CN110425520B - Flameless combustion system for semi-coke type flame-retardant fuel - Google Patents

Flameless combustion system for semi-coke type flame-retardant fuel Download PDF

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Publication number
CN110425520B
CN110425520B CN201910667707.0A CN201910667707A CN110425520B CN 110425520 B CN110425520 B CN 110425520B CN 201910667707 A CN201910667707 A CN 201910667707A CN 110425520 B CN110425520 B CN 110425520B
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combustion chamber
flameless
spray pipe
combustion
flue gas
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CN110425520A (en
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王飞飞
李鹏飞
胡帆
杨晨
米建春
柳朝晖
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Peking University
Huazhong University of Science and Technology
ENN Science and Technology Development Co Ltd
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Peking University
Huazhong University of Science and Technology
ENN Science and Technology Development Co Ltd
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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 
    • F23C9/00—Combustion apparatus characterised by arrangements for returning combustion products or flue gases to the combustion chamber
    • F23C9/06—Combustion apparatus characterised by arrangements for returning combustion products or flue gases to the combustion chamber for completing combustion
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23D—BURNERS
    • F23D1/00—Burners for combustion of pulverulent fuel
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23J—REMOVAL OR TREATMENT OF COMBUSTION PRODUCTS OR COMBUSTION RESIDUES; FLUES 
    • F23J15/00—Arrangements of devices for treating smoke or fumes
    • F23J15/06—Arrangements of devices for treating smoke or fumes of coolers
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23K—FEEDING FUEL TO COMBUSTION APPARATUS
    • F23K3/00—Feeding or distributing of lump or pulverulent fuel to combustion apparatus
    • F23K3/02—Pneumatic feeding arrangements, i.e. by air blast
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23L—SUPPLYING AIR OR NON-COMBUSTIBLE LIQUIDS OR GASES TO COMBUSTION APPARATUS IN GENERAL ; VALVES OR DAMPERS SPECIALLY ADAPTED FOR CONTROLLING AIR SUPPLY OR DRAUGHT IN COMBUSTION APPARATUS; INDUCING DRAUGHT IN COMBUSTION APPARATUS; TOPS FOR CHIMNEYS OR VENTILATING SHAFTS; TERMINALS FOR FLUES
    • F23L9/00—Passages or apertures for delivering secondary air for completing combustion of fuel 
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E20/00—Combustion technologies with mitigation potential
    • Y02E20/30—Technologies for a more efficient combustion or heat usage
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E20/00—Combustion technologies with mitigation potential
    • Y02E20/34—Indirect CO2mitigation, i.e. by acting on non CO2directly related matters of the process, e.g. pre-heating or heat recovery

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)

Abstract

The invention belongs to the field of semicoke combustion, and particularly discloses a flameless combustion system for semicoke-type flame-retardant fuels, which comprises a combustion chamber, a burner, a powder feeding device and a flue gas treatment device, wherein the combustion chamber is divided into an inner combustion chamber and an outer combustion chamber by a partition plate, the burner is arranged at the lower end of the inner combustion chamber, a tangential diversion outlet is arranged at the upper end of the partition plate, a water cooling pipe and a flue gas outlet are arranged on the outer wall of the outer combustion chamber, and a return hopper is arranged at the bottom end of the outer combustion chamber; the combustor comprises a primary air spray pipe, a flame secondary air spray pipe, a flameless secondary air spray pipe and a material returning spray pipe which are coaxially arranged, and also comprises an ignition assembly extending into the inner combustion chamber; the powder feeding device is connected with the primary air spray pipe and is used for providing fuel for the primary air spray pipe; the flue gas treatment device comprises a waste heat exchanger and a dust remover which are connected in sequence. The invention separates the combustion process and the flue gas utilization process, can ensure the high-temperature environment required by the flameless combustion of the inner combustion chamber, and can realize the effective utilization of the heat of the flue gas.

Description

Flameless combustion system for semi-coke type flame-retardant fuel
Technical Field
The invention belongs to the field of semicoke combustion, and particularly relates to a flameless combustion system for semicoke type flame-retardant fuel.
Background
Semicoke is a by-product from coal hydro-gasification, a fuel with very low volatile content (typically < 5%) and high fixed carbon content. The semicoke has the characteristics of high ignition temperature, low reaction rate and long burnout time, and the existing combustion process is difficult to realize the high-efficiency utilization of the fuels. Therefore, special techniques and devices suitable for such fuels need to be developed to achieve large-scale application of the semicoke.
