterized in that the ultrafine powder feeding ports are arranged 2-10 according to the boiler capacity and the furnace size, and the lower layer secondary air ports (3) and the upper layer secondary air ports (5) are uniformly arranged 4-12 along the furnace.
5. The circulating fluidized bed boiler furnace according to claim 1, characterized in that the bottom is provided with an air chamber (1), the wall of the furnace is provided with a lower layer secondary air port (3) and a coal supply port (4), the coal supply port (4) is positioned above the lower layer secondary air port (3), the coal supply port (4) is provided with a circulating ash return port (6), the circulating ash return port (6) is provided below the upper layer secondary air port (5), the top of the air chamber (1) is provided with an air distribution device (2), and the lower layer secondary air port (3) is positioned above the air distribution device (2).
6. The circulating fluidized bed boiler furnace according to claim 5, characterized in that the air chamber (1) is provided with 1-8 slag discharge pipes (12), and the circulating ash return port (6) is provided with 1-8 according to the boiler capacity and the furnace size.
7. Circulating fluidized bed boiler, characterized in that it comprises a separator, a tail heating surface and a furnace as claimed in any one of claims 1 to 6, the furnace outlet (11) is connected to the flue gas inlet of the separator, and the bottom ash particle outlet of the separator is connected to the furnace; the outlet at the top of the separator is communicated with the flue gas inlet of the tail heating surface.
8. The operating method of a circulating fluidized bed boiler according to claim 7, wherein the fire coal burned in the furnace is divided into two parts and fed into the furnace, and one part is conventional fuel and occupies 50 to 100 percent of the total fuel; one part is the ultra-fine fuel which is fed from the ultra-fine fuel feeding port (7) and does not exceed 50 percent of the total fuel quantity.
9. The operating method of a circulating fluidized bed boiler according to claim 8, wherein the ultra fine pulverized fuel has a particle size d50＝30～50μm，dmaxIs 100 μm.
10. The method of operating a circulating fluidized bed boiler according to claim 8, wherein the fine particles after combustion leave the furnace through the furnace outlet, the fine particles leaving the furnace are separated by the separator, and a portion of the separated ash particles is returned to the furnace as circulating ash through the circulating ash return port.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202010183652.9A CN111237747A (en) | 2020-03-16 | 2020-03-16 | Circulating fluidized bed boiler, hearth and operation method |
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| CN202010183652.9A CN111237747A (en) | 2020-03-16 | 2020-03-16 | Circulating fluidized bed boiler, hearth and operation method |
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2020
- 2020-03-16 CN CN202010183652.9A patent/CN111237747A/en active Pending
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