For ultralow volatile fuel, CN103982894B proposes a combustion device for gasifying semicoke-like nonflammable fine particle fuel and a method for combusting by using the same, which is intended to solve the problem of low combustion efficiency of semicoke in a circulating fluidized bed, and the patent proposes that semicoke particle fuel enters a dense phase zone of a hearth for combustion through a raw material bin, a pneumatic injector, a return inclined tube and other devices, but in the combustion process, semicoke particles are directly sent into the hearth without being preheated, so that the burnout rate is still low and the combustion is easy to extinguish. CN106556007A proposes a method for burning gasified semicoke particles by using a thick-thin depth separation and a controllable vortex combustion stabilization technique, which proposes to separate the thick and thin of primary air carrying gasified semicoke powder to obtain thick-phase and thin-phase semicoke powder, and send the thick-phase and thin-phase semicoke powder to the inner layer, middle layer and outer layer nozzles of a combustion chamber respectively. Meanwhile, although the combustion device or the method can improve the utilization efficiency of the fuel to a certain extent, the restriction of the traditional combustion is still not broken away, and the emission of nitrogen oxides is still high due to the existence of a high-temperature combustion area in the furnace.
Flameless combustion is a volumetric combustion regime that occurs in an atmosphere of moderately or extremely dilute oxidant. Compared with the traditional combustion mode, the technology has the advantages that the reaction area is increased, the temperature is uniform, and no visible flame front exists; in industrial applications, the thermal efficiency can be improved by about 30%, while the NOx emission can be reduced by about 70%. The adoption of flameless combustion can improve the ignition performance of the semicoke fuel and increase the retention time of the semicoke fuel in a furnace, thereby improving the utilization efficiency of the semicoke fuel, but how to improve the utilization efficiency of the semicoke fuel in the flameless combustion is still a research hotspot.
Disclosure of Invention
Aiming at the defects or the improvement requirements of the prior art, the invention provides a flameless combustion system for semicoke type flame-retardant fuel, wherein a combustion chamber is divided into an inner combustion chamber and an outer combustion chamber by a partition plate, a tangential diversion outlet is arranged at the upper end of the partition plate, the combustion process and the heat exchange process can be separated, the flameless combustion is realized, and meanwhile, the utilization efficiency of the fuel can be improved by arranging a return hopper at the lower end of the outer combustion chamber, so that the flameless combustion system is particularly suitable for the utilization occasions of the semicoke type flame-retardant fuel.
In order to achieve the purpose, the invention provides a flameless combustion system for semi-coke type flame-retardant fuel, which comprises a combustion chamber, a combustor, a powder feeding device and a flue gas treatment device, wherein:
the combustion chamber is divided into an inner combustion chamber and an outer combustion chamber by a partition plate which is distributed annularly, the lower end of the inner combustion chamber is provided with a burner for mixing and spraying fuel and oxidant into the inner combustion chamber so as to realize flame combustion or flameless combustion, the upper end of the partition plate is provided with a tangential diversion outlet for sending smoke generated by combustion into the outer combustion chamber from the inner combustion chamber in a rotational flow manner, the outer wall of the outer combustion chamber is provided with a water cooling pipe and a smoke outlet for respectively absorbing heat of the smoke and discharging the smoke, and the bottom end of the outer combustion chamber is provided with a return hopper for collecting unburnt particles in the smoke;
the combustor comprises a primary air spray pipe, a flame secondary air spray pipe, a flameless secondary air spray pipe and a material returning spray pipe which are coaxially arranged, and also comprises an ignition assembly extending into the internal combustion chamber, wherein the primary air spray pipe is positioned at the center of the combustor and used for spraying an oxidant carrying fuel to the internal combustion chamber, the flame secondary air spray pipe is sleeved on the outer side of the primary air spray pipe and used for spraying the oxidant in a flame combustion stage, the flameless secondary air spray pipe is arranged on the outer side of the flame secondary air spray pipe and used for spraying the oxidant in the flameless combustion stage, the material returning spray pipe is arranged on the outer side of the flameless secondary air spray pipe, and an inlet of the material returning spray pipe is connected with the material returning hopper and used for spraying unburned particulate matters into the internal combustion chamber for secondary combustion;
the powder feeding device is connected with the primary air spray pipe and is used for providing fuel for the primary air spray pipe;
the flue gas treatment device comprises a waste heat exchanger and a dust remover which are sequentially connected, wherein an inlet of the waste heat exchanger is connected with a flue gas outlet, and during work, the flue gas preheats the oxidant in the waste heat exchanger and is discharged after being treated by the dust remover.
As a further preference, the ratio of the height of the tangential flow guide outlet to the height of the inner combustion chamber is preferably 1: 8-1: 5.
as a further preference, the air output ratio of the primary air nozzle to the flame secondary air nozzle is preferably 1: 6-1: 3, the air output ratio of the primary air spray pipe to the flameless secondary air spray pipe is preferably 1: 6-1: 3.
further preferably, the distance between the primary air nozzle and the flameless secondary air nozzle is 0.1-0.7 times of the hydraulic diameter of the inner combustion chamber.
More preferably, the outlet wind speed of the flameless overwind nozzle is 40-100 m/s.
As a further preference, the flameless overfire air nozzles are vertical direct current nozzles or one circular ring-shaped nozzle with a preset number.
As a further preferred option, the material return nozzles are vertical direct current nozzles or one circular ring nozzle of a preset number.
As a further preference, the outlet of the flamed secondary air nozzle is provided with a flame stabilizer.
Further preferably, the flame stabilizer is a swirl type flame stabilizer, a slotted bluff body flame stabilizer or a non-slotted bluff body flame stabilizer.
As a further preference, the fuel is a semi-coke fuel or a low-volatile coal powder, and the oxidant is air, a mixture of oxygen and an inert gas or a mixture of air and an inert gas.
Generally, compared with the prior art, the above technical solution conceived by the present invention mainly has the following technical advantages:
1. the invention separates the combustion chamber into an inner combustion chamber and an outer ring combustion chamber by a clapboard with lower heat conductivity coefficient, and arranges a water-cooling wall on the outer wall of the outer ring combustion chamber to separate the combustion process and the flue gas utilization process, thereby not only ensuring the high-temperature environment required by the flameless combustion of the inner combustion chamber, but also realizing the effective utilization of the heat of the flue gas, thereby improving the heat utilization efficiency of the system while reducing the NOx emission, in particular, the invention arranges a tangential diversion outlet on the upper end of the clapboard to ensure that the flue gas enters the outer ring combustion chamber in a rotational flow manner, further fully contacting with the water-cooling wall for heat exchange, simultaneously leading the unburnt particles in the flue gas to fall to a return hopper under the action of centrifugal force and gravity, and then entering the inner combustion chamber again for circulating combustion through a return nozzle, thereby increasing the residence time of the fuel in the furnace and improving the utilization rate of the fuel, the flame-free combustion device is suitable for flameless combustion of semi-coke or low-volatile coal powder and other flame-retardant fuels;
2. meanwhile, by optimizing various parameters in the flameless combustion system, the invention can ensure that the smoke forms an effective backflow space in the outer ring combustion chamber and has moderate flow resistance, and simultaneously ensures that the fuel is fully combusted in the inner combustion chamber, thereby improving the safety and the stability of the system.
Drawings
FIG. 1 is a schematic structural diagram of a flameless combustion system for semi-coke type nonflammable fuels constructed in accordance with a preferred embodiment of the present invention;
FIG. 2 is a cross-sectional view taken along the line A-A in FIG. 1;
FIG. 3 is a cross-sectional view taken along line B-B of FIG. 1;
FIG. 4 is a cross-sectional view taken along plane C-C of FIG. 2;
FIG. 5 is a schematic diagram of a tangential diversion outlet constructed in accordance with a preferred embodiment of the present invention;
FIG. 6 is a schematic structural view of a combustor constructed in accordance with a preferred embodiment of the present invention;
fig. 7 is a cross-sectional view taken along the plane D-D in fig. 6, in which (a) is a schematic view showing the distribution of the flameless overfire air nozzles and the return nozzles in the number of 1, (b) is a schematic view showing the distribution of the flameless overfire air nozzles and the return nozzles in the number of 2, (c) is a schematic view showing the distribution of the flameless overfire air nozzles and the return nozzles in the number of 4, and (D) is a schematic view showing the flameless overfire air nozzles and the return nozzles in the shape of circular nozzles.
Fig. 8 is a schematic diagram of the flow path of the internal gas flow of the flameless combustion system for semi-coke flame-retardant fuel provided by the invention.
The same reference numbers will be used throughout the drawings to refer to the same or like elements or structures, wherein:
1-oxidant inlet, 2-waste heat exchanger, 3-return hopper, 4-powder feeding device, 5-combustor, 6-internal combustion chamber, 7-tangential diversion outlet, 8-partition plate, 9-external ring combustion chamber, 10-flue gas outlet, 11-water wall, 12-dust remover, 13-standard flue gas, 14-temperature sensor, 15-unburned particulate matter, 51-combustor head, 52-return nozzle, 53-flameless secondary air nozzle, 531-flameless secondary air nozzle valve, 54-ignition assembly, 55-primary air nozzle, 56-flameless secondary air nozzle, 561-flameless secondary air nozzle valve and 562-stable combustion device.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
As shown in fig. 1 to 6, an embodiment of the present invention provides a flameless combustion system for semi-coke type nonflammable fuel, including a combustion chamber, a burner 5, a powder feeding device 4 and a flue gas processing device, wherein:
the combustion chamber is divided into an inner combustion chamber 6 and an outer ring combustion chamber 9 by a partition plate 8 which is distributed annularly, the lower end of the inner combustion chamber 6 is provided with a burner 5 which is used for mixing and spraying fuel and oxidant into the inner combustion chamber 6 so as to realize flame combustion or flameless combustion, the upper end of the partition plate is provided with a tangential diversion outlet 7 which is used for sending the flue gas generated by combustion into the outer ring combustion chamber 9 from the inner combustion chamber 6 in a rotational flow manner, the outer wall of the outer ring combustion chamber 9 is provided with a water cooling pipe 11 and a flue gas outlet 10 which are respectively used for absorbing the heat of the flue gas and discharging the flue gas, and the bottom end of the outer ring combustion chamber 9 is provided with a return hopper 3 which is used for collecting unburned particulate matters 15;
the burner 5 comprises a primary air nozzle 55, a flame secondary air nozzle 56, a flameless secondary air nozzle 53 and a return nozzle 52 which are coaxially fixed on the burner head part 51, and also comprises an ignition assembly 54 extending into the inner combustion chamber 6, wherein the ignition assembly 54 is an electronic ignition needle or an open flame ignition assembly, the primary air nozzle 55 is positioned at the center of the burner 5 and is used for injecting an oxidant carrying fuel into the inner combustion chamber 6, the flame secondary air nozzle 56 is sleeved outside the primary air nozzle 55 and is used for injecting the oxidant in the flame combustion stage, the flameless secondary air nozzle 53 is arranged outside the flame secondary air nozzle 56 and is used for injecting the oxidant in the flameless combustion stage, the return nozzle 52 is arranged outside the flameless secondary air nozzle 53, the inlet of the return nozzle is connected with the return hopper 3 and is used for injecting the unburned particulate matters 15 into the inner combustion chamber 6 for reburning;
the powder feeding device 4 is connected with the primary air spray pipe 55 and is used for supplying fuel to the primary air spray pipe;
the flue gas processing apparatus includes waste heat exchanger 2 and dust remover 12 that connect gradually, and the entry and the exhanst gas outlet 10 of waste heat exchanger 2 are connected, and the during operation flue gas preheats the oxidant in waste heat exchanger 2, then discharges flue gas 13 up to standard into the atmosphere after dust remover 12 handles.
Further, the ratio of the height of the tangential flow guiding outlet to the height of the inner combustion chamber 6 is preferably 1: 8-1: 5, this proportion scope can guarantee that the flue gas forms effectual backward flow space in outer ring combustion chamber 9, can also avoid causing the flow resistance of flue gas too big simultaneously.
The air output ratio of the primary air nozzle 55 to the secondary air nozzle 56 with flame is preferably 1: 6-1: 3, the air output ratio of the primary air nozzle 55 to the flameless secondary air nozzle 53 is preferably 1: 6-1: 3 to guarantee that fuel is at 6 abundant burning in interior combustion chamber, avoid appearing the fuel transport capacity not enough or the flame-out problem of fuel, when the operating mode that carries out flame burning and flameless burning switches, this proportion can be adjusted according to actual conditions, need not keep the same.
In order to ensure that the fuel forms stable flameless combustion in the inner combustion chamber 6, avoid the condition that the fuel cannot form flameless combustion due to early and full reaction, and simultaneously avoid the condition that the combustion area is close to the clapboard 8 to cause the damage of the combustion area, the distance between the primary air nozzle 55 and the flameless secondary air nozzle 53 is 0.1-0.7 times of the hydraulic diameter of the inner combustion chamber 6.
The total outlet area of the flameless secondary air nozzle 53 is adjusted according to actual conditions, and the outlet air speed of the flameless secondary air nozzle is ensured to reach 40-100 m/s, so that effective large-scale flue gas entrainment is formed in the inner combustion chamber 6, flameless combustion is realized, and meanwhile, overlarge resistance of an air conveying pipeline can be avoided.
Further, the flameless overfire air nozzles 53 and the return nozzles 52 are respectively vertical straight-flow nozzles or one circular nozzle with a preset number, as shown in fig. 7, (a) is a distribution schematic diagram when the flameless overfire air nozzles 53 and the return nozzles 52 are 1 vertical straight-flow nozzle, (b) is a distribution schematic diagram when the flameless overfire air nozzles 53 and the return nozzles 52 are 2 vertical straight-flow nozzles, (c) is a distribution schematic diagram when the flameless overfire air nozzles 53 and the return nozzles 52 are 4 vertical straight-flow nozzles, and (d) is a schematic diagram when the flameless overfire air nozzles 53 and the return nozzles 52 are one circular nozzle.
Further, the outlet of the flame secondary air nozzle 56 is provided with a flame stabilizer 562 for stabilizing the flame during the flame combustion stage, and the flame stabilizer 562 is a swirl type flame stabilizer, a slotted bluff body flame stabilizer or a non-slotted bluff body flame stabilizer.
Furthermore, the fuel is semi-coke fuel or low-volatile coal powder, the flameless combustion system provided by the invention can ensure that the difficult-to-burn fuel is combusted more fully by increasing the retention time of the fuel in the hearth, the utilization rate of the fuel is improved, and the oxidant is a mixture of air, oxygen and inert gas or a mixture of air and inert gas.
The operation of the flameless combustion system for semi-coke type nonflammable fuel provided by the present invention will be described in detail below.
(a) In the preheating stage, water circulation in the water-cooled wall 11 is closed, a flame secondary air nozzle valve 561 is opened, a flameless secondary air nozzle valve 531 is closed, secondary air enters the inner combustion chamber 6 through a flame stabilizer 562, meets primary air carrying semicoke fuel in the inner combustion chamber 6, and forms stable flame under the ignition of the ignition assembly 54, so that the secondary air passes through the flame combustion preheating combustion chamber, the power of the inner combustion chamber 6 is gradually increased in the process, smoke in the outer ring combustion chamber 9 passes through the waste heat exchanger 2 and the dust remover 12 in sequence and then is discharged, oxidant enters from the oxidant inlet 1 and enters the combustor 5 after being preheated in the waste heat exchanger 2, and unburned particulate matters 15 pass through the return hopper 3 and the return nozzle 52 and then return to the combustion chamber 6 for continuous combustion;
(b) in the stage of switching from the flame combustion to the flameless combustion, the temperature of the inner combustion chamber 6 is monitored through the temperature sensor 14, when the inner combustion chamber 6 is heated to 600-800 ℃, the valve 561 of the flame secondary air nozzle is gradually closed, and the valve 531 of the flameless secondary air nozzle is gradually opened, the inner combustion chamber 6 generates large-scale entrainment through high-speed jet flow, the flameless combustion is gradually formed, and the switching of the combustion mode is realized, wherein the flow path of the air flow in the system is shown in fig. 8;
(c) in the flameless combustion stage, after the stable flameless combustion of the inner combustion chamber 6 is realized, the water circulation in the water cooling wall 11 is opened to realize the separation of the combustion process and the heat exchange process, and the unburned particulate matters 15 can also return to the inner combustion chamber 6 through the return hopper 3, so that the efficient and low-pollution-discharge flameless combustion state of the semicoke fuel is realized.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims (10)

1. Flameless combustion system for semi-coke type nonflammable fuels, characterized by comprising a combustion chamber, a burner (5), a powder feeding device (4) and a flue gas treatment device, wherein:
the combustion chamber is divided into an inner combustion chamber (6) and an outer combustion chamber (9) by a partition plate (8) which is distributed in an annular manner, a combustor (5) is arranged at the lower end of the inner combustion chamber (6) and used for mixing and injecting fuel and an oxidant into the inner combustion chamber (6) so as to realize flame combustion or flameless combustion, a tangential diversion outlet (7) is arranged at the upper end of the partition plate and used for sending flue gas generated by combustion into the outer combustion chamber (9) from the inner combustion chamber (6) in a rotational flow manner, a water cooling pipe (11) and a flue gas outlet (10) are arranged on the outer wall of the outer combustion chamber (9) and are respectively used for absorbing heat of the flue gas and discharging the flue gas, and in addition, a return hopper (3) is arranged at the bottom end of the outer combustion chamber (9) and is used for collecting unburned particulate matters in the flue gas;
the combustor (5) comprises a primary air spray pipe (55), a flame secondary air spray pipe (56), a flameless secondary air spray pipe (53) and a material returning spray pipe (52) which are coaxially arranged, and also comprises an ignition assembly (54) extending into the inner combustion chamber (6), wherein the primary air spray pipe (55) is positioned at the center of the combustor (5) and used for spraying an oxidant carrying fuel to the inner combustion chamber (6), the flame secondary air spray pipe (56) is sleeved outside the primary air spray pipe (55) and used for spraying the oxidant in a flame combustion stage, the flameless secondary air spray pipe (53) is arranged outside the flame secondary air spray pipe (56) and used for spraying the oxidant in the flameless combustion stage, the material returning spray pipe (52) is arranged outside the flameless secondary air spray pipe (53), and the inlet of the material returning spray pipe is connected with the material returning hopper (3), for injecting the unburned particulate matter into the inner combustion chamber (6) for re-combustion;
the powder feeding device (4) is connected with the primary air spray pipe (55) and is used for providing fuel for the primary air spray pipe;
the flue gas treatment device comprises a waste heat exchanger (2) and a dust remover (12) which are sequentially connected, wherein an inlet of the waste heat exchanger (2) is connected with a flue gas outlet (10), and during operation, flue gas is preheated in the waste heat exchanger (2) and then is discharged after being treated by the dust remover (12).
2. The flameless combustion system for semi-coke type nonflammable fuel according to claim 1, wherein the ratio of the height of the tangential flow guiding outlet to the height of the inner combustion chamber (6) is 1: 8-1: 5.
3. the flameless combustion system for semi-coke type nonflammable fuel according to claim 1, wherein the air output ratio of the primary air nozzle (55) to the flamed secondary air nozzle (56) is 1: 6-1: 3, the air output ratio of the primary air spray pipe (55) to the flameless secondary air spray pipe (53) is 1: 6-1: 3.
4. the flameless combustion system for semi-coke type nonflammable fuel according to any one of claims 1 to 3, wherein the distance between the primary air nozzle (55) and the flameless secondary air nozzle (53) is 0.1 to 0.7 times the hydraulic diameter of the inner combustion chamber (6).
5. The flameless combustion system for semi-coke type nonflammable fuel according to claim 1, wherein the outlet wind speed of the flameless overfire air nozzle (53) is 40m/s to 100 m/s.
6. The flameless combustion system for semi-coke type nonflammable fuel according to claim 1, wherein the flameless overfire air nozzles (53) are a predetermined number of vertical straight flow nozzles or one circular ring nozzle.
7. The flameless combustion system for semi-coke type nonflammable fuel according to claim 1, wherein the return nozzle (52) is a predetermined number of vertical straight flow nozzles or a circular ring nozzle.
8. The flameless combustion system for semi-coke type nonflammable fuel of claim 1, wherein the outlet of the flamed secondary air nozzle (56) is provided with a flame stabilizer (562).
9. The flameless combustion system for semi-coke type nonflammable fuel of claim 8, wherein the flame stabilizer (562) is a swirl type flame stabilizer, a slotted bluff body flame stabilizer or a non-slotted bluff body flame stabilizer.
10. The flameless combustion system for the semicoke-type flame-retardant fuel according to any one of claims 5 to 9, wherein the fuel is a semicoke fuel or low-volatile coal powder, and the oxidant is air, a mixture of oxygen and inert gas or a mixture of air and inert gas.
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